A text-book of physiology for medical students and physicians

Front matter

HEALTH SCIENCES STANDARD

HX64088448 QP34 .H831 1911 A text-book of physi

RECAP

Preface To The Fourth Edition

A new edition of a text-book implies that the author has made diligent search through the literature of the subject to find what new facts have been discovered, what new views have been advanced, and what old views have been discarded. Everyone who is familiar with the great output of experimental work in physiology will appreciate the difficulties confronting an author who makes such an effort, and will be inclined, let us hope, to deal leniently with him as regards his sins of omission. Truly, the ever-widening boundaries of physiological literature make it more and more difficult for any one individual to gain a familiar knowledge not only of the highways, but of all the many by-ways, along which enthusiastic workers are following their investigations. One is tempted to conclude that the effort to cover the whole field must be futile, and that some other plan should be devised to furnish the student and general reader with a reliable summary of the knowledge and tendencies of the time. There is, for instance, the possibility that the general text-book may be replaced by a series of small monographs, dealing each with a separate part of the subject — that is to say, a small text-book on circulation by one author, another by a different writer on respiration, and so on. It is quite possible that such a plan might be very successful, but it is perhaps more probable that it would fall to the ground between the errors of excessive detail, on the one hand, and lack of continuity, on the other. At the other extreme the plan of a text-book which shall contain only the bare elements or outlines of physiology, with little discussion and no attention to the trend of contemporary investigation, has been tried and has not proved successful. Such a book spreads before the student an arid array of statements, dry and dogmatic in form, and more or less characterized by the lifelessness and

2 PREFACE.

the lack of suggestiveness that usually go with a categorical treatment.

No doubt text-books of these two and of other types will be written. It is, in fact, desirable that experiments of many kinds shall be made, but at present, so far as the author can judge, the larger amount of usefulness is likely to attach to the general text-book compiled by a single writer. This belief has at least served to encourage the present author in attempting a task which he is conscious cannot be discharged so successfully as to escape all criticism. So far as his duties as a teacher and investigator have permitted, he has made an earnest effort to keep this book in the current of the advancing tide of physiological knowledge.

W. H. Howell.

August, 1911.

Preface

In the preparation of this book the author has endeavored to keep in mind two guiding principles: first, the importance of simplicity and lucidity in the presentation of facts and theories; and, second, the need of a judicious limitation of the material selected. In regard to the second point every specialist is aware of the bewildering number of researches that have been and are being published in physiology and the closely related sciences, and the difficulty of justly estimating the value of conflicting results. He who seeks for the truth in any matter under discussion is oftentimes forced to be satisfied with a suspension of judgment, and the writer who attempts to formulate our present knowledge upon almost any part of the subject is in many instances obliged to present the literature as it exists and let the reader make his own deductions. This latter method is doubtless the most satisfactory and the most suitable for large treatises prepared for the use of the specialist or advanced student, but for beginners it is absolutely necessary to follow a different plan. The amount of material and the discussion of details of controversies must be brought within reasonable limits. The author must assume the responsibility of sifting the evidence and emphasizing those conclusions that seem to be most justified by experiment and observation. As far as material is concerned, it is evident that the selection of what to give and what to omit is a matter of judgment and experience upon the part of the writer, but the present author is convinced that the necessary reduction in material should be made by a process of elimination rather than by condensation. The latter method is suitable for the specialist with his background of knowledge and experience, but it is entirely unfitted for the elementary student. For the purposes of the latter brief, comprehensive statements are oftentimes misleading, or fail at least to make a clear impression. Those subjects that are presented to him must be given with a certain degree of fullness if he is expected to obtain a serviceable conception of the facts, and it follows that a treatment of the wide subject of physiology is possible, when undertaken with this intention, only by the adoption of a system of selection and elimination.

The fundamental facts of physiology, its principles and modes

4 PREFACE.

of reasoning are not difficult to understand. The obstacle that is most frequently encountered by the student lies in the complexity of the subject, — the large number of more or less dis- ' connected facts and theories which must be considered in a discussion of the structure, physics, and chemistry of such an intricate organism as the human body. But once a selection has been made of those facts and principles which it is most desirable that the student should know, there is no intrinsic difficulty to prevent them from being stated so clearly that they may be comprehended by anyone who possesses an elementary knowledge of anatomy, physics, and chemistry. It is doubtless the art of presentation that makes a text-book successful or unsuccessful. It must be admitted, however, that certain parts of physiology, at this particular period in its development, offer peculiar difficulties to the writers of text-books. During recent years chemical work in the fields of digestion and nutrition has been very full, and as a result theories hitherto generally accepted have been subjected to criticism and alteration, particularly as the important advances in theoretical chemistry and physics have greatly modified the attitude and point t of view of the investigators in physiology. Some former views have been unsettled and much information has been collected which at present it is difficult to formulate and apply to the explanation of the normal processes of the animal body. It would seem that in some of the fundamental problems of metabolism physiological investigation has pushed its experimental results to a point at which, for further progress, a deeper knowledge of the chemistry of the body is especially needed. Certainly the amount of work of a chemical character that bears directly or indirectly on the problems of physiology has shown a remarkable increase within the last decade. Amid the conflicting results of this literature it is difficult or impossible to follow always the true trend of development. The best that the text-book can hope to accomplish in such cases is to give as clear a picture as possible of the tendencies of the time.

Some critics have contended that only those facts or conclusions about which there is no difference of opinion should be presented to medical students. Those who are acquainted with the subject, however, understand that books written from this standpoint contain much that represents the uncertain compromises of past generations, and that the need of revision is felt as frequently for such books as for those constructed on more liberal principles. There does not seem to be any sound reason why a text-book for medical students should aim to present only those conclusions that have crystallized out of the controversies of other times, and ignore entirely the live issues of the day which are

PREFACE. 5

of so much interest and importance not only to physiology, but to all branches of medicine. With this idea in mind the author has endeavored to make the student realize that physiology is a growing subject, continually widening its knowledge and readjusting its theories. It is important that the student should grasp this conception, because, in the first place, it is true; and, in the second place, it may save him later from disappointment and distrust in science if he recognizes that many of our conclusions are not the final truth, but provisional only, representing the best that can be done with the knowledge at our command. To emphasize this fact as well as to add somewhat to the interest of the reader short historical resumes have been introduced from time to time, although the question of space alone, not to mention other considerations, has prevented any extensive use of such material. It is a feature, however, that a teacher might develop with profit. Some knowledge of the gradual evolution of our present beliefs is useful in demonstrating the enduring value of experimental work as compared with mere theorizing, and also in engendering a certain appreciation and respect for knowledge that has been gained so slowly by the exertions of successive generations of able investigators.

A word may be said regarding the references to literature inserted in the book. It is perfectly obvious that a complete or approximately complete bibliography is neither appropriate nor useful, however agreeable it may be to give every worker full recognition of the results of his labors. But for the sake of those who may for any reason wish to follow any particular subject more in detail some references have been given, and these have been selected usually with the idea of citing those works which themselves contain a more or less extensive discussion and literature. Occasionally also references have been made to works of; historical importance or to separate papers that contain the experimental evidence for some special view.

Section I. The Physiology Of Muscle And Nerve

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Chapter I. — The Phenomenon op Contraction 17

The Histological Structure of the Muscle Fiber, 18. — Its Appearance by Polarized Light, 19. — The Extensibility and Elasticity of Muscular Tissue, 20. — The Independent Irritability of Muscle, 22. — Definition and Enumeration of Artificial Stimuli, 24. — The Duration of the Simple Muscle Contraction, 25. — The Curve of a Simple Muscle Contraction, 26. — The Latent Period, 27. — The Phases of Shortening and Relaxation, 27. — Isotonic and Isometric Contractions, 27.— Maximal and Submaximal Contractions, 2S. — Effect of Temperature upon the Simple Contraction, 29. — Effect of Veratrin on the Simple Contraction, 31. — Contracture, 32. — Fatigue, the Treppe, and Effect of Rapidly Repeated Stimulation, 34. — -The Wave of Contraction and Means of Measuring, 35. — Idiomuscular Contractions, 36.— The Energy Liberated during a Muscular Contraction, 36. — The Proportional Amount of this Energy Utilized in Work, 37. — The Curve of Work and the Absolute Power of a Muscle, 38. — Definition of Tetanus or Compound Contraction, 41. — The Summation of Contractions, 42. — Discontinuity of the Processes of Contraction in Tetanus, 43. — The Muscle-tone, 43. — The Rate of Stimulation Necessary for Complete Tetanus, 44. — The Tetanic Nature of Voluntary Contractions, 45. — The Ergograph, 47. — Results of Ergographic Experiments, 49. — Sense of Fatigue, 50. — Muscle Tonus, 50. — Rigor Mortis and Rigor Caloris, 52. — The Occurrence and Structure of Plain Muscle Tissue, 55. — Distinctive Properties of Plain Muscle, 55. — The General Properties of Cardiac Muscular Tissue, 57. — The Contractility of Cilia and Their General Properties, 57.

Chapter II. — The Chemical Composition of Muscle and the Chemical Changes of Contraction and of Rigor Mortis 60

The Composition of Muscle Plasma, 60. — The Proteins of Muscle, 61. — The Carbohydrates of Muscle, 62. — Phosphocarnic Acid, 63. — Lactic Acid in Muscle, 63. — The Nitrogenous Extractives of Muscle, 64. — Pigments of Muscle, 64.— Enzymes of Muscle, 64. — Inorganic Constituents of Muscle, 65. — The Chemical Changes in Muscle during Contraction, 65. — The Chemical Changes during Rigor Mortis, 69. — The Relation of the Waste Products to Fatigue, the Chemical Theory of Fatigue, 69. — Theories of the Mechanism of the Contraction of Muscle, 71.

Chapter III. — The Phenomenon of Conduction. Properties of

the Nerve Fiber 76

General Statement Regarding Property of Conductivity, 76. — Structure of the Nerve Fiber, 76. — Function of the Myelin Sheath, 77. — Chemistry of the Nerve Fiber, 78. — The Nerve Trunk an Anatomical Unit Only, 80. — Definition of Afferent and Efferent Nerve Fibers, 80. — Classification of Nerve Fibers, 81. — The Bell-Magendie Law of the Composition of the Anterior and the Posterior Roots of the Spinal Nerves, 82. — Cells of Origin of the Anterior and Posterior Root Fibres, 84. — Origin of the Afferent and Efferent Fibers in the Cranial Nerves, 84. — Independent Irritability of Nerve Fibers, Artificial Nerve Stimuli, 85. — Du Bois-Reymond's Law of Stimulation by the Galvanic Current, S7. — Electrotonus, 88. — Pfliiger's Law of Stimulation, 89. — The Opening and the Closing Tetanus, 91. — Mode of Stimulating Nerves in Man, 91. — Motor Points of Muscles, 92. — Physical and Physiological Poles, 94.

Chapter IV. — The Electrical Phenomena Shown by Nerve and Muscle 96

The Demarcation Current, 96. — Construction of the Galvanometer, 98. — Construction of the Capillary Electrometer, 101. — Non-polarizable Electrodes, 101. — Action Current or Negative Variation, 103. — Monophasic and Diphasic Action Currents, 104.— The Rheoscopic Frog Preparation, 106. — Relation of Action Current to the Contraction Wave and Nerve Impulse, 107. — The Electrotonic Currents, 108. — The Core-model, 109

» TABLE OF CONTENTS.

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Chapter V. — The Nature of the Nerve Impulse and the Nutritive Relations of Nerve Fiber and Nerve Cell Ill

Historical, 111. — Velocity of the Nerve Impulse, 112. — Relation of the Nerve Impulse to the Wave of Negativity, 114. — Direction of Conduction in the Nerve, 115. — Effect of Various Influences on the Nerve Impulse, 117. — The Fatigue of Nerve Fibers, 118. — The Metabolism of the Nerve Fiber during Functional Activity, 120. — Theories of the Nerve Impulse, 121. — Qualitative Differences in Nerve Impulses, 124. — Doctrine of Specific Nerve Energies, 124. — Nutritive Relations of Nerve Fibers and Nerve Cells, 125. — Nerve Degeneration and Regeneration, 126. — Degenerative Changes in the Central End of the Neuron, 128.

Section II

THE PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM. Chapter VI. — Structure and General Properties of the Nerve

Cell 130

The Neuron Doctrine, 130. — The Varieties of Neurons, 132. — Internal Structure of the Nerve Cell, 135. — General Physiology of the Nerve Cell, 136. — Summation of Stimuli in Nerve Cells, 139. — Response of the Nerve Cell to Varying Rates of Stimulation, 140. — The Refractory Period of the Nerve Cell, 140.

Chapter VII. — Reflex Actions 142

Definition and Historical, 142. — The Reflex Arc, 142. — The Reflex Frog, 144.— Spinal Reflex Movements, 144. — Theory of Co-ordinated Reflexes, 146. — Spinal Reflexes in Mammals, 147. — Dependence of Co-ordinated Reflexes upon the Excitation of the Sensory Endings, 147. — Reflex Time, 148. — Inhibition of Reflexes, 149. — Influence of the Condition of the Cord on its Reflex Activities, 151. — Reflexes from Other Parts of the Nervous System, 151. — Reflexes Through Peripheral Ganglia, Axon Reflexes, 152. — The Tonic Activity of the Spinal Cord, 154. — Effects of the Removal of the Spinal Cord, 155. — Knee-jerk, 156. — Reinforcement of the Knee-jerk, 156. — Is the Knee-jerk a Reflex Act? 158. — Conditions Influencing the Extent of the Knee-jerk, 160. — The Knee-jerk and Spinal Reflexes as Diagnostic Signs, 161. — Other Spinal Reflexes, 161.

Chapter VIII. — The Spinal Cord as a Path of Conduction 163

Arrangement and Classification of the Nerve Cells in the Cord, 163. — General Relations of the Gray and White Matter in the Cord, 165. — The Methods of Determining the Tracts of the Cord, 165. — General Classification of the Tracts of the Cord, 166. — The Names and Locations of the Long Tracts, 168. — The Termination in the Cord of the Fibers of the Posterior Root, 169. — Ascending or Afferent Paths in the Posterior Funiculi, 170. — Ascending or Afferent Paths in the Lateral Funiculi, 173. — The Spinal Paths for the Cutaneous Senses (Touch, Pain, Temperature), 175. — The Homolateral or Contralateral Conduction of the Cutaneous Impulses, 177. — The Descending or Efferent Paths in the Anterolateral Columns (Pyramidal System), 179. — Less Well-known Tracts in the Cord, 181.

Chapter IX. — The General Physiology of the Cerebrum and Its

Motor Functions 183

The Histology of the Cortex, 184. — The Classification of the Systems of Fibers in the Cerebrum (Projection, Association, and Commissural), 185. — Physiological Deductions from the Histology of the Cortex, 187.- — Extirpation of the Cerebrum, 189. — Localization of Functions in the Cerebrum, Historical, 191. — The Motor Areas of the Cortex, 194. — Differences in Paralysis from Injury to the Spinal Neuron and the Pyramidal Neuron, 196. — Voluntary Motor Paths Other than the Pyramidal Tract, 197. — The Crossed Control of the Muscles and Bilateral Motor Representation in the Cortex, 197. — Are the Motor Areas Exclusively Motor? 198.

Chapter X. — The Sense Areas and the Association Areas in the

Cortex 200

The Body-sense Area, 201. — The Course of the Lemniscus, 203. — The Center for Vision, 205. — Histological Evidence of the Course of the Optic Fibers, 205. — The Decussation in the Chiasma, 207. — The Projection of the Retina on the Occipital Cortex, 208. — The Function of the Lower Visual Centers, 210. — The Auditory Center, 210. — Course of the Cochlear Nerve, 211. — The Physiological Significance of the Lower Auditory Centers, 212. — Motor Responses from the Auditory Cortex, 214.— The Olfactory Center, 214. — The Olfactory Bulb and its Connections, 215. — The Cortical Center for Smell, 216. — The Cortical Center for Taste, 216. — Aphasia, 217. — Sensory Aphasia, 219. — The Association Areas, 221. — Subdivision of the Association Areas, 223. — The Development of the Cortical Areas, 224. — Histological Differentiation in Cortical Structure, 227. — Physiology of the Corpus Callosum, 228. — Physiology of the Corpora Striata and Thalami, 229.

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Chapter XI. — The Functions of the Cerebellum, the Pons, and

the Medulla 231

Anatomical Structure and Relations of the Cerebellum, 231. — General Statement of Theories Regarding the Cerebellum, 235. — Experiments upon Ablation of the Cerebellum, 236. — Interpretation of the Experimental and Clinical Results, 237. — Conclusions as to the General Functions of the Cerebellum, 239. — The Psychical Functions of the Cerebellum, 241. — Localization of Function in the Cerebellum, 241. — The Functions of the Medulla Oblongata, 242. — The Nuclei of Origin and the Functions of the Cranial Nerves, 243.

Chapter XII. — The Sympathetic or Autonomic Nervous System . . . 248

General Statements, 248. — Autonomic Nervous System, 249. — The Use of the Nicotin Method, 250. — General Course of the Autonomic Fibers Arising from the Cord, 250. — -General Course of the Fibers Arising from the Brain, 251. — General Course of the Fibers Arising from the Sacral Cord, 253. — Normal Mode of Stimulation of Autonomic Iserve Fibers, 253.

Chapter XIII. — The Physiology of Sleep 255

General Statements, 255. — Physiological Relations during Sleep, 255. — The Intensity of Sleep, 256. — Changes in the Circulation during Sleep, 258. — Effect of Sensory Stimulation, 261. — Theories of Sleep, 262. — Hypnotic Sleep, 265.

SECTION ILL THE SPECIAL SENSES.

Chapter XIV. — Classification of the Senses and General Statements 266

Classification of the Senses, 266. — The Doctrine of Specific Nerve Energies, 268. — The Weber-Fechner Psychophysical Law, 270.

Chapter XV. — Cutaneous and Internal Sensations 273

General Classification, 273. — Protopathic, Epicritic, and Deep Sensibility, 273. — The Punctiform Distribution of the Cutaneous Senses, 275. — Specific Nerve Energies of the Cutaneous Nerves, 276. — The Temperature Senses, 277 .— The Sense of Pressure, 278. — The Threshold Stimulus and the Localizing Power, 279. — The Pain Sense, 281. — Localization or Projection of Pain Sensations, 281. — Reflected or Misreferred Pains, 282. — Muscular or Deep Sensibility, 282. — The Quality of the Muscular Sensibility, 284. — Sensations of Hunger and Thirst, 285. — The Sense of Thirst, 287.

Chapter XVI. — Sensations of Taste and Smell 288

The Nerves of Taste, 288. — The End-organ of the Taste Fibers, 290. — Classification of Taste Sensations, 290. — Distribution and Specific Energy of the Fundamental Taste Sensations, 291.— Method of Sapid Stimulation, 292. — The Threshold Stimulus for Taste, 293. — The Olfactory Organ, 293.— The Mechanism of Smelling, 294. — Nature of the Olfactory Stimulus, 295. — The Qualities of the Olfactory Sensations, 295. — Fatigue of the Olfactory Apparatus, 297. Delicacy of the Olfactory Sense, 297. — Conflict of Olfactory Sensations, 299. — Olfactory Associations, 299.

Chapter XVII. — The Eye as an Optical Instrument. Dioptrics

of the Eye 300

Formation of an Image by a Biconvex Lens, 300. — Formation of an Image in the Eye, 303. — The Inversion of the Image on the Retina, 305. — The Size of the Retinal Image, 306. — Accommodation of the Eye, 307. — Limit of the Power of Accommodation and Near Point of Distinct Vision, 310. — Far Point of Distinct Vision, 311. — The Refractive Power of the Surfaces in the Eye, 311. — Optical Defects of the Normal Eye, 312. — Spherical Aberration, 313. — Abnormalities in the Refraction of the Eye, Myopia, 314. — Hypermetropia, 314. — Presbyopia, 315. — Astigmatism, 316. — Innervation and Control of the Ciliary Muscle and the Muscles of the Iris, 318. — The Accommodation Reflex and the Light Reflex, 320. — Action of Drugs upon the Iris, 322. — The Antagonism of the Sphincter and Dilator Muscles of the Iris, 323. — Intraocular Pressure, 324. — The Ophthalmoscope, 325. — Retinoscope, 327.— Ophthalmometer, 328.

Chapter XVIII. — The Properties of the Retina. Visual Stimuli

and Visual Sensations 330

The Portion of the Retina Stimulated by Light, 330.— The Action Current Caused by Stimulation of the Retina, 331. — The Visual Purple, Rhodopsin, 332.— Extent of the Visual Field, Perimetry, 334. — Central and Peripheral

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Fields of Vision, 335. — Visual Acuity, 337. — Relation Between Stimulus and Sensation, Threshold Stimulus, 339. — The Light Adapted and the Dark Adapted Eye, 340. — Luminosity or Brightness, 341. — Qualities of Visual Sensations, 341. — The Achromatic Series, 343. — The Chromatic Series, 344. — Color Saturation and Color Fusion, 344. — The Fundamental Colors, 345. — The Complementary Colors, 345. — After Images, Positive and Negative, 346. — Color Contrasts, 347. — Color Blindness, 348. — Dichromatic Vision, 349. — Tests for Color Blindness, 350. — Achromatic Vision, 351. — Distribution of Color Sense in the Retina, 351.— Functions of the Rods and Cones, 352. — Theories of Color Vision, 354. — Entoptic Phenomena, 360. — Shadows of Corpuscles and Blood-vessels, 360. — Shadows from Lens and Vitreous Humor, 361.

Chapter XIX. — Binocular Vision 362

Movements of the Eyeballs, 362. — Co-ordination of the Eye Muscles, Muscular Insufficiency and Strabismus, 364. — The Binocular Field of Vision, 365. — Corresponding or Identical Points, 365. — Physiological Diplopia, 367. — The Horopter, 368. — Suppression of Visual Images, 368. — Struggle of the Visual Fields, 369. — Judgments of Solidity, 369. — Monocular Perspective, 370. — Binocular Perspective, 371. — Stereoscopic Vision, 372. — Explanation of Binocular Perspective, 374. — judgments of Distance and Size, 374. — Optical Deceptions, 375.

Chapter XX. — The Ear as an Organ for Sound Sensations 378

The Pinna or Auricle, 379. — The Tvmpanic Membrane, 379. — The Ear Bones, 380. — Mode of Action of the Ear Bones, 381. — Muscles of the Middle Ear, 383.— The Eustachian Tube, 384.— Projection of the Auditory Sensations, 384. — Sensory Epithelium of the Cochlea, 385. — Nature and Action of the Sound Waves, 386. — Classification and Properties of Musical Sounds, 387. — Upper Harmonics or Overtones, 389. — Sympathetic Vibrations and Resonance, 391. — Functions of the Cochlea, 391. — Sensations of Harmony and Discord, 395. — Limits of Hearing, 395.

Chapter XXI. — Functions of the Semicircular Canals and the

Vestibule 397

Position and Structure of the Semicircular Canals, 397. — Flouren's Experiments upon the Semicircular Canals, 398. — Temporary and Permanent Effects of the Operations, 399. — Effect of Direct Stimulation of the Canals, 409.— Effect of Section of the Ampullary or the Acoustic Nerve, 401. — Is the Effect of Section of the Canals due to Stimulation? 401. — Theories of the Functions of the Semicircular Canals, 401. — Summary of the Views upon the Function of the Semicircular Canals, 404. — Functions of the L'triculus and Sacculus, 405.

Section IV. Blood And Lymph

Chapter XXII. — General Properties of Blood. Physiology of

the Corpuscles 408

Histological Structure of Blood, 408. — Reaction of the Blood, 409. — Specific Gravity of the Blood, 411. — The Red Corpuscles, 412. — Condition of the Hemoglobin in the Corpuscles, 412. — Hemolysis, 413. — Hemolysis Due to Variations in Osmotic Pressure, 414.— Hemolysis Due to Action of Hemolysins, 415. — Nature and Amount of Hemoglobin, 418. — Compounds of Hemoglobin with Oxygen and Other Gases, 420. — The Iron in the Hemoglobin, 421. — Crystals of Hemoglobin, 422. — Absorption of Spectra Hemoglobin and Oxyhemoglobin, 423. — Derivative Compounds of Hemoglobin, 427. — Origin and Fate of the Red Corpuscles, 429. — Variations in the Number of Red Corpuscles, 431. — Physiology of the Blood Leucocytes, 433. — Variations in Number of the Leucocytes, 435. — Functions of the Leucocytes, 435. — Physiology of the Blood Plates, 436.

Chapter XXIII.— Chemical Composition of the Blood Plasma; Coagulation; Quantity of Blood; Regeneration after Hemorrhage 439

Composition of the Plasma and Corpuscles, 439. — Proteins of the Blood Plasma, 441. — Serum Albumin, 441. — Paraglobulin (Serum Globulin), 442. — Fibrinogen, 443. — Less Well-known Proteins of the Blood, 445. — Coagulation of Blood, 445. — Time of Clotting, 446. — Preparation of Solutions of Fibrinogen, 447. — Preparation of Thrombin, 448. — The Action of Thrombin on Fibrinogen, 449. — The Influence of Calcium, 450. — The Influence of Tissue-extracts, 450. — Theory of Coagulation, 451. — Why Blood Does Not Clot Within the Vessels, 453. — Metathrombin, 454. — Intravascular Clotting, 454. — Means of Hastening or of Retarding Coagulation, 455. — Total Quantity of Blood in the Body, 458. — Regeneration of the Blood after Hemorrhage, 459. — Blood Transfusion, 460.

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Chapter XXIV. — Composition and Formation of Lymph 462

General Statements, 462. — Formation of Lymph, 463. — Lymphagogues of the First Class, 465. — Lymphagogues of the Second Class, 466.— Summary of the Factors Controlling the Flow of Lymph, 468.

Section V. Physiology Of The Organs Of Circulation Of The Blood

AND LYMPH.

Chapter XXV. — The Velocity and Pressure of the Blood Flow . . 471

The Circulation as Seen Under the Microscope, 471. — The Velocity of the Blood Flow, 472. — Mean Velocity in the Arteries, Veins, and Capillaries, 475. — Cause of the Variations in Velocity, 477. — Variations of Velocity with the Heart Beat or Changes in the Blood-vessels, 477. — Time Necessary for a Complete Circulation of the Blood, 478. — The Pressure Relations in the Vascular System, 479. — Methods of Recording Blood-pressure, 479. — Systolic, Diastolic, and Mean Arterial Pressure, 483. — Method of Measuring Systolic and Diastolic Pressure in Animals, 485. — Data as to the Mean Pressure in Arteries, Veins, and Capillaries, 486. — Methods of Determining Blood-pressure in the Large Arteries of Man, 490. — Normal Arterial Pressure in Man and its Variations, 496. — The Method of Determining Venous Pressures and Capillary Pressures in Man, 497.

Chapter XXVI. — The Physical Factors Concerned in the Production of Blood-pressure and Blood-velocity 501

Side Pressure and Velocity Pressure, 501. — The Factors Concerned in Producing Normal Pressure and Velocity, 504. — General Conditions Influencing Blood-pressure and Blood-velocity, 505. — The Hydrostatic Effect, 506. — Accessory Factors Aiding the Circulation, 508. — The Conditions of Pressure and Velocity in the Pulmonary Circulation, 509. — Variations of Pressure in the Pulmonary Circuit, 510.

Chapter XXVII.— The Pulse 512

General Statement, 512. — Velocity of the Pulse Wave, 513. — Form of the Pulse Wave, Sphygmography, 515. — Explanation of the Catacrotic Waves, 517. — Anacrotic Waves, 518. — The Kinds of Pulse in Health and Disease, 519. — Venous Pulse, 520.

Chapter XXVIII.— The Heart Beat 525

General Statement, 525. — Musculature of the Auricles and Ventricles, 525. — The Auriculoventricular Bundle, 528. — Contraction Wave of the Heart, 531. — The Electrical Variation, 533. — Change of Form during Systole, 535. — The Apex Beat, 536. — Cardiogram, 537. — Intraventricular Pressure during Systole, 538. — The Volume Curve and the Ventricular Output, 540. — The Heart Sounds, 543. — The Third Heart Sound, 545. — Events Occurring during a Cardiac Cycle, 546. — Time Relations of Systole and Diastole, 547. — Normal Capacity of Ventricle and Work Done by the Heart, 547. — Coronary Circulation during the Heart Beat, 549. — Suction-pump Action of the Heart, 551. — Occlusion of the Coronary Vessels, 553. — Fibrillar Contractions of Heart Muscle, 553.

Chapter XXIX. — The Cause and the Sequence of the Heart Beat.

General Statement, 555. — The Neurogenic Theory of the Heart Beat, 557.— Myogenic Theory, 558. — Automaticity of the Heart, 560. — Action of Calcium, Potassium, and Sodium Ions on the Heart, 561. — Connection of Inorganic Salts with the Causation of the Beat, 563. — Maximal Contractions of the Heart, 564. — Refractorv Period of the Heart Beat, 564. — The Compensatory Pulse. 566. — Normal Sequence of the Heart Beat, 567. — Tonicity of the Heart Muscle, 570.