^ aP34- Digitized by the Internet Archive in 2010 with funding from Open Knowledge Commons http://www.archive.org/details/textbookofhumanp1889land A TEXT-BOOK HUMAN PHYSIOLOGY, STANDARD MEDICAL WORKS. ANDERSON (Prof. T. McCall). A Treatise on Diseases of the Skin; with Special Reference to Diagnosis and Treatment. With several full-page Plates, two of which are colored, and numerous Wood Engravings. Octavo. Cloth, ^4.50; Leather, 1^5.50. BYFORD (Prof. W. H.). The Diseases of Women. Fourth Edition. Re- vised and rewritten. With 306 Illustrations, over 100 of which are original with this work. Octavo. Cloth, $5.00 ; Leather, ^6.00. CAZEAUX AND TARNIER'S Midwifery, with Appendix by Paul F. MuNDE. Eighth American, from the Eighth French and First Italian Editions. Elegantly Illustrated with seven beautifully colored and five other full-page Plates, and many Wood Engravings. Octavo. Students' Edition. Cloth, $5.00; Leather, $6.00. FAGGE (Chas. Hilton, m. d.). The Principles and Practice of Medicine. Edited by P. H. Pye-Smith, m. d. Including a Section on Skin Diseases by the Editor, and a Chapter on Cardiac Diseases by Samuel Wilkes, m. d. 2 Vols. Octavo. Cloth, ^8.00; Leather, $10.00 ; Half Russia, $12.00. GOWERS (Prof. W^m. R.). Manual of Diseases of the Nervous System. A Complete Text-book. 341 Illustrations. Octavo. Cloth, $6.50; Leather, 57.50. HOLDEN (Luther, f.r.c.s.). A Manual of Anatomy. Fifth Edition. Care- fully revised and enlarged. 208 Illustrations. Octavo. Oilcloth, S4.50; Cloth, $5.00; Leather, $6.00. JACOBSON (W. H. A., f.r.c.s.). The Operations of Surgery. A Systematic Handbook for Practitioners, Students and Hospital Surgeons. 199 Illustra- tions (describing over 230 operations as performed at Guy's Hospital, London). Octavo. 1000 pages. Cloth, $5.00 ; Leather, 56.00. MEYER (Dr. Edouard). A Manual of Diseases of the Eye. Translated from the Third Edition by A. Freedland Fergus, m. b. (Glasgow). 270 Illustra- tions and two Colored Plates (by Liebreich). Octavo. Cloth, 54.50; Leather, $5.50. ROBERTS (Prof. Fred.). The Theory and Practice of Medicine. Seventh Edition. Thoroughly revised and Enlarged. Illustrated. Octavo. Cloth, 55.50; Leather, 56.50. WINCKEL (Prof. F.). Text-book on Midwifery, including the Diseases of Childbed. Authorized Translation by J. Clifton Edgar, m. d.. Lecturer on Obstetrics, University Medical College, New York. With 190 Illustrations, the majority of which are original with this work. Octavo. Nearly Ready. *^* These books may be obtained through any bookseller, or upon receipt of the price any book w^ill be sent, postage prepaid. Complete Catalogues upon appli- cation. P. BLAKISTON, SON & CO., Medical Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. A TEXT-BOOK HUMAN PHYSIOLOGY INCLUDING HISTOLOGY AND MICROSCOPICAL ANATOMY ; WITH SPECIAL REFERENCE TO THE REQUIREMENTS OF PRACTICAL MEDICINE. DR. L. LANDOIS, PROFESSOR OF PHYSIOLOGY AND DIRECTOR OP THE PHYSIOLOGICAL INSTITUTE, UNIVERSITY OF GREIFSWALU. THIRD AMERICAN, TRANSLATED FROM THE SIXTH GERMAN EDITION. WITH ADDITIONS BY WILLIAM STIRLING. M.D., Sc.D., BRACKENBURY PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN THE OWENS COLLEGE, AND PROFESSOR IN THE VICTORIA UNIVERSITY, MANCHESTER ; EXAMINER IN PHYSIOLOGY, UNIVERSITY OF OXFORD. WITH SIX HUNDRED AND NINETY-TWO ILLUSTRATIONS. PHILADELPHIA : P. BLAKISTON, SON & CO., IOI2 WALNUT STREET. 1889. [^// Rights Reserved. '\ WUl.^VIl t' /I" * ^ L232- Press of Wm. F. Fell & Oo., 1220-24 SANSOM ST., PHILAOCLPHIA. 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 Wht Pan of ^(itnstf WHOSE BRILLIANT DISCOVERIES HAVE REVOLUTIONIZED MEDICAL PRACTICE, AND CONTRIBUTED INCALCULABLY TO THE WELL-BEING OF MANKIND ; AND IN GRATITUDE TO ^Jxt ®ieadter, WHOSE NOBLE EARNESTNESS IN INCULCATING THE SACREDNESS OF HUMAN LIFE STIRRED THE HEARTS OF ALL WHO HEARD HIM : BY HIS FORMER PUPIL, THE TRANSLATOR. PREFATORY NOTE TO THE THIRD EDITION. In offering to the Profession this Third English Edition, I would only say that the whole work has again been thoroughly revised and in many parts extended. In all respects I have endeavored to keep it abreast of the latest investigations in Physiology and their bearing on Practical Medicine and Surgery. I have again to thank my publishers for enabling me to enhance the usefulness of the work by very numerous additions to the Illustrations, which now number 692 as compared with the 494 of the First Edition. Many of these new engrav- ings are original ; others are derived from the Sixth German Edition of the work, from Stohr's Lehrbuch der Histoiogie^OndUn^?, Anatomy, Ferrier's Functions of the Brain (Second Edition), H. Obersteiner's Anleitung beim Sttidium des Baues der nervosen Centralorgane, Rollett's Article on "Muscle" in the Real-Encyclop(Bdie, Gowers' Diseases of the Nervous System, and most of those for the chapter on Reproduction from Haddon's Introductio?i to Embryology. In addition, I have to tender special acknowledgments to my colleagues and friends, Professors A. H. Young, James Ross, A. W. Hare and Dr. Aug. D. Waller; as well as to Messrs. Carl Reichert, of Vienna; W. Petzold, of Leipzic; Rothe, of Prague; Maw, Cassella, Krohne and Sesemann, Evans & Wormall, of London, and Ferries & Co., of Bristol. For the first time the work appears here in one volume — an arrangement adopted both to meet the wishes of Students and to facilitate easy reference. I can but express a hope that the present Edition, in its new form, will meet with the same very kind reception accorded to its predecessors. WILLIAM STIRLING. The Owens College, Manchester. PREFACE TO THE FIRST EDITION. The fact that Professor Landois' ^' Lehrbtich 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 evamQwi pracitcaltty ; 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 practicing Physician of to-morrow. Thus, to every Section is appended — after a full description of the normal processes — a short resume of the pathological varia- tions, 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 patho- logical processes 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 processes, 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 : — (i) In the task of translating, I have endeavored throughout to convey the author's meaning accurately, without a too rigid adherence to the original. Those who from experience know something of the difficulties of such an undertaking will be most ready to pardon any shortcomings they may detect. (2) Very considerable additions have been made to the Histological, and also (where it has seemed necessary) to the Physiological sections. All such additions are enclosed within square brackets [ ]. I have to acknowledge my indebtedness to many valuable Papers in the various Medical Journals — British X PREFACE. and Foreign — and also to the Histological Treatises of Cadiat, Ranvier, and Klein; Qnain's A/i(7/o//iy, Vol. ii, Ninth Edition; Herma-nn's /fan(/hfc/i t/er Pkysio/ogt'e; and the Text-books on Physiology, by Rutherford, Foster, and Kirkes; Gamgee's Physiological Chemistry; Ewald's Digestion ; and Roberts' Digestive Ferments. (3) The Illustrations have been greatly increased in number, viz., from 275 in the Fourth German Edition to 494 in the English version. These additional Diagrams, with the sources whence derived, are distinguished in the List of Wood- cuts 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 McKendrick ; 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 Librarian of the Aberdeen Public Library, for much valuable assistance while the work was passing through the press. In conclusion — and forgetting for the moment my own connection with it — I heartily commend the woxV 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. GENERAL CONTENTS. INTRODUCTION. PAGK The Scope of Physiology and its Relations to other Branches of Natural Science, 33 Matter, 34 Forces, 35 Law of the Conservation of Energy, 3^ Animals and Plants, 39 Vital Energy and Life, 4^ I. PHYSIOLOGY OF THE BLOOD. SECTION 1 . Physical Properties of the Blood, 42 2. Microscopic Examination of the Blood, 44 3. Histology of the Human Red Blood Corpuscles, 46 4. Effects of Reagents on the Blood Corpuscles, 47 5. Preparation of the Stroma — Making Blood " Lake Colored," 49 6. Form and Size of the Blood Corpuscles of Different Animals 50 7. Origin of the Red Blood Corpuscles, 5^ 8. Decay of the Red Blood Corpuscles, 53 9. The Colorless Corpuscles — Leucocytes — Blood Plates — Granules, 53 10. Abnormal Changes of the Blood Corpuscles, 5^ 11. Chemical Constituents of the Red Blood Corpuscles, 59 12. Preparation of Hsemoglobin Crystals, 59 13. Quantitative Estimation of Haemoglobin, 60 14. Use of Spectroscope, 61 15. Compounds of Haemoglobin — Methfemoglobin, 62 16. Carbonic Oxide Haemoglobin — Poisoning with Carbonic Oxide, 65 17. Other Compounds of Hemoglobin, 66 18. Decomposition of Hsemoglobin, 66 19. Haemin and Blood Tests, 67 20. Hasmatoidin, 68 21. The Colorless Proteid of Haemoglobin, 68 22. Proteids of the Stroma, 69 23. The other Constituents of Red Blood Corpuscles, • 69 24. Chemical Composition of the Colorless Corpuscles, 69 25. Blood Plasma, and its Relation to Serum, ^o 26. Preparation of Plasma, • • 7° 27. Fibrin — Coagulation of the Blood, 7^ 28. General Phenomena of Coagulation, 7^ 29. Cause of Coagulation of the Blood, 74 30. Source of the Fibrin Factors, 77 31. Relation of the Red Blood Corpuscles to the Formation of Fibrin, 77 32. Chemical Composition of the Plasma and Serum, 7^ 33. The Gases of the Blood, • , 80 34. Extraction of the Blood Gases, 81 35. Quantitative Estimation of the Blood Gases, 82 36. The Blood Gases, 83 37. Is Ozone (O3) present in Blood? ^4 38. Carbon dioxide and Nitrogen in Blood, 85 39. Arterial and Venous Blood, °6 40. Quantity of Blood, " ' - 86 41. Variations firom the Normal Conditions of the Blood, 87 Xll CONTENTS. II. PHYSIOLOGY OF THE CIRCULATION. SECTION PACK 42. (leneral View of the Circulation, 91 43. The Heart 92 44. Arrangement of the Cardiac Muscular Fibres, 92 45. Arrangement of the Ventricular Fibres 94 46. Pericanlium. Endocardium, Valves, 95 47. Automatic Regulation of the Heart, 96 48. The Movements of the Heart, 98 49. Pathological Disturbances of Cardiac Action, loi 50. The Ajiex Beat— The Cardiogram, 102 51. The Time Occupied by the Cardiac Movements, 107 52. Pathological Disturbance of the Cardiac Impulse, no 53. The Heart Sounds, 112 54. Variations of the Heart Sounds, 114 55. The Duration of the Movements of the Heart, 116 56. Physical Examination of the Heart, 1 17 57". Innervation of Heart — Cardiac Nerves, 117 58. The Automatic Motor Centres of the Heart 119 59. The Cardiopneumatic Movements, 128 60. Influence of the Respiratory Pressure on the Heart, 129 THE CIRCULAnON. 61. The Flow of ?'luids through Tubes, 132 62. Propelling Force, Velocity of Current, Lateral Pressure, 132 63. Currents through Capillary Tubes 134 64. Movements of Fluids and Wave Motion in Elastic Tubes, . . 134 65. Structure and Properties of the Blood Vessels, 134 66. Investigation of the Pulse, 139 67. Pulse Tracing, or Sphygmogram, 144 68. Origin of the Dicrotic Wave, . . • 145 69. Dicrotic Pulse, 14^ 70. Characters of the Pulse, • 149 71. Variations in the Strength, Tension, and Volume of the Pulse, 150 72. The Pulse Curves of various Arteries, I5' 73. Anacrotism, '5^ 74. Influence of the Respiratory Movements on the Pulse Curve, 153 75. Influence of Pressure upon the Form of the Pulse Wave, 155 76. Rapidity of Transmission of Pulse Weaves, 156 77. Propagation of the Pulse Wave in Elastic Tubes, 156 78. Velocity of the Pulse Wave in Man, 156 79. Other Pulsatile Phenomena, 157 80. Vibrations communicated to the Body by the Action of the Heart, 158 8i. The Blood Current 159 82. Schemata of the Circulation, 161 83. Capacity of the Ventricles, 161 84. Estimation of the Blood Pressure, 161 85. Blood Pressure in the Arteries, 165 86. Blood Pressure in the Capillaries, 171 87. Blood Pressure in the Veins, 171 88. Blood Pressure in the Pulmonary Artery, 173 89. Measurement of the Velocity of the Blood Stream, 175 90. Velocity of the Blood in Arteries, Capillaries, and Veins 177 91. Estimation of the Capacity of the Ventricles, 179 92. The Duration of the Circulation, 179 93. Work of the Heart, 180 94. Blood Current in the Smallest Vessels, 180 95. Passage of the Blood Corpuscles out of the Vessels [Diapedesis], 182 96. Movement of the Blood in the Veins, 183 97. Sounds or Bruits within Arteries, 184 98. Venous Murmurs 185 99. The Venous Pulse — Phlebogram 185 100. Distribution of the Blood, 187 101. Plethysmography, 187 102. Transfusion of Blood, 189 CONTENTS. XIU THE BLOOD GLANDS. SECTION PAGK 103. The Spleen — Thymus — Thyroid — Suprarenal Capsules — Hypophysis Cerebri — Coccygeal and Carotid Glands, 102 104. Comparative, 201 105. Historical Retrospect, , . 202 III. PHYSIOLOGY OF RESPIRATION. 106. Structure of the Air Passages and Lungs, 203 107. Mechanism of Respiration, 209 108. Quantity of Gases Respired, 210 109. Number of Respirations, 211 no. Time occupied by the Respiratory Movements, 212 111. Pathological Variations of the Respiratory Movements, 215 112. General View of the Respiratory Muscles, 216 113. Action of the Individual Respiratory Muscles, 217 114. Relative Size of the Chest, 220 115. Pathological Variations of the Percussion Sounds, 222 116. The Normal Respiratory Sounds, 223 117. Pathological Respiratory Sounds, 224 118. Pressure in the Air Passages during Respiration, 225 119. Appendix to Respiration, 226 120. Peculiarly Modified Respiratory Sounds, 226 121. Quantitative Estimation of CO2, O, and Watery Vapor, 227 122. Methods of Investigation, 228 123. Composition and Properties of Atmospheric Air, 230 124. Composition of Expired Air 231 125. Daily Quantity of Gases Exchanged, 232 126. Review of the Daily Gaseous Income and Expenditure, 232 127. Conditions Influencing the Gaseous Exchanges, 232 128. Diffusion of Gases within the Lungs, 234 129. Exchange of Gases between the Blood and Air, 235 130. Dissociation of Gases, 237 131. Cutaneous Respiration, 238 132. Internal Respiration, 238 133. Respiration in a Closed Space 240 134. Dyspnoea and Asphyxia, 241 135. Respiration of Foreign Gases, 244 136. Accidental Impurities. of the Air, 244 137. Ventilation of Rooms, 245 138. Formation of Mucus, 245 139. Action of the Atmospheric Pressure, 247 140. Comparative and Historical, 249 IV. PHYSIOLOGY OF DIGESTION. 141. The Mouth and its Glands, 250 142. The SaUvary Glands, 252 143. Histological Changes in Salivary Glands, 253 144. The Nerves of the Salivary Glands, 255 145. Action of Nerves on the Salivary Secretion, 256 146. The Saliva of the Individual Glands, 260 147. The Mixed Saliva in the Mouth, 261 148. Physiological Action of Saliva, 262 149. Tests for Sugar, 264 150. Quantitative Estimation of Sugar, 265 151. Mechanism of the Digestive Apparatus, 266 152. Introduction of the Food, 267 153. The Movements of Mastication 267 154. Structure and Development of the Teeth, 268 155. Movements of the Tongue, 271 156. Deglutition, .' 272 157. Movements of the Stomach, 275 158. Vomiting, 276 159. Movements of the Intestine, 277 XIV CONTENTS. SECTION PACK 160. Excretion of Fecal Matter, 278 161. Conditions inlluencing the Movements of the Intestine 280 162. Structure of the Stomach, 284 i6j. The Gastric Juice, 287 164. Secretion of Gastric Juice, 288 165. Methods of obtaining Gastric Juice, 291 166. Process of Gastric Digestion, 292 167. (iases in the Stomach, 297 168. Structure of the Pancreas, 297 169. The Pancreatic Juice, 298 170. Digestive Action of the Pancreatic Juice, 299 171. The Secretion of the Pancreatic Juice, 302 172. Preparation of Peptonized Food, 303 173. Structure of the Liver, 303 174. Chemical Composition of the Liver Cells, 307 175. Diabetes Mellitus, or Glycosuria, 310 176. The Functions of the Liver 311 177. Constituents of the Bile 312 178. Secretion of Pile, 315 179. Excretion of Bile, 316 180. ReabsoriHion of Bile — Jaundice, 317 iSl. Functions of the Bile, 319 1S2. Fate of the Bile in the Intestine, 320 183. The Intestinal Juice, 321 184. Fermentation Processes in the Intestine, 324 185. Processes in the Large Intestine, 328 1S6. Pathological Variations, 331 187. Comparative Physiology, 333 188. Historical Retrospect, 334 V. PHYSIOLOGY OF ABSORPTION. 189. The Organs of Absorption, 336 190. Structure of the Small and Large Intestines, 336 191. Absorption of the Digested Food, 342 192. Absorptive Activity of the Wall of the Intestine, 344 193. Influence of the Nervous System. 347 194. Feeding with " Nutrient Enemala " 347 195. Chyle Vessels and Lymphatics, 348 196. Origin of the Lymphatics 348 197. The Lymph Glands, 351 198. Properties of Chyle and Lymph, 353 199. Quantity of Lymph and Chyle,. 354 200. Origin of Lymph, 355 201. Movement of Chyle and Lymph, 356 202. Absorption of Parenchymatous Effusions, 359 203. Dropsy, CEdema, Serous Effusions, 359 204. Comparative Physiology, 360 205. Historical Retrospect 361 VL PHYSIOLOGY OF ANIMAL HEAT. 206. Sources of Heat, 362 207. Homoiothermal and Poikilothermal Animals, 365 208. Methods of Estimating Temperature — Thermometry 366 209. Temperature Topography, 369 210. Conditions Influencing the Temperature of Organs, 370 211. Estimation of the Amount of Heat — Calorimetry 371 212. Thermal Conductivity of Animal Tissues, 373 213. Variations of the Mean Temperature, 373 214. Regulation of the Temperature, 376 215. Income and Expenditure of Heat, 379 216. Variations in Heat Production, 380 217. Relation of Heat Production to Bodily Work, 381 218. Accommodations for Different Temperatures, 381 219. Storage of Heat in the Body, 382 CONTENTS. XV SECTION PAGE 220. Fever, 383 221. Artificial Increase of the Temperatvtre, 384 222. Employment of Heat, 384 223. Increase of Temperature /^jAi'«(7;'/^w, 385 224. Action of Cold on the Body, 385 225. Artificial Lowering of Temperature, 386 226. Employment of Cold, 387 227. Heat of Inflamed Parts, 387 228. Historical and Comparative, 387 VII. PHYSIOLOGY OF THE METABOLIC PHENOMENA OF THE BODY. 229. General View of Food Stuifs, 388 230. Structure and Secretion of the Mammary Glands, 390 231. Milk and its Preparations, 392 232. Eggs, 395 233. Flesh and its Preparations, 396 234. Vegetable Foods, • 397 235. Condiments — Coffee, Tea, and Alcohol, 400 236. Equilibrium of the Metabolism, 402 237. Metabolism during Hunger and Starvation, 408 238. Metabolism during a purely Flesh Diet, 409 239. A Diet of Fat or of Carbohydrates, 410 240. Mixture of Flesh and Fat, 411 241. Origin of Fat in the Body, 411 242. Corpulence, . 413 243. The Metabolism of the Tissues, ' 414 244. Regeneration of Organs and Tissues, 416 245. Transplantation of the Tissues, 419 246. Increase in Size and Weight during Growth, 419 GENERAL VIEW OF THE CHEMICAL CONSTITUENTS OF THE ORGANISM. 247. Inorganic Constituents, 4?^ 248. Organic Compounds — Proteids, 423 249. The Animal and Vegetable Proteids and their Properties, 424 250. The Albuminoids, 426 251. The Fats, 429 252. The Carbohydrates 430 253. Historical Retrospect, 433 VIII. THE SECRETION OF URINE. 254. Structure of the Kidney, 434 255. The Urine, 440 256. Organic Constituents of Urine — Urea, 443 257. Qualitative and Quantitative Estimation of Urea, 446 258. Uric Acid, 447 259. Qualitative and Quantitative Estimation of Uric Acid, 449 260. Kreatinin and other Substances, 449 261. Coloring Matters of the Urine, 452 262. Indigo, Phenol, Kresol, Pyrokatechin, 453 263. Spontaneous Changes in Urine, Fermentations, 456 264. Albumin in Urine, 457 265. Blood in Urine 460 266. Bile in Urine, 462 267. Sugar in Urine, 462 268. Cystin, 465 269. Leucin, Tyrosin, , . • 465 270. Deposits in Urine, 465 271. General Scheme for Detecting Urinary Deposits, 4^7 272. Urinary Calculi, • . 468 273. The Secretion of Urine, 4^9 XVI CONTENTS. SECTION PAGE 274. The Formation of Urinary Constituents, 473 275. Passage of Various Substances into the Urine, 475 276. Influence of Nerves on the Renal Secretion, 47^ 277. Uri\;mia, Ammoniivmia, 479 278. Structure and Functions of the Ureter, 480 279. Urinary Bladder and Urethra, 481 280. Accumulation and Retention of Urine, 483 281. Retention and Incontinence of Urine, 486 282. Comparative and Historical, 486 IX. FUNCTIONS OF THE SKIN. 283. Structure of the Skin, Nails, and Hair, 487 284. The Glands of the Skin, 492 285. The Skin as a Protective Covering, 493 286. Cutaneous Respiration and Secretion — Sweat, 493 287. Conditions Influencing the Secretion of Sweat 495 288. Pathological Variations, 497 289. Cutaneous Absorption — Galvanic Conduction, 498 290. Comparative — Historical, 499 X. PHYSIOLOGY OF THE MOTOR APPARATUS. 291. Ciliary Motion, Pigment Cells, 5°° 292. Structure and Arrangement of the Muscles, • 502 293. Physical and Chemical Properties of Muscle, 511 294. Metabolism in Muscle, 5 '3 295. Rigor mortis 5'5 296. Muscular Excitability, S'9 297. Changes in a Muscle during Contraction, 5^4 298. Muscular Contraction, S^" 299. Rapidity of Transmission of a Muscular Contraction, 537 300. Muscular Work, 538 301. The Elasticity of Muscle, 54^ 302. Formation of Heat in an Active Muscle, 543 303. The Muscle Sound, 545 304. Fatigue and Recovery of Muscle, . . . . • 545 305. The Mechanism of the Joints, 547 306. Arrangement and Uses of the Muscles of the Body, 549 307. Gymnastics — Pathological Motor Variations 553 308. Standing, 554 309. Silting, 555 310. Walking, Running, and Leaping, • 555 311. Comparative, 55^ XI. VOICE AND SPEECH. 312. Voice and Speech, 559 313. Arrangement of the Larynx, 5^° 314. Organs of Voice — Laryngoscopy, 5^5 315. Conditions Modifying the Laryngeal Sounds, 5^8 316. Range of the Voice, 5^9 317. Speech — The Vowels, 5^9 318. The Consonants, 57^ 319. Pathological Variations of Voice and Speech, 573 320. Comparative — Historical, 573 XII. GENERAL PHYSIOLOGY OF THE NERVES AND ELECTRO-PHYSIOLOGY. 321. Structure and Arrangement of the Nerve Elements, 575 322. Chemical and Mechanical Properties of Nerve Substance, • 581 323. Metabolism of Nerves, 582 324. Excitability of Nerves — Stimuh, 583 325. Diminution of Excitability — Degeneration and Regeneration of Nerves, 587 CONTENTS. XVll SECTION PAGE 326. The Galvanic Current, 591 327. Action of the Galvanic Current — Galvanometer, 593 328. Electi-olysis, , • 594 329. Induction — Extra-Current — Magneto-Induction, 599 330. Du Bois-Reymond's Inductorium 601 331. Electrical Currents in Passive ^Muscle and Nerve, 603 332. Currents of Stimulated Muscle and Nerve, 607 333. Currents in Nerve and Muscle during Electrotonus, 611 334. Theories of Muscle and Nerve Currents, 613 335. Electrotonic Alteration of the Excitability, 615 336. Electrotonus — Law of Contraction, 617 337. Rapidity of Transmission of Nervous Impulses, 620 338. Double Conduction in Nerves, 623 339. Therapeutical Uses of Electricity — Reaction of Degeneration, 624 340. Electrical Charging of the Body, 629 341. Comparative- — Historical, 629 XIII. PHYSIOLOGY OF THE PERIPHERAL NERVES. 342. Classification of Nerve Fibres, 631 343. Nervus Olfactorius, 634 344. Nervus Opticus, 634 345. Nervus Oculomotorius, 637 346. Nervus Trochlearis, 639 347. Nervus Trigeminus, 640 348. Nervus Abducens, 649 349. Nervus Facialis, 649 350. Nervus Acusticus, 653 351. Nervus Glosso-pharyngeus, 655 352. Nervus Vagus, 656 353. Nervus Accessorius, 664 354. Nervus Hypoglossus, 664 355. The Spinal Nerves, 665 356. The Sympathetic Nerve, 670 357. Comparative — Historical, 673 XIV. PHYSIOLOGY OF THE NERVE CENTRES. 358. General, , . , 675 359. Structure of the Spinal Cord, 676 360. Spinal Reflexes, • . . . . • 686 361. Inhibition of the Reflexes, 689 362. Centres in the Spinal Cord, ^ 693 363. Excitability of the Spinal Cord, 695 364. The Conducting Paths in the Spinal Cord, 696 365. General Schema of the Brain, 7°° 366. The Medulla Oblongata, 705 367. Reflex Centres of the Medulla Oblongata, Jio 368. The Respiratory Centre, ' 7^2 369. The Cardio-Inhibitory Centre, 7"^ 370. The Accelerans Cordis Centre, 720 371. Vasomotor Centre and Vasomotor Nerves, 7^2 372. Vaso- dilator Centre and Vaso-dilator Nerves, 729 373. The Spasm Centre — The Sweat Centre, 73° 374. Psychical Functions of the Cerebrum, 73^^ 375. Structure of the Cerebrum — Motor Cortical Centres, 737 376. The Sensory Cortical Centres, 75^ 377. The Thermal Cortical Centres, 755 378. Topography of the Cortex Cerebri, 756 379. The Basal Gangha— The Mid-brain, 765 380. The Structure and Functions of the Cerebellum, 772 381. The Protective Apparatus of the Brain, 776 382. Comparative — Historical, 779 2 XVlll CONTENTS. XV. PHYSIOLOGY OF THE SENSE ORGANS. I. SIGHT. SECTION PAGE 383. Intraductory Observations 781 384. Histology of the Eye, 783 385. Dioptric Observations 792 386. Formation of a Retinal Image, 796 387. Accommodation of the Eye, 799 388. Normal and Abnormal Refraction, 803 389. The Power of Accommodation, 805 390. Spectacles, 806 391. Chromatic Aberration and Astigmatism, 807 392. The Iris, 808 393. Entoptical Phenomena, 812 394. Illumination of the Eye — The Ophthalmoscope, 814 395. Activity of the Retina in Vision, 818 396. Perception of Colors, 823 397. Color Blindness 828 398. Stimulation of the Retina 829 399. Movenientsof the Eyeballs, S^^ 400. Binocular Vision, 837 401. Single Vision — Identical Points, 837 402. Stereoscopic Vision, 839 403. Estimation of Size and Distance, 841 404. Protective Organs of the Eye, 843 405. Comparative — Historical, 845 2. HEARING. 406. Structure of the Organ of Hearing, 847 407. Physical Introduction, 848 408. Ear Muscles 849 409. Tympanic Membrane, 849 410. The Auditory Ossicles and their Muscles, 851 411. Eustachian Tube — Tympanum, 855 412. Conduction of Sound in the Labyrinth, 856 413. Structure of the Labyrinth, 857 414. Auditory Perceptions of Pitch, 860 415. Perception of Quality — Vowels, 863 416. Action of the Labyrinth, 867 417. Harmony — Discords — Beats, 868 418. Perception of Sound, 869 419. Comparative — Historical, 870 3. SMELL. 420. Structure of the Organ of Smell, 87 1 421. Olfactory Sensations, 872 4. TASTE. 422. Position and Structure of the Organs of Taste, 874 423. Gustatory Sensations, 876 5. TOUCH, 424. Terminations of Sensory Nerves 878 425. Sensory and Tactile Sensations, 881 426. The Sense of Locality, 882 427. The Pressure Sense, 885 428. The Temperature Sense 887 429. Common Sensation — Pain, 889 430. The Muscular Sense, 891 CONTENTS. XIX XVI. PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. SECTION _ PAGE 431. Forms of Reproduction, 893 432. Testis — Seminal Fluid, . . . , 896 433. The Ovary — Ovum — Uterus, 901 434. Puberty, 906 435. Menstruation, 007 436. Penis — Erection, 909 437. Ejaculation — Reception of the Semen, 911 438. Fertilization of the Ovum, 912 439. Impregnation and Cleavage of the Ovum, 913 440. Structures formed from the Epiblast, 917 441. Structures formed from the Mesoblast and the Hypoblast, 919 442. Formation of the Heart and Embryo, 921 443. Further fonnation of the Body, 922 444. Formation of the Amnion and Allantois, 923 445. Human Fcetal Membranes — Placenta, 925 446. Chronology of Human Development, 929 447. Formation of the Osseous System, 930 448. Development of the Vascular System, 934 449. Formation of the Intestinal Canal, 938 450. Development of Genito-Urinary Organs, 940 451. Formation of the Central Nervous vSystem, 943 452. Development of the Sense Organs, 944 453. Birth, 946 454. Comparative — Historical, 947 Appendix A. ; Bibliography, 950 Appendix B. ; Tables of Measure (Metric and Ordinary) and of Temperature, 954 Index, 955 LIST OF ILLUSTRATIONS. FIGURE PAGE 1. Human colored blood corpuscles, - 44 2. Apparatus of Abbe and Zeiss for estimating the blood corpuscles, 45 3. Mixer, 45 *4. Gower's hjemacytometer {^Haivksle)'), 46 *5. Crenation of human blood corpuscles, 47 6. Red blood corpuscles showing various changes of shape, 48 *7. Effect of reagents on blood corpuscles [Stirling), 49 8. Vaso-formative cells, 52 9. White blood corpuscles and fibrin, 54 *io. White blood corpuscles (A7«w), 55 11. Amcehoid movements of colorless corpuscles, 56 12. Blood plates and their derivatives, 57 13. Haemoglobin crystals, 59 *I4. Gowers' haemoglobinometer (Hawksley), 60 *I5. Fleischl's ha;mometer {^Reicherf), 61 16. Scheme of a spectroscope, 62 17. Various spectra of haemoglobin and its compounds, , . . . 63 18. Haemin crystals, 67 19. Hcemin ciystals prepared from traces of blood, 67 20. Hfematoidin crystals, 68 *2i. Hewson's experiment, 74 22. Scheme of Pfliiger's gas pump, 82 *23. Micrococcus, bacterium, vibrio, 90 *24. Bacillus anthracis, 90 25. Scheme of the circulation, 91 26. Muscular fibres from the heart, 92 27. Muscular fibres in the left auricle, 93 28. Muscular fibres in the ventricles, 94 *29. Lymphatic from the pericardium {Cadiat), 95 *30. Section of the endocardium {Cadiat), 95 *3I. Purkinje's fibres {Ranvier), 96 32. Cast of the ventricles of the human heart, 99 33. The closed semilunar valves, 100 *34. Gaule's maximum and minimum manometer (^Gscheidlen), loo *35. Manometer of Gaul e ( 6^jc^(?Z£f/f«), 100 *36. Various cardiographs {^Hermann), 103 *37. Cardiogram, 103 *38. Arteriogram and Cardiogram, 104 39. Curves of the apex beat, ' 104 40. Changes of the heart during systole, and sections of thorax, 105 *4I. Dog's heart, posterior surface [L^cdwig and Hesse), 106 *42. Left lateral surface (^Ludwig and Hesse), 106 *43. Anterior surface {Liidwig and Hesse), 106 *44. Base of heart i^Ludiuig arid Hesse), , 107 *45. Base of heart in systole and diastole (Ze^fl^w?^ rtw^ i^i-jf), 107 _ 46. Curves from a rabbit's ventricle, I08 *47. Marey's registering tambour [Hermann), 109 48. Curs'es obtained with a cardiac sound, no 49. Curves from the cardiac impulse, iii, 112 *5o. Scheme of cardiac cycle, 112 *5i. Position of the heart in the chest (Z^«f/iia a«(/ CazV^/wfr), 115 *52. Curves of excised rabbits' hearts (iVzV/zwo-, <2/?fr Waller), 1 16 *53. Heart of frog from the front (Z'ci^r), 1 18 xxi XXll LIST OF ILLUSTRATIONS. FIGURE PAGE *54. Heart of frog from behind I^Ecker), Ii8 *55. Auricular septum [Ecker], 119 *56. Bipolar nerve cells from a frog's heart, 1 19 *57. Scheme of frog's heart {Bntntnn), 1 19 *58. Stannius's experiment i^Bnutton), 1 19 *59. Luciani's groups of cardiac pulsations (//- ligatured (.S'//;7/«^'-) 521 *3l6. Scheme of the curara experiment (^t//^/- AW/z^/yi^rd'), 521 *3I7. Excitability in a frog's sartorius {SdrHui^, after Pollitzer), 522 *3l8. Exci ability in a curarized sartorius {Stirling^ after Pollitzer'), 522 319. Microscopic appearances in contracting muscle, 525 320. Helmholtz's myograph, 526 *32i. Pendulum myogiMjih, 5^7 *322. Scheme of the jicndulum myograph {Stirling), 528 *323. Du Hois- Reymond's spring myograph 529 324. Muscle curve, 5^9 *325. Muscle curve of pendulum myograph {Stirling), 530 *326. Method of studying a muscular contraction («/?«■;- /\?«/'//i';/(5r,/) 531 *327. Effect of make and break induction shocks {Stirling), 531 328. Muscle curves, Si^ 329. Muscle curve, opening and closing shocks, 532 *330. Veratrin curve {Stirling), ■ . 533 331. Muscle curves, tetanus, 534 *332. Staircase contractions {Buckiiiaster) 535 333. Curves of voluntary impulses, 535 *334. Curves of a red and pale muscle (A'rowifrXw ««(/ ^//V/iM^), 536 *33S- Muscle curves {Kronecker and Stirling), 536 *336. Tone inductorium (A'/-ow^C/^i?r rt«rt' ^^/r/z«^), 537 *337- Muscle curves (yl/rt;-(?)'), 53^ *338. Height of the hft by a muscle, 539 *339- Dynamometer, 54t> *340. Curve of elasticity (^y/^r y]/rtr^ji'), 54' *34i. Curve of elasticity of a muscle {after Alar ey), 54" *342. Curve of elasticity {A/arey), 54^ *343. Fatigue curve {Stirling), . 54^ *344. Fatigue curve ( JValler), • . . . • 547 *34S- Vertical section of articular cartilage (6'/i>//«^), 54^ *346. Orders of levers, 55' *347. Scheme of the. action of muscles on bones, 551 348. Phases of walking, 55^ 349. Instantaneous photograph of a person walking, 556 350. Instantaneous photograph of a runner, 557 351. Instantaneous photograph of a person jumping, 55^ 352. Larynx from the front, 5^' 353. Larynx from behind, 5^' 354. Larynx from behind 5^2 355. Nerves of the larynx, 5^2 356. Action of the posterior crico-arytenoid muscles, 563 357. Action of the arytenoid muscles, 5^3 358. Action of the lateral crico-arytenoid muscles, 5^3 359. Vertical section of the head and neck, ...... • . . 5^5 360. Examination of the larynx, 5^6 361. Laryngoscopic view of the larynx, 5^6 362. View of the larynx during a high note, 5^7 363. View of the larynx during a deep inspiration, 5^7 364. Rhinoscopy, 5^7 365. View of the posterior nares, • 5^^ 366. Parts concerned in phonation, 57' 367. Tumors on the vocal cords 573 368. Histology of nervous tissues, 57^ *369. Transverse section of nerve fibres (Ca^//rt/), 57^ *370. Sympathetic nerve fibre {Panvier), 57^ *37I. Medullated nerve fibre (Stirling), 57^ 372. Medullated nerve fibre, 57^ *373 Medullated nerve fibres {Schwalbe), 57^ *374. Ranvier's crosses (Ranvier), 579 375. Transverse section of a nerve, 579 *376. Cell from the Gasserian ganglion (5(r//7ersUiner'), 679 ♦446. Transverse section of the cord {Cadiat), 679 *447. Longitudinal section of the cord [Qidial) 680 *448. Multipolar nerve cell, 680 *449. Scheme of fibres in cord {Obersteiner), 680 *450. Glia cell [Ol>ersteiner), 681 *45I. Glia cells of cord {Ol>t-rsh'iner), 681 *452. Spinal cord injected [Ob^rsteiner), 682 *453. Injected blood vessels of the cord {^Kolliker) 682 454. Conducting paths in the cord, 683 *455. Degeneration paths in the cord [Brainwell), 685 ♦456. Scheme of a retlex act {Stirling), 686 *457. Sectijn of a spinal segment {Stirling), 686 *458. Propagation of reflex movements [Beaunis), 687 *459. Effect of section of half of the cord {Erb), 699 *46o. Brain, ventricles, and basal ganglia, 7°° 461. Scheme of the brain, "joi *462. Connections of the cerebellum, 702 ■*463. Diagram of a spinal segment {Bramwell), "jod *464. Section across the pyramids {Schwalbe), 7^7 *465. Section of the medulla oblongata [Schwalbe), 708 *466. Section of the olivary body {Schwalbe), 708 *467. Scheme of the respiratory centres {Rutherford'), 713 *46S. Action of vagus on frog's heart {Stirling), 7^9 *469. Scheme of the accelerans fibres {Stirling), 7^1 *470. Cardiac plexus of a cat {Bohin), 721 *47I. YvQg wiihoxxi Ms c&re.hr\\m {Stirling, after Goltz), 733 *472. Frog without its cerebrum (^/2>//«,^, rt/?^r Goltz), 733 *473. Pigeon with its cerebrum removed {after Dalton), 734 *474. Motor area of cerebral convolution (/vr^'/V/- rt'«(i'^. Zif.yw), 73^ *475. Cerebral convolution ; s^nsoxy zxt2.{Ferrier and B. Lewis), 73^ ■*476. Perivascular lymph spaces {Obersteiner), 73^ *477. Frontal convolution by Weigert's method {Obersteitier), 73^ *478. Cerebral convolution injected, 739 '*479. Left side of the human brain {Ecker), 74° *4So. Inner aspect of right hemisphere {Ecker), 74^ *4Sl. Left frontal lobe and island of Reil ( 7>/r«^r), 742 *482. Brain from above {Ecker), 743 483. Cerebrum of dog, carp, frog, pigeon, and rabbit, 745 484. Relation of the cerebral convolutions to the skull, 747 *485. Motor areas of a monkey's brain (//^;-j/^j' rtwo' 6"r//^^), 769 *504. Course of the fibres in pons {Erb'), 7^9 *505. Longitudinal section of a human brain ( ff'/V(/frj//d'm), 77^ *5o6. Section of the cerebellum {Sankey), 773 *507. Purkinje's cell ( Obersteiner), 773 *So8. Pigeon with its cerebellum removed {Dalton), 774 LIST OF ILLUSTRATIONS. XXIX FIGTJRE PAGE *509. Cortex cerebri and its membranes [Sckwalbe), 776 *5lo. Circle of Willis [Charcot), 778 *5II. Ganglionic axxerie?, [Charcot), 779 *5I2. Corneal corpuscles [Ranvier), 783 *5I3. Corneal spaces [Ranvier), 783 514. Junction of the cornea and sclerotic, 478 *5I5. Vertical section of cornea with nerve fibuli (i?rt«?>'zV;-), 785 *5l6. Horizontal section of cornea with nerve 't^wXx [Ranvier), 786 *5I7. Vertical section of choroid and sclerotic (6'z't)7zrJ, 786 518. Bloodvessels of the eyeball, 787 *5I9. Vertical section human retina [Cadiat), 788 520. Layers of the retina, 788 *52I. Vertical section of the fovea centralis [Cadiat), 789 *522. Fibres of the lens [Kolliker), 790 523. Section of the optic nerve, 791 524. Action of lenses on light, 793 525. Refraction of light, 794 526. Construction of the refracted ray, 794 527. Optical cardinal points, 795 528. Construction of the refracted ray, 796 529. Construction of the image, 79^ 530. Refracted ray in several media 797 531. Visual angle and retinal image, 797 532. Scheme of the ophthalmometer, 798 533. Horizontal section of the eyeball, 800 534. Scheme of accommodation, 801 535. Sanson-Purkinje's images, 801 *536. Phakoscope [AP Kendrick), 802 537. Scheiner's experiment, 803 538. Refraction of the eye, • 804 539. Myopic eye, 804 540. Hypermetropic eye, 804 541. Power of accommodation, 805 *542. Diagram of astigmatism [Frost), 808 543. Cylindrical glasses, 808 *544. Scheme of the nerves of the iris [Erb), 810 *545. Pupilometer [Gorhavi), 81 1 *546. Pupilometer [Gorhavi), 81 1 547. Entoptical shadows, 812 548. Scheme of the original ophthalmoscope, 814 549. Scheme of tne indirect method, 815 550. Action of a divergent lens, 815 551. Action of a divergent lens, 815 552. View of the fundus oculi, ^ 816 *553. Morton's ophthalmoscope (/"/(T/Jari/rtw^ G^rry), 816 *554. Frost's artificial eye (/''rwi'), 817 *555- Action of the orthoscope, 817 *556. Mariotte's experiment, S18 *557. Horizontal section of the right eye, 820 *558. WB.z.TAYsY>&r\mettx [Pickard and Curry), 821 *559- Priestley Smith's perimeter [Pickard and Curry), 821 560. Perimetric chart, 822 561. Geometrical color zone, 825 562. Action of light rays on the retina, 826 *563. Cones of the retina [Stirling after Engelmanri), 829 *564. Irradiation, 831 ■^565. Irradiation, 831 566. Scheme of the action of the ocular muscles, 835 567. Identical points of the retina, 838 568. The horopter, 838 569. Two stereoscopic drawings, 839 570. Wheatstone's stereoscope, 840 571. Brewster's stereoscope, • 840 572. Telestereoscope, 841 573. Wheatstone's pseudoscope, 841 XXX LIST OF ILLUSTRATIONS. FIGURE ^^'^^ 574. Rollett's apparatus, <^42 *575. Zollner's lines, 843 576. Section of an eyelid, S44 577. Scheme of the organ of hearing, 847 578. External auditory meatus, • • • • 849 579. Left tympanic membrane and ossicles, '. 850 580. Membrana tympani and ossicles, 850 581. Tympanic membrane from within, 850 ♦582. Ear specula (A>('//;/^ rtW(/ Sesemann), 850 *583- Toynbee's artificial membrana tympani {^Kro/tne and Sesemann), 851 584. Right auditoi-y ossicles 851 585. Tympanum and auditory ossicles, 852 586. Tensor tynnpani and Eustachian tube, • 853 587. Right stapedius muscle, 854 *58S. Eustachian catheter, 856 *589. Politzer's ear bag [A'rohne and Sesemann) 856 590. Right labyrinth, 856 591. Scheme of the cochlea 858 *592. Interior of the right labyrinth, 858 *593. Semicircular canals, 858 *594. Section of the macula acustica (A^ewt^/Vr), 859 595. Scheme of the canalis cochlearis, 860 *596. Qs2\X.orC%vi\i\^\\^ [Krohne and Sesemann), 862 597. Curve of a muscle note and its overtones, 864 *598. Kcenig's manometric capsule {Kcenig), 865 *599. Flame pictures of vowels (A'lvnig), 865 •*6oo. Kcenig's analyzing apparatus (A'(i'«2>), 866 601. Nasal and pharyngo-nasal cavities, 871 *6o2. Section of the olfactory region (5/<;//y-), 87 1 603. Olfactory cells, 872 *6o4. Filiform papill?e(i.7o//r), 874 *6o5. Fungiform papillae [Stohr), 874 606. Circumvallate papilla and taste bulbs, 875 *6o7. Papilla; fohatre {S/dhr), 875 608. Vertical section of skin, 878 609. Wagner's touch corpuscle [Ranvier), 878 610. Pacini's corpuscle, 879 *6li. End bulb from conjunctiva ((2«rt?'«), 879 *6i2. Tactile corpuscle from clitoris, (^«rt««), 879 *6i3. Tactile corpuscles from a duck's bill [Quain), 8S0 *6l4. Bouchon epidermique {Hanvier), 880 615. ^Esthesiometer, 882 *6i6. /Esthesiometer of Sieveking 883 *6i7. Aristotle's experiment, 884 618. Pressure spots, 885 619. Landois' pressure mercurial balance, 886 620. Cold and hot spots, 887 621. Cold and hot spots, ■••.... 887 622. Topography of temperature spots, 889 *623. Karyokinesis [Gegenliaitr), 893 *624. Typical nucleated cell {Camay), 893 *625. Mitosis or nuclear division [Fleniming) , 894 626. Ovum of Tania solium, 895 627. Cysticercus, 895 628. Cysticerci of Taenia solium, 896 629. Scolex, 896 630. Echinococcus, 896 631. Taenia solium. 896 *632. Section of testis {Schenk), 897 *633. Tubule of testis {Schenk), 898 *634. Section of epididymis, [Schenk), 898 635. Spermatic crystals, • 899 636. Spermatozoa, 9°° 637. Spermatogenesis, 9°° *638. A cat's ovary {Hart and Barbour, after Schron), 9°' LIST OF ILLUSTRATIONS. XXXI FIGURE _ PAGE *639. Section of an ovary {Turner), 901 640. Ripe ovum of rabbit, ■ 902 641. Ovary and polar globules, 903 642. Scheme of a meroblastic ovum, 904 643. White and yellow yelk, 904 *644. Hen's egg {Kolliker), . . : 905 *645. Mucous mtmhvan& of the uterus (Jlanf and Bariour, a/ier 7 urner), 905 ""646. Fallopian tube and its annexes {Henle), 905 *647. Section of Fallopian tube {Schenk), 906 *648. Uterus before menstruation {J. Williams), 907 *649. Uterus after menstruation {J. WilHa?ns), 907 650. Fresh corpus luteum, 908 651. Corpus luteum of a cow, 908 652. Lutein cells, 90S *653. Erectile tissue [Cadiat), 909 654. The urethra and adjoining muscles, 910 *655. Formation of polar globules, 913 656. Extrusion of a polar globule, . 913 657. Polar globules, male and female pronucleus, 914 *658. Segmentation of 2. x2kkis!C s osuva. {Quain, after v. Beneden), 914 659. Cleavage of the yelk, 914 *66o. 'Q\2iStoAerxmc.\es\c\.e oix^a^xt Quain, after V.Ben ederi), 915 661. The blastoderm, 915 *66?. Primitive streak {^Balfour), -. 916 *663. Transverse section of an embryo newt {Hertwig), 916 *664. Vertical section of a blastoderm (TT/fm), 917 665. Schemata of development, 918 *666. Embryo fowl, 2d day [Kollike!-), 919 *667. Transverse section of an embryo duck (^Balfour), 920 *668/ Uterine mucous membrane {Coste), 925 *669. Placental villi {Cadiat), 926 *670. Foetal circulation [Clelana) 928 *67i. Head of embryo rabbit [Kolliker), 931 672. Hare lip, 931 *673. Meckel's cartilage ( ^K K. Parke?'), 931 674. Centres of ossification in the innominate bone, 933 675. Development of the heart, 935 676. The aortic arches, 936 677. Veins of the embryo, 936 678. Development of the veins and portal system, 937 679. Development of the intestine, 938 680. Development of the lungs, 938 681. Formation of the omentum, ; 938 682. Development of the internal generative organs, 939 *683. Development of ova ( IViedersheim'), 940 684. Development of the external genitals, 942 *685. 1 ^ r 942 *f\9.i' \ Changes in the external organs of generation in the female [after Sckroeder), . . - ^ *688. J L 942 *689. Transverse section of an embryo brain [Kolliker), 943 *690. ILmhxyohvxn oi io^\ [Qiiain, after Mikalkowics), 944 691. Development of the eye, 945 *692. Development of the vertebrate ear i^Haddon), 945 [The illustrations indicated by the word Herviann, are from Hermann's Handbuch der Physiolo- gie ; by Cadiat, from Cadiat's Traite d' Anato/iiie Generate ; by Ranvier, from Ranvier's Traite Technique d" Histologie ; by Brunton, from Brunton's Text-book of Pharmacology, Therapeutics, and Materia Medica ; by Schenk, from Schenk's Grundriss der normalen Histologie ; by Ecker, irom Ecker's Anatomie des Frosches, 2d ed. ; by Quain, firom Quain's Anatoiny ; by Stohr, from Stohr's Lehrbuch der Histologie, Jena, 1887 ; by Obersteiner, from H. Obersteiner's Anleitung beim Studium des Baties der nervosen Cejitralorgane, Wien, 1888.] 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 distin- guish— (i) Animal Physiology ; (2) Vegetable Physiology ; and (3) the Physiology of the Lowest Living Organisms, which stand on the border line of animals and plants, /. e., the so-called Protistce of Haeckel, micro-organisms, and those ele- mentary 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, protistse, 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. Special Morphology. The doctrine of the parts and organs of organisms. (Organology — Anatomy) — [a) Phytotomy. {b) Histology of Animals, [b) Zootomy. II. Physiology. The doctrine of the vital phe- nomena of organisms. General Physiology. The doctrine of vital phenomena in gene- ral— {a) Of Plants. [b] Of Animals. Special Physiology. The doctrine of the activities of the in- dividual organs — {a) Of Plants. [b) Of Animals. III. Embryology. The doctrine of the generation and development of organisms. Morphological part of the doctrine of development, i. e., the doctrine of fo7-m in its stages of develop- ment— {a) General. [b] Special. r I History of the development of ] single beings, of the individual [e. g., of man) from the ovum onward (Ontogeny) — (a) In Plants. (b) In Animals. History of the development of a w/io/e stock of organisms from the lovv^est forms of the series upward (Phylogeny) — {a) In Plants. [b) In Animals. J Physiological part of the doctrine of development, i. e., the doctrine of the activity during develop- ment— (a) General. {b) Special. Morphology and Physiology are of equal rank in biological science, and a previous acquaintance with Morphology is assumed as a basis for the comprehen- 3 33 34 INTRODUCTION. sion of Physiology, since the work of an organ can only be properly understood when its external form and its internal arrangements are known. Development occupies a middle place between Morphology and Physiology ; it is a morpho- logical discipUne in so far as it is concerned with the description of the parts of the developing organism; it is a physiological doctrine in so far as it studies the activities and vital phenomena during the course of development. MATTER. — The entire visible world, including all organisms, consists of matter, /. e., of substance which occupies space. We distinguish ponderable matter which has weight, and imponderable matter which cannot be weiglied in a balance. The latter is generally termed ether. In ponderable materials, again, we distinguish \.\\^\x form, i.e., the nature of their limiting surfaces; further, their volume, i.e., the amount of space which they occupy ; and lastly, their aggregate condition, i. e., whether they are solid, fluid, or gaseous bodies. Ether. — The ether fills the space of the universe, certainly as far as the most distant visible stars. This ether, notwithstanding its imponderability, possesses distinct mechanical properties; it is infinitely more attenuated than any known kind of gas, and behaves more like a solid body than a gas, resembling a gelati- nous mass rather than the air. It participates in the luminous phenomena due to the vibrations of the atoms of the fixed stars, and hence it is the transmitter of light, which is conducted by means of its vibrations, with inconceivable rapidity (42,220 geographical miles per second), to our visual organs i^Tyndall). Imponderable matter (ether) and ponderable matter are not separated sharply from each oth^r ; rather does the ether penetrate into all the spaces existing between the smallest particles of ponderable matter. Particles. — Supposing that ponderable matter were to be subdivided con- tinuously into smaller and smaller portions, until we reach the last stage of division in which it is possible to recognize the aggregate condition of the matter operated upon, we should call the finely-divided portions of matter in this state particles. Particles of iron would still be recognized as solid, particles of water as fluid, particles of oxygen as gaseous. Molecules. — Supposing, however, the process of division of the particles to be carried further still, we should at last reach a limit, beyond which, neither by mechanical nor by physical means, could any further division be effected. We should have arrived at the molecules. A molecule, therefore, is the smallest amcrunt of matter which can still exist in a free condition, and which as a unit no longer exhibits the aggregate condition. Atoms. — But even molecules are not the final units of matter, since every molecule consists of a group of smaller units, called atoms. An atom cannot exist by itself in a free condition, but the atoms unite with other similar or dis- similar atoms to form groups, which are called molecules. Atoms are incapable of further subdivision, hence their name. We assume that the atoms are invari- ably of the same size, and that they are solid. From a chemical point of view, the atom of an elementary body (element) is the smallest amount of the element which can enter into a chemical combination. Just as ponderable matter consists in its ultimate parts of ponderable atoms, so does the ether consist of analogous small ether-atoms. Ponderable and Imponderable Atoms. — The ponderable atoms within ponderable matter are arranged in a definite relation to the ether-atoms. The ponderable atoms mutually attract each other, and similarly they attract the imponderable ether-atoms ; but the ether-atoms repel each other. Hence, in ponderable masses, ether-atoms surround every ponderable atom. These masses, in virtue of the attraction of the ponderable atoms, tend to come together, but only to the extent permitted by the surrounding ether-atoms. Thus the ponderable atoms can never come so close as not to leave interspaces. All matter must. INTRODUCTION. 35 therefore, be regarded as more or less loose and open in texture, a condition due to the interpenetrating ether-atoms, which resist the direct contact of the ponderable atoms. Aggregate Condition of Atoms. — The relative arrangement of the molecules, /. e., the smallest particles of matter which can be isolated in a free condition, determines the aggregate condition of the body. Within a solid body, characterized by the permanence of its volume as well as by the independence of its form, the molecules are so arranged that they cannot readily be displaced from their relative positions. Fluid bodies, although their volume is permanent, readily change their shape, and their molecules are in a condition of continual movement. When this movement of 'the molecules takes so wide a range that the individual molecules fly apart, the body becomes gaseous, and as such is characterized by the instability of its form as well as by the changeableness of its volume. Physics is the study of these molecules and their motions. FORCES. I. Gravitation — Work done. — All phenomena appertain to matter. These phenomena are the appreciable expression of the forces inherent in matter. The forces themselves are not appreciable, they are the causes of the phenomena. Gravitation. — The law of gravitation postulates that every particle of ponder- able matter in the universe attracts every other particle with a certain force. This force is inversely as the square of the distance. Further, the attractive force is directly proportional to the amount of the attracting matter, without any refer- ence to the quality of the body. We may estimate the intensity of gravitation by the extent of the movement which it communicates to a body allowed to fall, for one second, through a given distance, in a space free from air. Such a body will fall in vacuo 9.809 metres per second. This fact has been arrived at experi- mentally. Let us represent g^ 9.809 metres, the final velocity of the freely falling body at the end of one second. The velocity, V, of the freely falling body is proportional to the time, t, so that ^=gt (0; 2. e., at the end of the ist sec, and V =^, i =^ = 9.809 M — the distance traversed — 5 = ^/2 (2) : 2 ■ ' i. e., the distances are as the square of the times. Hence, from (i) and (2) it follows (by eliminat- ing t) that — V - V~'^^ (3)- The velocities are as the square roots of the distances traversed — Therefore — =j (4). The freely falling body, and in fact every freely moving body, possesses kinetic energy, and is in a certain sense a magazine of energy. The kinetic energy of any moving body is always equal to the product of its weight (estimated by the balance), and the height to which it would rise from the earth, if it were thrown from the earth with its own velocity. Let W represent the kinetic energy of the moving body, and P its weight, then W = P. s, so that from (4) it follows that — W = pJ (5). Hence, the kinetic energy of a body is proportional to the square of its velocity. 'Work. — If a force (pressure, strain, tension) be so applied to a body as to move it, a certain amount of work is performed. The amount of work is equal 36 INTRODUCTION. to the product of the amount of the pressure or strain which moves the body, and of the distance through which it is moved. Let K represent the force acting on the body, and S the distance, then the work W = KS. The attraction between the earth and any body raised above it is a source of work. It is usual to express the vahie of K in kilogrammes, and S in metres, so that the "unit of work " is the kilogramme-metre, i.e., the force which is required to raise i kilo, to the height of i metre. 2. Potential Energy. — The transformation of Potential into Kinetic Energy, and conversely : Besides kinetic energy, there is also "potential energy," or energy of position. By this term are meant various forms of energy, which are suspended in their action, and which, although they may cause vnoUon, are not in themselves motion. A coiled watch-spring kept in this position, a stone resting upon a tower, are instances of bodies possessing potential energy, or the energy of position. It requires merely a push to develop kinetic from the potential energy, or to transform potential into kinetic energy. Work, 7v, was performed in raising the stone to rest upon the tower. 7u = p, s, where/ ^ the weight and s = the height, p z= m. ^, is ^= the product of the mass {m), and the force of gravity (^), so that tv =^ tn g s. This is at the same time the expression for the potential energy of the stone. This potential energy may readily be transformed into kinetic energy by merely pushing the stone so that it falls from the tower. The kinetic energy of the stone is equal to the final velocity with which it impinges upon the earth. V •= i/2g s (see above (3) ). V« = 2g s. wV* = 2;« g s. — V * = m g s. 2 m g s was the expression for the potential energy of the stone while it was still in . . . resting on the height ; V2 is the kinetic energy corresponding to this potential energy {Briicke). ^ Potential energy may be transformed into mechanical energy under the most varied conditions ; it may also be transferred from one body to another. The movement of a pendulum is a striking example of the former. When the pendulum is at the highest point of its excursion, it must be regarded as absolutely at rest for an instant, and as endowed with potential energy, thus correspondmg with the raised stone in the previous instance. During the swing of the pendulum this potential energy is changed into kinetic energy, which is greatest when the pendulum is moving most rapidly toward the vertical. As it rises again from the vertical position, it moves more slowly, and the kinetic energy is changed into potential energy, which once more reaches its maximum when the pendulum comes to rest at the utmost limit of its excursion. Were it not for the resistances continually opposed to its movements, such as the resistance of the air and friction, the movement of the jjendulum, due to the alternating change of kinetic into potential energy and vice versa, \\ov\d continue uninterruptedly, as with a mathematical pendulum. Suppose the swinging ball of the pendulum, when exactly in a vertical position, impinged upon a resting but movable sphere, the potential energy of the ball of the pendulum would be transferred directly to the sphere, provided that the elasticity of the ball of the pendulum and the sphere were complete; the pendulum would come to rest, while the sphere would move onward with an equal amount of kinetic energy, provided there were no resistance to its movement. This is an example of the transference of kinetic energy from one body to another. Lastly, suppose that a stretched watch-spring on uncoiling causes another spring to become coiled ; and we have another example of the transference of kinetic energy from one body to another. The following general statement is deducible from the foregoing examples : If, in a system, the individual moving masses approach the final position of equi- librium, then in this system the sum of the kinetic energies increases ; if, on the other hand, the particles move away from the final position of equilibrium, then INTRODUCTION. 37 the sum of the potential energies is increased at the expense of the kinetic energies, /. e., the kinetic energies diminish {Brilcke^. The pendulum, which, after swinging from the highest point of its excursion, approaches the vertical position, i. e., the position of equilibrium of a passive pendulum, has in this position the largest amount of potential energy; as it again ascends to the highest point of its excursion on the other side, it again gradually receives the maximum of potential energy at the expense of the gradually diminishing movement, and therefore of the kinetic energy. 3. Heat. — Its Relation to Potential and Kinetic E7iei-gy. — If a lead weight be thrown from a high tower to the earth, and if it strike an unyielding substance, the movement of the mass of lead is not only arrested, but the kinetic energy (which to the eye appears to be lost) is transformed into a lively vibratory movement of the atoms. When the lead meets the earth, heat is produced. The amount of heat produced is proportional to the kinetic energy which is transformed through the concussion. At the moment when the lead weight reaches the earth, the atoms are thrown into vibrations ; they impinge upon each other ; then rebound again from each other in consequence of their elasticity, which opposes their direct juxtaposition ; they fly asunder to the maximum extent permitted by the attractive force of the ponderable atoms, and thus oscillate to and fro. All the atoms vibrate like a pendulum, until their movement is communicated to the ethereal atoms surrounding them on every side, i. e., until the heat of the heated mass is ' ' radiated. ' ' Heat is thus a vibratory movement of the atoms. As the amount of heat produced is proportional to the kinetic energy which is transformed through the concussion, we must find an adequate measure for both forces. Heat-Unit. — As a standard of measure of heat, we have the "heat-unit" or calorie. The "heat-unit" or calorie is the amount of energy required to raise the temperature of i gramme of water 1° Centigrade. The "heat-unit" corres- ponds to 425.5 gramme-metres, i. e., the same energy required to heat i gramme of water 1° C. would raise a weight of 425.5 grammes to the height of i metre; or, a weight of 425.5 grammes, if allowed to fall from the height of i metre, would by its concussion produce as much heat as would raise the temperature of i gramme of water 1° C. The " mechanical equivalent " of the heat-unit is, therefore, 425.5 gramme-metres. It is evident that from the collision of moving masses an immeasurable amount of heat can be produced. Let us apply what has already been said to the earth. Suppose the earth to be disturbed in its orbit, and suppose further that, owing to the attraction of the sun, it were to impinge on the latter (whereby, according to J. R. Mayer, its final velocity would be 85 geographical miles per second), the amount of heat produced by the collision would be equal to that produced by the combustion of a mass of pure charcoal more than 5000 times as heavy [Jtilius Robert Mayer, HebnhoUz). Thus, the heat of the sun itself can be produced by the collision of masses of cold matter. If the cold matter of the universe were thrown into space, and there left to the attraction of its particles, the collision of these particles would ultimately produce the light of the stars. At the present time, numerous cosmic bodies collide in space, while innumerable small meteors (94,000 to 188,000 billions of kilos, per minute) fall into the sun. The force of gravity is perhaps, in fact, the only source of all heat (_/. R. Mayer, Tyndall). We have a homely example of the transformation of kinetic energy into heat in the fact that a blacksmith may make a piece of iron red hot by hammering it. Of the conversion of heat into kinetic energy we have an example in the hot watery vapor (steam) of the steam engine raising the piston. An example of the conversion of potential energy into heat occurs in a metallic spring, when it uncoils and is so placed as to rub against a rough surface, producing heat by friction. 4. Chemical Affinity : Relation to Heat. — While gravity acts upon the particles of matter without reference to the composition of the body, there is another atomic force which acts between atoms of a chemically different nature ; this is chemical affinity. This is the force in virtue of which the atoms of chemically different bodies unite to form a chemical compound. The force itself varies greatly between the atoms of different chemical bodies ; thus we speak 38 INTRODUCTION. of strong chemical affinities and weak affinities. Just as we were able to estimate the potential energy of a body in motion from the amount of heat which was produced when it collided with an unyielding body, so we can measure the amount of heat which is formed when the atoms of chemically different bodies unite to form a chemical compound. As a rule, heat is formed when sejjarate chemically- different atoms form a compound body. When, in virtue of chemical affinity, the atoms of i kilo, of hydrogen and 8 kilos, of oxygen unite to form the chemical compound water, an amount of heat is thereby evolved which is equal to that produced by a weight of 47,000 kilos, falling and colliding with the earth from a height of 1000 feet above the surface of the earth. If i gramme of H be burned along with the requisite amount of O to form water, it yields 34,460 heat-units or calories : and i gramme carbon burned to carbonic acid (carbon dioxide) yields 8080 heat-units. Wherever, in chemical processes, strong chemical affinities are satisfied, heat is set free, i. e., chemical affinity is changed into heat. Chemical affinity is a form of potential energy obtaining between the most different atoms, which during chemical processes is changed into heat. Conversely, in those chemical processes where strong affinities are dissolved, and chemically-united atoms thereby pulled asunder, there must be a diminution of temperature, or, as it is said, heat becomes latent — that is, the energy of the heat which has become latent is changed into chemical energy, and this, after decomposition of the compound chemical body, is again represented by the chemical affinity between its isolated different atoms. LA^A/' OF THE CONSERVATION OF ENERGY.— Julius Robert Mayer and Helmholtz have established the important law that, in a system which does not receive any influence and impression from without, the sum of all the forces acting within it is always the same. The various forms of energy can be transformed one into the other, so that kinetic cne7-gy may be transformed into poten- tial energy and vice versa, but there is never any part of the energy lost. The transformation takes place in such measure that, from a certain definite amount of one form of energy a definite amount of another can be obtained. The various forms of energy acting in organisms occur in the following modifications: — 1. Molar motion (ordinary movements), as in the movements of the whole body, of the limbs, or of the intestines, and even those observable microscopically in connection with cells. 2. Movements of Atoms as Heat. — We know, in connection with the vibration of atoms, that the number of vibrations in the unit of time determines whether the oscillations appear as heat, light, or chemically-active vibrations. Heat-vibrations have the smallest number, while chemically-active vibrations have the largest number, light-vibrations standing between the two. In the human body we only observe heat-vibrations, but some of the lower animals are capable of exhibiting the phenomena of light. In the human organism the molar movements in the individual organs are con- stantly being transformed into heat, e.g., the kinetic energy in the organs of the circulation is transformed by friction into heat. The measure of this is the "unit of work" = i gramme-metre, and the "unit of heat" =:= 425.5 gramme-metres. 3. Potential Energy. — The organism contains many chemical compounds which are characterized by the great complexity of their constitution, by the imperfect saturation of their affinities, and hence by their great tendency to split up into simpler bodies. The body can transform the potential energy into heat as well as into kinetic energy, the latter always in conjunction with the former, but the former always by itself alone. The simplest measure of the potential energy is the amount of heat which can be obtained by complete combustion of the chemical compounds INTRODUCTION. 39 representing the potential energy. The number of work-units can then be calcu- lated from the amount of heat produced. 4. The phenomena of electricity, magnetism, and diamagnetism may be recognized in two directions, as movements of the smallest particles, which are recog- nized in the glowing of a thin wire when it is traversed by strong electrical currents (against considerable resistance), and also as molar movement, as in the attraction or repulsion of the magnetic needle. Electrical phenomena are manifested in our bodies by muscle, nerve, and glands, but these phenomena are relatively small in amount when compared with the other forms of energy. It is not improbable that the electrical phenomena of our bodies become almost completely transformed into heat. As yet experiment has not determined with accuracy "a unit of elec- tricity" directly comparable with the "heat-unit" and the "work-unit." It is quite certain that within the organism one form of energy can be trans- formed into another form, and that a certain amount of one form will yield a definite amount of another form ; further, that new energy never arises spontane- ously, nor is energy already present ever destroyed, so that in the organism the law of the conservation of energy is continually in action. ANIMALS AND PLANTS. — The animal body contains a quantity of chemically-potential energy stored up in its constituents. The total amount of the energy present in the human body might be measured by burning completely an entire human body in a calorimeter, and thereby determining how many heat- units are produced when it is reduced to ashes (see Animal Heat). The chemical compounds containing the potential energy are characterized by the complicated relative position of their atoms, by a comparatively imperfect saturation of the affinities of their atoms, by the relatively small amount of oxygen which they contain, by their great tendency to decomposition, and the facility with which they undergo decomposition. If a man were not supplied with food he would lose 50 grammes of his body weight every hour ; the material part of his body, which contains the potential energy, is used up, oxygen is absorbed, and a continual process of combustion takes place; by the process of combustion simpler substances are formed from the more complex compounds, whereby potential is converted into kinetic energy. It is immaterial whether the combustion is rapid or slow; the same amount of the same chemical substances always produces the same amonnt of kinetic energy, i.e., of heat. A person, when fasting, experiences after a certain time the disagreeable feeling of exhaustion of his reserve of potential energy, hunger sets in, and he takes food. All food for the animal kingdom is obtained, either directly or indirectly, from the vegetable kingdom. Even carnivora, which eat the flesh of other animals, only eat organized matter which has been formed from vegetable food. The existence of the animal kingdom presupposes the existence of the vegetable kingdom. All substances, therefore, necessary for the food of animals occur in vegetables. Besides water and the inorganic constituents, plants contain, among other organic compounds, the following three chief representatives of foodstuffs — fats, carbohydrates, and proteids. All these contain stores of potential energy, in virtue of their complex chemical constitution. The fats contain — I ^"^^■>-^^^^^ = ^^"y^^^^'l (§ 2=;0 ine tats.contam.— |_^ ^^j.j_^Qjj^^^g^y^^j.j^ | ^S 251;. The carbohydrates contain : — CeHjoOj . . (§ 252). rC. 5I-5-54-51 I H. 6.9- 7-3 The proteids contain per cent. : — \ N. 15. 2-17.0 \ (§§ 248 and 249"). ■ O. 20.9-23.5 I S. 0.3- 2.0J 40 INTRODUCTION. A man who takes a certain amount of this food adds thereto oxygen from the air in the process of respiration. Combustion or oxidation then takes place, whereby chemically-potential energy is transformed into heat. Tt is evident that the products of this combustion must be bodies of simpler constitution — bodies with less complex arrangement of their atoms, with the greatest possible saturation of the affinities of their atoms, of greater stability, partly rich in O, and possessing either no potential energy, or only very little. These bodies are carbon dioxide, CO., ; water, H.O ; and as the chief repre- sentative of the nitrogenous excreta, urea ( CO(NHo)._,), which has still a small amount of potential energy, but which outside the body readily splits into CO, and ammonia (NH.,). The human body is an organism in which, by the phenomena of oxidation, the complex nutritive materials of the vegetable kingdom, which are highly charged with potential energy, are transformed into simple chemical bodies, whereby the potential energy is transformed into the equivalent amount of kinetic energy (heat, work, electrical phenomena). But how do plants form these complex food-stuffs so rich in potential energy? It is plain that the potential energy of plants must be obtained from some other form of energy. This potential energy is supplied to plants by the rays of the sun, whose chemical light-rays are absorbed by plants. Without the rays of the sun there could be no plants. Plants absorb from the air and the soil CO.,, H.^O, NH3, and X, of which carbon dioxide, water, and ammonia (from urea) are also produced by the excreta of animals. Plants absorb the kinetic energy of light from the sun^ s rays and transform it into potential energy, which is accumulated during the growth of the plant in its tissues, and in the food-stuffs produced in them during their growth. This formation of complex chemical compounds is accom- panied by the simultaneous excretion of O. Occasionally, kinetic energy, such as we universally meet with in animals, is liberated in plants. Many plants develop considerable quantities of heat in their flowers, e.^^., the arum tribe. We must also remember that during the formation of the solid parts of plants, when fluid juices are changed into solid masses, heat is set free. In plants, under certain circumstances, O is absorbed, and CO.^ is excreted, but these processes are so trivial as compared with the typical condition in the vegetable kingdom, that they may be regarded as of small moment. Plants, therefore, are organisms which, by a reduction process, transform simple stable combinations into complex compounds, whereby potential solar energy is transformed into the chemically-potential energy of vegetable tissues. Animals are living beings, which by oxidation decompose or break up the com- plex grouping of atoms manufactured by plants, whereby potential is transformed into kinetic energy. Thus, there is a constant circulation of matter and a con- stant exchange of energy between plants and animals. All the energy of animals is derived from plants. All the energy of plants arises from the sun. Thus the sun is the cause, the original source of all energy in the organism, /, e., of the whole of life. As the formation of solar heat and solar light is explicable by the gravitation of masses, gravity \s perhaps the original form of energy of all life. We may thus represent the formation of kinetic energy in the animal body from the potential energy of plants. Let us suppose the atoms of the substances formed in organisms, as simple small bodies, balls, or blocks. As long as these lie in a single layer, or in a few layers, upon the surface, there is a stable arrange- ment, and they continue to remain at rest. If, however, an artificial tower be built of these blocks, so that an unstable erection is produced, and the same tower be afterward knocked down, then for this purpose we require (i) the motor power of the workman who lifts and carries the blocks; (2) a blow or other impulse from without applied to the unstable structure — when the atoms will fall together, and as they fall collide with each other and produce heat. Thus, the INTRODUCTION. 41 energy employed by the workman is again transformed into the last-named form of energy. In plants the complex unstable building of the groups of atoms is carried on, the constructer being the sun. In animals, which eat plants, the complex groups of the atoms are tumbled down, with the liberation of kinetic energy. Vital Energy and Life. — The forces which act in organisms, in plants, and animals are exactly the same as are recognizable as acting in dead matter. A so- called " vital force," as a special force of a peculiar kind, causing and governing the vital phenomena of living beings, does not exist. The forces of all matter, of organized as well as unorganized, exist in connection with their smallest particles or atoms. As, however, the smallest particles of organized matter are, for the most part, arranged in a very complicated way, compared with the much simpler com- position of inorganic bodies, so the forces of the organism connected with the smallest particles yield more complicated phenomena and combinations, whereby it is excessively difficult to ascribe the vital phenomena in organisms to the simple fundamental laws of physics and chemistry. The Exchange of Material, or Metabolism {" Sioffwechser') as a Sign of Life. — Nevertheless, there appears to be a special exchange of matter and energy peculiar to living beings. This consists in the capacity of organisms to assimilate the matter of their surroundings, and to work it up into their own con- stitution, so that it forms for a time an integral part of the living being, to be given off again. The whole series of phenomena is called metabolism or " StofTwechsel," which consists in the introduction, assimilation, integration, and excretion of matter. We have already shown that the metabolism of plants and that of animals are quite different. The processes, as already described, actually occur in the typical higher plants and animals. But there is a large group of organisms which, throughout their entire organiza- tion, exhibit so low a degree of development, that by some observers they are considered as undifferentiated "ground-forms." They are regarded as neither plants nor animals, and are the most simple forms of animated matter. Haeckel has called these organisms Protistse, as being the original and primitive forms. We must assume that, corresponding with their simpler vital conditions, their metabolism is also simpler, but on this point we still require further observations and experiments. Physiology of the Blood. [The blood is aptly described by Claude Bernard as an internal medium which acts as a "go-between" or medium of exchange for the outer world and the tissues. Into it are poured those substances which have been subjected to the action of the digestive fluids, and in the lungs or other respiratory organs it receives oxygen. It thus contains 7iew substances, but in its passage through the tissues it gives up some of these new substances, and receives in exchange certain waste products which have to be got rid of. Its composition is thus highly complex. Besides carrying the neiv nutrient fluids to the tissues, it is also the great oxygen carrier, as well as the medium by which some of the waste products, e.g., C0._,, urea, are removed y>v/// the tissues, and brought to the organs, e. g., the lungs, kidneys, skin, which eliminate them from the body. It is at once a great pabulum-supplying medium and a channel for getting rid of useless mate- rials. As the composition of the organs through which the blood flows varies, it is evident that its composition must vary in different parts of the circulatory system ; and it also varies in the same individual under different conditions. Still, with slight variations, there are certain general physical, histological, and chemical properties which characterize blood as a whole. '\ I. PHYSICAL PROPERTIES.— (i) Color.— The color of blood varies from a bright scarlet-red in the arteries to a deep, dark, bluish-red in the veins. Oxygen (and, therefore, the air) makes the blood bright red] want of oxygen makes it dark. Blood free from oxygen (and also venous blood) is dichroic — /. e., by reflected light it appears dark red, while by transmitted light it is green. [Arterial blood is monochroic] In thin layers blood is opaque, as is easily shown by shaking blood so as to form bubbles, or by allowing blood to fall upon a plate with a pattern on it, and pouring it off again, [Printed matter cannot be read through a thin layer of blood spread on a glass slide.] Blood behaves, therefore, like an "opaque color," as its coloring matter is suspended in the form of fine particles — the blood corpuscles. Hence, it is possible to separate the coloring matter from the fluid part of the blood by filtration. This is accomplished by mixing the blood with fluids which render the blood corpuscles sticky or rough. If mammalian blood be treated with one-seventh of its volume of solution of sodic sulphate, or if frog's blood be mixed with a 2 per cent, solution of sugar {Joh. Ali'dler) and filtered, the shriveled corpuscles, now robbed of part of their water, remain upon the filter. (2) Reaction. — The reaction is alkaline, owing to the presence of disodic phosphate, Na.HPOi, and bicarbonate of soda. After blood is shed, its alkalinity rapidly diminishes, and this occurs more rapidly the greater the alkalinity of the blood. This is due to the formation of an acid, in which, perhaps, the colored corpuscles take part, owing to the decomposition of their coloring matter. A high temperature and the addition of an alkali favor the formation of the acid (iV. Zuntz). The alkaline reaction of blood is diminished: (a) by great muscular exertion, owing to the formation of a large amount of acid in the muscles; (/3) during coagulation; (y) in old blood, or blood dissolved by water from old blood stains, such blood being usually acid ; fresh cruor has a 42 PHYSICAL PROPERTIES OF THE BLOOD. 4S stronger alkaline reaction than serum ; (d) after the prolonged use of soda the alkalinity is increased after the use of acids it is decreased. Methods. — Owing to the color of the blood we cannot employ ordinary litmus paper to test its reaction. One of the following methods maybe used: (i) Moisten a strip of glazed red litmus paper with solution of common salt, and allow a drop of blood to fall on the paper; then rapidly wipe it off before its coloring matter has time to penetrate and tinge the paper l^Zuniz). (2) Lie- breich used thin plates of plaster- of- Paris of a perfectly neutral reaction. These are dried, and afterward moistened with a neutral solution of litmus. When a drop of blood is placed upon the porous plate, the fluid part of the blood passes into it, while the corpuscles are washed off with water, and the altered color of the litmus-stained slab is apparent. [(3) Schafer uses dry, faintly- reddened, glazed litmus paper, and on it is placed a drop of blood, which is wiped off after a few seconds. The place where the blood rested is indicated by a blue patch upon a red or violet ground.] Estimation of the Alkalinity. — A very dilute solution of tartaric acid (i cubic centimetre combines with 3. 1 milligrams of soda, /. e., I litre of water contains 7.5 grams of crystallized tartartic acid) is added to blood until a blue litmus paper is turned red (by Zuntz's method). 100 grams of rabbit's blood have an alkalinity corresponding to 150 milligrams of soda; the blood of carnivora to about 180 milligrams [Lassar), while loo c.c. of normal human blood have an alkalinity equal to 260-300 milligrams of soda (v. Jakscli). The following method can be used with a few drops of blood : To neutralize the blood, tartaric acid in the above concentration is used. Prepare the following mixture by mixing it with a concentrated solution of sodic sulphate, and then adding sodic sulphate until the mixture is com- pletely saturated. I, 10 parts of solution of tartaric acid to 100 parts of concentrated sodic sulphate solution; II, 20 parts tartaric acid solution to 90 sodic sulphate solution; III contains these sub- stances in the proportion of 30 to 80; IV, 40 to 70; V, 50 to 60; VI, 60 to 50; VII, 70 to 40; VIII, 80 to 30; IX, 90 to 20; and X, loo to 10. Excess of sodic sulphate is present in all the flasks. A known volume of the blood to be investigated is mixed with an equal volume of each of the mixtures, in a small tube, which is made by drawing out a glass tube i millimetre in diameter to a fine point. To calibrate this tube, suck up water, say, to the height of 8 mm., make a mark on the tube with a fine file, then suck up the water until its lower level corresponds with the mark. Again mark the upper limit of the water. To test the blood, suck a drop of the mixture I up to the level of the first mark on the glass pipette, and, after wiping its point, suck up an equal quantity of blood. Again clean the point of the pipette, and blow its contents into a watch glass; then mix, and test the reaction with sensitive violet-colored litmus paper. Proceed in the same way with the several mixtures, II to X, until the alkaline reaction disappears or the acid appears. The narrow strips of litmus paper are dipped into each of the mixtures, the corpuscles remain in the wetted part of the paper, while the fluid permeates further and shows the reaction. As a rule, the degree of alkalinity in human blood corresponds to VI. Human blood can be sucked directly from a small wound made by a needle, either by attaching an elastic tube or a small hypodermic syringe to the pipette {^Latidois). Pathological. — The alkalinity is increased during persistent vomiting, and decreased in pro- nounced anaemia, cachexia, uraemia, rheumatism, high fever, diabetes, and cholera. [Immediately before death by cholera it may be acid {^Cantani).'\ (3) Odor. — Blood emits a peculiar odor, the halitus sanguinis, which differs in animals and man. It depends upon the presence of volatile fatty acids. If concentrated sulphuric acid be added to blood, whereby the volatile fatty acids are set free from their combinations with alkalies, the characteristic odor, somewhat similar to that of butyric acid, becomes much more perceptible. (4) Taste. — Blood has a saline taste, depending upon the salts dissolved in the fluid of the blood. (5) Specific Gravity. — The specific gravity is 1056-1059 in man, 1051-1055 in woman ; in children less. The specific gravity of the blood corpuscles is 1105, that of the plasma 1027. Hence the corpuscles tend to sink. Clinical Method. — A thin glass tube is drawn out till it is of small calibre, and then bent at a right angle, and closed above with a caoutchouc cap. Press slightly on the caoutchouc cap, and suck up a drop of the freshly-drawn blood obtained by pricking the finger. The fine capillary tube is at once immersed in a solution of sodic sulphate, and a drop of the blood expressed into the saline solution. It is necessary to prepare several solutions of sodic sulphate with specific gravities varying from 1050-1070. The solution in which the corpuscles remain suspended indicates the specific gravity of the blood {Hoy, Landois). The drinking of water and hunger diminish the specific gravity temporarily, while thirst and the digestion of dry food raise it. If blood be passed through an organ artificially, its specific gravity 44 MICROSCOPIC EXAMINATION OF THE I5LOOD. rises in consequence of the absorption of dissolved matters and the giving off of water. It falls after hemorrhage, and is diminished in badly-nourished individuals. [By working with solutions of glycerine, Jones finds that it is highest at birth, is at a minimum between the second week and the second year; it rises gradually until the 35th-45th year. It is usually higher in the male than the female, is diminished by pregnancy, the ingestion of solid or liquid food, and gentle exercise.] [(6) Temperature. — Blood is viscid, and its temperature varies from 36.5" C. (97.7° F.) to 37.8° C. (100° F.). The wannest blood in the body is that of the hepatic vein (ij 210^.] 2. MICROSCOPIC EXAMINATION.— [Blood, when examined by the microscope, is seen to consist of an enormous number of corpuscles — ( olored and colorless — floating in a transparent fluid, the plasma, or liquor san- guinis. Human Red Blood Corpuscles. — (a) Form. — They are circular, coin- shaped, homogeneous disks, with saucer-like depressions on both surfaces, and with rounded margins ; in other words, they are bi-concave, circular, non-nucle- ated disks. Fig. I. A B A, human colored blood corpuscles — i, on the flat; 2, on edge; 3, rouleau of colored corpuscles. B, amphibian colored blood corpuscles — i, on the flat ; 2, on edge. C, ideal transverse section of a human colored blood corpuscle magnified 50C0 times linear — ai, diameter; erf, thickness. (d) Size. — The diameter (ad) is 7.7/j'-,* (6.7-9.3/7.) the greatest thickness (cd) 1.9,'i (Fig. I, C), [/.moglobin from the stroma ( IT. J\ol>frfs). The usual effect is to produce one or more granular buds of hii^moglobin on the side of the corpuscles (Fig. 7, /', f) ; more rarely the hremoglobin collects around the nucleus, if such be present (Fig. 7, d), or is extruded, as shown in Fig. 7, e,'\ [Ammonium or Potassium Sulpho-cyanide removes the hivmoglobin, and reveals a reticular structure iiitra-nttclcar plexus of fibrils [Stir/itig and Rannie).'\ The Amount of Gases in the blood exercises an important influence on their solubility. The corpuscles of venous blood, which contains much CO.^, are more easily dissolved than those of arterial blood ; while between both stands blood containing CO. 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. If certain salts be added in substance to blood, they make blood lake-colored; potassic sulpho- cyanide, sodic chloride, etc. [Kowaiewsky). 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 l with blood obtained by picking 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 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 distilled water have been added to the blood {LtinJois). There are some individuals whose blood is more soluble than that of others; their corpuscles are soft, and readily undergo changes. Many conditions, such as cholcemia, poisonmg with sub- stances which dissolve the corpuscles, and a markedly venous condition of the blood, affect the corpuscles. Interesting observations may be made on the blood in infectious diseases, hemoglobin- uria, and in cases of burning. In an.-emia and fever, the capacity for resistance seems to be diminished. 6. FORM AND SIZE OF THE BLOOD CORPUSCLES OF ANIMALS. — All marnmals (with the exception of the camel, llama, alpaca, and their allies), and the cyclostomata among fishes, e.g., Petromyzon, 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. i, B, i, 2), and fishes (except cyclostomata) have nucleated, elliptical, bi-convex corpuscles. j Size (n = o.ooi Millimetre) Of the Disk-shaped Corpuscles. Of the Elliptical Corpuscles. Short Diameter. Long Diameter. Elephant 9.4 u j Llama, 4.0 jx 8.0 fi Man, 7-7 " Dove, 6.5 " 14.7 Dog. 7.3 " Frog 15-7 " 22.3 Rabbit, 6.9 " Triton, 19.5 " 29.3 I Cat, 6.5 " Proteus, 35.0 " 58.0 Sheep, 5-0 " | Goat, 41" The corpuscles of -Amphiuma are nearly one-third larger Musk-deer, .... 2.5 " than those of Proteus (/vV(/r/^/). Among vertebrates, amphioxus has colorless blood. The large blood corpuscles of many amphibia, e.g., amphiuma,are visible to the naked eye. The blood corpuscles of the frog contain, in addition to a nucleus, a nucleolus {Auerbach, Jianvier), [and the same is true of the colored corpuscles of the newt {Stirling). The nucleolus is revealed by acting on the corpuscles with dilute alcohol (i, alcohol; 2, water; Ranvier's ^^ alcool ait tiers''' (Fig. 7,^.).] It is evident that the larger the blood corpuscles are, the smaller must be the number and total superficies of the cor- puscles in a given volume of blood. In birds, however, the number is relatively larger than in ORIGIN OF THE RED BLOOD CORPUSCLES. 51 other classes of vertebrates, 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. Goat's blood contains 9,720,000 corpuscles per cubic millimetre; llama's, 13,000,000; bullfinches, 3,600,000; lizard's, 1,420,000; frog's, 404,000; and that of proteus, 36,000 ( J^/it/J^;?-). In hibernating animals, the number diminishes from 7,000,000 to 2,000,000 per cubic millimetre. No relation exists between the size of the animal and that of its blood corpuscles. The invertebrata generally have colorless blood, with colorless corpuscles ; but the earth-worm, and the larva of the large gnats, etc., have red blood whose plasma contains haemoglobin, while the blood corpuscles themselves are colorless. Many invertebrates possess red, violet, brown or green opalescent blood with colorless corpuscles (amceboid 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. 7. ORIGIN OF THE RED BLOOD CORPUSCLES.— (xV) Dur- ing Embryonic Life. — Blood corpuscles 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 develop- ing body of the chick, 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 protoplasm, 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 also proliferate, and give rise to new cells, which are washed away to form blood corpuscles.] At first the corpuscles exhibit amoeboid movements, are devoid of pigment, nucleated, globular, larger and more irregular than the permanent corpuscles. They become colored, retain their nucleus, and are capable of undergoing multiplication by division ; Remak observed all the stages of the process of division, which is best seen from the third to the fifth day of incubation. Increase by division also takes place in the larvae of the salamander, triton and toad (^Flemming) ; and during the intra-uterine life of a mammal, in the spleen, bone-marrow, the liver, and the circulating blood {^izzozero). Neumann found in the liver of the embryo protoplasmic cells containing red blood corpuscles. Cells, some with, others without, haemoglobin, but with large nuclei, have been found. These cells increase by division, their nucleus shrivels, and they ultimately form blood corpuscles {Lowif) The spleen is also regarded as a centre of their formation, but this seems to be the case only during embryonic life {Neumami). Here the red corpuscles are said to arise from yellow, round, nucleated cells, which represent transition forms. Foa and Salvioli found red corpuscles forming endogenously within large, protoplasmic cells in lymphatic glands. In the later period of embryonic life, the characteristic non-nu- cleated 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 ]4,-yi of the total corpuscles, while at the end of foetal life nucleated blood corpuscles are very rarely found. Of course, in animals with nucleated blood corpuscles, the nucleus of the embryonic blood corpuscles remains. (B) 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 corpuscles lose their nuclei and protoplasm, become hollowed out, join with neighboring capillaries, and thus 52 ORIGIN OF THE RED BLOOD CORPUSCLES. Fig. S. Formation of red blood 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 cell ; a, a, processes which ultimately unite to form capillaries. form new blood channels. J. Arnold and Golubew oppose thi.s view, asserting 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; after their i)rotoplasm and contents disappear they become hol- low, and a branched system of capillaries is formed in the tissues. Ranvier noticed the same mode of growth in the omentum of newly-born kittens. Young rabbits, a week old, have, in their omentum, small white or milk spots {Ra/ivier), in which lie "vaso-formative cells," ;. e., highly refractive cells of variable shape, with long cylindrical protoplasmic processes (Fig. 8). In its refractive 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 proto- plasm. These vaso-formative cells give off protoplasmic processes {a, a), some of which end free, while others form a network. Here and there elongated connective-tissue corpuscles lie on the branches, and ultimately form the adventitia of the blood vessel. The vaso-formative cells have many forms: they may be elongated cylinders ending in points, or more round and oval, resembling lymph cells, or modi- fied connective-tissue corpuscles. These cells are ahoays the seat of origin oj 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, by means of their processes, form connections with the circulatory system. Probably 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 Schiifer also prove the intra-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, be- come 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.] Neumann observed similar formations in the embryonic liver; Wissotzky in the rabbit's amnion; Klein in the embryo chick ; and Bayerl in ossifying cartilage. All these observations go to show that at a certain early period of development blood 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. (C) Later Formation. — Most observers agree that the red blood corpuscles are formed from special nucleated cells, which gradually assume the form and color of the perfect red corpuscle. According to Neumann, however, these cor- puscles are pigmented from the first. In the tailed amphibians and fishes, the spleen, in all other vertebrates the red marrow of bone, are the seats of formation of these corpuscles, which subsequently increase by division {Neumann, Rindfleisch, Bizzozero). In the red marrow of bone we can study all the stages THE COLORLESS BLOOD CORPUSCLES. 53 of the transformation ; especially pale contractile cells similar to colorless corpus- cles, and also red nucleated corpuscles, which are similar to the nucleated corpus- cles of the embryo, and the progenitors of the red corpuscles. 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. After copious hemorrhage, these transition forms appear in numbers in the blood stream. The small veins, and, perhaps, the capillaries of the red mar- row of bone and the spleen have no proper walls, so that the red corpuscles when formed can pass into the circulation. Red or blood-forming marrow occurs in the bones of the skull, and in most 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. Where the blood-regeneration process is very active, however, the yellow marrow may be changed into red, even throughout all the bones of the extremities [Netimamt). 8. DECAY OF THE RED BLOOD CORPUSCLES.— The blood corpuscles 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 portal vein. The splenic pulp contains cells which indicate that colored corpuscles are broken up within it. These are the so-called " blood-corpuscle-containing cells " (§ 102), 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 the white blood corpuscles in the hepatic capillaries, 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 de- posited in a granular form, or are dissolved. Part of the products of decompo- sition is used for the formation of new blood corpuscles in the marrow and in the spleen, and also perhaps in the liver, while a portion of the iron is excreted by the liver in the bile. That the normal red blood corpuscles and other particles suspended in the blood stream are not taken up in this way, may be due to their being smooth and polished. As the corpuscles grow older and become more rigid, they, as it were, are caught by the amoeboid cells. As cells contain- ing blood corpuscles are very rarely found in the general circulation, one may assume that the occurrence of these cells within the spleen, liver, and marrow of bone is favored by the slowness of the circulation in these organs [Quincke). Pathological. — In certain pathological conditions, ferruginous substances derived from the red blood corpuscles are found in masses in the spleen, the marrow of bone, and the capillaries of the liver: (i) When the disintegration of blood corpuscles is increased, as in ansemia [Stahel). (2) When the formation of red blood corpuscles from the old material is diminished. If the excretion 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. When the amount of blood in dogs is greatly increased, 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, liver cells, and the epithelium of the cortex of the kidney. The iron reaction in the last two situations occurs after the introduction of hsemoglobin, or of salts of iron into the blood ( Glae- veck, V. Shirk). When we reflect how rapidly large quantities of blood are replaced after hemorrhage and after menstruation, it is evident that there must be a brisk manu- factory 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. COLORLESS CORPUSCLES, BLOOD PLATES AND GRAN- ULES.— White Blood Corpuscles. — Blood, like many other tissues, con- tains a number of cells or corpuscles which reach it from without ; the corpuscles 54 THE COLORLESS BLOOD CORPUSCLES. ^ Y vary somewhat in form, and are called colorless or white blood corpuscles, or "leucocytes" {^Hewson, 1770). Similar corpuscles are found in lymph, adenoid tissue, marrow of bone, and as wandering cells or leucocytes in connective tissue, and also between glandular and epithelial cells. So that these corpuscles are by no means peculiar to blood alone. They all consist of more or less spher- ical masses of protoplasm, which is sticky, highly refractile, soft, capable of move- ment, and devoid of an envelope (Fig. 9). When they are quite fresh (A) it is difficult to detect the nucleus, but Fu;. 9. after they have been shed for some C 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 ma- genta solution causes the nuclei to stain 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 size of the corpuscles varies from 4-13 m, and ■'. ^ ^ _ as a rule they are about -gxoir ^^ ^" ' \ ^ ', inch in diameter; in the smallest * u T forms the layer of the proto- plasm is extremely thin. They all exhibit amoeboid movements A, human white blood corpuscles, without any reagent; B, after -,,l,;„u „_„ ,rorir ar>r>ar*^nf- in tVip the action of water ; C, after acetic acid; D, frog's cor- WhlCh are Very apparent in tUe puscles, changes of shape due to amoeboid movement; E, larger COrpUSCleS, and WCre dlSCOV- fibrils of fibrin from coagulated blood ; F, elementary gran- °, . \,,, -, • , i,ies " ered by Wharton Jones in the skate (1846), and by Davine in the corpuscles of man (1850). Max Schultze describes three different forms in human blood : — (i) The smallest, spherical forms, less than the red corpuscles, with one or two nuclei, and a very small amount of protoplasm. (2) Spherical forms, the same size as the colored blood corpuscles. (3) The large amoeboid corpuscles, with much protoplasm and distinctly evi- dent movements. [On examining human blood microscopically, 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, which contains the following varieties : — (i) The large, finely granular corpuscle, which is about yj|j 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 tri-partite 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 detected 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 AMCEBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. 55 usually more blunt than those emitted by (i^ has not been ascertained. The relation between these two kinds of corpuscles Fig. io. (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 (i) and (2) exist in frog's blood. In the coarsely granu- lar 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. The nature of the latter is unknown. Very large colorless corpuscles exist in the axolotl's blood. [Action of Reagents. — (a) Water, when added slowly, causes the colorless corpuscles to become globular, and the granules within them to exhibit Brownian movements. {^) Pigments, such as magenta or carmine, stain the nuclei very deeply, and the protoplasm to a less extent, (c) 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, especially in horse's blood, indicating the presence of glycogen. (/) Dilute Alcohol causes the formation of clear blebs on the surface of the corpuscles, and brings the nuclei into view (yRanvier, Stir ling). '\ [A delicate plexus of the 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. 10).] The colorless corpuscles divide, and in this way reproduce themselves. The Number of Colorless Corpuscles is very much less than that of the red corpuscles, and is subject to con- siderable variations. It is certain that the colorless cor- puscles are very much fewer in shed blood than in blood still within the circulation. Immediately after blood is shed, an enormous number of white corpuscles disappear (§ 31). Al. Schmidt estimates the number that remain at ^-^ of the whole originally present in the circu- lating blood. The proportion is greater in children than in adults. The following table gives the number in shed blood ; — Plexus of fibrils in a colorless blood corpuscle. Number of White in Proportion to Red Blood Corpuscles : — In Normal Conditions. In Different Places. In DiflFerent Conditions. 335 {Welcker). 357 \MoleschoU). Splenic Vein, i : 60 Splenic Artery, I : 2260 Hepatic Vein, i : 170 Portal Vein, i : 740 Generally more numerous in Veins than Arteries. Increased by Digestion, Loss of Blood, Prolonged Sup- puration, Parturition, Leu- ksemia, Quinine, Bitters. Diminished by Hunger, Bad Nourishment. [The number also varies with the Age and Sex : — Age. Sex. White. Red. 1 General Conditions. White. Red. Girls, Boys, Adults, ........ Old Age, I : 405 I : 226 I : 335 I : 381 ! While fasting, After a meal, During pregnancy, . . . 1 : 716 I : 347 I : 281] 1 1 II. The amceboid movements of the white corpuscles (so called because they resemble the movements of amoeba) consist in an alternate contraction and relax- 56 AMCliBOID MOVEMENTS OF THE COLORLESS CORPUSCLES. Fig II. Human leucocytes, showing amoeboid movements. ation of the protoplasm surrounding the nucleus. Processes are given off from the surface, and are retracted again. 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 dividing. The karyo- kinetic aster, and convolution of the intra- nuclear plexus have been seen.] Two series of phenomena result from these move- ments: (i) The "wandering" or loco- motion of the corpuscles due to the exten- sion 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, and may eventually be excreted, just as particles are taken up by amceba and the effete particles excreted. [Max Schultze observed that colored par- ticles were readily taken up by these cor- puscles. Conditions for movement. — In order that the amoeboid movements of the leucocytes may take place, it is necessary that there be — (i) a certain temperature and normal atmospheric pressure; (2) the surrounding medium, within certain limits, must be "indiffer- ent," and contain a sufficient amount of water and oxygen; (3) there must be a basis or supjDort to move on.] Struggle between Microbes and the Organism. — 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." Thev may be found in the atrophied tails of batrachians, the cells containing in their interior whole pieces of nerve fibre and primitive muscular bundles. Schizomycetes which have found their way into the blood {\ 183) have been found to be partly taken up by the colorless corpuscles. [The spores of a kind of yeast are similarly attacked in the transparent tissues of the water flea by the leucocytes, and the connective-tissue cells also destroy microbes.] Effect of Reagents. — On a hot stage (3S°-4o° 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 spherical, and, if the shocks be not too strong, their movements recom- mence. Strong and continued shocks kill them, causing them to swell up, and completely disintegrating them. Diapedesis. — These amoeboid movements are of special interest on account of the "wandering out" (diapedesis) of colorless blood corpuscles through the walls of 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 i per cent, solution at first accelerates their movements, but afterward produces a tetanic contraction, and, it may be, expulsion of any food particles they contain. The Cinchona alkaloids — quinine, quinidine, cinchonidine (i : 1500) — quickly arrest the locomotive 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 movements of the leucocytes when applied to them directly, but when injected into the circu- lation of a frog the leucocytes no longer pass through the walls of the capillaries (Binz). THE BLOOD PLATES. 57 The chyle contains leucocytes, which are more resistant than those of the blood, but less so than those of the coagulable transudations. The leucocytes of the lymphatic glands may also be dissolved {^RauschenbacJi). 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 Ehrhch distinguishes " eosinophile," " basophile," and " neu- trophile " granules within the cells. Eosinophile granules occur in the leucocytes which come from bone marrow, the myelogenic leucocytes. The small leucocytes, i. e., those about the size of a colored blood corpuscle or sHghtly larger, are formed in the lymphatic glands, the lymphogenic. The large amoeboid multi- nucleated cells, which are found outside the vessels in inflammations, 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. The eosinophile corpuscles are considerably increased in leuksemia. The basophile granules occur also in connective-tissue corpuscles, especially in the neighborhood of epithelium; they are always greatly increased where chronic inflammation occurs. III. Blood Plates. — Special attention has recently been directed to a third element of the blood, the "blood plates" or "blood tablets" of Bizzozero ; pale, colorless, oval, round, or lenticular disks of variable size (mean, 3 ,a). In Fig. 12. I © O © ^wlj "Blood plates" and their derivatives, i, a red blood corpuscle on the flat; 2, on the side; 3, unchanged blood plates ; 4, lymph corpuscle, surrounded by blood plates ; 5, altered blood plates ; 6, lymph corpuscle with two heads 'of fused blood plates and threads of fibrin; 7, group of fused blood plates; 8, small group of partially dissolved blood plates with fibrils of fibrin. a healthy man Fusari found 18,000 to 250,000 in i cubic millimetre of blood. These blood plates may be recognized in the circulating blood of the mesentery of a chloralized guinea-pig and the wing of the bat. They are precipitated in enormous numbers upon threads suspended in fresh shed blood. They may be obtained from blood flowing directly from a blood vessel, on mixing it with i per cent, solution of osmic acid. They rapidly change in shed blood (Fig. 12, 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. These masses may be associated in coagulated blood with fibrils of fibrin (Fig. 12). [These blood plates are best seen in the shed blood of 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 regards them as the agents which immediately induce coagulation and take part in the formation of fibrin during coagulation of the blood ; Eberth and Schimraelbusch ascribe the initial formation of white thrombi to them. According to Lowit they are formed from partially disinte- grated leucocytes, as a consequence of alteration of the blood. Along with the leucocytes they are concerned in the formation of fibrin {Hlava). These structures were known to earlier observers; but their significance has been variously interpreted. Hayem called them haematoblasts. Halla 58 CHANGES OF THE BLOOD CORPUSCLES. found that they increased in pregnancy, Afanassiew in conditions of regeneration of the blood, and Fusari in febrile anrijmia ; they are diminished in fever. [As to the haematoblasts, or, as they have also been called, the " globules of Donnd " 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, while the latter are the blood plates. The " invisible blood corpuscles" described by Norris seem to be simply decolorized red corpuscles [Hart, Git>son).'\ IV. Elementary Granules. — Blood contains elementary granules (Fig. 9, F), \_i.c., the elementary particles of Zinimermann and Deale. They are ir- regular bodies, much smaller than the ordinary corpuscles, and appear to consist of masses of protoplasm detached from the surface of leucocytes, or derived from the disintegration of these corpuscles, or of the blood plates. Others, again, are coiTipletely spherical granules, either consisting of some proteid substance or fatty in their nature. The protoplasmic and the proteid granules disai)pear on the addition of acetic acid, while the fatty granules (which are most numerous after a diet ricli in fats) dissolve in ether]. V. In coagulated blood, delicate threads of fibrin (Figs. 9, E, and 12, 6, 7, 8) are seen, more especially after the corpuscles have run into rouleaux. At the nodes of these fibres are found granules which closely resemble those described under III. [When the blood-forming process is particularly active, " nucleated colored corpuscles " or the " corpuscles of Neumann," are sometimes found in the blood. They are identical with the nucleated colored blood corpuscles of the fcetus, being somewhat larger than the non-nucleated colored corpuscle (§ 7).] 10. ABNORMAL CHANGES OF THE BLOOD CORPUSCLES.— (i) Hemor- rhages diminish the number of red corpuscles (at most one-half), and so does menstruation. The loss is partly covered by the absorption of fluid from the tissues. Menstruation shows us that a moderate loss of red corpuscles is replaced withm twenty-eight days. When a large amount of blood is lo.st, so that all the vital processes are lowered, the time may be extended to five weeks. In acute fevers, as the temperature increases, the number of red corpuscles diminishes, while the white corpuscles increase in number. By greatly cooling peripheral parts of the body, as by keep- ing the hands in iced water, in some individuals possessing red blood corpuscles of low resisting power, these corpuscles are dissolved, the blood plasma is reddened, and even hivmoglobinuria may occur (^ 265). Diminished production of new red corpuscles causes a decrease, since blood corpuscles are continually being used up. In chlorotic females there seems to be a congenital weakness in the blood-forming and blood-propelling apparatus, the cause of which is to be sought for in some faulty condition of the mesoblast. In them the heart and the blood vessels are small, and the absolute number of corpuscles may be diminished one-half, although the relative number may be retained, while in the corpuscles themselves the haemoglobin is diminished almost one-third ; but it rises again after the administration of iron {Ilayem). The administration of iron increases the amount of haemoglobin in the blood. [The action of iron in anaemic persons has been known since the time of Sydenham.. Hayem also finds in certain forms of anix-mia that there is considerable varia- tion in the size of the red corpuscles, and that in chronic anaemia the mean diameter of the cor- puscles is always less than normal (7 // to 6 u). There i;, moreover, a persistent alteration in the volume, coloring pcnuer, and consistence of the corpuscles, consequently a want of accord between the number of the corpuscles and their coloring power, i.e., tlie amount of haemoglobin which they contain. In pernicious anaemia, in which the continued decrease in the red corpuscles may ultimately produce death, there is undoubtedly a severe affection of the blood-forming appa- ratus. The corpuscles assume many abnormal and bizarre forms, often being oval or tailed, irregularly shaped, and sometimes very pale; while numerous cells containing blood-corpuscles are found in the marrow of bone. In this disease, altiiough the red blood corpuscles are diminished in number, some may be larger and contain more haemoglobin than normal corpuscles. The number of colored corpuscles is also diminished in chronic poisoning by lead or miasmata, and also by the poison of syphilis. (2) The size of the corpuscles varies in disease from 2.9-12.9 n (mean 6-8 /z) ; "dwarf cor- puscles" or microcytes (6 ti and less) are regarded as young forms, and occur plentifully in nearly all cases of anaemia. " Giant blood corpuscles " or macrocytes (10 // and more) are constant in pernicious anremia, and sometimes in leuka-mia, chlorosis, and liver cirrhosis [Gram). (3) Abnormal forms of the red corpuscles have been observed after severe burns [Lesser) ; the corpuscles are much smaller, and under the influence of the heat, particles seem to be detached Irom them just as can be seen happening under the microscope as the eflfect of heat. Disintegra- PREPARATION OF IL^MOGLOBIN CRYSTALS. 59 tion of the corpuscles into fine droplets has been observed in various diseases, as in severe malarial fevers. The dark granules of a pigment closely related to haematin are derived from the granules arising from the disintegration of the blood corpuscles, and these particles float in the blood (melanaem-ia). This condition can be produced artificially by injecting bisulphide of carbon (7 to 70 of oil) subcutaneously into rabbits [Schwalbe). They are partly absorbed by the colorless corpuscles, but they are also deposited in the spleen, liver, brain, and bone marrow. (4) Sometimes the red corpuscles are abnormally soft, and readily yield to pressure. Parasites of Blood Corpuscles.— Within the red blood corpuscles of birds, fishes, and tor- toises, parasites are occasionally developed in the form of round " pseudo-vacuoles " from which free parasites are subsequently discharged {Danilewsky). In malarial conditions in man, proto- zoon-like organisms have been seen within the red corpuscles, the plasmodium malaria {Mar- chiafava). The white corpuscles are enormously increased in number in leukaemia {J. H. Bennett, Virchow). In some cases the blood looks as if it were mixed with milk. The colorless cor- puscles seem to be formed chiefly in bone-marrow (^E. Ahimiami), and. also in the spleen and lymphatic glands (myelogenic, splenic, and lymphatic leukjemia). II. CHEMICAL CONSTITUENTS OF THE RED BLOOD CORPUSCLES.— (i) The coloring matter or hemoglobin (Hb) is the cause of the red color of blood ; it also occurs in muscle, and in traces in the fluid part of blood, but in the last case only as the result of the solution of some red corpuscles. Its percentage composition is: C 53.85, H 7.32, N 16.17, Fe 0.42, S 0.39, O 21.84 (dog). Its rational formula is unknown, but Preyer Although it is a colloid Fig. 13. gives the empirical formula Cgoo, Hgeo, N154, Fe, S3, Oi substance it crystallizes in all classes of verte- brates, according to the rhombic system, and chiefly in rhombic plates or prisms; in the guinea- pig in rhombic tetrahedra; in the squirrel, how- ever, it yields hexagonal plates. The varying forms, perhaps, correspond to slight differences in the chemical composition in different cases. Crystals separate from the blood of all classes of vertebrata during the slow evaporation of lake- colored blood, but with varying facility (Fig 13). The coloring matter crystallizes very readily from the blood of man, dog, mouse, guinea-pig, rat, cat, hedgehog, horse, rabbit, birds, fishes ; with difficulty from that of the sheep, ox, and pig. Colored crystals are not obtained from the blood of the frog. More rarely a crystal is formed from a single corpuscle enclosing the stroma. Crystals have been found near the nucleus of the large corpuscles of fishes, and in this class of vertebrates colorless crystals have been ob- served. Dichroism. — Hsemoglobin crystals are doub- ly refractive and pleo-chromatic; they are Haemogi^in crystals from biood. bluish-red with transmitted light, scarlet-red by human ; c, cat ,- ^, guinea-pig ; . ° •^ ster ; f, squirrel. reflected light. They contam from 3 to 9 per cent, water of crystallization, and are soluble in water, but more so in dilute alkalies. They are insoluble in alcohol, ether, chloroform, and fats. The solu- tions are dichroic : red in reflected light, and green in transmitted light. In the act of crystallization the haemoglobin seems to undergo' some internal change. Before it crystallizes it does not diffuse like a true colloid, and it also rapidly decomposes hydric peroxide. If it be redissolved after crystallization, it diff"uses, although only to a small extent, but it no longer decomposes hydric peroxide, and is decolorized by it. [The presence of O favors crystallization.] 12. PREPARATION OF HAEMOGLOBIN CRYSTALS.— Method of Rollett.— Put defibrinated blood in a platinum capsule placed on a freezing mixture, freeze the blood, and then thaw it; pour the lake-colored blood into a plate, until it forms a stratum not more than l^'^ mm. in thickness, and allow it to evaporate slov^'Iy in a cool place, when crystals will separate. Method of Hoppe-Seyler.— Mix defibrinated blood with 10 volumes of a 20 per cent, salt solution, and allow it to stand for two days. Remove the clear upper fluid with a pipette, wash ham- 60 QUANTITATIVE ESTIMATION OF H.EMOGLOBIN. the thick deposit of blood corpuscles wilh water, and afterward shake it for a long time with an equal volume of ether, which dissolves the blood corpuscles. Remove the ether, filter the lake- colored bloml, add to it )+ of its volume of cold alcohol (o°), and allow the mixture to stand in the cold for several days. The numerous crystals can be collected on a filter and pressed between folds of blotting p.iper. Method of Gscheidlen. — Take defibrinated blood, which has been exposed for twenty-four hours to the air, and keep in a closed tube of narrow calibre for several days at 37° C. Wiien the blood is spread on glass, the crystals form rapidly. [Vaccine tubes answer very well.] [Method of Stirling and Brito. — It is in many cases sufficient to mix a drop of blood wilh a few drops of water on a glass slide, and to seal up the preparation. After a few days beautiful cr)'Stals are developed. The addition of water to the blood of some animals, such as the rat and the guinea])ig, is rapidly followed by the formation of crystals of luvmoglobin. Very large crystals may be obtained from the stomach of the leech several days after it has sucked blood.] 13. QUANTITATIVE ESTIMATION OF HAEMOGLOBIN.— («) From the Amount of Iron. — As dry (100° C.) lutmoglobin contains 0.42 per cent, of iron, the amount of h.vmoglobin may be calculated from the amount of iron. If m represents the percentage amount \oom of metallic iron, then the percentage of hemoglobin in blood is = ^~.^- The procedure is the following : Calcine a weighed quantity of blood, and exhaust the ash with HCl to obtain ferric chloride, which is transformed into ferrous chloride. The solution is then titrated with potassic permanganate. (^) Colorimetric Method. — Prepare a dilute watery solution of hemoglobin crj'stals of a known strength. With this compare an aqueous dilution of the blood to be investigated, by adding water to it until the color of the test solution is obtained. Of course, the solutions must be compared in vessels with parallel sides and of exactly the same width, so as to give the same thickness of fluid (Hoppe-Scvlfr). [In the vessel with parallel sides, or hsematinometer, the sides are exactly i centimetre apart. Instead of using a standard solution of oxyhemoglobin, a solution of picro- carminate of ammonia may be used {Rajewsky, Malaisez)^^ {c) By the Spectroscope. — Preyer found that an 0.8 per cent, watery solution (i cm. thick), allowed the red, the yellow, and the first strip of green to be seen (Fig. 17, l). Take the blood to be investigated (about 0.5 c.cm.), and dilute it with water until it shows exactly the same optical effects in the spectroscope. If k is the percentage of lib, which allows green to pass through (0.8 l)er cent.), b, the volume of blood investigated (about 0.5 c.cm.), iu, the necessary amount of water added to dilute it, then x = the percentage of Hb in the blood to be investigated — k{w + b) Fig. 14. IJ B, It is very convenient to add a drop of caustic potash to blood and then to saturate it with CO. [((/) The Haemoglobinometerof Gowers is used for the clinical esti- mation of hemoglobin (Fig. 14). " The tint of the dilution of a given volume of blood with distilled water is taken as the index of the amount of hemoglobin. The distilled water rapidly dissolves out all the hemo- globin, as is shown by the fact that the tint of the dilution undergoes no change on standing. The color of a dilution of average normal blood one hundred times is taken as the standard. The quantity of hemoglobin is indi- cated by the amount of distilled water needed to obtain the tint with the same volume of blood under ex- amination as was taken of the stand- ard. On account of the instability of a standard dilution of blood, tinted (lowers' hxmoglobinomctcr. A, pipette boltle for distilled water „, capilhry pipette : C, graduated tube : D, tube with standard dilu- glycerine jelly is employed instead t.on : F. lance, for pricking the finger. T,,is j^ perfectly Stable, and by means ,..,,,,,, of carmine and picro-carmine the exact tint of dduted blood can be obtained. The apparatus consists of two glass tubes of exactly the same sue. One contains (D) a standard of the tint of a dilution of 20 cubic mm. of blood, in 2 cubic centimetres of water (i in loo). The second tube (Cj is graduated, 1 00 degrees = 2 USE OF THE SPECTROSCOPE. 61 Fig. 15. centimetres (100 times 20 cubic millimetres). The 20 cubic millimetres of blood are measured by a capillary pipette (B). This quantity of the blood to be tested is ejected into the bottom of the tube, a few drops of distilled water being first placed in the latter. The mixture is rapidly agitated to prevent the coagulation of the blood. The distilled water is then added drop by drop (from the pipette stopper of a bottle (A) supplied for that purpose), until the tint of the dilution is the same as that of the standard, and the amount of water which has been added [i. e., the degree of dilution) indicates the amount of haemoglobin." " Since average normal blood yields the tint of the standard at loo degrees of dilution, the number of degrees of dilution necessary to obtain the same tint with a given specimen of blood is the percentage proportion of the hsemoglobin contained in it, compared to the normal. For instance, the 20 cubic millimetres of blood from a patient with anemia gave the standard tint of 30 degrees of dilution. Hence it contained only 30 per cent, of the normal quantity of hsemoglobin. By ascertaining with the hjemacytometer the corpuscular richness of the blood, we are able to compare the two. A fraction, of which the numerator is the percentage of haemoglobin, and the denomi- nator the percentage of corpuscles, gives at once the average value per corpuscle. Thus the blood mentioned above containing 30 per cent, of hsemoglobin, contained 60 per cent, of corpuscles; hence the average value of each corpuscle was l^ or ^ of the normal. Variations in the amount of h2emoglobin may be recorded on the same chart as that employed for the corpuscles. The instrument is only expected to yield approximate results, accurate within 2 or 3 per cent. It has, however, been found of much utility in clinical observation."] {e) Fleischl's Haemometer.— For clinical purposes this instrument (Fig. 15) is useful. A cylinder G, of two compartments a and a^ , rests on a metallic table. Both compartments are filled with water, but in one [a) is placed a known quantity of blood measured in a measuring tube of known capacity. The red color of the solution of hsemoglobin thus obtained is compared with a red wedge of glass (K), which is moved by means of a wheel (R and T) under the other compartment [a') until the two colors are identical. The illumination of the dilute blood solution and the red glass wedge is done from below by lamp light reflected from the white reflecting surface (S). The frame in which the red glass wedge is fixed bears numbers, and when the color is identical in the two compartments a and a^, the percentage of hiemoglobin as compared with normal blood can be read off" directly. Suppose it to be 80 on the scale, then the blood examined contains 80 per cent, of the hsemoglobin of normal blood. The amount of haemoglobin in man is 13.77 per cent., in the woman 12.59 per cent., during pregnancy 9 to 12 per cent. \Preyer). According to Leich- tenstern, Hb is in greatest amount in the blood of a newly-born infant, but after ten weeks the excess disappears. Between six months and five years it is smallest in amount; it reaches its second highest maximum between twenty-one and forty-five, and then sinks again. From the tenth year onward, the blood of the female is poorer in Hb. The taking of food causes a temporary decrease of the Hb, owing to the dilution of the blood. In Animals.— In the dog, 9.7 ; ox, 9.9 ; sheep, 10.3 ; pig, 12.7 ; horse, 13. i ; birds, 16-17 per cent. Pathological. A decrease is observable during recovery from febrile conditions, and also during phthisis, cancer, ulcer of the stomach, cardiac disease, chronic diseases, chlorosis, leukaemia, pernicious ansemia, and during the rapid mercurial treatment of syphilitic persons. 14. THE SPECTROSCOPE.— As the spectroscope is frequently used in the investigation of blood and other substances, a short description of the instrument is given here (Fig. 16). It Fleischl's h3emometer. K, red colored wedge of glass moved by R ; G, mixing vessel with two compartments a and a' ; M, table with hole to read off the percentage of haemoglobin on the scale P ; T, to move K; S, mirror of plaster-of-Paris. 62 COMPOUNDS OF H.EMOGLOBIN. consists of — (i) a tube, A, which has at its peripheral end a slit, S (that can be narrowed or widened). At the other end a collecting lens, C (called a collimator), is placed, so that its focus is in exact line with the slit. Light (from the sun or a lamp) passes through the slit, and thus goes parallel through C to (2) the prism, P, which decomposes the ]>arallel rays into a colored spec- trum, r, V. (3) An astronomical telescope is directed to the sjiectrum /-, r', and the observer, h, with the aid of the telescope, sees the spectrum magnified from six to ciglit times. (4) A third tube, D, contains a delicate scale, M, on glass, whose image, when illuminated, is reflected from the prism to the eye of the observer, so that he sees the spectrum, and over or above it the scale. To keep out other rays of light the inner ends of the three tubes are covered by metal or by a dark cloth (see also i, 265). [The micro-spectroscope, t-.^., as made by Browning or Zeiss, may be used when small quan- tities of a solution are to be examined. Every spectroscope ought to give two spectra, so that the position of any absorjition band may be definitely ascertained. The spectroscope is fitted into the ocular end of the tube of a microscope instead of the eye-piece. Small cells for containing the fluid to be ex.imined are made from short pieces of barometer tubes cemented to a plate of glass.] Absorption Spectra. — If a colored medium (EMATOIDIN.— Virchow discovered this important derivative of hemoglobin. It occurs in the body wherever blood stagnates outside the circulation, and becomes decomposed — as when blood is extra- Hxmatoidin crystals. ... , .' 1 1 ■ • i-i-/-i vasated into the tissues — e.g., the brain — in solidified blood plugs or thrombi ; especially in veins ; invariably in the Graafian follicles. It contains no iron ( C3,,H.„;N406), and crystallizes in clino-rhombic prisms (Fig. 20) of a yellowish-brown color. It is soluble in warm alkalies and chloroform. Very probably it is identical with the bile-pigment — bilirubin. [When acted upon by impure nitric acid (Gmelin's reaction), it gives the same play of colors as bile.] Pathological. — In cases where a large amount of blood has undergone solution within the blood vessels (as by injecting foreign blood) hrematoidin crystals have been found in the urine. For their occurrence in the urine in jaundice (^ 180), and in the sputum (^ 138). 21. (B.) THE COLORLESS PROTEID OF HiEMOGLOBIN.— It is closely related to globulin ; but, while the Jatter is preci])itated by all acids, even by CO,, and re-dissolved on passing O through it, the proteid of hemoglobin, on the other hand, is not dissolved after precipitation on passing through it a stream of O. As crystals of hcemoglobin can be decolorized under special circumstances, it is probable that these owe their crystalline form to the proteid which they contain. Landois placed crystals of hemoglobin along with alcohol in a dialyser, putting ether acidulated with sulphuric acid outside, and thereby obtained colorless crystals. [If frogs' blood be sealed up on a microscopic slide along COMPOSITION OF THE WHITE CORPUSCLES. 69 with a few drops of water for several days, long, colorless, acicular crystals are developed in it {^Stirling and Brito).'\ 22. II. PROTEIDS OF THE STROMA.— Dry red human blood cor- puscles contain from 5. 10-12. 24 per cent, of these proteids, but little is known about them {y^ildeil'). One of them is globulin, which is combined with a body resembling nuclein {^Wooldridge), and traces of a diastatic ferment {v. WitticK). The stroma tends to form masses which resemble fibrin. L. Brunton found a body resembling mucin in the nuclei of red blood corpuscles, and Miescher detected nuclein (| 250, 2). 23. OTHER CONSTITUENTS OF RED BLOOD COR- PUSCLES.— III. Lecithin (0.35-0.72 per cent.) in dry blood corpuscles (§ 250, 2). Cholesterin (0.25 per cent.) (§ 250, III.), no Fats. Lecithin is regarded as a glycero-phosphate of neurin, in which, in the radical of glycero- phosphoric acid, two atoms of H are replaced by two of the radical of stearic acid. By gentle heat glycero-phosphoric acid is split up into glycerine and phosphoric acid (§ 250). These substances are obtained by extracting old stromata or isolated blood corpuscles with ether. When the ether evaporates, the characteristic globular forms (" my elin-forms ") of lecithin, and crystals of cholesterin are recognized. The amount of lecithin may be determined from the amount of phosphorus in the ethereal extract. IV. Water (681.63 pe^" 1°°° — C. Schmidt'). V. Salts (7.28 per 1000), chiefly compounds oi potash and phosphoric acid ; the phosphoric acid is derived only from the burned lecithin ; while the greater part of the sulphuric acid is derived from the burning of the haemoglobin in the analysis. Analysis of Blood. — 1000 parts, by weight, of horse's blood contain — 344.18 blood corpuscles (containing about 128 per cent, of solids). 655.82 plasma (containing about 10 per cent, of solids). 1000 parts, by weight, of moist blood corpuscles contain — Solids, 367.9 (pig); 400.1 (ox). Water, 632.1 " 599-9 " The solids are — Pig. Ox. Hsemoglobin, , 261 280.5 Proteids, 86.1 107 Lecithin, Cholesterin, and other Organic Bodies, . . . 12.0 7.5 Inorganic salts, 8.09 4.8 f Potash, 5.543 0.747 I Magnesia, 0.158 0.017 Including -j Chlorine, i-504 1-635 Phosphoric Acid, 2.067 o-7°3 Soda, o 2.og;^[B2e>2ge). [An approximate estimate of the composition of human blood is given in the following table : — Composition of Human Blood as a Whole. Water, 780 Solids — of these — Corpuscles, 134 1 Serum-albumin, "I Serum-globulin, j ' | Fibrin of Clot (? Fibrinogen) 2.2 [- 220 Inorganic Salts (of serum), 6.0 I Extractives, 6.2 | Fatty matters, 1.4 J Gases, O, COj, N.] 24. CHEMICAL COMPOSITION OF THE WHITE CORPUS- CLES.— Investigations have been made on pus cells, which closely resemble colorless blood corpuscles. They contain several proteids ; alkali-albuminate, a 70 PREPARATION OF PLASMA. proteid which coagulates at 48° C, an albuminate resembling myosin, paraglobu- lin, peptone, and a coagulating ferment; nuclein in the nuclei (§ 250, 2), gly- cogen (§252), lecithin, cerebrin, cholesterin, and fat. ICO parts, hy weight, of dry pus, contain the following Salts : — Earthy Phosphates, 0.416 Potash, 0.201 Sodic Phosphate, 0.606 I Sodic Chloride, 0.143 25. BLOOD PLASMA AND ITS RELATION TO SERUM.— The unaltered tluid in which the blood corpuscles float is called blood plasma, or liquor sanguinis. This fluid, however, after blood is withdrawn from the vessels, rapidly undergoes a change, owing to the formation of a solid fibrous substance — fibrin. After this occurs, the new fluid which remains, no longer coagulates sponta- neously (it is plasma, vii7ms the fibrin factors), and is called serum. Apart from the presence of the fibrin factors, the chemical composition of plasma and serum is the same. [When blood coagulates, Table I shows w-hat takes place, while Table II shows what occurs when it is beaten : — I. Coagulation. Blood. I Plasma. Corpuscles. II. When beaten. Blood. I Plasma. Corpuscles. Serum. Fibrin factors. Fibrin factors. Serum. I I i I Blood Clot. Fibrin. Deiibrinated Blood. Plasma is a clear, transparent, slightly thickish fluid, which, in most animals (rabbit, ox, cat, dog), is almost colorless ; in man it is yellow, and in the horse citron jellow. 26. PREPARATION OF PLASMA.— (A) Without Admixture.- Taking advantage of the fact that plasma, when cooled to 0° outside the body, does not coagulate for a considerable time, Brilcke prepares the plasma thus : The blood of the horse (because it coagulates slowly, and its corpuscles sink rapidly to the bot- tom) is received, as it flows from an artery, into a tall, narrow glass, placed in a freezing mixture, and cooled to 0°. The blood remains fluid, the colored cor- puscles subside in a few hours, while the plasma remains above as a clear layer, which can be removed with a cooled pipette. If this plasma be then passed through a cooled filter, it is robbed of all its colorless corpuscles. [Burdon- Sanderson uses a vessel consisting of three compartments — the outer and inner contain ice, while the blood is caught in the central compartment, which does not exceed half an inch in diameter.] The quantity of plasma may be roughly (but only roughly) estimated by using a tall, graduated measuring glass. If the plasma be warmed, it soon coagulates (owing to the formation of the fibrin), and passes into a trembling jelly. If, however, it be beaten with a glass rod, the fibrin is obtained as a white, stringy mass, adhering to the rod. The quantity of fibrin in a given volume of plasma is very small (p. 71), although it varies much in difterent cases. (B) With Admixture. — Blood flowing from an artery is caught in a tall vessel containing 4- of its volume of a concentrated solution of sodic sulphate {Hewsoti) —or in a 25 per cent, solution of magnesic sulphate (t vol. to 4 vols, blood — Simmer) — or i vol. blood with 2 vols, of a 4 per cent, solution of monophosphate of potash (Masia). When the blood is mixed with these fluids and put in a cool place, the corpuscles subside, and the clear stratum of plasma mixed with the salts COAGULATION OF THE BLOOD. 71 may be removed with a pipette. [The plasma so obtained is called " salted plasma."] If the salts be removed by dialysis, coagulation occurs ; or it maybe caused by the addition of water {J^oh. Midler). Blood which is mixed with a 4 per cent, solution of common salt does not coagulate, so that it also may be used for the preparation of plasma. [For frogs' blood Johannes Miiller used a ^ per cent, solution of cane sugar, which permits the corpuscles to be separated from the plasma by filtration. The plasma mixed with the sugar coagulates in a short time.] 27. FIBRIN— COAGULATION OF THE BLOOD— General Char- acters.— Fibrin is that substance which, becoming solid in shed blood, in plasma and in lymph causes coagulation of these fluids. In these fluids, when left to them- selves, fibrin is formed, consisting of innumerable, excessively delicate, closely packed, microscopic, doubly refractive fibrils (Fig. 7, E). These fibrils entangle the blood corpuscles as in a spider's web, and form with them a jelly-like solid mass called the blood clot or placenta sanguinis. At first the clot is very soft, and after the first 2 to 15 minutes a few fibres may be found on its surface ; these may be removed with a needle, while the interior of the clot is still fluid. The fibres ultimately extend throughout the entire mass, which, in this stage, has been called cruor. After from 12 to 15 hours the fibrin contracts, or, at least, shrinks more and more closely round the corpuscles, and a fairly solid, trembling, jelly-like clot, which can be cut with a knife, is formed. During this time the clot takes the shape of the vessel in which the blood coagulates, and expresses from its substance a fluid — the blood serum. Fibrin may be obtained by washing away the cor- puscles from the clot with a stream of water. Crusta Phlogistica. — If the corpuscles subside very rapidly, and if the blood coagulates slowly, the upper stratum of the clot is not red, but only yellowish, on account of the absence of colored corpuscles. This is regularly the case in horse's blood, and in human blood it is observed especially in inflammations; hence this layer has been called crusta phlogistica. Such blood contains more fibrin, and so coagulates more slowly. The crusta is formed under other circumstances, e.g., with increased sp. gr. of the corpuscles, or diminished sp. gr. of the plasma (as in hydrsemia and chlorosis), whereby the corpuscles sink more rapidly, and also during pregnancy. The taller and narrower the glass, the thicker is the crusta (compare | 41). The upper end of the clot, where there are few corpuscles, shrinks more, and is therefore smaller than the rest of the clot. This upper, lighter- colored layer is called the " buffy coat ;" but it gradually passes, both in size and color, into the normal dark- colored clot. [Sometimes the upper surface of the clot is concave or " cupped." The older physicians attached great importance to this condition, and also to the occurrence of the buffy coat.] Defibrinated Blood. — If freshly-shed blood be beaten or whipped with a glass rod, or with a bundle of twigs, fibrin is deposited on the rod or twigs in the form of a solid, fibrous, yellowish-white, elastic mass, and the blood which remains is called ^'' defibrinated blood'''' (p. 70). [The twigs and fibrin must be washed in a stream of water to remove adhering corpuscles.] Coagulation of Plasma. — Plasma shows phenomena exactly analogous, save that the clot is not so well marked, owing to the absence of the resisting corpus- cles ; there is, however, always a soft trembling jelly formed when plasma coagu- lates. [In Hewson's experiment on the blood of a horse tied in a vein, he found that the plasma coagulated — fibrin being formed, so that he showed coagulation to be due to changes in the plasm.a itself (§ 29).] Properties of Fibrin. — Although the fibrin appears voluminous, it only occurs to the extent of 0.2 per cent. (o. i to 0.3 per cent.) in the blood. The amount varies considerably in two samples of the same blood. It is insoluble in water and ether ; alcohol shrivels it by extracting water ; dilute hydrochloric acid (o. I per cent.) causes it to swell up and become clear, and changes it into syntonin 72 GENERAL TIIENOMENA OF COAGULATION. or acid albumin (§ 249, III). When fresh, it has a grayish-yellow, fibrous appear- ance, and is elastic ; when dried, it is horny, transparent, brittle, and friable. When fresh it dissolves in 6-S per cent, solutions of sodium nitrate or sulphate, in dilute alkalies, and in ammonia, thus formint; aikali-albuminate. Ileat does not coagulate these solutions. [It is also solul)le in, or rather decomposed by, 5-10 i)er cent, solutions of neutral salts, f.^>;:, NaCl, yielding two fibro-globulins ( G'r<-c-n).'\ llydric peroxide is rapidly decomposed by fibrin into water and O {VViiiinn/ ). Fibrin which has been exposed to the air for a long lime is no longer soluble in solution of potassic nitrate, but in neurin I^Maiilhner). During putrefaction it passes into solu- tion, albumin being formed. I'ibrin contains, entangled in it, ferric, calcic, and magnesic phosphates, and calcium sulphate whose origin is unknown. Time for Coagulation. — The first appearance of a coagulum occurs in man's blood after 3 minutes 45 seconds, in woman's blood after 2 min. 20 sec. (yV. A'asse). Age has no effect; with- drawal of food accelerates coagulation ( //. l'ic'7-orJf). 28. GENERAL PHENOMENA OF COAGULATION.— I. Blood in direct contact with living unaltered blood vessels does not coagu- late. [Hewson (1772) found that when he tied the jugular vein of a horse in two places, and e.xcised it, the blood did not coagulate for a long time.] Briicke filled tlie heart of a tortoise with blood which had stood 15 minutes e.xposed to the air at 0°, and kept it in a moist chamber ; at 0° C. the blood was still unco- agulated in the contracting heart after eight days. Blood in a contracting frog's heart preserved under mercury does not coagulate. If the wall of the vessel be altered by pathological processes (^.^., if the intima becomes rough and uneven, or undergoes inflammatory change), coagulation is apt to occur at these places. Blood rapidly coagulates in a dead heart, or in blood vessels (but not in capillaries) or other canals (e.g., the ureter). If blood stagnates in a living vessel, coagu- lation begins in the central axis, because here there is no contact with the wall of the living blood vessel. II. Conditions which Hinder or Delay Coagulation. — {a) The addition of small quantities o( alka/ics, ammonia, or concentrated solutions of neutral salts of the alkalies a//^/ lood coagulates more slowly in a smooth than a rough vessel, and also in a shallow vessel than in a deep one.] Hamophilia.— A very slight scratch in some persons may cause very free bleeding. These persons are called colloquially "bleeders," and are said to have haemophilia or the hemorrhagic diathesis. In "bleeders" coagulation seems not to take place, owing to a want of the substances producing fibrin ; hence, in these cases, wounds of vessels are not plugged with fibrin. [A tendency to hemorrhage occurs in scurvy, purpura, in some infectious diseases, such as typhus, plague, yellow fever, and in poisoning with phosphorus.] GENERAL PHENOMENA OF COAGULATION. 73 Injection of Peptones. — Albertoni observed that if tryptic pancreas ferment (dissolved in glycerine) be injected into the blood of an animal, the blood does not coagulate. Schmidt-Miilheim found that after the injection oi pni-e peptone into the blood (0.5 gram per kilo.) of a dog, the blood lost its power of coagulating. [This occurs in the dog, but not in the rabbit. Peptonized blood coagulates when it is treated with COj or water. It appears, however, that it is not the peptone which prevents the coagulation, but the albumoses adhering to it which do so.] A substance is formed in the plasma, which prevents coagulation, but which is precipitated by COj. Lymph behaves similarly [Faiio). After peptones are injected, there is a great solution of leucocytes in the blood (v. Samson- Himmehtjenia). The secretion of the mouth of the medicinal leech [although its action is not due to a ferment {Hayc7-afi)'\ and snake poison also prevent coagulation ( Wall). [Diastatic ferment also prevents coagulation [Salvioli).'] III. Coagulation is accelerated — (a) By contact with foreign Sub- stances of all kinds, but only when the blood adheres to them, hence, threads or needles introduced into arteries are rapidly covered with fibrin. Blood does not coagulate in contact with bodies covered with fat or vaseline {^Freund'). Even the introduction of air bubbles into the circulation or the passage of indifferent gases, N or H, through blood, accelerates it. The pathologically altered wall of a vessel acts like a foreign body. Blood shed from an artery rapidly coagulates ■on the walls of vessels, on the surfaces exposed freely to air, and on the rods or twigs used to beat it. (Jb) The products of the retrogressive metabolism of proteids (uric acid, glycin, leucin, taurin, kreatin, sarkin, but not urea) favor coagulation by increased ferment formation ; but if they are added in excess, they retard the process. From a watery extract of the testis or thymus, on the addition of acetic acid, is precipitated a substance which is soluble in sodic carbonate. It is a mixture of lecithin and albumin, and when it is injected into the blood stream it causes almost instantaneous death by intravascular coagulation ( Wooldridge) . (c) During rapid hemorrhage, the last portions of blood coagulate most rapidly (^Holzmami). {d) Heating the blood from 39° to 55° C. {Heiosoii). {e) Agitation of the blood {HewsoJi and Hunter'). [(_/) The addition of a small quantity of water. \g) A watery condition of the blood. The clot is small and soft. {h) Contact with oxygen.] IV. Rapidity of Coagulation. — Among vertebrates, the blood of birds (especially of the pigeon) coagulates almost momentarily; in cold-blooded animals coagulation occurs much more slowly, while man:imals stand midway between the two. [The blood of a fowl begins to coagulate in J^ to i y'^ minute ; pig, sheep, rabbit, in. }4 to i]4 minute; dog, l to 3 minutes; horse and ox, 5 to 13 mmutes; man, 3 to 4 minutes; solidification is completed in 9 to 1 1 minutes [A^asse).^ The blood of invertebrates, which is usually colorless when it is oxidized (| 32), forms a soft, whitish clot of fibrin. Even in lymph and chyle, a small soft clot is formed. V. When coagulation occurs, the aggregate condition of the fibrin factors is altered, so that heat must be set free {Valentin, 1844). VI. In blood shed from an artery, the degree of alkalinity diminishes from the time of its being shed until coagulation is completed {Pflilger and Zuntz). This is probably due to a decomposition in the blood, whereby an acid is devel- oped, which diminishes the alkalinity (p. 72). VII. During coagulation there is a diminution of the O in the blood, although a similar decrease also occurs in non-coagulated blood. Traces of ain- nwnia are also given off, which Richardson erroneously supposed to be the cause of the coagulation of the blood. [This is refuted — (i) by the fact that blood, when collected under mercury (whereby no escape of ammonia is possible), also coagulates; and (2) by the following experiment of Lister: He placed two ligatures on a vein containing blood, moistening one-half of the outer surface of the 74 CAUSE OF COAGULATION OF BLOOD. FlO. 21. Vein of horse tied be- tween two ligatures. P. plasma ; W C, vein with ammonia, leaving the other half intact. The blood coagulated in the first half, and not in the other, owing to the properties of the wall of the vein of the former being altered. Neither the decrea<;e of O nor the evolution of ammonia seems to have any causal connection with the formation of fibrin.] Pathological. — When the blood coagulates within the vessels during life, the process is called thrombosis, and the coagulum or plug so formed is termed a thrombus. When a clot of blood or other bodv is carried by the blood stream to another part of the vascular system where it blocks up a vessel, the plug is called an embolus, and the result embolism. 29. CAUSE OF THE COAGULATION OF BLOOD.— [Hewson's Experiments (1--2.) Hewson tied the jugular vein of a horse between two ligatures, removed it, and then sus- pended it by one end (Fig. 21). He found that the blood remained fluid for a long time (48 hours), the red corpuscles sank (RC) and left a clear layer of plasma on the surface (I*). On drawing off some of this clear plasma it co- agulated, thus proving coagulation to be due to changes in the plasma. Lister repeated this experiment, and found that, even if the upper end of the tube be opened and the blood freely exposed to the air, coagulation is but slightly hastened. He showed that the blood might be poured from one vein into another, just as one might pour fluid from one test tube into another. In this case there were two test tubes, i.e., the veins — and although the blood, on being poured from the one to the other, came into contact with the air, it did not coagulate. Hewson, however, found that blood poured from the vein into a glass vessel coagulated, so that, in his opinion, the blood vessels exerted a restraining influence on coagulation. By cooling the blood and preventing it from coagulating, he proved that coagulation was not due to the loss of heat. Nor could it be a vital act, as sodic sulphate or other neutral salt prevented coagulation indefinitely, but coagulation took place when the blood was diluted with water.] [Buchanan's Researches. — The serous sacs of the body contain a fluid which in some respects closely resembles lymph. The pericardial fluid of some animals coagulates spontaneously {e.g., in the rabbit, ox, horse, and sheep) if the fluid be removed immediately after death. If this be not done white.and R C, red till sez-eral hours after death the fluid does not coagulate spontaneously. The corpiLscles. fluid of the tunica vaginalis of the testis sometimes accumulates to a great extent, and constitutes hydrocele, but this fluid shows no tendency to coagulate spontaneously. Andrew Buchanan found, however, that if to the fluid of ascites, pleuritic fluid, or hydrocele fluid, there be added clear blood serum, then coagulation takes place, i. e. two fluids — neither of which shows any tendency l>y itself to coagulate — form a clot when they are mixed (1831). He also found, that if "washed blood clot" (which consists of a mixture of fibrin and colorless corpuscles) be added to hydrocele fluid, coagulation occurred. He compared the action of washed blood clot to the action of rennet in coagulating milk, and he imagined the agents which determined the coagulation to he colorless corpuscles. Thus, the bufi"y coat of horses' blood is a IX)werfuI agent, and it contains numerous colorless corpuscles. He finally concluded that some constituent in the plasma, to which he gave the name of a " soluble fibrin," is acted upon by the colorless corpuscles and converted into fibrin. The soluble fibrin of Buchanan is comparable to the fibrinogen in Hammarsten's theory. Buchanan, however, did not separate the substance.] [Denis's Plasmine (1859). — Denis mixed uncoagulated blood with a saturated solution of sodic sulphate, and allowed the corpuscles to subside. The salted plasma thus obtained he pre- cipitated with sodic chloride. The precipitate, when washed with a saturated solution of sodic chloride, he called plasmine. If plasmine be mixed with water, it coagulates spontaneously, resulting in the formation of fibrin, while another proteid remains in solution. According to the view of Denis, fibrin is produced by the splitting up of plasmine into two bodies — fibrin and a soluble proteid.] [A. Schmidt's Researches (1S61). — This observer re-discovered the chief facts already known to Buchanan, viz., that some fluids which do not coagulate spontaneously, clot when mixed with other fluids which show no tendency to coagulate spontaneously, ^.^., hydrocele fluid and blood serum. He isolated from these fluids the bodies described as fibrinogen and fibrino-plastin. The bodies so obtained were not pure, but Schmidt supposed that the formation of fibrin was due to the interaction of these two proteids. The reason hydrocele fluid does not coagulate, he says, is that it contains fibrinogen and no fibrino plastin, while blood serum contains the latter, but not the former. Schmidt afterwards discovered that these two substances may be present in a fluid, and yet coagulation may not occur {e.g., occasionally in hydrocele fluid). He supposed, therefore, that blood or blood serum contained some other constituent necessary for coagulation. This he after- wards isolated in an impure condition and called fibrin-ferment.'] A. Schmidt's theory is that fibrin is formed by the coming together of two proteid substances which occur dissolved in the plasma, viz. : (i) fibrinogen, THE FIBRIN FACTORS. 75 /. e., the substance which yields the chief mass of the fibrin, and (2) fibrino- plastic substance or fibrino-plastin (serum-globulin or paraglobulin, § 32). In order to determine the coagulation a ferment seems to be necessary, and this is supplied by (3) the fibrin-ferment. 1. Properties. — Fibrinogen and fibrino-plastin belong to the group of pro- teids called globulins, i.e., they are insoluble in pure water, but are soluble in dilute solutions of common salt (§ 249), and are not distinguished from each other by well-marked chemical characters. Still they differ, as follows: — Fibrino-plastin is more easily precipitated from its solutions than fibrinogen. It is more readily redissolved when once it is precipitated. It forms when pre- cipitated a very light granular powder. Fibrinogen adheres as a sticky deposit to the side of the vessel. It coagulates at 56° C. On account of their great similarity, both substances are not usually prepared from blood plasma. Fibrinogen is prepared from serous transudations (pericardial, abdominal, or pleuritic fluid, or the fluid of hydrocele), which contain no fibrino- plastin. Fibri7io-plastin is most readily prepared from serum, in which there is still plenty of fibrino-plastin, but no fibrinogen. 2. Preparation of Fibrino-plastin, Serum-globulin, or Paraglobulin. — {a) Dilute blood serum with twelve times its volume of ice-cold water, and almost neutralize it with acetic acid [add 4 drops of a 25 per cent, solution of acetic acid to every 120 c. c. of diluted serum] ; or (J?) pass a stream of carbon dioxide through the diluted serum, which soon becomes turbid ; after a time a fine white powder, copious and granular, is precipitated. [(<;) Method of Hammarsten. — All the fibrino-plastin in serum is not pre- cipitated either by adding acetic acid or by COj. Hammarsten found, however, that if crystals of magnesium sulphate be added to complete saturation, it precipi- tates the whole of the serum-globulin, but does not precipitate serum-albumin ; serum-globulin is more abundant than serum-albumin in the serum of the ox and horse, while in man and the rabbit the reverse obtains ; (compare § 32).] Schmidt found that 100 c.c. of the serum of ox blood yielded 0.7 to 0.8 grm.; horse's serum, 0.3 to 0.56 grm. of dry fibrino-plastin. Fibrino-plastin occurs not only in serum, but also in red blood corpuscles, in the fluids of connective tissue, and in the juices of the cornea. 3. Preparation of Fibrinogen. — This is best prepared from hydrocele fluid, although it may also be obtained from the fluids of serous cavities, e.g., the pleura, pericardium, or peritoneum. It does not exist in blood serum, although it does exist in blood plasma, lymph, and chyle, from which it may be obtained by a stream of CO2, after the paraglobulin is precipitated, {ci) Dilute hydrocele fluid with ten to fifteen times its volume of water, and pass a stream of CO2 through it for a longtime, {b) Add powdered conwion salt to saturation to a serous trans- udation, when a sticky, glutinous (not very abundant) precipitate of fibrinogen is obtained. [Hammarsten and Eichwald find that, although paraglobulin and fibrinogen are soluble in solu- tions of common salt (containing 5 to 8 per cent, of the salt), a saline solution of 12 to 16 per cent, is required to precipitate the fibrinogen, leaving still in solution paraglobulin, which is not precipitated until the amount of salt exceeds 20 per cent.] Properties of the Fibrin Factors.— They are insoluble in pure water, but dissolve in water containing O in solution. Both are soluble in very dilute alkalies, e. g., caustic soda, and are precipitated from this solution by CO2. They are soluble in dilute common salt — like all globulins — but if a certain amount of common salt be added in excess, they are precipitated. Very dilute hydrochloric acid dissolves them, but after several hours they become changed into a body resembling syntonin or acid albumin (§ 249, III.). Fibrinogen held in solution by common salt coagulates at 52° to 55° C. [Fredericq finds that fibrinogen 76 THE FIBRIN FACTORS. exists as such in the plasma ; it coagulates at 56° C, and the plasma thereafter is uncoagulable.] 4. Preparation of the Fibrin-Ferment. — {a) Mix blood serum (ox) with twenty times its volume of strong alcohol, and alter one month filter off the deposit thereby i)roduced. The deposit on the filter consists of coagulated insolu- ble albumin and the ferment ; dry it carefully over sulpiiuric acid, and reduce to a powder. Triturate i gram of the powder with 65 c.c. of water for ten minutes, and filter. The ferment is dissolved by the water, and passes through the filter, while the coagulated albumin remains behind (Sc/uniW/). [(/') Gamgee's Method. — Buchanan's "washed blood clot" (p. 74) is digested in an 8 per cent, solution of common salt. The solution so obtained possesses in an intense degree the proper- ties of Schmidt's fibnn- ferment.] In the preparation of fibrino-plastin, the ferment is carried down with it mechanically. The ferment seems to be formed first in fluids outside tlie body, very probably by the solution of the colorless corpuscles. More ferment is formed in the blood the longer the interval between its being shed and its coagulation. It is destroyed at 70° C. Blood flowing directly from an artery into alcohol contains no ferment. It is also formed in other protoplasmic parts [Raiischenbach), e.g., in dead muscle, brain, suprarenal capsule, spermatozoa, testicle [Foa and Pe/lacani), and in vegetable micro organisms [^. f^., yeast] and protozoa (^Grohiiiann) [so that it would seem to be a general product of protoplasm. As the ferment does not pre- exist in colorless blood corpuscles, it seems to be formed from some mother substance in them, the blood plasma itself decomposing this sub- stance.] Coagulation Experiments. — According to A. Schmidt, if pure solutions of (i; fibrinogen, (2) fibrino-plastin, and (3) fibrin-ferment be mixed, fibrin is formed. The process goes on best at the temperature of the body ; it is delayed at 0° ; and the ferment is destroyed at the boiling point. The presence of O seems necessary for coagulation. The amount of the ferment appears to be imma- terial ; large quantities produce more rapid coagulation, but the amount of fibrin formed is not greater. [Foa and Pellacani find that a filtered watery extract of fresh brain, capsule of the kidneys, testes, and some other tissues, when injected into the blood vessels of a rabbit, causes coagulation of the blood in the jiulmonary circulation and the heart, death being caused by the action of a substance identical with the fibrin-ferment.] The amount of salts present has a remarkable relation to coagulation. Solu- tions of the fibrin factors deprived of salts, and redissolved in very dilute caustic soda, when mixed, do not coagulate until sufficient NaCl be added to make a i per cent, solution of this salt {Schmidt). [Green finds that calcium sulphate brings about coagulation in plasma which shows little or no tendency to clot, while coagulation in its absence is almost or quite prevented.] When blood or blood plasma coagulates, all the fibrinogen is used up, so that the serum contains only fibrino-plastin and fibrin-ferment ; hence, the addition of hydrocele fluid (which contains fibrinogen) to serum causes coagulation. [Hammarsten's Theory. — Hammarsten's researches led him to believe that fibrino-plastin is quite unnecessary for coagulation. According to him, fibrin is formed from one body, \\z., fibrinogen, which is present in plasma when it is acted upon by \.\\t fibrin-fermetit ; the latter, however, has not been obtained in a pure state. Neither he nor Schmidt asserts that this body is of the nature of a ferment, although they use the term for convenience. It is quite certain that fibrin may be formed when no fibrino-plastin is present, coagulation being caused by the addition of calcic chloride or casein prepared in a special way. But, whether one or two proteids be required, in all cases it is clear that a certain quantity of salts, especially of NaCl, is necessary.] [The main drift of the foregoing evidence points to the presence of one proteid —fibrinogen~\n the plasma, which under certain circumstances yields fibrin. In shed blood this act seems to be determined by a ferment, perhaps derived from the disintegration of colorless corpuscles.] SOURCE OF THE FIBRIN FACTORS. 77 [Theory of Wooldridge. — Wooldridge attributes great importance to lecithin. In shed blood the coagulation is brought about by the interaction of the plasma and the colorless corpuscles. If lecithin (which is present in considerable amount in the colorless corpuscles) diffuses into the blood, coagulation takes place. When peptone is injected into the blood of the dog, the blood does not clot ; this is due, according to Wooldridge, to the peptone " preventing the interaction of leucocytes and plasma." If, however, the corpuscular elements are removed by the centrifugal machine, the peptone plasma can be made to clot. He also believes that fibrin-ferment does not pre-exist in normal plasma, but that " it may make its appearance in that plasma in the absence of all cellular elements, and must therefore come from some constituent or constituents of the plasma itself."] 30. SOURCE OF THE FIBRIN FACTORS.— Al. Schmidt maintains that all the three substances out of which fibrin is said to be formed, arise from the breaking up of colorless blood corpuscles. In the blood of man and mammals, fibrinogen exists dissolved in the circulating blood as a dissolution product of the retrogressive changes of the white corpuscles. Plasma contains dissolved fibrino- gen and serum-albumin. The circulating blood is very rich in colorless blood corpuscles, much richer, indeed, than was formerly supposed. As soon as blood is shed from an artery, enormous numbers of the colorless corpuscles are dissolved — according to Al. Schmidt 71.7 per cent, (horse). First the body of the cell disappears, and then the nucleus. The products of their dissolution are dissolved in the plasma, and one of these products vi fibrino-plastin. At the same time the fibrin-ferment is also produced, so that it would seem not to exist in the intact blood corpuscles. Fibrino-plastin and fibrin-ferment are also produced by the " transitio?i forms " of blood corpuscles, t. e., those forms which are intermediate between the red and the white corpuscles. They seem to break up immediately after blood is shed. The blood plates (p. 57) are also probably sources of these substances. In amphibians and birds the red nucleated corpuscles rapidly break up after blood is shed, and yield the substance or substances which form fibrin. Al. Schmidt convinced himself that in these animals fibrinogen is originally a constituent of the blood corpuscles. It is clear, therefore, according to Schmidt's view, that as soon as the blood corpuscles, white or red, are dissolved, the fibrin factors pass into solution, and the formation of fibrin by the interaction of the three substances will ensue. If a large number of leucocytes be introduced into the circulation of an animal, the leucocytes are dissolved in great numbers in the blood, so that death takes place by diffuse coagulation. Should the animal survive the immediate danger of death, the blood, owing to the want of leucocytes, is completely incapable of coagulating i^Groth). [And. Buchanan thought that the potential element of his " washed bloo'd clot" resided in the colorless corpuscles, " primary cells or vesicles." He, like Schmidt, found that the buffy coat of horses' blood, which is very rich in white corpuscles, produced coagulation rapidly. Buchanan com- pared the action of his washed clot to that of rennet in coagulating milk.] Pathological. — Al. Schmidt and his pupils have shown that some ferment, probably derived from the dissolution of colorless corpuscles, is found in circulating blood, and that it is more abund- ant in venous than in arterial blood, while it is most abundant in shed blood. It is specially remarkable that in septic fever the amount of ferment in blood may increase to such an extent as to permit the occurrence of spontaneous coagulation (thrombosis), which may even produce death (Ai-n. K'dhler). In febrile cases generally, the amount of ferment is somewhat more abundant \Edelberg and B irk). After the injection of ichor into the blood an enormous number of colorless corpuscles are dissolved [F. Hoff/nann). The injection of peptone, Hb, and to a less degree of distilled water, is followed by dissolution of numerous leucocytes. There are changes in the blood, constituting true blood diseases, in which the physiological metabolism of the colorless corpuscles is enormously increased, so that the metabolic products accumulate in the blood {Alex. Schmidt). The result of this is spontaneous coagulation within the circulatory system, and death even may occur; there is always an increase of temperature. After such a condition, the coagulability of the blood is diminished. 31. FORMATION OF FIBRIN. — After several observers had shown that the red blood cor- puscles (bird, horse, frog) participate in the production of fibrin, Landois observed, in 1874, under the microscope, that the stromata of the red blood corpuscles of mammals passed into fibrin. If a 78 COMTOSITION OF PLASMA AND SERUM. drop of defibrinated rabbit's blood be placed in serum of frog's blood, without mixing them, the red corpuscles can be seen collecting together ; their surfaces are sticky, and they can only be separated by a certain pressure on the cover-glass, whereby some of the now spherical corpuscles are drawn out into threads. The corpuscles soon become spherical, and those at the margin allow the hamoglobin to escape, the decolorizalion progresses, from the margin inward, until at last there remain masses of stroma adhering together. The stroma substance is very sticky, but soon the cell contours disappear, and the stromata adhere and form (hie fibres. Thus (according to Landois) the formation of fibrin from red blood corpuscles can be traced step by step. The red corpuscles of man and animals, when dissolved in the serum of other animals, show much the same phenomena. Stroma-Fibrin and Plasma-Fibrin. — Landois calls fibrin formed direct from stroma, stromn- fibrin . fibrin formed in the usual way plasma-fibrin. The stroma fibrin is closely related chemi- cally to stroma itself ; as yet, however, the two kinds of fibrin have not been sharply distinguished chemically. Substances which rapidly dissolve red corpuscles cause extensive coagulation,^.^., injection of bile or bile salts, or lake-colored blood, into arterjes. After the injection of foreign blood the newly-injected blood often breaks up in the blood vessels of the recipient, while the finer vessels are frequently found plugged with small thrombi (§ 102). Coagulable Fluids. — With regard to coagulability, fluids containing proteids may be classified thus: — (i) Those that coagtilaie spontaneously, i. e., blood, lymph, chyle. (2) Those capable of coagulating, c. g., fluids secreted pathologically in serous cavities ; for example, hydrocele fluid, which, as usually containing fii)rinogen only, does not coagulate spontane- ously, but it coagulates on the addition of fibrino-plastin and ferment (or of blood serum in which both occur). (3) Those which do not coagulate, e. g., milk or seminal fluid, which do not seem to contain fibrinogen. 32. CHEMICAL COMPOSITION OF PLASMA AND SERUM. — I. Proteids occur to the amount of 8 to 10 per cent, in the plasma. Only 0.2 per cent, of these go to form fibrin. After the formation of the fibrin the plasma is converted into serum. The sp. gr, of human serum is 1027 to 1029. It contains several proteids. [According to Hammarsten, huma7i serum contains 9.207 percent, of solids, — of these, 3.103 = serum-globulin, and 4.516 = serum- albumin, /. e., in the ratio of i : 1.511. In horse serum the proportion is 4.5 : 2.6, in o.x serum 4. 16 : 3.29, and rabbit serum 6.22 : 1.78. The total amount of pro- teids in blood seems to be much more constant than are the relative proportions of serum-albumin and serum-globulin (.S't?/?^//).] (a) Serum-globulin or Paraglobulin (2 to 4 per cent.). If crystals of magnesium sulphate be added to saturation to serum at 35° C., serum-globulin is precipitated, but not serum-albumin. It is soluble in 10 per cent, solution of common salt, and coagulates at 69-75° C. Its specific rotatory power is — 47-8° i^Fredcncif). [Serum-globulin was described by Panuin under the name of "serum-casein" ; by Al. Schmidt, as •' fibrino-plastic substance " ; and by Kuhne, as " paraglobulin."] During hunger the globulin increases and the albumin diminishes. i^b) Serum-albumin (3-4 per cent.). Its solutions begin to be turbid at 60° C, and coagulation occurs at 73° C, the fluid becoming slightly more alka- line at the same time. If sodium chloride be cautiously added to serum, the coagtilating temperature may be lowered to 50° C. Its specific rotatory power is from — 62.6 to 64.5° {Starke). It is changed into syntonin or acid albumin by the action of dilute HCl, and by dilute alkalies into alkali-albuminate. Serum-albumin is absent from the blood of starving snakes ; and reappears after they are fed {Tiegel). [Serum-Albumin -■. Egg-Albumin— Although serum-albumin is closely related to egg- albumin they differ— f,7) as regards their action upon polarized light; {b) the precipitate pro- duced by adding HCl or HNU., is readily soluble in 4 c.c. of the reagent in the case of serum- albumm, while the precipitate in egg-albumin is dissolved with very great difficulty ; {c) egg- albumin, mjected into the veins, is excreted in the urine as a foreign body, while serum-albu- minis not; (t/) serum-albumin is not coagulated by ether, while egg-albumin is, if the solution PROTEIDS OF THE SERUM. 79 is not alkaline (| 249). Serum-albumin has never been obtained free from salts, even when it is dialysed for a very long time.] After all the serum-globulin in serum is precipitated by magnesium sulphate, serum-albumin still remains in solution. If this solution is heated to 40 or 50° C. a copious precipitate of non- coagulated serum-albumin is obtained, which is soluble in water. If the serum-albumin be filtered from the fluid, and if the clear fluid be heated to over 60° C, 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 " (/. dog = T3 (tt to iV) ^ cat = 2T. 5 ; birds = ^ iq ^; frog = J^ to ^L ; fishes = -jL to Y^-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 qiianiiiy 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 y^; the muscles of the skeleton, y^; the liver, i^; and other organs, ^ {Ranke')j\ 41. ABNORMAL CONDITIONS OF THE BLOOD.— (A) i Polysemia.— (i) An increase in the entire mass of the blood, uniformly in all organs, constitutes /(^/j/^wm 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, there is vertigo, congestion of the lungs, and breathlessness. After major amputations with little loss of blood a relative but transient increase of blood has been found (?) {plethora apocoptica). Transfusion. — Polysemia 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, 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. 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 Midler). 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. Hence, the blood at this time appears to be relatively richer in blood corpuscles [Panum, Lesser, Worm Miiller). 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 decomposition of the red corpuscles. Pronounced over-filling of the vessels causes loss of appetite and a tendency to hemor- rhage 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 decomposed 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 [Forsier, Landois). If serum from another species of animal be used {e.g., dog's serum transfused into a rabbit), the blood corpuscles of the 88 ABNORMAL CONDITIONS OF THE BLOOD. recipient are dissolved ; haemoglobinuria is produced [Ponjick) ; and if there be general dissolution of the corpuscles, death may occur (/..att Jot's). (3) 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 kidneys, which destroy their secreting parenchyma, produces this condition, and often general ilropsy, owing to the passage of water into the tissues. Ligature of the ureter produces a watery condition of the blood. (4) Plethora polycythaemica, Hyperglobulie. — An increase of the red corpuscles has been assumed to occur when periodically recurring hemorrhages are interrupted, olycythxmia, 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 remakable increase in the number of blood corpuscles (to S.82 millions per cubic milli- metre) in certain severe cardiac affections svhere there is great congestion, and much water trans- udes through the vessels. In cases of hemiplegia, for the same reason, the number of corpuscles is greater on the paralyzed congested side (Penso/t//). After diarrhcea, which diminishes the water of the blood, there is also an increase \Broitardel), and the same is the case after profuse sweating and polyuria. Drugs (alcohol, chloral, amyl nitrite) which act on the blood vessels aflect the number of corpuscles ; during contraction of the blood vessels their number increases, during dilatation they diminish in number [Andit'esen). There is a temporary increase in the hwmato- blasts as a reparative process after severe hemorrhage (^ 7), or after acute diseases. In cachectic conditions this increase continues, owing to the diminished non- conversion of these corpuscles into red coqiuscles. In the last stages of cachexia the number diminishes more and more until the formation of ha-matoblasts ceases [Hayen). (5) 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 (S/oA'tis, Lehmann). [The subcutaneous injection of human blood has been practiced with good results in anaemia (:■. Zieiiisscn). When defibrinated human blood is injected subcutaneously, 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 hemoglobin, 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 " i kilo. (2.2 lbs.) may be given off daily, when the quantity of urine may rise to 25 kilos. To replace this loss of grape sugar 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 (pulmonar)' 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 crystal- line lens becomes turbid from the amount of sugar in the fluid of the eye which extracts water from the lens, 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 disappear entirely. [The sugar in the blood is also increased after the inhalation of chloroform or amyl nitrite, and after the use of curara, nitro-benzole, and chloral [\ 175)] An excessive amount of inosite has been found in the blood and urine (^ 267), constituting mellituria inosita ( ]'ohl). Lipjemia, or an Increase of the Fat in the Blood, occurs after every meal rich in fat {e.g., in sucking kittens), so that the serum may become turbid like milk. Pathologically, this occurs in a high degree in drunkards 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. After injuries to bones affecting the marrow, not unfrequently fatty granules pass from the marrow through the imperfect walls of the blood vessels into the blood stream. These fatty particles may form fat emboli, e.g., in the liver or lungs, or they may appear in the urine. If granules of cinnabar or indigo are injected 'into the blood, they are taken up by the leucocytes, and by them are carried outside the blood stream. The cells of the splenic pulp, marrow of bone, and the liver also take up these particles [Siebei). The salts remain very persistently in the blood. The withdrawal of common salt produces albuminuria, and, if all salts be withheld, paralytic phenomena occur {Forster). 'Over- feeding with salted food, such as salt meat, has caused death through fatty degeneration of the tissues, especially of the glands. Withdrawal of lime and phosphoric acid produces atrophy and softening of the bones. In infectious diseases and dropsies the salts of the blood are often increased, and diminished in inflammation and cholera. [NaCl is absent from the urine in certain stages of pneu- monia, and It IS a good sign when the chlorides begin to return to the urine.] [In scurvy the ABNORMAL CONDITIONS OF THE BLOOD. 89 corpuscular 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 in inflammations of the lung and pleura [croupous pneu- monia, erysipelas], hence such blood forms a criista phlogistica {\ 27). In other diseases, where decomposition of the blood corpuscles occurs, the fibrin is increased, perhaps because the dissolved red corpuscles yield material for the formation of fibrin. After repeated hemorrhages, Sigm. Mayer found an increase of fibrin. Blood rich in fibrin is said to coagulate more slowly than when less fibrin is present — still there are many exceptions. (B) (I.) Diminution of the Quantity of Blood, or its Individual Constituents. — (i) Oligaemia vera, Anaemia, or diminution of the quantity of blood as a whole, occurs whenever there is hemorrhage. 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 fasces, and lastly, general convulsions, are sure signs of death by hemorrhage. In the gravest cases recovery is only possible by means of trans- fusion. Animals can bear the loss of one-fourth of their entire blood without the blood pressure in the arteries permanently falling, because the blood vessels contract and accommodate them- selves 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 consid- erably (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 gradually 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 (hydraemia), and at last abnormally poor in corpuscles (oligocythaemia, hypoglobulie). With the increased lymph stream which pours into the blood, the colorless corpuscles are consider- ably increased above norma), and during the period of restitution fewer red corpuscles seem to be used up {e.g., for bile). After moderate bleeding from an artery in animals, Buntzen observed that the volume of the blood was restored in several hours; after more severe hemorrhage in 24 to 48 hours. The red blood corpuscles, after a loss of blood equal to i.i to 4.4 per cent, of the body weight, are restored only after 7 to 34 days. The regeneration begins after 24 hours. During the period of regene- ration the number of the blood corpuscles in an early stage of development is increased. The newly.formed corpuscles contain less Hb than normal {Jac. G. OU). Even in man the duration of the period of regeneration depends upon the amount of blood lost {Lyon). The amount of haemoglobin is diminished nearly in proportion to the amount of the hemorrhage {Bizzozero and Sakdoli). Metabolism in Anaemia. — The condition of the metabolistn within the bodies of ansemic persons is important. The decomposition of proteids is increased (the same is the case in hunger), hence the excretion of urea is increased {Bauer). The decomposition of fats, on the contrary, is diminished, which stands in relation with the diminution of COj given off". Ansemic and chlorotic persons put on fat easily. The fattening of cattle is aided by occasional bleedings and by inter- current periods of hunger {Aristotle). (2) An excessive thickening of the blood through loss of water is called Oligaemia sicca. This occurs in man after copious watery evacuations, as in cholera, so that the thick tarry blood stagnates in the vessels. Perhaps a similar condition — though to a less degree — may exist after very copious perspiration. (3) If the proteids in blood be abnormally diminished the condition is called Oligaemia hyp- albuminosa ; they may be diminished about one-half. They are usually replaced by an excess of water in the blood [so that the blood is watery, constituting hydraemia]. Loss of albumin from the blood is caused directly by albuminuria (25 grams of albumin may be given off" by the urine daily), persistent suppuration, great loss of milk, extensive cutaneous ulceration, albuminous diar- rhoea (dysentery). Frequent and copious hemorrhages, however, by increasing the absorption of water into the vessels, at first produce oligemia hypalbuminosa. For the abnormal changes of the red and white blood corpuscles, see ? 10 ; for Haemophilia, a 28. 90 ORGANISMS IN THE BLOOD. [Organisms in the Blood. — The presence of animal and vegetable parasites in the blood gives rise to certain diseases. Some of these, and esiiecially the vegetable organisms, have the power of multiplying in the blood. The vegetable forms belonging to the schizomycetes are fre- quently spoken of collectively under the title bacteria. They are classified by Cohn into I. Spharobacteria. I }"• Desmobacterial^^j^j^^;^ ^^^^^^^^^^^^ II. Microbacteria, exhibit movements. | I\ . Spirobacteria j These forms are shown in Fig. 23. The micrococci (A) are examples of I; while Uacterium termo (B) is an example of II. In III the members are short cylindrical rods, straight (Bacillus, Fig. 23. Fig. 24. micrococcus ; B, bacterium ; C, vibrios ; D, bacilli; E, spirillum. Bacillus anthracis from the blood (ox) in splenic fever. D) or wavy (Vibrio, C). Splenic fever of cattle is due to the presence of Bacillus anthracis (Fig. 24). These rod-shaped bodies under proper conditions divide transversely and elongate, but they also form spores in their interior, which in turn under appropriate conditions may germinate (Fig. 24). Class IV is represented by two genera, Spirochxta and Spirillum (Fig. 23), the former with close, and the later with open spirals. The Spirochasta Obermeieri (often spoken of as " Spirillum") is present in the blood during the paroxysms in persons suffering from relapsing fever. Among animal parasites are Filaria sanguinis, and Bilharzia Ha^matobia, which occurs in the portal vein and in the veins of the urinary apparatus.] Physiology of the Circulation. Fig. 25. 42. GENERAL VIEW. — The blood within, the vessels is in a state of continual motion, being carried /r^;^z the ventricles by the large arteries (aorta and pulmonary) and their branches to the system of capillary vessels, from which again it passes into the veins that end in the atria of the auricles ( W. Harvey, 1628). The cause of the circulation is the difference of pressure which exists between the blood in the aorta and pulmonary artery on the one hand, and the two venae cavse and the four pulmonary veins on the other. The blood, of course, moves con- tinually in its closed tubular system in the direction of least resistance. The greater the difference of pressure, the more rapid the movement will be. The cessation of the difference of pressure (as after death) naturally brings the movement to a stand- still (§ 81). The circulation is usually divided into — (i) The greater, or systemic circulation, which includes the course of the blood from the left auricle and left ventricle, through the aorta and all its branches, the capillaries of the body and the veins, until the two vense cavs terminate in the right auricle. (2) The lesser, or pulmonic circulation, which includes the course from the right auricle and right ventricle, the pulmonary artery, the pul- monary capillaries, and the four pulmonary, veins springing from them, until these open into the left auricle. (3) The portal circulation is sometimes -^^^'-ft :4icTerT:'S^^^ spoken of as a special circulatory system, although tricle; i, pulmonary artery: 2, aorta: it represents only a second set of capillaries (within femic'' cLdLTionT^'<.!^thT^superio'r the liver) introduced into the course of a venous y^"^ <^a™: g, area supplying the , 4 . , . , interior vena cava, a; a, «:, intestine ; trunk. It consists of the vena portarum formed ?«, mesenteric artery ; ^, portal vein ; by the union of the intestinal or mesenteric and l, hver ,- a, hepatic vein. splenic veins, and it passes into the liver, where it divides into capillaries, from which the hepatic veins arise. The hepatic vein joins the inferior vena cava. Strictly speaking, however, there is no special portal circulation. Similar arrangements occur in other animals in different organs, e. g., snakes have such a system in their supra- renal capsules, and the frog in its kidneys. When an artery splits up into fine branches during its course, and these branches do not form capillaries, but reunite into an arterial trunk, a rete mirabile is formed, such as occurs in apes and the edentata. Microscopic retia mirabilia exist in the human mesentery [Sck'dbl). Similar arrangements may exist in connection with veins, giving rise to venous retia mirabilia. 91 92 ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. X3_ THE HEART. The muscular fibres of the mammalian heart consist of short (50 to -o /( in man), very line, transversely striated tihres, which are actual unicellular elements, devoid of a sarcolemma (15 to 25 // broad), and usually divided at their blunt ends, by which means they anastomose and form a network (Fig. 26, A, B). The individual muscle cells contain in their centre an oval nucleus, and are held together by a cement which is blackened by silver nitrate, and dis- solved by a ^;i per cent, solution of caustic potash. This cement is also dissolved by a 40 per cent, solution of nitric acid. The transverse strix- are not very distinct, and not unfreciuently there is an appearance of longitudinal striation, produced by a number of very small granules arranged in rows within the fibres. The fibres are gathered lengthwise in bundles, or fasciculi, surrounded and separated from each other by delicate processes of the perimysium. \Vhen the connective tissue is dissolved by prolonged boiling, these bundles can be isolated, and constitute the so-called "fibres" of the heart. The transverse sections of the bundles in the auricles are polygonal or rounded, while in the ventricles they are somewhat flattened. [The muscular mass of the heart is called the myocardium, and is invested by filirous tissue. It is important to notice that the connective tissue of the visceral pericardium (epicardium) is continuous with that of the endocardium by means of the perimysium surrounding the bundles of muscular fibres.] The fine spaces which exist between these bundles form narrow lacunne, lined with epithelium, and constituting part of the lymphatic sys- tem of the heart. [The cardiac muscular fibres occupy an intermediate position between striped and plain muscular fibres. Although they are striped, they are involuntary, not being directly under the intluence of the will, while they contract more slowly than a voluntary muscle of the skeleton.] In the frog's heart Fig. 26. A, muscular fibres from the heart of a mammal, and C from a frog; B, transverse section of the cardiac fibres; />, connective-tissue corpuscles ; c, capillaries. the muscular fibres are in shape elongated spindles, or fusiform, in this respect resembling the plain muscle cells, but they are transversely striped (Fig. 26, C). They are easily isolated by means of a 2S per cent, solution of potash or dilute alcohol. 44. ARRANGEMENT OF THE CARDIAC MUSCULAR FI- BRES.— The study of the embryonic heart is the key to a proper understanding of the complicated arrangement of the fibres in the adult heart. The simple tubu- lar heart of the embryo has an ou/er circular and an inner loni:;itiidinal layer of fibres. The septum is formed later ; hence, it is clear that a part, at least, of the fibres must be common to the two auricles, and a part also to the two ventricles, since there is, originally, but one chamber in the heart. The muscular fibres of the auricles are, however, completely separated from those of the ventricles by the fibro-cartilaginous rings. In the auricles the fundamental arrangement of the embryonic fibres partly remains, while in the ventricles it becomes obscured as the cavities undergo a sac-like dilatation, and also become twisted in a spiral manner. (i) The muscular fibres in the auricles are completely separated from the fibres of the ventricles by \.\\^ fibrous rings which surround the auriculo-ventricular orifices, and which serve as an attachment for the auriculo-ventricular valves (Fig. 27, I). The auricles are much thinner than the ventricles, and their fibres are generally arranged in two layers ; the o\x\.tx tra?isverse layer is continuous over ARRANGEMENT OF THE CARDIAC MUSCULAR FIBRES. 93 both auricles, while the inner one is directed iongiiudinaHy. The outer transverse fibres may be traced from the openings of the venous trunks anteriorly and poste- riorly over the auricular walls. The longitudinal fibres are specially well marked where they are inserted into the fibro-cartilaginous rings, while in some parts of the anterior auricular wall they are not continuous. In the auricular septum, some fibres, circularly disposed around the fossa ovalis (formerly the embryonic opening of the foramen ovale), are well marked. Circular bands of striped muscle exist around the veins where they open into the heart ; these are least marked on the inferior vena cava, and are stronger and reach higher (2.5 cm.) on the superior vena cava (Fig. 27, II). Similar fibres exist around the pulmonary veins, where they join the left auricle, and these fibres (which are arranged as an inner circular and an outer longitudinal layer) can be traced to the hilus of the lung in man and some mammals ; in the ape and rat they extend on the pulmonary veins right into the lung. In the mouse and bat, again, the striped muscular fibres pass so far into the lungs that the walls of the smaller veins are largely composed of striped muscle (Stieda). Fig. 27. I. Course of the muscular fibres on the left auricle with the outer transverse and inner longitudinal fibres, the circular fibres on the pulmonary veins {v. p.) ; V, the left ventricle {yohn Reid). II. Arrangement of the striped muscu- lar fibres on the superior vena cava (Elischer) — a, opening of vena azygos; v, auricle. Circular muscular fibres are found where the vena magna cordis enters the heart, and in the Valvula Thebesii which guards it. Physiological Significance. — (i) The auricles contract independently of the ventricles. This is seen when the heart is about to die ; when there may be several auricular contractions for one ventricular, and at last only the auricles pulsate. The auricular portion of the right auricle beats longest ; hence it is called the "ultimum moriens." Independent rhythmical contractions of the ven» cavae and pulmonary veins are often noticed after the heart has ceased to beat. [This beating can also be observed in those veins in a rabbit after the heart is cut out of the body.] (2) The double arrangement of the fibres (transverse and longitudinal) produces a simultaneous and uniform diminution of the auricular cavity (such as occurs in most of the hollow viscera). (3) The contraction of the circular muscular fibres around the venous orifices, and the subsequent contraction of the auricle, cause these veins to empty themselves into the auricle ; and by their presence and action they prevent any large quantity of blood from passing backward into the veins when the auricle contracts. [No valves are present in the superior and inferior vena cava in the adult heart, or in the pulmonary veins ; hence the contraction of these circular muscular fibres plays an im- portant part in preventing any reflux of blood during the contraction of the auricles.] 94 ARRANGEMENT OF THE VENTRICULAR FIBRES. 45. ARRANGEMENT OF THE VENTRICULAR FIBRES.— (2) The muscular fibres in the thick wall of the ventricles are arranged in several layers (Fig. 28, A) under the pericardium. First, there is an outer longi- ttuiinal layer (A) which is in the form of single bundles on the right ventricle, but forms a complete layer on the left ventricle, where it measures about one- eighth of the thickness of the ventricular wall. A second lotigiiudinal layer of fibres lies on the inner surface of the ventricles, distinctly visible at the orifices, and within the vertically placed papillary muscles, while elsewhere it is replaced by the irregularly arranged trabeculae carneae. Between these two layers there lies the thickest layer, consisting of more or less transversely arranged bundles, which may be broken up into single layers more or less circularly disposed. The deep lymphatic vessels run between the layers, while the blood vessels lie within the substance of the layers, and are surrounded by the primitive bundles of mus- cular fibres. All three layers are not completely independent of each other ; on Fig. 2S. Course of the ventricular muscular fibres. A, on the anterior surface; B, view of the apex with the vortex- C course of the fibres within the ventricular wall ; D, fibres passing into a papillary muscle. ' ' the contrary, the fibres which run obliquely form a gradual transition between the transverse layers and the inner and outer longitudinal layers. It is not, however, quite correct to assume that the outer longitudinal layer gradually passes into the transverse, and this again into the inner longitudinal layer (as is shown schemat- ically in C) ; because, as Henle pointed out, the transverse fibres are relatively far greater in amount. In general, the outer longitudinal fibres are so arranged as to cross the inner longitudinal layer at an acute angle. The transverse layers lying between these two form gradual transitions between these directions. At the apex of the left ventricle, the outer longitudinal fibres bend or curve so as to meet at the so-called vortex B, where they enter the muscular substance, and, taking an upward and inward direction, reach the papillary muscles, P, D ; although it is a mistake to say that all the bundles which ascend to the papillary muscles arise trom the vertical fibres of the outer surface: many seem to arise independently within the ventricular wall. According to Henle, all the external longitudinal PERICARDIUM, ENDOCARDIUM, VALVES. 95 fibres do not arise from the fibrous rings or the roots of the arteries. The mitral orifice is surrounded by circular fibres which act like a sphincter {Henle). [The assumption that the muscles of the ventricle are arranged so as to form a figure of 8, or in loops, seems to be incorrect ; thus, fibres are said to arise at the base of the ventricle, to pass over it, and to reach the vortex, where they pass into the interior of the muscular substance, to end either in the papillary muscles or high up on the inner surface of the heart at its base. Figs. C and D give a schematic representation of this view.] Only the general arrangement of the ventricular muscular fibres has been indicated. According to Pettigrew, there are seven layers in the ventricle, viz., three external, a fourth or central layer, and three internal. These internal layers are continuous with the corresponding external layers at the apex, thus — one and seven, two and six. 46. PERICARDIUM, ENDOCARDIUM, VALVES.— The pericardium encloses within its two layers [visceral and parietal] a lymph space — the pericardial space — which contains a small quantity of lymph — the pericardial fluid. It has the structure of a serous mem- Fig. 29. brane, i. e., it consists of connective tissue mixed with fine elastic fibres arranged in the form of a thin delicate membrane, and cov- ered on its free surfaces with a single layer of epithelium or endothelium, composed of ir- regular, polygonal, flat cells. A rich lymphatic network lies under the pericardium (Fig. 29) and endocardium ; also in the deeper layers of the visceral pericardium next the heart and between muscular bundles [Salvioli). No stomata exist either on its visceral or parietal layers. Around the coronary arteries of the heart exist lymph vessels and deposits of fat, which lie in the furrows and grooves in the subserosa of the epicarditim (visceral layer). The endocardium, next the cavity of the heart, consists of a single layer of polygonal, flat, nucleated endothelial cells. [Under this there is a nearly homogeneous hyaline layer (Fig. 30, a), slightly thicker on the left side, which gives the endocardium its polished ap- pearance.] Then follows, as the basis of the membrane, a layer oifine elastic fibres — stronger in the auricles, and in some places thereof assuming the characters of a fenestrated membrane. Between these fibres a small quantity of connective Fig. Lymphatic of the pericardium, epithelium stained with nitrate of silver. 30. tissue exists, which is in larger amount and more areolar in its characters next the myo- cardium. Bundles of non-striped muscular fibres (few in the auricles) are scattered and arranged for the most part longitudinally be- tween the elastic fibres. These seem evi- dently meant to resist the distention which is apt to occur when the heart contracts and great pressure is put upon the endocardium. In all cases where high pressure is put upon walls composed of soft parts, we always find muscular fibres present, and never elastic fibres alone. No blood vessels occur in the endocardium [Longer). The valves also belong to the endocardium — both the semilunar valves of the aorta and pulmonary artery, which prevent the blood from passing back into the ventricles, and the tricuspid (right auriculo-ventricular) and mitral (left auriculo-ventricular), which protect the auricles from the same result. The lower vertebrata have valves in the orifices of the venae cavse, which prevent regurgitation into them ; while in birds and some mammals these valves exist in a rudimentary condition. The valves are fixed by their base to xt?,\sidint fibrous Section of the endocardium, a. hyaline layer ; b, network of fine elastic fibres ; c, network of stronger elastic fibres; d, myocardium with blood vessels, which do not pass into the endocardium. 96 AUTOMATIC KEt.ULATlUN OF THE HEART. Fi( rings, consisting of elastic and fibrous tissue. They are formed of two layers — (I ) ihtjibrous, which is a direct continuation of the fibrous rings, and (2) a layer of elastic elements. The elastic layer of the auriculo-ventricular valves is an immediate prolongation of the endocardium of the auricles, and is directed toward the auricles. The semilunar valves have a thin elastic layer directed toward the arteries, which is thickest at their base. The connective-tissue layer directed toward the ventricle is about half the thickness of the valve itself. The auriculo-ventricular valves also contain striped muscular fibres. Ra- diating fibres proceed from the auricles and pass into tlie valves, which, when the atria contract, retract the valves toward their base, and thus make a larger opening for the passage of the blood into the ventricles ; according to Paladino, they raise the valves after they have been pressed down by the blood current. This observer also described some longitudinal fibres which proceed from the ventricles to enter these valves. There is also a concentric layer of fibres arranged near their point of attachment, and directed more toward their ventricular sur- face. These fibres seem to contract sphincter-like when the ventricle contracts, and thus approximate the base of the valves, and so prevent too great tension being put upon them. The larger chordae tendineae also contain striped muscle, while a delicate muscular network exists in the valvula Thebesii and valvula Eustachii. Purkinje's Fibres consist of an anastomosing system of grayish fibres which exist in the sub- endocardial tissue of the ventricles, especially in the heart of the sheep and ox. The fibres are made up of polyhedral clear cells, containing some granular protoplasm, and usually two nuclei (f^'g- 3')- The margins of the cells are striated. Transition forms are found between these cells and the ordinary cardiac fibres; in fact, these cells become continuous with the true fully developed cardiac fibres. They represent cells which have been arrested in their development. They are absent in man and the lower vertebrates, but in birds and some mammals they are well marked {ScJncout the sue of the closed fist of the individual.] Blosfeld and Dieberg give 346 grms. for the male, and 310 to 340 grms. for the female heart. The specijic gravity of the heart muscle is 1.069. Ihe thickness of the left ventricle in the middle in man is 11.4 mm.,' and in woman 11. 15; that of the right is 4.1 and 3.6 mm. respectively. 47- AUTOMATIC REGULATION OF THE HEART.— Anatomical Investiga- tions.— The two coronary arteries arise from the first part of the aoita in the re-ion of the sinus of \alsalva. The position of origin varies— (i) either the orifices lie within the sinus, or (2) their openings are only partially reached by the margins of the semilunar valves (which is usually the case in the left coronary artery of man and the ox), or (3) their orifices lie clear above the margins of the valves. Post-mortem observations seem to show that during contraction of the ventricle it is very improbable that the semilunar valves constantly cover the origin of the coro- nary arteries. LIGATURE OF THE CORONARY ARTERIES. 97 Automatic Regulation of the Heart. — Briicke attempted to show that during the systole, or contraction of the ventricle, the semilunar valves covered the openings of the coronary arteries, so that these vessels could be filled with blood only during the diastole or relaxation of the ventricle. To him it seemed that (a) the diastolic filling of the coronary arteries would help to dilate the ven- tricles ; (d) on the contrary, a systolic filling of these arteries would oppose the contraction, because the systolic filling and expulsion of the blood from the coronary arteries would diminish the force of the ventricular contraction. [To this supposed arrangement Briicke gave the name "Selbststeuerung," which may be rendered as above, or as "self-controlling" action of the heart by the aortic valves. ] Arguments against Briicke's View. — The following considerations militate against this theory : (i) Filling the coronary vessels under a high pressure in a dead heart causes a diminution of the ventricular cavity [v. Wiltick). (2) The chief trunks of the coronary arteries lie in loose sub- pericardial fatty tissue in the cardiac sulci, hence a dilatation of the ventricle through this agency is most unlikely [Landois). (3) Experiments on animals have shown that a coronary artery spouts, like all arteries, during the systole of the ventricle. Von Ziemssen found that in the case of a woman who had a large part of the anterior wall of the thorax removed by an operation, the heart being covered only by a thin membrane, the pulse in the coronary arteries was synchro- nous with the pulse in the pulmonary artery. H. N. Martin and Sedgwick placed a manometer io connection with the coronary artery, and another with the carotid in a large dog, and they found that the pulsations occurred sinmltaneonsly. When a coronary artery is divided, the blood flows out continuously, but undergoes acceleration during the systole of the ventricles [Endemann, Perls). (4) If a strong intermittent current of water be allowed to flow through a sufficiently wide tube into the left auricle of a fresh pig's heart, so that the water passes into the aorta, and if the aorta be provided with a vertical tube, the water flows continuously from the coronary arteries, and is accelerated during the systole. (5) It is exceedingly improbable that the coronary arteries should be filled during the diastole, while all the other arteries are filled during systole of the ventricle. (6) There is always a sufficient quantity of blocd in the sinus of Valsalva to fill the arteries during the first part of the systole. (7) The valves, when raised, are not applied directlv to the aortic wall [Hamberger, Rildinger) even by the most energetic pressure from the ventricle [Sandborg and Worm Mailer). (8) Observations on voluntary muscles have shown that the small arteries dilate during contraction of the muscle, and the blood stream is accelerated. (9) By the systolic filling of the aorta the arterial path is elongated — this elastic distention is compensated before the diastole occurs. By the recoil of the aortic walls the layer of blood in them is driven backward and closes the valves \Ceradini). According to Sandborg and Worm Miiller, the semilunar valves close just after the ventricles have begun to relax, which agrees with the curve obtained from the cardiac impulse (Fig. 39, A). During the systole, the small arterial trunks lying next the ventricular cavities have to bear a higher pressure than that borne by the aorta, and their lumen must be compressed during the systole so that their contents are propelled toward the veins. Peculiarities of the Cardiac Blood Vessels. — The capillary vessels of the myocardium are very numerous, corresponding to the energetic activity of the heart. Where they pass into veins, several unite at once to form a wide venous trunk, whereby an easy passage is offered to the blood. The veins are provided with valves so that (i) during systole of the right auricle the venous stream is interrupted; (2) during contraction of the ventricles, the blood in the coronary veins is similarly accelerated as in the veins of muscles. The coronary arteries are characterized by their very thick connective tissue and elastic intima, which perhaps accounts for the frequent occurrence of atheroma of these vessels (^Henle). Some observers -maintain that the coronary arteries do not anastomose, but this is denied by Langer and Krause. [West has injected the one artery from the other.] Many of the small lower vertebrates have no blood vessels in their heart muscle, e. g., frog [Ilyrtl). Ligature of the Coronary Arteries. — The phenomena produced by par- tial obliteration or ligature of the coronary arteries are most important. In man analogous conditions occur, as in atheroma or calcification of these arteries. See and others have ligatured the coronary arteries in dogs, and found that after two minutes the cardiac contractions gave place to twitchings of the muscular fibres, and ultimately the heart ceased to beat. Ligature of the anterior coronary artery alone, or of both its branches, is sufficient to produce this result. If the coro- 7 98 MOVEMENTS OF THE HEART. nary arteries be compressed or tied in a rabbit in the angle between the bulbus aortse and the ventricle, the heart's action is soon weakened, owing to the sudden anaemia and to the retention of the decomposition products of the metabolism in the heart muscle. Ligature of one artery first affects the corresjionding ventricle, then the otlier ventricle, and, last of all, the auricles. Hence, compression of the left coronary artery (with simultaneous artificial respiration in a curarized animal) causes slowing of the contractions, esjjecially of tiie left ventricle, while the right one at first contracts more quickly, and then, gradually, its rhythm is slowed. The contractions of the left ventricle are not only slowed but also weakened, while the right pulsates with undiminished force. Hence it follows that, as the left half of the heart cannot expel the blood in sufficient quantity, the left auricle becomes filled, while the right ventricle, not being affected, pumps blood into the lungs. (Edema of the lungs is produced by the high pres- sure in the pulmonary circulation, which is propagated from the right heart through the pulmonary vessels into the left auricle {Samurlson and Grinihagen). According to Sig. Mayer, protracted dyspncea causes the left ventricle to beat more feebly sooner than the right, so that the left side of the heart becomes con- gested. Perhaps this may explain the occurrence of pulmonary oedema during the death agony. Cohnheim and v. Scliulthess-Rechberg found, after ligature of one of the large branches of a coronar\' artery in a dog, that at the end of a minute the pulsations become intermittent. This intermittence becomes more pronounced, the two sides of the heart do not contract simultaneously (arhythmia), the heart beats more slowly, and the blood pressure falls. Suddenly, about 105 seconds after the ligature is applied, both ventricles cease to beat, and there is a great fall of the blood pressure. After an arrest lasting for 10 to 20 seconds, twitching movements occur in the ventricles, while the auricles pulsate regularly, and may continue to do so for many minutes, but the ventricles cease to beat altogether after 50 seconds. According to Lukjanow, there is a peri- staltic condition which operates upward and downward, and occurs in the period between the regular contraction and the twitching vibratory movement. Stimulation of the vagus does not arrest these peristaltic movements. Pathological. — In so-called sclerosis of the coronary arteries in old age, there are attacks of diminished cardiac activity, weakness of the heart, an altered rhythm and frequency, with conse- quent breathlessness ; there may also be loss of consciousness, congestions, and attacks of pulmonary cedema. Death may take place unexpectedly from sudden arrest of the heart's action. 48. MOVEMENTS OF THE HEART.— Cardiac Revolution.— The movement of the heart is characterized by an alternate contraction and relaxation of its walls. The total cardiac movement is called a " cardiac revolution" or a "cardiac cycle," and consists of three acts — the contraction or systole of the auricles, tlie contraction or systole of the ventricles, and the pause (Fig. 50). During the pause, the auricles and ventricles are relaxed ; during the contraction of the auricles the ventricles are at rest ; while during the contraction of the ventricles the auricles are relaxed. The rest during the phase of relaxation is called the diastole. Tlie following is the sequence of events in the heart during a cardiac revolution : — (A) The blood flows into the auricles, and thus distends them and the auricular appendices. This is caused by — (i) ^\\t pressure of the blood in the venae cavae (right side) and the pulmonary veins (left side) being greater than the pressure in the auricles. (2) The elastic traction of the lungs (§ 68), which, after complete systole of the auricles, pulls asunder the now relaxed and yielding auricular walls. The auricular appendages are also filled at the same time, and they act to a certain extent as accessory reservoirs for the large supply of blood streaming into the auricles. (B) The auricles contract, and we observe in rapid succession — (i) The contraction and emptying of the auricular appendix toward the atrium. Simultaneously the mouths of the veins become narrowed, owing to the contraction of their circular muscular fibres (more especially the superior vena cava and the pulmonary veins) ; (2) the auricular walls contract simultaneously toward the MOVEMENTS OF THE HEART. 99 auriculo-ventricular valves and the venous orifices, whereby (3) the blood is driven into the relaxed ventricles, which are considerably distended thereby. The contraction of the auricles is followed by (a) A slight stagnation of the blood in the large venous trunks, as can be observed in a rabbit after division of the pectoral muscles so as to expose the junction of the jugular with the subclavian vein. There is no actual regurgitation of the blood, but only a partial interruption of the inflow into the auricles, because the mouths of the veins are contracted, and the pressure in the superior vena cava and pulmonary veins soon holds in equilibrium any reflux of blood ; and lastly. Fig. 32. Cast of the ventricles of the human heart viewed from behind and above ; the walls have been removed, and only the fibrous rings and the auriculo-ventricular valves are retained. L, left, R, right ventricle ; S, septum ; F, left fibrous ring, with mitral valve closed ; D, right fibrous ring, with tricuspid closed ; A, aorta, with the left (Ci) and right (C) coronary arteries ; S, sinus of Valsalva; P, pulmonary artery. because any reflux into the cardiac veins is prevented by valves. The movement of the heart causes a regular pulsatile phenomenon in the blood of the vense cavse, which under abnormal circumstances may produce a venous pulse (see § 99). {F) The chief motor effect of the contraction of the auricles is the dilatation of the relaxed ventricle, which has already been dilated to a slight extent by the elastic traction of the lungs. Aspiration of the Ventricles. — The dilatation of the ventricles has been ascribed to the elasticity of the muscular walls — the strongly contracted ventricular walls (like a compressed india- rubber bag), in virtue of their elasticity, are supposed, in returning to their normal resting form, to 100 MOVEMENTS OF THE HEART. suck in or aspirate the blood under a negative pressure; this power on the part of the ventricle is not great (see below). (c) When the ventricles are distended by the inflowing blood, the auriculo- ventricular valves are floated up, partly by the recoil or reflexion of the blood from the ventricular wall, and partly owing to their lighter specific gravity, whereby they easily float into a more or less horizontal position. The valves are also raised to a slight extent by the longitudinal muscular fibres, which pass from the auricles into the cusps of the valve. (C) The ventricles now contract, and simultaneously the auricles relax, whereby — (i) 'hie muscular walls contract forcibly from all sides, and thus diminish the ventricular cavity. (2) The blood is at once pressed against the under surface of tlie auriculo-ventricular valves, whose curved margins are opposed to each other like teeth, and are pressed hermetically against each other (Fig. 32). It is impos- sible for tiie blood to push the cusps backward into the auricle, as the chordae tendinese hold fast their margins and surfaces like a taut sail. The margins of the neigliboring cusps are also kept in apposition, as the chordoe tendineoe from one papillary muscle always pass to the adjoining edges of two cusps. The extent to which the ventricular wall is shortened is compensated by the contraction of the ])apillary muscle, and also of the large muscular chorda;, so that the cusps cannot be pushed into the auricle. When the valves are closed, their surfaces are hori- zontal, so that, even when the ventricles are contracted to their greatest extent, there remains in the supra-papillary space a small amount of blood which is not expelled {Sandborg^ and Worm Miiller). (3) When the i)ressure within the ven- tricles exceeds that in the arteries, the semilunar valves are forced open and stretched like a sail across the pocket-like sinus, without, however, being directly applied to the wall of the arteries (pulmonary and aorta), and thus the blood enters the arteries. (D) Pause. — As soon as the ventricular contraction ends, and the ventricles begin to relax, the semilunar valines close ( Vig. t^i). The diastole of the ventricles is followed by the pause. Un- der normal circumstances, the right and left halves of the heart always contract or relax uniformly and simultane- ously. Negative Pressure in the Ventricle. — Goltz and Gaule found that there was a ttei^ative pjessiire of 23.5 mm. Hg (dog) in the in- terior of the ventricle during a certain ])hase of the heart's action. This they determined by a maximal and minimal manometer. They surmised that this phase coincided with the diastolic dilatation, for which they assumed a consideral^le power of aspiration. Moens is of o]iinion that this negative pressure within the ventricle obtains shortly before the systole has reached its heit^ht, i. ^., just before the inner surface of the ventricles and the valves, after the blood is ex- ]:)elled, are nearly in ap])osition. He explains this aspiration as being due to the formation of an empty space in the ventricle caused by the energetic expulsion of the blood through the aorta and pulmonary artery. Fig. 35. Fig ,,,..: of the 11 Irom be- Fig. 34. laximum and minimum manometer. [Maximum and Minimum Manometer. — Into the tube connecting the interior of the ventricle of the heart with the ordinary U-shaped mercury manometer, is introduced the maximum manome- PATHOLOGICAL CARDIAC ACTION. 101 • ter, which is constructed on the principle of a ball and cup valve (Fig. 34), the ball A being kept closed in B by a spring C. To make it a maximum manometer, the end A is connected with the heart, and B with the mercurial manometer (Fig. 35). When a clamp is placed on the upper limb the valve is acted on only at each systole of the heart, blood is driven beyond it, but during diastole it closes and no blood can return. This goes on until the pressure beyond the valve in the mercury manometer is the same as in the heart. If the valve be reversed, it is converted into a minimum manometer.] 49. PATHOLOGICAL CARDIAC ACTION.— Cardiac Hypertrophy.— All resistances to the movement of the blood through the various chambers of the heart, and through the vessels communicating with it, cause a greater amount of work to be thrown upon the portion of the heart specially related to this part of the circulatory system ; consequently, there is produced an increase in the thickness of the muscular walls and dilatation of the heart. If the resistance or obstacle does not act upon one part of the heart alone, but on parts lying in the omuard direction of the blood stream, these parts also subsequently undergo hypertrophy. If, in addition to the muscular thickening of a part of the heart, the cavity is simultaneously dilated, it is spoken of as eccentric hypertrophy or hypertrophy with dilatation. The obstacles most likely to occur in the blood vessels are narrowing of the lumen or want of elasticity in their walls ; in the heart, narrowing of the arterial or venous orifices or insufficiency or incompetency of the valves. Incompetencyof the valves forms an obstruction to the movement of the blood, by allowing part of the blood to flow back or regurgitate, thus throw- ing extra work upon the heart. Thus arise — (i) Hypertrophy of the left ventricle, owing to resistance in the area of the sys- temic circulation, especially in the arteries and capillaries — not in the veins. Among the causts are — constriction of the orifice or other parts of the aorta, calcification, atheroma, and want of elas- ticity of the large arteries and irregular dilatations or aneurisms in their course ; insufficiency of the aortic valves, in which case the same pressure always obtains within the ventricle and in the aorta ; and, lastly, cirrhosis of the kidneys, whereby the excretion of water by these organs is diminished. Even in mitral insufficiency, compensatory hypertrophy of the left ventricle must occur, owing 10 the hypertrophy of the left atrium in consequence of the increased blood pressure in the pulmonary circuit. (2) Hypertrophy of the left auricle occurs in stenosis or constriction of the left auriculo-ven- tricular orifice, or in insufficiency of the mitral valve, and it occurs also as a result of aoriic insufficiency, because the auricle has to overcome the continual aortic pressure within the ven- tricle. (3) Hypertrophy of the right ventricle occurs [a) when there is resistance to the blood stream through the pulmonary circuit. The resistance may be due to (a) obliteration of large vascular areas in consequence of destruction, shrinking or compression of the lungs, and the disappearance of numerous capillaries in emphysematous lungs; (/?) overfilling of the pulmonary circuit with blood in consequence of stenosis of the left auriculo-ventricular orifice, or mitral insufficiency — consequent upon hypertrophy of the left auricle resulting from aortic insufficiency, [b] When the valves of the pulmonary artery are insufficient, thus permitting the blood to flow back into the ven- tricle, so that the pressure within the pulmonary artery prevails within the right ventricle (very rare). (4) Hypertrophy of the right auricle occurs in consequence of the last-named condition, and also from stenosis of the tricuspid orifice, or insufficiency of the tricuspid valve (rare). Artificial Injury to the Valves. — If the aortic valves are perforated, with or without simultaneous injury to the mitral or tricuspid valves, the heart does more work; thus the physical defect is overcome for a time, so that the blood pressure does not fall. The heart seems to have a store of reserve energy which is called into play. Soon, however, dilatation takes place, on account of the regurgitation of the blood into the heart. Hypertrophy then occurs, but the compensation meanwhile must be obtained through the reserve energy of the heart [O. Rosenhacli). Impeded Diastole. — Among causes which hinder the diastole of the heart are — copious effusion into the pericardium, or the pressure of tumors upon the heart. The systole is greatly interfered with when the heart is united to the pericardium and to the connective tissue in the mediastinum. As a consequence the connective tissue, and even the thoracic wall, are drawn in during contraction of the heart, so that there is a retraction of the region of the apex beat during systole, and a protrusion of this part during the diastole. [Palpitation is a symptom indicating generally very rapid and quick action of the heart, the pulsations often being unequal in time and intensity, while the person is generally conscious of the irregularity of the cardiac action. It may be due to some organic condition of the heart itself, espe- cially where the cardiac muscles are weak, in cases of dilatation and hypertrophy of the left ventricle, where the heart is gradually becoming unable to overcome the resistances offered to its work, and especially during exertion when the heart is taxed above its strength. It may also occur where the blood pressure is low, as in anaemia, so that the heart contracts quickly, there being little resistance ooposed to its action. The excitability of the cardiac muscle may be increased, as in fatty heart, 102 THE CARDIOGRAM. • when very slight exertion may excite it often in a paroxysmal way. In other cases, it is nervous in its origin, l)eing either diect or reflex. In very emotional and excitable people (especially in women) it is easilv set up, and in some people it may be produced rellexly by gastric or intestinal irritation or dyspepsia. It also fre(iuently results from excesses of all kinds and the over-use of tobacco. The remedies to be used obviously depend on the cause. Where the blood pressure is low, as in anixMiiia, digitalis and iron will do good; the former by increasing the blood [iressure, and the latter i>y imjiroving the general nutrition of the body and the blood in particular. In neurotic cases cardiac sedatives are indicated, while in cases due to indigestion hydrocyanic acid is useful {Brun/on).^ [Fainting or Syncope. — In fainting, the person loses consciousness, owing to a sudden arrest of the biooti supjjly to the brain, the face is pallid, the respiration is feeiile or ceases, while the heart beats but feebly or not at all. The defective supply of blood to the brain may depend upon sudden arrest of the hearts action, caused, it may be, by a fright, or the heart's action may be arrested reflexly. Any cause which suddenly diminishes the blood pressure may produce it, or when jjressure is suddenly removed from the large vessels, as in tapping the abdomen in ascites, without at the same time giving sufticient support to the abdominal viscera. When a person has been long in the recumbent position, on being rapidly set up in bed he may faint. In some forms of heart liisease, sudden exertion or change of posture may produce it.] [Treatment. — The oiiject is to restore consciousness and the action of the heart. Place the person in the horizontal position, keep the head low, even lower than the body, and do not support it with pillows. Dashing cold water on the face, so as to stimulate the fifth nerve, usually succeeds in causing the person to take a deep inspiration. In other cases a snitf of smelling salts or am- monia, acting through the nasal branch of the fifth nerve, will excite the cardiac and respiratory functions (g 36S).] 50. THE APEX BEAT, CARDIOGRAM.— Cardiac Impulse.— By the term " apex beat " or " cardiac impulse " is understood, under normal circumstances, an elevation (perceptible to touch and sight) in a circumscribed area of the Ji/ih left intercostal space, and caused by the movement of the heart. [The apex beat is felt in the fifth left intercostal space, 2 inches below the nipple, and I inch to its sternal side, or at a point 2 inches to the left of the sternum.] The impulse is more rarely felt in the fourth intercostal space, and it is much less distinct when the heart beats against the fifth rib itself. The position and force of the cardiac impulse vary with changes in the position of the body. [The cardiac impulse is synchronous with the systole of the heart, but although this name and apex beat are frequently used as synonymous terms, it is to be remembered that the impulse may be caused by different parts of the heart being in contact with the chest wall. The cardiac impulse is usually higher than normal in children, while it is lower during inspiration than expira- tion.] [Methods. — To obtain a curve of the apex beat or a cardiogram, we may use one or other of the following cardiographs (Fig. 36). Fig. 36, A, is the first form used by Marey, and it consists of an oval wooden capsule applied in an air-tight manner over the apex beat. The disk, /, capable of being regulated by the screw, s, presses upon the region of the apex beat, while / is a tube which may be connected with a recording tambour (Fig. 47). B is an improved form of the instrument, consisting essentially of a tambour, while attached to the membrane is a button, /, to be applied over the apex beat. Tiie movements of the air within the capsule are com- municated by the tube, /, to a recording tambour. Fig. 36, C, is the pansphygmograph of Brondgeest, which consists of a Marey's tambour, in an iron horse-shoe frame, and adjustable Viy means of a screw, J. Burdon Sanderson's cardiograph is shown in D. The button, /, carried by the spring, e, does not rest upon the caoutchouc membrane, but on an aluminium plate attached to it. The apparatus is adjusted to the chest by three supports. Fig. 36, E, shows a modified instrument on the same principle, by Clrummach and v. Knoll. In all these figures the / indicates the exit tube communicating with a recording tambour (Fig. 47). D and E may be used for other purposes, e. i^., for the pidse, so that they are polygraphs. .See also Fig. 76.] Fig. 39, A, shows the cardiogram or the impulse curve of the heart of a healthy man ; B, that of a dog, obtained by means of a sphygmograph. In both the following points are to be noticed : ab, corresponds to the time of the pause and the contraction of the auricles. As the atria contract in the direction of the axis of the heart from the right and above toward the left and below, the apex of the heart moves toward the intercostal space. The two or three smaller elevations are perhaps caused by the contractions of the ends of the veins, the auricular appendices, and the atria themselves. THE CARDIOGRAM. 103 The portion be, which communicates the greatest impulse to the instrument, and also to one's hand when it is placed on the apex beat, is caused by the con- traction of the ventricles, and during it the first sound of the heart occurs. Fre- FiG. 36. Cardiographs. A, Marey's original form ; B, Marey's improved form ; C,pansphygmograph (Brondgeest) ; D, cardio- graph (Biirdon-Sanderson) ; E, that of v. Knoll. quently, but erroneously, the cardiac impulse has been ascribed to the contraction of the ventricles alone. It, however, is due to all those conditions which cause an elevation in the region of the cardiac impulse. [Edgren recorded a human cardiogram, and listened at the same time to the heart sounds, re- cording the latter by means of an electric signal. The curve rises at a, with the beginning of Fig. 37. Cardiogram, a-f: i, beginning of ist, and 2, 2d sound. the first sound, i. e., with the contraction of the ventricles, and reaches the abscissa at / with the beginning of the second sound, i.e., when the semilunar valves are closed. The relation between a and the points intermediate between it andy, and to the pulse curve of the carotid, is shown in Fig. 38. The letters with the dash correspond to the unmarked letters in the cardiogram.] 104 CAUSE OF THE CARDIAC IMPULSE. Fi( The cause of the ventricular impulse has been much discussed. It depends upon the following : — (i ) The base of the heart (auric- ulo-ventricular groove) represents during diastole a irausversely- placed ellipse (Fig. 40, I, FCi), while during contraction it has a more circular figure, ab. Thus, the long diameter of the ellipse (FG) is diminished, the small diameter dc is increased, while the base is brought nearer to the chest wall e. This alone does not cause the impulse, but the basis of the heart, being hardened during the systole and brought nearer to the chest wall, allows the apex to execute the movement which causes the impulse (p. 102). (2) During relaxation, the ventricle lies with its apex (Fig. 40, II, 0 obliquely The upper curve (n.ui the human carotid ; the lower a cardio- gram taken simultaneously. Y-.c. 39 Curves from the apex beat. A, normal curve (man) ; B, from a dog; C, very rapid curve (dog) ; Dand E, normal curves (man) registered on a vibrating glass plate where each indentation = 0.01613 sec. '" ^" '^^ curves ab means contraction of the auricles, and be of the ventricles ; d, closure of the aortic, and e, of the pulmonary valves ; ef, diastole of the ventricle. downward, and with its long axis in an oblitjue direction — so that the angles {bci, aci) formed by the axis of the ventricles with the diameter of the base are unequal CAUSE OF THE CARDIAC IMPULSE. 105 — during systole it represents a regular cone, with its axis at right angles to its base. Hence, the apex (/) must be erected from below and behind (/), forward and upward (Harvej — "cor sese erigere "), and when hardened during systole presses itself into the intercostal space (Fig. 40, II). (3) The ventricles undergo during systole a slight spiral twisting on their long axis (" lateralem inclinationem " — Harvey), so that the apex is brought from be- hind more forward, and thus a greater portion of the left ventricle is turned to the front. This rotation is caused by the muscular fibres of the ventricles, which proceed from that part of the fibrous rings between the auricles and ventricles which lies next the anterior thoracic wall. The fibres pass from above obliquely downward, and to the left, and also run in part upon the posterior surface of the ventricles. When they contract in the axis of their direction, they tend to Fig. 40. I. Schematic horizontal section through the heart, lungs, and thorax, to show the change of shape which the base ot the heart undergoes during contraction of the ventricle — F, G, transverse diameter of the ventricle during dias- tole; c, position of the thoracic wall : a, i^, transverse diameter of the heart during systole, with ^, position ot the anterior thoracic wall during systole. II. Side view of the heart — i, apex during diastole ; /, during systole. raise the apex, and also to bring more of the posterior surface of the heart in relation with the anterior thoracic wall. It is favored by the slightly spiral arrangement of the aorta and pulmonary artery. These are the most important causes, but the minor causes are — (4) The " reaction iniptilse " or " recoil,'" or that movement which the ventricles are said to undergo (like an exploded gun or rocket), at the moment when the blood is discharged into the aorta and pulmonary artery, whereby the apex goes in the opposite direction, i. e., downward and slightly outward. Landois, how- ever, has shown that the mass of blood is discharged into the vessels 0.08 of a second after the beginning of the systole, while the cardiac impulse occurs with the first sound. (5) When the blood is discharged into the aorta and pulmonary artery, these 106 CHANGE IN SHAPE OF HEART. vessels are slightly elongated, owing to the increased blood pressure. As the heart is suspended from above by these vessels, the apex is pressed slightly down- ward and forward toward the intercostal space (?). As the cardiac impulse is observed in the empty hearts of dead animals, (4) and (5) are certainly of only second rate importance. Filehne and Pentzoldt maintain that the apex during systole does not move to the left and downward, as must be the case in (4) and (5), but that it moves upward and to the riglit — a result corroborated by v. Ziemssen. [Harr attributes the cause of the impulse to the rigidity or hardening of the ventricle during systole, to the rotatory movement and lengthening downward of the blood column in the aorta and pulmonary artery, while toward the end of the systole the maximum of recoil takes place and also contributes to cause it.] It is to be remembered that as the apex is always applied to the chest wall, separated from it merely by the thin margin of the lung, it only presses against the intercostal space during systole (A'lWjr//). After the apex of the curve, c, has been reached at the end of the systole, the curve falls rapidly, as the ventricles quickly become relaxed. In the descending part of the curve, at ^/and e, are two elevations, which occur simultaneously with the second sound. These are caused by the sudden closure of the semilunar valves, whereby an impulse is propagated through the axis of the ventricle to its apex, and thus causes a vibration of the intercostal space ; (^/corresponds to the closure of the aortic valves, and e to the closure of the pulmonary valves. The closure of the valves in these two vessels is not simultaneous, but is separated by an interval of 0.05 to 0.09 sec. The aortic valves close sooner on account of the greater blood ])ressure there. Complete diastolic relaxation of the ventricle occurs from e iof in the curve. It is clear, then, that the cardiac impulse is caused chiefly by the contraction of the ventricles, while the auricular systole and the vibration caused by the closure of the semilunar valves are also concerned in its production. [Change in Shape of Heart. — The experiments of Ludwig and Hesse on the heart of the dog show that the shape of the ventricles varies remarkably in systole and diastole, and that the shape of the heart as found post-mortem is not its natural shape.] [Method. — Bleed a dog rapidly from the carotids, defibrinate the blood, expose the heart, tie graduated straight tubes into the pulmonary artery and aorta, and ligature the auricular vessels. I'our the blood into the heart until it is dilated under a pressure equal to the mean arterial pressure Fig. 41. Fig. 42. Fig. 43. Projection of a dog's heart. Anterior surface. Left lateral surface. Posterior surface. (150 mm.). The ventricles are in the diastolic phase, the auricles still pulsate. A plaster cast is now rapidly made of the ventricles. This represents the diastolic phase. To obtain what may be regarded as the systolic phase, a heart, similarly prepared but emptied of blood, is suddenly plunged into a hot (50° C.) saturated solution of potassic bichromate, when the heart gives one rapid and final contraction and remains permanently contracted, owing to the heat rigor, its proteids being coagulated [\ 295). This is the systolic phase. Little pins with twisted points are previously inserted in the organ to mark certain parts of both hearts for comparison.] [In diastole, the shape of the ventricle is hemispheroidal, the apex being rounded, while the posterior surface is flatter than the anterior (Fig. 41). In the plane of THE TIME OF THE CARDIAC MOVEMENTS. 107 the ventricular base, the greatest diameter is from right to left, and the shortest from base to apex. The conus arteriosus is above the plane of the base. During systole, the apex is more pointed, the ventricle more conical, while all the diameters in the plane of the base are equally diminished, hence the vertical measurement from base to apex is longer now than either of the diameters at the base (Fig. 43). The conus arteriosus sinks toward the plane of the base, while the base of the ventricle becomes more circular, so that the difference of the curvatures of the anterior and posterior surfaces van- ishes (Fig. 42). In all these figures Fig. 44. Fia45. the shaded part represents diastole and the clear part systole. The most remarkable point is that the vertical measurement remains unchanged. This refers to the left ventricle, which of course forms the apex; the right is shortened. The plane of the ven- tricular base in systole is about one- half of what it is in diastole, as is „!,„ „ ,■„ T?,'™ . . T'U.,^ i-U^ V.^^^*- ,'r. Projection of the base in sys- A, aorta; PA, pulmonary shown m Fig. 44. i huS the heart is •'tole and diastole. RV, artery; M, mitral, and diminished in all its diameters except right, and lv, left ventri- t, tricuspid orifice. one, the arterial orifices are scarcely affected, while the area of the auriculo-ventricular orifices (M, T) is diminished about one-half (Fig. 45). This is most important in connection with the closure of the auriculo-ventricular valves ; as it shows that the muscular fibres of the heart, by diminishing these orifices during systole, greatly aid in the perfect closure of these valves. Thus we explain why defective nutrition of the cardiac muscle may give rise to incompetency of these valves, without the valves themselves being diseased {Macalisier).'] [In order to account for the vertical diameter remaining unchanged, we may represent the ventricular fibres as consisting of three layers, viz., an inner and outer set, more or less longitudinal, and a middle set, circular. Both sets will tend, when they contract, to diminish the cavity, but the shortening of the longi- tudinal layers is compensated for by the contraction, t. e., the elongation produced by the circular set.] [In order to obtain the shape of the cavities, dogs were taken of the same litter and as nearly alike as possible. One heart was filled with blood, as already described, and placed in a cool solution of potassic bichromate, whereby it was slowly hardened in the diastolic form, while the other was plunged, as before, into a hot solution. Casts were then made of the cavities.] 51. THE TIME OF THE CARDIAC MOVEMENTS.— Methods.— The time occupied by the various phases of the move)?ienls of the heart may be determined by studying the apex beat curve. (i) If we know at what rate the plate on which the curve was obtained moved during the experiment, of course all that is necessary is to measure the distance, and so calculate the time occupied by any event (see Pulse, | 67). (2) It is preferable, however, to cause a tuning fork, whose rate of vibration is known, to write its vibrations under the curve of the apex beat, or the curve may be written upon a plate attached to a vibrating tuning fork (Fig. 39, D, E). Such a curve contains fine teeth caused by the vibrations of the tuning fork. D and E are curves obtained from the cardiac impulse in this way from healthy students. In D the notch d is not indicated. Each complete vibration of the tuning fork, reckoned from apex to apex of the teeth = 0.01613 second, so that it is simply necessary to count the number of teeth and multiply to obtain the time. The values obtained vary within certain limits even in health. The value oi a b ^= pause + contraction of the auricles, is subject to the greatest variation, and depends chiefly upon the number of heart beats per minute. The more quickly the heart beats, the shorter is the pause, and conversely. In some curves, even when the heart beats slowly, it is scarcely possible to distinguish 108 THE TIME OF THE CARDIAC MOVEMENTS. the auricular contraction (indicated by a rise) from the ])art of the curve corres- ponding to the pause (indicated by a horizontal line). In one case (heart beats 55 per minute) the pause = 0.4 second, the auricular contraction = 0.177 second, in Fig. 39, A, the time occupied by the pause -f- the auricular contraction (74 beats per minute) = 0.5 second. In D, a />:^ 19 to 20 vibrations^ 0.32 second ; in E = 26 vibrations = 0.42 second. The ventricular systole is calculated from the beginning of the ( ontraction d, to e wiien the semilunar valves are closed ; it lasts from the first to the second sound. It also varies somewhat, but is more constant. Wlien the heart beats rapidly, it is somewhat shorter — during slow action longer. In E = 0.32 second ; in D =: 0.29 second ; with 55 beats per minute Landois found it = 0.34, with a very high rate of beating = 0.199 second. When the ventricles beat feebly, they contract more slowly, as can be shown by applying the registering apparatus to the heart of an animal just killed. In Fig. 46, from the ventricle of a rabbit just killed, the slow heart beats, B, are seen to last longest. In cases of enormous hypertrophy and dilatation of the left ventricle, the duration of the ventricular systole is not longer than normal (Z(7«./M.f). In calculating the lime occupied by the ventricular systole we must remember — (i) T/te time between the two sounds of the heart, i. e., from the beginning of the first to the end of the second sound [/> to e). (2) T/ie time the blood flows into the aorta, which comes to an end at the depression between c and d (in Fig. 39, E). Its commencement, however, does not coincide with b, as the aortic valves open 0.085 to 0.073 second after the beginning of the ventricular systole. Hence the aortic current lasts 0.08 to 0.09 second. This is calculated in the following way : The time between Fig. 46. Curves recorded by the ventricle of a rabbit, upon a vil)ratinf; plate attached to a tuning fork (vibration = 0.01613 sec). A, soon after death ; B, from the dying ventricle. the first sound of the heart and the pulse in the axillary artery is 0.137 second, and of this time 0.052 second is occupied in the propagation of the pulse wave along the 30 cm. of artery lying betsveen the root of the aorta and the axilla. Thus the pulse wave in the aorta occurs 0.137 minus 0.052 = 0.085 second after the beginning of the first sound. The current in the pulmonary artery is inter- rupted in the depression between d and e. (3) Lastly, the time occupied by the muscular contraction of the ventricle, which begins at /', reaches its greatest extent at c, and is completely relaxed at f. The apex of the curve, c) is feelile because the ventricle is imperfectly fdicd. The ciosufes of the two valves, c, ventricular sysKilc : d, closure of aortic, and ,-, of pulmonary valves ; e/, diastole of ventricle : P, y, hypertroi)hy and dilatation of the left ventricle; E, stenosis of the aortic orifice; K, mitral insufficiency; G, mitral stenosis; L, nervous palpitation in Ba.sedow's disease; M, so-called hemisystole. being overdistended, while the left is nearly empty, so that the right side requires to contract more energetically than the left. It does not seem that the right ventricle alone contracts in these cases, but rather that the action of the left side is very feeble. 53. THE HEART SOUNDS.— On listening over the region of the heart in a healthy man, either with the ear applied directly to the chest wall {Harvey), or by means of a stethoscope {Laennec, 1819), we hear two characteristic sounds, the so-called "heart sounds," The two sounds are called first and second, and together they correspond to a single cardiac cycle. These sounds are separated by silences. [Fig. 50 shows the relation of the events occurring in the heart during a cardiac cycle to the sounds and silences.] 1. The first sound. 2. The first or short silence. 3. The second sound. 4. The second or long silence. [Relative Duration, — There is no absolute duration of each phase of a cardiac cycle, but we may take the aver- Scheme of a canliac cycle. The inner circle shows what events occur in the heart, and the outer, the relation of the sounds and silences to these events. CAUSES OF THE HEART SOUNDS. 113 age duration calculated from the measurements of Gibson, in a case of fissure of the sternum, to be as follows : — Auricular systole, 112 sec. Ventricular systole, 368 " Ventricular diastole, • 57^ " Cardiac cycle, 1.058 sec. Suppose we divide the cycle into tenths ( Walshe), then the first sound will last ^, the first silence -^y the second sound -^, and the long silence -^ of the entire period.] The first sound [long or systolic] is twice as long as, somewhat duller, and one-third or one-fourth deeper than, the second sound ; it is less sharply defined at first, and is synchronous with the systole of the ventricles. The second sound [short or diastolic] is clearer, sharper, shorter, more sud- den, and is one-third to one-fourth higher; it is sharply defined and synchronous with the closure of the semilunar valves. The sounds emitted during each cardiac cycle have been compared to the pronunciation of the syllables lubb, dUp. Or the result may be expressed thus — to lili^^^^^ ^ Bu - tup. Bu - tap. [It is to be remembered that in reality four sounds are produced in the heart, but the two first sounds occur together and the two second, so that only a single first and a single second sound are heard.] The causes of the first sound are due to two conditions. As the sound is heard, although enfeebled, in an excised heart in which the movements of the valves are arrested, and also when the finger is introduced into the auriculo-ven- tricular orifices so as to prevent the closure of the valves (C. Ludwig and Dogiel), one of the chief factors lies in the ^'muscle sound '^ produced by the contracting muscular fibres of the ventricles. This sound is supported and increased by the sound produced by the tension and vibration of the auriculo-ventricular valves and their chordae tendinese, at the moment of the ventricular systole. Wintrich, by means of proper resonators, has analyzed the first sound and distinguished the clear, short, valvular part from the deep, long, muscular sound. The muscle sound" produced by transversly striped muscle does not occur with a si?nple contrac- tion (p. 127), but only when several contractions are superposed to produce tetanus (§ 303). The ventricular contraction is only a simple contraction, but it lasts considerably longer than the contrac- tion of other muscles, and herein lies the cause of the occurrence of the muscle sound during the ventricular contraction. Defective Heart Sounds. — In certain conditions (typhus, fatty degeneration of the heart),, where the muscular substance of the heart is much weakened, the first sound may be completely inaudible. In aortic insufficiency, in consequence of the reflux of blood from the aorta into the ventricle, the mitral valve is gradually stretched, and sometimes even before the beginning of the ventricular systole, the first sound may be absent. Such pathological conditions seem to show that> for the production of the first sound, muscle sound and valve sound must eventually work together^ and that the tone is altered, or may even disappear, when one of these causes is absent. [Yeo and Barrett state that the sound is purely muscular (?).] The cause of the second sound is undoubtedly due to the prompt closure, and therefore sudden stretching or tension, of the semilunar valves of the aorta and pulmonary artery, so that it is purely a valvular sound. Perhaps it is aug- mented by the sudden vibration of the fluid particles in the large arterial trunks. [The second sound has all the characters of a valvular sound. That the aortic 8 114 VARIATIONS OF THE HEART SOUNDS. valves are concerned in its production, is proved by introducing a curved wire through the left carotid artery and hooking up one or more segments of the valve, when the sound is modified, and it may disappear or be replaced by an abnormal sound or " murmur." Again, when these valves are diseased, the sound is altered, and it may be accompanied or even displaced by murmurs.] Although the aortic and pulmonary valves do not close simultaneously, usually the difference in time is so small that both valves make one sound, but the second sound may be double or divided when, through increase of the difference of pressure in the aorta and pulmonary artery, the interval becomes longer. Even in health this may be the case, as occurs at the end of inspiration or the beginning of expira- tion yv. Dusch). Where the Sounds are Heard Loudest. — The sound produced by the tricuspid valvr is heard loudest at the junction of the lower right costal cartilages with the sternum ; as the mitral valve lies more to the left and deeper in the chest, and is covered in front by the arterial orifice, the mitral sound is best heard at the apex beat, or immediately above it, where a strip of the left ventricle lies next the chest wall. [The sound is conducted to the part nearest the ear of the listener by the muscular substance of the heart.] The aortic and pulmonary orifices lie so close together that it is convenient to listen for the second {aortic) sound in the direction of the aorta, where it comes nearest to the surface, i.e., over the second right costal cartilage or aortic cartilage close to its junction with the sternum. The sound, although produced at the semilunar valves, is carried upward by the column of blood and by the walls of the aorta. The sound produced by the pulmonary artery is heard most distinctly over the third left costal cartilage, somewhat to the left and external to the margin of the sternum (Fig. 50- 54. VARIATIONS OF THE HEART SOUNDS.— Increase of the first sound of both ventricles indicates a more energetic contraction of the ventricles and a simultaneously greater and more sudden tension of the auriculo-ventricular valves. Increase of the second sound is a sign of increased tension in the interior of the corresponding large arteries. Hence increase of the second (pulmonary) sound indicates overfilling and excessive tension in the pulmonary circuit. A feeble action of the heart, as well as abnormal want of blood in the heart, causes weak heart sounds, which is the case in degenerations of the heart muscle. Irregularities in structure of the individual valves may cause the heart sounds to become " im- pure." If a pathological cavity, filled with air, be so placed, and of such a form as to act as a resonator to the heart sounds, they may assume a "metallic" character. The first and second sounds may be " reduplicated " or [although " duplication " is a more accurate term [Barry\ doubled. The reduplication of the first sound is explained by the tension of the tricuspid and that of the mitral valves not occurring simultaneously. Sometimes in disease a sound is produced by a hypertrophied auricle producing an audible presystolic sound, /. e., a sound or " murmur " pre- ceding the first sound. [This has been questioned quite recently.] As the aortic and pulmonary valves do not close quite simultaneously, a reduplicated second sotind\?, only an increase of a physio- logical condition. All conditions which cause the aortic valves to close rapidly (diminished amount of blood in the left ventricle) and the pulmonary valves to close later (congestion of the right ventricle — both conditions together in mitral stenosis), favor the production of a reduplicated second sound. Cardiac Murmurs. — If irregularities occur in the valves, either in cases of stenosis or in insuf- ficiency, so that the blood is subjected to vibratory oscillations and friction, then, instead of the heart sounds, other sounds — murmurs or bruits — arise or accompany these. A combination of these sounds is always accompanied by disturbances of the circulation. [These murmurs may be produced within the heart, when they are termed endocardial ; or outside it, when they are called exocardial murmurs. But other murmurs are due to changes in the quality or amount of the blood, when they are spoken of ashaemic murmurs. In the study of all murmurs, note their rhythm or exact relation to the normal sounds, \k\€\i point of »iaxi»iiim intensity, and the direction in which the tnurniur is propagated.'] It is rare that tumors or other deposits projecting into the ventricles cause murmurs, unless there be present at the same time lesions of the valves and disturbances of the circulation. The cardiac murmurs are always related to the systole or diastole, and usually the systolic are more accentuated and louder. Sometimes they are so loud that the thorax trembles under their irregular oscillations {fremitus, fr^missement cataire). In cases where diastolic murmurs are heard, there are always anatomical changes in the car- VARIATIONS OF THE HEART SOUNDS. 115 diac mechanism. These are insufficiency of the arterial valves, or stenosis of the auriculo -ventricu- lar orifice (usually the left). Systolic murmurs do not always necessitate a disturbance in the cardiac mechanism. They may occur on the left side, owing to insufficiency of the mitral valve, stenosis of the aorta, and in the calcification and dilatation of the ascending part of the aorta. These murmurs occur very much less frequently on the right side, and are due to insufficiency of the tricuspid and stenosis of the pulmonary orifice. Fig. 51, The heart — its several parts and great vessels in relation to the front of the thorax. The lungs are collapsed to their normal extent, as after death, exposing the heart. The outlines of the several parts of the heart are indi- cated by very fine dotted lines. The area of propagation of valvular murmurs is marked out by more visible dotted lines. A, the circle of mitral murmur, corresponds to the left apex. The broad and somewhat diffused area, roughly triangular, is the region of tricuspid murmurs, and corresponds generally with the right ventricle, where it is least covered by lung. The letter C is in its centre. The circumscribed circular area, D, is the part over which the pulmonic arterial murmurs are commonly heard loudest. In many cases it is an inch, or even more, lower down, corresponding to the conus arteriosus of the right ventricle, where it touches the wall of the thorax. The internal organs and parts of organs are indicated by letters as follows : — r. au, right auricle, traced in fine dotting ; ao, arch of aorta, seen in the first intercostal space, and traced in fine dotting on the sternum ; V. i., the two innominate veins ; r. v., right ventricle ; I. v., left ventricle. Functional Murmurs. — Systolic murmurs often occur without any valvular lesion, although they are always less loud, and are caused by abnormal vibrations of the valves or arterial walls. They occur most frequently at the orifice of the pulmonary artery [and are generally heard at the base], less frequently at the mitral, and still less frequently at the aortic or the tricuspid orifice. Ansemia, general malnutrition, acute febrile affections, are the causes of these murmurs. [Some of 116 DURATION OF THE MOVEMENTS OF THE HEART. Fig. 52. these are due to an altered condition of the blood, and are called hsemic, and others to defective" cardiac muscular nutrition, and are called dynamic {lV(i/s/ic).'\ Sounds may also occur during a certain stage of inflammation of the pericardium (pericarditis) from the roughened surfaces of this membrane rubbing upon each other. Audible friction sounds are thus produced, and the vibration may even be perceptible to toucli. [These are " friction sounds," and quite distinct from sounds produced within the heart itself.] 55. DURATION OF THE MOVEMENTS OF THE HEART.— The heart continues to beat for some time after it is cut out of the body. The movement lasts longer in cold- blooded animals (frog, turtle) — extend- ing even to days — than in mammals. A rabbit's heart beats from 3 minutes up to 36 minutes after it is cut out of the body. The average of many experi- ments is about II minutes. [Waller and Reid recorded the ventricular con- tractions of a rabbit's heart 72 minutes after its excision. Fig. 52 shows the prolongation of the ventricular systole Curves of excised r.-ibbit's heart, i, 6 mins. after excision ; in an cxcised rabbit's heart, the move- 2, lo mins : 3, 20 mins. ; 4. 7° m'ns. (After iVaiier j^gnts being recordcd by a Icver resting and Retd.) 1 n -n, r 1 on the heart. J Panum found the last trace of contraction to occur in the right auricle (rabbit) 15 hours after death ; in a mouse's heart, 46 hours ; in a dog's, 96 hours. An excised frog's heart beats, at the longest, 2^ days {Valentin). In a human embryo (third month) the heart was found beating after 4 hours. In this condition stimulation causes an increase and acceleration of the action. The ventricular contraction weakens, and soon each auricular contraction is not followed by a ventricular contraction, two or more of the former being succeeded by only one of the latter. At the same time the ventricles contract more slowly (Fig. 46), and soon stop altogether, while the auricles continue to beat. If the ventricles be stimulated directly, as by pricking them with a pin, they may execute a contraction. The left auricle soon ceases to beat, while the right auricle still continues to contract. The right auricular ap- pendix continues to beat longest, as was observed by Galen and Cardanus (1550), and it is termed " ultimum moriens." Similar observations have been made upon the hearts of persons who have been executed. If the heart has ceased to beat, it may be excited to contract for a short time by direct stimulation, more especially by heat (^Harvey) ; even under these cir- cumstances the auricles and their appendices are the last parts to cease contracting. As a general rule, direct stimulation, although it may cause the heart to act more vigorously for a short time, brings it to rest sooner. In such cases, therefore, the regular sequence of events ceases, and there is usually a twitching movement of the muscular fibres of the heart. C. Ludwig found that, even after the excitability is extinguished in the mammalian heart, it may be restored by injecting arterial blood into the coronary arteries ; conversely lesion of these vessels is followed by enfeebled action of the heart (§ 47). Hammer found that in a man whose left coronary artery was plugged the pulse fell from 80 to 8 beats per minute. [The beats of the excised heart of a rabbit gradually decline in force and frequency, the latent period and contraction become longer and the excitability more obtuse. The duration of a con- traction may be 6 sec, the normal being .3 sec. The beats have often a bigeminal character. An excised heart may be frozen quite hard, yet on being thawed it contracts spontaneously. The con- traction proceeds in a wave from the spot stimulated in the frog's heart at 8° to 12° C. at 30 to 90 mm. per sec. ; in the mammalian excised heart about 8 metres per sec. ( Waller and Iieid)J] Action of Gases on the Heart. — During its activity the heart uses O, and produces COj, so that it beats longest in pure O (12 hours), and not so long in N, — H (i hour) — CO, (10 minutes) INNERVATION OF THE HEART. 117 — CO (42 minutes) — CI (2 minutes), or in a vacuum (20 to 30 minutes), even when there is watery- vapor present to prevent evaporation. If the heart be reintroduced iato O it begins to beat again. [A frog's heart ceases to beat in compressed O (10 to 12 atmospheres) in about one-third of the time it would do were it simply excised and left to itself. An excised heart suspended in ordinary air beats three to four times as long as a heart which is placed upon a glass plate.] [56. PHYSICAL EXAMINATION OF THE HEART.— The phy- sical methods of diagnosis enable us to obtain precise knowledge regarding the actual state of the heart. The methods available are : — 1. Inspection. 2. Palpation. 3. Percussion. 4. Auscultation. To arrive at a correct diagnosis all the methods must be employed.] [Inspection. — The person is supposed to have his chest exposed and to be in the recumbent position. It is important to remember the limits of the heart. The base corresponds to a line joining the upper margins of the third costal cartilages, the apex to the fifth interspace, while transversely it extends from a little to the right of the sternum to within a little of the left nipple ; this area occupied by the heart being called the deep cardiac region. By the eye we can detect any alteration in the configuration of the prsecordia, bulging or retraction of the region as a whole or of the intercostal spaces, and we may detect variations in the position, character, extent of the cardiac impulse, or the presence of other visible pulsations.] [Palpation. — By placing the whole hand flat upon the prsecordia, we can ascertain the presence or absence, the situation and extent, and any alterations in the characters of the apex beat ; or we may detect the existence of abnormal pulsations, vibrations, thrills, or friction in this region. In feeling for the apex beat, if it be at all feeble, it is well to make the patient lean forward. Of course, it must be remembered that the whole heart may be displaced by tumors or accumulations of fluids pressing upon it, i. Jj, right and left auricles ; /}/, communication between the right and left auricle. opens into the singte ventricle (Fig. 53, zi), 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. The various orifices are guarded by projec- tioiis of tissue, which act like valves. The two auricles are completely separated by a septum. This septum ends posteriorly in a free concave margin 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.] MOTOR CENTRES OF THE HEART. 119 [Nerves. — The two cardiac branches of the vagi — the nervi cardiaci — proceed to the posterior surface of the sinus venosus, and where the latter joins the auricle they interlace, and are mixed with a number of ganglion cells (Fig. 57). This spot is called Remak's ganglion, is sometimes 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. 54). The cardiac nerves proceed downward on the auricular septum, Fig. 55. Fig. 56. Auricular septum of a frog's heart, a, anterior, and/, posterior branch of the cardiac vagus ; B, Bidder's ganglion. Pyriform ganglionic bi-polar nerve cell from the heart of a frog. »z, sheath ; «, straight process ; o, spiral process. exchanging fibres in their course to join two ganglia at the auriculo-ventricular groove, and known as Bidder's ganglia (Fig. 57). 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-medul- lated fibre, a tri-radiate nucleus exists which gives off fibrils to the muscular bundles. There is a Fig. 58. B.A Scheme of nerves of frog's heart. R. Remak's, and B. Bidder's ganglia ; S.V., sinus venosus ; A, auricles ; V, ventricle; B.A. , bulbus arterio- sus ; z'ag; vagi. Stannius's experiment. A, auricle; V, ventricle; S.V., sinus venosus. The zig-zag lines indicate which parts con- tinue to beat ; in 2 the ventricle beats at a different rate. 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 endocardial muscles. The parietal layer of the pericardium contains (sensory) nerve fibres. The following kinds of nerve cells are found — unipolar cells, the single processes of which afterward divide ; bipolar pyri- form cells (Fig. 56), which in the frog possess a straight («) and usually also a spiral process {0). 58. THE AUTOMATIC MOTOR CENTRES OF THE HEART.— (i) It is generally assumed that the nervous centres which excite the cardiac movements, 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, 120 MOTOR CENTRES OF THE HEART. all its parts move in rhythmical sequence from a principal central point, an impulse being conducted from this centre through the conducting paths. What the "dis- charging forces" of these regular progressive movements are, is unknown. If, however, the heart be subjected to the action of diffuse stimuli {e.g., strong elec- trical currents), all the centres are thrown into action, and a spasm-like action of the heart occurs. The dotninating centre lies in the an fides, hence the regular pro- gressive movement usually starts from them. If the excitability is diminished, as by touching the septum with opium, other centres seem to undertake this function, in which case the movement may extent from the ventricles to the auricles. Ac- cording to Kronecker and Schmey, in the do^ s heart there is a spot above the lower limit of the upper third of the ventricular septum, which, when it is injured, e.g., by destroying it with a stout needle, brings the heart to a standstill ; this has been called a coordinating 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) Single very weak stimuli, which have no effect on the heart when applied singly, if repeated sufficiently often, may become active, owing to " summation of the stimuli " {v. Basch). (5) Even the weakest stimulus which can excite a contraction always causes an energetic contraction, /. » --— » — • After the heart is fixed by the clamp, 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 efifect of the vagus and other nerves upon the heart.] (3) Section. — \. Pick showed that the process of excitement in the con- tractile tissue of the frog's heart is propagated in all directions (1874), so that to a certain extent the whole frog's heart behaves like one continuous muscular fibre ; thus one transverse cut into the ventricle does not prevent contraction from taking place in the separated parts. Engelmann's experiments also 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 15 mm. per sec. Hence, it appears that the conducting paths for 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. [.\ccording 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 ex- citement 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 appara- tus. In fact, in the mammalian heart the muscular fibres of the auricles are quite distinct from those of the ventricles.] (4) When the apex of a frog's heart is ligatured off from the rest of the heart, it no longer pulsates {Heidenhain, Goltz), but such an apex, if stimulated directly, e. g., by a prick of a pin, responds with a single contraction. If the "heart apex" be filled with normal saline solution under pressure, which acts as a stimulus, the heart begins to pulsate, and the same is the case with a solution of delphinin or quinine. If a cannula be tied into the heart over the auriculo-ventricular groove, the ventricle does not beat, but if the ventricle be filled through the cannula with blood containing oxygen, under a constant and sufficient pressure, it also pulsates {Ludwig and Alerurioiuicz). (5) Luciani found that a heart ligatured above the auriculo-ventricular groove, when filled with pure serum, produced groups of pulsations with a long diastolic pause between every two groups (Fig. 59). The successive beats in each group assume a "staircase " character (p. 126). 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 defibrin- ated blood or serum containing hemoglobin or normal saline solution is used {Rossbach). They also occur when the blood within the heart has become dark- colored, /, 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.] ACTION OF FLUIDS ON THE HEART. 123 (6) 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 rhytJunically. This is an important fact in connection with any theory of the cardiac beat.] Fig. 59. Four groups of pulsations with intervening pauses, with their " staircase" character. were marked every 10 seconds. The points on the abscissa Fig. 60. (7) If the bulbus aortae (frog) be ligatured, it still pulsates, provided the inter- nal pressure be moderate. Should it cease to beat, a single stimulus makes it respond by a series of contractions. Increase of temperature to 35° C, and rais- ing the pressure within it, increase the number of pulsations {Engelmanti). Action of Fluids. — 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. 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. [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 (Fig. 60) consists of (i) a double. way cannula, c, which is tied into the heart, h ; (2) a manometer, ?ii, 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; ^is a glass vessel for fluid, in which the heart pulsates, e^ and e are electrodes, e is inserted into the fluid in d, e' is attached to the German silver cannula which is shown in Fig. 6r.] [In the tonometer of Roy (Fig. 62) the ventricle, h, or the whole heart, is placed in an air-tight chamber, o, filled with oil. Asbefore, 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, 0. When the ventricle contracts, it becomes smaller, diminishes the pres- sure within 0, and hence the piston and lever rise ; con- versely, 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 Scheme of a trog manometer, a, b, Mari- it.l ott-'s flasks for the nutrient tiuids ; s, [Two preparations of the frog's heart have been used— stop-cock; c, cannula; .« manometer; I hysiologically 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 Fig. 61. Fig. 62. K \i ^ d ^ Periusiun c.inmila for a frog's heart. C, for fixing an electrode; rf, the heart is tied over the flanges, preventing it from slipping out ; f, section of d. Roy's heart tonometer, /t, heart ; o, air-tight chamber ; />, piston ; /, writing lever ; e, outflow tube. 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 im- portant factor in the causation of the spontaneous beats of the apex. If blood serum, to which a trace of delphinin is added, be transfused or "/>er/iised" through the heart, it begins to beat within a minute, continues to beat for several seconds, and then stands still in diastole [Bo^vditch). Quinine and a mixture of atropine and muscarin have a similar action. These experiments show \.hzi, prozided no nervom apparatus exists 7uithin the heart apex, the cause of the varying contrac- tion is to be sought for in the musculature of the heart, and that the stimulus necessary for the systole of the heart's apex may arise within itself. If there is no nervous apparatus of any kind present, then we must assume that the heart muscle may execute rhythmical movements independently of the presence of any nervous mechanism, although it is usually assumed that the ganglia excite the heart muscle to pulsate rhythmically. It is by no means de/uiite/y proved Xhai 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 adds 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, ACTION OF MECHANICAL AND ELECTRICAL STIMULI. 125 barium, and veratria act like alkalies, while saponin, muscarin, and pilocarpin have the effect of acids (^ 65). An isolated frog's heart, fatigued after being supplied with a solution of blood, is caused to beat more vigorously by a solution of kreatinin, or extract of meat (Mays).'] [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. 120).] 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 fre- quency and the amplitude of the pulsations, as well as the duration of the systole and diastole and the excitability of the heart.] Descartes (1644) observed that heat increases the number of pulsations of an eel's heart. As the temperature increases, the number of beats is at first considerably increased, but afterward the beats again become fewer, and if the tempera- ture is raised above a certain limit the heart stands still, the myosin of which its fibres consist is coagulated, and " heat rigor" occurs. Even before this stage is reached, however, the heart may stand still, the muscular fibres appearing to re- main contracted. The ventricles usually cease to beat before the auricles [Sckelske). The size and extent oi the contractions increase up to about 20° C, but above this point they diminish (Fig. 63). The time occupied by any single contraction at 20° C. is only about -^^ of the time occupied by a contraction occur- A, contractions of a frog's heart at 19° C. ; B, at 34° C. ; C, at 3° C. ring at 5° C. A heart which has been warmed is capable of reacting pretty rapidly to intermittent stimuli, while a heart at a low temperature reacts only to stimuli occurring at a considerable interval [Gaule). Cold. — When the temperature of the blood is diminished, the heart beats more slowly. A frog's heart, placed between two watch glasses and laid on ice, beats very much more slowly. The pul- sations of a frog's heart stop when the heart is exposed to a temperature of 4° C. to 0°. 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). [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.] {b) Mechanical Stimuli. — Pressure applied to the heart from without 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. 124). If the pressure within the heart be increased, the heart beats are gradually increased, if it be diminished the number of beats diminishes (Ludzvig and Tkiry'). If the intra- cardiac pressure be very greatly increased, the heart's action becomes very irregular and slower. A heart which has ceased to Ijeat may, under certain circumstances, be caused to execute a sitigle contraction if it be stimulated mechanically. {c) Electrical Stimuli. — A constant electrical current of moderate strength increases the number of heart beats. V. Ziemssen found, in the case of Frau Serafin (§ 47, 3), that the number 126 ACTION OF CHEMICAL STIMULI. of beats was doubled when a constant uninterrupted strong current was passed through the ventri- cles. If the constant current be very strong, or if tetanizing induction currents be used, the cardiac muscle assumes a condition resembling, but not iilentical with, tetanus {Ludwi;^ and Hoffa), and, of course, this results in a fall of the blood pressure. If the auriculo-ventricular groove be compressed so as to cause the ventricle of a frog's heart to cease to beat, on placing one electrode of a constant current on the ventricular wall and the other electrode on an indifferent part of the body, we obtain, on making the current, a systolic contraction of the ventricle only when the cathode touches the ventricle ; and conversely on breaking, only when the anode is on the heart [Biedermatin). When a single induction shock is applied to the ventricle of a frog's heart during systole, it has no apparent etTect ; but if it is applied during diastole, the succeeding contraction takes place sooner. The auricles and also the apex 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. Even when strong tetanizing induction shocks are applied to the heart, they do not produce ietantix of the entire cardiac musculature, or as it is said, "the heart knows no tetanus " {A'ronecl-er and Slirlin>^). Small, white, local, wheal-like elevations — 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 i^Bowdilch). [Break 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 contract, always cause a maximal contraction, so that a minimal stimulus acts at the same time like a ma^^i- mal stimulus. The heart either contracts or it does not contract, and when it contracts, the result is always a "maximal" contraction [Kronecker and S(i?-iini;). Bowditch found that the excita- bility 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 was produced (Fig. 59). Under certain circumstances, however, a skeletal muscle gives contractions of a "staircase" character. 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. 122). 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 con- traction, 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 ampli- tude of the contraction bears a relation to the stimulus, while in the heart the contraction is always maxt>naL'\ Human Heart. — V. Ziemssen found that he could not alter the heart beats of the human heart {Fran 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. The normal pulse rate of 80 was reduced to 60 and 50 when the number of shocks was reduced in the .same ratio. [In Frau Serafin's case the electrodes 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. Herbst and Dixon Mann obtained negative results with both kinds of electricity in the normal thorax.] [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 and bile salts diminish the heart beats (also when they are absorbed into the blood, as in jaundice) ; in very dilute solutions both increase the heart beats. A similar result is produced by acetic, tartaric, citric, and phosphoric acids. Chloroform and ether, applied to the inner surface, rapidly diminish the heart beats, and then paralyze it; but very small quantities of ether (i per cent.) accelerate the heart beat of the frog {Kronecker and M' Gregor- Robertson), while a solution of l^ to 2 per cent, passed through the heart arrests it temporarily or completely. Dilute solutions of opium, strychnia, or alcohol applied to the endocardium, increase the heart beats; if concentrated they rapidly'arrest its action. Chloral hydrate paralyzes the heart. NATURE OF A CARDIAC CONTRACTION. 127 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 COj paralyzes it, and the presence of COj is more injurious than the want of O. Blood or serum completely saturated with CO2 exhausts the heart {Saltei and Kronecker), but it recovers itself when the CO, is removed. H and N have no effect.] Cardiac Poisons are those substances whose action is characterized by special effects upon the movements of the heart. Among these are neutral potash salts, which cause the heart to stand 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. 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 fiiuscular 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 cotmected with the atitoi?iatic ganglia by conducting channels. Muscarin and all other trimethylammonium bases stimulate permanently the inhibitory ganglia, so that the heart stands still {Schmiedeberg atid Koppe). [According to Gaskell, however, when the action of the sinus is arrested by muscarin, there is no deflection of the galvanometer similar to that produced by the excitation of the vagus. He infers that muscarin does not cause arrest of the beat by acting as an excitant of inhibitory mechanisms, but as a depressant to motor activity.] As atropin and daturin paralyze these ganglia, the standstill of the heart brought about by muscarin rnay 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 withir^ 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.] Physostigmin or Calabar bean excites the energy of the cardiac muscle to such an extent, that stimulation of the vagus no longer causes the heart to stand still. lodine-aldehyd, chloroform, and chloral hydrate paralyze the automatic ganglia. The heart stands still, and it cannot be made to contract again by atropine. The cardiac muscle itself remains excitable after the action of muscarin and iodine- 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. 138, \ 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. So 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 prepa- ration 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) con- tracts. 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" contraction occurs when the nerve is applied to a muscle tetanized by the action of strychnia, and the con- tracted diaphragm gives a similar result. The question whether the heart can be tetanized has been answered in the negative, and as yet it has not been shown that the heart can be tetanized in the same way that a skeletal muscle is tetanized.] [Mac William finds, when the quadriceps extensor cruris contracts to cause the knee jerk, that a sound similar to the first sound of the heart is heard. As the former is regarded as a simple con- traction, it is argued that a simple contraction can produce a muscle sound. Fredericq regards the ventricular systole not as a simple contraction, but as composed of three or more fused contractions corresponding to tetanus. This he concludes from a study of cardiograms as well as from the electro-motive phenomena of the heart.] The peripheral or extra-cardiac nerves (§§ 369 and 370). 128 THE CARDIO-PNEUMATIC MOVEMENT. 59. CARDIO-PNEUMATIC MOVEMENT.— As the heart within the thorax occupies a smaller space during the systole than during the diastole, it follows that, when the glottis is open, air must be drawn into the chest when the heart contracts; whenever the heart relaxes, /.son). If a branch ije ojiened from a tube, the princijial current is accelerated to a considerable extent, no matter at what angle the branch may be given olT. 63. FLOW IN CAPILLARY TUBES.— Poiseuille proved experimentally that the flow in the capillaries is subject to special conditions : — ( 1 ) The quantity of fluid which flows out of the S(jf/ie capillary tube is proportional to the pressure. (2) The time necessary for a given quantity of fluid to flow out (withthe 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 cipillaries is proportional to the velocity of the current. 64. FLOW IN ELASTIC TUBES.— (i) When an uninterrupted unifortn current flows through an elastic tube, it follows exactly the satne la~u's as if the tube had rigid 'walls. If the pro- pelling 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, /. 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 com- municated to all the fluid particles from the beginning to the end of the tube ; a positive -•.uave 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 fro 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 alteration 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, the 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 luave movement, iht oscillatory movement, 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 sys- tem. The blood in the arteries is already in a state of continual movement, directed from the aorta to the capillaries ; by means of the systole of the left ventricle a quantity of fluid is suddenly pumped into the aorta, and causes & positive 7oa7'e, the 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. — If a 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 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 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 difi'erent, 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 outflow synchronous with the inflow, and the outflow becomes continuous only when the inflow is continuous 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 VES- SELS.— 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. STRUCTURE OF ARTERIES. 135 [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 irrigating 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 characteristic feature.] A typical artery consists of three coats (Fig. 68). (i) The tunica intima, or inner coat, consists of a layer of {a) irregular, long, fusiform, nucleated, squamous cells forming the excessively thin, transparent endothelium, immediately in contact with the blood stream. [Like other endo- thelial 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 lay €7- — in which numerous spindle or branched protoplasmic cells lie embedded within a corresponding system of plasma canals. Outside this is an elastic lamina [b], which in the smallest arteries is a structure- FiG. 69. Capillaries. The outlines of the nucleated endothelial cells with the cement blackened by the action of silver nitrate. Coats of a small artery, a, endothelium ; b, internal elastic lamina ; c, circular muscular fibres of the middle coat ; d, the outer coat. less or fibrous elastic membrane — in arteries of medium size it is a fenestrated membrane [JJenle), while in the largest arteries there may be several layers of elastic laminse or fenestrated elastic mem- brane mixed with connective tissue. [In some arteries the elastric membrane is distinctly fibrous, the fibres being chiefly arranged longitudinally. It can be stripped off, when it forms a brittle elastic membrane, 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. 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 uniform calibre. (2) The tunica media, or middle coat, contains much non-striped muscle (f), which in the smallest arteries consists of transversely disposed non-striped muscular 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 136 STRUCTURE OF VEINS. Fig number of muscular fibres becomes so great as to form a well marked fibrous ring of non-sti-iped luiisile, 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 numer- ous (as many as fifty) thick, elastic, fibrous or fenestrated laniin;\? are concentrically arranged. A few non-striped fibres lie scattered among these, and some of them are arranged transversely, while a few have an obli(iue 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 po]iliteal have longitudinal libres between the transverse ones. Longitudinal bundles lying inside the media occur in llie renal, sulenic, and internal spermatic 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 sinalhst arteries consists of a structureless membrane with a few connective- tissue corpuscles attached to it; in ioiiteichat larger arteries there is a layer of fine fibrous elastic tissue mi.\ed with bundles of fibrillar connective tissue (a). In arteries of »iuii/!e size, and in the laigest arteries, the chief mass consists of bundles of fibrillar connective tissue containing 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 lamellte. In medium-sized and small arteries the elastic tissue next the media takes the form of an independent clastic membrane (Ilenle's external elastic membrane). Hundles of non-striped muscle, arranged longitudinally, occur in the adventitia of the arteries of the penis, and in the renal, s[5lenic, 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 tissues. The diameter of the capil- laries varies considerably, but as a general rule it is such as to admit freely a single row of blood corpuscles. In the retina and the muscles the diameter is 5-6 //, and in bone marrow, liver, and choroid 10-20 ,«. The tubes consist of a single layer of transparent, excessively thin, nucleated, endothelial cells joined to each other by their margins. [The nuclei contain a well marked intranuclear ])lexus of fibrils, like other nuclei.] The cells are more fusiform in the smaller capillaries and more polygonal m the larger. The body of the cells 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 (p. 138). 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 re- vealed 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 through which colorless corpuscles may pass out of the vessels, or are merely larger accumula- tions of the cement substance. [If a capillary is examined in a perfectly fresh condition (while living) and without the addition of any reagent, it is impossible to make out any line of demarcation Ijetween adjacent cells, owing to the uniform refractive index of the entire wall of the tube.] [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 apart. 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 ( 7/ioma), and jiarticles of cinnabar and China ink are fixed in it, when tlicse substances are injected into the blood i^Foa).'\ Fine anastomosing fibrils derived from non-medullated nerves terminate in small end-buds in relation with the capillary wall; ganglia in connection with the nerves of \ 7 capillaries occur only in the region of the sympathetic. The small vessels next in size to the capillaries, and con- tinuous with them, have a completely structureless covering in addition to the endothelium. Longitudinal section of a vein at the level of a tit »t>i- • 11 j- ^' • 1 j valve, a.hyalinelayerof the internal coat; ^''^- The VCinS are generally distinguished ^;,l!?fiKl^'"l'•"'^J''i^''''"'"°^T°°i^'""^" from the arteries by \.\\e\r h/men being wide?- than cular hbres divided transversely ; d, longi- , , r i t • i • tudinai muscular fibres in the adventitia. the luiiien 01 the Corresponding artcrics ; their STRUCTURE OF VEINS. 137 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. Structure. — (i) The tunica intima consists of a layer oi 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 exist 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 smallest veins the media is formed of fine connective 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 con- nective tissue, usually arranged longitudinally, and not much elastic tissue. I>ongitudinally arranged muscular Jibres 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 netwurk exists on their convex surface, and both surfaces are covered by endothelium. The valves contain many muscular fibres (Fig. 70). [Ranvier has shown. that the shape of the epithelial cells on the side over which the blood passes is more elongated than on the cardiac side of the valve, where the long axes of the cells 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 endo- thelium on their surfaces, that are in contact with the blood. The surrounding wall consists of con- nective 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 artei'ies are the carotid gland of the frog, and a similar structure on the pulmonary arteries and aorta of the turtle, and the coccygeal gland of man. 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, surrounded and permeated by non-striped muscle. 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 afterwards 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 cylin- drical tubes composed of several layers of various tissues, more especially elastic tissue and smooth muscular fibres, and the whole is lined by a smooth polished layer of endothelium. One of the most important properties is the contractility of the vascular wall, in virtue of which the calibre of the vessel can be varied, and therefore the supply of blood to a part is altered. The contractility is due to the plain muscular fibres, which are, for the most part, arranged circularly. It is most marked in the small arteries, and of course is absent where no muscular 138 PROPERTIES OK THE liLOOD VESSELS. tissue occurs. The amount and intensity of the contraction depend upon the de- velopment 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 atmos- phere acting upon the muscular fibres.] [Action of Drugs on the Vascular System. — Gaskell finds that a very dilute solution of lactic acid 1 1 : 10,000 parts of saline solution), passed through the blood vessels of a frog, alwavs enlarges the calibre of the blood vessels, while an alkaline solution (i part sodium hydrate to 10,000 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. Dilute alka- line solutions act on the heart in the same way. After a series of beats the ventricle stops beating, the standstill being in a state of contraction. Very dilute lactic acid causes the ventricle to stand still in the phase of complete relaxation. Thfe acid and alkaline saline solutions are antagonistic in their action on the ventricle. Cash and Brunton find that dilute acids have a tendency to increase the transudation through the vessels and produce adenta of the surrounding tissues. They also observed that barium, calcium, strontium, copper, iron, and tin produce contraction of the blood vessels when solutions of their salts are driven through them, while 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.] If blood containing certain drugs be perfused through the blood vessels of a freshly excised organ, the blood vessels are dilated; e. s;., by amyl nitrite, chloral hydrate, morphia, CO, paraldehyde, kairin, quinine, atropin, ferricyanide of potassium, (urea and sodic chloride in the renal vessels), — they are contracted by digitalin, veratria, helleborin [A'obert). Heat causes contraction of the blood vessels of the frog's mesentery [Gartner). According to Roy the blood vessels shorten when heated. That the capillaries undergo dilatation and contraction, owing to variations in the size of the protoplasmic elements of their walls, must be admitted. Strieker has described capillaries as "protoplasm in tubes," and observed that in the tadpole they exhibited movements when stimulated. Golubew described an active state of contraction of the capillary wall, but he regarded the nuclei as the parts which underwent change. Rouget observed the same result in the capillaries of newborn mammals. 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 contrac- tility of the capillaries and especially of their nuclei as influencing the blood stream. Oxygen acts on the nuclei of the capillary wall (membrana nictitans of frog) and causes them to swell, while CO2 has an opposite effect. The circulation through a lung suddenly filled with O or atmos- pheric air is at first very rapid, but soon diminishes, while with CO., the circulation remains con- stant.] As the capillaries are excessively thin, soft, and delicate, 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 which 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 (A't'naut). [It is well known 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 these 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."] Physical Properties. — Among the physical properties of the blood vessels, elasticity is the most important; their elasticity is s/na// in amotint, i.e., they otter little resistance to any force applied to them so as to distend or elongate them, but it \% perfect in quality, i.e., the blood vessels rapidly regain their original size and form after the force distending them is removed. [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, THE PULSE. 139 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 moist tissues generally is not proportional to the weight used to extend it, the elongation being relatively 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 -aX 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, espe- cially 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 experimented upon the elastic properties of the arterial 7vall. A portion of an artery, so that it could be distended by any desired internal pressure, was enclosed in a small vessel contain- ing olive oil arranged in the same way as in Fig. 62, for the heart. The variations of the contents were recorded by means of a lever writing on a revolving cylinder. The instrument is termed a sphygmotonometer. The ao7-ta and other large arteries are most elastic and most distensible at pressures corresponding more or less exactly to their normal blood pressure, while in veins the rela- tion between internal pressure and the cubic capacity is very different. In them the maximum 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 qtiadrupled 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 capacity (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 differ- ences in the quantity of blood which they contain.] 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. In some old people they become atheromatous and even calcified. Cohesion. — The cohesion of blood vessels is very great, and in virtue of this they are able to resist even considerable internal pres- sure without 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 (Volkmami). Given a vein and an artery of the same thick- ness, a greater pressure is required to rupture the former than the lat- ter. The human carotid or iliac artery resists a pressure of 8 atmos- pheres, the veins about the half of this. Fig. 71, 66. INVESTIGATION OF THE PULSE.— [The charac- ters of the pulse maybe investigated by — (i) the eye {inspectioii) ; (2} the finger (^palpatioti) ; (3) instruments. Two or three fingers are placed over the course of the radial artery, and the various phenomena in connection with the pulse are noted. It takes much practice for the physician to acquire the tactus eruditus, Sphygmome- and notwithstanding the value of instruments, every physician should ^^^^°l ^^^ make a careful study of the pulse beat with his finger. In order to Cheiius. feel the pulse beat or to take a pulse tracing, there must be some resist- ant body, e.g., a bone behind the artery, and a certain degree of pressure must be exerted on the artery.] The individual phases of the movement of the pulse can only be accurately investigated by the application of instruments to the arteries. 140 INSTRUMENTS FOR INVESTIGATING THE PULSE, (i) Poiseuille's Box Pulse Measurer (1829). — An artery is exposed and placed in an oblong box filled with an indifferent Huid. A vertical tube witli a scale attached communicates with the interior of the box. The cuhiiun of fluid undert^ocs a variation with every pulse heat. (2) Herisson's Tubular Sphygmometer consists of a gla.ss tube whose lower end is covered with an ela.stic membrane (Fig. 71;. The tube is partly fdied with llg. The membrane is placed over the position of a pulsating artery, so that its beat causes a movement in the Mg. Chelius u.sed a similar instrument, and he succeeded with this instrument in showing the existence of the double beat (dicrotism) in the normal pulse (1S50). (3) Vierordt's Sphygmograph (1855^— In ''"«. one of the earliest sphygmographs, Vierordt departed from the principle of a fluctuating fluid column, and adopted the prmciple of the lever. Fic. 72. Scheme of M.irey's sphygmograph. A. spring with ivory pad, j', which rests on the artery ; e, weak spring pressing k into / ; V, writing lever ; P, piece of smoked glass or paper moved by clockwork, U ; H, screw to limit excur- sion of A ; S, arrangement for fixing the instrument to the arm of the patient. Upon the artery rested a small pad, which moved a complicated system of levers. At first he used a straw 6 inches long, which rested on the artery. The point of one of the levers inscribed its movements upon a revolving cylinder. This instrument was soon discarded. (4) Marey's Sphygmograph consists of a combination of a lever with an elastic spring. The elastic sjiring (Fig. 72, A) is fixed at one end, 2, free at the other end, and provided with an ivory pad, y, wliich is pressed by the spring upon the radial artery. On the upper surface of the pad there is a vertically placed fine-toothetl rod, k, wliich is pressed upon by a weak spring, e, so that its teeth dovetail with similar teeth in tlie small wheel, /, from whose axis there projects a long, light, Fig. 73. Marey's improved sphygmograph. A, steel spring; B, first lever; C, WTiting lever; C, its free writing end ; D, screw for bringing B in contact with C ; G, slide with smoked paper; H, clockwork; L, screw for increasing the pressure ; M, dial indicating the pressure; K, K, straps for fi.xing the instrument to the arm, and the arm to the double inclined plane or support. wooden lever, v, running nearly parallel with the elastic spring. This lever has a fine style at its free end, s, which writes upon a smoked plate, P, moved by clockwork, U, in front of the style. Marey's instrument, as improved by Mahomed and others, has been very largely used. [Its more complete form, as in Fig. 73, where it is shown applied to the arm, consists of (i) a steel spring. A, which is provided with a pad resting on the artery, and moves with each movement of the artery ; (2) the lever, C, which records the movement of the artery and spring in a magnified form on the smoked paper, G; (3) an arrangement, L, whereby the exact pressure exerted upon the artery is indicated on the dial, M ; (4) the clockwork, H, which moves the smoked paper, G, at a uniform rate ; (5) a framework to which the various parts of the instrument are attached, and by means of which the instrument is fastened to the arm by straps K, K (Byrom Bramwell).'\ INSTRUMENTS FOR INVESTIGATING THE PULSE. 141 [Application. — In applying the sphj'gmograpli, cause the patient to seat himself beside a low table, and place his arm on the double inclined plane (Fig. 73). In the newer form of instrument, the lid of the box is so arranged as to unfold to make this support. The fingers ought to be semi- flexed. Mark the position of the radial artery with ink. See that the clockwork is wound up, Fig. 74. Ludwig's Sphygmograph. and apply the ivory pad exactly over the radial artery where it lies upon the radius, fixing it to the arm by the non-elastic straps, K, K. Fix the slide holding the smoked paper in position. The best paper to use is that with a very smooth surface, or an enameled card smoked over the flame of a turpentine lamp, over a piece of burning camphor, or over a fan-tailed gas burner. The writing Fig. 75. Dudgeon's Sphygmograph. style is so arranged as to write upon the smoked paper with the least possible friction. It is most important to regulate the pressure exerted upon the artery by means of the milled head, L. This must be determined for each pulse, but the rule is to graduate the pressure until the greatest ampli- tude of movement of the lever is obtained. Set the clockwork going, and a tracing is obtained. 142 INSTRUMENTS FOR INVESTIGATING THE PULSE. which must be " fixed " by dipping it in a rapidly drying varnish, ^. j-., photographic. In every case scratch on the tracing, with a needle, the name, date, and amount of pressure employed.] [(5) Dudgeon's Sphygmograph. — This is a convenient form of sphygmograph, although Broadbent regards its results as untrustworthy. The instrument after being carefully adjusted upon the radial arter)' is kept in position by an inelastic strap. The pressure of the spring is regulated, Scheme of Brondgeest's sphygmograph. S, S', receiving and recording (S, S') tambours with writing levers, Z .ind Z'; K, K', conducting tubes: /, over heart,/', over a distant artery. by the eccentric wheel, to any amount from i to 5 ounces. As in other instruments the tracing paper is moved in front of the writing needle by means of clockwork. The writing levers are so adjusted that the movements of the artery are magnified fifty times (Fig. 75).] (6) [Ludv^fig's improved form is a very serviceable instrument (Fig. 74).] Fig. 77. Scheme of Landois' Angiograph. (7) Marey's tambours are also employed for registering the movements of the pulse. They *'^^"^ed in the same way as the pansphygmograph. Two pairs of metallic cups (Fig. 76, S, S, and S', S^, Lpham's capsules) are pierced in the middle by thin metal tubes, whose free ends are connected with caoutchouc tubes, K and K^. All the four metallic vessels are covered with an elastic membrane. On S and S^ are fixed two knob-like pads,/ and/', which are applied to the INSTRUMENTS FOR INVESTIGATING THE PULSE. 143 pulsating arteries, and the metal arcs, B and B', retain them in position. On the other tambours are arranged the writing levers, Z and Z^. Pressure on tlie one tambour necessarily compresses the air, and makes the other, with which it is connected, expand, so as to move the writing lever. This arrangement does not give absolutely exact results ; still, it is very easily used, and is convenient. In Fig. 76 a double arrangement is shown, whereby one instrument, B, may be placed over the heart and the other, B^, on a distant artery. (8) Landois' Angiograph. — To a basal plate, G, G, are fixed two upright supports,/, which carry between them at their upper part the movable lever, d, r, carrying a rod bearing a pad, e, directed downward, which rests on the pulse. The short arm carries a counterpoise, d, so as exactly to balance the long arm. The long arm has fixed to it at r a vertical rod provided with teeth, h, which is pressed against a toothed wheel firmly fixed on the axis of the very light writing lever, e,f, which is supported between two uprights, q, fixed to the opposite end of the basal plate, G, G. The ■writing lever is equilibrated by means of a light weight. The writing needle, k, is fixed by a joint to e, and it writes on the plate, t. The first mentioned lever, d, r, carries a shallow cup, Q, just above the pad, FiG. 78. into which weights may be put to press on the pulse. In this instrument the weight can be measured and varied ; the writing lever moves vertically, and not in a curve as in Marey's apparatus, which greatly facili- tates the measuring of the curves (Fig. 77). Other sphygmographs are used, both in this country and abroad, including that of Sommerbrodt, which is a complicated form of Marey's sphygmograph, and those of Pond and Mach. In every pulse curve — sphygmogram or arteriogram — we can distinguish the ascending part (ascent) of the curve, the apex, and the descending part (descent). Secondary elevations scarcely ever occur in the ascent, which is usually represented by a Normal pulse curve of the radial artery, obtained by the angiograph writing upon a plate at- tached to a vibrating tuning-fork. Each double vibration ^ 0.01613 sec. Fig. 80. Fig. 79. Gas Sphygraoscope of S. Mayer. Haemautographic curve of the posterior tibial artery of a dog. P, primary pulse wave ; R, dicrotic wave ; e, e, elevations due to elasticity. Straight line, while they are always present in the descent. Such elevations occurring in the descent are called catacrotic, and those in the ascent, ana- crotic. When the recoil elevation or dicrotic wave occurs in a well-marked form in the descent, the pulse is said to be dicrotic, and when it occurs twice, tricrotic. 144 THE rULSE CURVE. Measuring Pulse Curves. — If the smoked surface on which the tracing is inscribed is moved at a uniform rate tiy means of the clockwork, then the height and length of the curve are measured by means of an ordinary rule. If we know the rate at which the paper was moved, then it is easy to calculate the duration of any event in the curve. The curve may be recorded on a plate of glass fixed to a tuning-fork kept in vibration. Every part of the curve shows little elevations (whose rate of vibration is known beforehand). All that is reiiuiretl is to count the number of vibrations in order to ascertain the duration of any part of the curve (Fig. 78). Gas Sphygmoscope. — A small metallic or glass capsule (Fig. 79), provided with an inlet and an outlet tube, and closed below Ijy a fine membrane, is placed over an artery. The inlet tube is connected to a gas supply, and the outlet to a rat-tail gas burner (/>). The gas jet responds to every pulse beat. C/erinac f>hotoj:;rtiplted 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. The curve so obtained (Fig. 80) shows, in addition to the primary wave, P, a distinct dicrotic wave, R, and slight vibrations, e, e, due to the variations in the elasticity of the arterial wall, which shows that the movements occur in tiie blood itself, and are communicated as waves to the arterial wall. Hy 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 tatil of time, during arterial dilata- tion, rather more than t-Mice as much blooil flows out as compared with what occurs during arterial contraction. 67. PULSE TRACING OR SPHYGMOGRAM.— [The Pulse.— With each systole of the heart, a certain quantity of blood is forced into the already filled and partially distended arteries, the resistance in the vessels is lowest between the pulsations, and at this time the arterial tubes are somewhat flattened, but with each systole of the left ventricle the pulse wave, or rather the liquid pressure within the vessel, is increased, thus forcing Fig. 81. the artery back into the circular form. " The change of shape, from the flat- tened condition impressed upon the vessel by the finger or the sphygmo- graph lever, to the round cylindrical shape which it assumes under the dis- tending force of the blood within it, constitutes the pulse " and it in- Sphygmogram of radi.il artery: pressure 2 oz. Each dicatCS the degree and duratioH of pare 01 the curve between the base of one up-stroke , . ," . , and the base of the next up-stroke corresponds to a the increased preSSUre in the beats°aXari'of a°s[xi'h."''' '''^"''' '^°''" ^'"^ ''"''"'' arterial System caused by the ventri- cular systole {Broadbent').'\ Analysis. — A sphygmogram or pulse tracing consists of a series of curves (Fig. 81) each of whicii corresponds with one beat of the heart. Each pulse curve consists of — 1. The line of ascent {a to b in Fig. 81). 2. The apex (P in Fig. Zt^, and b in Fig. 81). 3. The line of descent (^ to k). (i) The line of ascent, up-stroke, or percussion stroke, is nearly vertical, and occurs during the dilatation of the artery produced by the systole of the left ventricle, when the aortic valves are forced open and the ventricular contents are projected into the arterial system. [The ascent is nearly vertical, but in some cases, where the ventricle contracts very suddenly, as occasionally happens in aortic regurgitation, it is quite vertical (Fig. 85).] (2) The apex or percussion ^vave in a normal pulse is pointed. .(3) The line of descent is gradual, and corresponds to the diminution of diameter or contraction of the artery. It is interrupted by two cotnpletely distinct elevations ox secondary waves. Such elevations are called " catacrotic." The more distinct of the two occurs as a well-marked elevation about the middle of the descent (R in Fig. 83 and / in Fig. 81) ; it is called the dicrotic wave, or. ORIGIN OF THE DICROTIC WAVE. 145 with reference to its mode of origin, the " recoil wave.'''' [As the descent cor- responds to the time when blood is flowing out of the arteries at the periphery into the capillaries, its direction will depend on the rapidity of the outflow. Thus it will be more rapid in paralysis of the arterioles and very rapid in aortic regurgi- tation, where, of course, much of the blood flows backward into the left ventricle (Fig. 85). 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, or recoil wave, corresponds to the time following the closure of the aortic valves, and is preceded in the descent by a slight depression, the aortic notch. [The tidal wave, or pre-dicrotic, occurs between the apex and the dicrotic wave (Fig. 81, rt^). It occurs on the descent, and during the contraction of the ventricle. 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. 82), 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.] 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 Fig. 82. Irregular pulse of mitral regurgitation. 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).] The pulse curve indicates the variations of pressure which the blood exerts on the arterial walls, for the lever rises and falls with the pressure, hence v. Kries calls it the " pressure pulse." 68. ORIGIN 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, where- by 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 rhore blood flows into the arterial system, the arteries, which were previously distended 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 positive wave, which is propagated peripherally through the arteries, where it disappears 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 10 146 CHARACTERS OF THE DICROTIC WAVE. must appear later in the peripheral arteries. Both kinds of waves, the pri- mary 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. Fig. 83. XII XIII XIV XV I, II, 111. sphyemograms ot carotid arter>- : 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, dicroti. elevations due to elasticity ; K. elevation caused by the closure of the semilunar valves of the aorta. tic wave ; e, e. [The conditions which favor dicrotism are low blood pressure and a rapid, sharp cardiac con- traction. When the blood pressure is low, there is less resistance to the inflow of blood at the aorta from the left ventricle, so that its systole occurs sharply, forcing on the blood and distend- ing the arterial walls. The elastic coats rebound on the contained blood, and thus start a wave from the closed semilunar valves.] CONDITIONS INFLUENCING ARTERIAL TENSION, 147 The following points regarding the dicrotic wave have been ascertained experi- mentally, chiefly by Landois : — 1. The dicrotic wave occurs later in the descending part of the curve, the further the artery experimented upon is distant from the heart. Compare the curves. Fig. 83. 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 beginning of the curve. It varies with the height of the individual. 2. The dicrotic elevation in the descent is lower, and is less distinct, the further the artery is situated from the heart, so that the longer the distance which the wave has to travel the less distinct it becomes. 3. It is best marked in a pulse where the primary pulse wave is short and energetic. It is greatest relatively when the systole of the heart is short and energetic. 4. It is better marked the lower the tension of the blood within the arteries [and is best developed in a soft pulse]. In Fig. ^i, IX and X were obtained when the tension of the arterial was low ; V and VI, medium; and VII with high tension. Conditions influencing Arterial Tension. — It is diminished at the beginning of inspiration [\ 74), by hemorrhage, stoppage of the heart, heat, an elevated position of parts of the body, amyl nitrite, nitro-glycerine, and the nitrites generally. [Both drugs accelerate the pulse beats and Fig. 84. Fig. 8";. Pulse tracings. A, normal ; A', one minute after inhalation ot amyl nitrite ; B, normal ; B', after a dose ot nitro- glycerine {Stirling, after Murrell). produce marked dicrotism; with amyl nitrite the full effect is obtained in from 15 to 20 sec. after the inhalation of the dose (Fig. 84, A, A^), but with nitro-glycerine not until 6 or 7 min. (Fig. 84, B, W) and in the latter case the effects last longer.] It is increased at the beginning of expiration, by accelerated action of the heart, stimulation of vaso-motor nerves, diminished outflow of blood at the periphery, and by inflammatory congestion 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 ex- posed, the stimulation of the air causes it to contract, resulting in an increased tension within the vessel. In many diseased conditions the arterial tension is greatly increased — \_e-g-i 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 appar- ently more independent elevation. Moens has shown that the time between the primary elevation ^nd dicrotic wave in- creases with increase in the diameter of the tube, with diminu- tion 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. 85). In this figure observe also the vertical character ot the up-stroke.] Elastic Elevations. — Besides the dicrotic wave, a number of small less- marked elevations occur in the course of the descent in a sphygmogram (Fig. Aortic Regurgitation. 148 DICROTIC PULSE. 83, e, e). These elevations are caused by the elastic tube being thrown into vibra- tions 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 suddenly from the distended to the relaxed condition. These small eleva- tions in the pulse curve, caused by the elastic vibrations of the arterial wall, are called "elastic elevations " by Landois. (i) 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 elevations." (3) In diseases of the arterial walls affecting their elasticity, these elevations 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 the pulse curves obtained from different arteries of the body. 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 may be felt, each pulse beat, as it were, being composed of two beats (Fig. 83, 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 _ •. Fig. 86. Development of the Pulsus dicrotus — P. caprizans ; P. monocrotus. more than the greatly increased dicrotic elevation, which, under ordinary conditions, is not felt by the finger. Condi;ions. — The occurrence of a dicrotic pulse is favored (i) by a short primary pulse wave, as in fevers, where the heart beats rapidly. • (2) 'By diminished arterial tension. 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 condi- tions favorable to its occurrence appear to exist. This 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° to 40° C), whereby the artery is more distended, and the heart beat is shorter and more prompt. (3) It is absolutely necessary that the elasticity of the arterial wall be normal. The dicrotic pulse does not occur in old persons with atheromatous arteries. Monocrotic Pulse.— In Fig. 86, A, B, C, we observe a gradual passage of the normal radial curve, A, mto the dicrotic beat, B, and C, where the dicrotic wave, r, appears as an independent CONDITIONS AFFECTING THE PULSE RATE. 149 Hyperdicrotic Pulse. 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 dis- •^^*^- °1- appears, 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. e., below where the up-stroke begins, the pulse is said to be hyperdicrotic (Fig. 87). This form occurs during high fever (104° F.), and is usually a grave sign, indicating exhaustion and the need for stimulants. ] 70. CHARACTERS OF THE PULSE.— [The three factors concerned in the produc- tion of the pulse are, (i) the action of the heart, (2) the elasticity of the large vessels. (3) the resistance in the small arteries and capillaries. Any or all or several of these factors may be modified.] (i) Frequency. — According as a greater or less number of beats occurs in a given time, e. g., per minute, the pulse is said to be frequent or infrequent. The normal rate, in man = 71 per minute, and somewhat more in the female; in fever it may exceed 120 (250 have been counted by Bowles), while in other diseases it may fall to 40, and even 10 to 15; but such cases are rare, and are probably due to an affection of the cardiac nerves (§ 41). The frequency of the pulse is usually increased when the respirations are deeper, but not more numerous, i. e., rapid shallow respirations do not affect the frequency of the pulse, but deep respirations do. [The frequency may be regular or irregular with regard to time.] (2) Celerity or Rapidity. — If the pulse wave is developed, so that the distention of the artery slowly reaches its height, and the relaxation also takes place gradually, we have the p. tardus or slow or long pulse; the opposite condition gives rise to the p. celer or quick or short pulse. The rapidity of the pulse is increased by quick action of the heart, power of expansion of the arterial walls, easy efflux of blood owing to the dilatation of the small arteries, and by nearness to the heart. [The quickness has reference to a single pulse beat, ihtfreqiiency to a nutnber of beats.] In a quick pulse, the curve is high and the angle at the apex is acute, while in a slow pulse the ascent is low and the angle at the apex is large. (3) Conditions Affecting the Pulse Rate. — Frequency in Health. — In man the normal pulse rate ^71 to 72 beats per minute, in the female about 80. In some individuals the pulse rate may be higher (90 to 100), in others lower (50), and such a fact must be borne in mind. {a) Age:— Beats per Minute. 5 years, 94 to 90 10 "' about 90 10 to 15 years 78 15 to 20 " 70 20 to 25 " 70 Beats per Minute. Newly born, , . . 130 to 140 1 year, 120 to 130 2 years, 105 3 " 100 4 " 97 Beats per Minute 25 to 50 years, .... 70 60 years, 74 80 " 79 80 to 90 years, . . over 80 {b') The length of the body has a certain relation to the frequency of the pulse. The following results have been obtained by Czarnecki from the formulae of Volkmann and Rameaux : — Length of Body in 10 cm. 140 to 150, 69 150 to 160, 67 160 to 170, 65 170 to 180, 63 Above 180, 60 Pulse. Calculated. Observed. 74 68 65 64 60 Length of Body Pulse. in 10 cm. Calculated. Observed. 80 to 90, 90 103 90 to 100, 86 91 IOC to no 81 87 no to 120, 78 84 120 to 130, 75 78 130 to 140, 72 86 (c) The pulse rate is increased by muscular activity, by every increase of the artei-ial blood pressure, by taking of food, increased temperature , painful sensations, by psychical disturbances, and \in extreine debility^. Increased heat, fever, or pyrexia increases the frequency, and as a rule the increase varies with the height of the temperature. [Dr. Aitken states that an increase of the tem- perature of 1° F. above 98° F. corresponds with an increase of ten pulse beats per minute; thus — Temp. F. 98° . 99° . 100° . Pulse Rate. . . 60 - . 70 . . 80 Temp. F. 101° . 102° . 103° . Pulse Rate. . . 90 . . 100 . . 1 10 Temp. F. 104° . 105° . 106° . Pulse Rate. . . 120 . . 140 150 VARIATIONS IN THE CHARACTERS OF THE PULSE. 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. 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 r.M. ; toward 3 (at dinner time) another increase takes place and goes on until 6 to 8 i-.M. =^ 70; and it falls until midnight rT= 54. It then rises again toward 2 A.M., when it soon fnlls again, and afterward rises as before toward 3 to 6 a.m. [Pulse Rate in Animals. — {Colin.)'\ Per Mil). Per Min. Lioness 68 Tiger 74 Sheep, 70-80 Goat, 70-80 Leopard 60 Wolf (female), . . 96 Hyivna, 55 Elephant, 25-28 Camel 28-32 Giraffe, 66 Horse, 36-40 Ox 45-50 Tapir, 44 Ass, 46-50 Pig 70-80 Lion, 40 Dog, 90-100 Cat, 120-140 Rabbit, . . Mouse, . . Goose, . . Pigeon, . . Hen, . . . Snake, . . Carp, . . , Frog, . . . Salamander, Per Min. . . 120-150 120 no 136 . . 140 • • 24 . . 20 . . 80 • • 77 (4) Variations in the Pulse Rhythm ( AUorhythmia). — On applying the fingers to the normal pulsfe, 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 ^= 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 (Fig. 88). In the p. bigeminus of Traube the beats occur in Fic. 88. Pulsus alternans. 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 much 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 {Rtegel). Complete irregularity of the heart's action is called arhythmia cordis. 71. VARIATIONS IN THE CHARACTERS OF THE PULSE.— Compressibility. — The relative strength or compressibility of the pulse (p. fortis and debilis), ;". e., whether the pulse is strong or weak, is estimated by the weight which the pulse is able to raise. A sphygmo- graph, provided with an index indicating the amount of pressure exerted upon the spring pressing upon the artery, may be used (Fig. 73). 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 resistance 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 important 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 com- pressible 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 msufficiency of the aortic valves. In this case, after the systole of the left ventricle, owing to the THE PULSE CURVES OF VARIOUS ARTERIES. 151 incompetency of the aortic semilunar valves, a large amount of 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. 85).] 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 jwa// 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.— i. Carotid (Fig 83, I, II, III; Fig. 93, C and C^). The ascending part is very steep — the apex of the curve (Fig. 83, P) is sharp and high. Below the apex there is a small notch — the " aortic notch " (Fig. 83, 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. 83, 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. 83, III, R). 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. 83, 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 permits a greater development of the dicrotic wave. Further on, two or three small elastic vibrations occur, e, e. 3. Radial Artery (Fig. 78; Fig. 83, V to X; Fig. 93, R and RJ. The line of ascent (Fig. 83) is tolerably high and sudden — somewhat in the form of a long/". The apex, P, is well marked. Below this, if the tension be high, two elastic vibrations may occur (V, e, e), but if it be low, only one (VI to IX, e). About the middle of the curve is the well-marked dicrotic elevation, R. This wave is least pronounced in a small hard pulse, and when the artery is much distended (Fig. 83, VII, Rj) ; it is larger when the tension is low (Fig. 83, IX, R), and is greatest of all when the pulse is dicrotic (X, R). Two Fig. or three small elastic elevations occur in the lowest part of the curve. 4. Femoral Artery (Fig. 83, XI, XII). The ascent is steep and high — the apex of the curve is not unfrequently broad, and in it the closure of the aortic valves (K) is indi- cated. The curve falls rapidly toward its lowest third. The dicrotic elevation, R, occurs late after the beginning of the curve, and there are also small elastic elevations [e, e). 5. Pedal Artery (Fig. 83, XIV, XV), and Posterior Tibial (Fig. 89 and Fig. 83, XIII). In pulse curves obtained from ^-^^^^by^r angiograph^'upon these arteries, there are well-marked indications that the appara- a vibrating plate. tus (heart) producing the waves is placed at a considerable dis- tance. The ascent is oblique and low — the dicrotic elevation occurs late. Two elastic vibrations (Fig. 83, XIV, e, e) occur in the descent, but they are very close to the apex, ^jrhile the elastic vibrations at the lower part of the curve are feebly marked. Fig. 89 is from the posterior tibial. When measured it gives the following result : — I to 2 9.5 1 I to '2 20 ^ -^ - r I vibration is ^ 0.01613 sec. . I to 4 30.5 I -5 [ I to 6 61 J 73, ANACROTISM. — As a general rule, the line of ascent of a pulse curve has the form of any, and is nearly vertical. The arterial walls are thrown into elastic vibration by the pulse beat, and the number of vibrations depends greatly upon the tension of the arterial walls. The disten- 152 ANACROTISM. tion of the artery, or what is the same thing, the ascent of the sphygmogram usually occurs so ra|>iiily that it is equal to onf elastic vibration. The elongated /-shape of the ascent is fundament- ally just a |irolonged elastic vibration. When the number of vibrations causing the elastic variation is small, and when the line of ascent is prolonged, two elevations occasionally occur in the line of ascent. Such a condition may occur normally (Fig. S3, V'lII, at I and 2; X, at I and 2). When a series of closely-placed elastic vibrations occur in the upper part of the line of ascent, so that the aoex appears dentate and forms an angle with the line of ascent, then the condition becomes one of anacrotism (Fig. 90, <;, a), which, when it is so marked, may be characterized as pathological. Anacrotism of the pulse occurs when the time of the intlux of the blood is longer than the time occupied bv an elastic vibration. Hence it takes |ilace — (i) In dilatation and hypertrophy of the left ventricle, e.g., Fig. 90, A, a tracing from the Anacrotic radial curves, a, a, llie anacrotic parli. radial artery of a man suffering trom contracted kidney. The large volume ol blood expelled with each svstole requires a long time to dilate the tense arteries. 1 21 When the extensibility of the arterial wall is diminished, even the normal amount ot blood expelled from the heart at every systole requires a long time to dilate the artery. This occurs in old people where the arteries tend to become rigid, e. g., in atheroma. Cold also stimulates the arteries, so that they become less extensile. Within one hour after a tepid bath, the pulse assumes the anacrotic form (Fig. 90, D) G. v. Liebig). (3) When the blood stagnates in consequence of great diminution in the velocity of the blood stream, as occurs in paralyzed limbs, the volume of blood propelled into the artery at every sys- Fn: 9r. 1. II. III. I, II. Ill, curves with anacrotic elevations a, in insufficiency ot the aortic valves. tole no longer produces the normal distention of the arterial coats, and anacrotic notches occur (Fig. 90. B). (4) After ligature of an artery, when blood slowly reaches the peripheral part of the vessel through a relatively small collateral circulation, it also occurs. If the brachial artery be com- pressed so that the blood slowly reaches the radial, the radial pulse may become anacrotic. It often occurs in stenosis of the aorta, as the blood has difficulty in getting into the aorta (Fig. 90, C). Recurrent Pulse. — If the radial artery be compressed at the wrist, the pulse beat reappears on the distal side of the point of pressure through the arteries of the palm of the hand {Janaud, Neidert). The curve is anacrotic, and the dicrotic wave is diminished, while the elastic elevations are increased. : INFLUENCE OF RESPIRATION ON THE PULSE CURVE. 153 (5) A special form of anacrotism occurs in cases of well-marked insufficiency of the aortic valves. Practically, in these cases, the aorta remains permanently open. The contraction of the left auricle causes in the blood a wave motion, which is at once propagated through the open mouth of the aorta into the large blood vessels. This wave is followed by the wave caused by the con- traction of the hypertrophied left ventricle, but of course the former wave is not so large as the latter. In insufficiency of the aortic valves, the auricular wave occurs before the ventricular wave in the ascending part of the curve. The auricular is well marked only in the large vessels, for it soon becomes lost in the peripheral vessels. Fig. 91, I, was obtained from the carotid of a man suffering from ■well-marked insufficiency of the aortic valves, with considerable hypertrophy of the left ventricle and left auricle. The ascent is steep, caused by the force of the contracting heart. In the apex of the curve are two projections; A is the anacrotic auricular wave, and V is the ventricu- lar wave. Fig. 91, II, is a curve obtained from the subclavian artery of the same individual. In the femoral artery the auricular projection is only obtained when the friction of the writing style is reduced to the minimum, and when it occurs it immediately precedes the beginning of the ascent (Fig. 86, III, a). The pulse curve, in cases of aortic insufficiency, is also characterized by (i) its considerable height ; (2) the rapid fall of the lever from the apex of the curve, because a large part of the blood which is forced into the aorta regurgitates into the left ventricle when the ventricle relaxes; (3) not unfrequently a projection occurs at the apex, due to the elastic vibration of the tense arterial wall; (4) the dicrotic wave (R) is small compared with the size of the curve itself, because the pulse wave, owing to the lesion of the aortic valves, has not a sufficiently large surface to be reflected from (Fig. 85). The great height of the curve is explained by the large amount of blood projected into the aortic system by the greatly hypertrophied and dilated ventricle. 74. INFLUENCE OF RESPIRATION ON THE PULSE CURVE. — The respiratory movements influence the pulse (i) in a purely- physical way. Stated broadly, the blood pressure rises during inspiration and falls during expiration, but when we consider the effect on the pulse curve, it is found that it varies with the depth, rapidity, and ease of respiration ; (2) the res- FiG. 92. Influence of the respiration upon the pulse. J, inspiration; E, expiration. piratory movements are accompanied by stimulation of the vasomotor centre, which produces variations of the blood pressure. 1. Normal Respiration. — Fig. 92 shows what sometimes, but by no means always, happens. During inspiration, owing to the dilatation of the thorax, more arterial blood is retained within the chest, while at the same time venous blood is sucked into the right auricle by the aspiration of the thorax ; as a conse- quence of this, the tension in the arteries during inspiration must be less. The diminution of the chest during expiration favors the flow in the arteries, while it retards the flow of the venous blood in the venae cavse, two factors which raise the tension in the arterial system. The difference of pressure explains the differ- ence in the form of the pulse curve obtained during inspiration and expiration, as in Fig. 92 and Fig. 83, 1, III, IV, in which J indicates the part of the curve which occurred during inspiration, and E the expiratory portion. The following are the points of difference: (i) The greater distention of the arteries during expi- ration causes all the parts of the curve occurring during this phase to be higher; (2) the line of the ascent is lengthened during expiration, because the expiratory- thoracic movement helps to increase the force of the expiratory wave ; (3) owing to the increase of the pressure, the dicrotic wave must be less during expiration ; {4) for the same reason the elastic elevations are more distinct and occur higher in the curve near its apex. The frequency of the pulse is slightly greater during expiration than during inspiration. 2. This purely mechanical effect of the respiratory movements is modified by the simultaneous stimulation of the vasomotor centre which accompanies these 154 INFLUENCE OF RESPIRATION ON THE PULSE CURVE. movements. At the beginning of inspiration the blood pressure in the arteries is lowest, but it begins to rise during inspiration, and increases until the end of the inspiratory act, reaching its maximum at the beginning of expiration ; during the remainder of the expiration the blood pressure falls until it reaches its lowest level again at the beginning of inspiration (compare § 85,/) ; the pulse curves are similarly modified, and exhibit the signs of greater or less tension of the arteries corresponding to the phases of the respiratory movements. [There is, as it were, a displacement of the blood-pressure curve relative to the respiratory curve.] Forced Respiration. — With regard to the effect produced on the pulse curve by a powerful expiration and a forced inspiration, observers are by no means agreed. Valsalva's Experiment. — Strong expiratory pressure is best produced by closing the mouth and nose, and then making a great exi)iratory effort (§ 60) ; at first there is increase of blood pressure, while the form of the pulse waves resem- bles that which occurs in ordinary expiration, the dicrotic wave being less devel- oped ; but, when the forced pressure is long continued, the pulse curves have all the signs of diminished tension. This effect is due to the action of the vasomotor centre, which is affected reflexly from the pulmonary nerves. We must assume Fig. 93. C, cunretrom the carotid, and R, radial, during Miiller's experiment; Q and Rj, during Valsalva's experiment. Curves written on a vibrating surface. that forced expiration, such as occurs in Valsalva's experiment, acts by depressifi^t^ the activity of the vasomotor centre (§ 371, II). Coughing, singing, and declaiming act like Valsalva's experiment, while the frequency of the pulse is increased at the same time. After the cessation of Valsalva's experiment, the blood pressure rises above the normal state {Sommerbrodt), almost as much as it fell below it ; the normal condition being restored within a few minutes {Lenz- mann). Miiller's Experiment, — When the thorax is in the expiratory phase, close the mouth and nose, and take a deep inspiration so as forcibly to expand the chest (§ 60). At first the pulse curves have the characteristic signs of diminished tension, viz., a higher and more distinct dicrotic wave; then the tension can, by nervous influences, be increased, just as in Fig. 93, where C and R are tracings taken from the carotid and radial arteries respectively, during Miiller's experiment, in which the dicrotic waves, r, r, indicate the diminished tension in the vessels. In Ci and R,, taken from the same person during Valsalva's experiment, the opposite condition occurs. Compressed Air. — On expiring into a vessel resembling a spirometer (see Respiration), (Wal- denburg's respiration apparatus), and filled with compressed air, the same result is obtained as in INFLUENCE OF PRESSURE ON THE PULSE CURVE. 155 Valsalva's experiment — the blood pressure falls and the pulse beats increase ; conversely, the inspi- ration from this apparatus of air under less pressure acts like Miiller's experiment, i. e., it increases the effect of the inspiration, and afterward increases the blood pressure, which may either remain increased on continuing the experiment, or may fall [Lenzmann). The inspiration of compressed air diminishes the mean blood pressure [Zuntz), and the after- effect continues for some time. The pulse is more frequent both during and after the experiment. Expiration in rarefied air increases the blood pressure. The effects which depend upon the action of the nervous system do not occur to the same extent in all cases. Exposure to compressed air in a pneumatic cabinet lowers the pulse curve, the elastic vibrations become indistinct, and the dicrotic wave diminishes and may disappear {v. Vivenot). The heart's beat is slowed and the blood pressure raised [Bert). Exposure to rarefied air causes the opposite result, which is assign of diminished arterial tension. Pulsus Paradoxus. — Under pathological conditions, especially when there is union of the heart or its large vessels with the surrounding parts, the pulse during inspiration may be extremely Fig. 94. Pulsus paradoxus (after Kussmaul). E, expiration ; J, inspiration. small and changed, or may even be absent (Fig. 94). This condition has been called pulsus paradoxus [Griesinger, Kussmaul). It depends upon a diminution of the arterial lumen during the inspiratory movement. Even in health, it is possible by a change of the inspiratory movement to produce the p. paradoxus {^Riegel, Sommerbrodt). 75. INFLUENCE OF PRESSURE ON THE PULSE CURVE.— It is most important to know the actual pressure which is applied to an artery while a sphygmogram is being taken. The changes affect i\ieform of the curve as well as the relation of individual parts thereof. In Fig. 95, a, b, c, d, e are radial curves; a was taken with a minimal pressure, b with loo, c 200, d 250, and e 450 grams pressure, while A, B, C, D show the relations as to the time of occur- rence of the individual phenomena where the weight was successively increased. The study of these curves yields the following results: (i) When the weight is small, the dicrotic wave is relatively less; the whole curve is high; (2) with a moderate weight (100 to 200 grams) the Fig. 95. Various forms 01 curves (radial) obtained by gradually increasing the pressure. dicrotic wave is bestmarked, the whole curve is somewhat lower; (3) on increasing the "ttrei^t the size of the dicrotic wave again diminishes ; (4) the fine elastic vibrations preceding the dicrotic wave appear first when a weight of 220 to 300 grams is used; (5) the rapidity of the pulse changes with increasing weight, the time occupied by the ascent becoming shorter, the descent becoming longer; (6) the height of the entire curve decreases as the weight increases. In every sphygmo- gram the pressure under which it was obtained ought always to be stated. In Fig. 95, A, B are curves obtained from the radial artery of a healthy student. The pressure exerted upon the artery for A was icx); B, 220 grms. (i vibration = 0.01613 sec). 156 VELOCITY OF THE PULSE WAVE IN MAN. " If pressure be exerted upon an artery for a long time, the strength of the pulse is gradually increased. If, after subjecting an artery to considerable pressure, a lighter weight be used, not unfrequently the pulse curve assumes the form of a dicrotic pulse, owing to the greater develop- ment of the dicrotic elevation. When strong pressure is applied, the blood is forced to find its way through collateral channels. When the chief artery ceases to be compressed, the total area is, of course, considerably and suddenly enlarged, which results in the production of a dicrotic elevation. Kig. 83, X, is such a dicrotic curve obtained after considerable pressure had been applied to the artery. 76. TRANSMISSION OF PULSE V^AVES.— The pulse wave proceeds throughout the arterial system from the root of the aorta, so that the ])ulse is felt sooner in parts lying near the heart than in the peripheral arteries. E. H. Weber calculated the velocity of the pulse wave as 9.240 metres [28'.'^ feet] per second, from the difference in time between the pulse in the external maxillary artery and the dorsal artery of the foot. Czermak showed that the elasticity was not equal in all the arteries, so that the velocity of the pulse wave cannot be the same in all. The pulse wave is propagated more slowly in the arteries with soft extensile walls than in arteries with resistant and thick walls, so that it is transmitted more rapidly in the arteries of the lower extremities than in those of the upper. It is still slower in children. 77. PULSE WAVE IN ELASTIC TUBES. — Waves similar to the pulse may be pro- duced in elastic tubes, (i) According to E. H. Weber the velocity of propagation of the waves is 11.205 metres per sec; according to Bonders, 11-13 metres (34-42 feet). (2) According to E. H. Weber increased internal tension causes only an inconsiderable decrease; Rive found a great decrease; Donders found no obvious difference; while Marey found an increased velocity. (3) Bonders found the velocity to be the same in tubes 2 mm. in diameter as in wider tubes, but Marey believes that the velocity varies when the diameter of the tube changes. (4) The velocity is less, the smaller the elastic coeflicient. (5) The velocity increases with increased thickness of the wall, while it diminishes when the specific gravity of the fluid increases. Moens has recently formulated the following laws as to the velocity of propagation of waves in elastic tubes: (i) It is inversely proportioml to the square root of the specific gravity of the fluid; (2) it is as the square root of the thickness of the wall, the lateral pressure being the same ; (3) it is inversely as the square root of the diameter of the tube, the lateral pressure being the same; (4) it is as the square root of the elastic coefficient of the wall of the tube, the lateral pressure being the same ( Valentin"). (A) The velocity of the wave is 11.809 nietres per second. (B) The inlra-vascular pressure has a decided influence on the velocity: thus, in the tube, A, with 18 cm. (Hg.) pressure, the velocity per metre := 0.093 second, while with 21 cm. pressure {Hg.) ^0.095 second per metre. (C) The specific gravity of the liquid influences the velocity of the pulse wave. In mercury the wave is propagated four times more slowly than in water. (D) The velocity in a tube which is more rigid and not so extensile is greater than in a tube which is easily distended. 78. VELOCITY OF THE PULSE WAVE IN MAN.— Landois obtained the follow- ing results in a student : Difference between carotid and radial = 0.074 second (the distance being taken as 62 centimetres) ; carotid and femoral ^= 0.068 second; femoral (inguinal region) and posterior tibial = 0.097 second (distance estimated at 91 centimetres). [Waller obtained between the heart and carotid o.io second ; heart and femoral, 0.18 sec. ; heart and dorsalis pedis, 0.22.] The velocity of the pulse wave in the arteries of the upper extremities = 8.43 metres per second, and in those of the lower extremity 9.40 metres per second, {i.e., about 30 feet per second]. The velocity is greater in the less extensile arteries of the lower extremities than in those of the upper limb. For the same reason it is less in the peripheral arteries and in the yielding arteries of children {Czennak). E. H. Weber estimated the velocity at 9.24 metres per second; Garrod, 9-10.8 metres; Grashey, 8.5 metres; Moens, S. 3 metres, and with diminished pressure during Valsalva's experiment 7.3 metres (? 60, § 74). Influencing Conditions. — In animals, hemorrhage, slowing of the heart produced by stimula- tion of the vagus {Moens), section of the spinal cord, deep morphia narcosis, and dilatation of the blood vessels by heat, produce slowing oi the velocity, while stimulation of the spinal cord accelerates it [Grunmach). OTHER PULSATILE PHENOMENA. 157 The wave length of the pulse wave is obtained by multiplying the dura- tion of the inflow of blood into the aorta rrr 0.08 to 0.09 second (§ 51), by the velocity of the pulse wave. Method. — Place the knobs of two tambours (Fig. 76) upon the two arteries to be investigated, or place one over the apex beat and the other upon an artery. These receiving tambours are connected with two registering tambours, as in Brondgeest's pansphygmograph (§ 67, Fig. 76), so that their writing levers are directly over each other, and so arranged as to write simultaneously on one vibrating plate attached to a tuning-fork. [Or they may be made to write upon a revolving cylinder, whose rate of movement is ascertained by causing a tuning-fork of a known rate of vibra- tion to write under them.] The apparatus is improved by using rigid tubes and filling them with water, in which all impulses are rapidly communicated. In arteries which are distant from each Fig. 96. A, curve of radial artery on a vibrating surface (i vib. = 0.01613 sec.) ; P, apex cf curve ; e, e, elastic vibrations ; R, dicrotic wave. B, curve of same radial taken along with the heart beat; v, H, P, contraction of the ventricle. other, or in the case of the heart and an artery, the two knobs of the receiving tambours may be connected by means of a Y-tube with one writing lever. In Fig 96, B is a curve from the radial artery taken in this way. In it z/ H P indicates contraction of the ventricle; H, the apex of the ventricular contraction ; P, the primary apex of the radial curve; v, the beginning of the ventricular contraction ; /, of the radial pulse. A is the curve of the radial artery alone. From these curves it is evident that in this instance nine vibrations occur between the beginning of the ventricular contraction and the beginning of the pulse in the radial artery = 0.15 sec. In Fig. 97 the difference between the carotid and the posterior tibial pulse = 0.137 sec. Pathological. — In cases of diminished extensibility of the arteries, e. g., in atheroma (^ 77, D), the pulse wave is propagated more rapidly. Local dilatations of the arteries, as in aneurisms, cause a retardation of the wave, and a similar result arises from local constrictions. Relaxation of the walls of the vessels in high fever retards the movement {Uamernik). Fig. 97. Tib.fost. I : Garot. : Curves ot the carotid and posterior tibial taler incisors very lightly, we detect a double beat of the lower against the upper teeth, owing to the pulse beat in the external iDaxillary artery raising the lower jaw. The second elevation is due to the closure of the semilunar valves, and not to a dicrotic wave. 6. Brain and Fontanelles. — The large arteries at the base of the brain communicate a move- ment to it, while similar movements occur with respiration — rising during expiration and falling during inspiration. These movements are visible in the fontanelles of infants. The respiratory movements depend upon variations in the amount of blood in the veins of the cranial cavity, and also upon the respiratory variations of the blood pressure. 7. Among pathological phenomena are (a) the beating in the epigastrium, e. _q:, in the hyper- trophy of the right or left ventricle, caused, it may be, by deep insertion of the diaphragm, and it may be, partly, by the beating of a dilated abdominal aorta or coeliac axis. t. (b) Aneurisms or abnormal dilalations of the arteries cause an abnormal pulsation, while they Fig. 98. 1. Elastic support for registering the molar motions of the body — K, woodenjbox ; B, feet of patient ; /.cardiograph ; a ^, elastic tubing. II. Vibration curves of a healthy person. III. Curve obtained from a patient with insuffi- ciency of the aortic valves and great hypertrophy of the heart. produce a slowing in the velocity of the pulse wave in the corresponding artery. Hence the pulse appears later in such an artery than in the artery on the healthy side. Hypertrophy and dilatation of the left ventricle cause the arteries near the heart to pulsate strongly. In the analogous condition of the right ventricle, the beat of the pulmonary artery may be seen and felt in the second left inter- costal space. 80. VIBRATIONS OF THE BODY DUE TO THE HEART.— The beating of the heart and large arteries communicates vibrations to the body as a whole ; the vibration being not simple but compound. Gordon was the first to represent this pulsatory vibration graphically. If a person be placed in an erect attitude in the scale-pan of a large balance, the index oscillates, and its movements coincide with the heart's movements. Method.— Take a long four-sided box, K, open at the top, and arrange several coils, a, b, ot stout caoutchouc tubing round one end (Fig. 98). A wooden board, B, is so placed that it rests with one end on the caoutchouc tubing, and with the other on the narrow end of the box. The person to be experimented upon, A, stands vertically and firmly on this board. A receiving tam- bour,/, is placed against the surface of the board next the elastic tube, which registers the vibrations of the foot support. Fig. Ill is a curve showing such vibrations, each heart beat being followed in this case by four oscillations. To ascertain the relations and causes of these vibrations, it is necessary to obtain, simultaneously, a tracing of the heart and the vibratory curve. For this purpose use the THE BLOOD CURRENT. 159 two tambours of Brondgeest's pansphygmograph (§ 67, 76), placing one knob or pad over the heart and the other on the foot support, and allow the writing tambours to inscribe their vibrations on a glass plate attached to a tuning-fork. In the lower or cardiac impulse curve (Fig. 99), the rapidly rising part is due to the ventricular systole. It contains eight vibrations (i vib. = 0.01613 sec). The beginning of the ventricular systole is indicated in the figure by -36, -3, -17. If the corresponding numbers in the upper or vibratory curve are studied, it is obvious that at the moment ef ventricular systole the body makes a downward vibration, i. e., it exercises greater pres- sure upon the foot support. Gordon interprets his curve as giving exactly the opposite result. This downward motion, however, lasted only during five vibrations of the tuning-fork ; during the last Fig. 99. The upper curve is the vibration curve of a healthy person, and the lower one a tracing of the apex beat. three vibrations, corresponding to the systole, there is an ascent of the body corresponding to a less pressure upon the foot plate. When the ventricle empties itself, it undergoes a movement in a downward and outward direction. — Gutbrodt's " reaction impulse." In the upper curve analogous numbers are employed to indicate the vibrations occurring simul- taneously, viz., -28, -11, -10. The closure of the semilunar valves is well marked in the three heart beats at 20, -20. This closure is indicated in analogous points in both curves, after which there is a descent of the foot support, and this corresponds to the downward propagation of the pulse wave through the aorta to the vessels of the feet. Pathological. — In insufficiency of the aortic valves, as shown in Fig. 98, III, the vibration com- municated to the body is very considerable. 81. THE BLOOD CURRENT.— Cause.— The closed and much- branched vascular system, whose walls are endowed with elasticity and contrac- tility, is not only completely filled with blood, but it is over-filled. The total volume of the blood is somewhat greater than the capacity of the entire vascular system. Hence it follows that the mass of blood must exert pressure on the walls of the entire system, thus causing a corresponding dilatation of the elastic vascular walls {Brunner). This occurs during life ; after death the muscles of the vessels relax, and fluid passes into the tissues, so that the blood vessels come to contain less fluid, and some of them may be empty. If the blood were uniformly distributed throughout the vascular system and under the same pressure, it would remain in a position of equilibrium (as after death). If, however, the pressure be raised in one section of the tube, the blood will move from the part where the pressure is higher to where it is lower ; so that the blood current is a result of the difference of pressure within the vascular system. If either the aorta or the venae cavse be suddenly ligatured in a living animal, the blood continues to flow, but gradually more slowly, until the difference of pressure is equalized throughout the entire vascular system. The velocity of the current will be greater the greater the difference of pres- sure, and the less the resistance opposed to the blood stream. The difference of pressure which causes the current is produced by the heart. Both in the systemic and pulmonary circulation the point of greatest pressure is in the root or beginning of the arterial system, while the point of 160 THE BLOOD CURRENT. lowest pressure is in the terminal portion of the venous orifices at the heart. Hence the blood flows continually from the arteries through the capillaries into the venous trunks. The heart keeps up the difference of pressure required to produce this result ; with each systole of the ventricles a certain quantity of blood is forced into the beginning of the arteries, while at the same time an equal amount flows from the venous orifices into the auricles during their diastole {E. H. Weber). Bonders showed that the action of the heart not only causes the difference of pressure necessary to establish a blood current, but also raises the mean pres- sure within the vascular system. The terminations of the veins at the heart are wider and more extensible than the arteries where they arise from the heart (Fig. 133). As the heart propels a volume of blood into the arteries equal to that which it receives from the veins, it follows that the arterial pressure must rise more rapidly than the venous pressure diminishes, since the arteries are not so wide nor so extensible as the veins. Thus the total pressure must also increase. Cause of Continuous Flow. — The volume of blood expelled from the ven- tricles at every systole would give rise to 2. jerky or intermittent movement of the blood stream (i) if the tubes had rigid walls, as in such tubes any pressure ex- erted upon their contents is propagated momentarily throughout the length of the tube, and the motion of the fluid ceases when the propelling force ceases ; (2) the flow would also be intermittent in character in elastic tubes if the time between two successive systoles were longer than the duration of the current necessary for the compensation of the diff"erence of pressure caused by the systole. If the time between two successive systoles be shorter than the time necessary to equilibrate the pressure, the current will become continuous, provided the resistance at the periphery of the tube be sufficiently great to bring the elasticity of the tube into action. The more rapidly systole follows systole, the greater the diff'erence of pressure becomes, and the more distended the elastic walls. Although the current thus produced is continuous, a sudden rise of pressure is caused by the forcing in of a mass of blood at every systole, so that with every systole there is a sudden jerk and acceleration of the blood streaiti corresponding to the pulse (com- pare § 64). The sudden jerk-like acceleration of the blood current is propagated throughout the arterial system with the velocity of the pulse wave ; both phenomena are due to the same fundamental cause. Every pulse beat causes a temporary rapid pro- gressive acceleration of the particles of the fluid. But just as the form movement of the pulse is not a simple movement, neither is the pulsatile acceleration a simple acceleration. It follows the course of the development of the pulse wave. The pulse curve is the graphic representation of the pulsatory acceleration of the blood stream. Every rise in the curve corresponds to an acceleration, every depression to a retardation of the current. [Method : Ri^d and Elastic Tubes. — These facts are easily demonstrated. Tie a Higgin- son's sjTinge to a piece of an ordinary gas pipe. On forcing water through the tube, by compress- ing the elastic pump, the water will flow out at the other end of the tube in jets, while during the intervals of pulsation no water will flow out. As the walls of the tube are rigid, just as much fluid flows out as is forced into the tube. If a similar arrangement be made, and a long elastic tube be nsed, a continuous outflow is obtained, pro%-ided the pulsations occur with sufiicient rapidity and the length of the tube, or the resistance at its periphery-, be sufiScient to bring the elasticity of the tube into action. This can be done by putting a narrow cannula in the outflow end of the tube, or by placing a clamp on it so as to diminish the exit aperture. This apparatus converts the intermit- tent flow into a continuous current.] The fire-engine is a good example of the conversion of an intennittent inflow into a uniform outflow. The air in the reser^'oir is in a state of elastic tension, and it represents the elasticity of the vascular walls, ^^■hen the pump is worked slowly, the out- flow of the water occurs in jets, and is interrupted. If the pumping movement be sufficiently rapid, the compressed air in the reservoir causes a continuous outflow, which is distinctly accelerated at every movement of the pump. [The ordinary spray-producer is another good example.] [Thuii, there are two factors — a central one, the heart,— and a peripheral ESTIMATION OF THE BLOOD PRESSURE. 161 one, the amount of resistance in the arterioles. Either or both may be varied, and as this is done, so will the pressure and velocity vary.] Current in the Capillaries. — In the capillaries the pulsatile acceleration of the current ceases with the extinction of the pulse wave. The great resistance which is offered to the current toward the capillary area causes both to disappear. It is only when the capillaries are greatly dilated, and when the arterial blood pres- sure is high, that the pulse is propagated through the capillaries into the beginning of the veins. A venous pulse is observed in the veins of the sub-maxillary gland after stimulation of the chorda tympani nerve, which contains the vaso-dilator nerves for the blood vessels of this gland. If the finger be constricted with an elastic band, so as to hinder the return of the venous blood, and to increase the arterial blood pressure, while at the same time dilating the capillaries, an inter- mittent increased redness occurs, which corresponds with the well-known throb- bing sensation in the swollen finger. This is due to the capillary pulse. [Roy and Graham Brown found that pulsatile phenomena were produced in the capil- laries by increasing the extra-vascular pressure (§ 86). Quincke called attention to the capillary pulse, which can often be seen under the finger nails. Extend the fingers completely, when a whitish area appears under the nails. A red area near the free margin of the nail advances and retires with each pulse beat. It is well marked in some diseased conditions of the heart, especially in incompetence of the aortic valves, and is probably produced by increased extra-vascular pres- sure.] 82. SCHEMATA OF THE CIRCULATION.— E. H. Weber constructed a scheme of the circularion. It consisted of a force pump with properly arranged valves to represent the heart, portions of gut for the arteries and veins, and a piece of glass tubing containing a piece of sponge to represent the capillaries. Various schemes have been invented, including the very complicated one of Marey [the extremely ingenious one of v. Thanhoffer, and the thoroughly practical one of Rutherford] . 83. CAPACITY OF THE VENTRICLES.— Since the right and left ventricles contract simultaneously, and just the same volume of blood passes through the pulmonary as through the systemic circulation, it follows that the right ventricle must be just as capacious as the left. The capacity of the ventri- cles has been estimated in the following ways : — Methods. — (i) Directly, by filling the dead relaxed ventricle with blood or an injection mass. This method is unsatisfactory and inaccurate. (2) Indirectly. Volkmann 11850) estimated it thus: Estimate the sectional area of the aoita, and the velocity of the blood stream in it (?. i). From this calculate the amount of blood passing through the aorta in the unit of time. As the total quantity of blood in the body is known ( =r ^ of the body weight), we can easily calculate how long this takes to flow through the aorta. We must also know the number of beats during the time of the circulation. From these data, and from experiments on animals, Volkmann estimated the volume of blood discharged at each systole by the ventricle to be xo-o °f '^^ body weight. For a man weighing 75 kilos, this is 187.5 grams. This estimate still leaves much to be desired. Place calculates it in the following manner : A man uses about 500 litres of O in 24 hours. To absorb this into the venous blood (which contains about 7 vols, per cent less O than arterial), about 7000 litres of blood must pass through the lungs in 24 hours. If one calculates 100,000 heart beats in 24 hours, then at each systole only 70 cubic centimetres are discharged. 84. ESTIMATION OF THE BLOOD PRESSURE.— (A) In Animals : (i) Methods of Hales. — The Rev. Stephen Hales (1727) was the first to introduce a long glass tube into a blood vessel in order to estimate the blood pressure by measuring the height of the column of blood. The tube was provided at its tower end with a copper tube bent at a right angle (Pitot's tube). [The tube he used was one- sixth of an inch bore and about 9 feet long, and was inserted into the femoral artery of a horse. The height to which the blood rose in the tube was noted, as well as the oscillations that occurred with every pulsation. From the height of the column of flcdd he calcu- lated the force of the heart.] (2) The Haemadynamometer of PoiseuUIe (1828). — This observer used a U-shaped tube partiallv filled with mercury — a manometer — which was brought into connection with a blood vessel by means of a rigid tube. [The merctiry oscillated with every pulsation, and the extent of II 162 LUDWIG S KYMOGRAPH. the oscillations was read off by means of a scale attached to the bent tube. He called the instru- ment a humaityiiamoiiielerr^ [(3) Vierordt used a tube 5 or 6 feet long, and filled it with a solution of sodium carbonate, thus preventing much blood from entering the tube, while at the same time the soda solution ])revented the coagulation of the blood.] Fig. 100. r\ c- b I. Scheme of C. Ludwig's kymograph. II. Kick's spring kyniogriiph. Fig. lor. P^T^ISST^ Ludwig's improved revolving cylinder, R, moved by the clockwork in the box A, and regulated by a Foucault's regulator placed on the top of the box. The disk, D, moved by the clockwork, presses upon the wheel, n, which can be raised or lowered by the screw, L, thus altering the position of « on D, so as to cause the cylinder to rotate at different rates. The cylinder it- self can be raised by the handle, U. On the left side of the figure is a mercurial manometer. When the cylin- der is used, it is covered with smoked smooth paper. (4) C. Ludwig's Kymograph. — C. Ludwig employed a U-shaped manometer, but he placed a light float (Fig. 100, d, s) upon the surface of the mercury in the open limb of the tube. A writing style,/, placed transversely on the free end of the float, inscribed the movements of the float — and, there- fore, 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 pulsa- tile 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 cor- responding column of blood. Setsche- now placed a stop-cock in the lower bend, h, of the tube. If this be closed so as just to permit a small aperture of communication to remain, the pulsatile vibrations no longer appear, and the apparatus indicates the mean pressure. METHOD OF ESTIMATING BLOOD PRESSURE. 163 By the term mea?i 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. 102, each of the smaller waves corresponds to a heart beat, the ascent corresponds to the systole and the descent to the diastole. The large undulations are due to the respiratory movements. It is clear that the heart beat is expressed as a simple rise and fall (Fig. 102), so that the curve of the heart beat obtained with a mercurial kymograph differs from a sphygmographic curve. Faults of a Mercurial Manometer. — A perfect recording instrument ought to indicate the height of the blood pressure, 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 registering the blood pressure, and not for obtaining the exact form of the pulse wave. Instruments with less inertia, and with no vibrations pecuUar to themselves, are required for this purpose. Fig. 102. Blood-pressure curve of the carotid of a dog obtained with a mercurial manometer. C-;f== line of no pressure, zero line, or abscissa ■ y-y 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. [Method. — Expose the carotid of a chloralized rabbit, and isolate a portion of the vessel between two ligatures, or two spring clamps. With a pair of scissors make an oblique slit in the artery, and into it tie a straight glass cannula, directing the pointed end of the cannula toward the heart. Fill the cannula with a saturated solution of sodium carbonate, taking care that no air bubbles enter, and connect it with the lead tube which goes to the ascending limb of the manometer. The tube which 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 carbonate, 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 positive pressure of mercury in the manometer about equal to the estimated blood pressure, and then clamp the tube of the pressure bottle where it joins the lead tube. This positive pressure prevents the escape of blood from the artery into the solution of sodium carbonate. 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. Peptones, 164 SPRING KYMOGRAPH. or rather the albumoses, when injected into the blood keep it from coagulating (p. 73). Roy finds that oil may take the place of sodic carbonate.] [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 blood pressure. This may be secured by giving curara and keeping up artilicial respiration, or by the carefully regulated inhalation of ether. When a drug is to be injected to test its action, if it be introduced into the jugular vein it is apt to afl'ect the heart directly. This may be avoided by injecting it into a vein of the leg, 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. 100). Various arrangements are employed for this purpose, but it is usual to cause 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 oflT the strip of paper, which is kept applied to the revolving surface by ivory friction wheels. In Ilering's complicated kymograph a long strip of smoked paper is used. The writing style may consist of a sable brush, or a tine glass pen filled with aniline blue disM)lved 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. 102 O - X is the zero line or the 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 pressure is obtained by drawing ordinates from the curve to the abscissa, measuring their length, and multi- plying by two.] (5) Spring Kymograph. — A. Fick (1864) uses a "hollow spring kymo- graph " on the principle of Bourdon's manometer (Fig. 100, II). 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 l>lood 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, d, there is fixed a vertical rod attached to a series of levers, //, ?', ^, 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. 103). a,l>, c, is the hollow spring filled with alcohol, and communicating at a with the lead Fig. 103. lube, (/, 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, ressure between the arterial and venous systems increase the venous pressure, and vice versa. 172 BLOOD PRESSURE IN THE VEINS. (2) General plethora of blood increases it ; aniemia diminishes it. (3) Respiration, or the aspiration of the thorax, affects specially the pres- sure 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 fills during expiration. 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. Every surgeon is acquainted with the fact that air is particularly liable to be sucked into the veins, especially in operations near the root of the neck. This is due to the negative intra-thoracic pressure occurring during inspiration.] (4) Aspiration of the Heart. — Blood is sucked or aspirated^ into the auricles when they dilate (p. 100), 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 retardation of the blood stream in the venae cavae^ caused by the contraction of the auricle (p. 99, a). The respiratory and cardiac undulations are occasionally observable in the jugular vein of a healthy person (§99)- YiQ ,,0 (5) Change in the /^ in the peripheral end of the artery [e. g., carotid) ; the bulb, A, is filled with oil, and B with dehbrinated 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 defibrinat'ed 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 (I sec.) IS calculated from the time necessary to fill the bulb with blood. Important results are obtained by means of this instrument. [Suppose 50 c.cm. of blood are delivered in 100 sees., then i c.cm. flows through in 2 sees. Suppose the sectional area of the artery to be 3^ mm. As the velocity is measured by the ratio of the quantity to the sectional area, then 5°°° 314 159 mm. per second.] [As peptone injected into the blood prevents it from coagulating (dog), this fact has been turned to account in using the rheometer.] (3) Vierordt's Haematachometer (1858) consists of a small metal box (Fig. 113, I) with parallel glass sides. To the narrow sides of the box are fitted an inlet, ) When pressure is exerted upon an artery, e. g., by the pressure of the greatly enlarged arteries during pregnancy, or by a large tumor pressing upon a large artery. Spontaneous Murmurs. — In cases where no source of external pressure is discoverable, and when no aneurism is present, the spontaneously occurring sounds are favored, when at the moment of arterial rest (cardiac systole) the arterial walls are distended to the slightest extent, and when during the movement of the pulse (cardiac diastole) the tension is most rapid [Traul>e, ll^eil), i. e.,. when the low systolic minimum tension of the arterial wall passes rapidly into the high maximum tension. This is especially the case in insufficiency of the aortic valves, in which case the sounds in the arteries are audible over a wide area. If the minimum tension of the arterial wall is relatively great, even during diastole, the sounds in the arteries are greatly diminished. Arterial murmurs are favored by (i) Sufficient delicacy and elasticity of the arterial walls. (2) Diminished peripheral resistance, e.g., an easy outflow of the fluid at the end of the stream. (3) Accelerated current in the vascular system generally. (4) A considerable difference of the pressure in the narrow and wide portions of the tube. (5) Large calibre of the arteries. In normal pulsating arteries, sounds may be heard especially at an acute bend of the artery. Murmurs of this sort are loudest where several large arteries lie together; hence, during pregnancy, we hear the uteriiie murmur, or placental bruit, or souffle in the greatly dilated uterine arteries. It is much less distinct in the umbilical arteries of the cord (umbilical murmurs). Similar sounds are heard through the thin walls of the head of infants, and a murmur is sometimes heard in the enlarged spleen in ague [Maissurianz). Auscultation of the Normal Pulse. — On auscultating the radial artery under favorable cir- cumstances, and especially in old, thin persons with wide arteries and dicrotic pulse, one may hear two sounds corresponding to the primary and dicrotic waves. In insufficiency of the aortic valves, characteristic sounds may be heard in the crural artery. If pressure be exerted upon the artery, a double blowing murmur is heard; the first one is due to a large mass of blood being propelled into the artery synchronously with the heart beat, the second to the fact that a large quantity of blood flows back into the heart during diastole. If no pressure be exercised two sounds are heard, and these seem to be due to a wave propagated into the arteries by the auricles and ventricles respectively— compare f 73, Fig. 86, III. In atheroma a double sound may sometimes be heard (g 73, 2). THE VENOUS PULSE PHLEBOGRAM. 185 98. VENOUS MURMURS.— I. Bruit de Diable.— This sound is heard above the clavicles in the furrow between the two heads of the sterno-mastoid, most frequently on the right side, and in 40 per cent, of all persons examined. It is either a continuous or a rhythmical murmur, occurring during the diastole of the heart or during inspiration ; it has a whistling or rushing character, or even a musical quality, and arises within the bulb of the common jugular vein. When this sound is heard without pressure being exerted by the stethoscope, it is a pathological phenomenon. If, however, pressure be exerted, and if, at the same time, the person examined turn his head to the opposite side, a similar sound is heard in nearly all cases. The pathological bruit de diable occurs especially in anaemic persons, in lead poisoning, in syphilitic and scrofulous persons, sometimes in young persons, and less frequently in elderly people. Sometimes a thrill of the vascular wall may be felt. Causes. — It is due to the vibration of the blood flowing in from the relatively narrow part of the common jugular vein into the wide bulbous portion of the vessel, and seems to occur chiefly when the walls of a thin part of the vein lie close to each other, so that the current must purl through it. It is clear that pressure from without, or lateral pressure, as by turning the head to the opposite side, must favor its occurrence. Its intensity will be increased when the velocity of the stream is increased, hence inspiration and the diastolic action of the heart (both of which assist the venous current) increase it. The erect attitude acts in a similar manner. A similar bruit is sometimes, though rarely, heard in the subclavian, axillary, thyroid, facial, innominate and crural veins, and superior cava. II. Regurgitant Murmurs. — On making a sudden effort, a murmur may be heard in the crural vein during expiration, which is caused by a centrifugal current of blood, owing to the incompetence or absence of the valves in this region. If the valves at the jugular bulb are not tight, there may be a bruit with expiration (expiratory '■\\x'gv\2x vein bruit — Hamernjk), or during the cardiac systole (jyj^o/iV jugular vein bruit — v. Bat?iberger). III. Valvular Sounds in Veins. — When the tricuspid valve is incompetent, during the ven- tricular systole, a large volume of blood is propelled backward into the venae cavse. The venous valves are closed suddenly thereby and a sound produced. This occurs at the bulb or dilatation on the jugular vein (v. Bamberger^, and in the crural vein at the groin (N. Friedreich), i. e., only as long as the valves are competent. Forced expiration may cause a valvular sound in the crural vein. No sound is heard in the veins under perfectly normal circumstances. 99. THE VENOUS PULSE— PHLEBOGRAM.— Methods.— A tracing of the move- ments of a vein, taken with a lightly weighted sphygmograph, has a characteristic form, and is called a phlebogram (Fig. 117). In order to interpret the various events of the phlebogram, it is most important to record simultaneously the events that take place in the heart. The auricular contraction (compare Fig. 39) is synchronous with a b ; be, with the ventricular systole, during which time the first sound occurs, while a ^ is a presystolic movement. The carotid pulse coincides nearly with the apex of the cardiogram, i. e., almost simultaneously with the descending limb of the phlebogram (^Riegel). Occasionally in healthy individuals a pulsatile movement, synchronous with the action of the heart, may be observed in the common jugular vein. It is either confined to the lower part of the vein, the so-called bulb, or extends further up along the trunk of the vein. In the latter case, the valves above the bulb are insufficient, which is by no means rare, even in health. The wave motion passes from below upward, and is most obvious when the person is in the passive hori- zontal position, and it is more frequent on the right side, because the right vein lies nearer the heart than the left. It is propagated more slowly than the arterial pulse wave. The venous pulse resembles very closely the tracing of the cardiac impulse. Compare Fig. 117, i, with Fig. 39. It is obvious that, as the jugular vein is in direct communication with the right auricle, and as the pressure within it is low, the systole of the right auricle must cause a positive wave to be propagated toward the peripheral end of the jugular vein. Fig. 117, 9 and 10, are venous pulse tracings of a healthy person with insufficiency of the valves of the jugular vein. In these curves, the part a b cor- 186 LIVER PULSE. responds to the contraction of the auricle. Occasionally this part consists of two elevations, corresponding to the contraction of the atrium and auricle respectively. As the blood in the right auricle receives an impulse from the sudden tension of tlie tricuspid valve, synchronous with the systole of the fight ventricle, there is a positive wave in the jugular vein in Fig. 117, 9 and 10, indicated by b, c. Lastly, the sudden closure of the pulmonary valves may even be indicated (^). As the aorta lies in direct relation with the pulmonary artery, the sudden closure of its valves may also be indicated (Fig. 91, 9, at d^. During the diastole of the auricle and ventricle, blood flows into the heart, so that the vein partly collapses and the lever of the recording instrument descends. Sinus and Retinal Pulse. — The blood in the sinuses of the brain also undergoes a pulsatile movement, owing to the fact that during cardiac diastole much blood flows into the veins (^Mosso). L'nder favorable circumstances, this movement may be propagated into the veins of the retina, constituting the zenous retinal tulse of the older observers {/lelfreich) . Fig. 117. '\cDO\is, ■p\i\s<£A (J-'riedreich). i-3, trom insufficiency ot the tricuspid; 9, 10, pulse ot the jugular vein ol a healthy person. In all the curves, a b = contraction of the right auricle ; 6 c, oi the right ventricle ; d, closure of the aortic valves ; f, closure of the pulmonary valves ; ^,^, diastole of the right ventricle. Pathological Jugular Vein Pulse. — The venous pulse in the jugular vein is far better marked in insufficiency of the tricuspid valve, zx\A the vein may pulsate violently, but if its valves be perfect, the pulse is not propagated along the vein, so that a pulse in the jugular vein is not necessarily a sign of insufficiency of the tricuspid valve, but only of insufficiency of the valve of the jugular vein {^Friedreich). Liver Pulse. — The ventricular systole is propagated into the valveless inferior vena cava, and causes the liver pulse. With each systole blood passes into the hepatic veins, so that the liver undergoes a systolic swelling and injection. Fig. 117, 2-8, are curves of the pulse in the common jugular vein. Although at first sight the curves appear to be very different, they all agree in this, that the various events occurring in the heart during a cardiac revolution are indicated more or less completely. Li all the curves, ab = auricular contraction. The auricle, when it contracts, excites a positive wave in the veins. The elevation, b c, is caused by the large blood wave produced in the veins, owing to the emptying of the ventricle. It is always greater, of course, in insufficiency of the tricuspid valves than under normal circumstances (Fig. 117, 9 and 10). In the laUer case, the closure of the tricuspid valve causes only a slight wave motion in the auricle. The apex, c, of this wave may be higher or lower, accord- DISTRIBUTION OF THE BLOOD. 187 ing to the tension in tlie vein and the pressure exerted by the sphygmograph. As a general rule, at least one notch (4, 5, 6, e) follows the apex, due to the prompt closure of the valves of the pulmonary artery. The closure of the closely adjacent aortic valves may cause a small secondary wave near to e (as in i and 2, d). The curve falls toward /, corresponding to the diastole of the heart. A well-marked venous pulse occurs when the r?^k( auricle is greatly congested, as in cases of insufficiency of the mitral valve or stenosis of the same orifice. In rare cases, in addition to the pulse in the common jugular vein, the external jugular, the facial, thyroid, external thoracic veins, or even the veins of the upper and lower extremities may pulsate. A similar pulsation must occur in the pulmonary veins in mitral insufficiency, but of course the result is not visible. On rare occasions, a pulse occurs in the veins on the back of the hand and foot, owing to the arterial pulse being propagated through the capillaries into the veins. This may occur under normal circumstances, when the peripheral ends of the arteries become dilated and relaxed [Quincke^, or when the blood pressure within these vessels rises rapidly and falls as suddenly, as in insufficiency of the aortic valves. In progressive effusion into the pericardium the carotid pulse at iirst becomes smaller and the venous pulse larger; beyond a certain stage of pressure the latter ceases {^Riegel). 100. DISTRIBUTION OF THE BLOOD.— In the rabbit, one-fourth of the total amount of the blood is found in each of the following : a, in the passive muscles ; b, in the liver ; c, in the organs of the circulation (heart and vessels) ; d, in all other parts together. Methods. — The methods adopted do not give exact results. J. Ranke ligatured the parts during life, removed them, and investigated the amount of blood while the tissues were still warm. Influencing Conditions. — The amount of blood is influenced by (i) the anatomical distribu- tion of the vessels (vascularity or the reverse) as a whole ; (2) the diameter of the vessels, which depends upon physiological causes {a) on the blood pressure within the vessels ; {b) on the condi- tion of the vasomotor or vaso -dilator nerves; (f) on the condition of the tissues themselves, d".^., the vessels of the intestine during absorption ; by the vessels of muscle during muscular contraction ; of vessels in inflamed parts. The most important factor, however, is the state of activity of the organ itself; hence, the saying, " ubi irritatio, ibi afifiuxus." We may instance the congestion of the salivary glands and the gastric mucous membrane during diges- tion, and the increased vascularity of muscles during contraction. As the activity of organs varies at different times, the amount of blood in the part or organ goes hand in hand with the variations in its states of activity. When some organs are congested, others are at rest ; during digestion, there is muscular relaxation and less mental activity : violent muscular exertion retards digestion — during great congestion of the cutaneous vessels the activity of the kidneys diminishes. Many organs (heart, muscles of respiration, certain nerve centres) seem always to be in a nearly uniform state of activity and vascularity. During the activity of an organ, the amount of blood in it may be increased 30 per cent., nay, even 47 per cent. The motor organs of young muscular persons are relatively more vascular than those of old and feeble persons (y. Ranke^. In the condition of increased activity a more rapid renewal of the blood seems to occur ; after muscular exertion the duration of the circulation diminishes {Vierordt'). During a condition of mental activity, the carotid is dilated, the dicrotic wave in the carotid curve is increased (the radial shows the opposite condition), and the pulse is increased in frequency {Gley). Age. — The development of the heart and large vessels determines a different distriburion of the blood in the child from that which obtains in the adult. The heart is relatively small from infancy up to puberty, the vessels are relatively large ; while after puberty the heart is large, and the vessels are relatively smaller. Hence it follows that the blood pressure in the arteries of the systemic circulation must be lower in the child than in the adult. The pulmonary artery is relatively wide in the child, while the aorta is relatively small; after puberty both vessels have nearly the same size. Hence, it follows that the blood pressure in the pulmonary vessels of the child is relatively higher than that in the adult [Berteke). loi. PLETHYSMOGRAPHY.— In order to estimate and register the amount of blood in a limb Mosso devised an instrument (Fig. 118), which he termed a plethysmograph. 188 PLETHYSMOGRAPHY. It consists of a long cylindrical glass vessel, G, suited to accommodate a limb. The opening through which the limb is introduced is closed with caoutchouc, and the vessel is filled with water. There is an opening in the side of the vessel in which a manometer tube, filled to a certain height with water, is fixed. As the arm is enlarged owing to the increased supply of arterial blood passing into it at each pulse beat, of course the water column in the manometer is raised. Kick placed a float upon the surface of the water, and thus enabled the variations in the volume of the fluid to be inscribed on a revolving cylinder. The curve obtained resembled the pulse curve; it was even dicrotic. In Fig. ii8 the movement of the fluid is represented as conveyed to a Marey's tambour, T, similar to the recording apparatus employed in Brondgeest's pansphygmo- graph (Fig. 76). The cylinder C may be filled with air. Kries fills it with gas and connects the tube leading to T to a gas burner. The variations in the gas flame are then photographed. Results. — (t) Pulsatile Variations in the Volume. — As the venous cur- rent is regarded as uniform in the passive limb, every increase of the volume curve indicates a greater velocity of the arterial current toward the periphery, and vice versa (^Fick). The curves registered by the apparatus are volume pulses, and they resemble the curve of the dromograph (Fig. 113, III). The ascent of the curve indicates a greater, the descent a diminished inflow of arterial blood. At first sight the plethysmograph curve (volume pulse, ^ 90, 7) is very like the pulse curve (pressure pulse) ; both are dicrotic. But there are differences; the volume pulse curve beyond the apex falls more rapidly. This rapid fall, which is not accompanied by a corresponding fall of the pressure, is attributed by v. Kries to peripheral reflexion. The dicrotic wave occurs sooner in the volume pulse than in the pulse curve. Fig. 118. Mosso's plethysmograph. G, glass vessel for holding a limb ; F, flask for varying the water pressure in G ; T, recording apparatus. (2) The respiratory undulations correspond to similar variations in the blood pressure tracing (§ 85,/). Vigorous respiration and cessation of the respi- ration cause a diminution of the volume. The limb swells during straining and coughing, but diminishes during sighing. (3) Certain periodic undulations occur, due to the regular periodic contractions of the small arteries. (4) Other undulations, due to various accidental causes, affect the blood pressure : changes of the position of a limb acting hydrostatically, and dilatation or contraction of the vessels in other vascular regions. (5) Movement of the muscles of the limb under observation causes diminution of volume, as the venous current is accele- rated, the musculature is also very slightly diminished in volume, even when the mtra-muscular vessels are dilated. (6) Menial exercise causes a diminution in the volume of the limb, and so does sleep (Mosso). Music influences the blood pressure in dogs, the pressure rising or falling under different conditions. The stimulation of the auditory nerve is transmitted to the medulla oblongata, where it acts so as to cause acceleration of the action of the heart (Dogiel). (7) Com- pression of the afferent artery causes a decrease, and compression of the vein an mcrease in the volume of the limb {^Mosso). (8) Stimulation of the vasomotor nerves causes a decrease, that of the vaso-dilators an increase in the volume {Bow- ditch and Warren'). TRANSFUSION OF BLOOD. 189 102. TRANSFUSION OF BLOOD.— Transfusion is the introduction of blood from one animal into the vascular system of another animal. (a) The red corpuscles are the most important elements in connection with the restorative powers of the blood. They seem to preserve their functions even in blood which has been defibrinated outside the body (§ 4, A). (^b) With regard to the gases present in the blood, arterial blood never acts injuriously ; but venous blood overcharged with carbonic acid ought only to be transfused when the respiration is sufficient to oxygenate the blood as it passes through the pulmonary capillaries, whereby venous is transformed into arterial blood. If the respiratory movements have ceased, or are imperfectly performed, the blood becomes rapidly richer in carbonic acid, and in this condition reaches the heart ; thence it is propelled into the blood vessels of the medulla oblongata, where it acts as a powerful stimulus of the respiratory centre, causing dyspnoea, convulsions, and death. (^) The fibrin, and the substances from which it is formed, do not seem to play any part in connection with the restorative powers of the blood ; hence de- iibrinated blood performs all the functions of non-defibrinated blood within the body {^Paniim, Landois). {d) The investigations of Worm Miiller showed that an excess of 83 per cent, of blood may be transfused into the vascular system of an animal (dog) without producing any injurious effects. Hence it follows that the vascular system has the power of accommodating large quantities of blood within it. That the vascular system can accommodate itself to a diminished amount of blood has been known for a long time (§ 85, c). [It is very important to observe that the transfusion of a large quantity of blood does not materially or permanently raise the blood pressure.] When Employed. — The transfusion of blood is used (i) in acute anaemia (§ 41, I), e.g., after copious hemorrhage. New blood (150 to 500 c. c), from the same species of animal, is introduced directly into the vessels, to supply the place of the blood lost by the hemorrhage. (2) In cases of poisoning, where the blood has been rendered useless by being mixed with a poisonous substance, and hence is unable to support life. In such cases remove a considerable quantity of the blood, and replace it by fresh blood. Carbonic oxide is a poison of this kind, and its effects on the body have already been described (§16). A similar practice is indicated in poisoning with ether, chloral, chloroform, opium, morphia, strychnine, cobra poison, and such substances as dissolve the blood corpuscles, e.g., potassic chlorate. (3) Under certain pathological conditions, the blood may become so altered in quality as to be unable to support life. The morphological elements of the blood may be altered, and so may the relative proportion of its other constituents. Among these conditions may be cited the pathological condition of uraemia, due, it may be, to the accumulation of urea or the products of its decomposition within the blood ; accumulation of the biliary constituents in the blood, and great increase of the carbonic acid. All these three conditions, when very pronounced, may cause death. In these cases, part of the impure blood may be replaced by normal human blood. Among conditions where the morphological constituents of the blood are altered qualitatively or quantitatively are : hydrsemia (excessive amount of water in the blood, § 41, i) ; oligocythaemia (abnormal diminution of red blood corpuscles). When these conditions are highly developed, more especially in pernicious anaemia (§ 10, 2), healthy blood may be substituted. Transfusion is not suited for persons suffering from leukaemia (compare p. 59). After- Effects. — A quarter or half an hour after normal blood has been injected into the blood vessels of a man, there is a greater or less febrile reaction, according to the amount of blood transfused (Fever, § 220). 190 TRANSFUSION OF BLOOD. Operation. — The operative procedure to be adopted in the process of transfusion varies according as defibrinated or nondetibrinated blood is used. In order to defibrinate blood, some blood is withdrawn from a vein of a healthy man in the ordinary way, collected in an open vessel, and whipped or beaten with a glass rod until all the fibrin is completely removed from it. It is then filtered through an atlas filter, heated to the temperature of the body (by placing it in a vessel in warm water), and injected by means of a syringe into an artery ojiened for the purpose. A vein {e.!^., basilic or great saphenous) may be selected for the transfusion, in which case the blood is driven inward in the direction of the heart; if an artery is selected (radial or posterior tibial) the blood is injected toward the periphery {Hiiter), or toward the heart {Landois, Schd/er). If non-defibrinated human blood is used, the blood may be passed directly from the arm of the giver to the arm of the receiver by means of a flexible tube. The tube used must be filled with normal saline solution to prevent the entrance of air. [J. Duncan collects the blood shed during an operation in a 5 per cent, solution of sodic phosphate {Pavy'), and injects the mixture especially where much blood has been lost previously.] Dangers. — It is most important that no air be allowed to pass into the circulation, for if it be introduced in sufficient quantity it may cause death. When air enters the circulation it reaches the right side of the heart, where, owing to the movement of the blood, it forms air bubbles and makes a froth. The air-bubbles are pumped into the branches of the pulmonary artery, in which they become impacted, arrest the pulmonary circulation, and rapidly cause death. Peritoneal Transfusion. — Recently, the injection of defibrinated blood into the peritoneal cavity has been recommended. The blood so injected is absorbed {Fonfick). Even after twenty minutes the number of blood corpuscles in the blood of the recipient (rabbit) is increased, and the number is greatest on the first or second day. The operation, however, may cause death, and one fatal case, owing to peritonitis, is recorded [Afosler). It is evident that this method of transfusion is not applicable in cases where blood must be introduced into the circulation as rapidly as possible {e.g., after severe hemorrhage or in certain cases of poisoning). [Blood has been injected into the subcutaneous cellular tissue of the abdomen in cases of great debility.] Heterogeneous Blood. — The blood of animals ought never to be transfused into the blood 7'essels of man. It is to be remembered, however, that the blood corpuscles of the sheep are rapidly dissolved by human blood, so that tlie active constituents of the blood are rendered useless {La/tdois). As a general rule, the blood serum of some mammals dissolves the blood corpuscles of other mammals (§ 5, 5). Solution of the Blood Corpuscles. — The serum of dog's blood is a powerful solvent, while that of the blood of the horse and rabbit dissolves corpuscles relatively slowly. The blood cor- puscles of mammals vary very greatly with reference to their power to resist the solvent action of the serum of other animals. The red blood corpuscles of rabbits' blood are rapidly dissolved by the blood serum of other animals, while those of the cat and dog resist the solvent action much longer. Solution of the corpuscles occurs in defibrinated as well as in ordinary blood. When the blood of a rabbit or lamb is injected into the blood vessels of a dog, the red blood corpuscles are dissolved in a few minutes. If blood be withdrawn by pricking the skin with a needle, the par- tially dissolved corpuscles may be detected. Liberation of Haemoglobin and Haemoglobinuria. — As a result of the solution of the colored corpuscles, the blood plasma is reddened by the liberated haemoglobin. Part of the dissolved material may be used up in the body of the recipient, some of it for the formation of bile, but if the solution of the corpuscles has been extensive, the haemoglobin is excreted in the urine (haemoglobinuria), in less amount in the intestine, the bronchi, and the serous cavities. Bloody urine has been observed in man after the injection of lOO grammes of lamb's blood. Even some of the recipient's blood corpuscles are dissolved by the serum of the transfused blood, e. g., on transfusing dog's blood into man. In the rabbit, whose corpuscles are readily dissolved, the transfusion of tiie blood scrum of the dog, man, pig, sheep, or cat produces serious symptoms, and even death. The dog, whose corpuscles are more resistant, bears transfusion of other kinds of blood well. Dangers. — When foreign or heterogeneous blood {i. ski); cholesterin, a gluten-like body, inosit, a pigment containing iron, and even free iron oxide [N'asse). The ash is rich in phosphoric acid and iron (p. 195) — poor in chlorine compounds. The splenic juice is alkaline in reaction ; the specific gravity of the spleen =r 1059-1066. The functions of the spleen are obscure, but we know some facts on which to form a theory. [The Elements of human splenic pulp. i j'cr r ..u ■ ii i. t I, colorless cells: 2, endothe- splceu differs from Other organs ni that no very apparent lium; 3, colored blood cor- effect is pfoduced by it, so that we must determine its puscles ; 4, cells Containing . \ ■' ^ ... . , . granules, the upper one with uscs lu the ccouomy from a Consideration of such facts end!,°ser"°°'^'°''^"'''^''^' ^s the followiug : (i) The effects of its removal or ex- tirpation. (2) The changes which the blood undergoes as it passes through it. (3) Its chemical composition. (4) The results of experi- ments upon it. (5) The effects of diseases.] (i) Extirpation. — The spleen may be removed from an animal — old or young — without the organism suffering any very obvious change {Galen). The human spleen has been successfully removed by Koberle, Fean, and others. As a result (compensatory ?) the lymphatic glands enlarge, but not constantly, while the blood-forming activity of the red marrow of bone is increased. Small brownish- red patches were observed in the intestines of frogs after extirpation of the spleen. These new formations are regarded by some observers as compensatory organs. Tizzoni asserts that new splenic structures are formed in the omentum (horse, dog) after the destruction of the parenchyma and blood vessels of the spleen. The spleen is absent extremely seldom. [The weight- of the animal (dog) diminishes after the operation, but afterward increases. The number of red blood corpuscles is lessened, reaching its minimum about the 150th to the 200th day, while the colorless corpuscles are increased in number. The lymphatic glands (especially the in- ternal, and those in the neck, mesentery, and groin) enlarge, while on section the cortical substance of these structures is redder, owing to the great number of red corpuscles, many of them are nu- cleated in the lymph spaces {Gibson). The marrow of all the long bones (those of the foot ex- cepted), becomes very red and soft, with the characters of embryonic bone-marrow. Such animals withstand hemorrhage (to r^ of the total amount of blood) without any specially bad results ( Ttzzoni, Winogradcnu). Schindeler observed that animals after extirpation of the spleen became very ravenous.] [Regeneration. — After entire removal of the spleen, nodules of splenic tissue are reproduced (fox) ; while new adenoid tissue is formed in the lymphatic glands, and in Peyer's patches, the pa- renchyma of the former coming to resemble splenic tissue ( Tizzoni, Eternod.)^ CONTRACTION OF THE SPLEEN. 195 (2) According to Gerlach and Funke the spleen is a blood-forming gland. The blood of the splenic vein contains far more colorless corpuscles than the blood of the splenic artery (p. 55). Many of these corpuscles undergo fatty degenera- tion, and disappear in the blood stream. That colorless blood corpuscles are formed within the spleen seems to be proved by the enormous number of these corpuscles which are found in the blood in cases of leukaemia {Beiineit (\%'^2), Virchow). Bizzozero and Salvioli found that, several days after severe hemor- rhage, the spleen became enlarged, and its parenchyma contained numerous red nucleated hsematoblasts. (3) Other observers {^Kolliker and Ecker) regard the spleen as an organ in which colored blood corpuscles are destroyed, and they consider the large proto- plasmic cells containing pigment granules as a proof of this (p. 53). According to the observations of Kusnetzow, these structures are merely lymph corpuscles, which, in virtue of their amceboid movements, have entangled colored blood cor- puscles. [Such corpuscles exhibit similar properties when placed upon a warm stage.] Similar cells occur in extravasations of blood. The colored blood cor- puscles within the lymph cells gradually become disintegrated, and give rise to the production of granules of hsematin and other derivatives of haemoglobin. [The spleen contains so much free iron that a section of this organ, especially from a young animal, when treated with Tizzoni's fluid, /. ^., with potassic ferrocyanide and hydrochloric acid, gives a distinct blue color (§ 174, 4).] Hence, the spleen contains more iron than corresponds to the amount of blood present in it. When we consider that the spleen contains a large number of extractives derived from the decomposition of proteids, it is very probable that colored blood corpuscles are destroyed in the spleen. Further, the juice of the spleen contains salts similar to those that occur in the red blood corpuscles. The blood from the spleen is said to have undergone other changes, but the following statement must be accepted with caution: The blood of the splenic vein contains more water and fibrin, its red blood corpuscles are smaller, brighter, less flattened, more resistant, and do not form rouleaux ; its haemoglobin crystallizes more easily, and there is a large proportion of O during digestion. [The spleen has therefore very direct relations to the blood ; in it colored blood corpuscles undergo disintegration, it produces colorless corpuscles, and it is said to transform white corpuscles into red.] (4) Contraction. — In virtue of the plain muscular fibres in its capsule and trabeculae, the spleen undergoes variations in its volume. Stimulation of the spleen or its nerves, by cold, electricity, quinine, eucalyptus, ergot of rye, and other "splenic reagents" causes it to contract, whereby it becomes paler, and its surface may even appear granular. After a meal, the spleen increases in size, and it is usually largest about five hours after digestion has begun, z. ). They have also been compared to similar bodies which occur in the prostate. They are most numerous when the gland undergoes its retrograde metamorphosis." Sig. Mayer finds that the thymus of the frog con- tains structures, with transverse markings, identical with the stripes of striped muscular fibres. The structures are identical with those called " sarcoplasts " by Margo and Paneth, and " sar- colytes" by Sig. Mayer. They also occur in large numbers in the tail of the larvae of batrachians, when the tail is undergoing a retrograde metamori^hosis.] Simon, His, and others described a convoluted blind canal, the " central canal," as occurring within the gland, and on it the follicles were said to be placed. Other observers, Jendrassik and Klein, either deny its existence or regard it merely as a lymphatic or an artificial product. Numer- ous fine lymphatics penetrate into the interior of the organ, and many are distributed over its sur- face, but their mode of origin is unknown. [They seem to be channels through which the lymph corpuscles are conveyed away from the gland.] Numerous blood vessels are also distributed to the septa and follicles (Fig. 125, c). Chemical Composition. — Besides gelatin, albumin, soda albumin, there are sugar and fat, leucin, xanthin, hypoxanthin, formic, acetic, butyric, and succinic acids. Potash and phosphoric acid are more abundant in the as/t than soda, calcium, magnesium (? ammonium), chlorine, and sulphuric acid. Function. — As long as it exists, it seems to perform the functions of a true lymph gland. This view is supported by the fact that in reptiles and amphibians, which do not possess lymph glands, the thymus remains as a permanently active organ. [Extirpation gave few positive results, but chemical investigation shows that the i)arenchyma contains a large number of products indicating considerable metabolic activity {Fried/fben).'] III. The Thyroid. — Structure. — The gland consists of lobes and lobules held together by connective tissue rich in cells. Each lobule is made up of numerous completely closed sacs (0.04 to 0.1 mm. in diameter), which in Fk; IT' •Ji--' :^ >' Section of ihe thyroid ghiiid. a, closed vesicles; b, distended by colloid masses and lined by low columnar epithelium ; c, inter-vesicular connective tissue. the embryo and the newly-born animal are composed of a membrana propria lined by a single layer of nucleated cells (Fig. 127). The sacs contain a transparent, viscid, albuminous fluid. [Not unfrequently the sacs contain many colored blood corpuscles {Balfer).'] Each sac is surrounded by a l)lexus of capillaries which do not penetrate the membrana propria. There are also numerous lymphatics. At an early period the sacs dilate, their cellular lining atro- phies, and their contents undergo colloid degeneration. When the gland vesicles are greatly enlarged, " goitre " is produced. The chemical composition of this gland has not been much investigated. In addition to the ordinary constituents, leucin, xanthin. sarkin, lactic, succinic, and volatile fatty acids have been found. [Excision. — The effects differ according to the animal operated on. This gland has been excised in the human subject in cases of goitre. Reverdin pointed out that a pe- culiar condition results, called cachexia stumipriva, and practically the human being becomas a cretin. This operation, therefore, is highly (|uestionable when performed on man. Rabbits endure the operation well, and so do the sheep, calf, and horse. Of dogs, cats, and foxes, only a very small number survive, nearly all die. It appears therefore that herbivora bear the operation and suffer fewer after-effects than carnivora [San- quirico and Orecchia). The immediate effects are fibrillar contractions, which ultimately influence the gait of the animak. convulsions, anresthesia, great diminution of sensibility, loss of flesh, redness of the ears and intense heat of the skin (which disappear after several days), difficulty in seizing and eatmg food, keratoconjunctivitis, and frequently disturbance of the rhythm of respiration with dysp- ntea and spasms of the abdominal muscles {Schiff). The arterial blood contains about the same amount of O as venous blood. Certain parts of the peripheral nerves undergo a kind of degenera- FUNCTIONS OF THE THYROID GLAND. 199 tion similar to that found after nerve stretching. There is albuminuria and fall of the blood pressure. Death usually occurs between the third and fourth day, the animals being comatose ( Wagner). Schiff found that if one-half of the gland was excised at once, and the other half a month afterward, death did not occur; but Wagner denies this, for he asserts that the remaining half hypertrophies, and if it be excised, death occurs with the usual symptoms. In monkeys, five days after the opera- tion, there are symptoms of nervous disturbance. The animals have lost their appetite, there are fibrillar contractions of the muscles of the face, hands, and feet, but the tremors disappear on volun- tary effort. The appetite returns and is increased, but notwithstanding, the animal grows thin and pale ; while the tremors increase and affect all the muscles of the body. These tremors are of central origin, because they disappear on dividing the nerve. Thus there is profound alteration of the motor powers. Among the outward symptoms are puffiness of the eyelids, swelling of the abdo- men, increased hebetude, and dyspnoea, while afterward there is a fall of the temperature and im- becility ; the tremors disappear, there is a pallor of the skin, and ultimately after five to seven weeks the animals die comatose. Thus there is a slow onset of hebetude, terminating in imbecility. Very remarkable changes occur in the blood. There is a steady fall of the blood pressure ; a diminution of the red blood corpuscles, or rather profound ansemia ; leucocythaemia, the colorless corpuscles being increased to the ratio of four to fourteen ; and lastly mucin is present in the blood, although normally it is not so. The salivary glands are hypertrophied, owing to the presence of mucin, which is found even in the parotid, although this is normally a serous gland (§ 141). The swelling of the abdomen is due to hypertrophy of the great omentum. Mucin is found in the peritoneal fluid, and the spleen is also enlarged. Thus these symptoms present many features in common with those of myxcedema as described by Ord {v. Horsley).'] [Stages. — Horsley distinguishes three stages. In the first or neurotic stage the animals exhibit constant tremors, 8 per second, and young animals do not appear to survive this stage. In the second or mucinoid stage, mucin is deposited in the tissues and blood ; this change, however, is only seen to perfection in monkeys. If these animals be kept at a high artificial temperature, their life is considerably prolonged. In the third, atrophic, or marasmic period, the animals die of marasmus, while they lose their excess of mucin. Age seems to exert an important influence in thyroidectomy ; young dogs survive but a short time, while old dogs merely exhibit symptoms of indolence and incapacity ; and^ as a matter of fact, the activity of the gland seems to be most active when tissue metabolism is most active.] [The following table, after Horsley, indicates the symptoms that follow loss of the function of the thyroid gland : — Stages. Duration. Symptoms. Remarks. I. Neurotic. I to 2 weeks in dogs; Tremors, rigidity, dysp- Young dogs and monkeys I to 3 weeks in noea. alike die in this stage. monkeys. II. Mucinoid. ^ to I week in dogs; Commencing hebetude Dogs survive only to the 3 to 7 weeks in and mucinoid degen- beginning of this stage; monkeys. eration of the connec- monkeys die at the end. tive tissues. if not treated. III. Atrophic. 5 to 8 weeks in mon- Complete imbecility and Monkeys survive according keys. atrophy of all tissues. to the temperature of the especially muscles. air-bath.] Functions. — The functions of the thyroid gland are very obscure. Perhaps it may be an appa- ratus for regulating the blood supply to the head (?). It becomes enlarged in Basedow's disease, in which there is great palpitation, as well as protrusion of the eyeball or exophthalmos, which seem to depend upon a simultaneous stimulation of the accelerating nerve of the heart, and the sympa- thetic fibres of the smooth muscles in the orbital cavity and the eyelids, as well as of the inhibitory fibres of the vessels of the thyroid. In many localities it is common to find swelling of the thyroid constituting goitre, which is sometimes, but far from invariably, associated with idiocy and cretinism. [Horsley finds that its removal is the essential cause of myxoedema and cretinism. He regards it (i) as a blood-forming gland, so that it has a hsemapoietic function, but Gibson finds no grounds for supporting this view. During the anemia resulting from its removal, the blood of the thyroid vein contains 7 per cent, more red blood corpuscles than the corresponding artery {Horsley). (2) It seems to regulate the formation of mucin in the body. After its removal the normal meta- bolism is no longer maintained, and there is a corresponding increasingly defective condition of nutrition.] In the Tunicata, this gland, represented by a groove, secretes a digestive fluid. In vertebrates, it is an organ which has undergone a retrograde change [Gegenbaur). 200 THE SUPRARENAL CAPSULES. Fk IV. The Suprarenal Capsules. — Structure. — These organs are invested by a thin capsule which sends processes into the substance of the organ. They consist of an outer (broad) or cortical layer and an inner (narrow) or medullary layer. The former is yellowish in color, firm and striated, while the latter is softer and deeper in tint. In the outermost zone of the cortex (Fig. 128, i), the trabecuL-E form ix)lygonal meshes, which contain the cellsof the gland substance; in the broader middle zone the meshes are elongated, and the cells fdling them are arranged in columns radiating outward. Here the cells are transparent and nucleated, often containing oil globules; in the inner- most narrow zone the j)olygonal arrangement prevails, and the cells often contain yellowish-brown pigment. In the medulla (c), the stroma forms a reticulum containing groups of cellsof very irregu- lar shape. Numerous blood vessels occur in the gland, especially in the corte.x. [The nerves are extremely numerous, and are derived from the renal and solar plexuses. Many of the fibres are medullated. After they enter the gland, numerous ganglionic cells occur in the plexuses which they form. Indeed, some observers regard the cells of the medulla as nervous. Undoubtedly, numerous viiiltipoldr nerve cells exist within the gland.] Chemical Composition. — The suprarenals contain the constituents of connective and nerve tissue ; also leucin, hypoxanthin, benzoic, hippuric, and taurocholic acids, taurin, inosit, fats, and a body which becomes pigmented by oxidation. Among inorganic substances potash and phosphoric acid are most abundant. The function of the suprarenal bodies is very obscure. It is noticeable, however, that in Addison's disease (" bronzed skin "), which is perhaps primarily a nervous affection, these glands have frequently, but not invariably, been found to be diseased. Owing to the injury to adjacent abdominal organs, extirpation of these organs is often, although not always, fatal ; in dogs pigmented patches have been found in the skin near the mouth. Brown-Sequard IJiinks they may be concerned in preventing the over-pro- duction of pigment in the blood. [Spectrum. — MacMunn finds that the medulla of the suprarenal bodies (in man, cat, dog, guinea pig, rat, etc.) gives the spectrum of hremochromogen (^ 18), while the cortex shows that of what he calls histohaematin, the latter being a group of respiratory pigments. He finds that linsmochromogen is only found in excretory organs (the liile, the liver), hence he regards the medulla as excre- tory, so that part of the function of the adrenals may be " to metamorphose effete haemoglobin or hajmatin into hsemochromogen," and when they are diseased, the effete pigment is not removed, hence the pigmentation of the skin and mucous membranes. Taurocholic acid has been found in the medulla by Vulpian, and pyrocatechin by Krukenberg. MacMunn believes that " they have a large share in the downward metamorphosis of coloring matter."] V. Hypophysis Cerebri — Coccygeal and Carotid Glands. — The hypophysis cerebri, or pituitary body, consists of an anterior lower or larger lobe, partly embrac- ing the posterior lower or smaller lobe. These two lobes are distinct in their structure and development. The posterior lobe is a part of the brain, and belongs to the infundibulum. The nervous elements are displaced by the Section of a human supraren.'il capsule, a, ingrowth of Connective tissue and blood vessels. The capsule ; b, gland cells of the cortex ar- . • _^- , ■ a ^ j j i_ i^ j ranged in columns :<:,glandularnetwork of ''"'^^/''^'"PO^'O" '■^P'^es^"'^ ^" mflected and much altered the medulla; d, bloodvessels. portion of ectoderm, from which it is developed. It con- tains gland-like structures, with connective tissue, lym- phatics, and blood vessels, the whole being surrounded by a capsule. According to Ecker and Mihalkowicz, it resembles the suprarenal capsule in its structure, while, according to other observers, in some animals it is more like the thyroid. Its functions are entirely unknown. [Excision. — Horsley has removed this gland twice successfully in dogs, which lived from five to six months. No nervous or other symptoms were noticed, but when the cortex of the brain was exposed and stimu- lated, a great increase in the excitability of the motor regions was induced, even slight stimulation bemg followed by violent tetanus and prolonged epilepsy.] Coccygeal and Carotid Glands. — The former, which lies on the tip of the coccyx, is composed to a large exient of plexuses of small, more or less cavernous, arteries, supported and enclosed by septa and a capsule of connective tissue {Luschka). Between these lie polyhedral granular cells arranged in networks. The carotid gland has a similar structure (p. 118). Their functions are quite unknown. Perhaps both organs may be regarded as the remains of embryonal blood vessels {Arnold). COMPARATIVE ANATOMY OF THE CIRCULATION. 201 104. COMPARATIVE. — The heart in fishes (Fig. 129, I), as well as in the larvse of amphi- bians with gills, is a simple venous heart, consisting of an auricle and a ventricle. The ventricle propels the blood to the gills, where it is oxygenated (arterialized) ; thence it passes into the aorta to be distributed to all parts of the body, and returns through the capillaries of the body and the veins to the heart. The amphibians (frogs) have two auricles and one ventricle (Frog, II). From the latter there proceeds one vessel which gives off the pulmonary arteries, and as the aorta supplies the rest of the body with blood, the veins of the systemic circulation carry their blood to the right auricle, those of the lung into the left auricle. In fishes and amphibians there is a dilatation at the commencement of the aorta, the bulbus arteriosus, which is partly provided with strong muscles. The reptiles (III) possess two separate auricles, and two imperfectly separated ventricles. The aorta and pulmonary artery arise separately from the two latter chambers. The venous blood Fig. 129. Schemata of the circulation. \. Fish.— A, auricle; .S, sinus venosus ; K, ventricle ; ^, bulbus aortae : c, branchial arteries ; /, branchial vessels ; Vv, branchial veins ; E, circulns cephalicus aortae ; F, common aorta ; G, caudal artery; //, duct of Cuvier ; /, anterior, and iT, posterior cardinal veins ; Z, caudal vein ; ^, Af, kidneys. II. Frog. — I, sinus venosus; II and III, right and left auricles; IV, ventricle ; V, aorta with the bulb ; _i, pul- monary arteries; 2, arch of the aorta; 3, carotid ; 4, lingual; s, carotid gland, and 6, axillary arteries; 7, common aorta; 8, cceliac artery ; 9, cutaneous artery; Vv, pulmonary veins; /, /, lungs. III. Saurians. — I, right auricle, with the venae cavs ; II, right ventricle; III, left auricle; IV, left ventricle. V, anterior common aorta ; i, pulmonary artery ; 2, arch of the aorta; 3, carotid artery ; 4, posterior common aorta ; 5, cceliac, and 6, subclavian, arteries ; 7, pulmonary veins ; 8, lungs. IV. Tortoise. — I, right auricle with the venae cavae ; II, right, and IV, left ventricles ; III, left auricle ; i and 2, right and left aortae ; 3, posterior common aorta; 4, ccfiliac; 5, subclavian ; 6, carotid, and 7, pulmonary arteries ; 8, pulmonary veins. of the systemic and pulmonary circulations flows separately into the right and left auricles, and the two streams are mixed in the ventricle. In some reptiles the opening in the ventricular septum seems capable of being closed. The complete separation of the ventricle into two is seen in Fig. IV, in the tortoise. The lower vertebrates have valves at the orifices of the vense cavse, which are rudimentary in birds and some mammals. All birds and mammals have two completely separate auricles and two separate ventricles. In the halicore the apex of the ventricles is deeply cleft. Some animals have accessory hearts, e.g., the eel in its caudal vein. They are very probably lymph hearts {Robin). The veins of the wing of the bat pulsate {Schiff). The lowest vertebrate, amphioxus, has no heart, but only a rhythmically pulsating vessel. Among blood glands, the thymus and spleen occur throughout the vertebrata, the latter being absent only in amphioxus and a few fishes. 202 HISTORICAL RETROSPECT OF THE CIRCULATION. Among invertebrata a closed vascular system^ with pulsatile movement, occurs here and there, e.s;.y among echinodermata (star fishes, sea urchins, holothurians) and the higher worms. The insects have a pulsating " dorsal vessel" as the central organ of the circulation, which is a contractile tube provided with valves and dilated by muscular action ; the blood being propelled rhythmically in one direction into the spaces whicn lie among the tissues and organs, so that these animals do not possess a closed vascular system. The mollusca have a heart with a lacunar vascular system. The cephalopods (cuttle fish) have three hearts — a simple arterial heart, and two venous simple gill hearts, each placed at the base of the gills. The vessels form a completely closed circuit. The Icnvest animals have either a pulsatile vesicle, which propels the colorless juice into the tissues (in- fusoria), or the vascular apparatus may be entirely absent. 105. HISTORICAL RETROSPECT. — The ancients held various theories regarding the movement of the blood, but they knew nothing of its circulation. According to Aristotle (384 H.C.), the heart, the acropolis of the body, prepared in its cavities the blood, which streamed through the arteries as a nutrient fluid to all parts of the body, but never returned to the heart. With Herophilus and Erasistratus (300 B.C. ), the celebrated physicians of the Alexandrian school, originated the erroneous view that the arteries contain air, which was supplied to them by the respiration (hence the name artery). They were led to adopt this view from the empty condition of the arteries after death. By experiments upon animals, Galen disproved this view (131-201 a.d.) — "Whenever I injured an artery," he says, "blood always flowed from the wounded vessel. On tying part of an artery between two ligatures, the part of the artery so included is always filled with blood." Still, the idea of a single centrifugal movement of the blood was retained, and it was assumed that the right and left sides of the heart communicated directly by means of openings in the septum of the heart, until Vesalius showed that there are no openings in the septum. Michael Servetus (a. Spanish monk, burned at Geneva, at Calvin's instigation, in 1553) discovered the pulmonary circula- tion. Cesalpinus confirmed this observation, and named it " Circulatio." Fabricius ab Aqua— pendente (Padua, 1574) investigated the valves in the veins more carefully (although they were known in the 5th century to Theodoretus, Bishop in Syria), and he was acquainted with the centri- petal movement of the blood in the veins. Up to this time it was imagined that the veins carried blood from the centre to the periphery, although Vesalius was acquainted with the centripetal direc- tion of the blood stream in the large venous trunks. At length William Harvey, who was a pupil of Fabricius (1604), demonstrated the complete circulation (1616-1619), and published his great discovery in 1628. [For the history of the discovery of the circulation of the blood, see the works of Willis on " W. Harvey," " Servetus and Calvin," those of Kirchner, and the various Harveian orations.] According to Hippocrates, the heart is the origin of all the vessels ; he was acquainted with the large vessels arising from the heart, the valves, the chordre tendinere, the auricles, and the closure of the semilunar valves. Aristotle was the first to apply the terms aorta and vtn-x. cavK ; the school of Erasistratus used the term carotid, and indicated the functions of the venous valves. In Cicero a distinction is drawn between arteries and veins. Celsus mentions that if a vein be struck below the spot where a ligature has been applied to a limb, it bleeds, while Aretaeus (50 a.d.) knew that arterial blood was bright and venous dark. Pliny (179 a.d.) described the pulsating fontanelle in the child Galen (131-203 a.d.) was acquainted with the existence of a bone in the septum of the heart of large animals (ox, deer, elephant). He also surmised that the veins communicated with the arteries by fine tubes. The demonstration of the capillaries, however, was only possible by the use of the microscope, and employing this instrument, Malpighi (1661) was the first to demonstrate the capillary circulation. Leuwenhoek (1674) described the capillary circulation more carefully, as it may be seen in the web of the frog's foot and other transparent membranes. Blancard (1676) proved the existence of capillary passages by means of injections. William Cooper (1697) proved that the same condition exists in warm-blooded animals, and Ruysch made similar injections. Stenson (born 1638) established the muscular nature of the heart, although the Hippocratic and Alexandrian schools had already surmised the fact. Cole proved that the sectional area of the blood stream became widertoward the capillaries (1681). Joh. Alfons Borelli (1608-1679) was the first to estimate the amount of work done by the heart. Physiology of Respiration. The object of respiration is to supply the oxygen necessary for the oxidation processes that go on in the body, as well as to remove the carbon dioxide formed within the body. The most important organs for this purpose are the lungs. There is an outer and an inner respiration — the former embraces the exchange of gases between the external air and the blood gases of the respiratory organs (lungs and skin) — the latter, the exchange of gases between the blood in the capillaries of the systemic circulation and the tissues of the body. [The pulmonary apparatus consists of (i) an immense number of small sacs — the air vesicles — filled with air, and covered externally by a very dense plexus of capillaries; (2) air passages — the nose, pharynx, larynx, trachea, and bronchi communicating with (i) ; (3) the thorax with its muscles, acting like a pair of bellows, and moving the air within the lungs.] 106. STRUCTURE OF THE AIR PASSAGES AND LUNGS.— The lungs are compound tubular glands, which separate CO2 from the blood. Each lung is provided with an excretory duct (bronchus) which joins the common respiratory passage of both lungs — the trachea. Trachea. — The trachea and extra-pulmonary bronchi are similar in structure. The basis of the trachea consists of 16—20 C-shaped incomplete cartilaginous hoops placed over each other. These rings consist of hyaline cartilage, and are united to each other by means of tough fibrous tissue containing much elastic tissue, the latter being arranged chiefly in a longitudinal direction. The function of the cartilages is to keep the tube open under varying conditions of pressure. Pieces of cartilage having a similar function occur in the bronchi and their branches, but they are absent from the bronchioles, which are less than i mm. in diameter. In the smaller bronchi, the carti- lages are fewer and scattered more irregularly. [In a transverse section of a large intra-pulmo- nary bronchus, two, three, or more pieces of cartilage, each invested by its perichondrium, may be found.] At the points where the bronchi subdivide, the cartilages assume the form of irregular plates embedded in the bronchial wall. An external fibrous layer of connective tissue and elastic fibres covers the trachea and the extra- pulmonary bronchi externally. Toward the oesophagus, the elastic elements are more numerous, and there are also a few bundles of plain muscular fibres arranged longitudinally. Within this layer there are bundles of non-striped muscular fibres which pass transversely between the carti- lages behind, and also in the intervals between the cartilages. [These pale reddish fibres constitute the trachealis muscle, and are attached to the inner surfaces of the cartilages at a little distance from their free ends. The arrangement varies in different animals — thus, in the cat, dog, rabbit, and rat the muscular fibres are attached to the external surfaces of the cartilages, while in the pig, sheep, and ox they are attached to their internal surfaces {Stirling).'] Some muscular fibres are arranged longitudinally external to the transverse fibres. The function of these muscular fibres is to prevent too great distention when there is great pressure within the air passages. The mucous membrane consists of a basis of very fine connective tissue, containing much adenoid tissue with numerous lymph corpuscles. Numerous elastic fibres are arranged chiefly in a longitudinal direction under the basement membrane. They are also abundant in the deep layers of the posterior part of the membrane opposite the intervals between the cartilages. A small quan- tity of loose submucous connective tissue containing the large blood vessels, glands, and lymphatics unites the mucous membrane to the perichondrium of the cartilages. The epithelium consists of a layer of columnar ciliated cells with several layers of immature cells under them. [The super- ficial layer of cells is columnar and ciliated (Fig. 130, b), while those lying under them present a variety of forms, and below all is a layer of somewhat flattened squames, c, resting on the basement membrane, d. These squames constitute a layer quite distinct from the basement membrane, and they form the layer described as D6bove's membrane. They are active germinating cells, and play a most important part in connection with the regeneration of the epithelium, after the super- ficial layers have been shed, in such conditions as bronchitis. Not unfrequently a little viscid 203 204 STRUCTURE OF THE TRACHEA AND BRONCHI. mucus (a) lies on the free ends of the cilia. In the intermediate layer, the cells are more or less pyriform or battledore-shaped, with their long tapering process inserted among the deepest layer of squames. According to Drasch, this long process is attached to one of these cells and is an outgrowth from it, the whole constituting a "foot cell."] Under the epithelium is the homogeneous basement membrane, through which fine canals pass, connecting the cement of the epithelium with spaces in the mucosa. [This membrane is well marked in the human trachea, where it plays an important part in many pathological condi- tions, e.^i^., bronchitis. It is stained bright red with picrocarmine.] The cilia act so as to carry any secretion toward the larynx. Goblet Fic. no. z^ ^^mm^^m cells exist between the ciliated columnar cells. Numerous small compound tubular mucous glands occur in the mucous membrane, chietly Ijetween the cartilages. Their ducts open on the surface by means of a slightly funnel - shaped aperture, into which the ciliated epithelium is pro- longed for a short distance. [The acini of some of these glands lie outside the trachealis muscle. The acini are lined by cubical or columnar secretoiy epithelium. In some animals (dog) these cells are clear, and present the usual characters of a mucus- secreting gland ; in man, some of the cells may be clear, and others "granular," but the appearance of the cells depends upon the physiological state of activity.] These glands secrete the mucus, which entangles particles inspired with the air, and is car- ried toward the larynx by ciliary action. [Numerous lymphatics exist in the mu- cous and submucous coat, and not unfre- quently small aggregations of adenoid tissue occur (especially in the cat) in the mucous coat, usually around the ducts of tiie glands. They are comparable to the solitary follicles of the alimentary tract. The blood ves- sels are not so numerous as in some other mucous membranes. [A plexus of nerves containing numerous ganglionic cells at the nodes exists on the posterior surface of the trachealis muscle. The fibres are derived from the vagus, recurrent laryngeal, and sympathetic ( C. Frankenhatiser, W. Stir- Transverse section of part of a human bronchus ( X 450). a, pre cipitated mucus; h, ciliated columnar epithelium; c, deep //«.„i,_„„„ „f tt,<> ♦..„ ment membrane ; e, elastic fibres divided transversely (inner [^lie mUCOUS membrane of the tra- fibrous layer) ; f, bronchial muscle ; g, outer fibrous layer with chea and extra - pulmonary bronchl, leucocytes and pigment granules (black); below a mass of therefore, Consists of the following layers adenoid tissue. r -^t • . j o .< from within outward : — (i) Stratified columnar ciliated epithelium. (2J A layer of flattened cells (Debove's membrane). (3) A clear homogeneous basement membrane. (4) A basis of areolar tissue, with adenoid tissue and blood vessels, and outside this a layer of longitudinal elastic fibres. Outside this, again, is the submucous coat, consisting of loose areolar tissue, with the larger vessels, lymphatics, ner\es, and mucous glands.] [The Bronchi. — In structure the extra-pulmonary bronchi resemble the trachea. As they pass into the lung they divide very frequently, and the branches do not anastomose. In the intra- pulmonary bronchi the subdivisions become finer and finer, the finest branches being called terminal bronchi, or bronchioles, which open separately into clusters of air vesicles.] [Eparterial and Hyparterial Bronchi. — As the bronchi proceed, one main trunk passes into the lung, running toward its base, and from it are given off branches dorsally and ventrally, and these branches again subdivide. In man one main branch comes off from the right bronchus and proceeds to the upper right lobe, above the place where the pulmonary artery crosses the bronchus. Such branches are called eparterial, and they are more numerous in birds. In man, all the branches, both on the right and left side, come off below the point where the pulmonary artery crosses the bronchus, and are called hyparterial bronchi (C. Aeby).'\ STRUCTURE OF THE BRONCHIOLES AND AIR CELLS. 205 [In the middle-sized intra-pulmonary bronchi, the usual characters of the mucous membrane are retained, only it is thinner; the cartilages assume the form of irregular plates situated in the outer wall of the bronchus ; while the muscular fibres are disposed in a complete circle, constituting the bronchial muscle (Fig. 130,/). When this muscle is contracted, or when the bronchus as a whole is contracted, the mucous membrane is thrown into longitudinal folds, and opposite these folds the elastic fibres form large elevations. This muscle is particularly well developed in the smaller microscopic bronchi. Numerous elastic fibres, e, disposed longitudinally, exist under the basement membrane, d. They are continuous with those of the trachea, and are prolonged onward into the lung. The mucous membrane of the larger intra-pulmonary bronchi consists of the fol- lowing layers from within outward : — (1) Stratified columnar ciliated epithelium (Fig. 130, F). (2) Debove's membrane (Fig. 130, c). (3) Transparent homogeneous basement membrane (Fig. 130, d'). (4) Areolar tissue with longitudinal elastic fibres (Fig. 130, e). (5) A continuous layer of non-striped muscular fibres disposed circularly [bronchial muscle, Fig. Outside this is the submucous coat, consisting of areolar tissue mixed with much adenoid tissue (Fig. 130,^), sometimes arranged in the form of cords, the lymph-follicular cords. It also con- tains the acini of the numerous mucous glands, blood vessels, and lymphatics. The ducts of the glands perforate the muscular layer, and open on the free surface of the mucous membrane. The submucous coat is connected by areolar tissue with the perichondrium of the cartilages. Outside the cartilages are the nerves and nerve ganglia accompanying the bronchial vessels. The branches of the pulmonary artery and of the pulmonary vein usually lie on opposite sides of the bronchus, while there are several branches of the bronchial arteries and veins. Fat cells also occur in the peribronchial tissue.] In the small bronchi the cartilages and glands disappear, but the circular muscular fibres are well developed. They are lined by lower columnar ciliated epithelium, containing goblet cells. Bronchioles. — After repeated subdivision, the bronchi form the " smallest bronchi" (about 0.5 to I mm.) or lobular bronchial tubes. Each tube is lined by a layer of ciliated epithelium, but the glands and cartilages have disappeared. These tubes have a few lateral alveoli or air cells com- municating with them. Each smallest bronchus ends in a" respiratory bronchiole [Kolliker), which gradually becomes beset with more air cells, and in which squamous epithelium begins to appear be- tween the ciliated epithelial cells. [Each bronchiole opens into several wider alveolar or lobular passages. Each passage is completely surrounded with air cells, and from it are given off several similar but wider blind branches, the infundibula, which, in their turn, are beset on all sides with alveoli or air cells. Several infundibula are connected with each bronchiole, and the former are wider than the latter. Each bronchiole, with its alveolar passages, infundibula, and air vesicles, is termed a lobule, whose base is directed outward, and whose apex may be regarded as a terminal bronchus. The lung is made up of an immense number of these lobules, separated from each other by septa of connective tissue, the interlobular septa (Fig. 133, e) which are continuous on the one hand with the sub-pleural connective tissue, and on the other with the peribronchial connective tissue.] [There is an alteration in the structure of the bronchi, as we proceed from the larger to the smaller tubes. The cartilages and glands are the first structures to disappear. The circular bron- chial muscle is well developed in the smaller bronchi and bronchioles, and exists as a continuous thin layer over the alveolar passages, but it is not continued over and between the air cells. Elastic fibres, continuous, on the one hand, with those in the smaller bronchi, and on the other with those in the walls of the air cells, lie outside the muscular fibres in the bronchioles and infundibula. In the respiratory bronchioles, the ciliated epithelium is reduced to a single layer, and is mixed with the stratified form of epithelium, while, where the alveolar passages open into the air cells or alveoli, the epithelium is non- ciliated, low, and polyhedral.] Alveoli or Air Cells. — The form of the cells, which are 250 ^i {-^-^ inch) in diameter, may be more or less spherical, polygonal, or cup-shaped. They are disposed around and in communication with the alveolar passages. Their form is determined by the existence of a nearly structureless membrane, composed of slightly fibrillated connective tissue containing a few corpuscles. This is surrounded by numerous fine elastic fibres, which give to the pulmonary parenchyma its well-marked elastic characters (Fig. 132, e, e). These fibres often bifurcate, and are arranged with reference to the alveolar wall. They are very resistant, and in some cases of lung disease may be recognized in the sputum. A few non-striped muscular fibres exist in the delicate connective tissue between adjoining air vesicles. These muscular fibres sometimes become greatly developed in certain diseases {^Arnold, W. Stirling). The air cells are lined by two kinds of cells ; (i) large, transparent, clear, polygonal (nucleated ?) squames or placoids (22-45 <") lying over and between the capillaries in the alveolar wall (Fig. 131, a) ; (2) small, irregular, " granular," nucleated cells (7-15 ,«) arranged singly or in groups (two or three) in the interstices between the capillaries. They are well seen in a cat's lung (Fig. 131, a;). [When acted on with nitrate of silver the cement substance bounding the clear cells is stained, but the small cells become of a uniform brown, granular appearance, so 206 THE BLOOD VESSELS OF THE LUNGS. that they are readily recognized. Small holes or " pseudostomata " seem to exist in the cement substance, and are most obvious in distended alveoli. They open into the lymph-canalicular system of llu- alveolar wall [K'/ein), and through them the lymph corpuscles, which are always to be founil on the surface of the air vesicles, migrate, and carry with them into the lymphatics particles of carbon derived from the air.] In the alve- Fic. 131. olar walls is a very dense plexus of fine capillaries (Fig. 132, c), which lie more toward the cavity of the air vesicle, being covered only by the epithelial lining of the air cells. I'.etween two adjacent alve- oli 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, 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 sur- face of the body (.8 to .9 s([. metre).] 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 arteri- ole splitting up into capillaries for several air cells (Fig. 132, z-, 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 fulmonary veins, which, again, are joined in their course by a few small bronchial veins. 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 pulmonary capillaries must be more rapid than that in the capillaries of the body generally. The pulmonary 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 bron- chial walls, and the interlobular septa. The blood which issues from their capillaries is returned — 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 pulmonary vein {Zttckerkandl.) [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 also continuous with the interlobular septa. The interlobular septa (Fig. 133, e) consist of bands Air vesicles injected with silver nitrate, a. outlines of squamous epithelium ; b, alveolar wall ; c, young epithelium cell ; d, ag- gregation of young epithelial cells germinating. THE LYMPHATICS OF THE LUNG. 207 of fibrous tissue separating adjoining lobules, and they become continuous with the peribronchial connective tissue entering the lung at its hilum. Thus the fibrous framework of the lung is con- tinuous 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. 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. Arnold, 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 pleura there is a (a) sub-pleural plexus of lymphatics partly derived from the pleura, but chiefly Fig. 132. 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; /, alveolar epithelium shown alone ; e, e, elastic tissue of the lung. from the lymph- canalicular system of the pleural alveoli. Some of these branches proceed to the bronchial glands, but others pass into the interlobular septa, where they join [b) the perivascular lymphatics which arise in the lymph-canalicular system of the alveoli. These trunks, pro\-ided 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.] 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 ; or, according to Klein, they pass through actual holes or pores in the cement (p. 206).] [This pigmentation is well seen in coal-miner's lung or anthracosis, where the particles of carbon pass into and are found in the IjTnphatics. Sikorski and Kiittner showed that pigment reached the lymphatics in this way during life. If pigment, 208 THE NERVES OF THE LUNG. 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. Schestopal used China ink and cinnabar suspended in }( per cent, salt solution.] Exces- sively 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. According to Pierrot and Renaut every air cell of the lung of the o.\ is surrounded by a large lymph space, such as occurs in the salivary glands. When a large (juantity of fluid is injected into the lung, it is absorbed with great rapidity ; even blood corpuscles rapidly pass into the lymphatics. The superficial lymphatics of the pulmonary pleura communicate with the pleural cavity by means of free openings or stomata, 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 lymphatics in the costal pleura occur over the intercostal p-jg ,,-, spaces and not over the ribs (Z'j/^/'OT^/j/t/).] The large arteries of the lung are provided with lymphatics which lie between the middle and outer coats. [The movements of the lung during respiration are most important factors in moving the lymph onward in the pulmonary lymphatics. The reflux 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 distribution of the bronchi, several sections of nerve trunks being usually found in a transverse section of a large bronchial tube. The nerves lie outside the cartilages, and are in close relation with the branchesof the bronchial arteries. jSIedullated and non-medullated nerve fibres occur in the nerves, which also contain numerous small ganglia [Remak, Klehi, Stirling). In the lung of the calf the ganglia are large. The exact mode of termination of the nerve fibres within the lung has yet to be ascer- tained 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, Stir- ling), 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 pulmonary 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, the " lung- tonus " during increased tension depends upon these muscles. [Effect of Nerves.— By connecting the interior of a small bronchus with an oncograph (? 103) m curanzed dogs (the thorax being opened), Graham Brown and Roy found that section 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. Human lung (^ 50 auil reduced >/). a, small bronchus; i, b, pulmonarj- artery ; c, pulmonar>' vein ; e, interlobular septa, continuous with the deep layer of the pleura,/. MECHANISM OF RESPIRATION. 209 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 cerebro-spinal centres and the bronchi is through the vagi.] Pathological. — Stimulation of the smooth muscles, whereby a spasmodic narrowing of the smaller bronchi is produced, may excite asthmatic attacks. If the expiratory blast be interfered with, acute emphysema may take place i^Bierniei'). 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, potash, magnesium, oxide of iron, much phosphoric acid, also chlorine, sulphuric and silicic acids — in dia- betes 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 tyrosin. [Physical Properties of the Lungs. — The lungs, in virtue of the large amount of elastic tissue which they contain, are endowed with elasticity; and 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 patho- logical 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 hydrostatic test is largely used in medico-legal cases, as a test of the child's 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 gran- ules 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 sur- vive 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 surfaces 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 cov- ered 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. The move- ments of the lungs, therefore, are entirely passive, and are dependent on the thoracic movements. 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, z. e., they are in a certain state of elastic tension (§ 60). The tension is greater the more distended the thoracic cavity, and vice versa. As soon as the pleural cavity is opened by per- foration from without, the lungs, in virtue of their elasticity, collapse, and a space 14 210 QUANTITY OF GASES RESPIRED. filled with air is formed between the surface of the lungs and the inner surface of the thoracic wall (pneumothorax), The lungs so affected are rendered useless for respiration ; hence a double pneumothorax causes death. Pneumothorax. — It is also clear that, if the pulmonary pleura be perforated from within the Umil;. air will pass from the respiratory passages into the pleural sac, and also give rise to pneumo- thorax. [Not unfrequently the surgeon is called on to open the chest, say by removing a portion of a rib, to allow of the free exit of pus from the pleural cavity. If this be done with proper precautions, and if the external wound be allowed to heal, after a time the air in the pleural cavity becomes absorbed, the collapsed lung tends to reign its original form, and again becomes functionally active.] Estimation of Elastic Tension. — If a manometer be introduced through an intercostal space into the pleural cavity, in a dead subject, we can measure, by means of a column of mercury, the amount of the elastic tension required to keep the lung in its position. This is equal to 6 mm. in the dead subject, as well as in the condition of expiration. If, however, the thorax be brought into the position of inspiration by the application of traction from without, the elastic tension may be in- creased to 30 mm. Ilg [Dottders). If the glottis be closed and a deep inspiration taken, the air within the lungs must become rarefied, because it has to fill a greater space. If the glottis be sud- denly opened, the atmospheric air passes into the lungs until the air within the lungs has the same density as the atmosphere. Conversely, if the glottis be closed, and if an expiratory effort be made, the air within the chest must be compressed. If the glottis be suddenly opened, air passes out of the lungs until the pressure out- side and inside the lung is equal. As the glottis remains open during ordinary respiration, the equilibration of the pressure within and without the lungs will take place gradually. During tranquil inspiration there is a slight negative pressure; during expiration, a slight positive pressure in the lungs; the former ^ i mm., the latter 2-3 mm. Hg in the human trachea (measured in cases of wounds of the trachea). 108. QUANTITY OF GASES RESPIRED.— As the lungs within the chest never give out all the air they contain, it follows that only a part of the air of the lungs is changed during inspiration and expiration. The volume of this air will depend upon the depth of the respirations. COMPl.EMENTAL AIR, no 5 Hutchinson defined the following : — ^^ (i) Residual air is the volume of air which remains in the ^ 53 chest a/ler the most complete expiration. It is ;= 1 230-1 640 c. c. o ^ [100-130 cubic inches]. §- ^ (2) Reserve or supplemental air is the volume of air which - o" Kj can be expelled from the chest after a normal quiet expiration. 5' o It is ^ 1240-1S00 c. c. [100 cubic inches]. RESERVE AIR, i n" ~ (3) Tidal air is the volume of air which is taken in and given 100 I "2 °"' ^* ^■&.c\\. rfespiration. It is ■^=: 500 cubic centimetres [20 cubic inches]. TIDAL AIR, 20 RESIDUAL AIR, j • (4) Complemental air is the volume of air that can be forcibly inspired over and above what is taken in at a normal respiration. — I It amounts to about 1500 c. c. [100-130 cubic inches]. 100 (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 {Haeset-). Hence, after every quiet inspiration, both lungs contain (i + 2 + 3) =r= 3000 to 3900 c. cm. [220 cubic inches]; after a quiet expiration (i -f 2) = 2500 to 3400 c. cm. [200 cubic inches]. So that about i to i of the air in the lungs is subject to renewal at each ordinary respiration. _ Bonders calculated that the entire bronchial system and the trachea contain about 500 c. c. of NUMBER OF RESPIRATIONS. 211 Fig, Estimation of Vital Capacity. — This was formerly thought to be of great utility, but at the present time not much importance is attached to it, nor is it frequently measured in cases of disease. It is estimated by means of the spiro- meter of Hutchinson (Fig. 134), which consists of a graduated cylinder filled with water and inverted like a gasometer over water, and balanced by means of a counterpoise. Into the cylinder a tube projects, and this tube is connected with a mouth-piece. The person to be experimented upon takes the deepest possible inspiration, closes his nostrils, and breathes forcibly into the mouth- piece of the tube. After domg 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 indi- cates 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 foHowing circumstances affect the vital capa- city : — (i) 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 tlie normal by 7 per cent, there is a dimi- nutioi'. 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 and Occupation. — More air is respired in the erect than in the recumbent position. (6) Disease. — Abdominal and thoracic diseases di- minish it. Scheme of Hutchinson's Spirometer. 109. NUMBER OF RESPIRATIONS.— In the adult, the number ot 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 con- ditions : — (i) 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) Age. — Quetelet found the mean number of respirations in 300 individuals to be : — Year. Respirations. Year. Respirations. 0 to I, 44 1 Average 20 to 25, 18.7 -) Average 5> 26 V Number per 25 to 30, 16 Number per 15 to 20, 20 ) Minute. 30 to 50, 18.I J Minute. (3) The State of Activity. — Gorham counted in children of 2 to 4 years of age during standing 32, in sleep 24, respirations per minute. During bodily exertion the number of respirations increases before the heart beats. [Very slight nmscidar 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.] 212 TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. Rliinoccros, Hippopotamus Horse, . . . Ass, . . . . Per Mill. • 55 . 2IO . lOO 6-IO 'i IO-I2 . 7 Per Min. Pigeon, 30 Siskin, 100 Canary, 18 Birds. Condor, . . Sparrow, . . Reptiles. Snake, . . . . Tortoise, . . . [(S) In Animals — Mammals. ! ^^^^j I'er Min. ,> » / 1 • \ TiL-er 6 ' ^^^^ (waking) Lion,' : : ; : : : lol Rat(asleep), jaguar, II Panther 18 Cat, 24 I Dog, 15 Dromedary, ... 1 1 Giratle, .... S-lo Ox, 15-18 Squirrel, 70 [(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 ancemia; 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.] 6 90 Raja, Torpedo, Fish. Per Min. Perch, 30 Mullet, 60 Eel 50 Hippocampus, . . 33 Invertebrata. Crab, 12 Mollusca, . . 14-65 {P.Beri.)'\ Fid. 135. A, Brondgeest's tambour for registering the respiratory movements. /5, c, inner and outer caoutchouc membranes; a, the capsule; (/.(Z, cords for fastening the instrument to the chest; 5, tube to the recording tambour. BJ normal respiratory curve obtained on a vibrating plate (each vibration ^ 0.01613 sec). 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 by means of recording apparatus. Methods. — The graphic method can be employed in three directions: (i) To record the movements of individual parts of the chest wall. (i) 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. Reigel (1873) constructed a "double stethograph" on the same principle. This instrument is so arranged that one arm of the lever may be applied in connection with the healthy side of a person's chest, and the other on the dis- eased side. In the case of animals placed on their backs, Snellen introduced a long needle vertica ly through the abdominal walls into the liver. Rosenthal opened the abdomen and apiilied a lever to the under surface of the diaphragm, and thus registered its movements (Phrenograph). r => o (2) An air tambour, such as is used in Brondgeest's pansphygmograph (Fig. 135, A) may be employed. It consists of a brass vessel, a, shaped like a small saucer. The mouth of the brass TIME OCCUPIED BY THE RESPIRATORY MOVEMENTS. 213 vessel is covered vtritli a double layer of 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 communi- cates by means of a caoutchouc tube, .f, with a recording tambour, which inscribes its movements upon a revolving cylinder. 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.] A cannula or oesophageal sound may be intro- duced into that portion of the oesophagus which lies in the chest, and a connection estabhshed with Marey's tambour [Rosenthal). [This method also enables one to measure the inlra-thoracic pressure?^ Marey's Stethograph or Pneumograph. — [There are two forms of this instrument, one modi- fied by P. Bert and tiie more modern form (Fig. 136). A tambour {h) is fixed at right angles to a thin elastic plate of steel (/). The aluminium disk on the caoutchouc of the tambour is attached to an upright {b), whose end lies in contact with a horizontal screw [g). Two arms [d, c) are attached to opposite sides of the steel plate, and to them the belt {i) which fastens the instrument to the chest is attached. When the chest expands, these two arms are pulled asunder, the steel plate is bent, and the tambour is affected, and any movement of the tambour is transmitted to a registering tambour by the air in the tube (a)]. (2) To record variation in volume of the thorax or of the respired gases. For this purpose E. Hering secures the animal, and places it in a tight box provided with two openings in its side ; one hole contains a tube, which is connected to a cannula tied into the trans- versely divided trachea of the ani- mal, so that respiration can go on FiG. 136. undisturbed. In the other orifice is ^.My:P> f^6 fixed a water manometer provided with a swimmer arranged to write on a recording surface. Gad regis- tered graphically the respired air by means of a special apparatus; the expired air raised a very light and carefully equipoised box placed over water. As it was raised, it moved a writing style. During inspiration the box sank. (3) To record the rate at which the respiratory gases are exchanged. If the trachea of an animal, or the mouth of a man (the nostrils being closed), be connected with a tube like that of the dromograph (Fig. 113), then during inspiration and expiration the pendulum will be moved to and fro by the air, and the movements of the pendulum can be registered, years ago, an instrument, called the " Anapnograph," was constructed on this principle.] The curve (Fig, 135, B) was obtained by placing the tambour of a Brondgeest's pansphygmograph upon the xiphoid process, and recording the movement upon a plate attached to a vibrating tuning fork. The inspiration (ascending limb) begins with moderate rapidity, is accelerated in the middle, and toward the end again becomes slower. The expiration also begins with moderate rapidity, is then accelerated, and becomes much slower at the latter part, so that the curve falls very gradually. Inspiration is slightly shorter than Expiration. — According to Sibson, the ratio for an adult is as 6 to 7 ; in women, children, and old people, 6 to 8 or 6 to 9. Vierordt found the ratio to be 10 to 14. i (to 24.1) ; J. R. Ewald, 11 to 12. It is only occasionally that cases occur where inspiration and expiration are equally long, or where expiration is shorter than inspiration. When respiration proceeds quietly and regularly, there is usually no pause (complete rest of the chest walls) between the ifispiration and expiration. The very flat part of the Marey's Stethograph. [Some 214 TYPE OV RESPIRATION. expiratory curve has been wrongly regarded as due to a pause. Of course, we may make a voluntary pause between two respirations, or at any part of a respi- ratory act. Some observers, however, have ilescribed a pause as occurring between the end of expiration and the beginning of the next inspiration (expiration pause), and also another pause at the end of inspi- ration (inspiration pause). The latter is always of very short duration, and considerably shorter than the former. During very deep and slow respiration, there is usually an expiration pause, while it is almost invariably absent during ra[jid breathing. An inspiration pause is always absent under normal circumstances, but it may occur under pathological conditions. In certain parts of the respiratory curve slight irregularities may appear, which are sometimes due to vibrations communicated to the thoracic walls by vigorous heart beats (Fig. 137). The "type" of respiration may be ascertained by taking curves from various parts during the respiratory movements. Hutchinson showed that, in the female, Fin. 137. Pneiimatograms obtained by means of Riegel's stethograph. I, normal curves; II, curve from a case ot emphy- sema; a, ascer.dmg limb; i, apex; ) When the air entering large bronchi causes the formation of bubbles in the mucus which may have accumulated there " mucous rales " are produced. They also occur in small spaces when the walls are separated from their fluid contents by the air entering during inspira- tion, or when the walls, being adherent to each other, are suddenly pulled asunder. The riles are distinguished as tftoisi (when the contents are fluid), or as dry (when the contents are sticky); they may be inspiratory, expiratory, or continuous, or they may be coarse or fine; funher, there is the very fine crepitation, or crackling sound, and, lastly, the metallic tinkling caused in large cavities through resonance. [Crepitation or vesicular rales are fine crepitating sounds like those pro- duced by rubbing a lock oi^ hair between the fingers near one's ear; they occur only during inspira- tion, and are a proof that some air is entering the air vesicles. It is heard in its typical form during the first stage of pneumonia, and seems to be produced by the bursting of minute bubbles of air in a fluid.] (<-) When the mucous membrane of the bronchi is greatly swollen, or is so covered with viscid mucus that the air must force its way through, deep sonorous rhonchi (rhonchi sonori) may occur in the large air passages, and clear, shrill sibilant sounds (rhonchi sibilantes) in the smaller ones. [Rhonchi are usually due to catarrh or to affections of the bronchial mucous membrane or bronchitis ] When there is extensive bronchial catarrh, not unfrequently we feel the chest wall vibrating with the rk\e sounds (bronchial fremitus). (4) If fluid and air occur together in one pleural cavity in which the lung is collapsed, on shaking the person's thorax vigorously we hear a sound such as is produced when air and water are shaken together in a bottle. This is the succussion sound of Hippocrates. Much more rarely this sound is heard under similar conditions in large pulmonary cavities. (5) Pleural Friction. — When the two opposed surfaces of the pleura are inflamed, have become soft, and are covered wiih exudation, they move over each other during respiration, and in doing so give rise to friction sounds, which can be felt (often by the patient himself), and can also be heard. The sound is comparable to the sound produced by bending new leather. (6) Pectoral Fremitus. — When we speak or sing in a loud tone, the walls of the chest vibrate, because the vibration of the vocal cords is propagated throughout the entire bronchial ramifications. The vibration is, of course, greatest near the trachea and large bronchi. The ear cannot delect the sounds distinctly. If there be much exudation or air in the pleura, or great accumulation of mucus in the bronchi, the pectoral fremitus is diminished or altogether absent. [In health, when a person PRESSURE IN THE AIR PASSAGES DURING RESPIRATION. 225 speaks, the vocal resonance over the trachea, although loud, may be inarticulate ; and on listening over the sternum the sound is diminished and quite inarticulate ; while over the chest wall generally the sound, though distinct, is feeble. All conditions which cause bronchial breathing increase the pectoral fremitus. Under normal circumstances, therefore, it is louder where bronchial breathing is heard normally. The ear hears an intensified sound, called bronchophony [which is a sound like that heard normally over the trachea or bronchi, but audible over the vesicular lung tissue. The conditions that cause it are the same as those on which bronchial breathing depends, so that it is heard in pneumonia and phthisis. If, through effusion into the pleura or inflammatory processes in the lung tissue, the bronchi are pressed flat, a peculiar bleating sound (aegophony) may be heard.] ii8. PRESSURE IN THE AIR PASSAGES DURING RESPI- RATION.— Respiratory Pressure. — If a manometer be tied into the trachea of an animal, so that the respiration goes on completely undisturbed, /. e., normal respiration, during every inspiration there is a negative pressure (-3 mm. Hg) and during expiration a positive pressure. Bonders placed the U-shaped manometer tube in one nostril, closed his mouth, leaving the other nostril open, and respired quietly. During every quiet inspiration the mercury showed a nega- tive pressure of- i mm., and during expiration a positive pressure of 2-3 mm. Forced Respiration. — As soon as the air was inspired or expired with greater force, the variations in pressure became very much greater, e. g., during speaking, singing, and coughing. The inspiratory pressure was = - 57 mm. (36-74), the greatest expiratory pressure -f 87 (82-iooj mm. Hg. The pressure of forced expiration, therefore, is 30 mm. greater than the inspiratory pressure {Donders). Resistance to Inspiration. — Notwithstanding this, we must not conclude that the expiratory muscles act more powerfully than the inspiratory ; for during inspiration a variety of resistances have to be overcome, so that after these have been met, there is only a residue of the force for the aspiration of the mercury. The resistances to be overcome by the inspiratory muscles are : (i) The elastic tension of the lungs, which during the deepest expirations = 6 mm. ; during the deepest inspirations = 30 mm. Hg (§ 107). (2) The raising of the weight of the chest. (3) The elastic torsion of the costal cartilages. (4) The depression of the abdominal contents, and the elastic distention of the abdominal walls. All these not inconsiderable resistances, which the inspiratory muscles have to overcome, act during expiration, and aid the expiratory muscles. The forces concerned in inspiration are decidedly much greater than those of expiration. Intra-thoracic Pressure. — As the lungs within the chest, in virtue of their elasticity, continually strive to collapse, necessarily they must cause a negative pressure within the chest. This amounts in dogs, during inspiration, to -7.1 to -7.5 mm. Hg, and during expiration to - 4 mm. Hg. The corresponding values for man have been estimated at - 4.5 mm. Hg and - 3 mm. Hg, by Hutchinson. [We must distinguish between the respiratory pressure of the air withui the respiratory passages, and the intra-thoracic pressure. The former is the same as the atmospheric pressure when the chest is passive, but less than it as the chest is being enlarged, and greater than it when it is being diminished in size. The intra-thoracic pressure is the pressure within the chest, but outside the hings, i. e., in the pleura, mediastinum, etc. It is negative, i. e., less than the atmospheric pres- sure, and must vary with the degree of distention of the lungs.] [Method. — A direct estimation was made by Adamkiewicz and Jacobson. A trocar with its stylet was forced into the fourth left intercostal space near the sternum and pushed into the peri- cardium (sheep). The stylet was then withdrawn, and the trocar connected with a manometer, and the negative pressure of - 3 to - 5 mm. Hg was obtained. During severe dyspnoea it was - 9 mm. Hg. Rosenthal introduced an oesophageal sound with an elastic ampulla on its lower end into the oesophagus, so that the ampulla came to lie opposite the posterior mediastinum. The sound was connected with a registering tambour or manometer. During inspiration the manometer fell, and during expiration it rose.] Even the greatest inspiratory or expiratory pressure is always much less than the blood pressure in the large arteries ; but if the pressure be calculated upon the entire respiratory surface of the thorax, very considerable results are obtained. 15 226 MODIFIED RESPIRATORY MOVEMENTS. Pneumatometer. — This instrument of Waldenburg is merely a mercurial manometer fixed to a stand, and connected to an elastic tube with a suitable mouth-piece, which is fitted over the mouth and nose, while the variations of the Hg can be read oft' on a scale. [In the male, the expiratory pressure is 90-120 mm. Ilg, and the respiratory 70-100. The relation of the pressures during expiration and inspiration is more important than the absolute j^ressure.] The inspiratory pressure is diminished in nearly all diseases where tlie expansion of the lung is impaired [phthisis], or the expiratory pressure is diminished, as in emphysema and asthma. Effects of the first Respiration on the Thorax. — Until birth, the airless lungs are completely collapsed (atelectic) within the chest, and fill it, so that on opening the chest in a dead foetus, pneumothorax does not occur [Bernstein). Supposing, however, respiration to have been fully established after birth, and air to have freely entered the lungs, if a manometer be placed in con- nection with the trachea, and the chest be opened, the manometer will register a pressure of 6 mm. Hg, due to the collapse of the elastic lungs. Bernstein supposes that the thorax assumes a new permanent form, due to the first respiratory distention ; it is as if, owing to the respiratory elevation of the ribs, the thorax had become permanently too large for the lungs, which are, there- fore, kept permanently distended, but collapse as soon as air passes into the pleura. When a lung has once been filled with air, it cannot be emptied by pressure from without, as the small bronchi are compressed before the air can pass out of the alveoli. The expiratory muscles cannot jx)ssibly expel all the air from the lungs, while the inspiratory muscular force is sufiicient to distend the lungs beyond their elastic equilibrium. Inspiration distends the lungs, increasing their elastic tension, while expiration diminishes the tension without abolishing it. 119. APPENDIX TO RESPIRATION.— Nasal Breathing.— During quiet respiration we usually breathe — or ought to breathe — through the nostrils, the mouth being closed. The current of air passes through the pharyngo-nasal cavity — so that, in its course during inspiration, it is (i) wanned and rendered moist, and thus irritation of the mucous membrane of the air passages by the cold air is prevented ; (2) ?,m3.\\ parficles of soot, or other foreign substances in the air, adhere to, and become embedded in the mucus covering the somewhat tortuous walls of the respiratory passages, and are carried outward by the agency of the ciliated epithelium of the respiratory passages ; (3) disagreeable odors and certain impurities are detected by the sense of smell. If a lung be inflated, air constantly passes through the walls of the alveoli and trachea. This also occurs during violent expiratory efibrts (cutaneous emphysema in whooping cough), so that pneumothorax may occur [J. R. Ezuald and Kobert'). Pulmonary CEdema, or the exudation of lymph into the pulmonary alveoli, occurs (i) \\Tien there is very great resistance to the blood stream in the aorta or its branches, e.g., by ligaturing all the arteries going to the head or the arch of the aorta, so that only one carotid remains pervious. (2) When the pulmonary veins are occluded. (3) When the left ventricle, owing to meciianical injury, ceases to beat, while the right ventricle goes on contracting (\ 47). These conditions pro- duce at the same time anxmia of the vasomotor centre, which results m stimulation of that centre, and consequent contraction of all the small arteries. Thus the blood stream through the veins to the right heart is favored, and this in its turn favors the production of oedema of the lungs. [The injection of muscarin rapidly causes pulmonary cedema, due to the increase of pressure and slowing of the blood stream in the pulmonary capillaries. It is set aside by atropin ( Weinzweig, Gross- mann)."] 120. MODIFIED RESPIRATORY MOVEMENTS.— (i) Coughing consists in a sudden violent expiratory explosion after a previous deep inspiration and closure of the glottis, whereby the glottis is forced open, and any substance, fluid, gaseous, or solid, in contact with the respiratory mucous membrane is violently ejected through the open mouth. It is produced volun- tarily or refiexly; in the latter case, it can be controlled by the will only to a limited extent. [Causes. — A cough may be discharged reflexly from a large number of surfaces : (i) A draught of cold air striking the sitn, especially of the upper part of the body. This may cause congestion of blood in the air passages, this in turn exciting the cough. (2) More frequently it is discharged from the respiratory mucous membrane, especially of the larynx, the sensory branches of the vagus and the superior laryngeal nerve being the afferent nerves. A cough cannot be dis- charged from every part of the larynx : thus there is none from the true vocal cords, but only from the glottis respiratoria. All other parts of the lar>-nx are inactive, and so is the trachea as far as the bifurcation, where stimulation excites cough {Kohts). (3) Sometimes an offending body, such as a pea or inspissated cerumen in the external auditory meatus, gives rise to coughing, the afferent nerve being the auricular branch of the vagus. (4) There seems to be no doubt that there may be a ''gas- tric or stomach cough,'' produced by stimulation of the gastric branches of the vagus, especially in cases of indigestion, accompanied by irritation of the larynx and trachea. (5) Irritation of the costal pleura and even of the cesophagus {Kohts). (6) Irritation of some parts of the nose. CHEMISTRY OF RESPIRATION. 227 (7) Sometimes also from irritation of the pharynx, as by an elongated uvula. (8) In some diseases of the liver, spleen, and generative organs, when pressure is exerted on these parts.] (2) Hawking, or clearing the throat. An expiratory current is forced in a continuous stream through the narrow space between the root of the tongue and the depressed soft palate, in order to assist in the removal of foreign bodies. When the act is carried out periodically, the closed glottis is suddenly forced open, and it is comparable to a voluntary gentle cough. This act can only be produced voluntarily. (3) Sneezing consists in a sudden violent expiratory blast through the nose, for the removal of mucus or foreign bodies (the mouth being rarely open) after a simple or repeated spasm-like inspira- tion— the glottis remaining open. It is usually caused reflexly by stimulation of sensory nerve fibres of the nose [nasal branch of the fifth nerve], or by sudden exposure to a bright light [the afferent nerve is the optic]. This reflex act may be interfered with to a certain extent, or even prevented, by stimulation of sensory nerves, or firmly compressing the nose where the nasal nerve issues. The continued use of sternutatories, as in persons who take snuff, dulls the sensory nerves, so that they no longer act when stimulated reflexly. [Sternutatories or Errhines, such as powdered ipecacuanha, snuff, and euphorbium, also in- crease the secretion from the nasal glands. The afferent impulses sent to the respiratory centre also affect the vasomotor centre, so that, even when sneezing does not occur, the blood pressure throughout the body is raised.] (4) Snoring occurs during respiration through the open mouth, whereby the inspiratory and expiratory stream of air throws the uvula and soft palate into vibration. It is involuntary, and usually occurs during sleep, but it may be produced voluntarily. (5) Gargling consists in the slow passage of the expiratory air current in the form of bubbles through a fluid lying between the tongue and the soft palate, when the head is held backward. It is a voluntary act. (6) Crying, caused by emotional conditions, consists in short, deep inspirations, long expirations with the glottis narrowed, relaxed facial and jaw muscles, secretion of tears, often combined with plaintive inarticulate expressions. When crying is long continued, sudden and spasmodic involun- tary contractions of the diaphragm occur, which cause the inspiratory sounds in the pharynx and larynx known as sobbing. This is an involuntary act. (7) Sighing is a prolonged inspiration, usually combined with a plaintive sound, often caused involuntarily, owing to painful or unpleasant recollections. (8) Laughing is due to short, rapid expiratory blasts through the tense vocal cords, which cause a clear tone, and there are characteristic inarticulate sounds in the larynx, with vibra- tions of the soft palate. The mouth is usually open, and the countenance has a characteristic expression, owing to the action of the M. zygomaticus major. It is usually involuntary, and can only be suppressed, to a certain degree, by the will (by forcibly closing the mouth and stopping respiration). (9) Yawning is a prolonged deep inspiration occurring after successive attempts at numerous inspirations — the mouth, fauces, and glottis being wide open ; expiration shorter — both acts often accompanied by prolonged characteristic sounds. It is quite involuntary, and is usually excited by drowsiness or ennui. [(10) Hiccough is due to a spasmodic involuntary contraction of the diaphragm, causing an inspiration, which is arrested by the sudden closure of the glottis, so that a characteristic sound is emitted. Not unfrequently it is due to irritation of the gastric mucous membrane, and sometimes it is a very troublesome symptom in ursemic poisoning.] 121. CHEMISTRY OF RESPIRATION— CARBON DIOXIDE, OXYGEN, and WATERY VAPOR GIVEN OFF.— I. Estimation of COj.— i. The volume of CO2 is estimated by means of the anthracometer (Fig. 143, II). The volume of gas is collected in a graduated tube, ;', r, provided with a bulb at one end (previously filled with water and carefully calibrated, i. e., the exact amount which each part of the tube contains is accurately measured), and the tube is closed. The lower end has a stop-cock, k, and to this is screwed a flask, n, com- pletely filled with a solution of caustic potash ; the stop-cock is then opened, the potash solution is allowed to ascend into the tube, which is moved about until all the COj unites with the potash to form potassium carbonate. Hold the tube vertically and allow the potash to run back into the flask, close the stop-cock, and remove the bottle with the potash. Place the stop-cock under water,, open it, and allow the water to ascend in the tube, when the space in the tube occupied by the fluid indicates the volume of CO2 which is combined with the potash. 2. By Weight. — A large quantity of the mixture of gases which has to be investigated is made to pass through a Liebig's bulb filled with caustic potash. The potash apparatus having been care- fully weighed beforehand, the increase of weight indicates the amount of COj which has been taken up by the potash from the air passed through it. 3. By Titration. — A large volume of the air to be investigated is conducted through a known volume of a solution of barium hydrate. The COj unites with the barium and forms barium car- bonate. The fluid is neutralized with a standard solution of oxalic acid, and the more barium that has united with the COj the smaller will be the amount of oxalic acid used, and vice versa. 228 ANDRAL AND GAVARRET S APPARATUS. II. Estimation of Oxygen. — According to volume (a) Uy the union of the O with potassium pyrogaliate. The same procedure is adopted as for the estimation of CO^, only the flask, w, is filled with the pyrogaliate solution instead of potash. {/>) By explosion in an eudiometer (see Blood Gases, ? 35). III. Estimation of Watery Vapor. — The air to be investigated is passed through a bulb containing concfntratc-d su'if'huric add, or through a tube filled with pieces of calcititn chloride. The amount of water is directly indicated by the increase of weight. 122. METHODS OF INVESTIGATION.— I. Collecting the Expired Air.— (i) The air expired may be collected in tlie cylinder of the spirometer, which is suspended in concentrated salt solution to avoid the absorption of CO.^ (? 108). Andral and Gavarret's Apparatus. — The operator breathed several times into a capacious cylinder (Fig. 143). A mouth-piece (M) was placed air-tight over the mouth, while the nostrils were closed? The direction of the respiratory current was regulated by two so-called " Miiller's Valves " (mercurial), (a and /'). With every inspiration the bottle or valve, a (filled below with Ilg and hermetically closed above), permits the air inspired to pass to the lungs — during every expiration the expired air can pass only through b to the collecting cylinder C. (2) If the gases given ofi" by the skin are to be collected, a limb, or whatever part is to be inves- tigated, is secured in a closed vessel, and the gases so obtained are analyzed. Fig. 143. O^ ^ o ^#9 E I. Apparatus ot Andral and Gavarret for collecting the expired air. C, large cylinder to collect the air expired ; P, weight to balance cylinder ; a, b, two Miiller's valves ; M, mouth-piece. II. Anthracometer of Vierordt. II. The most important apparatus for this purpose are those of («) Scharling (Fig. 144), which consists of a closed box, A, of suflicient size to contain a man. It is provided %vith an inlet 2 and outlet b. The latter is connected with an aspirator, C, a large barrel filled with water. When the stop-cock, h, is opened and the water flows out of the barrel, fresh air will rush in con- tinuously into the box. A, and the air mixed with the expired gases will be drawn toward C. A Liebig's bulb, d, filled with caustic potash, is connected with the entrance tube, z, through which the in-going air must pass, whereby it is completely deprived of CO.^, so that the person experi- mented on is supplied with air free from C()2. The air passing out by the exit tube, b, has to pass first through e, where it gives up its watery vapor to sulphuric acid, whereby the amount of watery vapor is estimated by the increase of the weight of the apparatus, e. Afterward the air passes through a bulb, /, containing caustic potash, which absorbs all the CO.^, while the tube, g, filled with sulphuric acid, absorbs any watery vapor that may come from /. The increase in weight of / and g indicates the amount of COj, The total volume of air used is known from the capacity of C. (^) Regnault and Reiset's Apparatus is more complicated, and is used when it is necessary to keep animals for some time under observation in a bell-jar. It consists of a globe, R, in which is placed the dog to be experimented on (Fig. 145). Around this is placed a cylinder, SCHARLING, REGNAULT AND REISET's APPARATUS. 229 g,g (provided with a thermometer, /), which may be used for calorimetric experiments. A tube, c, leads into the globe, R ; through this tube passes a known quantity of pure oxygen (Fig. 145, O). To absorb any trace of COj, a vessel containing potash (Fig. 145, CO2) is placed in the course of the tube. The vessel for measuring the O is emptied toward R, through a solution of calcium chloride from a large pan (CaClj) provided with large flasks. Two tubes, d and e, lead from R, Fig. 144. / / >■ Z_ A b d / Scharling's apparatus, d, bulb containing caustic potash to absorb COo from in-going air; A, box for animal experi- mented on ; e and^, tubes containing sulphuric acid to absorb watery vapor ; /, potash bulb to absorb COo given off; C, vessel filled with water to aspirate air ; h, stop-cock. and are united by caoutchouc tubes with the potash bulbs (KOH, K^^), which can be raised or depressed alternately by means of the beam, W. In this way they aspirate alternately the air from R, and the caustic potash absorbs the COj. The increase in weight of these flasks after the experiment indicates the amount of COj expired. The manometer, /, shows whether there is a difference of the pressure outside and inside the globe, R. Koh Scheme of tVie respiration apparatus of Regnault and Reiset. R, globe for animal ; g, g, outer casing for R . provided with a thermometer, t ; d and e, exit tubes to movable potash bulbs, KOH and Y^oh ; O, in-going oxygen ; CO2, vessel to absorb any carbonic acid ; CaCla, apparatus for estimating the amount of O supplied ; y, manometer. (c) V. Pettenkofer has invented the most complete apparatus (Fig. 146). It consists of a chamber, Z, with metallic walls, and provided with a door and a window. At a is an opening for the admission of air, while a large double suction pump, PPj (driven by means of a steam engine) continually renews the air within the chamber. The air passes into a vessel, 6, filled with pumice- 230 COMPOSITION OF ATMOSPHERIC AIR stone saturated with sulphuric acid, in which it is dried; it then passes through a large j^as meter, c which measures the total amount of the air passing through it. After the air is measured, it is emptied outward by means of the pump, I'P,. From the chief exit tube, .r, of the chamber, provided with a small manometer, loi). Loss by Skin. — A healthy man loses by the skin, in 24 hours, ^ of his body weight, which is greater than the loss by the lungs, in the ratio of 3 : 2. Only 10 grammes — 150 grains, — or it may be 3.9 grammes, 60 grains, — of the entire loss are due to the CO,, given off by the skin. The remainder of the excretion from the skin is due to \vater [i.',-2 lb daily] containing a few salts in solution. When the surrounding temperature is raised, the CO2 is increased, in fact it may be doubled ; violent muscular exercise has the same effect. O Absorbed. — The O taken up by the skin is either equal to, or slightly less than, the CO, given off. As the CO. excreted by the skin is only ^^ of that excreted by the lungs, while the O taken in ^ y^l^ of that taken in by the lungs, it is evident that the respiratory activity of the skin is very slight. Animals whose skin has been covered by an impermeable varnish die, not from suffocation, but from other causes (§ 225). In animals with a thin, moist epidermis (frog) the exchange of gases is much greater, and in them the skin so far supports the lungs in their function, and may even partly replace them func- tionally. In mammals with thick, dry cutaneous appendages, the exchange of gases is, again, much less than in man. 132. INTERNAL RESPIRATION.— \A^here CO, is formed.— By the term "internal respiration " is understood the exchange of gases between the capillaries of the systemic circulation and the tissues of the organs of the body. As organic constituents of the tissues, during their activity, undergo gradual oxidation, and form among other products, CO,,; we may assume (i) that the chief focus for the absorption of O and the formation of CO2 is to be soueht for within the tissues themselves. That the O from the blood in the capillaries rapidly penetrates or diffuses into the tissues, is shown by the fact that the blood in the capillaries rapidly loses O and gains CO,,, while blood containing O, and kept warm outside the body, changes very slowly and incompletely. If portions of fresh tissues be placed in defibrinated blood containing O, then the O rapidly disai)pears. Frogs deprived of their blood exhibit an exchange of gases almost as great as normal. This shows that the exchange of gases must take place in the tissues themselves. If the chief oxidations took place in the blood and not in the tissues, then, during suffocation, when O is excluded, the substances which use up O, i.e., those substances which act as reducing agents, ought to accumulate in the blood. But this is not the case, for the blood of asphyxiated animals contains mere traces of reducing materials {FJliiger). It is difficult to say how the O is absorbed by the tissues, and what becomes of it immediately it comes in contact with the living elements of the tissues. Perhaps it is temporarily stored up, or it may form certain intertnediate less oxidized com- pounds. This may be followed by a period of rapid formation and excretion of CO^. On this supposition, it is evident that the absorption of O and the excre- tion of CO, need not occur to the same extent, so that the amount of CO.^ given off at any period is not necessarily an index of the amount of O absorbed during the same period (§ 127). TENSION OF THE GASES IN CAVITIES AND LYMPH. 239 [There are two views as to where the CO2 is formed as the blood passes through the tissues. One view is that the seat of oxidation is in the blood itself, and the other is that it is formed in the tissues. If we knew the tension of the gases in the tissues, the problem would be easily solved, but we can only arrive at a know- ledge of this subject indirectly, in the following ways] : — CO2 in Cavities. — That the CO2 is formed in the tissues, is supported by the fact that the amount of CO2 in the fluids of the cavities of the body is greater than the CO2 in the blood of the capillaries. The tension of CO2 in — Mm. I Mm. Arterial blood, . . 12.28 Hg tension. | Bile, .... 50.0 Hg tension. Peritoneal cavity, . . 58.5 " " I Hydrocele fluid, . . 46.5 " " Acid urine, . . 68.0 " " | {Pfli'tger and Slrassburg). The large amoicnl of CO., in these fluids can only arise fro7n the CO^ of the tissues passing into the7?i. Gases of Lymph. — In the lymph of the ductus thoracicus the tension of COj = 33.4 to 37.2 mm. Hg, which is greater than in arterial blood, but considerably less than in venous blood (41.0 mm. Hg). [^Ltidwig and Hammarsten, Tschirjew.'] This does not entitle us to conclude that in the tissues from M^hich the lymph comes only a small quantity of COj is formed, but rather that in the lymph there is less attraction for the COj formed in the tissues than in the blood of the capil- laries, where chemical forces are active in causing it to combine, or that in the course of the long lymph current, the COj is partly given back to the tissues, or that CO2 is formed in the blood itself. Further, the m.uscles, which are by far the largest producers of CO3 contain few lymphatics, never- theless they supply much CO2 to the blood. The amount of free " non-fixed " CO2 contained in the juices and tissues indicates that the COj passes from the tissues into the blood; still, Preyer believes that in venous blood COj undergoes chemical combination. The exchange of O and COj varies much in the different tissues. The muscles are the most important organs, for in their active con- dition they excrete a large amount of CO2, and use up much O. The O is so rapidly used up by them that no free O can be pumped out of muscular tissue (Z. Hermattn). The exchange of gases is more vigorous during the activity of the tissues. Nor are the salivary glands, kidneys, and pan- creas any exception, for although, when these organs are actively secreting, the blood flows out of the dilated veins in a bright red stream, still the relative diminution of COj is more than compen- sated by the increased volume of blood which passes through these organs. Reductions by the Tissues. — The researches of Ehrlich have shown that in most tissues very energetic reductions take place. If coloring matters, such as alizarin blue, indophenol blue, or methyl blue, be introduced into the blood stream, the tissues are colored by them. Those tissues or organs which have a particular affinity for O {e.g., liver, cortex of the kidney, and lungs), absorb O from these pigments, and render them colorless. The pancreas and sub-maxillary gland scarcely reduce them at all. (2) In the blood itself, as in all tissues, O is used up and CO2 is formed. This is proved by the following facts : That blood withdrawn from the body becomes poorer in O and richer in CO2 ; that in the blood of asphyxia, free from O, and in the blood corpuscles, there are slight traces of reducing agents, which become oxidized on the addition of O. Still, this process is comparatively insig- nificant as against that which occurs in all the other tissues. That the walls of the vessels — more especially the muscular fibres in the walls of the small arteries — use O and produce CO2 is unquestionable, although the exchange is so slight that the blood in its whole arterial course undergoes no visible change. Ludwig and his pupils have proved that CO2 is actually formed in the blood. If the easily oxidiz- able lactate of soda be mixed with blood, and this blood be caused to circulate in an excised but living organ, such as a lung or kidney, more O is used up and more COj is formed than in unmixed blood similarly tran.sfused. (3) That the tissues of the living lungs use O and give off CO2 is probable. When C. Ludwig and Miiller passed arterial blood through the blood vessels of a lung deprived of air, the O was diminished and the CO2 increased. As the total amount of CO2 and O found in the entire blood at any one time is only 4 grammes, and as the daily excretion of CO2 = 900 grammes, and the O absorbed daily = 744 grammes, it is clear that exchange of gases must go on with great rapidity, that the O absorbed must be used quickly, and the CO2 must be rapidly excreted. 1>4() RESPIRATION IN A LIMITED SI'ACE. Still, it is a striking fact that oxidation processes of such magnitude, as <■.(,■-., the union of C to form CO,, occur at the relatively low temperature of the blood and tissues. It has been surmised that the blood acts as an ozone producer, and transforms this active form of O to the tissues. Liebig showed that the alkaline reaction of most of the juices and tissues favors the processes of oxidation. Numerous organic substances, which are not altered by O alone, become rapidly oxidized in the presence of free alkalies, e.g., gallic acid, pyrogallic acid, and sugar; while many organic acids, which are unaffected by ozone alone, are changed into carbonates when in the form of alka- line salts ( GorupBesanez) ; and, in the same way, when they are introduced into the body in the form of acids, they are partly or wholly excreted in the urine, but when they are administered as alkaline compounds they are changed into carbonates. 133. RESPIRATION IN A LIMITED SPACE.— Respiration in a limited space causes (i) a gradual diminution of O ; (2) a simultaneous in- crease of CO.^ ; (3) a diminution in the volume of the gases. If the space be of moderate dimensions, the animal uses up almost all the ©contained therein, and dies ultimately of spasms caused by the asphyxia. The O is absorbed, therefore — independently of the laws of absorption — by chemical means. The O in the blood is almost completely used up (§ 129). In a larger space, the CO.^ accumulates rapidly, before the diminution of O is such as to affect the life of the animal. As CO^ can only be excreted from the blood when the tension of the CO., in the blood is greater than the tension of CO.^ in the air, as soon as the CO.^ m the surrounding air in the closed space becomes the same as in the blood, the CO2 will be retained in the blood, and finally CO.^ may pass back into the body. This occurs in a large closed space, when the amount of O is still sufficient to support life, so that death occurs under these circumstances (in rabbits) through poisoning with CO.^ causing diminished excitability, loss of consciousness, and lowering of temperature, but no spasms {JVorm Miiller). In pure O animals breathe in a normal way; the quantity of O absorbed and the CO,, excreted is quite independent of the percent- age of O, so that the former occurs through chemical agency independent of pres- sure. In limited spaces filled with O, animals died by absorption of the CO.,, excreted. Worm Miiller found that rabbits died after absorbing CO.,, equal to half the volume of their body, although the air still contained 50 per cent. O. Animals can breathe quite quietly a mixture of air containing 14.8 percent. (20.9 percent, normal); with 7 per cent, they breathe with difliculty ; with 4.5 per cent, there is marked dyspnoea; with 3 per cent. O there is tolerably rapid asphyxia. The air expired by man normally contains 1410 18 per cent. O. According to Hemp- ner, mammals placed in a mixture of gases poor in O use slightly less O. Dyspnoea occurs when the respired air is deficient in O, as well as when it is overcharged with CO.^, but the dyspnoea in the former case is prolonged and severe ; in the latter, the respiratory activity soon ceases. The want of O causes a greater and more prolonged increase of the blood pressure than is caused by an excess of CO.^. Lastly, the consumption of O in the body is less affected when the O in the air is diminished than when there is an excess of COj. If air containing a diminished amount of O be respired, death is preceded by violent phenomena of excitement and spasms, which are absent in cases of death caused by breathing air overcharged with COj. In poisoning with CO^, the excretion of COj is greatly diminished, while with diminution of O it is almost unchanged. If animals be supplied with a mixture of gases similar to the atmosphere, in which N is replaced by H, they breathe quite normally {^Lavoisier and Segiiin) ; the H undergoes no great change. CI. Bernard found that, when an animal breathed in a limited space, it became partially accustomed to the condition. On placing a bird under a bell-jar, it lived several hours ; but if several hours before its death, another bird fresh from the outer air were placed under the same bell-jar, the second bird died at once of convulsions. Frogs, when placed for several hours in air devoid of O, give off just as muchCOj as in air con- taining O, and they do this without any obvious disturbance. Hence, it appears that the formation of CO2 is independent of the absorption of O, and the CO^ must be formed from the decomposition of other compounds. Ultimately, however, complete motor paralysis occurs, while the circulation remains undisturbed {Aubert). PHENOMENA OF ASPHYXIA. 241 [134. DYSPNCEA AND ASPHYXIA.— For the causes of dyspnoea see § III, and those of asphyxia see § 368. If from any cause an animal be not sup- plied with a due amount of air, normal respiration becomes greatly altered, passing through the phases of hyperpncEa, or increased respiration, dyspnoea, or diffi- culty of breathing, to the final condition of suffocation or asphyxia. The phenomena of asphyxia may be developed by closing the trachea of an animal with a clamp, or by any means which prevents the entrance of air or blood into the lungs. The phenomena of asphyxia are usually divided into several stages: i. During the first stage there is hyperpnoea, the respirations being deeper, more frequent, and labored. The extraordinary muscles of respiration — both those of inspiration and expiration (§ 118) — are called into action, dyspnoea is rapidly produced, and the struggle for air becomes more and more severe. At the same time the oxygen of the blood is being used up, while the blood itself becomes more and more venous. The venous blood circulating in the medulla oblongata and spinal cord stimulates the respiratory centres, and causes the violent respira- tions. This stage usually lasts about a minute, and gradually gives place to — 2. The second stage, when the inspiratory muscles become less active, while those concerned in labored expiration contract energetically, and indeed almost every muscle in the body may contract ; so that this stage of violent expiratory efforts ends in general convulsions. The convulsions are due to stimulation of the respiratory centres by the venous blood. The convulsive stage is short, and is usually reached in a little over one minute. This storm is succeeded by — 3. The third stage, or stage of exhaustion, the transition being usually some- what sudden. It is brought about by the venous blood acting on and paralyzing the respiratory centres. The pupils are widely dilated, consciousness is abolished, and the activity of the reflex centres is so depressed that it is impossible to dis- charge a reflex act, even from the cornea. The animal lies almost motionless, with flaccid muscles, and to all appearance dead, but every now and again, at long intervals, it makes a few deep inspiratory efforts, showing that the respira- tory centres are not quite, but almost paralyzed. Gradually the pauses become longer and the inspirations feebler and of a gasping character. As the venous blood circulates in the spinal cord, it causes a large number of muscles to con- tract, so that the animal extends its trunk and limbs. It makes one great inspira- tory spasm, the mouth being widely opened and the nostrils dilated, and ceases to breathe. After this stage, which is the longest and most variable, the heart becomes paralyzed, partly from being over-distended with venous blood, and partly, perhaps, from the action of the venous blood on the cardiac tissues, so that the pulse can hardly be felt. To this pulseless condition the term "asphyxia " ought properly to be applied. In connection with the resuscitation of asphyxiated persons, it is important to note that the heart continues to beat for a few seconds after the respiratory movements have ceased. The whole series of phenomena occupies from 3 to 5 minutes, according to the animal operated on, and depending also upon the suddenness with which the trachea was closed. If the causes of suffocation act more slowly, the phenomena are the same, only they are developed more slowly. The Circulation. — The post-mortem appearances in man or in an animal are generally well marked. The right side of the heart, the pulmonary artery, the venge cavse, and the veins of the neck are engorged with dark venous blood. The left side is comparatively empty, because the rigor mortis of the left side of the heart, and the elastic recoil of the systemic arteries, force the blood toward the systemic veins. The blood itself is almost black, and is deprived of almost all its oxygen, its haemoglobin being nearly all in the condition of reduced haemoglobin, while ordinary venous blood contains a considerable amount of oxyhsemoglobin as well as reduced Hb. The blood of an asphyxiated animal 16 242 THE CHANGES OF THE CIRCULATION DURING ASPHYXIA. practically contains none of the former and much of the latter. It is important to study the changes in the circulation in relation to phenomena exhibited by an animal during suffocation. We may measure the blood pressure in any artery of an animal while it is being asphvxiated, or we may oj^en its chest, maintain artificial res|)iration, and place a manometer in a systemic artery, e. g., the carotid, and another in a branch of the pulmonary artery. In the latter case, we can watch the order, of events in the heart itself, when the artificial respiration is interrupted. It is well to study the events in both cases. If the blood pressure be measured in a systemic artery, e. g., the carotid, it is found tiiat the blood pressure rises very rapidly, and to a great extent during the first and second stages ; the pulse beats at first are quicker, but soon become slower and more vigorous. During the third stage it falls rapidly to zero. The threat rise of the blood pressure, during the first and second stages, is chiefly due to the action of the venous blood on the general vasomotor centre, causing con- striction of the small systemic arteries. The peripheral resistance is thus greatly increased, and it tends to cause the heart to contract more vigorously, but the slower and more vigorous beats of the heart are also partly due to the action of the venous blood on the cardio-inhibitory centre in the medulla. If the second method be adopted, viz., to open the chest, keep up artificial respiration, and measure the blood pressure in a branch of the pulmonary artery, as well as in a systemic artery — e. g., the carotid — we find that when the artificial respiration is stopped, in addition to the rise of the blood pressure indicated in the carotid manometer, the cavities of the heart and the large veins near it are engorged with venous blood. There is, however, but a slight comparative rise in the blood pressure in the pulmonary artery. This may be accounted for, either by the pulmonary artery not being influenced to the same extent as other arteries by the vasomotor centre, or by its greater distensibility (§ 88). But, as the heart itself is supplied through the coronary arteries with venous blood, its action soon becomes weakened, each beat becomes feebler, so that soon the left ventricle ceases to contract, and is unable to overcome the great peripheral resistance in the systemic arteries, although the right ventricle may still be contracting. As the blood becomes more venous, the vasomotor centre becomes paralyzed, the small systemic arteries relax, and the blood flows from them into the veins, while the blood pressure in the carotid manometer rapidly falls. The left ventricle, now relieved from the great internal pressure, may execute a few feeble beats, but they can only be feeble, as its tissues have been subjected to the action of the very impure blood. More and more blood accumulates in the right side from the causes already mentioned. The violent inspiratory efforts in the early stages aspirate blood from the veins toward the right side of the heart, but of course this factor is absent when the chest is opened.] [Convulsions during asphyxia occur only in warm-blooded animals, and not in frogs. If a drug when injected into a mammal excites convulsions, but does not do so in the frog, then it is usually concluded that the convulsions are due to its action on the circulation and respiration, and not to any direct stirnulating effect upon the motor centres. But if the drug excites convulsions both in the mammal and frog, then it probably acts directly on the motor centres {J3runtoti).~\ [Recovery from the condition of Asphyxia. — If the trachea of a dog be closed suddenly and compleiely, the average duration of the respiratory movements is 4 minutes 5 seconds, while the heart continues to beat for about 7 minutes. Recovery may be obtained if proper means be adopted before the heart ceases to beat; but after this, never. If a dog be drowned, the result is different. After complete submersion for i^ minutes, recovery did not take place. In drown- ing, air passes out of the chest, and water is inspired into and fills the air vesicles. It is rare for recovery to take place in a person deprived of air for more than five minutes. If the state- ments of sponge divers are to be trusted, a person may become accustomed to the deprival of air for a longer time than usual. In cases where recovery takes place after a much longer period of ARTIFICIAL RESPIRATION IN ASPHYXIA, 243 submersion, it has been suggested that, in these cases, syncope occurs, the heart beats but feebly or not at all, so that the oxygen in the blood is not used up with the same rapidity. It is a well-known fact that newly- born and young puppies can be submerged for a long time before they are suffocated.] Artificial Respiration in Asphyxia. — In cases of suspended animation, artificial respiration must be performed. The first thing to be done is to remove any foreign substance from the respira- tory passages (mucus or oedematous fluids) in the newly-born or asphyxiated. In doubtful cases, open the trachea and suck out any fluid by means of an elastic catheter {v. Hiiter'). Recourse must in all cases be had to artificial respiration. There are several methods of dilating and compressing the chest so as to cause an exchange of gases. One method is to compress the chest rhythmically with the hands. [Marshall Hall's Method. — "After clearing the mouth and throat, place the patient on the face, raising and supporting the chest well on a folded coat or other article of dress. Turn the body very gently on the side and a little beyond, and then briskly on the face, back again, repeating these measures cautiously, efficiently, and perseveringly, about fifteen times in the minute, or once every four or five seconds, occasionally varying the side. By placing the patient on the chest, the weight of the body forces the air out ; when turned on the side, this pressure is removed, and air enters the chest. On each occasion that the body is replaced on the face, make uniform but efficient pressure with brisk movement on the back between and below the shoulder blades or bones on each side, removing the pressure immediately before turning the body on the side. During the whole of the operations let one person attend solely to the movements of the head and of the arm placed under it."] [Sylvester's Method. — "Place the patient on the back on the flat surface, inclined a little upward from the feet ; raise and support the head and shoulders on a small firm cushion or folded article of dress placed under the shoulder-blades. Draw forward the patient's tongue, and keep it projecting beyond the lips; an elastic band over the tongue and under the chin will answer this purpose, or a piece of string or tape may be tied round them, or by raising the lower jaw the teeth may be made to retain the tongue in that position. Remove all tight clothing from about the neck and chest, especially the braces." " To Imitate the Alovenients of Breathing. — Standing at the patient's head grasp the arms just above the elbows, and draw the arms gently and steadily upward above the head, and keep them stretched upward for two seconds. By this means air is drawn into the lungs. Then turn down the patient's arms, and press them gently and firmly for two seconds against the sides of the chest. By this means air is pressed out of the lungs. Repeat these measures alternately, deliberately, and perseveringly about fifteen times in a minute, until a sponta- neous effort to respire is perceived, immediately upon which cease to imitate the movements of breathing, and proceed to induce circulation a7id zvarmtk"~\ Howard advises rhythmical compression of the chest and abdomen by sitting like a rider astride of the body, while Schiiller advises that the lower ribs be seized from above with both hands and raised, whereby the chest is dilated, especially when the thigh is pressed against the abdomen to compress the abdominal walls. The chest is compressed by laying the hands flat upon the hypo- chondria. Artificial respiration acts favorably by supplying O to, as well as removing COj from, the blood ; further, it aids the movement of the blood within the heart and in the large vessels of the thorax. If the action of the heart has ceased, recovery is impossible. In asphyxiated newly-born children, we must not cease too soon to perform artificial respiration. Even when the result appears hopeless, we ought to persevere. PHiiger and Zuntz observed that the reflex excitability of the fcetal heart continued for several hours after the death of the mother. Resuscitation by compressing the heart. — Bohm found that in the case of cats poisoned with potash salts or chloroform, or asphyxiated, so as to arrest respiration and the action of the heart — even for a period of forty minutes — and even when the pressure within the carotid had fallen to zero, he could restore animation by rhytlunical compression of the heart, combined with artificial respiration. The compression of the heart causes a slight movement of the blood, while it acts at the same time as a rhythmical cardiac stimulus. After recovery of the respiration, the reflex excita- bility and gradually also voluntary movements are restored. The animals are blind for several days, the brain acts slowly, and the urine contains sugar. These experiments show how important it is in cases of asphyxia to act at the same time upon the heart. For physiological purposes, artificial respiration is often made use of, especially after poi- soning with curara. Air \% forced into the lungs by means of an elastic bag or bellows, attached to a cannula tied in the trachea. The cannula has a small opening in the side of it to allow the expired air to escape. Pathological. — After the lungs have once been properly distended with air, it is impossible by any amount of direct compression of them to get rid of all the air. This is probably due to the pressure acting on the small bronchi, so as to squeeze them, before the air can be forced out of the air vesicles. If, however, a lung be filled with CO.,, and be suspended in water, the CO2 is absorbed by the water, and the lungs become quite free from air and are atelectic [Hermann and Kellej-). ' The atelectasis, which sometimes occurs in the lung, may thus be explained : If a bronchus is stopped with mucus or exudation, CO., accumulates in the air vesicles belonging to this bronchus. If the 244 ACCIDENTAL IMPURITIES OF THE AIR. CO is absorbed by ihe blood or lymph, the corresponding area of the lung will become atelectic. Sometimes there is spasm of the respiratory muscles, brouglit about by direct or reflex stimulation of the respiratory centre. 135. RESPIRATION OF FOREIGN GASES. — No gas wiihout a sufficient admixture of O can support life. Even with completely innocuous and indifTerent gases, if no O be mixed with tlitni, thev cause sutTocation in 2 to 3 minutes. I. Completely indifferent Gases are N, H, CH^. The living blood of an animal breathing these gases yields no O to them {/'/liii^c!). II. Poisonous Gases. — O displacing Gases. — {a) Those that displace O, and form a stable compound with tlie ha'moglobin (I) CO (j;^ 1 6 and 17). (2) CNIl (hydrocyanic acid) displaces (?) O Irom hremoglobm, forming a more stable compound, and kdls exceedingly rapidly. Blood corpuscles charged with hydrocyanic acid lose the property of decomposing hydric peroxide into water and O ({; I7< 5)- {b) Narcotic Gases.— (i) CO.^. — v. Peltenkofer characterizes atmospheric air containing .1 per cent. CO., as "bad air;" still, air in a room containing this amount of CO., produces a disagreeable feeling, rather from the impurities mixed with it than from the actual amount of CO.^ itself. Air contaming i per cent. CO., produces decided discomfort, and with 10 per cent, it endangers life, while larger amounts cause death, with symptoms of coma. (2) N,/J (nitrous oxide), respired, mixed with \ volume O, causes, after i to 2 minutes, a short temporary stage of excitement ^" Laugh- ing gas" oflL Davy), which is succeeded by unconsciousness, and afterward by an increased excretion of CO.^. (3) Ozonized air causes similar effects [Binz). {c) Reducing Gases. — (i) H.^S (sulphuretted hydrogen) rapidly robs blood corpuscles of O, S and I1.,0 being formed, and death occurs rapidly before the gas can decompose the hivmoglobin to form a sulphur-metha-moglobin compound. (2) PH3 (phosphuretted hydrogen) is oxidized in the blood to form phosphoric acid and water, with decomposition of the hamoglobin. (3) AsH, (arseniuretted hydrogen) and SbH., (antimoniuretted hydrogen) act like PH3, but the hcemoglobin passes out of the stroma and appears in the urine. (4) CNj (cyanogen) absorbs O, and decomposes the blood. III. iVrespirable Gases, z. 1?., gases which, on entering the larynx, cause reflex spasm of the glottis. When introduced into the trachea, they cause inflammation and death. Under this cate- gory come hydrochloric, hydrofluoric, sulphurous, nitrous, and nitric acids, ammonia, chlorine, fluorine, and ozone. 136. ACCIDENTAL IMPURITIES OF THE AIR.— Among these are dust particles, which occur in enormous amount suspended in the air, and thereby act injuriously upon llie respi- ratory organs. The ciliated epithelium of the respiratory passages eliminates a large number of them (Pig. 148). Some of them, however, reach the air vesicles of the lung, where they penetrate the epithelium, reach the interstitial lung Fig. 148. tissue and lymphatics, and so pass with .f,, ,, the lymph stream into the bronchial , i^.^Cll'Ii7il7v/"it;, u,,, glands. Vziruclts o( coal or c/iarcoal Epithelium. ■- ; r ■-:-' -'- -L^i^. ^ ^_^^ are found in the lungs of all elderly in- " ' ■ ^1 ^^^ '^ ■ dividuals, and blacken the alveoli. In x'M moderate amount, these black particles do not seem to do any harm in the tis- \ sues, but when there are large accumu- VVVj*!^' ' l^ '^'^Ari ' Intermedi- lations they give rise to lung afiections, ^ ■s^;^.''^'.:-'f):f^^ ate forms. which lead to disintegration of these r),:hnvr'<: ^^i t i orijans. [In coal miners, for example, i_/cuovc s -, ^^ ^ -Oi". — • Inner layer ^ *- , 1 r 1. Membrane. " ^ _ ~% -^^^ the lung tissues along the track ot the Ciliated tpithelium. lymphatics and in the bronchial glands are quite black, constituting '-coal miners' lung."] In many trades various particles occur in the air; miners, grinders, .stone masons, file makers, weavers, si)inners, tobacco manufacturers, millers, and bakers suffer fr<;m lung afl'ections caused by the introduction of particles of various kinds inhaled during the lime they are at work. Germs. — There seems no doubt that the seeds of some contagious diseases may be inhaled. Diphtheritic bacteria (Bacillus diphtheria?) become localized in the pharynx and in the larynx — glanders in the nose — measles in the bronchi — whooping cough in the bronchi — hay monads in the nose— the Bacillus pneumoniae of pneumonia in the pulmonary alveoli. Tuberculosis, accord- mg to R. Koch, is due to the introduction and development of the Bacillus tuberculosis in the lungs, the bacillus being derived from the dust of tuberculous sputa. The same seems to be the case with the Bacillus of leprosy and with Bacillus malaria, which is the cause of malaria. The latter organism thus reaches the blood ; it changes the Hb within the red blood corpuscles into melanin (| 10, 3), and causes them to break up. The Micrococcus vaccinae of smallpox gains VENTILATION OF ROOMS. 245 access to the blood in the same way, also the Spirillum of remittent fever (Fig. 23), the Microbe of scarlet fever, etc. Seeds of disease passing into the mouth along w^ith air, and also with the food, are swallowed, and undergo development in the intestinal tract, as is probably the case in cholera (Comma bacillus of R. Koch), dysentery, typhoid, and anthrax which is due to Bacterium anthracis (Fig. 24). 137. VENTILATION OF ROOMS. — Fresh air is as necessary for the healthy as for the sick. Every healthy person ought to have a cubic space of at the very least 800 cubic feet, and every sick person at the very least 1000 cubic feet of space. [The cubic space allowed per individual varies greatly, but 1 000 cubic feet is a fair average. If the air in this space is to be kept sweet, so that the CO.^ does not exceed .06 per cent., 3000 cubic feet of air per hour must be supplied, i. e., the air in the space must be renewed three times per hour.] [Floor Space. — It is equally important to secure sufficient floor space, and this is especially the case in hospitals. If possible, 100-120 square feet of floor space ought to be provided for each patient in a hospital ward, and if it is obtainable a cubic space of 1500 cubic feet (^Pa7'kes). In all cases the minimum floor space should not be less than J^ of the cubic space.] Overcrowding. — When there is overcrowding in a room, the amount of COj increases, v. Pettenkofer found the normal amount of CO., (.04 to .05 per 1000) increased in comfortable rooms to 0.54-0.7 per 1000 ; in badly ventilated sick chambers = 2.4; in overcrowded auditoriums, 32; in pits = 4.9 ; in school rooms, 7.2 per 1000. Although it is not the quantity of CO., which makes the air of an overcrowded room injurious, but the excretions from the outer and inner surfaces of the body, which give a distinct odor to the air, quite recognizable by the sense of smell, still the amount of CO.^ is taken as an index of the presence and amount of these other deleterious sub- stances. Whether or not the ventilation of a room or ward occupied by persons is sufficient, is as- certained by estimating the amount of COj. A room which does not give a disagreeable, somewhat stuffy, odor has less than 0.7 per 1000 of C0,2, while the ventilation is certainly insufficient if the CO2 = I per 1000. As the air contains only 0.0005 cubic metre COj in i cubic metre of air, and as an adult produces hourly 0.0226 cubic metres CO2, calculation shows that every person requires 113 cubic metres of fresh air per hour, if the COj is not to exceed 0.7 per 1000 ; for 0.7 : 1000 =^ (0.0226 -(- X X 0.0005) • -^j ^- ^•,x= 113. [Vitiating Products. — In a state of repose, an adult man gives off from 12 to 16 cubic feet of COj in twenty-four hours, or on an average .6 cubic feet per hour. To this must be added a certain quantity of organic matter, which is extremely deleterious to health. While the COj dif- fuses readily and is easily disposed of by opening the windows, this is not the case with the organic matter, which adheres to clothing, curtains, and furniture; hence, to get rid of it, a room, and espe- cially a sleeping apartment, requires to be well aired for a long time, together with the free admission of sunlight. We must also remember that an adult gives off" from 25 to 40 oz. of water by the skin and lungs. The nature of the organic matters is not precisely known, but some of it is par- ticulate, consisting of epithelium, fatty matters, and organic vapors from the lungs and mouth. It blackens sulphuric acid, and decolorizes a weak solution of potassic permanganate. As a test, if we expire through distilled water, and this water be set aside for some time in a warm place, it will soon become fcetid. We must al^o take into consideration the products of combustion ; thus i cubic foot of coal gas, when burned, destroys all the O in 8 cubic feet of air {Pa7'kes).'\ Methods. — In ordinary rooms, where every person is allowed the necessary cubic space (looo cubic feet), the air is sufficiently renewed by means of the pores in the walls of the room, by the opening and shutting of doors, and by the fireplace, provided the damper is kept open. It is most important to notice that the natural ventilation be not interfered with by dampness of the walls, for this influences the pores very greatly. At the same time, damp walls are injurious to health by con- ducting away heat, and in them the germs of infectious diseases may develop. [Natural Ventilation. — By this term is meant the ventilation brought about by the ordinary forces acting in nature ; such as diffusion of gases, the action of winds, and the movements excited ■owing to the different densities of air at unequal temperatures.] [Artificial Ventilation. — Various methods are in use for ventilating public buildings and dwell- ing houses. Two principles are adopted for the former, viz., extraction and propulsion of air. In the former method, the air is sucked out of the rooms by a fan or other apparatus, while in the latter, air is forced into the rooms, the air being previously heated to the necessary temperature.] [A very convenient method of introducing air into a room is by means of Tobin's tubes, placed in the walls. The air enters through these tubes from the outside near the floor, and is car- ried up six or more feet, to an opening in the wall ; the cool air thus descends slowly. For a sit- ting room, a convenient plan of window ventilation is H. Bird's Method : Raise the lower sash and place under it, so as to fill up the opening, a piece of wood 3 or 4 inches high. Air will then pass in, in an upward direction, between the upper part of the lower sash frame and the lower part of the upper one.] 138. FORMATION OF MUCUS— SPUTUM.— The respiratory mucous membrane is covered normally with a thin layer of mucus (Fig, 130, a). It so far inhibits the formation of new mucus by protecting the mucous glands from the 246 THE SPUTUM. action of cold or other irritative agents. New mucus is secreted as that already formed is removed. An increased secretion accompanies congestion of the res- piratory mucous membrane [or any local irritation]. Division of the nerves on one side of the trachea (cat) causes redness of the tracheal mucous membrane and increased secretion {Ross(?iuh), [but the two processes do not stand in the relation of cause and effect]. [The secretion cannot be excited by stimulating the nerves going to the mucous membrane. This merely causes anaemia of the mucous membrane, while the secretion continues]. Modifying Conditions. — If ice be placed on the belly of an aniinal so as to cause the animal " to take (7 cold," the respiratory mucous membrane first becomes pale, and afterward there is a copious mucous secretion, the membrane becoming deeply congested. The injection of sodium carbonate and ammonium chloride into the blood limits the secretion. The local application of alum, silver nitrate, or tannic acid, makes the mucous membrane turbid, and the epithelium is shed. The secretion is excited by apomorphin, emetin, pilocarpin, and ipecacuanha when given internally, while it is limited by atropin and morphia [Hossbach). Fig. 149. Variou<; objects found in sputum, i, detritus and particles of dust : 2, alveolar epithelium with pigment; 3, fatty and pigmented alveolar epithelium ; 4, alveolar epithelium with myclin-forms ; 5, free myelin-forms ; 6, 7, ciliated epithelium, some without cilia; 8, squamous epithelium from the mouth; 9, leucocytes ; 10, elastic fihres; ii, fibrin cast of a small bronchus ; 12, leptothrix buccalis with cocci, bacteria, and spirocha;tae ; a, fatty acid crys- tals and free fatty granules ; b, ha:matoidin ; c, Charcot's crystals ; d, cholesterin. [Expectorants favor the -removal of the secretions from the air passages. This they may do either by {a) altering the character and qualities of the secretion itself, or {b) by affecting the expul- sive mechanism. Some of the drugs already mentioned are examples of the first class. The second class act chiefly by influencing the respiratory centre, e. g., ipecacuanha, strychnia, ammonia, senega; emetics also act energetically as expectorants, as in some cases of chronic bronchitis; warmth and moisture in the air are also powerful adjuncts.] Sputum. — Under normal circumstances, some mucus — mixed with a little saliva — may be coughed up from the back of the throat. In catarrhal conditions of the respiratory mucous membrane, the sputum is greatly increased in amount, and is often mixed with other characteristic products. Microscopically, sputum contains — I. Epithelial Cells, chiefly squames from the mouth and pharynx (Fig. 149), more rarely alveolar epithelium and ciliated epithelium (7) from the respiratory ACTION OF THE ATMOSPHERIC PRESSURE. 247, passages. They are often altered owing to maceration or other changes. Thus some cells may have lost their cilia (6). The epithelium of the alveoli (2) is squamous epithelium, the cells being two to- four times the breadth of a colorless blood corpuscle. These cells occur chiefly in the morning sputum in individuals over 30 years of age. In younger persons their presence indicates a pathological con- dition of the pulmonary parenchyma. They often undergo fatty degeneration, and they may contain pigment granules (3) ; or they may present the appearance of what Buhl has called '■'■ viyeliii degenerated cells" i.e., cells filled with clear refractive drops of various sizes, some colorless, others with colored particles, the latter having been absorbed (4). Mucin in the form of myelin drops (5) is always present in sputum. 2. Lymphoid cells (9) are colorless blood corpuscles which have wandered out of the blood vessels ; they are most numerous in yellow sputum, and less numerous in the clear, mucus-like excretion. The lymph cells often present altera- tions in their characters ; they may be shriveled up, fatty, or presei:it a granular appearance. The fluid substance of the sputum contains much mucus, arising from the mucous glands and goblet cells, together with nuclein, and lecithin, and the con- stituents of saliva, according to the amount of the latter mixed with the secretion. Allmtiiin occurs only during the inflammation of the respiratory passages, and its amount increases with the degree of inflammation. Urea has been found in cases of nephritis. In cases of catarrlj, the sputum is at first usually sticky and clear (sputa cruda), but later it becomes more firm and yellow (sputa cocta). Under pathological conditions, there may be found in the sputum — («) red blood corpuscles from rupture of a blood vessel, [b) Elastic fibres (10) from disintegration of the alveoli of the lung; usually the bundles are fine, curved, and the fibres branched. [In certain cases it is well to add a solution of caustic potash, which dissolves most of the other elements, leaving the elastic fibres untouched.] Their presence always indicates destruction of the lung tissue, [c) Colorless plugs of fibrin (xi), casts of the smaller or larger bronchi, occur in some cases of fibrinous exudation into the finer air passages, {d) Crystals of various kinds — crystals o^ fatty acids in bundles of fine needles (Fig. 149, a). They indicate great decomposition of the stagnant secretion. Leucin and tyrosin crystals are rare {\ 269). Tyrosin occurs in considerable amount when an old abscess breaks into the lungs. Colorless, sharp pointed, octagonal or rhombic plates — Charcot's crystals (c) — have been found in the expectoration in asthma, and exudative affections of the bronchi. Hsematoidin [b) and cholesterin crystals [d') occur much more rarely. Fungi and other lowly organisms are taken in during inspiration (§ 136). The threads of Leptothrix buccalis (12), detached from the teeth, are frequently found (| 147). Mycelium and spores are found in thrush (Oidium albicans), especially in the mouths of sucking infants. In mal-odorous expectoration rod-shaped bacteria are present. In pulmonary gangrene are found monads, and cercomonads; in pulmonary phthisis the tubercle bacillus; very rarely sarcina, which, however, is often found in gastric catarrh in the stomach and also in the urine (| 270). Physical Characters. — Sputum, with reference to its physical characters, is described as mucous, muco-purulent, or purulent. Abnormal coloration of the sputum — red from blood ; when the blood remains long in the lung it undergoes a regular series of changes, and tinges the sputum dark red, bluish brown, brownish yellow, deep yellow, yellowish green, or grass green. The sputum is sometimes yellow in jaundice. The sputum may be tinged by what is inspired [as in the case of the "black spit" of miners]. The odor of the sputum is more or less unpleasant. It becomes very disagreeable when it has remained long in pathological lung cavities, and it is stinking in gangrene of the lung. 139. ACTION OF THE ATMOSPHERIC PRESSURE.— At the normal pressure of the atmosphere (height of the barometer, 760 millimetres Hg), pressure is exerted upon the entire surface of the body = 15,000 to 20,000 kilos., according to the extent of the superficial area. This pressure acts equally on all sides upon the body, and also occurs in all internal cavities containing air, both those that are constantly filled with air (the respiratory passages and the spaces in the superior maxillary, frontal, and ethmoid bones), and those that are temporarily in direct communication with the outer air (the digestive tract and tympanum). As the fluids of the body (blood, lymph, secretions, parenchymatous juices) are practically incompressible, their volume remains unchanged under the pressure ; 248 ACTION OF DIMINISHED ATMOSPHERIC PRESSURE. but they absorb gases from the air corresponding to the prevailing pressure (/'. e., the partial pressure of the individual gases), and according to their temperature (^ T^T^). The solids consist of elementary parts (cells and fibres), each of which jyresents only a microscopic surface to the ])ressure, so that for each cell the pre- vailing pressure of the air can only be calculated at a few millimetres — a pressure under which the most delicate histological tissues undergo development. As an example of the action of the pressure of the atmospheric i)ressure upon large masses, take that brought about by the adhesion of the smooth, sticky, moist, articular surfaces of the shoulder and hip joints; the arm and the leg are supported without the action of muscles. The thigh bone remains in its socket after section of all the muscles and its capsule. Even when the cotyloid cavity is perforated, the head of the femur does not fall out of its socket. The ordinary barometric variations affect the respiration — a rise of the barometric pressure excites, while a fall dimin- ishes, the resi)irations. The absolute amount of CO2 remains the same (§ 127, 8). Great diminution of the atmospheric pressure, such as occurs in ballooning (highest ascent, 8600 metres), or in ascemling mountains, causes a series of characteristic jilienomena : (l) In con- sequence of the diminution of tlie pressure upon the parts directly in contact with the air, ihey become greatly congested, hence there is redness and swelling of the skin and free mucous mem- branes; tiiere maybe hemorrhage from the nose, lungs, gums; turgidity of the cutaneous veins; copious secretion of sweat; great secretion of mucus. (2) A feeling of weight in the limbs, a pressing outward of the tympanic membrane (until the tension is equilibrated by opening the Eustachian tube), and as a consequence noises in the ears and difficulty of hearing. (3) In conse- (pience of the diminished tension of the O in the air (§ 129), there is difficulty of breathing, pain in the chest, whereby the respirations (and pulse) becotne more rajjid, deeper, and irregular. When the atmospheric ]5resfure is diminished Yz-y^, the amount of O in the blood is diminished, the COj is imperfectly removed from the blood, and in consequence there is diminished o.xidation within the body. When the atmospheric pressure is diminished to one-half, the amount of CO., in arterial blood is lessened ; and the amount of N diminishes proportionally with the decrea.^e of the atmos- l)heric pressure. The diminished tension of the air prevents the vibrations of the vocal cords from occurring so forcibly, and hence the voice is feeble. (4) In consequence of the amount of blood in the skin, the internal organs are relatively anaemic; hence, there is diminished secretion of urine, muscular weakness, disturbances of digestion, dullness of the senses, and it may be unconsciousness, and all these phenomena are intensified by the conditions mentioned under (3). Some of these phenomena are modified by usage. The highest limit at which a man may still retain his senses is placed by Tissandier at an elevation of 8000 metres (2S0 mm. Hg). In dogs the blood pressure falls, and the pulse becomes small and diminished in frequency, when the atmospheric pressure falls to 200 mm. Ilg. Those who live upon high mountains suffer from a disease "mal de montagne," which consists essentially in the above symptoms, although it is sometimes complicated with ananiiaof the internal organs. Al. v. Humboldt found that in those who lived on the Andes the thorax was capacious. At 6000 to 8000 feet above sea level, water contains only one-third of the absorbed gases, so that fi>hes cannot live in it. Animals may be subjected to a further diminution of the atmospheric pressure by being placeil under the receiver of an air pump. Birds die when the pressure is reduced to 120 mm. Hg ; mammals at 40 mm. Ilg; frogs endure repeated evacuations of the receiver, whereby they are much di.stended, owing to the escape of gases and wafer, but after the entrance of air they become greatly compressed. The cause of death in mammals is ascribed by Hoppe-Seyler lo the evolution of bubbles of gas in the blood; these bubbles stop up the capillaries, and the circu- lation is arrested. Local diminution of the atmospheric pressure causes marked congestion and swelling of the part, as occurs when a cupping gla.ss is used. Great increase of the atmospheric pressure causes phenomena, for the most part, the reverse of the foregoing, as in pneumatic cabinets and in diving bells, where men may work even under 4)^ atmospheres pressure, (i ) Paleness and dryness of the external surfaces, collapse of the cutaneous veins, diminution of perspiration, and mucous secretions. (2) The tympanic membrane is pressed inward (until the air escapes through the Eustachian tube, after causing a sharp sound), acute .sounds are heard, pain in the ears, and difficulty of hearing. (3) A feeling oflightness and freshness during respiration, the respiration becomes slower (by 2-4 per minute), inspiration easier and shorter, expiration lengthened, the pause distinct. The capacity of the lungs increases, owing to the freer movement of the diaphragm, in con.sequence of the diminution of the intestinal gases. Owing to the more rapid oxidations in the body, muscular movement is easier and more active. The O absorbed and the CO.^ excreted are increased. The venous blood is reddened. (4) Difficulty of speaking, alteration of the tone of the voice, inability to whistle. (5) Increase of the urinary secretion, more muscular energy, more rapid metabolism, increased appetite, subjective feeling of warmth, pulse beats slower, and pulse curve is lower (compare \ 74). In animals subjected to COMPARATIVE AND HISTORICAL. 249 excessively high atmospheric pressure, P. Bert found that the arterial blood contained 30 vols, per cent. O fat 760 mm. Hg) ; when the amount rose to 35 vol. per cent., death occurred with convul- sions. Compressed air has been used for therapeutical purposes, but in doing so a too rapid increase of the pressure is to be avoided. Waldenburg has constructed such an apparatus, which may be used for the respiration of air under a greater or less pressure. Frogs, when placed in compressed O (at 14 atmospheres), exhibit the same phenomena as if they were in a vacuum, or pure N. There is paralysis of the central nervous system, sometimes preceded by convulsions. The heart ceases to beat (not the lymph hearts), while the excitability of the motor nerves is lost at the same time, and lastly the direct muscular excitability disappears. An excised frog's heart placed in O under a very high pressure (13 atmospheres), scarcely beats one-fourth of the time during which it pulsates in air. If the heart be exposed to the air again, it begins to beat, so that compressed O renders the vitality of the heart latent before abolishing it. Phosphorus retains its luminosity under a high pressure in O, but this is not the case with the luminous organisms, e. g., Lampyris, and luminous bacteria. High atmospheric pressure is also injurious to plants. 140. COMPARATIVE AND HISTORICAL.— Mammals have lungs similar to those of man. The lungs of birds are spongy, and united to the chest wall, while tliere are openings on their surface communicating with thin- walled " air-sacs,'' which are placed among the viscera. The air sacs communicate with cavities in the bones, which give the latter great lightness. The diaphragm is absent. In reptiles the lungs are divided into greater and smaller compartments; in snakes one lung is abortive, while the other has the elongated form of the body. The amphi- bians (frog) possess two simple lungs, each of which represents an enormous infundibulum with its alveoli. The frog pumps air into its lungs by the contraction of its throat, the nostrils being closed and the glottis opened. When young — until their metamorphosis — frogs breathe like fishes by means of gills. The perennibranchiate amphibians (Proteus) retain their gills throughout life. Among fishes, which breathe by gills and use the O absorbed by the water, the Dipnoi have in addition to gills a swim bladder provided with afferent and efferent vessels, which is comparable to the lung. The Cobitis respires also with its intestine. Insects and centipedes respire by "tracheae,'' which are branched canals distributed throughout the body; they open on the surface of the body by openings (stigmata) which can be closed. Spiders respire by means of tracheae and tracheal sacs, crabs by gills. The mollusks and cephalopods have gills ; some gasteropods have gills and others lungs. Among the lower invertebrata some breathe by gills, others by means of a special '' water vascular system," and others again by no special organs. Historical. — Aristotle (384 B.C.) regarded the object of respiration to be the cooling of the body, so as to moderate the internal warmth. He observed correctly that the warmest animals breathe most actively, but in interpreting the fact he reversed the cause and effect. Galen (131-203 A.D.) thought that the "soot" was removed from the body along with the expired water. The most important experiments on the mechanics of respiration date from Galen; he observed that the lungs passively follow the movements of the chest ; that the diaphragm is the most important muscle of inspiration ; that the external intercostals are inspiratory ; and the internal, expiratory. He divided the intercostal nerves and muscles, and observed that loss of voice occurred. On dividing the spinal cord higher and higher, he found that as he did so the muscles of the thorax lying higher up became paralyzed. Oribasius (360 A.D.) observed that in double pneumothorax both lungs collapsed. Vesalius (1540) first described artificial respiration as a means of restoring the beat of the heart. Malpighi (1661) described the structure of the lungs. J. A. Borelli (f 1679) gave the first fundamental description of the mechanism of the respiratory movements. The chemical processes of respiration could only be known after the discovery of the individual gases therein concerned. Van Helmont (f 1644) detected COg. [Joseph Black (1757) discovered that CO,, or " fixed air," is given out during expiration.] In 1774 Priestley discovered O. Lavoisier detected N (1775), and ascertained the composition of atmospheric air, and he regarded the formation of COj and H2O of the breath as a result of a com- bustion within the lungs themselves. J. Ingen-Houss (1730-1799) discovered the respiration of plants. Vogel and others proved the existence of COj in venous blood, and Hoffmann and others that of O in arterial blood. The more complete conception of the exchange of gases was, how- ever, only possible after Magnus had extracted and analyzed the gases of arterial and venous blood (§ 36). Physiology of Digestion. 141. THE MOUTH AND ITS GLANDS.— The mucous membrane of the cavity of the month, which becomes continuous with the skin at the red margin of tlie lips, lias a number of sebaceous glands in the rei;ion of the red part of the lip. The buccal mucous membrane consists of bundles of tine fibrous tissue mixed w^ith elastic fibres, which traverse it in every direction. Papillae — simple or compound — occur near the free surfaces. The submucous tissue, which is directly continuous with the fibrous tissue of the mucous membrane itself, is thickest where the mucous membrane is thickest, and densest where it is firmly fixed to the periosteum of the bone Fig. 151. Kpithe- lium. Closed follicles. Mucous gland. Cells of stratified squamous epithe lium detached from the mouth s, salivary corpuscles. Section of a mucous follicle from the tongue. and to the gum; it is thinnest where the mucous memljrane is most movable, and where there are most folds. The cavity of the mouth is lined by stratified squamous epithelium (Fig. 150), which is thickest, as a rule, where the longest papillae occur. All the glands of the mouth, including the salivary glands, may be divided into different classes, according; to the nature of their secretions. 1. The serous or albuminous glands [true salivary], whose secretion contains a certain amount of albumin, e. g., the human parotid. 2. The mucous glands, whose secretion, in addition to some albumin, con- tains the characteristic constituent mucin. 3. The mixed [or muco-salivary] glands, some of the acini secreting an albuminous fluid and others mucin, e. g., the human maxillary gland. Numerous mucous glands (labial, buccal, palatine, lingual, molar) have the appearance of small macroscopic bodies lying in the sub-mucosa. They are branched tubular glands, and the contents of their secretory cells consist partly of mucin, which is expelled from them during secretion. The excretory ducts of these glands, which are lined by cylindrical epithelium, are constricted where they enter the mouth. Not unfrequently one duct receives the secretion of a neighboring gland. The glands of the tongue form two groups, which differ morphologically and physiologically, (l) The mucous glands {IVeber's glands), occurring chiefly near the root of the tongue, are 250 THE MOUTH AND ITS GLANDS. 251 branched tubular glands lined with clear, transparent, secretory cells whose nuclei are placed near the attached end of the cells. The acini have a distinct membrana propria. (2) The serous glands {Ebner's) are acinous glands occurring in the region of the circumvallate papillee (and in animals near the papillze foliatse). They are lined with turbid granular epithelium with a central nucleus and secrete saliva. (3) The glands of Blandin and Nuhn are placed near the tip of the tongue, and consist of mucous and serous acini, so that they are mixed glands {Pod-ioiso(zky). The blood vessels are moderately abundant, and the larger trunks lie in the sub-mucosa, while the finer twigs penetrate into the papillse, where tliey form either a capillary network or simple loops. The larger lymphatics lie in the sub-mucosa, while the finer branches form a fine network placed in the mucosa. The lymph follicles also belong to the lymphatic system (^ 197). On the dorsum of the posterior part of the tongue they form an almost continuous layer. They are round or oval (1-1.5 mm. in diameter), lying in the sub-mucosa, and consist of adenoid tissue loaded with lymph corpuscles. The outer part of the adenoid reticulum is compressed so as to form a kind of capsule for each follicle. Similar follicles occur in the intestine as solitary follicles; in the small intestine they are collected together into Peyer's patches, and in the spleen they occur as Malpighian corpuscles. On the dorsum of the tongue several of these follicles form a slightly oval elevation, which is surrounded by connective tissue. In the centre of this elevation there is a depression, into which a mucous gland opens, which fills the small crater with mucus (Fig. 151). The tonsils have fundamentally the same structure. On their surface are a number of depres- sions into which the ducts of small mucous glands open. These depressions are surrounded by groups (10-20) of lymph follicles, and the whole is environed by a capsule of connective tissue (Fig. 152). Large lymph spaces, communicating with lymphatics, occur in the neighborhood of the tonsils, but as yet a direct connection between the spaces in the follicles and the lymph vessels has not been proved to exist. Similar structures occur in the tubal and pharyngeal tonsils. [Stohr asserts that an enormous number of leucocytes wander out of the tonsils, solitary and Peyer's glands, and the adenoid tissue of the bronchial mucous membrane. The cells pass out between the epithelial cells, but do not pass into the interior of the latter.] Nerves. — Numerous medtiUated nerve fibres occur in the sub-mucosa, pass into the mucosa, and terminate partly in the individual papillae in Krause's end bulbs, which are most abundant in the lips and soft palate, and not so numerous in the cheeks and floor of the mouth. The nerves administer not only to common sensation, but they are also the organs of transmission for tactile (heat and pt'essure) im- pressions. It is highly Fig. 152. probable, however, that • — ^— '»»-^_ some nerve fibres end in ^ ^ fine terminal fibrils, be- ^^-^ tween the epithelial cells, as in the cornea and else- where. [ Secretory glands may be simple (Fig. 153, B, C, D) or compound (E). In the latter case the duct is branched. In the process of develop- ment, a solid process of the epithelium sinks into the subjacent fibrous tis- sue, and, to form a simple gland, a cavity appears in this bud, but for a com- pound gland, other epi- thelial buds sprout from its blind end. Each bud acquires a central cavity, these elongate and in- crease in number, tlius forming a much branched system, the terminal blind ends forming the acini, alveoli or true secretory part. If the alveoli are tubular in shape, the gland is called a compound tubular gland. Thus in the compound glands some parts aie secretory, and others act as ducts, while in the simple glands, all the parts may be secretory. All the glands opening on the surface of the body are of epiblastic origin. The secretory cells lining the acini rest on a basement mem- brane, and outside this are the lymph spaces and capillary blood vessels.] Epithelium. A Tunica propria. Vertical section of a human tonsil, X 20. i, cavity; 2, epithelium infiltrated with leucocytes below and on the left, but free on the right; 3, adenoid tissue with sec- tions a, b, c, of masses of it ; 4, fibrous sheath ; 5, section of a gland duct ; d, blood vessel. 252 THE SALIVARY fJLANDS. 142. THE SALIVARY GLANDS. — The three pairs of salivary glands, sub-maxillary, sublingual, ami parotid, are coni|)ouiul tiil)uiar glands. Fig. 155, A, shows a fine duct, termi- nalinLj in the more or less llask siiaped alveoli or acini. [Kach gland consists of a niimiier of lobes, and each lube in turn of a number of lobules, which, again, are composed of acini. All these are held together by a framework of connective tissue. The larger branches of the duct lie between the lobules, and constitute the interlobular ducts, giving branches to each lobule which they enter, constituting the intralobular liucts, which branch and finally terminate in connection with the alveoli, by means of an intermediary or intercalary part. The larger interlobar and interlobular ducts consist of a meml)rana jnopiia, strengtiiened outside with fibrous and elastic tissue, and in some places also by non striped muscle, while the ducts are lined by columnar e|)ithelial cells. In the largest branches, there is a second row of smaller cells, lying between the large cells and the niembrana propria. The intralobular ducts are lined by a single layer of large cylindrical epithelium with the nucleus about the Fir,. 153. middle of the cell, while the outer half of the cell is finely striated longitudi- nally, or "rodded," which is due to fibrillar (Fig. 154) ; the inner half next the lumen is granular. The interme- diary part is narrow, and is lined by a single layer of flattened cells, each with an elongated oval nucleus. There is usually a narrow "neck," where the intralobular duct becomes continuous with the intermediary part, and here the cells are polyhedral.] Fic. 154. ''"'//Iii;';i»'' Evolution of glands. A, schema of skin ; e/, epidermis ; d, cutis with a capillary c; B, simple gland with its bloodvessels; C, D, more complex glands ; E, compound gland, blood vessels omitted. Fig. 155. Rodded epithelium lining the duct of salivary gland. A, duct and acini of the parotid gland of a dog; B, acini ol the sub-maxillary gland of a dog; c, refractive mucous cells; **^^-*:^^« ^ I. tnim'^m^^Sr^ ^^ Sections of a " serous" gland. The parotid of a rabbit. Fig. 157, at rest; Fig. 158, after stimulation of the cervical sympathetic. factured, which disappear during the activity of the cells, the disappearance taking place from without inward. Similar changes occur in the cells of the pancreas.] [More complex changes occur in the mucous glands, such as the submaxillary or orbital glands of the dog (^Lavdovsky). The appearances vary according to the intensity and duration of the secretory activity. The mucous cells at rest are large, clear, and refractive, containg a flattened nucleus (Fig. 155, C), surrounded with a small amount of protoplasm, and placed near the basement membrane. The clear substance does not stain with carmine, and consists of mucigen lying in the wide spaces of an intracellular plexus of fibrils. After prolonged secretion, produced, it may be, by strong and continued stimulation of the chorda, the mucous cells of the sub-maxillary gland of the dog undergo a great change.] The distended, refractive, and "mucous cells," which occur in the quiescent gland, and which do not stain with carmine, do not appear after the gland has been in a state of activity. Their place is taken by small, dark, protoplasmic cells devoid of mucin (Fig. 155, C). These cells readily stain with carmine, while their nucleus is scarcely, if at all, colored by the dye. The researches of R. Heidenhain (1868) have shed much light on the secretory activity of the salivary glands. THE NERVES OF THE SALIVARY GLANDS. 255 The change maybe produced in two ways. Either it is due to the "mucous cells" during secretion becoming broken up, so that Ihey yield their mucin directly to the saliva; in saliva rich in mucin, small microscopic pieces of mucin are found, and sometimes mucous cells themselves are present. Or, we must assume that the mucous cells simply eliminate the mucin from their bodies {Ewald, Stohr) ; while, after a period of rest, new mucin is formed. Accordmg to this view, the dark granular cells of the glands, after active secretion, are simply mucous cells, which have given out their mucin. If we assume, with Heidenhain, that the mucous cells break up, then these granular non-mucous cells must be regarded as new formations produced by the proliferation and growth of the composite marginal cells, i. e., the crescents, or half-moons of Gianuzzi. [During rest, the protoplasm seems to manufacture mucigen, which is changed into and discharged as mucin in the secretion, when the gland is actively secreting. Thus, the cells become smaller, but the protoplasm of the cell seems to increase, new mucigen is manufactured during rest, and the cycle is repeated.] 144. THE NERVES OF THE SALIVARY GLANDS.— The nerves are for the most part medullated, and enter at the hilum of the gland, where they form a rich plexus provided with ganglia between the lobules. [There are no ganglia in the parotid gland {KIein).'\ All the salivary glands are supplied by branches from two different nerves — from the sympathetic and from a cranial nerve. Fig. 159. Scheme of the nerves of the salivary glands. P., pons ; M. O., medulla oblongata ; J. N., nerve of Jacobson; O., S. M., I. M,, ophthalmic, superior, and inferior maxillary divisions of fifth nerve, V. ; VII., seventh nerve ; S.s.p., small superficial petrosal nerve; Vag, vagus ; Sym., sympathetic ; O. G., otic, and S. G., sub-ina.xillary ganglia; P., S., and S. L., parotid, sub-maxillary, and sublingual glands : T., tongue. 1. The sympathetic nerve gives branches {a) to the sub-maxillary and the sublingual glands, derived from the plexus on the external maxillary artery ; (F) to the parotid gland from the carotid plexus (Fig. 159). 2. The facial nerve gives branches to the sub-maxillary and sublingual glands from the chorda tympani, which accompanies the lingual branch of the fifth nerve (Fig. 159). The branches to the parotid arise from the tympanic branch of the glosso-pharyngeal nerve (dog). The tympanic plexus sends fibres to the small superficial petrosal nerve, and with it these fibres run to the anterior surface of the pyramid in the temporal bone, emerging from the skull through a fissure between the petrous and great wing of the sphenoid, and then joining the otic ganglion. This ganglion sends branches to the auriculo-temporal nerve (itself derived from the third branch of the trigeminus), which, as it passes upward to the temporal region under cover of the parotid, gives branches to this gland. The sub-maxillary ganglion, which gives branches to the sub-maxillary and sublingual glands, receives fibres from the tympanico-lingual nerve (chorda 256 ACTION OF NERVES ON THE SECRETION OF SALIVA. tympani) as well as sympathetic fibres from the plexus on the external maxillary artery. Termination of the Nerve Fibres. — With regard to the ultimate distribution of these nerves we can distinguish (i) the vasomotor nerves, which give brandies to the walls of the blood vessels, and (2) the secretory nerves proper. rflui^er states, with regard to the latter, that (a) medullated nerve fibres penetrate tlie acini ; the sheath of Schwann unites with the membrana propria of the acinus; the medullated fibre — still medullaieil — passes between the secretory cells, where it divides and becomes non-medullated, and its axial cylinder terminates in connection with the nucleus of a secretory cell. [This, however, is not pr()ven celU, which lie outside the wall of the acinus, and these cells send branches to the secretory cells of the acini. [These cells probably correspond to the branched cells of the basket-shaped structure.] (r) Again, he describes medullated fibres which enter the attached end of the cylin- drical epithelium lining the excretory ducts of the glands (E). Pfiiiger thinks that those fibres entering the acini directly are cerebral, wiiile those with ganglia in their course are derived from the sympatlietic system. [(58 REFLEX SECRETION OF SALIVA. Extirpation of Salivary Glands. — When the chorda tympani is extirpated on one side in young dogs, the sub-maxillary gland on that side does not develop so much — its weight is 50 per cent, less — while the mucous cells and the "crescents" are smaller than on the sound side [Bitfitlini). During secretion, the temperature of the gland rises 1.5° C. {Ludwig), and the blood flowing from the veins is often warmer than the arterial blood. [The electro-motive changes are referred to on p. 256.] " Paralytic Secretion " of Saliva. — By this term is meant the continued secretion of a thin, watery saliva from the sub-maxillary gland, which occurs twenty- four hours after the section of the cerebral nerves (chorda of the seventh), i.e., those branches of them that go to this gland, whether the sympathetic be divided or not {CI. Bernard). It increases until the eighth day, after which it gradually diminishes, while the gland tissue degenerates. The injection of a small quantity of curara into the artery of the gland also causes it. [Heidenhain showed that section of one chorda is followed by a continuous secretion of saliva hova bo(k sub-maxillary glands. The term "paralytic" secretion is applied to that which takes place on the side on which the nerve is cut, and Langley proposes to call the secretion on the opposite side the antilytic. Apnoea (^ 368) stops both the paralytic and antilytic secretion, while dyspnoea increases the flow in both cases; and as section of the sympathetic fibres to the gland (where the chorda is cut) arrests the paralytic secretion excited by dyspncea, it is evident that both the paralytic secretion and the secretion following dyspncea are caused by stimuli traveling down the sympathetic fibres. In the later stages of the paralytic secretion, the cause is in the gland itself, for it goes on even if all the nerves passing to the gland be divided, and is probably due to a local nerve centre. In this stage the secretion is arrested by a large dose of chloroform. The paralytic secretion in the first stage may be owing to a venous condition of the blood acting on a central secretory centre whose excitability is increased ; and in the latter stages probably on local nerve centres within the gland. The fibres of the chorda in the cat are only partially degenerated thirteen days after section {Langley).'] [Histological Changes. — In the gland during paralytic secretion, the gland cells of the alveoli (serous, mucous, and demilunes) diminish in size and show the typical " resting " appearance, even to a greater extent than the normal resting gland [Langley).'] B. Sub-lingual Gland. — Very probably the same relations obtain as in the sub-maxillary gland. C. Parotid Gland. — In the dog, stimulation of the sympathetic alone causes no secretion ; it occurs when the glosso-pharyngeal branch to the parotid is simultaneously excited. This branch may be reached within the tympanum in the tympanic plexus. A thick secretion containing much organic matter is thereby obtained. Stimulation of the cerebral hra.nc\\ alone yields a clear, thin, watery secretion, containing a very small amount of organic substances, but a considerable amount of the salts of the saliva. [Stimulation of Jacobson's Nerve (Parotid of Dog) — Total Solids. Salts. Organic Matter. Without sympathetic, . . 0.56 per cent. 0.31 0.24 With sympathetic, . . . 2.42 per cent. 0.36 2.06] [Reflex Secretion of Saliva. — If a cannula be placed in Wharton's duct, e.g., in a dog, during fasting, no saliva will flow out, but on applying a sapid substance to the mucous membrane of the mouth or the tongue, there is a copious flow of saliva. If the sympathetic nerve be divided, secretion still takes place when the mouth is stimulated, but if the chorda tympani be cut, secretion no longer takes place. Hence, the secretion is due to a reflex act ; in this case, the lingual is the afferent, and the chorda the efferent nerve carrying impulses from a centre situated in the medulla oblongata (Fig. 160).] In the intact body, the secretion of saliva occurs through a reflex stimulation of the nerves concerned, whereby, under normal circumstances, the secretion is always watery (chorda or facial saliva). The centripetal or afferent nerve fibres concerned are : (i) The nerves of taste. (2) The sensory branches of the trigeminus of the entire cavity of the mouth and the glosso-pharyngeal REFLEX SECRETION OF SALIVA. 259 Fig. 1 60. Mucous Membrane <=t-^=^ ^.^ '" Afferent// >'ervey// 5f Duct of Gland. Nerve i I^M. Secretory N Centre. ^^K. — *" "^^ ^t ^fl % Secreting f cells. Vai so.dilator\\^ 1 Nerve. ^Jy Bloodvessels of Gland. Diagram of a salivary gland. (which appear to be capable of being stimulated by mechanical stimuli, pres- sure, tension, displacement). The movements of mastication also cause a secretion of saliva. Pfliiger found that one-third more saliva was secreted on the side where mastication took place ; and CI. Bernard observed that the secre- tion ceased in horses during the act of drinking. (3) The nerves of smell, excited by certain odors. (4) The gas- tric branches of the vagus. A rush of saliva into the mouth usually precedes the act of vomiting (§ 158). (5) The stimulation of distant sensory nerves, e. g., the central end of the sciatic — certainly through a complicated reflex mechan- ism— causes a secretion of saliva ( Owsjamtikow and Tschierjew). Stimulation of the conjunc- tiva, e. g., by applying an irritating fluid to the eye of carnivorous animals, causes a reflex secre- tion of saliva (^Aschenbrandf). Perhaps the secretion of saliva which sometimes occurs during pregnancy is caused in a similar reflex manner. (6) The movements of mastication excite secretion, but although, during the act of rumination, this is the case in ruminants, in whom the process of mastication is very thorough, there is no secretion from the sub-maxillary gland, although the parotid secretes {Colin, Ellenberger and Hofmeister'). The reflex centre for the secretion of saliva lies in the medulla oblongata, at the origin of the seventh and ninth cranial nerves. The centre for the sympathetic fibres is also placed here. This region is connected by nerve fibres with the cere- brum ; hence, the thought of a savory morsel, sometimes, when one is hungry, causes a rapid secretion of a thin, watery fluid — [or, as we say, ''makes the mouth water "]. If the centre be stimulated directly by a mechanical stimulus (puncture), salivation occurs, while asphyxia has the same effect. The reflex secretion of .saliva may be inhibited by stimulation of certain sensory nerves, e. g., by pulling out a loop of the intestine. Stimulation of the cortex cerebri of a dog, near the sulcus cruciatus, is often followed by secretion of saliva. Disease of the brain in man sometimes causes a secretion of saliva, owing to the effects produced on the intracranial centre. So long as there is no stimulation of the nerves, there is no secretion of saliva, as in sleep. Immediately a/Ur the section of all nerves, secretion stops, for a time at least. Pathological Conditions and Poisons. — Certain affections, as inflammation of the mouth, neuralgia, ulcers of the mucous membrane, and affections of the gums, due to teething or the prolonged administration of mercury, often produce a copious secretion of saliva or ptyalism. Certain poisons cause the same effect by direct stimulation of the nerves, as Calabar bean (physostigmin), digitalin, and especially pilocarpin. Many poisons, especially the narcotics — above all, atropin — paralyze the secretory nerves, so that there is a cessation of the secretion and the mouth becomes dry ; while the administration of muscarin in this condition causes secretion. Pilocarpin acts on the chorda tympani, causing a profuse secretion, and if atropin be given, the secretion is again arrested. Conversely, if the secretion be arrested by atropin, it may be restored by the action of pilocarpin or physostigmin. Nicotin, in small doses, excites the secretory nerves, but in large doses paralyzes them. Daturin, cicutin, and iodide of aethylstrychnin, paralyze the chorda. The saliva is diminished in amount in man, in cases of paralysis of the facial ox sympathetic nerves, as is observed in unilateral paralysis of these nerves. [Sialogogues are those drugs which increase the secretion of saliva. Some are topical, and take effect when applied to the mouth. They excite secretion reflexly by acting on the sensory nerves of the mouth. They include acids, and various pungent bodies, such as mustard, ginger, pyrethrum, tobacco, ether, and chloroform; but they do not all produce the same effect on the amount or quality of the saliva ; others, the general sialogogues, cause salivation when introduced 260 THE PAROTID SALIVA. into the blood ; physostigmin, nicotin, pilocarpin, muscarin. The drugs named act after all the nerves going to the gland are divided, so that they stimulate the peripheral ends of the nerves in the glands. The two former also excite the central ends of the secretory nerves.] [Antisialics are those substances which diminish the secretion of saliva, and they may take effect upon any part of the reflex arc, i. e., on the mouth, the afterent nerves, the nerve centre and aflerent nerves, or upon the blood stream through the glands, or on the glands themselves. Opium and morphia affect the centre, large doses of physostigmin affect the blood supply, but atropin is the most powerful of all, as it paralyzes the terminations of the secretory nerves in the glands, e.g., the chorda tympani, and even the sympathetic in the cat (but not in the dog).] [Excretion by the Saliva. — Some drugs are excreted by the saliva. Iodide of potassium is rapidly eliminated by the kidneys, and by the salivary glands, and so also is iodide of iron.] Theory of Salivary Secretion. — Ileindenhain has recently formulated the following theory regarding the secretion of saliva : " During the passive or quiescent condition of the gland, the organic materials of the secretion are formed from and by the activity of the protoplasm of the secretory cells. A quiescent cell, which has been inactive for some time, therefore contains little protoplasm, and a large amount of these secretory substances. In an actively secreting gland, there are two processes occurring together, but independent of each other, and regulated by two different classes of nerve- fibres; secretory fibres cause the act of secretion, while trophic fibres cause chemical processes within the cells, partly resulting in the formation of the soluble constituents of the secre- tion, and partly in the growth of the protoplasm. According to the number of both kinds of fibres present in a nerve passing to a gland, such nerve being stimulated, the secretion takes place more rapidly (cerebral nerve) or more slowly (sympathetic), while the secretion contains less or more solid constituents. The cerebral ntrxts contain many secretory fibres and few trophic fibres, while the sympathetic contain more trophic but few secretory fibres. The rapidity and chemical com- position of the secretion vary according to the strength of the stimulus. During continued secretion, the supply of secretory materials in the gland cells is used up more rapidly than it is replaced by the activity of the protoplasm ; hence, the amount of organic constituents diminishes, and the micro- scopic characters of the cells are altered. The microscopic characters of the cells are altered also by the increase of the protoplasm, which takes place in an active gland. The mucous cells disappear, and seem to be dissolved after prolonged secretion, and their place is taken by other cells derived from the proliferation of the marginal cells. The energy which causes the current of fluid depends upon the protoplasm of the gland cells." 146. THE SALIVA OF THE INDIVIDUAL GLANDS.— (a) Parotid saliva is obtained by placing a fine cannula in Steno's duct ; it has an alkaline reaction, but during fasting, the first few drops may be neutral or even acid on account of free CO2; its specific gravity is 1003 to 1004. After standing it becomes turbid, and deposits, in addition to albuminous matter, calcium car- bonate, which is present in the fresh saliva in the form of bicarbonate. It contains small quantities (more abundant in the horse) of a globulin-like body, and never seems to be without CNKS, /. e., sulphocyanide of potassium (or sodium), — which, however, is absent in the sheep and dog. [The sulphocyanide gives a dark red color (ferric sulphocyanide) with ferric chloride, and the color is discharged by mercuric chloride, but this is not the case with meconic acid, which gives a similar color reaction.] It also reduces iodic acid when added to saliva, causing a yellow color from the liberation of iodine, which may be detected at once by starch [Solera). Among the organic substances the most important are ptyalin, a small amount of urea, and traces of a volatile acid. Mucin is absent, hence the parotid saliva is not sticky, and can readily be poured from one vessel into another. It contains 1.5 to 1.6 per cent, of solids in man, of which 0.3 to i.o per cent, is inorganic. Of the inorganic constituents — the most abundant are potassium and sodium chlorides ; then potassium, sodium, and calcium carbonates, some phosphates, and a trace of an alkaline sulphate. Salivary calculi are formed in the ducts of the salivary glands owing to the deposition of lime salts, and they contain only traces of the other salivary constituents ; in the same way is formed the tartar of the teeth, which contains many threads of leptothrix, and the remains of low organisms which live in decomp>osing saliva in carious cavities between the teeth. {b) Sub-maxillary saliva is obtained by placing a cannula in Wharton's duct ; it is alkaline, and may be strongly so. After standing for a time, fine crystals of calcium carbonate are deposited, together with an amorphous albu- minous body. It always contains mucin (which is precipitated by acetic acid) ; THE MIXED SALIVA IN THE MOUTH. 261 hence, it is usually somewhat tenacious. It contains ptyalin, but in less amount than in parotid saliva; and, according to Oehl, only 0.0036 percent, of potassium sulphocyanide. Chemical Composition. — Sub-maxillary saliva (dog) : — Water, 991-45 per 1000, Organic Matter, 2.89 " " Inorganic Matter, 5.66/ 4."'5o NaCl and CaCl, . \ i.iSCaCOg, Calcium and Magnesium phosphates. Mixed Saliva Parotid Sub-maxillary (Human) (Human) (Dog) (Jacudowzisck). {Hopi>e-Seyler). (Herter). [Water, 99-51 99-32 99.44 Solids, 0.49 0.68 0.56 Soluble organic bodies (ptyalin), . . , 0.13 \ 0.34 f 0.066 Epithelium, mucin, 0.16 J 1 0.17 Inorganic salts, . 0.102 0.34 0.43 Potassic sulphocyanide, 0.006 0.03 . . Potassic and sodic chlorides, .... 0.084 • • • • ] Gases. — Pfliiger found that 100 cubic centimetres of the saliva contained 0.6 O ; 64.7 CO2 (part could be pumped out, and part required the addition of phosphoric acid) ; 0.8 N. ; or, in 100 vol. gas, 0.91 O; 97.88 COj; 1.21 N. [It therefore contains much more COo than venous blood. Kiilz obtained from 100 c.c. of human saliva 7 c.c. of gas — O = i c.c, N = 2.5 c.c. and COj = 3.5 c.c. Besides this there is 40-60 c.c. of fixed COj in the form of carbonates.] (<:) Sub-lingual saliva is obtained by placing a very fine cannula in the ductus Rivinianus ; it is strongly alkaline in reaction, very sticky and cohesive, contains much mucin, numerous salivary corpuscles, and some potassium sulpho- cyanide. 147. THE MIXED SALIVA IN THE MOUTH.— The mixed saliva in the mouth is a mixture of the secretions from the salivary, mucous, and other glands of the mouth. (i) Physical Characters. — It is an opalescent, tasteless, odorless, slightly glairy fluid, with a specific gravity of 1004 to 1009, and an alkaline reaction. The amount secreted in twenty-four hours = 200 to 1500 grammes (7 to 50 oz.) ; according to Bidder and Schmidt, however, = 1000 to 2000 grammes. The solid constituents = 5.8 per 1000. Composition. — The solids are : Epithelium and mucus, 2.2 ; ptyalin and albumin, 1.4; salts, 2.2; potassium sulphocyanide, 0.04 per 1000. The ash contains chiefly potash, phosphoric acid, and chlorine [Hamnierbacher). Decomposition products of epithelium, salivary corpuscles, or the remains of food, may render it acid iemp07-arily, as after long fasting, and after much speaking ; the reaction is acid in some cases of dyspepsia and in fever, owing to the stagnation and insufficient secretion. (2) Microscopic Constituents. — («) The salivary corpuscles are slightly larger than the white blood corpuscles (8 to 11 /j.), and are nucleated protoplasmic globular cells without an envelope (Fig. 150, s). During their living condition, the particles in their interior exhibit molecular or Brownian movement. The dark granules lying in the protoplasm are thrown into a trembling movement, from the motion of the fluid in which they are suspended. This dancing motion stops when the cell dies. [The Brownian movements of these suspended granules are purely physical, and are exhibited by all fine microscopic particles suspended in a limpid fluid, e. g., gamboge rubbed up in water, particles of carmine, charcoal, etc.] {b) Pavement epithelial cells from the mucous membrane of the mouth and tongue; they are very abundant in catarrh of the mouth (Fig. 150). (c) Living organisms, which live and thrive in the cavities of teeth, nourished by the remains of food. Among these are Leptothrix buccalis (Fig. 149, 12) and small bacteria-like organ- isms. The threads of the leptothrix penetrate into the canals of the dentine, and produce dental caries. [Miller has found twenty-five varieties of microorganisms, including cocci, bacteria, vibrios, spirilla, and spirochsetse, eight of them present in the stomach and twelve in the intestines.] 262 PHYSIOLOGICAL ACTION OF SALI\A. (3) Chemical Properties, — (a) Organic Constituents. — Senim-aUmmin is precipitated by heat and by the addition of alcohol. In saliva, mixed with much water and shaken up with COj, a globulin-like body is precipitated ; mucin occurs in small amount. Among the extractives, the most important is ptyalin ; fats and urea occur only in traces. In twenty-four hours 130 milligrammes of potassium or sodium sulphocyanide are secreted. (/^) Inorganic Constituents. — Sodium and potassium chlorides, potassium sulphate, alkaline and earthy phosphates, ferric phosphate. According to Schonbein, the saliva contains traces of nitrites (detected by adding dilute sulphuric acid and diamido-benzol to dilute saliva), which give a yellow color {Gries). There are also traces of ammonia (Uriicke). Abnormal Constituents. — In diabetes mellitus, lactic acid, derived from a further decompo- sition of £;rape sugar, is found. It dissolves the lime in the teeth, giving rise to diabetic dental caries. Frerichs found leucin, and Vulpian increase of albumin in albuminuria. Of foreign sub- stances taken into the body, the following appear in the saliva : Mercury, potassium, iodine, and bromine. Saliva of New-born Children. — In new-born children, the parotid alone contains ptyalin. The diastatic ferment seems to be developed in the sub-maxil- lary gland and pancreas, at the earliest after two months. Hence, it is not advi- sable to give starchy food to infants. No ptyalin has been found in the saliva of infants suffering from thrush (O'l'dium albicans — Zweifel). The diastatic action of saliva is not absolutely necessary for the suckling, feeding as it does upon milk. The mouth durirfg the first two months is not moist, but at a later period saliva is copiously secreted {Korowin) ; after the first six months, the salivary glands increase considerably. The eruption of the teeth — owing to the irritation of the mucous membrane — produce a copious secretion of saliva. 148. PHYSIOLpGICAL ACTION OF SALIVA.— I. Diastatic Action. — Tlie most important chemical action exerted by saliva in digestion is its diastatic or amylolytic action (Leuchs, 1831), /. e., the transformation of starch into dextrin and some form of sugar. This is due to the ptyalin — a hydrolytic ferment or enzym — which, even when it is present in very minute quantity, causes starch to take up water and become soluble, the ferment itself undergoing no essential change in the process. [Ptyalin belongs to the group of unorganized ferments (§ 250, 9). Like all other ferments it acts only within a certain range of temperature, being most active about 40° C. Its energy is permanently destroyed by boiling. It acts best in a slightly alkaline or neutral medium.] [Action on Starch. — Starch grains consist of granulose or starch enclosed by_ coats of cellulose. Cellulose does not appear to be affected by saliva, so that saliva acts but slowly on raw, unboiled starch. If the starch be boiled, so as to swell up the starch grains and rupture the cellulose envelopes, the amylolytic action takes place rapidly. If starch paste or starch mucilage, made by boiling starch in water, be acted upon by saliva, especially at the temperature of the body, the first physical change observable is the liquefaction of the paste, the mixture becoming more fluid and transparent. The change takes place in a few minutes. When the action is continued, important chemical changes occur.] According to O' Sullivan, Musculus, and v. Mering, the diastatic ferment of saliva (and of the pancreas), by acting upon starch or glycogen, forms dextrin and maltose (both soluble in water). Several closely allied varieties of dextrin, distinguishable by their color reactions, seem to be produced {Britcke). Ery- throdextrin is formed first, it gives a red color with iodine ; then a reducing dextrin — achroodextrin, which gives no color reaction with iodine. The sugar formed by the action of ptyalin upon starch is maltose (C,,Ho.,0„ -f H^G), which is distinguished from grape sugar (C12H04O10) by containing one molecule less of water, which, however, it holds as a molecule of water of hydration. [Maltose also differs from grape sugar in its greater rotatory power on polarized FUNCTIONS OF SALIVA. 263 light, the former = + 150°, the latter -j- 56°, the ratio being 61 : 100 ; and in its smaller power of reducing cupric oxide. Thus, between the original starch and the final product, maltose, several intermediate bodies are formed. The starch gives a blue with iodine, but after it has been acted on for a time it gives a red or violet color, indicating the presence of erythrodextrin, there being a sim- ultaneous production of sugar ; but ultimately no color is obtained on adding iodine — achroodextrin, which gives no color with iodine, maltose being formed. The presence of the maltose is easily determined by testing with Fehling's solution.] [Brown and Heron suggest that the final result of the transformation may be represented by the equation — io(Ci2H,oOio) + 8H20 = 8(Ci2H,,On) + 2(C,,H,oOio) Soluble starch. Water. Maltose. Achroodextrin. The ferment slowly changes maltose into grape sugar or dextrose. This result may be brought about much more rapidly by boiling maltose with dilute sulphuric or hydrochloric acid.] Achroodextrin ultimately passes into maltose, and this again into dextrose ; the other form of dextrin does not seem to undergo this change (Seegen's Dystropodextrin). For the further changes that maltose under- goes in the intestine, see § 183, II, 2. [The formula of starch is usually expressed as CgHjoOj, but the researches already mentioned, and those of Brown and Heron, make it probable that it is more complex, which we may provisionally represent by ^(Cj^HjjOk,). According to Musculus and Meyer, erythrodextrin is a mixture of dex- trin and soluble starch.] Preparation of Ptyalin. — (i) Like all other hydrolytic ferments, it is carried down with any copious precipitate that is produced in the fluid which contains it, and it can be isolated from the precipitate. The saliva is acidulated with phosphoric acid, lime-water is added until the reaction becomes alkaline, when a precipitate of the basic calcium phosphate occurs, which carries the ptya- lin along with it. This precipitate is collected on a filter, washed with water, which dissolves the ptyalin, and from its watery solution it is precipitated by alcohol as a white powder. It is redissolved in water and reprecipitated, and is obtained pure {Cohnheini). (2) Glycerine or v. Wittich's Method. — The salivary glands [rat] are chopped up, placed in absolute alcohol for twenty-four hours, taken out and dried, and afterward placed in glycerine for several days, which extracts the ptyalin. It is precipitated by alcohol from the glycerine extract. (3) WilHam Roberts recommends the following solutions for extracting ferments from organs which contain them: (i) A 3 to 4 percent, solution of a mixture of 2 parts of boracic acid and I part borax. (2) Water, with 12 to 15 per cent, of alcohol. (3) i part chloroform to 200 of water. Diastatic Action of Saliva. — {a) The diastatic or sugar-forming action is known by (i) The disappearance of the starch. When a small quantity of starch is boiled with several hundred times its volume of water, starch mucilage is obtained, which strikes a blue color with iodine. If to a small quantity of this starch a sufficient amount of saliva be added, and the mixture kept for some time at the temperature of the body, the blue color disappears. (2) The presence of sugar is proved directly by using the tests for sugar (§ 149)- {b) The action takes place more slowly in the cold than at the temperature of the body — its action is enfeebled at 55° C, and destroyed at 75° C. [Paschutin). The most favorable temperature is 35° to 39° C. (c) The ptyalin itself does not seem to be changed during its action, but ptyalin which has been used for one experiment is less active when used the second time [PaschtiHn). Ptyalin differs from diastase — the ferment in germinating grains — in so far that the latter first begins to act at -j- 66° C. Ptyalin decomposes salicin into saligenin and grape sugar [Frerichs and Stadler). {d) Saliva acts best in an exactly neutral medium, but it also acts in an alkaline and even in a slightly acid fluid ; strong acidity prevents its action. The ptyalin is only active in the stomach when the acidity is due to organic acids (lactic or butyric), and not when free hydrochloric acid is present {van de Velde). In both cases, however, dextrin is formed. Ptyalin is destroyed by hydrochloric acid or digestion by pepsin [Chiftendefi and Griswold, Langley). Even butyric and lactic acids formed from grape sugar in the stomach may prevent its action ; but if the acidity be neutralized, the action is resumed (C/. Bernara). {e) The addition of common salt, ammonium chloride, or sodium .sulphate (4 per cent, solution), increases the activity of the ptyaHn, and CO2, acetate of quinine, strychnia, morphia, curara, 0.025 per cent, sulphuric acid, have the same effect. 264 TESTS FOR SUGAR. {J) Much alcohol and caustic potash destroy the ptyalin ; long exposure to the air weakens its action ; sodium carbonate and magnesium sulphate delay the action [Pfeiffer). Salicylic acid and much atropin arrest the formation of sugar. [g) Ptyalin acts very feebly and very gradually upon raw starch, only after 2 to 3 hours [Schiff); while upon boiled starch it acts rapidly. [Hence the necessity for boiling thoroughly all starchy foods.] (//) The various kinds of starch are changed more or less rapidly according to the amount of cel- lulose which they contain ; raw potato starch after 2 to 3 hours, raw maize starch after 2 to 3 minutes {^Haiinnarslen') ; wheat starch more quickly than that of rice. When the starches are powdered and boiled, they are changed with equal rapidity. (/') A mixture of the saliva from all the glands is more active than the saliva from any single gland {Jakubo-oitsch), while mucin is inactive. [Effect of Tea. — Tea has an intensely inhibitory effect on salivary digestion, which is due to the large quantity of tannin contained in the tea-leaf. Coffee and cocoa have only a slight effect on salivary digestion. The only way to mitigate the inhibitory effect of tea on salivary digestion is "not to sip the beverage with the meal, but to eat first and drink afterward" {Roberts).'\ II. Saliva dissolves those substances which are soluble in water ; while the alka- line reaction enables it to dissolve some substances which are not soluble in water alone, but require the presence of an alkali. III. Saliva moistens dry food and aids the formation of the "bolus," while by its mucin it helps the act of swallowing, the mucin being given off unchanged in the faeces. The ultimate fate of ptyalin is unknown. [IV. Saliva also aids articulation, while according to Liebig it carries down into the stomach small quantities of O.] [V. It is necessary to the sense of taste to dissolve sapid substances, and bring them into relation with the end organs of the nerves of taste.] Saliva has no action on proteids or on fats. The presence of a peptone-forming ferment has recently been detected in saliva {Hii/ner, Munk, JCiihne). [Perfectly healthy human saliva has no poisonous properties.] 149. TESTS FOR SUGAR.— I. Trommer's test depends upon the fact that, in alkaline solutions, sugar acts as a reducing agent ; in this case a metallic oxide is changed into a sub-oxide. To the fluid to be investigated, add ^ of its volume of a solution of caustic potash (soda), specific gravity 1.25, and a few drops of a weak solution of cupric sulphate, which causes at first a bluish precipi- tate, consisting of hydrated cupric oxide, but it is redissolved, giving a clear blue fluid, if sugar be present. Heat the upper stratum of the fluid, and a yellow or red ring of cuprous oxide is obtained, which indicates the presence of sugar; 2CuO — 0 = Cu.,0. The solution of hydrated cupric oxide is caused by other organic substances; but the final stage, or the production of cuprous oxide, is obtained only with certain sugars — grape, fruit and milk (but not cane) sugar. Fluids which are turbid must be previously filtered, and if they are highly colored, they must be treated with basic lead acetate ; the lead acetate is afterward removed by the addition of sodium phosphate and subsequent filtration. If very small quantities of sugar are present along with compounds of ammonia, a yellow color instead of a yellow precipitate may be obtained. In doing the test, care must be taken not to add too much cupric sulphate. [2. Fehling's Solution is an alkaline solution of potassio-tartrate of copper. Boil a small quantity of the deep-blue colored Fehling's solution in a test-tube, and add to the boiling test a few drops of the fluid supposed to contain the sugar. If siigar be present, the copper solution is reduced, giving a yellow or reddish precipitate. The reason for boiling the test itself is, that the solution is apt to decompose when kept for some time, when it is precipitated by heat alone. This is one of the best and most reliable tests for the presence of sugar. In Pavy's modification of this test, ammonia is used instead of a caustic alkali (§ 267).] (3) Bottger's Test. — .'Mkaline bismuth oxide solution is best prepared, according to Nylander, as follows: 2 grms. bismuth subnitrate, 4 grms. potassic and sodic tartrate, 100 grms. caustic soda of 8 per cent. Add i c.c. to every 10 c.c. of the fluid to be investigated. When boiled for several QUANTITATIVE ESTIMATION OF SUGAR. 265 minutes, the sugar causes the reduction and deposits a black precipitate of metallic bismuth. [According to Salkowski, the urine of a person taking rhubarb gives the same reaction with this test.] (4) Moore and Heller's Test. — Caustic potash or soda is added until the mixture is strongly alkaline ; it is afterward boiled. If sugar be present, a yellow, brown, or brownish-black coloration is obtained. If nitric acid be added, the odor of burned sugar (caramel) and formic acid is obtained. (5) Mulder and Neubauer's Test. — A solution of indigo- carmine, rendered alkaline with sodic carbonate, is added to the sugar solution until a slight bluish color is obtained. When the mixture is heated, the color passes into purple, red, and yellow. When shaken with atmospheric air, the fluid again becomes blue. Molisch's Test. — To 5 c.cm. of the fluid add 2 drops of a 17 per cent, alcoholic solution of a-naphthol, or a solution of thymol. Add i to 2 c.cm. of concentrated sulphuric acid, and shake the mixture. The presence of sugar colors the a-naphthol mixture deep violet, the thymol deep red. The subsequent addition of water causes a precipitate of similar color, which is insoluble in concentrated hydrochloric acid. Albumin, casein and peptone give the same reaction [Seegen), but the deposit on the addition of water is soluble in concentrated hydro- chloric acid. Other tests are described in § 266. In all cases where albumin is present it must be removed — in urine by acidulating with acetic acid and boiling ; in blood, by adding four times its volume of alcohol and afterward filtering, while the alcohol is expelled by heat. 150. QUANTITATIVE ESTIMATION OF SUGAR.— I. By Fermentation.— In the glass vessel (Fig. 161, a) a measured quantity (20 c.cm.) of the fluid (sugar) is placed along with some yeast, while b contains concentrated sulphuric acid. The whole apparatus is then weighed. When exposed to a sufficient temperature (io° to 40° C), the sugar splits into 2 molecules of alcohol and 2 of carbon dioxide, C.HjA = 2 (C^HgO) -f 2 (CO,), Grape sugar = 2 alcohol + 2 carbon dioxide ; and in addition there are formed traces of glycerine and succinic acid. The CO, escapes from b, and as it passes through the H2S0^, the CO, yields to the latter its water. The apparatus is weighed after two days, when the Fig. 161. reaction is ended, and the amount of sugar is calculated from the loss of weight in the 20 c.cm. of fluid. 100 parts of water- free sugar = 48.89 parts CO.,, or 100 parts CO, correspond to 204.54 parts of sugar. II. Titration. — By means of Fehling's solution, which is made of such strength that all the copper in 10 cubic centi- metres of the solution is reduced by 0.05 gramme of grape sugar (I 267). III. Circumpolarization. — The saccharimeter of Soleil- Ventzke may be used to determine the amount of sugar present. Apparatus for the quantitative estimation It may also be used for the quantitative estimation of albumin. of sugar by fermentation. Sugar rotates the ray of polarized light to the right and albumin to the left. The amount of rotation, or "specific rotatory power," is directly proportional to the amount of the rotating substance present in the solution, so that the amount of rotation of the ray indicates the amount of the substance present. By the term "specific rotatory power" is meant the degree of rotation which is produced by i grm. of the substance dissolved in i c.cm of water, when examined in a layer i decimeter thick. For yellow light the specific rotation of grape sugar is -|- 56°. In Fig. 162 the light from the lamp falls upon a crystal of calc-spar. Two Nicol's prisms are placed at v and s, v is movable round the axis of vision, while s is fixed. In m Soleil's double plate of quartz is placed, so that one-half of it rotates the ray of polarized light as much to the right as the other rotates it to the left. In n the field of vision is covered by a plate of left-rotatory quartz. At b c\% the compensator, composed of two right-rotatory prisms of quartz, which can be displaced laterally by the milled head, g, so that the polarized light passing through the apparatus can be made to pass through a thicker or thinner layer of quartz. When these right-rotatory prisms are placed in a certain position, the rotation of the left-rotatory quartz at n is exactly neutralized. In this position the scale on the compensator has its nonius exactly at 0, and both halves of the double plate zXtn appear to have the same color to the observer, who from v looks through the telescope placed at e. Rotate the Nicol's prism at v until a bright rose-colored field is obtained. In this position the telescope must be so adjusted that the vertical line bounding the two halves shall be distinctly visible. The apparatus is now ready for use. Fill a tube, I decimetre in length, with urine containing sugar or albumin, the urine being per- fectly clear. The tube is placed between m and n. By rotating the Nicol's prisms, v, the rose color is again obtained. The compensator at g is then rotated until both halves of the field of vision 266 MECHANISM OF THE DIGESTIVE APPARATUS. have exactly the same color. When this is obtained, read oft" on the scale the number of degrees the nonius is displaced to the right (sugar) or to the left (albumin) from zero. The number of degrees indicates directly the number of grammes of the rotating substance present in loo c. c. of the fluid. If the fluid is very dark colored, it must be decolorized by filtering it through animal charcoal (S^e^c-n), [or the coloring matter may be precipitated by the addition of lead acetate]. If the sugary urine contains albumin, the latter must be removed by boiling and filtration. A turbidity not removed by filtration may be got rid of by adding a drop of acetic acid or several drops of sodic carbonate or milk of lime, and afterward filtering. [One may also employ the apparatus of Mit- scherlich, or the "half-shadow apparatus" of Laurent.] Fig. 162. Soleil-Ventzke's Polarization Apparatus. 151. MECHANISM OF THE DIGESTIVE APPARATUS.— This embraces the following acts : — 1. The introduction and mastication of the food; the movements of the tongue ; insalivation ; formation of the bolus of food. 2. Deglutition. 3. The movements of the stomach, small and large intestine. 4- The excretion of fecal matters. MASTICATION. 267 152. INTRODUCTION OF THE FOOD.— Fluids are taken into the mouth in three ways: (i) By suction, the lips are applied air-tight to the vessel containing the fluid, while the tongue is retracted (the lower jaw being pften depressed) and acts like the piston in a suction pump, thus causing the fluid to enter the mouth. Herz found that the negative pressure caused by an infant while sucking == 3 to 10 mm. Hg. (2) The fluid is lapped when it is brought into direct contact with the lips, and is raised by aspiration and mixed with air so as to produce a characteristic sound in the mouth. (3) Fluid may be poured into the mouth, and as a general rule the lips are applied closely to the vessel containing the fluid. Solids, when they consist of small particles, are licked up with the lips, aided by the movements of the tongue. In the case of large masses, a part is bitten off with the incisor teeth, and is afterward brought under the action of the molar teeth by means of the lips, cheeks, and tongue. 153. MASTICATION. — The articulation of the jaw is provided with an interarticular carti- lage— the meniscus — which prevents direct pressure being made upon the articular surface when the jaws are energetically closed, and which also divides the joint into two cavities, one lying over the other. The capsule is so lax that, in addition to the raising and depressing of the lower jaw, it permits of the lower jaw being displaced forward, whereby the meniscus moves with it, and covers the articular surface. The process of mastication embraces: («) The elevation of the ja-w, accomplished by the combined action of the Temporal, Masseter, and Internal Pterygoid Muscles. If the lower jaw was previously so far depressed that its articular surface rested upon the tubercle, it now passes backward upon the articular surface. {d) The depression of the lower jaw is caused by its own weight, aided by the action of the anterior bellies of the Digastrics, the Mylo- and Genio-hyoid and Platysma. The muscles act especially during forcible opening of the mouth. The necessary fixation of the hyoid bone is obtained through the action of the Omo- and Sterno-hyoid, and by the Sterno-thyroid and Thyro-hyoid. When the articular surface of the lower jaw passes forward on to the tubercle, the External Pterygoids actively aid in producing this (^Berard). if) Displacement of the Articular Surfaces. — During rest, when the mouth is closed, the incisor teeth of the lower jaw are within the arch of the upper incisors. When in this position the jaw is protruded by the External Pterygoids, whereby the articular surface passes on to the tubercle (and, there- fore, downward), while the lateral teeth are thereby separated from each other. The jaw is retracted by the Internal Pterygoids without any aid from the posterior fibres of the Temporals. When one articular surface is carried forward, the jaw is protruded and retracted by the External and Internal Pterygoid of the same side. At the same time, there is a transverse movement, whereby the back teeth of the protruded side are separated from each other. During mastication, the individual movements of the lower jaw are variously combined, and especially with lateral grinding movements, while the food to be masticated is kept from passing outward by the action of the muscles of the lips (Orbicularis oris) and the Buccinators, while the tongue continually pushes the particles between the molar teeth. The energy of the muscles of mastication is regulated by the sensibility of the teeth, and the muscular sensibility of the muscles of mastication, as well as by the general sensibility of the mucous mem- brane of the mouth and lips. At the same time, the mass is mixed with saliva, the divided particles cohere, and are formed into a mass or bolus, of a long, oval shape, by the muscles of the tongue. The bolus then rests on the back of the tongue, ready to be swallowed. Nerves of Mastication. — The muscles of mastication receive their motor nerves from the third branch of the trigeminus, the mylo-hyoid and the anterior belly of the digastric being sup- 268 STRUCTURE AND DEVELOPMENT OF THE TEETH. Fig. 163. Pulp Cavitv. plied from the same source. The genio-, omo-, and sterno-hyoid, sternothyroid, and thyrohyoid are supplied by the hypoglossal, while the facial supplies the posterior belly of the digastric, the stylohyoid, the platysma, the buccinator, and the muscles of the lips. The general centre for the muscles of mastication lies in the medulla oblongata (^ 367). \Vhen the mouth is closed, the jaws are kept in con- tact by the pressure of the air, as the cavity of the mouth is rendered free from air, and the entrance of air is pre- vented anteriorly by the lips, and posteriorly by the soft palate. The pressure exerted by the air is from 2 to 4 mm. Hg. {Mc/z;^'cr and DoHcfers). [Effect on the Circulation. — Marey found that mas- tication trebled the velocity of the blood current in the carotid (horse), while Francois Frank observed that the circulation of the brain (in man) is increased ; hence it is evident that mastication implies an increased supply of blood to the nerve centres.] 154. STRUCTURE AND DEVELOPMENT OF THE TEETH.— .\ tooth is just a papilla of the mucous membrane of the gum, which has undergone a characteristic development. In its simplest form, as in the teeth of the lamprey, the connective-tissue basis of the papilla is covered with many layers of corneous epi- thelium. In human teeth, part of the papilla is trans- formed into a layer of calcified dentine, while the epi- thelium of the papilla produces the enamel, the fang of the tooth being covered by a thin accessory layer of bone, the crusta petrosa or cement. The dentine or ivory which surrounds the pulp cavity and the canal of the fang (Fig. 163) is very firm, elastic, and brittle. Dentine, like the matrix of bone, when treated in a certain way, presents a fibrillar structure. It is permeated by innumerable long, tortuous, wavy tubes — the dentinal tubules — each of which communicates with the pulp cavity by means of a fine opening, and passes more or less horizontally outward as far as the outer layers of the dentine. The tubules are bounded by an extremely resistant, thin, cuticular membrane, which strongly resists the action of chemical reagents. These tubules are filled completely by soft fibres, the "fibres of Tomes," which are merely greatly elongated and branched processes of the odontoblasts of the pulp. The dentinal tubules, as well as the fibres of Tomes, anastomose throughout their entire extent by means of fine processes. As the fibres approach the enamel, which they do not penetrate, some of them bend on themselves, and form a loop (Fig. 166, c), while others pass into the "inter- globular spaces " (Fig. 165) which are so abundant in the outer part of the dentine. The inter- globular spaces are small spaces bounded by curved surfaces. Certain curved lines, " Schreger's lines," may be detected with the naked eye in the dentine {e. g., of the elephant's tusk) running parallel with the contour of the tooth. They are caused by the fact that at these parts all the chief curves in the dentinal tubules follow a similar course. The enamel, the hardest substance in the body (resembling apatite), covers the crown of the teeth. It consists of hexagonal flattened prisms arranged side by side like a palisade (Fig. 166, B and C). They are 3 to 5 /i (soW inch) broad, not quite uniform in thickness, curved slightly in different directions, and, owing to inequalities of thickness, they exhibit transverse markings. They are elongated, calcified, cylindrical, epithelial cells. Retzius described dark brown lines running parallel with the outer boundary of the enamel, due to the presence of pigment (Fig. 163). The fully-formed enamel is negatively doubly refractive and uniaxial, while the developmg enamel is positively doubly refractive [Hoppe-Seyler). The cuticula or Nasmyth's membrane covers the free surface of the enamel as a completely structureless membrane i to 2 // thick, but in quite young teeth it exhibits an epithelial structure, and is derived from the outer epithelial layer of the enamel organ. The cement or crusta petrosa is a thin layer of bone covering the fang (Fig. 167, a). The bone lacunae communicate directly with the dental tubules of the fang. Haversian canals and lamellae are only found where the layer of cement is thick, and the former may communicate with the pulp cavity. Very thin layers of cement may be devoid of bone corpuscles. Sharpey's fibres occur in the cement of the dog's tooth ; while in the horse's tooth single bone corpuscles are developed by a capsule. In the periodontal membrane, which is just the periosteum of the Longitudinal section of an incisor tooth. CHEMISTRY OF A TOOTH. 269 alveolus, coils of blood vessels similar to the renal glomeruli occur. They anastomose with each other, and are surrounded by a delicate capsule of connective tissue. Chemistry of a Tooth. — The teeth consist of a gelatine-yielding matrix infiltrated with calcium phosphate and carbonate (like bone), (i) The dentine contains — organic matter, 27.70; calcium phosphate and carbonate, 72.06; magnesium phosphate, 0.75; with traces of iron, fluorine, and sulphuric acid. Fig. 165. Fig. 164. Transverse section of dentine. The light rings are the walls of the dentinal tubules ; the dark centres with the light points are the fibres of Tomes lying in the tubules. Interglobular spaces in dentine. Fig. 167. Section of a tooth between the dentine and enamel, a, enamel ; Transverse section of the fang, a, cement c, dentinal tubules ; B, enamel prisms highly magnified ; C, trans- with bone corpuscles ; b, dentine with verse sections of enamel prisms. tubules ; c, boundary between both. (2) The enamel contains anorganic proteid matrix allied to the substance of epithelium. It consists of 3.60 organic matter and 96.00 of calcium phosphate and carbonate, 1.05 magnesium phosphate, with traces of calcium fluoride and an insoluble chlorine compound. (3) The cement is identical with bone. The pulp in a fully-grown tooth represents the remainder of the dental papilla around which the dentine was deposited. It consists of a very vascular, indistinctly fibrillar connective tissue, laden with cells. The layers of cells, resembling epithelium, which lie in direct contact with the dentine, 270 DEVELOPMENT OK A TOOTH. are called odontoblasts, /. e., those cells which build up the dentine. These cells send off long- branched jirocesses into the dentinal tubules, while their nucleated bodies lie on the surface of the pulp, and form connections by processes with other cells of the pulp and with neighboring odonto- blasts. Numerous non-medilllated nerve fibres (sensory from the trigeminus), whose mode of termination is unknown, occur in the pulp. The periosteum or periodontal membrane of the fang is, at the same time, the alveolar l>eriosteum, and consists of connective tissue with elastic fibres and many nerves. The gums are devoid of mucous glands, very vascular, and often provided with long vascular papilhv, wliich are sometimes compound. Development of a Tooth. — It begins at the end of the second month of foetal life. Along the whole length of the fcptal gum is a thick projecting ridge (Fig. i6S, a) composed of many layers of epithelium. A depression, the dental groove, also filled with epithelium, occurs in the gum, and runs along under the ridge. The dental groove becomes deeper throughout its entire length, and on transverse section presents the appearance of a dilated flask {b), while at the same time it is rilled with elongated epithelial cells, which form the " enamel organ." A conical papilla, the " dentine germ," grows up from the mucous tissue, of which the gum consists, toward the enamel organ (Fig. 169, t), so that the apex of the papilla comes to have the enamel organ resting upon it like a double cap. Afterward, owing to the development of connective tissue, the parts of the enamel organ lying between and uniting the individual dentine germs, disappear, and gradually the connective tissue forms a tooth sac enclosing the papilla and its enamel organ (d). Those epithehal cells (Fig. 169, 3) of the enamel organ which lie next the top of the papilla, are cylindrical, and become calcifted to form enamel prisms. The layer of cells of the double cap, which Fk;. 168. Fig. 169. Fig. 170. Fig. 168. — a. Dental ridge; b, enamel organ; c, beginning of the dentine germ; d, first indication of the tooth sac. Fig. 169. — a. Dental ridge ; t, enamel organ with (i) outer epithelium, (2) middle stellate layer, (3) enamel prism- cell layer; c, dentine germ with blood vessels and the long osteoblasts on the surface ; d, tooth sac ; e, secondary enamel germ. Fig. 170. — a. Dental ridge : b, enamel organ ; c, dentine germ ; /, enamel ; g, dentine ; h, interval between enamel organ and the position of the tooth ; k, layer of odontoblasts. is directed toward the tooth sac (i), becomes flattened, fuses, undergoes a horny transformation, and becomes the cuticula, while the cells which lie between both layers undergo an intermediate meta- morphosis, so that they come to resemble the branched stellate cells of the mucous tissue (2), and gradually disappear altogether. The dentine is formed in the most superficial layer of the projecting connective tissue of the dental papilla, owing to the calcification of the continuous layer of odontoblasts which occur there (Figs. 169 and 170, k). During the process, fibres or branches of these cells are left unaffected, and remain as the fibres of Tomes. Exactly the same process occurs as in the formation of bone, the odontoblasts forming around themselves a calcified matrix. The cement is formed from the soft connective tissue of the dental alveolus. Dentition. — During the development of the first temporary or milk teeth a special enamel organ (Fig. 169, ciatn. ii;;.iiiient ; 5, cotyloid cavity ; B, bulbo- T^^^T°^"^ """scle ; Ts, superficial transverse perineal muscle ; F, fascia of the deep transverse perineal muscle; J, ischio-cavernosus muscle ; M, obturator internus ; S, external anal sphincter ; L, levator ani ; P, pyriformis. become "formed " in the lower part of the great intestine. The faeces are grad- ually carried along by the peristaltic movement, until they reach a point a little above that part of the rectum which is surrounded by both sphincters, the internal sphincter consisting of non-striped, and the external of striped muscle. EXCRETION OF FECAL MATTER. 279 Immediately after the expulsion of the faeces the external sphincter (Fig. 172, S, and Fig. 173) usually contracts vigorously, and remains so for some time. Afterward it relaxes, when the elasticity of the parts surrounding the anal opening, particularly of the two sphincters, suffices to keep the anus closed. In the inter- val between two evacuations, there does not seem to be a continued tonic con- traction of the sphincters. As long as the faeces lie above the rectum, they do not excite any conscious sensations, but the sensation of requiring to go to stool occurs when the faeces pass into the rectum. At the same time, the stimulation of the sensory nerves of the rectum causes a reflex excitement of the sphincters. The centre for these movements (Budge's centrum ano-spinale) lies in the lumbar region of the spinal cord (§ 362) ; in the rabbit between the sixth and seventh, and in the dog at the fifth lumbar vertebra (^Masius). Fig. 173. Levator ani and sphincter ani externus. In animals whose spinal cord is divided above the centre, a slight touch in the region of the anus causes this orifice to contract, but after this lively reflex contraction, the sphincters relax again, and the anus may remain open for a time. This occurs because the voluntary impulses which proceed from the brain to cause the contraction of the external sphincter are absent. Landois observed that in dogs with the posterior roots of their lower lumbar and sacral nerves divided, the anus remained open, and not unfrequently a mass of fseces remained half ejected. As the sensibility of the rectum and anus was abolished in these animals, the sphincters could not contract reflexly, nor could there be any voluntary contraction of the sphincters, the result of sensory impulses from the rectum. The external sphincter can be contracted voluntarily, like any voluntary muscle, but the closure of the anus can only be effected up to a certain degree. When the pressure from above is very great, the energetic peristalsis at last overcomes the strongest voluntary impulses. Stimulation of the peduncles of the cerebrum 280 DEFECATION. and of the spinal cord below this point causes contraction of the external sphincter. Defecation. — The evacuation of the faeces, which in man usually occurs at certain times, begins with a lively peristalsis of the large intestine, which passes downward to the rectum. In order that the mass of freces may not excite reflexly the sphincter muscles, in consequence of mechanical stimulation of the sensory nerves of the rectum, there seems to be a centre which inhibits the reflex action of the sphincters, which is called into play, owing, as it appears, to voluntary impulses. Its seat is in the brain, perhaps in the optic thalami. When this inhibitory apparatus is in action, the fecal mass passes through the anus, without causing it to close reflexely. The strong peristalsis which precedes defecation can be aided, and to a certain degree excited, by rapid voluntary movements of the external sphincter and levator ani, whereby the plexus myentericus of the large intestine is stimulated mechanically, thus causing lively peristaltic movements in the large intestine. The expulsion of the freces is also aided by the pressure of the abdominal muscles, and most efificiently when a deep respiration is taken, so as to fix the diaphragm, whereby the abdominal cavity is diminished to the greatest extent. The soft parts of the floor of the pelvis, during a strong eff"ort at stool, are driven downward in the form of -a cone, causing the mucous mem- brane of the anus, which contains much venous blood, to be everted. The function of the levator ani (Figs. 172, 173) is to raise voluntarily the soft parts Fir,. 174. Auerbach's plexus sliown in section (human), a. ganglionic cells ; t, nerve fibres ; c, section of the circular muscul.tr fibres ; ; 136, II). (4) Mineral salts (2 per 1000), and a milk-curdling ferment. They are chiefiy sodium and potassium chlorides, less calcic chloride (ammonium chloride, also in animals), and the compounds of phosphoric acid with lime, magnesium and iron. Among foreign substances, which may be introduced into the body, the following appear in the gastric juice — HI, after the use of potassium iodide — potassium sulphocyanide, ferric lactate, and sugar ; and ammonium carbonate in uremia. [Composition of Gastric Juice {Hoppe-Scyler, after C. Schmidt.). Constituents. Water, . . . . Organic matter, Free HCI, . . CaClj, . . . . NaCl, . . . . KCl, NH^Cl, . . . . Ca32(POj, . . Mg32(PO,). . . FePO, Human. Dog. III. 994.404 3-195 0.200 0.061 1.465 0.550 I °'^^ I i With saliva. 971.171 17336 2-337 I.66I 3-147 1-073 0-537 2.294 0.323 0.1 2 1 No saliva. 973.062 17.127 3.050 0.624 2.507 1. 125 0.468 1.729 0.226 0.082 IV. Sheep. 986.143 4-055 1-234 0.II4 4-369 1. 518 0.473 1. 182 0-577 0.331 Good human saliva is not .so dilute or so poor in HCI as I. Szabo has found even 3 of HCI per 1000 in man.] 164. SECRETION OF GASTRIC JUICE.— After the discovery of the two kinds of glands in the stomach and the two kinds of cells in the fundus glands, the question arose as to whether the different constituents of gastric juice were formed by different histological elements. Changes of the Cells during Digestion. — During the course of digestion, the cells of the fundus (and pyloric glands, dog) undergo important changes [Jleidenhain). During hunger, the SECRETION OF GASTRIC JUICE. 289 chief cells are clear and large, the parietal investing cells are small, the pyloric cells clear and of moderate size. During the first six hours of digestion, the chief cells become enla,rged and moder- ately turbid or granular, the parietal cells also enlarge, while the pyloric cells remain unchanged. The chief cells become diinmisked and more turbid or granular until the ninth hour, the parietal cells are still swollen, and the pyloric cells enlarge. During the last hours of digestion, the chief cells again become larger and clearer, the parietal cells diminish, the pyloric cells decrease in size and become turbid (Figs. 183 and 184). [Langley gives a different description of the appearances presented by these cells. The results may be reconciled by remembering that the gland cells were examined under different conditions. The secretory cells consist of a cell substance composed of {a) a framework of living protoplasm, either in the form of an intracellular fibrillar network, or in flattened bands. The meshes of this framework enclose at least two chemical substances, viz., [b) a hyaline substance in contact with the framework, and [c) spherical granules which are efnbedded in the hyaline substance. During active secretion, the granules decrease in number and size, the hyaline substance increases in amount, the network grows. This is the reverse of what is stated above as the observation of Heidenhain, but the granular appearance described by Heidenhain after secretion is very probably due to the action of the hardening agent, alcohol. Langley found that in the living condition, or after the use of osmic acid, in some animals at least, the chief cells are granular during rest, but during a state of activity two zones are differentiated, an outer one, which is clear, owing to the dis- appearance of the granules, and an inner more or less granular one. Granules reappear in the outer part after rest. During digestion, the parietal cells increase in size, but do not become granular. In all cells containing much pepsinogen, distinct granules are present, and the quantity of pepsinogen varies directly with the number and size of the granules. In the glands of some animals there is little difference between the resting and active phases. Compare Serous Glands, \ 143, and Pancreas, \ 168.] The pepsin is formed in the chief cells (^Heidenhain). When these are clear and large, they contain much pepsin ; when they are contracted and turbid, the amount is small. The pyloric glands are also said to secrete pepsin, but only to a small extent. Pepsin accumulates during the first stage of hunger, and it is eliminated during digestion and also during prolonged hunger. Pepsin, as such, is not present within the cells, but only as a " mother substance," a pepsinogen substance (zymogen), or pro-pepsin, which occurs in the granules of the chief cells. This zymogen, or mother substance, by itself, has no effect upon proteids ; but if it be treated with hydrochloric acid or sodium chloride, it is changed into pepsin. Pepsin and pepsinogen may be extracted from the gastric mucous mem- brane by means of water free from acids. [Pepsinogen and Pepsin. — Glycerine extracts very little pepsin from the perfectly fresh gastric mucous membrane, but a large amount is afterward obtained by extracting it with dilute hydrochloric acid, or with this acid and glycerine. The relative amount of pepsinogen and pepsin in a fluid may be determined approximately by the method of Langley and Edkins. A i per cent, solution of sodic carbonate exerts a greater destructive action on pepsin than on pepsinogen, while a current of COj destroys pepsinogen to a greater extent than pepsin. Both substances are unaffected by CO, but are destroyed at 54° to 57° C] The pyloric glands secrete pepsin, but no acid. Klemensiewicz excised in a living dog the pyloric portion of the stomach, and afterward stitched together the duodenum and the remaining part of the stomach. The excised plyoric part, with its vessels intact, he stitched to the abdominal wall, after sewing its lower end. The animals experimented on died, at the latest, after six days. The secretion of this part was thin, alka- line, and contained 2 per cent, of solids, including pepsin. [Pyloric Fistula. — In Fig. 185 P represents the excised pyloric portion, C the cardiac. The parts a, a, and a' a' were then stitched together, and the continuity of the organ established. The lower end {d) of P was closed by sutures, while the edges of Diagram of Klemensiewicz's experi- P at O were stitched to the abdominal walls, thus making a py- '"^"' ^^^'''^'"s) loric fistula.] In the frog the alkaline glands of the oesophagus contain only chief cells which ^9 290 INFLUENCE OF THE NERVES ON THE SECRETION. produce pepsin ; while the stomach has glands which secrete acid (and perhaps some pepsin), and are lined by parietal cells. Among fishes the carps have no fundus glands in the stomach (^Luchau). [The secreting por- tions of glands of the cardiac sac (crop) of the herring are lined by a single layer of polygonal cells {W. Stirlins).\ The hydrochloric acid is formed, according to Heidenhain, by the parietal cells. It occurs on the free surface of the gastric mucous membrane as well as in the ducts of the fundus glands. The deep parts of the glands are usually alkaline. Free HCl is detected in human gastric juice, within 45 minutes to i to 2 hours after a moderate meal, but in 10 to 15 minutes in a fasting condition after drink- ing water; the amount gradually increases during the process of digestion. Lactic acid, perhaps derived from the food, is found in the stomach immediately after taking food, after half an hour along with HCl, while after an hour only HCl is found {^Ejvald and Boas). CI. Bernard injected potassium ferrocyanide and afterward lactate of iron into the veins of a dog. After death, blue coloration occurred only in the upper acid layers of the mucous membrane. Nevertheless, we must assume that the hydrochloric acid is secreted in the parietal cells of the fundus of the glands, and that it is rapidly carried to the surface along with the pepsin. Briicke neutralized the surface of the gastric mucous membrane with magnesia usta, chopped up the mucous membrane with water, and left it for some time, when the fluid had again an acid reaction. As to the formation of a free acid, the following statements may be noted : The parietal cells form the hydrochloric acid from the chlorides which the mucous membrane takes up from the blood. According to Voit, the formation of acid ceases, if chlorides be withheld from the food. Maly suggests that the active agent is lactic acid, which splits up sodium chloride and forms free HCl. The base set free is excreted by the urine, rendering it at the same time less acid. The formation of acid is arrested during hunger. According to H. Shultz, watery solutions of alkaline and earthy chlorides are decomposed, even at a low tempera- ture, by CO.,, free hydrochloric acid being formed. [The source of the HCl is undoubtedly the sodic chloride in the blood and lymph, but what other acid displaces the HCl is a matter of conjecture. In this connection, it is important to remember that Jul. Thomsen has shown that every acid can displace a part of another acid from its combina- tion with its base, and the weaker acid may even combine with the greater part of the base. Thomsen calls this " avidity." Even strong mineral acids may be displaced by weak organic ones. Thus the free CO2 in the alkaline blood may set free a small quantity of HCl from the sodic chloride. What is still more remarkable is, that the free HCl should be transferred by the cells toward the gland duct, while the sodic carbonate diffuses toward the blood and lymph. J Secretion. — When the stomach is empty, there is usually no secretion of gastric juice ; this takes place only after appropriate (mechanical, thermal, or chemical) stimulation. In the normal condition, it takes place immediately on the introduc- tion of food, but also of indigestible substances, such as pebbles. The mucous membrane becomes red, and the circulation more active, so that the venous blood becomes brighter. [That the vagi are concerned in this vascular dilatation, is proved by the fact, that if both nerves be divided during digestion, the gastric mucous membrane becomes pale {Ruiherford).'] The secretion is probably caused reflexly, and the centre perhaps lies in the wall of the stomach itself (Meissner's plexus in the submucous coat). It is asserted that the idea of food, especially during hunger, excites secretion. As yet we do not know the effect produced upon the secretion by stimulation or destruction of other nerves, e.g., vagus, sympathetic. [There is no nerve passing to the stomach, whose stimulation causes a secretion of gastric juice, as the chorda tympani does in the sub-maxillary gland. If the vagi be divided sufficiently low down not to interfere with respiration, the introduction of food still causes a secretion of gastric juice ; even if the sympathetic branches be divided at the same time, secretion still goes on {Heidenhaifi). This experiinent points to the existence of local secretory centres in the stomach. But there is evidence to show that there is some connection, perhaps indirect, between METHODS OF OBTAINING GASTRIC JUICE. 291 the central nervous system and the gastric glands. Richet observed a case of complete occlusion of the oesophagus in a woman, produced by swallowing a caustic alkali. A gastric fistula was made, through which the person could be nourished. On placing sugar or lemon juice in the person's mouth, Richet observed a secretion of gastric juice. In this case no saliva could be swallowed to excite secretion, so that it must have taken place through some nervous channels. Even the sight or smell of food caused secretion. Emotional states also are known to interfere with gastric digestion.! Effect of Abiorption. — Heidenhain isolated apart of the mucous membrane of the fundus so as to form a blind sac of it, and he found that mechanical stimu- lation caused merely a scanty local secretion at the spots irritated. If, however, at the same time, absorption of digested matter also occurred, secretion took place over larger surfaces. [He distinguishes a primary and merely local secretion excited by the mechanical stimulus of the ingesta, and a secondary depending on absorption, and extending to the whole of the mucous membrane.] The statement of Schiff, that active gastric juice is secreted only after absorption of the so-called peptogenic substances (especially dextrin), is denied. The acid contents of the stomach called chyme, which pass into the duodenum after gastric digestion is completed, are neutralized by the alkali of the intestinal mucous membrane and the pancreatic juice [at the same time, a precipitate is formed and deposited on the walls of the duodenum, and it carries the pepsin down with it]. Part of the pepsin is reabsorbed as such, and is found in traces in the urine and muscle juice (Briicke). If the gastric juice be completely discharged externally through a gastric fistula, the alkalinity of the intestine is so strong that the urine becomes alkaline {^Maly). The acid gastric juice of the new-born child is already fairly active ; casein is most easily digested by it, then fibrin and the other proteids [Zweifel). When the amount of acid is too great in the stomach of sucklings, large, firm, indigestible masses of casein are apt to be formed, especially after the use of cow's milk (^ 230). [Action of Drugs on Gastric Secretion. — Dilute alkalies, if given before food; saliva; some substances called peplogens by Schiff, such as dextrin and peptones, alcohol and ether, all excite secretion, the last being very powerful. When the secretion is excessively acid, antacids are given, some diminishing the acidity in the stomach, as the carbonates and bicarbonates of the alkalies, liquor potassse, and the carbonate of magnesia; while the citrates and tartrates of the alkalies, be- coming converted into carbonates in their passage through the organism, diminish the acidity of the urine.] Small doses of alcohol, introduced into the stomach, increase the secretion of gastric juice ; large doses arrest it. Artificial digestion is affected by 10 per cent, of alcohol, is retarded by 20 per cent., and is arrested by stronger doses. Beer and wine hinder digestion, and in an undiluted form interfere with artificial digestion. 165. METHODS OF OBTAINING GASTRIC JUICE.— Historical.— Spallanzani caused starving animals to swallow small pieces of sponge enclosed in perforated lead capsules, and after a time, when the sponges had become saturated with gastric juice, he removed them from the stomach. To avoid the admixture of saliva, the sponges are best introduced through an opening in the cesophagus. Dr. Beaumont (1825), an American physician, was the first to obtain humaa gastric juice, from a Canadian named Alexis St. Martin, who was injured by a gunshot wound, whereby a permanent gastric fistula was established. Various substances were introduced through the exter- nal opening, which was partially covered with a fold of skin, and the time required for their solu- tion was noted. Bassow (1842), Blondlot (1843), and Bardeleben (1849), were thereby led tO' make artificial gastric fistulse. Gastric Fistula. — The anterior abdominal wall is opened by a median incision just below the ensiform cartilage, the stomach is exposed, and its anterior wall opened and afterward stitched to the margins of the abdominal walls. A strong cannula is placed in the fistula thus formed. The tube is kept corked. If the ducts of the salivary glands be tied, a perfectly uncomplicated object for investigation is obtained. According to Leube, dilute human gastric juice may be obtained by means of a siphon-like tube introduced into the stomach. Water is introduced first, and after a time it is withdrawn. An important advance was made when Eberle (1834) prepared artificial gastric juice, by extracting the pepsin from the gastric mucous membrane with dilute hydrochloric acid. Four litres of solution of hydrochloric acid, containing 4 ,to 8 c.c. HCl per looo, are sufficient to extract the 292 PROCESS OF GASTRIC DIGESTION. chopped-up mucous membrane of a pig's stomach. Half a litre is infused with the stomach and renewed every six hours. The collected fluid is afterward filtered. The sub.stance to be digested is placed in this fluid, and the whole is kept at the temperature of the body, but it is necessary to add a iitile IICl from timetotime (Si/nonnn). The HCl maybe replaced by ten times its volume of lactic acid and also by nitric acid; while oxalic, sulphuric, phosphoric, acetic, formic, succinic, tartaric, and citric acids are much less active ; butyric and salicyclic acids are inactive. Von Wittich's Method. — () Or the mucous membrane may be placed for twenty- four hours in alcohol, and afterward dried and extracted for eight days with glycerine, (c) Wm. Roljerts has used other agents for extracting enzymes (^ 148). Preparation of Pure Pepsin. — Briicke pours on the pounded mucous membrane of the pig's stomach a 5 percent, solution of phosphoric acid, and afterward adds lime-water until the acid re- action is scarcely distinguishable. A copious precipitate, which carries the pepsin with it, is pro- duced. This precipitate is collected on cloth, repeatedly washed with water, and afterward dissolved in very dilute IICl. A copious precipitation is caused in this fluid by gradually adding to it a mix- ture of cholesterin in four parts of alcohol and one of ether. The cholesterin pulp is collected on a fdter, washed with water containing acetic acid, and afterward with pure water. The cholesterin pulp is placed in ether to dissolve the cholesterin, and the ether is then removed. The small watery deposit contains the pepsin in solution. Pepsin so prepared is a colloid substance ; it does not react like albumin with the following tests, viz. : It does not give the xanthroprotein reaction (§ 248), is not precipitated by acetic acid and potassium ferrocyanide, nor by tannic acid, mercuric chloride, silver nitrate, or iodine. In other respects it belongs to the group of albuminoids. It is rendered inactive in an acid fluid by heating it to 55° to 60° C. 166. PROCESS OF GASTRIC DIGESTION.— [In the process of gastric digestion we have to consider — 1. The secretion of gastric juice and its action on food. 2. The absorption of the products of this digestion. 3. The movements of the stomach itself.] Chyme. — The finely divided mixture of food and gastric juice is called chyme. The gastric juice acts upon certain constituents of chyme. I. Action on Proteids. — Pepsin and the dilute hydrochloric acid, at the temperature of the body, transform proteids into a soluble form, to which Lehmann (1850) gave the name of *' peptone" (§ 249, III). Fibrin (or coagulated pro- teids) first becomes clear and swollen up. [It is commonly stated that the first product formed during the gastric digestion of proteids is syntonin or parapeptone, then hemi-albumose or propep- tone, and finally peptone. The products vary, however, with the proteid digested. Kiihne has shown that the proteid molecule is split up, and yields two groups, which he calls anti-peptone and hemi-peptone ; the former can be split up into leucin and tyrosin by trypsin, while the latter does not undergo this change. A mixture of the two he calls ampho-peptone. The intermediate body or propeptone, is really a mixture of several bodies. Kiihne calls it hemi- albumose. These intermediate bodies from albumin are called albumoses, from globulins globuloses, from casein caseoses. Halliburton calls all these interme- diate bodies " proteoses."] Properties. — Hemi-albumose, although a composite body, gives the following reactions : It is highly soluble in water; when heated to 50° to 60° it becomes somewhat turbid, but when boiled it becomes clear, and gets turbid again on cooling. This effect is most marked when it is treated with acetic acid and sodic chloride, or the latter alone. It is precipitated by acetic acid and potas- sic ferrocyanide, but the precipitate disappears on heating and reappears on cooling. It gives the biuret rosy tint reaction like peptones. It is precipitated by nitric acid, and the precipitate adheres to the glass, but is soluble in the acid with the aid of heat, yielding a yellow fluid, but is precipitated on cooling. It is precipitated by boiling with acetic acid and a strong solution of sodic sulphate, PROCESS OF GASTRIC DIGESTION. 293: raetaphosphoric acid, and pyrogallic acid [Kuhne). It is said to be present in all animal tissues except muscle and nerve (^ 293). [Albumoses are the first products of the splitting up of proteids by enzymes, and from them peptones are ultimately formed. They may be made from Witte's peptone, or by the peptic digestion of fibrin. Such a mixture, on being neutral- ized with sodic carbonate, gives a copious precipitate of parapeptones, which can be filtered off, leaving a clear solution of albumoses. On saturating the clear fluid with NaCl, a dense white precipitate, consisting of three albumoses, called proto-, dys-, and hetero-albumose is obtained ; a fourth, deutero-albu- mose, remains in solution, but can be precipitated by adding acetic acid. If the albumose precipitate be treated with 10 percent. NaCl solution, proto- and hetero- albumose are dissolved, leaving dys-albumose undissolved. Dialysis of the saline solution precipitates hetero-albumose, leaving proto-albumose in solution. It is probable, however, that hetero- and dys-albumose are identical, or that the former is merely an insoluble form of the latter. The albumoses are bodies intermediate between albumins and peptones, and of the three, deutero-albumose is nearest to peptones.] [Properties. — Proto-albumose is soluble in distilled water, is not changed by heat, but is pre-' cipitated by saturation of the solution with sodic chloride, by HNO3, acetic acid, potassic ferrocya- nide, copper sulphate, mercuric chloiide. Deutero-albumose is very like the foregoing, but it is not precipitated by HNO3 or on adding sodic chloride to saturation, but precipitation occurs when 20 to 30 per cent, of acetic acid is added. Hetero-albumose resembles a globulin in its proper- ties; it is insoluble in distilled water, but is soluble in saline solutions (10 to 15 per cent.), and is partly precipitated from its solution by saturation with NaCl or dialysis. It is coagulated by heat. All give the rosy-pink color with the biuret reaction, and they are all precipitated by saturation with neutral ammonia sulphate, which peptones are not [Kuhne and Chittenden).'\ [Globuloses from the globulin of ox serum are obtained in the same way, although the ferment has much less action on globulin than on albumin. Speaking generally, they resemble the albu- moses.] By the continued action of the gastric juice, the propeptone passes into a true soluble peptone. The unchanged albumin behaves like an anhydride with respect to the peptone. The formation of peptone is due to the taking up of a molecule of water, under the influence of the hydrolytic ferment pepsin, and the action takes place most readily at the temperature of the body. Gelatin is changed into a gelatin-peptone. According to Kiihne, the proteid molecule contains two substances preformed : anti- albumin and hemi-albumin. Gastric juice at first converts them into anti-albumose and hemi-albumose, and both ultimately into anti-peptone and hemi-peptone (^ 170, II). Only the latter is split up by trypsin into leucin and tyrosin. The greater the amount of pepsin (within certain limits), the more rapidly does the solution take place. The pepsin suffers scarcely any change, and if care be taken to renew the hydrochloric acid, so as to keep it at a uniform amount, the pepsin can dissolve new quantities of albumin. Still, it seems that some pepsin is used up in the process of digestion {Griltzner). Proteids are introduced into the stomach either in a solid (coagulated) or fluid condition. Casein alone of the fluid forms is precipitated or coagulated, and afterward dissolved. The non- coagulated proteids are transformed into syntonin, without being previously coagu- lated, and are then changed into propeptone and directly peptonized, i. e., actually dissolved. When albumin is digested by pepsin at the temperature of the body, a not inconsiderable amount of heat disappears, as can be proved by calorimetric experiment {Alaly). Hence, the temperature of the chyme in the stomach falls o°.2 to o°.6 C. in two to three hours (v. Vintschgau and Dieil). Coagulated albumin may be regarded as the anhydride of the fluid form, and the latter again as the anhydride of peptone. The peptones, therefore, represent the highest degree of hydration of the proteids. 294 PROPERTIES OK I'EITONES. Hence iMrrtones may be fonncd from prolcids by those reagents which usually cause hydration vi " .realS "h MroHR .cids (from Lin. with 0.2 HCl). caust.c alkal.es. putrefact.ve and various other ferments, and o/oiie. The anhydride proteid has been prepared from the hydrated fortii. Henniger and Hofmeister. by boiling pure peptone with dehydrating substances (anhydrous acetic acid at 80° C), have succeeded in decomposing it into a body resembhng '^Peptoncs.-( . ) They are completely soluble in water. (2) They diffuse very cas.U through tnembranes. (3) They filter quite easily through the pores of animal membranes. (4) They are no/ precipitated \^y boiling, nitric acid, acetic acid and potassium ferrocyanide, acetic acid and saturation with common salt, (c) They are precipitated from neutral or feebly acid solutions by mercuric chloride, tannic acid, bile acids, and phosphoro-molybdic acid. (6) With Millon's reagent they react like proteids, and give a red color, and with nitric acid give the yellow xanthoprotein reaction. (7) With caustic potash or soda and a small quantity of cupric sulphate [or Fehling's solution] they give a beautiful rosy-red co\ox, the biuret reaction. (8) They rotate the plane of polar- ized light to' the left. [Kuhne and Chittenden, making use of the fait that ammonium sulphate to saturation precipitates all proteids from solution except peptone, have reinvesti- gated the subject, and they find that many of the peptones of commerce contain albumoses. Pure jjeptone has remarkable properties. When dissolved in water, it hisses and froths like phosphoric anhydride, heat is evolved, and a brown solu- tion IS formed. It is difiicult to preserve it. It is not precipitated by NaCl, or NaCl and acetic acid, but is completely precipitated by phospho-tungstic and phosi)ho-molybdic acids, tannin, iodo-mercuric iodide, picric acid. Peptones have a cheesy taste, while albumin and albumoses are tasteless.] The biuret reaction is obtained with propeptone, as well as with a form of albumin, which is formed durinp artificial digestion and is soluble in alcohol. It is called " alkophyr " by Briicke. [Darby's fluid meat gives all the above reactions, and is very useful for studying the tests for peptiines] The rapidity of solution of fibrin is tested by placing fibrin which is swollen up by the action of 0.2 per cent. HCi in a glass funnel, and adding the digestive fluid, observing the rapidity with which the fluid, the altereues. They are not formed by the activity of microorganisms. .Some seem to be formed in muscle, and are cksely allied to creatin and xanihin.] Peptones are undoubtedly those modifications of albumin or proteids which, after their absorption from the intestinal canal into the blood, are destined to make good the proteids used up in the human organism. By giving peptones (instead of albumin) as food, life cannot only be maintained, but there may even be an increase of the body weight {Plbsz and Maty, Adamkiewicz). Very probably, before being absorbed into the blood stream, peptones are re-trans- formed into serum albumin (§ 192). Conditions affecting Gastric Digestion.— The presence of already-formed peptones interferes with the action of the gastric juice, in so far as the greater concentration of the fluid interferes with and limits the mobility of the fluid particles. Boiling, concentrated acids, alum, and tannic acid, ntkalinity of the gastric juice (<•. g., by the admixture of much saliva), abolish the action ; also sul. phurous and arsenious acids and potassic iodide. The salts of the heavy metals, which cause pre- ARTIFICIAL DIGESTION OF THE PROTEIDS. 295 cipitates with pepsin, peptone, and mucin, interfere with gastric digestion, and so do concentrated solutions of alkaUne salts, common salt, magnesium and sodium sulphates. A small quantity of NaCl increases the secretion [Griiizner) and favors the action of pepsin. Alkalies rapidly destroy pepsin, but less rapidly pro-pepsin [Langley). Alcohol precipitates the pepsin, but by the subsequent addition of water it is redissolved, so that digestion goes on as before. Any means that prevent the proteid bodies from swelUng up, as by binding them firmly, impede digestion. Slightly over half a pint of cold water does not seem to disturb healthy digestion, but it does so in cases of disease of the stomach. Copious draughts of water, and violent muscular exercise, disturb digestion ; while warm clothing, especially over the pit of the stomach, aids it. Menstruation retards gastric digestion. [Oddi finds that the presence of large quantities of ox bile, or even of its own bile in the stomach of a dog, does not aff"ect the activity of the gastric juice, does not precipitate peptones, and does not excite vomiting.] [Artificial Digestion. — The action of gastric juice on proteids may be observed outside the body, and we can prove, as is shown in the following table, after Rutherford, that pepsin and an acid — e. g., hydrochloric, along with water — are essential to the formation of gastric peptones : — Beaker A. Beaker B. Beaker C. Water. Pepsin, 0.3 per cent. Fibrin. Water. HCl, 0.2 per cent. Fibrin. Water. Pepsin, 0.3 per cent. HCl, 0.2 Fibrin. Keep all in water bath at 38° C. Unchanged. Fibrin swells up, becomes clear, and is changed into acid albumin or syntonin. Fibrin ultimately changed into peptone.] [In all animals, gastric digestion is essentially an acid digestion, and between the native proteid, fibrin, albumin, or any other form of proteid, and the end product peptone, there are numerous intermediate substances, many of whose properties and characters have still to be investigated.] [Exclusion of the Stomach. — Ogata finds that if the stomach be divided at the pyloric end so as to exclude the stomach from the digestive apparatus, a dog can be nourished for a long time by introducing food through the pylorus into the duodenum. A dog has lived several years after excision of its stomach [Czerny). Raw flesh so introduced is digested more rapidly in the small intestine than in the stomach. The stomach not only digests, but it acts on the connective tissue of flesh so as to prepare the latter for intestinal digestion.] II. Action on other Constituents of Food. — Milk coagulates when it enters the stomach, owing to the precipitation of the casein, and in doing so it entangles some of the milk globules. During the process of coagulation, heat is given off. The free hydrochloric acid of the gastric juice is itself sufficient to pre- cipitate it ; the acid removes from the alkali-albuminate or casein the alkali which keeps it in solution. Hammarsten separated a special ferment from the gastric juice — quite distinct from pepsin — the milk-curdling ferment which, quite independently of the acid, precipitates the casein either in neutral or alkaline solu- tions. It is this ferment or rennet which is used to coagulale casein in the making of cheese. [Rennet is an infusion of the fourth stomach of the calf in brine (§ 231). The ferment which coagulates milk is quite distinct from pepsin. If magnesic carbonate be added to an infusion of calf's stomach, a precipitate is obtained. The clear fluid has strongly coagulating properties, while the pre- cipitate is strongly peptic] The action of the milk-curdling ferment is, perhaps, like the action of all ferments, a hydration of casein ; it is greater in the presence of 0.2 HCl. One part of the rennet ferment can precipitate 800,000 parts of casein. When casein coagulates, two new proteids seem to be formed — the coagulated proteid which constitutes cheese, and a body resembling peptone dissolved in the whey. The addition of calcium chloride accelerates, while 29<; ACTION Ol- GASTRIC JUKE ON THE VARIOUS TISSUES. w.ter retard* the coagulation (? 231) {Ihmmarsten). [A ferment similar to rennet is contained in the sec«l» of W'ithama iOHipilans (S. Lflidifies in the cold, but a ::;elatin-pcptonf is formed, which is soluble and diffusible, although it differs from true [leptonc. In the dog, connective tissues are especially acted on in the stomach, while the other parts of organs used as food are prepared for digestion in the small intestine, where the cellul.ir and nuclear elements are digested by the pancreatic juice [Bikfalvi).'] (2) The Structureless membranes (menibranx propria) of glands, sarcolemma, Schwann's sheath of nerve fibres, c.ipsule of the lens, the elastic laminx of the cornea, the membranes of fat cells are dissolved, but the true elastic (fenestrated) membranes and fibres are not affected. (3) Striped muscle, after solution of the sarcolemma, breaks up transversely into disks, and, like non-striped muscle, is dissolved, and forms a true soluble pejMone, but parts of the muscle always pass into the intestine. (4) The albuminous constituents of the soft cellular elements of glands, stratified epi- thelium, endothelium, and lymph cells, form peptones, but the nuclein of the nuclei does not seem to \tc dissolved. (5) The horny parts of the epidermis, nails, hair, as well as chitin, silk, conchioUn, and s|x)ngin of the lower animals are indigestible, and so are amyloid substance and wax. (6) The red blood corpuscles are dissolved, the haemoglobin decomposed into haematin and a globulin- like substance; the latter is peptonized, while the former remains unchanged, and is partly absorbed and transformed into bile pigment. Fibrin is easily dissolved to form hemi- and anti-peptone. (7) Mucin, which is .al>o secreted by the goblet cells of the stomach, passes through the intestines unchanged. (S) Vegetable fats are not affected by the gastric juice ; these cells yield their proto- pla.smic contents to fonn pei)tn!R-s, while the cellulose of the cell wall, in the case of man at least, remains undigi-sti-*! (■; 1S4). Why the Stomach does not digest itself.— That the stomach can digest living things is shown by the following facts : l{cm.ard introc inner zone ,s j^reaily enlarged and granular, whi^e the outer zone is small ( Kit;. .87.3)- I'^nng hunger the outer zone agam enlarges (F.g. 787 I) In a glan.l where paralytic secretion takes place, the gland .s much dmi.n.shed in s.ze, Ihc cells are shriveled ( F.g. 1 87, 4) and greatly changed. According to Ogata, some cells actually disai>i)car durini? secretion. . , n <• .• The axially placed excretory duct consists of an inner th.ck and an outer loose wa 1 of connective and elastic tissues, lined by a single layer of columnar epithelium. Small mucous glands he in the Unrest trunks. Non-medullaied nei^es, with ,c<7«;V/V7 in their course, pass to the acmi. but their mode of termination is unknown. The blood vessels form a rich capillary plexus round some acini while round others there are verv' few. Kiihne and I.ea found peculiar small cells in groups between the alveoli, and supplied with convoluted cai.illaries like glomeruli. 1 heir signihcance is entirely unknown. [They are probably lymphatic in their nature ] The lymphatics resemble those of the' salivar)- glands. When a coloretl injection is forced into the ducts under a high pressure, fine intercellular passages between the secreting cells are formed {Saviolli's canals), but they are artificial products.] ... ... [Number of Ducts.— In making evjieriments upon the pancre.itic secretion, it n important to rememU-r that the number of pancreatic ducts varies in ditferent animals. In man there is one duct oix-ning along with tlie common bile duct at \'ater's ampulla, at the junction of the middle and lower thiril of the duodenum. The r.ibbit ha.s two ducts, the larger oi>ening .separately aliout 14 inches (30 to 35 cm.) below the entrance of the bile duct. The dog and cat have each two ducts opening separately] Chemistry. — The fresh pancreas contains water, proteids, ferments, fats, and salts. In a gland which has l)cen exjx)sed for some time, much leucin, isoleucin. butalin, tyrosin, often xanthin and guanin, are found : lactic and fatty acids seem to be formed from chemical decomix)sitions taking place. 169. THE PANCREATIC JUICE.— Method.— Regner de Graaf (1664) tied a cannula in the pancreatic duct of a dog, and collected the juice in a small bag. Other experimenters made a temporary fistula. To make a permanent fistula, the abdomen is opened (dog), the pancreatic duct pulled forward, and stitched to the abdominall wall, with which it unites. Heidenhain cuts out the part of the duocienum where the duct opens into it, from its continuity with the intestine, and fixes it out.side the alKiominal wound. The secretion obtained from a permanent fistula is a copious, slightly active, watery secretion, containing much sodium carbonate; while the thick fluid obtained from the fistula before inflammation sets in, or that from a temporary fistula, acts far more energetically. This thick secretion, which is small in amount, is the «e which are formed when fresh nerve fibres are texsed >n water An.mal ods emuls.omze more rcad.iv than vegetable oils; castor oil does not emuls.onue (Go,/)- [H is extremely d.Hjcult to oUain a ,K-rfectly nelitrnl oil. xs most oils contain a trace of a fatty acid. In fact, if on addmg a weak volution of sckUc carlK>nate to oil or fatty matters, tluid at the temperature of the body, an emul- sion is obtaine.l. one may Ik; sure that the oil contained a fatty acid, so that Bernard s v,ew about an "cmuLsive fennent" being neces^n' is not endorsed. The fatty acid set free by the fat-splitting ferment <-nabl.-s the alkaline pancreatic juice at once to produce an emulsion.] Fat-Splitting Ferment.— This is a very unstable body, and must be prepared from the perfectly Ircsh glan.l by rubbing it up with powdered glass, glycerine, and a I per cert, solution of iodic c'arlKmatc. and allowing it to stand for a day or two (G/ii/zner). [This ferment is said to cause an emulsion of oil and mucilage tinged blue with litmus at 40° C. to become red (Gamo^eg). In performing this experiment notice that the mucilage is perfectly neutral, as gum arabic is fre- quently acid.] [Pancreatic Extracts.— The action of the pancreas may be tested by making a watery extract of a perfectly fresh gland. Such an extract always acts upon starch and generally upon fats, but this extract and also the glycerine extract vary in their action upon proteids at different times. If the extract— watery or glycerine — be made from the pancreas of a fasting animal, the tryptic action is slight or absent, but is active if it be prepared (rom a gland 4 to 10 hours after a meal. The pancreatic preparations of Benger of Manchester, Savory and Moore, or Burroughs and Welcome, all possess active diastatic and proteolytic properties.] [Pancreas Salt. — Prosser-James proposes to employ common salt mixed with pepsin, which he calls j)epiic s.ilt ; and he advocates the use of another preparation composed of the pancreatic ferments and common salt, pancreatic salt] The pancreas of new born children contains trypsin and the fat-decomposing ferment, but not the diastatic one {Zwtifel). \ slight diastatic action is obtained after two months, but the full effect is not obtained until after the first year [Koroivin). IV. The pancreas contains a milk-curdling ferment, which may be extracted by means of a concentrated solution of common salt. 171. THE SECRETION OF THE PANCREATIC JUICE.— Rest and Activity. — .Vs in other glands, we distinguish a quiescent state, during which the gland is soft and pale, and a state of secretory activity, during which the organ swells up and appears pale red. The latter condition only occurs after a ineal, and is caused probably reflexly, owing to stimulation of the nerves of the stomach and duodenum. KUhne and I>ea found that all the lobules of the gland were not active at the same time. The pancreas of the herbivora secretes unin- terruptedly [l)ul in the dog secretion is not constant]. Time of Secretion. — According to Bernstein and Heidenhain, the secretion begins to flow when food is introduced into the stomach, and reaches its maxi- mum 2 to 3 hours thereafter. The amount falls toward the 5th or 7th hour,, and rises again (owing to the entrance of the chyme into the duodenum), toward the Qlh and nth hour, gradually falling toward the 17th to 24th hour, until it ceases completely. When more food is taken, the same process is repeated. As a general rule, a rapidly-formed secretion contains less solids than one formed slowly. Condition of Blood Vessels.— During secretion, the blood vessels behave like the blood vessels of the salivary glands after stimulation of the chorda — they dilate, and the venous blood is bright red— thus, it is probable that a similar nervous mechanism exists [but as yet no such mechanism has been discovered]. The secretion is excreted at a pressure of more than 17 mm. Kg. (rabbit). ' ^ Effect of Nerves.— The nerves arise from the hepatic, splenic, and superior mesenteric plexuses, together with branches from the vagus and sympathetic. The secretion is excited by stimulation of the medulla oblongata, as well as by direct stimulation of the gland itself by induction shocks. [It is not arrested by section of the cervical spinal cord.] The secretion is suppressed by atropin PREPARATION OF PEPTONIZED FOOD 303 Sub-Iobular Vein. Fig. i88. Intra-Iobular Vein. [in the dog, but not the rabbit], by producing vomiting, by stimulation of the central end of the vagus, as well as by stimulation of other sensory nerves, e. g., the crural and sciatic. Extirpation of the nerves accompanying the blood vessels prevents the above-named stimuli from acting. Under these circumstances, a thin "paralytic secretion," with feeble digestive powers, is formed, but its amount is not influenced by the taking of food. [Secretion is excited by the injection of ether into the stomach.] Extirpation of the gland may be performed, or the duct ligatured in animals, without causing any very great change in their nutrition; the absorption of fat from the intestine does not cease. After the duct is ligatured it may be again restored. Ligature of the duct may cause the formation of cysts in the duct and atrophy of the gland substance. Pigeons soon die after this operation. [172. PREPARATION OF PEPTONIZED FOOD.— Peptonized food may be given to patients whose digestion is feeble {Roberts). Food may be pep- tonized either by peptic or tryptic digestion, but the former is not so suitable as the latter, because in pep- tic digestion the grateful odor and taste of the food are destroyed, while bitter by-products are formed, so that pancreatic digestion yields a more palatable and agreeable product. As tryp- sin is destroyed by gastric digestion, obviously it is use- less to give extract of the pancreas to a patient along with his food.] [Peptonized Milk. — "A pint of milk is diluted with a quarter of a pint of water and heated to 60° C. Two or three teaspoonfuls of Ben- ger's liquor pancreaticus, together with 10 or 20 grains of bicarbonate Section of human liver, X 20, showing the liver lobules and the radiate of soda are then mixed therewith." arrangement of their cells from the central or intra-lobular vein. Keep the mixture at 38° C. for about two hours, and then boil it for two or three minutes, which arrests the ferment action.] [Peptonized Gruel, prepared from oatmeal, or any farinaceous food, is more agreeable than peptonized milk, as the bitter flavor does not appear to be developed in the pancreatic digestion of vegetable proteids.] [Peptonized Milk Gruel yielded Roberts the most satisfactory results, as a complete and highly nutritious food for weak digestions. Make a thick gruel from any farinaceous food, e.g., oatmeal, and while still hot add to it an equal volume of cold milk, when the mixtm-e will have a temperature of 52° C. (125° F.). To each pint of this mixture add two or three teaspoonfuls of liquor pancreaticus and 20 grains of bicarbonate of soda. It is kept warm for two hovus under a " cosey." It is then boiled for a few minutes and strained. The bitterness of the digested milk is almost completely cov- ered by the sugar produced during the process.] [Peptonized soups and beef tea have also been made and used with success, and have been adminis- tered both by the mouth and rectum.] [ I 'eptonizing powders containing the proper proportions of ferment and sodic bicarbonate are pre- pared by Benger, and Burroughs and Welcome.] 173. STRUCTURE OF THE LIVER. -The liver, the largest gland in the body, consists of innuinerable small lobules or acini, i to 2 millimetres (t4" to tV i"ch) in diameter. These lobules are visible to the naked eye. All the lobules have the same structure. 304 STRUCTURE OK THE LIVER. 1 The Cosule -The liver is covered by a thin, f.brou.s. tlrmly adherent capsule, which has onitsTrt furFacealaye of en.lothelium derived from the peritoneum. The capsule sends fine «Va int.^Se orea' Jween ,hc lobules, but it is also continued mto the .nter.or at the transverse filTurc where U surrounds the ,K.rtal vein, hepatic artery, and b.le-duct and accompanies these ^ciur."« the capsule of Gl.Uon, or intcr-lobulnr connective tissue 1 he spaces in which hese S^T^c^u cs h/arc- known as portal canals. In some animals (pig, camel, polar hear) the £tSc>a" ".mratoHromenchothcrbytho x.mcwhat lamcll.aled connective tissue of ^'I'^son s cai>- sule but in man this is but sliRhllv ue. but small in amount, is also found w.thm the lobules. Leucocytes are somttinu-s foun.l in the tissue of Cdisson's cai)sulc. . T Blood Ves5els.-(-,) Branches of the Venous System.- 1 Ik- portal vein after its entrar^ce into the liver at the ,x.rtal hssurc, gives off numerous branches lying between the lobules, and ulti- mately fonning small trxmks which reach the periphery of the lobuks. where they form a ncli plexus. These are the inter-lobular veins (Figs. iS8, 189. r,i). I-rom these vems numerous capillaries KiG. 189. 1, Scheme of a liver lobule — K.i, K.;, intcr-lohular veins (port.il) : f-'.c, central or intra-lobular vein (hepatic) ; c,c, capilLiries between both; Ki, sul>-lobular vein ; Kr', vena vascularis; .-J, .4, hepatic artery, giving branches, r, r, to Otiss'in's capsule and the larger vessels, and ultimately forming the venae vasculares at i, i, opening into the intra-lobular capillaries; g, bile ducts; jr, x, intra-lobular biliary channels between the liver cells ; d, d, position of the liver cells between the meshes ot the blood cipillaries. 11, Isolated liver cells — c, a blood capil- lary ; a, fine bile-capillary channel. [c, f) are given off to the entire periphery of the lobule. The capillaries converge tow.ard the centre of the lobule. .\s they proceed inward, they form elongated me.shes, and between the capillaries lie rows or columns of liver cells (uri.rhun«rThe l.vc-r colls arc fi.u-lv ^-ranular an.l ver)- cloudy (P.g. 191) [and contain l.ttle ilmv' n "«. .i^MUcn. Rranules. and' .he nucleus is more frequently absent. Often free nucleoh undV\c nuc ci Ari found (£//r»fi.r,'.r and liou,,,^. Durnig activity. , .after a full meal, licSlv of st^hv foous,K-nd«l the nucleus. .Ml the hepatic cells are not in the same phase of activity at Z'Ll time. Afnna.ssiew finds that if the fonnation of bile m the liver be increa.sed (.. g., by section of .he hemtic nerN-es. or feeling with proteids). the cells are moderately enlarged in size, and contain numeroJ granule., which are pro.eid in their nature; .uch cells resist the action of caus ic potash. When there is a grea. formation of glycogen (as after feeding with potatoes and sugar), all the cells are vrr>- large and sh-oq^lv definc-d, and contain many granules of glycogen, the cells being so large as to compress the cnpillanes. These cells dissolve llurcnfur. Ktinnve ihc liver immediately after death, cut it into tme pieces and pl.nce these in 60,/inP water, and Uil it for some time in order to ohtain a watery extract of the liver. 1 he boiling water destroys the ferment su,,ix.sed to be present in the liver, which wouk transform the glycogen into craiK- suL'.ar To the col.l filtrate are added alternately dilute hydrochloric acid and i^tassio- nu-rcuric i.Kli.le. which precipitates the proteids. Filter, when a clear opalescent fluid, containing the glycogen in solution, is obtained. The glycogen is precipitated from the t.ltrate. as a white amor- nhous'ix.w,ler. on adding an excess of 70 to 80 jx^r cent, alcohol. The precipitate is wa.shed with 60 per cent and afterward with 95 ]xr cent, alcohol, then with ether, and la.stly, with absolute alcohol ; It is dried over sulphuric acid and weighed (Briicke). Kiilz modifies the method somewhat. After Imiling the liver for half an hour, it is rubbed up with liquor jjota-sse ( 100 grms. liver. 4 grms. KHO). Evaporate in the water bath until all is dissolved, which occurs in about 3 hours. After cooling, neu- trali/c with HCl and precii)ilate the i)roteids as alwve. V. Eves a-sserts that iht post-mortem conver- sion of sugar in the liver is not attributable to a ferment action, and the rapid appearance of sugar in the liver after death is due to the siKcific metalx)lic activity of the dying cells.] Sources.— The "mother substance" of the glycogen of the liver has been variously stated to be the carbohydrates of the food {Fa7)y) ; fats (olive oil, Salomon) ; glycerine, taurin, and glycin (the latter splitting into glycogen and urea), the proteids (C/. Bernard) ; and gelatin {Salomon). If it is derived from the albumins, it must be formed from a non-nitrogenous derivative thereof. Rohmann found that the use of ammonia carlx)nate and asparagin or glycin, along with a carbo- hydrate diet, in rabbits considerai)ly increased the formation of glycogen. The excessive formation of acid ol>served by Stadelmann in diabetes unites with the ammonia and diminishes considerably the fonnation of glycogen. Effects of Food. — Rabbits, whose livers have been rendered free from glyco- gen by starvation, yield new glycogen from their livers when they are fed with cane sugar, grape sugar, maltose, or starch. Forced muscular movements soon make the liver of dogs free from glycogen, exposure to cold diminishes its amount. Dextrin and grape sugar occur in the dead liver, but, in addition, some glycogen is found for a considerable time after death in the liver and in the muscles. If glycogen is injected into the l)lood, achroodextrin appears in the urine, and also haemoglobin, as glycogen dissolves red blood corjjuscles. Ligature of the bile duct causes decrease of the glycogen in the liver. Other Situations. — Glycogen is not confined to the liver cells; it occurs during foetal life in all the tissui> of the Irnly of the emlirvo [including ihe eml)rv-onic skeleton], in young animals [A'ii/ine], the placenta 1 Betnard ). [It occurs in large amount in the liver during intra-uterine life.] In the adult it occurs in the testicle, in the muscles ( MacDounel, O. Nasi.e\, in numerous pathological products, in inflamed lungs \ Kiihne\. and also in the corresponding tissues of the lower animals. It also occurs in the chorionic villi, in colorless blood corpuscles, in fre.sh pus cells which .still exhibit amoeboid move- ments, and in fact in all developing animal cells, w ith amrtboid movement ; it is a never failing con- stituent in cartilage, and in the muscles and liver of invertebrata, such as the oyster. There is none in the frc-sh brain of the dog or rabbit, but it is found in the brain in diabetic coma (Abeles)l\ Modifying Conditions. — If large quantities of starch, milk-, fruit-, or cane- sugar, or glycerine, but not mannite, or glycol, or inosite, be added to the pro- teids of the food, the amount of glycogen in the liver is very greatly increased (to 12 per cent, in the fowl), while a purely albuminous or purely fatty diet diminishes it enormously. During hunger it almost disappears. The injection of dissolved carbohydrates into a me.senteric vein of a starving rabbit causes the liver pre- viously free from glycogen to contain glycogen. CHEMICAL COMPOSITION OF THE LIVER CELLS. 309 [Bffect of Drugs. — Arsenic, phosphorus and antimony destroy the glycogenic function of the liver, no glycogen being present in the liver in animals poisoned with these drugs, so that punctiue of the iloor of the fourth ventricle no longer causes glycosuria in them. In animals poisoned by strych- nia or curara, it is greatly diminished, both in the liver and in the muscles. Sugar is always present in the lurine in the latter case but not in the former.] During life, under normal conditions, the glycogen in the liver is either not transformed into grape sugar (^Pavy), or, what is more probable, only a very small amount of it is so changed. The normal amount of sugar in blood is 0.5 to i per 1000, although the blood of the hepatic vein contains somewhat more. A considerable amount is transformed into sugar only when there is a decided derangement of the hepatic circulation, and in these circumstances the blood of the hepatic vein contains more sugar. The glycogen undergoes this change very rapidly after death, so that a liver which has been dead for some time always con- tains more sugar and less glycogen. The diastatic ferment in the liver is small in amount, and can be obtained from the extract of the liver cells by the same means as are applicable for obtain- ing other similar ferments, such as ptyalin ; but it does not seem to be formed within the liver cells, but only passes very rapidly from the blood into them. The ferment seems to be rapidly formed when the blood stream undergoes considerable derangement. A similar ferment is formed when red blood corpuscles are dis- solved (^Tiegel), and, as red blood corpuscles are continually destroyed within the liver, there is one source from which the ferment may be formed, whereby minute quantities of sugar would be continually formed in the liver. According to Seegen, the blood of the hepatic vein contains twice as much sugar (0.23 per cent.) as that in the portal vein (0.II9 per cent.); observations on dogs showed that the blood flowing through the liver gives up over 400 grms. sugar in 24 hours. Hence, in carnivora, the greatest part of the C of the animal food must pass into sugar, .so that the formation of sugar in the liver, and its decomposition in the blood, or in the organs traversed by the blood, must be a very important function of the metabohsm. Seegen is also of opinion that the liver glycogen takes no part in the formation of sugar in the liver. [Blood when perfused through a freshly excised liver (or through the kidneys, lungs, or muscles), gains lactic acid {^G.Agiio and I'Vissokowitsch).'] (3) Fats, in the form of highly refractive granules, occur in the liver cells, as well as free in the bile ducts ; sometimes, when the food contains much fat (more abundant in drunkards and the phthisical), olein, palmatin, stearin, volatile fatty acids, and sarcolactic acid are found. There are also found traces of cholesterin, minute quantities of urea, uric acid, and the little-known body jecorin. [Jecorin, discovered by Drechsel, contains S and P, and reduces alkahne solutions of copper like grape sugar. It is also found in the spleen, muscles, and blood {Baldi). The Hver of birds contains a relatively large amount of uric acid, even 6 to 14 times as much as the blood {v. Sckrcede!').'] [Leucin (Pguanin), sarkin, xanthin, cystin, and tyrosin occur pathologically in certain diseases where marked chemical decompositions occur.] [Fatty Degeneration and Infiltration. — Fatty gi-anules are of common occurrence within the cells of the liver, constituting fatty infiltration, and when not too numerous do not seem to interfere greatly with the functions of the liver cells. Fatty particles occur if too much fatty food be taken, and they are commonly found in the livers of stall-fed animals; t\\e \\e\\-\ino\\'n pdte-de-foi gras is largely composed of the livers of geese, which have been fed on large amounts of farinaceous food, and which have been subjected to other unfavorable hygienic conditions. Fatty granules are recog- nized by their highly refractive appearance, by their solubility in ether, and by being blackened by osmic acid.] (4) The inorganic substances in the human liver are — potassium, sodium, calcium, magnesium, iron, manganese, chlorine, and phosphoric, sulphuric, car- bonic, and silicic acids ; while copper, zinc, lead, mercury, and arsenic may be accidentally deposited in the hepatic tissue. Tizzoni's Reaction. — If a section of a liver (especially of a young animal) hardened in alcohol be treated with a solution of potassic ferrocyanide, and then with dilute hydrochloric acid, as a general rule, the preparation becomes blue, even to the naked eye ; but failing that, one can usually see with the microscope granules of Prussian blue in the protoplasm of the cells, indicating the presence of free iron oxide.] 310 DIADETKS MELI.ITUS AND GLYCOSURIA. 175. DIABETES MELLITUS AND GLYCOSURIA.— [Glycosu- ria IS tharattcri/cd by the presence of grape sugar in the urine. According to Briicke a trace of sugar exists normally in urine, and when this amount is increased we have glycosuria. When the normal amount of grape sugar in the blood is increased, grape sugar appears in the urine. In diabetes mellitus, grape sugar also appears in the urine, but this is really a serious disease, involving the alteration of many tissues, and distinguished by profound disturbance of the whole metabolic activity, which leads to numerous pathological changes and often to death. The appearance of grape sugar in urine does not necessarily mean that a person is suffering tVom this disease.] The formation of large quantities of grape sugar by the liver, and its passage into the blood, and from the blood into the urine, constitute glycosuria. Extirpa- tion of the liver in frogs, or destruction of the hepatic cells, as by fatty degeneration from poisoning with phosphorus or arsenic, does not cause this condition. It occurs for several hours after the injury of a certain part — the centre for the he|)atic vasomotor nerves — of they?^^;^ of the lower part of the fourth ventricle {CI. Bernard's " piqflre ") ; also after section of the vasomotor channels in the spinal cord, from above down as far as the exit of the nerves for the liver, viz., to the lumbar region, and in the frog to the fourth vertebra {Schiff). When the vaso- motor nerves, which proceed from this centre to the liver, are cut or paralyzed in any part of their course, melhturia or glycosuria is produced. All the nerve channels do not run through the spinal cord alone. A number of vasomotor nerves leave the spinal cord higher up, pass into the sympathetic, and thus reach the liver; so that destruction of the superior {Favy), as well as of the inferior cervical sympathetic ganglion, and the first thoracic ganglion {Eckhara) of the abdominal sympathetic, and often of the splanchnic itself produces it. The paralysis of the blood vessels causes the liver to contain much blood, and the intra-hepatic blood stream is slowed. The disturbance of the circulation causes- a great accumulation of sugar in the liver, as the blood ferment has time to act upon the glycogen and transform it into sugar. By stimulation of the sympathetic at the lowest cervical and first thoracic ganglion, the hepatic vessels at the periphery of the liver lobules become contracted and pale {Cyon). It is remarkable that glycosuria when present may be set aside by section of the splanchnic nerves. This is explained by supposing that the enormous dilatation and congestion, or the hyperiumia of the abdominal blood vessels thereby produced, renders the liver anaemic. Continued stimulation of jx-riphcral nen-es may act reflexly w^xyw the centre for the vasomotor nenes of the liver. Dialietes has been observed to occur after stimulation of the central end of the vagus {CI. Bernard), and also after stimulation of the central end of the depressor nerve {Fihhne). Kven section and sul)se<|uent stimulation of the cantral end of the sciatic nerve causes diabetes. This may cxjilain the occurrence of diabetes in people who suffer from sciatica. [It may occur also after perverteil ner%ous activity, a.s psychical excitement, neuralgias (sciatica, trigeminal or occipital), concussion of the brain, as well as after certain injuries to the skull and vertebral column and some Ccrel>ral diseases.] According to Schiff, the stagnation of blood in other vascular regions of the body may cause the fennent to accumulate in the blood to such an extent that diabetes occurs. The glycosuria that occurs after compression of the aorta or portal vein may perhaps be ascribed to this cause, but perhaps. the pressure caused by these procedures may paraly/.e certain nerves. According to Eckhard, injury to the vermiform process of the cerebellum of the rabbit causes diabetes. In man, affections of the atx)ve- named ner%ous regions cause dial>etes. [In most individuals the use of a large quantity of sugar in the food is not followed by the appear- Tr^m „.?>"" '? t """''=• T-^ u*""^ exceptional cases it is often present, e.g., in persons suffering: from gastnc catarrh, especially if they are gouty.] ^ & 1 v s (Ji. ""w*?"" "f P°.'Sons which paralyze the hepatic vasomotor nerves produce diabetes ; curara delDhin^ r 'c^^^T " T- '"^'"'^Td) CO, amyl nitrite, ortho-nitro-propionic acid, and methyl- delphinin ; less certainly morphia, chloral hydrate, IICX, and some other drugs ; [phlorizin [v. Mer- ^ •..•''"V'°'"' '"^''/'""■' "^T-"!'- i^"t congestion of the liver produced in o he? ways appears to cau.e dialx^tes, .. g., after mechanical stimulation of the liver. To this class belongs th J in^e^ction of THE FUNCTIONS OF THE LIVER. 311 dilute saline solutions into tlie blood [Bock, Hoffmann), whereby either the change in form or the solution of the colored blood corpuscles causes the congestion. The circumstance that repeated blood letting makes the blood richer in sugar, may perhaps be explained by the slowing of the circulation. [Most of the means which produce glycosui-ia in other animals fail to do so in birds; even the piqure rarely produces it. This Thiel and Minkowski attribute to the intensely active oxidation processes in birds. Phlorizin causes glycosuria, even after extirpation of the liver, which shows that in these cases there are other causes at work that obtain in the forms of glycosuria.] Phlorizin makes animals which are free from carbohydrates diabetic. In this case the sugar must be derived from proteids [v. Mering ). Theoretical. — In order to explain the more immediate cause of these phenomena several hypo- theses have been advanced : — {a) The liver glycogen may be transformed unhindered into sugar, as the blood in its passage through the liver deposits or gives up the ferment to the liver cells. So that the normal function of the vasomotor system of the liver, and its centre in the floor of the fourth ventricle, may be regarded as, in a certain sense, an " inhibitory system" for the formation of sugar. (3) If we assume that, normally there is continually a small quantity of sugar passing from the liver into the hepatic vein, we might explain the diabetes as due to the disappearance of these decom- positions— diminished burning up of the sugar in the blood, which are constantly removing the sugar from the blood. In fact, diabetic persons have been found to consume less O and to have an increased formation of urea. [Injection of Grape Sugar into the Blood. — ^^^len grape sugar is injected into the jugular vein of a dog, only 33 per cent, at most is given off in the urine ; within 2 to 5 hours the urine is free from sugar. Even within a few minutes after the injection, only a certain proportion (/^-X) <^f ^'^ sugar is found in the blood ; part of the sugar has been detected in the muscles, liver, and kidneys, but the fate of the remainder is not known. Immediately after the injection, the amount of hsemoglobin and also of serum-albumin is diminished (50 per cent.), which is due to increase of the quantity of water within the vessels ; but within two hours the normal state is restored ( Brasol) . In a curarized dog the injection of grape sugar into a vein increase the blood pressure, but this effect is not observed after the injection of morphia and chloral.] Persons suffering from diabetes require a large amount of food ; they suffer greatly from thirst, and drink much fluid. They exhibit signs of marked emaciation, when the loss of the body is gi'eater than the supply. [In advanced diabetes the glycogenic function of the liver is almost abolished, as was proved by removing with a trocar a small part of the liver from man, when almost no glycogen was found {Eh7-lich). The absorbed sugar in the portal vein passes directly into the general circulation without being submitted to the action of the liver [v. Freric/is).'] In severe cases, toward death, not unfrequently a peculiar comatose condition — diabetic coma — occurs, when the breath often has the odor of aceton, which is also fonnd in the urine. But neither aceton nor its precursor, aceto-acetie acid, nor jethyl-diacetic acid, nor the unknown substance, in diabetic urine, which gives the red color with ferric chloride {v. Jakscli), is the cause of the coma [Frerichs and Brieger). 176. THE FUNCTIONS OF THE LIVER.— [To understand the functions of the liver, we must remember its unique relation to the vascular and digestive systems, whereby many of the products of gastric and intestinal digestion have to traverse it before they reach the blood, and some of them as they traverse the liver are altered. We have still much to learn regarding the liver. It has several distinct functions — some obvious, others not. (i) The liver secretes bile, which is formed by the hepatic cells, and leaves the organ by the bile ducts, to pass into the duodenum. (2) The liver cells also form glycogen, which does not pass into the ducts, but in some altered and diffusible form passes into the blood stream, and leaves the liver by the hepatic veins. Hence, the study of the liver materially influences our conception of a secreting organ. In this case, we have the products of its secretory activity leaving it by two different channels — the one by the ducts, and the other by the blood stream. The liver, therefore, is a great storehouse of carbohydrates, and it serves them out to the economy as they are required. All this points to the liver as being an organ intimately related to the general metabolism of the body. (3) In a certain period of development it is concerned in the formation of blood corpuscles (§ 7). (4) It has some relation to the breaking up of blood corpuscles and the forma- tion of urea and other metabolic products (§ 20, § 177, 3). (5) Brunton attributes some importance to the liver in connection with the arrest of certain substances absorbed from the alimentary canal, whereby they are either destroyed, stored up in the liver, or, it may be, prevented from entering the general circula- 312 CONSTITUENTS OF THE BILE. tion in too large amount. It is possible that ptomaines may be arrested in this way (§ 166).] FThr liv,T ha> no special nclion on ccrtnin mineral substances which traverse it in the blood, e. g., •,I..rii^in ( //. AV;v/-j).] 177. CONSTITUENTS OF THE BILE.— Bile is a yellowish-brown or dark grccn-t olorcd transparent fluid, with sweetish, strongly bitter taste, feeble musk-like odor, and neutral reaction. The specific gravity of human bile from the gall bladder = 1026 to 1032, while that from a fistula = 1010 to ion. It contains — (1) Mucus, which gives bile its sticky character, and not unfrequently makes it alkaline ; it is the product of the mucous glands and the goblet cells of the mucous membrane of the larger bile ducts. When bile is exposed to the air, the mucus causes it to putrefy rapidly. It is precipitated by acetic acid or alcohol. [The bile formed in the ultimate bile ducts does not seem to contain mucin or mucus, but bile from the gall bladce.ss is arrested, bilicyanin {llcynsius, Camf>bel!), in acid solution l.lue (in alkaline violet), is obtained, which shows two ill-dehned absoqj- tion bonds near 1) (Jajjf^)- \^v \ • \ \^ t\ yd\ Bilifuscin occurs in small amount in decomposing bile and m gall stones = bilirubm + H^U. (<■) Biliprasin (.V/.Tr/Zt-r) also occurs -- Bilirubin 4- n.p + (J. (/) The v.llow pifjnunt. which ultimately results from the prolonged action of the oxidizing rcnRcnt. is tlie choletelin (C,eH„N,0,) of Maly; it is amoqjhous, and soluble in water, alcohol, aci) Simultaneous ligature of the hepatic artery (diameter, 5^ mm.) and the portal vein (diameter,. 16 mm.) abolishes the secretion i^Rohrig). These two vessels supply the raw material for the secre- tion of bile. (f) If the hepatic artery be ligatxu-ed, the portal vein alone supports the secretion. Ligature of the artery or one of its branches ultimately causes necrosis of the parts supplied by that branch, and eventually of the entire liver, as this artery is the nutrient vessel of the liver. {d) If the branch of the portal vein to one lobe be ligatured, there is only a slight secretion in that lobe, so that the bile must be fonned from the arterial blood. Complete ligature of the portal veia rapidly causes death (| 87). Neither ligature of the hepatic artery by itself, nor gradual obliteration of the portal vein by itself, causes cessation of the secretion, but it is diminished. That sudden ligature of the portal vein causes cessation is due to the fact that, in addition to diminution of the secretion, the enormous stagnation of blood in the rootlets of the portal vein in the abdominal organs makes the liver very anaemic, and thus prevents it from secreting. (if) If the blood of the hepatic artery is allowed to pass into the portal vein (which has been liga- tured on the peripheral side), secretion continues [Sckiff). (/) Profuse loss of blood arrests the secretion of bile before the muscular and nervous apparatus- become paralyzed. A more copious supply of blood to other organs — e.g., to the muscles of the trunk — 310 lULIAKV 1-ISTUIJE. durins viRoroa. exercise, diminishes the secretion, while the transfusion of large quantities of blood incri-aU It. hut if iw hi^h n pressure is caused in the jwrtal vein, by introducuig blood from the caro- tid of anothiT animal, it is diminished. • i i i . IP-) Influence of Nerves.— All conditions which cause contraction of the alxlommal blood vcs-t-ls f ■' simulation of the an>a \ieussenii. of the inferior cervical ganglion, of the hepatic ncr>c>.'of""thc spljinchnics. of the spinal cord (either directly by stiychnia, or reflexly through stimu- lalion of senior)- ner%es). affect the secretion; and so do all conditions which cause stagnation or congestion of the blood in the hepsitic vessels (section of the splanchnic nerves, diabetic puncture, J 175). ■•^-c''"" "f '''*^ cer%ic.il spinal cord. Paralysis (ligature) of the hepatic nerves causes at first an increase of the biliarj- secretion. (*i Portal and Hepatic Veins.— With regard to the raw m.atenal supplied to the liver by its bloo imix.ilaiit to note the dilTerence in the com]K)sition of the blood of the hepatic and portal veins. The bkxxl of the hepatic vein contains more sugar (?), lecithin, cholesterin ^DrosJoff), and blood corjmscles, but less albumin, fibrin, h.-emoglobin, fat, water, and salts. [(«| ltTelm.inn ol)servcd that the flow of bile from a person with a biliary fistula was arrested during fever.] (6) The formation of bile is largely dependent upon the decomposition of red blood corpuscles, as they supply the material necessary for the formation of some of its constituents. Hence, all conditions which cause solution of the colored blood corpuscles are accompanied by an increased fonnaiion of bile ({! iSo). (7) Of course a normal condition of the hepatic cells is required for a normal secretion of bile. Biliary Fistulac. — Tlie mechanism of the biliarv* secretion is .studied in animals by means of biharj' fi-stuKv. Schwann opened the belly by a vertical incision a little to the right of the ensiform process, cut into the fundus of the gall bladder, and sewed its margins to the edges of the wound in the abdomen, and afterward introduced a can- nula into the wound (Fig. 197). To secure that all the bile is discharged externally, tie the com- mon bile duct in two [Maces and divide it between the two ligatures. After a fistula is fj-eshly made the secretion falls. This depends upon the re- moval of the bile from the body. If bile be supplied, the secretion is increased Regenera- tion of the divided bile duct may occur in dogs. V. Wittich observed a bilian,- fistula in man. [A temporar}- biliarj- fistula may also be made. The abdomen is opened in the same way as described above. A long bent gla.ss cannula is introduced and tied into the common bile duct, and the cystic duct is ligatured or clamped (Fig. 197). The tube is brought out through the wound in the al)domen. [Influence of the Liver on Metabolism.— If the liver be excluded from the circulation, important changes must necessarily occur in the metabolism. In birds (the goose) there is an anastomosis l)etween the jx)rtal system of the liver and that of the kidneys, .so that, when the portal circulation IS interrupted m these animals, there is never any great congestion in the abdominal ^■^"m"' r ,r ^"*^ ^"^•' g^"<^'"^"y eight to ten hours after the operation, the uric acid in the urine rapidly falls to a minimum {^ to ^^ of normal); the chief constituent of the urine is then sarcolactic acid, while m normal unne there is none ; the ammonia is increased ( MinkowskiV This experiment goes to indic.ite that unc acid is formed in the liver. Dog.-lf the liver be excluded fiom the portal circulation by connecting the portal vein with the inferior vena cava, and ligaturing the h^atic arter>-. a dog will hve m the former case three to six days, and in the latter one to two. The liver does not undergo necrosis nor does bile cease to be secreted. The liver is nourished by the blood in f^«/ST. 'n"'-1 P / fi"','"u'^" 7'" '^'"S P''^^^'^'y ""-^^^ ^^ ^he respiraton- movements iSr/n.. X fl.i 1 f T ' '^','" ^"^^2'^ ^ ^onmov, of nitrogenous balance, some drugs which increase the flow of bile (^. g., salicylate and benzoate of soda, colchicum, perchloride of mercurv- and wK a ^e,^" Hi'r^t f j^^'^^^'^" «/ ""'^^ •' h^""' ^e Concludes that the formation of urea hi the hver bears a \er>- direct relationship to the secretion of bile (§ 256) ] 179. EXCRETION OF BILE.-[In this connection we must keep in ir„nnn tb 1 "' r'T'u ''' Jhe bile-secreting mechanism depend- ent upon the hver cells, ^vhlch are always in a greater or less degree of acti^vity ; Schwann's permanent fistuLn, and a temporary fistula. .1^/, .ibdominal w.ill : G. I!., gall bladder ; INT., intestine ; T., tube in temporary fistida [Stirling). EXCRETION OF BILE. 317 (2) the bile-expelling mechanism, which is specially active at certain periods of digestion (§ 178). Excretion of bile is due to (i) the continual pressure of the newly-formed bile within the inter-lobular bile ducts forcing onward the bile in the excretory ducts. (2) The interrupted periodic compression of the liver from above, by the diaphragm, at every inspiration. Further, every inspiration assists the flow of blood in the hepatic veins, and every respiratory increase of pressure within the abdomen favors the current in the portal vein. It is probable that the diminution of the secretion of bile, which occurs after bilateral division of the vagi, is to be explained in this way; still, it is to be remembered that the vagus sends branches to the hepatic plexus. It is not decided whether the biliary secretion is diminished after section of the phrenic nerves and paralysis of the abdominal muscles. (3) The contraction of the smooth muscles of the larger bile ducts and the gall bladder. Stimulation of the spinal cord, from which the motor nerves for these structures pass, causes acceleration of the outflow, which is afterward followed by a diminished outflow. Under normal conditions, this stimulation seems to occur reflexly, and is caused by the passage of the ingesta into the duodenum, which, at the same time, excites movement of this part of the intestine. (4) Direct stimulation of the liver, and reflex stimulation of the spinal cord, diminish the excretion ; while extirpation of the hepatic plexus and injury to the floor of the fourth ventricle do not exert any disturbing influence. (5) A relatively small amount of resistance causes bile to stagnate in the bile ducts. Secretion Pressure. — A manometer, tied into the gall bladder of a guinea pig, supports a column of 200 millimetres of water ; and secretion can take place under this pressure. If this pressui-e be increased, or too long sustained, the watery bile passes from the liver into the blood, even to the amount of four times the weight of the liver, thus causing solution of the red blood corpuscles by the absorbed bile ; and very soon thereafter haemoglobin appears in the urine. [This fact is of practical importance, as duodenitis may give rise to symptoms of jaundice, the resistance of the inflamed mucous membrane being sufficient to arrest the outflow of bile.] Passage of Substances into the Bile. — Some substances which enter the blood pass into the bile; especially the metals, copper, arsenic, iron, etc.; potassium iodide, bromide, and sulphocyanide and turpentine ; to a less degree, cane sugar and grape sugar ; sodium sahcylate, and carbohc acid. If a large amount of water be injected into the blood, the bile becomes albuminous ; mercuric and mercurous chlorides cause an increase of the water of the bile. Sugar has been found in the bile in diabetes ; leucin and tyrosin in typhus, lactic acid and albumin in other pathological conditions of this fluid. 180. REABSORPTION OF BILE; JAUNDICE.— I. Absorption Jaundice.— When resistance is offered to the outflow of bile into the intestine, e. g., by a plug of mucus, or a gall stone which occludes the bile duct, or where a tumor or pressure from without makes it impervious — the bile ducts become filled with bile and cause an enlargement of the liver. The pressure within the bile ducts is increased. As soon as the pressure has reached a certain amount, which it soon does when the bile duct is occluded (in the dog 275 mm. of a column of bile), reabsorption of bile from the distended larger bile ducts takes place into the lymphatics (not the blood vessels) of the liver, the bile acids pass into the lymphatics of the liver. [The lymphatics can be seen at the portal fissure filled with yellow-colored lymph.] The lymph passes into the thoracic duct, and so into the blood (yFleischl). Even when the pressure is very low within the portal vein, bile may pass into the blood without any obstruction to the bile duct being present. This is the case in Icterus neonatorum, as after ligature of the umbilical cord no more blood passes through the umbilical vein ; further, in the icterus of hunger, " hunger jaundice" as the portal vein is relatively empty, owing to the feeble absorption from the intestinal canal (C/. Bernard). II. Cholsemia may also occur, owing to the excessive production of bile (hypercholia), the bile not being all excreted into the intestine, so that part of it is reabsorbed. This takes place when there is solution of a great number of blood corpsucles (^ 178, 6), which yield material for the formation of bile. Thick, inspissated bile accumulates in the bile ducts, so that stagnation, with subsequent reabsorption of the bile, takes place. The tranfusion of heterogeneous blood obtained by dissolving colored blood corpuscles acts in this direction. Icterus is a common phenomenon after too copious transfiision of the same blood. The blood corpuscles are dissolved by the injection into the blood of heterogeneous blood serum, by the injection of bile acids into the vessels, and by other salts, by 318 REABSORPTION OF BILE; JAUNDICE. phosphoric acid, water, chloral, inhalation of chloroform and ether; the injection of dissolved Lvni. vlol-in into thf artcrios or into a loop of the small intestine acts m the same way. Icterus Neonatorum.— WhtM). owinj,' to compression of the placenta withm the uterus, too much bUxxl IS fi.rced into the l-lootl vessels of the newly-horn infant, a part of the surplus blood durmg the fir.t few days becomes dissolved, part of the hemoglobin is converted nito bilirubin, thus causing iauiulice ( I'irihow, I'io/ft). Absorption Jaundice.— When the jaundice is caused by the absorption of bile already formed in the liver, it is called hepatogenic or absorption jaundice. The following are the symptoms : — (1) Hile pij^nents and bile .acids pxss into the tissues of the body; hence, the most pronounced external symptom is the yellowish tint o\ jaundice. The skin and the sclerotic become deeply colored yellow. In pregn.incy the fietus is also tinged. (2) Hile pigments aiid bile acids pass into the urine (not into the saliva, tears, or mucus) (^ 177). When there is much bile pigment, the urine is colored a deep yellowish brown, and its froth is citron yellow ; while strijjs of gelatin or paper dipped into it also become colored. Occasionally bilirubin (= h.x-matoidin) crystals occur in the urine (ly, partly owing to the hardness of the f.vces, partly because of the absence of the ]>eristaltic movements of the intestine, owing to the want of the stimulating action of the bile. (4) The heart beats are greatly diminished, e.g., to 40 per minute. This is due to the action of the bile salts, which at first slimul.ate the cardiac ganglia, and then weaken them Bile salts injected into the heart produce at first a lemix)rar)" acceleration of the pulse, and afterward slowing (R'ohrig). The same occurs when they are injected into the blood, but in this case the stage of excitement is ver>- short. The jihenomenon is not affected by section of the vagi. It is probable, that when the action of the bile salts is long continued, they act upon the heart nuiscle. In addition to the action on the heart, there is slowing of the respiration and diminution of temperature. (5) That the nervous system, and perhaps also the muscles, are affected, either by the bile salts or by the accumulation of cholesterin in the blood, is shown by the very general relaxation, sensation of fatigue, weakness, drowsiness, and lastly, deep coma — sometimes there is sleeplessness, itchiness of the skin, even mania, and spasms. Luwit, after injecting bile into animals, observed phenomena referable to stimulation of the respirator)-, cardio-inhibitory, and vasomotor nerve centres. (6) In very pronounced jaundice there may be '' yello7v vision,'' owing to the impregnation of the retina and macula lutea with the bile pigment. (7) The bile acids in the blood dissolve the red blood corpuscles. The haemoglobin is changed into new bile pigment, and the globulin-like Ixidy of the haemoglobin may form urinary cylinders or casts in the urin.ary tui)ules, which are ultimately washed out of the tubules by the urine. [Influence of Drugs on the Secretion of Bile. — On animals one may make either a perma- nent or a temiHirary fistula. Tlie latter is the more satisfactory method, and the experiments are u^ually m.ide on fasting curarized dogs. .\ suitable cannula is introduced into the common bile duct ' '■'g- '971. the animal is curarized, artificial respiration being kept up, while the drug is injected into the stom.ach or intestine. Rohrig used this method, which was improved by Rutherford and Vignal. Rohrig found that some purgatives, croton oil, colocynth, jalap, aloes, rhubarb, senna, and other .substances, increased the secretion of bile. Rutherford and Vignal investigated the action of a large niimber of drugs on the bile-secreting mechanism. They found that croton oil is a feeble hepatic stimulant, while jxKlophyllin. aloes, colchicum, euonj-min, iridin, sanguinarin, ipecacuan, colocynth, sodium phosphate, phytolaccin, sodium benzoate, sodium salicylate, dilute nitro-hydrochloric acid ammonium phos,)hate, mercuric chloride (corrosive sublimate), are all powerful, or very considerable, hepatic stimulants Some substances stimulate the intestinal glands, but not the liver, e. r., magnesium sulphate, castor oil, gamboge, ammonium chloride, manganese sulphate, calomel. Other substances stimulate the liver as well as the intestinal glands, although not to the same extent, e. -., scammony (powerful intestinal, feeble hepatic stimulam); colocynth excites both powerflillv; jalap, sodium sulphate, and baptism, act with considerable power lx)th on the liver and the intestinal glands. Calabar l.ean stimulates the liver, and the increased secretion caused thereby may be reduced by sulphate of atropin. although the latter drug, when given alone, does not notably affect the secretion was nroHn?.H 'IT 1 " TV T " "\'^^'^^' '''?^'^'''' '^^ ^"'^^^''°"- ^" ^" ^^^^ ^'^ere purgation T'^^rtZlJir -A ■'fA''T^''T' T^ "' niagnesium sulphate, gamboge, and castor oil, ofZTZ.ll Itf, 7'"r 1 ^" ^" ^"^h e^lf i-^ents it is most important that the temf^erature t^^LrZ^Lti^ Yi. .K V^%^^^'-,^''°" °f bile diminishes. Paschkis's results on dogs differ considerablj fi^om those of Rutherford Me asserts that only the bile acids (salts) of all the substances he mvestigated excite a prompt and distinct cholagogue action.] suosiances FUNCTIONS OF THE BILE. 319 [As yet we cannot say definitely whether or not these substances stimulate the secretion of bile, by exciting the mucous membrane of the small intestine, and thereby inducing reflex excitement of the liver. Their action does not seem to be due to increase of the blood stream through the liver. More probably, as Rutherford suggests, these drugs act directly on the hepatic cells or their nerves. Acetate of lead directly depresses the biliary secretion, while some substances affect it indirectly.] [Cholesteraemia. — Flint ascribes great importance to the excretion of cholesterin by the bile, with reference to the metabolism of the nervous system. Cholesterin, which is a normal ingredient of nervous tissue, is excreted by the bile; and if it be retained in the blood " cholesteroemia," with grave nervous symptoms, is said to occur. This, however, is problematical, and the phenomena described are probably referable to the retention of the bile acids in the blood.] i8i. FUNCTIONS OF THE BILE.— [(i) Bile is concerned in the digestion of certain food stuffs; (2) part is absorbed; (3) part is excreted.] (A) Bile plays an important part in the absorption of fats : — (i) It eniulsionizes neutral fats, whereby the fatty granules pass more readily through or between the cylindrical epithelium of the small intestine into the lacteals. It does not decompose neutral fats into glycerine and a fatty acid, as the pancreas does (§ 170, III). When, however, fatty acids are dissolved in the bile, the bile salts are decomposed, the bile acids being set free, while the soda of the decomposed bile salts readily forms a soluble soap with the fatty acids. These soaps are soluble in the bile, and increase considerably the emulsifying power of this fluid. Bile can dissolve fatty acids to form an acid fluid, which has high emulsionizing properties i^Steiner). Emulsification is influenced by a i per cent, solution of NaCl, or Na^SO^. (2) As fluid fat flows more easily through capillary tubes moistened with bile, it is concluded that when the pores of the wall of the small intestine are moistened with bile, the fatty particles pass more easily through them. (3) Filtration of fat takes place through a membrane moistened with bile or bile salts under less pressure than when it is moistened with water or salt solution {y. Wistinghausen) . (4) As bile, like a solution of soap, has a certain relation to watery solutions, as well as to fats, it permits diffusion to take place between these two fluids, as the membrane is moistened by both fluids. It is clear, therefore, that the bile is of great importance in the absorption of fats. This is strikingly illustrated by experiments on animals, in which the bile is entirely discharged externally through a fistula. Dogs, under these conditions, absorbed at most 40 per cent, of the fat taken with the food [60 per cent, being given off by the faeces, while a normal dog absorbs 99 per cent, of the fat]. The chyle of such animals is very poor in fat, is not white but transparent ; the f^ces, however, contain much fat, and are oily ; the animals have a ravenous appetite ; the tissues of the body contain little fat, even when the nutrition of the animals has not been much interfered with. Persons suff"ering from disturbances of the biliary secretion, or from liver affections, ought, therefore, to abstain from fatty food. [The digestion of flesh and gelatin is not interfered with in dogs by the removal of the bile [v. Voit).'] (B) Fresh bile contains a diastatic ferment, which transforms starch into sugar, and also glycogen into sugar. (C) Bile excites contractions of the muscular coats of the intestine, and contributes thereby to absorption. (i) The bile acids act as a stimulus to the muscles of the villi, which contract from time to time, so that the contents of the origins of the lacteals are emptied toward the larger lymphatics, and the villi are thus in a position to absorb more. [The villi act like numerous small pumps, and expel their contents, which are prevented from returning by the presence of valves in the larger lymphatics.] (2) The musculature of the intestine itself seems to be excited, pei'haps thi-ough the agency of the plexus myentericus. In animals with a biliary fistula, and in which the bile duct is obstructed, the intestinal peristalsis is greatly diminished, while the salts of the bile acids administered by the mouth causes diarrhoea and vomiting. As contraction of the intestine aids absorption, bile is also necessary in this way for the absorption of the dissolved food stuffs. (D) The presence of bile seems to be necessary to the vital activity of the intes- tinal epithelium in its supposed function of being concerned in the absorption of fatty particles (§ 190). (E) Bile moistens the wall of the intestines, and gives to the faeces their normal 320 FATE OF THE BILE. amount of water, so that they can be readily evacuated. Anirnals with biliary fistula, or persons with obstruction of the bile ducts, are very costive. The mucus aids the forward nvnement of the ingesta through the intestinal canal. [Thus, in a certain sense, bile is a natural pur^^aiii'e.'\ (F) The bile diminishes i)utrefactive decomposition of the intestinal contents, esjKJcially with a fatty diet, § 190. [Thus, it is an antiseptic, although this is doubted by v. Voit.] (G) When the strongly acid contents of the stomach pass into the duodenum, the glycocholic acid is ])recipitated by the gastric acid, and carries the pepsin with it (Burkart). Some of the albumin, which has been simply dissolved (but not peptone or propeptone), is also precipitated, by the taurocholic acid {Maly and Emiih). The bile salts are decomposed by the acid of the gastric juice. When the mixture is rendered alkaline by the pancreatic juice and the alkali derived from the decomposition of the bile salts, the pancreatic juice acts energetically in this alkaline medium i^Molescholt). [Taurocholic .ncid .iml its soda salts precipitate alliuniin, i)ut not peptone; glycocholic acid does not precipitate albumin, so that in the intestine the peptone is separated from the albumin (and s)Titonini. and m.iy therefore be more readily absorbed, while the precipitate adhering to the intestinal wall can Ik; further digested {Maly ami Emith). Taurocholic acid behaves in the same way toward gelatin ]H-ptone.] Bilious Vomit. — When bile passes into the stomach, as in vomitittg, the acid of the gastric juice unites with the b.ises of the bile salts; scnlium chloride and free bile acids are formed, and the acid reaction is thereby somewhat iliminished. The bile acids cannot carrv' on gastric digestion; the neutralization alx) causes a precipitation of the jjepsin and mucin. As soon, however, as the walls of the stonunch secrete more acid, the pejjsin is redissolved. The bile which passes into the stomach deranges ga.stric e-Seyler uses it as a good source whence to obtain this pigment It gives a spectrum of a Uxly rilati-rought together with sutures, so as to establish the continuity of the intestinal canal (Fig. 201, 2). The excised piece of intestine yields a secretion which is uncontaminated with any other digestive Fir.. 19Q. Cavity of the gland. Fig. 200. — Crypt. Glandular epithelium. I'lood vessel. TransvcHc section of Lieberkiihn's follicles. Fig. 201. Abd Abd Abd Abd Lieberkahn's gland from the large intestine (dog). Scheme of Thiry's Fistula, i, 2, 3, 4, Vella's Fistula. AA'are stitched together ; Ait/, Abdominal wall (Stirling). secretion [Thiry's method is N-x;ry unsatisfactory, as judged from the action of the separated loop in [^juTd".!; i"Smration:r ^"^ °""' '^ '^^ '"""" "'"'''"' '"^"'"^ ^'™P''^' '^°"^ "'^^ ' °^ rlTr^^ ^^""'f. "'f'^y " ""''". °P^"'"^ '" '^^ intestine, through which he introduces two small collapsed md.a-rubber balls, one above and the other below the opening, which are then distended by mflatton unt.I they comp leely block a certain length of the intis'ine.^ The loop thus blocked off havmg l>een previously well wa.shed out, is allowed to become filled with succus, wh ch is ecretedvfn the apphcation of vanous st.muh. By means of Bernard's gastric cannula (2 165) 'nserted ntrthe fistula m the loop, the secretion can be removed when desired 1 ^ msenea mio tne ^t'^'"*'^ ^■".'""^^--^l^" the belly of a dog, and pull out a loop (30 to 50 ctm Ul to l^ feetl Ir^tin SU cTl fenT o^ tf f ' ^'°^^ ^"' '^'°^^'' --^=^'''^h the cLSn'/y'^of .h^reS ol ^Vh.^u ■ r • ^ ^^^ '°°P ""^ '"testme into the wound in ihe linea alba ( Fi^ 201 4> a'ndtwtTpi^ir'eT '"""^ ^"'^ '"^ '^ " '^^^^ ^^^^^^^ ^"'^ "^^^-' '^^'^'^"^ and S a^ip^e^; ACTIONS OF THE INTESTINAL JUICE. 323 The intestinal juice of such fistulse flows spontaneously in very small amount, and is increased during digestion ; it is increased — especially its mucus — by mechanical, chemical, and electrical stimuli ; at the same time, the mucous mem- brane becomes red, so that loo centimetres yield 13 to 18 grammes of this juice in an hour {Thiry). The juice is light yellow, opalescent, thin, strongly alkaline, specific gravity loii, evolves CO2 when an acid is added; it contains albumin, ferments, and mucin — especially the juice of the large intestine. Its composition is — water, 97,59; proteids, 0.80; other organic substances ^ 0.73 ; salts, 0.88 per cent. ; among these, sodium carbonate, 0.32 to 0.34 per cent. [The intestinal juice obtained by Meade Smith's method contained only 0.39 per cent, of organic matter, and in this respect agreed closely with the juice which A. Moreau procured by dividing the mesenteric nerves of a ligatured loop of intestine. The secretion of the large intestine is much more viscid than that of the small intestine,] Actions of Succus Entericus. — It is most active in the dog, and in other animals it is more or less inactive, (i) It is less diastatic than the saliva and the pancreatic juice, but it does not form maltose ; while the juice of the large intestine does not possess this property {Eichhorst). (2) It converts maltose into grape sugar. It seems, therefore, to continue the diastatic action of saliva (§ 148) and pancreatic juice (§ 170), which usually form only maltose. According to Bourquelot this action is due to the intestinal schizomycetes and not to the intestinal juice as such, the saliva, gastric juice or invertin. The greater part of the maltose appears, however, to be absorbed imchanged. (3) Fibrin is slowly (by the trypsin and pepsin — Kuhne) peptoni-zed {Thiry, Leube); less easily albumin {Masioff), fresh casein, flesh raw or cooked, vegetable albumin ; probably gelatin also is changed by a special ferment into a solution which does not gelatinize (^Eichhorst). (4) Fats are only partly emulsionized {Schijff^,2ind afterward decomposed ( Vella). (5) According to CI. Bernard, invertin occurs in intestinal juice (this ferment can also be extracted from yeast). It causes cane sugar (C12H22O11) to take up water (-f- H^O), and converts it into invert-sugar, which is a mixture of left- rotating sugar (laevulose, CgHijOe) and of grape sugar (dextrose, CgHijOg). Heat seems to be absorbed during the process. [Hoppe-Seyler has suggested that this ferment is not a natural product of the body, but is intro- duced from without with the food. Matthew Hay, however, finds it to be invariably present in the small intestine of the foetus. ] [Effect of Drugs. — The subcutaneous injection of pilocarpin causes the mucous membrane of a Vella's fistula to be congested, when a strongly alkaline, opalescent, watery, and shghtly albuminous secretion is obtained. This secretion produces a reducing sugar, converts cane sugar into invert-sugar, emulsifies neutral fats, ultimately spiriting them up, peptonizes proteids, and coagulates milk, even although I he milk be alkaline. The juice attacks the sarcous substance of muscle before the connective tissues — the reverse of the gastric juice. The mucous membrane in a Vella's fistula does not atrophy. K. B. Lehmann finds that the succus entericus obtained from the intestine of a goat by a Vella fistula has no digestive action.] The Action of Nerves on the secretion of the intestinal juice ^ is not well determined. Section or stimulation of the vagi has no apparent effect; while extirpation of the large sympathetic abdom- inal ganglia causes the intestinal canal to be filled with a watery fluid, and gives rise to diarrhoea. This may be explained by the paralysis of the vasomotor nerves, and also by the section of large lymphatic ves- sels during the operation, whereby absorption is interfered with and transudation is favored. Moreau's Experiment. — Moreau placed four ligatures on a loop of intestine at equal distances fi-om each other (tig. 202). The ligatures were tied so that three loops of intestine were shut off. The nerves (N) to the middle loop were divided, and the intestine was replaced in the abdominal cavity. After a time. Scheme of Moreau's experiment a very small amount of secretion, or none at all, was found in two of the ligatured compartments of the gut, i. e., in those with the nerves and blood vessels intact (l, 3), 324 FERMENTATION IN THE INTESTINE. hut the comiwrtineiil (2) whose nerves had l>ecn divided contained a watery secretion. Perhaps the secretion which iKCurs after section of the inesenteiic nerves is a paralytic secretion, 'llie secretion of the intestinal and (,'astric juices is diminished in man in certain nervous afiections (hysteria, hypo- chondria-si-, and various cerebral diseases) ; while in other conditions these .secretions are increased. Excretion of Drugs.— If an isolated intestinal fistula he made, and variousdrugs administered, the mucous m.nii)rane excretes ioi>sin; while the dijistatic and i>eptic ferments of the pancre.as disajjpear under the intluence of the acid ffrnuntalion in the large intestine.] 184. FERMENTATION IN THE INTESTINE.— Those processes whi< h are to be regarded as fermentations or putrefactive processes, are quite dif- ferent from tliose caused by the digestive enzymes or ferments just considered. The putrefactive changes are connected with the presence of lower organisms, so-called fermentation or putrefaction producers ; and they may develop in suitable media outside the body. The lowly organisms which cause the intestinal fermentation are swallowed with the food and drink, and also with the saliva. When they are introduced, fermentation and putrefaction begin, and gases are ei'olvci. Intestinal Gases. — During the whole of the foetal period, until birth, fermentation cannot occur; hence gases are never present in the intestine of the newly-born. The first air bubbles pass into the intestine with the saliva which is swallowed, even before food has been taken. The germs of organisms are thus introduced into the intestine, and give rise to the formation of gases. The evolu- tion of intestinal gases goes hand-in-hand with the fermentations. Air is also swallowed, and an exchange of gases takes place in the intestine, so that the composition of the intestinal gases depends upon various conditions. Kolbe and Ruge collected the gases from the anus of a man, and found in 100 vols. : — Food. CO,. H. CH4. N. HjS. Milk nesh, .... Peas, .... 1 6.8 12.4 21.0 43-3 2.1 4-0 0.9 275 55-9 38.3 57-8 18.9 Quantity not estimated. 1. Air bubbles are swallowed with the food. The O is rapidly absorbed in the intestinal tract, so that in the lower part of the large intestine, even traces of O are absent. In exchange, the blood vessels in the intestinal wall give off CO, into the intestine, so that part of the CO^ in the intestine is driven by diffusion from the blood. 2. H, CO-i, NH3, and CH« are also formed from the intestinal contents by fermentation, which takes place even in the small intestine. Fungi.— The chief agents in the prwluciion of fermentations, ]nitrefaction and other similar decom- poMtions are undoubtedly the group of fungi called schizomycetes. They are small unicellular organisms of various fonn.s— globular, micrococcus ; short rods, bacterium'; long rods, bacillus ; or spiral thread.s. vibno, spirillum, spirochaeta (Fig. 23). The mode of reproduction is by division, and they may either remain single or unite to form colonies. Each organism is usually capable of some degree o motion 1 hey pro6 FERMENTATION OF PROTEIDS. This fungus (Fig. 203, B) is a true anxrohc, and grows only in the absence of O. The lactic acid fungus u-scs O very largely, and is, therefore, its natural precursor. The butyric acid fermentation is the last ch-ingc undergone by many carbohydrates, especially by starch and inulin. It takes place constantly in the feces. (3) Certain micrococci cause alcohol X.o be formed from carbohydrates. The presence of yeast may cause the formation of alcohol in the intestine, and in both cases also from milk sugar, which first becomes changed into dextrose. (4) Bacterium aceti (Fig. 203, A) converts alcohol into acetic acid outside the body. Alcohol (C,H,0) 4- O = CjH^O (Aldehyd) + II.p. Acetic acid (QII^Oj) is formed from aldehyd by oxidation. .According to NSgeli, the same fungus causes the formation of a small amount of CO^ and H,0. As the acetic fermentation is arrested at 35° C, this fermentation cannot occur in the intestine, and the acetic acid, which is constantly found in the faces, must be derived from another source. During putrefaction of the protcids, with exclusion of air, acetic acid is produced {Nencki). (5) Starch and cellulose are partly dissolved by the schizomycetes (Bac. butyricus and Vibrio rugula) of the intestine. If cellulose be mixed with cloaca! mucus, or with the contents of the intestine, it passes into a saccharine carbo- hydrate which decomposes into equal volumes of CO2 and CH4 {^Hoppe-Seyler). (6) P\mgi, whose nature is unknown, can partly transform starch (? and cellu- lose) into sugar. (7) Others produce invertin. Invertin changes cane sugar into invert-sugar Fig. 204. Bacillut tMbtilis. 1, spore ; a, 3, 4, its germination ; 5, 6. short rods ; 7, jointed thread, with the formation of spores in e.ich segment ; 8, short rods, some of them containing spores ; 9, spores in single short rods; 10, fungus with a C§ 183, II, 5). Cane sugar, Cj.H^^O.i + H,0 = CeHi.Os (Dextrose) + CeHj^Os (Lnevulose). II. Fermentation of Fats (§ 251). During putrefaction, organisms of an unknown nature cause neutral fats to take up water and split into glycerine and their corresponding fatty acid (§ 170). Glycerine is capable of undergoing several fermentations, according to the fungus which acts upon it (§ 251). With a neutral reaction, in addition to succinic acid, a number of fatty acids, H and CO,, are formed. Fitz found that the hay bacillus (Bacillus subtilis, Fig. 204) formed alcohol with caproic, butyric, and acetic acids; in other cases, especially butylic alcohol, van de Velde found butyric, lactic, and traces of succinic acid with CO5, HjO, N. The fatty acids, especially as chalk soaps, form an excellent material for termentation Calcium formiate mixed with cloacal mucus ferments and yields calcium carbonate, CO, and H ; calcium acetate, under the same conditions. produces calcium carbonate, CO., and CH, Among the oxy-acids, we are acnuainted with the fermentations of lactic, glycerinic, malic, tartaric, and citric acids. Accor^ng to Fitz^^^/. ^«^ (in combination with chalk) produces propionic and acetic acids, CO,. H,0. Other ferments cause the formation of valerianic acid. Glycerinic acid, in addition to REACTIONS FOR INDOL. 327 alcohol and succinic acid, yields chiefly acetic acid ; malic acid forms succinic and acetic acid. The other acids above enumerated yield somewhat similar products. III. Fermentation of Proteids (§ 249). — The undigested proteids and their derivatives appear to be acted upon by fungi. Many schizomycetes (hay bacillus and Bac. subtilis), however, can produce a peptonizing ferment. We have already seen that pancreatic digestion acts upon the proteids, forming, among other products, amido-acids, leucin, tyrosin, and other bodies (§ 170, II). Under normal conditions, this is the greatest decomposition produced by the pancreatic juice. The putrefactive fermentation of the large intestine causes further and more profound decompositions. Leucin (CgHigNOj) takes up two molecules of water and yields valerianic acid (C5H10O2), ammonia, CO2 and 2(112) 'i glycin behaves in a similar manner. Tyrosin (CgHuNOg) is decom- posed into indol (CgH^N), which is constantly present in the intestine along with COjjHaO,!!. If O be present, other decompositions take place. These putrefactive products are absent from the intestinal canal of the foetus and the newly-born. During the putrefactive decomposition of proteids, CO2, HjS, H, and CH4, are formed ; the same result is obtained by boiling them with alkalies. Gelatin, under the same conditions, yields much leucin and ammonia, CO2, acetic, butyric, and valerianic acids, and glycin. Mucin and nuclein undergo no change. Artificial pancreatic digestion experiments rapidly tend to undergo putrefaction. The substance which causes the peculiar fecal odor is produced by putrefaction, but its nature is not known. It clings so firmly to indol and skatol that these substances were formerly regarded as the odorous bodies, but when they are prepared pure they are odorless [Bayer). Among the solid substances in the large intestine formed only by putrefaction is indol (CsHtN), a substance which is also formed when proteids are heated with alkalies, or by superheating them with water to 200° C. It is the stage preceding the indican in the urine. If the products of the digestion of the proteids — the peptones — are rapidly absorbed, there is only a slight formation of indol ; but when absorption is slight, and putrefaction of the products of pancreatic diges- tion occurs, much indol is formed, and indican appears in the urine. Jaffe found much indican in the urine in strangulated hernia, and when the small intestine was obstructed. Reactions for Indol. — Acidulate strongly with HCl, and shake vigorously after adding a few drops of turpentine. If there be an intense red color, the pigment is removed by ether. The sub- stance which is formed after the digestion of fibrin by trypsin, and which gives a violet color with bromine water (§ 170, 2), can be removed by chloroform. In addition to the last pigment, there is a second one, which passes over during distillation, and which can be extracted from the distillate by ether. Both substances seem to belong to the indigo group [Krukenberg). A. Bayer prepared indigo-blue artificially from ortho-phenyl-propionic acid, by boiling it with dilute caustic soda, after the addition of a little grape sugar. He obtained indol and skatol from indigo- blue. Hoppe-Seyler found that on feeding rabbits with ortho-nitrophenyl -propionic acid, much indican was present in the urine. Phenol (CgHgO) is formed during putrefaction in the intestine, and it is also formed when fibrin and pancreatic juice putrefy outside the body, while Brieger found it constantly in the faeces. It seems to be increased by the same circum- stances that increase indol, as an excess of indican in the urine is accompanied by an increase of phenylsulphonic acid in that fluid (§ 262). From putrefying flesh and fibrin, amido-phenylpropionic acid is obtained, as a decomposition pro- duct of tyrosin. A part of this is transformed by putrefactive ferments into hydrocinnamic acid (phenylpropionic acid). The latter is completely oxidized in the body into benzoic acid, and appears as hippuric acid in the urine. Thus is explained the formation of hippuric acid from a purely albu- minous diet; Skatol (C9H9N = methyl-indol) is a constant human fecal substance, and has been prepared artificially by Nencki and Secretan from egg albumin, by allowing 323 PROCESSES IN THE LARGE INTESTINE. it to putrefy for a long time under water. It also appears in the urine as a sulphur compound. The excretin of human fceces, described by Marcet, is related to cholcsterin, but its history and constitution are unknown. According to Salkowski. skntol and indol arc both formed from a common substance which exists preformed in albumin, and which, when it is decomposed, at one time yields more indol, at another skatol, nccordinj; a.s the h>pothctical " indol fungus," or '' skatol fungus;' is the more abundant. It is of the Utmost importance, in connection with the processes of putrefaction, to determine whether they take place when oxygen is excluded, or not. When O is absent, reductions take place ; oxy-acids are reduced to fatty acids, and H,CH^ and H,S are formed : while the H may produce further reductions. If O be present, the nascent H separates the molecule of free ordinary oxygen (= O,) into two atoms of active oxygen (r=r O). Water is formed on the one hand, while the second atom of O is a powerful oxidizing agent {Hoppe-Sey/er). It is remarkable that the putrefactive processes, after the development of phenol, indol, skatol, crcsol. phcnvlpropionic and phenylacctic acids are subsequently limited, and after a certain concentra- tion is rcacheii, they ccuse altogether. The putrefactive process produces antiseptic substances which kill the micro orjjanisms, so we may assume that these substances limit to a certain extent the putrefac- tive processes in the intestine. The reaction of the intestine immediately below the stomach is acid, but the pancreatic and intestinal juices cause a neutral and afterward an alkaline reaction, which obtains along the whole small intestine. In the large intestine, the reaction is generally acid, on account of the acid fermentation and the decomposition of the ingesta and the fceces. 185. PROCESSES IN THE LARGE INTESTINE.— Within the large intestine, the fermentative and putrefactive ])rocesses are certainly more prominent than the digestive processes proper, as only a very small amount of the intestinal juice is found in it. The absorptive function of the large intestine is greater than its secretory function, for at the beginning of the colon its contents are thin and watery, but in the further course of the intestine they become more solid. Water and the products of digestion in the solution are not the only sub- stances absorbed, but under certain circumstances, unchanged fluid egg albumin, milk and its proteids, flesh juice, solution of gelatin, myosin with common salt, may also be absorbed. Experiments with acid albumin, syntonin, or blood serum gave no result. Toxic substances are certainly absorbed more rapidly than from the stornach. [In the dog the secretion of the large intestine has no digestive properties, but tats are absorbed in it. Klug and Koreck regard its Lieberkuhnian glands not as secreting but as absorbing structures.] The fecal matters are formed or rather shaped in the lower part of the gut. The cKcum of many animals, e. ,«,-., rabbit, is of considerable size, and in it fermentation seems to occur with considerable energy, giving rise to an acid reaction. In man, the chief function of the caecum is absorption, as is shown by the great number of lymphat- ics m Its walls. From the lower part of the small intestine and the csecum onward, the ingesta assume the fecal odor. The amount of faeces is about [5 oz. or] 170 grms. (60 to 250 grms.) in twenty-four hours ; but if much indigestible food be taken, it may be as much as 500 grms. The amount is less, and the absolute amount of solids is less, after a diet of flesh and albumin, than after a vegetable diet. The fsces are rendered lighter by the evolution of gases, and hence they float in water. The consistence depends on the amount of water present— usually about 75 per cent I he amount of water depends partly on the food— pure flesh diet causes relatively dry faeces, while substances rich in sugar yield f^ces with a rela- tively large amount of water. The quantity of water taken has no effect upon the amount of water in the faeces. But the energy of the peristalsis has. The more energetic the peristalsis is, the more watery the faeces are, because sufficient COMPOSITION OF THE F^CES. 329 time is not allowed for absorption of the fluid from the ingesta. Paralysis of the blood and lymph vessels, or section of the nerves, leads to a watery condition of the faeces (§ 183"). The reaction is often acid, in consequence of lactic acid being developed from the carbohydrates of the food. Numerous other acids produced by putrefaction are also present (§ 184). If much ammonia be formed in the lower part of the intestine, a neutral or even alkaline reaction may obtain. A copious secretion of mucus favors the occurrence of a neutral reaction. The odor, which is stronger after a flesh diet than after a vegetable diet, is caused by some fecal products of putrefaction, which have not yet been isolated ; also by volatile fatty acids and by sulphuretted hydrogen, when it is present. The color of the faeces depends upon the amount of altered bile pigments mixed with them, whereby a bright yellow to a dark brown color is obtained. The color of the food is also of importance. If much blood be present in the food, the fseces are almost brownish- black, from hamatin ; green vegetables = brownish-green, from chlorophyll ; bones {dog) = white, from the amount of lime ; preparations of iron =^ black, from the formation of sulphide of iron. The faeces contain — (i) The unchanged residue of animal or vegetable tissues used as food ; hairs, horny and elastic tissues ; most of the cellulose, woody fibres, spiral vessels of vegetable cells, gums. (2) Portions of digestible substances, especially when these have been taken in too large amount, or when they have not been sufficiently broken up by chewing. Portions of muscular fibres, ham, tendon, cartilage, particles of fat, coagulated albumin — vegetable cells from potatoes, and other vegetables, raw starch, etc. All food yields a certain amount of residue — white bread, 3.7 per cent. ; rice, 4. 1 per cent. ; flesh, 4.7 per cent. ; potatoes, 9.4 per cent. ; cabbage, 14.9 per cent. ; black bread, 15 per cent. ; yellow turnip, 20.7 per cent. {Rubner). (3) The decomposition products of the bile pigments, which do not now give Gmelin's reaction ; as well as the altered bile acids (§ 177, 2). This reaction, however, may be obtained in pathological stools, especially in those of a green color; unaltered bilirubin, biliverdin, glycocholic and taurocholic acids occur in meconium (§ 182). [MacMunn found no unchanged bile pigments in the fseces. A substance called stercobilin is obtained from the fseces, and it closely resembles what has been called " febrile " urobiUn, but it is certainly different from normal urobilin.] (4) Unchanged mucin and nuclein — the latter occasionally after a diet of bread, together with partially disintegrated cylindrical epithelium from the intestinal canal, and occasionally drops of oil. Cholesterin is very rare. [Ten grains of a substance, stercorin, said to be a modification of cholesterin, occur in the faeces, {Flint).'\ The less the mucus is mixed with the faeces, the lower the part of the intestine from which it was derived {JVofhnagel). (5) After a milk diet, and also after a fatty diet, crystalline needles of lime combined with fatty acids and chalk soaps constantly occur, even in sucklings {Wegscheider). Even unchanged masses of casein and fat occur during the milk cure. Compounds of ammonia, with the acids mentioned as the result of putre- faction (§ 184, III), belong to the fecal matters {Brieger). (6) Among inorganic residues, soluble salts rarely occur in the faeces because they diffuse readily, e. g., common salt, and the other alkaline chlorides, the com- pounds of phosphoric acid, and some of those of sulphuric acid. The insoluble compounds of which ammoniaco-magnesic or triple phosphate, neutral calcic phosphate, yellow-colored lime salts, calcium carbonate, and magnesium phos- phate are the chief, form 70 per cent, of the ash. Some of these insoluble sub- stances are derived from the food, as lime from bones, and in part they are 330 COMPOSITION OF THE F^CES. excreted after the food has been digested, as ashes are eliminated from food which has been burned. Concretions —The excretion of inorganic substances is sometimes so great, that they form incrus- UUons around other fecal matters. L'sually ammoniaco-magnesic phosphate occurs in large crystals by itself, or it may l>c mixcsorl)cd. In the evacuations is the characteristic slender Bacterium coli commune (Fig. 205, I). In addition, occasionally there are other Ijacilli, cocci, spores of yeast, and a mould. Fig. 205. 0 1 / 6 } Vk^ I, Bacterium coli commune; 2, bacterium laclis aerogenes ; 3 and 4, the large bacilli of Bienstock, with partial endo- genous spore formation : 5, the various stages in the development of the bacillus which causes the fermentation of albumin. In the faeces of an adult. Bienstock detected two large forms of bacilli (Fig. 205, 3, 4), closely resembling Bacillus subtilis in form and size, but distinguished from it only by the form of its pure cultivation, by the mode of growth of its spores, and by the absence of movements. These two forms can \tc di.>itinguished microscopically by the mode of their cultivation, which is either in the form of a grape or a (1at membrane. These two do not excite a fermentative action. A third micrococcus-like, small, ver)' slowly developing bacillus occurs in three-fourths of all stools. A fourth kind ( absent in sucklings) is the specific bacillus (>,_ 184, III), causing the decomposition of albumin, resulting in the products of putrefaction and a fecal odor. This is the only bacillus that excites these processes in the intestine; but it does not decompose casein and alkali albumin. In Fig. 205, 5, a-g, the stages in the development of this bacillus are represented, but the stages from c and^ are absent in the faeces, and are found only in artificial cultivations. If the f.tces are simply investigated microscopically and without special precautions, there are other fungi, some of which may l)e introduced through the anus. In stools that contain much starch, the bacillus but)Ticus, which is tinged blue with iodine, occurs (^ 184), and other small globular or rod- like fungi, which give a similar reaction {Nothnagel, Uffelmann). The changes of the intestinal contents have been studied on persons with an accidental intestinal fistula, or an artificial anus. [The follow ing scheme from Krukenberg shows graphically the reaction of the contents of the various parts of the alimcntan,- canal, and also the distribution of the ferments.] . \ / 1 /■ \ •v.. ■" "•-.. J. •C^ MOUTH i (IS0PH*Gu3 STOMACH SMALL INTESTINE ALKtUHE URGE INTESTItiE ALKALIHE Amylol/tic ferment Hilk coiiulat'ng ferment Peptin Trypsin Bacttrit PATHOLOGICAL VARIATIONS OF DIGESTION. 331 i86. PATHOLOGICAL VARIATIONS.— A. The taking of food may be interfered with by spasm of the muscles of mastication (usually accompanied by general spasms), stricture of the ceso- phagus, by cicatrices after swallowing caustic fluids [e.g., caustic potash, mineral acids), or by the presence of a tumor, such as cancer. Inflammation of all kinds in the mouth or pharynx interferes with the taking of food. Inability to swallow occurs as part of the general phenomena in disease of the medulla oblongata, in consequence of paralysis of the motor centre (superior olives) for the facial, vagus, and hypoglossal nerves, and also for the afferent or sensory fibres of the glosso-phar^iigeal, vagus, and trigeminus. Stimulation or abnormal excitation of these parts causes spasmodic swallowing, and the disagreeable feeling of a constriction in the neck (globus hystericus). B. The secretion of saliva is diminished during inflammation of the salivary glands ; occlusion of their ducts by concretions (salivary calculi) ; also by the use of atropin, daturin, and during fever, whereby the secretory (not the vasomotor) fibres of the chorda appear to be paralyzed ( ^ 145 ). When the fever is very high, no saliva is secreted. The saliva secreted during moderate fever is turbid and thick, and usually acid. As the fever increases, the diastatic action of the saliva diminishes. The secretion is increased by stimulation of the buccal nerves (inflammation, ulceration, trigeminal neu- ralgia), so that the saliva is secreted in great quantity. Mercmy- and jaborandi cause secretion of saliva, the former causing stomatitis, which excites the secretion of saliva reflexly. Even diseases of the stomach accompanied by vomiting cause secretion of saliva. A very thick, tenacious, sympathetic saliva occurs when there is violent stimulation of the vascular system during sexual excitement, and also during cer- tain psychical conditions. The reaction of the saliva is acid in catarrh of the mouth, in fever in consequence of decomposition of the buccal epithelium, and in diabetes mellitus in consequence of acid fermentation of the saliva which contains sugar. Hence, diabetic persons often suffer fi-om carious teeth. Unless the mouth of an infant be kept scrupulously clean, the saliva is apt to become acid. C. Disturbances in the activity of the musculature of the stomach may be due to paralysis of the muscular layers, whereby the stomach becomes distended, and the ingesta remain a long time in it. A special form of paralysis of the stomach is due to non-closure of the pylorus [Ebsiein]. This may be due to disturbances of innervation of a central or peripheral nature, or there may be actual paralysis of the pyloric sphincter, or anaesthesia of the pyloric mucous mem- brane, which acts reflexly upon the sphincter muscle; and lastly, it may be due to the reflex impulse not being transferred to the efferent fibre within the nerve centre. Abnormal activity of the gastric musculature hastens the passage of the ingesta into the intestine; vomiting often occurs. D. Gastric digestion is delayed by violent bodily or mental exercise, and sometimes it is arrested altogether. Sudden mental excitement may have the same effect. These efforts are very probably caused through the vasomotor nei-ves of the stomach. Feeble and imperfect digestion may be of a purely nervous nature (Dyspepsia nervosa — Letibe ; Nevirasthenia gastrica — [Burkart). An excessive formation of acid may be due to nervous disturbance, and is called "nervous gastroxynsis " by Ross- bach. [Action of Alcohol, Tea, etc., in Digestion. — According to J. W. Fraser, all infused beverages, tea, coffee, cocoa, retard the peptic digestion of proteids, with few exceptions. The retarding action is less with coffee than with tea. The tannic acid and volatile oil seem to be the retarding ingredients in teas. Distilled Spirits — brandy, whisky, gin — have but a trifling retarding effect on the digestive processes ; and when one considers their action on the secretory glands, it follows that in moderate dietetic doses they promote digestion. Wines are highly inimical to salivary digestion, but this is due to their acidity ; and this effect can be removed by the addition of an alkali. Wines retard peptic digestion, the sparkling less than the still wines. Tea has an intensely inhibitory action on salivary digestion ; in fact a small quantity paralyzes the action of saliva, while coffee has only a slight effect. This action of tea is due to the tannin. Tea, coffee, and cocoa all retard peptic digestion, when they form 20 per cent, of the digestive mixture ( W. Roberts) P^ Inflammatory or catarrhal affections of the stomach, as well as ulceration and new formations, interfere with digestion, and the same result is caused by eating too much food which is difficult of digestion, or taking too much highly spiced sauce or alcohol. In the case of a dog suffering from chronic gastric catarrh, Griitzner observed that the secretion took place continuously, and that the gas- tric juice contained little pepsin, was turbid, sticky, feebly acid, and even alkaline. The introduction of food did not alter the secretion, so that in this condition the stomach really obtains no rest. The chief cells of the gastric glands were tiu-bid. Hence, in gastric catarrh, we ought to eat frequently, but take little at a time, while at the same time dilute hydrochloric acid ought to be administered (0.4 per cent.). Small doses of common salt seem to aid digestion. [Absence of HCl. — HCl is almost always absent in carcinoma of the stomach {van de Vetde), amyloid degeneration of the gastric mucous membrane {Edinger), and sometimes in fever. In all these cases the acid reaction is due to lactic or butyric acid. The absence of HCl in cancer of the stomach is an important diagnostic and prognostic symptom. It is not absent in simple dilatation of the stomach. Test the contents of the stomach for free HCl with tropseolin (red colon, methyl violet (blue),, and with ferric chloride and carbolic acid ( Uffelmann). ^V P^"^ cent, of free HCl causes the 332 PATHOLOGICAL VARIATIONS OF DIGESTION. aniclhvst l.luc of ihe last to »)CCome steel Rray. %vhile somewhat more discharges the color altogether, r In tcMinc for the nrcsc-nce of free lactic acid in the gastric contents use L t elmann s reaction ( ^, 163). ■Vhe lactic acid is casilv eMracled by ether from the gastric contents and the reaction can then he ,x-rfoniud with the residue obtained after evaiH.raling the ether. A solution of I drop of the liquor pcrchloride in 50 c. c. of water is made yellow l.y lactic acid.] . , , . Feeble digestion mav U- caused either by imperfect formation of acid or pepsin, so that both sulMances mav W a.lminiitered in such a condition. [It may also be due to dehcient muscular power in the wall of the stomach.] In other cases, lactic, butyric, and acetic acids are formed, owing to the presence of lowlv organi.sms. In such cases, small doses of salicylic acid, together with some hydro- chloric acid are u.seful. I'epsin need not he given often, as it is rarely absent, even from the diseased Rastric mucous memi)rane. Albumin has been found in the gastric juice in cases of gastric catarrh and cholera. . r » 1 • c-^ E. Digestion during fever and Anaemia.— lieaumont found that in the ca.se of Alexis bt. Martin, when fever occurre.l. a small amount of gastric juice was secreted; the mucous membrane was dr>-. red. and irritable. Dogs sulTering from septicemic fever, or rendered anemic by great loss of blood, secrete gastric juice of feeble digestive iwwer and containing little acid {Manassein). [In acute diseases accompanied by fever, the inner cells of the fundus glands of the human stomach may di.sappcar (C. h'upffer).'] Hoppe-Seyler investigated the gastric juice of a typhus patient in which van de Velde found no free acid. Usually no free hydrochloric acid is found in cancer of the stomach. The ga-stric juice of the tv-jihus patient did not digest artificially, even after the addition of hydrochloric acid. The diminution of acid, under these circumstances, favors the occurrence of a neutral reaction, so that, on the one hand, digestion cannot proceed, and on the other, fermentative processes (lactic and Imtyric acid fermentations with the evolution of gases) occur. These results are a,ssociated with the presence of micro-organisms and Sarcina veutriciili (GoocJsir). Ufl'elmann found that the secretion of a j>eptone- forming gastric juice cexsed in fever, when the fever is severe at the outset, when a feeble condition occurs, or when the temper.iture is very high. The amount of juice secreted is certainly diminished during fever. The excitability of the mucous membrane is increased, so that vomiting readily occurs. The increased excitability of the vasomotor nerves during fever is disadvantageous for the secretion of the digestive fluids \,Ueiiienhain'). Beaumont observed that fluids are rapidly alisorlied from the stomach during fever, but the ab.sorption of peptones is diminished on account of the accompanying catairhal condition of the stomach, and the altered functional activity of the muscular mucos,e ( Leube). Many salts, when given in lar^e amount, disturb gastric digestion, e. <^., the sulphates. While the alkaloids, morphia, strychnia, digitalin, narcotin, veratria have a similar action, quinine favors it ( IVolberg). In some nervous individuals " p>eristaltic unrest of the stomach," conjoined with a dys- peptic condition, occurs (A'/^jwr?///). [Professor James directs attention to the value of peptic and pancreatic salts, which are preparations of common salt mixed with pepsin and the ferments of the pancreas res]icclively.] [Artificial Digestion is affected by various salts according to their nature and dilution. The digestion oi fihrin hy pef'sin goes on best without the addition of salts, being diminished by magnesic sulphate, .soe arrested. G. Gall Stones. — When decomposition of the bile occurs, gall stones are formed in the gall Haddfr or in the bile duds. .Some are white, and consist almost entirely of stratified layers of crystals of cholesterin. The hro-ae(l nuiscul.-ir fibres (Fig. 207). (3) The sub mucous coat consists of loose connective tissue containing large blood vessels and nerves, and it connects the muscular with the mucous coat. (4) The mucous coat is the most internal coat, and its absorbing surface is largely increased bv fordf^fTh" y conmventes and villi. [The valvule conniventes are peramnent folds of the mucous membrane of the small intestine, arranged across the long axis of the g^t. Thev pass round a half or more of the mner surface of the gut. They begin a little below the commence- 336 STRUCTURE OF A VILLUS. 33 ment of the duodenum, and are large and well marked in the duodemmi, and remain so as far as the upper half of the jejunum, where they begin to become smaller, and finally disappear about the lower part of the ileum.] The villi are characteristic of the small intestine, and are confined to it; they occur everywhere as closely-set projections over and between the valvulse conniventes (Fig. 207). When the inner surface of the mucous membrane is examined in water, it has a velvety appearance owing to their presence. [They vary in length from -jL to -J^ of an inch, are largest and most nvmie- rous in the upper part of the intestine, duodenum, and jejunum, where absorption is most active, but they are less abundant in the ileum. Their total number has been calculated at four millions by Krause ] Each villus is a projection of the Fig. 207. Villi with epi- thelium. entire mucous membrane, so that it contains within itself representatives of all the tissue elements of the mucosa. The orifices of the glands of Lieber- kiihn open between the bases of villi (Fig. 207). Each villus, be it cylindrical or conical in shape, is covered by a single layer of columnar epithelium, whose protoplasm is reticulated, and contains a well-defined nucleus with an intra- nuclear plexus of fibrils. The enHs of the epithelial cells directed toward the gut are polygonal, and present the appearance of a mosaic (Fig. 208, D). When looked at fi-om the side, their Iree surface is seen to be covered with a clear, highly refractive disk or " cuticula," which is marked with vertical striae. These striae were supp"sed by Kolliker to represent pores for the absorption of fatty particles, 1 ut this has not been confirmed, while Brettauer and Steinach regarded them as produced by prisms placed side by ^ide. According to v. Thanhoffer, however, this clear disk is comparable to the thickened flange around the bottom of a vessel, such as is used for collecting gases. On this suppositii 'U, the upper end of each cell is open, and from it there project pseudopodia-like bundles of protopla.smic pro- cesses (Fig. 208, B) These processrs are sup- posed to be extended beyond the margin of the cell, and again rapidly retracted, and in so acting they are said to carry the fatty particles into the interior of the cells, much as the pseudopodia of an amoeba entangle its food. [This view has not been confirmed by a sufficient number of ob- servers.] Between the epithelial cells are the so-called goblet cells (Fig. 208, C). [Each goblet cell is more or less like a chalice, narrower above and below, and broad in the middle, with a tapering fixed extremity. The outer part of these cells is filled with a clear substance or mucigen, which, on the addition of water, yields mucus. The mucigen lies in the interva's of a fine network of fibrils, which pervades the cell protoplasm, while the protoplasm containing a globular or triangular nucleus, is pushed into the lower part of the cell. Those goi)let cells are simply altered columnar epithelial cells, which secrete mucus in their interior. They are more niunerous under certain conditions. Not unfirequently in a section of the mucous membrane of the gut, after it is siained with logwood, we may see a deep blue plug of mucus partly exuded from these eel's. When looked at f om above they give the appearance seen in Fig. 208, I).] The epithelial cells are shed in enormous numbers in cholera, and in poisoning with arsenic and muscaiin {Bohiti). [The epithelial cells covering the villus are placed upon a layer of squamous epithelium (basement membrane) — the sub-epithelial membrane of Debove. This basement membrane is said to be connected by processes with the so-called liranched cells of the adenoid tissue of the villus, while it also sends up processes between the epithelial covering.] The villus itself consists of a basis of adenoid tissue, containing in its centre one or more lacteals, closely invested with bundles of longitudinal smooth muscular fibres, derived fi-om the musrularis mucosae, and a plexus of blood vesse's. The adenoid tissue of the vil us consists of a reticulum of fibrils with endothelial plates at its nodes. The spaces of the adenoid tissue form a spongy network Longitudinal section of the small intestine of a dog through a Peyer's patch. 338 Fic. 209. Capillaryi . Artery. Vein. Injected blood vessels of a villus. of inter-communicating channels con- taining stroma cells or leucocytes (Fig. 208, A, e, e). These leucocytes or lymph corpu.scles have been seen to contain fatty granules, and they are perhaps concerned in the absorption of fatty particles. The lymphatic or lacteal lies in the axis of the villus (Fig. 210, af). Some regard the lacteal merely as a space in the centre of the villus, but more probably it has a distinct wall composed of endothelial cells, with apertiu-es or stomata here and there between the cell plates. These stomata place the interior of the lacteal in direct communication with the spaces of the adenoid tissue. Perhaps, white blood corpuscles wander out of the blood vessels of the villi into the spaces of the adenoid tissue where they become loaded with fatty gran- ules, and pass into the central lacteal. Zuwarj'kin and Wiedersheim suppose that the leucocytes pass from the parenchyma of the villus toward the epithelial layer, and even between the epithelial cells, from which they re- turn toward the axis of the. villus, laden with .substances which they have taken into their interior (^ 192, II). GLANDS IN THE INTESTINE. 339 A small artery placed eccentrically passes into each villus (Fig. 209). In man it begins to divide about the middle of the villus, but in animals it usually runs to the apex before it divides. The capillaries resulting fi-om the division of the artery form a fine dense network placed stiperficially , immediately under the epithelium of the surface. The blood is can-ied out of a villus by one or two veins (Figs. 207, 209). Non-striped muscular fibres are present in villi. They are arranged longitudinally in several bundles from base to apex, immediately outside the central lacteal. When they contract they tend to empty the lacteal. A few muscular fibres are placed more superficially, and run in a more trans- verse direction. [The longitudinal bundles of non-striped muscle in the villi are connected together by oblique strands; while the longitudinal bundles shorten the villus, the oblique fibres keep the lacteal open; thus the parenchyma of the villus is also compressed transversely, whereby the products of absorption are forced into the lacteal. The muscles are fixed by cement to the sub- epithelial basal membrane. The muscular fibres of the villi are direct prolongations of the muscularis mucosae.] Nerves pass into the villi from Meissner's plexus lying in the sub-mucous coat. The nerves to the vilU are said to have small granular ganglionic cells in their course, and they terminate partly in the muscular fibres and partly in the arteries of the villi. [On making a vertical section of the mucous membrane of the small intestine, it is seen to consist of a network of adenoid tissue loaded with leucocytes. This tissue forms its basis, and in it are placed vertically, side by side, like test-tubes in a stand, immense numbers of simple tubular glands — the crypts of Lieberkiihn (Fig. 207).] [Kultschitzki finds that the connective-tissue framework of the mucous membrane of the small intestine is not true adenoid tissue, but a transition form between the latter and loose fibrous tissue.] Lieberkiihn's glands open above at the bases of the villi, while their closed lower extremity reaches almost to the muscularis mucosae. Each tube consists of a base- ment membrane lined by a single layer of columnar epithelium, leaving a wide lumen, the cells lining them being continuous with those that cover the mucous membrane. Some goblet cells are often found between the columnar epithelium. Immediately below the bases of the follicles of Lieber- kiihn is the muscularis mucosae, consist- ing of two or three narrow layers of non- striped muscular fibres arranged circularly and longitudinally. [It is continuous with the muscularis mucosa? of the stomach, and extends throughout the whole intestine, not as a continuous layer, but as a close net- work of bundles of smooth muscle. It sends fibres upward into the villi (Fig. 212, e).-\ [Brunner's Glands are compound tubu- lar glands lying in and confined to the sub- mucous coat of the duodenum (Fig. 198). Their ducts perforate the muscularis mucosa to open on the surface. They seem to be the homologues of the pyloric glands of the stomach.] [Solitary Follicles are small round or oval white masses of adenoid tissue with their deeper parts embedded in the sub- mucosa, and their apices projecting into the mucosa of the intestine. They begin at the pyloric end of the stomach and are found throughout the whole intestine. They con- FiG. 210. sist of small masses of adenoid tissue loaded Mucous membrane of the small intestine of the dog ; with leucocytes (Fig. 214). They are well ?re black, and the blood vessels lighter. the lacteals , artery ; b, supphed with blood vessels (| 1 97 ) , although L^ebSi's'gllnds! °^ ""P'""""' ™ ''^" ^'"' ' '^' ^^"""^ = '' no lymphatic vessels enter them. They are surrounded by lymphatics, and, in fact, they may be said to hang into a lymph stream. The distribu- tion of solitary follicles is fairly uniform in the small intestine ; their number generally increases from the stomach to the large intestine; although there are considerable variatioris in different individuals, there seems to be the same number of solitary follicles and Peyer's patches in the infant as in the adult (^Passow).'\ [Peyer's glands, or agminated glands, consist of groups of lymph fohicles like the foregoing (Figs. 207, 213). The masses are often more or less fused together, their bases lie in the sub-mucosa, 340 peyer's glands. while their summits project into the mucosa, wliere they are covered merely by the columnar epithelium of the intestine. The iymi)h corpuscles often pass between the ejiithelial cells. Ihe patches so formed have their long axis in the axis of the intestine, and they are always placed opix)site the attach- YlC. 211. Villi wllli blood vessels injccicJ. Solitary follicle. Muscular coat. Traiiiverse scciiuii ol" Juodenuni of a rabbit injected, X 30. ■■-■■A'. Q WftN ig' m^^i^^p-ssm^ ^'i— Section °f =« -l;'^^;^/^'"'^'^ °\ 'h«= 7=',".J"t«stine (human), a. lymph follicle covered with epithelium (/,) which has lallen from the villi, c. d, Lieberkuhn s follicle ; e, muscularis mucosae ; /, sub-mucous tissue. ment of the mesentery. Like the solitary gland.s. they are well supplied with blood vessels, while around them is a dense plexus of lymphati.-s or lacteals. They are most abundant in the low^r part of the Ileum. These glands are specially affected in tj-phoid fever.] NERVES OF THE INTESTINE. 341 Nerves of the Intestine.— Throughout the whole intestinal tract there exists the plexus of Auerbach, lying between the longitudinal and circular muscular coats (Figs. 174, 175). This Fig. 213. Diagram of a vertical section of the mucous membrane of the small intestine of a dog, showing the closed follicles, aa ; b, muscularis mucosse. Fig. 214. Epi- thelium. Mucous Membrane. Capillary. Solitary follicle. Circular fibres. Muscular coat. Longitudinal fibres. Sub- tnucous coat. Longitudinal section of the large intestine. plexus consists of non-medullated nerves with groups of ganglionic cells at the nodes. Fibres are given off by it to the muscular coats. Connected by branches with the foregoing, and lying in the sub- 342 FORCES CONCERNED IN ABSORPTION. mucoM. b the plexus of Meissner, which is much finer, the meshes being wider, the nodes smaller, but nlM» providol with j,'nngl'"'>'C ceils. It supplies the muscular fibres and arteries of the mucosa, incluHinj; tho^ of the villi. It al.so sends branches to I.ieberkiihn's glands (Fig. 176). [Structure of the Large Intestine. — It has four coats, like those of the small intestine. The serous coat has the same >truct6re as that of the small intestine. The muscular coat has external lomptuiiinitl fibres occurring all round the gut, but they form three flat, ribl on-like longitudinal bands in the cecum and colon (Fig. 214). Inside this coat are the circular fibres. The sub-mucosa is practically the >amc as that of the iimaU intestine. The mucosa is distinguished by negative character.. It has no villi and no I'cyer's patches, but otherwise it resembles structurally the small intotinc, consisting of a basis of adenoid tissue with the simple tubular glands of Lieberkiihn (Fig. 199V The-se glands are very numerous and somewhat longer than those of the small intestine, and they always contain far more goblet cells — about ten times as many. The cells lining them are devoid of a clear di.sk. Solitary glands occur throughout the entire length of the large intestine. At the basis of I.ieberkiihn's glands is the muscularis mucosae. The blood vessels and nerves have a >imilar arrangement to tho.se in the .stomach.] [Blood Vessels. — On looking down on an opaque injection of the mucous membrane of the stomach, one sees a dease meshwork of polygonal areas of unecjual size, with depressions here and there. The orifices are the orifices of the gastric glands, each surrounded by a capillary. A some- what similar appearance is .seen in an opaque injection of the mucous membrane of the large intestine, but in the latter the meshwork is uniform, all the orifices (of Lieberkiihn's glands) being of the same size. ] 191. ABSORPTION OF THE DIGESTED FOOD.— The physical forces concerned are endosmosis, diffusion, and filtration. All the constituents of the AkkI, with the exception of the fats, which in part are changed into a fine emulsion, are brought into a .state of solution by the digestive proce.sses. These substances pass through the walls of the intestinal tract, either into the blood vessels of the mucous membrane or into the beginning of the Ij-mphatics. In this passage of the fluids two physical processes come into play — cntiosmoiii and diffusion, as well as Jillration. I. Endosmosis and diffusion occur between two fluids which are capable of forming an intimate mixture with each other, e. ;'., hydrochloric acid and water, but never between two fluids which do not form a jierfect mixture, such as oil and water. If two fluids capable ot Fig, 215. mixing with each other, but of different compositions, be separated from each ^ other by means of a septum with physical pores (which occur even in a homo- geneous membrane), an exchange of the constituents in the fluids occurs until both fluids have the same composition. This exchange of fluids is termed endosmosis or diosmosis. Diffusion. — If the two mixable fluids are placed in a vessel, the one fluid over the other, but without being separated by a porous septum, an exchange of the particles of the fluids aLso occurs, until the whole mixture is of uniform comix)>ition. This process is called diffusion. Conditions Influencing Diffusion.— Graham's investigations showed that the rapidity of difi'usion is influenced by (i) The nature of the fluids them- selves ; acids diffu.se most rapidly ; the alkaline salts more slowly ; and most slowly, fluid albumin, gelatin, gum, dextrin. These last do not cr)'staUize, and perhaps do not form true solutions. (2) The more concentrated the solutions, the greater the diffusion. (3) Heat accelerates, while cold retards, the process. (4) If a .solution of a body which diffuses with difficulty be mixed with an easily diffusible one, the former diff'uses with still greater difficulty. (5) Dilute solutions of .several substances diffu.se into each other without any difficulty, but if concentrated solutions are employed the process is retarded. (6) Double salts, one constituent of which diffuses more readily than the other, may be chemically separated by diffusion. Endosmometer.— The exchange of the fluid particles takes place inde- pendenlly of the hydrostatic pressure. An endosmometer (Fig. 215) consists of a glass cylinder filled with distilled water, and into this is placed a flask, J, without a lx)ttom, instead of which a membrane, w, is tied on. A glass tube, K, IS fixed firmly, l;y means of a cork, into the neck of the flask. The flask is filled up to the lower end of the tube with a concentrated salt .solution, and is •ru" n^ [^ • '" '^^ cylindrical vessel until both fluids are on the same level, x. 1 he fluid m the tube, R, soon begins to rise, because water passes through the membrane into the concentrated .solution in the flask, and this independently of the hydrostatic pressure. Particles of the concentrated salt solution pass into continue nntil th. fl "1 ".u !" """"i '"'^,^'th the water, F. These outgoing and ingoing currents Lwavs stld hLLr '' ^" ""»5, ""^'" J ^""^ °f ""'f°"" composition, whereby The fluid in R al*a)s standi higher {e.g., at v), while it is lowered in the cylinder The circumstance of the level f "^ Endosmometer. COLLOIDS. 343 of the fluid within the tube being so high, and remaining so, is due to the fact that the pores in the membrane are too fine to allow the hydrostatic pressure to act through them. Endosmotic Equivalent. — Experiment has shown that equal weights of different soluble sub- stances attract different amounts of distilled water through the membrane i. e., a known weight of a soluble substance (in the flask) can be exchanged by endosmosis for a definite weight of water. The term "endosmotic equivalent" indicates the weight of distilled water that passes into the flask of the endosmometer, in exchange for a known weight of the soluble substance [Jolly). For i grm. alcohol 4.2 grms. water were exchanged; while for I grm. NaCl, 4.3 grms. water passed into the endosmo- meter. The following numbers give the endosmotic equivalent of — Acid potassium sulphate, . = 2.3 Common salt, . . . . = 4.3 Sugar, =7.1 Sodium sulphate, . . . =11.6 Magnesium sulphate, . . =11.7 Potassium sulphate, . . = 12.0 Sulphvuic acid, . . . . = 0.39 Potassium hydrate, . . . — 915 n The amount of the substance which passes through the membrane into the water of the cylinder is proportional to the concentration of the solution. If the water in the cylinder, therefore, be repeatedly renewed, the endosmosis takes place more rapidly, and the process of equilibration is accelerated. The larger the pores of the membrane, and the smaller the molecules of the substance in solution, the more rapid is the endosmosis. Hence, the rapidity of endosmosis of different substances varies, e. g,, the rapidity of sugar, sodium sulphate, common salt, and urea is in the ratio of I : I.I : 5 : 9.5. The endosmotic eijuivalent is 710I constant for each substance. It is influenced by (l) The temperature, which, as it increases, generally increases the endosmotic equivalent. (2) It also varies with the degree of concentration of the osmotic solutions, being greater for dilute solutions of the substances. If a substance other than water be placed in the cylinder, an endosmotic cuiTent occurs on both sides until complete equality is obtained. In this case, the currents in opposite directions disturb each other. If two substances be dissolved in the water in the flask at the same time, they diffuse into water without affecting each other. (3) It also varies with membranes of varying porosity. Common salt, which gives an endosmotic equivalent with a pig's bladder = 4.3, gives 6.4 when an ox bladder is used; 2.9 with a swimming bladder; and 20.2 with a collodion membrane. Colloids. — There are many fluid substances which, on account of the great size of their molecules, do not pass, or pass only with difficulty, through the pores of a membrane impregnated with gelatinous bodies, which diffuse slowly. These substances are not actually in a true state of solution, but exist in a very dilute condition of imbibition. Such substances are the fluid proteids, starches, dextrin, gum, and gelatin. These diffuse when no septum is present, but diffuse with difficulty, or not at all, through a porous septum. Graham called these substances colloids, because, when concentrated, they present a glue-like or gelatinous appearance ; farther, they do not crystallize, while those sub- stances which diffuse readily are crystalline, and are called crystalloids. Crystallizable substances may be separated from non-crystallizable by this process, which Graham called dialysis. Mineral salts favor the passage of colloids through membranes. That endosmosis takes place in the intestinal tract, through the mucous mem- brane and the delicate membranes of the blood and lymph capillaries, cannot be denied. On the one side of the membrane, within the intestine, are relatively concentrated solutions of highly diffusible salts, peptones, sugar and soaps, and within the blood vessels are the colloids which are scarcely diffusible, e.g., the proteids of blood and lymph. II. Filtration is the passage of fluids through the coarse intermolecular pores of a membrane owing to pressure. The greater the pressme, and the larger and more numerous the pores, the more rapid does the fluid pass through the membrane ; increase of temperature also accelerates it. Those substances which are imbibed by the membrane filter most rapidly, so that the same substance filters through different membranes with varying rapidity. The filtration is usually slower, the greater the concentration of the fluid. The filter has the property of retaining some of the substances from the solution passing through it, e.g., colloid substances — or water (in dilute solutions of nitre). In the foi-mer case the filtrate is more dilute, in the latter more concentrated, than before filtration. Other substances filter without undergoing any change of concentration. Many membranes behave differently, according to which surface is placed next the fluid ; thus the shell membrane of an egg permits filtra- tion only from without inward ; [and the same is true to a much less extent with filter paper ; the smooth side of the filter paper ought always to be placed next the fluid to be filtered. The intact skin of the grape prevents the entrance of fungi into the fi-uit] . There is a similar difference with the gastric and intestinal mucous membrane. [By using numerous layers of filter paper, many colloids and crystalloids are retained in the filter, e.g., hemoglobin, albumin, and many coloring matters, especially aniline colors, the last being arrested by glass wool [Krysinski).'] [Filtration of Albumin. — Rimeberg finds that the amount of albumin in pathological transu- dations varies with (i) the capillary area, being least in cedema of the subcutaneous tissue. (2) The 344 ABSORPTION OF SOLUBLE CARBOHYDRATES. preencc or al>scncc of inflammatory procestfs in the vascular wall, non-inflammatory pleuritic eftu- lion containinR 2 ix-r cent., and inflammatory 6 i>er cent., of albumm. (3) 1 he condi ion and amount of alhumi,, m iht bloci. The amount of albumin in the transudate never reaches, although it some- time ai.pnmchi-s. that in bloosorl)c(l and others are not. The following are absorbed: alcohol, part of which ap|)ears in the urine (not in the ex])ired air), viz., that p.irt which is not changed into COj and H,0, within the IkhIv ; tartaric, citric, malic, and lactic acids; glycerine, inulin ; gum and vegetable mucin, which give rise to the formation of glycogen in the liver. .\mong coloring matters, aliiiarin (from madder), alkannet, indigo-sulphuric acid, and its soda salt arc absorbed; h;emalin is jiartly absorbed, while chlorophyll is not. Metallic salts seem to be kept ill solution l)y proteids, are perhaps absorbed along with them, and are partly canied by the blood of the portal vein to the liver (ferric sul])hate has been found in chyle). Numerous poisons are ver)- ra])idly absorl)ed, e. ^., hydrocyanic acid after a few seconds ; potassium cyanide has been found in the chyle. [If salts (KI, sulphocyanide of ammonium) be injected into a ligatured loop of intestine (dog, cat, rabbit), these substances are absorbed both by the blood and lymph vessels, and in lx)th nearly simultaneously.] Even for the ab.soqotion of completely fluid substances, endosmosis and filtration seem to be scarcely sufficient. An active participation of the protoplasm of the cells seems here also — in part at least — to l)e necessary, else it is diftiult to explain how very slight dis- turbances in the activity of these cells, e. i^, from intestinal catarrh, cause sudden variations of absorp- tion, and even the passage of fluids into the intestine. If al>sor]ilion were due to dilTusion alone, when alcohol is injected into the intestine, water ought to pass into the intestine, but this does not occur. Hrieger found that the injection of a 0.5 to 1 per cent, solution of salts into a ligatured loop of intestine did not cause water to pass into the intestine; but it appc.ind wli.n a 20 per cent, solution was injected. II. Absorption of the Smallest Particles.— The largest amount of the fats is absorbed in the form of a milk-like emulsion, formed by the action of the bile and the pancreatic juice, and consisting of excessively small granules of uniform size (§170, III; §181). The fats themselves are not chemically changed, but remain as undecomposed neutral fats. The particles seem to be surrounded by a delicate albuminous envelope, or haptogen membrane, partly derived from the pancreatic juice [probably from its alkali-albuminate]. The villi of the small intestine are the chief organs concerned in the absorption of the fatty emulsion, but the epithelium of the stomach and that of the large intestine also take a part. The fatty granules are recognized in the villi (i) Within the delicate canals? (§ 190) in the clear band of the epithelium {Kolliker). [It is highly doubtful if the vertical lines seen in the clear disk of the epithelium of the intestine are due to pores.] (2) The protoplasm of the epithelial cells is loaded with fatty granules of various sizes during the time of absorption, while the nuclei of the cells remam free, although, from the amount of fat within the cells, it is often difficult to distinguish them. (3) The granules pass into the spaces of the parenchyma of the vill, ; these spaces communicate freely with each other. (4) I he origin of the lacteal in the axis of the villus is found to be filled with fatty granule.s. The amount of fat in the chyle of a dog, after a fatty meal, is 8 to 10 per cent., while the fat disappears from the blood within thirty hours With regard to the forces concerned in the absorption of fats, v. Wist- inghausen proved, that when a porous membrane is moistened with bile the NUTRIENT ENEMATA. 347 passage of fatty particles through it is thereby facilitated, but this fact alOne does not explain the copious and rapid absorption of fats. It is possible that the proto- plasm of the epithelial cells is actively concerned in the process, and that it takes the particles into its interior. Perhaps a fine protoplasmic process is thrown out by these cells, just as pseudopodia are thrown out and retracted by lower organ- isms. It is possible that absorption may take place through the open mouths of the goblet cells. The protoplasm of the epithelial cells is in direct communica- tion with the numerous protoplasmic lymph cells within the reticulum of the villi, so that the particles may pass into these, and from them through the stomata (?) between the endothelial cells into the central lacteal of the villus. According to this view, the absorption of fatty particles, and perhaps also the absorption of true proteids, is due to an active vital process, as indicated by the observations of Briicke and v. Thanhoffer. This view is supported by the obser- vation of Griinhagen, that the absorption of fatty particles in the frog is most active at the temperature at which the motor phenomena of protoplasm are most lively. That it is due to simple filtration alone is not a satisfactory explanation, for the amount of fatty particles in the chyle is independent of the amount of water in it. If absorption were chiefly due to filtration, we would expect that there would most probably be a direct relation between the amount of water and fat {^Ludwig and Zawilsky). [The observations of Watney have led him to sup- pose that the fatty particles do not pass through the cell protoplasm to reach the lacteal, but that they pass through the cement substance between the epithelial cells covering a villus. If this view be correct, the absorbing surface is thereby greatly diminished. Zuwarykin and Schafer suggest that the leucocytes, which have been observed between the columnar cells of the villi of the small intestine, are carriers of at least part of the fat from the lumen of the gut to the lacteal ; they also, perhaps, alter it for further use in the economy. According to Zu- warykin, Peyer's patches in the rabbit seem to be especially active in the absorp- tion of fat, so that he attaches great importance to the leucocytes of the adenoid tissue in the absorption of fat.] [According to Griinhagen, there are several channels for the absorption of fats, but they are different in different animals. Some are absorbed by the columnar epithelium cells themselves, and some passes between them.] The activity of the cells of the intestine with pseudopodial processes may be studied in the intestinal canal of Distomum hepaticum. Sommer has figm-ed these pseudopodial processes actively engaged in the absorption of particles from the intestine. 193. INFLUENCE OF THE NERVOUS SYSTEM.— With regard to the influence of the nervous system upon intestinal absorption, we know very little. After extirpation of the semilunar ganglion, as well as after section of the mesenteric nerves {Moreau), the intestinal contents become more fluid, and are increased in amount (§ 183). This may be partly due to diminished absorption, v. Thanhoffer states that he observed the protrusion of threads from the epithelial cells of the small intestine only after the spinal cord, or the dorsal nerves, had been divided for some time. 194. " NUTRIENT ENEMATA."— In cases where food cannot be taken by the mouth, e.g., in stricture of the oesophagus, continued vomiting, etc., food is given per rectum. As the digestive activity of the large intestine is very slight, fluid food ought to be given in a condition ready to be absorbed, and this is best done by introducing it into the rectum through a tube with a funnel attached, and allowing the food to pass in slowly by its own weight. The patient must endeavor to retain the enema as long as possible. When the fluid is slowly and gradually introduced, it may pass above the ileo-csecal valve. Soliitions of grape sugar, and perhaps a small amount of soap solution, are useful ; and among nitro- genous substances the commercial flesh-, bread-, or milk peptones of Sanders-Ezn, Adamkiewicz, in Germany, and Darby's fluid meat, and Carnrick's beef peptonoids in this country, are to be recom- mended. The amount of peptone required is i .1 1 grm. per kilo, of body weight ( Catilloii ) ; less useful are buttermilk, egg albumin with common salt. Leube uses a mixture of 150 grms. flesh with 50 grms. pancreas and loo grms. water, which he slowly injects into the rectum, where the proteids 348 CIIVI.E VESSELS AND LYMPHATICS. •re p«Moni/cd and aJ«orl«d. [Peptonized food prepared after the method of Roberts is very useful ({172) 1 The mrthoues which do not contain blood vessels, e.g., the cornea, or in those which contain few I.UkxI ve.ssels, there exi.sts a system of vessels or channels which contain the juices of the tivues, an.l within these vessels the tluid always moves in a centripetal direction. These canals ■rise within the ti.ssues in a variety of ways, and unite in their course to form delicate and afterward thicker IuIh-s, w ich ultimately terminate 'in two large trunks which open at the junction of the jugu- lar and sulKrlavian veins; that' on the left side is the thoracic duct, and that on the right, the right lymphatic trunk. With regard to the lymph and its movements in different organs, it is to be noticed that this occurs in different ways in different places, (i) In many tissues the lymphatics represent the nutrient channels by which the fluid that transudes through the neighboring vessels is distributed, as in the cornea and in many con- nective tissues. (2) In many tissues, as in glands, e.g., the salivary glands and the testis, the lymph spaces are the chief reservoirs for fluid, from which the cells during the act of secretion derive the fluid necessary for that process. (3) The lymphatics have the general function of collecting the fluid which saturates the tissues, and carrying it bark again to the blood. The capillary blood system may be regarded as an irrigation system, which supplies the tissues with nutri- ent fluids, while the lymphatic system may be regarded as a drainage apparatus, which conducts away the fluids that have transuded through the capillary walls. Some of the decomjjosition products of the tissues, proofs of their retrogressive metabolism, become mixed with the lymph stream, so that the lymphatics are at the same time absorbing vessels. Substances introduced into the parenchyma of the ti.ssues \x\ other ways, e. g., by subcutaneous injection, are partly absorbed by the lymphatics. .\ study of these conditions shows that the lymphatic system represents an appendix to the blood-vascular system, and further that there can be no lymph system when tlie blood stream is completely arrested ; it acts only as a part of the whole, and with the whole. Lacteals. — When we speak of the lymphatics proper as against the chyle vessels or lacteals, we do so from anatomical reasons, because the important and considerable lyinphatic channels coming from the whole of the intestinal tract are, in a certain sense, a fairly independent province of the lymphatic vascular area, and are endowed with a high absorptive activity, which, from ancient times, has attracted the notice of observers. The contents of the chyle vessels or lacteals are mixed with a large amount of fatty granules, giving the chyle a white color, which distinguishes them at once from the true lymphatics with their clear, watery contents. From a physiological point of view, however, the lac- teals must be classified with the lymphatics, for, as regards their structure and function, they are true lymphatics, and their contents consist of true lymph mixed with a large amount of absorbed substances, chiefly fatty granules. [The con- tents of the lacteals are white only during digestion ; at other times they are clear, like lymph.] ^ 196. ORIGIN OF THE LYMPHATICS. -(i) Origin in Spaces. -Within the con- nective t.s,sues (connective tissue proper, bone) are numerous stellate, irregular or branched spaces, which communicate with each other by numerous tubular processes (Fig 216 s\- in these com- nletT SdTv fh . u' f l'"'""- '''""'r'" "^ '^''" "■'^^"'^- 'Th"*^ ^P^^^^' however, are not com- ^c/wh ^h ' '•'V '•, '" "!!"''"' \"''' ^"'^"^*^" '^^ ^^>- °f the cell and the wall of the space, w hich is grea er or less according to the condition of movement of the protoplasmic cell These spaces are the so-called "juice canals" or "Saft-canalchen," and they represent the origin of the lymphatic vessels (t;. Reckhn.hausen). As they communicate with neighboring spaces he move W°of Jh^Tells'r'JiSIln'n'"- '''.? -"%-'-h 'ie in the spaces exiibit aLUd movements. borne 01 these cells remain permanently, each in its own space, within which however it mav change Its form-these are the so-called •• fixed connective-tiLsue corpuscles,'' and bone iorTs^ clcs-while others merely wander or pass into these spaces, and are called " wandering ceUs," ORIGIN OF THE LYMPHATICS. 349 or " leucocytes ; " but the latter are merely lymph corpuscles, or colorless blood corpuscles which have passed out of the blood vessels into the origin of the lymphatics. These cells exhibit amoe- boid movements. These spaces communicate with the small tubular lymphatics — the so-called lymph capillaries (L). The spaces lie close together where they pass into a lymph capillary («). Fig. 216. The lymph capillary, which is usually of greater diameter than the blood capillary, generally lies in the middle of the space within the capillary arch (B). The finest lymphatics are lined by a layer of delicate, nucleated, endo- thelial cells (1?, e), with characteristic sinous margins, whose characters are easily revealed by the action of silver nitrate (Fig. 217, L). This substance blackens the cement substance which holds the endothelial cells together. Between the endothelial cells are small holes, or stomata, by means of which the lymph capillaries communicate (at x) with the juice canals. It is assumed by Arnold that the blood ves- sels communicate with the juice canals, and that fluid passes out of the thin-walled capil- laries through their stomata into these spaces [\ 65). This fluid nourishes the tissues, the tissues take up the substances appi-opriate to each, while the effete materials pass back into the spaces, and from these reach the lym- phatics, which ultimately discharge them into the venous blood. Whether the cells within these spaces are actively concerned in the pouring out of the blood plasma, or take part in its movement, is matter of conjecture. We can imagine that by contracting their body, after it has been impregnated with fluid, this fluid may be propelled from space to space toward the lymphatics. The leucocytes wander through these spaces until they pass into the lymphatics. Fine particles which are contained in these spaces — e.g., after tattooing the skin, and even fatty particles after inunction — are ab- sorbed by the leucocytes and carried by them to other parts of the body. [The pigment particles used to tattoo the finger are usually found within the first lymphatic gland at the elbow.] The migration of cellular elements from the blood ves- sels into the origin of the lymphatics is to be considered as a normal process. Granu- lar coloring matter passes from the blood into the protoplas- mic body of the cells within the lymph spaces ; and only when the granular pigment is in large amount, does it ap- pear as a granular injection in the branches of the juice spaces. (2) Origin within villi i. e. of Pleural surface of the central tendon of the diaphragm of the rabbit thp rhvlp vp?s;p1 or Inrtpal hns been stained with silver nitrate. L, lymphatic with its sinuous endothe- tne cnyle vessel or laCteal — nas Oeen j^^^^ . ^^ ^,^,1^ ^^ ^^^ connective tissue brought into view by the silver described (^ 190). nitrate. Origin of lymphatics from the central tendon of the diaphragm stained with nitrate of silver, s, the juice canals, commu- nicating at X with the lymphatics; a, origin of the lym- phatics by the confluence of several juice canals. Fig. 217. 350 ORIGIN OF THE LYMPHATICS. f •?> Origin in perivascular spaces (I'ij;;. 21S). — Tlie smallest blood vessels of hone, the central I,, , tn. retina ami the liver, are coiniilelely surrounded l)y wide lymphatic tubes, so that the 1 are completely bathetl by a lymph stream. In the brain these lymphatics are partly I delicate connective tissue fibres, which traverse the lym|)h space and become attached I, I the include a |K-riva.scular s|>ace, the passage of lymj^h and blood coq)uscles into the l}Tnph- :r Iv facilitated. In the tortoise the large blood vessels are often surrounded with perivas- Lu.... I ...lUcs. Kig. 21S, A, gives a re|)resentation of the aorta surrounded by a perivascular space which rs vi>il)le to the unaided eye. In nianunals the periva.scular spaces are microscopic. (4) Origin in the form of interstitial slits within organs. — Within the testis the lymphatics U-gin simply in the form of numerous slits, which occur between the coils and twists of the seminal tubules. They take the form of elongated spaces Ixjunded by the curved cylindrical surfaces of the tubules. The surfaces, however, are covered with endothelium. The lymphatics of the testis get indejK-ndent walls after they leave the parenchj-ma of the organ. In many other glands the gland Fl.:. 21S. Fig. 219. ^^^ Perivaicular lymphatics. A. aorta of tortoise; B, artery from the brain. Stomata in the great lymph sac (frog), half-closed ; c, closed. I open ; l>. sul,stancc '« similarly surrounded by a lymph space. The blood vessels pour the Ivmph into these simcc.s. and from them the secretiug cells obtain the materials necessary for the formation of their secretion. ^ (5) Origin by means of free stomata on the walls of the larger serous cavities, which (Fig. 2lr, „, CM,nmun.cate freely with the lymphatics. The investigation of the serous surfaces is most e.i>,ly accomplished on the septum of the great aklominal lymph sac of the frog. Silver nitrate vZhl^L '"'""7'" f7<-;l'»l'vely large free o,>enings or stomata lying between The endothelium. undrnroT;!, ',' TV ■ '"'T' e^'^'^a'i"? "lis, which have a granular appearance, and the^ celK h^'il? '.'''• '° '^' "'" ^"" "'' "^'' ^'""^-"^ '•'=1'^"^'^ "PO" "^^ degree of contraction of iJeThe ori;in nf .t' f °'"?. T >' '^ °I>^" '«'- ^alfopen (/,,. or completely closed (.). These stomata Stidl nlaced in ,h^ '>"'P*^""": The serous cavities belong therefore to the lymphatic system, and preta'^trilrdiumTr.' ""^"^'V^ P^^^ ["^^ 'he h-mphatics. The cavities of the peritoneum, TaSLfth^r^; r?'"^"'''^^ ^'""''""'^ space, aqueous chambers of the eye, and the mSann 1. fern, d tha.T' '^L?^ '''""'' ^f t^^ ""'^ '^^>' '^•^"^^'" '^ '^ '^^ '"^g-'-d^d L lymph, the gc^^al ;;iSm ] ""' ''^^ ^"^^""^ '^^ ^'^'"^'^ '" '"^^ ^-g -^ -"ds branches beLJen the tnrin" Mnpha^rcs". 1^'Tn Ih"}, "^'T"' °? "^^^ "'"'"" -'''«^-«^^. ^vhich are regarded as Stru^turV Th '^i' !h^.^''0"chi, na.sal mucous membrane, trachea and larynx LYMPHATIC GLANDS. 851 Fig. 220. 197. THE LYMPH GLANDS.— The lymphatic glands belong to the lymph apparatus. They are incorrectly termed glands, as they are merely much- branched lacunar labyrin- thine spaces composed of adenoid tissue, and interca- lated in the course of the lymphatic vessels. There are simple and compound lymph glands. /^) (i) The simple lymph glands, ^^ or, more correctly, lymph follicles, ylj are small rounded bodies, about the '■ size of a pin head. They consist of a mass of adenoid tissue (Fig. 220, A), i. e., of a very delicate network of fine reticular fibres with nuclei at their points of intersection, and in the spaces of the meshwork ^^^ ^^^^^ folliclelT A. a small follicle highly magnified, showing the lie the lymph and the IjTnph corpus- adenoid reticulum ; B, a follicle less highly magnified, showing cles. Near the siu-face, the tissue is injected bloodvessels, somewhat denser, where it forms a capsule, which is not, however, a true capsule, as it is permeated with numerous small sponge-like spaces. Small lymphatics come directly into contact with these lymph folUcles, and often cover their surface in the form of a close network. The surface of the l}-mph follicles is not unfrequently placed in the wall of a lymph vessel, so that it is directly bathed by the lymph stream. Although no direct canal-like opening leads from the follicle into the lymphatic stream in relation with it, a communica- tion must exist, and this is obtained by the numerous spaces in the folhcle itself, so that a lymph follicle is a true l)Tnphatic apparatus whose juices and lymph corpuscles can pass into the nearest lymphatic. The follicles are sun-ounded by a network of blood vessels which sends loops of capilla- ries into their interior (Fig. 220, B). We may assume that lymph corpuscles pass fi-om these capil- laries into the folhcle. In connection with these follicles, including those of the back of the tongue, the solitary glands of the intestine and the adenoid tissue in the bronchial tract, the tonsils, and Peyer's patches, it is import- ant to remember that enormous num- bers of leucocytes pass out between ric 221. the epithelial cells covering these follicles. The extruded leucocytes undergo disintegration subsequently. (2) The compound lymph glands — the lymphatic glands — represent a collection of lymph folli- cles, whose form is somewhat altered. Every lymph'gland is covered exter- nally with a connective-tissue cap- sule (Fig. 221, c), which contains numerous non- striped muscular fibres . From its inner surface, numerous septa and trabeculee (/r.) pass into the interior, so that the gland sub- stance is divided into a large number of compartments. These com- partments in the cortical portion of the gland have a somewhat rounded form, and constitute the alveoli, while in the medullary portion they have a more elongated and irregular form. [On making a section of a lymph gland we can readily distinguish the cortical from the medullary pro- tion of the gland,] All the com- partments are of equal dignity, and they all communicate with each other by means of openings, so that the septa bound a rich network of spaces within the gland, which communicate on all sides with each other. These spaces are traversed by therfollicular threads (Fig. 222,/,/). These represent the con- Diagrammatic section ot a lymphatic gland, a. I., aflferent, e. I., efiferent .•^. lymphatics; C, cortical substance: M, reticular cords of medulla; :, /. s., lymph sinus ; c, capsule, with trabeculse, tr. 852 LYMPHATIC GLANDS. lenU of the spaces, but ore smaller than the spaces in which they lie, and do not come into contact anywhere with the walls of the spaces. If we imagine the spaces to be injected with a mass, which ultimately shrinks to one-half of Us original volume, we obtain a conception of the relation of these follicular'lhrcads to the spaces of the gland. The blood vessels of the gland {i) lie within these follicular threads. Thev are surrounded by a tolerably thick crust of adenoid tissue, with very fine meshes (.r, x) filled with lymph corj^uscles, and with its surface {0,0) covered by the cells of the adenoid reticulum, in such a way as to leave free communications through the narrow meshes. Between the surface of the follicular threads and the inner wall of all the spaces of the gland, lies the lymph channel or lymph path (B, B), which is traversed by a reticulum of adenoid tissue, containing relatively few lymph cor|)Uscles. It is very probable that these lymph paths are lined by endothelium. The vasa afTcrentia (Kig. 221, <;./.), of which there are usually several, expand upon the surface Fi<".. 222. follicular MnuxU from The lymph pa.h' ' ' ' ^'°°'* ''"'"''= "• "' "="^^ovv.meshed part limiting the To -n e va'sa effTen ia Is''*" '' '"^ ^""^ '^'1' ^°"^^°'^ '"^^ '^' ^^'^P'^ P^'^s of the gland form Hr.rui . *^"'^"*'=' "*"^^ '^-^ '"' """"^rous than the afTerentia, and come out at the hilum, h^^ hTl K • ' cavernous dilatations and they anastomose near the gland (. /) ThroLh el :h and'pats'rn^Th^lVm'h ''?r' ^'^ °' ''^ S'^"^" '^^^ >ymph%rcoL;es^through the t'he 3fferent'a':?:fferTn't l>m,!hTelK'^' "'"' "^"""^ ^ ''"' ^^ '^'^ '"'^^'^^^ '"^-P°-d '-' — Iy.^p"""hrouU'r|tanH?r'e,;ri: ^'P,""''^ '""'^^ ^-^^'^"^ °f ^P^"^' '^e movement of the n^it hasv.ryhttle loul^^^^^^^^^^^ '"^ '^' ""'""°"^ resistances which occur in Us COMPOSITION OF LYMPH AND CHYLE. 353 cytes wander out into the follicular threads. The movement of the lymph through the gland is favored by the muscular action of the capsule. When the capsule contracts energetically, it must compress the gland like a sponge, and the direction in which the fluid moves is regulated by the position and arrangement of the valves. Chemistry. — In addition to the constituents of lymph, the following chemical substances have been found in lymphatic glands : leucin and xanthin. ig8. PROPERTIES OF CHYLE AND LYMPH.— Chyle and lymph are albuminous, colorless, clear juices, containing lymph corpuscles, which are identical with the colorless blood corpuscles (§ 9). In some places, e.g., in the lymphatics of the spleen, especially in starving animals, and in the thoracic duct, a few colored blood corpuscles have been found. The lymph corpuscles are supplied to the lymph and chyle from the lymphatic glands and the adenoid tissue. As to their source see § 200, 2. They also pass out of the blood vessels and wander into the lymphatics. As red blood corpuscles have also been seen to pass out of the blood vessels, this explains the occasional presence of these cor- puscles in some lymphatics ; but when the pressure within the veins is high, near the central orifice of the thoracic duct, red blood corpuscles may pass into the thoracic duct. But we are not entitled to conclude from their presence that lymph cells form red blood corpuscles. In addition, the chyle contains numerous fatty granules, each surrounded with an albuminous envelope. [Thus the chyle, in addition to the constituents of the lymph, contains, especially during digestion, a very large amount of fat, in the form of the finely emul- sionized fat of the food, which gives it its characteristic white or milky appearance. During hunger, the fluid in the lacteals resembles ordinary lymph. The fine fat granules constitute the so-called "molecular basis" of the chyle.] Composition of Lymph. — The lymph consists of lymph plasma with lymph corpuscles suspended in it. The corpuscles or leucocytes are described in § 24. The lymph plasma contains the three so-called fibrin factors, derived very probably from the breaking up of lymph corpuscles (§ 29). When lymph is withdrawn from the body, these substances cause it to coagulate. Coagulation occurs slowly, owing to the formation of a soft, jelly-like, small " lymph clot," which contains most of the lymph corpuscles. The exuded fluid or lymph serum contains alkali albuminate (precipitated by acids), serum albumin (coagu- lated by heat), and paraglobulin — the two latter occurring in the same proportion as in blood serum ; 37 per cent, of the coagulable proteids is paraglobulin. (i) Chyle, which occurs within the lacteals of the intestinal tract, can only be obtained in very small amount before it is mixed with lymph, and hence the difii- culty of investigating it. A few lymph corpuscles occur even in the origin of lacteals within the villi, but their number increases in the vessels beyond the intestine, more especially after the chyle has passed through the mesenteric glands. The amount ot solids, which undergoes a great increase during digestion, on the contrary, diminishes when chyle mixes with lymph. After a diet rich in fatty matters, the chyle contains \wxi\xx^&x2\At fatty granules (2-4 //. in size). [This is the so-called "molecular basis" of the chyle.] The amount oi fibrin factors increases with the increase of lymph corpuscles, as they are formed from the break- ing up of the lymph-corpuscles ; a diastatic ferment absorbed from the intestine ; occasionally sugar (to 2 per cent.); after much starchy food, lactates ; peptone in the leucocytes (§ 192, I, 3), and traces of urea and leucin. The Chyle of a person who was executed contained 90.5 per cent, of water. f Fibrin, trace I Albumin, . . . . . 7.1 1 Fats, . . . . . 0.9 Solids, ... . . • 9'5 1 I Extractives, . . . . i.o [ Salts, 0.5 23 ;554 QUANTITY OF LYMPH AND CHYLE. Schmidt found the following inorganic siil)-tances in looo parts of chyle :— Sodic chloride, Stxla, Totash, 584 1.17 Sul])huric acid, rho-.|)horic acitl, Ca'cic pho-^ohaie. 0.05 0.05 0.20 \Iagnesic phosphate, 0.05 Iron, . trace. (Horse.) (2) The lymph obtained from the beginning of the lymphatic system contains very few lymjih corpuscles ; it is clear, transparent, and colorless, and closely resembles the fluids of serous cavities. That the lymph coming from different tissues varies somewhat, is highly probable, but this has not been proved. After lymph has passed through lymphatic glands, it contains more corpuscles, and also more solids, especially albumin and fat. Ritter counted 8200 lymph corpuscles in I cubic centimetre of the lymph of a dog. Pure lymph obtained from a lymphatic fistula in the leg of a man has an alkaline reaction' and a saline taste, and the following composition : — Pure Lymph (HfHien &' Dahnhardt). Water, 98.63 Solids 1.37 hibrin o.ll AUiumin o 14 Alkali-albuminate, . . 0.09 Extractives, Urea, Leucin, .... 105 Salts, 0.88 70 vol. per cent, of absorbed CO,, 50 per cent, could be pumped out, and 20 per cent. i)V the addition of an acid. Cercbro-spinal Fluid ( Hoppe-Seyler). ?8-74 1.25 0.16 The cerebro-spinal fluid and ab- dominal lymph contain a kind of sugar (without the property of rotating polarized light — Hoppe- SeyUr). Pericardial Fluid (». Gorup-Besanei). 95 5' 4.48 0.08 2.46 1.26 100 parts of the ash of lymph contained the following substances : — Sodium chloride, . . . 74 48 Soda, 10.36 Potash, 3.26 Sulphuric acid, . . . . 1.28 Carbonic acid, .... 8.21 Iron oxide 0.06 Lime, 0.98 Magnesia 0.27 Phosphoric acid, . , . i .09 Just as in blood, potash and phosphoric acid are most abundant in the corpuscles; while soda (chiefly sodium chloride) is most abundant in the lymph serum. The potash and phosphoric acid compounds are most abundant in cerebro-spinal fluid, according to C. Schmidt. The amount of \vater in the lymph rises and falls with that of the blood. Gases. — Dog's lymph contains much CO. — more than 40 vols, per cent., of which 17 per cent, can be pumped out, and 23 per cent, expelled by acids, while there are only traces of O and 1.2 vols, per cent. N i^Liuiwig, H amine rsteti). [The cerebro-spinal fluid contains a substance which reduces an alkaline solution of cupric hydrate. The jjotassic are in excess of the soda salts, while the fluid of the meningoceles and chronic hydrocephalus contains proto-albumose, some serum globulin, no serum albumin, but the last is present in acute hydrocephalus fluid. No albumo.se is found in pericardial or pleuritic fluids {HaUibiitt.n V] 199. QUANTITY OF LYMPH AND CHYLE.— When it is stated that the total amount of the lymph and chyle passing through the large vessels in twenty-four hours is equal to the amount of the blood, it must be remembered that this is merely a conjecture. Of this amount one-half may be lymph and the other half chyle. The formation of lymph in the tissues takes place continually, and without interruption. Nearly 6 kilos, of lymph were collected in twenty-four hours from a lymphatic fistula in the arm of a woman, by Gubler and Quevenne ; 70 to 100 grms. were collected in i'^ to 2 hours from the large lymph trunk in the neck of a young horse. The following conditions affect the amount of chyle and lymph : — ORIGIN OF LYMPH. 355 (i) The amount of chyle undergoes very considerable increase during digestion, more especially after a full meal, so that the lacteals of the mesentery and intestine are distended with white or milky chyle. During hunger the lymph vessels are collapsed, so that it is difficult to see the large trunks. (2) The amount of lymph increases especially with the activity of the organ from which it proceeds. Active or passive muscular movements greatly increase its amount. Lesser obtained in this way 300 cubic centimetres of lymph from a fasting dog, whereby its blood became so inspissated as to cause death. (3) All conditions which increase the pressure upon the juices of the tissues increase the amount of lymph, and vice versa. These conditions are : — (fl) An increase of the blood pressure, not only in the whole vascular system, but also in the vessels of the corresponding organ, augments, the amount of lymph and vice versa {Ltidtvig, Tomsa). This, however, is doubtful, as has been shown by Paschutin and Emminghaus. [In order to increase the amount of lymph depending upon pressure within the vessels, what must happen is increased pressure within the capillaries and veins.] ((6) Ligature or obstruction of the efferent veins greatly increases the amount of lymph which flows fi-ora the corresponding parts {^Bidder-, Em7?iinghaus). It may be doubled in amount. Tight bandages cause a swelling of the parts on the peripheral side of the bandage, owing to a copious effusion of lymph into the tissue (congestive oedema). (f) An increased supply of arterial blood acts in the same way, but to a less degree. Paraly.-is of the vasomotor nerves, or stimulation of vaso-dilator fibres, by increasing the supply of blood increases the amount of lymph; while diminution of the blood supply, owing to stimulation of vaso- motor fibres or other causes, diminishes the amount. Even after ligature of both carotids, as the head is still supplied with blood by the vertebrals, the lymph stream in the large cervical lymphatic does not cease. (4) WTien the total amount of the blood is increased, by the injection of blood or serum into the arteries, much fluid passes into the tissues and increases the formation of lymph. (5) The formation of Ijinph still goes on for a short time after death, and after complete cessation of the aciion of the heart, but only to a slight extent. If fresh blood be caused to circulate in the body of an animal, while it is still warm, more lymph flows from the lyrrphatics. It appears as if the tissues obtained plasma from the blood for a time after the stoppage of the circulation. This perhaps explains the circumstance that some tissues, e. g., connective tissues, contain more fluid after death than during life, while the blcod vessels have given out a considerable amount of their plasma after death. (6) The amount of lymph is increased under the influence of curara, and so is the amount of soUds in the lymph [Lesser). A large amount of lymph collects in the IjTnph sacs [especially the sub- lingual] of firogs poisoned with curara, which is partly explained by the fact that the lymph hearts are paralyzed by curara. The amount of lymph is also increased in inflamed parts. 200. ORIGIN OF LYMPH.— (i) Source of the Lymph Plasma.— The lymph plasma may be regarded as fluid which has been pressed through the walls of the blood vessels by the blood pressure, /. e., by filtration into the tissues. The salts which pass most readily through membranes, go through nearly in the same proportion as they exist in blood plasma — \.\\tfibriti factors to about two- thirds, and albumin to about one-half of that in the blood. As in the case of other filtration processes, the amount of lymph must increase with increasing pressure. This was proved by Ludwig and Tomsa, who found that when they passed blood serum under varying pressures through the blood vessels of an excised testis, the amount of transuded fluid which flowed from the lymphatics varied with the pressure. This " artificial lymph " had a composition similar to that of the natural lymph. Even the amount of al 'umin increased with increasing pressure. The lymph plasma is mixed in the different tissues with the decomposition products, the results of the metabolism of the tissues. When the muscles act, not only is the lymph poured out more rapidly, but more lymph is formed. The tendons and fascise of the muscles of the skeleton, which are provided with numerous small stomata, absorb the lymph from the muscles. By the alternate contraction and relaxation of these fibrous structures, they act like suction pumps, whereby the lymphatics are alternately filled and emptied, while the lymph is propelled onward. Even passive movements 356 MOVEMENT OF CHYLE AND LYMPH. act in the same way. If solutions be injected under the fascia lata, they may be propelled onward to the thoracic duct by passive movements of the limb {Ludwig, Schu>eig^(^er-Sei(icl ). (2) The source of the lymph corpuscles varies. — (i) A very considerable number of lymph corpuscles are derived from the lymphatic glands ; they are washed out of these glands into the vas efferens by the lymph stream, hence, the lymph always contains more corpuscles after it has passed through a lymph gland. Small isolated lymph follicles permit corpuscles to pass through their limiting laver into the lymph stream. (2) Those organs whose basis consists of adenoid tissue, and in whose meshes numerous lymph corpuscles occur, e. g., the mucous membrane of the entire intestinal tract, red marrow of bone, and the spleen (,§ 103). The cells reach the origin of the lymph stream by their own amoeboid movements. (3) As lymph corpuscles are returned to the blood stream, where they appear as colorless blood corpuscles, so they again pass out of the blood capillaries into the tissues, partly owing to their amoeboid movements, and they are partly expelled by the blood pressure. In rare cases lymph corpuscles wander from lymphatic spaces back again into the blood vessels. Fine particles of cinnabar or milk globules intro luced into the blood soon pa«s into the lymphatics. The extrusion of particles is gieater during venous congestion than when the circulation is undisturbed, just as with diapedesis (?. 95) ; intlammatoiy affections of the vascular wall also fa^or their passage. The vessels of the portal system are especially pervious. (4) By division of the lymph corpuscles, and also by proliferation of the fixed connective-tissue corpuscles. This process certainly occurs during inflammation of many organs. This has been proved for the excised cornea kept in a moist chamber ; the nuclei of the cornea corpuscles also proliferate. That the connective-tissue corpuscles proliferate is shown by the enormous product'on of lymph corpuscles in acute inflammations (with the formation of pus), e. ^s;-, in extensive erysipelas, and in- flammatory purulent effusions into serous cavities, where the number of corpuscles is too gieat to be explaine 1 by the wandering of blood coqjuscles out of the blood vessels. Decay of Lymph Corpuscles. — The lymph corpuscles disappear partly where the lymphatics arise. The presence of the fibrin factors in the lymph — formed as they are from the breaking up of lymph corpuscles — seems to indicate this. In inflammation of connective tissue, in addition to the formation of numerous new lymph corpuscles, a considerable number seems to be dissolved ; hence the lymph, and also the blood, in this case contains more fibrin. Lymph corpuscles are also dissolved within the blood stream, and help to form the fibrin factors. 201. MOVEMENT OF CHYLE AND LYMPH.— The ultimate cause of the movement of the chyle and lymph depends ui)on the difference of the pressure at the origin of the lymphatics, and the pressure where the thoracic duct opens into the venous system. (i) The forces which are active at the origin of the lymphatics are concerned in moving the lymph, but these must vary according to the place of origin, (a) The lacteals receive the first impulse toward the movements of their contents — the chyle — from the contraction of the muscular fibres of the villi (pp. 339, 344). When these contract and shorten, the axial lacteal is compressed, and its contents are forced in a centripetal direction toward the large lymphatic trunks. When the villi relax, the numerous valves prevent the return of the chyle into the villi, {b) Within those lymphatics which take the form of perivascular spaces, every time the contained bloodvessel is dilated the surrounding lymph will be pressed onward, (r) In the case of the pleural lymphatics with open mouths, every inspiratory movement acts like a suction pump upon the lymph, and the same is the case with the openings or stomata of the lymphatics on the abdominal side of the. diaphragm, {d) In the case of those vessels which begin MOVEMENT OF CHYLE AND LYMPH. 357 by means of fine juice canals, the movement of the lymph must largely depend upon the tension of the juices of the parenchyma, and this again must depend upon the tension or pressure in the blood capillaries, so that the blood pressure acts like a vis a tergo in the rootlets of the lymphatics. [In some organs peculiar pumping arrangements are brought into action. The abdominal sur- face of the central tendon of the diaphragm is provided with stomata, or open communications between the peritoneal cavity and the lymphatics in the substance of the tendon. Von Recklinghausen found that milk put upon the peritoneal surface of the central tendon showed little eddies, caused by the milk globules passing through the stomata and entering the lyrphatics. The central tendon consists of two layers of fibrous tissue arranged in diflerent directions (Fig. 223, b, c). ^\^len the Fig. 22' Section ot central tendon of diaphragm. The injected lymph spaces, h and h, are black. At f the walls of the space have collapsed. diaphragm moves during respiration, these layers are alternately pressed together and pulled apart. Thus the spaces are alternately dilated and contracted, lymph being drawn into the lymphatics through the stomata (Fig. 223, h^. The same kind of pumping mechanism exists over the costal pleura. The fascia covering the muscles is another similar mechanism. The fascia consists of two layers of fibrous ti-sue, with intervening lymphatics (Fig. 224). WTien a muscle contracts, lymph is forced out fi-om between the layers of the fascia, while when it relaxes, the lymph fi-om the muscle, carrying with it some of the waste products of muscular action, passes out of the muscle into the fascia, between the now partially separated layers.] [Ludwig's Experiment. — Tie a respiration cannula in the trachea of a dead rabbit ; cut across the body of the animal immediately below the diaphragm ; remove the viscera, and ligature the vessels passing between the thorax and abdomen ; tie the thorax to an iron ring, and hang it up with the head downward ; pour a solution of Berlin blue upon the peritoneal surface of the diaphragm ; Fig. 224. Injected lymph spaces (black) from the fascia lata of the dog. connect the respiration cannula either with a pair of bellows or an apparatus for artificial respiration, and imitate the respiratory movements. After a few minutes the lymphatics are filled with a blue injection showing a beautiful plexus.] (2) Within the lymph trunks themselves, the independent contraction of their muscular fibres partly aids the lymph stream. Heller observed in the mesentery of the guinea pig that the peristaltic movement of the lymphatic wall passed in a centripetal direction. The numerous valves prevent any reflux. The contraction of the surrounding muscles, and pressure upon the vessels and the tissues, aid the current. If the outflow of blood from the veins is interfered with, lymph flows copiously from the corresponding tissues. [If a 358 MOVEMENT OF THE LYMPH. cannula be tied in a lymphatic of a dog, a few drops of lymph flow out at long intervals. But if even />assivc movements of the limb be made, e. g., simply flexing and extending the limb, the outflow becomes very considerable and continuous.] (3) Tlie lymph glands, which occur in the course of the lymphatics, offer very considerable resistance to the lymph stream, which must pass through the lymph paths, whose spaces are traversed by adenoid tissue, and contain a few lymph corpuscles. But this is, to a certain extent, compensated for by the non- striped muscle which exists in the capsule and trabecular of the glands. When they contract they force on the lymph, while the valves prevent its reflux. En- larged lymphatic glands have been seen to contract when stimulated electrically. [Botkin has stimulated enlarged lymphatic glands with electricity in cases of leu- kaemia.] (4) The lymph vessels gradually join to form larger vessels, and finally end in one trunk. Thus the sectional area diminishes, so that the velocity of the cur- rent and the pressure are increased. Nevertheless, the velocity is always small ; it varied from 230 to 300 millimetres per minute in the large lymphatic in the neck of a horse, a fact which enables us to conclude that the movement must be very slow in small vessels. The lateral pressure at the same place was 10 to 20 mm., and in the dog 5 to 10 mm. of a weak solution of soda, although it was = 12 mm. Hg in the thoracic duct of a horse. (5) The respiratory movements exercise a considerable influence upon the lymph stream in the thoracic duct, and in the right lymphatic duct ; every inspi- ration fiivors the passage of the venous f "^- 2-5- blood, and also of the lymph toward the I „^ heart, whereby the tension in the thoracic duct may even become negative. [The diastolic suction of the heart, by diminish- ing the pressure in the subclavian vein, also favors the inflow of lymph into the thorax.] (6) Lymph hearts exist in certain cold- blooded animals. The frog has two axillary hearts (above the shoulder near the vertebral col- umn), and two sacral hesxis, one on each side of the coccyx near the anus (Fig. 225, L). They beat, but not synchronously, about sixty times per minute, and contain 10 cubic centimetres of lymph. They have transversely striped muscular iibrcs in their walls, and are also provided with ne7",;rate, a considerable percentage of allumin is necessary. When the pressure within the serous cavity rises above that in the smiU blood vessels, 360 (EDEMA AND DROPSY. water may pass into the blood. These sero-purulent effusions not unfrequently undergo changes, and yield deconiposiiion products, such as leuciii. tyrosin, xantbin, kreatin, krealinin (?), uric acid (?), urea. Endothelium from the .senms caviiy, sus^ar in pleuritic efl'usions and in ademas with little albumin, cholesterin frequently in hydrocele fluid, and succinic acid in the fluid of echinococci, have all been found in these efl'usions. The eflusion of hmph may arise not only from pressure upon the lymphatics, l)ut also from inflammation and thrombosis of the lymphatics themselves, in which cases not unfrec|uently new lymphatics are formed, so that the comnumication is reestablished. Sometimes the ductus thoracicus bursts, and lymph is poured directly into the abdomen or thorax. [Ligature of the thoracic duct results in rupture of the receptaculum chyli and escape of chyle and lymph into the large serous cavities (Z^«(/7i'/i,'-). When dropsy or eflusion of fluids occurs into serous cavities, there is always a greater transudation of fluid through the blood vessels. The abdominal blood vessels, and those which yield a watery effusion under normal circumstances, are those mo.st liable to be affected. Transudation is favored by (i) Venous congestion, so as to r.iise the blood pressure, in which case the eflusion usually contains little albumin and few lymjih corpuscles, while the colored corpuscles, on the contrary, are more numerous the greater the venous obstruction. Ranvier pro- duced.oedema artificially l)y ligaturing the vena cava in a dog, and at the same time dividing the sciatic nerve. The paralytic dilatation of the blood vessels thereby produced caused an increa5ed amount of blood to pass to the limb, while the blood pressure was raised, and both factors favored the transudation of fluid. [Ranvier's experiment proves that mere ligature of the venous trunk of a limb by itself is not sufficient to cause cedema. The ccdema is due to the concomitant paralysis of the vasomotor nerves. If the motor roots of the sciatic nerve alone be divided along with ligature of the vena cava, no oedema occurs, but if the vasomotor fibres are divided at the same time, the limb rapidly becomes oedematous. There is such an increased transudation through the vascular walls that the veins and h-mphatics cannot remove it with sufficient rapidity, and oedema occurs. If there be weakness of the vasomotor nerves, slight obstruction is sufficient to produce oedema,] When the leg veins are occluded with an injection of gypsum, cedema occurs. (2) Some unknown physical changes occur in the protoplasm of the endothelium of the capillaries and blood vessels, which favor the transudation of albumin, haemoglobin, and even blood corpuscles. 1 his occurs when abnormal substmces accumulate in the blood — e.g., dissolved haemoglobin — and when the blood contains little O or albumin. The same has been obsers-ed after exposure to too high temperatures, and the swelling of soft pans in the neighborhood of an inflammator)- focus seems due to the transu- dation of fluid through the altered vascular wall. It is probable that a nervous influence may affect particular areas through its act on on the blood vessels of the part (it may be upon the protoplasm of the blood ca()illaries). The transudations of this nature usually contain much albumin and many lymph corpusc'es. (^) Wlien the blood contains a very large amount of water, the tendency to transudation of fluid is increa--ed. After a time it may produce the changes indicated in (2). and when long continued may increase the permeability of the vascular wall. Watery hTiiphatic effusions from watery blood — " cachectic cedema" — occur in feeble and badly-nouri.shed individuals. [One of the commonest foims of dropsy is the slight oedema of the legs in anremic persons, in whom the heart and lungs are healthy. Many factors are involved — the blood pressure, watery condiiion of the blood, the condition of nutrition of the capillaries, and probably a tendency to vasomotor paresis [The fluid poured out varies according to the rapidity with which this occurs. In acute inflam- mations eflusif n or exudation takes place rapidly, and the fluid contains the fibrin factors, so that it tends to coagulate spontaneously. There is every gradation between the non-coagulable hydrocele fluid and the coagulable exudation in inflammation. The fluids in ditTerent dropsies vary in comj o- sition, and some have more cells in them, depending on local causes, as in some situations absorption is more active than in others. The pleural fluid contains most solids, then ascitic, cerebro-spinal, and lastly that in the subcutaneous tissue. Transudation corresponds to the process of filtration through animal membranes, /. e., the transudation contains only those substances already present in the blood plasma. The filtra'e may even contain more salts than the original fluid, as is often the case with fluids containing cry-talloid and colloid bodies. .Senator finds, in cases of oedema of the leg, that increase of the venous pressure increases the proteids in the transudation, but causes no essential change in the amount of the salts.] [(4) Ostroumoff found that stimulation of the lingual nerve n' prevent any heat from without from acting upon the inner ice. The heat given off from the combustion chamber causes a certain amount of the ice to melt, and the water thereby produced is collected and measured. It requires 79 heat units to melt I grm. of ice to I grm. of water at 0° C. [The amount of heat produced by a living animal is similarly measured. The animal (Fig. 227), in a cage, is placed in a large vessel, which is placed wiihin another vessel, and the inter-space filled wiih water. The whole should be enclosed in a large box packed wiih fur, shavings, feathers, or other bad conductor of heat. A tube, D, opens into the inner space, and from it there is an exit tube, D', which winds many times in the water space beneath. Air passes in through D and out by D''. The temperature of the water is ascertained by thermometers T and T^, while the water is moved by a stirrer (S) placed between the two.] Just as in a calorimeter, although ??izich more slowly, the food stuffs within our body are burned up, oxygen being supplied, and thus potential energy is trans- formed into kinetic energy, which, in the case of a person at rest, almost com- pletely appears in the form of heat. Heat Units. — Favre, Silbermann, Frankland, Rechenberg, B. Danilewskj, and others have made calorimetric experiments on the heat produced by food. According to Danilewsky, I gramme of the following dry substances yields heat units : — Water calorimeter of Dulong. Casein, . , . Fibrin, .... Peptone, . . . Glufin, . . , Ox-blood, . . Ox-flesh, . . . Vegetable fibrin, Gluten, . . . Legumin, . , Palmitin, . . . 5855 5772 4876 5493 5900 572-1 6231 6141 5573 Olein, . . 8958 Stearin, . 9036 Ox-fat, . 9686 Glycerine, 4179 Starch, 4479 Dextrose, 3939 Maltose, . 4163 Milk sugar. 4162 Cane sugar. 4173 Cow's milk, 5733 Woman's milk. Egg yelk, . Potatoes, Rye bread, Wheat bread Rice, . . . Peas, . . . Buckwheat, Mai2e, . . 4837 4479 4234 4471 4351 4288 5188 Alcohol, . . . . 6980 Urea, . . . . . 2537 Muscle ^ Extractives V4400 (Liebig's) 1 Flesh extract, . . 3216 Acetic acid, .3318 Butyric acid, . . 5647 Palmitic acid, . . 9316 As albumin is only oxidized to the stage of urea, we must deduct the heat units obtainable from urea horn those of albumin, and as I pare of albumin yields in round numbers about j^ of lurea, we obtain about 5100 calories [ = 2170 kilogram -metres] fir I grm. of albumin. Isodynamic foods, i, e., those that produce an equal amount of heat ; loo grms. animal albumin (afier deducting the heat units of urea) = 52 fat= II4 starch = 129 dextrfise; loo grms. fat are isodynamij with 243 dry flesh or 225 of dry syntonin [Riibtier) ; 100 grms. of vegetable albumin ^ 55 fat = 121 starch = 137 dextrose [Dafii/eicisky). Rubner calculated that in man, with a mixed diet, the available heat units for I grm. of albumin ^= 4100 ; i grm. fat = 9300; and for i grm. carbohydrate = 4100 calories. When we know the weight of any of the above-named substances consumed by a man in twenty-four hours, a simple calculation enables us to determine how many heat units are formed in the body by oxidation, i. e., provided the substance is completely oxidized. 364 CHEMICAL SOURCES OF HEAT. [Several sources of heat production or thermogenesis are to be found in all tissues wherever oxidation is going on. The metabolism of protoplasm is always associated with the evolution of heat.] (i) /// the transformation of the chemical constituents of the food, endoived with a large amount of potential energy, into such substances as have little or no energy. The organic substances used as food consist of C, H, O, N, so that there takes place ((I) Combustion of C into CO.^, of H into H,0, whereby heat is pro- duced ; I grm. C burned to produce CO2 yields 8080 heat units, while i grm. H oxidized to W-.O yields 37,460 heat units. The O necessary for these purposes is absorbed during respiration, so that, to a certain extent at least, the amount of heat produced may be estimated from the amount of O consumed. The same consumption of O gives rise to the same amount of heat whether it is used to oxidize H or C {Ffliiger). There is a relation, amounting to cause and effect, between the amount of heat produced in the body and the O consumed. The cold-blooded animals, which consume little O, have a low temperature ; among warm-blooded animals, i kilo, of a living rabbit takes up within an hour 0.914 grm. O, and its body is heated to a mean of 38° C. i kilo, of a living fowl uses 1. 186 grms. O, and gives a mean temperature of 43.9° C. The amount of heat produced is the same whether the combustion occurs slowly or quickly; the rapidity of the metabolism, therefore, affects the rapidity, but not the absolute amount of heat production. The combustion of inorganic substances in the body e.g., of the sulphur into sulphuric acid, the phosphorus into phosphoric acid, is another, although very small, source of heat. [The muscles form about the half of the whole mass of the body and the bones nearly the other half. In the latter, oxidation does not go on actively, so that the muscles must be the great seats of heat production or thermogenesis in the body. This view is supported by the fact that the blood leaving a muscle at rest contains more CO, than the blood in the right ventricle. Muscular exercise greatly increases the metabolism and the CO., excreted (§ 127), but at the same time, there is a great increase in heat production. The muscles, therefore, are the great thermogenic tissues, and they yield \ of the heat in health. The sev- eral secreting glands, especially the liver, and the alimentary canal, during digestion, are also foci of heat formation.] {b) In addition to the processes of combustion or oxidation, all those chemical processes in our body, by which the amount of the available potential energy which is present is diminished, in consequence of a greater satisfaction of atomic affinities, lead to the production of heat. In all cases where the atoms assume more stable positions with their affinities satisfied, chemical energy passes into kinetic thermal energy, as in the alcoholic fermentation of grape sugar and other similar processes. Heat is also developed during the following chemical processes : — (a) During the union of bases with acid's. The nature of the base determines the amount of heat produced, while ihe nature of the acid is without eflect. Only in those cases where the acid, e.,i^., CO2, is unable to set aside the alkaline reaction, the amount of heat produced is less. The forma- tion of compounds of chlorine ((f-.i,'., in the stomach) produces heat. (,3) When a neutral salt is changed into a basic one. In the blood the su'phuric and jihosphoric acids derived from the combustion of S and P are united with the alkalies of the blood to form bas-ic salts. The decomposition of the carbonates of the blood by lactic and phosphoric acids forms a double source of heat, on the one hand, by the formation uf a new salt, and on the other, by the liberation of CO,,, wh'ch is partly absorbed by the blood. ()) The combination of haemoglobin with O (§ 36). During those chemical processes, whereby the heat of the body is produced, heat-absorbing intermediate compounds are not unfrequently formed. Thus, in order that the final stage of more complete saturation of the affinities be reached, HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS* 365 intermediary atomic groups are formed, whereby heat is absorbed. Heat is also absorbed when the solid aggregate condition is dissolved' during retrogressive pro- cesses. But these intermediary processes, whereby heat is lost, are very small compared with the amount of heat liberated when the end products are formed. (2) Certain physical processes are a second source of heat, (a) The transformation of the kinetic mechanical energy of internal organs, when the work done is not transferred outside the body, produces heat. Thus the whole of the kinetic energy of the heart is changed into heat, owing to the resistance opposed to the blood stream (§ 93). The same is true of the mechan- ical energy evolved by many muscular viscera. The torsion of the costal cartilages, the friction of the current of air in the respiratory organs, and the ingesta in the digestive tract, all yield heat. An excessively minute amount of the mechanical energy of the heart is transferred to surrounding bodies by the cardiac impulse and the superficial pulse beats, but this is infinitesimally small. During respiration, when the respiratory gases and other substances are expired, a very small amount of energy disappears externally, which does not become changed into heat. If we assume that the daily work of the circulation exceeds 86,000 kilogram-metres, the heat evolved is equal to 204,000 calories, in twenty-four hours (| 93), which is sufficient to raise the temperature of a person of medium size 2° C. (J)) When, owing to muscular activity, the body produces work which is trans- ferred to external objects, e.g., when a man ascends a tower or mountain, or throws a heavy weight, a portion of the kinetic energy passes into heat, owing to friction of the muscles, tendons, and the articular surfaces, as well as to the shock and pressure of the ends of the bones against each other. (c) The electrical currents which occur in muscles, nerves, and glands very probably are changed into heat. The chemical processes which produce heat evolve electricity, which is also changed into heat. This source of heat, however, is very small. {d) Other processes are the formation of heat from the absorption of CO^, by the concentration of water as it passes through membranes, in imbibition, and the formation of the solids, e. g., of chalk in the bones. After death, and in some pathological processes during life, the coagulation of blood and the production of rigor mortis are sources of heat. 207. HOMOIOTHERMAL AND POIKILOTHERMAL ANI- MALS.— In place of the old classification of animals into "cold-blooded" and "warm-blooded," another basis of classification seems desirable, viz., the relation of the temperature of the body to the temperature of the surrounding medium. Bergmann introduced the word homoiothermal for the warm- blooded animals (mammals and birds), because these animals can maintain a very uniform temperature, even although the surrounding temperature be subject to considerable variations. The so-called cold-blooded animals are called poikilo- thermal, because the temperature of their bodies rises or falls, within wide limits, with the heat of the surrounding medium. When homoiothermal animals are kept for a long time in a cold medium, their heat production is increased, and when they are kept for a long time in a warm medium it is diminished. Fordyce gave a proof of the nearly uniform temperatiure in man. A man remained ten minutes- in an oven containing very dry hot air (§ 218), and yet the temperature of the palm of his hand, mouth, and urine was increased only a few tenths of a degree. Becquerel and Brechet investigated the temperature of the human biceps (by means of thermo-electric needles), when the arm had been one hour in iced water, and yet the temperature of the muscular tissue was cooled only 0.2° C. The same muscle did not undergo any increase in temperature, or at most 0.2° C, when the man's arm was placed for a quarter of an hour in water at 42° C. If heat be rapidly abstracted (§ 225) or rapidly supplied (§ 221) to the body, so as to produce rapid variation of the temperature, life is endangered. 366 THERMOMETRY. Poikilothermal animals behave very differently ; the temperature of their bodies generally follows; although with considerable variations, the temperature of the surroundings. When the temperature of the surroundings is increased, the amount of heat produced is increased, and when the surrounding temperature falls, the amount of heat evolved within the body also falls. The following table shows very clearly the characters of poikilothermal animals, e.g., frogs, which were placed in air and water of varj'ing temperatures. They were immersed up to the mouth. The temperature was measuied by means of a thermometer introduced through the mouth into the stomach. In Water. In Air. Temperature of the Water. Temperature of Frog's Stomach. Temperature of the Air. Temperature of Frog's Stomach. 41.0° C. 30.0 20.6 5-9 2.8 38.0° C. 29.6 20.7 8.0 5-3 40.4° C. 27.4 16.4 6.2 5-9 31 7° C. 19.7 14.6 7.6 8.6 Birds. Temp. Thalassidroma, . . . 40.30 ProctUaria, 40.80 Goose, 41-70 c f 39-o8 Sparrow, ^I^^^j^^ Pigeon, . . . 41.80-42.50 Turkey, 4270 Guinea fowl, .... 43-90 Duck { 4^-9° ^^^^ \ 42.50 Crow, 4117 [Temperature of Different Animals. Temp. Swallow, 44.03 Gull, 37.8 Mammals. Tiger, 37.20 Horse, .... 36.80-37.50 Rat, 38.80 Hare, 37-8o Cat, 38.30-38.90 Guinea pig 38 80 f 37-40 Dog, \ 39-00 ( 39-60 Temp, Panther, 3890 Mouse, 41. 1 Dolphin, 35.5 ( 37-30-40.00 Sheep, . . . . -^ 39.50-40.00 ( 40.00-40 50 Ape, . 35.50 Guinea pig, . . 35.76-38.00 Rabbit, . . . 37.50-38.00 Ox, 37.50 Ass, 3695 {^Gavarret dr' Rosenthal).'\ Reptiles — Snakes, io°-i2°, but higher when incubating. Amphibians and fishes — o 5°-3° above the temperature of the surroundings. Arthropoda — o.i°-5.8° above the surroundings. Bees in a hive, 30'^-32°, and when swarming, 40°. The followmg animals have a temperaiure higher than the surrounding temperature : Cephalopods, 0.57°; mollusks, 0.46° ; echinoderms, O 40 ; medusre, 0.27° ; polyps, 0.21° C. 208. ESTIMATION OF TEMPERATURE. — By using thermometric apparatus, we are enabled to obtain information regardint; the degree of heat of the body to be investigated. For this purpose the following methods are employed : — A. The Thermometer. — Celsius (i 701-1744) divided his thermometer into 100 parts, and each part was again divided into 10 parts, sa that -^^° C. could be easily read off. All thermometers which have been used for a long time gi%'e too high readings; hence they should be compared, from time to time, with a normal thermometer. When taking the temperature, the bulb ought to be surrounded for fifteen minutes, and during the last five minutes the mercury column ought not to vary. A very sensitive thermometer will indicate the temperature after seven seconds if the urine stream be directed upon its bulb. Minimal and maximal thermometers are often of use to the physician. [Clinically, one of the thermometers shown in Fig. 228 may be used. They are self-registering maximum thermometers, z. ^., a portion of the mercury is separated from the mercurial column, to form the index, the top of which indicates the temperature. Before being used, the index must be well below the normal temperature. Various forms of surface thermometers have been used.] THERMO-ELECTRIC MEASUREMENT OF HEAT. 367 Walferdin's metastatic thermometer (Fig. 229) is specially useful for comparative observation. The tube is very narrow in comparison with the bulb, and in order that the stem be not too long, it is constructed so that the Fig. 228. amount of mercury can be varied. A quantity of mercury is taken, so that with the tempera- ture expected the thread of mercury will Fig. 229. A, Cassella's " infallible," B, " Ferris' perfect," and C, Evans' and Wormull's thermometers. 'standard" clinical Stand about the middle of the stem. A small bulb at the upper part of the stem receives the excess of Hg. Suppose a temperature between 37°-40° C. is to be meas- ured, the bulb is first heated a little over 40° C, it is then suddenly cooled, and shaken at the same time, so that the thread of mercury is thereby suddenly broken above 40°. The tube is so narrow that 1° C. is equal to about 10 centimetres of the length of the tube, so that ^50° ^- '^ ^'■^^^ ^ millimetre in length. The scale is divided empirically, but the value ot the divisions must be compared with a normal thermometer. Kronecker and Meyer used verj' small maximal "outflow thermometers," and caused them to pass through the intestinal canal, or through large blood vessels. The mercury flows out of the short open tube, and of course more flows out, the higher the temperature. After these small bulbs have passed through the animal, a comparison is instituted with a normal thermometer, to determine at what temperature the mercury reaches the free margin of the tube. B. Thermo-electric Method. — This method enables us to determine the tempera- ture accurately and rapidly (Fig. 230, I). The thermo-electric galvanometer of Meissner and Meyerstein consists of a circular magnet (w) suspended by a thread of silk (c), to which a small mirror (S) is attached. A large stationary bar magnet (M) is placed near the magnet (w), so that the north poles (« and iSi) of bclh magnets point in the same direction, and it is so arrarged that the suspended magnet is caustd to point to the north by a minimal action of M. A thick copper wire {/>,^) is coiled several times round m (although in the figure it is represented as a single coil), and the ends of the wire are soldered to two thermo-elements, each composed of two different metals — iron and German silver, the two similar free elements being united by a wire [d), so that the two thermo-elements form part of a closed circuit. A horizontal scale (K, K) is placed at a distance of 3 metres from the mirror, so that the divisions of the scale are seen in the mirror. The scale itself rests upon a telescope (F) directed toward the mirror. The observer (B), who looks through the telescope, can see the divisions of the scale in the mirror. When the magnet, and with it the mirror, swing out of the magnetic meridian, the observer notices ctlier divisions of the scale in the mirror. When one of the thermo- elements IS heated, an electrical current is produced, which passes from the iron to the German silver in the heated couple, and causes a deviation of the suspended magnet. Suppose a person were swimming in the direction of the current in the conducting wire, then the north pole of the magnet goes to the north [Ampere). The tangent of the angle (j>, through which the freely movable magnet is diverted by a galvanic current, from its position of rest or zero, in the magnetic meridian, is the same as the galvanic stream; G G is proportional to the magnetic energy D, i. e., tang. ' large transverse section. The vibrating magnet induces in this closed circuit a current of electricity, whose intensity is greatest when the velocity of the excursion of the majrnet is greatest, and which takes the opposne direction as soon as the magnet returns toward zero. These induced currents cause a diminution of the vibration of the magnet in this way, that the arc of vibra- tion of the magnet diminishes very rapidly, almost in a geometrical progression. The induced damping current is stronger, the less the resistance in the closed circuit, and in the damper or dead- beat arrangement itself, the greater the section of the copper ring. This damping arrangement limits Fir,. 230. i m Scheme of thermo-electric arrangements for estimating the temperature. the oscillations of the magnet, and it comes to rest rapidly and promptly after 3 or 4 small vibrations, so that much time is saved. The angle of deviation is so small that the angle itself may be taken instead of the tangent. The thermo-electric needles of Dutrochet (II) may be placed in the circuit. They consist of iron and German silver soldered at their points ; or the needles of Becquerel (III) may be used. They consist of the same metal soldered in a straight line, one behind the other. The needles must always be covered by a varnish, which will prevent the parenchymatous juices from acting upon them, and so causing a current. Before the experiment we must determine what extent of excursion on the scale is obtained with a certain temperature. In order to determine this, a delicate thermometer is fixed TEMPERATURE TOPOGRAPHY. 369 to each of the thenno-couples, and both are placed in oil baths, which differ in temperature say by 1° C. — as can be determined by the themiometer. \\Tien the current is closed, the excursion on the scale will indicate i° C. Suppose that the excursion was 150 mm., then each mm. of the scale would be equal to yi^" C. AATien this is determined, the two thermo-needles may be placed in the different tissues or organs of animals, and, of coiu-se, we obtain the difference of temperature in these places. Or one thermo-couple may be placed in a bath of constant temperature (near-ly that of the body), in which is placed a delicate thermometer, while the other needle is introduced into the organ to' be investigated. In this case, we obtain the difference of temperature between the tissue and the source of the constant heat. The electric current passes in the warmer needle from the iron to the German silver, and thus through the wires of the apparatus. For small differences of temperature, such as occur in the body, the thermo-electric energy is always proportional to the difference of temperature of the two needles or couples. In place of a single pair of needles several may be used, whereby the sensitiveness of the apparatus is gi-eatly increased. Helmholtz found that by using sixteen antimony-bismuth couples, he could detect an increase of ^^ oW° C. Schiffer prepared a simple thennopile (IV) by soldering together alternately four pairs of wires of iron (/) and German silver {a). These are placed in the two organs (A and B) which are to be investigated, whereby a very high degree of exactness is obtained. 209. TEMPERATURE TOPOGRAPHY.— Although the blood, in virtue of its continual motion (completing, as it does, the circulation in twenty- three seconds), must exercise a very considerable influence on the equilibration of the temperature in different organs, nevertheless, a completely uniform tempera- ture does not exist, and the temperature varies in different parts : — Skin (/. Davy). Middle of the sole of the foot, 32.26° C. Near tendo-Achillis, .... 33.85 Anterior surface of leg, . . . 33.05 Middle of calf, 33.85 Bend of knee, 35-oo Middle of upper arm, 35-40° C. Inguinal fold, 35 -80 Near cardiac impulse, 34-40 Face, 31 -oo Nose and tip of ear, . 22.24 In the closed axilla, 36.49 (mean, of 505 individuals) ; — 36.5 to 37.25 ( Wimderlic/i) ; — 36.89° C. {Liebermeister). The skin over muscles is warmer than that over bone [K'unkel). The temperature of the skin of the head is higher in the forehead and parietal region than in the occipital region ; the skin on the left side of the head is warmer than on the right. Dyspnoea increases the temperature of the skin. Method. — Liebemieister determines the temperature of free cutaneous surfaces thus : The bulb of the thermometer is heated slightly above the temperature expected ; after the mercury begins to fall, the bulb is placed on the skin, and if the bulb has the same temperature as the skin, the mercury remains stationary. This experiment must be repeated several times. 2. Cavities. ' Mouth under the tongue, . . 37.19° C. I Vagina, 38.30° C. Rectum, 38 01 | Urine, 37.03 Uterine cavity somewhat warmer; cervical canal of the uterus somewhat cooler. The temperature falls in the stomach during digestion (§ 166, i). Cold injections (11° C.) into the rectum rapidly lower the temperature in the stomach 1° C. ( Winternitz^. 3. The temperature of the blood is, as a mean, 39° C. The venous blood in internal viscera is warmer than the arterial, but it is cooler in peripheral parts : — Blood of the right heart, t^%.^° I Blood of the superior vena cava, . . . 36.78° left heart, 38.6 | " inferior vena cava, . . . 38. II ^orta, 38.7 " crural vein, 37-20 hepatic vein, 39.7 | " {CI. Bernard and v. Liebig.) The lower temperature of the blood in the left heart may be explained by the blood becoming cooled in its passage through the lungs during respiration. According to Heidenhain and Korner, the right heart is slightly warmer because it lies in relation with the warm liver, while the left heart IS surrounded_ by the lung, which contains air. This observation is disputed by others, who say that the left heart is slightly warmer because the combustion processes are more active in arterial blood, and heat is evolved during the formation of oxyhjemoglobin. The blood in the veins is usually cooler than in the corresponding arteries, owing to the superficial position of the former, whereby they give off heat during their long course; thus the blood of the jugular vein is ^ to 2° C. lower than the blood in the carotid ; the crural veiti }( to 1° cooler than in the crtiral artery. Superficial veins, more especially those of the skin, give off much heat, and their blood is, therefore, somewhat cooler. 24 370 TEMPERATURE OF ORGANS. The warmest blood is that of the hepatic vein, 39.7° C, partly owing to the great chemical changes which occur within the liver, from its secretory activity (^ 210, a), and partly to its protected situation. 4. The individual tissues are warmer : (i) The greater the transformation of kinetic energy into lieat, i.e., the greater the tissue metabolism; (2) the more blood they contain ; (3) and the more protected their situation. According to Heidenhain and Korner, the cerebrum is the warmest organ in the body. Subcutaneous tissue (sheep), . . 37.35° Brain, 4025 Liver, 41-25 Lungs, 41 40 Rectum 40.67° C. Right hearf, • . . 41.60 Left heart, 40.90 Becquerel and Brechet found the temperature of the human subcutaneous tissue to be 2.1° C. lower than that of the neighboring muscles. The horny tissues do not produce heat, and their low tempera- ture is due to the conduction of heat from the parts on which they grow. The temperature of the cornea partly depends on that of the iris, and the more contracted the pupil is, the more heat it receives from the blood vessels of the iris. 210. CONDITIONS AFFECTING THE TEMPERATURE OF ORGANS. — The temperature of the individual organs is by no means constant ; it is influenced by many conditions ; among these are the following : — (i) T/ie more heat produced independently within a part, the higher is its temperature. As the amount of heat produced within a part depends upon its metabolism, therefore, when the metabolism is increased, the amount of heat pro- duced is similarly increased. (a) Glands produce more heat during the act of secretion, as is proved by the higher temperature of their secretion, or by the higher temperature of the venous blood flowing out of their veins. Ludwig found that when he stimulated the chorda tympani, the saliva of the submaxillary gland was 1.5° C. wanner than the blood in the carotid, which supplied the gland with blood (p. 258). The blood in the renal vein in a kidney which is secreting is warmer than the l)lood in the renal artery. The secreting liver produces much heat (i! 178). CI. Bernard investigated the temperature of the blood of the portal and hepatic veins during hunger, at the beginning of digestion, and when digestion was most active, and he found : — Temperature of jxjrtal vein, . " hepatic vein. Temperature of portal vein, . " hepatic vein. Temperature of jxjrtal vein,. " hepatic vein. In the dog a moderate diet, chemical or mechanical stimulation of the gastric mucous membrane, or even the sight of food, raises the temperature in the stomach and intestine. {b) When the muscles contract, they evolve heat. Davy found that an active muscle became 0.7° C. warmer; while Becquerel, by means of a thermo- galvanometer, found that human muscles, when kept contracted for five minutes, became 1° C. warmer (§ 302). This is one of the reasons why the temperature may rise alx)ve 40° during rapid running. A temperature obtained by energetic muscular action usually does not fall to the nomial until after resting for lyz hour. The low temperature of paralyzed limbs depends partly upon the absence of the mus- cular contractions. {c) With regard to the effect of sensory nerves upon the temperature, some of the chief points to ascertain are — whether the circulation is accelerated or retarded by their stimulation, or whether the respiration is increased or dimin- ished (§ 214, II, 3), and whether the muscles of the skeleton are relaxed or con- tracted reflexly (§ 214, I, 3). In the former case the temperature of the interior and rectum is increased ; in the latter, diminished. 37-8° C. I After 4 days' r Blood of right heart. 38.4 starvation. I 38.8° (Hunger period.) 39-9 1 Beginning of 39-5 digestion. 39-7 } Digestion most ( Blood of right heart, 41-3 active. I during digestion, 39.2°, 372 CALORIMETRY. I-IC. 2^1. Kopp's Method. — The solid to be investigated is hroken in pieces about the size of a pea, and placed in a test-tube. A, with thin walls, which is closed above with a cork, from which a co])])er wire with a hook on it projects (I'ig. 231). The test-tube contains a certain quaniily of fluid which does not dissolve the sui)stance, but which lies between its pieces and covers it. It is weighed three times to ascertain the weight (i) of the empty glass, (2) after it is filled with the solid substance, (3) after the fluid is added, so that we obtain the weight of the solid substance, w, and that of the fluid, f. The test-tube and its contents are placed in a mercttry balh, HH, and this again in an oil bath, CC, and the whole is raised to a high temperature. Into BB there is introduced a fine thermometer, T, When the tube. A, has reached the necessary tem- perature (say 40°), it is rapidly placed in the water of the accompanying calorimeter box, 1)1). The water in this box, which also contains a thermometer, D, is kept in motion until it has completely absorbed all the heat given off" by A. Let T represent the tem- perature to which A and its contents were raised in the mercury bath, and T, the tem- perature to which it fell in the calorimeter ; let s be the specific heat, and m the weight of the solid sul)stance in the test tulie, while o and // represent the specific heat of the weight of the interstitial fluid in the test-tube ; and lastly, let w ecjual the amount of water in contact with A, which absorbs and gives oft" heat ; then \V represents the amount of heat which the test-tube and its contents give oft during cooling. W ={s .viAriv -\- c //) (T-T,) . The amount of heat, Wj, absorbed by the calorimeter is where M represents the amount of water in the calorimeter, / the original temperature of the water in the calorimeter, and /, the temperature to which it is raised by placing A in it. If W and Wj are equal, then ,M(/,-0-(7£' + ^.(i° , while it is 37.17° on ordinary d^ys (§ 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 con- siderably. Schmidt starved a cat — on the 15th day the temperature was 38.6°; on the i6th, 38.3°; 17th, 37.64; i8th, 35.8; 19th (death) =33.0°. Chossat found that starving mammals and birds had a temperature 16° C. below normal on the day of their death. (3) A-ge 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. 374 VARIATIONS OF TEMPERATURE. Age. Mean Temperature at the Ordinary Temperature. Normal Limits. Where Measured. Xewly-born, 37-45° C. 37-35-37-55° C. Rectum. S-9 year, 37-72 36.87-37.62 JMouth and Rectum. 15-20 " 37-37 36. 1 2-38. 1 Axilla. 21-30 " 37.22 « 25-30 " 36-91 " 31-40 " 37-1 36-25-37-5 « 41-50 " 36.87 t< 51-60 " 36-83 « 80 « 37-46 Mouth. Newly-born animals exhibit peculiarities owing to the sudden change in their conditions of existence. Immediately after birth, the infant is 0.3° 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 occur during the first weeks of life. During sleep, the temperature of an infant falls 0.34° 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. (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. Fig. 232. Variations of the daily temperature in health during twenty-four hours. after Jiirgensen. L , after Liebermeister ; J , The mean height of all the temperatures taken during a day in a patient is called the "daily mean," and according to Jaeger it is 37.13° in the rectum in health. A daily mean of more than 37.8° is a "fever temperature," while a mean under 37.0° C. is regarded as a " collapse temperature." VARIATIONS OF TEMPERATURE. 375 Time. Barensprung. J. Davy. Hallman. Gierse. Jiirgensen. Jager. Morning, 5 . . 36-7 36.6 36.9 6 36.68 • • 36-7 36.4 37.1 7 36.94- 36.63 36.98 36.7* 36.5* 37.5* 8 37-16* 36.S0* 37.08* 36.8 36.7 37.4 9 36.89 36-9 36.8 37-5 10 37.26 io>^= 37-36 37.23 37-0 37-0 37-5 II 36.89 37.2 37-2 37-3 Mid-day, 12 36.87 . . 37-3* 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 3748 37.05* 5^^=37.31 37.43 37-5 37.5 37 5 6 6>^ = 36.83 37-29 37-5 37-6 37-4 7 37.43 7>^= 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 II 36.85 36.72 36.70 36.81 37-2 37.1 36.8 Night, 12 . . 37-1 36.9 369 I 36.65 36.44 . . 37-0 36.9 36.9 2 369 36-7 36.8 3 36.8 36-7 36-7 4 36.31 367 36.7 36.7 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* indicates taking of food.] The daily variation in the frequency of the pulse often coincides with variation of the tempera- ture. Barensprung found that the mid-day temperature maximimi slightly preceded the pulse maxi- mum (I 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 reversed. 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 tem- perature is less than in the case of a person at rest. 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 tempera- ture there is a rapid fall at 6 A. M., which reaches its minimum at 9 to 10 A. M. This is followed by a slow rise, which reaches a high maximum after dinner ; it falls between I to 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 corre.sponds to a rise of temperature in internal parts. (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 of ^ to 2° C. Very long-con- tinued hemorrhage (dog) causes it to fall to 31° or 29° C. This is obviously due to the diminution of the processes of oxidation in the ansemic 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 enormously slowed, diminishes the temperature several degrees in rabbits {^Landois and Amnion). 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 (§ 102). 376 REGULATION OF THE TEMPERATURE. (6) Many poisons diminish the temperature, e. g.^ chloroform and the anaes- thetics, alcohol (>; 235), digitalis, quinine, aconitin, niuscarin. These appear to act partly by rendering the tissues /ess liable to undergo molecular transforma- tions for the production of heat. In the case of the anaesthetics, this effect per- haps occurs, and is due i)ossibly to a semi-coagulation of the nervous substance (?). They may also act partly by influencing the giving off of heat (§ 214, II). Other i)oisons increase the temperature for opposite reasons. The temperature is increased bv strychnin, nicotin, ])icrotoxin, veratrin, laudanin. {7) Various diseases diminish the tcin[)erature, which may be due either to lessened production of lieat (dimiiuition 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 temperature was 30° to 31° C, in diabetes 30° C, or less ; the lowest temperature observed and life retained in a drunk person was 24° C. The temperature is increased in fe7'er, and the highest point reached just before death, and recorded by Wunderlich, was 44.65° C. (compare \ 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. [The constancy or thermostatic condition of the temperature is brought about by three co-operant factors, the thermogenic or heat producing, the thermo- lytic or heat discharging, and the thermotaxic or mechanism by which heat production and heat loss are balanced, and it is obvious that the last must be in relation with the other two. The thermotaxic mechanism is developed last, is least pronounced in the lower vertebrata, and is most easily liable to fail under injury or disease {Mac A lister). '\ I. Regulatory Arrangements governing the production of Heat. — Liebermeister estimated the amount of heat produced by a healthy man at 1.8 calorie per minute. It is highly probably that, within the body, there exist mechanisms which determine the molecular transformations upon which the evo- lution of heat depends. 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 irritated, whereby impressions are conveyed to th -• heat centre, which sends out impulses through efferent fibres to the depots of potential energy, either to increase or diminish the extent of the transforma- tions occurring in them. The nerve channels herein concerned are entirely un- known. Many considerations, however, go to support such an hypothesis (§ 377). [Thermotaxic Mechanism, Thermal Nerves and Centres. — Just as the respiration and the state of the blood vessels are regulated from a central focus, so the question arises, does the same obtain with regard to temperature? .Studying this question, however, it must be borne in mind that thermometric observations alone are not sufficient ; the true test must be calorimetric. Sir Benjamin Brodie observed that in a case of injury of the spinal cord in the neck the temperature in the thigh rose very high. In some cases the temperature falls. Wood has shown that section of the cord above the origin of the splanchnics leads to decided increase in the amount of heat dissipated, but to a decided diminution of heat production. The vasomotor paralysis has much to do in these cases with the loss of heat. In warm-blooded animals, exposed to a high temperature, the heat production is diminished, but when they are exposed to a low temperature it is increased. If a warm-blooded animal's medulla oblongata be divided, there is a fall of temperature, chiefly due to its vasomotor paralysis, and such an animal behaves, as regards the effect of heat and cold, exactly like a poikilo- thermal animal, i.e., its metabolism and heat production are increased by cold and diminished by heat. If, however, the incision be made above the pons, so as to leave the vasomotor centre intact ill the dog, there is a rise of the temperature and increased heat production for 24 hours afterward. .REGULATION OF THE TEMPERATURE. 377 This suggests the idea that this region is traversed by inhibitory nerves, so that when they are cut oft from their centres situate above, the augmentor nerves can act more vigorously. This suggests the existence of thermo-inhibitory centres situate higher up in the brain. If an animal be curarized, not only is there paralysis of voluntary motor acts, but on stimulating an ordinary motor nerve, not only is there no muscular contraction, but there is no rise of temperature of the muscles supplied by that nerve. In such an animal the temperature rises and falls with the temperature of the sur- rounding medium. Even although the respirations be kept constant and the vasomotor nerves intact, the thermogenic activity of muscles, therefore, seems to be dependent on their innervation.] [Cerebral Centres. — Apart from the cortical heat centres (^ 377), Ott, Aronsohn, Sachs, Richet and others have shown that if a needle be thrust through the skull and brain, so as to injure certain deeper-seated parts, there is a rise of temperature and increased heat production for several hours. The experiment may be repeated several times in the same rabbit. Ott gives three areas which, when so injured, cause these effects : (l) a part of the brain in the median side of the corpus striatum, and near the nodus cursorius ; (2) a part between the corpus striatum and the optic thalamus ; and (3) the anterior end of the optic thalamus itself. From the effect of atropin, Ott suggests the existence of spinal centres as well.] 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 aiiiount of CO2 excreted, by in- creasing the production of heat, while the O consumed is also increased simul- taneously; heating the surrounding medium diminishes the CO2 (§ 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.^ given off, when the surroundings were cooled from 38° to 6° or 7° C. ; while the excretion was diminished when the surrounding temperature was raised from 4°-9° to 35°-37°, so that the thermal stimulation, due to the temperature of the surrounding medium, acted upon the combustion within the body. Pfliiger found that a rabbit which was dipped in cold water used more O and excreted more COj. If the cooling action was so great as to reduce the bodily temperature to 30°, the exchange of gases diminished, and where the temperatiu-e fell to 20°, the exchange of gases was diminished one-half. It is to be remembered, however, that the excretion of COj does not go hand in hand with the formation of COj. If mammals be placed in a warm bath which is 2° to 3° higher than their own temperature, the excretion of COj and the consumption of O are increased, owing to the stimulation of their metabolism, while the excretion of urea is also increased in animals and in man (| 133, 5). (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 {FJiilger). 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 for hunger and the appe- tite 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. II. Regulatory Mechanisms governing the Excretion of Heat or Thermolysis. — 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. (i) Heat causes dilatation of the cutaneous vessels ; the skin becomes red, congested, and soft ; it contains more fluids, and becomes a better conductor of heat ; the epithelium is moistened, and sweat appears on the surface. Thus 378 REGULATION OF THE TEMPERATURE. increased excretion of heat is provided for, while the evaporation of the sweat also abstracts heat. The amount of heat necessary to convert into vapor i grm. of water at ioo° C, is equal to that re(iuired to heat lo grnis. from 0° to 53.67° C. The sweat as secreted is at the temperature of the body ; if it were completely changed into vapor, it would rerjuire 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 l)ale, 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. 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. By the systematic application of stimuli, e.g.,c.o\di 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 energeti- cally prevented, so that cold l)aths 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. (2) Increased temperature causes increased heart beats, while dimin- ished 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 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 conversely. Hence, the frequency of the heart beat is in direct relation to the rapidity of cooling. In very hot air (over 100° C.) the pulse rises to over 160 per minute. The same is true in fever (§ 70, 3 c). Liebermeister gives the following numbers in an adult :— Pulse beats, per min., . . . 78.6 91.2 99.8 108.5 "'^ '37-5 Temperature in C°., ... 37° 38° 39° 40° 41° 42° (3) Increased Temperature Increases the Number of Respirations. — Under ordinary circumstances, a much larger volume of air passes through the lungs when it is warmed almost to the temperature of the body. Further, a certain amount of watery vapor is given off with each expiration, which must be evaporated, thus abstracting heat. Energetic respiration aids the circulation, 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, whereby the increased respiration must act in producing an amount of heat greater than normal (§ 127, 8). This excess is more than compensated for by the cooling factors above mentioned. Forced respiration produces cooling, even when the air breathed is heated to 54° C, and saturated with watery vapor. (4) Covering of the Body. — Aniinals 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 HEAT BALANCE. 379 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. Tf a rabbit be kept exposed to the air with its legs extended for three hours, the rectal temperature will fall from 39° C. to 37° C. Man may influence his temperature by remaining in a warm or a cold room — by taking hot or cold drinks — hot or cold baths — remaining in air at rest or air in motion, e.g., by using a fan. CLOTHING. — Warm Clothing is the Equivalent of Food. — As clothes are intended to keep in the 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 condtiction. — Those substances which conduct heat badly keep us warmest. Hare skin, down, beaver skin, raw silk, taffeta, sheeps' wool, cotton wool, flax, spun silk, are given in order, from the worst to the best conductors. (2) The capacity for radiatio7t. — Coarse materials radiate more heat than smooth, but color has no effect. (3) Relation to the stints 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 perme- ability 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. HEAT BALANCE. — As the temperature of the body is maintained within narrow limits, the amount of heat taken in must balance the heat given off, /. 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. An adult produces as much heat in half an hour as will raise the temperature of his body 1° C. If no heat were 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 sub- ject : — A. Helmholtz was the first to estimate numerically the amount of heat produced by a man : — (i) Heat Income. — (tf) A healthy adult, weighing 82 kilos., expires in twenty- four hours 878.4 grms. COj {^Scharling). The combustion of the C therein into COj produces 1,730,760 cal. if) But he takes in more O than reappears in the COj; the excess is used in oxidation processes, e.g., for the formation of HjO, by union with H, so that 13,615 grms, H will be oxidized by the excess of O, which gives 318,000 " 2,049,360 " [c] About 25 per cent, of the heat must be referred to sources other than com- bustion (Z'm/ow^), so that the total =2,732,000 " 2,732,000 calories are actually sufficient to raise the temperature of an adult, weighing 80 to 90 kilos., from 10° to 38° or 39° C, /. e., to a normal temperature. (2) Heat Expenditure. — (a) Heating the food and drink, which have a mean temperature of 12° C 70)I57 cal. = 2.6 per cent. [p) Heating the air respired ^^ 16,400 grms. with an initial temperature of 20° C 70,032 " = 2.6 " ( When-the temperature of the air is 0°, 140,064 cal. = 5.2 per cent.) (c) Evaporation of 656 grms. water by the lungs, 397,536 " = 14.7 " (d) The remainder given off by radiation and evaporation of water by the skin, (7 j,^ per cent, to) =81.1 " 380 VARIATIONS IN HEAT PRODUCTION. B. Dulong. — (I) Heat Income. — Dulong and others sought to estimate the amount of heat from the C and II contained in tlie food. As we know that the combustion of i grm. C =^ S040 heat units, and I grm. II ;= 34,460 heat units, it would be easy to determine the amount of heat were the C simply converted into CO., and the H into II.^O. l>ut Dulong omitted the II in the carbohydrates {e.^'., grape sugar = CgH^.O^") as producing heat, because the II 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, /. c\, 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 : — Proteids, 120 grms, contain 64.18 C. and 8.60 H. Fat, 90 " " 70.20 " 10.26 Starch 330 " " 146.S2 . . 2S1.20 The urine and flvces contain still unconsumed, .... 29.8 Remainder to be burned, 251.4 " 12.56 As I grm. C. = S040 heat units and I grm. H = 34,460 heat units, we have the following calcu- lation : — 251.4 X 8,040 = 2,031,312 (from combustion of C). 12.56X34,460= 432,818 (" " H), 2,464,130 heat units. (2) Heat Expenditure : — Per cent, of Heat units, the e.\creta. 1. 1900 grms. are excreted daily by the urine and faeces, and they are 25° warmer than the food 47,500 1.9 2. 13.000 grms, air are heated (from 12° to 37° C.) (heat capacity of the air = 0.26), 184,500 3.38 3. 330 grms. water are evaporated by the respiration (i grm. = 582 heat units), 192,060 7.68 4. 660 grms, water are evaporated from the skin, 384,120 15-37 Total, 708,180 Remainder radiated and conducted from the skin, . . . 1,791,820 7167 Total amount of heat units given off, 2,500,000 too. 00 C. Heat Income. — Frankland burned the food directly in a calorimeter, and found that i grm. of the following substances yielded : — Albumin, i grm. 4998 heat units. Grape sugar, i grm., 3217 " Ox fat, I grm., 9069 " The albumin, however, is only oxidized to the stage of urea, hence the heat units of urea must be deducted from 499S, which gives 4263 heat units obtainable from I grm. albumin. When we know the number of grammes consumed, a simple multiplication gives the number of heat units. The heat units will vary, of course, with the nature of the food. J. Ranke gives the following : — With animal diet, 2,779,524 heat units. " food free from N, 2,059,506 " " mixed diet, 2,200,000 " " during hunger, 2,012,816 " 216. VARIATIONS IN HEAT PRODUCTION.— (i) Influence of Bodily Surface.— Rubner found that the production of heat depended more upon the size of the body and its superfi- cial area than upon the body weight. Small or young animals have a relatively larger surface than large or older ones, and as the removal of the heat takes place chiefly from the external surface, animals with a larger surface must produce more heat. Small animals used relatively more O. Rubner's investigations on dogs of different size gave a heat production of 1,143,000 calories for every square metre of cutaneous surface. On comparing the body weight with the cutaneous surface in different animals, he found that for every i kilo, of body weight there was in the rat 1650, rabbit 946, man 2S7 square centimetres of surface. RELATION OF HEAT PRODUCTION TO WORK. 381 (2) Age and Sex. — The heat production is less in infancy and in old age, and it is less in pro- portion in tlie female than in the male. (3) Daily Variation. — The heat production shows variations in twenty-four hours corresponding ■with the temperature of the body (| 213, 4). (4) The heat production is greater in the waking condition, during physical and mental exertion, 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 resting condition, almost all the potential energy is changed to heat ; the workman, however, transforms potential energy into work — mechanical work — in addition to heat. These two may be compared by using an equivalent measurement, thus, i heat unit (energy required to raise i gramme of water 1° C.) = 425.5 gramme-metres. Relation of Heat to Work. — The following example may serve to illustrate the relation between heat production and the production of work : Suppose a small steam engine to be placed within a capacious calorimeter, and a certain quantity of coal to be burned, then as long as the engine does not perform any mechanical work, heat alone is produced by the burning of the coal. Let this amount of heat be estimated, and a second 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 arrangement. 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 experiment, 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 [Hu-n). Compare this with what happens within the body : A man in a passive condition forms from the potential energy of the food between 2^ to 2^ million calories. The work done by a workman is reckoned at 300,000 kilo- gramme-metres (§ 300). If the organism were precisely 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 when mechanical work is done. There is one point of difference between a workman and a working machine. The workman consumes much more potential energy in the same time than a passive person ; much more is transformed in his body ; and hence the increased consumption is not only covered, but even over- compensated. Hence, the workman is warmer than the passive person, owing to the increased muscular activity (§ 210, I, ^). Take an example : Hirn remained passive, and absorbed 30 grms. 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 grms. 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 we must take into account that we overcome the resistance of the air and the activity of the muscles. The organism is superior to a machine in as far as it can, from the same amount of potential energy, produce rnore work in proportion to heat. While the very best steam engine gives \ of the potential energy in the form of work, and f as heat, the body produces ^ as work and 4 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 contact 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 conduct more heat than other bodies. Thus the water of a cool bath, being a better 382 STORAGE OF HEAT. conductor of heat, is always thought to be colder tlian air at the same temperature. In our climate it appears to us that — Air, at i8° C. is moderately warm; I Water, at i8° C. is cold ; " at 25°-2S° C, hot ; I " from i8°- 29° C, cool ; '' above 28°, very hot. | " " 29°-30° C, warm ; " " 37-5° and above, hot. Warm Media. — As long as the temperature of the body is higher than that of the surrounding medium, heat is given off, and that the more rapidly the better the conducting power of the surrounding medium. As soon as the temperature 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 conducting power of the medium. Hence, hot water appears to be warmer than air at the same tempera- ture. A person may remain eight minutes in a bath at 45.5° C. (dangerous to life ! ) ; the hands may be plunged into water at 50.5° C, but not at 51.65° C, while at 60° violent pain is produced. A person may remain for eight minutes in hot air at 127° C, and a tempera- ture of 132° C. has been borne for ten minutes, and yet the body temperature rise only to 38.6° or 38.9°. 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 diminishes, the body becomes unable to endure a hot atmosphere ; hence it is that in air containing much watery vapor a person cannot endure nearly so high a temperature as in dry air, so that heat must accumulate in the body. In a Turkish vapor bath of 53° to 60° C, the rectal temperature rises to 40.7° or 41.6° C. A person may work continuously in air at 31° C. which is almost saturated with moisture. If a person be placed in water at the temperature of the body, the normal temperature rises 1° C. in one hour, and in i^ hour about 2° C. A gradual increase of the temperature from 38.6° to 40.2° C. causes the axillary temperature to rise to 39.0'^ within fifteen minutes. 219. STORAGE OF HEAT. — As the uniform temperature of the body, under normal circumstances, is due to the reciprocal relation 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 increased. Heat may be stored up when — {a) The skin is extensively stimulated, whereby the cutaneous vessels are temporarily contracted. (/J) Any other circumstances prevent heat from being given off by the skin, (c) When the vaso- viotor centre is excited, causing all the blood vessels of the ])ody— those of the skin included — to contract. This seems to be the cause of the rise of temperature after transfusion of blood, and the rise of temperature after the sudden rewova/ 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. (!iorteni rise of temperature (see ^ 295) ; a rapid coagu'ation of the blood has a similar result (| 28, 5). (2) Imme-liately after death a series of chemical processes occur within the body, whereby heat is produced. Valentin placed a dead rabbit 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 processes whicti cause a rise of iem^traiVLxe post-tnortem 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. (3) Another cause is the diminished excretion of heat post-mortem. After the circulation is abolished, within a {^vr minutes little heat is given off from the surface of the body, as rapid excretion imp'ies 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. The slight rise, when it occurs, is due to the stimulation of the skin causing reflexly a more rapid molecular transformation, and therefore a greater production of heat, while the amount of heat given off is diminished owing to contraction of the small cutaneous vessels and the skin itself (yLiebermeister). The continuous and intense application of cold causes a decrease of the temperature, chiefly by conduction, notwithstanding that at the same time there is a greater production of heat. After a cold bath the temperature may be 34°, 32°, and even 30° C. As an after-effect of the great abstraction of heat, the temperature of the body after a time remains lower than it was before ("/r/wary after-effect^'' — Liebermeister) ; thus after an hour it was 0.22° C. in the rectum. There is a *' secondary after-effect''' which occurs after the first after-effect is over, when the temperature rises {^Jilrgensen). This effect begins five to eight hours after a cold bath, and is equal to -j- 0.2° C. in the rectum. Hoppe-Seyler found that some time after the application of heat there was a corresponding lowering of the temperature. Taking Cold. — If a rabbit be taken from a surrounding temperatm-e of 35° C, and suddenly cooled, it shivers, and there may be diarrhoea. After two days the temperature rises 1.5° 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. Perhaps the greatly cooled blood acts as an irritant causing inflammation. Action of Frost.— The continued application of a high degree of cold causes at first contraction of the blood vessels of the skin and its muscles, so that it becomes pale. If continued paralysis of the cutaneous vessels occurs, the skin becomes red, owing to congestion of its vessels. As the passage of fl-uids through the capillaries is rendered more difficult by the cold, the blood, stagnates, and the skin aisume? a livid appearance, as the 0 is almost completely used up. Thus the peripheral circu- 25 386 ARTIFICIAL LOWERING OF THE TEMPERATORE. lation is slowed. If ihe action of the coM be still more intense, the peripheral circulation stops completely, especially in the thinnest and most exj osed organs — ears, nose, toes, and tingers. The sensorv nerves are paralyzed, so that tiiere is numbness with loss of sensibility, and the parts may even be frozen through and through. As the slowing of the circulation in the superficial vessels gradually aftccts other areas of the circulation, the pulmonary circulation is enfeeblerl, and diminished oxidation of the blood occurs, nutwithstanding the greater amount of O in the cold air, so that the nerve cttttres are affected. Hence arise great dislike to making movements or any muscular effort, a painful sensation of fatigue, a peculiar and almost irresistible desire to sleep, cerebral inactivity, blunting of the sense organs, and lastly, coma. The blood freezes at — 3.9° C, while the juices oi 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 unfrequenily produced by the prolonged action of cold. 225. ARTIFICIAL LOWERING OF THE TEMPERATURE.— Phenomena. — The artificial cooling ot warm-blooded animals, by placing them in cold air or in a freezing mixture, gives rise to a series of oiiaracteristic phenomena. If the animals (rabbits) are cooled so that the temperature (rectum) falls to 1 8°, 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 respira- tions are few and shallow. Suffocation does not cause spasms, the secretion of urine stops, and the liver is congested. The animal may 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 corpuscles have been destroyed. The retina becomes pale, and death occurs with spasms and the signs of asphyxia If the bodily temperature be reduced to 17° and under, the voluntary movements cease before the reflex acts. An animal cooled to 18° C, and left to itself, at the same temperature as the surrounding, does not recover of itself, but if artificial respiration be employed, the temperature rises 10° C. If this be combined with the application of external warmth, the animals may recover completely, even when they have been apparently dead for forty minutes. Walther cooled adult animals to 9° C, and recovered them by artificial respira- tion and external warmth ; while Horvath cooled young animals to 5° C. Mammals, which are born blind, and birds which come out of the egg devoid of feathers, cool more rapidly than others. Morphia, and more so, alcohol, ac- celerate the cooling of mammals, at the same time the exchange of gases falls considerably ; hence, drunken men are more liable to die when exposed to cold. Artificial Cold-blooded Condition.— CI. Bernard made the important observation, that the muscles of animals that had been cooled remained irritable for a long time, to direct stimuli as well as to stimuli applied to their nerves ; and the same is the case when the animals are asphyxiated for want of O. An '^artifi- cial cold-blooded condition,'" i. i 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. 226. EMPLOYMENT OF COLD.— Cold may be applied to the whole or part of the surface 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 gi-adually 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. The addition of stimulating substances, e. g., salts, which cause dilatation of the cutaneous vessels, facilitates the excretion of heat ; even salt water conducts heat better. If alcohol be given internally at the same time, it lowers the temperature. (/') Cold may be applied locally by means of ice in a bag, which causes contraction of the cutane- ous vessels and contraction of the tissues (as in inflammation), while at the same time heat is abstracted locally. (c) Heat may be abstracted locally by the rapid evaporation of volatile substances (ether, carbon disulphide), which causes numbness of the sensory nerves. The introduction of media of low tem- perature 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 important to notice that the initial contraction of the vessels and the contraction of the tissues are followed by a greater dilatation and turgescence, /. 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 (paid). 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 this has been contradicted. 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 pre- vailed in the time of Hippocrates and Galen, and occurs even in Cartesius and Bartholinus (1667, " flammula cordis "). The iatro-mechanical school i^Boerkave, van Swieteii) 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 absorbed sub- stances into the blood (7)an Helinout, Sylvius, Ettinilller). Lavoisier (1777) vvas 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 thermometric observations on sick persons, while the first calorimetric observations were made by Lavoisier and Laplace. Comparative observations are given at \ 207, and also under Hibernation (| 225). Physiology-Metabolic Phenomena. By the term metabolism we mean 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 organ- ism 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 potential 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 tisbues, and the formation 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, especially 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 organ- isms live in water, and even in running water, a saying which ranks with tlie old saying — " Corpora non agunt nisi fluida." Water — as far as it is not a con tituent of all fluid foods — occurs in different forms as drink: (l) Rain water, which most closely resembles distilled or chemically pure water, always contains minute quantities of CO.„ NH.,, n'itious and nitric acids. (2) Spring water usually contains much mineral suljstance. It is formtd from the deposition of watery vapor or rain from the air, which ].ermeates the soil, containing much CO.^; the CO.^ 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) River water usually contains much less mineral matter than spring water. Spring water floating on the surface rapidly gives off its CO.^, whereby many substances — e. g., lime — are thrown out of solution, and deposited as insoluble precipitates. Gases. — Spring water contains little O, but much CO.^, 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 CO.^, and absorbs O from the air, and thus affords the necessary conditions for the existence of fishes and other marine animals. River water contains ^^ to ^L of its volume of absorbed gases, which may be expelled by l)oiling 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 fiher may be usid, as the charcoal acts as a disinfectant. Alum has a remarkable action. When added to give a dilu.io.i containing o.OOOl per cent., it makes turbid water clear. 388 WATER. 389 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 recognized by heating it to 50^^ C, and adding a little caustic soda. It ought not to be too hard, i. e., it ought not to contain too much lime (and magnesia) salts. By the term "degree of hardness" of a water is meant the unit amount of lime (and magnesia) in 100,000 parts of water; a water of 20 degrees of hardness contains 20 parts of lime (calcium oxide) combined with CO2, sulphuric, or hydrochloric acids (the small amount of magnesia may he neglected). A good drinking water ouL^ht not to exceed 20 degrees of hardness. The hardness is determined by titrating the water with a standard soap solution, the result being the formation of a scum of lime soap on the surface. The hardness of tmboiled water is called its total hardness, while that of boiled water is called permanent hardness. Boiling drives off the COj, and pre- cipitates the calcium carbonate, so that the water at the same time becomes softer. The presence of sulphuric acid, or sulphates, is determined by the water becoming tiubid on adding a solution of barium chloride and hydrochloric acid. Chlorine occurs in small amount in pure spring water, but when it occurs there in large amount — apart from its being derived from saline springs, near the sea or manufactories — we may conclude that the water is contaminated from water closets or dunghills, so that the estimation of chlorine is of importance. For this piu-pose use a solution. A, of 1 7 grms. of crystallized silver nitrate in i litre of distilled water; i cubic centimetre of this solution precipitates 3.55 milligrammes of chlorine as silver chloride. Use also B, a cold saturated solution of neutral potassium chromate. Take 50 cubic centimetres of the water to be investigated, and place it in a beaker, add to it 2 to 3 drops of B, and allow the fluid A to run into it from a burette until the white precipitate first formed remains red, even after the fluid has been stin-ed. Multiply the number of cubic centimetres of A used by 7.1, and this will give the amount of chlorine in 100,000 parts of the water. Example — 50 c. cmtr. requires 2.9 c. cmtr. of the silver solution, so that 100,000 parts of the water contain 2.9 X 7-1 -= 20.59 parts chlorine [Kiibel Tieniann). Good water ought not to contain more than 15 milli- grammes of chlorine per litre. The presence of lime may be ascertained by acidulating 50 cubic centimetres of the water with HCl, adding ammonia in excess, and afterward adding ammonia oxalate ; the white precipitate is lime oxalate. According to the degree of turbidity, we judge whether the water is " soft" (poor in lime), or "hard" (rich in lime). Magnesia is determined by taking the clear fluid of the above operation, after removing the pre- cipitate of lime, and adding to it a solution of sodium phosphate and some ammonia ; the crystalline precipitate which occurs is magnesia. The more feeble all these reactions which indicate the presence of sulphuric acid, chlorine, lime, and magnesia, are, the better is the water. In addition, good water ought not to contain more than traces of nitrates, nitrites, or compounds of ammonia, as their presence indicates the decomposhion of nitrogenous organic substances. For nitric acid, take 100 cubic centimetres of water acidulated with two or three drops of con- centrated sulphuric acid, add several pieces of zinc together with a solution of potassium iodide, and starch solution — a blue color indicates nitric acid. The following test is very delicate : Add to half a drop of water in a capsule two drops of a watery solution of Brucinum sulphuricum, and aftei-ward several drops of concentrated sulphuric acid ; a rose-red coloration indicates the presence of nitric acid. The presence of nitrous acid is ascertained by the blue coloration which results from the addition of a solution of potassium iodide, and solution of starch, after the water has been acidulated with sulphuric acid. Compounds of ammonia are detected by Nessler's reagent, which gives a yellow or reddish coloration when a trace of ammonia is present in water; while a large amount of these compounds gives a brown precipitate of the iodide of mercury and ammonia. The contamination of water by decomposing animal substance is determined by the amount of N it contains. In most cases it is sufficient to determine the amount of nitj-ic acid present. For this purpose we require (A) a solution of 1.871 grms. potassium nitrate in I litre distiliel water — I cubic centimetre contains I milligramme nitric acid; (B) a dilute solution of indigo, which is prepared by rubbing together one part of pulverized indigotin with six parls H^SO^, and allowing the deposit, to subside, when the blue fluid is poured into forty times its volume of distilled water and filtered.- This fluid is diluted with distilled water until a layer, 12 to 15 mm. in thickness, begins to be trans- parent. To test the activity of B, place l cubic centimetre of A in 24 cubic centimetres water, add some- common salt and 50 cubic centimetres concentrated sulphuric acid, and allow B to flow from a burette into this mixture until a faint green color is obtained. The number of cubic centimetres of B used correspond to i milligramme of nitric acid. Twenty-five cubic centimetres of the water to be investigated are mixed with 50 cubic centimetres of concentrated H2SO4, and titrated with B until a green color is obtained. This process must be: 390 MAMMARY GLANDS. Fig. 233. repeated, and on the second occasion the solution R must be allowed to flow in at once, when usually somewhat more indigo solution is required to obtain the green solution. The number of cubic centi- metres of B (corresponding to the strength of H, as determined alx)ve) indicates the amount of nitric acid present in 25 c.cmtr. of the water investigated. As much as 10 milligiammcs nitric acid have been found in spring water [J/tirx, TroiniiisJorff'). Sulphuretted Hydrogen is recognized by its d'^/^;-; also by a piece of blotting paper moi.siened with alkaline .solution of lead becoming brown when it is held over the boiling water. If it occurs as a contpoutiti in the water, .sodium nitro-prussitle gives a reddish-violet color It is of the greatest importance that drinking water should be free from the presence of organic matter in a state of decomposition. Organic matter in a state of dccom])osition, and the organisms therewith associated, when introduced into the body, may give rise to fatal maladies, e. ^., cholera and typhoid fever. This is the case when the water supply has been contaminated from water which ha.s percolated from water closets, privies and dung jiits. T/ie presenre of ori;(7ttic inatler tuny he detecletl thus (\) A considerable amount of the water is evaporatal to diyness in a porcelain vessel, if the residue be heated again a Ijrown or black color indicates the presence of a considerable amount of organic matter; and if it contain N, there is an odor of ammonia. Clood water treated in this way gives only a light brown .stain. The presence of micro-organisms may be determined microscopic- ally after evaporating a small quantity of the water on a glass slide. (2) The addition of potassio- golii chloride to the water gives a black frothy precipitate after long .standing. (3) A solution of potassium permtjit^anate, added to the water in a covered jar, giadually becomes decolorized, and a brownish precipitate is fomied. Water containing much organic matter should ue~c). Formation of Milk. — Concerning the formation of the individual constituents of milk, H. Thierfelder, who digested fresh mammary glands directly after death, found that dming the digestion of the glands, at the temperature of the body, a reducing substance, probably lactose, was formed by a process of fermentation. The mother substance (saccharogen) is soluble in water, but not in alcohol or ether, is not destroyed by boihng, and is not identical with glycogen The ferment which forms the lactose is connected with the gland cells— it does not pass into the milk, nor into a watery extract of the gland. During the digestion of the mammary glands at the temperature of the body, casein is formed, probably from serum albumin, by a process of fermentation. This ferment occurs in the milk. The nipple and its areola are characterized by the presence of pigment— more abundant during pregnancy— in the rete Malpighii of the skin, and by large papillse in the cutis vera. Some of the papillae contain touch corpuscles. Numerous non-striped muscular fibres surround the milk ducts in the deep layers of the skin and in the subcutaneous tissue, which contains no fat. These muscular fibres can be traced, following a longitudinal course, to the terminati.'U of the ducts on the surface. The small o-/an^s of Alontiroinery, which occur on the areola during lactation, are just small milk glands, each with a special duct opening on the surface of the elevation. Arteries proceed from several sources to supply the mamma, but their branches do not accompany the milk ducts ; each gland acinus is surrounded by a network of capillaries, which communicate with those of adjoining acini by small arteries and veins. The veins of the areola are arranged in a circle (circulus Halleri). The nerves are derived from the supraclavicular, and the II-IV-VI inter- costals; they proceed to the skin over the gland, to the very sensitive nipple, to the blood vessels and non-striped muscle of the nipple, and to the gland acini, where their mode of termination is still Inactive acinus of the mamma II. During the secretion of milk — a, i5, milk globnles ; c, d, e, colostrum corpuscles ; f, pale cells (bitch). unknown. Lymphatics sm-round the alveoli, and they are often full. The milk appears to \>^ prepired from the lymph contained in the lymphatics suiTOunding the acini. The comparative anatomy of the mamma. — The rodents, insectivora, and carnivora have lo to 12 teats, while some of them have only 4. The pachydermata and ruminantia have 2 to 4 abdominal teats, the whale has 2 near the vulva. The apes, bats, vegetable-feeding whales, elephants, and sloths have 2, like man. In the marsupials the tubes are arranged in groups, which open on a patch of skin devoid of hair without any nipple. The young animals remain within the mother's pouch, and the milk is expelled into their mouths by the action of a muscle — the compressor mammae. The development of the human mamma begins in both sexes during the third month; at the fourth and fifth months a few simple tubular gland ducts are arranged radially around the position of the future nipple, w ich is devoid of hair. In the new-born child the ducts are branched twice or thrice, and are provided with dilated extremities, the future acini. Up to the twelfth year, in both sexes, the ducts continue to divide dendritically, but without any proper acini being f -rmed. In the girl at puberty, the ducts branch rapidly; but the acini are formed 07ily at the periphery of the gland; durin; pregnancy, acini are also formed in the centre of the gland, while the connective tissue at the same time becomes somewhat more opened out. At the climacteric period, or meno- pause, all the acini and numerous fine milk ducts degenerate. In the adult )uale,the gland remains in the non developed infantile condition. Accessory or supernumerary glands upon the breast and abdomen are not uncommon ; sometimes the mamma occurs in the axilla, on the back, over the acromion process, or on the leg. A slight secretion of milk in a newly-born infant is normal. During the evacuation of the milk (500-1500 cubic centimetres daily"), there is not only the mechanical action of sucking-, but also the activity of the gland itself (| 152). This consists in the erection of the nipple, whereby its non-striped muscular fibres compress the sinuses on the milk duct<, and empty them, so that the milk may flow out in streams. The gland acini are also excited to 392 MILK AND ITS PREPARATIONS. Fig. 235. secretion reflexly by the stimulation of tlie sensory nerves of the nipple. The vessels of the gland are dilated, and there is a copious transudation into the gland — the transuded fluid being manufac- tured into milk under the intlutnce of the .secrttoiy protopla.sm. 'Jlie amount of .secrttion depends upon the blood pressure (AV'7/ /-/;-). During .sucking, not only is the milk in the gland extracted, but new milk is farmed, owing to the accelerated .secretion. Emotional di lurbances — anger, fear, etc. — arrest the secretion. I affont found that stimulation of the mammar}' nerve (ijitch) caused erection of the teat, dilatation of the vessels, and secretion of milk. After section of the cerebro-spinal nerves going to the mamma, Eckhard observed that erection of the teat ceased, although the secretion of milk in a goat was not interrupted. The rarely observed galactorrhoea is perhaps to be regarded as a parahtic secretion analogous to the paralytic secretion of saliva, lleidenhain and Pratsch found that the secretion (bitch) was increased by injecting strychnine or curara after section of the nerves of the gland. The "milk fever," which accompanies the first secretion of milk, [probably depends on stimulation of the vasomotor nerves, but this condition must be studied in relation with the otiier changes which occur within the pehic cavity after birth. [Some substances, such as atropin, aiTest the secretion of milk.] 231. MILK AND ITS PREPARATIONS.— Milk represents a com- plete or typical food in which are present all the constittients necessary fur maintaining the life and growth of the body of an infant (§ 236). [If an adult were to live on milk alone, to get the 23 oz. of dry solids necessary, he would have to take 9 pints of milk daily, which would give far too much water, fat, and pro- teids.] To every 10 parts of proteids there are 10 parts tat and 20 parts sugar. Relatively more of the fat than the albumin of the milk is absorbed {Ru/>ner) ; while a part of both is excreted in the faeces. Characters. — Milk is an opaque, bluish-white fluid with a sweetish taste and a characteristic odor, probably due to the peculiar volatile substances derived from the cutaneous secretions of the glands, and it has a specific gravity of 1026 to 1035. When it stands for a tiine, numerous milk globules, butter globules, or cream, collect on its surface, under which there is a bluish watery fluid. Human milk is always aika- line, cow's milk may be alkaline, acid, or amphoteric ; while the milk of carnivora is ahvavs acid. Milk Globules. — When milk is examined microscopically, it is seen to contain numerous small, highly refractive oil globules, floating in a clear fluid — the milk plasma ( Figs. 234, a, b, 235); while colostrum corpuscles and epithelium from the milk ducts are not so numerous. The white color and opacity of the milk are due to the presence of the milk globules, which reflect the light ; the globules consist of a fat, or butter, and are said by some to be surrounded with a very thin envelope of casein or haptogen membrane. If acetic acid be added to a microscopic preparation of milk, the fatty granules run together to form irregular masses. If cow's milk be shaken with caustic potash, the casein envelopes are dis- solved, and if ether be added, the milk becomes clear and transparent, as the ether dissolves out all the fatty particles in the solution. Ether cannot extract the fat from cow's milk until acetic acid or caustic potash is aided to liberate the fats from their envelopes; but shaking with ether is .sufficient to extract the fats from human milk. Some observers deny thit an envelope of casein exists, and according to them milk is a simple emulsion, kept emulsionized owing to the colloid swollen-up casein in the milk plasma. The treatment of milk with pDtash and ether makes the casein unible any longer to preserve the emulsion i^Soxhlet). The fats of the milk globules are the triglycerides of stearic, palmitic, oleic (very little), myristic, arachinic (butinic), capric, caprylic, caproic, and butyric acids, with traces of acetic and formic acids and cholesterin. Microscopic appearance of milk, (M) upper half, anU colostrum ^C) lower half. FAT AND PLASMA OF MILK. 393 Butter. — ^\Vhen milk is beaten or stiiTed for a long time (i.e., churned), the fat of the milk glo'iules is ultimately olitained in the form o^ butter, owing to the rupture of the envelopes of casein. Butter is soluble in alcohol and ether, and it is clarified by heat (60° C), or by washing in water at 40° C. When allowed to stand exposed to the air, it first becomes sour, owing to the formation of lactic acid, and afterward rancid, owing to the glycerme of the neutral fats being decomposed by fungi into acrolein, and formic acid, while the volatile fatty acids give it its rancid odor. The milk plasma, obtained by filtration through a clay filter or membranes, is a clear, slightly opalescent fluid, and contains casein (§ 249, III, 3), some serum albumin (§ 32), peptone (0,13 per cent.), nuclein, and a trace of diastatic ferment (in human milk). The presence of other peculiar chemical bodies, e.g., lactoprotein, globulin, albumose, galactin, etc., is disputed by some chemists. When milk is boiled the albumin coagulates, while the surface also becomes covered with a thin scum or layer of casein, which has become insoluble [the rest of the milk remaining fluid]. Casein. — When milk is filtered through fresh animal membranes or through a clay filter, the casein does not pass through. Precipitation. — It is precipitated by adding crystals of MgSO^ to saturation. [If to milk twice its volume of a saturated solution of NaCl and crystals of NaCl be added, and tiie whole shaken thoroughly, casein is precipitated, and carries down with it fat, so that the clear filtrate contains the lactose, salts, and coagulable proteids.] The plasma contains milk sugar (§ 252) ; a carbohydrate resembling dextrin, (? lactic acid), lecithin, urea, extractives, kreatin, sarkin (potassic sulphocyanide in cow's milk), sodic and potassic chlorides, alkaline phosphates, calcium and magnesium sulphates, alkaline carbonates, traces of iron, fluorine, and silica, CO2, N, and O. The coagulation of milk depends upon the coagulation of its casein. In milk, casein is com- bined with calcium phosphate, which keeps it in solution ; ac'ds which act on the calcium phosphate cause coagulation of the casein (acetic and tartaric acids in excess redissolve it). All acids do not coagulate human milk. It is coa.julated by two or more drops of hydrochloric acid (o.l per cent.) or acetic acid (0.2 per cent.). The spontaneous coagulation of milk after it has stood for a time, especially in a warm place, is due to the production of lactic acid, which is formed from the milk sugar in the milk by the action of bacillus acidi lactici [which is introduced from without] (^ 184, I). It changes the neutral alkaline phosphate into the acid phosphate, takes the casein from the calcium phosphate, and precipitates the casein. The sugar is decomposed into lactic acid and CO.^. Rennet (§ 250, 9, d, \ 166, II) coagulates milk with an alkaline reaction (sweet whey). This ferment decomposes the casein into the precipitated cheese and also into the slightly soluble whey albumin, so that the coagulation by rennet is a process quite distinct from the coagulation of milk by the gaitric and pancreatic juices, [and also from the precipitation produced by acids. The presence of calcium phosphate seems to be necessary for the complete action of the rennet ( Ha mniarstenY\. [Experiments. — Warm a little milk to 40° C, and add a few drops of commerciil rennet, setting aside the mixture in a warm plice; a solid coagulum is then formed, and by and by the whey separates from it. If the milk be previously diluted with water, no coagulum is formed ; and if the rennet be boiled before, it, like othtr ferments, is destroyed. A solution of rennet may be prepared by extracting the fourth stomach of the calf with glycerine. [When the milk is coagulated we obtain the curd, consisting of casein with some milk globules entangled in it ; tlie whey contains some soluble albumin and fat, and the great proportion of the salts and milk sugar, together with lactic acid.] [A milk-coagulating ferment is found in certain plants (artichokes, figs, Carica papaya), and causes milk to coagulate in neutral or alkaline solutions. It is also found in the small intestine of the calf, while a 5 per cent. NaCl solution of the seeds of Withania coagtilans coagulates milk in an alkaline medium.] Boiling (by killing all the lower organisms), sodium bicarbonate (xoW)' ammonia, salicylic acid (WoT^' glycerine, and ethereal oil of mustard prevent the spontaneous coasjulation. Fresh milk makes tincture of guaiacum blue, but boiled milk does not do so. When milk is exposed to the air for a long time, if gives off" CO2 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. According to Schmidt- Miilheim, some of the casein becomes converted into peptone, but this occurs only in unboiled milk. 394 TESTS FOR MILK. Composition. — loo parts of milk contain — Human. Cow. Goat. Ass. Water 87.24 to 90.58 86.23 86.S5 S9.0I Solids 9-42" 12.39 13.77 13.52 10.99 Casein 2.91 " 3.92 "I . . . f 3.2^ 2 5? ) Albumin, ^ ^ J- 1.90 to 2.36 1 3^3 ^ 5. | 3.57 Butter, 267" 4.30 4.50 4.34 1.S5 Milk sugar, 3.15 " 6.09 4.93 3.78 \ Salts, 0.14" 0.28 0.61 0.65 / 505 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 COj ; 0.09 to 0.32 O; 0.70 to 1. 41 N, according to volume. Only part of the C(\ is expelled by pho.sphoric acid. Salts. — The /o/as/i sa//s {a.s in blood and muscle) are more abundant than the soda compounds, while there is a considerable amount of calcium phosphate, which is necessary ior forviin<^ the bones of the infant. Wddenstein found in loo parts of the ash of human milk — sodium chloride, 10.73; potassium chloride, 26.33 ; potash, 21.44; lime, 1S.7S ; magnesia, 0.S7 ; phosphoric acid, 19 ; ferric phosphate, 0.21 ; sulphuric acid, 2.64 ; silica, traces. The amount of salts present is affected by the salts of the food. Conditions Influencing the Composition. — The oftener 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. Some substances are diminished and others increased in amount, according to the time after delivery. The following are increased : Until the second month after delivery, casein and fat; until the 5th month, the silts (which diminish progres- sively from this time onward); from the Sth to the loth month, the sugar. The following are diminished : From loth to 24th month, casein ; from 5th to 6th and loth to llth month, fat ; during 1st month, the sugar ; from the 5th month, the salts. 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 primiparais less watery. Rich feeding, especially proteids (small amount of vegetable food), increases the amount of milk and the casein, sugar and fat in it ; a large amount of carbohydrates (not fats) increases the amount of sugar. [Modifying Conditions. — That cow's milk is influenced by the pasture and food is well krown. Turniji as food gives a peculiar odor, taste, and flavor to the milk, and so do the fragrant grasses. Thcmental stale of the nurse influences the quantity and quality of the milk. 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 deleterious gases; by the secre:ion being altered in diseased animals.] Milk ought not to be kept in zinc vessel-:, owing to the formation of zinc lactate. 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 ca.sein of cow's milk differs qualitatively from that of human milk ; its coagulated flocculi or curd are much coarser than the fine curd of human milk, and they are only i,^ dissolved by the digestive juices, while human milk is completely dissolved. Cow's milk when bjiled is less digestible than unboiled. 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 10 to 24 vols, per cent. [The cream is generally about yf^.] The specific gravity (fresh cow's milk, 1029 to 1034; when creamed, 1032 lo 1040) is estimated with the lactometer at 15° C. The sugar is estimated by titration with Fehling's solution \\ 150, II), but in this cnse I cubic centimetre of the solution corresponds to 0.0067 g^rn of milk sugar; or its amount may be estimated with the polariscopic apparatus (\ 150). The proteids are precipitated and the fats e.xtracted with ether. The fats in fresh milk form about 3 per cent., and in skimmed milk i^ per cent. The amount of water in relation to the milk globules is estimated by the lacto- scope or the diaphanometer of Donne (modified by Vogel and Hoppe-Seyler), which consists of a glass vessel with plane parallel sides placed I centimetre apart. A measured quantity of milk is taken, and water is added to it from a burette until the outline of a candle flame placed at a distance of I metre can be distinctly seen through the diluted milk. This is done in a dark room For I cubic centim-rti-e of g'^od cow's milk, 70 to 85 centimetres water are required. [Other forms of licto- scope are used, all depending on the same principle of an optical te-^t, viz., that the opacity of milk varies with and is proportional to the amount of butter-fats present, i.e., the oil globules. Bond u=es a shallow cylindrical vessel with the bottom covered by black lines on a white surface. A measured PREPARATIONS OF MILK. 395 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.; chloral, rhubarb, opium, indigo, salicylic acid, iodine, iron, zinc, mercury, lead, bismuth, antimony. In osteomalacia the amount of lime in the milk is increased i^Giissero^v). Potassium iodide diminishes the secretion of milk by affecting the secretory function. Among abnormal constituents are — haemoglobin, bile pigments, mucin, blood corpuscles, pus, fibrin. Numen us fungi and other low organisms develop in evacuated milk, and the rare blue milk is due to the development of bacillus cyanogeneum. The milk serum is blue, not the fungus. Blue milk is unhealthy, and causes diarrhoea. There are fungi which make milk bluish- black or green. Red and yellow milk are produced by a similar action of cbromogenic fungi (§ 184). The fomiir is produced by Micrococcus prodigiosus, which is colorless. The color seems to be due to fuchsin. The yellow color is produced by bacillus synxanihus. Some of the pigments seem to be related to the aniline and others to the phenol colonng matters [Iliippe). The rennet-like action of bacteria is a widely diffused property of these organisms; they coagu- late and peptonize casein and may ultimately produce further decompositions. The butyric acid bacil us (I 184) first coagulates casein, then peptonizes it, and finally splits it up, with the evolution of ammonia [Hilppe) Milk becomes stringy owing to the action of cocci which form a stringy substance \_^ dextran, CjjHjqOjq [Scheibler)'\,]\ist as beer or wine undergoes a similar or ropy change. [The milk of dis- eased animals may contain or transmit directly infectious matter.] - Preparations of Milk. — (i) Condensed milk — 80 grms. cane sugar are added to i litre of milk; the whole is evaporated to -1-; and while hot sealed up in tin cans. 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. After the. addition of koumiss and sour 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 afterwards partly re-dissolved and changed into acid albumin and peptone. Tartar koumiss seems to be produced by the action of a special bacterium (Diaspora caucasia). (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 fi-om the formation of soda albuminate; in many cases it becomes semi- fluid, when it takes the characters of peptones. When further decomposition occm^s, 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 recall the digestive processes. [Cheese is coagulated casein entanghng more or less fat. so that the richness of the cheese will depend upon the lind of milk from which it is made. There are, in this sense, three kinds of cheese, whole milk, skimmed milk, and cream cheese, the last being represented by Stilton, Roquefort, Cheshire, etc. The composition is shown in the following table, after Bauer : — Water. Nitrogenous Matter. Fat. Extractives. Ash. Cream cheese, . . Whole milk, . . . Skim milk, .... 35-75 46.82 48.02 7.16 27.62 32.65 30-43 20.54 8.41 2-53 2-97 6.80 4-13 3-05 4.12 Cream cheese, especially if it be made fi-om goat's milk, acquires a very high odor and strong flavor when it is kept and " ripens " ; the casein is partly decomposed to yield ammonia and ammonium sulphide, while the fats yield butyric, caproic, and other acids ] 232. EGGS must be regarded as a complete food, as the organism of the young chick is developed from them. The yolk contains a characteristic proteid body — vitellin (§ 249), and an albu?ninate in the envelopes of the yellow yolk spheres — nuclein, from the white yolk ; fats in the yellow yolk (palmitin, olein), cholesterin, much lecithin ; and as its decomposition product, glycerin-phosphoric acid — grape sugar, pigmefits (lutein), and a body containing iron and related to haemoglobin ; 396 FLESH AND ITS TREPARATIONS. lastly, salfs qualitatively the same as in blood — quantitatively as in the blood cor- puscles— and gases. The chief constituent of the white of egg is eg^ albumin (§ 249), together with a small amount of palmitin and olein ])artly saponified with soda ; grape sugar, extractives ; lastly salts, qualitatively resembling those of blood, but quantitatively like those of serum, and a trace of fluorine. Relatively more of the nitrogenous constituents than of the fatty constituents of eggs are absorbed (^Rubncr). [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 mitter.) A hen's egg weighs about i^/ oz., of which the shell forms about y'^. Note the amount of fats in the yolk.] Composition : — White of Egg. Yolk. White of Egg. Yolk. Water, 84.8 51.5 ! Mineral matter, 1.2 1.4 Proteids 12.0 15.0 Pigment extractives, 2.1 Fats, etc., 2.0 30.0 233. 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 those constituents. The chief proteid constituent of the contractile muscular substance is myosin ; serum albumin occurs in the fluid of the fibres, in the lymph and blood of muscle. The/^7/i- are for the most part derived from the interfascicular fat cells, while lecithin and choleslerin 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 haemoglobin present in the sarcous substance, but in some muscles, e.g., the heart, there is a special pigment, myohjematin {MacMuun). Elastin occurs in the sarcolemma, neuri- lemma, and in the elastic fibres of the perimysium and walls of the vessels; the sinall amount of keratin is derived from the endothelium of the vessels. The chief muscular substance, the result of the retrogressive metabolism of the sarcous substance, is /vva//// ( — 0.05 per cent.); kreatiiiin, the mcowsiSint. 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 (o. i per cent.) dextrin (in horse or rabbit, not constant) ; grape sugar, but this is very probably derived post-mortem from glycogen (0.43 per cent.), which occurs in considerable amount in foetal muscles ; lastly fatty acids. Among the salts, potash and phosphoric acid compounds are most abundant ; magnesium phosphate exceeds calcium phosphate in amount. [The composition varies somewhat even in different muscles of the sanie animal.] In IOC parts Flesh there are, according to Schlossberger and v. Bibra — Ox. }- Water I 77 5° Solids, I 22.50 Soluble album'n. Coloring matter, Giutin, 1.30 Alcoholic extract, . 1.50 Fats, Insoluble albumin. Blood vessels, etc., 17.50 Calf, 78.20 21.80 2.60 1.60 1.40 16.2 Deer. 7463 25-37 1.94 0.50 4-75 1.30 Pig. 7830 21.70 2.40 0.80 1. 70 16.81 i 16.81 Man. 74 45 25-55 1-93 2.07 3-7 1 2.30 •5-54 Fowl. 77-30 22.7 3o{ 1.2 1-4 16.5 Carp. 7978 20.22 2.35 i".98 3-47 I. II Frog. 80.43 19-57 1.86 2.'48 3-46 O.IO 11.31 I 11.67 FLESH AND ITS PREPARATIONS. In loo parts Ash there are — 397 Potash, .... Soda, Magnesia, . . . Chalk, Potassium, . . . Sodium, .... Chlorine, .... Iron oxide, . . . Phosphoric Acid, Sulphuric " Silicic " Carbonic " Ammonia, . . . Horse. 3940 4.86 3.88 1.80 1.47 I.O 46.74 o. ;o Ox. 35 94 3-31 1-73 5-36 4.86 0.96 34-36 3-37 2.07 8.02 0.15 Calf. 34-40 235 1-45 1.99 } IO-59 { 0.27 48-13 0.81 Pis 37-79 4.02 4.81 7-54 0.40 0.62 0-35 44-47 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, 104; sheep, 3.9 ; wild goose, 8.8; fowl, 2.5 percent. 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, whereby sarcolaclic 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. 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 mto sarcolactic acid and the glycogen into sugar, and this again into lactic acid, whereby the elements of flesh undergo a kind of maceration. Finely divided flesh is more digestible than when it is eaten in large pieces. In cooking meat, the best ought not to be too intense, and ought not to be continued too long, as the muscular fibres thereby become hard and shrink very much. Those parts are most digestible which are obtained from the centre of a roast where they have been heated to 60° to 70° C, as this temperature is sufficient, with the aid of the acids of the flesh, to change the connective tissue into gelatin, whereby the fibres are loosentd, so that the gastric juice readily attacks them. In roasting beef, apply heat suddenly at first, to coagu- late a layer on the surface, which prevents the escape of the juice. 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 100 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 was coagulated and 3.3 remained dissolved in the soup. By boiling for a very long time, part of the albumin may be redissolved. The dissolved substances are: (i) Inorganic salts of the meat, of which 82.27 per cent, pass into the soup; the earthy phosphates chiefly remain in the cooked meat. (2) Kreatin, kreatinin, the inosinates and lactates which give to broth or beef tea their stimulating quahties, and a small amount of aromatic extractives. (3) Gelatin, more abundantly extracted from the flesh of young animals. According to these facts, therefore, flesh broth or beef-tea is a powerful stimulant, supplying muscle with re-,toratives, but is not a food in the ordinary sense of the term, as kreatin in general leaves the body unchanged {v. Voii). 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. The more fats that are contained in the vegetable food, the less are the carbohydrates digested and absorbed. 398 VEGETABLE FOODS. I. The cereals are most important vegetable foods; they contain proteids, starch, salts, and water about 14 per cent. The nitrogenous body glutin is most abundant under the husk (Fig. 236, c). The use of whole meal containing the outer layers of the grain is highly nutritive, but bread containing much bran is somewhat indigestible (^Rubner). Their composition is the following : — 100 Parts of the Dry Meal contain ! 100 Parts of Ash contain Of Albumin. Starch. i Red Wheat. White Wheat. Wheat, Rye, Barley, Maize, Rice, Buckwheat, . . . 16.52% II 92 17.70 1365 7.40 6.8-10.5 56.25% 60 91 38.31 77-74 86.21 6505 27.87 15-75 1-93 9.60 1.36 4936 0.13 1 Potash, 33.84 Soda j Lime, 3.09 Magnesia .... '3-54 Iron oxide .... 031 Phosphoric Acid, 59.21 Silica, •lU Ot- is; d, 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 [Oatmeal contains more nitrogenous substances (gliadin and glutin-casein) than wheaten Hour, but owing to the want of adhesive properties it cannot be made into bread. The amount of fat and salts is large.] In the preparation of bread the meal is kneaded with water until dough is formed, and to it is added salt and yeast (Saccharomycetes cerevisire). Fig. 236. When j>laced in a warm oven, the proteids of the meal begin to decompose and act as a ferment upon the swoUen-up starch, which becomes in part changed into sugar. The sugar is further decom- posed into CO., and alcohol, the C(.)., forms bubbles, which cause the bread to " rise " and thus become spongy and porous. The alcohol is driven oft" by the baking (200°), while much soluble dextrin is formed in the cru.st of the bread. [But CO.^ may be set free within the dough by chemical means, without yeast or leaven, thus fonning unfermente 1 bread. This is done by mixing with the dough an alkaline carbonate and then adding an acid. Uaking jjowders consist of carbonate of soda and tartaric acid. In I)aughlish"s process for aerated bread, the CO., is forced into water, and a dough is made with this water under pressure, and when the dough is heated, the CO.^ expands and forms the .spongy bread. Bread as an article of food is defi- cient 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).] 2. The pulses contain much albumin, especially legumin ; together with starch, lecithin, cholesterin, and 9 to 19 per cent, water. Peas contain 18.02 proteids, and 34.81 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 pro- teids which they contain, they are admirably adapted as food for the poorer classes. [3. The whole group of farinaceous sub.stances used as " pudding stuffs," such as com-fiour, arrow-root, rice, hominy, are really very largely composed of starchy substances.] 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, and a trace of asparagin. The envelopes of the cells swell up by boil- ing, and are changed into sugar and gums by dilute acids. The poisonous solanin Microscopic characters of wheat (+ 20o). n, c the bran; ^, cells of thin cuticle ; c, glutin eel starch cells. UTILIZATION OF FOOD. 399 occurs in the sprouts. In loo parts oi potato ash, May found 49.96 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 so-called pectin (Ca-^HigOaj), 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 anti- scorbutic] [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 miUtary expeditions.] [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 : — Weight of Food. Vegetable. Animal. Digested. Undigested. Digested. 1 Undigested. Of 100 parts of solids, " 100 " albumin, " 100 " fats or carbohydrates, . . 75 5 46.6 903 24.5 53-4 9-7 899 81.2 96.9 II. I 18.8 3-1] [The following table, abridged from Parkes, shows the composition of the chief articles of diet, and is also used for calculating diet tables: — Articles. Water. Proteids. Beefsteak, .... Fat pork, Smoked ham, . . . White fish, .... Poultry, White wheaten bread, Wheat flour, . . . Biscuit, Rice, Oatmeal, Maize, Macaroni, .... Arrow root, .... Peas (dry), .... Potatoes, Carrots, Cabbage, Butter, Egg (tV for shell), . Cheese, Milk (S. G. 1032), Cream, . . . " . . . Skimmed milk, . . Sugar, 74-4 20.5 390 98 27.8 24.0 78.0 18.1 74.0 21.0 40.0 8.0 15.0 II.O 8.0 15-6 1 0.0 5.0 15.0 12.6 13-5 lO.O 131 9.0 15.4 0.8 150 22.0 74.0 2 0 85.0 1.6 91.0 1.8 6.0 03 73-5 13-5 368 33-5 86.8 4.0 66.0 2.7 88.0 4.0 3-0 3-5 48.9 365 2.9 3-^ 1-5 2.0 1-3 0.8 5-6 6.7 03 2.0 0.16 0.25 5-0 91.0 1 1.6 24-3 3-7 26.7 1.8 Carbo- hydrates. 492 70-3 73-4 83.2 63.0 64.5 76.8 83.3 53-0 21,0 8.4 5-8 4.8 2.8 5-4 96.5 Salts. 1.6 2.3 lO.I I.O 1.2 1-3 1-7 1-7 0.5 3-0 I 4 0.8 0.27 2.4 1.0 1.0 0.7 2.7 1.0 54 0.7 1.8 0.8 05] 400 ACTION OF ALCOHOL. 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 exeited partly upon the organ of taste and partly upon the nerv- ous 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] Their chief active ingredients are respectively caffein. thein (CgHj^N^O^ -f H.^O), and theobromin (C;HgN/3.^), which are regarded as alkaloids of the vegetable bases, and which have recently been prepared aitificially from xanthin (£■. Fischer). [Guarana, or Brazilian cocoa, is made of the seeds ground into a ]iaste in the form of a sausage. Mate or Par.igiiay tea (the leaves of a species of holly) is used in South America, and so aho is the coca of the Andes (Erythroxylon Coca).] These "alkaloids" occur as such in the plants containing them; they behave like ammoni.i ; they have an alka'ine reaction, and form crv-staliine salts with acids. All these vegetAl)le bases act upon the nervous system; some more feebly (as the above), others more powerfully (quinine) ; some stimulate powerfully, or com- pletely paralyze (morphia, atropin, strychnin, curarin, nicotin). Effects. — All these substances act on the nervous system ; they quicken thought, accelerate movement, and stir one to greater activity. In these respects they resemble the stimulating extractives of beef tea. Coffee contains about yi per cent, of caffein, part of which only is liberated by the act of roasting. Tea has 6 per cent, of thein ; while green tea contains i per cent, ethereal oil, and black tea ]A per cent. ; in green tea there is 18 per cent., in 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 importance; tea contains 3.03 per cent, of salts, and among these are soluble compounds 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. Alcohol, when taken into the body, undergoes certain changes and produces certain effects : (i) About 95 per cent, of it is oxidized chiefly into CO^ and H.^0, so that it is so far a source of heat. As it undergoes this change very readily 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 unnecessary. 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 diminish the decomposition of tlie 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 nervous 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 vessels, 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 physical 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 PREPARATION OF ALCOHOLIC DRINKS. 401 system, 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 judgi7ient is affected first, although the imagination and " emotions may be more than usually active." The jHoior 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. EUipsoideus is the species present (Fig. 237). 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 dur- ing the process, and there Fig are produced alcohol and CO, (I 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 con- tains its spores. When yeast is completely excluded, or if it be killed by boiling [or if its action be prevented by the presence of some germicide], the fermentation does not occur, alcohohc fermentation is due to the activity of a low organism. 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 ex- pressed from the grapes, is exposed to the air at 10° to 15° C, and the yeast cells, which are float- ing about, drop into it and excite fermentation, which lasts 10 to 14 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 COj, which is accompanied by the deposition 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 whie is obtained. Wine contains 89 to 90 per cent, water, 7 to 8 per cent, alcohol, together with Eethylic, propylic, and butylic alcohol. The 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 cenanthic 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 temperature rises, and the starch (68 per cent, in barley) is changed into sugar. Thus "malt" is formed, which is dried, and afterward pulverized, and extracted with water at 70° to 75°, the watery extract being the "wort." Hops are added to wort, and the whole is evaporated, when the proteids are coagulated. Hops give beer its bitter taste, and 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 (l2° C.) ; yeast is added, and fermentation goes on rapidly and with considerable effervescence at 10° to 14°. Beer contains 75 to 95 per cent, water ; alcohol, 2 to 5 per cent, (porter and ale, to 8 per cent.) ; COj, o.l 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. 26 I, Isolated yeast cells; 2, 3, yeast cells budding; 4, 5, so-called endogenous formation of cells; 6, sprouting and formation of buds. The 402 EQUILIBRIUM OF THE METABOLISiM. 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, 3919 18.88 200.73 DAILY QUANTITY OF FOOD REQUIRED. 407 Add 744.11 grm. O from the air by respiration. " 2818 " H.fi. " 32 " Inorganic compounds (salts). The whole is equal to 3^ kilos. [7 lbs.], /. e., about -^ of the body weight; so that about 6 per cent, of the water, about 6 per cent, of the fat, about i percent, albumin, and about 0.4 per cent, of the salts of the body are daily transformed within the organism. An Adult doing a Moderate Amount of Work gives off, in grammes : — By respiration, Perspiration, Urine, . . . . Faeces, . . . . Water. 330 660 1700 128 2818 c. 2.6 9.8 20.0 281.2 3-3 30 6.3 15-8 3-0 651-15 7.2 II. I ' 12.0 681.45 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 34.89 grms. H, and 263.41 grms. O; 26 grms. of salts are given off in the urine, and 6 by the faeces. 96.5 grms. of proteid (= 1.46 grm. per kilo.) are used up by a resting adult in 24 hours; but while working 107.6 grms. are used. Nominally 2.3 times as much fat as albumin are used up. The investigations of the Munich School have shown that the following numbers represent the minimum amount of food necessary for different ages : — Age. Child until i^ years, . . " from 6 to 15 years, Man (moderate work), . Woman, " Old man, Old woman, Nitrogenous. 20-36 grms. 70-80 1x8 92 Fat. 30-45 grms. 37-50 " 56 " 44 " 68 " 50 " Carbohydrates. 60-90 grms. 250-400 " 500 " 400 " 350 " 260 " Small animals have a more lively metabolism than large ones. In small animals the decomposi- tion of albumin per unit weight of body is greater than in large animals [v. Vuit). Small animals as a rule consume more proteid than larger ones, because they generally have less bodily fat {^Ricbner'). 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 I : 4|-. 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 pro- portion in his food, he must consume far too much food. In order to obtain the 130 grammes of proteids necessary a person must use Cheese, 388 grms. Lentils, 491 " Peas, 582 " Beef, 614 grms. Eggs, 968 " Wheat bread, . . . 1444 " Rice, . . . Rye bread. Potatoes, . 2562 grms 2875 " 10,000 ' ' provided he were to take only one of these substances as food ; so that if a work- man were to live on potatoes alone, in order to get the necessary amount of N he would have to consume an altogether excessive 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, . . . 625 " Lentils, 806 " Peas 819 grms. Eggs, 902 " Rye bread, .... 930 " Cheese, 201 1 grms. Potatoes, .... 2039 " Beef, 2261 " 408 LOSS OF WEIGHT DURING STARVATION. 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 herbivora, the pro])oriion of nitrogenous to non-nitrogenous food necessar)- is l of the former to 8 or 9 parts of the latter. 237. 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 mechanical work, transform and utilize the potential energy of the constituents of its own body. The result is that its body weight diminishes from day to day, until death occurs from star- vation. 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. Urine. Urea. Inorganic Substances in Urine. Dry Faeces. Expired C. Water in Urine and Faeces. I. 2464 98 7-9 1-3 1.2 139 91.4 2. 2297 II.5 54 5-3 0.8 1.2 12.9 50-5 3- 2210 45 4.2 0.7 I.I '3 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 1 1.9 54-1 6. 2024 44 4-3 0.6 0.6 11.6 41. 1 7- 1946 40 3-8 0-5 0.7 II 37-5 8. 1873 42 3-9 0.6 I.I 10.6 40 9- I7S2 15.2 42 4 0.5 1-7 10.6 41.4 10. I717 35 3-3 04 1-3 lo-s 34 II. 1695 4 32 2.9 0-5 I.I 10.2 30.9 12. 1634 22.5 30 2.7 0.4 I.I 10.3 29.6 13- 1570 71 40 3-4 0.5 0.4 10. 1 36.6 14- 1518 3 41 3-4 05 03 9-7 38 15- 1434 41 2.9 0.4 0.3 9-4 38.4 16. 1389 48 3 0.4 0.2 8.8 45-5 17- 1335 28 1.6 0.2 0.3 7.8 26.6 i8.t 1267 13 0.7 0.1 0-3 6.1 190.7 12.9 734-4 -II97 131-5 733 65.8 9.8 157 The cat lost 1197 grms. in weight before it died, and this amount is apportioned in the following way: 204.43 grams. (=17.01 per cent.) loss of albumin; 132.75 grms. (= 11.05 per 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 (i) to weigh the animal daily; (2) to estimate daily all the C and N given off from the body in the faxes, 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 to 24 days — (6 melancholies who took water died after 51 days) ; small mammals and birds 9 days, and frogs 9 months. Vigorous adults die when they lose ^*j of their body weight, but young individuals die much sooner than adults. The symptoms are obvious: The mouth is drj', the walls of the alimentary canal become thin, and the digestive secretions cease to be formed; pulse beats and respirations are fewer; urine ver)' acid, from the presence of an in- creased 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 diminu- tion in the excretion of urea is much greater than that of CO2, which is due to METABOLISM ON A FLESH DIET. 409 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 starvation continues, the proteids are decomposed in much smaller amounts from day to day, although the drinking of water accelerates their decomposition. Loss of ^A^eight 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 decom- position, 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. 1. Fat, 97 26.2 10. Lungs, 17.7 0.3 2. Spleen, 66.7 0.6 11. Pancreas, 17.0 o.i 3. Liver, 53.7 4.8 12. Bones, 13.9 5.4 4. Testicles, 40.0 o.i i I3- Central Nervous Sys- Per cent, the total lo body weig 26.2 of ;sof ht. 10. 0.6 II. 4.8 12. O.I 13- 42.2 0.6 14- 15- tern 3.2 O.I Heart, 2.6 0.02 Total loss of the rest of the body, . . . 36.8 5.0 5. Muscles, 30.5 6. Blood, 27.0 7. Kidneys, 25.9 8. Skin, 20.6 9. Intestine, 18.0 There is a very important difference according as the animals before inanition have been fed freely on flesh and fat [/. e., if they have a surplus store of food within themselves], or as they have merely had a subsistence diet. Well-fed ani- mals lose weight much more rapidly during the first few days than on the later 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 rapidly 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.— A man is not able to maintain his metabolism in equilibrium on a purely flesh diet; if he were compelled to live on such a diet, he would succumb. The reason is obvious. In beef the proportion of nitrogenous to non-nitrogenous elementary constituents of food is I : 1.7 (p. 405). A healthy person excretes 280 grammes [8 to 9 oz.] 01 carbon in the form of CO2, 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 fluids, 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 23- to 2V P^''^ ^^ 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, until the limit of its diges- tive capacity is reached. If a well-nourished dog is fed on less than ^-g to -^^ of its body weight of flesh, it uses part of its own fat and muscle, gradually diminishes in weight, and ultimately 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 (i) on the amount of proteids ingested, 410 A DIET OF FAT OR OF CARBOHYDRATES. for the great mass of these becomes changed into circulating albumin ; (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) 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 meta- bolism is reduced by fat. This is spoken of as the "albumin-sparing action " of fats.] Exactly the same result occurs with other forms of proteids, as with flesh. It has been proved that gelatin may to a certain extent replace proteids in the food, in the proportion of 2 of gelatin to i of albumin. The carnivora, which can maintain their metabolism in 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. [Gelatin. — Voithas 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 available directly for the growth and repair of tissues.] Owing to the great solubility of gelatin, its value as a food used to be greatly discussed. 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. [The Metabolism of Peptones. — Most of the proteids absorbed into the blood are previously converted into peptones by the digestive juices. It has been asserted, more especially by Briicke, that some albumin is absorbed unchanged (§ 192, 4), and that only this is capable of forming organic albumin, while the peptones, after undergoing a reconversion into albumin, undergo decomposition as such. This view is opposed by many observers, who maintain that peptones perform all the functions of proteids, so that peptones, with the other necessary constituents of an adequate diet, suffice to maintain a proper standard of health.] 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 excretes even less urea than when it is starving ; so that the consumption of fat limits the decomposition of the animal's own proteids. As fat is an easily oxi- dized body, it yields heat chiefly, and becomes sooner oxidized than the nitrogen- ous 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 CO2 of the expired air ; so that the body must acquire fat, while at the same time it decom- poses proteids. The animal thus becomes poorer in proteids and richer in fats at the same time. [The metabolism of fats is not dependent on the amount of fats taken with the food. I. It is largely influenced by work, /. e., by the activity of the tissues, and in fact with muscular work CO., is excreted in greatly increased amount (§ 127, 6). 2. By the temperature of the surroundings, as more CO^ is pro- duced in the cold (§ 214, 2), and far more fatty foods are required in high lati- tudes. In their action on the organism, proteids and fats so far oppose each other, as the former increase 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 individuals. 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 diges- tion into sugar. The result of such feeding coincides pretty nearly with feeding ORIGIN OF FAT IN THE BODY. 411 with fat alone. But the sugar is more easily burned or oxidized within the body than the fat, and 17 parts of carbohydrate are equal to to 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 also serves to diminish the proteid metabolism, as they are rapidly burned up, and thus "spare" the circulating 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 fats. By being consumed they protect the proteids and fats from consumption.] The direct introduction of grape and cane sugar into the blood does not increase the amount of O used, but the amount of J^Oj is increased. [The doctrine of Liebig, that the oxygen taken in is 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. — An amount of flesh equal to ^V to -jio of the weight of the body is required to nourish a dog, which is fed on a purdy flesh diet; if the necessary amount of fat or carbohydrates be added to the diet, a smaller quantity of flesh is required {v. Voit). 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 carbohydrates are added, then 100 parts of fat = 230 to 250 of the latter (^Rubner). 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. 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, IViil). [Glycerin in small doses has no effect on the meta- bolism of proteid, but in large doses it increases it. It is consumed in the body, as shown by experi- ments on the respiratory products, and it prevents a certain amount of fat from being used up. About 20 per cent, is excreted in the urine {Arnschink).'] 241. ORIGIN OF FAT IN THE BODY.— I. Fart oi tht 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 a deposition of a larger aniount of fat in the body {v. Voit, Hofmami). [Hofmai:in starved a fat dog for 30 days until all its fat was used up. He fed it on lard and a little albumin for 5 days and then killed it. In 5 days it absorbed 1854 grms. of fat and 254 grms. of albumin. It added to its body 1353 grms. of fat; but this amount could not be formed from the proteids of the food, and therefore the fat must have come from the fat of the food. Pettenkofer and Voit arrived at -the same result in another way. They fed dogs on fish and much fat, and by their respiration apparatus e.slimated the gaseous income and expenditure {\ 122). All the N taken in reappeared in the excreta, bid not all the C. The amount of C retained was very large, there- fore a non-nitrogenous residue must have been laid up in the body, and it could only be fat, as this was the only substance found in large amount in the body. They estimated the possible amoimt of 412 ORIGIN OF FAT IN THE BODY. fat that could be formed from the proteids, and found that the amount stored up was far greater than this; so that the fat of the food must have been stored up in the tissues.] Lebedefl" found that dogs, which were starved for a month, so as to get rid of all their own fat, on being fed with linseed oil, or mutton suet and Hesh, had these fats restored to their tissues. These fats, therefore, must have been absorbed and deposited. J. Munk found the same on feeding animals with rape-seed oil. Fatty acids may also contribute to ihc formation of fats, as glycerin when formed in the body must be stored up during metabolism {J. Munk). Fatty acids may contribute to the formation of fats by union with the glycerin of the body during the metabolism. II. A second source of the fats is albuminous bodies. In the case of the formation of fats from proteids, which may yield ii per cent, of fat (according to Henneberg loo 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 albumin, when it is not coptpletely oxidized into CO.^, and H2O, 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 from proteids is shown by the following: I. A cow which produces i 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 rich 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 a 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 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. [7. In starving dogs, Bauer estimated the N and CO.^ given off, and O taken in, and then slowly poisoned them with phosphorus, and he found that the excretion of N was increased twofold, while the excretion of CO^ and the absorption of O were diminished one-half Therefore from a large amount of nitrogenous tissue, a nitrogenous body and a small amount of a carbonaceous compound were excreted, while a large amount of a non-nitrogenous residue was retained unconsumed. There was fatty degeneration of all the organs, the fat being derived from the non-nitrogenous part of the proteid. The same obtains with arsenic and antimony.] 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, are : I. Fattening occurs with flesh and soaps ; it is most improbable that the soaps are transformed into neutral fats by taking up gly- cerin and giving up alkali. 2. If a lean dog be fed with flesh and palmitin- and stearin-^oda soap, the fat of its body contains, in addition to palmitin and stearin, o/ein 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 fit, 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 ail the fat arises in this way, and that none of it is absorbed and redeposited (§ 241, I). 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 the addition of carbohydrates, it is assumed that the carbohydrates are consumed 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, and others, think they are entitled to conclude that the carbohydrates absorbed are directly concerned in the formation of fats, a view which is supported by Henneberg, B. Schulze, and Soxhlet. According to Pasteur, glycerin (the basis of neutral fats) may be formed from carbohydrates. [Tscherwinsky fed two similar pigs from the same litter; No. I weighed 7300 grms. ; No. II 7290 grms. No. I was killed and its fat and proteids estimated. No. II was fed for four months on grain and then killed, the grain and excreta and the undigested fat and proteids were aiialyzed, so that the amount of fat and proteid absorbed in four months was estimated. The pig then ■weighed 24 kilos., it was killed and its fat and proteids estimated. CORPULENCE. 413 No. II contained 2.50 kilos, albumin and 9.25 kilos, fat. No. I " 0.96 " " o.( Assimilated, 1.56 " " Taken in in food, 7.49 '* '• Difference, — 5.93 " " + 7-90 " " There M'ere therefore 7.90 kilos of fat in the body which could not be accounted for in the fat of the food. The 5.93 kilos, of albumin of the food which were not assimilated as albumin could yield only a small part of the 7.90 kilos of fat, so that at least 5 kilos, of fat must have been formed from carbohydrates. Lawes and Gilbert calculated that 40 per cent, of the fat in pigs was derived from carbohydrates. How the carbohydrates are changed into fat in the body is entirely unknown.] 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 phenome- non which is attended with disagreeable consequences. With regard to the causes of obesity, without doubt there is an inherited tendency (in ^;^ to 56 per cent, of the cases) 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, 2. e., more than the amount requiied 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 condi- tions of nutrition (^ 236). Conditions favoring Corpulence. — (i) A diet rich in /r(?/fza'j-, with a corresponding addition oi fat or carbohydrates. As flesh or muscle is formed from proteids, and part of the fat of the body is also formed from albumin ; the assumption that fats and carbohydrates fatten, or, when taken alone, act as fattening agents, is completely without foundation. (2) Diniinished disintegration of materials within the body, e.g., (a) diminished nniscitlar activity (much sleep and little exercise); ((5) abrogation of the sexzial fnnctio7is (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) ; (^) diviinished mental activity (the obesity of dementia), phlegmatic temperament. On the contrary, vigorous mental work, excitable temperament, care and sorrow, counteract the deposit of fat; (y two channels, viz., by the veins and by the lymphatics, so that if these be interfered 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 con- siderable swelling of the tissues or oedema may occur (§ 203). The action of the muscles and fascise are very important in removing these effete matters. 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. 1. Upon their activity. — The increased activity of an organ is indicated by the increased amount of blood going to 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 fluid 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)\. Langley and Sewell have recently observed directly the metabolic changes within suffi- ciently thin lobules of glands durmg life. The cells of serous glands (§ 143), and those of mucous, 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 CO2 (§ 127, 9) and urea (§ 257), which may be expressed graph- ically 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. 374). 2. The composition 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, cholera, makes the tissues dry, while if much water be absorbed into the blood, the tissues become more succulent and even oedema occur. When much common salt is present in the blood, and when the red blood corpuscles contain a dimin- ished 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 CO2 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 cessa- tion of the z;2/(?r;za/ respiration, occurs. Fermentation is interrupted by the same substance in a similar way. A diniinutio7i of the total amount of the blood causes more fluid to pass from the tissues into the blood, but the absorption of sub- stances— 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, when it is greatly increased, causes the tissues to con- tain more fluid, while the blood itself becomes more concentrated, to the extent of 3 to 5 per 1000. We may convince ourselves that blood plasma easily passes 416 REGENERATION OF ORGANS AND TISSUES. through the capillary wall, by j)ressing 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 tlie use of P, Cu, ether, chloroform, and chloral. 4. Increased temperature of the tissues (several hours daily) does not increase the breaking up of albumin and fats. (See §§ 220, 221, 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 vasomotor nerves, whereby it influences the amount of blood supplied, and also affects the blood pressure. But quite independently of the blood vessels, it is probable that certain special nerves — the so-called trophic nerves — influence the metal)olism or nutri- tion of the tissues (§ 342, c). That nerves do influence directly the transforma- tion 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 oxidation (^Pfliiger) (§ 127, 8). [Gaskell has raised the question as to the existence of katabolic and anabolic nerves controlling respectively the analytic and synthetic metabolism of the tissues.] 244. REGENERATION. — The extent to which lost parts are replaced varies greatly in different organs. Among ilie /o7ver animals, the parts of organs are replaced to a far greater extent than among wa-m-blooded animals. When a hydra is divided into two parts, each part forms a new indi- vidual— 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 repro- ducing lost parts {Bu^es). Spiders and crabs can reproduce lost feeler~, 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 trilon rejiroduces an amputated limb, the lower jaw, and the eye. This reproduction necessitates that a small stump be left, while total extirpation of the parts prevents reproduction. In amphibians and reptiles the regeneration of organs and tissues, as a whole, takes place after the type of the embryonic development, and the same is true as regards the histological processes which occur in the regenerated tail and other parts of the body of the earth-worm. 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, including the plasma, the colorless and colored corpuscles. (§ 7 and § 41,) 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. Wiien these are destroyed cell regeneration from below ceases, and the cells at the margins are concerned in filling up the deficiency. Regeneration, 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. [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, the other hairs of the body somewhat more slowly. If the papilla of the hair follicle be destroyed, the hair is not reproduced. Cut- REGENERATION OF ORGANS AND TISSUES. 417 ting 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 secre- tory 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 spermatoblasts. In ca- tarrhal conditions of mucous membranes, there is a great increase in the formation and excretion of new epithelium, while many cells are but indifferently foroied and constitute mucous corpuscles. The crystalline lens, which is just modified epithelium, is reorganized 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. [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 regene- rated 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. Lymphatics behave in the same way as blood vessels ; after removal of a lymphatic 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. After several days, the sarcolemma contains numerous nuclei which reproduce new muscular nuclei and the contractile substance. 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 filDres, at first without trans- verse striation, but with striation ultimately. If a large extent of a muscle be removed, it is replaced by cicatricial connective tissue. Non-striped muscular fibres are also reproduced ; the nuclei of the injured fibres divide after becoming enlarged, and exhibit a well-marked intra-nuclear plexus of fibrils. The nuclei divide into two, and from each of these a new fibre is formed, probably by the differentiation of the perinuclear protoplasm. 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 tmnk, the peripheral end of the divided nerve de- generates, the axial cylinder and the white sulDstance of Schwann disappear. The inter\'al 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 consecutive forma- tion of new fibres (Si'gm. 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 27 418 REGENERATION OF BONE. that voluntary movements could be executed (§ 338, 3). Vaulair, 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. In many glands, the regeneration of their cells during normal activity is very active — sebaceous, mucous, Liebcrkiihnian, uterine, mauimary glands during j^reg- nancy — in others less. If a large portion of a secretory gland be removed, as a general rule, it is not reproduced. A gland, if injured, and if sujjpuration follows, is not regenerated. But the bile ducts (^ 173) and the pancreatic duct may be reproduced (§ 171). According to PhiliiJiJcaux and Grilhni, if part of the spleen be removed it is rejiroduced (i; 103). Tizzoni and Collucci observed the formation of new liver cells and bile ducts afier injury to the liver (§ 173), and Pisenti makes the same statement as regards the kidney. After mechanical injury to the secretory cells of glands (liver, kidney, salivary, Meibomian;, neighboring cells undergo pro- liferation and aid in the restoration of the cells. 7. Among connective tissues, cartilage, provided its perichondrium be not injured, reproduces itself by division of its cartilage cells ; 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 sawn off heal again, and become united with the original bone. A tooth may be removed, replanted in tlie alveolus, and become fixed there. If a piece of periosteum be transplanted to another region of the body, it eventu- ally 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 osteo- blasts adhering to the osseous tissue. In fracture of a long bone, the periosteum deposits on the surface of the ends of the broken bones a ring of suljstance 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 connective-tissue corpuscles, and partly to the osteoblasts of the periosteum and 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 or arsetiious acid to the food causes consid- erable 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. 2. When food devoid of litne sails \% gw&n to an animal, the growth of the bones is not arrested, but the bones become thinner, whereby all parts, even the organic basis of the bone, undergo a uniform diminu- tion. 3. Feeding with madder makes the bones red, as the coloring matter is deposited with the bone salts in the bone, especially in the growing and last formed parts. In birds the shell of the egg becomes colored. 4. The continued use of lactic acid dissolves the bones. The ash of bone is thereby diminished. 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. A\Tien 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 INCREASE IN SIZE AND WEIGHT. 419 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 protoplasm cells, from which giant cells are developed. 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, 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. Reverdin cut a piece of skin into pieces about the size of a pea and fixed them on an ulcerated surface, 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. [White skin transplanted to a negro ultimately becomes pig- mented, and black skin transplanted to a white person becomes white.] The excised sptcr of a cock was transplanted and fixed in the comb of the same animal, where it grew [Jokit 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. Oilier 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, sub-maxillary gland, kidney, and under the skin of a rabbit, attach themselves and grow, and the growth is more rapid the more vascular the site on which the tissue is transplanted. The cartilage is not essentially different from hyaline car- tilage, 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. Tissues transplanted from embryonic structures grow far better than adult tissues. If a portion of the cornea of a rabbit be transplanted to a human eye, provided Descemet's membrane be clear, it will grow and remain clear (v. HippeU). A rabbit's nerve has been transplanted to the human subject, but without success.] Many of these results seem only to be possible between individuals of the same species, although Helferich has recently f^und that a piece of a 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 peri- toneal cavity, without exciting any inflammatory reaction; they, in fact, behave like inert foreign matter. 246. INCREASE IN SIZE AND WEIGHT.— The length of the body, which at birth is usually J-^ 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 5 j^ 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 to 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. Length (Cmtr.). Weight (Kilo.). Length (Cmtr.). Weight (Kilo.). Age. Age. Man. Woman. Man. Woman. Man. Woman. Man. Woman. 0 49-6 48.3 3.20 2.91 15 155.9 147.5 46.41 41.30 I 69.6 69.0 10.00 9-30 16 161.O 150.0 53.39 44 44 2 79.6 78.0 12.00 11.40 17 167.0 154.4 57.40 49.08 0 86.0 85.0 13.21 12.45 18 170.0 156.2 61.26 53-10 4 93-2 91.0 15-07 14.18 19 170.6 63.32 5 99.0 97.0 16.70 15-50 20 171. 1 157.0 65.00 54-46 6 104.6 103.2 18.04 16.74 i 25 172.2 157.7 68.29 55.08 7 III. 2 109.6 20.16 18.45 i 30 172.2 157.9 68.90 55-14 8 I I 7.0 "3-9 22.26 19.82 40 171-3 155.5 68.81 56.65 9 122.7 120.0 24.09 22.44 50 167.4 153.6 67.45 5S.45 10 128.2 124.8 26.12 24.24 60 163.9 I5I.6 65.50 56-73 II 132.7 127.5 27.85 26.25 70 162.3 151.4 63-03 53-72 12 135-9 132.7 31.08 30-54 80 161.3 150.6 61.22 51-52 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 Q uetelet.) 420 INXREASE IN SIZE AND WEIGHT. 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 Quetelt-t, are given on the jireceding page. Between the twelfth and fifteenth ye.irs 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 si.xth to the n'nth year until the thirteenth to the sixteenth. Tiie full stature is reached about tliiriy, but not the greatest weight. GENERAL VIEW OF THE 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. ; white enamel contains the least, 0.2 per cent, ('i, 229). According to some observers, peroxide of hydrogen (^H^O.,) is also present in the body. [Approximately, water forms about two-thirds of the weight of the body, so that a body weighing .75 kilos. (165 lbs.) contains .50 kilos, (no lbs.) of water. The following table, modified from Beaunis, shows the percentage of water in several tissues and organs : — Solids. Tissue or Organ. Water. Solids, i Tissue or Organ. Water. Solids. | Tissue or Organ. Water. Solids. Enamel, . . Dentine, . . Bone, . . . Fat, . . . Elastic tissue, Cartilage, . . Liver, . . . lo.o 48.6 29.9 49.6 55-0 69.3 Blood, , . . . . 79 I b6 4 89.1 90.1 92.8 Bile, Milk, .... Liquor sanguinis. Chyle, .... 998 90.0 514 70.1 504 45-0 30.7 20.9 136 10. 9 9-9 72 Spinal Cord, . White matter ) of brain, J Skin, . . . Brain, .... Muscles, . . Spleen, . . . Liqu Lymph, . . . Serum, . . . Gastric juice, . Inle-tinal juice. Tears, .... 69.7 70.0 72.0 75-0 757 75-8 ds. 95 95 97 97 30-3 30.0 28.0 25.0 24-3 24.2 4.2 4-1 2.7 2.5 1.8 Thymus, . . Connective tissue, . . Kidney, . . . Gray matter of brain, . . . Vitreous humor 77.0 79.6 82.7 85.8 98.7 Aqueous humor, 98 6 Cerebro-spinal fluid, . . . Saliva 99.5 Sweat, 99.5 98.8 20 4 17-3 14.2 13 1.4 1.2 0-5 05 II. Gases.— O, - ozone {\ 37) - H, - N - CO, (| 38). Marsh gas CH^ (| 124), NH3 (| 30, I 124, \ 184), H,S (? 184). 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 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 (p. 424). Sometimes it exists in a state of combination with proteid 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 the twenty-four hours, chiefly ■ by the urine. Boussingault showed that the addition of common salt to the food of cattle greatly improved their condition.] [Calcium phosphate (CajPoOg) 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 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 {V'Hsi^O^j, acid sodium phosphate [ViiSi^O^i, acid potassium phosphate [V^^^aO^. 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.] [Sodium carbonate (Na^COg) and sodium bicarbonate (NaHCOg) exist in small quantities in the food, and are formed in the body from the decomposition of the salts of the vegetable acids. 421 422 INORGANIC CONSTITUENTS OF THE BODY. They occur in the blood plasma, wiiere they play an important part in carrying the CO.^ from the tissues to the liinc;?.] I Sodium and potassium sulphates (NhjSO^ and K^SO^) exist in very small quantity in the bodv, and are introduced with the food, but part is formed in the body from the oxidation of organic bodies containinj^ sulphur.] [Potassium chloride ( KCI) is pretty widely distiibuted, and occurs specially in muscle, colored blood corpuscles, and milk. Calcium fluoride (CaFl.^) occurs in small quantity in bones and teeth. Calcium carbonate (CaCO.,) is associated with calcium phosphate m bone, tooth, and in some fluids, but it occurs in relatively much smaller amount. It is Icept in solution by alkaline chlorides, or by the presence of free carbonic acid. Ammonium chloride (NH^CI). — Minute traces occur in the gastric juice and the urine. Magnesium phosphate (MgsI'O^) occurs along \sith calcium phosphate, but in very much smaller (juantity.] Table, by Beaunis, of the relative proportions of Salts. Heintz. Staffel. Bone. Muscle of calf. Breed. Brain. Oidtmann. Liver. C. Schmidt Lungs. Oidtmann. Spleen. Sodic chloride, Potassic chloride, . . . . Soda, Potash, Lime, Magnesia, . Ferric oxide, Chlorine, Fluorine Phosphoric acid (free), . . Phosphoric acid (combined Sulpiiuric acid, Carbon dioxide, Silicic acid, Ferric phosphate, . . . . 3758 1.22 1.66 53 3J 547 10.59 2-35 3440 1.99 1.45 48-13 081 4-74 10.69 3442 o 72 1.23 9-'5 39.02 0.75 0.12 1.23 14-51 2523 3.61 0.20 2.74 2.58 5018 o 92 0.27 13.0 195 1-3 1-9 1-9 3-2 48.5 1.4 44-33 9.60 7.48 0.49 7.28 0.54 27.10 254 017 Table, by Beaunis, of the Mineral Matter in Animal Fluids. Verdeil. Weber. Weber. Dahn- hardt. Porter. Wilder- stein. Rose. Porter. Blood. Blood serum. Blood. Lymph. Urine. Bulk. Bile. Faeces. Sodic chloride, . Potassic chloride. Soda, Potash, .... Lime, Magnesia, . . . Ferric oxide, . . Phosphoric acid, . Suli)liuric acid, . Carbon dioxide, . Silicic acid, . . . 58.81 4-15 11.97 1.76 1. 12 8.37 10.23 1.67 1.19 72.88 1293 2-95 2.28 0.27 0.26 1-73 2.10 4.40 0.20 '7-36 2987 3-55 22.36 2.58 0.53 10.48 10.64 0.09 2.17 0.42 74.48 10-35 325 097 0.26 0.50 I 09 8.20 1.27 67.28 1-33 13-64 I-«5 1-34 11.21 4.06 10.73 26.33 21-44 18.78 .0.87 O.IO 19.00 2.64 27.70 36-73 4.80 1-43 0-53 0-33 10.45 6-39 11.26 0.36 4-33 5-07 6.10 26.40 10.54 2.50 36.03 313 IV. Free Acids. — Hydrochloric acid (liCl) [occurs /ree in the gastric juice, but in combina- tion with the alkalies it is widely distributed as chlorides]. Sulphuric acid (IL^SO^) [is said to occur free in the saliva of certain gasteropods, as Dolium galea. In the body it forms sulphates, chiefly in combination with soda and potash]. V. Bases. — Silicon as silicic acid (SiOj); manganese, iron, the last forms an integral con- stituent of hasmoglobin ; copper [?), (^ 174)- CHARACTERS OF THE TROTEIDS. 423 248. (B) ORGANIC COMPOUNDS. — I. The Albuminous or Proteid Substances. — (i) True Proteids and their allies are composed of C, H, O, N, and S, and are derived from plants (see hitrodiutioii). [The formation of albumin from the elements is accomplished only by plants. What the chemical processes are is quite unknown. We only know that the N is in the first instance obtained from the nitric acid or ammonia of the soil. The former is probably not used directly as such, but serves, perhaps, for the formation of amides or amido acids, from which, by the action of non-nitrogenous bodies, proteids are formed.] [According to Hoppe Seyler their general percentage composition is — O. H. N. C. S. From 20.9 6.9 15.2 51.5 0.3 To 23.5 to 7.3 to 17.0 to 54.5 to 2.O.] They exist in almost all animal fluids and tissues partly in the fluid form, although Briicke maintains that ihe 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 biie 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 CO,, HjO, 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 j'ield ammonia readily when they are decomposed, and partly in a more fixed condition. According to Pfliiger, part of the N in living proteia bodies exists in the form of cyanogen. [Loew supports Pfliiger's view that the molecule of living (active) albumin ditTers from that of dead albumin, as he finds that the living protoplasm of certain alg^ can reduce silver in very dilute alkaline solutions, which dead protoplasm cannot do.] The proteid molecule is very large, and is a very 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 Xh^ fatty bodies ; during the oxidation of albumin fatty acids especially are developed. Carbohydrates may also appear as decomposition products. For the decompositions during digestion see \ 170, and during putrefaction § 184. The proteids form a large group of closely related substances, all of w^hich 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 (§ 19 1 ), and therefore do not diffuse easily through animal membraaes ; they are amorphous and do not crystallize, and hence are isolated with difficulty; some are soluble, others are msoluble in water ; insoluble in alcohol and ether ; rotate the ray of polarized light to the left ; when burned 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 theprolonged action of alcohol. Cau.stic 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. Decomposition. — [The number and varieties of these products are exceedingly great, so that it is not easy to separate the several products. In the first place, there is great difficulty in getting in sufficient quantity a perfectly pure proteid, wherewith to institute the necessary experiments. The decomposition products of albumin when acted on by barium hydrate have been most fully investi- gated. The action of concentrated HCl,potassic permanganate, and bromine has also been studied. The action of the animal or vegetable digestive ferments is very important (| 170), and especially that of bacteria causing putrefaction (§ 184).] \'VTien acted upon in a suitable manner by acids and alkalies, they give rise to the decomposition products — leucin (10 to 18 per cent.), tyrosin (o 25 to 2 per cent.), aspartic acid, glutamic acid, and also volatile fatty acids, benzoic and hydrocyanic acids, and aldehydes of benzoic and fatty acids; also indol [Hlasiwetz, Heberiiiami). Similar products are formed during pancreat.c digestion [\ 170) and during putrefaction (§ 184). [Although it is assumed that the proteids have the closest relation to urea, no one, so far, has succeeded in preparing urea by the direct decomposition of albumin. Both by the action of acids and baiium hydrate, the splitting up into simpler compounds does not take place at once, but by successive stages, on to the formation of different bodies. Proteids, when fully decomposed, either by acids or alkalies, yield as the final products ammonia, and amido acids; by alkalies also carbonic, acetic, and oxalic acids. The amido acids contain several series including leucin, tyrosin, and glutamic acid. But all proteids do not yield these three bodies, for tyrosin may be absent, while leucin, so far, has been always found. It has therefore been attempted to classify proteids into those that yield tyrosin (i.e., aromatic com- pounds) and those that do not. Classes I-VII, p. 424, yield when decomposed aromatic bodies (tyrosin, indol, phenol), while gelatin-yielding bodies and spongin yield no aromatic bodies ] General Reactions. — (i ) Xanthoproteic Reaction. — Heated with strong nitric acid they give a yellow, the addition of ammonia gives a deep orange color. (2) With Millon's reagent they give a precipitate, and when heated with this reagent above 424 NATIVE ALBUMINS AND GLOBULINS. 60° C. they give a red one, probably owing to the formation of lyrosin. [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 a dilute solution of cupric sulphate, and the subsequent addition of caustic potash or soda, give a vicict color, which flepcnds on boiling ; [the same color is obtained by adding a few drops of Fehling's solution (biuret reaction)]. (4) They are precipitated afier strong acidulation by acetic acid and by potassium ferrocyanide. (5) When boiled with concentrated hydrochloric acid, they give a violet- red color (Liebermann's reaction). (6) Sulphuric acid containing molybdic acid gives a blue color {Frohde). (7) Their solution in acetic acid is colored violet with concentrated sulphuric acid, and shows the absorption band of hydrobilirubin (//^^/////(vVwVc). (8) Iodine is a good microscopic reagent, which strikes a brownish yellow, while sulphuric acid and cane sugar give a purplish violet i^E. Schnltze). [{9) \Yhen rendered strongly acid with acetic acid and boiled with an equal volume of a con- centrated solution of sodic sulphate, they are precipitated. This method is used for removing proteids from other li(|uids, as it does not interfere with the presence of other substances. Saturation with sodio-magnesic sulphate precipitates the proteids, but not peptones, and the same is the case with saturation with neutral ammonia sulphate {\ 249).] [(10) The precipitation of albumin by <;c?(/5 is more delicate when the acid is dissolved in alcohol containing 10 per cent, of ether ; the precipitate is not dissolved by an excess of the reagent.] [(II) Most of them are /rc-^z/Z/ftto/ by strong mineral acids, and metaphosphoric acid, tannic acid (in an acid solution), phcsphowolframic and phospho-molybdic acids (in acid solution); potassio- mercuric iodide (in acid solutions); many metallic salts, e.g., of Cu, Pb, Ag, Hg; chloral, phenol, trichloracetic acid, picric acid, alcohol. Taurocholic acid precipitates albumin and syntonin, but not peptone or hemi-albumose (§ 275).] 249. THE ANIMAL PROTEIDS AND THEIR CHARACTERS.— Class I.— Native Albumins occur in a natural condition in animal solids and fluids. They are soluble in water, and are not precipitated by alkaline carbonates, NaCl, or by very little dilute acids. Their solutions are coagulated by heating at 65° to 73° C. Dried at 40° C, they yield a clear, yellow, amber- colored, friable mass, " soluble albumin," which is soluble in water. (i) Serum albumin (^ 32 and \ 41). — [Its specific rotatory power is — 56°.] Almost all its salts may be removed fnmi it by dialysis, when it is no longer coagulated by heat. It is coagulated by strong alcohol ; and not very readily precipitated by hydrochloric acid, whde the precipitate so formed is easily dissolved on adding more 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 iis presence in urine, see \ 264. (2) Egg albumin. — \Mien injected into the blood vessels or under the skin, or even when intro- duced in large (juantity into the intestine, part of it appears unchanged in the urine (§ 192, 4, and \ 264). When shaken with ether it is precipitated. These two reactions serve to distinguish it from (i). The specific rotation is — 35-5°, i- e., for yellow light. Amount of S, 1.6 per cent. (Metalbumin and Paralbumin have been found by Scherer in ropy solutions in ovarian cysts; they are only panially precipitated by heat. The precipitate thrown down by the action of strong alcohol is soluble in water.) Class II. — Globulins are native proteids, insoluble in distilled water, but soluble in dilute neu ral saline solutions, i.e., neutral solutions of the alkalies and alkaline earths, e.g., NaCl, KCI, NH^Cl, MgSO^, (but not Na.jCOg, NajHPO^), sodium chloride of i per cent., and in mag- nesium sulphate. These soluions are coagulated by heat, and are precipitated by the addition of a large quantity of water. Most of them oxe precipitated from their sodium chloride solution by the addition of crystals of sodium chloride, and also by saturating their neutral solution at jo° 7vith crystals of viagnesium sulphate. When acted upon by dilute acids they yield acid albumin, and by dilute alkalies, alkali albumin. (i) Globulin (Crystallin) is obtained by passing a stream of CO, through a watery extract of the crystalline lens. (2) Vitellin is the chief proteid in the yolk of egg. It is also said to occur in the chyle (?) and in the amniotic fluid ( Weyl). Both the foregoing are not precipitated from their neutral solutions by saturation with sodium chloride. (3) Paraglobulin or Serum globulin [\ 29), and in urine {\ 264). . (4) Fibrinogen {\ 29). — In the clear jelly-like secretion of the vesiculse seminales of the guinea pig, there is a globulin-like body closely resembling fibrinogen. It contains 29 per cent, of albumin, with scarcely any ash. If it be touched with a trace of blood serum, without mixing them, it gradu- ally and completely forms a solid mass quite like fibrin. (5) Myosin is the chief proteid in dead muscle. Its coagulation in muscle post-mortem con- stituus rigor mortis. If muscle be repeatedly washed, and afterward treated with a 10 per cent, solution of sodium or ammonium chloride, it yields a viscid fluid which, when dropped into a large ALBUMINATES AND OTHER PROTEIDS. 425 quantity of distilled water, gives a white flocculent precipitate of myosin. It is also precipitated from its NaCl solution by crystals of NaCl. For Kiihne's and other methods see ^ 293. (6) Globin [Freyer), the proteid residue of hsemogoblin (§ 18). Class III. — Derived Albumins (Albuminates). — (i) Acid albumin or Syntonin. — When proteids aie dissolved in the stronger acids, ^.^., hydrochloric, they become changed into acid albumin«. They are precipitated from solution by the addition of many salts, sodic chloride, acetate or phosphate, 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 looo) upon minced muscles, is also an acid albumin. It is formed also in the stomach during digestion (| 166, I). According to Soyka, the alkali and acid albumins differ from each other only in so far as the pioteid 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 for some time by dilute alkalies, a solution of alkali albumin is obtained. Strong caustic potash acts upon white of egg, and yields a thick jelly, Lieberkiihn's jelly. The solution is not precipitated by heat, but it is precipitated by the addition of an acid. [Although alkali albumin is precipitated on neutralization, this is not the case in the presence of alkaline phosphates, e. g., sodic phosphate.] (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 it contains more N. It contains a large amount of phosphorus (0.S3 per cent.). It may be precipitated from milk by diluting it with sevei^al times its volume of water and adding dilute acetic acid, or by adding mag- nesium sulphate crystals to milk and shaking vigorously. Ov^^ing to the large amount of phosphorus which it contains, it is sometimes referred to the nucleo-albumins. When it is digested with dilute HCl (o. I per cent.) and pep.-in at the temperature of the body, it gradually yields nuclein. Class IV. — Fibrin. — (§ 27) and for the fibrin factors (^ 29). Class V. — Peptones. — For peptones and propeptone or the albumoses (§ 166, I) , in urine {I 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) ; also the indigestible amyloid substance 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. — Coagulatfed Proteids. — When any native albumins or globulins are coagulated, €, g., at 70° C, they yield bodies Avith altered characters, insoluble in water and saline solutions, but soluble ill 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 vegetable proteids have a great resemblance to animal proteids. They have frequently been obtained in a crystalline form, «■. ^., from the seeds of the gourd and various oleaginous seeds. They occur in greatest bulk in the seeds of plants, aleurone grains being for the most part composed of them. In seeds, globulins and " vegetable peptone " lorm the greater proportion of the proteid constituents.] [Globulins. — These varieties have been described as occurring in the seeds of plants : vege- table myosin, vitellin and paraglobulin (^Marti7i). 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 seed of legumiiiosse, in flour, and in the potato.] [Albumin. — The existence of a body corresponding to egg or serum albumin in the vegetable kingdom is doubtful [Ritthaiisen). Such a body has been described in papaw juice iyMartiti).'] [Vegetable Peptone ; Albumoses. — A true peptone has not yet been recognized in plants : what has been described as such is hemi-albumose ( Vines). Albumoses have been found in the seeds of leguminosse, in flour, and in papaw juice. In the last, two forms occur, called respec- tively a- and /3- phytalbumose. The former, a-phytalbumose, agrees with the hemi-albumose 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, fi 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 wiih sodium chloride, and gives a faint biuret reaction [A/artin).'] [Vegetable Casein is said to occur in the seeds of leguminosse ; and it is slightly soluble in water, but readily so in weak alkalies and in solutions of basic calcic phos-phate. A solution of this body is precipitated by acids and rennet. Two varieties have been described — (a) legumin, in peas, beans, lentils; acid in reaction, soluble in weak alkalies and very dilute HCl or acetic acid; (/3) conglutin, a very similar body occurring in hops and almonds. The existence of vegetable casein is denied. 426 ALBUMINOIDS. Vines slates that both legumin and conglulin are artificial products, being formed from the globulins present liv ihe dilute alkali used in exlraciicm of tiie proieids. This is denied by Rilthausen.] [Gluten and Glutin. — Cluten is reaiily prepared from flour by washing and kneading it in a muslin 1 a^ under a htream of water. So prepared it is yellowish brov n in color, very sticky, and capable of being drawn out into long shreils. It is insoluble in water, soluble (but not completely) by prolonged action in dilute acids nnd alkalies (.2 per cent. K HO and HCl). The prolonged action of alcohol [So to S5 pir cent.) dissolves part of the substance of gluten, leaving a residue, called by Liebig plant fibrin and by Ritlhausen gluten casein. The alcohol contains gliadin (glulin), gluten fibrin, and mucedin. Gluten casein is readily soluble in dilute alkalies, almost insoluble in dilute acetic aciil. and (|uue insoluble in cold and bodm..; waier ; the pro iucts of its decomposi- tion, by heating wi h H.,SO.,, are leucin, tyrosin, glutamic, and as|)araginic acids. The three liodies di-solved from glulin by alcohi Idifier chiefly in their solubility in alcohol and water. Gluten fibrin, the least soluble, is c.»agulated by the action of absolute alcohol; it is readily soluble in dilute aciHs and alkalies, being precipitated by neutralization. Gliadin (glutin, plant gelatin) may be prepared by boilin.; gluten with water : it deposits on cooling tiie solution Though soluble in water at 100° C. at fir.»t, it becomes insoluble by the prolonged aclion 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. The water used in washing the flour in the preparation ol gluten contains hemi- albumose ( / 'hies) and a globulin ( IVeyl). Rye flour, as well as wheaten, yields gluten under similar ireatmeiu with water.] [Nitrogenous Crystalline Principles. — Leucin, tyrosin, asparagin, and glutamic acid have been found in tlie seeds ol plants.] 250. (2) THE ALBUMINOIDS. — These substances closely resemble true proteids in their compojilion 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 pro- ducts closely resemble those of the proteids; some of them i)roduce, in addition to leucin and lyiosin, glycin and alanin (amidopropionic acid). They occur as organized constituents of the tissues and also in fluid form. It is unknown whether they are farmed by oxidation from proteid bodies or by synthesis. 1. Mucin is the characteristic substance present in mucus. That obtained from the sub-maxil- lary gland contains — C 52.31, H 7.22, N 11.84,028.63. According to Hammarslen it contains S 1.79 and N 13.5 per cent. It dissolves in water, making 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.j and other mineral aciiis precipitate it. It occurs in saliva (^ 146), in bile, in mucous glands, secretions of mucous membranes, in mucous tissue, in synovia, and in tendons. Pathologically it occurs not unfrequently in cysts; in the animal kmgdom, especially in snails and in the skin of hololhurians. It yields lucin and 7 ])er cent, of tyrosin when it is decomposed by prolonged boiling wiih sulphuric acid. [ The precipitate called mucin has not always the same characters, and, in fact, it ditfers according to the animal from which it is obtained {Landwe/ir.)'\ 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 HNO3; it gives the biuret I eaci ion ; no reaction with Millon's reagent ; when decomposed it yields phosphorus. It occurs in the nuclei of pus and blood corpuscles \\ 22), in spermatozoids, yelk spheres, liver, brain, and milk, veast. fungi, and many seeds. It has resemblances to mucin, and is perhaps an intermediate jiroduct ijetween albumin and lecithin {Hoppe-Seyler). It is prepared by the artificial digestion of )ius, when it remains as an indigestible residue ; acids precipitate it from an alkaline solution. It gives a feeble xanthoproteic reaction; 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 {A'assel). 3. Keratin occurs in all horny and epidermic tissues (epidermic scales, hairs, nails, feathers) — C 50.3-52.5, H 6.4-7, ^^ 16.2-17,0 20.8-25, S 0.7-5 P^"" ^^"f- — is .soluble in boiling cau. Intestinal i juice. 1. Diastatic i 2. Proteolytic, 3. Invertin, 4. Milk-curdling, Does not form maltose, but maltose is changed into glucose (^ 183). Fibrin into peptone (?). Changes cane- into grape sugar. (? in small intestine). Blood Chyle Liver (?), . . . Milk, .... Most tissues . . V Diastatic ferments • • Muscle, . . . Urine, .... V Pepsin and other ferments. Blood Fibrin-forming ferment. [(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 CO,^ 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 fennentation. As yet no one has succeeded 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 {P. Bert). But it is important to note that Hoppe-Seyler has extracted from deaxidation of fatty acids and glycolic acid, water being removed. It is important to note their origin from substances lich in carbon, c.g.^ fats, carbohydrates, and proteids. (a) Oxalic Acid, C.,0.,(OH),, arises from the oxidation of glycol, glycin, cellulose, sugar, starch, glycerin, and many vegetable acids — it occurs in the urine as calcium oxalate (? 260). (h) Succinic Acid, C^H,0.,(OH),,, has been found in small amount in animal solids and fluids; spleen, liver, thymus, thyroid ; in the fluids of echinococcus, hydrocephalus, and hydrocele, 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). (5) Cholalic Acid in the bile (? 177) and in the intestine [\ 182). (6) Aromatic Acids contain the radicle of benzol. Benzoic acid (=: phenyl-formic acid) occurs in urine united with glycerin, as hippuric acid (| 260). III. Alcohols. Alcohols are bodies which originate from carbohydrates, in which the radical hydroxyl (HO) is H ) substituted for one or more atoms of H. They may be regarded as water, it > 0, in which the half ' C H 1 of the H is replaced by a CH compound. Thus, C^Hg (ethyl hydrogen) passes into '^yfi \ O (ethylic alcohol). PHI (rt) Cholesterin, ^^yx^ f Oj 's a true monatomic alcohol, and occurs in blood, yelk, brain, bile (§ 177, 4), and generally in vegetable cells, and it is the only solid monatomic alcohol in the body.' rOH {b) Glycerin, CjHj-j OH, is a triatomic alcohol. It occurs in neutral fats united with fatty acids iOH and oleic acid ; it is formed by the splitting up of neutral fats during pancreatic digestion (| 170, 111), and during the alcoholic fermentation (iJ 150). {c) Phenol (= phenylic acid, carbolic acid, oxybenzol) (? 184, III). {d) Pyrokatechin (=r dioxybenzol) (^ 252). (f ) The Sugars are closely related to the alcohols, and they may be regarded as poly-atomic alcohols. Their constitution is unknown. Together with a series of closely related bodies they form the great group of the carbohydrates, some of which occur in the animal body, while others are widely d.stributed in the vegetable kingdom. 252. THE CARBOHYDRATES. — Occur in plants and animals, and received their name, because in addition to C (at least 6 atoms), they contain H and (), in the proportion in which these occur in water. They are all solid, chemically indifferent, and without odor. They have either a sweet taste (sugars), or can be readily changed into sugars by the action of dilute acids; they rotate the ray of polarized light either to the right or left; as far as their constitution is concerned, they may be regarded as fatty bodies, as hex-atomic alcohols, in which 2H are wanting. CARBOHYDRATES. 431 They are divided into the following groups : — 1. Division.— Glucoses (CgH,20g). — (i) Grape sugar (glucose, dextrose, or diabetic sugar) occurs in minute quantities in the blood, chyle, muscle, liver i?), urine, and in large amount in the urine in diabetes mellitus (| 175). It is formed by the action of diastalic ferments upon other carbohydrates, during digestion. In the vegetable kingdom, it is extensively distributed in the sweet juices of many fruits and flowers (and thus it gets into honey). It is formed from cane sugar, maltose, dextrin, glycogen, and starch, by boiling with dilute acids. It crystallizes in warty masses with one molecule of water of crystallization; unites with bases, salts, acids, and alcohols, but is easily decomposed by bases; it reduces many metallic oxides (§ 149). Fresh solutions have a rotatory power of -j- 106°. By fermentation with yeast it splits up into alcohol and COj {I 150) ; .with decomposing proteids it splits into 2 molecules of lactic acid (§ 184, I) ; the lactic acid splits up under the same conditions in alkaline solutions, into butyric acid, CO.^, and H. For the quali- tative and quantitative estimation of glucose, see ^ 149 and g 150. In alcoholic solution, it forms very insoluble compounds with chalk, barium, and potassium, and it also forms a crystalline com- pound with common salt (Estimation, | 150)- (2) Galactose, obtained by boiling milk sugar (lactose) with dilute mineral acids; it crystallizes readily, is very fermentable, and gives all the reactions of glucose. When oxidized with nitric acid it becomes transformed into mucic acid. Its specific rotatory power = + 88.oS°. (3) Laevulose (left-fruit-, invert-, or mucin sugar) occurs as a colorless syrup in the acid juices of some fruits and in honey ; is non-crystallizable, and insoluble in alcohol ; specific rotatory power = — io6°. It is formed normally in the intestine (^ 183), and occurs rarely as a pathological product in urine. II. Division. — This contains carbohydrates with the formula Q,H.„Oji, and its members may be regarded as anhydrides of the first division— i. Milk sugar or lactose occurs only in milk, crystallizes in cakes (with I molecule of water) from the syrupy concentrated whey; it rotates polarized light to the right = + 59.3, and is much less soluble in water and alcohol than grape sugar. When boiled with dilute mineral acids it passes into galactose, and can be directly trans- formed into lactic acid only by fermentation; the galactose, however, is capable of undergoing the alcoholic fermentation with yeast (Koumiss preparation, g 232). For its quantitative estimation (I 231). Rare in urine (§ 267). 2. Maltose (CjgHjP^^) + Hfi {O' Sullivan) has i molecule of water less than grape sugar (C12H24O12), is formed during the action of a diastatic ferment, such as saliva upon starch (| 148); is soluble in alcohol, right-rotatory power = + 150°; it is crystalline, while its reducing power is only two-thirds that of dextrose. [The ratio of the reducing power of maltose to that of glucose is 100 to 66.] (3. Saccharose (cane sugar) occurs in sugar cane and some plants, it does not reduce a solution of copper, is insoluble in alcohol, is right-rotatory, and not capable of fermentation. When boiled with dilute acids, it becomes changed into a mixture of easily fermentable glucose (right-rotatory) and laevulose (invert sugar, \ 183, 5, and § 184, I, 6), which ferments with difficulty and is left- rotatory (^ 183). When oxidized with nitric acid, it passes into glucic acid and oxalic acid.) (4. Meiitose, from Eucalyptus manna; Meleztose, from Larch manna; Trehalose (Mycose), from Ergot: all are right-rotatory, and do not reduce alkaline cupric solutions.) III. Division. — This contains carbohydrates, with the formula, CgHjoOj, which may be regarded as anhydrides of the second division. 1. Glycogen, with a dextro-rotatory power of 211°, does not reduce cupric oxide. It occurs in the liver (^ 174), muscles, many embryonic tissues, the embryonic area of the chick {Ki'dz), in normal and pathological epithelium; in diabetic persons it is widely distributed; brain, pancreas, and cartilage; and in the spleen, pancreas, kidney, ovum, brain, and blood, together with a small amount of glucose {Pavy). It also occurs in the oyster and some of the moUusks {Bizio), and indeed in all tissues and classes of the animal kingdom. 2. Dextrin was discovered by Limpricht in the muscles of the horse. It is right-rotatory = -f- 138°, soluble in water, and forms a very sticky solution, from which it is precipitated by alcohol or acetic acid ; it is tinged slightly red with iodine. It is formed in roasted starch (hence it occurs in large quantity in the crust of bread — see Bread, | 234), by dilute acids, and in the body by the action of ferments (^ 148). It is formed from cellulose by the action of dilute sulphuric acid. It occurs in beer, and is found in the juices of most plants. 3. Amylum or Starch occurs in the "mealy" parts of many plants, is formed within vegetable cells, and consists of concentric layers with an eccentric nucleus (Fig. 239). The diameter and characters of starch grains vary greatly with the plant from which they are derived. At 72° C. it: swells up in water and forms a mucilage ; in the cold, iodine colors it blue. Starch grains always contain more or less cellulose and a substance, erythrogranulose, which is colored red with iodine (I 148). It &nd glycogen axe. transformed into dextrose by certain digestive ferments in the saliva, pancreatic, and intestinal juices, and artificially by boiling with dilute sulphuric acid. (4. Gum, C^oH20*-'iO' occurs in vegetable juices (especially in acacise and mimosje), also in the salivary glands, mucous tissue, lungs, and urine; is partly soluble in water (arabin), partly swells. 4o2 CARBOHYDRATES. up like mucin (bassorin). Alcohol precipitates it. It is fermentable, and when boiled with dilute acids yields a reducing sugar.) (5. Inulin, a crystalline powder occurring in the root of chicory, dandelion, and specially in the bulbs of the dahlia; it is not colored blue by iodine.) (6. Lichenin occurs in the intercellular substance of Iceland moss (Cetraria islandica) and algx; is transformed into glucose by dilute suii»huric acid.) (7. Paramylum occurs in the form of granules resembling starch, in the infusoria, Euglena viridis.^ (8. Cellulose occurs in the cell walls of all plants (in the exo-skeleton of arthropoda, and the skin of snakes); soluble only in ammonio-cupric oxide ; rendered blue by sulphuric acid and iodine. Boiled with dilute sulphuric acid, it yields dextrin and glucose. Concentrated nitric acid mixed «^ C-: a. West Indian arrowroot ; c, Tahiti arrowroot ; d, Potato starch. with sulphuric acid changes it (cotton) into nitro-cellulose (gun cotton), C6H7(N0.2)305, which dissolves in a mixture of ether and alcohol and forms collodion.) (9. Tunicin is a substance resembling cellulose, and occurs in the integument of the Tunicata or Ascidians.) IV. Division. — This contains the carbohydrates which do not ferment. I. Inosit (phaseo-mannit, muscle sti'^ar) occurs in muscle [Sc/ierer], lung, liver, spleen, kidney, brain of ox, human kidney ; pathologically in urine and the fluid of echinococcus. In the vegetable kingdom, in beans (leguminosse), and the juice of the grape. It is an isomer of grape sugar; optically it is inactive, crystallizes in warts with 2 molecules of water, in long monoclinic crystals; it has a sweet taste, is insoluble in water, does not give Trommer's reaction, is cap.able of undergoing: only lh.e sarcolactic acid fermentation. (Nearly allied are Sorbin, trom sorbic acid — Scyllit, from the intestnies of the hag fish and skate— and Eukalyn, arising from the fermentation of melitose.) IV. Derivatives of Ammonia and their Compounds. The ammonia derivatives are obtained from the proteids, and are decomposition products of their metabolism. (i) Amines, /. ^., compound ammonias which can be obtained from ammonia (Xllg), or from ammonium hydroxide (NH^ — OH), by replacing one or all the atoms of H by groups of carbo- hydrates (alcohol radicals). The amine derived from one molecule of ammonia is called mon- amine. We are only acquainted with H ^ CH,^ H I N Methylamine and Tri-Methylamine. CH^ \ N, CH,j ChJ as decomposition products of cholin (neurin) and of kreatin. Neurin occurs in lecithin in a very complex combination (see Lecithin, p. 429, and also ^ 23). (21 Amides, i. e., derivatives of acids, which have exchanged the hydroxyl (HO) of the acids for NH.,. Urea, CO(NH2)^, the bi-amid of CO,, is the chief end product of the metaboii.'^m of the nitrO;jenous constituents of our bodies (see Urine, ^ 256). Carbon dioxide containing water = CO(OH).„ where both OH are replaced by NH,— thus we get CO(NH.,).j, urea. {3) Amido acids, /. e., nitrogenous compounds, which show partly the character of an acid and partly that of a weak base, in which the atoms of H of the acid radical are replaced by NH^, or by the substituted ammonia groups. {n) Glycin (or amido-acetic acid, glycocoll, gelatin sugar, ? 177, 2) is formed by boiling gelatin with dilute sulphuric acid. It has a sweet taste (gelatin sugar), behaves as a weak acid, but also unites with acids as an amine base. It occurs as glycin + benzoic acid = hippuric acid in urine (g 260); and also as glycin -|- cholalic acid = glycocholic acid in bile (^ 177). {b) Leucin HISTORICAL. 433 — (^ 170) = amido-caproic acid. (2' dulla. j Transverse section") of tubules in V3 boundary layer. ) Fat of renal sinus. 4. FlC. 240. i" Labyrinth. , / Medullary \ rays. MEDULLA. Transversely "j coursing medul- !>- lary rays. ) Artery. 5. Artery. 5. ( Branch of A ( renal artery. Longitudinal section through the kidney ( Tyson, after Henle). kidney, consisting of composed of about tw toward and embraced is further subdivided to Klein, the relative papillary portion, 4. aspect, with radiating an outer cortical and an inner medullary, or pyramidal portion, the latter elve conical papilla;, or pyramids of Malpighi, with their apices directed bythecalices of the pelvis of the kidney (Fig. 240). The medullary portion into the boundary layer of Ludwig and the papillary portion. According proportions of these three parts are — corte.x, 3.5 ; boundary layer, 2.5 ; and The cortex has a light brown color, and when torn presents a slightly granular lines running at regular distances. The granules are due to the presence'of the 434 STRUCTURE OF THE KIDNEY. 435 Malpighian corpuscles, and the strise to the medullary rays. The boundary zone is darker, and often purplish in color. It is striated with clear and red hnes alternating with opaque ones, the former being blood vessels and the latter uriniferous tubules. The papillary zone is nearly white and uniformly striated, the striee converging to the apex of the pyramid. The medulla is Fig. 241. 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. 241, 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 II centimetres (4.4 inches) in length, 5 centimetres (2 inches) wide, and 3 centimetres (i inch) in thickness. It weighs in the male 1 13.5 to 170 grms. (4 to 6 oz.), in the female 1 13.5 to 156 grms. (4 to $}4 oz.). The width of the cortex is usually 5 to 6 millimetres (i to iinch).] I. The uriniferous tubules all rise within the labyrinth of the cortex by means of a globular enlargement, 200 to 300 /j, [j^q to j^j inch] in diameter, called Bowman's capsule (Figs. 242, 243). After pursuing a complicated course, altering their direction, diameter, and structure, and being joined by other tubules, they ultimately form large collect- ing tubes, which terminate by minute apertures, visible with the aid of a hand lens, on the apices of the papillae projecting into the calices of the kidney. Each urinary tubule is com- posed 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 epithelium 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. 242, i), which invests (in the manner presently to be described) the tuft of capillary blood vessels called a glomerulus or Malpighian corpuscle. By means of a short and narrow neck (2) the capsule becomes continuous with a con- voluted tubule, X in Fig. 243. This tubule is of considerable length, forming many windings in the cortex (Fig. 242, 3) ; the first part of it is 45 /i wide, constituting the proximal or first convo- luted tubule. It becomes continuous with a 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 boundary zone, the spiral tubule suddenly becomes smaller and passes into the descend- ing portion of Henle's loop (5), which is 14 // in breadth, and is continued downward through the boundary zone into the medulla, where it forms the narrow loop of Henle (6), which runs backward in the medullary part to the boundary zone. Here it becomes wider (20-26 /i), and as it continues its undulating course, it enters a medullary ray, where it constitutes the ascending looped tube (7), which becomes narrower in the cortex. Leaving the medullary ray again, it passes into the labyrinth, where it forms a tube with irregular angular outlines —the irregular tubule (10), which is continuous with (Fig. 243, n, n) the second or distal convoluted tubule (11), which resembles the proximal tubule of the same name. Its diameter is 40//. A short, narrow, wavy junctional or curved collecting tubule (12) connects the latter with one of the straight collecting tubes (13) of a medullary 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 of the collecting tubes (Fig. 243, 0), which unite with one another at acute angles to form the larger straight excretory tubes or ducts of Belhni (15), which open on the summit of Papillary zone. Longitudinal section of a Malpighian pyramid. PF, pyra- mids of Ferrein; R A, branch of renal artery; RV, lumen of a renal vein receiving an inter-lobular vein ; VR, vasa recta ; PA, apex of a renal papilla : b, b, embrace the bases of the renal lobules. 436 STRUCTURE OF THE TUBULES. the Malpighian pyramids into a calyx of the pelvis of the kidney. In the cortex the collecting tubules are 45 // in diameter, but where they have formed an excretory tube (O), their diameter is 200 to 300 // ; 24 to So of these tubes ojien on the apex of each of the 12 to 15 Malpii;hian pyra- mids. In the lowest and broadest part, tlie membrana propria is strcni^lhened l)y the presence of a thick supportintj framework of connective tissue. Structure of the Tubules. — [Itciow the neck, tlie tubules arc lined everywhere by a single layer of nucleated epithelium.] Bowman's capsule, which is about .,1^, inch in diameter (I*'ig. 244, II), consists of a homogeneous basement memlirane lined internally by a single continuous layer of flattened cells [^•). According to Kotli, the basement membrane itself is composed of Fic. 4. Spiral tube. 13. Straight part of col- lecting tube. 9. Wavy part of ascend- ing limb of Henle's loop. Inner stratum of corte-v without Malpighian corpuscles. 7 and 8. Ascending limb of Henle's loop tube. Sub-cap.sular layer without Malpigh- ian corpuscles. First part of col- lecting tube. Distal convoluted tubule. CORTEX. Irregular tubule. 3. Proximal convo- luted tubule. 9. Wavy part of as- cending limb. 2. Constriction or neck. 4. Spiral tubule. I. Malpighian tuft surrounded b y Bowman's cap- sule. . 8, Spiral part of as- cending limb of Henle's loop. B. BOUNDARY ZONE. 5. Descending limb of Henle's loop tube. 6. Henle's loop. C. P API LLAR Y ZONE. Diagram of the course of two uriniferous tubules (Kieiit and Noblc-Stnitli), endothelial cells. [In the fcetus the lining cells are more polyhedral.] Within the capsule lies the glomerulus or tuft of blood vessels. The cells lining the capsule 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 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 raljbit. sheep, mouse, and frog, are ciliated. The proximal convoluted tubule is lined by characteristic epithelium. The cells, which are short or polyhedral, contain a turbid or cloudy protoplasm (Fig. 244, III, i and 2), which not STRUCTURE OF THE TUBULES. 437 Fig unfrequently contains oil globules, and they form a single layer. Each cell consists 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 " redded," from the presence of rods or fibrils placed vertically to the basement membrane (Fig. 245). 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 neigh- boring cells interlock by means of the branched ridges on their sur- faces (III, i) — {Heidetthain, Scha- chowa). The lumen is well de- fined, but its size seems to depend upon the state of imbibition of the cells bounding it. The spiral tubule has similar epithelium and a corresponding lumen, although the epithelium becomes lower and somewhat al- tered in its characters at the lower part of the tube. The descending limb of Hen- le's loop, and the loop itself with a relatively wide lumen, are bounded by clear, flattened, epi- thelial 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 capil- laries, but in addition to their squa- irious 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, ex- cepting 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 poly- hedral 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 " char- acter is much coarser and more defined (Fig. 246). 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 by clear, somewhat flattened cells. The collecting tubes have a distinct lumen, and are lined by clear', somewhat irregular, cubical cells (Fig. 244, V), which in the larger excretory tubes are distinctly columnar (VI). The base- ment membrane is said to be absent in the larger tubes. [Klein describes a thin, delicate, nucleated, centro-tubular membrane lining the surface of the epithelium next the lumen.] I, Blood vessels and uriniferous tubules of the kidney (semi-diagrammatic) ; A, capillaries of the cortex^ B, of the medulla; a, inter-lobular 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, f, Henle's loop ; n, n, junctional piece ; /, 180), where Gmelin's test sometimes fails to reveal the presence of bile pigments, urobilin occurs. This " urobilin- icterus" {Gerhardt) occurs chiefly after the absorption of large extravasations of blood. According to Cazeneuve, the urobilin is increased in all diseases where there is increased disintegration of blood corpuscles. 2. Urochrome ( Tkudickuvi) 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. When acted on by acids, new decomposition products are formed, e.g., uromelanin. 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 precipitating the uric acid by hydrochloric acid, a considerable amount may be obtained {Kunkel). 4. Urine boiled with HCl yields a garnet-red crystalline pigment, urorubin, to ether. 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 [Ktinkel). 262. INDIGO, PHENOL, KRESOL, PYROKATECHIN, AND SKATOL FORMING SUBSTANCES. — i. Indican [C,H,NSOJ, or indigo-forming substance {Schunck), is derived from indol, CsHyN, the basis of INDICAN, PHENOL AND PARAKRESOL. 453 indigo, which is formed in the intestine by the pancreatic digestion of proteids (§ 170, II), but it also arises as a putrefactive product (§184, 6). Indol, when united with the radical of sulphuric acid, HSO3, and combined with potassium, forms the so-called indigogen or indie an of urine (^Brieger, Baumami). This sub- stance (C8H6NS04K= potassium indoxyl-sulphate) forms white glancing tablets and plates ; readily soluble in water, and less so in alcohol. By oxidation it forms indigo- blue ; 2 indican + 03 = CigHjoNaOa (indigo blue) + 2HKSO4 (acid potassic sul- phate). It is more abundant in the urine in the tropics, and it is absent from the urine of the newly born {Senatot'). Tests. — (i) 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 blue (rhombic) and indigo red attest its presence. Putrefaction causes a similar decomposition in indican; hence, we not unfrequently observe a bluish-red pellicle of micioscopic cr}-stals of indigo blue, or even a precipitate of the same. (2) Mix in a beaker equal quantities of urine and hydrochloric acid, and add two drops of solution of chlormated 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). Quantity. — 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 sub- cutaneous injection of indol increases the indican in the urine {Jaffe). E. Ludwig obtained indican by heating hsematin 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 intestine (^ 172, H), e.g., in typhus, lead colic, trichinosis, catarrh, 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. 2. Phenol, CgHsO (carbolic acid, § 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 Bau- mann, " phenolsulphonic acid" (C6H50,S03H), which in urine is united with potash. Phenol is derived from the decomposition of proteids by pancreatic digestion (| 172, II), and also from putrefaciion (| 184, 6), the mother substance being tyrosin. Hence the formation of phenol- sulphonic acid is analogous to the formation of indican. If in the employment of carbolic acid it be absorbed, the phenolsulphonic acid becomes greatly increased in amount, so that sulphm-ic acid must be united with it; hence, alkaline sulphates are decomposed in ihe 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 sul- phate are added, yields phenolsulphonic acid ; while, under the same circumstances, pyrokatechin forms ethersulphonic acid. Carboluria. — WTien 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 (orthobioxybenzol = CgHg02), which for the most part appears in the urine as ethersulphonic acid [Batiniann and others). 3. Parakresol (hydroxyltoluol, C^HgO), with its isomers ortho- and meta- kresol (the latter in traces), is more abundant in urine (^Bmimann, Preusse). It also occurs in combination with sulphonic acid. Test for phenol (and also kresol) : Distill 150 c.c. urine with dilute sulphuric acid. The distil- late gives a brown crystalline deposit of tribromophenol with bromine water, as well as a red color with Millon's reagent. Hydroxybenzol (pyrokatechin, hydrochinon) is obtained from lorine, when it is heated for a long time with hydrochloric acid. Resorcin, which is an isomer of hydrochinon, when administered internally, also appeai-s in the lu-ine as ethersulphonic acid. Toluol and naphthalin behave similarly. Benzol is oxidized to phenol. 4. Pyrokatechin = CgHeOa (metadihydroxylbenzol), is formed along with 454 PYROKATECHIN AND SKATOL. hydrochinon from phenol, and is an isomer of the former. It behaves like indol and phenol, for when united with sulphonic acid, it yields the pyrokatechin-forming substance. Small quantities sometimes occur in human urine ; it is more abun- dant in the urine of children ; it becomes darker when the urine putrefies. 5. Skatol, which is crystalline, and is formed during putrefaction in the intes- tine, also appears in the urine as a compound of sulphonic acid (§ 252). 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 fuming nitric acid, which precipitates red flakes (.Vifncii). 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 albu- min) occur in the urine [Baumann, g 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, C9HjjX03-f- H.j^CjHjqOj (hydro- paracumaric acid) -^ NH,. CgHjf,03t= CgHj^O (paraethylphenol, not yet proved) -4- COj. CgH,gO + 03=C5H-03 (paraoxyphenylacetic acid) — H,0. qHg03=C-Hj,0 (parakresol) + COj. C^HgO -j- 03= C.HgOj (paraoxybenzoic acid, not yet proved) — H.^O. C.H5O =CgH50 phenol + COj. 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. Miink). One litre of human urine contains 0.02 to 0.08 gramme combined with an alkali. Succinic Acid (C^HgO^) occurs chiefly after a diet of flesh and fat, and almost disappears after a vegetable diet. It is a decomposition product of asparagin, and occurs in considerable amount in the urine after eating asparagus. It is also a product of the alcoholic fermentation (| 150), and as it passes out of the body unchanged, it occurs in the urine of those who imbibe spirituous liquors. It passes unchanged into the urine (^Xetibauer). Lactic acid (C3H5O3) is a constant constituent of urine. Other observers have found ferment- able lactic acid in diabetic urine ; sarcolactic acid after poisoning with phosphorus and in trichinosis. Occasionally traces of volatile fatty acids are present. Some animal gum occurs in urine (p. 431), and Bechamp's " nephrozymose " consists for the most part of gum {Landwehr). This substance is precipitated from urine by adding to it three times its volume of 90 per cent, alcohol. It is not a simple body, but at 60' to 70^ C. it transforms starch into sugar {v. Vintschgau). Ferments. — Traces of diastatic, peptic, and rennet ferment have been found, especially in urine of high specific gravity. Tn.-psin is said not to occur normally [Leo). Traces of sugar (Brucke, Bence Jones), to the amount of 0.05 to O.OI per cent., 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 {IVorm-Miiller — \ 267,7). Kryptophanic acid (C3HJNO5), according to Thudichum, occurs as a fi-ee acid in urine, but Landwehr regards it as an animal gum. Aceton iCjHgO) is formed when normal urine is oxidized with potassic bichromate and sulphuric acid, and it is formed from a reducing substance present in normal urine (apparently derived from the graj)e 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). Lieben's Test. — Acidulate half a litre of urine with HQ and distill ; 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 bases to form salts. The quantity of salts excreted daily in the urine is 9 to 25 grammes [J^ to 3^ oz.]. I. 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 ; it is diminished under the opposite conditions. In disease it is greatly diminished ; in pneumonia and other inflammations accompanied by PHOSPHORIC AND SULPHURIC ACID. 455 efhisions, 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 depression the reverse is the case (Z£?;//3fr). ,• j 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 common salt, and also for the cr\-stals of sodic chloride and urea (^ 256, 4). 2. Phosphoric acid occurs in urine as acid sodic phosphate and acid calcic and magnesic phosphates to the amount of about 2 grammes daily [30 grains] ; it is more abundant after an animal than after a vegetable diet. The amotmt increases after a midday meal until evening, and falls during the night until next day at noon. It is partly derived from the alkaline and earthy phos- phates of the food, and partly as 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 sub- stance. 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, andoxaluria; after the administration of lactic acid, morphia, chloral, or chloroform 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. [Tests.— To urine add nitric acid and solution of ammonium molybdate and boil, a canaiy yellow precipitate of ammonium phosphomolybdate indicates the presence of phosphoric acid. Or, add half Its volume of caustic potash to urine, and boil. The earthy phosphates are precipitated, but not the alkaline phosphates.] Earthy phosphates are precipitated by heat in some pathological urines. 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.] Quantitative.— The amotint of phosphoric acid is estimated by titration with a standard solution of ttranium acetate ; ferrocyanide of potassium being the indicator. The indicator gives a brownish 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), which occurs to the amount of 15 milligrammes m a litre of^urine; it is increased in nervous diseases and after chlorotorm narcosis. 3. Sulphuric acid occurs in the urine, the greater part in combination with the alkalies, and the remainder united with indol, skatol, and pyrokatechm, m the form of aromatic ethersulphonic compounds, the ratio being i : 0.1045. All condi- tions which favor the formation of indol, skatol, or pyrokatechm, increase the amount of combined sulphuric acid. The total daily amount of sulphuric acid is 2.5 to 3.5 grammes [37 to 52 grains]. It is increased by the administration of sulphur i^Kraiisi). 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 sulphm-), in the case of rabbits, ( but not in carnivora or man), increases the sulphuric acid in the urine {^Salkowski). According to Zulzer, a copious secre- tion of bile lessens the relative amount of sulphuric acid in the urine. , ki • Test.— Barium chloride gives a copious white heavy precipitate of barium sulphate, insoluble m °'ln addition to sulphuric acid, sulphur (i) occurs in an incompletely oxidized foi-m in the urine (potassium sulphocyanide, cystin, and sulphur-bearing compounds derived from the bile) {Kiinkel, v. Voit—l 177, 6). Hvposulphnrous acid, as an alkaline salt, is an abnormal constituent in typtius; and so 'is sulphuretted hydrogen, which is recognized by the blackening of a piece of paper moist- ened with lead acetate and ammonia, held over the urine. 456 ACID FERMENTATION OF URINE. 4. Excessively minute traces of silicic acid and nitric acid derived from drink- ing water have been found in urine. Organic acids, e.g., citric and tartaric, when taken internallv, 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 phosi)horic and uric acids; potassium (which is about yi of the sodium) is chiefly combined with chlorine. In fevers, more ])Otash is excreted than soda, and during convalescence, the reverse is the case ; calcium and magnesium exist in normal acid urine as chlorides or acid phosphates. If the urine is neutral, neutral calcium phosphate and magnesium phosphate are precipitated. Kl)stein found the latter in alkaline urine, as large, clear, four-sided i)risms, in diseases of the stomach. If the urine is alkaline, calcium carbonate (Fig. 281) and 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 {Neuhauer, Brilcke), and the amount is greater with an animal than with a vegetable diet {Coranda). The amount of fixed ammonia is increased by the administration of mineral acids ( ^^zZ/^r, Schmiedeberg, Gdthgens). Iron (i to 1 1 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. CO.,, 2.74 O, 13.86 N. Afier severe muscular action, the amount of COj may be doubled; digestion also increases it, copious dnnking dimini.shes it. 263. FERMENTATIONS OF URINE. — Acid Fermentation.— When perfectly fresh urine is set aside, it gradually becomes more acid from day to day. This is called the " acid fermentation." It seems to be due to the devel- opment of special fungi (Fig. 260, a), and the process is accompanied by the Fic. 260. ^^^•i ■4-- 6 Deposit in "acid fermentation" of urine, a, fungus; i, amorphous sodium urate ; c, uric acid; t/, calcium ox- alate. Deposit in ammoniacal urine (alkaline fermentation). a, acid ammonium urate ; d, ammonio-magnesium phosphate; (, bacterium ureae. deposition of uric acid (c), acid sodium urate, in amorphous grains {b), 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 scad formic acids have been found as abnormal decompo- ALKALINE FERMENTATION OF URINE. 457 sition products of other urinary constituents. When the acid fermentation begins, the urine absorbs 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 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. 261). This condition is accompanied by the formation of the micrococcus ureae (Fig. 262) {Pasteur, Cohn) and Bacterium ureae (Fig. 261), which causes the urea to take up water and decompose into CO.^ and ammonia. Urea [C0(HN2)., + 2(H20) = ammonium carbonate [(NHJ^COj]. 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 {Musctilus), which, however, only passes from the body of the cells into the fluid after the cell or organism has been killed by alcohol {Lea). The presence of ammonia causes the urine to become turbid, and those substances which are insoluble in an alkaline urine are precipitated — earthy phosphates, consisting of the amorphous calcic phosphate, acid ammonium urate (Fig. 261, 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. 282). [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. y\g 262 Its presence, therefore, always indicates ammoniacal fer- mentation of the urine.] In cases of catarrh or inflam- mation of the bladder, this decomposition may take 1 ^""^ place within the bladder, when the urine always contains \,^:P\^ pus cells (Fig. 267) and detached epithelium. When j^^oG much pus is present, the urine contains albumin. Am- moniacal urine forms white fumes of ammonium chloride. Micrococcus urese. when a glass rod dipped in hydrochloric acid is brought near it. [When ammonia is added to normal urine, triple phosphate is precipitated in a feathery form (Fig- 283).] [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.^, 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.] 264. ALBUMIN IN URINE OR ALBUMINURIA.— Serum albu- min is the most important abnormal constituent in urine which engages the attention of the physician. It occurs in blood (§ 32), and its characters are described in § 249. Causes of Albuminuria. — i. Serum albumin may appear in urine without any apparent ana- tomical or structural change of the renal tissues. This condition has been called by v. Bamberger " Hcematogenous albutninuria.''' It occurs but rarely, however, and sometimes in healthy individ- uals when there is an excess of albumin in the blood plasma {e.g., after suppression of the secretion 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 pleuritic effusions, infiltrations of the lungs, and after compression of the chest, causing congestion in the pulmonary circuit, which extends even into the renal veins, 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. 458 TESTS FOR ALBUMIN IN URINE. 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.] Con- vulsh'e disorders, e.^., epilepsy, the spasms of dyspnrea after strychnin poisoninp;, in shock of the brain, apojilexy, spinal paralysis, and violent emotions ; the excessive use of moqihia, which, perhaps, acts on the vasomotor centres. 5. It may accompany many acute febrile diseases, e.i^., the exanthe- mata (scarlet fever), typhus, pneumonia, and pyxmia. In these cases, it may l)e due to the increase of temperature paralyzing the vessels, but more probably the secretory apparatus of the kidney is .so changed (f^-, cloudy swelling of the renal epithelium) that the albumin can pass through the renal membrane. 6. Certain degenerations and inflammations of the kidneys at several of their stages. 7. Inflammation or suppuration in the ureter or urinary pa.ssages. 8. Certain chemical substances which irritate the renal parenchyma, e.(;., cantharides, carbolic acid. 9. The complete withdrawal of common salt from the food. The albumin disappears when the common salt is given again. lO. The epitheliuiit may be in such a condition that it cannot retain the alhttniin within the vessels, due to imperfect nourishment and functional weakness of the excretory elements. This includes the albu- minuria of ischi^mia, and that after hemorrhage, in anaemia, scorbutus, icterus, diabetes. [Grainger Stewart finds that albuminuria is more common among presumably healthy people than was formerly supposed.] [Besides being derived from the secreting parenchyma of the kidney, albumin may be present owing to 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 all)U- 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 membrane 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 with the usual tests for albumin. Posner precipitated the urine with alcohol, washed the precipitate, dissolved it in acetic acid, and tested it with the ferrocyanide test for albumin. He finds that minute traces of proteid are detected by the following modification of the biuret test : Make the urine alkaline, and by the " contact method " bring a layer of very dilute cupric sulphate over it ; when the two fluids touch, a reddish-violet ring is obtained.] The tests for albumin in urine depend upon the facts that it is coagulated by heat in neutral or acid sohitions, and it is precipitated by various reagents. [(i) Heller's Test. — Place 10 c.c. of the urine in a test-glass, and pour in pure colorless HNO3 so as to run down the side of the glass, forming a layer beneath the urine. A white zone of coagu- lated 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.] [(2) 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 to 12 drops of HNO,. If the turbidity disappears it is due to phosphates, while if any remain 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 lube, else the tube is liable to break, {c) In performing this test with a «^w/r<7/ solution, note when the precipitate falls, for albumin is precipitated about 70° C, phosphates not till about the boiling point. (odies, concretions, stricture, swelling of the prostate. 2. Paralysis or exhaustion of the musculature of the bladder; the latter sometimes occurs after delivery, in consequence of the pres ure of the child against the bladder. 3. After section of the spinal cord (p. 484). 4. Where the voluntarj- impulses are unaiile to act upon the inhibitor)' apparatus of the sphincter urethrpe reflex, as well as when the sphincter urethrae reflex is increased. Incontinence of urine (stillicidium urinae) occurs in consef|uence of — i. Paralysis of the sphincter uretlira\ 2. Loss of sensibility of the urethra, which of course abolishes the reflex of the sphincter. 3. Trickling of the urine is a secondary consequence of section of the spinal cord, or of its degeneration. Strangury is an excessive reflex contraction of the walls of the bladder and sphincter, due to stimulation of the bladder and urethra; it is observed in inflammation, neuralgia [and after the use of some poisons, e. g., cantharides]. Enuresis nocturna, or involuntary emptying of the bladder at night, may be due to an increased reflex excitability of the wall of the bladder, or weakness of the sphmcter. 282. COMPARATIVE AND HISTORICAL.— Among vertebrates, the urinary and genital organs are frequently combined, except in the osseous fishes. The Wolffian bodies which act as organs of excretion during the embryonic period, remain throughout life in fishes and amphibians and continue to act as such. Fishes. — The tnyxinoids (cyclostomata) have the simplest kidneys ; on each side is a long ureter with a series of short-stalked glomeruli with capsules arranged along it. Both ureters open at the genital pore. In the other fi.shes, the kidneys lie often as elongated compact masses along both sides of the vertebral column. The two ureters unite to form a urethra, which always opens behind the anus, either united with the opening of the genital organs, or behind this. In the sturgeon and hag fish, the anus and orifice of the urethra together form a cloaca. Bladder-like formations, which, however, are morphologically homologous with the urinary bladder of mammals, occur in fishes, either on each ureter (ray, hag-fish), or where both join. In amphibians, the vasa efferentiaof the testicles are united with the urinary tubules; the duct in the frog unites with the one on the other side, and both conjoined ojiens into the cloaca, while the capacious urinary bladder opens through the anterior wall of the cloaca. From reptiles upward, the kidney is no longer a persistent Wolffian body, but a new organ. In reptiles, it is usually flat- tened and elongated; the ureters open singly into the cloaca. .Saurians and tortoises have a urinary bladder. In birds, the isolated ureters open into the uro-genital sinus, which opens into the cloaca, internal to the excretory ducts of the genital apparatus. The urinary bladder is always absent. In mammals, the kidneys often consist of many lobules, e. g., dolphin, ox. Among invertebrates, the moUusca have excretory organs in the form of canals, which are provided with an outer and an inner opening. In the mussel, this canal is provided with a sponge- like organ, often with a central cavity, and consisting of ciliated secretory cells, placed at the base of the gills (organ of Bojanus). In gasteropods, with analogous organs, uric acid has been found. Insects, spiders, and centipedes have the so-called Malpighian vessels, which are excretory organs, partly for uric acid and partly for bile. These vessels are long tubes, which open into the first part of the large intestine. In crabs, blind tubes connected with the intestinal tube, perhaps have the same functions. The vermes also have renal organs. Historical. — Aristotle directed attention to the relatively large size of the human bladder — he named the ureters. Massa (1552) found lymphatics in the kidney. Eustachius (f 1 580) ligatured the ureters and found the bladder empty. Cusanus (1565) investigated the color and weight of the urine. Rousset (1581) described the muscular nature of the walls of the bladder. Vesling described the trigone (1753). The first important chemical investigations on the urine date from the time of van Helmont (1644). He isolated the solids of the urine and found among them com- mon salt ; he ascertained the higher specific gravity of fever urine, and ascribed the origin of urinary calculi to the solids of the urine. Scheele (1766) discovered uric acid and calcium phosphate; Arand and Kunckel, phosphorus; Rouelle (1773), urea; and it got its name from Fourcroy and Vauquelin (1799). Berzelius found lactic acid; Seguin, albumin in pathological urine; Liebig, hippuric acid ; Heintz and v. Pettenkofer, kreatin and kreatinin ; Wollaston (1810), cystin. Marcet found xanthin ; and Lindbergson, magnesic carbonate. Functions of the Skin. Fis. 293. 283. STRUCTURE OF THE SKIN, HAIRS, AND NAIL.— The skin (3.3 to 2.7 mm. thick; specific gravity, 1057) consists of — [i. The epidermis ; 2. The chorium, or cutis vera, with the papillse (Fig. 294).] The epidermis (0.08 to 0.12 mm. thick) consists of many layers of stratified epithelial cells united to each other by cement substance (Figs. 293, 294). The superficial layers — stratum corneum — consist of several layers of dry, horny, non-nucleated squames, which swell up in solution of caustic soda (Fig. 294, E). [It is always thickest where intermittent pressure is applied, as on the sole of the foot and palm of the hand.] The next layer is the stratum lucidum, which is clear and transparent in a section of skin, hence the name, and consists of compact layers of clear cells with vestiges of nuclei. Under this is the rete mucosum or rete Malpighii (Fig. 294, d), consisting of many layers of nucleated protoplasmic epithelial cells which contain pigment in the dark races, and in the skin of the scrotum, and around the anus. [The superficial cells are more fusiform and con- tain granules which stain deeply with carmine. They constitute, 3, the stratum granulosum. In these cells the formation of keratin is about to begin, and the granules have been called eleidin granules by Ranvier. They are chemi- cally on the way to be transformed into keratin. All corneous structures contain similar granules in the area where the cells are becoming corne- ous. Then follow several layers of more or less polyhedral cells, softer and more plastic in their nature, and exhibiting the characters of so- called " prickle cells " (Fig. 294, R). [The spaces between the fibrils connecting adjacent cells are lymph spaces.] The deepest layers of cells are more or less columnar, and the cells are placed vertically upon the papillse. Granular leucocytes or wandering cells are sometimes found between these cells. This, the fourth layer, has been called the stratum Malpighii. The rete Malpighii dips down between adjacent papillse and forms interpapillary processes. Ac- cording to Klein, a delicate basement mem- brane separates the epidermis from the true skin.] The superficial layers of the epidermis are continually being thrown oiif, while new cells are continually being formed in the deeper layers of the skin by proliferation of the cells of the rete Malpighii. There is a gradual change in the micro- scopic and chemical characters of the cells from the deepest to the superficial layers of the epider- mis. [In a vertical section of the skin stained with picro-carmine, the S. granulosum is deeply stained red, and is thus readily distinguished among the other layers of the epidermis.] (i) Stratum corneu7n, \ p t-iVlp (2) Stratum lucidum, J (3) Siratzim granulomm, j Rete Mucosum.] (4) Stratum Malpighii, J 487 _Stratum corneum. Stratum lucidum. Stratum -granu- losum. _Stratum Malpighii. Vertical section of the human epidermis ; the nerve fibrils, n, b, stained with gold chloride. [Epidermis (Fig. 293), 488 STRUCTURE OF THE EPIDERMIS. No pigment is formed within the epidermis itself ; when it is present, it is carried by leucocytes from the subcutaneous tissue {Kieh/, Ehrmann, Achy). This explains how it is that a piece of white skin, transplanted to a negro, becomes black [Kari^'). The chorium (^Fig. 294, I, C) is beset over its entire surface by numerous (0.5 to O.I mm. high) papillae (Fig. 294). the largest being upon the volar surface of the hand and foot, on the nipple and glans penis. Most of the papill;i2 contain a looped capillary (^), while in certain regions some of th'em contain a touch corpuscle (Fig. 295, «). The papilla- are disposed in groups, whose Fir,. 294. I, Vertical section of the skin, with a hair and sebaceous gland, T. Epidermis and chorium shortened— i, outer ; 2, inner fibrous layer of the hair follicle ; 3, its hyaline layer ; 4. outer root sheath ; 5, Huxley's layer of the inner root sheath ; 6, Henle's layer of the same; /, root of the hair, with its papilla; A, arrcctor pili muscle; C, chorium; a, subcutaneous fatty tissue; h, epidermis (horny layer); d, rete Malpighii ; ^, blood vessels of papillje ; t, lymphatics of the same ; h, horny or corneous substance ; /, medulla or pith ; k. epidermis or cuticle of hair; K, coil of sweat gland ; E, epidermal scales (seen from above and en/ace) from the stratum corneum ; R, prickle cells from the rete Malpighii ; «, superficial, and m, deep cells from the nail ; H, hair magnified; e, cuticle : c, medulla, with cells ; /,/, fusiform fibrous cells of the substance of the hair ; x, cells of Huxley's layer ; /, those of Henle's layer ; S, transverse section of a sweat gland from the axilla ; a, smooth muscular fibres sur- rounding it ; /, cells from a sebaceous gland, some of them containing granules of oil. arrangement varies in different parts of the body. In the palm of the hand and sole of the foot they occur in rows, which are marked out by the existence of delicate furrows on the surface visible to the naked eye. The chorium consists of a dense network of bundles of white fibrous tissue mixed with a network of elastic fibres, which are more delicate in the papillne. In silversmiths the elastic fibres are blackened by the partial deposition of reduced silver, and the same obtains in those who take silver nitrate in such quantity as to produce argyria. The connective tissue contains many connective-tissue corpuscles and numerous leucocytes. The deeper connecti\% tissue layers DEVELOPMENT OF THE NAILS. 489 of the chorium gradually pass into the subcutaneous tissue, where they form a trabecular arrange- ment of bundles, leaving between them elongated rhomboidal spaces filled for the most part with groups of fat cells (Fig. 294, a, a). [In microscopic sections, after the action of alcohol, the fat cells not unfrequently contain crystals of margarin.] The long axis of the rh'omb corresponds to the greater tension of the skin at that part [C. Langer'). In some situations the subcutaneous tissue is devoid of fat [penis, eyelids]. In many situations, the skin is fixed by solid fibrous bands to subja-- cent structures, as fascise, ligaments or bones (tenacula cutis) ; in other parts, as over bony promi- nences, bursa; partially lined with endothelium and filled with synovia-like fluid, occur. Smooth muscular fibres occur in the chorium in certain situations on extensor surfaces {^Neu- mann) ; nipple, areola mammae, prepuce, perinasum, and in special abundance in the tunica dartos of the scrotum. [Guanin in the Skin. — The skin of many amphibians and reptiles contains brown or black pig- ment granules, and other granules of a white, silvery, or chalky appearance. Ewald and Krukenberg have shown that the latter consists of guanin, and that this substance is very widely diffused in the skin of fishes, amphibians, and reptiles. Test : Select a piece of skin from the belly of a frog ; place it in a porcelain capsule as for the murexide test ; add concentrated nitric acid, and heat to dryness, when a yellow residue is obtained; on adding a drop of caustic soda a red color is struck. The yellow residue gives no reaction with ammonia. If to the fluid more water be added, and it be then heated, distributed over the surface of the capsule, and cooled by blowing upon it, various shades of purple and violet are obtained.] The nails (specific gravity I.19) consist of numerous layers of solid, horny, homogeneous, epidermal, or nail cells, which may be isolated with a solution of caustic alkali, when they swell up and exhibit the remains of an elongated nucleus (Fig. 294, 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. 296, e). The chorium under the nail is covered through- out its entire extent by longitudinal rows of FiG. 295. papillae (Fig. 296, d). Above this there lies, as in the skin, many layers of prickle cells like those in the rete Malpighii (Fig. 294, a), and above this again is the substance of the nail (Fig. 296, a). [The stratum granulosum is rudimentary in the nail bed. The substance of the nail represents the stratum lucidum, there being no stratum corneum (^K'lein).'] The pos- terior part of the nail groove and the half moon, brighter part or lunula, form the root of the nail. They are, at the same time, the matrix, from which growth of the nail takes place. The Papill» of the skin, epidermis removed blood vessels 1 ,. °^. -i.j -ij-j injected: some contain a Wagners touch corpuscle, a, lunule is present m an isolated nail, and is due ^^^ others a capillary loop. 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). Fig. 296. Transverse section of one-half of a nail, a, nail substance: b, more open layer of cells of the nail bed; c, stratum Malpighii of the nail bed ; d, transversely divided papillse ; e, nail groove ; f, horny layer of e projecting over the nail ; g, papillse of the skin on the back of the finger. 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 490 STRUCTURE OF A HAIR FOLLICLE. Fir.. 297. matrix. These layeis 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 thickiness in this region. In the course of a year the fingers produce al)out 2 grms. of nail substance, and relatively more in summer than in winter. Development — i. From the second to the eighth month of fretal life, the position of the nail is indicated by a ]iaitial but marked horny condition of the epidermis on the back of the first phalanx, the " eponychium." The remainder of this substance is represented during life by the normally formed epidermal laver, 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 eponychium) covers the whole extent of the nail bed. 3. When, at a later period, the e[ionychium splits off, the nail is uncovered. After birth the papillae are formed on the bed of the nail, while simultaneously the matrix passes backward to the most posterior part of the groove ( Unna). 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. 294, I,/) which passes obliquely through the thickness of the skin, sometimes as far as the subcutaneous tissue. The structure of a hair follicle is the following : I. The outer fibrous layer (Figs. 294, 1, 293), 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 sur- rounding chorium.] 2. The inner fibrous layer (Figs. 294, 2, 297) 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 transparent, hya- line, glass-like basement membrane (Figs. 292, 3, 297), which ends at the neck of the hair follicle ; while above it is continued as the basement membrane which exists between the epideiTnis and chorium. In addition to these coverings, a hair follicle has epi- thelial coverings which must be regarded in relation to the layers of the epidennis. Immediately within the glass-like membrane is the outer root sheath (Figs. 294, 4, 297, 298), which consists of so many layers of epithelial cells that it forms a conspicuous covering. It is, in fact, a direct continuation of the stratum Malpighii, and consists of many layers of soft cells, the cells of the outer layer being cylindrical. Toward the base of the hair follicle it becomes miTOwer, and is united to, and continues 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 con- Transverse section of a hair and its sists of (l) a single layer of elongated, flat, homogeneous, non- follicle, a, outer fibrous coat with nucleated Cells (Figs. 294, 6, 297,/ — Henlis layer) placed next dis'XTajxt/ J.'irs^ikl^ayjl^; and wUhin the outer root sheath. Within this lies (2) Huxle/s e, outer, y;^, inner, root sheath:/, layer (Figs. 294, 5, 297, g), consistmg of nucleated elongated outer layer of the same (Henle's polygonal cells (Fig. 294, X, and 3), while the cuticle oivhe. hair muxLV-s^'sireTth)''T,°c;uicle''7 follicle is Composed of cells analogous to those of the surface of hair. ' ' the hair itself. Toward the bulb of the hair these three layers become fused together. [Coverings of a hair follicle arranged from without inward — ./ — I. Fibrous layers. f [a) Longitudinally aiTanged fibrous tissue. \ [b] Circularly arranged spindle cells. f Henle's layer. \ Huxley's layer. 2. Glass-like (hyaline) membrane. !{a) Outer root sheath. \b) Inner root sheath, (c) Cuticle of the hair. 4. The hair itself.] The arrector pill muscle ( Fig. 294, A) is a fan-like arrangement of a layer of smooth muscular fibres, attached below to the side of a hair follicle and extending toward the surface of the chorium ; as it stretches obhquely 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 DEVELOPMENT AND PROPERTIES OF HAIR. 491 Fig. 298. i M follicle lies the sebaceous gland]. When these muscles contract, they raise and erect the hair folli- cles, producing the condition of cutis anserina or gooseskin. As the sebaceous gland lies in the angle between the muscle and the hair follicle, contraction of the muscle compresses the gland and favors the evacuation of the sebaceous secretion. It also compresses the bloodvessels of the papilla {^Unnd). The hair with its large bulbous extremity — hair bulb — sits upon or rather embraces, the papilla. It consists of (l) the 7narrow or medulla (Fig. 294, ?), which is absent in woolly hah and in the hairs formed during the first year of life. It is composed of two or three rows of cubical cells (H, /oth are formed in glands derived from the outer layer of the embryo. P>oth secretions are formed from lymph supplied by the blood stream, and if the lymph be in sufificient 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 glands have secretory nerves distinct from the nerves of the blood vessels; both glands 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, ^. ,?■., pilocarpin. In the gland cells of both, histological changes accom- pany the secretory act, and no doubt similar electromotor 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, /. iino), and the same is the case in artificial sweating (Leuht') ; lactic acid is present in the sweat in pueq:)eral 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 [Reviy). 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 womi-shaped secretion is called " comedo." 289. 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. TTiis 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 Riihrig, 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., j)0tassium iodide in an ointment so rubbed in is absorbed ; so is mercu- rial 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 previously 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 practi- cally passes into the lymph spaces and comes into direct relation with the lymph and bloodstream; absorption takes place with great rapidity, even move so than from the stomach.] Gases. — Under normal conditions, minute traces of O are absorbed from the air ; hydrocyanic acid, sulphuretted hydrogen — CO, CO.^, the vapor of chloroform and ether may be absorbed ( Chaussier, Gerlach, Rohrig). In a bath containing sulphuretted hydrogen, this gas is absorbed, while CO^ is given off into the water {Rohrig). Absorption of watery solutions takes place rapidly through the skin of the frog {Gtittmann, W. Stirling, v. IVitlich). Even after the circulation is excluded and the central nervous system ?) Muscular Movement. — 15y tar the greatest number of the movements occurring in our bodies is accomplished through the agency of muscular fibre, which, when it is e.xcited 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.] \(^b) Amoeboid Movement. — Motion is also exhibited by colorless blood corpuscles, lymph corpuscles, leucocytes, and some other corpuscles. In these structures we have examples of amoeboid movement (^ 9), which is movement in an indefinite direction.] \{c) Ciliary Movement. — There is also a peculiar form of movement, known as ciliary movonent. 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. 300).] [Ciliated epithelium — where found. — In the nasal mucous meml)rane, 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 ^5^5 inch in length, and are apparently homo- geneous 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 the 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 they are regarded as prolongations of the intra-epithelial plexus of fibrils. They are spe- cially modified parts of an epithelial cell, and are contractile and elastic. They are colorle.'-s, tolerably strong, not colored by .staining reagents, and are possessed of considerable rigidity and flexibility. They are always connected with the protoplasm of cells, and are never outgrowths of the solid cell membranes. There may be ten to twenty cilia distributed uniformly on the free surface of a cell (Fig. 300).] [In the large ciliated cells in the intestine of some mollusks (mussel), the ci'ia perforate the clear refractile disk, which appears to consist of small glolniles — basal pieces — united by thtir edge, so that a cilium seems to spring from each of these, while continueil downward into the pro- toplasm of the cell, but not attached to the nucleus, there is a single varicose fibril — rootlet, and the lea.sh of these fibrils passes through the substance of the cell and may unite toward its lower tailed extremity [Engehnann).'\ [Ciliary motion may be .studied in the gill of a mussel, a small part of the gill being teased in sea water ; or the hard palate of a frog, newly killed, may be scraped and the scraping examined in 3^^ p. c. salt solution. ()n analyzing the movement, all the cilia will be ol)served 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 hke a field of corn 500 Inner layer. FUNCTIONS OF CILIA. 501 moved by the wind. Each vibration of a cihum consists of a rapid forward movement or flexion, the tip moving more than the base, and a slower backward movement, the cihum again straightening itself. The forward movement is about twice as rapid as the backward movement. 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 twelve times per second. 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 adjoin- ing cells do not move at once, but in regular succession, the movement traveling from one cell to the other, but how this co-ordination is brought about we do not know. At least it is quite independent of the nervous system, as cihary movement 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 ciliary move- ment may go on, it is essential that (l) the ciHa be connected with part of a cell; (2) moisture; (3) oxygen be present; and (4) the temperature be 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 ciha are contractile, the motor impulse probably proceeds from the cell. Each cell can regulate its own nutrition, for during life they resist the entrance of certain colored fluids.] [Effect of Reagents. — Gentle heat accelerates the number and intensity of the movements, cold retards them. A temperature of 45° C. causes coagulation of their proteids, makes them per- manently rigid, and kills them, just in .the same way as it acts on muscle, causing heat stiffening (§ 295, i). 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 epithe- lium 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 locomotion, 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 incHned 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 the nucleus ; in the former case, the skin of the frog appears dark in color, in the latter, it is but slightly pigmented (Fig. 301). Tlie 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 502 STRUCTURE AND ARRANGEMENT OF MUSCLES. Fic state of dift'usion of the pigment, as v. Witiich found tliat turpentine or electricity caused the cells of the tree frog to contract, and the same effect is produced by light. In Rana temporaria local irrita- tion has little effect, but light, on the contrary, h.is, although the effect of light seems to be brought about through the eye, probably by a retlex mechanism [Lister). A pale-colored frog, put in a dark place, assumes, after a time, a ditTerent 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 pigment cells in its skin, covered as they are by epidermis, containing a thin stratum of air [BriicA'e). 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, tlie area supplied by the nerve changes to black. The condition of its skin, therefore, is readily affected by the con- dition of its nervous system, for psy- chical 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. Pigment cells from the web of frog s foot; i diffused; l>, granules more concentrated; c, more concentrated." IS notorious mat tlie Color 01 nsnes still ; d, cells with guanin granules (Stirling). IS adapted to the Color of their environ- ment. 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.] [Guanin in Cells. — Besides the pigment cells in the web of a frog's foot (especially in Rana temporaria) there are other cells which contain granules of guanin (Fig. 301, d). If the web of a frog's foot be mounted in Canada balsam and examined microscopically between crossed Nicol's prisms, each guanin cell is seen to contain numerous very strongly doubly refractive granules of guanin ^§ 283).] 292. STRUCTURE AND ARRANGEMENT OF MUSCLES.— [Muscular Tissue is endowed with contractility, so that when it is acted upon by certain forms of energy or stimuli, it contracts. There are two varieties of this tissue — (i) Striped, striated (or voluntary); (2) Non-striped, smooth, organic (or involuntary). Some muscles are completely under the control of the will, and are hence called "voluntary," and others are not directly subject to the control of the will, and are hence called "involuntary;" the former are for the most part striped, and the latter non-striped; but the heart muscle, although striped, is an involuntary muscle.] I. Striped Muscles. — The surface of a muscle is covered with a connective-tissue envelope or perimysium externum, from which septa, carrying blood vessels and nerves, the perimysium internum, pass into the substance of the muscle, so as to divide it into bundles of fibres or fasciculi, which are fine in the eye muscles and coarse in the glutei. In each such compartment or mesh there lie a number of tyiiisctilar fibres arranged more or less ]5arallel to each other. [The fibres are held together by delicate connective tissue or endomysium, which sunounds groups of the fibres; each fibre being, as it were, separated from its neighbor by 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. 307). In a contracted muscle, the cap llaries may be slightly sinuous in their course, Ijut 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 ccsophagu.s, muscles of the middle ear and pinna, the true sphincter of the urethra, and external anal sphincter.] STRUCTURE AND ARRANGEMENT OF MUSCLES. 503 A muscular fibre (Fig. 302, i) is a more or less cylindrical or polygonal fibre, 11 to 67 // {^^^ to g^o in.] in diameter, and never longer than 3 to 4 centimetres [i to i^ in.]. Within short mus- cles, e.£:, 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, or by a 36 per cent, solution of caustic potash. [Each muscular fibre consists of the following parts : — 1. Sarcolemma, an elastic sheath, with transverse partitions, stretching across the fibre at regular intervals — the iiiet}ibrane of Kraitse ; 2. The included sarcous substance ; 3. The nuclei or muscle corpuscles.] Fig. 302. Histology of muscular tissue, i, Diagram of part of a striped muscular fibre; S, sarcolemma ; Q, transverse stripes ; F, fibrillse ; K, the muscle nuclei ; N, a nerve fibre entering it with a, its axis cylinder and Kijhne's motorial end plate, e, seen in profile; 2, transverse section of part of a muscular fibre, showing Cohnheim's areas, c ; 3, iso- lated muscular fibrillae; 4, part of an insect's muscle greatly magnified ; a, Krause-Amici's line limiting the mus- cular cases ; ^, the doubly refractive substance; c, Hensen's disk; ^, the singly refractive subsiance; 5, fibres cleaving transverselj' into disks ; 6, muscular fibre from the heart of a frog; 7, development of a striped muscle from a human fcetus at the third month; 8, 9, muscular fibres of the heart; c, capillaries ; 3, connective-tissue corpuscles ; 10, smooth muscular fibres; 11, transverse section of smooth muscular fibres. Sarcolemma. — Each muscular fibre is completely enclosed by a thin, colorless, structureless, trans- parent elastic sheath (Fig. 302, i, S), which, chemically, is midway between connective and elastic tissue, and within it is the contractile substance of the muscle, [^^^len a muscular fibre is being digested by trypsin, Chittenden observed, at the beginning, the sarcolemma raised from its sarcous contents as a folded tube, but it is ultimately digested by trypsin. It is thus distinguished from the collagen substance of connective tissue, which is not digested by trypsin. It is not dissolved by boil- ing, and it resists the action of acids and dilute alkalies, while it is dissolved by concentrated alkalies. Thus, it differs from elastic fibres, and" on the whole, chemically, it seems to be most closely related to the membrana propria of glands. 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 o04 STKUCIURE OF A MUSCULAR FIBRILLA. ]"IG. ^O^. observe the sarcous substance torn across, with the unniplured sarcoleninia stretching between the ends of the mptured sarcous substance. If muscular fibres be teased in distilled water, sometimes tine clear blebs are seen along the course of the fil)re, due to the sarcolemma being raised by the lluid ciitTusing under it. The sarcous substance, imt not the sarcolemnn, may be torn across by plunging a muscle in water at 55° C, and kee|)ing it there for some time (Rnnvier).^ Sarcous Substance. — The sarcous substance is marked transversely by alternate light and dim l.iyers, bands, stripes or disks (Kig. 302, I, Q), so that each fibre is saidto 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 Ilydrophilus piceus are well .suited for this purpose. So is the crab's mu.scle. In examining a living muscle microscopically, no fluid e.\cept the muscle juice should be added to the preparation, and very high powers of the micro- scope are required to make out the finer details.] Bowman's Disks. — If a mu.scular fibre be subjected to the action of hydrochloric acid (1 per looo), or if it be digested by gastric juice, or if it be frozen, it tends to cleave transversely into disks {Bowinan), which are artificial products, and resemble a pile of coins which has been knocked over (Fig. 302. 5). Fibrillae. — Under certain circum.stances, a fibre may t\\\\h\i longitudinal striaiion. This is due to the fact that it may be split up longitudinally into an immense number of ( I to 1. 7 fi in diameter) fine, contractile threads, the primitive fibrillae (Fig. 302, i, F), placed side by side, each of which is also transversely striped, and they are so united to each other by semi fluid cement substance, that the transverse markings of all the fibrilhv lie at the same level. Several of these fibrils are united together owing to the mutual pre.s.sure, and prismatic in form, so that when a transverse 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. 302, 2). [Each bundle of fibrils or j)olygonal area represents what KoUiker called a " Muscle Column."] F'ibrillx- are easily obtained from insects' muscles, while those from a mammal's muscle are readily i.solated by the action of dilute alcohol, Midler's fluid [or, best of all, -^ per cent, solution of chromic acid] (Fig. 302, 3). [In studying the structure of muscle, it is well to remember that there are consideral)le differences between the muscles of Vertebrates and those of .\rlhropoda.] [When a living unaltered vertebrate muscular fibre is ex- amined microscopically, in its own juice, we observe the alternate dim and light transverse disks. Amici, Krause, and Dobie showed that a fine dark line runs across the light disk, and divides it into two (Fig. 303). Amici resolved it into a row of granules, and by others (e. g., Krause) it is regarded as due to the e.xi.stence of a membrane — hence it is called Krause's membrane, — which runs transversely across the fibre, being attached all round to the sarcolemma, thus dividing each fibre into a series of comparl- tnents placed end to end. Hensen described a disk or stripe in the centre of the dim disk.] [On Krause's theory, each muscular compartment contains (i) a broad dim disk, which is the y 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 30 // [^^^ to y\,, in.] in Icn^nh, and 4 to 10 11 [scVn '° 2Z7i6 '"•] '" 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 envelope]. In some places it shows longitudinal tii)rillation. [Method. — This fibrillation is revealed more distinctly thus : Place the mesentery of a newt (K'/fin) or the bladder of the salamandra niaculata (I-'lemtninif) in a 5 per cent, solution of ammonium chromate, and afterward stain it w ith picro carmine. Each cell consists of a thin elastic sheath ( sarcolemma of Krause) enclosing a bundle of fibrils ( I") which run in a longitudinal direction within the fibre ( P'ig. 313). 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 con- tractile part, and when they contract the sheath becomes shriveled transversely and exhil)ils what looks like thickenings (S). These fibrils have been observed by Flemming in the cells while livitig. 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 lamelhie, 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 (Fig. 312, II) ihey appear oval or polygonal, with the delicate homogeneous cement between them ; but, as the Fir.. 313. Fic. 312. Fig Smooth muscular fibres (10) ; (11) transverse section. Smooth muscular fibre from the mesentery of a newt (ammo- nium chromate). N, nucleus ; F, fibrils; S, markings in the sheath. Termination of nerve in non-striped muscle. fibres are cut at various levels, the areas are unequal in size, and all of them, of course, are not divided at the position of the nucleus.] They vary in length from yj^ to ij^tj of an inch ; those in the middle coat of the arteries 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 striaiion, but to a partial contraction. Occasionally they have a tendinous insertion. Blood Vessels. — 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 muscle]. Lym- phatics 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 jjerimysium. [The fibres are surrounded with an endothelial sheath.] Small branches [com]X)sed 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 intermedial y plexus, the finest fibrillas (^0.3 to 0.5 //) pa.ss off, either singly or in groups, and re- unite to form the intermuscular plexus (Fig. 314, d), which lies in the cement substance between PHYSICAL AND CHEMICAL PROPERTIES OF MUSCLE. 511 the muscle cells, to end, according to Frankenhauser, in the nucleoli of the nucleus, or in the neigh- borhood of the nucleus [Liisiig). 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 Lowit, the fibrils reach only the interstitial substance, while Gscheidlen also observed that the finest terminal fibrils, one of vs'hich goes to each muscular fibre, ran along the margins of the lat'er (Fig. 314). 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 brash-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.— I. The consistence of the sarcous substance is the same as that of living protoplasm, e: g., of lymph cells; it is semi-solid, /. e., it is not fluid to such a degree as to flow like a fluid, nor is it so solid that, when its parts are separated, these parts are unable to come together to form a continuous whole. The con- sistence 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 views expressed above : [a) The analogy between the function of the sarcous substance and the conti-aciile protoplasm of cells (^ 9). (^) The so-called Porret's phenomenon, 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 fi-om the positive to the negative pole (as in all other fluids), so that the fibre swells at the negative pole yKilkne). [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 tract behind it [Kilhne, Ebertli). 2. Polarized Light. — The contractile substance doubly refracts fight, 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 contractile part of the fibre becomes narrower, and at the same time broader, while 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, ietision is produced — the tension of bodies subjected to imbibition — which results in double refi-action, and so gives rise to the condition called anisotropous. During a sustained contraction, the index of refrac- tion of the muscular fibre increases iExner). * [Reaction. — If a transverse section of a living excised muscle be pressed upon a strip of blue litmus paper, the latter may assume a reddish tinge, and if upon a red litmus paper the latter may assume a bluish tinge, but it will not alter violet litmus paper. This is the amphochromatic or amphoteric reaction, indicating that the muscle is neutral. It may, however, give only an alkaline reaction. A living muscle plunged into boilmg water still retains its neutral or alkaline reaction ; but a muscle, which has been tetanized, or is in rigor mortis, is decidedly acid.] 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. Kiihne bled frogs, cooled their muscles to 10° or 7° C., pounding them in an iced mortar, and expressed 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 plasnaa, it coagulates spontaneously; at first it is like a uniform soft jelly, but soon becomes opaque ; doubly refractive fibres 512 CHEMICAL COMPOSITION OF MUSCLE SERUM. and specks, similar to the fibrin of blood, ap|)ear in the jelly, and as these begin to contract, they squeeze out of the jelly an <7r/V/ " muscle serum." [Halli- burton finds that the muscles of warm-blooded animals yield a similar muscle plasma.] 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 temperature rises, while coagulation takes place very rapidly at 40° C. in cold-blooded animals, or at 48° to 50° C. in warm-blooded animals. The addition of distilled water or an acid to muscle plasma causes coagulation at once. The coagulated proteid, most al)undant in muscle, and which arises from the doubly refractive substance, is called " myosin " ( //'. Kuhne). Myosin. — It is a globulin (\ 245), and is s-olubie in strong (10 per cent.) solution of common salt, and is again precipitated from such a solution by dilution with water, or by the addition of very small quantities of acids (o. I to 0.2 per cent, lactic or hydrochloric acid). It is soluble in dilute alkalies or slightly stronger acids (0.5 per cent, lactic or hydrochloric acid), and also in 13 per cent, ammonium chloride solution. [The more myosin is freed from salts (especially of calcium) by washing, the more insoluble does it become, both in saline solutions and weak hydrochloric acid. When once precipitated from its solution, it can be redissolved, reprecipitated, and again undergo coagulation a second or even a third time i^Hallilnirloii).'\ Like tibrin, myosin rapidly decomposes hvdric peroxide. When treated with dilute hydrochloric acid and heat, it is very rapidly changed i' to svntonin ( ii 245). Myosin may be extracted from muscle by a 10 1015 per cent, solution of XII^Cl, and if it be heated to 65°, it is precipitated again (Danielc~usky). 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, according to Kiihne, still contains three proteids (2.3 to 3 per cent.), viz. : i. Alkali albuminate, which is precipitated on adding an acid, even at 20° to 24° C. 2. Ordinary serum albumin, 1.4 to 1.7 per cent. (§ 32, a), which coagulates at 73° C. 3. An albuminate which coagulates at 47° C. [Halliburton finds, however, the following proteids in muscle plasma: — '^TJlfaf'^ Saturation with NaCl or NajSO^. 1 Paramyosinogen, j 47° C. Myosinogen, 56° Myoglobulin, 63° Albumin, 73° Causes precipitation. \ Proteids which go to " " J form muscle clot. ^ . 1 Proteids of the i^ 1 I muscle serum. Myoalbumose, Not \. Although the first two go to form the clot of muscle or myosin, paramyosinogen is not essential for coagulation. Besides these bodies there are haemoglobin and also myo-hsematin, which is not identical with the blood pigment. It can be ex- tracted by ether from muscle () venous blood flowing from an active muscle of a limb contains less O {Ludwig, Sczclkow, andAl. Schmidt). Neverthe- less, the increase of O used up by the active muscle is not so great as the amount of CO, given off" {v. Pettenkofer and v. Voit). The increase of O used up may be ascertained even during the period of rest directly following the period of activity, and the same is the case with the CO., excreted (ik Frey). As yet, it is not possible to prove by gasometric methods, that O is used up in an excised muscle free from blood. Indeed, the presence of O does not 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 energeti- cally than those which have been kept in a state of continued activity {Griitzner, Gscheid/en~). 4. Glycogen. — The amount of glycogen (0.43 per cent, in the muscles of a frog or rabbit) and grape sugar is diminished in an active muscle {O. JVasse, Weiss), but muscles devoid of glycogen do not lose their excitability and con- tractility. 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 i^Ltichsinger). [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. Helmhoitz, 1845) '> ^"^ ^^so contains less of the substances which form CO, {Ranke) ; less fatty acids {^Sczelkow); less kreatin and kreatinin (v. Voit). 6. During contraction, the amount of water in the muscular tissue increases, while that of the blood is correspondingly diminished (/. Ranke). The solid substances of the blood are increased, while they (albumin) are diminished in the lymph {Fa no). 7. Urea. — The amount of urea excreted from the body is not materially in- creased during muscular exertion {v. Voit, Fick and Wislicenus). According to Parkes, however, although the excretion of urea is not increased immediately, yet after i to i)^ day 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. Smiih, Parkes, and others have made numerous investigations on this subject. Fick and Wislicenus (1S66) ascended the Faulhorn, and for seventeen METABOLISM IN MUSCLE. 515 hours before 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 : — Pick. Wisliceiius. 1. Urea of II hours before the ascent, . . 2. " 8 " during " . . 3. " 6 " after " . . 238.55 grs. 221.05 grs. 103.46 " \rQ..r 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 [Pick), and 176.71 (^Wislicentis). 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 ihe 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 effected, 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 {/. 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 carbohy- drates 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 glyco- gen diminishes after ligature of the blood vtssth {Chandelon) . A muscle in which the blood circulates freely is capable of doing more work than one devoid of blood, and even in the intact body, more blood is always supplied to the con- tracted muscles. [Source of Muscular Energy. — The experiment of Fick and Wislicenus definitely proved that the proteids are not the exclusive, or by any means the chief source of muscular energy. As it is conclusively proved that during muscular work there is a great increase in the amount of O absorbed, and CO2 given off, it is evident that the non-nitrogenous substances of the food must be the chief sources of this energy. We turn naturally to the carbohydrates, and as the latter are chiefly stored up m the form of glycogen in the muscles, it is assumed that gl\cogen is the chief source of the energy. Glycogen in muscle diminishes during muscular work, and is stored up during rest {Bernard). Kiilz also found that in dogs the glycogen disappears from the liver during work, and Voit found that the muscle glycogen disappears before that in the liver. It appears, there- fore, that the carbohydrates are a source of muscular energy. But they, again, are not the only source. It is highly probable that glycogen can be formed from proteids, and it is allowable, therefore, to assume that proleids may also serve as a source of muscular energy. If this be not so, it is difificult to understand how carnivora can be fed and maintained in good health for long periods on lean flesh. The fats are probably also another source. Hence, it would appear that all three of the chief groups of food stuffs — carbohydrates, proteids, and fats — may serve as the source of muscular energy ; but that, so long as non-nitrogenous elements are supplied in the food in sufficient quantity, or are stored up in the body, the muscles do their work chiefly on these. After they are used up, the proteids are, as it were, called up.] 295. RIGOR MORTIS. — Cause. — Excised striped, or smooth muscles, and also the inuscles of an intact body, at a certain time after death, pass into a condition of rigidity — cadaveric rigidity or rigor mortis. When all the 516 CAUSE OF RIGOR MORTIS. muscles of a corpse are tlnis affected, the whole cadaver becomes completely stiff or rigid. The cause of this phenomenon depends upon the spontaneous coagu- lation of a proteid, viz., the myosin of the muscular fibres (Kiihne). Under certain circumstances, the coagulation of the other proteids of the muscle may increase the rigidity. During the process of coagulation, an acid is formed, heat is set free {v. Walther, Fick — § 223), owing to the passage of the fluid myosin into the solid condition, and also to the simultaneous and subsequently increased density of tlie tissue. Properties of a Muscle in Rigor Mortis. — It is shorter, thicker, and some- what denser {SchmiileTi'itscli) ; 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 direc- tion) ; its reaction is acuf, owing to the formation of both forms of lactic acid (§ 293), glycero-phosphoric acid {Diakanow) ; while it also develops free CO.. When an incision is made into a rigid muscle, a fluid, the muscle serum, appears spontaneously in the wound (§ 293). The first formed lactic acid converts the salts of the muscle into acid salts ; thus, potassium lactate and acid potassium phosphate are formed from jxatassium phosphate. The lactic acid, which i> formed thereafter, remains free and ununited in the muscle. Amount of Glycogen. — The newest observations of Hohm are against the view that, during rigor mortis, a ]jarlial or complete transformation of the glycogen into sugar and then into lactic acid takes place. During digestion, a temporarj- 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 diminution 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 [Deiiiant, Boliiii'). 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 CO.^ is formed from a rigid muscle, the more CO.^ it has given off previously, during muscular exertion. A rigid muscle gives ofi" 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). [The myosin ferment seems not to be identical with the fibrin ferment (p. 512).] [Rigor Mortis and Coagulation of Blood. — Thus, there is a marked analogy between the coagulation of the blood and that of muscle. In both ca.ses, a fluid body yields a solid body, fibrin from blood, and myosin from muscle ; the coagulation of blood is prevented by neutral salts, and so is the coagulation of myosin ; dilution of the salted plasma produces coagulation in both cases ; and perhaps the coagulation in both is due to the action of a ferment, the one the fibrin ferment, the other the myosin ferment. There are, however, points of difference, for myosin can be dissolved, reprecipitated, and coagulated several times, while fibrin does not undergo recoagulation ; the formation of myosin from myosinogen, again, is accompanied by the development of an acid, whereas that of fibrin from fibrinogen is not : further, the formation of myosin is not accom- panied by the formation of another globulin, whereas that of fibrin from fibrino- gen is.] 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 phenomena above mentioned. The onset of the rigidity varies in man from ten minutes to seven hours [but as a rule it is complete 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 STAGES OF CADAVERIC RIGIDITY. 517 decompositions and an alkaline reaction, become soft, and the rigidity disappears i^Nysteii). 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 (§ 352). Disappearance of the rigidity occurs first in the muscles first affected {Nysteii). Great muscular activity before 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. 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 0° C. does not begin to exhibit cada- veric 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 {SchmiileivitscK) ; thereafter stiffness occurs, the one stage following closely upon the other {Swammej'dam, 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 muscular substance after four to five hours, and then cadaveric rigidity set in. Pathological. — \\nien the blood vessels of a muscle are occkided, by coagulation taking place within them, 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 (/?. Volkinanii). Occlusion of the blood vessels of muscles by infarcts, especially in persons with atheromatous arteries, may even cause necrosis of the muscles implicated i^Finch, Girandeati). If the circulation be re-established during the first stage of the rigidity, the muscle soon recovers its excitability (^Stannius). When the second stage has set in, restitution is impossible {Kuhne). In cold-blooded animals, cadaveric rigidity does not occur for several days after ligaturing the blood vessels. Brown-Sequard, by injecting fresh oxygenated blood into the blood vessels, succeeded in restoring the excitability of the muscles of a human cadaver four hours after death, /. e., during the first stage of cadaveric rigidity. Ludwig and Al. Schmidt found that the onset of cadaveric rigidity was greatly retarded in excised muscles, when arterial blood was passed through their blood vessels. Blood deprived of its O did not produce this effect. Cadaveric rigidity occurs relatively early after severe hemor- rhage. If a weak alkaline fluid be perfused through the blood vessels of the dead muscles of a frog, cadaveric rigidity is prevented {SchipilofT). Section of Nerves. — Preliminary section of the motor nerves causes a later onset of the rigidity in the corresponding muscles (^Brown-Sequard, Hemeke). [The same result occurs after a hemi-section of the spinal cord or after removal of one cerebral hemisphere {Bierfreund).'\ In fishes, whose medulla oblongata is suddenly destroyed, cadaveric rigidity occurs much more slowly than in those animals that die slowly (^Blane). [Other Influences. — Rigidity begins much later in the red (11 to 15 hours) than in pale muscles (l to 3 hours post-mortem) ; the rigor is complete in the white muscles in 10 to 14 hours, in the red in 52 to 58 hours. The extent of shortening due to the rigor is 2 to 2j4 times as great as in the white. In both muscles the resolution of the rigor begins 12 to 15 hours after the completion of the rigidity, so that the red muscles are not completely rigid before the other muscles appear to have passed from a state of rigidity. Temperature has a marked effect, but it acts more on the resolution than on the onset of the rigor. At 60° C. the onset begins almost at once, and is complete in a few minutes [Bierfreund). Ether and chloroform injected into the blood vessels cause almost instantaneous rigor Rigidity may be produced artificially by various reagents : — I. Heat [" Heat stiffening"] causes the myosin to coagulate at 40° C. in 518 EFFECT OF HEAT, WATER AND ACIDS ON MUSCLE. cold-blooded animals, in birds about 53° C. and in mammals at 48° to 50° C. The protoplasm of plants and animals, e. g., of the amccba, 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 re(|uired to produce stilTening. Meat stiffening differs from cadaveric rigidity thus : a 13 per cent, solution of ammonium chloride dissolves out the m> osin from a cadaveric rigid muscle, but not from one rendered rigid by heat {Schi/>i/off). If the ligid cadaveric muscles of a frog be heated, another proteid coagulates at 45°, and Ixstly at 75° the seium 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 me.ans do not {Biedfrinnnu). If the upper limb of a frog be ligatured, deprived of its skin, and dipped in warm water, it becomes rigid. If the ligature 1)C removed and ihe 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 10 per cent, solution of common salt, which dissolves the coagulum of myosin [Preyer). 3. Acids, even CO,, ra])idly produce "acid stiffening," which is probably different from ordinary stiffening, as such muscles do not evolve any free CO., (Z. Hermann). The injection of o. i to 0.2 per cent, solutions of lactic or hydrochloric 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 myosin {Schipi/off). 4. Freezing and thawing a part alternately, rapidly produce 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 fro/, produces rigor mortis], veratrin, hydrocyanic acid, ether, chloroform, the oil of mustard,, fennel, and aniseed; direct contact of muscular tissue with potassium sulphocyanide [Fiernard, SetschenDw), ammonia, alcohol, and metallic salts. Position of the Body. — The aUitude of the body during cadaveric rigidity is generally that occupied at death ; the jiosition 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 {Somnier). 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 Brucke, there is always a very short relaxation. Muscles which have been i:)lunged into boiling water do not undergo rigor mortis, neither do they become acid (Du Bois- Kevmond), nor evolve free CO,^ (A. Hermami). 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, less with heavier weights, than when a living muscle is stimulated with a maximal stimulus. 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 CO.^ and the other acids from the same source; [both acts take place without the consumption of O]. The form of the contracted and of the stiffened muscles is shorter and thicker; both are denser, le.ss elastic, and evolve heat ; in both cases, the muscular contents behave negatively as regards their electro-motive force, in reference to the unaltered, living, resting substance. Hence, he is inclined to regard a muscular contraction as a temporary, physiological, rapidly disappearing rigor. Rigor mortis is in a certain sense the last flickering act of a living muscle [and he regards contraction as partial death of a muscle. But this is no explanation, and moreover there are important points of difference. We have no proof of a coagulum being formed during contraction, while the extensibility is increased during contraction and much diminished during rigor.] MUSCULAR EXCITABILITY. 519 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 microorganisms and the evolution of ammonia and putrefactive gases (H.^S, N, CO2 — § 184). [Hermann and Bierfreund attach much importance to the resolution of rigor mortis independently of putrefaction.] 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 min.) ; iris (105 min.) ; muscles of face and tongue (180 min.) ; the extensors of the extremities (ab jut 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 of a muscle in virtue of which it responds to stimuli, at the same time becoming shorter and correspondingly thicker. The condition of excitement is the active condition 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 "dis- charging forces." [These " discharging forces " may themselves be very feeble, but they are capable of causing the manifestation of the transformation of a large amount of energy.] The normal temperature of the body is most favorable for maintaining the normal muscular excitability ; the excitability varies as the tem- perature rises or falls. As long as the bloodstream 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). Effects 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 exci- tability which is entirely independent of the existence of motor nerves, but is dependent on certain constituents of the sarcous substance. Excitability, or the property of responding to a stimulus, is a widely distributed function of protoplasm or its modifications. A colorless blood corpuscle or an amoeba is excitable, and so are secretory and nerve cells. In the first case, the application of a stimulus results in motion in an indefinite direction, in the second in the formation of a 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 depend- ing on the contractility of the sarcous substance. There are many considerations which show that excitability is iiidependent of the nervous system, although in the higher animals, nerves are the usual medium through which the excitability is brought into action. Plants, however, are excitable, and they contain no nerves.] Numerous experiments attest the ' ' independent excitability ' ' of muscles : i . There are chemical stimuli, which do not cause movement when applied to motor nerves, but do so when they are applied directly to muscle ; ammonia, lime-water, 520 ACTION OF CURARA. 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 {A'ii/i/ic). 3. Ciirara paralyzes the extremities of the motor nerves, while the muscles themselves remain excitable (C/. Bernard, Ko/liker). The action of cold, or arrest of the blood supply in an animal, abolishes the excitability 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-Seqiiard, 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 discover- able 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. 523). 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 volun- tar}-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. — (i) Local Application. — Bernard took two nerve-muscle prepa- rations, put some solution of curara into two watch glasses, and dipped the nerve into one glass and the muscle of the other preparation into the other glass. The curara penetrated into both preparations, and he found, on stimulating the nerve which had been steeped in curara, that its muscle still contracted, so that the curara had not acted on the motor nerve fibres ; while stimulation of the nerve of the other preparation produced no contraction, although the corresponding muscle contracted. In the latter case, the curara had penetrated into the muscle and affected the intra- muscular portions of the nerve.] [(2j 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, except the sciatic nerve, at the upjjer part of a thigh (Fig. 315). Inject curara into the dorsal lymph sac. The poisoned blood will, of course, circulate 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 jX)isoned 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 poi- son 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 gastrocnemius of that side contracts, although the whole length of the nerve trunk was supplied by poi- soned blood. Therefore, it is the intra-muscular tenninations of the nerves which are acted on.] [By means of the following arrangement we may prove that the terminal parts of the nerve 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, expose 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, with the gastrocnemii uppermost, as in Fig. 316. Place the two nerves, N, on electrodes attached to two wires coming from a commutator, ACTION OF CURARA. 521 C (Fig. 316). From the opposite binding screws of tlie commutator two wires pass to the gastrocnemii. The other two binding screws of the commutator are connected with the secondary coil of an 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 (NP) 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, but 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 excita- bility 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 terminations are paralyzed. A feebler induced shock suffices to cause a muscle to contract when it is applied to Frog with sciatic artery liga- tured. S.P., spinal cord with afferent and efferent nerves; P., poisoned, N.P., non-poisoned leg; M, gastrocnemius mus- cles. Scheme of the curara experiment. B, bat- tery; I, primary; II, secondary spiral; N, nerves; F, cl^mp ; NP, non-poisoned leg ; P, poisoned leg ; C, commutator ; K, key. the nerve than when it is applied to the muscle itself directly. In large doses, curara also affects the spinal cord (p. 523).] [On what structures does curara act ? — These experiments prove that cvu-ara does not paralyze the motor nerve trunks, nor the muscular fibres, and that it acts on the motor terminations within the muscles, but they do not enable us to state the precise part of the nerve ending so affected. It may act on (l) the nerve just before it pierces the sarcolemma, (2) the sub-lemmar axis cylinder, (3) the end plates, (4) the terminal branches or spray. Kiihne and Pollitzer have made it probable that, even when a muscle is thoroughly impregnated with curara, some of the nervous apparatus is unaf- fected. The sartorius is most excitable where there are most nerves (Fig. 318), and even in a muscle profoundly poisoned with ciu-ara, the distribution of excitability varies with the number of nerves m the several parts of the muscle (Fig. 317) just as in a normal muscle, with this difference, that the excitability of all the parts of the muscle containing nerves is less than normal. That this variation in excitability is due to nervous structures, is shown by using a polarizing anelectrotonic_ cmrent (§ 335)> which depresses the excitability of nerve fibres, and then this difference of excitability dis- appears, the curve of excitability running parallel with the abscissa, so that the difference does not seem to be due to purely muscular causes.] [Pollitzer, speculating as to which part of the terminal nerve is affected, supposes that all parts 522 MUSCULAR AND CHEMICAL STIMULL beyond the last node of Ranvier retain their functions, and he supposes that it is not the axis cylinders themselves, hut the cement at the noHes, on which the drug exerts its specific action.] Neuro-Muscular Cells. — Even in (he lower animals, <•. .(,"•., Hydra and Mcihis.v, there are uni- cellular structures called " )iiui}0 mtisrular cells" in which the nervous and muscular substances are represented in the same cell i^Kleitienbeii; and Eimer^. [The outer part of these cells is adapted for the action of stimuli, and corresponds to the nervous recejitive 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 acting upon its motor nerve, or upon the muscular substance itself (^ 324). [The former is called indirect stimulation, the latter direct stimulation.] 1. Under ordinary circumstances, the normal stimulus exciting a muscle to contract is the nerve impulse which passes along a nerve, but its exact nature is unknown. 2. Chemical Stimuli. — All chemical substances which alter the chemical composition of a muscle with sufficient rapidity, act as 7nuscular stimuli. Mineral acids (HCl o.i per cent.), acetic and oxalic acids, the salts of iron, zinc, copper, Fig. 317. Fig. 31S. Curve showing the excitability in the sar- torius of a frog in a normal and curarized muscle. Distnlnitioii of nerves in the sartorius of a frog and the curve of e.\ci la- bility in different parts of the muscle, i.e., the excitability is greatest where there are most nerve endings. silver, and lead, bile, all act in weak solutions as muscular stimuli ; 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. [The lower end of the sartorius, which contains no nerves, may be dipped into glycerin, and it will not contract, but if it be dipped deeper to where there are nerve endings, it will contract at once.] 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. JVitfich), while a 0.6 per cent, solution of NaCl may be passed through a muscle for days without causing contraction {KoUiker, O. Nasse). [Carslaw, under Ludwig's direction, however, found that solutions containing 0.5 to 0.2 percent. NaCl, when perfused through the muscles of a frog, excite many short, powerful attacks of tetanus, separated from each other by periods of rest. Solutions containing 0.5 to 0.7 per cent. NaCl, /. e., so-called "indifferent fluids" or " normal saline," are not without THERMAL, MECHANICAL AND ELECTRICAL STIMULI. 523 influence, but of all known saline solutions, they injure a nerve-muscle preparation least. Solutions of i to 2 per cent, rapidly kill the muscle.] Acids, alkalies, and extract of flesh diminish the muscular excitability, while the muscular stimuli, in small doses, increase.it {Rafike). Gases and vapors stimulate muscle; they cause either a simple contraction (^. g., HCl), or at once permanent contraction or contracture {e. g., CI). Long exposure to the gas causes rigidity. The vapor of bisulphide of carbon stimulates only the nerves, while most vapors {e. g., HCl) kill without exciting them {^Killme and Jani). Method. — In making experiments upon tlie chemical stimulation of muscle, it is inadvisable to dip the transverse section of the muscle into the solution of the chemical reagent {^Hei-uig). The chemical stimulus ought to be applied in solution to a limited portion of the uninjured surface of the mnscle ; 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), e. g., the intestine, uterus, ureter, blood vessels, and also in the striped but involuntary cardiac mus- culature (I 58), they are not, as a rule, very common in striped voluntary muscle. Chemical stimuli are particularly effective in producing them.] If the sartorius of a curarized frog be dipped into a solution composed of 5 grms. NaCl, 2 grms. alkaline sodium phosphate, and 0.5 gnn. sodium car- bonate in I litre of water, at 10° C, the muscle contracts rhythmically, and may do so for several days, especially with a low temperature {Bieder7)iann). This recalls the rhythmical contraction 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 to 28° C, a gradually increasing contraction occurs, which, at 30° C, is more pronounced, reaching its maximum at 45° C. 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 {Griin- hagen'). If a frog's muscle be cooled to 0°, it is very excitable to mechanical stimuli (^Griinhagen) ; it is even excited by a temperature under 0° i^Eckhard). CI. Bernard observed that the muscles of animals, artificially cooled, remained excitable many hours after death {\ 225). Heat causes the excitability to disappear rapidly, but increases it temporarily. 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 wheal-like, long-continued contraction at the part stimulated (§ 297, 3, a). Moderate tension of a muscle increases its excitability. 5. Electrical Stimuli will be referred to when treating of the stimulation of nerve (§ 324). Other Actions of Curara. — When it is injected into a frog, either into the blood or subcuta- neously, it causes at first paralysis of the intra-nmscutar ends of the motor nei-ves (p. 520), while the muscles themselves remain excitable. The sensory nerves, the central nervous system, viscera, heart, intestine, and the blood vessels are not affected at first (C/. Bernard, Kolliker). [If the skin be stimulated, the frog pulls up the ligatured leg reflexly, although the other leg remains 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 ligatiu-ed 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 are 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 sub- cutaneously, the animal may remain motionless for days and yet recover, the poison being elimi- nated by the urine [Kiihne). If the dose be large, the inhibitory fibres of the vagus may be paralyzed. In electrical fishes, the sensory nerves, and in frogs, the lymph hearts are paralyzed. A dose sufficient to kill a frog, when injected imder its skin, will not 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 poi- 524 CHANGES IN A MUSCLE DURING CONTRACTION. sonous when eaten. If, however, the ureters be lied, the jwison collects in the blood, and poisoning takes ]ilace (/,. Hfniiann). [In this case the mammal may exhibit convulsions. NVhy ? Curara jiaraly/cs the respiratory nerves, so that as|)liyxia is ]>roducc(l from the venosity of the blood. It atTects 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. 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, poiion uninjured animals even when given by the nioulh. The nerves and muscles of poisoned animals exhibit con- siderable electro-motive force. [ For the effect of curara on lymph formation see (i; 199, 6).] Atropin appears to be a specific poison for smooth muscular tissue, but ditferent muscles are differently affected {Szpi/i>ii7nit, Luchsiii^er). [This is doubtl'ul. A small c|uantity of atropin seems to affect the motor nerves of smooth muscle in the same way that curara does those of stripel 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 a-sophagus in different animals. S/.pdmaim and Luchsinger found that, after the action of airopin, stimulation of the peripheral end of the vagus will still cause contraction of the stri|)ed muscvUar fibres in the oesophagus, but not of the smooth fibres, although both forms of muscular tissue respond to direct stimulation.] After section of the motor nerve of a muscle, the excitability undergoes remarkable changes; after three to four days the excital)ilily of the paraly/.ed muscle is diminished, both for direct and indirect stimuli (p. 522) ; this condition is followed by a stage, during which a constant current is more active than normal, while induced currents are scarcely or not at all effective (i; 339, I ). The excita- bility to mechanical 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 degeneration begins in the second week after section of the motor nerve, and goes on until there is complete nuiscular atrophy. Immediately after section of the sciatic nerve, Schmulewitsch found that the excital)ility of the muscles sujiplied by it was increased. 297. CHANGES IN A MUSCLE DURING CONTRACTION.— I. Macroscopic Phenomena. — i. When a muscle contracts, it becomes shorter and at tlie same time correspondingly thicker. The degree of contraction, which in very excitable frogs may be 65 to 85 per cent. (72 per cent, mean) of the total lengih of the muscle, depends upon various conditions : [a) Up to a certain point, increasing the strength of the stimulus causes a greater degree of contraction; (b) as the muscular fatigue increases, /. c, after continued vigorous exertion, the stimulus remaining the same, the extent of contraction is diminished ; {c) the temperature of the surroundings has a certain effect. The extent of the contraction is increased in a frog's nuiscle — the strength of stimulus and degree of fatigue remaining the same — when it is heated to '^2>° C. If the temperature be increased above this point, the degree of contraction is diminished {SclimulewitscK). 2. The volume of a contracted muscle is slightly diminished {S'loammerdam, t 1680). Hence, the specific gravity of a contracted muscle is slightly increased, the ratio to the non-contracted muscle being 1062 : 1061 {Valentin); the diminu- tion in volume is, however, onlv ysViT' although this has recentlv been denied by J. Ewald. Methods. — {a') Erman placed jjortions of the body of a live eel in a glass vessel tilled with an indifferent fluid. A narrow tube 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. (3) 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 diminishes. The same experiment may lie 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 e.xcitement to all its parts. Under certain circumstances, however, this is not the case, viz. : {a) When the muscle is greatly fatigued, or when it is about to die, violent mechanical stimuli, as a vigorous tap with the finger or a percussion hammer fand also chemical or electrical stimuli), cause a localized con- traction 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 instnmient is drawn transversely over the direction of the muscular fibres. ib) Under certain as yet but imperfectly known conditions, a muscle exhibits TOTAL AND PARTIAL MUSCULAR CONTRACTION. 525 so-called fibrillar contractions, /. 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 hypoglossal nerve ; and in the muscles of the face, after section of the facial nerve. [In some phthisical patients there is marked muscular excitability, 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 contrac- tions may continue for months, even when the divided nerve has healed and is stimulated above the cicatrix so as to produce movements in the con-esponding half of the tongue. Stimulation of the lingual nerve increases the fibrillar contractions or an-ests 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 petmit free circulation, the muscles of the face contracted. Section of the motor nerves of the face did not abolish the phenomenon, but compression of the arteries did. The cause of the phenomenon, therefore, seems to lie within the muscles them- selves. This phenomenon may be compared to \}a& paralytic secretion of saliva and pancreatic juice which follows section of the nerves going to these glands (pp. 258, 303). 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 (| 103, III). Some drugs cause fibrillar contractions, e.g., aconitin, guanidin, nicotin, pilocarpin, but physostigmin produces them in warm-blooded animals (not in frogs). According to Brunton these drugs probably act by irritating the motor nerve endings, as the contractions are gradually abolished by curara.] II. Microscopic Phenomena. — i. Single muscular yf^^r///^ 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, and that the transverse striae approach nearer to each other (^Bowman, 1840). 3. There is great difference of opinion as to the behavior of the doubly refractive (anisotropous) and the singly refractive media. Engelmann's View. — Fig. 319, i, on the left represents a passive muscular element — from c to d is the doubly refractive contractile substance, with the median disk, a, b, in it; h and^ are the lateral disks. Besides these, in each of Fig. 319. the singly refractive disks there is a clear disk — " secondaiy disk "y and d', which is only slightly doubly refractive. This occurs only in the muscles of insects. Fig. I, on the right, shows the same ele- ment in polarized light, whereby the mid- dle area of the element, as far as the contractile substance proper extends, is, owing to its double refi-action, bright ; while the other part of the muscular ele- ment, owing to its being singly refractive, is black. Fig. 319, 2, is the transition stage, and 3 the proper stage of contrac- tion of the muscular element. In both cases, the figures on the left are viewed in ordinary light, and on the right, in polarized light. During contracion (Fig. 319, 3), the singly refractive disk becomes as a whole more refractive, the doubly refractive less so. Consequently, a fibre at a certain degree of contraction (2), when viewed in ordinary light, may appear homogeneous and but slightly striped transversely = the hofnogeneotts or transition stage. Duiing a greater degree of contraction (3), veiy dark transverse stripes reappear, corresponding to the singly refractive disks. At every stage of the contraction, as well as in the transition stage, the singly and doubly refractive disks are shai-ply defined, and are recognized by the polariscope as regular alternating layers (in i, 2, and 3 on the The microscopic appearances during a muscular contraction in the individual elements of the fibrillse. i, 2, 3 (after Engeliitann) ; 4, s (after Merkel). 526 MUSCULAR CONTRACTION AND MYOGRAPHS. right). These do not change places during the contraction. The height of both disks is diminished during contraction, but the singly refractive do so more rapidly than the doubly refractive disks. The total volume of each element does mjt 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, tluid passes from tlie singly refractive into the doubly refractive disks; the former shrink, the latter swell. Merkel's view is partially difTerent. In Fig. 319, 4, are two muscular elements at rest; in (5), two in a slate 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, r), and places itself at the lateral disks, 5 at i" and d, while the clear substance leaves the lateral disk, 4, e and d, and ap|ilies itself to both surfaces of the median disk, 5, c. The clear substance of the isotropuus disks is fluid, and plays a more passive role; duiing contraction it is in part absorbed by the dark substance which thus swells up. This mutual excliange of place of the substances is accompanied by an intermediate "stage of t/isso////to>t," in which the whole contents of the element appear equally homogeneous, in which, therefore, the fluid singly refractive sulistance has uniformly penetrated the doubly refractive sub- stance. 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 pas?es over part of the fibres, the disks become shorter and broader ; at the same time, in the fully contracted part, tlie 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 difTerent stages of rest or con- traction, by suddenly plunging the muscular fibrilkx; of insect's muscles into alcohol or osmic acid, which coaL;ulales the muscle substance. The actual contraction may be observed under the micro- scope in the transparent parts of the larvse of insects. Spectrum. — A thin muscle, e.g., the sartorius of the frog, when placed directly behind a narrow slit running at right angles to the C( urse 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.— Methods.— In order to deter- mine the duration of each phase of a muscuhir contraction, myographs of vari- ous forms are used. Fig. Scheme of v. Helmholtz's myograph, clamp, K: F, writing style; P V. Helmholtz's Myograph is shown in Fig. 320. A muscle, >I — say the gastrocne- mius of a frog attached to the femur — is fixed by the femur in a clamp, K ; its lower end is 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 raises the lever. At the free end of the lever is a movable style, F, which inscribes its movements on a revolving cylinder caused to rotate at a uniform rate by means of clock- work. The cylinder is covered with smoked enameled paper in the flame of a turpentine lamp. When the muscle contracts, it inscribes a curve — the " muscle curve," or " myo- gram." The abscissa of the curve indicates the duration of the contraction, but of course the rate at which the cylinder is moving must be known. The ordinates represent the height of contraction at any particular part of the curve. The muscle curve may be inscribed upon a muscle fixed in » „^ ...uo weight or counterpoise » -^ —"-^v-"- v.u..v, .nu^ .^v, inov,.! for the lever; W, scale pan for weights; S, S, supports for smoked glass plate attached to one limb of a the lever. vibrating tuning fork. Such a curve registers the time units in all its parts. Suppose each vibration of the tuning fork =001613 second, then the duration of any part of such a curve is obtained by counting the number of vibrations and multplying by 0.01613 second. [Pick's Pendulum Myograph. — A board fixed to the wall carries a heavy iron pendulum, P, whose axis, A, A, moves on friction rollers (Fig. 321). At the lower swinging end are two glass PENDULUM MYOGRAPH. 527 plates, G and G^, fixed to a bearer, T. The plates can be adjusted by means of the screw, s, so that several curves can be written one above the other. The plate, G'', on the posterior 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 outward, are used to fix the pendulum by the teeth, a, a, when it is drawn to one side. The pendulum 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 one side to the other, the projecting points, a, a, knock over the contact key, b, and Pick's pendulum myograph, as improved by v. Helmholtz (Jj natural size), side and front view. 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 smoked surface of the glass. Of course, when the pendulum swings, it moves with imequal velocities at different parts of its course.] [When using the pendulum myograph to study a muscular contraction, arrange it as in Fig. 322. The fi-og's muscle is attached to a writing lever, which is very like the lever in Fig. 321, 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^, is closed and placed 528 MYOGRAM UK MUSCLE CURVE. primary circuit, while two wires from the secondary coil of an induction machine are attached muscle. When the pendulum swings, the projecting tooth, S, knocks over the contact at K', in the to the muscle. When ttie penc and breaks the primary circuit, when a shock is instantly transmitted through the muscle. Before Fu;. 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 1 )uprc's electric chronograph. I)upr6's chronograph is merely a small electro-magnet with a fine writing style attached, 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 fori;.] [Du Bois' Spring Myograph. — It consists of a glass plate fixed in a frame, and moving on two polished steel wires, stretched between the supports A and B (Fig. 323). Ai h is a spring which, when it is compressed between the upright, 15, and the knob, h, drives the glass plate from H to A. As the plate moves from one side to the other, a small tooth, d, on its under surface, opens the key, //, 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.] [Marey's Simple Myograph. — The gastrocnemius is attached to a horizontal lever, which inscribes its movements on a revolving cylinder. This form of myograph, when provided with two levers, is very useful for comparing the action of a poison on one limb, the other being unpoisoned.] [Pfliiger's stationary form is simply a Ilelmholtz's myograph (Fig. 320) 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 " Fallmyograph." In all these experiments it is necessary to indicate at the same time the moment of stimulation. Contraction Curve of Human Mus- cle.— 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, such as is used in Brondgeest's pansphygmo- graph (Fig. 36). [The thickening of the adductor muscles of the thumb may be reg- istered by ineans of Marey's pince myo- graphique.] I. Simple Contraction. — If a single shock or stimulus of ?nofnentary duration be applied to a muscle, a "simple muscular contraction ' ' [or shortly, a contraction or twitch] is the result, /. . Roth). 305. MECHANISM OF THE BONES AND JOINTS.— Bones exhibit in the inner architecture of their spongiosa an arrangement of their lamellae and spicules which represents the static results of those forces — pressure 648 MECHANISM OF THE BONES AND JOINTS. and traction — wliich act on the developing bone (Structure of Bone, § 447). They are so arranged that, with the minimum of material, they afford the greatest resistance as a supporting structure or framework (//. <'. Meyer, Culmann, Jul. Wolffs. I. The joints permit the freest movements of one bone upon another [such as exist between the extremities of the bones of the limbs. In other cases, sutures arc formed, which, while permitting no movement, allow the contents of the cavity which they surround to enlarge, as in the case of the cranium]. The articular end of a fresh bone is covered with a thin layer or plate of hyaline carti- latje, which in virtue of its elasticity moderates any shocks or impulses communicated to the bones. The surface of the articular cartilage is perfectly smooth, and facilitates an ea.sy gliding movement of the one surface upon the other. At the outer boundary Ime of the cartilage, there is fixed the capsule of the joint, which encloses the articular ends of the bones like a sac. The inner .surface of the capsule is lined by a synovial membrane, which secretes the sticky, semi lluid synovia, moisten- ing the joint. The outer surface of the capsule is provided at various parts with bands of fibrous tissue, some of which strengthen it, while others restrain or limit the movement of the joint. Some osseous processes limit the movements of particular joints, e. g., the coronoid process of the ulna, which permits the forearm to be flexed on the upper arm only to a certain extent ; the olecranon, which prevents over-extension at the elbow joint. The joint surfaces are kept in apposition (i) by the adhesion of the synovia-covered, smooth, articular surface; (2) by the capsule and its fibrous bands; and (3) by the elastic tension and contraction of the muscles. [Structure of Articular Cartilage. — The thin layer of hyaline encrusting cartilage is fixed by an irregular surface upon the corresponding surface of the head of the bone (Kig. 345). In a ver- tical section through the articular cartilage of a bone which has been softened in chromic or other suitable acid, we observe that the cartilage cells are flattened near the free surface of the cartilage, and their long axes are parallel to the surface of the joint ; lower down, the cells are arranged in irregular groups, and further down still, nearer the bone, in columns or rows, whose long axis is in the long axis of the bone. These rows are produced by transverse cleavage of preexistmg cells. In the upper two-thirds, or thereby, the matrix of the cartilage is hyaline, but in the lower third, near the bone, the matrix is granular and sometimes fibrillated. This Fig. 345. is the calcified zone, which is impregnated with lime salts, and sharply defined by a nearly straight line from the hyaline zone above it, and by a very bold wavy line from the osseous head of the bone.] Synovial Membrane. — Synovial membrane consists of bun- dles of delicate connective tissue mixed with elastic tissue, while on its inner surface it is provided with folds, some of which con- tain fat, and others blood vessels (synovial villi). The inner surface is lined with endothelium. The intracapsular liga- Hyaline ments and cartilages are not covered by the synovial membrane, cartilage, j^qj. ^^g jj^gy Covered by endothelium. The synovia is a color- less, stringy, alkaline fluid, with a chemical composition closely allied to that of transudations, with this difierence, that it con- tains much mucin, together with albumin and traces of fat. Excessive movement diminishes its amount, makes it more inspis- sated, and increases the mucin, but diminishes the salts. Bone. Vertical section of articular cartila {.Stirling.) Calcified cartilage. Joints may be divided into several classes, accord- ing to the kind of movement which they permit : — I . Joints -vith movement around one axis : (a) The Gin- glymus, or Hinge Joint. — The one articular surface represents a portion of a cylinder or sphere, to which the other surface is adapted by a corresponding depression, so that, when flexion or extension of the joint takes place, it moves only on one axis of the cylinder or sphere. The joints of the fingers and toes are hinge joints of this description. Lateral ligaments, which pre- vent a lateral displacement of the articular surfaces, are always present. The Screw-hinge Joint is a modification of the simple hinge form {Langer, I/en/:e), e. g., the humero-ulnar articulation. Strictly speaking, simple flexion and extension do not take place at the elbow joint, but the ulna moves on the cupitellum of the humerus like a nut on a bolt ; in the right humerus, the screw is a right spiral, in the left, a left spiral. The ankle joint is another exam- ple ; the nut or female screw is the tibial surface, the right joint is hke a left-handed screw, the left the reverse, {d) The Pivot Joint (rotatoria), with a cylindrical surface, e.g., the joint between MECHANISM OF THE BONES AND JOINTS. 549 the atlas and the axis, the axis of rotation being around the odontoid process of the axis. In the acts of pronation and supination of the forearm at the elbow joint, the axis of rotation is from the middle of the cotyloid cavity of the head of the radius to the styloid process of the ulna. The other joints which assist in these movements are above the joint, between the circumferential part of the head of the radius and the sigmoid cavity of the ulna, and belozv the joint, between the sigmoid cavity of the radius which moves over the rounded lower end of the ulna. 2. Joints with movements around two axes. — {a) Such joints have two unequally curved surfaces which intersect each other, but which lie in the same direction, e. g., the atlanto-occipital joint, or the wrist joint, at which lateral movements, as well as flexion and extension, take place. [U) Joints with curved surfaces, which intersect each other, but which do not lie in the same direction. To this group belong the saddle- shaped articulations, whose surface is concave in one direction, but convex in the other, f.^., the joint between the metacarpal bone of the thumb and the trapezium. The chief movements are (l) flexion and extension, (2) abduction and adduction. Further, to a limited degree, movement is possible in all other directions; and, lastly, a pyramidal movement can be described by the thumb. 3. Joints ivith inovement on a spiral articular surface [spiral joints)), e.g., the knee joint {Goodsir). The condyle of the femur, curved from before backward, in the antero-posterior sec- tion of its articular surface, represents a spiral [Ed. Weber), whose centre lies nearer the posterior part of the condyle, and whose radius vector increases from behind, downward and foi"vvard. Flexion and extension are the chief movements. The strong lateral ligaments arise from the condyles of the femur corresponding to the centre of the spiral, and are inserted into the head of the fibula and inter- nal condyle of the tibia. \Vhen the knee joint is strongly flexed, the lateral ligaments are relaxed — they become tense as the extension increases; and when the knee joint is fully extended, they act quite like tense bands which secure the lateral fixation of the joint. Corresponding to the spiral form of the articular surface, flexion and extension do not take place around otie axis, but the axis moves continually with the point of contact; the axis moves also in a spiral direction. The greatest flexion and extension cover an angle of about 145°. The anterior crucial ligament is more tense during extension, and acts as a check ligament for too great extension, while the posterior ismore tense during flexion, and is a check ligament for too great flexion. The movements of extension and flexion at the knee are further complicated by the fact that the joint has a screw-like movement, in that during the greater extension the leg moves outward. Hence, the thigh, when the leg is fixed, must be rotated outward during flexion. Pronation and supination take place during the greatest flexion to the extent of 41° {Albert) at the knee joint, while with the greatest extension it is nil. It occurs because the external condyle of the tibia rotates on the internal. In all positions during flexion the crucial ligaments are fairly and uniformly tense, whereby the articular surfaces are against each other. Owing to their arrangement, during increasing tension of the anterior ligament (exten- sion), the condyles of the femur must roll more on to the anterior part of the articular surface of the tibia, while by increasing tension of the posterior ligament (flexion), they must pass more backward. 4. Joints zvith the axis of rotation round one fixed point. — These are the freely movable arthrodial joints. The movements can take place around innumerable axes, which all intersect each other in the centre of rotation. One articular surface is nearly spherical; the other is cup-shaped. The shoulder and hip joints are typical " ball-and-socket joints." We may represent the movements as taking place around three axes, intersecting each other at right angles. The movements which can be performed at these joints maybe grouped as : (l) pendu- lum-like movements in any plane, (2) rotation round the long axis of the limb, and (3) circum- scribing movements [circumduction], such as are made round the .circumference of a sphere; the centre is in the point of rotation of the joint, while the circumference is described by the limb itself Limited arthrodial joints are ball joints with limited movements, and where rotation on the long axis is wanting, e.g., the metacarpo-phalangeal joints. 5. Rigid joints or amphiarthroses are characterized by the fact that movement may occur in all directions, but only to a very limited extent, in consequence of the tough and unyielding external ligaments. Both articular surfaces are usually about the same size, and are nearly plane smfaces, e.g., the articulations of the carpal and the tarsal bones. II. Symphyses, synchondroses, and syndesmoses unite bones without the formation of a proper articular cavity, are movable in all directions, but only to the slightest extent. Physiologically they are closely related to amphiarthrodial joints. III. Sutures unite bones without permitting any movement. The physiological importance of the suture is that the bones can still grow at their edges, which thus renders possible the distention of the cavity enclosed by the bones [Herm. v. Meyer). . 306. ARRANGEMENT AND USES OF MUSCLES.— The muscles form 45 percent, of the total mass of the body, those of the right side being heavier than those on the left. Muscles may be arranged in the following groups, as far as their mechanical actions are concerned : — 550 SPHINCTER AND OTHER MUSCLES. A, Muscles without a definite origin and insertion : — 1. The hollow muscles surrounding globular, oval, or irregular cavities, such as the urinary bladder, gall bladder, uterus, and heart ; or the walls of more or less cylindrical canals (intestinal tract, muscular gland ducts, ureters, Fallopian tubes, vasa deferentia, blood vessels, lymphatics). In all these cases the muscular fibres are arranged in several layers, e.g., in a longitudinal and a circular layer, and sometimes also in an oblique layer. All these layers act together and thus diminish the cavity. It is inadmissible to ascribe different mechanical effects to the different layers, e.g., that the circular fibres of the intestine narrow it, while the longitudinal dilate it. Both sets of fibres rather seem to act simultaneously, and diminish the cavity by making it narrower and shorter at the same time. The only case where muscular fibres may act in partially dilating the cavity is when, owing to pressure from without, or from partial contraction of some fibres, a fold, projecting into the lumen, has been formed. When the fibres, necessarily stretching across the depression thereby produced, contract, they must tend to undo it, /. e., enlarge the cavity. The various layers are all innervated from the same motor source, which supports the view of their conjoint action. 2. The sphincters surround an opening or a short canal, and by their action they either constrict or close it, e.g., sphincter pupill?e, palpebrarum, oris, pylori, ani, cunni, urethrae, B. Muscles with a definite origin and insertion : — 1. The origin is completely fixed when the muscle is in action. The course of the muscular fibres, as they pass to where they are inserted, permits of the insertion being approximated in a straight line toward their origin during contraction, e. g., the attollens, attrahens, and retrahentes of the outer ear, and the rhomboidei. Some of these muscles are inserted into soft parts which necessarily must follow the line of traction, e.g., the azygos uvulae, levator palati mollis, and most of the muscles which arise from bone and are inserted into the skin, such as the muscles of the face, styloglossus, stylopharyn- geus, etc. 2. Both Origin and Insertion movable. — In this case the movements of both points are inversely as the resistance to be overcome. The resistance is often voluntary, which may be increased either at the origin or insertion of the muscle. Thus, the sterno-cleido-mastoid may act either as a depressor of the head or as an elevator of the chest ; the pectoralis minor may act as an abductor and depressor of the shoulder, or as an elevator of the 3d to 5 th ribs (when the shoulder girdle is fixed). 3. Angular Course. — INIany muscles having a fixed origin are diverted from their straight course ; either their fibres or their tendons may be defi/ out of the straight course. Sometimes the curving is slight, as in the occipito-frontalis and levator palpebrae superioris, or the tendon may form an angle round some bony process, whereby the muscular traction acts in quite a different direction, /. e., as if the muscle acted directly from this process upon its point of insertion, e.g., the obliquus oculi superior, tensor tympani, tensor veli palatini, obturator internus. 4. Many of the muscles of the extremities act upon the long bones as upon levers : («) Some act upon a lever with one arm, in which case the insertion of the muscle (power) and the weight lie upon one side of the fulcrum or point of support, c. g. , biceps, deltoid. The insertion (or power) often lies very close to the fulcrum. In such a case, the i-apidity of the movement at the end of the lever is greatly increased, but force is lost [/. e., what is gained in rapidity is lost in power]. This arrangement has this advantage, that, owing to the slight contrac- tion of the muscle, little energy is involved, which would be the case had the muscular contraction been more considerable (§ 300, I, 3). (J)) The muscles act VARIOUS KINDS OF LEVERS ACTED ON BY MUSCLES. 551 upon the bones as upon a lever with two arms, in which case the power (insertion of the muscle) lies on the other side of the fulcrum opposite to the weight, e.g., the triceps and muscles of the calf. In both cases, the muscular force necessary to overcome the resistance is estimated by the principles of the lever : equilibrium is established when the static yig. 346. moments (== product of the power in its vertical distance from the fulcrum) are equal ; or when the power and weight # F ^ are inversely proportional, as their vertical distance from w a p ^^' the fulcrum. . [The Bony Lever. — All the three orders of levers are met with in the body. Indeed, in the elbow joint all the three orders are represented. The annexed scheme shows the relative positions of P, W, and F (Fig. 346). The first order represented by such a movement as nodding the W (2) (3) head, the second by raising the body on the tiptoes by the muscles of the \v p calf, and the third by the action of the biceps in raising the forearm. At the elbow joint the first order is illustrated by extending the flexed The three orders of levers. forearm on the upper arm, as in striking a blow on the table, where the triceps attached to the olecranon is the power, the trochlea the fulcrum, and the hand the weight. If the hand rest on the table and the body be raised on it, then the hand is the fulcrum, while the triceps is the power raising the humerus and the parts resting on it (W). The third order has already been referred to, e.g., flexing the forearm.] Direction of Action — It is most important to observe the direction in which the muscular force and weight act upon the lever arm. Thus, the direction may be vertical to the lever in one position, while after flexion it may act obliquely upon the lever. The static moment of a power acting obliquely on the lever arm is obtained by multiplying the power with the power acting in a direction vertical to the point of rotation. Examples. — In Fig. 347, I, B x represents the humerus, and x Z the radius; Aji', the direc- tion of the traction of the biceps. If the biceps acts at a right angle only, as by lifting horizon- tally a weight (P) lying on the forearm or in the hand, then the power of the biceps (= A) is obtained from the formula, A y x ='? x Z, i. e., A ^= (F x Z) : y x. It is evident that, when the Scheme of the action of the muscles on bones. radius is depressed to the position x C, the result is different ; then the force of the biceps = Aj = (PjW x) : 0 X. In Fig. 347, II, TF is the tibia, F, the ankle joint, MC, the foot in a horizontal position. The power of the muscles of the calf (^ a) necessary to equalize a force,/, directed from below against the anterior part of the foot, would be a := (/ AI F) : F C. If the foot be altered to the position R S, the force of the muscles of the calf would then be a-^ = (/^ M F) : F C. In muscles also, which, like the coraco-brachialis, are stretched over the angle of a hinge, the same result obtains. 552 SYNERGETIC AND ANTAGONISTIC MUSCLES. In Fig. 347, III, II E is the humerus, E, ihe elbow joint, E R, the radius, B R. the coracobrachi- alis. Its moment in tliis position is = A, a E. When the radius is raised to E R,, then it is = A, a E. \Ve must notice, however, that B R, <; B R. Hence, the absolute muscular force must be less in the flexed position, because ever>- muscle, as it becomes shorter, Ufts less weight. What is lost in power is gained by the elongation of the lever arm. 5. Many muscles have a double action ; when contracted in the ordinary way they execute a combined movement, e.g., the biceps is a flexor and supinator of the forearm. If one of these movements be prevented by the action of other muscles, the muscle takes no part in the execution of the other movement. If the forearm be strongly pronated and flexed in this position, the biceps takes no part therein; or, when the elbow joint is rigidly supinated, only the supinator brevis acts, not the biceps. The muscles of mastication are another example. The masseter elevates the lower jaw, and at the same time pulls it forward. If the depressed jaw, however, be strongly pulled backward when the jaw is raised, the masseter is not concerned. The temporal muscle raises the jaw, and at the same time pulls it backward. If the depressed jaw be raised after being pushed forward, then the temporal is not concerned in its elevation. 6. Muscles acting on two or more joints are those which, in their course from their origin to their insertion, pass over two or more joints. Either the tendons may deviate from a straight course, e.g., the extensors and flexors of the fingers and toes, as when the latter are flexed ; or the direction is always straight, e. g., the gastrocnemius. The muscles of this group present the following points of interest: (a) The phenomenon of so-called "active insufficiency." If the position of the joints over which the muscle passes be so altered that its origin and insertion come too near each other, the muscle may require to contract so much before it can act on the bones attached to it, that it cannot contract actively any further than to the extent of the shortening from which it begins to be active; e.g., when the knee joint is bent, the gastrocnemius can no longer produce plantar flexion of the foot, but the traction on the tendo-Achilles is pro- duced by the soleus. (/>) " Passive insufficiency" is shown by many-jointed muscles under the following circumstances : In certain positions of the joint, a muscle may be so stretched that it may act like a rigid strap, and thus limit or prevent the action of other muscles, e.g., the gastrocnemius is too short to permit complete dorsal flexion of the foot when the knee is extended. The long flexors of the leg, arising from the tuber ischii, are too short to permit complete exten- sion of the knee joint when the hip joint is flexed at an acute angle. The extensor tendons of the fingers are too short to permit of complete flexion of the joints of the fingers when the hand is completely flexed. 7. Synergetic muscles are those which together subserve a certain kind of movement, e.g., the flexors of the leg, the muscles of the calf, and others. The abdominal muscles act along with the diaphragm in diminishing the abdomen during straining, while the muscles of inspiration or expiration, even the different origins of one muscle, or the two bellies of a biventral muscle, may be regarded from the same point of view. Antagonistic muscles are those which, during their action, have exactly the opposite eff'ect of other muscles, e.g., flexors and extensors— pronators and supi- nators— adductors and abductors — elevators and depressors — sphincters and dila- tors— inspiratory and expiratory. When it is necessary to bring the full power of our muscles into action, we quite involuntarily bring them beforehand into a condition of the greatest tension, as a muscle in this condition is in the most favorable position for doing work (§ 300, I, 3). Conversely, when we execute delicate movements requiring little energy, we select a position in which the corresponding muscle is already shortened. All the fasciae of the body are connected with muscles, which, when they contract, alter the tension of the former, so that they are, in a certain sense, aponeuroses or tendons of the latter (K. Bardelebett). [For the importance of muscular movements and those of fascioe in connection with the movements of the lymph, see \ 201.] GYMNASTICS, MASSAGE AND CHANGES IN MUSCLE. 553 307. GYMNASTICS; MOTOR PATHOLOGICAL VARIATIONS.— Gymnastic exercise is most important for the proper development of the muscles and motor power, and it ought to be commenced in both sexes at an early age. Systematic muscular activity increases the volume of the muscles, and enables them tQ do more work. The amount of blood is increased with increase in the muscular development, while at the same time the bones and ligaments become more resistant. As the circulation is more lively in an active muscle, gymnastics favor the circulation, and ought to be practiced, especially by persons of sedentary habits, who are apt to suffer from con- gestion of blood in abdominal organs {e.g., haemorrhoids), as it favors the movement of the tissue juices [^ 201]. An active muscle also uses more O and produces more CO.,, so that respiration is also excited. The total increase of the metabolism gives rise to the feeling of well-being and vigor, diminishes abnormal irritability, and dispels the tendency to fatigue. The whole body becomes firmer, and specifically heavier {Jager). By Ling's, or the Swedish system, a systematic attempt is made to strengthen certain weak muscles, or groups of muscles, whose weakness might lead to the production of deformities. These muscles are exercised systematically by opposing to them resistances, which must either be overcome, or against which the patient must strive by muscular action. Massage, which consists in kneading, pressing, or rubbing the muscles, favors the blood stream; hence, this system maybe advantageously used for such muscles as are so weakened by disease that an independent treatment by means of gymnastics cannot be adopted. [The importance of massage as a restorative practice in getting rid of the waste products of muscular activity has been already referred to (I 304).] Disturbances of the normal movements may partly affect the passive motor organs {e.g., the bones, joints, ligaments, and aponeuroses), or the active organs (muscles with their tendons, and motor nerves). Passive Organs. — Fractures, caries and necrosis, and inflammation of the bones, which make movements painful, influence or even make movement impossible. Similarly, dislocations, relaxation of the ligaments, arthritis, or anchylosis interfere with movement. Also curvature of bones, hyper- ostosis or exostosis; lateral curvature of the vertebral column (Scoliosis), backward angular curva- ture (Kyphosis), or forward curvature (Lordosis). The latter interfere with respiration. In the lower extremities, which have to carry the weight of the body, genu valgum, may occur in flabby, tall, rapidly-growing individuals, especially in some trades, e.g., in bakers. The opposite form, genu varum, is generally a result of rickets. Flat foot depends upon a depression of the arch of the foot, which then no longer rests upon its three points of support. Its causes seem to be similar to those of genu valgum. The ligaments of the small tarsal joints are stretched, and the long axis of the foot is usually directed outward ; the inner margin of the foot is more turned to the ground, while pain in the foot and malleoli make walking and standing impossible. Club foot (Talipes varus), in which the inner margin of the foot is raised, and the point of the toes is directed inward and downward, depends upon imperfect development during foetal life. All children are born with a certain very slight degree of bending of the foot in this direction. Talipes equinus, in which the toes, and T. calcaneus, in which the heel touches the ground, usually depend upon contracture of the muscles causing these positions of the foot, or upon paralysis of the antagonistic muscles. Rickets and Osteomalacia. — If the earthy salts be withheld from the food, the bones gradually undergo a change ; they become thin, translucent, and may even bend under pressure. In certain persistent defects of nutrition, the lime and other salts of the food are not absorbed, giving rise to rachitis, or rickets, in children. If fully formed bones lose their lime salts to the extent of ^ to j^ (halisterisis), they become brittle and soft (osteomalacia). This occurs to a limited extent in old age. Muscles. — The normal nutrition of muscle is intimately dependent on a proper supply of sodium chloride and potash salts in the food, as these form integral parts of the muscular tissue {ICemmerich , Foj-ester). Besides the atrophic changes which occm: in the muscles when these sub- stances are withheld, there are disturbances of the central nervous system and digestive apparatus, and the animals ultimately die. The condition of the muscles during inanition is given in § 237. If muscles and bones be kept inactive, they tend to atrophy (| 244). In atrophic muscles, and in cases of anchylosis, there is an enormous increase, or " atrophic proliferation," of the muscle corpuscles, which takes place at the expense of the contractile contents {Cohnkeim). A certain degree of mus- cular atrophy takes place in old age. The uterus, after delivery, undergoes a great decrease in size and weight — from 1000 to 350 grammes — due chiefly to the diminished blood supply to the organ. In chronic lead poisojzing, the extensors and interossei chiefly undergo atrophy. Atrophy and degeneration of the muscles are followed by shortening and thinning of the bones to which the muscles are attached. Section and paralysis of the motor nerves cause palsy of the muscle, thus rendering them inactive, and they ultimately degenerate. Atrophy also occurs after inflammation or softening of the multipolar nerve cells in the anterior horn of the gray matter of the spinal cord, or the motor nuclei (facial, spinal accessory, and hypoglossal of Stilling in the medulla oblongata), in the muscles con- nected with these parts. Rapid atrophy takes place in certain forms of spinal paralysis and in acute bulbar paralysis (paralysis of the medulla oblongata), and in a chronic form in progressive muscular 554 STANDING. atrophy, ami progressive bulbar paralysis. The muscles and their nerves become small and soft. The muscles show many nuclei, the sarcous substance becomes fatty, and ultimately disappears. Accord- ing to Charcot, these areas are at the same time the trophic centres for the nerves j)roceeding from them, as well as for the muscles belonging to them. According to Friedreich, the primary lesi ,n in progressive muscular atrophy is in the muscles, and is due to a primar)- interstitial inflammation of the muscle, resulting in atrophy and degenerative changes, while the nerve centres are aflected secondarily, just .is after amputation of a limb, the corresponding part of the spinal cord degenerates. In pseudo-hypertrophic muscular atrophy the muscular fibres atrophy completely, with copi- ous development of fat and connective tissue between the fibres, without the nerves or spinal cord undergoing degeneration. The muscular substance may also undergo amvloid or 7i>ax-like degen- eration, whereby the amyloid substance infilirates the tissue ({; 249, VI). Sometimes atrophic mus- cles have a deep brown color, due to a change of the haemoglobin of the muscle. When muscles are much used, they hypertrophy, as the heart in certain cases of valvular lesion or obstruction {\ 40), the bladder, and intestine. [In true hypertrophy there is an increased number or increase in the size of its tissue elements, throughout the entire tissue or organ, without any deposit of a foreign body. Perhaps, in hypertrophy of the bladder, the thickened muscular coat not only serves to overcome resistance, but it offers greater resistance to bursting under the increased intra-vesical pressure. Mere enlargement is not hypertrophy, for this may be brought about by foreign elements. In atrophy there is a diminution in size or bulk, even when the Ijlood stream is kept up, the decrease being due to pressure. An atrophied organ may be even enlarged, as seen in pseudo hypertrophic paralysis, where the muscles are larger, owing to the interstititial growth of fatty and connective tissue, while the true muscular tissue is diminished and truly atrophied.] 308. STANDING. — The act of standing is accomplished by muscular action, and is the vertical position of eciuilibrium of the body, in which a line drawn from the centre of gravity of the body falls within the area of both feet placed upon the ground. In the military attitude, the muscles act in two direc- tions— (i) to fix the jointed body, as it were, into one unbending column ; and (2) in case of a variation of the equilibrium, to compensate by muscular action for the disturbance of the equilibrium. The following individual motor acts occur in standing : — 1. Fixation of the head upon the vertebral column. The occiput may be moved in various directions upon the atlas, as in the acts of nodding. As the long arm of the lever lies in front of the atlas, necessarily when the muscles of the back of the neck relax, as in sleep or death, the chin falls upon the breast. The strong neck muscles, which pull from the vertel)ral column upon the occiput, fix the head in a firm position on the vertebral column. The chief rotatory movement of the head on a vertical axis occurs round the odontoid process of the axis. The artirular surfaces on the pedicles, and part of the bodies of the ist and 2d vertebra^ are convex toward each other in the middle, becoming somewhat lower in front and behind, so that the head is highest in the erect posture. Hence, when the head is greatly rotated, compression ofthe medulla oblongata is prevented (Henke). In standing, these muscles do not require to be fixed by muscular action, as no rotation can take place when the neck muscles are at rest. 2. Fixed Vertebral Column. — The vertebral column itself must be fixed, especially where it is most mobile, i.e., in the cervical and lumbar regions. This is brought about by the strong muscles situate in these regions, e.g., the cervical spinal muscles, Extensor dorsi comniiinis and Quadratus lumbortttn. Mobility of the Vertebrae. — The least movable vertebrae are the 3d to the 6th dorsal ; the sacrum is quite immovable. For a certain length of the column, the mobility depends on [a) the number and height of the inter-articular (ibro-cartilages. They are most numerous in the neck, thickest in the lumbar region, and relatively also in the lower cervical region. They permit movement to take place in every direction. Collectively the inter-articular disks form one-fourth of the height of the whole vertebral column. They are compressed somewhat by the pressure of the body; hence, the body is longest in the morning and after lying in the horizontal position. The smaller periphery of the bodies of the cervical vertebrae favors the mobility of these vertebni; compared with the larger lower ones, {b) The position ofthe processes also influences greatly the mobility. The strongly de- pressed spines ofthe dorsal region hinder hyper-extension. The articular processes on the cervical vertebrae are so placed that their surfaces look obliquely from before and upward, backward, and downward ; this permits relatively free movement, rotation, lateral and nodding movements. In the dorsal region, the articular surfaces are directed vertically and directly to the front, the lower directly backward ; in the lumbar region, the position of the articular processes is almost completely vertical and antero-posterior. In bending backward, as far as possible, the most mobile parts of the column are the lower cervical vertebrae, the lith dorsal to the 2d lumbar and the lower two lumbar vertebn^ {E. H. Weber). 3. The centre of gravity of the head, trunk, and arms when fixed as above, lies in front of the loth dorsal vertebra. It lies further forward, in a horizontal plane, passing through the xiphoid pro- WALKING, RUNNING AND SPRINGING. 555 cess, the greater the distention of the abdomen by food, fat, or pregnancy. A line drawn vertically downward from the centre of gravity passes behind the line uniting both hip joints. Hence, the trunk would fall backward on the hip joint, were it not prevented partly by ligaments and partly by muscles. The former are represented by the ileo-femoral band and the anterior tense layer of the fascia lata. As ligaments alone, however, never resist permanent traction, they are aided, especially by the ileo- psoas muscle inserted into the small trochanter, and in part, also, by the rectus femoris. Lateral move- ment at the hip joint, whereby the one limb must be abducted and the other adducted, is prevented especially by the large mass of the glutei. When the leg is extended, the ileo-femoral ligament, aided by the fascia lata, prevents adduction. 4. The rigid part of the body, head, and trunk, with the arms and legs, whose centre of gravity lies lower and only a little in front, so that the vertical line drawn downward intersects a line connecting the posterior surfaces of the knee joints, must now be fixed at the knee joint. Falling backward is prevented by a slight action of the quadriceps femoris, aided by the tension of the fascia lata. In- directly it is aided also by the ileo-femoral ligament. Lateral movement of the knee is prevented by the disposition of the strong lateral ligaments. Rotation cannot take place at the knee joint in the extended position (| 305, I, 3). 5. A line drawn downward from the centre of gravity of the whole body, which lies in the pro- montory, falls slightly in front of a line between the two ankle joints. Hence, the body would fall forward on the latter joint. This is prevented especially by the muscles of the calf, aided by the muscles of the deep layer of the leg (tibialis posticus, flexors of the toes, peroneous longus et brevis). Other Factors. — {n) As the long axis of the foot forms with the leg an angle of 50°, falling forward can only occur after the feet are in a position more nearly parallel with their long axis, (b) The form of the articular surfaces helps, as the anterior broad part of the astragalus must be pressed between the two malleoli. The latter mechanism cannot be of much importance. 6. The metatarsus and phalanges are united by tense ligaments to form the arch of the foot, which touches the ground at three points — tuber calcanei (heel), the head of the first metatarsal bone (ball of the great toe), and of the fifth toe. Between the latter two points, the heads of the metatarsal bones also form points of supports. The weight of the body is transmitted to the highe.stpart of the arch of the foot, the caput tali. The arching of the foot is fixed only by ligaments. The toes play no part in standing, although, when moved by their muscles, they greatly aid the balancing of the body. The maintenance of the erect attitude fatigues one more rapidly than walking. 309. SITTING. — Sitting is that position of equilibrium whereby the body is supported on the tubera ischii, on which a to and fro movement may take place {^H. v. Mever'). The head and trunk together are made rigid to form an immovable column, as in standing. We may distinguish: (l) the forward posture, in which the line of gravity passes in fi-ont of the tubera ischii ; the body being sup- ported either against a fixed object, e.g., by means of the arm on a table, or against the upper surface of the thigh. (2) The backward posture, in which the hne of gravity falls behind the tubera. A person is prevented from falling backward either by leaning on a support, or by the counter-weight of the legs kept extended by muscular action, whereby the sacrum forms an additional point of support, while the trunk is fixed on the thigh by the ileo-psoas and rectus femoris, the leg being kept extended by the extensor quadriceps. Usually the centre of gravity is so placed that the heel also acts as a point of support. The latter sitting posture is of course not suited for resting the muscles of the lower limbs. (3) When " sitting erect " the line of gravity falls between the tubera themselves. The muscles of the legs are relaxed, the rigid trunk only requires to be balanced by slight muscular action. Usually the balancing of the head is sufficient to maintain the equilibrium. 310. WALKING, RUNNING, AND SPRINGING.— By the term •walking is understood progression in a forward horizontal direction with the least possible muscular exertion, due to the alternate activity of the two legs. Methods. — The Brothers Weber were the first to analyze the various positions of the body in walking, running, and springing, and they represented them in a continuous series, which represents the successive phases of locomotion. These phases may be examined with the zoetrope (| 398, 3.) Marey estimated the ti»ie relations of the individual acts, by transferring the movements, by means of his air tambours, to a recording surface. Recently, by means of a revolving camera, he has succeeded in photographing, in instantaneous pictures (yoVo second), the whole series of acts. Of course this series, when placed in the zoetrope, represents the natural movements. Figs. 349, 350, 351 represent these acts. In walking, the legs are active alternately; while one — the ''supporting" or "active" leg — carries the trunk, the other is ''inactive" or "passive." Each leg is alternately in an active and a passive phase. Walking may be divided into the following movements: — I. Act (Fig. 348, 2). — The active leg is vertical, slightly flexed at the knee, and it alone supports the centre of gravity of the body. The passive leg is completely extended, and touches the ground 556 WALKING, RUNNING AND SPRINGING. onlv with the tip of the great toe {z). This position of the leg; correspondstoarifjht-angled triangle, in wliich the active leg and the ground fonn two sides, while the passive leg is the hypothenuse. II. Act. — For the forward movement of the trunk, the active leg is inclined slightly from its vertical position (cathctiis) to an ohlique and more forward (hypothenuse) position ( 3V In order that the trunk may remain at the same height, it is necessary that the active leg he lengthened. This is accomplished by completely extending the knee (3, 4, 5), as well as by lifting the heel from the Phases of walking. The thick lines represent the active, the thin the passive leg: /(, the hip joint; i-. f, b, ankle ; c, d, heel ; m, e, ball of the tarso-metatarsal joint ; 2, g, point of great toe. knee ; ground (4, 5), so that the foot rests on the balls or the heads of the metatarsal bones, and, lastly, by elevating it on the point of the great toe (2, thin line). During the extension and forward move- ment of the active leg, the tips of the toes of the passive leg have left tl>€ ground (3). It is slightly flexed at the knee joint (owing to the shortening), it performs a" pendulum-like movement" (4, 5), whereby its foot is moved as far in front of the active leg as it was formerly beliind it. The foot is then placed fiat upon the ground (l, 2, thick lines) ; the centre of gravity is now transferred to this Fig. 349. — 1 — - — \ ^ 1 ^ — 1 1 0 (>.:',(> 1 1.5iJ 2 2.50 3 Metrn^ Phases of slow walking. Instantaneous photograph (^farey), only the side directed to the observer is shown. From the vertical position of the right, active leg ; (I), all the phases of this leg are represented in six pictures (I to Vl), while after VI the vertical position is regained. The Ar.-ibic numerals indicate the simultaneous posi- tion of the corresponding left leg ; thus i = I, 2 = II, etc., so that during the position IV of the right leg, at the same time the left leg has the position as i. active leg, which, at the same time, is slightly flexed at the knee, and placed vertically. The first act is then repeated. Simultaneous Movements of the Trunk. — During vj^alking, the trunk performs certain characteristic movements. (l) It leans every time toward the active leg, owing to the traction of the glutei and the tensor fascice lat.-e, so that the centre of gravity is moved, which in short, heavy persons with a broad pelvis leads to their " waddling" gait. (2) The trunk, especially during rapid walking, is inclined slightly forward to overcome the resistance of the air. (3) During the " pendulum- WALKING, RUNNING AND SPRINGING. 557 like action," the trunk rotates slightly on the head of the active femur. This rotation is compensated, especially in rapid walking, by the arm of the same side as the oscillating leg swinging in the opposite direction, while that on the other side at the same time swings in the same direction as the oscillating limb. Modifying Conditions: i. The Duration of the Step. — As the rapidity of the vibration of a pendulum (leg) depends upon its length, it is evident that each individual, according to the length of his legs, must have a certain natural rate of walking. The '■'■duration of a step''' depends also upon the time during which both feet touch the ground simultaneously, w'hich, of course, can be altered voluntarily. When "walking rapidly" the time ^ O, i. e., at the same moment in which the active leg reaches the ground, the passive leg is raised. 2. The length of the step is usually about 6 to 7 decimetres [23 to 27 inches], and it must be greater, the more the length of the hypothenuse of the passive leg exceeds the cathetus of the active one. Hence, during a long step, the active leg is greatly shortened (by flexion of the knes), so that the trunk is pulled downward. Similarly, long legs can make longer steps. According to Marey and others, the pendulum movement of the passive leg is not a true pendulum movement, because its movement, owing to muscular action, is of more uniform rapidity. During the pendulum movement of the whole limb, the leg vibrates by itself at the knee joint i^Lucce, H. Vierordl). Fixation of the Femur. — ^According to Ed. and W. Weber, the head of the femur of the passive leg is fixed in its socket chiefly by the atmospheric pressure, so that no muscular action is necessary for carrying the whole limb. If all the muscles and the capsule be divided, the head of the femur Fig. 350. 2.75 3 Mf.tm Instantaneous photograph of a rvmne^r {Marey). Ten pictures per second. The abscissa indicates the length of the step in metres. Still remains in the cotyloid cavity. Rose refers this condition not to the action of the atmospheric pressure, but to two adhesion surfaces united by means of synovia. The experiments of Aeby show that not only the weight of the limb is supported by the atmospheric pressure, but that the latter can support several times this weight. When traction is exerted on the limb, the margins of the cotyloid ligament of the cotyloid cavity are apphed like a valve tightly to the margin of the cartilage of the head of the femur. According to the Brothers Weber, the leg falls from its socket as soon as air is admitted by making a perforation into the articular cavity. Work done during Walking. — Marey and Demery estimate the amount done by a man weighing 64 kilos. [10 stones], when walking slowly, as = 6 kilogramme-metres per second; rapid running := 56 kilogramme-metres. The work done is due to the raising of the entire body and extremi- ties, to the velocity communicated to the body, as well as to the maintenance of the centre of gravity. In springing or leaping, the body is rapidly projected upward by the greatest possible and most rapid contraction of the muscles, while at the same time the centre of gravity is maintained by other muscular acts (Fig. 351). The pressure upon the sole of the foot in "walking is distributed in the following manner : The supporting leg always presses more strongly on the ground than the other; the longer the step the greater the pressure. The heel receives the maximum amount of pressure sooner than the point of the foot {Car let). Running is distinguished from rapid walking by tlie fact that, at a particular moment both legs do not touch the ground, so that the body is raised in the air. 558 WALKING, RUNNING AND SPRINGING. The active leg, as it is forciby extended from a flexed position, gives the l)ody the necessary impetus (Fig. 350). Pathological. — V.iriations of the walking movements depend primarily upon diseases of bones, ligaments, muscles, and tendons, and also U]X)n affections of the motor nerves. The effect of sensory nerves and the reflex mechanism of the spinal cord, and also of the muscular sense on walking, are stated in {-i; 355, 360, 430. 311. COMPARATIVE. — The absolute muscular force in animals is not, as a rule, much different from that in man. The great motor power exerted by animals results from the thickness and number of the muscles, as well as from the different arrangement of the levers and the action of muscles on them. Insects particularly exert a large amount of force; some insects can drag a body sixty-seven times their own weight; a horse scarcely its own weight. A man pressing upon a dyna- mometer with one hand exerts pressure -= 0.70 times his own weight, while a dog lifting its lower jaw exerts 8.3 times. A crab by closing its pincers 28.5 times. A mussel on closing its shell 382 times its body weight {Plateau). In mammals standing is much more easy, as they have four supporting surfaces. The springing animals have a sitting attitude, while the tail is often used as a support (kangaroo, squirrel). In birds, there is a mechanical arrangement by which, while perching, the tendons are flexed; hence, Fig. 351. High leap. Instantaneous photograph (Marey). The pictures partly overlap each other, as soon as the velocity of the forward movement on the descent diminishes after springing. In the left-hand corner is the dial plate, the radius of which moved one division in -^ second. The abscissa indicates the distance in metres. a bird while sleeping can still retain its hold (Cuvier). In the stork and crane, which stand for a long time on one leg, this act is unaccompanied by muscular action, as the tibia is fixed by means of a process which fits into a depression of the articular surface of the femur. In walking, we distinguish in mammals the step (le pas) — the four feet are generally moved in four tempo, and usually diagonally, ^.i,i-., in the horse right fore, left hind; left fore, right hind. [The camel is an exception — it moves the fore and hind limbs simultaneously on each side.] In trotting this movement is accelerated; the two limbs in a diagonal direction lift together, so that only two hoof sounds are heard while at the same time, the body is raised more in the air. During the interval between two hoof beats the body is free in the air, all the limbs having left the ground. Strictly speaking, the fore limb leaves the ground slightly .sooner than the hind one. The gallop. — When a (right) galloping horse moves in the air, the upper part of its body is fairly horizontal; when it touches the ground, the left hind foot is the first to touch the ground. Shortly thereafter, the left fore and right hind foot touch the ground, while the right fore leg has not yet reached the ground and is directed forward. The upper part of the body still retains its horizontal .?«., Processus muscularis of Cart, arj taen ; L. er.-ar., Ligam. crico-arytsean ; C.s., Cornu superius ; C.z"., Cornu inferius Cart, thyre- oidea. L. ce.-cr. p. i., Lig. kerato-cricoi- deum. post, inf.; C./r., Cart, tracheales; P.m.tr., Pars membranacea trachese. I. The glottis is dilated by the action of the posterior crico-arytenoid muscles. When they contract they pull both processus musculares of the arytenoid cartilages backward, downward, and toward the middle line (Fig. 356), so that the processus vocales (I, I) must go apart and upward (II, II). Thus, between the vocal cords (glottis vocalis), as well as between the inner margins of the aryte- noid cartilages, a large triangular space is formed (glottis respiratoria), and these spaces are so arranged that their bases come together, so that the aperture between the cords and the arytenoid cartilages has a rhomboidal form. Fig. 356 shows the action of the muscles. The vocal cords, represented by lines converging in front, arise from the anterior angle of the arytenoid cartilages (I, I). When 36 662 ACTION OF THE LARYNGEAL MUSCLES. these cartilages are rotated into the position (II, II), the cords take the position indicated by the dotted lines. The widening of the respiratory portion of the glottis between the arytenoid cartilages is also indicated in the diagram. Pathological. — When these muscles are paralyzed, the wideninjr of the glottis does not take place, and there may be severe dyspnoea during inspiration, although the voice is unaffected {A'iei^g/, L. Weber^. In a larynx just excised, the dilators are the first to lose their excitability (Semon and Horsley). 2. The entrance to the glottis is constricted by the arytenoid muscle (transverse), which extends transversely between both outer surfaces of the aryte- Fir.. 354. Fig. 355. Larynx from behind with its muscles. £., Epiglottis, with the cushion (W.); C.W., Cart. Wrisbergii ; C.S., Cart. Santorini ; C.c, Cart, cricoidea. Cornu sup. — Cornu inf., Cart, thyreoideae; Af. ar. tr.. Muse, arytanoideus transversus ; Ahn. ar. obi., Musculi arytEenoidei obliqui ; M. cr.-aryt. post., Miisculus crico-arytEenoideus post- icus; /Virj car^.. Pars cartilaginea ; Pars memb.. Pars membranacea tracheae. Nerves of the larynx. O.h. Os hyoideum ; C.th., Cart, thyreoidea ; Cc, Cart, cricoi- dea; 7r., Trachea ; M. ih.-ar.,'M.. thyreo- arytaenoideus yJ/, cr.-ar. p., M. crico- arytaenoideus posticus ; M. cr.-ar. I., M. crico-arytsen. lateralis ; M. cr.-th., M. crico- thyreoideus ; N.lar. si4p. v., N. laryngeus sup. ; R.I,, Ramus internus ; R.E., Ramus ext. ; N. lar, rec. v., N. laryngeus recur- rens ; R.I.N.L.R., Ramus int.; R.E.N. L.R., Ramus ext. nervi laryngei recurrentis vagi. noids along their whole length (Fig. 357)- On the posterior surface of this muscle is placed the cross bundles (Fig. 354) of the thyro-aryei^iglotticus (or arytsenoidei obliqui) ; they act like the foregoing. The action of these muscles is indicated in Fig. 357; the arrows point to the line of traction. Pathological. — Paraly.sis of this muscle enfeebles the voice and makes it hoarse, as much air escapes between the arytenoid cartilages during phonation. 3. In order that the vocal cords be approximated to each other, which occurs during phonation, the processus vocales of the arytenoid cartilages must be closely apposed, whereby they must be rotated inward and downward. This ACTION OF THE LARYNGEAL MUSCLES. 563 result is brought about by the processus musculares being moved in a forward and upward direction by the thyro-arytenoid muscles. These muscles are applied to, and in fact are imbedded in, the substance of the elastic vocal cords, and Fig. 356. Fig. 357. Schematic horizontal section of the larynx. I, Position of the horizontally divided arytenoid cartilages dur- ing respiration ; from their anterior processes run the converging vocal cords. The arrows show the line of traction of the posterior crico-arytenoid muscles; II, II, the position of the arytenoid mus- cles as a result of this action. Schematic horizontal section of the larynx, to illustrate the action of the arytenoid 77iuscle. I, I, position of the arytenoid cartilages during quiet respiration. The arrows indicate the direction of the contraction of the muscle ; II, II, the position of the arytenoid car- tilages after the arytenoideus contracts. their fibres reach to the external surface of the arytenoid cartilages. When they contract, they rotate these cartilages so that the processus vocales must rotate inward. The glottis vocalis is thereby narrowed to a mere slit (Fig. 358), while the glottis respiratoria remains as a broad triangular opening. The Fig. 358. action of these muscles is indicated in Fig. 358. The lateral crico-arytenoid muscle is inserted into the anterior margin of the articular surface of the arytenoid cartilage ; hence, it can only pull the cartilage forward ; but some have supposed that it can also rotate the arytenoid cartilage in a manner similar to the thyro- arytenoid (?), with this difference, that the processus vocales do not come so close to each other. Pathological. — Paralysis of both thyro- arytenoid muscles causes loss of voice. 4. The vocal cords are ren- Scheme of the closure of the glottis by the thyro-arytenoid muscles. II, II, position of the arytenoid cartilages dur- ing quiet respiration. The arrows indicate the direction of the muscular traction. I, I, position of the arytenoid car- tilages after the muscles contract. dered tense by their points of attachment being removed from each other by the action of muscles. The chief agents in this action are the crico-thyroid muscles, which pull the thyroid cartilage forward and downward. At the same time, however, the 564 RELAXATION OF THE VOCAL CORDS. posterior crico-arytenoids must pull the arytenoid cartilages slightly backward, and also keep them fixed. The geniohyoid and thyro-hyoid, when they contract, pull the thyroid upward and forward toward the cliin, and also tend to increase the tension of the vocal cords [C. Mayer, Griitzner). Pathological. — Paralysis of the crico thyroid causes the voice to l)ecome harsh and deep, owing to the voc.ll cords not being sutViciently tense. Position during Phonation. — The tension of the vocal cords brought about in this way is not of itself sufficient for phonation. The triangular aperture of the glottis respiratoria between the arytenoid cartilages, produced by the unaided action of the internal thyro-arytenoid muscles (see 3) must be closed by the action of the transverse and oblique arytenoid muscles. The vocal cords themselves must have a concave margin, which is obtained through the action of the crico-thyroids and posterior crico-arytenoids, so that the glottis vocalis presents the appearance of a myrtle leaf {Henle), while the rima glottidis has the form of a linear slit (Fig. 362). The contraction of the internal thyro-arytenoid converts the concave margin of the vocal cords into a straight margin. This muscle adjusts the delicate variations of tension of the vocal cords themselves, causing more especially such variations as are necessary for the production of tones of slightly different pitch. As these muscles come close to the margin of the cords, and are securely woven, as it were, among the elastic fibres of which the cords consist, they are specially adapted for the above- mentioned purpose. When the muscles contract, they give the necessary resistance to the cords, thus favoring their vibration. As some of the muscular fibres end in the elastic fibres of the cords, these fibres, when they contract, can render cer- tain parts of the cords more tense than others, and thus favor the modifications in the formation of the tones. The coarser variations in the tension of the vocal cords are produced by the separation of the thyroid from the arytenoid cartilages, while ih^Jiner variations of tension are produced by the thyro-arytenoid muscles. The value of the elastic tissue of the cords does not depend so much upon its extensibility, as upon its property of shortening without forming folds and creases. Pathological. — In paralysis of these muscles, the voice can only be produced by forcible expira- tion, as much air escapes through the glottis ; the tones are at the same time deep and impure. Paraly- sis of the muscle of one side causes flapping of the vocal cord on that side [Gerhardt). 5. The relaxation of the vocal cords occurs spontaneously when the stretching forces cease to act ; the elasticity of the displaced thyroid and arytenoid cartilages comes into play, and restores them to their original position. The vocal cords are also relaxed by the action of the thyro-arytenoid and lateral crico- arytenoid muscles. It is evident, from the above statements, that tension of the vocal cords and narrowing of the glottis are necessary for phonation. The tension is produced by the crico-thyroids and posterior crico-arytenoids ; the narrowing of the glottis respiratoria by the arytenoids, transverse and oblique, the glottis vocalis being narrowed by the thyro-arytenoids and (? lateral crico-arytenoids), the former muscles causing the cords themselves to become tense. Nerves (§352,5). — The crico-thyroid is supplied by the superior laryngeal branch of the vagus, which at the same time is the sensory nerve of the mucous membrane of the larynx. All the other intrinsic muscles of the larynx are supplied by the inferior laryngeal. The mucous membrane of the larynx is richly supplied with elastic fibres, and so is the sub- mucosa. The sub-mucosa is more lax near the entrance to the glottis and in the ventricles of Mor- gagni, which explains the enormous swelling that sometimes occurs in these parts in oedema glottidis. A thin, clear, limiting membrane lies under the epithelium. The epithelium is stratified, cylindrical, and ciliated with intervening goblet cells. On the true vocal cords and the anterior sur- face of the epiglottis, however, this is replaced by stratified squamous epithelium, which covers the small papillse of the mucous membrane. Numerous branched mucous glands occur over the car- LARYNGOSCOPY. 565 tilages of Wrisberg, the cushion of the epiglottis, and in the ventricles of Morgagni ; in other situa- tions, as on the posterior surface of the larynx, the glands are more scattered. The blood vessels form a dense capillary plexus under the membrana propria of the mucous membrane ; under this however, there are other two strata of blood vessels. The lymphatics form a superficial, narrow meshwork under the blood capillaries, with a deeper, coarser plexus. The medullated nerves have ganglia in their branches, but their mode of termination is unknown. [W. Stirling has described a rich sub- epithelial plexus of medullated nerve fibres on the anterior surface of the epi- glottis, while he finds that there are ganglionic cells in the course of the superior laryngeal nerve.] Cartilages. — The thyroid, cricoid, and nearly the whole of the arytenoid cartilages consist of hyaline cartilage. The two former are prone to ossify. The apex and processus vocalis of the arytenoid cartilages consist oi yellozv fibro-cartilage, and so do all the other cartilages of the larynx. The larynx grows until about the sixth year, when it rests for a time, but it becomes again much larger at puberty (? 434). Fig. 359. Vertical section through the head and neck, to the first dorsal vertebra, a, position of the laryngoscope on observing the posterior part of the glottis, arytenoid cartilages, and upper surface of the posterior wall of the larynx ; b, its position on observing the anterior angle of the glottis. Large, a, and b, small laryngoscopic 314. LARYNGOSCOPY. — Historical. — After Bozzini (1807) gave the first impulse toward the investigation of the internal cavities of the body, by illuminating them with the aid of mirrors, Babington (1829) actually observed the glottis in this way. The famous singer, Manuel Garcia (1854), made investigations both on himself and other singers, regarding the movements of the vocal cords, during respiration and phonation. The examination of the larynx by means of the laryngoscope was rendered practicable chiefly by Tiirck (1857) and Czermak, the latter observer being the first to use the light of a lamp for the illumination of the larynx. Rhinoscopy was actu- ally first practiced by Baumes (1838), but Czermak was the first person who investigated this subject systematically. 56G lilK LARYNGOSCOPE. The Laryngoscope consists of a small miiror fixed to a long handle, at an anyle of 125° to 130° (Fig. 359, a, 6). When the mouth is opened, and the tongue drawn forward, the mirror is introduced, as is shown in Fig. 360. The position of the mirror must be varied, according to the portion of the larA'nx we wish to examine ; in some cases, the soft palate has to be raised by the back of the mirror, as in the position d. A picture of the part of the larynx examined is formed in the small mirror, tiie rays of light passing in the direction indicated l)y the dotted lines from the mirror; they are retlected at the same angle through the mouth into the eye of the observer, who must place himself in tlie direction of the reflected rays. The illumination of the larynx is accomplished either by means of direct sunlight or by light from an artificial source, e.^--., an ordinary lamp, an oxyhydrogen limelight, or the electric light. Method of examining the larynx. The beam of light impinges upon a concave mirror ol 15 to 20 centimetres focus, and 10 centimetres in width, and from its surface the concentrated beam of light is reflected through the mouth of the patient, and directed upon the small mirror held in the back part of the throat. The beam of light is reflected at the same angle toward the larynx by the small throat mirror, so that the larynx is brightly illuminated. The observer has now to direct his eye in the same direction as the illumina- ting rays, which can be accomplished by having a hole in the centre of the concave mirror, through which the observer looks. I'ractically, however, this is unnecessary ; all that is necessary is to fix the concave mirror to the forehead by means of a broad elastic band, so that the observer, by looking just under the margin of the concave mirror, can see the picture of the larynx in the small throat mirror (Fig. 360). In order to examine the larj'nx, place the patient imme- diately in front of you, and cause him to open his mouth and protrude his tongue. A lamp is placed at the side of the head of the patient, and light from this source is reflected from the concave miiTor on the observer's fore- head, and concentrated upon the larj'ngoscopic mirror introduced into the back part of the throat of the patient (Fig. 360). Oertel was able by means of a rapid intermittent illu- mination of the larynx through a stroboscopic disk, to tudy the movements of the vocal cords directly with the eye. Simanowsky put a photographic camera in the po- sition of the eye and photogi-aphed the movements of the vocal cords of an artificial larynx. [Brown and Behnke have photographed the human vocal cords.] Laryngeal Electrodes. — v. Ziemssen introduces glot~tis; A. jy., true vocal cords ;. 5. iJ/., sinus long narrow electrodes into the larynx, to stimulate the Morgagni,z.z/..r., false vocal cords; /'.,po- muscles and Study their actions. Rossbach finds that the wy^^'^^il:^:^^^^^' --cles and nerves of the interior of the larynx may be stimulated by stimulatmg the skin, t. e., percutaneously. Those methods are used both for physiological and therapeutical purposes. The larynx, as seen with the laryngoscope, tongue; A"., epiglottis ; K, valleculla LARYNGOSCOPIC IMAGE. 567 Picture of the Larynx. — Fig. 361 shows the following structures: L., the root of the tongue, with the ligamentum glosso-epiglotticum continued from its middle; on each side of the latter are V. V., the so-called valleculce. The epi- glottis (-5'.) appears like an arched upper lip ; under it, during normal respiration, are the lancet-shaped glottis {J?.) and on each side of it the true vocal cords (Z.z;.). The length of the vocal cord in a child is 6 to 8 mm., in the female 10 to 15 mm. when they are relaxed, and 15 to 20 mm. when tense. In man, the lengths under the same conditions are 15 to 20 mm. and 20 to 25 mm. The breadth varies from 2 to 5 mm. On the external side of each vocal cord is the entrance to the sinus of Morgagni {S. M.'), represented as a dark line. Further upward and more external are (Z. v. s.) the upper or false vocal cords. [The upper or false vocal cords are red, the lower or true, white.] On each side of P. are {S. S.), Fig. 364. Fig. 362. Position of the vocal cords on uttering a high note. Fig. 363. View of the rings and bifurcation of trachea. Position of the laryngoscopic mirror in rhinoscopy. the apices of the cartilages of Santorini, placed upon the apices of the arytenoid cartilages, while immediately behind is the wall of the pharynx, P. In the aryteno-epiglottidean fold are (VV. W.) the cartilages of Wrisberg, while outside these are the depressions ( S.p.^ constituting the sinus piriformes. During normal respiration, the glottis has the form of a lancet-shaped slit between the bright, yellowish-white, vocal cords (Fig. 362). If a deep inspira- tion be taken, the glottis is considerably widened (Fig. 363), and if the mirror be favorably adjusted we may see the rings of the trachea, and even the bifurcation of the trachea. If a high note be uttered, the glottis is contracted to a very narrow slit (Fig. 362). 568 CONDITIONS INFLUENCING THE LARYNGEAL SOUNDS. Composite rhinoscopic view. S.n., Septum nari- um ; C.i., Cm., C.s., lower, middle, and upper turbinated bones; T, Eustachian tube; II'., tubular eminence ; R., groove of Rosenmiiller ; Rhinoscopy. — Tf a. small mirror, fixed to a handle at an angle of lOO° to llO°, be introduced into the jiharynx, as shown in V\g. 364, and if the mir- Fig. 365. ror be directed iifnoard, certain structures are with ^^ ^.^;^--- - _^^ -_ difficulty rendered visible (Fig. 365). In the middle is the septum narium {S. «.), and on each side of it the long oval large jiosterior nares (C^.), below this the soft />a/ate {P. >n.), \s\\.h the pendant uvula {U.). In the posterior nares are the posterior extremities of the lower (6".?.), middle {C.»i.), and uppev /ur/>iuiUeJ iones (C.S.). At the upper part, a jwrtion of the roof of the l^harynx (O.J?.) is seen, with the arched masses of adenoid tissue lying between the openings of the Eusta- chian tubes ( T. 7\), and called by Luschka the///«^'«- geal tonsils. External to the openings of the Eustachian tube is the tubular eminence {IV.), and outside this is the gi-oove of Rosenmiiller {^. )• Experiments on the Larynx. — Ferrein (g 741) and Job. Miiller made experiments upon the excised larynx. A tracheal tube was tied into the excised human larynx, and air was blown through it, the pres- sure being measured by means of a mercurial mano- meter, while various arrangements were adopted for fvuTa' ^"'^^ ^^''^'^ ■ '^•■^•''■°"''°'"P^">'"''- ^■' putting the vocal cords on the stretch and for opening or closing the glottis. 315. CONDITIONS INFLUENCING THE LARYNGEAL SOUNDS. — The pitch of the note emitted by the larynx depends upon — 1. The Tension of the Vocal Cords, /. e., upon the degree of contraction of the crico-thyroid and posterior crico-arytenoid muscles, and also of the internal thyro-arytenoids (§ 313, II, 4). 2. The Length of the Vocal Cords. — (a) Children and females with short vocal cords produce high notes. (/) If the arytenoid cartilages are pressed together by the action of the arytenoid muscles (transverse and oblique), so that the vocal cords alone can vibrate, while their intercartilaginous portions lying between the processus vocales do not, the tone thereby produced is higher (Gara'a). In the production of low notes, the vocal cords, as well as the margins of the arytenoid cartilages, vibrate. At the same time the space above the entrance to the glottis is enlarged and the larynx becomes more prominent, (c) Every individual has a certain medium pitch of his voice, which corresponds to the smallest possible tension of the intrinsic muscles of the larynx. 3. The Strength of the Blast. — That the strength of the blast from below raises the ])itch of the tones of the human larynx is shown by the fact, that tones of the highest pitch can only be uttered by powerful expiratory efforts. With tones of medium pitch, the ])ressure of the air in the trachea is 160 mm., with /lig/i ])itch 200 mm., and with very high notes 945 mm., and in whispering t^o mm., of water {Cagfiiard-Latour). These results were obtained in a case of tracheal fistula. Accessory Phenomena. — The following as yet but partially exjslained phenomena are observed in connection with the jjroduction of high notes : (a) As the pitch of the note rises, the larynx is elevated, partly because the muscles raising it are active, partly because the increased intra-tracheal pressure so lengthens the trachea, that the larynx is thereby raised ; the uvula is raised more and more (Labus). {b) The upper vocal cords approximate to each other more and more, without, how- ever, coming into contact, or participating in the vibrations, (c) The epiglottis inclines more and more backward over the glottis. 4. The falsetto voice with its soft timbre and the absence of resonance or pectoral fremitus in the air tubes is particularly interesting. Oertel observed that, during the falsetto voice, the vocal cords vibrated so as to form nodes across them, but sometimes there was only one node, so that the free margin of the cord and the basal margin vibrated, being separated from each other by a nodal line (par- RANGE OF THE VOICE. 569 allel to the margins of the vocal cord). During a high falsetto note, there may be three such nodal lines parallel to each other. The nodal lines are produced probably by a partial contraction of the fibres of the thyro-arytenoid muscle (p. 563), while at the same time the vocal cords must be reduced to as thin plates as possible by the action of the crico-thyroid, posterior arytenoid, thyro- and genio-hyoid muscles {Oeriel). The form of the glottis is elliptical, while with the chest voice the vocal cords are limited by straight surfaces ; the air also passes more freely through the larynx. Oertel also found that during the falsetto voice the epiglottis is erect. The apices of the aryte- noid cartilages are slightly inclined backward, the whole larynx is larger from before backward, and narrower from side to side, the aryepiglottidean folds are tense with sharp margins, and the entrance to the ventricles of Morgagni is narrowed. The vocal cords are narrower, the processus vocales toach each other. The rotation of the arytenoid cartilages necessary for this is brought about by the action of the crico- arytenoid alone, while the thyro-aiytenoid is to be regarded only as an accessory aid. The pitch of the note is increased solely by increased tension of the vocal cords. In addition, there are a number of transverse and longitudinal partial vibrations. During the chest voice, a smaller part of the margin vibrates than in the falsetto voice, so that in the production of the latter we are conscious of less muscular exertion in the larynx. The uvula is raised to the horizontal position. Production of Voice. — In order that voice be produced, the following condi- tions are necessary: (i) The necessary amount of air is collected in the chest ; (2) the larynx and its parts are fixed in the proper position \ (3) air is then forced by an expiratory effort either through the linear chink of the clossed glottis, so that the latter is forced open, or at first some air is allowed to pass through the glottis without producing a sound, but as the blast of air is strengthened the vocal cords are thrown into vibration. 316. RANGE OF THE VOICE.— The range of the human voice for chest notes is given in the following scheme : — 256 Soprano. 171 Alto. 684 EFGAB cdefgab c' d' e' f^ s:'a^b/ 1024 :tz= c//(i//e//f ^'g^/a^' \i"'ii'" 80 Bass. 342 128 Tenor. 512 The accompanying figures indicate the number of vibrations per second in the corresponding tone. It is evident that from c' to f is common to all voices, nevertheless, they have a different timbre. The lowest note or tone, which, however, is only occasionally sung by bass singers, is the contra-F, with 42 vibrations — the highest note of the soprano voice is a'" , with 1708 vibrations. Timbre. — The voice of every individual has a peculiar quality, clang, or timbre, which depends upon the shape of all the cavities connected with the larynx. In the production of nasal tones, the air in the nose is caused to vibrate strongly, so that the entrance to the nares must necessarily be open. 317. SPEECH — THE VOWELS. — The motor processes connected with the production of speech occur in the resonating cavities, the pharynx, mouth, and nose, and are directed toward the production of musical tones and noises. 570 THE FORMATION OF VOWELS. Whispering and Audible Speech. — When sounds or noises are produced in the resonating chambers, the larynx being passive, the vox clandestina, or whispering is produced ; when the vocal cords, however, vibrate at the same time, " audible speech " is produced. [Whispering, therefore, is si)eech with- out voice.] Whispering may be fairly loud, but it recjuires great exertion, /. e., a great expiratory blast for its production ; hence it is very fatiguing. It may be performed both with inspiration and expiration, while audible speech is but tem- porary and indistinct, if it is produced during inspiration. Whispering is caused by the sound produced by the air passing over the obtuse margins of the cords. During the production of audible soimds, however, the sharp margins of the vocal cords are directed toward the air by the position of the processus vocales. During speech the soft palate is in action ; at each word it is raised, while at the same time, Passavant's transverse band is formed in the pharynx (§ 156). The soft palate is raised highest when u and i are sounded, then with 0 and e, and least with a. When sounding m and n it does not move; it is high (like n) during the utterance of the explosives. With 1, s, and especially with the guttural r, it exhibits a trembling movement [Gentzen, Falkson). Speech is composed of vowels and consonants. A. Vowels (analysis and artificial formation, § 415). — A. During whisper- ing, a vowel is the musical tone produced, either during expiration or inspiration, by the inflated characteristic form of the mouth, which not only has a definite pitch, but also a particular and characteristic timbre. The characteristic form of the mouth may be called ^^ vowel cavity. '' I. The pitch of the vowels may be estimated musically. It is remarkable that the funda- mental tone of the " vowel cavity" is nearly constant at different ages and in the sexes. The different capacities of the mouth can be compensated for by different sizes of the oral aperture. The pitch of the vowel cavity may be estimated by placing a number of vibrating tuning forks of different pitch in front of the mouth, and testing them until we find the one which corresponds with the fundamental tone of the vowel cavity. This is known by the fact that the tone of the tuning-fork is intensified by the resonance of the air in the mouth, or the vibrations may be trans- ferred to a vibrating membrane and recorded on a smoked surface, as in the phonautograph of Bonders. According to Konig, the fundamental tones of the vowel cavity are for U = b, O = b', A = b", E = \J", I = b"". If the vowels be whispered in this series, we find at once that their pitch rises. The fundamental tone in the production of a vowel may vary within certain limits. This may be shown by giving the mouth the characteristic position and then per- cussing the cheeks {Aiierbach) ; the sound emitted is that of the vowel, wliose pitch will vary according to the position of the mouth. When sounding A, the mouth has the form of a funnel widening in front (Fig. 366, A). The tongue lies in the floor of the mouth, and the lips are wide open. The soft palate is moderately raised [Czermak). It is more elevated successively with O, E, U, I. The hyoid bone appears as if at rest, but the larynx is slightly raised. It is higher than with U, but lower than with I. If we sound A to I, the larynx and the hyoid bone retain their relative position, but both are raised. In passing from A to U, the larynx is depressed as far as possible. The hyoid bone passes slightly forward {Briic/ie). When sounding A, the space between the larynx, posterior wall of the pharynx, soft palate, and the root of the tongue, is only moderately wide ; it becomes wider with E, and especially with I (I'ur/cinje), but it is smallest with U. When sounding U (Fig. 366), the form of the cavity of the mouth is like that of a capacious flask with a short, narrow neck. The whole resonance apparatus is then longest. The lips are protruded as far as possible, are arranged in folds and closed, leaving only a small opening. The larynx is depressed as far as possible, while the root of the tongue is approximated to the posterior margin of the palatine arch. When sounding O, the mouth, as in U, is like a wide-bellied flask with a short neck, but the latter is shorter and wider as the lips are nearer to the teeth. The larynx is slightly higher than with U, while the resonance chambers also are shorter (Fig. 366). When sounding I, the cavity of the mouth, at the posterior part, is in the form of a small-bellied flask with a long narrow neck, of which the belly has the fundamental tone, f, the neck that of d^''. The resonating chambers are shortest, as the larynx is raised as much as possible, while the mouth, DIPHTHONGS AND NASAL TIMBRE OF VOWELS. 571 owing to the retraction of the lips, is bounded in front by the teeth. The cavity between the hard palate and the back of the tongue is exceedingly narrow, there being only a median narrow slit. Hence, the air can only enter with a clear piping noise, which sets even the vertex of the skull in vibration, and when the ears are stopped the sounds seem very shrill. When the larynx is depressed and the lips protruded, as for sounding U, I cannot be sounded. When sounding E, which stands next to I, the cavity has also the form of a flask with a small belly (fundamental tone, F), and with a long, narrow neck (fundamental tone, \>'"'). The neck is wider, so that it does not give rise to a piping noise. The larynx is slightly lower than for I, but not so high as for A. Fundamentally, there are only three pri77tary vowels — I, A, U, the others and the so-called diph- thongs standing between them \Brucke). Diphthongs occur when, during vocalization, we pass from the position of one vowel into that of another. Distinct diphthongs are sounded only on passing from one vowel with the mouth wide open to one with the mouth narrow ; during the converse process, the vowels appear to our ear to be separate (^Brilcke). II. Timbre or Clang Tint. — Besides its pitch, every vowel has a special timbre, quality, or clang tint. The vocal timbre of U (whispering) has, in addition to its fundamental tone, b, a deep piping timbre. The timbre depends upon the number and pitch of the partials or overtones of the vowel sound {\ 415). Fig. ^66. Section of the parts concerned in phonation. Z, tongue ; /, soft palate; .f, epiglottis ; ^.glottis; ,4, hyoid bone; i, thyroid, 2, 3, cricoid, 4, arytenoid cartilage. Nasal Timbre. — The timbre is modified in a special manner when the vowels are spoken with a " nasal" twang, which is largely the case in the French language. The nasal timbre is produced by the soft palate not cutting off the nasal cavity completely, which happens every time z. pure vowel is sounded, so that the air in the nasal cavity is thrown into sympathetic vibration. When a vowel is spoken with a nasal timbre, air passes out of the nose and mouth simultaneously, while with a pure vowel sound, it passes out only through the mouth. When sounding a pure vowel (non-nasal), the shutting off of the nasal cavity from the mouth is so complete, that it requires an artificial pressure of 30 to 100 mm. of mercury to overcome it \^Hartman7i). The vowels, a, a (se), 6 (ce), o, e, are used with a nasal timbre — a nasal i does not occur in any language. Certainly it is very difficult to sound it thus, because when sounding i, the mouth is so narrow that when the passage to the nose is open, the air passes almost completely through the latter, while the small amount passing through the mouth scarcely suffices to produce a sound. In sounding vowels, we must observe if they are sounded through a previously closed glottis, as is done in the German language in all words beginning with a vowel (spiritus lenis). The glottis, however, may be previously opened with a preliminary breath, followed by the vowel sound; we obtain the aspirate vowel (spiritus asper of the Greeks). B. If the vowels are sounded in an audible tone, /. «?., along with the sound from the larynx, the fundamental tone of the vocal cavity strengthens in a charac- teristic manner the corresponding partial tones present in the laryngeal sound {Wheatstone, v. Helmholtz). 572 CLASSIFICATION OF CONSONANTS. 318. CONSONANTS.— The consonants are noises which are produced at certain parts of the resonance chamber. [As their name denotes, they can only be sounded in conjunction with a vowel.] ClassiBcation. — The most obvious classification is according to (I) Their acoustic properties, so that they are divided into (i) liquid consonants, i. e., such as are appreciable without a vowel (m, n, 1, r, s) ; (2) viutes, including all the others, which cannot be distinctly heard without an accom. panying vowel. (II) According to their mechanistn of fonnation, as well as the type of the organ of speech, by whicli ihey are produced. They are divided into — 1. Explosives. — Their enunciation is accompanied by a kind of bursting open of an obstacle, or an explosion, occasioned by the confined and compressed air which causes a stronger or weaker noise ; or, conversely, the current of air is suddenly interrupted, while, at the same lime, the nasal cavities are cut off by the soft palate. 2. Aspirates, in which one part of the canal is constricted or stopped, so that the air rushes out through the constriction, causing a faint whistling noise. (The nasal cavity is cut off.) In uttering T, which is closely related to the aspirates, but differs from them in that the narrow passage for the rush of air is not in the middle, but at both sides of the middle of the closed part. (The nasal cavity is shut off.) 3. Vibratives, which are produced by air being forced through a narrow portion of the canal, so that the margins of the narrow tube are set in vibration. (The nasal cavity is shut off.) 4. Resonants (also called nasals or semi-vowels). The nasal cavity is completely free, while the vocal canal is completely closed in the front part of the oral channel. According to the position of the obstruction in the oral cavity, the air in a larger or smaller portion of the mouth is thrown into sympathetic vibration. We may also classify them according to the position in 7vhich ihey are produced — the " articulation positions " of Briicke. These are : — A. Between both lips ; B, between the tongue and the hard palate ; C, between the tongue and the soft palate ; D, between the true vocal cords. A. Consonants of the First Articulation Position. 1. Explosive Labials. — b, the voice is sounded before the slight explosion occurs; p, the voice is sounded after the much stronger explosion has taken place {A'empeleft). [The former is spoken of as " voiced " and the latter as " breathed."] 2. Aspirate Labials. — f, between the upper incisor teeth and the lower lip (labio-dental). It is absent in all true .Slavic words {Pttrkine) ; v, between both lips (labial) ; w is formed when the mouth is in the position for f, but instead of merely forcing in the air, the voice is sounded at the same time. Really there are two different w — one corresponding to tlie labial f, as in wiirde, and the labiodental, e. g., quelle (Briicke). 3. Vibrative Labials. — The burring sound, emitted by grooms, but not used in civilized language. 4. Resonant Labials. — m is formed essentially by sounding the voice whereby the air, in the mouth and nose, is thrown into sympathetic vibration [" voiced "]. jB. Consonants of the Second Articulation Position. 1. The explosives, when enunciated sharply and witliout the voice, are T hard (also dt and th); when they are' feeble and produced along with simultaneous laryngeal sounds (voice), we have D soft. 2. The aspirates embrace S, including s sharp, written s s or s z, which is produced without any audible laryngeal vibration ; or soft, which requires the voice. Then, also, there are modifica- tions according to the position where the noises are produced. The shaip aspirates include Sch, and the hard English Th ; to the soft belong the French J soft, and the English Th soft. L, which occurs in many modifications, appears here, e.g., the L soft of the French. L may be sounded soft with the voice, or sharp without it. 3. The vibrative, or R, which is generally voiced, but it can be formed without the larynx. The resonants are N sounds, which also occur in several modifications. C. Consonants of the Third Articulation Position. 1. The explosives are the K sounds, which are hard and breathed and not voiced; G sounds, which are voiced. 2. The aspirates, when hard and breathed but not voiced, the Ch, and when sounded softly and not voiced, J is formed. 3. The vibrative is the palatal R, which is produced by vibration of the uvula [Briicke). 4. The resonant is the palatal N. PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH. 573 D. Consonants of the Fourth Articulation Position. t. An explosive sound does not occur when the glottis is forced open, if a vowel is loudly- sounded with the glottis previously closed. If this occurs during whispering, a feeble short noise, due to the sudden opening of the glottis, may be heard. 2. The aspirates of the glottis are the H sounds, which are produced when the glottis is moder- ately wide. 3. A glottis vibrative occurs in the so-called laryngeal R of lower Saxon {^Brilcke). 4. A laryngeal resonant cannot exist. The combination of different consonants is accomplished by the successive movements necessary for each being rapidly executed. Compound consonants, however, are such as are formed when the oral parts are adjusted simultaneously for two different consonants, so that a mixed sound is formed from two. Examples: Sch — tsch, tz, ts — Ps (1/') — Ks (XS). 319. PATHOLOGICAL VARIATIONS OF VOICE AND SPEECH.— Aphonia.— Paralysis of the motor nerves (vagus) of the larynx by injury, or the pressure of tumors, causes aphonia or loss of voice [Galen). In aneurism of the aortic arch, the left recurrent nerve may be paralyzed from pressure. The laryngeal nerves may be temporarily paralyzed by rheumatism, over-exertion, and hysteria, or by serous effusions into the laryngeal muscles. If the tensors are paralyzed, monotonia is the chief result : the disturbances of respiration in paralysis of the larynx are important. As long as the respiration is tranquil, there may be no disturbance, but as soon as increased respiration occurs, great dyspnoea sets in, owing to the inability of the glottis to dilate. If only one vocal cord is paralyzed, the voice becomes impure and falsetto-like, while we may feel from without that there is less vibration on the paralyzed side [Gerhardt)^ Sometimes the vocal cords are only so far paralyzed that they do not move during phonation, but do so during forced respiration and during coughing (phonetic paralysis). Diphthongia. — Incomplete unilateral paralysis of the recurrent nerve is sometimes followed by a double tone, owing to the unequal tension of the two vocal cords. According to Tiirck and Schnitzler, however, the double tone occurs when the two vocal cords touch at some part of their course [e.g., from the presence of a tumor. Fig. 367), so that the glottis is divided into two unequal portions, each of which produces its own sound. Hoarseness is caused by mucus upon the vocal cords, by roughness, swelling, or laxness of the cords. If, while speaking, the cords are approximated, and suddenly touch each other, the "speech is broken," owing to the formation of nodal points (^ 352). Disease of the pharynx, naso-pharyngeal cavity, and uvula may produce a change in the voice reflexly. Paralysis of the soft palate (as well as congenital perforation or cleft palate) causes a nasal timbre of all vowels; the former renders difficult the normal formation of consonants of the third articulation position ; resonance is imperfect, while the explosives are weak, owing to the escape of the air through the nose. Paralysis of the tongue weakens I; E and A (^) are less easily pronounced, while the formation of consonants of the second and third articulation position is affected. The term aphthongia is applied to a condition in which every attempt to speak is followed by spasmodic movements of the tongue {^Fleury'). In paralysis of the lips [facial nerve), and in hare-lip, regard must be had to the fonnation of consonants of the first articulation position. When the nose is closed, the speech has a characteristic sound. The normal formation of resonants is of course at an end. After excision of the larynx, a metal reed, enclosed in a tube, and acting like an artificial larynx, is introduced t;^^^,^ ^^ the^cal cords causing between the trachea and the cavity of the mouth [Czerny). double tone from the larynx. Stammering is a disturbance of the formation of sounds. [Stammering is due to long-continued spasmodic contraction of the diaphragm, just as hiccough is (^ 120), and, therefore, it is essentially a spasmodic inspiradon. As speech depends upon the expiratory blast, the spasm prevents expiration. It may be brought about by mental excitement or emotional conditions. Hence, the treatment of stammering is to regulate the respirations. In stutter- ing, which is defective speech due to inability to form the proper sounds, the breathing is normal.] 320. COMPARATIVE — HISTORICAL. — Speech may be classified with the " expression of the emotions" [Darwin). Psychical excitement causes in man characteristic movements, in which certain groups of muscles are always concerned, e.g., laughing, weeping, the facial expression in anger, pain, shame, etc. These movements afford a means whereby one creature can communicate with another. Primarily in their origin, the movements of expression are reflex motor phenomena; when they are produced for purposes of explanation, they are voluntary imitations of this reflex. Besides the emotional movements, impressions upon the sense organs produce characteristic reflex movements, which may be used for purposes of expression [Geiger),e. g., stroking or painful stimula- tion of the skin, movements after smelling pleasant or unpleasant or disagreeable odors, the action of sound and light, and the perception of all kinds of objects. 574 COMPARATIVE AND HISTORICAL. The expression of the emotions occurs in its simjilest form in what is Icnown as expression by means of signs or pantomime or mimicry. Another means is the imitation of sounds by the organ of speech, constituting onainatopoesy, e.g., the hissing of a stream, the roll of thunder, the tumult of a storm, whistling, etc. The expression of speech is, of course, dependent upon the jiro- cess of ideation and perception. The occurrence of different sounds in different languages is very interesting. Some languages {e. ^., of the Hurons) have no labials ; in some .South Sea Islands, no laryngeal sounds are spoken; / is absent in Sanscrit and Finnish ; the sliort e, o, and the soft sibilants in Sanscrit ; d, in Chinese and Mexican; s, in many Polynesian languages; r, in Chinese, etc. Voice in Animals. — Animals, more especially the higher forms, can express their emotions by facial and other gestures. The vocal organs of mammals .ire es.sentially the .same as tho.se of man. Special resonance organs occur in the orang-outang, mandril, macacus, and mycetes monkeys, in the form of large cheek pouches, which can be inflated with air, and open between the larynx and the hyoid bone. Birds have an upper (larynx) and a lower larynx (syrinx) ; the latter is placed at the bifurcation of the trachea, and is the true vocal organ. Two folds of mucous membrane (three in singing birds) project into each bronchus, and are rendered tense by muscles, and are thus adapted to serve for the production of voice. .\mong reptiles, the tortoises produce merely a sniffing sound, which in the Emys has a peculiar piping character. The blind snakes are voiceless, the chameleon and the lizards have a very feeble voice ; the cajnnan and crocodile emit a feeble roaring sound, which is lost in some adults owing to changes in the larynx. The snakes have no special vocal organs, but by forcing out air from their capacious lung, they make a peculiar hissing sound, which in some species is loud. Among amphi- bians, the frog has a larynx provided with muscles. The sound emitted without any muscular action is a deep intermittent tone, while more forcible expiration, with contraction of the laryngeal constrictors, causes a clearer continuous sound. The male, in Rana esculenta, has at each side of the angle of the mouth a sound bag, which can be inflated with air and acts as a resonance chamber. The " croaking " of the male frog is quite characteristic. In Pipa, the larynx is provided with two cartilaginous rods, which are thrown into vibration by the blast of air, and act like vibrating rods or the limbs of a tuning fork. Some fishes emit sounds, either by rubbing together the upper and lower pharyngeal bones, or by the expulsion of air from the swimming bladder, mouth, or anus. Some insects cause sounds partly by forcing the expired air through their stigmata provided with muscular reeds, which are thus thrown into vibration (bees and many diptera). The wings, owing to the rapid contraction of their muscles, may also cause sounds (flies, cockroach, liees). The Sphinx atropos (death-head moth) forces air from its sucking stomach. In others, sounds are pro- duced by rubbing their legs on the wing cases (Acridium), or the wing cases on each other (Gryllus, locust), or on the thorax (Cerambyx), on the leg (Geotrupes), on the abdomen or the margin of the wing (Nekrophorus). In CicadacicC, membranes are pulled upon by muscles, and are tlms caused to vibrate. Friction sounds are produced between the cephalo-thorax and the abdomen in some spiders (Theridium), and in some crabs (Palinurus). Some moUusca (Pecten) emit a sound on separating their shells. Historical. — The Hippocratic School was aware of the fact that division of trachea abolished the voice, and that the epiglottis prevented the entrance of food into the larynx. Aristotle made numerous observations on the voice of animals. The true cause of the voice escaped him as well as Galen. Galen observed complete loss of voice after double pneumothorax, after section of the intercostal muscles or their nerves, as well as after destruction of part of the spinal cord, even although the diaphragm still contracted. He gave the cartilages of the larynx the names that still distinguish them; he knew some of the laryngeal muscles, and asserted that voice was produced only when the glottis was narrowed. He compared the larynx to a flute. The weakening of the voice, in feeble conditions, especially after loss of blood, was known to the ancients. Dodart (ijcxj) was the first to explain voice as due to the vibration of the vocal cords by the air passing between them. The production of vocal sounds attracted much attention among the ancient Asiatics and Arabians — less among the Greeks. Pietro Ponce (11584) was the first to advocate instruction in the art of speaking in cases of dumbness. Bacon (1638) studied the shape of the mouth for the pronunciation of the various sounds. Kratzenstein (1781) made an artificial apparatus for the production of vowel sounds, by placing resonators of various forms over vibrating reeds. Von Kempelen (1769 to 1791) constructed the first speaking machine. Rob. Willis (1828) found that an ela.stic vibrating spring gives the vowels in the series — U, O, A, E, I — according to the depth or height of its tone ; further, that by lengthening or shortening an artificial resonator on an artificial vocal apparatus, the vowels may be obtained in the same series. The newest and most important investigations on speech are by Wheatstone, v. Helmholtz, Bonders, Brucke, etc., and are mentioned in the context. Hensen suc- ceeded in showing exactly the pitch of vocal tone, thus : The tone is sung against a Konig's capsule with a gas flame. Opposite the flame is placed a tuning fork vibrating horizontally, and in front of one of its limbs is a mirror, in which the image of the flame is reflected. When the vocal tone is of the same number of vibrations as the tuning fork, the flame in the mirror shows one elevation, if double, i.e., the octave, 2, and with the double octave, 4 elevations. General Physiology of the Nerves AND Electro-Physiology. 321. STRUCTURE OF THE NERVE ELEMENTS.— Thenervous elements present two distinct forms : — I. Nerve Fibres. { m ^^-'^fl'ff ^^'^- II. Nerve Cells, j Of radons forms [ Medullated. ( and functions. An aggregation of nerve cells constitutes a nerve ganglion. The yf<^r^j- repre- sent a conducti?ig apparatus, and serve to place tlie central nervous organs in connection with peripheral end organs. The nerve cells, however, besides trans- mitting impulses, act as physiological cenlres for automatic or reflex movements, and also for the sensory, perceptive, trophic, and secretory functions. I. (i) The non-medullated nerve fibres occur in several forms: — 1. Primitive Fibrils. — The simplest form of nerve fibre, which is visible with a magnifying power of 500 to 800 diameters linear, consists of primitive nerve fibrils. They are very delicate fibres (Fig. 368, i), often with small varicose swellings here and there in their course, which, how- ever, are due to ch.a.ng&s pos(-mo7'tent. They are stained of a brown or purplish color by the gold chloride method, and they occur when a nerve fibre is near its termination, being formed by the splitting up of the axis cylinder of the nerve fibre, e. g., in the terminations of the corneal nerves, the optic nerve layer in the retina, the terminations of the olfactory fibres, and in a plexiform arrangement in non-striped muscle (p. 510). Similar fine fibrils occur in the gray matter of the brain and spinal cord, and in the finely divided processes of nerve cells. 2. Naked or simple axial cylinders (Fig. 368, 2), which represent bundles of primitive fibrils held together by a slightly granular cement, so that they exhibit very delicate longitudinal striation with fine granules scattered in their course. The best example is the axial cylinder process of nerve cells (Fig. 368, I, z). [The thickness of the axis cylinder depends upon the number of fibrils entering into its composition.] 3. Axis cylinders surrounded with Schwann's sheath, or Remak's fibres (3.8 to 6.8 fi broad), the latter name being given to them from their discoverer (Fig. 368, 3). [These fibres are also called pale or non-medullated, and from their abundance in the sympathetic nervous system, sympathetic. '\ They consist of a sheath, corresponding to Schwann's sheath [neurilemma, or primitive sheath, which encloses an axial cylinder; while lying here and there under the sheath, and between it and the axial cylinder are nerve corpuscles. These fibres are always fibrillated longitudi- nally]. The sheath is delicate, structureless, and elastic. Dilute acids clear the fibrils without causing them to swell up, while gold chloride makes them brownish-red. They are widely distributed in the sympathetic nerves, \^e.g., splenic], and in the branches of the olfactory nerves. All nerves in the embryo, as well as the nerves of many invertebrata, are of this kind. [Accord- ing to Ranvier, these fibres do not possess a sheath, but the nuclei are merely applied to the surface, or slightly embedded in the superficial parts of the fibre, so that they belong to the fibre itself These fibres also branch and form an anastomosing network (Fig. 370). This the medullated fibres never do. These fibres, when acted on by silver nitrate, never show any crosses. The branched forms occur in the ordinary nerves of distribution, and they are numerous in the vagus, but the olfac- tory nerves have a distinct sheath which is nucleated.] (2) Medullated fibres occur also in several forms : — 4. Axis cylinders, or nerve fibrils, covered only by a medullary sheath, or white substance of Schwann, are met with in the white and gray matter of the central nervous system, in the optic and auditory nerves. These medullated nerve fibres, without any netirilemma, often show after death, varicose swellings in their course [due to the accumulation of fluid between the medulla of myelin and the axis cylinder.] Hence they are called varicose fibres. [The varicose appearance is easily produced by squeezing a small piece of the white matter of the spinal cord between a slide 575 570 STRUCTURE OF NERVE FIBRES. and a cover glass. Nitrate of silver does not reveal any crosses, and there are no nodes of Ranvier. When acted upon by coagulating reagents, ^. ,;•-., chromic acid, the medullary sheath appears lami- nated, so that on transverse section, when the axis cylinder is stained, it is surrounded by concentric circles (Fig. .>69). 5. Meduliated Nerve Fibres with Schwann's Sheath (Fig. 36S, 5, 6).— These are the most Fig. 368. 1, Primitive fibrillae ; 2, axis cylinder; 3, Remak's fibres ; 4, meduUaf^d varicose fibre ; 5, 6, meduliated fibre, with Schwann's sheath : c, neurilemma ; t, t, Ranvier's nodes ; b, white substance of Schwann ; d, cells of the en- doneurium ; a, axis cylinder ; x, myelin drops; 7, transverse section of nerve fibres ; 8, nerve fibre acted on with silver nitrate and showing Fromann's lines. I, multipolar nerve cell from the spinal cord ; z, axial cylinder pro- cess ; ^.protoplasmic processes— to the right of it a bipolar cell. II, peripheral ganglionic cell, with a con- nective-tissue capsule. Ill, ganglionic cell, with o, a spiral, and n, straight process ; m, sheath. complex nerve fibres, and are lo to 22.6 }i [77^50 *o sA 0 inch] broad. They are most numerous in, and in fact they make up the great mass of, the cerebro-spinal nerves, although they are also present in the sympathetic nerves. [WTien examined in the fresh and living condition m siiu, they appear refrac- tive and homogeneous [Ranvier, Stirling) ; but if acted upon by reagents, they are not only refractive, but exhibit a double contour, the margins being dark and well defined.] Each fibre consists of — STRUCTURE OF NERVE FIBRES. 577 [i. Schwann's sheath, neurilemma, or primitive sheath ; 2. White substance of Schwann, medullary sheath, or myelin ; 3. Axis cylinder composed of fibrils and surrounded by a sheath called the axilemma ; 4. Nerve corpuscles.] A. The axis cylinder, which occupies ^ to i of the breadth of the fibre, is the essential part of the nerve, and lies in the centre of the fibre like the wick in the centre of a candle (Fig. 368, 6, a). Its usual shape is cylindrical, but sometimes it is flattened or placed eccentrically — [this is most probably due to the hardening process employed]. It is composed oi fibrils [united by cement or stroma; they become more obvious near the terminations of the nerve, or after the action of reagents, which sometimes cause the fibrils to appear beaded. It is quite transparent, and stains deeply with carmine or logwood], while during life, its consistence is semi-fluid. According to Kupffer, a fluid — " neuroplasma " — lies between the fibrils [while, according to other observers, the whole cylinder is enclosed in an elastic sheath peculiar to itself and composed of neuro-keratin. This sheath is called by Kiihne, the axilemma. Each axis cylinder is an enormously long process of a ganglionic cell]. Fromann's Lines. — Chloroform and collodion render it visible, while it is most easily isolated as a solid rod, by the action of nitric acid with excess of potassium chlorate. When acted on by silver nitrate, Fromann observed transverse markings on it, but their significance is unknown (Fig. 368, 8). B. The white substance of Schwann, medullary sheath or myelin, surrounds the axis cylinder, like an insulating medium around an electric wire. In the perfectly fresh condition it is quite homogeneous, highly glistening, bright, and refractive ; its consistence is fluid, so that it oozes out of the cut ends of the fibres in spherical drops (Fig. 368, x) [myelin drops, which are always marked by concentric lines, are highly refractive, and best seen when a fresh nerve is teased in salt solution]. After death, or after the action of reagents, it shiinks slightly from the sheath, so that the fibres have a double contour, while the substance itself breaks up into smaller or larger droplets, due not to coagulation [Pertik], but, according to Toldt, to a process like emulsification, the drops pressing against each other. Thus the fibre is broken up into masses, so that it has a characteristic appearance (Fig. 368, 6). It contains a large amount of cerebrin and lecithin, which swell up to form myelin-like forms in warm water. It also contains fatty matter, so that these fibres are black- ened by osmic acid [while boiling ether extracts cholesterin from them]. Chloroform, ether, and benzin, by dissolving the fatty and some other constituents of the fibres, make them very trans- parent. [Some observers describe a fluid lying between the medulla and the axis cylinder.] C. The Sheath of Schwann or the neurilemma, lies immediately outside of and invests the white sheath (Fig. 368, 6, c'), and is a delicate structureless membrane, comparable to the sarcolemma of a muscular fibre. D. Nerve Corpuscles. — At fairly wide intervals under the neurilemma, and lying in depressions between it and the medullary sheath, are the nucleated nerve corpuscles, which are readily stained by pigments (Fig. 371). [They may be compared to the muscle corpuscles, the nuclei being sur- rounded by a small amount of protoplasm which sometimes contains pigment. They are not so numerous as in muscle.] [Adamkiewicz describes nerve corpuscles, or " demilunes " under the neurilemma, quite distinct from the ordinary nerve corpuscles. They are stained yellow by safranin, while the ordinary nerve corpuscles are stained by methylanilin.] Ranvier's Nodes or Constrictions. — The neurilemma forms in broad fibres at longer, and in narrower ones at shorter intervals, the nodes ox constrictions of Ranvier (Fig. 368, 6, t, t ; Fig. 37I; Fig. 372, /yj. They are constrictions which occur at regular intervals along a nerve fibre; at them the white substance of Schwann is interrupted, so that the sheath of Schwann lies upon the axis cylinder [or its elastic sheath] at the nodes. The part of the nerve lying between any two nodes is called an inter-annular or inter-nodal segynent, and each such segment contains one or more nuclei, so that some observers look upon the whole segment as equivalent to one cell. The function of the nodes seems to be to permit the diffusion of plasma through the outer sheath into the axis cylinder, while the decomposition products are similarly given off. [A coloring matter like picro-carmine diffuses into the fibre only at the nodes, and stains the axis cylinder red, although it does not diffuse through the white substance of Schwann.] Incisures (of Schmidt and Lantermann). — Each inter- annular segment in a stretched nerve shows, running across the white substance, a number of oblique lines, which are called incisures (Figs. 372, 373). They indicate that the segment is built up of a series of conical sections, each of which is beveled at its ends, and the bevels are arranged in an imbricate manner, the one over the other, while the slight interval between them appears as an incisure. Each such section of the white matter is called a cylinder cone {^Kiihnt). Neuro-Keratin Sheath. — According to Ewald and Kiihne, the axis cylinder, as well as the white subtance of Schwann, is covered with an excessively delicate sheath, consisting of netiro-keratin, and the two sheaths are connected by numerous transverse and oblique fibrils, which permeate the white substance. [The myelin seems to lie in the interstices of this meshwork.] [Rod-like Structures in Myelin. — If a nerve be hardened in ammonium ckromate {or picric acid), M'Carthy has shown that the myelin exhibits rod-hke structures, radiating from the axis 37 578 STRUCTURE OF NERVE FIBRES, Fig. 369. Fir.. 371. I^'iG. 373- a— Node of jj Fig. 372. Ranvier Primitive „ _ Sheath. JV1 A MeduUated nerve White fibres blackened Sub- by osmic acid, stance of /s, R a n v i e r ' s Schwann, node: s c h , Schwann's sheath. -P "-iii s- Node of Ranvier. \k MeduUated nerve fibres with osmic acid. a, axis cylinder; s, sheath of Schwann : n, nucleus ; /,/, granular substance at the poles of the nucleus ; >-, r, Ranvier's nodes where the medullary sheath is interrupted and the axis cylinder appears ; i, i, incisures of Schmidt, Remak's fibre from vagus of dog. 6, fibrils ; «, nucleus ; /, proto- plasm surrounding it. MeduUated nerve fibre of a rab- bit acted on by osmic acid, X 400, STRUCTURE OF NERVE FIBRES. 579 Fig. 374. cylinder outward, which are stained with logwood and carmine. The rods are probably not distinct from each other, but are perhaps part of the neuro- keratin network already described.] Action of Nitrate of Silver. — When a small nerve, e.g., the intercostal nerve of a mouse, is acted on by silver nitrate, it is seen to be covered by an endothelial sheath composed of flattened endothelial cells (Fig. 374), while the nerve fibres themselves exhibit crosses along their course. These crosses are due to the penetration of the silver solution at the nodes, where it stains the cement substance and also part of the axis cylinder, so that the latter sometimes exhibits transverse mark- ings called Fromann's lines (Fig. 368, 8).] [New Methods. — Much progress has recently been made in tracing the course of medullated nerve fibres by the aciion of new staining reagents ; thus acid fuchsin stains the myelin deeply, leav- ing the other parts unstained, at least it can be so manipulated as to yield this result. Weigert's Method and its modifications have yielded most important results, and proved that medullated nerve fibres exist in many parts of the central nervous system where they cannot be seen in the ordinary way. The nerve tissue is hardened in a solution of a chromium salt, and placed in a half- saturated solution of cupric acetate; it is then stained with logwood, and afterward the elements are differentiated by steeping the sections in a solution of ferricyanide of potash and borax. The myehn is colored a logwood tint.] In the spinal nerves, those fibres are thickest which have the longest course before they reach their end organ [Schivalbe), while those ganglion cells are largest which send out the longest nerve fibres {Pierret). [Gaskell finds that the longest nerves are not necessarily the thickest, for the visceral nerves in the vagus are small nerves, and yet run a very long course.] Division of Nerves. — Nerve fibres run in the nerve trunks without dividing; but when they approach their termination they intercostal nerve of a mouse (single often divide dichotoraously [at anode], giving rise to two similar fasciculus of nerve fibres) stained fibres, but there may be several branches at a node (Fig. 376, /). with silver nitrate. Endothelial n^i J.-- . , it-j IT sheath stained, and some nodes of [The divisions are numerous in motor nerves to striped muscles.] Ranvier indicated by crosses. In the electrical nerves of the malapterurus and gymnotus, there is a gr^at accumulation of Schwann's sheaths round a nerve, so that a nerve fibre is as thick as a sewing needle. Such a fibre, when it divides, breaks up into a bundle of smaller fibres. Fig ^^-^%:#^^i' Trans, section of a nerve (median), ep, epineurium; ^e, perineurium; ed, endoneurium. [Nerve Sheaths. — A nerve trunk consists of bundles of nerve fibres. The bundles are held together by a common connective-tissue sheath (Fig. 375, ep), the epineurium which contains the larger blood vessels, lymphatics, and sometimes fat and plasma cells. Each bundle is surrounded 580 STRUCTURE OF NERVE FIBRES. with its own sheath or perineurium (/c), which consists of lamellated connective tissue disjx>sed circularly, and between the lamelLv are lymph spaces lined by flattened endothelial plates. These lymph spaces may be injected from and communicate with the lymphatics [Axel Key and Ketzius).'\ The nerve tibres within any bundle are held together by delicate connective tissue, which penetrates between the adjoininjj tibres, constituting the endoneurium (cv/). It consists of delicate fibres with branched connective-tissue corpuscles (Fig. 36S. 6, d), ami in it lie the capillaries, which are not very numerous, and are arranged to form elongated open meshes. [Henle's Sheath. — When a nerve is traced to its distribution, it branches and becomes smaller, until it may consist only of a few bundles or even a single bundle of nerve fibres. As the bundle branches, it has to give off part of its lamellated sheath or ])erineurium to each branch, so that, as we pass to the periphery, the smaller bundles are surrounded by few lamelhi;. In a bundle contain- ing only a few fibres, this sheath may be much reduced, or m.iy consist only of thin, flattened, con- nective-tissue corpuscles with a few fibres. A .sheath surrounding a few nerve fibres is called Henle's Shealh by Ranvier.] [Nervi Nervorum. — Marshall and v. Ilorsley have shown that the nerve sheaths are provided with special nerve fibres, in virtue of which they are endowed with sensibility.] Development. — At first nerve fibres consist only of fibrils, i.e., of axis cylinders, which become covered with connective substance, and ultimately the white substance of Schwann is developed in some of them. The growth in length of the fibres takes place by elongation of the individual " mter-annular " segments, and also by the new formation of these ( Vii^nal^. II. Ganglionic or Nerve Cells. — i. Multipolar nerve cells (Fig. 368, I) occur partly as large cells (loo //), and are visible to the unaided eye as in the anterior horn of the .spinal cord, and in a differ- ent form in the cerel)ellum, and partly in a smaller form (20 to 10 ^i) in the posterior horns of the spinal cord, many parts of the cerebrum and cerebellum, and in the retina. They may be spherical, ovoid, pyramidal [cerebrum], pear- or flask-shaped [cerebellum], and are provided with numerous branched processes which give the cells a characteristic appearance. [Deiters isolated such cells from the anterior horn of the gray matter of the .spinal cord, so that this special form of cell is sometimes called " Deiters' cell " (Fig. 368, I).] They are devoid of a cell envelope, are of soft consistence, and exhibit a fibrillated structure, which may extend even into the processes. Fine granules lie scattered throughout the . cell substance between the fibrils. Not unfrequently yellow or brown granules of pigment are also found, either collected at certain parts in the ceM or scattered throughout it. The relatively large nucleus consists of a clear envel- ope enclosing a resistant substance. It does not appear to have a membrane in youth [Schzvallie). Within the nucleus lies the nucleolus, which in the recent condition is angular, provided with processes and capable of motion, but after death is highly refractive and spherical. There is always one unbranched process, constituting the axial cylinder process (I, :) which remains unbranched, but it soon be- comes covered with the substance of Schwann, and the other sheaths of a medullated nerve, so that it becomes the axial cylinder of a nerve fibre. [Thus a nerve fibre is merely an excessively long, un- branched process of a nerve cell pushed outward toward the peri- phery.] It is not definitely ascertained that the cerebral cells have such processes. All the other processes divide very frequently until they form a branched, root -like, complex arrangement of the finest primitive fibriks. These are called protoplasmic processes (I, _)/). By means of these processes, adjoining cells are brought into commu- nication with each other, so that impulses can be conducted from one cell to another. Further, many of these fibrils approximate to each other and join together to form axis cylinders of other nerve fibres, [v. Thanhofler states that he has traced the axis-cylinder process to the nucleus and nucleolus.] 2. Bipolar cells are best developed in fishes, e.g., in the .spinal ganglia of the skate, and in the (lasserian ganglion of the pike. They appear to be nucleated, fusiform enlargements of the axis cylinder (Fig. 36S, on the right of I). The white substance often stops short on each side of the enlargement, but sometimes the white substance and the sheath of Schwaim pass over the enlargement 3. Nerve cells with connective-tissue capsules occur in the peripheral ganglia of man (Fig. 368, II), e.g., in the spinal ganglia. The soft body of the cell, which is provided with several processes, is covered by a thick, tough capsule composed of several layers of connective-tissue cor- Cell from the Gasserian ganglion. «, nuclei of the sheath ; t, fihre dividing at a node of Ranvier. CHEMISTRY OF NERVOUS MATTER. 581 puscles ; while the inner surface of the composite capsule is lined by a layer of delicate endothelial cells (Fig. 376). The body of the cells in the spinal ganglia is traversed by a network of fine fibrils i^Memming). The capsule is continuous with the sheath of the nerve fibre. Rawitz and G. Retzius find that the cells of the spinal ganglia are unipolar, the outgoing fibre taking a half-turn within the capsule before it leaves the cell (Fig. 376). Retzius [and Ranvier] observed the process to divide like a T. Perhaps this division corresponds to the two processes of a bipolar cell. The jugular ganglion and plexus gangliiformis vagi in man contain only unipolar cells, so that, in this respect, they may be compared to spinal ganglia. The same is the case in the Gasserian ganglion ; while the ciliary, spheno-palatine, otic, and submaxillary ganglia structurally resemble the ganglia of the sympathetic. 4. Ganglionic cells with spiral fibres occur chiefly in the abdominal sympathetic of the frog {Beale,J. Arnold). The body of the cell is usually pyriform in shape, and from it proceeds a straight unbranched process (Fig. 368, III, «), which ultimately becomes the axis cylinder of a nerve. A spiral fibre springs from the cell (? a network), emerges from it, and curves in a spiral direction round the former [o). The whole cell is surrounded by a nucleated capsule (w). We know nothing of the significance of the different fibres. 322. CHEMICAL AND MECHANICAL PROPERTIES OF NERVOUS SUBSTANCE.— I. Proteids.— Albumin occurs chiefly in the axis cylinder and in the substance of the ganglionic cells. Some of this proteid substance presents characters not unlike those of myosin (§ 293). Dilute solution of common salt extracts a proteid from nervous matter, which is precipitated by the addition of much water and also by a concentrated solution of common salt {Feirowsky). Potash albumin and a globulin-like sicbstance are also present. Nuclein occurs especially in the gray matter (§ 250, 2), while neuro-keratin, a body containing much sulphur and closely related to keratin, occurs in the cor- neous sheath of nerve fibres (p. 577). If gray nervous matter be subjected to artificial digestion with trypsin, both of these substances remain undigested {Kiihne and Ew aid). Pure neuro-keratin is obtained by treating the residue with caustic potash. The sheath of Schwann does not yield gelatin, but a substance closely related to elastin (§ 250, 6), from which it differs, however, in being more soluble in alkalies. The connective tissue of nerves yields gelatin. 2. Fats and other allied substances soluble in ether, more especially in the white matter: {a) Cerebrin, free from phosphorus (§ 250, 3). Cerebrin is a white powder composed of spherical granules soluble in hot alcohol and ether, but insoluble in cold water. It is decomposed at 80° C., and its solutions are neutral. When boiled for a long time with acids, it splits up into a left-rotatory body like sugar and another unknown pro- duct. Preparation. — Rub up the brain into a thin fluid with baryta water. Extract the separated coagulum with boiling alcohol. The extract is fi-equently treated with cold ether to remove the cholesterin {W. Milller). Parkus separated from cerebrin its homologue, homocerebrin, which is slightly more soluble in alcohol, and the clyster-like body, encephalin, which is soluble in hot water. {b') Lecithin and its decomposition products — glycero-phosphoric acid and oleo-phosphoric acid (§ 251). Neurin (or Cholin = C5H15NO2) is a strongly alkaline, colorless fluid, forming crystalline salts with acids. It is soluble in water and alcohol, and has been formed synthetically from glycol and trimethylamin. Lecithin is a salt of the base neurin. {c) Protagon, which contains N and P, is similar to cerebrin, and is, accord- ing to its discoverer, the chief constituent of the brain {^Liebreich'). According to Hoppe-Seyler and Diaconow, it is a mixture of lecithin and cerebrin. [The inves- tigations of Gamgee and Blankenhorn have shown, however, that protagon is a definite chemical body. They find that, instead of being unstable, it is a very stable body.] It is a glucoside, and crystalline, and can be extracted from the brain by warm alcohol, and when boiled with baryta yields the decomposition products of lecithin. 3. The following substances are extracted by water: Xanthin and hypoxanthin {Sckerer), kreatin {Lerck), inosit ( W. Milller), ordmary lactic acid {Gsfkeidlen), acetic and foi-mic acids, uric acid (?), and volatile fatty acids; leucin (in disease), urea (in ursemia), and a substance like starch in the human brain {Jaffe). All these substances are for the most part products of the regressive metabol- ism of the tissues. 582 METABOLISM OF NERVES. Reaction. — Nervous substance, when passive, is neutral or feebly alkaline in reaction, while active (? and dead) it is acid {Fttnke). The gray matter of the brain, when quite fresh, is alkaline {LiebreicJi), but death rapidly causes it to become acid ^Gscheidlen). The reaction of nerve fibres varies during life. After introducing methyl blue into the body of a living animal, Klirlich found that the axis cylinder became blue, ;. ^ 298, III). A motor nerve has a greater specific excitability for electrical stimuli than the muscle substance. This is proved by the fact that, a feebler stimultis suffices to excite a muscle when applied to the nerve than when it is applied to the mtiscle directly, as occurs when the terminations of the motor nerves are paralyzed by curara (^Rosenthal). Soltmann found that the excitability of the motor nerves of new-born animals for electrical stimuli is less than in adults. The excitability increases until the 5th to loth month. Unequal Excitability. — Under certain circumstances, the nearer the part of the motor nerve stimulated lies to the central nervous system, the greater is the effect produced (contraction) ; [or what is the same thing, the further the point of a nerve which is stimulated is from the muscle, the stimulus being the same, the greater is the contraction. This led Pfliiger to his "avalanche theory," ;. e., that the " nerve motion " increases in the nerve as it passes toward the muscles. This effect is explained, however, by the unequal excitability of different parts of the sanie nerve]. According to Fleischl, all parts of the nerve are equally excitable for chemical stimuli. Further, it is said that the higher placed parts of a nerve are more excitable only when the stimulating current passes in a descending direction ; the reverse is the case when the current ascends (Hermann). On stimulating a sensory nerve, Rutherford and Hallsten found that the reflex contraction was greater the nearer the stimulated point was to the central nervous system. Unequal Excitability in the same Nerve. — Nerve fibres, even when func- tionally the same and included in the same nerve trimk, are not all equally excitable. Thus, feeble stimulation of the sciatic nerve of a frog catises contraction of the flexor muscles, while it requires a stronger stimulus to prodtice contraction of the extensors {Ritter, 1805, Rollett). According to Ritter, the nerves for the flexors die first. Direct stimulation of the muscles in curarized animals shows that the flexors contract with a feebler stimulus (but also fatigue sooner) than the extensors; the pale muscles of the rabbit are UNIPOLAR STIMULATION AND NORMAL NUTRITION. 587 also more excitable than the red. As a rule, poisons affect the flexors sooner than the extensors. In some muscles some pale fibres are present, and they are more excitable than the red [Grilizner) (^ 298). If a frog's nerve-muscle preparation be exposed to the action of ether, on strong stimulation of the sciatic nerve, flexion occurs (^Griltzner, Bowditch), but if the current be made stronger, extension takes place. During deep ether-narcosis, strong stimulation of the recurrent nerve causes dilatation, and with slight narcosis, narrowing of the glottis takes place ; dilatation occurs on slight stimulation {^Bowditch). The adductor muscle of the claw of a crayfish is relaxed under a weak stimulus, but it contracts when a strong stimulus is applied to it. The reverse is the case with the muscle which opens the claw [Biedermann). Unipolar Stimulation. — Hone electrode of an induction apparatus be applied to a nerve, it may act as a stimulus. Du Bois-Reymond has called this "unipolar induction action." It is due to the movement of the electrical current to and from the free ends of the open induction current at the moment of induction. [Unipolar induction is more apt to occur with the opening than the closing shock, because the former is more intense.] Upon muscle, electrical stimuli act quite as they do upon nerves. Electrical currents of very short duration have no effect upon muscles whose nerves are paralyzed by curara {Briicke), and the same is true of greatly fatigued muscles, or muscles about to die or greatly weakened by diseased conditions (§ 399). 325. DIMINUTION OF THE EXCITABILITY— DEGENERA- TION AND REGENERATION OF NERVES.— i. Normal Nutri- tion.— The continuance of the normal excitability in the nerves of the body depends upon the maintenance of the normal nutrition of the nerves themselves and a due supply of blood. Insufficient nutrition causes, in the first instance, increased excitability, and if the condition be continued the excitability is diminished (§ 339, I). When the physician meets with the signs of increased excitability of the nerves, under bad or abnormal conditions of nutrition, this is to be regarded as the beginning of the stage of decrease of the nerve energy. Invigorating measures are required. If the terminal nervous apparatus be subjected to a temporary disturbance of its nutrition, the return of the normal nutritive process is heralded by a more or less marked stage of excitement. The more excitable the nervous apparatus, the shorter must be the duration of the disturbance of nutrition, e.g., cutting off the arterial blood supply or interfering with the respiration. 2. Fatigue. — Continued excessive stimulation of a nerve, without sufficient intervals of repose, causes fatigue of the nerve, and by exhaustion rapidly diminishes the excitability. A nerve is more slowly fatigued than a muscle {^Bernstein), but it recovers more slowly (§ 304). [Nerves of cold-blooded animals ( Widenskii) and mammals {BowditcJi) may be tetanized for hours without becoming fatigued.] [To show that a muscle is much more rapidly fatigued than a nerve, Bernstein arranged two nerve-muscle preparations so that both nerves were tetanized simultaneously, but through one of the nerves, a polarizing constant current was passed by means of non-polarizable electrodes (^ 327), so that the condition of anelectrotonus (| 335) was set up in this nerve, and thus "blocked" the propagation of impulses to the corresponding muscle. Only one muscle, therefore, was tetanized. Both nerves were continuously stimulated until fatigue of the contracting muscle took place, and on breaking the polarizing current applied to the other nerve, the corresponding muscle at once became tetanic. Now, as both nerves were equally stimulated, and the muscle in connection with one nerve was fatigued, while the other muscle at once contracted, it is evident that a muscle is much more rapidly fatigued than a motor nerve. In sensory nerves, fatigue and recovery are analogous to the corresponding processes in motor nerves {^Bernstein). '\ Recovery. — When a nerve recovers, at first it does so slowly, then more rapidly, and afterward again more slowly. If recovery does not occur within half an hour after a frog's nerve has been subjected to very long and intense stimulation, it will not take place at all. 3. Continued inaction of a nerve diminishes, and may ultimately abolish the excitability. 588 DEGENERATION OF NERVE FIBRES. Thus, the central ends of divided sensory nenes, after amputation of a limb, lose their excita- bility, although the nerves are still connected with the central nervous system, because the end organs through which they were normally excited have been removed. Fio. 377. Degeneration and regeneration of nerves. A, subdivision of the myelin; B, further disintegration thereti (osmic acid staining) ; C, interruption of the axial cylinder, which is surrounded with the broken-iip ,j myelin; D, accumulation of nuclei, with the remainder of the myelin in a spindle-shaped fibre ; E, a ^ new nerve fibre, with a new sheath of Schwann, sn, within the old sheath of Schwann, sa; F, a ncwj nerve fibre passing in a cur\'ed course through an old nerve fibre sheath. Fig. 378 Diagram of the roots of a spinal nerve, showing the effect of section (the black parts represent the degenerated parts). A, section of the nerve trunk beyond the ganglion; B, of the anterior root, and C, of the posterior; D, excision of the ganglion; a, anterior,/, posterior root; ^, ganglion. 4. Separation from their Nerve Centres. — The nerve fibres remain in a condition of normal nutrition, only when they are directly connected with their centre, which governs the nutritive processes within the nerve. If a nerve within the body be separated from its " nutritive centre " — either by section TRAUMATIC AND FATTY DEGENERATION. 589 of the nerve or compressing it — within a short time it loses its excitability, and XhQ peripheral &r\6. undergoes fatty degeneration, which begins in four to six days in warm-blooded animals, and after a long time in cold-blooded ones {/oh. Millie?'^. See also the changes of the excitability during this condition, the so-called " Reaction of degeneration " (§ 339). If the sefisory nerve fibres of the root of a spinal nerve be divided on the central side of the ganglion, the fibres on the peripheral side do not degenerate, for the ganglion is the trophic or nutritive centre for the sensory nerves ; but the fibres still in connection with the cord degenerate ( Waller^. [Wallerian Law of Degeneration. — If a spinal nerve be divided, the peripheral part of the nerve and its branches, including the sensory and motor fibres, degenerate completely (Fig. 378, A), while the central parts of the nerve remain unaltered. If the anterior root of a spinal nerve alone be divided before it joins the posterior root, all the peripheral nerve fibres connected with the anterior root degenerate (Fig. 378, B), so that in the nerve of distribution only the motor fibres degenerate. The portion of the nerve root which remains attached to the cord does not degenerate. If tht posterior root alone be divided, between the spinal cord and the ganglion, the effect is reversed, the part of the nerve root lying between the section and the spinal cord degenerates, while the part of the nerve connected with the ganglion does not degenerate (Fig. 378, C). The central fibres degenerate because they are separated from the ganglion. If the ganglion be excised, or if separated, as in Fig. 378, D, both the central and peripheral parts of the posterior root degenerate. These experiments of Waller show that the fibres of the anterior and posterior roots are governed by different centres of nutrition or "trophic centres." As the anterior root degenerates when it is separated from the cord, and the posterior when it is separated from its own ganglion, it is assumed that the trophic centre for the fibres of the anterior root lies in the multipolar nerve cells of the anterior horn of the gray matter of the spinal cord, while that for the fibres of the posterior root lies in the cells of the ganglion placed on it. The nature of this supposed trophic influence is entirely unknown.] Traumatic and Fatty Degeneration. — Both ends of the nerve at this point of section imme- diately begin to undergo " traumatic degeneration." (In the frog on the 1st and 2d day.) After a time neither the myehn nor axis cylinder is distinguishable {^Schiff'). According to Engel- mann, this condition extends only to the nearest node of Ranvier, and afterward the so-called " fatty degeneration" begins. The process of '■^ fatty" degeneration begins simultaneously in the whole peripheral portion; the white substance of Schwann breaks up into masses (Fig. 377, A), just as it does after death, in microscopic preparations ; afterward, the myelin forms globules and round masses (B), the axial cylinder is compressed or constricted, and is ultimately broken across (C) in many places (7th day). The nerve fitire seems to break up into two substances — one fatty, the other proteid in constitution, the fat being absorbed (.S". A'layer). The nuclei of Schwann's sheath swell up and proliferate (D — until the loth day). According to Ranvier, the nuclei of the inter-annular segments and their surrounding protoplasm proliferate, and ultimately interrupt the continuity' of the axis cylinder and the myelin. They then undergo considerable development with simultaneous dis- appearance of the medulla and axis cylinder, or at least fatty substances formed by their degeneration, so that the nerve fibres look like fibres of connective tissue. [According to this view, the process is in part an active one, due to the growth of the nerve corpuscles breaking up the contents of the neurilemma, which then ultimately undergo chemical degenerative changes.] According to Ranvier, Tizzoni, and others, leucocytes wander into tlie cut ends of the nerves, and also at Ranvier's nodes, insinuating themselves into the nerve fibres, where they take myelin into their bodies, and subject it to certain changes. [These cells are best revealed by the action of osmic acid, which blackens any myehn particles in their interior.] Degeneration also takes place in the motorial end plates, begin- ning first in the non-meduUated branches, then in the terminal fibrils, and lastly in the nerve truaks ( Gessle}-) . Regeneration of Nerves. — In order that regeneration of a divided nerve may take place {Cridckshank, 1795), the divided ends of the nerve must be brought into contact (| 244). In man this is done by means of sutures. About the middle of the fourth week, small clear bands appear within the neurilemma, winding between the nuclei and the remains of the myelin (E). They soon become wider, and receive myelin with incisures, and nodes, and a sheath of Schwann (2d to 3d 590 TROPHIC CENTRES AND MODIFYING CONDITIONS. month — F), The regeneration process takes place in each inter-annular segment, while the individual segments unite end to end at the nodes of Kanvier (§ 321, I, 5). On this view, each nerve segment of the fibre corresponds to a " cell unit" (A'. A'eur/iann, Eichhorst'). The same process occurs in nerves ligatured in their course. Sereral new fibres may be formed within one old nerve sheath. The divided axis cylinders of the crntrit/ end of the nerve begin to grow about the I4ih day, until they meet the newly ft)nned ones, with which they unite. [Primary and Secondary Nerve Suture. — Numerous experiments on anim.ils and man have established the fact that, immediate or primary suture of a nerve, after it is divided, either accidentally, or intentionally, hastens reunion and regeneration, and accelerates the restoration of function. Secondary suture, i. e., bringing the ends together long after the nerve has been divided, has been jiracticed with success. Surgeons have recorded cases where the function was restored after dividon had taken place for 3 to 16 months, and even longer, and in most cases the sensibility was restored first, the average time being 2 to 4 weeks. Motion is recovered much later. The ends of the nerve should be stitched to each other with catgut, the muscles at the same time being kept from becoming atrophied by electrical stimulation and the systematic use of massage (? 307). After suture of a nerve, conductivity is restored in the ral)bit in 40 days, on the 31st in dogs, and 25th in fowls, but after simple division without suture, not until the 60th day in the rabbit. Transplantation of nerve does not succeed {Johnson).'] Union of Nerves. — The central end of a divided motor nerve may unite with the peripheral end of another, and still conduct impulses {/\ava). [It is stated that sensory fibres will reunite with sensory fibres, and motor fibres with motor fibres, and the regenerated nerve will, in the former case, conduct sensory impulses, and the latter motor impulses. There is very considerable diversity of opinion, however, as to the regeneration or union of sensory with motor fibres. Paul Bert made the following experiment : He stitched the tail of a rat into the animal's back, and after union had taken place, he cut the tail from the body at the root, so that the tail, as it were, grew out of the animal's back, broad end upjiermost. On irritating the end of the tail, which was formerly the root, the animal gave signs of pain. This experiment was devised by Bert to try to show that nerve fibres can conduct impulses in both directions. One of two things must have occurred. Either the motor fibres, which normally carried impulses down the tail, now convey them in the opposite direction, and convey them to sensory fibres with which they have united ; or the sensory fibres, which normally conducted impulses from the tip upward, now carrying them in the opposite direction. If the former were actually what happened, it would show that nerve fibres of different function do unite (? 349). Reichert asserts that he has succeeded in uniting the hypoglossal with the vagus in the dog. According to Gessler the end plate is the first to regenerate.] Trophic Centres. — The regeneration of the nerves seems to take place under the influence of the nerve centres, which act as their nutritive, or trophic centres. Nerves permanently separated from these centres never regenerate. During the regeneration of a mixed nerve, sensibility is restored first, subse- quently voluntary motion, and lastly the movements of the muscles, when their motor nerves are stimulated directly {Schiff, Erb, v. Ziemssen). Wallerian Method of Investigation. — As \.\it peripheral er\A^ of a nerve undergoes degenera- tion after section, we use this method for determining the course of nerve fibres in a complex arrange- ment of nerves. The course of special nerve fibres may be ascertained by tracing the degeneration tract {IValler). If after section, reunion or regeneration of a motor nerve does not take place, the muscle supplied by this nerve ultimately undergoes fatty degeneration. 5. Modifying Conditions. — Under the action of various operations, e. g., compresshigdi nerve [so as not absolutely to sever the physiological continuity], it has been found that voluntary impulses or stimuli applied above the compressed spot, give rise to impulses which are conducted through the nene, and in the case of a motor nerve, cause contraction of the muscles, while the excitability of the parts below the injured spot is greatly diminished {Sclu'ff). In a similar manner, it is found that the nerves of animals poisoned with COj, curara orconiin, sometimes even the nerves of paralyzed limbs in man, are not excitable to direct stimuli, while they are capable of conducting impressions coming from the central nervous system {Duchenne). The injured part of the nerve, therefore, loses its excitability sooner than its power of conducting an impulse. 6. Certain poisons, such as veratrin, at first increase the excitability of the nerves, and afterward abolish it ; with some other poisons, the abolition of the excitability passes off very rapidly, e.g., curara. Conium, cynoglossum, iodide of methylstrychnin, and iodide of jethylstrychnin have a similar action. RITTER-VALLI LAW AND ELECTRO-PHYSIOLOGY. 591 If the nerve or muscle of a frog be placed in a solution of the poison, we obtain a different effect from that which results when the poison is injected into the body of the animal. Atropin diminishes the excitability of a nerve-muscle preparation of the frog without causing any previous increase, while alcohol, ether, and chloroform increase and then diminish the excitabihty i^Mqmtnseti). 7. Ritter-Valli Law. — If a nerve be separated from its centre, or if the centre die, the excitability of the nerve is increased ; the increase begins at the central end, and travels toward the periphery — the excitability then falls until it disappears entirely. This process takes place more rapidly in the central than in the peripheral part of the nerve, so that the peripheral end of a nerve separated from its centre remains excitable for a longer time than the central end. The rapidity of the transmission of impulses in a nerve is increased when the excitability is increased, but it is lessened when the excitability is diminished. In the latter condition, an electrical stimulus must last longer in order to be effective ; hence rapid induction shocks may not produce any effect. The law of contraction also undergoes some modification in the different stages of the changes of excitabihty (| 336, II). 8. Excitable Points. — Many nerves are more excitable at certain parts of their course than at others, and the excitability may last longer at these parts. One of these parts is the upper third of the sciatic nerve of a frog, just where a branch is given off {Budge'). The motor and sensory fibres of the upper third of the sciatic nerve of a frog are more excitable for all stimuli than the lower parts {^Gri'ttzner and Elpon). Whether this arises from injury during preparation (a branch is given off there), or is due to anatomical conditions, eg., more connective tissue and more nodes in the lower part of the sciatic, is undetermined i^Clara Halperson). This increased excitability may be due to injur}' to the nerve in preparing it for experiment. After section or compression of a nerve, all electrical currents employed to stimulate the nerve are far more active when the direction of the current passes away from the point of injury, than when they pass in the opposite direction. This is due to the fact, that the current produced in the nerve after the lesion is added to the stimulation current (| 331, 5). Even in intact nerves — sciatic of a frog — where the nerve ends at the periphery or at the centre, or where large branches are given off, there are points which behave in the same way as those points where a lesion has taken place {^Grutzner and Moschner') . Death of a Nerve. — In a dead nerve the excitability is entirely abolished, death taking place according to the Ritter-Valli Law, from the centre toward the periphery. The reaction of a dead nerve has been found by some observers to he acid (§ 322). The functions of the brain cease immediately death takes place, while the vital functions of the spinal cord, especially of the white matter, last for a short time; the large nerve trunks gradually die, then the nerves of the extensor muscles, those of the flexors after three to four hours ; while the sympathetic fibres retain their excitability longest, those of the intestine even for ten hours [Onimns). Compare § 295. The nerves of a dead frog may remain excitable for several days, provided the animal be kept in a cool place. Electro-Physiology. — Before beginning the study of electro-physiology, the student ought to read and study carefully the following short preliminary remarks on the physics of this question : — 326. PHYSICAL— THE GALVANIC CURRENT— RHEOCORD. — i. Electro- motive Force. — If two of the under-mentioned bodies be brought into direct contact, in one of them positive electricity, and, in the other, negative electricity can be detected. The cause of this phe- nomenon is the electro-motive force. The electro-motive substances may be arranged in a series of the first class, so that if the first-mentioned substance be brought into contact with any of the other bodies, the first substance is negatively, the last positively, electrified. This series is : carbon, plati- num, gold, silver, copper, iron, tin, lead, zinc + . The amount of the electro-motive force produced by the contact of two of these bodies is greater, the further the bodies are apart in the series. The contact of the bodies may take place at one or more points. If several of the bodies of this series be arranged in a pile, the electrical tension thereby produced is just as great as if the two extreme bodies were brought into contact, the intermediate ones being left out. 2. The nature of the two electricities is readily determined by placing one of the bodies of the series in contact with a fluid. If zinc be placed in pure or acidulated water, the zinc is -|- (posi- 592 ohm's law, strength and density of galvanic currents. live) and the water — (negative). If copper be taken instead of zinc, the copper is -f but the fluid — . Experiment shows that those metals, in contact with fluid, are negatively electrified most strongly which are most acted on chemically by the fluid in whicli they are placed. Each such com- bination affords a constant difference of tension or potential. The tension [or jiower of overcoming resistance] of the amount of electricity obtained from both bodies depends upon the size of the sur- faces in contact. The fluids, i-. j,--., the solutions of acids, alkalies, or salts, are called exciters of electricity of the second class. They do not form among themselves a definite series with different tensions. When placed in these fluids, the metals lying next the -)- end of the above scries, espe- cially zinc, are most strongly electrified negatively, and to a less extent those lying nearer the — end of the series. 3. Galvanic Battery. — If two different exciters of the first class be placed in fluid, without the bodies coming into contact, e.g., zinc and copper, the projecting end of the (negative) zinc shows free negative electricity, while the free end of the (jxjsitive) copper shows free positive electricity. Such a combination of two electro- motors of the first class with an electromotor of the second class is called z. galvanic bailery. As long as the two metals in this fluid are kept se[)arate, the circuit is said to be broken or open, but as soon as the free projecting ends of the metals are connected outside the fluid, e. g., by a copper wire, the circuit or current is tnaiieox closed, and a galvanic or constant current of electricity is obtained. The galvanic current has resistance to encounter in its course, which is called " coHt/iic/ion resislance" (W). It is directly proportional (l) to the length (/) of the circuit ; (2) and with the same length of circuit, inversely as the section (r/) of the same ; and (3) it also depends on the molecular properties of the conducting material {specific conduction resistance ^ s), so that the conduction resistance, W^ (5. /) : q. The resistance to conduction increases with the increase of the temperature of the metals, but diminishes under similar conditions with fluids. Ohm's Law. — The strength of a galvanic current (S), or the amount of electricity passing through the closed circuit, is proportional to the electro-molive force (E) — or the electrical tension, but inversely proportional to the total resistance to conduction (L) — So that S = E : L (Ohm's Law, 1827). The total resistance to conduction, however, in a closed circuit is composed of (i) the resistance outside the battery (" extraordinary resistance") ; and (2) the resistance within the battery itself ("essential resistance"). The specific resistance to conduction is very variable in different sub- stances; it is relatively small in metals {e. g., for copper^ i, iron = 6.4, Gennan silver = 12), but very great in fluids {e.g., for a concentrated solution of common salt 6,515,000, for a concen- trated solution of copper sulphate 10,963,600). Conduction in Animal Tissues. — It is also very great in animal tissues, almost a million times greater than in metals. When a constant current is applied to the skin so as to traverse the body, the resistance diminishes because of the conduction of water in the epidermis under the action of the constant current (| 290), and the congestion of the cutaneous blood vessels in consequence of the stimulation. But the resistance varies in different parts of the skin, the least being in the palm of the hand and sole of the foot. The chief seat of the resistance is the epidermis, for after its removal by means of a bli.ster, the resistance is greatly diminished. Dead tissue, as a rule, is a worse conductor than living tissues {Jolly'). When the current is passed transversely to the direc- tion of the fibres of a muscle, the resistance is nearly nine times as great as when the current passes in the direction of the fibres — a condition which disappears in rigor mortis {Hermann). In nerves, the resistance longitudinally is two and a half million times greater than in mercury, transversely about twelve million times greater {Hermann). Tetanus and rigor mortis diminish the resistance in muscle {Du Bois-Keymond). Deductions. — It follows from Ohm's law that — I. If there is very great resistance to the current outside the battery [?'. e., between the electrodes], as is the case when a nerve or a muscle lies on the electrodes, the strength of the current can only be increased by increasing the number of the electro- motive elements. II. When, however, the extraordinary resistance is very small compared with that within the battery itself, the strength of the current cannot be increased by increasing the number of the elements, l)ut only by increasing the surfaces of the plates in the battery. Strength and Density. — We must carefully distinguish the strength (intensity) of the current from its density. As the same amount of electricity always flows through any given transverse section of the circuit, then, if the size of the transverse section of the circuit varies, the electricity must be of greater density in the narrower parts, and it is evident that the density will be less where the transverse section is greater. Let S = the strength of the current, and q the transverse section of the given part of the circuit, then the density {d) at the latter part is ^ = S : ^. If the galvanic current passing from the positive pole of a battery is divided into two or more streams, which are again reunited at the other pole, then the sum of the strength of all the streams is equal to the strength of the undivided stream. If, however, the difterent streams are different as regards length, section and material, then the strength of the current passing in each of the streams is inversely proportional to the resistance to the conduction. Du Bois-Reymond's Rheocord. — This instrument, constructed on the principle of the "secondary" or " short circuit," enables us to graduate the strength of a galvanic current to any RHEOCORD GALVANOMETER. 593 required degree, for the stimulation of nerve and muscle. From the two poles (Fig. 379, a, b) of a constant battery, there are two conducting wires {a, c and d, b), which go to the nerve of a frog's nerve-muscle preparation (F). The portion of nerve (c, d^ introduced into this circuit {a, c, d, b) ofiers very great resistance. The second stream or secondary circuit (a A, b B) conducted from a and b passes through a thick brass plate (A, B), consisting of seven pieces of brass (l to 7) placed end to end, but not in contact. They can all, with the exception of i and 2, be made to form a continuous conductor by placing in the spaces between them the brass plugs (Sj to S5). Evidently, with the arrangement shown in Fig. 379, only a minimal part of the current will pass through the nerve {c, a), owing to the very great resistance in it, while by far the gi-eatest part will pass through the good conducting medium of brass (A, L, B). If new resistance be introduced into this circuit, then the a, c, d, b stream will be strengthened. This resistance can be introduced into the latter circuit by means of the thin wires marked \ a,\b, I <;-, II, V, X. Suppose all the brass plugs from Sj to Sg to be removed, then the current entering at A must traverse the whole system of thin wires. Thus, there is more resistance to the passage of this current, so that the current through the nerve must be strengthened. If only one brass plug be taken out, then the current passes through only the corresponding length of wire. The resistances offered by the different lengths of wire from I a to X are so arranged that \ a,\ b and I c each represents a unit of resistance ; 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 of 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 i and 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 resist- ance of a galvanic current ( IVheatstone). 327. ACTION OF THE GALVANIC CURRENT ON A MAGNETIC NEEDLE— GALVANOME- TER.— 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 oppo- site 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 constant 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. Multiplicator. — 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 tmn of the wire be properly insulated from the other]. An instrument constructed on this principle is called a multiplicator or 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 tis- sues) 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 butsmall, ^.^.,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. 38 Scheme of du Bois-Reymond's rheocord. 594 GALVANOMETER. 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. Tlie needle is continually acted upon by the directive magnetic influence of the earth, which tends to keep it in the magnetic meredian, 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 sufticiently 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. 380). [If both needles are equally magnetized, then the earth's influence on the needle is neutralized, so that the needles no longer adjust themselves to 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 me- ridian, 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 does the angle formed by the direction of the free deviation with the magnetic meridian become a right angle. The greater, therefore, the astatic con- dition, the fewer vibrations will the astatic system make 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 in- dicated by a sio'w 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 im- proved by du Bois-Reymond, the upper needle swings above a card divided into degrees (Fig. 380), on which the e-xtent 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 near one of the poles of the upper needle to compensate for the action of the iron on the needles. y p Scheme of the galvanometer. N, N, astatic needles sus- pended by the silk fibre, G ; P, P, non-polarizable electrodes, containing zinc sulphate solution, j, and pads of blotting paper, b, covered with clay, t, t, on which the muscle, M, is placed; II and 111, arrangement of the muscle on the electrodes; IV, non-polarizable elec- trodes ; Z, zinc wire ; K, cork ; «, zinc sulphate solu- tion ; t, t, clay points. 328. ELECTROLYSIS, POLARIZATION, BATTERIES.— Electrolysis.— Every gal- vanic 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 (-J-) being called the anode [aid, up, oJof, a way], the negative pole ( — ) the cathode (Ka-a, down, b^oq, 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 resist- ance is said to ht 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. The 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 polari- zation current has a direction opposite to the original current ; hence, we speak of negative polariza- ELECTROLYSIS, POLARIZATION, BATTERIES. 595 tion. When the two currents have the i2ixa& ^\x^c'C\ox\, positive polarization o\i\.2!Yas. 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- 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, especiallj' 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 decomposes the water, and uses the oxygen of the water to oxidize itself, while the hydrogen is deposited seconda- rily 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 temperature. 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., the construction of constant galvanic batteries, and non-polarizable electrodes {du Bois-Reymond). Constant Batteries, Elements, or Cells. — A per- fectly 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 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 cell has two metals and two fluids (Fig. 381). The zinc is in the form of a roll placed in dilute sulphuric acid [i 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 — [H2 -f HNO3 = HNO2 + H2O.] [Platinum is the -\- pole, and zinc the — .] Large Grove's cell. [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 evaporating chamber, or under glass. The fumes also attack instruments.] Bunsen's cell is 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 -f- pole, the zinc_the — .] [Daniell's cell consists of an outer vessel of glass or earthenware, and sometimes of metallic copper, filled with a saturated solution of cupric sulphate (Fig. 382). A roll of copper, perforated with a few holes, is placed in the copper solution, and in order that the latter be kept saturated, 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 (i : 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 generally taken as the standard of comparison.] [The copper is the -j- pole, zinc the — .] [Smee's cell contains only one fluid, viz., dilute sulphuric acid (l : 7), in which the two metals^ zinc and platinum, or zinc and platinized silver, are placed. The platinum is the -j- pole, and zinc the — .] [Grennet's or the Bichromate cell consists of one plate of zinc and two plates of compressed 596 DANIELL, SMEE, GRENNET, AND LECLANCH^'S ELEMENT. carbon in a fluid, containiuij bichromate of potash, sulphuric acid, and water. The fluid consists of I part of potassium bichromate dissolved in 8 parts of water, to which one part of sulphuric acid is added. Measure by 'weight. The cell consists of a wide-mouthed glass bottle (Fig. 383) ; the carbons remain in the fluid, while the zinc can be raised or depressed. ^\ hen not in action, the zinc, which is attached to a rod (B), is lifted out of the fluid. 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 -|- pole, and the zinc the — .] Fig. 382. — ^UUUUtJ^ Fig. 384. Daniell's Cell. Fig. 383. Leclanche's cell. A, outer vessel ; T, porous cylinder, containing K, carbon ; B, binding screw ; Z, zinc ; C, binding screw of negative pole. Grennet's cell. A, glass vessel ; K, K, car- bon ; Z, zinc; D, E, binding screws for the wires ; B, rod to raise the zinc from the fluid ; C, screw to fix B.| [Leclanche's cell (Fig. 384) 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 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 -(- pol^j ^"^ 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 REFLECTING GALVANOMETER AND SHUNT. 597 electrolysis must occur, and in consequence thereof polarization takes place. In order to avoid this, non-polarizable electrodes (Figs. 380, 385) are used. Such electrodes are made by taking two pieces of carefully amalgamated, pure, zinc wire (z, s), and dipping these in a saturated solution of zinc sulphate contained in tubes (a, a), whose lower ends are closed by means of modeler'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. [The brush electrodes of v. Fleischl are very serviceable (Fig. 386). The lower end of the glass tube is plugged with a camel-hair pencil, moistened with modeler's clay, otherwise the arrangement is the same as shown in Fig. 380, IV.] 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 be one of the forms described above, or the original form used by du Bois-Reymond. (Fig.|38o). The last consists of two zinc troughs (j>, p) thoroughly amalgamated inside, insulated on vulcanite, Fig. 385. Fig. 387. Non-polarizable electrode of du Bois-Reymond. Z, zinc ; H, movable support ; C, clay point — the whole on a universal joint. Fig. 386. Brush electrodes of v. Fleischl. jmson's reflecting galvanometer. u, upper, /, lower coil ; s, s, level- ing screws ; }fi, magnet on a brass support, 6. and filled with a saturated solution of zinc sulphate {s, s). In each trough is placed a thick pad or cushion of white blotting paper {i>, b) 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 modeler'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. 380). [Reflecting Galvanometer. — The form of galvanometer, used in this country for physiological purposes, is that of Sir William Thomson (Fig. 387). In Germany, Weidemann'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 aluminium, and each set of needles is surrounded by a separate coil of wire, 598 REFLECTING GALVANOMETER AND SHUNT. Lamp and for 'I'hoiiison's gal kanometer. Shunt for galvanometer. the lower coil (/) winding in a direction opposite to that of the upper (tt). A small, round, light, slightly concave mirror is fixed to the upper set of needles. The needles are suspended by a delicate silk til^ril, 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 F'k^.. "^SS. Fig. 389. vulcanite base, which is leveled ijy three screws (s, s). On a brass rod (6) is a feeble magnet (w), 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 instru- iiunt is to be used, place it so that the coils face east and west. At 3 feet dis- tant from the front of the galvanometer, facing west, is placed the lamp and scale (Fig. 388). 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, w. The needles are most sensitive when the oscil- lations occur slowly. The sensitiveness of the needles can be regulated by means of the magnet. In every case the in.strument must be (juite 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 (F"ig. 389) consists of a brass box containing coils of German silver wire, and is constructed on the same prin- ciple as resi-Stance coils or the rheocord (^ 326). On the upper surface of the box are several plates of brass separated from each other, like tho^e 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. V>y 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 mu.st pass through the galvanometer. If ofie plug be placed between the central disk of brass and the plate marked i (the other being left out), then J^ of the cun-ent goes through the galvanometer and -^^ to the electrodes. If the plug be placed as shown in the figure opposite -Jtj, then ^J^ part of the current goes to the galvanometer, while j'j^^ are short circuited. If the plug be placed opposite ^Ig, only yjjVff P''*'"' 8°^^ through the galvanometer.] Internal Polarization of Moist Bodies. — Nerves and muscular fibres, the juicy parts of vege- tables and animals, fibrin, and other similar bodies possessing a porous structure filled with fluid, exhibit the [ihenomena 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 the interior of these bodies which are better conductors, produce electrolysis 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 (^ 33i)- 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 particles pass in the direction of the galvanic current, from the -(- to the — pole, so that after some time, the fluid in the one-half of the vessel increases, while it diminishes in the other. The phenomena of direct transference were called by du Bois-Reymond the cataphoric action of the constant 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,^). External Secondary. Resistance. — This condition also depends on cataphoric action. If the copper electrodes of a constant battery be placed in a vessel filled with a solution of cupric sulphate, and from each electrode there project a cushion saturated with this fluid, then, on placing 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 variation of the current. If the direction of the current be reversed, it first becomes stronger, but afterward diminishes. By constantly altering the direction of the current we cause the same changes in the intensity. If a prismatic strip of coagulated albumin be used for the experiment, we observe that, simultaneously with the enfeeblement of the current in the neighborhood of the + pole, the albumin loses water and becomes more shriveled, while at the — pole the albumin is swollen up and contains INDUCED OR FARADIC ELECTRICITY. 599 more water. If the direction of the current be altered, the phenomena are also changed. The shriveling and removal of water in the albumin at the positive pole must be the cause of the resist- ance in the circuit, which explains the enfeeblement of the galvanic current. This phenomenon is called "external secondary resistance" [die Bois-Reymo7id). 329. INDUCTION— EXTRA CURRENT— 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 made or 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 electrodes, so that a person can hold one in each hand, 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 elec- tric current in the adjoining coils of the same spiral. At the moment of closing or making the cir- cuit in the spiral, the induced current is in the opposite direction to the galvanic current in the circuit ; hence its strength is lessened, and it causes no shock. At the moment of opening, how- ever, 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 into 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, and the other away from him, and if, further, the positive current traverse 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 dis- appears. 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 con- stant 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 sec- ondary 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 betvireen the Opening [break] and Closing [make] Shocks. — The opening and closing shocks in the secondary spiral are distinguished from each other in the following respects (Fig. 390) : 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 high maximum, and this occurs more slowly. [In Fig. 390, Pj and Sq are the abscissae of the primary (inducing) and induced currents respectively. The vertical lines or ordinates re'preseni the intensity of the current, while the length of the abscissa indicates its duration. Curve I indicates the course of the primary current, and 2, that in the secondary spiral (induced) when the current is closed, v;\i\\& at I the primary current is suddenly opened, when it gives rise to the induced current, 4, in the secondary spiral.] The cause of the difference is the following: When the primary 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. Break or Opening Shock. — [On applying a single induction shock to a nerve or a muscle, the effect is greater with the break or opening shock. If the secondary spiral be separated from the pri- mary, 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 break or opening shock will cause a contraction before the closing one does so.] Helmholtz's Modification. — Under certain circumstances, it is desirable to equalize the make and break shocks. This may be done by greatly weakening the extra current, which may be accom- plished 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 600 UNIPOLAR INDUCTION. the current in tlie primary spiral never completely disapjiears, but by alternately making and breaking this secondary circuit where the resistance is much less, it is ahernately weakened and strengthened. [In Fig. 391 a wire is introduced between a and /", while the binding screw,/, is separated from the platinum contact, c, of Neefs hammer, but, at the same time, the screw, ti, is raised so that it touches Neefs hammer. The current passes from the battery, K, through tiie pillar, a, to/ in the direction of the arrow, through the primary spiral, P, to the coil of soft wire, r', and back to the bat- tery, through h and e. But .j,'' is magnetized thereljy, and when it is so, it attracts c and makes it touch the screw, d. Thus a sccondaiT circuit, or short circuit, is formed through a, l>, c, d, e, which weakens the current passing through the electro magnet, ,?•, 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. 390 the lines i and 7 indicate the course of the current in the primary circuit at closing (a), and opening (e). It must be remembered that in this arrangement there is always a current passing through the primary spiral, P (Fig. 391). The dotted lines, 6 and 8, above and below Sg, represent the course of the opening [a) and closing shocks (c) in the secondary spiral. Even with this arrangement the opening is still slightly stronger than the closing shock.] The two shocks, however, may be completely equalized by placing a resistance coil or rheostat in the short circuit, which increases the resistance, and thus increases the current through the primary spiral when the short circuit is closed. Fig. 390. Scheme of the induced currents. Pj, abscissa of the primary, and Sq, of the secondary cur- rent ; A, beginning, and E, end of the inducing current; i, curve of the primary current weak- ened by the extra current; 3, where the pri- mary current is opened; 2 and 4, correspond- ing currents induced in the secondary spiral ; P5, height, i. e., the strength of tlie constant inducing current ; 5 and 7, the curve of the in- ducing current when it is opened and closed during Helmholtz's modification ; 6 and 8, the corresponding currents induced in the second- ary circuit. Fig. 391. Helmholtz's modification of Neefs hammer. As long as c is not in contact with d,gh remains magnetic ; thus c is attracted to d and a secondary circuit, «, b, c, d, e, is formed ; c then springs back again, and thus the process goes on. A new wire is introduced to connect a withyi K, bat- tery. Unipolar Induction. — ^Vhen there is a very rapid current in the primary spiral, not only is there a current induced in the secondary spiral, when its free ends are closedi^-.o"., by being connected with an animal tissue, but there is also a current when one wire is attached to a binding screw connected with one end of the wire of the secondary spiral (p. 587). A muscle of a frog's leg, when connected with this wire, contracts, and this is called a unipolar induced contraction. It usually occurs when the primary circuit is opened. The occurrence of these contractions is favored when the other end of the spiral is placed in connection with the ground, and when the frog's muscle preparation is not completely insulated. Magneto-Induction. — If a magnet be brought near to, or thrust into the interior of, a coil of wire, it excites a current, and also when a piece of soft iron is suddenly rendered magnetic or sud- denly demagnetized. The direction of the current so induced in the spiral is exactly the same as that with Faradic electricity, i.e., the occurrence of the magnetism, on approximating the spiral to a magnet, excites an induced current in a direction opposite to that supposed to circulate in the mag- net. Conversely, the demagnetization, or the removal of the spiral from the magnet, causes a cur- rent in the same direction. Acoustic Tetanus. — If a magnet be rapidly moved to and fro near a spiral, which can easily be done by fixing a vibratory magnetic rod at one end and allowing the other end to swing freely near DU BOIS-REYMOND S INDUCTORIUM. 601 the spiral, then the pitch of the note of the vibrating rod gives us the rapidity of the induction shocks. If a frog's nerve-muscle preparation be stimulated, we get what Grossmann called "acoustic tetanus." 330. DU BOIS-REYMOND'S INDUCTORIUM— MAGNETO-INDUCTION AP- PARATUS.— The inductoriumof du Bois-Reymond, which is used for physiological purposes, is a modification of the magneto-electromotor apparatus of Wagner and Neef. A scheme of the apparatus is given in Fig. 392. D represents the galvanic battery. The wire from the positive pole, a, passes to a metallic column, S, which has a horizontal vibrating spring, F, attached to its upper end. To the outer end of the spring a square piece of iron, e, is attached. The middle point of the upper surface of the spring [covered with a little piece of platinum] is in contact with a movable screw, b, A moderately thick copper wire, c, passes from the screw, b, to the primary spiral or coil, X, X, which contains in its interior a number of pieces of soft iron wire, i, i, covered with an insulating varnish. The copper wire which surrounds the primary spiral is covered with silk. The wire, d, is continued from the primary spiral to a horseshoe piece of soft iron, H, around which it is coiled spirally, and from thence it proceeds, at/", back to the negative pole of the battery, g. When the current in this circuit — called the primary circuit — is closed, the following effects are produced : The horseshoe, H, becomes magnetic, in consequence of which it attracts the movable spring or Neef's hammer, e, whereby the contact of the spring, F, with the screw, b, is broken. Thus the current is broken, the horseshoe is demagnetized, the spring, e, is liberated, and, being elastic, it Fig. 392. I v c _ > W flTf r/^ 41^ jljL iJJLi|_l_ i !> Ill wft '^VV.\ L>V\ iiirV\.\ I, Scheme of du Bois-Reymond's sledge induction machine. D, galvanic battery : a, wire from -f pole, (^) — pole ; S, brass upright ; F, elastic spring ; i, binding screw ; c, wire round primary spiral (jr, jc), containing {i, i) soft iron wire; K, K, secondary spiral, with board (/,/) on which it can be moved; H, soft iron magnetized by current (^,y") passing round it. II, key for secondary circuit; as shown it is short-circuited. Ill, electrodes {r, r), with a key (K) for breaking the circuit. springs upward again to its original position in contact with b, and thus the current is reestablished. The new contact causes H to be remagnetized, so that it must alternately rapidly attract and liberate the spring, e, whereby the primary current is rapidly made and broken between F and b. A secondary spiral or coil (K, K) is placed in the same direction as the primary {x, x), but having no connection with it. It moves in grooves upon a long piece of wood (/,/). The second- ary spiral consists of a hollow cylinder of wood covered with numerous coils of thin, silk-covered wire. The secondary spiral, moving in slots, can be approximated to or even pushed entirely over the primary spiral, or can be removed from it to any distance desired. [Fig. 393 shows the actual arrangement of du Bois-Reymond's inductorium. The primary coil (R'') consists of about 150 coils of thick insulated copper wire, the wire being thick to offer slight resistence to the galvanic current. The secondary coil (R^^) consists of 6000 turns of thin insulated copper wire arranged on a wooden bobbin; the whole spiral can be moved along the board (B) to which a millimetre scale (I) is attached, so that the distance of the secondary from the primary spiral may be ascertained. At the left of the apparatus is Wagner's hammer, as adapted by Neef, which is just an automatic arrangement for opening and breaking the primary circuit. WTien Neef's hammer is used, the wires from the battery are connected as in the figure ; but when single shocks are required, the wires from the battery are connected with a key, and this again with the 602 MAGNETO-INDUCTION. Fi<-.. 394. two terminals of the primary spiral, S'' and S'^'. In the improved form of this apparatus (Fig. 394) the secondary spiral is equipoised over a pulley with a back weight, so that it can move easily in a vertical direction to and from the primary spiral. A. de Walteville has used a form similar to this for a long time.] According to the law of induction (§ 329), when the primary circuit is closed, a current is induced in the secondary circuit in a direction the reverse oi that in the primary, while, when it is opened, the induced current has the same direction. Further, according to the laws of magneto induction, the magnetization of the iron rods {/, /) within the primary spiral (.r, .r), causes a reverse current in the secondary spiral (K, K), while the demagnetization of the iron rods, on opening the pi imary circuit causes an induced current in the same direction. Thus, we ex- plain the much more powerful action of the opening or break shock as compared with the closing or make shock (p. 53')- [The direction of the in.iucing current remains the same, while the induced currents are constantly reversed.] The magneto-induction (R) apparatus of Pi.xii, as improved by Stohrer, consists of a very powerful horseshoe steel mag- net (Fig. 395). Opposite its two poles (N and S) is a horse- shoe-shaped jMece of iron (H), which rotates on a horizontal axis (a, V). On the ends of the horseshoe are fixed wooden bobbins (f, i)lies these conditions. In such a muscle, we distinguish the surface or the natural longitudinal section, its tendinous ends or the natural transverse section ; furtlier, when the latter is ciivide-in, n) is applied to a line so drawn as exactly to divide tlie length of the muscle into halves. .\s the cur- rents are very feel^le, it is necessary to use a galvanometer with a periodic damped magnet (Figs. 380, I, and 3S7), or a tangent mirror boussole similar to that used for thermo-electric purposes ( Fig. 230). The wires leading from the tissue are connected with non-polari/able electrodes (Fig. 380, 1', P). The capillary electrometer of Lippmann may be used for detecting the current (Fig. 400). 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 mercur}'. 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. R is a capillary glass tube, filled from above with mercury, and from below with Fii;. 400, Scheme of the muscle current. Capillary electrometer. R. mercury in tube ; capillary tube ; s, sulphuric acid ; y, Hg ; B, observer; M, microscope. 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 (17), and this again is covered with dilute sulphuric acid {s). The wires are connected with non-polarizable electrodes applied to the + and — surfaces of the muscle. On closing the circuit, the thread of mercury passes downward from c in the direction of the arrow. Compensation. — The strength of the current in animal tissues is best measured by the com- pensation method of Poggendorf and du Bois-Reymond. .\ 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.] [Hermann calls the current obtained from an injured muscle, /. e., one on which an artificial transverse or other section has been made, a demarcation current, while the currents obtained when such a muscle contracts, he calls action cur- ELECTRICAL CURRENTS IN NERVE AND MUSCLE. 605 rents. This section deals with demarcation currents, or the muscle current of du Bois-Reymond.] 1. Perfectly fresh uninjured muscles yield no current, and the same is true of dead muscle (Z. Hermann, 1867). 2. Strong electrical currents are observed when the traftsverse section of a muscle is placed on one of the cushions of the non-polarizable electrodes (Fig. 380, 1, M), while the surface is in connection with the other {Nobili, Matteucci, du Bois- Reymond^. The direction of the current is from the (positive) longitudinal section to the (negative) transverse section in the conducting wires (z". e. , within the muscle itself from the transverse to the longitudinal section (Figs. 380, I, and 399, 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 {I 334, 11). 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 ( + ) to the point lying further from it ( — ), but of course this direction is reversed within the muscle itself (Fig. 399, II, ke and ie). (d) Similarly weak currents are obtained by connecting points of the transverse sec- tion 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. 399, II, /, c). 4. When two points on the surface are equidistant from the equator (Fig. 399, I, X, y, V, z, — II, r, e^, or two equidistant from the centre of the transverse section (II, c) are connected, no current is obtained. [Because the points are iso-electrical, that is of equal potentiality.] 5. If the transverse section of the muscle be oblique (Fig. 399, 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 positive to the one lying near to the acute angle. The equator is oblique {a, c). These currents are called '■'■deviation currents or inclination currents''' by du Bois- Reymond, and their course is indicated by the lines 1,2, and 3. The electromotive 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 maybe o.l Daniell. The muscles of a curarized animal at first yield stronger currents ; fatigue of the muscle diminishes the strength of the current (^Roeber),vi\\As. it is completely abolished when the muscle dies. i%(7/z>zo- a muscle increases the current; but above 40° C. it is diminished i^Steiner). Cooling diminishes the electromotive force. The warmed livitig muscular and nervous substance is positive to the cooler portions {^Her- mann) ; while, if the dead tissues 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 electromotive force of the strongest nerve current, according to du Bois-Reymond, is 0.02 of a Daniell. Heating a nerve from 15° to 25° C. increases the nerve current, while high tem- peratures diminish it [Sieiner) 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 (^Mendelssohn and Christiani) . The electromotive force increases with the length of the nerve and with the area of its transverse section. Fatigue {e. g-, tetanic stimulation) weakens it, especially in motor nerves, and to a less extent in centripetal nerves. 606 SELF-STIMULATION OF THE MUSCLE. [Nerve-muscle Preparation. — This term has been used on several occasions. It is simply the sciatic nerve with the gastrocnemius of the frog attached to it (Fig. 401). The sciatic nerve is dissected out entire from the vertebral column to the knee ; the muscles of the thigh sepa- rated from the femur, and the latter divided about its middle, so that the preparation can be fixed in a clamp by the remain- ing portion of the femur; while the tendon of the gastrocne- mius is divided near to the foot. If a straw flag is to be attached to the foot, do not divide the tendo-Achillcs.] Rheoscopic Limb. — The existence of a muscle current may be proved without the aid of a galvanometer : i. By means of a sensitive nerve-muscle preparation of a frog, or the so-called ^''physiological rheoscope.^' Place a moist con- ductor on the transverse and another on the longitudinal sur- face of the gastrocnemius of a frog. On placing the sciatic nerve of a nerve-muscle preparation of a frog on these con- ductors, so as to bridge over or connect their two surfaces, contraction of the muscle connected with the nerve occurs at Nerve-muscle preparation oucc ) and the samc occurs whcn the nerve is removed. of a frog. F, femur; Make a transvcrse section of the gastrocnemius muscle of a S, sciatic nerve; I, • . 1 11 1 • • tendo-Achiiies. frog s ncrve-muscle preparation, and allow the sciatic nerve to fall upon this transverse section ; the limb will contract as the muscle current from the longitudinal to the transverse surface now traverses the nerve {Galvani, Al. v. Humboldt). These experiments have long been known as " contraction without metals." [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 fnll upon the gastrocnemius, and the muscle will contract, but it is better to allow the nerve to fall suddenly u]3on 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.] 2. Self-stimulation of the Muscle. — We may use the muscle current o{ 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 Fig. 402. its own demarcation current (oih ends of a nerve, and is composed of very rapid, successive, periodic interruptions of the original current, just as in a contracted muscle {Bernstein). Hering succeeded in obtaining from a nerve, as from a muscle, a secondary con- traction or secondary tetanus. The amount of the negative variation depends upon the extent of the jirimary deflection, also upon the degree of 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 fol- lowed by ^positive variation, which occurs immediately after the former, /. e., it is diphasic. It increases to a certain degree with the duration of the stimulation, as well as with the strength of the stimulus, and with the drying of the nerve {Hemi). {Effect of Eh-ctrotoiiiis, § 335, I). EiG. 406. Scheme of Bernstein's diflferential rheotome ; N «, nerve : J. induction machine; G, galvanometer, .r,,)*, deflection of needle ; E, batter)' and prim.yy circuit with C fer opening it at o ; c, for closing galvanometer circuit ; z z, electrodes in galvanometer circuit ; S, motor. Negative Variation of the Spinal Cord. — This is the same as in nerves generally. If a current be conducted from the transverse and longitudinal surfacesof the upper part of the medulla oblongata, we observe spontaneous, intermittent, ne'^atii'e 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 measurable velocity along the nerve, most rapidly at 15° to 25° C. (Steiner), and at the same rate as the velocity of the nervous impulse itself, about 27 to 28 metres per second. The duration of a single variation (of which the process of negative variation is composed) is only 0.0005 'o 0.0008 second, while the wave length in the nerve is calculated by Bernstein at 18 mm. Differential Rheotome. — J. Btrnstein estimated the velocity of the negative variation in a nerve by means of a differential rheotome thus (Fig. 406) : A long stretch of a nerve (N n) 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 (w) 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 circumference is an arrangement ELECTRICAL CURRENTS DURING ELECTROTONUS. 611 (c) by which the galvanometer circuit is closed and opened during each revolution. Thus, the stimu- lation 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 J. 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 o) along the circumference, that the galvanometer circuit is closed somewhat /a^er than the nerve is stimulated, then the current is weakened by the negative variation (the needle passing backward to jr). 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 ;z. The negative variation is absent in degenerated nerves as soon as they lose their excitability. Retinal and Eye Currents. — If a freshly-excised eyeball be placed on the non-polarizable electrodes connected 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 [Hobngren, AP Kendrick and Dewar). The inner surface of t\ie 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. Retinse, in which the visual purple has disappeared owing to the action of light, show smaller variations [Kilkne and Steiner). Stimulation of the secretory nerves of the ^/a«(/z//ar 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 occasion- ally in the opposite direction {Hermann). If the current be conducted uniformly from both hind feet of a cat, on stimulating the sciatic nerve of one side, not only is there a secretion of sweat (g 288), but a secretion current is developed [Lticksinger and Hermann). If two symmetrical parts of the skin in the leg or arm of a man be similarly tested, and the muscle of one side be con- tracted, 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 sub-maxillary gland is referred to in ^ 145 [Bayliss and Bradford)^ 333. ELECTROTONIC CURRENTS IN NERVE AND MUS- CLE.—[When a constant current called the "polarizing current" is passed through a stretch of nerve, the nerve is thrown into a peculiar condition, called the -''electrotonic condition," or briefly electrotonus. In this condition, the vital properties of the nerve are modified, i. e. — (i) Its electromotivity (§ 333). (2) Its excitability (§ 335). The former is considered in this section, and the latter in a subsequent section.] 1. Positive Phase of Electrotonus. — If a nerve be so arranged upon the electrodes (Fig. 407, I) that its transverse section lies on one, and its lon- gitudinal on the other electrode, then the galvano- meter indicates a strong current. If now a constant current be transmitted through the end of the nerve projecting beyond the electrodes (the so-called "Z^- larizing^^ end of the nerve), and if the direction of this current coincide 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. 407, II), there is a diminution of the electromotive force of the latter — "negative phase of electrotonus." Fig. 407. Nerve current in electrotonus. vanomeler ; b, electrodes ; slant current. 612 MUSCLE CURRENT DURING ELECIROTONUS. 3. Equator. — If two points of the nerve equidistant from the equator be placed on the electrodes (III), there is no deflection of the galvanometer needle (p. 605, 4). If a constant current be passed through one free projecting end of the nerve, then the galvanometer indicates an electromotive effect in the same direction as the constant current. Electrotonus. — These experiments show that a constant current causes a change of the electromotive force of the part of the nerve directly traversed by the constant current, /'. e., in the intra-polar area, and also in the part of the nerve outside the electrodes, /. ommon salt, or the tentacles of a lobster when moistened with saline solution, and traversed by a constant current, exhibit similar electrotonic currents {Hering).'] THEORIES OF MUSCLE AND NERVE CURRENTS. 613 334. THEORIES OF MUSCLE AND NERVE CURRENTS.— I. Molecular or pre-existence Theory.- — To explain the currents in muscle and nerve, du Bois-Reymond proposed the so-called molecular theory. Accord- ing 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 + longitudinal surface is connected with 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 electropositive 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 -\- in relation to the surface. Cauterization destroys it. [It is supposed to be favored by cold.] The negative variation is explained by supposing that, during the action of a muscle and nerve, the electromotive 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 polarizing 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 electrodes, the further removed it is, the less precisely are the molecules airanged. Hence, the swing of the needle is less, the further the extra-polar portion is from the electrodes. II. Difference or Alteration Theory. — The difference theory was proposed by L. Hermann, and, according to him, the four following considerations are sufficient to explain the occurrence of the galvanic phenomena in living tissues ; (i) Protoplasm, 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, becomes positive, and by cooling negative, to the unchanged part. (4) Proto- plasm is ?,txong\y polarizable on its surface (muscle, nerve), the polarization con- stants diminishing Avith excitement and in the process of dying. Streamless Fresh Muscles. — It seems that passive, uninjured, and abso- lutely fresh nerves, and muscles, are completely devoid of a current, e.g., the heart (^Engelmanti), also the musculature of fishes while still covered by the skin. [According to Hermann, the currents obtained from muscle are due to injury of the muscle substance, whereby a difference of potential is set up, the injured part being negative to the uninjured. In fact, it is impossible to isolate a muscle with- out injuring it, owing to its connections. Frogs exhibit skin currents after the skin is destroyed ; the muscles still exhibit currents, but Hermann explains this by the action of the irritant, used to destroy the skin, also affecting the muscle. In fishes, however, there are no skin currents, and if they be curarized, absolutely no current is obtained from their uninjured muscles {Hermann). The heart also when passive and uninjured gives no current, although it exhibits an action current when it contracts, and every injured part in it possesses a negative electrical potential with reference to the rest.] 614 ACTION CURRENTS. 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. [By means of his " Fall-rheotom," an arrangement wherein' a weigiit, covered with shagreen, injured a muscle, and at the same time, closed and opened a galvanometer circuit, Hermann was able to show that the current — demarcation current — took a certain time to develop. Had it been preexistent, as supposed by du Bois-Reymond, this ought not to have lieen the case.] Demarcation Current. — Eveiy injury of a muscle or nene causes at the ])oint of injury {demar- cation siirfiic() a dying sulistance, which behaves negatively to the positive intact substance. The current thus produced is called by Hermann the 'Uiemarcation current." If individual parts of a muscle be moistened with potash salts or muscle juice, they become negatively electrical ; if these substances be removed the.se parts cease to be negative {Bieder/nann). It appears that all living jjrotoiilasmic substance has a special property, whereby injury of a part of it makes it, when dying, negative, while the intact parts remain jxisitively 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 si ream- less, then the absolutely dead substance behaves essentially as an indifferent moi.st 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 can no longer be maintained. Theoretical. — Grunhagen and L. Hennann explain the electrotonic currents as lieing due to internal polarization in the nerve fibre between the conducting core of the nerve and the enclosing 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 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 (p. 6l2). The polarization developed on the surface of the wire by its transition resistance causes the conducted current to extend much beyond the electrodes. Muscles and nerves consist of fibres surrounded by indifterent conductors. 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 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 or nerve. When a single stimulation wave (contraction) passes along muscular fibres, which are connected at two points with a galvanometer, then that ]X)int through which the wave is just passing is negative to the other. Occasionally, in excised muscles, local con- tractions occvu", and these points are negative to the other passive parts of the muscle (Biedermann). In order, therefore, to explain the currents obtained from a frog's leg during tetanus, we mu.st assume that the end of the fibre which is negative participates less in the excitement than the middle of the fibre. But this is the case only in dying or fatigued muscles. According to ' to apply the stimulus at the same time by the electrode itself, e.g., either mechanically or by conducting the stimulating cm-rent through the polarizing current ( 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 satm-ated solution of common salt, reflex movements are excited in the other leg, the spinal cord being intact. These disappear as soon as a constant current is applied to the nerve, provided the salt lies in the anelectrotonic area {PJluger and Ziirhelle, 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 Fig. 410. Scheme of the distribution of an electrical current in the nerve on galvanizing the ulnar nerve. side, a constant descending current be passed through the other intact vagus, the number of pulse beats is again decreased (descending extra-polar anelectrotonus). If, however, the current through the nerve be an ascending one, then with tveak currents the number of heart beats increases still more (ascending extra-polar 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 intfa-polar portion is altered. The delay in the conduction is confined to this area alone {v. Bezold) — compare § 337, i. 336. ELECTROTONUS— LAW OF CONTRACTION.— Opening and Closing Shocks. — A nerve is stimulated both at the moment of the occur- rence and that of disappearance of electrotonus {i. e., by closing and opening the current — Ritter) : (i) When the current is closed, the stimulation occurs only at the cathode, z. e., at the moment when the electrotonus takes place. (2) When the current is opened, stimulation occurs only at the anode, /- e., at the moment when the electrotonus disappears. [This is Pfliiger's well-known principle — "A given tract of nerve is stimulated by the appearance of cathelectrotonus and the dis- appearance of anelectrotonus — not, however, by the disappearance of cathelectrotonus nor by the appearance of anelectrotonus. ' ' From this principle can be deduced the 618 THE LAW OF CONTRACTION. law of contraction.] (3) The stimulation at the occurrence of cathelectrotonus is stronger than that at the disappearance of anelectrotonus (^Pflih^er). Hitter's Opening Tetanus. — That stimulation occurs only at the anode, when the current is opened, was j^roved by Ptiiiger by means of " Kilter's opening tet.nnus." Hitter's tetanus consists in this, that when a constant current is passed for a long time through a long stretch of nerve, on open- ing 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 intra-polar 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 efl'ect on the tetanus. Ptiiiger and v. Bezold found a further \)\ool that the closing or make contraction proceeds from the cathode, and the opening or break contraction from the anode, by showing that with a descending current, the closing contraction in the muscle, at the moment of closing occurred earlier, while the opening contraction at the moment of opening occurred later ; 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 pulse in the intra-jx>lar region (? 337V If a lai-ge part of the intra-polar region in a frog's nerve be rendered ine.xcitable by apply- ing ammonia to it, then only the electrode next the muscle stimulates, /. e., always on closing or making a descending current and on opening or breaking an ascending one {Biedermann). A. The la'w of contraction is valid for all kinds of nerves — I. The contrac- tion occurring at tlie closing or opening of a constant current varies with (a) the direction (P/af), and {b) the strength of the current {Heidenhain). (i) Very feeble currents, in conformity with the third of the above state- ments, cause only a closing contraction, both with an ascending and a descend- ing current. The disappearance of electrotonus is so feeble a stimulus as not to excite the nerve. (2) Medium currents cause opening or closing contractions both with an ascending and descending current. (3) Very strong currents cause only a closing contraction with a descending current ; the opening shock does not occur, because, with very strong currents, almost the whole of the intra-polar portion of the electrotonic nerve is incapable of conducting an impulse (p. 615), Ascending currents cause only an opening contraction for the same reason. With a certain strength of current, the muscle remains tetanic while the current is closed {" c/osing 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 C R R C C C C c R c R Medium, Strong, II. In a dying nerve, losing its excitability, according to the Ritter-^'alli law (§ 325, 7), the law of contraction is modified. In the stage of increased excita- bility, weak currents cause only closing contractions with both directions of the current. In the following stage, when the excitability begins to diminish, weak currents cause opening and closing contractions with both currents. Lastly, when the excitability is very greatly diminished, the descending current is followed only by a closing contraction, and the ascending by an opening contraction {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 and Fick, the living intact nerve shows only a closing contraction with both directions 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 respect to the fact, that the excitability varies at certain points in the course of a nerve. The sciatic nerve is divided into three areas : (i) Stretches from the muscle to the place where the branches for THE LAW OF COXTR.\CTION. 619 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 excitability of the nerve is the same for ascending and descending currents. The diflference in the activity, due to the direc- tion of the current, is greater for each stretch of nerve the greater this stretch is distant 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 ner^'e of a rabbit, one-half of the tongue exhibited a tj embling movement instead of a contraction, while on closing a descending ciurrent, 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. ^Sloleschott, v. Bezoldj and Bonders have found similar results for the vagus, \vith 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 is at the periphery (muscle). Pfliiger studied the effect of closing and opening 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 : j//-*?//^ descending currents only opening contractions; 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 of the current (^Volfa). Analogous phenomena have been observed in the sense organs 1 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 ner%-e were stimulated (z'. 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 current 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 contraction which extends to the anode, but which is weaker there than at the cathode ; at the same time, the muscle remains contracted d-uring the time the current is closed. On opening, the contraction begins at the anode; even after opening, 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 Engebnantt, 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. 329, 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 (5. 298, TIT). By acting on a muscle with a 2 per cent, saline solution containing sodic carbonate, the duration of the contraction is increased consider- ably, and occasionally the muscle shortens rhythmically 1 'i_ 296') \ Biedennann). 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 (JVundt). Inhibitory Action. — The constant current, when applied to a muscle in a condition of continued and sustained contraction, has exactly the opposite effect 620 ritter's opening tetanus. 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 procedes from the cathode. Corresponding to this remarkable phenomenon, Biedermann found as regards the currents in the muscle substance following the ordinary law, that every contracted part is negative to every passive section of the muscle. Perhaps the experiment of Pawlow, who found nerve fibres in the adductor muscle of the mussel, whose stimulation caused relaxation of the muscular contraction, may throw some light on this question. 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 \Voltd). According to Griitzner and Ti^erstedt, the cause of the opening contraction is partly due to the occurrence of polarizing after currents (§ 333), and according to Hermann to a diminution of the anodic positive polarization. Engelmann andGriinhagen 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 themselves 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 obtained 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 an 1 Griinhagen's sense. Simultaneous action of the constant current and the nerve current. — Action of two currents. In a nerve-muscle preparation used to j^rove the law of contraction, of course a demar- cation current is developed in the nerve {\ 334, II). If an artificial weak stimulating current be applied to such a nerve, we obtain an inteference effect due to these two currents ; closing a weak constant current causes a contraction, which, however, is not properly a closing contraction, but depends upon the opening (or derivation) of a branch of the demarcation current; conversely, the opening of a weak constant current may excite a contraction, which is really due to the closing of a side branch of the nerve current, in a secondar)^ circuit through the electrodes [Ilerin^, Bieder- mann, Griitzner'). If two induction shocks be simultaneously applied to a motor nerve, two cases are possible. Either the one shock is so feeble that the nerve is not thereby sufficiently excited to cause a contrac- tion, while the other shock causes only a feeble contraction. In this case, the sub-maximal shock plays the part of a weak constant current, and the size of the contraction depends only upon whether the effective stimulus was applied in the area of the anode or the cathode of the sub-maximal shock {Seroall, Griinkagen, IVerigo). If, however, unequal, strong induction shocks, each of which is effective — but separated from each other on account of the electrotonic action — be applied to a nerve, then the result is as if the stronger alone was active. The feebler wave of excitation passes completely into the stronger one [Griin/iajen. IVtvigo). 337. TRANSMISSION OF NERVOUS IMPULSES.— i. If a motor nerve be stimulated at its central end (i) a condition of excitation is set up, and (2) an impulse is transmitted along the nerve to the muscle with a certain velocity. The latter depends on the former and represents the function of con- ductivity. The velocity is about 271^ metres [about 90 feet] per second {v. Hi'/mho/tz), and for the human motor nerves 33.9 [too to 120 feet per second] (i). Helinholtz and Baxt). The velocity is less in the visceral nerves, e.g., in the pharyngeal branches of the vagus 8.2 metres [26 feet] lC/ianveau\ ; 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 NERVE IMPULSE IN SENSORY NERVES AND REACTION TIME. 621 and low temperatures of the nerve (above or below 15° to 25° C.) lessen it {Steiner and Trojtzky) ; also airara, the electrotonic condition {v. Bezold) ; or only anelectro- tonus, 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. Hdmholtz and Baxi), although not at first (v. Vintschgaii). Methods. — l. 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 gal- vanometer is deflected by a current of very short duration, the extent of the FiG. 411. deflection being 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 appUcation of the stimulus and the beginning of the contraction of the muscle, /. e., the deflection of the gal- vanometer, will be less than in the former case, as the impulse has to traverse the whole length of the nerve to reach the muscle. The difference between the two times is the time re- quired by the impulse to traverse a given distance of nerve. Fig. 41 1 shows in a diagrammatic manner the arrangement of the experiment. The galvanojneter, 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 d depresses 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 W k V. Helmholtz's method of estimating the velocity of a nerve pulse. opened, the circuit being z, k, I (ele- ment), 771,0 (primary spiral),/. There- by an opefiifig 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 propa- gated through the nerve to the muscle, M, and the latter contracts when the impulse reaches it, at the same time opening the time- 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 de- flection 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 Fig. 412. that the point, e, comes into contact Scheme for measuring the velocity of nerve ener^^^ /; clamp for r ' ' femur; ?«, muscle ; N, nerve; a;, near, 6, removed irom, C com- mutator ; II, secondary ; I, primary spiral of induction machine ; B, battery ; 1,2, key ; 3, tooth on the smoked plate, P. with the underlying 5o/zV plate, y, the contact at f still remains 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 022 METHOD OF ESTIMATING RAPIDITY OF A NERVE IMPULSE. is greater in the former tlian in the latter case. From the difierence 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. 412. Use a pendulum or spring myograph (Fig. 323^ and suspend in a suitable manner a frog's gas- trocnemius ( 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 (H), and the primary cir- cuit of the induction machine (I). To the secondary coil (II) attach two wires, and connect them with a zomvc\M\.2Xox 7vi thou t cross bars (C). Connect the other binding screws of the commutator with two pairs of wires, arranged so that one pair can stimulate the nerve near the muscle {a), and the other at a distance from it (d^). When the glass plate flies 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 glass plate to fly again. This time the induced current will stimulate the nerve at b, and a second con- traction, a Utile later than the first one, will be obtained. Register the velocity of the glass plate by means of a timing fork, and the curve obtained will be something like Fig. 413, although this curve was obtained on a c} Under traveling at a uniform Fig. 413. I, 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). 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 <^ to be 2 inches, and the time required by the impulse to travel from ^ to ^ to be -^^ second, then we have the simple calculation — 2 inches : 12 inches :: -^^' : -^' , or 80 feet per second. In Fig. 413 the experiment was made on man ; the curve i 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 vertical lines corresponds to y^^ second, /. e., the time required by the nerve impulse to pa«s along 30 centimetres of nerve, which is ecjual 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 thum.b to write oft' their contractions on a rapidly revolving cylinder. [In this case the " pince myographique " of Marey may be used (^ 708). 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 rotatory 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 NERVE IMPULSE IN SENSORY NERVES AND REACTION TIME. 623 taken by the impulse to traverse the above-mentioned length of nerve. [The time is easily ascer- tained 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 to 30 metres [280 to 90 feet] per second (v. Helmholtz). Method. — Two points are chosen as far apart as possible, and at unequal distances from the brain, and they are successively excited by a momentaiy stimulus, e. g., an opening niduction shock applied successively to the tip of the ear and the great toe. The moment of the application of the stimulus 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 reac- tion is called the " reactiott timer It is made up of the time necessaiy for conduction in the sensory nerve, that for the process of perception in the brain, for 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. 528). The reaction time is usually about 0.125 ^'^ 0-2 second (\ 374). Pathological. — The conduction in the cutaneous nerves is sometimes greatly delayed, in altera- tions of the cutaneous sensibihty, 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 i^Naunyn). It is rarely that voluntar}' movements are executed much more slowly from causes depending on the motor nerves, but occasionally the time between the voluntary impulse and the contraction is lengthened, but there may be in addition slower or longer continued contrac- tion of the muscle. In tabes dorsalis or locomotor ataxia, the discharge of rejlex movements'\% delayed; it is slower with thermal stimuli (60°) than with cold ones (0.52° 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 hnpulse. [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 molecular vibration.] The conductivity is destroyed by all influences or conditions 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 c ent7'ifuga I dLixtction toward the muscles, and in sensory nerves in a centripetal di^ixtoXxoxi, i. e., toward the centre; nevertheless, experiment has proved that a nerve conducts an impulse in both directions, just as in a non-living conduc- tor. 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.''^ Proofs. — I. If a nerve be stimulated, its electro-motive properties are affected both above and below the point of stimulation (see Negative Variation in Nerves, § 332). 2. Electrical Nerves. — If the posterior 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 discharges its elec- tricity (^Babuchin, Ma7ttey). 3. Kuhne's Experiments. — The sartorius of the frog has no nerve fibres at its upper and lower ends. If the lower end be cut off, and if the lower third of the muscle be suspended and divided vertically, on stimulating mechanically one apex of the muscle, then the impulse passes in the motor nerves centripetally to the place where the nerve fibre bifurcates in the muscle, and from thence centrifugally into the other or non-stimulated apex, and causes it to contract. 624 PROOFS OF DOUBLE CONDUCTION IN NERVES. Fir.. 414. [The Gracilis of the frog is divided into a larger and smaller portion (L) by a tendinous inscription ( K) running across it (Fig. 414). The nerve (N) enters at the hilum in the larger portion. ])ifurcates, and gives a branch (/') to the smaller portion and another to the larger portion of the muscle. Let the muscle be cut as shown in Fig. 414, avoiding injury to the nerves, so that only the nerve twig {k) connects the larger and smaller portions of the muscle. If the tongue or tip of muscle (Z) with its nerves be stimulated, contraction occurs both in L and M, which is due to centripetal conduction in the motor nerve. The nerve fibres divide dichotomously above where the nerves are given off to the portions L and M.] [If the inscription be left, and the lower tip of the muscle (which is devoid of nerves) be stimulated, only the lower and not the ujiper part twitches ; but if a part of the muscle con- taining nerves common to both parts be stimulated, then both parts of the muscle contract. This also proves that j)ure muscu- lar excitation does not travel backward from the muscle to the nerves. How this comes about, we are entirely ignorant.] The following experiments used to be cited as proofs, but they do not stand the test of criticism. 4. Union of Motor and Sensory Nerves. — Tf the hypoglossal and Ungual 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 Kuhne's Gracilis ex- periment. Fig. 415. Fig. 416. Fk;. 417. months after the union and restitution of the nerves, stimulation of the cen- tral end of the lingual causes con- traction in the corresponding half of the tongue. Hence, it has been as- sumed that the lingual, which is the sensoyy nerve of the tongue, must conduct the impulse in a peripheral direction to the end of the hypoglos- sal. This experiment is not conclu- sive, 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 hjpoglossal. Further, if the chorda be divided and allowed to degenerate before the above described experiment is made, then no contrac- tions occur on .stimulating the lingual above the point of union {\ 349). 5. Bert's Experiment. — Paul Bert removed the skin from the tip of the tail of a rat, and stitched it into the skin of the back of the animal, where it united with the tissues. After the first union had taken place, the tail was then divided at its base, so that the tail, as it were, grew out of the skin on the back of the animal. On stimulating the tail, the animal exhib- ited signs of sensation. For the expla- nation of this experiment, see ^ 325. 339. ELECTRO-THERAPEUTICS— REACTION OF DEGENERATION.— Elec- tricity is frequently employed for therapeutical puqDOses, the rapidly interrupted current of the induction machine, or Faradic current, being frequently used (especially since Duchenne, 1847), the W(7^«^/(?-^/if(-/r/ftf/ apparatus, and the i?jr/ra-«i I 3 2 I O N obturator. M. pectineus. M. adductor magnus. M. adduct.longus. N. peroneus, M. tibial, antic. M. e.xten. dig.com. long. M. peroneus longus. M. peroneus bre vis. M. extens. hallucis long. M. extens. digit, comm brevis. N. cruralis. M. tensor fasciae latse (Nn. glut. sup.). M. quadriceps femoris (general centre). M. rectus femoris. M. cruralis. M. vastus externus. M. vastus internus. I M. gastrocnem. extern M. soleus. M. flexor hallucis long. M. abductor digiti. min. Mm. interossei dorsales. 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). by Stimulating at the entrance of the nerve, each muscle may be caused to contract singly. In \ 349 the motor points of the face, and in \ 347 those of the neck, are indicated. The constant current may be employed as a stimulus, when it is closed and opened, in the form of an internipteJ currtxw., by altering its direction and increasing or diminishing its intensity, but it also causes upoiur action. On ciosini^ 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 eiectrotonus 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 REACTION OF DEGENERATION. 627 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 recover after the passage of a constant current through them. 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. 415); while, if the motor nerves are the primary seat, then the electrodes are applied over them. The current used must be only of ve>y moderate strength ; strong tetanic contractions are injurious, and so is too prolonged application i^Eulenburg). Fig. 421. M. biceps fern. (cap. long.) (grt. sciat.). M. biceps fern. (cap. brev.) (grt. sciat.). N. peroneus. M. gluteus maxiraus (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. comra. long. M. flexor hallucis longus. N. tibialis. Motor points of the sciatic nerve and its branches ; the peroneal and tibial nerves. The galvanic current may also be applied to the muscles or to their motor nerves, or to the centres 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 apphed 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 rot 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 {x2j^\d\y interrupted) and the constant current. This is called the " reaction of degeneration." We must remember the physiological fact that a dying 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. Baierlacher, in 1859, 028 REACTION OF DEGENERATION. 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 be abnormally increased, but may disappear on recovery taking place. According to Neumann, it is the longer duration of the constant current as opjwsed to the momentary closing and opening of the induced current which makes the contraction of the muscle possible. If thp constant current be broken as rapidly as the Faradic current is broken, then the constant current does not cause contraction. Conversely, the induced current may be rendered efiective 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 energetically upon curarized muscles ( Briicie). 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 tiie magnetic needle depends ujxjn these two factors. [Galvanic excitability is the tenn applied to the condition of a nerve or muscle, whereby it responds to the opening or closing of a continuous current. The effects difl'er according as the current is opened or closed, and according to its strength. As a rule, the cathode causes a con- traction chiefly at closure, the anode at opening the current, while the cathode is the stronger stimulus. With a 7t>fi7/: current, the cathode produces a simple contraction on closing the current, but no contraction from the anode. With a medium cun^ent, we get with the cathode a strong closing contraction but no opening contraction, while the anode excites feeble opening and closing contractions. With a strong current, we get with the cathode a tetanic contraction at closure, and a perceptible contraction at opening, while with the anode there is contraction both at opening and closing.] [The law of contraction is usually expressed by the following formula {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 — 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 Oc.} [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 to 58th day ; it again diminishes, however, with variations, from the 7 2d to 80th day ; the anode closing contraction is stronger than the cathode closing contraction. The contractions in the affected muscles occur slowly in a peristaltic manner, and are local, in contrast with the rapid contraction of normal muscle. The diminution of the excitability of the nenies 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," which is constantly present in progressive muscular atrophy {EH?). [The "reaction of degeneration" may occur before there is actual paralysis, as in lead poison- ing. When it occurs we have to deal with some affection of the nerve fibres, or of the trophic nerve cells. When it is established, (i) stimulation of the nerve with Faradic and galvanic electricity 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, but the contraction is longer and more of a tonic character, and shows a tendency to become tetanic. The electrical excitability is generally unaffected in paralysis of cerebral origin, and in some forms of spinal paralysis, as primary lateral sclerosis and transverse myelitis, 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 0/ degeneration''' [E. Reviak, Erb). II. In Various Forms of Spasm (spasms,contracture, muscular tremor) the constant current is most effective [Re'nak). liy 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 irritants from the seat of the irritation. APPLICATIONS OF ELECTRICITY IN DISEASE. 629 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. Faradization 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 [Eeinak), 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 is frequently used (Fig. 417). 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 rejiexly and accelerate the blood stream, increase the heart's action, and constrict the blood vessels, while strong c\y\:x^w\.% cause the opposite effects (C. 7Vaznding to the motorial end jjlates of the muscular fibres, the contraciile sutistance having disappeared, .so that during phy>iological activity the chemical energy is changed into electricity alone, while there is no •' work " done. This view is supported by the observation of Baljuchin, that during development the organs are originally formed like musclts ; 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 — IVeyl). Ihe organs manifest fatigue; they have a "latent period" of 0016 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 jjrocess {Marey). Mechanical, chemical, thermal, and electrical stimuli cause a dis- charge; a single induction shock is not effective (Jfrtf//.?). During the electrical discharge the current traverses the muscles of the animal itself; the latter co.itract in the toqiedo, while they do not do so in the gyninotus and malapterurus during the discharge (S/einer). A torpedo 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 C. makes it more so. The organ becomes tetanic with strychnin [Becquerel], while curara paralyzes it {Sachs). Stimulation of the electrical organ of the torpedo causes a discharge (Malleitcci) ; cold retards it, while section of the electrical nerves paralyzes the organ. The electri- cal fishes themselves are but slightly affected by very .strong induction .shocks transmitted through the water in which they are swimming [du Bois-Reyinond). The substance of the electrical organs is singly refractive; excised ])ortions give a current during rest, which has the same direction as the shock; tetanus of the organ weakens the current [Sachs, dti Buis-Keymond). Perhaps the electrical organ of malapterurus is evolved from modified cutaneous glands {Frilsch). 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 electro- lysis with the electrical discharge. Becquerel, Brechet, and Matteucci studied \h& direction o{ \!af: 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 (lalvani (1791), who observed that frogs' legs connected with an electrical machine contracted, and also when they were toucher! with two difterent metals. He believed that nerves and muscles generated electricity. Alessandro Volta ascribed the second experiment to the electrical current proiuced by the contact of dissimilar metals, and therefore outside the tissues of the frog. The contraction without metals described by Oalvani was confirmed by Alex. V. Humboldt (1798). PfafT ( 1 793 ) first observed the efiect 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 onward. Physiology t°h'k 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 distributed to a special area within which, under normal circumstances, in the intact body, it performs its functions. This function of the individual nerves, determined by their anatomical connections, is called their " specific energy." I. Centrifugal or Efferent Nerves. — (a) Motor. — Those nerve fibres whose peripheral end organ consists of a muscle, the central ends of the fibres being connected with nerve cells : — 1. Motor fibres of striped muscle (^^ 292 to 320). 2. Motor nerves of the heart (^ 57). 3. Motor nerves of smooth muscle, 1?.^., the intestine (^ 171). 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, according to the kind of nerve fibres present in the nerve. Thus, the secretory and vasomotor nerves of glands maybe 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. In some tissues, we know of a direct connection of their elements with nerve fibres, which may influence their nutrition. Nerves are connected with the corneal corpuscles (^ 201, 7), with the pigment cells of the frog's skin (^,^r;«a««), the connective -tissue corpuscles of the serous membrane of the stomach of the frog, and the cells around the stomataof lymphatic surfaces (^ 196, 5) [£. F. Hoffmann). Trophic Influence of Nerves. — The trophic functions of certain nerves are referred to as follows : On the influence of the trigeminus on the eye, the mucous membrane of the mouth and nose, the face (§ 347); the influence of the vagus on the lungs (| 352) ; motor nerves on muscle (? 307) ; nerve centres on nerve fibres (^ 325, 4) ; certain central organs upon certain viscera {I 379)- Section of certain nerves influences the growth of the bones. H. Nasse found that, after sec- tion of their nerves, the bones showed an absolute diminution of all their individual constituents, while there was an increase of the fat. Section of the spermatic nerve is followed by degeneration of the testicle [Nelaton, Obolensky). After extirpation of their secretory nerves, there is degenera- tion of the sub-maxillary glands (p. 258). Section of the nerves of the cock's comb inter- feres with the nutrition of that organ [Legros, Schiff). After section of the 2d cervical nerve in rabbits and cats, the hair falls ofl" the ear on that side [Joseph). Section of the cervical sympa- thetic nerve in young, groaning 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^ ; 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], 631 632 TROPHIC NERVES AND TROPHO-NEUROSES. Blood Vessels. — Lewaschew found tliat prolonged, uninterrupted stimulation of the sciatic nerve of dogs, by means of chemical stimuli [threads dii)ped in sulphuric acid], caused hypertrophy of the lower limb and foot, together with the formanon of aneurismal dilatations upon the blood vessels. Skin and Cutaneous Appendages. — In man, stimulation or paralysisof nerves, or degeneration of tlie gr.iy mailer of the spinal con), is not un frequently followed by changes in the pigmentation of the skin, in llie nails, in the hair and its mode of growth and color (Jtirisch). [Injury to the brain, as by a fall, sometimes results in paralysis of the hair follicles, so that, after such an injur)-, the hair is lost over nearly the whole of the body.] Sometimes there may be eruptions u|)on the skin, apparantly traumatic in their origin (r'. BarenspniUi^ ). .Sometimes there is a tendency to decubitus {\ 379), and in some rare cases of tabes, there is a peculiar degeneration of the joints (Charcot's disease). The changes which take place in a nerve separated from its centre are described in § 325. [Tropho-neuroses. — Some of the chief data on which the existence of trophic nerves is assumed are indicated alxive. 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 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-hyper- trophic 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 ijulk their power is diminished.] Cutaneous Trophic Affections. — Among these may be mentioned the occurrence of red patches or er)'thema, urticaria or nettle-rash, some forms of lichen, eczema, the bulla; 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 cutaneous eruption and the distribu- tion of a nerve is sometimes ver)' marked in herpes zoster, which fre(|uently follows the distribution of the intercostal and supraorbital nerves. Glossy skin (Paget, lVei>- Mitchell) is a condition depending 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 disappeared. In myxcedema, the subcutaneous tissue and other organs are infiltrated with, while the blood con- tains, mucin. The subcutaneous tissue is swollen, and the patient looks as if suffering from renal dropsy. There is marked alteration of the cerebral faculties, and a condition resembling a " cretinoid state '" occurs after the excision of the thyroid gland. Victor Ilorsley has shown that a similar condition occurs in monkeys after excision of the thyroid gland (^ 103, III). [Laycock described a condition of nervous cedema 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 localized leucoderma, where circumscribed patches of the skin are devoid of pigment. The pigmentation 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. In anaesthetic leprosy, the anaesthesia is due to the disease of the nervous structure, which results in disturbance 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 decubi- tus 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 the erythematous dusky patch to inflammation, ulceration, and gangrene of the buttock — is completed in a few days. An acute bed sore may form when every attention 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 anjesthetic side, a fact which seems to show that the trophic, like the sensory fibres, decussate in the cord {Ross).'\ [There are other forms due to nervous disease, including symmetrical gangrene and local asphyxia of the terminal parts of the body, such as toes, nose, and external ear, caused perhaps by spasm of the small arterioles (Raynaud's disease) ; and the still more curious condition of per- forating ulcer of the foot. Hemorrhage of nervous origin sometimes occurs in the skin, including those that occur in locomotor ataxia after severe attacks of pain, and haematoma aurium, or the insane ear, which is specially common in general paralytics.] INHIBITORY AND AFFERENT NERVES. 633 (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) ; see also 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 especially in ^ 237. [There is the greatest uncertainty as to the nature and mode of action of inhibitory nerves, but take as a type the vagus, 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 ; hence, he groups it as anabolic nerve, the outward symp- toms 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. Beside motor nerves to striped muscle, he groups them as follows : — - 1. Nerves to vascular muscles. (a) Vasomotor, i. e., vaso-constrictor, accelerators and augmentors-of the heart. (^) Vaso-inhibitory, i. e., vaso- dilators and inhibitors of the heart. 2. Nerves of the visceral muscles. {a) Visce7'o-motor. (b) Viscero-inhibitory. 3. Glandular nerves.] [Other terms are applied to nerves with reference to the chemical changes they excite in a tissue in which they terminate. The ordinary metabolism is the resultant of two processes — one constructive, the other destructive, or of assimila- tion and dissimilation respectively. The former process is anabolism, the latter katabolism. A motor nerve excites chemical destructive changes in a muscle, 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, and brings about a. constructive metabolism of the cardiac tissue, is an anabolic nerve (^Gaskell>).'\ II, Centripetal or Afferent Nerves. — (a) Sensory Nerves (sensory in the narrower sense), which by means of special end organs conduct sensory impulses to the central nervous Fig. 422. system. (b) Nerves of Special Sense. (c) Reflex or Excito-motor Nerves. — When the periphery of one of these nerves is stimulated, an im- pulse is set up which is conducted by them to a nerve centre, from whence it is transferred to a centrifugal or efferent fibre, and the mechanism (I, a, b, c, d) in con- nection with the peripheral end of this efferent fibre is set in action ; thus, there are — Reflex motor, Reflex secretory, and Reflex inhibitory fibres. [Fig. 422 shows the simplest mechanism necessary for a reflex Scheme of a reflex motor act. s, motor act. The impulse starts from the skin, S, travels nerve ceU; ^yf efferent fibre. ' up the nerve, af, to the nerve centre or nerve cell, N, situate in the spinal cord, where it is modified and transferred to the outgoing fibre, n a A), or even in the trigeminus {Schiff, v. Griife). Atropin paralyzes the intra-bulbar 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 pu])il is dilated in paralysis of the oculomotorius, in asphyxia, sudden cerebral anremia {^e. g., by ligature of the carotids, or beheading), sudden venous congestion, and at deatli. Pathological. — Complete paralysis of the oculomotorius is followed by (i) drooping of the upper eyelid (ptosis paralytica) ; (2) immobility of the eyeball ; (3) squinting (strabismus) outward and downward, and consequently there is double vision (diplopia) ; (4) slight protnision of the eye- ball, 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 retractor bulbi muscle, the protrusion of the eyeball is more pronounced; (5) moderate dilatation of the pupil (mydriasis paralytica); (6) the pupil does not contract to light; (7) inability to accommodate for a near object. It is to be noted, however, that the paralysis may be confined to individual branches of the ner\'e, /. e., there may be incomplete paralysis. [Squinting. — In paralysis of the superior rectus, the eye cannot be moved upward, and espe- FiG. 426. ty'vfty"vX/''vtyU Internal External Superior Inferior Inferior Superior rectus. rectus. rectus. oblique. rectus. oljlique. The black cress r!presents the true image, the light cross the false image. The left eye is represented as affected in all cases (Bristmv). cially 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. 426, 3). Inferior Rectus. — Defect of downward, and especially downward and outward movement, the eye being directed upward 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. 426, 5). Internal Rectus. — Defective inward movement, diver- gent stjuint, 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 healtliy side, when looking at an object, while there is secondary deviation of the healthy eye outward (Fig. 426, i). Inferior oblique is rare, the eye is turned slightly downward and inward, and defective movement upward. Diplopia with the false image above the true one, especially on looking upward; the false image is obHque, and directed to the patient's left when the left eye is affected (Fig. 426, 4).] Stimulation of the branch supplying the levator palpebnx; in man causes lagophthalmus spasticus, while stimulation of the other motor fibres causes a corresponding strabismus spasticus. The latter form of scjuinting may be caused also refie.xly — e.g., in teething, or in cases of diarrhoea 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 m.^y be produced by stimulation of the corpora quad- rigemina, as well as by other means. Tonic contraction of the sphincter pupilla; is called myosis spastica, and clonic contraction, hippus. .Spasm of the muscle of accommodation (ciliary muscle) is sometimes observed ; owing to the imperfect judgment of distance, this condition is not unfre- -aiiss, Block). Section of the facial in young animals causes atrophy of the corresjwnding nmsclcs. The facial bones are also imperfectly develojied; they remain smaller, and hence the bones of the sound side of the face grow toward, and ultimately across, the middle line toward the affected side {^Broivn- Si'ijtiard). The salivary glands also remain smaller. Stimulation — or irritation in the area of the facial — causes partial or extensive, either direct or reflex, tonic or clonic spasms. The extensive forms are known as " mimetic facial spasm." Among the partial forms are tonic contraction of the eyelid (blepharospasm), which is most common; and is caused reflexly by stimulation of the sensory nerves of the eye, e.g., in scrofulous NERVUS ACUSTICUS. 653 ophthalmia, or from excessive sensibility of the retina (photophobia). More rarely, the excitement proceeds from some more distant part, e.g., in one case recorded by v. Grafe, from inflammatory stimulation of the anterior palatine arch. The centi-e for the reflex is the facial nucleus. The clonic form of spasm — spas??iodtc winking (spasmus nictitans) — is usually. of reflex origin, due to irrita- tion of the eye, the dental nerves, or even of more distant nerves. In severe cases, the affection may be bilateral, and the spasms may extend to the muscles of the neck, trunk, and upper extremities. Contraction of the muscles of the lip may be excited by emotions (rage, grief), or reflexly. Fibrillar contractions occur after section of the facial as a " degeneration phenomenon " (p- 525). [If the facial be torn out of the stylo-mastoid foramen, there is paralytic oscillation of the lip muscles {Sc/iiff). If, in such an animal, the posterior root of the annulus of Vieussens be stimulated electrically, as it contains vaso-dilator fihres [Dastre and Morat), not only do the blood vessels of the cheek and lips dilate, but the veins pulsate and florid blood escapes from the veins, just as occurs in the sub-maxillary gland when the chorda is stimulated. On stimulating the ansa, after section of the seventh, there is a pseudo-motor effect on the muscles of the cheek and lips, so that there is an analogy between the chorda and the ansa {^Rogo%!jicz).'\ /«/ra-irr««Z(?/ stimulation of the most varied description may cause spasms. Lastly, facial spasm may be part of a general spasmodic condition, as in epilepsy, cholera, hysteria, tetanus. Aretjeus (81 a.d.) made the interesting observation that the muscles of the ear contracted during tetanus. Very rarely have spasmodic elevation of the palate and increased salivation been described as the result of irritation of the facial i^Leube). Moos observed a profuse secretion of saliva on stimulating the chorda during an operation on the tympanic cavity. 350. VIII. NERVUS ACUSTICUS.— Arises by iwo roots {Stieda) ; a larger anterior and a smaller posterior one. From the former proceeds the vestibular nerve, and from the latter the cochlear nerve; these are separated in the sheep and horse [Horbaczeivski). Each root springs from a median and a lateral nucleus, so that there are four nuclei. Some fibres come from the cerebellum, and these may be connected with equilibration. The chief mass of the posterior ganglion fibres of the cochlear nerve cross and pass to the corpora quadrigemina, the internal geniculate, and Finally to the temporo-sphenoidal lobe (^ 378, IV, 2). After extirpation of the temporo-sphenoidal lobe, these fibres atrophy into the internal capsule and internal geniculate body {v. Monakow). The strise acusticse form a second decussating projection system. The origins of both acoustic nerves are connected by commissures in the brain i^Flechsig). In the course of the internal auditory meatus, the auditory and portio intermedia of the facial exchange fibres, but the physiological significance of this is unknown. Function. — The acusticus or auditory nerve has a double function : i. It is the nerve of hearing; when stimulated, either at its origin, in its course, or at its peripheral terminations, it gives rise to sensations of sound. Every injury, accord- ing to its intensity and extent, causes hardness of hearing or even deafness. 2. Quite distinct from the foregoing is the other function, which depends upon the semicircular canals, viz., that stimulation of the peripheral expansions in the ampullae influences the movements necessary for maintaining the equilibrium of the body. Brenner's Formula.— The relation of the auditory nerve to the galvanic current is very important. In healthy persons, when there is closure at the cathode, there is the sensation of a clang (or tone) in the ear, which continues with variations while the current is closed. When the anode is opened, there is a feebler Xo^sx^ (^Brenner'' s Normal Acoitstic Formula). This clang coincides exactly with the resonance fundamental tone of the sound-conducting apparatus of the ear itself Pathological. — Increased sensibility oi the auditory nerve in any part of its coiu"se, its centre, or peripheral expansions, causes the condition known as hyperakusis, which usually is a sign of greatly increased nervous excitability, as in hysteria. When excessive, it may give rise to distinctly painful impressions, which condition is known as acoustic hyperalgia (^Etdenburg). Stimulation of the parts above named causes sensations of sound, the most common being the sensation oi singing in the ears, or tinnitus. This condition is often due to changes in the amount of blood in the blood vessels of the ear — either anaemic or hypersemic stimulation. There is well- marked tinnitus after large doses of quinine or salicin, due to the vasomotor effect of these drugs upon the vessels of the labyrinth (A'zVf/^w^/-). Not unfrequently, in cases of tinnitus, the reaction due to the galvanic current is increased. More rarely there is the so-called '■'■paradoxical reaction" — z.^?., on applying the galvanic current to one ear, in addition to the reaction in this ear, there is the opposite result in the non- stimulated ear. In other cases of disease of the auditory nerve, noises rather than musical notes are produced by the current; stimulation, especially of the cortical centre of the auditory nerve, chiefly in lunatics, may cause auditory delusions [\ 378, IV.). According as the excitability of the auditory nerve is diminished or abolished, there is the condition of nervous hardness of hearing (hypakusis), or nervous deafness (anakusis). 054 THE SEMICIRCULAR CANALS. The Semicircular Canals of the Labyrinth. — Section or injury to these canals does not interfere with hearing, l)ut other important symptoms follow their injury, such as disturbances of equilibrium due to a feeling of giddiness, especially when the injury is bilateral (yvVwr^/Zj-). This does not occur in ^<>\\Q<,{Kiese/bach). The pendulum-like movement of the head, in the direction of the plane of the injured canal, is very characteristic. If the horizontal canal be divided, the head (of the pigeon) is turned alternately to the right and left. The rotation takes place, especially when the animal is about to execute a movement : when it is at rest, the movement is less pronounced. The phenomenon may last for months, and injury to \\\q. posterior vertical canals causes a well-marked up and down move- ment or nodding of the head, the animal itself not unfrequently falling forward or backward. Injury to the superior vertical canals also causes pendulum-like vertical movements of the head, while the animal often falls forward. When all the canals are destroyed, various pendulum-like movements are performed, while standing is often impossible. Breuer found that electrical stimulation of the canals caused rotation of the head, while Landois, on applying a solution of salt to the canals, observed pendulum-like movements, which, however, disappeared after a time. A 25 per cent, solution of chloral dropped into the ear of a rabbit causes, after fifteen minutes, a similar destruction of the canals (Vulpian). Section of the acoustic nerves within the cranium has the same result (^Bechterew). Explanation. — tioltz regards the canals as organs of sense for ascertaining the equilibrium or position of the head in space ; Mach, as an organ for ascertaining the movements of the head. According to Goltz's statical theory, every position of the head causes the endolymph to exert the greatest pressure upon a certain part of the canals, and thus e.xcites in a varying degree the nerve terminations in the ampulla. According to Breuer, when the head is rotated, currents are produced in the endolymph of the canals, which must have a fixed relation to the direction and extent of the movements of the head, and these currents, therefore, when they are perceived, afford a means of determining the movement of the head. The nervous end organs of the ampullre are arranged for ascertaining this perception. If the semicircular canals are an apparatus — in fact, " sense organs " — for the sensation of the equilibrium, and if their function is to determine the position or movements of the head, necessarily their destruction or stimulation must alter these perceptions, and so give rise to abnormal movements of the head. Vulpian regards the rotation of the head as due to strong auditory perceptions (?) in consequence of affections of the canals. Bottcher, Tomaszewicz, and Baginsky regard the injury to the cerebellum as the cause of the phenomena. The pendulum-like movements, however, are so characteristic that they cannot be confounded with disturbances of the equilibrium which result from injury to the cerebellum. [Kinetic Theory. — In 1S75 Crum Brown pointed out that, if a person be rotated passively, his eyes being bandaged, he can, up to a certain point, indicate pretty accurately the amount of move- ment, but after a time, this cannot be done, and if the rotation, as on a potter's wheel, be stopped, the sense of rotation continues. Crum Brown suggested that cur- FlG. 432. rents were produced in the endolymph, while the terminal hair ceils lagged behind, and were, in fact, dragged through the fluid. He pointed out that the light posterior canal is in line with the left superior, and the left posterior with the right superior, a fact which is readily observed by looking from behind at a skull, with the semicircular canals exposed (Fig. 432). He assumes that the canals are paired organs, and that each pair is connected with rotation or movement of the head in a particular direction.] Giddiness. — This feeling of false impressions as to the relations of the surroundings and consequent move- LP ■/ N Rp ments of the body, occurs especially during acquired Diagram of the disposition of the changes in the normal movements of the eyes, whether semicircular canals. Rs and (j^g jq invohmtary to and fro movemcnts of the eye- L.S, right and left superior; LP , ,, , ^ , . ^ , and RP, right and left posterior ; balls ( nystagmus), or to paralysis of some eye muscle. ^eLT'^ ^^' ''^''' ^"'^ ''^' '''' Active or passive movements of the head or of the body are normally accompanied by simultaneous move- ments of both eyeballs, which are characteristic for every position of the body. The general character of these "compensatory" bilateral movements of the eyes consists in this, that during the various changes in the position of the head GIDDINESS, NYSTAGMUS, MENIERE'S DISEASE. Q55 and body, the eyes strive to maintain their primary passive position. Section of the aqueduct of Sylvius at the level of the corpora quadrigemina, of the floor of the fourth ventricle, of the auditory nucleus, both acustici, as well as destruction of both membranous labyrinths, causes disappearance of these movements; while, conversely, stimulation of these parts is followed by bilateral associated move- ments of the eyeballs. Compensatory movements of the eyeballs, under normal circumstances, may be caused reflexly from the membranous labyrinth. Nerve channels, capable of exciting reflex movements of both eyes, proceed from both labyrinths, and, indeed, both eyes are affected from both labyrinths. These channels pass through the auditory nerve to the ce7itre (nuclei of the 3d, 4th, 6th, and 8th cranial nerves), and from the latter efferent fibres pass to the muscles of the eye (^Hogyes). Cyon found that stimulation of the horizontal semicircular canal was followed by horizontal nystag- mus ; of the posterior, by vertical, and of the anterior canal, by diagonal nystagmus. Stimulation of one auditory nerve is followed by rotating nystagmus, and rotation of the body of the animal on its axis toward the stimulated side. Poisons. — Chloroform and other poisons enfeeble the compensatory movements of the eyeballs, while nicotin and asphyxia suppress them, owing to their action on their nerve centre. It is probable that the disturbances of equilibrium and the feeling of giddiness which follow the passage of a galvanic current through the head between the mastoid processes, are also due to an action upon the semicircular canals of the labyrinth (§ 300). Deviation of the eyeballs is produced by such agalvanic current {Hitzig). The same result is produced when the two electrodes are placed in the external auditory meatuses. Pathological. — Meniere's Disease. — The feeling of giddiness, not unfrequently accompanied by tinnitus, which occurs in Meniere's disease, mast be referred to an affection of the nerves of the ampullae or their central organs, or of the semicircular canals themselves. By injecting fluid violently into the ear of a rabbit, giddiness, with nystagmus and rotation of the head toward the side operated on, are produced i^Baginsky). In cases in man, where the tympanic membrane was defective, Lucas, when employing the so-called ear air douche at o.i atmosphere, observed abduction of the eyeball with diplopia, giddiness, darkness in front of the eyes, while the respiration was deeper and accelerated. These phenomena must be due to stimulation or exhaustion of the vestibular branch of the auditory nerve {^Hogyes). In chronic gastric catarrh, a tendency to giddiness is an occasional symptom (Trousseau's gastric giddiness). This may, perhaps, be caused by stimulation of the gastric nerves exciting the vasomotor nerves of the labyrinth, which must affect the pressure of the endo- lymph. Analogous giddiness is excited from the larynx ( C^arcc'/'), and from the urethra [Erlenmeyer) . [Vertigo or giddiness is a very common symptom in disease, and may be produced by a great many different conditions. It literally means" a turning." As Cowers points out, the most common symptom is that the patient himself has a sense of movement in one or other direction ; or objects may appear to move before him ; and more rarely there is actual movement" commonly in the same direction as the subjective sense of movement." It is sometimes due to a want of harmony between the impressions derived from different sense organs or " contradictoriness of sensory impressions lyGrainger Steivart), as is sometimes felt on ascending or descending a stair, or by some persons while standing on a high tower, constituting tower or cliff giddiness. One of the most remarkable conditions is that called "agoraphobia" [Benedikt, IVestphal). The person can walk quite well in a narrow lane or street, but when he attempts to cross a wide square, he experiences a feeling closely allied to giddiness. The giddiness of sea-sickness is proverbial, while some persons get giddy with waltzing or swinging. Besides occurring in Meniere's disease, it sometimes occurs in locomotor ataxia, and some cerebral and cerebellar affections, including cerebral anaemia. Very distressing giddiness and headache are often produced by paralysis of some of the ocular muscles, d'.^., the external rectus. Defective or perverted ocular impressions, as well as similar auditory impressions, may give rise to vertigo ; in the latter or labyrinthine form the vertigo may be very severe. Severe vertigo is often accompanied by vomiting. A hard plug of ear wax may press on the membrana tym- pani and cause severe giddiness. The forms of dyspeptic giddiness and the toxic forms due to the abuse of alcohol, tobacco, and some other drugs are familiar examples of this condition.] [Tinnitus Aurium, or subjective noises in the ear, is a very common symptom in disease of the ear ; the noise may be continuous or discontinuous, be buzzing, singing, or rumbling in character.] 351. IX. NERVUS GLOSSO-PHARYNGEUS.— Anatomical. — This nerve (Fig. 429, 9) arises from the nucleus of the same name, which consists partly of large cells (motor) and partly of small cells (belonging to the gustatory fibres). The nucleus lies in the lower half of the fourth 656 THE GLOSSO-PHARYNGEAL NERVE. ventricle, deep in the medulla oblongata, near the olive (Fig. 427), and ]X)steriorly it abuts on that ot the vagus. The anterior ])art of the central nucleus is regarded as the root of the portio intermedia of the facial (^ 349)- The nerve also receives tibres from the vagal centres. The tilires collect into • two trunks, which afterward unite and leave the medulla oblongata in front of the vagus. In the fossula petrosa it has on it the petrous ganglion, from which, occasionally, a special part on the posterior twig is separated within the skull as the ganglion of Ehrenritter. Communicaling branches are sent from the petrous ganglion to the trigeminus, facial (f and rr), vagus and carotid plexus. From this ganglion also the tympanic nerve (/.) ascends vertically in the tympanic cavity, where it unites with the tympanic plexus. This branch (| 349, 4) gives sensory tibres to the tympanic cavity and the Eustachian tube ; while, in the dog, it also carries secretory fibres for the parotid into the small superficial petrosal nerve {^Heidenhain — \ I45). Function. — i. It is the nerve of taste for the posterior third of the tongue, the lateral part of the soft palate, and the glosso-palatine arch (compare § 422). [This is denied by Gowers (p. 682, Am. Ed., 1888).] The nerve of taste for the anterior two-thirds of the tongue is referred to under the lingual {\ 347, III, 4) and chorda tympani nerves [\ 349, 4). The glossal branches are provided with ganglia, especially where the nerve divides at the base of the circumvallate papilhx; i^J\emak, Kolliker, Stir- lini;). The nerve ends in the circumvallate papillce (Fig. 429, U), and the end organs are repre- sented l)y the taste bull)S (§ 422). 2. It is the sensory nerve for the posterior third of the tongue, the anterior surface of the epiglottis, the tonsils, the anterior palatine arch, the soft palate, and a part of the pharynx. From this nerve there may be discharged reflexly, move- ments of deglutition, of the palate and pharynx, which may pass into those of vomiting (§ 158). These fibres, like the gustatory fibres, can excite a reflex secre- tion of saliva (§ 145)- 3. It is motor for the stylo-pharyngeus and middle constrictor of the pharynx ^{VolkmanTi) ; and, according to other observers, to the (?) glasso-palatinus (_Hein) and the (??) levator veli palatini and azygos uvulce (coinpare Spheno-palatine ganglion, § 347, II). It is doubtful whether the glosso-pharyngeal nerve is really a motor nerve at its origin — although Meynert and others have described a motor nucleus — or whether the motor fibres reach the nerv^e at the petrous ganglion, through the communicating branch from the facial. 4. A twig accompanies the lingual artery; this nerve, perhaps, is vaso-dilator for the lingual blood vessels. Pathological. — There are no satisfactorj' observations on man of uncomplicated affections of the glosso-pharj^ngeal nerves. 352. X. NERVUS VAGUS.^Anatomical. — The nucleus from which the vagus arises along with the 9th and iith nerve is in (i) the ala cinerea in the lower half of the calamus scrip- torius (Fig. 427, 10) [and it is very probably the representative of the cells of the vesicular column of Clarke (^ 366)]. (2) Other fibres come from the " longitudinal bundle " or " respirator)- bundle " lying outside the nucleus, and reaching down into the cervical enlargement. (3) A motor nucleus — the nucleus ambiguus — a prolongation of some of the cells of the anterior horn of the spinal cord, gives some motor fibres. It leaves the medulla oblongata by 10 to 15 threads behind the 9th nerve, between the divisions of the lateral column, and has a ganglion (jugular) upon it in the jugular foramen (Fig. 428, VIII). Its branches contain fibres which subserve different functions. 1. The sensory meningeal branch from the jugular ganglion accompanies the vasomotor fibres of the sympathetic on the middle meningeal artery, and sends fibres to the occipital and transverse sinus. When it is irritated, as in congestion of the head and inflammation of the dura mater, it gives rise to vomiting. 2. The auricular branch (Fig. 433, au.^ from the jugular ganglion receives a communicating branch from the petrous ganglion of the 9th nerve, traverses the canaliculus mastoideus, crossing the course of the facial, with which it exchanges fibres whose function is unknown. On its course, it gives sensory branches to the posterior part of the auditory meatus, and the adjoining part of the outer ear. A branch runs along with the posterior auricular branch of the facial, and confers sensibility on the muscles. THE CONNECTING AND OTHER BRANCHES OF THE VAGUS. 657 When this nerve is irritated, either through inflammation or by the presence of foreign bodies in the outer ear passage, it may give rise to vomiting. Stimulation of the deep part of tlie external auditory meatus in the region supplied by the auricular branch causes coughing reflexly \_e.g., from the presence of a pea in the ear] . Similarly, contraction of the blood vessels of the ear may be caused reflexly {^Snellen, Loven). The nerve is the remainder of a considerable branch of the vagus which exists in fishes and the larvae of frogs, and runs under the skin along the side of the body. 3. The connecting branches of the vagus are : (i) A branch which directly connects the petrous ganghon of the 9th with the jugular gangHon of the loth; its function is unknown. (2) Directly above the plexus gangliiformis vagi, the vagus is joined by the whole inner half of the spinal accessory. This nerve conveys to the vagus the motor fibres for the larynx, and the cervical part of the oesophagus (which, according to Steiner, lie in the inner part of the nerve trunk), as well as the xrCtX'CoxXoxy fibres for the heart (^Cl. Bernard). (3) The plexus ganghiformis fibres, whose function is unknown, join the trunk of the vagus from the hypoglossal, superior cervical ganglion of the sympathetic, and the cervical plexus. 4. Pharyngeal Plexus. — The vagus sends one or two branches (Fig. 433, 2) from the upper part of the plexus gangliiformis to th.t pharyngeal plexus, where at the level of the middle constrictor of the pharynx, it is joined by the pharyngeal branches of the 9th nerve and those of the upper cervical sympathetic ganglion, near the ascending pharyngeal artery, to form the pharyngeal plexus. The vagal fibres in this plexus supply the three constrictors of the pharynx with motor fibres, while the tensor palati (^Otic ganglion, § 347, III) and levator of the soft palate (compare Spheno-palatine ganglion, % 347, 11) also receive motor (? sensory) fibres. Sensory fibres of the vagus from the pharyngeal plexus supply the pharynx from the part beneath the soft palate downward. These fibres excite the pharyngeal constrictors reflexly, during the act of swallowing (§ 156). If stimulated very strongly, they may cause vomiting. (The sympathetic fibres of the oesophageal plexus give vaso- motor nerves to the oesophageal vessels ; for the oesophageal branches of the 9th nerve, see above.) 5. The vagus supplies two branches to the larynx, the superior and inferior laryngeal. {a) The superior laryngeal (Fig. 433, 3) receives vasomotor fibres from the superior cervical ganglion of the sympathetic. It divides into two branches, external and internal: (i) The external branch receives vasomotor fibres from the same source (they accompany the superior thyroid artery), and supply the crico-thyroid muscle with motor fibres, and sensory fibres to the lower lateral portion of the laryngeal mucous membrane. (2) The internal branch gives off sensory branches only to the glosso-epiglottidean fold, and the adjoining lateral region of the root of the tongue, the ary-epiglottidean fold, and to the whole anterior part of the larynx, except the part supplied by the external branch {Longet). Stimulation of any of these sensory fibres causes coughing reflexly. Coughing is produced by stimulation of the boundaries of the glottis respiratoria, but not of the vocal cords, and by stimulation of the sensory branches of the vagtis to the tracheal mucous membrane, especially at the bifurcation, and also from the bronchial mucous membrane {Kohts). Coughing is also caused by stimulation of the auricular branch of the vagus, especially in the deep part of the external auditory meatus, of the pulmonary tissue, especially when altered pathologically ; in pathological con- ditions (inflammation) of the pleura (? certain changes in the stomach [stomach cough]), of the liver and spleen {Naunyn). The coughing centre is said to lie on each side of the raphe, in the neighborhood of the ala cinerea {Kohts). _ Cases of violent coughing may, owing to stimulation of the pharynx, be accompanied by vomiting as an associated movement (§ 120). In many individuals, coughing can be excited by stimulation of distant sensory nerves (| 120, i), e. g., from the outer ear (auricular nerve), nasal mucous membrane, liver, spleen, stomach, intestine, uterus, mammse, ovaries, and even from certain cutaneous areas (£dstein). It is uncertain if these 42 fi<;- 433- 658 SUPERIOR AND INFERIOR LARYNGEAL NERVES. 659 conditions act directly upon the coughing centre, or first of all affect the vascularization and secre- tion of the respiratory organs, which in their turn affect the coughing centre. The cough (dog, cat) caused by stimulation of the trachea and bronchi occurs at once, and lasts as long as the stimulus lasts ; in stimulation of the larynx, the first effect is inhibition of the respira- tion accompanied by movements of deglutition, while the cough occurs after the cessation of the stimulation [Kandarazky). The superior laryngeal contains afferent fibres which, when stimulated, cause ai-rest of the res- piration and closure of the rima glotlidis {^Rosenthal) — (see Respiratory centre, \ 368). Lastly, fibres which are efferent and serve to excite the vasomotor centre, and are in fact '■^ pressor fibres " — (see Vaso?7iotor centre, \ 371, II). (U) The inferior laryngeal or recurrent bends on the left side around the arch of the aorta, and on the right around the subclavian, and ascends in the groove between the trachea and oesophagus, giving motor fibres to these organs, and the lower constrictors of the pharnyx, and passes to the larynx, to supply motor fibres to all its muscles, except the crico-thyroid. It also has an inhibitory action upon the respiratory centre (see § 368). A connecting branch runs from the superior laryngeal to the inferior (the anastomosis of Galen), which occasionally gives off sensory branches to the upper half of the trachea (sometimes to the larynx?); perhaps also to the oesophagus [Longet], and sensory fibres (?) for the muscles of the larynx supplied by the recurrent laryngeal. According to Francois Franck, sensory fibres pass by this anastomosis from the recurrent into the superior laryngeal. According to Waller and Burck- hard, the motor fibres of both laryngeal nerves are all derived from the accessorius ; while Chauveau maintains that the crico-thyroid is an exception. Stimulation of the superior laryngeal is painful, and causes contraction of the crico-thyroid muscle (while the other laryngeal muscles contract refikxly). Section of both nerves, owing to paralysis of the crico-thyroids, causes slight slowing of the respirations (SklareK). In dogs, the voice becomes deeper and hoarser, owing to diminished tension of the vocal cords (JLonget). The larynx becomes insensible, so that saliva and particles of food pass into the trachea and lungs, without causing reflex contraction of the glottis or coughing. This excites ''traumatic pneumonia," which results in death (^Fried lander). Stimulation of the recurrent nerves causes spasfn of the glottis. Section of these nerves paralyzes the laryngeal muscles supplied by them, the voice becomes husky and hoarse (in the pig — Galen, Riolan, i6i8) in man, dog, and cat; while rabbits retain their shrill cry. The glottis is small, with every inspiration the vocal cords approximate considerably at their anterior parts, while, during expira- tion they are relaxed and are separated from each other. Hence, the inspiration, especially in young individuals whose glottis respiratoria is narrow, is difficult and noisy {Legallots) ; while the expiration takes place easily. After a few days, the animal (carnivore) becomes more quiet, it respires with less effort, and the passive vibratory movements of the vocal cords become less. Even after a considerable interval, if the animal be excited, it is attacked with severe dyspnoea, which dis- appears only when the animal has become quiet again. Owing to paralysis of the laryngeal muscles, foreign bodies are apt to enter the trachea, while the paralysis renders difficult the first part of the process of swallowing in the oesophageal region. Broncho-pneumonia may be produced (^Arjisferger). FIGURE 433, p. 658. I. Scheme 0/ the distribution of the vagus and accessorius.— la, Exit of left vagus from the skull; loi, right vagus • g, glosso-pharyngeal ; 7, facial; i, deep post-auricular from the facial; 2, pharyngeal branches of vagus ; 6, pharyngeal branch of the glosso-pharyngeal ; 3, superior lar>'ngeal, with its anastomoses,/, with the sympathetic and its division, 4, into its internal, v, and external branches, e\ 5, inferior or recurrent laryngeal ; au., auricular branch of vagus. Cardiac nerves : g, cardiac branches from the vagus and superior laryngeal; /, h, the three cardiac branches from the upper, j^, middle, x, and lower, >/, cervical ganglion of the sympathetic; k, nng of Vieusses; /, cardiac branch from the recurrent laryngeal; L, lung with the anterior and posterior pulmonary plexuses ; r, oesophageal plexus ; 00, gastric branches, and near them the hepatic branches, n ; m, cffihac plexus ; k, splanchnic entering former; 11, accessory nerve sending its inner branch into the gangliform plexus of the vagus — its outer branch, ac, supplies the sterno-mastoid, St and aci, and the trapezius, Cc ; O, external auditory meatus; 0/j, hyoid bone ; A', thyroid cartilage ; r, trachea; i7, heart ; P, pulmonary artery ; ^ ^, aorta; c, right carotid; Ci, left carotid; j and Si, right and left subclavian artery; Z Z, diaphragm; iV, kidney; iV«, suprarenal capsule; j^f, stomach ; ;«, spleen ; Z Z, lung and liver. II. Scheme of the course of the depressor and accelerans in the cat. 660 THE DEPRESSOR NERVE. Fi( 434- VAfi 6. The depressor nerve, whiih in the rabbit arises by one l>ranch from the su])eri()r laryngeal, and usually also by a second root from the trunk of the vagus itself [runs down the neck m close relation with the vagus, sympathetic, and carotid artery, enters the thorax], and joins the cardiac plexus (Fig. 434, sc). It is an afferent nerve, and when its cc/z/ra/ tnd is stimulated [pro- vided both vagi be divided], it diminishes the energy of the vasomotor centre, and thus causes a fall of the blood pres- sure (hence the name given to it by Cyon and Ludvvig, § 371, II). At the same time [if the vagus on the opposite side be intact], its stimulation affects the cardio-inhibitory centre, and thus reflexly diminishes the number of heart beats. [Its stimulation also gives rise to pain, so that it is the sensory nerve of the heart. If in a rabbit the vagi be divided in the middle of the neck, and the central end of the depressor nerve, which is the smallest of the three nerves near the carotid, be stimulated, after a short time there is no alteration of the heart beats, but there is a steady fall of the blood pressure (Fig. 106), which is due to a reflex inhibi- tion of the vasomotor centre, resulting in a dilatation of the blood vessels of the abdomen. Of course, if the vagi be intact, there is a reflex inhibitory effect on the heart. It is doubtful if the depressor comes into action when the heart is over-distended. If it did, of course the blood prosure would be reduced by the reflex dilatation of the abdominal blood vessels.] The depressor nerve is present in the cat {\ 370), hedgehog [Aitbert, /?07'er), rat and mouse; in the horse and in man, fibres analogous to the depressor reenter the trunk of the vagus {^Bernhardt, Kreidinanti). Depressor fibres are also found in the rabbit, in the trunk of the vagus {Dreschfeldt, Stelling). 7. The cardiac branches (Fig. 433, g, /), as well as the cardiac plexus, have been described in § 57. These nerves contain the inhibitory fibres for the heart (Fig. 434, ic — cardio-inhibitory — Edward Weber, November, 1845 j Biuli^e, independently m May, 1846), also sensory fibres for the heart [in the frog {Budge), and partly in mammals (Go/tz)']. Lastly, in some animals the heart receives some of the accelerating fibres through the trunk of the vagtis. Feeble stimulation of the vagus occasionally causes acceleration of the beats of the heart (^Schiff). [This occurs when the vagus contains accelerator fibres.] In an animal poisoned with nicotin, or atropin, which paralyzes the inhibitory fibres of the vagus, stimulation of the vagus is followed by acceleration of the heart beats {Schiff, Schmiedeberg) [owing to the unopposed action of any accelerated fibres that may be present in the nerve, e. g., of the frog]. 8. The pulmonary branches of the vagus join the anterior and posterior pul- monary plexuses. The anterior pulmonary plexus gives sensory and motor fibres to the trachea, and runs on the anterior surface of the branches of the bronchi into the lungs (Z). The posterior plexus is formed by three to five large branches from the vagus, near the bifurcation of the trachea, together with branches from the lowest cervical ganglion of the sympathetic and fibres from the cardiac plexus. The plexuses of opposite sides exchange fibres, and branches are given off which accompany the bronchi in the lungs. Ganglia occur in the course of the pulmonary branches in the frog {Arnold, W. Stirling) [newt — W. Stirling; and in mammals {Remak, Egoroiv, \V. Stirling)'], in the larynx \_Cock, IV. Stirling'], in the trachea and bronchi \^IV. Stirling, Kandarazki]. Branches Scheme of the cardiac nerves in the rabbit. P, pons; M, meduUa ob- longata ; Vag, v.igus ; SL, superior, il, inferior laryngeal ; sc, superior cardiac or depressor ; ic, inferior cardiac or cardio-inhibitory ; H, heart. PULMONARY BRANCHES OF THE VAGUS. 661 proceed from the pulmonary plexus to the pericardium and the superior vena cava {Luschka, Zuckerkandl). The functions of the pulmonary branches of the vagus are — (i) they supply motor branches to the smooth muscles of the whole bronchial system (§ io6) ; (2 ) they supply a small part of the vasomotor nerves of the pulmonary vessels (Sc/izjf), but by far the largest number of these nerves (? all) is supplied from the connection with the sympathetic (in animals from the iirst dorsal ganglion) — (^BrowJi-Seqiiard, A. Fick, Badoud, Lichtheirn)) (3) they supply sensory (cough- exciting) fibres to the whole bronchial system, and to the lungs ; (4) they give afferent fibres, which, when stimulated, diminish the activity of the vasomotor centre, and thus cause a fall of the blood pressure during forced expiration • (5) similar fibres which act upon the inhibitory centre of the heart, and so influence it as to accelerate the pulse beats (§ 369, II). Simultaneous stimulation of 4 and 5 alters the pulse rhythm {Sommerbrodt) ; (6) they also contain afferent fibres from the pulmonary parenchyma to the medulla oblongata, which stimulate the respira- tory centre. [These fibres are continually in action], and consequently section of both vagi is followed by diminution of the number of respirations ; the respirations become at the same time deeper, while the same volume of air is changed ( Valentin). Stimulation of the central ^.w^l of the vagus again accelerates the respirations (^Traube, /. Rosenthal). Thus, labored and difficult respiration is explained by the fact that the influences conveyed by these fibres which excite the respiratory centre reflexly are cut off ; so it is evident, that centripetal or afferent impulses proceeding upward in the vagus are intimately concerned in maintaining normal reflex respira- tion ; after these nerves are divided, conditions exciting the respiratory movements must originate directly, especially in the medulla oblongata itself (§ 368). Pneumonia after Section of both Vagi. — The inflammation which follows section of both vagi has attracted the attention of many observers since the time of Valsalva, Morgagni (1740), and Legallois (1812). In attempting to explain this phenomenon, we must bear in mind the following considerations : (a) Section of both vagi is followed by loss of j?iotor power in the muscles of the larynx, as well as the sensibility ot the larynx, trachea, bronchi, and the lungs, provided the section be made above the origin of the superior laryngeal nerves. Hence, the glottis is not closed during swallowing, nor is it closed reflexly when foreign bodies (saliva, particles of food, irrespirable gases) enter the respiratory passages. Even the reflex act of cotigkin^^, which, under ordinary circumstances, would get rid of the offending bodies, is abolished. Thus, foreign bodies may readily enter the lungs, and this is favored by the fact that, owing to the simultaneous paralysis of the oeso- phagus, the food remains in the latter for a time, and may therefore easily enter the larynx. That this constitutes one important factor was proved by Traube, who found that the pneumonia was prevented when he caused the animals to respire by means of a tube inserted into the trachea through an aperture in the neck. If, on the contrary, only the motor recuirent nerves were divided and the oesophagus ligatured, so that in the process of attempting to swallow, food must necessarily enter the respiratory passages, " traumatic pneumonia " was the invariable result ( Traube, O. Frey). (b) A second factor depends on the circumstance that, owing to the labored and difficult respiration, the lungs become surcha7-ged with blood,h&C2M%&AMx'Ya^\\\^\ong time that the thorax is distended, the pres- sure of the air within the lungs is abnormally low. This condition of congestion, or abnormal filling of the pulmonary vessels with blood, is followed by serous exudation (pulmonary oedema), and even by exudation of blood and the formation of pus in the air vesicles {Frey). This same circumsance favors the entrance of fluids through the glottis (^ 352, b). The introduction of a tracheal cannula will prevent the entrance of fluids and the occurrence of inflammation. It is probable that a partial paralysis oi the ptilmonary vasomotor nerves maybe concerned in the inflammation, as this conduces to an engorgement of the pulmonary capillaries, (c) Lastly, it is of consequence to determine whether trophic fibres are present in the vagus, which may influence the normal condition of the pulmonary tissues. According to Michaelson, the pneumonia which takes place immediately after section of the vagi occurs especially in the lower and middle lobes ; the pneumonia which follows section of the recurrents occurs more slowly, and causes catarrhal inflammation, especially in the upper lobes. Rabbits, as a rule, die within twenty- four hours, with all the symptoms of pneumonia ; when the above-mentioned precautions are taken, they may live for several days. Dogs may live for a long time. If the 9th, lolh, and 12th nerves be torn out on one side in a rabbit, death takes place from pneumonia [Gri'inhagen). In birds, bilateral section of the vagi is not followed by pneumonia [^Blainville, Billroth), because the upper larynx remains capable of closing firmly — death takes place in eight to ten days with the symptoms of ina7iitio7t [Einbrodt, Zander, v. Anrep), 662 CESOPHAGEAL AND GASTRIC PLEXUSES. while the heart undergoes fatty degeneration {Eich/icrst), and so do the liver, stomach and muscles {v. Aiirep). Accordiiii,' to WassilielV, the heart shows cloudy swelling and slif,'ht wax-hke de^eneraiion. Frogs, which at every respiration open the gloUis, and close it during tlie pause, die of "asphyxia. Section of the jnilnunary i)ranches has no injurious efl'ect {Bidder). [Unilateral sec- tion of the vagus in rabbits is fullowed within forty-eight hours hy the apiiearance of yellowish- while spots on the myocardium, especially near the inter ventricular septum, on the papillary muscles, and along the furrows for the coronaiy arteries. The muscular fibres exhibit retrogressive changes, whereby their strin; disappear; they become swollen up and filled with albuminous granules. After eight to ten days, the interstitial tissue of these foci becomes infiltrated with small round granular cells, especially near the blood vessels. At a later stage, the interstitial c mncctive tissue increases in amount, and the muscle atrophies. No efifect is produced by section of the depressor or sympa- thetic, and Kantino concludes that some of the fibres of the vagus exert a trophic action on the myocardium.] 9. The oesophageal plexus (Fig. 434, ;-) is formed principally by branches from the vagus above the inferior laryngeal, from the pulmonary ])lexiis, and below from the trunk itself. Thi.s jjlexus supplies the oesophagus with motor power (§ 156), the sensibility which is present only in the upper part, and it also sup- plies fibres capable of exciting reflex actions. 10. The gastric plexus {00) consists of {a) the anterior (left) termination of the vagus, which supplies fibres to the oesophagus and courses along the small curvature, and sends a few fibres through the portal fissure into the liver ; (^) the posterior (right) vagtis, after giving off a few fibres to the oesophagus, takes part in the formation of the gastric plexus to which (/) sympathetic fibres are added at the pylorus. Section of the vagi is followed by hyperaemia of the gastric mticous mem- brane {Panuvi, Fincus), but it does not interfere with digestion (Bidder and Schmidt), even when it is performed at the cardia {Kritzler, Schiff). 11. About two-thirds of the right vagus on the stomach joins the coeliac plexus, and from it branches accompany the arteries to the liver, spleen, pancreas, duodenum, kidney, and suprarenal capsules. The vagus supplies motor fibres to the stomach, which belong to the root of the vagus itself and not to the acce.ssorius {Stilling, Bischoff). The gastric branches also contain afferent fibres, which, when stimu- lated, catise reflexly a secretion of saliva (§ 145). It is undetermined whether they also cause vomiting. For the effect of the vagus upon the movements of the intestine (see § 161). According to some observers, stimulation of the vagus is followed by movement of the large as well as of the small intestine {Stilling, Kupffer, C. Ludwig, Remak). Stimulation of the peripheral end of the vagus causes con- traction of the smooth muscular fibres in the capsule and trabeculae of the spleen (m the rabbit and dog, § 103). Stimulation of the vagus at the cardia causes in- crease in the secretion of urine with dilatation of the renal vessels, while the blood of the renal vein becomes more arterial {CI. Bernard^. According to Ro.ssbach and Quellhorst, a few vasomotor fibres are supplied by the vagus to the abdominal organs, while the greatest number comes from the splanchnic. 12. Reflex Effects. — The vagtis and its branches contain fibres, some of which have been referred to already, which act reflexly (afferent) upon certain nervous mechanisms. (a) On the vasomotor centre there act (o) /;wjo^ fibres (especially in both laryngeal nerves), whose stimulation is followed by a reflex contraction of the arterial blood channels, and thus cause a rise of the blood pressure; (/J) depressor fibres (in the depressor or the vagus itself), which have exactly an opposite effect. (This subject is specially referred to under the head of the Vaso- motor nerve centre, \ 371.) {b) On the respiratory centre there act (o) fibres (pulmonary branches) whose stimulation is followed by acceleration of the respiration; and (,9) inhibitory fibres (in both laryngeals), whose stimulation is followed by slowing or arrest of the re^piration. (See Respiratory centre, \ 368.) (c) On the cardio-inhibitory system. — [When the central end of one vagus is stimulated, provided the other vagus is intact, the heart may be arrested reflexly in the diastolic phase.] Mayer and Pribram observed that sudden distention of the stomach caused slowing and even arrest of the heart, while, at the same time, there was contraction of the arteries of the medulla oblongata and increase of the blood pressure. ((/) On the vomiting centre. — This centre may be affected by stimulation of the central PATHOLOGICAL CONDITIONS OF THE VAGUS. 663 end of the vagus, and, as already mentioned, by stimulation of many afferent fibres in the vaarus (I 158). (e) On the pancreatic secretion. — Stimulation of the cent}-al end of the vagus is followed by arrest of this secretion (| 171). (/■) According to CI. Bernard, there are fibres present in the pulmonary nerves, which, when they are stimulated, increase reflexly the formation of sugar in the liver, perhaps through the hepatic branches of the vagus. Unequal Excitability. — The various branches of the vagus are not all endowed with the same degree of excitability. If the peripheral end of the vagus be stimulated, first of all with a weak stimulus, the laryngeal muscles are first affected, and afterward the heart is slowed [Ruther- ford). If the central end be stimulated with feeble stimuli, the " excito-respiratory " fibres are exhausted before the " inhibito-respiratory " [Burkart). According to Steiner, the various fibres are so arranged in the vagus that the afferent fibres he in the outer, and the efferent in the inner, half of the trunk, in the cervical region. Pathological. — Stimulation or paralysis in the area of the vagus must necessarily present a very different picture according as the affection is referred to the whole trunk or only to some of its branches, or whether the affection is unilateral or bilateral. Paralysis of the pharynx and oesophagus, which is usually of central or intracranial origin, interferes with or abolishes degluti- tion, so that when the oesophagus becomes filled with food there is difficulty of breathing, and the food may even pass into the nasal cavities. A peculiar sonorous gurgling is occasionally heard in the relaxed canal (deglutatio sonora). In incomplete paralysis, the act of deglutition is delayed and rendered more difficult, while large masses are swallowed more easily than small ones. In- creased contraction and spasmodic stricture of the oesophagus are referred to under the phenomena of general nervous excitability (§ 186). Spasm of the laryngeal muscles causes spasmodic closure of the glottis {^Spasnms glottidis). This condition is most apt to occur in children, and takes place in paroxysms, with symptoms of dyspnoea and crowing inspiration; if the case be very severe, there may be muscular con- tractions (of the eye, jaw, digits, etc.). The symptoms are very probably due to the reflex spasms which may be discharged from the sensory nerves of several areas (teeth, intestine, skin). The impulse is conducted along the sensory nerves proceeding from these areas to the medulla oblongata, where it causes the discharge of the reflex mechanism which produces the above- mentioned results. There maybe spasm of the dilators of the glottis and other laryngeal muscles [Frantzel). Stimulation of the sensoj-y nerves of the larynx, as is well known, produces coughing. If the stimulation be very intense, as in whooping-cough, the fibres lying in the laryngeal nerves, which inhibit the respiratory centre, may also be stimulated ; the number of respirations is diminished, and ultimately the respiration ceases, the diaphragm being relaxed ; while, with the most intense stimu lation, there may be spasmodic expiratory arrest of the respiration with closure of the glottis, which may last for fifteen seconds. Paralysis of the laryngeal nerves, which causes disturbances of speech, has been referred to in \ 313. In bilateral paralysis of the recurrent nerves, in consequence ot tension upon them due to dilatation of the aorta and the subclavian artery, a considerable amount of air is breathed out, owing to the futile efforts which the patient makes in trying to speak ; expectora- tion is more difficult, whUe violent coughing is impossible [v. Ziemssen). Attacks of dyspnoea occur just as in animals, if the person make violent efforts. Some observers [Salter, Bergson) have referred the paroxysms of nervous asthma, which last for a quarter of an hour or more, and constitute asthma bronchiale, to stimulation of the pulmonary plexus, causing spasmodic contraction of the bronchial muscle (§ 106). Physical investigation during the paroxysms reveals nothing but the existence of some rhonchi (§ 1 17). If this condition is really spasmodic in its nature (? of the vessels), it must be usually of a reflex character; the afferent nerves may be those of the lung, skin, or geni- tals (in hysteria). Perhaps, however, it is due to a temporary paralysis of the pulmonary nerves (afferent), which excite the respiratory centre (excito-respiratory). Stimulation of the cardiac branches of the vagus may cause attacks of temporary suspension of the cardiac contractions, which are accompanied by a feeling of great depression and of impending dissolution, with occasionally pain in the region of the heirt. Attacks of this sort may be produced reflexly, e.g., by stimulation or irritation of the abdominal organs (as in the experiment of Goltz of tapping the intestines). Hennoch and Silbermann observed slowing of the action of the heart in children suffering from gastric irritation. Similarly, the respiration may be affected reflexly through the vagus, a condition described by Hennoch as asthma dyspepticum. In cases of intermittenc paralysis of the cardiac branches of the vagus, we rarely find acceleration of the pulse above 160 [Riegel), 200 ( Tuczek, L. Langer) ; even 240 pulse beats per minute have been recorded [Kuppei't), and in such cases, the beats vary much in rhythm and force, and they are very irregular. These cases require to be more minutely analyzed, as it is not clear how much is due to paralysis of the vagus and how much to the action of the accelerating mechanism of the heart. Little is known of affec- tions of the intra-abdominal fibres of the vagus. It seems that the sensory branches of the stomach do not come from the vagus. If the trunk of the vagus or its centre be paralyzed, there are labored, deep, slow respirations, such as follow the section of both vagi [Gutf>nann). (364 SPINAL ACCESSORY AND HYPUCLOSSAL NERVES. 353. XI. NERVUS ACCESSORIUS WILLISII.— Anatomical— This nerve arises by two completely separate roots; chc- from the accessorius nucleus of the medulla oblongata (F'ig. 427, 11), which is connected with the vagus nucleus; while the o/Aer root arises between the anterior and jx)sterior nerve roots from the spinal cord, usually between the 5th and 6th cervical vertebra?. In the sjiinal cord, its fibres can be traced to an elonijated nucleus lying on the outer side of the anterior cornu, as f.ir downward as the 5th cervical vertebra. Near the jugular foramen both portions come together, but do not exchange fibres (//o//); both roots afterward separate from each other to form two distinct branches, the anterior (inner), which arises from the medulla oblongata, passing en masse into the plexus gangliiformis vagi. This branch supplies the vagus with most of its motor fibres (compare (J 352, 3), and also its ra/v//(5-/w///7'»/<»;j fibres (Fig. 433). [The upper cervical metameres or segments give origin not only to the anterior and posterior roots of the corresponding nerve roots, but heticeen these roots arise the roots of the spinal accessory nerve. This nerve contains large meduUated nerve fibres, and fine medullated fibres such as characterize the visceral branches of the thoracic and sacral regions ( ^ 356 )• The nerve passes by the jugular ganglion of the vagus, then divides into the external and internal branch. All the large fibres pass into the external branch, which, along with branches from the cervical plexus, supply the sterno-mastoid and trapezius. The internal branch, composed of small fibres, passes into the ganglion of the trunk of the vagiis. Gaskell therefore regards the internal branch " as formed by the rami viscerales of the upper cervical and vagus nerves." These fine medullated nerve fibres probably arise from the cells of the posterior vesicular column of Clarke. The motor fibres to the trapezius and sterno-mastoid arise from the cells of the lateral horn of gray matter.] If the accessorius be pulled out by the root in animals, the cardio-inhibitory fibres midergo degeneration. If the trunk of the vagus be stimulated in the neck four to five days after the operation, the action of the heart is no longer arrested thereby [owing to the degeneration of the cardio-inhibitory fibres] (^JVal/er, Schiff, Dasz- kieivicz, Heidenhain) \ according to Heidenhain, the heart beats are accelerated immediately after pulling out the nerve. The external branch arises from the spinal roots. This nerve communicates with the sensory branches of the posterior root of the ist, more rarely of the 2d cervical nerve, and these fibres supply sensibility to the muscles ; it then turns backward above the transverse process of the atlas, and terminates as a motor nerve in the sterno-mastoid and trajjezitis, (Fig. 433). The latter muscle usually receives motor fibres also from the cervical ple.vus (Fig. 429). The external branch communicates with several cervical nerves. These fibres either participate in the innervation of the above-named muscles, or the accessorius returns pari of the sensory fibres sup- plied by the posterior roots of the two upper cervical nerves. Pathological. — Stimulation of the outer brancli causes tonic or clonic spasm of the above- named muscles, usually on one side. If the branch to the sterno-mastoid be affected alone, the head is moved with each clonic spasm. If the aftection be bilateral, the spasm usually takes place on opposite sides alternately, while it is rare to have it on both sides simultaneously. In spasm of the trapezius the head is drawn backward and to the side. Tonic contraction of the tlexors of the head causes the characteristic jx)sition of the head known as caput obstipum (spasticum) or wryneck. \vi paralysis of one of these muscles, the head is drawn toward the sound side (torticollis paraly- ticus). Paralysis of the trapezius is usually only partial. Paralysis of the whole trunk of the spinal accessor)' (usually caused by central conditions), besides causing paralysis of the sterno-mastoid and trapezius, also paralyzes the motor branches of the vagus already referred to {Erl>, P'rlinkel). 354. XII. NERVUS HYPOGLOSSUS.— Anatomical.— It arises from two large-celled nuclei within the lowest part of the calamus scriptorius, and one adjoining small-celled nucleus {Roller), while additional fibres come from the brain (^ 378), and also perhaps from the olive (Fig. 427, 12 I. It springs by ID to 15 twigs in a line with the anterior roots of the spinal nerve (Fig. 420, IX). In its development part of the hypoglossal behaves as a spinal nerve (Froriep). Function. — It is motor to all the muscles of the tongue, including the genio-hyoid and thyro-hyoid. Connections. — The trunk of the hypoglossal is connected with (i) the superior cervical gan- glion of the sy??ipathetic, which supplies it with vasomotor fibres for the bl'^od vessels of the tongue. After section of the hypoglossal and lingual nerves, the corresponding half of the tongue becomes red and congested [Schiff ). (2) There is also a branch from the plexus gangliiformis vagi, its small lingual branch, to the commencement of the hypoglossal arch. These fibres supply the hypoglossal with sensory fibres for the muscles of the tongtie, for even after section of the lingual the tongue still possesses dull sensibility.^ It is uncertain whether fibres with a similar function are . THE SPINAL NERVES. 665 partly derived from the cervical nerves or from the anastomosis which takes place with the lingual. (3) It is united with the upper cervical nerves by means of the loops known as the ansa hypoglossi. These connecting fibres run in the descendens noni to the sterno-hyoid, omo-hyoid, and stemo-thyroid. Cervical fibres do not, as a rule, enter the tongue ; stimulation of the root of the hypoglossal acts upon the above-named muscles only very rarely and to a very slight extent ( Volk?7ianti) . (Compare I 297, 3, and § 336, III.) Bilateral section of the nerve causes complete motor paralysis of the tongue. Dogs can no longer lap, they bite the flaccid tongue. Frogs, which seize their prey with the tongue, must starve ; when the tongue hangs from the mouth, it must prevent the closure of the mouth, so that these animals must die from asphyxia, as air is pumped into the lungs only when the mouth is closed. Pathological. — Paralysis of the hypoglossal (glossoplegia), which is usually central in its origin, causes disturbance of speech {\ 319). [In unilateral palsy, the tongue lies in the mouth in its normal position, but the base is more prominent on the paralyzed side. When the tongue is pro- truded, it passes to the sound side by the genio-hyoglossus (| 155).] Paralysis of the tongue also interferes with mastication, the formation of the bolus in the mouth, and deglutition in the mouth. Owing to the imperfect movements of the tongue, taste is imperfect, and the singing of high notes and the falsetto voice, which require certain positions of the tongue, appear to be impossible i^Bennati). Spasm of the tongue, which causes aphthongia (| 318), is usually reflex in its origin, and is extremely rare. Idiopathic cases of spasm of the tongue have been described ; the seat of the irri- tation lay either in the cortex cerebri or in the oblongata {^Berger, E. Remak). For Pseudo-motor Action, see p. 650. 355. THE SPINAL NERVES. — Anatomical. — The thirty-one pairs of spinal nerves arise by means of a posterior [superior, gangliated] root (consisting of a few large rounded bundles), from the sulcus between the posterior and lateral columns of the spinal cord, and by means of an anterior [inferior, non-gangliated] root (consisting of numerous fine flat strands), iirom the furrow between the anterior and lateral columns. Fig. 435. The posterior roots, with the exception of the 1st cervical nerve, are the larger. Occasionally the roots on opposite sides are not symmetrical; one or other root, or even a whole nerve, may be absent from the dorsal region {Adamkiewicz). On the posterior root is the spindle-shaped spinal ganglion (? 321, II, 3), which is occasionally double on the lumbar and sacral nerves. Beyond the ganglion, the two roots unite to form within the spinal canal the mixed trunk of a spinal nerve. The branches of the ners^e trunk invariably contain fibres coming fi-om both roots. The number of fibres in the nerve trunk is exactly the same as in the two roots ; hence, we must conclude that the nerve cells in the spinal ganglion ai-e intercalated in the course of the fibres [Gaule and Birge). Varieties. — The spinal ganglion is sometimes double, and according to Hyrtl, isolated ganglionic cells frequently occur in the posterior root, between the ganglion and the cord. Occasionally the roots are somewhat unsym metrical on opposite sides ; in the dorsal part one or other, or both roots of a spinal nerve are sometimes absent {Adamkiewicz). [Morphology of the Spinal Nerves and Limb Plexuses. — A typical segmental spinal nerve (Fig. 435), divides, after its formation, into three parts, a dorsal branch, or superior primary division distributed to the back, a somatic branch, or inferior primary division, supplying the body wall or limbs ; and a splanchnic or visceral branch, or ramus communicans, connected with the sympa- thetic gangliated cord, and distributed to the large vessels and viscera. The somatic branch is the largest, and is generally, by human anatomists, spoken of as the " anterior primary division." In the thoracic and upper lumbar regions, the distribution of this nerve is simple. It divides into an external (or lateral) branch, and an internal (or anterior) branch, which supply respectively the lateral and anterior portions of the thoracic and abdominal walls.] [In the region of the neck, and in relation to the limbs, the arrangement of the somatic branches becomes complicated by the formation of the plexuses. In the embryo, however, the distribution of the nerves is simpler, and a comparison can be made both with the adult arrangement, and with the typical nerve as seen in the thoracic region. In the embryo, the neck as such does not exist, and the upper limb sprouts out directly beyond the segmented visceral arches. In this state, the somatic branch is distributed as in the thoracic region ; the nerve divides into an external and an internal branch, distributed to the side and front of the corresponding part of the arches in the neck, in the regions where the limbs are appearing as two flattened buds from the ventro-lateral aspect of the body. The somatic branch sweeps round into the blastema forming the limb, and divides into its two branches, external and internal, or dorsal and ventral, which are distributed to the outer (dorsal) and inner (ventral) surfaces, respectively, of the primitive limb. At this time, the cardlaginous and muscular elements of the limb have not become differentiated. Wbile this is occurring, the dorsal and ventral parts of the somatic branches of the nerves entering the limb unite with adjacent dorsal and ventral branches, in various combinations, so as to produce the limb plexuses. The nerves re- sulting from these combinations are distributed to the primitive, dorsal, and ventral surfaces of the limbs. Thus, the plexuses are formed, and the peripheral distribution of the nerves has taken place 666 STRUCTURE OF A SPINAL GANGLION. before the period of flexion and angulation of the limbs. These processes mark the conditions in the adult ; but even then it is easy to make out that the nerves in the upper limb derived from the posteiior (dorsal) cords of the l)rachiai plexus supply the scapular region, extensor surface of the arm and forearm, and the back of the hand — parts which are derived from the dorsal surface of the primitive limb; while the nerves j^ro luced from the anterior (ventral) cords supply the pectoral region, front of the arm, forearm, and hand — parts representing the jirimitive ventral surface.] [In the lower limb, the nerves deiived from a union of the posterior branches are the external cutaneous, anterior crural, gluteal, and external popliteal. These suj^iply the iliac surfaces, the front of the thigh, leg, and foot — belonging to the primitive dorsal surface of the limb. The nerves formed by the union of anterior branches — genito-crural, obturator, and internal |])opliteal, in like manner supply the parts of the limb corresponding to the ventral surface — the inner side and back of the thiL;h. the back of tlie leg, and the sole of the foot (^. M. Pateison).'] [Structure of a Spinal Ganglion. — The ganglion is invested by a thin, firmly adherent, sheath of connective tissue, which sends processes into the swelling, and is continuous with the sheaths of the nerve entering and leaving the ganglion (Fig. 436, c). In mammals, e. ;■-., rabbit, a longitudi- nal stction of such a ganglion exhibits the cells arranged in grou]3s, with strands of nerve fibres Fk;. 436. liiiiii Fig. 435. Diagram of a spinal nerve ; C, spinal cord ; />•, ar, posterior and anterior roots ; SPD, IPD, superiorand inferior prim,iry divi- sions ; d, V, dorsal and ventral branches ; sr, sympathetic root (Ross). Longitudinal section of a spinal ganglion, a, nerve fibre ; b, nerve cells ; c, capsule. coursing longitudinally between them (Fig. 436, a, b). The nerve cells are usually globular in form, with a distinct capsule Imed with epithebum, and the cell substance itself contains a well-defined nucleus with a nuclear envelope and a nucleolus. The capsule of the cell is continuous with the sheath of Schwann of a nerve fibre. The exact relation between the nerve fibres and the nerve cells is difficult to establish, but it is probable that each nerve cell is connected with one nerve fibre, i. e., they are unipolar. In the spinal ganglia of the vertebrates above fishes, and also in the Gasserian ganglion, cells are found with a single process or fibre attached to them, the nerve fibre process not unfrequently coiling a few times within the capsule. This process, after emerging from the capsule, becomes coated with myelin, and usually soon divides at a node of Ranvier (Fig. 341, /). Ranvier, who first observed this arrangement, describes it as a T-shaped fibre. These nerve cells with T- shaped fibres have been observed in the spinal ganglia of all vertebrates above fishes, in the Ciasse- rian and geniculate ganglia, as well as in the jugular and cervical ganglia of the vagus. In fishes the nerve cells of the spinal ganglia are bipolar (Fig. 368, 4). There is a rich plexus of capillaries in these ganglia, and each cell is surrounded by a meshwork of capillaries, which never penetrate the cell capsules.] bell's law and deductions therefrom. 667 Bell's Law. — Sir Charles Bell discovered (rSii) that the anterior roots of the spinal nerves are motor, the posterior are sensory. Recurrent Sensibility. — Magendie discovered (1822) the remarkable fact that sensory fibres are also present in the anterior roots, so that their stimulation causes pain. This is due to the fact that sensory fibres pass into the anterior root after the two roots have joined, and these fibres run in the anterior root in a centripetal direc- tion {Schiff, CI. Bernard^. The sensibility of the anterior root is abolished at once by section of the posterior root. This condition is called "recurrent sensi- bility " of the anterior root. When the sensibility of the anterior root is abolished, so is the sensibility of the surface of the spinal cord in the neighborhood of the root. A long time after section of the anterior, and when the degeneration phenomena have had time to develop (§ 325), a few non-degenerated sensory fibres are always to be found in the central stump {Schiff, Vulpian'). Schiff found that, in cases where the motor fibres had undergone degeneration, there were always non-degene- rated fibres to be found in the anterior root, which passed into the membranes of the spinal cord. The sensory fibres pass into the motor root, either at the angle of union of the roots, or in the plexus, or in the region of the peripheral termina- tions. Sensory fibres enter many of the branches of the motor cranial nerves at their periphery, and afterward run in a centripetal direction (p. 650). Even into the trunks of sensory nerves, sensory branches of other sensory nerves may enter. This explains the remarkable observation, that after section of a nerve trunk {e. g., the median), its peripheral terminations still retain their sensibility {Arloing and Tripier'). The tissue of the motor and sensory nerves, like most other tissues of the body, is provided with sensory nerves (^IVervi jzervorum, p. 580). [It does not follow that section of a peripheral cutaneous nerve will cause anaesthesia in the part to which it is distributed; in fact, one of the principal nerve trunks of the brachial plexus may be divided without giving rise to complete anaesthesia in any part of the area of distribution of the sensory branches of the nerve, and even if there be partial or complete cutaneous anaesthesia, it is much less in extent than corresponds to the anatomical area of distribution. The ansesthetic area tends to become smaller in extent [Ross). Thus, there is not complete independence in the distribution of these nerves. These results are explained by the anastomosis between branches of nerves, the exchange of fibres in the terminal networks, while some sensory fibres enter the peripheral parts of a nerve and run centripetally, perhaps being distributed to the skin and conferring recurrent sensibility on the peripheral part of the nerve.] Relative Position of Motor and Sensory Fibres. — In embryos (rabbit) the motor fibres stain more deeply with carmine than the sensory fibres, so that their position in the peripheral nerves of distribution may thereby be made out. In the anterior branch of a spinal nerve, the sensory fibres lie in the outer part of the branch, the motor in the inner part ; while this relation is reversed in the posterior root (Z. Lowe). Deduction from Bell's Law. — Careful observations of the effects of section of the roots of the spinal nerves {^Magendie, 1822), as well as the discovery of the reflex relation of the stimulation of the sensory roots to the anterior, constituting reflex movements (^Marshall Hall, Johannes Miiller, 1832), enables us to deduce the following conclusions from Bell's law: i. At the moment of section of the anterior root, there is a contraction in the muscles supplied by this root. 2. There is at the same time a sensation of pain due to the '' recurrent sensibility." 3. After the section, the corresponding muscles are paralyzed. 4. Stimulation of the peri- pheral trunk of the anterior root (immediately after the operation) causes contraction of the muscles, and eventually pain, owing to the recurrent sensibility. 5. Stimu- lation of the central end is without effect. 6. The sensibility of the paralyzed parts is retained completely. 7. At the moment of section of the posterior root, there is stwQXQ. pain. 8. At the same time movements are discharged reflexly. 9. After the section, all parts supplied by the divided roots are devoid of sensibility. 10. Stimulation of the peripheral trunk of the divided nerve is without effect. 1 1 . Stimulation of the central end csiuses pain and reflex movements. 12. The central end ultimately degenerates. 13. Movement is retained completely in the paralyzed parts, e.g., in the extremities. 668 INCUCJRDINATED MOVEMENTS OE INSENSIBLE LIMBS. The ultimate effect, known as Wallerian degeneration, which follows section of the nerve or its roots, is referred to in § 325. Recently, Joseph has slightly modified the statements of Waller on the degeneration in the posterior roots. According to him, the spinal ganglion is the nutritive centre for by far the largest number of the fibres of this root ; but individual fibres traverse the ganglion with- out forming connections with its cells, so that the nutritive or trophic centre for this small number of nerve fibres is in the spinal cord. Incoordinated Movements of Insensible Limbs. — After section of the ix)sterior roots, e.g., of the nerves for the ]io.sterior exlremilies, the muscles retain their movements; nevertheless there are characteristic disturbances of their motor power. This is expre-sed in the awkward manner in which the animal V\c,. 438. executes its movement — it has lost to a large extent iis harmony and elegance of motion. This is due to the fact that, owing to the absence of the sensibility of the muscles and skin, the animal is no longer conscious of the resistance which IS opposed to its movements. Hence, the degree of muscular energy necessary for any particular effort cannot be accurately graduated. Animals which have lost the sensibility of their extremities often allow their limbs to lie in abnormal positions, such as a healthy animal would not Fir.. 437. 10 me Distribution of the cutaneous nerves of the arm. A, Dorsal surface — / jf, supra-clavicular; 5 a.r, axillary ; _yf/j, superior posterior cutaneous ; 4 cmd, median cutaneous ; j cpi, inferior posterior cutaneous ; 6 cm, median cutaneous ; 7 cl, lateral cutaneous ; ^», ulnar; 9 ra, radial; /o w/^, median. B, volar surface — isc, supra-clavicular; 2 ax, axillary; j cmtf, internal cutaneous; 4 cl, lateral cutaneous ; j cm, cutaneous medius ; 6 me, median ; 7 «, ulnar. Distribution of the cutaneous nerves of the leg {3.her Henle). A, Anterior surface — i, crural nerve; 2, external lateral cutaneous ; 3, ilio- inguinal ; 4, lumbo-inguinal ; 5, external spermatic; 6, posterior cutaneous; 7, obtu- rator; 8, great saphenous ; 9, communicating peroneal; 10, superficial peroneal ; 11, deep peroneal; 12, communicating tibial. B, Pos- terior surface — i, posterior cutaneous; 2, external femoral cutaneous; 3, obturator; 4, median posterior femoral cutaneous; 5, communicating peroneal; 6, great saphe- nous; 7, communicating tibial; 8, plantar cutaneous; 9, median plantar; 10, lateral plantar. tolerate. In man also, when the peripheral ends of the cutaneous nerves are degenerated, there are ataxic phenomena (? 364, 3). FUNCTIONS OF THE SPINAL ROOTS. 669 Increased Excitability. — Harless (1858), Ludwig, and Cyon (controverted by v. Bezold, Uspensky,. Griinhagen, and G. Heidenhain) observed that the anterior root is more excitable as long as the posterior roots remain intact and are sensitive, and that their excitability is diminished as soon as the posterior roots are divided. In order to explain this phenomenon, we must assume that, in the intact body, a series of gentle impulses (impressions of touch, temperature, position of limbs, etc.) are continuously streaming through the posterior roots to the spinal cord, where they are transferred to the motor roots, so that a less stimulus is required to excite the anterior roots than when these reflex impulses of the posterior root, which increase the excitability, are absent. Clearly, a le 5 S a .Ht3 u H S.2 a w M f" The inhibitory nerves of the circular muscles of the alimentary canal and its appendages leave the central nervous system in the anterior roots, and pass out among the fine medullated fibres of the rami viscerales into the distal ganglia without communication with the proximal ganglia" [Structure of a Ganglion.— The structure _ ^ ■t^ 5i c of the sympathetic nerve fibres and nerve cells has already been de-cribed in ^321. On mak- ing a section of a sympathetic ganglion, e. g., the human superior cervical, we observe groups of cells with bundles of nerve fibres chiefly non- medullated — running between them, and the whole surrounded by a laminated capsule of connective tissue, which sends septa into the ganglion. The nerve cells have many processes, and are, therefore, multipolar, and each cell is surrounded by a capsule with nuclei on its inner surface (Fig. 368, II). The processes pierce the capsule, and one of them certainly — and perhaps all the processes — aie connected with a nerve fibre. Ranvier states that each cell has a fibrillated outer portion and a more granular inner part. Each of the pro- cesses becomes continuous with a fibre of Re- mak. Not unfrequently yellowish-brown pig- ment is found in the cell substance. Similar cells have been found in the ophthalmic, sub- maxillary, otic, and spheno-palatine ganglia. The number of medullated nerve fibres dimin- ishes as the sympathetic nerves are traced toward their distribution. Ranvier states that it is possible in the rabbit to trace the conversion ^ of a medullated fibre into a branched fibre of "^J" Remak. The blood vessels of the sympa- o thetic ganglia in mammals are pecuhar. The fe arteries are small, and after subdivision form a capillary network, each mesh of which en- closes several ganglionic cells. The veins, on the contrary, are very large, tortuous, varicose, and often terminate in culsde-sac, into which several capillaries open. The arrangement of the veins is spoken of as the venous sinuses of these ganglia, being compared by Ranvier to the sinuses of the dura mater and venous ^ plexuses of the spinal canal.] :| Functions. — The following is t! merely a general summary : — .| I. Independent Functions of | the sympathetic are those of certain t nerve plexuses which remain after all | a the nervous connections with the cb ^ cerebro-spinal branches have been di- | (S vided. The activities of these plexuses | | may be influenced — either in the direc- | _ tion of inhibition or stimulation — | through fibres reaching them from the '^ cerebro-spinal nerves. -■-.■•^^ m To these belong : — 1. The automatic gangha of the heart _(§ 58). 2. The mesenteric plexus of the intestine (§ 161). ^ .^ a a 3. The plexuses of the uterus, Fallopian tubes, ureters (also of the blood ana lymph vessels). . , • , /n +.1,^ II. Dependent Functions.— Fibres run in the sympathetic, which (like the S o cU ■5-S (U ^- o cj u ca S u G 13 672 THORACIC AND ABDOMINAL SYMPATHETIC. j)eripheral nerves) are active only when their connection with the central nervous system is maintained, e.g., the sensory fibres of the splanchnic. Others again con- vey impulses from the central nervous system to the gang/ia, while the ganglia in turn modify the impulses which inhibit or excite the movements of the correspond- ing organs. The following statement is a restinic of the functions of the sympathetic, according to the anatomi- cal arrangement : — A. Cervical Part of the Sympathetic, i. Pupil-dilating fibres (com- l)arc Ciliary ganglion, % 347, I, and Iris, %. 392). According to Budge, these fibres arise from the spinal cord, and run through the upper two dorsal and lowest two cervical nerves into the cervical sympathetic, which conveys them to the head. Section of the cervical synijjathetic or its rami commimicantes causes contraction of the pupil. (The central origin of these fibres is referred to in § 362, i, and § 367, S.) 2. Motor fibres tor Miiller's smooth muscle of the orbit, and partly for the external rectus muscle (§ 348). 3. Vasomotor branches for the outer ear and the side of the face {CI. Bernard^, tympanum (Frussak), 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 {Donders and Callen/els). 4. In the cervical portion are afferent fibres which excite the vasomotor centre in the medulla {Aubert'). 5. Secretory ( troi>hic) and vasomotor fibres for the salivary glands (§ 145). 6. Sweat-secretory fibres (see § 288, II). 7. According to Wolferz and Demtschenko the lachrymal glands receive sympa- thetic secretory fibres (?). B. Thoracic and Abdominal Sympathetic. — First of all there is — 1. The s\mi)athetic portion of the cardiac plexus (§ 57, 2), which receives accelerating or augmentor fibres for the heart from the lower cervical and ist thoracic ganglion {CI. Bernard, v. Bezold, Cyon, Schmiedeberg). The fibres arise partly from the sympathetic and partly from the plexus around the vertebral artery {v. Bezold, Bever^. (Compare § 370.) 2. For the vasomotor fibres passing through the sympathetic to the extremities, skin of the trunk, and lungs (see § 371). For vaso-dilators (§ 472). 3. The cervical sympathetic and the splanchnic contain fibres which, when their central ends are stimulated, excite the cardio-inhibitory system in the medulla oblongata {Bernstein). 4. The functions of the splanchnic are referred to in §§ 164, 175, 276, and 371. 5. The functions of the coeliac and mesenteric plexuses are referred to 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), jireters, uterus (running in the hypogastric plexus), vas deferens, and vesi- culse seminales. Stimulation of all of these nerve channels causes increased move- ment of the organs, but it must be remembered that the diminished supply of blood thereby produced also acts as a stimulus (§ 161). Section of these nerves is fol- lowed 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. Affections involving the vaso- motor system are referred to in \ 371. SECTION OF THE CERVICAL SYMPATHETIC. 673 The cervical sympathetic is most frequently paralyzed or stimulated by traumatic conditions, wounds by bullets or knives, tumors, enlarged lymph glands, aneurisms, inflammations of the apices of the lungs and the adjacent pleurae, while exostoses of the vertebrcie may stimulate it in part or paralyze it in part. The phenomena so produced have been partly analyzed in treating of the ciliary ganglion (§ 347, I). Stimulation of the cervical sympathetic in man causes dilatation of the pupil (mydriasis spastica), pallor of the face, and occasionally hyperidrosis or profuse sweating (I 289, 2, and I 288) ; disturbance of vision for near objects, as the pupil cannot be contracted (see AccofUfnodation), 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 secreiion 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 tiie nerve in the neck, and immediately thereafter (i) the ear and adjoining parts on that side become greatly congested with blood, blood vessels appear that were formerly not visible, and as a result of the increased quantity of blood in the ear (hypersemia), there is (2) a rise of the temperature amounting to even 4° to 6° C. (C/. Bernard). These are the vaso- motor 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 ocuh-pupillary sym'ptoms. Stimulation (electrical) of the peripheral end produces the opposite results, — pallor of the ears, owing to contraction of the blood vessels, with consequent fall of the temperature ; dilatation of the pupil, bulging of the cornea, protrusion of the eyeball (exophthalmos), and widening 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 membrane and lachrymal gland are influenced by the sympathetic] [Division of the cervical sympathetic in young, groiving animals results in hypertrophy of the ear and increased growth of the hair on that side [Bidde?-, IV. Siirling).'] [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 ist and 5th dorsal vertebrse, where the fibres pass out with the rami communicantes to enter the cervical sympathetic {Dastra and Morai). The vaso-dilator fibres occiur in the posterior segment of the ring of Vieussens, and when they are stimu- lated after section of the 7th cranial nerve, there is a " pseudo-motor " 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 constipation), slowing of the heart's action, brought about reflexly, just as in Goltz's "tapping" experiment (§ 369). Irritation in the area of the sensory nerves of the sympathetic may give rise to that con- dition which is called by Romberg neuralgia hypogastrica, a painful affection of the lower abdominal and sacral regions, hysteralgia, neuralgia testis, which are locaUzed in the plexuses of the sympathetic. In affections^of the abdojninal sympathetic, there may be severe constipation, with diminished or increased secretion of the intestinal glands (| 186). 357. COMPARATIVE— HISTORICAL. — Comparative. — Some of the cranial nerves may be 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 respiratoi-y movements, diminishes more and more in the lower classes of the vertebrata,/ar?/aj-K< with the diminution of the facial muscle. In birds and reptiles, it supplies the muscles of the 43 674 COMPARATIVE AND HISTORICAL. 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 sj'jringing from the trigeminus. In fishes, the 5th and 7lh 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 nerve. In the cyciostomata (lamprey) there is an inde- pendent lacial. The 2', for post, cornu ; j/^, inter-funicular; la, hit, Ip, anterior, median, and posterior lateral. arteries, which reach it through the inter-vertebral foramina, and pass to the cord along the anterior and posterior roots.] [Blood Vessels. — The anterior median (or anterior spinal) (Fig. 452) artery gives off branches, which dip into the fissure of the same name, pass to its base, and, after perforating the anterior commissure, divide into two branches, one for each mass of gray matter, and each branch in turn splits into three, which supply part of the anterior, median, and posterior gray matter. The arteries lying in the sulci are called arteriae sulci {s) by Adamkiewicz. In the gray matter, there is usually a special branch to Clarke's column [rl). The vaso-coronary arteries include all those arterial branches wliich proceed from the periphery into the white matter; the finer branches pass only into the white matter, but the larger into the gray substance. The largest branch is the artery of the posterior fissure (./^), which passes along the posterior septum and reaches almost to the commissure, giving branches in its course. There is a large artery between the column of (loll and the postero- external column, viz., the inter-funicular artery [if). Arteries enter along the anterior and posterior roots (;'<7, rp). There are also a median lateral artery (/w), and an anterior and posterior lateral flechsig's systems of conducting fibres. 683 (Ip, la), which enter the lateral column. The generel result is that the gray matter is much more vascular than the white, as is shown in Fig. 453. 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 re-enforcing 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 consider- able resistance to the blood stream. Hence, perhaps, the reason why the lower part of the cord is so apt to be affected by various pathological conditions.] [Functions of the Spinal Cord. — (i) It is a great conducting medium, conducting impulses upward and downward, and within itself from side to side ; (2) the great reflex centre, or rather series of so-called centres; (3) impulses originate within it.] Conducting Systems. — The whole of the longitudinal fibres of the spinal cord may be arranged systematically in special bundles, according to their func- tion. [Methods. — The course of the fibres and their division into so-called systems has been ascer- tained partly by anatomical and embryological, partly by physiological and pathological means. Apart from experimental methods, such as dividing one column of the cord and observing the results, we have the following methods of investigation : (i) 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, /. 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 becoming medullated latest which had the longest course. In this way he mapped out the following systems : — Flechsig's Systems of Fibres. — i. In the anterior column lie («) the un- crossed, anterior, or direct pyramidal tract [also called the Column of Tiirck'] ; and external to it is (J?) the anterior ground bundle, or anterior radicular zo7ie (Fig. 454). [The direct pyramidal tract varies in size, and it generally extends downward in the cord to about the middle of the dorsal region, diminish- ing steadily in its course ; so that it would seem "^ ^^ \^^^^~X f that this tract contains chiefly fibres for the arm. " '^ We do not know, exactly, how these fibres end, whether they cross to the opposite side, or re- main on the same side, but most probably most ^ of them pass through the anterior commissure to the gray matter of the opposite side.] 2. In the posterior column he distinguishes ^ """ "^liw ((f) GoU's column, or the postero-median (pos- ; c tero-internal) column; and (^) the funicu- d; lus cuneatus, BurdacKs column, ox the /^.- Scheme^onhe^ conducing p^^^^^^^^^ tenor radicular Z07ie, or the pOSterO-external part is the gray matter, v, anterior, hm, J posterior, root ; a, direct, and g, crossed, column. pyramidal tracts ; b, anterior column ■x. In the lateral column are (e~) the antero- ground bundle ,- c Goii's column; (/,pos- ,'-', i^/-\i i\li -J tero-external column ; e and J, mixed lateral tract, and (/} the lateral mixed lateral paths ; a, direct cerebellar tracts. paths, or lateral limiting tract, (g) the lateral or crossed pyramidal tract, and (/z) the direct cerebellar tract. (384 fleciisig's systems of conducting fibres. [All the impulses from the central convolutions or motor areas of the cerebrum, by means of which voluntary movements are executed, are conducted by the pyra- midal tracts a and,;,- (>; 365). The fibres in these tracts descend from the central convolutions, /. e., the motor areas pass througli 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 ])Osterior segment (the fibres for the face at the knee, and behind this in order those for the arm and leg), they then enter the middle third of the crusta (Fig. 502, Py), 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 i, a small part descend- ing in the cord on the same side as the antero-median tract (direct pyramidal tract, a). The crossed pyramidal tract lies external to the posterior half of the gray matter in the lateral column (Fig. 454, ^i,*-), and it extends throughout the length of the cord. In the greater part of its course, it is separated from the surface by the direct cerebellar tract, but where the latter lies further forward, as at the third cervical segment and lower dorsal region, its posterior surface reaches the surface, while from the last dorsal segment, throughout the lumbar region, it comes quite to the surface, as the direct cerebellar tract ceases at the first lumbar vertebra. The i)yramidal tract diminishes from above downward, and its fibres pass into the gray matter of the anterior cornu, and in all probability they subdivide to form fine fibrils, which become connected with the dense plexus of fine fibrils produced by the subdivision of the processes of the multipolar nerve cells. From each multi- polar nerve cell, a nerve fibre proceeds and passes into the anterior root. The direct cerebellar tract {h) begins about the first lumbar nerve, and increases somewhat in thickness from below upward, but most of its fibres enter it at the first lumbar and lowest dorsal nerves. It forms a thin layer on the surface of the cord. Its fibres very probably arise in the cells of Clarke's column. As Clarke's column is connected with some of the fibres of the posterior root (for the trunk of the body), it follows that this tract connects certain parts of the posterior roots with the cerebellum. The fibres pass up through the cord and restiform body to the cerebellum. When it is divided, it degenerates upward, so that it conducts im- pulses in a centripetal direction.] The anterior (^) and lateral paths (/) and the anterior ground bundle {b) represent 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 continua- tion 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 process 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 columns run upward as far as the inter-olivary layer and the decus- sation of the pyramids, where they seem to end, or at least form connections with the nerve cells of the funiculi graciles [clava] and cuneati [triangular nucleus]. A small part as arcuate fibres join the restiform body, and thus the cerebellum is connected with the posterior columns. Further, the transverse sectional area of the direct and crossed pyramidal tracts (rr and_§-),the lateral cerebellar tract \h), and Goll's column (t) gradually diminish from alxjve downward; they serve to connect intra-cranial central parts with the ganglionic centres distributed along the spinal cord. The anterior root bundle (/'), the funiculus cuneatus (a'), and the anterior mixed lateral tracts (^) vary SECONDARY DEGENERATION OF TROPHIC CENTRES. 685 in diameter at different parts of the cord, corresponding to the number of nerve roots. It has been concluded from this that these tracts serve to connect the gray matter at different levels in the cord with each other, and ultimately with the medulla oblongata, so that they do not pass directly to the higher parts of the brain (Fig. 443). Nutritive Centres of the Conducting Paths. — Tiirck observed that the destruction of certain parts of the brain caused a secondary degeneration of certain parts of the cord, corresponding to the parts called pyj-amidal tracts by Flechsig (Fig. 455). P. Schieferdecker found the same effects beloiv where he divided the spinal cord in a dog. Hence, it is concluded that the nutritive or tro- phic centre of the pyramidal tracts lies in the cerebrum. [Section of the cord, or an injury compressing the cord, besides giving rise to loss of certain functions (p. 698), results in structural changes in certain limited areas of the cord itself Below the section after a time, the direct and crossed pyramidal tracts (Fig. 455, I, i', 2, 2') degenerate downward, i. e., they undergo descending secondary degeneration, because they are cut off from their nutritive or trophic centres, which are situated above in the pyramidal cells of the motor areas of the brain (§ 378)' The trophic centre for the fibres of the anterior root lies in the multi- polar nerve cells of the anterior cornu of the gray matter of the cord. After section of the spinal cord, GoU's column and the direct cerebellar tracts degenerate upward, i. e., they undergo ascending secondary degeneration. If the pos- terior columns even be divided, Goll's column degenerates upward toward the medulla oblongata, and the degeneration ends in the pos- ^^'^- 455- terior pyramidal nucleus or clava. The same result occurs if the posterior nerve roots of the Cauda equina be injured. Hence, fibres seem to pass from the posterior root into these columns, and the nerve cells in the clava must also have an important relation to these nerve fibres and the parts whence they are derived. The postero-external column re- mains undegenerated, so that there is a very sharp 'distinc- tion between the two parts of the posterior column. As Goll's column degenerates up- ward, it points to its fibres conducting impulses in a cen- tripetal direction, and to the nutritive centre for its nerve fibres being below. The trophic centre is probably in the spinal ganglion of the posterior root.] [If the cord be divided above the junction of the dorsal and lumbar regions, the direct cerebellar tract undergoes ascending degeneration, which extends through the restiform body to the cerebellum. Its trophic centre is probably in the cells of Clarke's column.] Those fibres of the spinal cord which do not degenerate after section of the cord, especially numerous in the lateral and anterior columns [anterior ground bundle, the anterior and lateral mixed zones of the lateral column, and the postero-external part of the posterior column], are commissural in function, connecting ganglionic cells with each other, and are, therefore, provided with a trophic centre at both ends. 3' 3 TR Transverse section of the spinal cord, showing the secondai-y degenera- tion tracts. AR, anterior, TR, posterior root; i, i' (CPT), region of the crossed pyramidal tract; 2, 2' (DPT), direct pyramidal tract; PEC, postero-external column ; LC, lateral column. 6S6 SPINAL REFLEX ACTIONS AND SPASMS. Time of Development. — With regard to the time of development of the individual systems, Flechsig tinds thai the first formed paths are those between the periphery and the central gray matter, esjiecially the mn'^ roots, t. e., they are the first to be covered with the myelin. Then fibres which connect the gray matter at different levels are formed — the fibres which connect the gray matter of the cord with the cerebellum, and also the former with the tegmentum of the cerebral peduncle. At la->t the fibres which coimect the ganglia of the jiedunculus cerebri, and jierhaps also the gray matter of the cortex cerebri with the gray matter of the cord are formed. In cases of anen- cephalous fa-tuses, /. e., where the cerebrum is absent, neither the pyramidal tracts nor the pyramids are developed. In the brain before birth, medullated nerve fibres are formed in the jiaracentral, central, and occipital convolutions, and in the island of Reil, and last of all in the frontal convolu- tions ( Tticzek). 360. SPINAL REFLEXES.— By the term reflex movement is meant a movement caused by the stimulation of an afferent (sensory) nerve. The stimuhis, on being apphed to an afferent nerve, sets up a state of excitement (nervous impulse) in that nerve, which state of excitement is transmitted or conducted in a lenfn'pefai d'wQcUon along the nerve to the centre (spinal cord in this case) ; where the nerve cells represent the nerve centre in the cord, the impulse is transferred to the motor, efferent or centrifugal channel. Three factors, therefore, are essential for a reflex motor act — a centripetal or afferent fibre, a transferring centre, a centrifugal or efferent fibre ; these together constitute a reflex arc (Fig. 456). In a purely reflex act, all voluntary activity is excluded. Fig. 456. Fic. 457. Scheme of a reflex arc. S,skin;M, muscle; N, nerve cell, with a/, afferent, and e/, efferent fibres. Section of a spinal segment, showing a unilateral and crossed reflex act. A, anterior, and P, posterior surface ; M, muscle; S.skin; G, ganglion. Reflex movements may be divided into the three following groups : — I. The simple or partial reflexes, which are characterized by the fact that stimulation of a sensory area discharges movement in one muscle only, or at least in one limited group of muscles. Examples : A blow upon the knee causes a contraction in the quadriceps extensor cruris; contact with the conjunctiva causes closure of the eyelids. In the former case, the aff"erent channels arise in the tendon of the quadriceps, and the eff"erent channels lie in the nerve which supplies the quadriceps; in the latter case, the afferent nerve is the 5th and the efferent the 7th cranial nerve. In the former case the centre is in the lumbar region of the cord ; in the latter, in the gray matter of the medulla oblongata. IL The extensive incoordinate reflexes, or reflex spasms. — These movements occur in the form of clonic or tetanic contractions; individual groups of muscles, or all the muscles of the body may be implicated. Causes : A reflex spasm depends upon a double cause — (rt) Either the gray matter or the spinal cord is in a condition of exalted excitability, so that the nervous impulse, after having reached the centre, is easily transferred to the neighboring centres. This excessive excitability is produced by certain poisons, more especially by strychnin, brucia, caffein, atropin, nicotin, carbolic acid, etc. The slightest touch applied to an animal poisoned with strychnin is sufficient to throw the animal at once into REFLEX SPASMS AND SUMMATION OF STIMULI. 687 Fig. 4.';8. spasms. Pathological conditions may cause a similar result ; thus, there is exces- sive excitability in hydrophobia and tetanus. On the other hand, the central organ may be in such a condition that extensive reflexes cannot take place ; thus, in the condition of apnoea, the spasms that occur in poisoning with strychnin do not take place (y. Rosenthal and Leube), and the same result is brought about by passive artificial respiratory movements (§ 361, 3). The performance of other passive periodic movements in various parts of the body also produces a similar condition {Bi/chheim). If the spinal cord be cooled very considerably, reflex spasms may not occur (^Kunde). {]?) Extensive reflex movements may also take place when the discharging stiinulus is very strong. Examples of this condition occur in man, thus — intense neuralgia may be accompanied by extensive spasmodic movements. [Fig. 458 shows the mechanism of simple and complex reflex movements. Suppose the skin to be stimulated at P, an impulse is sent to A and from it to a muscle I on the same side, resulting in a unilateral simple reflex movement — the resistance being less in this direction than in the other channels. If the impulse be stronger, or the transverse resistance in the cord diminished, the impulse may pass to B, thence to 2, resulting in a symmetrical reflex movement on both sides. But if a very strong impulse reach the cord, or if the excitability of the gray matter be increased, e.g., by strychnin, the resistance to the diffusion of the impulse is diminished, and it passes upvi^ard to C and D, resulting in more complex movements — thus there is irradiation — or it may even affect the centres in the medulla oblongata, E, giving rise to general convulsive movements.] General spasms usually manifest themselves as " extensor tetanus," because the extensors overcome the flexor muscles. Nerves which arise from the medulla oblongata may be excited through the stimulation of distant afferent nerves, without general spasms being produced. Strychnin is the most powerful reflex-producing poison we possess, and it acts upon the gray matter of the spinal cord. [An animal poisoned with strychnin exhibits tetanic spasms on the application of the slightest stimulus. All the muscles become rigid, but the extensors overcome the flexors.] If the heart of a frog be ligatured, and the poison afterward ap- plied directly to the spinal cord, reflex spasms are produced, proving that strychnin acts upon the spinal cord. During the spasm the heart is arrested in dias- tole, owing to the stimulation of the vagus, while the arterial blood pressure is greatly increased, owing to stimulation of the central vasomotor centres of the medulla oblongata and spinal cord. Mammals may die from asphyxia during the attack ; and, after large doses, death may occur, owing to paralysis of the spinal cord, due to the frequently recurring spasms. Fowls are unaffected by comparatively large doses. [We can prove that strychnin does not produce spasms by acting on the brain, muscle, or nerve. Destroy the brain of a frog, divide one sciatic nerve high up, and inject a small dose of strychnin into the dorsal lymph sac ; in a few minutes all the muscles of the body, except those supplied by the divided nerve, will be in spasm, showing that, although the poisoned blood has circulated in the nerves and muscles of the leg, it does not act on them. Destroy the spinal cord, and the spasms cease at once.] Summation of Stimuli. — By this term is meant, that a single weak stimulus, which in itself is incapable of discharging a reflex act, may, if repeated sufficiently often, pro- Scheme ot mode ot propagation ot reflex move- j ^v- , Vpi ■ 1 • 1 ments. P, skm ; A, B, C, D, motor cells m duce this act. Ihe single impulses are con- ^^-^^^y ^^^^.^ j_ 2; 3^ \^ {^ muscles. ducted to the spinal cord, in which the pro- cess of " summation " takes place. According to J. Rosenthal, 3 feeble stimuli per second are capable of producing this effect, although 16 stimuli per second are most effective. On increasing the number of stimuli per second, no further increase of the reflex act is possible. Other observers {Stirling, Ward') have found 688 EFFECT OF DRUGS ON REFLEX ACTION. that stimuli, such as induction shocks, are active within much wider limits, ^. ^^., from 0.05 to 0.4 second interval. W. Stirling has shown it to be extremely prob- able that all reflex acts are due to the rei>etition of imi)ulses in the nerve centres. [Strychnin interferes with tlie summation of stimuli, hut the reflex excitability is so greatly exalted that a minimal stimulus is at the same lime a maximal one.] Pfliiger's Law of Reflex Actions. — (l) The retlex movement occurs on the same side on which the sensor}- nerve is stimulated ; while only those muscles contract whose nerves arise from the same segment of the spinal cord. (2) If the reflex occur on the other side, only the corresponding muscles contract. (3) If the contractions he unequal upon the two sides, then the most vigorous contractions always occur on the side which is stimulated. (4) If the reflex excitement extend to other motor nerves, those nerves are always alTected which lie in the direction of the medulla oblon- gata. Lastly, all the mu.scles of the hotly may he thrown into contraction. Crossed Reflexes. — There are exceptions to the.'^e rules. If the region of the eye he irritated in a [xog whose cerebrum is removed, there is frequently a rellex contraction in the hind limb of the opposite side [Luchsini^er, LangenJorff). In beheaded tritons and tortoi.ses, and in deeply narcot- ized dogs and cats, tickling one fore limb is frequently followed by a movement of the hind limb of the opposite side (Z«<;7/««j,w). This phenomenon is called a " crossed reflex " (Fig. 457). If the spinal cord be divided along the middle line throughout its entire extent, then, of course, the reflexes are conlined to one side only [Schiff). III. Extensive co-ordinated reflexes are due to stimulation of a sensory nerve, causing the discharge of complicated reflex movements in whole groups of different muscles, the movements being "purposive " in character, /. e., as if they were intended for a particular purpose. Methods. — The experiments are made upon cold-blooded animals (decapitated or pithed frogs, tortoises, or eels) or upon tnanunals. In the latter, artificial respiration is kept up, and the four arteries going to the head are ligatured, in order to eliminate the action of the brain {Sig. Mayer, Lucksinger). The reflexes of the lower part of the spinal cord maybe studied on animals (or men), in cases where the spinal cord is divided transversely in the upper dorsal region. In such ca.ses, some time must elapse in order that the primary effect of the lesion (the so-called .shock), which usually causes a diminution of the reflexes, may pass oft". Very young mammals exhibit reflexes for a considerable time after they are beheaded. Examples : i. The protective movements of pithed or decapitated frogs. [If a drop of a dilute acid be applied to the skin of such a frog, immediately it strives to get rid of the offending body, and it generally succeeds m doing so.] Similarly, it kicks against any fixed body pushed against it. These movements are so pur- posive in their character, and the actions of groups of muscles are so adjusted to perform a particular act, that Pfliiger regarded them as directed by, and due to " consciousness of the spinal cord." If a flame be applied to the side or part of the body of an eel, the body is moved away from the flame. The tail of a decapi- tated triton, tortoise, newt, eel, or snake is directed toward a gentle stimulus, but if a violent stunulus is used, it is directed away from it {Ltichsi tiger). 2. Goltz's Croaking Experiment. — A pithed (male) frog, /. e., one with its cerebral lobes alone removed (or one with its eyes or ears destroyed — Latigeiidot'ff), croaks every time the skin of its back or flanks is gently stroked. [Some male frogs, when held up by the finger and thumb immediately behind the fore legs, croak every tiine gentle pressure is made on their flank.] 3. Goltz's " Embrace Experiment." — During the breeding season in spring, the part of the body of the male frog between the skull and the fourth vertebra, embraces every rigid object, which is brought into contact with, and gently stimulates, the skin over the sternum. In the intact animal, the exciting stimulus lies in the degree of filling of the male seminal organ {Tarchanoff). The reflex ceases at once on gently stimulating the optic lobes [Albertoni). 4. In mammals (dogs), the following reflex acts are performed by the posterior part of the spinal cord, even after it is separated from the rest of the cord : Scratch- ing with the hind feet a part of the skin which has been tickled (just as in intact animals) ; the movements necessary for emptying the bladder and for defaecation, REFLEX TIME AND INHIBITION OF REFLEXES. 689 as well as those necessary for erection ; the movements necessary for parturition {Goltz, Freusberg and Gergens). Coordinated movements do not, as a rule, occur simultaneously in portions of the spinal cord lying widely apart after removal of the medulla oblongata. According to Ludwig and Owsjannikow, the medulla oblongata perhaps contains a reflex organ of a higher order, which forms, as it were, a centre for combining, through the medium of the nerve fibres, the various reflex provinces in the spinal cord. 5. Coordinated reflexes may occur in man during -sleep, and during patho- logical comatose conditions. Most of the movements which we perforin while we are awake, and which we execute uncon- sciously— or even when our psychical activities are concentrated upon some other object — really belong to the category of coordinated reflexes. Many complicated motor acts must first be learned — e. g., dancing, skating, riding, walking — before unconscious harmonious coordinated reflexes can again be discharged. The coordinated reflex movements of coughing, sneezing, and vomiting depend upon the spinal cord, together with the medulla oblongata. The following facts are also important : — 1. Reflexes are more easily and more completely discharged, when the specific end organ of the afferent nerve is stimulated, than when the trunk of the nerve is stimulated in its course (^Marshall Hall, 1837). [Thus, by gently tickling the skin, it is easy to discharge a reflex act, while it requires a strong stimulus to be applied to an exposed sensory nerve in order to do so.] 2. A j-/';^^;^^^r j-^/wz^j/z^j is required to discharge a reflex movement than for the direct stimulation of motor nerves. 3. A movement produced reflexly is of shorter duration than the corresponding movement executed voluntarily. Further, the occurrence of the movement after the moment of stimulation is distinctly delayed. In the frog, a period nearly twelve times as long elapses before the occurrence of the contraction, than is occupied in the transmission of the impulse in the sensory and motor nerves (^Hebnholtz, 1854.) Thus, the spiiial cord offers resistance to the transmission of impulses through it. The term "reflex time " is applied to the time necessary for transferring the impulse from the afferent fibre to the nerve cells of the cord, and from them to the efferent fibre. In the frog it is equal to 0.008 to 0.015 second. The time, however, is increased by almost one-third, if the impulse pass to the other side of the cord, or if it pass along the cord, e. g., from the sensory nerves of the anterior extremity to the motor roots of the posterior limb. Heat diminishes the reflex time and increases the reflex excitability. Lowering the temperature (winter frogs), as well as the reflex- exciting poisons already mentioned, lengthens the rejiex time, while the reflex excitability is simulta- neously increased. Conversely, the reflex time diminishes as the strength of the stimulus increases, and it may even become of minimal duration (/. Rosenthal). The reflex time is determined by ascer- taining the moment at which the sensory nerve is stimulated, and the subsequent contraction occurs. Deduct from this the time of latent stimulation (§ 298, I), and the time necessary for the conduction of the impulse (§ 298) in the afferent and efferent nerves (v. Helmholtz,J. Rosenthal, Exner, Wundt). [Influence of Poisons. — The latent period and reflex time are influenced by a large number of conditions. In a research as yet unpublished, W. Stirling finds that the latent period may remain nearly constant in a pithed frog for nearly two days, when tested by Tiirck's method. Sodic chloride does not influence the time, nor does sodic bromide or iodide. Potassic chloride, however, lengthens it enormously, or even abolishes reflex action after a very short time, and so do potassic bromide, ammonium chloride and bromide, chloral and croton-chloral. The lithia salts also lengthen the reflex time, or abolish the reflex act after a time.] 361. INHIBITION OF THE REFLEXES.— Within the body there are mechanisms which can suppress or inhibit the discharge of reflexes, and they may therefore be termed mechanisms inhibiting the reflexes. These are : — I. Voluntary Inhibition. — Reflexes may be inhibited voluntarily, both in the region of the spinal cord and brain. Examples : Keeping the eyelids open when the eyeball is touched ; arrest of movement when the skin is tickled. We must observe, however, that the suppression of reflexes is possible only up to a certain point. If the stimulus be strong, and repeated with sufficient frequency, the reflex impulse ultimately overcomes the voluntary effort. It is impossible to 44 690 EXAMPLES AND NATURE OF INHIBITION. suppress those reflex movements which cannot at any time be performed voluntarily. Thus, erection, ejaculation, parturition, and the movements of the iris, are neither direct voluntary acts, nor can they, when they are excited reflexly, be suppressed by the will. 2. Setschenow's inhibitory centre is another cerebral apparatus, which in the frog is placed in the optic lobes. If the optic lobes be separated from the rest of the brain and spinal cord, by a section made below it, the reflex excitability is increased. If the lower divided surface of the optic lobes be stimulated with a crystal of common salt or blood, the reflex movements are suppressed. The same results obtain when only one side is operated on. Similar organs are supposed to be present in the corpora quadrigemina and medulla oblongata of the higher verte- brates. From I and 2 we may exi)lain why reflex movements occur more regularly and more readily after separation of the brain from the spinal cord. [Quinine greatly diminishes the reflex excitability in the frog, but if the medulla oblongata be divided, the reflex excitability of the cord is restored. The depression is ascribed by Chaperon to the action of the quinine on Setschenow's centres.] 3. Strong stimulation of a sensory nerve inhibits reflex movements. The reflex does not take place if an afterent nerve be stimulated very powerfully {Goifz, Lczuissofi). Examples : Suppressing a sneeze by friction of the nose [compressing the skin of the nose over the exit of the nasal nerve] ; suppression of the move- ments produced by tickling, by biting the tongue. Very violent stimulation may even suppress the coordinated reflex movements usually controlled by voluntary impulses. Violent pain of the abdominal organs (intestine, uterus, kidneys, bladder, or liver) may ])revent a person from walking or even from standing. To the same category belongs the fact that persons fall down when internal organs richly sup- plied with nerves are injured, there being neither injury of the motor nerves nor loss of blood to account for the phenomenon. Excitement of the central organs through other centripetal channels (nerves of special sense, and those of the generative organs) diminishes the reflexes in other channels. 4. It is important to note that in the suppression of reflexes, antagonistic muscles are often thrown into action, whetlier voluntarily or by the stimulation of sensory nerves, i. e., reflexly. In some cases, in order to cause suppression of the reflex, it appears to be sufficient to direct our attention to the execution of such a complicated reflex act. Thus, some persons cannot sneeze when they think intently upon this act itself (Diif~:ain). The voluntary impulse rapidly reaches tlie reflex centre, and begins to influence it so that the normal course of the reflex stimulation, due to an impulse from the periphery, is interfered with (Sc/i/osser). 5. Poisons. — Chloroform diminishes the reflex excitability by acting upon the centre, and a similar effect is produced by picrotoxin, morphia, narcotin, thebain, aconitin, quinine, hydrocyanic acid. [W. Stirling finds that chloral, potassic bromide and chloride, ammonium chloride, but not sodium chloride, greatly dimin- ish the reflex excitability. Nicotin increases it in frogs {Freusl>erg).'\ A constant current of electricity passed longitudinally through the cord diminishes the reflexes {Ranke), especially if the direction of the current is from above downward (^Legros and Oniinus, Uspensky). [Some drugs affect the reflex excitability directly by acting on the spinal cord, e.g., methylconine, but other drugs may produce the same result indirectly by afiecting the heart and the l)lood supply to the cord. If the abdominal aorta of a rabbit be compressed for a few minutes to cut off the supply of blood to the cord and lower limbs, temporary paraplegia is produced.] If frogs be asphyxiated in air deprived of all its O, the brain and spinal cord become completely unexcitable, and can no longer discharge reflex acts. The motor nerves and the muscles, however, suffer very little, and may retain their excitability for many days {Aubert). [Nature of Inhibition. — The foregoing view assumes the existence of inhibitory centres, but it is important to point out that it has been attempted to explain this phenomenon without postulating the existence of inhibitory centres. During inhibition the function of an organ is restrained — during paralysis it is abolished, so that there is a sharp distinction between the two conditions. The analogy between inhibitory phenomena and the effects of interference of waves of light or sound has been pointed out by Bernard and Romanes, while Lauder Brunton has tried to explain the question on a TURCK'S method THEORY OF REFLEX ACTION. 691 physical basis, indicating that inhibition is not dependent on the existence of special inhibitory centres but that stimulation and inhibition are different phases of excitement, the two terms being relative conditions depending on the length of the path along which the impulse has to travel and the rate of its transmission. Brunton points out that the known facts are more consistent with an hypothesis of the interference of waves, one with another, than with the supposition that they are inhibitory centres for every so-called inhibitory act in the body. In discussing this question great regard must be had to the action of the vagus on the heart (| 369).] Tiirck's method of testing the reflex excitability of a frog is the following: A frog is pithed, and after it has recovered from the shock, its foot is dipped into dilute sulphuj'ic acid [2 per 1000]. The time which elapses between the leg being dipped in and the moment it is withdrawn is noted. [The time may be estimated by means of a metronome, or the movements may be inscribed upon a recording surface. The time which elapses is known as the " period of latent stimulation."] This time is greatly prolonged after the optic lobes have been stimulated with a crystal of common salt or blood, or after the stimulation of a sensory nerve. Setschenow distinguished tactile reflexes, which are discharged by stimulation of the nerves oj touch; and pathic, which are due to stimulation of sensory (pain-conducting) fibres. He and Paschutin suppose that the tactile reflexes are suppressed by voluntary impulses, and the pathic by the centre in the optic lobes. Theory of Reflex Movements. — The following theory has been propounded to account for the phenomena already described: It is assumed that the affere7tt fibre within the gray matter of the spinal cord joins one or more nerve cells, and thus is placed in communication in all directions with the network of fibres in the gray substance. Any impulse reaching the gray matter of the cord has to overcome considerable resistance. The least resistance hes in the direction of those efferent fibres which emerge in the same plane and upon the same side as the entering fibre. Thus, the feeblest stimulus gives rise to a simple reflex, which generally is merely a simple protective movement for the part of the skin which is stimulated. Still greater resistance is opposed in the direction of other motor ganglia. If the reflex impulse is to pass to these ganglia, either the discharging stimulus mu.st be considerably increased, or the resistance within the connections of the gangha of the gray matter must be diminished. Ihe latter condition is produced by the action of the above-named poisons, as well as during general increased nervous excitability (hysteria, nervousness). Thus, extensive reflex spasms may be produced either by increasing the stimulus, or by diminishing the resistance to conduction in the spinal cord. Those conditions which render the occurrence of reflexes more difficult, or abolish them altogether, must be regarded as increasing the resistance in the reflex arc in the cord. The action of the reflex inhibitory mechanism may be viewed in a similar manner. The fibres of the reflex arc must have a connection with the reflex inhibitory paths ; we must assume that equally by the reflex inhibitory stimulation resistance is introduced into the reflex arc. The explanation of extensive coordinated movements is accompanied with difficulties. It is assmned, that by use and also by heredity, those ganglionic cells which are the first to receive the impulse are placed in the path of least resistance in connection with those cells which transfer the impulse to the groups of muscles, whose contraction, resulting in a coordinated purposive movement, prevents the body or the limb from being affected by any injurious influences. Pathological. — Anomalies of reflex activity afford an important field to the physician in the investigation of nervous diseases. Enfeeblement, or even complete abolition of the reflexes may occur: (i) Owing to diminished sensibihty or complete insensibility of the afferent fibres; (2) in analogous affections of the central organ; (3) or, lastly, of the efferent fibres. Where there is general depression of the nervous activity (as after shocks, compression or inflammation of the central nervous organs; in asphyxia, in deep coma, and in consequence of the action of many poisons), the reflexes may be greatly diminished or even abolished. [Reflexes. — The physician, by studying the condition of the reflexes, can form an idea as to the condition of practically every inch of the spinal cord. There are three groups of reflexes, {a) the superficial, {b) the deep or tendon, (r) the organic reflexes.] [The superficial or skin reflexes are excited by stimulating the skin, e. g., by tickling, pricking, scratching, etc. We can obtain a series of reflexes from below as far up as the lower part of the cervical region. The plantar reflex is obtained by tickling the soles of the feet, when the leg on that side, or, it may be, both legs are drawn up. It is always present in health, and its centre is in the lumbar enlargement of the cord. The cremasteric reflex is well marked in boys, and is easily produced by exciting the skin on the inner side of the thigh, when the testicle on that side is retracted. The gluteal reflex consists in a contraction of the gluteal 692 THE SUPERFICIAL REFLEXES. muscles, when the skin over the buttock is stimulated. The abdominal reflex consists in a similar contraction of the abdominal muscles, when the skin over the abdomen in the mammary line is stimulated. The epigastric reflex is obtained l)y stimulating the skin in front between the fourth and sixth ribs. The inter- scapular reflex results in a contraction of the muscles attached to the scapula, when the skin between the scapul?e is stimulated. Its centre corresponds to the lower cervical and upper dorsal region.] [The following table, after Gowers, shows the relation of each reflex to the spinal segment or segments on which it depends : — t:eryical, 6 l \ Lumbar 1 1 Cremasteric. ••••••• 7 Interscapular. 1 [[ '.'.'.'.'.'.'. I) \ Knee Reflex. Dorsal, \ '.'.'.'.'.'. l \ \ " 4 1 (j 5 1 ' " . -5 6 V Epigastric. 7 J 8 ] 9 I lo j- Abdominal. " I 12 J Sacral, i 2 1- "^ I ] Plantar. " 3J"^Cj|. Vesical. " 4 ( Rectal. " 5 J Sexual.] Another important diagnostic reflex is the "abdominal reflex," which consists in this, that when the skin of the abdomen is stroked, ,?. ^j,--., 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 diff'use disease of the brain ; its absence on one side indicates a local affection of the opposite half of the brain. The cremasteric, conjunctival, mammillary, pupillary, and nasal reflexes may also be specially investigated. In hemiplegia complicated with cerebral lesions, the reflexes on the paralyzed side are diminished, while not unfrequently the patellar reflex may be increased. In extensive cerebral affections accompanied by coma the reflexes are absent on both sides, including, of course, those of the anus and bladder ((?. Rosenbach). [Horsley finds that in the deepest narcosis produced by nitrous oxide gas the superficial reflexes {e.g., plantar, conjunctival) are abolished, while the deep (knee jerk) remain. Anamia of the lumbar enlargement (compression of the abdominal aorta) causes disaj^pearances 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 contraction of the rectus femoris is due to local irritation of the muscle from sudden elongation.] Deep or 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 {IVestphal, Erb, 1875). The patellar tendon reflex (also called '' knee phenomenon''^ or simply " knee reflex," or "knee jerk," is mvariably 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 patellar, and is due to a single spasm of the rectus. The latent period is 0.03 to 0.04 second, and it is argued by Waller and others that it is doubtful if this tendon reflex is subserved 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). 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 occur 0.03 to 0.04 second, and according to Eulenburg, 0.032 second after the blow. According to Westphal, these phe- nomena are not simple reflex processes, but complex conditions intimately dependent PATELLAR REFLEX AND ANKLE CLONUS. 693 upon the muscle tonus, so that when the tonus of the quadriceps femoris is dimin- ished, the phenomenon is abolished. In order that the phenomenon may take place, it is necessary that the outer part of the posterior column of the spinal cord remain intact (^Westphal). [The knee jerk can be increased or reinforced by volitional acts directed to other parts of the body, e.g., by exercising voluntary pressure with the hand (^JeiidrdssiK).'\ [A "jaw jerk " is obtained by suddenly depressing the lower jaw {Gowe?-s, Beezwr, and De Waiteville), and the last observer finds that the latent period is 0.02 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.] [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 exaggerated 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 suddenly 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 modi- fication elicited by tapping the muscles of the front of the leg, the '^ front-tap contraction.'^ Ankle clonus is excessive in sclerosis of the lateral columns and spastic paralysis.] [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 0.03 to 0.04 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 abdomi- nal, 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 (C. RosenbacJi). 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 reflexes, it is evident that in affections of the spinal cord there are frequent disturbances of the vol- untary movements, eheadecl 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. Luihcig 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 Luihing and Dittmar — § 364, 10). Stimula- tion of these fibres, although it affects the vasomotor centre reflexly, does not cause sensation. 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 produced 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 1st 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 diood overheated, then spasms, contraction of the vessels, and secretion of siveat occur in the hind limbs, together with evacuation of the contents of the bladder and rectum, while there are movements of the uterus and vas deferens. Some poisons act in a similar manner. In animals with the medulla oblongata divided, rhythmical re.spiratory movements may be produced if the spinal cord has been previously rendered very sensitive by strychnin or overheated blood [P. v. Rokitansky, v. Schroff — | 368). The ganglion cells of the anterior cornu can be excited mechanically {Birge), and according to Biedermann the gray matter also responds to electrical stimuli. Hyperaesthesia. — After unilateral section of the cord, or even only of the posterior or lateral columns, there is hyperesthesia on the same side below the point of section {Fodcra, 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 permanently 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. The excitability of the cord is intimately dependent on the continuance of the circulation, for ligature of the abdominal aorta rapidly paralyzes the lower extremi- ties {Stenson, 1667), due to anaemia of the cord {Schiffer). Later, the anterior roots of the spinal nerves, and the anaemic part of the gray matter of the cord, undergo degeneration. 364. THE CONDUCTING PATHS IN THE SPINAL CORD. — [Posterior Root. — {a) The inner part, or internal radicular fasciculus is supposed to convey the impressions from tendons and those for touch and locality. When the postero-external column is diseased, as in locomotor ataxia, the deep reflexes, especially the patellar tendon reflex, are enfeebled, or it may be abolished, while the implication of the fibres of the internal fasciculus gives rise to severe pain, {b) The outer radicular fibres enter the gray matter of the posterior horn, and are supposed 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 (Fig. 449)-]. I. Localized tactile sensations (temperature, pressure, and the muscular CONDUCTING PATHS IN SPINAL CORD. 697 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 GoU's column, while those for the arms run in the ground bundle (Fig. 454) [Flecksig). In rabbits, the path of locahzed tactile impressions lies in the lower dorsal region in the lateral cdhimns [^Ludwig and Woroschiloff, Oit 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 sensibiliiy is lost is known as anmsthesia. 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. Every motor nerve libre is connected with a nerve cell in the anterior horn of the frog's spinal cord (6^az^/^ a;^^^/;'_o-,f). 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. 443]. 3. Tactile reflexes (extensive and coordinated). — 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. 684). 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 tne posterior columns. After degeneration of the latter, there is not only ansesthesia, 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 manner materially 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 tlie disturbances of sensation which characterize the degenerations of these parts [Chai-cot and Pier7-ei). But even the posterior roots themselves may undergo degenera- tion, and this may also give rise to disturbances of sensation (p. 667). The sensory disturbances usually consist in an abnormal increase of the tactile or pamful sensations, with lightning pains shooting down the limbs, and this condition may lead to one where the tactile and painful sensations are abolished. At the same time, owing to stimulation of the posterior columns, the tactile sensi- bility is altered, giving rise to the sensation of formication, or a feehng of constriction [" girdle sensation "]. The conduction of sensory impressions is often slowed (g 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, becaiise by cutting off the guiding sensations obtained through the optic nerve, the other enfeebled impulses obtained from the skin and the deeper struc- tures are too feeble to excite propor 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 698 CONDUCTION IN THE SPINAL CORD. of these impulses in the cord, the conducting fibres j)assing from one side to tlie other. The further course of these fibres to the brain is given in § 365. If all the gray matter be divided, except a small connecting portion, this is sufficient to conduct painful impressions. In this case, however, ihe conduction is slower [Schiff). Only when the gray matter is comjiletely divided, is the conduction of jiainful im])re.ssions from below completely inter- rupted. This gives rise to the condition of analgesia, in which, when (he posterior columns are still intact, tactile impressions are still conducted. This condition is sometimes obser\'ed in man during incomplete narcosis from chloroform and morphia ( Thiersrh). Those poisons act sooner on the nerves which administer to painful sensations than on those for tactile impressions, so that the person operated on is conscious of the contact of a knife, but not of the painful sensations caused by the knife dividing the parts. As painful impressions are conducted by tiie 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, ])roceeding from a particular tooth, the pain may be felt in the whole jaw, or it may be over one side of the head. According to Bechterew, the paths for the conduction of painful impressions lie in the anterior part of the lateral column (dog, rabbit). 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 com- pletely sensibility and motility on both sides. The anterior columns and the gray matter are not sufficient to maintain these. The conduction of spasmodic, involuntary, inco-ordinated movements takes place through the gray matter, and from the latter through the anterior roots. It occurs in epilepsy, poisoning with .strjxhnin, uraemic poisoning, and tetanus {'i 360, II). The ansemic and dyspnoeic spasms are excited in and conducted from the medulla oblongata, and commu- nicated 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. 458), and, lastly, into the anterior roots, under the conditions alreadv referred to in § 360, II. 8. The inhibition of pathic reflexes occurs through the anterior columns downward, and then into tiie 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 in the posterior roots, run upward in the lateral columns, and undergo an incomplete decussation {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 satne side, and after forming connections with the ganglia of the gray matter 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 nervts, on the same or on both sides. Section of the cord above EFFECTS OF SECTION OF THE CORD. 699 Fig. 459. the origin of the phrenic nerves causes death, owing to the paralysis of these nerves of the diaphragm (?ii3). . , 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 hypersesthetic 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. 455). 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.] [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 exhibit 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 diminished on both sides (Fig. 459). There is bilateral anaesthesia. On the opposide 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. 459, d), corresponding to the sensory nerve fibres destroyed at the level of the section. The sensory nerves decussate shortly after they enter the cord, hence the anaes- thesia 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 dimin- ished sensibility in a circular area on the same side. There is a narrow hyperaesthetic area on the same side as the lesion, at the upper limit of the paralyzed cutaneous area (Fig. 459, 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 hemi-section 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 anaes- 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 para- lyzed 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.] Diagrammatic represen- tation of a lesion of the left half of the spinal cord in the dorsal region, (a) oblique lines, motor and vasomotor para- lysis ; {b, d), com- plete anaesthesia ; {a, c), hyperaesthesia of the skin. THE BRAIN. 365. GENERAL SCHEMA OF THE BRAIN.— In an organ so complicated in its structure as the brain, it is necessary to have a general view of the chief arrangements of its individual parts. Me\nertgave a plan of the general arrangement of this organ, and although this plan may not be quite correct, still it is useful in the Fin. 460. study of brain function. The weight of the brain is in man aljout 1358 grammes, and in woman 1 220 grammes [^Bischoff'). [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- ovalc. The gray matter is folded into gyri or convolutions separated from ach other liy fissures or sulci. Some uf the latter are veiy marked, and serve to separate adjacent lobes, while the lobes themselves are further sub- divided by sulci into convolutions. For a description c f 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 lenticu- lar nucleus (Fig. 460, b), the optic thalamus which lies behind the former, and bounds the 3d ventricle (Fig. 460,^/), the corpora quadri- gemina lying on the upper surface of the crura cerebri (Fig. 480, hi); within the tegmentum of the crura cerebri are the red nucleus and locus niger (Fig. 502). Lastly, there is the continuation of the gray matter of the cord up through the medulla, pons, and around the iter, forming the cen- tral gray tube and terminating an- teriorly at the tuber cinereum. These various parts are connected in a variety of ways wuth each other, some by transverse fibres stretching between the two sides of the brain, while other longitudinal fibres bring the hinder and lower parts into 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 sulci, the "peripheral gray matter" (Fig. 461, C), which is recognized as a nervous structure, from the presence in it of numerous ganglionic cells \\ 358, l). 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 700 Dissection of the brain from above, showing the lateral, 3d, and 4th ventricles, with the basal ganglia, and surrounding parts, a, knee of the corpus callosum ; ^.anterior part of the right corpus striatum; b' , gray matter dissected off to show white fibres ; c, points to taenia semicircularis ; dy optic thalamus ; e, anterior pillars of fornix, with 5th ventricle in front of them, between the two laminae of the septum lucidum ; f, middle or soft commissure ; g, 3d ventricle; A, /, corpora quadrigemina ; ^, superior cerebellar peduncle; /, hippocampus major; nt, posterior cornu of lateral ventricle ; «, eminentia collateralis ; o, 4th ventricle ; /, medulla oblongata ; s, cerebellum, with r, arbor vita:. SCHEME OF THE CENTRAL NERVOUS SYSTEM. 701 Fig. 461 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 they enter the cord, as is represented in Fig. 463. 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 I, Scheme of the brain. — C, C, cortex cerebri ; C.J, corpus striatum ; N./, nucleus lenticularis ; T.o, optic thalamus ; V, corpora quadrigemina ; P, pedunculus cerebri; H, tegmentum ; and/, crusta ; i, i, corona radiata of the corpus striatum ; 2, 2, of the lenticular nucleus ; 3, 3, of the optic thalamus ; 4, 4, of the corpora quadrigemina ; S, pyramidal fibres from the cortex cerehri {/^/ec/tsig-) ; 6, 6, fibres from the corpora quadrigemina to the teg- mentum ; }>i, 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, trans- verse section of the spinal cord; z/.W, anterior, and /i.W, posterior roots, (Z, 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, — /, crusta of the peduncle; j, substantia nigra; z/, corpora quadrigemina, with a section of the aqueduct. Ill, The same of the dog ; IV, of an ape ; V, of the guinea pig. [See p. 700.] of the caudate nucleus and lenticular nucleus (N./),) optic thalamus (T.o), and corpora quadrigemina — some fibres form connections with cells within this central gray matter. The fibres which proceed from the cortex through the corona radiata in a radiate direction constitute Meynerf s first projection system. Besides these, the white substance also contains two other systems of fibres: {a) Com- missural fibres, such as the corpus callosum and the anterior commissure {c, c), which are supposed 702 CEREBRO-SPINAL CONNECTIONS. to connect the two hemispheres with each other ; and (i>) a connecting:; or association system, whereby two ditVerent areas of tlie same side are connected together (, posterior median fissure; jr, groups of ganglionic cells in the base of the posterior cornu. X 6. [The olivary body forms a well marked oval or olive-shaped body, which does not extend the whole length of the medulla (Fig. 466, o). 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 longitudinal 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'wers).'\ [Decussation of the pyramids is the term given to those fibres which cross obliquely in several bundles, at the lower part of the medulla, fi-om the anterior pyramid of the medulla into the lateral 708 STRUCTURE OF TIIK MEDULLA OBLONGATA. column of the cord of tlie opposite side (Fig. 4^4. ''') to form its lateral pyramid tracts, or crossed p>Tamidal tracts. The number of fibres wliich decussate varies, and in some cases all the fibres may Cross.] . [ Ihe gray matter of ihe medulla is largely a continuation of that of the cord, although it is arranged ditVerently. As the fibres from the lateral column of the cord pass over to form part of the anterior pyramid of the medulla on the opj^site side, they traverse the gray matter, and thus cut off the tip of the anterior cornu, which is also pu--hed backward i)y the olivary body, and exists as a dis- tinct mass, the nucleus lateralis (Fig. 465, til). Part of the anterior gray matter also appears in the floor of the 4th ventricK- as the eminence of the fasciculus teres, and from part of it springs the hypoglossal nerve (Fig. 466, X/I). The neck joining the modified anterior and posterior cornua is much broken up bv the passage of longitudinal and transverse fibres tlirough it, so that it forms a formatio reticularis, separating the two cornua (Fig. 465,/;). The caput cornu posterioris comes Fin. 465. Section of the medulla oblongata at the so-called upper decussation of the pyramids. _/?«, ante- rior, slfi, posterior median fissure ; nX/, nu- cleus of the accessorius vagi ; nX!I, nucleus of the hypoglossal : cia, the so-called superior or anterior decussation of the pyramids; py, anterior pyramid; n.ar, nucleus arciformis; f, median parolivary body: O, beginning of the nucleus of the olivary body : nl, nucleus of the lateral column; Fr, formalio reticularis; g, substantia gelatinosa, with {a K) the ascend- ing root of the trigeminus; nc, nucleus of the funiculus cuneatus; «f', external nucleus of the funiculus cuneatus ; ng, nucleus of the fu- niculus gracilis (or clava) ; //', funiculus gra- cilis ; //'.funiculus cuneatus ; cc, central canal ; /a,/a^ ,/a'^ , external arciform fibres. X 4- Fig. 466. nc. n.ar Section of the medulla oblongata through the olivary body. nXlI, nucleus of the hypoglossal; nX, nX^, more or less celhilar parts of the nucleus of the vagus ; XII, hypo- glossal nerve; A', vagus ; ti.atn, nucleus ambiguus ; nl, nucleus lateralis; tj, olivary nucleus; fla/,external, and oa»t, internal parolivary body ; /s, the round bundle, or funiculus solitarius ; CV, restiform body ; /, anterior pyramid, surrounded by arciform fibres ; fae,pol, fibres proceeding from the olive to the raphe (pedunculus olivae) ; r, raphe. X 4- to be covered higher up by the a.scending root of the 5th nerve (Fig. 465, a V), and arcuate fibres passing to the resiiform body. The jwsterior cornu is also i)roken up and is thrown outward, its caput giving rise to ])art of the elevation seen on the surface and described as the funiculus of Rolando, while jiart of the base now greatly enlarged forms the gray matter in the funiculus gracilis [clavate nucleus] (Fig. 464, ng) and funiculus cuneatus [cuneate or triangular nucleus] (Fig. 464, nc). Nearer the middle line, tlie gray matter of the posterior gray cornu appears in the floor of the 4th ventricle, above the jwint where the central canal opens into it, as the nuclei of the spinal acces- sory, vagus, and glosso-pharj'ngeal 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 spring the several bundles forming the hypoglossal nerve; it is the hypoglossal nucleus (Fig. 466, nX//),ihe nerve fibres passing obliquely outward to appear between the anterior pyramid and the olivary body. THE GRAY MATTER OF THE MEDULLA OBLONGATA. 709 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. 466, nt). Around the central canal at the lower part of the medulla is a group of cells (Fig. 466, tiXI), which becomes displaced laterally as it comes nearer the surface in the floor of the medulla oblongata, where it lies outside the hypo- glossal nucleus, and corresponds to the prominence of the ala cinerea (Fig. 466, nX') ; and from it and its continuation upward arise from below upward part of the spinal accessory (nth), and the vagus (loih), corresponding to the position of the eminentia cinerea (Fig. 466, X), so that this colunnn of cells forms the vago-accessorius nucleus. External to and in front of this is the nucleus for the glosso-phar}'ngeal 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 (Sth) in great part arises ; it is the principal auditory nucleus, and lies just under the commencement of the inferior cerebellar peduncle (Fig. 427, 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 vestibular 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 (hilum), and into it run white fibres forming its peduncle (Fig. 466,/, 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. 465, 0^, o^') 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 from the dentate body by the roots of the hypoglossal nerve. The latter is sometimes called the internal parolivary body, or nucleus of the pyramid.] [The formatio reticularis occupies the greater part of the central and lateral parts of the medulla, and is produced by the inter-crossing of bundles of fibres running longitudinally and more or less transversely in the medulla (Fig. 465, y^). 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 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. 683). The horizontal fibres are formed by arcuate fibres, some of which run more or less transversely outward from the raphe. The superficial arctiate fibres (Fig. 466, y, 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. 707), but they are reinforced by some of the deep arcuate fibres which traverse the olivary body (p. 707)- 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. 427) 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 the 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 foi"ward and outward, to a column of cells more deeply placed in the medulla than any other nucleus in the lower part." But the seventh has no real origin from this nucleus. Facial Nerve. — The nucleus Ues 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. 427, 7). It extends downward about as far as the auditory strife, or a httle lower. The fifth nerve arises from its motor nucleus (with large multipolar cells), which lies more superficially above and external to the 6th (Fig. 427, 5). The fibres run backward, where they are joined by fibres from the upper sensory nucleus, but another sensory nucleus extends down nearly to the lower end of the medulla (5^^). Doubtless this extensive origin brings this nerve into intimate relation with the other cranial nerves, and accounts for the numerous reflex acts which can be discharged through the fifth nerve. Some sen sory fibres are said to pass up beneath the corpora quadrigemina [Goivers'). The fourth nerve arises from the valve of Vieussens, i. e., the lamina of white and gray matter which stretches between the superior cerebellar peduncles. It arises, therefore, behind the fourth ventricle, but some of the fibres spring from nerve cells at the lower part of the nucleus of the 3d nerve. Some fibres also 710 FUNCTIONS OF THE MFIDULLA OBLONGATA. descend in the pons to form n connection with the nucleus of the 6th nerve. The fil)res decussate behind the aqueial paralysis (Dii<:h,nnf, iS6o), in which there is a progressive invasion of the dilTcrent nene 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 /outfit,-, accomjianied by tibrillar contractions, whereby speech, formation of the food into a bolus, and swallowing are inlirfcred with (jS 354). The secretion of thick, viscid saliva points to the imjKissibility of secreting a thin, wnlery, /i 313, II, i, and \ 352, 5,/'), 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 afiects 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. RESPIRATORY CENTRE. INNERVATION OF THE RESPIRATORY ORGANS.— Ihc respiratory centre lies in the medulla oblongata {Lfi^a/Zois, iSii). behind the su[)erficial origin of the vagi, on both sides of the posterior aspect of the ajjex of the ( alamiis scriptorius, between the nuclei of the vagus and accessorius, 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 {Longef, 1847), whereby the respiratory movements con- tinue symmetrically on both sides. Section of Vagi. — If one vagus be divided, rcsi)iration on that side is shmu'd. If both vagi l)e 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 stimulation of the trigeminus on one side {Lartgendorff). When the centre is divided transversely on one side, the respiratory movements on the same side cease {Scliiff). Most probably the domi- nating respiratory centre lies in the medulla oblongata, and upon it depend 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, respiratory movements of the thorax are some- times observed {Bracket, 1835). [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 I^ngendorff assumes the existence of a spinal respiratory centre, which he finds is also influenced by reflex stimulation of sensory nerves.] Nitschmann, by means of a vertical incision into the cervical cord, divided the spinal centre into two equal halves, each of which acted on both sides of the diaphragm after the medulla was divided just below the calamus scriptorius. 'Die spinal centres mu.st, therefore, be connected with each other in the cord. The spinal respiratory centre can be excited or inhibited reflexly ( Wertheimer). Anatomical. — Schift' locates the respiratory centre near the lateral margins of the gray matter in the floor of the 4th ventricle, but not reaching so far backward as the ala cinerea. According to Gierke, Heidenhain, and I^ngendorfl^, those parts of the medulla oblongata whose destruction causes cessation of the respiratory movements are single or double strands of nervous matter, containing gray nervous substance with small ganglion cells, and 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 glossopharyngeal {Meynert), forming connections by means of" fibres with the other side, and descending as far downward as the cervical enlargement of the spinal cord [Golf). According to this view, this strand represents an inter-central band connecting the spinal cord (the place of origin of the motor respiratory nerves) with the nuclei of the above-named cranial nerves. CEREBRAL RESPIRATORY CENTRE. 713 Fig. 467. Cerebral Inspiratory Centre. — According to Christiani, there is a cerebral inspiratory centre in tlie 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 ; Avhen it is stimulated directly, it deepens and accelerates the inspira- tory movements, 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 aqueduct of Sylvius. Martin and Booker de- scribe a second cerebral inspiratory centre in the posterior pair of the corpora quadrige- mina. These three centres are connected with the centres in the medulla oblongata. The respiratory centre consists of two centres, which are in a state of activity alter- nately— an inspiratory and an expiratory centre (Fig. 467), each one forming the motor central point for the acts of inspiration and expiration (§ 112). The centre is auto- matic, for, after section of all the sensory ^ ^ ^ ^ ^. ^^'^' , ._, _ „ _t „„£]„ 1 „„„ i-U„ i ^ bcheme 01 the chiei respiratory nerves """" " spiratory, and ^^/, expiratorj' centre — motor nerves are in smooth lines Expiratory motor nerves to abdominal muscles, ah ; to muscles of back, do. Inspiratory motor nerves. /A, phrenic to diaphragm, d\ int, intercostal nerves; r/, recurrent laryngeal; e.r, pulmonary fibres of vagus that excite in- spiratory centre ; ex' , pulmonary fibres that excite expiratory' centre ; ejc" , fibres of sup. larj'ngeal that excite expiratory centre ; ink, fibres of sup. laryngeal that inhibit the in- spiratory centre. nerves which can act reflexly upon the centre, it still retains its activity. The degree of excitability 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 CO2 (/■ -Rosenthal). Accord- ing to the condition of the centre, there are several well-recognized respiratory con- ditions : — I. Apnoea. — Complete cessation of the respiration constitutes 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 CO2. 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. Apnceic Blood. — -A. Ewald found that the arterial blood of apnoeic animals was completely- saturated with O, while the CO2 was diminished ; the venous blood contained less O than normal — this latter condition being due to the apnceic blood causing a considerable fall of the blood pressure and consequent slowing of the blood stream, so that the O can be more completely taken from the blood in the capillaries [PJliiger). The amount of O used in apnoea on the whole is not increased (^ 127). Gad remarks that during forced ai-tificial 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. According to Gad and Knoll, the excitability of the respiratory centre is reduced during apnoea, and this is caused reflexly during artificial respiration by the distention of the lungs stimulating the branches of the vagus. In quite young mammals apnoea cannot be produced {^Rtmge). [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.] 711 EUPNCEA, DVSPNfEA AND ASPHYXIA. 2. Eupnoea.— The normal stimulation of the resiMratory centre, eupmva, is caused by the blood, in which the amount of O and CO, does not exceed the normal limits (vj§ 35 and 36). . 3. Dyspnoea. — All conditions which diminisli the O and increase the CO,, in the blood t ir< ulating through the medulla and respiratory centre cause acceleration and deepening of the respirations, which may ultimately i)ass into vigorous and labored activity of all the respiratory muscles, constituting dyspnea, \\\\t\\ the difficulty of breathing is very great (§ 134). [Changes in the rhythm, § iii.] During normal respiration, and witli the commencement of the need for more air, according to Gad, the gases of the blood excite only the inspiratory centre; while the expiration follows owing to reflex stimulation of the pulmonary vagus by the distention of the lungs (p. 716). He is also of opinion that the normal respiratory movements are excited by the CO.^. [Muscular work, as is well known, increases tlie respirations and may even cause dyspnoea. Tins is not due to the nervous connections of the muscles or other organs with the respiratory centre, but to changes in the blood, t'icppert and Zunlz have shown, however, that the result cannot be explained by changes in the blood caused cither by diminution of O or increase of QO.,. It seems to lie due to the blood taking up some as yet unknown products from the contracting muscle, and carrying them to the resjiiratory centre, which is directly excited by them. The nature of these sultttances is unknown. It has been shown that the alkalinity of the blood is reduced by the forma- tion of an acid. The substances, whatever they may be, are not excreted l)y the urine, and are therefore, perhaps readily oxidized {^Lonoy). C. Lehmann has proved that, in rabbits, the acidifica- tion of the blood produced by muscular exertion plays an imjiortant part in the stimulation of the respiratory centre.] 4. Asphyxia. — If blood, abnormal as regards the amount and quality of its gases, continue to circulate in the medulla, or if the condition of the blood become 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 respira- tory muscles cease, and the heart itself soon ceases to beat. This constitutes the condition oi asphyxia, zwd. if it be continued, death from suffocation takes place. (LangendorfT 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 i)revented under favorable circum- stances, esjjecially by using artificial respiration (§ 134); the respiratory muscles 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 occur without there being any symptoms of dyspnoea, as happens when death takes place quietly and very gradually (!; 324, 5). Causes of Dyspnoea. — (i) Direct limitation of the activity of the respiratory organs; diminution of the respiratory surface by inflammation, acute oudema [\ 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 degenera- tion of the heart, valvular cardiac disease, and artificially by ligature of the carotid and vertebral arteries {Kmsmaul and Tenner), or by preventing the free eillux of venous blood from the skull, or by the injecti n 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 (/. Rosenthal). This is the cause of the "biting or .snapping at the air" manifested by the decapitated heads of young animals, e. ^., kittens. [The phenomenon is well marked in the head of a tortoise separated from the body ( W. Stirling)!] If we study the rapidly fatal effects of these factors on the respiratory activity, we observe that at first the respirations become quicker and deeper, then after an attack of general convulsions, ending in expiratory spasm, there follows a stage of complete cessation of respiration. Before death takes place, there are usually a few " snapping" or gasping efforts at inspiration {Bogyes, Sigm. Mayer — ^ "0- Condition of the Blood Gases. — As a general rule, in the production of dyspnoea, the want of O and the excess of CO_, act simultaneously {Ffliiger and Dohtnen), but each of these alone may act as an efficient cause. According to Bernstein, blood containing a small amount of O acts chiefly CONDITIONS ACTING ON THE RESPIRATORY CENTRE. 715 upon the inspiratory centre, and blood rich in COj on the expiratory centre, (i) DyspncEa, from want of O, occurs during respiration in a space of 77ioderate size (| 133), in spaces where the tension of the air is diminished, and by breathing indifferent gases or those containing no free O. When the blood is freely ventilated with N or H, the amoimt of COj in the blood may even be diminished, and death occurs with all the signs of asphyxia {Pfli'iger). (2) Dyspncea, from the blood being overcharged with COj, occurs by breathing air containing much COj (§ 133)- Air containing much CO2 may cause dyspncea, even when the amount of O in the blood is greater than that in the atmosphere (^T/iiry). The blood may even contain more O than normal [P/iuger). Heat Dyspncea. — An increased temperature increases the activity of the respiratory centre (§ 214, II, 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 [Ackermantt). Emetics act in a similar .manner [Hermann and Gn>?im). Electrical stimulation of the medulla oblongata, after it is separated from the brain, discharges respiratory movements or increases those already present [Kronecker and Mai-ckwald). Langen- dorff 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 standstill 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 tinie, and we may also voluntarily change the rhythm of respiration. 2. The respiratory centre maybe 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, auditory, and cuta- neous nerves; 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 slo\ver 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 (p. 712). The amount of air taken in the CO., given off, however, is unchanged, but the inspiratory efforts are more vigorous and not so purposive {Gad). Weak tetanizing currents applied to the central &wA of the vagus, cause acceleration of the respirations, while, at the same time, the efforts of the respiratory muscles may be increased, or diminished, or remain unchanged (Gad). Strong tetanizing currents cause standstill of the respiration in the inspiratory phase (Traube), or especially in fatigue of the nerves, in the expiratory phase {Budge, Burkart). Single induction shocks have no effect {Marckwald and Kronecker). [Marckwald, while admitting that the respiratory centre is automatically active, as well as capable of being affected reflexly, comes to the conclusion, that, when the centre is separated from all nerve channels by which afferent impulses can be conveyed to it, it is incapable of discharging rhythmical respiratory movements. He also asserts that the normal rhythmical respiration is a reflex act discharged chiefly through the vagi, and that the normal excitant of the respirator)^ centre is not dependent on the condition of the blood, either on the diminution of O, or the increase of CO2. These results are opposed to the usually accepted view, and they are controverted by Loewy. Division of the medulla oblongata above the respiratory centre, so as to cut off" all cerebral channeb of communication, has very little effect on the respirations. If, after this, one, or both vagi be divided, there is (i) an exfraordinary slowing oi the respiration; the number of respirations may fall in the rabbit, from 20 to 2 or 4 per minute; (2) the rhythm is changed, in some cases the 716 CONDITIONS ACTING ON THE RESPIRATORY CENTRE. inspiration mav l)e twice or thrice as long as the expiration, l)ut, whatever the ratio of inspiration to expiration, the respiration is rhythmical; (3) the vp!u>,u- of air respired is diminished (p. 715), but the volume for each respiration is deeper; 1^4) the intra thoracic pressure is increased, during inspira- tion, and during expiration it is the same as before the vagotomy.] Before Vagotomy. 1 After Vagotomy. J a K Intra-thoracic Pressure. B u 3 v d •IS. > Intra-thoracic Pressure. c •Sd 2. d 1) X KM d It > 3 V c a 1? ■IS. > Is- ,5<2 mm. com. com. c.cm. !< ?< I -30 to -40 20 3»o-35o 16 -60 to -70 4 •y2 130-140 59 33 100 2 -22 to -24 32 530-540 16 -50 to -60 ^y^ 'A 105-120 79-5 40 150 [The above table (from Loewy) shows the result. Loewy finds that, if a centre be separated from all centripetal channels, it still discharges respiratory movements, which are rhythmical, and he has shown that these ihylhmical discharges are due to the condition of the blood.] [If one lung be made atelectic, /. e., devoid of air, e.g., by plugging its bronchus with a sponge tent, then the pulmonary fibres of the vagus from this lung are no longer excited during respiration, and their section has no effect on the respiration. Section of the vagus on the sound side, however, has the same consecjuence as double vagotomy (Zc^«'j').] Wedenski and Heidenhain find that a temporary, 7veak, electrical stimulus applied to the central end of the vagus,-at the beginning of inspiration (rabbit), affects the depth of the succeeding inspira- tions, while a similar strong stinmlus affects also the depth of the following expiration. 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 stimulation is stronger, inspiration and expiration are dimini-hed with or without alteration of the frequency, and with the strongest stimuli, respirations cease either in the inspiratory or expiratory phase. {b) The inhibitory nerves which affect the respiratory centre run in the supe- rior laryngeal nerve {Rosenthal), and also in the inferior {Pfliiger and Burkart, Hering, Breuer), to the respiratory centre (Fig. 467, ink). According to I^ngendorff, direct electrical, mechanical, or chemical stimulation of the centre may arrest respiration, perhaps in consequence of the stimulus affecting the central ends of these inhibitory nerves where they enter the ganglia of the res[)iratory centre. During the reflex inhibition of the respiration in the expiratory phase, there is a suppression of the motor impulse in the inspiratory centre ( iVegete). Stimulation of the superior or inferior laryngeal nerves (<5) or their central ends causes slowing, and even arrest of the respiration (in expiration — Rosenthal). Arrest of the respiration in expiration is also caused by stimulation of the nasal {Hering and Kratschmer) and ophthalmic branches of the trigeminus (Christiani), of the olfactory, and glosso-pharyngeal {Marckwalii). [Kratschmer found that tobacco smoke blown into a rabbit's nostrils, or puffed through a hole in the trachea into the nose, by stimulating the nasal branch of the fifth nerve, arrested the respiration in the expiratory phase ; while it had no effect when blown into the lungs. Ammonia vapor applied to the nostrils arrests it in the same way. If ammonia vapor be blown into the lungs (the nasal cavity being protected from its action), the respiration may be accelerated, or deepened, or arrested occasionally in expiration, /. e., according to the fibres of the vagus acted on by the vapor in the lungs (A'/w//).] Stimulation of the pulmonary branches of the vagus by breathing irritating gases (Knoll) causes standstill in expiration, although some other gases cause standstill in inspiration. Chemical stimulation of the trunk of the vagus — by dilute solutions of sodic carbonate — causes expiratory inhibition of the respira- tion ; and mechanical stimulation — rubbing with a glass rod — inspiratory inhibition STIMULATION AND REGULATION OF THE RESPIRATORY CENTRE. 717 {Knon). 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 standstill in expiration, the first cause often giving rise to temporary clonic contractions of the respiratory 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 inspi- ratory efforts [Gad). The volume of the gases which passes through the lungs during a given time remains unchanged ( Valentiti), and the gaseous exchanges are not altered at first ( Voit and Rauber) . Automatic Regulation. — Under normal circumstances, 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-adjusting xi\Qc\\2js\\'i'ca. ; thus, the inspira- tory dilatation of the lungs stimulates mechanically the fibres which reflexly excite the expiratory centres, while the diminution of the lungs during expiration excites the nerves which proceed to the inspiratory ctvAxt i^Hering a^id Breuer, ffead). [Thus, blowing into the lungs excites the act of expiration, and sucking air out of them excites inspiration.] In this way we may explain the alternate play of inspiration and expiration. In deep narcosis, however, dilatation of the thorax in animals is followed first by cessation of the respiratory movements, and then by inspiration [P. Giittmann). 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 CO2 in the blood, so that the condition of the fcetal 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 respiratory 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 fcetus 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 dyspnceic blood upon the medulla oblongata. [The excitability of the respiratory centre is less in the foetus than in the newly born, and it increases from day to day after birth. Among the causes of the dimin- ished excitability are the small amount of O in fcetal blood, and the slow velocity of the circulation. If an inspiration is discharged in the foetus, it is at once inhibited by fluid passing into the nostrils and inhibiting the act reflexly. The chief cause of the first respiration after birth, is undoubtedly the increasing venosity of the blood, and also the disappearance of the above named reflex inhibitory process.] Death of the mother acts like compression of the umbiHcal 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 {Ztmtz). If the mother be rapidly poisoned with CO (§ 17), the foetus may live longer, as the CO-h^moglobin of the maternal blood cannot take any O from the fcetal blood (g 16 — Hogyes). In slow poisoning the CO passes into the foetal blood {Grekant and Quinquand). In many cases, especially in cases of very prolonged labor, the excitability of the respiratory centre may be so diminished, that after birth, the dyspnceic -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 [Pflilger], 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 718 DIRECT STIMULATION OF THE CARDIO-INHIBITORY CENTRE. friction or sharp blows, or the application of a cold douche, excites the respiratory centre. When the placental circulation is intact, cutaneous stimuli do not discharge respiratory movements (Z«m/« and Ci'/instrin\, (Artificial respiration. ^ i.u)- [Action of Drugs on the Respiratory Centre. — .\mmonia, salts of zinc and copper, strychnin, atropin. dulioisin, aponiorphin, emctin, the di(;il.ilis group, and heat increase the rapidity and depth of the respirations, while they become frequent and shallower after the uix.'ar to be decisive evidence that the vagus acts on muscle directly, and not simply on automatic motor ganglia, as was liehl according to the old view (.1/' W'llliiim).^ Poisons. — Muscariti stimulates the tenninations of the vagus in the heart, and causes the heart to stand still in diastole (Schiniedeber)^ and A'op/'e). [See p. 127 for Gaskell's views.] \i a/ropin be applied in solution to the heart, this action is set aside, and the heart begins to beat again. [Atropin alx>lishes completely the inhibitory action of the vagus on the heart. If it be injected into the jugular vein-of a rabbit, the pulse beats are increased 27 per cent , in the dog, they may be trebled, and in a man under its full influence the pulse beats may rise from 70 to 150 or more. After atropin, it is impossible to arrest the action of the heart by stimulation of the vagus, and in the frog this cannot be done even by siimulalion of the inhibitory centre in the heart itself, so that atropin must be regarded as paralyzing the iiitra-cardiac termiuatious of the vagus. J Dii^italiit dimini.shes the number of heart beats by stimul.iting 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 l>eats are thereby increa'^ed. In small doses, digitalin raises the blood j^ressure by stimulating the vasomotor centre and the elements of the vascular wall (A'/z/j,'). Nicotin first excites the vagus, then rapidly paralyzes it. Hydrocyanic acid has the same eft'ect (Preyer). Atropin {v. Bezold) and ciirara (large dose — CI. Bernard and A'dlliker) paralyze the vagi, and so does a very low temperature or high fever. 370. CENTRE FOR THE ACCELERATING CARDIAC NERVES. — Nervus Accelerans. — It is more than prcjbable 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 ]jart 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 ])ass 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. 469, 470). [These fibres, i)rocceding from the spinal cord, frequently accompany the nerve running along the vertebral artery], and they constitute the Nenms accelerans con/is. [Fig. 470 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 cervical spinal cord, even of the lower cervical ganglion, or of the upi)er dorsal ganglion of the sympathetic {Gang, stellatum), causes acceleration of the heart beats in the dog and rabbit, withotit the blood jiressure undergoing any change {CI. Bernard, v. Bezold, Cyan'). On stimulating the medulla oblongata, or the cervical portion of the spinal cord, the vasomotor net-fes are, of course, simultaneously excited. The consequence is that the blood vessels, supplied by vasomotor nerves from the spot which is stimulated, contract, and the blood pressure is greatly increased. Again, a simple 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 (when, 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 this increase cannot be due to the increased blood pressure. Indirectly it may be shown, by dividing or extiq^aling all the ner\-es of the cardiac plexus, or at least all the nerves going to the heart, that stimulation 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 NERVUS ACCELERANS AND CARDIAC PLEXUS. 721 The accelerating centre is certainly not continually in a state of tonic excite- ment, as section of the accelerans nerve does not cause 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 bv 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 accelerating centre, when it is in reality due to the diminished blood pressure (^Cyoii). 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 Fig. 469. Fig. 470. Fig. 469. — Scheme of the course of the accelerans fibres. P, pons; MO, medulla oblongata; C, spinal cord; V, inhibitory centre for heart ; A, accelerans centre ; Vag., vagus; SL, superior; I L, inferior laryngeal ; SC, supe- rior, IC, inferior cardiac ; H, heart; C, cerebral impulse ; S, cervical sympathetic ; a, «, accelerans fibres. Fig. 470. — Cardiac ple.xus, and ganglion stellatum of the cat. R, right, L, left X i/4; i, vagus; 2', cervical sym- pathetic, and in the annulus of Vieussens; 2, communicating branches from the middle cervical ganglion and the ganglion stellatum ; 2', thoracic sympathetic ; 3, recurrent laryngeal; 4, depressor nerve ; 5, middle cervical ganglion ; 5', communication between 5 and the vagus ; 6, ganglion stellatum (ist thoracic ganglion) ; 7, commu- nicating branches with the vagus ; 8, nervus accelerans , 8, 8', 8", roots of accelerans ; 9, branch of the ganglion stellatum. vagus to reach the heart (§ 352, 7), and when they are stimulated, either the heart beat is accelerated or the cardiac contractions strengthened {Heidenhain and Lowit), or the latter alone occurs (^Pawlow). The inhibitory fibres of the vagus lose their excitability more readily than the accelerating fibres, but the vagus fibres are more excitable than those of the accelerans. Tarchanoff has described some very rare cases of individuals who, by a merely voluntary effort, and while at rest, the respirations remaining unaffected, could nearly double the number of their pulse beats. 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 46 722 niE VASOMOTOR CENTRE. long latent period. Further, the acceleration thus produced disappears gradually. If the vagus ami accelerans fibres be stimulated simultaneously, only the inhibitory action of the vagus is manifested. If. \ohile ihc acccleraus is beini; stimulated, the v.agus be suddenly excited, llicre 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 rajiidly manifested {C. Liiihvij^ with SchmieJeberf^^ Bo-wdilch, Haxt). According to the experiments of Strieker and SVa^ner on dogs, with both vagi divided, a diminution of the number of the heart beats occurred when both accelerantes were divided. This would indicate a tonic innervation of the latter nerves. [Accelerans in the Frog. — (iaskell showed that stimulation of the vagus might produce two opposing efferts ; the one of the nature of inhibition, the other of augmentation. In the crocodile, the accelerans fibres leave the symi)athetic 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 anasto- mosing with branches of the vagus, pass to the heart. "Stimulation of these fibres increases the rate of the cardiac rhythm, and augments \.\\t 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 symi)athetic. The so-called vagus of the frog, in reality, consists of ])ure vagus fibres and sym- pathetic fibres, and is in fact a vago-symjxithetic. Ciaskell 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; hence, Gaskell suggests that they ought to be called " augmentor," or simply cardiac sympathetic nerves.] [In his more recent researches Gaskell asserts that vagus stimulation produces /fr^/ 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 regar Is it as a true anabolic nerve [\ 342, d).] 371. VASOMOTOR CENTRE AND VASOMOTOR NERVES. — Vasomotor Centre. — The chief dominating or general centre, which supplies all the non-striped muscles of the arterial system with motor nerves (vasomotor, vaso-constrictor, vaso-hypertonic nerves), lies in the medulla oblongata, 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 1J2 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. P2ach half of the body has its own centre, placed 2)^2 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, 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 increase 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 pressere. Under ordinary circumstances, the vasomotor centre is in a condition of moderate ionic excitement (§ 366). Just as in the case of the cardiac and respiratory centres, the vasomotor centre mav be excited directly and reflexly. [Position — How ascertained. — As stimulation of the central end of a sensory 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 DIRECT STIMULATION OF THE VASOMOTOR CENTRE. 723 the centre is not in the cerebrum itself. For the effect of chloral, under the same conditions, see p. 724. By making a series of sections from above down- ward, 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 oblongata 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 multipolar nerve cells, described by Clarke as the antero-lateral nucleus.] I. Direct Stimulation of the Centre. — The atnount and quality of the gases contained in the blood flowing through the medulla are of primary import- ance. In the condition of apnoea (§ 368, i), 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 movements 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„ the centre is strongly excited, so that all the arteries of the body contract, while the venous system and the heart become distended with blood {Thiry). At the same time, the velocity of the blood stream is increased {Heidenhain). The same result is produced by ligature of both the carotid and subclavian arteries, thus causing sudden ansemia of the medulla oblongata ; and, no doubt, also by the sudden stagnation of the blood in venous hyperaemia. 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 ot the medulla oblongata, due to the ansemia, may ultimately cause constriction of the small arteries, and thus arrest the bleeding. Thus, surgeons are acquainted with the fact that dangerons hemorrhage is often arrested as soon as unconsciousness, due to cerebral anaemia, occurs. If the heart be ligatured in a froj, 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 oblongata is destroyed than when it is intact {v. Bezold, Gscheidleii). [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 hemor- ihage is severe. The bearing of this experiment on conditions of " shock" is evident.] Action of VQ\sor^s.— Strychnin stimulates the centre directly, even in curarized dogs, and so do nicotin and Calabar bean. 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 to 12 strong., or 20 to 25 moderately strong shocks per second are applied {Kronecker and AUcolaides'). Course of the Vasomotor Nerves. — From the vasomotor centre fibres proceed directly through some of the cranial nerves to their area of distribution ; through the trigeminus partly to 724 COURSE OF THE VASOMOTOR FIBRES. the interior of the eye (§ 347, I, 2), through the hngual 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 (? 352. >i). All the other vasomotor nerves descend into the lateral columns of the spinal cord (^ 364, 9); hence, stimulation of the lower cut end of the spinal cord causes contraction of the hlootl vessels supplied by the nerves below the point of section [P/liij^ei). 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 pass through the rami communicantes into the sympathetic, and from them reach the blood vessels to which they are distributed (? 356) [see Fig. 439]. The following is the arrangement of these nerves in the region of the head: Thtcerficaf portion 0/ the sympathetic supplies the great majority of the blood vessels of the htz(\ [set Sympathetic, § 356, A, 3). In some animals, i\\Q great auricular nerve supplies a few vasomotor fibres to its own area of distribution [Sc/iiff, Lovin, Moreau). The vasomotor ners'es to tlie upper extremities pass through the anterior roots of the middle dorsal nerves into the thoracic sympathetic, and upward to the I't th )racic 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 extremities pass through the nerves of the lumbar and sacral plex- uses into the sympathetic, and from thence to the lower limbs (P/iiiger, Schiff, CI. Bernard). The lungs, in addition to a few fibres through tiie vagus, are supplied from the cervical spinal cord through the 1st thoracic ganglion (Bro-wn-Scijuard, Pick and Badoitd, Lichtheim). The splanchnic is the greatest vasomotor nerve in the body, and supplies the abdominal viscera (| 356, B — V. Bezold, Lud-wig 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 ist dorsal vertebrae. [Gaskell finds that in the dog (Fig. 439) they begin to leave the cord at the 2d dorsal nerve y\ 366).] As a general rule, the blood vessels for the skin 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 differently with regard to the intensity of the action of the vasomotor nerves. The most powerful vasomotor nerves are those that act upon the blood vessels of peripheral parts, ;>. ^'•.,the toes, the fingers, and ears ; while those that act upon central parts seem to be less active [Lewaschew), e.g., on the pulmonic circulation (§ 88). II. Reflex Stimulation of the Centre. — There are fibres contained in the different afferent nerves, whose stimulation affects the vasomotor centre. There are nerve fibres whose stimulation excites the vasomotor centre, thus causing a stronger contraction of the arteries, and consequently an increase of the arterial blood pressure. These are called *' pressor " fibres. Conversely, there are other fibres whose stimulation reflexly diminishes the excitability of the vasomotor centre. These act as reflex inhibitory nerves on the centre, and are known as "depressor ' ' fibres. Pressor, or e.Kcito-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, amyl 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 Pribram 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 ner\-e 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.] REFLEX STIMULATION OF THE VASOMOTOR CENTRE. 725 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 opposite effect, i. e., a depressor effect, with simultaneous decrease of the cardiac activity. Griitzner and Heidenhain found that contact with the skin caused a pressor effect, while painful impressions produced no effect. The application of heat and cold to the skin produces reflexly a change in the lumen of the blood vessels and in the cardiac activity [Rohrig, Winterniiz). Pinching the skin causes contraction of the vessels of the pia mater of the rabbit [Sckiiner), 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 coldconstrictingthe cutaneous vessels. Heat, of course, has the opposite effect. Inman,most stimuli appliedtosensorynerves produce an effect : feeble cutaneous stimuli, tickling (even unpleasant odors, bitter or acid tastes, optical and acoustic stimuli) at the parts where they are applied, cause a fall of the cutaneous temperature, and diminution of the volume of the corresponding limb, sometimes increase of the general blood pressure and charge of the heart beat. The opposite effects are produced by painful stimulation, the action of heat (and even by pleasant odors and sweet tastes). The former cause simultaneously dilatation of the cerebral vessels and increase the vascular contents of the skull — the latter cause the opposite results i^Isiominow and Tarchanoff). Depressor fibres, /, e., fibres whose stimulation diminishes the activity of the vasomotor centre, are present in many nerves. They are specially numerous in the superior cardiac branch of the vagus, which is known as the depressor nerve (§ 352, 6). The trunk of the vagus below the latter also contains depressor fibres (v.Bezold), as well as the pulmonary fibres (dog). The latter also act as depressors, during expiratory efforts (§ 74); while Hering found that inflating the lungs (to 50 ram. Hg pressure) caused a fall of the blood pressure (and also accelerated the heart beats — § 369, TI). Stimulation 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 by 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 cefitrai&ud of the great auricular 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, con- tract, 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 stimulated, there is a rise of the general blood pressure, but a local dilatation of the saphena artery in the limb of that side (^Lovai). Again, the temperature of one hand and the condition of its blood vessels influence 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 vasomotor centre, therefore, primarily regulates the condition of the blood vessels, but through them it obtains its importance by regulating and controlling the blood supply 2iZCOxA\x\g\.o 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 sensoiy 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 on which direct pressure is made, as occurs, for example, when the sphygmograph is applied for a long time — the pulse curves become larger, and there are signs of diminished arterial tension (^ 75). Rhythmical Contraction of Arteries.— In the intact body slow alternating contraction and dilatation, without 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 vascular movement." This movement maybe useful when a vessel is occluded, as after ligatiu-e, and may help to establish more rapidly the collateral circulation. Stefani has shown that this occurs with more difficulty after section of the nerves. Direct local applications may influence the lumen of the blood vessels; cold and moderate electrical stimuli cause contraction; while, conversely, heat and strong mechanical or electri- cal stimuli cause dilatation, although with the last two there is usually a preliminar}^ constriction. Poisons. — Almost all the digitalis group of substances cause constriction; quinine and salicin constrict the splenic vessels. The other febrifuges dilate the vessels [Thomson). See p. 138. 726 LOCAL AND SECONDARY RESULTS OF VASOMOTOR ACTION. 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 (siich as the ear of the rabbit), the intra-arterial pressure dilating the j)aralyzed walls of the vessels. IMuch arterial blood, therefore, passes into and causes congestion and redness of the parts, or hyperaemia, 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 the blood stream, the blood may flow from the veins almost arterial (bright red) in its characters, and the pulse may even be propagated into the veins, so that the blood spouts from them (C/. 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. Continued stimulation ultimately exhausts the nerve, and causes at the same time the phe- nomena of i)aralysis of the vascular wall. Secondary Results. — The immediate results of paralysis of the vasomotor nerves lead to other 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 par.ily/ed muscles no longer contract to aid in the production of heat (jJ 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. The 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 para- lyzed, 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 (Tse/ietse/iu/iin, Naitnyn, Quincke) 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 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 considerable 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 circum- stances. This occurs wiien 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 {Sassetki and Manassein). Conversely, stimulation of the vasomotor nerves of a large area increases the temperature, because the constricted vessels give off less heat. The temperature in fever may be partly explained in this way (§ 220, 4). The activity of the heart, /. e., the number and energy of the cardiac con- tractions, is intiuenced by the condition of the vasomotor nerves. When a large vasomotor area is paralyzed, the 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 feeble contractions. Strieker observed that the heart of a dog ceased to beat on extir- pating the spinal cord from the ist cervical to the 8th dorsal vertebra. Conversely, CONDITIONS AFFECTING THE VASOMOTOR CENTRE. 727 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, Slavja?isky). 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 (§ i6i) ; 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 ansemic, and the animal may even die from '■ being bled into its own belly," i. e., from what has been called " intra- vascular hemorrhage." Animals whose portal vein is ligatured die for the same reason (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, the blood stream at the same time 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. 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 gray matter of the spinal cord, as is proved by the follow- ing 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 regain 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 — § 362, 7). The subordinate spinal centres may, further, be stimulated directly by dyspnoeic blood, and also reflexly, in the rabbit and fiog {Ustimowilsch). After destruction of the medulla oblongata, the arteries of the frog's web still contract reflexly when the sensory nerves of the hind leg are stimulated (^Putnam, Niissbaum, Vidpian). In the dog, opposite the 3d to 6th dorsal nerve is a spinal vasomotor centre (origin of the splanchnic), which can be excited reflexly [Smirnow), and there is a similar one in the lower part of the spinal cord ( Viilpiaii). If 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. [It is to be recollected that the existence of these peripheral nervous mechanisms has not been proved.] These ganglia [or peripheral nervous mechanisms] might be compared to the gan- glia 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 of arterial 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 stimuU 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. 728 PATHOLOGICAL VASOMOTOR PHENOMENA. 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 contracted them. It is, however, doubtful if the variations of the vascular lumen depend upon the stimulation of the peripheral nervous mechanisms. Ani} 1 nitiiie and digitalis are supposed to act on those hypothetical mechanisms. T\\t 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 [Lttchsinger, Schiff). Influence of the Cerebrum. — The cerebrum influences the vasomotor centre, as is proved by the sutldcn i)alIor 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, e. g., of the hepatic (§ 175) and /-(?;/«/ centres (§ 276). Many poisons excite the vasomotor nerves, such as ergotin, tannic acid, copaii>a, and cubebs; others first excite, and then paralyze, e.g., chloral hydrate, morphia, laudanosin, veratrin, nicotin. Calabar bean, alcohol ; others rapidly pa ?-alyze them,^._f'., amyl nitrite, CO (| 17), atropin, muscarin. The paralytic action of the poison is proved by the fact that, after section of the vagi and accele- rantes, neither the pressor nor the depressor nerves, when stimulated, produce any effect. Many pathological infective agents affect the vasomotor nerves. The veins are also influenced by vasomotor nerves, 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 important group of diseases. The parts primarily affected may be either the peripheral nervous mechanisms, tlie subordinate centres in the cord, the doniinatini; centre in the medulla, or the gray matter of the cerebrum. The effect may be direct or reflex. The dilatation of the vessels may al?o be due to stimulation of vaso-dilator nerves, and the physician must be careful to distinguish 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 maybe circumscribed affections. Sometimes, owing to the stimulation of indiviilual vasomotor nerves, there are local cutaneous arterio-spasms i^Xothnagelj. In certain acute febrile attacks — after previous initial violent stimulation of the vasomotor nerves, especially (luring the cold stage of fever — there maybe different forms of paralytic phenomena of the cutaneous vessels. In some cases of epilepsy in man. Trousseau observed irregular, red, angio-paralytic patches (ataches cer^brales). Continued strong stimulation may lead to interruption of the cir- culation, which may result in gangrene of the skin and deeper-seated parts {^IVeiss). Hemicrania, due to unilateral spasm of the branches of the carotid on the head, is accompanied by severe headache {Du BoisReymomf). The cervical sympathetic nerve is intensely stimulated — a pale, collapsed, and cool side of the face, contraction of the temporal artery like a finn whipcord, dilatation of the pupil, secretion of thick saliva, are sure signs of this afifedion. 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 129-200 beats per minute), causing palpitation; there is swelling of the thyroid gland (struma), and projection of the eyeballs (exophthalmos"), with unperfectly coordinated mo*'ements 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 (ated in the monkey, there is no motor or sensory disturbance in this animal ; it still exhibits emotional feeling, all its special senses remain, and the power of voluntary motion is retained ; but, nevertheless, there is a decided alteration in the animal's character and behavior, so that it exhibits considerable psychological alterations, and, according to Fcrrier, " 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 case communicated by Longet : A boy, i6 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 protnided, which was removed. On the 35th day he got intoxicatetl, tore off the bandages, and with them a part of tiie brain matter. After his recovery, the boy still retained his intelligence, but he was hemiplegic. Even when both hemispheres are wo^/^'r^/^'A' 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 peculiarly alters the charac- ter. We must be extremely careful, however, in forming conclusions in all such cases [In the celebrated " American crow-bar case" recorded by Bigelow , a young man was hit by a bar of iron I '4 inch in diameter, which traversed the anterior part of the left hemisphere, going clean out at the top of his head. This man lived for thirteen years without any permanent alterations of motor or sensory functions; but "the man's disposition and character weie observed to have undergone a serious change. There were, however, some changes which might I e 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 affected by " psychical disturb.inces, 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 inllammation, degene- ration, pressure, anremia 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 l>sychical process. From his experiments on pigeons, he concluded that, if a small part of the hemi- spheres remained intact, it was sufficient for the manifestation of the mental functions; just in pro- portion as the gray matter of the hemispheres is removed, all the functions of the cerebrum are enfeebled, 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, (loltz holds a somewhat similar view to that of Flourens. lie 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 difierent parts of the brain, and it is as>umed that a large development of a particular organ maybe detected by examining the external configuration of the head (Cranioscopy). Removal of the Cerebrum. — After the removal of both cerebral hemi- spheres, in most animals, every vohintary movement and all 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). Sudden cessation of the circulation in the brain, e.g., by decapitation, is followed at once by cessa- tion of the mental faculties. When Hayem and Barrier perfused the blood of a horse through the carotids of a decapitated dog's head, the head showed signs of consciousness and will for 10 seconds, but not longer. The mid-brain (corpora quadrigeniina) is connected not only with the gray matter of the spinal cord and medulla oblongata, the seat of extensive reflex REMOVAL OF THE CEREBRUM FROM A FROG. 733 Fig. 472. mechanisms (§ 367). but it also receives fibres coming from the higher organs of sense, which also excite movements 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 execution of movements, and this even in a higher degree than the medulla oblongata itself (6^(?//s). Animals with their corpora quadrigemina intact retain the equilibrium 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 mammals, in front of the inspiratory centre in the 3d ventricle (§ 368). 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 equilib- rium in nystagmus (§ 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 illus- trated in cases of locomotor ataxia (p. 697).] 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 Fig. 471. gives one or two springs, and then comes to restj 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. Unless it is stimulated, it never makes independent, voluntary, purposive movements. It sits in the same place con- tinually 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 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. 471). 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. 472), it does not fall off, as a frog with only 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. 472, 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.] ' i I / Frog without its cere- brum avoiding an object placed in its path. Frog without its cerebrum moving on inclined board {Goltz). 734 REMOVAL OF THE CEREBRUM. A pigeon without its cerebral hemispheres behaves in a similar manner (Fig. 473). 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 dis- charge 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 con- tract ; it turns away its head when the vapor of ammonia is applied to its nos- _ trils. All these impressions are not per- - ' f'-\' ''-■':^"r^'^^ 7' ceived as conscious percei)tions. The ilIjimI hcnusplicres removed. • ' 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 {Flourens). Fish appear to behave differently. A carp with its cerebrum removed (Fig. 483, VI, i) can see and may even select its food, and seems to execute its move- ments voluntarily {Sfeiiier, Vulpiati). 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, blindfolded 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 th.at 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. 483, VI, represents the brain of a carp ; V, of a frog ; and IV, of a pigeon. In all these cases I 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. 483, II) the hemispheVes completely cover the corpora quadrigemina, but the cere- bellum stdl lies behind the cerebrum. In man the occipital lobes of the cerebrum completely over- lap the cerebellum (Fig. 479). [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. 461, II, is a transverse section of the posterior corpora quadrigemina, with the aqeduct of Sylvius and both cerebral peduncles of an adult man ; /, /, is the crusta of each REACTION TIME. 735 peduncle, and above it lies the locus niger, s. Fig. 461, 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 corre- sponding 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. 461, IV, V, VI) ; in the rabbit there are two shallow furrows on each side (III). The dog has a com- pletely furrowed cerebrum (I, II). Most remarkable is the complexity of the sulci and convolutions 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 a guide to intelligence. The elephant has absolutely the heaviest brain, but man has relatively the heaviest brain. [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. Shock on left hand, Shock on forehead, Shock on toe of left foot, Sudden noise, Visual impressions of electric spark. Hearing a sound, Currrent to tongue causing taste, Saline taste, Taste of sugar, " acids, " quinine, Reaction Time. .12 •13 •17 •13 •15 .16 .16 •15 .16 .16 •23 Name of Observer. Exner. do. do. do. do. Bonders. v. Vintschgau and Honigschmied. do. do. do. do. Reaction Time. — This time is known as " reaction tit?te" 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 consis's of the following events: (l) 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, i. e., the duration of apperception ; 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 oi sound is 0.136 to 0.167 second; for taste, 0.15 to 0.23; touch, 0.133 to 0.201 second [Horsck,v. Vintschgau and Honigschniect); iox olfactory impressions, 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 stimulants to be applied, all diminish the time. Tactile impressions are most rapidly perceived when they are applied to the most sensitive parts (v. Vintschgati). The time is increased with very strong stimuli, and when objects difficult to be distinguished are applied (y. Helmholtz and Baxt). The time required to direct the attention to a number consisting of I to 3 figures, Tigerstedt and Bergquist found to be 0.015 to 0.035 second. Alcohol and the anaes- thetics 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 he is not told whether the right or left side is to be stimulated, or what colored disc 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 really 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 736 HYPNOTISM. 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 is about to waken, psychical activity may manifest itself in the form of dreams, which differ, however, from normal mental processes. They con'^ist 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 (iii 70, 3, f), the respiration (g 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 dur- ing sleep, the deeper the latter is; so that in the deepest sleep they do not become contracted on the apj)lication of light. The pupils dilate when sensory or auditory stimuli are applied, and the lighter the sleep, the more is this the case; they are widest at the moments of awaking (^Plotke). [Huglilings Jackson fmds that the retina is more ancemic 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 (Rosenbac/i). The soundness of the sleep may be determined by the intensity of the sound required to waken a person. Kohlschiiiter found that at first sleep deepens verv quickly, then more slowly, and the maximum is reached after cne hour (according to Monninghoff and Preisbergen after i^^ hour); 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 anremic, that the arteries and veins of the pia mater are contracted during sleep and the brain 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 decompo- sition products of the nervous activity may also act as producers of sleep ( ? lactates — Preyer.) Sleep cannot be kept up for above a certain time, nor can it be interrupted voluntarily. Many nar- cotic-, 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 other external, represented by 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 shut- ting 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, whose results are confirmed by many of the recent re-discoveries of Wein- hold, Heidenhain, and others.] 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 nerv'e (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 attributes great importance [as did Carpenter and Braid long ago] to the psychological factor, whereby the attention was directed to a particular part of the body. The facility with which different per- sons becotne hypnotic varies very greatly. When the hypnotic condition has been produced a number of times, its subsequent occurrence is facilitated, 2 3 /4 ^wi/*f* A* Cortex of occipital lobe, i, super- ficial layer; 2, small angular cells ; 3, 5, pyramidal cells ; 4, granule layer ; 6, granules and ganglionic layer ; 7, spindle cells. {Ferrier, after Bevan Leiois.) 738 Perivascular and 1 : > in jj h spaces, a, capill.iry wjili .i lymph space communicating with the peri- cellular lymph space b, round the cell a lymph space c, containing two lymph corpuscles. X 150. Fig. 477. Vertical section of a frontal con- volution (Weigert's method) X 50. P. pia mater; 1-5, five layers of ^leynert; a, super- ficial layer of connective tissue; b, i, successive layers of medul- lated nerve fibres; /t, white matter. BLOOD VESSELS OF THE CEREBRUM. 739 [Nerve Fibres in the Cortex. — The ordinary methods of hardening the brain do not enable us to detect the enormous number of medullated nerve fibres in the gray matter. By using Exner's osmic acid method, or Weigert's or Pal's method, we obtain such a result as is shown in Fig. 477. Under the pia (P) is a layer of connective tissue («) devoid of nerve fibres. Beneath it is a layer ((^) occupying about the half of the outer layer, which is almost entirely taken up by medullated nerve fibres; most of these are fine, but a few of them are coarse, and run parallel to the surface and tangential to the arc of the outer contour of the convolution. Internal to this is a layer of medullated fibres (<:), which cross each other in various directions; while a similar network [d) occurs in the small-celled layer. (2) In the layer of large pyramidal cells (3) there are bundles of medullated fibres, running radially (^e) ; but at the lower part of this layer there is a very dense network (/), ft^rming (in a Weigert's preparation") a dense, dark band, corresponding to the outer layer of Baillanger. In the layers marked {^g and h), which are partly in the third and partly in the fourth cortical layer, the radial arrangement is more marked and more compact, and the thick fibres are more numerous. In the middle is {h) a narrow, dense network corresponding to Baillanger's inner layer. The lower part of the fourth layer, and the whole of the fifth, are occupied by i. It is to be remembered that all the convolutions do not present exactly the same structure and arrangement [Obersteinei-).'] [Variations. — The gray matter diifers in different parts of the brain. In the gray matter of the cornu ammonis, the large pyramidal cells of (3) make up the chief mass ; in the claustrum (4) is most abundant. In the central convolutions (ascending frontal and parietal), according to Betz, Mierzejewski, and Bevan Lewis, very large pyramidal cells are found in the lower part of the third layer. Similar cells have been found in the posterior extremities of the frontal convolutions in some animals — the posterior parietal lobule, and para-central lobule, all of which have motor functions. In those convolutions which are regarded as subserving sensory functions, a somewhat different type prevails, e.g., the occipital gyri or annectant convolution [B. Lezvis). The very large pyra- midal cells are absent, while the granule layer exists as a well-marked layer between the layer of large pvramidal cells and the ganglion cell layer (Fig. 475).] [Fuchs finds that there are no medullated fibres either in the cortex or medulla until the end of the first month of life. The medullated fibres appear in the uppermost layer at the fifth month, and in the second at the end of the first year, the radial bundles in the y\g 478 deeper layers at the second month. The medullated fibres increase until the seventh or eighth year, when they have the same arrangement as in the adult.] [Blood Vessels. — The adventitia of the small cerebral vessels contains pigment and granular cells, filled with oil granules. In the newborn child the bloodvessels of the brain are beset with cells, filled with fatty granules. Perhaps the gi-anules supply part of the material for the formation of the myelin sheath on the nerve fibres. About the fifth year the fat is repla'^ed by a yellow pigment. In adults, yellow or brown glancing pigment granules are found i'l the adventitia of the arteries. In the adventitia of the veins there is no pigment, but generally some fat. The gray matter is much more vascular than the white, and when injected, a section of a convolution pre- sents the appearance shown in Fig. 478. The nutritive arteries consist of \a) the long medullary arteries (i) which pass from the pia mater through the gray matter into the central white matter or centrum ovale. They are terminal arteries, and do not communicate with each other in their course; thus, they supply independent vascular areas ; nor do they anastomose with any of the arteries derived from the ganglionic system of blood vessels; 12 to 15 of them are seen in a section of a convolution, (b') The short cortical nutritive articles (2) are smaller and shorter than the foregoing. Although some of them enter the white matter, they chiefly supply the cortex, where medullary arter es ; and i', i", in groups between the convolu- tions, 2, 2, arteries of the cortex cerebri; a, large-meshed plexus in first layer; b, closer plexus in middle layer; c, opener plexus in the gray matter next the white substance, with its vessels {d). 740 CONVOLUTIONS OF THE CEREBRUM. they form an open-meshed plexus in the first layer (a), while in the next layer (/;) the plexus of capillaries is dense, the plexus again being wider in the inner layers (c).] [Central or Ganglionic Arteries. — From the trunks constituting the circle of Willis (Fig. in Tus is involved. It may be that the impulses go first to their own side, and cross afterward.] [4. We do not know the centre for taste, and even the course of the nerve of taste is disputed. Ferrier places it close to that of smell.] On stimulating the subiculum in monkeys, dogs, cats, and rabbits, he observed peculiar move- ments of the lips and partial closure of the nostrils on the same side [\ 365). In man, subjective olfactory and gustatory perceptions are regarded as irritative phenomena, while loss of these sen- sory activities, often complicated with other cerebral phenomena, is regarded as a symptom of their paralysis. [The gustatory path crosses in the posterior part of the posterior segment of the internal cap- sule. While Gowers admits that the chorda tymjjani is the nerve of taste for the anterior two-thirds of the tongue, he thinks that it reaches the facial nerve from the spheno-palatine ganglion through the Vidian nerve. He denies that the glosso-pharyngeal is concerned in ta.ste, and "he believes that taste impressions reach the brain solely by the roots of the 5th nerve." lie admits that the nerves of taste to the back part of the tongue may be distrihuled with the glosso-pharj'ngeal, reaching them through the otic ganglion by the small superficial petrosal and tympanic plexus.] [5. Ferrier places the centre for tactile sensation in the hippocampal region close to the distribution of part of the posterior cerebral artery ; so far this has not been confirmed. The centre for the sensation of pain has not been defined ; probably it is very diffuse. The limbic lobe, according to Broca, includes the hippocampal convolution and the gyrus fornicatus. Ferrier found that removal of the hippocampal region resulted in a diminution of the sensibility of the opposite side of the body. Horsley and Schafer observed only a temporary THERMAL CORTICAL CENTRES. 755 hemiangesthesia, but they found that an extensive lesion of the gyrus fornicatus was followed by hemianaesthesia, more or less marked and persistent. From their experiments, these observers conclude that the limbic lobe "is largely, if not exclusively, concerned in the appreciation of sensations, painful and tactile."] 6, Munk is of opinion that the surface of the cerebrum in the region of the motor centres acts at the same time as " sensory areas " {'^Fiihlsphdre"), i. e., they serve as centres for the tactile and muscular sensations and those of the innervation of the opposite side. He asserts that after injury to these regions the corresponding functions are affected. According to Bechterew, the centres for the perception of tactile impressions, those of innervation, of the muscular sense, and painful impressions are placed in the neighborhood of the motor areas (dog) ; the first immediately behind and external to the motor areas, the others in the region close to the origin of the Sylvian fissure. [So far this agrees with the views of Starr (p. 749).] Goltz, who first accurately described the disturbances of vision following upon injuries to the cortex in dogs, is opposed to the view of sensory localization. He believes that each eye is connected with both hemispheres. He asserts that the disturbance of vision, after injm-y to the brain, consists merely in a diminished color and space sense. The recovery of the visual perception of one eye after injury of one side of the cortex cerebri, he explains by supposing that this injury merely causes a temporary inhibition of the visual activity in the opposite eye, which disappears at a later period. Instead of psychical blindness and deafness he speaks of a " cerebro- optical and " cerebro-acoustical weakness." 377. THERMAL CORTICAL CENTRES.— Eulenberg and Landois discovered an area on the cortex cerebri, whose stimulation produced an undoubted effect upon the temperature and condition of the blood vessels of the opposite extremities. This region (Fig. 483, I, /) generally embraces the area in which, at the same time, the motor centres for the flexors and rotators of the fore limb (3), and for the muscles of the hind limb (4) are placed. The areas for the anterior and posterior limbs are placed apart ; that for the anterior limb lies somewhat more anteriorly, close to the lateral end of the crucial sulcus. Destruction of this region causes increase of the temperature of the opposite extremities; the temperature may vary considerably (1.5° to 2°, and even rising to 13° C). This result has been confirmed by Hitzig, Bechterew, Wood, and others. This rise of the temperature is usually present for a considerable time after the injury, although it may undergo variations. Sometimes it may last three months, in other cases it gradually reaches the normal in two or three days. In well-marked cases, there is a diminution of the resistance of the wall of the femoral artery to pressure, and the pulse curve is not so high [Reinke). Local electrical stimula- tion of the area causes a slight temporary cooling of the opposite extremities, which may be detected by the thermo-electric method. Stimulation by means of common salt acts in the same way, but in this case the phenomena of destruction of the centre soon appear. As yet, it has not been proved that there is a similar area for each half of the head. The cerebro-epileptic attacks (| 375) increase the bodily temperature, partly owing to the increased production of heat by the muscles (§ 302), partly owing to diminished radiation of heat through the cutaneous vessels, in consequence of stimulation of the thermal cortical nerves. The experiments led to no definite results when per- formed on rabbits. According to Wood, destruction of these centres occasions an increased produc- tion of heat that can be measured by calorimetric methods, while stimulation causes the opposite result. These experiments explain how psychical stimulation of the cerebrum may have an effect upon the diameter of the blood vessels and on the temperature, as evidenced by sudden paleness and congestion (§378,111). [Heat Production. — Injury to the fore-brain has no effect on the temperature. If the brain of a rabbit be punctured through the large fontanelle, and the stylet be forced through the gray matter on the surface, white matter and the median portion of the corpus striatum right to the base of the brain, there is a rapid rise of the temperature which may last several days. Injury to the gray cortex does not affect the temperature. After puncture of the corpus striatum, the highest tempera- ture is reached only after twenty-four to seventy hours, but when the puncture reaches the base of the brain this result occurs in two to four hours. Electrical stimulation of these areas causes the same effect on the temperature. Direct injury to certain parts of the brain is followed by a rise of the temperature — or fever. See also, p. 376, for further evidence of the existence of thermal centres. There is at the same time an increase of the O taken in, the COj given off and a decided increase of the N given off, indicating an increase in the proteid metabolism, which points to an increased pro- duction of heat [Aronsokn and Sacks, Richet, Wood^.'\ General and Theoretical. — Goltz's View. — Goltz uses a different method to remove the cortex cerebri — he makes an opening in the skull of a dog, and by means of a stream of water washes away the desired amount of bram matter. He describes, first of all, inhibitory phenomena, which are temporary and due to a temporary suppression of the activity of the nervous apparatus, which, however, is not injured anatomically; this may be explained in the same way as the suppression of reflexes by strong stimulation of sensory nerves (| 361, 3). In addition, there are the permanent 756 TOPOGRAPHY OF THE MOTOR CENTRES. phenomena, due to the disappearance of the activity of the nervous apparatus, which is removed by the operation. A dog, with a large mass of its cerebral cortex removed, may be compared to an eating, complex, retlcx machine. It behaves like an intensely stupid dog, walks slowly, with its head hanging down ; its cutaneous sensibility is diminished in all its ([ualities — it is less sensitive to pressure on the skin; it takes less cognizance of variations of temperature, and does not comprehend how to feel; it can with difficulty accommodate itself to the outer world, especially with regard to seeking out and taking its food. On the other hand, there is no paralysis of its muscles. The dog still sees, but it does not understand what it does see ; it looks like a somnambulist, who avoids obstacles without obtaining a clear perception of their nature. It hears, as it can be wakened from sleep by a call, but it hears like a person just wakened from a deep sleep by a voice — such a person does not at once obtain a distinct perception of the sound. The same is the case with the other senses. It howls from hunger, and eats until its stomach is tilled ; it manifests no symptoms of sexual excitement. Goltz supposes that every part of the brain is concerned in the functions of willing, feeling, percep- tion, and thinking. Every section is, independently of the others, connected by conducting paths with all the voluntary muscles, and, on the other hand, with all the sensory nerves of the body. He regards it as possible that the individual lobes have different functions. After removal of the anterior or frontal convolutions and the motor areas, there is at first uni- lateral motor and sensory paralysis and affection of vision. After some months, there remains only the loss of the muscular sense. If the. operation be bilateral, the phenomena are more marked; there are innumerable purposeless associated movements, and the dogs become vicious. Marked and permanent disturbance in the capacity to utilize the impressions from the sen.se organs is not a necessary consequence of removal of the frontal convolutions. Removal of the occipital lobes interferes most with vision. Bilateral removal makes the animal almost blind. The dog remains obedient and lively. There is no disturbance of motion or of the muscular sense. Inhibitory Phenomena. — Injury to the brain also causes inhibitory phenomena, such as the disturbances of motion, the complete hemiplegia which is frequently ol)served after large unilateral injuries of the cortex cerebri ; these are regarded by Goltz as inhibitoiy phenomena, due to the injury acting on lower infra-cortical centres, whose action inhibits movement, but these movements are recovered as soon as the inhibitory action ceases. 378. TOPOGRAPHY OF THE CORTEX CEREBRI.— A short resinne of the arrangement of convolutions, according to Kcker, is given in § 375. I. The cortical motor areas for the face and the limbs are grouped around Fig. 488. Fn;. 4S9. Motor areas in man shaded— outer surface of the left side Inner surface of right hemisphere. AS, area governing of human brain. Dotted area, the aphasic region the movements of the arm and shoulder; Tr, ot (modified from Gowers). the trunk ; leg, those of the leg : Gf, gyrus forni- catus ; CC, corpus callosum ; i/, uncinate gyrus ; O, occipital lobe. the fissure of Rolando, including the ascending frontal, ascending parietal, and part of the parietal lobule (Fig. 4883. The centre for the face occupies the lowest third of the ascending frontal convolution, and reaches also to the lowest fifth of the ascending parietal. The arm centre occupies the middle third of the ascending frontal and middle three-fifths of the ascending parietal convolutions, while the leg centre lies at the upper end of the sulcus and extends backward into the parietal lobule (and perhaps on to the superior frontal convolution) (Fig. 488). TOPOGRAPHY OF THE MOTOR CENTRES. 757 The leg centre is continued over on to the paracentral lobule, opposite the upper end of the fissure of Rolando, in the marginal convolution on the mesial aspect of the hemisphere (Fig. 490), where the centres for the muscles of the trunk also exist (p. 748). The centre for speech is in the posterior part of the third left frontal convolution (Fig. 488). Blood Supply. — These convolutions are supplied with blood from four to five branches of the Sylvian artery, which may sometimes be plugged with an embolon. When a clot lodges in this artery, the branches to the basal ganglia may remain pervious, while the cortical branches may be plugged {Duvet, Heubner^ (| 381). [Hemiplegia consists of motor paralysis of one-half of the body, although, as a rule, all the muscles are not paralyzed to the same extent ; in some there may be complete paralysis, /. e., they are entirely removed from voluntary control, while in others, there is merely impaired voluntary control. It may be caused by affections of the cortical areas or by lesion of the motor tracts above the medulla, and the paralysis is always on the side op- FiG. 490. posite to the lesion, owing to the decussation of the motor paths in the medulla. If the case be a severe one, we have what Charcot terms hemiplegie centralevulgai7-e, or "complete hemi- plegia," due to lesion of the corti- cal centres for the face, arm, and leg. While the arm and leg are com- pletely paralyzed, the lower part of the face is more affected than the upper half, which is usually not much affected. All those move- ments under voluntary control, and Transverse section of a cerebral hemisphere. CCa, corpus cal- losum; NC, caudate nucleus; NL, lenticular nucleus; IC, internal capsule; CA, internal carotid artery; aSL, lenticulo- striate artery; ("Artery of hemorrhage"); F, A, L, T, position of motor areas governing the movements of the face, arm, leg, and trunk muscles of the opposite side {Uorsley). Scheme of the innervation of bilaterally associated muscles {Ross). especially those that have been learned, are abolished, while the associated and bilateral movements, which even animals can execute immediately after birth, remain more or less unaffected. Hence, the hand is more paralyzed than the arm; this, again, than the leg; the lower facial branches more than the upper ; the nerves of the trunk scarcely at all (^Ferrier). When an extraordi- nary effort is made, it will be found that there is some impairment of the power of the muscles of mastication and respiration, although the muscles on opposite sides act together {Gowers). The trunk muscles, as a rule, are but slightly affected, or not all, as their centre is elsewhere. There may be alterations of sensibility and of the reflexes.] 758 HEMIPLEGIA. [Conduction through the whole of the pyramidal fibres coming from one hemisphere may be interrupted, and yet all the muscles on the opposite side of the body are not paralyzed. The muscles which are comparatively unafl'ected are those associated in their action with the muscles of the opposite side, <'.,i,':, the respiratory muscles. Broadbent assumes that such muscles have a bilateral representation in the motor areas. Suppose in Fig. 491, 15, B'', to represent the cerel)ral cortex; M, M, motor centres in it ; N, N'', nerve nuclei in the spinal cord or medulla oblongata; P, P'', the pyramidal tracts passing to spinal nuclei N, N**; w, m' , nerves proceeding from the last. 1, 2, 3, 4, 5, represent difl'erent lesions. In the case of muscles on opposite sides of the body, which act independently, c•._^^, those of the hand, this is all the mechanism, but in bilaterally associated muscles there is another mechanism, viz., commissural fibres between the nerve nuclei, the one c conducting from right to left, and c' from left to right. When there is an injury at I or 3, impulses can still pass from the uninjured side M to N' and through c' to the muscles in, m' . In this way, both muscles receive motor impulses from one hemisphere (;?cw).] Conjugate deviation of the eyes, with rotation of the head, is frequently present in the early period of hemiplegia, aitliough it usually disappears. When a person turns his head to one side, there is an associated movement of certain of the ocular muscles with those of the neck. The head and eyes are usually turned to the side of the lesion ; this is termed " conjugate deviation," so that the power of voluntarily moving the eyes and head to the paralyzed side is temporarily lost. The unopposed muscles rotate the head and eyes to the sound side. If the lesion be in the posterior part of the pons, the deviation is to the paralyzed side {Frevost). [Subsequent Effects. — If there be a hemorrhage, say into these motor regions, or from the lenticulo-striate artery, so as to compress the pyramidal fibres in the knee and anterior two-thirds of the posterior segment of the internal capsule, then there is usually tonic or persistent contraction of the muscles affected. These tonic spasms may accompany the hemorrhage, or come on a few days after it, and set up the condition of early rigidity. The contraction or spasm — if any — accompany- ing the hemon'hage, is due to direct irritation of the pyramidal fibres, while that which comes on a few days later, and usually lasts a few weeks, is also due to irritation of these fibres, probably produced by inflammatory action in and around the seat of the lesion. The affected limb is stiff and resists passive movement. After a few weeks, late rigidity sets in and is persistent, and it is character- ized by structural changes in the pyramidal paths which lead to other results. There is secondary descending degeneration in the pyramidal tracts, which causes " contracture " in the paralyzed limbs, while at the same time, the deep or tendinous and periosteal reflexes (ankle clonus, rectus clonus, and the deep reflexes of the arm tendons, are exaggerated). The spastic rigidity is usually more marked in the arm than in the leg, and it generally aflects the flexors more than the extensors, so that the upper arm is drawn close to the trunk, the elbow, arm, and fingers flexed ; in the leg, the extensors of the leg overcome the peronei. Hitzig has pointed out that the contracture is less during sleep, and after rest. The muscles at first can be stretched by sustained pressure, l)ut after months or years, structural changes occur in the muscles, ligaments, and tendons, and the limbs assume a per- manent and characteristic attitude.] In hemiplegic persons, the power of the unparalyzed side is sometimes diminished, which is not sufficiently explained by the fact that some bundles of the pyramidal tracts remain on the same side i^Brown- Sequard , Charcot). Acquired Movements. — Some movements performed by man are learned only after much practice, and are only completely brought under the influence of the will after a time, such as the movements of the hand in learning a trade. Such movements are re-acquired only very slowly, or not at all, after injury to the motor areas in which they are represented. Those movements, however, which the body performs without previous training, such as the associated movements of the eyeballs, the face, and some of those of the legs, are rapidly recovered after such an injury, or they suffer but little, if at all. Thus, the facial muscles seem never to be so completely paralyzed after a lesion of the facial cortical centre, as in affections of the trunk of the facial nerve ; the eye especially can be closed. Sucking movements have been observed in hemicephalous foetuses. Degeneration of the Pyramidal Tracts. — After destruction of the cortical motor areas, descending degeneration of the cortico-motor paths, or "pyramidal tracts,'' takes place (§ 365). Degenerative changes have been found to occur within the white matter under the cortex in the anterior two-thirds of the posterior segment of the internal capsule, [in the middle third of the crusta (Figs. 492, *, 493, L], pons, in the anterior pyramids of the medulla oblongata (Fig. 492), and thence they have been traced into the pyramidal paths (direct and crossed) of the spinal cord (Charcot, Si>iger). It is evident that lesions of these tracts at any part of their course must have the same result, viz., to produce hemi- plegia. (For the subsecjuent effects, see p. 699.) In a case of congenital absence of the left forearm, Edinger found that the right central convolutions were less developed. DEGENERATION OF THE PYRAMIDAL TRACTS. 759 It is doubtful if the muscular sense is represented in the motor areas ; Nothnagel supposes it to be located in the temporal parietal lobes. It is to be noted, however, that in man there may be general loss of the muscular sense or of motor representations, and, on the other hand, a pure motor paralysis without loss of the former. Ataxic motor conditions, similar to those that occur in animals (p. 750), take place in man, and are known as cerebral ataxia. The position of the centres is given at p, 746. [But we may have localized lesions affecting one or more of the cortical motor areas ; these are called monoplegise. Cases in man are now sufficiently numerous to permit of accurate diagnosis.] Crural monoplegia [rare lesions recorded in the convolutions at the upper end of the fissure of Rolando, and the continuation of this area on to the paracentral lobule of the marginal convolu- tion],— brachio-crural, more common, in the upper and middle thirds of the Fig. 492. Secondary descending degeneration in middle third of right crus and medulla, after destruction of the cortical motor centres on the right side. Horizontal section of the cerebral peduncle in second- ary degeneration of the pyramidal tracts, where the lesion was limited to the middle third of the pos- terior segment of the internal capsule. F, healthy crusta; L, locus niger ; P, internal third of the crustaon the diseased side; D, secondary degenera- tion in the middle third of the crusta ; CQ, corpora quadrigemina with the iter below them. ascending frontal and ascending parietal convolutions — brachial, brachio-facial — facial, the last in the lowest part of the central convolutions. Paralysis of the muscles of the neck and throat indicates a lesion of the central convolutions, and so does paralysis of the muscles of the eye. Lesions of the cortex always cause simultaneous move- ments of the head and eyeballs. Irritation of the Motor Centres. — If the motor centres are irritated by pathological processes, such as hypersemia, or inflammation in a syphilitic diathesis — more rarely by tumors, tubercle, cysts, cicatrices, fragments of bone — there arise spasmodic movements in the corresponding muscle groups. This condition of a sudden discharge of the gray matter resulting in local spasms is called " Jack- sonian cerebral epilepsy." [Convulsions and spasms may be discharged from motor cortical lesions, and 760 POSITION OF THE MOTOR CENTRES. these, whether they affect the general or localized areas, give rise to unilateral con- volutions and monospasm respectively.] Monospasm. — According to the seat of the spasm, it is called /^rw/, brachial, crural mono- spasm, etc. Of course these spasms may affect several groups of muscles. Bartholow and Sciamanna have stimulated the exposed human brain successfully with electricity. Cerebral Epilepsy. — Very powerful stimulation of one side may give rise to bilateral spasms, with loss of consciousness. In this case, impulses are conducted to the other hemisphere by commissural fibres (§ 379). Movements of the Eye. — Nothing definite is known regarding the centre in the corte.x for volun- tary combined movemenls of the eyeballs in man. In paralytic alTectious of the cortex and of the paths proceeding from it, we occasionally find both eyes with a lateral deviation. If the paralytic affection lies in one cerebral hemisphere, the conjugate deviation of the eyeballs is toward the sound side (p. 638). If it is situated in the conducting paths, after these have decussated, viz., in the pons, the eyes are turned toward the paralyzed side {Pri-vost). If the part be irritated so as to produce spasms in the opposite side of the body, of course the eyes are turned in the direction opposite to that in pure paralysis. Instead of the lateral deviation of the eyeballs already described, there is occasionally in cerebral paralysis merely a weakening of the lateral recti muscles, so that during rest the eyes are not yet turned toward tlie sound side, but they cannot be turned strongly toward the affected side {Leichtenstem, Niinnius). The centre for the levator palpebne superioris appears to be placed in the angular gyrus {Grassel, Landouzy). II. The Centre for Speech. — The investigations of Bouilland [1825], Dax [1S36], Kroca [1861], Kussmaul, Broadbent and others have shown that the third left frontal convolution of the cerebrum (Figs. 484, F3, and 488) is of essential importance for speech, while probably the island of Reil is also concerned. The island is deeply placed, and is seen on lifting up the overhanging part of the brain called the operculum, lying between the two branches of the Sylvian fissure (S). The motor centres for the organs of speech (lips, tongue) lie in this region, and here, also, the psychical processes in the act of speech are completed. In the great majority of mankind, the centre for speech is located in the left hemisphere. The fact that most men are right-ha?ided a-ho points to a finer construction of the motor apparatus for the upper extremity, which must also be located in the left hemisphere. Men, therefore, with pronounced right-handedness ("droiters") are evidently left- brai ned {" ga.nchQrs du cerveau" — Broca). By far the greater num- ber of mankind are '' left-brained speakers^ ^ (^Kussmaul) ; still there are exceptions. As a matter of fact, cases have been observed of left-handed persons who lost their power of speech after a lesion of the right hemisphere {Ogle'). Investigations on the brains of remarkable men have shown that in them the third frontal convolu- tion is more extensive and more complex than in men of lower mental calibre. In deaf mutes it is very simple ; microcephales and monkeys possess only a rudi- mentary third frontal {Riidinger). The motor tract for speech passes along the upper edge of the island of Reil, then into the substance of the hemispheres internal to the posterior edge of the knee of the internal capsule ; from thence, through the crusla of theleft cerebral peduncle into the left half of the pons, where it crosses then into the medulla oblongata, which is the place where all the motor nerves (trigeminus, facial, hypoglossal, vagus and the respiratory nerves) concerned in speech arise. Total destruction ot these paths, therefore, cause total aphasia ; while partial destruction causes a greater or less disturbance of the mechanism of articulation, which has been called" anarthria" by Leyden and Wernicke. Conditions. — Three activities are required for speech — (i) the normal move- ment of the vocal apparatus (tongue, lips, mouth and respiratory apparatus) ; (2) a knowledge of the signs for objects and ideas (oral, written and imitative or mimetic signs) ; (3) the correct union of both. Aphasia (« priv. and ^aiTj? speech) — Injury of the speech centre causes either a loss or more or less considerable disturbance of the power of speech. The loss of the power of speech is called "aphasia.'^ [Aphasia, as usually understood. APHASIA. 761 means the partial or complete loss of the power of articulate speech from cerebral causes.] The following forms of aphasia may be distinguished : — 1. Ataxic aphasia (or the oro-lingual hemiparesis of Ferrier), i. e., the loss of speech owing to inability to execute the various movements of the mouth necessary for speech. Whenever such a person attempts to speak, he merely executes incoordinated grimaces and utters inarticulate sounds. [The muscles concerned in articulation, however, are not paralyzed, but there is an absence of coordination of these muscles due to disease of the cortical centre.] Hence, the patient cannot repeat what is said to him. Nevertheless, \h& psychical processes necessary for speech are completely retained, and all words are remembered ; and hence, these persons can still give expression to their thoughts graphically or by writing. If, however, the finely adjusted movements necessary for writing are lost, owing to an affection of the centre for the hand, then there arises at the same time the condition of agraphia, or inability to execute those movements necessary for writing. Such a person, when he desires to express his ideas in writing, only succeeds in making a few unintelligible scrawls on the paper. Occasionally such patients sufler from loss of the power of imitation or the execution of particular movements of the limbs and body constituting /flw/cwz'wf speech or amimia i^Ktisstnaul'). 2. Amnesic Aphasia, or Loss of the Memory of Words. — Should the patient, however, hear the word, its significance recurs to him. The movements necessary for speech remain intact ; hence, such a patient can at once repeat or write down what is said to him. Sometimes only certain kinds of words are forgotten, or it may be even only parts of certain words, so that only part of these words is spoken. [Nouns and proper names usually go first.] Cases of amnesic aphasia, or the mixed ataxic-amnesic form of disturbance of speech, point to a lesion of the third frontal convolu- tion and of the island of Reil on the left side. Another form of amnesic aphasia consists in this that the words remain in one's memory but do not come when they are wanted, i. e., the association between the idea and the proper word to give expression to it is inhibited i^Kussmaul). It is common for old persons to forget the names of persons or proper names; indeed, such a phenomenon is common within physiological limits, and it may ultimately pass into the pathological condition of amnesia senilis. Among the disturbances of speech of cerebral origin, Kussmaul reckons the following : — 3. Paraphasia, or the inability to connect rightly the ideas with the proper words to express these ideas, so that, instead of giving expression to the proper ideas, the sense may be inverted, or the form of word^ may be unintelligible. It is as if the person were continually making a " slip of the tongue." 4. Agrammatism and ataxaphasia, or the inability to form the words grammatically and to arrange them synthetically into sentences. Besides these, there is — 5. A pathological slow way of speaking (bradyphasia), or a pathological and stuttering way of reading (tumultus sermonis), both conditions being due to derangement of the cortex {^Ktissmaul). The disturbances of speech depending essentially upon affections of the peripheral nerves, or or the muscles of the organs of the voice and speech, are already referred to in \\ 319, 349, and 354. [In word blindness, the person cannot name a letter or a word, so that he cannot understand symbols, such as printed or written words, or it may be any familiar o b j e c t, al- though he can see ^ig. 494- Fig. 495- quite well, while he can speak fluently and write correctly.] [In wo r d d e a f- ness, the person hears other sounds and is not deaf, but he does not hear words.] [The study of aphasia in its various forms is simplified by a study of the mode of acquisition of language by a child. The child hears spoken words and obtains auditory memories or impres- sions of these sounds (called by Lichtheim " auditory word representations "), and this must form the starting-point of language, and by and by it begins to coordinate its muscles to produce Schemes of aphasia. A, centre for auditory images; M, for motor images; B, perception centre; Oc, eye; E, reading centre; i to 7, lesions {Lich- theim'). 762 APHASIA. sounds imitative of these. Thus we have two centres, one for •• auditory images " (Fig. 494, A), and the other for " motor images " (Fig. 494, M), and these two must be connected, thus estab- hshini^ a retlex arc. There is a receptive and an emissive department as represented in the scheme. We must .issume the existence of a higher centre (B), "in which concepts are elaborated," where these sounds become intelligible. Volitional language reijuires a conneciion between H and M, as well as between A and M. But we have also reading and writing. Suppose O to re|)resent a centre for visual impressions (printed words or writing) : these we can understand through the con- nection between such visual impressions and auditory inijiressions, whereby a jiath is estal)lished through ().\ (Fig. 495). In reading aloud, however, the oro-lingual muscles must be coordinated, so we have the path OAM opened up. In writing, or copying written characters, the movements of the hand are special, and perhaps require a special centre, or at least a special arrangement of the channels for impulses in the centre; the movements are learned under the guidance of ocular impres- sions, so we connect O and E, E being the centre guiding the movements in writing. As to volitional writing, the impulse passes through M — but does it pass directly to E, or indirectly through A ? Lichtheim assumes that it goes direct from M to E. It is evident that there are seven channels which may be interrupted, each one giving rise to a different form of aphasia (l to 7).] [Looked at from another point of view, either the ingoing (,-7) or outgoing ( w) channels or centres, or the commissural fibres between both, may be affected. If the motor centre is affected, we have Wernicke's "motor aphasia;" if the sensory, his " sensory aphasia."] [In the most common form, or ataxic aphasia [A'uss///) also of written words, (c) and the faculty of copying. If the lesion be in A, we have the " sensorial aphasia " of Wernicke, ?'. e., in the acoustic word centre; we find loss of (i) understand- ing of spoken language, (2) also of written language, (3) faculty of repeating words, (4) and of writing to dictation, (5) and of reading aloud; there will exist (tr) the faculty of writinn;, (6) of copying words, and (c) of volitional speech, but the volitional speech is imper- fect, the wrong word being often used, so that there is the condition of "paraphasia." If the connection between A and M be destroyed, other results will follow, and such cases of "commissural" apha'^ia have been described by Wernicke. If the interruption be between B and M, we have a not uncommon variety of motor aphasia (4). when there is loss of (i) volitional speech, and (2) volitional writing, and there exist (a) under- standing of spoken language, [/>) of written language, (c) and the faculty of copying; but it differs from Broca's aphasia in that there also exists the faculty [d) of repeating, words, (e) of writing to dictation, {/) and of reading aloud. If the lesion is in Mm (5), the symptoms will be those of Broca's aphasia, but there will exist (i) the faculty of volitional writing, and (2) of writing to dictation. Many examples of this occur where patients have lost the faculty of speaking, but can express their thoughts in writing. In lesions of the path A B (6), there will be loss of (l) understanding of spoken language, and (2) of written language, and there will exist () volitional writing (but it will have the characters of paragraphia), (c) the faculty of repeating words, (d) reading aloud, {e) writing to dictation, and (/) power of copying words. The person will be quite unable to understand what he repeats, reads aloud, or copies.] [Fig. 496 shows diagrammatically the conditions in motor and sensory aphasia. From the eye and ear centripetal fibres (v and a) ascend to terminate in the visual (V) and auditory centres (A), in the cortex, while afferent fibres (s, s'', s^'), indicated by dotted lines, also pass from the articula- tions, muscles of the hand, and orbit to the cerebnnn. The dotted lines on the surface of the cortex represent the association system of fibres which connects the centres with each other. The centres for vocal (V) and written expression (W) are connected by centrifugal fibres, m and m'', with the hand and larynx respectively (A'(?yj-).] THE AUDITORY, GUSTATORY, AND OLFACTORY CENTRES. 763 III. The thermal centre for the extremities is associated with the motor areas (^ 377). Injury or degeneration of these areas causes inequality of the temperature on both sides {^Bechierew). IV. The sensory regions are those areas in which conscious perceptions of the sensory impressions are accomplished. Perhaps they are the substratum of sensory perceptions, and of the memory of sensory impressions. 1. The visual centre, according to Munk, includes the occipital lobes (Fig. 484, o^, o^ o^), while, according to Ferrier, it also includes the angular gyrus. Huguenin observed, in a case of long-standing blindness, consecutive disappear- ance of the occipital convolutions on both sides of the parieto-occipital fissure, while Giovanardi, in a case of congenital absence of the eyes, observed atrophy of the occipital lobes, which were separated by a deep furrow from the rest of the brain. Stimulation of the centre gives rise to the phenomena of light and color. Injury causes disturbance of vision, especially hemiopia of the same side (§ 344 — Westphal). When o/ie centre is the seat of irritation, there is photopsia of the same halves of both eyes ( Charcot). Stimulation of both centres causes the occurrence of the phenomena of light or color, or visual hallucinations in the entire field of vision. Cases of injury to the brain, where the sensations of light and space are quite intact, and where the color sense alone is abolished, seem to indicate that the color sense centre must be specially localized in the visual centre {SamelsoJui). After injury of certain parts, especially of the lower parietal lobe, ^^ psychical blindness'''' may occur, A special form of this condition is known as " word blindness " or alexia (Coecitas verbalis), which consists in this, that the patient is no longer able to recognize ordinary written or printed characters (p. 761). Charcot records an interesting case of psychical blindness. After a violent paroxysm of rage, an intelligent man suddenly lost the memory of visual impressions; all objects (persons, streets, houses) which were well known to him appeared to be quite strange, so that he did not even recognize himself in a mirror. Visual perceptions were entirely absent from his dreams. Clinical observations on hemianopia (§ 344) show that the field of vision of each eye is divided into a larger outer and a smaller inner portion, separated from each other by a vertical line passing through the macula lutea. Each right or left half of both visual fields is related to (?«^ hemisphere ; both left halves are projected upon the left occipital lobes, and both right upon the right occipital lobes (Fig. 487). Thus, in binocular vision, every picture (when not too small) must be seen in two halves ; the left half by the left, the right half by the right hemisphere ( Wei-tticke). As a result of pathological stimulation of the visual centre, especially in the insane, visual spectres may be produced. Pick observed a case where the hallucinations were confined to the right eye. Celebrated examples of ocular spectra occurred in Cardanus, Swedenborg, Nicolai, J. Kerner, and Holderlin. After degeneration of the cortical centre, the fibres which connect the occipital lobes with the external geniculate body, the anterior corpora quadrigemina, pulvinar, these structures themselves, and the origin of the optic tract undergo degeneration {y. Monakow) . 2. The auditory centre lies on both sides (crossed) in the temporo-sphenoidal lobes [according to Ferrier in the superior temporal convolution] ; when it is completely removed, deafness results, while partial (left side) injury causes psychical deafness. [See p. 754 for contradictory results.] Among the phenomena caused by partial injury is sicrditas ve7'balis (\A^ord deafness), which may occur alone or in conjunction with coecitas verbalis. Wernicke found in all cases of word deafness softening of the first left temporo-sphenoidal convolution (p. 754). In left-handed persons, the centre lies perhaps in the right temporo-sphenoidal lobes {JVestphal'). Clinical. — We may refer word blindness and word deafness to the aphataxic group of diseases, in so far as they resemble the amnesic form. A person word blind or word deaf resembles one who in early youth has learned a foreign tongue, which he has completely forgotten at a later period. He hears or reads the words and written characters; he can even repeat or write the words, but he has completely lost the significance of the signs. While an amnesic- aphasic pei'son has only lost the key to open his vocal treasure, in a person who is word blind or word deaf even this is gone. From a case of recovery it is known that to the patient the words sound like a confused noise. Huguenin found atrophy of the temporo-sphenoidal lobes after long-continued deafness. 3. Gustatory and Olfactory Centre. — In the uncinate gyrus on the inner side of the temporo-sphenoidal lobe (especially on the inner side of that marked 764 THE PSYCHO-SENSORIAL PATHS. U in Fig. 480), Ferrier locates the joint centres for smell and taste. These two centres do not seem to be distinct, locally, from each other. 4. Tactile Areas. — According to Tripier and others, all the tactile cerebral fields from different parts of the body coincide with the motor cortical centres for these parts [compare p. 755]. Occasionally, in epileptics, strong stimulation of the sensory centres, as expressed in the excessive subjective sensations, accompanies the spasmodic attacks (compare i! 393, 12). Such epileptiform hallucinations, however, occur without spasms, and are accompanied only by disturbances of con- sciousness of very short duration i^Berger). Course of the Sensory Paths. — The nerve fibres which condnct impulses from the sensory organs to the sensory cortical centres pass through the posterior third of the posterior limb of the internal capsule between the optic thalamus and the lenticular nucleus (Fig. 500, S). Hence, section of this part of the internal capsule causes hemianaesthesia of the opposite half of the body {Charcot). In such a case, sensory functions are abolished — only the viscera retaining their sensi- bility. There may also be loss of hearing, smell, and taste, — and hemiopia {Bech- tereiu). Pathological — In cases where there is more or less injury or degeneration of these paths, there is a corresponding greater or less pronounced loss of the pressure and temperature sense, of the cutaneous and muscular sensibility, of taste, smell, and hearing. The eye is rarely quite blind, but the shai-pness of vision is interfered with, the field of vision is narrowed, while the color sense may be partially or completely lost. The eye on the same side may suffer to a slight extent. V. Numerous cases of injury of the anterior frontal region, without inter- ference with motor or sensory functions have been collected by Charcot, Ferrier, and others. On the other hand, Fig. 497. enfeeblement of the intelligence and idiocy are often observed in acquired or congenital de- fects of the prefrontal region. In highly intellectual men, Rii- dinger found in addition a con- siderable development of the temporo-sphenoidal lobe. Ac- cording to Flechsig, there is no doubt that the frontal lobes and the temporo-occipital zone are related to intellectual processes, more especially the "higher" of these. Topography of the Brain. — The relations of the chief fissures and convolutions of the brain to the sur- face of the skull are given in Fig. 484, the brain being represented after Ecker. [Turner and others have given minute directions for finding the position of the different convolu- tions by reference to the sutures and other prominent parts of the skull. The annexed diagram by R. W. Reid shows the relations of the con- volutions to certain fixed lines (Fig. 497)0 [The position of the fissure of Ro- lando, where its upper end joins the great longitudinal fissure, is ob- tained by measuring on the scalp, K, in the middle line, the distance between the glabella and the external occipital protuberance, or the inion, which, in ordinary heads, varies from 11 to 13 inches Relation of the fissures and convolutions to the surface of the scalp. -f- , most prominent part of the parietal eminence; a, convex line bounding parietal lobe below ; b, convex line bounding the temporo-sphenoidal lobe behind (/?. \V. Reid). THE BASAL GANGLIA. 765 (Fig. 499). Measured from before backward, along this line, the distance from the glabella to the top of the fissure is 55.7 per cent, of the length of the whole line. The direction of the fissure is downward and forward, and the long axis of the fissure forms, with the average mesi.1l line, an angle of 67°, the angle opening forward. [The fissure of Sylvius is found by drawing a line from the external angular process of the frontal bone backward to the occipital protuber- ance, taking the nearest route between these two points. A point l^^ i°ch backward from the angular process along this line, marks the origin of the fissure ; while a straight line drawn to the centre of the parietal eminence marks the course of its posterior limb. The parieto-occipital fissure will be two inches behind the upper end of the Rolandic fissure {A. W. Hare).'] [Corpus Callosum. — It is usually stated that the corpus callosum con- nects the convolutions of one side of the brain with those on the other, i. e., that it is an inter-hemispherical com- missure. D. T- Hamilton, however, is of opinion that it is not an inter- hemispheric commissure, but is due to cortical fibres coming from the cortex cerebri to be connected with the basal ganglia of the opposite side. On this view, the "corona radiata," as usually understood, consists only of the fibres which pass from the cerebral peduncle directly up to the cortex on the same side, and are contained in the poste- rior division and knee of the internal capsule. They correspond to the motor pyramidal tracts. Hamilton maintains that all the other fibres of the internal capsule pass into the crossed callosal tract, and instead of running directly up to the cortex on the same side, cross in the corpus callosum to the cortex of the opposite side. Beevor, relying on the exam- ination of the brain of monkeys, by •Weigert's method, denies that any fibres of the corpus callosum pass into the external or internal capsules, and he supports the old view that the corpus callosum is a commissure be- tween the two hemispheres.] Erb observed a case of its almost complete destruction without any con- siderable effect on motility, coordi- nation, sensibility, reflexes, senses, speech, or any marked impairment of intelligence. 379. BASAL GANGLIA — MID - BRAIN. — [The corpus striatum consists of two parts, an intra-ventricular portion projecting into the lateral ventricle, the caudate Its average length is 3^ inches.] The fissures of Rolando and Sylvius are marked as broad dark lines. The shaded circles mark approximately the motor areas. i» lower extremity ; 2, 3, 4, 5, 6, and a, b, c, d, upper extremity ; 7, 8, 9, 10 II, oro-Iingual muscles (^. Jf. Zfcr^). Fig. 499. PDF O.P Head, skull, and cerebral fissures. OPr, occipital protuberance : KAP, external angular process ; SF, Sylvian fissure; A, its ascending limb ; "FR, fissure of Rolando; PE, parietal_ eminence; INIMA, middle meningeal artery; _TS, tipot temporo-sphenoidal lobe; B, Broca's convolution: IF, in- ferior frontal sulcus; POF, parieto-occipital fissure; IFF, iutra-parietal sulcus {A. IV. Hare). 766 THE BASAL GANGLIA. nucleus, and an extra-ventricular portion, the lenticular nucleus. Between the head of the caudate nucleus internally, and the lenticular nucleus externally, lies the anterior division of the internal capsule. The fibres which pass between these ganglia do not seem to form connections with them. The expanded head of the caudate nucleus is in front, and lies inside and around the front, of the lenticular nucleus, with which and the anterior ]:)erforated space it is continuous ; it sweeps backward into a tailed extremity, which nearly surrounds the lenticular nucleus like a loop. The lenticular nucleus is biconvex in a horizontal section, but triangular and subdivided into three divisions when seen in a vertical section (Fig. 501). The older observations on the corpora striata in man may be dis- missed, as a distinction was not drawn between injury to its two parts on the one hand and the internal cai)sule on the other. [The caudate nucleus and lenticular nucleus in their development are codrdinate with the develoi)ment of the cortex cerebri. Electrical stimulation of these ganglia causes general muscular contractions in the opposite half of the body, which are due to simultaneous stimulation of the neighboring cortico-mus- cular paths. The same result is obtained as if all the motor cortical centres were stimulated simultaneously.] Gilky did not obsa-ve movements on stimulating the corpus striatum in rabbits ; it would seem that, in these animals the motor paths do not traverse these ganglia, but merely pass alongside of them. [Lesions of the lenticular nucleus or of the caudate nucleus do not seem to give rise to any permanent symptoms, provided the internal capsule be not injured.] Destruction of the internal capsule, however, causes paralysis of motion or sen- sibility, or both, on the opposite side of the body, according to the part of it which is injured. The corpus striatum is quite insensible to painful stimulation {Longet). PathologicaL — In man, a lesion, not too small, destrojing the anterior part of the corpus striatum is followed by permanent paralysis of the opposite side, provided the internal capsule is injured, but the paralysis gradually disappears, if the lenticular and caudate nucleus only are affected (compare i 365). Sometimes there is dilatation of the blood vessels in consequence of vasomotor paralysis (I 377) 'f 'h^ posterior part is injured [Xothnagel) ; redness and a slightly increased temperature of the paralyzed extremities, at least for a certain time; swelling or fedema of the extremities ; sweating ; anomalies of the pulse detectable by the sphygmograph ; decubitus aculus on the paralyzed side; abnormalities of the nails, hair, skin ; acute inflammation of joints, especially of the shoulder. Later, contracture or permanent contraction of the paralyzed muscles takes place (Hiiguenin, Charcot). In some cases there is cutaneous anajsthesia, and occasionally enfeeblement of the sense organs of the paralyzed side, and both when the posierior third or sensory crossway of the posterior section of the internal capsule is affected. Usually, however, hemiplegia and hemianasthesia occur together. Optic Thalamus. — Ferrier did not observe any movements on stimulating the. optic thalami with electricity. As the pulvinar, or posterior extremity of the optic thalamus, is in part the origin of the optic nerve, and is also connected by fibres with the cortex cerebri, it is probably related to the sense of sight. Injury to its posterior third in man, results in disturbance of vision (^■olh?jagel). Ferrier surmises that the sensory fibres pass through the optic thalami on their way to the cortex, so that when they are destroyed, insensibility of the opposite half of the body is produced. Removal of the optic thalamus, or destruction of the part in the neighborhood of the inspiratory centre in the wall of the third ventricle, influ- ences the coordinated movements in the rabbit {Christiani). We know very little definitely as to the functions of these organs. After injur}- to one thalamus, there has been observed enfeeblement or paralysis of the muscles of the opposite side, together with mouvements de manege ; ar.d sometimes hemianaesthesia of the opposite side, with or without affec- tions of the motor areas, have been recorded. Extirpation of certain cortical areas (rabbit) is followed by atrophy of certain parts of the thalamus (z'. Monakow). [Internal Capsule. — In connection with the functions of the basal ganglia it is most important to remember their relation to the internal capsule. The corpus THE INTERNAL CAPSULE. 767 striatum consists of an intra-ventricular part, the caudate nucleus ; and an extra- ventricular part, the lenticular nucleus. The lenticular nucleus consists of three parts, best seen in a vertical section (501, i, 2, 3), with white matter between them, the striae medullares. The anterior limb of the internal capsule sweeps Fig. 500. Sepituu lucidum Columnae fomicis Corpus striatum. Stria terminalis. Thalamus opticus. Cornu anticum. Caput uuclel caudati Capsnla interna (anterior limb). Capsula externa. Island of BeiL leus lentiformis. Claustnim. Brachium conjunc- tiynm anticum. Peduuculus ceiebr f ad corpora iquadrige- miua. Crus J ad medullam jerebelli | ot>longa*nm Capsula interna (posterior limb). Thalamus opticas. Corpus genicula- tum niedlale. Caudate nucleus Hippocampus. '\~il^ Funiculus gracilis. Human brain with the hemispheres removed by a horizontal incision on the right side. 4, trochlear ; 8, acoustic nerve; 6. origin of the abducens ; F, A, L, position of the pyramidal (motor) fibres for the face, arm, and leg; S, sensory fibres. between the caudate and lenticular nucleus, while the posterior segment lies between the optic thalamus and the lenticular nucleus (Fig. 500). External to the first division of the lenticular nucleus is the external capsule (Figs. 500, 501), whose function is unknown. External to this is the claustrum, whose function is also 768 PEDUNCLE AND PONS. unknown. It is evident that hemorrhage into or about the basal ganglia is apt to involve the fibres of the internal capsule.] When the lenticulo-striate artery, or as it is called the "artery of hemorrhage," ruptures (Fig. 490, aSL), it may not only destroy the lenticular nucleus, but the internal capsule will be compressed ; and the same is the case with the lenticulo-optic artery — the external capsule will tend to force the blood inward. We know that, in the posterior segment of the capsule, the volitional or pyramidal fibres lie in the following order from before backward — those for the face (and tongiie) in the knee, in the anterior third those for the arm and hand, and in the middle third for the leg, and perhaps behind these those for the trunk (Fig. 500, F, A, L), so that a very small lesion in this region will affect a large number of these fibres, converging as they do like the rays of a fan from the motor cortical areas, where the arrangement of these centres is a supero-inferior one (Fig. 488), to become an antero-posterior one in the knee and posterior limb of the in- I'' 501 ternal capsule (Fig. 500). The posterior third of this limb is sensory and is the " sensory cross way. ' ' [Horsley points out that hemor- rhage from the lenticulo-striate artery affects in order the muscles of the face, arm, leg and trunk, while recovery is in the inverse order.] [Tlie crura cerebri Fig. 461, P), or cerebral pedun- cles, are two thick strands as they emerge above the pons, and as they are much larger than the pyramidal tracts, they must receive many fibres within the pons. A trans- verse section (Fig. 502) shows that, on them posteriorly and connecting them, are the cor- pora quadrigemina. (CQ). The crus proper is divided by the substantia nigra (SN) into a lower part, the crusta or basis, and an upper part, or tegmentum. The crusta is composed of ascending and descending nerve fibres; but the tegmentum, in addition to many nerve fibres, contains much gray matter with nerve cells. Near the middle is the " red nucleus " or " tegmental nucleus " (RN). Outside this is the fillet (F), a well-defined bundle of nerve fibres running upward from the pons. Above the nucleus, near the middle line, is the "posterior longitudinal bundle" (p. 1. b), which is triangular in section. Above the tegmen- tum lie many nerve cells, the origin of the third nerve (III), and arranged around the iter is much gray matter.] Injury to one cerebral peduncle causes, in the first place, violent pain and spasm of the opposite side, while the blood vessels on that side contract, and the salivary glands secrete. These phenomena of irritation are followed by paralytic symptoms of the opposite side, viz., anaesthesia (§ 365) and paresis, or incomplete voluntary control over the muscles, as well as paralysis of the vasomotor nerves. In affections of the cerebral peduncle in man, we must remember the relation of the oculomotorius to it, as the latter is often paralyzed on the same side [while the Nucleus caudatus. Corpus caliosum. Pillars of the fornix. Internal capsule. Optic thalamus. Soft com- Extemal capsule. Claustrum. — — == Frontal section through the right cerebral hemisphere in front of the soft commissure (posterior surface of the section). PONS VAROLII. 769 extremities, tongue, and half the face are paralyzed on the opposite side from the lesion]. The middle third of the crusta of the cerebral peduncle (Fig. 502) includes the direct pyramidal tracts (1^ 365, 378). The fibres of the inner third connect the frontal lobes with the cerebellum through the superior cerebellar peduncles. In the outer third are fibres which connect the pons with the temporal and occipital cerebral lobes {Flech- sig). The fibres which pass from the tegmentum into the corona radiata conduct sensory impulses [Flechsig) . [The pons varolii contain ascending and descending fibres, as well as transverse ones, and, in addition, the continuation upward of gray matter from the medulla, special masses of gray matter, and the nuclei of certain cranial nerves. Its appearance in section necessarily varies with the region where the section is made. Fig. 503 is a transverse section through part of the seventh nerve. The lower part shows the superficial (s.t.f.) and deep (d.t.f.) transverse fibres, with the pyra- midal fibres (Py) between them.] Stimulation or section of the pons causes pain and spasms; after the section, there may be sensory, motor, and vasomotor paralysis, together with forced movements. For diagnostic purposes in man, it is important to observe if alter- nate hemiplegia be present. [In lesions situated in the lower half of one side of the pons, there is facial paralysis on the same side as the lesion and paralysis (motor and sensory, and more or less complete) on the opposite side Scheme of transverse section of the cerebral peduncles. CQ, corpora quadrigemina ; Aq, aqueduct; p.l.b., posterior longitudinal bundle ; F, fillet or lemniscus ; RN, red nucleus ; SN, substantia nigra; III, third nerve; Py, pyramidal tracts ; FC,fronto-cerebellar; and TOC, temporo-occioital fibres of the crusta; CC, caudate-cerebellar fibres in upper part of crusta (after Wernicke and Gowers). Fig. 503. Transverse section of the pons through part of the seventh nerve. X 2- F.R., formatio reticularis; VII, seventh nerve ; Va, ascending root, and Vm, motor root of the fifth nerve; F, fillet ; s.o., superior olive; s.l.b., superior longi- tudinal bundle ; Py, pyramidal fibres ; R, restiform body; M.P., middle peduncles ot cerebellum ; d.t.f. and s.t.f., deep and transverse superficial fibres of the pons (after Wernicke). Scheme of the fibres in the pons. PT, pyramidal tracts ; F, facial fibres ; ti, upper ; /, lower lesjon ; MO, medulla oblongata ; DP, decussation of pyramids. of the body — this is called alternate paralysis ; while, if the lesion be in the upper half of one side of the pons, the facial paralysis is on the same side as the paralysis of the body. But the parts supplied by the 5th and 6th nerves may also be involved. This is explained by Fig. 504, where the upper facial fibres cross in the pons. Sudden and extensive lesions of the pons are frequently asso- 49 770 CORPORA QUADRIGEMINA. ciated with hyperpyrexia, the temperature often rising rapidly within an hour, perhaps from the gray matter in the floor of the 4th ventricle being affected ; but whether it is due to some effect on a heat- regulating or heat-producing centre is uncertain. Tumors of considerable size may press on the pons without producing very marked symptoms, as tumors tend to push aside tissues, unless they be infiltrating in their character. Lesions of the transverse superficial fibres (middle cerebellar peduncles) often give rise to involuntary forced movements, there being a tendency to move to one side or the other.] The Corpora Quadrigemina. — Destruction of these bodies on one side in mammals (or their homologues, the optic lobes in birds, amphibians, and fishes) causes actual blindness, which may be on the same or the opposite side, according to the relation of the fibres crossing at the optic chiasma (§ 344). Total destruc- tion causes blindness of both eyes. At the same time, the reflex contraction of the pupil, due to stimulation of the retina with light, no longer takes place {Flourens'), where the optic is the afferent and the oculomotorius the efferent nerve (§ 345). If the cerebral hemispheres alone be removed, the pupil still contracts to light, as well as after mechanical stimulation of the optic nerve {H. Aaayo). Destruction of the corporo quadrigemina interferes with the comj)lete harmony of the motor acts ; disturbance of equilibrium and incoordination of movements occur (Serres). In frogs, Goltz observed not only awkward, clumsy movements, but at the same time the animals have to a large extent lost the power of completely balancing the body (p. 733). A similar result was observed in pigeons i^M' Kendrick) and rab- bits {Ferrier). Extirpation of the eyeball is followed by atrophy of the opposite anterior corpus quadrigeminum {Gudden'). According to Bechterew, the fibres of one optic tract pass through the anterior brachium (Fig. 500) into the anterior pair (nates) of the corpora quadrigemina ; while those fibres which cross in the chiasma (Fig. 425) pass into the posterior pair (testes). According to this arrangement we have partial blindness, according as one or other pair of these bodies is destroyed. [In man, very little is known regarding the effects of disease of tiie corpora quadrigemina, inter- ference with the ocular muscles being the most marked symptom; t)ut the incoordination of move- ment which has been observed may be due to pressure upon the superior cerebellar peduncle, while it is by no means certain that the defects of vision are directly due to lesions of these bodies.] Stimulation of the Corpora Quadrigemina. — The corpora quadrigemina react to electrical, chemical, and mechanical stimuli. The results of stimulation are very variously stated. According 10 some observers, there is dilatation of the pupil on the same side ; according to Ferrier, it may be the pupil on the opposite or on the same side. The stimulation may be conducted from the corpora (|uadrigemina to the medulla oblongata, and to the origin of the sympathetic, for, after section of the sympathetic nerve in the neck, dilatation of the pupil no longer takes place. According to Knoll, the contraction of the pupil observed by the older experimenters occurs only when the adjoining optic tract is stimulated. Stimulation of the right anterior corpus quadrigeminum causes deviation of botk eyes to the left (and conversely); on continuing the stimulation, the head is turned to this side. On dividing the corpora quadrigemina by a vertical median incision, stimulation of one side causes the result to take place only on one side {Adamiik). Ferrier observed signs of pain on stimulating these organs in mammals. Carville and Duret conclude from their experiments, that these organs are centres for the extensor movements of the trunk. Ferrier found, on stimulating one optic lobe in a pigeon, dilatation of the opposite pupil, turning of the head toward the other side and backward, movement of the opposite wing and leg; strong stimulation caused flapping movements of both wings. Danilewsky, Ferrier, and Lauder Brunton observed a rise of the blood pressure and slowing of the heart beat, together with deeper inspiration and expiration. Bechterew ascribes all the phenomena, except those of vision itself, which accompany injur>' or stimulation of these bodies, to affections of deeper-seated parts. He asserts that the corpora quadri- gemina contain neither the centre for the movements of the pupils nor that for the combined move- ments of the eyeballs; not even the centre for maintaining the equilibrium of the body. Stimulation of these bodies causes the animals to perform marked movements. Reflex phenomena, nystagmus, forced movements, and unsteadiness of the gait only occur, however, when the deeper parts are injured. Pathological. — Lesions of the anterior pair in man, according to the extent of the lesion, cause disturbance of vision, failure of the pupil to contract to light, and even blindness ; there may be paralysis of the oculomotorii on both sides. Disease of the posterior pair may be associated with •disturbances of coordination [A^othnagel). Forced Movements. — It is evident from what has been said regarding the importance of the corpora quadrigemina for the harmonious execution of move- FORCED MOVEMENTS NYSTAGMUS. 771 merits, that unilateral injury of such parts as are connected with them by conducting channels, must give rise to peculiar unilateral disturbance of the equilibrium, causing variations from the symmetrical movements of both sides of the body. These movements are cdX^^td. forced movements. To this class belong the " mouve- ments de manege," where the animal, instead of moving in a straight line, runs round in a circle; index movements, where the anterior part of the body is moved round the posterior part, which remains in its place, just like the movements of an index round its axis ; and rolling movements, when the animal rolls on its long axis. All these forms of movement may pass into each other, and they are, in fact, merely different varieties of the same kind of movement. The parts of the nervous system whose injury produces these movements are the corpus striatum, optic thalamus, cerebral peduncle, pons, middle cerebellar peduncles, and certain parts of the medulla oblongata. Eulenburg observed index movements in the rabbit, after injury to the surface of the brain, and Bechterew observed the same in dogs. Forced movements, together with nystagmus and rotation of the eyeballs, are caused by injury to the olives (^Bechterew). The statements of observers vary as to the direction and kind of movement produced by injuring individual parts. The following observations have been made : Section of the anterior part of the pons, and of the crura cerebelli causes index, or, it may be, rolling movements toward the other side ; section of the posterior part of the same regions causes rolling movements toward the same side, while the same result is caused by a deeper puncture into the tuberculum acusticum, or into the restiform body. Section of one cerebral peduncle causes mouvements de manege, while the body is curved with the convexity toward the same side. The nearer to the pons the section is made, the smaller is the circle described ; ultimately index movements occur. Injury to one optic thalamus produces results similar to punc- ture of the anterior part of the cerebral peduncle, because the latter is injured along with it at the same time. Injury to the anterior part of one optic thalamus causes the opposite kind of forced movement, viz., with the concavity of the body toward the injured side. Injury to the spinal portion of th'=' medulla oblongata is followed by bending of the head and vertebral column, with the convexity toward the injured side, along with movements in a circle. When the anterior end of the calamus and the part above it are injured, the movements are toward the sound side. Strabismus and Nystagmus. — Among the forced movements may be reck- oned deviation of the eyeballs, strabismus or squinting, and involuntary oscillation of the eyeballs, constituting nystagmus. The latter condition occurs after super- ficial lesions of the restiform body, as well as of the floor of the 4th ventricle. A unilateral, deep, transverse injury, from the apex of the calamus upward as far as the tuberculum acusticum, causes the eye of the same side to squint downward and forward, that of the other side backward and upward. Section of both sides causes this condition to disappear {Schwahn). Hence, Eckhard assumes that the medulla oblongata is the seat of an apparatus controlling the movements of the eyes (^Eckhard'), which can be excited by sudden anaemia, e. g., ligature of the cephalic arteries in a rabbit. In pathological degeneration of the olivary body of the medulla oblongata in man, Meschede observed intense rotatory movements toward the same side. Theory. — In order to explain the occurrence of forced movements, it is suggested that there is unilateral incomplete paralysis i^L afar que), so that the animal in its efforts to move onward leaves the paralytic side slightly behind the other, and hence there is a variation from the symmetry of the movements. Brown-Sequard regards the matter in exactly an opposite light, viz., as due to stimulation from injury, causing an excessive activity of one-half of the body. Henle ascribes the movements to vertigo, or a feeling of giddiness caused by the injury. In all operations on the central nervous system, where the equilibrium is deeply affected, there is a considerable increase in the number and depth of the respirations {^Landois). Other Effects. — Some observers noticed variations of the blood pressure and a change in the 772 PINEAL AND PITUITARY BODIES. ^ SG Teh z number of heart beats after stimulation of the cortex cerebri, e.g., after electrical stimulation of the motor areas for the extremities [Boc/iefotttaine). Balogh observed acceleration of the pulse, on siiniulaling several points on the cortex cerebri of a Ao^, and from one point slowing of the pulse. Eckhard stimulated the surface of the brain in rabbits, and, as a rule, he observed that, as long as single crossed movements occurred in the anterior exiremiiies, there was no effect upon the heart, but that the heart became affected as soon as other movements occurred. This consists in slow strong pulse beats, with occasional weaker beats, while at the same time the blood pressure is slightly increased ^Bochefontaine). If the vagi be divided beforehand, the effect upon the pulse disappears, while the increase of the blood pressure remains. That jjsychical processes affect the action of the heart was known to Homer and Chrysipp. Bochefontaine and Lupine, on stimulating several points, especially in the neighborhood of the sulcus cruciatus in the dog, observed increased secretion of saliva, slowing of the movements of the stomach, peristalsis of the intestine, contraction of the spleen, of the uterus, of the bladder, and increased respirations. Bufalini, on stimulating those parts of the cortex which cause movements of the jaw, observed secretion of gastric juice with increase of the temperature of the stomach. Schiff, Brown-Sequard, El>tein, Klosterhalfen, and others have observed that injury to the pons, corpus striatum, thalamus, cerebral peduncle, and medulla oblongata often causes hyperemia and hemorrhage into the lung (according to Brown-S^quard, especially after injury to one side of the pons, which affects the opposite lung), under the pleura, in the stomach, intestine, and kidneys. Gastric hemorrhage is common after injury to the pons just where the cerebral peduncles join it. Similar phenomena have been observed in man after apoplexy or cerebral hemorrhage. Specially interesting is the cerebral unilateral decubitus acutus or bedsore, described by Charcot, which always occurs on the paralyzed side of the body, i. e., on the side opposite to the cerebral injury. It begins on the second YiQ CQ- or third day, rapidly causes enormous destruction and sloughing of the tissues on the back and lower extremities, and death soon takes place. Tiie decubitus which occurs after spinal injuries, usually begins in the middle line of the buttocks, and extends symmetrically on both sides. In cases of unilateral injury to the spinal cord, the decubitus occurs on the corres- ponding side of the sacral regijn Cp. 632). [The Pineal Gland or epiphysis cerebri lies on the back of, and is con- nected with, the third ventricle (Fig. 505, Z). It projects backward between the corpora quadrigemina. It is originally developed as a hollow outgrowth from that part of the embryonic brain which becomes the third ventricle. The hollow centre usually disappears, while the distal portion becomes enlarged and is often lobulated. Its distal portion may ter- minate outside the skull ; and in some animals there is developed in the median line of the skull an eve — pineal eye — arranged on the invertebrate plan, as in Anguis, Hatteria,etc. {^De Graaf, Spencer) {I 405).] [The pituitary body or hypophysis cerebri consists of two lobes, different in origin and structure (Fig. 505, H). T\it posterior lobe is developed as a hollow outgrowth from the part of the embryonic brain connected with the third ventricle. It loses its cavity and its nervous tissue; is permeated by connective tissue and blood vessels; and is connected with the floor of the third ventricle by the infundibulum. The anterior lobe is developed as a tubular invagination of the stomodreum, i. e, from the ectoderm of the buccal cavity; but it soon loses its connection with this cavity as the upper end enlarges, and the stalk atrophies. In mammalia, the upper expanded end unites with the anterior lobe to form the pituitary body. For the effects of its removal, see § 103, v.] 380. STRUCTURE AND FUNCTIONS OF THE CEREBELLUM.— [Structure. — On examining a vertical section of a cerebral leaflet, we observe the following microscopic appear- ances: Externally is the pia mater with its lilood vessels (Fig. 506, «), which penetrate into the gray matter; within is the medulla, composed of white fibres. The gray matter consists of b, a broad outer or molecular layer, largely composed of branched fibrils; and internal lo it is d, the JM' HIT Longitudinal section of an adult human brain. Ag, aqueduct of Sylvius; ^, corpus callosum ; Gi, anterior commissure ; Cm, middle commissure; Col, lamina terminalis ; C/>, posterior commissure; ^iV/, foramen of Munro ; (J, fornix; //.pituitary body : ////, cerebellum ; MH, corpora quadrigemina ; />///, medulla oblongata; P, pons Varolii: i^, spinal cord; Sp, septum lucidum ; /.infundibulum; 7VA, tela choroidea ; 'Jo, optic thalamus ; VH, cerebrum ; Z, pineal gland ; /, olfactory lobe and nerve ; //, optic nerve. STRUCTURE AND FUNCTIONS OF THE CEREBELLUM. 773 " granular," nuclear, or rust-colored layer. On the boundary line between these two, is the layer of Purkinje's cells, c. The cells of Purkinje form a single layer of large multipolar flask-shaped nerve cells, which have been compared to the Fig. 506. branched antlers of a stag (Fig. 507). From their outer surface is given off a process which rapidly divides, and gives rise to a large num- ber of smaller processes running outward in the outer gray layer. Some of these processes form part of the ground plexus of fibrils in this layer. An unbranched axial cylinder process is sent inward to the granular layers, where it becomes continuous with a nerve fibre — every cell of Purkinje being continuous with a straight unbranched medullated nerve fibre. The unbranched fibres run straight firom the medulla through the granular layer, forming no connection with its granules. A second set of bi-anched or anastomosing, often vari- cose, nerve fibres, finer than the foregoing, pass from the medulla into the granular layer, where they form a network which is continued Fig. 507. Vertical section of the cerebellum, a, pia mater; h, external layer; c, layer of Purkinje's cells; d, inner layer; e, medullary white matter. Purkinje's cell, sublimate preparation. X 120. into the molecular layer. The granular layer is composed of closely packed granules of two kinds; one is stained by hgematoxylin, and the other with eosin {Denissenko). The hsematoxylin stained cells are most numerous ; they consist of a nucleus surrounded by protoplasm, and are what were formerly called granules. The eosin-stained cells, which are also stained by nigrosin {Beevoi-), are interposed in the course of medullated nerve fibres. The hsematoxylin cells, called glia cells by Beevor, have processes, and form a network throughout the granular layer, which also extends into the molecular layer. This network is regarded as the continuation of the modified myelin of the nerve fibres, and it forms a capsule for the cells of Purkinje. The molecular layer consists of a ground substance, composed of a spongy network of fine fibrils, which seem to be of the nature of neuro-keratin, strengthened here and there by stronger fibres. In the meshes lies a homogeneous substance. Some of this substance is more condensed to form a limiians externa on the surface of the cerebellum, while on the boundary line next the granular layer the branches of the gha cells form a liinitans interna, and between the two stretches the neuro-keratin network. Some small variocose nerve fibres exist in this layer continuous with those in the granular layer. The branched process of the cells of Purkinje is fibrillated, and the finer processes are composed also of fibrils, which are gradually distributed until they become isolated. It is suggested by Beevor that these fibrils bend at a right angle in a plane parallel to the smrface, and rearrange themselves as fibres 774 FUNCTIONS OF THE CEREBELLUM. surrounded by a medullated sheath, and that these fibres run inward through the molecular and granular layers — as the branched fibres — to the medulla.] Function. — Injuries of the cerebellum cause disturbances in the harmony of the movements of the body. Most probably, the cerebellum is a great and important central organ for the finer coordination and integration of movements. The fact that it is connected with all the columns of the spinal cord and with all the central ganglionic masses, renders this very probable. The direct cerebellar tracts from the lateral column of the cord conduct sensory impressions to the cerebellum, and thus indicate the posture of the trunk. The cerebellum may affect the motor nerves of the cord through fibres whicli pass downward in the lateral columns of the cord from the restiform bodies {F/echsig). Injury of the cerebellum neither produces disturbance of the psychical activities, nor does it interfere with the will or consciousness. Injuries to the cerebellum itself do not give rise to pain. According to SchifT, the cerebellum does not actually regulate the coordination of movements. According to him, there is a mechanism on both sides of the middle line, which increases all the complicated muscular movements — not only those for powerful contractions, but also the peculiar fine movements which fix the limbs and joints. Luciani asserts that destruction of the cerebellum produces a condition of incomplete tonus, there being a want of energy to control the voluntary muscles. Each half of the organ acts on both halves of the body. Injury or Removal of Cerebellum. — The immediate results produced by injury to or removal of the cerebellum have been admirably described by Flourens (Fig. 508). On removing the most Fig. 508. superficial layers in a pigeon, the ani- mal merely showed signs of weakness and interference with the uniformity of its movements. On removing more of the cerebellum, the animal became greatly excited, and made violent ir- regular movements, which did not par- take of the character of convulsions. The sensorium was unaffected, while vision and hearing were intact. Co- ordinated movements, such as walking, flying, springing, and turning, could be executed but imperfectly. After re- moval of the deepest layers, the power of executing the above-named move- ments was completely abolished. On placing the pigeon on its back, it could not get on its legs ; at the same time it made continually the greatest exertions in its movements, but these were always incoordinated, and therefore without any satisfactory result. The will, intelli- gence, and perception remained intact; the animal could see and hear, and sought to avoid obstacles placed in its way. It gradually exhausted itself in fruitless efforts to get on its legs, and ultimately remained in its abnormal position, quite exhausted. Flourens concluded from these experiments that the cerebellum is the centre for coordinating voluntary movements. Lussana and Morganti regard the cerebellum as the seat of the muscular sense. [Extirpation in Mammals. — The dangers attending this operation are so great, that but few animals survive. Luciani, however, by using antiseptic and other precautions, has been able to operate so that complete cicatrization was obtained, the animal (young bitch) being restored to health for a few months. The cerebellum alone was removed, but not its peduncles. As in all other similar operations, we must distinguish sharply the phenomenon manifested during recovery from those after complete recovery. During \.\\e first period oi sw weeks, from the time of the operation until complete recovery, the symptoms are those of injury and irritation of the divided peduncles, along with those resulting from the removal of the organ. They are clonic contractions of the Pigcuii Willi lib cerebellum removed. EXTIRPATION OF THE CEREBELLUM. 775 muscles of the fore limb, neck, and back, passing into tonic contractions when the animal attempts to move, and also weakness of the hind legs, so that all the normal voluntary movements are inter- fered with, i. e., incoordinated, although these symptoms may be explained by the injury to adjoining parts. There was no sensory disturbance or loss of the muscular sense, although closing the eyes rendered standing impossible. As recovery takes place, these symptoms disappear, and the animal enters on the second period, where the symptoms depending on the actual loss of the organ are pro- nounced. The contracture and pseudo-paralytic weakness disappear, while there are alterations in the tone of the individual muscles, producing a sort of " cerebellar ataxy." The dog could swim in quite a normal manner, its power of equilibration was not interfered with, but acts requiring a greater development of muscular energy could not be properly executed. This period lasted four to five months. After this time its health gave way, there was otitis, conjunctivitis, articular and cutaneous inflammations, while a peculiar form of marasmus set in, the animal dying after eight months. In fishes, also, the removal of the cerebellum does not affect their power of locomotion {Bandeloi)^^ Duration of the Phenomena. — After superficial lesions, or after a deep incision, the disturbances of coordination soon pass away {^Floiirens). If the injury affects the lowest third of the cerebellum, the motor disturbances remain permanently. Symmetrical lesions do not disturb coordination {Schiff). After removing the greater portion of the cerebellum in birds, Weir Mitchell has observed that the original disturbances gradually disappear; and after inonths only slight weakness and a condition of rapid fatigue remain. After ablation of the cerebellum, secondary degeneration occurs in the part of the pons around the pyramids, the lower olives, all the cerebellar peduncles and the direct cerebellar tract, usually on the same side [Flecksig). It is found also in individual fibres in all the cranial nerves and the anterior roots of the spinal nerves [Marchi). In the dog, superficial injuries of the vermiform process, or of one-half of the organ, produce merely temporary disturbances; while deep injuries to the vermiform process, or removal of one hemisphere and a part of the vermiform process, cause permanent rigidity of the legs and shaking of the head ; if the worm and both halves are destroyed, there follows permanent pronounced dis- turbance of coordination {v. Mering). According to Baginsky, destruction of a large part of the vermiform process alone causes in mammals permanent disturbance of coordination. Ferrier found that a vertical section of the cerebellum in monkeys produced only inconsiderable disturbances of the equilibrium; after injury of the anterior part of the middle lobe, the animal often tumbles for- ward; while, when the posterior part is injured, it falls backward. After injury of the lateral lobe, the animal is drawn toward the affected side [Sckiff, Vidpian, Ferrier, Hiizig). If the middle commissure be injured, the animal rolls violently on its long axis toward the injured side [Afagendie) . Paralysis never occurs after injuries of the cerebellum, nor is there ever disturbance of sensation or of the sense of touch. Luciani found that, in animals with the cerebellum extirpated, marasmus ultimately set in. In frogs, an important organ concerned with motion lies at the junction of the oblongata with the cerebellum {£c^/iard). After it is removed the animal can no longer execute coordinated jumping movements, nor can it crawl i^Goltz). [In man, the cerebellum is connected with the maintenance of the equilibrium. There may be a lesion of the hemispheres without any marked symptoms; but if the middle lobe be injured or pressed on by a tumor, there is usually a reeling or staggering gait, like that of a drunken man. Ross points out that, if the tumor affect the upper part of this lobe, the tendency is to fall backward, and if in the lower part, to fall forward or to revolve round a horizontal axis. Vomiting is fre- quently persistent and well marked, while there may be nystagmus and tonic retraction of the head.] After injuries of the cerebellum, involuntary oscillations of the eyeballs or nystagmus, as well as squinting \Magendie, Heriwig), have been observed; while Ferrier observed movements of the eye- balls after electrical stimulation. According to Curschmann, Eckhard and Schwann, this occurs only when the medulla oblongata is involved (\ 379). Effects of Electricity and Vertigo — If an electrical current be passed through the head, by placing the electrodes in the mastoid fossae behind both ears, with the -j- pole behind the right and the — pole behind the left ear, then on closing the current, there is severe vertigo, and the head and body lean to the -{- pole, while the objects around seem to be displaced to the left. If the eyes be closed, while the current is passing, the movements appear to be transferred to the person himself, so that he has a feeling of rotation to the left [Purkinje). At the moment the head leans toward the anode, the eyes turn in that direction, and often exhibit nystagmus. The electrical current probably stimulates the nerves of the ampullae, as we know that affections of these bodies cause vertigo (§ 31^0). The cerebellum has no relation to the sexual activities, as was maintained by Gall. The contractions of the uterus observed by Valentin, Budge, and Spiegelberg, after stimulation of the cerebellum, are as yet unexplained. 776 PROTECTIVE AND NUTRmVE APPARATUS UF THE BRAIN. Vertical section of the cortex cerebri and its membranes ; X sj-j. co, cortex cerebri ; /, intima pise dipping into the sulci ; a, arach- noid, connected with /> by means of the loose subarachnoid tra- beculae in the subarachnoid space, sa; v, v, blood vessels ; d, dura ; sd, subdural space. Pathological. — Lesions of one hemisphere may give rise to no symptoms; but if the middle lobe is involved, there is incoordination of movement, especially a tendency to fall, unsteady gait and pronounced vertigo. Irritative lesions of the middle peduncle cause complete gyrating move- ments of the body around its axis, together with rotation of the eyes and head {A'othnai).'\ Blood vessels occur only in the outer margm of the cornea Vertical section of the cornea stained with gold chloride. 71, nerve fibrils ; a, \r\g. 5IS, v), and extend 2 mm. perforated branch ; r, nucleus ; p, b, inter-epithelial termination of fibrils ; over the cornea above, 1.5 mm. j, anterior elasticlamina. below, and I mm. laterally — the most external capillaries form arched loops, and thus turn on themselves. The cornea is nourished from the blood vessels in its margin. Opacities of the cornea give rise to many forms of visual detects. The sclerotic is a thick fibrous membrane, composed of, p, circular (equatorial) and, u, longi- tudinal (meridional) bundles of connective tissue woven together (Fig. 514). The spaces between the bundles contain colorless and pigmented connective-tissue corpuscles and also leucocytes. It is thickest posteriorly, thinner at the equator, while in front of this it again becomes thicker, owing to the insertion of the tendons of the straight muscles of the eyeball. It contains few blood vessels, which form a wide-meshed capillary plexus, immediately under its deep sui-face. Other vessels form an arterial ring around the entrance of the optic nerve. It rarely is quite spherical ; it rather resem- bles an ellipsoid, which we might imagine to be formed by the rotation of an elhpse around its short axis (short eyes) or around its long axis (long eyes). Above and below, the sclerotic overlaps like a fold the clear margin of the cornea; hence, when the cornea is viewed from before, it appears trans- versely elliptical, when seen from behind, it appears circular. Following the margin of the cornea, but lymg still within the substance of the sclerotic, is the circular canal of Schlemm (z), which communicates with other anastomosing veins, the venous plexus of Leber [k). Schwalbe and Wal- deyer regard Schlemm's canal as a lymphatic. Posteriorly, the sclerotic becomes continuous with the fibrous covering of the optic nerve derived from the dura mater. The sclerotic is provided with nerves, which are said to terminate in the cells of the scleral substance {Helfreicli). The tunica uvea, or the uveal tract, is composed of the choroid, the ciliary part of the choroid, and the iris. The choroid is composed of the following layers (Fig. 517) : (i) Most internally is the trans- 50 786 THE IRIS. parent limiting membrane, 0.7 // in thickness, but it is slightly tliickor anteriorly. (2) The very vascular capillary network of the chorio-capillaris, or membrane of Kuysch, embedded in a homogeneous layer. Then follows (3) a Iner of a thick elastic network, covered on both surfaces by endothelium {Saft/er). (4) The choroid proper consists of a layer with pigmented connective- tissue corpuscles, together with a thick elastic network,containing the numerous venous vessels as well as the arteries. The pigmented layers are known as the supra-choroidea, or lamina fusca, which surrounds the large lymphatic space lined with endothelium and called the perichoroidal space, q. In newborn infants, which according to Aristotle have the iris dark blue, the uveal tissue is devoid of pigment ; in brunettes it is developed later, and in blondes not at all. In the ciliary part of the choroid, the pigmented connective-tissue corpuscles are not so numerous. The ciliary muscle (tensor choroidea\ or muscle of accommodation) is placed in this region. It arises (.?), by means of a l)ranched, reticulated, connective-tissue origin, from the inner side of the junction of the cornea and the sclerotic, near the canal of Schlemm, and passes backward to be inserted into the choroid. This con.stitutes the radiating fibres. Other fibres lying internal to these are arranged circularly, /, in bundles in the ciliary margin. These circular fibres are sometimes called Heinrich Midler's muscle. The muscle consists of smooth muscular fibres, and is supplied by the oculomotorius (^^ 345, 3). Fig. 517. Fig. 516, Nerve plexus in the cornea after gold chloride. «, nerve ; a, fibrils. Vertical section of the choroid and a part of the scle- rotic, (i) sclerotic; (2) lamina supra-choroidea; (3) layer of large vessels; (4) limiting layer; (5) chorio-capillaris; (6) hyaline membrane; (7) pig- ment epithelium ; (g) large blood vessels ; {/>) pigment cells ; (c) sections of capillaries. The iris consists of the following parts from before backward : a layer of epithelial cells {v) con- tinuous with those covering the posterior surface of the cornea, a layer of reticulated connective tissue, the layer of blood vessels, and lastly a posterior limiting membrane, which contains the pigmentary epithelium {x) {Mic/iel). In brunettes, the texture of the iris contains pigmented connective tissue corpuscles. The iris in some animals is described as containing two muscles composed of smooth muscular fibres — one set constituting the sphincter pupillae (circular — Fig. 533), which surrounds the pupil, and lies nearer the posterior than the anterior surface of the iris (J. 392). Its nerve of supply is derived from the oculomotorius (§ 345, 2). The other fibres constitute the dilator pupillse (radiating), which consists of a thinner layer of fibres ananged in a radiate manner. Some of the fibres reach to the margin of the pupil, while others bend into the sphincter. [The existence of a dilator pupillne in man is denied (| 392).] Ax. the outer margin of the iris, the radial bundles are arranged in anastomosing arches, and form a circular muscular \diy ex (Merkel). The chief nerve of supply for the dilator fibres is the sympathetic (? 347, 3"). Ganglia occur in the ciliary nerves in the choroid [and they are found also in the iris]. Gerlach has recently applied the temi ligarnentum anfiulare bulbi to that complex fibrous arrangement which sunounds the iris, and at the same time BLOOD VESSELS OF THE EYEBALL. 787 Fig. 518. forms the point of union of the ciliary body, iris, ciliary muscle, sinus venosus iridis, and the line of junction of the cornea and sclerotic. The choroidal vessels are of great importance in connection with the nutrition of the eye. According to Leber, they are arranged as follows : The arteries are — i. The short posterior cili- ary, which are about twenty in number and per- forate the sclerotic near the optic nerve (Fig. 518, a, a). They terminate in the vascular network of the chorio-capillaris (/«), which reaches as far as the era serrata. 2. The long posterior ciliary ; one of these lies on the nasal and the other on the temporal side, and they run (b) to the ciliary part of the choroid, where they divide dichotoniously, and penetrate into the iris, where they help to form the circulus arteriosus iridis major (/). 3. The anterior ciliary ( 'hen so is D D, j^ A B; for a plane surface A B is the horizontal, and G D the vertical line. If the surface be spherical, then the vertical line is the Fir.. 526. ■-""f" irj'trnirn fi llliUUiiii!!|it'i;li:;;::j;;iJ, ;;;:; i,;:.;:.!l prolonged radius of this sphere. If, however, the ray of light fall obliquely upon the surface, it is "refracted," /. e., it is bent out of its original course. The incident and the refracted ray never- theless lie in one plane. When the oblique incident ray passes from a less dense medium {e. _s^., air) into one wcri? a'(?«.f^' (^.^^., water), the refracted or excident ray is htni foivard ih^ perpendicular. If, conversely, it pass from a more dense to a less dense medium, it is bent azuay from the perpen- dicular. The angle (/, G D S) which the incident ray (S IJ) forms with the perpendicular (G D) is called the angle of incidence, the angle fjrmed by the refracted ray (D S,) with the prolonged perpendicular (D D) is called the angle of refraction, D D S, [r]. The refractive power is expressed as the refractive index. The term refractive index («) means, that number which shows for a certain substance, how many times the sine of the angle of incidence is greater than the s:ne of the angle of refraction, w-hen a ray of light passes from the air into that substance. Thus, n = sin. i : sin. r = ad, : id. On comparing the refractive indices of two media, we always assume that the ray passes from air into the medium. On passing from the air into water, the ray of light is so refracted that the sine of the angle of incidence is to the sine of the angle of refraction, as 4 : 3 ; the refractive index = — (or more exactly = 1.336). With glass the proportion is ^ 3 : 2 (^ 1.535 — Snellitis, 1620 ; Descartes). The sine of the incident and refractive angles are related as the velocity of light with both media. The construction of the refracted ray, the refractive index being given, is simple : Example. — Suppose in Fig. 526, L =r the air, G ^ a dense medium (glass) with a spherical surface, xy, and with its centre at ;«; p 0 ^ the oblique incident ray the tn Z is the peqDcndicular <^ ) ^ e the angle ACTION OF A CONVEX LENS. 795 ■5 of incidence. The refractive index given is — ; the object is to find the direction of the refracted way. From o as centre describe a circle with a radius of any length ; from a draw a perpendicular, a b to m Z- then a b \s 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., \o p. Draw the line p parallel to m Z. The hne joining o to n is the direction of the refracted ray. On making a line, n s, perpendicular to m Z,n s ^ b p. Further, n s ■= sine <) = r. So that a b : s n ox : b p')=^ ^ : i or sin. i : sin. r _3 2* Optical cardinal point of a simple collecting system. — Two refractive media (Fig. 527, L and G), which are separated firom each other by a spherical surface («, b), form a simple collecting sy.'item. It is easy to estimate the construction of an incident ray coming from the iirst medium (L) and falhng 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. 527) is the first, and G the second medium, a, b = the spherical surface whose centre is m. Of course, all the radii drawn from f/i to a b {m x, vi n) are perpendiculars, so that all rays falhng 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 hne 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 principal point. The fol- FiG. 527. lowing facts have been ascertained : (i) All rays {a to a-^, 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^ of the second medium. This is called the second principal focus. A plane in this point perpendicular to O Q is called the second focal plane (C D). (2) All rays {c to c^, which in the first medium are parallel to each other, but not parallel to O Q, reunite in a point of the second focal plane {f), where the non-refracted directive ray [c-^, m r) meets this. (In this case, the angle formed by the rays c to c^ with C Q must be very small.) The propositions I and 2 of course may be reversed ; the divergent rays proceeding from p toward a b pass into the first medium parallel to each other, and also with the axis C Q («: to a.^ ; and the rays proceeding from r pass into the first medium parallel to each other, but not parallel to the axis O Q (as ^ to c^. (3) All rays, which in the second medium are parallel to each other [b to b-^ 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 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^ from the principal focus {x) ; thus m x ^ p^ x — p x. From these comparatively simple proposi- tions it is easy to determine the following points : — I. The construction of the refracted ray. — Let A be the first (Fig. 528) ; B, the second medium ; c d, the spherical surface separating the two ; a b, the optical axis ; k, the nodal point ; /, the first and /j the second principal focus ; C, D, the second focal plane. Suppose x y to represent the direction of the incident ray, what is the construction of the refracted ray in the second medium? Prolong the refracted ray, P, i,-Q parallel to x,y, then y, Q is the direction of the refracted ray (according to 2). 796 ACTION OF A CONVEX LENS. 2. Construction of the image for a given object.- FiG. 528. In Fig. 529, H, c, d, a, b, k, p, and /,, C, 1) are as before. Suppose a luminous ]X)int {o] in the first medium, vhat is the position of the image in the second medium ? Prolong the unrefracled ray (t?, I /•, P), and draw the ray (, until it ! intersects the ray {o, P), then the j image of 0 is at P, the rays of I light (o X and o k) proceeding ii.i from the luminous point {o) re- '" unite in P. Construction of the refracted ray and the image in several refractive media. — If several refractive media be placed behind each other, we must proceed from medium to medium with the same metliods 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," /. e., if all have the same optic axis, then the refractive indices of Fig. 529. such a centred system may be represented by two equal, strong, refractive surfaces at a certain dis- tance. 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 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 distance of the refractive surfaces from each other. Construction of the refracted ray is accomplished as follows : Let a b represent the optical axis (Fig. 530, I) ; H, the first focal point determined by calculation; h h, the principal plane; H, the second focal point; //j, /^,, the second princijial plane; X', the first, and k^ the second nodal point; F, the second focal point; and I*",, F,, the second focal plane. Make the ray of direction / /^j parallel to in., w,. According to proposition 2,/, /(•, and /«,. «, mu-t meet in a point of the plane F, Fj. As/> k^ passes through unrefracted, the ray from «, must fall at r; «j r is, therefore, the direction of the refracted ray. Construction of the focal point. — Let , k i^^ : f k. All these values are known, viz., k g ^ 15- 1 6 mm.; further, f k ^ a k yC^ a,f, where a f is measured directly, and a k = 7.44 mm. The size of A B is meas- ured directly. The angle, \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, x y, and r s, must have the same visual angle. Hence, all the three objects, A B, x y, 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 consecpiently form retinal images of the same size, have the same " apparent size." In order to determine the ojitical cardinal points by calculation, after the method of Gauss, we must know the following factors: — 1. The refractive indices: for the cornea, 1.377 ; aqueous humor, 1.377: lens, 1.454 (as the mean value of all the layers) ; vitreous humor, 1.336 ; air being taken as i, and water 1.335. 2. The radii of the spherical refractive surfaces : 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 Kiihne's artilicial eye, the course of the rays of light being visible in water tinged with eosine.] Ophthalmometer. — This is an instrument to enable us to measure the radii of the refractive media of the eye. As the normal curvature cannot be accurately measured on the dead eye, owing t3 the rapid collapse of the ocular tunics, we have recourse to the process of Kohhausch, for calcu- Scheme of the ophthalmometer of Helmhohz. lating the radii of the refractive surfaces from the size of the reflected images in the living eye. TAe size of a luminous body is to the size of its reflected image, as the distance of both to half the 7-adius of the convex mirror. Hence, it is necessary to measure the size of the reflected image. This is ACCOMMODATION OF THE EYE. 799 done by means of the ophthalmometer of Helmholtz (Fig. 532). 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 obhquely in front of the upper half of its objective, he sees the corneal reflected image, a b, of the eye, B, and the image appears to be displaced laterally, viz., Xoa' 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, cor- responding to the middle line of the objective, intersect at an angle, then the observer sees the re- flected 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 reflected 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 and others^. 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 iipright. By a 'psychical d.zl, 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 ^ is referred to A, that of , /^ ; the observed eye is placed at the side of the box opjx)site to C. When a candle is held in front of the prisms, b and ^', three pairs of images are seen in the observed eye. Ask the person to accommodate for a distant object, and note the position of the images. On pushing up the slide C witli a pin attached to it, and asking him to accommodate for the pin, ;. f., for a near object, the position and size of the middle images chiefly will be seen to alter as described above.] 2. In consequence of the increased curvature of the lens during accommodation for a near object, the refractive indices within the eye must undergo a change. According to v. Helmhoitz, the annexed measurements obtain in nega- tive and jjositive accommodation respectively. 3. Lateral View of the Pupil. — If the passive eye be looked at from the side, we observe only a small black strip of the pupil, which becomes broader as soon as the person experimented on accommodates for a near object, as the whole pupil is pushed more forward. 4. Focal Line. — If light be admitted through the cor- nea into the anterior chamber, the " focal line " formed by Phakoscope of Helmhoitz. '^^ concave surface of the cornea falls upon the iris. If the experiment be made upon a person whose eye is accom- modated foradistant object, so that the line lies near the margin of the pupil, it gradually recedes Accommodation. iNegative — Mm. Positive — Mm Radius of the cornea, Radius of anterior surface of lens, Radius of posterior surface of lens Position of the vertex of the outer surface of the lens behind the 1 vertex of the cornea J Position of the posterior vertex of the lens, Position of the anterior focal point, Position of the first principal point, Position of the second principal point, Position of the posterior focal point behind the anterior vertex of) the cornea J 8 8 10 6 6 5-5 3-6 3-2 7.2 7.2 12.9 11.24 1.94 2.03 6.96 6.51 22.23 20.25 toward the scleral margin of the iris, as soon as the person accommodates for a near object, because the iris becomes more oblique as its inner margin is pushed forward. 5. Change in Size of Pupil. — On accommodating for a near object, the pupil contracts, while in accommodation for a distant object, it dilates (Descartes, 1637). The contraction takes place slightly after the accommodation [Do/u/ers). This phenomenon may be regarded as an asso- ciated movement, as both the ciliary muscle and the sphincter pupiilce are supplied by the oculomo- torius (^. 345. 2, 3). A reference to Fig. 533 shows that the latter also directly supports the ciliary muscle; as the inner margin of the iris passes inward (toward r), its tension tends to be propagated to the ciliary margin of the choroid, which also must pass inward. The ciliary processes are made tense, chiefly by the ciliaiy muscle (tensor choroidse). Accommodation can still be performed, even though the iris be absent or cleft. 6. Internal Rotation of the Eye. — On rotating the eyeball inward, accommodation for a near object is performed involuntarily. As rotation of both eyeballs inward takes place when the axes of SCHEINER S EXPERIMENT. 803 Fig. 537. vision are directed to a near object, it is evident that this must be accompanied involuntarily by an accommodation of the eye for a near object. 7. Time for Accommodation. — A person can accommodate from a near to a distant object (which depends upon relaxation of the cihary muscle) much more rapidly than conversely, from a distant to a near object ( Vierordi, Aeby). The process of accommodation requires a longer time, the nearer the object is brought to the eye ( Vierordi, Volckers and Hensen). The time necessary for the image reflected from the anterior surface of the lens to change its place during accommodation is less than that required for subjective accommodation {^Aiibei-t and Angelucci). 8. Line of Accommodation. — When the eye is placed in a certain position during accommoda- tion, we may see not one point alone distinctly, but a whole series of points behind each other. Czerm^ak called the line in which these points lie the line of accotnmodation. The more the eye is accommodated for a distant object, the longer does this line become. All objects placed at a greater distance from the eye than 60 to 70 metres appear equally distinct to the eye. The line becomes shorter the more we accommodate for a near object — i. e., when we accommodate as much as possi- ble for a near object, a second point can only be seen indistinctly at a skori distance behind the object looked at. 9. The nerves concerned in the mechanism of accommodation are referred to under Oculomotoritis {I 345, and again in I 704). Scheiner's Experiment. — The experiment which bears the name of Scheiner (1619) serves to illustrate the refractive action of the lens during accommodation for a near object, as well as for a distant object. Make two small pin holes (S, d^ in a piece of cardboard (Fig. 537, K, Kj), the holes being nearer to each other than the diameter of the pupil. On look- ing through these holes, S, d, at two needles (/ and r) placed behind each other, then on accommodating for the near needle (/) the far needle (r) becomes double and in- verted. On accommodating for the near needle (/), of course the rays proceeding from it fall upon the retina at the focus (a) 'i while the rays coming from the far needle (r) have already united and crossed in the vitreous humor, whence they diverge more and more and form two pictures (^/'O ^'^ ^^ retina. If the right\\o\^ in the cardboard (^) be closed, the left picture on the retina (r^^) of the double images of the far needle disappears. An analogous result is obtained on accommodating for the far needle (R). The near needle (P) | gives a double image (P^, P^^), because the rays from it have not yet come to a focus. On closing the right hole {d^, the right double image (P^) disappears (Forterjieid). When the eye of the observer is accommo- dated for the near needle, on closing one aperture the double image of the distant point disappears on that side ; but if the eye is accommodated for the distant needle, on closing one hole the crossed image of the near needle disappears. 388. REFRACTIVE POWER OF THE EYE— ANOMALIES OF REFRACTION. — The limits of distinct vision vary very greatly in different eyes. We distinguish the far point [p. r., punctum remotum] and the near point [p. p., punctum proximum] ; the former indicates the distance to which an object may be removed from the eye, and may still be seen distinctly ; the latter, the distance to which any object may be brought to the eye, and may still be seen distinctly. The distance between these two points is called the range of accommodation. The types of eyeball are characterized as follows: — K P. •• '■" R, Scheiner's Experiment. 804 EMMETROPIC AND MYOPIC EYES. I. The normal or emmetropic eye is so arranged when at rest that parallel rays (Fig. 538, r, r) coming from tlie most distant objects can be focused on the retina (r,). The /?r point, therefore, is = 00 (infinity). When accommodating as much as possible for a near object, whereby the convexity of the lens is increased (Fig. 538, a) rays from a luminous point placed at a distance of 5 inches are still focused on the retina, ;". e., the near ^'^'* 53°- /o/fi/ is =r 5 inches (i inch = 27 mm.). The range of accommoda- tion, or \_"//ie range of distinct vision^^\ therefore, is from 5 inches (10-12 cm.) to 00. 2. The short-sighted, myopic eye (or long eye) cannot, when at rest, bring parallel rays from infinity to a focus on the retina (Fig. 539). These rays decussate within the vit- reous humor (at O), and after cross- ing form diffusion circles upon the retina. The object must be removed from \k\e passive eye to a distance of 60 to 1 20 inches (to/), in order that Condition of refraction in the nox\n^\ passive eye and during ^J^g raVS maV be foCUSCd On the retina. The passive myopic eye, therefore, can only focus divergent rays upon the retina. The far point, therefore, lies abnormally near. With an intense effort at accommodation, objects at a dis- tance of 4 to 2 inches, or even Fig. 539. less, from the eye may be seen distinctly. The fwar point, therefore, lies abnormally near; the range of accommodation is diminished. Short-sightedness, or myopia, usually depeiuls u])on congenital, and frequently hereditary, elongation of the eyeball. This anomaly of the refractive media is easily corrected by using a diverging lens (con- Myopic Eye. cave), which makes parallel rays divergent, so that they can be brought to a focus on the retina. It is remarkable that most children are myopic when they are born. This myopia, however, depends upon a too-curved condition of the cornea and lens, and on the lens being too near the cornea. As the eye grows, this short-sightedness disappears. The cause of myopia in children is ascribed to the continued activity of Fig. .^^^ 540. the ciliary muscle in reading, writing, etc., or Ihe continued convergence of the eyeballs, whereby the external pressure upon the eyeball is in- creased. 3. The long-sighted, hyperme- tropic eye, hyperoptic (flat eye) when at rest, can only cause convergent rays to come to a focus on the retina (Fig. 540). Distinct images can only be formed when the rays proceeding from objects are rendered convergent by means of a convex lens, as parallel rays would come to a focus behind the retina (at/). All rays proceeding from natural objects are either divergent, or at most nearly -:~^^^f Hypermetropic Eye. THE POWER OR FORCE OF ACCOMMODATION. 805 parallel, never convergent. Hence, a long-sighted person, when the eye \% passive, i. e., is negatively accommodated, cannot see distinctly without a convex lens. When the ciliary muscle contracts, slightly convergent, parallel, and even slightly divergent rays may be focused, according to the increasing degree of the accom- modation. The far point of the eye is negative, the near point abnormally distant (over 8 to 80 inches), while the range of accommodatio7i is infinitely great. The cause of hypermetropia is abnormal shortness of the eye, which is generally due to imperfect development in all directions. It is corrected by using a convex lens. [Defective Accommodation. — In the presbyopic eye, or long-sighted eye of old people, the near point is further away than normal, but the far point is still unaffected. In such cases, the person cannot see a near object distinctly, unless it be held at a considerable distance from the eye. It is due to a defect in the mechanism of accommodation, the lens becoming somewhat flatter, less elastic, and denser with old age, while the ciliary muscle becomes weaker. In hyperme- tropia, on the contrary, the mechanism of accommodation may be perfect, yet from the shape of the eye the person cannot focus on his retina the rays of light from a near object. In presbyopia the range of distinct vision is diminished. The defect is remedied by weak convex glasses. The defect usually begins about forty-five years of age.] Estimation of the Far Point — Snellen's Types. — In order to determine the yh:r/(?zW of an eye, gradually bring nearer to the eye objects which form a visual angle of 5 minutes [e.g., Snellen's small-type letters, or the 7nedium type, 4 to 8, of Jaeger), until they can be seen distinctly. The distance from the eye indicates the far point. In order to determine the far point of a tnyopic person, place at 20 inches distant from the eye the same objects which give a visual angle of 5 minutes, and ascertain the concave lens which will enable the person to see the objects distinctly. To estimate the near point, bring small objects {e.g., the finest print) nearer and nearer to the eye, until it finally becomes indistinct. The distance at which one can still see distinctly indicates the far point. Optometer. — The optometer may also be used to determine the near a.ndi far points. A small object, e.g., a needle, is so arranged as to be movable along a scale, along which the eye to be investigated can look as a person looks along the sight of a rifle. The needle is moved as near as possible, and then removed as far as possible, in each case as long as it is seen distinctly. The distance of the near and far point and the range of accommodation can be read off directly upon the scale [Graefe). 389. FORCE OF ACCOMMODATION. — Force.— The range of accommodation, which is easily determined experimentally, does not by itself determine the proper power or force of accom- modation. The measure of the latter depends upon the mechanical work done by the muscle of accommodation, or the ciliary muscle. Of course this cannot be directly determined in the eye itself. Hence, this force is measured by the optical effect, which results in consequence of the change in the shape of the lens, brought about by the energy of the contracting muscle. In the normal eye, during the passive condition, the rays coming from infinity, and therefore parallel (which are dotted in Fig. 541), are focused upon the retina at _/". If rays coming from a distance of 5 inches (p. 806) are to be focused, the whole available energy of the ciliary muscle must be brought into play to allow the lens to become more convex, so that the rays may be brought to a focus 2X f The energy of accom- modation, therefore, produces an optical effect in as far as it increases the con- vexity of the anterior surface of the passive lens (A), by the amount indi- cated by B. Practically, we may regard the matter as if a new convex lens (B) were added to the existing convex lens (A). What, therefore, must be the focal distance of the lens (B), in order that rays coming from the near point (5 inches) may be focused upon the retina at/? Evidently, the lens B must make the diverging rays coming from/, parallel, and then A can focus them at/. Convex lenses cause those rays proceeding from their: focal points to pass out at the other side as parallel rays (| 385, I). Hence, in our case, the lens must have a focal distance of 5 inches. The normal eye, therefore, with Fig. 541. 806 SPECTACLES. ihe far point = oc , and the near point = 5 inches, has a ]io\ver of accommodation equal to a lens of 5 inches focal distance. When the lens by the energy of accommodation is rendered more powerfully refractive, the increase (B) can readily be eliminated l)y placin}^ before the eye a concave lens which possesses exactly the opjiosite optical effect of the increxse of accommodation (H). Hence, it is possii)le to indicate the jwwer (force) of accommodation of the eye by a lens of a definite focal distance, /. e., by tlie optical effect produced by the latter. Therefore, according to Doiulers, the measure of the force of accommodation of the eye is the reciprocal value of the focal distance of a concave lens, which, when placed before the accommodated eye, so refracts the rays of light coming from the near jioint (/>) as if they came from the far ]ioint. Example. — We may calculate the force of the accommodation according to the following formula: ^ ^ , ;. €., the force of accommodation, expressed as the dioptric value of a lens (of j«r inch X p r focal distance), is equal to the difference of the reciprocal values of the distances of the near point (/>) and of the far point (r) of the eye. In the emmetropic eye, as already mentioned, /> ^ 5, r = 00 . Its force of accommodation is therefore = , so that jc = 5, i. e,, it is equal to a lens of 5 X p a III. inches focal distance. In a myopic eye,/ = 4, r = 12, so that -= , t. e., x ^ 6. In X 4 I ^ another myopic eye, with /^ 4 and r= 20, then jr = 5, which is a normal force of accommodation. Hence, it is evident that two different eyes, possessing a very different ran^e of accommodation, may nevertheless have the svivat force of accommodation. Example. — The one eye has/ ^4, r z^ao , the other, / = 2, r = 4. In both cases, - = , so that the force of accommodation of both eyes X 4 is equal to the dioptric value of a lens of 4 inches focal distance. Conversely, two eyes may have the same range of accommodation, and yet their force of accommodation be very unequal. Example. — The one eye has / = 3, r ^ 6 ; the other / = 6, r = 9. Both, therefore, have a range of accommodation of 3 inches. P'or these, the force of accommodation, - z= -,x=^6; and i = J —Ijc—lS Jr 3 6 X 6 9 ' Relation of range to force of accommodation. — The general law is, that, the ranges of accommodation of two eyes being eciually great, then \\\€\x forces of accommodation are eriual, ])ro- vided that their near points are the same. If the rrtw^'^ of accommodation for both eyes are equally great, but their near jioints unequal, then the forces of accommodation are also unequal — the latter being greater in the eyes with the smallest near point. This is due to the fact that every difference of distance near a lens has a much greater effect upon the image as compared with differences in the distance y(zr from a lens. The emmetropic eye can see distinctly objects at 60 to 70 metres, and even to infinity, without accommodation. While/ and r may he directly estimated in the emmetropic and myopic eyes, this is impossible with the hj-permetropic (long-sighted) eye. The far point in the latter is negative; indeed, in very pronounced hypermetropia even the near point may l)e negative. The far point may be estimated by making the hypermetropic eye practically a normal eye by using suitable convex lenses. The relative near jx)int may then be determined by means of the lens. Even from the 15th year onward, the power of accommodation is generally diminished for near objects— perhaps this is due to a diminution of the elasticity of the lens [Donders). 390. SPECTACLES. — The focal distance of concave (diverging), as well as convex (converg- ing), spectacles, depends upon the fefractive index of the glass (usually 3:2), and on the length of the radius of curvature. If the curvature of both sides of the lens is the same (biconcave or bicon- vex), then, with the ordinary' refractive index of glass, the focal distance is the same as the radius of curvature. If one surface of the lens is plane, then the focal distance is twice as great as the radius of the spherical surface. Spectacles are arranged according to \ht\r focal distance in inches, but a lens of shorter focal distance than I inch is generally not used. They may also be arranged according to their refractive power. In this case, the refractive power of a lens of i inch focus is taken as the unit. A lens of 2 inches focus refracts light only half as much as the unit measure of i inch focus; a lens of 3 inches focus refracts ^^ as strongly, etc. This is the case l^oth with convex and concave lenses, the latter, of course, having a negative focal distance; thus, " concave — ^," indicates that a concave lens diverges the rays of light one eighth as strongly as the concave lens of I inch (negative) focal distance. Choice of Spectacles. — Having determined the near point in a myopic eye, of course we require to render parallel the divergent rays coming from the far point, just as if they came from infinity. This is done by selecting a concave lens of the focal distance of the far i)oint. The greatest distance is the far point of the emmetropic eye. Suppose a myopic eye with a far point of 6 inches, then such a person requires a concave lens of 6 inches focus to enalile him to see distinctly at the greatest distance. Thus, in a myopic eye, the distance of the far point from the eye is directly equal to the focus of the (weakest) concave lens, which enables one to see distinctly objects at the greatest distance. These lenses generally have the same number as the spectacles required to correct the DIOPTRIC CHROMATIC ABERRATION, 807 defect. Example. — A myopic eye with a far point of 8 inches requires a concave lens of 8 inches focus, i. e., the concave spectacles No. 8. For the hypermetropic (long-sighted) eye, the focal distance of the strongest convex lens, which enables the hypermetropic eye to see the most distant objects distinctly, is at the same time the distance of the far point from the eye. Example. — A hypermetropic eye which can see the most distant objects with the aid of a convex lens of I2 inches focus has a far point of I2 ; the proper spectacles are convex No. I2. [Diopter or Dioptric. — The focal length of a lens used to be expressed in inches; and as the unit was taken as i inch, necessarily all weaker lenses were expressed in fractions of an inch. In the method advocated by Bonders, the standard is a lens of a focal distance of i metre (39.370 English inches, about 40 inches), and this unit is called a dioptric. Thus, the standard is a weak lens, so that the stronger lenses are multiples of this. Hence, a lens of 2 dioptrics = one of about 20 inches focus; 10 dioptrics = 4 inches focus; and so on. The lenses are numbered Irom No. I, i. e., I dioptric onward. It is convenient to use signs instead of the words convex and concave. For convex the sign pbcs -\- is used, and for concave the sign mimts — . Thus a -\- 4.0 means a convex lens of 4 dioptrics, and a — 4.0 = a concave lens of 4 dioptrics.] In all cases of myopia or hypermetropia, the person ought to wear the proper spectacles. In a myopic eye, when the far point is still more than 5 inches, the patient ought always to wear spec- tacles; but generally the working distance, e. g., for reading, writing and for handicrafts, is about 12 inches from the eye. If the person desires to do finer work (etching, drawing), requiring the object to be brought nearer to the eye, so as to obtain a larger image upon the retina, then he should either remove the spectacles altogether or use a weaker pair. The hypermetropic person ought to wear his convex spectacles when looking at a near object, and especially when the illumination is feeble, because then, owing to the dilatation of the pupil, the diffusion circles of the eye tend to become very pronounced. It is advisable to wear at first convex spectacles, which are slightly too strong. Cylindrical lenses are referred to under Astigmatism. Spectacles provided with dull colored or blue glasses are used to protect the retina when the light is too intense. Stenopaic spectacles are narrow diaphragms placed in front of the eye, which cause it to move in a definite direction in order to see through the opening of the diaphragm. 391. CHROMATIC AND SPHERICAL ABERRATION, ASTIG- MATISM.— Chromatic Aberration. — All the rays of white light which undergo refraction are at the same titne broken up by dispersion into a bundle of rays which, Avhen they are received on a screen, form a spectrum. This is due to the fact that the different colors of the spectrum possess different degrees of refran- gibility. The violet rays are refracted most strongly ; the red rays least. A white point on a black ground does not form a sharp simple image on the retina, but many colored points appear after each other. If the eye is accommodated so strongly as to focus the violet rays to a sharp image, then all the other colors must form concentric diffusion circles, which become larger toward the red. In the centre of all the circles, where all the colors of the spectrum are superposed, a white point is produced by their mixture, while around it are placed the colored circles. The distance of the focus of the red rays from that of the violet in the eye = 0.58 to 0.62 mm. The focal distance for red is, according to v. Helmholtz, for the reduced eye, 20.524 mm.; for violet, 20.140 mm. Thus, the near and far points for violet light are nearer each other than in the case of red light ; white objects, therefore, appear reddish when beyond the far point, but when nearer than the near point they are violet. Hence the eye must accommodate more strongly for red rays than for violet, so that we judge red objects to be nearer us than violet objects placed at an equal distance (^Brilcke). Monochromatic, or Spherical Aberration. — Apart from the decomposition or dispersion of white light into its components — the rays of white light, proceeding from a point if transmitted through refractive spherical surfaces — we find that, before the rays are again brought to a focus the marginal ra.ys are more strongly refracted than those passing through the central parts of the lens. Hence, there is not otte focus, but many. In the eye this defect is naturally corrected by the iris, which, acting as a diaphragm, cuts off the marginal rays (Fig. 531), especially when the lens is most convex, when the pupil also is most contracted. In addition, the margin of the lens has less refractive power than the central substance; lastly, the margins of the refractive spherical surfaces of the eye are less curved toward their margins than the parts lying nearer to the optical axis. Compare the form of the cornea (p. 783) and the lens (p. 790). Imperfect Centring of the Refractive Surfaces. — The sharp projection of an image is some- what interfered with by the fact that the refractive surfaces are not exactly centred (^Brilcke). Thus, the vertex of the cornea is not exactly in the termination of the optic axis ; the vertices of both surfaces of the lens, and even the different layers of the lens itself, are not exactly in the optic axis. The variations, however, and the disturbances produced thereby are very small indeed. Regular Astigmatism. — When the curvature of the refractive surfaces of the eye is unequally great in its different meridians, of course the rays of light cannot be united or focused in one point. Generally, in such cases, the cornea is more curved in its vertical meridian and least in the horizontal 808 ASTIGMATISM. (as is shown by ophthalmometric measurements, p. 798). The rays passing through the vertical meridian come to a focus, y//'.f/, in a horizontal focal line; while the rays entering horizontally unite afterward in a vertical line. There is thus no common focus for the light rays in the eye; hence the name " astigmatism." The lens also is unequally curved in its meridians, hut it is the reverse of the cornea; consequently, a part of the inequality of the curvature of the cornea is thereby com- pensated, and only a part of it affects the rays of light. The emmetropic eye has a very slight degree of this inequality (normal astigmatism). If two very fine lines of equal thickness be drawn on white paper, so as to intersect each other at right angles, it will be found that, in order to see the horizontal line quite sharply, the paper must be brought slightly nearer to the eye than when we focus the vertical line. When the inequality of curvature of the meridian is considerable, of course exact vision is no longer possible. [Kig. 542 shows the efiect of an astigmatic surface on the rays of light. Let a d c dhs such a surface, and suppose diverging rays to proceed from /. The rays passing through c d come to a Fig. 542. Action of an astigmatic surface on a cone of light {Frost). focus at /j, while those passing through the vertical meridian are focused atyT,. The outline of the cone of rays between abed and f^_ varies, as shown in the figure. At a certain part it is oval, with its axis vertical, at another the long axis of the oval is horizontal, while at other places it is circular, or the rays are focused in a horizontal or vertical line.] Correction. — This condition is corrected by a cylindrical lens, /. e., a lens so cut as to be without curvature in one direction, while in the other direction (vertical to the former) it is curved. The lens is placed in front of the eye, so that the direction of its curvature coin- cides with the direction of least curvature of the eye [v. Hehnholtz, Knapp, Donders). The section Q. a b c y stimidation of the optic nerve itself (^Herbe7-t MayOjf 1852). This movement is a reflex act [the (T^^rt'w^ nerve being the optic and the e_ferentlhe oculomotorius ; the impulse is transferred from the former to the latter in a centre situated somewhere below the corpora quadrigemina (Fig. 544, C)]. The older observers locate the centre in the corpora quadrigemina, the recent observers in the medulla oblongata (p. 711). .5(?/^ pupils always react, although only one retina be stimulated ; generally under normal circumstances both contract to the same extent (Donders), owing to intercentral communication [coupling] of the two pupillo-constrict- ing centres. [This is called consensual contraction of the pupil.] After section of the optic nerve the pupil dilates, and subsequent section of the oculomotorius no longer produces any further dilata- tion [Knoll). 2. The centre for the dilator fibres of the pupil (pupillo-dilating centre) is excited by dysp- nxic blood (§ 367, 8). If the dyspncea ultimately passes into asphyxia, the dilatation of the pupil diminishes. Of course, if the peripheral dilating fibres (| 247,3) ['^-^'-jthe sympathetic nerve in the neck] be previously divided, this effect cannot take place, as the dyspnceic blood acts on the centre and not on the nerve fibres. 3. The centre, as well as the subordinate " cilio-spinal region " of the spinal cord (§ 362, i), is also capable of being excited refiexly ; painful stimulation of sensory nerves, in addition to causing protrusion of the eyeballs (| 347), a fact proved in the case of persons subjected to torture, produces dilatation of the pupils {Arndt, Bernard, Westphal, Luchsingei-) ; while a similar effect is caused by labor pains, a loud call in the ear, stimulation of the nerve5 of the sexual organs, and even by sligtit tactile impressions (Fod and Schiff). According to Bechterew, the foregoing results are due to inhi- bition of the light reflex in the sense expressed in \ 361, 3. 4. The condition of the blood vessels of the iris influences the size of the pupil ; all conditions causing injection or congestion of these vessels contract the pupil, all conditions diminishing them dilate it. The pupil, therefore, is contracted by forced expiration, which prevents the return of venous blood from the head, momentarily by evtry pulse-beat, owing to the diastolic filling of the arteries; diminution of the ititraoctdar pressure, e.g., after puncture of the anterior chamber, because, owing to the diminished intraocular pressure, there is less resistance to the passage of blood into the blood vessels of the iris [Hensen and Volckers); paralysis of the vasomotor fibres of the iris (| 347, 2). Conversely, the pupil is dilated by conditions the reverse of those already mentioned, and also by strong muscular exertion, whereby blood flows freely into the dilated muscular blood vessels ; also,when 810 ACTION OF DRUGS ON THE I'UPIL. ¥u:. 544. death lakes place. The condition of the filHng of the hlood vessels also explains tho fact that the pupil dilated with atropin becomes smaller when a part of the sympathetic in tlie upper cervical ganglion, carrying the vasomotor fibres of the iris, is excised ; also, that after extirpation of this gan- gli'in, atro[)in always causes a loss diminution of the jiujiil on this side. The fact that when the pupil is already tlilated by stimulation of the sympathetic, it is further dilated byatro])in, is due to a dimin- isheistein and Dogiel). Stimulation near the centre of the cornea contracts the i)upi! {E. II. IVeber). In addition, we must assume that the iris itself contains elements that iniluencc the diameter of the pupil {Sig. Alayer and Pribram). Our knowledge of the action of poisons on the iris is still very obscure. Those sutwtances which dilate the pupil are called mydriatics, e.g., atropin, homa- tropin, duboisin,dalurin, and hyoscyamin. They act chiefly by paralyzing the oculomotorius. But, in addi- tion, there must be also an effect upon the dilating fibres for after complete paralysis (section) of the ocu- lomotorius, the wo(j'i?rrt'/^ dilatation of the pupil thereby produced [\ 345, 5) is still further increased by atropin. Minimal doses of atropin contract the pupil, owing to stimulation of the pupillo-constrictor filires; enormous doses cause moderate dilatation of the pupil in con- sequence of paralysis of the dilating as well as of the constricting nerve fibres. Atropin acts after destruc- tion of the ciliary [ophthalmic] ganglion [Hensen and Volekers) [and division of all the nerves except the optic], and in the excised eye [De Riiyter), (so that atropin is a local mydriatic. In moderate do.ses it paralyzes the nervous terminations of the 3d nerve (but not in birds whose iris contains striped mu.scle),andin larger doses it also paralyzes the muscular fibres]. [Cocaine, or cocaine, is obtained from the leaves of Erythroxylon coca. When applied locally it acts as a powerful local anaesthetic, and hence it is very useful for operations about the mucocutaneous orifices. A 4 per cent, solution dropped into the eye produces complete insensibility of the cornea in a few minutes. It causes dila- tation of the pupils, though they react to light and to the movements of accommodation. It also causes temporary paralysis of accommodation, a sensation of heaviness and coldness of the eyeball, enlargement of the palpebral fissure, constriction of the small peripheral vessels, and slight lachry- mation. Myotics are those substances which contract the pupil : Physostigmin (= Eserin, the alkaloid of Calabar bean), nicotin, pilocarpin, muscarin, morphia, according to some observers {Griinhagen) cau>e stimulation of the oculomotorius, while others say they paralyze the sympathetic. As these substances cause spasm of the ciliary muscle, it is suppo.sed that the first of these has an analogous action on the sphincter. It \s probable that they paralyze the dilator fibres and stimulate the oculo- Schemeof the nerves of the iris. B, centrum optici ; C, oculomotor centre ; D, dilator centre (spinal); E, iris ; G, optic nerve ; H, oculomoior (sphinc- ter) roots ; 1, sympathetic (dihttor) ; K, L, an- terior roots: M, N, O, posterior roots; A, seat of lesion, causing pupillary immobility ; * prob- able seat of lesion, causing myosis. GORHAM S PUPIL PHOTOMETER. 811 motor fibres. [Among local myotics, i. e., those which act on the eye, some act on the muscular fibres of the iris, e. g., physostigmin or eserin, while others act on the peripheral terminations of the 3d nerve, e.g., pilocarpin, muscarin. Muscarin causes very great contraction of the pupil from spasm of the circular fibres, due to its action on the 3d nerve; eserin, on the other hand, although contract- ing the pupil, also affects the dilator fibres. The contraction of the pupil due to opium is central in its cause.] If the one pupil be contracted or dilated by these substances, the other pupil, conversely, is dilated or contracted, owing to the change in the amount of light admitted into the eye into which the poison has been introduced. The anaesthetics (ether, chloroform, alcohol, etc.), when they begin to cause stupor, contract the pupil, and when their action is intense they dilate it [Dogiel). Chloroform dur- ing the stage when it causes excitement (preceding the narcosis), stimulates the centre for the dilata- tion of the pupil ; after a time this centre is paralyzed, so that the pupil no longer dilates on the application of external stimuli. Thereafter the pupilloconstrictor centre is stimulated, whereby the pupil may be contracted to the size of a pin's head ; ultimately this centre is paralyzed, and the pupil becomes dilated. Time for Movements of Iris. — The reflex dilatation of the pupil occurs slightly later than the reflex contraction, the time in the two cases being 0.5 and 0.3 second respectively, after stimulation by light {v. Vintschgaii). A certain time always elapses, until the iris, corresponding to the strength of the stimulus of light exciting the retina, " adapts" itself to produce a suitable size of the pupil [Aubert). Contraction of the pupil occurs very rapidly after stimulation of the oculomolorius in birds; in rabbits 0.89 second elapses after stimulation of the sympathetic, until the dilatation begins {Arli). Excised Eye. — Light causes contraction of the pupil in the excised eye of amphibians and fishes [Arnola). Even the iris of the eel, when cut out and placed in normal saline solution, contracts to Fig. 545. Fig. 546. Gorham's pupil photometer. Fig. 545 shows the disk with a slot and two holes. Fig. 546 gives a side view with the diameter of the pupil marlied on it. The upper end is closed by the disk, while the lower end is open. light [Arnold), the green and blue rays being most active. Increase of the temperature causes mydriasis in the excised eye of the frog or eel, while cooling causes myosis (//. Mi'dler). [Size of the Pupil. — Jonathan Hutchinson recommends a pupilometer, consisting of a metal plate perforated with a series of holes of different sizes. The smallest hole measures about ^^Jof aline, and the largest is 41^ lines. The plate is placed just below the patient's eye, and the hole is selected which corresponds with the size of the pupil.] [Gorham's Pupil Photometer. — This ingenious instrument may be used as a pupilometer, and also as a photometer. It consists of apiece of bronzed tubing 1.9 in. long and 1.5 in. diameter (Figs. 545 and 546). One end is closed by a disk or cap, which is pierced in its radii by a series of holes at distances varying from .05 m. to .28 ?n. There is a slot in the cap which allows one pair of holes to be visible at a time, while on the cyhnder is engraved the linear distance of each pair of holes. In using the instrument as a pupilometer, look through the open end of the tube (the bot- tom in Fig. 546), with both eyes open, toward a sheet of white paper or the sky, when two disks of light will be seen. Then revolve the lid or cap slowly until the two white A\sks just touch one another at their edges. The decimal fraction opposite the two apertures seen on the scale outside indicates the diameter of the pupil in looths of an inch. When using it as a photometer, it is assumed that the size of the pupil gives an index of the intensity of the amount of light which influ- ences the diameter of the pupil.] Intraocular Pressure. — The movements of the iris are always accompanied by variations of the intraocular pressure. The muscles of the iris affect the intraocular pressure, in that the dilatation of the pupil increases it, while contraction of the pupil diminishes it. The increased or diminished tension can be felt when two fingers are pressed on the eyeball. Stimulation of the sympathetic increases, while its section diminishes the pressure. Action of Drugs. — Atropin dropped into the 812 ENTOPTICAL PHENOMENA. eye, after producing a short temporary diminution of the tension, increases it; eserin, after a primary increase, causes a Jiniinution of the pressure [Griist-r uiui J/o/zkt-). 393. ENTOPTICAL PHENOMENA.— Entoptical phenomena de- pend upon the perception of objects present within the eyeball itself. I. Shadows are formed upon the retina by different opaque bodies. In orderto see them in one's own eye, proceed thus : I>y means of a strong convex lens project a small image of a flame upon a paper screen, prick a small opening through the image of the Hame, and place one eye at the other side of the screen, so that the illuminated puncture lies in the anterior focus of the eye, ;. e., al)Out 13 mm. in front of the cornea. As the rays proceeding from this point pass parallel through the media of the eye, a diffuse bright field of vision, surrounded by the black margins of the iris, is obtained. All dark bodies which lie in the course of the rays of light throw a shadow upon the retina, and appear as specks. There are various forms of these shadows (Fig. 547) : — (a) The spectrum mucro-lacrimale, especially upon the margin of the eyelids, depending upon particles of mucus, fat globules from the Meibomian glands, dust mixed with tears, causing cloudy or drop-like retinal shadows, which are removed by winking. (b) Folds in the cornea. — If the cornea be pressed laterally with the finger, wrinkled shadows, due to temporary w rinkles in the cornea, are produced. (c) Lens shadows. — IJead-like or dark specks, bright and star-like figures, the former due to deposits on and in tlie lens, the latter to the radiate structure of the lens. (d) Muscae volitantes (T)echales, 1690), like strings of beads, circles, groups of balls or pale stripes, depend upon opaque particles (cells, disintegrating cells, granular fibres) in the vitreous humor. They move about when the eye is moved rapidly. I.istmg (1845) showed that one may determine pretty accurately the position of these objects. While making the observation upon one's own eyes, raise or depress the source of light ; those shadows which are caused by bodies on a level Entoptical shadows with the pupil retain their relative positions in the bright fields of vision. Shadows which appear to move in the same direction as the source of light are caused by bodies which lie in front ol\\i& plane of the pupil — those, however, which appear to move in the opposite direction depend upon objects behind the plane of the pupil. 2. Purkinje's figure (1819) depends upon the blood vessels within the retina, which cast a shadow upon the most external layer of the retina, viz., upon the rods and cones, these being the parts acted upon by light. In ordinary' virion we do not observe these shadows. According to v. Helmholtz, this is due to the fact that the sensibility of the shaded parts of the retina is greater, and their excitability is less exhausted, than ail the other parts of the retina. .\s soon, however, as we change the position of the shadow of the blood vessels, instead of being directly behind, so that the blood vessels come to lie more laterally and behind them, i. ^.,upon places which do not receive shadows from the blood vessels when the rays of light pass through the eye in the ordinary way, then the figure of the blood vessels becomes apparent at once. All that is necessary is to cause the light to enter the eyeball obliquely. Method. — (l) This may be done bypassing an intense light through the sclerotic, e.g., by throwing upon the sclerotic a small, bright, luminous image from a source of light. On moving the source of light, the figure of the blood vessels moves in the same direction. (2) Look directly upward to the sky, wink with the upper eyelid drooping, so that for a moment, corre>ponding to the act of winking, rays of light enter obliquely the lowest part of the pupils. (3) Look through a small aperture toward a bright sky, and move the aperture rapidly to and fro, so that from both sides of the blood vessels shadows fall rapidly upon the nearest series of rods and cones. (4) In a darkened room look straight ahead, and move a light to and fro close under the eyes. Occasionally, while performing this experiment, one may see the macula lutea as a non-vascular shaded depression, and, owing to the inversion of the objects, it lies on the inner side of the entrance of the optic nerve. ENTOPTICAL PHENOMENA. 813 3. Movements of the blood corpuscles in the retinal capillaries. — On looking, without accommodating the eye, toward a large bright surface, or through a dark blue glass toward the sun, we see bright spots, like points, formmg longer or shorter chains, moving in tortuous paths. The phenomenon is, perhaps, caused by the red blood corpuscles (in the capillaries posterior to the exter- nal granular layer) acting as small light collecting concave disks, concentrating the light falling upon them fiom bright surfaces, and throwmg it upon the rods of the retina. Each corpuscle must be in a special position ; should it rotate, the phenomenon disappears. Vierordt, who projected the move- ment upon a screen, calculated, from the velocity of their motion, the velocity of the blood stream in the retinal capillaries as equal to 0.5 to 0.75 mm. in a second, which corresponds very closely with the results obtained directly in other capillaries by E. H. Weber and Volkmann (^ 90, 4). When the carotids are compressed, the movement is slower on freeing them from the compression ; during short forced expirations the movement is accelerated (^La7tdois). 4. The entoptical pulse (^ 79, 2) depends upon the pulsating arteries irritating mechanically the rods lying outside them. 5. Pressure Phosphenes. — Pressure applied to the eye causes a series of phenomena : (a) Par- tial pressure upon the eyeball causes the so-called illuminated " pressure picture " ox phosphene, which was known to Aristotle. As the impression upon the retina is referred to something outside the eye, the phosphene is always perceived on the side of the field of vision opposite to where the pressure affects the retina, f. ^., pressure upon the outer surface of the eyeball causes the flash of light to appear on the inner side. If the retina is not well lighted, the phosphene appears luminous ; if the retina is well lighted, it appears as a dark speck, within which the visyal perception is momentarily abolished, (li) If a uniform pressure be applied to the eyeball continuously from before backward, as Purkinje pointed out, after some time there appear in the field of vision very sparkling variable figures, which perform a wonderful fantastic play, and often resemble the sparkling effects obtained in a kaleidoscope [y. Hehnholtz), and are probably comparable to the feeling of formication produced by pressure upon sensory nerves (" sleeping of the limbs "). [c) By applying equable and continued pressure, Steinbach and Purkinje observed a network with moving contents of a bluish-silvery color, which seemed to correspond to the retinal veins. Vierordt and Laiblin observed the branching of the blood vessels of the choroid &% a red network upon a black ground, [d) According to Houdin, we may detect the position of the yellow spot by pressure upon the eyeball. 6. The entrance of the optic nerve may be detected on moving the eye rapidly backward, and especially inward, as a fiery ring or semicircle about the size of a pea. Probably, owing to the movement of the retina, the entrance of the optic nerve is stimulated mechanically by the rapid bending. Purkinje and others observed that the ring remained persistent on turning the eye strongly inward. If the retina be brightly illuminated, the ring appears dark, and when the field of vision is colored, the ring has a different tint. If Purkinje's figure be produced at the same time, one may observe that the vascular trunk proceeds from this ring — a proof that the ring corresponds to the entrance of the optic nerve i^Landois). 7. Accommodation Spot. — On accommodating the eye strongly toward a white surface, there appears in the middle a small, bright, trembling shimmer, and in its centre a coarse brown speck, about the size of a pea, is seen [Ptirkinje). If pressure be applied externally to the eyeball, this speck becomes more distinct. After having once observed the phenomenon, occasionally on pressing laterally upon the opened eye we may see it as a bright speck in the field of vision — another proof that the intraocular pressure is increased during accommodation. 8. Mechanical Optical Stimulation. — On dividing the optic nerve in man, as in extirpation of the eyeball, a flash of light is observed at the moment of section by the person operated on. The section of the nerve fibres themselves is painless, but section of the sheaths is painful. 9. The accommodation phosphene is the occurrence of a fiery ring at the periphery of the field of vision, seen on suddenly bringing the eyes to rest after accommodating for a long time in the dark (^Purkinje'). The sudden tension of the zonule of Zinn resulting from the relaxation causes a mechanical stretching of the outermost part of the margin of the retina, or it may be of a part of the retina behind this. Purkinje observed the phenomenon after suddenly relaxing the pressure on the eye. 10. Electrical Phenomena. — Electrical currents, when applied to the eye, cause a strong flash of light over the whole field of vision. One pole of the battery may be placed on the under eyelid and the other on the neck. The flash at closing [making] the current is strongest with an ascend- ing current, that with opening [breaking] the current with a descending current. If a uniform con- tinuous ascending current be transmitted through the closed eyes, the dark disk of the elevation at the entrance of the optic nerve appears in a vi\\\iv^h.-violet field of vision ; with a descending current, the field of vision is reddish and dark, in which the position of the optic nerve appears light blue [y. Hehnholtz). If external colors are looked at simultaneously, these colors blend to form a violet or yellow with the colors looked at [Schelske). During the passage of the ascending current we see external objects indistinctly and smaller when the eyes are open; while with the descending current they are larger and more dis.inct (Riiter). Sometimes the position of the macula lutea appears dark on a bright ground, or the reverse, according to the direction of the current. If the current be opened [broken] the phenomena are reversed (| 335), and the eye soon returns to rest. 814 ILLUMINATION OF THE EYE. 11. The yellow spot appears sometimes as a dark circle when there is a uniform blue illumina- tion. In a strong light the position of the yellow spot is surrounded by a bright area, twice or thrice as large, called " Lowe's ring." [Clerk Maxwell's Experiment. — On looking through a solu- tion of chrome alum in a bottle or vessel with parallel gl.iss sides, we observe an oval ])urplish spot in the greenish color of the alum. This is due to the pigment of the yellow spot.] Haidinger's Brushes. — On directing the eye toward a source of polarized light, " Haidinger's polarized brushes " appear at the point of fixation. They are seen on looking through a Nicol's prism at a bright cloud (-'. Helinhollz). They are bright and bluish on a surface, bounded by two neighboring hyperbola on a white field ; the dark bundle separating them is smallest in the centre and yellow. Of the various colors of homogeneous light, blue alone shows the brushes [Stokes). According to v. Ilelmholtz, the seat of the phenomenon is the yellow spot, and is due to the yellow- colored elements of the yellow .spot being slightly doubly refractive, while at one part they absorb more, at another less, of the rays entering the eye. 12. Lastly, there are the visual sensations depending on internal causes, e. ;'., increased bound- ing of the blood through the retina, as during violent coughing, increased intraocular pressure. Stimulation of the visual areas {\ 378, IV) may produce spectra, which Cardanus (1550), Goethe, Kicolai, and Johannes Miiller could produce voluntarily. 394. ILLUMINATION OF THE EYE.— OPHTHALMOSCOPE. - The light which enters the eye is partly absorbed by the black uveal pigment, and partly again reflected from the eye, and always in the same direction in which the rays entered the eye. By placing one's self in front of the eye of another person, of course, the head, being an opaque body, cuts off a large number of rays. Owing to the position of the head, no rays of light can enter the eye ; and of course none can be reflected back to the eye of the observer. Hence, the eye of the person being examined always appears black, because those rays which alone Fig. 548. Arrangement for examining the eye of B. A, eye of observer ; .r, source of light ; S, S, plate of glass directed obliquely, reflecting light into B. could be reflected in the direction of the eye of the observer are cut off. As soon, however, as we succeed in causing rays of light to enter the eye at the same time and in the same direction in which we observe the eye of another person, the fundus of the eye appears brightly illuminated. The following simple arrangement is sufficient for the purposes (Fig. 548) : Let B be the eye of the patient, A that of the obser\-er, and let a flame be placed at x. The rays of light proceeding from X impinge upon the obliquely placed plate of glass (S, S), and are reflected in the direction of the dotted lines into the eye (B). The fundus of the eye appears in this position to be brightly illu- minated in diffusion circles around b. \% the observer (A) can .see through the obliquely placed glass plate (S, S), and in the same direction as the reflected rays (-v, j'), he sees the retina around b brightly illuminated. THE OPHTHALMOSCOPE. 815 In order that this method be made available for practical purposes, we must, of course, be able to distinguish the details, such as the blood vessels of the fundus of the eye, the macula lutea, the entrance of the optic nerve, abnormalities of the retina, and the choroidal pigment, etc. The follow- ing considerations show us how to proceed in order to accomplish this. As already mentioned, and Fig. 549. as Fig. 531 shows, a small inverted image is formed on the retina (c, d) when we look at an object (A, B) ; conversely, according to the same dioptric law, an enlarged inverted real image of a small distinct area of the retina (c, d — depending on the distance for which the eye was accommodated) must be formed outside the eye (A, B). Fig. 550. 5. If the fundus of this eye be sufficiently illuminated, this aerial image will be correspondingly bright. In order to see the individual parts of the retinal picture more distinctly, the observer must accom- modate his own eye for the position of this image. In such circumstances the eye of the observer would be too near the observed eye. His eye when so accommodated is removed from the eye of Fig. 551. the patient by his own visual distance, and by the visual distance of the patient. As this distance is considerable, the individual small details of the fundus cannot be seen distinctly. Further, owing to the contraction of the pupil of the patient, only a small area of the fundus can be seen, and this only under a small visual angle, quite apart from the fact that it is often impossible to accommodate for the real image of the fundus of the patient. 816 THE OPHTHALMOSCOPE. Hence, the eye of the observer must be brought nearer to the eye of the patient. This may be done in two ways: (l) Either by placing in front of the eye of the patient a slronfj conzrx lens (of I to 3 inches focus — Kig. 549, C). This causes the retinal image to be nearer to the eye (at H), owin.^ to the strong lens refracting the rays of light. 'Ihe observer (M) can come nearer to the eye, and can still accommodate for the image of the fundus of the eye. (2) Or a concave lens is l)laced immediately in front of the eye of the patient (Fig. 550, 0). The rays of light emerging from the eye of the patient (P) are ei'her made parallel by the concave lens (o), and are brought to a focus on the retina of the emmetropic observer (A) ; or, if the lens causes the rays to diverge (Fig. 551), an erect, virtual image is formed at a distance behind the eye of the patient (at R). In these cases, also, the observer can go much nearer to the eye of the patient. The ophthalmoscope invented by v. Heliiiholtz enables us to examine the whole of the fundus of the eye. [Direct Method. — Use a concave mirror of 20 centimetres focal distance, with a central opening. Reflect a beam of light into the patient's eye, where the rays cro-;s in the vitreous and illuminate the fundus of the eye. These rays again pass out of the eye and reach the observer's eye through the central hole in the mirror. If the observer be emmetropic they come to a focus on his retina. In this way all the parts of the retina are seen in their normal position, but enlarged. Hence, it is some- F:g. 553. The entrance of the optic nerve with the adjacent parts of the fundus of the normal eye. a, ring of connective tissue ; b, choroidal ring ; c, arteries ; d, veins ; g, divi- sion of the central artery ; h, division of the central vein; L, lamina cribrosa ; /, temporal (outer) side; n, nasal (inner; side. Morton's Ophthalmoscope. times called the examination of the upright image. The eye of the patient and observer must be at rest, i. e., be negatively accommodated, while the mirror must be brought as near as possible to the eye of the patient.] [Indirect Method, by which a more general view of the fundus is obtained. Throw the light into the patient's eye by an ophthalmoscopic mirror as above, but held at a distance of about 50 cm. (10 inches) from the patient's eye. Hold a biconvex lens of 14 dioptrics focal length vertically between the mirror and the patient's eye (Fig. 549), the observer looking through the hole of the minor. What he does see is an inverted aerial image at B. Only a small part of the fundus oculi can be seen at one lime.] [The ophthalmoscope, besides being used for examining the interior of the eyeball, is of the utmost use in determining the existence and amount of anomalies of refraction in the refractive media. I-'or this purpose an ophthalmoscope requires to be provided with f>!its and i/itntts lense^, which can be readily brought before the eye of the observer. This is readily done by an incienious mechanism devised by Couper, and made use of in the handy students' ophthalmoscope of Morton (Fig. 553). The lenses are moved by a driving wheel on the left figure, while at the same time is indicated at a certain aperture the lens presented at the sight hole. The instrument is also provided with a mov- RETINOSCOPY. 817 able arrangement carrying a concave mirror at either end. One of these mirrors is lo inches in focus, and is used for indirect examination and retinoscopy, while the other is of 3 inches focus for direct examination, and is fixed at an angle of 25°.] [Retinoscopy. — The ophthalmoscope is used also for this purpose. A beam of light is reflected into the eye by the ophthalmoscopic mirror, and the play of light and shade on the fundus oculi observed. A study of this is important in determining anomalies of refraction. P'or the method the student is referred to a text-book on " Diseases of the Eye."] [Artificial Eye. — The student may practice the use of the ophthalmoscope on an artificial eye, such as that of Frost (Fig. 554") or Perrin.] Illumination. — In oi'der to illuminate the interior of the eye, v. Helmholtz used several plates of glass, placed behind each other, in the position of S, S, in Fig. 548. Afterward he used a plane or concave mirror of 7 inches focus (Fig. 549), with a hole in the centre. Fig. 552 shows the appear- ance of the fundus of the eye, as seen with the ophthalmoscope. In albinos the fundus of the eye appears red, because light passes into the eye through the sclerotic and uvea, which are devoid of Fig. 554. Frost's Artificial Ej'e. Action of the Orthoscope. pigment. If a diaphragm be placed over the eye, so that the pupil alone is free, the eye appears black {Danders). Tapetum. — In many animals the eyes have a bright green lustre. These eyes have a special layer, the tapetum, or the membrane versicolor of Fielding ; in carnivora it consists of cells, in her- bivora of fibres, placed between the capillaries of the choroid and the stroma of the uvea. These structures exhibit interference colors and reflect much light, so that the colored lustre appears in the eye. Oblique illumination is used with advantage for investigating the anterior chamber. A bright beam of light, condensed by a convex lens, is thrown laterally upon the cornea into the eye, and so directed upon the point to be investigated as to illuminate it. A point so illuminated, e.g., a part of the iris, may be examined from a distance by means of a lens, or even by a microscope {Liebreich). The Orthoscope. — Czermak constructed this instrument, in which the eye is placed under water (Fig. 555). It consists of a small glass trough with one of its walls removed. The margins of the open side are pressed firmly against the region of the eye. The eye and its surroundings form, as it were, the sixth side of the trough, which is filled with water, so that the cornea is bathed therewith. As the refractive index of water is almost the same as the refractive index of the media of the eye, the 52 818 EXPERIMENTS ON THE RETINA. rays of light pass into the eye in a straight direction without being refracted. Hence, ol)jects in the anterior chamber can be seen directly, as if they were not within the eye at all. Another advantage is that ihe objects can be brought nearer to the eye of tlie ol)server. The rays of light emerging from the point (ject becomes indistinct, and finally disajijx;ars. The process of testini; is continued by placing the arc successively in the different meridians of the field of vision. [M'Hardy's perimeter is a very convenient form (Fig. 55S). It consists of two ujirights (C and D), which are fixed to the opposite ends of a tlat basal plate (A).' C carries an arrangement for sup- porting the patient's head, while D carries the automatic arrangement lor the perimetric record. Both of these can be raised or dei^ressed by the screws (Cj and /'). The patient's chin rests on tlie chin- rest (E), while in the mouth is placed Landoll's l)iting fixation (L), which is detachable. The posi- tion of the head can be altered by sliding F on L, which can be fixed in any position by the screw 'initu Horizontal section of the right eye. «, cornea; ^.conjunctiva; c, sclerotic; d, anterior chamber containing the aqueous humor ; e, iris ; _/"/', pupil ; g, posterior chamber; /, Petit's canal ; j, ciliary muscle ; k, corneo-scleral limit ; :, canal of Schlemm ; >«, choroid ; «, retina ; o, vitreous humor ; A'o, optic nerve ; y, nerve sheaths ; /, nerve-fibres ; /c, lamina cribrosa. The line O A indicates the optic axis ; S r, the a.\is of vision ; r, the posi- tion of the fovea centralis. (O). The porcelain button (I) just below the patient's eye (/) is connected with the adjustment of the " fixation point." The automatic recording apparatus consists of a revolving quadrant (>4, ^,), which describes a hemisphere round a horizontal axis passing through the centre of the hollow male axle, turning in the female end of a, which is supported by D. The quadrant can be fixed at any point by <>-. On the front concave surface of the quadrant is fixed a circular white piece of ivory, representing the " fixation point," from which a needle projects, and which is the zero of the instru- ment. A carriage (?'), in which the test objects are placed, can be moved in the concave face of the quadrant by means of the milled head (y), which moves the carriage by means of a tooth and pinion wheel.] PRIESTLEY SMITH S PERIMETER. Fig. 558. 821 M'Hardy's perimeter, I, porcelain button; M, bit; E, for fixing the head; ^, A, quadrant ; o, fixation point;/, pointer for piercing the record chart held in the frame {e) which moves on c ; D, upright supporting the quadrant and the automatic arrangement of slides (A and I), which are moved hyj. [When the milled head (j) is turned, it moves the carriage and two slides (/& and /), the two slides moving in the ratio of 2 to i. The rate of the carriage is so adjusted that it travels ten times faster than /, and five times faster than /e. The pointer (/) is con- nected with these slides, so that it moves when they move, and records its movements by piercing the record chart, which is fixed in the double-faced frame (f). The frame for the record chart is hinged near c to the upright (D). The frame, when upright, comes so near the pointer that the latter can pierce a chart placed in the frame. The patient is directed to look at the " fixation point," which is merely a small ivory button placed in the imaginary axis of the hemi- sphere on the front of the centre of the concave surface of the quadrant ; the projecting needle point (o) indi- cates its position. This is the zero of the quadrant, and on each side of it the quadrant is divided into 90°.] [In testing the field of vision, place the carriage so as to cover zero, adjust the eye for the fixation point, and look steadily at it, when, if all is right, the pointer ( p) ought to pierce the centre of the chart. Move the carriage along the quadrant by y until it disappears from the field of vision, and when it does so the pointer is made to pierce the chart. Make another observation in another direc- tion by altering the position of the quadrant, an'l go on doing so until a complete record is obtained Fig. 559. Priestley Smith's Perimeter. 822 PERIMETRIC CHARTS. of the field of vision. Test the other eye in the same way. The color field may he tested hy using colored papers in the carriasjc] [Priestley Smith's Perimeter (Fig. 559V — The wooden knob on the left of the figure is placed under the eye of the p.iticnt, who stares at the fixed jxjint in the axis of the (juadrant, which can be moved in any meridian. The test object is a square piece of white paper, which is moved along the quadrant The chart is placed on the posterior surface of the hand wheel and moves with it, so that the meridians of the chart move with the quadrant. There is a scale behind the hand wheel corre- sjiondinij with the circles on the chart, so that the observer can prick off his observations directly.] [Scotoma is tlic term applied to dimness or blindness in certain parts of the field of vision, which may be central, marginal, or in patches.] The capacity for distinguishing colors diminishes more rapidly at the periphery of the retina, than that for distinguishing differences in the brightness or intensity of light. In fact, the periphery of the retina is slightly red blind. The diminution is greater in the vertical meridian of the eye than in the horizontal, and it diminishes with the distance from the fixation point [Aubert and Fig. 560. Perimetric chart of a healthy and a diseased eye. Forster). These observers also state that, during accommodation for a distant object, the diminution of the capacity to distinguish brightness and color toward the periphery of the lens, occurs more rapidly than with near vision. The excitability of the retina for colors and brightness is greater at a point equally distant from the fovea centralis on the temporal than on the nasal side of the eye (Sf/ion). Perimetric Chart. — If the arc of the perimeter (Fig. 559) be divided into 90 degrees, beginning at the fixation point (central point), and proceeding to L and M (Fig. 560); and if a .series of concentric circles be inscribed on this, with the point of fixation as their centre, we can construct a topographical chart of the visual capacity of the normal or healthy eye from the data obtained by the examination of the retina. Fig. 560 is an example ; the i/izci lines indicate a diseased eye, the corresponding fkhi lines a healthy eye. The continuous line indicates the limits for the perception of white; the interrupted line that for blue; the punctuated and interrupted line that for red ; ;« is the blind spot. In the normal eye the limits for the perception of colors are as follows : — RETINAL STIMULATION OPTOGRAM. 823 Externally, Internally, Upward, . Downward, 7o°-88° 50°-6o° 45°-55° 650-70° Blue. 65° 60° 45° 60° Red. 60° 50° 40° 50° Green. 40° 40° 30°-35° 35° V. Specific Energy. — The rods and cones alone are endowed with what Johannes Miiller called '■'specific energy,'''' i. e., they alone are set into activity by the ethereal vibrations, to produce those impulses which result in vision. Mechan- ical 2s\^ electrical stimuli, however, when applied to any part of the course of the nervous apparatus, produce visual phenomena. Mechanical stimuli are more intense stimuli than light rays, as is shown by performing the dark-pressure figure with the eyes open (§ 393, 5, a), whereby the circulation in the retina is interfered with; in the region of pressure, we cannot see external objects which affect the retina uniformly and continuously. VI. The duration of the retinal stimulation must be exceedingly short, as the electrical spark lasts only 0.000000868 second ; still, as a general rule, a shorter time is required, the larger and brighter the object looked at. Alternate stimu- lation with light 17 to 18 times per minute, is perceived most intensely {Brilcke). Further, an increase or diminution of o.oi part of the intensity of the light is perceptible (§ 383). A shorter time is required to perceive yellow than is required for violet and red {yierorcW). The retina becomes more sensitive to light, after a person has been kept in the dark for a long time, and also after repose during the night. If light be allowed to act on the eyes for a long time, and especially if it be intense, it causes fatigue of the retina, which begins sooner in the centre than in the periphery of the organ (^AuberC). At first the fatigue comes on rapidly and afterward develops more slowly — it is most marked in the morning {A. Pick). The periphery of the retina is specially characterized by its capacity for distin- guishing movements (^Exner). VII. Visual Purple. — The mode of the action of light upon the end organs of the retina has already been referred to (p. 789) in connection with the " visual pu7'ple'''' or rhodopsin {Boll, Kiihne). Kiihne showed that, by illuminating the retina, actual pictures {e. g. the image of a window) could be produced on the retina, but they gradually disappeared. From this point of view we might regard the retina as comparable, to a certain extent, to the sensitive plate of a photographic apparatus. Optogram. — The visual purple is formed by the pigment epithelium of the retina. Perhaps we might compare the process to a kind of secretion. The visual purple may be restored in a retina by laying the latter upon living choroidal epithelium. The pigment disappears from the mammalian retina by the action of light 60 times more rapidly than from the retina of the frog. In a rabbit's eye, whose pupil was dilated with atropin, Ewald and Kiihne obtained a sharp picture or optogram of a bright object placed at a distance of 24 cm. from the eye — the image was " fixed " by a 4 per cent, solution of alum. Vibual purple withstands all the oxidizing reagents ; zinc chloride, acetic acid, and corrosive sublimate change it into a yellow substance — it becomes white only through the action of light ; the dark heat rays are without effect, while it is decomposed above a temperature of 52° C. [As visual purple is absent from the cones, and cones only are present in the fovea centralis, we cannot explain vision by optograms formed by the visual purple.] VIII. Destruction of the rods and cones of the retina causes corresponding dark spots in the field of vision. 396. PERCEPTION OF COLORS. — Physical. — The vibrations of the light ether are per- ceived by the retina only within distinct limits. If a beam of white light, e.g., from the sun, be transmitted through a prism, the light rays are refracted and dispersed, and a " prismatic spectrum " is obtained (Fig. 17). Whiite light contains rays of very different wave lengths or periods of vibration. The dark heat rays, whose wave length is 0.00194 mm., are refracted least {^Fizeau). They do not 824 PERCEPTION OF COLORS. act upon the retina, and are therefore invisible. They act, however, upon sensory nerves. Aoou. 90 per cent, of these rays is absorbed by the media of the eye [Briicl-e and Ktioblaticli). From Frauenhofer's line, A, onward, the oscillations of the light ether excite the retina in the following order: /iV(/ with 4S1 billions of vibrations per second, oram^e with ^t,2, ye/hmi with 563, ^v^fw with 607, l>liie with 653, indigo with 676, and violet with 764 billion vibrations per second. The sen- sation of color therefore depends on the number of vibrations of the light ether, just as the pitch of a note depends on the number of vibrations of the sounding body [A'ewton, 1704; Hartley, 1 772V Beyond the violet lie the chemically-active [actinic] rays of the spectrum. After cutting out all the spectrum, including the violet rays, v. Helmholtz succeeded in seeing the ultra'^violet rays, which had a feeble grayish-blue color. The heat rays in the colored part of the spectrum are trans- mitted by the media of the eye in the same way as through water. The existence of the ultra-violet rays is best ascertained by the phenomenon of fluorescence. \'on Helmholtz, on illuminating a solution of sulphate of quinine with the ultra-violet rays, saw a bluish-white light proceeding from all parts of the solution which were acted on by the ultra-violet rays. As the media of the eye themselves exhibit fluorescence {v. Helmholtz), they must increase the power of the retina to distin- guish these rays. The ultra-violet rays are not largely absorbed by the media of the eye [Briicke). In order that a color be perceived, it is essential that a certain amount of light fall upon the retina. Blue, when at the lowest degree of brightness, gives a color sensation with an amount of light which is sixteen times less than that required for red {Dobro~wloskyY Intensity of the Impression of Light. — ^Vhile light of different periods of vibration applied to the eye excites the different sensations of color, the amplitude of the vibrations (height of the waves) determines the intensity of the impression of light; just as the loudness of a note depends on the ampHtude of the vibrations of the sounding body. The sun's light contains all the rays which excite the sensation of color in us, and when all these rays fall simultaneously upon the retina we ex- perience the sensation of white. If the colors of the spectrum ol)tained by means of a prism be reunited, white light is again obtained. If no vibrations of the light-ether reach the retina, every sensation of light and color is absent, but we can scarcely apply the term black to this condition. It is rather the absence of sensation, such as, for example, is the case when a beam of light falls on the skin of the back. This does not give the sensation of black, but rather that of no sensation of light. Simple and Mixed Colors. — We distinguish simple colors, e. g., those of the spectrum. In order to perceive these, the retina must be excited (set into vibration) by a distinct number of oscillations (see above). Further, we distinguish "mixed colors," whose sensations are produced when the retina is excited by two or more simple colors, simultaneously or rapidly alternating. The most com- plex mixed color is white, which is composed of a mixture of all the simple colors of the sjjectrum. The " complementary colors" are important. Any two colors which together give the sensation of white are complementary to each other. The " con- trast colors" are mentioned here merely to complete the list. They are closely related to the complementary colors. Any two colors which, when mixed, supple- ment the generally prevailing tone of the light, are contrast colors. When the sky is blue, the two contrast colors must be bhiish-white : with bright gaslight they must be yellowish-white, and in pure white light of course all the complementary are the same as the contrast colors {^Briicke). Methods of Mixing Colors. — i. Two solar spectra are projected upon a screen, and the spectra are so arranged as to cause any one part of one spectrum to cover any part of the other. 2. Look obliquely through a vertically arranged glass plate at a color placed behind it. Another color is placed m front of the glass plate, so that its image is also reflected into the eye of the observer; thus, the light of one color transmitted through the glass plate and the reflected light from the other color reach the eye simultaneously. [Lambert's Method. — This is easily done by Lambert's method. Use colored wafers and a slip of glass ; place a red wafer on a sheet of black paper, and about 3 inches behind it another blue one. Hold the plate of glass midway and vertically between them, and so incline the glass that, while looking through it at the red wafer, a reflected image of the blue one will be projected into the eye in the same direction as that of the red image, when we have the sensation of purple], 3. A rotatory disk, with sectors of various colors, is rapidly rotated in front of the eyes. On rapidly rotating the colored disk, the impressions produced by the individual colors are united to produce a mixed color. If the rotating disk, which yields, let us suppose, white, on mixing the colors of the spectrum, be reflected in a rapidly rotating mirror, then the individual components of the while reappear. 4. Place in front of each of the small holes in the cardboard used for Scheiner's experiment GEOMETRICAL COLOR TABLE. 825 (Fig. 537) two differently colored pieces of glass ; the colored rays of light passing through the holes unite on the retina, and produce a mixed color [CzermaJi). Complementary Colors. — Investigation shows that the following colors of the spectrum are complementary, {. e., every pair gives rise to white : — Red and greenish-blue, Orange and Cyan blue. Yellow and indigo blue, ' Greenish-yellow and violet, while green has the compound complementary color, purple {v. Hehnholtz). The mixed colors may be determined from the following table. At the top of the vertical and horizontal columns are placed the simple colors ; the mixed colors occur where they intersect the corresponding vertical and horizontal columns (Dk. = dark; wh. = whitish) : — Violet. Indigo. Cyan blue. Bluish-green. Green. Greenish- yellow. Yellow. Red Orange Yellow Gr. -yellow Green Bluish -green Cyan blue Purple Dk. rose Wh. rose White White-blue Water blue Indigo Dk. rose Wh. rose White Wh.-green Water blue Water blue Wh. rose White Wh.-green Wh.-green Bl.-green. White Wh.-yellow Wh.-yellow Green Wh.-yellow Yellow Gr.-yellow Gold-yellow Yellow Orange The following results have been obtained from observations on the mixture of colors : — 1. If two simple, but non-complementary, spectral colors be mixed with each other, they give rise to a color sensation, which may be represented by a color lying in the spectrum between both, and mixed with a certain quantity of white. Hence we may produce every impression of mixed colors by a color of the spec- trum -L white (^Grassmati). 2. The less white the colors contain, the more " saturated " they are said to be ; the more white they contain, the more unsaturated do they appear. The saturation of a color diminishes with the intensity of the illumination. Geometrical Color Table. — Since the time of Newton, attempts have been made to construct a so-called " geometrical color table," which will enable any mixed color to be readily found. Fig. 561 shows such a color table ; white is placed in the middle, and from it to every point in the curve — which is marked with the names of the colors — suppose each color to be so placed that, proceeding from white, the colors are arranged, beginning with the brightest tone, always followed by the most saturated tone, until the pure saturated spectral color lies in the point of the curve marked with the name of the color. The mixed color, purple, is placed between violet and red. In order to determine from this table the mixed color of any two spectral colors, unite the points of these colors by a straight line. Suppose weights corresponding to the units of intensity of these colors, to be placed on both points of the curve indicating colors, then the position of the centre of gravity of both in the line connecting the colors indi- cates the position of the mixed color in the table. The mixed color of two .spectral colors always lies in the color table in the straight line connecting the two color points. Vioiet YeUow Orange Red Geometrical color cone or table. Further, the impression of the mixed color cor- responds to an intermediate spectral color mixed with white. The complementary color of any spectral color is found at once by making a line from the point of tliis color through white, until it intersects the opposite margin of the color table; the point of intersection indicates the complementary color. If pure white be produced by mixing two complementary co'ors, the color lying nearest white on the connecting line must be specially strons;, as then only would the centre of gravity of the lines uniting both colors lie in the point marked white. 826 YOUNG-HELMHOLTZ THEORY OF COLOR SENSATION. By means of the color table we may ascertain the mixed color of three or more colors. For example, it is required to find the mixed color resuhin;T from the union of the point, a (pale yellow), /' (fairly saturated l)luisli-gieen), and c (fairly saturated blue). On the three jxiints place weights corresixjnding to their intensities, and ascertain the centre of gravity of the weight, a, />, c ; it will lie at /. It is obvious, however, that the impression of this mixed color, whitish green-blue, can be produced by green-blue -J- white, su that / may be also the centre of gravity of two weights, which lie in the line connecting white and green-blue. We may describe a triangle, V, Gr, R, about the color table so as to enclose it completely. The three fundamental or primary colors lie in the angles of this triangle, red, green, violet. It is evident that each of the colored impressions, /. e., any point of the color table, may be determined by placing weights corresponding to the intensity of the primary colors at the angles of the triangle, so that the point of the color table, or what is the same thing, the desired mixed color, is the centre of gravity of the triangle with its angles weighted as above. The intensity of the three primary colors, in order to proiluce the mixed color, must be represented in the same proportion as the weights. Theories. — Various theories have been proposed to account for color sensation. 1. According to one theory, color sensation is produced by one kind of element present in the retina, being excited in different ways by light of different colors (oscillations of the light ether of different wave lengths, number of vibrations, and refractive indices). 2. Young-Helmholtz Theory. — The theory of Thomas Young (1807) and V. Helmholtz (1852) assumes that three different kinds of nerve elements, corresponding to the three primary colors, are present in the retina. Stimulation of the first kind causes the sensation of red, of the second green, and of the third violet. The elements sensitive to red are most strongly excited by light with the longest wave length, the red rays ; those for green by medium wave lengths, green rays ; those for violet by the rays of shortest wave length, violet rays. Further, it is assumed, in order to explain a number of phenomena, that every color of the spectrum excites all the kinds of fibres, some of them feebly, others strongly. Fig. 562. Suppose in Fig. 562 the colors of the spectrum are arranged in their natural order from red to violet horizontally, then the three curves raised upon the abscissa might indicate the strength of the stimu- lation of the three kinds of retinal elements. The continuous curve corresponds to the rays pro- ducing the sensation of red, the dotted line that of green, and the broken line that of violet. Pure rc\ the term color blindness ( dyschromatopsy) is meant a pathological condition in which .some individuals are unable to distinguish certain colors. Huddart (1777) was acquainted with tlie condition, but it was first accurately described by Dalton (1794), who himself was red blind. The term color blindness was given to it by Brewster. The supporters of the Young-Helmhohz theory assume that, corresponding to the paralysis of the three color perceiving elements of the retina, there are the following kinds of color blindness : — I. Red blindness. 2. Green blindness. 3. Violet blindness. The highest degree being termed complete color blindness. The supporters of E. Bering's theorj- of color sensation distinguish the following kinds: — 1. Complete Color Blindness (Achromatopsy). — The spectrum appears achromatic; the position of the greenish-yellow is the brightest, while it is darker on both sides of it. A colored pic- ture appears like a photograph or an engraving. Occasionally the difierent degrees of light intensity are perceived in one shade of color, e. g., yellow, which cannot be compared with any other color. O. Becker and v. Hippel observed cases of unilateral congenital complete color blindness, while the other eye was normal for color perception. 2. Blue-yellow blindness. — The spectrum is dichromatic, and consists only of red and green. The blue-violet end of the spectrum is usually greatlv shortened. In pure cases only the red and green are coirectly distinguished (Mauthner's erythrochloropy), but not the other colors. Unilateral cases have been observed. 3. Red-green Blindness. — The spectrum is also dichromatic. Yellow and blue are correctly distinguished ; violet and blue are both taken for blue. The sensations for red and green are absent altogether. There are several forms of this — {a) Green blindness, or the red-green blindness, with undiminished spectrum (Mauthner's xanthokyanopy), in which bright green and dark red are confounded. In the spectrum yellow abuts directly on blue, or between the two, at most there is a strip of gray. The maximum of brightne^s is in the yellow. It is often unilateral and often heredi- tary. (/') Red blindness (or the red-green blindness with undiminished spectrum, also called Daltonism ), in which bright red and dark green are confounded. The spectrum consists of yellow and blue, but the yellow lies in the orange. The red end of the spectrum is uncolored, or even dark. The greatest brightness, as well as the limit between yellow and blue, lies more toward the right. 4. Incomplete color blindness, or a diminished color sense, indicates the condition in which the acuteness of color perception is fiiminished, so that the colors can be detected only in large objects, or only when they are near, and when they are mixed with white they no longer appear as such. A certain degree of this form is frequent, in as far as many persons are unable to distinguish greenish- blue from bluish-green. Acquired color blindness occurs in diseases of the retina and atrophy of the optic nerve in commencing tabes, in some forms of cerebral disease (p. 763), and intoxications. At first green- blindness occurs, which is soon followed by red blindness. The peripheral zone of the retina suffers sooner than the central area. In hysterical per.sons there may be intermittent attacks of color- blindness [Charcot) ; and the same occurs in hypnotized persons (p. 736). H. Cohn found that, on heating the eyeball of some color-blind persons, the color blindness disappeared temporarily. Occasionally in persons without a lens red vision is present, and is due to unknown causes. Percentage. — Holmgren found that 2.7 per cent, of persons were color blind, most being red &nA green blind, and very few violet blind. Limits of Normal Color Blindness. — The investigations on the power of color perception in the normal retina are best carried out by means of Aubert-Forster's perimeter, or that of MTIardy (? 395)' It 's found that oitr color perception is complete only in the middle of the field of vision. Around this is a middle zone, in which only blue and yellow are perceived, in which, therefore, there is red blindness. Outside this zone, there is a peripheral girdle, where there is complete color blindness (^ 395). Hence a red-blind person is distinguished from a person with normal vision, in that the central area of the normal field of vision is absent in the former, this being rather included in the middle zone. The field of vision of a green-blind person diflers from that of a person with normal vision, in that his peripheral zone corresponds to the intermediate and peripheral zones of the normal eye. The violet-blind person is distinguished by the complete absence of the normal peri- pheral zone. The incomplete color blindness of these two kinds is characterized by a uniformly diminished central field. [When very intense colors are used, such as those of the solar spectrum, the retina can distinguish them quite up to its margin [Lattdolt).'] STIMULATION OF THE RETINA. 829 In poisoning with santonin, violet blindness (yellow vision) occurs in consequence of the pa- ralysis of the violet perceptive retinal elements, which not unfrequently is preceded by stimula- tion of these elements, resulting in violet vision, i. e., objects seem to be colored violet (^Hilfitei-). Such is the explanation of this phenomenon given by Holmgren. Max Schultze, however, refen-ed the yellow vision, i. e., seeing objects yellow, to an increase of the yellow pigment in the macula lutea. ^^^len colored objects are very small, and illuminated only for a short time, the normal eye first fails to perceive red i^Aubert) ; hence, it appears that a stronger stimulus is required to excite the sensation of red. Briicke found that very rapidly intermittent white light is perceived as green, because the short duration of the stimulation fails to excite the elements of the retina connected with the sensation of red. [The practical importance of colorblindness was pointed out by George Wilson, and again more recently by Holmgren.] No person should be employed in the marine or railway service until he has been properly certified as able to distinguish red i^rom green. Methods of Testing Color Blindness. — Following Seebeck, Holmgren used small skeins of colored wools as the simplest material, in red, orange, yellow, greenish-yellow, green, greenish- blue, blue, violet, purple, rose, brown, gray. There are five finely graduated shades of each of the above colors. ^Vhen testing a person, select only one skein — e- g-, a bright red or rose — from the mass of colored wools placed in front of him, and place it aside, asking him to seek out those skeins which he supposes are nearest to it in color. Mace and Nacati have measured the acuteness of vision by illuminating a small object with differ- ent parts of the spectrum. They compared the observations on red- and green-blind persons with their own results, and found that a red-blind person perceives green light as much brighter than it appears to a normal person. The green-blind had an excessive sensibility for red and violet. It appears that what the color blind lose in perceptive power for one color they gain for another. They have also a keen sense for variations in brightness. 398. STIMULATION OF THE RETINA.— As with every other ner- vous apparatus, a certain but determinable time elapses after the rays of light fall upon the eye before the action of the light takes place, whether the light acts so as to produce a conscious impression, or produces merely a reflex effect upon the pupil. The strength of the impression produced depends partly and chiefly upon the excitability of the retina and the other nervous structures. If the light acts for a long time with equal intensity, the excitation, after having reached its culminat- ing point, rapidly diminishes again, at first more rapidly, and afterward more and more slowly. [When the retina is stimulated by- light, there is (i) an effect on the rhodopsin (p. 790). (2) The electro-motive force is diminished (§ 332). (3) The processes of the hexagonal pigment cells of the retina dipping between the rods and cones are affected ; thus they are retracted in darkness, and protruded in the light (Fig. 563). (4) Engelmann has shown that the length and shape of the cones vary with the action of light. The cones are retracted in darkness and protruded under the influence of light (Fig. 563). This alteration in the shape of the cones takes place even if the light acts on the skin, and not on the eyeball at all.] After-images. — If the light acts on the eye for some time so as to excite the retina, and if it be suddenly withheld, the retina still remains for some time in an excited condition, which is more intense and lasts longer, the stronger and the longer the light may have been applied, and the more excitable the condition of the retina. Thus, after every visual perception, especially if it is very distinct and bright, there remains a so-called " after-image.'' We distinguish a " positive after-image," which is an image of similar brightness, and a similar color. Fig. 563 The cones of the retina and pigment cells (of the frog) as affected by light and darkness ; i after two days in darkness ; 2. after ten minutes in daylight. 830 AFTER-IMAGES. " That the impression of any picture remains for ?ome time ujion the eye is a jiliysiological phe- nomenon ; when such an im])ression can be seen for a long time, it becomes ])athological. The weaker the eye is, the lunger tlie image remains upon it. The retina does not recover itself so ([uickly, and we may regard the action as a kind of paralysis. This is not to be wondered at in the case of dazzling pictures. After looking at the sun, the image may remain on the retina for several days. A similar result sometime-; occurs w ith pictures which are not dazzling. Husch reconls that the impres- sion of an engraving, with all its detads, remained on his eye for 17 minutes" {Goetfie). Experiments and Apparatus for Positive After-images. — 1. When a burning stick is rapidly rotated, it appears as a liery circle. 2. The phanakistoscope {Plateau) or the stroboscopic 6\%\i% [Slaiiipfer). Upon a di.sk or cylinder, a series of objects is so depicted that successive drawings rejiresent individual factors of one continuous movement. On looking through an opening at such a disk rotated rapidly, we see pictures of the ditTerent phases moving so quickly that each rapidly follows the one in front of it. As the imjiression of the one picture remains until the following one takes its ]>lace, it has the ajipear- ance as if the successive phases of the movement were continuous, and one and the same figure. The apparatus under the name of zoetrope, which is extensively used as a toy, is generally stated to have been invented in 1832. It was described by Cardanus in 1 550. It may be u.sed to represent certain movements, t". ^^•■., of the spermatozoa and ciliary motion, the movements of the heart and those of locomotion. 3. The color top contains on the sectors of its disk the colors which are to he mixed. As the color of each sector leaves a condition of excitation for the whole duration of a revolution, all the colors must be perceived simultaneously, /. e., as a mixed color. [Illusions of Motion. — Silvanus V. Thompson points out that if a series of concentric circles in black and white be made on paper, and the sheet on which the circles are drawn be moved with a motion, as if one were rinsing out a pail, but with a very minute radius, then all the circles appear to rotate with the same angular velocity as that imparted. Professor Thompson has contrived other forms of this illusion, in the form of strobic disks.] Negative After-images. — Occasionally, when the sthnulation of the retina is strong and very intense, a " negative," instead of a positive after-image, appears. In a negative after-image, the bright parts of the object appear dark, and the colored parts in corresponding contrast colors (p. 824). Examples of Negative After-images. — After looking for a long time at a dazzlingly illumi- nated white window, on closing the eyes we have the impression of a bright cross, or crosses, as the case may be, with dark panes. Negative colored after-images are beautifully shown by Norrenberg's apparatus. Look steadily at a colored surface, e. g., a yellow board with a small blue square attached to the centre of its surface. A white screen is allowed to fall suddenly in front of the board — the white surface now has a bluish appearance, with a yellow square in its centre. The usual explanation of dark negative after-images is that the retinal elements are fatigued by the light, so that for some time they become less excitable, and consequently light is but feebly per- ceived in the corresponding areas of the retina ; hence, darkness prevails. Ilering explains the dark after-images as due to a process of assimilation in the black-white visual substance. In explaining colored after images, the Young-Helmholtz theory assumes that, under the action of the light waves, e. g., red, the retinal elements connected with the perception of this color are paralyzed. On now looking suddenly on a white surface, the mixture of all the colors appears as white minus red, i.e., the white afipears green. In bright daylight the contrast color lies very near the complementary color. According to Ilering, the contrast after-image is explained by the assimilation of the corresponding colored visual substance, in this case, of the " red-green " (§ 397)- From the commencement of a momentary illumination until the appearance of an after-image, 0.344 sec. elapses (y. V'intschgau and Lusdg). Not unfrequently, after intense stiinulation of the retina, positive and negative after-images alternate with each other until they gradually fuse. After looking at the dark-red setting sun we see alternate disks of red and green. The phenomena of contrast undergo some modification in the peripheral areas of the retina, owing to the partial color blindness which occurs in these areas (^Ada- jni'ick and IVoinow). Irradiation is the tenn applied to certain phenomena where we forin a false estimate of visual impressions, owing to inexact accommodation. If, from inexact accommodation, the margins of the object are projected upon the retina in diffusion circles, the mind tends to add the undefined margin to those parts of the visual image which are most prominent in the image itself. What is bright appears larger SIMULTANEOUS CONTRAST. 831 and overcomes what is dark, while an object, without reference to brightness or color, has the same relation to its background (Fig. 564). When the accommoda- tion is quite accurate, the phenomenon of irradiation is not present. [On looking at Fig. 565 from a distance, the white squares appear larger and as if they were united by a white band.] " A dark object appears smaller than a bright one of the same size. On looking at the same time from a certain distance at two circles of the same size, a white one on a black background, and a black on a white background, we estimate the latter to be about one-fifth less than the former (Fig. 564). On making the black circle one-fifth larger they will appear equal. Tycho de Brahe remarks that the moon, when in conjunction (dark), appears to be one-fifth smaller than in opposition (full, bright). The first lunar crescent appears to belong to a larger disk than the dark one adjoining it, which can occasionally be distinguished at the time of the new light. Black clothes make persons appear to be much smaller than light clothes. A light seen behind a margin gives the appearance of a cut in the margin. A ruler, behind which is placed a lighted candle, appears to the observer to have a notch in it. The sun, when rising and setting, appears to make a depression in the horizon" {^Goethe). [Contrast. — The fundamental phenomena are such as these, that a bright object looks brighter surrounded by objects darker than itself; and darker with surround- ings brighter than itself. There may be contrasts either with bright or dark objects or with colored ones.] Fig. 564. Fig. 565. For Irradiation. For Irradiation. Simultaneous Contrast. — By this term is meant a phenomenon like the fol- lowing : When bright and dark parts are present in a picture at the same time, the bright (white) parts always appear to be more intensely bright the less white there is near them, or, what is the same thing, the darker the surroundings, and, conversely, they appear less bright the more white tints that are present near them. A similar phenomenon occurs with colored pictures. A color in a picture appears to us to be more intense the less of this color there is in the adjoining parts, that is, the more the surroundings resemble the tints of the contrast color. Simul- taneous contrast arises from simultaneous impressions occurring in two adjoining and different parts of the retina. Examples of Contrast for Bright and Dark. — i. Look at a white network on a black ground ; the parts where the white lines intersect appear darker, because there is least black near them. 2. Look at a point of a small strip of dark gray paper in front of a dark black background. Push a large piece of wliite paper between the strip and the background; the strip on the white ground now appears to be much darker than before. On again removing the white paper, the strip at once again appears bright [Hering). 3. Look with both eyes toward a grayish-white surface, e. g., the ceiling of a room. After gazing for some time, place in firont of the eye a papei tube eight inches long, and an inch to an inch and a quarter in diameter, blackened in the inside. The part of the ceiling seen through the tube appears as a round white spot i^Landois). 832 EXAMPLES OF CONTRAST. Examples for Colors. — i. Place a piece of gray paper on a red, yellow, or blue ground; the contrast colors appear at once, viz., green, blue, or yellow. The phenomenon is made still more distinct by covering the whole with transparent tracing paper [I/erni. Meyer). Under similar cir- cumstances, printed matter on a colored ground appears in its complementary color ( /F. v. BtzoU). 2. An air bubble in the stron<;ly tinged field of vision of a thick microscopical preparation appears with an intense contrast color {^Lattdois). 3. Paste four green sectors upon a rotatory white disk, leave a ring round the centre of the disk imcovered by green, and cover it with a black strip. On rotating such a disk the black part appears red and not gray [Biiicke). 4. Ix)ok with both eyes toward a grayish-white surface, and place in front of one eye a tube about the length and breadth of a finger, composed of transparent oiled paper, gummed together to such thickness as will permit light to pass through its walls. The part of the surface seen through the tube appears in its contrast color. The experiment also shows the contrast in the intensity of the illumination (LanJois). A white piece of j^aper, with a round black spot in its centre, when looked at through a blue glass appears blue with a black spot. If a white spot of the same size on a black ground be placed in front, so that it is reflected in the glass plate and just covers the black spot, it shows the contrast color yellow {Rai^ona Sana). 5. The colored shadows also belong to the group of simultaneous contrasts. " Two conditions are necessary for the production of colored shadows — fii^stly, that the light gives some kind of a color to the white surface; second, that the shadow is illuminated, to a certain extent, by another light. During the twilight, place a short lighted candle on a white surface, between it and the fading day- light hold a pencil vertically, so that the shadow thrown by the candle is illuminated, but not abol- ished by the feeble daylight; the shadow appears of a beautiful />///e. The blue shadow is easily seen, but it requires a little attention to observe that the white paper acts like a reddish-yellow sur- face, whereby the blue color apparent to the eye is improved. One of the most beautiful cases of colored shadows is seen in connection with the full moon. The light of the candle and that of the moon can be completely equalized. Both shadows can be obtained of efpal strength and distinct- ness, so that both colors are completely balanced. Place the plate opjjosite the light of the moon, the lighted candle a little to one side at a suitable distance. In front of the plate hold an opaque body, when a double shadow appears, the one thrown by the moon and lighted by the candle being bright reddish-yellow ; and, conversely, the one thrown by the candle and lighted by the moon appears of a beautiful blue. Where the two shadows come together and unite is black " [Goethe). 6. " Take a plate of green glass of considerable thickness and hold it so as to get the bars of a window rellected in it, the bars will be seen double, the image formed by the under surface of the glass being green, while the image coming from the under surface of the glass, and which ought really to be colorless, appears to l>e purple. The experiment may be performed with a vessel filled with water, with a mirror at its base. With pure water colorless images are obtained, while by coloring the water colored images are produced" [Goethe). Explanation of Contrast. — Some of these phenomena may be explained as due to an error of judgment. During the simultaneous action of several impressions, the judgment errs, so that when an effect occurs at one place, this acts to the slightest extent in the neighbormg parts. When, there- fore, brightness acts upon a part of the retina, the judgment ascribes the smallest possible action of the brightness to the adjoining parts of the retina. It is the same with colors. It is far more probable that the phenomena are to be referred to actual physiological processes [I/ering). Partial stimulation toith light affects not only the part so acted on, but also the surrounding area of the retina (p. 827) ; the part directly excited undergoing increased disassimilalion, the (indirectly stimu- lated) adjoining area undergoing increased assimilation ; the increase of the latter is gi-eatest in the immediate neighborhood of the illuminated portion, and rapidly diminishes as the distance from it increases. By the increase of the assimilation in those parts not acted on by the image of the object, this is prevented, so that the diffused light is perceived. The increase of the assimilation in the immediate neighborhood of the illuminated spot is greatest so that the perception of this relatively stronger different light is largely rendered impossible [Hering). [Helmholtz thus ascribed the phenomena of contrast to psychical conditions, i. e., errors of judg- ment, but this explanation is certainly not complete. A far more satisfactory solution of the problem is that of Hering, that stmiulation of one part of the retina affects the condition of adjoining parts. If a white disk on a black background be looked at for a tim-;, and then the eyes be closed, a nega- tive after-image of the disk appears, but it is darker and blacker than the visual area, and it has a light area around, brightest close to the di-.k, /. e., the adjacent part of the retina is affected. This Hering has called successive light induction.] Successive Contrast. — Look for a long time at a dark or bright object, or at a colored [e. g., red) one, and then allow the effect of the contrast to occur on th= retina, /. interfered with, as in cases of hanging. 2. By contraction of the smooth muscular fibres in Tenon's capsule, in the spheno-maxillary fissure, and in the eyelids (| 404), which are innervated by the cervical sympathetic nerve. 3. By voluntary forced opening of the palpebral fissure, whereby the pressure of the eyelids acting on the eyeball is diminished. 4. By the action of the oblique muscles, which act by pulling the eyeball inward and forward If the superior oblique be contracted when the eye- lids are forcibly opened, the eyeball may be protruded about I mm. When protrusion of the eyeball occurs pathologically (as in i and 2), the condition is called exophthalmos. Retraction of the eyeball is the opposite condition, and is caused^ i. By closing the eyelids forcibly. 2. By an empty condition of the retro-bulbar blood vessels, diminished succulence, or dis- appearance of the tissue of the orbit. 3. Section of the cervical sympathetic in dogs causes the eye- ball to sink somewhat in the orbit. The smooth muscular fibres of Tenon's capsule are perhaps antagonistic in their action to the four recti when acting together, and thus prevent the eyeball from being drawn too far backward. Many animals have a special retractor bulbi muscle, e.g.., amphibi- ans, reptiles, and many mammals ; the ruminants have four. The movements of the eyes are almost always accompanied by similar move- ments of the head, chiefly on looking upward, less so on looking laterally, and least of all when looking downward. The difficult investigations on the movements of the eyeballs have, been carried out, especially by Listing, Meissner, Helmholtz, Bonders, A. Fick, and E. Hering. Axes. — All the movements of the eyeball take place round its point of rotation (Fig. 566, O), which lies 1. 77 mm. behind the centre of the visual axis, or 10.957 mm. from the vertex of the cornea i^Donders). In order to determine more carefully the movements of the eyeball, it is neces- sary to have certain definite data: i. The visual axis (S, Sj), or the antero-posterior axis of the eyeball, unites the point of rotation with the fovea centralis, and is continued straight forward to the vertex of the cornea. 2. The transverse, or horizontal axis (Q, Qj), is the straight linj connect- ing the points of rotation of both eyes and its extension outward. Of course, it is at right angles to i. 3. The vertical axis passes vertically through the point of rotation at right angles to i and 2. These three axes form a coordinate system. We must imagine that in the orbit there is a fixed determinate axial system, whose point of intersection corresponds with the point of rotation of the eyeball. When the eye is at rest (primary position), the three axes of the eyeball completely coincide with the three axes of the coordinate system in the orbit. When the eyeball, however, is moved, two or more axes are displaced from this, so that they must form angles with the fixed orbital system. Planes of Separation. — In order to be more exact, and also partly for further estimations, let us suppose three planes passing through the eyeball, and that their position is secured by any two axes. I. The horizontal plane of separation divides the eyeball into an upper and lower half; it is deter- mined by the visual transverse axis. In its course through the retina it forms the horizontal line of separation of the latter; the coats of the eyeball itself cut it in their horizontal meridian. 2. The vertical plane divides the eyeball into an inner and outer half; it is determined by the visual and vertical axes. It cuts the retina in the vertical line of separation of the latter and the pe- riphery of the bulb in the vertical meridian of the eyeball. 3. The equatorial plane divides the eyeball into an anterior and posterior half; its position is determined by the vertical and transverse axes, and it cuts the sclerotic in the equator of the eyeball. The horizontal and vertical lines of separation of the retina, which intersect in the fovea centralis, divide the retina into four quadrants. In order to define more precisely the movements of the eyeball, v. Helmholtz has introduced the following terms : He calls the straight line which connects the point of rotation of the eye with the fixed pomt in the outer world, the visual line (" Blicklinie"), while a plane passing through these lines in both eyes he called the visual plane ; the ground line of this plane is the line uniting the two points of rotation, viz., the transverse axis of the eyeball. Suppose a sagittal section (antero- posterior) to be made through the head, so as to divide the latter into a right and left half, then this 53 834 POSITIONS OF THE EYEBALL. plane would halve the ground line of the visual plane, and when prolonged forward would intersect the visual plane in the median line. The visual point of the eye can lie (i) raised or lowered — the field which it traverses being called the visual tield (" Hlickfeld ") ; it is part of a spherical surface with the point of rotation of the eye in its centre. Proceedinjj from the primary position of both eves, which is characterized by botli visual lines being parallel with each other and horizontal, then the elevation of the visual plane can be determineti by the angle which this forms with the plane of the primary jx)sition. This angle is called the ani^le of e/nuition — it is positive when the visual plane is raised (to the forehead), and negative when it is lowered (chinward). (2) From the pri- mary position, the visual line can be turned laterally in the visual plane. The extent of this lateral deviation is measured by the angle of lateral rotation, /. ,•., by the angle which the visual line forms with the median line of the visual plane; it is said to be positive when the posterior part of the visual line is turned to the right, negative when to the left. The following are the positions of the eyeball : — 1. Primary position [or "position of rest"], in which both the lines of vision are parallel with each other, and the visual planes are horizontal. The three axes of the eyeball coincide with the three fixed axes of the coordinate system in the orbit. 2. Secondary positions are due to movements of the eye from the primary position. There are two different varieties — i^a) where the visual lines are parallel, but are directed upward or dinomvard. The transverse axis of both eyes remains the same as in the primary position ; the deviations of the other two axes expressed by the amount of the angle of elevation of the line of vision. (/') The second variety of the secondary position is produced by the convergence or divergence of the lines of vision. In this variety the vertical axis, round which the lateral rota- tion takes place, remains as in the primary position; the other axes form angles; the amount of the deviation is expressed by the " angle of lateral rotation." The eye, when in the primary position, can be rotated from this position 42° outward, 45° inward, 34° upward, and 57° downward {Schuurmann'). 3. Tertiary position is the position brought about by the movements of the eye, in which the lines of vision are convergent, and are at the same time inclined upward or downward. [Listing's Law is that which expresses the movements of the eyeball. When the eyeball moves from the primary position, or position of rest, the angle of rotation of the eye in the second position is the same as if the eye were turned about a fixed axis perpendicular to botli the first and the second positions of the visual line {^Hel»iholtz).'\ All the three axes of the eye are no longer coincident with the axes in the pri- mary position. The exact direction of the visual lines is determined by the amount of the angle of lateral rotation and the angle of elevation. There is still another important point. The eyeball is always rotated at the same time round the line of vision and round its axis {Volkmann, Hering^. As the iris rotates round the visual line like a wheel round its axis, this rotation is called " circular rotation " (" Raddrehung'') of the eye, which is always connected with the ter- tiary positions. Even oblique movements may be regarded as composed of — (i) a rotation round the vertical axis, and (2) round the transverse axis; or it may be referred to rotation round a single constant axis placed between the above- named axes, passing through the point of rotation of the eyeball, and at right angles to the secondary and primary direction of the visual axis (line of vision) — {Listing). The amount of circular rotation is measured by the angle which the horizontal separation line of the retina forms with the horizontal separation of the retina of the eye in the primary position. This angle is said to be positive, when the eye itself rotates in the same direction as the hand of a watch observed by the same eye, /. e., when the upper end of the vertical line of separation of the retina is turned to the right. According to Bonders, the angle of rotation increases with the angle of elevation and the angle of lateral rotation — it may exceed 10°. With equally great elevation or depression of the visual plane, the rotation is greater, the greater the elevation or depression of the line of vision. THE OCULAR MUSCLES. 835 On looking upward in the tertiary position, the upper ends of the vertical lines of separation of the retina diverge ; on looking downward they converge. If the visual plane be raised, the eye, when it deviates laterally to the right, makes a circular rotation to the left. When the visual plane is depressed, on deviating the eye to the right or left, there is a corresponding circular rotation to the right or left. Or we may express the result thus : When the angle of elevation and the angle of devia- tion have the same sign (-|- or — ), then the rotation of the eyeball is negative; when, however, the signs are unequal, the rotation is positive. In order to make the circular rotation visible in one's own eye accommodate one eye for a sirrface divided by vertical and horizontal lines until a positive after- image is produced, and then rapidly rotate the eye into the third position. The lines of the after- image then form angles with the lines of the background. As the position of the vertical meridian of the eye is important from a practical point of view, it is necessary to note that, in the primary and secondary positions of the eyes, the vertical meridian retains its vertical position. On looking to ^A^^ 'S>^^ E i I Scheme of the action of the ocular muscles. the left and upward, or to the right and downward, the vertical meridians of both eyes are turned to the left ; conversely, they are turned to the right on looking to the left and downward, or to the right and upward. In the secondary positions of the eye, rotation of the axis of the eye never occurs [Listing). Very shght rolling of the eyes occurs, however, when the head is inclined toward the shoulder, and in the direction opposite to that of the head, it is about i° for every io° of inclination of the head {Skrebitzk). Ocular Muscles. — The movements of the eyeball are accomplished by means of the four straight and two oblique ocular muscles. In order to understand the action of each of these muscles, we must know the plane of traction of the muscles and the axis of rotation of the eyeball. The plane of traction is found by the plane lying in the middle of the origin and insertion of the muscle and 836 ACTION OF THE OCULAR MUSCLES. the point of rotation of the eyeball. Tlie axis of rotation is always at right angles to the jtlane of traction in the point of rotation of the eyeball. I. The rectus internus (I) and externus (E) rotate the eye almost exactly inward and outward (Fig. 566). The plane of traction lies in the plane of the paper; Q, E, is the direction of the traction of the external rectus, Q,, I, that of the internal. The axis of rotation is in the point of rotation, O, at right angles to the plane of the paper, so that it coincides with the vertical axis of the eyeball. 2. The axis of rotation of the R. superior and inferior (the dotted line, R. sup., R. inf.), lies in the horizontal plane of separation of the eye, but it forms an angle of about 20° with the transverse axis (Q, Q,) ; the direction of the trac- tion for both muscles is indicated by the line s, i. By the action of these muscles, the cornea is turned upward and slightly inward, or downward and slightly inward. 3. The axis of rotation of both oblique muscles (the dotted lines, Obi. sup. and Obi. inf.) also lies in the horizontal i)lane of separation of the eyeball, and it forms an angle of 60° with the tran.sverse axis. The direction of the traction of the inferio?- oblique gives the line, a, b ; that of the superior, the line, c, d. The action of these muscles, therefore, is in the one case to rotate the cornea out- ward and upward, and in the other outward and downward. These actions, of course, only obtain when the eyes are in the primary position ; in every other position the axis of rotation of each muscle changes. When the eyes are at rest, the muscles are in equilibrium. Owing to the power of the internal recti, the visual axes converge and would meet, if prolonged 40 centimetres in front of the eye. In the movements of the eyeball, one, two, or three muscles may be concerned. One muscle acts only when the eye is moved directly outward or inward, especially the internal and external rectus. Two muscles act when the eyeball is moved directly upward (superior rectus and infe- rior oblique) or downward (inferior rectus and superior oblique). Three muscles are in action when the eyeballs take a diagonal direction, especially for imvard and upioard, by the internal and the superior rectus and inferior oblique ; for inward and doivnward, the internal and inferior rectus and superior oblique ; for outward and downward, the external and inferior rectus and superior oblique ; for outward and up'ivard, the external and superior rectus and inferior oblique. [The following table shows the action of the muscles of the eyeball : — In- card. Outward, Upward, Dowmvard, Inward and upivard. Rectus inturnus. Rectus externus. f Rectus superior. \ Obliquus inferior, f Rectus inferior. \ Obliquus superior. {Rectus internus. Rectus superior. Obliquus inferior. Inward and doxonward , Outward and upward. Outward and downward, Rectus internus. Rectus inferior. Obliquus superior. Rectus externus. Rectus superior. Obliquus inferior. Rectus externus. Rectus inferior. Obliquus superior.] Ruete imitated the movements of the eyeballs by means of a model, which he called the ophthalmotrope. The size of the eyeball and its length diminish with age. The mobility is less in the vertical than in the lateral direction, and less upward than downward. The normal and myopic eye can be moved more outward, and the long-sighted eye more inward; the external and internal recti act most when the eye is moved outward, the obliqui when it is rotated inward. An eye can be turned inward to a greater extent when the other eye at the same time is turned outward than when the other is turned inward. During near vision, the right eye can be turned less to the right, and the left to the left, than during distant vision [Hering). Simultaneous Ocular Movements. — Both eyes are always moved simul- taneously. Even when one eye is quite blind, the ocular muscles move when the whole eyeball is excited. When the head is straight, the movements always take place so that both visual planes (visual axes) lie in the same plane. In front both visual axes can diverge only to a trifling extent, while they can converge consider- BINOCULAR VISION. 837 ably. If individual ocular muscles are paralyzed, the position of the visual axis in the same place is disturbed, and squinting results, so that the patient no longer can direct both visual axes simultaneously to the same point, but he directs the one eye after the other. Even nystagmus (p. 771) occurs in both eyes simultaneously, and in the same direction. The innate simultaneous movement of both eyes is spoken of as an associated movement (/( the sensory apparatus for the action of moderate or weak stimuli. This movement in both membranes is brought about rejlexly, 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 expi- ration, 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. Mi'dler). If air be blown into the external auditory meatus, both tensores tympani contract, and in consequence of this the hearing of the other ear is temporarily affected [Gellc). Normally, the tensor tympani is excited reflexly. The muscle is not directly and by itself subject to the control of the will. According to L. Fick, the following phenomenon is due to an " associated movement " of the tensor : When he jjressed his jaws firmly against each other, he heard in his ear a piping, singing tone, while a capiilaiy tube, which was fixed air-tight into the meatus, had a drop of water which was in it rapidly drawn inward. During this experiment, a person with normal hearing hears all musical tones as if they were louder, while all the highest non-musical tones are enfeebled ( Lucae). When ya-vnifig, v. Helmholtz and Tolitzer 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 g vibrates more readily to higher tones than when it is at rest. On ^^ ■ exposing the tympanum in cats and dogs, it was found that this contraction or twitch occurs only at the beginning of the sound, and that it soon ceases, although the sound may continue. Action of the Stapedius. — The muscle arises within the emi- nentia pyramidalis, and is inserted into the head of the stapes and Sylvian ossicle (Fig. 583); when it draws upon the head of the stapes, as indicated in Fig. 577, by the small curved arrow, it must place the bone obliquely, whereby the posterior end of the plate of Right stapedius the stapes is pressed somewhat deeper inward into the fenestra muscle. ovalis, whilc the anterior is, as it were, displaced somewhat out- ward. The stapes is thereby more fixed, as the fibrous mass [annular ligament] which surrounds the fenestra ovalis and keeps the stapes in its place becomes more tense. 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. It is supplied by the facial nerve (§ 349, 3). The stapedius in many persons executes an associated movement, when the eyelids are forcibly closed (I 349). Some persons can cause it to contract reflexly by scratching the skin in front of the meatus, or by gently stroking the outer margin of the orbit (Henle). It seems to be excited reflexly in many diseases of the ear when the tympanum is being syringed. Other Views. — According to Lucae, when the stapes is displaced obliquely, its head forces the THE EUSTACHIAN TUBE. 855 long process of the incus, and also the membrana tjTnpani, outward, so that it is regarded as an a7itagonist 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 communi- cated 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. 648, and for the stapedius, p. 652. 411. EUSTACHIAN TUBE— TYMPANUM.— The Eustachian tube [4 centimetres in length, if^ 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. 577, 586). 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, how- ever, the tube is opened, owing to the traction of the fibres of the tensor veli pala- tini [spheno-salpingo-staphylinus sive abductor tubae (v. TrdlfscJi), sive dilator tubae {Rudinger)'] inserted into the membrano-cartilaginous part of the tube {Toynbee, Politzer). (Compare § 139, 2.) When the tube is closed, the vibra- tions of the mem.brana 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, becoixies drawn inward, thus causing difficulty of hearing. As the tube is lined by ciliated epithelium it carries outward to the pharynx the secretions of the tympanum (p. 501). Noise in the Tube. — K 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 adhe- sive surfaces of its lining membrane. Another person may hear this noise by using a stethoscope 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 tjTnpanic 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. 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. 354, W). Hence, when this muscle contracts and its belly thickens, as at the commencement of the act of deglutition and during phonalion, the lower wall of the pharyngeal opening is raised, and the opening thereby narrowed [Lucae). The contrac- tion 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 vfdXl is formed by the membrana tympani, while on the ^t^ner^\3l\ are the fenestra ovalis and rotunda, the ridge of the aqueductus Fallopii, the promontory, and the pyramid. 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 856 CONDUCTION OF SOUND IN THE LABYRINTH. 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 communicates 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. S4S, 3), but normally this is so slight, when compared with the conduction through the auditor)' ossicles, that it scarcely need be taken into account. Structure. — The tube and tympanum are lined l>y common mucous membrane, covered by ciliated epithelium, while the membrana is lined by a layer of squamous epithelium. Mucous glands were found by Tn'^ltsch and \Vcndt in the mucous membrane. [The epi- FlG. 588. thelium covering the ossicles and tensor tympani is not ciliated.] ^^ Pathological. — The tube is often occluded, owing to chronic catarrh ^^^ and narrowing from cicatrices, hypertrophy of the mucous membrane, or the presence of tumors. The deafness thereby produced may often be cured by calheterizini; the tube from the nose (Fig. 5SS). Eflusions into or suppuration within the tympanum of course paralyze the sound-conduct- ing mechanism, while indammation often causes subsequent affections of the plexus tympanicus. If the temporal bone be destroyed by progressive caries Fi<;. 5S9. Eustachian Catheter. Politzer's Ear Bag. within the tympanum, inflammation of the neighboring cerebral structures may occur and cause death. [Methods. — Not unfrequent'y 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. 588K At other times he requires to till the tympanic cavity with air, which is easily done by means of a Politzer's bag (Fig. 589). 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 meinbrana secundaria, which dtiring rest bulges in- ward to the scala tympani, and can be bulged outward toward the tympanic cavity by the impulse communicated to it by the movement of the perilymph (Fig. 577, ;-). The flexion waves must correspond in number and intensity to the vibrations of the auditory ossicles, and must also excite the free terminations External appea.ance of of the auditorv nerve, which float free in the endolymph. the labyrinth, fenestra . , / , , /- , 1 1 • 1 1 • ■ ^i ovalis, cochlea to the As the endolymph of the saccule and utricle lying in the (l^'hor1z^lai',\nd^") vestibule receives the first impulse, and as these communicate posterior sem'icircuiar anteriorly with the cochlea, and posteriorly with the semicir- '^^"^ ^^'^' cular canals, consequently the motion of the perilymph must be propagated through these canals. To reach the cochlea, the movement passes Fig METHOD OF TESTING SOUND CONDUCTION. 857 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 movem.ent is propagated through the semicircular cafials. Politzer observed that the endolyraph in the superior semicircular canal rose when he caused contraction of the tensor tympani by stimu- lating the trigeminus, just as the base of the stapes must be forced against the perilymph with every vibration of the membrana tympani. [Practical. — It is well to view the organ of hearing as consisting of two mechanisms : — 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- 753)-] [Testing the Sound conduction. — In any case of deafness, it is essential to estimate the degree of deafness by the methods stated at p. 848, 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-perceivi^ig apparatus is aifected. 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, if it be heard dis- tinctly, 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 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 (^Macli). If, on the contrary, the sound be heard loudest in the good ear, then in all probability 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 con- nect 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 tele- phones, 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. LABYRINTH AND AUDITORY NERVE.— Scheme.— The vestibule (Fig. 591, III) contains two separate sacs: one of them, the saccule, j (round sac or S. hemisphasricus), com- municates with the ductus cochlearis, Cc, of the cochlea : the other, the utricle, U (elliptical sac, or sacculus hemiellipticus), communicates with the semicircular canals, Cs, Cs. The cochlea consists of 2}^ turns of a tube disposed round a central column or modiolus. The tube is divided into two compartments by a horizontal septum, partly osseous and partly membranous, the lamina spiralis ossea and membranacea (Fig. 595 ; Fig. 591,1). The lower compartment 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. 591, 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 helico- trema (Fig. 577). The scala vestibuli is divided by Reissner's membrane (Fig. 591, I), 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, Cc, 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 canaUs cochlearis 858 STRUCTURE OF THE COCHLEA. is blind. Ill, and divided toward the saccule, wiih which it communicates by means of the small canalis reuniens, Cr {//ensen). The utricle (Fig. 591, III, U) communicates with the three semicircular canals, Cs, Cs — each by means of an ampulla, within which lie the terminations of the ampullary nerves, but as the posterior and the superior canals unite, there is only one common ampulla for them. The membranous semicircular canals lie within the osseous canals, perilymph Fig. 591. I, transverse section of a turn of the cochlea ; II, A, ampulla of a semicircular canal with the crista acustica ; a,p, auditory cells; /, provided with a fine hair ; T, otoliths; HI, scheme of the human labyrinth; IV, scheme of^a bird's labyrinth ; V, scheme of a fish's labyrinth. lying between the two. Perilymph also fills the scala vestibuli and tympani, so that all the spaces within the labyrinth are filled by tluid, 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 Fig. 593. The interior of the right labyrinth with its membranous canals and nerves. In Fig. 592, the outer wall of the bony labyrinth is removed to show the membranous parts within — i, 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. 593 shows the membranous labyrinth and nerves detached— i, facial nerve in the internal auditory meatus ; 2, an- terior 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 ; ir, posterior extremity of the horizontal canal. the utricle, the ductus cochlearis with the saccule through the canalis reuniens ; and lastly, the saccule and utricle through the " saccus endolymphaticus," which springs by an isolated limb from each sac ; the limbs then unite, as in the letter Y, and pass through the osseous aqueductus vestibuli to end blindly in the dura mater of the brain (Fig. Ill, R — Boucher, Retzhis). The aqueductus coch- lea; is another narrow passage, which begins in the scala tympani, immediately in front of the fenestra CRISTA ACUSTICA AND COCHLEA. 859 rotunda, and opens close to tlie fossa jugularis. It forms a direct means of communication between the perilymph of the cochlea and the subarachnoid space. Semicircular Canals and Vestibular Sacs. — The membranous semicircular canals do not fill the corresponding osseous canals completely, but are separated from them by a pretty wide space, which is filled with perilymph (Fig. 592). At the concave margin they are fixed by connective tissue to the osseous walls. The ampuUse, however, completely fill ihe 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. 593). In the ampullae (Fig. 591, II, A), the nerve {c) terminates in connection with the crista acustica, which is a yellow elevation projecting into the equator 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 {0, p) 90 // in length, so that YiG. 594. the crista is largely covered with these hair cells, but between t\ a /it them are supporting cells hke cylindrical epithelium (a), and not /I 1 I unfrequently containing granules of yellow pigment. The hairs or [ il // If" " auditory hairs " [M. Schultze) are composed of many fine fibres ^ __ZL. /\^A — _Zi [Relzius). An excessively fine membrane (membrana tectoria) - " ^ — " covers the hairs [Friickard, Lang). ] Maculae Acusticae. — The nerve terminations in the maculae acus- ticse of the saccule and utricle are exactly the same as in the am- pullae, 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 fi.xed in the viscid endolymph. The non-medullated axis cylinders of the saccular nerves enter directly '' ~~~ 7^ — c — ^ into the substance of the hair cells. The terminations of the nerves ", /,"!?/, 1 " / I ) have been investigated, chiefly in fi.shes, in the rays. 1 | /*^' ' I C „ [Fig. 594 is a vertical section of a macula acustica of the rabbit. "j / ) ' -CS The medullated nerves («) lose their myelin at the external limiting - / P^'- '\ -i "^ membrane, become non-medullated, pierce this membrane, and form ^~ ' ^ — -^ a basal plexus [pi>) between (z) the epithelial cells, and finally ter- minate in the sensory ciliated cells (;■). The epithelium itself con- . < -^ sists of basal cells (cd), fusiform or supporting cells {/), and the /f , \ ' 'n -^ ciliated neuro-epithelium (r),*each cell being provided with a cilium, "-=/-, ^ , *.*_'. \ 1 which perforates the external limiting membrane [a). There is thus a remarkable likeness to the olfactory epithelium.] ^^" aclisdcaTf iVibbU^*^"'^ 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. 591, I, Q.C, and III, Cr, and Fig. 595), the small triangular chamber [or scala media,] cut off" from the scala vestibuU by the membrane of Reissner. Corti's organ is placed on the lamina spiralis mem- branacea, and consists 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 rods do not form an arch, as there are always three inner to two outer rods [Clatidius). 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 /i in the upper, the outer rods 47 fi and 69 fjL respectively. The span of the arches also increases [Hensen). [The arches leave a tri- angular tunnel beneath them.] The proper end organs of the cochlear nerve are the cylindrical " hair cells " {^KoUiker') previously observed by Corti, which are from 16,400 to 20,000 in number [Heitsett, Waldeyer). There is one row of inner cells (z) which rests on a layer of small granular cells (K) {Bottcher, Waldeyer) ; the outer cells {a, a) number 12,000 in man {Retzius), 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 nin 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. 591, 595, I, G), and end by fine varicose fibrils in the hair cells (Fig. 595) {Waldeyer, Gottstein, Lavdowsky, Retzhis). 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 cement substance holding these parts together [Lavdowsky). [Springing from the outer end of the lamina spiralis, or crista spiralis, is the mem- brana tectoria, sometimes called the membrane of Corti. It is a well-defined structure, often 860 MUSICAL TUNES AND NOISES. librillated in appearance, and extends outward over the organ of Corli.] Waldeyer regards it as a dani])ing apparatus for this organ (Fig. 595, Mb. Corli). [Basilar Membrane. — Its hreaclth incre.ises from the base to the ape.x of the cochlea. This fact is imj ortaiit in connection with the theory of the ]ierception of lone. It is supposed that high notes are appreciated by structures in connection wilii the former, and low notes liy the ujjper parts of the basilar memiirane. In one case, recorded by Moos 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 atro]ihied.] Intra-Labyrinthine Pressure. — The lymph within the labyrinth is under a certain pressure. Every diminuiion 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. Bezol, to give the characteristic.quality. Accordmg to v. Ilelmholtz, when we sound the vowels on b b, for each of the three vowels, one overtone is specially characteristic for A-b^ 1> ; for O-b' b ; for U-f. The other vowels and the diphthongs have each two specially characteristic overtones, because in these cases the mouth is so shaped that the posterior larger cavity, and also the anterior narrower part, each yields a special tone (^ 316, I and E). These two overtones are for E-B"i b and f ; for I-div and f; for A-g'" and d" ; 6-c"i # and f I ; for U-glH and f. These, however, are only the special upper tones. There are many more upper tones, but they are not so prominent. Artificial Vowels. — Just as it is possible to analyze a vowel into its fundamental tone and its upper tones, it is possible to compound tones to produce the vowels by simultaneously sounding the fundamental tone and the corresponding upper tones. (l) A vowel is produced simply by singing loudly a vowel, e. g.. A, upon a certain note against the free strings of an open piano, while by the pedal the damper is kept raised. As soon as we stop singing, the characteristic vowel is sounded by the strings of the piano. The voice sets into sympathetic vibration all those strings whose overtones (in addition to the fundamental tone) occur in the vocal compound tone, so that they vibrate for a time after the voice ceases {v. Ilelmholtz). (2) The vowel apparatus devised by v. Helmholtz con- sists of numerous tuning forks, which are kept vibrating by means of electro-magnets. The lowest tuning fork gives the fundamental tone, B b, and the others the overtones. A resonator is placed in front of each tuning fork, and the distance between the two can be varied at pleasure. The koenig's apparatus. 865 resonators can be opened and closed by a lid passing in front of their openings. When the resonator IS closed, we cannot hear the tone emitted by the tuning-fork placed in front of it; but when one or more resonators are opened the tone is heard distinctly, and it is louder the more the resonator is Fig. 598. Koenig's raanometric capsjile (A) and mirror {lli)~(Koenig). Fig. 599. 55 Flame pictures of the vowels ou, o, and A (Koenig). 866 KOENIG S APPARATUS. opened. By means of a series of keys, like the keys of a pianoforte, we can rapidly open and close the resonators at will, and thus combine various overtones with the fundamental tone so as to pro- duce vowels with different tiuali ies. v. lldniliollz makes the following compositions : U = B b with b ? weak and f i ; C) ;= clamped B ? with hi ;' strong and weaker b ?, f ' , d" ; A = b b (fundamental tone) with moderately strong bl i> and f", and strong b" t> and dm ; A = b l> (fundamental tone) with b' ? and f" somewhat stronger than for A, tl strong, b'l 1? weaker, d'H and fm as strong as possible; E = b b (as fundament.al tone) moderately strong, with b' b and f moderate also, and f "' , ab'" , and bm b as strong as possible ; I could not be jiroduced. In Appunn's apparatus, the fundamental tone and the overtones are produced by means of organ jiipes, whose tones can be combined to produce the vowels, but it is not so good as the tuning forks, since tiie organ pipes do not yield simple tones, but nevertheless some of the vowels can be admirably reproduced with this apparatus. Edison's Phonograph. — If we utter the vowels against a delicate membrane. stretched over the Fitt. 600. Koenig's apparatus for analyzing a conipound tone with the funJamenlal tone UTo. end of a hollow cylinder, and if a writing style be fixed to the centre of the membrane, and the style be so arranged that it can write or record its movements on a piece of soft tinfoil arranged on a revolving apparatus, then the vowel curve is stamped as it were upon the tinfoil. If the style now be made to touch the tinfoil while the latter is moved, then the style is moved — it moves the membrane, and we hear distinctly by resonance the vowel sound reproduced. [Koenig's Manometric Flames. — By means of this apparatus the quality of the vowel sounds is easily shown. It consists of a small wooden capsule, A, divided into two compartments by a piece of thin sheet india-rubber. Ordinary gas passes into the chamber on one side of the membrane, through the stop-cock, and it is lighted at a small burner. To the other compartment is attached a wider tube with a mouthpiece. The whole is fixed on a stand, and near it is placed a four-sided rotating mirror, M, as suggested by Wheatstone (Fig. 598). On speaking or singing a vowel into the mouthpiece, and rotating the mirror, a toothed or zigzag flame picture is obtained in the mirror. The form of the flame pic'ure is characteristic for each vowel, and varies, of course, with the pitch]. ACTION OF THE LABYRINTH DURING HEARING. 867 [Fig. 599 shows the form of the flame picture obtained in the rotating mirror when the vowels, ou, O, A, are sung at a pitch of ut^, sol^, and iit^. This series shows how they differ in quality.] [Koenig has also invented the apparatus for analyzing any compound tone whose fundamental tone is UXj (Fig. 600). It consists of a series of resonators, from UT, to uXj, fixed in an iron frame. Each resonator is connected with its special flame, which is pictured in a long, narrow, square, rotating muTor. If a tuning fork UT^ be sounded, only the flame UTj is affected, and so on with each tuning fork of the harmonic series. Suppose a compound note containing the flmdamental tone UT2, and its harmonics be sounded, then the flame of VY^, and those of the other harmonics in the note are also affected, so that the tone can be analyzed optically. The same may be done with the vowels.] 416. LABYRINTH DURING HEARING.— If we ask what role the ear plays in the perception of the quality of sounds, then we must assume that, just as with the help of resonators a musical note can be resolved into its fundamental tone and overtones, so the ear is capable of performing such an analysis. The ear resolves the complicated wave forms of musical tones into their components. These components it perceives as tones harmonious with each other ; with marked attention each is perceived singly, so that the ear distinguishes as different tone colors only different combinations of these simple tone sensations. The resolution of complex vibrations, due to quality, into simple pendulum-like vibrations is a characteristic function of the ear. What apparatus in the ear is capable of doing this? If we sing vigorously, e. g., the musical vowel A on a definite note, say b b — against the strings of an open pianoforte while the damper is raised, then we cause all those strings, and o/i/y those, to vibrate sympathetically, which are contained in the vowel so sung. We must, therefore, assume that an analogous sympathetic apparatus occurs in the ear, which is tuned, as it were, for different pitches, and which will vibrate sympathetically like the strings of a pianoforte. "If we could so connect every string of a piano with a nerve fibre that the nerve fibre would be excited and perceived as often as the string vibrated, then, as is actually the case in the ear, every rnusical note which affected the instrument would excite a series of sensations exactly corresponding to the pendulum-like vibrations into which the original movements of the air can be resolved ; and thus the existence of each individtial overtone would be exactly perceived, as is actually the case with the ear. The perception of tones of different pitch would, under these circum- stances, depend upon different nerve fibres, and hence would occur quite independ- ently of each other. Microscopic investigation shows that there are somewhat similar structures in the ear. The free ends of all the nerve fibres are connected with small elastic particles which we must assume are set into sympathetic vibra- tion by the sound waves" (v. HelmJioltz). 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 notes, 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 tOAvard the apex of the cochlea, are now regarded as the vibrating threads {Henseii). Thus, a string-like fibre of the membrana basi- laris, 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.] 868 SIMULTANEOUS ACTION OF TWO TONES. This assumption also explains the perception of noises. Of noises in the strictly physical sense, it is a-^sumed that they, like single im])iilses, arc perceived by the aid of the saccules and the ampulla. it is assumed that tlie saccules and the ampullae are concerned in the general perception of hearing, /. f.^ of shocks ( omnnmicated 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 cciuilibrium of the body is referred to in § 350. 417. SIMULTANEOUS ACTION OF TWO TONES— HAR- MONY-BEATS—DISCORDS— DIFFERENTIAL TONES.— When huo tones of different pitch fall upon the ear simultaneously, they cause different sensUions according to the difference in pitch. 1. Consonance. — If the number of vibrations of the two tones is in the ratio of simple multii)les, as i : 2 : 3 : 4, so that when the low notes make one vibration the higher one makes 2 : 3 or 4 . . . . then we experience a sensation of complete 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, correspond- ing 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. Tlie 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 2,Z 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. 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 wliirring 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 {" K/dnge"). — 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 overtones. Hence the degree of dissonance of two musical tones is the more pronounced the more the fundamental tones and the overtones (and the " differential " tones) produce beats which number about 33 per second. 5. Differential Tones. — Lastly, two "klangs," or two simple musical tones PERCEPTION OF THE DIRECTION OF SOUNDS. 869 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 difference between the two primary tones, and hence it is called a '■'■ differe?itial tone. ' ' Summational Tones. — It was formerly supposed that new tones could arise from the summa- tion 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— OBJECTIVE AND SUB- JECTIVE AUDITION— AFTER-SENSATION.— Objective and 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 auditory 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 voices, 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 noise mixed with musical tones come than that of tones (^Rayleigli). 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 difiicult 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, so as to form an open cavity behind them, we are apt to suppose that a sounding body placed in front is behind us. The semicircular canals are said also to be concerned, as sound coming from a certain direction must always excite one canal more than the others. Thus, the left horizontal canal is most stimulated by horizontal sound waves coming from the left (^Preyer'). Other observers assert that the membrana tympani localizes the sound, as only certain parts of it are affected by the sound waves. 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 vibratiotis , especially of intense and continued musical tones ; the tinnitus aurium (p. 655), 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, givingrise to subjective sounds; the hearing is rendered more acute by strychnin ; while quinine and sodic salicylate in large doses cause ringing in the ears {B}-imto7t).'\ 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 hypereesthesia of the auditory nerve [Bremtef). 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 recovery, however, takes place in a few seconds i^Urbantschitsch). 870 AUDITORY AFTER-SENSATIONS AND COLOR ASSOCIATIONS. Auditory After-Sensations. — (l) Those that correspond to /^j/V/fi? 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 ( Urbanlschilsch). (3) There seems also to be a form corresjxjnding to negative after-images. In some persons, the perception of a tone is accompanied by the occurrence of subjective colors, or the sensation of light, e.g., the sound of a trumpet, accompanied by the sensation of yellow. More seldom visual sensations of this kind are observed when the nerves of taste, smell, or touch are excited [iViisslximiier, Lehinann and Blculer). It is more common to find that an intense sharp sound is accompanied by an associated sensation of the sensory nerves. Thus many people experience a cold shudder 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 Galton remarks that it is rather common in children, although in an ill-developed degree, and the tendency seems to be very hereditary. Sometimes a particular color is associated with a particular letter, vowel sounds particularly evoking colors. Galton has given colored rcj re=entations of these color associations, and he points out their relation to what he calls number forms, or the associa- tion of certain fornis 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 auditoi-y centres of both sides {Vrbaiiischitsch, Eitelherg^. Other Stimuli. — The auditor)- apparatus, besides being excited by sound 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 witli auditory hairs containing otoliths, and communicating with twa 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 labjTinth communicate with the swimming bladder. In amphibia, the structure of the labyrinth is somewhat like that in fishes, but the cochlea is not tyjjically developed. Most amphibia, except the frog, are devoid of a membrana tympani. Only the fenestra ovalis (not the rotunda) exists, 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 crocodile 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 (Ing. 591, IV, U S'') are united i^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 otie column-like rod, cor- responding to the stapes, and called the columella. The lowest mammals (Echidna) have structures very like those of birds, while the higher mammals have the same type as in man (Fig. 591, IIIl. The Eustachian tube is always open in the whale. Among invertebrata, the auditoiy organ is very simple in medusa; and mollusca. It is merely a bladder filled with fluid, with the auditory nerves provided with the ganglia in its walls. Hair cells occur in the interior, provided with one or more otoliths. Hensen observed that in some of theannulosa, 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 membranous and cartilaginous labyrinth. Historical. — Empcdocles (473 n. c.) referred auditory impressions to the cochlea. The Hippo- cratic School was acquainted with the tympanum, and Aristotle (384 K. c. ) with the Eu.stachian 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 tympani, the two fene.strse, the cochlea, and the aqueduct. Eustachius (t 1570) described the modiolus, 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 (i64i)the .stapedius. Mersenne (1618) was acquainted with overtones; Gassendus (1658) experimented on the conduction of sound. Acoustics were greatly advanced by the work of Chladni (1802). The most recent and largest work on the ear in vertebrates is by G. Retzius (1881-84). THE SENSE 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, and part of the middle [Cm) turbinated bone (Fig. 601, Cs). AH the remainder of the nasal cavity is called the regio respiratoria. These two regions are distinguished as follows : (i) The regio olfactoria has a thicker mucous membrane. (2) It is covered by a single layer of cylindrical epithelium, the cells being often branched at their lower ends, and contain a yel- low or brownish-red pigment (Figs. 602, 603, E). (3) It is colored by this pigment, and is thereby distinguished from the uncolored regio respiratoria, which is covered by ciliated epithelium. (4) It Nasal and pharyngo-nasal cavities. L, levator eleva- tion ; P.s.p., plica salpingo-palatina ; Cs, Cm, Ci, the three turbinated bones {UrbantschitscJi). ar/-^ Vertical section of the olfactory region (rabbit), . X 560. s, disk : zo, zone of oval, and zr of spherical nuclei; ^, basal cells; (/r, part of a Bowman's gland ; n, branch of the olfactory nerve. contains peculiar tubular glands (Bowman's glands), described as " mixed glands" by Paulsen (§ 142), while the rest of the mucous membrane contains numerous acinous serous glands [Heiden- hain) ; but in man the latter are said to be mixed glands [Stohr) (Fig. 602). Lymph follicles lie in the mucous membrane, and from them numerous leucocytes pass out on to free surface [Stohr). (5) Lastly, the regio olfactoria embraces the end organs of the olfactory nerve. The long, narrow olfactory- cells (Fig. 603, N) are distributed between the ordinary cylindrical epithelium (E) covering the regio 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 ji) 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 part of the mucous membrane, the olfactory cells pass into, and become continuous with, varicose fine nerve fibres, which pass into the olfactory nerve (| 321, 1, i). Accord- ing 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 871 872 OLKACTOKY SENSATIONS. fatty degeneration, even on the 15th day. v. Hrunn fi)unil a homogeneous limiting membrane, which had holes in it for transmitting the processes of the olfactory cells only. [The respiratory part of ihe nasal mucous membrane is lined by ciliated epithelium stratified like that in the trachea ard resinig on a basement membrane. Below tliis there are many lymph corpuscles and ai^gregalions 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 fur- FlG. 603. row or into the naso-palatine canal (dog). The wall next the middle line is covered by olfactory tpiliielium, and receives olfactory nerves (rabliit, guinea- pig), and it contains glands similar to iho^e of the olfactory region; the outer wall is covered by columnar epithelium ciliated in some animals (A7«*«).] 421. OLFACTORY SENSATIONS.— Olfactory sensa- tions are produced by the action of gaseous, odorous substances, being brought into direct contact with the olfactory cells, during Ciie act of hreathin:^. 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 pos- terior nares are said not to be smelt {Bidder). [This is certainly not true, as has been i)roved by Aronsohn.] [It is usually stated that only odorous particles suspended in air excite the sensation of smell. This is certainly not the whole truth — otherwise, how do aquatic animals, like fish, smell ? Moreover, the mucous membrane is always moist, and in some cases where tliere is a profuse secretion from the olfactory mucous membrane, tiiere is no impairment of the sense of smell.] During inspiration, the air streams along close to the septum, while little of it passes through the nasal passages, especially the superior [Paulsen afid Exner). [The expired air takes almost the same course as the inspired air.] The yfz-j/ 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 per- ception, we sniff stwtxdA times, /. e. , a series of rapid inspirations are taken, the mouth being kept closed. During sniffing, the air within the nasal cavities is rarefied, and as air rushes in to equilibrate the pressure, the air, laden with odorous particles, streams over the olfactory region. Odorous fluids are said not to give rise to the sensation of smell when they are brought into direct contact with the olfactory mucous membrane, as by pouring eau de Cologne into the nostrils (7'///- dif- ferent gustatory qualities, the sensations of i. Sweet; 2. Bitter; 3. Acid; 4. Saline. Acid and saline substances at the same time also stimulate the sensory nerves of the tongue, but when greatly diluted, they only excite the end organs of the specific nerves of taste. Perhaps there are special nerve fibres for each different gustatory quality (v. Vinischgaii). Conditions. — Sapid substances, in order that they may be tasted, require the following conditions: They must be dissolved in the fluid of the mouth, espe- cially substances that are solid or gaseous. The intensity of the gustatory sensa- tion depends on : I. The size of the surfyce acted on. Sensation is favored by rubbing in the substance between the papill?c, in fact, this is illustrated in the rub- bing movements of the tongue during mastication (§ 354). 2. The concentration of the sapid substance is of great importance. Valentin found that the following series of substances ceased to be tasted in the order here stated, as they were gradu- ally diluted — syrup, sugar, common salt, aloes, quinine, sidphuric acid. Quinine can be diluted 20 times more than common salt and still be tasted (^Camerer). 3. The //;«^ which elapses between the application of the sapid substance and the pro- duction of the sensation varies with different substances. Saline substances are tasted most rapidly (after 0.17 second, according to v. Vintschgaii), then sweet, acid and bitter (quinine after 0.258 second, v. Vintschgau). This even occurs with a mixture of these substances {Schirmer). The last-named substances produce the most persistent " after-taste." 4. The delicacy of the sense of taste is partly congenital, but it can be greatly improved by practice. If a person continues to taste the same sapid substance, or a nearly related one, or even any very intensely sapid substance, tlie gustatory sense is soon affected, and it becomes impossible to give a correct judgment as to the taste of the sapid body. 5. Taste is greatly aided by the sense of smell, and in foct we often confound taste with smell ; thus, ether, chloroform, musk, and assafoetida only affect the organ of smell. [The combined action of taste and smell in some cases gives rise to flavor (p. 873).] The eye even may aid the determination, as in the experiment where in rapidly tasting red and white wine one after the other, when the eyes are covered, we soon become unable to distinguish between the one and the other. 6. The most advantageous temperature for taste is between 10° to 35° C. ; hot and cold water temporarily paralyze taste. Ice placed on the tongue suppresses, sometimes entirely, the whole gustatory apparatus; cocain alone, bitter tastes, and water containing 2 per cent, of H._,S04, excite afterward a sweet taste [Aducco and Jllosso). Electrical Current. — The constant current, when applied to the tongue, excites, both during its passage and when it is opened or closed, a sensation of acidity at the -j- pole, and at the — pole an alkaline taste, or, more correctly, a harsh, burning sensation [Sulzer, 1752). This is not due to the action of the electrolytes of the fluid in the mouth, for even when the tongue is moistened with an acid fluid the alkaline sensation is experienced at the — pole ( Volla). We cannot, however, set aside the supposition that perhaps electrolytes, or decomposition products, may be formed in the deeper parts and excite the gustatory tilnes. Rapidly interrupted currents do not excite taste {Gn'inkagen). v. Vintschgau, who has only incomplete taste on the tip of tiie tongue, fmds that when the tip of the tongue is traversed by an electrical current, there is never a gustatory sensation, but always a distinct tactile one. In experiments on Ilonigschmied, who is possessed of normal taste in the tip of thetongue, there was often a metallic or acid taste at the + pole on the tip of the tongue, while at the — pole taste was often absent, and when it was present it was almost always alkaline, and acid only exceptionally. After interrupting the current there was a metallic after- taste with both directions of the current. [Testing Taste. — Direct the pers-:on to put out his tongue and close his eyes, and after drying the tongue apply the sapid substance by means of a glass rod or a small brush. Try to confine the stimulus as much as possible to one place, and after each experirnent rinse the mouth with water. A wine-taster chews an olive PATHOLOGICAL COMPARATIVE HISTORICAL. 877 to "clean the palate," as he says. For testing bitter {zsie. use a solution of qui- nine or quassia; for sweet, sugar [or the intensely sweet substance '-'saccharine" obtained from coal tar]; saline, common salt; and acid, dilute citric or acetic acid. The galvanic current may also be used.] Pathological. — Diseases of the tongue, as well as dryness of the mouth caused by interference with the salivary secretion, interfere with the sense of taste. Subjective gustatory impressions are common among the insane, and are due to some central cause, perhaps to irritation of the centre for taste (^ 378, IV, 3). After poisoning with santonin, a bitter taste is experienced, while after the subcutaneous injection of morphia, there is a bitter and acid taste. The terms hypergeusia, hypo- geusia, and ageusia are applied to the increase, dimmution, and abolition of the sense of taste. Many tactile impressions on the tongue are frequently confounded with gustatory sensations, e.g., the so-called biting, cooling, prickling, sandy, mealy, astringent, and harsh tastes. Comparative. — About 1760 taste bulbs occur on the circumvallate papillae of the ox. The term papilla foliata is applied to a large folded gustatory organ placed laterally on the side of the tongue (Fig. 607), especially of the rabbit [Rapf, 1832), which in man is represented by analogous organs, composed of longitudinal folds, lying in the fimbriae lingase on each side of the posterior part of the tongue {^Kraiise, v. Wyss). Taste bulbs are absent in reptiles and birds. They are numerous in the gill slits of the tadpole [F. E. Schultze), while the tongue of the frog is covered with epithelium resembling gustatory cells {^Billroth, Axel Key^. The goblet-shaped organs in the skin of fishes and tadpoles have a structure similar to the taste bulbs, and may perhaps have the same function. There are taste bulbs in the mouth of the carp and ray. Historical. — Bellini regarded the papillee as the organs of taste (171 1). Richerand, Mayo, and Fodera thought that the lingual was the only nerve of taste, but Magendie proved that, after it was divided, the posterior part of the tongue was still endowed with taste. Panizza (1834) described the glosso-pharyngeal as the nerve of taste, the gustatory as the nerve of touch, and the hypoglossal as the motor nerve of the tongue. THE SENSE OF TOUCH. 424. TERMINATIONS OF SENSORY NERVES.— i. The touch corpuscles of \Vagner and Meissner lie in the papillae of the cutis vera (^ 283), and are most numerous in the palm of the hand and the sole of the foot, especially in the fingers and toes, there being alwut 21 to every square millimetre of skin, or loS to 400 of the papilke containing bloodvessels. They are less abundant on the back of the hand and foot, mamma, lips, and tii^ of the tongue, rare on the glans clitoridis, and occur singly and .scattered on the volar side of the forearm, even in the anthro- poid apes. They are oval or elliptical liodies, 40-200 // long [^i^ in.], and 60-70 // broad [-^^j^ to j-^jf in.], and are covered externally by layers of connective tissue arranged transversely in layers, and within is a granular mass with elongated striped nuclei (Figs. 60S, 609, e). One to three medullated nerve fibres pass to tlie lower end of each corpuscle, and surround it in a spiral manner two or three Fig. 608. Fig. 609. Wagner's touch corpuscle from the palm, treated with gold chloride: n, nerve fibres ; a, a, groups ot d C glomeruli. Vertical section of the skin of the palm of the hand, a, blood vessels ; l>, papilla of the cutis vera; c, capillary; d, nerve fibre passing to a touch corpuscle ; /", nerve fibre divided transversely ; e, Wagner's touch corpuscle ; g; cells of the Malpighian layer of the skin. times; the fibres then lose their myelin, and, after dividing into 4 to 6 fibrils, branch within the cor- puscle. The exact mode of termination of the fibrils is not known. Some observers suppose that the transverse fibrillation is due to the coils or windings of the nerve fibrils ; while according to others, the inner part consists of numerous flattened cells lying one over the other, between which the pale terminal fibres end either in swellings or with disk-like expansions, such as occur in Merkel's corpuscles. [These do not contain a soft core such as exists in Pacini's corpuscles. The corpuscles appear to consist of connective tissue with imperfect septa passing into the interior from the fibrous capsule. After the nerve fibre enters it loses its myelin, and then branches, while the branches anastomose 878 PACINI S CORPUSCLES. 879 and follow a spiral course within the corpuscle, finally to terminate in slight enlargements. According to Thin, there are simple and compound corpuscles, depending on the number of nerve fibres enter- ing them.] Kollmann describes three special tactile areas in the hand : (i) The tips of the fingers with 24 touch corpuscles in a length of 10 mm. ; (2) the three eminences lying on the palm behind the slits between the fingers, with 5.4-2.7 touch corpuscles in the same length; and (3) the ball of the thumb and little finger with 3.1-3.5 touch corpuscles. The first two areas also contain many of the cor- puscles of Vater or Pacini, while in the latter these corpuscles are fewer and scattered. In the other parts of the hand the nervous end organs are much less developed. 2. Vater's (1741) or Pacini's corpuscles are oval bodies (Fig. 610), 1-2 mm. long, lying in the subcutaneous tissue on the nerves of the fingers and toes (600-1400), in the neighborhood of Fig. 610. Fig. 611. End bulb from human conjunctiva, a, nucleated capsule ; b, core ; c, fibre entering and branching, terminating in core at d. Fig. 612. Vater's or Pacini's corpuscle, a, stalk ; b, nerve fibre entering it ; c, d, con- nective-tissue envelope; e, axis cylin- der, with its end divided aty. Tactile corpuscles, clitoris of rabbit. joints and muscles, the sympathetic abdominal plexuses, near the aorta and coccygeal gland on the dorsum of the penis and clitoris, and in the mesocolon [and mesentery] of the cat. [They also occur in the course of the intercostal and periosteal nerves, and Stirling has seen them in the capsule of lymphatic glands. They are attached to the nerves of the hand and feet, and are so large as to be visible to the naked eye, both in these regions and between the layers of the mesentery of the cat. They are whitish or somewhat transparent, with a white line in the centre (cat) ; in man they are -^^ to Y^Q inch long, and J^ to Jg- inch broad, and are attached by a stalk or pedicle (Fig. 610, a) to the nerve.] They consist of numerous nucleated connective- tissue capsules or lamellae lined by endo- thelium, separated firom each other by fluid, and lying one within the other like the coats of an onion, while in the axis 'is a central core. A meduUated nerve fibre passes to eachj where its sheath of 880 TERMINATIONS OF SENSORY NERVES. Schwann unites with the capsule. It loses its myelin, and passes into the interior as an axial cylinder (Fig. 6io f), where it either ends in a small knob or may divide dichotomously (Fig. 6io,/), each branch terminating in a small pear-shaped enlargement. [Each large corpuscle is covered by 40-50 lamellae, or tunics, which are thinner and closer to each other (?"ig. 610, d) internally than in the outer part, where they are thicker and wider apart. The lamelUv; are like the laminx in the 1am- ellated sheath of a nerve, and are composed of an elastic basis mixed with white libres of connective tissue, while the inner surface of each lamella is lined by a single continuous layer of endothelium continuous with that of the perineurium. It is easily stained with silver nitrate. The efferent nerve fibre is covered with a thick sheath of lamellated connective tissue (sheath of Henle), which becomes blended with the outer lamella.' of the corpuscle. The medullatcd nerve is sometimes accompanied by a blood vessel, and pierces the various tunics, retaining its myelin until it reaches the core, where it terminates as already described.] 3. Krause's end bulbs very probably occur as a regular mode of nerve termination in the cutis and mucous membranes of all' mammals (Fig. 61 1). They are elongated, oval or round bodies, 0.075 'o °'4 "^"^- 'o"g> ^"'1 \\7^\^ been found in the deeper layers of the conjunctiva bulbi, floor of the mouth, margins of the lips, nasal mucous membrane, epiglottis, fungiform and circumvallate papilhi;, glans penis and clitoris, volar surface of the toes of the guinea pig, ear and body of the mouse, and in the wing of the bat. [In the calf, the " cylindrical end bulbs " are oval, with a nerve fibre terminating within them. The .sheath of Henle becomes continuous with the nucleated capsule, while the axial cylinder, devoid of its myelin, is continued into the soft core. In man the end bulbs are " spheroidal," and consist of a nucleated connective-tissue capsule continuous with Henles sheath of the nerve, and enclosing many cells, among which the axis cylinder which enters Fic. 614. Fir,. 613. 0^^^';m^^.^ Tactile corpuscles from the duck's tongue. A, composed of three cells with two interposed disks.with axis cylinder, «, passing into them. B, two tactile cells and one disk. Bouchon epidermique from the groin of a guinea-pig, after the action of gold chloride, k, nerve fibre; a. tactile cells; »•/, tactile disks ; c, epithelial cells. the bulb branches and terminates.] The spheroidal end bulbs occur in man, in the nasal mucous membrane, conjunctiva, mouth, epiglottis, and the mucous folds of the rectum. According to Waldeyer and Longworth, the nerve fibrils terminate in the cells within the capsule. These cells are said to be comparable to Merkcl's tactile cells ( IVaUeyer). The genital corpuscles of Krause, which occur in the skin and mucous membrane of the glans penis, clitoris, and vagina, appe.ir to be end bulbs more or less fused together (Fig. 612). The articulation nerve corpuscles occur in the synovial mucous membrane of the joints of the 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 touchcorpuscles 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 (Fig. 613). 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, Izqtiieriio, Hesse) in the protoplasmic transparent substance or disk lying between the cells. [This intercellular disk is the " disk tactil " of Ranvier, or the " Tastplatte " 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.] SENSORY AND TACTILE SENSATIONS. 881 [According to Merkel, tactile cells, either isolated or in groups, but in the latter case never forming an independent end organ, occur in the deeper layers of the epidermis of man and mammals and also in the papillse. They consist of round or ilask-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 is bordered on each side by a row of nuclei.] In the nose of the mole there is a peculiar end organ [Einier), 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 (| 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 [" boidons terminals''') (Fig. 614,12). 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. 293).] 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. Prus found ganglion cells more frequently in the subcutaneous tissue than in the corium, and they appeared to have some relation to the blood vessels and sweat glands. 425. SENSORY AND TACTILE SENSATIONS.— In the sensory nerve trunks there are two functionally different kinds of nerve fibres : (i) Those which administer to /azVz/z^/ impressions, which are sensory nerves in the narrower sense of the word ; and (2) those 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 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, mclud- ing 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 temperature 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, i and 5). This renders probable the assumption that their central and peripheral ends also are different. 3. Very probably the reflex acts discharged by both kinds of nerve fibres — the tactile and pathic — are controlled, or even inhibited, by special central nerve organs (§ 361 — ?). 4. Under pathological conditions, and under the action of narcotics, the one sensation may be suppressed while the other is retained (§ 364, 5)- . . Sensory Stimuli. — In order to discharge a painful impression from sensory nerves, relatively strong stimuli are required. The stimuli may be mechanical, chemical, electrical, thermal, and somatic, the last being due to inflammation or anomalies of nutrition and the like. Peripheral Reference of the Sensations. — These nerves are excitable along their entire course, and so is their central termination, so that pain may be produced by stimulating them in any part of their course, but this pain, according to the " law of peripheral perception," is always referred to the periphery. The tactile nerves can only discharge a tactile impression or sensation of contact when moderately strong mechanical pressure is exerted, while thermal stimuli are 56 882 THE SENSE OF LOCALITY. reciiiired to produce a temperature sensation, and in both cases, the results are obtained only when the appropriate stimuli are ajiplied 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 tlie 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. The law of the specific energy of nerves leads us to assume that the cutaneous nerves contain different kinds of nerve fibres with different kinds of end organs, which subserve different kinds of impressions, e.g., pressure, temperature, and pain. Blix and Goldscheider have found such differences. Electrical stimulation causes different sensations according to the part of the skin where it is applied ; at one spot, pain only is produced, at another a sensation of cold, at a third a sensation of heat, and at a fourth, a sensation of pressure. At every temperature^ point or spot, there is insensibility for pain or pressure. The "pressure points" or pressure spots lie much closer together, and are more numerous than the tempera- ture points. There are special " pain spots " and even " tickling spots." These spots are arranged in a linear chain, which usually radiates from the hair follicles. The " tickling spots " coincide with the pressure and pain spots. The feeling of tickling corresponds to the feeblest stimulation of a nerve fibre, and pain to the strongest. The pain spots can be isolated by means of a needle, or electrically, especially in the cutaneous furrows, in which the pressure sense is absent. Goldscheider removed from his own body small pieces of skin, in which he had previously ascer- tained the presence of these " spots," and then investigated the excised skin microscopically. At each such spot he found a rich supj^Iy of nerves ; at the pressure sjiots, there were no touch corpuscles. [By means of the skin, impressions are supplied also to the brain, whereby we become conscious of the amount and direction of a body moved in contact with the skin. Indeed, the discriminative sensibility is more acute for motion than for touch ; but the liability to error in judging of the distance and direction is great [HuH).'] [Very complex sensations are obtained by means of the combined action of the skin and muscles, £. o-., those kn^wn as " feelings of double contact." These sensations are of the greatest ad- vantage in acquiring the use of instrumenls and tools. If we touch an object with a rod, we seem to feel the object at the point of the tod, and not in the hand where the cuta- FlG. 615. neous nerves are actually stimulated. With a walking stick, we feel the ground at the end of the stick. Touch the tips of the hair, or a tooth, and the sensa- tion is referred to the tips of the hair in the one case, and the crown of the tooth in the otherJ(Zaa'(?).] 426. SENSE OF LOCALITY.— We are not only able to distinguish differences of pressure or temperature by our sensory nerves, but we are able to distinguish the part which has been touched. This capacity is spoken of as the sense of space or locality. Methods of Testing. — i. Place the two blunted points of a pair of com- passes (Fig. 615) 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 aesthesiometer may be used instead (Fig. 616) ; one of the points is movable along a gi-aduated rod, while the other is fixed. 2. The distance be- tween the points of the instrument being kept the same, touch several part* of the skin, and ask if the person feels the impression of the points coming nearer to ^sthesiometer. or going wider apart. 3. Touch apartol the skin with a blunt instrument, and observe if the point touched is correctly indicated by the patient. 4. Separate the points of two pairs of compasses unequally, and place their points upon difterent parts of the skin, and ask the person to state when the points of both appear to be equally far apart. A distance of 4 lines on the forehead appears to be equal to a distance of 2.4 lines on the upper lip. This is Fech- ner's "methods of equivalents." The following results have been obtained. The sense of locality of a part of the skin is more actite under the following conditions : — I. The greater the number of tactile nerves'm the corresponding part of the skin. MODIFYING CONDITIONS. 883 2. The greater the mobility of the fart, ^o 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 yi on the flexor surface of the upper limb, and i^ on the extensor surface. 4. The mode of application of the points of the sesthesiometer : (d) According as they are applied one after the other, instead of simultaneously, or as they are considerably warmer or colder than the skin {^Klug), a person may distinguish a less distance between the points. (^F) If we begin with the points wide apart and approximate them, then we can distinguish a less distance than when we proceed from imperceptible distances to larger ones, {c) If the one point is warm and the other cold, on exceeding the next distance we feel two impressions, but we cannot rightly judge of their relative positions {CzertJiak). 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 {Volkmann). [Fr. Galton finds that the reputed increased acuteness of the other senses in the case of the blind is not so gi-eat as is generally alleged. He tested a large number of boys at an educational blind Fig. 616. ^sthesiometer of Sieveking. asylum, with the result that the performances of the blind boys were by no means superior to those 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 in any 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 {Suslowd). The sense of locality is rendered more acute at the cathode when a constant current is used {Suslowd), and when the skin is congested by stimulation {Klinkenberg), and also by slight stretching of the skin iSchney) ; further, by baths of carbonic acid {v. Basch and v. Dietl), or warm common salt, and temporarily by the use of caffein i^Rumpf). 7. Ancemia, produced by elevating the limbs, or venous hypercemia (by compress- ing 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 abdomen during pregnancy, previous exertions of the muscles under the part of the skin tested, and some poisons, e. g., atropin, daturin, morphin, strychnin, alcohol, potassium bromide, cannabin, and chloral hydrate. 884 .ESTHESIOMETRY. Smallest Appreciable Distartce. — J'hc following statement gives the smallest distance, in millnneires, at which two points of a pair of compasses can still be distinguished as double by an adult. The corresponding numbers for a boy twelve years of age are given within brackets. Millimetres. I.I [I.I] .3[..7j Tip of tongue Third phalanx of finger, volar sur face, 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 sur- face, 5. -5.5 Third phalanx of finger, dorsal surface, 6.8 [4.5] Tip of nose, 6.8 [4.5] Head of metacarpal bone, volar, 5. -6.8 [4.5] liall of thumb, 6.5-7. Ball of little finger, 5-5-6. Centre of palm, 8. -9. Dorsum and side of tongue, white of the lips, metacarpal part of the thumb, Tiiird phalanx of the great toe, plantar surface, Second phalanx of the fingers, dorsal surface. Back, ... .... [6.8] [6.8] [9- ] [9- ] Millimetres. Eyelid, 11.3 [ 9. ] Centre of hard palate, 13-5 ["-3] Lower third of the forearm, volar surface, 15. In front of the zygoma, 15.8 [11.3' Plantar surface of the great toe, . . 1 5.8 " 9. Inner surface of the lip, 20.3 13.5 I5ehind the zygoma, 22.6 f 15. 8' Porehead, 22.6 [18. Occiput, 27.1 [22.6 Back of the hand 31.6 22.6 • 33-8 [22.6] ' "31.6- 22.6' Under the chin, 33.8 Vertex Knee 36.1 Sacrum, gluteal region, 44.6 | 33.8' Forearm and leg, 45.1 [33.8" Neck, 54.1 [36.1" Back, at the fifth dorsal vertebra, lower dorsal and lumbar region, 54. 1 Middle of the neck, 67.7 Upper arm, thigh, and centre of the back, 67.7 [31.6-40.6] Illusions of the sense of locality occur very frequently; the most marked are : (i) A uniform movement over a cutaneous surface apj^iears to be quicker in those places which have the finest sense of locality. (2) If we merely touch the skin with the two points of an a^sthesiometer, then they feel as if they were wider apart than when the two points are moved along the skin [Fcchner). (3) A sphere, when touched with short rods, feels larger than when long rods are used ( Tourlual). (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. 617, B), it feels as if two balls were present, but with the fingers uncrossed single ] (5) When i)ieces of skin are transplanted, e. g., Fig. 617. from the forehead, lo form a nose, the person operated on feels, often for a long time, the new nasal jiart as if it were his forehead. Theoretical. — Numerous experiments were made by E. II. Weber, Lotze, Meissner, Czer- mak, 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 impression, and administer thereto, lie called the part of the skin to which each single nerve fibre is distributed a "circle of sensation." 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 g the tsvo points stmiulated. This explanation, Aristotle's Experiment. * based upon anatomical considerations, does not explain how it is that, with practice, the circles of sensation become smaller, and also how it is that only one sensation occurs, when both points of the instruments are so applied that both points, although further apart than the diameter 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 wnth 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 (ocaiiiy of the sensation. Every cutaneous area, therefore, gives to the tactile sensation a THE PRESSURE SENSE. 885 "local 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 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 sensation changes so little that two separate impressions fuse into ojie. 427. PRESSURE SENSE. — By the sense of pressure we obtain a knowl- edge of the amount of weight or pressure which is being exercised at the time on the different parts of the skin. A specific end apparatus arranged in a punc- y\g. 618. tated manner is connected with the pressure sense (Fig. 618). These points or spots are called .•...*.;••;• :'••*.•;*••'■.*.' ;".v :•••;.. "pressure spots" or " pressure points" '... y'.'-.^: ':•'•.;.••:•.*• '-v^i:-^ i^Blix), and are endowed with varying degrees of "•-■.■.•• .::••.". .■•■•"*•:•'•/.* *""■•'■ sensibility ; at some places (back, thigh) they are "' * ' : " distinguished by a markedly pronounced after- "' . , f , , ' . , . rr>i , r ^^ Pressure spots, a, middle of the sole of the sensation. Ihe arrangement of the pressure foot; ^, skin of zygoma ; t, skin of the back. spots follows the type of the arrangement of the temperature spots. The pressure spots have usually another direction than that of hot and cold spots ; as a rule, they are denser. The minimal distance at which two pressure spots, when simultaneously stimulated, are felt as double, is— on the back, 4 to 6 mm.; breast, 0.8; abdomen, 1.5 to 2; cheek, 0.4 to 0.6; upper arm, 0.6 to 0.8 ; forearm, 0.5 ; back of the hand, 0.3 to 0.6; palm, o.i to 0.5 ; leg, 0.8 to 2 ; back of foot, 0.8 to i ; sole of foot, 0.8 to i mm. Methods. — i. Place, on the part of the skin to be inve.stigated, 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 dis- placement of the weights — the weights must always be placed on the same spot, and the skin should be covered beforehand with a disk, while the muscular sense must be eliminated (^ 430). [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. Eulenburg 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 mercu- rial balance (Fig. 619). 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 (w) on which an equilibrating weight (S) can be moved. The 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 adjoin- ing 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 without 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 temperatures 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 sensation. 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 head and forearm, which perceive a pressure of 0.002 grm. ; the fingers first feel with a weight of 886 RESULTS OF THE PRESSURE SENSE. 0.005 ^o 0-015 grin- '. the chin, abdomen and nose with 0.04 to 0.05 grm. ; the finger nail 1 grm. {Kam/nler and Auberi). The greater the sensibility of the skin, the more r.ipidly can 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 lingers, and still be felt singly {Block). 2. Intermittent variations of pressure, as in Goltz's tube, are felt more acutely by the tips of the fingers than with the forehead. ' 3. Differences between two weights are perceived by the tips of the fingers when the ratio is 29 : 30 (in the forearm as 1S.2 : 20), provided the weights are not too light or too heavy. In jiassing from the use of very light to heavy weights, the acuteness or fineness of the perception of difference increases at once, but with Fig. 619. Landois' Mercurial Balance for Testing the Pressure Sense. heavier weights, the power of distinguishing differences rapidly diminishes again {E. Hering, Biedermanti). This observation is at variance with the psycho-physical law of Fechner (§ 383). 4. A. Eulenburg found the following gradations in the fineness of the pressure sense : The forehead, lips, dorsum of the cheeks and temples appreciate differences of J^ to Jq (200 : 205 to 300 : 310 grm.). The dorsal surface of the last phalanx of the fingers, the forearm, hand, ist and 2d phalanx, the volar surface of the hand, forearm and upper arm, distinguish 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 THE TEMPERATURE SENSE. 887 weight, which, when added to i grm. already resting on the skin, was appreciated as a difference, and he found that for the 3d phalanx of the finger it was 0.499 grm. ; back of the foot, 0.5 grm. ; 2d phalanx, 0.771 grm. ; ist phalanx, 0.02 grm. j leg, i grm. ; back of the hand, 1.156 grm. ; palm, 1.018 grm. ; patella, 1.5 grm. ; forearm, 1.99 grm. ; mubilicus, 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 (^. 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 ^I-q to -gJ-g- 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 of strings are distinguished as such when the number of vibrations is 1506 to 1552 l)er second (v. Witiich atid Grilnhageri). 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 t/ie limit of the fluid, on the volar surface of the finger, at the limit of the surface of the mercury. 428. TEMPERATURE SENSE.— The temperature sense makes us acquainted with the variations of the heat of the skin. A specific end apparatus arranged in a punctated manner is connected with the temperature sense. These "temperature spots " are arranged in a linear manner or in chains, which are usually slightly curved (Figs. 620, 621). They generally radiate from certain points of the skin, usually the hair roots. The chain of the " cold spots " usually does not coincide with those of the " hot spots," although the point Fig. 620. (^■F. W.F. -<-«■ C D C, cold spots, and D, warm spots of the radial A, cold spots, B, hot spots, from the volar surface of half of the dorsal surface of the wrist. The the terminal phalanx of the index finger to the arrow indicates the direction in which the hair margins of the nail. points. from which they radiate may be the same. Frequently, these punctated lines are not complete, but they may be indicated by scattered points, between which, not unfrequently points or spots for other qualities of sensation may be intercalated. Near the hairs there are almost always temperature spots. In parts of the skin, where the temperature sensibility is slight, the temperature points are present only near the hairs. The sensation of cold occurs at once, while the sensation of heat develops gradually. Mechanical and electrical stimulation also excite the sensation of 888 THE TEMPERATURE SENSE. temperature. A gentle touch of the temperature spots is not perceived ; these points seem to be aniv:sthetic toward pressure and i)ain. As a general rule, the cold spots are more abundant over the whole body — there are more of them in a given area — while the hot spots may be cjuite absent. The hot spots are, as a rule, perceived as double at a greater distance apart than the cold spots. Tiie minimal distance on the forehead is o.S mm. for the cold spots, and 4 to 5 mm. for the warm spots ; on the breast the corresponding numbers are 2 and 4 to 5 ; back, 1.5 to 2 and 4 to 6 ; back of hand 2 to 3 and 3 to 4 ; palm, 0.8 to 2 .; thigh and leg, 2 to 3 and 3 to 4 mm. Method. — To test the hot and cold spots, use a hot or cold metallic rod; at the cold spots, when they are lightly touched, only the sensation of cold will be felt, and a corresponding effect with a hot rod at tlie hot spots. Both spots are insensible to objects of the same temperature as the skin. According to E. Hering, what determines the sensation of temperature is the temperature of the thermic end apparatus itself, /. e., its zero temperature. As often as the temperature of a cutaneous area is above its zero temperature, we feel it as viarm ; in the opposite case, cold. The one or the other sensation is more marked, the more the one or other temperature varies from the zero tem- perature. The zero temperature can undergo changes within considerable limits, owing to external conditions. 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 : i. 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.— ^i. Asa 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.i6° R. with the tips of the fingers {^E. H. Weber). Tem- peratures just below that of the blood (33°-27° C. — Nothnagel) are distinguished most distinctly by the most sensitive parts, even to differences of 0.05° C. {Linder- mann). Differences of temperature are less easily made out when dealing with temperatures of 33°-39° C, as well as between i4°-2 7° C. A temperature of 55° C, and also one a few degrees above zero (2.8° C), cause distinct pain in addition to the sensation of temperature. 4. The sensibility for cold is generally greater than for warmth, — that of the left hand is greater than the right {Goldscheider). The different parts of the skin also vary in the acuteness of their thermal sense, and in the following order : Tip of the tongue, eyelids, cheeks, lips, neck and body. The perceptible minimum Nothnagel found to be 0.4° on the breast; 0.9° on the back; 0.3°, back of the hand; 0.4°, palm; 0.2, arm; 0.4°, back of the foot; 0.5°, thigh; 0.6°, leg; o.4°-o.2°,cheek ; o.4°-o.3° C, temple. The thermal sense is less acute in the middle line, e.g., the nose, than on each side of it {E.If. Weber). Fig. 622 shows that in one and the same portion of skin, the cold and hot spots are differently located, i.e., their different topography. If the mucous membrane of the mouth be penciled with a 10 per cent, solution of cocain, the sensibility for heat is abolished; the cooling sensation of menthol depends upon its stimulation of the cold nerves; CO2 applied to the skin excites the heat nerves (^Goldscheider). 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. THE TEMPERATURE SENSE. 889 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 {M. Alsberg). When la7'ge areas of the skin are touched, the perception of differ- ences is more acute than with small areas. Rapid variations of the temperature produce more intense sensations than gradual changes of temperature. Fatigue occurs soon. Illusions are very common : i. The sensations of heat and cold sometimes alternate in a paradoxical 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, eg., the whole hand when placed in water at 29 5° C. feels warmer than when a finger is dipped into water at 32° C. 3. Cold weights are judged to be heavier than warm ones. Pathological. — Tactile sensibility is only seldom increased (hyperpselaphesia), but great sensibility 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. Fig. 622. ••::::::K::illill!j'---lillll Cold and hot spots from the same part of the anterior surface of the forearm, a, cold spots ; ^, hot spots. The dark parts are the most sensitive, the hatched the medium, the dotted the feebly, and the vacant spaces the non- sensitive. 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 \6vai, {Stir ling). '\ A remarkable variation of the sense of locahiy 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 csXltdi " partial tactile paralysis." Limbs which are " sleeping''^ feel heat and not cold i^Herzen). 429. COMMON SENSATION— PAIN.— By the term common sensa- tion we understand pleasant or unpleasant sensations in those parts of our bodies 800 COMMON SENSATION I'MX. which :ire encluwcd with sensibility, and which arc not referable to external objects, and whose cliaracters 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 breathing. Pain may occur wherever sensory nerves are distributed, and it is invariably causctl 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 appears to l)e especially active, as many tissues become extremely painful during inflamma- tion {e.^., 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 perijiheral 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 central part of the nerve, such an impression is still referred to the peri])heral end of the nerve. Thus we explain the paradoxical anaesthesia dolorosa. In connection with painful impressions, the patient is often unable to localize them exactly. 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 /(^/w^^Z/V intensification, as in some neuralgias. The intensity of the jjain depends especially upon the excitability of the sensory nerves. There are considerable individual variations in this resi)ect, 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 importance, in as far as the same stimulation, when long continued, may become unbearable. We speak of piercing, cutting, boring, burning, throbbing, pressing, 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 anaesthe- tics and narcotics, such as ether, chloroform, morphia, etc. (§ 364, 5). Methods of Testing. — To test the cutaneous sensibility, we usually employ the constant or induced electrical current. Determine first the niiniiiiuni sensibility, i. e., the strength of the current which excites the first trace of sensation, and also the minimum of pain, i. e., the feeblest strength of the current which first causes distinct impressions of pain. The electrodes consist of thin metallic needles, and are placed i to 2 cm. apart. Pathological. — When the excitability of the nerves which administer to painful sensations is increased, 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, disagreeable, or painful sensations 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 liy supposing that in a part of the nerve the condition is delayed (^ 337, 2). In neuralgia there is severe pain, occurring in paroxysms, with violent exacerbations and pain shooting into other parts (p. 648). Very frequently excessive pain is produced by pressure on the nerve where it makes its exit from a foramen 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 lon^ duration the sensibility may MUSCULAR SENSE. 891 be diminished even to the condition of analgesia ( Tilrck) ; in the latter case there may be pronounced anaesthesia dolorosa (p. 890). 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 hemianeesthesia, 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 anaesthetic. This condition has been spoken of as transference of sensibility. The phenomenon is not due to galvanic currents developed by the metals ; but it may be, 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 [Rti?npf). 430. MUSCULAR SENSE.— Muscular Sensibility.— The sensory nerves of the muscles (§ 292) always convey to us impressions as to the activity 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 disturb- ance. 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 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 move- ments of the limbs in space; and (/^) those of resistance where there is opposition to the movetxient, as in lifting a weight. In the latter case the sensations 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 sensorium, we form judg- ments 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 intimately related to, and often combined with, the exercise of the sensation 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 impaired, as in locomotor ataxia, the patient may move to and fro, or even fall (p. 697), 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.] A healthy person perceives a weight of I gramme applied to his upper arm; when a weight of 15 grms. is applied, he perceives an addition of i grm. If the original weight be 50 grms. , he will detect the addition of 2 grms. ; if the original weight be loo grms., he will detect 3 grms. The weight detectable by the individual finger varies. With the leg, when the weight is applied at the knee, the individual may detect 30 to 40 grms. ; but sometimes only a greater weight. Often one can detect a difference of 10 to 20, or 30 to 70 grms. 892 MUSCULAR SENSE. Section of a sensory nerve causes disturbance of the fine graduation of movement (p. 668). Meynert supposes that the cerebral centre for muscular sensibility lies in ihe 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 hyperali^ia ami hvper- trsthesiii),zs, in an.xietas libianiin,A painful condition of unrest which leads to a continual chani^e in the i^osition of ihe limbs. In cramp there is intense pam, due to stimulation of the sensory nerves of the muscle, and the same is tliecase in inflammaiion. Diminution of the muscular sensibility occurs in some choreic and ataxic persons (^ 364, 5). In locomotor ataxia the muscular sense of the upper extremities may lie normal or weakened, while it is usually considerably 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 spontanea, spontaneous generation). — It was formely 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 organisms. 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, " Omne vivum ex ovo " {Harvey, or, ex vivo). Some highly organized invertebrate animals (Gordius, Anguillula, Tardi- grada, 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 Fig. 624. 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 maybe divided into pieces, and each piece gives rise to a new individ- ual [although under normal circumstances the hydra gives off buds, and is provided with genera- tive organs]. [Division of Cells. — Although a cell is de- fined as a "nucleated mass of living protoplasm," recent researches have shown that, from a histo- FiG. 623. Fig. 623. — Changes in a cell nucleus during karyokinesis. Fig. 624 — Typical nucleated cell of the intestinal epithelium of a flesh maggot, mc, membrane of cell ; vin, mem- brane of nucleus ; pc, cellular protoplasm, with the radiating retictdutii, and the enchylema enclosed in its meshes ; j>n, plasma of nucleus ; bn, nuclear filament showing numerous twists. logical as well as from a chemical 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 homogene- ous substance in its meshes, while a similar network of fibrils exists within the nucleus itself (Fig. 623).] [The nucleus of a typical cell is a spherical vesicle, consisting of a membrane containing what is called " achromatin," because it is not readily stained by staining reagents. Flemming has also called it nuclear fluid, or intermediate substance. The achromatin substance is permeated by a deli- cate reticular network, or plexus of fibrils, which has been called " chromatin," " nucleoplasm," "karyoplasma," and " karyomiton." The network stains readily with pigments, hence the name " chromatin" given to it by Flemming. The nodal points of the network give a dotted or granular appearance to the nucleus, especially when it is examined with a low power. The nuclear 893 894 DIVISION OF CELLS. membrane also consists of chromatin (Vig. 624). In tlie meshes of the network lie nucleoli, which seem to differ in constitution, ami perhaps in function. According to Flemming, there are principal and accessory nucleoli in some nuclei. In Carnoy's nomenclature the several parts are spoken of as a line reticulum of lihrils, enclosing in its meshes a fluid — the enchyUma — which contains various particles in suspension.] [Direct Cell Division. — 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.] [Indirect Cell Division. — Recent observations, confirmed by a great number of investigators, conclusively prove that the process of division in cells is a very complicated one, the changes in the nucleus being very remarkable. The terms karyokinesis, mitosis, or indirect division have been applied to this process. Figs. 623, 625 show the changes that take ])lace in the nucleus. The chromatin or intranuclear network (^, B) passes into a convolution of tibrils, while the nuclear envelope becomes less distinct, the fibiils 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, rosetie, or spirem (C). The fibres curve round both at the periphery and the centre and form loops; but when their peripheral connections are severed or dissolved, we obtain a star-shaped former aster (D), composed of single loops radiating from the centre (f). The loops divide in the direction of their length; their number is doubled, but they are thinner. By this further subdivision, the whole is compo.sed of tine radiating fibrils (/), which gradually arrange themselves around two poles, or new centres, to form the barrel-form or pithode (E) ; the two groups of loops then .separate still further, and arrange themselves so as form a diaster, or double star {g), the two groups being sepa- Mitosis. A, nuclear reticulum, resting state ; B, preparing for division; C, wreath stage; D, monaster stage; barrel stage ; F, diaster stage ; G, daughter wreath stage ; H, daughter cells, passing to resting stage. E, • rated 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 proto- plasm separates into two parts. In each of these parts the chromatin rearranges itself into an irreg- ular coil, and the whole is called dispirem (G), and when division is complete, the chromatin fila- ments assume the form seen in a resting nucleus. This whole complex process may be accomplished in I to 4 hours. 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 origi- nal cell.] The following scheme represents some of the more important changes : — Mother nuc/eus. I Daughter nuclei, 1. Network. | 8. Network. 2. Convolution. I 7. Convolution. 3. Wreath or Spirem. 6. Dispirem. 4. A.ster. I 5. Disaster. Equatorial grouping of chromatin. III. Budding or gemmation occurs in a well-marked form among the polyps and in some infu- soriaHS (\'orticella). 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 thepolyzoa. In .some com- posite animals (siphonophora) the different polyps perform different functions. Some have a diges- tive, 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 FORMS OF REPRODUCTION. 895 animals (polyps, infusoria), which can reproduce themselves by buds or division, there is also the formation of male and female elements of generation, so that they have a sexual and a non-sexual mode of reproduction. IV. Conjugation is a form of reproduction which leads up to the sexual form. It occurs in the unicellular Gregarinje. 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 numer- ous oblong structures — the pseudo navicelli — are developed. Those 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 fiom 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 Y\G. 627. repeat the same cycle of changes. Metamorphosis occurs extensively among the insrcts; some of them have several ap///// /'///'//'// stages (holo-metabolic), and others have few stages (hemi- mmt sllllM'mt' ' '' metabolic). It also occurs in some arthropoda, and worms, ^.^., trichina; the sexual form of the animal occurs in the intestine, the numerous larva wander into the muscles, where they become encysted, and form undeveloped sexual Fig. 626. A ripe egg taken from the uterus of Taenia solium, a. Albumi- nous envelope ; b, remains of the yelk; c, covering of the embryo ; d, embryo with embryonal booklets. Encapsuled cysticercus from Taenia solium em- bedded in a human sartorius. Natural size. 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 (5V^^«i-/ri//).— 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 seg- ments of the tapeworm are called proglottides (Fig. 631 ), 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 (Fig. 626), and from them is developed an elliptical embryo, provided with six booklets, which is swallowed by another animal, the host. These embryos bore their way into the tissues of the host, where they undergo development, forming the encysted stage (Cysticercus (Fig. 627), Coenurus, or Echinococcus (Fig. 630). The encysted capsule may contain one (cysticercus) or many (coenurus) sessile heads of the taenia. In order to undergo further development, the cysticercus must be eaten alive by another animal, when the head or scolex fixes itself by the booklets and suckers to the intestine of its new host (Fig. 629), 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 cellulosas (Fig. 628), in the pig, when it con-titutes the 7neasle in pork; Taenia mediocanellata (Fig. 631), the encysted 896 TESTIS. stage, in the ox ; Taenia coenurus, in the dog's intestine; the encysted stage, or Coenurus cere- bralis, in llie brain of the sheep, where it j^ives rise to the condition of "staggers" ; Taenia echi- nococcus, in the dog's intestine : the embryos or scolices occur in the hverof man as " hydatids." The medusLV also exhibit alternation of generations, and so ilo some insects, especially the plant lice or aphides. VII. Parthenogenesis {Owen, v. Sie/whi). — In this variety, in addition to sexual reproduction, new individuals may be produced without sexual union. The nonsexually produced brood is always Fig. 628. Fig. 630. Cysticerci from Taenia solium removed from their capsule, i, natural size ; 2, magni- fied a, embryo sac : <^, cavity produced by budding of the embryo sac; c, suc- torial disks and booklets. Cysticercus of Taenia soli- um, with its head and segments protruded. a, caudal sac ; b, head of the tapeworm, with disksand booklets (sco- lex) ; c, neck. Part of an Kchinococcus capsule, with developing buds. «, sheath; ^, parenchymatous layer ; «^, ger- muiating capsule tilled with scolices. of one sex, as in the bees. A bee hive contains a queen, the workers, and the drones or males. During the nuptial (light, 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 unfertilized 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, while, fibrous covering, the tunica albuginea, composed chiefly of white, interlacing, fibrous tissue. Externally, this layer is covered by the visceral layer Fig. 6-, I. Taenia Mediocanellata. Natural size. of the serous membrane, or the tunica vaginalis, which invests the testis and epididymis. The tunica albuginea is prolonged f)r some di.stance as a vertical septum into the posterior part of the testis, to furm 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 STRUCTURE OF A SEMINAL TUBULE. 897 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 compartments to support the structures lying in these compartments.] [Arrangement of Tubules. — Each compartment contains several seminal tubules, long con- voluted tubules (ji^ in. in diam.) which rarely branch except at their outer end ; they are about 2 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. 632). 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. 632). 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 vascu- losi — which together form the head -"^i*^- "32. of the epididymis. These tubes T. albuginea. gradually unite with each other and form the body and globus minor of the epididymis, which, when unraveled, is a tube about 20 feet long, terminat- ing 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. 637). 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 sperm a'.ozoa, and they constitute the spermatoblasts. These several layers of cells leave a distinct lumen. The tubuli recti are narrow in diame- ter, and lined by a single layer of squamous or flattened epithelium (Fig. 633). The rete testis consists merely of channels in the fibrous stroma without a distinct memhrana propria, but lined by flattened epithe- lium. The vasa efferentia and coni vasculosi have circular smooth mus- cular 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 epi- didymis, whose tubules have the same structure (Fig. 634). In sheep, pigment cells are often found in the basement membrane. The vas deferens is lined by several layers of columnar epithelium resting 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 submucous coat connecting the muscular and mucous coats together; outside all is the fibrous adventitia.] [The interstitial tissue (Fig. 632), supportiijg the seminal tubules, is laminated and covered by endothelial plates, with slits or spaces between the lamellae, which form the origin of the lym- phatics. These lymph spaces are easily injected by the puncture method. In fact, if Berlin blue 57 Septum. Transverse section of the testis (low-power view 898 CHEMICAL COMPOSITION OF THE SEMINAL FLUID. be forced into the testis, the lymphatics of the testis and spermatic cord are readily filled with the injection. In some animals (boar^l, and to 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 Wollhan bodies (A'/f/M), or, according to Waldeyer, they are plasma cells. Tlie blood vessels are numerous, and form a dense plexus outside the basement ineml)rane 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 vesiculic 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 ^' spermatin " by Vauquelin. 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 Fir.. 6??. Tubulus rectus. End of convolu- ted tube. Narrow part. Fig. 63t. Bloodvessel. Rete testis. Convoluted seminal opening into a straight tube. tubule narrow Blood vessel Interstitial — connective tissue. Transverse section of the tubules of the epi- didymis. water it becomes gelatinous, and from it separate whitish transparent flakes. When long exposed, it forms rhomboidal crystals, which, according to Schreiner, consist of phosphatic salts with an organic base (C.II-N). These crystals (Fig. 635) are said to be derived from the prosta'ic fluid, and are identical with the so-called Charcot's cr)-stals (Fig. 149, c, and iJ 138). The prostatic fluid is thin, milky, amphoteric, or of slightly acid reaction, and is possessed of the seminal odor. The phos- phoric acid necessary for the formation of the cry.stals is obtained from the seminal fluid. A some- what similar odor occurs in the albumin of eggs not quite fresh. The non-poisonous ptomain, cadaverin (pentamethyldiamin of LanJenhurg), isolated by Brieger from dead bodies, has a similar odor. The secretion of the vesiculae seminales of the guinea-pig contains much fibrinogen (p. 424). The spermatozoa are 50/7. long, and consist of a flattened pear-shaped head (Fig. 636, I and 2, k), which is followed by a rod-shaped middle piece, w (Schweigger-Seidel'), and a long tail-like prolongation or cilium,/. The sperma- tozoon 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 moverrient is most rapid immediately after the fluid is shed, but it gradually becomes feebler. SPERMATOZOA. 899 Fig. 635. 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. Jietzius). These consist of a flattened, long, narrow, transparent, protoplasmic mass, with a fibre composed 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. Kranse, Gibbes). G. Retzius describes a special terminal filament (Fig. 636, e). An axial thread surrounded by an envelope of protoplasm, traverses the middle piece and the tail [Einier, 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 exhibit spontaneous movements for many hours or days.] The movements are due to the lash- ing movements of the tail, which moves in a circle or rotates on its long axis, the impulse to move- ment proceeding from the protoplasm of the middle piece and the tail, which seem to be capable of moving when they are detached [^Evner). These movements are comparable to those that occur in cilia (g 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 or vaginal mucus i^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 qui- escence produced by water may be set aside by dilute alkalies ( Virchow), as with cilia (p. 501). Engelmann finds that minute traces of acids, alco- hol, and ether excite movements. The spermato- zoa of the frog may be frozen four times in succes- sion 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 (^Mantegazzd). Resistance. — Owing to the large amounts 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 amor- phous masses. Their organic basis resembles the semi-solid albumin of epithelium. Seminal fluid, besides spermatozoa, also con- tains seminal cells, a few epithelial cells from the seminal passages, numerous lecithin granules, stratifled amyloid bodies (inconstant), granular yellow pigment, especially in old age, leucocytes, and sperma crystals {^Fiir binge j-). 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. 637, I, b, and IV, }i), 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 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- matoblast elongates into a tail (IV, r), while the deeper part forms the head and middle pieces of the future spermatozoon (IV, ^). At this stage the spermatoblast 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 Crj'stals from spermatic fluid. 900 DEVELOPMENT OF SPERMATOZOA. the tail and the middle piece (III, /). Between the spermatoblasts are numerous round ama>boid cells devoid of an envelope, and connected to each other by pro- Fir,. 6^,6. Sper.Tiatozoa. i, human (X 600), ihc head seen Iruui the side ; 2, on edge ; k, head ; ;//, middle piece ; /, tail.; e, terminal 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 (F) ; 10, from cobitis. ces 65. They seem to secrete the y?///V/part of the semen, and they may therefore be called seminal cells (I, s, II, III, IV, />). A sjiermatozoon, therefore, is a detached, independently mobile cilium of an enlarged eijithelial cell. Some ob- Fin. 637. •""M-O^^ Semi-diagrammatic spermatogenesis : I, Transverse section of a seminal tubule — a, membrane ; b, protoplasmic inner lining ; c, spermatoblast ; s, seminal cells. II, Unripe spermatoblast— y. rounded clavate lobules ; p, seminal cells. IV, Spermatoblast, with ripe spermatozoa (k) not yet detached ; tail, r ; «, wall of the seminal tubule ; h, its pro- toplasmic layer. Ill, Spermatoblast with a spermatozoon free,/. servers adhere to the view that the spermatozoa are, in part at least, formed within round cells, by a process of endogenous development. STRUCTURE OF THE OVARY. 901 Section of a cat's ovary. The place of attachment or hilum is below. On the left is a corpus luteum. According to Benda and v. Ebner, the spermatoblasts are formed by the coalescence (copula- tion) of a group of seminal cells with the lower part of the foot plate and stalk of the spermato- blasts. Each seminal cell forms firom its nucleus the head, and from its pro- yig 6''8 toplasm the tail of a spermatozoon. For the complete formation of these ])arts, there must be a coalescence of the seminal cells with the spermato- blasts. 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 corkscrew (singing birds, paludina), or merely like hairs (insects — Fig. 636). Immobile seminal cells, quite different from the ordinary forms, occur in myria- poda and the oyster. 433. THE OVARY — OVUM — UTERUS. — [Structure of the Ovary. — The ovary consists of a connective- tissue framework, with blood vessels, nerves, lymphatics and numerous non- striped muscular fibres. The ova are embedded in this matrix (Fig. 638). The surface of the ovary is covered with a layer of columnar epithelium (Fig. 639, e), the remains of the germ epithelium. The most super- ficial layer is called the albu- Fig 639. ginea ; it does not contain any ova. Below it is the cortical layer of Schron, which contains the smallest Graafian follicles (1^0 inch— Fig. 638), while deeper down are the larger folli- cles (Jq to jig 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 £. v. Bear, 1827) is 0.18 to 0.2 mm. [xio ^"0 in diameter, and is a spherical cellular body with a thick, solid, elastic envelope, the zona pel- lucida, with radiating strise (Fig. 640). The zona pellucida en- closes the cell contents repre- sented by the protoplasmic, gran- ular, contractile vitellus or yelk, which in turn contains the eccen- trirallv nlared =;nhprirnl niiHeiiq Section ot an ovary. ^, germ epithelmm ; i, large sized follicles ; 22, mcaiiy piacea spnerical nucleus middle sized, and 3, 3, smaller sized follicles ; o, ovum within a Graafian or germinal vesicle (40-50 /z follicle; v, z/, blood vessels of the stroma;^, cells of the membrana — Purkinje, 1825 ; Coste, 1834). granulosa. The germinal vesicle contains the nucleolus or germinal spot (5-7 {i — R. Wagner, 1835). The chemical composition 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 ^(Figs. 640, 641, V, Z), to which cells the Graafian folUcles are often adherent, is a cuticular membrane formed secondarily by the follicle i^PflUger). According to Van 902 DEVELOPMENT OF Till-: OVA. Beneden, it original cell is lined hy a thin membrane next the vitellus, and he regards the thin membrane as the membrane of the ovum. The fine radiating stria' in the zona arc said to be due to the existence of numerous canals Fig. 640. Cells of discus proligerus. Ger- minal spots. Acces- sory nu- cleoli, alsoyC [A'olliker, v. Sc/ikn). It is still undecided whether there is a special tnicropyle or hole for the entrance of the spermatozoa. A micropyle has been ob- served in some ova (holothurians, many fishes, mussels). The ova of some animals (many insects, e. g., the tlea) 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 : Tlie surface of the ovary is cov- ered with a layer of cylin- drical epithelium — the so- called " germ epithe- lium " — and between these cells lie somewhat spherical Ripe ovum of rabbit. " primordial ova " (Fig. 641, I, a, a). The epithe- lium covering the surface dips into the ovary at various places to form " ovarian tubes" (Fig. 683). 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 continuations 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 number of rounded compartments — snared off, as it were, by the ingrowth of the ovarian stroma (I, c). Each compartment so snared off usually contains one, or at most two, ova (IV, o, 0), and becomes developed into a (iraafian follicle. The embryonic follicle enlarges, and fluid appears within it ; while its lateral small cells become changed into the epitheliimi lining the Graafian follicle itself, or those of the raembrana 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. 639).] When a Graafian follicle with its ovum is about to ripen (IV), it sinks or passes downward into the substance of the ovary, and enlarges at the same time by the accumulation 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 e])itlielium constituting the membrana granulosa (IV, ^). When a Graafian follicle is about to burst, it again rises to the surface of 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 DEVELOPMENT OF THE OVA. 903 follicles undergo development normally, by far the greatest number atrophy and never ripen. (The study of the development of the ova and the ovary was ad- vanced particularly by Martin Barry, Pfliiger, Billroth, Schron, His, Waldeyer, Kolliker, Koster, Lindgren, Schulin, Foulis, Balfour and others.) According to Waldeyer, the mammalian ovum is not a simple cell, but a compound structure. The original primitive ovum is, according to him, formed only of the germinal vesicle and germinal spot, vi^ith the surrounding membranous clear part of the vitellus (Fig. 641, III). The remainder of the vitellus is developed by the transformaiion of granulosa cells, which also form the zona pellucida. Holobiastic and Meroblastic Ova. — The ova of frogs and cyclostomata have the same type as mammalian ova; they are called holobiastic ova, because all their contents go to form cells vv^hich take part in the formation of the embryo. In contrast with these, the birds, the mono:remes alone among the mammals {Caldwell), the reptiles and the other fishes have meroblastic ova {Reicheri). Fig. 641. I, An ovarian tube in process of development (newborn 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 {o, d) and the tunica granulosa {g) of a bitch. V, Part of the surface of a ripe ovum of a rabbit— s, zona pellucida ; d, vitellus ; e, adherent cells of the membrana granulosa. VI, First polar globule formed. VII, Formation of the second polar globule [Fol). The latter, in addition to the white or formative yelk, which corresponds to the yelk of the holo- biastic eggs, and gives rise to the embryonic cells, contains the food-yelk (yellow in birds), which during development is a reserve store of food for the developing embryo. Hen's Egg. — The small, white, round, finely granular speck, the cicatricula, blastoderm, or tread, which is 2.5-3.5 i""^- broad and 0.28-0.37 thick, lying upon the surface of the yellow yelk, corresponds to the contents of the mammalian ovum, and is, therefore, the formative yelk. In the cicatricula lie the germinal vesicle and spot (Fig. 642). From the tread in which lie the charac- teristic white yelk elements, processes pass into the yellow yelk. A part passes as an exceedingly thin layer round the yelk, or cortical protoplasm. [The 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 fecun- dated egg the cicatricula has a white margin (the area opaca), smrrounding 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 904 STRUCTURK OF A HEN S EGG. white and yellow yelk. The outermost layer is a thin layer of white yelk, which is slightly thicket at the margin of the cicatricula. Within the centre of the yelk is a flask-shaped mass of white yelk, the neck of the llask being connected with the while yelk outside. This flask shaped mass does not become so hard on being boiled, and its upper expandeil 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 /i in diameter, and tlity are often polvhedral from mutual pressure' (Fig. 643, /'). [They are very delicate and non-nucleated, but filled with fine granules, which are, perhaps, proteid in their nature, as they are in.soluble in ether and alcohol. They are developed by the proliferation of the granulosa cells of the Graalian follicle, which also seem ultimately to form the granulo-tibrous double envelope or the vitelline membrane {Eimt-r). The whole yelk of the hen's egg is regarded by some observers as c<|uivalent to the mammalian ovum////.f (he corpus luteum. Microscopically, the white yelk consists of small vesicles (5-75 ,") containing a refractive substance and larger spheres containing several smaller spherules (Fig. 643, a). 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 Clraafian follicles of the hen's ovarium, the follicle bursts and discbarges 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 chalazae. [The chalazae are two twisted cords composed of twisted layers of the outer denser part of the albumin. They extend Fig. 642. Fig. 643. Blastoderm. Its processes. Scheme of a meroblastic egg. a, White ; 6, yellow yelk granules. 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 (Fig. 644). 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 thein 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 spiral manner around the albumin ^Lindvall and Ilamarsien). [F^xternal 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 [Pt-oiit, Gritwe, although this is denied by Poll and Preyei-). The pigment which often occurs in many layers of 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 pres- ence of lutein, which contains iron. It contains several proteids [including a globulin body called vitellin (p. 424)], a body resembling nuclein, lecithin, vitellin, glycerin-phosphoric acid, choles- terin, 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.] STRUCTURE OF THE UTERUS. 905 [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 Fig. 645. Fowl's egg'after thirty hours' incubation, a, shell ; /', shell membrane ; i', air chamber; c, boundary between outer and middle portion of albumin ; d, more fluid albumin; e, chalazae; v, yelk; av, area'opaca; ao, area vasculosa, and in its centre is the embrj'O. ; Vertical section of the mucous membrane of the human uterus, e, columnar epithelium, the cilia absent ; £■£■, utricular glands ; ci. intra-glandular connective tissue ; 21V, blood vessels ; mm, muscularis mucosae. Fig. 646. Left broad ligament. Fallopian tube, ovary, and parovarium, a, uterus ; 5, isthmus of Fallopian tube; c, ampulla; ^, fimbriated end of the tube, with the parovarium to its right ; e, ovary ; y, ovarian ligament. internally by a mucous membrane, while between the two is the thick muscular coat com- posed of j^smooth muscular fibres arranged in a great number of layers and in different directions. 906 FALLOPIAN TUBES. The mucous membrane of the body of the uterus in the unimpregnated condition has no folds, while the muscularis mucosae is very well developed, and forms a great part of the uterine muscular wall. The mucous membrane is lined by a single layer of columnar ciliated ejiithelium. A vertical section shows the mucous memlrane to contain numerous tubular glands (Kig. 645)— the uterine glands — which branch toward tlieir 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 intrauterine life {T/t/nfr), nor are there any glands in the human uterus at birth {(J./. Engelmann). There are numerous slit-like lymphatic spaces in the mucous Fic. 647. Transverse section of the Fallopian tube. 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 vitx. 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. 646). 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. 647).] 434. PUBERTY. — The term puberty is applied to tlie period at which a human being becomes capable of procreating, which occurs from the 13th to 15th years in the female, and the 14th to i6th in the male. In warm climates, puberty may occur in girls even at 8 years of age. Toward the 40th to 50th year, the pro- creative faculty ceases in the female with the cessation of the menses; this con- stitutes the menopause or grand climacteric, while in man the formation of seminal fluid has been observed up to old age. From the period of puberty onward, the sexual appetite occurs, and the ripe ova are discharged from the ovary. [But ova are discharged even before puberty or menstruation has occurred.] At puberty, the internal and external generative organs and their annexes become more vas- cular and undergo development ; the pelvis of the female assumes the character- istic female shape. For the changes in the mammse 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 lar\nx becomes longer, while the compass of the voice is increased. The vital capacity (| io8\ corresponding to the increase in the size of the chest, undergoes a con- siderable increase; the whole form and expression assume the characteristic sexual appearance, while the psychical energies also receive an impulse. SIGNS OF MENSTRUATION. 907 435. 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 {Strohl'). 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 {Aris- totle), while apes in their wild condition have a well-marked menstrual discharge {Neiibert^. [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, 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 faeces and urine, and in the secretion of sweat. The discharge is sli?ny at first, and then becomes bloody, lasting three to four days ; the blood is venous, and shows little tendency to coagulate, provided it is mixed with much alkaline mucus from the genital passages ; but, if the hemorrhage be free, the blood Yio. 648. Fig. 640. may be clotted. The quantity of blood is 100 to 200 grms. [The blood contains many white blood corpuscles and epithelial cells.] After cessation of - . the discharge of blood there is a moderate amount / \ of mucus given off. / The characteristic internal phenomena which accompany menstruation are : (i) The changes in the uterine mucous mem- brane ; and (2) the rupture of the Graafian follicle. 1. Changes in the uterine mucous membrane. — The uterine mucous mem- brane is the chief source of the blood. The ciliated epithelium of the congested, swol- len, 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 con- tains 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 intact, and from them, after menstruation is over, the new mucous membrane is developed {Kundrai and G. J. Engelmanft). [Leopold denies the existence of this fatty degeneration. According to Williams, the entire mucous membrane is removed at each menstrual period, and it is regen- erated from the muscular coat (Fig. 649). The mucous membrane of the cervix remains free from these changes.] 2. Ovulation. — The second important internal phenomenon is ovulation, in which process the ovary becomes more vascular — the ripe follicle is turgid with fluid, and in part projects above the surface of the ovary. The follicle ultimately Diagram of the uterus j ust before menstruation. The shaded portion represents the mu- cous membrane. Uterus when menstrua- tion has just ceased, showing the cavity of the body deprived of mucous membrane (J. WiUiams). 908 THEORIES OF OVULATION. bursts, its membranes and the epithelium covering of the ovary are 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 is applied to the ovary, so that the dis- charged ovum, with its adherent granulosa cells, and the liquor foUiculi, are caught by the funnel-shaped extremity of the tube (Fig. 646). The ovum, when dis- charged, 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 uleiine mucous membrane. Pfliiger regards the bloody discharge from the superficial layers of the uterine mucous membrane as a phy.'-ioiogical prepa- ration or " freshening"' of the tissue (in the surgical sense), by which it will be prepared to receive the ovum when the latter reaches the uterus, so that union can lake place between the ovum and the freshly-exposed surface of the mucous membrane, and thus the ovum will receive nourishment 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, wherel)y Fig. 650. Fresh corpus luteum. it becomes more vascular, more spongy, and swollen up. The mucous membiane so al- tered is spoken of as the tneinbrana decidua tiienstrudlis, and from its nature it is in a proper condition to receive, retain, and nour- ish a ferlilized ovum which may come into contact with it. If the ovum, however, be layer and tunica propria, not fertilized, and escape from the genital passages, then the uterine mucous membrane degenerates, and blood is shed as above described. According to this view, the hem- orrhage 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 men- FlG. 651. Stroma of ovary. Outer layer of follicle. Vessels between outer Folded and thickened tunica propria. ( Corpus 1 luteum -< with a / fibrous Stroma of ovary with blood- vessels. Fig. 652. Lutein cells from the corpus luteum of cow. Corpus luteum of cow (;< stnial 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 menstruation, but from some time between the last menstruation and the period which does not occur. ERECTION OF THE PENIS. 909 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 efiusion of blood, which soon coagulates. The small rupture soon heals, after the serum is absorbed. The vascular wall of the follicle swells up. Villous prolongations or granulations of young connective tissue, rich in capillaries and cells, grow into the interior of the follicle (Fig. 651). 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 degeneration, lutein, and fatty matter being formed, and it is this mass which gives the corpus luteum its yellow color (Fig. 652). 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 deriva- tives of hemoglobin, while there is a gradual shriveling of the whole mass, which is complete in about four weeks, only a very small remainder being left. Such a corpus luteum i.e., one not accompanied by pregnancy, is called a false corpus luteum. If, however, pregnancy occurs, then the corpus luteum, instead of shriveling, grows and becomes a large body, especially at the third and fourth month, the walls are thicker, the color deeper, so that the corpus luteum at the period of delivery may be 6 to 10 mm. in diameter, and its remains may be found in the ovary for a very long time thereafter (Fig. 651). This form is sometimes spoken of as a true corpus luteum. [We cannot draw a sharp distinction between these two forms.] Only a very small number of the ova in the ovary undergo development and are discharged; by far the greater number degenerate iySlavjaiisky'). 436. PENIS — ERECTION. — Penis. — [The penis is composed of the two long cylindrical cor- pora cavernosa, the corpus spongiosum, which lies between and below them, and surrounds the urethra; these are held together by fibrous and muscular sheaths, and are composed of erectile tissue.] Our knowledge of the distribution of the blood within the penis is chiefly due to C. Langer's researches. The albuginea of the corpus spongiosum consists of tendinous connective tissue, con- taining thickly- woven elastic tissue and smooth muscular fibres, which together form a solid fibrous envelope, from which numerous interlacing trabeculse pass into the interior, so that the corpus spongi- osum comes to resemble a sponge. The anastomosing spaces bounded by these trabeculse form a series of inter-communicating venous spaces or sinuses filled with blood FiG. 653. and lined by a layer of endothelium constituting erectile tissue (Fig. 653). The largest sinuses lie in the lower and external part of the corpus caver- nosum, while they are less numerous and smaller in the upper part. The small arteries arise from the A. profunda penis, which runs along the septum, and pass to the trabecule after following a very sinuous course. At the outer part of the corpus spongiosum, some of the small arte- ries become directly continuous with the larger venous sinuses ; some of them, however, terminate in capilla- ries, both in the outer part and within the corpus spongiosum, the capillaries ultimately terminating in the venous sinuses. The helicine arteries of the penis described by Joh. Miiller are merely much twisted arteries. The deep veins of the penis arise by fine veinlets within the body of the organ, while the veins proceeding fi^om the cavernous spaces pass to the dorsum of the penis to form the vena dorsalis penis. As these vessels have to traverse the meshes of the vascular network in the cortex of the corpora cavernosa penis, it is evident that, when the network is congested by being filled with blood, it must compress the outgoing venous trunks. The corpus cavernosum urethrse consists for the most part of an external layer of closely packed anastomosing veins, which surround the longitu- dinally directed blood vessels of the urethra. In the dog, all the arteries of the penis run at first toward the surface, where they divide into penicilli. The veins arise from the capillary loops in the papillre, and they empty their blood into Erectile tissue. a, trabeculse of connective tissue with elastic fibres and smooth muscle (c) ; b, venous spaces. 910 MECHANISM OF ERECTION. the cavernous spaces. Only a small part of the blood passes to the cavernous spaces through the internal capillaries and veins, but arterial blood never Hows directly into these spaces [M. v. Frey). Mechanism of Erection. — Erection is due to the overfilling of the blood vessels of the penis with blood, whereby the volume of the organ is increased four or five times, while, at the same time, there are also a higher temperature, increased blood pressure (to \ of that in the carotid — Eckhard), with at first a pulsatile movement, increased consistence, and erection of the organ. Regner de Graaf obtained complete erection of the penis by forcibly injecting its blood vessels (1668). The preliminary phenomena consist in a considerable increase of the arterial blood supply, the arteries being dilated and pulsating strongly. The arteries are controlled by the nervi erigentes. The nervi erigentes [called by Gaskell the pelvic splanchnics (Fig. 439)] arise chiefly from the second (more rarely the third) sacral nerves (dog), and have ganglionic cells in their course {Lovc/i, Nikolsky). These nerves contain vaso-dilator fibres, which can be excited in part reflexly from the sensory nerves of the penis, the transference centre being in the centre for erection in the spinal cord (§ 372, 4). Sensory impressions produced by voluntary movements of the genital apparatus (by the ischio- and bulbo-cavernosi and cremaster muscles) can also dis- Fic. 654. charge this reflex; while the thought of sexual impulses, referable to the penis, tends to induce erection. The nervi erigentes also supply the longi- tudinal fibres of the rectum {Fellner). The centre for erection in the spinal cord (§ 362, 2) is, however, controlled by the dominating vaso- dilator centre in the medulla oblon- gata (§ 372), and the two centres are connected by fibres within the cord ; hence stimulation of the upper part of the cord, as by asphyxiated blood (§ 362, 5) or muscarin, may also be followed by erection {Niko/sky). [The seminal fluid is frequently found dis- charged in persons who have been hanged.] The psychical activity of the cerebrum has a decided influence on the genital vaso-dilator nerves. Just as the psychi- cal disturbance which accompanies anger or shame is followed by dilata- tion of the blood vessels of the head, owing to stimulation of the vaso-dilator fibres, so when the attention is directed to the sexual centres there is an action upon the nervi erigentes. This action of the brain is more comprehensible, since we know that the diameter of the blood vessels is affected by the cortex cerebri (§ 377). The fibres probably pass from the cerebrum through the peduncles of the cerebrum and the pons ; as a matter of fact, if these parts be stimulated erection may take place (§ 362, 4) i^Eckharcf). When the impulse to erection is obtained by the increased supply of arterial blood, the full completion of the act is brought about by the activity of the following Anterior wall of the pelvis with the uro-genital septum seen from the front. The corpus cavernosum (4) with the urethra (3) is cut across below its exit from the pelvis. ' I, symphysis pubis; 2, dorsal vein of the penis; 5, part of the bulbo-cavernosus ; /, deep transversus peri- nei with its fascia (/); 6, vena profunda penis; 7, artery and vein of the bulbo-cavernosus. EJACULATION AND RECEPTION OF THE SEMEN. 911 transversely striped muscles : (i) The ischio-cavernosus arises from the coccyx, and by its tendinous union surrounds the root of the penis (Fig. 172). When it contracts, it compresses the root of the penis from above and laterally, so that the outflow of blood from the penis is hindered. It has no action on the dorsal vein of the penis, as this vessel lies in a groove on the dorsum of the penis, and is therefore protected from compression by the tendon. (2) The deep transversus perinei is perforated by the venae profundae penis, which come from the corpora cavernosa, so that when it contracts it must compress these veins between the tense horizontal fibres (Fig. 654, 6). The deep veins of the penis join the common pudendal vein and the plexus Santorini. (3) Lastly, the bulbo-cavernosiis is con- cerned in the hardening of the urethral corpus spongiosum, as it compresses the bulb of the urethra (Figs. 654, 5, 172). All these muscles are partly under the control of the will, whereby the erection may be increased. Normally, however, their contraction is excited reflexly by stimulation of the sensory nerves of the penis (§ 362, 4). The congestion of blood is not complete, else, in pathological cases, continuous erection, as in satyriasis, would give rise to gangrene. The accumulation of the blood in the penis is favored by the fact that the origins of the veins of the penis lie in the corpus cavernosum, which, when it enlarges, must compress them. There are also trabecular, smooth, muscular fibres, which compress the large venous plexus of Santorini. That erection is a complex motor act depending on the nervous system, is proved by an experiment of Hausmann, who found that section of the nerves of the penis prevented erection in a stallion. The imperfect erection which occurs in the female is confined to the corpora cavernosa clitoridis and the bulbi vestibuli. During erection, the passage from the urethra to the bladder is closed, partly by the swelling of the caput gallinaginis, and partly by the action of the sphincter urethrse, which is con- nected with the deep transversus perinei. 437. EJACULATION— RECEPTION OF THE SEMEN.— In con- nection with the ejaculation of the seminal fluid, we must distinguish two differ- ent factors — (i) its passage from the testicles to the vesiculse seminales; (2) the act of ejaculation itself. The former is caused by the newly-secreted fluid forcing on that in front of it, by the action of the ciliated epithelium (which lines the epididymis to the beginning of the vas deferens), and also by the peristaltic move- ments of the smooth muscular fibres of the vas deferens. Ejaculation, however, requires strong peristaltic contractions of the vasa deferentia and the vesiculae semi- nales, which are brought about by the reflex stimulation of the ejaculation centre in the spinal cord (§ 362, 5). As soon as the seminal fluid reaches the urethra, there is a rhythmical contraction of the bulbo-cavernosus muscle (produced by the mechanical dilatation of the urethra), whereby the fluid is forcibly ejected from the urethra. Both vasa deferentia and vesiculse do not always eject their contents into the urethra simultaneously. With moderate excitement the contents of only one may be discharged. The ischio-cavernosus and deep transversus perinei con- tract at the same time as the bulbo-cavernosus, although the former have no effect on the act of ejaculation. In the female also, under normal circumstances, at the height of the sexual excitement there is a reflex movement corresponding to ejacu- lation. It consists of a movement analogous to that in man. At first there is a reflex peristaltic movement of the Fallopian tube and uterus, proceeding from the end of the tube toward the vagina, and produced reflexly by the stimulation of the genital nerves. Dembo observed that stimulation of the anterior upper wall of the vagina in animals caused a gradual contraction of the uterus. By this movement, corresponding to that of the vasa deferentia in man, a certain amount of the mucus normally lining the uterus is forced into the vagina. This is followed by the rhythmical contraction of the sphincter cunni (analogous to the bulbo-cavernosus), also of the ischio-cavernosus, and deep transversus perinei. The uterus is erected by the powerful contraction of its muscular fibres and round ligaments, while at the same time it descends toward the vagina, its cavity is more and more diminished, and its mucous contents are forced out. When 912 FERTILIZATION OF THE OVUM. the uterus relaxes after the stage of excitement, it aspirates into its cavity the seminal fluid injected into the vestibule (^Aristotle, Bischojff"). But the suction of the greatly excited uterus is not necessary for the reception of the semen {Aris' totlf). The spermatozoa may wrigt;le by their own movements from the vagina into the orilice of the uterus {A'riste/ler). The cases of pregnancy where, from some pathological- causes (partial closure of the vagina or vulva), the penis has not passed into the vagina during coition, prove that the sperma- tozon can traverse the whole length of the vagina, and pass into the uterus. 438. FERTILIZATION OF THE OVUM.— The ovum is fertilized by one spermatozoon i)assing into it. Swanimerdani (f l6^)5) proved that contact of the semen with the ovum was necessary for fertiliza- tion. Spallanzani (1768) jiroved that the fertilizing agent was the spermatozoa, and not the clear filtered fluid part of the semen, and that the spermatozoa, even after being enormously diluted, were still capable of action. Martin Barry (1S50) was the first to observe the entrance of a spermatozoon into the ovum of the r.ibbit. This occurs pretty rapidly, by a boring movement through the vitelline membrane {Leuck/tart). The entrance is effected either through the porous canals or the micropyle {^Keber, p. 902). Theories. — As to the manner in which the spermatozoon affects the ovum, there are great differ- ences of opinion. Aristotle compaied it to an action like that of rennet on milk; Bischoff, to that of yeast on a fermentable mass, i. c, to a catalytic action. These theories, however, are quite unsatisfactory, as we know that the unfertilized ova of the hen, rabbit [I/enxen), pig (Bischoff^, saljia {/\ii/>/>/e)-) (but not the frog — Pfluger') can undergo the initial .stages of development as far as the stage of cleavage, and the star fishes even as far as the larval form (^Greef.) Place of Fertilization. — The place where fertilization occurs is either the ovary, as indicated by the occurrence of abdominal pregnancy, or the Fallopian tube, and the numerous recesses in the latter afford a good temporary nidus for the spermatozoa. This view is supported by the occurrence of tubal pregnancy. Thus, the spermatozoa must be able to pass through the Fallopian tube to the ovary, which is probably brought about chiefly by the movements proper to the spermatozoa themselves. It is uncertain whether the peristaltic movements of the uterus and Fallopian tube are concerned in this process ; certainly ciliary movement is not concerned, as the cilia of the Fallopian tube act from above downward. When once the ovum has passed unfertilized into the uterus, it is not fertilized in the uterus. It is assumed that the ovum reaches the uterus within 2 to 3 weeks (in the bitch, 8 to 14 days). T\vins occur in i in 87 pregnancies, but oftener in warm climates; triplets, I : 7600 ; four at a birth, i : 330,000. More than six at a time have not been observed. The average number of pregnancies in a woman is 4^. Superfecundation. — By this term is understood the fertilization of two ova at the same men- slniatioi:, by two ditTerent ads of coition. Thus, a mare may throw a foal and a mule, after being covered first by a stallion and then by an ass. A white and a black child have been born as twins by a woman. Superfoetation is when a second impregnation takes place at a later period of pregnancy, as in the second or third month. This, however, is only possible in a double uterus, or when men- struation persists until the time of the second impregnation. It is said to occur frequently in the hare. Hybrids are produced when there is a cross between different species (horse, ass, zebra — dog, jackal, wolf — goat, ibex — goat, sheep — species of llama — camel, dromedary — tiger, lion— species of pheasant — goose, swan — carp, crucian — species of butterflies). Most hylirids are sterile, especially as regards the formation of properly formed spermatozoa ; while the hybrid females are for the most part fertile with the male of both parents, e.g., the mule; but the characters of the offspring tend to return to those of the species of the parents. Very few hybrids are fertile when crossed l>y hybrids. In many species of frogs the absence of hybrids is accounted for by the mechanical obstacles to fer- tilizalion of the ova. Tubal Migration of the Ovum. — Under exceptional circumstances, the ovum discharged from a ruptured Graafian follicle passes into the Fallopian tube of the o/her side, as is proved by the occurrence of tubal pregnancy and pregnancy of an abnormal rudimentary horn of the uterus, in which case the true corpus luteum is found on the other side of the ovary. This is spoken of as " external migration " (Kussinaul, Leopold^. This observation coincides with experiment, as granular fluids, e.g., China-ink, when injected into the peritoneal cavity, pass IMPREGNATION CLEAVAGE OF THE YELK. 913 into both Fallopian tubes, and are carried by the ciliated epithelium to the uterus (JPinner). In animals with a double uterus with two orifices, the ova may migrate through the os of the one into the other uterus, a condition which is spoken of as " internal migration." 439. IMPREGNATION— CLEAVAGE— LAYERS OF THE EM- BRYO.— Maturation of the Ovum. — In birds and mammals, important changes occur in the ovum before impregnation. The germinal vesicle comes to the surface and disappears from view, while the germinal spot also disappears. In place of the germinal vesicle, a spindle-shaped body appears. The granular elements of the protoplasmic vitellus arrange themselves around each of the two poles of the spindle, in the form of a star, the double star, or diaster of Fol — nuclear spindle (Figs. 655, 656). When this takes place, the peripheral pole of the nucleus or altered germinal vesicle, along with some of the cellular substance of the ovum, protrudes upon the surface of the vitellus, where they are nipped off from the ovum in the form of small corpuscles just like an excretory product (Fig. 657). These bodies, which are not made use of in the further development and growth of the ovum, are called polar or directing globules i^Fol, Butschli, O. Hertwig'), although the elimination of small bodies from the yelk was known to Fig. 655. •Fig. 656. Formation of polar globules in a star-fish (Asterias glacialis). A, ripe ovum Egg of Scorpaena scrofa. The ger- with eccentric germinal vesicle and spot ; B-E, gradual |metamorphosis of minal vesicle is extruding a germinal vesicle and spot, as seen in the living egg,\x\to two asters ; F, polar globule, and vi'ithdrawing formation of first polar globule, and withdrawal of the remaining part of toward the centre of the ovum, the nuclear spindle within the ovum ; G, surface view of living ovum with Near it is the male pronucleus, view of first polar globule ; H, formation of second polar globule ; I, a later stage, showing the remaining internal part of the spindle in the form of two clear vesicles; K, ovum with two polar globules and radial striae around the female pronucleus ; L, extrusion of polar globule. (Geddes : A-K, after Fol: L, after O. Hej-iwig.) Dumortier [1837], Bischoff, P. J. van Beneden, Fritz Miiller [1848], Rathke, and others. The remaining part of the germinal vesicle stays within the vitellus and travels back toward the centre of the ovum, to form the female pronucleus {O. Hertwig, Fol, Selenka, E. van Beneden). [Before, however, the altered germinal vesicle travels downward again into the substance of the ovum, it divides again as before, and from it is given off the second polar globule, and then the remain- der of the germinal vesicle forms the female pronucleus (Fig. 655). At the same time the vitellus shrinks somewhat within the vitelline membrane.] Impregnation. — As a rule, only one spermatozoon penetrates the ovum, and as it does so, it moves toward the female pronucleus, while its head becomes surrounded with a star; it then loses its head and cilium, or tail, the latter only serving as a motor organ, while the remaining middle piece swells up to form a second new nucleus, the male pronucleus {Fol, Selenka). According to Flem- ming, it is the anterior part of the head, and according to Rein and Eberth, it is , the head which is so changed. Thereafter, the male and female pronucleus unite, undergoing amcBboid movements at the same time, to form the new nucleus of the fertilized ovum. The female pronucleus receives the male pronucleus in a little depression on its surface. Thereafter the yelk assumes a radiate appearance 58 914 CLEAVAGE OF THE YELK. {Reifi). [The union of the representatives of tlie male and female elements forms \\\t first entbryotiic segmentation sphere ox blastosphere, which divides into two cells, and these again into four, and so on Fig. 657. (Fig. 658).] In Echinoderms, O. Ilertwig and Fol observed that several emliryos were formed when, under ab- normal conditions, several spermatozoa penetrated an ovum. The male pronuclei, formed from the several spermatozoa, then fused each with a fragment of the female pronucleus. Under similar circumstances, liorn observed in amphibians abnormal cleavage, but t.-. .■•. ■ . . V - .'- .••■■• :\ 1 no further development. k!? /;•;;;'.'"> Cleavage of the Yelk. — In an ovum so ^i^i'- ;■ ■ ■'; -■ ■■ fertilized the yelk contracts somewhat around the newly-formed nucleus, so that it becomes slightly separated from the vitelline mem- brane, and for the first time the nucleus and the yelk divides into two nucleated spheres. This process is spoken of as a complete cleavage or fission (Fig. 658). Each of these two cells again divides into two, and the process is repeated, so that Egg of .1 Star-Ti-h '^Astcr. triided pol.ir globules, nuclei near each other. inlhion) with two ex- Male and female pro- Segmentation of a rabbit's ovum, a, two-celled stagcl; /', four-celled stage ; c, eight-celled stage ; d, e, many blasto- meres showing the more rapid division of the outer-layer cells, and the gradual enclosure of the inner-layer cells ; ect, outer-layer cells; ent, inner-layer cells; /£■/, polar globules; ;:/, zona pellucida. 4, 8, 16, 32, and so on, spheres are formed (Fig. 659). This constitutes the cleav- age of the yelk, and the process goes on until the whole yelk is subdivided into P , numerous small, nucleated spheres, the '"^' "mulberry mass" or "segmenta- tion spheres" or "morula," or the protoplasmic primordial spheres (20 to 25 ,'j.) which are devoid of an envelope. [Each cell divides by a process of karyo- kinesis. According to Van Beneden, the segmentation begins in 1-2 hours after the union of the pronuclei, and the process is complete in about 75 hours. These primitive cells, from which all the tissues of the future embryo are formed, are called blastomeres.] Cleavage of the yelk of the egg of Anchylostomum duo- denale. STRUCTURE OF THE BLASTODERM. 915 Variation of Lines of Cleavage. — According to the observations of Pfluger, the ova of the frog can be made to undergo cleavage in very different directions, according to the angle between the axis of the egg and the line of gravitation. This, of course, we can alter as we please, by placing the eggs at any angle to the line of gravitation. By the axis of the ovum is meant a line connecting the centre of the black surface and the middle of the white part, which, in the fertilized ovum, is always vertical. In such cases of abnormal cleavage the deposition of the organs takes place from other constituents of the egg than those from which they are formed under normal conditions. Under normal circumstances, according to Roux, the first line of cleavage in the frog is in the same direc- tion as the central nervous system. The second intersects the first at a right angle, so as to divide the mass of ovum into two unequal -p^ris, the larger of which forms the anterior part of the embryo. Blastoderm. — During this time the ovum is enlarging by absorption of fluid into its interior. All the cells, from mutual pressure against each other, become polyhedral, and are so arranged as to form a cellular envelope or bladder, the blastoderm or germinal membrane, which lies on the internal surface of the vitelline membrane {De Graaf, v. Baer, Bischoff, Coste). A small part of the cells not used in the formation of the blastoderm is found on some part of the latter. [In the ovum of the bird, where there is only partial segmentation, the blasto- derm is a small, round body resting on the surface of the yelk, under the vitelline membrane, so that it does not completely surround the yelk, or a hollow cavity, as in mammals. In mammals, this cavity is called the segmentation cavity.] Fig. 660. cnh. Fig. Blastodermic vesicle of a rabbit, ect, ectoderm, or outer layer of cells ; f«^, inner layer of cells. Pr, primitive streak ; R, medullary groove ; U, first proto-vertebra. The hollow sphere, composed of cells, is called the blastodermic vesicle by Reichert (Fig. 660), and in the human embryo it is formed at the loth to 12th day, in the rabbit at the 4th, the guinea-pig at the 3)^, the cat 7th, dog nth, fox 14th, ruminantia at the loth to 12th day, and the deer at the 60th day. When the blastoderm grows to 2 mm. (rabbit), whereby the vitelline membrane is distended to a very thin, delicate membrane, then at one part of it there appears the germinal area, the area germinativa, or the embryonal shield ( Coste, Kolli- ker), as a round white spot, in which the blastoderm, owing to the proliferation of its cells, becomes double. The upper layer is called the ectoderm or epiblast, and in some animals it consists of several layers of cells, while the lower layer is the endoderm or hypoblast. The hypoblast continues to grow at its edges, so that it ultimately forms a completely closed sac, on which the epiblast is applied concentrically. The embryonal area soon becomes more pear-shaped, and afterward biscuit-shaped. At the same time the surface of the zona pellucida develops numerous small, hollovv, structureless villi, and is called the primitive chorion. At the posterior part, or narrow end, of the embryonic shield, the primitive streak (Fig. 661, I, Fr) appears at first as an elongated opaque circular thicken- ing, and later as a longer streak or groove, the primitive groove. [The opacity 916 STRUCTURE OF THE BLASTODERM. is due to the fact that there are several layers of cells in this region (Fig. 662). In a transverse section through the primitive streak, three layers of cells are seen. They form part of the middle layer or mesoblast, and are originally derived from the hypoblast. Tiiese cells fuse with those of the epiblast. The remainder of the hypoplastic cells retain their stellate character.] At the same time a new layer of Fig. 662. /4' » Transverse section of the primitive streak of a fowl's blastoderm, ep, epiblast ; hy, hypoblast ; in, mesoblast ; pv, primitive groove ; ^/i.yoke of germinal wall. cells is developed between the epiblast and hypoblast, the mesoderm or meso- blast (Fig. 662, I), which soon extends over the embryonal area, and into the blastoderm. [There has been Fio. 663. much discussion as to the origin of the mesoblast, but in verte- brates it seems to be originally developed from the hypoblast. Fig. 663 shows a portion of the hypoblast in its axial part, in process of forming the noto- chord, which is described as mesoblastic] Blood vessels are formed within the meso- Transverse section of an embryo newt, a, mesenteron ; a.r. /y, axial DiaSt, and are UlStriDUteCl OVet hypoblast, forming the notochord ; ^f, coelom or body cavity : ep, ^j^g blaStodcrm tO fomi tllC epiblast; /y, digestive hypoblast; som, somatic mesoblast; sptn, »p.l*i. splanchnic mesoblast; np, neural plate. area vascuiosa. Medullary Groove. — A longitudinal groove, the medullary groove, is formed at the anterior part of the embryonal shield, but it gradually extends posteriorly, embracing the anterior part of the primitive streak with its divided posterior end, while the primitive streak itself gradually becomes relatively and absolutely smaller and less distinct, until it disappears altogether (Fig. 661, I, and II, Pr). The position of the embryo is indicated by the central part becoming more transparent, — the area pellucida, — which is surrounded by a more opaque part — the area opaca. [The area opaca rests directly upon the white yelk in the fowl, and it takes no share in the formation of the embryo, but gives rise to structures which are temporary, and are connected with the nutrition of the embryo. The embryo is formed in the area pellucida alone.] From the epiblast {^neuro-epidertnal /aye?-] are developed the central nervous system and epidermal tissues, including the epithelium of the sense organs. From the mesoblast are formed most of the organs of the body [including the vascular, muscular, and skeletal systems, and, according to some,' the connective tissue. It also gives rise to the generative glands and excretory organs]. STRUCTURES FORMED FROM THE EPIBLAST. 917 Vertical section of part of the unincubated blastoderm of a hen. a, epiblast ; b, hypoblast; c, formative cells resting on white yelk; y, archenteron. From the hypoblast epithelio-glandular layer [which is the secretory layer], arise the intestinal epithelium, and that of the glands which open into intestine. The notochord is also formed from its axial portion. [The mouth and anus being formed by an inpushing of the epiblast, are lined by epiblast, and are sometimes called the stomodaeum and proctodaeum respectively.] [Structure of the Blastoderm (Fig. 664). — Originally it is composed of only two layers, and in a vertical section of it the epiblast consists of a single row of nucleated granular cells, arranged side by Fig. 664. side, with their long axes placed vertically. The hypoblast consists of larger cells than the fore- going, although they vary in size. They are spher- ical and very granular, so that no nucleus is visible in them. The cells form a kind of network, and occur in more than one layer, especially at the periphery. It rests on white yelk, and under it are large spherical refractive cells, spoken of as formative cells (). On the surfaces of these plates, which are directed toward each other, the endothelium lining the pleuro-peritoneal cavity is developed. On the surface of the median plate, directed toward the ccelom, some cylindrical cells, P'iG. 667. Transverse section of an embryo duck, am, amnion ; aa, aorta ; ca.7/, cardinal vein ; c/t, notochord ; A)', hypoblast ; >«j, muscle plate ; j<7, somatopleure ; j/, splanchnopleure ; j/.c, spinal cord; J/-^, spinal ganglion ; j/, segmen- tal tube ; n'rf. Wolffian (segmental) duct. of VValdeyer, remain, which form the ovarian tubes the " germ epithelium and the ova (§ 43^). According to Remak, the skin, the muscles of the trunk, and the blood vessels, and according to His, only the musculature of the trunk, are derived from the somatopleure. Both observers agree that the splanchnopleure furnishes the musculature of the intestinal tract. Parablastic and Archiblastic Cells. — According to His, the blood vessels, blood, and connective tissue are not developed from true mesoblastic cells, but he asserts that for this purpose certain cells wander in from the margins of the blasto- derm between the epiblast and hypoblast, these cells being derived from outside the ])osition of the embryo, from the elements of the white yelk. His calls these structures />arad/as//c, in opposition to the archiblastic, which belong to the three layers of the embryo. Waldeyer also adheres to the parablastic structure of blood and connective tissue, but he assumes that the material from which the latter is formed is continuous protoplasm, and of equal value with the elements of the blastoderm. HEAD AND TAIL FOLDS HEART. 921 The hypoblast does not undergo any change at this time ; it applies itself to the inner layer of the raesoblast, as a single layer of cells, to form the splanchno- pleure. 442. FORMATION OF EMBRYO, HEART, PRIMITIVE CIR- CULATION.—Head and Tail Folds.— Up to this time the embryo lies with its three layers in the plane of the layers themselves. The cephalic end of the future embryo is first raised above the level of this plane (Fig. 665, V). In front of, and under the head, there is an inflection or tucking-in of the layers, which is spoken of as the head-fold (V, r). [It gradually travels backward, so that the embryo is raised above the level of its surroundings.] The raised cephalic end is hollow, and it communicates with the space in the interior of the umbilical vesicle. The cavity in the head is spoken of as the head-gut or fore-gut (V, D.). The formation of the fore-gut, by the elevation of the head from the plane of the three layers, occurs on the second day in the chick, and in the dog on the 2 2d day. The tail-fold is formed in precisely the same way, in the chick on the 3d day, and in the dog on the 22d day. The tail-fold, S, also is hollow, and the space within it is the hind-gut, d. Thus, the body of the embryo is supported or rests on a hollow stalk, which at first is wide, and communicates with the cavity of the umbilical vesicle. This duct or communication is called the omphalo-mes- enteric duct, or the vitello-intestinal or vitelline duct. The saccular vesicle attached to it in mammals is called the umbilical vesicle (VII, N), while the analogous much larger sac in birds, which contains the yellow nutritive yelk, is called the yelk sac. The omphalo-mesenteric or vitelline duct in course of time becomes narrower, and is ultimately obliterated in the chick on the 5th day. The point where it is continuous with the abdominal wall is the abdominal umbilicus, and where it is inserted into the primitive intestine, the intestinal umbilicus. [Sometimes part of the vitelline duct remains attached to the intestine, and may prove dangerous by becoming so displaced as to constrict a loop of intestine, and thus cause strangulation of the gut.] Heart. — Before this process of constriction is complete, some cells are mapped off from that part of the splanchnopleure which lies immediately under the head- gut ; this indicates \\\& position of the heart, which appears in the chick at the end of the first day, as a small, bright red, rhythmically contracting point, \k\t pimctum saliens, or the (jTiyirq y.tvouij.i'rq of Aristotle. In mammals it appears much later. The heart, VI, begins first as a mass of cells, some of which in the centre dis- appear to form a central cavity, so that the whole looks like a pale hollow bud (originally a pair) of the splanchnopleure. The central cavity soon dilates ; it grows, and becomes suspended in the coelom by a duplicature like a mesentery (mesocardium), while the space which it occupies is spoken of as iht fovea cardica. The heart now assunes an elongated tubular form, with its aortic portion directed forward, and its venous end backward ; it then undergoes a slight /-shaped curve (Fig. 675, i). From the middle of the 2d day, the heart begins to beat in the chick, at the rate of about 40 beats per minute. [It is very important to note that at first, although the heart beats rhythmically, it does not contain any nerve cells.] From the anterior end of the heart, there proceeds from the bulbus aortge, the aorta which passes forward and divides into two primitive aortae, which then curve and pass backward under the cerebral vesicles, and run in front of the proto- vertebrse. Opposite the omphalo-mesenteric duct, each primitive aorta in the chick sends off one, in mammals several (dog 4 to 5), omphalo-mesenteric arteries (VI, A, 6), which spread out to form a vascular network within the mesoblast of the umbilical vesicle. From this network, there arise the omphalo-mesenteric veins, which run backward on the vitelline duct, and end by two trunks in the venous end of the tubular heart. In the chick, these veins arise from the sinus terminalis of the future vena terminalis of the area vasculosa. Thus, the first or primitive circulation is a closed system, and functionally it is concerned in 922 FORMATION OF THE BODY. carrying nutriment and oxygen to the embryo. In the bird, the latter is supplied through the porous shell, and the former is supplied uj) to the end of incubation by the yelk. In mammals, both arc sui)plied by the blood vessels of the uterine mucous membrane to the ovum. In birds, owing to the absorption of the con- tents of the yelk sac, the vascular area steadily diminishes, until ultimately, toward the end of the period of incubation, the shriveled yelk sac slijjs into the abdominal cavity. In mammals, the circulation on the umbilical vesicle /. >fi>> a Titriiine- Ifte body, soBK S'ape s^ar, area, aaaBoaaBa coatiumarp, very probaUy demvd ftvHi tdte deoampo- gD— of area, uwiiaif v> hcnc acid aad 1 ii.Miaiii, cakic salphate and phoyhair, and ooiiion sak. Abotf the ■addle of lac^aaarj, it ■■iiaai todboat 1-1.5 kila. [2.2-3.3 ^b.], and m. the end aboat o.5k9ik. TWa^aBBOclBaidisof Cnrlalon^iiB^asisi^KMnl^'ilsoooaiTCnoeiabiids.and aoaasBdannatkrea^AeiBaalaieaJhunes. Ia BSHnlsi, Ihe anne of dK fixtas faims pot of k Amms dg aecaad InJf of lacgaaaLf i{'Sm!xtneap\. Ia the palhnihifflcal onadition of hydramnion, Ae Mood ^i^aA of Ae aieriae — coar 1 wlajite secrete a wabny flaid. The flaid preserres the daboAe^cEeisof «heie«alfadaTsfcqaiTriMairal ii^aries; itpenaite theli»bsto : hedf, aad pratoo^ thea inm giuai^ to|;eidhcr; said, l^df, it is iBportant far dilating the AadaglabQK. The aaaaoa is enable of coatianiina at the 7th day ia thechict; aad thb E dae to ihe aaoolh aKscabr Ores ahich are devdoped ia theoataaeoas plate ia its iKsoblastic Anantois. — Tram die anterior sncface of the caudal end of the embryo, theie grows om a smaD doidile projection, which becomes hollowed oat to form a sac pnifectii^ into the cavirf ^ die cadom or pleaio-peritoneal caTity (Fig. 665) ; it cwiVLJiuies the mffftrmimf, and is fanned in the duck before the 5tli day, and in man. daring the 2d week. Beii^ a trae pra^ectiMi fiom the hind got, the allantois has two lajecs, one fitom the hypoblast, and the other from die moscdUr layer, so tint it K an ofl^ioot from the sidanchnopleaie. From both sides, there pass e interior of &e ^eJD ss a li^illy vascalar and saocolar iM*mne lfeaBteries»e JtfiBtbraarhfsof thepriwilireaortaE,fant with thedewdopmentof the poateiim t iitm iniitrM \ thn' appear as lajanWi. of the hypcgastnc aiteries. Two alHantoidal or ■lafiffii Ml" iiiraii |a»r>iiiii iiiiimhi miaii iiiiiia 1 n[iii]llliarii iinirnBM iilDiliiai They pag baci-wad thww^ AeaMMkag,arfMlS»aaaitear3&the-toi»qF>>«icwiMS tojoiafliei«BO^ la bads Ab eacalMiua oa Ae afcamis, or setmmd tanmleiiem, is irtipiialury in Amctian, as its ^e»efe acne fir Ae csxha^ie of gases Ana^ die ponsas ^elL The cirealatiaa gtadaaiOy asstones Ae ic^piEritaEyiiacliaBsof the oailaKcall xvatAt^as the taw»T gm«fanilly iw'nffif^ ■^iwillfT mH aaadler, aad cei^s to be a swtBirarat respiotanr'Cggam. Towaid the ead of the period of incdbotian the dndc ■o^ brea^e and ory wodia the ^beSI ^Arisioile) — aproof that AerBpnratxxy fondiaBof theaSaaAois ispa«^tAeae doua), and the seoetian pasres BJinMigh A^ wfliMiiiriir^ JUT A» laJhaliOTK mbw «w pTTJyfltfyTi!! pmt of thf TaTJmury 3aC- Remak iband ^atooaiaM aad Midiaai acae, affitaattoia, grape sigar, and salts ia the caaiemtsrfdaerflanaois. From Ac SA di7 oaanad, da aibwanit; cf the cUdk b oawtractile ( rib^Kca ), omii^ to Ae piesenoe of ■wawA fibres deuwed inan the fpilaarftiannifrani.. Lya^dniics aooonpony the JuMirliwc of Ae Allantois in Mammals. — In ntaimmly and man, the relation of the aDantois KstMnewhat diffiaent. The first part or its otigin farms the minaiy bladder, and M» the vertex dL the latter there proceeds dnoi^ the ombiUciB a tnbe, the oradms, whitji is t^pen at irst {F%. 665, Tm, «). Tbe blind part of die sac of die allanlDB ootside Ae abdomen is in some animads filled with a fluid like iirine. In man, howerer, tins sac disappears dming the 2d mgnth, so tiiat there remains oidy Ae vessds whidi lie in tl^ Twr^irwlar part of die allantok. In some animaUj FCETAL MEMBRANES. 925 however, the allantois grows larger, does not shrivel, but obtains through the urachus from the bladder an alkaline turbid fluid, which contains some albumin, sugar, urea, and allantoin. The relations of the umbilical vessels will be described in connection with the fcetal membranes. 445. FCETAL MEMBRANES, PLACENTA, FCETAL CIRCU- LATION.— Decidua. — When a fecundated ovum reaches the uterus, it becomes surrounded by a special covering, which William Hunter (1775) described as the membrana decidua, because it was shed at birth. We distinguish the decidua vera (Fig. 665, YIII,/), which is merely the thickened, very vascular, softened, more spongy, and somewhat altered mucous membrane of the uterus. [Some- times in a diseased condition, as in dysmenorrhcea, the superficial layer of the uterine mucous membrane is thrown off nearly en fnasse in a triangular form (Fig. 668). This serves to show the shape of the decidua, which is that of the uterus.] When the o\aim reaches the uterus, it is caught in a crypt or fold of the decidua, and from the latter there grow up elevations around the ovum ; but these elevations are thin, and soon meet over the back of the ovum to form the decidua reflexa (Fig. 665, VIII, r). At the 2d to 3d month, there is still a space in the uterus outside the reflexa ; in the 4th month, the whole cavity is filled by the ovum. At one part the ovum lies directly upon the d. vera [and that part is spoken of as the decidua serotina], but by far the great- est part of the surface of the ovum is in contact with the re- FiG. 668. Adysmeaorrh'sal membrane laid open. flexa. In the region of the d. serotina the placenta is ultimately formed. Structure of the Decidua Vera. — The d. vera at the 3d month is 4 to 7 mm. thick, and at the 4tli only I to 3 mm., and it no longer has any epithelium; but it is very vascular, and is possessed of lymphatics around the glands and blood vessels (^Leopold), and in its loose substance are large round cells (decidua cells — A'tV/z'/J^r), which in the deeper parts become changed into fibre cells — there are also ijTnphoid cells. The uterine glands, which become greatly developed at the com- mencement of pregnancy, at the 3d to the 4th month form non-cellular, wide, bulging tubes, which become indistinct in the later months, and in which the epithelium disappears more and more. The d. reflexa, much thinner than the vera from the middle of pregnancy, is devoid of epithelium, and is without vessels and glands. Toward the end of pregnancy both deciduie unite. The o\ami, covered at first with small hollow villi, is surrounded by the decidua. From the formation of the amnion it follows that, after it is closed, a completely closed sac passes away from the embryo to He next the primitive chorion. This membrane is the "serous covering" of v. Baer (Fig. 665, VII, s), or the false amnion. It becomes closely applied to the inner surface of the chorion, and extends even into its villi. The allantois proceeding from the umbilicus comes to lie directly in contact with the fcetal membrane; its sac disappears about the 2d month in man, but its vascular layer grows rapidly and lines the whole of the inner surface of the chorion, where it is found on the iSth day i^Coste). From the 4th week the blood vessels, along with a covering of connective tissue, branch and 926 THE PLACENTA. penetrate into the hollow cavities of the villi, and comi)letely fill them. At this time the primitive chorion disappears. Thus, we have a stage of general vasculari- zation of the chorion. In the ])lace of the derivative of the zona pellucida we have the vascular villi of the allantois, which are covered by the epiblastic cells derived from the false amnion. This stage lasts only until the 3d month, when the chorionic villi disappear all over that part of the surface of the ovum which is in contact with the decidua reflexa. On the other hand, the villi of the chorion, where they lie in direct contact with the decidua serotina. become larger and more branched. Thus, there is distinguished the chorion laeve and c. frondosum. The chorion laeve, which consists of a connective-tissue matrix covered externally by several layers of cells, has a few isolated vilH at wide intervals. Between the chorion and the amnion is a gelatinous substance (membrana intermedia) or undeveloped connective tissue. Placenta. — The large villi of the chorion frondosum penetrate into the tissue of the decidua serotina of the uterine mucous membrane. [It was formerly sup- posed that the chorionic villi entered the mouths of the uterine glands, but the researches of Ercolani and Turner have shown that, although the uterine glands enlarge during the early months of utero-gestation, the villi do not enter the glands. The villi enter the crypts of the uterine mucous membrane. The glands of the inner layer of the decidua serotina soon disappear.] As the villi grow into the decidua serotina, they push ^'*^- ^^9- against the walls of the large blood vessels, which are simi- lar to capillaries in structure,' so that the villi come to be bathed by the blood of the mother in the uterine sinuses, or they float in the colossal decidual capillaries (Fig. 665, VH, I?). The villi do not float naked in the maternal blood, but they are covered by a layer of cells derived from the decidua. Some villi, with bulbous ends, unite firmly with the tissue of the uterine part of the placenta to form a firm bond of connection. [The placenta is formed by the mutual intergrowth of the chorionic villi and the decidua serotina.] Thus, it consists of a foetal part, including all the villi, and a maternal or uterine part, which is the very vascular decidua serotina. At the time of birth, both parts are so firmly united that they cannot be separated. Aroimd the margin of the placenta is a large venous vessel, ih^ marginal sinus of the placenta. [Friedlander found the uterine sinuses below the placental site blocked by giant cells after the 8th month of preg- nancy. Leopold confirms this, and found the same in the serotinal veins.] Func- tions.— The placenta is the nutritive, excretory, and respiratory organ of the ftetus (§ 368) ; the latter receives its necessary pabulum by endosmosis from the maternal sinuses through the coverings and vascular wall of the villi in which the fcetal blood circulates. [The placenta also con\.3\\\s gIycogen.'\ Human placental villi. Blood vessels black. UTERINE MILK. 927 [Structure. — A piece of fresh placenta teased in normal saline solution, shows the villi provided Vi^ith lateral offshoots, and consisting of a connective-tissue framework, containing a capillary network with arteries and veins, while the villi themselves are covered by a layer of somewhat cubical epithelium (Fig. 669).] Uterine Milk. — Between the villi of the placenta there is a clear fluid, which contains numerous small, albuminous globules, and this fluid, which is abundant in the cow, is spoken of as the uterine milk. It seems to be formed by the break- ing up of the decidual cells. It has been supposed to be nutritive in function. [The maternal placenta, therefore, seems to be a secreting structure, while the foetal part has an absorbing function. The uterine milk has been analyzed by Gamgee, who found that it contained fatty, albuminous, and saline constituents, while sugar and casein were absent.] The investigations of Walter show, that after poisoning pregnant animals with strychnin, morphia, veratrin, curara, and ergotin, these substances are not found in the foetus, although many other chemical substances pass into it. [Savory found that strychnin injected into a foetus in utero caused tetanic convulsions in the mother (bitch), while syphilis may be communicated from the father to the mother through the medium of the foetus [Htitchinson). A. Harvey's record of observations on the crossing of breeds of animals — chiefly of horses and allied species — show that materials can pass from the foetus to the mother.] On looking at a placenta, it is seen that its villi are distributed on large areas separated from each other by depressions. This complex arrangement might be compared with the cotyledons of some animals. The position of the placenta is, as a rule, on the anterior or posterior wall of the uterus, more rarely on the fundus uteri, or laterally from the opening of the Fallopian tube, or over the internal orifice of the cervix, the last constituting the condition of placenta praevia, which is a very dangerous form of placental insertion, as the placenta has to be ruptured before birth can take place, so that the mother often dies from hemorrhage. The umbilical cord may be inserted in the centre of the placenta {inserdo centralis), or more toward the margin (ins. marginalis), or the chord may be fixed to the chorion laeve. Sometimes, though rarely, there are small sub- sidiary placentas (/>/. sticcentia-iata), in addition to the large one. 'SMien the placenta consists of two halves, it is called duplex or bipartite, a condition said by Hyrtl to be constant in the apes of the old world. Structure of the Cord. — The umbilical cord (48 to 60 cm. [20 to 24 inches] long, II to 13 mm. thick) is covered by a sheath from the amnion. The blood vessels make about forty spiral turns, and they begin to appear about the second month. [The cause of the twisting is not well understood, but Virchow has shown that capillaries pass from the skin for a short distance on the cord, and they do so unequally, and it may be that this may aid in the production of the torsion.] It contains two strongly muscular and contractile arteries, and one umbilical vein. The two arteries anastomose in the placenta (^Hyrtl). In addition, the cord con- tains the continuation of the urachus, the hypoblastic portion of the allantois (Fig. 665, VIII, a), which remains until the second month, but afterward is much shriveled. The omphalo-mesenteric duct of the umbilical vesicle (N) is reduced to a thread-like stalk (Fig. 665, VIII, D). Wharton's jelly surrounds the umbilical blood vessels. Wharton's jelly is a gelatinous-like connective tissue, consisting of branched corpuscles, lymphoid cells, some connective-tissue fibrils, and even elastic fibres. It yields mucin. It is traversed by numerous juice canals lined by endothelial cells, but other blood and lymphatic vessels are absent. Nerves occur 3-8-1 1 cm. from the umbilicus {Schott, Valentin). The foetal circulation, which is established after the development of the allan- tois, has the following course (Fig. 670) : The blood of the foetus passes from the hypogastric arteries through the two umbilical arteries, through the umbilical cord to the placenta, where the arteries split up into capillaries. The blood is returned from the placenta by the umbilical vein, although the color of the blood cannot be distinguished from the venous or impure blood in the umbilical arteries. The 928 THE FCETAL CIRCULATION. umbilical vein (Fig. 673, 3, //) returns to the umbilicus, passes upward under the margin of the liver, gives a branch to the vena portje (a), and runs as the ductus venosus into the inferior vena cava, Kic. 670. which carries the blood into the right auricle. Directed by the Eustachian valve and the tubercle of Lower (Fig. 675, 6, /Z), the great mass of the blood passes through the foramen ovale into the left auricle, owing to the i)resence of the valve of the foramen ovale. From the left auricle it passes into the left ventricle, aorta, and hypogastric arte- ries, to the umbilical arteries. The blood of the superior vena cava of the f(etus passes from the right auricle into the right ventricle (Fig. 675, 6, Cs). From the right ventricle it passes into the pulmonary artery (Fig. 675, 7, />), and through the ductus arteriosus of Botalli (jB) 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 ])ulmonary artery to the lungs (Fig. 675, 7, I, 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 ligaments of the bladder, while their lower parts remain as the superior vesical arteries. 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 ovule is closed, and the ductus arteri- osus is obliterated, the latter forming the lig. arteriosus. The condition of the membranes where there are more foetuses than one : (i) With twins there are two completely separated ova, with two placenta; and two deciduje reflexse. (2) Two completely separated 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 lamellx 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 wiih 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. — The oldest mammals have no placenta or umbilical vessels; these are the Mammalia implacentalia, including the monetremata and marsupials. The second group includes the Mammalia placentalia. Among these (a) the non-deciduata pos- sess only chorionic villi supplied by the umijihcal vessels, which project into the depressions of the uterine mucous membrane, and from which they are pulled out at birth (PI. diffusa, e.g., pachy- dermata, cetacea, solidungula, camelidx). In the ruviinants, the villi are arranged in groups or cotyledons, which grow into the uterine mucous menibrane, from which they are pulled out at birth. Course of the fcetal circulation (Cleland). CHRONOLOGY OF HUMAN DEVELOPMENT. 929 (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 discoid (apex, insectivora, edentata, rodentia). 446. CHRONOLOGY OF HUMAN DEVELOPMENT.— Development during the ist 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 (^Reicherf). At the 15th— 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 laminse 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, umbiUcal 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 bulbous aortas, but neither auri- cles 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 (vitelhne) is still quite open, and two primitive aortse run in front of the protovertebras. The allantois attached to the foetal membranes is provided with blood vessels. The two omphalo-mesen- teric 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 probably 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 embyro 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 \^mbs are still absent [His). At the 2ist 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 fi?-st 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 superior maxillary processes, the heart with two ventricles and two auricles. End of the ist 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, 5 5 mm., with blood vessels. 2d Month. — The embryos of 28-35 days are more elongated, and all the branchial clefts are closed except the first. The allantois has now only three vessels, as the right umbilical vein is obliterated. At the 5th week the nasal pits are united with the angle of the mouth by furrows, which close to form canals at the 6th week [Toldt^. At 35-42 days the nasal and oral orifices are separated, 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. Length of body at 7th to 8th week, i. 6-4.1 cm. End of the 2d Month. — Ovum, 61^ cm.; vilh, 1.3 mm. long; the circulation on the imibilical vesicle has disappeared; embryo, 26 mm. long, and weighs 4 grammes. Eyehds and nose present, umbilical cord 8 mm. long, abdominal 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, length of body, 9.7-14.7 cm., total length 18 to 28 cm., weighing 2S4 grammes; hair on the head and lanugo distinct; skin still somewhat red and thin, and covered with vernix caseosa [\ 287, 2), is less transparent; weight of placenta, 178 grammes; umbilical cord, 31 cm. long. 6th Month. — Foetus, length of body, 15-18. 7, total length, 29—37 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, length of body, 18-22.8, total length, 35-38 cm., 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 ossification in the os calcis. 59 930 FORMATION OF THE OSSEOUS SYSTEM. 8th Month. — Kcvtus, length of body, 24-27. S. total length 42 cm., weighing 1.5 to 2 kilos. (3.3 to 4.4 11 >. 1; hair 01 the hend abundant, I 3 cm. long, nails with a small margin, umbilicus below the middle of the linca alba, one testicle in the scrotum. gth Month. — l-utus, length of Iwly, 30-37, total length, 47-67 cm., weighing 2234 grammes, anil is not distinguishable from the chilil at the full j>eriod. . FcEtus at the Full Period. — Length of body, 51 cm. [20 inches], weight, 3 '4 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 [Sc/unk). Pays. D.iys. Weeks. I Weeks. Coluber, .... 12 Rabbit, • ■ • • ^ ,2 ^*°^' ) Sheep, 21 Hen, ••••)-,, Hare, . . . . 1" -^ Vox \ 9 ^odi\. .-,, . ..... --, ^- _ 22 Duck, .... J " Weeks. Foumart, ... J Roe 24 Goose, 29 Rat, 5 Badger, . . • \ jq Bear 1 Stork, 42 ' Guinea-pig, ... 7 Wolf, . . . . j Small apes, ../•'" Cassowary, ... 65 Cat, "to Lion, 14 Deer, .... 36-40 Mouse 24 Marten, . . . j , I'ig, 17 , Woman 40 Horse, Camel, 13 months; Rhinoceros, 18 months; and the Elephant, 24 months. Limitation of the supply of O to eggs during incubation, leads to the formation of dwarf chicks. 447. FORMATION OF THE OSSEOUS SYSTEM.— Vertebral Column.— The ossifi- cation of the vertebrae begins at the Sth 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, 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 ist year. The three points of the sacral vertebrre unite or anchylose between the 2d and the 6th year, and all the vertebrre (sacral) become united to form one body between the I^>th and 25th years. Each of the four coccygeal vertebrae has a centre from the ist to loth year. The vertebra in later years produce i to 2 centres in each process; i to -2 centres in each transverse process; i in the mamillary process of the lumbar vertebra; and I in each articular process (8 to 15 years). Of the upper and under surfaces of the tody of a vertebra each forms an epiphyseal 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 coccygeal vertebra*, the odontoid process, and the base of the skull are cartilaginous, they still contain the remains of the chorda (H. Miiller). The coccygeal vertebra.- form the tail, and they originally project in man like a tail (Fig. 665, IX, T), which is ultimately covered over Ijy the growth of the soft parts (His). The ribs bud out from the prolovertebra% 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 [Jiathke'), 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 the 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 I 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 2d month the basal por- tion 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 temporal bone, the ethmoid 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 membranous primordial cranium. I. The occipital bone has a centre of ossification in the basilar part at the 3d month, and one in the condyloid part and another in the fossa cerebelli, while there are two centres in the membranous 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 supeiior maxil- lary process of the first branchial arch. During the first half of fcetal life these centres unite as far as the great wings ; the dorsum sella and the clinoid process, as far as the synchondrosis spheno- occipitalis, are still cartibginous, but they ossify at the 13th vear. III. The pre-sphenoid at the Sth 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. DEVELOPMENT OF THE OSSEOUS SYSTEM. 931 Fig. 671. r*"^ IV. The ethmoid 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 pterj-goid 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 parie- tal bones (one centre), the tympanic ring (one centre), the lachrymal, vomer, and intermaxillary bone. The facial bones are intimately related to the transformations of the branchial arches and bran- chial clefts (Fig. 671). 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. 665, IX). From above downward there grows as an elongation of the basis cranii the frontal process (i-), a broad process with a point (_;') at its lower and outer angle, the inner nasal process. The frontal and the superior maxil- lary 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 («), 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 apertm^es 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 intermaxillary process [Goethe) — the latter is present in man, but is united to the upper jaw. The intermaxillary bone, which in many animals remains as a separate bone (os > incisivum), carries the incisor teeth. At the oth week the Head of embri-o rabbit of 10 days (>< 12). a •" : . "^ , eye; at, atFium or primitive auricle of 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 maxillary 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 supe- rior maxillary processes, then the mouth is not separated from the nose. This separation may occur only in the soft parts, constituting hare-lip (Fig. 672) ; or it m^ay involve the hard palate, constitut- ing cleft palate. Both conditions may occur on one or both sides. From the posterior part of the heart ; b, aortic bulb ; k' , k" , k'" , first (mandibular), second (hyoid), third (ist branchial) visceral arch ; ?«, mouth; s, superior, and u, inferior maxillary pro- cess ; s, mid-brain ; v, part of head and fore-brain ; v, ventricle of heart. Fig. 672. Fig. 673. Fig. 672.^Hare-lip on the left side. Fig. 673. — Inner view of the lower jaw of an embryo pig 3 inches long (X 3%)- f^k, Meckel's cartilage; d, dentary bone ; cr, coronoid process ; ar, articular process (condyle) ; ag; angular process ; tnl, malleus ; m6, manubrium. first branchial arch are formed the malleus (ossified at the 4th month), and Meckel's cartilage (Fig. 673), which proceeds from the latter behind the tympanic ring as along 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 articulation. ISTear where it leaves the malleus is the processus Folii [Baumiiller). A part of its median end ossifies, 932 THE BRANCHIAL CLEFrS AND THEIR RELATION TO NERVES. and unites with the lower jaw. The lower jaw is laid down in memhrane from the first branchial arch, while the angle and condyle are formed from a cariiiaginous process. The union of both bones to form the chin occurs at the 1st year. I'rom the superior maxillary process are formed the inner lamella of the pterj-goid process, the jialaline process of the upper jaw, and the palatine bone at the end of the 2d month, and lastly the malar bone. The second arch [Ayoit/], arising from the temporal bone, and running parallel with the first arch, gives rise to the stapes (although acccirding to Salensky, this is derived from tiie first arch), the emmentia pyramidalis, with the stapedius muscle, the incus, the styloid process of the temporal bone, the (foimerly cartilt^inous) stylohyoid ligament, the smaller cornu of the hyoid bone, and lastly the gIoS!-o-palatine arch [His). The third arch [t/iyro-hyoia) forms the greater cornu and body of the hyoid bone and the pharyngo-palatine arch {//is). The fourth arch gives rise to the thyToid cartilage {//is). Branchial Clefts. — The fust 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. IJranchiogenic tumors and cysts depend upon the branchial arches (A'. I'o/kwnnn). [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 lac/t- ry ma I sVii between the frontal and nasal processes is supplied by Kh^/irs/ diTision of the tris;emitius. Ihe nasal slil between the superior maxillary process and the nasal process is supplied by the bifur- cation of the ////>,/ wf/tc. The orv;/ c/^//, between the superior maxillary processes and the mandi- bular arch, is supplied by the second and third divisions of the trii^eminus. The first post-oral or tympanic- Eustachian cleft, between the mandibular arch (ist) and the hyoid arch, is su])plied by the portio dura. The next cleft is supplied by the glosso-pharyni;eal, and the succeeding clefts by branches of the vai:;us.'\ The thymus and thyroid glands are formed as paired diverticula from the epithelium covering the branchial arches. The epithelium of the last two clefis does not disappear (pig), but prolifer- ates and pushes inward cylindrical processes, which develop into two epithelial vesicles, the paired commencement of the thyroid glands. These vesicles have at first a central .'■lit, which communi- cates w ith the pharynx ( IVo/jier). According to His, the thyroid gland appears as an epithelial vesicle 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 oi ihe thymus \\\\\ch remains is the so-called concentric corpuscles (p. 198). According to Born, this gland is a diverticulum from the 3d cleft, while His xscribes its origin to the 4th and 5th aortic arches in man at the 4ih 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 (p. 666) show that the upper extremity was originally placed much nearer to the cranium, while the position of the posterior pair corresponds to the last lumbar and the 3d or 4th sacral vertebrae {//is). The clavicle, according to Bruch, is not a membrane bone, but is formed in cartilage like the furculum of birds {Gegettbauer). 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 {Go/te). Ruge regards pieces of cariilages existing between the clavicle and the sternum as the analogues of the episternum of animals. The clavicle is absent in many mammals (camivora) ; it is very large in Hying 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 it has a metlian centre of ossification, which rapidly extends. Morphologically, the accessory centre in the coracoid process is interesting ; the latter al>o 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 supra-scapular bone of many animals. The other centres of ossification are — one in the lower angle, two or three in the acromion, one in the articu- lar surface, and an inconstant one in the spine. Complete consolidation occurs at puberty. The humerus ossifies at the 8th to the gih 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 loth year) ; one in the trochlea (12th year). The epiphyses unite with the shaft at the l6th to 20lh year. The radius ossifies in the shaft at the 3d month. The rther centres are — one in the lower epi- physis (5ih year), one in the upper 1 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 DEVELOPMENT OF THE BONES OF THE IJMBS. 933 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. 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, semi-lunar, 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 {e. ^^., salamander). In man the common position of the 4th and 5th fingers is represented by the unciform bone. Morphologi- cally, 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 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 mag- num, unciform (ist year), cuneiform (3d year). Fig. 674. trapezium, semilunar (5th year), scaphoid (6th year), trapezoid (7th year), and pisiform (i2th year). The metacarpal bones have a centre in their diapbyses at the end of the 3d month, and so have the phalanges. All the phalanges and the first bone of the thumb have their cartilagi- nous 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 pha- langes 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 cen- tres— one in the ilium (3d to 4th month), one in I 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 acetabu- lum, another in the superficies auricularis, and one in the symphysis. Other accessory centres are : One in the anterior inferior spine, the crests of the ilium, the tuberosity and the spine of the ischium, the tuberculum pubis, eminentia iliopectinea, and floor of the acetabulum. 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. 674). The femur has its middle centre at the end of the 2d month. At birth, there is a centre in the lower epiphyses; slightly later in the head. In addition, there is one in the great trochanter (3d to nth 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. The 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 calcis ossifies at the beginning of the 7th month, the astragalus at the beginning of the 8th month, the cuboid at the end of the loth, the scaphoid (ist to 5th year), the I and II cuneiform (3d year), and the III cuneiform (4th year). An accessory centre is formed in the heel of the calcaneum at the 5th to loth year, which consolidates 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 pre- ceded by cartilage, is called endochondral bone. Some bones, such as the tabular bones of the vault of the cranium, the facial bones, and part of the lower jaw, are not preceded by cartilage. In the latter there is merely a membrane present, while from and in it the future bone is formed. It becomes the future periosteum as well. This is called the intra-membranous or periosteal mode of formation.] [Endochondral Formation. — (i) The cartilage has the shape of the future bone only in minia- ture, and it is covered with periosteum. In the cartilage an opaque spot or centre of ossification appears, due to the deposition of lime salts in its matrix. The cartilage cells proliferate in this area, Centres of ossification of the innominate bone. 934 DEVELOPMENT AND GROWTH OF BONE. but the first bone is fonned 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) Bloodvessels, accompanied by osteoblasts and connective tissue, grow into the cartilage from the osteogenic layer of the periosteum ( /<<^rios/i-ii/ /roiesses of N'irchow), so that tlie cartilage becomes channeled and vas- cular. As these channels extend they open into the already enlarged cartilage lacun;v. 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 fonned. They contain the primary or cartihu^e marrcno, consisting of blood vessels, osteoblasts, and osteo- clasts, carried in from the osteogenic layer of the jieriosteum, and of course the carlilai^e cells that have been liberated from their lacuniv. (3) The osteoblasts are now in the interior of the cartilage, where they (lis]iose themselves on the calcified cartilage, and secrete or fomi 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 primar)- 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 witli the deposition of the new bone, bone and cartilage are being absorbed by the osteoclasts.] Chemical Composition of Bone. — Dry bone contains ■( of organic matter or ossein, from which gelatin can be extracted by prolonijed boiling; and about -3 mineral matter, which consi.sis of neutral calcic phosphate, 57 per cent.; calcic carbonate, 7 per cent.; magnesic phosphate, I to 2 per cent.; calcic lluoride, I per cent., with traces of chlorine ; and water, about 23 per cent. The marrow contains fluid fat, albumin, hypoxanthin, cholesterin, and extractives. The reil marrow- contains more iron, correspDnding to its larger proportion of hii^moglobin [iVasse). [The medullary cavity of a long bone is occupied hy yeiimu marrow, which contains about 96 per cent, of fat. The rt'd 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 hlood-formini:; tissue (p. 53)-] 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 lamella;. [Miiller and Schafer have shown that there are also fibres in the peripheric lamella, 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 (Dtthaviel). The growth in length takes place by the continual growth and ossification of the epiphyseal cartilage. The cartilage is gradually 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. Hunier).'\ When the growth of bone is at an end, the epiphysis becomes united to the diaphysis, the epiphyseal cartilage itself becoming ossified. It is not detinitely proved whether there is an interstitial expansion or growth of the true osseous substance itself, as maintained by Wolfi" (^ 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 lacunae — on the fang of a temporarj' tooth, when it is being absorbed. They are readily seen in a microscopical section of spongy bones 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 " foregut." 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. 675, i)], and there are indications of its being subdivided into (a) an upper aortic part with the bulbus arteriosus ; {b) a middle or ventricular part ; and {v) a lower venous or auricular part. The heart then curves on itself in the form of a horseshoe (2), so that the venous end {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, o, 0,). 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, z-), which joins with the middle of the posterior wall of the auricular part, is composed of the superior and inferior venas cava\ This common trunk is absorbed at a later period into the DEVELOPMENT OF THE HEART. 935 enlarging auricle, and thus arise the separate terminations of the superior and inferior venae cavce. In man, the heart soon comes to lie in a special cavity, which ia part is bounded by a portion of the ■diaphragm [His). At the 4th to 5th week, the lieart begins to be divided into a right and a left half. Corresponding to the position of the vertical ventricular furrow, a septum grows upward verti- cally in the interior of the heart, and divides the ventricular part into a right and left 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 communi- cates by a right and left auriculo-ventricular opening with the corresponding ventricle (5). At the same time two septa (4,/ a) appear in the interior of the truncus arteriosus (4,/), which ulti- mately meet, and thus divide this tube into two tubes (5, a p), the latter forming the aorta and Development of the heart, i, Early appearance of the heart — /?, aortic part, with the bulbus, b; v, venous end. 2, Horseshoe-shaped curving of the heart — a, aortic end, with the bulbus, d ; V, ventricle ; A, auricular part. 3, Formation of the auricular appendages, o, o-^, and the external furrow in the ventricle. 4, Commencing division of the aorta, /, into two tubes, a. 5, View from behind of the opened auricle, v, v, into the L, and R, ventricles, 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 (Cf) and inferior vena cava [Ci) to the auricle (schematic view from above)— .r, direction of the blood of the superior vena cava into the right auricle ; _j', that of the inferior cava to the left auricle; tL, tubercle of Lower. 7, Heart of the ripe foetus — R, right, L, left ventricle ; «, aorta, with the innominate, c, c, carotid, c, and left subclavian artery, i- ; B, ductus arteriosus ; J>, pulmonary artery, with the small branches / and 2, to the lungs. pulmonary artery, and are disposed toward each other like the tubes in a double-barreled 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 In the auricle a septum grows from the front and behind, ending internally with a concave mar- gin. 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 fora- men 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, j; on the right of the orifice 936 DEVELOPMENT OF THE AORTIC ARCHES. 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 auricle, through the ]>ervious foramen ovale. Comjjare the fcttal circulation (p. 92cS). After birth, the valve of the foramen ovale closes that aperture, while the ductus arteriosus also becomes imjier- vioiis, so that the blood of the pulmonary arlerj is forced to go through the pulmonary branches proceeding to the expanding lungs. .Sometimes the foramen ovale remains pervious, giving rise to serious syrnptoms after a time, and constituting morbus ceruleus. Fic. 676. 1. The aortic arches, i. The first position of the 1,2, and 3 arches. 2. 5 aortic arches ; tii, common aortic trunl: ; ad, descending aorta. 3. Disappearance of the upper two arches on each side — S, subclavian artery; v, vertebral artery; aj-, axillary artery. 4. Transition to the final stage — P, pulmonary artery ; ./4, aorta ; rfZ?, ductus arte- riosus (Sotalli) ; S, right subclavian, united with the right common carotid, which divides into the internal (C7) and external carotid (C). The stalk becomes the oplic nerve. At the under surface of the depression there is a slit— the choroidal fissure — which permits some of the mesoblast to gain access to the interior of the eye. This slit forms the coloboma (II) ; it is prolonged backward on the stalk, and contains the central artery of the retina. The margins of the coloboma afterward unite completely with each other, but in some rare conditions this does not take jilace, in which case we have to deal with a coloboma of the choroid or retina, as the case may be. In the bird the embryonic coloboma slit does not close up, but a vascular process of the mesoblast dips into it, and passes into the eye to form the pecten (p. 846). The same is the casein fishes, where there is a large vascular process of the meso- and epiblast forming ihs processus falciformis (p. 846). The depression or inflection of the optic vesicle is due to the downgrowth into it of a thickening of the epiblast ( I, L). It is hollow, and as it grows inward ultimately becomes spherical and separated from the epiblast to form the crystalline lens, so that the lens is epiblastic in its origin, while the capsule of the lens is a cuticular structure formed from the epiblast. That part of the epiblast which covers the vesicle in front of the lens ultimately becomes the stratified epithelium of the cornea. The layer of pigment of the invaginated oplic vesicle is applied to the ciliary body, and the posterior sur- face of the iris, when the latter is formed. The cornea is formed at the sixth week. The substance DEVELOPMENT OF THE SENSE ORGANS. 945 •of the choroid, sclerotic, and cornea is formed around the position of the eye from the mesoblast (w). The capsule of the lens is at first completely surrounded by a vascular membrane — the membrana capsulo-pupillaris. Afterward, the lens passes more posteriorly into the eye — the anterior part of the capsulo pupillary membrane, however, remains in the anterior part of the eye, while toward it grows the margin of the iris (seventh week), so that the pupil is closed by this part of the vascular capsule, membrana pupillaris. The blood vessels of the iris are continuous with those of the pupillary membrane ; those of the posterior capsule of the lens give off the hyaloid artery, a continuation of the Development of the eye. I, Inflexion of the sac of the lens (L) into the primary optic vesicle (P) — e, epidermis ; tn, mesoblast. II, The inflexion seen from below — «, optic nerve ; e, the outer; i, the inner layer of the inflected vesicle; L, lens. Ill, Longitudinal section of II. IV, Further development — -. Hermann). 453. BIRTH. — With the growth of the ovtim, the uterus becomes inore dis- tended, hs walls more muscular and more vascular, although the uterine walls are not thicker at the end of pregnancy. Toward the end of gestation the cervical canal is intact until labor begins, or at any rate it is but slightly opened up at its upper part. After a period of 280 days of gestation, "labor" begins, whereby the contents of the uterus are discharged. The labor pains occur rhythmically and periodically, being separated from each other by intervals free from pain. F^ach pain begins gradually, reaches a ma.ximum, and then slowly declinesj. With each pain the heat of the uterus increases (§ 303), while the heart-beat of the foetus becomes slower and feebler, which is due to stimulation of the vagus in the medulla oblongata (§369, 3). [At the full time the membranes and i)lacenta line the uterus. The mem- branes consist, from within outward, of amnion, chorion, decidua reflexa, and decidua vera. The fundi of the uterine glands persist in the deep part of the decidua vera, and thus form a spongy layer, the part above this being the compact layer in the deep part of the placenta, e. g., near the uterine wall; we have also the fundi of the uterine gland persisting in the decidua serotina. When the pla- centa and membranes are expelled after birth, the line of separation takes place in the part of the membranes and placenta where the fundi of the glands persist. After labor is completely fini.shed, the uterus is lined by the remains of the spongy layer of the decidua vera and serotina, e. g., is lined by a layer which contains the fundi of the uterine glands. The new mucous membrane is regenerated by the growth of the epithelium and connective tissue in this part. The membranes expelled are made up of amnion, chorion, deciduse reflexae, and the compact layer of the decidua vera.] The uterine movements during labor proceed in a peristaltic manner from the Fallopian tube to the cervix, and occupy 20 to 30 seconds. In the curve registered by these movements there is usually a more steep ascent tl"ran descent. [Power in Ordinary Labor. — Sometimes the ovum is expelled whole, the membranes contain- ing the liquor amnii remaining unruj)lured. Poppel has pointed out that the force whicli ruptures the bag of meml)ranes is sufficient to complete delivery, so that, as Matthews Duncan remarks, the strength of the memliranes gives us a means of ascertaining the power of labor in the easiest class of natural labors. MaUhews Duncan, from experiments on the pressure required to rupture the membranes, concludes that the great majority of labors are completed by a propelling force not exceeding 40 II s.] Polaillon estimates the pressure exerted by the uterus upon the foetus at each pain to be 154 kilos. [338.8 lbs.], so that, according to this calcuhtion, ihe uterus at each pain performs 8820 kilogram- metres of work {\ 301). [ Th s estimate is certainly far too high.] After-Birth. — After the foetus is expelled, the placenta remains behind; but it is soon expelled by tht; contractions of the uterus. During the comraciion of the uterus to expel the placenta, a not inconsideial)le amount of the placental blood is forced into the child (i) 40). [It is more probable that the child aspirates the blood from the foetus portion of the placenta. This can be seen in late ligature of the cord. The child may thus gain two ounces of blood.] After a time the placenta, the membranes and the decidua — constituting the after-birth — are expelled. Influence of Nerves on the Uterus. — i. Stimulation of the hypogastric plexus causes con- traction of the uterus. The fibres arise from the spinal cord, from the last dorsal, and upper three or four lumbar nerves, run into the sympathetic, and trien reach the hypogastric plexus (Frafikeiihduser). 2. Stimulation of the nervi erigentes, which are derived from the sacral plexus, causes movement (v. Bascli and //o/mann). 3. Stimulation of the lumbar and sacral parts of the cord causes powerful movements {Spie:,'elberg]. There is a centre for the act of parturition in the lumbar region of the cord (^ 362,6). The uterus, like the intestine, probably contains independent or parenchymatous nerve centres {/Corner), which can be excited by suspension of the respiration, and INFLUENCE OF NERVES ON THE UTERUS. 947 by ansemia (by compressing the aorta, or rapid hemorrhage). Decrease of the bodily temperature diminishes, while an increase of the temperature increases the movement, which, however, ceases during high fever (^Fronune). The experiments made by Rein upon bitches show that, if all the nerves going to the uterus be divided, practically all the functions connected with conception, preg- nancy, and parturition can take place, even although the uterus is separated from all its cerebro- spinal connections. Hence, we must look to the presence of some automatic ganglia in the uterus itself. According to Dembo, there is a centre in the anterior wall of the vagina of the rabbit. According to Jastreboff, the vagina of the rabbit contracts rhythmically. Sclerotic acid greatly excites the uterine conKxzsXxoxvs, [v. Swiecicki), so does ax\xm\a. (^Ki-oiiecker and Jastreboff). 4. The uterus contracts reflexly on stimulating the central end of the sciatic nerve {v. Basch and Hof- mann), the central end of the brachial plexus {^Schlesinge}-), and the nipple {Scanzoni). 5. The uterus is supplied by vasomotor nerves (hypogastric plexus), which come from the splanchnic; and also by vaso- dilator fibres, the latter through the nervi erigentes. The vasomotor nerves are affected reflexly by stimulation of the sciatic nerve (y. Basch and Hof77iann). [In the rabbit the vagina and uterine cornua exhibit regular movements of a "peristaltic" nature. These exist apart from any extraneous stimulus, and are probably a vital property of the tissue. They can be demonstrated in animals a few weeks old, and have been recorded continuously for many hours. JVequently they are more vigorous six hours after than at the beginning, showing that they are not due to the irritation of the operation necessary to demonstrate them. Their rate and extent vary. In young animals they are frequent (l to 4 per minute), but irregular in character. In nuUiparous adults they are less frequent and somewhat more regular. During preg- nancy they increase greatly in extent, and their rate becomes i in 120 to 130 seconds. These char- acters are retained alter pregnancy for many months at least. They are diminished or abolished by chloroform narcosis, are scarcely affected by ether. Water at 100° to 120° F. produces a persistent contraction accompanied by blanching of the tissue. Similar effects are produced by dilute acetic acid {^Milne Murray). "] Lochia. — After birth the whole mucous membrane (decidua) is shed ; its inner surface, therefore, represents a large wounded surface, on which a new mucous membrane is developed. The discharge given off after birth constitutes the lochia. Involution of the Uterus. — After birth the thick muscular mass decreases in size, some of its fibres undergoing fatt)' degeneration. Within the lumen of the blood vessels of the uterus itself, there begins in the interna of these vessels a pro- liferation of the connective-tissue elements, whereby within a few months the blood vessels so affected become completely occluded. The smooth muscular fibres of the middle coat of the arteries undergo fatty degeneration. The relatively large vascular spaces in the region of the placenta are filled by blood clots, which are ultimately traversed by outgrowths of the connective tissue of the vascular walls. Milk Fever. — After birth, there is a peculiar action on the vasomotor system,, constituting milk fever, while at the 2d to 3d day there is a more copious supply of blood to the mammary gland for the secretion of milk (§ 231). [After birth the pulse becomes slow and remains so in a normal puerperium. The so-called milk fever is not found in cases where strict cleanliness is observed during the labor and puerperium.] For the cause of the first respiration in the child,, see p. 717. 454. COMPARATIVE — HISTORICAL. — A sketch of the development of man must neces- sarily have some reference to the general scheme of development in the Animal Kingdom. The question as to how the numerous forms of animal life at present existing on the globe have arisen has been answered in several ways. It has been asserted that each species has retained its characters unchanged from the beginning, so that we speak of the " constancy of species." This view, developed by Linnseus Cuvier, Agassiz, and others, is opposed by that supported by Lamarck, 1809, or the doctrine of the " Unity of the Animal Kingdom," corresponding to the ancient view of Empedocles, that all species of animals were derived by variations from a few fundamental forms ; that at first there were only a few lower forms from which the numerous species were developed — a view sup- ported by Geoffrey St. Hilaire and Goethe. After a long period this view was restated and eluci- dated in the most brilliant and most fruitful manner by Charles Darwin in his " Origin of Species " (1859) and other works. He attempted to show how modifications may be brought about by uniform and varying conditions acting for a long time. Among created beings each one struggles with its neighbor, so that there is a real " struggle for existence." Many quahties, such as vigor, rapidity, color, reproductive activity, etc., are hereditary, so that in this way by " natural selection " there may be a gradual improvement, and therewith a gradual change of the species. In addition, organ- 948 COMPARATIVE HISTORICAL. isms can, wiihin certain limits, accommodate themselves to their surroundings or environment. Thus certain useful organs or parts may undcrs^o development, while inactive or useless parts may undergo retrogres>ion, and form " rudimentary organs." This procefs of " natural selection," causing gradual changes in the form of ori^anisms, fin. Is its counterpart in " artificial selection " among plants and animals. Breeders of animals, for example, by .selecting the proper crosses, can within a relatively short time produce very material alterations in the form and characters of the animals which they hreed, the changes being more pronounced than many of those that se[)arate well-defmed species. Hut, just as with artificial selection, there is s mietimes a sudden " reversion " to a former type, so in the development of species by natural selection there is sometimes a condition of atavism. ( )bviously, a wide distribution of one sjiecies in different climates must increase the liability to change, as very different conditions of environment come into play. Thus, the migration of organi>ms may gradually lead to a change of species. Biological Law. — Wiihout di.'^cussing the development of different organisms, we may refer to the "/«/;sure being applied to it. In the Talmud it is stated that an animal with its uterus extirpated may live, that thepubes separates during birth, and there is a record of a case of Ca^sarean section, the child being saved. Sylvius described the value of the foramen ovale; Vesalius (1543) ihe ovarian follicles; Eustachius (f 1570) the ductus arteriosus (Botalli) and the branches of the umbilical vein to the liver. Arantius investigated the duct which bears his name, and he asserted that the umbilical arteries do not anastomose with the maternal vessels in the placenta. In Libavius (1597) it is stated that the child may cry in utero. Riolan ( 1618) was aware of the existence of the corpus Elighmorianum testis. Pavius (1657) investi- gated the position of the testes in the lumbar region of the foetus. Harvey (1633) stated the funda- mental axiom, " Otmie viviim ex ovo^ Fabricius ab Aquapendente fl6oo) collected the materials known for the history of the development of the chick. Regner de Graaf described more carefully HISTORICAL. 949 the follicles which bear his name, and he found a mammalian ovum in the P'allopian tube. Swam- merdam (f 1685) discovered metamorphosis, and he dissected a butterfly from the chrysalis before the Grand Duke of Tuscany. He described the cleavage of the frog's egg. Malpighi (f 1694) gave a good description of the development of the chick with illustrations. Hartsoecker (1730) asserted that the spermatozoa pass into the ovum. The first half of the 1 8th century was occupied with a discussion as to whether the ovum or the sperm was the more important for the new forma- tion (the Ovulists and Spermatists ) ; and also as to whether the fcetus was formed or developed within the ovum (Epigenesis), or if it merely increased in growth. The question of spontaneous generation has been frequently investigated since the time of Needham in 1745. New Epoch. — A new epoch began with Caspar Fried. Wolff (1759), who was the first to teach that the embiyo was formed from layers, and that the tissues were composed of smaller parts (corres- ponding to the cells of the present period). He observed exactly the formation of the intestine, William Hunter (1775) described the membranes of the pregnant uterus. Soemmering (1799) described the formation of the external human configuration, and Oken and Kieser that of the intes- tines. Oken and Goethe taught that the skull was composed of vertebrse. Tiedemann described the formation of the brain, and Meckel that of monsters. The basis for the study of the develop- ment of an animal from the layers of the embryo was laid by the researches of Pander (1817), Carl Ernst V. Baer (1828-1834), Remak, and many other observers; and Schwann was the first to trace the development of all the tissues from the ovum. [Schlaiden enunciated the cell theory with refer- ence to the minute structure of vegetable tissues, while Schwann applied the theory to the structin-e of animal tissues. Among those whose names are most prominent in connection with the evolution of this theory are Martin Barry, von Mohl, Leydig, Remak, Goodsir, Virchow, Beale, Max Schultze Briicke, and a host of recent observers.] APPENDIX A. General Bibliography. SYSTEMATIC WORKS AND TEXT-BOOKS —A. v. Haller, Elementa physiologire cor- poris humani, 1757-1766,8 vols., Auctarium, 1780. — F. Magendie, Precis elementaire de physi- ologic, 1816, 2cl ed., 1825. — ^Johannes Miiller, Ilandbuch der l*hysioloh ed , 1878). — W. Wundt, Lehrbuch der Physiologic, 4th ed., 1878, and Grundziige d. physiol. Psycholog., 3d ed., Leip., 1887. — M. Fester, Text-book of Physiology, 4th ed., 18S3. — H. Milne-Edwards, Legons sur la physiologic et I'analomie comparee, 14 vols., 1857-18S0. — G. Colin, Traile de Physi- ologic comparee des animaux, Paris, 1871-1873. — Bernard, Leg. de Pathol, exper., Paris, 1872. — Marshall, Phys. (Diagrams and Text), 1875. — Strieker, \'orles. ii. allg. u. exp. Path., Wien, 1878. — Munk, Physiologic d. Menschen u. d. Saugcthierc, Berlin, 2d ed., 1888. — Schmidt-Mulheim, Grundriss d. spec. Physiologic d. Ilaus-augethierc, Leipzig, 1879. — Vierordt, Grunrlriss d. Physiol- ogic d. Menschen, 5th ed., Tubingen, 1857. — Todd and Bowman's Cyclopaedia of Anat. and Phys. — Hermann, Expt. Toxicologic, 1S74. — W. Rutherford, .V Text-book of Physiology, pt. i, Edin- burgh, 1S80. — W. B. Carpenter, Princip. of Phys., 8th ed., edited by Power, London, 1876. —J. Beclard, Traite elem. de Phys., Paris, 1880. — Cohnheim, N'orlcsungen ii. allgem. Pathologic, Berlin, 1880. — Huxley's Ivlements, 1885. — H. Beaunis, Nouveaux elements de Physiologic hu- maine, 2d ed., 1881. — Flint, Textbook, New York, 1876; and Phys. of Man, 1S66-1873. — Kirkes, Handbook of Physiology, nth ed., 1884.— Dalton, Text-book, 1882.— -J. G. M'Kendrick, Text- book of Physiology, Glasgow, 18S8. — Samuel, Ilandb. d. allg. Path., Slutt., 1879. — The works of Herbert Spencer and G. H. Lewes. — E. D. Mapother, Manual of Physiology, 3d ed., re- written by L L. Knott, Dublin, 1882. — A. Fick, Compendium d. Phys., 18S2. — Steiner, Physiol- ogic, 4th ed., Leipzig, 1S88. — Nuel and Fredericq, Elem. de Phys., Gand, 1883.— Preyer, Ele- mente der allgemeinen Physiologic, 1883. — T. Lauder-Brunton, Pharmacology, Therapeutics, and Materia Medica, 1887. — H. Power, Elements of Physiol., London, 18S4. — Wundt, Phys. med., 1878 — Daniell, Text-book of the Principles of Physics. 1884.— Fick, Med. Physik., 2d ed., 1884. — M'Gregor Robertson, Physiological Physics, London, 1885.— Draper, Med. Phys-ics, 1.885. — Yeo, Manual of Physiology, 2d ed., London, 1887. — L. v. Thanhoffer, tirundziige d. vergl. Physiologic u. Histologic, Stuttgart, 1885. — Ziegler, Text-book of Path. Anat. (trans, by D. Macalister), 1883-1S84.— P. H. Pye-Smith, Syllabus of Lectures on Physiology, London, 1885. — Chapman, Treatise on Human Phys, Philad., 1S87. — Klein, Microorganisms and Disease, 1884. — Magnin and Steinberg, Bacteria, 1884. — W^oodhead and Hare, Mycology, 1885. — Crook- shank, Bacteriology, 1886. — Davis, Text-book of Biol., London, 18S8. — Vines, Physiology of Plants. — Albertoni and Stefani, Manualc di Fisiol. umana, 1888. — Ellenberger, Lehrb. d. verg- leich. Histol. u. Physiol, d. Llaunhiere, Berlin, 1887. — Landois and Stirling, Text-book, ^d ed., 1888. YEARLY REPORTS. BIBLIOGRAPHICAL WORKS.— 1834-1837 : " Jahresberichte iiber die Fortschritte der Physiologic," by Job. Muller,in his Archiv. — 1 838-1846 : by Th. L. Bischoff, ebenda. — 1836-1843: in " Repertorium fiir Anatomic und Physiologic," by G. Valentin, 8 vols. — 1856-1871 : in " Zeitschrift fiir rationelle Medicin," by G. Meissner, and continued since 1872 under the title — "Jahresberichte iiber die Fortschritte der Anatomic und Physiologic," by F. Hof- mann, and G. Schwalbe, Leipzig. — 1841-1865 : Jahresbericht uber die Fortschritte der gcsammten 950 GENERAL BIBLIOGRAPHY. 951 Medicin, by Canstatt, continued by Virchow and Hirsch. — 1822-1849 : Froriep's Notizen, loi vols. (References and Bibliogr=iphy). — Centralblatt fiir die medicinisclien Wissenschaften, Berlin ; yearly since 1863. — Biologisches Centralblatt, Erlangen, since 1881. — 1817-1818: Isis, by Oken. — Catalogue of Scientific Papers compiled and published by the Royal Society of London, 1800-1873, 8 vols. — Engelmann, 1700-1846: Bibliotheca historico-naturalis (Titles of Books on Comparative Physiology). — Jahrbuch der gesammten Medicin, by Schmidt, since 1826. — Bibliotheca anatomica qua scripta ad anatomen et physiologiam facientia a reruni initus recensentur auctore Alberto von Haller, 2 vols, (important for the older literature up to 1776). — Yearly Reports on Physiology, in Journal of Anat. and Phys., by Rutherford, Gamgee, and Stirling ; also Monthly Reports in London Med. Record, since its commencement in 1873. — Index medicus. — Neurologisches Central- blatt.— Med. Bibliographic by A. Wiirzburg, since 1886. — Fortschritt d. Med. HISTORICAL. — Kurt Sprengel, Versuch einer pragmatischen Geschichte der Arzneykunde, 3d ed., 1821. — W. Hamilton, Hist, of Med. Surg, and Anat., 1831. — Bostock's Syst. of Phys., 3d ed., 1836. — ^J. C. Poggendorf, Geschichte der exacten Wissenschaft, 1863. — J. Goodsir, Titles of Papers on Anat. and Phys., 1849-1852, Edin., 1853. — Meyer, Gesch. d. Botanik, Konigs., 1854-1857. — H. Haeser, Lehrbuch der Geschichte der Medicin, Jena, 1875. — Julius Sachs, Geschichte der Botanik seit 16. Jahrh. bis i860; 1875. — Bouchut, Hist, de la med., Paris, 1873. — Fournie, Applic. de la scien. a la med., Paris, 1873. — Willis's William Harvey, 1878; and his Servetus and Calvin, London, 1877. Biographisches Lexikon, Vienna, 1884. ENCYCLOP.-EDIAS.— R. Wagner, Handworterbuch der Physiologic, 4 vols., 1842-1853.— R. B. Todd, The Cyclopfedia of Anatomy and Physiology, 1836-1852. — Pierer and N. Choulant, Anatomisch-physiologisches Realworterbuch, 8 vols., 1816-1829. — L. Hermann, Handbuch der Physiologic, 1879-1884. Real-Encyclop. d. gesam. Med., edited by Eulenberg, Wien, 1888. PRACTICAL WORK IN THE LABORATORY.— R. Gscheidlen, Physiol ogische Meth- odik, 1876 (not yet completed). — E. Cyon, Methodik der physiologischen Experimente u. Vivisek- tionen, with Atlas, 1876 (only one part issued). Ott, The Actions of Medicines, Phil., 1878. — Claude Bernard and Huette Precis iconographique de medecine operatoire etd'anatomie chirurgi- cale, with 113 plates, 1873 '■> ^^^o Legons de physiologic operatoire (edited by Duval), Paris, 1879. — Sanderson, Foster, Klein, and Brunton, Handbook for the Physiological Laboratory (Text and Atlas). The French edition contains additional matter. — Rutherford, Outlines of Pract. Hist., 1876. — Meade-Smith, Trans, of Hermann's Toxicol. — ^J.BurdonSanderson, Practical Exercises in Physiology, London, 1882. — Foster and Langley, Pract. Phys., London. 1884. — B. Stewart and Gee, Pract. Physics. — Vierordt, Anat. Physiol, u. Physik. Daten u. Tabellen, Jena, 1888 — Miiller-Pouillet, Lehrb. d. Physik., 8th ed., Braunschweig. — Wiillner, Lehrb. d. exp. Physik. — Livon, Manuel de Vivisect., Paris, 1882. — Harris and Power, Manual for the Phys. Lab., 5th ed., 1888. — Straus-Durckheim, Anat. descrip. comp. du. chat, Paris, 1845. — ^- Krause, Die Anato- mic des Kaninchens, Leipzig, 2d ed., 1883 — A. Ecker, Die Anatomic des Frosches, 1864-1S82, 2d ed., pt. i, 1888. — Biolog. Memoirs, edited by Burdon-Sanderson. — Stirling, Outlines of Pract. Physiol., Lond., 1888. SPECIAL LABORATORY REPORTS.— Ludwig and his pupils, Arbeiten aus der physio- logischen Anstalt zu Leipzig, since 1866. — Burdon-Sanderson and Schafer, Collected papers from the Physiological Laboratory of University College, London, 1876— 1885. — Gamgee, .Studies from the Physiological Laboratory of Owens College, Manchester, 1877-78. — Traube, Beitr. z. Path. u. Phys., Berlin, 1871. — ^J. Czermak, Gesammelte Schriften, 1879. — Marey, Physiologic ex- perimentale, Travaux du laboratoire, Paris, 1875. — L. Ranvier, Laboratoire d'histologie du College de France, Paris, since 1875. — Loven, Physiol. Mittheil., Stockholm, 1882-84. — W. Kiihne, Un- tersuchungen des physiologischen Instituts der Universitat, Heidelberg, since 1877. — R. Heiden- hain, Studien des physiologischen Instituts zu Breslau, 1861-68. — Strieker, Studien aus dem Insti- tute fur experimentelle Pathologic, Vienna. — John Reid, Physiological and Anatomical Researches, Edinburgh, 1848. — Rollett's Untersuch. a. d Inst, zu Gratz, since 1870. — Schenk, Mitth. a. d. embryol. Inst. z. Wien, 1877-. — Preyer, Sammlung phys. Abhandl., Jena, 1877. — Von Wit- tich, Mitth. a. d. Konigsb. Phys. Lab., 1878. — Rossbach, Pharmacol. Unters. Wiirzb., 1873. — Fick, Arb. a. d. Wiirzburger Hochschule, Wiirzburg, 1872. — Hoppe-Seyler, Med.-chem. Unters., 1866-71. — Laborde, Travaux de Lab. de Phys. de la Faculte de Med., Paris, 1885. Studies from the Biol. Lab. of Owens College, pt. i, 1886. — Tigerstedt, Mitth. v. d. phys. Lab. in Stockholm, 1888. JOURNALS, PERIODICALS.— Archiv fur die Physiologic, by J. C. Reil and Autenreith, 12 vols., Halle, 1796-1815. Continued as — Deutsches Archiv fiir die Physiologic, by J. F. Meckel, 8 vols., Halle, 1815-1823. Continued as — Archiv fiir Anatomic und Physiologic, by J. F. Meckel, 6 vols., Leipzig, 1826-1832. Continued as — Archiv iiir Anatomic und wissenschaftliche Medicin, by Johannes Miiller, 25 vols., Berlin, 1834-1858. Continued under the same titiehy — C. B. Reichert and E. du Bois-Reymond, 1859-1876. When it was divided into — Zeitschrift fiir Anatomic und Entwickelungsgeschichte, by W. His and Braune, and Archiv fiir Physiologic, by 952 GENERAL BIBLIOGRAPHY. E. du Bois-Reymond, until 1S77. Is ,oitliuued as — Archiv fiir Anatomic und Physiologic by W. His, W. Braune, and E. du Bois Reymond. — Archiv fiir die gesamnite Physiologic des Menschcn uinl dcr Thicro, liy E. F. W. Pfliiger, Bonn, since 1S6S. — Zcitschrifl fiir Biologic, edited from 1S65 hy Buhl, Pettenkofcr, Voit, and Radlkofcr ; from 1S75 i)y the first three, and since 18S0 by Pettcnkofcr and Voit, iHCsenlly by Voit and Kiihne.— Journal de Physiologic exp6ri- mentale ct pathologii|ue, liy F. Magcndie, II vols., Paris, 1821-1.S31. — Zeitschrift fiir die organische Physik. by C. F. Heusinger, 4 vols., Eisenach, 1S27-182S— Zt-itschrift fiir Physiologic, by F. Tiedemann and Treviranus, 5 vols., 1S24-1S33. — journal de I'anatomie et de la physiologic normales et iiathiilogi(|ues de riiomme et des animaux, by Ch. Robin and Pouchet, since 1864. — Archives dc physiologic normalc et pathologiquc, by Brown- Scquard, Charcot, Vulpian, Paris, since 186S. — Journal of Anatomy and Physiology, edited by Humphry. Turner, and M'Kendrick, since 1867.— Journal of Physiology, edited by M. Foster, since 1S7.S. — Archives Italiennes de Biologic, by C. Emery and A. Mosso, since 1881. — Annaks de sciences natiirelles, Paris, since I S24.— Archives de Zoologie experimentale et generale by Lacaze-Duthiers, Paris, since 1872. — Archives de Biologic, by Ed. van Beneden, and Ch. van Bambeke, since 1880. — Physiolog. Centralblatt, by Exner and Gad, since 1S.S7.— Zeitschrift fiir wissenschaltlichc Zoologie, by C. T. von Siebold and A. von Kolliker, Leipzig, since 1849. — Archiv fiir pathologischc Anatomic und Physiologic und fiir klinische Medicin, by R. Virchow, Berlin, since 1S47. — Ztsit. f. wisscnsch. Mikroscoj). , Behrcns, Braunschweig. — Archiv fiir Xaturgeschichte, by Wiegmann ; conthmed by Erichsen and Troschcl, Berlin, since 1835. — Untersuchun^cn zur Naturlehre des .Menschcn und der Thiere, liy Jac. Moleschott, since 1857. — Zeitschrift fiir rationelle Medicin, Henle, Pfeufer, and Meissner. — .Sitzungsbcrichte der Akademie der Wis-enschaften (Math. Nat.-Wiss. Clause), Vienna. — Pliilosophical Transactions, London. — Proceedings of the Royal Society, London. — Trans- actions of the Royal .Society, Edinburgh. — Proceedings of the Royal Society, Edinburgh. — Quar- terly Microscopical Journal, London. — Monthly Microscopical Journal, London. — Journal of the Royal Microscopical Society, London. — Comjites rendus, Paris. — Anatomisches Anzeiger. — Index Mcdicus. — Cohn, IJcitragc zur Physiologic der Pflanzen, Brcslau, 1872. — The Philosophical Maga- zine, Edinburgh, London, and Cambridge. — Boston Medical and Surgical Journal. — ^'erhandlungen der physikal.-medicinischen Gcsellschaft zu Wiirzburg. — Archives of Medicine, edited by L. Beale, London, 1856. — Annals and Magazine of Natural History. — Annales (Memoircs) Archives du Museum d'histoire naiurelle, Paris. — Jenaische Zeitschrift fiir Naturwisscnschaft. — Memoircs de r Academic dc5 Sciences de rinstitut de France, Paris. — Morphologisches Jahrbuch, by C. Gegen- baur, since 1876. — Nova Acta Acadcmi;e Leopoldino-Carolinre. — Zoologischer Anzeiger, by V. Carus, since 1878. — Abhandlungen and Monatsberichtc der k. preussischen Akademie der Wissen- schafi zu Berlin. — Archiv fiir expcrimentelle Pathologic und Pharmakologie, l>y Naunyn and Schreiber. Leipzig, since 1873. — Deutsches Archiv fiir klin. Medicin, by v. Ziemssen and Zen- ker, Leipzi'T. — lournal de Pharmacie et de Chimie, Paris. —Archiv fiir Psychiatric und Nervenkrank- hciten, by Gudden and others, Berlin, since 1S68. — Archiv fiir \vissen=chaftliche und praktische Thierhcilkunde, by Roloff, Berlin, 1S74. — Archives generales de medecinc, Paris. — Brain, since 1879, edited by de Wattevillc. — Archives dc Neurologic, by Charcot, Paris, 1875. — Zeit. f Hy- giene, by Koch and Fliigge. — The various Medical Journals, including the Lancet and British Medical Journal, Edinburgh Medical Journal, Ix)ndon Medical Record, New York Med. Record, Practitioner, Medical Clironicle. — .\rch. for Otology, N. Y. — Arch, for Ophthal., N. Y. — Internat. Jour, of Med. Sciences, Edin. — Revue de Med., Paris. — Zeit. f Klin. Med., Berlin. — Intern. Mo- natssch. f Anat. u. Physiol. — Asclepiad. — Nature. HISTOLOG^'. — Henle, Ilandbuch der sy.stematischen Anatomic des Menschcn, 3d ed., 1866- 1883. — Rutherford, < )utlines of Pract. Histol., 1876. — W. Krause, Allgemeine und Mikroskop- ische Anatomic, Hannover, 1876. — F. Leydig, Lehrbuch der Histologic des Menschen und der Thiere. Hamm, 1857; and his Untersuchungen, 1883; and his Zell u. Gewebe, Bonn, 1885. — V. Mihalkovics, General Anatomy (Hungarian), 1881. — L. Ranvier, Traite technique d'histologic, Paris, 1875-18S8. — G. Schwalbe, Lehrbuch der Neurologic, Erlangen, 1881 ; Lehrb. d. Anat. d. Sinnesorgane. — S. Strieker, Handbook of Histology (translated by the New Sydenham .Society), 1871-1873. — Archiv fiir mikrrskorische Anatomic, Bonn ; edited formerly by Max Schultze, and presently by Waldeyer and La Valette. — (Quarterly Microscopical Journal, London. — Monthly iMicroscopical Journal, London. — Journal of the Royal Microscopical Society, London. — Schwann, Mikrosk. Untcrsuch., 1838 (translated by the Sydenham Society, 1847). — W. Kiihne, Das Proto- plasma, Leipzig, 1864. — Max Schultze, Das Protoplasma, Leipzig, 1863. — R. Virchow, Die Cel- lular Pathologic (translated by Chance), i860. — L. Beale, The .Structure of the Elementary Tis- sues, London, 1881. — A. Kolliker, A Manual of Human Microscopic Anatomy, London, i860; and his Icones Histolog., Leip., 1864. — J. Goodsir, Anatomical and Pathological Observations, edited by W. Turner, Edinburgh. — Quain's Anatomy, 9th cd., edited by A. Thomson, Schafer> and Thane, London, 1S82. — Rindfleisch, A Manual of Pathological Anatomy (translated by R. Baxter), London, 1873.— C. Toldt, Lehrbuch der Gcwebclehrc, Stuttgart, 3d cd., 1888.— E. Klein and E. Noble-Smith, Atlas of Histology, Ix>ndon, 1S72. — H. Frey, Handbuch der His- tologic und Ilislochemie des Menschen, Leipzig, 1S76, Grundziige, 1SS5, and Das Mikroskop., 8th td., 1886. — Fol, Lehr. d. vergleich. mikros. Anatomic, Leip., 1885. — Behrens, Tabellen z. GENERAL BIBLIOGRAPHY. 953 Gebrauch b. mik. Arbeiten, Braunschweig, 1887. — Fearnley, Pract. HistoL, 1887. — Brass, Kurzes Lehrb. d. HistoL, Leip., 1888. — Beale, How to Work with the Micros., Lond., 1880. — W. Stir- ling, Histological Memoranda, Aberdeen, 1880. — E. A. Schafer, Practical HistoL, 1877; and Essentials of HistoL, 1887. — W. Stirling, Text-book of Practical Histology, London, iS8r. — Heitzmann, Microsc. Morphology, 1882. — Purser, Man. of Hist, Dubhn. — E. Klein, Elements of Hist., London, 1883.— W. Flamming, Zellsubst. u. Zelltheil., Leipzig, 1882. — Cadiat, Traite d'anat. gen,, Paris, 1879. — Bizzozero, Hand. d. klin. Mikroskop., Erlang., 2ded., 1888. — Carnoy, Gilson and Denys. Biol. Cellul., Louvain, 1S84-88. — Friedlander, Mik. Technik., 3d ed., Berlin, 1888. — Gierke, Farberei z. mik. Zvvecken., Braun., 1885. — Frommann, Unters. u. thier. u. pflanz. Zellen, Jena. 1884. — Wiedersheim, Lehrb. d. vergl. Anat., Jena, 1888. — S. L. Schenk, Grun- driss der Histologic d. iNIenschen, Vienna, 1885. — Orth, Cursus d. norm. HistoL, 4th erl., 1886. — S. Mayer, Histolog. Taschenbuch, Prag., 18S7. — Stohr, Lehrb. d. HistoL, Jena, 1888. — Lee and Henneguy, Traite de meth. de I'Anat., Paris, 1SS8. PHYSIOLOGICAL CHEMISTRY.— Hoppe-Seyler, Physiologische Chemie, Berlin, 1877- 1879. — Lehmann, Lehrb. d. phys. Chem., 3d ed., Leipzig, 1853 ; and Handbuch, 1859. — ^J. Konig, Chemie der menschlichen Nahrung und Genussmittel, 2d ed., Berlin, 1883. — Leo. Liebermann, Grundziige der Chemie des Menschen, Stuttgart, 1880. — Robin and Verdeil, Traite de chim, anat. et phys. (with Atlas), Paris, 1853. — ^J. Moleschott, Physiologic der Xahrungsmittel, 2d ed., Giessen, 1859. — E. Smith, Foods, 1873. — A. Wynter Bl3rth, Foods, 1887. — Gorup-Besanez, Anleitung zur Zoochemischen Analyse. 1871. — Gautier, Chimie applique a la Physiologic, 1874. — Lehmann's Phys. Chem. (translated by Cavendish Soc, 1851-54), with Atlas of O. Funke's plates. — Kingzett, Animal Chem., 1878. — Thudichum, Ann. of Chem. Med., 1879. — A. Gamgee, Physiological Chem- istry of the Animal Body, vol. i, 1880. — Hoppe-Seyler, Medicinische Chemische Untersuchungen, Berlin. — Zeitschriftfiirphysiologische Chemie, by Hoppe-Seyler, Strassburg, since 1877. — Watts' Dic- tionary of Chemistry, second supplement, London, 1S75. — Ralfe, Clinical Chemistr)', London, 1880; and Clinical Chem., 1883. — -Wurtz, Traite de chim. bioL, Paris, 1880. — T. C. Charles, Physiological and Pathological Chemistr)^, London, 1884. — Parkes' Hygiene, 7th ed. — Fliigge, Lehrb. d. hygien. Untersuchung., Leip., 1881. — Maly's Jahresb. ii. Thierchemie since 1870. — Landolt, Das opt. Drehungsvermog. org. Subst. Braun., 1879. — Articles in Hermann's Handbuch d. Physiologic, 1 879-1 884, and the various Text-books on Organic Chemistry. — Roscoe and Schorlemmer, (Organic) Chem., 1884. — Nowak, Le'nrbuch d. Hygiene, Wien. — Beilstein, Handb. d. org. Chem., Hamb. and Leip., 2d ed., 1825 — Ladenburg, Handb. d. Chemie, Breslau, 1883. — Rosenthal, Vorles. ii. offent. u. priv. Gesundheitspflege, Erlangen, 1887. — Kossel, Leitfaden f. med.-chem. Curse, 2d ed., Berlin, 18S8. 954 COMPARISON OF METRICAL WITH COMMON MEASURES. APPENDIX B. COMPARISON OF THE METRICAL WITH THE COMMON MEASURES. By Dr. Warren De la Rue. MEASURES OF LENGTH. In English Inches. In English Feet = iz Inches. In English Yards 3 Feet. Millimetre Centimetre Decimetre Metre . . Decametre Hectometre Kilometre Myriometre 003937 0.39371 3-93708 39.37079 393.70790 3937.07900 39370.79000 393707.90000 0.0032809 0.0328090 0.3280899 3.2808992 32.8089920 328.0899200 3280.8992000 32808.9920000 0.0010936 0.0109363 0.1093633 1.0936331 10.9363310 109 3633100 1C93. 6331000 10936.3310000 1 Inch = 3.539954 Centimetres. I Foot = 3.0479449 Decimetres. | i Yard = 0.91438348 Metre. MEASURES OF CAPACITY. In Cubic Inches. In Cubic Feet = 1728 Cubic Inches. In Pints ^ 34.65923 Cubic Inches. Millilitre or cubic centimetre . . Centilitre or 10 cubic centimetres Decilitre or loo cubic centimetres Litre or Cubic decimetre .... Decalitre or centistere Hectolitre or decistere Kilolitre or stere, or cubic metre . Myriolitre or decastere 0.061027 0.610271 6. 102705 61.027032 610.270515 6102.705152 61027.051519 610270.515194 0.0000353 0.0003532 0.0035317 0.0353166 0.3531658 3-53i658i 35.3165807 353.1658074 0.001761 0.017608 0.176077 1.760773 17 607734 176.077341 1 760. 7734 14 17607.734140 1 Cubic Inch = 16.3861759 Cubic Centimetres. | i Cubic Foot = 28.3153119 Cubic Decimetres. The UNIT OF voLtjMB is I Cubic Centimetre. MEASURES OF WEIGHT. Milligramme . Centigramme . Decigramme . Gramme . . , Decagramme . Hectogramme Kilogramme Myriogramme In English Grains. 0.015432 01 54323 1-543235 15-432349 154.323488 1543-234880 15432.348800 154323.488000 In Troy Ounces = 480 Grains. 0.000032 0.000322 0.003215 0.032151 0.321507 3.215073 32.150727 321.507267 In Avoirdupois Lbs. 7000 Grains. O.O0O0O32 o 0000220 0.0002205 0.0022046 0.0220462 0.2204621 2.2046213 22.0462126 The UNIT OF MASS in the metrical system is 1 Gramme, which is the mass or weight of i Cubic Centimetre (1 c.c.) of water at 4° C, i.e., at its temperature of maximum density. CORRESPONDING DEGREES IN THE FAHRENHEIT AND CENTIGRADE SCALES. Fahr. Cent. 500" . 450° • 400° . 350°. 300^ • 2H° . 210° . 205° . aoo° . 195°. 190° , 185°. 180° . 175°. 170° , 165O , 160° 1550 150° 145° a6o°.o 232°.2 , ao4°.4 176°. 7 • '48°.9 . 100° .0 ■ 98° 9 . 96"^ 1 93°-3 • 90° 5 . 87°. 8 . 85°.o . 82°.2 • 79°-4 • 76°. 7 • 73°-9 . 7i°.i . 68°. 3 • 65°.S . 62°.8 Fahr. Cent. 140" .35° 130° 125° 120° 115° 110° 95°. 90° . 85°. 80° . 75°. 70° , 65°, 60°. 55° ^o 45° 6o°.o 57°.2 S4°-4 5i°.7 48°.9 , 46°. 1 . 43°- 3 . 40°. 5 •37°.8 ■ 35°-o . 32°.2 . 29°.4 . 26°. 7 • 23°-9 . 2I°.l . 18° 3 . iS°-5 . I2°.8 . iey°.o . 7°.2 Fahr. 40° 35° 32° 30° 25° —25" -30° —45" -50°, Cent. 4°.4 i°.7 o°.o - 1^.1 - 3°.9 - 6°.7 - 9°.4 , —12°. 2 . — 15°.0 —17° 8 , —20° 5 • -23°. 3 ,—26°. I . — 28°.9 -3i°-7 . -34°-4 • -37°-2 . — 40°.o . —42°. 8 . -45°.6 Cent. Fahr, 100° ... 212°.0 2o8°.4 204°.8 , 201°.2 197° 6 i94°.o 190°. 4 , i86°.8 . 183°. 2 , i79°.6 1760.0 , I72°.4 , i68°.8 . i65°.2 i6i°.6 i58°.o 1 54°- 4 . i5o°.8 147°.2 143°.6 96° . 88° 86° 84° 82° 80° 76° 74° K 70° 68°- 66° 64° 6.!° Cent. 60°... 58° ... 56° ... 54° ... I 52q ... 48° ... 46° ... 4°"' 38°. 36°, M°. 32° . 30°. 28° , 26° . 24°, Fahr. i40°.o 136°.4 132°.8 129°. 2 125°6 ia2°.o ii8°.4 ii4°.8 11I°.2 io7°.6 lo4°.o 100°. 4 96°.8 93°-2 89°. 6 86°.o 82°. 4 78°. 8 75O2 7i°.6 Cent. Fahr. 20° ... 68°.o - 64°.4 6o°.8 57°. 2 53°.6 50°.o 46°.4 42°.8 39O.2 35°-6 32°.o 28°.4 24°. 8 21°.2 17°.6 i4°.o 10°. 4 6°.8 3°-2 -o°.4 -4°.o 16° .., 8°... 6°.., 4°.., — 6° .., — 8° ... — 10° .. To turn C° into F°, multiply by 9, divide by 5, and add 32°. To turn F° into C°, deduct 32, multiply by 5, and divide by 9. INDEX. Abdominal muscles in respira- tion, 217 Abdominal reflex, 692 Abducens, 649 Aberration, chromatic, 807 spherical, 807 Abiogenesis, 893 Absolute blindness, 752 Absorption by fluids, 80 by solids, 80 forces of, 342 influence of nerves on, 347 organs of, 336 Absorption of- — ■ Carbohydrates, 344 Coloring matter, 346 Digested food, 342 Effusions, 359 Fat soaps, 345 Grape sugar, 344 Inorganic substances, 344 Nutrient enemata, 347 Oxygen, 232, 236 Peptones, 345 Small particles, 346 Solutions, 344 Sugars, 344 Unchanged proteids, 345 Absorption spectra, 62 Accelerans nerve, 720 in frog, 722 Accommodation of eye, 799 defective, 805 force of, 805 line of, 803 nerves of, 803 phosphene, 813 range of, 806 spot, 813 time for, 803 Accord, 861 Acetic acid, 429 Aceton, 454, 464 Acetylene, 66 Achromatin, 893 Achromatopsy, 828 Achroodextrin, 262 Acid albumin, 425 Acid haematin, 66 Acids, free, 422 Acoustic nerve, 653 tetanus, 600 Acquired movements, 758 Acrylic acid series, 429 Action currents, 605 Active insufficiency, 552 Addison's disease, 200, 498 Adelomorphous cells, 285 Adenin, 433 Adenoid tissue, 351 Adipocere, 412 Adventitia, 137 ^gophony, 225 Aerobes, 325 ^sthesiometer, 882 ^sthesodic substance, 695 Afferent nerves, 633 After-birth, 946 After-images, 829 After-sensation, 782 Ageusia, 877 Agoraphobia, 655 Agrammatism, 761 Agraphia, 761 Ague, 197 Air, changes in respiration, 231 collection of, 228 composition of, 230 diffusion of, 234 expired, 231 impurities in, 244 quantity exchanged, 232 Air cells, 205 Albumimeter, 459 Albuminoids, 426 Albumin of egg, 905 Albumins, 423 Albuminuria, 457 Albumoses, animal, 425 vegetable, 425 Alcohol, 400 Alcohols, 430 Alcoholic drinks, 400 Alcool au tiers, 50 Aleurone grains, 425 Alexia, 763 Alkali albiunin, 425 Alkali hsematin, 66 Alkaline fermentation, 457 Alkaloids, 400 Allantoin, 402, 452 Allantois, 924 Allochiria, 8S9 AUorhythmia, 150 Alloxan, 449 Almen's test, 461 Alternate hemiplegia, 705 955 Alternate paralysis, 705, 769 Alternation of generations, 895 Amaurosis, 637 Amblyopia, 637 American crow-bar case, 731 Amido acids, 432 Amidoacetic acid, 312, 432 Amido -caproic acid, 300 Amimia, 761 Amines, 432 Ammonisemia, 479 Amnesia, 761 Amnion, 923 Amniota, 924 Amniotic fluid, 924 Amoeboid movement, 55, 500 Ampere's rule, 593 Amphiarthroses, 549 Ampho peptone, 292 Amphoric breathing, 224 AmygdaUn, 359 Amyloid substance, 425 Amylopsin, 299 Amylum, 431 Anabiosis, 893 Anacrotism, 151 Anaemia, 58, 89 metabolism in, 89 pernicious, 58 Anserobes, 325 AnKsthesia dolorosa, 890 Ansesthetic leprosy, 632 Anjesthetics, 890 Anabolic nerves, 633 Anabolism, 388 Anakusis, 653 Analgesia, 698 Analgia, 891 Anamnia, 924 Anarthria, 760 Anasarca, 359 Anelectrotonus, 616 Aneurism, 157, 158 Angiograph, 143 Angiometer, 151 Angioneuroses, 728 AnidrosiS, 497 Animals, characters of, 39 Animal foods, 405 magnetism, 736 Anions, 594 Anisotropous substance, 504 Ankle clonus, 693 Anode, 584 •JoG INDEX. Anosmia, 634 Antagonistic muscles, 552 Anihrncometer, 22S Anthracosis, 207 Ami albumin, 293 Antiar, 358 Anti-emetics, 277 Amihydrotics, 496 Antipeptone, 292 Antiperistalsis, 278 Antipyretics, 384 Antisialics, 260 Aortic valves, 95 insufficiency of, 1 53 Aperistalsis, 281 Apex beat, 102, 110 Aphakia, 79 1 Aphasia, 760 Aphonia, 573 Apncea, 713 Appunn's apparatus, 866 Apselajihesia, SS9 Aqueous humor, 792 Arachnoid mater, 776 Archiblastic cells, 920 Area opaca, 916 pellucida, 916 vasculosa, 922 Argyll Robertson pupil, 810 Arhythmia cordis, 98 Aristotle's experiment, 8S4 Aromatic acids, 430 oxyacids, 433 Arrector pili muscle, 490 Arterial tension, I47 Arteries, 137 blood pressure in, 165 central, 740 develoi>mcnt of, 936 emptiness of, 723 rhythmical contraction of 725 sounds in, 184 structure of, 135 tension in, 165 termination in veins, iSl Arterioijram, 143 Arthroidal joints, 549 Articular cartilage, 548 Articu lation nerve corpuscles, 880 Artificial cold-blooded condi- tion, 386 Artificial eye, 798 digestion, 295 gastric juice, 291 pancreatic juice, 300 respiration, 243 ^Iarshall Hall's me- thod, 243 Sylvester's method, 243 selection, 948 Aspartic acid, 301, 433 Asphyxia, 241, 714 artificial respiration in, 243 Asphyxia, recovery from, 242 Aspirates, 572 Aspiration of heart, 172 thoracic, 172 ventricles, 99 Assimilation, 388 Associated movement, 810, S37 Astatic needles, 594 Asteatosis, 498 Asthma nenosum, 663 dyspepticum, 663 Astigmatism, 807 correction of, 808 test for, 808 Atavism, 948 Ataxaphasia, 761 Ataxia, 668, 750, 759 Ataxic tabes, 697 Atelectasis, 226, 243 Atmospheric pressure, 247 diminution of, 248 increase of, 248 Atresia ani, 923 Atrophy, 554 of the face, 648 A tropin, 524 in eye, 638, 810 Attention, time for, 735 Audible tone, lowest, 862 Auditory after-sensations, 870 area, 753 aurie, 754 centre, 753 delusions, 653 meatus, 849 nerve, 847 ossicles, 851 paths, 754 perceptions, 860 sac, 945 Auerbach's plexus, 281, 341 Augmentor nerves, 722 Auricles of heart, 91, 93 development of, 935 Auscultation of heart, 117 of lungs, 223 Automatic excitement, 675 Autonomy, 737 Auxocardia, 128 Avidity, 290 Axis of vision, 819 Bacillus, 324 acidi lactici, 325 anihracis, 90 butyricus, 325 I subtilis, 326 ! tubercle and others, 244 Bacterium, 90, 324, 330 aceti, 325 coh, 330 fceiidum, 498 I lactis, 330 synxanthum, 395 l?nll and socket joints, 549 Hantingism, 413 Hancsthesiometer, 885 Basal development, 943 ganglia, 701, 765 Basedow's disease, 199, 728 Bases, 422 Basilar membrane, 860 Bass-deafness, 863 Batteries, galvanic, 594 ]>unsen's, 595 Daniell's, 595 Grennet's, 595 j Grove's, 595 Leclanche's, 596 Smee's, 595 Beats, 868 isolated,' 868 successive, 868 Bed-sores, 632 Beef tea. 397 Beer, 401 Bell's law, 667 deductions from, 667 Bell's paralysis, 652 Benzoic acid, 451 Bert'f experiment, 624 Bidder's ganglion, 119 Bile, 312 acids, 312 composition of, 315 crystallized, 312 ducts, 306 ligature of, 307 j effects of drugs on, 318 I excretion of, 316 fate of, 320 functions of, 319 gases of, 314 passage of drugs into, 317 pigments, 313 pressure, 317 reabsorption of, 317 secretion of, 315 spectrum of, 314 test for, 313, 314 Biliary fistula, 316 Bilicyanin, 314 Bilifuscin, 314 Biliprasin, 314 Bilirubin, 313 Biliverdin, 313 Binocular vision, 837 Biological law, 948 Biology, 33 Biot's respiration, 216 Birth, 946 Biuret reaction, 424 Blastoderm, 903, 915 Blastomere, 914 Blastosphere, 914 Blepharospasm, 652 Blind spot, 818 Blood, 33 abnormal, 87 analysis, 69 INDEX. 957 Blood, arterial, 86 carbon dioxide in, 85 clot, 70 coagulation, 72 color, 33 coloring matter, 59 composition of, 61 defibrinated, 70 distribution of, 187 electrical condition of, 629 extractives, 80 fats in, 79 fibrin in, 58, 71 gases in, 80 granules of, 58 islands, 51, 922 lake- colored, 49 loss of, 89 microscopic examination of, 44 _ nitrogen in, 86 odor, 43 organisms in, 90 oxygen in, 83 ozone in, 84 plasma, 70 plates, 57 portal vein, 86 proteids of, 78 quantity, 86 reaction, 33 salts in, 80 serum, 70 specific gravity of, 43 taste, 43 temperature, 44 transfusion of, 87 variations in, 87 venous, 86 water in, 80 Blood channels, intercellular, 137 Blood corpuscles — stroma, 49 abnormal changes, 58 action of reagents on, 47, 49,56 amoeboid movements, 55 change of form, 47 chemical composition, 59 circulation, 180 color, 47 colorless, 53 conservation of, 49 crenation, 47 decay, 53 diapedesis, 56, 182 effect of drugs, 56 effect of reagents, 47 form, 44, 50 Gower's method, 46 histology of, 46 human, red, 44 white, 53, 69 intracellular origin, 52 Malassez's method, 45 Blood corpuscles, nucleated, 58 number, 44, 58 of newt, 54 origin, 5 1 parasites of, 59 pathological changes, 58 proteids of, 69 rouleaux of, 47 size, 44,50, 58 staining of, 48 stroma, 46 transfusion of, 87 weight, 44 white, 53 Blood current, 180 in capillaries, 181 velocity of, 177 Blood gases, 80 estimation of, O, COj, and N, 83 extraction, 81 gas-pumps for, 81 quantity, 82 Blood glands, 192 Blood islands, 51, 922 Blood plasma, 70 Blood pressure, 161 arterial, 165 capillary, 1 71 estimation of, 161 in pulmonary artery, 173 in veins, 171 relation to pulse, 170 variations of, 165, 170 Blood vessels, 134 action of drugs on, 138 cohesion of, 139 elasticity of, 138 lymphatics, 137 pathology of, 139 properties of, 137, 138 structure of, 134 Blue pus, 498 sweat, 498 Body, vibrations of, 158 Body-wall, formation of, 922 Bone, chemical composition of, 934 callus of, 418 development of, 933 effect of madder on, 418 fracture of, 418 growth of, 934 histogenesis of, 933 red marrow, 53 Bones, mechanism of, 547 Bottger's test, 264 Boutons terminals, 88 1 Bowman's tubes, 785 glands, 871 Box pulse-measurer, 140 Bradyphasia, 761 Brain, 700 arteries of, 777, 77^ blood vessels of, 777 general scheme of, 700 Brain impulses, course of, 683 in invertebrata, 780 membranes of, 776 motor centres of, 742 movements of, 777 of dog, 744 pressure on, 779 protective apparatus of, 776 psychical functions of, 731. pulse in, 158 pyramidal tracts of, 703, 7S8 topography of, 756, 764 we ght of, 700 Branchial arches, 923 clefts, 923, 932 Brandy, 401 Bread, 398 Brenner's formula, 653 Broca's convolution, 760 Bromidrosis, 498 Bronchial breathing, 223, 224 fremitus, 224 Bronchiole, 205 Bronchophony, 225 Bronchus, extra-pulmonary, 204 intra-pulmonary, 204, 205 small, 205 Bronzed skin, 200 Brownian movement, 261 Bruit, 184 de diable, 185 Brunner's glands, 321, 339 Buchanan's experiments, 74 Bulbar paralysis, 712 Bulbus arteriosus, 934 Butter, 393 Butyric acid, 325, 429 Cachexia, 198 Caffein, 400 Calabar bean on eye, 638 Calcic phosphate, 421 CalcuU, bihary, 314, 332 salivary, 260, 331 urinary, 468 Callus, 418 Calorimeter, 362 Canal of cochlea, 857 hyaloid, 791 Nuck, 941 of spinal cord, 676 of Stilling, 791 Petit, 790 Schlemm, 785 semicircular, 859 CanaHs cochlearis, 857 reuniens, 858 Capillaries, 136 action of silver nitrate on, 136 blood current in, 181 958 INDEX. Capillaries, circulation, l8l contractility of, 139 development of, 53 form and arrange- ment of, I So pressure in, 171 slijjmata of, 136 velocity of blood in, 178 Capillary electrometer, 603 Capsule, external, 767 Cilisson's, 304 internal, 766 of Tenon, 791 Carbohydrates, 436 fermentation of, 325 Carbolic acid urine, 453 Carbon dioxide, conditions af- fecting, 232 estimation of, 229 excretion of, 232, 236 in air, 230 in blood, 85 in expired air, 231 where formed, 238 Carbonic oxide haemoglobin, 65 oxide, 65 poisoning by, 65 Cardiac cycle, 98 dullness, 117 ganglia, 1 18 hypertrophy, IIO impulse, 102, no movements, 107 murmurs, 1 14 nerves, 1 18 nutritive fluids, 120 plexus, 118 poisons, 127 revolution, 98 sounds, 1 12 Cardinal points, 796 Cardiogram, 102 Cardiograph, 102 Cardio-inhibitory centre, 1 68, 7 1 8 nerves, 718 Cardio - pneumatic movement, 12S Caricin, 301 Carnin, 396 Carotid gland, n8, 137, 200, 201 Cartilage. 548, 923 Casein, 393, 425 Catacrotic pulse, 145 Cataphoric action, 598 Cataract, 790 Cathartics, 284 Cathelectrotonus, 615 Cathode, 594 Caudate nucleus, 765, 766 Cavernous formations, 137 Cells, division of, S93 Cellulose, 262 Cement, 268 Cement, action of silver nitrate on, 136 substance, 136 Centre, accelerans, 720 ano-spinal, 694 auditory, 763 cardio-inhibitory, 718 cilio-spinal, 693 closure of eyelids, 710 coughing, 711 dilator of pupil, 693, 7 1 1 ejaculation, 694 erection, 694, 910 for coughing, 71 1 for defalcation, 694 for mastication and suck- ing, 7H for saliva, 711 gustatory, 763 heat regulating, 730 micturition, 694 olfactory, 763 parturition, 694 pupil, 711 respiratory, 712 sensory, 751 sneezing, 710 spasm, 730 speech, 760 swallowing, 71 1 sweat, 694, 730 vaso-dilator, 694, 729 vasomotor, 694, 722 vesico spinal, 694 visual, 763 vomiting, 711 Centre of gravity, 554 Centrifugal nerves, 63 1 Centripetal nerves, 633 Centro-acinar cells, 297 Cereals, 398 Cerebellum, 772 Action of electricity on, 775 Connections of, 702 Function of, 774 Pathology of, 776 Removal of, 774 Structure of, 772 Cerebral arteries, 740, 777, 778 epilepsy, 745, 759 fissures, dog, 744 inspiratory centre, 713 motor centres, 756 sensory centres, 763 vesicles, 918 Cerebrin, 428,581 Cerebro-spinal Huid, 354 Cerebrum, 700 blood vessels of, 739, 740, 777 convolutions of, 740 epilepsy of, 745 excision of centres, 750 Flourens' doctrine, 732 Cerebrum, functions of, 731 (Joltz's theory of 755 imperfect develop ment of, 732 lobes of, 740 motor regions of, 744 movements of, 777 removal of, 732 sensory centres, 751 structure of, 737 sulci and gyri of, 740, 741 thermal centres of, 755 weight of, 700 Cerumen, 494 Cervical sympathetic, section of, 673 Chalazre, 904 Charcot's crystals, 247 disease, 632 Cheese, 395 Chemical affinity, 37. Chess-board phenomenon, 842 Chest, dimensions of, 220 Cheyne - Stokes' phenomenon, 216 Chiasma, 635 Chitin, 428 Chloasma, 495 Chloral, 724 Chlorophane, 790 Chlorosis, 58 Chocolate, 400 Chokiemia, 317 Cholalic acid, 312, 430 Cholesterrcmia, 319 Cholesterin, 69,314, 320, 582 Choletelin, 314 Cholin. 581 Choloidinic acid, 313 Choluria, 462 Chondrin, 427 Chondrogen, 427 Chorda dorsalis, 919 Chorda tympani, 650, 729 Chordie tenclineje, ico Chorion la;ve, 926 frondosum, 926 primitive, 925 Choroid, 785 Choroidal fissure, 944 Christison's formula, 440 Chromatic aberration, 807 Chromatin, 893 Chromalophores, 499 Chromatopsia, 637 Chroraidrosis, 498 Chromophanes, 790 Chronograph, 530 Chyle, 353 movement of, 356 vessels, 348 Chylous urine, 467 INDEX. 959 Chyme, 292 Cicatricula, 903 Cilia, 500 conditions for movement, 501 effect of reagents on, 501 functions of, 501 Ciliary ganglion, 641 motion, 500 force of, 501 muscle, 786, 801 nerves, 641 Ciliated epithelium, 500 Cilio-spinal region, 693 Circle of Willis, 778 (circulating albumin, 403 Circulation, capillary, 181 duration of, 179 firvt, 921 foetal, 927 portal, 91 pulmonary, 91 schemata of, 161 second, 922 systemic, 91 Circumpolaiization, 265 Circumvallate papillae, 874 Claustrum, 767 Cleft sternum, 109 palate, 931 Clerk - Maxwell's experiment, 814 Cleavage of yelk, 914 lines of, 915 partial, 917 Climacteric, 906 Clitoris, 942 Closing, continued contraction, 619 Closing shock, 599 Clothing, 379 Coagulable fluids, 78 Coagulated proteids, 425 Coagulation experiments, 76 Coagulation of blood, 71, 72, 74 theories of, 74, 77 Cocaine, 810 Coccygeal gland, 137, 200 Cochlea, 857 Cocoa, 400 Coecitas verbalis, 763 Coelom, 920 Coffee, 400 Cold-blooded_ animals, 365 Cold on the body, 385 uses of, 387 Cold spots, 887 Collagen, 426 Colloids, 343 Coloboma, 944 Colostrum, 394 Color associations, 870 Color blindness, 828 acquired, 828 testing, 829 Color sensation, 824 Color, Hering's theory, 827 Young- Helmholtz theory, 826 Colored shadovs's, S32 Colorless corpuscles, 53 Color top, 830 Colors, complementary, 824 contrast, 830 geometrical table, 825 methods of mixing, 824 mixed, 825 simple, 824. Columella, 870 Columns of the cord, 677 Coma, diabetic, 31 1 Comedo, 498 Common sensation, 889 Comparative — Circulation, 201 Digestion, 334 Hearing, 870 Heat, 387 Kidney and urine, 486 Metabolism. 433 Motor organs, 558 Nerve centres, 779, 780 Nerves and electro-physiology, 629 Peripheral nerves, 674 Reproduction and develop- ment, 947 Respiration, 249 Sight, 845 Skin, 499 Smell, 873 Taste, 877 Voice and Speech, 574 Compensation, 604 Complemenlal air, 210 Compleinenlary colors, 824 Compound eye, 845 Concretions, 330 Condensed milk, 395 Condiments, 400 Conduction in the cord, 683, 696 Conductivity, 623 Conglutin, 425 Congo red, 288 Conjugate deviation, 638, 758 Conjugation, 895 Connective-tissue spaces, 348 Consonance, 868 Consonants, 572 Constant current, action of, 532 Constant elements — Bunsen's, 595 Daniell's, 595 Grennet, 595 Grove's, 50,5 Leclanche's, 596 Smee's, 595 Constipation, 332 Contraction, cardiac, 127 fibrillar, 526 initial, 537 Contraction, muscular (see Myo- grani) of blood vessels, 137 remainder, 530 rhythmical, 523 secondary, 609 without metals, 606 Contracture, 529 Contrast, 830 colors, 824, 830 Convergent lens, action of, 793 Cornea, 783, 784 Coronary vessels, 97 effects of ligature of, 97 Corpora quadrigemina, 700, 702, 770 Corpulence, 413 Corpus callosum, 765 luteum, 909 spongiosum, 909 striatum, 700, 765 Corresponding points, 837 Cortical blindness, 752 Corti's organ, 857 Cotyledons, 928 Coughing, 226 centre for, 711 Cracked-pot sound, 223 Cramp, 892 Cranial flexures, 918 nerves, 634 Cranioscopy, 732 Creamometer, 394 Cremasteric reflex, 691 Crepitation, 224 Crescents of Gianuzzi, 253 Crista acustica, 859 Crossed reflexes, 688 Crura cerebri, 768 Crusta, 769 pelrosa, 268 phlogislica, 71 Crying, 227 Crystallin, 424, 790 Crystalline lens, 790 spheres, 845 Crystallized bile, 312 Ciystalloids, 343 Cubic space, 245 Curara, action of, 520, 523, 724 Cutaneous respiration, 238 trophic affections, 631 Cuticular membrane, 268 Cyanogen, 66 Cylindrical lenses, 807 Cynuric acid, 452 Cyrtometer, 220 Cysticercus, 895 Cystin, 464 Cytozoon, 48 Daltonism, 827 Damping apparatus, 851 Darby's fluid meat, 294 960 INDEX. Death of a nerve, 591 I )el>ove's niemhrane, 203 Decidua rellexa, 925 serotina, 925 vera, 925 Decubitus :iculus, 632, 772 I )ecussation of pyramids, 707 Def.ccaiion, 2S0 centre for, 694 Degeneration, fatty, 414, 5S9 traumatic, 589 Deglutition, 272 nerves of, 273 Deiter's cells, 859 Delomori)hous cells, 285 Demarcation current, 604 Demodex foUiculorum, 494 Denis's plasmine, 74 1 )intine, 268 1 )entilion, 270 Depressor fibres, 660, 662, 725 nerve, 167, 660 Deutero-albumose, 293 Development, chronology of, 929 Dextrin, 431 Dextrose, 431 Diabetes mellitus, 310 Diabetic coma, 31 1 1 )ialysis, 343 Diapedesis, 182 Di.iphanometer, 394 1 )iaphoretics, 496 Diaphragm, 217 1 )iarrhnea, ^^^ Diastatic action, 262, 299, 323, 428 Diastole, 98 Dichroism, 59 I )icrotic pulse, 148 wave, 145 Diet, ade(]uate, 406 effect of age on, 407 effect of work on, 407 flesh, 409 flesh and fat, 41 1 of carbohydrates, 410 quality of, 403 (luantity, 403 Difference theory, 613 Differential rheotom. 610 tones, 868 Diffusion, 342 circles, 799 of gases, 80 Digestion durmg fever, 332 in plants, 334 Digestion, 250 artificial, 295, 300 Digestive apparatus, 266 Dilatation of pupil, centre for, 693 Dilator pupiilx, 809 Dilemma, 735 Dioptric, S07 observations, 792 Diphthongia, 573 Diphthongs, 57 1 I )iplacusis, 863 Diplopia, 63S, S37 Direct vision, S19 Direction, 869 Discharging forces, 519 Discus proligerus, 902 Disdiaciasts, 51 1 Dissociation, 237 Dissonance, 868 Distance, esiimalion of, 843 false estimate ol, 843 smallest appreciable, 884 Diuretics, 471 I )ivision of cells, 893 1 )ouble conduction in nerve, 623 Double contact, feeling of, 882 Double images, neglect of, 839 Dreams, 736 Drcpanidium, 48 Dromograph, 177 Dropsy, 359 Duct of Cuvier, 936 Ciaertner, 941 Ductus arteriosus, 928 venosus, 928 Dura mater, 776 Dust particles, 244 Dvs albumose, 293 Dyschromatopsy, 828 Dyslysin, 313 Dysperistalsis, 281 Dyspnoea, 215, 241, 714 Ear, S47 conduction in, 887 development of, 945 external, 849 fatigue of, 869 fineness of, 862 labyrinth of, 946 meatus of, 849 ossicles of, 851 sj-)eculum, 849 tympanum of, 849 Earthy jjhosphates, 455 Eccentric hypertrophy, loi Echo speech, 737 Ectoderm, 915 Ectopia cordis, 109 Efferent nerves, 631 Effusions, 359 Egg albumm, 424, 459 Egk's, 395 Ejaculation, centre for, 694 Elastic after effect, 139, 541 elevations, 147 tension, 173 tubes, 134 Elasticity of blood vessel^, 138 lens, 801 lungs, 209 muscle, 541 Elastin, 426 Electrical charge of body, 629 lishes, 629 nerves, 623 organs, 529 Electrical currents of muscle, 603, 607 eye, 6n glands, 611 heart, 608 mucous membranes, 611 nerve, 603, 607 plants, 615 skin, 611 Electricity, therapeutical uses, 624 Electrodes, non-polarizable, 596 other forms, 625 Electrolysis, 594 Electrometer, 603 Eleclro-motive force, 591 Electro physiology, 591 Electro-therapeutics, 624 Electrotonus, 611, 612 currents in, 61 1 in conductors, 6l2 in inhibitory nerves, 617 in motor nerves, 611, 615 in muscle, 617 in sensory nerves, 617 Eleidin, 4S7 Elementary granules of blood, 58 Embryo, formation of, 921 Emetics, 276 Emmetropic eye, 800, 804 Emotions, expression of, 573 Emulsitication, 301 Emulsin, 359 Emulsion, 301 Emydin, 425 Enamel, 269 Enamel organ, 270 Enchylema, 894 End arteries, 192 bulbs, 880 organs, 63 1 plate, 507 Endocardial pressure, 109 Endocardium, 95 Endoderm, 915 Endolymph, 858 Endomysium, 502 ' Endoneurium, 580 Endc-mometer, 342 Endosmosis, 342 Endosmotic equivalent, 343 Enemata, 347 Energy, conservation of, 38 potential, 38 Eneuresis nocturna, 486 Entoptical phenomena, 8l2 pulse, 813 Entotical perceptions, 869 INDEX. 961 Enzym, 427 Epiblast, 915 Epicardium, 92 Epidermal appendages, 416 Epididymis, 897 Epidural space, 777 Epigenesis, 949 Epiglottis, 273 injury to, 273 Epilepsy, 731, 745 Epineurium, 579 Epiphysis cerebri, 772 Epithelium, ciliated, 203, 500 Eponychium, 490 Equator, 612 Equilibrium, 653, 697, 732 Erectile tissue, 909 Erection, centre for, 909 of penis, 909 Erect vision, 799 Errhines, 227 Erythrochlorophy, 828 Erythro-dextrin, 262 -granulosa, 431 Esbach's method, 459 Eserine, 810, Ether, 34 Eudiometer, 81 Eukalyn, 432 Euperistalsis, 281 Eupnoea, 714 Eustachian catheter, 856 tube, 855 Excitability, action of poisons on, 696 Excitable points of a nerve, 591 Excito-motor nerves, 633 Excretin, 328 Excretion of fsecal matter, 278 Exophthalmos, 833 Expectorants, 247 Experimentum mirabile, 737 Expiration, 213 Expiratory muscles, 217 Explosives, 572 Extensor tetanus, 687 External capsule, 767 genitals, 941, 942 Extra current, 599 Extrapolar region, 615 Extremities, development of, 923 . Exudation, 360 Eye, 783 accommodation of, 799 artificial, 778 astigmatism, 807 chromatic aberration of, 807 compound, 843 development of, 944 effect of electrical ciurents, 813 emmetropic, 800 entoptical phenomena, 812 epiphyseal, 846 excised, 81 1 61 Eye, fundus of, 816 hypenmetropic, 804 illumination of, 814 movements of, 833 muscles of, 833 myopic, 804 pineal, 846 presbyopic, 805 protective organs of, 843 refractive power of, 803 structure of, 783 Eyeballs, axis of, 833 movements of, 835 muscles of, 835 planes of, 833 positions of, 834 protrusion of, 833 retraction of, 833 simultaneous move- ments of, 830 Eye currents, 611 Eyehds, 843 Facial nerve, 649 Fsecal matter, 328 excretion of, 278 Fainting, 102 Fallopian tubes, 905 Fall-rhetom, 614 Falsetto voice, 568 Faradic current, 599 Faradization in paralysis, 627 Far point, 803 Fascia, lymphatics of, 357 Fatigue of muscle, 545 stuffs, 545 Fats, 429 decomposition of, 301 metabolism of, 410 origin of, 411 Fat-splitting ferment, 301 Fatty acids, 429 degeneration, 414 Febrifuges, 384 Fechner's lavv^, 782 Fehling's solution, 264, 463 Fermentation, 401 in intestine, 324 test, 265 Ferments, 428 fate of, 324 organized, 428 unorganized, 427 Fertilization of ovum, 912 Fever, 383 after transfusion, 189 Fibres of Tomes, 268 Fibrillar contraction, 525 Fibrin, 58, 71 Fibrin factors, 75 Fibrin-ferment, 76 Fibrinogen, 75, 424 Fibrinoplastin, 75 Fibroin, 426 Field, of vision, 799 Field of vision, contest of, 841 Filaria sanguinis, 467 ■ Filiform papillse, 874 Filtration, 344 First respiration, discharge of, 717 effects of, on thorax, 226 Fish extract, 397 Fission, 893 Fistula, biliary, 316 gastric, 291 intestinal, 322 pancreatic, 298 pyloric, 289 Thiry's, 322 Vella's, 322 Flame spectra, 62 Flavor, 873 Fleischl's law of contraction, 618 hsemometer, 61 Flesh, 396 Flight, 559 Floor space, 245 Flourens' doctrine, 732 Fluid vein, 184 Fluids, flow of, 132 introduction of, 267 Fluorescence, 824 of eye, 799 Fluorescin, 792 Focal distance, 793 line, 802 point, 794 Foetal circulation, 927 membranes, 925 Follicles, solitary, 339 Fontana's markings, 582 Fontanelle, pulse m, 158 Foods, isodynamic, 363 plastic, 403 quantity, 403, 406 respiratory, 403 utilization of, 399 vegetable, 397 Foramen ovale, 928 of Magendie, 776 Force of accommodation, 805 Forced movements, 770 Forces, 35 Fore-gut, 921 Formatio reticularis, 709 Formative cells, 918 Fovea cardica, 921 centralis, 789, 819 Fractional heat coagulation, 70 Free acid, formation of, 290 Fremitus, 224 Friction sounds, 224 Frog current, 607 Fromann's lines, 579 Fruits, 399 Fundamental note, 863 Fundus glands, 285 Fungi, 324 Fungiform papillae, 874 961^ INDEX. Gaertner, ducts of, 941 tialactorrha^a, 392 Galactose, 431 Gallop, 55S Gall stones, 332 Galton's whistle, 862 Galvanic battery, 594 excital)iliiy, 628 Galvano-cautery, 629 Galvanometer, 594 rellecting, 597 Galvano-puncture, 629 tonus, 5S6 Gamgee's method, 76 Ganglionic arteries, 740 Gangrene, 632 Gargling, 227 Gaseous exchanges, 232 Gases, al)Sorpti()n of. So diffusion of, 80 extraction of, 81 in blood. So indifferent, 244 in lymph, 239 in stomach, 297 irrespirable, 244 poisonous, 244 respired, 232 Gaskell's clamp, 122 Gas-pump, 81 Gasserian ganglion, 641, 642 Gas sphygmoscope, 144 Gastric digestion, 292 conditions affecting, 294 fistula, 291 pathological variations, 331 Gastric giddiness, 655 Gastric juice, 287 action of drugs on, 291 action on tissues, 296 actions of, 292 artificial, 291 Gaule's experiment, 48 Gelatin, 296, 410, 426 Gelatin v. albumin, 410 Gemmation, 894 Genital cord, 941 corpuscles, 880 eminence, 941 Genu valgum, 553 varum, 553 Geometrical color table, 825 Gerlach's theory, 6S0 Germ epithelium, 901, 920 Germinal area, 915 membrane, 915 Germinating cells, 350 Germs, 244 Gestation, period of, 930 Giddiness, 654, 655 Ginglymus, 548 Girald^s, organ of, 941 Girdle sensation, 699 Gizzard, 275 Glance, 841 Glands, album nous, 250 15o\vman's, 871 Brunner's, 321, 339 buccal, 250 carotid, 118, 137, 200, 201 ceruminous, 494 changes in, 253 coccygeal, 137, 200 Ebner's, 251 fundus, 2S5 llarderian, 846 lachrymal, 844 Licberkiihn's, 322, 339 lingual, 250 lymph, 351 mammary, 390 Meibomian, 843 mixed, 253 Moll's, 492 mucous, 250 Nuhn's, 251 parotid, 258 peptic, 285 I'eyer's, 339 pyloric, 2S6 salivary, 250 sebaceous, 492 serous, 250 solitary, 339 sublingual, 258 submaxillary, 253 sweat, 492 uterine, 906 \Vel)cr's, 250 Glaucoma, 644 Gliadin, 426 Glisson's capsule, 304 Globin, 425 Globulins, 424 (Jlobuloses, 293 (domerulus, 435 Glosso-pharyngeal nerve, 655 Glossoplegia, 665 Glossy skin, 632 Glottis, 561, 562 Glucose, 310, 431, 462 tests for, 264, 265, 462 Glucosides, 428 Glutamic acid, 433 Gluteal reflex, 691 Gluten. 426 Glycerin, 429, 430 method, 263 Glycerin-phosphoric acid, 430 Glycin, 432 Glycocholic acid, 312 Glycogen, 308, 431 Glycoiic acid, 430 Glycosuria, 310, 462 Gmelin-IIeintz' reaction, 314 Goblet cells, 337 Goitre, 198 Goll's column, 683 Goltz's balancing experiments, 733 Goltz's croaking experiment, 68S embrace experiment,688 oesophagus experiments, 274 Gorham's pupil photometer, 8n Gout, 89 Graafian follicle, 901 Gracilis experiment, 624 Grandry's corpuscles, 880 Granules, elementary, 58 Granulose, 262 Grape-sugar, 431, 462 absorption of, 344 estimation of, 265 injection of, 309 fn urine, 462 tests for, 264 volumetric analy- sis, 463 Gravitation, 35 Great auricular nerve, 725 Green blindness, 828 Green vegetables, 399 Growth, 420 Guanidin, 532 Guanin, 489, 502 Guarana, 400 Gubernaculum testis, 941 Gum, 431 Gustatory centre, 754, 763 fibres, 650 region, 874 sensations, 876 Gymnastics, 553 Gymnotus, 629 Gyri, 700 Hay's reaction, 313,462 ILtmacylometer, 46 IIa:madroniometer, 1 75 Ha^madyiiamometer, 161 Ha?matin, 66, 67 Hcematoblasts, 57 Hsematohidrosis, 498 Hasmatoidin, 68 Haematoma aurium, 632 Hrematoporphyrin, 67 Hremaluria, 460 Hremautography, 144 Htcmin and its tests, 67, 461 Hsemochromogen, 66 Ha?mocyanin, 79 Ilivmocytolysis, 48 IIa?mocytometer, 46 Haemocytotrypsis, 48 Hremodynamometer, 161 Haemoglobin, 59 amount of, 6 1 analysis, 59 carbonic oxide, 65 compounds of, 62 crystals, 59 decomposition of, 66 INDEX. 963 Haemoglobin, estimation of, 60 nitric oxide, 66 pathological, 61 preparation, 59 proteids of, 68 reduced, 63 spectrum, 62 Hsemoglobinometer, 60 Hsemoglobinuria, 460 Hsemometer, 61 Haemophilia, 72 Hemorrhage, death by, 89 effect on, 723 Hemorrhagic diathesis, 72 Hasmotachometer, 176 Haidinger's brushes, 814 Hair, 490 cells, 859 follicle, 490 Halisterisis, 553 Hallucinations, 782 Hammarsten, 75 on blood, 75 Harderian gland, 846 Hare-lip, 931 Harmony, 868 Harrison's groove, 215 Hassall's corpuscles, 198 Hawking, 227 Hay's test, 313 Head- fold, 921 Head-gut, 921 Hearing, 847 Heart, 92 accelerated action, 108 ■ action of fluids on, 123 action of gases, 127 action of poisons on, 124, 127 apex, 124 apex beat, 102 arrangement of fibres, 92 aspiration of, 172 auricular systole, 98 automatic centres, 121 automatic regulation, 96 97 blood vessels of, 97 changes in shape, 106 chordae tendineae, lOO cutting experiments, 109 development of, 921, 934 diastole, 98 duration of movements, 116 endocardium, 95 examination of, 117 frog's, 118 ganglia of, 1 18 hypertrophy of, loi impulse of, 102 innervation of, 117 movements of, 98 muscular fibres, 94 myocardium, 92 nerves, 118 Heart nutritive fluids, 120 palpitation of, loi pause of, 100, 107 pericardium, 95 Purkinje's fibres, 96 regulation of, 96, 97 section of, 122 sounds of, 112 staircase beats of, 122, 126 systole, 98 valves of, 95 weight, 96 work of, 180 Heat-, 37 balance of, 379 calorimeter, 371 centres, 377, 755 conductivity, 373 dyspnoea, 215, 715 employment of, 384 estimation of, 371 excretion of, 377 income and expenditure, 380 in inflamed parts, 387 in muscle, 543 latent, 362 production, 364 regulating centre, 376 relation to work, 381 sources of, 362 specific, 371 stiffening, 517 storage of, 382 units, 37, 363 variations in production, 380 Helicotrema, 857 Heller's test, 265, 458 blood test, 461 Helmholtz's modification, 599 Hemeralopia, 637 Hemialbumin, 293 Hemialbumose, 292, 293 Hemianaesthesia, 744 Hemianopsia, 636 Hemicrania, 728 Hemiopia, 636 Hemipeptone, 292 Hemiplegia, 757 Hemisystole, 112 Henle's loop, 435 sheath, 580 Hen's egg, 903 _ Hensen's experiments, 867 Hepatic cells, 305 chemical composition of, 307 zones, 305 Hepatogenic icterus, 317 Herbst's corpuscles, 881 Hermann's theory of tissue cm-- rents, 613 Herpes, 632 Hetero-albumose, 293 Hetero-xanthin, 450 Heterologous stimuli, 781 Hewson's experiments, 74 Hibernation, 386 Hiccough, 227 Hippocampus, 738 Hippuric acid, 451 Hippus, 638 Histo-hsematin, 200 Historical — Absorption, 361 Circulation, 202 Digestion, 334 Hearing, 870 Heat, 387 Kidney and urine, 486 Metabolism, 433 Nerves and electro-physiology, 629 Nerve centres, 780 Peripheral nerves, 674 Reproduction and develop- ment, 948 Respiration, 249 Sight, 845 Skin, 499 Smell, 873 Taste, 877 Voice and speech, 573 Hoarseness, 573 Holoblastic ova, 903 Homoiothermal animals, 365 Homologous stimuli, 781 Horopter, 838 Hot spots, 887 Howship's lacunae, 934 Humor, aqueous, 792 Hunger and starvation, 408 Hyaloid canal, 791 Hybrids, 912 Hydatids, 896 Hydrsemia, 89 Hydramnion, 924 Hydrobilirubin, 314 Hydrocele, 75 Hydrocephalus, 778 Hydrochinon, 453 Hydrochloric acid, 288 Hydrocyanic acid, 66 Hydrogen in body, 421 Hydrolytic ferments, 427 Hydronephrosis, 485 Hydrostatic test, 209 Hydroxylbenzol, 453 Hyo-cholalic acid, 313 Hypakusis, 653 Hypalgia, 891 Hyperaesthesia, 696 Hyperakusis, 653 Hyperalgia, 653 Hyperdicrotism, 149 Hypergeusia, 877 Hyperglobulie, 88 Hyperidrosis, 498 Hyperkinesia, 696 Hypermetropia, 804 964 INDEX. Hyperoptic, S04 Hyperosniia, 634 Hy|)eri>selaphe.sia, 8S9 Hypertrophy of heart, loi, in of muscle, 554 Hypnotism, 736 Hypoblast, 915 Hypogeusia, S77 Hypoglossal nerve, 664 Hypophysis cerebri. 200, 772 I lypopselaphesia, 8S9 Hyposmii, 634 Hypospadias, 941 Hypoxanthin, 433 ichthidin, 425 Icterus, 318 Identical points, 837 Ileo colic valve, 277 Ileus, 278 Illumination of eye, 814 Illusion, 782 Images, formation of, 79S Imbibition currents, 615 Impregnation, 913 Impulse, cardiac, I02 Impulses in brain, course of, 704 Inanition, 233 Incisures, 578 Income, 406 Indican, 452 Indifferent point, 615 Indigo blue, 453 Indigo carmine test, 463 Indigogen, 453 Indirect vision, 819 Indol, 300, 327 Induction, 599 Inductorium, 601 Inferior maxillary nerve, 645 Inhibition, nature of, 690 Inhibition of reflexes, 689 Inhibitory action of brain, 756 nerves, 633 for heart, 718 for intestine, 282 for respiration, 716 Inion, 764 Initial contiaction, 537 Inosinic acid, 433 Inosit, 432 Insectivorous plants, 334 Inspiration, 213 centre for, 713 muscles of, 216 ordinary, 216 Intelligence, degree of, 734 Intercellular blojd channels, Intercentral nerves, 633 Intercostal muscles, 218 Interference, 868 Interglobular spaces, 268 Interlobular vein, 304 Internal capsule, 766 Internal reproductive organs, 940 respiration, 203, 23S Intestinal fistula, 322 gases, 324 juice, 323 actions of, 323 paresis, 282 Intestine, 278 artificial circulation, 283 development of, 938 effect of drugs on, 283 fermentation processes in. 324 large, 328, 342 movements of, 278 small, 336 Intra-labyrinthine pressure, 860 Intralobular vein, 304 Intraocular pressure, 644, 792, 811 Intrathoracic pressure, 225 Intra-vascular hemorrhage, 727 Inulin, 432 Inunction, 498 Invertin, 326 Invert sugar, 326 Inverted miage, 798 .Ions, 594 Iris, 786 action of poisons on, 810 blood vessels of, 787 functions of, 808 movements of, 809 muscles of, S09 nerves of, 809 Irradiation, 830 of pain, 698, 890 Ischuria, 486 Island of Reil, 741 Isodynamic foods, 363 Isolated beats, 868 Isometrical act, 537 Isotropous, 511 I Jacksonian epilepsy, 746, 759 Jacobson's organ, 872 Jaeger's types, 805 Jaundice, 317 Jaw jerk, 693 j Joints, 54S I arthrodial, 549 ball and socket, 549 ginglymus, 548 ' mechanism of, 547 I rigid, 549 , screw hinge, 548 ] Juice canals, 348 Karyokinesis, 894 Karyomiton, 893 Karyopla>ma, 893 Katabolic metabolism, 388 nerves, 633 Katalepsy, 737 Kations, 594 Keratin, 426 Keratitis, 652 Keys — Capillary contact, 603 Friction, 602 Plug, 602 Kidney, 434 blood of, 475 chemistry of, 475 condit ions affecting, 476 reabsorption in, 473 structure of, 434 volume of, 477 Kinxsodic substance, 695 Kinetic energy, 362 theory, 654 Klang, 864 Knee phenomenon, 693 jerk, 693 reflex, 693 Koenig's monometric flames, 866 Koumiss, 395 Krause's end bulbs, 880 Kreatin, 433 Kreatinin, 433, 449 properties, 449 quantity, 449 test, 449 Kresol,433 Kryptophanic acid, 454 Kiihne's ariiticia! eye, 798 experiments, 606, 625 pancreas powder, 301 Kymograph, 162 Kick's, 165 Hcring's, 164 Ludwig's, l6z Kyphosis, 553 Labials, 572 Labor, power of, 946 Labyrinth, 856 Lachrymal apparatus, 844 Lacteals, 336, 348 Lactic acid, 288, 393, 430 ferment, 296 Lactometer, 394 Lactoprotein, 393 Lactoscope, 394 Lactose, 431 Lcevulose, 326, 431 Lagophthalmus, 638 Lambert's meihod, 824 Lamince dorsalcs, 918 Lamina spiralis, 857 Language, 761 Lanoline, 494 Lanutjo, 491 i Lapping, 267 ! Lardacein, 425 ; Large intestine, 328, 342 ' absorption I -,28 INDEX. 965 Laryngoscope, 566 Larynx, cartilages of, 560 during respiration, 567 experiments on, 568 illumination of, 565 mucous membrane of, 564 muscles of, 561 view of, 566 vocal cords, 560 Latent heat, 362 period, 528 Lateral plates, 920 Laughing, 227 Law of conservation of energy, contraction, 618 isolated conduction, 623 peripheral perception, 881 specific energy, 781 Leaping, 557 Lecithin, 69, 429, 518 Legumin, 398 Lens, chemistry of, 790 crystalline, 790 development of, 945 Lenticular nucleus, 766 Leptothrix epidermalis, 498 buccalis, 261 Leucic acid, 430 Leucin, 300 Leucocytes, 54 LeuCQderma, 632 Leucomaines, 294 Leuksemia, 59 Levers, 551 Lichenin, 432 Lichen's test, 454 Lieberkiihn's glands, 321 jelly ,425 Liebermann's reaction, 424 Liebig's extract, 397 Life, 38 Limbic lobe, 754 Limb plexus, 669 Liminal intensity, 781 Line of accommodation, 803 Ling's system, 553 Lingual nerve, 646 Lipsemia, 88 Liquor sanguinis, 70 Listing's reduced eye, 797 law, 834 Liver, 303 action of drugs on cells, 306 chemical composition, 307 _ cirrhosis of, 307 development of, 939 fat in, 309 functions of, 311 glycogen in, 308 influence on metabolism, 316 Liver, pathology of, 307 pulse in, 186 regeneration of, 307 structure of, 303 Lobes of brain, 740 Locality, sense of, 882 illusions of, 884 Lochia, 947 Locomotor ataxia, 697 Lordosis, 553 Loss by skin, 238 Loss of weight, 409 Lowe's ring, 814 Lungs, 203 chemical composition of, 209 development of, 939 elastic tension of, 129, 173, 210 examination of, 220 excision of, 209 limits of, 221 physical properties, 209 structure of, 205 tonvis, 208 Lunule, 489 Lutein, 909 Luxus consumption, 403 Lymph, 353 movement of, 356 gases of, 239, 354 Lymphatics, 348 of eye, 791 origin of, 348 Lymph corpuscles, 352 origin and decay of, 355) 356 follicles, 351 glands, 351 hearts, 358 Macropia, 638 Macula lutea, 789 Maculae acusticse, 859 Madder, feeding with, 418 Magnetization, 599 Magneto-induction, 600 Major chord, 861 Malapterurus, 629 Malt, 401 Maltose, 262, 431 Mammary glands, 390 changes in, 390 development of, 391 structure of, 390 Manometer, 161 frog, 123 maximum, lOO minimum, lOO Manometric flames, 866 Marey's tambour, 109 Margarin, 489 Marginal convolutions, 74I Mariotte's experiment, 818 Massage, 553 Mastication, 267 Mastication, muscles of, 267 nerves of, 267 Mat6, 400 Matter, 34 Maturation of ovum, 913 Meat soup, 397 Meckel's caitilage, 931 ganglion, 645 Meconium, 320 Medulla oblongata, 705 Functions of, 710 Gray matter of, 708 Reflex centres in, 710 Structure of, 705 Medullary groove, 916 tube, 918 Meibomian glands, 843 Meiocardia, 128 Meissner's plexus, 275, 281, 342 Melansemia, 59 Melanin, 429 Melitose, 431 Mellitsemia, 88 Mellituria, 88 Membrana decidua menstrualis, 925 flaccida, 849 reticularis, 860 reuniens, 922 secundaria, 856 tectoria, 859 tympani, 849 Membranes of brain, 776 Meniere's disease, 655 Menopause, 906 Menstruation, 907 Mercurial balance, 885 Merkel's cells, 880 Meroblastic ova, 903 Mesentery, development of, 939 Mesoblast, 916 Mesonephros, 941 Metabolic equilibrium, 402 phenomena, 388 Metabolism, 388 in anaemia, 89 on flesh and other diets, 409 Metakresol, 453 Metalbumin, 424 Metallic tinkhng, 224 Metalloscopy, 891 Metamorphosis, 895 Metanephros, 941 Meteorism, 282 Methsemoglobin, 64 Methylamine, 432 Meynert's projection systems, 700 theory, 734 Micrococci, 457 Micrococcus ure^e, 457 Microcytes, 58 Micropyle, 902 Microscope, iSo Microorganisms, 330 9G6 INDEX. Micro-spectroscope, 62 Micturition, 4S3 centre for, 694 Migration of ovum, 912 Milk, 392 action of drusiiion of, 39I curdling ferment, 288, 393 digestion of, 295 fever, 392. 947 globules of, 392 peptonized, 303 plasma, 392 preparations of, 395 substitutes for, 394 sugar, 393 tests for, 394 Millon's reagent, 423 Mimetic spasm, 652 Mimicry, 574 Minor chord, 861 Mitosis, S94 Mixed colors, S25 Modiolus, S57 Molecular basis of chyle, 353 Molecules, 34 Molisch's test, 265 Monoplegia, 759 Monospasm, 760 Moore's test, 265 Moreau's experiment, 323 Mormyrus, 629 Morphology, 33 Morula, 914 Motion, illusions of, S30 Motor areas, 756 Motor centres, dog, 742, 744 excision of, 749 in man, 749 in monkey, 746 nerves, 631 paths, 703 points on the surface, 624, 625 Mouth, 250 glands of, 250 Mouvements de manege, 771 Movements of the eye, 833 acquired, 750 forced, 770 incoordinated, 668 Mucedin, 426 Mucigen, 337 Mucin, 312, 426 Mucous membrane currents, 611 tissue, 791 Mucus, effect of dnigs on, 247 formation of, 245, 312 Mulberrj- mass, 914 Mulder's test, 265 Miiller's ducts, 940 experiment, 129, 154 fibres, 7S9 valve, 22S Multiplicator, 593 Murexide test, 449 Murmurs, cardiac, 115 venous, 185 Muscx volitantes, 812 Muscarin, 720 Muscle, 502 ' action of two stimuli on, 533 action of veratrin, 532 active changes in, 524 arrangement of, 549 atrophic proliferation of, 554 blood vessels of, 506 cardiac, 92, 509 changes during contrac- tion, 524 chemical composition, 5" current, 597 ciu-ve of, 528 degenerations of, 554 development of, 509 effect of acids on, 518 effect of cold on, 518 effect of distilled water on, 518 effect of exercise on, 553 effect of heat on, 5 1 7 elasticity of, 541 electric currents of, 604 excitability of, 519 extractives of, 514 fatigue of, 545 ferments, 512 fibrillar, 504 formation of heat in, 543 gases in, 513 glycogen in, 512, 514 hypertrophy, 554 involuntary, 502 lymphatics of, 507 metabolism of, 513 myosin of, 572 nerves of, 507 nutrition of, 553 of heart, 92, 509 perimysium of, 502 physical characters, 511 plasma of, 511 plate, 922 polarized light on, 5 1 1 reaction, 511 recovery of, 547 red and pale, 509 relation to tendons, 506 rhvthmical contraction, '523 rigor mortis of, 515 rods, 505 sensibility, 508, 543 serum of, 512 smooth, 502, 509 sound of, 545 Muscle, spectrum of, 509 staircase of, 535 stimuli of, 522 structure of striped, 502 tetanus, 534 tonus, 543, 694 uses of, 549 volume of, 524 voluntary, 502 work of, 538 Muscle current, 603 theories, 613 Muscular contraction (see Myo- S^ram), rate of, 537 Muscular energy, 515 exercise, 233 sense, 89 1 work, 514 laws of, 538 Mutes, 572 Mydriasis, 638 Mydriatics, 810 Myelin forms, 577 Myocardium, 92 Myogram, 528 effect of constant cur- rent on, 532 effect of fatigue on, 531 effect of poisons on, 532 effect of veratrin on, 532 effect of weights on, 53' method of studying, 526 stages of, 529 Myograph, Helmholtz's, 526 pendulum, 526 Pfliiger's, 528 simple, 528 spring, 528 Myohoematin, 429, 509 Myopia, 804 Myoryctes Weismanni, 5 1 1 Myosin, 424, 512 ferment, 512 Myosis, 639 Myotics, 811 Myxoedema, 199, 632 Nails, 4S9 Narcotics, 890 Nasal breathing, 226 timbre, 571 Nasm>1;h's membrane, 268 Native albumins, 424 Natural selection, 947 Near point, 803 Neefs hammer, 601 Negative accommodation, 800 after images, 83O pressure, 344 variation, 607, 609 INDEX. 967 Nephrozymose, 454 I Nerve cells, 575, 5S0 | bipolar, 580 j multipolar, 580, 679 of cerebrum, 737 Purkinje's, 773 with a spiral fibre, 581 Nerve centres, general functions, 675 Nerve current, 603 Nerve fibres, 575 action of nitrate of silver on, 579 . . chemical properties of, 581 classification of, 631 death of, 591 degeneration of, 587 development of, 580 division of, 579 effect of a constant cur- rent on, 585 electrical current of, 603 electrical stimuli, 585 excitability of, 583 fatigue of, 587 incisures of, 578 mechanical properties of. 582 meduUated, 575 metabolism of, 582 nutrition of, 588 Ranvier's nodes, 578 reaction of, 582 recovery of, 587 regeneration of, 587, 589 sheaths of, 579 stimuli of, 583 structure of, 575 suture of, 590 terminations of, 878 to glands, 256 traumatic degeneration of, 589 trophic centres of, 589 unequal excitability of, 586 union of, 590 unipolar stimulation of, 587 Nerve impulse, rate of, 620 method of measuring, 621 modifying conditions of, 620 Nerve motion, 623 Nerve-muscle preparation, 606 Nerves, 631 afferent, 633 anabolic, 633 centrifugal, 631 centripetal, 633 cranial, 634 electrical, 623 intercenlral, 633 katabolic, 633 Nerves, motor, 63 1 | secretory, 631 sensory, 633 | special sense, 633 spinal, 665 ■ j trophic, 631 ! union of, 590 vaso-dilator, 729 vasomotor, 722 I visceral, 633 Nerve stretching, 583 Nervi nervorum, 580 Nervous system, 575 development, 943 Nervus abducens, 649 accelerans, 720 accessorius, 664 acusticus, 653 depressor, 660 erigens, 693, 729, 910 facialis, 649 glossopharyngeus, 655 hypoglossus, 664 oculomotorius, 637 olfactorius, 634 opticus, 634 sympathicus, 670 trigeminus, 640 trochlearis, 639 vagus, 657 Neubauer s test, 265 Neuralgia, 648 Neurogha, 681, 682 Neural tube, 918 Neurasthenia gastrica, 331 Neurin, 581 Neuro-epithelium, ^88 Neuro-keratin, 578 Neuro-muscular cells, 522 New-born child, digestion of 291 pulse, 149 size, 419 temperature, 374 urine of, 440 weight, 419 Nictitating membrane, 846 Nitrites, 64 on pulse, 147 I Nitrogen in air, 230 i in blood, 85 in body, 421 given off, 402 Noeud vital, 712 Noises, 860 Nose, development of, 931 structure, 871 Notochord, 919 Nuclear spindle, 861 Nuclein, 426 Nucleus of Pander, 904 Number forms, 870 Nussbaum's experiments, 472 Nutrient enemata, 347 Nyctalopia, 6^7 Nystagmus., 654, 771 Oatmeal, 398 Octave, 861 Oculomotorius, 637 Odontoblasts, 268 CEdema, 359 cachectic, 360 pulmonary, 226 CT^sophagus, 274, 275 Ohm's law, 592 Oleic acid, 429 OligJemia, 89 Olivary body, 707 Olfactory centre, 754, 763 nerve. 634 sensations, 872 Omphalo-mesenteric duct, 921 vessels, 922 Onamatopoesy, 574 Oncograph, 195, 477 Oncometer, 477 Ontogeny, 948 Opening shock, 599 Ophthalmia neuro - paralytica, 644 intermittens, 644 sympathetic, 644 Ophthalmic nerve, 641 Ophthalmometer, 798 Ophthalmoscope, 814 Optic nerve, 634, 813 I radiation, 635 1 thalamus, 766 tract, 634 vesicle, 919 Optical cardinal points, 795 I Optogram, 823 1 Optometer, 805 ' Ordmates, 164 : Organic albumin, 403 I compounds, 423 : reflexes, 693 j Ortho-kresol, 453 I Orthopnoea, 215 Orthoscope, 817 Osmasome, 397 Ossein, 427 Osseous system, formation of, 930 Osteoblasts, 934 Osteoclasts. 934 Osteomalacia, 553 Otic ganglion, 646 Ovarian tubes, 902 Ovary, 901 Overcrowding, 245 Ovulation, 907 i theories of, 90S ] Ovum, 901 ; development of, 902 discharge of, 908 fertilization of, 912 impregnation of, 913 maturation of, 913 migration of, 912 structure of, 901 Oxalic acid, 430, 450 968 INDEX. Oxalic acid series, 430 I Oxaluria, 430 Oxaliiricacid, 429 Oxy-acids, 454 | Oxyakoia, 652 j Oxygen in blood, 83 j estimation of, S3, 228 forms of, 85 ill body, 421 Oxyhemoglobin, 62 Ozone in blood, 84 Pacchionian bodies, 777 Pacini's corpuscles, 879 Pain, 889 irradiation of, 890 points, 882 Painful impressions, conduction of, 697 Palmitic acid, 429 Palpitation, loi Pancreas, 297 changes in, 298 development of, 939 fistula of, 298 juice of, 299 paralytic secretion, 303 powder, 301 salt, 302 Pancreatic secretion, 298 actions of, 299 artificial juice, 300 action of nerves on, 302 action of poisons on, 303 com|)osition, 298, 299 extracts, 302 Panophtlialmia, 643 Pansphygmograph, 102 Papain, 301 Papilla foliata, 875 Papilla; of tongue, S74 Parablastic cells, 920 Paradoxical contraction, 612 Paraglobulin, 78 Parakresol, 433, 453 Paralbumin, 423 Paralgia, 890 Paralytic secretion of saliva, 258 pancreatic juice, 303 Paramylum, 432 Para pe[)tone, 292 Paraphasia, 761 Paraxanthin, 433, 450 Parelectronc.my, 613 Paridrosis, 498 Paroophoron, 941 Parotid gland 252, 258 Parovarium, 941 Parthenogenesis, 896 Partial pressure. Si reflexes, 686 Particles, 34 Parturition, centre for, 694 Passive insufficiency, 552 Patellar reflex, 692 Pavy's test, 264 Pecten, 846 Pectoral fremitus, 224 IV'dunculi cerebri, 768 Tenis, erection of, 909 Pepsin, 2S8 Pepsinogen, 289 Peptic glands, 285 changes in, 289 Peptogenic substances, 291 Peptone, 292, 294 absorption of, 345 forming ferment, 288 injection of, 73, 345 metabolism of, 410 tests for, 294 Peptonized foods, 303 Peptonuria, 459 Percussion of heart, 117 lungs, 222 sounds, 222 wave, 145 Perforating ulcer of the foot, 632 Pericardium, 95 fluid of, 354 Perilymph, 858 Perimeter, Aubert and Forster, S19 M' Hardy's, 820 Priestley Smith's, 822 Perimetric chart, 820 Perimetry, S19 Perimysium, 92, 502 Perineurium, 5S0 Periodontal membrane, 268 Peristaltic movement 277 action of blood on, 281 action of nerves on, 283 Peritoneum, development of, 939 Perivascular spaces, 738 Pernicious an;omia, 58 Pettenkofer's test, 313 apparatus, 229 Peyer's glands, 339 Pfliiger's law, 617 law of reflexes, 688 Phagocytes, 56 Phakoscope, S02 Phanakistoscope, 830 Phases, displacement of, 864 Phenol, 327, 453 Phenylsulphonic acid, 453 Phlebogram, 185 Phloro-glucin-vanilin, 288 Phonation, 564 Phonograph, 866 Phonometry, 223 Phosphenes, 813 Phosphoric acid, 455 Photohitmatachomeier, 1 77 Photophobia. 653 Photopsia, 637 Phrenograph, 212 Phrenology, 732 Phylogeny, 948 Physostigmin, 810 Phytalbumose, 425 Phytomycetes, 466 Pia mater, 676 Picric acid test, 459 Picro-saccharimeter, 463 Pigment cells, 501 Pineal eye, 772 gland, 772 Pitch, 861 Pituitary body, 772 Placenta, 926 Placental bruit, 184 Plantar reflex, 691 Plants, characters of, 39 digestion by, 334 electrical currents in, 615 Plasma cells, 776 of blood, 70, 78 of invertebrates, 79 of lymph, 353 of milk, 392 of muscle, 511 Plasmine, 74 Plethora, 88 Plethysmography, 187 Pleura, 206 Pleuro- peritoneal cavity, 920 Pleximeter, 221 Pneumatic cabinet, 155 Pneumatogram, 214 Pneumatometer, 226 Pneumograph, 128, 213 Pneumonia after section of vagi 661 Pneumothorax, 210 Poikilothermal animals, 365 Poiseuille's space, 181 Poisons, heart, 127 Polar globules, 913 Polarization, galvanic, 594 internal, 598 Polarizing after-currents, 612 Politzer's ear bag, 856 Polyxmia, 87 apocoptica, 87 aquosa, 87 hyperalbuminosa, 88 polycytha;mica, 88 serosa, 87 Polyopia monocularis, 808 Pons Varolii, 769 Porret's phenomenon, 598 Portal canals, 304 circulation, 91 system, development of, 937 vein in liver, 304 Positive accoinmodation, 800 after-images, 829 Potash salts, 421 Potassium sulphocyanide, 260, I 454 INDEX. 969 Potatoes, 398 Presbyopia, 805 Pressor fibres, 724 Pressure, arterial, 165 atmospheric, 247 intra-labyrinlhine, 860 of blood, 161 phosphenes, 813 points, 882, 885 respiratory, 225 sense of, 885 Presystolic sound, 115 Prickle cells, 487 Primitive anus, 923 aorta, 921 chorion, 915, 925 circulation, 921 groove, 915 kidneys, 940 mouth, 923 streak, 915 Primordial cranium, 930 ova, 902 Principal focus, 793 Proctodseum, 918 Proglottis, 895 Progressive muscular atrophy, 554 Pronephros, 941 Pronucleus, male, 913 female, 913 Propepsin, 289 Propeptone, 292 Protagon, 428 Proteids, 423 coagulated, 425 gastric digestion of, 292 fermentation of, 327 metabolism of, 409 pancreatic digestion of, 300 reactions of, 423 vegetable, 425 Proteolytic ferments, 427 Proteoses, 292 Protistse, 33, 41 Proto-albumose, 293 Protovertebr^^, 919 Pseudo-hypertropic paralysis, 554 Pseudo-motor action, 650, 653 Pseudoscope, 841 Pseudo-stomata, 206 Psychical activities, 731 blindness, 752 deafness, 753 processes, time of, 735 Psycho-physical law, 781 Ptomaines, 294 Ptosis, 638 Ptyalin, 263, 264 Ptyalism, 259 Puberty, 906 Pulmonary artery, pressure in, 173 vessels, 206 Pulmonary oedema, 226 Pulp of tooth, 269 of spleen, 192 Pulse, 139 anacrotic, 153 capillary, 161 catacrotic, 145 characters of, 144 conditions affecting, 149 curve, 144 dicrotic, 148 entoptical, 157 hyperdicrotic, 149 in animals, 150 in jugular vein, 186 in liver, 186 influence of pressure on, . ^55 influence of respiration on, 153 instruments for investiga- ting, 140 monocrotic, 148 of various arteries, 151 paradoxical, 155 pathological, 158 rate, 149, 170 recurrent, 152 tracing, 144 trigeminal, 150 variations in, 150 venous, 185 wave, 156 Pulses, 398 Pulsus alternans, 150 bigeminus, 150 caprizans, 149 dicrotus, 149 intercurrens, 150 myurus, 150 Pumping mefhanisms, 357 Pupil, 802 action of poisons on, 810 Argyll Robertson, 810 functions of, 808 movements of, 809 photometer, 8ll size of, 811 Pupilometer, 8n Purgatives, 283 Purkinje, cells of, 773 fibres of, 96, 509 figure, 812 Sanson's images, 801 Pus corpuscles, 182 Putrefaction, pancreatic, 300 Putrefactive processes, 328 Pyloric glands, 286 changes in, 289, 290 fistula, 289 Pyramidal cells, 739 tracts, 684 degeneration of, 758 Pyrokatechin, 430, 453 Pyuria, 465 Quality of a note, 861, 863 Quantity of blood, 86 of food, 405 of gases, 232 Rales, dry, 224 moist, 224 Rami communicantes, 670 Range of accommodation, 806 Ranvier's nodes, 578 Raynaud's disease, 632 Reaction impulse, 105 Reaction of degeneration, 627 Reaction time, 624, 735 Recoil wave, 145 Rectum, 283 Recurrent pulse, 152 sensibility, 667 Red blindness, 828 Reduced eye of Listing, 797 Reducing agents, 84 Reductions in intestine, 328 Reflex acts, examples of, 687 inhibition of, 689 law of, 688 movements, 686 Reflex movements, theory of, 691 nerves, 633 organic, 693 spasms, 686 tactile, 697 time, 689 tonus, 695 Reflexes, crossed, 688 deep, 692 spinal, 686 organic, 694 Refracted ray, 794 Refractive indices, 794 Regeneration of tissues, 416 of nerve, 589 Regio olfactoria, 871 respiratoria, 871 Regnault's apparatus, 228 Reissner's membrane, 857 Relative proportions of diet, 405 Remak's ganglion, 1 19 Renal plexus, 476 Rennet, 295, 393 Reproduction, forms of, 893 Requisites in a proper diet, 405 Reserve air, 210 Residual air, 210 Resistance, 132 Resonance organs, 560 Resonants, 572 Resonators, S67 Resorcin, 453 Respiration, 203 amphoric, 224 artificial, 243 Biot's, 216 bronchial, 224 centre for, 712 chemistry of, 227 970 INDEX. Respiration, cog-wheel, 224 cutaneous, 238 first, 717 forced, 216 foreign gases, 244 in a closed space, 240 in animals, 212 internal, 238 mechanism of, 209 muscles of, 216 nasal, 226 number of, 211 pathological, 215 periodic, 216 pressure during, 225 pressure on heart, 128 sounds of, 223 time of, 212 type, 214 variations of, 21 1 vesicular, 223 Respiratory apparatus, 203 Andral and Gavar- ret, 228 centre, 712 mechanism of, 209 v. Pettenkofer, 229 quotient, 231 Regnault and Rei- set, 229 Scharling, 229 undulations, 167 Restiform bodies, 705 Rete mirabile, 91 Retina, 787 activity in vision, 818 blood vessels of, 789 capillaries, movements in, 813 chemistry of, 790 epithelium of, 789 rods and cones of, 788, 819 stimulation of, 829 structure of, 787 visual purple of, 789 Retinal image, formation of, 798 size of, 798 Retinoscopy, 817 Reversion, 948 Rheocord, 592 Rheometer, 176 Rheophores, 625 Rheoscopic limb, 6g6 Rheostat, 593 Rheotom, 610 Rhinoscopy, 568 Rhodophane, 790 Rhodopsin, 789 Ribs, 218 Ricket's, 553 Rigor mortis, 515 Ritter's opening tetanus, 618 tetanus, 618 Ritter-Valli law, 591 Rods and cones, 7SS, S19 Rods of Corti, 859 Rosenthal's modification, 521 Rotatory disk for colors, 824 Rudimentary organs, 948 Rumination, ^33 Running, 555 Saccharomycetes, 401 Saccharose, 431 Saccule, 857 Saftcanalchen, 348 Saline cathartics, 284 Saliva, action of nerves on, 256 action of poisons on, 257 action on starch, 262 chorda, 256 composition of, 261 facial, 256 functions of, 263 mixed, 261 new-born child, 262 paralytic secretion, 258 parotid, 260 pathological, 331 ptyalin, 260, 263 reflex secretion of, 258 sublingual, 261 submaxillary, 260 sympathetic, 256 theory of secretion, 260 Salivary corpuscles, 261 Salivary glands, 252 changes in, 253 development of, 939 extirpation of, 258 nerves of, 255 Salts, 421 Sanson-Purkinje's images, 801 Saponification, 301 Sarcina ventriculi, 332 Sarcoglia, 508 Sarcolactic acid, 512 Sarcolemma, 503 Sarcolytes, 509 Sarcoplasts, 509 Sarcous elements, 504 Sarkin, 450 Sarkosin, 433 Saviotli's canals, 298 Scheiner's experiment, 803 Schiff 's test, 449 Schizomycetes, 90, 324 Schmidt's researches, 74 Schreger's lines, 268 Schwann's sheath, 578 Sclerotic, 785 Scoliosis, 553 Scotoma, 822 Screw-hinge joint, 548 Scrotum, formation of, 941 1 Scurvy, 58 Scyllit, 432 Sebaceous glands, 492 secretion, 493 Seborrhcea, 498 Secondary circulation, 922 contraction, 609 decompositions, 595 degeneration, 683 tetanus, 609 Secretion currents, 611 Secretory nerves, 631 Sectional area, 178 Segmentation sphere, 914 Self-stimulation of muscle, 606 Semen, composition of, 898 ejaculation of, 911 reception of, 911 Semicircular canals, 654, 859 Sensation, 781 Sense organs, 781 development of, 944 Sensory areas, 751 crossway, 705> 7^^ paths, 704 sensations, 881 Serin, 433 Serous cavities, 350 Serum of blood, 71 Serum albumin, 78, 424 Serum globulin, 78, 424 Setschenow's centres, 690 Sex, difference of, 942 Shadows, lens, 812 colored, 832 Sharpey's fibres, 934 Short-sightedness, 804 Shunt, 598 Sialogogues, 259 Sighing, 227 Silver lines, 136 Simple colors, 824 Simultaneous contrast, 830 Sinuses, 137 Sitting, 555 Size, 419, 420 estimation of, 841 increase in, 419 false estimate of, 843 Skatol, 300,327,454 Skin, absorption by, 498 chorium of, 487 currents of, 607 epidermis, 487 functions of 487 galvanic conduction of, 499 glands of, 492 historical, 499 pigments, 495 protective covering, 493 respiratory organ, 238, 493 structure of, 487 varnishing the, 493 Skin currents, 61 1 Sleep, 735 Small intestine, 336 INDEX. 971 Small intestine, absorption by,344 structure of, 336 Smegma, 494 Smell, sense of, 871 Sneezing, 227 Snellen's types, 805 Sniffing, 872 Snoring, 227 Sodic chloride, 421 salts, 421 Solitary follicles, 339, 342 Somatopleure, 920 Somnambulism, 734 Sorbin, 432 Sound, 848 cardiac, 1 09 conduction to ear, 848, 857 direction of, 869 distance of, 869 perception of, 869 reflection of, 848 Sounds, cardiac, 112 cracked pot, 223 respiratory, 223 tympanitic, 223 vesicular, 223 Spasm centre, 730 Spasmus nictitans, 653 Specific energy, 781, 823 Spectacles, 806 Spectra, absorption, 62 flame, 62 ocular, 814 Spectroscope, 61 Spectrum mucro-lacrimale, 812 of bile, 314 of blood, 62 of muscle, 509 Speech, 569 centre for, 760 pathological variations, 573 Spermatin, 898 Spermatozoa, 898 Spermatoblasts, 899 Spheno-palatine ganglion, 645 Spherical aberration, 807 Sphincters, 552 Sphincter ani, 279 pupillse, 786 urethras, 483 Sphygmogram, 144 Sphygmograph, 140 Dudgeon's, 142 Ludwig's, 142 Marey's, 141 SphygmometA-, 140 Sphygmomanometer, 165 Sphygmoscope, 144 Sphygmotonometer, 139 Spina bifida, 776, 922 Spinal accessory nerve, 664 Spinal cord, 676 action of blood and poi- sons on, 696 Spinal cord, blood vessels of, 682 centres, 693 conducting paths in, 683 conducting system of,683, 696 degeneration of, 685 development of, 944 excitability of, 695 Flechsig's systems, 683 functions of, 683 ganglion, 666 Gerlach's theory, 680 nerves, 665 neuroglia of, 681 nutritive centres in, 685 reflexes, 686 regeneration of, 731 secondary degeneration of, 685 segment of, 685 structure of, 676 time of development, 686 transverse section of, 699 iinilateral section of, 699 vasomotor centres in, 727 Spinal cord, Woroschiloff's ob- servations, 697 Spinal nerves, 665 anterior roots of, 669 posterior roots of, 669 Spiral joints, 549 Spirillum, 90, 324 Spirochseta, 90, 324 Spirometer, 21 1 Splanchnic nerve, 282 Splanchnopleure, 920 Spleen, 192 action of drugs on, 197 chemical composition, 194 contraction of, 195 extirpation of, 194 functions of, 194 influence of nerves on, 196 oncograph, 195 regeneration of, 194 structure, 192 tumors of, 197 Spongin, 426 Spontaneous generation, 893 Spores, 326 Spring kymograph, 164 Spring myograph, 529 Springing, 555 Sputum, abnormal coloration, 248 normal, 247 Squint, 638 Staircase, 535 Stammering, 573 Standing, 554 Stannius's experiment, 121 Stapedius, 854 Starch, 431 Starvation, 408 Stasis, 183 Statical theory of Goltz, 654 Stationary vibrations, 848 Steapsin, 301 Stenopaic spectacles, 807 Stenosis, 112 Stenson's experiment, 517 Stercobilin, 314, 329 Stercorin, 329 Stereoscope, 841 Stereoscopic vision, 839 Sternutatories, 227 Stethograph, 213 Stigmata, 136 Stilling, canal of, 791 Stimuli, 519 adequate, 781 heterologous, 781 homologous, 781 muscular, 522 Stoffwechsel, 41 Stomach, 284 cancer of, 331 catarrh of, 331 changes in glands, 288 gases in, 297 glands of, 285, 286 movements of, 275 structure of, 284 Stomata, 182, 350 Stomodseum, 918 Storage albumin, 403 Strabismus, 771 Strangury, 486 Strassburg's test, 462 Strise medullares, 767 Strobic disks, 830 Stroboscopic disks, 830 Stroma-fibrin and plasma-fibrin, 78 Stromuhr, 176 Struggle for existence, 947 Struma, 728 Strychnin, action of, 687 Stuttering, 573 Subarachnoid space, 776 fluid, 776 Subdural space, 776 Subjective sensations, 782 Sublingual gland, 258 Submaxillary ganglion, 647 atropin on, 257 g'and, 253 saliva, 260 Substantia gelatinosa, 678 Successive beats, 868 contrast, 832 light-induction, 832 Succinic acid, 454 Succus entericus, 323 action of drugs on, 323 Suction, 267 Sudorifics, 495 Sugars, 435 estimation of, 265 tests for, 264 972 INDEX. Sulphindigotate of soda, 472 Summation of stimuli, 534, 687 Summational tones, 869 Superfecundation, 91 2 Superficial reflexes, 691 Superfoetation, 912 Superior maxillary nerve, 644 Supplemental air, 210 Supra-renal capsules, 200 Surditas verbal is, 763 Suture, secondary, 590 Sutures, 549 Swallowing fluids, 719 Sweat, 494 chemical composition, 494 conditions influencing se- cretion, 495 excretion of substances by, 495 glands, 492 insensible, 494 nerves, 496 pathological variations of, 497 Sweat centre, 496, 497, 731 spinal, 730 Swimming, 559 Sympathetic ganglion, 671 nerve, 670 section of, 673, 726 stimulation of, 673, 726 Symphyses, 549 Synchondroses, 549 Syncope, 102 Synergetic muscles, 552 Synovia, 548 Syntonin, 292, 425 Systole, cardiac, 98 Tabes, 697 Taches cerebrales. 728 Tactile areas, 764 corpuscles, 880 sensations, 881 sensations, conduction of, 696 Taenia, 895 Tail- fold, 921 Talipes calcaneus, 553 equinus, 553 varus, 553 Tambour, Marey's, 142 Tapetum, Si 7 Tapping experiment, 718 Taste, centre for, 754 organ of, 874 testing, 876 Taste bulbs, 875 Taurin, 433 Taurocholic acid, 433 Tea, 400 eftects of, 264 Tears, 844 Tegmentum, 768 Tel; stereoscope, 841 Telolemma, 508 Temperature of animals, 366 accom modation for, 381 artificial increase of, 384 estimation of, 366 febrile, 383 how influenced, 370 lowering of, 386 post mortem, 385 regulation of, 376 topography of, 369 variations of, 373 Temperature sense, 887 illusions of, 889 Tendon, 506 nerves of, 511, 881 reflexes, 692 Tensor choroideae, 801 tympani, 853 Terminal arteries, 181 Testicle, descent of, 941 Testis, 896 Tetanomotor, 584 Tetanus, 534, 536, 586 secondary, 609 Tetronerythrin, 79 Theobromin, 400 Thermal centre, 376 nerves, 376 Thermo-electric methods, 367 needles, 368 Thermogenesis, 364 Thermometer, 366 clinical, 366 maximal and minimal, 366 metastatic, 368 outflow, 367 Thermometry, 366 Thirst, 403 Thiry's fistula, 322 Thomsen's disease, 533 Thoracometer, 220 Thrombosis, 74 Thymus, 197 development of, 932 Thyroid, 198 development of, 932 Tidal air, 210 wave, 145 Timbre, 569, 571, 861 Time in psychical processes, 735 Time sense, 863 Tinnitus, 655 Tissue formers, 403 metabolism of, 405 regeneration of, 406 Tizzoni's reaction, 309 Tobin's tubes, 245 Tomes, fibres of, 268 Tone inductorium, 537 Tones, 863 Tongue, glands of, 250 movements of, 271 nerves of, 272 taste bulbs of, 875 Tonometer, 123 Tonsils, 251 Tonus, 694 Tooth, 268 action of drugs on, 271 chemistry of, 269 development of, 270 eruption of, 270, 271 permanent, 271 pulp of, 268 structure of, 268 temporary, 270 Topography, cerebral, "J $6, 764 Toricelli's theorem, 132 Torpedo, 629 Torticollis, 664 Touch corpuscles, 878 Touch, sense of, 878 Trachea, 203 Transfusion, 189 of blood, 189 of other fluids, 191 Transitional epithelium, 480 Transplantation of tissues, 419 Transudations, 360 Trapezius, spasm of, 664 Traube-Hering curves, 168 Traumatic degeneration of nerves, 589 Trehalose, 431 Trichina, 895 Trigeminus, 640 gangHaof,64l,645, 646, 647 inferior maxillary branch, 645 neuralgia of, 648 ophthalmic branch, 641 paralysis of, 649 pathological, 648 section of, 643, 648 superior maxillary branch, 644 trophic functions of, 643 Triple phosphate, 457 Trismus, 648 Trochlearis, 639 Trommer's test, 2^4 TropKolin, 288 Trophic centres, 589 fibres, 589 nerves, 589, 632 Trophoneuroses, 632 Trotting, 558 Trypsin, 300 Trypsinogen, 300 INDEX. 973 Tryptone, 299 Tube casts, 466 Tubes, capillary, 134 division of, 134 elastic, 134 movements of fluids in, 134 rigid, 134 Tumultus sermonis, 761 Tunicin, 432 Turacin, 429 Tiirck's meiiod, 691 Twins, 912 Twitch, 528 Tympanic membrane, 849 artificial, 851 Tyrosin, 300, 433, 465 Ulcer of foot, perforating, 632 Umbilical arteries, 924 cord, 927 veins, 924 vesicle, 921 Unipolar induction, 600 stimulation, 587 Upper tones, 863 Urachus, 924 Uraemia, 479 Urates, 448 Urea, 443 antecedents of, 445 compounds of, 445 decomposition of, 444 effect of exercise on, 444 ferment, 457 formation of, 445, 473, .474 nitrate of, 445 occurrence of, 445 oxalate of, 446 pathological, 445 phosphate of, 446 preparation of, 445 properties of, 443 qualitative estimation of, 446 quantitative estimation of, 446 quantity of, 444 relation of, to muscular work, 444 Ureameter, 446 Ureter, ligature of, 474 pressure in, 471 structure and functions of, 480 Uric acid, 447 diathesis, 480 formation of, 474 occurrence, 448 properties of, 447 qualitative estimation, 449 quantitative estimation of, 449 acid, quantity, 447 Uric acid, solubility, 448 tests for, 449 Urinary bladder, 481 calculi, 468 closure of, 483 deposits, 465 development of, 925 organs, 434 pressure in, 485 Urine, 440 accumulation of, 483 aceton in, 464 acid fermentation, 456 acidity, 443 albumin in, 457 alkaline fermentation, 457 alkaloids, 480 amount of solids, 441 bile in, 462 blood in, 460 calculi, 468 changes of in bladder, 485 characters of, 440 color, 441 coloring matters of, 452 consistence, 442 cystin in, 465 deposits in, 465 dextrin in, 464 effect of blood pressure on, 470 egg albumin in, 459 electrical condition of, 629 excretion of pigments by, 473 fermentations of, 456 ferments in, 454 fluorescence, 442 fungi in, 466 gases in, 456 globulin in, 459 hemi-albumose, 459 incontinence of, 486 influence of nerves on, 476 inorganic constituents, 454 inosit in, 464 leucin in, 465 milk-sugar in, 464 movement of, 481 mucin in, 442, 460 mucus in, 442, 460 organisms in, 465 passage of substances into, 475 peptone in, 459 phosphoric acid in, 455 physical characters of, 440 pigments of. 452 propeptone in, 459 quantity, 440 Urine, reaction, 442 retention of, 486 secretion of, 469 siHcic acid in, 456 sodic chloride in, 454 solids of, 441 specific gravity, 440 spontaneous changes in, 456 sugar in, 462 sulphuric acid in, 455 taste of, 442 taste for albumin in, 458 tube casts in, 466 tyrosin in, 465 Urinometer, 440 Urobilin, 67, 452 Urochrome, 452 Uroerythrin, 452 Uro-genital sinus, 942 Uromelanin, 452 Urorubin, 452 Urostealith, 468 Uterine milk, 927 Uterus, 905 development of, 940 involution of, 947 nerves of, 946 Utricle, 858 Uvea, 785 Vagotomy, 716 Vagus, 656 cardiac branches, 660 depressor nerve of, 167, 660 effect of section, 66 1 on heart, 169 pathological, 663 pneumonia after section, 661 reflex effects of, 662 stimulation of, 169, 719 unequal excitability of, 663 Valleix's points douloureux, 890 Valsalva's experiment, 129, 154 Valve, ileo-colic, 277 pyloric, 275 Valves of heart, 95 disease of, iii injury to, lOl of veins, 136 ■ sounds of, 185 Valvulse conniventes, 336 Varicose fibres, 575 Varix, 172 Varnishing the skin, 387 Vas deferens, 897 Vasa vasorum, 137 Vascular system, development of, 934 Vaso dilator centre, 729 nerves, 729 Vaso-formative cells, 52 974 INDEX. Vasomotor centre, 4^2 destruction of, 723 nerves, 722 spinal, 727 Vasomotor nerves, course of, 723 Vater's corpuscles, 879 Vegetable all)umin, 425 casein, 425 foods, 397 preserveti, 399 proteids, 425 Veins, 136 cardinal, 936 development of, 936 movement of blood in, 183 murmurs in, 1S5 pressure in, 171 pulse in, 1S5 structure of, 137 tonus of, 723 valves in, 137, 1S5 valvular sounds in, 1 85 varicose, 172 velocity of blood in, 1S3 Vella's fistula, 322 Velocity of blood stream, 132 Venous blood, 86 Ventilat on, 245 Ventricles, 94, 108 aspiration, 99 brain, 776 capacity of, 161, 179 fibres of, 94 impulse of, 104 negative pressure in, 100 systole of, 100, 108 Veratrin, 532 Vemix caseosa, 494 Vertebrct, mobility of, 554 Vertebral column, 922 Vertigo, 655 Vestibular sacs, 859 Vibrations of body, 158 Vibralives, 572 Vibrio, 90 Villus, intestinal, 337 absorption by, 346 chorionic, 925 Villus, contractility of, 339 placental, 926 Violet-blindness, 828 Visceral arches, 923 clefts, 923 1 Vision, binocular, 837 stereoscopic, 839 Visual angle, 79S apparatus, 783 centre, 752, 763 pur|)le, 789, 823 Vital capacity, 210 Vitellin, 424 Vitelline duct, 921 Vitreous humor, 791 Vocal cords, 559 conditionsinfluencing the, 568 N'oice, 509 falsetto, 568 [ in animals, 574 pathological variations of, 573 physics of, 560 pitch of, 560 production of, 569 range of, 569 \olunie pulse, 188 \'olumetric method, 447 Vomiting, 276 centre for, 276, 711 Vowels, 570 analysis of, 570, 864 artificial, 864 formation of, 570 Ka'nig's apparatus for, 867 Wagner's corpuscles, 878 Waking, 735 Walking, 555 Wallerian law of degeneration, 589 Wandering cells, 349 Warm-blooded animals, 365 Washed blood clot, 74 Water, 38S, 421 absorbed by skin, 498 absorption of, 344 exhaled by skin, 238, 492 Water, exhaled from lungs, 232 hardness of, 389 impurities, 388 in urine, 440 vapor of, in air, 231 Wave pulse, 145 propagation of, 154 Wave motion, 134 Wave movements, 848 Waves, in elastic tubes, 156 Weber's paradox, 543 law, 782 Weigert's method, 579 Weight, 419 Weyi's test, 449 Wharton's jelly, 927 Whispering, 570 White of egg, 423 Wine, 401 Wolffian Ixidies, 940 ducts, 940 Word blindness, 761 Word deafness, 754, 761 Work, 539 unit of, 36 Xanthin, 450 Xanthokyanopy, 828 Xanthophane, 990 Xanthoproteic reaction, 423 Xerosis, 644 Yawning, 227 Yeast, 428 Yelk, 904 cleavage of, 914 sac, 921 Yellow spot, 814 Young- Helniholtz theory, 826 Zero temperature, 888 Zimniemiann, blood particles of, Zinn, zonule of, 790 Zoetrope, 830 Zollner's lines, 843 Zona pellucida, 901 Zooglrta, 325 Zymogen, 300