An elementary treatise on human physiology : on the basis of the Précis elémentaire de physiologie

Front matter

THE

ABNER WELLBORN CALHOUN

MEDICAL LIBRARY

Introduction

In the year 1822, the undersigned published a translation of " The Summary of Physiology" by M. Magendie. It was most favourably received by the profession, two large editions having been rapidly disposed of. For reasons over which the editor had no control, and which are at present unimportant to the public, no new edition of this translation has appeared since the second. The original work, however, has gone through several large editions with increasing reputation, and now occupies the highest rank among standard works, not only in France, but throughout Europe. Since the period alluded to, the science of Physiology has undergone, on many points, a complete revolution, in the accomplishment of which M. Magendie has acted a very conspicuous part. Since the death of Sir Charles Bell, perhaps there is no physiologist who stands so pre-eminent as an original observer and inquirer, or who has contributed so much to the present improved state of the science by his individual efforts. In facility in experimenting upon living animals, and extended opportunities of observation, no one has surpassed him ; while, through a long professional career, his attention has been chiefly devoted to physiological inquiries.

There is one excellence which constitutes a predominant feature in his system of Physiology that cannot be estimated too highly by the student of medicine. I allude to the severe system of induction that he has pursued, excluding those imaginative and speculative views, which rather belong to metaphysics than physiology. The work is also remarkable for the conciseness and perspicuity of its style, the clearness of its descriptions, and the admirable arrangement of its matter.

The present work is a translation of the fifth and last edition of the " Precis Elementaire de Physiologie" in which the science is brought down to the present time. It is not, like many modern systems, merely eclectic, or a compilation of the experiments and doctrines of others. On the contrary, all the important questions discussed, if not originally proposed and investigated by the author, have been thoroughly examined and experimented

IV INTRODUCTION.

upon by him. His observations, therefore, on all these important subjects, carry with them great interest and weight derived from these investigations.

It has been the purpose of the translator and editor, while faithfully adhering to the spirit of the author, to endeavour, as far as can be done consistently with this, to strip the work of its foreign costume, and naturalize it to our language. He has added a large number of diagrams and pictorial illustrations of the different organs and structures, taken from the highest and most recent authorities, in the hope of rendering clearer to the student of medicine the observations and reasonings on their functions. He has also made a number of additions on subjects which he thought had been passed over in too general a manner in the original work of M. Magendie. The additional matter is indicated by brackets. In a word, it has been his aim to present a system of human physiology which shall exhibit in a clear and intelligible manner the actual state of the science, and adapted to the use of students of medicine in the United States.

John Revere, M.D.

New- York : University Medical College,

Preface

The natural sciences, like history, have had their fabulous period. Astronomy commenced in astrology ; chemistry was not long since alchemy ; and medicine but a combination of absurd hypotheses. Strange condition of the human mind, which seems to require that it should long exercise itself in error before it dare approach the truth ! Such were the natural sciences before the seventeenth century, when Galileo appeared, and discovered to mankind that to understand nature, it is not enough to imagine or believe, as the ancients supposed, but to observe, and, above all, to inquire by experiments. This was the spirit that inspired the labours of the immortal Newton, and of those men of genius, who, during the last century, annihilated the antique doctrines of the four elements, and replaced them by the pneumatic theory. The same spirit animates the natural philosophers and chemists of the present day ; guides them in their ingenious and useful researches, and forms between them a new and indissoluble bond.

Glory, then, to Galileo ! In demonstrating by memorable example the immense advantages of observation and experiment ; in turning the human mind from the false direction where its powers had exhausted themselves for ages in vain efforts, he really laid the foundation of the physical sciences ; of those sciences which elevate the dignity of man, increase incessantly his power, secure the wealth and happiness of nations, place our civilization above that of all preceding ages, and open to posterity a brilliant future.

Would that I could say that Physiology, in the language of Bacon, the science of ourselves, has pursued the same course, and undergone the same metamorphosis as the physical sciences. But, unfortunately, this is not the case ; Physiology is still, in the minds of many, and in some of our books, a mere work of the imagination ; it has its different creeds, and opposite and contending sects ; it admits the existence of fabulous beings, who, like the pagan gods, preside over the phenomena of life ; the authority of authors calling themselves infallible is invoked ; in a word, it may be said to be the framework of a religion strangely filled with scientific terms.

Still there are men who have successfully applied the experimental method to the study of life ; great discoveries have been the fruits of their efforts ; science is enriched — extended, iut its general form, its method of investigation, remains the sarJe; a*** by the side of the phenomena of the circulation of t*e blood, of respiration, muscular contraction, &c, are placed, in the

VI PREFACE.

same line, such metaphors as the organic sensibility, or such offspring of the imagination as the nervous fluid, or such unintelligible expressions as the vital force or principle.

The object of this work is to endeavour to change the state of Physiology in this respect ; to lead it back to positive facts ; in one word, to impart to that beautiful science the happy renovation which has taken place in the physical sciences. I am not ignorant of the difficulties before me ; I fully appreciate them ; they belong to the nature of man, and are but physiological phenomena.

Numerous prejudices separate Physiology at present from the exact sciences : extreme repugnance to experiments on living animals ; the pretended impossibility of applying these deductions to man ; the almost absolute ignorance as to the method of proceeding so as to attain truth ; attachment to old ideas, always sustained by carelessness and indolence ; a kind of passion among men to cling to old errors, even contrary to their own interests — these are some of the obstacles which it will be necessary to surmount. They are certainly great, but, trusting to the gentle but steady influence of truth, I cannot doubt that success is not remote. Already the hypothesis of the organic functions is no longer received with the same favour ; and to a work on speculative physiology, some experiments are indispensable. The belief, so injurious and absurd, that physical laws have no influence on living bodies, has no longer the same force. The choicer spirits begin to admit that there may be in the living animal different orders of phenomena, and that acts simply physical do not exclude actions purely vital. It is no longer doubted that researches made upon animals apply with remarkable precision to the phenomena of life in man ; the vivid light that recent experiments relative to the nervous functions have thrown upon pathology, has removed all uncertainty on this point.

But what proves better than anything I can say, how much the utility of physiological experiments are perceived, is the great number of persons who have engaged in these investigations ; and also the rapidity with which important discoveries, even the most unexpected, have succeeded each other, so as to make the science of life a new science. In a few years, Physiology, so intimately connected with the physical sciences, can no longer advance but by their aid. It will acquire the vigour of their method, the precision of their language, and the certainty of their results. In raising itself thus, it will be removed from that ignorant and vain crowd always ready to repel truth and protect error. Medicine, which is but the physiology of man diseased, will not fail to follow in the same direction and attain the same height. Wq shall then see those erroneous explanations disappear which havt misled the best minds, and disfigured it so long.

Contents

Introduction. — Objects and Design of this Work Page iii

Preface. — Progress of the Natural Sciences. — Their Condition previous to the Time of Galileo. — Their Improvement depends on Induction, founded on exact Observations and Experiments. — Physiology has been too Imaginative. — Connected with Creeds. — This abandoned by most recent and ablest Inquirers. — Object of this Work to establish Physiology on positive Facts v

Chapter I. Preliminary Observations

Physiology divided into Vegetable, Comparative, and Human. — Substances and their Divisions. — Substances Ponderable and Imponderable ; Simple and Compound. — Differences between Organic and Inorganic Bodies ; between Vegetables and Animals. — Man in the Class Mammiferi. — Structure of the Body of Man. — Solids and Fluids. — Fluids exceed Solids.— Contained in Canals and Cavities. — Solids present numerous Forms. — In their Study Physics and Chemistry should be combined. — Tables of Tissues.— Physical Properties of the Organs. — One of the most remarkable, Imbibition. — The Membranes traversed by Gases. — Chemical Properties of Organs. — Immediate Principles of. — List of Liquids ; their Classification. — Vital Properties considered. — Causes of Vital Phenomena 13

Chapter II. Characteristics Of Man

Erect Attitude not only imparts Dignity, but necessary in many Conditions. — All the Details of Organization adapted to it. — Is Bimanous and Biped. — Differs in this from all other Animals. — Compared with Anthropomorphous Animals. — Conformation of Superior and Inferior Extremities. — Vertebral Column ; its Peculiarities in Man. — The Pelvis highly Characteristic. — The Form of Thorax also modified. — Head seat of Encephalon. — Its peculiar Form and Position in Man. — Facial Angle of Camper ; in Man and the Horse. — The Base of the Cranium. — The Face. — Intellect the Cause of his Superiority. — Is necessarily Social. — Intellect capable of great Improvement. — His Sense of Religion Characteristic 27

Chapter III. Classification Of The Functions

Relation, Nutrition, Generation. — Mode of Investigation to be pursued. — Functions of Relation, what. — Sensations and the Senses. — Vision. — Excitant Light; Properties of. — Views of Newton and Des Cartes. — Optics, Catoptrics, and Dioptrics. — Light does not pass Instantaneously. — Its Velocity. — A Ray of Light. — Its Media, Reflection, and Refraction. — Effects of dense Media. — Influence of curved and other Surfaces. — Inverted Image. — Light a Compound Body. — Solar Spectrum. — Apparatus of Vision. — Different Parts ; their Uses. — Apparatus of Tears ; their Uses. — Globe of the Eye ; its Humours, Membranes, and Coats. — The Optic Nerves ; their Origin and Connexion ; Experiments on. — Mechanism of Vision. — Eye compared to Camera Obscura. — Uses of Cornea, Aqueous, Crystalline, and Vitreous Humours. — Experiments. — Motions of Iris ; their Uses. — Ciliary Processes, what; their Uses. — Action of Retina. — Peculiarities in certain Birds. — Action of Optic Nerve in Vision. — Action of both Eyes in estimating Distance, Size, and Motion of Objects. — Optical Illusions, how produced.— Vision at different Ages. — Imperfect Vision. — Myopia, Presbyopia, and Cataract, what 35

Chapter IV. Hearing

How Produced.— Sound considered according to Intensity, Note,. and Tone. — Apparatus of Hearing : External Cartilage ; Meatus Auditorius Externus ; Middle Ear ; Tympanum ; Labyrinth ; Auditory Nerve. — Mechanism of Hearing. — Uses of different Parts. — Action of both Ears. — Listening with one or both Ears. — Sight assists Hearing.-— Pathological Tendencies. — Apparatus Simple, securely placed, and less prone to Disease than Vision, but less controlled by Art.— Affections of Eustachian Tube.— Puncturing Membrana Tympani— Deleau — Injections of Eustachian Tube.— Frequently interested in Cerebral Diseases.— Modifications by Age 77

Vlll CONTENTS.

Chapter V. Sense Of Smell

Destined to recognise Odours ; their Nature. — Difference in Odorous Bodies, supposed Nutritious, Medicinal, Poisonous. — The Air the Vehicle of Odours.— Apparatus of Smell— Differs from those of Vision or Hearing.— The Pituitary Membrane.— Lines Nasal Passages. — Its Structure. — Arrangement of Nasal Passages.— Maxillary and Frontal Sinuses.— Olfactory Nerve ; its Properties.— Mechanism of Smell.— Differs from Vision and Hearing. — In them general distinct from special Sensibility. — Difficult to distinguish in Smell.— Experiments.— Smell Active during passage of Air through Nasal Fossae.— Nasal Mucus.— Uses of Nose in Smelling ; Effects of its Loss, and of Artificial Nose.— Connexion of Smell with Digestive and Respiratory Apparatus.— Smell co-operates with Taste.— Instinct more perfect in Inferior Animals than Man.— Direction and Force of Odorous Particles upon the Organ influence the Function.— Sense lost when Membrane inflamed.— Modifications by Age . . . Page 92

Chapter VI. Sense Of Taste

Excited by Sapid Bodies. — In some Respects Chemical. — Varieties. — Apparatus of Taste. — Parts situated within the Cavity of the Mouth. — Tongue the principal Organ. — The Lingual Nerve of the Fifth Pair usually considered the principal Nerve of Taste, but others Auxiliary. — Mechanism of Taste. — Papilla? of the Tongue ; their State. — Sapid Body in contact with Tongue; dissolved in Saliva. — Teeth affected. — Experiments on Effects of Sapid Bodies on different Parts of the Mouth. — Most Vivid on Apex and Edges of Tongue. — Sometimes judge accurately. — Effects of Division of Lingual Nerve. — This Sense Sentinel to Digestive Apparatus ; several of the other Senses concur. — Tongue Part of Digestive Apparatus. — Intimately connected with Smell. — Like other Senses, capable of great Improvement. — Modification by Age . 100

Chapter VII. Touch

Makes us acquainted with greatest Number of Properties. — Less subject to Error ; but overrated. — Difference between Sensation and Touch. — Apparatus of Touch. — Its Importance in the Animal Economy. — Exists in some Degree in the whole Integument, but more especially in the Extremity of Fingers. — Connected with Muscular Contraction. — Structure of the Skin. — Dermis and Epidermis, Rete Mucosum. — Cutaneous Papilla? ; their Structure according to M. Gautier. — Mechanism of Sensation. — Judgment of Temperature.— Sensation varies in different Parts of Skin. — Sensibility greatest in Lips, Tongue, Conjunctiva, and Mucous Membranes. — Mechanism of Touch. — In Man, the Hand, Arrangement of Epidermis and Rete Mucosum, Ball of Finger. — Flexibility of Hand. — Views of Condillac and Buffon. — Modifications by Age. — Internal Sensations. — Sensation exists in most of the Structures, a few excepted, as Bones, Tendons, and certain Nerves. — First observed, as respects the last, by Haller. — Of a supposed Sixth Sense 107

Chapter VIII. Of Sensations In General

All Substances act upon the Senses. — The only Means of our Knowledge of their Existence.— Nerves essential to Organs of Sense. — They have two Extremities, one in the Brain, the other in the Organs. — Same Nervous Filament, according to Bell, performs but one Office. — When Organ has many distinct Nerves, possesses several distinct Powers. — Structure of Nerves, except Optic, Disposition of Organic Extremity, unknown.— Consist of Filaments enclosed in Neurilema. — Ganglions ; their Structure and Connexion with Nerves. — Of their Interfacings, called Plexus. — Ganglia of great Sympathetic ; their Offices. — Experiments upon them. — Physiological Explanation of Sensations ; different Conjectures. — Are to be Classed among Vital ; not susceptible of Explanation.— Wound of Nervous Trunk. — Nerves, how divided into Sensible and Insensible.— Those included in First and Second Class. — Phenomena of Sensation instinctively referrible to external Cause. — Supposed Series of Acts that constitute Sensation ; this Imaginary ; cannot be proved. — Sensations Vivid or Weak. — Effects of Habit. — Influence of different Sensations on each other. — Case of James Mitchel, deaf and blind. — Case of Laura Bridgman, deaf, blind, Taste imperfect. — Modes of Communication adopted. — Instructed in the Use of Letters. — Course adopted by Dr. Howe, and Results. — We may infer from this Case that Understanding may be highly developed without Vision or Audition. — Effects of Restoration of the Senses after being lost for considerable Time. — Sensations Agreeable or Disagreeable . . .115

Chapter IX. Functions Of The Encephalon

Functions of Relation our most admirable Faculties. — Directly on Brain. — Views entertained respectng their Nature. — Under Encephalon include Cerebrum, Cerebellum, and

. CONTENTS. IX

Medulla Spi7ialis.— Subject extremely complicated; recently much elucidated.— Tw tamina Cerebri. — The Hair, Scalp, Cranium, Dura Mater ; their peculiar Characters. — Longitudinal Section of Cranium and Encephalon. — Base of Encephalon. — Arrangement of Medulla Spinalis, and Bony Cavity in which enclosed. — The Cephalo-rachidian Fluid, Arachnoides, Pia Mater, Plexus Ohoroides. — Complicated Structure of Brain in Man ; more Voluminous than other Animals ; generally proportioned to Capacity of Mind ; not always. — Circumvolutions and Inequalities of Surface. — Divided into Hemispheres, Cavities, or Ventricles. — Substance of Brain, Medullary and Cineritious. — Chemical Composition. — Blood-vessels. — Characters in Man and living Animals of Brain; its Motions. — Pressure; its Effects. — Sensibility of its Tissues; its Uses in the Economy. — Of the Understanding. — Sensibility. — Memory.— Judgment. — Desire or Will. — Mode of acquiring Ideas; these Acquirements depend upon Ourselves ; the Sum of our Ideas Real or Imaginary. — Of Instinct ; divided into Intelligent, and Blind or Brutal.— Of the Passions ; their End Page 135

Chapter X. Offices Of Cerebrum And Cerebellum

Centres of Nervous System, and supposed Seat of Intellection. — Relation between the Mass and Intellectual Manifestations. — Views of Camper, Gall, Spurzheim. — Doctrines of latter awakened Spirit of Inquiry. — Countenanced by isolated Character of Intellectual Faculties. — Loss of Memory of Words complicated with Lesion of Anterior Lobes. — How far supported by Cases and Comparative Anatomy. — 'Independent Development of Ossific Structures. — Cortical Substance, how far concerned in Intellection. — Experiments of Flourens. — Effects of Inflammation. — Case of Dr. Boerstler. — Results of Pathological Anatomy not satisfactory on this Subject. — Cadaveric Appearances in Maniacs. — Induration of Cortical Substance. — Phenomena when Brain undeveloped or atrophied. — Inferences as to Seat of Intellection. — Of Voluntary Motion and Sensation ; former attributed to Cerebrum; latter, Cerebellum. — Symmetrical Character; its Influence on Functions. — Offices of Cerebellum ; supposed Seat of Venereal Appetite.— Effects of Wounds of Cerebellum ; Inflammation ; effusion of Blood. — Emasculation in Man and Animals. — Experiments of Lassaigne. — Atrophy of Cerebellum. — Doctrine not sustained. — Medulla Spinalis. — Functions intimately connected with Cerebrum and Cerebellum; part of Encephalon. — Investigated by Sir Charles Bell and Magendie ; Diagram of. — Vertical Section by Milne Edwards. — Portion showing Origin of Compound Nerves. — Importance of Medulla Oblongata in Functions of Organic Life. — Cerebro-spinal Nerves impart Sensation and Voluntary Motion. — Their Connexion with great Sympathetic. — Connexion of Sensibility with Voluntary Motion in Paralytics. — Effects of Injuries of different Portions of the Medulla Spinalis ; its Disorganization.— Cerebro-spinal Axis Centre of Nervous System. — Action of the Nerves. — Mr. Mayo's Experiments on their reflex Action. — Inflammation of different Portions of Nerves ; its Effects. — Hence Obscurity in Diagnosis. — Anomalous Symptoms in Diseases called Neuroses. — Lesions of the Nerves at Encephalic and Sentient Extremities.—Their Effects .■*''.'. 157

Chapter XI. Muscular Contraction And The Voice

By their Agency act on foreign Bodies and communicate our Ideas. — Parts concerned in Muscular Contraction, Brain, Nerves, and Muscles. — Parts of Encephalon destined to Motion. — The Nerves of Motion. — Parts may lose their Power of Motion and retain their Sensibility, and Reverse. — Experiments of Sir C. Bell on Nerves of the Face. — Structure of the Nerves. — Of Muscles, Muscular Fibre. — Phenomena of Muscular Contraction-Zigzag Inflections when seen by Microscope. — Muscular Fibres with beaded Filaments; their Primary Cells; separation into Disks; in a State of Contraction.— All the Fibres do not contract at same Moment. — Influence of Chemical and Mechanical Agents. — Their alternate Contraction and Relaxation. — The Nerves form a sort of Loop in the Muscles. — Rigor Mortis, what. — Change in Muscles during Contraction regulated by Brain ; astonishing Force in Maniacs. — Cannot continue long. — When Morbid, as in Spasms and Convulsions. — Modification by Age. — Of the Voice. — Produced by Air traversing Larynx. — Mechanism illustrated by Wind Instruments.— Latter how formed ; Theory of their Mode of Action in producing Musical Sounds. — Mouth and Reeded Instruments. — Latter most nearly resembles Organ of Voice. — How Constructed — Use of Reed and Tube.— Apparatus of Voice. — The Larynx : Situation and Constitution ; Vertical Section and bird's-eye View of. — Cartilages and Muscles. — Lining Membrane, Blood-vessels, Nerves, and Ligaments. — Mechanism of the Voice. — Experiments with recent Larynx and Trachea ; with living Animals. — Analogy with Reeded Instruments. — Views of M. Savart. — Intensity or Volume of Voice.— Depends on Extent of Vibrations.— Timbre.— Notes.— Experiments on Dog.— Artificial Larynx of Latour.— Lengthening and shortening of Trachea. —Larynx elevated in Acute Sounds.— Influence of Ventricles of Larynx.— Intensity of the Voice depends on Vocal Tube. — Influence of Mouth, Nasal Passages, Palate, &c. — Ressonnance of Chest. — Cries, expression of vivid Sensations. — Acquired Voice, cannot be acquired if Deaf.— How differs from Cries.— Language composed of Words ;

B

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Words of Letters ; they of Modifications of Voice. — Curious Case of Convict at Toulon.— Difference between Articulation and Speech. — Singing, how differing from Speech. — Notes of the first Register and Falsetto. — Action of the Larynx. — Inspiratory Voice. — Ventriloquism ; Imitation of Sounds ; avoid Words with Labial Consonants; Effect increased by combining other Illusions. — Modifications of Voice by Age. ■ — Change at Puberty ; falls an Octave ; connected with Development of Larynx. — Relations between Hearing and Voice. — Those born Deaf maybe made to Speak. — Sudden Recovery of Hearing, curious Case of. — Case of Honore Tresel. — Sounds Independent of the Voice Page 179

Chapter XII. Attitudes And Movements

Effects of Muscular Contraction. — Mechanical Principles involved. — Vertical Line. — Equilibrium. — Base of Support. — Levers. — Moving Power, what. — Friction and Adhesion.— Of the Bones. — Short. — Flat and' Long. — Articulations of Bones ; how arranged. — Synovia. — Cartilages. — Ligaments. — Vertebral Column supports the Weight of Head and Trunk, and transmits it to inferior Extremities through Pelvis. — It possesses great Strength and Solidity.— Thigh Bones transmit Weight to Tibia?.— Latter to Feet, which support whole Weight of the Body. — Their Form and Structure. — Altitude most Firm when Feet parallel and little separated. — The more the Base of Support diminished less secure. — Standing upon one Foot insecure and fatiguing.— Kneeling, in fact, Base of Support small, hence insecure. — Sitting: Base of Support' large; Attitude easy and secure. — Recumbent Posture. — Motions. — Partial of the Face, of the Eyelids, of the Eye. — Action of the Recti Muscles; Experiments of Sir C. Bell; of Magendie. — Wound of Peduncle of Brain ; Effects on the Motions of Eyes.— Expression of Countenance, Physiognomy. — Motions of the Head on Vertebral Column. — Effects on Vision, Hearing, Smelling, and Voice. — Movements of Trunk, Thorax, Abdomen, and Pelvis. — Motions of Superior Extremities, Hands, admirable Mechanism.— Movements of Inferior Extremities. — Of Walking, Leaping, Running, Swimming.— Influence of the Brain on Motions. — Of the Hemispheres. — Of the Corpora Striata. — Of the Cerebellum. — Of the Pons Varolii. — Of the Pyramidalia. — Of Attitudes and Movements at different Ages. — Relation of Sensations to Attitudes. — Influence of Vision, of Gestures, of Hearing, of Internal Sensations. — Relations of Attitudes and Motions to the Will said to be Voluntary. — Will and Action of Brain in Muscles ; distinct Phenomena. — Shown by Experiments. — Curious Case. — Paralysis. — Relations of Attitudes and Motions to Instincts and Passions, and the Voice . 219

Chapter XIII. Nutritive Functions

Constantly losing the Materials of the Body by Perspiration, Respiration, &c. — Repaired by Aliments. — Digestion ; Organs of, numerous and important. — Relation between the Food and Apparatus. — Different Portions of the Alimentary Canal. — Digestive Organs in Man and Animals. — Of Hunger and Thirst. — These characterized by peculiar Sensations.— Intensity of, varies in different Individuals and Circumstance. — Causes of Hunger. — Desire for Drink increased by certain Causes. — Some seldom experience Sensation ; others frequent and urgent. — Of Aliments, how divided. — Drinks divided according to Chemical Composition. — Particular Acts of Digestion. — Prehension of Solid Aliments.— -Lips, Jaws, Teeth. — Mechanism of Prehension of Solids. — Mastication and Insalivation. — Change of Temperature. — Action of Tongue. — Form of Molar Teeth. — Mechanism of Mastication and Insalivation. — Deglutition of Aliments. — Action of Veil of Palate. — Pharynx. — Oesophagus. — Mechanism of Deglutition. — Formation of Morsel ; Passage through Pharynx and Oesophagus to Stomach. — Abdomen ; its division into Regions, and its Muscles. — Action of Stomach on Aliments. — Form of Stomach.— Membranes. — Cardiac and Pyloric Orifices. — Accumulation of Aliments in the Stomach ; Change they undergo. — Contraction and Relaxation of Cardiac Orifice. — At last Contractions extend to Pylorus. — Contents converted into Chyme. — Passes into Duodenum. — All Alimentary Substances not converted into Chyme. — Precise Nature of Chyme not understood. — Views, Spallanzani and Montegre. — Case of San Martin, reported by Dr. Beaumont. — Experiments of Dr. Lovel on San Martin. — Inquiry how far Solvent Properties of Gastric Juice connected with certain Acids, particularly the Acetic and Muriatic. — Influence of Nerves of Eighth Pair in Chymification. — Experiments. — Dr. Philip on Electricity. — Action of Small Intestines. — Divided in Duodenum, Jejunum, and Ilium. — Accumulation and Passage of Chyme into Small Intestines. — Entrance not continuous. — Peristaltic Action impels the Chyme. — Analysis of Chyme taken from a Dog. — Intestinal Juice ; its Action on Aliments.— Experiments. — Large Intestines divided into Coecum, Colon, and Rectum ; their Structure and Action in Digestion. — Accumulation and Passage of Fecal Matter; its Changes in Ihe Large Intestines. — Chemical Analysis. — Defecation. — Digestion of Drinks; their Prehension ; Deglutition; Accumulation in the Stomach ; how long retained there; their Alteration. — Action of Small Intestines on Drinks.— Chyme, produced by Drinks. — Absorption of Nutritious Liquids introduced through Rectum. — Deglutition of Atmospheric Air. — Regurgitation and' Vomiting. — Modification of Di-

CONTENTS. XI

gestion by Age. — Connexion of Digestion with Functions of Relation. — The Senses Sentinels over these Organs; stimulate their Functions. — Influence of Brain and Great Sympathetic in Digestion Page 256

Chapter XIV. Absorption And Course Of The Chyle And Lymph

End of Digestion to supply Chyle to the Blood. — Nature of the Chyle. — How procured for Experiment. — Its Properties. — Apparatus of Absorption and the Course of the Chyle. — Of the Lacteal Vessels. — Mesenteric Glands. — Thoracic Duct. — Absorption of the Chyle ; how accomplished ; apparently by a mere Physical Process. — Imbibition.— Absorbent Vessels have visible Orifices. — Magnified View of Intestinal Villus of a Hare. — Another from the Human Duodenum. — A third, with commencement of a Lacteal. — Chyle traverses Lacteals. — Mesenteric Glands. — Thoracic Duct ; Causes which give it Motion. — Absorption of Lymph. — Appearance of Lymph when seen by Microscope; Mode of procuring; resembles Blood ; Chemical Analysis of. — Apparatus of Absorption and Course of the Lymph. — Lymphatics ; Functions of. — Origin of Lymph. — Absorption of Veins ; Experiments on. — Lymph passes from different Parts of Body to Thoracic Duct ; from it to the Veins ; Experiments on . . 320

Chapter XV. Course Of The Venous Blood

Object of Venous System : Colour of its Blood, and other Properties. — Analysis of Serum. — Crassamentum, analysis. — Colouring Matter, analysis. — Fibrine. — Apparatus of Venous Blood : Veins — arrangement — extremities. — Connexion with Arteries and Lymphatics, in the Brain. — Valves, where found. — Right Cavities of the Heart : Auricle, Ventricle. — Pulmonary Artery. — Propelling Power in Veins not well understood, — Hydrostatic Principle applicable to. — Course modified by a number of Circumstances. — Absorption by the Veins : absorb Liquids and Gases. — Experiments with Camphor. — Effects of Air and other Substances injected into Veins. — Skin, when deprived of Cuticle, absorbs rapidly. — Experiments upon, by Seguin, Hunter, Flandrin, Magendie. — New Facts observed respecting Imbibition of Tissues. — Great Influence on Reasonings of Physiologists. — Influence of warm Water injected into Veins. — Experiments. — How far is Venous Absorption a Physical Phenomenon ? — Experiments. — Passage of Venous Blood through Right Cavities of the Heart. — Mode of penetrating into Auricle and Ventricle. — Dilatation of Ventricle, how far active. — Action of Ventricle in agita ting Blood during Systole. — Passage of Venous Blood through Pulmonary Artery. — Action of the Signoid Valves, how brought in contact. — Pulsation of the Artery, what. — Contraction of Right Auricle. — Capacity of Arteries increases as divided into Branches.— Contractions of Pulmonary Artery not Muscular. — Quantity of Blood at each Systole of Ventricle . . . ... 354