THIS BOOK IS THE GIFT OF 
 The Van Cleef Library 
 
Cornell University Library 
 QP 34.D15 1864 
 
 A treatise on human physiology. 
 
 3 1924 001 037 591 
 
 JAN 5 
 
 1965 
 
 Date Due 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Library Burea 
 
 Cat. No. 1137 
 
 
The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924001037591 
 
A TREATISE 
 
 HUMAN PHYSIOLOGY 
 
 DESIGNED FOB TUB USE OP 
 
 STUDENTS AND PMCTITIONERS OF MEDICINE. 
 
 BY 
 
 JOHN C. DALTON, Jr., M. D., 
 
 PhOFESSOR OF PHYBIOLOaT AND MICROSCOPIC AWATOMT IN THE COLLEGE OF PHYSICIANS AND BURGEONS, 
 
 NEW TOKK ; MEMBER OF THE NEW YORK ACADEMY OF MEDICINE j OF THE NEW YORK 
 
 PATHOLOGICAL SOCIETY ; OP THE AMERICAN ACADEMY OP ARTS AND SCIENCES, 
 
 BOSTON, MASS. ; AND OF THE BIOLOGICAL DEPARTMENT OF THE 
 
 ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA. 
 
 SC^irJj ffibittflti, '^zbisz'a aitb dnlargcb. 
 
 TWO HUNDRED AND SEYENTY-THREE ILLUSTKATIONS. 
 
 PHILADELPHIA: 
 
 BLANCHAED AND LEA. 
 1864. 
 
KsiERED according to the Act of Congress, in the year 1864, by 
 
 BLANCHARD AND LEA, 
 
 in the Oifice of the Clerk of the District Court of the United States in and for 
 the Eastern District of the State of Pennsylvania. 
 
 54- 
 PlS 
 
 PHILADELPHIA: 
 COLLIKS, PKISTBH, 705 JAYNB STKEET. 
 
TO MY FATHER, 
 
 JOHN C. DALTON, M.D., 
 
 IH 
 
 HOMAGE OP HIS LONG AND StJOCESSPUL DEVOTION 
 
 TO THE • 
 
 SCIENCE AND ART OF MEDICINE, 
 
 AND I 17 
 
 • GRATEFUL RECOLLECTION OP HIS PROFESSIONAL PRECEPTS AND EXAMPLE, 
 
 f lis ifllumj 
 
 IS RESPECTFULLY AND AFFECTIONATELY 
 
 INSCEIBED. 
 
 ( iii ) 
 
PREFACE TO THE THIRD EDITION. 
 
 In the present edition of this work, the general plan and arrange- 
 ment of the two former ones are retained. The improvements and 
 additions which have been introduced consist in the incorporation 
 into the text of certain new facts and discoveries, relating mainly 
 to details, which have made their appearance within the last three 
 years. Such are the experiments of the author with regard to the 
 secretion and properties of the parotid saliva in the human subject, 
 and the quantitative analysis of this fluid by Mr. Perkins ; the 
 valuable observations of Prof. Austin Flint, Jr., on Stercorine, 
 Oholesterin, and the effects of permanent biliary fistula, and those 
 of Prof. Jeffries Wyman on Fissure of Hare-lip in the median 
 line, from arrest of development. Three new illustrations have 
 been introduced, one of which (Fig. 183) repkces a previous one. 
 The author ■ is much indebted to his friend. Dr. Foster Swift, for 
 aid in carrying the work through the press. 
 
 New Yoek, January, 1864. 
 
 (V) 
 
PREFACE TO THE SECOND EDITION. 
 
 In presenting a new edition of this work, tlie author desires to 
 express his sincere acknowledgments to hia professional brethren 
 for the very favorable manner in which it was received at the 
 time of its first appearance, two years ago. In the present edition, 
 the author has endeavored to supply, as fully as possible, the 
 deficiencies which, he is well aware, existed in the former volume. 
 Some of these deficiencies were evident to his own mind, while 
 others were indicated by the suggestions of judicious criticism. 
 These suggestions, accordingly, have been adopted in all cases in 
 which they appear to be well founded, and not inconsistent with 
 the general plan of the work. In those instances, on the other 
 hand, in which the views of the author on physiological questions 
 seemed to him to be positively sustained by the results of observa- 
 tion, he has retained these views unchanged in the present edition. 
 At the same time, he has abstained^ as before, from the lengthened 
 discussion of theoretical points, and has purposely avoided even 
 the enumeration of new experiments and observations, wherever 
 they have not materially affected the position of physiological 
 doctrines; for in a work like the present, it is not the object of 
 the writer to give a detailed history of physiological science, but 
 only such prominent and essential points in its development as 
 will enable the reader fully to comprehend its actual condition at 
 the present time. 
 
 The principal additions and alterations which have thus been 
 found advisable are: — 
 
 First, the. introduction of an entire chapter devoted to the con- 
 sideration of the Special Senses, which were only incidentally treated 
 of in the former edition. 
 
 ( vii ) 
 
Vm PKEFACE TO THE SECOND EDITION. 
 
 Second, the re-arrangement of the chapter on the Oranial Nerves, 
 and the introduction of some new views and facts in regard to their 
 physiology. 
 
 Third, an account of some new experiments, original with the 
 ■ author, relating to the function of the Cerebellum, and the conclu- 
 sions to which they lead. 
 
 Fourth, certain considerations respecting the general properties 
 of Sensation and Motion, as resident in the nervous system, which 
 are important as an introduction to the more detailed study of 
 these functions. 
 
 Fifth, the introduction of a chapter on Imbibition and Exhalation 
 and the functions of the Lymphatic System; including the study of 
 endosmosis and exosmqsis, and their mode of action in the animal 
 frame, the experiments of Dutrochet, Chevreuil, Gosselin, Matteucci) 
 and others, on this subject, the constitution and circulation of the 
 lymph and chyle, and, finally, a quantitative estimate of the entire 
 processes of exudation and reabsorption, as taking place in the 
 living body. 
 
 Additions have also been made, in various parts, to the chapter.s 
 on Secretion, Excretion, the Circulation, and the functions of the 
 Digestive Apparatus. In every instance, these alterations have 
 been incorporated with the text in such a manner as to avoid, so 
 far as possible, increasing unnecessarily the size of the book. 
 
 Twenty-two new and original illustrations have been introduced 
 into the present volume, of which number five replace others in 
 the former edition, which were regarded as imperfect, either in 
 design or execution. The remaining seventeen are additional. 
 
 It is hoped that the above alterations and additions will be found 
 to be improvements, and that they will enable the work, in its pre- 
 sent form, to accomplish more fully the object for which it was 
 designed. 
 
 New Yoek, February, 1861. 
 
PREFACE TO THE FIRST EDITION. 
 
 This volume is offered to the medical profession of the United 
 States as a text-book for students, and also as a means of commu 
 nicating, in a condensed form, such new facts and ideas in physio- 
 logy as have marked the progress of the science within a recent 
 period. Many of these topics are of great practical importance to 
 the medical man, as influencing, in various ways, his views on 
 pathology and therapeutics; and they are all of interest for the 
 physician who desires to keep pace with the annual advance of his 
 profession, as indicating the present position and extent of one of 
 the most progressive of the departments of medicine. 
 
 It has been the object of the author, more particularly, to pre- 
 sent, at the same time with the conclusions which physiologists 
 have been led to adopt on any particular subject, the experimental 
 basis upon which those conclusions are founded; and he has en- 
 deavored, so far as possible, to establish or corroborate them by 
 original investigation, or by a repetition of the labors of others. 
 This is more especially the case in that part of the book (Section 
 I.) devoted to the function of Nutrition; and as a general thing, 
 throughout the work, any statement of experimental facts, not 
 expressly referred to the authority of some other writer, is given 
 by the author as the result of direct personal observation. ' 
 
 The illustrations for the work have been prepared with special 
 reference to the subject-matter ; and it is hoped that they will be 
 found of such a character as materially to assist the student in 
 comprehending the most important and intricate parts of the sub- 
 ject. It is more particularly in the departments of the Nervous 
 System and Embryonic Development that simple, clear, and faithful 
 
 (ix) 
 
X PREFACE TO THE FIRST EDITTOK. 
 
 illustrations are indispensable for the proper understanding of the 
 printed descriptions ; the latter being often necessarily somewhat 
 intricate, and requiring absolutely the assistance of properly 
 arranged figures and diagrams. Of the two hundred and fifty- 
 four illustrations in the present volume, only eleven have been 
 • borrowed from other writers, to whom they will bf found duly 
 credited in the list of woodcuts. 
 
 Of the remaining illustrations, prepared expressly for the pre- 
 sent work, the drawings of anatomical structures, crystals, and 
 microscopic views generally were all taken from nature. The 
 diagrams were arranged, for purposes of convenience, in such 
 a manner as to illustrate known anatomical or physiological ap- 
 pearances, in Uhe most compact and intelligible form. 
 
 Physiological questions which are in an altogether unsettled 
 state, as well as purely hypothetical topics have been purposely 
 avoided, as not coming within the plan of this work, nor as calcu- 
 lated to increase its usefulness. 
 
 New York, January 1, 1859. 
 
CONTENTS. 
 
 INTRODUCTIO-N. 
 
 s PAGE 
 
 Definition of Physiology — Its mode of study — Nature of Vital Phenomena — 
 Division of the subject 49-59 
 
 SECTION I. 
 NUTEITION. 
 
 CHAPTER I. 
 
 PROXIMATE PRINCIPLES IN GENERAL. 
 
 Definition of Proximate Principles — Mode of their extraotion^Manner in which 
 they are associated with each other — Natural variation in their relative 
 quantities — Three distinct classes of proximate principles . . . 61-68 
 
 CHAPTER II. 
 
 PROXIMATE PRINCIPLES OF THE EIRST CLASS. 
 
 Inorganic substances — Water — Chloride of Sodium — Chloride of Potassium — 
 Phosphate of Lime — Carbonate of Lime — Carbonate of Soda — Phosphates of 
 Magnesia, Soda, and Potassa — Inorganic proximate principles not altered in 
 the body — Theii: discharge — Nature of their function .... 69-78 
 
 CHAPTER III. 
 
 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 
 
 Staboh — Percentage of starch in different kinds of food — Varieties of this 
 substance — Properties and reactions of starch — Its conversion into sugar — 
 SoGAB — Varieties of sugar — Physical and chemical properties — Proportion 
 in different kinds of food — Fats — Varieties — Properties and reactions of fat 
 — Its crystallization — Proportion in different kinds of food — Its condition in 
 the body — Internal production of fat — Origin and destination of proximate 
 principles cf this class 79-94 
 
 ( xi ) 
 
XU CONTENTS. 
 
 CHAPTER IV. 
 
 PROXIMATE PRINCIPLES OE THE THIRD CLASS. 
 
 PACE 
 
 General characters of organic substances — Their chemical constitution — Hygro- 
 scopic properties — Coagulation — Catalysis — Fermentation — Putrefaction — 
 Fibrin — Albumen — Casein — Globuline — Pepsine — Pancreatine — Mucosine — 
 Ostelne' — Cartllaglne — Musculine — Hsematine — Melanine — Biliverdine — 
 tJrosaclne — Origin and destruction of proximate principles of this class 95-104 
 
 CHAPTER V. 
 
 or FOOD. 
 
 Importance of inorganic substances as ingredients of food — Of saccharine and 
 starchy substances — Of fatty matters — Insufficiency of these substances 
 when used alone — Effects of an exclusive non-nitrogenous diet — Organic 
 substances also Insufficient by themselves — Experiments of Magevdle on 
 exclusive diet of gelatine or fibrin — Food requires to contain all classes of 
 proximate principles — Composition of various kinds of food — Dally quantity 
 of food required by man — Digestibility of food — Effect of cooking . 105-114 
 
 CHAPTER YI. 
 
 DIGESTION. 
 
 Kature of digestion — Digestive apparatus of fowl — Of ox — Of man — Mastica- 
 tion — Varieties of teeth — Effect of mastication — Saliva — Its composition — 
 Daily quantity produced — Its action on starch — Effect of its suppression — 
 Function of the saliva — Gastric Juice, and Stomach Digestion — Structure of 
 gastric mucous membrane — Dr. Beaumont's experiments on St. Martin — 
 Artificial gastric fistulse — Composition and properties of gastric juice — Its 
 action on albuminoid substances — Peristaltic action of stomach — Time re- 
 quired for digestion — Daily quantity of gastric juice — Influences modifying 
 
 its secretion^-lNTESTiNAL Juices, and the Digestion op Sugae and Starch 
 
 Follicles of Intestine — Properties of intestinal juice — Pancreatic Juice, and 
 
 the Digestion of pat — Composition and properties of pancreatic juice Its 
 
 action on oily matters — Successive changes in intestinal digestion The large 
 
 intestine and its contents 115-161 
 
 CHAPTER VII. 
 
 ABSORPTION. 
 
 Closed follicles and villi of small Intestine — Peristaltic motion Absorption 
 
 by bloodvessels and lymphatics — Chyle — Lymph — Absorbent system— Jl,ac ■ 
 teals and lymphatics — Absorption of fat — Its accumulation in the blood 
 during digestion — Its final decomposition and disappearance . . 162-174 
 
CONTENTS. Xm 
 
 CHAPTER VIII. 
 
 THE BILE. 
 
 PAGE 
 
 Physical properties of tlie bile — Its composition^— Blliverdine — Cholesterin — 
 Biliary salts — Their mode of extraction — Crystallization — Grlyko-cholate of 
 soda — Tanro-eholate of soda — Biliary salts in different species of animals 
 and in man — Tests for bile— Variations and functions of bile — Daily quan- 
 tity — Time of its discharge into intestine — Its disappearance from the ali- 
 mentary canal-^Its reabsorption — Its ultimate decomposition . . 175-199 
 
 CHAPTER IX. 
 
 FORMATION OF SUGAR IN THE LIVER. 
 
 Existence of sugar in liver of all animals — Its percentage — Internal origin of 
 liver-sugar — Its production after death — Glycogenic matter of the liver — Its 
 properties and composition — Absorption of liver-sugar by hepatic veins — 
 Its accumulation in the blood during digestion — Its final decomposition and 
 disappearance ........ 200-207 
 
 CHAPTER X. 
 
 THE SPLEEN. 
 
 Capsule of Spleen — Variations in size of the organ — Its internal structure — 
 Malpighian bodies of the spleen — Action of spleen on the blood — Effect 
 of its extirpation ....... '208-212 
 
 CHAPTER XI. 
 
 "^ THE BLOOD. 
 
 Red Globules of the blood — Their microscopic characters — Structure and com- 
 position — Variations in size in different animals — White Globdlbs of the 
 blood — Independence of the two kinds of blood-globules — Plasma — Its com- 
 position — Fibrin — Albumen — Fatty matters — Saline ingredients — Extractive 
 matters — Coagulation of the Blood — Separation of clot and semm — Influ- 
 ences hastening or retarding coagulation — Coagulation not a commencement 
 of organization — Formation of bnffy coat — Entire quantity of blood in body 
 
 213-231 
 
 CHAPTER XII. 
 
 RESPIRATION. 
 
 Respiratory apparatus of aquatic and air-breathing animals — Structure of 
 lungs in human subjects — Respiratory movements of chest — Of glottis — 
 Changes in the air during respiration — Changes in the blood — Proportions 
 of oxygen and carbonic acid, in venous and arterial blood — Solution of gases 
 by the blood-globules — Origin of carbonic acid in the blood — Its mode of 
 production — Quantity of carbonic acid exhaled from the body — Variations 
 according to age, sex, temperature, &c. — Respiration by the skin . 232-252 
 
S;iV CONTENTS. 
 
 CHAPTER XIII. 
 
 ANIMAL HEAT. 
 
 PAGE 
 
 Standard temperature of animals — How maintained — Production of heat by 
 Vegetables — Mode of generation of animal heat — Theory of combustion — 
 Objections to this theory — No oxidation in vegetables during production of 
 heat — Quantities of oxygen and carbonic acid in animals do not correspond 
 ■with each other — Production of animal heat a local process — Depends on 
 the chemical phenomena of nutrition . . . . • 253-263 
 
 CHAPTER XIV. 
 
 THE CIRCULATION. 
 
 Giroulatory apparatus of fish — Of reptiles — Of mammalians — Course of blood 
 through the heart— Action of valves — Sounds of heart — Movements — Im- 
 pulse — Successive pulsations — Arterial system — Movement of blood through 
 the arteries — Arterial pulse — Arterial pressure — Rapidity of arterial circula- 
 tion — The veins — Causes of movement of blood in the veins — Rapidity of 
 venous current — Capillary circulation — Phenomena and causes of capillary 
 circulation — Rapidity of entire circulation — Local variations in different 
 parts ......... 264-306 
 
 CHAPTER XV. 
 
 IMBIBITION AND EXHALATION. — THE LYMPHATIC SYSTEM. 
 
 Endosmosis and exosmosis — Mode of exhibiting them — Conditions which regu- 
 late their activity — Nature of the membrane — Extent of contact — Constitu- 
 tion of the liquidS-^Temperature — Pressure — Nature of endosmosis — Its 
 conditions in the living body— Its rapidity— Phenomena of endosmosis in 
 the circulation — The lymphatics — Their origin — Constitution of the lymph 
 and ehyle— Their quantity— Liquids secreted and jreabsorbed in twenty- 
 four hours ........ 307-323 
 
 CHAPTER XVI. 
 
 SECRETION. 
 
 Nature of secretion — Variations in activity — Mucus — Sebaceous matter Its 
 
 varieties — Perspiration — Structure of perspiratory glands — Composition and 
 quantity of the perspiration— Its use in regulating the animal temperature- 
 Tears — Milk— Its acidification— Secretion of bile — Anatomical peculiarities 
 
 324-340 
 
COXTENTS. XT 
 
 CHAPTER XYII. 
 
 EXCRETION. 
 
 PAGE 
 Nature of excretion — Exorementitious substances — Effect of their retention — 
 Urea — Its source — Couversiou into carbonate of ammonia — Dally quantity 
 of urea — Creatine — Creatinine — Urate of soda — Urates of potassa and ammo- 
 nia — General characters of the urine — Its composition — Variations — Acci- 
 dental Ingredients of the urine — Acid and alkaline fermentations — Final 
 decomposition of the urine . . . ' . . • 341-364 
 
 SECTION II. 
 NERVOUS SYSTEM. 
 
 CHAPTER I. 
 
 GENERAL CHARACTER AND FUNCTIONS OF THE NERVOUS SYSTEM. 
 
 Nature of the function performed by nervous system — Two kinds of neryous 
 tissue — Fibres of white substance — Their minute structure — Division and 
 inosculation of nerves — Gray substance — Nervous system of radiata — Of 
 moUusoa — Of artlculata — Of mammalia and human subject — Structure of 
 encephalon — Connections of its different parts . . . 365-?87 
 
 CHAPTER II. 
 
 OF NERVOUS IRRITABILITY, AND ITS MODE OF 'ACTION. 
 
 Irritability of muscles — How exhibited — Influences which exhausj; and destroy 
 it — Nervous irritability — How exhibited — Continues after death — Exhausted 
 by repeated excitement — Influence of direct and inverse electrical currents 
 — Nervous Irritability distinct from muscular irritability — Nature of the 
 nervous force — Its resemblance to electricity — Differences between the two 
 
 388-397 
 
 CHAPTER III. 
 
 THE SPINAL CORD. 
 
 Power of sensation — Power of motion — Distinct seat of sensation and motion 
 in nervous system — Sensibility and excitability — Distinct seat of sensibility 
 and excitability in spinal cord — Crossed action of spinal cord — Independent 
 and associated action of motor and sensitive filaments — Reflex action of 
 spinal cord — How manifested during disease — Influence in health on 
 sphincters, voluntary muscles, urinary bladder, &c. . . . 398-416 
 
XVI contents'. 
 
 CHAPTER IV. 
 
 THE BRAIN. 
 
 PAGE 
 
 Seat of sensibility and excitability in different parts of the encephalon — Olfac- 
 tory ganglia — Optic tlialami— Corpora striata — Hemispheres — Remarkable 
 cases of injury of hemispheres — Effect of their removal — Imperfect develop- 
 ment in idiots — Aztec children — Theory of phrenology — Cerebellum — Effect 
 of its injury or removal — Comparative development in different classes — 
 Tubercula quadrigemina — Tuber annulare— MeduUaoblongata — Three kinds 
 of reiiex action in nervous system ..... 417-445 
 
 CHAPTER V. 
 
 THE CRANIAL NERVES. 
 
 Olfactory nerves — Optic nerves — Auditory .nerves — Classification of cranial 
 nerves — Motor nerves — Sensitive nerves — Motor oeuli communis — Patheti- 
 cus — Motor externus — Fifth pair — Its sensibility — Effect of division — Influ- 
 ence on mastication — Influence on the organ of sight — Facial nerve— Effect 
 of its paralysis — Glosso-pharyngeal nerve — Pneumogastric — Its distribution 
 — Influence on phj^rynx and CBSophagus — On larynx — On lungs — On stomach 
 and digestion — Spinal accessory nerve — Hypoglossal . . . 446-477 
 
 CHAPTER VI. 
 
 THE SPECIAL SENSES. 
 
 General and special sensibility — Sense of touch in the skin and mucous mem- 
 branes — Nature of the special senses — Tastk — Apparatus of this sense — Its 
 conditions — Its resemblance to ordinary sensation — Injury to the taste in 
 paralysis of the facial nerve — Smell — Arrangement of nerves in nasal pas- 
 sages — Conditions of this sense — Distinction between odors and irritating 
 vaporsr-SiGHT— Structure of the eyeball — Special sensibility of the retina — 
 Action of the lens — Of the iris — Combined action of two eyes — Vivid nature 
 of the visual impressions — Hearino — Auditory apparatus — Action of mem- 
 brana tympani — Of chain of bones — Of their muscles — Appreciation of the 
 direction of sound — Analogies of hearing with ordinary sensation . 478-513 
 
 CHAPTER VII. 
 
 SYSTEM OF THE GREAT SYMPATHETIC. 
 
 Ganglia of the great sympathetic — Distribution of its nerves — Sensibility and 
 excitability of sympathetic — Sluggish action of this nerve — Influence over 
 organs of special sense — Elevation of temperature after division of sympa- 
 thetic — Contraction of pupil following the same operation — Reflex actions 
 taking place through the great sympathetic .... 514-524 
 
CONTENTS. 2V11 
 
 SECTION III. 
 REPRODUCTION. 
 
 CHAPTER I. 
 
 ON THE NATURE OP EEPRODUOTION, AND THE ORIGIN OF PLANTS AND 
 
 ANIMALS. 
 
 PAGE 
 
 Nature and objectg of the function of reproduction — Mode of its accomplish- 
 ment — By generation from parents — Spontaneous generation — Mistaken in- 
 stances of this mode of generation — Production of inffisoria — Conditions of 
 their development — Schultze's experiment on generation of infusoria — Pro- 
 duction of animal and vegetable parasites — Encysted entozoa — Trichina 
 spiralis' — Taenia, — Cysticerous — Production of taenia from oysticercus — Of 
 cysticercus from eggs of taenia — Plants and animals always produced by 
 generation from parents ...... 525-539 
 
 CHAPTER II. 
 
 ON SEXUAL (^ENERATION AND THE MODE OP ITS ACCOMPLISHMENT. 
 
 Sexual apparatus of plants — Fecundation of the germ — Its development into 
 a new plant — Sexual apparatus of animals — Ovaries and testicles — Uni- 
 sexual and bisexual species — Distinctive characters of the two sexes 640-543 
 
 CHAPTER III. 
 
 ON THE EGG, AND THE PEMALE ORGANS OP GENERATION. 
 
 Size and appearance of the egg — Vitelline membrane — Vitellus — Germinative 
 vesicle — Germinative spot — Ovaries — Graafian follicles — Oviducts — Female 
 generative organs of frog — Ovary and oviduct of fowl — Changes in the egg, 
 while passing through the oviduct — Complete fowl's egg — Uterus and ova- 
 ries of the sow — Female generative apparatus of the human subject — Fal- 
 lopian tubes — Body of the uterus — Cervix of the uterus . . 644-555 
 • 
 
 CHAPTER IV. 
 
 ON THE SPERMATIC PLUID, AND THE MALE ORGANS OP GENERATION. 
 
 The spermatozoa — Their varieties in different species — Their movement — For- 
 mation of spermatozoa in the testicles — Accessory male organs ol^eneration 
 — Epididymis — Vas deferens — Vesiculae seminales — Prostate — Cowper's 
 glands — Function of spermatozoa — Physical conditions of fecundation 556-562 
 
 2 • 
 
XVIU CONTENTS. 
 
 CHAPTER V. 
 
 t 
 
 I ON PEKIODICAL OVULATION, AND THE FUNCTION OF MENSTRUATION. 
 
 . PAGE 
 
 Periodioai, Ovulatioit — Pre-existence of eggs in the ovaries of all animals — 
 Their Increased development at the period of puberty— Their successive 
 ripening and periodical discharge — Discharge of eggs independently of sexual 
 intercourse — Rupture of Graafian follicle, and expulsion of the egg — Pheno- 
 mena of oestruation — Menstkuation — Correspondence of menstrual periods 
 with periods of ovulation in the lower animals — Discharge of egg during 
 menstrual period — Conditions of its impregnation, after leaving the ovary 
 
 663-575 
 
 CHAPTER VI. 
 
 ON THE CORPUS LUTEUM OF MENSTKUATION AND PREGNANCY. 
 
 CoEPtJS LvTEum. OP Menstritation — Discharge of blood into the ruptured Graafian 
 follicle — Deoolorization of the clot, and hypertrophy of the membrane of the 
 vesicle — Corpus luteum of menstruation, at the end of three weeks^Tellow 
 coloration of convoluted wall — Corpus luteum of menstruation at the end 
 of four weeks — Shrivelling and condensation of Its tissues; — Its condition p,i 
 the end of nine weeks — Its final atrophy and disappearance^CoEpus Lcteum 
 OF Presnakcy — Its continued development after the third week — Appearance 
 at the end of second month — Of fourth month — At the termination of preg- 
 nancy — Its atrophy and disappearance after delivery — Distinctive characters 
 of corpora lutea of menstruation and pregnancy . f . 576-585 
 
 CHAPTER VII. 
 
 ON THE DEVELOPMENT OF THE IMPREGNATED EGGi. 
 
 Segmentation of the vitellus — Formation of blastodermic membrane — Two 
 layers of blastodermic membralie — Thickening of external layer — Formation 
 of primitive trace — Dorsal plates — Abdominal plates — Closure of dorsal and 
 abdominal plates on the median line — Formation of intestine — Of mouth 
 and anus — Of organs of locomotion^Continued development of organs, after 
 leaving the egg ........ 586-595 
 
 CHAPTER VIII. 
 
 THE UMBILICAL VESICLE. 
 
 Separation of vitelline sac into two cavities — Closure of abdominal walls and 
 formation of umbilical vesicle in fish — Mode of its disappearance after hatch- 
 ing — Umbilical vesicle in human embryo — Formation and growth of pedicle 
 — Disappearance of umbilical vesicle during embryonic life . . 696-598 
 
CONTENTS. XIX 
 
 CHAPTER IX. 
 
 AMNION AND ALLANTOIS — DEVELOPMENT OP THE CHICK. 
 • PAGE 
 
 Necessity for accessory organs iu the development of birds and quadrupeds — 
 Formation of amniotic folds — TJieir union and adhesion — Growth of allantois 
 from lower part of intestine — Its vascularity — Allantois iu the egg of the - 
 fowl — Respiration of the egg — Absorption of calcareous matter from the 
 shell — Ossification of skeleton — Fracture of egg-shell — Casting off of amnion 
 and allantois ........ 599-607 
 
 CHAPTER X. 
 
 DEVELOPMENT OF THE EGG IN THE HUMAN SPECIES — FORMATION OF THE 
 
 CHORION. 
 
 Conversion of allantois into chorion — Subsequent changes of the chorion — 
 Its villosities — Formation of bloodvessels in vUlosities — Action of villi of 
 chorion in providing for nutrition of foetus — Proofs that the chorion is formed 
 from the allantois — Partial disappearance of villosities of chorion, and 
 changes in its external surface ...... 608-613 
 
 CHAPTER XI. 
 
 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE — FORMATION OF THE 
 
 DECIDUA. 
 
 Structure of uterine mucous membrane — Uterine tubules — Thickening of ute- 
 rine mucous membrane after impregnation — Decidua vera — Entrance of egg 
 into uterus — Deoidua reflexa — Inclosure of egg by decidua reflexa — Union 
 of chorion with decidua — Changes in the relative development of different 
 portions of chorion and decidua ..... 614-620 
 
 CHAPTER XII. 
 
 THE PLACENTA. 
 
 Nourishment of foetus by maternal and foetal vessels — Arrangementof the 
 vascular membranes in different species of animals — Membranes of foetal 
 pig — Cotyledon of cow's uterus — Development of foetal tufts in human pla- 
 centa — Development of uterine sinuses — Relation of foetal and maternal 
 bloodvessels in the' placenta — Proofs that the maternal sinuses extend 
 through the whole thickness of the placenta — Absorption and exhalation 
 by the placental vessels ...... 621-629 
 
XX CONTENTS. 
 
 CHAPTER XIII 
 
 DISCHARGE OF THE OVUM, AND INVOLUTION OF THE UTERUS. 
 
 ' PAG» 
 
 Enlargement of amniotic cavity— Contact of amnion and chorion— Amniotic 
 fluid— Movements of fcetus- Union of deoidua vera and reflexa— Expulsion 
 of the ovum and discharge of decidual membrane— Separation of the pla- 
 centa — Formation of new mucous membrane underneath the old deoidua 
 Fatty degeneration and reconstruction of muscular -walls of uterus 630-636 
 
 CHAPTER XIV. 
 
 DEVELOPMENT OP THE EMBRYO — NERVOUS SYSTEM, ORGANS OP SENSE, 
 SKELETON AND LIMlBS. 
 
 Formation'of spinal cord and cerebro-spinal axis — Three cerebral vesicles — 
 Hemispheres — Optic thalami — Tubercula quadrigemina — Cerebellum — Me- 
 dulla oblongata — Eye — Pupillary membrane — Skeleton — Chorda dorsalis — 
 Bodies of the vertebrse— Laminae and ribs— Spina bifida — Anterior and pos- 
 terior extremities — Tail — Integument — Hair — Vernix caseosa — Exfoliation 
 of epidermis ........ 637-643 
 
 CHAPTER XT. 
 
 DEVELOPMENT OF THE ALIMENTARY CANAL AND ITS APPENDAGES. 
 
 Formation of intestine — Stomach — Duodenum — Convolutions of intestine — 
 Large and small intestine— Caput coli and appendix vermiformis — Umbi- 
 lical hernia — Formation of urinary bladder — Uraohus — Vesico-rectal septum 
 — Perineum — Liver — Secretion of bile — Gastric juice — Meconium — Glyco- 
 genic function of liver — Diabetes of foetus — Bharynx and oesophagus — Dia- 
 phragm — Diaphragmatic hernia — Heart and pericardium — Ectopia cordis — 
 Development of the face ...... 644-654 
 
 CHAPTER XYI, 
 
 DEVELOPMENT OF THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL ORGANS 
 * OF GENERATION. 
 
 Wolflan bodies — Their structure — First appearance of kidneys — Growth of 
 kidneys, and atrophy of Wolffian bodies — Testicles and ovaries — Descent of 
 the testicles — Tunica vaginalis testis — Congenital inguinal hernia — Descent 
 of the ovaries— Development of the uterus .... 655-664 
 
CONTENTS. XXI 
 
 CHAPTER XVII. 
 
 DEVELOPMENT OF THE CIRCULATORY APPARATUS. 
 
 PAGE 
 
 First, or vitelline circulation — Area vasculosa — Sinus terminalis — Vitelline 
 circulation of fish — Arrangement of arteries and veins in body of foetus — 
 Second, or placental circulation — Omphalo-mesenterio arteries and vein-^- 
 Ciroulation of the umbilical vesicle — Of the allantois and placenta — Umbi- 
 lical arteries and veins — Third, or adult circulation — Portal and pulmonary 
 systems — Development of the arterial system — Development of the venous 
 system — Changes in the hepatic circulation — Portal vein — Umbilical vein 
 — Ductus venosuS''— Changes in the cardiac circulation — Division of heart 
 into right and left cavities-r-Aorta and pulmonary artery — Ductus arteriosus 
 — Foramen ovale and Eustachian valve — Changes in circulation at the 
 period of birth 665-686 
 
 CHAPTER XVIII. 
 
 DEVELOPMENT OF THE BODY AFTER BIRTH. 
 
 Condition of foetus at birth — Gradual establishment of respiration — Inactivity 
 of the animal functions — .Preponderance of reflex actions in the nervous 
 system — peculiarities in the action of drugs on infant — Difference in relative 
 size of organs, in infant and adult — Withering and separation of umbilical 
 cord — Exfoliation of epidermis — First and second sets of teeth — Subsequent 
 changes in osseous, muscular and tegumentary systems, and general devel- 
 opment of the body . 687-690 
 
LIST OF ILLUSTRATIONS, 
 
 ALL OF WHICH HAVE BEEN PEEPAEED PBOM OEIMNAL DBAWINOS, WITH THE 
 EXCEPTION OF TEN, CREDITED TO THEIR AUTHOEITIES. 
 
 FIO. 
 
 1. Fibula tied in a knot, after maceration in a dilate acid 
 
 2. Grains of potato starcK . 
 
 3. Starch grains of Bermuda arrowroot 
 
 4. Starch grains of wheat flour 
 
 5. Starch grains of Indian com 
 ^. Starch grains from wall of lj,teral ventricle 
 
 7. Stearine .... 
 
 8. Oleaginous principles of human fat 
 
 9. Human adipose tissue 
 
 10. Chyle 
 
 11. Gclohulea of cow's milk 
 
 12. Cells of costal cartilages 
 
 13. Hepatic cells 
 
 14. Uriniferous tubules of dog 
 
 15. Muscular fibres of human uterus 
 
 16. Alimentary canal of fowl 
 
 17. Compound stomach of ox 
 
 18. Human alimentary canal 
 
 19. Skull of rattlesnake 
 
 20. Skull of polar bear 
 
 21. Skull of the horse 
 
 22. Molar tooth of the horse 
 
 23. Human teeth — upper jaw 
 
 24. Buccal and glandular epithelium deposited from saliva . 
 
 25. Gastric mucous membrane, viewed from above . 
 
 26. Gastric mucous membrane, in vertical section . 
 
 27. Mucous membrane of pig's stomach 
 
 28. Gastric tubules from pig's stomach, pyloric portion 
 
 29. Gastric tubules from pig's stomach, cardiac portion 
 
 30. Confervoid vegetable, growing in gastric juice . 
 
 31. Follicles of Lieberkiihn . . . . . 
 
 32. Brunner'a duodenal glands . . . . 
 
 33. Contents of stomach, during digestion of meat . 
 
 34. From duodenum of dog, during digestion of meat 
 
 35. From middle of small intestine . . . . 
 
 From Rymer Jones 
 
 From Aohille 
 
 Richard 
 
 PAGE 
 
 75 
 
 .80 
 
 80 
 
 81 
 
 81 
 
 82 
 
 87 
 
 88 
 
 90 
 
 90 
 
 91 
 
 91 
 
 92 
 
 92 
 
 93 
 
 117 
 
 118 
 
 119 
 
 121 
 
 122 
 
 122 
 
 122 
 
 123 
 
 124 
 
 133 
 
 133 
 
 134 
 
 134 
 
 134 
 
 140 
 
 151 
 
 152 
 
 158 
 
 158 
 
 159 
 
 XXUl 
 
XXIT 
 
 LIST OF ILLUSTKATIONS. 
 
 36. From last quarter of small intestine 
 
 37. One of the closed follicles of Peyer's patches 
 
 38. Grlandulse agminatse 
 
 39. Extremity of intestinal villus 
 
 40. Panizza's experiment on absorption by bloodvessels 
 
 41. Chyle, from commencement of thoracic duet 
 
 42. Laoteals, thoracic duct, &c. 
 
 43. Lacteals and lymphatics . 
 
 44. Intestinal epithelium, in intervals of digestion 
 
 45. Intestinal epithelium, during digestion . 
 
 46. Cholesterin .... 
 
 47. Ox-bile, crystallized 
 
 48. Glyko-oholate of soda from ox-bile 
 
 49. Glyko-oholate and tauro-cholate of soda, from ox-bile 
 
 50. Dog's bile, crystallized 
 51.* Human bile, showing resinous matters . 
 
 52. Crystalline and resinous biliary substances, from dog's intestine 
 
 53. Duodenal fistula .... 
 
 54. Human blood-globules 
 
 55. The same, seen out of focus 
 
 56. The same, seen within the focus . 
 
 57. The same, adhering together in rows 
 
 58. The same, swollen by addition of water 
 
 59. The same, shrivelled by evaporation 
 
 60. Blood-globules of frog 
 
 61. White globules of the blood . • 
 
 62. Coagulated fibrin .... 
 
 63. Coagulated blood .... 
 
 64. Coagulated blood, after separation of clot and serum 
 
 65. Recent coagulum .... 
 
 66. Coagulated blood, clot buffed and cupped 
 
 67. Head and gills of menobranchus . 
 
 68. Lung of frog . . ♦ . 
 
 69. Human larynx, trachea, bronchi, and lungs 
 
 70. Single lobule of human lung 
 
 71. Diagram illustrating the respiratory movements 
 
 72. Small bronchial tube 
 
 73. Human larynx, with glottis closed 
 
 74. The same, with glottis open 
 
 75. Human larynx — posterior view . 
 
 76. Circulation of fish 
 
 77. Circulation of reptiles 
 
 78. Circulation of mammalians 
 
 79. Human heart, anterior view 
 
 80. Human heart, posterior view 
 
 81. Right auricle and ventricle, tricuspid valve open, arterial valves closed 
 
 82. Right auricle and ventricle, tricuspid valve closed, arterial valves open 
 
 83. Course of blood through the heart . . . . . 
 
 84. Illustrating production of valvular sounds .... 
 
 85. Heart of frog, in relaxation ...... 
 
LIST OF ILLUSTRATIONS. 
 
 XXV 
 
 PIG. 
 
 86. 
 
 87. 
 88. 
 
 91. 
 
 92. 
 
 93. 
 
 94. 
 
 95. 
 
 96. 
 
 97. 
 
 98. 
 
 99. 
 100. 
 101. 
 102. 
 103. 
 104. 
 105. 
 106. 
 107. 
 108. 
 109. 
 110. 
 111. 
 112. 
 113. 
 114. 
 115. 
 116. 
 117. 
 118. 
 119. 
 120. 
 121. 
 122. 
 123. 
 124. 
 125. 
 126. 
 127. 
 128. 
 129. 
 130. 
 131. 
 132. 
 133. 
 134. 
 136. 
 
 Heart of frog, in contraction 
 
 Simple looped fibres .... 
 
 Bullock's heart, showing superficial muscular fibres 
 
 Left ventricle of bullo'ek's>Tieart, showing deep fibres 
 
 Diagram of circular fibres of the heart 
 
 Converging fibres of the apex of the heart 
 
 Arterj in pnlsation 
 
 Curves of the arterial pulsation 
 
 Volkmann's apparatus . 
 
 The same .... 
 
 Vein, with valves open . 
 
 Vein, with valves closed 
 
 Small artery, with capillary branches . 
 
 Capillary network 
 
 Capillary circulation 
 
 Diagram of the circulation 
 
 Follicles of a compound mucous glandule 
 
 Meibomian glands 
 
 Perspiratory gland . .n 
 
 Glandular structure of mamma 
 
 Colostrum corpuscles 
 
 Milk-globules .... 
 
 Division of portal vein in liver 
 
 Lobule of liver 
 
 Hepatic cells 
 
 Urea .... 
 
 Creatine 
 
 Creatinine 
 
 Urate of soda 
 
 Uric acid 
 
 Oxalate of lime . 
 
 Phosphate of magnesia and ammonia 
 
 Nervous filaments, from brain . 
 
 Nervous filaments from sciatic nerve 
 
 Division of a nerve 
 
 Inosculation of nerves . 
 
 Nerve cells . . • . 
 
 Nervous system of starfish 
 
 Nervous systemuaf aplysia 
 
 Nervous system of centipede 
 
 Cerebro-spinal system of man . 
 
 Spinal cord 
 
 Brain of alligator 
 
 Brain of rabbit 
 
 Medulla oblongata of human brain 
 
 Diagram of human b>ain 
 
 Experiment showing irritability of muscles 
 
 Experiment showing irritability of nerve 
 
 Action of direct and inverse currents 
 
 Diagram of spinal cord and nerves 
 
 From KoUiker 
 
 From Ludovic 
 
 From Todd and Bowman 
 
 From Lehmann (Funke's Atlas) 
 From Lehmann (Funke's Atlas) 
 From Lehmann (Fnnke's Atlas) 
 
XXVI 
 
 LIST OF ILLUSTEATIONS. 
 
 PIG. 
 
 136. Spinal oord in vertical section 
 
 137. Experiment, showing effect of poisons upon nerves 
 
 138. Pigeon, after removal of the hemispheres 
 
 139. Aztec children 
 
 140. Brain in situ .... 
 
 141. Transverse section of brain 
 
 142. Pigeon, after removal of the cerebellum 
 
 143. Brain of healthy pigeon in profile 
 
 144. Brain of operated pigeon in profile 
 
 145. Brain of healthy pigeon, posterior view 
 
 146. Brain of operated pigeon, posterior view 
 
 147. Inferior surface of brain of cod 
 
 148. Inferior surface of brain of fowl . 
 
 149. Course of optic nerves in man . 
 
 150. Distribution of fifth nerve upon the face 
 
 151. Facial nerve .... 
 
 152. Pneumogastrie nerve 
 
 153. Diagram of tongue 
 
 154. Distribution of nerves in the nasal passages 
 
 155. Vertical section of eyeball 
 
 156. Dispersion of rays of light 
 
 157. Action of crystalline lens 
 
 158. Myopia ...... 
 
 159. Presbyopia .... 
 
 160. Vision at short distance 
 
 161. Vision at long distance . 
 
 162. Eefraotion of lateral rays 
 
 163. Skull, as seen by left eye 
 
 164. Skull, as seen by right eye 
 
 165. Human auditory apparatus 
 
 166. Great sympathetic 
 
 167. _Cat, after division of sympathetic in the neck 
 
 168. Different kinds of infusoria 
 
 169. Experiment on spontaneous generation 
 
 170. Trichina spiralis 
 
 171. Taenia ..... 
 
 172. Cystieercus, retracted . . . • 
 
 173. Cystieercus, unfolded 
 
 174. Blossom of Convolvulus purpureus 
 
 175. Single articulation of Taenia crassicollis 
 
 176. Human ovum ... 
 
 177. Human ovum, ruptured by pressure 
 
 178. Female generative organs of frog 
 
 179. Mature frogs' eggs ... 
 
 180. Female generative organs of fowl 
 
 181. Fowl's egg ... . 
 
 182. Uterus and ovaries of the sow . 
 
 183. Generative organs of human female 
 
 184. Spermatozoa 
 
 185. Graafian follicle .... 
 
 From 
 
 Sehultze 
 
LIST OF ILLUSTRATIONS. 
 
 XXTll 
 
 pie. 
 
 186. Ovary with Graafian follicle ruptured . 
 
 187. Graafian follicle, ruptured and filled with blood 
 
 188. Corpus luteum, three weeks after menstruation 
 
 189. Corpus luteum, four weeks after menstruation 
 
 190. Corpus luteum, nine weeks after menstruation 
 
 191. Corpus luteum of pregnancy, at end of second month 
 
 192. Corpus luteum of pregnancy, at end of fourth month 
 
 193. Corpus luteum of pregnancy, at term . 
 
 194. Segmentation of the vitellus 
 
 195. Impregnated egg, showing embryonic spot 
 
 196. Impregnated egg, showing two layers of blastodermic membrane 
 
 197. Impregnated egg, farther advanced 
 
 198. Prog's egg, at an early period . 
 
 199. Egg of frog, in process of development 
 
 200. Egg of frog, farther advanced 
 
 201. Tadpole, fully developed 
 
 202. Tadpole, changing into frog 
 
 203. Perfect frog 
 
 204. Egg of fish 
 
 205. Young fish, with umbilical vesicle 
 
 206. Human embryo, with umbilical vesicle 
 
 207. Fecundated egg, showing formation of amnion . 
 
 208. Fecundated egg, showing commencement of allantois 
 
 209. Fecundated egg, with allantois nearly complete 
 
 210. Fecundated egg, with allantois fully formed 
 
 211. Egg of fowl, showing area vasoulosa 
 
 212. Egg of fowl, showing allantois, amnion, &c. 
 
 213. Human ovum, showing formation of chorion 
 
 214. Compound villosity of human chorion 
 
 215. Extremity of villosity of chorion 
 
 216. Human ovum, at end of third month . 
 
 217. Uterine mucous membrane 
 
 218. Uterine tubules .... 
 
 219. Impregnated uterus, showing formation of decidua 
 
 220. Impregnated uterus, showing formation of decidua reflexa 
 
 221. Impregnated uterus, with decidua reflexa complete 
 
 222. Impregnated uterus, showing union of chorion and decidua 
 
 223. Pregnant uterus, showing formation of placenta 
 
 224. Foetal pig, with membranes 
 
 225. Cotyledon of cow's uterus 
 
 226. Extremity of foetal tuft, human placenta 
 
 227. Foetal tuft of human placenta injected 
 
 228. Vertical section of placenta 
 
 229. Human ovum, at end of first month 
 
 230. Human ovum, at end of third month . 
 
 231. Gravid human uterus and contents 
 
 232. Muscular fibres of unimpregnated uterus 
 
 233. Muscular fibres of human uterus, ten days after parturition 
 
 234. Muscular fibres of human uterus, three weeks after parturition 
 236. Formation of cerebro-spinal axis .... 
 
XXVIU 
 
 LIST OF ILLUSTKATIONS. 
 
 pia. 
 
 236. Formation of cerebro-spinal axis 
 
 237. Foetal pig, showing brain and spinal cord 
 
 238. FcEtal pig, showing brain and spinal oord 
 
 239. Head of foetal pig ... . 
 
 240. Brain of adult pig .... 
 
 241. Formation of alimentary canal . 
 
 242. Foetal pig, showing Umbilical hernia 
 
 243. Head of human embryo, at twenty days 
 
 244. Head of human embryo, at end of sixth week . 
 
 245. Head of human embryo, at end of second month 
 
 246. Foetal pig, showing Wolffian bodies 
 
 247. Foetal pig, showing first appearance of kidneys 
 
 248. Internal organs of generation 
 
 249. Internal organs of generation . 
 
 250. Formation of tunica vaginalis testis 
 
 251. Congenital Inguinal hernia . . 
 
 252. Egg of fowl, showing area vasculosa 
 
 253. Egg of fifih, showing vitelline circulation 
 
 254. Young embryo and its vessels . 
 
 255. Embryo and its vessels, farther advanced 
 
 256. Arterial system, embryonic form . ' . 
 
 257. Arterial system, adult form 
 
 258. Early condition of venous system 
 
 259. Venous system, farther advanced 
 
 260. Continued development of venous system 
 
 261. Adult condition of venous system 
 
 262. Early form of hepatic circulation 
 
 263. Hepatic circulation farther advanced 
 
 264. Hepatic circulation, during latter part of foetal life 
 
 265. Adult form of hepatic circulation 
 
 266. Foetal heart 
 . 267. Foetal heart 
 
 268. Foetal heart 
 
 269. Foetal heart 
 
 270. Heart of infant 
 
 271. Heart ef human foetus, showing Eustachian valve 
 
 272. Circulation through the foetal heart 
 
 273. Adult circulation through the heart 
 
 From 
 
 Longet 
 
 PASE 
 
 638 
 
 638 
 
 639 
 
 639 
 
 639 
 
 645 
 
 646 
 
 652 
 
 652 
 
 653 
 
 655 
 
 657 
 
 657 
 
 659 
 
 660 
 
 661 
 
 666 
 
 666 
 
 667 
 
 668 
 
 670 
 
 670 
 
 672 
 
 673 
 
 673 
 
 674 
 
 675 
 
 676 
 
 676 
 
 677 
 
 678 
 
 678 
 
 678 
 
 679 
 
 679 
 
 681 
 
 682 
 
 685 
 
HUMAN PHYSIOLOGY. 
 
 INTRODUCTION. 
 
 * 
 
 I. Physiology is the study of the phenomena presented by 
 organized bodies, animal and vegetable. 
 
 These phenomena are different from those presented by inorganic 
 substances. They require, for their production, the existence of 
 peculiarly formed animal and vegetable organisms, as well as the 
 presence of various external conditions, such as warmth, light, air, 
 moisture, &c. 
 
 They are accordingly more complicated than the phenomena of 
 the. inorganic world, and require for their study, not only a pre- 
 vious acquaintance with the laws of chemistry and physics, but, in 
 addition, a careful examination of other characters which are pecu- 
 liar to them. 
 
 These peculiar phenomena, by which we so readily distinguish 
 living organisms from inanimate substances, are called Vital pheno- 
 mena, or the phenomena of Life. Physiology consequently includes 
 the study of all these phenomena, in whatever order or species of 
 organized body they may originate. 
 
 "We find, however, upon examination, that there are certain 
 general characters by which the vital phenomena of vegetables 
 resemble each other, and by which they are distinguished from the 
 vital phenomena of animals. Thus, vegetables absorb carbonic 
 acid, and exhale oxygen ; animals absorb oxygen, and exhale car- 
 bonic acid. Vegetables nourish themselves by the absorption of 
 unorganized liquids and gases, as water, ammonia, saline solutions, 
 &c.; animals require for their support animal or vegetable sub- 
 stances as food, such as meat, fruits, milk, &c. Physiology, then, 
 4 ( 49 ) 
 
50 INTRODUCTION. 
 
 is naturally divided into two parts, viz., Vegetable Physiology, and 
 Animal Physiology. 
 
 Again, the different groups and species of animals, while they 
 resemble each other in their general characters, are distinguished 
 by certain minor differences, both of structure and function, which 
 require a special study. Thus, the physiology of fishes is not 
 exactly/* the same with that of reptiles, nor the physiology of birds 
 with that of quadrupeds. Among the warm-blooded quadrupeds, 
 the carnivora absorb more oxygen, in proportion to the carbonic 
 acid exhaled, than the herbivora. Among the herbivorous quad- 
 rupeds, the process of digestion is comparatively simple in the 
 horse, while it is complicated in the ox, and other ruminating ani- 
 mals. There is, therefore, a special physiology for every distinct 
 species of animal. 
 
 Human Physiology treats of the .vital phenomena of the human 
 species. It is more practically important than the physiology of 
 the lower animals, owing to its connection with human pathology 
 and therapeutics. But it cannot be made the exclusive subject of 
 our study ; for the special physiology of the human body cannot 
 be properly understood without a previous acquaintance with the 
 vital phenomena common to all animals, and to all vegetables; 
 beside which, there are many physiological questions that require 
 for their solution experiments and observations, which can only be 
 made upon the lower animals. 
 
 While the following^ treatise, therefore, has for its principal sub- 
 ject the study of Human Physiology, this will be illustrated, when- 
 ever it may be required, by what we know in regard to the vital 
 phenomena of vegetables and of the lower animals. 
 
 II. Since Physiology is the study of the active phenomena of 
 living bodies, it requires a previous acquaintance with their struc- 
 ture, and with the substances of which they are composed; that is, 
 with their anatomy. 
 
 Anatomy, again, requires a previous acquaintance with inorganic 
 substances ; since some of these inorganic substances enter into the 
 composition of the body. Chloride of sodium, for example, water, 
 and phosphate of lime, are component parts of the animal frame, 
 and therefore require to be studied as such by the anatomist. 
 Now these inorganic substances, when plaped under the requisite , 
 external conditions, present certain active phenomena, which are 
 characteristic of them, and by which they may be recognized. 
 
INTHODUCTIOX. 51 
 
 Thus lime, dissolved in water, if brought into contact with car- 
 bonic acid, alters its condition, and takes part in the formation of 
 an insoluble substance, carbonate of lime, which is thrown down 
 as a deposit. A knowledge of such chemical reactions as these is 
 necessary to the anatomist, since it is by them that he is enabled to 
 recognize the inorganic substances, forming a part of the animal 
 body. 
 
 It is important to observe, however, that a knowledge of these 
 reactions is necessary to the anatomist only in order tp enable him 
 to judge of the presence or absence of the inorganic substances to 
 which they belong. It is the object of the anatomist to make him- 
 self acquainted with every constituent part of the body. Those 
 parts, therefore, which cannot be recognized by their form and 
 texture, he distinguishes by their chemical reactions. But after- 
 ward, he has no occasion to decompose them further, or to make 
 them enter into new combinations ; for he only wishes to know 
 these substances as they exist in the body, and not as they may exist 
 under other conditions. 
 
 The unorganized substances which exist in the body as .compo- 
 nent parts of its structure, such as chloride of sodium, water, phos- 
 phate of lime, &o., are called the proximate principles of the body. 
 Mingled together in certain proportions, they make up the animal 
 fluids, and associated also in a solid form, they constitute the tissues 
 and organs, and in this way make up the entire frame. 
 
 Anatomy makes us acquainted with all these component parts of 
 the body, both solid and fluid. It teaches us the structure of the 
 body in a state of rest ; that is, just as it would be after life had 
 suddenly ceased, and before putrefaction had begun. On the other 
 hand, Physiology is a description of the body in a state of activity. 
 It shows us its movements, its growth, its reproduction, and the 
 chemical changes which go on in its interior ; and in order to com- 
 prehend these, we must know, beforehand, its entire mechanical, 
 textural, and chemical structure. 
 
 It is evident, therefore, that the description of the proximate prin- 
 ciples, or the chemical substances entering into the constitution of 
 the body, is, strictly speaking, a part of Anatomy. But there are 
 many reasons why this study is more conveniently pursued in con- 
 nection with Physiology; for some of the proximate principles are 
 derived directly, as we shall hereafter show, from4he external world, 
 and some are formed from the elements of the food in the process 
 of digestion ; while most of them undergo certain changes in the 
 
52 INTRODUCTIOlSr. 
 
 interior of the body, which result in the formation of new sub- 
 stances ; all these active phenomena belonging necessarily to the 
 domain of Physiology. 
 
 The description of the proximate principles of animals and vege- 
 tables will therefore be introduced into the following pages. 
 
 The description of the minute structures of the body, or Micro- 
 scopic Anatomy, is also so closely connected with some parts of Phy- 
 siology as to make it convenient to speak of them together ; and 
 this will accordingly be done, whenever the nature of the subject 
 may make it desirable. 
 
 III. The study of Physiology, like that of all the other natural 
 sciences, is a study of phenomena, and of phenomena alone. The 
 essential nature of the vital processes, and their ultimate causes, 
 are questions which are beyond the reach of the physiologist, and 
 cannot b§ determined by the means of investigation which are at 
 his disposal. 
 
 Consequently, all efforts to- solve them will only serve to mislead 
 the investigator, and to distract his attention from the real subject 
 of examination. Much time has been lost, for example, in discuss- 
 ing the probable reason why menstruation returns, in the human 
 female, at the end of every four weeks. But the observation of 
 nature, which is our only means of scientific investigation, cannot 
 throw any light on this point, but only shows us the fact that men- 
 struation does really occur at the above periods, together with the 
 phenomena which accompany it, and the conditions under which it 
 is hastened or retarded, and increased or diminished, in intensity, 
 duration, &c. If we employ ourselves, consequently, in the discus- 
 sion of the reason above mentioned, we shall only become involved 
 in a network of hypothetical surmises, which can never lead to any 
 definite result. Our time, therefore, will be much more profitably 
 devoted to the study of the above phenomena, which can be learned 
 from nature, and which constitute afterward, a permanent acquisi- 
 tion. 
 
 The physiologist, accordingly, confines himself strictly to the 
 study of the vital phenomena, their characters, their frequency, 
 their regularity or irregularity, and the conditions under which 
 they originate. 
 
 When he has discovered that a certain phenomenon always takes 
 place in the presence of certain conditions, he has established what 
 is called a general principle, or a Law of Physiology. 
 
INTRODUCTION. 53 
 
 As, for example, wlieii he has ascertained that sensation and 
 motion occupy distinct situations in every part of the nervous 
 system. 
 
 This " Law," however, it must be remembered, is not a discovery 
 by itself, nor does it give him any new information, but is simply 
 the expression, in convenient and comprehensive language, of the 
 facts with which he was already previously acquainted. It is very 
 dangerous, therefore, to make these laws or general principles the 
 subjects of our study instead of the vital phenomena, or to suppose 
 that they have any value, except as the expression of previously 
 ascertained facts. Such a misconception would lead to bad prac- 
 tical results. For if we were to observe a phenomenon in discord- 
 ance with a " law" or " principle," we might be led to neglect or 
 misinterpret the phenomenon, in order to preserve the law. But 
 this would be manifestly incorrect. For the law is not superior to 
 the phenomenon, but, on the contrary, depends upon it, and derives 
 its whole authority from it. Such mistakes, however, have been 
 repeatedly made in Physiology, and have frequently retarded its 
 advance. 
 
 IV. There is only one means by which Physiology can be 
 studied : that is, the observation of nature. Its phenomena cannot 
 be reasoned out by themselves, nor inferred, by logical sequence, 
 form any original principlefe, nor from any other set of phenomena 
 whatever. 
 
 In Mathematics and Philosophy, on the other hand, certain truths 
 are taken for granted, or perceived by intuition, and the remainder 
 afterward derived from them by a process of reasoning. But in 
 Physiology, as in all the other natural sciences, there is no such 
 starting point, and it is impossible to judge of the character of a 
 phenomenon until after it has been observed. Thus, the only way 
 to learn what action is exerted by nitric acid upon carbonate of 
 soda is to put the two substances together, and observe the changes 
 which take place ; for there is nothing in the general characters of 
 these two substances which could guide us in anticipating the result. 
 
 Neither can we infer the truths of Physiology from those of 
 Anatomy, nor the truths of one part of Physiology from those of 
 another part ; but all must be ascertained directly and separately 
 by observation. 
 
 For, although one department of natural science is almost always 
 a necessary preliminary to the study of another, yet the facts of 
 
54 INTRODUCTION. 
 
 the latter can never he in the least degree inferred from those of the 
 former, but must be studied by themselves. 
 
 Thus Chemistry is essential to Anatomy, because certain sub- 
 stances, as we have already shown, belonging to Chemistry, such 
 as chloride of sodium, occur as constituents of the animal body. 
 Chemistry teaches us the composition, reactions, mode of crystal- 
 *lization, solubility, &c., of chloride of sodium ; and if we did not 
 know these, we could not extract it, or recognize it when extracted 
 from the body. But, however well we might know the chemistry 
 of this substance, we could never, on that account, infer its presence 
 in the body or otherwise, nor in what quantities nor in what situa-r 
 tions it would present itself. These facts must be ascertained for 
 themselves, by direct investigation, as a part of anatomy proper. 
 
 So, again, the structure of the body in a state of rest, or its 
 anatomy, is to be first understood ; but its active phenomena or its 
 physiology must then be ascertained by direct observation and 
 experiment. The most intimate knowledge of the minute struc- 
 ture of the muscular and nervous fibres could not teach us any- 
 thing of their physiology. It is only by experiment that we 
 ascertain one of them to be contractile, the other sensitive. 
 
 Many of the phenomena of life are chemical in their character, 
 and it is requisite, therefore, that the physiologist know the ordi- 
 nary chemical properties of the substances composing the animal 
 frame. But no amount of previous" chemical knowledge will 
 enable him to foretell the reactions of any chemical substance in 
 the interior of the body; because the peculiar conditions under 
 which it is there placed modify these reactions, as an elevation or 
 depression of temperature, or other external circumstance, might 
 modify them outside the body. 
 
 We must not, therefore, attempt to deduce the chemical phe- 
 nomena of physiology from any previously established facts, since 
 these are no safe guide ; but must study them by themselves, and 
 depend for our knowledge of them upon direct observation alone, 
 
 V. By the term Vital phenomena, we mean those phenomena 
 which are manifested in the living body, and which are character- 
 istic <Sf its functions. 
 
 Some of these phenomena are physical or mechanical in their 
 character; as, for example, the play of the articulating surfaces 
 upon each other, the balancing of the spinal column with its ap- 
 pendages, the action of the elastic ligaments. Nevertheless, these 
 
INTKODUCTION. 65 
 
 phenomena, thougli strictly physical in character, are often entirely 
 peculiar and different from those seen elsewhere, because the me- 
 chanism of their production is peculiar in its details. Thus the 
 human voice and its modulations are produced in the larynx, in 
 accordance with the general physical laws of sound; but the 
 arrangement of the elastic and movable vocal chords, and their 
 relations with the columns of air above and below, the moist and 
 flexible mucous membrane, and the contractile muscles outside, are 
 of such a special character that the entire apparatus, as well as the 
 sounds produced by it, is peculiar ; and its action cannot be properly 
 compared with that of any other known musical instrument. 
 
 In the same manner, the movements of the heart are so compli-. 
 cated and remarkable that they cannot be comprehended, even by 
 one who is acquainted with the anatomy of the organ, without a 
 direct examination. This is not because there is anything essen- 
 tially obscure or mysterious in their nature, for they are purely 
 mechanical in character ; but because their conditions are so pecu- 
 liar, owing to the tortuous course of the muscular fibres, their 
 arrangement in interlacing layers, their attachments and relations, 
 that their combined action produces an effect altogether peculiar, 
 and one which is not similar to anything outside the living body. 
 
 A very large and important class of the vital phenomena are 
 those of a chemical character. It is one of the characteristics of 
 living bodies that a succession of chemical actions, combinations 
 and decompositions, is constantly going on in their interior. It is 
 one of the necessary conditions of the existence of every animal 
 and every vegetable, that it should constantly absorb various sub- 
 stances from without, which undergo different chemical alterations 
 in its interior, and are finally discharged from it under other forms. 
 If these changes be prevented from taking place, life is immedia,tely 
 extinguished. Thus animals constantly absorb, on the one hand, 
 water, oxygen, salts, albumen, oil, sugar, &c., and give up, on the 
 other hand, to the surrounding media, carbonic acid, water, ammonia, 
 urea, and the like ; while between these two extreme points, of ab-. 
 sorption and exhalation, there take place a multitude of different 
 transformations which are essential to the continuance of life. 
 
 Some of these chemical actions are the same with those which 
 are seen outside the body ; but most of them are entirely peculiar, 
 and do not take place, and cannot be made to take place, anywhere 
 else. This, again, is not because there is anything particularly 
 mysterious or extraordinary in their nature, but because the con- 
 
56 INTRODUCTION". 
 
 • 
 
 ditions necessary for their accomplishment exist in the body, and 
 do not exist elsewhere. All chemical phenomena are liable to be 
 modified by surrounding conditions. Many reactions, for example, 
 which will take place at a high temperature, will not take place at 
 a low temperature, and vice versd. Some will take place in the light, 
 but not in the dark ; others will take place in the dark, but not in 
 the light. If a hot concentrated solution of sulphate of soda be 
 allowed to cool in contact with the atmosphere, it crystallizes; 
 covered with a film of oil, it remains fluid. Because a chemical 
 reaction, therefore, takes place under one set of conditions, we can- 
 not be at all sure that it will also take place under others, which 
 are different. 
 
 The chemical conditions of the Jiving body are exceedingly com- 
 plicated. In the animal solids and fluids there are many substances 
 mingled together in varying quantities, which modify or interfere 
 with each other's reactions. New substances are constantly entering 
 by absorption, and old ones leaving by exhalation ; while the circu- 
 lating fluids are constantly passing from one part of the body to 
 another, and coming in contact with different organs of different 
 texture and composition. All these conditions are peculiar, and so 
 modify the chemical actions taking place in the body, that they are 
 unlike those met with anywhere else. 
 
 If starch and iodine be mingled together in a watery solution, 
 they unite with each other, and strike a deep opaque blue color ; 
 but if they be mingled in the blood, no such reaction takes place, 
 because it is prevented by the presence of certain organic substances 
 which interfere with it. 
 
 If dead animal matter be exposed to warmth, air, and moisture, 
 it putrefies ; but if introduced into the living stomach, even after 
 putrefection has commenced, this process is arrested, because the 
 fluids of the stomach cause the animal substance to undergo a 
 peculiar transformation (digestion), after which the bloodvessels 
 immediately remove it by absorption. There are also certain sub- 
 stances which make their appearance in the living body, both of 
 animals and vegetables, and which cannot be formed elsewhere • 
 such as fibrin, albumen, casein, pneumio acid, the biliary salts, mor- 
 phine, &c. These substances cannot be manufactured artificially, 
 simply because the necessary conditions cannot be imitated. They 
 require for their production the presence of a living organism. 
 
 The chemical phenomena of the living body are, therefore, not 
 different in their nature from any other chemical phenomena ; but 
 
INTKODUCTION. 57 
 
 they are different in their conditions and in their results, and are 
 consequently peculiar and characteristic. "" 
 
 AnQther set of vital phenomena are those which are manifested 
 in the processes of reproduction and development. They are again 
 entirely distinct from any phenomena which are exhibited by 
 matter not endowed with life. An inorganic substance, even when 
 it has a definite form, as, for example, a crystal of fluor spar, has 
 no particular relation to any similar form which has preceded, or 
 any other whidh is to follow it. On the other hand, every animal 
 and every vegetable owes its origin to preceding animals or vege- 
 tables of the same kind ; and the manner in which this production 
 takes place, and the different forms through which the new body 
 successively passes in the course of its development, constitute the 
 ■phenomena of reproduction. These phenomena are mostly depend- 
 ent on the chemical processes of nutrition and growth, which take 
 place in a particular direction and in a particular manner ; but their 
 results, viz., the production of a connected series of different forms, 
 constitute a separate class of phenomena, which cannot be explained 
 in any manner by the preceding, and require, therefore, to be studied 
 by themselves. 
 
 Another set of vital phenomena are those which belong to the 
 nervous system. These, like the processes of reproduction and 
 development, depend on the chemical changes of nutrition and 
 growth. That is to say, if the nutritive processes did not go on in 
 a healthy manner, and maintain the nervous system in a healthy 
 condition, the peculiar phenomena which are characteristic of it 
 could not take place. The nutritive processes are necessary condi- 
 tions of the nervous phenomena. But there is no other connection 
 between them ; and the nervous phenomena themselves are distinct 
 from all others, both in their nature and in the mode in which they 
 are to be studied. 
 
 A troublesome confusion might arise if we were to neglect the 
 distinction that really exists between these different sets of phe- 
 nomena, and confound them together under the expectation of 
 thereby simplifying our studies. Since this can only be done by 
 overlooking real points of difference, its effect will merely be to 
 introduce erroneous ideas and suggest unfounded similarities, and 
 will therefore inevitably retard our progress instead of advancing it. 
 
 It has been sometimes maintained, for example, that all the vital 
 phenomena, those of the nervous system included, are to be reduced 
 to the chemical changes of nutrition, and that these again are to be 
 
58 INTEODUCTION'. 
 
 I 
 
 regarded as not at all different in any respect from tlie ordinary 
 oliemical changes taking place outside the body. This, however, 
 is not only erroneous in theory, but conduces also to a vicious 
 mode of study. For it draws away our attention from the phe- 
 nomena themselves and their real characteristics, and leads us to 
 deduce one set of phenomena from what we know of another ; a 
 - method which we have already shown to be unsafe and pernicious. 
 It has also been asserted that the phenomena of the nervous 
 system are identical with those of electricity; for no other reason 
 than that there exist between them certain general resemblances. 
 But when we examine the phenomena in detail, we find that, beside 
 these general resemblances, there are many essential points of dis- 
 similarity, which must be suppressed and kept out of sight in order 
 to sustain the idea of the assumed identity.. This assumption is 
 consequently a forced and unnatural one, and the simplicity which 
 it was intended to introduce into our physiological theories is 
 imaginary and deceptive, and is attained only by sacrificing a part 
 of those scientific truths, which are alone the real object of our 
 study. We should avoid, therefore, making any such unfounded 
 comparisons ; for the theoretical simplicity which results from them 
 does not compensate for the loss of essential scientific details. 
 
 VI. The study of Physiology is naturally divided into three dis- 
 tinct Sections : — 
 
 The first of these includes everything which relates to the Nutei- 
 TION of the body in its widest sense. It comprises the history of 
 the proximate principles, their source, the manner of their produc- 
 tion, the proportions in which they exist in different kinds of food 
 and drink, the processes of digestion and absorption, and the c®n- 
 stitution of the circulating fluids ; then the physical phenomena of 
 the circulation and the forces by which it is accomplished; the 
 changes which the blood undergoes in different parts of the body ; 
 all the phenomena, both physical and chemical, of respiration ; those 
 of secretion and excretion, and the character and destination of the 
 secreted and excreted fluids. All these processes have reference to 
 a common object, viz., the preservation of the internal structure and 
 healthy organization of the individual. With certain modifications, 
 they take place in vegetables as well as in animals, and are conse- 
 quently known by the name of the vegetative functions. 
 
 The Second Section, in the natural order of study, is devoted to 
 the phenomena of the Neevous System. These phenomena are 
 
INTRODUCTION. 59 
 
 not exhibited by vegetables, but belong exclusively to animal or- 
 ganizations. They bring the animal body into relation vrith the 
 external world, and preserve it from external dangers, by means of 
 sensation, movement, consciousness, and volition. They are more 
 particularly distinguished by the name of the animal functions. 
 
 Lastly comes the study of the entire process of Eepbodtjction. 
 Its phenomena, again, with certain modifications, are met with in 
 both animals and vegetables ; and might, therefore, with some pro- 
 priety, be included under the head of vegetative functions. But 
 their distinguishing peculiarity is, that they have for their object 
 the production of new organisms, which take the place of the old 
 and remain after they h^ve disappeared. These phenomena do 
 not, therefore, relate to the preservation of the individual, but to 
 that of the species; and any study which concerns the species 
 comes properly after we have finished everything relating to the 
 individual. 
 
SECTION I. 
 NUTRITION. 
 
 CHAPTER I. 
 
 PEOXIMATE PRINCIPLES IN GENERAL. 
 
 The study of Nuteition begins naturally with that of the prom- 
 mate principles, or the substances entering into the composition of 
 the different parts of the body, and the different kinds of food. In 
 examining the body, the anatomist finds that it is composed, first, 
 of various parts, which are easily recognized by the eye, and which 
 occupy distinct situations. In the case of the human body, for 
 example, a division is easily made of the entire frame into the 
 head, neck, trunk, and extremities. Bach of these regions, again, 
 is found, on examination, to contain several distinct parts, or 
 " organs," which require to be separated from each other by dissec- 
 tion, and which are distinguished by their form, color, texture, and 
 consistency. In a single limb, for example, every bone and every 
 muscle constitutes a distinct organ. In the trunk, we have the 
 heart, the lungs, the liver, spleen, kidneys, spinal cord, &c., each of 
 which is also a distinct organ. When a number of organs, differing 
 in size and form, but similar in texture, are found scattered through- 
 out the entire frame, or a large portion of it, they form a connected 
 set or order of parts, which is called a " system." Thus, all the 
 muscles taken together constitute the muscular system ; all the 
 bones, tlie osseous system ; all the arteries, tbe arterial system. 
 Several entirely different organs may also be connected with each 
 other, so that 'their associated actions tend to accomplish a single 
 object, and they then form an "apparatus." Thus the heart, arte- 
 ries, capillaries, and veins, together, form the circulatory apparatus^ 
 the stomach, liver, pancreas, intestine, &c., the digestive apparatus. 
 Every organ, again, on microscopic examination, is seen to be made 
 
 (61 ) 
 
62 PROXIMATE PRINCIPLES IS GENERAL. 
 
 up of minute bodies, of definite size and figure, whicli are so small 
 as to be invisible to the naked eye, and -which, after separation 
 from each other, cannot be further subdivided without destroying 
 their organization. They- are, therefore, called "anatomical ele- 
 ments." Thus, in the liver, they are hepatic cells^ capillary blood- 
 vessels, the fibres of Glisson's capsule, and the ultimate filaments 
 of the hepatic nerves. Lastly, two or more kinds of anatomical 
 elements, interwoven with each. other in a particular manner, form 
 a "tissue." Adipose vesicles, with capillaries and nerve tubes, 
 form adipose tissue. White fibres and elastic fibres, with capillaries 
 and nerve tubes, form areolar tissue. Thus the solid parts of the 
 entire body are made up of anatomical elements, tissues, organs, 
 system's, and apparatuses. Every organized frame, and even every 
 apparatus, every organ, and every tissue, is made up of different 
 parts, variously interwoven and connected with each other, and it 
 is this character which constitutes its organization. 
 
 But beside the above solid forms, there are also certain fluids, 
 which are constantly present in various parts of the body, and which,- 
 from their peculiar constitution, are termed " animal fluids." These 
 fluids are just as much an essential part of the body as the solids. 
 The blood and the lymph, for example, the pericardial and synovial 
 fluids, the saliva, which always exists more or less abundantly in 
 the ducts of the parotid gland, the bile in the biliary ducts and the 
 gall-bladder : all these go to make up the entire body, and are quite 
 as necessary to its structure as the muscles or the nerves. Now, if 
 these fluids be examined, they are found to be made up of many 
 different substances, which are mingled together in certain propor- 
 tions; these proportions being constantly maintained at or about 
 the same standard by the natural procesSes of nutrition. Such a 
 fluid is termed an organized fluid. It is organized by virtue of the 
 numerous ingredients -rohich enter into its composition, and the 
 regular proportions in which these ingredients are maintained. 
 Thus in the plasma of the blood, we have albumen, fibrin, water, 
 chlorides, carbonates, phosphates, &c. In the urine, we find water, 
 urea, urate of soda, creatine, creatinine, coloring matter, salts, &c. 
 These substances, which are mingled tog'ether so as to make up, in 
 each instance, by their intimate " union, a homogeneous liquid, are 
 called the proximate principles of the animal fluid. • 
 
 In the solids, furthermore, even in those parts which are appa- 
 rently homogeneous, there is the same mixture of different ingre- 
 dients. In the hard substance of bone, for example, there is, first 
 
PROXIMATE PRINCIPLES IN GENERAL. 63 
 
 water, -which may be expelled by evaporation ; second, phosphate 
 and carbonate of lime, which may be extracted by the proper sol- 
 vents ; third, a peculiar animal matter, with which these calcareous 
 salts are in union ; and fourth, various other saline substances, in 
 special proportions. In the muscular tissue, there is chloride of 
 potassium, lactic acid, water, salts, albumen, and an animal matter 
 termed musculine. T^e difference in consistency between the solids 
 and fluids does not, therefore, indicate any radical difference ia their 
 constitution. Both are equally made up of proximate principles, 
 mingled together in various proportions. 
 
 It is important to understand, however, exactly what are proxi- 
 mate principles, and what are not such ; for since these principles 
 are extracted from the animal solids and fluids, and. separated from 
 each other by the help of certain chemical manipulations, such as 
 evaporation, solution, crystallization, and the like, it might be sup- 
 posed that every substance which could be extracted from an organ- 
 ized solid or fluid, by chemical means, should be considered as a 
 . proximate principle. That, however, is not the case. A proximate 
 principle is properly defined to be amj substance, whether simple or 
 compound, chemically speaking, which exists, under its own form, in the 
 animal solid or fluid, and which can be extracted by means which do 
 not alter or destroy its chemical properties. Phosphate of lime, for 
 example, is a proximate' principle of bone, but phosphoric acid is 
 not so, since it does not exist as such in the bony tissue, but is 
 produced only by the decomposition of the calcareous .-salt ;" still 
 less phosphorus, which is obtained only bv the decomposition of 
 the phosphoric acid. 
 
 Proximate principles may, in fact, be said to exist in all solids or 
 fluids of mixed composition, and may be extracted from them by 
 the same means as in the case of the animal tissues or secretions. 
 Thus, in a watery soltition of sugar, we have two proximate prin- 
 ciples, viz : first, the water, and second, the sugar. The water may 
 be separated by evaporation and condensation, after which the 
 sugar remains behind, in a crystalline form. These two substances 
 have, therefore, been simply separated from each other by the pro- 
 cess of evaporation. They have not been decomposed, nor their 
 chemical properties altered. On the other hand, the oxygen and 
 hydrogen of the water were not proximate principles of the original 
 solution,, and did not exist in it under their own forms, but only in 
 a state of combination ; forming, in this condition, a fluid substance 
 (water), endowed with sensible properties entirely different from 
 
64 PROXIMATE PRINCIPLES IN GENERAL,. 
 
 theirs. If we wish to ascertain, accordingly, the nature and proper- 
 ties of a saccharine solution, it will afford us but little satisfaction to 
 extract its ultimate chemical elements ; for its nature and properties 
 depend not so much on the presence in it of the ultimate elem£nts, 
 oxygen, hydrogen, and carbon, as on the particular forms of com- 
 bination, viz., water and sugar, under which they are present. 
 
 If is very essential, therefore, that in extracting the proximate 
 principles from the animal body, only such means should be adopted 
 as will isolate the^substances already existing in the tissues and 
 fluids, without decomposing them, or altering their nature. A 
 neglect of this rule has been productive of much injury in the pur- 
 suit of organic chemistry ; for chemists, in subjecting the animal 
 tissues to, the action of acids and alkalies, of prolonged boiling, or 
 of too intense heat, have often obtained, at the end t)f the analysis, 
 many substances which were erroneously described as proximate 
 principles, while they were only the remains of an altered and dis- 
 organized material. Thus, the fibrous tissues, if boiled steadily for 
 thirty-six hours, dissolve, for the most part, at the end of that time, 
 in the boiling water ; and on cooling the whole solution sslidifies 
 into a homogeneous, jelly-like substance, which has received the 
 name of gelatine. But this gelatine does not really exist in the body 
 as a proximate principle, since'the fibrous tissue which produces it 
 is not at first soluble, even in boiling water, and its ingredients 
 become altered and converted into a gelatinous matter only .by pro- 
 longed ebullition. So, again, an animal substance containing ace- 
 tates or lactates of soda or lime will, upon incineration in the open 
 air,, yield carbonates of the same bases, the organic acid having been 
 destroyed, and replaced by carbonic acid ; or sulphur and phospho- 
 rus, in the animal tissue, may be converted by the same means into 
 sulphuric and phosphoric acids, which, decomposing the alkaline 
 carbonates, become sulphates and phosphates. In either case, the 
 analysis of the tissues, so conducted, will be a deceptive one, and 
 useless for all anatomical and physiological purposes, because its 
 real ingredients have been decomposed, and replaced by others, in 
 the process of manipulation. 
 
 It is in this way that different chemists, operating upon the same 
 animal solid or fluid, by following different plans of analysis, have 
 obtained different results ; enumerating as ingredients of the body 
 many artificially formed substances, which are not, in reality, 
 proximate principles, thereby introducing much confusion into 
 physiological chemistry. 
 
PROXIMATE PEINCIPLES IN GENEliAL. 65 
 
 It is to be kept constantly in view, in the examination of an 
 animal tissue or fluid, that the object of the operation is simply the 
 separation of its ingredients from each other, and not their decomposi- 
 tion oj: ultimate analysis. Only the simplest forms of chemical 
 manipulation should, therefore, be employed. The substance to 
 be examined should first be subjected to evaporation, in order to 
 extract and estimate its water. This evaporation must be conducted 
 at a heat not above 212° F., since a higher temperature would de- 
 stroy or alter some of the animal ingredients.^Then, from the 
 dried residue, chloride of sodium, alkaline sulphates, carbonates, 
 and phosphates may be extracted with water. Coloring matters 
 may be separated*by alcohol. Oils may be dissolved out by ether, 
 &o. &c. When a chemical decomposition is unavoidable, it must 
 be kept in sight fcd afterward corrected. Thus the glyko-cholate 
 of soda of the bile is separated from certain other ingredients by 
 precipitating it with acetate of lead, forming glyko-cholate of lead ; 
 but this is afterward decomposed, in its turn, by carbonate of soda, 
 reproducing the original glyko-cholate of soda. Sometimes it is 
 impossible to extract a proximate principle in an entirely unaltered 
 form. Thus the fibrin of the blood can be separated only by allow- 
 ing it to coagulate ; and once coagulated, it is permanently altered, 
 and can no longer present all its original characters of fluidity, &c., 
 as it existed beforehand in the blood. In such instances as this, 
 we can only make allowance for an unavoidable difficulty, and be 
 careful that the substance suffers no further alteration. By bearing 
 in mind the above considerations, we may form a tolerably correct 
 estimate of the nature and quantity of all of the proximate princi- 
 ples existing in the substance under examination. 
 
 The manner in which the proximate principles are associated 
 together, so as to form the animal tissues, is deserving of notice. 
 In every animal solid and fluid, there is a considerable number of 
 proximate principles, which are present in certain proportions, and 
 which are so united with each other that the mixture presents a 
 homogeneous appearance. But this union is of a complicated cha- 
 racter ; and the presence of each ingredient depends, to a certain 
 extent, upon that of the others. Some of them, such as the alkaline 
 carljonates and phosphates, are in solution directly in the water. 
 Some, which are insoluble in water, are held in solution by the 
 presence of other soluble substances. Thus, phosphate of lime is 
 held in solution in the urine by the bi-phosphate of soda. In the 
 blood, it is dissolved by the albumen, which is itself fluid by union 
 5 
 
66 rHOXIMATE PRINCIPLES IN GKNEEAL. 
 
 with the water. The same substance may be fluid in one part of 
 the body, and solid in another part. Thus in the blood and secre- 
 ' tions the water is fluid, and holds in solution other substances, both 
 animal and mineral, while in the bones and cartilages it is sglid— 
 not crystallised, as in the case of ice St of saline substances which 
 contain water of crystallization, but amorphous and solid, by the 
 fact of its intimate union with the animal and saline ingredients, 
 which are abundant in quantity, and which are themselves present 
 in the solid foriit Again, the phosphate of lime in the blood is 
 fluid by solution in the albumen ; but in the bones it forms a solid 
 substance with the animal matter of the osseous tissue; and yet 
 the union of the two is as intimate and honlogen%ous in the bones 
 as in the blood. A proximate principle, therefore, never exists 
 alone in any part of the body, but is always intifciately associated 
 with a number of others, by a kind of homogeneous mixture or 
 solution. 
 
 Every animal tissue and fluid contains a number of proximate 
 principles which are present, as we have already mentioned, in 
 certain characteristic proportions. Thus, water is present in very* 
 large quantity in the perspiration and the saliva, but in very small 
 quantity in the bones and teeth. Chloride of sodium is compara- 
 tively abundant in the blojd and deficient in the muscles. On the 
 other hand, chloride -of potassium is more abundant in the muscles, 
 less so in the blood. But -these proportions, it is important to ob- 
 serve, are nowhere absolute or invariable. There is a great differ- 
 ence, in this respect, between the chemical composition of an inor- 
 ganic substance and the anatomical constitution of an animal fluid. 
 The former is always constant and definite; the latter is always 
 subject to certain variations.- Thus, water is always composed of 
 exactly the same relative quantities of oxygen and hydrogen ; and 
 if these proportions be altered in the least, it thereby ceases to be 
 water, and is converted into same other substance. But in the 
 urine, the proportions of. water, urea, urate of soda, phosphates, 
 &c., vary within certain limits in different individuals, and even in 
 the same individual, from one hour to another. This variation, 
 which is almost constantly taking place, within the limits of health,' 
 is characteristic of all the animal solids and fluids; for they are 
 composed of different ingredients which are supplied by absorption . . 
 or formed in the interior, and which are constantly given up again, 
 under the same or different forms, to the surrounding media by the 
 unceasing activity of the vital processes. Every variation, then, 
 
PROXIMATE PRIKCIPLES IX GENERAL. oJ 
 
 in the general condition of the body, as a whole, is accompanied by 
 a corresponding variation, more or less pronounced, in the consti- 
 tution of its different parts. This constitution is consequently of 
 a very different character from the chemical constitution of an 
 oxide or a salt. Whenever, therefore, we meet with the quanti- 
 tative analysis of an animal fluid,. in which the relative quantity 
 of its different ingredients is represented in numbers, we must 
 understand that such an analysis is always apprtji^MnSJtlve, and not 
 absolute. ^ 
 
 The proximate principles are naturally divided into three differ- 
 ent classes. 
 
 The first of these classes comprises all the proximate principles 
 which are purely inorganic in their nature. These principles are 
 derived mostly from the exterior. They are found everywhere, in 
 unorganized as well as in organized bodies ; and they present them- 
 selves under the same forms and with the sanje properties in the 
 interior of the animal frame as elsewhere, ^^ey jfre crystallizable, 
 and have a definite chemical composition* They comprise such 
 substances as water, chloride of- sodium^arbonate and phosphate 
 of lime, &c. c} 
 
 The second class of proximate pnncipje^s »kiaS wn as crystAl- 
 LIZABLE SUBSTANCES OF ORGANIC OBiGK^'-, f Thfsis the name given 
 to them by Eobin and Verdeil,' whose jt^lassification of the proxi- 
 mate principles is the best whMi has yet "beA offered. They are 
 crystallizable, as their name indicates, and have a definite chemical 
 composition. They are said to be of " organic origin," because they 
 first make their appearance in the intfrior of organized bodies, and 
 are not found in external nature afthe ingredients of inorganic 
 substances. Such are the difierent kinds of sugar, oil, and starch. 
 
 The third class comprises,jf'very extensive and important order 
 of proximate principles, *which go by the name of the Organic 
 Substances proper. They are sometimes known as " albuminoid" 
 substances or " protein compounds." The name organic substances 
 is given to them in consequence of the striking difference which 
 exists between them and all the other ingredients of the body. The 
 substances of the second class difl'er from those of the first by their 
 
 ' Chimie Anatomiqna ct Physiologique. Paris, 1853. 
 
to PKOXIIIATE PRINCIPLES IN GENEKAL. 
 
 (exclusively organic origin, but they resemble the latter in their crys- 
 tallizability and their definite chemical composition ; in consequence 
 of which their chemical investigation may be pursued in nearly 
 the same manner, and their chemical changes expressed in nearly 
 the same terms. But the proximate principles of the third class 
 are in every respect peculiar. They have an exclusively organic 
 origin ; not being found except as ingredients of living or recently 
 dead animals or vegetables. They have not a definite chemical 
 composition, and^e consequently not crystallizable ; and the forms 
 which they present, and the chemical changes which they undergo 
 in the body, are such as cannot be expressed by ordinary chemical 
 phraseology. This class includes such substances as albumen, 
 fibrinj' casein, &c. 
 
PROXIMATE PEINCIPLES OF THE F1E3T CLASS. ^ 
 
 CHAPTER II. 
 
 J. 
 
 PROXIMATE PEINCIPLES OF THE BIRBT CLASS. 
 
 The proximate principles of the first class, or those of axi-inor- 
 ganic nature, are very numerous. Their most prominent chaMcters 
 have already been stated. They are all crystallizable, and have a 
 definite chemical composition. They are met -with extensively in 
 the inorganic world, and form a large part of the crust of the earth. 
 They occur abundantly in the different kinds of food and drink; 
 and are necessary ingredients of the food, since they are necessary 
 ingredients of the animal frame. Some of them are found universally 
 in all parts of the body, others are met with only in particular 
 regions ; but there are hardly any which are not present at the 
 same time in more than one animal solid or fluid. The following 
 are the most prominent of them, arranged in the order of their 
 respective importance. 
 
 1. "Wateb. — Water is universally present in all the tissues and 
 'fluids of the body. It is abundant in the blood and secretions, 
 where its presence is. indispensable in order to give them the fluidity 
 which is necessary to the performance of their functions ; for it 
 is by the blood and secretions that new substances are introduced 
 into the body, and old ingredients discharged. And it is a neces- 
 sary condition both of the introduction and discharge of substances 
 naturally solid, that they assume, for the time being, a fluid form ; 
 Avater is therefore an essential ingredient of the fluids, for it holds 
 their solid materials in solution, and enables them to pass and repass 
 through the animal frame. 
 
 But- water is an ingredient also of the solids. For if we take a 
 muscle or a cartilage, and expose it to a gentle heat in dry air, it 
 loses water by evaporation, diminishes in size and weight, and be- 
 comes dense and stiff. Even the bones and teeth lose water by 
 evaporation in this way, though in smaller quantity. In all these 
 solid and semi-solid tissues, the water which they contain is useful 
 
10 
 
 PROXIMATE PEINCIPLES OP THE FIRST CLASS. 
 
 by giving them the special consistency which is characteristic of 
 them, and which would be lost without it. Thus a tendon, in its 
 natural condition, is white, glistening, and opaque ; and though very 
 strong, perfectly flexible. If its water be expelled by evaporation 
 it becomes yellowish in color, shrivelled, semi-transparent, inflexi- 
 ble, and totally unfit for performing its mechanical functions. The 
 same thing is true of the skin, muscles, cartilages, &c. 
 
 The following is a list, compiled by Eobin and Yerdeil from 
 various observers, showing the proportion of water per thousand 
 parts, in different solids and fluids : — 
 
 Qv. 
 
 KTiTi OF Water ik 1,000 paets in 
 
 Epidermis 
 
 .37 
 
 Bile . 
 
 . 880 
 
 Teeth 
 
 . 100 
 
 Milk 
 
 . 887 
 
 Bones 
 
 . 130 
 
 Pancreatic juice 
 
 , 900 
 
 Cartilage . 
 
 . .-iSO. 
 
 Urine 
 
 . 936 
 
 Muscles . 
 
 . 750 
 
 Lymph 
 
 . 960 
 
 Ligaments 
 
 . 768 
 
 Gastric juice 
 
 . 975 
 
 Brain 
 
 . 789 
 
 Perspiration 
 
 . 986 
 
 Blood . 
 
 . 795 
 
 Salira 
 
 . 995 
 
 Synovial fluid 
 
 . 805 
 
 
 
 According to the best calculations, water constitutes, in the 
 human subject, between two-thirds and three-quarters of the entire 
 weight of the body. 
 
 The water which thus forms a part of the animal frame is derived 
 from without. It is taken in the different kinds of drink, and also 
 forms an abundant ingredient in the various articles of food. For 
 no articles of food are taken in an absolutely dry state, but all 
 contain a larger or smaller quantify of water, which may readily 
 be expelled by evaporation. The quantity of water, therefore, 
 which is daily taken into the system, cannot be ascertained in any 
 case by simply measuring the quantity of drink, but its proportion 
 in the solid food, taken at the same time, must also be determined 
 by experiment, and this ascertained quantity added to that which 
 is taken in with the fluids. By measuring the quantity of fluid 
 taken with the drink, and calculating in addition the proportion 
 existing in the solid food, we have found that, for a healthy adult 
 man, the ordinary quantity of water introduced per day, is "a little 
 over4J pounds. 
 
 After forming part of the animal solids and fluids, and taking 
 part in the various physical and chemical processes of the body, the 
 water is again discharged; for its presence in the body, like that 
 of all the other proximate principles, is not permanent, but only 
 
OHLOBIDE OF SOIJIL'M. 71 
 
 temporary. After being taken in with the food and drink, it is 
 associated with other principles in the fluids and solids, passing 
 from the intestine to the blood, and from the blood to the tissues 
 and secretions." It afterward makes its exit from the body, from 
 which it is discharged by four different passages, viz., in a liquid 
 form with the urine and the feces, and in a gaseous form with the 
 breath and the perspiration. Of all the water which is expelled in 
 this way, about 48 per cent, is discharged with the urine and ,feces,' 
 and about 52 per cent, by the lungs and skin. The researches of 
 Lavoisier and Seguin, Valentin, and others, show that from a pound 
 and a half to two pounds is discharged daily by tha skin, a little 
 over one pound by exhalation from the lungs, and a little over two 
 pounds by the urine. Both the absolute and relative amount dis- 
 charged, both- in a liquid and gaseous form, varies according to 
 circumstances. There is particularly a compensating action in this 
 respect between the kidneys and the skin, so that when the cutane- 
 ous perspiration is very abundant the urine is less so, and vice versd. 
 The quantity of water exhaled from the lungs varies also with the 
 state of the pulmonary circulation, and with the temperature and 
 dryness of the atmosphere. The water is not discharged at any 
 time in a state of purity, but is mingled in the urine and feces with 
 saline substances which it holds in solution, and in the cutaneous 
 and pulmonary exhalations with animal vapors and odoriferous 
 substances of various kinds. In the perspiration it is also mingled 
 with saline substances, which it leaves behind on evaporation. 
 
 2. Chloride of Sodium. — This substance is found, like water, 
 throughout the different tissues and fluid's of the body. The only 
 exception to this is perhaps the enamel of the teeth, where it has 
 not yet been discovered. Its presence is important in the body, as 
 regulating the phenomena of endosmosis and exosmosis in different 
 parts of the frame. For we know that a solution of common salt 
 passes through animal membranes much less readily than pure 
 water ; and tissues which have been desiccated will absorb pure 
 water more abundantly than a saline solution. It must not be sup- 
 posed, however, that the presence or absence of chloride of sodium, 
 or its varying quantity in the animal fluids, is the only condition 
 which regulates their transudation through the animal membranes. 
 The manner in which endosmosis and exosmosis take place in the 
 
 ' Op. cit., vol. ii. pp. 143 and 145. 
 
72 PKOXIMATK PRINCIPLES OF THE FIRST CLASS. 
 
 animal frame depends upon the relative quantity of all the ingre^ 
 dients of the fluids, as well as on the constitution of the solids 
 themselves; and the chloride of sodium, as one ingredient among 
 many, influences these phenomena to a great extent; though it does 
 not regulate them exclusively. 
 
 It exerts also an important influence on the solution of various 
 other ingredients, with which it is associated. Thus, in the blood 
 it increases the solubility of the albumen, and- perhaps also of the 
 earthy phosphates. The blood-globules, again, which become dis- 
 integrated and dissolved in a solution of pure albumen, are main- 
 tained in a state of integrity by the presence of a small quantity of 
 chloride of sodium. 
 
 It exists in the following proportions in several of the solids and 
 fluids :'— 
 
 QjIANTITT OF ChLOKIDE OP SODIUM IN 1,000 PARTS IM THE 
 
 Muscles . . '' . . 2 Bile 
 
 Bones 
 Milk 
 Saliva 
 Urine 
 
 2.5 Blood 
 
 1 Mucus . 
 
 1.5 Aqueous humor 
 
 3 Vitreous humor 
 
 3.5 
 4.5 
 
 11 
 14 
 
 In the blood it is rather more abundant than all the other saline 
 ingredients taken together. 
 
 Since chloride of sodium is so universally present in all parts of 
 the body, it is an important ingredient also of the food. It occurs, 
 of course, in all animal food, in the quantities in which it naturally 
 exists in the corresponding tissues; and in vegetable food also, 
 though in smaller amount. Its proportion in muscular flesh, , 
 however, is much less than in the blood and other fluids. Conse- 
 quently, it is not supplied in suificient quantity as an ingredient of 
 animal and vegetable food, but is taken also by itself as a condi- 
 ment. There is no other substance so universally used by all races 
 and conditions of men, as an addition to the food, as chloride of 
 sodium. This custom does not simply depend on a fancy for grati- 
 fying the palate, but is based upon an instinctive desire for a sub- 
 stance which is necessary to the proper constitution of the tissues 
 and fluids. Even the herbivorous animals are greedy of it, and if 
 freely supplied with it, are kept in a much better condition than 
 when deprived of its use. 
 
 The importance of chloride of sodium in this respect has been 
 well demonstrated by Boussingaulf, in his experiments on the 
 
 ' Robin and Verdeil. 
 
CHLORIDE OF SODIUM. 73 
 
 fattening of animals. These observations were made upon six 
 bullocks, selected, as nearly as possible, of tbe same age and vigor, 
 and subjected to comparative experiment. They were all supplied 
 with an abundance of nutritious food ; but three of them (lot No. 
 1) received also a little over 500 grains of salt each per day. The 
 remaining three (lot No. 2) received no salt, but in other respects 
 were treated like the first. The result of these experiments is given 
 by Boussingault as follows : — * 
 
 " Though salt administered with the food has but little effect in 
 increasing the size of the animal, it appears to exert a favorable 
 influence upon his qualities and general aspect. Until the end of 
 March (the, experiment began in October) the two lots experimented 
 on did not present any marked difference in their appearance ; but 
 in the course of the following April, this difference became quite 
 manifest, even to an unpractised eye. The lot No. 2 had then been 
 without salt for six months. In the animals of both lots the skin 
 had a fine and substantial texture, easily stretched and separated 
 from the ribs ; but the hair, which was tarnished and disordered in 
 the bullocks of the second lot, was smooth and glistening in those 
 of the first. As the experiment went on, these characters became 
 more marked ; and at the beginning of October the animals of lot 
 No. 2, after going without salt for an entire year, presented a rough 
 and tangled hide, with patches here and there where the skin was 
 entirely uncovered. The bullocks of lot No. 1 retained, on the 
 contrary, the ordinary aspect of stall-fed animals. Their vivacity 
 and their frequent attempts at mounting contrasted strongly with 
 the dull and unexcitable aspect presented by the others. No doubt, 
 the first lot would have commanded a higher price in the market 
 than the second." 
 
 Chloride of sodium acts also in a favorable manner by exciting 
 the digestive fluids, and assisting in this way the solution of the 
 food. For food which is tasteless, however nutritious it may be in 
 other respects, is taken with reluctance and digested with difiSculty ; 
 while the attractive flavor which is developed by cooking, and by 
 the addition of salt and other condiments in proper proportion, 
 excites the secretion of the saliva and gastric juice, and facilitates 
 consequently the whole process of digestion. The chloride of 
 sodium is then taken up by absorption from the intestine, and is 
 deposited in various quantities in different parts of the body. 
 
 ' Chimie Agricole, Paris, 1854, p. 271. 
 
7-i PROXIMATE PRINCIPLES OF THE FIRST CLASS. 
 
 It is discharged with the urine, mucus, cutaneous perspiration, 
 &c., in solution in the water of these fluids. According to the esti- 
 mates of M. Barral' a small quantity of chloride of sodium dis- 
 appears in the body; since he finds by accurate comparison that all 
 the salt introduced with the food is not to be found in the excreted 
 fluids, but that about one-fifth of it remains unaccounted for. This 
 portion is supposed to undergo a double decomposition in the blood 
 with phosphate of potassa, forming chloride of potassium and phos- 
 phate of soda. By far the greater part of the chloride of sodium, 
 however, escapes under its own form with the secretions. 
 
 3. Chloride of Potassium. — This substance is found in the 
 muscles, the blood, the milk, the urine, and various other fluids 
 and tissues of the body. It is not so universally present as chlo- 
 ride of sodium, and not so important as a proximate principle. 
 In some parts of the body it is more abundant than the latter salt, 
 in others less so. Thus, in the blood there is more chloride of 
 sodium than chloride of potasssium, but in the muscles there is more 
 chloride of potassium than chloride of sodium. This substance is 
 always in a fluid form, by its ready solubility in water, and is easily 
 separated by lixiviation. It is introduced mostly with the food, but 
 is probably formed partly in the interior of the body from chloride 
 of sodium by double decomposition, as already mentioned. It is 
 discharged with the mucus, the saliva, and the urine. 
 
 4. Phosphate of Lime. — This is perhaps the most important 
 of the mineral ingredients of the body next to chloride of sodium. 
 It is met with universally, in every tissue and every fluid. Its 
 quantity, however, varies very much in different parts, as will be 
 seen by the following list : — 
 
 QtTANTiTT OP Phosphate op Lime is 1,000 parts in the 
 Enamel of the teeth . . S85 Muscles . . . . 2.,5 
 
 Dentine . . . .643 Blood . . . .03 
 
 Bones .. . . . 5,50 Gastric juice . . .0.4 
 
 Cartilages ... 40 
 
 It occurs also under different physical conditions. In the bones, 
 teeth, and cartilages it is solid, and gives to these tissues the" resist- 
 ance and solidity which are characteristic of them. The calcareous 
 salt is not, however, in these instances, simply deposited mechani- 
 cally in the substance of the bone or cartilage as a granular powder, 
 
 ' In Robin and Verdeil, op. cit., vol. ii. 193. 
 
PHOSPHATE OF LIME. 
 
 75 
 
 Fig. 1. 
 
 but is intimately united witli the animal matter of tbe tissues, like 
 a coloring matter in colored glass, so as to present a more or less 
 homogeneous appearance. It can, however, be readily dissolved 
 out by maceration in dilute muriatic acid, leaving behind the 
 animal substance, which still retains the original form of the bone 
 or cartilage. It is not, therefore, united with the animal matter so 
 as to lose its identity and form a new chemical substance, as where 
 an acid combines with an alkali to form a salt, but in the same 
 manner as salt unites with water in a saline solution, both sub- 
 stances retaining their original character and composition, but so 
 intimately associated that they cannot be separated by mechanical 
 means. 
 
 In the blood, phosphate of lime is in a liquid form, notwithstand- 
 ing its insolubility in water and in alkaline fluids, being held in 
 solution by the albuminous matters of the circulating fluid. In the 
 urine, it is retained in solution by the bi-phosphate of soda. 
 
 In all the solid tissues it is useful by giving to them their proper 
 consistence and solidity. For example, in the ena- 
 mel of the teeth, the hardest tissue of the body, it 
 predominates very much over the animal matter, 
 and is present in greater abundance there than Tn 
 any other part of the frame. In the dentine, a 
 softer tissue, it is in somewhat smaller quantity, 
 and in the bones smaller still ; though in the bones 
 it continiies to form more than one-half the entire 
 mass of the osseous substance. The importance of 
 phosphate of lime, in communicating to bones their 
 natural stiffness and consistency, may be readily 
 shown by the alteration which they suffer from its 
 removal. If a long bone be macerated in dilute 
 muriatic acid, the earthy salt, as already mentioned, 
 is entirely dissolved out, after which the bone loses 
 its rigidity, and may be bent or twisted in any di- 
 rection without breaking. (Fig. 1.) 
 
 Whenever the nutrition of the bone during life 
 is interfered with from any pathological cause, so 
 that its phosphate of lime becomes deficient in 
 amount, a softening of the osseous tissue is the 
 consequence, by which the bones yield to external 
 pressure, and become more or less distorted. (Osteo-malakia.) 
 
 After forming, for a time, a part of the tissues and fluids, the 
 
 Fibula tied is 
 A K5 0T, after mu- 
 ceration in a dilute 
 acid. (From a. speci- 
 men in ttie mufjenm 
 of the Coll. of Physi- 
 ciaQB and Surgeons.) 
 
76 PBOXTMATE PRINCIPLES OF THE FIRST CLASS. 
 
 phosphate of lime is discharged from the body by the urine, the 
 perspiration, mucus, &c. Much the larger portion is discharged by 
 the urine. A small quantity also occurs in the feces, but this is pro- 
 bably only the superfluous residue of what is takenin with the food. ■ 
 
 5. Carbonate of Lime. — Carbonate of lime is to be found in 
 the bones, and sometimes in the urine. The concretions of the 
 internal ear are almost entirely formed of it. It very probably 
 occurs also in the blood, teeth, cartilages, and sebaceous matter ; 
 but its presence here is not quite certain, since it may have been 
 produced from the lactate, or other organic combination, by the 
 process of incineration. In the bones, it is in much smaller quan- 
 tity than the phosphate. Its solubility in the blood and the urine 
 is accounted for by the presence of free carbonic acid, and also of 
 chloride of potassium, both of which substances exert a solvent 
 action on carbonate of lime. 
 
 6. Carbonate of Soda. — This substance exists in the bones, 
 blood, saliva, lymph, and urine. As it is readily soluble in water, 
 it naturally assumes the liquid form in the animal fluids. It is 
 important principally as giving to the blood its alkalescent reaction, 
 by which the solution of the albumen is facilitated, and various 
 other chemico-physiological processes in the blood accomplished. 
 The alkalescence of the blood is, in fact, necessary to life ; for it is 
 found that, in the living animal, if a mineral acid be gradually 
 .injected into the blood, so dilute as not to coagulate the albumen, 
 death takes place before its alkaline reaction has been completely 
 neutralized.' , 
 
 The carbonate of soda of the blood is partly introduced as such 
 with the food ; but the greater part of it is formed within the body 
 by the decomposition of other salts, introduced with certain fruits 
 and vegetables. These fruits and vegetables, such as apples, cher- 
 ries, grapes, potatoes, &c., contain malates, tartrates, and citrates 
 of soda and potassa. Now, it has been often noticed that, after 
 the use of acescent fruits and vegetables containing the above salts, 
 the urine becomes alkaline in reaction from the presence of the 
 alkaline carbonates. Lehmann' found, by experiments upon his 
 own person, that, within thirteen minutes after taking half an ounce 
 
 ' 01. Bernard. Lectures on the Blood ; reported by W. F. Atlee, M. D. Phila- 
 delphia, 1854, p. 31. * 
 ' Physiological Chemistry. Philadelphia ed., vol. i. p. 97. 
 
PHOSPHATES OF MAGNESIA, SODA, AXD POTASSA. 77 
 
 of lactate of soda, the urine had an alkaline reaction. He also ob- 
 served that, if a solution of lactate of soda were injected into the 
 jugular vein of a dog, the urine became alkaline at the end of five, 
 or, at the latest, of twelve minutes. The conversion of these salts 
 into carbonates takes place, therefore, not in the intestine but in the 
 blood. The same observer' found that, in many persons living on 
 a mixed diet, the urine became alkaline in two or three hours after 
 swallowing ten grains of acetate of soda. These salts, therefore, 
 on being introduced into the animal body, are decomposed. Their 
 organic acid is destroyed and replaced by carbonic acid ; and they 
 are then discharged under the form of carbonates of soda and potassa. 
 
 7. Caebonate of Potassa. — This substance occurs in very 
 nearly the same situations as the last. In the blood, however, it is 
 in smaller quantity. It is mostly produced, as above stated, by 
 the decomposition of the malate, tartrate, and citrate, in the same 
 manner as the carbonate of soda. Its function is also the same as 
 that of the soda salt, and it is discharged in the same manner from 
 the body. 
 
 8. Phosphates of Magnesia, Soda, and Potassa. — All these 
 substances exist universally in all the solids and fluids of the body, 
 but in very srtiall quantity. The phosphates of soda and potassa 
 are easily dissolved in the animal fluids, owing to their ready solu- 
 bility in water. The phosphate of magnesia is held in solution in 
 the blood by the alkaline chlorides and phosphates ; in the urine, 
 by the acid phosphate of soda. 
 
 A peculiar relation exists between the alkaline phosphates and 
 carbonates in different classes of animals. For while the fluids of 
 carnivorous animals contain a preponderance of the phosphates, 
 those of the herbivora contain a preponderance of the carbonates : 
 a peculiarity readily understood when we recollect that muscular 
 flesh and the animal tissues generally are comparatively abundant 
 in phosphates ; while vegetable substances abound in salts of the 
 organic acids, which give rise, as already described, by their decom- 
 position in the blood, to the alkaline carbonates. 
 
 The proximate principles included in the above list resemble 
 each other not only in their inorganic origin, their crystallizability, 
 
 ' Physiological Chemistry, vol. ii. p. 130. 
 
78 PKOXIMATE PRINCIPLES OF TUB FIKriT CLASS. 
 
 and their definite chemical "composition, but ailso in the part which 
 they take in the constitution of the animal frame. They are 
 distinguished in this respect, first by being derived entirely from 
 without. There are a few exceptions to this rule ; as, for example, 
 in the case of the alkaline carbonates, which partly originate in 
 the body from thfe decomposition of malates, tartrates, &c. These, 
 however, are only exceptions ; and in general, the proximate prin- 
 ciples belonging to the first class are introduced with the food, 
 and taken up by the animal tissues in precisely the same form 
 under which they occur in external nature. The carbonate of lime 
 in the bones, the chloride of sodium in the blood and tissues, are 
 the same substances which are met with in the calcareous rocks, 
 and in solution in sea water. They do not suffer any chemical 
 alteration in becoming constituent parts of the animal frame. 
 
 They are equally exempt, as a general rule, from any alteration 
 while they remain in the body, and during their passage through 
 it. The exceptions to this rule are very few ; as, for example, where 
 a small part of the chloride of sodium suffers double decomposition 
 with phosphate of potassa, giving rise to chloride of potassium and 
 phosphate of soda ; or where the phosphate of poda itself gives up 
 a part of its base to an organic acid (uric), and is converted in this 
 way into a bi-phosphate of soda. 
 
 Nearly the whole of these substances, finally, are taken up un- 
 changed from the tissues, and discharged unchanged with the excre- 
 tions. Thus we find the phosphate of lime and the chloride of so- 
 dium, which were taken in with the food, discharged again under 
 the same form in the urine. They do not, therefore, for the most 
 part, participate directly in the chemical changes going on in the 
 body ; but only serve by their presence to enable those changes to 
 be accomplished in the pther ingredients of the animal frame, which 
 are necessary to the process of nutrition. 
 
PKOXIMATE PKIKCIPLES OP THE SECOND CLASS. 79 
 
 CHAPTER III. 
 
 PEOXIMATE PKINCIPLES OP THE SECOND CLASS. 
 
 The proximate principles belonging to the second class are 
 divided into three principal groups, viz: starch, sugar, and oil. 
 They are distinguished, in the first place, by their organic origin. 
 Unlike the principles of the first class, they do not exist in 
 external natiire, but are only found as ingredients of organized 
 bodies. They exist both in animals and in vegetables, though.^ 
 somewhat different proportions. All the substances belonging to 
 this class have a definite chemical composition ; and are further 
 distinguished by the fact that they are composed of oxygen, 
 hydrogen, and carbon alone, without nitrogen, whence they are 
 sometimes called the "non-nitrogenous" substances. 
 
 1. Starch (C,jHh,0,o). — The first of these sub-stances seems to 
 form an exception to the general rule in a very important particu- 
 lar, viz., that^ it is not crystallizable. Still, since it so closely 
 resembles the rest in all its general properties, and since it is easily 
 convertible into sugar, which is itself crystallizable, it is naturally 
 included in the second class of proximate principles. Though not 
 crystallizable, furthermore, it still assumes a distinct form, by 
 which it differs from substances that are altogether amorphous. 
 
 Starch occurs in some part or other of almost all the flowering 
 plants. It is very abundant in corn, wheat, rye, oats, and rice, in 
 the parenchyma of the potato, in peas and beans, and in most 
 vegetable substances nsed as food. It constitutes almost entirely, 
 the different preparations known as sago, tapioca, arrowroot, &c., 
 which are nothing more than varieties of starch, extracted from 
 different species of plants. 
 
 The following is a list showing the percentage of starch occurring 
 in different kinds of food : — ' 
 
 ' Pereira on Food and Diet, New York, 1843, p. 39. 
 
80 
 
 PROXIMATE I'RIXCIPLES OF THE SECOND CLASS. 
 
 
 QtTASTiTT OP Starch 
 
 IN 100 PARTS IN 
 
 
 Rice 
 
 . 85.07 
 
 Wheat flour . 
 
 . 56.50 
 
 Maize . 
 
 . 80.92 
 
 Iceland moss 
 
 . 44.60 
 
 Barley meal 
 
 . 67.18 
 
 Kidney bean . 
 
 . 35.94 
 
 Eye meal 
 
 . 61.07 
 
 Peas 
 
 . 32.45 
 
 Oat meal 
 
 . 59.00 
 
 Potato . 
 
 . 15.70 
 
 Grains op Potato Starch. 
 
 When purified from foreign substances, starch is a white, light 
 powder, which gives rise to a peculiar crackling sensation when 
 
 rubbed between the fingers. 
 '^' ■ It is not amorphous, as we 
 
 have already stated, but is 
 composed of solid granules, 
 which, while they have a 
 general resemblance to each 
 other, differ somewhat in va- 
 rious particulars; The starch 
 grajns of the potato (Fig. 2) 
 vary considerably in size. 
 The smallest have a diameter 
 of rAnn, the largest ^U of 
 an inch. They are irregu- 
 krly pear-shaped in form, 
 and are marked by concen- 
 tric laminae, as if the matter 
 of which they are composed had been deposited in successive layers. 
 At one point on the surface of every starch grain, there is a minute 
 
 pore or depression, called the 
 hilm, around which the cir- 
 cular markings are arranged 
 in a concentric form, 
 
 The starch granules of 
 arrowroot (Fig. 3) are gene- 
 rally smaller and more uni- 
 form in size, than those of 
 the potato. They vary from 
 3 At to 5^x7 of an inch in 
 diameter. Thgy are elongated 
 and cylindrical in form, and 
 the concentric markings are 
 less distinct than in thjQipre- 
 ceding variety. The hilus 
 
 Fig. 3. 
 
 Starch Grains of Bermuda Arrowroot. 
 
STABOH. 
 
 81 ^^ 
 
 Stauch Guaixs nF Whkat Ploub. 
 
 has here sometimes the form of a circular pore, and sometimes that 
 of a transverse fissure or slit. . 
 
 The grains of wheat starch (Fig. 4) are still smaller than those 
 of arrovfToot. They vary 
 
 from rsi^s to ^^a of an inch ^'S- ^• 
 
 in diameter. They are 
 nearly circular in form, with 
 a round or transverse hilus, 
 but without any distinct 
 appearance of lamination. 
 Many of them are flattened 
 or compressed laterally, so 
 that they present a broad 
 surface in one position, and 
 a narrow edge when viewed 
 in the opposite direction. 
 
 The starch grains of In- 
 dian corn ,(Fig. 5) are of 
 nearly the same size with 
 those of wheat flour. They are somewhat more irregular and 
 angular in shape ; and are often marked with crossed or radiating 
 lines, as if from partial fracture. 
 
 Starch is also an ingre- Fig- 5- 
 
 dient of the animal bcidy. 
 It was first observed by 
 Purkinje, and afterward by 
 Kdlliker,' that certain bodies 
 are to be found in the interior 
 of the brain, about the late- 
 ral ventricles, in the fornix, 
 septum lucidum and other 
 parts, which present a cer- 
 tain resemblance to starch 
 grains, and which have there- 
 fore been called "corpora 
 amylacea." Subsequently 
 Vircho'vf' ^ccyrobojated the 
 above observations, and ascertained the corpora amylacea to be 
 
 Starch Grains of Isdiaw Coex. 
 
 ' Handbuch der Gewebelelire, Leipzig, 1852, p. 311. 
 ' In American Journal Med. Sci., April, 1854, p. 466. 
 
82 PROXIMATE FRIKCIPLES OP THE SECOND CLASS. 
 
 Starch Grains from Walt, of Lati^ral 
 
 y E.NTRIGLES; frOCl & VlOlliSLU Aged 3j. 
 
 really substances of a starchy nature ; since they exhibit the usual 
 chemical reactions of vegetable starch. 
 
 The starch granules of the human brain (Fig. '6) are tri^nsparent 
 
 and colorless, like those from 
 ^^^'- *•• plants. They refract the light 
 
 strongly, and vary in size 
 from ^i^^ to ttVtt of ayi 
 inch. Their average is jg^ir 
 of an inch. They are some- 
 times rounded or oval, and 
 sometinies angular in shape. 
 They resemble considerably 
 in appearance the starch 
 granules of Indian corn. The 
 largest of them present a 
 very faint concentric lamina- 
 tion, but the greater number 
 are destitute of any such 
 appearance. They have 
 nearly always a distinct hilus, which is sometimes circular and 
 sometimes slit-shaped. They are also often marked with delicate 
 radiating lines and shadows. On the addition of iodine, they become 
 colored, first purple, afterward of a deep blue. They are less firm 
 in consistency than vegetable starch grains, and can be more readily 
 disintegrated by pressing or rubbing them upon the glass. 
 
 Starch, derived from all these different sources, has, so far as 
 known, the same chemical composition, and may be recognized by 
 the same tests. It is insoluble in cold water, but in boiling water 
 its granules first swell, become gelatinous and opaline, then fuse 
 with each t)ther, and finally liquefy altogether, provided a sufficient 
 quantity of water be present. After that, they cannot be made to 
 resume their original form, but on cooling and drying merely solidify 
 into a homogeneous mass or paste, more or less consistent, accord- 
 ing to the quantity of water which remains in union with it. The 
 starch is then said to be amorphous or " hydrated." By this process 
 it is not essentially altered in its chemical properties, but only in 
 its physical condition. Whether in granules, or in solution, or in 
 an amorphous and hydrated state, it strikes a deep blue color on 
 the addition of free iodine. 
 
 Starch may be converted into sugar by three different methods. 
 First, by boiling with a dilute acid. If starch be boiled with dilute 
 
SUGAR. 83 
 
 nitric, sulphuric, or muriatic acid during thirty-six hours, it first 
 changes its opalescent appearance, and becomes colorless and trans- 
 parent; losing at the same time its power of striking a blue color 
 with iodine. After a time, it begins to acquire a sweet taste, and 
 is finally altogether converted into a peculiar species of sugar. 
 
 Secondly, by contact^ with certain animal and vegetable^ sub- 
 stances. Thus, boiled starch mixed with human saliva and kept 
 at the temperature of 100° F., is converted in a few minutes into 
 sugar. 
 
 Thirdly, by the processes of nutrition and digestion in animals 
 and vegetables. A'large part of the starch stored up in seeds and 
 other vegetable tissues is, at some period or other of the growth of 
 the plant, converted into sugar by the molecular changes going on 
 in the vegetable fabric. It is in this way, so far as we know, that 
 all the sugar derived from vegetable sources has its origin. 
 
 Starch, as a proximate principle, is more especially important as 
 entering largely into the composition of many kinds of vegetable 
 food. With these it is introduced into the alimentary canal, and 
 there, during the process of digestion, is converted into sugar. 
 Consequently, it does not appear in the blood, nor in any of the 
 secreted fluids. 
 
 2. SuGAE. — ^This group of proximate principles includes a con- 
 siderable number of substances, which differ in certain minor 
 details, while they resemble each other in the following partici^ars : 
 They are readily soluble in water, and crystallize more or less 
 perfectly on evaporation ; they have a distinct sweet taste ; and 
 finally, by the process of fermentation, they are converted into 
 alcohol and carbonic acid. 
 
 These substandes are derived from both animal and vegetable 
 sources. Those varieties of sugar which are most familiar to us 
 are the following six, three of which are of vegetable and three of 
 animal origin. 
 
 {Cane sugar, . . , /-Milk sugar, 
 
 Grape sugar, ^"'"^^ Liver sugar, 
 
 Sugar of starch. ' ^"^"^* ^ Sugar of honey. 
 
 The cane and grape sugars are held in solution in the juices of 
 the plants from which they derive their name. Sugar of starch, or 
 glucose, is produced by boiling starch for a long time with a dilute 
 acid. Liver sugar and sugar of poilk are produced .in the 
 tissues of the liver and the mammary gland, and the sugar of 
 
84 PROXIMATE PRINCIPLES OP THE SECOND CLASS. 
 
 honey is prepared in some way by tte bee from materials of vege- 
 table origin. 
 
 These varieties differ but little in their ultimate chemical compo- 
 sition. The following formulae have been established for three of 
 them. 
 
 Cane sugar 
 
 Milk sugar 
 
 Glucose 
 
 Gane sugar is sweeter than most of the other varieties, and more 
 soluble in water. Some sugars, such as liver sugar and sugar of 
 honey, crystallize only with great difficulty ; but this is probably 
 owing to their being mingled with other substances, from which it 
 is difficult to separate them completely. If they could be obtained 
 in a state of purity, they would doubtless crystallize as perfectly as 
 cane sugar. The different sugars vary also in the readiness with 
 which they undergo fermentation. Some of them, as grape sugar 
 and liver sugar, enter into fermentation very promptly ; others, 
 such as milk and cane sugar, with considerable difficulty. 
 
 The above are not to be regarded as the only varieties of sugar 
 existing in nature. On the contrary, it is probable that nearly 
 every different species of animal and vegetable produces a distinct 
 kind of siigar, differing slightly from the rest in its degree of sweet- 
 ness, its solubility, its crystallization, its aptitude for fermentation, 
 and perhaps in its elementary composition. Nevertheless, there is 
 so clese a resemblance between them that they are all properly 
 regarded as belonging to a single group. 
 
 The test most commonly employed for detecting the presence of 
 sugar is that known as Trommer's test. It depends upon the fact 
 that the saccharine substances have the power of reducing the 
 persalts of copper when heated with them in an "alkaline solution. 
 The test is applied in the following manner : A very small quantity 
 X)f .sulphate of copper, in solution should be added to the suspected 
 liquid, and the mixture then rendered distinctly alkaline by the 
 addition of caustic potassa. The whole solution then takes a deep 
 blue color. On boiling the mixture, if sugar be present, th& in- 
 soluble suboxide of copper is thrown down as an opaque red, 
 yellow, or orange-colored deposit; otherwise no change of color 
 takes place. 
 
 This test requires some precautions in its application. In the 
 first place, it is not applicable to all varieties of sugar. Cane 
 sugar, for example, when pure, has no power of 'reducing the salts 
 
SU6AB. 85 
 
 of copper, even when present in large quantity. Mapte sugar, also, 
 which resembles cane sugar in some other respects, reduces the 
 copper, in Trommer's test, but slowly and imperfectly. Beet-root 
 sugar, according to Bernard, presents the same peculiarity. If 
 these sugars, however, be boiled for two or three minutes with a 
 trace of sulphuric acid, they become converted into glucose, and 
 acquire the power of reducing the salts of copper. Milk sugar, 
 liver sugar, and sugar of honey, as well as grape sugar and glucose, 
 all act promptly and perfectly with Trommer's test in their natural 
 condition. 
 
 Secondly, care must be taken to add to the suspected liquid only 
 a small quantity of sulphate of copper, just sufficient to give to the 
 whole a distinct blue tinge, after the addition of the alkali. If a 
 larger quantity of the copper salt be used, the sugar in solution 
 may not be sufficient to reduce the whole of it ; and that which 
 remains as a blue sulphate will mask the yellow color of the sub- 
 oxide thrown down as a deposit. By a little care, however, in 
 managing the test, this source of error may be readily avoided. 
 
 Thirdly, there are some albuminous substances which have the 
 power of interfering with Trommer's test, and prevent the reduc- 
 tion of the copper even when sugar is present. Certain animal 
 matters, to be more par.ticularly described hereafter, which are 
 liable to be held in solution in the gastric juice, have this effect. 
 This source of error may be avoided, and the substances in ques- 
 tion eliminated when present, by treating the suspected fluid with 
 animal charcoal, or by evaporating and extracting it with alcohol 
 before the application of the test. 
 
 A less convenient but somewhat more certain test for sugar is 
 that of fermentation. The saccharine fluid is mix€d with a little 
 yeast, and kept at a temperature of 70° to 100° F. until the fer- 
 • menting process is completed. By this process, as already men- 
 tioned, the sugar is converted into alcohol and carbonic acid. The 
 gas, which is given off in minute bubbles during fermentation, 
 should be collected and examined. The remaining fluid is purified 
 by distillation and also subjected to examination. If the gas be 
 found to be carbonic acid, and the remaining fluid contain alcohol, 
 there can be no doubt that sugar was present at the commencement 
 of the operation. 
 
 The following list shows the percentage of sugar in various 
 articles of food.' 
 
 ' Pereira, op. cit., p. 55. 
 
PROXIMATE PRINCIPLES OF THE SECOND CLASS. 
 
 62.50 
 
 Wheat flour . 
 
 4.20 to 8.48 
 
 18.12 
 
 Eye meal 
 
 3.28 
 
 16.48 
 
 Indian meal 
 
 1.45 
 
 12.50 
 
 Peas . 
 
 2.00' 
 
 11.52 
 
 Cow's milk . 
 
 4.77 
 
 9.00 
 
 Ass's milk . 
 
 6.08 
 
 6.00 
 
 Human milk 
 
 6.50 
 
 5.21 
 
 
 
 Qdantitt of Sooar in 100 parts is 
 
 Figs . 
 
 Cherries 
 
 Peaches 
 
 Tamarinds 
 
 Pears 
 
 Beets 
 
 Sweet almonds 
 
 Bariey meal . 
 
 Besides the sugar, tterefore, which is taken into the alimentary- 
 canal in a pure form, a large quantity is also introduced as an in- 
 gredient of the sweet-flavored fruits and vegetables. All the 
 starchy substances of the food are also converted into sugar in the 
 process of digestion. Two of the varieties of sugar, at least, 
 originate in the interior of the body, viz., sugar of milk and liver 
 sugar. The former exists in a solid form in the substance of the 
 mammary gland, from which it passes in solution into the milk. 
 The liver sugar is found in the substance of the liver, and almost 
 always also in the blood of the hepatic veins. The sugar which is 
 introduced with the food, as well as that which is formed in the 
 liver, disappears by decomposition in the animal fluids, and does 
 not appear in any of the excretions. 
 
 3. Fats. — These substances, like the sugars, are derived from 
 both animal and vegetable sources. There are three principal 
 varieties of them, which may be considered as representing- the 
 class, viz : — 
 
 Oleine = Cg, Hg, 0,5 
 
 Margarine ..... 
 
 Stearine 
 
 The principal difference between the oleaginous and saccharine 
 substances, so far as regards their, ultimate chemical composition, 
 is that in the sugars the oxygen and hydrogen always exist together 
 in the proportion to form water ; while in the fats the proportions of 
 carbon and hydrogen are nearly the same, but that of oxygen is 
 considerably legs. The fats are a,ll fluid at a high temperature, but 
 assume the solid form on cooling. Stearine, which is the most 
 solid of the three, liquefies only at 143" F. ; margarine at 118° F. ; 
 while oleine remains fluid considerably, below 100° F., and even 
 very near the freezing point of water. The fats are all insoluble 
 in water, but readily soluble in ether. By prolonged boiling in 
 water with a caustic all^ali, they are decomposed, and as the result of 
 the decomposition there are formed two new bodies ; first, glycerine. 
 
FAT3. 
 
 87 
 
 ■whicli is a neutral fluid substance, and secondly, a fatty acid, viz : 
 oleic, margaric, or stearic acid, corresponding to the kind of fat 
 whicli has been used in the experiment. The glycerine remains in 
 a free state, while the fatty acid unites with the alkali employed, 
 forming an oleate, margarate, or stearate. This combination is 
 termed a soap, and the process by which it is formed is called 
 saponification. This process, however, is not a simple decomposition 
 of. the fatty body, since it can only take place in the presence of 
 water ; several equivalents of which unite with the elements of the 
 fatty body, and enter into the composition of the glycerine, &c., so 
 that the &,ttj acid and the glycerine together weigh more than the 
 original fatty substance which was decomposed. It is not proper, 
 therefore, to regard an oleaginous body as formed by the union of a 
 fatty acid with glycerine. It is formed, on the contrary, in all pro- 
 bability, by the direct combination of its ultimate chemical elements. 
 The different kinds of oil, fat, lard, suet, &c., contain the three 
 oleagin«us matters mentioned above, mingled together in different 
 proportions. The more solid fats contain a larger quantity of 
 stearine and margarine ; the less consistent varieties, a larger pro- 
 portion of oleine. Neither of the oleaginous matters, stearine, 
 margarine, or oleine, ever occur separately; but in every fatty sub- 
 stance they are mingled together, so that the more fluid of thepa hold 
 in solution the more solid. 
 Generally speaking, in the '^" 
 
 iiving body, these mixtures 
 are fluid, or nearly so ; for 
 though both stearine and 
 margarine are solid, when 
 pure, at the ordinary tem- 
 perature of the body, they 
 are held in solution, during 
 life, by the oleine with which 
 they are associated. After 
 death, however, as the body 
 cools, the stearine and mar- 
 garine sometimes separate 
 from the mixture in a crys- 
 talline form, since the oleine 
 can no longer hold in solu- 
 tion so large a quantity of them as it had dissolved at a higher 
 temperature. 
 
 Steakihb crystallized from 
 Olelae. 
 
 Warm Sulutioa ia 
 
88 
 
 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 
 
 Fig. 8. 
 
 These substances crystallize in very slender needles, wliicli are 
 sometimes straight, but more often somewhat curved or -wavy in 
 their outline. (Fig. 7.) 
 
 They are always deposited in a more or less radiated form ; -and 
 have sometimes a very elegant, branched, or arborescent arrange- 
 ment. 
 
 "When in a fluid state, the fatty substances present themselves 
 
 under the form of drops or 
 globules, which .vary indefir 
 nitely in size, but which 
 may be readily recognized 
 by their optical properties. 
 They are circular in shape, 
 and have a faint amber color, 
 distinct in the larger globules, 
 less so in the sma,ller. They 
 have a sharp, well* defined 
 outline (Fig. 8) ; and as they 
 refract the light strongly, 
 and act therefore as double 
 convex lenses, they present 
 a brilliant centre, surrounded 
 by a dark border. These 
 marks will generally be 
 sufficient to distinguish them under the microscope. 
 
 The foil-owing list shows the percentage of oily matter present in 
 various kinds of animal and vegetable food." 
 
 QftASTiTY OP Fat ix 100 parts in- 
 
 Oli!aoinops Pkinciplbb of Human Fat. 
 Steai'ine and Margarine crystallized ; Oleine fluid. 
 
 Filberts . 
 
 . 60.00 
 
 Ordinary meat 
 
 14.30 
 
 Walnuts 
 
 . 50.00 
 
 Liver of the ox 
 
 3.89 
 
 Cocoa-nuts 
 
 . 47.00 
 
 Cow's milk . 
 
 3.13 
 
 Olives . 
 
 . 32.00 
 
 Human milk 
 
 3.55 
 
 Linseed 
 
 . 22.00 
 
 Asses' milk . 
 
 0.11 
 
 Indian Corn . 
 
 . 9.00 
 
 Goats' milk . 
 
 3.32 
 
 Yolk of eggs . 
 
 . 28.00 
 
 , 
 
 
 The oleaginous matters present a striking peculiarity as to the 
 form under which they exist in the animal body; a peculiarity 
 which distinguishes them from all the other proximate principles. 
 The rest of the proximate principles are all intimately associated 
 together by molecular union, so as to form either clear solutions or 
 
 ' Pereira, op. cit., p. 81. 
 
PATS. 89 
 
 homogeneous solids. Thus, the sugars of the blood are in solution 
 in water, in company with the albumen, the phosphate of lime, 
 chloride of sodium, and the like ; all of them equally distributed 
 throughout the entire mass of the fluid. In the bones and car- 
 tilages, the animal matters and the calcareous salts are in similarly 
 intimate union with each otiier ; and in every other part of the 
 body the animal and inorganic ingredients are united in the same 
 way. But it is different with the fats. For, while the three prin- 
 cipal varieties of oleaginous matter are always united with each 
 other, they are not united with any of the other kinds of proximate 
 principles; that is, with water, saline substances, sugars, or albu- 
 minous matters. Almost the only exception to this is in the nerv- 
 ous tissue; in which, according to Eobin and Verdeil, the oily 
 matters seem to be united with an albuminoid substance. Another 
 exception is, perhaps, in the bile ; since some of the biliary salts 
 have the power of dissolving a certain quantity of fat. Every- 
 where else, instead of forming a homogeneous solid or fluid with 
 the other proximate principles, the oleaginous matters are found 
 in distinct masses or globules, which are suspended in serpus fluids, 
 interposed in the interstices between the anatomical elements, in- 
 cluded in the interior of cells, or deposited in the substance of 
 fibres or membranes. Even in the vegetable tissues, the oil is 
 always deposited in this manner in distinct drops or granules. 
 
 Owing to this fact, the oils can be easily extracted from the 
 organized tissues by the employment of simply mechanical pro- 
 cesses. The tissues, animal or vegetable, are merely cut into small 
 pieces and subjected to pressure, by which the oil is forced out 
 from the parts in which it was entangled, and separated, without 
 any further manipulation, in a state of purity. A moderately 
 elevated temperature facilitates the operation by increasing the 
 fluidity of the oleaginous matter ; but no other chemical agency is 
 required for its separation. Under the microscope, also, the oil- 
 drops and- granules can be readily perceived an* distinguished 
 from the remaining parts of the tissue, and can, moreover, be 
 easily recognized by the dissolving action of ether, which acts 
 upon them, as a general- rule, without attacking the other proxi- 
 mate principles. 
 
 Oils are found, in the animal body, most abundantly in the 
 adipose tissue. Here they are contained in the interior of the 
 adipose vesicles, the cavities of which they entirely fill, in a state 
 
90 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 
 
 HnuAN Adipose Tissue. 
 
 of health. These vesicles afe transparent, and have a somewhat 
 angular form, owing to their mutual compression. (Fig. 9.) They 
 
 vary in diameter, in the hu- 
 . '*■ ■ man subject, from ^f u to j^^ 
 
 of an inch, and are composed 
 of a thin, structureless ani- 
 mal membrane, forming a 
 closed sac, in the interior of 
 which the oily matter is con- 
 tained. There is here, accord- 
 ingly, no union whatever of 
 the oil with the other proxi- 
 mate principles, but only a 
 mechanical inclusion of it in 
 the interior of the vesicles. 
 Sometimes, when emaciation- 
 is going on, the oil partially 
 disappears from the cavity of 
 the adipose vesicle, and its place is taken by a watery serum ; but 
 the serous and oily fluids always remain distinct, and occupy differ- 
 ent parts of the cavity of the vesicle. 
 
 In the chyle, the oleaginous matter is in a state of emulsion or 
 suspension in the form of minute particles in a serous fluid. Its 
 
 subdivision is here more com- 
 a's- 10. plete, and its molecules more 
 minute, than anywhere else 
 in the body. It presents the 
 appearance of a fine granular 
 dust, which has been known 
 by the name of the "molecu- 
 lar base of the chyle." A 
 few of these granules are to 
 be seen which measure TTr^Ttr 
 of an inch in diameter ; but 
 they are generally much less 
 than this, and the greater part 
 are so small that they cannot 
 be accurately measured. (Fig. 
 10.) For the same reason 
 they do not present the bril- 
 liant centre and dark border of the larger oil-globules ; but appear 
 
 Chti.e, from commcQcemeDt of Thoracic Duct, 
 from the Dog. 
 
FATS. 
 
 91 
 
 by transmitted light only as minute dark grannies. The white 
 color and opacity of the chyle, as of all other fatty emulsions, 
 depend upon this molecular condition of the oily ingredients. " The 
 albumen, salts, &c., which are in intimate union with each other, 
 and in solution in the water, would alone make a colorless and 
 transparent fluid ; but the oily matters, suspended in distinct par- 
 ticles, which have a different refractive power from the serous fluid, 
 interfere with its transparency 
 
 and give it the white color and ^'S- H- 
 
 opaque appearance which are 
 characteristic of emulsions. 
 The oleaginous nature of these 
 particles is readily shown by 
 their solubility in ether. 
 
 In the milk, the oily matter 
 occurs in larger masses than 
 in the chyle. In cow's milk 
 (Fig. 11), these oil-drops, or 
 "milk-globules," are not quite 
 fluid, but have a pasty con- 
 sistency, owing to the large 
 quantity of margarine which 
 they contain, in proportion to 
 
 the oleine. When forcibly amalgamated with each other and 
 collected into a mass by prolonged beating or churning, they con- 
 stitute butter. In cow's milk, 
 
 Globiti.es of Cow^s Milk. 
 
 the globules vary somewhat 
 in size, but their average 
 diameter is ^^Vtt of an inch. 
 They are simply suspended 
 in the serous fluid of the 
 milk, and are not covered 
 with any albuminous mem- 
 brane. 
 
 In the cells of the laryn- 
 geal, tracheal, and costal car- 
 tilages (Fig. 12), -there is 
 always more or less fat de- 
 posited in the form of rounded 
 globules, somewhat similar to 
 those of the milk. 
 
 Fig. 12. 
 
 GrTiLS of Cmstaz. Cartilaoks, costalaiog Oal^ 
 Globules. Huniaa. 
 
92 PEOX-IMATE PKINCIPLES OP THE SECOND CLASS. 
 
 Fis. 13. 
 
 Hepatic Cellb. Humao, 
 
 In the glandular cells of the liver, oil occurs constantly, in a 
 
 state of health. It is here deposited in the substance of the cell 
 
 (Fig.lS), generally in smaller 
 globules than the preceding. 
 In some cases of disease, it 
 accumulates in excessive 
 quantity, and produces the 
 state known as fiatty degene- 
 ration of the liver. This is 
 consequently only an ex- 
 aggerated condition of that 
 which normally exists in 
 health. 
 
 In the carnivorous animals 
 oil exists in considerable 
 quantity in the convoluted 
 •portion of the uriniferous 
 tubules. (Pig. 14.) It is here 
 
 in the form of granules and rounded drops, which sometimes appear 
 
 to fill nearly the whole calibre, of the tubules. 
 
 It is found also in the secreting cells of 'the sebaceous and other 
 
 glandules, deposited in. the 
 same manner as in those of 
 tte liver, but in smaller 
 quantity. It exists, beside, 
 in large proportion, in a 
 granular form, in the secre- 
 tion of the sebaceous gland- 
 ules. 
 
 It occurs abundantly in . 
 the marrow of the bones, 
 both under the form of free 
 oil-globules and inclosed in 
 the vesicles of adipose tissue. 
 It is found in considerable 
 quantity in the substance of 
 the yellow wall of the corpus 
 luteum, and is the immediate 
 
 cause of the peculiar color of this body. 
 
 It occurs also in the form of granules and oil-drops in the 
 
 muscular fibres of the uterus (Fig. 15), in which it begins to be 
 
 Fig. 14. 
 
 ' URisipEKons Tdbules op Dog, from Cortical 
 Portion of Kidney. 
 
JATS. 
 
 93 
 
 MnsCPLAR FlBRKS OP II UMA N UTERUS 
 
 weektt ul'ter parturition. 
 
 three 
 
 deposited soon after delivery, and where it continues to be present 
 during the whole period of the resorption or involution of this organ. 
 
 In all these instances, the oleaginous matters remain distinct in 
 form and situation from the 
 
 other ingredients of the ani- 'S- • • 
 
 mal frame, and are only me- 
 chanically entangled among 
 its fibres and cells, or im- 
 bedded separately in their 
 interior. 
 
 A large part of the fal 
 which is found in the body 
 may be accounted for by that 
 which is taken in with the 
 food, since oily matter occurs 
 in both animal and vegetable 
 substances. Fat is, however, 
 formed in the body, independ- 
 ently of what is introduced 
 with the food. This im- 
 portant fact has been definitely ascertained by the experiments of 
 MM. Dumas and Milne-Edwards on bees,' M. Persoz on geese,' and 
 finally by those of M. Bou^singault on geese, ducks, and pigs.' The 
 observers first ascertained the quantity of fat existing in the whole 
 body at the commencement of the experiment. The animals were 
 then subjected to a definite nutritious regimen, in which the 
 quantity of fatty matter was duly ascertained by analysis. The 
 experiments lasted for a period varying, in different instances, from 
 thirty- one days to eight months; after which the animals were 
 killed and all their tissues examined. The result of these investi- 
 gations showed that considerably more fat had been accumulated 
 by the animal during the course of the experiment than could be 
 accounted for by that which existed in the food ; and placed it 
 beyond a doubt that, oleaginous substances may be, and actually 
 are, formed in the interior of the animal body by4he decomposition 
 or metamorphosis of other proximate principles. 
 
 It is not known from what proximate principles the fat is pro-" 
 duced, when it originates in this way in the interior of the body. 
 Particular kinds of food certainly favor its production and accu- 
 
 I Annales de Chim. et de Phys., 3d series, xol. xiv. p. 400. 
 ' Chiiuie Agrioole, Paris, 1854. 
 
 ' Ibid., p. 408. 
 
94: PBOXIMATE PRINCIPLES OF THE SECOND CLASS. 
 
 mulation to a considerable degree. It is well known, for instance, 
 that in sugar-growing countries, as in Louisiana and the West 
 Indies, during the few weeks occupied in gathering the pane and 
 extracting the sugar, all the negroes employed on the plantations, 
 and even the horses and cattle, that are allowed to feed freely on 
 the saccharine juices, grow remarkably fat; and that they again lose 
 their superabundant flesh when the season is past. Even in these 
 instances, however, it is not certain whether the saccharine substances 
 are directly converted into fat, or whether they are first assimilated 
 and only afterward supply the materials for its production. The 
 abundant accumuMion of fat in certain regions of the body, and its 
 absence in others ; and more particularly its constant occurrence in 
 certain situations to which it could not beiransported by the blood, 
 as for example the interior of the cells of the costal cartilages, the 
 substance of the muscular fibres of the uterus after parturition, &c., 
 make it probable that under ordinary conditions the oily matter is 
 formed by decomposition of the tissues upon the very spot where 
 it subsequently makes its appearance. 
 
 In the female during lactation a large part of the oily matter 
 introduced, with the food, or formed in the body, is discharged with 
 the milk, and goes to the support of the infant. But in the female 
 in the intervals of lactation, and in the male at all times, the oiljr ■ 
 matters almost entirely disappear by decomposition in the interior 
 of the body; since the small quantity which is discharged with the 
 sebaceous matter by the skin bears only an insignificant proportion 
 to that which is introduced daily with the food. 
 
 The most important characteristic, in a physiological point- of 
 view, of the proximate principles of the second class, relates to their 
 origin and their final destination. Not only are they all of a purely 
 organic origin, making their appearance first in the interior of vege- 
 tables ; but the sugars and the oils are formed also, to a certain ex- 
 tent, in the bodies of animals ; continuing to make their appearance 
 when no similar substances, or only an insufficient quantity of them, 
 have been taken with the food. Furthermore, when introduced 
 with the food, or formed in the body and deposited in the tissues, 
 these substances do not reappear in the secretions. They, therefore, 
 for the most part disappear by decomposition in the interior of the 
 body. They pass through a series of changes by which their es- 
 sential characters are destroyed ; and they are finally replaced in 
 the circulation by other substances, which are discharged with the 
 excreted fluids. 
 
PROXIMATE PBINCIFLES OF THE TUIKD CLASS. 95 
 
 CHAPTER IV. 
 
 PROXIMATE PRINCIPLES OP THE THIRD CLASS. 
 
 The substances belonging to this class are very important, and 
 form by far the greater part of the entire mass of the body. They 
 are derived both from animal and vegetable sources. They have 
 been known by the name of the "protein compounds" and the 
 " albuminoid substances." The name organit substances was given 
 to them by Eobin and Verdeil, by whom their distinguishing pro- 
 perties were first accurately described. They have not only an 
 oi-ganio origin, in common with the proximate principles of the 
 second class, but their chemical constitution, their physical struc- 
 ture and characters, and the changes which they undergo, are all so 
 different from those met with in any other class, that the terra " or- 
 ganic substances" proper appears particularly appropriate to them. 
 
 Their first peculiarity is that they are not crystallizable. They 
 always, when pure, assume an amorphous condition, which is some- 
 times solid (organic substance of the bones), sometimes fluid (albu- 
 men of the blood), and sometiipes semi-solid in consistency, midway 
 between the solid and fluid condition (organic substance of the 
 muscular fibre). 
 
 Their chemical constitution differs from that of bodies of the 
 second class, first in the fact that they all contain the four chemical 
 elements, oxygen, hydrogen, carbon, and nitrogen; while the 
 starches, sugars, and oils are destitute of the last named ingredient. 
 The organic matters have therefore been sometimes know;n by the 
 name of the " nitrogenous substances," while the sugars, starch, and 
 oils have been called " non-njtrogenous." Some of the organic mat- 
 ters, viz., albumen, fibrin, and casein, contain sulphur also, as an in- 
 gredient ; and others, viz., the coloring matters, contain iron. The 
 temainder consist of oxygen, hydrogen, carbon, and nitrogen alone. 
 
 The most important peculiarity, however, of the organic sub- 
 stances, relating to their chemical composition, is that it is not 
 definite. That is to say, they do not always contain precisely the 
 same proportions of oxygen, hydrogen, carbon, and nitrogen ; but 
 
96 PROXIMATE PKINCIPLES OF THE THIBD CLASS. 
 
 • the relative quantities of, these elements vary within certain limits, 
 in different individuals and at different times, without modifying, in 
 any essential degree, the peculiar properties of the animal matters 
 which they constitute. This fact is altogether a special one, and 
 characteristic of organic substances. No substance having a definite 
 chemical composition, like phosphate of lime, starch, or olein, can 
 suffer the slightest change in its ultimate constitution without being, 
 by that fact alone, totally altered in its essential properties. If 
 phosphate of lime, for example, were to lose one or two equivalebts 
 of oxygen, an entire destruction of the salt would necessarily result, 
 and it would cease to be phosphate of lime. For its properties as a 
 salt depend entirely upon its ultimate (ftiemioal constitution ; and if 
 the latter be changed in any way, the former are necessarily lost. 
 
 But the properties -which distinguish the organic substances, and 
 which make them important as ingredients of the body, do not 
 depend immediately upon their ultimate chemical constitution, and 
 are of a peculiar character ; being such as are only manifested in 
 the interior of the living organism. Albumen, therefore, though 
 it may contain a few equivalents more or less of Oxygen or nitrogen, 
 does not on that account cease to be albumen, so long as it retains 
 its fluidity and its aptitude for undergoing the processes of, absorp- 
 ■ tion and transformation, which characterize it as an, ingredient of 
 the living body. 
 
 It is for this reason that considerable discrepancy has existed at 
 various times among chemists as to the real ultimate composition 
 of these substances, different experimenters often obtaining differ- 
 ent analytical results. This is not owing to any inaccuracy in the 
 analyses, but to the fact that the organic substance itself really has 
 a different ultimate constitution at, different times. The most ap- 
 proved formulae are those which have been established by Liebig 
 for the following substances : — 
 
 F'*'"° =C„JWN,„o„s, 
 
 ^l**"™*" = Cj,6H„,N„0„,S, 
 
 C^^«'" • = C,,,H,,,Nj|Os„S, 
 
 Owing to the above mentioned variations, however, the same 
 degree of importance does not attach to the quantitative ultimate 
 analysis of an organic matter, as to that of other substances. 
 „., This absence of a definite chemical constitution in the organic sub- 
 stances is undoubtedly connected with their incapacity for crystalli- 
 zation. It is also connected with another almost equally peculiar 
 fact, viz., that although the organic substances unite with acids and 
 
ORGANIC SUBSTANCES. 97 
 
 •with alkalies, they do not play the part of an acid towards the base, 
 or of a base towards the acid ; for the acid or alkaline reaction of 
 the substance employed is not neutralized, but remains as strong 
 after the combination as before. Futhermore, the union does not 
 take place, so far as can be ascertained, in any definite proportions. 
 The organic substances have, in fact, no combining equivalent ; and 
 their molecular reactions and the changes which they undergo in 
 the body cannot therefore be expressed^by the ordinary chemical 
 phrases which are adapted to inorganic substances. Their true 
 characters, as proximate principles, are accordingly to be sought 
 for in other properties than those which depend upon their exact 
 ultimate composition. 
 
 One of these characters is that they are hygroscopic. As met with 
 in different parts of the body, they present different degrees of con- 
 sistency ; some being nearly solid, others more or less fluid. But on 
 being subjected to evaporation they all lose water, and are reduced 
 to a perfectly solid form. If after this desiccation they be exposed 
 to the contact of moisture, they again absorb water, swell, and 
 regain their original mass and consistency. This phenomenon is 
 quite different from that of capillary attraction, by which some in- 
 organic substances become moistened when exposed to the contact 
 of water ; for in the latter case the water is simply entangled me- 
 chanically in the meshes and pores of the inorganic body, while that 
 which is absorbed' by the organic matter is actually united with its 
 substance, and difiused equally throughout its entire mass. Every 
 organic matter is naturally united in this way with a certain quantity 
 of water, some more and some less. Thus the albumen of the blood 
 is in union with so much water that it has the fluid form, while the 
 organic substance of cartilage contains less and is of a firmer con- 
 sistency. The quantity of water contained in each organic sub- 
 stance may be diminished by artificial desiccation, or by a deficient 
 supply ; but neither of them can be made to take up more than a 
 certain amount. Thu? if the albumen of the blood and the organic 
 substance of cartilage be both reduced by evaporation to a similar 
 degree of dryness and then placed in water, the albumen will absorb 
 so much as again to become fluid, but the cartilaginous substance 
 only so much as to regain its usual nearly solid consistency. Even 
 where the organic substance, therefore, as in the case of albumen, 
 becomes fluid under these circumstances, it is not exactly a solution 
 of it in water, but only a reabsorption by it of that quantity of fluid 
 with which it is naturally associated. 
 7 
 
98 PROXIMATE PBINCIPLBS OF THE THIRD CLASS. 
 
 Another peculiar phenomenon characteristic of organic substances 
 is their coagulation. Those which are naturally fluid suddenly as- 
 sume, under certain conditions, a solid or semi-solid consistency. 
 They are then said to be coagulated ; and after coagulation they 
 cannot be made to resume their original condition. Thus fibrin 
 coagulates on being withdrawn from the bloodvessels, albumen on 
 being subjected to the temperature of boiling water, casein on being 
 placed in contact with ai^ acid. When an organic substance thus 
 coagulates, the change which takes place is a peculiar one, and has 
 no resemblance to the precipitation of a solid substance from a 
 watery solution. On the contrary, the organic substance merely 
 assumes a special condition ; and in passing into the solid form it 
 retains all the water with which it was previously united. Albumen, 
 for example, after coagulation, retains the same quantity of water in 
 union with it, which it held before. After coagulation, accordingly, 
 this water may be driven off by evaporation, in the same manner 
 as previously ; and on being again exposed to moisture, the organic 
 matter will again absorb the same quantity, though it will not re- 
 sume the fluid form. 
 
 By coagulation, an organic substance is permanently altered ; and 
 though it may be afterwards dissolved by certain chemical re-agents, 
 as, for example, the caustic alkalies, it is not thereby restored to its 
 original condition, but only suffers a still further alteration. 
 
 In many instances we are obliged to resort to coagulation in 
 Order to separate an organic substance from the other proximate 
 principles with which it is associated. This is the case, for example, 
 with the fibrin of the blood, which is obtained in the form- of floc- 
 culi, by beating freshly-drawn blood with a bundle of rods. But 
 when separated in this way, it is already in an unnatural condition, 
 and no longer represents exactly the original fluid fibrin, as it ex- 
 isted in the circulating blood. Nevertheless, this is the only mode 
 in which it can be examined, as there are no means of bringing it 
 back to its previous condition. 
 
 Another important property of the organic substances is that 
 they readily excite, in other proximate principles and in each other, 
 those peculiar indirect chemical changes which are termed catalyses 
 or catalytic transformations. That is to say, they produce the changes 
 referred to, not directly, by combining with the substance which 
 suffers alteration, or with any of its ingredients ; but simply by their 
 presence which induces the chemical change in an indirect manner. 
 Thus, the organic substances of the intestinal fluids induce a cata- 
 
OKGANIC SUBSTANCES. 99 
 
 lytic action by whicTi starch is converted into sugar. The albumen 
 of the blood, by contact with the organic substance of the muscular 
 fibre, is transformed into a substance similar to it. The entire 
 process of nutrition, so far as the organic matters are concerned, 
 consists of such catalytic transformations. Many crystaUizable 
 substances, which when pure remain unaltered in the air, become 
 changed if mingled with organic substances, even in small quantity. 
 Thus the casein of milk, after being exposed for a short time to a 
 warm atmosphere, becomes a catalytic body, and converts the sugar 
 of the milk into lactic acid. In this change there is no loss nor 
 addition of any chemical element, since lactic acid has precisely the 
 same ultimate composition with sugar of milk. It is simply a 
 transformation induced by the presence of the casein. Oily matters, 
 which are entirely unalterable when pure, readily become rancid at 
 warm~temperatures, if mingled 'with an organic impurity. 
 
 Fourthly, The organic substances, when beginning to undergo 
 decay, induce in certain other substances the phenomena of fer- 
 mentation. Thus, the mucus of the urinary bladder, after a short 
 exposure to the atmosphere, causes the urea of the urine to be con- 
 verted into carbonate of ammonia, with the development of gaseous 
 bubbles. The organic matters of grape juice, under similar circum- 
 stances, give rise to fermentation of the sugar, by which it is con- 
 verted into alcohol and carbonic acid. 
 
 Fifthly, The organic substances are the only ones capable of 
 undergoing the process of putrefaction. This process is a compli- 
 cated one, and is characterized by a gradual liquefaction of the ani- 
 mal substance, by many mutual decompositions of the saline matters 
 which are associated with it, and by the development of peculiarly 
 fetid and unwholesome gases, among which are carbonic acid, 
 nitrogen, sulphuretted, phosphoretted, and carburetted hydrogen, 
 and ammoniacal vapors. Putrefaction takes place constantly after 
 death, if the organic tissue be exposed to a moist atmosphere at a 
 moderately warm temperature. It is much hastened by the presence 
 of other organic substances, in which decomposition has already 
 commenced. 
 
 The organic substances are readily distinguished, by the above 
 general characters, from all other kinds of proximate principles. 
 They are quite numerous ; nearly every animal fluid and tissue 
 containing at least one which is peculiar to itself. They have not 
 as yet been all accurately described. The following list, however, 
 comprises the most important of them, and those with whixsh we are 
 
100 PROXIMATE PBINCIPLES OF THE THIRD CLASS. 
 
 at present most thoroughly acquainted. The first seven are fluid, 
 or nearly so, and either colorless or of a faint yellowish tinge. 
 
 1. FlBRHsr. — Fibrin is found in the blood ; where it exists, in the 
 human su]?ject, in the proportion of two to three parts per thousand. 
 It is fluid, and mingled intimately with the other ingredients of the 
 blood. It occurs also, but in much smaller quantity, in the lymph. 
 It is distinguished by what is called its " spontaneous" Coagulation ; 
 that is, it coagulates on being withdrawn from the vessels, or on the 
 occurrence of any stoppage to the circulation. It is rather more 
 abundant in the blood of some of the lower animals than in that of 
 th human subject. In general, it is found in larger quantity in 
 the blood of the herbivora than in that of the camivora. 
 
 2. Albumen. — Albumen occurs in the blood, the lymph, the 
 fluid of the pericardium, and in that of the serous cavities gene- 
 rally. It is also present in the fluid which may be extracted by 
 pressure from the muscular tissue. In the blood it occurs in the 
 proportion of about seventy -five parts per thousand. The white of 
 egg, which usually goes by. the same name, is not identical with the 
 albumen of the blood, thoiigh it resembles it in some respects ; it is 
 propeirly a secretion from the mucous membrane of the fowl's ovi- 
 duct, and should be considered as a distinct organic substance. 
 Albumen coagulates on being raised to the teniperature of 160° F.; 
 and the coagulum, like that of all the other proximate principles, is 
 soluble in caustic potassa. It coagulates also by contact with alco- 
 hol, the mineral acids, ferrocyanide of potassium in an acidulated 
 solution, tannin, and the metallic salts. The alcoholic coagulum, if 
 separated from the alcohol by washing, does not redissolve in water. 
 A very smaH quantity of albumen has been sometimes found in the 
 saliva. • 
 
 8. 'CaseiN;— This substance exists in milk, in the proportion of 
 about forty parts per thousand. It coagulates' by contact with all 
 the acids, mineral and organic ; but is not affected by a boiling 
 •temperature. It is coagulated also by the juices of the stomach. 
 It is impoJtant as ssn article of food, being the principal organic 
 ingredient m all the preparations of milk. In a coagulated form, 
 it constitutes the different varieties of cheese, which are more or 
 less highly flavored with various oily matters remaining entangled 
 in the coagulated casein. 
 
GLOBULINE. — MUCOSINE. 101 
 
 What is called vegetable casein or "legumine," is different from 
 tbe casein of milk, and constitutes the organic substance present in 
 various kinds of peas and beans. 
 
 4. GLOBULiNE.^This is the organic substance forming the prin- 
 cipal mass of the red globules of the blood. It is nearly fluid in 
 its natural condition, and readily dissolves in water. It does not 
 dissolve, however, in the serum of the blood ; and the globules, 
 therefore, retain their natural form and consistency, unless the 
 serum be diluted with an excess of water. Globuline resembles 
 albumen in coagulating at the temperature of boiling water. It is 
 said to differ from it, however, in not being coagulated by contact 
 with alcohol. 
 
 5. Pepsine. — T-his substance occurs as an ingredient in the gas- 
 tric juice. It is not the same substance which Schwann extracted 
 by maceration from the mucous membrane of the stomach, and 
 which is regarded by Eobin, Bernard, &c., as only an artificial pro- 
 duct of the alteration of the gastric tissues. There seems no good 
 reason, furthermore, why we should not designate by this name the 
 organic substance which really exists in the gastric juice. It occurs 
 in this fluid in very small qu9,ntity, not over fifteen parts per 
 thousand. It is coagulable.by heat, and also by contact with alco- 
 hol. But if the alcoholic coagulum be well washed,' it is again 
 soluble in a watery acidulated fluid. 
 
 6. Pancbeatine. — This is the organic substance of the pancrQ9,tic 
 jilice, where it occurs in great abundance. It coagulates by heat, 
 and by contact with sulphate of magnesia in excess. In its natural 
 condition it is fluid, but has a considerable degree of viscidity. 
 
 7. MuscosiNE is the organic substance which is found in the dif- 
 ferent varieties of mucus, and which imparts to them their viscidity 
 and other physical characters. Some of these mucous secretions 
 are so mixed with other fluids, that their consistency is more or less 
 diminished ; others, which remain pure, like that secreted by the 
 mucous follicles of the cervix uteri, have nearly a semi-solid con- 
 sistency. But little is known with regard to their other specific 
 characters. 
 
 The next three organic substances are solid or semi-solid in con- 
 sistency. 
 
102 PBOXIMATE PEINCIPLES OF THE THIBD CLASS. 
 
 8. OsTEiNE is the organic substance of the bones, in which it is 
 associated with a large proportion of phosphate of lime. It exists, 
 in those bones which have been examined, in the proportion of 
 about two hundred parts per thousand. It is this substance which 
 by long boiling of the bones is transformed into gelatine or glue. 
 In its natural condition, however, it is insoluble in water, even, at 
 the boiling temperature, and becomes soluble only after it has been 
 permanently altered by ebullition. 
 
 9. Caetilagine. — This forms the organic ingredient of cartilage. 
 Like that of the bones, it is altered by long boiling, and is converted 
 into a peculiar kind of gelatine termed "chondrine." Chondrine 
 differs from the gelatine of bones principally in being precipitated' 
 by acids and certain metallic salts which have no effect on the latter. 
 Cartilagine, in its natural condition, is very solid, and is closely 
 united with the calcareous salts. 
 
 10. MusouLiNE. — This substance forms the principal mass of the 
 muscular fibre. It is semi-solid, and insoluble in water, but soluble 
 in dilute muriatic acid, from which it may be again precipitated by 
 neutralizing with an alkali. It closely resembles albumen in its 
 chemical composition, and like it, contains, according to Scherer, 
 two equivalents of sulphur. 
 
 The four remaining organic substances form a somewhat peculiar 
 group. They are the coloring matters of the body. They exist 
 alw'ays in small quantity, compared with the other ingredients, but 
 communicate to the tissues and fluids a very distinct coloration. 
 They all contain iron as one of their ultimate elements. 
 
 11. H^MATiNE is the coloring matter of the red globules of the 
 blood. It is nearly fluid like the globuline, and isunited with it 
 in a kind of mutual solution. It is much less abundant than the 
 globuline, and exists in the proportion of about one part of hsema- 
 tine to seventeen parts of globuline. The following is the formula 
 for its composition which is adopted by Lehmann : — 
 
 Haematine = C^^HjjNjOjFe. 
 
 When the blood-globules from any cause become disintegrated, the 
 haematine is readily imbibed after death by the walls of the blood- 
 vessels and the neighboring parts, staining them of a deep red 
 color. This coloration has sometimes been mistaken for an evidence 
 
MELANINE. — UROSAOINE. 103 
 
 of arteritis ; but is really a simple effect of post-mortem imbibition, 
 as above stated. 
 
 12. MeIiAnine. — This is the blackish-brown, coloring matter 
 which is found in the choroid coat of the eye, the iris, the hair, and 
 more or less abundantly in the epidermis. So far as can be ascer- 
 tained, the coloring matter is the same in all these situations. It is 
 very abundant in the black and brown races, less so in the yellow 
 and white, but is present to a certain extent in all. Even where 
 the tinges produced are entirely different, as, for example, in brown 
 and blue eyes, the coloring matter appears to be the same in cha- 
 racter, and to vary only in its quantity and the mode of its arrange- 
 ment; for the tinge of an animal tissue does not depend on its 
 local pigment only, but also on the muscular fibres, fibres of areolar 
 tissue, capillary bloodvessels, &o. All these ingredients of the 
 tissue are partially transparent, and by their mutual interlacement 
 and superposition modify more or less the effect of the pigment 
 which is deposited below or among them. 
 
 Melanine is insoluble in water and the dilute acids, but dissolves 
 slowly in caustic potassa. Its ultimate composition resembles that 
 of hsematine, but the proportion of iron is smaller. 
 
 13. BiLiVEBDiNE is the coloring matter of the bile. It is yellow 
 by transmitted light, greenish by reflected light. On exposure to 
 the air in its natural fluid condition, it absorbs oxygen and assumes 
 a bright grass-green color. The same effect is produced by treating 
 it with nitric aicid or other oxidizing substances. It occurs in very 
 small quantity in the bile, from which it may be extracted by pre- 
 cipitating it with milk of lime (Eobin), from which it is afterward 
 separated by dissolving out the lime with muriatic acid. Obtained 
 in this form, however, it is insoluble in water, having been coagu- 
 lated by contact with the calcareous matter ; and is not, therefore, 
 precisely in its original condition. 
 
 14. Urosacinb is the yellowish -red coloring matter of the urine. 
 It consists of the same ultimate elements as the other coloring mat- 
 ters, but occurs in the urine in such minute quantity, that the 
 relative proportion of its elements has never been determined. It 
 readily adheres to insoluble matters when they are precipitated from 
 the urine, and is consequently found almost always, to a greater or 
 less extent, as an ingredient in urinary calculi formed of the urates 
 
104 PROXIMATE PRINCIPLES OP THE THIRD CLASS. 
 
 or of uric acid. Wheu the urates are thrown down also in the form 
 .of a powder, as a urinary deposit, they are usually colored more or 
 less deeply, according to the quantity of urosacine which is preci- 
 pitated with them. 
 
 The organic substances which exist in the body require for their 
 production an abundant supply of similar substances in the food. 
 All highly nutritious articles of diet, therefore, contain more or less 
 of these substances. Still, though nitrogenous matters must be 
 abundantly supplied, under some form, from without, yet the par- 
 ticular kinds of organic substances, characteristic of the tissues, are 
 formed in the body by a transformation of those which are intro- 
 duced with the food. The organic matters derived from vegetables, 
 though similar in their general characters to those existing in the 
 animal body, are yet specifically different. The gluten of wheat, 
 the legumine of peas and beans, are not the same with animal albu- 
 men and fibrin. The only organic substances taken with animal 
 food, as a general rule, are the albumen of eggs, the casein of milk, 
 and the musculine of flesh ; and even these, in the food of the 
 human species, are so altered and coagulated by the process of 
 cooking, as to lose their specific characters before being introduced 
 into the alimentary canal. They are still further changed by the 
 process of digestion, and are absorbed under another form into the 
 blood. But from their subsequent metamorphoses there are formed, 
 in the different -parts of the body, osteine, cartilagine, hsematine, 
 globuline, and all the other varieties of organic matter that cha- 
 racterize the different tissues. These varieties, therfefore, originate 
 as such in the animal economy by the catalytic changes which the 
 ingredients of the blood undergo in nutrition. 
 
 Only a very sinall quantity of organic matter is discharged 
 with the excretions. The coloring matters of the bile and urine, 
 and the mucus of the urinary bladder, are almost the only ones 
 that find an exit from the body in this way. There is a minute 
 quantity of organic matter exhaled in a volatile form with the 
 breath, and a little also, in all probability, from the cutaneous sur- 
 fece. But the entire quantity so discharged bears but a very small 
 proportion to that which is daily introduced with the food. The 
 organic substances, therefore, are decomposed in the interior of- the 
 body. They are transformed by the process of destrustive assimi- 
 lation, and their elements are finally eliminated and discharged 
 under other forms of combination. 
 
OF FOOD. 105 
 
 CHAPTER V. 
 
 OF FOOD. 
 
 Under tte term " food" are included all those substances, solid 
 and liquid, which are necessary to sustain the process of nutrition. . 
 The first act of this process is the absorption from without of all 
 those materials which enter into the composition of the living frame, 
 or of others which may be converted into them in the interior of 
 the body. * 
 
 The proximate principles of the first class, or the "inorganic 
 substanf es," require to be supplied in sufficient quantity to keep up 
 the natural proportion in which they exist in the various solids and 
 fluids. As we have found it to be characteristic of these substances, 
 except in a few instances, that they suffer no alteration in the in- 
 terior of the body, but, on the contrary, are absorbed, deposited in 
 its tissue, and pass out of it afterward unchanged, nearly every one 
 of them requires to be present under its ovm proper form, and in 
 sufficient quantity in the food. The alkaline carbonates, which 
 are formed, as we have seen, by a decomposition of the malates, 
 citrates and tartrates, constitute almost the only exception to this 
 rule. 
 
 Since water enters so largely into the composition of nearly every 
 part of the body, it is equally important as an ingredient of the 
 food. In the case of the human subject, it is probably the most 
 important substance to be supplied with constancy and regularity, 
 and the system suffers more rapidly when entirely deprived of 
 fluids, than when th^ supply of solid food only is withdrawn. A 
 man may pass eight or ten hours, for example, without so'lid food, 
 and suffer little or no inconvenience; but if deprived of water for 
 the same length of time, he becomes rapidly exhausted, and feels 
 the deficiency in a very marked degree. Magendie found, in his 
 experiments on dogs subjected to inanition,' that if the animals 
 
 ■ Comptes Rendns, vol. xiii. p. 256. 
 
106 OP FOOD. 
 
 were supplied with -water alone they lived six, eight, and even ten 
 days longer than if they were deprived at the same time of both 
 solid and liquid food. Chloride of sodium, also, is usually added 
 to the food in considerable quantity, and requires to be supplied 
 with tolerable regularity ; but the remaining inorganic materials, 
 such as calcareous salts, the alkaline phosphates, &o./ occur natu- 
 rally in sufficient quantity in most of the articles which are used as 
 food. 
 
 The proximate principles of the second class, so far as they con- 
 stitute ingredients of the food, are naturally divided into two 
 groups : 1st, the sugar, and 2d, the oily matters. Since starch is 
 always converted into sugar in the process of digestion, it may. be 
 included, as an alimentary substance, in the same group with the 
 sugars. There is a natural desire in the human species for both 
 saccharine and olea,ginous food. In the purely carnivorous animals, 
 however, though no starch or sugar be taken, yet the body is main- 
 tained in a healthy condition. It has been supposed, therefore, that 
 saccharine matters could not be absolutely necessary as fqpd ; the 
 more so since it has been found, by the experiments of CI. Bernard, 
 that, in carnivorous animals kept exclusively on a diet of flesh, 
 sugar is still formed in the liver, as well as in the mammary gland. 
 The above conclusion, however, which has been drawn from these 
 fects, does not apply practically to the human species. The car- 
 nivorous animals have no desire for vegetable food, while in the 
 human species there is a natural craving for it, which is almost 
 universal. It may be dispensed with for a few days, but not with 
 impunity for any great length of time. The experiment has often 
 enough been tried, in the treatment of diabetes, of confining the 
 patient to a strictly animal diet. It has been invariably, found that, 
 if this regimen be continued for some weeks, the desire for vegetable 
 food on the part of the patient becomes so imperative that the plan 
 of treatment is unavoidably abandoned. 
 
 A similar question has also arisen with regard to the oleaginous 
 matters. Are these substances mdispensable as ingredients of the 
 food, or may they be replaced by other proximate principles, such 
 as starch or sugar ? It has already been seen, from the experiments 
 of Boussingault and others; that a certain amount of fat is produced 
 in the body over and above that which is taken with the food ; and 
 it appears also that a regimen abounding in saccharine substances 
 is favorable to the production of fat. It is altogether probable, 
 therefore, that the materials for the production of fat may be 
 
OF POOD. 107 
 
 derived, tinder these circumstances, either directly or indirectly 
 from saccharine matters. But saccharine matters alone are not 
 entirely sufficient. M. Huber' thought he had demonstrated that 
 bees fed. on pure sugar -would produce enough wax to show that 
 the sugar could supply all that was necessary to the formation of 
 the fatty matter of the wax. DumaS and Milne-Edwards, however, 
 in repeating Huber's experiments,^ found that this was not the case. 
 Bees, fed on pure sugar, soon cease to work, and sometimes perish 
 in considerable numbers ; but if fed with honey, which contains 
 some waxy and other matters beside the sugar, they thrive upon 
 it ; and produce, in a given time, a much larger quantity of fat 
 than was contained in the whole supply of food. 
 
 The same thing "was established by Boussingault with regard to 
 starchy matters. He found that in fattening pigs,. though the 
 quantity of fat accumulated by the animal considerably exceeded 
 that contained" in the food, yet fat must enter to s»me extent into 
 the composition of the food in order to maintain the animals in a 
 good condition ; for. pigs, fed on boiled potatoes alone (an article 
 abounding in starch but nearly destitute of oily matter), fattened 
 slo\yly and with great difficulty ; while those fed on potatoes mixed 
 with a greasy fluid fattened readily, and accumulated, as mentioned 
 above, much more fat than was contained in the food. 
 
 The apparent discrepancy between these facts may be easily ex- 
 plained, when we recollect that, in order that the animal may become 
 fattened, it is necessary that 'he be supplied not only with the 
 materials of the fat itself, but also with everything else which is 
 necessary to maintain the body in a healthy condition. Oleaginous 
 matter is one of these necessary substances. The fats which are 
 taken in with the food are not destined to be simply transported 
 into the body and deposited there unchanged. On the contrary, 
 they are altered and used up in the processes of digestion and 
 nutrition ; while the fats which appear in the body as constituents 
 of the tissues are, in great part, of new formation, and are produced 
 from materials derived, perhaps, from a variety of different sources. 
 
 It is certain, then, that either one or the other of these two 
 groups of substances, saccharine or oleaginous, must enter into the 
 composition of the food; and furthermore, that, though, the oUy 
 matters may sometimes be produced in the body from the sugars, 
 
 ' Natural Hiatory of Bees, Edinburgh, 1821, p. 330, 
 
 ' Annales de Chim. et de Fhys., 8d series, vol. zir. p. 400. 
 
108 OF FOOD. 
 
 it is also necessary for the perfect nutrition of the body, that fat be 
 supplied, under its own form, with the food. For the human 
 species, also, it is natural to have them both associated in the 
 alimentary materials. They occur together in most vegetable sub- 
 stances, and there is a natural desire for them both, as elements of 
 the food. * 
 
 They are not, however, when alone, or even associated with each 
 other, sufficient for the nutrition of the animal body. Magendie 
 found that dogs, fed exclusively on starch or sugar, perished after a 
 short time with symptoms of profound disturbance of the nutritive 
 functions. An exclusive diet of butter or lard had a' similar effect. 
 The animal became exceedingly debilitated, though without much 
 emaciation; and after death, all the internal organs and tissues 
 were found infiltrated with oil. Boussingault' performed a similar 
 experiment, with a like result, upon a duck, which was kept upon 
 an exclusive regimen of butter. " The duck received 1350 to 1500 
 grains of butter every day. At the end of three weeks it died of 
 inanition. The butter oozed from every part of its body. The 
 feathers looked as though they had been steeped in melted butter, 
 and the body exhaled an unwholesome odor like that of butyric 
 acid." 
 
 Lehmann was also led to the same result by some experiments;, 
 which he performed upon himself for the purpose of. ascertaining 
 the effect produced on the urine by different kinds of food." 
 This observer confined himself first to a purely animal diet for 
 three weeks, and afterwards to a purely vegetable one for sixteen 
 days, without suffering any marked inconvenience. He then put 
 himself upon a regimen consisting entirely of non-nitrogenous sub- 
 stances, starch, sugar, gum, and oil, but was only able to continue 
 this diet for two, or at most for three days, owing to the marked 
 disturbance of the general health which rapidly supervened. The 
 unpleasant symptoms, however, immediately disappeared on his 
 return, to an ordinary mixed diet. The same fact has been esta- 
 blished more recently by Prof. Wm. A. Hammond,^ in a series of 
 experiments which he performed upon himself. He was enabled 
 to live for ten days on a diet composed exclusively of boiled starch 
 and water. After the third day, however, the general health began 
 
 ' Chimie Agrioole, p. 166. 
 
 * Journal fur praktische Chemie, vol. xxvii. p. 257. 
 
 ' Experimental Researches, &c., being the Prize Essay of the American Medical 
 Association for 1857. 
 
OF FOOD. 109 
 
 to deteriorate, and became very much disturbed before the termi- 
 nation of the experiment. The prominent symptoms were debility, 
 headache, pyrosis, and palpitation of the heart. After the starchy 
 diet was abandoned, it required some days to restore the health to 
 its usual condition. 
 
 The proximate principles of the third class, or the organic sub- 
 stances proper, enter so largely into the constitution of the animal 
 tissues and fluids, that -their importance; as elements of the food, is 
 easily understood. No food can be long nutritious, unless a certain 
 proportion of these substances be present in it. Since they are so 
 abundant as ingredients of the body, their loss or absence from the 
 food is felt more speedily and promptly than that of any other sub- 
 stance except water. They have, therefore, sometimes received the 
 name of "nutritious substances," in contradistinction to those of 
 the second class, which contain, no nitrogen, and which have been 
 found by the experiments of Magendie and others to be insufficient 
 for the support of life. The organic substances, however, when 
 taken alone, are no more capable of supporting life indefinitely than 
 the others. It was found in the experiments of the French " Gela- 
 tine Commission'" that animals fed on pure fibrin and albumen, as 
 well as those fed on gelatine, become, after a short time, much en- 
 feebled, refuse the food which is offered to them, or take it with 
 reluctance, and finally die of inanition. This result has been 
 explained by supposing that these substances, when taken alone, 
 excite after a time such disgust in the animal that they are either 
 no longer taken, or if taken are njDt digested. But this disgust 
 itself is simply an indication that the substances used are insufficient 
 and finally useless as articles of food, and that the system, demands 
 instinctively other materials for its nourishment. 
 
 The instinctive desire of animals for certain substances is the 
 surest indication that they are in reality required' for the nutritive 
 process; and on the other hand, the indifference or repugnance 
 manifested for injurious or useless substances,- is an equal evidence 
 I of their unfitness as articles of food. This repugnance is well de- 
 scribed by Magendie, in the report of the commission above alluded 
 to, while detailing the result of his investigations on the nutritive 
 qualities of gelatine. " The result," he says, " of these first trials 
 was that pure gelatine was not to the taste of the dogs experimented 
 on. Some of them suffered the pangs of hunger with the gelatine 
 
 ' Comptes Rendns, 1841, vol. xiii. p. 2 7. 
 
110 OF FOOD. 
 
 ■within their reach, and would not touch it ; others tasted of it, but 
 would not eat ; others still devoured a certain quantity of it once 
 or twice, and then obstinately refused to make any further use of it." 
 
 In one instance, however, Magendie. succeeded in inducing a dog 
 to take a considerable quantity of pure fibrin daily throughout the 
 whole course of the experiment; but notwithstanding this, the 
 animal became emaciated like the others, and died at last with the 
 same symptoms of inanition. 
 
 The alimentary substances of the second class, however, viz., the 
 sugars and the cals, have been sometimes thought less important 
 than the albuminous matters, because they do not enter so largely 
 or so permanently into the composition of the solid tissues. The 
 saccharine matters, when taken as food, cannot he traced farther 
 than the blood. They undergo already, in the circulating fluid, 
 some change by which their essential character is lost, and they 
 cannot be any longer recognized. The appearance of .sugar in the 
 mammary gland and the milk is only exceptional, and does not 
 occur at all in the male subject. The fats are, it is true, very gene- 
 rally distributed throughout the body, but it is only in the brain 
 and nervous matter that they exist intimately united with the re- 
 maining ingredients of the tissues. Elsewhere, as already mentioned, 
 they are deposited in distinct drops and granules, and so long as 
 they remain in this condition must of course be inactive,- so far as 
 regards any chemical nutritive process. In this condition they 
 seem to be held in reserve, ready to be absorbed by the blood, 
 whenever they may be required for the purposes of nutrition. On 
 being reabsorbed, however, as soon as they again enter the blood 
 or unite intimately with the substance of the tissues, they at once 
 change their condition and lose their former chemical constitution 
 and properties. 
 
 It is for theSb reasons that the albuminoid matters have been 
 sometimes considered as the only " nutritious" substances, because 
 they alone constitute under their own form a great part of the 
 ingredients of the tissues, while the sugars and the oils rapidly dis- 
 appear by decomposition. It has even been assumed that the pro- 
 cess by which the sugar and the oils disappear is one of direct 
 combustion or oxidation, and that they are destined solely to be 
 consumed in this way, not to enter at all into the composition of 
 the tissues but only to maintain the heat of the body by an inces- 
 sant process of combustion in the blood. They have been therefore 
 termed the "combustible" or "heat-producing" elements, while tha 
 
OF FOOD. Ill 
 
 albuminoid substances were known as the nutritious or " plastic" 
 elements. 
 
 This distinction, however, has no real foundation. In the first 
 place, it is not at all certain that the sugars and the oils which dis- 
 appear in the body are destroyed by combustion. This is merely 
 an inference which- has been made without any direct proof. All 
 we know positively in regard to the matter is that these substances 
 soon become so altered in the blood that they can no longer be 
 recognized by their ordinary chemical properti«s ; but we are still 
 ignorant of the exact nature of the transformations which they 
 undergo. Furthermore, the difference between the sugars and the 
 oils on the one hand, and the albuminoid substances on the other, 
 so far as regards their decomposition and disappearance in the 
 body, is only a difference in time. The albuminoid substances 
 become transformed more slowly, the sugars and the oils more 
 rapidly. Even if it should be ascertained hereafter that the sugars 
 and the oils really do not unite at all with the solid tissues, but are 
 entirely decomposed in the blood, this would not make them any 
 less important as alimentary substances, since the blood is as 
 essential a part of the body as the solid tissues, and its nutrition 
 must be provided for equally with theirs. 
 
 It is evident, therefore, that no single proximate principle, nor 
 even any one class of them alone, can be sufficient for the nutrition 
 of the body; but that the food, to be nourishing, must contain 
 substances belonging to all the different groups of proximate prin- 
 ciples. The albuminoid substances are first in importance because 
 they constitute the largest part of the entire mass of the body ; and 
 exhaustion therefore follows more rapidly when they are withheld 
 than when the animal is deprived of other kinds of alimentary 
 matter. But starchy and oleaginous substances are also requisite ; 
 and the body feels the want of them sooner or later, though it may 
 be plentifully supplied with albumen and fibrin. Finally, the in- 
 organic saline matters, though in smaller quantity, are also neces- 
 sary to the continuous maintenance of life. In order that the 
 animal tissues and fluids remain in a healthy condition and take 
 their proper part in the functions of life, they must be supplied 
 with all the ingredients necessary to their constitution ; and a man 
 may be starved to death at last by depriving him of chloride of 
 sodium or phosphate of lime just as surely, though not so rapidly, 
 as if he were deprived of albumen or oil. 
 
 In the different kinds of food, accordingly, which have been 
 
112 OF FOOD. 
 
 adopted by the universal and instinctive choice of man, the three 
 different classes of proximate principles are all more or less abund- 
 ;antly represented. In all of them there exists naturally a certain 
 proportion of saline substances ; and water and chloride of sodium 
 are generally taken with them in addition. In milk, the first food 
 supplied to the infant, we have casein which is an albuminoid sub- 
 stance, butter which represents the oily matters, and sugar of milk 
 belonging to the saccharine group, together with water and saline 
 matters, in the following proportions : — ' 
 
 Composition of Cow's Milk. 
 
 Water 87.02 
 
 Casein 4.48 
 
 Buttei- . 3.13 
 
 Sugar of milk 4.77 
 
 Soda 
 
 Chlorides of potassium and sodium .... 
 
 Phosphates of soda and potassa 
 
 Phosphate of lime 
 
 " magnesia . . . . . 
 
 Alkaline carbonates 
 
 Iron, &c 
 
 0.60 
 
 100.00 
 
 In wheat flour, gluten is the albuininoid inatter, sugar and starch 
 the non-nitrogenous principles. 
 
 
 Composition op Wheat Flour 
 
 Gluten . 
 
 . 10.2 Gum 
 
 Starch . 
 
 . 72.8 Water . 
 
 Sugar 
 
 . 4.2 
 
 10.0 
 
 100.0 
 
 The other cereal grains mostly contain oil in addition to the 
 above. 
 
 Compositk)!! of Dried Oatmeal. 
 
 Starch 59.00 
 
 Bitter matter and sugar 8.25 
 
 Gray albuminous matter 4.30 
 
 Fatty oil , . . . . 2.00 
 
 Gum 2.50 
 
 Husk, mixture, and loss 23.95 
 
 100.00 
 
 Eggs contain albumen and salts in the white, with the addition 
 of oily matter in the yolk. 
 
 ' The accompanying analyses of various kinds of food are taken from Pereira 
 on Food and Diet, New York, 1843. 
 
OF F,OOD. 113 
 
 CoMPosiTioK OF Egos. 
 
 White of Egg. Yolk of Egg. 
 
 Water .... 80.00 63.78 
 
 Albumen and mucus . 15.28 12.75 
 
 Yellow oil ... 28.75 
 
 Salts .... 4.72 ....;. 4.72 
 
 100.00 100.00 
 
 In ordinary flesh or butcher's ipeat, we have the albuminoid 
 matter of the muscular fibre and the fat of the adipose tissue. 
 
 CoUFOSITION OF ObDINABY BcTrCBEB's MeAT. 
 
 f Water .... 63.418 
 Meat devoid of fat . . 85.7 IgoUd matter , . . 22.282 
 
 Fat, cellular tissue, &c 14.300 
 
 100.000 
 
 From what has been said above, it will easily be seen that the 
 nutritious character of any substance, or its value as an article of 
 food, does not depend simply upon its containing either one of the 
 alimentary substances mentioned above in large quantity; but upon 
 its containing them mingled together in such proportion as is 
 requisite for the healthy nutrition of the body. What these pro- 
 portions are cannot be determined from simple chemical analysis, 
 nor from any other data than those derived from direct observation 
 and experiment. 
 
 The total quantity of food required by man has been variously 
 estimated. It will necessarily vary, indeed, not only with the con- 
 stitution and habits of the individual, but also with the quality of 
 the food employed ; since some articles, such as corn and meat, con- 
 tain very much more alimentary material in the same bulk than 
 fresh fruits or vegetables. Any estimate, therefore, of the total 
 quantity should state also the kind of food used ; otherwise it will 
 be altogether without value. From experiments performed while 
 living on an exclusive diet of bread, fresh meat, and butter, with 
 coflee and water for drink, we have found that the entire quantity 
 of food required during twenty-four hours by a man in full health, 
 and taking free exercise in the open air, is as follows : — 
 
 Meat 16 ounces or 1.00 lb. Avoirdupois. 
 
 Bread 19 " « 1.19 " 
 
 Butter pr fat. . . . 3J » « 0.22 " 
 
 Water 52 fluid oz." 3.38 " " 
 
 That is to say, rather less than two and a half pounds of solid food, 
 and rather over three pints of liquid food. 
 8 
 
114: OP FOOD. 
 
 Another necessary consideration, in estimating the value of any 
 substance as an article of food, is its digestibility. A vegetable or 
 animal tissue may contain an abundance of albuminoid or starchy 
 matter, but may be. at the same time of such an unyielding consist- 
 ency as to be insoluble in the digestive fluids, and therefore useless 
 as an article of food. Bones and cartilages, and the fibres of yellow- 
 elastic tissue, are indigestible, and therefore not nutritious. The 
 same remark may be made with -regard to the substances contained 
 in woody fibre, and the hard coverings and kernels of various fruits. 
 Everything, accordingly, which softens or disintegrates a hard ali- 
 mentary substance renders it more digestible, and so far increases 
 its value as an article of food. 
 
 The preparation of food by cooking has a twofold object : first, 
 to soften or disintegrate it, and second, to give it an attractive 
 flavor. Many vegetable substances are so hard as to be entirely 
 indigestible in a raw state, Eipe peas and beans, the different kinds 
 of grain, and many -roots and fruits, require to be softened by boil- 
 ing, or some other culinary process, before they are ready for use. 
 With them, the principal change produced by cooking is an altera- 
 tion in consistency. With most kinds of animal food, however, the 
 effect is somewhat different. In the case of muscular flesh, for ex- 
 ample, the muscular fibres themselves are almost always more or 
 less hardened by boiling or roasting; but, at the same time, the 
 fibrous tissue by which they are held together is gelatinized and 
 softened, so that the muscular fibres are more easily separated from 
 each other, and more readily attacked by the digestive fluids. " But 
 beside this, the organic substances contained in meat, which are all 
 of them very insipid in the raw state, acquire by the action of heat 
 in cooking, a peculiar and agreeable flavor. This flavor excites 
 the appetite and stimulates the flow of the digestive fluids, and 
 renders, in this way, the entire process of digestion more easy and 
 expeditious. 
 
 The changes which the food undergoes in the interior of the body 
 may be included under three different heads : first, digestion,- or the 
 preparation of the food in-the alimentary canal ; second, assimilation, 
 by which the elements of the food are converted into the animal 
 tissues ; and third, excretion, by which they are again decomposed, 
 and finally discharged from the body. 
 
DIGESTION. 115 
 
 CHAPTER VI. 
 
 DIGESTION. 
 
 Digestion is that process by wHcli the food is reduced to a form 
 in which it can be absorbed from the intestinal canal, and taken up 
 by the bloodvessels. This process does not occur in vegetables. 
 For vegetables are dependent for their nutrition, mostly, if not 
 entirely, upon a supply of inorganic substances, as water, saline 
 matters, carbonic acid, and aminonia. These materials constitute 
 the food upon which plants subsist, and are converted in their inte- 
 rior into other substances, by the nutritive process. These mate- 
 rials, furthermore, are constantly supplied to the vegetable under 
 such a form as to be readily absorbed. Carbonic acid and ammonia 
 exist in a gaseous form in the atmosphere, and are also to be found 
 in solution, together with the requisite saline matters, in the water 
 with which the soil is penetrated. All these substances, therefore, 
 are at once ready for absorption, and do not require any preliminary 
 modification. But with animals and man the case is different 
 They cannot subsist upon these inorganic substances alone, but 
 require for their support materials which have already been organ- 
 ized, and which have previously constituted a part of animal or 
 vegetable bodies. Their food is almost invariably solid or serai-solid 
 at the time when it is taken, and iiisoluble in water. Meat, bread, 
 fruits, vegetables, &c., are all taken into the stomach in a solid and 
 insoluble condition ; and even those substances which are naturally 
 fluid^ such as milk, albumen, white of egg. are almost always, i^ 
 the human species, coagulated and solidified \)j the process of cook- 
 ing, before being taken into the stomach. 
 
 In animals, accordingly, the food requires to undergo a process 
 of digestion, or liquefaction, before it can be absorbed. In all cases, 
 the general characters of this process are the same. It consists 
 essentially in the food being received into a canal, running through 
 the body from mouth to anus, called the " alimentary canal," in 
 which it comes in contact with certain digestive fluids, which act 
 
116 DIGESTION. 
 
 upon it iu such a way as to liquefy and dissolve it. These fluids 
 are secreted by the mucous membrane of the alimentary canal, and 
 by certain glandular organs situated in its neighborhood. Since the 
 food always consists, as we have already seen, of a mixture of vari- 
 ous substances, having different physical and chemical properties, 
 the several digestive fluids are also different from each other; each 
 ''one of them exerting a peculiar action, which is more or less con- 
 fined to particular species of food. As the food passes through the 
 intestine from above downward, those parts of it which become 
 liquefied are successively removed by absorption, and taken up by 
 the vessels ; while the remaining portions, consisting of the indi- 
 gestible matter, together with the refuse of the intestinal secretions, 
 gradually acquire a firmer consistency owing to the absorption of 
 the fluids, and are finally discharged from the intestine under the 
 form of feces. 
 
 In "different species of animals, however, the difference in their 
 habits, in the constitution of their tissues, and in the character of 
 their food, is accompanied with a corresponding variation in the 
 anatomy of the digestive apparatus, and the character of the secreted 
 fluids. As a general rule, the digestive apparatus of herbivorous 
 animals is more complex than that of the carnivora ; since, in vege- 
 table substances, the nutritious matters are often present in a very 
 solid and unmanageable form, as, for example, in raw starch and 
 the cereal gr%ins, and are nearly always entangled among vegetable 
 cells and fibres of an indigestible character^ In those instajices 
 where the food consists mostly of herbage, as grass, leaves, &c./ the 
 digestible matters bear only a small proportion to the entire quan- 
 tity ; and a large mass of food must therefore be taken, in order 
 that the requisite amount of nutritious material may be extracted 
 from it. In such cases, accordingly, the alimentary canal is large 
 and long; and is divided into many compartments, in which 
 different processes of disintegration, transformation, and solution 
 are carried on. 
 
 In the common fowl, for instance (Fig. 16), the food, which con- 
 sists mostly of grains, and frequently of insects with hard, coria- 
 ceous integument, first passes down the oesophagus (a) into a 
 diverticulum or pouch (6) termed the crop. Here it remains for 
 a time mingled with a watery secretion in which the grains are 
 macerated and softened. The food is then carried farther down 
 until it reaches a second dilatation (c), the proventriculus, or 
 secreting stomach. The mucous membrane here is thick and 
 
DIGESTION. 
 
 117 
 
 glandular, and is provided with numerous se- Pig- IS- 
 
 creting follicles or crypts. From them an 
 acid fluid is poured out, by which the food is 
 subjected to further changes. It next passes 
 into the gizzard (d), or triturating stomach, a 
 cavity inclosed by thick muscular walls, and 
 lined with a remarkably tough and horny 
 epithelium. Here it is subjected to the crush- 
 ing and grinding action of the muscular pa- 
 rietes, assisted by grains of sand and gravel, 
 which the animal instinctively swallows with 
 the food, by which it is so triturated and dis- 
 integrated, that it is reduced to a uniform pulp, 
 upon which the digestive fluids can effectually 
 operate. The mass then passes into the intes- 
 tine (e), where it meets with the intestinal 
 juices, which complete the process of solution ; 
 and from the intestinal cavity it is finally ab- 
 sorbed in a liquid form, by the vessels of the 
 mucous membrane. 
 
 In the ox, again, the sheep, the camel, the 
 deer, and all ruminating animals, there are 
 four distinct stomachs through which the 
 food passes in succession; each lined with 
 mucous membrane of a different structure, , 
 and adapted to perform a different part in 
 the digestive process. (Fig. 17.) "When first 
 swallowed, the food is received into the ru- 
 men, or paunch (b), a large sac, itself par- 
 tially divided by incomplete partitions, and 
 lined by a mucous membrane thickly set 
 with long prominences or villi. Here it ac- 
 cumulates while the animal is fepding, and is 
 retained and macerated in its own fluids. "When the animal has 
 finished browsing, and the process of rumination commences, the 
 food is regurgitated into the mouth by an inverted action of the 
 muscular walls of the paunch and oesophagus, and slowly masticated. 
 It then desoends again along the oesophagus ; but instead of enter- 
 ing the first stomach, as before, it is turned off by a muscular valve 
 into the second stomach, or reticulum (c), which is distinguished 
 by the intersecting folds of its mucous membrane, Tjrhich give it 
 
 Alihsxtart Canal of 
 Fowl. — n. (Enophugas. 6. 
 Crop. c. Proventriculus, or 
 Becreting stomach, d. Gizzard, 
 or triturating fitORiaeh. e Iq- 
 testiae. /. Two long ciecal 
 tubeg which open into the in- 
 testine a short distance above 
 its termination. 
 
 1, 
 
118 
 
 DIGESTION. 
 
 CoMPOCNU Stomach op Ox. — n. (Esopha- 
 gus b, Rnmen, or first stoniach. c. Keticuluin, or 
 second, d. OmAsns, or tbird. e. Abomasus, or 
 fourth. /. Daodenum. (From Bfmer Jones.) 
 
 a toney-combed or reticulated appearance. Here the food, already 
 
 triturated in the mouth, and 
 *''8- 17. mixed with the saliva, is further 
 
 macerated in the fluids swal- 
 lowed by the animal, which al- 
 ways accumulate in considerable 
 quantity in the reticulum. The 
 next, cavity is the omasus, or 
 " psalterium" (d), in which the 
 mucous membrane is arranged 
 in longitudinal folds, alternately 
 broad and narrow, lying parallel 
 with each other like the leaves 
 of a book, so that the extent of 
 mucous surface, brought in con- 
 tact with the food, is very much 
 increased. The exit from this 
 cavity leads directly into the 
 ahomasus, or "rennet" (e), which 
 is the true digestive stomach, in which the mucous membrane is 
 softer, thicker, and more glandular than elsewhere, and in which 
 an acid and highly solvent fluid is secreted. Then follows the in- 
 testinal canal with its various divisions aiid variations. 
 
 In the carnivora, on the other hand, the alimentary canal is 
 shorter and narrower than in the preceding, and presents fewer 
 complexities. The food, upon which these animals subsist, is softer 
 than that of the herbivora, and less encumbered with indigestible 
 matter ; so that the process of its solution requires a less extensive 
 apparatus. 
 
 In the human species, the food is naturally of a mixed cha- 
 racter, containing both animal and vegetable substances. But the 
 djpestive apparatus in man resembles almost exactly that of the 
 caro^ora. For the vegetable matters which we take as food are, 
 in the first place, artificially separated, to a great extent, from indi- 
 gestible impurities; and secondly, fhey are so softened by the 
 process of cooking as .to become nearly or quite as easily digestible 
 as animal substances. 
 
 In the human species, howeVer, the process of digestion, though 
 -simpler than in the herbivora, is still complicated. The alimentary 
 canal is here, also, divided into different compartments or cavities, 
 which communicate with each other by narrow orifices. At its 
 
DIGESTION. 
 
 119 
 
 commencement (Fig. 18), we find, the cavity of the mouth, which is 
 guarded at its posterior extremity by the muscular valve of the 
 
 isthmus of the fauces. _. ,„ 
 
 Fig. 18. 
 
 Through the pharynx and 
 oesophagus (a), it commu- 
 nicates with the second 
 compartment, . or the sto- 
 mach {b), a flask-shaped 
 dilatation, which is guarded 
 at the cardiac and pyloric 
 orifices by circular bands 
 of muscular fibres. Then 
 comes the small intestine (e), 
 different parts of which, 
 owing to the varying struc- 
 ture of their mucous mem- 
 branes, have received< the 
 different names of duode- 
 num, jejunum, and ileum. 
 In the duodenum we have 
 the orifices of the biliary 
 and pancreatic ducts {f, g). 
 Finally, we have the large 
 intestine {h, i,j, k), separated 
 from the smaller' by the 
 ileo-csecal valve, and ter- 
 minating, at its lower e?;- 
 tremity, by the anus, at 
 which is situated a double 
 sphincter, for the purpose 
 of guarding its orifice. 
 Everywhere the alimentary 
 canal is composed of a 
 mucous membrane and a 
 muscular coat, with a layer 
 of submucous areolar tissue 
 between the two. The mus- 
 cular coat is everywhere 
 composed of a double layer of longitudinal and transverse fibres, 
 by the alternate contraction and relaxation of which the food is 
 carried through the canal from above downward. The mucous 
 
 HnUAX ALIHBlTTAaT C A K A Xi . ^ 0. (EsophagQs. 
 h. stomach, c. Cardiac orifice, d. Pylorus, e. SmaU 
 iutetitine.' /. Biliary duct, g: Pancreatic duct. A. As- 
 cendlDg colon, i. TransTerse colon. J, DescoDding 
 colon, k. Bectam. 
 
120 DIGESTION, 
 
 membrane presents, also, a different structure, and has different 
 properties in different parts. In the mouth and oesophagus, it is 
 smooth, -with a hard, whitish, and tessellated' epithelium. This kind 
 of epithelium terminates abruptly at the cardiac orifice of the 
 stomach. The mucous membrane of the gastric cavity is soft and 
 glandular, covered with a transparent, columnar epithelium, and 
 thrown into minute folds or projections on its free surface, which 
 are sometimes reticulated with each other. In the small intestine, 
 we find large transverse folds of mucous membrane, the vahulse 
 conniventes, the minute villosities which cover its surface, and the 
 peculiar glandular structures which it contains. Finally, in the 
 large intestine, the mucous membrane is again different. It is here 
 smooth and shining, free from villosities, and provided with a dif- 
 ferent glandular apparatus. 
 
 Furthermore, the digestive secretions, also, vary in these different 
 regions. In its passage from above downward, the food meets 
 with no less than five different digestive fluids. First it meets with 
 the saliva, in the cavity of the mouth ; second, with the gastric juice, 
 in the stomadh ; third, with the hile ; fourth, with the pancreatic 
 fluid; and fifth, with the intestinal juice. It is the most important 
 characteristic of the process of digestion, as established by modern 
 researches, that different elements of the food^are digested in different 
 parts of the alimentary canal by the agency of different digestive fluids. 
 By their action, the various ingredients of the alimentary mass are 
 successively reduced to a fluid condition, and are taken up by the 
 vessels of the intestinal mucous membrane. 
 
 The action which is exefted upon the food by the digestive 
 fluids is not that of a simple chemical solution. It is a transforma- 
 tion, by which the ingredients of the food are altered in character 
 at the same time that they undergo the process of liquefaction. 
 The active agent in producing this change is in every ipstance an 
 organic matter, which enters as an ingredient into the digestive 
 fluid^ and which, by coming in contact with the food, exerts upon 
 it a catalytic action, and transforms its ingredients into other sub- 
 stances, it' is these newly formed substances which are finally 
 absorbed by the vessels, and mingled with the general current of 
 the circulation. 
 
 In our study of the process of digestion, the different digestive 
 fluids will bei ^examined separately, and their action on the aliment- 
 ary substances in the different regions of the digestive apparatus 
 successively investigated. 
 
MASTICATION. 121 
 
 Mastication. — In the first division of the alimentary canal, viz., 
 the mouth, the food undergoes simultaneously two difierent opera- 
 tions, viz., mastication and insalivation. Mastication consists in 
 the cutting and trituration of the food by the teeth, by the action 
 of which it is reduced to a state of minute subdivision. This pro- 
 cess is entirely a mechanical one. It is necessary, in order to pre- 
 pare the food for the subsequent action of the digestive fluids. As 
 this action is chemical in its nature, it will be exerted more promptly 
 and efficiently if the food be finely divided than if it be brought in 
 contact with the digestive fluids in a solid mass. This is always 
 the case when a solid body is subjected to the chemical action of a 
 solvent fluid ; since, by being broken up into minute particles, it 
 offers a larger surface to the contact of the fluid, and is more readily 
 attacked and dissolved or decomposed by it. 
 
 In the structure of the teeth, and their physiological action, there 
 are certain marked differences, corresponding with the habits of the 
 animal, and the kind of food- upon which it subsists. In fish and 
 serpents, in which the food is swallowed entire, and in which the 
 process of digestion, accordingly, is comparatively slow, the teeth 
 are simply organs of prehension. They have generally the form 
 of sharp, curved spines, with their points set backward (Fig. 19), 
 and arranged in a* double or triple row 
 about the edges of the jaws, and sometimes 
 covering the mucous surfaces of the mouth, 
 tongue, and palate. They serve merely to 
 retain the prey, and prevent its escape, 
 after it has been seized by the animal. In 
 the carnivorous quadrupeds, as those of SKni, of kattleskakb. 
 
 -^ 1 I'l 11 .'1 (After AchiLle-Kicbm'd.) 
 
 the dog and cat kind, and other similar 
 
 families, there are three different kinds of teeth adapted to different 
 mechanical, purposes. (Fig. 20.) First, the incisors, twelve in num- 
 ber, situated at the anterior part of the jaw, six in the superior, 
 and six in the inferior maxilla, of flattened form, and placed with 
 their thin edges running from side to side. The incisors, as their 
 name indicates, are adapted for dividing the food by a cutting 
 motion, like that of a pair of shears. Behind them come the canine 
 teeth, or tusks, one on each side of the upper and under jaw. 
 These are long, curved, conical, and pointed; and are used as 
 weapons of offence, and for laying hold of and retaining the prey. 
 Lastly, the_ molars, eight or more in number on each side, are 
 larger and broader than the incisors, and provided with serrated 
 
122 
 
 DIGESTION. 
 
 Fig. 20. 
 
 edges, each presenting several sharp points, arranged generalljin 
 a direction parallel with the line of the jaw. In these animals, 
 
 mastication is very imperfect, since 
 the food is not ground up, but only 
 pierced and mangled by the action 
 of the teeth before being swallowed 
 into the stomach. In the herbi'- 
 vora, on the other hand, the inci- 
 sors are present only in the lower 
 jaw in the ruminating animals, 
 though in the horse they are found 
 in both the upper and lower max- 
 illa. (Fig. 21.) They are used merely 
 for cutting off the bundles of grass 
 or herbage, on which the animal feeds. The canines are either 
 absent or slightly developed, and the real process of mastication is 
 
 Skui.l of PotAK BriAR. Anterior 
 rlew; Khowiog incisurs and cauines. 
 
 Fig. 21. 
 
 Skull of thv Hobsb. 
 
 performed altogether by the molars. These are Iarge»and thick 
 (Fig. 22), and present a broad, flat surface, diversified by variously 
 folded and projecting ridges of enamel, with shal- 
 low grooves, intervening between them. By the 
 lateral rubbing motion of the roughened surfaces 
 against each other, the food is effectually commi- 
 nuted and reduced to a pulpy mass. 
 
 In the human subject, the teeth combine the 
 characters of those of the carnivora and the herbi- 
 vora. (Fig. 23.) The incisors (a), four in number 
 in each jaw, have, as in other instances, a cutting 
 
 Fig. 22. 
 
 mu!. 
 
 Molar Tooth of 
 THE HoBSE. Griod- 
 iiig^ Burface. 
 
SALIVA. 
 
 123 
 
 Fi3. 23. 
 
 dy 
 
 HUMAX TgBTH- 
 
 r. Anterior molars. 
 
 -UppkeJaw. —a. I Dcisors. 6. Cauines. 
 d. Poiiterior molars. 
 
 edge running froni,side to side. The canines (6), which are situated 
 immediately behind the former, are much less proihinent and 
 pointed than in the car- 
 nivora, and differ less 
 in form from the inci- 
 sors on the one hand, 
 and the ■first molars on 
 the other. The molars, 
 again (c, d), are thick 
 and strong, and have 
 comparatively flat sur- 
 faces, like those of the 
 herbivora; but instead 
 of presenting curvili- 
 near ridges, are covered 
 with more or less coni- 
 cal eminences, like those 
 ofthecarnivora. In the 
 human subject, therefore, the teeth are evidently adapted for a mixed- 
 diet, consisting of both animal and vegetable food. Mastication is 
 here as perfect as it is in the herbivora, though less prolonged and 
 laborious ; for the vegetable substances used by man, as already 
 remarked, are previously separated to a great extent from their 
 impurities, and softened by cooking ; so that they do not require, 
 for their mastication, so extensive and powerful a triturating ap- 
 paratus. Finally, animal substances are more completely masti- 
 cated in the hunian subject than they are in the carnivora, and 
 their digestion is accordingly completed with greater rapidity. 
 . We can easily estimate, from the facts above stated, the great 
 importance, to the digestive process, of a thorough preliminary 
 mastication. If the food be: hastily swallowed in undivided masses, 
 it must remain a long time undissolved in the stomach, where it 
 will become a source of irritation and disturbance ; but if reduced 
 beforehand, by mastication, to a state of minute subdivision, it is 
 readily attacked by the digestive fluids, and becomes speedily and 
 completely liquefied. 
 
 SALivA.-7-At the same time that the food is masticated, it is mixed 
 in the cavity of the moutb with the first of the digestive fluids, viz., 
 the saliva. Human saliva, as it is obtained directly from the buc- 
 cal cavity, is a colorless, slightly viscid and alkaline fluid, with a 
 
124 
 
 DlttESTION. 
 
 specific gravity of 1005. When first discharged, it is frothy and 
 6paiine> holding in suspension minute, whitish flocculi. On being 
 allowed to stand for some hours in a cylindrical glass vessel, an 
 opaque, whitish deposit collects at the bottom> while the supernatant 
 fluid becomes clear. The deposit, when examined by the micro- 
 
 Fig. 24. 
 
 scppe (Fig. 24), is seen to 
 consist of abutidant fepithe- 
 lium scales from the internal 
 surface of the mouth, de- 
 tached by mechanical irrita- 
 tion, minute, roundish, gra- 
 nular, nucleated cells, appa- 
 rently epithelium from the 
 mucous follicles, a certain 
 amount of granular matter, 
 and a few oil-globules. The 
 supernatant fluid has a faint' 
 bluish tinge, and becomes 
 slightly opalescent by boil- 
 
 B«CCAL AND OLANDUI.AEEpiTH£r.HJM, with i^g- ^^^ ^J t^S addltlOn Of 
 
 Granular Matter and Oil-globules; depoBited as sedi- nitric acid. ^Icohol in ex- 
 meat from humaa saliva. . .... 
 
 cess causes the precipitation 
 of abundant whitish flocculi. According to Bidder and Schmidt,' 
 the composition of saliva is as follows : — 
 
 Composition op Saliv*. 
 
 Water 995.16 
 
 Organic matter 1.34 
 
 Sulpho-oyanide of potassium 0.06 
 
 Phosphates of soda, lime, and magnesia .98 
 
 Chlorides of sodium and potassium .84 
 
 Mixture of epithelium 1.62 
 
 1000.00 
 
 The organic substance present in the saliva has been occasionally 
 known by the name of jptyaline. It is coagulable by alcohel, but 
 not by a boiling temperature. A very little albumen is also pre- 
 sent, mingled with the ptyaline, and produces the opalescence- 
 which appears in the saliva when raised to a boiling temperature. 
 The sulpho-cyanogen may be detected by a solution of chloride of 
 iron, which produces the characteristic red color of sulpho-cyanide 
 
 '• Verdauungssaefte und StoflFwechsel; Leipzig, 1852. 
 
SALIVA. 125 
 
 of iron. The alkaline reaction of the saliva varies in intensity 
 during the day, but is nearly always sufficiently distinct. 
 
 The saliva is not a simple secretion, but a mixture of four dis- 
 tinct fluids, ■whicli differ from each other in the source from which 
 they are derived, and in their physical and chemical properties. 
 These secretions are, in the human subject, first, that of the parotid 
 gland ; second, that of the submaxillary ; third, that of the sub- 
 , lingual ; and fourth, that of the mucous follicles of the mouth. 
 These different fluids have been comparatively studied, in the 
 lower animals, by Bernard, Frerichs, and Bidder and Schmidt. 
 The parotid saliva is obtained in a state of purity from the dog by 
 exposing the duct of Steno where it crosses the masseter muscle, 
 and introducing into it, through an artificial opening, a fine silver 
 canula. The parotid saliva then runs directly from its external 
 orifice, without being mixed with that of the other salivary glands. 
 It is clear, limpid, and watery, without the slightest viscidity, and 
 has a faintly alkaline reaction. The submaxillary saliva is ob- 
 tained in a similar manner, by inserting a canula into Wharton's 
 duct. It differs from the parotid secretion, so far as its physical 
 properties are concerned, chiefly in possessing a well-marked, vis. 
 cidity. It is alkaline in reaction. " The sublingual saliva is also 
 alkaline, colorless, and transparent, and possesses a greater degitee 
 of viscidity than that from the submaxillary. The mucous secre- 
 tion of the follicles of the mouth, whicli forms properly a part of 
 the saliva, is obtained by placing a ligature simultaneously on 
 Wharton's and Steno's ducts, and on that of the sublingual gland, 
 so as to shut out from the mouth all the glandular salivary secre- 
 tions, and then collecting the fluid secreted by the buccal mucous 
 membrane. This fluid is very scanty, and much more viscid than 
 either of the other secretions ; so much so, that it cannot be poured 
 out in drops wben received in a glass vessel, but adheres strongly 
 to the surface of the glass. 
 
 We bave obtained the parotid saliva of the human subject in a 
 state of purity by introducing directly into the orifice of Steno's 
 duct a silver canula ■ j'j to jV oi an inch in diameter. The other 
 extremity of the canula projects from the mouth, between the lips, 
 and the saliva is collected 'as it runs from the open orifice. This 
 method gives results much more valuable than observations made 
 on salivary fistulse and the like, since the secretion is obtained 
 under perfectly healthy conditions, and unmixed with other animal 
 fluids. 
 
126 DIGESTION. 
 
 The result of many different observations, conducted in this way, 
 is that the human parotid saliva, like that of the dog, is colorless, 
 watery, and distinctly alkaline in reaction. It difeers from the mixed 
 saliva of the mouth, in being perfectly clear, without any turbidity 
 or opalescence. Its flow is scanty while the cheeks and jaws remain 
 at rest • but as soon as the movements of mastication are excited by 
 the introduction of food, it runs in much greater arbundance. We 
 have collected, in this way, from the parotid duct of one side only, 
 in a healthy man, 480 grains of saliva in the course of twenty 
 minutes ; and in seven successive observations, made on dififerent 
 days, comprising in all three hours and nine minutes, we have 
 collected a little over 3000 grains. 
 
 The parotid saliva obtained in this way has been analyzed by 
 Mr. Maurice Perkins, Assistant to the Professor of Chemistry* in 
 the Qollege of Physicians and Surgeons, with the following result : — 
 
 • Composition op Hpman Parotid Saliva. 
 
 Water 983.300 
 
 , Organic matter precipitable by alcohol . . . . . 7.352 
 Substance destructible by heat, but not precipitated by alcohol 
 
 or acids 4.81 
 
 Sulpho-cyanide of sodium 0.33 
 
 = Phosphate of lime ......... 0,24 
 
 Chloride of potassium 0.90 
 
 Chloride of sodium and carbonate of soda . . . . 3.06 
 
 1000.00 
 Mr. Perkins found, in accordance with our own observations, 
 . that the fresh parotid saliva, when treated with perchloride of iron, 
 showed no evidences of sulpho-cyanogen ; but after the organic mat- 
 ters had been precipitated by alcohol, the filtered fluid was found 
 to contain an appreciable quantity of the sulpho-cyanide. 
 
 The organic matter in the parotid saliva is in rather large quan- 
 tity as compared with the mineral ingredients. It is precipitable by 
 alcohol, by a boiljng temperature, by nitric acid, find by sulphate 
 of soda in excess, but not by an acidulated solution of ferrocyanide 
 of potassium. It bears some resemblance, accordingly, to albumen, 
 but yet is not precisely identical with that substance. 
 
 The parotid saliva also differs from the mixed saliva of the mouth 
 in containing some substance which ma'sks the reaction of sulpho- 
 cyanogen. For if the parotid saliva and that from the mouth be 
 drawn from the same person within the same hour, the addition of 
 perchloride of iron will produce a distinct red color in the latter, while 
 no such change takes place in the former. And yet the parotid 
 
SALIVA. 127 
 
 saliva contains sulpho-cyanogen, -which may be detected, as we have 
 already seen, after the organic matters have been precipita,ted by 
 alcohol. 
 
 A very curious fact has been observed by M. Colin, Professor of 
 Anatomy and Physiology at the Veterinary School of Alfort,' viz., 
 that in the horse and ass, as well as in the cow and other ruminat- 
 ing animals, the parotid glands of the two opposite sides, during 
 mastication, are never in active secretion at the same time ; but 
 that they alternate with each other, one remaining quiescent while 
 the other is active, and vice versd. In these animals mastication is 
 said to be linilateral, that is, when the animal commences feeding 
 or ruminating, the food is triturated, for fifteen minutes or more, by 
 the molars of one side only. It is then changed to the opposite 
 side ; and for the next fifteen minutes mastication is performed by 
 the molars of that side only. It is then changed back again, and 
 so on alternately, so that the direction of the lateral movements of 
 the jaw may be reversed many times during the course of a meal. 
 By establishing a salivary fistula simultaneously on ieach side, it is 
 found that the flow of saliva corresponds with the direction of the 
 masticatory movement. When the animal masticates on the right 
 side, it is the right parotid which secretes actively, while but little 
 saliva is supplied by the left ; when mastication is on the left side, 
 the left. parotid pours out an abundance of fluid, while the right is 
 nearly inactive. • 
 
 We have observed a similar alternation in the flow of parotid 
 saliva in the human subject, when the mastication is changed from 
 side to side. In an experiment of this kind, the tube being inserted 
 into the parotid duct of the left side, the quantity of saliva dis- 
 charged during twenty minutes, while mastication was performed 
 mainly on the opposite side of the mouth, was 127.5 grains; while 
 the quantity during the same period, mastication being on the same 
 side of the mouth, was 374.4 grains — being nearly three times as 
 much in the latter case as in the former. 
 
 Owing to the variations in the rapidity of its secretion, and also 
 to the fact that it is not so readily excited by artificial means as 
 by fhe presence of food, it becomes somewhat difficult to estimate 
 the total quantity of saliva secreted daily. The first attempt to do so 
 was made by Mitscherlich,' who collected from two to three ounces 
 in twenty-four hours from an accidental salivary fistula of Steno's 
 
 • Traits de Pliysiologie ComparSe, Paris, 1854, p. 468. 
 ' Simon's Chemistry of Mau. Fhila. ed., 1846, p. 295. 
 
128 DIGESTION. 
 
 duct ia the human subject ; from which it was supposed that the 
 total amount secreted bj all the glands was from ten to twelve 
 ounces daily. As this man was a hospital patient, however, and 
 suffering from constitutional debility, the above calculation cannot 
 be regarded as an accurate one, and accordingly Bidder and Schmidt' 
 make a higher estimate. One of these observers, in experimenting 
 upon himself, collected from the mouth in one hour, without using 
 any artificial stimulus to the secretion, 1500 grains of saliva; and 
 calculates, therefore, the amount secreted daily, making an allow- 
 ance of seven hours for sleep, as not far from 25,000 grains, or 
 about three and a half pounds avoirdupois. 
 
 On repeating this experiment, however, we have not been able to 
 collect from the mouth, without artificial stimulus, more than 556 
 grains of saliva per hour. This quantity, however, may be greatly 
 increased by the introduction into the mouth of any smooth un- 
 irritating substance, as glass beads, or the like; and during the 
 mastication of food, the saliva is poured out in very much greater 
 abundance. The very sight and odor of nutritious food, when the 
 appetite is excited, will stimulate to a remarkable degree the flow 
 of saliva ; and, as it is often expressed, " bring the water into the 
 mouth." ■ Any estimate, therefore, of the ^otal quantity • of saliva, 
 based on the amount secreted in this intervals of mastication, would 
 be a very imperfect one. We may make a tolerably accurate 
 calculation, however, by ascertaifting how much is really secreted 
 during a meal, over and above that which is produced at other times. 
 We have found, for example, by experiments performed for this 
 purpose, that wheaten bread gains during complete mastication 55 
 per cent, of its weight of saliva ; and that fresh cooked meat gains, 
 under the same circumstances, 48 per cent, of its weight. We have 
 already seen that the daily allowance of these two substances, for a 
 man in full health, is 19 ounces of bread, and 16 ounces of meat. 
 The quantity of saliva, then, required for the mastication of these 
 two substances, is, for the bread 4,572 grains, and for the meat 3,360 
 grains. If we now calculate the quantity secreted between meals 
 as continuing for 22 hours at 556 grains per hour, we have : — 
 
 Saliva required for mastication of bread = 4572 grains. 
 " " " " " meat = 3360 " 
 
 secreted in intervals of meals ^ ] 2232 " 
 
 Total quantity in twenty-four hours = 20164 grains ; 
 
 or rather less than 3 pounds avoirdupois. 
 
 ' Op. cit., p. 14. 
 
SALIVA. 129 
 
 The most important question, connected 'witli this subject, relates 
 to the function of the saliva in the digestive process. A very remark- 
 able property of this fluid is that which was discovered by Leuchs 
 in Germany, viz., that it possesses the power of converting boiled 
 starch into sugar, if mixed with it in equal proportions, and kept 
 for a short time at the temperature of 100° F. This phenomenon 
 is one of catalysis, in which the starch is transformed into sugar by 
 simple contact with the organic substance contained in the saliva. 
 This organic substance, according to the experiments of Mialhe,' 
 may even be precipitated by alcohol, and kef)t in a dry state for an 
 indefinite length of time without losing the power of converting 
 starch into sugar, when again brought in contact with it in a state 
 of solution. 
 
 This action of ordinary human saliva on boMed starch takes place 
 sometimes with great rapidity. Traces of glucose may occasionally 
 be detected in the mixture in one minute after the two substances 
 have been brought in contact ; and we have even found that starch 
 paste, introduced into the cavity of the mouth, if already at the 
 temperaturei of 100° P., will yield traces of sugar at the end of half 
 a minute. The rapidity however, with which this action is mani- 
 fested, varies very much, as was formerly noticed by Lehmann, at 
 different times ; owing, in all probability, to the varying constitution 
 of the saliva itself. It is often impossible, for example, to find any 
 evidences of sugar, in the mixture of starch and saliva, under five, 
 ten, or fiftpen minutes ; and it is frequently a longer time than this 
 before the whole of the starch is completely transformed. Even 
 when the conversion of the starch commences very promptly, it is 
 often a long time before it is finished. If a'thin starch paste, for 
 example, which contains no traces of sugar, be taken into the mouth 
 and thoroughly mixed' with the buccal secretions, it will often, as 
 already mentioned, begin to show the reaction of sugar in the course 
 of half a minute ; but some of the starchy matter still remains, and 
 will continue to manifest its characteristic reaction with iodine, for 
 fifteen or twenty minutes, or even half an hour. 
 
 It was supposed, when this property of converting starch into 
 sugar was first discovered in the saliva, that it constituted the true 
 physiological action of this secretion, and that the function of the 
 saliva was, id reallity, the digestion and liquefaction of starchy 
 substances. It was very soon noticed, however, by the French 
 
 ' Chimie appliquee i, la Physiologie et h, la Therapentique, Paris, 1856, p. 43. 
 9 
 
130 DIGESTIOU'. 
 
 observers, tHat this property of the saliva was rather an accidental 
 than an essential one ; and that, although starchy^ substances are 
 really converted into sugar, if mixed with saliva in a test-tube, 
 yet they are not affected by it to the same degree in the natural 
 process of digestion. We have already mentioned the extremely 
 variable activity of the saliva, in this respect, at different times ; 
 and it must be recollected, also, that in digestion the food is not 
 retained in the cavity of the mouth, but passes at once, after mas- 
 tication, into the stomach. Several German observers, as Frerichs, 
 Jacubowitsch, Bidder 'and Schmidt, maintained at first- that the 
 saccharine conversion of starch, after being commenced in the 
 mouth, might be, and actually was, completed in the stomach. We 
 have convinced ourselves, however, by frequent experiments, that 
 this is not the case. «[f a dog, with a gastric fistula, be fed with a 
 mixture of meat and boiled starch, and portions of the fluid con- 
 tents of the stomach withdrawn afterward through the fistula, 
 the starch is easily recognizable by its reaction with iodine for ten, 
 fifteen, and twenty minutes afterward. In forty-five minutes it is 
 diminished in quantity, and in one hour has usually altogether dis- 
 appeared; but no sugar is to be detected at apy time. Somej;imes 
 the starch disappears more rapidly than this ; but at no time, accord- 
 ing to our observations, is there any indication of the presence of 
 sugar in the gastric fluids. Bidder and Schmidt have also concluded, 
 from subsequent investigations,' that the first experiments performed 
 under their direction by Jacubowitsch were erroneous ; and it is 
 now acknowledged by them, as well as by the French observers, 
 that sugar cannot be detected in the stomach, after the introduction 
 of starch in any form or by any method. In the ordinary process 
 of digestion, in fact, starchy matters do not remain long enough in 
 the mouth to be altered by the saliva, but pass at once into the sto- 
 mach. Here they meet with the gastric fluids, which become min- 
 gled with them, and prevent the change which would otherwise be 
 effected by the saliva. We have found that the gastric juice will 
 interfere, in this manner, with the action of the saliva in the test- 
 tube, as well as in the stomach. If two mixtures be made, one of 
 starch and saliva, the other of starch, saliva, and gastric juice, and 
 both kept for 'fifteen minutes at the temperature of 100° F., in the 
 first mixture the starch will be promptly converted into sugar, while 
 in the second no such change will take place. The above action, 
 
 ' Op oit., p. 26. 
 
SALIVA. 131 
 
 therefore, of saliva on starch, thougli a curious and interesting pro- 
 perty. Las no significance as to its physiological function, since it 
 does not take place in the natural digestive process. We shall see 
 hereafter that there are other means provided for the digestion of 
 starchy matters, altogether independent of the action of the saliva. 
 
 The true function of the saliva is altogether a physical one. Its 
 action is simply to moisten the food and facilitate its mastication, 
 as well as to lubricate the triturated mass, and assist its passage 
 down the oesophagus. Food which is hard and dry, like crusts, 
 crackers, &c., cannot be masticated and swallowed with readiness, 
 unless moistened by some fluid. If the saliva, therefore, be prevented 
 from entering the cavity of the mouth, its loss does not interfere 
 directly with the chemical changes of the food in digestion, but only 
 with its mechanical preparation. This is the result of direct experi- 
 ments performed by various observers. Bidder and Schmidt,' after 
 tying Steno's duct, together with the common duct of the sub- 
 maxillary and sublingual glands on both sides in the dog, found 
 that the immediate effect of such an operation was " a remarkable 
 diminution of the fluids which exude upon the surfaces of the mouth ; 
 so that these surfaces retained their natural moisture only so long 
 as the mouth was closed, and readily became dry on exposure to 
 contact with the air. Accordingly, deglutition became evidently 
 difl&cult and laborious, not only for dry food, like bread, but even 
 for that of a tolerably moist consistency, like fresh meat. The 
 animals also became very thirsty, and jfere constantly ready to 
 drink." 
 
 Bernard' also found that the only marked effect of cutting off 
 the flow of saliva from the mouth was a difficulty in the mechani- 
 cal processes of mastication and deglutition. He first administered 
 to a horse one pound of oats, in order to ascertain the rapidity with 
 which mastication would naturally be accomplished. The above 
 quantity of grain was thoroughly masticated and swallowed at the 
 end of nine minutes. An opening had been previously made in 
 the oesophagus at the lower part of the neck, so that none of the 
 food reached the stomach ; but each mouthful, as it passed down the 
 oesophagus, was received at the oesophageal opening and examined 
 by the experimenter. The parotid duct on each side of the face 
 was then divided, and another pound of oats given to the animal. 
 
 Mastication and deglutition were both- found to be immediately 
 
 I 
 ' Op. cit., p. 3. 
 * Lesons de Physlologie Expfirimentale, Paris', 1856, p. 146., 
 
132 DIGESTION. ■ 
 
 retarded. The alimentary masses passed down the oesophagus at 
 longer intervals, and their interior was no longer moist and pastj, 
 as before, but dry and brittle. Finally, at the end of twenty -five 
 minutes, the animal had succeeded in masticating and swallowing 
 only about three-quarters of the quantity which he had previously 
 disposed of in nine minutes. 
 
 It appears also, from the experiments of Magendie, Bernard, and 
 Lassaigne, on horses and cows, that the quantity of saliva absorbed 
 by the food during mastication is in direct proportion to its hard- 
 ness and dryness, but has no particular relation to its chemical 
 qualities. These experiments were performed as follows : The oeso- 
 phagus was opened at the lower part of the neck, and a ligature 
 placed upon it, between the wound and the stomach. The animal 
 was then supplied with a previously weighed quantity of food, and 
 this, as it passed out by the oesophageal opening, was received into 
 appropriate vessels and again weighed. The difi'erence in weight, 
 before and after swallowing, indicated the quantity of saliva absorbed 
 by the food. The following table gives the results of some of Las- 
 saigne's experiments,' performed upon a horse : — 
 
 Kind of Food employed. Quantity of Saliva absorbed. 
 
 For 100 parts of hay there were absorbed 400 parts saliva. 
 
 " barley meal " 186 " 
 
 " oats " 113 " 
 
 " green stalks and leaves " 49 " 
 
 It is evident from the above facts, that the quantity of saliva 
 produced has not so much to do with the chemical character of the 
 food as with its physical condition. When the food is dry and 
 hard, and requires ijiuoh mastipation, the saliva is secreted in 
 abundance ; when it is soft and moist, a smaller quantity , of the 
 secretion is poured out ; and finally, when the food is taken in a 
 fluid form, as soup or milk, or reduced to powder and moistened 
 artificially with a very large quantity of water, it is not mixed at 
 all with the saliva, but passes at once into the cavity of the stomach. 
 The abundant and watery fluid of the parotid gland is most useful 
 in assisting mastication ; while the glairy and mucous secretion of 
 the submaxillary gland and the muciparous follicles serve to lubri- 
 cate the exterior of the triturated mass, and facilitate its passage 
 through the oesophagus. 
 
 By the combined operation' of the two processes which the food 
 undergoes in the cavity of the mouth, its preliqiinary preparation 
 
 ^ ' Comptes Eendus, vol. xxi. p. 362. . 
 
GASTRIC JUICE, AND STOMACH DIGESTION. 
 
 133 
 
 is accomplisljed. It is triturated and disintegrated by the teeth, 
 and, at the same time, by the movements of the jaws, tongue, and 
 cheeks, it is intimately mixed with the salivary fluids, until the 
 whole is reduced to a soft, ,pasty mass, of the same consistency 
 throughout. It is then carried backward by the semi-involuntary 
 movements of the tongue into the pharynx, and conducted by the 
 muscular contractions of the oesophagus into the stoinach. 
 
 Gastric Juice, and Stomach DiGBSTiON.-r-The mucous mem- 
 branp of the stomach is distinguished by its great vascularity 
 and the abundant glandular apparatus with which it is provided. 
 Its entire thickness is occupied by certain glandular organs, the 
 gastric tubules or follicles, which are so closely set as to leave 
 almost no space between them except wha* is required for the 
 capillary bloodvessels. The free surface of the gastric mucous 
 membrane is not smooth, but is raised in minute ridges and pro- 
 jecting eminences. In the cardiac portion (Fig. 25)^ these ridges 
 are reticulated with each other, so as to include between them 
 polygonal interspaces, each of which is icncircled by a capillajy 
 network. In the pyloric portion (Fig. 26), the eminences are more 
 
 ^ig. 25. 
 
 Fig. 26. 
 
 Fig. 25. Free surfiico of Gastric Mucous MemsrAke, viewed from above; from Pig's Sto- 
 macli, Cardiac portion. Magnified 70 diameters. 
 
 Fig. 26. Free surface of Gastric Mucous Membrane, viewed in %'erticaL section; from 
 Pig's Stomach, Pyloric portion. Magnified 420 diameters. 
 
 or less pointed and conical *in form, and generally flattened from 
 side to side. They contain each a capillary bloodvessel, which re- 
 
134 
 
 DIGESTION. 
 
 turns upon itself in a loop at the extremity of the projection, and 
 communicates freely with adjacent vessels. The gastric follicles are 
 
 very different in different 
 ^'S- ^''- parts of the stomach. In the 
 
 pyloric portion (Fig. 27), they 
 are nearly straight, simple- 
 tubules, ^{jj of an inch in 
 diameter," easily separated 
 from each other, lined with 
 glandular epithelium, and ter- 
 minating in blind extremities 
 at the under surface of the 
 mucous membrane. They are 
 sometimes slightly branched, > 
 or provided with one or two 
 rounded diverticula, a. short 
 distance above their termina- 
 tion. They open on the free 
 surface of the mucous mem- 
 brane, in the interspaces be- 
 tween the projecting folds or villi. Among these tubular glandules 
 there is also found, in the gastric mucous membrane, smother kind 
 of glandular organ, consisting of closed follicles, similar to the soli- 
 
 MncoDS Membrane OF Pig's Stomach, from 
 Pyloric portion; vertical section; showing gastric 
 tubules, and, at a, a closed follicle. Magnified 70 
 diapetei's. 
 
 Fig. 28. 
 
 Fig. 29, 
 
 Fig, 28. Gastric Tubules from Pig's Stomach, Pyloric portion, showing their Csecal 
 Extremities. At a, the torn extremity of a tubnle, sho^v^Dg its cavity. 
 
 Pig. 29. Gastric Tubuj.es from Pig's Stomach; Cardiac portion. At a, a large tubule 
 dividing into two small ones. b. Portion of a tubule, been endwise, c. Its central cavity. 
 
GASTRIC JUICE, AND STOMACH DIGESTION. 135 
 
 tary glands of the small intestine. These follicles, which are not very 
 numerous, are seated in the lower part of the mucous membrane, 
 and enveloped by the caecal extremities of the tubules. (Fig! 27, a.) 
 
 In the cardiac portion of the stomach, the tubules are very wide 
 in the superficial part of the mucous membrane, and lined with 
 large, distinctly marked cylinder epithelium cells. (Fig. 29.) In the 
 deeper parts of the membi^ane they become branched and conside- 
 rably reduced in size. From the point where the branching takes 
 place to their termination below, they are lined with small glandular 
 epithelium cells, and closely bound together by intervening areolar 
 tissue, so as to present somewhat the appearance of compound 
 glandules. 
 
 The bloodvessels which come up from the submucous layer of 
 areolar tissue form a close plexus around all these glandules, and 
 provide the mucous membrane with an abundant supply of blood, 
 for the purposes both of secretion and absorption. 
 • That part of digestion which takes place in the stomach has 
 always been regarded as nearly, if not quite, the most important 
 part of the whole process. The first observers who made any 
 approximation to a correct idea of gastric digestion were Eeaumur 
 and Spallanzani, who showed by various methods that the reduction 
 and liquefaction of the food in the stomach could not be owing to 
 mere contact with the gastric mucous membrane, or to compression 
 by the muscular walls of the organ ; but that it must be attributed 
 to a digestive fluid secreted by the mucous membrane, which pene- 
 trates the food and reduces it to a fluid form. They regarded this 
 process as a simple chemical solution, and considered the gastric 
 juice as a universal solvent for all alimentary substances. They 
 succeeded even in obtaining some of this gastric juice, mingled 
 probably with many impurities, by causing the animals upon which 
 they experimented to swallow sponges attached to the ends of 
 cords, by which they were afterward withdrawn, the fluids which 
 they had absorbed being then expressed and examined. 
 
 The first decisive experiments on this point, however, were those 
 performed by Dr. Beaumont, of the U. S. Army, on the person of 
 Alexis St. Martin, a Canadian boatman, who had a permanent gas- 
 tric fistula, the result of an accidental gunshot wound. The musket, 
 which was loaded with buckshot at the time of the accident, was 
 discharged, at the distance of a few feet from St. Martin's body, in 
 such a manner as to tear away the integument at the lower part of 
 the left chest, open the pleural cavity, and penetrate, through the 
 
136 DIGESTION. 
 
 lateral portion of the diaphragm, into the great pouch of the stomach. 
 After the integument and the pleural and peritoneal surfaces had 
 united and cicatrized, there remained a permanent opening, of about 
 four-fifths of an inch in diarfteter, leading into the left extremity of 
 the stomach, which was usually closed by a circular valve of pro- 
 truding mucous membrane. This valve could be readily depressed 
 at any time, so as to open the fistula and allow the contents of the 
 stomach to be extraclied foi* examination. • 
 
 Dr. Beaumont experimented upon this person at various intervals 
 from the year 1825 to 1832." He established during the course of 
 his examinations the following important facts: First, that. the ac- 
 tive agent in digestion is an acid fluid, secreted by the walls of the 
 stomach ; secondly, that this fluid is poured out by the glandular 
 walls of the organ only during digestion, and under the stimulus of 
 the food ; and finally, that it will exert its solvent action upon the 
 food outside the body as well as in the stomach, if kept in glass 
 phials upon a sand bath at the temperature of 100° F. He made, 
 also a variety of other interesting investigations as to the efiect 
 of various kinds of stimulus on the secretion of the stomach, the 
 rapidity with whicb the process of digestion takes place, the com- 
 parative digestibility of various kinds of food, &c. &o. 
 
 Since Dr. Beaumont's time it has been ascertained that similar 
 gastric fistulas may be produced at will on some of the lower animals 
 by a simple operation ; and the gastric juice has in this way been 
 obtained, usually from the dog, by Blondlot, Schwann, Bernard, 
 Lehmann and others. The simplest and most expeditious mode 
 of doing the operation is the best. An incision should be made 
 through the abdominal parietes in the median line, over the gresat 
 curvature of the stomach. The anterior wall of the organ is then 
 to be seized with a pair of hooked forceps, drawn out at the external 
 wound, and opened with the point of a bistoury. A short silver 
 canula, .one-half to three-quarters of an inch in diameter, armed at 
 each extremity with a narrow projecting rim or flange, is then in- 
 serted into the wound in the stomach, the edges of which are fast- 
 ened round the tube with a ligature in order to prevent the escape 
 of the gastric fluids into the peritoneal cavity. The stomach is then 
 returned to its place in the abdomen, and the canula allowed to re- 
 main with its external flange resting upon the edges of the wound 
 in the abdominal integuments, which are to be drawn together by 
 
 ' Experiments and Observations upon the Gastric Juice. Boston, 1834. 
 
GASTRIC JUICE, AND STOMACH DIGESTION. 137 
 
 sutures. The animal may be kept perfectly quiet, during the ope- 
 ration, by the administration of ether or chloroform. In a few 
 days the ligatures come away, the wounded peritoneal surfaces are 
 united with each other, and the canula is retained in a permanent 
 gastric fistula ; being prevented by its flaring extremities both from 
 falling out of the abdomen and from being accidentally pushed into 
 the stomach. It is closed externally by a cork, which may be with- 
 drawn at pleasure, and the contents of the stomach withdrawn for 
 examination. 
 
 Experiments conducted in this manner confirm, in the main, the 
 results obtained by Dr. Beaumont. Observations of this kind are 
 in some respects, indeed, more satisfactory when made upon the 
 lower animals, than upon the human subject; since animals are 
 entirely under the control of the experimenter, and all sources of 
 deception or mistake are avoided, while the investigation is, at the 
 same time, greatly facilitated by the simple character of their food. 
 
 The gastric juice, like the saliva, is secreted in .considerable 
 quantity only under the stimulus of recently ingested food. Dr. 
 Beaumont states that it is entirely absent during the intervals of 
 digestion ; and that the stomach at that time contains no acid fluid, 
 but only a little neutral or alkaline mucus. He was able to obtain 
 a sufficient quantity of gastric juice for examination, by gently irri- 
 tating the mucous membrane with a gum-elastic catheter, or the end 
 of a glass rod, and by collecting the secretion as it ran in drops 
 from the fistula. ■ On the introduction of food, he found that the 
 mucous membrane became turgid and reddened, a clear acid fluid 
 collected everywhere in drops underneath the layer of mucus lin- 
 ing the walls of the stomach, and was soon poured out abundantly 
 into its cavity. We have found, however, that the rule laid down 
 by Dr. Beaumont in this respect, though correct in the main, is not 
 invariable. The truth is, the. irritability of the gastric mucous 
 membrane, and the readiness with which the.flow of gastric juice 
 may be excited, varies considerably in different animals ; even in 
 those belonging to the same species. In experimenting with gastric 
 fistul£e on different dogs, for example, we have found in one instance, 
 like Dr. Beaumont, that the gastric juice was always entirely absent 
 in the intervals of digestion ; the mucous membrane then present- 
 ing invariably either a neutral or slightly alkaline reaction. In 
 this animal, which was a perfectly healthy one, the secretion could 
 not be excited by any artificial means, such as glass rods, metallic 
 catheters, and the like; but only by the natural stimulus of ingested. 
 
138 DIGESTIOK. 
 
 food. We have even seen tough and indigestible pieces of tendon, 
 introduced through the fistula, expelled again in a few minutes, one 
 after the other, without exciting the flow of a single drop of acid 
 fluid ; while pieces of fresh meat, introduced in the same way, pro- 
 duced at once an abundatit supply. In other instances, on the con- 
 trary, the introduction of metallic catheters, &c., into the empty 
 stomach has produced a scanty flow of gastric juice; and in experi- 
 menting upon dogs that have been kept without food during various 
 periods of time and then killed by section of the medulla oblongata, 
 we have usually, though not always, found the gastric mucous mem- 
 brane to present a distinctly acid reaction, even after an abstinence 
 of six, seven, or eight days. There is at no time, however, under 
 these circumstances, any considerable amount of fluid present in 
 the stomach ; but only just suificient to moisten the gastric mucous 
 membrane, and give it an acid reaction. 
 
 The gastric juice, which is obtained by irritating the stomach 
 with a metallic catheter, is clear, perfectly colorless, and acid in 
 reaction. A suf&cient quantity of it cannot be obtained by this 
 method for any extended experiments ; and for that purpose, the- 
 animal should be fed, after a fast of twenty-four hours, with fresh 
 lean meat, a little hardened by short boiling, in order to coagulate 
 the fluids of the muscular tissue, and prevent their mixing with the 
 gastric secretion. No effect is usually apparent within the first five 
 minutes after the introduction of the food. At the end of that time 
 the gastric juice begins to flow ; at first slowly, and. in drops. It is 
 then perfectly colorless, but very soon acquires a slight amber 
 tinge. It then begins to flow more freely, usually in drops, but 
 often running for a few seconds in a continuous stream. In this 
 way from §ij to giiss may be collected in the course of fifteen 
 minutes. Afterward it becomes somewhat turbid with the debris 
 of the food, which has begun to be disintegrated ; but from this, it 
 may be readily separated by filtration. After three hours, it con- 
 tinues to run freely, but has become very much thickened, and 
 even grumous in consistency, from the abundant admixture of 
 alimentary debris. In six hours after the commencement of diges- 
 tion it runs less freely,* and in eight hours has become very scanty, 
 though it continues io preserve the same physical appearances as 
 before.' It ceases to flow altogether in from nine to twelve hours, 
 according to the quantity of food taken. 
 
 For purposes of examination, the fluid drawn during the first 
 .fifteen minutes after feeding should .be collected, and separated by 
 
GASTRIC JUICE, AND STOMACH DIGESTION. 139 
 
 filtration from accidental impurities. Obtained in this way, the 
 gastric juice is a clear, wa,tery fluid, without any appreciable vis- 
 cidity, very distinctly acid to test paper, of a faint ^mber color, 
 and with a specific gravity of 1010. It becomes opalescent on 
 boiling, owing to the coagulation of its organic ingredients. The 
 following is the composition of the gastric juice of the dog, based 
 on 'a comparison of various analyses by Lehmann, and Bidder and 
 Schmidt : — 
 
 Composition of Gastbio Jpick. 
 
 Water 975.00 
 
 Organic matter 15.00 
 
 Lactic acid 4.78 
 
 Chloride of sodium 1.70 
 
 " " potassium « 1.08 
 
 " " calcium 0.20 
 
 " " ammonium ........ 0.65 
 
 Phosphate of lime 1.48 
 
 " " magnesia 0.06 
 
 "■ " iron 0.06 
 
 1000.00 
 In place of lactic acid. Bidder and Schmidt found, in most of their 
 analyses, hydrochloric acid. Lehmann admits that a small quantity 
 of hydrochloric acid is sometimes present, but regards lactic acid 
 as much the most abundant and important of the two. Eobin and 
 Yerdeil also regard the acid: reaction of the gastric juice as due to 
 lactic acid ; and, finally, Bernard has shown,' by a series of well 
 contrived experiments, that the free acid of the dog's gastric juice 
 is undoubtedly the lactic ; and that the hydrochloric acid obtained 
 by distillation is really produced by a decomposition of the chlo- 
 rides, which enter into the composition of the fresh juice. 
 
 The free acid is an extremely important ingredient of the gastric 
 secretion, and is, in fact, essential to its physiological properties ; 
 for the gastric juice will not exert its solvent, action upon the food, 
 after it has been neutralized by the addition of an alkali or an 
 alkaline carbonate. 
 
 The most important ingredient of. the gastric juice, beside the 
 free acid, is its organic matter or " ferment," which is sometimes 
 known under the name of pepsine. This name, " pepsine," was 
 originally given by Schwann to a substance which he obtained 
 from the mucous membrane of the pig's stomach, by macerating it 
 in distilled water until a putrid odor began to be developed. The 
 
 > Leijons de Fhjsiologie Exp^rimentale, Paris, 1856, p. 396. 
 
140 
 
 DIGESTION. 
 
 substance in question was precipitated from the watery infusion by 
 the addition of alcohol, and dried ; and if dissolved afterward in 
 acidulated water, it was found to exert a solvent action on boiled 
 . white of egg. This substance, however, did not represent precisely 
 the natural ingredient of the gastric secretion, and was probably a 
 mixture of various matters, some of them the products of com- 
 mencing decomposition of the mucous membrane itself. The name 
 pepsine, if it be used at all, should be applied to the organic matter 
 which naturally occurs in solution in the gastric juice. It is alto- 
 gether unessential, in this respect, from what source it may be 
 originally derived. It has been regarded by Bernard and others, 
 on somewhat insufficient grounds, as a product of the alteration of 
 the mucus ^f the stomach. But whatever be its source, since it is 
 always present in the secretion of the stomach, and takes an active 
 part in the performance of its function, it can be regarded in no 
 other light than as a real anatomical ingredient of the gastric juice, 
 and as essential to its constitution. 
 
 Pepsine is precipitated from its solution in the gastric . juice by 
 absolute alcohol, and by various metallic salts, but is not affected 
 
 by ferrocyanide of potassium. 
 ^'S- 30- It is precipitated also,, and 
 
 coagulated, by a boiling tem- 
 perature; and the gastric 
 juice, accordingly, after being 
 boUed, becomes turbid, and 
 loses altogether its power of 
 dissolving alimentary sub- 
 stances. Grastric juice is also 
 affected in a remarkable 
 manner by being mingled 
 with Ule. "We have found 
 that four to six drops of dog's 
 bile precipitate completely 
 with 5j of gastric juice from 
 the same animal ; so that the 
 whole of the biliary coloring 
 matter is thrown down as a 
 deposit, and the filtered fluid is found to have lost entirely its 
 digestive power, though it retains an acid reaction. 
 
 A very singular property of the gastric juice is its inaptitude for 
 putrefaction. It may be kept for an indefinite length of time in a 
 
 CoNFERvoiD Vegetable, growing in the Gas- 
 tric Juice of the Dog. Tlie fibres have an average 
 diameter of 1-7000 of an incht 
 
GASTRIC JUICE, AND STOMACH UIGJiSTION. 141 
 
 common glass-stoppered bottle without developing any putrescent 
 odor. A light deposit generally collects at the Bottom, and a con- 
 fervoid vegetable growth or "mould" often shows itself in the fluid 
 after it has been kept for one or two weeks. This growth has the 
 form of white, globular masses, each of which is composed of deli- 
 cate radiating branched filaments (Fig. 30) ; each filament consisting 
 of a row of elongated cells, like other vegetable growths of a similar 
 nature. These growths, however, are not accompanied by any 
 putrefactive changes, and the gastric juice retains it's acid reaction 
 and its digestive properties for many months. 
 
 By experimenting artificially with gastric juice on various ali- 
 mentary substances, such as meat, boiled white of egg, &o., it is 
 found, as Dr. Beaumont formerly. observed, to exert a solvent action 
 on these sub"fetances outside the body, as well as in the cavity of the 
 stomach. This action is most energetic at the temperature of 100° 
 F. It gradually diminishes in intensity below that point, and ceases 
 altogether near 32°. If the temperature be elevated above 100° 
 the action also becomes enfeebled, and is entirely suspended about 
 160°, or the temperature of coagulating albumen. Contrary to 
 what was supposed, however, by Dr. Beaumont, and his predeces- 
 sors, the gastric juice is not a universal "solvent for all alimentary 
 substances, but, on the contrary, afiects only a single class of the 
 proximate principles, viz., the albuminoid or organic substances. 
 Neither starch nor oil, when digested in it at the temperature of 
 the body, suffers the slightest chemical alteration. Fatty matters 
 are simply melted by the heat, and starchy substances are only 
 hydrated and gelatinized to a certain extent by the combined influ- 
 ence of the warmth and moisture. Solid and semi-solid albuminoid 
 matters, however, are at once attacked and liquefied by the diges- 
 tive fluid. Pieces of coagulated white of egg suspended in it, in a 
 test-tube, are gradually softened on their exterior, and their edges 
 become pale and rounded. They grow thin and transparent; 
 and their substance finally melts away, leaving a light scanty de- 
 posit, which collects at the bottom of the test-tube. "While the 
 disintegrating process is going on, it may almost always be noticed 
 that minute, opa'que spots show .themselves in the substance of the 
 liquefying albumen, indicating that certain parts of it are less easily 
 attacked than the rest ; and the deposit which remains at the bot- 
 tom is probably also composed of some ingredient, not soluble in 
 the gastric juice. If pieces of fresh meat be treated in the same 
 manner, the areolar tissue entering into its composition is first 
 
142 DIGESTION. 
 
 dissolved, so that the muscular bundles become more distinct, and 
 separate from each otber^ They gradually fall apart, and a little 
 brownish deposit is at last all that remains at the bottom of the 
 tube. If the hard adipose tissue of beef or mutton be subjected 
 to the same process, the walls of the fat vesicles and the inter- 
 vening areolar tissue, together with the capillary bloodvessels, &c., 
 are dissolved ; while the oily matters are set free from their en- 
 velops, and collect in a white, opaque layer on the surface. In 
 cheese, the casein is dissolved, and the oil which it contains set 
 free. In bread the gluten is digested, and the starch left un- 
 changed. In milk, the casein is first coagulated by contact with 
 the acid gastric fluids, and afterward slowly liquefied, like other , 
 albuminoid substances. 
 
 The time required for the complete liquefaction ef these sub- 
 stances varies with the quantity of matter present, and with its state 
 of cohesion. The process is hastened by occasionally shaking up 
 the mixture, so as to separate the parts already disintegrated, and 
 bring the gastric fluid into contact with fresh portions of the diges- 
 tible substance. 
 
 The liquefying process which the food undergoes in the gastric 
 juice is not a simple solution. It is a catalytic transformation, 
 produced in the albuminoid substances by contact with the organic 
 matter of the digestive fluid. This organic matter acts in a similar 
 manner to that of the catalytic bodies, or "ferments," generally. 
 Its peculiarity is that, for its active operation, it requires to be dis- 
 solved in an acidulated fluid. In common with other ferments, it 
 requires also a moderate degree of warmth ; its action being checked, 
 both by a very low, a«id a very high temperature. By its opera- 
 tion the albuminoid matters of the food, whatever may have been 
 their original character, are all, without distinction, converted into 
 a new substance, viz., albuminose. This substance has the general 
 characters belonging to the class of organic matters. It is uncrys- 
 tallizable, and contains nitrogen as an ultimate element. It is pre- 
 cipitated, like albumen, by an excess of alcohol, and by the metallic 
 salts ; but unlike albumen, is not affected by nitric acid or a boil- 
 ing temperature. It is freely soluble in water, and after it is once 
 produced by the digestive process, remains in a fluid condition, 
 and is ready to be absorbed by the vessels. In this way,, casein, 
 fibrin, musculine, gluten, &c., are all reduced to the condition of 
 albuminose. By experimenting as above, with a mixture of food 
 and gastric juice in test-tubes, we have found that the casein of 
 
GASTRIC JUICE, AND STOMACH DIQESTION. 143 
 
 cheese is entirely converted into albuminose, and dissolved nnder 
 that form. A very considerable portion of raw white of egg, how- 
 ever, dissolves in the gastric juice directly as albumen, ^.nd retains 
 its property of coagulating by heat. Soft-boiled white of egg and 
 raw meat are principally converted into albuminose; but at the 
 same time, a small portion of albumen is also taken up unchanged. 
 
 The above process is a true liquefaction of the albuminoid sub- 
 stances, and not a simple disintegration. If fresh meat be cut into 
 small pieces, and artificially digested in gastric juice in test-tubes, 
 at 100° F., and the process assisted by occasional gentle agitation, 
 the fluid continues to take up more and more of the digestible 
 material for from eight to ten hours. At the end of that timfc if it 
 be separated and filtered, the filtered fluid has a distinct, brownish 
 color, and is saturated with dissolved animal matter. Its specific 
 gravity is found to have increased from 1010 to 1020 ; and on the 
 addition of alcohol it becomes turbid, with a very abundant whitish 
 precipitate (albuminose). There is also a peculiar odor developed 
 during this process, which resembles that produced in the malting 
 of barley. 
 
 Albuminose, in solution in gastric juice, has several peculiar 
 properties. One of the most remarkable of these is that it inter- 
 feres with the operation of Trommer's test for grape sugar (see 
 page 84). We first observed and described this peculiarity in 
 1854,' but could not determine, at that time, upon what particular 
 ingredient of the gastric juice it depended. A short time subse- 
 quently it was also noticed by M. Longet, in Paris, who published 
 his observations in the Gazette ffebdomadaire for February 9th, 
 1855.' He attributed the reaction not to the gastric juice itself, 
 but to the albuminose held in solution by it. We have since found 
 this explanation to be correct. Gastric juice obtained from the 
 empty stomach of the fasting animal, by irritation with a metallic 
 catheter, which is clear and perfectly colorless, does not interfere 
 in any way with Trommer's test ; but if it be macerated for some 
 hours in a test-tube with finely chopped meat, at a temperature of 
 100°, it will then be found to have acquired the property in a 
 marked degree. The reaction therefore depends undoubtedly upon 
 the presence of albuminose in solution. As the gastric juice, drawn 
 from the dog's stomach half an hour or more after the introduction 
 
 ' American Jonm. Med. Sci., Oct. 1854, p. 319. 
 
 2 Nouvelles recherches relatives h Taction du sue gastrique sur lea substances 
 albuminoidea. — Gaz. Hehd. 9 Ftvrier, lS55, p. 103. 
 
144 DIGESTION. 
 
 of food, already contains some albuminose in solutjon, it presents 
 the same reaction. If such gastric juice be mixed with a small 
 quantity of glucose, and Trommer's test applied, no peculiarity is 
 observed on first dropping in the 'sulphate of copper; but on adding 
 afterward the solution of potassa, the mixture takes a rich purple hue, 
 instead of the clear blue tinge which is presented under ordinary 
 circumstances. On boiling, the color changes to claret, cherry red, 
 and finally to a light yellow; but no oxide of copper is deposited, and 
 the fluid remains clear. If the albuminose be present only in small 
 quantity, an incomplete reduction of the copper takes place, so that 
 the mixture becomes opaline and cloudy, but still without any weU 
 marked deposit. This interference will take place when sugar is 
 present in very large proportion. We have found that in a mix- 
 ture of honey and gastric juice in equal volumes, no reduction of 
 copper takes place on the application of Trommer's test. It is 
 remarkable, however, that if such a mixture be previously diluted 
 with an equal quantity of water, the interference does not take 
 place, and the copper is deposited as usual. 
 
 Usually this peculiar reaction, now that we are acquainted with 
 its existence, will not practically prevent the detection of sugar, 
 when present ; since the presence of the sugar is distinctly indi- 
 cated by the change of color, as above mentioned, from purple to 
 yellow, though the copper may not be thrown down as a precipi- 
 tate. All possibility of error, furthermore, may be avoided by 
 adopting the following precautions. The purple color, already men- 
 tioned, will, in the first place, serve to indicate the presence of the 
 albuminoid ingredient in the suspected fluid. The mixture should 
 then be evaporated to dryness, and extracted with alcohol, in order 
 to eliminate the animal matters. After that, a watery solution of 
 the sugar contained in the alcoholic extract will react as usual with 
 Trommer's test, and reduce the oxide of copper without difficulty. 
 
 Another remarkable property of gastric juice containing albu- 
 minose, which is not, however, peculiar to it, but common to many 
 other animal fluids, is that of interfering with the mutual reaction 
 of starch and iodine. If 3j of such gastric juice be mixed with 3j 
 of iodine water, and boiled starch be subsequently added, no blue 
 color is produced ; though if a larger quantity of iodine water be 
 added, or if the tincture he used instead of the aqueous solution, 
 the superabundant iodine then combines with the starch, and pro- 
 duces the ordinary blue color. This property, like that described 
 above, is not possessed by pure, colorless, gastric juice, taken from 
 
GASTBIC JUICE, AND STOMACH DIGESTION. 145 
 
 the empty stomach, but is acquired by it on being digested with 
 albuminoid substances. 
 
 Another important action which takes place in the stomach, 
 beside the secretion of the gastric juice, is the peristfiMia movement 
 of the organ. This movement is accomplished by the alternate 
 contraction and relaxation of the longitudinal and circular fibres 
 of its muscular coat. The motion is minutely described by Dr. 
 Beaumont, who examined it, both by watching the movements of 
 the food through the gastric fistula, and also by introducing into 
 the stomach the bulb and stem of a thermometer. According to 
 his observations, when the food first passes into the stomach, and 
 the secretion of the gastric juice commences, the muscular coat, 
 which was before quiescent, is excited and begins to contract act- 
 ively. The contraction takes place in such a manner that the food, 
 after entering the cardiac orifice of the stomach, is first carried to 
 the left, into the great pouch of the organ, thence downward and 
 a,long the great curvature to the pyloric portion. At a short distance 
 from the pylorus. Dr. B. often found a circular constriction of the 
 gastric parietes, by which the bulb of the thermometer was gently 
 grasped and drawn toward the pylorus, at the same time giving a 
 twisting motion to . the stem of the instrument, by which it was 
 rotated in his fingers. In a moment or two, however, this constric- 
 tion was relaxed, and the bulb of the thermometer again released, 
 and carried together with the food along the small curvatui'e of 
 the organ to its cardiac extremity. This circuit was repeated so 
 long as any food remained in the stomach ; but, as the liquefied 
 portions were successively removed toward the end of digestion, it 
 became less active, and at last ceased altogether when the stomach 
 had become completely empty, and the organ returned to its ordi- 
 nary quiescent condition. 
 
 It is easy to observe the muscular action of the stomach during 
 digestion in the dog, by the assistance of a gastric fistula, artificially 
 established. If a metallic catheter be introduced through the fistula 
 when the stomach is empty, it must usually be held carefully in 
 place, or it will fall out by its own weight. But immediately upon 
 the introduction of food, it can be felt that the catheter is grasped 
 and retained with some force, by the contraction of the muscular 
 coat. A twisting or rotatory motion of its extremity may also be 
 frequently observed, similar to that described by Dr. Beaumont. 
 This peristaltic action of the stomach, however, is a gentle one, 
 and not at all active or violent in character. We have never seen, 
 10 
 
146 DIGESTION. 
 
 in opening the abdomen, any such energetic or extensive contrac- 
 tions of the stomach, even when full of food, as may he easily 
 excited in thb small intestine by the mere contact of the atmosphere, 
 or by pinching them with the blades of a forceps. This action of 
 the stomach, nevertheless, though quite gentle, is sufficient to pro- 
 duce a constant churning movement of the masticated food, by 
 which it is carried back and forward to every part of the stomach, 
 and rapidly incorporated with the gastric juice which is at the 
 same time poured out by the mucous membrane ; so l^at thjg 
 digestive fluid is made to penetrate equally every part of the ali- 
 mentary mass, and the digestion of all its albuminous ingredients 
 goes on simultaneously. This gentle and continuous movement of 
 the stomach is one which cannot be successfully imitated in experi- 
 ments on artificial digestion with gastric juice in test-tubes; and 
 consequently the process, under these circumstances, is never so 
 rapid or so complete as when it takes place in the interior of the 
 stomach. 
 
 The length of time which, is required for digestion varies in 
 different species of animals. In the carnivora, a moderate meal of 
 fresh uncooked meat reqjiires from nine to twelve hours for its 
 complete solution and disappearance from the stomach. According 
 to Dr. Beaumont, the average time required for digestion in the 
 human subject is considerably less; varying from one hour to five 
 hours and a half, according to the kind of food employed. This 
 is probably owing to the more complete mastication of the food 
 which takes place in man, than in the carnivorous animals. Bv 
 examinmg the contents of the stomach at various intervals after 
 feeding, Dr. Beaumont made out a list, showing the comparative 
 digestibility of different articles of food, of which the following are 
 the most important : — 
 
 Time required for digestion, according to Dr. Beaumont : — 
 
 KiSD OF Food. Hours. Mikutes. 
 
 Pig's feet . . 1 00 
 
 Tripe 1 00 
 
 Trout (broiled) 1 30 
 
 Venison steak 1 35 
 
 Milk 2 00 
 
 Roasted turkey 2 30 
 
 " beef 3 00 
 
 " mutton 3 15 
 
 Veal (broiled) 4 OO 
 
 Salt beef (boiled) 4 15 
 
 Roasted pork 5 15 
 
GASTRIC JOICE, AND STOMACH DIGESTION. 147 
 
 The comparative digestibility of different substances varies more 
 or less ia different individuals according to temperament ; but the 
 above list undoubtedly gives a correct average estimate of the time 
 required for stomach digestion under ordinary conditions. 
 
 A very interesting question is that which relates to the total 
 quantity of gastric juice secreted daily. Whenever direct experi- 
 ments have been performed with a view of ascertaining this point, 
 their results have given a considerably larger quantity than was 
 anticipated. Bidder and Schmidt found that, in a dog weighing 
 34 pounds, they were able to obtain by separate experiments, con- 
 suming in all 12 hours, one pound and three-quartfers of gastric 
 juice. The total quantity, therefore, for 24 hours, in the same ani- 
 mal, would be 3J pounds ; and, by applying the same calculation to 
 a man of medium size, the authors estimate the total daily quantity 
 in the human subject as but little less than 14 pounds (av.). This 
 estimate is probably not an exaggerated one. In order to deter- 
 mine the question, however, if possible, in a different way, we 
 adopted the following plan of experiment with the gastric juice of 
 the dog. It was first ascertained, by direct experiment, that the 
 fresh lean meat of the bullock's heart loses, by complete desiccation, 
 78 per cent, of its weight. 300 grains of such meat, cut into small 
 pieces, were then digested for ten hours, in Siss of -gastric juice at 
 100° F. ; the mixture being thoroughly agitated as often as every 
 hour, in order to insure the digestion of as large a quantity of meat 
 as possible. The meat remaining undissolved was then collected 
 on a previously weighed filter, and evaporated to dryness. The 
 dry residue weighed 55 grains. This represented, allowing for the 
 loss by evaporation, 250 grains of the meat, in its natural moist 
 condition ; 50 grains of meat were then dissolved by 3iss of gastric 
 juice, or 33J grains per ounce. 
 
 From these data we can form some idea of the large quantity of 
 gastric juice secreted in the dog during the process of digestion. 
 One pound of meat is only a moderate meal for a medium-sized 
 animal ; and yet, to dissolve this quantity, no less than thirteen 'pints 
 of gastric juice will be necessary. This quantity, or any approxi- 
 mation to it, would be altogether incredible if we did not recollect 
 that the gastric juice, as soon as it has dissolved its quota of food, 
 is immediately reabsorbed, and again enters the circulation, together 
 with the alimentary substances which it holds in solution. The 
 secretion and reabsorption of the gastric juice then go on simulta- 
 neously; and the fluids which the blood loses by one process are 
 
148 DIGESTION. 
 
 incessantly restored to it by the other. A very large quantity, 
 therefore, of the secretion may be poured out during the digestion 
 of a meal, at an expense to the blood, at any one time, of only two 
 or three ounces of fluid. The simplest investigation shows that 
 the gastric juice does not accumulate in the stomach in any con- 
 siderable quantity during digestion; but that it is gradually 
 secreted so long as any food remains undissolved, each portion, as 
 it is digested, being disposed of by reabsorption; together with its 
 solvent fluid. There is accordingly, during , digestion, a constant 
 circulation of the digestive fluids from the bloodvessels to the ali- 
 mentary canal, and from the alimentary canal back again to the 
 bloodvessels. 
 
 That this circulation really takes place is proved by the fol- 
 Ipwing facts : First, if a dog be killed some hours after feeding, 
 there is never more than a very small quantity of fluid found in 
 the stomach, just sujB&cient to smear over and penetrate the half 
 digested pieces of meat ; and, secondly, in the living animal, gastria 
 (juice, drawn from the fistula five or six hours after digestion has 
 been going on, contains little or no more organic matter in solution 
 than that extracted fifteen to thirty minutes after the introduction 
 of food. It has evidently been freshly secreted ; and, in order to 
 obtain gastric juice saturated with alimentary matter, it must be 
 artificially digested with food in test-tubes, where this constant ab- 
 sorption and renovation cannot take place; 
 
 An unnecessary difficulty has sometimes been felt in understand- 
 ing how it is that the gastric juice, which digests so readily all albu- 
 minous substances, should not destroy the walls of the stomach 
 itself, which are composed of similar materials. This, in fact, was 
 brought forward at an early day, as an insuperable objection to the 
 doctrine of Eeauraur and Spallanzani, that digestion was a process 
 of chemical solution performed by a digestive fluid. It was said 
 to be impossible that a fluid capable of dissolving animal matters 
 should be secreted by the walls of the stomach without attacking 
 them also, and thus destroying the organ by which it was itself 
 produced. Since that time, various complicated hypotheses have 
 been framed, in order to reconcile these apparently contradictory 
 facts. The true explanation, however, as we believe, lies in this — 
 that the process of digestion is not a simple solution, but a catalytic 
 transformation of the alimentary substances, produced by contact 
 with the -pepsine of the gastric juice. "We know that all the or- 
 ganic substances in the living tissues are constantly undergoing, in 
 
GASTRIC JUICE, AND STOMACH DIGESTION. 149 
 
 the process of mitrition, a series of catalytic changes, which are 
 characteristic of the vital operations, and which are determined by 
 the organized materials with which they are in contact, and by all 
 the other conditions present in the living organism. These changes, 
 therefore, of nutrition, secretion, &c., necessarily exclude for the 
 time all other catalyses, and take precedence of them. In the same 
 way, any dead organic matter, exposed to warmth, air, and moist- 
 ure, putrefies; but if immersed in gastric juice, at the same 
 temperature, the putrefective changes are stopped or altogether 
 prevented, because the catalytic actions, excited by the gastric 
 juice, take precedence of those which constitute putrefaction. For 
 a similar reason the organic ingredient of the gastric juice, which 
 acts readily on dead animal matter, has no effect on the living 
 tissues of the stomach, because they are already subject to other 
 catalytic influences, which exclude those of digestion, as well as 
 those of putrefaction. As soon as life departs, however, and the 
 peculiar actions taking place in the living tissues come to an end 
 with the stoppage of the circulation, the walls of the stomach are 
 really attacked by the gastric juice remaining in its cavity, and 
 are more or less completely digested and liquefied. In the human 
 subject, it is rare to make an examination of the body twenty-four 
 or thirty-six hours after death, without finding the mucous mem- 
 brane of the great pouch of the stomach more or less softened and 
 disintegrated from this cause. Sometimes the mucous membrane 
 is altogether destroyed, and the submucous cellular layer exposed ; 
 and occasionally, when death has taken place suddenly during' 
 active digestion, while the stomach contained an abundance of 
 gastric juice, all the coats of the organ have been found destroyed, 
 and a perforation produced leading into the peritoneal cavity. 
 These post-mortem changes show that, after death, the gastric juice 
 really dissolves the coats of the stomach without difiBculty. But 
 during life, the chemical changes of nutrition, which are going on 
 in their tissues, protect them from its influence, and effectually 
 preserve their integrity. 
 
 The secretion of the gastric juice is much influenced by nervous 
 conditions. It was noticed by Dr. Beaumont, in his experiments 
 upon St. Martin, that irritation of the temper, and other moral 
 causes, would frequently diminish or altogether suspend the supply 
 of the gastric fluids. Any febrile action in the system or any 
 unusual fatigue, was liable to exert a similar effect. Every one is 
 aware how readily any mental disturbance, such as anxiety, anger. 
 
150 DIGESTION. 
 
 or vexation, will take away the appetite and interfere with diges- 
 tion. Any nervous impression of this kind, occurring at the com- 
 mencement of digestion, seems moreover to produce some change 
 which has a lasting effect upon the process ; for it is very often 
 noticed that when any annoyance, hurry, or anxiety occurs soon 
 after the food has been taken, though it may last only for a few 
 moments, the digestive process is not only liable to be suspended 
 for the time, but to be permanently disturbed during the entire 
 day. In order that digestion, therefore, may go on properly in the 
 stomach, food must be taken only when the appetite demands it ; 
 it should also be thoroughly masticated at the outset ; and, finally, 
 both mind and body, particularly during the commencement of the 
 process, should be free from any unusual or disagreeable excite- 
 ment. 
 
 Intestinal Juices, and the Digestion op Sugar and Starch. 
 — From the stomach, those portions of the food which have not 
 already suffered digestion pass into the third division of the ali- 
 mentary canal, viz., the sinall intestine. As already mentioned, it 
 is only the albuminous matters which are digested in the stomach. 
 Cane sugar, it is true, is slowly converted by the gastric juice, out- 
 side the body, into glucose. We have found that ten grains of 
 cane sugar, dissolved in gss of gastric juice, give traces of glucose 
 at the end of two hours ; and in three hours, the quantity of this 
 substance is considerable. It cannot be shown, however, that the 
 " gastric juice exerts this effect on sugar during ordinary digestion. 
 If pure sugar cane be given to a dog with a gastric fistula, while 
 digestion of meat is. going on, it disappears in from two to three 
 hours, without any glucose being detected in the fluids withdrawn 
 from the stomach. It is, therefore, either directly absorbed under 
 the form of cane sugar, or passes, little by little, into the duodenum, 
 where the intestinal fluids at once convert it into glucose. 
 
 It is equally certain that starchy matters are not digested in the 
 stomach, but pass unchanged into the small intestine. Here they 
 meet with the mixed intestinal fluids, which act at once upon the 
 starch, and convert it rapidly into sugar. The intestinal fluids,- 
 taken from the duodenum of a recently killed dog, exert this 
 transforming action upon starch with the greatest promptitude, if 
 mixed with it in a test-tube, and kept at the temperature of 100° F. 
 Starch is converted into sugar by this means much more rapidly 
 and certainly than by the saliva ; and experiment shows that the 
 
INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 151 
 
 intestinal fluids are the active agents in its digestion during life. 
 If a dog be fed with a mixture of meat and boiled starch, and killed 
 a short time after the meal, the stomach is found to contain starch 
 but no sugar ; while in the small intestine there is an abundance of 
 sugar, and but little or no starch. If some observers have failed 
 to detect sugar in the intestine after feeding the animal with 
 starch, it is because they have delayed the examination until too 
 late. For it is remarkable how rapidly starqhy substances, if pre- 
 viously disintegrated by boiling, are disposed of in the digestive 
 process. If a dog, for example, be fed as above with boiled starch 
 and meat, while some of the meat remains in the stomach for 
 eight, nine, or ten hours, the starch begins immediately to pass into 
 the intestine, where it is at once converted into sugar, and then as 
 rapidly absorbed. The whole of the starch may be converted into 
 sugar, and completely absorbed, in an hour's time. We have even 
 found, at the end of three-quarters of an hour, after a tolerably 
 full meal of boiled starch and meat, that all trace of both starch 
 and sugar had disappeared from both stomach and intestine. The 
 rafndity with which this passage of the starch into the duodenum 
 takes place varies, to some 
 
 extent, in different animals, '^'^" ^^* 
 
 according to the general ac- 
 tivity of the digestive appa- 
 ratus; but it is always a 
 comparatively rapid process, 
 when th^ starch is already 
 liquefied and is administered 
 in a pure form. There can 
 be no doubt that the natural 
 place for the digestion of 
 starchy matters is the small 
 intestine, and. that it is ac^ 
 coraplished by the action of 
 the intestinal juices. 
 
 Our knowledge is not very 
 complete with regard to the 
 exact nature of the fluids by which this digestion of the starch is 
 accomplished. The juices taken from the duodenum are generally 
 a mixture of three different secretions, viz., the bile, the pancreatic 
 fluid, and the intestinal juice proper. Of these, the bile may be 
 left out of the question ; since it does not, when in a pure state. 
 
 Follicles of Liebi^bkitqn, 
 testiue of dog. 
 
 from Small la- 
 
152 
 
 DIGESTION. 
 
 exert any digestive action on starch. The pancreatic juice, on the 
 other hand, has the property of converting starch into sugar ; but 
 . it is not known whether this fluid be always present in the duode- 
 num. The true intestinal juice is the product of two sets of glan- 
 dular organs, seated in the substance of or beneath the mucous 
 ■ membrane, .viz., the follicles of Lieberkiihn and the glands of Brun- 
 ner. The first of these, or Lieberkiihn's follicles (Fig. 31), are the 
 most numerous. They are simple, nearly straight tubules, lined 
 with a continuation of the intestinal epithelium, and somewhat 
 similar in their appearance to the follicles of the pyloric portion of 
 the stomach. They, occupy the whole thickness of the mucous 
 membrane, and are found in great numbers throughout the entire 
 length of the small and large intestine. 
 
 The glands of Brunner (Fig. 32), or the duodenal glandulss, as 
 they are sometimes called, are confined to the upper part of the duO' 
 
 denum, where they exist as a 
 ^'^" ^^' closely set layer, in the deeper 
 
 portion of the mucous mem- 
 brane, extending, downward a 
 short distance from the pylo- 
 rus. They are composed of 
 a great number of rounded 
 follicles, clustered round' a 
 central excretory duct. Each 
 follicle consists of a delicate 
 membranous wall, lined with 
 glandular epithelium, and 
 covered on its surface with 
 small, distinctly marked nu- 
 clei. The follicles collected 
 around each duct are bound 
 together by a thin layer of 
 areolar tissue, and covered with a plexus of capillary bloodvessels. 
 The intestinal juice, which is the secreted product of the above 
 glandular organs, has been less successfully studied than the other 
 digestive fluids, owing to the difiiculty of obtaining it in a pure 
 state. The method usually adopted has been to make an opening 
 in the abdomen of the" living animal, take out a loop of intestine, 
 empty it by gentle pressure, and then to shut off a portion of it 
 from the rest of the intestinal cavity by a couple of ligatures, 
 situated six or eight inches apart ; after which the loop is returned 
 
 . Portioa of one of Buunner's 
 Glands, from Humau Intetstine, 
 
 DnoDESi 
 
PANCKEATIO JUICE, ^ND THE DIGESTION OF FAT. 153 
 
 into the abdomen, and the external wound closed by sutures. 
 After six or eight hours the animal is killed, and the fluid, which 
 has collected in the isolated portion of intestine, taken out and 
 examined. The above was the method adopted by Frerichs. Bid- 
 der and Schmidt, in order to obtain pure intestinal juice, first tied 
 the biliary and pancreatic ducts, so that both the bile and the pan- 
 creatic juice should be shut out from the intestine, and then estab- 
 lished an intestinal fistula below, from which they extracted the 
 fluids which accumulated in the cavity of the gut. Frora the great 
 abundance of the follicles of Lieberkiihn, we should expect to find 
 the intestinal juice secreted in large quantity. It appears, however, 
 in point of fact, to be quite scanty, as the quantity collected in the 
 above manner by experimenters has rarely been sufficient for a 
 thorough examination of its properties. It seems to resemble very 
 closely, in its physical characters, the secretion of the mucous folli- 
 cles of the mouth. It is colorless and glassy in appearance, viscid 
 and- mucous in consistency, and has a distinct alkaline reaction. ' 
 It has the property when pure, as well as when mixed with other 
 secretions, of rapidly converting starch into sugar, at the tempera- 
 ture of the living body. 
 
 Pancreatic Juice, and the Digestion of Fat. — The only re- 
 maining ingredients of the food that require digestion are the oily 
 matters. These are not affected, as we have already stated, by con- 
 tact with the gastric juice ; and examination shows, furthermore, 
 that they are not digested^in the stomach. So long as they remain 
 in the cavity of this organ they are unchanged in their essential 
 properties. They are merely melted by the warmth of the stomach, 
 and set free by the solution of the vesicles, fibres, or capillary tubes 
 in which they are contained, or among which they are entangled ; 
 and are still readily discernible by the eye, floating in larger or 
 smaller drops on the surface of the semi-fluid alimentary mass. 
 Very soon, however, after its entrance into the intestine, the oily 
 portion of the food loses its characteristic appearance, and is con- 
 verted into a white, opaque emulsion, which is gradually absorbed. 
 This emulsion is termed the chyle, and is always found in the small 
 intestine during the digestion of fat, entangled among the valvular 
 conniventes, and adhering to the surface of the villi. The digestion 
 of the oil, however, and its conversion into chyle, does not take 
 place at once upon its entrance into the duodenum, but only after 
 it has passed the orifices of the pancreatic and biliary ducts. Since 
 
154 DIGESTIOjr. 
 
 these ducts almost invariably open into the intestine at or near the 
 same point, it was for a long time difficult to decide by which of 
 the two secretions the digestion of the oil was accomplished. M. 
 Bernard, however, first threw some light on this question by ex- 
 perimenting on some of the lower animals, in which the two ducts 
 open separately. In the rabbit, for example, the biliary duct opens 
 as usual just below the pylorus, while the pancreatic duct com- 
 municates with the intestine some eight or ten inches lower down. 
 Bernard fed. these animals with substances containing oil, or in- 
 jected melted butter into the stomach ; and, on killing them after- 
 ward, found that there was no chyle in the intestine between the 
 opening of the biliary and pancreatic ducts, but that it was abun- 
 dant immediately below the orifice of the latter. Above this point, 
 also, he found the lacteals empty or transparent, while below it 
 they were full of white and opaque chyle. The result of these ex- 
 periments, which have since been confirmed by Prof. Samuel Jack- 
 son, of Philadelphia,' led to the conclasion that the pancreatic fluid 
 is the active agent in the digestion of oily substances ; and an ex- 
 amination of the properties of this secretion, when obtained in a 
 pure state from the living animal, fully confirms the above opinion. 
 In order to obtain pancreatic juice from the dog, the animal 
 must be etherized soon after digestion has commenced, an incision 
 made in the upper part of the abdomen, a little to the right of the 
 median line, and a loop of the duodenum, together with the lower 
 extremity of the pancreas which lies adjacent to it, drawn out at 
 the external wound. The pancreatic duct is then to be exposed 
 and opened, and a small silver canula inserted into it and secured 
 by a ligature. The whole is then returned into the abdomen and 
 the wound closed by sutures, leaving only the end of the canula 
 projecting from it. In the dog there are two pancreatic ducts, 
 situated from half an inch to an inch apart. The lower one of 
 these, which is usually the larger of the two, is the one best adapted 
 for the insertion of the canula. After the eftects of etherization 
 have passed off, and the digestive process has recommenced, the 
 pancreatic juice begins to run from the orifice of the canula, at first 
 very slowly and in drops. Sometimes the drops follow each other 
 with rapidity for a few moments, and then an interval occurs during 
 which the secretion seems entirely suspended. After a time it re- 
 commences, and continues to exhibit similar fluctuations during 
 
 ' American Journ. Med. Soi., Oct. 1S54. ■ ■ 
 
PANCREATIC JUICE, AND THE DIGESTION OF FAT. 155 
 
 the whole course of the experiment. Its flow, however, is at all 
 times scanty, compared with that of the gastric juice ; and we have 
 never been able to collect more than a little over two fluidounces_ 
 and a half during a period of three hours, in a dog weighing not 
 more than forty-five pounds. This is equivalent to about 864 
 grains per hour ; but as the pancreatic juice in the dog is secreted 
 with freedom only during digestion, and as this J)rocess is in opera- 
 tion not more than twelve hours out of the twenty-four, the entire 
 amount of the secretion for the whole day, in the dog, may be esti- 
 mated at 4,368 grains. This result, applied to a man weighing 140 
 pounds, would give, as the total daily quantity of the pancreatic 
 juice, about 13,104 grains, or 1,872 pounds avoirdupois. 
 
 Pancreatic juice obtained by the above process is a clear, color- 
 less, somewhat viscid fluid, with a distinct alkaline reaction. Its 
 composition, according to the analysis of Bidder and Schmidt, is as 
 follows : — 
 
 Composition of PA^•CIlEATIO Juice. 
 Water ... 900.76 
 
 Organic matter (pancreatine) 90.38 
 
 Chloride of sodium 7.36 
 
 Free soda 0.32 
 
 Pliosphate of soda 0.45 
 
 Sulphate of soda 0.10 
 
 Sulphate of potassa O.02 
 
 r Lime 54 
 
 Combinations of J Magnesia 0.05 
 
 I Oxide of iron 0.02 
 
 1000.00 
 The most important ingredient of the pancreatic juice is its 
 organic matter, or pancreatine. It will be seen that this is much 
 more abundant in proportion to the other ingredients of the secre- 
 tion than the organic matter of any other digestive flaid. If is 
 coagulable by heat ; and the pancreatic juice often solidifies com- 
 pletely on boiling, like white of egg, so that not a drop of fluid re- 
 mains after its coagulation. It is precipitated, furthermore, by 
 nitric acid and by alcohol, and also by sulphate of magnesia in 
 excess. By this last property, it may be distinguished from albu- 
 men, which is not affected by contact with sulphate of magnesia. 
 
 Fresh pancreatic juice, brought into contact with oily matters at 
 the temperature of the body, exerts upon them, as was first noticed 
 by Bernard, a very peculiar effect. It disintegrates them, and re- 
 duces them to a state of complete emulsion, so that the mixture is 
 at once converted into a white, opaque, creamy-looking fluid. This 
 
156 UIGESTION. 
 
 effect is instantaneous and permanent, and only requires that the 
 two substances be well mixed by gentle agitation. It is singular 
 that some of the German observers should deny that the pancreatic 
 juice possesses the property of emulsioning fat, to a greater extent 
 than the bile and some other digestive fluids ; and should state that 
 although, when shaken up with oil, outside the body, it reduces 
 the oily particles to a state of extreme minuteness, the emulsion 
 is not permanent, and the oily particles "soon separate again on 
 the surface.'" We have frequently repeated this experiment with 
 different specimens of pancreatic juice obtained from the dog, and 
 have never failed to see that the emulsion produced by it is by 
 far more prompt and complete than that which takes place with 
 saliva, gastric juice, or bile. The effect produced by these fluids is 
 in fact altogether insignificant, in comparison with the prompt and 
 energetic action exerted by the pancreatic juice. The emulsion 
 produced with the latter secretion may be kept, furthermore, for at 
 least twenty-four hours, according to our observations, without any 
 appreciable separation of the oily particles, or a return to their 
 original condition. 
 
 The pancreatic juice, therefore, is peculiar in its action on oily 
 substances, and reduces them at once to the condition of an emul- 
 sion. The oil, in this process, does not sufier any chemical altera- 
 tion. It is not decomposed or saponified, to any appreciable extent. 
 It is simply emulsioned ; that is, it is broken up into a state of minute 
 subdivision, and retained in suspension, by contact with the organic 
 matter of the pancreatic juice. That its chemical condition is not 
 altered is shown by the fact' that it is still soluble in ether, which 
 will withdraw the greater part of the fat from a mixture of oil and 
 pancreatic juice, as well as from the chyle in the interior of the 
 intestine. In a state of emulsion, the fat, furthermore, is capable 
 of being absorbed, and its digestion may be then said to be accom- 
 plished. 
 
 We find, then, that the digestion of the food is not a simple 
 operation, but is made up of several different processes, which 
 commence successively in different portions of the alimentary 
 canal. In the first place, the food is subjected in the mouth to the 
 physical operations of mastication and insalivation. Eeduced to a 
 soft pulp and mixed abundantly with the saliva, it passes, secondly, 
 into the stomach. Here it excites the secretion of the gastric juice, 
 
 ' Lehmann's Physiological Chemistry. Philada. ed., vol. i, p. 507. 
 
PHENOMENA OF INTESTINAL DIGESTION. 157 
 
 by the influence of whicli its chemical transformation and solution 
 are commenced. If the meal consist wholly or partially of mus- 
 cular flesh, the first effect of the gastric juice is to dissolve the 
 iiitervening cellular substance, by which the tissue is disintegrated 
 and the muscular fibres separated from each other. Afterward 
 the muscular fibres themselves become swollen and softened by 
 the imbibition of the gastric fluid, and are finally disintegrated 
 and liquefied. In the small intestine, the pancreatic and intestinal 
 juices convert the starchy ingredients of the food into sugar, and 
 break up the fatty matters into a fine emulsion, by which they are 
 converted into chyle. 
 
 Although the separate actions of these digestive fluids, however, 
 commence at different points of the alimentary canal, they after- 
 ward go on simultaneously in the small intestine ; and the changes 
 which take place here, and which constitute the process of intestinal 
 digestion, form at the same time one of the most complicated, and 
 one of the most important.parts of the whole digestive function. 
 
 The phenomena of intestinal digestion may be studied, in the 
 dog, by killing the animal at various periods after feeding, and 
 examining the contents of the intestine. We have also succeeded, 
 by establishing in the same animal an artificial intestinal fistula, 
 in gaining still more satisfactory information on this point. The 
 fistula may be established, for this purpose, by an operation .precisely 
 similar to that already described as employed for the production of 
 a permanent fistula in the stomach. The silver tube having been 
 introduced into the lower part of the duodenum, the wound is 
 allowed to heal, and the intestinal secretions may then be with- 
 drawn at will, and subjected to examination at different periods 
 during digestion. 
 
 By examining in this way, from time to time, the intestinal 
 fluids, it at once becomes manifest that the action of the gastric 
 juice, in the digestion of albuminoid substances, is not confined to 
 the stomach, but continues after the food has passed into the intes- 
 tine. About half an hour after the ingestion of a meal, the gastric 
 juice begins to pass into the duodenum, where it may be recognized 
 by its strongly-marked acidity, and by its peculiar action, already 
 described, in interfering with Troramer's test for grape sugar. It 
 has accordingly already dissolved some of the ingredients of the 
 food while still in the stomach, and contains a certain quantity of 
 albuminose in solution. It soon afterward, as it continues to pass 
 into the duodenum, becomes mingled with the debris of muscular 
 
158 
 
 DIGESTION. 
 
 Fig. 33. 
 
 fibres, fat vesicles, and oil drops; substances whicli are easily 
 recognizable under the microscope, and which produce a grayish 
 
 turbidity in the fluid drawn 
 from the fistula. This turbid 
 admixture grows constantly 
 thicker from the second to 
 the tenth or twelfth hour; 
 after which the intestinal 
 ■ fluids become less abundant, 
 and finally disappear almost 
 entirely, as the process of di- 
 gestion comes to an end. 
 
 The passage of disintegrated, 
 muscular tissue into the intes- 
 tine may also be shown, as, 
 already mentioned, by killing 
 the animal and examining 
 the contents of the alimentary 
 canal. During the digestion 
 of muscular flesh and adipose, 
 tissue, the stomach contains 
 masses of softened meat, 
 smeared over with gastric 
 juice, and also a moderate 
 quantity of grayish, grumous 
 fluid, with an acid reaction. 
 This fluid contains, muscular 
 fibres, isolated from each 
 other, and more or less dis- 
 integrated, by the action of 
 the gastric juice. (Fig. 33.) 
 The fat vesicles are but little 
 or not at sd\ altered in the 
 stomach, and there are only 
 a few free oil globules to be 
 
 Contents of Stomach during Digestion 
 OF Meat, from the Dog.— n. Fat Vesicle, filled with 
 opaque, solid, granular fat. &, b. Bits of pUrtially 
 dieiiategrated muscular fibre, c. Oil globules. 
 
 Fig. 34. 
 
 From Duodknum of Dog, during Diges- 
 tion OP Meat. — fi. Fat Vesicle, with its contents 
 diminishing. The vesicle is beginning to shrivel and' 
 the fat breaking up. h, b. Disintegrated muscular SCeU floating in the mixCd 
 
 iibre. CO. Oil Globules. fluids. Contained in the cavity 
 
 of the organ. In the duodenum the muscular fibres are further* 
 disintegrated. (Fig. 34.) They become very much broken up, pale 
 and transparent, but can still be recognized by the granular mark- . 
 ings and striations which are characteristic of them. The fat vesi-- 
 
PHENOMENA OF INTESTINAL DIGESTION. 
 
 159 
 
 From Middlk op Small iNTKariHE.- 
 Fat vesicles, nearly emptied of their contenta. 
 
 Fig. 36. 
 
 cles also begin to become altered in the duodenum. The solid 
 granular fat of beef, and similat kinds of meat, becomes liquefied 
 and emulsioned ; and appears 
 under the form of free oil ^'^' ^^' 
 
 drops and fatty molecules; 
 while the fat vesicle itself is 
 partially emptied, and becomes 
 more or less collapsed and 
 shrivelled. In the middle 
 and lower parts of the intes- 
 tine (Figs, 35 and 36) these 
 changes continue. The mus- 
 cular fibres become constantly 
 more and more disintegrated, 
 and a large quantify of granu- 
 lar debris is produced, which 
 is at last also dissolved. The 
 fat also progressively disap- 
 pears, and the vesicles may 
 be seen in the lower part of 
 the intestine, entirely collapsed 
 and empty. 
 
 In this way the digestion of 
 the different ingredients of 
 the food goes on in a continu- 
 ous manner, from the stomach 
 throughout the entire length 
 of the small intestine. At the 
 same time, it results in the 
 production of three different 
 substances, viz : 1st. Albumi- 
 nose, produced by the action 
 of the gastric juice on the 
 albuminoid matters; 2d. An 
 oily emulsion, produced by the action of the pancreatic juice on 
 fat ; and, 3d. Sugar, produced from the transformation of starch, 
 by the mixed intestinal fluids. These substances are then ready 
 to be taken up into the circulation ; and as the mingled ingredients 
 of the intestinal contents pass successively downward, through the 
 duodenum, jejunum, and ileum, the products of digestion, together 
 with the digestive secretions themselves, are gradually absorbed, 
 
 Fhom last quarter of Small Intestine. 
 — a, a. Fat vesicles, quite empty and shrivelled. 
 
160 DIGESTION. 
 
 one after anotlier, by tlie vessels of tlie mucous membrane, and 
 carried away by the current of the circulation. 
 
 The Large Intestine and its Contents. — Throughout the 
 small intestine, as we have just seen, the secretions are intended 
 exclusively or mainly to act upon the food, to liquefy or disinte- 
 grate it, and to prepare it for absorption. But below the situation 
 of the ileo-caecal valve, and throughout the large intestine, the con- 
 tents of the alimentary canal exhibit a diflferent appearance, and 
 are distinct in their color, odor, and consistency. This portion of 
 the intestinal contents, or the feces, are not composed, for the most 
 part, of the undigested remains of the food, but consist principally 
 of animal substances discharged into the intestine by excretion. 
 These substances have not all been fully investigated ; for although 
 they are undoubtedly of great importance in regard to the preser- 
 vation of health, yet the peculiar manner in which they are dis- 
 charged by the mucous membrane and united with each other in 
 the feces has interfered, to a great extent, with a thorough investi- 
 gation of their physiological characters. Those which have been 
 most fully examined are the following : — 
 
 Excretine. — This was discovered and described by Dr. W. Mar- 
 cet,' as the most characteristic ingredient in the contents of the 
 large intestine. It is a slightly alkaline, crystallizable substance, 
 insoluble in water, but soluble in ether and hot alcohol. It crys- 
 tallizes in radiated groups of four-sided prismatic needles. It fuses 
 at 204° F., and burns at a higher temperature. It is non-nitrogen- 
 ous, and consists of carbon, hydrogen, oxygen, and sulphur, in the 
 following proportions : — 
 
 C78 H78 O2 S. 
 It is thought to be present mostly in a free state, but partly in union 
 with certain organic acids, as a saline compound. 
 
 Stercorine. — This substance was found to be an ingredient of the 
 human feces by Prof. A. Flint, Jr.^ It is soluble in ether and 
 boiling alcohol, and, like excretine, crystallizes in the form of 
 radiating needles, but fuses at a much lower temperature. It is 
 regarded by its discoverer as produced, by transformation, from 
 cholesterine, one of the ingredients of the bile. 
 
 Beside these substances, the feces contain a certain amount of 
 
 ' American Journal of the Medical Sciences, January, 1855, and January, 1858. 
 » Ibid., October, 1862. 
 
THE LARGE INTESTINE AND ITS CONTENTS. 161 
 
 fat, fatty acids, and the remnants of undigested food. Vegetable 
 cells and fibres may be detected, and some debris of the disin- 
 tegrated muscular fibres may almost always be found after a meal 
 composed of animal and vegetable substances. But little absorp- 
 tion, accordingly, takes place in the large intestine. Its of&ce is 
 mainly confined to the separation and discharge of certain excre- 
 mentitious substances. 
 
 11 
 
162 
 
 AB30BPTI0K. 
 
 CHAPTEE VII. 
 
 ABSORPTION. 
 
 . Beside the glands of Brunner and the follicles of LieberkHhn, 
 already described, there are, in the inner part of the walls of the 
 
 intestine, certain glandular- 
 ^'^' ^^' looking bodies vrhich are 
 
 termed "glandulae.solitariaB," 
 and "glandulaa agminatse." 
 The glandulae solitarisB are 
 globular or ovoid bodies, . 
 about one-thirtieth of an inch 
 in diameter, situated partly 
 in and partly beneath the in- 
 testinal mucous membrane. 
 Each glandule (Fig. 37) is 
 formed of an investing cap- 
 sule, closed on all sides, and 
 containing in its interior a 
 „ „ , soft pulpy mass, which con- 
 
 Onr of the closed Follicles of Pkyeb's , . 
 
 Patches, from Small Intestine of Pig. Miigniaod sistS of minutC Cellular bodicS, 
 50 diameter-. 
 
 Fii. 38. 
 
 Glakdoi.^ AilMivAT.B, fom Small Inteatine 
 if Vii. Maii'uifled 20 dlamuters. 
 
 imbedded in a homogeneous 
 substance. The inclosed mass 
 is. penetrated by capillary 
 bloodvessels, which pass in 
 through the investing cap- 
 sule, inosculate freely with 
 each other, and return upon 
 themselves in loops near the 
 centre of the glandular body. 
 There is no external opening 
 or duct; in fact, the contents 
 of the vesiicle, being pulpy 
 and vascular, as already de- 
 scribed, are not to be regarded 
 as a secretion, but as consti- 
 tuting a kind of solid gland- 
 
ABSOBPTIOX. 
 
 163 
 
 Fig. 39. 
 
 tissue. The glandulse agminatse (Fig. 38), or " Peyer's patches," as 
 they are sometimes called, consist of aggregations of similar globular 
 or ovoid bodies, found most abundantly toward the lower extremity 
 of the small intestine. Both the solitary and agminated glandules 
 are evidently connected with the lacteals and the system of the 
 mesenteric glands, which latter organs they resemble very much in 
 their minute structure. They are probably to be regarded as the 
 first row of mesenteric glands, situated in the walls of the intestinal 
 canal. 
 
 Another set of organs, intimately connected with the process of 
 absorption, are the villi of the small intestine. These are conical 
 vascular eminences of the mucous membrane, thickly set over the 
 whole internal surface of the small intestine. In the upper portion of 
 the intestine, they are flattened and triangular in form, resembling 
 somewhat the conical projections of the pyloric portion of the sto- 
 mach. In the lower part they are long and filiform, and often 
 slightly enlarged, or club-shaped at their free extremity (Fig. 39), 
 and frequently attaining the length of 
 one thirty-fifth- of an inch. They are 
 covered externally with a layer of 
 columnar epithelium, similar to that 
 which lines the rest of the intestinal 
 mucous membrane, and contain in their 
 interior two sets of vessels. The most 
 superficial of these are the capillary 
 bloodvessels, which are supplied in each 
 villus by a twig of the mesenteric 
 artery, and which form, by their fre- 
 quent inosculation, an exceedingly close 
 and abundant network, almost imme- 
 diately beneath the epith^ial layer. 
 They unite at the base of the villus, 
 and form a minute vein, which is one 
 of the commencing rootlets of the por- 
 tal vein. In the central part of the vil- 
 lus, and lying nearly in its axis, there 
 is another vessel, with thinner and more 
 
 transparent walls, which is the commencement of a lacteal. The 
 precise manner in which the lacteal originates in the extremity of 
 the villus is not known. It commences near the apex, either by a 
 blind extremity, or by an irregular plexus, passes, in a straight or 
 
 J:IXTUBUlT]f UF iNTJJSTlNAr. 
 
 Villus, from the Dog.— «. Liiyer o( 
 epithelium, b. Blood veitBel. c. Lacteal 
 vessel. 
 
164 ABSORPTION. 
 
 somewhat wavy line, toward the base of the villus, and then be- 
 comes continuous, with a small twig of the mesenteric lacteals. 
 
 The villi are the active agents in the process of absorption. By 
 their projecting form, and their great abundance, they increase enor- 
 mously the extent of surface over which the digested fluids, come 
 in contact with the intestinal mucous membrane, and increase, also, 
 to a corresponding degree, the energy with which absorption takes 
 place. They hang out into the nutritious, semi-flu-id mass cont^iiied 
 in the intestinal cavity, as the roots of a tree penetrate the soil; and 
 they imbibe the liquefied portions of the food, with a rapi(Jj.ty which 
 is in direct proportion to their extent of surface, and the activity of 
 their circulation. 
 
 The process of absorption is also hastened by the peristaltic 
 movements of the intestine. The muscular layer here, as in other 
 parts of the alimentary canal, is double, consisting of both circular 
 and longitudinal fibres. The action of these fibres ma,y be readily 
 seen by pinching the exposed intestine with the blades of a' forceps. 
 A contraction then takes place at the spot irritated, by which the 
 intestine is reduced in (|iameter, its cavity obliterated, and its con- 
 tents forced onward into the succeeding portion of the alimentary 
 canal. The local contraction then propagates itself to the neighbor- 
 ing parts, while the portion originally contracted becomes relaxed; 
 so that a slow, continuous, creeping motion of the intestine is pro- 
 duced, by successive waves of contraction and relaxatipn, which 
 follow each other from above downward. At the same time, the ' 
 longitudinal fibres have a similar alternating action, drawing the 
 narrowed portions of intestine up and down, as they successively 
 enter into contraction, or become relaxed in the intervals. .The effect 
 of the whole is to produce a peculiar, writhing, worm-like, or 
 "vermicular" motion, among the different coils of intestine. During 
 life, the vermicular or peristaltic motion of the intestine is excited 
 by the presence of food undergoing digestion. By its action, the 
 substances which pass from the stomach into the intestine are 
 steadily carried from above downward, so. as to traverse the entire 
 length of the small intestine, and to come in contact successively 
 with the whole extent of its mucous membrane. During this pas- 
 sage, the absorption of the digested food, is constantly going on. 
 Its liquefied portions are taken up by the villi of the mucous mem- 
 brane, and successively disappear ; so that, at the termination of the 
 snfall intestine, there remains only .the Undigestible portion of the 
 food, together with the refuse of the intestinal "secretions. These 
 
ABSORPTION. 165 
 
 pass throTigh the ileo-csecal orifice into the large intestine, and there 
 become reduced to the condition of feces. 
 
 The absorption of the digested fluids is accomplished both by 
 the bloodvessels and the lacteals. It was formerly supposed that 
 the lacteals were the only agents in this process ; but it has now 
 been long known that this opinion was erroneous, and that the 
 bloodvessels' take at least an equal part in absorption, and are in 
 some respects the most active and important agents of the two. 
 Abundant experiments have demonstrated not only that soluble 
 substances introduced into the intestine may be soon afterward 
 detected in the blood of the portal vein, but that absorption takes 
 place more rapidly and abundantly by the bloodvessels than by 
 the lacteals. The most decisive of these experiments were those 
 performed by Panizza on the abdominal circulation.' This ob- 
 server opened the abdomen of a horse, and drew out a fold of the 
 small intestine, eight or nine inches in length (Fig. 40, a, a), which 
 
 Fiff. 40., 
 
 Panizza's Expekiment. — 'in. iDtestiud. ft. Point of ligature of mesenterie vein. c. Opening 
 in intestiue for introduction of poison, d. , Opening i a meHBUteric vein behind the ligature. 
 
 he incliided between two ligatures. A ligature was then placed (at 
 b) upon the mesenteric vein receiving the blood from this portion 
 of intestine; aud, in order that the circulation might not be inter- 
 rupted, an opening was inade (at d) in the vein behind the ligature, 
 so that the blood brought by the mesenteric artery, after circulating 
 
 ' In Matteucci'd Lecjtures on the Pliysical Phenomena of Living Beings, Pereira'a 
 edition, p. 83. . 
 
166 ABSORPTION. 
 
 « 
 in the intestinal capillaries, passed out at the opening, and was 
 
 collected in a vessel for examination. Hydrocyanic acid was then 
 introduced into the" intestine by an opening at c, and almost imme- 
 diately afterward its presence was detected in the venous blood 
 flowing from the orifice at d. The animal, however, was not poi- 
 . soned, since the acid was prevetited from gaining an entrance into 
 the general circulation by the ligature at b. 
 
 Panizza afterward varied this experiment in the following man- 
 ner : Instead of tying the mesenteric vein, he simply compressed it. 
 Then, hydrocyanic acid being introduced into the intestine, as above, 
 no effect was produced on the animal, so long as compressioii was 
 maintained upon the vein. But as soon as the blood was allowed 
 to pass again through the v«ssels, symptoms of general poisoning 
 at once became manifest. Lastly, in a third experiment, the same 
 observer removed all the nerves and lacteal vessels supplying the 
 intestinal fold, leaving the bloodvessels alone untouched. Hydro- 
 cyanic acid now being introduced into the intestine, found an 
 entrance at once into the general circulation, and the animal was 
 immediately poisoned. The bloodvessels, therefore, are not only 
 capable of absorbing fluids from the intestine, but may even take 
 them up more rapidly and abundantly than the lacteals. 
 
 These two sets of vessels, however, do not absorb all the aliment- 
 ary matters indiscriminately. It is one of the most important of 
 the facts which have been, established by modern researches on 
 digestion that the different substances, produced by the operation of 
 the digestive fluids on the food, pass into the circulation by different 
 routes. The fatty matters are taken up by the lacteals under the form 
 of chyle, while the saccharine and albuminous matters pass by ab- 
 sorption into the portal vein. Accordingly, after the digestion of a 
 meal containing starchy and animal matters mixed, albuminose and 
 sugar are both found in the blood of the portal vein, while they can- 
 not be detected, in any large quantity, in the contents of the lacteals. 
 These substances, however, do not mingle at once with the general 
 mass of the circulation, but owing to the anatomical distribution of 
 the portal vein, pass first through the capillary circulation of the 
 liver. Soon after being introduced into the blood and coming in 
 contact with its organic ingredients, they become altered and con- 
 verted, by catalytic transformation, into other substances. The 
 albuminose passes into J^he condition of ordinary albumen, and 
 probably also partly into that of fibrin ; while the sugar rapidly 
 .becomes decomposed, and loses its characteristic properties; so 
 
ABSORPTION. 
 
 167 
 
 Fiff. 41. 
 
 that, on arriving at the entrance of the general circulation, both 
 these newly absorbed ingredients have become already assimilated 
 to those which previously existed in the blood. 
 
 The chyle in the intestine consists, as we have already mentioned, 
 of oily matters which have not been chemically altered, but simply 
 reduced to a state of emulsion. In chyle drawn from the lacteals 
 or the thoracic duct (Fig* 41), it still presents itself in the same 
 condition and retains all the 
 chemical properties of "oil. 
 Examined by the microscope, 
 it is seen to exist under the 
 form of fine granules and 
 molecules, which present the 
 ordinary appearances of oil 
 in a state of minute subdivi- 
 sion. The chyle, therefore, 
 does not represent the entire 
 product of the digestive pro- 
 cess, but contains only the 
 fatty substances, suspended 
 by emulsion in a serous fluid. 
 
 During the time that intes- 
 tinal absorption is going on, chti,e trom commf.ncemkxt op thoe^cio 
 
 ^ • • ^ Dpct, from the Dog.— The molecales vary in size 
 
 after a meal containing fatty from i-io,oooth of an inch downward, 
 ingredients, the lacteals may 
 
 be seen as white, opaque vessels, distended with milky chyle, pass- 
 ing through the mesentery, and converging from its intestinal bor- 
 der toward the receptaculum chyli, near the spinal column. During 
 their course, they pass through several successive rows of mesenteric 
 glands, which also become turgid with chyle, while the process of 
 digestion is going on. The lacteals then conduct the chyle to the 
 receptaculum chyli, whence it passes upward through the thoracic 
 duct, and is finally discharged, at the termination of this canal, into 
 the left subclavian vein. (Fig. 42.) It is then mingled with the 
 returning current of venous blood, and passes into the right cavities 
 of the heart. 
 
 The lacteals, however, are not a special system of vessels by them- 
 selves, but are simply a part of the great system, of " absorbent" or 
 " lymphatic" vessels, which are to be found everywhere in the integu- 
 ments of the head, the parietes of the trunk, the upper and lower 
 extremities, and in the muscular tissues and mucous . membranes 
 
168 
 
 ABSORPTION. 
 
 throughout tbe body. The walls of these vessels are thinner and 
 more transparent than those of the arteries and veins, tad they are 
 consequently less easily detected by ordinary dissection. They 
 
 originate in the tissues of the 
 above-mentioned parts by an 
 irregular plexus. They pass 
 from the 'extremities toward 
 the trunk, converging and 
 uniting with each other like the 
 veins, their principal branches 
 taking usually the same di- 
 rection with the nerves and 
 bloodvessels, and passing, at 
 various points in their course> 
 through certain glandular bo- 
 dies, the "lymphatic" or "ab- 
 sorbent" glands. The lym- 
 phatic glands, among which 
 are included the mesenteric 
 glands, consist of an external 
 layer of fibrous tissue and a 
 contained pulp or parenchy- 
 ma. The investing layer of 
 fibrous tissue sends off thin 
 septa or laminae from its in- 
 ternal surface, which pene- 
 trate the substance of the gland 
 in every direction and unite 
 with each other at various 
 points. In this way they form 
 an interlacing laminated framework, which divides the substance 
 of the gland into numerous rounded spaces or alveoli. These alveoli 
 are not completely isolated, but communicate with each other by 
 narrow openings, where the intervening septa are incomplete. These 
 cavities are filled .with a soft, reddish pulp, which is penetrated, 
 according to Kdlliker, like the solitary and agmiiiated glands of the 
 intestine, by a fine network of capillary bloodvessels. The solitary 
 and agminated glands of thfe intestine are, therefore, closely analo- 
 gous in their structure to the lymphatics. The former are to be 
 regarded as simple, «the latter as compound vascular glands. 
 
 The .arrangement of the lymphatic vessels in the interior of the 
 
 '■■■a. 
 
 Lacteals, Thoracic Duct^ &c. — a.. Intes- 
 tine, h. Vena cava inferior. c, c. Bight and left 
 Bubclavian veins, e/. Point of opening of thoracic 
 duct into left suhclavian. 
 
ABSOBPTIOX. 169 
 
 glands, is not precisely understood. Each lymphatic vessel, as it 
 enters the gland, breaks up injo a number of minute ramifications, 
 the vasa afferentia; and other similar twigs, forming the vasa effer- 
 entia, pass off in the opposite direction^ from the farther side of the 
 gland ; but the exact mode of communication between the two has 
 not been definitely ascertained. The fluids, however, arriving by 
 the vasa afferentia, must pass in some way through the tissue of 
 , the gland, before they are carried away again by. the vasa efferentia. 
 From the lower extremities the lymphatic vessels enter the abdomen 
 at the groin and converge toward the receptaculum chyli, into 
 which their fluid is discharged, and afterward conveyed, by the 
 thoracic duct, to the left subclavian vein. 
 
 The fluid which these vessels contain is called the lymph. It is 
 a colorless or slightly yellowish transparent fluid, which is absorbed 
 by the lymphatic vessels from the tissues in which they originate. 
 So far as regards its composition,, it is known to contain, beside 
 water and saline matters, a small quantity of fibrin and albumen. 
 Its ingredients are evidently derived from the metamorphosis of 
 the tissues, and are returned to the centre of the circulation in 
 order to be eliminated by excretion, or in order to undergo some 
 new transforming or renovating process. We are ignorant, how- 
 ever, with regard to the precise nature of their character and 
 destination. 
 
 The lacteals are simply that portion of the absorbents which 
 originate in the mucous membrane of the small intestine. During 
 the intervals of digestion, these vessels contain a colorless and 
 transparent lymph, entirely similar to that w'hich is found in other 
 parts of the absorbent system. After a meal containing only 
 starchy or albuminoid substances, there is no apparent change in 
 the character of their contents. But after a meal containing fatty 
 matters, these substances are taken up ' by the absorbents of the 
 intestine, which then become filled with the white chylous emul- 
 sion, and assume the appearance of lacteals. (Fig. 43.) It is for 
 this reason that lacteal vessels do not show themselves upon the 
 stomach nor upon the first few inches of the duodenum ; because 
 oleaginous matters, as we have seen, are not digested in the stomach, 
 but only aftqr they have entered the intestine and passed the orifice 
 of the pancreatic duct. 
 
 The presence of chyle in the lacteals is, therefore, not a con- 
 stant, but only a periodical phenomenon. The fatty substances 
 constituting the chyle begin to be absorbed during the process of 
 
170 
 
 ABSORPTION. 
 
 digestion, as soon as they have been disintegrated and emulsione^ 
 by the potion of the intestinal fluids. As digestion proceeds, they 
 accumulate in larger quantity, and gradually fill the whole lacteal 
 
 ■ Fig. 43. 
 
 liACTEALS AND LyjIFHATICS. 
 
 system and the thoracic duct. As they are discharged into the 
 subclavian vein, and mingled with the blood, they can still be dis- 
 tinguished in the circulating fluid, as a mixture of oijy molecules 
 and granules, between the orifice of the thoracic duct and the right 
 side of the heart. While passing through the pulmonary circula- 
 tion, however, they disappear. Precisely what becomes of them, 
 or what particular chemical changes they undergo, is not certainly 
 
ABSOKPTION. 171 
 
 known. They are, at all events, so altered in the blood, while 
 passing through the lungs, that they lose the form of a fatty emul- 
 sion, and are no longer to be recognized by the usual tests for 
 oleaginous substances. 
 
 The absorption of fat from the intestine is not, however, exclu- 
 sively performed by the lacteals. Some of it is also taken up, 
 under the same form, by the bloodvessels. It has been ascertained 
 by the experiments of Bernard'*that the blood of the mesenteric 
 veins, in the carnivorous animals, contains, during intestinal diges- 
 tion, a considerable amount of fatty matter in a state of minute 
 subdivision. Other observers, also (Lehmann, Schultz, Simon), have 
 found the blood of the portal vein to be considerably richer in fat 
 than that of other veins, particularly while intestinal digestion ife 
 going On with activity. In birds, reptiles, and fish, furthermore, 
 according to Bernard, the intestinal lymphatics are never filled 
 with opaque chyle, but only with a transparent lymph ; so that these 
 animals may be said to be destitute of lacteals, and in them the fatty 
 substances, like other alimentary materials, are taken up altogether 
 by the bloodvessels. In quadrupeds, on the other hand, and in 
 the human subject, the absorption of fat is accomplished both by 
 the bloodvessels and the lacteals. A certain portion is taken up 
 by the former, while the superabundance of the fatty emulsion is 
 absorbed by the latter. 
 
 A dif&oulty has long been experienced in accounting for the ab- 
 sorption of fat from the intestine, owing to its being considered as a 
 non-endosmotic substance ; that is, as incapable, in its free or undis- 
 solved condition, of penetrating and passing through an animal 
 membrane by endosmosis. It is stated, indeed, that if a fine oily 
 emulsion be placed on one side of an animal membrane in an endos- 
 mometer, and pure water on the other, the water will readily pene- 
 trate the substance of the membrane, while the oily particles cannot 
 be made to pass, even under a high pressure. Though this be true, 
 however, fdr pure water, it is not true for slightly alkaline fluids, 
 like the serum of the blood and the lymph. This has been de- 
 monstrated by the experiments of . Matteucci, in which he made 
 an emulsion with an alkaline fluid containing 43 parts per thou- 
 sand of caustic potassa. Such a solution has no perceptible alkaline 
 taete, and its action on reddened litmus paper is about equal to 
 that of the lymph and chyle. If this emulsion were placed in an 
 
 < Lefons dH Phjsiologie GxpSrimentale. Paris, 1856, p. 325. 
 
172 
 
 ABSORPTION. 
 
 Intestinal Epithelium 
 fasting. 
 
 from the Dog, while 
 
 endosmometer, together with a watery alkaline solution of similar 
 strength, it was found that the oily particles penetrated through the 
 
 animal membrane without 
 
 ^'S- ^^ much difficulty, and mingled 
 
 with the fluid on the opposite 
 
 side. Although, therefore, 
 
 we cannot explain the exact 
 
 mechanism of absorption in 
 
 the case of fat, still we know 
 
 that it is not in opposition to 
 
 the ordinary phenomena of 
 
 endosmosis; for endosmosia 
 
 will take place with a fatty 
 
 emulsion, provided the fluids 
 
 used in the experiment be 
 
 slightly alkaline in reaction. 
 
 It is, accordingly, by a pro^ 
 
 cess of endosmosis, or imbi- 
 
 * bition, that the villi take up 
 
 the digested fatty substances. There are no open orifices or canals, 
 
 into which the oil penetrates ; but it passes directly into and through 
 
 the substance of the villi; 
 ^" ' " The epithelial cells covering 
 
 the external surface of the 
 villus are the first active 
 agents in tbis absorption. In 
 the intervals of digestion (Fig. 
 44) these cells are but slightly 
 granular and nearly trans- 
 parent in appearance. But if 
 examined during the diges;- 
 tion and absorption of fat 
 (Fig. 45), their substance ia 
 seen to be crowded with oily 
 particles, which they hav« 
 taken up from the intestinal 
 cavity by absorption. The 
 oily matter then passes q/a.- 
 ward, penetrating deeper and d;eeper into the substance of the villus, 
 until it is at last received by the capillary vessels and lacteals in its 
 centre. 
 
 I STK3TISAL Epithelium; 
 the digestioa of fat. 
 
 from tlie Dog, dnring 
 
ABSOBPTION. 173 
 
 The fatty substances taken up by the portal vein, like those ab- 
 sorbed by the lacteals, do not at once enter the general circulation, 
 but pass first through the capillary system of the liver. Thence 
 they are carried, with the blood of the hepatic vein, to the right 
 side of the heart, and subsequently through the capillary system of 
 the lungs. During this passage they become altered in character, 
 as above described, and lose for the most part the distinguishing 
 characteristics of oily matter, before they have passed beyond the 
 pulmonary circulation. 
 
 But as digestion proceeds, an increasing quantity of fatty matter 
 finds its way, by these two passages, into the blood ; and a time at 
 last arrives when the whole of the fat so introduced is not destroyed 
 during its passage through the lungs. Its absorption taking place 
 at this time more rapidly than its decomposition, it begins to ap- 
 pear, in moderate quantity, in the blood of the general circulation ; 
 and, lastly, when the intestinal absorption is at its point of greatest 
 activity, it is found in considerable abundance throughout the 
 entire vascular system. At this period, some hours after the inges- 
 tion of food rich in oleaginous matters, the blood of the general 
 circulation everywhere contains a superabundance of fat, derived 
 from the digestive process. If blood be then drawn from the veins 
 or arteries in any part of the body, it will present the peculiar 
 appearance known as that of " chylous" or " milky" blood. After 
 the separation of the clot, the serum presents a turbid appearance ; 
 and the fatty substances, which it contains, rise to the top after a 
 few hours, and cover its surface with a partially opaque and creamy- 
 looking pellicle. This appearance has been occasionally observed 
 in the human subject, particularly in bleeding for apoplectic attacks 
 occurring after a full meal, and has been mistaken, in some instances, 
 for a morbid phenomenon. It is, however, a perfectly natural one, 
 and depends simply on the rapid absorption, at certain periods of 
 digestion, of oleaginous substances from the intestine. It can be 
 produced at will, at any time, in the dog, by feeding him with fat 
 meat, and drawing blood, seven or eight hours afterward, from the 
 carotid artery or the jugular vein. 
 
 This state of things continues for a varying length of time, ac- 
 cording to the amount of oleaginous matters contained in the food. 
 • When digestion is terminated, and the fat ceases to be introduced 
 in unusual quantity into the circulation, its transformation and 
 decomposition continuing to take place in the blood, it disappears 
 gradually from the veins, arteries, and capillaries of the general 
 
174 ABSOBPTION. 
 
 system ; and, finally, ■when the whole of the fat has been disposed 
 of by the nutritive processes, the serum again becomes transparent, 
 and the blood returns to its ordinary condition. 
 
 In this manner the nutritive elements of the food, prepared for 
 absorption by the digestive process, are taken up into the circulation 
 under the different forms of albuminose, sugar, and chyle, and accu- 
 mulate as such, at certain times, in the blood. But these conditions 
 are only temporary, or transitional. The nutritive materials soon 
 pass, by catalytic transformation, into other forms, and become 
 assimilated to the pre-existing elements of the circulating fluid. 
 Thus they accomplish finally the whole object of digestion ; which 
 is to replenish the blood by a supply of new materials from without. 
 There are, however, two other intermediate processes, taking place 
 partly in the liver and partly in the intestine, at about the same 
 time, and having for their object the final preparation and perfec- 
 tion of the circulating fluid. These two processes require to be 
 studied, before we can pass on to the particular description of the 
 blood itself. They are : 1st, the secretion and reabsorption of the 
 bile ; and 2d, the production of sugar in the liver, and its subse- 
 quent decomposition in the blood. 
 
TUB BILE. 175 
 
 CHAPTER VIII. 
 
 THE BILE. 
 
 The bile is more easily obtained in a state of purity than any 
 other of the secretions which find their way into the intestinal 
 canal, owing to the existence of a gall-bladder in which it accu- 
 mulates, and from which it may be readily obtained without any 
 other admixture than the mucus of the gall-bladder itself. Not- 
 withstanding this, its study has proved an unusually difficult one. 
 This difficulty has resulted from the peculiar nature of the biliary 
 ingredients, and the readiness with which they become altered by 
 chemical manipulation ; and it is, accordingly, only quite recently 
 that we have arrived at a correct idea of its real constitution. 
 
 The bile, as.it comes from the gall-bladder, is a somewhat viscid 
 and glutinous fluid, varying in color and specific gravity according 
 to the species of animal from which it is obtained. Human bile is 
 of a dark golden brown color, ox bile of a greenish yellow, pig's 
 bile of a nearly clear yellow, and dog's bile of a deep brown. We 
 have found the specific gravity of human bile to be 1018, that of 
 ox bile 1024, that of pig's bile 1030 to 1036. The reaction of the 
 bile with test-paper cannot easily be determined ; since it has only 
 a bleaching or decolorizing effect on litmus, and does not turn it 
 either blue or red. It is probably either neutral or very slightly 
 alkaline. A very characteristic physical property of the bile is 
 that of frothing up into a soap-like foam when shaken in a test- 
 tube, or when air is forcibly blown into it through a small glass 
 tube or blowpipe. The bubbles of foam, thus produced, remain 
 for a long time without breaking, and adhere closely to each other 
 and to the sides of the glass vessel. 
 
 The following is an analysis of the bile of the ox, based on the 
 calculations of Berzelius, Frerichs, and Lehmann : — 
 
176 THE BILE. 
 
 CoMPiisiTios or Ox Bile. 
 
 Water 888.00 
 
 Glyko-oholate of soda" 1 90 00 
 
 Tauro-cholate " " ' 
 
 Biliverdine j 
 
 Fats ! 13.42 
 
 Oleates, margarates, and stearates ofsoda and potassa . i 
 
 Cholesterin , ^ J 
 
 Chloride of sodium 1 
 
 Phosphate of soda ■ | 
 
 " " lime } 15.24 
 
 " " magnefiia 
 
 Carbonates of soda and potassa J 
 
 Mucus of the gall-bladder .1.34 
 
 1000.00 
 
 BiLiVEBDiNE. — Of the above mentioned ingredients, biliverdine 
 is peculiar to the bile, and therefore importafnt; though not pre- 
 sent in large quantity. This is the coloring matter of the bile. 
 It is, like the other coloring matters, an uncrystallizable organic 
 substance, containing nitrogen, and yielding to ultimate analysis a 
 small quantity of iron. It exists in such small quantity in the bile 
 that its exact proportion has never been determined. It is formed, 
 so far as can be ascertained, in the substance of the liver, and does 
 not pre-exist in the blood. It may, however, be reabsorbed in 
 cases of biliary obstruction, when it circulates with the blood and 
 stains nearly all the tissues and fluids of the body, of a peculiar 
 lemon yellow color. This is the symptom which is characteristic 
 of jaundice. 
 
 Cholestebin;(C25H220). — This is a crystallizable substance which 
 resembles the fats in many respects ; since it is destitute of nitrogen, 
 readily inflammable, soluble in alcohol and ether, and entirely in- 
 soluble in watel". It is not saponifiable, however, by the action of 
 the alkalies, and is distinguished on this account from the ordinary 
 fatty substances. It occurs, in a Crystalline form, mixed with color- 
 ing matter, as an abundant ingredientiin most biliary calculi ; and 
 is found also in different re^ons of the body, forming a part of 
 various morbid deposits. We have met with it in the fluid of 
 hydrocele, and in the interior of many encysted tumors. The 
 crystals of cholesterin (Fig. 46) have the form of very thin, color- 
 less, transparent, rhomboidal plates, portions of which are often 
 cut out by lines of cleavage parallel to the sides of the crystal. 
 They frequently occur deposited in layers, in which the outlines of 
 
THE BILE. 
 
 177 
 
 Fig. 46. 
 
 the subjacent crystals show; very distinctly through. the substance 
 of those which are placed above. Cholesterin is not formed in the 
 liver, but originates in the 
 substance of the brain and 
 nervous tissue, from -which 
 it may be extracted in large 
 quantity by the action of 
 alcohol. It has> also been 
 found, by Dr. W. Marcet,' to 
 exist, in considerable abund- 
 ance, in the tissue of the 
 spleen. From all these tis- 
 sues it is absorbed by the 
 blood, then conveyed to the 
 liver, and discharged with 
 the bile. 
 
 Cholestebik, from an EaCyHted Tumor. 
 
 This fact has been fully 
 confirmed by the researches 
 
 of Prof. A. Flint, Jr.,' who has found that there is nearly one-quarter 
 part more cholesterin in the blood of the jugular vein, returning 
 from the brain, tha,n in that of the carotid artery, before its passage 
 through that organ ; and that, on the other hand, the blood of the 
 hepatic artery, as well as that of the portal vein, loses cholesterin 
 in passing through the liver, so that but a small quantity can be 
 found in the blood t>t the hepatic vein. 
 
 The cholesterin, however, after #being poured into the iiitestine 
 with the bile, is decomposed or transformed into some other sub- 
 stance, since it is nat discharged with the feces.^ Its decomposition 
 is probably effected by the contact of the intestinal fluids. - 
 
 BiLiABT Salts.— rBy far the most important and charaeteristic 
 ingredients of this secretion are the two saline substances mentioned 
 above as the ghfho-cholate and tauro-cholate of. soda. These sub- 
 stances were first discovered by Strecker, in 1848, in the bile of the 
 ox. They are both freely soluble in water and in alcohol, but in- 
 soluble in ether. One of theni, the tauro-cholate, has the property, 
 
 I In American Joum. Med. Sci., January, 185S. 
 ' American Joum. Med. Sci., October, 1862. 
 » Trof. A. 'Flint, Jr., iu Ala. Journ. Med. Sci., Oct. 1862. 
 12 
 
178 
 
 TEB BILE. 
 
 •when itself in solution in water, of dissolving a certain quantity of 
 fat ; and it is probably owing to this circumstance that some free 
 fat is present in the bile. The two biliary substances' are obtained 
 from'ox bile in the following manner : — 
 
 The bile is first evaporated to dryness by the water-bath. The 
 dnr residue is then pulverized and treated with. absolute alcohol, in 
 the proportion of at least 3j of alcohol to every five grains of dry 
 residue. The filtered alcoholic solution has a clear yellowish color. 
 It contains, beside the glyko-cholate and tauro-oholate of soda, the 
 coloring matter and more or less of the fats originally, present in 
 the bile. On the addition of a small qua,ntity of ether, a dense, 
 whitish precipitate is formed, which disappears again on agitating 
 and thoroughly mixing the fluids. On the repeated addition of 
 ether, the precipitate again falls down, and when the ether has been 
 added in considerable excess, six to twelve times the volume of the 
 alcoholic solution, the precipitate remains permanent, and the whole 
 mixture is filled with a dense, whitish, opaque deposit, consisting 
 of the fflyko-cholate and tauro-cholate of soda, thrown down under 
 the form of heavy flakes and granules, part of which subside to^ 
 
 Fig. 47. 
 
 Fig. 49. 
 
 Ox-bile, extracted with abnolute 
 alcohol and precipitated with ether. 
 
 Gi.TKO-rnoLATE OF Soda prom Ox-bile, 
 after two dajm' crystalUialion. At the lower part of 
 the figure the crystalB are melting into drops, from the 
 eraporatton of the ether and absorption of moisture. 
 
 .the bottom of the test-tube, while part remain fo'r a time in suspen- 
 sion. Gradually these flakes and granules., unite 'wjth each other 
 and fuse together into clear, brownish-yellow> oily,, or resinous^ 
 
TH£ BILE. 
 
 179 
 
 looking drops. At the bottom of the test-tube, after two or three 
 hours, there is usually collected a nearly homogeneous layer of 
 this deposit, while the remainder continues to adhere to the sides 
 of the glass in small, circular, transparent di;ops. The deposit is 
 semi-fluid in consistency, and sticky, like Canada balsam or half- 
 melted resin ; and it is on this account that the ingredients compoS' 
 ing it have been called the " resinous matters" of the bile. They 
 have, however, no real chemical relation with true resinous bodies, 
 since they both contain nitrogen, and differ from resins also in 
 other important particulars. 
 
 At the end of twelve to twenty-four hours, the glyko-cholate of 
 soda begins to crystallize. The crystals radiate from various points 
 in the resinous deposit, and shoot upward into the supernatant 
 fluid, in white, silky bundles. (Fig. 47.) If some of these crystals 
 be removed and examined by the microscope, they are found to be 
 of a very delicate acicular form, running to a finely pointed 
 extremity, and radiating, as already mentioned, from a central 
 point. (Fig. 48.) As the ether evaporates, the crystals absorb 
 moisture from the air, and melt up rapidly into clear resinous 
 drops ; so that it is difficult to keep them under the microscope 
 long enough for a correct 
 drawing and measurement 
 The crystallization in the 
 test-tube goes on after the 
 first day, and the crystals in- 
 crease in quantity for three 
 or four, or even five or six 
 days, until the whole of the 
 glyko-cholate of soda present 
 has assumed the solid form. 
 The tauro-oholate, however, 
 is uncrystallizable, and re- 
 mains in an amorphous con- 
 dition. If a portion of the 
 deposit be now removed and 
 
 Jig. 49. 
 
 Gltko-ch 
 
 TAUEO-CHOL ATE OP 
 
 examined by the microscope, soda, prom ox-bub, after hx days* crystamzii- 
 
 ... ..1 J j1 i. ^ e tion. The glyko-cholate is crystallized: the tanro- 
 
 It is seen that the crystals of ^^„,,^ j. ,/j^i, ^^p,. 
 glyko-cholate of soda have 
 
 increased considerably in thickness (Fig. 49), so that their trans- 
 verse diameter may be readily estimated. The uncrystallizable 
 taui-o-cholate appears under the form of circular drops, varying 
 
180 ' THE BILE. 
 
 considerably in size, clear, transparent, strongly refractive, and 
 bounded by a dark, well-defined outline. These drops are not to be 
 distinguished, by any of their optical properties, from oil-globuhs, as 
 they usually appear under tbe microscope. They have the same 
 refractive power, the same dark outline and bright centre, and the 
 same degree of consistency. They would consequently be liable at 
 all times to be mistaken for oil-globules, were it not for the complete 
 dissimilarity of their chemical properties. 
 
 Both the glyko-cholate and tauro-cholate of soda are very freely 
 soluble in water. If the mixture of alcohol and ether be poured 
 off and distilled water added, the deposit dissolves, rapidly and 
 completely, with a more or less distinct yellowish color, according 
 to the proportion of coloring matter originally present in the bile. 
 The two biliary substances present in the watery solution may be 
 • separated from each other by the following means. On the addi- 
 tion oi acetate of lead, the glyko-cholate of soda is decomposed, 
 and precipitates as a glyko-cholate of lead. The precipitate, sepa- 
 rated by filtration from the remaining fluid, is then decomposed in 
 turn by carbonate of soda, and the original glyko-cholate of soda 
 reproduced. The filtered fluid which remains, and which contains 
 the tauro-cholate of soda, is then treated with subacetate of lead, 
 which precipitates a tauro-cholate of lead. This is separated by 
 ■filtranon, washed, and decomposed again by carbonate of soda, as 
 in the former case. 
 
 The two biliary substances in ox bile may, therefore, be dis- 
 tinguished by their reactions with the salts of lead. Both are 
 precipitable by the subacetate ; but the glyko-cholate of soda is 
 precipitable also by the acetate, while the tauro-cholate is not so. 
 If subacetate of lead, therefore, be added to the mixed watery solu- 
 tion of the two substances, and the whole filtered, the siibsequent 
 addition of acetate of lead to the filtered fluid will produce no pre- 
 cipitate, because both the biliary matters have been entirely thrown 
 down with the deposit ; but if the acetate of lead be first added, it 
 will precipitate the glyko-cholate alone, and the tauro-cholate may 
 afterward be thrown down separately by the subacetate. 
 
 These two substances, examined separately, have been found to 
 possess the following properties : — 
 
 Glyko-cholate of soda (NaOjOjjH^jNO,,) crystallizes, when precipi- 
 tated by ether frSm its alcoholic solution, in radiating bundles of , 
 fine white silky needles, as above described. It is composed of 
 soda, united with a peculiar acid of organic origin, viz., glyko-eholic 
 
THE BILE. 181 
 
 acid (C^jjHjj!N"0„,HO). This acid is crystallizable and contains nitro- 
 gen, as shown by the above formula, which is that given by Leh- 
 mann. If boiled for a long time with a dilute solution of potassa, 
 glyko-cholic acid is decomposed with the production of two new 
 substances; the first a non-nitrogenous acid body, cholic acid 
 (O^gHjgOgjHO) ; the second a nitrogenous neutral body, glycine 
 (O^HjNOJ. Hence the name glyko-cholic acid, given to the 
 original substance, as if it were a combination of cholic acid with 
 glycine. In reality, however, these two substances do n(Jt exist 
 origfnally in the glyko-cholic acid, but are rather new combinations 
 of its elements, produced by long boiling, in contact with potassa 
 and water. They are not, therefore, to be regarded as, in any way, 
 natural ingredients of the bile, and do not throw any light on the 
 real constitution of gfyko-cholic acid. 
 
 Tauro-cholate of soda (NaO,CjjH^S20„) is also a very abundant 
 ingredient of the bile. It is said by Eobin and Verdeil' that it is 
 not crystallizable, owing probably to its not having been separated 
 as yet in a perfectly pure condition. Lehmann states, on the con- 
 trary, that it may crystallize,* when kept for a long time in contact 
 with ether. We have not been able to obtain this substance, how- 
 ever, in a crystalline form. Its acid constituent, tauro-choUc acid, 
 is a nitrogenous body, like glyko-cholic acid, but differs from the 
 latter by containing in addition two equivalents of sulphur. By 
 long boiling in a dilute solution of potassa, it is decomposed with 
 the production of two other substances; the first of them, the same 
 acid body mentioned above as derived from the glyko-cholic, viz., 
 cholic add; and the second a new nitrogenous neutral body, viz., 
 taurine (C^HjNSjOj). The same remark holds good with regard t© 
 these two bodies, that we have already made in respect to the sup^ 
 posed constituents of glyko-cholic acid. Neither cholic acid nor 
 taurine can be properly regarded as really ingredients of tauro- 
 cholic acid, but only as artificial products resulting from its altera- 
 tion and decomposition. 
 
 The glyko-cholates and tauro-cholates are formed, so far as we 
 know, exclusively in the liver ; since they have not been found in 
 the blood, nor in any other part of the body, in healthy 'animals ; 
 nor even, in the experiments of Kunde, Moleschott, and Lehmann 
 on frogs,' after the entire extirpation of the liver, and consequent 
 
 ' Chimie Anatomiqne et Physiologiqne, vol. ii. p. 473. 
 
 * Pliysiologicai Chemistry, Phil, ed., vol. i. p. 209. 
 
 » Lehmann's Physiological Chemistry, Phil, ed., vol. i. p. 47G. 
 
182 
 
 THE BILK. 
 
 Fig. 50. 
 
 suppression of the bile. These substances are, therefore, produced 
 in the glandular cells of the liver, by transformation of some other 
 of their ingredients. They are then exuded in a soluble form, as 
 part of the bile, and finally discharged by the excretory hepatic 
 ducts. 
 
 The two substances described above as the tauro-oholate and 
 glyko-cholate of soda exist, properly speaking, only in the bile of 
 the ox, -where they were first discovered by Strecker. In examin- 
 ing the biliary sepretions of difierent species of animals, Strecker 
 found so great a resemblance between them, that he was disposed 
 to rega,rd their ingredients as essentially the same. Having estab- 
 lished the existence in ox-bile of two peculiar substances, one 
 crystallizable and non-sulphurous (glyko-cholate), the other uncrys- 
 tallizable and sulphurous (tauro-cholate), he was led to consider 
 the'bile in all species of animals as containing the same substances, 
 and as differing only in the relative qtfentity in which the two 
 were present. The only exception to this was 
 supposed to be pig's bile, in which Strecker found 
 a peculiar organic acid, the "hyo-cholic" or 
 " hyo-cholinic" acid, in combination with soda as 
 a base. 
 
 The above conclusion of his, however, was not 
 entirely correct. It is true that the bile of all 
 animals, so far as examined, contains peculiar 
 substances, which resemble each other in being 
 freely soluble in water, soluble in absolute alco- 
 hol, and insoluble in ether ; and in giving also a 
 peculiar reaction with Pettenkofer's test, to be 
 described presently. But, at the same time, these 
 substances present certain minor differences in 
 different animals, which show them not to be 
 identical. 
 
 In dog's bile, for example, there are, as in ox- 
 bile, two substances precipitable by ether from 
 their alcoholic solution; one crystallizable, the 
 other not so. But the former of these substances 
 crystallizes much more readily than the glyko- 
 cholate of soda from ox-bile. ' Dog's bile will not unfrequently begin 
 to crystallize freely in five to six hours after precipitation by ether 
 (Fig. 50) ; while in ox-bile it is usually twelve, and often twenty- 
 four or even forty-eight hours before crystallizatioii is fully estab- 
 
 D * s B T I. B, extract- 
 ed withaljsoluteaylcohol 
 and precipitated with 
 ether. * 
 
THE BILE. 
 
 183 
 
 llshed. But it is more particularly in their reaction with the salts 
 of lead that the difference between these substances becomes mani- 
 fest. For while the crystallizable substance of ox-bile is precipi- 
 tated by acetate of lead, that of dog's bile is not affected by it. If 
 dog's bile be evaporated to dryness, extracted with absolute alcohol, 
 the alcoholic solution precipitated by ether, and the ether precipitate 
 then dissolved in water, the addition of acetate of lead to the watery 
 solution produces not the slighest turbidity. If subacetate of lead 
 be then added in excess, a copious precipitate falls, composed of both 
 the crystallizable and uncrystallizable substances. If tlfe lead pre- 
 cipitate be then separated by filtration, washed, and decomposed, 
 as above described, by carbonate of soda, the watery solution will 
 contain the re-formed soda salts of the bile. The watery solution 
 may then be evaporated to dryness, extracted with absolute alcohol, 
 and the alcoholic solution precipitated by ether ; when the ether 
 precipitate crystallizes partially after a time as in fresh bile. Both 
 the biliary matters of dog's bile are therefore 
 precipitable by subacetate of lead, but neither of 
 them by the acetate. Instead of calling them, 
 consequently, glyko-cholate and tauro chelate of 
 soda, we shall speak of them simply as the " crys- 
 talline" and " resinous" biliary substances. 
 
 In cat's bile, the biliary substances act very 
 much as in dog's bile. The ether precipitate of 
 the alcolfclic solution contains here also a crys- 
 talline and a resinous substance ; both of which 
 are precipitable from their watery solution by 
 subacetate of lead, but neither of them by the 
 acetate. 
 
 In pig's bile, on the other hand, there is no 
 crystallizable substance, but the ether precipitate 
 is altogether resinous in appearance. Notwith- 
 standing this, its watery solution precipitates 
 abundantly by both the acetate and subacetate of 
 lead. 
 
 In human bile, again, there is no crystallizable 
 substance. We have found that the dried bile, 
 extracted with absolute alcohol, makes a clear, brandy-red solution, 
 which precipitates abundantly with ether in excess ; but the ether 
 precipitate, if allowed to stand, shows no sign of crystallization, even 
 at the end of three weeks. (Fig. 51.) If the resinous precipitate 
 
 Human Bi>LE, ex- 
 tracted with ahfielnte 
 alcohol and precipitated 
 bj ether. 
 
18i THK BILE. 
 
 be separated by decantation and dissolved in water, it precipitates, 
 as in the case of pig's bile, by both the acetate and subacetate of 
 lead. This might, perhaps, be attributed to the presence of two 
 different substances, as in ox-bile, one precipitated by the acetate, 
 the other by the subacetate of lead. Such, however, is not the case. 
 For if the watery solution be precipitated by the acetate of lead 
 and then filtered, the filtered fluid gives no precipitate afterward 
 by the subacetate; and if first precipitated by the subacetate it 
 gives no precipitate after filtration by the acetate. The entire 
 biliary in^edients, therefore, of human bile are precipitated by 
 both or either of the salts of lead. 
 
 Different kinds of bile vary also in other respects ; as, for ex- 
 ample, their specific gravity, the depth and tinge of their color, the 
 quantity of fat which they contain, &c. &c. We have already 
 mentioned the variations in color and specific gravity. The alco- 
 holic solution of dried ox-bile, furthermore, does not precipitate at 
 all on the addition of water ; while that of human bile, of pig's 
 bile, and of dog's bile precipitate abundantly with distilled water, 
 owing to the quantity of fat which they hold in solution. These 
 variations, however, are of secondary importance compared with 
 those which we have already mentioned, and which show that the 
 crystalline and resinous substances in different kinds of bile, though 
 resembling each other in very many respects, are yet in reality far 
 from being Identical. 
 
 Tests fob Bile. — In investigating the physiology of any animal 
 fluid it is, of course, of the first importance to have a convenient 
 and reliable *test by which its presence may be detected. For a 
 long time the only test employed in the case of bile, was that which 
 depended on a change of color produced by oxidizing substances. If 
 the bile, for example, or a mixture containing bile, be exposed in 
 an open glass vessel for a few hours, the upper layers of the fluid, 
 which are in contact with the atmosphere, gradually assume a 
 greenish tinge, which becomes deeper with the length of time which 
 elapses, and the quantity of bile existing in the fluid. Nitric acid, 
 added to a mixture of bile and shaken up, produces a dense preci- 
 pitate which takes a bright grass-green hue. Tincture of iodine 
 produces the same change of color, when added in small quantity ; 
 and probably there are various other substances which would have 
 the same effect. It is by this test that the bile has so often been 
 recognized in the urine, serous effusions, the solid tissues, &c., in 
 
TESTS FOR BILE. 185 
 
 cases o^ jaundice. But it is very insufficient for anything . like 
 accurate investigation, since t^e appearances are produced simply 
 by the action of. an oxidizing agent on the coloring matter of the 
 bile. A green color produced by nitric acid does not, therefore, 
 indicate the presence of the biliary substances proper, but only of 
 the biliverdine. On the other hand, if the coloring matter be ab- 
 sent, the biliary substances themselves cannot be detected by it. 
 For if the biliary substances of dog'« bile be precipitated by ether 
 from an alcoholic solution, dissolved in water and decolorized by 
 animal charcoal, the colorless watery solution will then give no 
 green color on the addition of nitric acid or tincture of iodine, 
 though it may precipitate abundantly by subacetate of lead, and 
 give the other reactions of the crystalline and resinous biliary 
 matters in a perfectly distinct manner. 
 
 Pettenkofer's Test. — This is undoubtedly the best test yet pro- 
 posed for the detection of the biliary substances. It consists in 
 mixing with a watery solution of the bile, or of th^ biliary sub- 
 stances, a little cane sugar, and then adding sulphuric acid to the 
 mixture until a red, lake, or purple color is produced. A solution 
 may be made of cane sugar, in the prop'ortion of one part of sugar to 
 four parts of water, and kept for use. One drop of this solution is 
 mixed with the suspected fluid, and the sulphuric acid then imme- 
 diately added. On first dropping in the sulphuric acid, a whitish 
 precipitate falls, which is abundant in the case of ox-bile, less so in 
 that of the dog. This precipitate redissolves in a slight excess of 
 sulphuric acid, which should then continue to be added until the 
 mixture assumes a somewhat syrupy consistency and an opalescent 
 look, owing to the development of minute bubbles of air. A red 
 color then begins to show itself at the bottom of the test-tube, and 
 afterward spreads' through the mixture, until the whole fluid is of 
 a clear, bright, cherry red. This color gradually changes to a lake, 
 and finally to a deep, rich, opaque purple. If three or four vol- 
 umes of water be then added to the mixture, a copious precipitate 
 falls down, and the color is destroyed. 
 
 Various circumstances modify, to some extent, the rapidity and 
 distinctness with which the above changes are produced. If the 
 biliary substances be present in large quantity, and nearly pure, 
 the red color shows itself at once after adding an equal volume of 
 sulphuric acid, and almost immediately passes into a strong purple. 
 If they be scanty, on the other hand, the red color may not show 
 itself for seven or eight minutes, nor the purple under twenty 
 
186 THE BILE. 
 
 or twenty-five minutes. If foreign matters, again, not of a biliary 
 nature, be also present, tbey are apt to be acted on by the sulphuric 
 acid, and, by becoming discolored, interfere with the clearness and 
 brilliancy of the tinges produced. On this account it is indispen- 
 sable, in delicate examinations, to evaporate the suspected fluid to 
 dryness, extract the dry residue with absolute alcohol, precipitate 
 the alcoholic solution with ether, and dissolve the ether-precipitate 
 in water before applying the test. In this manner, all foreign sub- 
 stances which might do harm will be eliminated, and the test will 
 succeed without difficulty. 
 
 It must not be forgotten, furthermore, that the sugar itself is 
 liable to 'be acted on and discolored by sulphuric acid when added 
 in excess, and may therefore by itself give rise to confusion. A little 
 care and practice, however, will enable the experimenter to avoid 
 all chance of deception from this source. "When sulphuric acid is 
 mixed with a watery solution containing cane sugar, after it has 
 been added i«i considerable excess, a yellowish color begins to show 
 itself, owing to the commencing decomposition of the sugar. This 
 color gradually deepens until it has become a dark, dingy, muddy 
 brown ; but there is never at any time any clear red or purple 
 color, unless biliary matters be present. If the bile be present in 
 but small quantity, the colors produced by it may be modified and 
 obscured by the *ngy yellow and brown of the sugar ; but even 
 this difficulty may be avoided by paying attention to the following 
 precautions. In the first place, only very little sugar should be 
 added to the suspected fluid. In the second place, the sulphuric 
 acid should be added very gradually, and the mixture closely 
 watched to detect the first changes of color. If bile be present, the 
 red color peculiar to it is always produced before the yellowish 
 tinge which indicates the decomposition of the sugar. "When the 
 biliary matters, therefore, are present in small quantity, the addi- 
 tion of sulphuric acid should be stopped at that point, and the 
 colors, though faint, will then remain clear, and give unmistakable 
 evidence of the presence of bile. 
 
 The red color alone is not sufficient as an indication of bile. It 
 is in fact only the commencement of the change which indicates the 
 biliary matters. If these matters be present; the color passes, as 
 we have already mentioned, first into a lake, then into a purple ; 
 and it is this lake and purple color alone which can be regarded as 
 really characteristic of the biliary reaction. 
 
 It is important to observe that Pettenkofer's reaction is produced 
 
TESTS FOB BILE. 187 
 
 by the presence of either or both of the biliary substances proper ; 
 and is not at all dependent on the coloring matter of the bile. For 
 if the two biliary substances, crystalline and resinous, be extracted 
 by the process above described, and, after being dissolved in water, 
 decolorized with animal charcoal, the watery solution will still give 
 Pettenkofer's reaction perfectly, though no coloring matter be pre- 
 sent, and though no green tinge can be produced by the addition 
 of nitric acid or tincture of iodine. If the two biliary substances 
 be then separated from each other, and tested in distinct solutions^ 
 each solution will give the same reaction promptly and completely. 
 
 Yarious objections have been urged against this test. It has 
 been stated to be uncertain and variable in its action. Eobin and 
 Verdeil' say that its reactions " do not belong exclusively to the 
 bile, and may therefore give rise to mistakes." Some fatty sub^ 
 stances and volatile oils (oleine, oleic acid, oil of turpentine, oil of 
 caraway) have been stated to produce similar red and violet colors, 
 when treated with sugar and sulphuric acid. These objections, 
 however, have not much, if any, practical weight. The test no 
 doubt requires some care and practice in its application, as we have 
 already pointed out; but this is the case also, to a greater or less 
 extent, with nearly all chemical tests, and particularly with those 
 for substances of organic origin. No other substance is, in point 
 .of fact, liable to be met with in the intestinal fluids or fhe blood, 
 which would simulate the reactions of the biliary matters. We 
 have found that the fatty matters of the chyle, taken from the tho- 
 racic duct, do not give any coloration which would be mistaken for 
 that of the bile. "When the volatile oils (caraway and turpentine) 
 are acted on by sulphuric acid, a red color is produced which after- 
 ward becomes brown and blackish, and a peculiar, tarry, empyren- 
 matic odor is developed- at the same time ; but we do not get the 
 l^te and purple colors spoken of above. Finally, if the precaution 
 be observed — first of extracting the suspected matters with absolute 
 alcohol, then precipitating with ether and dissolving the precipitate 
 in water, no ambiguity could result from the preseace of any of the 
 above substances. 
 
 Pettenkofer's test, then, if used with care, is extremely useful, 
 and may lead to many valuable results. Indeed, no other test than 
 this can be at all relied on to determine the presence or absence of 
 the biliary substances proper. 
 
 ' Op. cit., vol. ii.^ p. 46S. 
 
188 THE BILE. 
 
 Yabiatioits and Functions of Bile. — ^Witk regard to the 
 entire quantity of bile secreted daily, we have had no very positive 
 knowledge, until the experiments of Bidder and Schmidt, published 
 in 1852.' These experiments were performed on cats, dogs, sheep, 
 and rabbits, in the following manner. The abdomen was opened, 
 and a ligature placed upon the ductus communis choledochus, so 
 as to prevent the bile finding its way into the intestine. An open- 
 ing was then made in the fundus of the gall-bladder, by which 
 the bile was discharged externally. The bile, so discharged, was 
 received into previously weighed vessels, and its quantity accurately 
 determined. Bach observation usually occupied about two hoUrs, 
 during which period the temporary fluctuations occasionally observ- 
 able in the quantity of bile discharged were mutually cco-rected, so 
 far as the entire result was concerned. The animal was then killed, 
 weighed, and carefullf examined, in order to make sure that the 
 biliary duct had been securely tied, and that no inflammatory alter- 
 ation had taken place in the p,bdominal organs. The observations 
 were made at very different periods after the last meal, so as to 
 determine the influence exerted by the digestive process upon the 
 rapidity of the secretion. The average quantity of bile for twenty- 
 four hours was then calculated from a comparison of the above 
 results ; and the quantity of its solid ingi-edients was also ascer- 
 tained in^each instance by evaporating a portion of the bile in the 
 water bath, and weighing the dry residue. 
 
 Bidder and Schmidt found in this way that the daily quantity 
 of bile varied considerably in different species of animals. It was 
 very much greater in the herbivorous animals used for experiment 
 than in the carnivora. The results obtained by these observers 
 are as follows : — 
 
 For every pound weight of the entire body there is secreted 
 
 during twenty -four hours • 
 
 Fresh Bile. Dbt Residue. 
 
 In the cat 102 grains. 5.712 grains. 
 
 •'dog 140 " 6.916 " 
 
 " . sheep .• 178 " 9.408 " 
 
 - " rabbit 9.')8 " 17.290 " 
 
 Since, in\he human subject, the digestive processes and the 
 nutritive actions generally resemble those of the carnivora, rather 
 than those of the herbivora, it is probable that the daily quantity 
 of bile in man is very similar to that in the carnivorous animals. 
 
 ' Verdau:igssaefte und StoiTwechBel. Leipzig, 1852. 
 
VARIATIONS AND FUNCTIONS OF BILE. 
 
 189 
 
 If we apply to the human subject the average results obtained by 
 Bidder and Schmidt from the cat and dog, we find that, in an adult 
 man, weighing 140 pounds, the daily quantity of the bile will be 
 certainly not less than 16,940 grains, or very nearly 2| pounds 
 avoirdupois. 
 
 It is a matter of great importance, in regard to. the bile, as well 
 as the other intestinal fluids, to ascertain whether it be a constant 
 secretion, like the urine and perspiration, or whether it be intermit- 
 tent, like the gastric jiiic% and discharged only during the digestive 
 process. In order to determine this point, we have performed the 
 following series of experiments on dogs. The aniipala were kept 
 confined, and killed at various periods after feeding, sometimes by 
 the inoculation of woorara, sometimes by hydrocyanic acid, but 
 most frequently by section of the medulla oblongata. The con- 
 tents of the intestine were then collected and examined. In all 
 instances, the bile was also taken from the gall-bladder, and treated 
 in the same way, for purposes of comparison. The intestinal con- 
 tents always presented some peculiarities of appearance when treated 
 with alcohol and ether, owing probably to the presence of other 
 substances than the bile; but they ailways gave evidence of the 
 presence of biliary matters 
 as well. The biliary sub- 
 stances could almost always 
 be recognized by the mi- 
 croscope in the eth«r preci- 
 pitate of the alcoholic solu- 
 tion ; the resinous substance, 
 under the form of rounded, 
 oily-looking drops (Fig. 52), 
 and the other, under the 
 form of crystalline groups, 
 generally presenting the 
 appearance of double bun- 
 dles of slender, radiating, 
 slightly curved or wavy, 
 needle - shaped crystals. 
 These substances, dissolved 
 in water, gave a purple 
 
 color with sugar and sulphuric acid. These experiments were 
 tried after the animals had been kept for one, two, three, five, six, 
 seven, eight, and twelve days without food. The result showed that. 
 
 Cbtstait.ike akj) EESisniTs BiiiART Srn- 
 BTAXCES; fromSmall Intestine of Dog, after two days 
 ftstlng. 
 
190 
 
 THE BILE. 
 
 ia all these instances, bile was present in the small intestine. It is, 
 therefore, plainly not an intermittent secretion, nor one which is 
 concerned exclusively in the digestive process ; but its secretion is 
 constant, and it continues to be discharged into the intestine for 
 many days after the animal has been deprived of food. 
 
 The next point of importance to be examined relates to the time, 
 after feeding at which the bile passes into the intestine in the greatest 
 abundance^ Bidder and Schmidt have already investigated this 
 point in the following manner. They operated, as above described, 
 by tying the common bile-duct, and then opening the fundus of the 
 gall-bladfler, so as to produce a biliary fistula, by which the whole 
 of the bile was drawn off. By doing this operation, and collecting 
 and weighing the fluid discharged at diflferent periods, they came 
 
 to the conclusion that the flow 
 *^8' 53. Qf l^jlg begins to increase within 
 
 two and a half hours after the 
 introduction of food into the 
 stomach, but that it does ■ not 
 reach its maximum of activity 
 till the end of twelve or fifteea , 
 hours. Other observers, how- 
 ever, have obtained different 
 results. Arnold;' for example, 
 found the quantity to be largest 
 soon after meals, decreasing • 
 again after the fourth hour. 
 Kolliker and Muller,' again, 
 found it largest between the 
 sixth and eighth hours. Bidder 
 and Schmidt's experiments, in- 
 deed, strictly speaking, show 
 only the time at which the bile 
 is most actively secreted by the 
 liver, but not when it is actually 
 discharged into the intestine. 
 Our own experiments, bear- 
 ing on this point, were performed on dogs, by making a permanent 
 duodenal fistula, on the same plan that gastric fistulse have so often 
 
 DnoDBNAi. Fistula.— «. Stomach. 6. Dao- 
 deaum. c^ c^ c. Pancreas; its two dacts are seen 
 opening into tlie duodenum, one near the orifice 
 of the biliary duct, <2, the other a Khort distance 
 lower down. e. Silver tube paRsin^ through the 
 abdomiual walls and openiu(^ into the duodenum. 
 
 > lu Am, Joarn. Med. Sci., April, 1856. 
 
 « Ibid., April, 1857. 
 
VARIATIONS AND PDNCTIONS OF BILK. 191 
 
 been established for the examination of the gastric juice. (Fig. 53.) 
 An ineisioa was made through the abdqminal walls, a short distance 
 to the right of the median line, the floating portion of the duodenum 
 drawn up toward the external wound, opened by a longitudinal in- 
 cision, and a silver tube, armed at each end with a narrow projecting 
 collar or flange, inserted into it by one extremity, five and a half 
 inches below the pylorus, and two and a half inches below the 
 orifice of the lower pancreatic duct. The other extremity of the 
 tube was left projecting from the external opening in the abdominal 
 parietes, the parts secured by sutures, and the wound allowed to 
 heal. After cicatrization was complete, and the animal had entirely 
 recovered his healthy condition and appetite, the intestinal fluids 
 were drawn off at various intervals after feeding, and their contents 
 examined. This operation, which is rather more difficult than that 
 of making a permanent gastric fistula, is nevertheless exceedingly 
 useful wheii it succeeds, since it enables us to study, not only the 
 time and rate of the biliary, discharge, but also, as mentioned in a 
 previous chapter (Chap. VI.), many other extremely interesting^ 
 matters connected with intestinal digestion. 
 
 In order to ascertain the absolute quantity of bile discharged 
 into the intestine, and its variations during digestion, the duodenal 
 fluids were drawn off, for fifteen minutes at a time, at various 
 periods after feeding, collected,, weighed, and examined separately, 
 as follows : each separate quantity was evaporated to dryness, its , 
 dry residue extracted with absolute alcohol, the alcoholic solution 
 precipitated with ether, and the ether-precipitate, regarded as repre- 
 senting the amount of biliary matters present, dried, weighed, and 
 then treated with Pettenkofer's test, in order to determine, as nearly 
 as possible, their degree of purity or admixture. The result of 
 these experiments is given in the following table. At the eigh- 
 teenth hour so small a quantity of fluid was obtained that the 
 amount of its biliary ingredients was not ascertained. It reacted 
 perfectly, however, with Pettenkofer's test, showing that bile was 
 really present. 
 
192 
 
 
 THE BILE, 
 
 • 
 
 
 
 Time after 
 
 Quantity of fluid 
 
 Dry residue 
 
 Quantity of 
 
 Proportion of 
 
 feetfittg. 
 
 is 15 lainutes. 
 
 of same. 
 
 biliary matters. 
 
 VlllaryMnatters 
 io dry residue. 
 
 Iintuediatel^ 
 
 640 grains 
 
 33 grains 
 
 10 grains 
 
 .30 
 
 1 hoar 
 
 1,990 " 
 
 105 " 
 
 4 '• 
 
 .03 
 
 3 hours 
 
 780 " . 
 
 60 " 
 
 4 " 
 
 .07 
 
 1 6 " 
 
 750 " 
 
 73 " 
 
 3 " 
 
 .05 
 
 9 " 
 
 860 " 
 
 78 " 
 
 4. " 
 
 .06 
 
 12 " 
 
 325 . " 
 
 23 " 
 
 3| " 
 
 .16 
 
 15 " 
 
 347 " 
 
 18 " 
 
 4 u 
 
 .22 
 
 18 " 
 
 
 
 
 
 — 
 
 
 
 21 " 
 
 384 " 
 
 11 " 
 
 1 " 
 
 .09 
 
 24 " 
 
 163 " 
 
 9.i " 
 
 3J " 
 
 .34 
 
 25 " - 
 
 151 " 
 
 5 " 
 
 3 " 
 
 .60 
 
 From this it appears that the bile passes into the intestine in by 
 far the largest quantity immediately after feeding, and within the 
 first hour. After that time its discharge remains pretty constant ; 
 not varying much from four grains of solid biliary matters every 
 fifteen minutes, or sixteen grains per hour. The animal used for 
 the above observations weighed thirty^six and a half pounds. 
 
 The next point to be ascertained with regard to this question is 
 the following, viz : What becomes of the bile in its passage through 
 the intestine P Our experiments, performed with a view of settling 
 this point, were tried on dogs. The animals were fed with fresh 
 meat, and then killed at various Intervals after the meals, the abdo- 
 men opened, ligatures placed npon the intestine at varions points, 
 and the contents of its upper, middle, and lower portions collected 
 and examined separately. The results thus obtained show that, 
 under ordinary circumstances, the bile, which is quite abundant in 
 the duodenum and upper part of the small intestine, diminishes in 
 quantity from above downward, and is not to be found in the large 
 intestine. The entire quantity of the intestinal contents also dimi- 
 nishes, and their consistency increases, as we approach the ileo- 
 csecal valve; and at the same time their color changes from flight 
 yellow to a dark bronze or blackish-green, which is always strongly 
 pronounced in the last quarter of the small intestine. 
 
 The contents of the small and large intestine were furthermore 
 evaporated to dryness, extracted with absolute alcohol, and the 
 alcoholic solutions precipitated with ether; the quantity of ether- 
 precipitate being regarded as representing approximately that of 
 the biliary substanc^ proper. The result showed that the quantity 
 of this ether-precipitate is, both positively and relatively, very much 
 . less in the large intestine than in the small. Its proportion to the 
 entire solid contents is only one-fifth or one-sixth as great in the 
 
VARIATIONS AND FUNCTIONS OF BILE. 193 
 
 large intestine as it is in the small. But even this inconsiderable 
 quantity, found in contents of the large intestine, does not con- 
 sist of biliary matters ; for the watery solutions being treated with 
 sugar- and sulphuric acid, those from both the upper and lower 
 portions of the small intestine always gave Pettenkofer's reaction 
 promptly and perfectly in less than a minute and a half; while in 
 that from the large intestine no red or purple- color was produced, 
 even at the end of three hours. 
 
 The small intestine consequently contains, at all times, substances 
 giving all the reactions of the biliary ingredients; while in the 
 contents of the large intestine no such substances can be recognized 
 by Pettenkofer's test. 
 
 The biliary matters, therefore, disappear in their passage through 
 the intestine. 
 
 In endeavoring to ascertain what is the precise function of the bile 
 in the intestine, our first object must be to determine what part, if 
 any, it takes in the digestive process. As the liver is situated, like 
 the salivary glands and the pancreas, in the immediate vicinity of 
 the alimentary canal, and lik-e them, discharges its secretion into 
 the cavity of the intestine, it seems at first natural to regard the 
 bile as one of the digestive fluids. We have previously shown, 
 however, that the digestion of all the different elements of the food 
 is provided for by other secretions ; and furthermore, if we examine 
 experimentally the digestive power of bile on alimentary substances, 
 we obtain only a negative result. Bile exerts no special action upon 
 either albuminoid, starchy, or oleaginous matters, when mixed with 
 them in test-tubes and kept at the temperature of 100° F. It has 
 therefore, apparently, no direct influence in the digestion of these 
 substances. 
 
 It is a very remarkable fact, in this connection, that the bile pre- 
 cipitates by contact with the gastric juice. If four drops of dog's bile 
 be added to 3j of gastric juice from the same animal, a copious 
 yellowish-white precipitate falls down, which contains the whole of 
 the coloring matter of the bile which has been added ; and if the 
 mixture be then filtered, the filtered fluid passes through quite 
 colorless. The gastric juice, however, still retains its acid reaction. 
 This precipitation depends upon the presence of the biliary sub- 
 stances proper, viz., the glyko-cholate and tauro-cholate of soda, and 
 not upon that of the incidental ingredients of the bile. For if the 
 bile be evaporated to dryness and the biliary substances extracted 
 13 
 
194 THE BILE. 
 
 by alcohol and precipitated by ether, as above described, their 
 watery solution will precipitate with gastric juice, in the same 
 manner as fresh bile would do. 
 
 Although the biliary matters, however, precipitate by contact 
 with fresh gastric juice, they do not do so with gastric juice which holds 
 alhuminose in solution. We have invariably found that if the gas- 
 tric juice be digested for several hours at the temperature of 100° 
 F., with boiled white of egg, the filtered fluid, which contains an 
 abundance of albuminose, will no longer give the slightest precipi- 
 tate on the addition of bile, or of a watery solution of the biliary 
 substances, even in very large amount. The gastric juice and the 
 bile, therefore, are not finally antagonistic to each other in the 
 digestive process, though at first they produce a precipitate on 
 being mingled together. 
 
 It appears, however, from the experiments detailed above, that 
 the secretion of the bile and its discharge into the intestine are not 
 confined to the periods of digestion, but take place constantly, and 
 continue even after the animal has been kept for many days with- 
 out food. These facts would lead us to jegard the bile as simply 
 an excrementitious fluid ; containing only ingredients resulting from 
 the waste and disintegration of the animal tissues, and not. intended 
 to perform any particular function, digestive or otherwise, but 
 merely to be eliminated from the blood, and discharge'Il from the 
 system. The same view is more or less supported, also, by the 
 following facts, viz : — 
 
 1st. The bile is produced, unlike all the other animal secretions, 
 from venous blood ; that is, the blood of the portal vein, which has 
 already become contaminated by circulation through the abdominal 
 organs, and may be supposed to contain disorganized and efiete in- 
 gredients; and 
 
 2d. Its complete suppression produces, in the human subject, 
 symptoms of poisoning of the nervous system, analogous to those 
 which follow the suppression of the urine, or the stoppage of respi- 
 ration, and the patient dies, usually in a comatose condition, at the 
 end of ten or twelve days. 
 
 The above circumstances, taken together, would combine to 
 make it appear that the bile is simply an excrementitious fluid, not 
 necessary or useful as a secretion, but only destined, like the urine, 
 to be eliminated and discharged. Nevertheless, experiment has 
 shown that such is not the case ; and that, in point of fact, it is 
 necessary for the life of the animal, not only that the bile be secreted 
 
VARIATIONS AND FUNCTIONS OF BILE. 195 
 
 and discharged, but furthermore that it be discharged into the 
 intestine, and pass through the tract of the alimentary canal. The 
 most satisfactory experiments of this kind are those of Bidder and 
 Schmidt, '"in which they' tied the common biliary duct in dogs, and 
 then established a permanent fistula in the fundus of the gall-bladder, 
 ■ through which the bile was allowed to flow by a free external orifice. 
 In this manner the bile was effectually excluded from the intestine, 
 but at the same time was freely and wholly discharged from the 
 body, by the artificial fistula. If the bile therefore were simply an 
 excrementitious fluid, its deleterious ingredients being all eliminated 
 as usual, the animals would not suffer any serious injury from this 
 operation. If, on the contrary, they were found to suffer or die in 
 consequence of it; it would show that the bile has . really some 
 important ftmction to perform in the intestinal canal, and is not 
 simply excrementitious in its nature. 
 
 The result showed that the effects of such an experiment were 
 fatal to the animal. Four dogs only survived the immediate effects 
 of the operation, and were afterward frequently used for purposes 
 of experiment. One of them was an animal from which the spleen 
 had been previously removed, and whose appetite, as usual after 
 this operation, was morbidly ravenous; his system, accordingly, 
 being placed under such unnatural conditions as to make him an 
 unfit subject for further experiment. In the second animal that 
 survived, the communication of the biliary duct with the intestine 
 became re-established after eighteen days, and the experiment con- 
 sequently had no result. In the remaining two animals, however, 
 everything was successful. The fistula in the gall-bladder became 
 permanently established ; and the bile-duct, as was proved subse- 
 quently by post-mortem examination, remained completely closed, 
 so that no bile found its way into the intestine. Both these ani- 
 mals died ; one of them at the end of twenty-seven days, the other 
 at the end of thirty-six days. In both, the symptoms were nearly 
 the same, viz., constant and progressive emaciation, which proceeded 
 to such a degree that nearly every trace of fat disappeared from the 
 body. The loss of flesh amounted, in one case, to more than two- 
 fifths, and in the other to nearly one-half the entire weight of the 
 animal. There was also a falling off of the hair, and an unusually 
 disagreeable, putrescent odor" in the feces and in the breath. Not- 
 withstanding this, the appetite remained good. Digestion was not 
 
 ' Op. oit., p. 103. 
 
- 1, 
 
 196 THE BILE. 
 
 essentially interfered with, and none of the food was discharged 
 with the feces ; but there was much rumbling and gurgling in the 
 intestines, and abundant discharge of flatus, more strongly marked 
 in one instance than in the other. There was no pain ; and death 
 took place, at last, without any violent symptoms, but by a simple 
 and gradual failure of the vital powers. 
 
 A similar experiment has been successfully performed by Prof. 
 A. Flint, Jr.' In this instance the animal lived for thirty-eight 
 days after the operation, and died finally of inanition ; the symp- 
 toms agreeing in every important particular, with those reported 
 by Bidder and Schmidt. 
 
 How is it, then, that although the bile be not an active agent in 
 digestion, its presence in the alimentary canal is still essential to 
 life ? What office does it perform there, and how is it finally dis- 
 posed of? 
 
 We have already shown that the bile disappears in its passage 
 through the intestine. This disappearance may be explained in 
 two different ways. First, the biliary matters may be actually re- 
 absorbed from the intestine, and taken up by the bloodvessels ; or 
 secondly, they may be so altered and decomposed by the intestinal 
 fluids as to lose the power of giving Pettenkofer's reaction with 
 sugar and sulphuric acid, and so pass off with the feces in an 
 insoluble form. Bidder and Schmidt^ have finally determined this 
 point in a satisfactory manner; and have demonstrated that the 
 biliary substances are actually reabsorbed, by showing that the 
 quantity of sulphur present in the feces is far inferior to that 
 contained in the biliary ingredients as they are discharged into the 
 intestine. 
 
 These observers collected and analyzed all the feces passed, dur- 
 ing five days, by a healthy dog, weighing 17.7 pounds. The entire 
 fecal mass during this period weighed 1508.15 grains. 
 
 Containing I '^^*^' 874.20 grains. 
 
 I. Solid residue 633.95 " 
 
 1508.15 
 
 ' American Journ. Med. Soi., October, 1862. 
 ' Op. cit., p. 217. 
 
VAKIATION'S AND FUNCTIONS OF BILE, 197 
 
 The solid residue was composed as follows : — 
 
 Neutral fat, soluble In ether . , 43.710 grains. 
 
 Fat, with traces of biliary matter . 77.03S " 
 
 Alcohol extract with biliary matter 58.900 containing 1.085 grs. of sulphur. 
 
 Substances not of a biliary nature 
 
 extracted ' by muriatic acid and 
 
 hot alcohol . . . . 148.800 containing 1.302 grs. of sulphur. 
 
 2.387 
 Fatty acids with oxide of iron . 98.425 
 
 Residue consisting of hair, sand, &c., 207.080 
 
 633.950 
 
 Now, as it has already been shown that the dog secretes, during 
 24 hours, 6.916 grains of solid biliary matter for every pound weight 
 of the whole body, the entire quantity of biliary matter secreted 
 in five days by the above animal, weighing 17.7 pounds, must have 
 been 612.5 grains, or nearly as much as the whole weight of the 
 dried feces. But furthermore, the natural proportion of sulphur 
 in dog's bile (derived from the uncrystallizable biliary matter), is six 
 per cent, of the dry residue. The 612.5 grains of dry bile, secreted 
 during five days, contained, therefore, 36.75 grains of sulphur. 
 But the entire quantity of sulphur, existing in any form in the 
 feces, was 5.952 grains; and of this only 2.387 grains were derived 
 from substances which could have been the products of biliary 
 matters — ^the remainder being derived from the hairs which are 
 always contained in abundance in the feces of the dog. That is, 
 not more than one-fifteenth part of the sulphur, originally present 
 in the bile, could be detected in the feces. As this is a simple 
 chemical element, not decomposable by any known means, it must, 
 accordingly, have been reabsorbed from the intestine. 
 
 We have endeavored to complete the evidence thus furnished by 
 Bidder and Schmidt, and to demonstrate directly the reabsorption 
 of the biliary matters, by searching for them in the ingredients of 
 the portal blood. We have examined, for this purpose, the portal 
 blood of dogs, killed at various periods after feeding. The animals 
 were killed by section of the medulla oblongata, a ligature imme- 
 diately placed on the portal vein, while the circulation was still 
 active, and the requisite quantity of blood collected by opening 
 the vein. The blood was sometimes immediately evaporated to 
 dryness by the water bath. Sometimes it was coagulated by boil- 
 ing in a porcelain capsule, over a spirit lamp, with water and an 
 excess of sulphate of soda, and the filtered watery solution after- 
 ward examined. But most frequently the blood, after being col- 
 
198 THE BILE. 
 
 lected from the vein, was coagulated by the gradual addition of 
 three times its volume of alcohol at ninety-five per cent., stirring 
 the mixture constantly, so as to make the coagulation gradual and 
 uniform. It was then filtered, the moist mass remaining on the filter 
 subjected to strong pressure in a linen bag, by a porcelain press, 
 and the fluid thus obtained added to that previously filtered. The 
 entire spirituous solution was then evaporated to dryness, the dry 
 residue extracted with absolute alcohol, and the alcoholic solution 
 treated as usual, with ether, &c., to discover the presence of biliary 
 matters. In every instance blood was taken at the same time from 
 the jugular vein, or the abdominal vena cava, and treated in the 
 same way for purposes of comparison. 
 
 We have examined the blood, in this way, one, four, six, nine, 
 eleven and a half, twelve, and twenty hours after feeding. As the 
 result of these examinations, -fre have found that in the venous 
 blood, both of the portal vein and of the general circulation, there 
 exists a substance soluble in water and absolute alcohol, and pre- 
 cipitable by ether from its alcoholic solution. This substance is 
 often considerably more abundant in the portal blood than in that 
 taken from the general venous system. It adheres closely to the 
 sides of the glass after precipitation, so that it is always dif&cult, 
 and often impossible, to obtain enough of it, "mixed with ether, for 
 microscopic examination. It dissolves, also, like the biliary sub- 
 stances, with great readiness in water ; but in no instance have we 
 ever been able to obtain from it such, a satisfactory reaction with 
 Pettenkofer's test, as would indicate the presence of bile. This is 
 not because the reaction is masked, as might be suspected, by some 
 of the other ingredients of the blood ; for if at the same time, two 
 drops of bile be added to half an ounce of blood taken from the 
 abdominal vena cava, and the two specimens treated alike, the ether- 
 precipitate may be considered more abundant in the case of the 
 portal blood ; and yet that from the blood of the vena cava, dis- 
 solved in water, will give Pettenkofer's reaction for bile perfectly, 
 while that of the portal blood will give no, such reaction. 
 
 Notwithstanding, then, the irresistible evidence afforded by the 
 experiments of Bidder and Schmidt, that the biliary matters are 
 really taken up by the portal blood, we have failed to recognize 
 them there by Pettenkofer's test. They must accordingly undergo 
 certain alterations in the intestine, previously to their absorption, 
 so that they no longer give the ordinary reaction of the biliary sub- 
 stances. We cannot say, at present, precisely what these alterations 
 
VARIATIONS AND FUNCTIONS OF BILE. 199 
 
 are ; but they are evidently transformations of a catalytic nature, 
 produced by the contact of the bile with the intestinal juices. 
 
 The bile, therefore, is a secretion which has not yet accomplished 
 its function when it is discharged from the liver and poured into the 
 intestine. On the contrary, during its passage through the intestine 
 it is still in the interior of the body, in contact with glandular sur- 
 faces, and mingled with various organic substances, the ingredients 
 of the intestinal fluids, which act upon it as catalytic bodies, and 
 produce in it new transformations. • This may account for the fact 
 stated above, that the bile, though a constant and uninterrupted 
 eecretiori, is nevertheless poured into the intestine in the greatest 
 abundance immediately after a hearty meal. This is not because it 
 is to take any direct part in the digestion of the food; but because 
 the intestinal fluids, being themselves present at that time in the 
 greatest abundance, can then act upon and decompose the greatest 
 quantity of bile. At all events, the biliary ingredients, after being 
 altered and transformed' in the intestine, as they might be in the 
 interior of a glandular organ, re-enter the blood under some new 
 form, and are carried away by the circulation, to complete their 
 function in some other part of the body. 
 
200 FOBMATION OF SU.GAS IN THE LIVER. 
 
 CHAPTER IX. 
 
 POEMATION OF SUGAE IN THE LIVER. 
 
 Beside the secretion of bile, tlie liver performs also another 
 exceedingly important function, viz., the production of sugar by a 
 metamorphosis of some of its organic ingredients. 
 
 Under ordinary circumstances a considerable quantity of sac- 
 charine matter is- introduced with the food, or produced from 
 starchy substances, by the digestive process, in the intestinal canal. 
 In man and the herbivorous animals, accordingly, an abundant 
 supply of sugar is derived from these sources; and, as we have 
 already shown, the sugar thus introduced is necessary for the proper 
 support of the vital functions. For though the saccharine matter 
 absorbed from the intestine is destroyed by decomposition soon 
 after entering the circulation, yet the chemical changes by which 
 its decomposition is effected are themselves necessary for the proper 
 constitution of the blood, and the healthy nutrition of the tissues. 
 Experiment shows, however, that the system does not depend, for 
 its supply of sugar, 'entirely upon external sources ; but that sac- 
 charine matter is also produced independently, in the tissue of the 
 liver, whatever may be the nature of the food upon which the 
 animal subsists. 
 
 This important function was first discovered by M. Claude Ber- 
 nard' in 1848, and described by him under the name of the glyco- 
 genic function of the liver. 
 
 It has long been known that sugar may be abundaiitly secreted, 
 under some circumstances, when no vegetable matters have been 
 taken with the food. The milk, for example, of all animals, car- 
 nivorous as well as herbivorous, contains a notable proportion of 
 sugar ; and the quantity thus secreted, during lactation, is in some 
 instances very great. In the human subject, also, when suffering 
 from diabetes, the amount of saccharine matter discharged with the 
 
 ' Nouvelle Fonotion dn Foie. Paris, 1853. 
 
FORMATION OF SUGAB IN THE LIVER. 201 
 
 urine lias often appeared to be altogether out of proportion to tliat 
 whicli could be accounted for by the vegetable substances taken as 
 food. The experiments of Bernard, the most important of which 
 we have repeatedly confirmed, in common with other investigators, 
 show that in these instances most of the sugar has an internal 
 origin, and that it first makes its appearance in the tissue of the 
 liver. 
 
 If a carnivorous animal, as, for example, a dog or a cat, be fed 
 for several days exclusively upon meat, and then killed, the liver 
 alone of all the internal organs is found to contain sugar among its 
 other ingredients. For this purpose, a portion of the organ should 
 be cut into small pieces, reduced to a pulp by grinding in a mortar 
 with a little water, and the mixture coagulated by boiling with an 
 excess of sulphate of soda, in order to precipitate the albuminous 
 and coloring matters. The filtered fluid will then reduce the oxide 
 of copper, with great readiness, on the application of Trommer's 
 test. A decoction of the same tissue, mixed with a little yeast, will 
 also give rise to fermentation, producing alcohol and carbonic acid, 
 as is usual with saccharine solutions. On the contrary, the tissues 
 of the spleen, the kidneys, the lungs, the muscles, &c., treated in 
 the same way, give no indication of sugar, and do not reduce the 
 salts of copper. Every other organ in the body may be entirely 
 destitute of sugar, but the liver always contains it in considerable 
 quantity, provided the animal be healthy. Even the blood of the 
 portal vein, examined by a similar process, contains no saccharine 
 element, and yet the tissue of the organ supplied by it shows an 
 abundance of saccharine ingredients. 
 
 It is remarkable for how long a time the liver will continue to 
 exhibit the presence of sugar, after all external supplies of this 
 substance have been cut off. Bernard kept two dogs under his own 
 observation, one for a period of three, the other of eight months,' 
 during which period they were confined strictly to a diet of animal 
 food (boiled calves' heads and tripe), and then killed. Upon exa- 
 mination, the liver was found, in each instance, to contain a propor- 
 tion of sugar fully equal to that present in the organ under ordinary 
 circumstances. 
 
 The sugar, therefore, which is found in the liver after death, is a 
 normal ingredient of the hepatic tissue. It is not formed in other 
 parts of the body, nor absorbed from the intestinal canal, but takes 
 
 ' Nouvelle Fonotion du Foie, p. 50. 
 
202 FORMATION OF SUGAR IN THE LIVER. 
 
 its'origiu in the liver itself; it is produced, as a new formation, by 
 a secreting process in the tissue of the organ. 
 
 The presence of sugar in the liver is common to all species of 
 animals, so far as is yet known. Bernard found it invariably in 
 monkeys, dogs, cats, rabbits, the horse, the ox, the goat, the sheep, 
 in birds, in reptiles, and in most kinds of fish. It was only in two 
 species of fish, viz., the eel and the ray (Muriena anguilla and Eaia 
 batis), that he sometimes failed to discover it ; but the failure in 
 these instances was apparently owing to the commencing putres- 
 cence of the tissue, by which the sugar had probably been destroyed. 
 In the fresh liver of the human subject, examined after death from 
 accidental violence, sugar was found to be present iii the proportion 
 of 1.10 to 2.14 per cent, of the entire weight of the organ. 
 
 The following list shows the average percentage of sugar present 
 in the healthy liver of man and different species of animals, accord- 
 ing to the examinations of Bernard: — 
 
 In man , 
 " monkey 
 " dog . 
 " cat . 
 " rabbit 
 " sheep 
 
 Pekcentage op Sdgak in the Livek. 
 
 . 1.68 In ox . . . . 2.30 
 
 . 2.15 " horse . . . 4.08 
 
 . 1.69 " goat .... 3.89 
 
 . 1.94 " birds . . . 1.49 
 
 . 1.94 " reptiles . . . 1.04 
 
 . 2.00 " fish . . . . 1.45 
 
 With regard to the nature and J)roperties of the liver sugar, it 
 resembles very closely glucose, or the sugar of starch,, the sugar of 
 honey, and the sugar of milk, though it is not absolutely identical 
 with either one of them. Its solution reduces, as we have seen, the 
 salts of copper in Trommer's test, and becomes colored brown when 
 boiled with caustic potassa. It ferments very readily, also, when 
 mixed with yeast and kept at the temperature of 70" to 100° F. 
 It is distinguished from all the other sugars, according to Bernard,* 
 by the readiness with which it becomes decomposed in the blood — 
 since cane sugar and beet root sugar, if injected into the circulation 
 of a living animal, pass through the system without sensible decom- 
 position, and are discharged unchanged with the urine ; sugar of 
 milk and glucose, if injected in moderate quantity, are decomposed 
 in the blood, but if introduced in greater abundance make their 
 appearance also in the urine; while a solution of liver sugar, though 
 injected in much larger quantity than either of the others, may dis- 
 
 ' Lemons de Physiologie Experimentale. Paris, 1855, p. 213. 
 
FORMATION OF SUGAR IN THE LIVER. 203 
 
 appear altogether in the circulation, without passing off by the 
 kidneys. 
 
 This substance is therefore a sugar of animal origin, similar in 
 its properties to other varieties of saccharine matter, derived from 
 different sources. 
 
 The sugar of the liver is not produced in the blood by a direct 
 decomposition of the elements of the circulating fluid in the vessels 
 of the organ, but takes its origin in the solid substance of the hepatic 
 tisstce, as a natural ingredient of. its organic texture. The blood 
 which may be pressed out from a liver recently extracted from the 
 body, it is true, contains sugar ; but this sugar it has absorbed from 
 the tissue of the organ in which it circulates. This is demonstrated 
 by the singular fact that the fresh liver of a recently killed animal, 
 though it may be entirely drained of blood and of the sugar which 
 it contained at the moment of death, wUl still continue for a certain 
 time to produce a saccharine substance. If Such a liver be injected 
 with water by the portal vein, and all the blood contained in its 
 vessels washed, out by the stream, the water which escapes by the 
 hepatic vein will still be found to contain sugar. M. Bernard has 
 found' that if all the sugar contained ia a fresh liver be extracted in 
 this manner by a prolonged watery injection, so that neither the 
 water which escapes by the hepatic vein, nor the substance of the 
 liver itself, contain any further traces of sugar, and if the organ be 
 then laid aside for twenty -four hours, both the tissue of the liver and 
 the fluid which exudes from it will be found at the end of that time 
 to have again become highly saccharine. The sugar, therefore, is 
 evidently not produced in the blood circulating through the liver, 
 but in the substance of the organ itself. Once having originated 
 in the hepatic tissue, it is absorbed thence by the blood, and trans- 
 ported by the circulation, as we shall hereafter show, to other parts 
 of the body. 
 
 The sugar which thus originates in the tissue of the liver, is pro- 
 duced by a mutual decomposition and transformation of various 
 other ingredients of the hepatic substance ; these chemical changes 
 being a part of the nutritive process by which the tissue of the 
 organ is constantly sustained and nourished. There is probably a 
 series of several different transformations which take place in this 
 manner, the details of which are not yet known to us. It has been 
 discovered, however, that one change at least precedes the final 
 
 • Gazette Hebdomadaire, Paris, Oct. 5, 1855. 
 
204 FORMATION OF SUGAR IN THE LIVER. 
 
 production of saccharine matter ; and that the sugar itself is pro- 
 duced by the transformation of another peculiar substance, of ante- 
 rior formation. This substance, which precedes the formation of 
 sugar, and which is itself produced in the tissue of the liver, is 
 known by the name of glycogenic matter, or glycogene. 
 
 This glycogenic matter may be extracted from the liver in the 
 following manner. The organ is taken immediately from the body 
 of the recently killed animal, cut into small pieces, and coagulated by 
 being placed for a few minutes in boiling water. This is in order 
 to prevent the albuminous liquids of the organ from acting upon 
 the glycogenic matter and decomposing it at a medium temperature. 
 The coagulated tissue is then drained, placed in a mortar, reduced 
 to a pulp by bruising and grinding, and afterward boiled in dis- 
 tilled water for a quarter of an hour, by which the glycogenic 
 matter is extracted and held in solution by the boiling water. 
 
 The liquid of decoction, which should be as concentrated as pos- 
 sible, must then be expressed, strained, and filtered, after which it 
 appears as a strongly opalescent fluid, of a slightly yellowish tinge. 
 The glycogenic matter which is held in solution may be precipi- 
 tated by the addition to the filtered fluid of five times its volume 
 of alcohol. The precipitate, after being repeatedly waslied with 
 alcohol in order to remove sugar and biliary matters, may then be 
 redissolved in distilled water. It may be precipitated from its 
 watery solution either by alcohol in excess or by crystallizable 
 acetic acid, in both of which it is entirely insoluble, and may be 
 afterward kept in the dry state for an indefinite time without losing 
 its properties. 
 
 The glycogenic matter, obtained in this way, is regarded as 
 
 intermediate in its nature and properties between hydrated starch 
 
 and dextrine. Its ultimate composition, according to M. Pelouze,' 
 
 is as follows : — 
 
 Ci^HjuOij. 
 
 When brought into contact with iodine, it produces a coloration 
 varying from violet to a deep, clear, maroon red. It does not 
 reduce .the salts of copper in Troinmer's test, nor does it ferment 
 when placed in contact with yeast at the proper temperature. It 
 does not, therefore, of itself contain sugar. It may easily be con- 
 verted into sugar, however, by contact with any of the animal 
 ferments, as, for example, those contained in the saliva, or in the 
 
 ■ Journal de Physiologie, Paris, 1858, p. 552. 
 
FORMATION OF SUGAR IN THE LIVER. 205 
 
 Mood. If a solution of glycogenic matter be mixed with fresh 
 human saliva, and kept for a few minutes at the temperature of 
 100° ¥., the mixture will then be found to have acquired the power 
 of reducing the salts of copper and of entering into fermentation by 
 contact with yeast. The glycogenic matter has therefore been 
 converted into sugar by a process of catalysis, in the same manner 
 as vegetable starch would be transformed under similar conditions. 
 
 The glycogenic matter which is thus destined to be converted 
 into sugar, is formed in the liver by the processes of nutrition. It 
 may be extracted, as we have seen above, from the hepatic tissue 
 of carnivorous animals, and is equally present when they have been 
 exclusively confined for many days to a meat diet. It is not in- 
 troduced with the food ; for the fleshy meat of the herbivora does 
 not contain it in appreciable quantity, though these animals so 
 constantly take starchy substances with their food. In them, the 
 starchy matters are transformed into sugar by digestion, and the 
 sugar so produced is rapidly destroyed after entering the circula- 
 tion ; so that usually neither saccharine nor starchy substances are 
 to be discovered in the muscular tissue. M. Poggiale' found that in 
 very many experiments, performed by a commission of the French 
 Academy for the purpose of examining this subject, glycogenic 
 matter was detected in ordinary butcher's meat only once. We 
 have also found it to be absent from the fresh meat of the bullock's 
 heart, when examined in the manner described above. Neverthe- 
 less, in dogs fed exclusively upon this food for eight days, glycogenic 
 matter may be found in abundance in the liver, while it does not 
 exist in other parts of the body, as the spleen, kidney, lungs, &c. 
 
 Furthermore, in a dog fed exclusively for eight days upon the 
 fresh meat of the bullock's heart, and then killed four hours after 
 a meal of the same food, at which time intestinal absorption is 
 going on in full vigor, the liver contains, as above mentioned, both 
 glycogenic matter and sugar ; but neither sugar nor glycogenic mat- 
 ter can be found in the blood of the portal vein, when subjected to 
 a similar examination. 
 
 The glycogenic matter, accordingly, does not originate from any 
 external source, but is formed in the tissue of the liver ; where it 
 is soon afterward transformed into sugar, while still forming a part 
 of the substance of the organ. 
 
 The formation of sugar in the liver is therefore a function com- 
 
 ' Journal d« Phyaiologie, Paris, 1858, p. 558. 
 
206 FORMATION OP SUGAR IN THE LIVER. 
 
 posed of two distinct and successive processes, viz : first, the forma- 
 tion, in the hepatic tissue, of a glycogenic matter, having some 
 resemblance to dextrine; and secondly, the conversion of this 
 glycogenic matter into sugar, by a process of catalysis and trans- 
 formation. 
 
 The sugar thus produced in the substance of the liver is absorbed 
 from it by the blood circulating in its vessels. The mechanism of 
 this absorption is probably the same with that which gQCS on in 
 other parts of the circulation. It is a process of transudation and 
 ^ endosmosis, by which the blood in the vessels takes up the saccha- 
 rine fluids of the liver, during its passage through the organ. 
 While the blood of the portal vein, therefore, in an animal fed 
 exclusively upon meat, contains no sugar, the blood of the hepatic 
 vein, as it passes upward to the heart, is always rich in saccharine 
 ingredients. This difference can be easily demonstrated by exa- 
 mining comparatively the two kinds of blood, portal and hepatic, 
 from the recently killed animal. The blood in its passage through 
 the- liver is found to have acquired a new ingredient, and shows, 
 upon examination, all the properties of a saccharine liquid. 
 
 The sugar produced in the liver is accordingly to be regarded as 
 a true secretion, formed by the glandular tissue of the organ, by a 
 similar process to that of other glandular secretions. It differs 
 from the latter, not in the manner of its production, but only in 
 the mode of its discharge. For while the biliary matters produced 
 in the liver are absorbed by the hepatic ducts and conducted down- 
 ward to the gall-bladder and the intestine, the sugar is absorbed by 
 the bloodvessels of the organ and carried upward, by the hepatic 
 veins, toward the heart and the general circulation. 
 
 The production of sugar in the liver during health is a constant 
 process, continuing, in many cases, for several days after the animal 
 has. been altogether deprived of food. Its activity, however, like 
 that of most other secretions, is subject to periodical augmentation 
 and diminution; Under ordinary circumstances, the sugar, which 
 is absorbed by the blood from the tissue of the liver, disappears 
 very soon after entering the circulation. As the bile is transformed 
 in the intestine, so the sugar is decomposed in the blood. We are 
 not yet acquainted, however, with the precise nature of the changes 
 which it undergoes after entering the vascular system. It is very 
 probable, according to the views of Lehmann and Eobin, that it is 
 at first converted into lactic acid {C^'H. fi^), which decomposes in 
 turn the alkaline carbonates, setting free carbonic acid, and forming 
 
FORMATION OF SUGAR IN THE LIVER. 207 
 
 lactates of soda and potassa. But whatever be the exact mode of 
 its transformation, it is certain that the sugar disappears rapidly ; 
 and while it exists in considerable quantity in the liver and in the 
 blood of the hepatic veins and the right side of the heart, it is not 
 usually to be found in the pulmonary veins nor in the blood of the 
 general circulation. 
 
 About two and a half or three hours, however, after the ingestion 
 of food, according to the investigations of Bernard, the circulation 
 of blood through the portal system and the liver becomes consider- 
 ably accelerated. A larger quantity of sugar is then produced in 
 the liver and carried away from the organ by the hepatic veins ; 
 so that a portion of it then escapes decomposition while passing 
 through' the lungs, and begins to appear in the blood of the arterial 
 system. Soon afterward it appears also in the blood of the capil- 
 laries; and from four to six hours after the commencement of 
 digestion it is produced in the liver so much more rapidly than it 
 is destroyed in the blood, that the surplus quantity circulates 
 throughout the body, and the blood everywhere has a slightly sac- 
 charine character. It does not, however, in the healthy, condition, 
 make its appearance in any of the secretions. 
 
 After the sixth hour, this unusual activity of the sugar-producing 
 function begins again to diminish ; and, the transformation of the 
 sugar in the circulation going on as before, it gradually disappears 
 as an ingredient of the blood. Finally, the ordinary equilibrium 
 between its production and its decomposition is re-established, and 
 it can no longer be found except in the liver and in that part of 
 the circulatory system which is between the liver and the lungs. 
 There is, therefore, a periodical increase in the amount of unde- 
 composed sugar in the blood, as we have already shown to be the 
 case with the fatty matter absorbed during digestion; but this 
 increase is soon followed by a corresponding diminution, and during 
 the greater portion of the time its decomposition keeps pace with 
 its production, and it is consequently prevented from appearing in 
 the blood of the general circulation. 
 
 There are produced, accordingly, in the liver, two different secre- 
 tions, viz., bile and sugar. Both of them originate by transforma- 
 tion of the ingredients of the hepatic tissue, from which they are 
 absorbed by two different sets of vessels. The bile is taken up by 
 the biliary ducts, and by them discharged into the intestine ; while 
 the sugar is carried off by the hepatic veins, to be decomposed in the 
 circulation, and become subservient to the nutrition of the blood. 
 
208 THE SPLEEN. 
 
 CHAPTER X. 
 
 THE SPLEEX. 
 
 The spleen is an exceedingly vascular organ, situated in the 
 vicinity of the great pouch of the stomach and supplied abund- 
 antly by branches of the cceliao axis. Its veins, like those of the 
 digestive abdominal organs, form a part of the great portal system, 
 and conduct the blood which has passed through it to the' liver, 
 before it mingles again with the general current of the circulation. 
 
 The spleen is covered on its exterior by an investing membrane 
 or capsule, which forms a protective sac, containing the soft pulp 
 of which the greater part of the organ is composed. This capsule, 
 in the spleen of the ox, is thick, whitish, and opaque, and is com- 
 posed to a great extent of yellow elastic tissue. It accordingly 
 possesses, in a high degree, the physical property of elasticity, and 
 may be widely stretched without laceration ; returning readily to 
 its original size as soon as the extending force is relaxed. 
 
 In the carnivorous animals, on the other hand, the capsule of 
 the spleen is thinner, and more colorless and transparent. It con- 
 tains here but very little elastic tissue, being composed mostly of 
 smooth, involuntary muscular fibres, connected in layers by a little 
 intervening areolar tissue. In the herbivorous animals, accordingly, 
 the capsule of the spleen is simply elastic, while in the carnivora it 
 is contractile. 
 
 In both instances, however, the elastic and contractile properties 
 of the capsule subserve a nearly similar purpose. There is every 
 reason to believe Ijiat the spleen is subject to occasional and per- 
 haps regular variations in size, owing to the varying condition of 
 the abdominal circulation. Dr. William Dobson* found that the 
 size of the organ increased, from the third hour after feeding up to 
 the fifth; when it arrived at its maximum, gradually decreasing 
 after theft 'period. When these periodical congestions take place, 
 
 ' In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40. 
 
THE SPLBEir. 209 
 
 the organ becoming turgid witli blood, the capsule is distended ; 
 and limits, by its resisting power, the degree of tumefection to 
 which the spleen is liable. When the disturbing cause has again 
 passed away, and the circulation is about to return to its ordinary 
 condition, the elasticity of the capsule in the herbivora, and its con- 
 tractility in the carnivora, compress the soft vascular tissue within, 
 and reduce the organ to its original dimensions. This contractile 
 action of the invested capsule can be readily seen in the dog or 
 the cat, by opening the abdomen while digestion is going on, 
 exposing the spleen and removing it, after ligature of its vessels. 
 When first exposed, the organ is .plump and rounded, and presents 
 externally a smooth and shining surface. But as soon as it has 
 been removed from the abdomen and its vessels. divided, it begins 
 to contract sensibly, becomes reduced in size, stif^ and resisting to 
 the touch ; while its surface, at the same time, becomes uniformly 
 wrinkled, by the contraction of its muscular fibres. 
 
 In its interior, the substance of the spleen is traversed everywhere 
 by slender and ribbon-like cords of fibrous tissue, which radiate 
 from the sheath of its principal arterial trunks, and are finally 
 attaphed to the internal surface of its investing capsule. Thes© 
 fibrous cords, or trabeculse, as they are called, by their frequent 
 branching and mutual interlacement, form a kind of skeleton or 
 framework by which the soft splenic pulp is embraced, and the 
 shape and integrity of the organ maintained. They are composed 
 of similar elements to those of the investing capsule, viz., elastic 
 tissue and involuntary muscular fibres, united with each other by 
 a varying quantity of the fibres of areolar tissue. 
 
 The interstices between the trabeculae of the spleen are occupied 
 by the splenic pulp; a soft, reddish substance, which contains, 
 beside a few nerves and lymphatics, capillary bloodvessels in great 
 profusion, and certain whitish globular bodies, which may be re- 
 garded as the distinguishing anatomical elements of the organ, and 
 which are termed the Malpighian bodies of the spleen. 
 
 The Malpighian bodies are very abundant, and are scattered 
 throughout the splenic pulp, being most frequently attached to the 
 sides, or at the point of bifarcation of some small artery. They 
 are readily visible to the naked eye in the spleen of the ox, upon a 
 fresh section of the organ, as minute, whitish, rounded bodies, which 
 may be separated, by careful manipulation, from the surrounding 
 parts. In the carnivorous animals, on the other hand, and in the 
 human subject, it is more difficult to distinguish them by the un- 
 14 
 
210 THE SPLEEN. 
 
 aided eye, though they always exist in the spleen in a healthy 
 condition. Their aiverage diameter, according to KoUiker, is jjJj of 
 an inch. They consist of a closed sac, or capsule, containing in 
 its interior a viscid, semi-solid mass of cells, cell-nuclei, and homo- 
 geneous substance. Each Malpighian body is covered, on its exte- 
 rior, by a network of fine capillary bloodvessels ; and it is now 
 perfectly well settled, by the observations of various anatomists 
 (KoUiker, Busk, Huxley, &c.), that bloodvessels also penetrate into 
 the substance of the Malpighian body, and there form an internal 
 capillary plexus. 
 
 The spleen is accordingly a glandular organ, analogous in its 
 minute structure to the solitary and agminated glands of the small 
 intestine, and to the lymphatic glands throughout the body. Like 
 them, it is a gland without an excretory duct ; and resembles, also, 
 in this respect, the thyroid and thymus glands and the supra-renal 
 capsules. All these organs have a structure which is evidently 
 glandular in its nature, and yet the name of glands has been some- 
 times refused to them because they have, as above mentioned, no 
 duct, and produce apparently no distinct secretion. We have 
 already seen, however, that a secretion may be produced in, the 
 interior of a glandular organ, like the sugar in. the substance of the 
 liver, and yet not be discharged by its excretory duct. The veins 
 of the gland, in this instance, perform the part of excretory ducts. 
 They absorb the new materials, and convey them, through the 
 medium of the blood, to other parts of the body, where they suffer 
 subsequent alterations, and are finally decomposed in the circula- 
 tion. 
 
 The action of such organs is consequently to modify the consti- 
 tution of the blood. As the blood passes through their tissue, it 
 absorbs from the glandular substance certain materials which it did 
 not previously contain, and which are necessary to the perfect con- 
 stitution of the circulating fluid. The blood, as it passes out from 
 the organ, has therefore a different composition from that which it 
 possessed before its entrance ; and on this account the name of vas- 
 cular glands has been applied to all the glandular organs above- 
 mentioned, which are destitute of excretory ducts, and is eminently 
 applicable to the spleen. 
 
 The precise, alteration, however, which is effected in the blood 
 during^ its passage through the splenic tissue, has nqt yet been 
 discovered. Various hypotheses have been advanced from time to 
 time, as to the processes which go on in this organ ; many of them 
 
THE SPLEEN. 211 
 
 vague and indefinite in character, and some of them directly con- 
 tradictory of each other. None, however, have yet been offered 
 which are entirely satisfactory' in themselves, or which rest on suf- 
 ficiently reliable evidence. 
 
 A very remarkable fact with regard to the spleen is that it may 
 be entirely removed in many of the lower animals, without its loss 
 producing any serious permanent injury. This experiment has 
 been frequently performed by various observers, and we have our- 
 selves repeated it several times with similar results. The organ 
 may be easily removed, in the dog or the cat, by drawing it out of 
 the abdomen, through an opening in the median line, placing a few 
 ligatures upon the vessels of the gastro-splenic omentum, and then 
 dividing the vessels between the ligatures and the spleen. The 
 wound usually heals without difficulty ; and if the animal be killed 
 some weeks afterward, the only remaining trace of the operation 
 is an adhesion of the omentum to the inner surface of the abdomi- 
 nal parietes, at the situation of the original -wound. 
 
 The most constant and permanent effect of a removal of the 
 spleen is an unusual increase of the appetite. This symptom we 
 have observed in some instances to be excessively developed ; so 
 that the animal would at all times throw himself, with an unnatural 
 avidity, upon any kind of food offered him. We have seen a dog, 
 subjected to this operation, afterward feed without hesitation upon 
 the flesh of other dogs ; and even devour greedily the entrails, taken 
 warm from the abdomen of the recently killed animal. The food 
 taken in this unusual quantity is, however, perfectly well digested ; 
 and the animal will often gain very perceptibly in weight. In one 
 instance, a cat, in whom the unnatural appetite was marked though 
 not excessive, increased in weight from five to six pounds, in the 
 course of a little less than two months ; and at the same time the 
 fur became sleek and glossy^ and there was a considerable improve- 
 ment in the general appearance of the animal. 
 
 Another symptom, which usually follows removal of the spleen, 
 is an unnatural ferocity of disposition. The animal will frequently 
 attack others, of its own or a different species, without any appa- 
 rent cause, and without any regard to the difference of size, strength, 
 &c. This symptom is sometimes equally excessive with that of an 
 unnatural appetite ; while in other instances it shows itself only in 
 occasional outbursts of irritability and violence.. 
 
 Neither of the symptoms, however, which we have just de- 
 scribed, appears to exert any permanently injurious effect upon the 
 
212 THE SPLEEN. 
 
 animal whicli has been subjected to the operation ; and life inay be 
 prolonged for an indefinite period without any serious disturbance 
 of the nutritive process, after the spleen has been completely 
 extirpated. 
 
 We must accordingly regard the spleen, not as a single organ, 
 but as associated, with others, which may completely, or to a great 
 extent, perform its functions after its entire removal. We have 
 already noticed the similarity in structure between the spleen and 
 the mesenteric and lymphatic glands; a similarity which has led 
 some writers to regard them as more or less closely associated with 
 each other in function, and to consider the spleen as an unusually 
 developed lymphatic or mesenteric gland. It is true that this 
 organ is provided with a comparatively scanty supply of lymphatic 
 vessels ; and the chyle, which is absorbed from the intestine, does 
 not pass through the spleen, as it passes through the remaining 
 mesenteric glands. Still, the physiological action of the spleen 
 may correspond with that of the other lymphatic glands, so far as 
 regards its influence on the blood ; and there can be little doubt 
 that its function is shared, either by them or by some other glan- 
 dular organs, which become unnaturally active, and more or.less 
 perfectly supply its place after its complete removal. 
 
BLOOD-GLOBULES. 213 
 
 CHAPTER XI. 
 
 THE BLOOD. 
 
 The blood, as it exists in its natural condition, while circulating 
 in the vessels, is a thick opaque fluid, varying in color in different 
 parts of the body from a brilliant scarlet to a dark purple. It has 
 a slightly alkaline reaction, and a specific gravity of 1055. It 
 is not, however, an entirely homogeneous fluid, but is found on 
 microscopic examination to consist, first, of a nearly colorless, 
 transparent, alkaline fluid, termed the plasma, containing water, 
 fibrin, albumen, salts, &c., in a state of mutual, solution; and, 
 secondly, of a large number of distinct cells, or corpuscles, the 
 bhod-gilobuhs, swimming freely in the liquid plasma. These glo- 
 bules, which are so small as not to be distinguished by the naked 
 eye, by being mixed thus abundantly with the fluid plasma, give 
 to the entire mass of the blood an opaque appearance and a uniform 
 red color. 
 
 Blood-globules. — On microscopic examination it is found that 
 the globules of the blood are of two kinds, viz., red and white ; of 
 these the red are by far the most abundant. 
 
 The red globules of the blood present, under the microscope, a 
 perfectly circular outline and a smooth exterior. (Fig. 54.) Their 
 size varies somewhat, in human blood, even in the same specimen. 
 The greater number of them have a transverse diameter of -g-^^ of 
 an inch ; but there are many smaller ones to be seen, which are 
 not more than -j^Vtr or even ^jVtt of ^^ i^ch in diameter. Their 
 form is that of a spheroid, very much flattened on its opposite 
 surfaces, somewhat like a round biscuit, or a thick piece of money 
 with rounded edges. The blood-globule accordingly, when seen 
 flatwisfe, presents a comparatively broad surface and a circular out- 
 line (a); but if it be made to roll over, it will present itself edge- 
 wise during its rotation and assume the flattened form indicated at 
 b. The thickness of the globule, seen in this position, is about 
 
214 
 
 THE BLOOD. 
 
 Human Bi.ood-qlobui.es. 
 seeu flatwise. 6. Ked globules, 
 White globule. 
 
 -a. Eed globnies, 
 seen edgewise, e. 
 
 TsioTT of an inch, or a little less than one-fifth of its transverse 
 diameter. 
 
 When the globules are examined lying upon their broad sur- 
 faces, it can be seen that these surfaces are not exactly flat, but that 
 
 there is on each side a slight 
 "'^' ■ central depression, so that 
 
 the rounded edges of the 
 blood-globule are evidently 
 thicker than its middle por- 
 tion. This inequality pro- 
 duces a remarkable optical 
 effect. The substance of 
 which the blood-globule is 
 composed refracts light more 
 strongly than the fluid plas- 
 ma. Therefore, when exa- 
 mined "with the microscope, 
 by transmitted light, the 
 thick edges of the globules 
 act as double convex lenses, 
 and concentrate the light 
 
 ^K.v..^ .^^ .^,^. V-. ^^. Consequently, if the object-glass be 
 
 carried upward by the adjusting screw of the microscope, and lifted 
 
 away from the stage, so that 
 F'S: •''S- the blood-globules fall be- 
 
 yond its focus, their edges 
 will appear brighter. But 
 the central portion of each 
 globule, being excavated on 
 both sides, acts as a double 
 concave lens, and disperses 
 the light from a point below 
 the level of the fluid. It, 
 therefore, grows brighter as 
 the object-glass is carried 
 downward, and the object 
 falls within its focus. An 
 alternating appearance of the 
 blood-globules may, there- 
 fore, be produced by view: 
 ing them first beyond and then within the focus of the instrument. 
 
 .above the level of the fluid. 
 
 Red Globules of the Blood 
 beyond tlie t'ucus of the microscope. 
 
 seen a little 
 
BLOOU-GLOBULES. 
 
 215 
 
 Fig. 56. 
 
 The same, seen a little within the focus. 
 
 When beyond the focus, the globules will be seen with a bright 
 rim and a dark centre. (Fig. 55.) When within it they will appear 
 with a dark rim and a bright 
 centre. (Fig. 56.) 
 
 The blood-globules accord- 
 ingly have the form of a 
 thickened disk with rounded 
 edges and a double central 
 excavation. They have, con- 
 sequently, been sometimes 
 called " blood-disks," instead 
 of blood-globules. The term 
 
 ' disk," however, does not in- 
 dicate their exact shape, any 
 more than the other; and 
 the term "blood-corpuscle," 
 which is also sometimes used, 
 does not indicate it at all. 
 And although the term "blood-globule" may not be precisely a 
 correct one, still it is the most convenient ; and need not give rise 
 to any confusion, if we remember the real shape of tjie bodies' de- 
 signated by it. This term will, consequently, be employed when- 
 ever we have occasion to 
 speak of the blood-globules ^'s- ^'^• 
 
 in the following pages. 
 
 Within a minute after being 
 placed under the microscope, 
 the blood-globules, after a 
 fluctuating movement of 
 short duration, very often 
 arrange themselves in slight- 
 ly curved rows or chains, in 
 which they adhere to each 
 other by their flat surfaces, 
 presenting an appearance 
 which has been aptly com- 
 pared with that of rolls of 
 coin. This is probably ow- 
 ing merely,to the coagulation 
 
 of the blood, which takes place very rapidly when it is spread out 
 in thin layers and in contact with glass surfaces ; and which, by 
 
 6L0{)D-aL0BirLE 
 
 of coin. 
 
 adhering together, like rolls 
 
216 THE BLOOD. 
 
 compressing the globules, forces them into such a position that they 
 may occupy the least possible space. This position is evidently 
 that in which they are applied to each other by their flat surfaces, 
 as above described. , ^ 
 
 The color of the blood-globules, when viewed by transmitted 
 light and spread out in a thin layer, is a light amber ox pale yellow. 
 It is, on the contrary, deep red when they are seen by reflected 
 light, or piled together in comparatively thick layers. When viewed 
 singly, they are so transparent that the outlines of those lying under- 
 neath can be easily seen, showing through the substance of the 
 superjacent globules. Their consistency is peculiar. They are not 
 solid bodies, as they have been sometimes inadvertently described ; 
 but on the contrary have a consistency which is very nearly fluid. 
 They are in consequence exceedingly flexible, and easily elongated, 
 bent, or otherwise distorted by accidental pressure, or in passing 
 through the narrow currents of fluid which often establish them- 
 selves accidentally in a drop of blood under microscopic examina- 
 tion. This distortion, however, is only temporary, and the globules 
 regain their original shape, as soon as the accidental pressure is 
 taken off. The peculiar flexibility and elasticity thus noticed are 
 characteristic of the red globules of the blood, and may always 
 serve to distinguish them from any other free cells which may be 
 found in the animal tissues or fluids. 
 
 In structure the blood-globules are homogeneous. They have 
 been sometimes erroneously described as consisting of a closed 
 vesicle or cell- wall, containing in its cavity some fluid or semi-fluid 
 substance of a different character from that composing the wall of 
 the vesicle itself. No such structure, however, is really to be seen 
 in them. Each blood-globule consists of a mass of organized ani- 
 mal substance, perfectly or nearly homogeneous in appearance, and 
 of the same color, consistency and composition throughout. In 
 some of the lower animals (birds, reptiles, fish) it contains also a 
 granular nucleus, imbedded in the substance of the globule ; but 
 in no instance is there any distinction to be made out between an 
 external cell-wall and an internal cavity. 
 
 The. appearance of the blood-globules is altered by the addition 
 of various foreign substances. If water be added, so as to dilute 
 the plasma, the globules absorb it by imbibition, swell, lose their 
 double central concavity and become paler. If a larger quantity 
 of water be added, they finally dissolve and disappear altogether. 
 When a moderate quantity of water is mixed with the blood, the 
 
BLOOD-GLOBULES. 
 
 217 
 
 Bt.ood-globules, ewuliea by the imbibition of 
 
 edges of the globiiles, being thicker than the central portions, and 
 absorbing water more abundantly, become turgid, and encroach 
 gradually upon the central 
 part. (Fig. 58.) It is very ^'s- ^^■ 
 
 common to see the central 
 depression under these cir- 
 cumstances, disappear on one 
 side before it is lost on the 
 other, so that the globule, as 
 it swells up, curls over to- 
 wards one side, and assumes 
 a peculiar cup-shaped form 
 (a). This form may often be 
 seen in blood-globules that 
 have been soaking for some 
 time in the urine, or in any 
 other animal fluid of a less 
 density than the plasma of water" 
 the blood. Dilute acetic acid 
 
 dissolves the blood-globules more promptly than water, and solu- 
 tions of the caustic alkalies more promptly still. 
 
 If a drop of blood be allowed partially to evaporate while under 
 the microscope, the globules 
 near the edges of the prepa- '^' ' 
 
 ration often diminish in size, 
 and at the same time present 
 a shrunken and crenated ap- 
 pearance, as if minute gran- 
 ules were projecting from 
 their surfaces (Fig. 59); an 
 effect apparently produced 
 by the evaporation of part 
 of their watery ingredients. 
 For some unexplained rea- 
 son, however, a similar dis- 
 tortion is often produced in 
 some of the globules by the 
 addition of certain other ani- 
 mal fluids, as for example the 
 
 saliva ; and a few can even be seen in this condition after the 
 addition of pure water. 
 
 Blood-globules, slirunken, with their margins 
 crenated. 
 
218 THE BLOOD. 
 
 The entire mass of tlie blood-globules, in proportion to the rest 
 of the circulating fluid, can only be approximately measured by 
 the eye in a microscopic examination. In ordiaary analyses the 
 globules are usually estimated as amounting to about fifteen per 
 cent., by weight, of the entire blood. This estimate, however, refers, 
 properly speaking, not to the globules themselves, but only to their 
 dry residue, after the water which they contain has been lost by 
 evaporation. It is easily seen, by examination with the microscope, 
 that the globules, in their natural semi-fluid condition, are really 
 much more abundant than this, and constitute fully one-half the 
 entire mass of the blood ; that is, the intercellular fluid, or plasma, is 
 not niore abundant than the globules themselves which are sus- 
 pended in it. When separated from the other ingredients of the 
 blood and examined by themselves, the globules are found, ac- 
 cording to Lehmann, to present the following composition : — 
 
 Composition op the Buiod-Globuies is 1000 Pakts. 
 
 Water 688.00 
 
 Globuline 282.22 
 
 Hsematine lli.lCt 
 
 Patty substances 2.S1 
 
 Undetermined (extractive) matters 2.00 
 
 Chloride of soilium 
 
 " potassium ........ 
 
 Phosphates of soda and potassa ...... 
 
 Sulphate " " 
 
 Phosphate of lime 
 
 " " magnesia ' . . 
 
 8.12 
 
 lOUO.UO 
 
 The most important of these ingredients is the globuline. This 
 is an organic substance, nearly fluid in its natural condition by 
 union with water, and constituting the greater part of the mass of 
 the blood- globules. It is soluble in water, but insoluble in the 
 plasma of the blood, owing to the presence in that fluid of albumen 
 and saline matters. If the blood Tje largely diluted, however, the 
 globuline is dissolved, as already mentioned, and the blood-globules 
 are destroyed. Globuline coagulates by heat; but, according to 
 Eobin and Verdeil, only becomes opalescent at 160°, and requires 
 for its complete coagulation a temperature of 200° F. 
 
 . The hwmatine is the coloring matter of the globules. It is, like 
 globuline, an organic substance, but is present in much smaller quan- 
 tity than the latter. It is not contained in the form of a powder, 
 
BLOOD-GLOBULES. 
 
 219 
 
 mechanically deposited in the globuline, but the two substances are 
 iutimately mingled throughout the mass of the blood-globule, just 
 as the fibrin and albumen are mingled in the plasma. Hsematine 
 contains, like the other coloring matters, a small proportion of iron. 
 This iron has been supposed to exist under the form of an oxide ; 
 and to contribute idirectly in this way to the red color of the sub- 
 stance in question. But it is now ascertained that although the 
 iron is found in an oxidized form in the ashes of the blood-globules 
 after they have been destroyed by heat, its oxidation probably takes 
 place during the process of incineration. So far as we know, there- 
 fore, the iron exists originally in the haematine as an ultimate 
 element, directly combined with the other ingredients of this sub- 
 stance, in the same manner as the carbon, the hydrogen, or the 
 nitrogen. 
 
 The blood-globules of all the warm-blooded quadrupeds, with 
 .the exception of the family of the camelidas, resemble those of the 
 human species in shape and structure. They differ, however, some- 
 what in size, being usually rather smaller than in man. There are 
 but two species in which they are known to be larger than in man, 
 viz., the Indian elephant, in which they are jVbtt of an inch, and 
 the two-toed sloth {Bradypus didactylus), in which they are jgVxr of 
 an inch in diameter. In the musk deer of Java they are smaller 
 than in any other known species, measuring rather less than y^^ty^ 
 of an inch. The following is a list showing the size of the red 
 globules of the blood in the principal mammalian species, taken 
 from the measurement of Mr. Gulliver.' 
 
 
 D1A.METEB 
 
 OP 
 
 Red Globitles in thi 
 
 
 
 Ape 
 
 • 5l'iFi!°f *" i'"=l'- 
 
 Cat . 
 
 ■ Ij'ffilOf 
 
 an inch 
 
 Horse . 
 
 i^lSH 
 
 u 
 
 
 Fox . 
 
 IT^Sff 
 
 u 
 
 Ox 
 
 Ts'lff 
 
 11 
 
 
 Wolf . 
 
 sbVit 
 
 " 
 
 Sheep . 
 
 J^HIS 
 
 tt 
 
 
 Elephant 
 
 iAj 
 
 It 
 
 Goat . 
 
 einjs 
 
 u 
 
 
 Red deer 
 
 Tn'off 
 
 It 
 
 Dog . 
 
 ■ss'njs 
 
 u 
 
 
 Musk deer 
 
 • TsivB 
 
 tt 
 
 In all these instances the form and general appearance of the 
 globules are the same. The only exception to this rule among the 
 mammalians is in the family of the camelidse (camel, dromedary, 
 lama), in which the globules present an oval outline instead of a 
 circular one. In other respects they resemble the foregoing. 
 
 In the three remaining classes of vertebrate animals, viz., birds, 
 
 ' In Works of William Hewson, Sydenham edition, London, 1846, p. 327. 
 
220 
 
 THE BLOOD. 
 
 ■357 
 
 reptiles, and fish, the blood-globulea differ so much from the above 
 that they can be readily distinguished by microscopic examination. 
 They are oval in form, and contain a colorless granular nucleus 
 imbedded in their substance. They are also considerably larger 
 than the blood-globules of the mammalians, particularly in the 
 
 class of reptiles. In the frog 
 (Fig. 60) they measure t^uw 
 of an inch in their long 
 diameter; and in Menohrau' 
 chus, the great water lizard 
 of the northern lakes, ^^^ of 
 an inch. In Prot&us angui- 
 nits they attain the size, ac- 
 cording to Dr. Carpenter,^ of 
 of an inch. 
 Beside the corpuscles de- 
 scribed above, there are glo- 
 bules of another kind found 
 in the blood, viz., the white 
 globules. These globules are 
 very much less numerous 
 than the red ; the proportion 
 between the two, in human blood, being one whitie to two or three 
 hundred red globules. In reptiles, the relative quantity of the 
 white globules is greater, but they are always considerably less 
 abundant than the red. They differ also from the latter in shape, 
 size, color, and consistency. They are globular in form, white or 
 colorless, and instead of being homogeneous like the others, their 
 substance is filled everywhere with minute dark molecules, which 
 give them a finely granular appearance. (Fig. 54, c.) In size they 
 are considerably larger than the red globules, being about j^Vtr ot 
 an inch in diameter. They are also more consistent than the others, 
 and do not so easily glide along in the minute currents of a drop of 
 blood under examination, but adhere readily to the surfaces of the 
 glass. If treated with dilute acetic acid, they swell up and become 
 smooth and circular in outline ; and at the same time a separation 
 or partial coagulation seems to take place in the substance of which 
 they are composed, so that an irregular collection of granular 
 matter shows itself in their interior, becoming more divided and 
 
 Blood-glubul U6 OF Froq. — a. Blood-globule 
 Beea edgewise, b. White-globule. 
 
 The Microscope and Its Revelations, Philadelphia edition, p. 600. 
 
BLOOD-GLOBULES. 
 
 221 
 
 broken up as the action of the acetic acid upon the globule is 
 longer continued. (Fig. 61.) This collection of. granular matter 
 often assumes a curved or crescentic form, as at a, and sometimes 
 various other irregular shapes. It does not indicate the existence 
 of a nucleus in the white globiile, but it is merely an appearance 
 produced by the coagulating 
 and disintegrating action of ^'?- si- 
 
 acetic acid upon the substance 
 of which it is composed. 
 
 The chemical constitution 
 of the white globules, as 
 distinguished from the red, 
 has never been determined ; 
 owing to the small quantity 
 in which they occur, and the 
 difficulty of separating them 
 from the others for purposes 
 of analysis. 
 
 The two kinds of blood- 
 globules, white and red, are 
 to be regarded as distinct 
 and independent anatomical 
 forms. It has been sometimes supposed that the white globules 
 were converted, by a gradual transformation, into the red. There 
 is, however, no direct evidence of this ; as the transformation has 
 never been seen to take place, either in the human subject or in 
 the mammalia, nor even its intermediate stages satisfactorily ob- 
 served. When, therefore, in default of any such direct evidence^ 
 we are reduced to the surmise which has been adopted by some 
 authors, viz.,- that the change "takes place too rapidly to be de- 
 tected by our means of observation,'" it must be acknowledged 
 that the above opinion has no solid foundation. It has been stated 
 by some authors (KoUiker, Gerlach) that in the blood of the 
 batrachian reptiles there are to be seen certain bodies intermediate- 
 in appearance between the white and the red globules, and which 
 represent different stages of transition from one form to the other ; 
 but this is not a fact which is generally acknowledged. We have 
 repeatedly examiued, with reference to this point, the fresh blood 
 of the frog, as well as that of the menobranchus, in which the large 
 
 White Globules of the Blood; altered by 
 dilute acetic acid. 
 
 ■ EolUker, Handbuch der Grenrebelehre, Leipzig, 1852, p. 582. 
 
222 THE BLOOD. 
 
 size of the globules would give every opportunity for detecting any 
 such changes, did they really exist ; and it is our unavoidable con- 
 clusion from these observations, that there is no good evidence, even 
 in the blood of rdptiles, of any such transformation taking place. 
 There is simply, as in human blood, a certain variation in size and 
 opacity among the red globules ; but no such connection with, or 
 resemblance to, the white globules as to indicate a passage from one 
 form to the othfer. The red and white globules are therefore to be 
 regarded as distinct and independent anatomical elemeflts. They 
 are mingled together in the blood, just as capillary bloodvessels and 
 nerves are mingled in areolar tissue ; but there is no other connection 
 between them, so far as their formation is concerned, than that of 
 juxtaposition. 
 
 Neither is it at all probable that the red globules are produced or 
 destroyed in any particular part of the body. One ground for the 
 belief that these bodies were produced by a metamorphosis of the 
 white globules was a supposition that they were continually and 
 rapidly destroyed somewhere in the circulation ; and as this loss 
 must be as rapidly counterbalanced by the formation of new glo- 
 bules, and as no other probable source of their reproduction ap- 
 peared, they were supposed to be produced by transformation of 
 the white globules. But there is ho reason for believing that th,e 
 red globules of the blood are any less permanent, as anatomical 
 forms, than the muscular fibres or the nervous filaments. They 
 undeVgo, it is true, like all the constituent parts of the body, a 
 constant interstitial metamorphosis. They absorb incessantly nu- 
 tritious materials from the blood, and give up to the circulating 
 fluid, at the same time, other substances which result from their 
 internal waste and disintegration. But they do not, so far as we 
 know, perish bodily in any part of the circulation. It is not the 
 anatomical forms, anywhere, which undergo destruction and reno- 
 vation in'the nutritive process; but only the proximate principles of 
 which they are composed. The effect of this interstitial nutrition, ' 
 therefore, in the blood-globules as in the various solid tissues, is 
 merely to maintain them in a natural and healthy condition of 
 integrity. Their ingredients are incessantly altered, by transforma- 
 tion and decomposition, as. they pass through various parts of the 
 vascular system;' but the globules themselves retain their form 
 and texture, and still remain as constituent parts of the circulating 
 fluid. 
 
PLASMA. 
 
 223 
 
 1.55 
 
 Plasma. — The plasma of the blood, according to Lehmann, has 
 the following constitution : — 
 
 Composition of the Plasma in 1,000 parts. 
 
 Water 902.90 
 
 Fibrin . . '. 4.05 
 
 Albumen . . . ^ 78.84 
 
 Fatty matters 1.73 
 
 Undetermined (extractive) matters 3.94 
 
 Chloride of sodium 
 
 " potassium 
 
 Phosphates of soda and potassa 
 Sulphates " . " " 
 
 Phosphate of lime 
 
 " magnesia 
 
 1000.00 
 
 The above ingredients are all intimately mingled in the blood- 
 plasma, in a fluid form, by mutual solution ; but they may be sepa- 
 rated from each other for examination by appropriate means. The 
 two ingredients belonging to the class of organic substances are the 
 fibrin and the albumen. 
 
 ^he fibrin, though present in small quantity, is evidently an im- 
 portant element in the constitution of the blood. It may be ob- 
 tained in a tolerably pure form by gently stirring freshly drawn 
 blood with a glass rod or a bundle of twigs ; upon which the fibrin 
 coagulates, and adheres to the twigs in the form of slender threads 
 and flakes. The fibrin, thus coagulated, is at first colored red by 
 the haematine of the blood-globules entangled in it ; but it may be 
 washed colorless by a few hours' soaking in running water. The 
 fibrin then presents itself 
 
 under the form of nearly ^'S- ^^■ 
 
 white threads and flakes, 
 having a semi-solid consist- 
 ency, and a considerable de- 
 gree of elasticity. 
 
 The coagulation of fibrin 
 takes place in a peculiar 
 manner. It does not solidify 
 in a perfectly homogeneous 
 mass ; but if examined by the 
 microscope in thin layers it 
 is seen to have a fibroid or 
 filamentous texture. In this 
 condition it is said to be 
 
 /, /.I -Ti 111 /T-1. t\n\ mi CoAoni.ATED FlBKiN, showing itsabrillatedcon- 
 
 " fibnllated." (Fig. 62.) The diiioo. 
 
224 ■ THE BLOOD. 
 
 filaments of wliicli it is composed are colorless and elastic, and when 
 isolated are seen to be exceedingly minute, being not more than 
 ^Tshnv or even ^^Uu oi an inch in diameter. They are in part 
 arranged so as to lie parallel with each other ; but are more gene- 
 rally interlaced in a kind of irregular network, crossing each other 
 in every direction. On the addition of dilute acetic acid, they swell 
 up and fuse together into a homogeneous, mass, but do not dissolve. 
 They are often interspersed everywhere with minute granular mole- 
 cules, which render their outlines more or less obscure. 
 
 Once coagulated, fibrin is insoluble in water and can only be 
 again liquefied by the action of an alkaline or strongly saline solu- 
 tion, or by prolonged boiling at a very high temperature. These 
 agents, however, produce a complete alteration in the properties of 
 the fibrin, and after being subjected to them it is no longer the 
 same substance as before. 
 
 The quantity of fibrin in the blood varies in different parts of the 
 body. According to the observations of .various writers,' there is 
 more fibrin generally in arterial than in venous blood. The blood 
 of the veins near the heart, again, contains a smaller proportion of 
 fibrin than those at a distance. The blood of the portal vein con- 
 tains less than that of the jugular ; and that of the hepatic vein less 
 than that of the portal. 
 
 The albumen is undoubtedly the most important ingredient of the 
 plasma, judging both from its nature and the abundance in which 
 it occurs. It coagulates at once on being heated to 160° F., or by 
 contact with alcohol, the mineral acids, the metallic salts, or with 
 ferrocyanide of potassium in an acidulated solution. It exists natu- 
 rally in the plasma in a fluid form by reason of its union with 
 water. The greater part of the water of the plasma, in fact, is in 
 union with the albumen ; and when the albumen coagulates,, the 
 water remains united with it, and assumes at the same time the 
 solid form. If the plasina of the blood, therefore, after the removal 
 of the fibrin, be exposed to the |:emperature of 160° F., it solidifies 
 almost completely; so that only a few drops of water remain that j 
 can be drained away from the coagulated mass. The phosphates 
 of lime and magnesia are also held in solution principally by the 
 albumen, and are retained by it in coagulation. 
 
 The- fatty ^iters exist in the blood mostly in a saponified form, 
 excepting soon after the digestion of food rich in fat. At that 
 period, as we have already mentioned, the emulsioned fat finds its 
 
 Robin and Verdeil, op. oit., vol. ii. p. 202. 
 
COAGULATION OP THE BLOOD, 225 
 
 way into the blood, and circulates for a time uncnanged. After- 
 ward it disappears as free fat, and remains partly in the saponified 
 condition. 
 
 The saline ingredients of the plasma are of the same nature with 
 those existing in the globules. The chlorides of sodium and potas- 
 sium, and the phosphates of soda and potassa are the most abundant 
 in both, while the sulphates are present only in minute quantity. 
 The proportions in which the various salts are present are very dif- 
 ferent, according to Lehmann,' in the blood-globules and in the 
 plasma. Chloride of potassium is most abundant in the globules, 
 chloride of sodium in the plasma. The phosphates of soda and 
 potassa are more abundant in the globules than in the plasma. On 
 the other hand, the phosphates of lime and magnesia are more 
 abundant in the plasma than in the globules. 
 
 The substances known under the name oiextraciive matters consjst 
 of a mixture of different ingredients, belonging mostly to the class 
 of organic substances, which have not yet been separated in a state 
 of sufiScient purity to admit of their being thoroughly examined 
 and distinguished from each other. They do not exist in great 
 abundance, but are undoubtedly of considerable importance in the 
 constitution of the blood. Beside the substances enumerated in the 
 above list, there are still others which occur in small quantity as 
 ingredients of the blood. Among the most important are the alka- 
 line carbonates, which are held in solution in the serum. It has 
 already been mentioned that while the phosphates are most abun- 
 dant in the blood of the carnivora, the carbonates are most abun- 
 dant in that of the herbivora. Thus Lehmann' found carbonate of 
 soda in the blood of the ox in the proportion of 1.628 per thousand 
 parts. There are also to be found, in solution in the blood; urea, 
 urate of soda, creatine, creatinine, sugar, &c. ; all of them crystalHza- 
 ble substances derived from the transformation of other ingredients 
 of the blood, or of the tissues through which it circulates. - The 
 relative quantity, however, of these substances is very minute, and 
 has not yet been determined with precision. 
 
 Coagulation of the Blood. — A few moments after the blood 
 has been withdrawn from the vessels, a remarkable phenomenon 
 presents itself, viz., its coagulation or clotting. This process com- 
 mences at nearly the same time throughout the whole mass of the 
 blood. The blood becomes first somewhat diminished in fluidity, 
 ' Op. cit., vol. i. p. 546. * Op. cit., vol. i. p. 393. 
 
 15 
 
226 THE BLOOD. 
 
 SO that it will not run over the edge of the vessel, when slightly 
 inclined ; and its surface may be gently depressed with the end of 
 the finger or a glass rod. It then becomes rapidly thicker, and at 
 last solidifies into a uniformly red, opaque, consistent, gelatinous 
 mass, which takes the form of the vessel in which the blood was 
 received. Its coagulation is then complete. The process usually 
 commences, in the case of the human subject, in about fifteen min- 
 utes after the blood has been drawn, and is completed in about 
 twenty minutes. 
 
 The coagulation of the blood is dependent entirely upon the 
 presence. of the fibrin. This fact has been demonstrated in various 
 ways. In the first place, if frog's blood be filtered, so as to separate 
 the globules and leave them upon the filter, while the plasma is 
 allowed to run through; the colorless filtered fluid which contains 
 th.e fibrin soon coagulates ; while no coagulation takes place in the 
 moist globules remaining on the filter. Again, if the freshly drawn 
 blood be stirred with a bundle of rods, as we have already de- 
 scribed above, the fibrin coagulates upon them by itself, while the 
 rest of the plasma, mixed with the globules, remains perfectly fluid. 
 It is the fibrin, therefore, which, by its own coagulation, induces 
 the solidification of the entire blood. As the fibrin is uniformly 
 distributed throughout the blood, when its coagulation takes place 
 the minute filaments which make their appearance in it entangle 
 in their meshes the globules and the. albuminous fluids of the 
 plasma. A very small quantity of fibrin, therefore,- is sufficient to 
 entangle by its coagulation all the fluid and semi-fluid parts of the 
 blood, and convert the whole into a volumi- 
 Fig. 63. nous, trembling, jelly-like mass, which is 
 
 ^-— ■ 7-^ known by the name of the " crassamentum," 
 
 ^^I^BaBV/ or "clot." (Fig. 63.) 
 
 ^^^f^S^HI As soon as the clot has fairly formed, it 
 
 1 ^^^^^^V I begins to contract and diminish in size. Ex- 
 
 \^^B^^ I actly how this contraction of the clot is pro- 
 
 ^ ^^^^^ y duced, we are unable' to say ;. but it is proba- 
 
 . -^ ^ bly a continuation of the same process by 
 
 Bowl of reeentiy coAGu- which its Solidification is at first accomplished, 
 
 LATED BLOOD showing the ^j. ^^ Jg^^^ ^^^ g-j^^JJ^j. ^ J^ _^g ^^ 
 
 whole mass uuiformly sohdl- J 
 
 ■ fled. contraction proceeds, the albuminous fluids 
 
 begin to be pressed out from the meshes in 
 
 which they were entangled. A few isolated' drops first appear on 
 
 the surface of the clot. These drops soon increase in size and be- 
 
COAOULATION OF THE BLOOD. 
 
 227 
 
 Fig. 64.- 
 
 come more numerous. They run together and coalesce with each 
 other, as more and more fluid exudes from the coagulated mass, 
 until the whole surface of the clot is covered with a thin layer of 
 fluid. The clot at first adheres pretty strongly to the sides of the 
 vessel into which the blood was drawn ; but as its contraction goes 
 on, its edges are separated, and the fluid continues to exude between 
 it and the sides of the vessel. This exudation 
 continues for ten or twelve hours ; the clot 
 growing constantly smaller and firmer, and 
 the expressed fluid more and ipore abundant. 
 The globules, owing to their greater con- 
 sistency, do not escape with the albuminous 
 fluids, but remain entangled in the fibrinous 
 coagulum. Finally, at the end of ten or 
 twelve hours the whole of the blood has 
 usually separated into two parts, viz., the cht B(,„, „, coaoblateb 
 which is a red, opaque, dense and resisting blood, after twelve hour«, 
 
 ^r. p ^ Jl^ • J showinsf the clot cuntracted 
 
 semi-solid mass, consisting ot the fibrm and and aoating m the fluid serum. 
 the blood-globules ; and the serum, which is a 
 transparent, nearly colorless fluid, containing the water, albumen^ 
 and saline matters of the plasma. (Fig. 64.) 
 
 The change of the blood in coagulation may therefore be" ex- 
 pressed as follows :-^ 
 
 Before coagulation the blood consists of 
 
 1st. Globdles ; and 2d. Plasma — containing 
 
 After coagulation it is separated into 
 
 f Fibrin, 
 Albumen, 
 Water, 
 
 1st. Clot, containing < 
 
 Fibrin and 
 Globules ; 
 
 L 
 
 r Albumen, 
 
 and 2d. Sebum, containing \ Water, 
 
 y Salts. 
 
 The coagulation of the blood is hastened or retarded by various 
 physical conditions, which have been studied with care by various 
 observers, but more particularly by Robin and Verdeil. The con- 
 ditions which influence the rapidity of coagulation are as follows: 
 First, the rapidity with which the blood is drawn from the vein, 
 and the size of the orifice from which it flows; If blood be drawn 
 rapidly, iij a full stream, from a large orifice, it remains fluid for a 
 comparatively long time; if it be drawn slowly, from a narrow 
 orifice, it coagulates quickly. Thus it usually happens that in the 
 operation of venesection, the blood drawn immediately after the 
 
228 THE BLOOD. 
 
 opening of the vein runs freely and coagulates slowly ; -while that 
 which is drawn toward the end of the operation, when the tension 
 of the veins has been relieved and the blood trickles slowly from 
 the wound, coagulates quickly. Secondly, the shape of the vessel 
 into which the blood is received and' the condition of its internal 
 surface. The greater the extent of surface over which the blood 
 comes in contact with the vessel, the more is its coagulation 
 hastened. Thus, if the blood be allowed to flow into a tall, narrow, 
 cylindrical vessel, or into a shallow plate, it coagulates more rapidly 
 than if it be received into a hemispherical bowl, in which the ex- 
 tent of surface is less, in proportion to the entire quantity of blood 
 which it contains. For the same reason, coagulation takes place 
 more rapidly in a vessel with a roughened internal surface, than in 
 one which is smooth and polished. The blood coagulates most 
 rapidly when spread out in thin layers, and entangled among the 
 fibres of cloth or sponges. For the same reason, also, hemorrhage 
 continues longer from an incised wound than from a lacerated one ; 
 because the blood, in flowing over the ragged edges of the lace- 
 rated bloodvessels and tissues, solidifies upon them readily, and thus 
 blocks up the wound. 
 
 In all these cases, there is an inverse relation between 'the rapidity 
 of coagulation and the firmness of the clot. When coagulation 
 takes, place slowly, the clot afterward becomes small and dense, and 
 the serum is abundant. When coagulation is rapid, there is but 
 little contraction of the coagulum, an imperfect separation of the 
 serum, and the clot remains large, soft, and gelatinous. 
 
 It is well known to practical physicians that a similar relation 
 exists when the coagulation of the blood is hastened or retarded by 
 disease. In cases of lingering and exhausting illness, or in diseases 
 of a typhoid or exanthematous character, with much depression of 
 the vital powers, the blood coagulates rapidly and the clot remains 
 soft. In cases of active inflammatory disease, as pleurisy or pneu- 
 . monia, occurring in previously healthy subjects, the blood coagulates 
 slowly, and the clot becomes very firm. In every instance, the 
 blood which has coagulated liquefies again at th» commencement of 
 putrefaction. 
 
 The coagulation of the fibrin is not a commencement of organization. 
 The filaments already described, which show themselves in the clot 
 (Fig. 62), are not, properly speaking, organized fibres, and are en- 
 tirely different in their character from the fibres of areolar tissue, or 
 any other normal anatomical elements. They are simply the ulti- 
 
COAGULATION OF THE BLOOD. 229 
 
 mate form which fibrin assumes in coagulating, just as albumen 
 takes the form of granules under the same circumstances. The 
 coagulation of fibrin does not differ in character from that of any 
 Other organic substance; it merely differs in the physical conditions 
 which give rise to it. All the coagulable organic substances are 
 naturally fluid, and coagulate only when they are placed under 
 certain unusual conditions. But the particular conditions neces- 
 sary for coagulation vary with -the different organic . substances. 
 Thus albumen coagulates by the application of heat. Casein, which 
 is not affected by heat, coagulates by contact with an acid body. 
 Pancreatine, again, is coagulated by contact with sulphate of mag- 
 nesia, which has no eflect on albumen. So fibrin, which is naturally 
 fluid, and which remains fluid so long as it is circulating in the 
 vessels, coagulates when it is withdrawn from them and brought in 
 contact with unnatural surfaces. Its coagulation, therefore, is no 
 more "spontaneous," properly speaking, than that of any other 
 organic substance. Still less does it indicate anything like organ- 
 ization, or even a commencement of it. On the contrary, in the 
 natural process of nutrition, fibrin is assimilated by the tissues 
 and takes part in their organization, only when it is absorbed by 
 them from the bloodvessels in a fluid form. As soon as it is once 
 coagulated by any means, it passes into an unnatural condition, and 
 must be again liquefied and absorbed into the blood before it can 
 be assimilated. 
 
 As the fibrin, therefore, is maintained in its natural condition of 
 fluidity by the movement of the circulating blood in the interior of 
 the vessels, anything which interferes with this circulation will in- 
 duce its coagulation. If a ligature be placed upon an artery in the 
 living subject, the blood which stagnates above the ligature coagu- 
 lates, just as it would do if entirely removed from the circulation. 
 If the vessel be ruptured or lacerated, the blood which escapes from 
 it into the areolar tissue coagulates, because here also it is with- 
 drawn from the circulation. It coagulates also in the interior of 
 the vessels after death owing to the same cause, viz : stoppage of 
 the circulation. During the last moments of life, when the flow of 
 blood through the cavities of the heart is impeded, the fibrin often 
 coagulates, in greater or less abundance, upon the moving chordae 
 tendinesB and the edges of the valves, just as it would do if with- 
 drawn from the body and stirred with a bundle of twigs. In every 
 instance, the coagulation of the fibrin is a morbid phenomenon, de- 
 pendent on the cessation or disturbance of the circulation. 
 
230 
 
 THE BLOOD. 
 
 Fig. 65. 
 
 Vertical section of a Re- 
 cent CoAGULUM, showing 
 the greater accumulation of 
 blood-globules at the bottom. 
 
 If the blood be allowed to coagulate in a bowl, and the clot be 
 then divided by a vertical section, it will be seen that its lower 
 portion is softer and of a deeper red than the upper. (Fig. 65.) 
 This is because the globules, which are of 
 greater specific gravity than the plasma, sink 
 toward the bottom of the vessel before coagu- 
 lation takes place, and accumulate in the 
 lower portion of the blood. This deposit of 
 the globules, however, is only partial; be- 
 cause they are soon fixed and entangled by 
 the solid mass of the coagulum, and are thus 
 retained in the position in which they hap- 
 pen to be at the moment that coagulation 
 takes place. 
 
 If the coagulation, however, be delayed 
 longer than usual, or if the globules sink more rapidly than is cus- 
 tomary, they will have time to subside entirely from the upper por^ 
 tion of the blood, leaving a layer at the surface which is composed 
 of plasma alone. When coagulation then takes place, this upper 
 portion solidifies at the same time with the rest, and the clot then 
 presents two different portions, viz.j a lower portion of a dark red 
 color, in which the globules are accumulated, and an upper portion 
 from which the globules have subsided, and which is of a grayish 
 white color and partially transparent. This whitish layer on the 
 surface of the clot is termed the " buffy coat ;" and the blood pre- 
 senting it is said to be " buffed." It is an appearance which often 
 presents itself in cases of acute inflammatory disease, in which the 
 coagulation of the blood is unusually retarded. 
 
 When a clot with a buffy coat begins to contract, the contrac- 
 tion takes place perfectly well in its upper 
 portion, but in the lower part it is impeded 
 by the presence of the globules which have 
 accumulated in large quantity at the bottom 
 of the clot. While the lower part of the 
 coagulum, therefore, remains voluminous, 
 and hardly separates from the sides of the 
 vessel, its upper colorless portion diminishes 
 very much in size ; and as its edges separate 
 from the sides of the vessel, they curl over 
 toward each other, so that the upper surface 
 of the clot becomes more or less excavated or cup-shaped. (Fig. 66.) 
 
 Bowl of COAatJIjATRD 
 
 Blood, showing the clot 
 buffed and cupped. 
 
COAGOLATIOX OF THE BLOOD. 231 
 
 The blood is then said to be "buffed and cupped." These appear- 
 ances do not present themselves under ordinary conditions, but only 
 when the blood has become altered by disease. 
 
 The entire quantity of blood existing in the body has never been 
 very accurately ascertained. It is not possible to extract the whole 
 of it by opening the large vessels, since a certain portion will always 
 remain in the cavities of the heart, in the veins, and in the capil- 
 laries of the head and abdominal organs. The other methods 
 . which have, been practised or proposed from time to time are all 
 liable to some practical objection. We have accordingly only 
 been able thus far to ascertain the minimum quantity of blood 
 existing in the body. Weber and Lehmann' ascertained as nearly 
 as possible the quantity of blood in two criminals who suftered 
 death by decapitation ; in both of which cases they obtained essen- 
 tially similar results. The body weighed before decapitation 133 
 pounds avoirdupois. The blood which escaped from the vessels at 
 the time of decapitation amounted to 12.27 pounds. In order to 
 estimate the quantity of blood which remained in the vessels, the 
 experimenters then injected the arteries of the head and trunk with 
 water, collected the watery fluid as it escaped from the veins, and 
 ascertained how much solid matter it held in solution. This 
 amounted to 477.22 grains, which corresponded to 4.38 pounds of 
 blood. The result of the experiment is therefore as follows : — 
 
 Blood which escaped from the vessels 12.27 pounds. 
 
 " remained in the body ..... 4.38 " 
 
 Whole quantity of blood in the living body, 16.65 
 
 The weight of the blood, then, in proportion to the entire weight 
 of the body, was as 1 : 8 ; and the body of a healthy man, weighing 
 140 pounds, will therefore contain on the average at least 17J 
 pounds of blood. 
 
 ■ Physiological Chemistry, vol. i. p. 638. 
 
232 BESPIBATIOlir. 
 
 CHAPTER XII. 
 
 RESPIRATION. 
 
 The blood as it circulates in the arterial system has a bright 
 scariet color ; but as it passes through the capillaries it gradually 
 becomes darker, and on its arrival in the veins its color is a deep 
 purple, and in some parts of the body nearly black. There are, 
 therefore, two kinds of blood in the body ; arterial blood, which is 
 of a bright color, and venous blood, which is dark. Now it is found 
 that the dark-colored venous blood, which has been contaminated 
 by passing through the capillaries, is unfit for further circulation. 
 It is incapable, in this state, of supplying the organs with their 
 healthy stimulus and nutrition, and has become, on the contrary, 
 deleterious and poisonous. It is accordingly carried back to the 
 heart by the veins, and thence sent to the lungs, where it is recon- 
 verted into arterial blood. The process by which the venous blood 
 is thus arterialized and renovated, is known as the process of 
 respiration. 
 
 This process takes place very actively in the higher animals, and 
 probably does so to a greater or less extent in all animals without 
 exception. Its essential conditions are that the circulating fluid 
 should be exposed to the influence of atmospheric air, or of an 
 aerated fluid ; that is, of a fluid holding atmospheric air or oxygen 
 in solution. The respiratory apparatus consists essentially of a 
 moist and permeable animal membraije, the respiratory membrane, 
 with the bloodvessels on one side of it, and the air or aerated fluid 
 on the other. The blood and the air, consequently, do not come in 
 direct contact with each other, but absorption and exhalation take 
 place from one to the other through the thin membrane which lies 
 between. 
 
 The special anatomical arrangement of the respiratory apparatus 
 differs in different species of animals. In most of those inhabiting 
 the water, the respiratory organs have the form of gills or brcmchise ; 
 that is, delicate filamentous prolongations of some part of the 
 
EBSPIKATION. 233 
 
 integument or mucous membranes, -which contain an abundant 
 supply of bloodvessels, and which hang .out freely into the sur- 
 rounding water. In many kinds of aquatic lizards, as, for exam- 
 ple, in menobranchus (Fig. 67), 
 there are upon each side of the '^' 
 
 neck three delicate feathery 
 tufts of thread-like prolonga- 
 tions from the mucous mem- 
 brane of the pharynx, which 
 pass out through fissures in 
 the side of the neck. Each 
 tuft is composed of a prin- 
 cipal stem, upon which the „ ^ ■., 
 
 vy.^u,! ou^ ii, ^^^ v.^ V- Head ahd Gills or Mehobbaxchij;!. 
 
 filaments are arranged in a , 
 
 pinnated form, like the plume upon >the shaft of a feather. Each 
 filament, when examined by itself, is seen to consist of a thin, rib- 
 bon-shaped fold of mucous membrane, in the interior of which 
 there is a plentiful network of minute bloodvessels. The dark 
 blood, as it comes into the filament from the brailchial artery, is 
 exposed to the influence of the water in which the filament is 
 bathed, and as it circulates through the capillary network of the 
 gills is reconverted into arterial blood. It is then carried away by 
 the branchial vein, and passes into the general current of the cir- 
 culation. The apparatus is further supplied with a cartilaginous 
 framework, and a set of muscles by which the gills are gently waved 
 about in the surrounding water, and constantly brought into con- 
 tact with fresh portions of the aerated fluid. 
 
 Most of the aquatic animals breathe by gills similar in all their 
 essential characters to those described above. In terrestrial and 
 air-breathing animals, however, the respiratory apparatus is situated 
 internally. In them, the air is made to penetrate into the interior 
 of the body, into certain cavities or sacs called the lungs, which 
 are lined with a vascular mucous membrane. In the salamanders, 
 for example, which, though aquatic in their habits, are air-breathing . 
 animals, the lungs are two long cylindrical sacs, running nearly the 
 entire length of the body, commencing anteriorly by a communi- 
 cation with the pharynx, and terminating by rounded extremities 
 at the posterior part of the abdomen. These lungs, or air-sacs, 
 have a smooth internal surface ; and the blood which circulates 
 through their vessels is arterialized by exposure to the air contained 
 in their cavities. The air is forced into the lungs by a kind of 
 
234 
 
 BKSPIBATION. 
 
 swallowing movement, and is after a time regurgitated and dis- 
 charged, in order to make room for a fresh supply. 
 
 In frogs, turtles, serpents, &c., the structure of the lung, is a 
 little more complicated, since respiration is more active in these 
 animals, and a more perfect organ is requisite to accomplish the 
 arterialization of the blood. In these animals, the cavity of the 
 lung, instead of being simple,, is divided by incomplete partitions 
 into a number of smaller cavities or " cells." The cells all commu- 
 nicate with the central pulmonary cavity ; and the partitions^ which 
 join each other at various angles, are all composed of thin, pro- 
 jecting folds of the lining membrane, with bloodvessels ramifying 
 between them. (Fig. 68.) By this arrangement, 
 the extent of surface presented to the air by the 
 pulmonary memba-ane is much increased, and the. 
 arterialization of the blood takes place with a 
 corresponding degree of rapidity. • 
 
 In the human subject, and in all the warm- 
 blooded quadrupeds, the lungs are constructed 
 on a plan which is essentially similar to the 
 above, and which differs from it only in the 
 greater extent to which the pulmonary cavity is 
 subdivided, and the surface of the respiratory 
 membrane increased. The respiratory apparatus 
 (Fig. 69) commences with the larynx, which 
 communicates with the pharynx at the upper part of the neck. 
 Then follows the trachea, a membranous tube with cartilaginous 
 rings ; which, upon its entrance into the chest, divides into the right 
 and left bronchus. These again divide successively, into secondary 
 and tertiary bronchi ; the subdivision continuing, while the bron- 
 chial tubes grow smaller and more numerous, and separate con- 
 stantly from each other. As they diminish in size, the tubes grow 
 more delicate in structure, and the cartilaginous rings and plates 
 disappear from their walls. They are finally reduced, according to 
 Kolliker, to the size of ^^ of an inch in diameter ; arid are com- 
 posed only of a thin mucous membrane, lined with pavement epi- 
 thelium, which rests upon an elastic fibrous layer. They are then 
 known as the " ultimate bronchial tubes." 
 
 Each ultimate bronchial tube terminates in a division or islet of 
 the pulmonary tissue, about j'j of an inch in diameter, which is 
 termed a " pulmonary lobule." Each pulmonary lobule resembles 
 m its structure the entire frog's lung in miniature. It consists of a 
 
 LnNG OF Fkoo, 
 showing Ub internal sur- 
 face. 
 
RESPIRATION". 
 Fig. 69. 
 
 235 
 
 Fig. 70. 
 
 HtTMAN Lartnx, Trachea, Bbonchi, and Lungs; Bliowiug the niniiQcaiioD of Ilia 
 bronchi, and the dlvUion of the lungs into lobules. 
 
 vascular membrane inclosing a cavity; whicli cavity is divided 
 into a large number of secondary compartments by thin septa or 
 partitions, •whicli project from its internal surface. (Fig. 70.) These 
 secondary cavities are the "pulmonary 
 cells," or " vesicles." Each vesicle is about 
 7^^ of an inch in diameter ; and is covered 
 on its exterior with a close network of ca- 
 pillary bloodvessels, which dip down into 
 the spaces between the adjacent vesicles, and 
 expose in this way a double surface to the 
 air, which is contained in their cavities. 
 Between the vesicles, and in the interstices 
 between the lobules, there is a large quan- 
 tity of yellow elastic tissue, which gives 
 firmness and resiliency to the pulmonary 
 structure. The pulmonary vesicles, accord- 
 ing to the observations of Kdlliker, are J.l\'::,''^r,\L:LlZ 
 lined everywhere with a layer of pavement . "'•'"' '"h*- '■ cavity of lobuie. 
 
 .., ,. .. .,1 .1 . • .1 ' e. e. 0. Pulmonary cells, or vesi- 
 
 epithelium, continuous with that in the cies. 
 
2^36 EESPIRATION, 
 
 ultimate bronchial tubes. The whole extent of respiratory sur- 
 face in both lungs has been calculated by Lieberkuhn^ at fourteen 
 hundred square feet. It is plainly impossible to make a precisely 
 accurate calculation of this extent ; but there is every reason to 
 believe that the estimate adopted by Lieberkiihn, regarded as 
 approximative, ■ is not by any means an exaggerated one. The 
 great multiplication of the minute pulmonary vesicles, and of the 
 partitions between them, must evidently increase to an extraor- 
 dinary degree the extent of surface over which the blood, spread 
 out in a thin layer, is exposed to the action of the <iir. These 
 anatomical conditions are, therefore, the most favorable for its rapid 
 and complete arterialization. 
 
 Respiratory Movements of the Chest. — The air which is con- 
 tained in the pulmonary lobules and vesicles becomes rapidly vitiated 
 in the process of respiration, and requires therefore to be expelled 
 and replaced by a fresh supply. This exchange or renovation of 
 the air is eflPected by alternate movements of the chest, of expansion 
 and collapse, which are termed the " respiratory movements of the 
 chest." The expansion of the chest is effected by two sets of mus- 
 cles, viz., first, the diaphragm, and, second, the intercostals. While 
 the diaphragm is in a state of relaxation, it has the form of a vaulted 
 partition between the thorax and abdomen, the edges of which are 
 attached to the inferior extremity of the sternum, the inferior 
 costal cartilages, the borders of the lower ribs and the bodies of 
 the lumbar vertebrae, while its convexity rises high into the cavity 
 of the chest, as far as the level of the fifth rib. When the fibres 
 of the diaphragm contract, their curvature is necessarily dimi- 
 nished; and they approximate a straight line, exactly in proportion 
 to the extent of their contraction. Consequently, the entire con- 
 vexity of the diaphragm is diminished in the same proportion, 
 and it descends toward the abdomen, enlarging the cavity of the 
 chest from above downward. (Fig. 71.) At the same time the inter- 
 costal muscles.enlarge it in a lateral direction. For the ribs, arti- 
 culated behind with the bodies of the vertebrae, and joined in front 
 to th& sternum by the flexible and elastic costal cartilages, are so 
 arranged that, in a position of rest, their convexities look obliquely 
 outward and downward. When the movement of inspiration is 
 about to commence, the first rib is fixed by the contraction of the 
 
 ' In Simon's Chemistry of Man, Pliilada ed., 1846, p. 109. 
 
RESPIRATORY MOVEMENTS (JF THE CHEST. 
 
 237 
 
 Fig. 71. 
 
 scaleni muscles, and the intercostal muscles then contracting simul- 
 taneously, the ribs are drawn upward. In this movement, as each 
 rib rotates upon its articulation with the 
 spinal column at one extremity, and with 
 the sternum at the other, its convexity is 
 necessarily carried outward at the same 
 time that it is drawn upward, and the pa- 
 rietes of the chest are, therefore, expanded 
 laterally. Jhe sternum itself rises slightly 
 with the same movement, and enlarges to 
 some extent the antero-posterior diameter 
 of the thorax. By the simultaneous action, 
 therefore, of the diaphragm which descends, 
 and of the intercostal muscles which' lift 
 the ribs and the sternum, the cavity of the 
 chest is expanded in every direction^ and 
 the air passes inward, through the trachea 
 and bronchial tubes, by the simple force of 
 aspiration. 
 
 After the movement of inspiration is ac- 
 complished, and the lungs are filled with 
 air, the diaphragm and intercostal muscles 
 relax, and a movement of expiration takes 
 place, by which the chest is partially col- 
 lapsed, and a portion of the air contained 
 in the pulmonary cavity expelled. The 
 movement of expiration is entirely a passive 
 one, and is accomplished by the action of 
 three different forces. First, the abdominal 
 organs, which have been pushed out of their 
 usual position by the descent of the diaphragm, fall backward by 
 their own weight and carry upward the relaxed diaphragm before 
 them. Secondly, the costal cartilages, which are slightly twisted 
 out of shape when the ribs are drawn upward, resume their natural 
 position as soon as the "muscles are relaxed, and, drawing the ribs 
 down again, compress the sides of the chest. Thirdly, the pul- 
 monary tissue, as we have already remarked, is abundantly sup- 
 plied with yellow elastic fibres, which retract by virtue of their 
 own elasticity, in every part of the lungs, after they have been 
 forcibly distended, and, compressing the pulmonary vesicles, drive 
 out a portion of the air which they contained. By the constant 
 
 DrAGSAU ILLTTSTRATIXO 
 THE KESPIRATORT MOVE- 
 MENTS. — a. Cavity of tlie chest. 
 b. Diaphragm. The dark oat- 
 liaes show the fignre of the chest 
 when collapsed ; the dotted lines 
 show the same when expanded. 
 
238 'EESPIBATION. 
 
 recurrence of these alternating movements of inspiration and expi- 
 ration, fresh portions of air are constantly introduceji, into and 
 expelled from the chest. 
 
 The average quantity of atmospheric air, taken into and dis- 
 charged from the lungs with each respiratory movement, is, ac- 
 cording to the results of various observers, twenty cubic inches. At 
 eighteen respirations per minute, this amounts to 360 cubic inches 
 ofair inspired per minute, 21,600 cubic inches per hour, and 518,400 
 cubic inches per day. But as, the movements of respiration are 
 increased both in extent and rapidity by every muscular exertion, 
 the entire quantity of air daily used in respiration is not less than 
 600,000 cubic inches, or 350 cubic feet. 
 
 The whole of the air in the chest, however, is not changed at each 
 movement of respiration. On the contrary, a very considerable 
 quantity remains in the pulmonary cavity after the most complete 
 expiration ; and even after the lungs have been removed froni the 
 chest, they still contain a large quantity of air which cannot be 
 entirely displaced by any violence short of disintegrating and dis- 
 organizing the pulmonary tissue. It is evident, therefore, that only 
 a comparatively small portion of the air in the lungs passes in and 
 out with each respiratory movement ; a,nd it will require several 
 successive respirations before all the aii" in the chest can be entirely 
 changed. It has not been possible to ascertain with certainty the 
 exact proportion in volume which exists between the air which is 
 alternately inspired and expired, or "tidal" air, and that which 
 remains constantly in the chest, or " residual" air, as it is called. 
 It has been estimated, however, by Dr. Carpenter,' from the reports 
 of various observers, that the volume of inspired and expired air 
 varies from 10 to 13 per cent, of the entire quantity contained in 
 the chest. If this estimate be correct, it will require from eight to 
 ten respirations to change the whole quantity of aii* in the cavity 
 of the chest. 
 
 It is evident, however, from the foregoing, that the inspiratory 
 and expiratory movements of the chesfr cannot be sufScient to 
 change the air at all in the pulmonary lobules and vesicles. The 
 air which is drawn in with each inspiration penetrates only into 
 the trachea and -bronchial tubes, until it occupies the place of that 
 which was driven out by the last expiration. By the ordinary 
 respiratory movements, therefore, only that small portion of the 
 
 ' Human Physiology, Philada. ed., 1855, p. 300. 
 
RESPIRATORY MOVEMENTS OP THE GLOTTIS. 239 
 
 air lying nearest the exterior, in the trachea and large bronchi, 
 would fluctuate backward and forward, without ever penetrating 
 into the deeper parts of the lung, were there no other means pro- 
 vided for its renovation. There are, however, two other forces in 
 play for this purpose. The first of these is the diffusive power of 
 the gases themselves. The air remaining in the deeper parts of 
 the chest is richer in carbonic acid and poorer in oxygen than that 
 which has been recently inspired ; and by the laws of gaseous dif- 
 fusion there must -be a constant interchange of these gases between 
 the pulmonary vesicles and the trachea^ tending to mix them 
 equally in all parts of the lung. This mutual diffusion and inter- 
 mixture of the gases will therefore tend to renovate, partially at 
 least, the air in the pulmonary lobules and vesicles. Secondly, the 
 trachea and bronchial tubes, down to those even of the smallest 
 size, are lined with a mucous membrane which is covered with 
 ciliated epithelium. The- movement of those cilia is found to be 
 directed always from below upward; and, like ciliary motion 
 wherever it occurs, it has the. effect of producing a current in the 
 same direction, in the fluids covering the mucous membrane. The 
 air in the tubes must. partici- 
 pate, to a certain extent, in Fig. 72. 
 this current, and a double 
 stream of air therefore is estab- 
 lished in each bronchial tube ; 
 one current passing from with- 
 in outward along the walls of 
 the tube, and a return current 
 passing from without inward, 
 
 ^ ° , Shall BkonchialTude, snowing outward 
 
 along the central part of its and inward cnrrent, produced by ciliary motion. 
 
 cavity. (Fig. . 72.) By this 
 
 means a kind of aerial circulation is constantly maintained in the 
 interior of the bronchial tubes ; which, combined with the mutual 
 diffusion of the gases and the alternate expansion and collapse of 
 the chest, effectually accomplishes the renovation of the air contained 
 in all parts of the pulmonary cavity. 
 
 Respiratory Movements of the Glottis. — Beside the move- 
 ments of expansion and collapse already described, belonging to 
 the chest, there are similar respiratory movements which take place 
 in the larynx. If the respiratory passages be examined after death, 
 in the state of collapse in which they are usually found, it will be 
 
210 
 
 BESPIRATION. 
 
 noticed that the opening of the glottis is very much smaller than 
 the cavity of the trachea below. The glottis itself presents the 
 appearance of a narrow chink, while the passage for the inspired 
 air widens in the lower part of the larynx, and in the trachea 
 constitutes a spacious tube, nearly cylindrical in shape, and over 
 half an inch in diameter. We have found, for instance, that in 
 the human subject the space included between the vocal chords 
 has an area of only 0.15 to 0.17 square inch ; while the calibre 
 of the trachea in the middle of its length is '0.45 square inch. 
 This disproportion, however, which is so evident after death, does 
 not exist during life. While respiration is going on, there is a 
 constant and regular movement of the vocal chords, synchronous 
 with the inspiratory and expiratory movements of the chest, by 
 
 Fig. 73. 
 
 Fig. 74. 
 
 Hdhan Larynx, viewed from above 
 iu its ordinary post-mortem cooditLoa. — a. 
 Vocal chords. &. Thyroid cartilage, ce. Ary- 
 tenoid cartilages, o. Opening of theglottis. 
 
 The fame, with the glottis opened by 
 separation of the vocal chords. — a. Vocal 
 chords. &. Thyroid cartilage, cc. Aryte- 
 noid cartilages, o. Opening of the glottis. 
 
 which the size of the glottis is alternately enlarged and diminished. 
 At every inspiration, the glottis opens and allows the air to pass 
 freely into the trachea ; at every expiration it collapses, and the 
 air is driven, out through it from below. These movements are 
 called the " respiratory movements of the glottis." They correspond 
 in every respect with those of the chest, and are excited or retarded 
 by similar causes. Whenever the general movements of respiration 
 are hurried and labored, those of the glottis become accelerated'and 
 increased in intensity at the same time ; p,nd when the movements 
 of the chest are slower or fainter than usual, owing to debility, 
 coma, or the like, those of the glottis are diminished in the same 
 proportion. 
 
CHANGES IN THE AIB DUBING KESPIKATION. 
 
 241 
 
 Fig. 75. 
 
 HrHAN LARTNX, POSTERTOa 
 
 VIEW. — a. Thyroid cartilage. &. Epi- 
 glottis, cc. Arytenoid cartilageR. d. 
 Cricoid cartilage, ee, FoBterior crico- 
 arytenoid muscles. /. Trachea. 
 
 In the respiratory motions of the glottis, as in those of the chest, 
 the movement of inspiration is an active one, and that of expira- 
 tion passive. In inspiration, the glottis 
 is opened by contraction of the posterior 
 crico-arytenoid muscles. (Fig- 75.) 
 These muscles originate from the pos- 
 terior surface of the cricoid cartilage, 
 near the median line ; and their fibres, 
 running upward and outward, are in- 
 serted into the external angle of the 
 arytenoid cartilages. By the contrac- 
 tion of these muscles, during the move- 
 ment of inspiration, the arytenoid car- 
 tilaiges are rotated upon their articula- 
 tions with the cricoid, so that their 
 anterior extremities are carried outward, 
 and the vocal chords stretched and sepa- 
 rate from each other. (Fig. 74.) In this 
 way, the size of the glottis may be in- 
 creased from 0.15 to 0.27 square inch. 
 
 In expiration, the posterior crico- 
 arytenoid muscles are relaxed, and the elasticity of the vocal chords, 
 brings them back to their former position. 
 
 The motions of respiration consist, therefore, of two sets of move- 
 ments : viz., those of the chest and those of the glottis. These move- 
 ments, in the natural condition, correspond with each other both in 
 time and intensity. It is at the same time and by the same nervous 
 influence, that the chest expands to inhale the air, while the glottis 
 opens to admit it ; and in expiration, the muscles of both chest and 
 glottis are relaxed ; while the elasticity of the tissues, by a kind of 
 passive contraction, restores the parts to their original condition. 
 
 Changes in the Air during Respiration. — The atmospheric 
 air, as it is drawn into the cavity of the lungs, is a mixture of oxy- 
 gen and nitrogen, in the proportion of about 21 per cent., by volume, 
 of oxygen, to 79 per cent, of nitrogen. It also contains about one- 
 twentieth per cent, of carbonic acid, a varying quantity of watery 
 vapor, and some traces of ammonia. The last named ingredients, 
 however, are quite insignificant in comparison with the oxygen and 
 nitrogen, which form the principal parts of its mass. 
 
 If collected and examined, after passing through the lungs, the 
 16 
 
242 BESPIEATIOlir. 
 
 air is found to iave become altered in the following essential par- 
 ticulars, viz : — 
 
 1st. It lias lost oxygen. 
 
 2d. It has gained carbonic acid. And 
 
 3d. It has absorbed the vapor of water. 
 
 Beside the two latter substances, there are also exhaled with the 
 expired air a very small quantity of nitrogen, over and above what 
 was taken in with inspiration, and a little animal matter in a 
 gaseous form, which communicates a slight but peculiar odor to 
 the breath. The air is also somewhat elevated in temperature, by 
 contact with the pulmonary mucous membrane. 
 
 The watery vapor, which is exhaled with the breath, is given off 
 by the pulmonary mucous membrane, by which it is absorbed from 
 the blood. At ordinary temperatures it is transparent and invisi- 
 ble ; but in cold weather it becomes partly condensed, on leaving 
 the lungs, and appears under the form of a cloudy vapor discharged 
 with the breath. According to the researches of yalentin, the 
 average quantity of water, exhaled daily from the lungs, is 8100 
 grains, or about IJ pounds ayoirdupois. 
 
 By far the most important part, however, of the changes suffered 
 by the air in respiration, consists in its loss of oxygen, and its 
 a&sorption of carbonic acid. 
 
 According to the researches of Valentin, Vierordt, Begnault and 
 Eeiset, &c., the air loses during respiration, on an average, five per 
 cent, of its volume of oxygen. At each inspiration, , therefore, 
 about one cubic inch of oxygen is removed from the air and ab- 
 sorbed by the blood ; and as we have seen that the entire daily 
 quantity of air used in respiration is about 350 cubic feet, the entire 
 quantity of oxygen thus consumed in twenty-four hours is not less 
 than seventeen and a half cubic feet. This is, by weight, 7,134 
 grains, or a little over one pound avoirdupois. 
 
 The oxygen which thus disappears from the inspired air is not 
 entirely replaced in .the carbonic acid exhaled ; that is, there is less 
 oxygen in the carbonic acid which is returned to the air by expira- 
 tion than has been lost during inspiration. 
 
 ■ There is even more oxygen absorbed than is given off again in 
 both the carbonic acid and aqueous vapor together, which are 
 exhaled from the lungs.^ There is, then, a constant disappearance 
 of oxygen from the air used in respiration, and a constant accumu- 
 lation of carbonic acid. 
 
 ' Lehmann's Physiological Chemistry, Philada. ed., vol. ii. p. 432. 
 
CHANGES IN THE BLOOD DURING EESPIEATION. 243 
 
 The proportion of oxygen which disappears in the interior of the 
 body, over and above that which is returned in the breath under 
 the form of carbonic acid, varies in different kinds of animals. In 
 the herbivora, it is about 10 per cent, of the whole amount of oxy- 
 gen inspired ; in the camivora, 20 or 25 per cent, and even more. 
 It is a Very remarkable fact, also, and an important one, as regards 
 the theory of respiration, that, in the same animal, the proportion of 
 oxygen absorbed, to that of carbonic acid exhaled, varies according 
 to the quality of the food. In dogs, for instance, while fed on ani- 
 mal food, according to the experiments of Eegnault and Eeiset, 25 
 per cent, of the inspired oxygen disappeared in the body of the 
 animal; but when fed on starchy substances, all but 8 per cent, 
 reappeared in the expired carbonic acid. It is already evident, 
 therefore, from these facts, that the oxygen of the inspired air is 
 not altogether employed in the formation of carbonic acid. 
 
 Changes in the Blood dubing Eespibation. — If we pass from 
 the consideration of the changes produced in the air by respiration 
 to. those which take place in the blood during the same process, we 
 find, as might have been expected, that the latter correspond 
 inversely with the former. The blood, in passing through the 
 lungs, suffers the following alterations : — 
 
 1st. Its color is changed from venous to arterial. 
 
 2d. It absorbs oxygen. And 
 
 3d. It exhales carbonic acid and the vapor of water. 
 
 The interchange of gases, which takes place during respiration 
 between the air and the blood, is a simple phenomenon of absorp- 
 tion and exhalation. The inspired oxygen does not, as Lavoisier 
 once supposed, immediately combine with carbon in the lungs, and 
 return to the atmosphere under the form of carbonic acid. On the 
 contrary, almost the first fact of importance which has been estab- 
 lished by the examination of the blood in this respect is the fol- 
 lowing, viz : that carbonic acid exists ready -formed in the venoixs blood 
 before its entrance into the lungs ; and, on the other hand, that the 
 oxygen which is absorbed during respiration passes off in a free state 
 with the arterial blood. The real process, as it takes place in the 
 lung, is, therefore, for 'the most part, as foUows : The blood comes to 
 the lungs already charged with carbonic acid. In parsing through 
 the pulmonary capillaries, it is exposed to the influence of the air 
 in the cavity of the pulmonary cells, and a transudation of gases 
 takes place through the moist , animal membranes of the .lung. 
 
244 RiSSPIBATION. 
 
 Since the blood in tlie capillaries contains a larger proportion of 
 carbonic acid than the air in the air- vesicles, a portion of this gas 
 leaves the blood and passes out through the pulmonary membrane ; 
 while the oxygen, being more abundant in the air of the vesicles 
 than in the circulating fluid, passes inward at the same time, and is 
 condensed by the blood. 
 
 In this double phenomenon of exhalation and absorption, which 
 takes place in the lungs, both parts of the process are equally 
 necessary to life. It is essential for the constant activity and nutri- 
 tion of the tissues that they be steadily supplied with oxygen by the 
 blood ; and if this supply be cut of^ their functional activity ceases. 
 On the other hand, the carbonic acid which is produced in the body 
 by the processes of nutrition becomes a poisonous substance, if it 
 be allowed to collect in large quantity. Under ordinary circum- 
 stances, the carbonic acid is removed by exhalation through the 
 lungs as fast as it is produced in the interior of the body ; but if 
 respiration be suspended, or seriously impeded, since the production 
 of carbonic acid continues, while its elimination is prevented, it 
 accumulates in the blood and in the tissues, and terminates life in a 
 few moments, by a rapid deterioration of the circulating fluid, and 
 more particularly by its poisonous effect on the nervous system. 
 
 The deleterious effects of breathing in a confined space will 
 therefore very soon become apparent. As respiration goes on, the 
 oxygen of the air constantly diminishes, and the carbonic acid, 
 mingled with it by exhalation, increases in quantity. After a time 
 the air becomes .accordingly so poor in oxygen that, by that fact 
 alone, it is incapable of supporting life. At the same time, tlie 
 carbonic acid becomes so abundant in the air vesicles that it pre- 
 vents the escape of that which already exists in the blood ; and the 
 deleterious effect of its accumulation in the circulating fluid is 
 added to that produced by a diminished supply of oxygen. An 
 increased proportion of carbonic acid in the atmosphere is therefore 
 injurious in a similar manner, although there may be no diminution 
 of oxygen ; since by its presence it impedes the elimination of the 
 carbonic acid already formed in the blood, and induces the poison- 
 ous effects which result from its accumulation. 
 
 Examination of the blood shows furthermore that the interchange 
 of gases in the lungs is not complete but only partial in its extent. 
 It results from the experiments of Magendie, Magnus, and others, 
 that both oxygen and carbonic acid are contained in both venous 
 
CHANGES IN THE BLOOD DURING BESPIRATION. 245 
 
 and arterial blood. Magnus' found tliat the proportion of oxygen 
 to carbonic acid, by volume, in arterial blood was as 10 to 25 ; in 
 venous blood as 10 to 40. The venous blood, then, as it arrives at 
 the lungs, still retains a remnant of the oxygen which it had pre- 
 viously absorbed ; and in passing through the pulmonary capil- 
 laries it gives off only a part of the carbonic acid with which it has 
 become charged in the general circulation. 
 
 The oxygen and carbonic acid of the blood exist in a state of 
 solution in the circulating fluid, and not in a state of intimate chemi- 
 cal combiaation. This is shown by the fact that both of these 
 substances may be withdrawn from the blood by simple exhaustion 
 with an air-pump, or by a stream of any other indifferent gas, such 
 as hydrogen, which possesses suf&cient physical displacing power. 
 Magnus found* that freshly drawn arterial blood yielded by simple 
 agitation with carbonic acid more than 10 per cent, of its volume 
 of oxygen. The carbonic acid may also be expelled from venous 
 blood *by a current of pure oxygen, or of hydrogen, or, in great 
 measure, by simple agitation with atmospheric air. There is some 
 difSculty in determining, however, whether 'the .carbonic acid of 
 the blood be altogether in a free state, or whether it be partly in a 
 state of loose chemical combination with a base, under the form of 
 an alkaline bicarbonate. A solution of bicarbonate of soda itself • 
 will lose a portion of its carbonic acid, and become reduced to the 
 condition of a, carbonate by simple exhaustion under the air-pump, 
 or by agitation with pure hydrogen at the temperature of the body. 
 Lehmann has found' that after the expulsion of all the carbonic 
 acid removable by the air-pump and a current of hydrogen, there 
 still remains, ia ox's blood, 0.1628 per cent, of carbonate of soda ; 
 and he estimates that this' quantity is suf&cient to have retained all 
 the carbonic acid, previously given off, in the form of a bicarbonate. 
 It makes little or no difference, however, so far as regards the pro- 
 cess of respiration, whether the carbonic acid of the blood exist in 
 an entirely free state, or under the fornl of an alkaline bicarbonate; 
 since it may be readily removed from this combination, at the tem- 
 perature of the body, by contact with an indifferent gas. 
 
 The oxygen and carbonic acid of the blood are in solution prin- 
 cipally in the blood-ghbuks, and. not in the plasma. The researches 
 of Magnus have shown" that the blood holds in solution 2 J times 
 
 ' In Lehmann, op. cit., vol. i. p. 570. 
 
 « In Robin and Verdeil, op. oit., vol. il. p. 34. 
 
 ' Op. clt., vol i. p. 393. 
 
 * In Robin and Verdeil, op. oit., vol. ii. pp. 28—32. 
 
246 BESPIBATION. 
 
 as much oxygen as pure water could dissolve at the same tempera- 
 ture ; and that while the serum of the blood, separated from the 
 globules, exerts no more solvent power on oxygen than pure water, 
 defibrinated blood, that is, the serum and globules mixed, dissolves 
 quite as much oxygen as the fresh blood itself, ; The same thing is 
 true with regard to the carbonic acid. It is therefore the semi- 
 fluid blood-globules which retain these two gases in solution ; and 
 since the color of the blood depends entirely upon that, of the glo- 
 bules, it is easy to understand why the blood should alter its hue 
 from purple to scarlet in passing through the lungs, where the 
 globules give up carbonic acid, and absorb a fresh quantity of 
 oxygen. The above change may readily be produced outside the 
 body. If freshly drawn venous blood be shaken in a bottle with 
 pure oxygen, its color changes at once from purple to red ; and the 
 same change will take place, though more slowly, if the blood be 
 simply agitated with atmospheric air. It is for this reason that the 
 surface of defibrinated venous blood, and the external parts of a 
 dark-colored clot, exposed to the atmosphere, become rapidly red- 
 dened, while the interflal portions retain their original color. 
 
 The process of respiration, so far as we have considered it, con- 
 sists in an alternate interchange of carbonic acid and oxygen in the 
 blood of the general and pulmonary circulations. In the pulmonary 
 circulation, carbonic acid is given off and oxygen absorbed ; while 
 in the general circulation the oxygen gradually disappears, and is 
 replaced, in the venous blood, by carbonic acid. The oxygen which 
 thus disappears from the blood in the general circulation does not, 
 for the most part, enter into direct combination in the blood itself. 
 On the contrary, it exists there, as we have already stated, in the 
 form of a simple solution. It is absorbed, however, from the blood 
 of the capillary vessels, and becomes fixed in the substance of the 
 vascular tissues. The blood may be regarded, therefore, in this 
 respect, as a circulating fluid, destined to transport oxygen from the 
 lungs to the tissues ; for it is the tissues themselves which finally 
 appropriate the oxygen, and fix it in their substance. 
 
 The next important question which presents itself in the study 
 of the respiratory process relates to the origin of the carbonic add in 
 the venous blood. It was formerly supposed, when Lavoisier first 
 discovered the changes produced in the air by respiration, that the 
 production of the carbonic acid could be accounted for in a very 
 simple manner. It was thought to be produced in the lungs by a 
 
CHANGES IN THE BLOOD DUKING EESPIEATION. 247 
 
 direct union of the inspired oxygen with the carbon of the blood 
 in the pulmonary vessels. It was found afterward, however, that 
 this could not be the case ; since carbonic acid exists already formed 
 in the blood,^reviously to its entrance into the lungs. It was then 
 imagined that the oxidation of carbon, and the consequent produc- 
 tion of carbonic acid, tdok place in 'the capillaries of the general 
 circulation, since it could not be shown to take place.in the lungs, 
 nor between the lungs and the capillaries. The truth is, however, 
 that no direct evidence exists of such a direct oxidation taking 
 place anywhere. The formation of carbonic acid, as it is now 
 understood, takes place in three different modes : 1st, in the lungs ; 
 2d, in the blood ; and 3d, in the tissues. 
 
 First, in the lungs. There exists in the pulmonary tissue a pecu- 
 liar acid substance, first described by Verdeil' under the name of 
 " pneumic" or " pulmonic" acid. It is a crystallizable body, soluble 
 in water, which is produced in - the substance of the pulmonary 
 tissue by transformation of some of its other ingrfedients, in the 
 same manner as sugar is produced in the tissue of the liver. It is 
 on account of the presence of this substance that the fresh tissue of 
 the lung has usually an acid reaction to test-paper, and that it has 
 also the property, which has been noticed by several observers, of 
 decomposing the metallic cyanides, with the production of hydro- 
 cyanic acid ; a property not possessed by sections of areolar tissue, 
 the internal surface of the skin, &c. &c. When the blood, there- 
 fore, comes in contact with the pulmonary tissue, which is 
 permeated everywhere by pneumic acid in a soluble form, its 
 alkaline carbonates and bicarbonates, if any be present, are decom- 
 posed with the production on the one hand of the pneumates of 
 soda'and potassa, and on the other of free carbonic acid, which is 
 exhaled. M. Bernard has found" that if a solution of bicarbonate 
 of soda be rapidly injected into the jugular vein of a rabbit, it 
 becomes decomposed in the lungs with so rapid a development of 
 carbonic acid, that -the gas accumulates in the pulmonary tissue, ■ 
 and even in the pulmonary vessels and the cavities of the heart, to 
 such an extent as to cause immediate death by stoppage of the 
 circulation. In the normal condition, however, the carbonates and 
 bicarbonates of the blood arrive so slowly at the lungs that as fast 
 as they are decomposed there, the carbonic acid is readily exhaled 
 by expiration, and produces no deleterious effect on the circulation. 
 
 ' Robin and Verdeil, op. cit., rol. ii. p. 460. 
 » Archives Gto. de Med., xri. 222. 
 
248 EESPIEATION. 
 
 Secondly, in the blood. There is little doubt, although the fact has 
 not been directly proved, that some of the oxygen definitely dis- 
 appears, and some of the carbonic acid is also formed, in the sub- 
 stance of the blood-globules during their circulation" Since these 
 globules are anatomical elements, and since they undoubtedly go 
 through with nutritive processes analogofis to those which take 
 place in the elements of the solid tissues, there is every reason for 
 believing that they also require oxygen for their support, and that 
 they produce carbonic acid as one of the results of their interstitial 
 decomposition. While the oxygen and carbonic acid, therefore, 
 contained in the globules, are for the most part transported by 
 these bodies from the lungs to the tissues, and from the tissues back 
 again to the lungs, they probably take part, also, to a certain extent, 
 in the nutrition of the blood-globules themselves. 
 
 Thirdly, in the tissues. This is by far the most important source 
 of the carbonic acid in the blood. From the experiments of Spal- 
 lanz^ni, W. Edwards, Marchand and others, the following very 
 important fact has been established, viz., that every organized tissue. 
 and even every organic substance, when in a recent condition, has the 
 power of absorbing oxygen amd of exhaling carbonic acid. Gr. Liebig, 
 for example," foun'd that frog's muscles, recently prepared and com- 
 pletely freed from blood, continued to absorb oxygen and discharge 
 carbonic acid. Similar experiments with other tissues have led 
 to a similar result. The interchange of gases, therefore, in the 
 process of respiration, takes place mostly in the tissues themselves. 
 It is in their substance that the oxygen becomes fixed and assimi- 
 lated, and that the carbonic acid takes its origin. As the blood in 
 the lungs gives up its carbonic acid to the air, and absorbs oxygen 
 from it, so in the general circulation it gives up its oxygen to the 
 tissues, and absorbs from them carbonic acid. 
 
 We come lastly to examine the exact mode by which the car- 
 bonic acid originates in the animal tissues. Investigation shows 
 that even here it is not produced by a process of oxidation, or direct 
 union of oxygen with the carbon of the tissues, but in some other and more 
 indirect mode: This is proved by the fact that animals and fr^sh 
 animal tissues will continue to exhale carbonic acid in an atmo- 
 sphere of hydrogen or of nitrogen, or even when placed in a vacuum. 
 Marchand found* that frogs would live for from half an hour to an 
 hour in pure hydrogen gas ; and that during this time they exhaled 
 even more carbonic acid than in atmospheric air, owing probably 
 ' In Lehmann, op. cit., vol. ii. p. 474. " Ibid., p. 442. 
 
CHANGES IN THE BLOOD DURING EBS^IBATION. 249 
 
 to the superior displacing power of hydrogen for carbonic acid. 
 For while 15,500 grains' weight of frogs exhaled about 1.13 grain 
 of carbonic acid per hour in atmospheric air, they exhaled during 
 the same time in pure hydrogen as much as 4.07 .grains. The same 
 observer found that frogs would recover on the admission of air 
 after remaining for nearly half an hour in a nearly complete 
 vacuum ; and that if they were killed by total abstraction of the 
 air, 15,500 grains' weight of the animals were found to have 
 eliminated 9.3 grains of carbonic acid. The exhalation of carbonic 
 acid by the tissues does not, therefore, depend directly upon the 
 access of free oxygen. It cannot go on, it is true, for an indefinite 
 time, any more than the other vital processes, without the presence 
 of oxygen. But it may continue long enough to show that the 
 carbonic acid exhaled is not a direct product of oxidation, but that 
 it originates, on the contrary, in all probability, by a decomposi- 
 tion of the organic ingredients of the tissues, resulting in the pro- 
 duction of oarbonic acid on the one hand, and of various other 
 substances on the other, with which we are not yet fiilly acquainted ; 
 in very much the same manner as the decomposition of sugar 
 during fermentation gives rise to alcohol on the one hand and to 
 carbonic acid on the other. The fermentation of sugar, when it has 
 once commenced, does not require the continued access of air. It 
 will go on in an atmosphere of hydrogen, or even when confined in 
 a close vessel over mercury; since' its carbonic acid is not produced 
 by direct oxidation, but by a decomposition of the sugar already 
 present. For the same reason, carbonic acid will continue to be 
 exhaled by living or recently dead animal tissues, even in an atmo- 
 sphere of hydrogen, or in a vacuum. 
 
 Carbonic acid makes its appearance, accordingly, in the tissues, 
 as one product of their decomposition in the nutritive ;^rocess. 
 From them it is taken up by the blood, either in simple solution or 
 in loose combination as a bicarbonate, transported by the circulation 
 to the lungs, and finally exhaled from the pulmonary mucous mem- 
 brane in a gaseous form. 
 
 The carbonic acid exhaled from the lungs should accordingly be 
 studied by itself as one of the products of the animal organism, and 
 its quantity ascertained in the different physiological conditions of 
 the body. The expired air usually contains about four per cent, of 
 its volume of carbonic acid. According to the researches of Vier- 
 ordt,' which are regarded as the most accurate on this subject, an 
 ' In Lehmami, op. fit., vol. ii. p. 439. 
 
250 _ BESPIEATION. 
 
 adult man gives off 1.62 cubic inch of carbonic acid with each nor- 
 mal expiration. This amounts to very nearly 1,150 cubic inches 
 per hour, or fifteen and a half cubic feet per day. This quantity 
 is, by weight, 10,740 grains; or a little over one pound and a half. 
 The amount of carbonic acid exhaled, however, varies from time to 
 time, according to many different circumstances ; so that no such 
 estimate can represent correctly its quantity at all times. These 
 variations have been very fully investigated by Andral and Gavar- 
 ret,' who found that the principal conditions modifying the amount 
 of this gas produced were age, sex, constitution and development. 
 The variations were very marked in different individuals, notwith- 
 standing that the experiments were made at the same period of the 
 day, and with the suligect as nearly as possible in the same condi- 
 tion. Thus they found that the quantity of carbonic acid exhaled 
 per hour in five different individuals was as follows : — 
 
 Qdahtitt op Carbouio Acid pee houk. 
 
 In subject No. 1 1207 cubic inches. 
 
 " " " 2 . . . . . 970 " " 
 
 " •' " 3 1250 " «. 
 
 •' " « 4 1250 « « 
 
 " " « 5 1591 " 
 
 With regard to the difference produced by age, it was found that 
 &om the period of eight years up to puberty the. quantity of car- 
 bonic acid increases constantly with the age. Thus a boy of eight 
 years exhales, on the average, 564 cubic inches per hour; while a 
 boy of fifteen years exhales 981 cubic inches in the same time. 
 Boys exhale during this period more carbonic acid than girls of the 
 same age. In males this augmentation of the quantity of carbonic 
 . acid continues till the twenty -fifth or thirtieth year, when it reaches, 
 on the, average, 1398 cubic inches per hour. Its quantity then 
 remains stationary for ten or fifteen years ; then diminishes slightly 
 from the fortieth to the sixtieth year ; and after sixty years dimi- 
 nishes in a marked degree, so that it may fall s(S low as 1038 cubic 
 inches. In one superannuated person, 102 years of age, Andral 
 and Gravarret found the hourly quantity of carbonic acid to be 
 only 665 cubic inches. 
 
 In women, the increase of carbonic acid ceases at the period of 
 puberty ; and its production then remains constant until the cessa- 
 tion of menstruation, about the fortieth or forty-fifth year. At that 
 time it increases again until after fifty years, when it subsequently 
 
 ' Annales de Chimie et de Pharmacie, 1843, vol. viii. p. 129. 
 
CHANGES IN THE BLOOD DURING RSSPIBATION. 251 
 
 diminishes with the approach of old age, as in men. Pregnancy, 
 occurring at any time in the above period, immediately produces a 
 temporary incf ease in the quantity of carbonic acid. 
 
 The streugth of the constitution, and more particularly the deve- 
 lopment of the muicular system, was found to have a very great in- 
 , fluence in this respect ; increasing the quantity of carbonic acid 
 very much in proportion to the weight of the individual. The 
 largest production of carbonic acid observed was in a young man, 
 26 years of age, whose frame presented a remarkably vigorous and 
 athletic development, and who exhaled 1591 cubic inches per hour. 
 This large quantity of carbonic acid, moreover, in well developed 
 persons, is not owing simply to the size of the entire body, but 
 particularly to_ the development of the muscular system, since an 
 unusually large skeleton, or an abundant deposit of adipose tissue, 
 is not accompanied by any such increase of the carbonic acid. 
 
 Andral and Gavarret finally sum up the results of their investiga- 
 tions as follows : — 
 
 . 1. The quantity of carbonic acid exhaled from the lungs in a given 
 
 time varies with the age, the sex, and the constitution of the subject. 
 
 2. In the male, as well as in the female, the quantity of carbonic 
 
 acid varies aotording to the age ; and that independently of the 
 
 weight of the individual subjected to experiment. 
 
 S). During all the periods of life, from that of eight years up to 
 the most advanced age, the male and female may be distinguished 
 by the different quantities of carbonic acid which they exhale in a 
 given time. Other things being equal, the male exhales always a 
 larger quantity than the female. This difference is particularly 
 marked between the ages of l6 and 40 years, during which period 
 the male usually exhales twice as much carbonic acid as the female. 
 
 4. In the male, the quantity of carbonic acid increases constantly 
 from eight to thirty years ; and the rate of this increase undergoes 
 a rapid augmentation at the period of puberty. Beyond thirty 
 years the exhalation of carbonic acid begins to decrease, and its 
 diminution is more marked as the individual approaches extreme 
 old age, so that near the termination of life, the quantity of carbonic 
 acid produced may be no greater than at the age of ten years. 
 
 5. In the female, the exhalation of carbonic acid increases accord- 
 ing to the same law as in the male, from the age of eight years 
 until puberty. But at the period of puberty, at the same time with 
 the appearance of menstruation, the exhalation of carbonic acid. 
 
252 BESPIBATION. 
 
 contrary to what happens in the male, ceases to increase ; and it 
 afterward remains stationary so long as the menstrual periods recur 
 with regularity. At the cessation of the menses, the quantity of 
 carbonic acid exhaled increases in a notable manner ; then it de- 
 creases again, as in the male, as the woman advances toward old age. 
 
 6. During the whole period of pregnancy, the exhalation of car- 
 bonic acid rises, for the time, to the same standard as in women 
 whose menses have ceased. 
 
 7. In both sexes, and at all ages, the quantity of carbonic acid is 
 greater as the constitution is stronger, and the muscular system 
 more fully developed. 
 
 Prof. Scharling, in a similar series of investigations,* found that 
 the quantity of carbonic acid exhaled was greater during the diges- 
 tion of food than in the fasting condition. It is greater, also, in the 
 waking state than during sleep ;, and in a state of activity than in 
 one of quietude. It is diminished, also, by fatigue, and by most 
 conditions which interfere with perfect health, . 
 
 The process of respiration is not altogether confined to the lungs, 
 but the interchange of gases takes place, also, to some extent through 
 the skin. It has been found, by inclosing one of tiie limbs in an 
 air-tight case, that the air in which it is confined loses oxygen and 
 gains in carbonic acid. By an experiment of this sort, performed Jjy 
 Prof. Scharling,^ it was ascertained that the carbonic acid given off 
 from the whole cutaneous surface, in the human subject, is from 
 one-sixtieth to one-thirtieth of that discharged during the same 
 period from the lungs. In the true amphibious animals, that is, 
 those which breathe by lungs, and can yet remain nnder water for 
 an indefinite period without injury (as frogs, and salamanders), the 
 respiratory function of the skin is very active. In these animals, 
 the integument is very vascular, moist, and flexible ; and is covered, 
 not with dry guticle, but with a very thin and delicate layer of 
 epithelium. It, therefore, presents all the conditions necessary for 
 the accomplishment of respiration ; and while the animal remains 
 beneath the surface, and the lungs are in a state of inactivity, the 
 exhalation and absorption of gases continue to take place through 
 the skin, and the' process of respiration goes on in a nearly unin- 
 terrupted manner. 
 
 ' Annales de Chimin et He Pharmaoie, vol. viii. p. 490. 
 
 » lu Carpenter's Human Physiology, Philada. ed., 185S, p. 308. 
 
ANIMAL HEAT. 253 
 
 CHAPTER XIII. 
 
 ANIMAL HEAT. 
 
 One of the most important phenomena presented by animals and 
 vegetables is the property ■which they possess of maintaining, more 
 or less constantly, a standard temperature, notwithstanding the 
 external vicissitudes of heat and cold to which they may be sub- 
 jected. If a bar of iron, or a jar, of water, be heated up to 100° or 
 200° F., and then exposed to the air at 50° or 60°, it will imme- 
 diately begin to lose heat by radiation and conduction ; and this . 
 loss of heat will steadily continue, until, after a certain time, the 
 temperature of the heated body has become reduced to that of the 
 surrounding atmosphere. It then remains stationary at this point, 
 unless the temperature of the atmosphere should happen to rise or 
 fall : in which case, a similar change takes place in the inorganic 
 body, its temperature remaining constant, or varying with that of 
 the surrounding medium. 
 
 "With living animals the case is difierent. If a thermometer be 
 mtroduced into the stomach of a dog, or placed under, the tongue 
 of the human'subject, it will indicate a temperature of 100° F., very 
 nearly, whatever may be the condition of the surrounding atmo- 
 sphere at the time. * This internal temperature is the same in sum- 
 mer and in winter. If the individual upon whom the experiment 
 has been tried be afte:?ward exposed to a cold of zero, or even of 20° 
 or 30° below zero, the thermometer introduced into the interior of 
 the body will still stand at 100° F. As the body, during the whole 
 period of its, exposure, must have been losing heat by radiation and 
 conduction, like any inorganic mass, and has, notwithstanding, main- 
 tained a constant temperature, it is plain that a certain amount of 
 heat has been generated in the interior of the body by means of the 
 vital processes, sufficient to compensate for the external loss. The 
 internal heat, so produced, is known by the name of vital or animal 
 heat. 
 
 There are two classes of animals in which the production of vital 
 
254 ANIMAL HEAT. 
 
 heat takes place witli such activity that their blood and internal 
 organs are nearly always very much above the external temper- 
 ature; and which are therefore called "warm-blooded animals." 
 These are mammalia and birds. Among the birds, some species, 
 as the gull, have a temperature as low as 100° F. ; but in most of 
 them, it is higher, sometimes reaching as high as 110? or 111°. In 
 the mammalians, to which class man belongs, the animal tempera- 
 ture is never far from 100°. In the seal and the Greenland whale, 
 it has been found to be 104° ; and in the porpoise, which is an .air- 
 breathing animal, 99°.5. In the human subject it is 98? to 100°. 
 When the temperature of the air is below this, the external parts 
 of the body, being most exposed to the cooling influences of radia- 
 tion and conduction, fall a' little below the standard, and may indi- 
 cate a temperature of 97°, or even several degrees below this point. 
 Thus, on a very cold day, the thinner and more exposed parts, such 
 as the nose, the ears, and the ^nds of the fingers, may become 
 ' cooled down considerably below the standard temperature, and may 
 even be congealed, if the cold be severe ; bat the temperature of 
 the internal organs and of the blood still remains the same under 
 all ordinary exposures. 
 
 K the cold be so intense and long continued as to affect the 
 general temperature of the -blood, it at once becomes fatal. It has 
 been found that although a warm-blooded animal usually preserves 
 its natural temperature when exposed to external cold, yet if the 
 actual temperature of the blood become reduced by any means 
 more than "5° or 6° below its natural standard, death inevitably 
 results. The animal, under these circumstances, gradually becomes 
 torpid and insensible, and all the vital operations finally cease. 
 Birds, accordingly, whose natural temperature 'is about 110°, die if 
 the blood be cooled down to 100°, which is the natural temperature 
 of the mammalia ; and the mammalians die ff their blood be cooled 
 down below 94° or 95°. Each of these different classes has there- 
 fore a natural temperature, at which the blood must be maintained 
 in order to sustain life ; and even the different species of animials, 
 belonging to the same class, have each a specific temperature which 
 is characteristic of them, and which cannot be raised or lowered, to 
 any considerable extent, without producing death. 
 
 While in the birds and mammalians, however, the internal pro- 
 duction of heat is so active) that their temperature is nearly always 
 considerably above that of the surrounding media, and suffers but 
 little variation ; in reptiles and fish, on the other hand, its produc- 
 
ANIMAL HEAT. 
 
 255 
 
 tion is much less rapid, and the temperature of their bodies differs 
 but little from that of the air or water which they inhabit. Birds 
 and mammalians are therefore called " warm-blooded," and reptiles 
 and fish " cold-blooded" animals. There is, however, no other dis- 
 tinction between them, ia this respect, . than one of degree. In 
 reptiles and fish there is also an internal source of heat ; only this 
 is not so active as in the other classes. Even in these animals a 
 difference is usually found to exist between the temperature of their 
 bodies and that of the surrounding media. John Hunter, Sir 
 Humphrey Davy, Czermak, and others,' have found the temperature 
 of Proteus anguinus to be 63°.5, when that of the air was 55°.4 ; 
 that of a frog 48", in water at 44° .4 ; that of a serpent 88°.46, in 
 air at 81°.5 ; that of a tortoise 84°, in air at 79°.5 ; and that of fish 
 to be from 1°.7 to 2°.5 above that of the surrounding water. 
 
 The following list' shows the mean temperature belonging to 
 animals of different classes and species. 
 
 AiriMAL. 
 
 
 
 
 
 
 Mbah Tempebatuse. 
 
 
 • Swallow 1110.25 
 
 
 Heron . 
 
 
 
 
 
 
 1110.2 
 
 Birds. 
 
 Mammalia. 
 
 Beftile. ^ 
 
 Raven . 
 
 Pigeon . 
 .Fowl . 
 . OnU . 
 ■ Squirrel 
 
 Goat . 
 
 Cat 
 
 Hare 
 
 Ox 
 
 Dog . 
 
 Man . 
 .Ape . 
 
 Toad . 
 
 
 
 
 
 
 108O.5 
 
 1070.6 
 
 106O.7 
 
 1000.0 
 
 1050 
 
 1020.5 
 
 1010.3 
 
 1000.4 
 
 990.5 
 
 990.4 
 
 980.6 
 
 950.9 
 
 510.6 
 
 Fish. 
 
 |- Carp . 
 Tench , 
 
 
 
 
 
 
 510.25 
 520.10 
 
 In the invertebrate animals, as a general rule, the internal heat 
 is produced in too small quantity to be readily estimated. In some 
 of the more active kinds, however, such as insects and arachnida, 
 it is occasionally generated with such activity that it may be 
 appreciated • by the thermometer. Thus, the temperature, of the 
 butterfly, when in a state of excitement, is from 5° to 9° above 
 that of the air ; and that of the humble-bee from 3° to 10° higher 
 
 ' Simon's Chemistry of Man, Philadelphia edition, p. 124. 
 " Ibid., pp. 123—126. 
 
256 ANIMAL HEAT. 
 
 than the exterior. According to the experiments of Mr. Newport,' 
 the interior of a hive of bees may have a temperature of 48°.5. 
 when the external atmosphere is at 34°.5, even while the insects 
 are quiet ; but if they be excited, by tapping on the outside of the 
 hive, it may rise to 102°. In all cases, while the insect is at rest, 
 the temperature is very moderate ; but if kept in rapid motion in 
 a confined space, it may generate heat enough to affect the thermo- 
 meter sensibly, in the course of a few minutes. 
 
 Even in vegetables a certain degree of heat-producing power is 
 occasionally manifest. Usually, the exposed surface of a plant is 
 so extensive in proportion to its mass, that whatever caloric may 
 be generated is too rapidly lost by radiation and evaporation, to be 
 appreciated by ordinary means. Under some circumstances, how- 
 ever, it may accumulate to such an extent as to become readily 
 perceptible. In the process of malting, for example, when a large 
 quantity of germinating grain is piled together in a mass, its ele- 
 vated temperature may be readily distinguished, both by the hand 
 ^ and the thermometer. During the flowering process, also, an un- 
 usual evolution of heat takes place in plants. The flowers of the 
 geranium have been found to have a temperature of 87°, while 
 that of the air was 81°; and the thermometer, placed in the centre 
 of a clump of blossoms of arum cordifolium, has been seen to rise 
 to 111°, and even 121°, while the temperature of the external air 
 was only §6°.' 
 
 Dutrochet has moreover found, by a series of very ingenious and 
 delicate experiment,^ that nearly all parts of a living plant gene- 
 rate a certain amount of heat. The proper heat of the plant is 
 usually so rapidly dissipated by the continuous evaporation of its 
 fluids, that it is mostly imperceptible by ordinary means; but if 
 this evaporation be prevented, by keeping the air charged with 
 watery vapor, the heat becomes s^sible and can be appreciated by 
 a delicate thermometer. Dutrochet used for this purpose a thermo- 
 electric apparatus, so constructed that an elevation of temperature 
 of 1° ¥., in the substances examined, would produce a deviation in 
 the needle of nearly nine degrees. By this means he found that he 
 could appreciate, without difficulty, the proper temperature of the 
 plant* A certain amount of heat was constantly generated, during 
 
 ' Carpenter's General and Comparative Physiology, Philadelphia, 1851, p. 852. 
 
 ' Carpenter's Gen. and Comp. Physiology, p. 846. 
 
 ' Annales des Sciences Naturelles, 2d series, xii. p. 277. 
 
ANIMAL HEAT. 257 
 
 the day, in the green stems, the leaves, the buds, and even the 
 roots and fruit. The maximum temperature of these parts, above 
 that of the surrounding atmosphere, was sometimes a little over 
 one-half a degree Fahrenheit; though it was often considerably 
 less than this. 
 
 The different parts of the vegetable fabric, therefore, generate 
 different quantities of caloric. In the same manner, the heat- 
 producing power is not equally active in different species of ani- 
 mals; but its existence is nevertheless common to both animals 
 and vegetables. 
 
 With regard to the mode of generation of this internal or vital 
 heat, we may start with the assertion that its production depends 
 upon changes of a chemical nature, and is so far to be regarded as 
 a chemical phenomenon. The sources of heat which we meet with 
 in external nature are of various kinds. Sometimes the heat is of 
 a physical origin ; as, for example, that derived from the rays of 
 the sun, the friction of solid substances, or the passage of electric 
 currents. In other instances it is produced by chemical changes: 
 and the most abundant and useful source of artificial heat is the 
 oxidation, or combustion, of carbon and carbonaceous compounds. 
 Wood and coal, substances rich in carbon, are mostly used for this 
 purpose ; ailfl charcoal, which is nearly pure carbon, is frequently 
 employed by itself. These substances, when burnt, or oxidized, 
 evolve a large amount of heat ; and produce, as the result of their 
 oxidation, carbonic acid. In order that the process may go on, it 
 is of course necessary that oxygen, or atmospheric air, should have 
 free access to the burning body; otherwise the combustion and 
 evolution of heat cease, for want of a necessary agent in the chemi- 
 cal combination. In all these instances, the quantity of heat gene- 
 rated is in direct proportion to the amount of oxidation ; and may 
 be mSasured, either by the quantity of carbon consumed, or by that 
 of carbonic acid produced. It may be made to go on, also, either 
 rapidly or slowly, according to the abundance and purity in which 
 oxygen is supplied to the carbonaceous substance. Thus, if char- 
 coal be ignited in an atmosphere of pure oxygen, it burns rapidly 
 and violently, raises the temperature to a high point, and is soon 
 entirely consumed. On the other hand, if it be shut up in a close 
 stove, to which the air is admitted but slowly, it produces only a 
 slight elevation ef temperature, and may require a much longer 
 time for its complete disappearance. Nevertheless, for the same 
 quantity of carbon consumed, the amount of heat generated, and 
 17 
 
258 ANIMAL HEAT. 
 
 that of carbonic acid produced, will be equal ia the two cases. In 
 one instance we have a rapid combustion, in the other a slow com- 
 bustion ; the total effect being the same in both. 
 
 Such is the mode in which heat is commonly produced by artifi- 
 cial means, its evolution is here dependent upon two principal 
 conditions, which <ire essential to it, and by which it is always 
 accompanied, viz., the consumption of oxygen, and the production 
 of carbonic acid. 
 
 Now, since the two phenomena just mentioned are presented 
 also by the living body, iand since they are accompanied here, too, 
 by the production of animal heat, it was very natural to suppose 
 that in the animal organization, as well as elsewhere, the internal 
 heat must be owing to an oxidation or combustion of carbon. Ac- 
 cording to Lavoisier, the oxygen taken into the lungs was sup- 
 posed to combine immediately with the carbon of the pulmonary 
 tissues and fluids, producing carbonic acid, and to be at once re- 
 turned under that form to the atmosphere ; the same quantity of 
 heat resulting from the above process as would have been produced 
 by the oxidation of a similar quantity of carbon in wood or coal. 
 Accordingly, he regarded the lungs as a sort of stove or furnace, 
 by which the rest of the body was warmed, through the medium of 
 the circulating blood. * 
 
 It was soon found, however, that this view was altogether erro- 
 neous ; for the slightest examination shows that the lungs are not 
 perceptibly warmer than the rest of the body ; and that the heat- 
 producing power, whatever it may be, does not reside exclusively 
 in the pulmonary tissue. Furthermore, subsequent investigations 
 showed the following very important facts, which we have already 
 mentioned, viz., that the carbonic acid is not formed in the lungs, 
 but exists in the blood before its arrival in the pulmonary capilla- 
 ries ; and that the oxygen of the inspired air, so far from combining 
 with carbon in the lungs, is taken up in solution by the blood- 
 globules, and carried away by the current of the general circulation. 
 It is evident, therefore, that this oxidation or combustion of the 
 blood must take place, if at all, not in the lungs, but in the capil- 
 laries of the various organs and tissues of the body. 
 
 Liebig accordingly adopted Lavoisier's theory of the production * 
 of animal heat, with the above modification. He believed the heat 
 of the animal body to be produced by the oxidation or combustion 
 of certain elements of the food while still circulating in the blood ; 
 these substances being converted into carbonic acid and water by 
 
ANIMAL HKAT. 259 
 
 the oxidation of their carbon and hydrogen, and immediately ex- 
 pelled from the body without ever having formed a part of the solid 
 tissues. He therefore divided the food into two different' classes of 
 alimentary substances ; viz., 1st, the nitrogenous or plastic ehrmnts, 
 which are introduced in comparatively sniall quantity, and which 
 are to be actually converted into the substance of the tissues, such as 
 albumen, muscular flesh, &c. ; and 2d, the hydro-carbons or respiratory 
 ikments, such as sugar, starch, and fat ; which, according to his view, 
 are taken into the blood solely to be burned, never being assimilated 
 or converted into the tissues, but only oxidized in the circulation, 
 and immediately expelled, as above, under the form of carbonic 
 acid and water. He therefore regarded these elements of the food 
 only as so much fuel ; destined simply to maintain the heat of the 
 body, but taking no part in the proper function of nutrition. 
 
 The above theory of animal heat has been Very generally adopted 
 and acknowledged by the medical profession until within a recent 
 period. A few years ago, however, some of its deficiencies and 
 inconsistencies were pointed out, by Lehmann in Germany, and by 
 Eobin and Verdeil in France ; and since that time it has begun to 
 lose ground and give place to a different mode of explanation, more 
 in accordance with the present state of physiological science. We 
 believe it, in fact, to be altogether erroneous; and incapable of 
 explaining, in a satisfactory mariner, the phenomena of animal heat, 
 as exhibited by the living body. We shall now proceed to pass in 
 review the principal objections to the theory of combustion, con- 
 sidered as a physiologicail doctrine. 
 
 I. It is not at all necessary to regard the evolution of heat as 
 dependent solely on direct oxidation. This is only one of its 
 sources, as we see constantly in external nature. The sun's rays, 
 mechanical friction, electric currents, and more particularly a great 
 variety oi chemical actions, such as various saline combinations and 
 decompositions, are all capable of producing heat; and even simple 
 solutions, such as the solution of caustic potassa in water, the mixture 
 of sulphuric acid and water, or of alcohol and water, will often pro- 
 duce a very sensible elevation of temperature. Now we know that 
 in the interior of the body a thousand different actions of this 
 nature are constantly going on ; solutions, combinations and decom- 
 positions in endless variety, all of which, taken together, are amply 
 sufficient to account for the production of animal heat, provided the 
 theory of combustion should be found insufficient or improbable. 
 
260 ANIMAL HEAT. 
 
 II. In vegetables there is an internal production of heat, as well 
 as in animals ; a fact which has been fully demonstrated bj the 
 experiments of Dutrochet and others, already described. In vege- 
 tables, however, the a,bsorption of oxygen and exhalation of car- 
 bonic acid do not take place ; excepting, to some extent, during the 
 night. On the contrary, the diurnal process in vegetables, it is well 
 known, is exactly the reverse of this. Under the influence of the 
 solar light they absorb carbonic acid and exhale oxygen. And i» 
 is exceedingly remarkable that, in Dutrochet's experiments, he 
 found that the evolution of heat by plants was always accompanied 
 by the disappearance of carbonic acid and thes exhalation of oxygen. 
 Plants which, in the daylight, exhale oxygen and evolve heat, if 
 placed in the dark, immediately begin to absorb oxygen and exhale 
 carbonic acid ; and, at the same time, the evolution of heat is sus- 
 pended. Duttochet even found that the evolution of heat by plants 
 presented a regular diurnal variation ; and that its maximum of 
 intensity was about the middle of the day, jiist at the time when the 
 absorption of carbonic acid and the exhalation of oxygen are going on 
 with the greatest activity. The proper heat of plants, therefore, can- 
 not be the result of oxidation or Combustion, but must be dependent 
 on an entirely different orocess. 
 
 III. In animals, the quantities of oxygen absorbed and of carbonic 
 acid exhaled do not correspond with each other. Most frequently 
 a certain amount of oxygen disappears in the body, over and above 
 that which is returned in the breath under the form of carbonic 
 acid. This overplus of oxygen has been said to unite with the 
 hydrogen of the food, so as to form water which alst* passes out 
 by the lungs ; but this is a pure assumption, resting on no direct 
 evidence whatever, for we have no experimental proof that any 
 more watery vapor is exhaled from the lungs than is supplied by 
 the fluids taken into the stomach. It is superfluous, therefore, to 
 assume that any of it is produced by the oxidation of hydrogen. 
 
 Furthermore, the proportion of overplus oxygen which disap- 
 pears in the body, beside that which is exhaled in the carbonic acid 
 of the breath, varies greatly in the same animal according to the 
 quality of the food. Eegnault and Eeiset' found that in dogs, fed 
 on meat, the oxygen which reappeared under the form of carbonic 
 acid was only 75 per cent, of the whole quantity absorbed ; while 
 
 ' Annales de Chimie et de Physique, 3d series, xxvi. p. 428. 
 
ANIMAL HEAT. « 261 
 
 in dogs fed on vegetable substances it amounted to over 90 per 
 cent. In some instances,' where the animals (rabbits and fowls) 
 were fed on bread and grain exclusively, the proportion of expired 
 oxygen amounted to 101 or even 102 per cent. ; that is, more oxygen 
 was actually contained in the carbonic acid exhaled, than had been ab- 
 sorbed in a free state from the atmosphere. A portion, at least, of Jhe 
 carbonic acid must therefore have been produced by other means 
 than direct oxidation. 
 
 IV. It has already been shown, in a previous chapter, that the 
 carbonic acid which is exhaled from the lungs is not primarily 
 formed in the blood, but, makes its appearance in the substance of 
 the tissues themselves ; and furthermore, that even here it does not 
 originate by a direct oxidation, but rather by a process of decom- 
 position, similar to that by which sugar, in fermentation, is resolved 
 into alcohol and carbonic acid. We understand from this how to 
 explain the singular fact alluded to in the last paragraph, viz., the 
 abundant production of carbonic, acid, under some circumstances, 
 with a comparatively small supply of free oxygen. The statement 
 made by Liebig, therefore, that starchy and oily matters taken with 
 the food are immediately oxidized in the circulation without ever 
 being assimilated by the tissues, is without foundation. It never, 
 in fact, rested on any other ground than a supposed probability ; 
 and as we see that carbonic acid is abundantly produced in the 
 body by other means, we have no longer any reason for assuming, 
 without direct evidence, the existence of a combustive process in 
 the blood. 
 
 V. The evolution of heat in the animal body is not general, as it 
 would be if it resulted from a combustion of the blood ; but local, 
 since it takes place primarily in the substance of the tissues them- • 
 selves. Various causes will therefore produce a local elevation or 
 depression of temperature, by modifying the nutritive changes 
 Yhich take place in the tissues.. Thus, in the celebrated experiment 
 of Bernard, which we have often verified, division of the sympa- 
 thetic nerve in the middle of the neck produces very soon a marked 
 elevation of temperature in the corresponding side of the head and 
 face. Local inflammations, also, increase very sensibly the tempera- 
 ture of the part in which they are seated, while that of the general 
 
 ' Annajes de Chimie et de Physique, 3d series, xxvi. pp. 4C9— 451. 
 
262 ^ ANIMAL HKAT. 
 
 mass of the blood is not altered. Finally it has been demonstrated 
 by Bernard that in the natural state of the system there is a marked 
 difference in the temperature of the different organs and of the blood 
 returning from them.' The method adopted by this experimenter 
 was to introduce, in the living animal, the bulb of a fine thermo- 
 • meter successively into the bloodvessels entering and those leaving 
 the various internal organs. The difference of temperature in these 
 two situations showed whether the blood had lost or gained in heat 
 while traversing the capillaries of the organ. Bernard found, iu 
 the ;!irst place, that the blood in passing through the lungs, so far 
 from increasing, was absolutely diminished in temperature; the 
 blood on the left side of the heart being sometimes a little more 
 and sometimes a little less than one-third of a degree Fahr. lower 
 than on the right side. This slight cooling of the blood in the 
 lungs is owing simply to its exposure to the air through the pul- 
 monary membrane, and to the vaporization of water which takes 
 place in these organs. In the abdominal viscera, on the contrary, 
 the blood is increased in temperature. It is sensibly warmer in the 
 portal vein than in the aorta ; and very considerably warmer in the 
 hepatic vein than in either the portal or the vena cava. The blood 
 of the hepatic vein is in fact warmer than that of any other part 
 of the body. The production of heat, therefore, according to Ber- 
 nard's observations, is more active in the liver than in any other 
 portion of the system. As the chemical processes of nutrition are 
 necessarily different in the different tissues and organs, it is easy to 
 understand why a specific amount of heat should be produced in 
 each of them. A similar fact, it will be recollected, was noticed by 
 Dutrochet, in regard to the different parts of the vegetable organ- . 
 ization. 
 
 VI. Animal heat has been supposed to stand in a special relation 
 to the production of carbonic acid, because in warm-blooded animals 
 the respiratory process is more active than in those of a lower 
 temperature ; and because, in the same animal, .an increase or di- 
 minution in the evolution of heat is'accompanied by a correspond- 
 ing increase or diminution in the products of respiration. Bat 
 this is also true of all the other excretory products of the body. An 
 elevation of temperature is accompanied by an increased activity 
 of all the nutritive processes. Not only carbonic acid, but the 
 
 ' Gazette Htibdomaiiaire, Aug. 29 and Sept. 26, 1856. 
 
ANIMAL HEAT. 263 
 
 ingredients of the urine and the perspiration are discharged in larger 
 quantity than usual. An increased supply of food also is required, 
 as well as a larger quantity of oxygen; and the digestive and 
 secretory processes both go on, at the same time, with unusual 
 activity. 
 
 Animal heat, then, is a phenomenon ^yhich results from the 
 simultaneous activity of many different processes, taking place in 
 many different organs, and dependent, undoubtedly, on different 
 chemical changes in each one. The introduction of oxygen and 
 the exhalation of carbonic acid have no direct connection with each 
 other, but are only the beginning and the end of a long series of 
 continuous changes, in which all the tissues of the body successively 
 take a part. Their relation is precisely that which exists between 
 the food introduced through the stomach, and the urinary ingre- 
 dients eliminated by the kidneys. The tissues require for their 
 nutrition a constant supply of solid and liquid food which is intro- 
 duced through the stomach, and of oxygen which is introduced 
 through the lungs. The disintegration and decomposition of the 
 tissues give rise, on the one hand, to urea, uric acid, &c., which are 
 discharged with the urine, and on the other hand to carbonic acid, 
 which is exhaled from the lungs. But the oxygen is not directly 
 converted into carbonic acid, any more than the food is directly 
 converted into urea and the urates. 
 
 Animal heat is not to be regarded, therefore, as the result of a 
 combustive process. There is no reason for believing that the 
 greater part of the food is "burned" in the circulation. It is, on 
 the contrary, assimilated by the substance of the tissues ; and these, 
 in their subsequent disintegration, give rise to several excretory- 
 products, one of which is carbonic acid. 
 
 The numerous combinations and decompositions which folloV 
 each other incessantly during the nutritive process, result in the 
 production of an internal or vital heat, which is present in both 
 animals and vegetables, and which varies in amount in different 
 species, in the same individual at different times, and even in 
 different parts and organs of the same body. 
 
264 THE CIBCCLATIO>'. 
 
 CHAPTER XIV. 
 
 THE CIRCULATION. 
 
 The blood may be regarded as a nutritious fluid, holding in 
 solution all the ingredients necessary for the formation of the 
 tissues. In some animals and vegetables, of the lowest organization, 
 such as infusoria, polypes, algae, and the like, neither blood nor 
 circulation is required ; since all parts of the body, having a similar 
 structure, absorb nourishment equally from the' surrounding media, 
 and carry on nearly or quite the same chemical processes of growth 
 and assimilation. In the higher animals and vegetables, however, 
 as well as in the human subject, the case is different. In them, the 
 structure of the body is compound. Different organs, with widely 
 different functions, are situated in different part's of the frame ; and 
 each of these functions is more or less essential to the continued 
 existence of the whole. In the intestine, for example, the process 
 of digestion takes place ; and the prepared ingredients of the food 
 are thence absorbed into the bloodvessels, by which they are 
 transported to distant tissues and organs. In the lungs, again, 
 the blood absorbs oxygen which is afterward to be appropriated by 
 the tissues ; and carbonic acid, which was produced in the tissues, 
 is exhaled from the lungs. In the liver, the kidneys, and the skin, 
 other substances again are produced or eliminated, and these local 
 processes are all of them necessary to the preservation of the general 
 organization. The circulating fluid is, therefore, in the higher 
 animals, a means of transportatio7i, by which the substances pro- 
 duced in particular organs are dispersed throughout the body, or 
 by which substances produced generally in the tissues are conveyed 
 to particular organs, in order to be eliminated and expelled. 
 
 The circulatory apparatus consists of four different parts, viz : 
 1st. The heart ; a hollow, muscular organ, which receives the blood 
 at one orifice and drives it out, in successive impulses, at another. 
 2d. The arteries; a series of branching tubes, which cojjvey the 
 blood from the heart to the different tissues and organs of the body. 
 
THE HEART. 
 
 265 
 
 3d.' The capillaries; a network of minute inosculating tubules, 
 ■which are interwoven with the substance of the tissues, and which 
 bring the blood into intimate contact with the cells and fibres of 
 which they are composed ; and 4th. The veins ; a set of converg- 
 ing vessels, destined to collect the blood from the capillaries, and 
 return it to the heart. In each of these four different parts of the 
 circulatory apparatus, the movement of the blood is peculiar and 
 dependent on special conditions. It will therefore require to be 
 studied in each one of them separately. 
 
 THE HEAKT. 
 
 The structure of the heart, and of the ferge vessels connected 
 with it, varies considerably in difterent classes of animals, owing to 
 the different arrangement of the respiratory organs. For the respi- 
 ratory apparatus being one of the most important in the body, and 
 the one most closely connected 
 
 by anatomical relations with Fig. 76. 
 
 the organs of circulation, the 
 latter are neoessarily modified 
 in structure to correspond with 
 the former. In fish, for exam- 
 ple (Fig. 76), the heart is an 
 organ consisting of two princi- 
 pal cavities ; an auricle (a) into 
 which the blood is received from 
 the central extremity of the 
 vena cava, and a ventricle (b) 
 into which the blood is driven 
 . by the contraction of the auricle. 
 The ventricle is considerably 
 larger and more powerful than 
 the auricle, and by its contrac- 
 tion drives the blood into the 
 main artery supplying the gills. 
 In the gills (cc) the blood is 
 arterialized ; after which it is 
 collected by the branchial veins. 
 
 These veing unite upon the median line to form the aorta (d) by 
 which the blood is finally distributed throughout the frame. In 
 
 ClECFLATloK OF F18H. — a. Anricln. b. 
 Ventricle, cc. OiLls. d. Aorta, ee. Veuae cavas. 
 
266 
 
 THE CIKCULATIOIT. 
 
 Fig. 77. 
 
 these animalg the respiratory process is not a very active one ; but 
 the gills, which are of small size, being the only respiratory organs, 
 ■all the blood requires to pass through them for purposes of aeration. 
 The heart here is a single organ, destined only to drive the blood 
 from the termination of the venous system to the capillaries of the 
 gills; , ■ _ 
 
 In reptiles, the heart is composed of two auricles, placed side by 
 side, and one ventricle. (Fig. 77.) The venae cavse discharge their 
 
 blood into the right auricle (d), 
 whence it passes into the ventricle 
 (tf). From the ventricle, a part of it 
 is carried into the aorta and distri- 
 buted throughout the body, while a 
 part is sent to the lungs through the 
 pulmonary artery. The arterialized 
 blood, returning from the lungs by 
 .the pulmonary vein, is discharged 
 into the left auricle (b), and thence 
 into the ventricle (c), where , it 
 mingles with the venous blood 
 which has just arrived by the venae 
 cavse. In the reptile, therefore, the 
 ventricle is a common organ of pro- 
 pulsion, both for the lungs and for 
 the general circulation. In these 
 animals the aeration of the blood in 
 the lungs is only partial ; a certain 
 portion of the blood which leaves 
 the heart being carried to these organs, just as in the human subject 
 it is only a portion of the blood which is carried to the kidney by 
 the renal artery.^^ This arrangement is sufficient for the reptiles, , 
 because in many of them, such as serpents and turtles, the lungs 
 are much more extensive and efficient, as respiratory organs, than 
 the gills of fish; while in others, such as frogs and water-lizards, 
 the integument itself, which is moist, smooth, and naked, takes an 
 important share in the aeration of the blood. • 
 
 In quadrupeds and the human species, however, the respi- 
 ratory process is not only exceedingly active, but the lungs 
 are, at the same time, the only organs in which the aeration of 
 the blood can be fully accomplished. In them, accordingly^ we 
 find the two circulations, general and pulmonary, entirely dis- 
 
 ClRCULATION OF KKPTII.KS. — «. 
 
 Right auricle, 'b. Lertaaricln. «.-. VnDtricle. 
 d. Lungs, e. Aorta. /. Vena cava. 
 
THE HBABT. 
 
 267 
 
 tinct from each other. (Fig. 78.) All the blood returning from 
 the body by the veins must pass through the lungs before it is 
 again distributed through the 
 
 arterial system. We have J^'ig- 78- 
 
 therefore a double cireula- 
 tion, and also a double heart; 
 the two sides of which, 
 though united externally, 
 are separate internally. The 
 mammialian heart consists of 
 a right auricle and ventricle 
 (a, i), receiving the blood 
 from the vena cava (j), and 
 driving it to the lungs ; and 
 a left auricle and ventricle 
 (/, g) receiving the blood 
 from the lungs and driving 
 it outward through the arte- 
 rial system. 
 
 In the complete or double 
 mammalian heart, the differ- 
 ent parts of the organ present 
 certain peculiarities and bear 
 certain relations to each other, which it is necessary to understand 
 before we can properly appreciate its action and movements. The 
 entire organ has a more or less conical form, its base being situated 
 on the median line, directed upward and backward ;' the whole being 
 suspended in the chest, and loosely fixed to the spinal column, by 
 the great vessels which enter and leave it at this point. The apex, 
 on the contrary, is directed downward, forward, and to the left, sur- 
 rounded by the perieardiun^ and the pericardial fluid, but capable 
 of a very free lateral and rotatory motion. The aurioles, which 
 have a smaller capacity and thinner Walls than the ventricles, are 
 situated at the upper and posterior part of the organ, (Figs. 79 and 
 80); while the ventricles occupy its anterior and lower portions, 
 The two ventricles, moreover, are not situated on the same plane, 
 but the right ventricle occupies a position somewhat in front and 
 above that of the left ; so that in an anterior view of the heart the 
 greater portion of the left ventricle is concealed by the right (Fig. 
 79), and in a posterior view the greater portion of the right ven- 
 tricle is concealed by the left (Fig. 80) ; while in both positions the 
 
 CiBonr.ATiox iw MahmaiiIahs.— n. KigM 
 auricle, h. Right Teotricle. c. Pnlmonary artery. 
 d. Lunps. 0. Fntmonary vein. /. Left auricle, g. 
 Left Tentricle. K Aorta, i. Vena cava. 
 
268 
 
 THE CIRCULATIOX. 
 
 apex of the heart is constituted altogether by the point of the '. 
 ventricle. 
 
 Fig. 79. 
 
 Hdmah H£abt, anterior Yiev.-r 
 a. Bight Tentrlcle. b. Left ventricle, 
 c. Btglit auricle, d. Left auricle, e. 
 .Pttlmonary artery, /. Aorta. 
 
 Fig. 80. 
 
 HnHAH Heakt, posterior view.— 
 A. Right vedtricle. &. Left ventricle, 
 e. Bight auricle, d. Left auricle. 
 
 The different cavities of the heart and of the adjacent blood- 
 vessels, though continuous with each other,, are partially 'separated 
 by certain constrictidns. These constricted orifices, by which the 
 different caviti^. communicate, are known by the names of the 
 
 Fig. 81. 
 
 Eight Auricle and Ventricle; Auriculo-veotricular Valves open, Arterial Valveti closed. 
 
 auricular, auriculo-ventricular, and aortic and pulmonary orifices; 
 the auricular orifices being the passages from the vense cavae and 
 
THE HEART. 
 
 269 
 
 pulmonary veins into tHe right and left auricles; tlie auriculo- 
 ventricular orifices leading from the auricles into the ventricles ; 
 and the aortic and pulmonary orifices leading from the ventricles 
 into the aortic and pulmonary arteries respectively. 
 
 The aurict|Io-ventricular, aortic, and pulmonary orifices are fur- 
 nished with valves, which allow the blood to pass readily from the 
 auricles to the veiitricles, and from the ventricles to the arteries, 
 but shut back, with the contractions of the organ, so as to prevent 
 its return in an opposite direction. The course of the blood 
 through the heart is, therefore, as follows. From the vena cava it 
 passes into the right auricle ; and from the right auricle into the 
 right ventricle. (Fig. 81.) On the contraction of the right ventricle, 
 the tricuspid valves shut back, preventing its return into the auricle 
 (Fig. 82); and it is thus driven through the pulmonary artery to the 
 
 Fig. 82. 
 
 Eight Auricle and VBSTRicrjB; Aurlcnlo-ventricalar Valves closed, Arterial VaWes opea. 
 
 lungs. Eetuming from the lungs, it enters the left auricle, thence 
 passes into the left ventricle, from which it is finally delivered into 
 the aorta, and distributed throughout the body. (Fig. 83.) This 
 movement of the bipod, however, through the cardiac cavities, is 
 not a continuous and steady flow, but is accomplished by alternate 
 contractions and relaxations of the muscular parietes of the heart 
 so that with every impulse, successive portions of blood are received 
 by the auricles, delivered into the ventricles, and by them dis- 
 
270 THE CIRCULATION. 
 
 charged into the arteries. Each one of these successive actions is 
 called a beat, or pulsation of the heart. 
 
 Fig. 83. 
 
 C0UB8E OP Blood throdoh the Hrart. — n^o. Vena cava, superior and inferinr. 
 6. Biiflit ventricle, w. Pulmonary artery, d. Fulmiiuary vein. c. Left ventricle. /. Aorta. 
 
 Each pulsation of the heart is accompanied by certain important 
 phenomena, which require to be studied in detail. These are the 
 sounds, the movements, and the impulse. 
 
 The sounds of the heart are two in number. They can readily be 
 heard by applying the ear over the cardiac region, when they are 
 found to be quite different from each other in position, in tone, and 
 in duration. They are distinguished as the first and second sounds 
 of the heart. The first sound is heard with the greatest intensity 
 over the anterior surface of the heart, and more particularly over 
 the fifth rib and the fifth intercostal space. It is long, dull, and 
 smothered in tone, and occupies one-half the entire duration of a 
 single beat. It corresponds in time with the impulse of the heart 
 in the precordial region, and the stroke of the large arteries in the 
 immediate vicinity of the chest. The second sound follows imme- 
 diately upon the first. It is heard most distinctly at the situation 
 of the aortic and pulmonary valves, viz., over the sterrium at the 
 level of the third costal cartilage. It is short, sharp, and distinct 
 in tone, and occupies only about one-quarter of the whole time of 
 
THE HEART. 271 
 
 a pulsation. It is followed by an equal interval of silence ; after 
 whieh the first sound again recurs. The whole time of a cardiac 
 pulsation may then be divided into four quarters, of which the first 
 two are occupied by the first sound> the third by the second sound, 
 and the fourth by an interval of silence, as follows : — 
 
 Time of pulsation. 
 
 -iBt quarter Uj^^j^^^^^ 
 2d " i 
 
 3d " Second sound. 
 4th " Interval of silence. 
 
 t 
 The cause of the second sound is universally acknowledged to be 
 
 the sudden closure and tension of the aortic and pulmonary valves. 
 This fact is established by the following proofs.: 1st, this sound is 
 heard with perfect distinctness, as we have already mentioned, 
 directly over the situation of the above-mentioned valves ; 2d, the 
 farther we recede in any direction.from this point, the fainter be- 
 comes the sound ; and 3d, in experiments upon the living animal, 
 often repeated by difierent observers, it has been found that if a 
 curved needle be introduced into the base of the large vessels, so 
 as to hook back the semilunar valves, the second sound at once dis- 
 appears, and remains absent until the valve is again liberated. These 
 valves consist of fibrous sheets, covered with a layer of endocardial 
 epithelium. They have the form of semilunar festoons, the free 
 edge of which is directed away from the cavity of the ventricle, 
 while the attached edge is fastened to the inner surface of the base 
 of the artery. While the blood is passing from the ventricle to the 
 artery, these valves are thrown forward and relaxed ; but when the 
 artery reacts upon its contents they shut back, and their fibres, be- 
 coming suddenly tense, yield a clear, characteristic, snapping sound. 
 
 The production of the first sound has been attributed by some 
 writers to a combination of various causes ; such as the rush of 
 blood through the cardiac orifices, the muscular contraction of the 
 parietes of the heart, the tension of the auriculo- ventricular valves, 
 the collision of the particles of blood with each other and with the 
 surface of the ventricle, &c. &c. We believe, however, with Andry' 
 and some others, that the first sound of the heart has a similar 
 origin with the second ; and that it is dependent altogether on the 
 closure of the auriculo-ventricular valves. The reasons for this con- 
 clusion are the following : — 
 
 1st. The second sound is undoubtedly caused by the closurt of 
 
 ' Diseases of tdS Heart, Kneelai.d'8 translat:on, Boston. 1846 
 
272 THK CIRCULATION. 
 
 the semilunar valves, and in the action of the heart the shutting 
 back of the two sets of valves alternate with each other precisely 
 as do the first and second sounds ; and there is every probability, 
 to say the least, that the sudden tension of the valvular fibres pro- 
 duces a similar efiect in each instance. 
 
 2d. The first sound is heard most distinctly over the anterior 
 surface of the ventricles, where the tendinous cords supporting the 
 auriculo-ventriculai' valves are inserted, and where the sound pro- 
 duced by the tension of these valves would i>e most readily con- 
 (Jucted to the ear. 
 
 3d. There is no reason to believe that the current of blood 
 through the cardiac orifices could give rise to an appreciable sound, 
 so long as these orifices, and the cavities to which they lead, have 
 their normal dimensions. An unnatural souffle may indeed origi- 
 nate from this cause when the orifices of the heart are diminished 
 in size, as by calcareous or fibrinous deposits; and it may also 
 occur in cases of aneurism: A souffle may even be produced at 
 will in any one of the large arteries by pressing firmly upon it 
 with the end of a stethoscope, so as to diminish its calibre. But in 
 all these instances, the abnormal sound occurs only in consequence 
 of a disturbance in the natural relation existing between the volume 
 of the blood and the size of the orifice through which it passes. 
 In the healthy heart, the difi'erent orifices of the organ are in exact 
 proportion to the quantity of the circulating blood ; and there is no 
 more reason for believing that its passage should give rise to a 
 sound in the cardfao cavities than in the larger arteries or veins. 
 
 4th. The difference in character between the two sounds of the 
 heart depends, in all probability, on the different arrangement of 
 ' the two sets of valves. The second sound is short, sharp, and dis- 
 tinct, because the semilunar valves are short and narrow, superficial 
 in their situation, and supported by the "highly elastic, dense and 
 fibrous bases of the aortic and pulmonary arteries. The first sound 
 is dull and prolonged, because the auriculo- ventricular valves are 
 broad and deep-seated, and are attached, by their long chordae 
 tendinese to the comparatively soft and yielding fleshy columns of 
 the heart. The difference between,the first and second sounds can, 
 in fact, be easily imitated, by simply snapping between the fingers 
 two pieces of tape or ribbon, of the same texture but of different 
 lengths. (Fig. 84.) The short one will give out a distinct and sharp 
 sound; the long one a comparatively dull and' prolonged sound. 
 
 Together with the first sound of the heart there is also to be 
 
THE HEART. 273 
 
 heard a slight _^Wion sound, produced by the collision of the point 
 of the heart against the parietes of the chest. This sound, which is 
 heard in the fifth intercostal space, is very faint, and is more or less 
 
 Fig. 84. 
 
 masked by the strong valvular sound ■which occurs at the same 
 time. It is difierpnt, however, in .character from the latter, and 
 may usually be distinguished from it by careful examination. 
 
 The movements of the heart during the time of a pulsation are 
 of a peculiar character, and have been very often erroneously 
 described. In fact altogether the best description of the move- 
 ments of the heart which has yet appeared, is that given by Wil- 
 liam Harvey, in his celebrated work on the Motion of the Heart and 
 Blood, published in 1628. He examined the motion of the heart 
 by opening the chest of the living animal ; and though the same or 
 similar experiments have been frequently performed since his time, 
 the descriptions given by subsequent observers have been for the 
 most part singularly inferior to his, both in clearness and fidelity. 
 The method which we have adopted for examining the motions of 
 tbe heart in the dog is as follows : The animal is first rendered 
 insensible by ether> or by the inoculation of woorara. The latter 
 mode is preferable, since a long-continued etherization seems to 
 exert a sensibly depressing effect on the heart's action, which is 
 not the case with woorara. The trachea is then exposed and 
 opened just below the larynx, and the nozzle of a bellows inserted 
 and secured by'ligature. Finally, the chest is opened on the me- 
 dian line, its two sides widely separated, so as to expose the heart 
 and lungs, the pericardium slit up and carefully cut away from its 
 attachments, and the lungs inflated by insufilation through the 
 trachea. .By keeping up a steady artificial respiration, the move- 
 18 
 
274 THE CIBCULATION. 
 
 ments Gf the heart may be made to continue, in favorable cases, for 
 more than an hour ; and its actions may be studied by direct obser- 
 vation, like those of any external organ. 
 
 The. examination, however, requires to be conducted with certain 
 precautions, which are indispensable to success. When the heart 
 is first exposed, its movements are so complicated, and recur with 
 such rapidity, that it is difficult to distinguish them perfectly from 
 each other, and to avoid a certain degree of confusion. Singular 
 as it may seem, it is even difficult at first to determine what period 
 in the heart's pulsation corresponds to contraction, and what to 
 relaxation of the organ. "We have even seen several medical men, 
 watching together the pulsations of the same heart, unable to agree 
 upon this point. It is very evident, indeed, that several English 
 and continental observers have mistaken, in their examinations, the 
 contraction for the relaxation, and the relaxation for the contrac- 
 tion. The first point, therefore, which it is necessary to decide, in 
 examining the successive movements of a cardiac pulsation, is the 
 following, viz : Which is the contraction and which the relaooation of 
 the ventricles ? The method which we have adopted is to pass a 
 small silver canula directly through the parietes of the left ven- 
 tricle into its cavity. The blood is then driven from the external 
 orifice of the canula in interrupted jets ; each jet indicating the 
 time at which the ventricle contracts upon its contents. The 
 canula is then withdrawn, and the difierent muscular layers of the 
 ventricular walls, crossing each other obliquely, close the opening, 
 so that there is little or no subsequent hemorrhage. 
 
 When the successive actions of contraction and relaxation have 
 by this means been fairly recognized and distinguished from each 
 other, the Cardiac pulsations are seen to be characterized by the 
 following phenomena. The changes in form and position of the 
 entire heart are mainly dependent on those of the ventricles, whifth 
 contract simultaneously with each other, and which cotistitute much 
 the largest portion of the entire mass of the organ. 
 
 1. At the time of its contraction the heart hardens. This pheno- 
 menon is exceedingly well marked, and is easily appreciated by 
 placing the finger upon the ventricles, or by grasping them between 
 the finger and thumb. The muscular fibres become swollen and 
 indurated, and, if grasped by the hand, communicate the sensation 
 of a somewhat sudden and powerful shock. It is this forcible indu- 
 ration of the heart, at the time of contraction, which has been mis- 
 taken by some writers for an active dilatation, and described as 
 
THE HEAET. 275 
 
 such. It is, however, a phenomenon precisely similar to that which 
 takes place in the contraction of a voluntary muscle, which becomes 
 swollen and indurated at the same moment and in the same propor- 
 tion that it diminishes in length. 
 
 2. At the time of contraction, the ventricles elongate and the 
 poipt of the heart protrudes. This phenomenon was very well 
 described by Dr. Harvey.' " The heart," he says, " is erected, and 
 rises upward to a point, so that at this time it strikes against the 
 breast and the pulse is felt externally." The elongation of the 
 ventricles during contraction has, however, been frequently denied 
 by subsequent writers. The only modern observers, so far as we 
 are aware, who have recognized its existence, are Drs. C. W. Pen- 
 nock and Edward M. Moore, who performed a series of very careful 
 and interesting experiments on the action of the heart, in Philadel- 
 phia, in the year 1839.' These experimenters operated upon calves, 
 sheep, and horses, by stunning the animal with a blow upon the 
 head, opening the chest, and keeping up artificial respiration. They 
 observed an elongation of the ventricle at the time of contraction, 
 and were even able to measure its extent by applying a shoemaker's 
 rule to the heart while in active motion. We are able to corroborate 
 entirely the statement of these observers by the«result of our own 
 experiments on dogs, rabbits, frogs, &c. The ventricular contrac- 
 tion is an active movement, the relaxation entirely a passive one. 
 When contraction occurs and a stream of blood is thrown out of 
 the ventricle, its sides approximate each other and its point elon- 
 gates : so that the transverse diameter of the heart is diminished, 
 and its longitudinal diameter increased. This can be readily felt 
 by grasping the base of the heart and the origin of the large vessels 
 gently between the first and middle fingers;, and allowing the end 
 of the thumb of the same hand to rest lightly upon its apex. 
 With every contraction the thumb is sensibly lifted and separated 
 from the fingers, by a somewhat forcible elevation of the point of 
 the heart. 
 
 The same thing can be seen, and even measured by the eye, 
 in the following manner : If the heart of the frog or even pf any 
 small warm-blooded animal, as the rabbit, be rapidly removed from 
 the chest, it will continue to beat for some minutes afterward ; and 
 when the rhythmical pulsations have finally ceased, contractions 
 
 ' Works of William Harvey, M. P. Sydenham ed., London, 1847, p. 21. 
 • Philadelphia Medical Examiner, No. .44. 
 
276 
 
 THE CIBCULATION. 
 
 can still be readily excited by touching the heart with the point of 
 a steel needle. If the heart be now held by its base, between the 
 thumb and finger, with its point directed upward, it will be seen 
 to have a pyramidal or conical form, representing very nearly in 
 its outline an equilateral triangle (Fig. 85) ; its base, while in a 
 condition of rest, bulging out laterally, while the apex is compara- 
 tively obtuse. 
 
 Fig. 85. 
 
 Fig. 86. 
 
 Heart ov Froo 
 la A state uf relaxa- 
 tioa. 
 
 Heakt op Frog iQ contraction. 
 
 When the heart, held in this position, is touched with the point 
 of a needle (Fig. 86), it starts up, becomes instantly narrower and 
 longer, its sides approximating and its point rising to an acute 
 angle. This contraction is immediately followed by a relaxation ; 
 the point of the heart sinks down, and its sides again bulge out- 
 ward. 
 
 •Jjet us now see in what manner this change in the figure of the 
 ventricles dusing contraction is produced. If the muscular fibres 
 
 of the heart were arranged in the form of 
 simple loops, running parallel with the 
 axis of the organ, the contraction of these 
 fibres would merely have the efiFect of di- 
 minishing the size of the heart in every 
 direction. This effect can be seen in the 
 accompanying hypothetical diagram (Fig. 
 87), where the white outline represents 
 such simple looped fibres in a state of re- 
 laxation, and the dotted internal line indi- 
 cates the form which they would take in 
 contraction. In point of fact, however^' 
 none of the muscular fibres of the heart 
 run parallel to its longitudinal axis. They are disposed^ on the 
 contrary, in a direction partly spiral and partly circular. The most 
 superficial fibres start from the base of the ventricles, and pass 
 
 Diagram of Simple Looped 
 Fibres, in relaxation and con- 
 traction. 
 
THE HEART. 
 
 277 
 
 toward the apex, curling round the heart in such a manner as to 
 pass over its anterior surface in an obliquely spiral direction, from 
 above downward, and from right to left. (Fig. 88.) They converge 
 
 toward the point of the heart, curi- 
 a's- ^^' ing round the centre of its apex, and 
 then, changing their direction, be- 
 come deep-seated> run upward along 
 
 Pig. 89. 
 
 Bullock 'h Hi; art, anterior view, 
 showing the supei ficial m uscular fibres. 
 
 Left Vrntkicle op 
 Bullock's Heart, show- 
 ing tlie deep fibres. 
 
 the septum and internal surface of the ventricles, and terminate 
 in the columnas camese, and in the inner border of the aurioulo- 
 ventricular ring. The deepest layers of fibres, on the contrary, are 
 wrapped round the ventricles in a nearly circular direction (Fig. 
 89) ; their points of origin and attachment being still the auriculo- 
 ventricular ring, and the points of the fleshy columns. The entire 
 arrangement of the muscular bundles may be readily seen in a 
 heart which has been boiled for six or eight hours, so as to soften 
 the connecting areolar tissue, and enable the fibrous layers to be 
 easily separated from each other. 
 
 By far the greater part of the mass of the fibres have therefore 
 a circular instead of a longitudinal direction. When they contract, 
 their action tends to draw the lateral walls of the ventricles together, 
 and thus to diminish the transverse diameter of the heart ; but as 
 each muscular fibre becomes thickened in direct proportion to its 
 contraction, their combined lateral swelling necessarily pushes out 
 the apex of the ventricle, and the heart elongates at the same time 
 thatSts sides are drawn together. This efiect is illustrated in the 
 accompanying diagram (Fig. 90), where the white lines show the 
 figure of the heart during relaxation, with the course of its circular 
 
278 
 
 THE CIRCULATION. 
 
 fibres, while the dotted line shows the narrowed and elongated 
 figure necessarily produced by their contraction. This phenomenon, 
 
 therefore, of the protrusion of the apex 
 Fig. 90. of the heart at the time of contraction, is 
 
 not only fully established by observation, 
 but is readily explained by the anatomical 
 structure of the organ. 
 
 3. Simultaneously with the hardening 
 and elonga/tion of the heart, its apex moves 
 slightly from left to right, and rotates also 
 upon its own axis in the same direction. 
 Both these movements result from the 
 peculiar spiral arrangement of the cardiac 
 fibres. If we refer again to the preceding 
 DiagramofCjRcnT.ABFiBRKs . (Jiagrams^ we shall see that, provided the 
 
 0? THE Heart, aod their con- ■,..■,■,.■,. 
 
 traction. fibres wcre arranged in simple longitudi- 
 
 nal loops (Fig. 87), their contraction would 
 merely have the eflfect of drawing the point of the heart directly 
 upward in a straight line toward its base. On the other hand, if 
 they were arranged altogether in a circular direction (Fig, 90), 
 the apex would be simply protruded, also in a direct line, 
 without deviating or twisting either to the 
 Fig 91. right or to the left. But in. point of fact, 
 
 the superficial fibres, as we have already 
 described, run spirally, and, curling round 
 the point of the heart, turn inward toward 
 its base ; so that if the apex of the organ be 
 viewed externally, it will be seen that the 
 s.uperficial fibres converge toward its cen- 
 tral point in curved lines, as in Fig. 91. It 
 is well known. that every curved muscular, 
 fibre, at the time of its shortening,. necessa- 
 rily approximates more or less to a straight 
 line. Its curvature is diminished in exact proportion to the extent 
 of its contraction ; and if arranged in a spiral form, its contraction 
 tends in the same degree to untwist the spiral. During the con- 
 traction of the heart, therefore, its apex rotates on its own axis in 
 the direction indicated by the arrows in Fig. 91, viz., from left; to 
 right anteriorly, and from right to left posteriorly. This produces 
 a twisting movement of the apex in the above direction, which is 
 
 COHVERGING FTBRBR AT 
 
 THE Apex of the Heart, 
 
THE HEAKT. 279 
 
 very perceptible to tbe eye at each pulsation of the heart, when 
 exposed in the living animal. 
 
 4. The protrusion of the point of the heart at the time of con- 
 traction, together with its rotation upon its axis from left to right, 
 brings the apex of the organ in contact with the parietes of the 
 chest, and produces the shock or impulse of the heart,- which is 
 readily perceptible externally, both to the eye and to the touch. 
 In the human subject, when in an erect position, the heart strikes 
 the chest in the fifth intercostal space, midway between the edge 
 of the sternum and a line drawn perpendicularly through the left 
 nipple. In a supine position of the body, the heart falls away from 
 the anterior parietes of the chest so much that the impulse may 
 disappear for the time altogether. This alternate recession and 
 advance of the point of the heart, in relaxation and contraction, 
 is provided for by the anatomical arrangement of the pericardium, 
 and the existence of the pericardial fluid. As the heart plays back- 
 ward and forward, the pericardial fluid constantly follows its 
 movements, receding as the heart advances, and advancing as the 
 heart recedes. It fulfils, in this respect, the same purpose as the 
 synovial fluid, and the folds of adipose tissue in the cavity of the 
 large articulations ; and allows the cardiac movements to take place 
 to their full extent without disturbing or injuring -in any way the 
 adjacent organs. 
 
 5. The rhythm of the heart's pulsations js peculiar and somewhat 
 complicated. Each pulsation is made up of a double series of con- 
 tractions and relaxations. The two auricles contract together, and 
 afterward the two ventricles ; and in each case the contraction is 
 immediately followed by a relaxation. The auricular contraction 
 is short and feeble, and occupies the first part of the time of a 
 pulsation. The ventricular contraction is longer and more powerful, 
 and occupies the latter part of the same period. Following the 
 ventricular contraction there comes a short interval of repose, after 
 which the auricular contraction, agains recurs. The auricular and 
 ventricular contractions, however, do not alternate so distinctly 
 with each other (like the strokes of the two pistons of a fire engine) 
 as we should be led to believe from the accounts which have been 
 given by some observers. On the contrary, they are connected and 
 continuous. The contraction, which commences at the auricle, is 
 immediately propagated to the ventricle, and runs rapidly from the 
 base of the heart to its apex, very much in the manner of a peri- 
 staltic motion, except that it is more sudden and vigorous. 
 
280 THE CIRCULATION. 
 
 William Harvey, again, gives a better account of this part of the 
 heart's action than- has been published by any subsequent writer. 
 The following exceedingly graphic and appropriate description, 
 taken from his book, shows that he derived his knowledge, n6t 
 from any secondary or hypothetical sources, but from direct and 
 careful study of the phenomena in the living animal. 
 
 "First of all," he says,' "the auricle contracts, and in the course 
 of its contrafction throws the blood (which it contains in ample 
 quantity as the head of the veins, the storehouse and cistern of the 
 blood) into the ventricle, which being filled, the heart raises itself 
 straightway, makes all its fibres tense, contracts the ventricles, and 
 performs a beat, by which beat it immediately sends the blood 
 supplied to it by the auricle, into the arteries ; the -right ventricle 
 sending its charge into the lungs by the vessel which is called vena 
 arteriosa, but which, in structure and function, and all things else, 
 is an aj'tery ; the left ventricle sending its charge into the aorta, 
 and through this by the arteries to the body at large. 
 
 " These two motions, one of the ventricles, another of the auricles, 
 take place consecutively, but in such a manner that there is a kind 
 of harmony or rhythm preserved between them, the two concurring 
 in such wise j;hat but one motion is apparent, especially in the 
 warmer blooded animals, in which the movements in question are 
 rapid. Nor is this for any other reason than it is in a piece of 
 machinery, in which, though one wheel gives motion to another, 
 yet all the wheels seem tQ move simultaneously; or in, that 
 mechanical contrivance which is adapted to fire-arms, where the 
 trigger being touched, down comes the flint, strikes against the 
 steel, elicits a spark,, which falling among the powder, it is ignited, 
 upon which the flame extends, enters the barrel, causes the explo- 
 sion, propels the ball, and the mark is attained ; all of which inci- 
 dents, by reason of the celerity with which they happen, seem to 
 take place in the twinkling of an eye." 
 
 The above description indicates precisely the manner in which 
 the contraction of the ventricle follows successively and yet con- 
 tinuously upon that of the auricle. The entire action of the auricles 
 and ventricles during a pulsation is accor.dingly as follows : The 
 contraction begins, as we have already stated, at the auricle. 
 Thence it runs immediately forward to the apex of the heart. The 
 entire ventricle contracts vigorously, its walls -harden, its apex 
 
 • Op. oit., p. 31. 
 
THE ARTEBIES AND THE ABTEEIAL CIBCULATIOX. 281 
 
 protrudes, strikes against the walls of*tlie chest, and twists from 
 left to right, the auriculo-^entricular valves shut back> the first 
 sound is produced, and the blsod is driven into the aorta and 
 pulmonary artery. These phenomena occupy about one-half the 
 time of an entire pulsation. Then the ventricle is immediately 
 relaxed, and a short period of repose ensues. During this period 
 the blood flows in a steady stream from the large veins into the 
 auricle, and through the auriculo-ventricular orifice into the ven- 
 tricle; filling the ventricle, by a kind of passive dilatation, about 
 two-thirds or three-quarters fulL Then the auricle contracts with a 
 quick sharp motion, forces the last drop, of blood into the ventricle, 
 distending it to its full capacity, and then the ventricular contraction 
 follows, as above described, driving the blood into the large arteries. 
 These movements of contraction and relaxation continue to alter- 
 nate with each other, and form, by their recurrence, the successive 
 cardiac pulsations. 
 
 THE ARTERIES AND THE ARTERIAL CIRCULATION. 
 
 The arteries are a saries of branching tubes which commence 
 with the aorta and ramify throughout the body, distributing the 
 blood to all the vascular organs. They are composed of three 
 coats, viz: an internal homogeneous tunic, continuous with the 
 endocardium; a middle coat, composed of elastic and muscular 
 fibres ; and an external or " cellular" coat, composed of -condense'd 
 layers of areolar .tissue. The essential anatomical difference be- 
 tween the larger and the smaller arteries consists in the structure 
 of their middle coat. In the smaller arteries this coat is composed 
 exclusively of smooth muscular fibres, arranged in a circular man- 
 ner around the vessel, like the circular fibres of the muscular coat 
 of the intestine. In arteries of medium size the middle coat con- 
 tains both muscular and elastic fibres; while in those of the largest 
 calibre it consists of elastic tissue alone. The large arteries, ac- 
 cordingly, possess a remarkable degree of elasticity and little or no 
 contractility ; while the smaller are contractile, and but little or not 
 at all elastic. 
 
 It is found, by measuring the diameters of the successive arte- 
 rial ramifications, that the combined area of all the branches given 
 off from a trunk is somewhat greater than that of the original 
 vessel ; and therefore that the combined area of all the small arte- 
 ries must be considerably larger than that of the aorta, from which 
 
282 THE CIBCULATIOX. 
 
 the arterial system originStes. As the blood, consequently, in its 
 passage from the heart outward, flows successively through larger 
 and larger spaces, the rapidity of its circulation must necessarily 
 be diminished, in the same proportion as it recedes from the heart. 
 It is driven rapidly through the larger trunks, more slowly through 
 those of medium size, and more slowly still as it approaches the 
 termination of the arterial system and the commencement of the 
 capillaries. 
 
 The movement of the Mood through the arteries is primarily caused 
 by the contractions of the heart ; but is, at the same time, regulated 
 and modified by the elasticity of the vessels. The mode in which v 
 the arterial circulation takes place is as follows. The arterial sys- 
 tem is, as we have seen, a vast and connected ramification of tubular 
 canals, which may be regarded as a- great vascular cavity, divided 
 and subdivided from within outward by the successive branching 
 of its vessels, but communicating freely with the heart and aorta 
 at one extremity, and with the capillary plexus at the other; 
 and this vascular system is filled everywhere with the circulating 
 fluid. At the time of the heart's contraction, the muscular walls of 
 the ventricle act powerfully upon its fluid contents. The auriculo- 
 ventricular valves at the same time shutting back and preventing 
 the blood from regurgitating into the ventricle, it is forced out 
 through the aortic orifice. A charge of blood is therefore driven 
 into the arterial ramifications, distending their walls by the addi' 
 tional quantity of fluid forced into their cavities. When the ven- 
 tricle immediately afterward relaxes, the active distending force is 
 removed ; and the elastic arterial walls, reacting upon their contents, 
 would force the blood back again into the heart, were it not for the 
 semilunar valves, which shut together and close the aortic orifice. 
 The blood is therefore urged onward, under the pressure of the 
 arterial elasticity, into the capillary system. When the arteries 
 have thus again partially emptied themselves, and returned to their 
 original dimensions, they are again distended by another contraction 
 of the heart. In this manner a succession of impulses or distensions 
 is produced, which alternates with the reaction or subsidence of the 
 vessels, and which can be felt throughout the body, wherever the 
 arterial ramifications penetrate. This phenomenon is known by 
 the name of the arterial pulse. 
 
 When the blood is thus driven by the cardiac pulsations into the 
 arteries, the vessels are not only distended laterally, but are elongated 
 as well as widened, and enlarged in every direction. Particularly 
 
THE ABTEBIES AND THE ARTERIAL CIRCULATION. 283 
 
 when the vessel takes-a curved or serpentine course, its elongation 
 and the increase of its curvatures may be observed at every pulsa- 
 tion. This may be. seen, for example, in the temporal, or even 
 in the radial arteries, in emaciated persons. It is also very well 
 seen in the mesenteric arteries, when the abdomen is opened in the 
 living animal. At every contraction of the heart the curves of 
 the artery on each side become more strongly pronounced. (Fig. 
 92.) The vessel even rises up partially out of its 
 bed, particularly wjjere it runs over a bony sur- ^^' ^ 
 
 face, as in the case of the radial artery. In old 
 persons the curves of the vessels become perma- 
 nently enlarged from frequent distension ; and all 
 the arteries tend to assume, with the advance of 
 age, a more serpentine and even spiral course. 
 
 But the artCTial pulse has certain other pecu- 
 liarities which deserve a special notice. In the 
 first place, if we place one finger upon the chest 
 at the situation of the apex of the heart, and an- 
 other upon the carotid artery at the middle of 
 the neck, we can distinguish liltle or no difference 
 in time between the two impulses. The disten- Elongation and curva- 
 sion of the carotid seems to take place at the »"" »' "" a»teei i.^. 
 
 ^ rULSATlON. 
 
 same instant with the contraction of the heart. 
 But if the second finger be placed upon the temporal artery, instead 
 of the carotid, there is a perceptible interval between the two beats. 
 The impulse of the temporal artery is felt a little, later than that of 
 the heart. In the same way the pulse of the radial artery at the 
 wrist seems a little later than that of the carotid, and that of the 
 posterior tibial at the ankle joint a little later than that of the radial. 
 So that, the greater the distance from the heart at which the artery 
 is examined, the later is the pulsation perceived by the finger laid 
 upon the vessel. 
 
 But it has been conclusively sh"own, particularly by the investi- 
 gations of M. Marey,' that this difference in time of the arterial 
 pulsations, in different parts of the body, is rather relative than 
 absolute. By the contraction of the heart, the impulse is commu- 
 nicated at the same instant to all parts, of the arterial system ; but 
 the apparent difference between them, in this respect, depends upon 
 the fact, that, although all the arteries begin to be distended at the 
 
 ' Dr. Brown-Seqnard's Journal de Pliyslologie, April, 18.59. 
 
284 THE CIBCULATION. 
 
 same moment, yet those nearest the heart are distended suddenly 
 and rapidly, while for those at a distance, the distension takes place 
 more slowly and gradually. Thus the impulse given to the finger, 
 which marks the condition of maximum distension of the vessel, 
 occurs a little later at a distance from the heart, than in its imme- 
 diate proximity. 
 
 This modification of the arterial pnlse is produced in the follow- 
 ing way : — 
 
 The contraction of the left ventriqle is a bru^ue, vigorous and 
 sudden motion. The charge of blood, thus driven into the .arterial 
 system, meeting with a certain amount of resistance from the fluid , 
 already filling the vessels, does not instantly displace and force 
 onward a quantity of blood equal to its own mass, but a large 
 proportion of its force is used in expanding the Ostensible walls 
 of the vessels. In the immediate neighborhood, therefore, the 
 expansion of the arteries is sudden and momentary, like the con- 
 traction of the heart itself. But this expansion requires for itB 
 completion a certain expenditure, both of force and time ; so that 
 at a little distance farther on, the vessel is neither distended to the 
 same degree nor with the same rapidity. At the more distant 
 point, accordingly, the arterial impulse is less pow^irful and arrives 
 more slowly at its maximum. ' 
 
 On the other hand, when the heart becomes relaxed, the artery 
 in its immediate neighborhood contracts upon the blood by its own 
 elasticity ; and as its contraction at this time meets with no other 
 resistance than that of the blood in the smaller Vessels beyond, it 
 drives a portion of its own blood into them, and thus supplies these 
 vessels with a certain degree of distending force even in the inter- 
 vals of the heart's action. Thus the difference in size of the carotid 
 artery, at the two periods of the heart's contraction and its relaxa^ 
 tion, is very marked ; for the degree of its distension is great when 
 the heart contracts, and its own reaction afterward empties it of 
 blood to a very considerable extent. But in the small branches of 
 the radial or ulnar artery, there is less distension at the time of the 
 cardiac contraction, because this force has been partly expended in 
 overcoming the elasticity of the larger vessels; and there .'is less 
 emptying of the vessel afterward, because it is still kept partially 
 filled by the reaction of the aorta and its larger branches. In other 
 words, there is progressively less variation in* size, at the periods .of 
 distension and collapse, for the smaller and distant arteries than for 
 those which are larger and nearer the heart. 
 
THE ARTERIK3 AND THE ARTERIAL CIRCULATION. 285 
 
 Mr. Marey has illustrated these facts by an exceedingly ingenious 
 and effectual contrivance. He attached to the pipe of a small forcing 
 pump, to be worked by alternate strokes of the piston, a long elastic 
 tube open at the farther extremity. At diflferent points upon this 
 tube there rested little movable levers, which were raised by the 
 distension of the tube whenever water was driven into it by the 
 forcing pump. Each lever carried upon its extremity a small pen- 
 cil, which marked upon a strip of paper, revolving with uniform 
 rapidity, the lines produced by its alternate elevation and depression. 
 By these curves, therefore, both the extent and rapidity of distension 
 .of different parts of the elastic tube were accurately registered. 
 The curves thus produced are as follows : — 
 
 Fig. 93. 
 
 Curves op the Arterial PirLBATii>K,aa ilTaBtrated by M, Marey *8 experiment. — 1. Near 
 the dUtendiDg force. 2. At a distance from it. 3. Still farther reraoved. 
 
 It will be seen that the whole time of pulsation is everywhere of 
 equal length, and that the distension everywhere begins at the same 
 moment. But at the beginning of the tube the expansion is wide 
 and sudden, and occupies only a sixth part of the entire pulsation, 
 while all the rest is taken up by a slow reaction. At the more 
 repiote points, however, the period of expansion becomes longer 
 and that of collapse shorter; until at 3 the two periods are com- 
 pletely equalized, and the amount of expansion is at the same time 
 reduced one-half. Thus, the farther the blood passes from the heart 
 outward, the more uniform is its flow, and the more moderate the 
 distension of the arteries. 
 
 Owing to the alternating contractions and relaxations of the heart, 
 accordingly, the blood passes through the arteries, not in a steady 
 stream, but in a series of welling impulses ; and the hemorrhage 
 from a wounded artery is readily distinguished from venous or 
 capillary hemorrhage by the fact that the blood flows in successive 
 jets, as well as more rapidly and abundantly. If a puncture be 
 made in the walls of the ventricle, and a slender canula introduced. 
 
286 THE CIKOULATION, 
 
 the flow of the blood through it is seen to be entirely intermittent. 
 A strong jet takes place at each ventricular contraction, and at each 
 relaxation the flow is completely interrupted. If the puncture be 
 made, however, in any of the large arteries near the heart, the flow 
 of blood through the orifice is no longer intermittent, but is con- 
 tinuous ; only it is very much stronger at the time of ventricular 
 contraction, and diminishes, though it does not entirely cease, at 
 the time of relaxation. If the blood were driven through a series 
 of perfectly rigid and unyielding tubes, its flow would be every- 
 where intermittent ; and it would be delivered from an orifice situ- 
 ated at any point, in perfectly interrupted jets. But the arteries 
 are yielding and elastic; and this elasticity, as .we have already 
 explained, moderates the force of the separate arterial pulsations, 
 and gradually fuses them with each other. The interrupted, or 
 pulsating character of the arterial current, therefore, which is 
 strongly pronounced in the immediate vicinity of the heart, becomes 
 gradually lost and equalized, during its passage through the vessels, 
 until in the smallest arteries it is nearly impefceptible. 
 
 The same effect of an elastic medium in equalizing the force of 
 an interrupted current may be shown by fitting to the end of a 
 common syringe a long glass or metallic tube. Whatevar be the 
 length of the inelastic tubing, the water which is thrown into one 
 extremity of it by the syringe will be delivered from the other end 
 in distinct jets, corresponding with the strokes of the piston ; but if 
 the metallic tube be replaced by one of India rubber, of sufficient 
 length, the elasticity of this substance merges the force of the sepa- 
 rate impuls^ into each other, and the water is driven out from the 
 farther extremity in a continuous stream. 
 
 The elasticity of the arteries, however, never entirely equalizes 
 the force of the separate cardiac pulsations, since a pulsating cha- 
 racter can be seen in the flow of the blood through even the smallest 
 arteries, under the microscope ; but this pulsating character dimi- 
 nishes very considerably from the heart outward, and the current 
 becomes much more continuous in the smaller vessels than in the 
 larger. 
 
 The primary cause, therefore, of the motion of the blood in the 
 arteries is the contraction of the ventricles, which, by driving out 
 the blood in interrupted impulses, distends at every stroke the 
 whole arterial system. But the arterial pulse is not exactly syn- 
 chronous everywhere with the beat of the heart ; since a certain 
 amount of time is required to propagate the blood-wave from the 
 
THE ARTERIES AND THE ARTERIAL CIRCULATION. 287 
 
 centre of the circulation outward. The pulse of the radial artery 
 at the wrist is perceptibly later than that of the heart; and the 
 pulse of the posterior tibial at the ankle, again, perceptibly later 
 than that at the wrist. The arterial circulation, accordingly, is not 
 an entirely simple phenomenon ; but is made up of the combined 
 effects of two different physical forces. In the first place, there is 
 the elasticity of the entire arterial system, by which the blood is 
 subjected to a constant and uniform pressure, quite independent of 
 the action of the heart. Secondly, there is the alternating contrac- 
 tion and relaxation of the heart, by which the blood is driven in 
 rapid and successive impulses from the centre of the circulation, to 
 be thence distributed throughout the body. 
 
 The passage of the blood through the arterial system takes place 
 under a certain degree of constant pressure. For these vessels being 
 everywhere elastic, and filled with blood, they constantly tend to 
 react, more or less vigorously, and to compress the circulating fluid 
 which they contain. If any one of the arteries, accordingly, be 
 opened in the living animal, and a glass tube inserted, the blood 
 will immediately be seen to rise in the tube to a height of about 
 five and a half or six feet, and will remain at that level ; thus indi- 
 cating the pressure to which it was subjected in the interior of the 
 vessels. This constant pressure, which is thus due to the reaction 
 of the entire arterial system, is known as the m-terial pressure. 
 
 The degree of arterial pressure may be easily measured by con- 
 necting the open artery, by a flexible tube, with a small reservoir 
 of mercury, which is provided with a narrow upright glass tube, 
 open at its upper extremity. When the blood, therefore, urged by 
 the reaction of the arterial walls, praeses upon the surface of the 
 merctrry in the receiver, the mercury rises in the upright tube, to 
 a corresponding height. By the use of this instrument it is seen, 
 in the first place, that the arterial pressure is nearly the same all 
 over the body. , Since the cavity of the arterial system is every- 
 where continuous, the pressure must necessarily be communicated, 
 by the blood in its interior, equally in all directions. Accordingly, 
 the constant pressure is the same, or nearly so, in the larger and the 
 smaller arteries, in those nearest the heart, and those at a distance. 
 This constant pressure averages, in the higher quadrupeds, six 
 inches of mercury, which is equivalent to from five and a half to 
 six feet of blood. 
 
 It is also seen, however, in employing such an instrument, that 
 the level of the mercury, in the upright tube, is not perfectly steady. 
 
288 THE CIBCULATION. 
 
 but rises and falls with the pijlsations of the heart. Thus, at every 
 contraction of the ventricle, the mercury rises fbr about half an 
 inch, and at every relaxation it falls to its previous level. .Thus the 
 instrument becomes a measure, not only for the constant pressure of 
 the arteries, but also for the intermitting pressure of the heart ; and 
 on that account it has received the name of the cardiometer. It is 
 seen, accordingly, that each contraction of the heart is superior in 
 force to the reaction of the arteries by about one-twelfth ; and these 
 vessels are kept filled by a succession of cardiac pulsations, and 
 discharge their contents in turn into the capillaries, by their own 
 elastic reaction. 
 
 The rapidity with which the blood circulates through the arterial 
 system is very great. Its velocity is greatest in the immediate 
 neighborhood of the heart, and diminishes somewhat as the blood 
 recedes fai;ther and farther from the qentre of the circulationi i This 
 diminution in the rapidity of the arterial current is due to the suc- 
 cessive division of the aorta and its primary branches into smaller 
 and smaller ramifications, by which the total calibre of the arterial 
 system, as we have already mentioned, is somewhat increased. The 
 blood, therefore, flowing through a larger space as it passes outward, 
 necessarily moves more slowly. At the same time the increased 
 extent of the arterial parietes with which the blood comes in con- 
 tact, as well as the mechanical obstacle arising from the division of 
 the vessels and the separation of the streams, undoubtedly contri- 
 -butes more or less to retard the currents. The mechanical.obstacle, 
 however, arising from the friction of the blood against the walls of 
 the vessels, which would be very serious in the case of water or any 
 similar fluid flowing througli glass or metallic tubes, has compara- 
 tively little effect on the rapidity of the arterial circulation. This 
 can readily be seen by microscopic examination of any transparent ' 
 and vascular tissue. The internal surface of the arteries is so smooth 
 and yielding, and the consistency of the circulating fluid so accu- 
 rately adapted to that of the vessels which- contain it, that the 
 retarding effects of friction are reduced to a minimum, and tlie 
 blood in flowing through the vessels meets with the least possible 
 resistance. 
 
 It is owing to this fact that the arterial circulation, though some- 
 what slower toward the periphery than near the heart, yet retains 
 a very remarkable velocity throughout; and even in arteries of the 
 minutest size it is so rapid that the shape of the blobd-globules can- 
 not be distinguished in it on microscopic examination, but only a 
 
THB ARTEEIES AND THK AETKBIAL CIRCULATION, 289 
 
 mingled current shooting forward with increased velocity at every 
 cardiac pulsation. Volkmann, in Germany, has determined, by a 
 very ingenious contrivance, the velocity of the current of blood in 
 some of the large sized arteries in dogs, horses, and calves. The 
 instrument which he employed (Fig. 94) consisted of a metallic 
 cylinder (a), with a perforation running from end to end, and cor- 
 responding in size with the artery to be examined. The artery 
 was divided transversely, and its cardiac extremity fastened to the 
 upper end (b) of the instrument, while its peripheral extremity was 
 
 Fig. 94. 
 
 VoiHjrANN'B AppAKATUd for meaaaring thp rapidUy of the artorml circulation. 
 
 fastened in the same manner to the lower end (c). The blood 
 accordingly still kept on its usual course ; only passing for a short 
 distance through the artificial tube (a), between the divided extremi- 
 ties of the artery. The instrument, however, was provided, as shown 
 in the accompanying figures, with two transverse cylindrical plugs, 
 also perforated ; and arranged in such a manner, that when, at a 
 19 
 
290 THE CIRCULATION. 
 
 given signal, the two plugs were suddenly turned in opposite 
 directions^ the stream of blood would be turned out of its course 
 (Fig. 95), and made to traverse a long bent tube of glass {d, d, d), 
 before again finding its way back to the lower portion of the artery. 
 In this way the distance passed over by ttie blood in a given time 
 could be readily measured upon a scale attached to the side of the 
 glass tube. Volkmann found, as the liverage result of his obser- 
 vations, that the blood moves in the carotid arteries of warm-blooded 
 quadrupeds with a velocity of 12 inches per second. 
 
 VENOUS CIRCULATION. 
 
 The veins, which collect the blood from the tissues and return it 
 to the heart, are composed, like the;' arteries, of three coats; an inner, 
 middle, and exterior. In structure, they differ from the arteries in 
 containing a much smaller quantity of muscular and elastic fibres, 
 and a larger proportion of simple condensed areolar tissue. They 
 are conseqijently more flaccid and compressible than the arteries, 
 and less elastic and contractile. They are furthermore distin- 
 guished, throughout the limbs, neck, and external portions of the 
 head and trunk, by being provided with valves, consisting of fibrous 
 sheets arranged in the form of festoons, and so placed in the cavity 
 of the vein as to allow the blood to pjiss readily from the periphery 
 toward the heart, while they prevent altogether its reflux in an 
 opposite direction. 
 
 Although' the veins are provided with walls which are very much 
 thinner and less elastic than those of the arteries, yet, contrary to 
 what we. might expect, their capacity for resistance to pressure is 
 equal, or even superior, to that of the arterial tubes. Milne Ed- 
 wards' has collected the results of various experiments, which show 
 that the veins will sometimes resist a pressure which is sufficient to 
 rupture the walls of the arteries. In one instance the jugular vein 
 supported, without breaking, a pressure equal to a column of water 
 148 feet in height ; and in another, the iliac vein of a sheep resisted 
 a pressure of more than four atmospheres. The portal vein was 
 found capable of resisting a pressure of six atmospheres; and in 
 one case, in which the aorta of a sheep was ruptured by a pressure 
 of 158 pounds, the vena cava of the same animal supported a pres- 
 sure equal to 176 pounds. 
 
 , ' Le9on3 sur la Pliysiologie, &o., toI. iv. p. 301. 
 
VENOCra CIRCtTLATIOK. 291 
 
 This resistance of the veins is to be attributed to the large pro- 
 portion of white fibrous tissue which enters into their composition ; 
 the same tissue which forms nearly the whole of the tendons and 
 fasciae, and which is distinguished by its density and unyielding 
 nature. 
 
 The elasticity of the veins, however, is much less than that of the 
 arteries. When they are filled with blood, they enlarge to a certain 
 size, and collapse again when the pressure is taken off; but they do 
 not react by virtue of an elastic resilience, or, at least, only to a 
 slight extent, as compared with the arteries. Accordingly, when 
 the arteries are cut across, and emptied of blood, they still remain 
 open and pervious, retaining the tubular form, on account of the 
 elasticity of their walls ; while, if the veins be treated in the same 
 way, their sides simply fall together and remain in contact with each 
 other. 
 
 Another peculiarity of the venous system is the abundance of 
 the separate chanridsi which it affords, for the flow of blood from 
 the periphery towards the centre. • The arteries pass directly from 
 the heart outward, each separate branch, as a general rule, going 
 to a separate region, and supplying that part of the body with 
 all the blood which it 'requires ; so that the arterial system is kept 
 constantly filled to its entire capacity with the blood which passes 
 through it. But that is not the case with the veins. In injected 
 preparations of the vascular system, we have often two, three, 
 four, or even five veins, coming together from the same region of 
 the body. ' There are also abundant inosculations between the dif- 
 ferent veins. The deep veins which accompany the brachial artery 
 inosculate freely with each other, and also wiljh the superficial veins 
 of the arm. In the veins coming from the head, we have the ex- 
 ternal jugular communicating with the thyroid veins, the anterior 
 jugular, and the brachial veins. The external and internal jugulars 
 communicate with each other, and the two thyroid veins also form 
 an abundant plexus in front of the trachea. 
 
 Thus the blood, coming from the extremities toward the heart, 
 flows, not in a single channel, but in many channels ; and as these 
 channels communicate freely with each other, the blood passes some- 
 times through one of them, and sometimes through another. 
 
 The flow, of blood through the veins is less powerful and regular 
 than that through the arteries. It depends on the combined action 
 of three different forces. 
 
292 THE CIRCULATION. 
 
 1. The force of aspiration of the thorax. — When the chest expands 
 by the lifting of the ribs and the descent of the diaphragm, its 
 movement, of course, tends to diminish the pressure exerted upon 
 its contents, and so has the effect of drawing into the thoracic cavity 
 all the fluids which can gain access to it. The expanded cavity is 
 principally filled by the air, which passes in through the trachea 
 and fills the bronchial tubes and the pulmonary vesicles. But the 
 blood in the veins is also drawn into the chest at the same time and 
 by the same force. This force of aspiration, exerted by the expan- 
 sion of the chest, is gentle and uniform in character, like the move- 
 ments of respiration themselves. Accordingly its influence is ex- 
 tended, without doubt, to the farthest extremities of the venous 
 system, the blood being gently solicited toward the heart, at each 
 expansion of the chest, without any visible alteration in the size of 
 the veins, which are filled up from behind as fast as they are emptied 
 in front. 
 
 But if the movement of inspiration be sudden and violent, instead 
 of gentle and easy, a different effect is produced. For then the walls 
 of the veins, which are thin "and flaccid, cannot retain their position, 
 but collapse under the external pressure too rapidly to allow the 
 blood to flow in from behind. In this case, therefore, the vein is 
 simply emptied in the immediate neighborhood of the chest, but 
 the entire venous circulation is not assisted by the movement. 
 
 The same difference in the effect of an easy and a violent suction 
 movement, may be readily shown by attaching to the nozzle of an 
 air-tight syringe a flexible elastic tube with thin walls, and placing 
 the other extremity of the tube under water. If the piston of the 
 syringe be "now withdrawn with a gentle and gradual" motion, the 
 water will be readily drawn up into the tube, while the tube itself 
 suffers no visible change; but if the suction movement be made 
 rapid and violent, the tube will collapse instantly under the pres- 
 sure of the air, and will fail to draw the water into its cavity. 
 
 A similar effect shows itself in the living body. If the jugular 
 or subclavian vein be exposed in a dog or cat, it will be seen that 
 while the movements of respiration are natural and easy no fluc- 
 tuation in the vein can be perceived. But as soon as the respira- 
 tion becomes disturbed and laborious, then at each inspiration the 
 vein is collapsed and emptied ; while during expiration, the chest 
 being strongly compressed and the inward flow of the blood arrested, 
 the vein becomes turgid with blood which accumulates in it from 
 behind. In young children, also, the spasmodic movements of res- 
 
VEX0U3 CIRCULATION. 
 
 293 
 
 piration in crjing produce a similar turgescence and engorgement 
 of the large veins during expiration, while they are momentarily 
 emptied during the hurried and forcible inspiration. 
 
 In natural and quiet respiration, therefore; the movements of the 
 chest hasten and assist the venous circulation ; but in forced or 
 laborious respiration, they do not assist and may even retard its flow. 
 
 2. Tlie contrctction of the voluntarg muscles. — ^The veins which 
 convey the blood through the limbs, and the parietes of the head 
 and trunk, lie among voluntary muscles, which are more or less 
 constantly in a state of alternate contraction and relaxation. At 
 every contraction these muscles become swollen laterally, and, of 
 course, compress the veins which are situated between them. The 
 blood, driven out from the vein by this pressure, cannot regurgitate 
 toward the capillaries, owing to the valves, already described, which 
 shut back and prevent its reflux. It is accordingly forced onward 
 toward the heart; find when the muscle relaxes and the vein is 
 liberated from pressure, it again fills up from behind, and the cir- 
 culation goes on as before. This force is a very efficient one in 
 producing the venous circulation ; since the voluntary muscles are 
 more or less active in every position of the body, and the veins 
 constantly liable to be compressed by them. It is on this accoiint 
 
 Fig. 96. 
 
 Pig. 97. 
 
 VjilN with vulvcd open. 
 
 Vein with valves closed; stream of 
 blood passiDg off by a lateral cbanael. 
 
 that the veins, in the external parts of the body, communicate so 
 freely with each other by transverse branches ; in order that the 
 current of blood, which is momentarily excluded from one vein by 
 
294 THE CIRCULATION. 
 
 the pressure of the muscles, may readily find a passage through 
 others, which communicate by cross branches with the first. (Figs. 
 96 and 97.) ^ 
 
 S. The force of the capillary circulation. — THis last cause of the 
 motion of the blood through the veins is the most important of all, 
 as it is the only one which is constantly and universally active. In 
 fish, for example, respiration is performed altogether by gills ; and 
 in reptiles the air is forced down into the lungs by a kind of deglu- 
 tition, instead of being drawn in by the expansion of the chest. In 
 neither of these classes, therefore, can the movements of respiratioE 
 assist mechanically in the circulation of the blood. In the splanch- 
 nic cavities, again, of all the vertebrate animals, the veins coming 
 from the internal organs, as, for example, the cerebral, pulmonary, 
 portal, hepatic, and renal veins, are unprovided with valves; and 
 the passage of the blood through them cannot therefore be effected 
 by any lateral pressure. The circulation, however, constantly going 
 on in the capillaries, everywhere tends to crowd the radicles of the 
 veins with blood ; and this vis a tergo, or pressure from behind, fills 
 the whole venous system by a constant and steady accumulation. 
 So long, therefore, as the veins are relieved of blood at their cardiac 
 extremity by the regular pulsations of the heart, there is no back- 
 ward pressure to oppose the impulse derived from the capillary cir- 
 culation ; and the movement of the blood through the veins continues 
 in a steady and uniform course. 
 
 With regard to the rapidity of the venous circulation, no direct 
 results have been obtained by experiment. Owing to the flaecidity 
 of the venous parietes, and the readiness with which the flow of 
 blood through them is disturbed, it is not possible to determine this 
 point for the veins, in the same manner as it has been determined 
 for; the arteries. The only calculation which has been made in this 
 respect is based upon a comparison of the total capacity of the 
 arterial and venous systems. As the same blood which passes out- 
 ward through the arteries, passes inward again through the veins, 
 the' rapidity of its flow in each must be in inverse proportion to the 
 capacity of the two sets of vessels. That is to say, a quantity of 
 blood, which would pass in a given time, with a velocity of x, 
 through an opening equal to one square inch, would pass during 
 the same time through an opening equal to two square inches, with 
 a velocity of | ; and would require, on the other hand, a velocity 
 of 2 X, to pass in the same ^ime through an opening equal to one- 
 half a square inch. Now the capacity of the entire venous system. 
 
THE CAPILLABY CIBCULATIOX. 
 
 295 
 
 when distended by injection, is about twice as great as that of the 
 entire arterial system. During life, however, the venous system is 
 at no time so completely filled with blood as is the case with the 
 arteries, and, making allowance for this difference, we find that the 
 entire quantity of venous blood is to the entire quantity of arterial 
 blood nearly as three to two. The velocity of the venous blood, 
 as compared with that of the arterial, is therefore as two to three ;• 
 or about 8 inches per second. It will be understood, however, that 
 this calculation is altogether approximative, and not exact ; since 
 the venous current varies, according to many different circumstances, 
 in different parts of the body ; being slower near the capillaries, 
 and more rapid near the heart. It expresses, however, with suffi- 
 cient accuracy, the relative velocity of the arterial and venous cur- 
 rents, at corresponding parts, of their conrse. 
 
 Fig. 98. 
 
 THE CAPILLAET CIECULATION, 
 
 The capillary bloodvessels are minute inosculating tubes, which, 
 permeate the vascular organs in every direction, and bring the 
 blood into intimate contact with the substance of the tissues. They 
 are continuous with the terminal ramifications of the arteries on 
 the one hand, and with the com- 
 mencing rootlets of the veins on 
 the other. They vary somewhat 
 in size in different organs, and in 
 different species of animals ; their 
 average diameter in the human 
 subject being a little over 55*^^ of 
 an inch. They are composed of. 
 a single, transparent, homogene- 
 ous, somewhat elastic, tubular 
 membrane, which is provided at 
 various intervals with flattened, 
 oval nuclei. As the smaller arte- 
 ries approach the capillaries, they 
 diminish constantly in size by 
 successive subdivision, and lose 
 first their external or fibrous 
 tunic. They are then composed 
 
 only of the internal or homogeneous coat, and the middle or muscu- 
 lar. (Fig. 98, a.) The middle coat then diminishes, in thickness. 
 
 SmaT'Tj Artf.et, with ito musciilHr tunic 
 (fi), breaking np iuto caplllarieit. Fruui tUe-pla 
 nuiUr. 
 
296 
 
 THE CIKCULATION. 
 
 until it is reduced to a single layer of circular, fusiform, unstriped, 
 muscular fibres, whicli in their turn disappear altogether, as the 
 artery merges at last in the capillaries ; leaving only, as we have 
 already mentioned, a simple, homogeneous, nucleated, tubular mem- 
 brane, which is continuous with the internal arterial tunic. 
 
 The capillaries are further distinguished from both arteries and 
 •veins by their frequent inosculation. The arteries constantly 
 divide and subdivide, as they pass from within outward ; while 
 the veins as constantly unite with each other to form larger and 
 . less numerous branches and trunks, as they pass from the circum- 
 ference toward the centre.. But the capillaries simply inosculate 
 with each other in every direction, in such a manner as to form an 
 interlacing network or plexus,, the capillary plexus (Fig. 99), which 
 is exceedingly rich and abundant in some organs, less so in others. 
 The spaces included between the meshes of the capillary network 
 vary also, in shape as well as in size, in different parts of the body. 
 
 In the muscular tissue they 
 ^*8- 93. form long parallelograms ; in 
 
 the areolar tissue, irregular 
 shapeless figures, correspond- 
 ing with the direction of the 
 fibrous bundles of which the 
 tissue is composed. In the 
 mucous membrane of the 
 large intestine, the capillaries 
 include hexagonal or nearly 
 circular spaces, inclosing the 
 orifices of the follicles. In 
 the papillae of the tongue and 
 of the skin, and in the tufts 
 of the placenta, they are 
 arranged in long spiral loops, 
 and in the adipose tissue in wide meshes, among which the fat 
 vesicles are entangled. 
 
 The motion of the blood in the capillaries may be studied by 
 examining under the microscope any transparent tissue, of a 
 sufficient degree of vascularity. One of the most convenient parts 
 for this purpose is the web of the frog's foot. When properly 
 prepared and kept moistened by the occasional addition of water 
 to the integument, the circulation will go on in its vessels for an 
 indefinite length of time. The blood can be seen entering the 
 
 Capillar? Network from web of frog's foot. 
 
THE CAPILLAEY CIRCULATION. 
 
 297 
 
 Fig. 1(10. 
 
 field by the smaller arteries, shooting through them with great 
 rapidity and in successive impulses, and flowing oflF again by the 
 veins at a somewhat slow rate. In the capillaries themselves 
 the circulation is considerably less rapid than in either the arteries 
 or the veins. It is also perfectly steady and uninterrupted in its 
 flow. The blood passes along in a uniform and continuous current, 
 without any apparent contraction or dilatation of the vessels, very 
 much as if it were flowing 
 through glass tubes. An- 
 other very remarkable pe- 
 culiarity of the capillary 
 circulation is that it has no 
 definite direction. The nu 
 merous streams of which it 
 is composed (Fig. 100) do 
 not tend to the right or to 
 the left, nor toward any one 
 particular point. On the 
 contrary, they pass above 
 and below each other, at 
 right angles to each other's 
 course, or even in opposite 
 directions ; so that the blood, 
 while in the capillaries, merely circulates promiscuously among 
 the tissues, in such a manner as to come intimately in contact witb 
 • every part of their substance. 
 
 The motion of the white and red globules in the circulating blood 
 is also peculiar, and shows very distinctly the difl:erence in their 
 consistency and other physical properties. In the larger vessels 
 the red globules are carried along in a dense column, in the central 
 part of the stream ; while near the edges of the vessel there is a 
 transparent space occupied only by the clear plasma of the blood, 
 in which no red globules are to be seen. In the smaller vessels, 
 the globules pass along in a narrower column, two by two, or 
 following each other in single file. The flexibility and semi-fluid 
 consistency of these globules are here very apparent, from tlie 
 readiness with which they become folded up, bent or twisted in 
 turning corners, and the ease with which they glide, through minute 
 branches of communication, smaller in diameter than themselves. 
 The white globules, on the other hand, flow more slowly and with 
 greater difficulty through the vessels. They drag along the exter 
 
 Cafili.abt CiRODiArioN ill web uf r. og'a fuot. 
 
298 THE CIBCULATIOX. 
 
 nal portions of the current, and are sometimes momentarily arrested ; 
 apparently adhering for a few seconds to the internal surface of the 
 vessel. Whenever the current is obstructed or retarded in any 
 manner, the white globules accumulate in the afifected portion, and 
 become more numerous there in proportion to the red. 
 
 It is during the capillary circulation that the blood serves for 
 the nutrition of the vascular organs. Its fluid portions slowly 
 transude through the walls of the vessels, and are absorbed by the 
 tissues in such proportion as is requisite for their nourishment. 
 The saline , substances enter at once into the composition of the 
 surrounding parts, generally w:ithout undergoing any change. The 
 phosphate of lime, for example, is taken up in large quantity by 
 the bones and cartilages, and in smaller quantity by the softer parts ; 
 while the chlorides of sodium and potassium, the carbonates, sul- 
 phates, &o., are appropriated in special proportions by the diflPerent 
 tissues, according to the quantity necessary for their organization. 
 The albuminous ingredients of the blood, on the other hand, are 
 not only absorbed in a similar manner by the animal tissues, but at 
 the same time are transformed by catalysis, >nd converted into new 
 materials, characteristic of the different tissues. In this way are 
 produced the musculine of thQ muscles, the osteine of the bones, the 
 cartilagine of the cartilages, &c. &c. It is, probable .that this trans- 
 formation does not take place in the interior of the vessels them- 
 selves ; but that the organic ingredients of the blood are absorbed 
 by ,the tissues, and at the same moment converted into new mate- 
 rials, by contact with their substance. The blood in this way fur- • 
 nishes, directly or indirectly, all the materials necessary ibr the 
 nutrition of the body. 
 
 The physical conditions which influence the movement of the 
 blood in the capillaries, are somewhat different from those which 
 regulate the arterial and venous circulations. We must remember 
 that, as the arteries pass from the heart outward, they subdivide and 
 ramify to such an extent that the surface of the arterial walls is 
 very much increased in proportion to the quantity of blood which 
 they contain. It is on this account that the arterial pulsation is so 
 much equalized at a distance from the heart, since the influence of 
 the elasticity of the arterial coats is thus constantly increased from / 
 within outward. But as these vessels finally reach the confines 
 of the arterial system, having already been very much increased 
 in number and diminished in size, they suddenly break up into 
 
TUE CAPILLARY- CIRCULATION. 299 
 
 a terminal ramificatiou of still smaller and more numerous vessels, 
 and so lose themselves at last in the capillary network. 
 
 By this fii|jil increase of the vascular surface, the equalization of 
 the heart's action is completed. There is no longer any intermitting 
 or pjalsatile character in the force which acts upon the circulating 
 fluid; and the blood, accordingly, is delivered from the arteries into 
 the capillaries under a perfectly continuous and uniform pressure. 
 
 This pressure is sufficient to cause the blood to pass with con- 
 siderable rapidity, through the capillary plexus, into the commence- 
 ment of the veins. This fact was first demonstrated by Prof. 
 Sharpey," of London, who employed an injecting syringe with a 
 double nozzle, one extremity of which was connected with a mercu- 
 rial gauge, while the other was inserted into the artery of a recently 
 killed animal. When the syringe, filled with defibrinated blood, 
 was fixed in this position and the vessels of the animal injected, the 
 defibrinated blood would press with equal force upon the mercury 
 im the gauge and upon the fluid in the bloodvessels ; and thus it 
 was easy to ascertain the exact amount of pressure required to force 
 the defibrinated blood through the capillaries of the animal, and to 
 make it return by the corresponding vein. In this way Prof. 
 Sharpey found that when the free end of the injecting tube was 
 attached to the mesenteric artery of the dog, a pressure of 90 milli- 
 metres of mercury caused the blood to pass through the capillaries 
 of the intestine and of the liver ; and that under a pressure of 130 
 millimetres, it flowed iif a full stream from the divided extremity 
 of the vena cava. 
 
 We have also performed a similar experiment on the vessels of 
 the lower extremity. A full grown healthy dog was killed, and 
 the lower extremity immediately injected with defibrinated blood, 
 by the femoral artery, in order to prevent coagulation in the smaller 
 vessels. A syringe with a double flexible nozzle was then filled 
 with defibrinated blood, and one extremity of its injecting tube 
 attached to the femoral artery, the other to the mouthpiece of a 
 cardiometer. By making the injection, it was then found that the 
 defibrinated blood ran from the femoral vein in a continuous stream 
 under a pressure of 120 millimetres, and that it was discharged very 
 freely under a pressure of 130 millimetres. 
 
 Since, as we have already seen, the arterial pressure upon the 
 
 ' Todd and Bowmann, Physiological Anatomy and Pliysiology of man, vol. ii. p. 
 350. 
 
300 THE CIRCULATION. 
 
 blood is equal to six inches/ or 150 millimetres, of mercury, it is 
 evident that this pressure is sufficient to propel the blood through 
 the capillary circulation. ^ 
 
 Beside, the blood is not altogether relieved from the influence of 
 elasticity, after it has left the arteries. For the capillaries tjiem- 
 selves are elastic, notwithstanding the delicate texture of their 
 yralls ; and even the tissues of the organs which they, traverse 
 possess, in many instances, a considerable share of elasticity, owing 
 to the minute elastic fibres which are scattered through their sub- 
 stance. These elastic fibres are found in considerable quantity in 
 the lungs, the spleen, the skin, the lobulated glands, and more or 
 less in the mucous membranes. They are abundant, of course, in 
 the fibrous tissues of the extremities, in the fasciae, the tendons, and 
 the intermuscular substance. 
 
 In the experiment of injecting the vessels of the lower extremity 
 
 with defibrinated blood, if the injection be stopped, the blood does 
 
 H not instantly cease flowing from the extremity of the femoral vein, 
 
 but continues for a short time, until the elasticity of the intervening 
 
 parts is exhausted. 
 
 The same thing may be observed even in the liver. If the end 
 of a water-pipe be. inserted into the portal vein, and the liver in- 
 jected with water under the pressure of a hydrant, the liquid will 
 distend the vessels of the organ, and pass out by the hepatic veins. 
 But if the portal vein be suddenly tied or compressed, so as to shut 
 off the pressure from behind, the stream drill continue to run, for 
 several seconds afterward, from the hepatic vein, owing to the re- 
 action of the organ itself upon the fluid contained in its vessels. 
 
 As a general rule, also, the capillaries do not Suffer any backward 
 pressure from the venous system. On the contrary, as soon as the 
 blood has been delivered into the veins, it is hurried onward toward 
 the heart by the compression of the muscles and the action of the 
 venous valves. The right side of the heart itself continues the same 
 process, by its regular contractions, and by the action of its own 
 valvular apparatus ; so that the blood is constantly lifted away from 
 the capillaries, by the muscular action of the surrounding parts. 
 
 These are the most important of the mechanical influences under 
 which the blood moves through the continuous round of the circu- 
 lation. The heart, by its alternating contractions and relaxations, 
 and by the backward play of its valves, continually urges the blood 
 forward into the arterial system. The arteries, by their dilatable 
 and elastic walls, convert the cardiac pulsations into a uniform and 
 
THE CAPILLARY CIRCULATION. 301 
 
 steady pressure. Under this pressure, the blood passes through the 
 capillary vessels; and it is then carried backward to the heart 
 through the veins, assisted by the action of the muscles and the 
 respiratory movements of the chest. * 
 
 At the same time there are certain phenomena trhich are very 
 important in this respect, and which show that various local in- 
 fluences will either excite or retard the capillary circulation in par- 
 ticular parts, independently of the heart's action. The pallor or 
 suffusion of the face under mental emotion, the congestion of the 
 mucous membranes during the digestive process, the local and de- 
 fined redness produced in the skin by an irritating application, are 
 all instances of this sort. These phenomena are usually explained 
 by the contraction or dilatation of the smaller arteries immediately 
 supplying the part with blood, under the influence of nervous 
 action. As we know that the smaller arteries are in fact provided 
 with organic muscular fibres, this may Undoubtedly have something 
 to do with the local variations of the capillary circulation ; but the 
 precise manner in which these effects are produced is a(? present 
 unknown. 
 
 The rapidity of the circulation in the capillary vessels is much 
 less than in the arteries or the veins. It may be measured, with a 
 tolerable approach to accuracy, during the microscopic examination 
 of transparent and vascular tissues, as, for example, the web of the 
 frog's foot, or the mesentery of the rat. The results obtained in 
 this way by different observers (Valentine, Weber, Volkmann, &c.) 
 show that the rate of movement of the blood through the capil- 
 laries is rather less than one-thirtieth of an inch per second ; or not 
 quite two inches per minute. Since the rapidity of the current, as 
 we have mentioned above, must be in inverse ratio to the entire 
 calibre of the vessels through which it moves, it follows that the 
 united calibre of all the capillaries of the body must be from 350 to 
 400 times greater than that of the arteries. It must not be sup- 
 posed from this, however, that the whole quantity of blood contained 
 in the capillaries at any one time is so much greater than that in 
 the arteries ; since, although the united calibre of the capillaries is 
 very large, their length is very small. The effect of the anatomical 
 structure of the capillary system is, therefore, merely to disseminate 
 a comparatively small quantity of blood over a very large space, so 
 that the cheraico-physiological reactions, necessary to nutrition, may 
 take place with promptitude and energy. For the same reason, 
 although the rate of movement of the blood in these vessels is very 
 
302 THE CIRCULATION'. 
 
 slow, yet as the distance to be passed over between the arteries and 
 veins is very small, the blood really requires but a short time to 
 traverse the capillary system, and to commence its returning passage 
 By the veins. 
 
 GENERAL CONSIDERATIONS. 
 
 The rapidity with which the blood passes through the entire round 
 of the circulation is a point of great interest, and one which has 
 received a considerable share of attention. The results of such 
 experiments, as have been tried, show that this rapidity is much 
 greater than would have been anticipated. Hering, Poisseuille, and 
 Matteucci,' have all experimented on -this subject in the following 
 manner. A solution of ferrocyanide of potassium was injected 
 into the right jugular vein of a horse, at the same time that a liga- 
 ture was placed upon the corresporiding vein on the left side, and 
 an opening made in it above the ligature. The blood flowing from 
 the left jugular vein was then received in separate vessels, which 
 were changed every five seconds, and the contents afterward exa- 
 mined. It was thus found that the blood drawn from the first to 
 the twentieth second contained no traces of the ferrocyanide-; but 
 that which escaped from the vein at the end of from twenty to 
 twenty -five seconds, showed unmistakable evidence of the presence 
 of the foreign salt. The ferrocyanide of potassium must, therefore, 
 during this time, have passed from the point of injection to the 
 right side of the heart, thence to the lungs and through the pulmo- 
 nary circulation, returned to the heart, passed out again through 
 the arteries to the capillary system of the head and neck, and 
 thence have commenced its returning passage to the right side of 
 the heart, through the jugular vein. 
 
 By extending these investigations to different animals, it was 
 found that the duration of the circulatory movement varied, to 
 some extent, with the size and species. In the larger quadrupeds, 
 as a general rule, it was longer ; in the smaller, the time required 
 was less. 
 
 In the Horae,' tlie mean duration was 28 seconds. 
 " Dog " " " " 15 " 
 
 " Goat " " " " 13 « 
 
 '• Fox " " " " I2i " 
 
 " Rabbit '" " « "7 « 
 
 ' Physical Phenomena of Living Beings, Pereira's translation, Philada. ed., 1848, * 
 p. 317. 
 2 In Milne Edwards, Lepons aur la Physiologic, &o., vol. iv. p. 364. 
 
LOCAL VARIATIONS. 303 
 
 "When .these results were first published, it was thought to be 
 doubtful whether the circulation were really as rapid as they would 
 make it appear. It was thought that the saline matter which was 
 injected, "travelled faster than the blood ;" that it became " diffused" 
 through the circulating fluid ; that it transuded through dividing 
 membranes ; or passed round to the point at which it was detected, 
 by some short and irregular route. 
 
 But none of these explanations have ever been found to be cor- 
 rect. They are all really more improbable than the fact which 
 they are intended to explain. The physical diffusion of liquids 
 does not take place with such rapidity as that manifested by the 
 circulation ; and there is no other route so likely to give passage to 
 the injected fluid, as the bloodvessels and the movement of the blood 
 itself. Beside, the first experiments of Poisseuille and others have 
 not been since invalidated, in any essential particular. It was found, 
 it is true, that certain other substances, injected at the same time 
 with the saline matter, might hasten or retard the circulation to a 
 certain degree. But these variations were not very marked, and 
 never exceeded the limits of from eighteen to forty-five seconds. 
 There is no doubt that the blood itself makes the saime circuit in 
 very nearly the same interval, of time. 
 
 The truth is, however, that we cannot fix upon any absolutely 
 uniform rate which shall express the time required by the entire 
 blood to pass the round of the whole vascular system, and return 
 to a given point. The circulation of the blood, far from being a 
 simple phenomenon, like a current of water through a circular tube, 
 is, on the contrary, extremely complicated in all its anatomical and 
 physiological conditions ; and it differs in rapidity, as well as in its 
 physical and chemical phenomena, in different parts of the circu- 
 latory apparatus. We have already seen how much the form of 
 the capillary plexus varies in different organs. In some the vascu- 
 lar network is close, in others comparatively open. In some its 
 meshes are circular in shape, in others polygonal, in others rectan- 
 gular. In some the vessels are arranged in twisted loops, in others 
 they communicate by irregular but abundant inosculations. The 
 mere distance from the heart at which an organ is situated must 
 modify to some extent the time required for its blood to return 
 again tofthe centre of the circulation. The blood which passes 
 through the coronary arteries and the capillaries of the heart, 
 for example, must be returned to the right auricle in a compara- 
 tively short time ; while that which is carried by the carotids into 
 
301 THE CIKCULATIOX. 
 
 the capillary system of the head and neck, to return by the jugulars, 
 will require a longer interval. That, again, which descends by the 
 abdominal aorta and its divisions to the lower extremities, and 
 which, after circulating through the tissues of the leg and foot, 
 mounts upward through the whole course of the saphena, femoral, 
 iliac and abdominal veins, must be still longer on its way ; whije 
 that which circulates through the abdominal digestive organs and 
 is then collected by the portal system, to be again dispersed through 
 the glandular tissue of the liver, requires undoubtedly a longer 
 period still to perform its double capillary circulation. The blood, 
 therefore, arrives at the right side of the heart, from different parts 
 of the body, at successive intervals; and may pass several times 
 through one organ while performing a single circuiation through 
 another. 
 
 Furthermore, the chemical phenomena taking place in the blood 
 and the tissues vary to a similar extent in different organs. The 
 actions of transformation and decomposition, of nutrition and secre- 
 tion, of endosmosis and exosmosis, which go on simultaneously 
 throughout the body, are yet extremely varied in their character, 
 and produce a similar variation in the phenomena of the circula- 
 tion. In one organ the blood loses more fluid than it absorbs ; in 
 another it absorbs more than it loses. The venous blood, conse- 
 quently, has a difierent composition as it returns from different 
 organs. In the brain and spinal cord it gives up those ingredients 
 necessary for the nutrition of the nervous matter, and absorbs cho- 
 lesterine and other materials resulting from its waste ; in the muscles 
 it loses those substances necessary for the supply of the muscular 
 tissue, and in the bones those which are requisite for the osseous 
 system. In the parotid gland it yields the ingredients of the saliva ; 
 in the kidneys, those of the urine. In the intestine it absorbs in 
 large quantity' the nutritious elements of the digested food ; and in 
 , the liver, gives up substances destined finally to produce the bile, 
 at the same time that it absorbs sugar, which has been produced 
 in the hepatic tissue. In the lungs, again, it is the elimination of 
 carbonic acid and the absorption of oxygen that constitute its prin- 
 cipal changes. It has been already remarked that the temperature 
 of the blood varies in different veins, according to the peculiar 
 chemical and nutritive changes going on in the organs frofi which 
 they originate. Its color, even, which is also dependent on the 
 chemical and nutritive actions taking place in the capillaries, varies 
 in a similar manner. In the lungs it changes from blue to red ; 
 
LOCAL VABIATIONS. 
 
 305 
 
 Fig. 101. 
 
 in the capillaries of the general system, from red to blue. But its 
 
 tinge also varies very considerably in different paits of the general 
 
 circulation. The blood of the hepatic 
 
 ■veins is darker than that of the femoral 
 
 or brachial vein. In the renal veins 
 
 it is very much brighter than in the 
 
 vena cava ; and when the circulation 
 
 through the kidneys is free, the blood 
 
 returning from them is nearly as red 
 
 as arterial blood. 
 
 We must regard the circulation of 
 the blood, therefore, not as a simple 
 process, but as made up of many difier- 
 ent circulations, going on simultane- 
 ously in different organs. It has been 
 customary to illustrate it, in diagram, 
 by a double circle, or figure of 8, of 
 which the upper arc is used to repre- 
 sent the pulmonary, the lower the gen- 
 eral circulation. This, however, gives 
 but a very imperfect idea of the entire 
 circulation, as it really takes place. It 
 would be much more accurately re- 
 presented by such a diagram as that 
 in Fig. 101, in which its variations 
 in different parts of the body are 
 indicated in such a manner as to show, 
 in some degree, the complicated cha- 
 racter of its phenomena. The circula- 
 tion is modified in these different parts, 
 not only in its mechanism, but also in 
 its rapidity and quantity, and in the 
 nutritive functions performed by the 
 blood. In one part, it stimulates the 
 nervous centres and the organs of 
 special sense ; in others it supplies the 
 fluid secretions, or the ingredients of 
 the solid tissues. One portion, in 
 passing through the digestive appara- 
 tus, absorbs the materials requisite 
 
 for the nourishment of the body ; another, in circulating through 
 20 
 
 Diagram of the CiBciTLATion'. — 1- 
 Heart. 2. LoDnrs. 3. Head and upper 
 extremities. 4. Spleen. 5. Intestine. 6. 
 Kidney. 7. Lower extremities. 8. Liver. 
 
306 THE CIECULATION. 
 
 the lungSj exhales the carbonic acid which it has accumulated else- 
 where, and absorbs the oxygen which is afterward transported to 
 distant tissues by the current of arterial blood. The phenomena of 
 the circulation are even liable, as we have already seen, to periodical 
 variations in the same organ ; increasing or diminishing in intensity 
 with the condition of rest or activity of the whole body, or of the 
 particular organ which is the subject of observation-. 
 
IMBIBITION AND EXHALATION. 307 
 
 CHAPTEE XV. 
 
 IMBIBITION AND EXH AL ATI ON.— THE LYMPHATIC 
 
 SYSTEM. 
 
 During the passage of the blood through the capillaries of the 
 circulatory system, a very important series of changes takes place 
 by which its ingredients are partly transferred to the tissues by 
 exhalation, and at the same time replaced by others which the blood 
 derives by absorption from the adjacent parts. These phenomena 
 depend upon the property, belonging to animal membranes, of 
 imbibing or absorbing certain fluid substances in a peculiar way. 
 They are known more particularly as the phenomena of endosmosis 
 and exosmosis. 
 
 These phenomena may be demonstrated in the following way. If 
 we take two different liquids, for example a solution of salt and an 
 equal quantity of distilled water, and inclose them in a glass vessel 
 with a fresh animal membrane stretched between, so that there is 
 no direct communication from one to the other, the two liquids 
 being in contact with opposite sides of the membrane, it will be 
 found after a time that the liquids have become mixed, to a cer- 
 tain extent, with each other. A part of the salt will have passed 
 into the distilled water, giving it a saline taste ; and n part of the 
 water will have passed into the saline solution, making it more 
 dilute than before. If the quantities of the two liquids, which 
 have become so transferred, be measured, it will be found that a 
 comparatively large quantity of the water hag passed into the 
 saline solution, and a comparatively small quantity of the saline 
 solution has passed, out into the water. That is, the water passes 
 inward to the salt more rapidly than the salt passes outward to the 
 water. The consequence is, that an accumulation soon begins to 
 show itself on the side of the salt. The saline solution is increased 
 in volume and diluted, while the water is diminished in volume, 
 and acquires a saline ingredient. This abundant passage of the 
 water, through the membrane, to the salt, is called endosmosis ; and 
 
308 IMBIBITION AND EXHALATION. 
 
 the more scanty passage of the salt outward to the water is called 
 exosmosis. 
 
 The mode usually adopte,d for measuring the rapidity of endos- 
 mosis is to take a glass vessel, shaped somewhat like an inverted 
 funnel, wide at the bottom and narrow at the top. The bottom of 
 the vessel, is closed by a thin animal membrane, like the mucous 
 membrane of an ox-bladder, which is stretched tightly over its edge 
 and secured by a ligature. From the top of the vessel there rises 
 a very narrow glass tube, open at its upper extremity. When the 
 instrument is thus prepared, it is filled with a solution of sugar 
 and placed in a vessel of distilled water, so that the animal mem- 
 brane, stretched across its mouth, shall be in contact with pure 
 water on one side and with the saccharine solution on the other. 
 The water then passes in through the membrane, by endosmosis, 
 faster than the saccharine solution passes out. An accumulation 
 therefore takes place inside the vessel, and the level of the fluid 
 rises in the upright tube. The height to which the iluid thus rises 
 in a given time is a measure of the intensity of the endosmosis, and 
 of its excess over exosmosis. By varying the constitution of the 
 two liquids, the arrangement of the membrane, &c., the variation 
 in endosmotic action under different conditions may be easily 
 ascertained. Such an instrument is called an endosmometer. 
 
 If the extremity of the upright tube be bent over, so as to point 
 downward, as endosmosis continues to go on after the tube has 
 become entirely filled by the rising of the fluid, the saccharine solu- 
 tion will be discharged in drops from the end of the tube, and fall 
 back into the vase of water. A steady circulation will thus be 
 kept up for a time by the force of eiidosmosis. The water still 
 passes through the membrane, and accumulates in the endosmo- 
 meter ; but, as this is already full of fluid, the surplus immediately 
 falls back into the outside vase, and thus a current is established 
 which will go on until the two liquids have become intimately 
 mingled. 
 
 The conditions which influence the rapidity and extent of endos- 
 mosis have been most thoroughly investigated by Dutrochet, who 
 was the first to make a systematic examination of the subject. 
 
 The first of these conditions is the freshness of- the membrane itself. 
 This is an indispensable requisite for the success of the experiment. 
 A membrane that has been dried and moistened again, or one that 
 has begun to putrefy, will not produce the desired effect. It has 
 been also found that if the membrane of the endosmometer be 
 
THE LYMPHATIC SYSTEM. 309 
 
 allowed to remain and soak in the fluids, after the column has risen 
 to a certain height in the upright tube, it begins to descend again 
 as soon as putrefaction commences, and the two liquids finally sink 
 to the same level. 
 
 The next condition is the extent of contact between the membrane 
 and the two liquids. The greater the extent of this contact, the 
 more rapid and forcible is the current of endosmosis. An endos- 
 mometer with a wide mouth will produce more effect than with a 
 narrow one, though the volume of the liquid contained in it may 
 be the same in' both instances. The action takes place at the 
 surface of the membrane, and is proportionate to its extent. 
 
 Another very important circumstance is the constitution of> the two 
 liquids, and their relation to each other. As a general thing, if we 
 use water and a saline solution in our experiments, endosmosis is 
 more active, the more concentrated is the solution in the endosmo- 
 meter. A larger quantity of water will pass inward toward a dense 
 solution than toward one which is already dilute. But the force of 
 endosmosis varies with different liquids, even when they are of the 
 same density. Dutrochet measured the force with which water 
 passed through the mucous membrane of an ox-bladder into differ- 
 ent solutions of the same density. He found that the force varies 
 with different substances, as follows :' — 
 
 Eadosmosis of water, with a solution of albnmen . . 12 
 " " " sugar . . ..11 
 
 " " " gum ..." 5 
 
 " " " gelatiue . . 3 
 
 The position of the memirane also makes a difference. With some 
 fluids, endosmosis is more rapid when the membrane has its mucous 
 surface in contact with the dense solution, and its dissected surface 
 in contact with the water. With other substances the more favor- 
 able position is the reverse. Matteucci found that, in using the 
 mucous membrane of the ox-bladder with water and a solution of 
 sugar, if the mucous surface of the membrane were in contact with 
 the saccharine solution, the liquid rose in the endosmometer between 
 four and five inches. But if the same surface were turned outward 
 toward the water, the column of fluid was less than three inches in 
 height. Different membranes also act with different degrees of force. 
 The effect produced is not the same with the integument of different 
 animals, nor with mucous membranes taken from different parts of 
 the body. 
 
 ' In Mattpucci's Liectures on the Physical Phenomena of Living Beings. Philada., 
 1848, p. 48. 
 
810 IMBIBITION AND EXHALATION. 
 
 Generally speaking, endosnaosis is more active when the temper- 
 ature is moderately elevated. Dutrochet noticed that an endosmo- 
 meter, containing a solution of gum, absorbed only one volume of 
 water at a temperature of 32° Fahr., but absorbed three volumes 
 at a temperature a little above 90°. Variations of temperature will 
 sometimes even change the direction of the endosmosis altogether, 
 particularly with dilute solutions of hydrochloric acid. Dutrochet 
 found, for example,^ that when the endosmometer was filled with 
 dilute hydrochloric acid and placed in distilled water, at the tern-, 
 perature of 50° F., endosmosis took place from the acid to the water, 
 if the density of the acid solution were less than 1.020 ; but that it 
 took place from the water to the acid, if its density were greater 
 than this. On the other hand, at the temperature of 72° F., the 
 current was from within outward when the density of the acid solu- 
 tion was below 1.003, and from without inward when it was above 
 that point. 
 
 Finally, the pressure which is exerted upon the fluids and the 
 membrane favors their endosmosis. Fluids tha^s pass slowly under 
 a low pressure will pass more rapidly with a higher one. Different 
 liquids, too, require different degrees of pressure to make them 
 pass the same membrane. Liebig^ has measured the pressure re- 
 quired for several, different liquids, in order to make them pass 
 through the same membrane. He found that this pressure was 
 
 Ikches of Mebcdrt. 
 
 For alcohol 52 
 
 For oil 37 
 
 For solution of salt ....... 20 ^ 
 
 For water 13 ♦» • 
 
 There are some cases in which endosmosis takes place without 
 being accompanied by exosmosis. This occurs, for example, when 
 we use water and albumen as the two liquids. For while water 
 readily passes in through the' animal membrane, the albumen does 
 not pass out. If an. opening be made, for example, in the large 
 end of an egg, so as to expose the shell-membrane, and the wEble 
 be then placed in a goblet of water, endosmosis will take place very 
 freely from the w,ater to the albumen, so as to distend the shell- 
 membrane and make it protrude, like a hernia, from the opening in 
 the shell. But the albumen does not pass' outward through the 
 membrane, and the water in the goblet remains pure. After a time, 
 
 ' In Milne Edwards, Le<;ons sur la Physiologie, Ac, vol. r. p. 164. 
 2 111 Loiiget's Traite di Physiologie, vol. i. p." 384. 
 
THE LYJIPHATIC SYSTEM. 311 
 
 however, the accumulatiou of fluid in the interior becomes so ex> 
 oessive as to burst the shell-membrane, and then the two liquids 
 become mixed indiscriminately- together. 
 
 These are the principal conditions by which endosmosis is influ. 
 enced and regulated. Let us now see what is the nature of the 
 process, and upon what its phenomena depend. 
 
 Endosmosis is not dependent upon the simple force of diffusion 
 or admixture of two different liquids. F<3r sometimes, as in the 
 
 , case of albumen and water, all the fluid passes in one direction and 
 none in the other. It is true that the activity of the process de- 
 pends very much, as we have already seen, upon the difference in 
 constitution of the two liquids. "With water and a saline solution, 
 for instance, the stronger the solution of salt, the more rapid is the 
 endosmosis of the water. And if two solutions of salt be used, 
 with a membranous septum between them, endosmosis takes place 
 from the weaker solution to the stronger, and is proportionate in 
 activity to the difference in their densities. From this fact, Dutro- 
 chet was at first led to believe that the direction of endosmosis was 
 determined by the difference in density of the two liquids, and that 
 the current of accumulation was always directed from the lighter 
 liquid to the denser. But we now know that this is not the case. 
 For though, with solutions of salt, sugar, and the like, the current 
 of endosmosis is from the lighter to the denser liquid ; in other 
 instances it is the reverse. With water and alcohol, for example, 
 endosmosis takes place, not from the alcohol to the water, but from 
 the water to the alcohol ; that is, from the denser liquid to the lighter. 
 
 fcThe difference in density of the liquids, therefore, is not the only 
 condition which regulates the direction of the endosmotic current. 
 In point of fact, the process of endosmosis does not depend princi- 
 pally upon the attraction of the two liquids for each other, but 
 upon the attraction of the animal membrane for the two liquids. The 
 membrane is not a passive filter through which the liquids mingle, 
 but it is the active agent which determines their passage. The 
 membrane has the power of absorbing liquids, and of taking them 
 up into its own substance. This power of absorption, belonging to 
 the membrane, depends upon the organic or albuminous ingredients 
 of which it is composed'* and, with different animal substances, the 
 power of absorption is different. The tissue of cartilage, for exam- 
 ple, will absorb more water, weight for weight, than that of the 
 tendons ; and the tissue of the cornea will absorb nearly twice as 
 much as that of cartilage. 
 
312 IMBIBITION AND EXHALATION. 
 
 Beside, the power of absorption of an animal membrane is dif- 
 ferent for different liquids. Nearly all animal membranes absorb 
 pure water more freely than a solution of salt. If a membrane, 
 partly dried, be placed in a saturated saline solution, it will absorb 
 the water in larger proportion than the salt, and a part of the salt 
 will, therefore, be deposited in the form of crystals on the surface 
 of the membrane. 
 
 Oily matters, on the*other hand, are usually absorbed less readily 
 than efther water or saline solutions. 
 
 Chevreuil has investigated the absorbent power of different 
 animal substances for different liquids, by taking definite quanti- 
 ties of the animal substance and immersing it for twenty-four 
 hours in different liquids. At the end of that time, the substance 
 was rembVed and weighed. Its increase in weight showed the 
 quantity of liquid which it had absorbed. The results which were - 
 obtained are given in the following table : — ' 
 
 100 Pakts op 
 
 
 Water. 
 
 Saline Solution. 
 
 ■ Oil. 
 
 Cartilage, 
 
 
 ■ 231 parts. 
 
 125 parts. 
 
 
 Tendon, 
 
 
 178 " 
 
 114 " 
 
 8.6 parts 
 
 Elastic ligament. 
 
 absorb in 
 
 148 " 
 
 30' " 
 
 7.2 " 
 
 Cornea, 
 
 24 hours, 
 
 461 " 
 
 370 " 
 
 9.1 " 
 
 Cartilaginous ligament, 
 
 
 319 " 
 
 
 3.2 " 
 
 Dried fibrin. 
 
 
 . 301 " 
 
 154 « 
 
 
 The same substance, therefore, will' take up different quantities 
 of water, saline solutions, and oil. 
 
 Accordingly, when an animal membrane is placed in contact 
 with two different liquids, it absorbs one o^hein more abundantly., 
 than the other ; and that which is absorbed in the greatest quantity 
 is also diffused most abundantly into the liquid on the opposite side 
 of the membrane. A rapid endosmosis takes place in one direc- 
 tion, and a slow exosmosis in the other. Consequently, the least 
 absorbable fluid increases in volume by the constant admixture of 
 that which is taken up more rapidly. 
 
 The process of endosmosis, therefore, is essentially one of im- 
 bibition or absOTption of the liquid by an animal membrane, com- 
 posed of organic ingredients. We have already shown, in de- 
 scribing the organic proximate principles in a previous chapter, 
 that these substances have- the power of absorbing watery and 
 serous fluids in a peculiar way. In endosmosis, accordingly, the 
 
 ' In Longet's Traite de Physiologie, vol. i. p. 383. 
 
THE LYMPHATIC SYSTEM. 313 
 
 imbibed fluid penetrates tbe membrane by a kind of chemical 
 combination, and unites intimately with the substance of which its 
 tissues are composed. 
 
 It is in this way that all imbibition and transudation take place 
 in the living body. Under the most ordinary conditions, the transu- 
 dation of certain fluids is accomplished with great rapidity. It has 
 been shown by M. Gosselin,' that if a watery solution of iodide of 
 potassium be dropped upon the cornea of a living ra,bbit, the 
 iodine passes into the cornea, aqueous humor, iris, lens, sclerotic 
 and vitreous body, in the course of eleven minutes; and that it 
 will penetrate through the cornea into the aqueous humor in three 
 minutes, and into the substance of the cornea in a minute and a 
 half. In these experiments it was evident that the iodine actually 
 passed into the deeper portions of the eye by simple endosmosis, 
 and was not transported by the vessels of the general circulation ; 
 since no trace of it could be found in the tissues of the opposite 
 eye, examined at the same time. 
 
 The same observer showed that the active principle of belladonna 
 penetrates the tissues of the eyeball in a similar manner. M. Gos- 
 selin applied a solution 9f sulphate of atropine to both eyes of two 
 rabbits. Half an hour afterward, the pupils were dilated. Three 
 quarters of an hour later, the aqueous humor was collected by 
 puncturing the cornea with a trocar; and this aqueous humor, 
 dropped upon the eye of a cat, produced dilatation and immobility 
 of the pupil in half an hour. These facts show that the aqueous 
 humor of the affected, eye actually contains atropine, which it 
 absorbs from without through the corqea, and this atropine then 
 acts directly and locally upon the muscular fibres of the iris. 
 
 But in all the vascular organs, the processes of endosmosis and 
 exosmosis are very much accelerated by two important conditions, 
 viz., first, the movement of the blood in circulating through the 
 vessels, and secondly the minute dissemination and distribution of 
 these vessels through the tissue of the organs. 
 
 The movement of a fluid in a continuous current always favors 
 endosmosis through the membrane with which it is in contact. For 
 if the two liquids be stationary, on the opposite .sides of an animal 
 membrane, as soon as endosmosis commences they begin to ap- 
 proximate in constitution to each other by mutual admixture ; and, 
 as this admixture goes on, endosmosis of course becomes less active, 
 
 ' Gazette Hebdomadaire, Sept. 7, 1855. 
 
314 IMBIBITION AND EXHALATION. 
 
 and ceases entirely when the two liquids have become perfectly 
 alike in composition. But if one of the liquids be constantly 
 renewed by a continuous current, those portions of it which have 
 become contaminated are immediately carried away by the stream, 
 a'fid replaced by fresh portions in a state of purity. Thus the 
 . difference in constitution of the two liquids is preserved, and 
 transudation will continue to take place between them with una- 
 bated rapidity. 
 
 Matteucci demonstrated the effect of a current in facilitating 
 endosmosis by attaching to the stopcock of a glass reservoir filled 
 with water, a portion of a vein also filled with water. The vein 
 was then immersed in a very dilute solution of hydrochloric acid. 
 So long as the water remained stationary in the vein it did not give 
 any indications of the presence of the acid, or did so only very 
 slowly ; but if a current were allowed to pass through the vein by 
 opening fehe stopcock of the reservoir, then the fluid running from 
 its extremity almost immediately showed an acid reaction. 
 
 The same thing may be shown even more distinctly upon the 
 living animal. If a solution of the extract of nux vomica be in- 
 jected into the subcutaneous areolar tissue of the hind leg of two 
 rabbits, in one of which the bloodvessels of the extremity have 
 been left free, while in the other they have been previously tied, 
 so as to stop the circulation in that part — in the first rabbit, the 
 poison will be absorbed and will produce convulsions and death in 
 the course of a few nainutes; but in the second animal, owing to the 
 stoppage of the local circulation, absorption will be much retarded, 
 and the poison will find its way into the general circulation so 
 slowly, and in such small quantities, that its specific effects will show 
 themselves only at a late period, or even may not be produced at all. 
 
 The anatomical arrangement of the bloodvessels and adjacent 
 tissues is the second important condition regulating endosrnosis 
 and exosmosis. We have already seen that the network of capil- 
 lary bloodvessels results from the excessive division and ramifica- 
 tion of the smaller arteries. The blood, therefore, as it leaves the 
 arteries and enters the capillaries, is constantly divided into smaller 
 and more numerous currents, which are finally disseminated in the 
 most intricate manner throughout the substance of the organs and 
 tissues. Thus, the blood is brought into intimate contact with the 
 surrounding tissues, over a comparatively very large extent of sur- 
 face. It has already been stated, as the result of Dutrochet's inves- 
 tigations, that the activity of endosmosis is in direct proportion to 
 
THE LYMPHATIC SYSTEM. 315 
 
 the extent of surface over •which the two liquids come in contact 
 with the intervening membrane. It is very evident, therefore, that 
 it will be very much facilitated by the anatomical distribution of 
 the capillary bloodvessels. 
 
 It is in some of the glandular organs, however, that the transu- 
 dation of fluids can be shown to take place with the greatest rapi- 
 dity. For in these organs the exhaling and absorbing surfaces are 
 arranged in the form of minute ramifying tubes and follicles, which 
 penetrate everywhere through the glandular substance ; while the 
 capillary bloodvessels form an equally complicated and abundant 
 network, situated between the adjacent follicles and ducts. In this 
 way, the union and interlacement of the glandular membrane, on 
 the one hand, and the bloodvessels on the other, become exceed- 
 ingly intricate and extensive; and the ingredients of the blood are 
 almost instantaneously subjected, over a very large surface, to the 
 influence of the glandular membrane. 
 
 The rapidity of transudation through the glandular membranes 
 has been shown in a very striking manner by Bernard.' This ob- 
 server injected a solution .of iodide of potassium into the duct of 
 the parotid gland on the right side, in a living dog, and immediately 
 afterward found iodine to be present in the saliva of the correspond- 
 ing gland on the opposite side. In the few instants, therefore, re- 
 quired to perform the experiment, the salt of iodine must have 
 been taken up by the glandular tissue on one side, carried by the 
 blood of the general circulation to the opposite gland, and there 
 transuded through the secreting membrane. 
 
 We have a;lso found the transudation of iodine through the 
 glandular tissue to be exceedingly rapid, by the following experi- 
 ment. The parotid duct was exposed and opened, upon one side, 
 in a living dog, and a canula inserted into it, and secured by liga- 
 ture. The secretion of the parotid saliva was then excited, by in- 
 troducing a little vinegar into the mouth of the animal, and the 
 saliva, thus obtained, found to be entirely destitute of iodine. A 
 solution of iodide of potassium being then injected into the jugu- 
 lar vein, and the parotid secretion again immediately excited by 
 the introduction of vinegar, as before, the saliva first discharged 
 from the canula showed evident traces of iodine, by striking a blue 
 color on the addition of starch and nitric acid. 
 
 The processes of exosmosis and endosmosis, therefore, in the living 
 
 ' Le;ons de Pliysiologie Expfirimentale, Paris, 1856, p. 107. 
 
316 IMBIBITION AND EXHALATION. 
 
 bodj, are regulated by the same conditions as in artificial experi- 
 ments, but they take place with infinitely greater rapidity, owing to 
 the movement of the circulating blood, and the extent of contact 
 existing between the bloodvessels and adjacent tissues. We have 
 already seen that the absorption of the same fluid is accomplished 
 with different degrees of rapidity by different animal substances. 
 Accordingly, though the arterial blood is everywhere the same in 
 composition, yet its different ingredients are imbibed in varying 
 quantities by the different tissues. Thus, the cartilages absorb 
 from the circulating fluid a larger proportion of phosphate of lime 
 than the softer tissues, and the bones a larger proportion than "the 
 cartilages; and the watery and saline ingredients generally are 
 found in different quantities in different parts of the body. The 
 same animal membrane, also, as it has been shown by experiment, 
 will imbibe different substances with different degrees of facility. 
 Thus, the blood, for example, contains more chloride of sodium 
 than chl6ride of potassium ; but the muscles, which it supplies with 
 nourishnient, contain more chloride of potassium ,than chloride of 
 sodium. In this way, the proportion of each ingredient derived 
 from the blood is determined, in each separate tissue, by its special 
 absorbing or endosmotic power. 
 
 Furthermore, we have seen that albumen, under ordinary coiidi- 
 tions, is not endosmotic ; that is, it will not pass by transudation 
 through an animal membrane. For the same reason, the albumen 
 of the blood, in the natural state of the circulation, is not exhaled 
 from the secreting surfaces, but is retained within the circulatory 
 system, while the watery and saline ingredients transude in varying 
 quantities. But the degree oi pressure to which a fluid is subjected 
 has gfeat influence in determining its endosmotic action. A sub- 
 stance which passes but slowly under a low pressure, may pass 
 much more rapidly if the force be increased. Accordingly, we find 
 that if the pressure upon the blood in the vessels be increased, by 
 obstruction to the venous current and backward congestion of the 
 capillaries, then not only the saline and watery, parts of the blood 
 pass out in larger quantities, but the albumen itself transudes, and 
 infiltrates the neighboring parts. It is in this way that albumen 
 makes its appearance in the urine, in consequence of obstruction to 
 the renal circulation, and that local oedema or general anasarca 
 may follow upon venous congestion in particular regions, or upon 
 general disturbance of the circulation. 
 
 The processes -of imbibition and exudation, which thus take 
 
THB LYMPHATIC SYSTEM. 317. 
 
 place incessantly throughout the body, are intimately connected, 
 with the action of the great absorbent or lymphatic system of ves- 
 sels, which is to be considered as secondary or complementary to 
 that of the sanguiferous circulation. 
 
 The lymphatics may be regarded as a system of vessels, com- 
 mencing in the substance of the various tissues and organs, and 
 endowed with the property of absorbing certain of their ingredi- 
 ents. Their commencement has been demonstrated by injections, 
 naore particularly in the membranous parts of the body ; viz., in 
 the skin, the mucous membranes, the serous and synovial surfaces, 
 and the inner tunic of the arteries and veins. They originate in 
 these situations by vascular networks, not very unlike those of the 
 capillary bloodvessels. Notwithstanding this resemblance in form 
 between the capillary plexuses of the lymphatics and the blood- 
 vessels, it is most probable that they are anatomically distinct from 
 each other. It has been supposed, at various times, that there 
 might be communications between them, and even that the lymph- 
 atic plexus might be a direct continuation of that originating from 
 the smaller arteries ; but this has never been demonstrated, and it 
 is now almost universally conceded that the anatomical evidence is 
 in favor of a complete separation between the two vascular systems. 
 
 Commencing in this way in the substance of the tissues, by a 
 vascular network, the minute lymphatics unite gradually with each 
 other to form larger vessels ; and, after continuing their course for 
 a certain distance from without inward, they enter and are distri- 
 buted to the substance of the lymphatic glands. According, to M. 
 Colin,' beside the more minute and convoluted vessels in each gland, 
 there are always some larger branches, which pass directly through 
 its substance, from the afferent to the efferent vessels ; so that only 
 a portion of the lymph is distributed to its ultimate glandular 
 plexus. This portion, however, in passing through the organ, is 
 evidently subjected to some glandular influence, which may serve 
 to modify its composition. 
 
 After passing through these glandular organs, the lymphatic 
 vessels unite into two great trunks (Fig. 43) : the thoracic duct, which 
 collects the fluid from the absorbents of the lower extremities, the 
 intestines and other abdominal organs, the chest, the left upper 
 extremity, and the left side of the head and neck, and terminates 
 in the left subclavian vein, at the junction of the internal jugular ; 
 and the right lymphatic duct, which collects the fluid from the right 
 
 ' Physiologie comparfie des Animaux domestiques, Paris, 1856, vol. ii. p. 68. 
 
318 IMBIBITION AND EXHALATION, 
 
 upper extremity and right side of the head and neck, and joins the 
 right subclavian vein at its junction with the corresponding jugular. 
 Thus nearly all the lymph from the external parts, and the whole 
 of that from the abdominal organs, passes, by the thoracic duct, 
 into the left subclavian vein. 
 
 We already know that the lymphatic vessels are not to be re- 
 garded as the exclusive agents of absorption. On the contrary, 
 absorption takes place by the bloodvessels even more rapidly and 
 abundantly than Tay the lymphatics. Even the products of diges- 
 tion, including the chyle, are taken up from the intestine in large 
 proportion by the bloodvessels, and are only in part absorbed by 
 the lymphatics. But the main peculiarity of the lymphatic system 
 is that its vessels all pass in one direction, viz., from without inward, 
 and none from within outward. Consequently there is no circula- 
 tion of the lymph, strictly speaking, like that of the blood, but it 
 is all supplied by exudation and absorption from the tissues. 
 
 The lymph has been obtained, in a state of purity, by various 
 experimenters, by introducing a canula into the thoracic duct, at 
 the root of the neck, or into large lymphatic trunks in other parts 
 of the body. It has been obtained by Rees from the lacteal vessels 
 and the lymphatics of the leg in the ass, by Colin from the lacteals 
 and thoracic duct of the ox, and from the lymphatics of the neck 
 in the horse. We have also obtained it, on several different occa- 
 sions, from the thoracic duct of the dog and of the goat. 
 
 The analysis of these fluids shows a remarkable similarity in 
 constitution between them and the plasma of the blood. They 
 contain water, fibrin, albumen, fatty matters, and the usual saline 
 substances of the animal fluids. At the same time, the lymph is 
 very much poorer in albuminous ingredients than the blood; The 
 following is an analysis by Lassaigne,' of the fluid obtained from 
 the thoracic du(5t of the cow : — 
 
 Pakts per thousand. 
 
 Water 964.0 
 
 Fibrin . , . 0.9 
 
 Albumen 28.0 
 
 Fat , . . • 0.4 
 
 Chloride of sodium 6.0 
 
 Carbonic \ > 
 
 Phosphate and [ of soda 1.2 
 
 Sulphate ■' 
 
 Phosphate of lime 0.5 
 
 1000.0 
 
 ' Colin, Physiologie comparge des Animaux domestiquea, vol. ii. p. 111. 
 
THE LYMPHATIC SYSTEM. 319 
 
 It thus appears that both the fi*briii and the albumen of the blood 
 actually transude to a certain extent from the bloodTessels, even in 
 the ordinary condition of the circulatory system. But this transuda- 
 tion takes place in so small a quantity that the albuminous matters 
 are all taken up again by the lymphatic vessels, and do not appear 
 in the excreted fluids. 
 
 The first important peculiarity which is noticed in regard to the 
 fluid of the lymphatic system, especially in the carnivorous animals, 
 is that it varies very much, both in appearance and constitution, at 
 different times. In the ruminating and graminivorous animals, 
 such as the sheep, ox, goat, horse, &c., it is either opalescent in 
 appearance, with a slight amber tinge, or nearly transparent and 
 colorless. In the carnivorous animals, such as the dog and cat, it 
 is also opaline and amber colored, in the intervals of digestion, 'but 
 soon after feeding becomes of a dense, opaque, milky white, and con- 
 tinues to present that appearance until the processes of digestion 
 and intestinal absorption are complete. It then regains its original 
 aspect, and remains opaline or semi-transparent until digestion is 
 again in progress. 
 
 The cause of this variable constitution of the fluid disc*harged 
 by the thoracic duct is the absorption of fatty substances from the 
 intestine during digestion. Whenever fatty substances exist id con- 
 siderable quantity in the food, they are reduced, by the process of 
 digestion, to a white, creamy mixture of molecular fat, suspended 
 in an albuminous menstruum. The mixture is. then absorb.ed by 
 the lymphatics of the mesentery, and transported by them througlf 
 the thoracic duct to the subclavian vein. While this absorption is 
 going on, therefore, the fluid of the thoracic duct alters its appear- 
 ance, becomes white and opaque, and is then called chyh ; so that 
 there are two different conditions, in which the contents of the great 
 lymphatic trunks present different appearances. In the fasting 
 condition, these vessels contain a semi-transparent, or opaline and 
 nearly colorless lymph; and during digestion, an opaque, milky 
 chyle. It is on this account that the lymphatics of the mesentery 
 are called "lacteals." 
 
 The chyle, accordingly, is nothing more than the lymph which 
 is constantly absorbed by the lymphatic system everywhere, with 
 the addition of more or less fatty ingredients taken up from the 
 intestine daring the digestion of food. 
 
 The results of analysis show positively that the varying appear- 
 ance of the lymphatic fluids is really due to this cause ; for though 
 
Lymph. 
 
 Chyle. 
 
 9(i5.36 
 
 902.37 
 
 12.00 
 
 85.16 
 
 1.20 
 
 3.70 
 
 2.40 
 
 3.32 
 
 . 13.19 
 
 12.33 
 
 . traces. 
 
 36.01 
 
 6 85 
 
 7.11 
 
 1,000.00 
 
 1,000.00 
 
 320 IMBIBITION AND EXHALATION. 
 
 • 
 
 tte chyle is also richer than the lymph in albuminous matters, the 
 principal difference between them consists in the proportion of fat. 
 This is shown by the following comparative analysis of the lymph 
 and chyle of the ass, by Dr. Eees:' — 
 
 Water . 
 
 Albumen 
 
 Fibrin . , 
 
 Spirit extract 
 
 Water extract 
 
 Fat 
 
 Saline matter 
 
 When a canula, accordingly, is introduced into the thoracic duct 
 at various periods after feeding, the fluid whichia discharged varies 
 considerably, both in appearance and quantity. "We have found 
 that, in the dog, the fluid of the thoracic duct never becomes quite 
 transparent, but retains a very marked opaline tinge even so late 
 as eighteen hours after feeding, and at least three days and a half 
 after tKe introduction of fat food. Soon after feeding, however, as 
 we have a,lready seen, it becomes whitish and opaque, and remains 
 so while digestion and absorption are in progress. It also becomes 
 more abundant soon after the commencement of digestion, but 
 diminishes again in quantity during its latter stages. We have 
 found the lymph and chyle to be discharged from the thoracic duct, 
 in the dog, in the following quantities per hour, at different periods 
 of digestion. The quantities are calculated in proportion to the 
 entire weight of the animal. 
 
 Per Thousand Pabts. 
 8^ hours after feeding ...... 2.45 
 
 7 " " " '. 2.20 
 
 13 " " " 0.99 
 
 18 " " " 1.15 
 
 18J " " " 1.99 
 
 It would thus appear that the hourly quantity of lymph, after 
 diminishing during the latter stages of digestion, increases again 
 somewhat, about the eighteenth hour, though it is still considera- 
 bly less abundant than while digestion was in active progress. 
 
 The lymph obtained from, the thoracic duct at all periods coagu- 
 lates soon after its withdrawal, owing to the fibrin whiclf it contains 
 
 ' In Colin, op. cit., vol. ii. p. 18. 
 
THE LYMPHATIC SYSTEM. 821 
 
 iu small quantity. After coagulation, a separation takes place be- 
 tween the clot and serurn, precisely as. in the case of blood. 
 
 The movement of the lymph in the lymphatic vessels, from the 
 extremities toward the heart, is accomplished by various forces. 
 The first and most important of these forces is that by which the 
 fluids are originally, absorbed by the lymphatic capillaries. Through- 
 out the entire extent of the lymphatic system, an extensive process 
 of endosmosis is incessantly going on, by which the ingredients of 
 the lymph are imbibed from the surrounding tissues, and com- 
 pelled to pass into the lymphatic vessels. The lymphatics are thus 
 filled at their origin ; and, by mere force of accumulation, the fluids 
 are then compelled, as their absorption continues, to discharge 
 themselves into the large veins in which the lymphatic trunks 
 terminate. 
 
 The movement of the fluids through the lymphatic system is 
 also favored by the contraction of the voluntary muscles and the 
 respiratory motions of the chest. For as the lymphatic vessels are 
 provided with valves, arranged like those of the veins, opening 
 toward the heart and shutting backward toward the extremities, 
 the alternate compression and relaxation of the adjacent muscles, 
 and the expansion and collapse of the thoracic parietes, must have 
 the same effect upon the movement of the lymph as upon that of 
 the venous blood. By these different influence^ the chyle, and 
 lymph are incessantly carried front without inward, and discharged, 
 in a slow but continuous stream, into the returning current of the 
 venous blood. 
 
 The entire quantity of the lymph and chyle has been found, by 
 direct experiment, to be very much larger than was previously 
 anticipated. M. Colin' measured the chyle discharged from the 
 thoracic duct of an ox during twenty-four hours, and found it to 
 exceed eighty pounds. In other experiments of the same kind, he 
 obtained still larger quantities.' From two experiments on the 
 horse, extending over a period of twelve hours each, he calculates 
 the quantity of chyle and lymph in this animal as from twelve, to 
 fifteen thousand grains per hour, or between forty and fifty pounds 
 per day. But in the ruminating animals, according to his observa- 
 tions, the quantity is considerably greater. In an ordinary-sized 
 cow, the smallest quantity obtained in an experiment extending over 
 
 1 Gazette Hetidomadaire, April 24, 1857, p. 2S5. 
 ' Colin, op. oit., vol. ii. p. 100. 
 
 21 
 
322 IMBIBITION AND EXHALATIOII. 
 
 a period of twelve hours, was a, little over 9,000 grains in fifteen 
 minutes ; that is, five pounds an hour, or 120 pounds per day. In 
 another experiment, with a young bull, he actually obtained a little 
 over 100 pounds from a fistula of the thoracic duct, in twenty -four 
 hours. 
 
 We have also obtained similar results by .experiments upon the 
 dog and goat. In a young kid, weighing fourteen pounds, we have 
 obtained from the thoracic duct 1890 grains of lymph in three 
 hours and a naif. This quantity would represent 540 grains in an 
 hour, and 12,690 grains, or 1.85 pounds in twenty-four hours ; and 
 in a ruminating animal weighing 1000 pounds, this would corre- 
 spond to 132 pounds of lymph and chyle discharged by the thoracic 
 duct in the course of twenty-four hours. 
 
 The average of all the results obtained by us, in the dog, at dif- 
 ferent periods after feeding, gives very nearly four and a half per 
 cent, of the entire weight of the animal, as the total daily quantity 
 of lymph and chyle. This is substantially the same result as that 
 obtained by Colin, in the horse; and for a man weighing 140 
 pounds, it would be equivalent to between six and six and a half 
 pounds of lymph and chyle per day. 
 
 But of this quantity a considerable portion consists of the chyle 
 which is absorbed from the intestines during the digestion of fatty 
 substances. If ^e wish, therefore, to ascertain the total amount of 
 the lymph, separate from that of the chyle, the calculation should 
 - be based upon the quantity of fluid obtained from the thoracic 
 duct in the intervals of digestion, when no chyle is in process of 
 absorption. We have seen that in the dog, eighteen hours after 
 feeding, the lymph, which is at that time opaline and semi-transpa- 
 rent, is discharged from the thoracic duct, in the course of an hour, 
 in a quantity equal to 1.15 parts per thousand of the entire weight 
 ot the animal. In twenty-four hours this would amount to 27.6 
 parts per thousand ; and for a man weighing 140 pounds this would 
 .give 3.864 pounds as the total daily quantity of the lymph alone. 
 
 It will be seen, therefore, that the processes of exudation and 
 absorption, which go on in the interior of the body, produce a very 
 active interchange or internal circulation of the animal fluids, which 
 may be considered" as secondary to the circulation of the blood. 
 For all the digestive fluids, as we have found, together with the bile 
 discharged into the intestine, are reabsorbed in the natural process 
 of digestion and again enter the current of the circulation. These 
 fluids, therefore, pass and repass through the mucous membrane of 
 
THE LYMPHATIC SYSTEM. 323 
 
 the alimentary canal and adjacent .glands, becoming somewhat 
 altered in constitution at each passage, but still serving to. renovate 
 alternately the constitution of the blood and the ingredients of the 
 digestive secretions. Furthermore the elements of, the blood itself 
 also transude in part from the capillary vessels, and are again taken 
 up, by absorption, by the lymphatic vessels, to be finally restored 
 to the returning current of the venous blood, in the immediate 
 neighborhood of the heart. 
 
 The daily quantity of all the fluids, tjius secreted and reabsorbed 
 during twenty-four hours, will enable us to estimate the activity 
 with which endosmosis and exosmosis go on in the living body- 
 In the following table, the quantities are all calculated for a man 
 weighing 140 pounds. 
 
 Secbeted and Reabsorbed ddrino 24 hodrs. 
 Saliva 20,164 grains, or 2.880 pounds. 
 
 Gastric juice 98,000 " " 14.000 " 
 Bile 16.940 " " 2.420 " 
 
 Pancreatic juice 13,104 " " 1.872 " 
 Lymph 27,048 " " 3.8S4 ■' 
 
 25.036 
 
 A little over twenty-five pounds, therefore, of the animal fluids 
 transude through the internal membranes and are restored to the 
 blood by reabsorption in the course of a single day. It is by this 
 process that the natural constitution of the parts, though constantly 
 changing, is still maintained in its normal condition by the move- 
 ment of the circulating fluids, and the incessant renovation of their 
 nutritious materials. 
 
324 SECRETIOIT. 
 
 CHAPTER XVI. 
 
 SECRETION. 
 
 We have already seen, in a previous chapter, how the elements of 
 the blood are absorbed by the tissues during the capillary circula- 
 tion, and assimilated by them or converted into their own substance. 
 In this process, the inorganic or saline matters are mostly taken up 
 unchanged, and are merely appropriated by the surrounding parts in 
 particular quantities; while the organic substances are transformed 
 into new compounds, characteristic of the difierent tissues by which 
 they are assimilated. In this way the various tissues of the body, 
 though they have a different chemical composition from the blood, 
 are nevertheless supplied by it with appropriate ingredients, and 
 their nutrition constantly maintained. 
 
 Beside this process, which is known by the name of "assimila- 
 tion," there is another somewhat similar to it, which takes place in 
 the different glandular organs, known as the process of secretion. It 
 is the object of this function to supply certain fluids, differing in 
 chemical constitution from the blood, which are required to assist 
 in various, physical and chemical actions going on in the body. 
 These secreted fluids, or " secretions," as they are called, vary in 
 consistency, density, color, quantity, and reaction. Some of them 
 are thin and watery, like the teaffs and the perspiration ; others are 
 viscid and glutinous, like mucus and the pancreatic fluid. They 
 are alkaline like the saliva, acid like the gastric juice,, or neutral 
 like the bile. Each secretion contains water and the inorgaijic salts 
 of the blood, in varying proportions ; and is furthermore distin- 
 guished by the presence of some peculiar animal substance which 
 does not exist in the blood, but which is produced by the secreting 
 action of the glandular organ. As the blood circulates through the 
 capillaries of the gland, its watery and saline constituents transude 
 in certain quantities, and are discharged into the excretory duct. 
 At the same time, the glandular cells, which have themselves been 
 nourished by the blood, produce a new substance by the catalytic . 
 
• SECBETIOX. 325 
 
 transformation of their organic constituents; and this new substance 
 is discharged also into the excretory duct and mingled with the 
 other ingredients of the secreted fluid. A true secretion, therefore, , 
 is produced only in its -own particular gland, and cannot be formed 
 elsewhere, since the glandular cells of that organ are the only 
 ones capable of producing its most characteristic ingredient. Thus 
 pepsine is formed only in the tubules of the gastric mucous mem- 
 brane, pancreatine only in the pancreas, tauro-cholate of soda only 
 in the liver. 
 
 One secreting gland, consequently, can never perform vicariously 
 the office of another. Those instances which have been from time 
 to time reported of such an unnatural action are not, properly 
 speaking, instances of "vicarious secretion;" but only cases in 
 which certain substances, already existing in the^ blood, have made 
 their appearance in secretions to which they do not naturally belong. 
 Thus cholesterine, which is produced in the brain and is taken up 
 from it by the blood, usually passes out with the bile; but it may 
 also appear in the fluid of hydrocele, or in inflammatory exuda- 
 tions. The sugar, again, which is produced, in the liver and taken 
 up by the blood, when it accumulates in large quantity in the. cir- 
 culating fluid, may pass out with the urine. The coloring matter 
 of the bile, in cases of biliary obstruction, may be reabsorbed, and 
 so make its appearance in the serous fluids, or even in the perspira- 
 tion. In these instances, however, the unnatural ingredient is not 
 actually produced by the kidneys, or the perspiratory glands, but 
 is merely supplied to them, already formed, by the blood. Cases 
 of " vicarious menstruation" are simply capillary hemorrhages 
 which take place from various mucous membranes, owing to the 
 general disturbance of the circulation in amenorrhcea. A true 
 secretion, however, is always confined to the gland in which it 
 naturally originates. 
 
 The force by which the different secreted fluids are prepared in 
 the glandular organs, and discharged into their ducts, is a peculiar 
 one, and resident only in the glands themselves. It is not simply 
 a process of filtration, in which the ingredients of the secretion 
 exude from the bloodvessels by exosmosis under the influence of 
 pressure ; since the most characteristic of these ingredients, as we 
 have already mentioned, do not pre-exist in the blood, but are 
 formed in the substance of the gland itself. Substances, even, 
 which already exist in the blood in a soluble form, may not have 
 the power of passing out through the glandular tissue. Bernard 
 
f26 ' SKCBETION. • • 
 
 has found' that ferrocyanide of potassium, when injected into the 
 jugular vein, though it appears with great facility in the urine, 
 does not pass out with the saliva; and even that a solution of 
 the same salt, injected into the duct of the parotid gland, is ab- 
 sorbed, taken up by the blood, and discharged with the urine; but 
 does not appear in the saliva, even of the gland into which it has 
 been injected. The force with which the secreted fluids accumulate 
 • in the salivary ducts has also been shown by Ludwig's experi- 
 ments' to be sometimes greater than the pressure in the bloodves- 
 sels. This author found, by applying mercurial gauges at the same 
 time to the duct of Steho and to the artery of the parotid gland, that 
 the pressure in the duct from the secreted saliva was considerably 
 greater than that in the artery from the circulating blood ; so that 
 the passage of the secreted fluids had really taken place in a direc- 
 tion contrary to that which would have been caused by the simple 
 influence of pressure. ♦ 
 
 The process of secretion, therefore, is one which depends upon 
 the peculiar anatomical and chemical constitution of the glandular 
 tissue and its secreting cells. These cells have the property of 
 absprbing and transmitting from the blood certain inorganic and 
 saline substances, and of producing, by chemical metamorphosis, 
 certain peculiar animal matters from their own tissue. These sub- 
 stances are then mingled together, dissolved in the watery fluids 
 of the secretion, and discharged simultaneously by the excretory 
 duct. 
 
 All the secreting organs vary in activity at different periods'. 
 Sometimes they are nearly at rest; while at certain periods they 
 become excited, under the influence of an occasional or periodical 
 stimulus, and then pour out their secretion with great rapidity and in 
 large quantity. The perspiration, for example, is usually so slowly 
 secreted that it evaporates as rapidly as it is poured out, and the 
 surface of the skin remains dry ; but under the influence of unusual 
 bodily exercise or mental excitement it is secreted much faster 
 than it can evaporate, and the whole integument becomes covered 
 with moisture. The gastric juice, again, in the intervals of digestion, 
 is either not secreted at all, or is produced in a nearly inappreciable 
 quantity ; but on the introduction of food into the stomach, it is 
 immediately poured out in such abundance, that between two and 
 three ounces may be collected in a quarter of an hour. 
 
 ' Le(;6ns de Physiologie Expgrimeiitale. Paris, 1866, tome ii. p. 96 et seq. 
 2 Ibid., p. 106. 
 
MUCUS. 827 
 
 The principal secretions met with in the animal body are as 
 follo»ws : — 
 
 1. Mnona. • 6. Saliva. 
 
 2. Sebaceous matter. 7. Gastric jnioe'. 
 
 3. Perspiration. 8.' Pancreatic juice. 
 
 4. The tears. 9. Intestinal juice. 
 
 5. The milk. 10. Bile. 
 
 The last five of these fluids have already been described in the 
 preceding chapters. We shall therefore only require to examine 
 at present the five following, viz., mucus, sebaceous matter, per- 
 spiration, the tears, and the milk, together with some peculiarities 
 in the secretion of the bile. 
 
 1. Mucus. — Nearly all the mucous membranes are provided with 
 foUiqles or glandulae, in which the mucus is prepared; These folli- 
 cles are most abundant in the lining membrane of the mouth, nares, 
 pharyns, oesophagus, trachea and bronchi, vagina, and male urethra. 
 They are generally of a compound form, consisting of a number of 
 secreting sacs or cavities, , terminating at one end in a blind ex- 
 tremity, and opening by the other into a common dUct by which 
 the secreted fluid is discharged. Each ultimate secreting sac or 
 follicle is lined with glandular epithelium (Fig. 102), and surround-, 
 ed^on its external surface by a network of capillary bloodvessels. 
 These vessels, penetrating deeply into the p. j.„ 
 
 interstices between the follicles, bring the 
 blood nearly into contact with the epithelial 
 cells lining its cavity. It is these cells 
 which prepare the secretion, and discharge 
 it afterward into the commencement of the 
 
 excretory duct. _ fo,..ic,.b8 op a co„- 
 
 The mucus, produced in the manner rnuso un-.ova glajbclk. 
 
 , 't .,-,. _- T, n ' 1 From the Iiiiman subject. (Aftei 
 
 above described, is aT clear, coloriess fluid, Koiuker.)-", iiembiaDe of ti,e 
 which is poured out in larger or smaller '»>"<:'«■ >>••-■ Epitiieimm of the 
 
 1 n n t same. 
 
 ■ quantity on the surface ot the mucous 
 
 membranes. It is distinguished from other secretions by its vis- 
 cidity, which is its most marked physical property, and which 
 depends on the presence of a peculiar animal matter, known under 
 the name of mucosine. When unmixed with other animal fluids, 
 this viscidity is so great that the mucus has nearly a semi-solid or 
 gelatinous consistency. Thus, the mucus of the mouth, when ob- 
 tained unmixed with the secretions of the salivary glands, is so 
 
828 
 
 SECRETION. 
 
 tough and adhesive that the vessel containing it may be turned 
 upside down without its running out. The mucus of the cervix 
 uteri has a similar firm consistency, so as to block up the cavity 
 of this part of the organ with a semi-solid gelatinous mass. Mucus 
 is at the same time exceedingly smooth and slippery to the touch, 
 so that it lubricates readily the surfaces upon which it is exuded, 
 and facilitates the passage of foreign substances, while it defends 
 the mucus membrane itself from injury. 
 
 The composition of mucus, according to the analyses of Nasse," 
 
 is as follows :-^7 
 
 Composition of Pclmonaky Mucns. 
 Water 955.52 
 
 Animal matter . 
 
 Fat 
 
 Chloride of sodium . 
 Phosphates p{ soda and potassa 
 Sulphates * " " 
 
 Carbonates " " 
 
 33.57 
 2.89 
 6.83 
 1.05 
 0.65 
 0.49 
 
 1000.00 
 The animal matter of mucus is insoluble in water ; and conse- 
 quently mucus, when dropped into water, does not mix with it, but 
 is merely broken up by agitation into gelatinous threads and flakes, 
 which subside after a time to the bottom. It is miscible, however, 
 to some extent, with other animal fluids, and may be incorporated 
 with them, so as to become thinner and more dilute. It readily 
 takes on putrefactive changes, and communicates them to other 
 organic substances with which it may be in contact. 
 
 The varieties of mucus found in different parts of the body are 
 probably not identical in composition, but differ a little in the cha- 
 racter of their principal organic ingredient, as well as in the pro- 
 portions of their saline constituents. The function of mucus is for 
 the most part a physical one, viz., to lubricate the mucous surfaces, 
 to defend them from injury, and to facilitate the passage of foreign 
 substances through their cavities. 
 
 2. Sebaceous Matter. — ^The sebaceous matter is distinguished 
 by containing a very large proportion of fatty or oily ingredients. 
 There are three varieties of this secretion met with in the body, 
 viz., one produced by the sebaceous glands of the skin, another 
 by the ceruminous glands of the external auditory meatus, and 
 a third by the Meibomian glands of the eyelid. The sebaceous 
 
 Simon's Chemistry of Man, Philada., 184(), p. 352. 
 
SEBACEOUS MATTER. 329 
 
 glands of tlie skin are found most abundantly in those parts which 
 are thickly covered with hairs, as well as on the face, the labia 
 minora of the female generative organs, the glans penis, and the 
 prepuce. They consist sometimes of a simple follicle, or flask- 
 shaped cavity, opening by a single orifice ; but more frequently of 
 a number of such follicles grouped round a common excretory duct. 
 The duct nearly always opens just at the root of one of the hairs, 
 which is smeared more or less abundantly 
 with its secretion. Each follicle, as in the Fig- 103. 
 
 case of the mucous glandules, is lined 
 with epithelium, and its cavity is filled 
 with the secreted sebaceous matter. 
 
 In the Meibomian glands of the eye- 
 lid (Fig. 103), the follicles are ranged 
 along the sides of an es^retory duct, 
 situated just beneath the conjunctiva, on 
 the posterior surface of the tarsus, and 
 opening ' upon its free edge, a little be- 
 hind the roots of the eyelashes. The 
 ceruminous glands of the external audi- 
 tory meatus, again, have the form of long 
 tubes, which terminate, at the lower part 
 
 , ,, . , . Mbibomiax Glands, after 
 
 of the integument Immg the meatus, in ludovic. 
 a globular coil, or convolution, covered 
 externally by a network of capillary bloodvessels. 
 
 The sebaceous matter of the skin has the following composition, 
 according to Esenbeck.' 
 
 CoMFOsiTioH OP Sebaceous Mattes. 
 
 Animal substances 358 
 
 Fatty matters 368 
 
 Phosphate of lime .200 
 
 Carbonate of lime 21 
 
 Carbonate of magnesia X6 
 
 Chloride, of sodium 1 . . 37 • 
 Acetate of soda, &c. ' 
 
 1000 
 
 Owing to the large proportion of ste^rine in the fatty ingredients 
 of the sebaceous matters, they have a considerable degree of con- 
 sistency. Their ofSce is to lubricate the integument and the hairs, 
 to keep them soft and pliable, and to prevent their drying up by 
 
 ' Simon's Chemistry of Man, p. 379. 
 
330 
 
 SECRETION. 
 
 Fig. 104. 
 
 too .rapid evaporation. When the sebaceous glands of the scalp 
 are inactive or atrophied, the hairs become dry and brittle, are 
 easily split or broken off, and finally cease growing altogether. 
 The ceruminous matter of the ear is intended without doubt partly 
 to obstruct the cavity of the meatus, and hy its glutinous consist- 
 ency and strong odor to prevent small insects from accidentally 
 introducing themselves into the meatus. The secretion of the 
 Meibomian glands, by being smeared on the edges of the eyelids, 
 prevents the tears from running over upon the cheeks, and confines 
 them within the cavity of the lachrymal canals. 
 
 3. Pekspibation. — The perspiratory glands of the skin are scat- 
 tered everywhere throughout the integument, being most abundant 
 on the anterior portions of the body. They consist each of a slender 
 tube, about ^J^ of an inch in diamete:^ lined with glandular epi- 
 thelium, which penetrates nearly through the entire thickness of 
 the skin, and terminates below in a globular coil, very similar in 
 
 appearance to that of the cerumi- 
 nous glands of the ear. (Fig. 104.) 
 A network of capillary vessels 
 envelops the tubular coil and sup- 
 plies the gland with the materials 
 necessary to its secretion. 
 
 The§e glands are very abundant 
 in some parts. On the posterior 
 portion of the trunk, the cheeks, 
 and the skin of the thigh and leg 
 there are, according to Krause,' 
 about 500 to the square inch ; on , 
 the anterior part of the trunk, the 
 forehead, the neck, the forearm, 
 and the bacls of the hand and foot 
 1000 to. the square inch ; and on 
 the sole of the foot and the palm 
 of the hand about 2700 in the same space. According to the same 
 observer, the whole number of perspiratory glands is not less than 
 2,300,000, and the length of each tubular coil, when unravelled, 
 about yV of an inch. The entire length of the glandular tubing 
 must therefore be not less than 153,000 inches, or about two miles 
 and a half. 
 
 A Persptbatort Gland, with its ves- 
 sel b : magnified 35 times. (After Todd and Bow- 
 maa.) — rt. Glandular coiL b. Fiexas of veijaeln. 
 
 ' KiJllikeT, Handbuch rler Gewebelehre, Leipzig, 1852, p. 147. 
 
PEESPIKATION. 331 
 
 It is easy to understand, therefore, that a very large quantity of 
 £uid may be supplied from so extensive a glaudular apparatus. It 
 results from the researches of Lavoisier and Seguin" that the ave- 
 rage quantity of fluid lost by cutaneous perspiration during 24 
 hours is 13,500 grains, or nearly two pounds avoirdupois. A still 
 larger quantity than this may be discharged during a shorter time, 
 when the external temperature is high and the circulation active. 
 Dr. Southwood Smith* found that the laborers employed in gas 
 works lost sometimes as much as 3J pounds' weight, by both cuta- 
 neous and pulmonary exhalation, in less than an hour. In these 
 cases, as Seguin has shown, the amount of cutaneous transpiration 
 is about twice as great as that which takes place through the lungs. 
 
 The perspiration is a colorless watery fluid, generally with a 
 . distinctly acid reaction, and having a peculiar odor, which varies 
 somewhat according to the part of the body from which the speci- 
 men is obtained. ■ Its chemical constitution, according to Ansel- 
 mino,' is as 'follows : — ■ 
 
 CoMFOSITIOir OF THE PeBRFIBATION. 
 
 Water 995.00 
 
 Animal matters, with lime . .IQ 
 
 Sulphates, and substances soluble in water .... 1.05 
 
 Chlorides of sodium And potassium, and spirit-extract . . 2.40 
 
 Acetic acid, acetates, lao^tes, and alcohol-extract . . . 1.45 
 
 1000.00 
 
 The office of the cutaneous perspiration is principally to regulate 
 the temperature of the body. We have already seen, in a preced- 
 ing chapter, that the living body will maintain the temperature of 
 100° F., though subjected, to a much lower temperature by the 
 surrounding atmosphere, in consequence of the continued genera- 
 tion of heat which takes place in its interior ; and that if, by long 
 continued or severe exposure, the blood become cooled down much 
 below its natural standard, death inevitably results. But the body 
 has also the power of resisting an unnaturally high temperature, 
 as well as an unnaturally low one. If exposed to the influence of 
 an atmosphere warmer than 100° F., the body does not become 
 heated up to the temperature of the air, but remains at its natural 
 standard. This is provided for by the action of the cutaneous 
 glands, which are excited to unusual activity, and pour out a large 
 quantity of watery fluid upon the skin. This fluid immediately 
 
 ' Milne Edwards, Leijons snr la Physiologie, &o., vgl. ii. p. 623. 
 ' Piiilosophy of Health, London, 1838, chap. xiii. 
 s Simon. Op. cit., p. 374. 
 
832 SECRETION. 
 
 evaporates, and in assuming the gaseous form causes so much heat 
 to become latent that the cutaneous surfaces are cooled down to 
 their natural temperature. 
 
 So long as the air is dry, so that evaporation from the surface 
 can go on rapidly, a very, elevated temperature can be borne with 
 impunity. The workmen of the sculptor Chantrey were in the 
 habit, according to Dr. Carpenter, of entering a furnace in which 
 the air was heated up to 350° ; and other instances have been known 
 in which a temperature of 400° to 600° has been borne for a time 
 without much inconvenience. But if the air be saturated with 
 moisture, and evaporation from the skin in this way retarded, the 
 body soon becomes' unnaturally warm ; and if the exposure be long 
 continued, death is the result. It is easily seen that horses, when 
 fast driven, suffer much more from a warm and moist atmosphere 
 than from a warm and dry one. The experiments of Magendie and 
 others have shown' that quadrupeds confined in a dry atmosphere 
 suffer at first but little inconvenience, even when the temperature 
 is much above that of their own bodies ; but as soon as the atmo- 
 sphere is loaded with moisture, or the supply of perspiration is ex- 
 hausted, the blood becomes heated, and the animal dies. Death 
 follows in these cases as soon as the blood has'become heated up to 
 8° or 9° F., above its natural standard. The temperature of 110°, 
 therefore, which is the natural temperature of birds, is fatal to quad- 
 rupeds; and we have found that frogs, whose natural temperature 
 is 50° or 60°, die very soon if they are kept in water at 100° F. 
 
 The amount of perspiration is liable to variation, as we have 
 already intimated, from the variations in temperature of the sur- 
 rounding atmosphere. It is excited also by unusual muscular 
 exertion, and increased or diminished by various nervous condi- 
 tions, such as anxiety, irritation, lassitude, or excitement. 
 
 4. The Tears. — The tears are produced by lobulated glands 
 situated at the upper and outer part of the orbit of the eye, and 
 opening, by from six to twelve ducts, upon the surface of the con- 
 junctiva, in the fold between the eyeball and the outer pprtion of 
 the upper lid. The secretion is extremely watery in its composition, 
 and contains only about one part per thousand of solid matters, 
 consisting mostly of chloride of sodium, and animal extractive 
 matter. The office of the, lachrymal secretion is simply to keep the 
 
 ' Bernard, Lectures on the Blood. Atiee's translation, Phila., 1854, p. 25. 
 
THE MILK. 
 
 333 
 
 surfaces of the cornea and conjunctiva moist and polished, and to 
 preserve in this way the transparency of the parfs. The tears, 
 which are constantly secreted, are spread out uniformly over the 
 anterior part of the eyeball by the movement of the lids in wink- 
 ing, and are gradually conducted to the inner angle of the eye. 
 'Here they are taken up by the puncta lachrymalia, pass through 
 the lachrymal canals, and are finally discharged into the nasal pas- 
 sages beneath the inferior turbinated bones. A constant supply of 
 fresh fluid is thus kept passing over the transparent parts of the 
 eyeball, and the bad results avoided which would follow from its 
 accumulation and putrefactive alteration. 
 
 5. The Milk. — The mammary glands are conglomerate glands 
 resenibling closely in their structure the pancreas, the salivary, and 
 the lachrymal glands. They consist of numerous secreting sacs or 
 follicles, grouped together in lobules, each lobule being supplied 
 with a common excretory duct, which joins those coming from 
 adjacent parts of the gland. 
 
 (Fig. 105.) In this way, by Fig. 105. 
 
 their successive union, they 
 form larger branches and 
 trunks, until they are reduced 
 in numbers to some 15 or 20 
 cylindrical ducts, the lactifer- 
 ous ducts, which open finally 
 by' as many minute orifices 
 upon the extremity of the 
 nipple. 
 
 The secretion of the milk 
 becomes fairly established at 
 the end of two or three days 
 after delivery, though the 
 breasts often contalin a milky 
 
 fluid during the latter part of pregnancy. At first the fluid dis- 
 charged from the nipple is a yellowish turbid mixture, which is 
 called the colostrum. It has the appearance of being thinner than, 
 the milk, but chemical examinations have shown" that it really con- 
 tains a larger amdunt of solid ingredients than the perfect secre- 
 tion. When examined under the microscope it is seen to contain, 
 beside the milk-globules proper, a large amount of irregularly glo- 
 
 ' Lehmann, op. oit., vol. ii. p. 63. 
 
 Gr.ANDULAR Structcre of .Mamma 
 
334 
 
 SECRETION. 
 
 btilar or oval bodies, from ttbtt to sin o? an incli in diameter, 
 ■which are termed the "colostrum corpuscles." (Fig. 106.) These 
 
 bodies are more yellow and 
 Fig- 106. opaque than the true milk- 
 
 glob ules, as well as being very 
 much larger. They have or 
 well defined outline, and con- 
 sist apparently of a group of 
 minute oily granules or glo- 
 bules, imbedded in a mass 
 of organic substance. The 
 milk-globules at this time 
 are less abundant than after- 
 ward, and of larger size, 
 measuring mostly from j^^j^ 
 
 to tbVtt of ^^ i^oli ill dia- 
 meter. 
 
 At the end of a day or 
 two after its first appearance, 
 
 the colostrum ceases to be discharged, and is replaced by the true 
 
 milky secretion. 
 
 The milk, as it is discharged from the ijipple, is a white, opaque 
 
 fluid,, with a slightly alkaline reaction, and a specific gravity of 
 
 about 1030. Its proximate chemical constitution, according to 
 
 Pereira and, Lehmann, is as follows : — 
 
 Colostrum CoKPrscLES, Trith mllk-globulea ; 
 from a woman, one day after delivery. 
 
 .*««■' 
 
 Composition OP Cow'b Milk. 
 Wate* 
 Casein 
 Butter 
 Sugar 
 Soda 
 
 Chloriiles of sodium and potassium 
 Phosphates of soda and potassa 
 Phosphate of lime 
 
 " " magnesia 
 " iron . 
 Alkaline carbonates . 
 
 870.2 
 ^14.8 
 31.3 
 
 47.7 
 
 6.0 
 
 1000.0 
 
 Human milk is distinguished from the above -by containing less 
 casein, and a larger proportion of oily and saccharine ingredients. 
 The entire amount of -solid ingredients is also somewhat less than 
 in cow's milk. 
 
THE MILK, 
 
 335 
 
 The casein is one of the most important ingredients of the milk. 
 It is an extremely nutritious organic substance, which is held in a 
 fluid form by union with the water of the secretion. Casein is not 
 coagulable by heat, and consequently, milk may be boiled without 
 changing its consistency to any considerable extent. It becomes 
 a little thinner and more fluid during ebullition, owing to the melt- 
 ing of its oleaginous ingredients; and a thin, membranous film 
 forms upon its surface, consisting probably of a very little albumen, 
 which the milk contains, mingled with the casein. The addition of 
 any of the acids, however, mineral, animal, or vegetable, at once 
 coagulates the casein, and the milk becomes curdled. Milk is 
 coagulated, furthermore, by the gastric juice in the natural process 
 of digestion, immediately after being taken into the stomach; and 
 if vomiting occur soon after a meal containing milk, it is thrown 
 off in the form of semi- solid, curd-like flakes. 
 
 The mucous membrane of the calves' stomach, or rennet, also 
 has the power of coagulating casein; and when milk has been 
 curdled in this way, and its watery, saccharine, and inorganic in- 
 gredients separated by mechanical pressure, it is converted into 
 cheese. The peculiar flavor of the different Varieties' of cheese 
 depends on the quantity and quality of the oleaginous ingredients 
 which have been entangled with the coagulated casein, and on the 
 alterations which these sub- 
 stances have undergone by 
 the lapse of time and ex- 
 posure to the atmosphere. 
 
 The sugar and saline sub- 
 stances of the milk are in 
 solution, together with the 
 casein and water, forming a 
 clear, colorless, homogene- 
 ous, serous fluid. The but- 
 ter, or oleaginous ingredient, 
 however, is suspended in 
 this serous fluid in the form 
 of minute granules and 
 globules, the_ true "milk-, 
 globules." (Fig. 107.) These 
 globules are nearly fluid at 
 the teniperature of the body, and have a perfectly circular out- 
 line. In the perfect milk, they are very much more abundant and 
 
 Fig. 107. 
 To" 
 
 
 '0° o°o 
 
 0. 0„=°„oo Ooq"o'-'^<§) o 
 
 o o. 
 
 oO°0°0 ^OO", 
 ooo°oOOoO°oS°°° 
 
 Oo 
 
 ^°i,po ; o 
 
 oo 
 
 oO, 
 
 oOo 
 
 Mii.k-GlobuTiKe>; from same woman as above, 
 four days after delivery. Secretion fully etstablislied. 
 
336 SECRETION. 
 
 smaller in size than in the colostrum ; as the largest of them are 
 not over jtsVb of an inch in diameter, and the greater number 
 about YsUu of an inch. 
 
 The following is the composition of the butter of cow's milk, 
 according to Eobin and Verdeil : — 
 
 Margarine 68 
 
 Oleine 30 
 
 Butyrine 2 
 
 100 
 
 It is the last of these ingredients, the butjrine, which gives the 
 peculiar flavor to the butter of milk. 
 
 The milk-globules have sometimes been described as if each one 
 were separately covered with a thin layer of coagulated casein or 
 albumen. Nosucli investing membrane, however, is to be seen. 
 The milk-globules are simply small masses of semi-fluid fat,, sus- 
 pended by admixture in the watery and serous portions of the 
 secretion, so as to make an opaque, whitish emulsion. They do 
 not fuse together when they come in contact under the microscope, 
 simply because they are not quite fluid, but contain a large pro- 
 portion of margarine, which is solid at ordinary temperatures of the 
 body, and is only retained in a partially fluid form by the oleine 
 with which it is,associated. The globules may be made to fuse with 
 each other, however, by simply heating the milk and subjecting it 
 to gentle pressure between two slips of glass. 
 
 When fresh milk is allowed to remain at rest for twelve to twenty- 
 four hours, a large portion of its fatty matters rise to the surface, 
 and form there a dense and rich-looking yellowish- white layer, the 
 cream, which may be removed, leaving the remainder still opaline, 
 but less opaque than before. At*the end of thirty-six to forty-eight 
 hours, if the weather be warm, the casein 'begins to take on a 
 putrefactive change. In this condition it exerts a catalytic action 
 upon the other ingredients of the milk, and particularly upon the 
 sugar. A pure watery solution of milk-sugar (Cj^Hj^Oj^) may he 
 kept for an indefinite length of time, at ordinary temperatures, 
 without undergoing any change. But if kept in contact with the 
 partially altered casein, it suffers a catalytic transformation, and is 
 converted into lactic acid (CgHgOg). This unites with the free soda, 
 and decomposes the alkaline carbonates, forming lactates of soda 
 and potassa. After the neutralization of these substances has been 
 accomplished, the milk loses its alkaline reaction and begins to turn 
 sour. The fr^e lactic acid then coagulates the casein, and the milk 
 
SECEETION OF THE BILE. 337 
 
 is curdled. The altered organic matter also acts upon the olea- 
 ginous ingredients, which are partly decomposed; and the milk 
 begins to give off a rancid odor, owing to the development of 
 various volatile fatty acids, among which are butyric acid, and the 
 like. These changes are very much hastened by a moderately 
 elevated temperature, and also by a highly electric state of the 
 atmosphere. 
 
 The production of the milk, like that of other secretions, is liable 
 to be much influenced by nervous impressions. It may be increased 
 or diminished in quantity, or vitiated in quality by sudden emo- 
 tions ; and it is even said to have been sometimes so much altered 
 in this way as to produce indigestion, diarrhoea, and convulsions in 
 the infant. 
 
 Simon found' that the constitution of the milk varies from day to 
 day, owing to temporary causes ; and that it undergoes also more 
 permanent modifications, corresponding with the age of the infant. 
 He analyzed the milk of a nursing woman during a period of nearly 
 six months, commencing with the second day after delivery, and 
 repeating his examinations at intervals of eight or ten days. It 
 appears, from these observations, that the casein is at first in small 
 quantity ; but that it increases during the fir^t two months, and 
 then attains a nearly uniform standard. The saline matters also 
 increase in a nearly similar manner. The sugar, on the contrary, 
 diminishes during the same period ; so that it is less abundant in 
 the third, fourth, fifth and sixth months, than it is in the first and 
 second. These changes are undoubtedly connected with the in- 
 creasing development of the infant, which requires a corresponding 
 alteration in the character of the food supplied to it. Finally, the 
 quantity of butter in the milk varies so much from day to day, 
 owing to incidental causes, that it cannot be said to follow any 
 regular course of increase or diminution, 
 
 6. Secretion of the Bile. — The anatomical peculiarities in the 
 structure of the liver are such as to distinguish it in a marked 
 degree from the other glandular organs. Its first peculiarity is 
 that it is furnished principally with venous blood. For, although 
 it receives its blood from the hepatic artery as well as from the 
 portal vein, the qttantity of arterial blood with which it is supplied 
 is extremely small in comparison with that which it receives from 
 
 ' Op. oit., p. 337. 
 22 
 
338 
 
 SECRETION. 
 
 Fig. 108. 
 
 the portal system. The blood which has circulated through the 
 capillaries of the stomach, spleen^ pancreas, and intestine is col- 
 lected bj the roots of the corresponding veins, and discharged into 
 the portal vein, which enters the liver at the great transverse 
 fissure of the organ. Immediately upon its entrance, the portal 
 vein. divides into two branches, right and left, which supply the 
 corresponding portions of the liver; and these branches success- 
 ively subdivide into smaller twigs and ramifications, until they are 
 reduced to the size, according to Kolliker, of tAtt of ^^ inch in 
 diameter. These veins, with their terminal branches, are arranged 
 in such a manner as to include between them pentagonal or 
 hexagonal spaces, or portions of the hepatic substance, -j'g to -j-'j 
 of an inch in diameter in the human subject, which can readily be 
 distinguished by the naked eye, both on the exterior of the organ 
 and by the inspection of cut surfaces. The portions of hepatic 
 substance included in this way between the terminal branches 
 
 of the portal vein (Fig. 108) 
 are termed the " acini" or 
 "lobules" of the liver; and 
 the terminal venous branches, 
 occupying the spaces between 
 the adjacent lobules, are the 
 "interlobular" veins. In the 
 spaces between the lobules 
 we also find the minute 
 branches of the hepatic ar- 
 tery, and the commencing 
 rootlets of the hepatic ducts. 
 As the portal vein, the he- 
 patic artery, and the hepatic 
 duct enter the liver at the 
 transverse fissure, they are 
 closely invested by a fibrous 
 sheath, termed Glisson's capsule, which accompanies them in their 
 divisions and ramifications. In some of the lower animals, as in the 
 pig, this sheath extends even to the interlobular spaces, inclosing 
 each lobule in a thin fibrous in vestment,, by which it is distinctly 
 separated from the neighboring parts. In the human subject, how- 
 ever, Glisson's capsule becomes gradually thinner as it penetrates 
 the liver, and disappears altogether before reaching the interlobulaE? : 
 spaces ; so that here the lobules are nearly in contact with each 
 
 Ramification of Poetal Vein in Liter. — a. 
 Twitf of poi'lalvein. &,&, Interlobular veiue. c. Acini. 
 
SECRETION OF THE BILE. 339 
 
 Other by their adjacent surfaces, being separated only by the inter- 
 lobular veins and the minute branches of the hepatic artery and 
 duct previously mentioned. 
 
 From the sides of the interlobular veins, and also from their 
 terminal extremities, there are given off capillary vessels, which 
 penetrate the substance of each lobule and converge from its cir- 
 cumference toward its centre, inosculating at the same time freely 
 with each other, so as to form a minute vascular plexus, the "lobu- 
 lar" capillary plexus. (Fig. 109.) At the centre of each lobule, the • 
 
 Fig. 109. 
 
 LoBuiE OF Liter, ehowing distilbutlon of bloodvessels ; magnifled 22 diameters —a. n. In- 
 terlobular veins, b. latralobnlar vein, a, c, o. Lobular capillary plexus, d, d. Twigs ot inter- 
 lobular vein passing to adjacent lobules. 
 
 converging capillaries unite into a small vein (6), the " intralobu- 
 lar" vein, which is one of the commencing rootlets of the hepatic 
 vein. These rootlets, uniting successively with each other, so as 
 to form larger and larger branches, finally leave the liver at its 
 posterior edge, to empty into the ascending vena cava. ' 
 
 Beside the capillary bloodvessels of the lobular plexus, each 
 acinus is made up of an abundance of minute cellular bodies, about 
 TuVir of an inch in diameter, the " hepatic cells." (Fig. 110.) These 
 cells have an irregularly pentagonal figure, and a soft consistency. 
 They are composed of a homogeneous organic substance, in the 
 midst of which are imbedded a large number of minute granules, 
 and generally several well defined oil-globules. There is also a 
 round or oval nucleus, with a nucleolus, imbedded in the substance 
 
340 
 
 SECKETIOX. 
 
 of the cell, sometimes more or less obscured by the granules and 
 oil drops with which it is surrounded. 
 
 The exact mode in which these cells are connected with the 
 hepatic duct was for a long time the most obscure point in the 
 
 minute anatomy of the liver. 
 '^' ' It has now been ascertained, 
 
 however, by the researches of 
 Dr. Leidy, of Philadelphia,^ 
 and Dr. Beale, of London,' 
 that they are really contained 
 in the interior of secreting 
 tubules, which pass off from 
 the smaller hepatic ducts, and 
 penetrate everywhere the 
 substance of the lobules. 
 The cells fill nearly or com- 
 pletely the whole cavity of 
 the tubules, and the tubules, 
 themselves lie in close proxi- 
 mity with each other, so as 
 to leave no space between them except that which is occupied by 
 the capillary bloodvessels of the lobular plexus. 
 
 These cells are the active agents in accomplishing the function of 
 the liver. It is by their influence that the blood which is brought 
 in contact with them suffers certain changes which give rise to the 
 secreted products of the organ. The ingredients of the bile first 
 make their appearance in the substance of the cells. They are 
 then transuded from one to the other, until they are at last dis- 
 charged into the small biliary ducts seated in the interlobular 
 spaces. Each lobule of the liver must accordingly be regarded as 
 a mass of secreting tubules, lined with glandular cells, and invested 
 with a close network of capillary bloodvessels. It follows, there- 
 fore, from the abundant inosculation of the lobular capillaries, and 
 the manner in which they are entangled with the hepatic tissue, 
 that the blood, in passing through the circulation of the liver, 
 comes into the most intimate relation with the glaindular cells of 
 the organ, and gives up to them the nutritious materials which are 
 afterward converted into the ingredients of the bile. 
 
 Hepatic Cklls. Frum the human subject. 
 
 ' American Journal Meil. Sol., Januarjr, 1848. 
 
 ' On Some Points in the Minute Anatomy of tlie Liver. 
 
 London, 1856. 
 
EXCRETION, 341 
 
 CHAPTER XVII. 
 
 EXCRETION. 
 
 » 
 
 Wk have now come to the last division of the great nutritive 
 function, viz., the process of excretion. In order to understand fairly 
 the nature of this process we must remember that all the component 
 parts of a living organism are necessarily in a state of constant 
 change. It is one of the essential conditions of their existence and 
 activity that they should go through with this incessant transforma- 
 tion and renewal of their component substances. Every living 
 animal and vegetable, therefore, constantly absorbs certain materials 
 from the exterior, which are modified and assimilated by the pro- 
 cess of nutrition, and converted into the natural ingredients of the 
 organized tissues. But at the same time with this incessant growth 
 and supply, there goes on in the same tissues an equally incessant 
 process of waste and decomposition. For though the elements of 
 the food are absorbed by the tissues, and converted into musculine, 
 osteine, h^matine and the like, they do not remain permanently in 
 this condition, but almost immediately begin to pass over, by a con- 
 tinuance of the alterative process, into new forms and combinations, 
 which are destined to be expelled from the body, as others continue 
 to be absorbed. Thus Spallanzani and Edwards found that every 
 organized tissue not only absorbs oxygen from the atmosphere^ 
 and fixes it in its own substance ; but at the same time exhales 
 carbonic acid, which has been produced by internal metamorphosis. 
 This process, by which the ingredients of the organic tissues, al- 
 ready formed, are decomposed and converted into new substances, 
 is called the process of Destructive Assimilation. 
 
 Accordingly we find that certain substances are constantly mak- 
 ing their appearance in the tissues and fluids of the body, which 
 did not exist there originally, and which have not been introduced 
 with the food, but which have been produced by the process of in- 
 ternal metamorphosis. These substances represent the waste, or 
 physiological detritus of the animal organism. They are the forms 
 
342 EXCBETION. ■ , 
 
 under which those materials present themselves, ■which have once 
 formed a part of the living tissues, but which have become altered 
 by the incessant changes characteristic of organized bodies, and 
 which are consequently no longer capaWe of exhibiting vital pro- 
 perties, or of performing the vital functions. They are, therefore, 
 destined to be removed and discharged from the animal frame, and 
 are known accordingly by the name of Excrementitious Substances. 
 
 These excrementitious substances have peculiar characters by 
 which they may be distinguished from the other ingredients of the 
 living body ; and they might, therefore, be made to constitute a 
 fourth class of proximate principles, in addition to the three which 
 we have enumerated in the preceding chapters.. They are all sub- 
 stances of definite chemical composition, and all susceptible of 
 crystallization. Some of the most important of them contain nitro- 
 gen, while a few are non-nitrogenous in their composition. They 
 originate, in the interior of living bodies, and are not found else- 
 where, except occasionally as the result of decomposition. They 
 are nearly all soluble in water, and are soluble without exception in 
 the animal fluids. They are formed in the substance of the tissues, 
 from which they are absorbed by the blood, to be afterward conveyed 
 by the circulating fluid to certain excretory organs, particularly the 
 kidneys, from which they are finally dischai^ged and expelled from 
 the body. This entire process, made up of the production of the 
 ■ excrementitious substances, their absorption by the blood, and their 
 final elimination, is known as the process of excretion. 
 
 The importance of this process to the maintenance of life is readily 
 shown by the injurious effects which follow upcrti its disturbance. 
 If the discharge of the excrementitious substances be in any way 
 impeded or suspended, these substances accumulate, either in the 
 blood or in the tissues, or in both. In consequence of this retention 
 and accumulation, they become poisonous; and rapidly produce a 
 derangement of the vital functions. Their influence is principally 
 exerted upon the nervous system, through which they produce 
 most frequent irritability, disturbance of the special senses, deli- 
 rium, insensibility, coma, and finally death. The readiness with 
 which these effects are produced depends on the character of the 
 excrementitious substance, and the rapidity with which it is pro- 
 duced in the body. Thus, if the elimination of carbonic acid be 
 stopped, by overloading the atmosphere with an abundance of the 
 same gas, death takes place at the end of a few minutes ; but if the 
 elimination of urea by the kidneys be checked, it requires three or 
 
UREA. 
 
 343 
 
 four days to produce a fatal result. A fatal result,- however, is cer- 
 tain to follow, at I the end of a longer or shorter time, if any one of 
 these substances be compelled to remain in the body, and accumu- 
 late in the animal tissues and fluids. 
 
 The principal excrementitious substances known to ejdst in the 
 human body are as. follows: — 
 
 co„ 
 
 1. Carbonic acid 
 . 2. Urea . 
 
 3. Creatine . 
 
 4. Creatinine 
 
 5. Urate of soda 
 
 6. Urate of potassa 
 
 7. Urate of ammonia 
 
 CsHsNjO, 
 
 CsH,N302 
 
 NaO.CjHNjOj+HO 
 KG.CsHN^Oj . 
 NH40,2C5HNjOj4-HO 
 
 The physiological relations of carbonic acid have already been 
 studied, at suf&cient length, in the preceding chapters. 
 
 The remaining excrementitious substances may be examined 
 together with the more propriety, since they are all ingredients of 
 a single excretory fluid, viz., the urine, i 
 
 Ukea. — This is a neutral, crystallizable, nitrogenous substance, 
 very readily soluble in water, and easily decomposed by various 
 extemial influences. It occurs 
 
 in the urine in- the proportion Fig- m- 
 
 of 30- parts per thousand ; in 
 the blood, according to Picard,* 
 in the proportion of 0.16 per 
 thousand. The blood, how- 
 ever, is the source from which 
 this substance is supplied to 
 the urine; and it exists, ac- 
 cordingly, in but small quan- 
 tity in the circulating fluid, for 
 the reason that it is constantly 
 drained off by the kidneys. 
 But if the kidneys be extir- 
 pated, or the renal arteries tied, 
 or the excretion of urine sus- 
 
 pended by inflammation or otherwise, the urea then accumulates in 
 the blood, and presents itself there in considerable quantity. It has 
 been found in the blood, under these circumstances, in the propor- 
 
 TTeea, prepared from arine.and crystallized bv 
 sloir evaporation. (After Lehmann.) 
 
 ' In Milne Edwards, Lecjons snr la Fhyslologie, &e., Tol. i. p. 297. 
 
344 EXCRETION. 
 
 tion of 1.4 per thousand.' It is not yet known from what source 
 the urea is originally derived ; whether it be produced in the blood 
 itself, or whether it is formed in some of the solid tissues, and thence 
 taken up by the blood. It has not yet been found, however, in any 
 . of the solid tissues, in a state of health. 
 
 Urea is obtained most readily from the urine. For this purpose 
 the fresh urine is evaporated in the water bath until it has a syrupy 
 consistency. It is then mixed with an equal volume of nitric acid, 
 which forms nitrate of urea. This salt, being less soluble than pure 
 urea, rapidly crystallizes, after which it is separated by filtration 
 from the other ingredients. It is then dissolved in water and decom- 
 posed by carbonate of lead, forming nitrate of lead which remains 
 in solution, and carbonic acid which escapes. The solution is then 
 evaporated, the urea dissolved out by alcohol, and finally crystal- 
 lized in a pure state. 
 
 Urea has no tendency to spontaneous decomposition, and may 
 be kept, when perfectly pure, in a dry state or dissolved in water, 
 for an indefinite length of time. If the watery solution be boiled, 
 however, the urea is converted, during the process of ebullition, 
 into carbonate of ammonia. One equivalent of urea unites with 
 two equivalents of water, and becomes transformed into two equiva- 
 lents of carbonate of ammonia, as follows : — 
 
 C2HjNj02=Urea. NH3,C02=Carbonate of ammonia. . 
 
 2 
 
 Various impurities, also, by acting as catalytic bodies, will in- 
 duce the same change, if water be present. Animal substances in 
 a state of commencing decomposition are particularly liable to act 
 in this way. In order that the conversion of the urea be thus pro- 
 duced, it is necessary that the temperature of the mixture be not 
 far from 70° to 100° F. 
 
 The quantity of urea produced and discharged daily by a healthy 
 adult is, according to the experiments of. Lehmann, about 500 
 grains. It varies to some extent, like all the other secreted and 
 excreted products, with the size and development of the body. 
 Lehmann, in experiments on his own person, found the average 
 daily quantity to be 487 grains. Prof. "William A. Hammond,' 
 who is a very large man, by similar experiments found it to be 
 
 ' Robin and Verdeil, vol. il. p. 502. 
 
 ' American Journal Med. Soi , Jan., 1855, and April, 1856. 
 
UREA. 345 
 
 670 grains. Dr. John C. Draper' found it 408 grains. No urea is 
 to be detected in the urine of very young children ;' but it soon 
 makes its appe^arance, and afterward increases in quantity with the 
 development of the body. 
 
 The daily quantity of urea varies also with the degree of mental 
 and bodily activity. Lehmann and Hammond both found it very 
 sensibly increased by muscular exertion and diminished by repose. 
 It has been thought, from these facts, that this substance must be 
 directly produced from disintegration of the muscular tissue. This, 
 however, is by ho means certain ; since in a state of general bodily 
 activity it is not only the urea, but the excretions generally, carbonic 
 acid, perspiration, &c., which are increased in quantity simultane- 
 ously. Hammond has also shown that continued mental applica- 
 tion will raise the quantity of urea above its normal standard, 
 though the muscular system remain comparatively inactive. 
 
 The quantity of urea varies also with the nature of the food. 
 Lehmann, by experiments on his own person, found that the quan- 
 tity was larger while living exclusively on^ animal food than with 
 a mixed or vegetable diet ; and that its quantity was smallest when 
 confined to a diet of purely non-nitrogenous substances, as starch, 
 sugar, and oil. The following table' gives the result of these ex- 
 periments. 
 
 Kind op Food. Daily Quantity op Urea. 
 
 Animal . 798 grains. 
 
 Mixed . ..." 4S7 " 
 
 Vegetable ........ 337 " 
 
 Non-nitrogenous 231 " 
 
 Finally, it has been shown by Dr. John C. Draper' that there is 
 also a diurnal variation in the normal quantity of urea. A smaller 
 quantity is produced during the night than during the day ; and 
 this difference exists even in patients who are confined to the bed 
 during the whole twenty-four hours, as in the case of a man under 
 treatment for fracture of the leg. This is probably owing to the 
 greater activity, during the waking hours, of both the mental and 
 digestive functions. More urea is produced in the latter half than 
 in the earlier half of the day; and the greatest quantity is dis- 
 charged during the four hours from 6 J to 10^ P. M. 
 
 Urea exists in the urine of the carnivorous and many of the 
 
 ' New York Jonmal of Medicine. March, 1856. 
 
 ' Robin and Verdeil, vol. ii p. 500. 
 
 » Lehmnnn, op. eit., vol. ii. p. 163. * I>oc. cit. 
 
346 
 
 EXCRETIOIf. 
 
 Creatine, crystallized from hot water. (After 
 LehmauuJ 
 
 herbivorous quadrupeds ; but there is little or none to be found in 
 that of birds and reptiles. 
 
 Ceeatine. — This is a neutral crystallizable substance, found in 
 the muscles, the blood, and the. urine. It is soluble in water, very 
 
 slightly soluble in alcohol, and 
 Fig. 112. not at all so in ether. By boil- 
 
 ing with an alkali, it is either 
 converted into carbonic acid 
 and ammonia, or is decomposed 
 with the production of urea and 
 an artificial nitrogenous crys- 
 tallizable substance, termed sar- 
 cosine. By being heated with 
 strong acids, it loses two equiva- 
 lents of water, and is converted 
 into the substance next to be 
 described, viz., creatinine. 
 
 Creatine exists in the urine, 
 in the human subject, in the 
 proportion of about 1.25 parts, 
 and in the muscles in the proportion of 0.67 parts per thousand. 
 Its quantity in the blood has not been determined. In the muscu- 
 lar tissue it is simply in solution in the_ interstitial fluid of the parts, 
 so that it may be extracted by simply cutting the muscle into 
 small pieces, treating it with distilled water, and subjecting it to 
 
 pressure. Creatine evidently 
 Fig. 113. originates in the muscular tis- 
 
 sue, is absorbed thence by the 
 blood, and is finally discharged 
 with the urine. 
 
 Creatinine. — This is also a 
 crystallizable substance. It dif- 
 fers in composition from crea- 
 tine by containing two equiva- 
 lents less of the elements, of 
 water. It is more soluble in 
 water and in spirit than crea- 
 tine, and dissolves slightly also 
 in ether. It has a distinctly 
 
 Cruati 
 {After Lehmaun.) 
 
 INE, crystallized from bot water. 
 
CREATININE. — URATE OF SODA. 
 
 347 
 
 alkaline reaction. It occurs, like creatine, in the muscles, the blood, 
 and the urine ; and is undoubtedly first produced in the muscular 
 tissue, to be discharged finally by the kidneys. It is very possible 
 that it originates, not directly from the muscles, but indirectly, by 
 transformation of a part of the creatine ; since it may be artificially 
 produced, as we have already mentioned, by transformation of the 
 latter substance under the influence of strong acids, and since, fur- 
 thermore, while creatine is mores abundant in the muscles than 
 creatinine, in the urine, on the contrary, there is a larger quantity 
 of creatinine than of creatine. Both these substances have been 
 found in the muscles and in the urine of the lower animals. 
 
 Urate of Soda. — ^As- its name implies, this substance is a neu- 
 tral salt, formed by the union of soda, as a base, with a nitrogenous 
 animal acid, viz., uric acid (CjHNjO^jHO). Uric acid is sometimes 
 spoken of as though it were itself a proximate principle, and a 
 constituent of the urine; but it cannot properly be regarded as 
 such, since it never occurs in a free state, in a natural condition of 
 the fluids. When present, it has always been produced by decom- 
 position of the urate of soda. 
 
 Urate of soda is readily soluble in hot water, from which a large 
 portion again deposits on cooling. It is slightly soluble in alcohol, 
 and insoluble in ether. It 
 crystallizes in small globu- F'g- 114. 
 
 lar masses, with projecting, 
 curved, conical, wart-like 
 excrescences. (Fig. 114.) It 
 dissolves readily in the alka- 
 lies ; and by most acid solu- 
 tions it is decomposed, with 
 the production of free uric 
 acid. 
 
 Urate of soda exists -in 
 the urine and in the blood. 
 It is either produced origin- 
 ally in the blood, or is formed 
 in 'some of the solid tissues, 
 and absorbed from them by 
 the circulating fluid. It is 
 
 constantly eliminated by the kidneys, in company with the other 
 ingredients of the urine. The average daily quantity of urate of 
 
 Urate op Soda; from a arinaiy deposit. 
 
348 ■ EXCRETIOX. 
 
 soda discliarged by the healthy human subject is, according to 
 Lehmann, about 25 grains. This substance exists in the urine of 
 the carnivorous and omnivorous animals, but not in that of the her- 
 bivora. In the latter, it is replaced by another substance, differing 
 somewhat from it in composition and properties, viz., hippurate 
 of soda. The urine of herbivora, however, while still very young, 
 and living upon the milk of the mother, has been found to contain 
 urates. But when the young animal is weaned, and becomes her- 
 bivorous, the urate of soda disappears, and is replaced by the hip- 
 purate. 
 
 Urates of Potassa and Ammonia. — The urates of potassa and 
 ammonia resemble the preceding salt very closely in their physio- 
 logical relations. They are formed in very much smaller quantity 
 than the urate of soda, and appear like it as ingredients of the urine. 
 
 The substances above enumerated closely resemble each other in 
 their most striking and important characters. They all contain 
 nitrogen, are all crystallizable, and all readily soluble in water. 
 They all originate in the interior of the body by the decomposition 
 or catalytic transformation of its organic ingredients, and are all 
 conveyed by the blood to the kidneys, to be finally expelled with 
 the urine. These are the substances which represent, to a great 
 extent, the final transformation of the organic or albuminoid in- 
 gredients of the tissues. It has already been mentioned, in a pre- 
 vious chapter, that these organic or albuminoid substances are not 
 discharged from the body, under their own form, in quantity at all 
 proportionate to the abundance with which they are introduced. 
 By far the greater part of the mass of the frame is made up of 
 organic substances: albumen, musculine, osteine, &c. Similar 
 materials are taken daily in .large quantity with the food, in order 
 to supply the nutrition and waste of those already composing the 
 tissues; and yet only a very insignificant quantity of similar 
 material is expelled with the excretions. A minute proportion of 
 volatile animal matter is exhaled with the breath, and a minute 
 proportion also with the perspiration.- A very small quantity is 
 discharged under the form of mucus and coloring matter, with the 
 urine and feces ; but all these taken together are entirely insuffi- 
 cient to account for the constant and rapid disappearance of organic 
 matters in the interior of the body. These matters, in fact, before 
 being discharged, are converted by catalysis and decomposition into 
 new substances. Carbonic acid, under which form 3500 grains of 
 
GENERAL CHAKACTEBS OF THE UBINE. 349 
 
 carbon are daily expelled from the body, is one of these substances ; 
 the others are urea, creatine, creatinine, and the urates. 
 
 We see, then, in what way the organic matters, in ceasing to form 
 a part of the living body, lose their characteristic properties, and 
 are converted into crystallizable substances, of definite chemical 
 composition. It is a kind of retrograde metamorphosis, by which 
 they return more or less to the condition of ordinary inorganic 
 materials. These excrementitious matters are themselves decom- 
 posed, after being expelled from the body, under the influence of 
 the atmospheric air and moisture ; so that the decomposition and 
 destruction of the organic substances are at last complete. 
 
 It will be seen, consequently, that the urine has a character 
 altogether peculiar, and one which distinguishes it completely 
 from every other animal fluid. All the others are either nutritive 
 fluids, like the blood and milk, or are destined, like the secretions 
 generally, to. take some direct and essential part in the vital opera- 
 tions. Many of them, like the gastric and pancreatic juices, are 
 reabsorbed after they have done their work, and again enter the 
 current of the circulation. But the urine, is merely a solution of 
 excrementitious substances. Its materials exist beforehand in the 
 circulation, and are simply drained away by the kidneys from 
 the blood. There is a wide difference, accordingly, between the 
 action of the kidneys and that of the true glandular organs, in 
 which certain new and peculiar substances are produced by the 
 action of the glandular tissue. The kidneys, on the contrary, do 
 not secrete anything, properly speaking, and are not, therefore, 
 glands. In their mode of action, so far as regards the excretory 
 function, they have more resemblance to the lungs than to any 
 other of the internal, organs. But this resemblance is not complete ; 
 since the lungs perform a double function, absorbing oxygen at the 
 same time that they exhale carbonic acid. The kidneys alone are 
 purely excretory in their office. The urine is not intended to 
 fulfil any function, mechanical, chemical, or otherwise ; but is des- 
 tined only to be eliminated and expelled. Since it possesses so 
 peculiar and important a character, it will require to be carefully 
 studied in detail. -■. 
 
 The urine is a clear, watery, amber-colored fluid, with a distinct 
 acid reaction. It has, while still warm, a peculiar odor, which dis- 
 appears more or less completely on cooling, and returns when the 
 urine is gently heated. The prdinary quantity of urine discharged 
 daily by a healthy adult is about 3xxxv, and its mean specific 
 
350 EXCRETION. 
 
 gravity, 1024. Both its total quantity, however, and its mean 
 specific gravity are liable to vary somewhat from day to day, owing 
 to the different proportions of water and solid ingredients entering 
 into its constitution. Ordinarily the water of the urine is more 
 than sufficient to hold all the solid matters in solution ; and its pro- 
 portion may therefore be diminished by accidental causes without 
 the urine becoming turbid by the formation of a deposit. Under 
 such circumstances, it merely becomes deeper in color, and of a 
 higher specific gravity. Thus, if a smaller quantity of water than 
 usual be taken into the system with the drink, or if the fluid ex- 
 halations from the lungs and skin, or the intestinal discharges, be 
 increased, a smaller quantity of water will necessarily pass off by 
 the kidneys ; and the urine will be diminished in quantity; while its 
 specific gravity is increased. "We have observed the urine to be 
 reduced in this way to eighteen or twenty ounces per day, its specific 
 gravity rising at the same time to 1030. On the other hand, if the 
 fluid ingesta be unusually abundant, or if the perspiration be dimi- 
 nished, the surplus quantity of water will pass off by the kidneys; so 
 that the amount of urine in twenty-four hours may be increased to 
 forty-five or forty -six ounces, and its specific gravity reduced at 
 the same time to 1020 or even 1017. Under these conditions tbe 
 total amount of solid matter discharged daily remains about the 
 same. The changes above mentioned depend simply upon the 
 fluctuating quantity of water, which may pass off by the kidneys 
 in larger or smaller quantity, according to accidental circumstances. 
 In these purely normal or physiological variations, therefore, the 
 entire quantity of the urine and its mean specific gravity vary 
 always in an inverse direction with regard to each other ; the former 
 increasing while the latter diminishes, and vice versd. If, however, it 
 should be found that both the quantity and specific gravity of the 
 urine were increased or diminished at the same time, or if either 
 one were increased or diminished while the other remained station- 
 ary, such an alteration would show an actual change in the total 
 amount of solid ingredients, and would indicate an unnatural and 
 pathological condition. This actually takes place in certain forms 
 of disease. 
 
 The amount of variation in the quantity of water, even, may be 
 so great as to constitute by itself a pathological condition. Thus, 
 in hysterical attacks there is sometimes a very abundant flow of 
 limpid, nearly colorless urine, with a specific gravity not over 1005 
 or 1006. On the other hand, in the onset of febrile attacks, the 
 
DIURNAL VARIATIONS OF THE URINE. 351 
 
 quantity of water is often so mncli diminished tliat it is no longer 
 sufficient to retain in solution all the solid ingredients of the urine, 
 and the urate of soda is thrown down, after cooling, as a fine red 
 or yellowish sediment. So long, however, as the variation is con- 
 fined within strictly physiological limits, all the solid ingredients 
 are held in solution, and the urine remains clear. 
 
 There is also, in a state of health, a diurnal variation of the urine, 
 both in regard to its specific gravity and its degree of acidity. 
 The urine is generally discharged from the bladder five or six 
 times during the twenty^four hours, and at each of these periods 
 shows more or less variation in its physical characters. We have 
 found that the urine which collects in the bladder during the 
 night, and is first discharged in the morning, is usually dense, 
 highly colored, of a strongly acid reaction, and a high specific 
 gravity. That passed during the forenoon is pale, and of a low 
 specific gravity, sometimes not more than 1018 or even 1015. It 
 is at the same time neutral or slightly alkaline in reaction. Toward 
 the middle of the day, its density and depth of color increase, and 
 its acidity returns. All these properties become more strongly 
 marked during the afternoon and evening, and toward night the 
 urine is again deeply colored and strongly acid, and has a specific 
 gravity of 1028 or 1030. 
 
 The following instances will serve to show the general characters 
 of this variation : — 
 
 Obseevation First. March 20th. 
 Urine of Ist diapharge, acid, sp. gr. 1025. 
 " 2d " alkaline, " 1015. 
 
 " 3d " neutral, " 1018. 
 
 " 4th " acid, « 1018. 
 
 « 5th " acid, " 1027. 
 
 Observatios Second. . March 21st. 
 Urine of 1st discharge, acid, sp. gr. 1029. 
 " 2d " nentral, " 1022. 
 
 " 3d " neutral, " 1025. 
 
 " 4th " acid, " 1027. 
 
 " 5th " acid, " 1030. 
 
 These variations do not always follow the perfectly regular 
 course manifested in the above instances, since they are somewhat 
 liable, as we have already mentioned, to temporary modification 
 from accidental causes during the day ; but their general tendency 
 nearly always corresponds with that given above. 
 
 It is evident, therefore, that whenever we wish to test the specific 
 
12.45 
 
 352 EXCRKTIOX. 
 
 gravity and acidity of the urine in cases of disease, it will not be 
 sufficient to examine any single specimen taken at random ; but all 
 the different portions discharged during the day should be collected 
 and examined together. Otherwise, we should incur the risk of 
 regarding as a permanently morbid symptom what might be 
 nothing more than a purely accidental and temporary variation. 
 
 The chemical constitution of the urine as it is discharged from the 
 bladder, according to the analyses of Berzelius, Lehmann, Becquerel, 
 and others, is as follows : — 
 
 Composition op the Ueihe. 
 
 Water 938.00 
 
 Urea 30.00 
 
 Creatine 1'25 
 
 Creatinine 1-50 
 
 Urate of soda -i 
 
 " potaasa \ 1.80 
 
 " ammonia J 
 Coloring matter and 1 .... .30 
 
 Mueus > 
 
 Biphosphate of soda 
 Phosphate of soda 
 " potassa 
 
 " magnesia 
 
 " lime 
 
 Chlorides of sodium and potassinm 7.80 
 
 Sulphates of soda and potassa 6.90 
 
 1000.00 
 
 "We need not repeat that the proportionate quantity of these 
 different ingredients, as given above, is not absolute, but only 
 approximative ; and that they vary, from time to time, within 
 certain physiological limits, like the ingredients of all other animal 
 fluids. 
 
 The urea, creatine, creatinine and urates have all been suffi- 
 ciently described above. The mucus and coloring matter, unlike 
 the other ingredients of the urine, belong to the class of organic 
 substances proper. They are both present, as may be seen by the 
 analysis quoted above, in a very small quantity. The coloring 
 matter, or urosacine, is in solution in a natural condition of the 
 urine, but it is apt to be entangled by any accidental deposits which 
 may be thrown down, and more particularly by those consisting of 
 the urates. These deposits, from being often strongly colored red 
 or pink by the urosacine thus thrown down with them, are known 
 under the name of " brick -dust" sediments. 
 
 The mucus of the urine comes from the lining membrane of the 
 
EEACTIONS OF THE UKINE. 853 
 
 urinary bladder. When first discharged it is not visible, owing to 
 its being uniformly disseminated through the urine by mechanical 
 agitation ; but if the fluid be allowed to remain at rest for some 
 hours in a cylindrical glass vessel, the mucus collects at the bottom, 
 and may then -be seen as a light cottony cloud, interspersed often 
 with minute semi-opaque points. It plays, as we shall hereafter 
 see, a very important part in the subsequent fermentation and 
 decomposition of the urine. 
 
 Biphosphate of soda exists in the urine by direct solution, since it is 
 readily soluble in water. It is this salt which gives to the urine its 
 acid reaction, as there is no free acid present, in the recent condition. 
 It is probably derived from the neutral phosphate of soda in the 
 blood which is decomposed by the uric acid at the time of its form- 
 ation ; producing, on the one hand, a urate of soda, and converting 
 a part of the neutral phosphate of soda into the acid biphosphate. 
 
 The phosphates of lime and magnesia, or the " earthy phosphates," 
 as they are called, exist in the urine by indirect solution. Though 
 insoluble, or very nearly so, in pure water, they are held in solu- 
 tion in the urine by the acid phosphate of soda, above described. 
 They are derived from the blood, in which they exist in considera- 
 ble quantity. "When the urine is alkaline, these phosphates are 
 deposited as a light-colored precipitate, and thus communicate a 
 turbid appearance to the fluid. When the urine is neutral, they 
 may still be held in solution, to some extent, by the chloride of 
 sodium, which has the property of dissolving a small quantity of 
 phosphate of lime. 
 
 The remaining ingredients, phosphates of soda and potassa, sul- 
 phates and chlorides, are all derived from the blood, and are held 
 directly in solution by the water of the urine. 
 
 The urine, constituted by the above ingredients, forms, as we 
 have already described, a clear amber-colored fluid, with a reaction 
 for the most part distinctly acid, sometimes neutral, and occasion- 
 ally slightly alkaline. In its healthy condition it is affected by 
 chemical and physical reagents in the following manner. 
 
 Boiling the urine does not produce any visible change, provided 
 its reaction be acid. If it be neutral or alkaline, and if, at the same 
 time, it contain a larger quantity than usual of the earthy phos- 
 phates, it will become turbid on boiling ; since these salts are less 
 soluble at a high than at a low temperature. 
 
 The addition of nitric or other mineral acid produces at first only 
 23 
 
354 
 
 EXCRETION. 
 
 a slight darkening of the color, owing to the action, of the acid upon 
 the organic coloring matter of the urine. If the mixture, however, 
 be allowed to stand for some time, the urates of soda, potassa, &c., 
 will be decomposed, and pure uric acid, which is very insoluble, 
 will be deposited in a crystalline form upon the sides and bottom 
 of the glass vessel. The crystals of uric acid have most frequently 
 the form of. transparent rhomboidal plates, or oval laminae with 
 pointed extremities. They are usually tinged of a yellowish hue 
 by the coloring matter of the urine which is united with them 
 at the time Of their deposit. They are frequently arranged in 
 radiated clusters, or small spheroidal masses, so as to present the 
 
 appearance of minute calcu- 
 F>g- 115' lous concretions. (Fig. 115.) 
 
 The crystals vary very much 
 in size and regularity, ac- 
 cording to the. time occupied 
 in their formation. . 
 
 If a free alkali, such as 
 potassa or soda, be added to 
 the urine so as to neutralize 
 its acid reaotion, it becomes 
 immediately turbid from a 
 deposit of the earthy phos- 
 phates, which are insoluble 
 in alkaline fluids. 
 
 The addition of nitrate of 
 baryta, chloride of barium 
 or subacetate of lead to healthy urine, produces a dense precipi- 
 tate, owing to the presence of the alkaline sulphates. 
 
 Nitrate of silver produces a precipitate with the chlorides of 
 sodium and potassium. 
 
 Subacetate of lead and nitrate of silver precipitate also the or- 
 ganic substances, mucus and coloring matter, present in the urine. 
 All the above reactions, it will be seen, are owing to the presence 
 of the natural ingredients of the urine, and do not, therefore, indi- 
 cate any abnormal condition of the excretion. 
 
 Beside the properties mentioned above, the urine has several 
 others which are of some importance, and which have not been 
 usually noticed in previous descriptions. It contains, among other 
 ingredients, certain organic substances which have the power pi 
 interfering with the mutual reaction of starch and iodine, and feven 
 
 TJric Acid ; deputiited from urine. 
 
REACTIONS OF THE UBINB. 855 
 
 of decomposing the iodide of starch, after it has once been formed. 
 This peculiar action of the urine was first noticed and described 
 by us in 1856.' If 3j of iodine water be mixed with a solution 
 of starch, it strikes an opaque blue color ; but if 3j of fresh urine 
 be afterward added to the mixture, the color is entirely destroyed 
 at the end of four or five seconds. If fresh urine be mixed with 
 four or five times its volume of iodine water, and starch be 
 subsequently added, no union takes place between the starch and 
 iodine, and no blue color is produced. In these instances, the icfdine 
 unites with the animal matters of the urine in preference to com- 
 bining with the starch, and is consequently prevented from striking 
 its ordinary blue color with the latter. This interference occurs 
 whether the urine be acid or alkaline in reaction.' In all cases in 
 which iodine exists in the urine, as for example where it has been 
 administered as a medicine, it is under the form of an organic com- 
 bination ; and in order to detect its presence by means of starch, a 
 few drops of nitric acid must be added at the same time,' so as to 
 destroy the organic matters, after which the blue color immediately 
 appears, if iodine be present. This reaction with starch and iodine 
 belongs also, to some extent, to most of the other animal' fluids, as 
 the saliva, gastric and pancreatic juices, serum of the blood, &c. ; 
 but it is most strongly marked in the urine. 
 
 Another remarkable property of the urine, also dependent on its 
 organic ingredients, is that of interfering with Trommer's test for 
 grape sugar. If clarified honey be mixed with fresh urine, and sul- 
 phate of copper with an excess of potassa be afterward added, the 
 mixture takes a dingy, grayish-blue color. On boiling, the cgloi 
 turns yellowish or yellowish-brown, but the suboxide of copper is 
 not deposited. In order to remove the organic matter and detect 
 the sugar, the urine must be first treated with an excess of animal 
 charcoal and filtered. By this means the organic subsljinces are 
 retained upon the filter, while the sugar passes through in solution, 
 and may then be detected as usual by Trommer's test. 
 
 Accidental Ingredients of the Ueine. — Since the urine, in 
 its natural state, consists of materials which are already prepared in 
 the blood, and which merely pass out through the kidneys ^^y a 
 kind of filtration, it is not surprising that most medicinal and 
 poisonous substances, introduced into the circulation, should be 
 
 ' American Journal Med. Sei., April, 1856. 
 
356 EXCRETION". 
 
 expelled from the body by the same channel. Those substances 
 ■which tend to unite strongly with the animal matters, and to form 
 with them insoluble compounds, such as the preparations of iron, 
 lead, silver, arsenic, mercury, &c., are least liable to appear in the 
 urine. They may occasionally be detected in this fluid when they 
 have been given in large doses, but when administered in moderate 
 quantity are not usually to be found there. Most other substances, 
 however, accidentally present in the circulation, pass off readily by 
 the Sidneys, either in their original form, or after undergoing cer- 
 tain chemical modifications. 
 
 The salts of the organic acids, such as lactates, acetates, malates, 
 &c., of soda and potassa, when introduced into the circulation, are 
 replaced by the carbonates of the same bases, and appear under 
 that form- in the urine. The urine accordingly becomes alkaline 
 from the presence of the carbonates, whenever the above salts have 
 been taken in large quantity, or after the ingestion of fruits and 
 vegetables which contain them. We have already spoken (Chap. II.) 
 of the experiments of Lehmann, in which he found the urine exhi- 
 biting an alkaline reaction, a very few minutes after the administra- 
 tion of lactates and acetates. In one instance, by experimenting 
 upon a person with congenital extroversion of the bladder, in whom 
 the orifices of the ureters were exposed,' he found that the urine 
 became alkaline in the course of seven minutes after the ingestion 
 of half an ounce of acetate of potassa. 
 
 The pure alkalies and their carbonates, according to the same ob- 
 server, produce a similar effect. Bicarbonate of potassa, for example, 
 administered in doses of two or three drachms, causes the urine 
 to become neutral in from thirty to forty-five minutes, and alkaline 
 in the course of an hour. It is in this way that certain " anti-cal- 
 culous" or '' anti-lithic" nostrums operate, when given with a view 
 of dissol«?ing concretions in the bladder. These remedies, which 
 are usually strongly alkaline, pass into the urine, and by giving it 
 an alkaline reaction, produce a precipitation of the earthy phos- 
 phates. Such a precipitate, however, so far from indicating the 
 successful disintegration and discharge of the calculus, can only 
 tend to increase its size by additional deposit. 
 
 Ferrocyanide of potassium, when introduced into the circulation, 
 appears readily in the urine. Bernard' observed that a solution of 
 
 ' Physiological Chemiaty, vol. ii. p. 133. 
 
 ' Lemons de Physiologie ExpSrimentale, 1856, p. 111. 
 
ACCIDENTAL INGREDIENTS OF THE URINE. 357 
 
 this salt, after being injected into tlie duct of the submaxillary 
 gland, could be detected in the urine at the end of twenty minutes. 
 
 Iodine, in all its combinations, passes out by the same channel. 
 We have found that after the administration of half a drachm of 
 the syrup of iodide of iron, iodi|ie appears in the urine at the end 
 of thirty minutes, and continues to be present for nearly twenty- 
 four hours. In the case of two patients who had been taking iodide 
 of potassium freely, one of them for two months, the other for six 
 weeks, the urine still contained iodine at the end of three days 
 after the suspension of the medicine. In three days and a half, 
 however, it was no longer to be detected. Iodine appears also, 
 after being introduced into the circulation, both in the saliva and 
 the perspiration. 
 
 Quinine, when taken as a remedy, has also been detected in the 
 urine. Etiier passes out of the circulation in the same way. We 
 have observed the odor of this substance very perceptibly in the 
 urine, after it had been inhaled for the purpose of prpducing anaes- 
 thesia. The bik-pigment passes into the urine in great abundance 
 in some cases of jaundice, so that' the urine may have a deep yellow 
 or yellowish brown tinge, and may even stain linen clothes, with 
 which it comes in contact, of a similar* color. The saline biliary 
 substances, viz., glyko-cholate and tauro-cholate of soda, have occa- 
 sionally, according to Lehmann, been also found in the urine. In 
 these instances the biliary matters are reabsorbed from the hepatic 
 ducts, and afterward conveyed by the blood to the kidneys. 
 
 Sugar. — When sugar exists in unnatural quantity in the blood, 
 it passes out with the urine. We have repeatedly found that if 
 sugar be artificially introduced into the circulation in rabbits, or 
 injected into the subcutaneous areolar tissue so as to be absorbed by 
 the blood, it is soon discharged by the kidneys. It has been shown 
 by Bernard' that the rapidity with which this substance appears in 
 the urine under these circumstances varies with the quantity in- 
 jected and the kind of sugar used for the experiment. If a solution 
 of 16 grains of glucose be jnjected into the areolar tissue of a rabbit 
 weighing a little over two pounds, it is entirely destroyed in the 
 circulation, and does not pass out with the urine. A dose of 23 
 grains, however, injected in the same way, appears in the urine at 
 the end of two hours, 30 grains in an hour and a half, 38 grains in 
 an hour, and 188 grains in fifteen minutes. Again, the kind of 
 
 ■ Le?ons de Phys. Exp., 1855, p. 214 et seq. 
 
358 EXCRETION. 
 
 sugar used makes a difference in this respect. For while 15 grains 
 of glucose may be injected without .passing out by the kidneys, 
 7 1 grains of cane sugar, introduced in the same way, fail to be com- 
 pletely destroyed in the cirtiulation, and may be detected in the 
 urine. In certain forms of disease (diabetes), where sugar accu- 
 mulates in the blood, it is eliminated by the same channel ; and a 
 saccharine condition of the urine, accompanied by an increase in 
 its quantity and specific gravity, constitutes the most characteristic 
 feature of the disease. 
 
 Finally, albumen sometimes shows itself in the urine in conse- 
 quence of various morbid conditions. Most acute inflammations 
 of the internal organs, as pneumonia, pleurisy, &c., are liable to be 
 accompanied, at their outset, by a congestion of the kidneys, which 
 produces a temporary exudation of the albuminous elements of the 
 blood. Albumen has been found in the urine, according to Simon, 
 Becquerel, and others, in pericarditis, pneumonia, pleurisy, bron- 
 chitis, hepatitis, inflammation of the brain, peritonitis, metritis, &c. 
 We have observed it, as a temporary condition, in pneumonia and 
 after amputation of the thigh. Albuminous urine also occurs fre- 
 quently in pregnant women, and in those affected with abdominal 
 tumors, where the pressure upon the renal veins is suf&cient to 
 produce passive congestion of the kidneys. When the renal con- 
 gestion is spontaneous in its origin, and goes on to produce actual 
 degeneration of the tissue of the kidneys, as in Bright'^ disease, the 
 same symptom occurs, and remains as a permanent condition. In 
 all such instances, however, as the above, where foreign ingredients 
 exist in the urine, these substances do not originate in the kidneys 
 themselves, but are derived from the blood, in the same manner as 
 the natural ingredients of the excretion. 
 
 Changes in the Urine during Decomposition. — When the 
 urine is allowed to remain exposed, after its discharge, at ordinary 
 temperatures, it becomes decomposed, after a tilne, like any other 
 animal fluid; and this decomposition is characterized by certain 
 changes which take place in a regular order of succession, as fol- 
 lows : — 
 
 After a few hours of repose, the mucus qf the urine, as we have 
 mentioned above, collects near the bottom of the vessel as a light, 
 nearly transparent, cloudy layer. This mucus, being an organic 
 substance, is liable to putrefaction; and if the temperature to which 
 it is exposed be between 60° and 100° F., it soon becomes altered, 
 
ACID FERMENTATION OF THE UEINE. 359 
 
 and communicates these alterations more or less rapidly to the super- 
 natant fluid. The first of these changes is called the acid fermenta- 
 tion of the urine. It consists in the production of a free acid, usually 
 lactic acid, from some of the undetermined animal matters con- 
 tained in the excretion. This fermentation takes place very early ; 
 "within the first twelve, twenty-four, or forty-eight hours, according 
 to the elevation of the surrounding temperature. Perfectly fresh 
 urine, as we have already stated, contains no free acid, its acid 
 reaction with test paper being dependent entirely on the presence 
 of biphosphate of soda. Lactic acid nevertheless has been so fre- 
 quently found in nearly fresh urine as to lead some eminent 
 chemists (Berzelius, Lehmann) to regard it as a natural constituent 
 of the excretion. It has been subsequently found, however, that 
 urine, though entirely free from lactic acid when first passed, may 
 frequently present traces of this substance after some hours' expo- 
 sure to the air. The lactic acid is undoubtedly formed, in these 
 cases, by the decomposition of some animal substance contained in 
 the urine. Its production in this way, though not constant, seems 
 to be sufficiently frequent to be regarded as a normal process. « 
 
 In consequence of the presence of this acid, the urates are par- 
 tially decomposed ; and a crystalline deposit of free uric acid slowly 
 takes place, in the same manner as if a little nitric or muriatic acid* 
 had been artificially mixed with the urine. It is for this reason 
 that urine which is abundant in the urates freqiiently shows a de- 
 posit of crystallized uric acid some hours after it has been passed, 
 though it may have been perfectly free from deposit at the time 
 of its emission. 
 
 During the period of the " acid fermentation," there is reason to 
 believe that oxalip acid is also sometimes produced, in a similar 
 manner with tjie lactic. It is very certain that the deposit of oxa- 
 late of lime, far from Tseing a dangerous or even morbid symptom, 
 as it was at one time regarded, is frequently present in perfectly 
 normal urine after a day or two of exposure to the atmosphere. 
 "We have often observed it, under these circumstances, when no 
 morbid symptom could be detected in connection either with the 
 kidneys or with any other bodily organ. Now, whenever oxalic 
 acid is formed in the urine, it must necessarily be deposited under 
 the form of oxalate of lime ; since this salt is entirely insoluble 
 both in water and in the urine, even when heated to the boiling 
 point. It is difficult to understand, therefore, when oxalate of lime 
 is found as a deposit in the urine, how it can previously have been 
 
360 
 
 EXCKETION'. 
 
 Fig. lie. 
 
 held in solution. Its oxalic acid is in all probability gradually 
 formed, as we have said, in the urine itself; uniting, as fast as it is 
 produced, with the lime previously in solution, and thus appearing 
 as a crystalline deposit of oxalate of lime. It is much more probable 
 that this is the true explanation, since, in the_ cases to which we 
 allude, the crystals of oxalate of lime grow, as it were, in the cloud 
 of mucus which collects at the bottom of the vessel, while the 
 supernatant fluid remains clear. These crystals are of minute size, 
 
 transparent, and colorless, 
 and have the form of regular 
 octohedra, or double quad- 
 rangular pyramids, united 
 base to base. (Fig. 116.) They 
 make' their appearance usu- 
 ally about the commence- 
 ment of the second day, the 
 urine at the same time con- 
 tinuing clear and retaining 
 its acid reaction. This depo- 
 sit is of frequent occurrence 
 when no substance contain- 
 ing oxalic acid or oxalates 
 has been taken with the food. 
 At the end of some days 
 the changes above described 
 come to an end, and are succeeded by a different process known as 
 the alkaline fermentation. This consists essentially in the decom- 
 position or metamorphosis of urea into carbonate of ammonia. 
 As the alteration of the mucus advaiPces, it loses the power of pro- 
 ducing lactic and oxalic acids, and becomes a ferment capable of 
 acting by cataly^s upon the urea, and of exciting its decomposition 
 as above. We have already mentioned that urea may be converted 
 into carbonate of ammonia by prolonged boiling or by contact 
 with decomposing animal substances. In this conversion, the urea 
 unites with the elements of two equivalents of water ; and conse- 
 quently it is not susceptible of the transformation when in a dry 
 state, but only when in solution or supplied with a sufficient quan- 
 tity of moisture. The presence of mucus, in a state of incipient 
 decomposition, is also necessary, to act the part of a catalytic 
 body. Consequently if the urine, when first discharged, be passed 
 through a succession of close filters, so as to separate its mucus, it 
 
 Oxalate op Lime; deposited from liealtby urine, 
 during the acid fermentation. '' 
 
ALKALINE FERMENTATION OF THE URINE. 361 
 
 may be afterward kept, for an indefinite time, -witliout alteration. 
 But under ordinary circumstances, the mucus, as soon as its putre- 
 faction has commenced, excites the decomposition of the urea, and 
 carbonate of ammonia begins to be developed. 
 
 The first portions of the ammoniacal salt thts produced begin to 
 neutralize the biphosphate of soda, so that the acid reaction of the 
 urine diminishes in intensity. This 'reaction gradually becomes 
 weaker, as the fermentation proceeds, until it at last disappears 
 altogether, and the urine becomes neutral. The production of 
 carbonate of ammonia still continuing, the reaction of the fluid 
 then becomes alkaline, and its alkalescence grows more strongly 
 pronounced with the constant accumulation of the ammoniacal salt. 
 
 The rapidity with which this alteration proceeds depends on the 
 character of the urine, the quantity and quality of the mucus which 
 it contains, and the elevation of the surrounding temperature. The 
 urine passed early in the forenoon, which is often neutral at the 
 time of its discharge, will of course become alkaline more readily 
 than that which has at first a strongly acid reaction. In the summer, 
 urine will become alkaline, if freely exposed, on the third, fourth, 
 or fifth day ; while in the winter, a specimen kept in a cool place 
 may still be neutral at the end of fifteen days. In cases of paralysis 
 of the bladder, on the other hand, accompanied with cystitis, where 
 the mucus is increased in quantity and altered in quality, and the 
 urine is retained in the bladder for ten or twelve hours at the tem- 
 perature of the body, the change may go on much more rapidly, so 
 that the urine may be distinctly alkaline and ammoniacal at the 
 time of its discharge. In these cases, however, it is really acid 
 when first secreted by the kidneys, and becomes alkaline while 
 retained in the interior of the bladder. " ■ 
 
 The first effect of the alkaline condition of the urine, thus pro- 
 duced, is the precipitation of the earthy phosphates. These salts, 
 being insoluble in neutral and alkaline fluids, begin to precipitate as 
 soon as the natural acid reaction of the urine has £airly disappeared, 
 and thus produce in the fluid a whitish turbidity. This precipitate 
 slowly settles upon the sides and bottom of the vessel, or is partly 
 entangled with certain animal matters which rise to the surface and 
 form a thin, opaline scum upon the urine. There are no crystals 
 to be seen at this time, but the deposit is entirely amorphous and 
 granular in character. 
 
 The next change consists in the production of two new double 
 salts by the action of Ijarbonate of ammonia on the phosphates of 
 
362 
 
 EXCBETIOSr. 
 
 soda and magnesia. One of these is the "triple phosphate," phos- 
 phate of magnesia and ammonia (2MgO,]SrHp,POj+2HO). The 
 other is the phosphate of soda and ammonia (Na0,NH40,H0,P0j+ 
 8H0). The phosphate of magnesia and ammonia is formed from 
 the phosphate of magnesia in the urine (3MgO,POj4-7HO) by 
 the replacement of one equivalent of magnesia by one of am- 
 monia. The crystals of this salt are very elegant and charac- 
 teristic. They show themselves throughout all parts of the mix- 
 ture ; growing gradually in the mucus at the bottom, adhering to 
 
 the sides of the glass, and 
 scattered abundantly over 
 the film which collects upon 
 the surface. . By their. refract- 
 ive power, they give to this 
 film a peculiar glistening 
 and iridescent appearance, 
 which is nearly always visi- 
 ble at the end of six or seven 
 days. The crystals are per- 
 fectly colorless and transpa- 
 rent, and have the form of 
 triangular prisms, generally 
 with bevelled extremities. 
 (Fig. 117.) Frequently, also, 
 their edges and angles are 
 replaced by secondary facets. 
 They are insoluble in alkalies, but are easily dissolved by acids, 
 even in a very dilute form. At first they are of minute size, but 
 gradually increase, so that after seven or eight days they may 
 become visible to the naked eye. 
 
 The phosphate of soda and ammonia is formed, in a similar 
 manner to the above, by the union of ammonia with the phosphate 
 of soda ; previously existing in the urine. Its crystals resemble 
 very much those just described, except that their prisms are of a 
 quadrangular form, or some figure derived from it. They are 
 intermingled with the preceding in the putrefying urine, and are 
 affected in the same way by chemical reagents. 
 
 As the putrefaction of the urine continues, the carbonate of am- 
 monia which is produced, after saturating all the other ingredients 
 with which it is capable of entering into combination, begins to 
 be given off in a free form. The urine then acquires a strong 
 
 Phosphate of Magnrsia and Ammonia; 
 deposited from healthy urine, during all^aline termea- 
 tation. 
 
EENOVATION BY NUTBITIVE PROCESS. 
 
 363 
 
 ammoniacal odor ; and a piece of moistened test paper, held a little 
 above its surface, will have its color immediately turned by the 
 alkaline gas escaping from the fluid. This is the source of the 
 ammoniacal vapor which is so fl-eely given ofi' from stables and from 
 dung heaps, or wherever urine is allowed to remain and decompose. 
 This process continues until all the urea has been destroyed, and 
 until the products of its decomposition have either united with 
 other- substances, or have finally escaped in a gaseous form. 
 
 Eenovation of the Body by the Nutritive Process. — We 
 , can now estimate, from the foregoing details, the entire quantity of 
 material assimilated and decomposed by the living body. For we 
 have already seen how much food is taken into the alimentary canal 
 and absorbed by the blood after digestion, and how much oxygen 
 is appropriated!^ from the atmosphere in the process of respiration. 
 We have also learned the-amount of carbonic acid evolved with the 
 breath, and that of the various excretory substances discharged from 
 the body. The following table shows the absolute quantity of these 
 different ingredients of the ingesta and egesta, compiled from the 
 results of direct experiment which have already been given in the 
 foregoing pages. 
 
 Absorbed dubinq 24 
 
 HOURS. 
 
 DiSCHAHOED DUUIlfG 
 
 24 HOUBS. 
 
 Oxygen . 
 
 1.019 lbs. 
 
 Carbonic acid . 
 
 1.535 lbs 
 
 Water 
 
 4.735 " 
 
 Aqueous vapor 
 
 1.155 " 
 
 Albuminous matter . 
 
 .396 " 
 
 Perspiration . 
 
 1.930 " 
 
 Starch . 
 
 .660 " 
 
 Water of the urine 
 
 2.020 " 
 
 Fat . 
 
 .220 « • 
 
 Urea and salts 
 
 .110 " 
 
 Salts 
 
 .040 " 
 
 Feces 
 
 .320 •• 
 
 7.070 
 
 7.070 
 
 Eather more than seven pounds, therefore, are absorbed and dis- 
 charged daily by the healthy adult human subject ; and, for a man 
 having the average weight of 140 pounds, a quantity of material, 
 equal to the weight of the entire body, thus passes through the 
 system in the course of twenty days. 
 
 It is evident, also, that this is not a simple phenomenon of the 
 passage, or filtration, of foreign substances through the animal 
 frame. The materials which are absorbed actually combine with 
 the tissues, and form a part of their substance ; and it is only after 
 undergoing subsequent decomposition, that they finally make their 
 appearance in the excretions. None of the solid ingredients of the 
 food are discharged under their own form in the urine, viz., as 
 
364 EXCRETION. 
 
 starch, fat, or albumen ; but they are replaced by urea and other 
 crystallizable substances, of a different nature. Even the carbonic 
 acid exhaled by the breath, as experience has taught us, is not pro- 
 duced by a direct oxidation of carlJon ; but originates by a steady 
 process of decomposition, throughout the tissues of the body, some- 
 what similar to that by which it is generated in the decomposition 
 of sugar by fermentation. These phenomena, therefore, indicate an 
 actual change in the substance of which the body is composed, and 
 show that its entire ingredients are incessantly renewed under the 
 influence of the vital operations. 
 
SECTIO?^ II. 
 NERYOUS SYSTEM 
 
 chAptek I. 
 
 GBNEEAL STEUCTURB AND FUNCTIONS OP THE 
 NEBVOUS SYSTEM. 
 
 In entering upon the study of the nervous system, we commence 
 the examination of an entirely different order of phenomena from 
 those which have thus far engaged our attention. Hitherto we 
 have studied the physical and chemical actions taking place in the 
 body and constituting together the process of nutrition. We have 
 seen how the lungs absorb and exhale different gases; how the 
 stomach dissolves the food- introduced into it, and how the tissues 
 produce and destroy different substances by virtue of the varied 
 transformations which take place in their interior. In all these 
 instances, we have found each organ and each tissue possessing 
 certain properties and performing certain functions, of a physical 
 or chemical nature, which belong exclusively to it, and are charac- 
 teristic of its action. 
 
 The functions of the nervous system, however, are neither phy- 
 sical nor chemical in their nature. They do not correspond, in 
 their mode of operation, with any known phenomena belonging to 
 these two orders. The nervous system, on the contrary, acts only 
 upon other organs, in some unexplained manner, so as to excite or 
 modify the functions peculiar to them. It is not therefore an appa- 
 ratus.which acts for itself, but is intended entirely for the purpose 
 of influencing, in an indirect manner, the action of other organs. 
 Its object is to connect and associate the functions of different 
 
 ( 365 ) 
 
366 GENEBAL STRUCTURE AND FUNCTIONS 
 
 parts of the body, and to cause them to act in harmony with each 
 other. 
 
 This object may be more fully exemplified as follows : — 
 Bach organ and tissue in the body has certain properties peoiiliar 
 to it, which may be called into activity by the operation of a stimu- 
 lus or exciting cause. This capacity, which all the organs possess, 
 of reacting under the influence of a stimulus, is called their excita 
 bility, or irritability. We' have often had occasion to notice this pro 
 perty of irritability, in experiments related in the foregoing pages, 
 We have seen, for. ejcample, that if the heart of a frog, after being , 
 removed from the body, be touched with the point of a needle, it 
 immediately contracts, and repeats the movement of an ordinary 
 pulsation. If the leg of a frog be separated from the thigh, its 
 integument removed, and the poles of a galvanic battery brought 
 in contact with the exposed surface of the muscles, a violent con- 
 traction takes place every time the , electric circuit is completed. 
 In this instance, the stimulus to the muscles is supplied by the 
 electric discharge, as, in the case of the heart above mentioned, it is 
 supplied by the contact of the steel needle ; and in both, a muscu- 
 lar contraction is the immediate consequence. If we introduce a 
 metallic catheter into the empty stomach of a dog through a gastric 
 fistula, and gently irritate with it the mucous membrane, a secretion 
 of gastric juice at once begins to take place ; and if food be intro- 
 duced the fluid is poured out in still greater abundance. We know 
 also that if the integument be exposed to contact with a heated 
 body, or to friction with an irritating liquid, an excitement of the 
 circulation is at once produced, which again passes away after the 
 removal of the irritating cause. 
 
 In all these instances we find that the organ which is called into 
 activity is excited by the direct application of some stimulus to its 
 own tissues. But this is not usually the manner in which the dif- 
 ferent functions are excited during life. The stimulus which calls 
 into action the organs of the living body is usually not direct, but 
 indirect in, its operation. Very often, two organs which are situ- 
 ated in distant parts of the body are connected with each other by 
 such a sympathy, that the activity of one is influenced by the 
 condition of the other. The muscles, for example, are almost never 
 called into action by an external stimulus operating directly upon 
 their, own fibres, but by one which is applied to some other organ, 
 either adjacent or remote. Thus the peristaltic action of the mus- 
 cular coat of the intestine commences when the food is brought in 
 
OF THE NERVOUS SYSTEM. 367 
 
 contact with its mucous membrane. The lachrymal gland is excited 
 to increased activity by anything -which causes irritation of the 
 conjunctiva. In all such instances, the physiological connection 
 between two different organs is established through the medium of 
 the nervous system. 
 
 The function of the nervous system may therefore be defined, in 
 the simplest 'terms, as follows : It is intended to associate the different 
 parts of the body in such a manner, that stimulus applied to one organ 
 may excite the activity of another. 
 
 The instances of this mode of action are exceedingly numerous. 
 Thus, the light which falls upon the retina produces a contraction 
 of the pupil. The presence of food in the stomach causes the gall- 
 bladder to discharge its contents into the duodenum. The expul- 
 sive efforts of coughing are excited by a foreign body entangled in 
 the glottis. 
 
 It is easy to understand the great importance of this function, 
 particularly in the higher animals and in man, whose organization 
 is an exceedingly complicated one. For the different organs of 
 the body, in order to preserve the integrity of the whole frame, 
 must not only act and perform their functions, but they must act in 
 harmony with each other, and at the right time, and in the right 
 direction. The functions of circulation, of respiration, and of 
 digestion, are so mutually dependent, that if their actions do not 
 take place harmoniously, and in proper order, a serious disturb- 
 ance must inevitably follow. When the muscular system is ex- 
 cited by unusual exertion, the circulation is also quickened. The 
 blood arrives more rapidly at the heart, and is sent in greater 
 quantity to the lungs. If the movements of respiration were not 
 accelerated at the same time, through the connections of the nerv- 
 ous system, there would immediately follow deficiency of aeration, 
 vascular congestion, and derangement of the circulation. If the 
 iris were not stimulated to contract by the influence of the light 
 falling on the retina, the delicate expansion of the optic nerve 
 would be dazzled by any unusual brilliancy, and vision would be 
 obscured or confused. In all the higher animals, therefore, wtiere 
 the different functions of the body are performed by distinct organs, 
 situated in different parts of the frame, it is necessary that their 
 action should be thus regulated and harmonized by the operation 
 of the nervous system. 
 
368 GENERAL STRUCTURE AND FUNCTIONS 
 
 The manner in which this is accomplished is as follows :-^ 
 
 The nervous system, however simple or however complicated it 
 may be, consists always of two different kinds of tissue, which are 
 distinguished from each other by their color, their structure, and 
 their mode of action. One of these is known as the white substance, 
 or the fibrom tissue. It constitutes the whole of the substance of 
 the nervous trunks and branches, and is found in large quantity on 
 the exterior of the spinal cord, and in the central parts of the brain 
 and cerebellum. In the latter situations, it is of a soft consistency, 
 like curdled cream, and of a uniform, opaque white color. In 
 the trunks and branches of the nerves it has the same opaque 
 white color, but is at the same time of a firmer consistency, owing 
 to its being mingled with condensed areolar tissue. Examined by 
 the microscope, the white substance is seen to be composed every- 
 where of minute fibres or filaments, the " ultimate nervous fila- 
 ments," running in a direction very nearly parallel with each other. 
 These filaments are cylindrical in shape, and vary considerably in 
 size. Those which are met with in the spinal cord and the brain 
 are the smallest, and have an average diam^eter of xT^uTy of an 
 inch. In the trunks and branches of the nerves they average jtjVt 
 of an inch. 
 
 The structure of the ultimate nervous filament is as follows: 
 The exterior of each filament consists of a colorless, transparent 
 tubular membrane, which is seen with some difficulty in the natural 
 condition of the fibre, owing to the extreme delicacy of its texture, 
 and to its cavity being completely filled with a substance very 
 similar to it in refractive power. In the interior of this tubular 
 membrane there is contained a thick, semi-fluid nervous matter, 
 which is white and glistening by reflected light, and is called the 
 "white substance of Schwann." Finally, running longitudinally 
 through the central part of each filament, is a narrow ribbon- 
 shaped cord, of rather firm consistency, and of a semi-transparent 
 grayish color. This central portion is called the " axis cylinder," 
 or the " flattened band." It is enveloped everywhere by the semi- 
 fluid white substance, and the whole invested by the external tubu- 
 lar membrane. 
 
 When nervous matter is prepared for the microscope and exa- 
 mined by transmitted light, two remarkable appearances are ob- 
 served in its filaments, produced by the contact of foreign sub- 
 stances. In the first place the unequal pressure, to which the fila- 
 ments are accidentally subjected- in the process of dissection and 
 
OF THE NERVOUS SYSTEM. 
 
 Fig. 118. 
 
 preparation, produces an irregularly bulging or varicose appearance 
 in them at various points, owing to the readiness witii which the 
 semi-fluid white substance in their interior is displaced in diflerent 
 directions. (Fig. 11&.) Sometimes spots may be seen here and 
 there, where the nervous matter has been entirely pressed apart in 
 the centre of a filament, so 
 that there appears to be an 
 entire break in its continuity, 
 while the investing mem- 
 brane may be still seen, pass- 
 ing across from one portion 
 to the other. When a nerv- 
 ous filament is torn across 
 under the microscope and 
 subjected to pressure, a cer- 
 tain quantity of the semi- 
 fluid white substance is 
 pressed out from its torn 
 extremity, and may be en- 
 tirely separated from it, so 
 as to present itself under the 
 form of irregularly rounded 
 drops of various sizes (a, a, 
 
 a), scattered over the field of the microscope. The varicose appear- 
 ance above alluded to is more frequently seen in the smaller nerv- 
 ous filaments from the brain and spinal cord, owing to their soft 
 consistency and the readiness with which they yield to pressure. 
 
 The second efiect produced by the artificial preparation of the 
 nervous matter is a partial coagulation of the white substance of 
 Schwann. In its natural condition this substance has the same 
 consistency throughout, and appears perfectly' transparent and 
 homogeneous by transmitted light. As soon, however, as the nerv- 
 ous filament is removed from its natural situation, and brought in 
 contact with air, water, or other unnatural fluids, the soft substance 
 immediately under the investing' membrane begins to coagulate. 
 It increases in consistency, and at the same time becomes more 
 highly refractive; so that it presents on each side, immediately 
 underneath the investing membrane, a thin layer of a peculiar 
 glistening aspect. (Fig. 119.) At first, this change takes place 
 ' only in the outer portions of the whitf: " substance of Schwann. 
 The coagulating process, however, subsequently goes on, and 
 24 
 
 WFBVOua Filaments froin white aubstance of 
 braia, — a, u, a. Sort subntance of the fllamenta preHHCj} 
 out, and floating in irregulurlj rounded drops. 
 
370 
 
 GENERAL STBUCTCRK AND FUNCTIONS 
 
 gradually advances from the edges of the filament toward its 
 centre, until^ its entire thickness after a time presents the same 
 appearance. The effect of this process can also be seen in those 
 portions of the white substance which have been pressed out from 
 the interior of the filaments, and which float about in the form of 
 
 drops. (Fig. 118, a.) These 
 
 Pig.. 119. 
 
 drops are always covered 
 with a layer of coagulated 
 material which is thicker 
 and more opaque in propor- 
 tion to the Jength of time 
 which has elapsed since the 
 commencement of the alter- 
 ation. 
 
 The nervous filaments 
 have essentially the same 
 structure in the brain and 
 spinal cord as in the nervous 
 trunks and branches; only 
 they are of much smaller 
 size in the former than in 
 the latter situation. In the 
 nervous trunks and branches, 
 however, outside the cranial 
 and spinal cavities, there 
 exists, superadded to the 
 nervous filaments and interwoven with them, a large amount of 
 condensed areolar or fibrous tissue, which protects them from 
 injury, and gives to this portion of the nervous system a peculiar 
 density and resistance. This difference in consistency between the. 
 white substance of the nerves and that of the brain and spinal cord 
 is owing, therefore, exclusively to the presence of ordinary fibrous 
 tissue in the nerves, while it is wanting in the brain and spinal 
 cord. The consistency of the nervous filaments themselves is the 
 same, in each situation. 
 
 The nervous filaments are arranged; in the nervous" trunks and 
 branches, in a direction nearly parallel with each other. A certain 
 number of them are collected in the form of a bundle, which is 
 invested with a layer of fibrous tissue, in which run the small 
 bloodvessels, destined for the nutrition of the nerve. Thesfs pri- 
 mary bundles are ag^dn united into secondary, the secondary into 
 
 NEi^Togs FtT.AMEifTs from sciaticnerve, i^howJug 
 their cuagulntioii. — At li, the torn extremity of a 
 nervous filament with the axis cylinder {h) protruding 
 from it. At c, the white substance of Sohwaan is nearly 
 separated by accideotai compression, but the axis- 
 cylinder passes across the ruptured portion. The out- 
 line of the tubular membrane is also seen at c on the 
 outside of the nervous filament. 
 
OF THE NKBVOUS SYSTEM. 
 
 871 
 
 Fig. 120. 
 
 tertiary, &o. A nerve, therefore, consists of a large bundle of ulti- 
 mate filaments, associated with each other in larger or smaller 
 packets, and bound together by the investing fibrous layers. When 
 a nerve is said to become branched or " divided" in any part of its 
 course, this division merely implies that some of its filaments leave 
 the bundles with which they were 
 previously associated, and pursue 
 a different direction. (Fig. 120.) 
 A nerve which originates, for ex- 
 ample, from the spinal cord in the 
 region of the neck, and runs down 
 the upper extremity, dividing and 
 subdividing, to be finally distri- 
 buted to the integument and mus- 
 cles of the hand, contains at its 
 point of origin all the filaments' 
 into which it is afterward divided, 
 and which are merely separated 
 at successive points from the 
 main bundle. ' The ultimate fila- 
 ments, accordingly, are continu- 
 ous throughout, and do not them- 
 selves divide at any point between 
 their origin and their final distri- 
 bution. 
 
 When a nerve, furthermore, is 
 said to " inosculate" with another 
 nerve, as when the infra-orbital 
 inosculates with the facial, or the 
 cervical nerves inosculate with 
 
 each other, this means simply that some of the filaments composing 
 the first nervous bundle separate from it, and cross over to form a 
 part of the second, while some of those belonging to the second 
 cross over and join the first (Fig. 121) ; but the individual filaments 
 in each instance remain continuous and preserve their identity 
 throughout. This fact is of great physiological importance ; since 
 'the white or fibrous nerve-substance is everywhere simply an 
 organ of transmission. It serves to convey the nervous impulse in 
 various directions, from without inward, or from within outward ; 
 and. as each nervous filament acts independently of the others, it 
 will convey an impression or a stimulus continuously from its 
 
 Division of a Nrkvk, phowlnj? portion of 
 nervous trunk ("), aud the separation of its 
 filaments (ft, c, d, e). 
 
372 
 
 GKNEBAL STBUCTCRK AND FUNCTIONS 
 
 origin to its termination, and will always tave the same character 
 and function in every part of its course. 
 
 The other variety of nervous matter is known as the gray sub- 
 stance. It is sometimes called " cineritious matter," and sometimes 
 
 Fig. 121. 
 
 InoHCulation of N b r t k s . 
 
 "vesicular neurine." It is found in the central parts of the spinal 
 cord, at the base of the brain in isolated masses, and is also spread 
 
 out as a continuous layer on 
 
 Fig. 122. 
 
 NRRT8 Cbli.b, Intermingled with fibres; from 
 Bemilunar ganglion of cat. 
 
 the external portions of the 
 cere,brum and cerebellum. 
 It also constitutes the sub- 
 stance of all the ganglia of 
 the great sympathetic. Ex- 
 amined by the microscope, it 
 consists of vesicles or cells, of 
 various forms and sizes, im- 
 bedded in a grayish, granular, 
 intercellular substa'nce, and 
 containing, also, very fre- 
 quently, granules of grayish 
 pigmentary matter. It is to 
 the presence of this granular 
 pigment that this kind" of 
 
OF THE NERVOUS SYSTEM. 373 
 
 nervous matter owes the ashy or " cineritious" color from which it 
 derives its name. The cells composing it vary in size, according 
 to Kolliker, from ^Atr to ^^^ of an inch. The largest of them have 
 a very distinct nucleus and nucleolus. (Fig. 122.) Many of them 
 are provided with, long processes or projections, which are sometimes 
 divided into two or three smaller branches. These c6lls are inter- 
 mingled, in all the collections of gray matter, with nervous filaments, 
 and are entangled with their extremities in such a manner that it 
 is exceedingly difficult to ascertain the exact nature of the anato- 
 mical relations existing between them. - It is certain that in some 
 instances the slender processes running out from the nervous vesi- 
 cles become at last continuous with the filaments; but it is not 
 known whether this be the case in all or even in a majority of 
 instances. The extremities of the filaments, however, are at all 
 events brought into very close relation with the vesicles or cells of 
 the gray matter. 
 
 Every collection of gray matter, whatever be its situation or 
 relative size in the nervous system, is called a ganglion or nervous 
 centre. Its function is to receive impressions conveyed to it by the 
 nervous filaments, and. to send out by them impulses which are to 
 be transmitted to distant organs. The ganglia, therefore, originate 
 nervous power, so to speak; while the filaments and the nerves 
 only transmit it. Now we shall find that, in .the structure of every 
 nervous system, the ganglia are connected, first with the different 
 organs, by bundles of filaments which 
 are called nerves ; and secondly with Fig. 123. 
 
 each other, by other bundles which 
 are termed commissures. The entire 
 system is- accordingly made up of' 
 ganglia, nerves, and commissures. 
 
 The simplest form of nervous 
 system is probably that found in 
 the five-rayed starfish. This animal 
 belongs to the type known as radiata; 
 that is, animals whose organs radiate 
 from a central point, so as to form a 
 circular series of similar parts, each 
 organ being repeated at difierent nbrtoos system of staefibh. 
 points of the circumference. The 
 
 starfish (Fig. 123) consists of a central mass, with five arms or 
 limbs radiating from it. In the centre is the mouth, and immedi- 
 
374 GENERAL STBUCTUBE AND FUNCTIONS 
 
 ately beneath it the stomach or digestive cavity, which sends pro- 
 longations into every one of the projecting limbs. There is also 
 contained in each limb a portion of the glandular and muscular 
 systems, and the whole is covered by a sensitive integument. The 
 nervous system consists of five similar ganglia, situated in the 
 central portion, at the base of the arms. These ganglia are con- 
 nected with each other by commissures, so as to form a nervous 
 collar or chain, surrounding the orifice of the digestive cavity. 
 Each gailglion also sends off nerves, the filaments of which are 
 distributed to the organs contained in the corresponding limb. 
 
 We have already stated that the proper function of the nervous 
 system is to enable a stimulus, acting upon one organ, to produce 
 motion or excitement in another. This is accomplished, in the 
 starfish, in the following nianner : — 
 
 When any; stimulus or irritation is applied to the integument of 
 one of the arms, it is transmitted by the nerves of the integument 
 to the gahglion situated near the mouth^ Arrived here, it is 
 received by the gray matter of. the ganglion, and immediately con- 
 verted into an impulse which is sent out by other filaments to the 
 muscles of the corresponding limb; and a myscular contraction and 
 movement consequently take place. The muscles therefore contract 
 in consequence of an irritation which has been applied to the skin. 
 This is called the " reflex action" of the nervous system ; because the 
 stimulus is first sent inward by the nerves of the integument, and 
 then returned or reflected back from the ganglion upon the muscles. 
 It must be repollected that this action does not necessarily indicate 
 any sensation or volition, nor even any consciousness on tbe part of 
 the animal. The function of the gray matter is simply to receive 
 the impulse conveyed to it, and to reflect or send back another ; 
 and this may be accomplished altogether involuntarily, and without 
 the existence of any conscious p&rception. 
 
 Where the irritation applied to the integument is of an ordinary 
 character and not very intense, it is simply reflected, as above 
 described, from the corresponding ganglion back to the same limb. 
 But if it be of a peculiar character, or of greater intensity than usual, 
 it may be also transmitted by the commissures to the neighboring 
 ganglia'; and so two, three, four, or even all five of the limbs may 
 be set in motion by a stimulus applied to the integument of one of 
 them. Now, as all the limbs of the animal have the same structure 
 ^nd contain the same organs, their action will also be the same ; 
 and the effects of this communication of the stimulus from one to 
 
OF THE NERVOUS SV8TEM. 
 
 375 
 
 the other by means of commissures -will be a repetition, or rather 
 a simultaneous production of similar movements in different parts 
 of the body. According to the character and intensity, therefore, 
 of the original stimulus, it will be followed by a response from 
 one, several, or all of the different parts of the animal frame. 
 
 It will be seen also that there are two kinds of nervous filaments, 
 differing essentially in their functions. One set of these fibres run 
 from the sensitive surfaces to the ganglion, and. convey the nervous 
 impression inward. These Are caWed sensitive fibres. The othet 
 set run from the ganglion, to the muscles, and carry the nervous 
 impression outward. These are called motor fibres. 
 
 "In the starfish, where the body is composed of a repetition of simi- 
 lar parts arranged round a common centre, and where all the limbs 
 are precisely alike in structure, the several ganglia composing the 
 nervous system are also similar to each other, and act in the same 
 ■way. But in animals which are constructed upon a different plan, 
 and whose bodies are composed of distinct orgians, situated in dif- 
 ferent regi6i3S,'we find th'at ' the nervous ' ganglia, presiding over 
 the function of these organs, present a corresponding degree of 
 dissimilarity. 
 
 In Aplysia, for example, which belongs to the type of mollusca, 
 or soft-bodied animals, the digestive apparatus consists of a mouth, 
 an oesophagus, a triple stomach, and a some- 
 what convoluted intestine. The liver is 
 large, and placed on one side of the body, 
 while the gills, in the form of vascular 
 laminffi, occupy the Opposite side. There 
 are both testicles and ovaries in the same 
 animal, the male and female functions co- 
 existing, as in many other invertebrate 
 species. All the organs, furthermore, are 
 here arranged without any reference to a 
 regular or symmetrical plan. The body is 
 covered with a muscular mantle, which ex- 
 pands at the ventral surface into a tolerably 
 well-developed "foot," or organ of locomo- 
 tion, by which the animal is enabled to 
 change its position and move from one nbrtocs ststhm op 
 
 ■t -I'. , .y Api.tbia. — 1. Dij^estive or 
 
 locality to another. oesophageal ganRlion. 2. C«re. 
 
 The nervous system of this animal is con- *"*' ganglion. 3, 3. Podai .,r 
 
 , . , locomototy ganglia. 4. Eespi- 
 
 structed upon a plan correspondmg with ratoiygangiioW. 
 
 Fig. 124. 
 
376 
 
 GESEEAL STBOCTUBE ANDi FUNCTIONS 
 
 Fig. 125. 
 
 that of the entire body. (Fig. 124.) There is a small gianglion (i) 
 situated anteriorly, which sends nerves to the conimencement of the 
 digestive apparatus, and is regarded as the oesophageal or digestive 
 ganglion. Immediately behind it is a larger one (2) ca,lled the 
 cephalic or cerebral ganglion, which sends nerves to the organs of 
 special sense, and which is regarded as the seat of volition and 
 general sensation for the entire body. Following this is a pair of 
 ganglia (3, s), the pedal or locoraotory ganglia, which supply the 
 muscular mantle and its foot-like expansion, and which . regulate 
 the movement of these organs. Finally, another ganglion (4), situ- 
 ated at the posterior part of the body, sends nerves to the branchiae 
 or gills, and is termed the branchial or respiratory ganglion. All 
 these nervous centres are connected by commissures with the central 
 or cerebral ganglion, and may therefore act either independently 
 or in association with each other, by means of these connecting fibres. 
 In the third type of animals, again, viz., the articulata, the gene- 
 ral plan of structure of the body is different from 
 the foregoing, and the nervous system is accord- 
 ingly modified to correspond with it. In these 
 animals, the body is composed of a number of 
 rings or sections, which are articulated with each 
 other in linear series. A very good example of 
 this type may be found in the common centipedes, 
 or scolopendra. Here the body is composed of 
 twenty-two successive and nearly similar articu- 
 lations, each of which has a pair of legs attached, 
 and contains a portion of the glandular, respira- 
 tory, digestive and reproductive apparatuses. 
 The animal, therefore, consists of a repetition of 
 similar compound parts, arranged in a longitudi- 
 nal chain or series. The only exceptions to this 
 similarity are in the first and last articulations. 
 The first is large, and contains the mouth; the 
 last is small, and contains the anus. The first 
 articulation, which is called the "head," is also 
 furnished with eyes,' with antennae, and- with a 
 pair of jaws, or mandibles. 
 
 The nervous system of the centipede (Fig. 125), 
 
 corresponding in structure with the above plan, 
 
 consists of a linear series of nearly equal and similar ganglia arranged 
 
 in pairs, situated upon the median line, along the ventral surface of 
 
 Nl^RTOlTS STBTEK 
 
 OF Centipede, 
 
OF THE NERVOUS SYSTEM. 377 
 
 the alimentary canal. Each pair of ganglia is connected with the 
 integument and muscles of its own articulation by sensitive and 
 motor filaments ; and with those which precede and follow hy a 
 double cord of longitudinal commissural fibres. In the first articu- 
 lation, moreover, or the head, the ganglia are larger than elsewhere, 
 and send nerves to the antennae and to the organs of special sense. 
 This pair is termed the cerebral ganglion, or the "brain." 
 
 A reflex action may take place, in these animals, through either 
 one or all of the ganglia composing the nervous chain. An im- 
 pression received by the integument of any part of the body may 
 be transmitted inward to its own ganglion and thence reflected 
 immediately outward, so as to produce a movement of the limbs 
 belonging to that articulation alone; or it may be propagated, 
 through the longitudinal commissures, forward or backward, and 
 produce simultaneous movements in several neighboring articula- 
 tions ; or, finally^ it may be propagated quite up to the anterior pair 
 of ganglia or "brain," where its reception will be accompanied with 
 consciousness, and a voluntary movement reflected back upon any 
 or all of the limbs at once. The organs of special sense, also, com- 
 municate directly with the cerebral ganglia ; and impressions con- 
 veyed through them may accordingly give rise to movements in 
 any distant part of the body. In these animals the ventra,l gan^ia, 
 or those which simply stand as a medium of communication be- 
 tween the integument and the muscles, are nearly similar through- 
 out ; while the first pair, or those which receive the nerves of special 
 sense,- and which exercise a general controlling power over the rest 
 of the nervous system, are distinguished from the remainder by a 
 well-marked preponderance in size. 
 
 In the centipede it will be noticed that nearly all the organs and 
 functions are distributed in an equal degree throughout the whole 
 length of the body. The organs of special sense alone, with those 
 of mastication and the functions of perception and volition, are 
 confined to the head. The ganglia oeeupyinig this part are there- 
 fore the only ones which are distinguished by any external pecu- 
 liarities; the remainder being nearly uniform both in size and 
 activity. In some kinds of articulated animals, however, particular 
 functions are concentrated, to a greater or less extent, in particular 
 parts of the body ; and the nervous ganglia which preside over 
 them are modified in a corresponding manner. In the insects, 
 for example, the body is divided into three distinct sections, viz : 
 the head, containing the organs of prehension, mastication, tact 
 
378 GENERAL 8TRUCTUBK AND FUNCTIONS 
 
 and special sense ; the chest, upon which are concentrated the or- 
 gans of locomotion, the legs and wings ; and the abdomen, contain- 
 ing the greater part of the alimentary canal, together with the 
 glandular and generative organs. As the insects have a greater 
 kmount of intelligence and activity than the centipedes and other 
 worm-like articulata, and as the organs of special sense are more 
 perfect in them, the cerebral ganglia are also unusually developed, 
 and are evidently composed of several pairs, connected, by commis- 
 sures so as to form a compound mass. As the organs of locomo- 
 tion, furthermore, instead of being distributed, as in the centipede, 
 throughout the entire length of the animal, are concentrated upon 
 _ the chest, the locomotory ganglia also preponderate in size in this 
 region of the body ; while the ganglia which preside over the secre- 
 tory and generative functions are situated together, in the cavity of 
 the abdomen. 
 
 All the above parts, however, are connected, in the same manner 
 as previously described, with the anterior or cerebral pair of gan- 
 glia. In all articulate animals, moreover, the general arrangement 
 of the body is symmetrical. The right side is, for the most part, 
 precisely like the left, as well in the internal organs as in the ex- 
 ternal covering and the locomotory appendages. The only marked 
 variation between different parts of the body is in an antero-pos- 
 terior direction ; owing to different organs being concentrated, in 
 some cases, in the head, chest, .and abdomen. 
 
 Finally, in the vertebrate type of animals, comprising man, the 
 quadrupeds, birds, reptiles, and fish, the external parts of the body, 
 together with the locomotory. apparatus and the organs of special 
 sense, are symmetrical, as in the articulata ; but the internal organs, 
 especially those concerned in the digestive and secretory functions, 
 are unsymmetrical and irregular, as in the molluscs. The organs 
 of respiration, however, are nearly symmetl-ical in the vertebrata, 
 for the reason that the respiratory movements, upon which the 
 function of these organs is immediately dependent, are performed 
 by muscles belonging to the general locomotory apparatus. The 
 nervous system of the vertebrata partakes, accordingly, of the struc- 
 tural arrangement of the organs under its control. That portion 
 which presides over the locomotory, respiratory, sensitive, and in- 
 tellectual functions forms a system by itself, called the cerebrospinal 
 system. This system is arranged in a manner very similar to that 
 of the articulata. It is composed of two equal and symmetrical 
 halves, running along the' median line of the body, the different 
 
OF THE NERVOUS SYSTEM. 
 
 379 
 
 parts of ■wliicli are connected by transverse and longitudinal com- 
 missures. Its ganglia occupy the cavities of the cranium and the 
 spinal canal, and send out their nerves through openings in the 
 bony walls of these cavities. 
 
 The other portion of the nervous system of vertebrata is that 
 which presides over the functions of vegetative life. It is called 
 the ganglionic or great sympathetic system. Its ganglia are situated 
 anteriorly to the spinal column, in the visceral cavities of the body, 
 and are connected, like the others, by transverse and longitudinal 
 commissures. This part of the nervous system is symmetrical in 
 the heck and thorax; but is uusymmetrical in the abdomen, where 
 it attains its largest size and its niost complete developmdnt- 
 
 The vertebrate animals, as a general rule, are very much superior 
 to the other classes, in intelligence and activity, as well as in the 
 variety and complicated character of their motions; while their 
 nutritive or vegetative functions, 
 on the other hand, are not particu- 
 larly well developed. Accordingly 
 we find that in these animals the 
 Cerebro-spinal system of nerves 
 preponderates very much, in im- 
 portance and extent, over that of 
 the great sympathetic. The quan- 
 tity of nervous matter contained 
 in the brain and spinal cord is, 
 even in the lowest vertebrate ani- 
 mal, very much greater than that 
 contained in the system of the great 
 sympathetic; and this, preponder- 
 ance increases, in the higher classes, 
 just in proportion to their supe- 
 riority in intelligence, sensation, 
 power of motion, and other func- 
 tions of a purely animal character. 
 
 The spinal cord is very nearly 
 alike in the different classes of ver- 
 tebrate animals. It is a nearly 
 cylindrical cord, running from one 
 end of the spinal canal to the other, 
 and connected at its anterior ex- 
 tremity with the ganglia of the brain. (Fig. 126.) It is divided. 
 
 CSREBRO-BPfNAL ST8TEH OF MAN. 
 
 ^1. Corehrum. 2. Cereb'-llnm. 3,3,3. Spin.tl 
 cord and nerveA. 4, 4. Brachial nerveii 
 S, fi. Sacral nerves. 
 
380 GENEBAI, STRUCTURE AND FUNCTIONS 
 
 by an anterior and, posterior median fissure, into two lateral halves, 
 which still remain connected with each other by a central mass or 
 commissure. Its inner portions are occupied by gray, matter, 
 which forms a continuous ganglionic chain, running from one ex- 
 tremity of the cord to the other. Its oijter portions are composed 
 of white substance, the filaments of which, run for the most part in 
 a longitudinal direction, connecting the different parts of the cord 
 with each other, and the cord itself with the ganglia of the brain. 
 
 The spinal nerves are given off from the spinal- cord at regular 
 intervals, and in symmetrical pairs; one pair to each successive 
 portion of the body. ; Their filaments are distributed to the integu- 
 ment and muscles of the corresponding regions. . In serpents, where 
 locomotion is performed by simple, alternate, lateral movements 
 of the spinal column, the spinal cord and its nerves are of the 
 same size throughout. But in the other vertebrate classeSj where 
 there exist special organs of locomotion, such as fore and hind 
 legs, wings, and the like, the spinal cord is increased in size at 
 the points where the nerves of these organs are given off; and the 
 nerves themselves, which supply the limbs, are larger than those 
 originating from other parts of the spinal cord. Thus, in the hu- 
 man subject (Fig. 126), the cervical nerves, which go to the arms, 
 and the sacral nerves, which are distributed to the legs,; are larger 
 than the dorsal and lumbar nerves. They form, also, by frequent 
 inosculation, two remiarkable plexuses, before entering their corre- 
 spond ing limbs, viz., the bra- 
 ^'^' ^^^' chial plexus above, and the 
 
 sacral plexus below. The 
 • cOrd itself, moreover, pi-e- 
 sents two enlargements at 
 the point of origin of these 
 nerves, viz., the cervical en- 
 largement from which the 
 brachial nerves (4, 4) are 
 given off, and the lumbar 
 
 TranBTerso Section of Spikaj, CoBn.-n,*. Spinal enlargement from wMch the 
 nerves of riglit and left Bides Rho^rlnt,' tlielr two rootB. gaCral ncrVCS (s, s) Originate, 
 rf. Origin of anterior root. «. Origin of posterior root. Ti? T. ■ l J 
 
 <i. Ganglion of posterior root. If the Spinal cord be exa- 
 
 mined in transverse section 
 (Fig. 127), it will be seen that the gray matter in its central portion 
 forms a double cresceniic-shaped ma^s, with the concavity of the 
 crescents turned outward. These crescentic masses of gray matter, ' 
 
OF. THR NERVOUS SYaTBM. 381 
 
 occupying the two lateral halves of thei cord, are united with each 
 othet by a transverse band of the same substance, which is called 
 the gray commissure of the cord. Directly in front of this is a trans- 
 verse band of white substance, connecting in a similar manner the 
 white portions of the two lateral halves. It is called the white 
 commissure of the cord. 
 
 The spinal nerves originate from the cord on each side by two 
 distinct roots ; one anterior, and one posterior. The anterior root 
 (Fig. 127, d). arises from the surface of the cord near the extremity 
 of the anterior peak of gray matter. The posterior root (e) origi- 
 nates at the point corresponding with the posterior peak of gray 
 matter. Both roots are composed of a considerable number of 
 ultimate nervous filaments, united with each other in parallel 
 bundles. The posterior root is distinguished by the presence of a 
 small ganglion (c), which appears to be incorporated with it, and 
 through which its fibres pass. There is no such ganglion on the 
 anterior root. • The two roots unite with each other shortly after 
 leaving the cavity of the spinal canal, and mingle their filaments 
 in a single trunk. 
 
 It will be seen, on referring to the diagram (Fig. 127), that each 
 lateral half of the spinal cord is divided into two portions, an 
 anterior and a posterior portion. The posterior peak of gray mat- 
 ter comes quite up to the surface of the cord,, and it is just at this 
 point (e) that the posterior roots of the nerves have their origin. 
 The. whole of the white substance included between this point and 
 the posterior median fissure is called the jsosfen'or column of the 
 cord. That which is included between the same point and the 
 anterior median fissure is the anterior coluTtm of the cord. The 
 white substance of the cord may then be regarded as consisting 
 for the most part of four longitudinal bundles of nervous filament^, 
 viz., the right and left anterior, and the right and left posterior 
 columns. The posterior median fi.<ssure penetrates deeply into the 
 substance of the cord, quite down to the gray matter, so that the 
 posterior columns appear entirely separated from each other in a 
 transverse section ; while the anterior median fissure is more shal- 
 low and stops short of the gray matter, so that the a^rior columns 
 are connected with each other by the white commissure above men- 
 >^ioned. 
 
 By the eruxphahn we mean the whole of that portion of the 
 cerebro-spinal system which is contained in the cranial cavity. It 
 is divided into three principal parts, viz., the cerebrum, cerebellum, 
 
382 
 
 GENERAL gTRUCTUBE AND FUNCTIONS 
 
 Fig. 128. 
 
 and medulla oblongata. The anatomy of these parts, though some- 
 what complicated, can be readily understood if it be recollected 
 that they are simply a double series o/nervous ganglia, connected with 
 each other and with the spinal cord hy transverse and longitudinal 
 commissures. . The number and relative size of these ganglia, in 
 different kinds of animals, depend upon the perfection of the hodily 
 organization in general, and more especially on that of the intelli- 
 gence and the special senses. They are most readily described by 
 commencing with the simpler forms and terminating with thei more 
 complex. 
 
 The brain of the Alligator (¥\g. 128) consists of five pair of 
 ganglia,;ranged one behind the other in the interior of the cranium. 
 The first of theSe.are iwoi rounded masses (i), lying just above and 
 
 behind the nasal cavities, which distri- 
 bute their nerves upon the Schneiderian 
 .mucous membrane. These are the olfac- 
 tory ganglia. The f are connected with 
 tl^e rest of the brain by two long and 
 slender commissures, the " olfactory com- 
 rtissures." The next pair (s) are some- 
 what larger and of a triangular shape, 
 .wheR. viewed from above downward. 
 They are termed the "cerebral ganglia," 
 or the hemispheres. Immediately follow- 
 ing them are two quadrangular masses (a) 
 which give origin to the optic nerves, and 
 are therefore called the optic ganglia. 
 They are termed also the " optic tiiber- 
 cles ;" and in some of the higher animals, 
 where they present an imperfect division 
 into four nearly equal parts, they are 
 known as the " tubercula quadrigemina." 
 Behind them, we have a single triangular collection of nervous 
 matter(4), which is called the cerebellum. Finally, the upper por- 
 tion of the cord, just behind and beneath the cerebellum, is seen to 
 be enlarged and spread out laterally, so as to form a broad oblong 
 mass (s), the medulla oblongata. It is from this latter portion of the 
 brain that the pneumogastric or respiratory nerves originate, and 
 its ganglia are therefore sometimes termed the "pneumogastric" or 
 " respiratory'* ganglia. 
 
 It will be seen that the posterior columns of the cord, as they 
 
 GATOR.— 1, 
 
 Bbaik of a 
 factory ganglia. 2. Hemispheres. 3. 
 Optic tubercles. 4. Cerebellum. 5. 
 Medulla oblongata. 
 
OP THE NERVOUS SYSTEM. 
 
 383 
 
 diverge laterally in order to form the medulla oblongata, leave be- 
 tween; them an open space, which is continuous, with the posterior 
 median fissure of the cord. This space is known as the "fourth 
 ventricle." It is partially covered in by the backward projection 
 of the cerebellum, but in the alligator is still somewhat open pos- 
 teriorly, presenting a kind of chasm or gap between the two lateral 
 halves of the medulla oblongata. 
 
 The successive ganglia which compose the brain, being arranged 
 in pairs as above described, are separated from each other on Jhe 
 two sides by a longitudinal median fissure, which is continuous 
 with the posterior median fissure of the cord. In the brain of the 
 alligator this fissure appears to be interrupted at the cerebellum ; 
 but in the higher classes, where the lateral portions of the cerebel- 
 lum are more highly developed, as in the human subject (Fig. 126), 
 they are also separated from each other posteriorly on the median 
 line, and the longitudinal median fissure is complete throughout. 
 
 In birds, the hemispheres are of much larger size than in rep- 
 tiles, and partially conceal the optic ganglia.. The cerebellum, 
 also, is very well developed in this class, and presents on its sur- 
 face a number of transverse foldings or convolutions by which 
 the quantity of gray matter which 
 it contains is considerably in- 
 creased. The cerebellum here 
 extends so far backward as almost 
 completely to conceal the medulla 
 oblongata and the fourth ven- 
 tricle. 
 
 In the quadrupeds, the hemis- 
 pheres and cerebellum attain a 
 still greater size in proportion to 
 the remaining parts of the brain. 
 There are also two other pairs of 
 ganglia, situated beneath the he- 
 mispheres, and between them and 
 the tubercula quadrigemina. 
 These are the corpora striata in 
 front and the opiic thalami hehini. 
 In Fig. 129 is shown the brain of 
 the rabbit, with the heqiispheres 
 laid open and turned aside, so as to show the internal parts in their 
 natural situatiou. The olfactory ganglia are seen in front (i) con- 
 
 Brain op Rabbit, viewed from above. — 
 1. Olfactory gant^lia. 2. HemifipliereB, tara(>d 
 aside. 3. Corpora Ktriata. . 4. Optic thalarni. 
 6. Tubercula quadrigemica. 6. Cerebellutii. 
 
384 
 
 GENERAL STBUCTUBE AND FUNCTIONS 
 
 nected with the remaining psnts by the olfactory commissures. The 
 separation of the hemispheres (s, s) shows the corpora striata (s) and 
 the optic thalami (4). Then come the tubercula quadrigemina (i), 
 which are here composed, as above mentioned, of four rounded 
 masses nearly equal in size. The cerebellum (e) is considerably en- 
 larged by the development of its lateral portions, and shows an 
 abundance of transverse convolutions. It conceals from view the 
 fourth ventricle and most of the medulla oblongata. 
 
 In other species of quadrupeds the hemispheres increase in size 
 so as to project entirely over the olfactory ganglia in front, and to 
 cover in. the tubercula quadrigemina and the cerebellum behind. 
 The surface of the hemispheres also becomes covered with nume- 
 rous convolutions, which are curvilinear and somewhat irregular 
 in form and direction, instead of being transverse, like those of the 
 cerebellum. In man, the development of the hemispheres reaches 
 its highest point ; so that they preponderate altogether in size over 
 the rest of the ganglia constituting the brain. In the human brain, 
 accordingly, when viewed from above downward, there is nothing 
 to be seen but the convex surfaces of the hemispheres ; and even 
 in a posterior view, as seen in Fig. 126, they conceal everything 
 but a portion of the cerebellum. All the remaining parts, how- 
 ever, exist even here, and have the same connections and relative 
 situation as in other instances. They may 
 best be studied in the following order. 
 
 As the spinal cord, in the human subject, 
 passes upward into the cranial cavity, it en- 
 larges into the medulla oblongata as already 
 described. The medulla oblongata presents 
 on each side three projections, two anterior 
 a,iid one posterior. The middle projections 
 on its anterior surface (Fig. 130, 1, 1), which 
 are called the anterior pyramids, are the con- 
 tinuation of the anterior columns of the cord. 
 They pass onward, underneath the transverse 
 fibres of the pons Varolii, run upward to the 
 corpora striata, pass through these bodies, 
 and radiate upward and outward from their 
 external surface, to terminate in the gray 
 matter of the hemispheres. The projections 
 immediately on the outside of the anterior pyramids, in the medulla 
 oblongata, are the olivary Mies (i, 2). They contain in their in- 
 
 Fig. 130. 
 
 Medtm^a OBtasnATA 
 OF Hi'HAN Brain, aote- 
 rior view — 1, 1. Anterior py- 
 ramids: 2,2. Olivary bodies. 
 '3, 3. Restil'tfrm bodies. 4. De- 
 cii-ssatibn of 'the anterior co- 
 iiimiis. Tlie medulla oblonfr- 
 ftta is seen terminated above 
 by the transvertie fibres of the 
 pons Varolii. 
 
OF THE NERVOUS SYSTEM. 385 
 
 terior a thin layer of gray matter folded upon itself, the functions 
 and connections of which are but little understood, and are not, 
 apparently, of very great importance. 
 
 The anterior columns of xhe cord present, at the lower part of the 
 medulla oblongata, a remarkable interchange or crossing of their 
 fibres (4). The fibres of the left anterior column pass across the 
 median line at this spot, and becoming continuous with the right 
 anterior pyramid, are finally distributed to the right side of the 
 cerebrum ; while the fibres of the right anterior column, passing 
 over to the left anterior pyramid, are distributed to the left side of 
 the cerebrum. This interchange or crossing of the nervous fibres 
 is known as the decussation of the anterior columns of the cord. 
 
 The posterior columns of the cord, as they diverge on each side 
 of the fourth ventricle, form the posterior and lateral projections of 
 the medulla oblongata (3, 3). They are sometimes called the " res- 
 tiform bodies," and are extremely important parts of the brain. 
 They consist in great measure of the longitudinal filaments of 
 the posterior columns, which pass upward and outward, and are 
 distributed partly to the gray matter of the cerebellum. The 
 remainder then pass forward, underneath the tubercula quadri- 
 gemina, into and through the optic thalami ; and radiating thence 
 upward and outward, are distributed, like the continuation of the 
 anterior columns, to the gray matter of the cerebrum. The resti- 
 form bodies, however, in passing upward to the cerebellum, are 
 supplied with some fibres from the anterior columns of the cord, 
 which, leaving the. lower portion of the anterior pyramids, join the 
 restiform bodies, and are distributed with them to the cerebellum. 
 From this description it will be seen that both the cerebrum and 
 the cerebellum are supplied with filaments from both the anterior 
 and posterior columns of the cord. 
 
 In the substance of each restiform body, moreover, there is im- 
 bedded a ganglion which gives origin to the pneumogastric nerve, 
 and presides over the functions of respiration. This ganglion is 
 surrounded and covered by the longitudinal fibres passing upward 
 from the cord to the cerebellum, but may be discovered by cutting 
 into the substance of the restiform body, in' which it is buried. It 
 is the first important ganglion met with, in dissecting the brain 
 from below upward. 
 
 While the anterior columns are passing beneath the pons Varolii, 
 they form, together with the continuation of the posterior columns 
 and the transverse fibres of the pons itself, a rounded prominence 
 25 
 
GENKEAL STRUCTURE AND FUNCTIONS 
 
 or tuberosity, which is known by the name of the tuber annulare. 
 In the deeper portions of this protuberance there is situated, among 
 the longitudinal fibres, another collectM)n of gray matter, which 
 though not of large size, has very important functions and connec- 
 tions. This is known as the ganglion of the tuber annulare. 
 
 Situated almost immediately above these parts we have the cor- 
 pora striata in front, and the optie thalami behind, nearly equal in 
 size, and giving passage, as abov% described, to the fibres of the 
 anterior and posterior columns. Behind them still, and on a little 
 lower level, are the tuber^ula quadrigemina, giving origin to the 
 optic nerves. The offactory ganglia rest upon the cribriform plate 
 of the ethmoid bone, and send the olfactory filaments through the 
 perforations in this plate, to be distributed upon the mucous mem- 
 brane of the upper and middle turbinated bones. The cerebellum 
 covers in the fourth ventricle and the posterior surface of the 
 medulla oblongata ; and finally the cerebrum, which has. attained 
 the size of the largest ganglion in the cranial cavity, extends so far 
 in all directions, forward, backward, and laterally, as to form a con- 
 voluted arch or vault, completely covering all the remaining parts 
 of the encephalon. 
 
 The entire brain may therefore be regarded as a connected series 
 
 of ganglia, the arrangement of 
 which is shown in the accompany- 
 ing diagram. (Fig. 131.) These 
 ganglia occur in tlie following 
 order, counting from before back- 
 ward: 1st. The olfactory gan- 
 glia. 2d. The cerebrum or hemi- 
 spheres. 8d. The corpora striata. 
 4th. The optic thalami. 5th. The 
 tubercula quadrigemina. 6th. 
 The cerebellum. 7th. The gan- 
 glion of the tuber annulare. And 
 8th. The ganglion of the medulla 
 oblongata. Of these ganglia,- 
 only the hemispheres and cere- 
 bellum are convoluted, while the 
 remainder are smooth and round- 
 ed or somewhat irregular in 
 shape. The course of the fibres 
 coming from the anterior and posterior columns of the cord is also 
 
 Fig. 131. 
 
 Diagram of Humah Bbaiit, in vertical sec- 
 tion ; showing the situation of the different gan- 
 glia, and the course of the fibres. 1. Olfactory 
 ganglion. 2. Hemisphere. 3. Corpus striatum. 
 4.. Optic thalamus. 5. Tubercula quadrigemina. 
 6. Cerebellum. 7. Ganglion of tuber annulare. 
 8. Ganglion of medulla oblongata. 
 
OF THE NERVOUS SYSTEM. 387 
 
 to bef seen in tlie accompanying figure. A portion of the anterior 
 fibres, we have already observed, pass upward and backward, with- 
 the restifbrm bodies, to the cerebellum ; whUe the remainder run 
 forward through the tuber annulare and the corpus striatum, and- 
 then radiate to the gray matter of the cerebrum. The posterior 
 fibres, constituting the restiform body, are distributed partly to the 
 cerebellum, and then pass forward, as previously described, under- 
 neath the tubercula quadrigemina to the optic thalmi, whence they 
 are also finally distributed to the gray matter of the cerebrum. 
 
 The cerebrum and cerebellum, each of which is divided into two 
 lateral halves or "lobes," by the great longitudinal fissure, are both 
 provided with transverse commissures, by which a connection is 
 established between their right and left sides. The great trans- 
 verse commissure of the cerebrum is that layer of white substance 
 which is situated at the bottom of the longitudinal fissure, and 
 which is generally known by the name of the "corpus callosum." 
 It consists of nervous filaments, which originate from the gray 
 matter of one hemisphere, converge to the centre, where they be- 
 come parallel, cross the median line, and are finally distributed to 
 the corresponding parts of the, hemisphere upon the opposite side. 
 The transverse commissure of the cerebellum is the pons Varolii. 
 Its fibres converge from the -gray matter of the cerebellum on one 
 side, and pass across to the opposite ; encircling the tuber annulare 
 with a band of parallel curved fibres, to which the name of " pons 
 Varolii" hfis been given from their resemblance to an arched bridge. 
 
 The cerebro-spinal system, therefore, consists of a series of gan- 
 glia situated in the cranio-spinal cavities, connected with each other 
 by transverse and longitudinal commissures, and sending out nerves 
 to the corresponding parts of the body. The spinal cord supplies 
 the integument and muscles of the neck, trunk, and extremities ; 
 while the ganglia of the brain, besides supplying the corresponding 
 parts of the head, preside also over the organs of special sense, and 
 perform various other functions of a purely nervous cliaracter. 
 
388 OF NEEVOUS IBBITABILITY 
 
 CHAPTEE II. 
 
 OF NERVOUS IRRITABILITY AND ITS MODE OP 
 
 ACTION. 
 
 "We have already mentioned, in a previous chapter, that every 
 organ in the body is endowed with the property of irritability; that 
 is, the property of reacting in some peculiar manner when subjected 
 to the action of a direct stimulus. Thus the irritability of a gland 
 shows itself by increased secretion, that of the capillary vessels by 
 congestion, that of the muscles by contraction. Now the irritability 
 of the muscles, indicated as above by their contraction, is extremely 
 serviceable as a means of studying and exhibiting nervous pheno- 
 mena. "We shall therefore commence this chapter by a study of 
 some of the more important facts relating to muscular irritability. 
 
 . The irritability of the muscles is a property inherent in the muscular 
 fibre itself. The existence of muscular irritability cannot be ex- 
 plained by any known physical or chemical laws, so far as they 
 ■ relate to inorganic substances. It must be regarded simply as a 
 peculiar property, directly dependent on the structure and consti- 
 tution of the muscular fibre ; just as the property of emitting light 
 belongs to phosphorus, or that of combining with metals to oxygen. 
 This property may be called into action by various kinds of stimu- 
 lus ; as by pinching the muscular fibre, or pricking it with the point 
 of a needle, the application of an acid or alkaline solution, or the 
 discharge of a galvanic battery. All these irritating applications 
 are immediately followed by contraction of the muscular fibre. 
 This contraction will even take place under the microscope, when 
 the fibre is entirely isolated, and removed from contact with any 
 other tissue; showing that the properties of contraction and irrita- 
 bility reside in the fibre itself, and are not communicated to it by 
 other parts. 
 
 Muscular irritability continues for a certain time after death. The 
 stoppage of respiration and circulation does not at once destroy 
 the vital properties of the tissues, but nearly all of them retain 
 
AND ITS MODE OP ACTION. 389 
 
 these properties to a certain extent for some time afterward. It is 
 only when the constitution of the tissues has become altered by 
 being deprived of blood, and by the consequent derangement of 
 the nutritive process, that their characteristic properties are finally 
 lost. Thus, in the muscles, irritability and contractility may be 
 easily shown to exist for a short time after death by applying to 
 the exposed muscular fibre the same kind of stimulus that we have 
 already found to affect it during life. It is easy to see, in the 
 muscles of the ox, after the animal has been killed, flayed, and 
 eviscerated, different bundles of muscular fibres contracting irregu- 
 larly for a long time, where they are exposed to the contact of the 
 air. Even in the human subject the same phenomenon may be 
 seen in cases of amputation ; the exposed muscles of the amputated 
 limb frequently twitching and quivering for many minutes after 
 their separation from the body. 
 
 The duration of muscular irritability, after death, varies consider- 
 ably in different classes of animals. It disappears most rapidly 
 in those whose circulation and respiration are naturally the most 
 active ; while it continues for a longer time in those whose circula- 
 tion and respiration are sluggish. Thus in birds the muscular 
 irritability continues only a few minutes after the death of the 
 animal. In quadrupeds it lasts somewhat longer ; 
 while in reptiles it remains, under favorable cir- Fig- 132. 
 cumstances, for many hours. The cause of this 
 difference is probably that, in birds and quadrupeds, 
 the tissues being very vascular, and the molecular 
 changes of nutrition going on with rapidity, the 
 constitution of the muscular fibre becomes so 
 rapidly altered after the circulation has ceased, 
 that its irritabibty soon disappears. In reptiles, 
 on the other hand, the tissues are less vascular 
 than in birds and quadrupeds, and all the nutritive 
 changes go on more slowly. Eespiration and cir- 
 culation can therefore be dispensed with for a longer 
 period, before the constitution of the tissues be- 
 comes so much altered as to destroy altogether froo's lkg, wuh 
 their vital properties. i""'"' "' sawanic bat- 
 
 _. ,. I- • ft 1J1.1JJ '"y applied to the 
 
 Owing to this peculiarity or the cola-blooaea nmsciea at a, s. 
 animals, their tissues may be used with great ad- 
 vantage for purposes of experiment. If a frog's leg, for example, 
 be separated from the body of the animal (Fig. 132), the skin 
 
390 OF NERVOUS IRRITABILITY 
 
 removed, and the poles of a galvanic apparatus applied to the sur- 
 face of the muscle (a, h), a contraction takes place every time the 
 circuit is completed and a discharge passed through the tissues of 
 the limb. The leg of the frog, prepared in this way, may be em- 
 ployed for a long time for the purpose of exhibiting the effect of 
 various kinds of stimulus upon the muscles. All the mechanical 
 and chemical irritants which we have mentioned, pricking, pinching, 
 cauterization, galvanism, &o., act with more or less energy and 
 promptitude, though the most ef&cient of all is the electric discharge. 
 
 Continued irritation exhausts the irritability of the muscles. It is 
 found that the irritability of the muscles wears out after death more 
 rapidly if they be artificially excited, than if they be allowed to 
 remain at rest. During life, the only habituail excitant of mus- 
 cular contraction is the peculiar stimulus conveyed by the nerves. 
 After death this stimulus may be replaced or imitated, to a certain 
 extent, by other irritants ; but their application gradually exhausts 
 the contractility of the muscle and hastens its final disappearance. 
 Under ordinary circumstances, the post-mortem irritability of the 
 muscle remains until the commencement of cadaveric rigidity. 
 When this has become fairly established, the muscles will no longer 
 contract under the application of an artificial stimulus. 
 
 Certain pbisonous substances have the power of destroying the 
 irritability of the muscles by a direct action upon their tissue. 
 Sulphocyanide of potassium, for example, introduced into the cir- 
 culation in suf&oient quantity to cause death, destroys entirely the 
 muscular irritability, so that no contraction can afterward be pro- 
 duced by the application of an external stimulant. 
 
 Nervous Irritability. — The irritability of the nerves is the pro- 
 perty by which they may be excited by an external stimulus, so as 
 to be called into activity and excite in their turn other organs to 
 which their filaments are distributed. When a nerve is irritated, 
 therefore, its power of reaction, or its irritability, can only be esti- 
 mated by the degree of excitement produced in the organ to which 
 the nerve is distributed. A nerve running from the integument to 
 the brain produces, when irritated, a painful sensation; one dis- 
 tributed to a glandular organ produces increased secretion ; one dis- 
 tributed to a muscle produces contraction. Of all these effects, 
 muscular contraction is found to be the best test and measure of 
 nervous irritability, for purposes of experiment. Sensation cannot 
 of course be relied on for this purpose, since both consciousness and 
 volition are abolished at the time of death. The activity of the 
 
AND ITS MODE OF ACTION. 
 
 391 
 
 Fig. 133. 
 
 M 
 
 glandular organs, owing to the stoppage of the circulation, disappears 
 also very rapidly, or at least cannot readily be demonstrated. The 
 contractility of the muscles, however, lasts, as we have seen, for a 
 considerable time after death, and may accordingly be employed 
 with great readiness as a test of nervous irritability. The manner 
 of its employment is as follows : — 
 
 The leg of a frog is separated from the body and stripped of its 
 integument; the sciatic nerve having been previously dissected 
 out and cut off at its point of emergence from the 
 spinal canal, so that a considerable portion of it 
 remains in connection with the separated limb. 
 (Pig. 133.) If the two poles, of a galvanic appa- 
 ratus be now placed in contact with different 
 points (ab) of the exposed nerve, and a discharge 
 allowed to pass between them, at the moment 
 of discharge a sudden contraction takes place in 
 the muscles below. It will be seen that this ex- 
 periment is altogether different from the one re- 
 presented in Fig. 132. In that experiment the 
 galvanic discharge passes through the muscles 
 themselves, and acts upon them by direct stim- 
 ulus. Here, however, the discharge passes only 
 from a to & through the tissues of the nerve, and 
 acts directly upon the nerve alone ; while the 
 nerve, acting upon the muscles by its own pecu- 
 liar agency, causes in this way a muscular con- 
 traction. It is evident that in order to produce 
 this effect, two conditions are equally essential : 1st. 
 The irritability of the muscles ; and 2d. The irri- 
 tability of the nerve. So long, therefore, as the 
 muscles are in a healthy condition, their contraction, under the 
 influence of a stimulus applied to the nerve, demonstrates the irri- 
 tability of the latter, and may be used as a convenient measure of 
 its intensity. 
 
 27ie irritability of the nerve continues after death. The knowledo-e 
 of this fact follows from what has just been said with regard to ex- 
 perimenting upon the frog's leg, prepared as above. The irrita- 
 bility of the nerve, like that of the muscle, depends directly upon 
 its anatomical structure and constitution ; and so long as these re- 
 main unimpaired, the nerve will retain its vital properties, though 
 respiration and circulation may have ceased. For the same reason. 
 
 Frog's Leg, with 
 sciatic uei-ve (N) at* 
 tached. — a b. Poles of 
 galvanic battery, ap- 
 plied to nerve. 
 
392 ' OF NERVOUS lEBITABILITY 
 
 also, as that given above with regard to the muscks, nervous irri- 
 tability lasts much longer after death in the cold-blooded than in 
 the -warm-blooded animals. Various artificial irritants may be em- 
 ployed to call it into activity. Pinching or pricking the exposed 
 nerve with steel instruments, the application of caustic liquids, and 
 the passage of galvanic discharges, aU have this effect. The electric 
 current, however, is much the best means to employ for this pur- 
 pose, since it is more delicate in its operation than the others, and 
 will continue to succeed for a longer time. 
 
 The nerve is, indeed, so exceedingly sensitive to the electric cur- 
 rent, that it will respond to it when insensible to all other kinds of 
 stimulus. A frog's leg freshly prepared with the nerve attache^, 
 as in Fig. 133, will react so readily whenever a discharge is passed 
 through the nerve, that it forms an extremely delicate instrument 
 for detecting the presence of electric currents of low intensity, and 
 has even been used for this purpose by Matteucci, under the name 
 of the " galvanoscopic frog." It is only necessary to introduce the 
 nerve as part of the electric circuit; and if even a very feeble, cur- 
 rent be present, it is at once betrayed by a muscular contraction. 
 
 The superiority of electricity over other means of exciting nerv- 
 ous action, such as mechanical violence or chemical agents, pro- 
 bably depends upon the fact that the latter necessarily alter and 
 disintegrate more or less the substance of the nerve, so that its irri- 
 tability soon disappears. The electric current, on the other hand, 
 excites the nervous irritability without any marked injury to the 
 substance of the nervous fibre. Its action may, therefore, be con- 
 tinued for a longer period. 
 
 Nervous irritability, like that of the muscles, is exhausted hy repeated 
 excitement. If a frog's leg be prepared as above, with the sciatic 
 nerve attached, and allowed to remain at rest in a damp and cool 
 place, where its tissue will not become altered by desiccation, the 
 nerve will remain irritable for many hours ; but if it be excited, 
 soon after its separation from the body, by repeated galvanic shocks, 
 it soon begins to react with diminished energy, and becomes gra- 
 dually less and less irritable, until it at last ceases to exhibit any 
 further excitability. If it be now allowed to remain for a time at 
 rest, its irritability will be partially restored ; and muscular contrac- 
 tion will again ensue on the application of a stimulus to the nerve. 
 Exhausted a second time, and a second time allowed to repose, it 
 will again recover itself; and this may even be repeated several 
 times in succession. At each repetition, however, the recovery of 
 
AND ITS MODE OF ACTION. 393 
 
 nervous irritability is less complete, until it finally disappears alto- 
 gether, and can no longer be recalled. 
 
 Various accidental circumstances tend to diminish or destroy 
 nervous irritability. The action of the woorara poison, for example, 
 destroys at once the irritability of the nerves ; so that in animals 
 killed by this substance, no muscular contraction takes place on 
 irritating the nervous trunk. Severe and sudden mechanical inju- 
 ries often have the same effect ; as where death is produced by 
 violent and extensive crushing or laceration of the body or limbs. 
 Such an injury produces a general disturbance, or shock as it is 
 called, which affects the entire nervous system, and destroys or 
 suspends its irritability. The effects of such a nervous shock may 
 frequently be seen in the human subject after railroad accidents, 
 where the patient, though very extensively injured, may remain 
 for some hours without feeling the pain of his wounds. It is only 
 after reaction has taken place, and the activity of the nerves has 
 been restored, that the patient begins to be sensible of pain. 
 
 It will often be found, on preparing the frog's leg for experiment 
 as above, that immediately after the limb has been sjeparated from 
 the body and the integument removed, the nerve is destitute of 
 irritability. Its vitality has been suspended by the violence in- 
 flicted in the preparatory operation. In a few moment^, however, 
 if kept under favorable conditions, it recovers from the shock, and 
 regains its natural irritability. 
 
 The action of the galvanic current upon the nerves, as first shown 
 by the experiments of Matteucci, is in many respects peculiar. If 
 the current be' made to traverse the nerve in the natural direction 
 of its fibres, viz., from its origin towards its distribution, as from a 
 to 6 in Fig. 133, it is called the direct current. If it be made to 
 pass in the contrary direction, as from h to o, it is called the inverse 
 current. When the nerve is fresh and exceedingly irritable, a 
 muscular contraction takes place at both the commencement and 
 termination of the current, whether it be. direct or inverse. But 
 very soon afterward, when the activity of the nerve has become 
 somewhat diminished, it will be found that contraction takes place 
 only at the commencement of the direct and at the termination of the 
 inverse current. This may readily be shown by preparing the two 
 legs of the same frog in such a manner that they remain connected 
 with each other by the sciatic nerves and that portion of the spinal 
 column from which these nerves take their origin. The two legs, 
 so prepared, should be placed each in a vessel of water, with the 
 
3M OF NERVOUS IBEITABILITY 
 
 nervous connection hanging between. (Pig. 134.) If the positive 
 pole, a, of the battery be now placed in the vessel which holds leg 
 No. 1, and the negative pole, b, in that containing leg No. 2, it will 
 be seen that the galvanic current will traverse the two legs in op- 
 posite directions. In No. 1, it will pass in a direction contrary to 
 the course of its nervous fibres, that is, it will be for this leg an 
 
 Fig. 134. 
 
 inverse current ; while in No. 2 it will pass in the same direction 
 with that of the nervous fibres, that is, it will be for this leg a direct 
 current. It will now be found that at the moment when the cir- 
 cuit is completed, a contraction takes place in No. 2 by the direct 
 current, while No. 1 remains at rest ; but at the time the circuit is 
 broken, a contraction is produced in No. 1 by the inverse current, 
 but no movement takes place in No. 2. A succession of alternate 
 contractions may thus be produced in the two legs by repeatedly 
 closing and opening the circuit. If the position of the poles, a, b, 
 be reversed, the effects of the current will be changed in a corre- 
 sponding manner. 
 
 After a nerve has become exhausted by the direct current, it is 
 still sensitive to the inverse ; and after exhaustion by the- inverse, 
 it is still sensitive to the direct. It has even been found by Mat- 
 teucci that after a nerve has been exhausted for the time by the direct 
 current, the return of its irritability is hastened by the subsequent 
 passage of the inverse current ; so that it will become again sensi- 
 tive to th& direct current sooner than if allowed to remain at rest. 
 Nothing, accordingly, is so exciting to a nerve as the passage of 
 direct and inverse currents, alternating with each other in rapid 
 succession. Such a mode of applying the electric stimulus is that 
 
AND ITS MODE OF ACTION. 395 
 
 usually adopted in the galvanic machines used in medical practice, 
 for the treatment of certain paralytic affections. In these machines, 
 the electric circuit is alternately formed and broken with great 
 rapidity, thus producing the greatest effect upon the nerves with 
 the smallest expenditure of electricity. Such alternating currents, 
 however, if very powerful, exhaust the nervous irritability more 
 rapidly and completely than any other kind of irritation ; and in 
 an animal killed by the action of a battery used in this manner, the 
 nerves may be found to be entirely destitute of irritability from the 
 moment of death. 
 
 The irritability of the nerves is distinct from that of the muscles; and 
 the two may be destroyed or suspended independently of each other. 
 When the frog's leg has been prepared and separated from the 
 body, with the sciatic nerve attached, the muscles contract, as we 
 have seen, whenever the nerve is irritated. The irritability of the 
 nerve, therefore, is manifested in this instafice only through that of 
 the muscle, and that of the muscle is called into action only through 
 that of the nerve. The two properties may be separated from each 
 other, however, by the action of woorara, which has the power, as 
 first pointed out by Bernard, of destroying the irritability of the . 
 nerve without affecting that of the muscles. If a frog be poisoned 
 by this substance, and the leg prepared as above, the poles of a 
 galvanic battery applied to the nerve will produce no effect ; show- 
 ing that the nervous irritability has ceased to exist. But if the 
 galvanic discharge be passed directly throjigh the muscles, contrac- 
 tion at once takes place. The muscular irritability has survived 
 that of the nerves, and must therefore be regarded as essentially 
 distinct from it. 
 
 It will be recollected, on the other hand, that in cases of death 
 from the action of sulphocyanide of potassium, the muscular irri- 
 tability is itself destroyed ; so that no contractions occur, even when 
 the galvanic discharge is made to traverse the muscular tissue. 
 
 There are, therefore, two kinds of paralysis : first, a muscular 
 paralysis, in which the muscular fibres themselves are directly 
 affected ; and second, a nervous paralysis, in which the affection is 
 confined to the nervous filaments, the muscles retaining their natural 
 properties, and being still capable of contracting under the influence 
 of a direct stimulus. 
 
 Nature of the Nervous Force. — The special endowment by which 
 a nerve acts and manifests its vitality is a peculiar one, inherent in 
 the anatomical structure and constitution of the nervous tissue. It is 
 
396 OF NERVOUS IRRITABILITY 
 
 manifested, in the foregoing experiments, by its effect upon the con- 
 tractile muscles. But we shall hereafter see that this is, in reality, 
 only one of its results, and that it shows itself, during life, by a 
 variety of other influences. Thus it produces, in one case, sensa- 
 tion; in another, muscular contraction; in another, increased or 
 modified glaiidular activity ; in another, alterations in the pheno- 
 mena of the circulation. The force, however, which is exerted by 
 a nerve in a state of activity, and which brings about these changes, 
 is not directly appreciable in any way by the senses, and can be 
 judged of only by its secondary effects. "We understand enough 
 of its mode of operation, to know that it is not identical with the 
 forces of chemical affinity, of mechanical action, or of electricity. 
 
 And yet, by acting upon the organs to which the nerves are 
 distributed, it will finally produce phenomena of all these different 
 kinds. By the intervention of the muscles, it results in mechanical 
 action ; aind by its infiilfence upon the glands and bloodvessels, it 
 causes chemical alterations in the animal fluids of the most import- 
 ant character. 
 
 It will even produce well-marked electrical phenomena, which 
 in some cases are so decided, as to have long attracted the attention 
 of physiologists. 
 
 It has been fully demonstrated that certain fish (gymnotus and 
 torpedo) have the power of generating electricity, and of producing 
 electric discharges, which are often sufficiently powerful to kill 
 small animals that may come within their reach. That the force 
 generated by these animals is in reality electricity, is beyond a 
 doubt. 'It is conducted by the same bodies which serve as con- 
 ductors for electricity, and is stopped by those which are non-con- 
 ductors of the same.' All the ordinary phenomena produced bj 
 the electric current, viz : the heating and melting of a fine con- 
 ducting wire, the induction of secondary currents and of magnetism, 
 the decomposition of saline solutions, and even the electric spark 
 have all been 'produced by the force generated by these animals. 
 There is, accordingly, no room for doubt as to its nature. 
 
 The electrical phenomena, in these cases, are produced by certain 
 organs which are called into activity by the nervous influence. 
 
 The electrical organs of the gymnotus and torpedo occupy a con- 
 siderable portion of the body, and are largely supplied with nerves 
 which regulate their function. If these nerves be divided, tied, or 
 injured in any way, the electrical organ is weakened or paralyzed, 
 just as the muscles would suffer if the nerves distributed to them 
 
AND ITS MODE OP ACTION, 397 
 
 were subjected to a similar violence. The electricity produced by 
 these animals, accordingly, is not supplied by the nerves, but by a 
 special generating organ, the action of which is regulated by nerv- 
 ous influence. 
 
 Moreover, the experiments of Longet and Matteucci* have shown 
 that no electrical current is to be detected in a living nerve, even 
 when in a state of activity. The electrical phenomenon, when it 
 exists, is only a secondary effect, and is not the active force residing 
 in the nervous tissue. This force is special in its nature, and is 
 regulated by laws peculiar to itself. 
 
 ' Longet, Traits de Physiologie. Paris, 1850, vol. ii. p. 130. 
 
S98 THE SPINAL COBD. 
 
 CHAPTEE III. 
 
 THE SPINAL COED. 
 
 We have already seen that the spinal cord is a long ganglion, 
 'covered with longitudinal bundles of nervous filaipents, and occu- 
 pying the cavity of the spinal canal. It sends out nerves which 
 supply the muscles and integument of at least nine-tenths of the 
 whole body, viz., those of the neck, "trunk, and extremities. All 
 these parts of the body are endowed with two very remarkable 
 properties, the exercise of which depends, directly or indirectly, 
 upon the integrity and activity of the spinal cord, viz., the power 
 of sensation and. the power of motion. Both these properties are 
 said to reside in the nervous system, because they are so readily 
 influenced by its condition, and are so closely connected with its 
 physiological action. We shall therefore commence the study of 
 the spinal cord with an examination of these two functions, and of 
 the situation which they occupy in the nervous system. 
 
 Sensation. — The power of sensation, or sensibility, is the power 
 by which we are enabled to receive impressions from external 
 objects. These impressions are usually of such a nature that we 
 can derive from them some information in regard to the qualities 
 of external objects and the effect which they may produce upon 
 our own systems. Thus, by bringing a foreign body into contact 
 with the skin, we feel that it is hard or soft, rough or smooth, cold 
 or warm. We can distinguish the separate impressions produced 
 by several bodies of a similar character, and we can perceive whe- 
 ther either one of them, while in contact with the skin, be at rest 
 or in motion. This power, whrich is generally distributed over the 
 external integument, is dependent on the nervous filaments rami- 
 fying in its tissue. For if the nerves distributed to any part of the 
 body be divided, the power of sensation in the corresponding region 
 is immediately lost. 
 
SENSATioiir. 899 
 
 The sensibility, thus distributed over the integument, varies in, 
 its acuteness in different parts of the body. Thus, the extremities 
 of the fingers are more sensitive to external impressions than the 
 general surface of the limbs and trunk. The surfaces of the fingers 
 which lie in contact with each other are more sensitive than their 
 dorsal or palmar surfaces. The point of the tongue, the lips, and 
 the orifices of most of the mucous passages are endowed with a 
 sensibility which is more acute than that of the general integument. 
 
 If the impression to which these parts are subjected be harsh or 
 violent in its character, or of such a nature as to injure the texture 
 of the integument or its nerves, it then produces a sensation oipain. 
 It-is essential to notice, however, that the sensation of pain is not 
 a mere exaggeration of ordinary sensitive impressions, but is one 
 of quite a different character, which is superadded to the others, or 
 takes their place altogether. Just in proportion "as the contact of a 
 foreign body becomes painful, our ordinary perceptions of its phy- 
 sical properties, are blunted, and the sense of suffering predominates 
 over ordinary sensibility. Thus if the integument be gently touched 
 with the blade of a knife we easily feel that it is hard, cold, and 
 smooth ; but if an incision be made with it in the skin, we lose all 
 distinct perception of these qualities, and feel only the suffering 
 produced by. the incisi9n. We perceive, also, the difference in 
 temperature between cold and warm substances brought in contact 
 with the skin, so long as this difference is moderate in degree ; but 
 if a foreign body be excessively cold or excessively hot, we can 
 no longer appreciate its temperature by the touch, but only its 
 injurious and destructive effect. Thus the sensation caused by 
 touching frozen carbonic acid is the same with that produced by a 
 red-hot metal. Both substances blister the surface, but their actual 
 temperatures cannot be distinguished. 
 
 It is, therefore, a very important fact in this connection, that the 
 sensibility to pain is distinct from the power of ordinary sensation. This 
 distinction was first fully established by M. Beau, of Paris, who has 
 shown conclusively that the sensibility to pain may be diminished 
 or suspended, while ordinary sensation remains. This is often seen 
 in patients who are partially under the influence of ether > or chlo- 
 roform. The etherizfition may be carried to such an extent that 
 the patient may be quite insensible to the pain of a surgical opera- 
 tion, and yet remain perfectly conscious, and even capable of feeling 
 the incisions, ligatures, &c., though he does not suffer from them. 
 It not unfrequently happens, also, when opium has been adminis- 
 
400 THE SPINAL COED. 
 
 tered for the relief of neuralgia, that the pain is completely abolished 
 by the influence of the drug, while the patient retains completely 
 his Consciousness and his ordinary sensibility. 
 
 In all cases, however, if the influence of the narcotic be pushed 
 to its extreme, both kinds of sensibility are suspended together, and 
 the patient becomes entirely unconscious of extesrnal impressions. 
 
 Motion. — Wherever muscular tissue exists, in any part of the 
 body, we find the power of motion, owing to the contractility of 
 the muscular fibres. But this power of motion, as we have already 
 seen, is dependent on the nervous system. The excitement which 
 causes the contraction of the muscles is transmitted to them by the 
 nervous filaments ; and if the nerve supplying a muscle or,a limb 
 be divided or seriously injured, these. parts are at once paralyzed 
 and become incapable of voluntary movement. A nerve which, 
 when irritated, acts directly upon a muscle, producing contraction, 
 is said to be excitable; and its excitability, acting through the mus- 
 cle, produces motion in the part to which it is distributed. 
 
 The excitability of various nerves, however, oftein acts "during 
 life upon other organs, beside the muscles ; and the ultimate effect 
 varies, of course, with the properties of the organ which is acted 
 upon. Thus, the nervous excitement transmitted to a muscle pro- 
 duces contraction, while that transmitted to a gland produces an 
 increased secretion, and that conveyed to a vascular surface causes 
 congestion. In all such instances, the effect is produced by an 
 influence transmitted by the nerve directly to the organ which is 
 called into activity. 
 
 But in all the external parts of the body muscular contraction 
 is the most marked and palpable effect produced by the direct 
 influence of nervous excitement. "We find, therefore, that so far 
 as we have yet examined it, the nervous action shows itself princi- 
 pally in two distinct and definite forms ; first, as sensibility, or the 
 power of sensation, and second, as excitability or the power of pro- 
 ducing motion. 
 
 Distinct Seat of Sensation and Motion in the Nervous 
 System. — Sensation and motion are usually the first functions 
 which suffer by any injury inflicted on the nervous system. As a 
 general rule, they are both suspended or impaired at the same time, 
 and in a nearly equal degree. In a fainting fit, an attack of apo- 
 pleixy, concussion or compression of the brain or spinal cord, or a 
 
DISTINCT SEAT OF SENSATION AND MOTION. 401 
 
 wound of any kind involving the nerves or nervous centres, insen- 
 sibility and loss of motion usually appear simultaneously. It is 
 difftcult, therefore, under ordinary conditions,, to trace out the 
 separate action of these two functions, or to ascertain the precise 
 situation occupied by each. 
 
 This difficulty, however, may be remov^ by examining sepa- 
 rately different parts of the nervous system. In the instances 
 mentioned above, the injury whiqh is inflicted is comparatively an 
 extensive one, and involves at the s^me time many adjacent parts. 
 But instances sometimes occur in which the two functions, sensa- 
 tion and motion, are affected independently of each other, owing to 
 the peculiar character and situation of the injury inflicted. Sensa- 
 tion may be impaired without loss of motion, and loss, of motion 
 may occur without injury to- sensation. In tic douloureux, for 
 example, we have an exceedingly painful affection of the sensitive 
 parts of the face, without any impairment of its power of motion*, 
 and in facial paralysis we often see a complete loss of motion affect- 
 ing one side of the face, while the sensibility of the part remains 
 altogether unimpaired. 
 
 The above facts first gave' rise to the belief that sensation and 
 motion might occupy distinct parts of the nervous system ; since it 
 would otherwise be difficult to understand how the two could be 
 affected independently of each other by anatomical lesions. It has 
 accordingly been fully established by the labors of Sir Charles Bell, 
 Miiller, Panizza, and Lpnget, that the two functions do in reality 
 occupy distinct parts of the nervous system. 
 
 If any one of the spinal, nerves, in the living animal, after being 
 exposed at any part of its course outside the spinal canal, be divided, 
 ligatured, bruised, or otherwise seriously injured, paralysis of motion 
 and loss of sensation are immediately produced in that part of the 
 body to which" the nerve is distributed. If, on the other hand, the 
 same nerve be pricked, galvanized, or otherwise gently irritated, a 
 painful sensation and convulsive movements are produced in the 
 same parts. The nerve iS therefore said to be both sensitive and 
 excitable ; sensitive, because irritation of its fibres produces a pain- 
 ful sensation, and excitable, because the same irritation causes mus- 
 cular contraction in the parts below. 
 
 The result of the experiment, however, will be different if it be 
 
 tried upon the parts situated inside the spinal canal, and particularly 
 
 upon the anterior and posterior roots of the spinal nerves. If an 
 
 irritation be applied, for example, to the anterior root of a spinal 
 
 26 
 
402 THE SPINAL COKD. 
 
 nerve, in the living animal, convulsive movements are produced ini 
 the parts below, but there is no painful sensation. The anterior 
 root accordingly is said to be excitable, but not sensitive. , If the 
 posterior root, on the other hand, be irritated/ acute pain is pro- 
 duced, but no convulsive movements. The posterior root is therfe 
 fore sensitive, but not excitable. A similar result is obtained by a 
 complete division of the two roots. Division of the anterior root 
 produces paralysis of motion, but no insensibility; division of the 
 posterior root produces complete loss of sensibility, but no muscular 
 paralysis. 
 
 We have here, then, a separate localization of sensation and 
 motion in the nervous system ; and it is accordingly easy to under- 
 stand how. one may be impaired without injury to the other, or 
 how both may be simultaneously affected, according to the situation 
 and extent of the anatomical lesion. 
 
 The two roots of a spinal nerve differ from each other, further- 
 more, in their mode of transmitting the nervous impulse. If the 
 posterior root be divided (Fig. 135) at a b, and an irritation applied 
 
 Diagram of Spisai Coup and Nekveb. The posterior root is sees divided at a, b, the 
 anterior at c, d. * 
 
 to the separated extremity (a), no effect will be produced; but if 
 the irritation be applied to the attached extremity (6), a painful 
 sensation is immediately the result. The nervous force, therefore, 
 travels in the posterior root from without inward, but cannot pass 
 from within outward. If the anterior root, on the other hand, be 
 divided at c, d, and its attached extremity {d) irritated, no effect 
 
SENSIBILITY AND EXCITABILITr IN SPINAL COBD. 403 
 
 follows; but if the separated extremity (c) be irritated, convulsive 
 movements instantly take place. The nervous force, consequently, 
 travels in the anterior root from within outward, but cannot pass 
 from without inward. 
 
 *The same thing is true with regard to the transmission of sensa- 
 tion and motion in the spinal nerves outside the spinal canal. If 
 one of these nerves be divided in the living animal, and its attached 
 extremity irritated, pain is produced, but no convulsive motion ; if 
 the irritation be applied to its separated extremity, muscular con- 
 tractions follow, but no painful sensation. 
 
 There are, therefore, two kinds of filaments in the spinal nerves, 
 not distinguishable by the eye, but entirely distinct in theit charac- 
 ter and function, viz., the " sensitive" filaments, or those which 
 convey sensation, and the " motor" filaments, or those which excite 
 movement. These filaments are never confounded with each other 
 in their action, nor can they perform each other's functions. The 
 sensitive filaments convey the nervous force only in a centripetal, 
 the motor only in a centrifugal direction. The former preside over 
 sensation, and have nothing to do with motion ; the latter preside 
 over motion, and have nothing to do with sensation. Within the 
 spinal canal the two kinds of filaments are separated from each 
 other, constituting the anterior and posterior roots of each spinal 
 nerve; but externally they are mingled together in a common 
 trunk. "While the anterior and posterior roots, therefore, are ex- 
 clusively sensitive or exclusively motor, the spinal nerves beyond 
 the junction of the roots are called mixed nerves, because they Con- 
 tain at the same time motor and sensitive filaments. The mixed 
 nerves accordingly preside at the same tirne over the functions of 
 movement and sensation. 
 
 Distinct Seat of Sensibility and Excitability in the 
 Spinal Cobd. — Various experimenters have demonstrated the fact 
 that different parts .of the spinal cord, like the two roots of the 
 spinal nerves, are separately endowed with sensibility and excita- 
 bility. The anterior columns of the cord, like the anterior roots of 
 the spinal nerves, are excitable but not sensitive; the posterior 
 columns, like the posterior roots of the spinal nerves, are sensitive 
 but not excitable. Accordingly, when the spinal canal is opened 
 in the living animal, an irritation applied to the anterior columns* 
 of the cord produpes immediately convulsions in the limbs below ; 
 but there is no indication of pain. On the other hand, signs of 
 
404 THE. SPINAL CORP. 
 
 acute pain become manifest whenever the irritation is applied to 
 the posterior columns ; but no muscular contractions follow, other 
 than those of a voluntary character. Longet has found* that if the 
 spinal cord be exposed in the lumbar region and completely divided 
 at that part by transverse section, the application of any irritant to 
 the anterior surface of the separated portion produces at once con- 
 vulsions below ; while if applied to the posterior columns behind 
 the point of division, it has no sensible effect whatever. The an- 
 terior and posterior columns of the cord are accordingly, so far, 
 analogous in their properties to the anterior and posterior roots of 
 the spinal nerves, arid are plainly composed, to a greater or less ex- 
 tent, of a continuation of their filaments. 
 
 These filaments, derived from the anterior and posterior roots of 
 the spinal nerves, pass upward through the spinal cord toward the 
 brain. An irritation applied to any part of the integument is then 
 conveyed, along the sensitive filaments of the nerve and its pos- 
 terior root, to the spinal cord ; then upward, along the longitudinal 
 fibres of the cord to the brain, where it produces a sensation corres- 
 ponding in character with the original irritation. A motor im- 
 pulse, on the other hand, originating in the brain, is transmitted 
 downward, along the longitudinal fibres of the cord, passes outward 
 by the anterior root of the spinal nerve, and, following the motor 
 filaments of the nerve through its trunk and branches, produces at 
 last a muscular contraction at the point of its final distribution. 
 
 Crossed Action of the Spinal Cord. — As the anteripr columns 
 of the cord pass upward to join the medulla oblongata, a decussa- 
 tion takes place between them, as we have already mentioned in 
 Chapter I. The fibres of the right anterior column pass over to 
 the left side of the medulla oblongata, and so upward to the left side 
 of the brain ; while the fibres of the left anterior column pass over 
 to the right side of the medulla oblongata, and so upward to the 
 right side of the brain. This decussation m^ be readily shown 
 (as in Fig. 130) by gently separating the anterior columns from each 
 other, at the lower extremity of the medulla oblongata, where the 
 decussating bundles may be seen crossing obliquely from side to 
 side, at the bottom of the anterior median fissure. Below this 
 point, the anterior columns remain distinct from each other on each 
 Side, and do not communicate by any further decussation. 
 
 ■ Traits de Physiolpgie, toI. ii. part 2, p. 8. 
 
CBOQSED ACTION OF THE SPINAL COBD. 405 
 
 If the anterior columns of the spinal cord, therefore, be wounded 
 at any point in the cervical, dorsal, or lumbar region, a paralysis 
 of voluntary motion is produced in the limbs below, on the same 
 side with the injury. But if a similar lesion occur in the brain, the 
 paralysis which results is on the opposite side of the body. Thus 
 it has long been known that an abscess or an apoplectic hemorrhage 
 on the right side of the brain will produce paralysis of the left side 
 of the body; and injury of tlie lefib side of the brain will be fol- 
 lowed by paralysis of the right side of the body. 
 
 The spinal cord has also a crossed action in transmitting sensi- 
 tive as well as motor impulses. It has been recently demonstrated 
 by Dr. Brown-S^quard,' that the crossing of the sensitive fibres in 
 the spinal cord does not take place, like that of the motor fibres, 
 at its upper portion only, but throughout its entire length ; so that 
 the sensitive fibres of the right spinal nerves, very soon after their 
 entrance into the cord, pass over to the left side, and those of the 
 left spinal nerves pass over to the right side. For if one lateral 
 half of the spinal cord of a dog be divided in the dorsal region, 
 the power of sensation remains upon the corresponding side of the 
 body, but is lost upon the opgosite side. It has been shown, fur- 
 thermore, by the same observer,' that the sensitive fibres of the 
 spinal nerves when they first enter the cord join the posterior 
 columns, which are everywhere extremely sensitive ; but that they 
 very soon leave the posterior columns, and, passing through the 
 central parts of the cord* run upward to the opposite side of the 
 brain. If the posterior columns, accordingly, be alone divided at 
 any part of the spinal cord, sensibility is not destroyed in all the 
 nerves behind the seat of injury, but only in those which enter the 
 cord at the point of section ; since the posterior columns consist 
 of different nervous filaments, joining them constantly on one side 
 from below, and leaving them on the other to pass upward toward 
 the brain. 
 
 The spinal cord has therefore a crossed action, both for sensation 
 and motion ; but the crossing of the motor filaments occurs only at 
 the medulla oblongata, while that of the sensitive filaments takes 
 place throughout the entire length of the cord. 
 
 ' Experimental Researches applied to Physiology and Pathology. New York, 
 18r)3. 
 
 " Memoirs eur la Physiologie de la Moelle 4pini4re ; Gazette M^dicale de Paris, 
 1855. 
 
406 THE SPINAL CORD.' 
 
 There are certain important facts whicli sfill remain to be noticed 
 regarding the mode of action of the spinal cord and its nerves. 
 They are as follows : — 
 
 1. An irritation applied to a spinal nerve at the middle of its course 
 produces the same effect as if it traversed its entire length. Thus, if the 
 sciatic or median nerve be irritated at any part of its course, con- 
 traction is produced in the muscles to which these nerves are dis- 
 tributed, just as if the impulse had' originated as usual from the 
 brain. This fact, depends upon the character of the nervous fila- 
 ments, as simple conductors. Wherever the impulse may originate, 
 the* final effect is manifested only at the termination of the nerve. 
 As the impulse in the motor nerves travels always in an outward 
 direction, the effect is always produced at the muscular termination 
 of the filaments, no matter how small or how large a portion of 
 their length may hav6 been engaged in transmitting the stimulus. 
 
 If the irritation, again, be applied to a sensitive nerve in the 
 middle of its course, the painful sensation is felt, not at the point 
 of the nerve directly irritated, but in that portion of the integumeitt 
 to which its filaments are distributed. Thus, if the ulnar nerve he 
 accidentally struck at the point wheje it lies behind the inner con- 
 dyle of the humerus, a sensation of tingling and numbness is pro- 
 duced in the last two fingers of the corresponding hand. It is 
 common to hear patients who have suffered amputation complain of 
 painful sensations in the amputated limb for weeks or months, and 
 sometimes even for years after the operation. They assert that 
 th6y can feel the separated parts as distinctly as if they were still 
 attached to the body. This sensation, which is a. real one and not 
 fictitious, is owing to some irritation operating upon the divided 
 extremities of the nerves in the cicatrized wound. Such an irrita- 
 tion, conveyed to the brain by the sensitive fibres, will produce 
 precisely the same sensation as if the amputated parts were still 
 present, and the irritation actually applied to them. 
 
 It is on this account also that division of the trifacial nerve is 
 not always effectual for the cure of tic douloureux. If the cause of 
 the difficulty be seated upon the trunk of the nerve, between its 
 point of emergence froifi the bones and its origin in the brain, it is 
 evident that division of the nerve upon the face will be of no 
 avail; since the cause of irritation will still exist behind the point 
 of section, and the same painful sensations will still be produced in 
 the brain. 
 
 2. The irritability of the motor filaments disappears from within out- 
 
INDEPENliKNCE OP NEBVOUS FILAMENTS. 407 
 
 ward, that of the sensitive filaments from without inward. Immedi- 
 ately after tlie separation of the frog's leg from the body, irritation 
 of the nerve at any point produces muscular contraction in the 
 limb below. As time elapses, however, and the irritability of the 
 nerve diminishes, the galvanic current, in order to produce con- 
 traction, must be applied at a point nearer its termination. Subse- 
 quently, the irritability of the nerve is, entirely lost in its upper 
 portions, but is retained in the parts situated lower down, from 
 which also, in turn, it afterward disappears j receding in this man- 
 ner, farther and farther toward the terminal distribution of the 
 nerve, where it finally disappears altogether. 
 
 ,0n the other hand, sensibility disappears, at the time of death, 
 first in the extremities. From them the numbness gradually creeps 
 upward, invading successively the middle and upper portions of the 
 limbs, and the more distant portions of the trunk. The central 
 parts are the last to become insensible. , 
 
 3. JSach nervous filament acts independently of the rest throughout its 
 entire length, and does not communicate its irritation to those which are 
 in proximity with it. It is evident that this is true with regard to 
 the nerves pf sensation, from the fact that if the integument be 
 touched with the point of a needle, the sensation is referred to that 
 spot alone. Since the nervous filaments coming from it» and the 
 adjacent parts are all bound together in parallel bundles, to form 
 the trunk of the nerve, if any imitation were communicated from 
 one sensitive filament to another, the sensation produced would be 
 indefinite and diffused, whereas it is really confined to the spot irri- 
 tated. If a frog's leg, furthermore, be prepared, with the sciatic 
 nerve attached, a few of the fibres separated laterally frofii the 
 nervous trunk for a portion of its length, and the poles of a galvanic 
 battery applied to the , separated portion, the contractions which 
 follow in the leg will not be general, but will be confined to those 
 muscles in which the galvanized nervous fibres especially have 
 their distribution. There are also various instances, in the body, 
 of antagonistic muscles, ■wfhich must act independently of each 
 other, but which are supplied with nerves from a common trunk. 
 The superior and inferior straight muscles of the eyeball, for 
 example, are both supplied by the motor oculi communis nerve. 
 Extensor and flexor muscles, as, for example, those of the fingers, 
 are often supplied by the same nerve, and yet act alternately with- 
 out mutual interference. It is easy to see that if this were not the 
 
408 THE SPINAL COBD. 
 
 case, confusion would constantly arise, both in the perception of 
 sensations, and in the execution of movements. 
 
 4. There are certain sensations which are excited simultaneously 
 by the same causes, and which are termed associated sensations ; and 
 there are also certain movements which -take place simultaneously, 
 and are called associated movements. In the former instance, one of 
 the associated sensations is called up immediately upon the percep- 
 tion of the other, without requiring any direct impulse of its own. 
 Thus, tickling the soles of the feet produces a peculiar sensation 
 at the epigastrium. Nausea is occasioned by certain disagreeable 
 odors, or by rapid rotation of the body, so that the landscape seems 
 to turn round. A striking example of associated movements, on 
 the other hand, may be found in the action of the muscles of the 
 eyeball. The eyeballs always accompany each other in their lateral 
 motions, turning to the right or the left side simultaneously. It is 
 evident, however, that in producing this correspondence of motion, 
 _ the left internal rectus muscle must contract and relax together 
 with the right external ; while a similar harmony of action must 
 exist between the right internal and the left external. The explana- 
 tion of such singular correspondences cannot be found in the anato- 
 mical arrangement of the muscles themselves, nor in that of the 
 nervous "filaments by which they are directly supplied, but must he 
 looked for in some special endowment of the nervous centres from 
 which they originate. 
 
 Eeflex Action of the Spinal Cobd. — The spinal cord, as we 
 have thus far examined it, may be regarded simply as a great nerve ; 
 that IS, as a bundle of motor and sensitive filaments, connecting 
 the muscles and integument below with the brain above, and 
 assisting, in this capacity, in the production of conscious sensation 
 and voluntary motion. Beside its nervous filaments, however, it 
 contains also a large' quantity of gray matter, and is, therefore, 
 itself a ganglionic .centre, and capable of independent action as 
 such. We shall now proceed to study it in its second capacity, as 
 a distinct nervous centre. 
 
 If a frog be decapitated, and the body allowed to remain at rest 
 for a few moments, so as to recover from the depressing effects of 
 shock upon the nervous system, it will be found that, although sen- 
 sation and consciousness are destroyed, the power of motion still 
 remains. If the skin of one of the feet be irritated by pinching it 
 with a pair of forceps, the leg is immediately drawn up toward the 
 
KEFLEX ACTION OF THE SPINAL COKD. 409 
 
 • 
 
 body, as if to escape the cause of irritation. If the irritation applied 
 to the foot be of slight intensity, the corresponding leg only will 
 move ; but if it be more severe in character, motions will often be 
 produced in the posterior extremity of the opposite side, and even 
 in the two fore legs, at the same time. These motions, it is import- 
 ant to observe, are never spontaneous. The decapitated frog remains 
 perfectly quiescent if left to himself. It is only when some cause 
 of irritation is applied externally, that movements occur as above 
 described. 
 
 It will be seen that the character of these phenomena indicates 
 the active operation of some part of the nervous system, and par- 
 ticularly of some ganglionic centre. The irritation is applied to 
 the skin of the foot, and the muscles of the leg contract in conse- 
 quence; showing evidently the intermediate action of a nervous 
 connection between the two. 
 
 The effect in question is due to the activity of the spinal cord, 
 operating aS a nervous centre. In order that the movements may 
 take place as above, it is essential that both the integvment and the 
 muscles should be in communication with the spinal cord by nerv- 
 ous filaments, and that the cord itself be in a state of integrity. If 
 the sciatic nerve be divided in the upper part of the thigh, irritation 
 of the skin below is no longer followed by any muscular contrac- 
 tion. If either the anterior or posterior roots of the nerve be 
 divided, the same want of action results ; and finally, if, thfe nerve 
 and its roots remaining entire, the spinal cord itself be broken up 
 by a needle introduced into the spinal 
 
 canal, the integument may then be ^^^^^^Jg^36^^^^^^ 
 irritated or mutilated to* any extent, ^^^^^U^^^^^^^^f 
 without exciting the least muscular. ^^^^P^^^^j^^^^^^l 
 contraction. It is evident, therefore, ^^^^ ■ B^^^^^f 
 that the spinal cord acts, in this case, ^^^| 1^ ^S^^^l 
 as a nervous centre, through which ^^^H ■ iH^^^H 
 the irritation applied to the skin is ^^^H I, ^^K^^l 
 communicated to the muscles. The ^^^H ■ m^^^^^B 
 irritation first passes upward, as shown ^^^H ■ ^^^^^^H 
 in the accompanying diagram (Fig. ^^^^^^^^^^^^^^^M 
 136), along the sensitive fibres of the ^^^^^^^^^^^^^^^B 
 
 ^ . , Diagram of SPlKAL Cord im Vik- 
 
 posterior root (a) to the gray matter tic*!, skchoj., showing reflex action. 
 of the cord, and is then reflected back, -"• !'''»»•"<" ""' <•' •p"'»i -""•■ »• 
 
 Anterior root of spinal nerve. 
 
 along the motor fibres of the anterior 
 
 root (6), until it finally reaches the musclQp, and produces a contrac- 
 
410 THE SPINAL COBD. 
 
 • 
 tion. This action is known, accordingly, as the reflex action of the 
 
 spinal cord. 
 
 It will be remembered that this reflex action of the cord is not 
 accompanied by volition, nor even by any conscious sensation. 
 
 The function of the spinal. cord as a nervous centre is simply to 
 convert an impression, received from the skin, into a motor impulse 
 which is sent out again to the muscles. There is absolutely no 
 farther action than this ; no exercise of will, •consciousness, or judg- 
 ment. This action will therefore take place perfectly well after 
 the brain has been removed, and after the entire sympathetic sys- 
 tem has also been taken away, provided only that the spinal cord 
 and its nerves remain in a state of integrity. 
 
 The existence of this reflex action after death is accordingly an 
 evidence of the continued activity of the spinal cord, just as con- 
 tractility is an evidence of the activity of the muscles, and irrita- 
 bility of that of the nerves. Like the two last-mentioned properties, 
 also, it continues for a longer time after death in cold-blooded than 
 in warm-blooded animalsv It is for this reason that frogs and other 
 reptiles are the most useful subjects for the study of these pheno- 
 mena, as for that of most others belonging to the nervous system. 
 
 The irritability of the spinal cord, as manifested by its reflex 
 action, may be very much exaggerated by certain diseases, and by 
 the operation of poisonous substances. Tetanus and poisoning by 
 strychaine both act in this way, by heightening the irritability of 
 the spinal cord, and causing it to produce convulsive movements 
 on the application of external stimulus. It has been observed that 
 the convulsions in tetanus are rarely, if ever, spontaneous, but that 
 . they always require to be excited by some external cause, such as 
 the accidental movementfOf the bedclothes, the shutting of a door, 
 or the sudden passage of a current of air. Such slight causes of 
 irritation, which would be entirely inadequate to excite involuntary 
 movements in the healthy'Sondition, act upon the spinal cord, when 
 its irritability is heightened by disease, in such a manner as to pro- 
 duce violent convulsions. 
 
 Similar appearances are to be seen in animals poisoned by strych- 
 ninei, This substance acts upon the spinal cord and increases its 
 irritability, without materially affecting the functions of the brain. 
 Its effects will show themselves, consequently, without essential 
 modification, after the head has been removed. If a decapitated 
 frog be poisoned with a moderate dose of strychnine, the body and 
 limbs will remain quiesqpnt so long as there is no external source 
 
EKFLEX ACTION OF THE SPINAL CORD. 4.11 
 
 of excitement ; but the limbs*are at once thrown into convulsions 
 by the slightest irritation applied to the skin, as, for example, the 
 contact of a hair or a feather, or even ■ the jarring of the table on 
 which the animal is placed. That the convulsions iu cases of 
 poisoning by strychnine are always of a reflex character, and never 
 spontaneous, is shown by the following fact first noticed by Ber- 
 nard,' viz., that if a frog be poisoned after division of the posterior 
 roots of aU the spinal nerves, while the anterior roots are left un- 
 touched, death takes place as usual, but is not preceded by any con- 
 vulsions. In this instance the convulsions are absent simply 
 because, owing to the division of the posterior roots, external irri- 
 tations cannot be communicated to the cord. 
 
 The reflex action, above described, may be seen very distinctly 
 in the human smbject, in certain cases of disease of the spinal cord. 
 If the upper. portion of the cord be disintegrated by inflammatory 
 softening, so that its middle and lower portions lose their natural 
 connection with the brain, paralysis of voluntary motion and loss of 
 sensation ensue in all parts of the body below the seat of the ana- 
 tomical lesion. , Under these conditions, the patient is incapable of 
 making any muscular exertion in the paralyzed parts, and is uncon- 
 scious of any injury done to the integument in the same region. 
 Notwithstanding this, if the soles of the feet be gently irritated 
 with a feather, or with the point of a needle, a convulsive twitch- 
 ing of the toes will often take place, and even retractile movements 
 of the leg and thigh, altogether without the patient's knowledge^ 
 Such movements may frequently be excited by simply allowing 
 the cool air to come suddenly in contact with the lower extremities. 
 We have repeatedly witnessed these phenomena, in a case of dis- 
 ease of the spinal cord, where the paralysis and insensibility of the 
 lower extremities were complete. Many other similar instances 
 are reported by various authors. 
 
 The existence of this reflex action of the cord has enabled the 
 physiologist to ascertain several other important facts concerning 
 the mode of operation of the nervous system. M. Bernard has 
 dbmonstrated,' by a series of extremely ingenious experiments on 
 the action of poisonous substances, 1st, that the irritability of the 
 muscles may be destroyed, while that of the nerves remains unal- ■ 
 
 ' Iie(;ons surles effets des Substances toxlques et ipedicamentenses, Paris, 1857, 
 p. 357. 
 > Ibid., Cbaps. 23 and 24. 
 
412 
 
 THE SPINAL COBD. 
 
 tered; and 2d, thabthe motor and s^sitive nervous filaments may 
 be paralyzed independently of each other. The above facts are 
 shown by the three following experiments : — 
 
 1. In a.living frog (Fig. 137), the sciatic nerve {N) is exposed in 
 the back part of the thigh, after which a ligature is passed under- 
 neath it and drawn tight around the bone and the remaining soft 
 parts. In this way the circulation is entirely cut off from the limb 
 ((£), which remains in opnnection with the trunk only by means of 
 the sciatic nerve. A solution of sulphocyanide of potassium is ftien 
 
 introduced beneath the skin 
 ^'^- ^^^- of the back, at I, in sufficient 
 
 quantity to produce its speci- 
 fic effect. The poison is then 
 absorbed, and is carried by 
 the circulation throughout the 
 trunk and the three extremi- 
 ties a, h, c ; while it is pre- 
 vented from entering the limb 
 d, by the ligature' which has 
 been placed about the thigh. 
 Sulphocyanide of potassium 
 produces paralysis, as we have 
 previously mentioned, by act- 
 ing directly upon the muscu- 
 lar tissue. Accordingly, a gal- 
 vanic discharge passed through 
 the limbs a, b, and c, produces 
 no contraction in them, while 
 the same stimulus, applied to 
 d, is followed by a strong and 
 healthy reaction. But at the 
 moment when the irritation 
 is applied to the poisoned 
 limbs a, b, and c, though no 
 visible effect is produced in 
 them, an active movement 
 takes place in the. healthy 
 limb, d. This can only be 
 owing to a reflex action of the'spinal cord, originating in the inte- 
 gument of «, b, and c, and transmitted, by sensitive and motor fila- 
 ments, through the cord to d. While the muscles of the poitoned 
 
KEFLEX ACTION OF THE SPINAL CORl). 413 
 
 limbs, therefore, have been directly paralyzed, thd nerves of the same 
 parts have retained their irritability. ' 
 
 2. If a frog be poisoned with woorara by simply placing the 
 poison under the skin, no reflex action of the spinal cord can be 
 demonstrated after death. We have already shown, from experi- 
 ments detailed in Chapter II., that this substance destroys the irrita- 
 bility of the motor nerves, without affecting that of the muscles. In 
 the above instance, therefore, where the reflex action is abolished, its 
 loss may be owing to a paralysis of both motor and s^sitive fila- 
 ments, or to that of the motor filaments alone. The following experi- 
 ment, however, shows that the motor filaments are the only ones 
 affected. If a frog be prepared as in Fig. 137, and poisoned by the 
 introduction of woorara at I, when the limb d is irritated its own 
 muscles react, while no movement takes place in a, b, or c; but if 
 the irritation be applied to a, b, or c, reflex movements are imme- 
 diately produced in d. In the poisoned limbs, therefore, while the 
 motor nerves have been paralyzed, the sensitive filaments have retained 
 their irritability. 
 
 3. If a frog be poisoned with strychnine, introduced underneath 
 the skin in sufficient quantity, death takes place after general con- 
 vulsions, which are due, as we have seen above, to an unnatural 
 excitability of the reflex action. This is followed, however, by a 
 paralysis of sensibility, so that after death no reflex movements 
 can be produced by irritating the skin or even the posterior roots 
 of the spinal nerves. But if the anterior roots, or the motor nerves 
 themselves be galvanized, contractions immediately take place in 
 the corresponding muscles. In this case, therefore, the sensitive fila- 
 ments have been paralyzed, while the mator filaments and the mvscles 
 have retained their irritability. 
 
 "We now come to investigate the reflex action of the spinal cord, 
 as it takes place in a healthy condition during life. This action 
 readily escapes notice, unless our attention be particularly directed 
 to it, because the sensations which we are constantly receiving, and 
 the many voluntary movements which are continually executed, 
 serve naturally to mask those nervous phenomena which take place 
 without our immediate knowledge, and over which we exert no 
 voluntary control. Such phenomena, however, do constantly take 
 place, and are of extreme physiological importance. If the surface 
 of the skin, for example, be at any time unexpectedly brought in 
 contact with a heated body, the injured part is often withdrawn by 
 a rapid and convulsive movement, long before we feel the pain, or 
 
414 THE SPINAL COED. 
 
 even fairly understand the cause of the involuntary act. If the 
 body by any accident suddenly and unexpectedly loses its balance, 
 the limbs are thrown into a position calculated to protect the ex- 
 posed parts, and to break the fall, by a similar involuntary and in- 
 stantaneous movement. The brain does not act in these cases, for 
 there is no intentional character in the movement, nor even any 
 complete consciousness of its object. Everything indicates that it 
 is the immediate result of a simple reflex, action of the spinal cord. 
 
 The cord'exerts %lso an important and constant influence upon 
 the sphincter muscles. The sphincter ani is habitually in a state of 
 contraction, so that the contents of the intestine are not alloived to 
 escape. Whea any external irritation is applied to the anus, or 
 whenever the feces present themselves internlally, the sphincter 
 contracts involuntarily, and the discharge of the feces is prevented. 
 This habitual closure of the sphincter depends on the reflex action 
 of the spinal cord. It is entirely an involuntary act, and will con« 
 tinue, in the healthy condition, during profound sleep, as complete 
 and efficient as in the waking state. 
 
 When the rectum, however, has become filled by the accumula- 
 tion of feces from above, the nervous action changes. Then the 
 impression produced on the mucous membrane of the distended 
 rectum, conveyed- to the spinal cord, causes at the same time re- 
 laxation of the sphincter and contraction of the rectum itself; so 
 that a discharge of the feces consequently takes place. 
 
 Now all these actions are to some extent under the control of 
 sensation and volition. The distended state of the rectum is usually 
 accompanied by a distinct sensation, and the resistance of the 
 sphincter may be voluntarily prolonged for a certain period, just as 
 the respiratory movements, which are usually involuntary, may be 
 intentionally hastened or retarded, or even temporarily suspended. 
 But this voluntary power over the sphincter and the rectum is 
 limited. After a time the involuntary impulse, growing more 
 urgent with the increased distension of the . rectum, becomes irre- 
 sistible;' and the discharge finally takes place by the simple reflex 
 action of the spinal cord. 
 
 If the spinal cord be injured in its middle or upper portions, the 
 sensibility and voluntary action of the sphincter are lost, because its 
 connection with the brain has been destroyed. The evacuation 
 then takes place at once, by the ordinary mechanism, as soon aS 
 the rectum is filled,! but without any knowledge on the part of the 
 
KEFLEX ACTION OF THJ! SPINAL CORD. 415 
 
 patient. The discharges are then said to be " involuntary and un- 
 conscious." 
 
 If the irritability of the cord, on the other hand, be exaggerated 
 by disease, while its connection with the brain remains entire, the 
 distension of the rectum is announced by the usual sensation, but 
 the reflex impulse to evacuation is so urgent that it cannot be 
 controlled by the will, and the patient is compelled to allow it to 
 take place at once. The discharges are then said to be simply 
 " involuntary." 
 
 Finally, if the substance of the spinal cord be extensively de- 
 stroyed by accident or disease, the sphincter is permanently relaxed. 
 The feces are then evacuated almost continuously, without any 
 knowledge or control on the part of the patient, as fast as they 
 descend into the rectum from the upper portions of the intestine. 
 
 Injury of the spinal cord produces a somewhat different effect on 
 the urinary bladder. Its muscular fibres are directly paralyzed ; 
 and the organ, being partially protected by elastic fibres, both at 
 its own orifice and along the urethra, becomes gradually distended 
 by urine from the kidneys. The urine then overcomes the elas- 
 ticity of the protecting fibres, by simple force of accumulation, and 
 afterward dribbles away as fast as it is excreted by the kidneys. 
 Paralysis of the bladder, therefore, first causes a permanent 'disten- 
 sion of the organ, which is afterward followed by a continuous, 
 passive, and incomplete discharge of its contents. 
 
 Injury of the spinal cord produces also an important, though 
 probably an indirect effect on nutrition, secretion, animal heat, &c., 
 in the paralyzed parts. Diseases of the cord which result in it^ 
 softening or disintegration, are notoriously accompanied by consti- 
 pation, often of an extremely obstinate character. In complete 
 paraplegia, also, the lower extremities become emaciated. The 
 texture and consistency of the muscles are altered, and the animal 
 temperature is considerably reduced. All such disturbances of 
 nutrition, however, which almost invariably follow upon local para- 
 lysis, are no doubt immediately owing to the inactive condition of 
 the muscles ; a condition which naturally induces debility of the 
 circulation, and consequently of all those functions which are de- 
 pendent upon it. 
 
 It is less easy to explain the connection between injury of the 
 spinal cord and inflammation of the urinary passages. It is, how- 
 ever, a matter of common observation among pathologists, that 
 injury or disease of the cord, particularly in the dorsal and upper 
 
416 THE SPINAL CORD. 
 
 lumbar regions, is soon followed by catarrhal inflammation of the 
 urinary passages. This gives rise to an abundant production of 
 altered mucus, which in its turn, by causing an alkaline fermenta- 
 tion of the urine contained in the bladder, converts it into an irri- 
 tating and ammoniacal liquid, which reacts upon the mucous mem- 
 brane and aggravates the previous inflammation. 
 
 We find, therefore, that the spinal cord, in its character of a 
 nervous centre, exerts a general protective action over the whole 
 body, it presides over the involuntary movements of the limbs 
 and trunk ;. it regulates the action of the sphincters, the rectum, 
 and the bladder ^while at the same time it exerts an indirect influ- 
 ence on the nutritive changes in those parts which it supplies with 
 nerves. 
 
THE BEAIN. 417. 
 
 CHAPTER IV. 
 
 THE BRAIN. 
 
 By the brain, or enc^hahn, as it is sometimes called, we mean all 
 that portion of the nervous system which is situated within the 
 cavity of the cranium. It consists, as we have already shown, of 
 a series of different ganglia, connected with each other by transverse 
 and longitudinal commissures. 
 
 Since we have found the functions of sensation and motion, or 
 sensibility and excitability, so distinctly separated in the spinal 
 cord, we should expect to find the same distinction in the interior 
 of the brain. These two properties have indeed been found to be 
 distinct from each other, so far as they exist at al], in the encephalic 
 mass ; but it is a very remarkable fact that they are both confined 
 to very small portions of the brain, in comparison with its entire 
 bulk. According to the investigations of Longet, neither the 
 olfactory ganglia, the corpora striata, the optic thalami, the tuber- 
 cula quadrigemina, nor the white or gray substance of the cerebrum 
 or the cerebellum, are in the least degree excitable. Mechanical 
 irritation of these parts does not produce the slightest convulsive 
 movement in the muscles below. The application of caustic liquids 
 and the passage of galvanic currents are equally without effect. 
 The only portions of the brain in which irritation is followed by 
 convulsive movements are the anterior surface of the medulla ob- 
 longata, the tuber annulare, and the lower part of the crura cerebri ; 
 that is, the lower and central parts of the brain, containing continu- 
 ations of the anterior columns of the cord. On the other hand, 
 neither the olfactory ganglia, the corpora striata, the tubercula 
 quadrigemina, nor the white or gray substance of the cerebrum or 
 cerebellum, give rise, on being irritated, to any painful sensation. 
 The only sensitive parts are the. posterior surface of the medulla 
 oblongata, the restiform bodies, the processus e cerebello ad .testes, 
 and the upper part of the crura cerebri ; that is, those portions of 
 the base of the brain which contain prolongations of the posterior 
 columns of the cord. 
 27 
 
41^ TSE BKAIN. 
 
 The most central portions of the nervous system, therefore, ai^ 
 particularly the gray matter, are destitute of both excitability and 
 sensibility. It is only those portions which serve to conduct sen- 
 sations and nervous impulses that can be excited by mechanical 
 irritation ; not the ganglionic centres themselves, which receive and 
 originate the nervous impressions. 
 
 We shall now study in succession' the dififerent ganglia of which 
 the brain is composed. 
 
 Olfactoey GtANGLIA. — These ganglia, which in some of the 
 lower animals are very large, corresponding in size with, the ex- 
 tent of the olfactory membrane and the acuteness of the sense of 
 smell, are very small in the human subject. They are situated on 
 the cribriform plate of the ethmoid bone, on each side of the crista 
 galli, just beneath the anterior lobes of the cerebrum. They send 
 their nerves through the numerous perforations which exist in the 
 ethmoid bone at this part, and are connected with the base of the 
 brain by two longitudinal commissures. The olfaptory ganglia 
 with their commissures are sometimes spoken of as the " olfactory 
 nerves." They are not nerves, however, but ganglia, since they are 
 mostly composed of gray matter ; and the term " olfactory nerves" 
 can be properly applied only to the filaments which originate from 
 them, and which are afterward spread out in the substance of the 
 olfactory membrane. 
 
 It has been found difficult to determine the function of these 
 ganglia by direct experiment on the lower animals. They may he 
 destroyed by means of a strong needle introduced through the bones 
 of the cranium; but the signs of the presence or absence of the 
 sense of smell, after such an operation, are too indefinite to allow us 
 to draw from them a decided conclusion. The anatomical distribu- 
 tion of their nerves, however, and the evident correspondence which 
 exists, in different species of animals, between their degree of de- 
 velopment and that of the external olfactory organs, leaves no doubt 
 as to their true function. They are the ganglia of the speciail sense 
 of smell, and are not connected, in any appreciable degree, with 
 ordinary sensibility, nor with the production of voluntary move- 
 ments. 
 
 Optic Thalami. — These bodies are not, as their name would 
 imply, the ganglia of vision. Longet has found that the power of 
 sight and the sensibility of the pupil both remain, in birds, after 
 
CORPORA STRIATA. — HEMISPHERES. 419 
 
 the optic thalami Iiave been thorouglily disorganized ; and that arti- 
 ficial irritation of the same ganglia has no effect in producing 
 either contraction or dilatation of the pupil. The optic' thalami, 
 however, according to the same observer, have a peculiar crossed 
 action upon ' the voluntary movements.* If both hemispheres and 
 both optic thalami be removed in the rabbit, the animal is still 
 capable of standing and of using his limbs in progression. But if 
 the right optic thalamus alone be removed, the animal falls at once 
 upon his left side ; and if the left thalamus be destroyed, a similar 
 debility is manifest on the right side of the body. In these in- 
 stances there is no absolute paralysis of the side upon which the 
 animal falls, but rather a simple want of balance between the two 
 opposite sides. The exact mechanism of this peculiar functional 
 disturbance is not well understood; and but little light has yet 
 been thrown, either by direct experiment or by the facts of compa- 
 rative anatomy, on the real function of the optic thalami. 
 
 Corpora STRiATA.-^The function of these ganglia is equally 
 uncertain with that of the preceding. They are traversed, as we 
 have already seen, by fibres coming from the anterior columns of 
 the cord; and they are connected, by the continuation of these 
 fibres, with the gray substance of the hemispheres. They have 
 therefore, in all probability, like the optic thalami, some connection 
 with sensation and volition ; but the precise nature of this connec- 
 tion is at present altogether unknown. 
 
 Hemispheres. — The hemispheres, or the cerebral ganglia, con- 
 stitute in the human subject about nine-tenths of the whole mass 
 of the brain. Throughout their whole extent they are entirely 
 destitute, as we have already mentioned, of both sensibility arid ex- 
 citability. Both the white and gray substance may be wounded, 
 burned, lacerated, crushed, or galvanized in the living animal, with- 
 out exciting any convulsive movement or any apparent sensation. 
 In the human subject a similar insensibility has been observed 
 when the substance of the hemispheres has been exposed by acci- 
 dental violence, or in the operation of trephining. 
 
 Very severe mechanical injuries may also be inflicted upon the 
 hemispheres, even in the human subject, without producing any 
 directly fatal result. One of the most remarkable instances of this 
 fact is a case reported by Prof. William Detmold, of New York,' in 
 
 « 
 
 > Am, Journ. of Med. Sci., January, 1850. 
 
420 THE BRAIN, 
 
 which an abscess in the anterior lobe of the brain was opened by an 
 incision passing -through the cerebral substance, not only without 
 any immediate bad effect, but with great temporary relief to the 
 patient. This was the case of a laborer who was struck on the left 
 side of the forehead by a piece of falling timber, which produced a 
 compound fracture of the skull at this part. One or two pieces of 
 bone afterward became separated and were removed, and the wound 
 subsequently healed. Nine weeks after the accident, however, 
 headache and drowsiness came on ; and the latter symptom, becom- 
 ing rapidly aggravated, soon terminated in complete stupor. At 
 this time, the existence of an abscess being suspected, the cicatrix, 
 together with the adherent portion of the dura mater, was dissected 
 away, several pieces of fractured bone removed, and the surface of 
 the brain exposed. A knife was then passed into the cerebral sub- 
 stance, making a wound one inch in length and half an inch in 
 depth, when the abscess was reached and over two ounces of pus 
 discharged. The patient immediately aroused from his comatose 
 condition, so that he was able to speak ; and in a few days reco- 
 vered, to a very considerable extent, his cheerfulness, intelligence, 
 and appetite. Subsequently, however, the collection of pus re- 
 turned, accompanied by a renewal of the previous symptoms ; and 
 the patient finally died at the end of seven weeks from the time of 
 opening the abscess. 
 
 Another and still more striking instance of recovery from severe 
 injury of the brain is reported by Prof. H. J. Bigelow in the 
 American Journal of Medical Sciences for July, 1850. In this case, a 
 pointeS iron bar, three feet and a half in length, and one inch and a 
 quarter in diameter, was driven through the patient's head by the 
 ipremature blasting of a rock. The bar entered the left side of the 
 face, just in front of the angle of the jaw, and passed obliquely 
 'Upward, inside the zygomatic arch and through the anterior part 
 of i^he cranial cavity, emerging from the top of the frontal bone on 
 the median line, just in front of the point of union of the coronal 
 and sagittal sutures. The patient was at first stunned, but soon 
 rec&Vered himself so far as to be able to converse intelligently, rode 
 home in a common cart, and with a little assistance walked up stairs 
 to his room. He became delirious within two days after the acci- 
 dent, and subsequently remained partly delirious and partly coma- 
 tose for about three weeks. He then began to improve, and at the 
 end of rather more than two months from the date of the injury, 
 was able to walk' about. At the end of sixteen months he was in 
 
HEMISPHEBKS. 421 
 
 perfect health, with the wounds healed, and with the mental and 
 bodily functions entirely unimpaired, except that sight was perma- 
 nently lost in the eye of the injured side. 
 
 The hemispheres, furthermore, are not the seat of sensation or of 
 volition, nor are. they immediately essential to the continuance of 
 life. In quadrupeds, the complete removal of the hemispheres is 
 attended with so much hemorrhage that the operation is generally 
 fatal from this cause within a few minutes. In birds, however, it 
 may be performed without any immediate danger to life. Longet 
 has removed the hemispheres in pigeons and fowls, and has kept 
 these animals afterward for several days, with most of the organic 
 functions unimpaired. We have frequently performed the same 
 experiment upon pigeons, with a similar favorable result. 
 
 The effect of this mutilation is simply to plunge the animal into 
 a state of profound stupor, in which he is almost entirely inatten- 
 tive to surrounding objects. The bird remains sitting motionless 
 upon his perch, or standing upon the ground, with the eyes closed, 
 and the head sunk between the shoulders. (Fig. 138.) The plu- 
 
 Fig. 138. 
 
 Pigeon, after Removal of the Heuiepheres. 
 
 mage is smooth and glossy, but is uniformly expanded, by a kind 
 of erection of the feathers, so that thfe body appears somewhat 
 puffed out, and larger than natural. Occasionally the bird opens 
 his eyes with a vacant stare, stretches his neek, perhaps shakes his 
 bill' once or twice, or smooths down the feathers upon his shoulders, 
 and then relapses into his former apathetic condition. This state 
 of immobility, however, is not accompanied by the loss of sight, of 
 
422 THE BRAirr. 
 
 hearing, or of ordinary sensibility. All these functions remain, as 
 •well as that of voluntary motion. If a pistol be discharged behind 
 the back of the animal, he at once opens his eyes, moves his head 
 half round, and gives evident signs of having heard the report ; hut 
 he immediately becomes quiet again, and pays no farther attention 
 to it. Sight is also retained, since the bird will sometimes fix its 
 eye on a particular object, and watch it for several seconds together.' 
 Longet has even found that by moving a lighted candle before the 
 animal's eyes in a dark place, the head of the bird will often follow 
 the movements of the candle from side to side or in a circle, showing 
 that the impression of light is actually perceived by the sensorium. 
 Ordinary sensation also remains, after removal of the hemispheres, 
 together with voluntary motion. If the foot be pinched with a 
 pair of forceps, the bird becomes partially aroused, moves uneasily 
 once or twice from side to side, and is evidently annoyed at the 
 irritation. ' 
 
 The animal is still capable, therefore, after removal of the hemi- 
 spheres, of receiving sensations from external objects. But these 
 sensations appear to make upon him no lasting impression. He is 
 incapable of connecting with his perceptions any distinct succession 
 of ideas. He hears, for example, the report of a pistol, but he is not 
 alarmed by it ; for the sound, though distinctly enough perceived, 
 does not suggest any idea of danger or injury. There is accord- 
 ingly no power of forming mental associations, nor of perceiving 
 the relation between external objects. The memory, more particu- 
 larly, is altogether destroyed, and the recollection of sensation is 
 ' not retained from one moment to another. The limbs and muscles 
 are still under the control of the will ; but the will itself is inactive, 
 because apparently it lacks its usual mental stimulus and direction. 
 The powers which have been lost, therefore, by destruction of the 
 cerebral hemispheres, are altogether of a mental or intellectual 
 character ; that is, the power of comparing with each other different 
 ideas, and of perceiving the proper relation between them. 
 
 The same result is well known to follow, in the human subject, 
 from injury or disease of these parts. A disturbance of the mental 
 powers has long been redognized as the ordinary consequence of 
 lesions of the brain. In cases q{ impending apoplexy, for example, 
 or of softening of the cerebral substance, among the earliest and 
 most constant . phenomena is a loss or impairment of the memory. 
 The patient forgets the names of particular objects or of particular 
 persons"; or he is unable to calculate numbers with his usual facility. 
 
HEMISPHEEES. 423 
 
 His mental derangfement is often shown in the undue estimate which 
 he forms of passing events. He is no longer able to appreciate the 
 true relation between different objects and different phenomena. 
 Thus, he will show an exaggerated degree of solicitude about a 
 trivial occurrence, and will pay no attention to other matters of 
 real importance. As the difficulty increases, he becomes careless 
 of the directions and advice of his attendants, and must be watched 
 and managed like a child or an imbecile. After a certain period, 
 he no longer appreciates the lapse of time, and even loses the dis- 
 tinction between day and night. Finally, when the injury to the 
 hemispheres is complete, the senses may still remain active and 
 impressible, while the patient is completely deprived of intelligence, 
 memory, and judgment. 
 
 If we examine the comparative development of the hemispheres 
 in difi'erent species of animals, and in different races of men, we 
 shall find that the size of these ganglia corresponds very closely 
 with the degree of intelligence possessed by the individual. We 
 have already traced, in a preceding chapter, the gradual increase, 
 in size of the hemispheres in fish, reptiles, birds, and quadrupeds : 
 four classes of animals which may be arranged, with regard to the 
 amount of intelligence possessed by each, in precisely the same 
 order of succession. Among quadrupeds^ the elephant has much 
 the largest and most perfectly formed cerebrum, in proportion.' to 
 the size of the entire body ; and of all quadrupeds he is proverbially 
 the most intelligent and the most teachable.. It is important to 
 observe in this connection, that the kind of intelligence which 
 characterizes the elephant and some other of the lower animals, 
 and which- most nearly resembles that of man, is a teachable intelli- 
 gence ; a very different thing from the intelligence which depends 
 upon instinct, such as that of insects, for example, or birds of pas- 
 sage. Instinct is unvaTying, and always does the same thing in the 
 same manner, with endless repetition ; but intelligence is a power 
 which adapts itself to new circumstances, and enables its possessor, 
 by comprehending and retaining new ideas, to profit by experience. 
 It is this quality which distinguishes the higher classes of animals 
 from the lower ; and which, in a very much greater degree, con- 
 stitutes the intellectual superiority of man himself. The size of 
 the cerebrum in man is accordingly very much greater, in propor- 
 tion to that of the entire body, than in any of the lower animals ; 
 while other parts of the brain, on the contrary, such as the olfactory 
 ganglia or the optic tubercles, are frequently smaller in him than 
 
424 THE BEAIN. 
 
 in them. For wliile mau is superior in general intelligence to all 
 the lower animals, he, is inferior to many of them in the acutenesa 
 of the special senses. 
 
 As a general rule,, also, the size of the cerebrum in different 
 races and in different individuals corresponds with the grade of 
 their intelligence. The size of the cranium, as compared with that 
 of the face, is smallest in the savage negro and Indian tribes ; larger 
 in the civilized or semi-civilized Chinese, Malay, Arab, and Japan- 
 ese ; while it is largest of all in the enlightened European races. 
 This difference in the development of the brain is not probably an 
 effect bf long-continued civilization or otherwise ; but it is, on the 
 contrary, the superiority in cerebral development which makes 
 some races readily susceptible of civilization, while others are 
 either altogether incapable of it, or can only advance in it to a 
 certain limit. Although all races therefore may,' perhaps, be said 
 to start from the same level of absolute ignorance, yet after the 
 lapse of a certain time one race will have advanced farther in 
 civilization than another, owing to a superior capacity for improve- 
 ment, dependent on original organization. 
 
 The same thing is true with regard to different individuals. At 
 birth, all men are equally ignorant ; and yet at the end of a certain 
 period one will have acquired a very much greater intellectual 
 power than another, even under similar conditions of training, 
 education, &c. He has been able to accumulate more information 
 from the same sourqes, and to use the same experience to better 
 advantage than his associates; and the result of this is a certain 
 intellectual superiority, which becomes still greater by its own 
 exercise. This superiority, it. will be observed, lies not so much 
 in the power of perceiving' external objects and events, And of re- 
 cognizing the connection between them, as in that of drawing con- 
 clusions from one fact to another, and of adapting to new combina- 
 tions the knowledge which has already been acquired. 
 
 It is this particular kind of intellectual difference, existing in a 
 marked degree, between animals, races, and individuals, which cor- 
 responds with the difference in development of the cerebral hemi- 
 spheres. We have, therefore, evidence from three different sources 
 that the cerebral hemispheres are the seat of the reasoning powers, 
 or of the intellectual faculties proper. First, when these ganglia 
 are removed in the lower animals, the intellectual faculties are the 
 only ones which are lost. Secondly, injury to these ganglia) in the 
 human subject, is followed by a corresponding impairment of the 
 
HEMISPHERES. 425 
 
 same faculties. Thirdly, in different species of animals, as well as 
 in different races of men and in different individuals, the develop- 
 ment of these faculties is in proportion to that of the cerebral 
 hemispheres. 
 
 When we say, however, that the hemispheres are the seat of the 
 intellectual faculties, of memory, reason, judgment, and the like, 
 we do not mean that these faculties are, strictly speaking, located 
 in the substance of the hemispheres, or that they belong directly to 
 the matter of which the hemispheres are composed, ^he hemi- 
 spherical ganglia are simply the instruments through which the 
 intellectual powers manifest themselves, and which are accordingly 
 necessary to their operation. If these instruments be imperfect in 
 structure, or be damaged in any manner by violence or disease, the 
 manifestations of intelligence are affected in a corresponding degree. 
 So far, therefore, as the mental faculties are the subject of physio- 
 logical research and experiment, they are necessarily connected 
 with the hemispherical ganglia; and the result of investigation 
 shows this connection to be extremely intimate and important in 
 its character. 
 
 There are, however, various circumstances which modify, in 
 particular cases, the general rule given above, viz., that the larger 
 the cerebrum the greater the intellectual superiority. The func- 
 tional activity of the brain is modified, no doubt, by its texture as 
 well as by its size ; and an increased excitability may compensate, 
 partially or wholly, for a deficiency in bulk. This fact, is some- 
 times illustrated in the case of idiots. There are instances where 
 idiotic children with small brains are less imbecile and helpless 
 than others with a larger development, owing to a certain vivacity 
 and impressibility of organization which take the place, to a certain 
 extent, of the purely intellectual faculties. 
 
 This was the case, in a marked degree, with a pair of dwarfed 
 and idiotic Central American children, who were exhibited some 
 years ago. in various parts of the United States, under the name of 
 the "Aztec children." They were a boy and a girl, aged respectively 
 about seven and five years. The boy was 2 feet 9f inches high, and 
 weighed a little over 20 pounds. The girl was 2 feet 5J inches 
 high, and weighed 17 pounds. Their bodies were tolerably well 
 proportioned, but the cranial cavities, as shown by the accompany- 
 ing portraits, were extremely small. 
 
 The antero-posterior diameter of the boy's head was only 4J 
 inches, the transverse diameter less than 4 inches. The antero- 
 
426 THE BRAIN. 
 
 posterior diameter of the girl's head was 4J inches, the transverse 
 diameter only 3f inches. The habits of these children, so far as 
 regards feeding and taking care of themselves, were those of chil- 
 
 'Pi 
 
 Fig. 139. 
 
 
 Aztec Chii.dkeh. — Taken from life, at five and seven years of age. 
 
 dren two or three years of age. They were incapable of learning 
 to talk' and could only repeat a few isolated words. Notwithstand- 
 ing, however, the extremely limited range of their intellectual 
 powers, these children were rgpiarkably vivacious and excitable. 
 While awake they were in almost constant motion, and any new 
 object or toy presented to them immediately attracted their atten- 
 tion, and evidently awakened a lively curiosity. They were ac- 
 cordingly easily influenced by proper management, and understood 
 readily the meaning of those who addressed them, so far as this 
 meaningcould be conveyed by gesticulation and the tones of the 
 voice. Their expression and general appearance, though decidedly 
 idiotic, were not at all disagreeable or repulsive ; and they were 
 much less troublesome to the persons who had them in charge than 
 is often the case with idiots possessing a larger cerebral development. , 
 
 It may also be observed that the purely intellectual or reasoning 
 powers are not the only element in the mental superiority of certain 
 races or of particular individuals over their associates. There is 
 also a certain rapidity of perception and strength of will which may 
 sometimes overbalance greater intellectual acquirements and more 
 cultivated reasoning powers. These, however, are different facul- 
 ties from the latter ; and occupy, as we shall hereafter see, different 
 parts of the encephalon. 
 
 A very remarkable physiological doctrine, dependent partly on 
 the foregoing facts, was brought forward some years ago 'by Gall 
 
HEMISPHERES. 427 
 
 and Spurzheim, under the name of Phrenology. These observers 
 recognized the fact that the intellectual powers are undoubtedly- 
 seated in the brain, and that the development of the brain is, as a 
 general rule, in correspondence with the activity of these powers. 
 They noticed also that in other parts of the nervous system, different 
 functions occupy different situations; and regarding the mind as 
 made up of many distinct mental faculties, they conceived the idea 
 that these different faculties might be seated in different parts of 
 the cerebral mass. If so, each separate portion of the brain would 
 undoubtedly be more or less developed in proportion to the activity 
 of the mental trait or faculty residing in it. The shape of the head 
 would then vary in different individuals, in accordance with their 
 mental peculiarities ; and the character and endowment? of the in- 
 dividual might therefore be estimated from an examination of the 
 elevations and depressions on the surface of the cranium. 
 
 Accordingly, the authors of this doctrine endeavored, by examin- 
 ing the heads of various individuals whose character was already 
 • known, to ■ ascertain the location of the different mental faculties. 
 In this manner they finally, succeeded, as they supposed, in accom- 
 plishing their object ; after which they prepared a chart, in which 
 the surface of the cranium was mapped out into some thirty or forty 
 different regions, corresponding with as many different mental traits 
 or faculties. With the assistance of this chart it was thought that 
 phrenology might be practised as an art ; and that, by one skilled ^ 
 in its application, the character of a stranger might be discovered 
 by simply examining the external conformation of his head. 
 
 We shall not expend much time in discussing the claims of phre- 
 nology to rank as a science or an art, since we believe that it has 
 of late years been almost wholly discarded by scientific men, owing 
 to the very evident deficiencies of the basis upon which it was 
 founded. Passing over, therefore, many minor details, we will 
 merely point out, as matters of physiological interest, the principal 
 defects which must always prevent the establishment of phrenology 
 as a science, and its application as an art. 
 
 First, though we have no reason for denying that different parts 
 of the brain may be occupied by different intellectual faculties, 
 there is no direct evidence which would show this to be the case. 
 Phrenologists include, in those parts of the brain which they em- 
 ploy for examination, both the cerebrum and cerebellum ; and they 
 justly regard the external parts of these bodies, viz., the layer of 
 gray matter which occupies their surface, as the ganglionic portion 
 
428 
 
 THE BRAIN. 
 
 in which must reside .more especially the nervous functions which 
 they possess. But this layer of gray matter, in each principal por- 
 tion of the brain, is continuous throughout. There is no anatomical 
 division or limit between its different parts, like those between 
 the different ganglia in other portions of the nervous system ; and 
 consequently such divisions of the cerebrum and cerebellum must 
 be altogether arbitrary in character, and not dependent on any 
 anatomical basis. 
 
 Secondly, the only means of ascertaining the location of the 
 different mental traits, supposing them to occupy different parts of 
 the brain, would be that adopted by Gall and Spurzheim, viz., to 
 make an accurate comparison, in a suf&cient number of cases, of the 
 form of the head in individuals of known character. But the prac- 
 tical difficulty of accomplishing this is very great. It requires a 
 long acquaintance and close observation to learn accurately the 
 character of a single person ; and it is in this kind of observation, 
 more than in any other, that we are proverbially liable to mistakes. 
 It is extremely improbable, therefore, that either Gall or Spurzheim 
 could, in a single lifetime, have accomplished this comparison in so 
 many instances as to furnish a reliable basis for the construction of 
 a phrenological chart. 
 
 A still more serious practical difficulty, however, is tie following. 
 The different intellectual faculties being supposed to reside 'in the 
 layer of gray substance constituting the surfaces of the cerebrum 
 
 and cerebellum, they must of course be 
 distributed throughout this layer, where- 
 ever it exists. Gall and Spurzheim 
 located all the mental faculties in those 
 parts of the brain which are accessible 
 to external exploration. An examina- 
 tion of different sections of the . brain 
 will show, however, that the greater por- 
 tion of the gray substance is so placed, 
 that its quantity cannot be estimated by 
 an external examination through the 
 skull. The only portions which are 
 exposed to such an examination are the 
 upper and lateral portions of the con- 
 vexities of the hemispheres, together 
 with the posterior edge and part of the 
 under surface of the cerebellum. (Fig. 140.) A very extensive 
 
 Fig. 140. 
 
 Diagram of the Br AiH ik 6ITD, 
 showing those portions which are ex- 
 posed to examination. 
 
HKMISPHEEES, 
 
 429 
 
 portion of the cerebral surface, however, remains concealed in such 
 a manner that it cannot possibly be subjected to examination, viz., 
 the entire base of the brain, with the under surface of the ante- 
 rior and middle lobes (i, 2); the upper surface of the cerebellum 
 (3) and the inferior surface of the posterior lobe of the cerebrum 
 which covers it (4) ; that portion of the cerebellum situated alaove the 
 medulla oblongata (5) ; and the two opposite convoluted surfaces in 
 the fissure of Sylvius (e, 1), where the anteiior and middle lobes of 
 the cerebrum lie in contact with each other. The whole extent, 
 also, of the cerebral surfaces which are opposed to each other in the 
 great longitudinal fissure (Fig. 141), throughout its entire length, 
 are equally protected by their position, and 
 concealed from external examination. The 
 whole of the convoluted surface of the brain 
 must, however, be regarded as of equal im- 
 portance in the distribution of the mental 
 qualities; and yet it is evident that not 
 liiore than one-third or ©ne-quarter of this 
 surface is so placed that it can be examined 
 by external manipulation. It must further- 
 more be recollected that the gray matter of 
 the cerebrum and cerebellum is everywhere 
 convoluted, and that the convolutions pene- 
 trate to various depths in the substance of 
 the brain. Ev-en if we were able to feel, therefore, the external 
 surface of the brain itself, it would not be the entire convolutions, 
 but only their superficial edges, that we should really be able to 
 examine. And yet the amount of gray matter contained in a given 
 space depends quite as much upon the depth to which the convolu- 
 tions penetrate, as upon the prominence of their edges. 
 
 While phrenology, therefore, is partially founded upon acknow- 
 ledged physiological facts, there are yet essential deficiencies in its 
 scientific basis, as well as insurmountable difBculties in the way of 
 its practical application. 
 
 Transverse section of B r a I N, 
 showing depth of great longi- 
 tudinal flssare, at a. 
 
 Cerebellum. — The cerebellum is the second ganglion of the 
 encephalon, in respect to size. If it be examined, moreover, in 
 regard to the form and disposition of its convolutions, it will be 
 seen that these are much more complicated and more numerous 
 than in the cerebrum, and penetrate much deeper into its substance. 
 Though the cerebellum therefore is smaller, as a whole, than the 
 
430 THE BKAIN. 
 
 cerebrum, it contains, in proportion to its size, a mucli larger quan- 
 tity of gray matter. 
 
 In examining the comparative development of the brain, also, in 
 different classes and species of animals, we find that the cerebellum 
 nearly always keeps pace, in this respect, with the cerebrum. These 
 facts would lead us to regard it as a ganglion haitily secondary in 
 importance to the cerebrum itself. 
 
 Physiologists, however, have thus far failed to demonstrate the 
 nature of its function with the same degree of precision as that of 
 many other parts of the brain. The opinion of Gall, which located 
 in the cerebellum the sexual impulse and instincts, is at the present 
 day generally abandoned ; for the reason that it has not been found 
 to be sufficiently supported by anatomical and exiperimental facts, 
 many of which are indeed directly opposed to it. The opinion 
 which has of late years been received with the most favor is that 
 first advocated by Elourens, which attributes to the cerebellum the 
 power of associating or "co-ordinating" the different voluntary 
 movements. 
 
 It is evident, indeed, that such a power does actually reside in 
 some part of the nervous system. No movements are effected by 
 the independent contraction of single muscles; but always by 
 several muscles acting in harmony with each other. The number 
 and complication of these associated movements vary in different 
 classes of animals. In fish, for example, progression is accom- 
 plished in the simplest possible manner, viz., by the lateral flexion 
 and extension of the vertebral column. In serpents it is much the 
 same. In frogs, lizards, and turtles, on the other hand, the four 
 jointed- extremities come into play, and' the movements are some- 
 what complicated. They are still more so in birds and quadrupeds; 
 and finally, in the human subject they become both varied and 
 complicated in the highest degree. Bveti in maintaining the ordi- 
 nary postures of standing and sitting, there are many different mus- 
 cles acting together, in each of which the degree of contraction, in 
 order to preserve the balance of the body, must be accurately pro- 
 portioned to that of the others. In the motions of walking and 
 running, or in the still more delicate movements of the hands and 
 fingers, this harmony of muscular action becomes still more evident, 
 and is seen also to be absolutely indispensable to the efliciency of 
 the muscular apparatus. 
 
 The opinion Which locates the above harmonizing or associating 
 power in the cerebellum was first suggested by the effects observed 
 
CEREBELLUM. 431 
 
 after experimentally injuring or destroying this part of the brain. 
 If the cerebellum be exposed in a living pigeon, and a portion of 
 its substance removed, the animal exhibits at once a peculiar un- 
 certainty in his gait, and in the movement of his wings. If the 
 injury be more extensive, he loses altogether the power of flight, 
 and can walk, or even stand, only with great difficulty. This is not 
 owing to any actual paralysis, for the movements of the limbs are 
 exceedingly rapid and energetic ; but is due to a peculiar want of 
 .control over the muscular contractions, precisely similar to that 
 which is seen in a man in a state of intoxication. The movements 
 of the legs and wings, though forcible and rapid, are confused and 
 blundering ; so that the animal cannot direct his steps to any par- 
 ticular spot, nor support himself in the air by flight. He reels and 
 tumbles, bilt can neither walk nor fly. 
 
 Fig. 142. 
 
 PlOEOK, AFTER REBOTAI. OF THE CEREBELLUM. 
 
 The senses and intelligence at the same time are unimpaired. It 
 is extremely curious, as first remarked by Longet, to compare the 
 different phenomena produced by removal of the cerebrum and 
 that of the cerebellum. If we do these operations upon two dif- 
 ferent pigeons, and place the animals side by side, it will be seen 
 that the first pigeon, from whom the cerebrum only has been re- 
 moved, remains standing firmly upon his feet, in a condition of 
 complete repose ; and that when aroused and compelled to stir, he 
 
432 THE BKAIN. 
 
 moves sluggishly and unwillingly, but otherwise acts in a perfectly 
 natural manner. The second pigeon, on the other hand, from 
 whom the cerebellum only has been taken away, is in a constant 
 state of agitation. He is eaisily terrified, and endeavors, frequently 
 with violent struggles, to escape the notice of those who are 
 watching him; but his movements are sprawling and unnatural, 
 and are evidently no longer under the effectual control of -the will. 
 (Fig. 142.) If the entire cerebellum be destroyed, the animal is 
 no longer capable of assuming or retaining any natural posture. 
 His legs and wings are almost constantly agitated with ineffectual 
 struggles, which are evidently voluntary in character, but are at 
 the same time altogether irregular and confused. Death generally 
 takes place after this operation within twenty-four hours. 
 
 "We have often performed the above operation, and always with 
 the same effect. Indeed there are few experiments that have been 
 tried upon the nervous system, which give results so uniform and 
 so constant as this. Taken by themselves, these results would 
 invariably sustain the theory of Flourens, which, indeed, is founded 
 entirely upon them. 
 
 But we have met with another very important fact, in this respect, 
 which has hitherto escaped notice. That is, that birds, which have 
 lost their power of muscular co-ordination from injury of the cere- 
 bellum, may recover this power in process of time, notwithstanding that 
 a large portion of the cerebellum has been permanently removed. 
 Usually such an operation upon the cerebellum, as we have men- 
 tioned above, is fatal within twenty-four hours, probably on account 
 of the close proximity of the medulla oblongata. But in' some 
 instances, the pigeons upon which we have operated have survived, 
 and in these cases the co-ordinating power became re-established. 
 
 In the first of these instances, about two-thirds of the cerebellum 
 was taken away, by an opening in the posterior part of the cranium. 
 Immediately after the operation, the animal showed all the usual 
 effects of the operation, being incapable of flying, walking, or even 
 standing still, but reeled and sprawled about in a perfectly helpless 
 manner. In the course of five or six days, however, he had regained 
 a very considerable control over the voluntary movements, and at 
 the end of sixteen days his power of muscular co-ordination was 
 so nearly perfect, that its deficiency, if any existed, was impercep- 
 tible. He was then killed ; and on examination, it was found that 
 his cerebellum remained in nearly the same condition as immediately 
 after the operation ; about two-thirds of its substance being deficient. 
 
CKBEBELLUM. 433 
 
 and no attempt Laving been made at regeneration of the lost parts. 
 Tlie accompanying figures, 143 ta 146, show the appearances, in 
 this case, as compared with the brain of a healthy pigeon. 
 
 We have also met with three other cases, similar to the above, in 
 which about one-half of the cerebellum was removed by operation. 
 The loss of co-ordinating power, immediately after the operation, 
 though less complete than in the instance above mentioned, was 
 perfectly well marked in character ; and in little more than a fort- 
 Pig. 143. Fig. 144 
 
 Braik of HEiLTHT F I OE OS— Profile Bkaim op Operated Pioeos— 
 
 Tiew. — 1- HtimUphere. 2. Optic tubercle, 3. Profile view — showing the matilatioa 
 
 Cerebeilam. 4. Optic uerTe. 5. Medalla ob- of cerebellam. 
 longata. 
 
 Fig. 145. Fig. 146. 
 
 Braim of Healthi Pioeos— Foste- Braik of Operated PioEoir— 
 
 rior view. Fo9teri# view — showing the matila- 
 
 tioa of cerebellum. 
 
 night the animals had nearly or quite recovered the natural control 
 of their motions. 
 
 These instances show, accordingly, that a large portion of the 
 cerebellum may be wanting without a porresponding deficiency of 
 the co-ordinating power. If the theory of Flourens be correct, 
 therefore, these cases can only be explained by supposing that 
 those parts of the cerebellum which remain gradually become en- 
 abled to supply the place of those which are removed. It is more 
 probable, however, that the loss of co-ordinating power, which, is 
 immediately produced by taking away a considerable portion of 
 this nervous centre, is to be regarded rather as the effect of the 
 sudden injury to the cerebellum as a whole, than as due to the mere 
 removal of a portion of its mass. 
 28 
 
434 THE BEAIN, 
 
 Morbid alterations of the cerebellum, furthermore, particularly 
 of a chronic nature, such as slow inflammations, abscesses, tumors, 
 &c., have often been observed in the human subject, without giving 
 rise to any marked disturbance of the voluntar/ movements. 
 
 On the other hand, many facts derived from comparative anatomy 
 seem to favor the opinion of Flourens. If we compare different 
 classes of animals with each other, as fish with reptiles, or birds 
 with quadrupeds, in which the developnjent and activity of the 
 entire nervous system vary extremely, the results of the comparison 
 ■ will be often contradictory. But if the comparison ,be made be- 
 tween different species in which the general structure and plan of 
 organization are similar, we often find the development of the cere- 
 bellum to correspond very closely with the perfection and variety 
 of the voluntary movements. The frog, for example, is an aquatic 
 reptile, provided with anterior and posterior extremities; but its, 
 movements, though rapid and vigorous, are exceedingly simple in 
 character, consisting of little else than flexion and extension of the 
 posterior limbs. The cerebellum in this animal is exceedingly 
 small, as compared with the rest of the brain ; being nothing more ■ 
 than a thin, narrow ribbon of nervous matter, stretched across the 
 upper part of the fourth ventricle. In the common turtle we have, 
 another aquatic reptile, where the movements of swimming, diving, 
 progression, &c., are accomplished by the consentarfBbus action of 
 anterior and posterior extremities, and where the motions of the 
 head and neck are also much more varied than in the frog. In 
 this instance the cerebellum is very much more bighly developed 
 than in the former. lit the alligator, again, a reptile whose motions, 
 both of the head, limbs, and tail, approach very closely to those of 
 the quadrupeds, the cerebellum is still larger in proportion to the 
 remaining ganglia of the encephalon. 
 
 The complete function of the cerebellum, accordingly, as a nerv- 
 ous centre, cannot be regarded as positively ascertained ; but so far 
 as we may rely on the results of direct experiment, this organ has 
 evidently such an intimate and peculiar connection with the volun- 
 tary movements, that a sudden and extensive injury inflicted upon 
 its substance is always followed by an immediate, though tempo- 
 rary, disturbance of the co-ordinating power. 
 
 TuBEBCDLA QuADRiGEMiNA.— These bodies, notwithstanding 
 their small size, are very important in regard to their function. 
 They give origin to the optic nerves, and preside, as ganglia, over 
 
TUBEECULA QUADRIGEMINA. 435 
 
 the sense of sight ; on -which account they are also known by thd 
 name of the " optic ganglia." Their development corresponds very 
 closely with that of the external organs of vision. Thus, they ard 
 large in fish, reptiles, and birds, in which the eyeball is for th«f 
 most part very large in proportion to the entire head; and are small 
 in quadrupeds and in man, where the eyeball is, comparatively, 
 speaking, of insignificant siae. Direct experiment also shows tha 
 close connection between the tubercula quadrigemina and the sense 
 of sight. Section of the optic nerve at any point between the 
 retina and the tubercles, produces complete blindness ; and destruc- 
 tion of the tubercles themselves has the same effect. But if the 
 division be made between the tubercles and the cerebrum, or if the 
 cerebrum itself be taken away while the tubercles are left un- 
 touched, vision, as we have already seen, still remains. It is the 
 tubercles, therefore, in which the impression of light is perceived. 
 So long as these ganglia are iminjured and retain their connection 
 with the eye, vision. remains. As soon as this connection is cut 
 off) or the ganglia themselves are injured, the power of vision is 
 destroyed. 
 
 The tubercula quadrigemina not only serve as nervous centres 
 for the perception of light, but a reflex action also takes place 
 through them, by which the quantity of light admitted to the eye 
 is regulated to suit the sensibility of the pupil. In darkness and 
 in twilight, or wherever the light is obscure and feeble, the pupil 
 is enlarged by relaxation of its circular fibres, so as to admit as 
 large a quantity of light as possible. On first coming into a dark 
 room, accordingly, everything is nearly invisible ; but gradually, 
 as the pupil dilates and as more light is admitted, objects begin to 
 show themselves with greater distinctness, and at last we can see 
 tolerably well in a place where we were at first unable to perceive 
 a single object. On the other hand, when the eye is exposed to an 
 unusually brilliant light, the pupil contracts and shuts out so mucTi 
 of it as would be injurious to the retina. 
 
 The above is a reflex action, in which the impression received by 
 the retina is transmitted along the optic nerve to the tubercula 
 quadrigemina. From the tubercles, a motor impulse is then sent 
 out through the motor nerves of the eye and the filaments dis- 
 tributed to the iris, and a contraction of the pupil takes place in 
 consequence. The optic nerves act here as sensitive fibres, which 
 convey the impression from the retina to the ganglion ; and if 
 they be irritated in any part of their course with the point of a 
 
436 
 
 THE BBAIK. 
 
 needle, the result is a contraction of the pupil. This influence is 
 not communicated directly from the nerve to the iris, but is first 
 sent inward to the tubercles, to be afterward reflected outward by 
 the motor nerves. So long as the eyeball remains in connection 
 %ith the brain, mechanical irritation of the optic nerve, as we have 
 shown above, causes contraction of the pupil ; but if the nerve be 
 divided, and the extremity which remains, in connection with the 
 ieyeball be subjected to irritation, no effect upon the pupil is pro- 
 duced. 
 
 The anatomical arrangement of the optic nerves, and the connec- 
 tions of the optic tubercles, are modified in a remarkable degree in 
 different animals, to correspond with the position of the two eyes. 
 In fish, for example, the eyes are so placed, on opposite sides of the 
 head, that their axes cannot be brought into parallelism with each 
 other, and the two eyes can never be directed together at the same 
 object. In these animals, the optic nerves cross each other at the 
 base of the brain without any intermixture of their fibres ; that 
 from the right optic tubercle passing to the left eye, and that from 
 the left optic tubercle passing to the right eye. (Fig. 147.) The two 
 
 Fig. 147. 
 
 Fig. 148. 
 
 Inferior Surface of Bbatit 
 OF Cod.— 1. Rlglit optic nerve. 2. Left 
 optic nerve. 3. Right optic tubercle. 4. 
 Left optic tabercle. 5, 6. Hemispheres. 
 7. Medulla oblongata. 
 
 Inferior Surface of Brain o? 
 Vowh.—l. Right optic nerve. 3 Left optic 
 nerve. 3. Right o|>tic tubercle. 4. Left 
 optic tubercle, ff, 6. Hemitipheres. 7. Me- 
 dulla oblongata. 
 
 nervous cords are here totally distinct from each other throughout 
 their entire length ; and are only connected, at the point of cross- 
 
TUBEBCULA QUADBIGEMINA. 437 
 
 ing, by intervening areolar tisSue. ' Impression* made on the right 
 eye must therefore be perceived on the left side of the brain; while 
 those which enter the left eye are conveyed to the right side of the 
 brain. 
 
 In birds, also, the axes of the two eyes are so widely divergent 
 that an object cannot be distinctly in focus for both of them at the 
 same time. The optic nerves are here united, and apparently sol- 
 dered together, at their point of crossing ; but the decussation of 
 their fibres is nevertheless complete. (Fig. 148.) The nervous fila- 
 ments coming from the left side pass altogether over to the right ; 
 and those coming from the right side pass over to the left. The 
 result of direct experiment on the crossed action of the tubercles in 
 these animals corresponds with the anatomical arrangement of the 
 nervous fibres. If one of the optic tubercles be destroyed in the 
 pigeon, complete blindness is at once produced in the eye of the 
 opposite side ; but vision remains unimpaired in the eye of the side 
 on which the injury was inflicted. 
 
 Fie. 14fl. 
 
 ConKBE OP Optic Nerves iH Man.— 1, 2. Eight and left eyeballs. 3. Decossltion or optic 
 nerves. 4, 4. Tnbercala qnadrigemina. 
 
 In the human %ilbject, on the other hand, where the visual axes 
 are parallel, and where both eyes are simultaneously directed toward 
 
438 THE BRAIN. 
 
 the same object, the optic nerves dedtssate with each other hi such a 
 manner as to form a connection between the two opposite sides, as 
 well as between each tubercle and retina of the same side. (Fig. 
 149.) This decussation, which is somewhat complicated, takes place 
 in the following manner. From each optic tubercle three different 
 bundles or " tracts" of nervous fibres are given ofl". One set passes 
 across transversely at the point of decussation, and, turning back- 
 ward, terminates in the tubercle of the opposite side ; another, cross- 
 ing diagonally, continues onward to the opposite eyeball ; while a 
 third passes directly forwal-d to the eyeball of the same side. A 
 fourth set of fibres, still, passes across in front of the decussation, 
 from the retina of one eye to that of the opposite side. We have, 
 therefore, by this arrangement, the two retinae, as well as the two 
 optic tubercles, connected with each other by commissural fibres ; 
 while each tubercle is, at the same time, connected both with its 
 own retina, and with that of the opposite side. It is undoubtedly 
 owing to these connections that when, in the human subject, the 
 eyes are directed in their proper axes, the .two retinae, as well as 
 the two optic tubercles, act as a single organ. Vision is single, 
 therefore, though there are two images upon the retinae. Double, 
 vision occurs only when the eyeballs are turned out of their proper 
 direction, so th^t the parallelism of their axes is lost, and the image 
 no longer falls upon corresponding parts of the two retinae. 
 
 Tuber Ankulake. — The collection of gray matter imbedded in 
 the deeper portions of the tuber annulare occupies a situation near 
 the central part of the brain, and lies directly in the course of the 
 ascending fibres of the^anterior and posterior columns of the cord. 
 This ganglion is immediately connected with the functions of sensa- 
 tion and voluntary niotion. "We have already seen that these func- 
 tions are not destroyed by taking away the cerebrum, and that they 
 also remain after removal of the cerebellum. According to the ex- 
 periments of Longet, even after complete removal of the olfactory 
 ganglia, the cereibrum, cerebellum, optic tubercles, corpora striata 
 and optic thalami, and when nothing remains in the cavity of the 
 cranium but the tuber annulare and the medulla oblongata, the 
 animal is still sensitive to external impressions, and will still en- 
 deavor by voluntary movements to escape from a painful irritation. 
 The same observer has found, however, that as soon as the ganglion 
 of the tuber annulare is broken up, all manifestations of sensation 
 and volition cease, and even consciousness no longer appears to 
 
MEDULLA OBLONGATA. 48® 
 
 exist. The only movements whieh then follo-w external irritation 
 are the occasional convulsive motions which are due to reflex action 
 of the spinal cord, and which may be readily distinguished from 
 those of a voluntary character. The animal, under these circum- 
 stances, is to all appearance reduced to the condition of. a dead 
 body, except for the movements of respiration and circulation, 
 which still go on for a certain time. The tuber annulare must 
 therefore be regarded as the ganglion by which impressions, con- 
 veyed inward through the nerves, are first converted into conscious 
 sensations ; and in which the voluntary impulses originate, which 
 stimulate the muscles to contraction. 
 
 We must carefully distinguish, however, in this respect, a simple 
 sensation from the ideas to which it gives origin in the mind, and 
 the mere act of volition from the train of thought which leads to 
 it. Both these purely mental operations taike place,' as we have 
 seen, in the cerebrum; for mere sensation and volition may exist 
 independently of any intellectual action, as they may exist after 
 the cerebrum has been destroyed. A sensation may be fe^t for 
 example, without our having the power of thoroughly appreciating 
 it, or of referring it to its proper source. This condition is often 
 experienced in a state of deep sleep, when, the body being exposed 
 to cold, or accidentally placed in a constrained position, we feel a 
 sense of suffering without being able to understand its cause. We 
 may even, under such circumstances, execute voluntary movements 
 to escape the cause of annoyance; but these movements, not being- 
 directed by any active intelligence, fail of accomplishing their. ob- 
 ject. We therefore remain in a state of discomfort until, on awak^ 
 ening, the activity of the reason arid judgment is restored, when the 
 offending cause is at once removed. . , 
 
 We distinguish, then, between the simple power of sensation, 
 and the power of fully appreciating a sensitive impression and of 
 drawing a conclusion from it. We distinguish also between the 
 intellectual process which leads us to decide upon^ a voluntary 
 movement, and the act of volition itself. The former must precede, 
 the latter must follow. The former takes place, so far as experi- 
 ment can show, in the cerebral hemispheres ; the latter, in the gan- 
 glion of the tuber annulare. 
 
 Medulla Oblongata.— The last remaining ganglion of the en- 
 cephalon is that of the medulla oblongata. This ganglion, it will 
 be remembered, is imbedded in the substance of the restiform body, 
 
MO THE BBAIN. 
 
 occupying the lateral and posterior portions of the medulla, at the 
 point of origin of the pneumogastric nerves. This portion of the 
 brain has long been known to be particularly essential to the pre- 
 servation of life ; so that it has received the name of the " vital 
 point," or the "vital knot." All the other parts of the brain may 
 be injured or removed, as we have already seen, without the imme- 
 diate and necessary destruction of life ; but so soon as the medulla 
 oblongata is broken up, and its ganglion destroyed, respiration 
 ceases instantaneously, and the circulation also soon comes to an 
 end. Eemoval of the medulla oblongata produces, therefore, as its 
 immediate and direct result, a stoppage of respiration : and death 
 takes place principally as a consequence of this fact. 
 
 Flourens and Longet have determined, with considerable accu- 
 racy, the precise limits of this vital spot in the medulla oblongata. 
 Flourens ascertained that in rabbits it extended from just above 
 the origin of the pneumogastric nerve, to a level situated three lines 
 and a half below this origin. In larger animals, its extent is pro- 
 portionally increased. Longet ascertained, furthermore, that the 
 properties of the medulla were not the same throughout its entire 
 thickness ; but that its posterior and anterior parts might be de- 
 stroyed with comparative impunity, the peculiarly vital spot being 
 confined to the intermediate portions. This vital point accordingly 
 is situated in the layer of gray matter, imbedded in the thickness 
 of the restiform bodies, which has been previously spoken of as 
 giving origin to the pneumogastric nerves. 
 
 The precise nature of the connection between this ganglion and 
 J;he function of respiration may be described as follows. The 
 movements of respiration, which follow each other with incessant 
 regularity through the whole period of life, are not voluntary 
 movements. We may to a certain extent, hasten or retard them 
 at will, but our power over them, even in this respect, is extremely 
 limited; and in point of fact they are performed, during thg greater 
 part of the time, in a perfectly quiet and regular manner, without 
 our volition and even without our consciousness. They continue 
 uninterruptedly through the deepest' slumber, and even in a con- 
 dition of insensibility from accident or disease. 
 
 These movements are the result of a reflex action taking place 
 through the medulla oblongata. The impression which gives rise 
 to them originates principally in the lungs, from the accumulation 
 of carbonic acid in the pulmonary vessels and air-cells, is trans- 
 mitted by the pneumogastric nerves to the medulla, and is thence 
 
MEDULLA OBLONGATA. 441 
 
 reflected along the motor nerves to the respiratory muscles. These 
 muscles are then called into action, producing an expansion of 
 the chest. The impression so conveyed to the medulla is usually 
 unperceived by the consciousness. It is generally converted directly 
 into a motor impulse, without attracting our attention or .giving 
 rise to any conscious sensation. Eespiration, accordingly, goes on 
 perfectly well without our interference and without our knowledge. 
 The nervous impression, however, conveyed to the medulla, though 
 usually imperceptible, may be made evident at any time by volun- 
 tarily suspending the respiration. As the carbonic acid begins to 
 accumulate in the blood and in the lungs, a peculiar sensation makes 
 itself felt, which grows stronger and stronger with every moment, 
 and impels us to recommence the movements of inspiration. This 
 peculiar sensation, entirely different in character from any other, is 
 designated by the French under the name of "besoin de respirer." 
 It becomes more urgent and distressing, the longer respiration is 
 suspended, until finally the impulse to expand the chest can no 
 longer be resisted by any effort of the will. 
 
 During ordinary respiration, therefore, each inspiratory move- 
 ment is excited by the partial vitiation of the air contained in the 
 lungs. As soon as a new supply has been inhaled, the impulse to 
 respire is satilfied, the muscles relax, anS the chest collapses. In 
 a few seconds the previous condition recurs and tbfcame move- 
 ments are repeated, producing in this way a regular alternation of 
 inspirations and expirations. 
 
 Since the movements of respiration are performed partly by the 
 diaphragm and partly by the intercostal muscles, they will be 
 differently modified by injuries of the nervous system, according to 
 the spot at which the injury is inflicted. If the spinal cord, for 
 example, be divided or compressed in the lower part of the neck, 
 all the intercostal muscles will be necessarily paralyzed, and respi- 
 ration will then be performed entirely by the diaphragm. The 
 chest in these cases remaining motionless, and the abdomen alone 
 rising and falling with the movements of the diaphragm, such 
 respiration is called " abdominal" or " diaphragmatic" respiration. 
 It is a common symptom of fracture of the spine in the lower 
 cervical region. If the phrenic nerve, on the other hand, be 
 divided, the diaphragm will be paralyzed, and respiration will then 
 be performed altogether by the rising and falling of the ribs. It 
 is then called "thoracic" or "costal" respiration. If the injury 
 inflicted upon the spinal cord be above the origin of the second 
 
442 THE BRAIN. 
 
 and third cervical nerves, botli the phrenic and intercostal nerves 
 are at once paralyzed, and death necessarily takes place from suf- 
 focation. The attempt ,at respiration, however, still continues in 
 these cases, showing itself by ineffectual inspiratory movements of 
 the mouth and nostrils. Finally, if the medulla itself be broken up 
 by .a steel instrument introduced through the foramen magnum, so 
 as to destroy the nervous centre in which the above reflex action 
 takes place, both the power and the desire to breathe are at once 
 taken away. No attempt is made at inspiration, there is no strug- 
 gle, and no appearance , of suffering. The animal dies simply- by 
 a want of aeration of the blood, which leads in a few moments to 
 an arrest of the circulation. 
 
 It is owing to the above action of the medulla oblongata that in- 
 juries of this part are so promptly and constantly fatal. When the 
 "neck is broken," as in hanging or by sudden falls upon the head, . 
 a rupture takes place of the transverse ligament of the atlas ; the 
 head, together with the first cervical vertebra, is allowed to slide 
 forward, and the medulla is compressed between the odontoid pro- 
 cess of the axis in front and the posterior part of the arch of the 
 atlas behind. In cases of apoplexy, where any part of the hemi- 
 spheres, corpora striata, or optic thalami, is the seat of the hemor- 
 rhage, the patient generflly lives at least twelve hdurs; but if the 
 hemorrhagqjpikes place into the medulla itself, or at the base of th% 
 brain in its immediate neighborhood, so as to compress its sub- 
 stance, death follows instantaneously, and by the same mechanism 
 as where the medulla is intentionally destroyed. 
 
 An irregularity or want of correspondence in the movements of 
 respiration is accordingly found to be one of the most threatening 
 of all symptoms in affections of the brain. A disturbance or sus- 
 pension of the intellectual powers does not indicate necessarily any 
 immediate danger to life. Even sensation and volition may be im- 
 pa^f'ed without serious and direct injury to the organic functions. 
 These symptoms only indicate the threatening progress of the dis- 
 ease, and show that it is gradually approaching the vital centre. It 
 is common to see, however, as the medulla itself begins to be impli- 
 cated, a paralysis first showing itself in the respiratory movements 
 of the nostrils and lips, while those of the chest and abdomen still 
 go on as usual. The cheeks are then drawn in with every inspira- 
 tion and puffed out sluggishly with every expiration, the nostrils 
 themselves sometimes participating in these unnatural movements. 
 A still more threatening symptom, and one which frequently pre- 
 
MEDULLA OBLOifGATA. 443 
 
 # 
 
 cedes death, is an irregular, hesitating respiration, which sometimes 
 attracts the attention of the physician, even before the remaining 
 cerebral functions are seriously impaired. These phenomena de- 
 pend on the coimection between the respiratory movements and the 
 reflex action of the*medulla oblongata. 
 
 "We have now, in studying the functions of various parts of the 
 cerebro-spinal system, become familiar with three different kinds of 
 reflex action. 
 
 The first is that of the spinal cord. Here, there is no proper 
 sensation and no direct consciousness of the act which is performed. 
 It is simply a nervous impression, coming from the integument, 
 and transformed by the gray matter of the spinal cord into a motor 
 impulse destined for the muscles. This action will take place after 
 the removal of the hemispheres and the abolition of consciousness, 
 as well as in the ordinary condition. The respiratory action of the 
 medulla oblongata is of the same general character ; that is, it is 
 not necessarily connected with either volition or consciousness. 
 The only peculiarity in this instance is that the original|bervous 
 impression is of a special character, and its influence is finally 
 exert^ upon a special muscular apparatus. Actions of this nature 
 are termed, par excellence, reflex actions. 
 
 The second kind of reflex action takes place in the tuber annu- 
 lare. Here the nervous impression, which is conveyed inward 
 from tbe integument, instead of stopping at the spinal cord, passes 
 onward to the tuber annulare, where it first gives rise to a con- 
 scious sensation ; and this sensation is immediately followed by a 
 voluntary act. Thus, if a crumb of .bread fall into the larynx, the 
 sensation produced by it excites the movement of coughing. The 
 sensations of hunger and thirst excite a desire for food and drink. 
 The sexual impulse acts in precisely the same manner; the percep- 
 tion of particular objects giving rise immediately to special desires 
 of a sexual character. 
 
 It will be observed, in these instances, that in the first place, 
 the nervous sensation must be actually perceived, in order to pro- 
 duce its effect; and in the second place that the action which 
 follows is wholly voluntary in character. But the most important 
 peculiarity, in this respect, is that the voluntary impulse follows 
 directly upon the receipt of the sensation. There is no intermediate 
 reasoning or intellectual process. "We do not cough because we 
 know that this is the most effectual way to clear the larynx ; but 
 simply because we are impelled to do so by the sensation which is 
 
444 THE BRAIN. 
 
 felt at the time. "We do not take food or drink because we know 
 that they are necessary to support life, much less because we under- 
 stand the mode in which they accomplish this object; but merely 
 because we desire them whenever we feel the sensation of hunger > 
 and thirst. 
 
 All actions of this nature are termed instinctive. They are volun- 
 tary in character, but are performed blindly ; that is, without any 
 idea of the ultimate object to be accomplished by them, and simply 
 in consequence of the receipt of a particular sensation. Accord- 
 ingly experience, judgment, and adaptation Ifeve nothing to do with 
 these actions. Thus the bee builds his cell on the plan of a mathe- 
 matical figure, without performing any mathematical calculation. 
 The silkworm wraps himself in a cocoon of his own spinning, 
 certainly without knowing . that it is to afford him shelter during 
 the period of his metamorphosis.' The fowl incubates her eggs 
 and keeps them at the proper temperature for development, simply 
 because the sight of them creates in her a desire to do so. The 
 habits Hf these animals, it is true, are so arranged by nature, that 
 such instinctive actions are always calculated to accomplish an 
 ultimate object. But this calculation is not made by theapimal 
 himself, and does not form any part of his mental operations. 
 There is 'consequently no improvement in the mode of performing 
 such actions, and but little deviation under a variety of circufti- 
 stances. 
 
 The third kind of reflex action requires the co-operation of the 
 hemisphereg. Here, the nervous impression is not only conveyed 
 to the tuber annulare and converted into a sensation, but, still 
 following upward the course of the fibres to the cerebrum, it there 
 gives rise to a special train of ideas. We understand then the 
 external source of the sensation, the manner in which it is calcu- 
 lated to affect us, and how by our actions we may turn it to our 
 advantage or otherwise. The action which follows, therefore, in 
 these cases, is not simply voluntary but reasonable. It does not 
 depend directly upon the external sensation, but upon an intellec- 
 tual process which intervenes between the sensation and the voli- 
 tion. These actions are distinguished, accordingly, by a character 
 of definite contrivance, and a conscious adaptation of means to 
 ends ; characteristics which do not belong to any other operations 
 of the nervous system. 
 
 The possession of this kind of intelligence and reasoning power 
 is not confined to the human species. We have already seen that 
 
MEDULLA OBLONGATA. 445 
 
 there are many purely instinctive actions in man, as well as in 
 animals. It is no less true that in the higher animals there is often 
 the same exercise of reasoning power as in man. The degree of 
 this power is much less in them than in him, but its nature is the 
 same. Whenever, in an animal, we see any action performed with 
 the evident intention of accomplishing a particular object, to which 
 it is properly dfiapted, such an act is plainly the result of reason- 
 ing powers, not essentially different from our own. The establish- 
 ment of sentinels by gregarious animals, to warn the herd of the 
 approach of danger,the recollection of punishment inflicted for a 
 particular action, and. the subsequent avoidance or concealment of 
 that action, the teachability of many animals, and their capacity of 
 forming new habits or of improving the old ones, are all instances 
 of the same kind of intellectual power, and are quite different from 
 instinct, strictly speaking. It is this faculty which especially pre- 
 dominates over the others in the higher classes of animals, and 
 which finally, attains its maximum of development in the human 
 species. 
 
44:6 THE CRANIAL NEBVES. 
 
 CHAPTER V. • 
 
 THE CRANIAL NERVES. 
 
 In examining the cranial nerves, we shall find that although they 
 dt first seem quite different in their distribution and . properties 
 from the spinal nerves, yet they are in reality arranged for the 
 most part on the same plan, and may be studied in a- similar 
 manner. 
 
 At the outset, however, we find that there are three of the cra- 
 nial nerves, commonly so called, which must be arranged in a class 
 by themselves ; since they have no character in common with the 
 other nerves originating either from the brain or the spinal cord. 
 These are the three nerves of special sense; viz., the Olfactory, 
 Optic, and Auditory. They are, properly speaking, not so much 
 nerves as commissures, connecting different parts of the encephalic . 
 mass with each other. They are neither sensitive nor motor, in 
 the ordinary meaning of these terms ; but are capable of conveying 
 only the special sensation characteristic of the organ with which 
 they are connected, 
 
 Olfactoey Nerves. — We have already described the so-called 
 olfactory nerves as being in reality commissures, connecting the 
 olfactory ganglia with the central parts of the brain. The masses 
 situated upon the cribriform plate of the ethmoid bone are com- 
 posed of gray matter; and even the filaments which they send 
 outward to be distributed in the Schneiderian mucous membrane, 
 are gray and gelatinous in their texture, and quite different from 
 the fibres of ordinary nerves. The olfactory nerves are not very' 
 well adapted for direct experiment. It is, however, at least certain 
 with regard to them that they serve to convey the special sensation 
 of smell; that their mechanical irritation does not give rise to 
 either pain or convulsions; and finally that their destruction, 
 together with that of the olfactory ganglia, does not occasion any 
 paralysis nor loss of ordinary sensibility. 
 
THE CRANIAL NERVES. 447 
 
 Optic Nerves. — We have already given some account of these 
 nerves and their decussations, in connection with the history of the 
 tubercula quadrigemina.r They consist of rounded bundles of white 
 fibres, running between the tubercles and the retina. As the reti- 
 nae themselves are membranous expansions consisting mostly of 
 vesicular or cellular nervous matter, the optic nerves, or "tracts," 
 must be regarded as commissures connecting the retinae with the 
 tubercles. We have also seen that they serve, by some of their 
 fibres, to connect the two retinae with each other, as well as the two 
 tubercles with each other. 
 
 The optic nerves convey only the special impression of light from 
 without inward, and give origin to the reflex action, of the optic 
 tubercles, by which the pupil is made to contract. According to 
 Longet, the optic nerves are absolutely insensible to pain through- 
 out their entire length. When a galvanic current is passed through 
 the eyeball, or when the retina is touched in operations upon the 
 eye, the irritation has been found to produce the impression of lumi- 
 nous sparks and flashes, instead of an ordinary painful sensation. 
 The impression of colored rings or spots may be easily produced 
 by compressing the eye in particular ^jrections ; and a sudden 
 stroke upon the eyeball will often give rise to an apparent discharge 
 . of brilliant sparks. Division of the optic nerves produces complete 
 blindness, but does not destroy ordinary sensibility in any part of 
 the eye, nor occasion any muscular paralysis. 
 
 Auditory Nerves. — The nervous expansion in the cavity of 
 the internal ear contains, like the retina, vesicles or cells as well as 
 fibres ; and the auditory nerves are therefore to be regarded, like 
 the optic and ol&ctory, as commissural in their character. They 
 are also, like the preceding, destitute of ordinary sensibility. Ac- 
 cording to Longet, they may be injured or destroyed without giving 
 rise to any sensation of pain. They serve to convey to the brain 
 the special sensation of sound, and seem incapable of transmitting 
 any other. Longet" relates an experiment performed by Volta, in 
 which, by passing a galvanic current through the ears, the observer 
 experienced the sensation of an interrupted hissing noise, so long 
 as the connection of the wires was maintained. Inflammations 
 within the ear, or in its neighborhood, are often accompanied by 
 the perception of various noises, like the ringing of bells, the 
 
 > Traits de Physiologie, vol. ii. p 286. , 
 
448 
 
 THE CRANIAL NERVES. 
 
 washing of the waves, the humming of insects; sounds which have 
 no external existence, but which are simulated by the morbid irri- 
 tation of the auditory nerve. ^ 
 
 It is evident, from the facts detailed above, that the nerves of 
 special sense are neither motor or sensitive, properly speaking; 
 and that they are distinct in their nature from the ordinary spinal 
 nerves. 
 
 The remainder of the cranial nerves, however, present the 
 ordinary qualities belonging to the spinal nerves. Some of them 
 are exclusively motor in character, others exclusively sensitive; 
 while most of them exhibit the two properties, to a certain extent, 
 as mixed nerves. They may be conveniently arranged in three 
 pairs, according to the regions in which they are distributed, cor- 
 responding very closely with the motor and sensitive roots of the 
 spinal nerves. According to such a plan, the arrangement of the 
 cranial nerves would be as follows : — 
 
 1st FAIB. 
 
 2d FAIB. 
 3d FAIB. 
 
 J Cbaniai. Xebtes. 
 
 Nerves of Special Sense. 
 1. Olfaetory. 2. Optio. 3. Anditoiy. 
 Motor nerves. Sensitive Nerves. 
 
 ' Motor ocnii com. 
 Patheticus 
 Motor oc. eKtemns 
 Small root of 5th pair 
 Facial 
 
 Distributed to 
 
 Large root of 5th pair. Face. 
 
 J 
 
 Hypoglossal 
 Spinal accessory 
 
 Glossq-pharyngeal. 
 Fneumogastric. 
 
 Tongue. 
 Neck, &c. 
 
 The above arrangement of the cranial nerves is not absolutely 
 perfect in all its details. Thus, while the hypoglossal supplies the 
 muscles of the tongue alone, the glosso-pharyngeal sends part of 
 its sensitive fibres to the tongue and part to the pharynx ; and 
 while the large root of the 5th pair is mostly distributed in the 
 face, one of its branches, viz., the gustatory, is distributed to the 
 tongue. Notwithstanding these irregularities, however, the above 
 division of the cranial nerves is in the main correct, and will he 
 found extremely useful as an assistant in the study of their func- 
 tioi^s. 
 
 There is no impropriety, moreover, in regarding all the motor 
 branches distributed upon the face as one nerve ; since even the 
 anterior roots of the spinal nerves originate from the spinal cord, 
 each by several distinct filaments, which are associated into a single 
 
THE CRANIAL NERVES. 449 
 
 bundle only at a certain distance from their point of origin. The 
 mere fact that two nerves leave the cavity of the cranium by the 
 same foramen does not indicate that they have the same or even a 
 similar function. Thus the facial and auditory both escape from 
 the cavity of the cranium by the foramen auditorium internum, and 
 yet we do not hesitate to regard them as entirely distinct in their 
 nature and functions. It is the ultimate distribution of a nerve, 
 and not its course through the bones of the skull, that indicates 
 its physiological character and position. For while the ultimate" 
 distribution of any particular nerve is always the same, its arrange- 
 ment as to trunk and branches may vary, in different species 
 of animals, with the anatomical arrangement of the bones of the 
 skull. This is well illustrated by a fact first pointed out by Prof. 
 Jeffries Wyman* in the anatomy of the nervous system of the 
 bullfrog. In this animal, both the facial nerve and motor oculi 
 externus, instead of arising as distinct nerves, are actually given 
 off as branches of the 5th pair ; while their ultimate distribution is 
 the same as in other animals. All the motor and sensitive nerves 
 distributed to the face are accordingly to be regarded as so many 
 different branches of the same trunk : varying sometimes in their 
 course, but always the same in their ultimate distribution. 
 
 The motor nerves of the head are in all respects identical in their 
 properties with the anterior roots of the spinal nerves. For, in the 
 first place, they are distributed to muscles, and not to the integu- 
 ment or to mucous membranes; secondly, their division causes 
 muscular paralysis; and thirdly, mechanical irritation applied at 
 their origin produces muscular contraction in the parts to which 
 they are distributed, but does not give rise to a painful sensa- 
 tion. In several instances, nevertheless, the motor nerves, though 
 insensible at their origin, show a certain degree of sensibility when 
 irritated after their exit from the skull, owing to fibres of com-, 
 munication which they receive from the purely sensitive nerves. 
 In this respect they resemble the spinal nerves, the motor arid 
 sensitive filaments of which are at first distinct in the anterior 
 and posterior roots, but afterward mingle with each other, jon 
 leaving the cavity of the spinal canal. 
 
 The three sensitive nerves originating from the brain are the 
 
 ' Nervous System of Rana pipiens ; published by the Smithsonian Institution. 
 Washington, 1853. 
 29 
 
450 THE CRANIAL NERVES. 
 
 large root of tlie fiftb pair, the glosso-pharyngeal, and the pneumo- 
 gastric. It will be observed that, in all their essential properties, 
 they correspond with the posterior roots of the spinal nerves. Like 
 them they are inexcitable, but extremely sensitive. Irritated at 
 their point of origin, they give rise to acutely painful sensations, 
 but to no convulsive movements. Secondly, if divided at the same 
 situation, the operation is followed by loss of sensibility in the 
 parts to which they are distributed, without any disturbance of the 
 motive power. Each of these nerves, furthermore, like the poste- 
 rior root of a spinal nerve, is provided with a ganglion through 
 which its fibres pass : the ^fifth pair, with the Casserian ganglion, 
 situated'near the inner extremity of the petrous portion of the tem- 
 poral bone ; the glosso-pharyngeal, with the ganglion of Andersch, 
 situated in the jugular fossa; while the pneumogastric presents, 
 just before its passage through the jugular foramen, a ganglion 
 known as the ganglion of the pneumogastric nerve. Finally, the 
 sensitive fibres of all these nerves, beyond the situation of their gan- 
 glia, are intermingled with others of a motor origin. The large, root 
 of the fifth pair, which is exclusively sensitive, is accompanied by 
 the fibres of the small root, which are exclusively motor. The 
 glosso-pharyngeal receives motor filaments from the facial and spir 
 nal accessory, becoming consequently a mixed nerve outside the 
 crania] cavity ; while the pneumogastric is joined by fibres from the 
 spinal accessory and various other nerves of a motor character. 
 These nerves, accordingly, are exclusively sensitive only at their 
 point of origin. Though they afterward retain the predominating 
 character of sensitive nerves, they are yet found, if irritated in the 
 middle of their course, to be intermingled with motor fibres, and 
 to have consequently acquired, to a certain extent, the character of 
 mixed nerves. 
 
 The resemblance, therefore, between the cranial and spinal nerves 
 is complete. 
 
 Motor Oculi Communis.— This nerve, which is sometimes known 
 by the more convenient name of the ocuh-motorius, originates from 
 the inner edge of the crus cerebri, passes into the cavity of the 
 orbit by the sphenoidal fissure, and is distributed to the levator 
 palpebrse superioris, and to all the muscles moving the eyeball, 
 except the external rectus and the superior oblique. Its irritation 
 accordingly produces convulsive movements in these parts, and 
 
FIFTH PAIB. 451 
 
 its division has the effect of paralyzing the muscles to which it is 
 distributed. The superior eyelid falls down over the pupil, and 
 cannot be raised, owing to the inaction of its levator muscle, so 
 that the eye appears constantly half shut. This condition is known 
 by the name of " ptosis." The movements of the eyeball are also 
 nearly suspended, and permanent external strabismus takes place, 
 owing to the paralysis of the internal rectus muscle, while the ex- 
 ternal rectus, animated by a different nerve, preserves its activity. 
 
 PATHETIC0S. — This nerve, which supplies the superior oblique 
 musclfe of the eyeball, is similar in its general properties to the pre- 
 ceding. Its section causes paralysis of the above muscle, without 
 any loss of sensibility. 
 
 Motor Exteenus. — This nerve,- the sixth pair, according to the 
 usual anatomical arrangement, is distributed to the external rectus 
 muscle of the eyeball. Its division or injury by disease is followed 
 by internal strabismus, owing to the unopposed action of the internal 
 rectus muscle. 
 
 Fifth Pair. — This is one of the most important and remarkable 
 in its properties of all the cranial nerves. It is the. great sensitive 
 nerve of the face, and of the adjoining mucous membranes. Its 
 larger root, after emerging from the outer and under surface of the 
 pons Varolii, passes forward over the inner extremity of the petrous 
 portion of the temporal bone. It there expands into a crescentic- 
 shaped swelling, containing -a quantity of gray matter with which 
 its fibres are intermingled, and which is known as the Casserian 
 ganglion. The fibres of the smaller root, passing forward in com- 
 pany with the others, do not take any part in the formation of this 
 ganglion, but may be seen passing beneath it as a distinct bundle, 
 and continuing their course forward to the foramen ovale, through 
 which they emerge from the skull. In front of the anterior and 
 external border of the Casserian ganglion, the fifth nerve separates 
 into three principal divisions, viz., the ophthalmic, the superior 
 maxillary, and the inferior maxillary. The first of these divisions, 
 . viz., the ophthalmic, is so called because it passes through the orbit 
 ' of the eye. It enters the sphenoidal fissure, and runs along the 
 upper portion of the orbit, sending branches to the ophthalmic gan- 
 glion of the sympathetic, to the lachrymal gland, the conjunctiva, 
 
452 
 
 THE CRANIAL NERVES. 
 
 Fig. 150. 
 
 and the mucous membrane of the lachrymal sac. It also sends off 
 a small branch (nasal branch) which penetrates into the nasal pas- 
 sages and supplies the Schneiderian mucous membrane. It then 
 emerges upon the face by the supra-orbital foramen, and is distri- 
 buted to the integument of the forehead and side of the head as far 
 back as the vertex. 
 
 The second 'division of this nerve, or the superior maxillary, 
 passes out by the foramen rotundum, and runs along the longitu- 
 dinal canal in the floor of the orbit, giving off branches during its 
 passage to the teeth of the upper jaw and to the mucous membrane 
 of the antrum maxillare. It finally emerges upon the middle of the 
 face by the infra-orbital foramen, and is distributed to the integu- 
 ment of the lower eyelid, nose, cheek, and upper lip. 
 
 The third, or inferior maxillary division of the fifth pair, which 
 is the largest of the three, leaves the cavity of the cranium by the 
 
 foramen ovale. It comprises a con- 
 siderable portion of the large root 
 of the nerve, and all the fibres of 
 the small root. This division is 
 therefore a mixed nerve, containing 
 both motor and sensitive fibres, 
 while the two former are exclu- 
 sively sensitive. It is distributed^ 
 accordingly, both to muscles and 
 to the sensitive surfaces. Soon after 
 emerging from the foramen ovale 
 • it sends branches to the temporal 
 muscle, to the masseter, the bucci- 
 nator, and to the internal and ex- 
 ternal pterygoids; that is, to the 
 muscles which are particularly con- 
 cerned in the movements of the 
 lower jaw. It also sends sensitive 
 filaments to the integument of the 
 temple, to that of a portion of the external ear and external audi- 
 tory meatus. The third division of the fifth pair, then passing 
 downward and forward, gives off a branch of considerable size, the 
 lingual branch, which is distributed to the mucous membrane of the 
 anterior two-thirds of the tongue, and which also sends filaments to 
 the arches of the palate and to the mucous membrane of the cheek. 
 
 DiSTKIBlTTIOS OP FjPTH NeRTB 
 
 UPON THE Face. — a. Casserian j;f)iQglion. 
 I. Ophthalmic divisioa. ' 2. Superior maxil- 
 lary divisiOD. 3. Inferior maxillary division. 
 
FIFTH PAIR. 453 
 
 The remaining portion of the third division4 after giving a'few 
 branches to the mylo-hyoid muscle and to the anterior belly of the 
 digastric, then enters the inferior dental canal, sends filaments to 
 the teeth of the lower jaw, emerges at the mental foramen, and is 
 finally distributed to the integument of the chin, lower lip, and 
 inferior part of the face. 
 
 This nerve is accordingly distributed to the sensitive surfaces, 
 that is, the integument and mucous membranes about the face, and 
 to the muscles of mastication. A few of its fibres are sent also to 
 the superficial muscles of the face, such as the buccinator and the 
 orbicularis oris ; but- these fibres are sensitive in their character, 
 and serve' merely to impart to the muscles a certain degree of 
 sensibility. It has been ascertained by Longet that if the various 
 branches of this nerve be irritated by a galvanic current, no con- 
 vulsive movements whatever are produced in those superficial 
 muscles of the face, which it supplies with filaments; but if its 
 smaller or non-ganglionio root be irritated in the same way, con- 
 tractions instantly follow in the muscles of mastication. 
 
 The fifth pair is the most acutely sensitive nerve in the whole 
 body. Its irritation by mechanical means always causes intense 
 pain, and even though the animal be nearly unconscious from the 
 influence of ether, any severe injury to its large root is almost 
 invariably followed by cries which indicate the extreme sensibility 
 of its fibres. 
 
 If this nerve be completely divided, in the living animal, within 
 the cranium, at the situation of the Casserian ganglion, the operation 
 is followed by total loss of sensibility in the skin of the face and in 
 the adjacent mucous membranes. The conjunctiva, upon the affected 
 side, is then completely insensible, and may be touched with the 
 point of a needle or the blade of a knife, without exciting any un- 
 easiness, and even without the consciousness of the animal. Probes 
 and needles may be passed into the nostril, and the lips or the 
 cheek may be pinched, pierced or cut, without exciting the least 
 sign of sensibility. The animal is entirely indifferent to all me- 
 chanical injuries upon the affected side, though upon the opposite 
 side the parts retain their natural sensibility. 
 
 Owing to the paralysis of the lingual nerve, also, after this ope- 
 ratioii, the tongue, in its anterior two-thirds, becomes insensible to 
 ordinary irritations, and loses, beside, the power of taste. 
 
 Another peculiar effect of the division of the fifth pair depends 
 
454 THK CRANIAL NERVES. 
 
 Upon the paralysis of its motor fibres, which are distributed, as we 
 have seen, to the muscles of mastication. In many of the lower 
 animals, consequently, the movements of mastication become ex- 
 ceedingly enfeebled upon the affected side. In the cat, for example, 
 an animal in which mastication is usually very thoroughly per- 
 formed, this process becomes excessively laborious, so that the 
 animal after this operation cannot masticate solid meat, but requires 
 to be fed with that which has already been cut in pieces. 
 
 The fifth pair, beside supplying the sensibility of the integument 
 of the face, has a peculiar and important influence on the organs of 
 special sense. JThis influence appears to consist in some connection 
 between the action of the fifth pair and the processes of nutrition ; 
 so that when the former is injured, the latter very soon become 
 deranged. For the perfect action of any one of the organs of 
 special sense, two conditions are necessary : first, the sensibility of 
 the special nerve belonging to it, and secondly, the integrity of the 
 component parts of the organ itself. Now as the nutrition of the 
 organ is, to a certain extent, under the control of the fifth pair, any 
 serious injury to this nerve produces a derangement in the tissues 
 of the organ, and consequently interferes with the, due performance 
 of its function. 
 
 The mucous membrane of the nasal passages, for example, is 
 supplied by two different nerves; first, the olfactory, distributed 
 throughout its upper portion, by which it is endowed with the 
 special sense of smell ; and, secondly, the nasal branch of the fifth 
 pair, distributed s throughout its middle and lower portions, by 
 which it is supplied with ordinary sensibility. 
 
 Since the fifth pair, accordingly, supplies general sensibility, to 
 the nasal passages, this property wiU remain after the, special sense 
 of smell has been destroyed. If, however, the fifth pair itself he 
 divided, not only is general sensibility destroyed in the Schneiderian 
 mucous membrane, but a disturbance begins to take place in the 
 nutrition of its tissue, by which it is gradually rendered unfit for 
 the performance of its special function, and the power of smell is 
 finally lost. The mucous membrane, under these circumstances, 
 becomes injected and swollen, and the nasal passage is obstructed 
 by an accumulation of puriform mucus. According to Longet, the 
 mucous memT3rane also assumes a fungous consistency, and is liable 
 to bleed at the slightest touch. The effect of this alteration is to 
 blunt or altogether destroy the sense of smell. It is owing to a 
 similar unnatural condition of the mucoUs membrane that the power 
 
FIFTH PAIR. 455 
 
 of smell is always more or less impaired in cases of coryza and 
 influenza. The olfactory nerves become inactive in consequence 
 of the morbid alteration in their mucous membrane, and in the 
 secretions which cover it. 
 
 The influence of this nerve over the organ of vision is still more 
 remarkable. It has been known for many years that division of 
 the fifth pair within the cranium, or of its ophthalmic branch, is fol- 
 lowed by an inflammation of the corresponding eye, which usuliUy 
 goes on to complete and permanent destruction of the organ. 
 Immediately after the operation, the pupil becomes contracted and 
 the conjunctiva loses its sensibility. At the end of twenty-four 
 hours, the cornea begins to become opaline, and by the second 
 day the conjunctiva is already inflamed and begins to discharge a 
 purulent secretion. The inflammation, after commencing in the 
 conjunctiva, increases in intensity and soon spreads to the iris, 
 which becomes covered with a layer of inflammatory exudation. 
 The cornea grows constantly more opaque, until it is at last 
 altogether impermeable to light, and vision is consequently sus- 
 pended. Blindness, therefore, does not result in these instances 
 from any direct affection of the optic nerve or of the retina, but is 
 owing simply to opacity of the cornea. Sometimes the diseased 
 action goes on until it results in ulceration of the cornea and dis- 
 charge of the humors of the eye ; sometimes, after the lapse of 
 several days, the inflammatory appearances subside, and the eye is 
 finally restored to its natural condition. 
 
 It has been observed, however, that although the above conse- 
 quences always follow division of the fifth pair, when performed at 
 the level of the Casserian g-anglion, or between it and the eyeball, 
 they are either much diminished in intensity or altogether wanting 
 when the division is made at a point posterior to the ganglion. 
 This circumstance has led to the belief that the influence of the fifth 
 pair on the nutrition of the eyeball does not reside in its own proper 
 fibres, but in some filaments of the sympathetic nerve which join 
 the fifth pair at the level of the Casserian ganglion. If the section 
 accordingly be made at this point, or in front of it, the fibres of the 
 sympathetic will be divided with the others, and inflammation of 
 the eye will result ; but if the section be made behind the ganglion, 
 the fibres of the sympathetic will escape division, and the injurious 
 effects upon the eye will be wanting^ Such is the explanation 
 usually given of the above-mentioned facts ; but the question has 
 not as yet been determined in a positive manner. 
 
456 THE CRANIAL NERVES. 
 
 Division of the fiftli pair destroys also the general sensibility of 
 the external auditory meatus, the lining membrane of which is 
 supplied by its filaments. Inflammation of this membrane and its 
 consequent alterations, it is well known, interfere seriously with 
 the sense of hearing. It is no uncommon occurrence for an accu- 
 mulation of cerumen to take place after inflammation of this part, 
 so as to block up the auditory canal and produce partial or com- 
 plete deafness. It has not been ascertained, however, whether 
 division of the fifth pair is usually followed by similar changes in 
 this part. 
 
 The lingual branch of the fifth pair supplies the anterior ex- 
 tremity and middle portion of the tongue both with general sensi- 
 bility and with the power of taste. The sensibility of the tongue 
 is accordingly provided for by two different nerves ; in its anterior 
 two-thirds, by the lingual branch of the fifth pair ; in its posterior 
 third, by the fibres of the glosso-pharyngeal. 
 
 The facial branches of the fifth pair are the ordinary seat of tic 
 douloureux. This affection is not unfrequently confined to either 
 the supra-orbital, the infra-orbital, or the mental branch ; and the 
 pain may be accurately traced in the direction of their diverging 
 fibres. It has already been mentioned that the painful sensations 
 sometimes also follow the course of the facial, owing to some sensi- 
 tive filaments which that nerve receives from the fifth pair. 
 
 FACiAL.^This nerve was known to the older anatomists as the 
 "portio dura of the seventh pair." It leaves the cavity of the 
 cranium by the internal auditory foramen, in company with the 
 auditory nerve ; and, as the latter is of a softer consistency than the 
 former, they have received the names respectively of the "portio 
 mollis" and " portio dura" of the seyenth pair. There is, however, 
 no physiological connection between these two nerves ; for while 
 the auditory is spread out in the cavity of the internal ear, the facial 
 passes onward through the petrous portion of the temporal bone, 
 emerges at the stylo-mastoid foramen, bends round beneath the 
 external ear, and passes forward through the substance of the 
 parotid gland, forming a plexus called the " pes anserinus," by the 
 abundant inosculation of its different branches. It then sends its 
 filaments forward in a diverging course, and is finally distributed 
 to the muscles of the external ear, to the frontalis and superciliaris 
 mupcles, to the orbicularis oculi, the compressors and dilators of 
 the nares, the orbicularis oris, and to the elevators and depressors 
 
FACIAL NERVE, 
 
 I 457 
 
 Fig. 151. 
 
 FAOlAf. NekvB. 
 
 of the lips ; that is, to the superficial muscles of the face, which are 
 concerned in the production of expression. (Fig. 151.) 
 ; The facial, consequently, is the- 
 motor nerve of the face. It has 
 nothing to do with transmitting 
 sensitive impressions, since it has 
 been frequently shown that after 
 section of the fifth pair, the facial 
 remaining entire, the sensibility of 
 the face is completely lost ; set that 
 the integument may be cut, pricked, 
 pierced, or lacerated, without any 
 sign of pain being exhibited by the 
 animal. The facial,, therefore, does 
 not transmit sensation from these 
 parts ; and its division, which was 
 formerly resorted to in cases of 
 tic douloureux, is accordingly alto- 
 gether incapable of relieving neuralgic pains. 
 
 This nerve, however, is directly connected with muscular action, 
 since mechanical or galvanic irritation of its fibres produces con- 
 vulsive twitching in the ears, nostrils, lips, and cheeks. 
 
 If the facial nerve be divided in one of the lower animals, as, for 
 example, in the cat, immediately after its emergence from the 
 etylo-mastoid foramen, it will be found that complete muscular 
 paralysis has occurred in all those parts to which the nerve is dis- 
 tributed, while the power of sensation remains unimpaired. The 
 animal is incapiable of moving the ear, which remains constantly in 
 the same position. There is also incapacity of closing the eyelids, 
 owing to paralysis of the orbicularis oculi, and the eye accordingly 
 remains constantly open, even when the opposite eye is closed; 
 as during sleep, or in the act of winking. If the conjunctiva be 
 touched, the animal feels the irritation, and endeavors to escape 
 from it ; but the eyeball is only drawn partially backward into the 
 socket by the action of the recti muscles, and the third eyelid 
 pushed partly across the cornea. The complete closure of the eye 
 is impossible. It will be observed, accordingly, that precisely oppo- 
 site effects are produced upon the eyelids by -paralysis of the oculo- 
 motorius nerve, and by that of the facial. In the former instance, 
 owing to the paralysis of the levator palpebr^ superioris, the eye 
 is always partially closed ; in the latter, owing* to paralysis of the 
 
458 • THE OEANIAL NERVES. 
 
 orbicularis, it is always partially open. The movements of the 
 nares are also suspended on the side of the injury, and if the angle 
 of the mouth be examined on that side, it will be found to hang 
 down lower than on the opposite side, and to be constantly partly 
 open, owing to the paralysis of the orbicularis oris and the eleva- 
 tors of the angle of the mouth. 
 
 These are the only inconveniences which follow the division of 
 the facial nerve in the cat, but in some other of the lower animals, 
 where various muscular organs in this region are particularly de- 
 veloped, the consequences are more tr&ublesome. Thus, in the rabbit, 
 the ear, upon the affected side, falls down, and cannot be raised or 
 pointed in different directions ; and as the movements of the ear 
 are important in these animals, as aids to the hearing, the per- 
 fection of this sense must be considerably impaired by paralysis of 
 the facial nerve. In the horse, it has been noticed by Bernard,' 
 that division of the facial on both sides is fatal by suffocation. For 
 this animal breathes exclusively through the nostrils, which open 
 widely at the time of inspiration, to allow the admission of air. If 
 these movements be suspended, by paralysis of the facial nerve, the 
 nostrils immediately collapse, and the animal dies by suffocation. 
 
 In the human subject, the facial nerve is occasionally paralyzed 
 upon one side, sometimes from sympathetic irritation^ sometimes 
 from organic disease in the petrous portion of the temporal bone, 
 or within the cranial cavity near the origin of the nerve. In either 
 case, an extremely well-marked affection is the result, known as 
 " facial paralysis." This condition is chiefly characterized by an 
 entire absence of expression on the affected side of the face. The 
 lower eyelid sinks downward, from paralysis of the orbicularis 
 muscle, and cannot be closed. 
 
 The corner of the mouth also falls downward, and the whole 
 lower part of the face is drawn over to the opposite side, by the 
 force of the antagonistic muscles. The lips are unable to retain 
 the fluids of the mouth ; and the saliva dribbles away from between 
 them, giving to the face a remarkably vacant and helpless appear- 
 ance. 
 
 The principal inconvenience, however; suffered by the human 
 subject in facial paralysis, depends upon the want of action of the 
 muscles about the lips and cheek. In drinking, the fluids escape 
 
 ' Lemons sur la Pliysiologie et la Patkologie da Syst^me Nerreux, Paris, 1858, 
 Tol. ii. p. 38. 
 
GLOSSO-PHABYNaEAL NEBVE. 459 
 
 by the corner of the mouth, and in mastication the food has partly 
 a tendency to escape "by the same opening, and partly accumulates, 
 on the affected side, between the gums and the cheek, owing to the 
 paralysis of the buccinator muscle, which receives its motor fila- 
 ments from the facial nerve. Thus, the action of all this superficial 
 facial muscles is suspended, the expression of the face is destroyed, 
 and the movements of the lips and the prehension of the food 
 seriously interfered with. 
 
 Though the facial, however, be essentially a motor nerve, yet its 
 principal branches distributed to the face have a certain degree of 
 sensibility ; that is, when these branches are irritated iu the middle 
 of their course, the animal immediately gives evidence of a painful 
 sensation. Longet has shown, 'by an extremely ingenious mode 
 of experiment,' that this sensibility of the branches of the facial 
 does not depend on any sensitive fibres of their own, but lipon 
 those which they derive from inosculation with the fifth pair. He 
 exposes, for example, the facial nerve in the dog, and, irritating its 
 principal branches one after the other, at each application of the 
 irritant there are evident signs of pain. He then divides the facial 
 nerve at its point of exit from the stylo-mastoid foramen, and 
 finds that, after this operation, the sensibility of its branches still 
 remains. •The fibres,^ accordingly, upon which this sensibility 
 depends, do not pass out with the trunk of the nerve, but are 
 derived from some other source. The experimenter, then, upon 
 another animal, divides the fifth pair within the skull, leaving the 
 facial untouched; and afterward, on irritating as before the ex- 
 posed branches of the latter nerve, he finds that its sensibility has 
 entirely disappeared. It is by filaments, accordingly, derived from 
 the fifth pair, that a certain degree of sensibility is communicated 
 to the branches of the facial. 
 
 These facts account for the peculiar circumstance that, in cases 
 of tic douloureux, the spasmodic pain sometimes follows exactly 
 the course of the facial nerve, viz : from behind the ear forward 
 upon the side of the face ; and yet the section of this nerve does not 
 put an end to the neuralgia, but only causes paralysis of the facial 
 muscles. 
 
 Glosso-Phabyngeal. — This nerve originates from the lateral 
 portion of the medulla oblongata, passes outward, and enters the 
 
 ' Traitfi de Physiologie, vol. ii. pp. 354-357. 
 
460 THE CBANIAL NERVES, 
 
 posterior foramen lacerum in company with the pneumogastric and 
 spinal accessory. "While in the jugular fossa it presents a gangliform 
 enlargement, called the ganglion of Andersch, below the level of 
 which it receives branches of communication from the facial and 
 the spinal accessory. It then runs downward and forward, and is 
 distributed to the mucous membrane of the base of the tongue, 
 pillars of the fauces, soft palate, middle ear, and upper part of the 
 pharynx. It also sends some branches to the constrictors of the 
 pharynx and the neighboring muscles. Longet has found this 
 nerve at its origin to be exclusively sensitive ; but below the level 
 of its ganglion it has been found by him, as well as by various 
 other observers, to be both sensitive and motor, owing to the fibres 
 of communication received from the motor nerves mentioned above^ 
 Its final distribution is, however, as we have seen, principally to 
 sensitive surfaces. The principal ofiice of this nerve is to impart 
 the sense of taste to the posterior third of the tongue, to which it "is 
 distributed. It alSo presides over the general sensibility of this 
 part of the tongue, as well as that of the fauces and pharynx. 
 
 Dr. John Eeid,' who has performed a great variety of experiments 
 upon this nerve, comes to the following conclusions in regard to it. 
 First, that it is essentially a sensitive nerve, since there are unequi- 
 vocal signs of pain when it is pricked, pinched, or ctft. Second, 
 that irritation of this nerve produces convulsive movements of the 
 throat and. lower part of the face ; but that these movements are, in 
 great measure, not direct, but reflex in their character, since they 
 will take place equally well after the glosso-pharyngeal has been 
 divided, if the irritation be applied to its cranial extremity. Third, 
 that this nerve supplies the special sensibility of taste to a portion 
 of the tongue ; but that it is not the exclusive nerve of this sense, 
 since the power of taste remains, after it has been divided on both 
 sides. 
 
 There are certain reflex actions, furthermore, which take pl^ce 
 through the medium of the glosso-pharyngeal nerve. After the 
 food has been thoroughly masticated, it is carried, by the move- 
 ments of the tongue and sides of the mouth, through the fauces, 
 and brought in contact with the mucous membrane of the pharynx. 
 This produces an impression which, conveyed to the medulla 
 oblongata by the filaments of the glosso-pharyngeal, excites the • 
 
 ' In Todd's Cyclopaedia of Anatomy and Physiology, article Glosso-pharyngeal 
 Nerve. 
 
PNEUMOGASTRIC NERVE. 461 
 
 muscles of the fauces and pharynx by reflex action. The food is 
 consequently grasped by these muscles, without the concurrence of 
 the will, and the process of deglutition is commenced. This action 
 is not only involuntary, but it will frequently take place even in 
 opposition to the will. The food, once past the isthmus of the fauces, 
 is beyond the control of volition, and cannot be returned except by 
 convulsive action, equally involuntary in its character. 
 
 Natural stimulants, therefore, applied to the mucous membrane 
 of the pharynx, excite deglutition ; unnatural stimulants, applied 
 to the same part, excite vomiting. If ttie finger be introduced into 
 the fauces and pharynx, or if the mucous membrane of these parts 
 be irritated by prolonged tickling with the end of a feather, the 
 sensation of nausea, conveyed through the glosso-pharyngeal nerve, 
 is sometimes so great as to produce immediate and copious vomit- 
 ing. This method may often be successfully employed in cases of 
 poisoning, when it is desirable to excite vomiting rapidly, and when 
 emetic medicines are not at hand. 
 
 Pneumogasteio. — Owing to the numerous connections of the 
 pneumogastric with other, nerves, its varied and extensive distribu- 
 tion, and the important character of its functions, this is properly 
 regarded as one of the most remarkable nerves in the whole body. . 
 Owing to the wandering course of its fibres, which are distributed 
 to no less than four different vital organs, viz., the heart, luiigs, 
 stomach and liver, as well as to several other parts of secondary 
 importance, it has been often known by the name^of the par vagum. 
 The pneumogastric arises, by a number of separate filaments, from 
 the lateral portion of the medulla oblongata, in the groove between 
 the olivary and restiform bodies. These filaments unite into a 
 single trunk, which emerges from the cranium by the jugular fora- 
 men, where it is provided with a longitudinal ganglionic swelling, 
 the " ganglion of the pneumogastric nerve." Immediately below 
 the level of this ganglion* 'the nerve receives an important branch 
 of communication from the spinal accessory, and afterward from 
 the facial, the hypoglossal, and the anterior branches of. the first 
 and second cervicals. 
 
 At its origin, the pneumogastric is exclusively a sensitive nerve. 
 Irritated above the situation of its ganglion, it has been found to 
 convey painful sensations alone ; but if the irritation be applied at 
 a lower level, it causes at the same time muscular contractions, 
 owing to the filaments which it has received from the above-men- 
 
462 
 
 THE CRANIAL NERVES. 
 
 Fig. 152. 
 
 tioned motor nerves. It becomes, consequently, after emerging 
 from the cranial cavity, a mixed nerve ; and has, accordingly, in 
 nearly all its branches, a double distribution, viz., to the mucous 
 membranes' and the muscular coat of the organs to which it bel&ngs. 
 
 • The ordinary sensibility of the pneu- 
 mogastric nerve, however, as all experi- 
 menters have observed, is exceedingly 
 dull, in comparison with that of the other 
 sensitive cranial nerves. We have often 
 divided this nerve in the middle of the 
 neck, without any distinct manifestation 
 of pain being given by the animal ; and 
 thougB Bernard has found that at some 
 times its sensibility is well marked, while 
 at others it is very indistinct, he is not 
 able to say upon what special physio- 
 logical (3onditions this difference depends. 
 While the pneumogastric, however, is 
 decidedly deficient, as a general rule, in 
 ordinary sensibility, it possesses, as we 
 shall see hereafter, a sensibility of a pecu- 
 liar kind, which is exceedingly important 
 for the maintenance of the vital func- 
 tions. 
 
 In passing down' the neck, this nerve 
 sends branches to the mucous membrane 
 and muscular coat of the pharynx, ceso- 
 'phagus, and respiratory passages. Among 
 the most important of these branches are 
 the two laryngeal nerves, viz., the supe- 
 rior and inferior. The superior laryngeal - 
 nerve, which is given off from the trunk 
 of the pneumogastric jnst after it has 
 emerged from the cavity of the skull, 
 passes downward and forward, penetrates 
 the larynx by an opening in the side of 
 the thyro-hyoid membrane, and is distributed to the mucous mem- 
 brane of the larynx and glottis, and also to a single laryngeal mus- 
 cle, viz., the crico-thyroid. This branch is therefore partly mus- 
 cular, but mostly sensitive in its distribution. The inferior laryngeal 
 branch is. given off just after the pneumogastric has entered the 
 
 Diagram of Pneumogastric 
 N E R y E, wi th its principal branclieH. 
 — I. Pharyngeal brancli. 2. Supe- 
 rior laryngeal. 3 Inferior laryn- 
 geal. ' 4. Pulmonary branches. 6. 
 Stomach. 6. Liver. 
 
PNEUMOGASTBIC NERVE. 463 
 
 cavity of the chest. It curves round the subclaviaii artery on the 
 right side and the arch of the aorta on the left, and ascends in the 
 groove between the trachea and oesophagus, to the larynx. It 
 then enters the larynx between the cricoid cartilage and the pos- 
 terior edge of the thyroid, and is distributed to all the muscles of 
 the larynx, with the exception of the crico-thyroid. This branch 
 is, therefore, exclusively muscular in its distribution. 
 
 The trunk of the pneumbgastrio, after supplying the above 
 branches,, as well as sending numerous filaments to the trachea 
 and oesophagus in* the neck, gives off in the chest its pulmonary 
 branches, which follow the bronchial tubes in the -lungs to their 
 minutest ramifications. It then passes into the abdomen and sup- 
 plies the muscular and mucous layers of the stomach, ramifying 
 over both the anterior and posterior surfaces of the organ ; after 
 which its fibres spread but and ^re distributed to the liver, spleen, 
 pancreas, and gall-bladder. 
 
 .The functions of the pneumogastric will now be successively 
 studied in the various organs to which it is distributed. 
 
 Pharynx and, (Esophagus. — The reflex action of deglutition, which 
 has already been described as commencing in the upper part of the 
 pharynx, by means of the glosso-pharyngeal, is continued in the 
 lower portion of the pharynx and throughout the oesophagus by 
 the aid of the pneumogastric. As the food is compressed by the 
 superior constrictor muscle of the pharynx and forced downward, 
 it excites the mucous membrane with which it is brought in contact 
 and gives rise to another contraction of the middle ^constrictor. The 
 lower constrictor is then brought into action in its turn in a similar 
 manner ; and a wave-like or peristaltic contraction is thence pro- 
 pagated throughout the entire length of the oesophagus, by which 
 the food is carried rapidly from above downward, and conducted at 
 last to the stomach. Bach successive portion of the mucous mem- 
 brane, in this instance, receives in turn the stimulus of the food, 
 and excites instantly its own muscles to contraction ; so that the 
 food passes rapidly from one end of the oesophagus to the other, by 
 an action which is wholly reflex in character and entirely withdrawn 
 from the control of the will. Section of the pneumogastric, or of 
 its pharyngeal and oesophageal branches, destroys therefore at the 
 same time the sensibility and the motive power of these parts. The 
 food is no longer conveyed readily to the stomach, but accumulates 
 ii;;i the paralyzed oesophagus, into which it is forced by the voluntary 
 
464 THE CRANIAL NERVES. 
 
 movements of 'the mouth and fauces, and by the continued action 
 of the upper part of the pharynx. 
 
 It must be remembered that the general sensibility of the oeso- 
 phagus is very slight, as compared with that of the integument, or 
 even of the mucous membranes near the exterior. It is a general 
 rule, in fact, that the sensibility of the mucous membranes is most 
 acute at the external orifices of their canals ; as, for example, at the 
 lips, anterior nares, anus, orifice of the urethra, &c. It diminishes 
 constantly from without inward, and disappears altogether at a . 
 certain distance from the surface. The sensibility of the pharynx 
 is less acute than that of the mouth, but is still sufiicient to enable 
 us to perceive the contact of ordinary substances; while in the 
 oesophagus we are not usually sensible of the impression of the food 
 as it passes from above downward. The reflex action takes place 
 here without any assistance from the consciousness ; and it is only 
 when substances of an unusually pungent or irritating nature are 
 mingled with the food, that its passage through the oesophagus pro- 
 duces a distinct sensation. 
 
 ' Larynx. — We have already described the course and. distribution 
 of the two laryngeal branches of the pneumogastric. The superior 
 laryngeal nerve is principally the sensitive nerve of the larynx. 
 Its division destroys sensibility in the mucous membrane of this 
 organ, but paralyzes only one of its muscles, viz : the crico-thyroid. 
 Galvanization of this nerve has also been found to induce con- 
 tractions in the crico-thyroid, but in none of the other muscles 
 belonging to th§ larynx. The inferior laryngeal, on the other 
 hand, is a motor nerve. Its division paralyzes all the muscles of 
 the larynx except the crico-thyroid ; and irritation of its divided 
 extremity produces contraction in the same muscles. The muscles 
 and mucous membrane of the larynx are therefore supplied by two 
 different branches of the same trunk, viz., the superior laryngeal 
 nerve for the mucous membrane, and the inferior laryngeal nerve 
 for the muscles. 
 
 The larynx, in man and in all the higher animals, performs a 
 double function ; one part of which is connected with the voice, the 
 other with respiration. 
 
 The formation of the voice in the larynx takes place as follows. 
 If the glottis be exposed in the living animal, by opening the 
 pharynx and oesophagus on one side, and turning' the larynx for- 
 ward, it will be seen that so long as the vocal chords preserve 
 their usual relaxed condition during expiration, no sound is heard, 
 
PNEUMOGASTRIC NERVE. 465 
 
 except tlie ordinary faint whisper of the air passing gently through 
 the cavity of the larynx. "When a vocal sound, however, is to be 
 produced, the ch,ords are suddenly made tense and applied closely 
 to* each other, so as to diminish, very considerably the size of the 
 orifice; and the air, driven by an unusually forcible expiration 
 through the narrow opening of the glottis, in passing between the 
 vibrating vocal chords, is itself thrown into vibrations which pro- 
 duce the sound required. The tone, pitch, and intensity of this 
 sound, vary with the conformation of the larynx, the degree of ten- 
 sion and approximation of the vocal chords, and the force of the 
 expiratory effort. The narrower the opening of the glottis, and the 
 greater the tension of the chords, under ordinary circumstances, the 
 more acute the sound ; while a wider opening and a less degree of 
 tension produce a graver note. The quality of the sound is also 
 modified by the length of the column of air included between the 
 glottis and the mouth, the tense or relaxed condition of the walls 
 of the pharynx and fauces, and the state of dryness or moisture of 
 the mucous membrane lining the aerial passages. 
 
 Articulation, on the other hand, or the division of the vocal sound 
 into vowels and consonants, is accomplished entirely by the lips, 
 tongue, teeth, and fauces. These organs, however, are under the 
 control of other nerves, and the mechanism of their action need not 
 occupy us here. 
 
 Since the production of a vocal sound, therefore, depends upon 
 the tension and position of the vocal chords, as determined by the 
 action of the laryngeal muscles, it is not surprising that division of 
 the inferior laryngeal nerves, by paralyzing these muscles, should 
 produce a loss of voice. It has been sometimes found that in very 
 young animals the crico-thyrpid muscles, which are the only ones 
 not affected by division of the inferior laryngeal nerves, are still 
 Buf&cient to give some degree, of tension to the vocal chords, and 
 to produce in this way an imperfect sound ; but usually the voice 
 is entirely lost after such an operation. 
 
 It is a very remarkable fact, however, in this connection, that all 
 the motor filaments of the pneumogastric, which are concerned in 
 the formation of the voice, are derived from a single source. It 
 will be remembered that the pneumogastric, itself originally a 
 sensitive nerve, receives motor filaments, on leaving the cranial 
 cavity, from no less than five different nerves. Of these filaments, 
 however, those coming from the spinal accessory are the only ones 
 necessary to the production of vocal sounds. For it has been found 
 30 
 
466 THE CRANIAL NEBVES. 
 
 by Bischoff and by Bernard' that if all the roots of the spinal acces- 
 sory be divided at their origin, or if the nerve itself be torn away 
 at its exit from the skull, all the other cranial nerves remaining 
 untouched, the voice is lost as completely as if the inferior laryn- 
 geal itself had been destroyed. All the motor fibres of the pneu- 
 mo'gastrio, therefore, which act in the formation of the voice are 
 derived, by inosculation, from the spinal accessory nerve. 
 
 In respiration, again, the larynx performs another and still more 
 important function. In the first place, it stands as a sort of guard, 
 or sentinel, at the entrance of the respiratory passages, to prevent 
 the intrusion of foreign substances. If a crumb of bread accidentally 
 fall within the aryteno-epiglottidean folds, or upon the edges of the 
 vocal chords, or upon the posterior surface of the epiglottis, the 
 sensibility of these parts immediately excites a violent expulsive 
 cough, by which the foreign body is dislodged. The impression 
 received and conveyed inward by the sensitive fibres of the superior 
 laryngeal nerve, is reflected back upon the expiratory muscles 
 of the chest and abdomen, by which the instinctive movements of 
 coughing are accomplished. Touching the above parts with the 
 point of a needle, or pinching them with the blades of a forceps, 
 will produce the same effect. This reaction is essentially dependent 
 on the sensibility of the laryngeal mucous membrane ; and it can 
 no longer be produced after section of the pneumogastric nerve, or 
 of its superior laryngeal branch. 
 
 In the second place, the respiratory movements of the glottis, already 
 described jn a previous chapter, are of the greatest importance to 
 the preservation of life. "We have seen that at the moment of 
 inspiration the vocal chords are separated from each other, and the 
 glottis opened, by the action of the posterior crico-arytenoid muscles ; 
 and that in expiration the muscles and the vocal chords are both 
 relaxed, and the air allowed to pass out readily through the glottis. 
 The opening of the glottis in inspiration, therefore, is an active 
 movement, while its partial closure or collapse in expiration is a 
 passive one. Furthermore, the opening of the glottis in inspiratioft.. 
 is necessary in order to afford a sufficiently wide passage for the 
 air, in its way to the trachea, bronchi, and pulmonary vesicles. 
 
 Now we have found, as Budge and Longet had previously no- 
 ticed, that if the inferior laryngeal nerve on the right side be 
 divided while the glottis is exposed as above, the respiratory move- 
 
 ' Recherehes Exp6rimentales sur les fonctions du nerf spinal. Paris, 1851. 
 
PNEUMOGASTRIC NERVE. 46? 
 
 ments of the right vocal chord instantly cease, owing to the para- 
 lysis of the posterior crico-arytenoid muscle on that side. If the 
 inferior laryngeal nerve on the left side be also divided, the para- 
 lysis of the glottis is then complete, and its respiratory movements 
 cease altogether. A serious difficulty in respiration is the imme- 
 diate consequence of this operation. For the vocal chords) being 
 no longer stretched and separated from each other at the moment 
 of inspiration, but remaining lax and flexible, act as a double valve, 
 and are pressed inward by the column of inspired air ; thus par- 
 tially blocking up the passage and impeding the access of air to 
 the lungs. If the pneumogastrics be divided in the middle of the 
 neck, the larynx is of course paralyzed precisely as after section 
 of the inferior laryngeal nerves, since these nerves are given off 
 only after the main trunks have entered the cavity of the chest. 
 The immediate effect of either of these operations is to produce 
 a difficulty of inspiration, accompanied by a peculiar wheezing or 
 sucking noise, evidently produced in the larynx and dependent on 
 the falling together of the vocal chords. In very young animals, 
 as, for example, in pups a few days old, in whom the glottis is 
 smaller and the larynx less rigid than in adult dogs, this difficulty 
 is much more strongly marked. Legallois' has even seen a pup 
 two days old almost instantly suffocated after section of the two 
 inferior laryngeal nerves, We have found that, in pups two 
 weeks old, division of the inferior laryngeals is followed by death 
 at the end of from thirty to forty hours, evidently from impeded 
 respiration. 
 
 The importance, therefore, of these movements of the glottis in 
 respiration becomes very evident. They are, in fact, part and 
 parcel of the general respiratory movements, and are necessary to 
 a due performance of the function. It has been found, moreover, 
 that the motor filaments concerned in this action are not derived, 
 like those of the voice, from a single source. While the vocal 
 movements of the larynx are arrested, as mentioned above, by 
 division of the spinal accessory alone, those of respiration still go 
 on ; and in order to put a stop to the latter, either the pneumo- 
 gastrics themselves must be divided, or all five of the motor nerves 
 from which their accessory filaments are derived. This fact has 
 been noticed by Longet as showing that nature multiplies the safe- 
 guards of a function in proportion to its importance ; for while the 
 
 ' In Longet's Traite de Physiologie, toI. ii. p. 324. 
 
468 THE CRANIAL NERVES. 
 
 spinal accessory, or any other one of the above-mentioned nerves, 
 might be affected by local accident or disease, it would be very 
 improbable that any single injury should paralyze simultaneously 
 the spinal accessory, the facial, the hypoglossal, and the first and 
 second cervicals. The respiratory movements of the larynx are 
 consequently much more thoroughly protected than those which 
 are merely concerned in the formation of the voice. 
 
 Lungs. — The influence of the pneumogastric upon the function 
 of the lungs is exceedingly important. The nerve acts here, as in 
 most other organs to which it is distributed, in a double or mixed 
 capacity ; but it is princ;ipally as the sensitive nerve of the lungs 
 that it has thus far received attention. It is this nerve which 
 conveys from the lungs to the medulla oblongata that peculiar 
 impression, termed hesoin de respirer, which excites by reflex action 
 the diaphragm and intercostal muscles, and keeps up the play of 
 the respiratory movements. As we have already shown, this action 
 is an involuntary one, and will even take place when consciousness 
 is entirely suspended. It may indeed be arrested for a time by an 
 effort of the will ; but the impression conveyed to the medulla soon 
 becomes so strong, and the stimulus to inspiration so urgent, that 
 they can no longer be resisted, and the muscles contract in spite of 
 our attempts to restrain them. 
 
 - A very remarkable effect is accordingly produced on respiration , 
 by simultaneous division of both pneumogastric nerves. This 
 experiment is best performed on adult dogs, which may be ether- 
 ized, and the nerves exposed while the animal is in a condition of 
 insensibility, avoiding, in this way, the disturbance of respiration, 
 which would follow if the dissection were performed while the ani- 
 mal was conscious and sensible to pain. After the effects of the 
 etherization have entirely passed off, and respiration and circulation 
 have both returned to a quiescent condition, the two nerves, which 
 have been previously exposed and secured by a loose ligaturp, may 
 be instantaneously divided, and the effects of the operation readily 
 appreciated. 
 
 Immediately after the division of the nerves, when performed ia 
 the above manner, the respiration is hurried and difficult, owing to 
 the sudden paralysis of the larynx and partial closure of the glottis 
 by the vocal chords, as already described. This condition, how- 
 ever, is of short continuance. In a few moments, the difficulty of 
 breathing and the general agitation subside, the animal becomes 
 perfectly quiet, and the only remaining visible effect of the opera- 
 
PNEUMOGA.STSIC NERVE. 469 
 
 tion is a diminished frequency in the movements of respiration. This 
 diminution is frequently strongly marked from the first, the number 
 of respirations falling at once to ten or fifteen per minute, and be- 
 coming, in an hour or two, still farther reduced. The respirations 
 are performed easily and quietly ; and the animal, if left undisturbed, 
 remains usually crouched in a corner, without giving any special 
 signs of discomfort. If he be aroused and compelled to move 
 about, the frequency of the respiration is temporarily augmented ; 
 but as soon as he is again quiet, it returns to its former standard. 
 By the second or third day, the number of respirations is often 
 reduced to five, four, or even three per minute ; when this is the 
 case, the animal usually appears very sluggish, and is roused with 
 difficulty from his inactive condition. At this time the respiration 
 is not only diminished in frequency, but is also performed in a 
 peculiar manner. The movement of inspiration is slow, easy, and 
 silent, occupying several seconds in its accomplishment ; expiration, 
 on the contrary, is sudden and audible, and is accompanied by a well 
 marked expulsive efibrt, which has the appearance of being, to a 
 certain extent, voluntary in character. The intercostal spaces also 
 sink inward during the lifting of the ribs ; and the whole movement 
 of respiration has an appearance of insufficiency, as if the lungs 
 were not thoroughly filled with air. This insufficiency of respira- 
 tion is undoubtedly owing to a peculiar alteration in the pulmonary 
 texture, which has by this time already commenced. 
 
 Death takes place at a period varying from one to six days after 
 the operation, according to the age and strength of the animal. 
 The only symptoms accompanying it are a steady failure of the 
 respiration, with increased sluggishness and indisposition to be 
 aroused. There are no convulsions, nor any evidences of paii;. 
 After death the lungs are found in a peculiar state of solidification, 
 which is almost exclusively a consequence of. this operation, and 
 which is entirely different from ordinary inflammatory hepatization. 
 They are not swollen, but rather smaller than natural. They are 
 of a dark purple color, leathery and resisting to the feel, destitute 
 of crepitation, and infiltrated with blood. Pieces of the lung cut 
 out sink in water. The pleural surfaces, at the same time, are bright 
 and polished, and their cavity contains no effusion or exudation. 
 The lungs, in a word, are simply engorged with blood and empty 
 of air ; their tissue having undergone no other alteration. 
 
 These changes are not generally uniform over both lungs. The 
 organs are usually mottled on their exterior ; the variations in color 
 
470 THE CRANIAL NERVES. 
 
 corresponding with the different degrees of. alteration exhibited bj 
 different parts. 
 
 The explanation usually adopted of the above consequences fol- 
 lowing division of the pneumogastrics is as follows : The nerves 
 being divided, the impression which originates in the lungs from 
 the accumulation of carbonic acid, and which is destined to excite 
 the respiratory movements by reflex action, can no longer be trans- 
 mitted to the medulla oblongata. The natural stimulus to respira- 
 tion being wanting, it is, accordingly, less perfectly performed.' The 
 respiratory movements diminish in frequency, and, growing con- 
 tinually slower and slower, finally cease altogether, and death is 
 the result. 
 
 The above explanation, however, is not altogether suiBcient. It 
 accounts very well for the diminished frequency of respiration, but 
 not for its. partial continuance. For if the pneumogastric nerves 
 be really the channel through which the stimulus to respiration is 
 conveyed to the medulla, the difficulty is not to understand why 
 respiration should be retarded after division of these nerves, but 
 why it should continue at all. In point of fact, the respiratory 
 movements, though diminished in frequency, continue often for 
 some days after this operation. This cannot be owing to force of 
 habit, or to any remains of nervous influence, as has been some- 
 times suggested, since, when the medulla itself is destroyed, respira- 
 tion, as we know, stops instantaneously, and no attempt at move- 
 ment is made after the action of the nervous centre is suspended. 
 
 It is evident, therefore, that the pneumogastric nerve, though the 
 chief agent by which the respiratory stimulus is conveyed to the 
 medulla, is not the only one. The lungs are undoubtedly the 
 organs which are most sensitive to an accumulation of carbonic 
 acid, and an imperfect arterialization of the blood ; and the sensa- 
 tion which results from such an accumulation is accordingly first 
 felt in them. There is reason to believe, however, that all the vas- 
 cular organs are more or less capable of originating this impression, 
 and that all the sensitive nerves are capable, to some extent, of trans- 
 mitting it. Although the first disagreeable sensation, on holding 
 the breath, makes itself felt in the lungs, yet, if we persist in sus- 
 pending the respiration, we soon become conscious that the feeling 
 of discomfort spreads to other parts ; and at last, when the accu- 
 mulation of carbonic acid and the impurity of the blood have 
 become excessive, all parts of the body suffer alike, and are per- 
 vaded by a general feeling of derangement and distress. It is easy. 
 
PNECJIOGASTEIC NBBVB. 471 
 
 therefore, to understand wHy respiration should be retarded, after 
 section of the pneumogastrics, since the chief source of the stimulus 
 to respiration is cut ofi'; but the movements still go on, though more 
 slowly than before, because the other sensitive nerves, which con- 
 tinue to act, are also capable, in an imperfect manner, of conveying 
 the same impression. 
 
 The immediate cause of death, after this operation, is no doubt 
 the altered condition of the lungs. These organs are evidently 
 very imperfectly filled with air, for some time previous to death ; 
 and their condition, as shown in post-mortem examination, is evi- 
 dently incompatible with a due performance of the respiratory 
 function. It is not at all certain, however, that these alterations 
 in the pulmonary tissue are directly dependent on division of the 
 pneumogastric nerves. It must be recollected that when the sec- 
 tion of the pneumogastrics is performed in the middle of the neck, 
 the filaments of the inferior laryngeal nerves are also divided, and 
 the narrowing of the glottis, produced by their paralysis, must 
 necessarily interfere with the free admission of air into the chest. 
 This difficulty, either alone or combined with the diminished fre- 
 quency of respiration, must have a very considerable effect in im- 
 peding the pulmonary circulation, and bringing the lungs into such 
 a condition as unfits them for maintaining life. » 
 
 In order to ascertain the comparative influence upon the lungs 
 of division of the inferior laryngeals and that of the other filaments 
 of the pneumogastrics, we have resorted to the following experi- 
 ment. 
 
 Two pups were taken, belonging to the same litter and of the 
 same size and vigor, about two weeks old. In one of them (No. 1) 
 the pneumogastrics were divided in the middle of the neck ; and 
 in the other (No. 2) a section was made at the same time of the 
 inferior laryngeals, the trunk of the pneumogastrics being left un- 
 touched. For the first few seconds after the operation, there was 
 but little difference in the condition of the two animals. There was 
 the same obstruction of the breath (owing to closure of the glottis), 
 the same gasping and sucking inspiration, and' the same frothing at 
 the mouth. Very soon, however, in pup No. 1, the respiratory 
 movements became quiescent, and at the same time much reduced 
 in frequency, falling to ten, eight, and five respirations per minute, 
 as usual after section of the pneumogastrics ; while in No. 2 the 
 respiration continued frequent as well as laborious, and the general 
 signs of agitation and discomfort were kept up for one or two hours. 
 
472 THE CRANIAL NEKVJfiS. 
 
 i 
 
 The animal, however, after that time became exhausted, cool, and 
 partially insensible, like the other. They both died, between thirty 
 and forty hours after the operation. On post-mortem inspection it 
 was found that the peculiar congestion and solidification of the 
 lungs, considered as characteristic of division of the pneumogastrics, 
 existed to a similar extent in each instance ; and the only appre- 
 ciable difference between the two bodies was that in No. 1 the blood 
 was coagulated, and the abdominal organs natural, while in No. 2 
 the blood was fluid and the abdominal organs congested. We are 
 led, accordingly, to the following conclusions with regard to the 
 effect produced by division of this nerve. 
 
 1. After section of the pneumogastrics, death takes place by a pecu- 
 liar congestion of the lungs. 
 
 2. This congestion is not directly produced by division of the 
 nerves, but is caused by the imperfect admission of air into the 
 chest. 
 
 In adult dogs, the closure of the glottis from paralysis of the 
 laryngeal muscles is less complete than in pups; but it is still 
 sufficient to exert a very decided influence on respiration, and to 
 take an active part in the production of the subsequent morbid 
 phenomena. 
 
 We therefore regard the death which takes place after division 
 of both pneumogastric nerves, as produced in the following man- 
 ner: — 
 
 The glottis is first narrowed by paralysis of the laryngeal mus- 
 cles, and an imperfect supply of air is consequently admitted, by 
 each inspiration, into the trachea. Next, the stimulus to respiration 
 being very much diminished, the respiratory movements take place 
 less frequently than usual. From these two causes combined, the 
 blood is imperfectly arterialized. But the usual consequence of 
 such a condition, viz., an increased rapidity of the respiratory 
 movements, does not follow. The imperfect arterialization of 
 the blood does not excite the respiratory muscles to increased 
 activity as it would do in health, owing to the division of the pneu- 
 mogastrics. At the same time, the accumulation of carbonic acid 
 in the blood and in the tissues begins to exert a narcotic effect, 
 diminishing the sensibility of the nervous centres, and tending to 
 retard still more the movements of respiration. Thus all these 
 causes react upon and aggravate each other ; because the connec- 
 tion, naturally existing between imperfectly arterialized blood and 
 the stimulus to respiration, is now destroyed. The narcotism and 
 
PNEUMOGASTBIO NEBVE. 473 
 
 pulmonary engorgement, therefore, continue to increase, until the 
 lungs are so seriously altered and engorged that they are no longer 
 capable of transmitting the blood, and circulation and respiration 
 come to an end at the same time. 
 
 It must be remembered, also, that the pneumogastrio nerve has 
 other important distributions, beside those to the larynx and the 
 lungs; and the effect produced by its division upon these other 
 organs has no doubt a certain share in producing the results which 
 follow. Bearing in mind the very extensive distribution of the 
 pneumogastrio nerve and the complicated character of its func- 
 tions, we may conclude that after section of this nerve death takes 
 place from a combination of various causes; the most active of 
 which is a peculiar engorgement of the lungs and imperfect per- 
 formance of the respiratory function. 
 
 Stomach, and Digestive Function. — After division of the pneumo- 
 gastrio nerves, the sensations of hunger and thirst remain, and the 
 secretion of gastric juice continues. Nevertheless the digestive 
 function is disturbed in various ways, though not altogether abo- 
 lished. The appetite is more or less diminished, as it would be 
 after any serious operation, but it remains sufficiently active to 
 show that its existence is not directly dependent on the integrity of 
 the pneumogastrio nerve. Digestion, however, very seldom takes 
 place, to any considerable extent, owing to the following circum- 
 stances : The animal is frequently seen to take food and drink with 
 considerable avidity ; but in a few moments afterward the food and 
 drink are suddenly rejected by a peculiar kind of regurgitation. 
 This regurgitation does not resemble the act of vomiting, but the 
 substances swallowed are again discharged so easily and instan- 
 taneously as to lead to the belief that they had never passed into 
 the stomach. Such, indeed, is actually the case, as any one may 
 convince himself by watching the process, which is often repeated 
 by the animal at short intervals. The food and drink, taken volun- 
 tarily, pass down into the oesophagus, but owing to the paralysis of 
 the muscular fibres of this canal, are not conveyed into the stomach., 
 They accumulate consequently in the lower and middle part of the 
 oesophagus ; and in a few moments are rejected by a sudden anti- 
 staltic action of the parts, excited, apparently, through the influence 
 of the great sympathetic. 
 
 The muscular coat of the stomach is also paralyzed to a con- 
 siderable extent by section of this nerve. Longet has shown, by 
 introducing food artificially into the stomach, that gastric juice 
 
474 THE CBANIAL NEBVES. 
 
 may be secreted and the food be actually digested and disappear, 
 when introduced in small quantity. But when introduced in large 
 quantity, it remains undigested, and is found after death, with the 
 exterior of the mass softened and permeated by gastric juice, whUe 
 the central portions are unaltered, and do not even seem to have 
 come in contact with the digestive fluid. This is undoubtedly 
 owing both to the diminished sensibility of the mucous membrane 
 of the stomach, and to the paralysis of its muscular fibres. The 
 peristaltic action of the organ is very important in digestion, in 
 order to bring successive portions of the food in contact with its 
 mucous membrane, and to carry away such as are already softened 
 or as are not capable of being digested in the stomach. This 
 constant movement and agitation of the food is probably also one 
 great stimulus to the continued secretion of the gastric juice. The 
 digestive fluid will therefore be deficient in quantity after division 
 of the pneumogastric nerve, at the same time that the peristaltic 
 movements of the stomach are suspended. Under these circum- 
 stances, the secretion of gastric juice may be sufficient to permeate 
 and digest small quantities of food, while a larger mass may resist 
 its action, and remain undigested. The effect produced by division 
 of these nerves on the digestive, as on the respiratory organs, is 
 therefore of a complicated character, and results from the combined 
 action of several different causes, which influence and modify each 
 other. 
 
 The efiect produced upon the liver by section of the pneumo- 
 gastrics, as well as the influence usually exerted by these nerves 
 upon the hepatic functions, has been so little studied that nothing 
 definite has been ascertained in regard to it,. We shall therefore 
 pass over this portion of the subject in silence. 
 
 Spinal Acoessoet. — This nerve originatfes, by many filaments, 
 from the side of the medulla oblongata, below the level of the 
 pneumogastric, and also from the lateral portions of the spinal cord, 
 between the anterior and posterior roots of the upper five or six 
 cervical nerves. These fibres of spinal origin pass upward, uniting 
 into a slender rounded filament, which enters the cavity of the 
 cranium by the foramen magnum, and is then joined by the fibres 
 which originate from the medulla oblongata. The spinal accessory 
 nerve, thus constituted, passes qut from the cavity of the skull by 
 the posterior foramen lacerum, in company with the glosso-pharyn- 
 geal and pneumogastric nerves. Immediately afterward it divides 
 
SPINAL ACCESSORY. 475 
 
 into two principal branches: First the internal or anastomotic 
 branch, which joins the pneumogastric nerve, and becpmes mingled 
 with its fibres; and, secondly> the external or muscular branch, 
 which passes downward and outward, and is distributed to the 
 sterno-mastoid and trapezius muscles. 
 
 The spinal accessory is essentially a motor nerve. It has been 
 found, both by Bernard and Longet, to be insensible at its origin, 
 like the anterior roots of the spinal nerves ; but if irritated after 
 its exit from the skull, it gives signs of sensibility. This sensibi- 
 lity it acquires from the filaments of inosculation which it receives 
 from the anterior branches of the first and second cervical nerves. 
 Though its external branch, accordingly, is exclusively distributed 
 to muscles, as we have already seen, this branch contains some sensi- 
 tive fibres, which have the same destination. The reason for this 
 anatomical fact, viz., that motor nerves are supplied during their 
 course with sensitive fibres, becomes evident when we reflect that the 
 muscles themselves possess a certain degree of sensibility, though 
 less acute than that which belongs to the skin. The sensibility of 
 the muscles is undoubtedly essential to the perfect performance of 
 their function ; and as the motor nerves are incapable, by them- 
 selves, of transmitting sensitive impressions, they are joined, soon 
 after their origin, by other filaments which communicate to them 
 this necessary power. 
 
 The most important result which has been obtained by experi- 
 ment upon the spinal accessory nerve, is that its internal or anasto- 
 motic branch is directly connected vdth the vocal movements of the 
 glottis. It has been found by Bischofif, by Longet, and by Bernard, 
 that if the spinal accessory nerves on both sides, or their branches 
 of inosculation with the pneumogastric, be divided or lacerated, 
 the pneumogastric nerves themselves being left entire, the voice is 
 instantly lost, and the animal becomes incapable of making a vocal 
 sound. We have also found this result to follow, in the cat, after 
 the spinal accessory nerves have been torn out by their roots, 
 through the jugular foramen. The animal, after this operation, can 
 no longer make an audible sound. At the same time the respira- 
 tory movements of the glottis go on undisturbed, and most of the 
 other animal functions remain unaffected. 
 
 The fibres of communication, therefore, derived from the spinal 
 accessory, pass to the pneumogj^stric nerve and become entangled 
 with its other filaments, so that they can no longer be traced by 
 anatomical dissection. They pass downward, however, aiid become 
 
476 THE CRANIAL NERVES. 
 
 a part of the motor fibres of the inferior laryngeal or recurrent 
 branches of the pneumogastric ; being finally distributed to the 
 muscles of the larynx, which they supply with those nervous influ- 
 ences which are required for the formation of the voice. 
 
 The special function of the external or muscular branch of the 
 spinal accessory is not so fully understood. This branch, as we 
 have seen, is distributed to the stemo-mastoid and trapezius mus- 
 cles. But these muscles also receive filaments from the cervical 
 spinal nerves ; and, accordingly, they still retain the power of mo- 
 tion, to a certain degree, after the external branches of the spinal 
 accessory have been divided on both sides. 
 
 The spinal accessory is, accordingly, a n^rve of very peculiar 
 distribution. For it partly supplies motor fibres to the pneumo- 
 gastric nerve, and is partly distributed to two muscles, both of 
 which also receive motor nerves fifom another source. Sir Charles 
 Bell, noticing the close connection between this nerve and the 
 pneumogastric, regarded the two as associated also in their func- 
 tion, as nerves of respiration. He considered, therefore, the exter- 
 nal branch of the spinal accessory as destined to assist in the 
 movements of respiration, when these movements become unusu- 
 ally laborious, by bringing into play the sterno-mastoid and trape- 
 zius muscles, in aid of the action of the intercostals. He therefore 
 called this nerve the " superior respiratory nerve." 
 
 But the most satisfactory explanation of this peculiarity is that 
 proposed by M. Bernard. According to this explanation, whenever 
 a muscle, or set of muscles, derive their nervous influence from two 
 different sources, this is not for the purpose of assisting them in the 
 performance of the same function, but of enabling them to perform 
 two different functions. We have seen this already exemplified in 
 the muscles of the larynx. For these muscles perform certain 
 movements of respiration for which they receive indirectly filaments 
 from the facial hypoglossal, and cervical nerves. But they also 
 perform the movements necessary to the formation of the voice, the 
 nervous stimulus for which is derived altogether from the spinal 
 accessory. 
 
 The internal branch of the spinal accessory, accordingly, excites, 
 in the parts to which it is distributed a function which is incompa' 
 tible with respiration. For the movements of respiration cannot 
 go on while the voice is sounded; and a necessary preliminary 
 to the production of a vocal sound, is the temporary stoppage of 
 respiration. The movements of respiration, therefore, and the 
 
HYPOGLOSSAL. 477 
 
 movements of the voice alternate with each other, but are never 
 simultaneous ; so that the internal branch of the spinal accessory is 
 antagonistic to the motor fibres of the larynx derived from other 
 nerves. 
 
 It is thought by M. Bernard, that the fibres of the external 
 branch of the spinal accessory, have also a function which is anta- 
 gonistic to respiration. For respiration is naturally suspended in 
 all steady and prolonged muscular efforts. In these efforts, such as 
 those of straining, lifting, and the like, the movements of respira- 
 tion cease, the spinal column is made rigid by the contraction of 
 its muscles, and the head and neck are placed in a fixed position, 
 principally by the contraction of the sterno-mastoid and trapezius 
 muscles. The function of the spinal accessory, in both its branches, 
 is therefore regarded as destined to excite movements which are 
 incompatible with those of respiration ; and which accordingly come 
 into play only when the ordinary movements of respiration have 
 been temporarily suspended. 
 
 Hypoglossal. — The hypoglossal nerve originates from the ante- 
 rior and lateral portions of the medulla oblongata, and passing out 
 by the anterior condyloid foramen, is distributed exclusively to the 
 muscles of the tongue. Irritation of its fibres in any part of their 
 course produces convulsive twitching in this organ. Its section 
 paralyzes completely the movements of the tongue, without affect- 
 ing directly the sensibility of its mucous membrane. This nerve, 
 acQordingly, is the motor nerve of the tongue. If irritated at its 
 origin, the hypoglossal nerve, according to the experiments of 
 Longet, is entirely insensible ; but if the irritation be applied in the 
 middle of its course, signs of pain are immediately manifested. Its 
 sensibility, like that of the facial, is consequently derived from its , 
 inosculation with other sensitive nerves, after its emergence from 
 the skull. 
 
4:78 THE SPECIAL SENSES. 
 
 CHAPTER VI. 
 
 THE SPECIAL SENSES. 
 
 Geneeal and Special Sensibility. — We have already seen 
 that there exists, in the general integument, a power of sensation, by 
 which we are made acquainted with surrounding objects and some 
 of their most important physical qualities. By this power we feel 
 the sensations of heat and cold, and are enabled to distinguish 
 between hard and sofl; substances, rough bodies and smooth, solids 
 and liquids. This kind of power is termed General Sensibility, 
 because it resides in the general integument, and because by its 
 aid we obtain information with regard to the simplest and most 
 material properties of external objects. 
 
 The general sensibility, thus existing in the integument, is an 
 endowment of the sensitive nerves derived from the cerebro-spinal 
 
 , system. These nerves ramify in the substance of the skin, and by 
 subsequent inosculation form a minute plexus in the superficial 
 portions of the tissue of the corium. Froni this plexus, the ulti- 
 mate filaments, reduced to an exceedingly minute size, pass up- 
 ward into the conical ' papillae with which the free surface of the 
 corium is covered. In the papilla the nervous filaments terminate, 
 sometimes by loops returning upon themselves, and sometimes ap- 
 
 . parently by free extremities. The papillae are also supplied with 
 looped capillary bloodvessels, and are capable of receiving an 
 abundant vascular injection. 
 
 These papillae appear to be the most essential organs of general 
 sensation, since the sensibility of the skin is most acute where they 
 are most abundant and most highly developed, as, for exampl6, on 
 the palm of the hand and the tips of the fingers. 
 
 The best method of measuring accurately the sensibility of dif- 
 ferent regions is that adopted by Professors Weber and Valentin. 
 They applied the rounded points of a pair of compasses to the 
 integument of difierent parts, and found that if they were held 
 very near together they could no longer be distinguished as sepa- 
 
GENERAL AND SPECIAL SENSIBILITY. 479 
 
 rate points, but the two sensations were confounded into one. The 
 distance, however, at which the two points failed to be distinguished 
 from each other, was much shorter for some parts of the body 
 than for others. 'Prof. Valentin's measurements,^ which are the 
 most varied and complete, give the following as the limits of dis- 
 tinct perception in various parts : — 
 
 Paris Lihe. 
 
 At the tip of tongue .483 
 
 " palmar surface of tips of fingers .... .723 
 
 " " " of second phalanges . . . 1.558 
 
 " " " of first phalanges .... 1.650 
 
 " dorsum of tongue 2.500 
 
 " dorsal surface of fingers 3.900 
 
 " cheek 4.541 
 
 " back of hand 6.966 
 
 " skin of throat 8.292 
 
 " dorsum of foot 12.525 
 
 " skin over sternum 15.875 
 
 " middle of back . . • 24.208 
 
 This method cannot, of course, give the absolute measure of the 
 acuteness of sensibility in the different regions, since the' two points 
 might be less easily distinguished from each other in any one re- 
 gion, and yet the absolute amount of sensation produced might be 
 as great as in the surrounding parts ; still it is undoubtedly a very 
 accurate measure of the delicacy of tactile sensation, by which we 
 are enabled to distinguish slight inequalities in the surface of solid 
 bodies. We find, furthermore, that certain parts of the body are 
 particularly well adapted to exercise the function of general sen- 
 sation, not only on account of the acute sensibility of their integu- 
 ment, but also owing to their peculiar formation. Thus, in man, 
 the hands are especially well formed in this respect, owing to the 
 articulation and mobility of the fingers, by which they may be 
 adapted to the surface of solid bodies, and brought successively 
 in contact with all their irregularities and depressions. The hands 
 are therefore more especially used as organs of touch, and we are 
 thus enabled to obtain by their aid the most delicate and precise 
 information as to the texture, consistency,. configuration, &c., of 
 foreign bodies. 
 
 But the hands are not the exclusive organs of touch, even in the 
 human subject, and in some of the lower animals, the same func- 
 
 ' In Todd's Cyclopaedia of Anatomy and Physiology, vol. iv., article on Touch, 
 by Dr. Carpenter. 
 
480 THE SPECIAL SENSES. 
 
 tion is fully performed by various otter parts of the body. Thus 
 in the cat and in the seal, the long bristles seated upon the lips are 
 used for this purpose, each bristle being connected at its base with 
 a highly developed nervous papilla : in some of the monkeys the 
 extremity of the prehensile tail, and in the elephant the end of the 
 nose, which is developed into a flexible and sensitive proboscis, is 
 employed as an organ of touch. This function, therefore, may be 
 performed by either one part of the body or another, provided the 
 accessory organs be developed in a favorable manner. 
 
 About the head and face, the sensibility of the skin is dependent 
 mainly upon branches of the fifth pair. In the neck, trunk, and 
 extremities it is due to the sensitive fibres of the cervical, dorsal, 
 and lumbar spinal nerves. It exists also, to a considerable extent, 
 in the mucous membranes of the mouth and nose, and of the pas- 
 sages leading from them to the interior of the body. In these 
 situations, it depends upon the sensitive filaments of certain of the 
 cranial nerves, viz., the fifth pair, the glosso-pharyngeal, and the 
 pneumogastric. The sensibility of the mucous membranes is most 
 acute in those parts supplied by branches of the fifth pair, viz., the 
 conjunctiva, anterior part of the nares, inside of the lips and cheeks, 
 and the anterior two-thirds of the tongue. At the base of the 
 tongue and in the fauces, where the mucous membrane is supplied 
 by filaments of the glosso-pharyngeal nerve, the general sensibihty 
 is less perfect; and finally it diminishes rapidly from the upper 
 part of the oesophagus and the glottis toward the stomach and the 
 lungs. Thus, we can appreciate the temperature and consistency 
 of a foreign substance very readily in the mouth and fauces, but 
 these qualities are less distinctly perceived in the oesophagus, and 
 not at all in the stomach, unless the foreign body happen to be 
 excessively hot or cold, or unusually hard and angular in shape. 
 The general sensibility, which is resident in the skin and in a certain 
 portion of the mucous membranes, diminishes in degree from with- 
 out inward, and disappears altogether in those organs which are 
 not supplied with nerves from thq cerebro-spinal system. 
 
 It is particularly to be observed, however, that while the general 
 sensibility of the skin, and of the mucous membranes above men- 
 tioned, varies in aouteness in different parts of the body, it is every- 
 where the same in kind. The tactile sensations, produced by the 
 contact of a foreign body, are of precisely the same nature whether 
 they be felt by the tips of the fingers, the dorsal or palmar surfaces 
 of the hands, the lips, cheeks, or any other part of the integument. 
 
TASTE. 4.81 
 
 The only difference in tlie sensibility of these parts lies in the de- 
 gree of its development. 
 
 But there are certain other sensations which are different in kind 
 from those perceived by the general integutnent, and which, owing 
 to their peculiar and special character, are termed special sensations. 
 Such are, for example, the sensation of light, the sensation of sound, 
 the sensation of savor, and the sensation of odors. The special 
 sensibility which enables us to feel the impressions derived from 
 these sources is not distributed over the body, like ordinary sensi- 
 bility, but is localized in distinct organs, each of which is so con- 
 stituted as to receive the special sensation peculiar to ity and no 
 other. 
 
 Thus we have, beside the general sensibility of the skin and 
 mucous membranes, certain peculiar faculties or special senses, as 
 they are called, which enable us to derive information from ex- 
 ternal objects,*which we could not possibly obtain by any other 
 means. Thus light, however intense, produces no perceptible sen- 
 sation when allowed to fall upon the skin, but only when admitted 
 to the eye. The sensation of sound is perceptible only by the 
 ear, and that of odors only by the olfactory membrane. These 
 different sensations, therefore, are not merely exaggerations of 
 ordinary sensibility, but are each distinct and peculiar in their 
 nature, and are in relation with distinct properties of external 
 objects. 
 
 In examining the organs of special sense, we shall find that they 
 each consist — First, of a nerve, endowed with the special sensibility 
 required for the exercise of its peculiar function ; and, Secondly, of 
 certain accessory parts, forming an apparatus more or less compli- 
 ' cated, which is intended to assist in its performance and render it 
 more delicate and complete. We shall take up the consideration 
 of the special senses in the following order. First, the sense of 
 Taste ; second, that of Smell ; third, that of Sight ; and fourth, that 
 of Hearing, 
 
 Taste. — We begin the study of the special senses with that of 
 Taste, because this sense is less peculiar than any of the others, and 
 differs less, both in its nature and its conditions, from the ordinary 
 sensibility of the skin. In the first place, the organ of taste is no 
 other than a portion of the mucous membrane, beset with vascular 
 and nervous papillEe,' similar to those of the general integument. 
 31 
 
482 THE SPECIAL SENSES. 
 
 Secondly, it gives us impressions of such substances only as are 
 actually in contact with sensitive surfaces, and can establish no 
 communication with objects at a distance. Thirdly, the surfaces 
 which exercise the sense of taste are also endowed with general sen- 
 sibility ; and Fourthly, there is no one special and distinct nerve 
 of taste, but this property resides in portions of two different 
 nerves, viz., the fifth pair; and the glosso-pharyngeal ; nerves which 
 also supply general sensibility to the mouth and surrounding parts. 
 
 The sense of taste is localized in the mucous membrane of the 
 tongue, the soft palate, and the fauces. The tongue, which is more 
 particularly the seat of this sense, is a, flattened, leaf-like, muscular 
 organ, attached to the inner surface of the symphysis of the lower 
 jaw in front, and to the os hyoides behind. It has a vertical sheet 
 or lamina of fibrous tissue in the median line, which serves as a 
 framework, and is provided with an abundance of longitudinal 
 transverse and radiating muscular fibres, by which it can be elon- 
 gated, retracted, and moved about in every direction. 
 
 The mucous membrane of the fauces and posterior third of the 
 tongue, like that lining the cavity of the mouth, is covered with 
 minute vascular papillae, similar to those of the skin, which are, 
 however, imbedded and concealed in the smooth l^yer of epithe- 
 lium forming the surface of the organ. But about the junction of 
 its posterior and middle thirds, there is, upon the dorsum of the 
 tongue, a double row of rounded eminences, arranged in a V-shaped 
 figure, running forward and outward, on each side, from the situa- 
 tion of the foramen caecum ; and, from this point forward, the upper 
 surface of the organ is everywhere covered with an abundance of 
 thickly-set, highly' developed papillae, projecting from its surface, 
 and readily visible to the naked eye. 
 
 These lingual papillae are naturally divided into three different 
 sets or kinds. First, the filiform papillae^ which are the most nume- 
 rous, and which cover most uniformly the upper surface of the 
 organ. They are long and slender, and are covered with a some- 
 what horny epithelium, usually prolonged at their free extremity 
 into a filamentous tuft. At the edges of the tongue these papilla 
 are often united into parallel ranges or ridges of the mucous mem- 
 brane. Secondly, the fungiform papillae. These are thicker and 
 larger than the others, of a rounded club-shaped figure, and covered 
 with soft, permeable epithelium. They are most abundant at the 
 tip of the tongue, but may be seen elsewhere on the surface of the 
 organ, scattered among the filiform papillae. Thirdly, the circum- 
 
TASTE. 483 
 
 vallate papillae. These are the rounded eminences whicli form the 
 V-shaped figure near the situation of the foramen cseoum. They 
 are eight or ten in number. Each one of them is surrounded by 
 a circular wall, or circumvallation, of mucous membrane, which 
 gives to them their distinguishing appellation. The circumvalla- 
 tion, as well as the central eminence, has a structure similar to that 
 of the fungiform papillsB. 
 
 The sensitive nerves of the tongue, as we have already seen, are 
 two in number, viz., the lingual branch of the fifth pair, and the 
 lingual portion of the glosso-pharyngeal. The lingual branch of 
 the fifth pair enters the tongue at the anterior border of the hyo- 
 glossus muscle, and its fibres then run through the muscular tissue 
 of the organ, from below upward and from behind forward, with- 
 out any ultimate distribution, until they reach the mucous mem- 
 brane. The nervous filaments then penetrate into the lingual 
 papillae, where they finally terminate. The exact mode of their 
 termination is not positively known. According to Kolliker, they 
 sometimes seem to end in loops, and sometimes by free extremities. 
 
 The lingual portion of the glosso-pharyngeal nerve passes into 
 the tongue below the posterior border of the hyo-glossus muscle. 
 It tlien divides into various branches, which pass through the mus- 
 cular tissue, and are finally distributed to the mucous membrane of 
 the base and sides of the organ. 
 
 Pig. 153. 
 
 DlAQRAM OF ToNODB, With itJiseD-sItive nervesand papUljB.— 1. Lint'ual branch of fifth pnir, 
 2. Glosao-pharjogeaL nerve. 
 
 The mucous membrane of the base of the tongue, of its edges, 
 and its under surface near the tip, as well as the mucous membrane 
 of the mouthvand fauces generally, is also supplied with mucous 
 follicles, which furnish a viscid secretion by which the free surface 
 of the parts is lubricated. 
 
484 THE SPECIAL SENSES. 
 
 Finally, the muscles of the tongue, it will.be remembered, are 
 animated exclusively by the filaments of the hypoglossal nerve. 
 
 The exact seat of the sense of taste has been determined by 
 placing in contact with different parts of the mucous membrane a 
 small sponge, moistened with a solution of some sweet or bitter 
 substance. The experiments of Verni^re, Longet and others have 
 shown that the sense of taste resides in the whole superior surface, 
 the point and edges of the tongue, the soft palate, fauces, and part 
 of the pharynx. The base, tip, and edges of the tongue seem to 
 possess the most acute sensibility to savors, the middle portion of 
 its dorsum less of this sensibility, and its inferior surfaces little or 
 none. Now as the whole anterior p^t of the organ is supplied by 
 the lingual branch of the fifth pair alone, and the whole of its 
 posterior portion by the glosso-pharyngeal, it follows that the sense 
 of taste, in these different parts, is derived from these two different 
 nerves. 
 
 Furthermore, thd tongue is supplied, at the same time and by the 
 same nerves, with general' sensibility and with the special sensibility of 
 taste. The general sensibility of the anterior portion of the tongue, 
 and that of the branch of the fifth pair with which it is supplied, 
 are sufficiently well known. Section of the fifth pair destroys the 
 sensibility of this part of the tongue as well as that of the rest of 
 the face. Longet has found tfiat after the lingual branch of this 
 nerve has been divided, the mucous membrane of the anterior two- 
 thirds of the tongue may be cauterized with a hot iron or with 
 caustic potassa, in the living animal, without" producing any sign of 
 pain. Dr. John Eeid, on the other hand, together with other experi- 
 menters, has determined that ordinary sensibility exists in a marked 
 degree in the glosso-pharyngeal, and is supplifed by it to the parts 
 to which this nerve is distributed. 
 
 Accordingly we must distinguish, in the impressions produced 
 by foreign substances taken into the mouth, between the special 
 impressions derived from their sapid qualities, and the general sensa- 
 tions produiced by their ordinary physical properties. As the tongue is 
 exceedingly sensitive to ordinary impressions, and as the same body 
 is often capable of exciting both the tactile and gustatory functions, 
 these two properties are sometimes liable to be confounded with 
 each other by careless observation. The truly sapid qualities, 
 however, the only ones, properly speaking, which we perceive by 
 the sense of taste, are such savors as we designate by the term 
 sweet, bitter, salt, sour, alkaline, and the like. But there are many 
 
TASTE. 485 
 
 Other properties, belonging to various articles of food, which belong 
 really to the class of ordinary physical qualities and are appre- 
 ciated by the ordinary sensibility of the tongue, though we usually 
 speak of them as being perceived by the taste. Thus a siaircTiy, 
 viscid, watery, or oleaginous taste is merely a certain variety of con- 
 sistency in the substance tasted, which may exist either alone or in 
 connection with real savors, but which is exclusively perceived by 
 means of the general sensibility. So also with a pungent or burning' 
 taste, such as that of red pepper or any other irritating powder. 
 The quality of piquancy in the preparation of artificial kinds of 
 food is always communicated to them by the addition of some such 
 irritating substance. The styptic taste seems to be a corabination of 
 an ordinary irritant or astringent effect with a peculiar taste, which 
 we always associate with the former quality in astringent sub- 
 stances. 
 
 There is also sometimes a liability to confoniid the real taste of 
 certain substances with their odorous properties, or Jlavors. Thus 
 in most aromatic articles of food, such as tea and coffee, and in 
 various kinds of wine, a great part of what we call the taste is in 
 rea,lity due to the aroma, or smell which reaches the nares during 
 the act of swallowing. Even in many solid kinds of food, such as 
 freshly cooked meats, the odor produces a very important part of 
 their effect on the senses. We can easily convince ourselves of this 
 by holding the nose while swallowing such substances, or by recol- 
 lecting how much a common catarrh interferes with our perception 
 of their taste. 
 
 The most important conditions of the sense of taste are the fol- 
 lowing : — 
 
 In the first place, the sapid substance, in order that its taste may 
 be perceived, must be brought in contact with the mucous mem- 
 brane of the mouth in a state of solution. So loijg as it remains 
 solid, however marked a savor it -may possess, it gives no other 
 impression than that of any foreign body in contact with the sensi- 
 tive surfaces. But if it be applied in a liquid form, it is then spread 
 over the surface of the mucous membrane, and its taste is imme- 
 diately perceived. Thus it is only the liquid and soluble portions 
 of our food which are tasted, such as the animal and vegetable 
 juices and the soluble salts. Saline substances which are insoluble, 
 Hich as calomel or carbonate of lead, when applied to the tongue, 
 produce no gustatory sensation whatever. 
 
 The mechanism of the sense of taste is, therefore, in all proba- 
 
THE SPECIAL SENSES, 
 
 bility, a direct and simple one. The sapid substances in solution 
 penetrate the lingual papillae by endosmosis, and, coming in actual 
 contact with the terminal nej-vous filaments, excite their sensibility 
 by uniting with their substance. We have already seen that the 
 rapidity with which endosmosis will take place under certain con- 
 ditions is sufficiently great to account for the almost instantaneous 
 perception of the taste of sapid substances, when introduced into the 
 mouth. 
 
 It is on this account that a free secretion of the salivary fluids is 
 so essential to the full performance of the gustatory function. If 
 the mouth be dry and parched, our food seems to have lost its taste ; 
 but when the saliva is freely secreted, it is readily mixed with the 
 food in mastication, and assists in the solution of its sapid ingredi- 
 ents ; and the fluids of the mouth, thus impregnated with the savory 
 substances, are absorbed by the mucous membrane, and excite the 
 gustatory nerves. An important part, a,lso, is taken in this process 
 by the movements of the tongue ; for by these movements the food 
 is carried from one part of the mouth to another, pressed against 
 the hard palate, the gums, and the cheeks, its solution assisted, and 
 the penetration of the fluids into the substance of the papillae more 
 rapidly accomplished. If a little powdered sugar, or some vege- 
 table extract be simply placed upon the dorsum of the tongue, but 
 little effect is produced ; but as soon as it is. pressed by the tongue 
 against the roof of the mouth, as naturally happens in eating or 
 drinking, its taste is immediately perceived. This effect is easily 
 explained; since we know how readily movement over a free sur- 
 face, combined with slight friction, will facilitate the imbibition of 
 liquid substances. The nervous papillae of the tongue may there- 
 fore be regarded as the essential organs of the sense of taste, and 
 the lingual muscles as its accessory organs. 
 
 The full effectfof sapid svhstances is not obtained until they are actu- 
 ally swallowed. During the preliminary process of mastication a 
 sufScient degree of impression is produced to enable us to perceive 
 the presence of any disagreeable or injurious ingredient in the food, 
 and to get rid of it, if we desire. But it is only when the food is 
 carried backward into the fauces and pharynx, and is compressed 
 by the constrictor muscles, of these parts, that we obtain a complete 
 perception of its sapid qualities. For at that time the food is spread 
 out by the compression of the muscles, and brought at once in 
 contact with" the entire extent of the mucous membrane possessing 
 gustative sensibility. Then, it is no longer under the control of the 
 
TASTE. 487 
 
 will, and is carried by the reflex actions of the pharynx and oeso- 
 phagus downward to the stomacb. 
 
 The impressions of taste made upon the tongue remain for a cer- 
 tain time afterward. When a very sweet or very bitter substance 
 is taken into the mouth, we retain the taste of its sapid qualities 
 for several seconds after it has been ejected or swallowed. Conse- 
 quently, if several different savors be presented to the tongue in 
 rapid succession, we soon become unable to distinguish them, and 
 they produce only a confused impression, made up of the union of 
 various different sensations ; for the taste of the first, remaining in 
 the mouth, is mingled with that of the second, the taste of these 
 two with that of the third, and so on, until so mauy savors become 
 confounded together that we are no longer able to recognize either 
 of them. Thus it is notoriously impossible to recognize two or 
 three different kinds of wine with the eyes closed, if they be repeat- 
 edly tasted in quick succession. 
 
 K the stibstance first tasted have a particularly marked savor, 
 its taste will preponderate over that of the others, and perhaps pre- 
 vent our recognizing them at all. This effect is still more readily 
 produced by substances which excite the general sensibility of the 
 tongue, such as acrid or stimulating powders. In the same manner 
 as a painful sensation, excited in the skin, prevents the nerves, for 
 the time, from perceiving delicate tactile impressions, so any pungent 
 or irritating substance, which excites unduly the general sensibility 
 oft the tongue, blunts for a time its special sensibility of taste. This 
 effect is produced, however, in the greatest degree, by substances 
 which are at the same time sapid, pungent and aromatic, like sweet- 
 meats flavored with peppermint. Advantage is sometimes taken 
 of this in the administration of disagreeable medicines. By first 
 taking into the mouth some highly flavored and pungent substance, 
 nauseous drugs may be swallowed immediately afterward with but 
 little perception of their disagreeable qualities. 
 
 A very singular fact, in connection with the sense of taste, is that 
 it is sometimes affected in a marked degree by paralysis of the facial 
 nerve. No less than six cases of this kind, occurring in the human 
 subject, have been collected by M. Bernard, and we have also met 
 with a similar instance in which the peculiar phenomena were well 
 marked. M. Bernard has furthermore seen a similar effect upon 
 the taste produced in animals by division of the facial nerve within 
 the cranium. The result of' these experiments and observations is 
 as follows : When the facial nerve is divided or seriously injured 
 
483 THE SPECIAL SENSES. 
 
 by organic disease, before its emergence from the stylo-mastoid 
 foramen, not only is there a paralysis of the superficial muscles of 
 the face, but the sense of taste is diminished on the corresponding 
 side of the tongue. If the tongue be protruded,.and salt, citric acid 
 or sulphate of quinine be placed upon its surface on the two sides ' 
 of the median line, the taste of these substances is perceived on the 
 affected side more slowly and obscurely than on the other. It is 
 not, therefore, a destruction, but only a diminution of the sense of 
 taste, which follows paralysis of the facial in these instances. At 
 the same time the general tactile sensibility of the tongue is unal- 
 tered, retaining its natural acuteness on both sides of the tongue. 
 
 The exact mechanism of this peculiar influence of the facial nerve 
 upon the sense of taste is not perfectly understood. It may be 
 considered as certain, however, that it is derived through the 
 medium of that branch of the facial nerve known as the chwda 
 tympani. This filament , leaves the facial at the intumescentia 
 gangliformis, in the interior of the aqueduct of Fallopius, enters the 
 cavity of the tympanum, passes across the membrane of the tym- 
 panum, and then, emerging froji the cranium, runs downward and , 
 forward and joins the lingual branch of the fifth pair. It then ac- 
 companies this nerve as far as the posterior extremity of the sub- 
 maxillary gland. Here it divides into two portions ; one of which 
 passes to the submaxillary ganglion, and, through it, to the sub- 
 stance of the submaxillary gland, while the other continues onward, 
 still in connection with the lingual branch of the fifth pair, and, in 
 company with the filaments of this nerve, is distributed to the tongue. 
 
 The chorda tympani thus forms the only anatomical connection 
 between the facial nerve and the anterior part of the tongue. When 
 the facial, accordingly, is divided or injured after its emergence 
 from the stylo-mastoid foramen, no effect is produced upon the 
 sense of taste ; but when it is injured during its course through the 
 aqueduct of Fallopius, and before it has given off the chorda tym- 
 pani, this nerve suffers at the same time, and the sense of taste is 
 diminished in activity, as above described. It is probable that this 
 effect is produced in an indirect way, by a diminution in the activity 
 of secretion in the lingual follicles, or by some alteration in the 
 vascularity of the parts. 
 
 Smell. — The main peculiarity of the sense of smell consists in 
 the fact that it gives us intelligence of the physical chariacter of 
 bodies in a gaseous or vaporous condition. Thus we are enabled to 
 
SMELL. 
 
 489 
 
 perceive the existence of an odorous substance at a distance, and 
 when it is altogether concealed from sight. The minute quantity 
 of volatile material emanating ttora it, and thus pervading the 
 atmosphere, comes in contact with the mucous membrane of the 
 nose, and produces a peculiar and special sensation. 
 
 The apparatus of this sense consists, first, of the olfactory mem- 
 brane, supplied by the filaments of the olfactory nerve, as its 
 special organ ; and secondly, of the nasal passages, with the tur- 
 binated bones and the muscles of the anterior and posterior nares, 
 as its accessory organs. At the upper part of the nasal fossae, 
 the mucous membrane is very thick, soft, spongy and vascular, 
 and is supplied with mucous follicles which exude a secretion, by 
 which its surface is protected and kept in a moist and sensitive 
 condition. 
 
 It is only this portion of the mucous membrane of the nares 
 which is supplied by filaments of the olfectory nerve, and which is 
 capable of receiving the impressions of smell ; it is therefore called 
 the Olfactorp membrane. Elsewhere, the nasal passages are lined 
 with a mucous membrane which is less vascular and spongy in 
 structure, and which is called the Schndderian membrane. 
 
 The filaments derived from the olfaetory ganglia, and which 
 penetrate through the cribri- 
 form plate of the ethmoid 
 bone, are distributed to the 
 mucous membrane of the su- 
 perior and middle turbinated 
 bones, and to that of the upper 
 part of the septum nasi. The 
 exact mode in which these 
 filaments terminate in the ol- 
 factory membrane has not 
 been definitely ascertained. 
 They are of a soft consistency 
 and gray color, and, after di- 
 viding and ramifying freely 
 in the membrane, appear to 
 become lost in its substance. 
 It is these nerves which exer- 
 cise the special function of 
 smell. They are, to all appearance, incapable of receiving ordinary 
 impressions, and must be regarded as entirely peculiar in their 
 
 Fig. 154. 
 
 Distribution of Nertes ik the Nabal 
 Passaoeb. — 1, Olfactory ganglion, withita nerves 
 2. Naitat branch of fifth pair. 3. Spheno-palatiue 
 ganglion. 
 
490 THE SPECIAL SENSES. 
 
 nature and endowments. The nasal passages, however, are supplied 
 with other nerves beside the olfactory. The nasal branch of the 
 ophthalmic division of the fifth pair, after entering the, anterior part 
 of the cavity of the nares, just ia advance of the cribriform plate of 
 the ethmoid bone, is distributed to the mucous membrane of the in- 
 ferior turbinated bone and the inferior meatus. Thus the organ 
 of smell is provided with sensitive nerves from two different sources, 
 viz., at its upper part, with the olfactory nerves proper, deriyeid 
 from the olfactory ganglion (Fig. 154, i), which are nerves of special 
 sensation ; and secondly, at its lower part, with the nasal branch of 
 the fifth pair (a), a nerve of general sensation. Beside which, the 
 spheno-palatine ganglion of the great sympathetic (3) sends, fila- 
 ments to the mucous membrane of the whole posterior part of the 
 nasal passages, and to the levator palati and azygos uvulae muscles. 
 Finally, the muscles of the anterior nares are supplied by filaments 
 of the facial nerve. 
 
 The conditions of the sense of smell are much more special in 
 their nature than those of taste. For, in the first place, this sense is 
 excited, not by actual contact with the foreign body, but only with 
 its vaporous emanations ; and the quantity of these emanations, 
 sufi&cient to lexcite the smell, is often so minute as to be altogether 
 inappreciable by other means. We cannot measure the loss of 
 weight in an odorous body, though it may affect the atmosphere 
 of an entire house, and the senses of .all its inhabitants, for days 
 and weeks together. Secondly, in the olfactory organ, the special 
 sensibility of smell and the general sensibility of the mucous mem- 
 brane are separated from each other and provided for by different 
 nerves, not mingled together and exercised by the same nerves, as 
 is the case in the tongue. 
 
 In order to produce an olfactory impression, the emanations of 
 the odorous body must be drawn freely tKrough the nasal passages. 
 As the sense of smell, also, is situated only in the upper part of these 
 passages, whenever an unusually faint or delicate odor is to be per- 
 ceived, the air is forcibly directed upward, toward the superior 
 turbinated bones, by a peculiar inspiratory movement of the nos- 
 trils. This movement is very marked in many of the lower .animals. 
 As the odoriferous vapors arrive in the upper part of the nasal 
 passages, they are undoubtedly dissolved in the secretions of the 
 olfactory membrane, and thus brought into relation with its nerves. 
 Inflammatory disorders, therefore, interfere with the sense of smell, 
 both by checking or altering the secretions of the part, and by 
 
SMELL. 491 
 
 producing an unnatural tumefaction of the mucous membrane, 
 whicli prevents the free passage of the air through the nasal fossae. 
 
 As in the case of the tongue, also, we must distinguish here 
 between the perception of true odors, and the excitement of the 
 general sensibility of the Schneiderian mucous membrane by irri- 
 tating substances. Some of the true odors are similar in their nature 
 to impressions perceived by the sense of taste. Thua we have 
 sweet and sour smells, though none corresponding to the alkaline 
 or the bitter tastes. Most of the odors, however, are of a very 
 peculiar nature and are difficult to describe ; but they are always 
 distinct from the simply irritating properties which may belong to 
 vapors as well as to liquids. Thus, pure alcohol has little or no 
 odor, and is only irritating to the mucous membrane ; while the 
 odor of wines, of cologne water, &c., is commlinicated to them by 
 the presence of other ingredients of a vegetable origin. In the 
 same way, pure acetic acid is simply irritating ; while vinegar has 
 a peculiar odor in addition, derived from its vegetable impurities. 
 Ammonia, also, is an irritating vapor, but contains in itself no 
 odoriferous principle. 
 
 The sensations of smell, like those of taste, remain for a certain time 
 after they have been produced, and modify in this way other less 
 strongly marked odors which are presented afterward. As a 
 general thing, the longer we are exposed to a particular odor, the 
 longer its effect upon our senses continues ; and in some cases it 
 may be perceived many hours after the odoriferous substance has 
 been removed. Odors, however, are particularly apt to remain 
 after the removal or destruction of the source from which' they 
 were derived, owing to their vaporous character, and the facility 
 with which they are entangled and retained by porous substances, 
 such as plastered walls, woollen carpets, and hangings, and woollen 
 clothes. It is supposed to be in this way that the odor of a post- 
 mortem examinatioii will sometimes remain so as to be perceptible 
 for several hours or even an entire day afterward. But this alone 
 does not fully explain the fact. For if it depended simply on the 
 retention of the odor by porous substances, it would afterward be 
 perceived constantly, until it gradually and continuously wore off; 
 while in point of fact, the physician who has made an autopsy of 
 this kind does not afterward perceive its odor constantly, but only 
 occasionally, and by sudden and temporary fits. 
 
 The explanation is probably this. As the odor ' remains con- 
 stantly by us, we soon become insensible to its presence, as in the 
 
492 THE SPECIAL SENSES. 
 
 case of all other continuous and unvarying impfessions. Our at- 
 tention is only called to it when we meet suddenly with another 
 and familiar odor. This second odor, we find, does not produce its 
 usual impression, because it is mingled with and modified by the 
 other, which is more persistent and powerful. Thus we are again 
 made aware of the former one, to which we had become insensible 
 by reason*of its constant presence. 
 
 The sense of smell is comparatively feeble in the human species, 
 but is excessively acute in some of the lower animals. Thus, the 
 dog will not only distinguish different kinds' of game in the forest 
 by this sense, and follow them by their tracks, but will readily dis- 
 tinguish particular individuals by their odor, and will recognize 
 articles of dress belonging to them by the minute quantity of odor- 
 iferous vapors adhering to their substance. 
 
 Sight. — The sight undoubtedly occupies the first rank in the 
 list of special nervous endowments. It is the most peculiar in its 
 operation, and the most immaterial in its nature, of all the senses, 
 and it is through it that we receive the most varied and valuable 
 impressions. The physical agent, also, to which the organ of sight 
 is adapted, and by which its sensibility is excited, is more subtle 
 and peculiar than any of those which act upon our other senses. 
 For the senses of touch, taste, and smell require, for their exercise, 
 the actual contact of a foreign body, either in a solid, liquid, or 
 aeriform condition ; and even the hearing depends upon the me- 
 chanical vibrations of the atmosphere, or some other sonorous 
 medilim. But the eye does not need to be in contact with the 
 luminous body. It will receive the impressions of light with per- 
 fect distinctness, ev,en when they are transmitted from an immea- 
 surable distance, as in the case of the fixed stars ; and the light 
 itself is not only immaterial in its nature, so far as we can ascertain, 
 but is also capable of being transmitted through space without the 
 intervention of any material conducting medium, yet discoverable. 
 
 Finally, the apparatus of vision is more complicated in its struc- 
 ture than that of any other of the^speoial senses. This apparatus 
 eonsists, first, of the retina, as a special sensitive nervous membrane ; 
 and secondly, of the vitreous body, crystalline lens, choroid, scle- 
 rotic, iris and cornea, together with the muscles moving the eye- 
 ball and eyelids, lachrymal gland, &c., as accessory organs. The 
 arrangement of the parts, constituting the globe of the eye, is shown 
 in the following figure. (Fig. 155.) 
 
SIGHT. 493 
 
 The filaments of the optic nerve, after running forward and pene- 
 trating the posterior part of the eyeball, spread out into the sub- 
 stance of the retina (3), thus forming a delicate and vascular nerv 
 
 Fig. 155. 
 
 Vertical Section of the Eyeball. — 1. Sclerotic. 2. Choroid. 3. Retina. 4. Leos. 5. Hyalciil 
 membrane. 6. Goraea. 7. Iris, 8. Ciliary maBCle and processes. 
 
 ous expansioh, in the form of a spheroidal bag or sac, with a wide 
 opeiiing in front, where the retina terminates at the posterior mar- 
 gin of the ciliary body. This expansion of the retina is the essen- 
 tial nervous apparatus of the eye. It is endowed with the special 
 sensibility which renders it capable of receiving luminous impres- 
 sions; and, so far as we have been able to ascertain, it is incapable of 
 perceiving any other. On the outside, the retina is covered by the 
 choroid coat (s), a vascular membrane, which is rendered opaque by 
 the presence of an abundant layer of blackish-brown pigment-cells, 
 and which thus absorbs, the light which has once passed through 
 the retina, and prevents its being reflected in such a way as to 
 confuse and dazzle the sight. Inside the retina is the vitreous body, 
 a transparent spheroidal mass of a gelatinous consistency, which is 
 surrounded and retained in position by a thin, structureless mem- 
 brane, called the hyaloid membrance (s), lying immediately in 
 contact with the internal surface of the retina. The lens (4) is 
 placed in front of the vitreous body, in the central axis of the eye- 
 ball, enveloped in its capsule, which is continuous with the hyaloid 
 membrane. Just at the edge of the lens, the hyaloid membrane 
 divides into two laminae, which separate from each other, leaving 
 between them a triangular canal, the canal of Petit, which can be 
 seen in the above figure. In front of the lens is the iris (7), a nearly 
 
494 THE SPECIAL SENSES, 
 
 vertical muscular curtain, formed of radiating and concentric fibres, 
 pierced at its centre with a circular opening, the pupil, through 
 which the light is admitted, and covered on its posterior surface 
 with a continuation of the choroidal pigment, which excludes the 
 passage of any other rays than those which pass through the pupil. 
 At the same time, the whole globe is inclosed and protected by a 
 thick, fibrous, laminated tunic, which in its posterior and middle 
 portions is opaque, forming the sclerotic (i), and in its anterior.por- 
 tion is transparent, forming the cornea (s). The muscles of the eye- 
 ball are attached to the external surface of the sclerotic in such a 
 way that the cornea may be readily turned in various directions ; 
 while the eyelids, which may be opened and closed at will, protect 
 the eye from injury, and, with the aid of the lachrymal secretion, 
 keep its anterior surfaces moist, and preserve the transparency of 
 the cornea. 
 
 The organ of vision is supplied with nerves of ordinary sensi- 
 bility by the ophthalmic branch of the fifth pair. The filaments 
 of this nerve which terminate about the eye are distributed mostly 
 to the conjunctiva, lachrymal gland, and skin of the eyelids ; while 
 a very few of them run forward in company with the ciliary nerves 
 proper, and are distributed to the ciliary circle and iris. All these 
 parts, therefore, but more particularly the conjunctiva and skiii;.§f 
 the eyelids, possess ordinary sensibility, which appears to be totally 
 wanting in the deeper parts of the eye. The ophthalmic ganglion 
 gives off the ciliary nerves, which, are distributed to the iris and 
 ciliary muscle. Finally, the muscles moving the eyeball and eye- 
 lids are supplied with motor nerves from the third, fourth, sixth 
 and seventh pairs. 
 
 Of all the properties and functions belonging to the diflferent 
 structures of the eyeball, the most peculiar and characteristic is the 
 special sensibility of the retina. This sensibility is such that the 
 retina appreciates both the intensity, and the quality of the light- 
 that is to say, its color and the different shades which this color 
 may present. On account of the form, also, in which thc'retina is 
 constructed, viz., that of a spheroidal membranous bag, with an 
 opening in front, it becomes capable of appreciating the direction 
 from which the rays of light have come, and, of course, the situation 
 of the luminous body and of its different parts. For the rays which 
 enter through the pupil from below can reach the retifia only at its 
 upper part, while those which come in from above, can reach it 
 only at its lower part; so that in both instances the rays strike the 
 
SIGHT. 495 
 
 sensitive surface perpendicularly, and thus convey the impression 
 of their direction from above or below. 
 
 But beside the sensibility of the retina, the perfection and value 
 of the sense of sight depend very much on the arrangement of the 
 accessory organs, the most important of which is the crystalline lens. 
 
 The fwmtion of the crystalline lens is to produce distinct perception 
 offm-m and outline. For if the eye consisted merely of a sensitive 
 retina, covered with transparent integument, though the impressions 
 of light would be received by such a retina they could not give 
 any idea of the form of particular objects, but could only produce 
 the sensation of a confused luminosity. This condition is illus- 
 trated in Fig. 156; where the arrow, a, h, represents the luminous 
 object, and the vertical dotted line, at the right of the diagram, 
 represents the retina. Rays, of course, will diverge from every 
 point of the object in every direction, and will thus reach every 
 part of the retina. The different parts of the retina, consequently, 
 1, 2, 8, 4, will each receive rays coming both from the point of the 
 arrow, a, and from its butt, b. Thei'e will therefore be no distinc- 
 tion, upon the retina, between the different parts of the object, and no 
 
 Fig. 156. .. Fig. 157. 
 
 definite perception of its outline. But if, between the object and the 
 retina, there be inserted a double convex refracting lens, with the 
 proper curvatures and density, as in Fig. 157, the effect will be dif- 
 ferent. For then all the rays emanating from a will be concentrated 
 at X, and all those emanating from b will be concentrated at y. 
 Thus the retina will receive the impression of the point of the 
 arrow separate from that of the butt ; and all parts of the object, 
 in like manner, will be distinctly and accurately perceived. 
 
 This convergence of the rays of light is accomplished to a certain 
 extent by the other transparent and refracting parts of the eyeball ; 
 but the lens is the most important of all in this respect, owing to 
 its superior density and the double convexity of its figure. The 
 distinctness of vision, therefore, depends upon the action of the 
 
496 
 
 THE SPECIAL SENSES. 
 
 lens in converging all the rays of light, emanating from a given 
 point, to an accurate focus, at the surface of the retina. To accomplisli 
 this, the density of the lens, the curvature of its surfaces, and its 
 distance from the retina, must all b6 accurately adapted to each 
 other. For if the lens be too convex, and its refractive power con- 
 sequently too great, the rays will be converged to a focus too soon, 
 and will not reach the retina until aftef they have crossed each 
 other and become partially dispersed, as in Fig. 158. The visual 
 impression, therefore, coming from any particular point in the 
 object is not concentrated and distinct, but diffused and dim, from 
 being dispersed more or less over the retina, and interfering with 
 the impressions coming from other parts. This is the condition 
 which is present in myopia, or near-sightedness. On the other hand. 
 
 Fig. 158.. 
 
 Fig. 159. 
 
 Miopia. 
 
 Pkebbtopia. 
 
 if the lens be too flat, and its convergent power too feeble, as in 
 Fig. 159, the rays will fail to come together at all, and will strike 
 the retina separately, producing a confused image, as before. %ia 
 is the defect which exists in presbyopia, or long-sightedness. In 
 both cases, the immediate cause of the confusion of sight is the 
 same, viz., the rays coming from the same point of the object 
 striking the retina at different points ; but in the first instance, this 
 is because the rays have actually converged, and then crossed ; in 
 the second, it is because they have only approached each other, but 
 have never converged to a focus. 
 
 Another important particular in regard to the action of the lens 
 • is the accommodation of the eye to distinct vision at different distances. 
 It is evident that the same arrangement of the refractive parts, in 
 the eye, will not produce distinct vision when the distance of the 
 object from the eye is changed. If this arrangement be such that 
 the object is seen distinctly at a certain. distance, as in Fig. 160, 
 and the object be then removed to a remoter point, as in Fig. 161, 
 the image wiU become confused ; for the, rays will then be con- 
 
SIGHT. 
 
 497 
 
 verged to a focus at a point in front of the retina ; because, being 
 less divergent, when they strike the lens, the same amount of re- 
 fraction will bring them together sooner than before. On the other 
 hand, if the object be moved to a point nearer the eye, the rays, 
 becoming more divergent as they strike the lens, will be converged 
 less rapidly to a focus, and vision will again become indistinct. 
 
 This may easily be seen by the aid of a very simple experiment. 
 If two needles be placed upright, at different distances from the eye, 
 one for example at eight and 
 the other at eighteen inches, but 
 nearly in the same linear range, 
 and if then, closing one eye, we 
 look at them alternately, we shall 
 find that we cannot see both dis- 
 tinctly at the same time. For 
 when we look at the one near- 
 
 Fig. 160. 
 
 Fig. Itil, 
 
 est the eye, so as to perceive its form distinctly, the image of the 
 more remote one becomes confused ; and when we see the more re- 
 mote object in perfection, that which is nearer loses its sharpness of 
 outline. This shows, in the first place, that the same condition of 
 the eye will not allow us to see two objects at different distances 
 with distinctness at the same time ; and secondly that, on looking 
 from one to the other, there is a change of some kind in the focus of 
 the eye, by which it is adapted to difierent distances. Indeed we 
 are conscious of a certain effort at the time when the point of vision 
 is transferred from one object to the other, by which the eye is 
 adapted to the new distance ; and this alteration is not quite instan- 
 taneous, but requires a certain interval of time for its completion. 
 This accommodation of the eye to different distances is un- 
 doubtedly efiected by an antero-posterior movement of the lens 
 within the eyeball. It will at once be perceived, on referring to 
 Fig. 161, that if the lens were moved a little backward toward the 
 32 
 
498 THE SPECIAL SENSES. 
 
 retina, at the same time that the object is removed to a greater dis- 
 tance from the eye, the focus of the convergent rays would still 6,11 
 upon the retina, and the image would still be distinct. In the op- 
 posite case, where the object is brought nearer the eye, a similar 
 movement of the lens forward would again secure perfect vision. 
 Thus, when we look at near objects, the lens moves forward 
 toward the pupil ; when we look at remote objects, it moves back- 
 ward toward the retina. 
 
 This movement of the lens is apparently accomplished by the 
 action of the ciliary muscle. This muscle (Fig, 155, s) arises, in 
 front, from the conjunction of the sclerotic and the cornea, and run- 
 ning backward and outward, is inserted into the anterior part of 
 the choroid, about the situation at which, the hyaloid membrane 
 passes off, to become the suspeusory ligament of the lens. As 
 already mentioned, this muscle is supplied with nervous filaments 
 from the ophthalmic ganglion. Its action is to draw the lens for- 
 ward, by means of its attachment to the hyaloid' membrane and 
 choroid coat ; and, in the human subject, the retreat or retrogres- 
 sion of the lens toward the retina, after the ciliary muscle is relaxed, 
 seems to be due to the islastic resiliency of the remaining tissues of 
 the eyeball. 
 
 But in order to allow of such a backward and forward movement 
 of the lens, since the liquids of the eyeball are incompressible, there 
 must be a corresponding displacement of other parts, both before 
 and behind. This is undoubtedly provided for by the vascularity 
 of the choroid coat. This membrane is supplied with an exceedingly 
 abundant vascular plexus over its whole posterior portion ; and in 
 front it is thrown into a circle of prominent converging folds, or 
 processes, the ciliary processes, which are nothing more than erectile 
 congeries of bloodvessels, covered with the pigment of the choroid. 
 A portion of the ciliary processes projects in front of the lens, and 
 their vascular network is continued over a great part of the pos- 
 terior surface of the iris. Thus there is, both behind and in front 
 of the lens, an erectile system of bloodvessels ; and as these blood- 
 vessels become alternately empty or turgid, they will allow of the 
 displacement of the lens in an anterior or posterior direction. 
 
 Accordingly there is a certain accocamodation of the eye neces- 
 sary to the distinct sight of objects at different distances. But the 
 rfinge of this accommodation is limited, and the same eye cannot he 
 made to see distinctly at all distances. For all ordinary eyes, the 
 accommodation fails, and vision becomes imperfect, when the object 
 
. SIGHT, 499 
 
 is placed at less than six inches distance from the eye. But from 
 that point outward, the eye can adapt itself to any distance at which 
 light is perceptible, even to the immeasurable distances of the fixed 
 stars. A much greater accommodating power, however, is re- 
 quired for near distances than for remote, since the difference in 
 divergence between rays, entering the pupil from a distance of one 
 inch and from that of six inches, is greater than the difference be- 
 tween six inches and a yard, or even distances which are immea- 
 surably remote. Accordingly, near-sighted persons can see objects 
 distinctly when placed very near the eye; since, as their lens con- 
 verges the rays of light more powerfully than usual, they can be 
 brought to a focus upon the retina, even when excessively diverg- 
 ent at the time they enter the eye. But distant objects become 
 indistinct, since, however far backward the lens is moved, the rays 
 are still brought to a focus and cross each other, before reaching 
 the retina, as in Fig. 161. Near-sighted persons, therefore, have a 
 limited range of accommodation, like all others, only it is confined 
 within short distances, owing to the excessive refracting power of 
 the lens. 
 
 On the other hand, long-sighted persons can see remote objects 
 without trouble, since a very little movement of the lens will be 
 sufiicient to adapt it for long distances ; but within short distances, 
 the divergence of the rays becomes too great, and they cannot be 
 brought to a focus. 
 
 Circle of Vision. — Since the opening of the pupil will admit rays 
 of light coming from various directions, there is in front of the eye 
 a circle, or space, within which luminous objects are perceived, and 
 beyopd which nothing can be seen, because the rays, coming from 
 the side or from behind, cannot enter the pupil. This space, within 
 which external objects can. be perceived, is called the " circle of 
 vision." But, for short distances, there is only a single point, in the 
 centre of the circle of vision, at which objects can be seen distinctly. 
 Thus, if we place ourselves in front of a row of vertical stakes or 
 palisades, we can see those directly in front of the eye with perfect 
 distinctness, but those at a little distance on each side are only per- 
 ceived in a confused and uncertain manner. On looking at the 
 middle of a printed page, in the direct range of vision, we see the 
 distinct outlines of the letters ; while at successive distances from 
 this point, the eye remaining fixed, we can distinguish first only 
 the separate letters with confused outlines, then only the words, and 
 lastly only the lines and spaces. 
 
500 a HE SPECIAL SENSES. 
 
 This is because rays of light coming into the eye very obliquely, 
 in a lateral or vertical direction, are not brought to their proper focus. 
 Thus, in Fig. 162, the rays diverging from the point a, directly in 
 front of the eye, fall upon the lens in such a way that they are all 
 brought together at x, at the surface of the retina ; but those coming 
 from h fall upon the lens so obliquely that, for rays having an equal 
 divergence with those coming from a, there is more difference in their 
 angles of incidence, and of course more difference in the amount 
 of their refraction. They are consequently brought together more 
 rapidly, and on reaching the retina are dispersed over the space y, z. 
 
 Fig. Iii2. 
 
 The perfection of the eye, as a visual apparatus, is very much 
 increased by the action of the iris. This organ, as we have already 
 mentioned, is a nearly vertical muscular curtain, placed in front of 
 the lens, attached by its external margin to the junction, of the 
 cornea and sclerotic^ and pierced about its centre by the circular 
 opening of the pupil. It consists, according to most anatomis'ts,;of 
 two sets of muscular fibres — viz., the circular and the radiating. 
 The circular fibres, which are much the most abundant, are arranged 
 in concentric lines about, the inner edge of the irjs, near the pupil; 
 the others are said to radiate in a scattered manner, from its central 
 parts to its outer margin. The action of these two sets of fibres is 
 to contract and enlarge the orifice of the pupil. The circular fibres, 
 in contracting, draw together the edges of the pupil, and so diminish 
 its opening; and when these are relaxed, the radiating fibres come 
 into play, and by drawing apart the edges of 'the orifice, enlarge 
 
SIGHT. 501 
 
 the pupillary opening. The action of the ciroular fibres, at tlie 
 same time, is much the most marked and important of the two. 
 For when the whole muscular apparatus of the eye is paralyzed 
 by the action of belladonna, or by the division of the third pair of 
 nerves, or in the general relaxation of the muscular system at the 
 moment of death, the pupil is invariably dilated, probably by the 
 passive elasticity of its tissues. 
 
 During life, however, these different conditions of the pupil cor- 
 respond with the different degrees of light to which the eye is ex- 
 posed. In a strong light, the pupil contracts and shuts out the 
 superfluous rays; in a feeble light, it dilates, in order to collect 
 into the eye all the light which can be received from the object. 
 This contractile and expansive movement of the pupil is a reflex 
 action. It is not produced by the direct impression of the light 
 upon the iris itself, but upon the retina; since, if the retina be 
 affected with complete amaurosis, or if the light be entirely shut out 
 from it by an opacity of the lens, no such effect is produced, though 
 the iris itself be exposed to the direct glare of day. From the 
 retina the impression is transmitted, through. the optic nerve, to the 
 optic tubercles and the brain, 'thence reflected outward by the ooulo- 
 motorius nerve to the ophthalmic ganglion, and so through the 
 ciliary nerves to the iris. 
 
 The pupil is subject, however, to various other nervous influences 
 beside the impressions of light received by the retina. Thus in 
 poisoning by opium, it is contracted ; in coma from compression of 
 the brain, it is dilated ; in natural sleep it is contracted, and the eye- 
 ball rolled upward and inward. In various mental conditions, the 
 pupil is also enlarged or diminished, and thus modifies the expres- 
 sion of the eye; and in viewing remote objects, it is generally 
 enlarged, while, in looking at near objects, it is comparatively con- 
 tracted. But still, the most constant and important function be- 
 longing to the iris is the admission or exclusion of the rays, accord- 
 ing to the intensity of the light. 
 
 Our impressions of distance and solidity, in viewing external 
 objects, are produced mainly Tjy the combined action of the two eyes. 
 For, as the eyes are seated a certain distance apart from each other 
 in the head, when they are both directed toward the same object, 
 their axes meet at the point of sight, and form a certain angle with 
 each other ; and this angle varies with the distance of the object^ 
 Thus, when the object is within a short distance, the axes of the 
 two eyes will necessarily be very convergent, and the angl^ which 
 
502 
 
 THE SPECIAL SENSES. 
 
 they form with each other a large one ; but for remote objects, the 
 visual axes will become more nearly parallel, and their angle con- 
 sequently smaller. It is on this account that we can always dis- 
 tinguish whether any person at a short distance is looking at m, 
 or at some other olg'ect in our direction; since we instinctively 
 appreciate, from the appearance of the eyes, whether their visual 
 axes meet at the level of our own face. 
 
 In looking at a landscape, accordingly, we do not see the whole 
 of it distinctly at the same moment, but only those parts to which 
 out attention is immediately directed. This is because, in the first 
 place, the focus of distinct vision varies, in each eye, for different 
 distances, as we have seen in a former paragraph, and secondly, 
 because both eyes can only be directed together, at one time, to 
 objects at a certain distance. Thus, when we see the foreground 
 or the middle ground distinctly, the distance is vague and uncer- 
 tain, and when we direct our eyes more particularly to the horizon, 
 objects in the foreground become indistinct. In this way we ap- 
 preciate the difterence in distance between the various portions of 
 the landscape, as a whole. In the case of particular objects, we are 
 assisted also by the alteration in their individual characters ; for 
 distance produces a diminution, both in apparent size and in in- 
 tensity of color. 
 
 The combined action of the two eyes is also very valuable, for 
 near objects, in giving us an idea of solidity or projection^} For 
 within a certain distance, the visual axes when directed together 
 
 Fig. ltJ3 
 
 As SEEK BT THR LEFT Ete. 
 
 As SEEN BY THE RIGHT EVE. 
 
 at a solid object, are so convergent that -the two- eyes do not receive 
 the same image. As in Figs. 163 and 164, which represent a skull 
 
SIGHT. 503 
 
 as seen by the two eyes, when placed exactly in front of the ob- 
 server at the distance of eighteen , inches or two feet, the right eye 
 will see the object partly on one side, and the left eye partly on the 
 other. And by the union or combination of these two images by 
 the visual organs, the impression of solidity is produced. 
 
 By the employment of double pictures, so drawn as to represent 
 the appearances presented to the two eyes by the same object, and 
 so arranged that each shall be seen only by the corresponding eye, 
 a deceptive resemblance may be produced to the actual appearance 
 of. solid objects. This is accomplished in the contrivance known 
 as the Stereoscope. Thus, if two pictures similar to those in Figs. 
 163 and 164 be so placed that one shall be seen only with the right 
 eye and the other only with the left, the combination of the two 
 figures will take place as if they came from the real object, and 
 all the natural projections will come out in relief. 
 
 But this effect is produced only in the case of objects situated 
 within a moderately short distance. For very remote objects, we 
 lose the impression of solidity, since the difference in the images on 
 the two eyes becomes so slight as to be inappreciable, and we see 
 only a plane expanse of surface, with sharp outlines and various 
 shades of color, but no actual projections or depressions. 
 
 The sensibility of the retina is such that it cannot distinguish 
 luminous points which are received upon its surface at a very 
 minute distance from each other. In this particular, the sensibility 
 of the retina resembles that of the skin, since we have already 
 found that the integument cannot distinguish the impressions 
 made by the points of two needles placed a very short distance 
 apart. The delicacy of this discriminating power, in the retina, is 
 immeasurably superior to that of the skin; and yet it has its 
 limits, even in the nervous expansion of the eye. For if we look 
 at an object which is excessively minute, or which is so remote 
 that its apparent size is very much diminished, we lose the power 
 of distinguishing its difierent parts, and can no longer perceive 
 its real outline. This is a very different condition from that in 
 which the confusion of vision arises from defect of focusing in the 
 eye, as, for example, in long or short-sightedness, or where the 
 object is placed too near the eye or too much on one side. For 
 when the difSculty depends simply on its minute size or its remote- 
 ness, the rays coming from the top of the object and those coming 
 from the bottom, are all brought to their proper focus at distinct 
 points on the retina — only these points are too near each other fw the 
 
504r lUK SPECIAL SEXSES. 
 
 retina to distinguish them apart. Consequently we can no longer 
 appreciate the form of the object. 
 
 For the same reason, when we mix together minute grains of a 
 diiferent hue, we produce an intermediate color. If yellow and 
 blue be mingled in this way, we no longer perceive the separate 
 blue and yellow grains, but only a uniform tinge of green ; and 
 white and black granules, mixed together, produce, at a short dis- 
 tance, the appearance of a continuous shade of gray. 
 
 Impressions, once produced upon the retina, remain for a short time 
 afterward. Usually these impressions are so evanescent after the 
 removal of their immediate cause, and are so soon followed by 
 others which are more vivid, that we do not notice their existence. 
 They may very readily be demonstrated, however, by swinging 
 rapidly in a circle before the eyes, in a dark room, a stick lighted 
 at one end. As soon as the motion has attained a certain degree of 
 velocity, the impression produced on the retina, when the lighted 
 end of the stick arrives at any particular spot, remains until it has 
 completed its revolution and has again reached the same point; 
 so that the effect thus produced upon the eye is that of a continu- 
 ous circle of light. The same fact has been illustrated by the 
 optical contrivance, known as the Thaumatrope, in which successive 
 pictures of similar figures in different positions are made to revolve 
 rapidly before the eye, and thus to produce the apparent eflect of a 
 single figure in rapid motion ; — since the eye fails to percei^ the 
 intervals between the different pictures. 
 
 The sense of vision, therefore, through the impressions of lighf^ 
 gives us ideas of form, size, color, position, distance, and movement. 
 But these ideas may also be excited by impressions derived from 
 an internal source, as well as those produced by rays coming from 
 without. And it is one of the most striking peculiarities of the 
 sense of sight that these ideal or internal impressions which are 
 excited in it by various causes, are much more vivid and powerful 
 than those of any other of the senses. Thus, in a dream, we often see 
 external objects, with all their visible peculiarities of liglit, color 
 form, &c., nearly or quite as distinctly as when we are awake ; but 
 the imaginary impressions of sound, in this condition, are always 
 comparatively faint, and those of taste, smell, and touch, almost 
 entirely imperceptible. Even in a reverie, in the waking condi- 
 tion, when the absorption of the mind in its own thoughts is com- 
 plete, and we are withdrawn altogether from outward influences, 
 we see objects which have no present existence as if they were 
 
HEARING. 505 
 
 actually before us. It is this sense also whioli becomes most easily 
 and thoroughly excited in certain nervous disorders ; as, for exam- 
 ple, in delirium tremens, where the patient often sees passing before 
 his eyes extensive and magnificent landscapes, crowds of human 
 faces and figures, and series of towns and cities, which seem to be 
 depicted upon the imagination with a force and distinctness, much 
 superior to that of other delirious impressions. Since the sense of 
 sight, therefore, depends less directly than the other senses upon 
 the actual contact of material objects, it is also more easily thrown 
 into activity when withdrawn from their influence. 
 
 Hearing. — The sense of hearing depends upon the vibratioos 
 excited in the atmosphere by sonorous bodies, which are themselves 
 first thrown into vibration by various causes, and which then com- 
 municate similar undulations to the surrounding air. These sono- 
 rous vibrations are of such a character that they cannot be directly 
 appreciated by ordinary sensibility, but the result of numerous and 
 well-directed physical experiments on this subject leaves no doubt 
 whatever of their existence ; and when such vibrations are commu- 
 nicated to the auditory apparatus, they produce in it the sensation 
 of sound. 
 
 In the case of the aquatic animals, which pass their entire exist- 
 ence beneath the surface of the water, the water itself, which is 
 capaWe of vibrating in the same- way, communicates the sonorous 
 impressions to the organ of hearing; but in terrestrial animals, 
 and particularly in man, it is the atmosphere which always serves 
 as the medium of transmission. 
 
 The auditory apparatus, in man and in the quadrupeds, consists, 
 first, of a somewhat expanded and trumpet-shaped mouth, or ex- 
 ternal ear, destined to receive and collect the sonorous impulses 
 coming from various quarters. This external ear is constructed 
 of a cartilaginous framework, covered with integument, loosely 
 attached to the bones of the head, and more or less movable by 
 means of various muscles, which by their contraction turn its 
 expanded orifice in different directions. In man, the movements 
 of the external ear are almost always inappreciable, though the mus- 
 cles may be easily demonstrated ; but in many of the loWer animals 
 these movements are exceedingly varied and extensive, and play a 
 very important part in the working of the auditory apparatus. 
 
 At the bottom of the external ear, its orifice is prolonged into a 
 tube or canSil, the external auditory meatus, partly cartilaginous and 
 
606 THE SPECIAL SENSES. 
 
 partly bony, wMch penetrates the lateral part of the temporal bone 
 in a nearly horizontal and transverse direction. In the human 
 subject, this canal is a little over one inch in length, and is lined 
 by a continuation of the external integument. The integument 
 toward its outer portion is beset with small hairs, and provided 
 with ceruminous glands which supply a secretion of a waxy or 
 resinous consistency. By these means the passage is protected 
 from the accidental ingress of various foreign bodies. 
 
 Secondly, at the bottom of the external meatus the auditory pas- 
 sage is closed by a thin fibrous membrane, stretched across its. cavity, 
 called the membrana tympani. Upon this membrane are received the 
 sonorous vibrations which have been collected by the external ear 
 and conducted inward by the external auditory meatus. Behind 
 the membrana tympani is the cavity of the middle ear, or the cavity 
 of the tympanum. This cavity communicates posteriorly with the 
 mastoid cells, and anteriorly with the pharynx, by a narrow passage, 
 lined with ciliated epithelium, and running downward, forward and 
 inward, called the Eustachian tube. A chain of small bones, the 
 malleus, incus, and stapes, is stretched across the cavity of the 
 tympanum, and forms a communication between the membrana 
 tympani on the outside, and the membrane closing the. foramen 
 ovale in the petrous portion of the temporal bone. All the vibra- 
 tions, accordingly, which are received by the membrana tympani, 
 are transmitted by the chain of bones to the membrane of the 
 foramen ovale. The tension of the membranes is regulated by two 
 small muscles, the tensor tympani and stapedius muscles, which arise 
 from the bony parts in the neighborhood, and are inserted respect- 
 ively into the neck of the malleus and the head of the stapes, and 
 which draw these bones forward and backward upon their articu- 
 lations. 
 
 Thirdly, behind the membrane of the foramen ovale lies the 
 labyrinth, or internal ear. This consists of a complicated, cavity, 
 excavated in the petrous portion of the temporal bone, and com- 
 prising an ovoid central portion, the vestibule, a double spiral canal, 
 the cochlea, and three semicircular canals, all communicating by 
 means of the common vestibule. All parts of this cavity contain 
 a watery fluid termed the perilymph. The vestibule and semi- 
 circular canals also contain closed membranous sacs, suspended in 
 the fluid .of the perilymph, which reproduce exactly the form of 
 the bony cavities themselves, and communicate with each other in 
 a similar way. These sacs are filled with another iv-atery fluid. 
 
HEARING. 
 
 507 
 
 the endolymph ; and the terminal filaments of the auditory nerve 
 are distributed upon the membranous sac of the vestibule and upon 
 the ampullffi, or membranous dilatations, at the commencement of 
 the three semicircular canals. The remaining portion of the audi- 
 tory nerve is distributed upon the septum' between the two spiral 
 canals of the cochlea. 
 
 Thus, the. essential or fundamental portion of the auditory appa- 
 ratus is evidently the internal ear, a cavity, partly membranous and 
 partly bony, in which is distributed a nerve of special sense, the 
 auditory nerve, capable of appreciating sonorous impressions. The 
 accessory parts, on the other hand, are the chain of bones and the 
 membrane of the tympanum, which communicate the sonorous 
 vibrations directly to the internal ear ; and the meatus and external 
 ear, which collect them from the atmosphere. The reception of 
 
 Fig. 165. 
 
 Human Auditort ApPABATrs, showiug external auditory meatus, tympanuni, aad laby- 
 ri^h. 
 
 sonorous impulses is therefore accomplished in a very indirect way. 
 For the sonorous body first communicates its vibrations to the 
 atmosphere. By the atmosphere these vibrations are communicated 
 tci the membrana tympani. From the membrana tympani, they are 
 transmitted, through the chain of bones, to the membrane of the 
 foramen ovale ; thence to the perilymph, or fluid, of the labyrinthic 
 cavity, and from the perilymph to the membranous parts of the 
 labyrinth and the nerves which are distributed upon them. 
 
 The arrangement of the different parts composing the tympanum 
 is of the greatest importance for the perfect enjoyment of the sense 
 
508 THE SPKCIAL SENSES. 
 
 of hearing. For the air on the two sides of the membrane of, the 
 tympanum should be in the same condition of elasticity in order to 
 allow of the proper vibration of the membrane; and this equilibrium 
 would be liable to disturbance if the air within the tympanum were 
 completely confined, while that outside is subjected to variations 
 of barometric pressure. By means of the Eustachian tube, how- 
 ever, a communication is established between the cavity of the 
 tympanum and the exterior, and the free vibration of the membrane 
 is thus secured. 
 
 The exact tension of the membrana tympani itself is also provided 
 for, as we have already observed, by the action of the two muscles 
 inserted into the malleus and the stapes. By the contraction of 
 the internal muscle of the malleus, or tensor tympani, the membrane 
 of the tympanum is drawn inward and rendered more tense than 
 usual. The action of the stapedius muscle is by some thought to 
 relax the membrana tympani, by others to assist in the tension 
 both of this membrane and that of the foramen ovale, to which 
 the stapes is attached. But there is no doubt that both these mus- 
 cles, by their, combined or alternate action, can regulate the tension 
 of the tympanic membrane, to an extraordinary degree of nicety, 
 and thus increase the ease and delicacy with which various sounds 
 are distinguished. For if the membrane be so put upon the stretch 
 that its fundamental note shall be the same with that of the sound 
 which is to be heard, it will vibrate more readily in consonance 
 with the undulations of the atmosphere, and the sound will be 
 more distinctly heard. On the contrary, if the membrane be too 
 highly stretched, very grave sounds may not be heard at all, until 
 its tension is diminished to the requisite degree. 
 -. Contrary to what is sometimes asserted, the communication of 
 sonorous impulses to the internal ear is accomplished altogether by 
 means of the tympanum and chain of bones. It has been thought tHfet 
 sounds were transmitted, in many instances, directly to the internal 
 ear by the medium of the cranial bones. This was inferred from 
 such facts as the following. If a tuning-fork, in vibration, be taken 
 between the teeth, its sound will appear very much louder than 
 if it were simply held near the external ear ; and if, while it js so 
 held, one of the ears be closed, the sound will appear very much 
 louder on that side than on the other. The sound will also be heard 
 if the tuning-fork be applied to the upper part of the cranium or 
 the mastoid process, with a similar increase of resonance on closing 
 the ears. Finally our own voices are heard, though the ears b»" 
 
HEARING. 509 
 
 both closed, and the sound is much louder with the ears closed 
 than open. 
 
 These are the facts which have led to the belief that, in such 
 instances, the sound was communicated directly through the bones 
 of the head, vibrating in consonance with the sounding body. But 
 a little examination will show that such is not the case. When we 
 hold the end of a vibrating tuning-fork between the teeth, we no 
 longer hear the sound in the vibrating extremity of the instrument 
 or its neighborhood, but in the mouth and the nasal fossce. It is the 
 vibration of the air in these passages which produces the sound ; 
 and this vibration is communicated to the cavity of the tympanum 
 through the Eustachian tube. The apparent increase of sound, also, 
 on closing the ears, which could not be explained on the supposition 
 that it was conducted directly through the bones of the cranium, 
 is due to the same cause. For it can easily be seen, on trying the 
 experiment, either with a tuning-fork held between the teeth or 
 simply with our own voices, that this apparent increase of sound 
 takes place only when the ears are closed by genth pressure. If the 
 pressure be excessive, so that the integument is forced inward into 
 the meatus and the air in the meatus subjected to undue compres- 
 sion, the sound no longer appears louder in the corresponding ear, 
 and may even be lost altogether. 
 
 The apparent increase of sound, therefore, in such cases, when 
 the ear is gently closed, is due to the fact that the meatus is thus 
 converted into a reverberatory cavity, by which the vibrations of 
 the tympanum are increased in intensity. But if the air in the 
 meatus be too much compressed by forcible closure, the vibrations 
 of the tympanum are then interfered with and the sound is dimi- 
 nished or destroyed. 
 
 In all cases, then, it is the sonorous vibrations of the air which 
 produce the sound, and these vibrations are received invariably by 
 the membrape of the tympanum, and thence transmitted to the 
 internal ear by the chain of bones. The cranial bones are incapable 
 of communicating these vibrations to the labyrinth and its contents, 
 except very faintly and imperfectly. For common experience shows 
 that even the loudest and sharpest sounds, coming from without, 
 are almost entirely lost on closing the external ears ; and our own 
 respiratory and cardiac sounds, which are so easily heard as soon 
 as the chest is connected with the ear by a flexible stethoscope, are 
 entirely inaudible to us in the usual condition. 
 
 The exact function of the different parts of the internal ear is 
 
510 THE SPECIAL SENSES. 
 
 not well understood. It has been thought to be the office of the 
 semicircular canals to determine the direction from which the sono- 
 rous impulses are propagated. This opinion was based upon the 
 curious fact that these canals, always three in number, are placed 
 in such positions as to correspond with the three different directions 
 of vertical height, lateral extension, and longitudinal extension ; 
 for one of them is nearly vertical and transverse, another vertical 
 and longitudinal, and the third horizontal in position. The sono- 
 rous impulses, therefore, coming in either of these directions, would 
 be received by only one of the semicircular canals (by direct con- 
 duction through the bones of the head) perpendicularly to its own 
 plane; and an intermediate direction, it was thought, might be 
 appreciated by the combined effect of the impulse upon two adja- 
 cent canals. ' 
 
 Enough has already been said, however, in regard to the com- 
 munication of sound directly through the bones of the head to the 
 internal ear, to show that this cannot be the way in which the diree- 
 tion of sound is ascertained. Indeed, when we hear any loud and 
 well-marked sound coming from a particular region, such as the 
 music of a military band or the whistle of a locomotive, we have only 
 to close the external ears to lose our perception both of the sound 
 and its direction. The direction of sonorous impressions is appre- 
 ciated in a different way. In the first place, we feel that the sound 
 comes from one side or the other, by its making a more distinct 
 impression on one ear than the opposite; and by inclining the 
 head slightly in various directions, we easily ascertain whether the 
 sound becomes more or less acute, and so judge of its actual source. 
 Many of the lower animals, whose ears are very large and movable, 
 use this method to great extent. A horse, for example, when upon 
 the road, often keeps his ears in constant moixon, feeling, as it were, 
 in the distance, for the origin of the various sounds which excite 
 his attention. 
 
 .Beside the above, we are further assisted in our judgment of the 
 direction of sounds by our previous knowledge of the localities, 
 the direction of the wind, and the manner in which the sound is 
 reflected by surrounding objects. When these sources of informa- 
 tion fail us, we are often at a loss. It is notoriously difficult, for 
 example, to judge of the place of the chirping of a cricket in a 
 perfectly closed room, or of the direction of a bell heard on the 
 water in a thick fog. 
 
 The sense of hearing has a much closer analogy with ordinary 
 
ON THE SENSES IN GENERAL. 511 
 
 i 
 
 sensibility than that of sight. Thus, in the first place, hearing is 
 accomplished by the direct intervention and contact of a materia) 
 body — the atmosphere ; for sonorous impulses cannot be, produced 
 in a vacuum, and we hear no sound from a bell rung under an 
 exhausted receiver. Secondly, the nature of the impressions pro- 
 duced by sound is such that we can often describe them by the 
 same terms which are applied to ordinary sensations. Thus, we 
 speak of sounds, as sharp and dull, piercing, smooth, or rough ; and 
 we feel the impulse of a sudden and violent explosive sound, like 
 that of a blow upon the tympanum. 
 
 By {his sense, therefore, we distinguish the quality, intensity, 
 pitch, duration, and direction of sonorous impulses. The delicacy 
 with -which these distinctions are appreciated varies considerably 
 in different individuals ; and in different kinds of animals there is 
 reason tO believe that the diversity is much greater, some of them 
 being almost insensible to sounds which are readily perceived by 
 others. In man, the number and variety of tones which can usually 
 be discriminated is very great ; and this sense, accordingly, in the 
 complication and finish of its apparatus, and the perfection and deli- 
 cacy of its action, must be regarded as second only to that of vision. 
 
 On the Senses in Geneeal. — There are several facts connected 
 with the operation of the ^nses, both general and special, which 
 are common to all of them, and which still remain to be considered. 
 In the first place, an impression of any kind, made upon a sensi- 
 tive organ, remains for a time after the removal of its eaxiting cause. 
 We have already noticed this in regard to the senses of taste, smell, 
 and sight, but it is equally true of the hearing and the touch. 
 Thus, if the skin be touched with a piece of ice, the acute sensa- 
 tion remains for a few seconds, whether the ice be removed or not. 
 For the higher order of the special senses, the time during which 
 this secondary impression remains is a shorter one. In the case of 
 hearing, however, it has been measured with a tolerable approach 
 to accuracy ; for it has been found that, if the sonorous undulations 
 follow each other with a greater rapidity than sixteen times per 
 second, they become fused together into a continuous sound, pro- 
 ducing upon the ear the impression of a musical note. The varying 
 pitch of the note depends upon the rapidity with which the vibra- 
 tions succeed each other. When the succession of yibrations ia 
 very rapid, a high note is the result, and when comparatively slow, 
 a low note is produced ; but when the number of impulses falls 
 
512 THK SPECIAL SKNSE3. 
 
 k 
 
 below sixteen per second, we then begin to perceive the distinct 
 vibrations, and so lose the impression of a continuous note. 
 
 All the senses, in the second place, become accustomed to a con- 
 tinued impression, so that they no longer perceive its existence. 
 Thus, if a perfectly uniform pressure be exerted upon any part of 
 the body, the compressing substance after a time fails to excite any 
 sensation in the skin, and we remain unconscious of its existence. 
 In order to attract our notice, it is then necessary to increase or 
 diminish the pressure ; while, so long as this remains uniform, no 
 effect is perceived. But if, after the skin has thus become accus- 
 tomed to its presence, the foreign body be suddenly remo^^d, our 
 attention is then immediately excited, and we notice the absence of 
 an impression, in the same way as if it were a positive sensation. 
 
 "We all know how rapidly we become habituated to odors, whether 
 agreeable or disagreeable in their nature, in the confined air of a 
 close apartment; although, on first entering from without our 
 attention may have been attracted by them in a very decided 
 manner. A continuous and uniform sound, also, like the steady 
 rumbling of carriages, or the monotonous hissing of boiling water, 
 becomes after a time inaudible to us; but as soon as the sound 
 ceases, we notice the alteration, and our attention is at once excited. 
 The senses, accordingly, receive their stimulus more from the varia- 
 tions and contrasts of external impressions, than from these impres- 
 sions themselves. 
 
 Another important particular, in regard to the senses, is their 
 capacity for education. The proofs of this are too common and too 
 apparent to need more than a simple allusion. The touch may be 
 so trained that the blind may read words and sentences by its aid, 
 in raised letters, where an ordinary observer would hardly detect 
 anything more than a barely distinguishable inequality of surface. 
 The educated eye of the artist, or the naturalist, will distinguish 
 variations of color, size, and outline, altogether inappreciable to 
 ordinary vision ; and the senses of taste and stoell, in those who are 
 in thfe habit of examining wines and perfumes, acquire a similar 
 superiority of discriminating power. 
 
 In these instances, however, it is not probable that the organ of 
 sense itself becomes any more perfect in organization, or more 
 susceptible to sensitive impressions. The increased functional 
 power, developed by cultivation, depends rather upon the greater 
 delicacy of the perceptive and discriminative faculties. It is a mental 
 and not a physical superiority which gives the painter or the 
 
ON THE SKNSiJS IN GENERAL. 513 
 
 naturalist a greater power of distinguishing colors and outlines, 
 and which enables the physician to detect nice variations of quality 
 in the sounds of the heart or the respiratory murmur of the lungs. 
 The impressions of external objects, therefore, in order to produce 
 their complete effect, must first be received by a sensitive appa- 
 ratus, which is perfect in organization and functional activity; 
 and, secondly, these impressions must be subjected to the action of 
 an intelligent perception, by which their nature, source and rela- 
 tions may be fully appreciated. 
 
 That part of the nervous system which we have hitherto 
 studied, viz., the cerebro-spinal system, consists of an apparatus of 
 nerves and ganglia, destined to bring the individual into relation 
 with the external world. By means of the special senses, he is 
 made cognizant of sights, sounds, taste, and odors, by which he 
 is attracted or repelled, and which guide him in the pursuit and 
 choice of food. By the general sensations of touch and the volun- 
 tary movements, he is enabled to alter at will his position and 
 location, and to adapt them to the' varying conditions under which 
 he may be placed. The great passages of entrance into the body, 
 and of exit from it, are guarded by the same portion of the nerv- 
 ous system. The introduction of food into the mouth, and its 
 passage through the oesophagus to the stomach, are regulated by 
 the same nervous apparatus ; and even the passage of air through 
 the larynx, and its penetration into the lungs, are equally under 
 the guidance of sensitive and motor nerves belonging to the 
 cerebro-spinal system. 
 
 It will be observed that the above functions relate altogether 
 either to external phenomena or to the simple introduction into the 
 body of food and air, which are destined to undergo nutritive 
 changes in the interior of the frame. 
 
 If we examine, however, the deeper regions of the body, we find 
 located in them a series of internal phenomena, relating only to 
 the substances and materials which have already penetrated into 
 the frame, and which form or are forming a part of its structure. ' 
 These are the purely vegetative functions, as they are called ; or 
 those of growth, nutrition, secretion, excretion, and reproduction. 
 These functions, and the organs to which they belong, are not 
 under the direct influence of the cerebro-spinal nerves, but are 
 regulated by another portion of the nervous system, viz., the 
 "ganglionic system;" or, as it is more commonly called, the "sys- 
 tem of the great sympathetic." 
 33 
 
514 SYSTEM OF THE GR^AT SYMPATHETIC. 
 
 CHAPTER VII. 
 
 SYSTEM OP THE GREAT SYMPATHETIC. 
 
 The sympathetic system consists of a double chain of nervous 
 ganglia, running from the anterior to the posterior extremity of the 
 body, along the front and sides of the spinal column, and connected 
 with each other by slender longitudinal filaments. Each ganglion 
 is reiilforced by a motor and sensitive filament derived from the 
 cerebro-spinal system, and thus the organs under its influence are 
 brought indirectly into communication with external objects and 
 phenomena. The nerves of the great sympathetic are distributed 
 to organs over which the consciousness and the will have no imme- 
 diate control, as the intestine, kidneys, heart, liver, &o. 
 
 The first sympathetic ganglion in the head is ihQ ophthalmic gan- 
 glion. This ganglion is situated within the orbit of the eye, on the 
 outer aspect of the optic nerve. It communicates by slender fila- 
 ments with the carotid plexus, which forms the continuation of the 
 sympathetic system from, below ; and receives a motor root from 
 the oculo-motorius nerve, and a sensitive root from the .ophthalmic 
 branch of the fifth pair. Its filaments of distribution, known as the ■ 
 " ciliary nerves," pass forward upon the eyeball, pierce the sclerotic, 
 and finally terminate in the iris. 
 
 The next division of the great sympathetic in the head is the 
 spheno-palatirie ganglion, situated in the spheno-maxillary fossa. It 
 communicates, like the preceding, with the carotid plexus, and 
 receives a motor root from the facial nerve, and a sensitive root 
 'from the superior maxillary branch of the fifth pair. Its filaments 
 are distributed to the levator palati and azygos uvulae muscles, and 
 to the mucous membrane about the posterior nares. 
 
 The third sympathetic ganglion in the head is the suhmaxillary, 
 situated upon the submaxillary gland. It communicates with the 
 superipr cervical ganglion of the sympathetic by filaments which 
 accompany the facial and external carotid arteries. It derives its 
 sensitive filaments from the lingual braach of the fifth pair, and its 
 
SYSTEM OJT THE GREAT SYMPATHETIC. 
 
 515 
 
 motor filaments from the facial nerve, by means of the chorda 
 tympani. Its branches of distribution pass to the sides of the tongue 
 and to the submaxillary and sublingual glands. 
 
 The last sympathetic ganglion in the head is the otic ganglion. 
 It is situated just beneath the 
 
 base of the skull, on the inner Kg- 166. 
 
 side of the third division of 
 the fifth pair. It sends fila- 
 ments of communication to 
 the carotid plexus; and re- 
 ceives a motor root from the 
 facial nerve, and a sensitive 
 root from the inferior maxil- 
 lary division of the fifth pair. 
 Its branches are sent to the 
 internal muscle of the mal- 
 leus in the middle ear (tensor 
 tympani), and to the mucous 
 membrane of" the tympanum 
 and Eustachian tube. 
 
 The continuation of 'the 
 sympathetic nerve in the neck 
 consists of two and some- 
 times three ganglia, the su- 
 perior, middle, and inferior. 
 These ganglia communicate 
 with each other, and also 
 with the anterior branches 
 of the cervical spinal nerves. 
 Their filaments follow the 
 course of the carotid artery 
 and its branches, covering 
 them with a network of inter- 
 lacing fibres, and are finally 
 distributed to the substance of 
 the thyroid gland, and to the 
 walls of the larynx, trachea, 
 pharynx, and oesophagus. 
 
 By the superior, middle, and inferior cardiac nerves, they also supply 
 sympathetic fibres to the cardiac plexuses and to the substance of 
 the heart. 
 
 Course and distribatiou of the Great Sthpa- 
 
 THBTIC. 
 
516 SYSTEM OF THE GREAT SYMPATHETIC. 
 
 In the chest, the ganglia of the sympathetic nerve are situated on 
 each side the spinal column, just over the heads of the ribs, with 
 which they accordingly correspond in number. Their communi- 
 cations with the intercostal nerves are double; 'each sympathetic 
 ganglion receiving two filaments from the intercostal nerve next 
 above it. The filaments originating from the thoracic ganglia are 
 distributed upon the thoracic aorta, and to the lungs and oesophagus. 
 
 In the abdomen, the continuation of the sympathetic system con- 
 sists principally of the aggregation of ganglionic enlargements 
 situated upon the cceliac artery, known as the semilunar or cceliac 
 ganglion. From this ganglion a multitude of radiating and inoscu- 
 lating branches are sent out, which, from their diverging course and 
 their common origin from a central mass, are termed the "solar 
 plexus." From this, other diverging plexuses originate, which 
 accompany the abdominal aorta and its branches, and are distri- 
 buted to the stomach, small and large intestine, spleen, pancreas, 
 liver, kidneys, supra-renal capsules, and internal organs of gene- 
 ration; 
 
 Beside the above ganglia there are in the abdomen four other 
 pairsy situated in front of the luihbar vertebrae, and having similar 
 connections with those occupying the cavity of the chest. Their 
 filaments join the plexuses radiating from the semilunar, ganglion. 
 
 In the pelvis, the sympathetic system is continued by four or five 
 pairs of ganglia, situated on the anterior aspect of the sacrum, and 
 terminating, at the lower extremity of the spinal column, in a single 
 ganglion, the ''ganglion impar," which is probably to be regarded 
 as a fusion of two separate ganglia. 
 
 The entire sympathetic series is in this way composed of nume- 
 rous small ganglia which are connected throughout, first, with each 
 other ; secondly, with the cerebro-spinal system ; and thirdly, with 
 the internal viscera of the body. 
 
 The properties and functions of the great sympathetic have been 
 less successfully studied than those of the cerebro-spinal system, 
 owing to the anatomical difficulties in the way of reaching and 
 operating upon this nerve for purposes of experiment. The cerebro- 
 spinal axis and its nerves are easily exposed and subjected to exami- 
 nation. It is also easy to isolate particular portions of this system, 
 and to appreciate the disturbances of sensation and motion conse- 
 quent upon local lesions or irritations. The phenomena, further- 
 more, which result from experiments upon this part of the nervous 
 apparatus, are promptly produced, are well-marked in character. 
 
SYSTEM OF THE GBEAT SYMPATHETIC. 517 
 
 and are, as a general rule, readily understood by the experimenter. 
 On the other hand, the principal part of the sympathetic system is 
 situated in the interior of the chest and abdomen ; and the mere 
 operation of opening these cavities, so as to reach the ganglionic 
 centres, causes such a disturbance in the functions of vital organs, 
 and such a shock to the system at large, that the results of these 
 experiments have" been always more or less confused and unsatis- 
 factory. Furthermore, the connections of the sympathetic ganglia 
 with each other and with the cerebro-spinal axis are so numerous 
 and so scattered, that these ganglia cannot be completely isolated 
 without resorting to an operation still more mutilating and injuri- 
 ous in its character. And finally, the sensible phenomena which 
 are obtained by experimenting on the great sympathetic are, in 
 the majority of cases, slow in making their appearance, and not 
 particularly striking or pharacteristic in their nature. 
 
 Notwithstanding these difficulties, however, some facts have been 
 ascertained with regard to this part of the nervous system, which 
 give us a certain degree of insight into its character and functions. 
 
 The great sympathetic is endowed both with sensibility and the 
 power of exciting motion; but these properties are less active 
 here than in the cerebro-spinal system, and are exercised in a dif- 
 ferent manner. If we irritate, for example, a sensitive nerve in 
 one of the .extremities, or apply the galvanic current to the poste- 
 rior root of a spinal nerve, the evidences of pain or of reflex 
 action are acute and instantaneous. There is no appreciable inter- 
 val between the application of the stimulus and the sensations 
 which result from it. On the other hand, experimenters who have 
 operated upon the .sympathetic ganglia and nerves of the chest and 
 abdomen find that evidences of sensibility are distinctly manifested 
 here also, but much less acutely, and only after somewhat prolonged 
 application of the irritating cause. These results correspond very 
 closely with what we know of the vital properties of the organs 
 which are supplied either principally or exclusively by the sym- 
 pathetic; as the liver, intestine, kidneys, &o. These organs are 
 insensible, or nearly so, to ordinary impressions. "VVe are not con- 
 scious of. the changes and operations going on in them, so long as 
 these changes and operations retain their normal character. But 
 they are still capable of perceiving unusual or excessive irritations, 
 and may even become exceedingly painful when in a state of in- 
 iSammation. 
 
 There is the same peculiar character in the action of the motor 
 
518 SYSTEM OF THE GREAT SYMPATHETIC. 
 
 nerves belonging to the sympathetic system. If the facial or hypo- 
 glossal, or the anterior root of a spinal nerve be irritated, the con- 
 vulsive movement which follows is instantaneous, violent, and only 
 momentary in its duration. But if the semilunar ganglion or its 
 nerves be subjected to a similar experiment, no immediate effect is 
 produced. It is only after a few seconds that a slow, vermicular, 
 progressive contraction takes place in the corresponding part of the 
 intestine, which continues for some time after the exciting cause 
 has been removed. 
 
 Morbid changes taking place in organs supplied by the sympa- 
 thetic present a similar peculiarity in the mode of their produc- 
 tion. If the body be exposed to cold and dampness, for example, 
 congestion of the kidneys shows itself perhaps on the following 
 day. Inflammation of any of the internal organs is very rarely 
 established within twelve or twenty-four hours after the application 
 of the exciting cause. The internal processes of nutrition, together 
 with their derangements, wbich are regarded as especially under 
 the control of the great sympathetic, always require a longer time 
 to be influenced by incidental causes, than those which are regulated 
 by the nerves and ganglia of the cerebro-spinal system. 
 
 In the head, the sympathetic has a close and important connec- 
 tion with the exercise of the special senses. . This is illustrated 
 more particularly in the case of the eye, by its influence over the 
 alternate expansion and contraction of the pupil. The ophthalmic 
 ganglion sends off a number of ciliary nerves, which are distributed 
 to the iris. It is connected, as we have seen, with the remaining 
 sympathetic ganglia in the head, and receives, beside, a sensitive 
 root from the ophthalmic branch of the fifth pair, and a motor root 
 from the oculo-motorius. The reflex action by which the pupil 
 contracts under a strong light foiling upon the retina, and expands 
 under a diminution of light, takes place, accordingly, through this 
 ganglion. The impression conveyed by the optic nerve to the 
 tubercula quadrigemina, and reflected outward by the fibres of 
 the oculo-motorius, is not transmitted directly by the last named 
 nerve to the iris ; but passes first to- the ophthalmic ganglion, and 
 is thence conveyed to its destination by the ciliary nerves. 
 
 The reflex movements of the iris exhibit consequently a some- 
 what sluggish character, which indicates the intervention of a part 
 of the sympathetic system. The changes in the size of the pupil 
 do not take place instantaneously, with the variation in the amount 
 of light, but always require an appreciable interval of time. If 
 
SYSTEM OS" THE GEEAT SYMPATHETIC. 519 
 
 we pass suddenly from a brilliantly lighted apartment into a dark 
 room, -we are unable to distinguish surrounding objects until a 
 certain time has elapsed, and the expansion of the pupil has taken 
 place ; and vision even Continues to grow more and more distinct 
 for a considerable period afterward, as the expansion of the pupil 
 becomes more complete. Again, if we cover the eyes of another 
 person with the hand or a folded cloth, and then suddenly expose 
 them to the light, we shall find that the pupil, which is at first 
 dilated, contracts somewhat rapidly to a certain extent, and after- 
 ward continues to diminish in size during several seconds, until the 
 proper equilibrium is fairly established. Furthermore, if we pass 
 suddenly from a dark room into the bright sunshine, we are imme- 
 diately conscious of a painful sensation in the eye, which lasts for 
 a considerable time ; and which results from .the inability of the 
 pupil to contract with sufficient rapidity to shut out the excessive 
 amount of light. All such exposures should be made gradually, 
 so that the movements of the iris may keep pace with the varying 
 quantity of stimulus, and so protect the eye from injurious impres- 
 sions. 
 
 The reflex movements of the iris, however, though accomplished 
 through the medium of the ophthalmic ganglion, derive their 
 original stimulus, through the motor root of this ganglion, from 
 the ooulo-motorius nerve. For it has been found that if the oculo- 
 motorius nerve be divided between the brain and the eyeball, the 
 pupil becomes immediately dilated, and will no longer contract 
 under the influence of light. The motive power originally derived 
 from the brain is, therefore, in the case of the iris, modified by 
 passing through one of the sympathetic ganglia before it reaches 
 its final destination. 
 
 An extremely interesting fact in this connection is the following. 
 Of the three organs of special sense in the head, viz., the eye, the 
 nose, and the ear, each one is provided with two sets of muscles, 
 superficial and deep, which together regulate the qua,ntity of stimu- 
 lus admitted to the organ, and the mode in which it is received. 
 The superficial set of these muscles is animated by branches of the 
 facial nerve ; the deep-seated or internal set, by filaments from a 
 sympathetic ganglion. 
 
 T]hus, the front of the eyeball is protected by the orbicularis and 
 levator palpebrae superioris muscles, which open or close the eye- 
 lids at will, and allow a larger or smaller quantity of light to reach 
 the cornea. These muscles are supplied by the oculo-motorius and 
 
520 SYSTEM OP THE GREAT SYMPATHETIC. 
 
 facial nerves, and are for the most part voluntary in their action. 
 The iris, on the other hand, is a more deeply-seated muscular 
 curtain, which regulates the quantity of light admitted through the 
 pupil. There is also the ciliary muscle, which regulates the position 
 of the crystalline lens, and secures a correct focusing of the light, 
 at different distances. Both these 'muscles are supplied, as we have 
 seen, by filaments from the ophthalmic ganglion, and their move- 
 ments are involuntary in character. 
 
 In the olfactory apparatus, the anterior or superficial set of 
 muscles are the compressors and elevators of the alse nasi, which 
 are animated by filaments of the facial nerve. By their action, 
 odoriferous vapors, when faint and delicate in their character, are 
 snuffed up and directed into the upper part of the nasal passages, 
 where they come in contact with the most sensitive portions of the 
 olfactory membrane ; or, if too pungent or disagreeable in flavor, 
 are excluded from entrance. These muscles are not very im- 
 portant or active in the human subject ; but in many of the lower 
 animals with a more active and powerful sense of smell, as, for 
 example, the carnivora, they may be seen to play a very important 
 part in the mechanism of olfaction. Furthermore, the levators and 
 depressors of the velum palati, which are more deeply situated, 
 serve to open or close the orifice of the posterior nares, and accom- 
 plish a similar office with the muscles already named in front. The 
 levator palati and azygos uvulae muscles, which, by their action, 
 tend to close the posterior nares, are supplied by filaments from the 
 spheno-palatine ganglion, and are involuntary in their character. 
 
 The ear has two similar sets of muscles, similarly supplied. The 
 first, or superficial set, are those moving the external ear, viz., the 
 anterior, superior, and posterior auriculares. Like the muscles of 
 the anterior nares, they are comparatively inactive in man, but in 
 many of the lower animals are well developed and important. In 
 the horse, the deer, the sheep, &c., they turn the ear in various 
 directions so as to catch more distinctly faint and distant sounds, or 
 to exclude those which are harsh and disagreeable. These muscles 
 are supplied by filaments of the facial nerve, and are voluntary in 
 their action. 
 
 The deep-seated set are tlie muscles of the middle ear. In order 
 to understand their action, we must recollect that sounds are trans- 
 mitted from the external to the middle ear through the membrane 
 of the tympanum, which vibrates, like the head of a drum, on 
 receiving sonorous impulses from without. 
 
SYSTEM OF THE GREAT SYMPATHETIC. 521 
 
 The membrane of the tympanum, accordingly, -which is an elastic 
 sheet, stretched across the passage to the internal ear, may be made 
 more or less sensitive to sonorous impressions by varying its con- 
 dition of tension or relaxation. This condition is regulated, as we 
 have already seen, by the combined action of the two muscles of 
 the middle ear, viz., the tensor tympani and the stapedius. The 
 first named muscle, the action of which is perfectly well understood, 
 is supplied with nervous filaments from the otic ganglion of the 
 sympathetic. By its contraction, the handle of the malleus is drawn 
 inward, bringing the membrana tympani with it,, and putting this 
 membrane upon the stretch. On the relaxation of the muscle, the 
 chain of bones returns to its ordinary position, by the elasticity of 
 the neighboring parts, and the previous condition of the tympanic 
 membrane is restored. This action, so far as we can judge, is purely 
 involuntary. But the stapedius muscle is separately supplied by a 
 minute branch of the facial nerve. It is probable that this arrange- 
 ment enables us to make also a certain degree of voluntary exer- 
 tion, in listening intently for faint or distant sounds. 
 
 In all these instances, the reflex action taking place in the 
 deeper seated muscles, originates from a sensation which is con- 
 veyed inward to the cerebro-spinal centres, and is then transmitted 
 outward to its final destination through the medium of one of the 
 sympathetic ganglia.- 
 
 Another very striking fact, concerning the sympathetic, relates to 
 the changes produced by its division, in the nutritive processes of 
 the parts supplied by it. One of the most important and remark- 
 able of these changes is an elevation of temperature in the affected 
 parts. If the sympathetic nerve be divided on one side of the neck, 
 in the rabbit, cat, or dog, an elevation of temperature begins to be 
 perceptible on the corresponding side of the head in a very short 
 time. In the cat, we have found a very sensible difference in 
 temperature between the two sides at the end of ten minutes; 
 and in the rabbit, at the end of half an htjur. A vascular conges- 
 tion of the parts also takes place, which may be seen to great 
 advantage in the ear of the rabbit, when held up between the eye 
 and the light. The elevation of temperature, in these cases, is very 
 perceptible to the touch, and may also be measured by the thermo- 
 meter. Bernard' has found it to reach 8° or 9° F. The elevation 
 of temperature and congested state of the parts are sometimes found 
 to be diminished by the next day, and afterward disappear rapidly. 
 ' Rechcrches Gxpfrimentales sur le Grand Sympathique. Paris, 1854. 
 
522 SYSTEM OF THE GREAT SYMPATHETIC. 
 
 Occasionally, however, they last for a long time. Bernard (op, cit.) 
 has seen the unnatural temperature of the affected parts remain, in 
 the rabbit, from fifteen to eighteen days, and in the dog for two 
 months. Where the superior cervical ganglion has been extirpated, 
 he has even found the above appearances to continue, in the dog, for 
 a year and a half. They may also, according to the same authority, 
 be reproduced several times in the same animal, by repeated divi- 
 sions of the sympathetic nerve. 
 
 The above effect is due to a peculiar modification in the nutri- 
 tion of the affected parts, which has some analogy with inflamma- 
 tion. The unnatural heat, the congestion, and the increased sensi- 
 bility which are present, all serve to indicate a certain resemblance 
 between the two conditions. None of the more serious consequences 
 of inflammation, however, such as cedema, exudation, sloughing or 
 ulceration, have ever been known to follow from this operation; 
 and the term inflammation, accordingly, cannot properly be applied 
 to its results. 
 
 Division of the sympathetic nerve in the middle of the neck 
 has also a very singular and instantaneous effect on the muscular 
 apparatus of the eye. Within a very few seconds after the above 
 operation has been performed upon the cat, the pupil, of the cor- 
 responding eye becomes strongly contracted, and remains in that 
 condition. At the same time the third eyelid, or " nictitating mem- 
 brane," with which these animals 
 5''g- i67. are provided, is drawn partially 
 
 over the cornea, and the upper 
 and lower eyelids also approxi- 
 mate very considerably to each 
 other; so that all the apertures 
 guarding the eyeball are very 
 perceptibly narrowed, and the ex- 
 pression of the face on that side is 
 altered in a corresponding degree. 
 This effect upon the pupil has 
 been explained by supposing^ the 
 
 Cat, aftei aection of the right eympathetic. circular fibres of the. iris, Or the 
 
 constrictors of the pupil, to be 
 animated exclusively by nervous filaments derived from the oculo- 
 motorius ; and the radiating fibres, or the dilators, to be supplied 
 by the sympathetic. Accordingly, while division of the ooulo- 
 raotorius would produce dilatation of the pupil, by paralysis of 
 
SYSTEM OF THE GREAT SYMPATHETIC. 523 
 
 the circular fibres only, division of the sympathetic would be 
 followed by exclusive paralysis of the dilators, and a permanent 
 contraction of the pupil would consequently take place. The 
 above explanation, however, is not a satisfactory one ; since, in 
 the first place, division of the oculo-motorius, as the experiments of 
 Bernard have shown,^ does not by itself produce complete dilata- 
 tion of the pupil ; and, secondly, after division of the sympathetic 
 nerve in the cat, as we have already shown, not only is the pupil 
 contracted, but both the upper and lower eyelids and the nictitating 
 membrane are also partially drawn over the cornea, and assist in 
 excluding the light. The last-named effect cannot be owing to any 
 direct paralysis, from division of the fibres of the sympathetic. It 
 is more probable that the section of this nerVe operates simply by 
 exaggerating for a time the sensibility of the retina, as it does that 
 of the integument ; and that the partial closure of the eyelids and 
 pupil is a secondary consequence of that condition. 
 
 It will be remembered that in describing the inflammation of the 
 eyeball, consequent upon section of the fifth pair of nerves, we 
 found that there were reasons for believing this effect to be due 
 to injury of certain sympathetic fibres which accompany the fifth 
 pair. If the fifth pair in fact be divided at the level of the Cas- 
 serian ganglion, where it is joined by sympathetic fibres from the 
 carotid plexus, or between this ganglion and the eyeball, a destruc- 
 tive infiammation of the organ follows. But if the section be made 
 behind the ganglion, so as to avoid the filaments of communication 
 with the sympathetic, no inflammatory change takes place. If this 
 fact be really owing to the presence of sympathetic fibres which 
 accompany the fifth pair, it indicates a remarkable difference in the 
 effects of dividing the sympathetic near the eyeball and at a dis- 
 tance from it; since no real inflammation of the eyeball or its 
 appendages is ever produced by division of this nerve in the middle 
 of the neck, but only the elevation of temperature and increase of 
 sensibility, which have been already described. 
 
 The influence of the sympathetic nerve and the consequences 
 of its division upon the thoracic and abdominal viscera have been 
 only very imperfectly investigated by experimental methods. It 
 undoubtedly serves as a medium of reflex action between the sensi- 
 tive and motor portions of the digestive, excretory, and generative 
 
 ' Le(;on9 sur la Pliysiologie et la PatUologie du Systfeme Nervenx, Paris, 1858, 
 Tol. ii. p. 203. 
 
524 SYSTEM OF THE GREAT SYMPATHETIC. 
 
 apparatuses ; and it is certain that it also takes part in reflex actions 
 in which the cerebro-spinal system is at the same time interested. 
 There are accordingly three different kinds of reflex action, taking 
 place wholly or partially through the sympathetic system, which 
 may be observed to occur in the living body. 
 
 1st. Reflex, actions takings place from the internal organs, through 
 the sympathetic and cerebro-spinal systems, to the voluntary miiscles and 
 sensitive surfaces. — The convulsions of young children are often 
 owing to the irritation of undigested food in the intestinal canal. 
 Attacks of indigestion are also known to produce temporary amau- 
 rosis, double vision, strabismus, and even hemiplegia. Nausea, and 
 a diminished or capricious appetite, are often prominent symptoms 
 of early pregnancy, in'duced by the peculiar condition of the uterine 
 mucous membrane. 
 
 2d. Reflex actions taking place from the sensitive surfaces, through 
 the cerebrospinal and sympathetic systems, to the involuntar'y muscles 
 and secreting org'ans.-r— Imprudent exposure of the integument to 
 cold and wet, will often bring on a diarrhoea. Mental and moral 
 impressions, conveyed through the special senses, will affect the 
 motions of the heart, and disturb the processes of digestion and 
 secretion. Terror, or an absorbing interest of any kind, will pro- 
 duce a dilatation of the pupil, and communicate in this way a pecu- ' 
 liarly wild and unusual expression to the eye. Disagreeable sights 
 or odors, or even unpleasant occurrences, are capable of hastening 
 or arresting the menstrual discharge, or of inducing premature 
 delivery. 
 
 3d. Reflex actions taking place through the sympathetic system from 
 one part of the internal organs to another. — The contact of food with 
 the mucous membrane of the small intestine excites a peristaltic 
 movement in the muscular coat. The mutual action of the diges- 
 tive, urinary and internal generative organs upon each other takes 
 place through the medium of the sympathetic ganglia and their 
 nerves. The variations of the capillary circulation in different 
 abdominal viscera, corresponding with the state of activity or re- 
 pose of their associated organs, are to be referred to a similar nerv- 
 ous influence. These phenomena are not accompanied by any 
 consciousness on the part of the individual, nor by any apparent 
 intervention of the cerebro-spinal system; 
 
SECTION III. 
 REPRODUCTION. 
 
 CHAPTER I. 
 
 ON THE NATURE OP REPRODUCTION, AND THE 
 ORIGIN OP PLANTS AND ANIMALS. 
 
 The process of reproduction is the most characteristic, and in 
 many respects the most interesting, of all the phenomena presented 
 by organized bodies. It includes the whole history of the changes 
 taking place in the organs and functions of the individual at suc- 
 cessive periods of life, as well as the production, growth, and de- 
 velopment of the new germs which make their appearance by 
 generation. 
 
 For all organized bodies pass through certain well-defined epochs 
 or phases of development, by which their structure and functions 
 undergo successive alterations. We have already seen that the 
 living animal or plant is distinguished from inanimate substances 
 by the incessant changes of nutrition and growth which take place 
 in its tissues. The muscles and the mucous membranes, the osse- 
 ous and cartilaginous tissues, the secreting and circulatory organs, 
 all incessantly absorb oxygen and nutritious material from with- 
 out, and assimilate their molecules; while new substances, produced 
 by a retrogressive alteration and decomposition, are at the same 
 time excreted and discharged.* These nutritive changes correspond 
 in rapidity with the activity of the other vital phenomena ; since 
 the production of these phenomena, and the very existence of the 
 vital functions, depend upon the regular and normal continuance 
 of the nutritive process. Thus the organs and tissues, which are 
 always the seat of this double change of renovation and decay, 
 
 ( 525 ) 
 
526 NATURE OP REPEOUUCTION. 
 
 retain nevertlieless their original constitution, and continue to be 
 capable of exhibiting the vital phenomena. 
 
 The above changes, however, are not in reality the only ones 
 which take place. For although the structure of the body and the 
 composition of its constituent parts appear to be maintained in an 
 unaltered condition,^ by the nutritive pi'ocess, from one moment to 
 another, or from day to day, yet a comparative examination of 
 them at greater intervals of time will show that this is not pre- 
 cisely the case ; but. that the changes of nutrition are, in point of 
 fact, progressive as well as momentary. The composition and pro- 
 perties of the skeleton, for example, are not the same at the age of 
 twenty-five that they were at fifteen. At the later period it con- 
 tains more calcareous and less organic matter than before ; and its 
 solidity is accordingly increased, while its elasticity is diminished. 
 Even the anatomy of the bones alters in an equally gradual manner; 
 the medullary cavities enlarging with the progress of growth, and 
 the cancellated tissue becoming more open and spongy in texture. 
 We have already noticed the difference in the quantity of oxygen 
 and carbonic acid inspired and exhaled at difterent ages. The 
 muscles, also, if examined after the lapse of some years, are found 
 to-be less irritable than formerly, owing to a slow, but steady and 
 permanent deviation in their intimate constitution. 
 
 The vital properties- of the organs, therefore, change with their 
 varying structure ; and a time comes at last when they are per- 
 ceptibly less capable of performing their original functions than 
 before. This alteration, being dependent on the varying activity ' 
 of the nutritive process, continues necessarily to increase. The very 
 exercise of the vital powers is inseparably connected with the sub- 
 sequent alteration of the organs employed in them ; and the func- 
 tions of life, therefore, instead of remaining indefinitely the same, 
 pass through a series of successive changes, which finally terminate 
 in their complete cessation. 
 
 The histpry of a living animal or plant is, therefore, a history of 
 successive epochs or phases of existence, in each of which the struc- 
 ture and functions of the body differ more or less from those in 
 every other. Every living being hai a definite terra of life, through 
 which it passes by the operation of an invariable law, and which, 
 at some regularly appointed time, comes to an end. The plant 
 germinates, grows, blossoms, bears fruit, withers, and decays. The 
 animal is born, nourished, and brought to maturity, after which he 
 retrogrades and dies. The very commencement of existence, by 
 
NATUBB OF EEPBODUCTIOIT. 527 
 
 leading through its successive intermediate stages, conducts at last 
 necessarilj to its own termination. 
 
 But while individual organisms are thus constantly perishing and 
 disappearing from the stage, the particular kind, or species, remains 
 in existence, apparently without any important change in the cha- 
 racter or appearance of the organized forms belonging to it. The 
 horse and the ox, the oak and the pine, the different kinds of wild 
 and domesticated animals, even the different races of man himself, 
 have remained without any essential alteration ever since the earliest 
 historical epochs. Yet during this period innumerable individuals, 
 belonging to each species or race, must have lived through their 
 natural term and successively passed out of existence. A species 
 may therefore be regarded as a type or class of organized beings, in 
 which the particdlar forms or structures composing it die oflF con- 
 stantly and disappear, but which nevertheless repeats itself from 
 year to year, and maintains its ranks constantly full by the regular 
 accession of new individuals. This process, by which new organ- 
 isms make their appearance, to take the place of those which are 
 destroyed, is known as the process of reproduction or generation. Let 
 us now see in what manner it is accomplished. 
 
 It has always been known that, as a general rule in the process 
 of generation, the young animals or plants are produced directly 
 from the bodies of the elder. The relation between the two is that 
 of parents and progeny ; and the new organisms, thus generated, 
 become in turn the parents of o^ers which succeed them. For this 
 reason wherever such plants or animals exist, they indicate the 
 previous existence of others belonging to the same species ; and if 
 by any accident the whole species should be destroyed in any par- 
 ticular locality, no new individuals could be produced there, unless 
 by the previous importation of others of the same kind, 
 , The commonest observation shows this to be true in regard to 
 those animals and plants with whose history we are more familiarly 
 acquainted. An opinion, however, has sometimes been maintained 
 that there are exceptions to this rule ; and that living beings may, 
 under certain circumstances, be produced from inanimate substances, 
 without any similar plants or animals having preceded them ; pre- 
 senting, accordingly, the singular phenomenon of a progeny without 
 parents. Such a production of organized bodies is known'by the 
 name of spontaneous generation. It is believed by the large majority 
 of physiologists at the present day that no such spontaneous gene- 
 ration ever takes place; but that plants and animals are always 
 
528 NATURE OF REPRODUCTION. 
 
 derived, by direct reproduction, from previously existing parents 
 of the same species. As this, however, is a question of some im- 
 portance, and one which has been frequently discussed in works on 
 physiology, we shall proceed to pass in review the facts which have 
 been adduced in favor of the occurrence of spontaneous generation, 
 as well as those which would lead to its disproval and rejection. 
 
 It is evident, in the first place, that many apparent instances of 
 spontaneous generation are found to be of a very different character 
 as soon as they are subjected to a critical examination. Thus grass- 
 hoppers and beetles, earthworms and crayfish, the swarms of minute 
 insects that fill the air over the surface of stagnant pools, and even 
 frogs, moles, and lizards, have been supposed in former times to be 
 generated directly from the earth or the atmosphere ; and it was 
 only by investigating carefully the natural history of these animals 
 that they were ascertained to be produced in the ordinary manner 
 by generation from parents, and were found to continue the repro- 
 duction of their species in the same way. A still more striking 
 instance is furnished by the production of maggots in putrefying 
 meat, vegetables, flour paste, fermenting dung, &c. If a piece of 
 meat be exposed, for example, and allowed to undergo the process 
 of putrefaction, at the end of a few days it will be found to contain 
 a multitude of living maggots which feed upon the decomposing 
 flesh, l^ow these maggots are always produced under the same 
 conditions of warmth, moisture and exposure, and at the same stage 
 of the putrefactive process. They are never to be found in fresh 
 meat, nor, in fact, in any other situation than the one just mentioned. 
 They appear, consequently, without any similar individuals having 
 existed in the same locality ; and considering the regularity of their 
 appearance under the given conditions,, and their absence elsewhere, 
 it has been believed that they were spontaneously generated, under 
 the influence of warmth, moistnre, and the atmosphere, from the 
 decaying organic substances. 
 
 A little examination, however, discovers a very simple solution 
 of the foregoing difficulty. On watching the exposed animal or 
 vegetable substances during the earlier periods of their decompo- 
 sition, it is found that certain species of flies, attracted by the odor 
 of the decaying material, hover round it and deposit their eggs 
 upon its surface • or in its interior. These eggs, hatched by the 
 warmth to which they are exposed, produce the maggots ; which 
 are simply the young of the winged insects, and which after a time 
 become transfornied, by the natural progress of development, into 
 
INFUSORIAL ANIMALCULES. 529 
 
 perfect insects similar to their parents. The difficulty of account- 
 ing for the presence of the maggots by generation, therefore, de- 
 pends simply on the fact that they are different in appearance from 
 the parents that produce them. This difference, however, is merely 
 a temporary one, corresponding with the difference in age, and dis- 
 appears when the development of the animal is complete ; just as 
 the young chicken, when recently hatched, has a different form and 
 plumag^ from those which it presents in its adult condition. 
 
 Nearly all the causes of error, in fact, which have suggested at 
 various times the doctrine of spontaneous generation, have been 
 derived from these two sources. First, the ready transportation of 
 eggs or germs, and their rapid hatching under favorable circum- 
 stances ; and secondly, the different appearances presented by the 
 same animal at different ages, in consequence of which the youthful 
 animal may be mistaken, by an ignorant observer, for an entirely 
 different species. These sources of error are, however, so readily 
 detected, as a general rule, by scientific investigation, that it is 
 hardly necessary to point out the particular instances in which they 
 exist. In fact, whenever a rare or comparatively unknown animal 
 or plant has been at any time supposed to be produced by sponta- 
 neous generation, it has only been necessary, for the most part, to 
 investigate thoroughly its habits and functions, to discover its secret 
 methods of propagation, and to show that they correspond, in all 
 essential particulars, with the ordinary laws of reproduction. The 
 limits, therefore, within which the doctrine of spontaneous genera- 
 tion can be applied, have been narrowed in precisely the same 
 degree that the study of natural history and comparative physiology 
 has advanced. At present, indeed, there remain but two classes 
 of phenomena which are ever supposed to lend any support to the 
 above doctrine ; viz., tlie existence and production, 1st, of infuso- 
 rial animalcules, and 2d, of animal and vegetable parasites. We 
 shall now proceed to examine these two parts of the subject in 
 succession. 
 
 Infusorial Animalcules.— If water, holding in solution or. 
 ganic substances, be exposed to the contact of the atmosphere at- 
 ordinary temperatures, it is found after a short time to be filled 
 with swarms of minute living organisms, which are visible only by 
 the microscope. The forms of these microscopic animalcules are 
 exceedingly varied ; owing either to the great number of species 
 in existence, or to their rapid alteration during the successive pe- 
 34 
 
530 
 
 NATURE OP EEPKODUOTIOIf. 
 
 Different kinds of Infusoria. 
 
 riods of their growth. Ehrenberg has described more than 300 
 different varieties of them. They are generally provided with cilia 
 attached to the exterior of their bodies, and are, for the most part, 
 in constant and rapid motion in the fluid which they inhabit. 
 
 Owing to their presence in 
 '^' ■ ' animal aod vegetable watery 
 
 infusions, they have received 
 the name of "infusoria," or 
 " infusorial animalcules,". 
 
 Now these infusoria are 
 always produced under the 
 conditions which we have de- 
 scribed above. The animal 
 or vegetable substance used 
 for the infusion may be pre- 
 viously baked or boiled, so 
 as to destroy all living germs' 
 which it might accidentally 
 contain; the water in which 
 it is infused may be carefully 
 distilled, and thus freed from all similar contamination; and yet the 
 infusorial animalcules will make their appearance at the usual time 
 and in the usual abundance. It is only requisite that the infusion 
 be exposed to a moderately elevated temperature, and to the access 
 of atmospheric air; conditions which are equally necessary for 
 maintaining the life of all animal and vegetable organisms, what- 
 ever be the source from which they are derived. Under the above 
 circumstances, therefore, either the animalcules must have been 
 produced by spontaneous generation in the -water j infusion, or their 
 germs must have been introduced into it through the medium of 
 the atmosphere. No such introduction has ever been directly de- 
 monstrated, nor have even any eggs or germs belonging to the 
 infusoria ever been detected. 
 
 Nevertheless, there is every probability that the infusoria are 
 produced from germs, and not by spontaneous genei-ation. Since 
 ■ the infusoria themselves are microscopic in size, it is not surprising 
 that their eggs, which must be smaller still, should have escaped 
 observation. We know, too, that in many instances the minute 
 germs of animals or plants may be wafted about in a dry state by 
 the atmosphere, until, by accidentally cowling in contact with warmth 
 and moisture, they become developed and bring forth living organ- 
 
INPgSOBIAL .ANIMALCOLKS. 531 
 
 isms. The eggs of the infusoria, accordingly, may be easily raised, 
 and held suspended in the atmosphere, under the form of minute 
 dust-like particles, ready to germinate and become developed when- 
 ever they are caught by the surface of a stagnant pool, or of any 
 artificially prepared infusion. . In point of fact, the atmosphere 
 does really contain an abundance of such dust-like particles, even 
 when it appears to be most transparent and free from impurities. 
 This may be readily demonstrated by admitting a single beam of 
 sunshine into a darkened apartment, when the shining particles sus- 
 pended in the atmosphere become immediately visible in the track 
 of the sunbeam. Again, if a perfectly clean and polished mirjor 
 be placed with its face upward in a securely closed room, and left 
 undisturbed for several days, its surface at the end of that time will 
 be found to be dimmed by the settling upon it of minute dust, 
 deposited from the atmosphere. There is no reason, therefore, for 
 disbelieving that the air may always contain a sufl&cient number of 
 organic germs for the production of infusorial animalcules. 
 
 There is some difficulty, however, in obtaining direct proof that it 
 is through the medium of the atmosphere that organic germs pene- 
 trate into the watery infusions. It is true that if such an infusion 
 be prepared from baked meat or vegetables and distilled water, and 
 afterward hermetically sealed, no infusoria are developed in it ; but 
 this only shows, as we have already intimated, that the free access 
 of air is necessary to the development of all organic life, just as it is 
 to the support of animals and plants under ordinary conditions of 
 growth and reproduction. Such a result, therefore, proves nothing 
 with regard to the external origin of the infusoria. In order to be 
 conclusive, such an experiment should be so contrived that the 
 watery infusion, previously freed from all foreign contamination, 
 should be supplied with a free access of atmospheric air, while the 
 introduction of living germs by this channel should at the same time 
 be rendered impossible. An experiment of this kind has in reality 
 been contrived and successfully carried out by Schultze, of Berlin.' 
 
 This observer prepared an infusion containing organic substances 
 in solution, and inclosed it in a glass flask (Fig. 169, a) of such a 
 size, that the infusion filled about one-half the entire capacity of the 
 vessel. The mouth of the flask was fitted with an air-tight stopper 
 provided with two holes, through which were passed narrow glass 
 tubes bent at right angles. To each of these tubes was attached a 
 
 ■ Edinburgh New PhiloEophical Jonrnal, Oct. 1837. 
 
532 
 
 NATURE OF KEPRODUCTION. 
 
 Fig. 169. 
 
 potash-apparatus {b, c), similar to those used for condensing carbonic 
 acid in organic analyses. One of these (6) was filled with concen- 
 trated sulphuric acid, the other (c) with a solution of caustic potassa. 
 
 The flask with the organic infusion 
 having been subjected to a boiling 
 temperature, in order to destroy any 
 living germs which it might con- 
 tain, the stopper was inserted, and 
 the whole apparatus exposed to the 
 light, at the ordinary summer tempera- 
 ture. The connections of the apparatus 
 being perfectly tight, no air could pene- 
 trate into the flask, except by passing 
 through either the sulphuric acid or 
 the potassa; either of which would 
 retain and destroy any organic germs 
 which might be suspended in it. Every 
 day a fresh supply of air was introduced 
 into the flask by drawing it through 
 the tubes 6, c ; and in this way the atmospheric air above the infu^ 
 sion was constantly renewed, while at the same time the introduction 
 of living germs from without was effectually prevented. 
 
 Schultze kept this apparatus under his observation, as above, from 
 the last of May till the first of August; frequently examining the 
 edges of- the fluid with a lens, through the sides of the glass jar, 
 but without ever detecting in it any traces of living organisms. At 
 the end of that period the flask was opened, and the fluid which it 
 contained subjected to direct examination, equally without result. 
 It was then exposed, in the same vessel and in the same situation 
 as before, to the free access of the atmosphere, and at the end of 
 two or three days it was found to be swarming with infusoria. 
 
 It is plain, therefore, that the infusoria cannot be regarded as 
 produced by spontaneous generation, but must be considered as 
 originating in the usual manner from germs; since they do not 
 make their appearance in the watery infusion, when the accidental 
 introduction of germs from without has been effectually prevented. 
 
 Schnltze's experiment oa SpoWTA- 
 XEOcs Genebatioh.— a. Flask con- 
 taining watery infasion. b. Potash-ap- 
 paratus containing sulphuric acid. c. 
 Potash-apparatuH containing caustic po- 
 tassa. 
 
 Animal- and Vegetable Parasites. — This very remarkable 
 group of organized bodies is distinguished by the fact that they, 
 live either upon the surface or in the interior of other animal or 
 vegetable organisihs. Thus, the mist letoe fixes itself on the branches 
 
ANIMAL AND VEGETABLE PARASITES. 636 
 
 of aged trees ; the Oidium albicans vegetates upon the mucous sur- 
 faces of the mouth and pharynx ; the Botrytis Bassiana attacks the 
 body of the silkworm, and plants itself in its tissues ; while many 
 species of trematoid worms live attached to the gills of fish and of 
 ■water-lizards. 
 
 These plarasites are usually nourished by the fluids of the animal 
 whose body they inhabit. Bach particular species of parasite is 
 found to inhabit the body of a particular species of animal, and is 
 not found elsewhere. They are met with, moreover, as a general, 
 rule, only in particular organs, or even in particular parts of a 
 single organ. Thus the Tricocephalus dispar is found only in the 
 CEBCum; the Strongylus gigas in the kidney; the Distoma hepati- 
 cum in the biliary passages. The Distoma variegatum is found 
 only in the lungs of the green frog, the Distoma cylindraceum in 
 those of the brown. The Taenia solium is found in the intestine of 
 the human subject in certain parts of Europe, while the Taenia lata 
 occurs exclusively in others. It appears, therefore, as though some 
 local combination of/ conditions were necessary to the production 
 of these parasites; and they have been supposed, accordingly, to 
 originate by spontaneous generation in the localities where they 
 are exclusively known to exist. 
 
 A little consideration will show, however, that the above condi- 
 tions are not, 'properly speaking, necessary or sufficient for the 
 production, but only for the development of these parasites. All the 
 parasites mentioned above reproduce their species by generation. 
 They have male and female organs, and produce fertile eggs, often 
 in great abundance. The eggs coutained in a single female Ascaris 
 are to be counted by thousands ; and in a tapeworm, it is said, even 
 by millions. Now these eggs, in order that they may be hatched 
 and produce new individuals, require certain special conditions 
 which are favorable for their development; in the same manner' 
 as the seeds of plants require, for their germination and growth, a 
 certain kind of soil and a certain supply of warmth and moisture. 
 It is accordingly no more surprising that the Ascaris vermicularis 
 should inhabit the rectum, and the Ascaris lumbricoides the ileum, 
 than that the Lobelia inflata should grow only in dry pastures, and 
 the Lobelia cardinalis by the side of running brooks. The lichens 
 flourish on the exposed surfaces of rocks and stone walls ; while 
 the fungi vegetate in darkness and moisture, on the decaying trunks 
 of dead trees. Yet no one imagines these vegetables to be spon- 
 taneously generated from the soil which they inhabit. The truth 
 
534 NATUBK OF REPRODUCTION. 
 
 is simply this, that if the animal or vegetable germ be deposited in 
 a locality which affords the requisite conditions for its development, 
 it becomes developed ; otherwise not. Each female Ascaris pro- 
 duces, as we have stated above, many thousands of ova. Now, 
 though the chances are very great against any particular one of 
 these ova being accidentally transported into the intestinal canal of 
 another individual, it is easy to see that there are many causes in 
 operation by which some of them might.be so transported. By far 
 the greater number undoubtedly, perish, from not meeting with the 
 conditions necessary for their development. One in a thousand, or 
 perhaps one in a million, is accidentally introduced into the body 
 of another individual, and consequently becomes developed there 
 into a perfect Ascaris. 
 
 The circumstance, therefore, that particular parasites are confined 
 to particular localities, presents no greater difficulty as to their 
 mode of reproduction, than the same fact regarding other animal 
 and vegetable organisms. 
 
 Neither is there any difficulty in accounting for the introduction 
 of .parasitic germs into the interior of the body. The air and the 
 food offer a ready means of entrance into the respiratory and 
 digestive passages ; and, a parasite once introduced • into the intes- 
 tine, there is no difficulty in accounting for its presence in any of 
 the ducts leading from or opening into the alimentai-y canal. Some 
 parasites are known to insinuate themselves directly underneath 
 the surface of the skin; as the Pulex penetrans or ''chiggo" of 
 South America, and the Ixodes Americanus or "tick." Others, 
 like the (Estrus bovis, penetrate the integument for the purpose of 
 depositing their eggs in the subcutaneous areolar tissue. Some 
 may even gain an entrance into the bloodvessels, and circulate in 
 this way all over the body. Thus the Filaria rubella is found alive 
 in the bloodvessels of the frog, the Distoma haematobium in those 
 of the human subject, and a species of Spiroptera in those of the 
 dog. It is easy to see, therefore, how, by such means, parasitic 
 germs may be conveyed to any part of the body ; and may even be 
 deposited, by accidental arrest of the circulation, in the substance 
 of the solid organs. 
 
 The most serious difficulty, however, in the way of accounting 
 for the production of parasitic organisms, was that presented by the 
 existence of a.class known as the encysted or sexless entozoa. These 
 parasites for the most part occupy the interior of the solid organs 
 and tissues, into which they could not have gained access by the 
 
ANIMAL ANJJ VEGETABLE PARASITES. 535 
 
 mucous canals. Thus the Ccenurus cerebralis is found imbedded 
 in the substance of the brain, the Trichina spiralis between the 
 ^ fibres of the voluptary muscles, and the Cysticercus cellulosse in the 
 areolar tissue of various parts of the body. They are also distin- 
 guished from all other parasites by two peculiar characters. First, 
 they are inclosed in a distinct cyst, with which they have no organic 
 connection and from which they may be readily separated; and se- 
 condly, they have no genera- 
 tive organs, nor is there any Fig. 170. 
 
 apparent difference between 
 the sexes. The Trichina spi- 
 ralis, for example (Fig. 170), 
 is inclosed in an ovoid or 
 spindle-shaped cyst, swollen 
 in the middle and tapering at 
 each extremity, with a round- „ „ , , 
 
 \. Trichina Spiralis: from r«tun femoriN mus- 
 
 ed cavity in its central por- cle br human subject. Magumed SI diameters. 
 
 tion, in which the worm lies '^ 
 
 coiled up in a spiral form. The worm itself has neither testicles 
 nor ovaries, nor does it present any trace of a sexual organization. 
 
 Now we have seen that it is easy to account for the conveyance 
 of these or any other parasites into the interior of vascular organs 
 and tissues ; the eggs from which they are produced being trans- 
 ported by the bloodvessels to any part of the body, and there 
 retained by a local arrest of the capillary circulation. In the case 
 of the encysted entozoa, however, we have a much greater diffi- 
 culty; since these parasites, are entirely without sexual organs or 
 generative apparatus of any sort, nor have they ever been dis- 
 covered in the act of producing eggs, or of developing in any 
 manner a progeny similar to 'themselves. It appears, accordingly, 
 difficult to understand how animals, which are without a sexual 
 apparatus, should have been produced by .sexual generation. As 
 it is certain that they can have no progeny, it would seem equally 
 evident that they must have been produced without a parentage. 
 
 This difficulty, however, serious as it at first appears, is susceptible 
 of a very simple explanation. The case is in many respects analogous 
 to that of the maggots, hatched from the eggs of flies in putrefying 
 meat. These maggots are also without sexual organs; for they 
 are still imperfectly developed, and in a kind of embryonic cpndi- 
 tion. It is only after their metamorphosis into perfect insects, that 
 generative organs are developed and a distinction between the 
 
536 
 
 NATUKB OF BEPBODUCTIOK. 
 
 Pig. 171. 
 
 sexes manifests itself. This is, indeed, more or less the case with 
 all animals and with all vegetables. The blossom, which is the 
 sexual apparatus of the plant, does not appear, as a general rule, 
 until the, growth of the vegetable has continued for a certain time, 
 and it has acquired a certain age- and strength. Even in the human 
 subject the sexual organs, though present at birth, are still very 
 imperfectly developed as to size, and altogether inactive in func- 
 tion. It is only later that these organs acquire their full growth, 
 and the sexual characters become complete. In very many of the 
 lower animals the sexual organs are entirely 
 absent at birth, and appear only at a later 
 period of development. 
 
 Now the encysted or sexless entozoa are 
 simply the undeveloped young of other para- 
 sites which propagate by sexual generation; 
 the membrane in which they are inclosed 
 being either an embryonic envelope, or else 
 an adventitious cyst formed round the para- 
 sitic embryo. These embryos have come, in 
 the natural course of their migrations, into 
 a situation which is not suitable for their com- 
 plete development. Their development is 
 accordingly arrested before it arrives at matu- 
 'rity ; and the parasite never reaches the adult 
 condition, until removed from the situation in 
 which it has been placed, and transported to a 
 more favorable locality. 
 
 The above explanation has been demon- 
 strated to be the true one, more particularly 
 with regard to the Taenia, or tapeworm, and 
 several varieties of Cysticercus. The Txnia 
 (Fig. 171) is a parasite of -vyhich different species 
 are found in thes intestine of the human swbject, 
 the dog, cat, fox, and other of the lower animals. 
 Its upper extremity, termed the " head," con- 
 sists of a nearly globular mass, presenting upon 
 its lateral surfaces a set of four muscular disks, or " suckers,* and 
 terminating anteriorly in a conical projection which is provided 
 with a crown of curved processes or hooks, by wh^ph the parasite 
 attaches itself to the intestinal mucous membrane. ' To thfs " head" 
 succeeds a slender ribbon-shaped neck, which is at first smooth, but 
 
AKIMAL AND VEGETABLE PARASITES. 
 
 537 
 
 which soon becomes transversely wrinkled, and afterward divided 
 into distinct rectangular pieces or " articulations." These articula- 
 tions multiply by a process of successive growth or budding, from 
 the wrinkled portion of the neck ; and are constantly removed farther 
 and farther from their point of origin by new ones formed behind 
 them. As they gradually descend, by the process of growth, 
 farther, down the body of the tapeworm, they become larger and 
 begin to exhibit a sexual apparatus, developed in their interior. 
 In each fully formed articulation there are contained both male 
 and female organs of generation ; and the mature eggs, which are 
 produced in great numbers, are thrown off together with the articu- 
 lation itself from the lower extremity of the tapeworm. Since the 
 articulations are successively produced, as we have mentioned above, 
 by budding from the neck and the tack part of the head, the para- 
 site cannot be effectually dislodged by taking away any portion of 
 the body, however large ; since it is subsequently reproduced from 
 the head, and continues its growth as before. But if the head itself 
 be removed from the intestine, no further reproduction of the articu- 
 lations can take place. 
 
 The Gysticercus is an encysted parasite, different varieties of which 
 are found in the liver, the peritoneum, and the meshes of the areolar 
 tissue in various parts of the body. It ccmsists (Fig. 172) first, of 
 a globular sac, or cyst (a), which is not adherent to the tissues of 
 the organ in which the parasite is found, but may be easily sepa- 
 
 Fig. 172. 
 
 Kg. 173. 
 
 Gtsticbrcub. — a. External cyst, b In- 
 ternal Bac, coDtaininf^ fluid, c. Narrow canal, 
 formed by involution of walls'of sac, at the 
 bottom of wliicli is tlie head of the tsnia. 
 
 Cyi4Ticebcitb, unfolded. 
 
 rated from them. In its interior is found another sac (ft), lying 
 loose in the cavity of the former, and filled with a serous fluid. 
 This second sac presents, at one point upon its surface, a puckered 
 depression, leading into a long, narrow canal (c). This canal, which 
 
538 NATURE OF REPRODUCTION. 
 
 is formed by an iuvolution of the walls of the second sac, presents 
 at its bottom a small globular mass, like the head of the Tania, 
 provided with suckers and hooks, and supported upon a short 
 slender neck. If the oiiter investing sac be removed, the narrow 
 canal just described may be everted by careful manipulation, and 
 the parasite will then appear as in Fig. 173, with the head and neck 
 resembling those of a Taenia, but terniinating behind in a dropsical 
 sac-like swelling, instead of the chain of articulations which are 
 characteristic of the fully formed tapeworm. 
 
 Now it has been shown, by the experiments of Kiichenmeister, 
 Siebold, and- others, that the Oysticercus is only the imperfectly 
 developed embryo, or young, 'of the Taenia. "When the mature 
 articulation of the tapeworm is thrown off) as already mentioned, 
 from its posterior extremity, the eggs which it incloses have already 
 passed through a certain period of development, so that each one 
 contains an imperfectly formed embryo. The articulation, contain- 
 ing the eggs and embryos, is then taken, with the food, into the 
 stomach of another animal; the substance of the articulation, to- 
 gether with the external covering of the eggs, is destroyed by di- 
 gestion, and the embryos are thus set free. They then penetrate 
 through the walls of the stomach, into the neighboring organs or 
 the areolar tissue, and becoming encysted in these situations, are 
 there developed into cysticerci, as represented in Fig. 172. After- 
 ward, the tissues in which they are contained being devoured by 
 a third animal, the cysticercus passes into the intestine, fixes itself 
 to the mucous membrane, and, by a process of budding, produces 
 the long tape-like series of ■articulations, by which, it is finally con- 
 verted into the full-grown Taenia. 
 
 Prof. Siebold found the head of the Cysticercus fasciolaris, met 
 with in the liver of rats and mice, presenting so close a resem- 
 blance to the Taenia crassicOllis, inhabiting the intestine of the cat, 
 that he was led to believe the two parasites to be identical. This 
 identity was, in fact, proved by the experiments of Kiichenmeister ; 
 and Siebold afterward demonstrated' the same relation to exist 
 between the Cysticercus pisiformis, found in the peritoneum of rab- 
 bits, and the Taenia serrata, from the intestine of the dog. This 
 experimenter succeeded in administering to dogs a quantity of the 
 cysticerci, fresh from the body of the rabbit, mixed with milk ; and 
 
 ' In Baffalo Medical Journal, Feb. 1853 ; also in Siebold on Tape and Cystic 
 •Torms, Sydenham translation : London, 1857, p. 59. 
 
ANIMAL AND VEGETABLE PARASITES. 539 
 
 on killing the dogs, at various periods after the meal, from three 
 hours to eight weeks, he found the cysticerci in various stages of 
 development in the intestine, and finally converted into the full 
 grown Taenia, with complete articulations and mature eggs. 
 
 Dr. Kiichenmeister' has also performed the same experiment, with 
 success, on the human subject. A number of cystiperci were ad- 
 ministered to a criminal, at different periods before his executiorf, 
 varying from 12 to 72 hours ; and upon post-mortem examination 
 of the body, no less than ten young tseniae were found in the 
 intestine, four of whjoh could be distinctly recognized as specimens 
 of Taenia solium. 
 
 Finally, both Leuckart and Kiichenmeister' have shown, on the 
 other hand, that the eggs of Taenia solium, introduced into the body 
 of the pig, will give rise to the development of Cysticercus cellulosae ; 
 thus demonstrating that the two kinds of parasites are identical in 
 their nature, and differ only in the manner and degree of their 
 development. 
 
 There remains, accordingly, no good reason for believing that 
 even the encysted parasites are produced by spontaneous genera- 
 tion. Whatever obscurity may hang round the origin or reproduc- 
 tion of any class or species of animals, the direct investigations of 
 the physiologist always tend to show that they do not, in reality, 
 form any exception to the general law in this respect ; and the only 
 opinion which is admissible, from the facts at present within our 
 knowledge, is that organized beings, animal and vegetable, wherever they 
 may be found, are always the progeny of ^eviotisly existing parents. 
 
 ' On Animal and Vegetable Parasites, Sydenham translation : London, 1857, 
 p. 115. 
 
 2 Op. cit., p. 120. 
 
HO 
 
 SSXUAL GEXEBATIOK. 
 
 CHAPTER II. 
 
 ON SEXUAL GENERATION, AND THE MODE OP ITS 
 , ACCOMPLISHMENT. 
 
 Fig. 174. 
 
 The function of generation is performed by means of two sets of 
 organs, each of which gives origin to a, peculiar product, capable 
 of uniting with the other so as to produce a new individual. These 
 
 two sets of organs, belonging to the 
 two different sexes, are called the male 
 and female organs of generation. The 
 female organs produce a globular body 
 called the germ, or egg, which is capable 
 of being developed into the body of 
 the young animal or plant ; the male 
 organs produce a substance which is 
 necessary to fecundate the germ, and 
 enable it to go through with its natural 
 growth and development. 
 
 Such af6 the only essential and uni- 
 versal characters of the organs of gene- 
 ration. These organs, however, exhibit 
 various additions and modifications in 
 different classes of organized beings, 
 while they show throughout the same 
 fundamental and essential characters. 
 In the flowering plants, for example, 
 the blossom, which is the generative 
 ?,pparatus (Fig. 174), consists first of a 
 female organ containing the germ (a), situated usually upon the 
 highest part of the leaf-bearing stalk. This is surmounted by a 
 nearly straight column, termed the pistil (6), dilated at its summit 
 into a globular expansion, and occupying the centre of the flower. 
 Around it are arranged several slender filaments, or stamens, bear- 
 ing upon their extremities the male organs, or anthers (c, c). The 
 
 Blossom op CoNVOLVCLns 
 PuBPliBEtTS. (MorDing glory. ) — a. 
 Germ. b. Pistil, c. c. Stamens, with 
 aachers. d. Corolla, e. Calyx. 
 
SEXUAL GENERATION. 
 
 541 
 
 Fig. 175. 
 
 tvhole is surrounded by a circle or crown of delicate and brilliantly 
 colored leaves, termed the corolla (c^, which is frequently provided 
 with a smaller sheath of green leaves outside, called the calyx (e). 
 The anthers, when arrived at maturity, discharge a fine organic 
 dust, called the pollen, the granules of which are caught upon the 
 extremity of the pistil, and then penetrate downward through its 
 tissues, until they reach its lower extremity and come in contact 
 with the germ. The germ thus fecundated, the process of genera- 
 tion is accomplished. The pistil, anthers, and corolla wither and 
 fall off, while the germ increases rapidly in size, and changes in 
 form and texture, until it ripens into the mature fruit or seed. It 
 is then ready to be separated from the parent stem ; and, if placed 
 in the proper soil, will germinate and at last produce a new plant 
 similar to the old. 
 
 In the above instance, the male and female organs are both, 
 situated upon the same flower ; as in the lily, the violet, the con- 
 volvulus, &c. In other cases, there are separate male and female 
 flowers upon the same plant, of which the male flowers produce 
 only the pollen, the female, the 
 germ and fruit. In others still, 
 the male and female flowers are 
 situated upon different plants, 
 which otherwise resemble each 
 other, as in the willow, poplar, 
 and hemp. 
 
 In animals, the female organs 
 of generation are called ovaries, 
 since it is in them that the egg, 
 or "ovum," is produced.* The 
 male organs are the testicles, 
 which give origin to the fecun- 
 dating product, or "seminal 
 fluid," by which the egg is fer- 
 tilized. "We have already men- 
 tioned above that in the articula- 
 tions of the tapeworm the ovaries 
 and testicles are developed to- 
 gether. (Fig. 175.) The ovary 
 {a, a, a) is a series of branching follicles terminating in rounded 
 extremities, and communicating with each other by a central canal. 
 The testicle (6) is a narrow, convoluted tube, very much folded 
 
 SiNQLB Articulation of Tj&ni^a 
 CKA8S1C0LI.I8, from hmall iuteBtiue of cat.-* 
 a, a, a. Ovary filled with egga. b. Testicle, v. 
 Geoital orifice. 
 
542 SEXUAL GENERATION. 
 
 upon itself, which opens by an external orifice (c) upon the lateral 
 border of the articulation, about midway between its two ex- 
 tremities. The spermatic fluid produced in the testicle is intro- 
 duced into the female generative passage, which opens at the same 
 spot, and, penetrating deeply into the interior, comes in contact 
 with the eggs, which are thereby fecundated and rendered fertile. 
 The fertile eggs are afterward set free by the rupture or decay of 
 the articulation, and a vast number of young are produced by their 
 development. 
 
 In snails, also, and in some other of the lower animals, the ovaries 
 and testicles are both present in the same individual ; so that these 
 animals are soinetimes said to be " hermaphrodite," or of double 
 sex. In reality, however, it appears that the male and female 
 organs do not come to maturity at the same time ; but the ovaries 
 • are first developed and perform their function, after which the tes- 
 ticles come into activity in their turn. The same individual, there- 
 fore, is not both male and female at any one time; but is first 
 female and afterward male, exercising the two generative functions 
 at different ages. 
 
 In all the higher qpimals, however, the two sets of generative 
 organs are located in separate individuals; and the species is 
 consequently divided into two sexes, male and female. All that 
 is absolutely requisite to constitute the two sexes is the existence 
 of testicles in the one, and of ovaries in the other. Beside these, 
 however, there are, in most instances, certain secondary or acces- 
 sory organs of generation, which assist more or less in the accom- 
 plishment of the process, and which occasion a greater difference in 
 the anatomy of the two sexes. Such are the uterus and mammary 
 glands of the female, the vesicul^ seminales and prostate gland 
 of the male. The femal^naturally having the immediate care of 
 the young after birth, and the male being occupied in providing 
 food and protection for both, there are also corresponding differ- 
 ences in the getieral structure of the body, which affect the whole 
 externa;! appearance of the two sexes, and which even show them- 
 selves in their mental and moral, as well as in their physical 
 characteristics. In some cases this difference is so excessive that 
 the male and female would never be recognized as belonging to the 
 same species, unless they were seen in company with each other. 
 Not to mention some extreme instances of this among insects and 
 other invertebrate animals, it will be sufficient to refer to the well- 
 known examples of the cock and the hen, the lion and lioness, the 
 
SEXUAL GESEBATION. 5i3 
 
 buck and the doe. In the human species, also, the distinction 
 between the sexes shows itself in the mental constitution, the dis- 
 position, habits, and pursuits, as well as in the general conforma- 
 tion of the body, and the peculiarities of external appearance. 
 
 We shall now study more fully the character of the male and 
 female organs of generation, together with their products, and the 
 manner in which these are discharged from the body, and brought 
 into relation with each other. 
 
5U 
 
 EGG AND FEMALE OKGANS OF GENEHATIOK. 
 
 CHAPTER III. 
 
 ON THE EGG, AND THE FEMALE ORGANS OP 
 GENERATION. 
 
 Fig. 176. 
 
 The egg is a globular body which varies considerably in size in 
 different classes of animals, according to the peculiar conditions 
 under which its development is to take place. In the frog it mea- 
 sures y'j of an inch in diameter, in the lamprey 5^5, in quadrupeds 
 and in the human species t^j. It consists, first, of a membranous 
 external sac or envelope, the vitelline membrane ; and secondly, of a 
 spherical mass inclosed in its interior, called the viiellus. 
 
 The vitelline membrane in birds and reptiles is very thin, measur- 
 ing often not more than 75^5^ of an inch in thickness, and is at the 
 same time of a somewhat fibrous texture. 
 In man and the higher animals, on the 
 contrary, it is perfectly smooth, structure- 
 less and transparent, and is about f ^V^r of 
 an inch in thickness. Notwithstanding 
 its delicate and transparent appearance, it 
 has a considerable degree of resistance 
 and elasticity. ♦The egg of the humau 
 
 fibject, for example, may be perceptibly 
 attened out under the microscope by 
 pressing with the point of a needle upon 
 the slip of glass which covers it ; but it 
 still remains unbroken, and when the 
 pressure is removed, readily resumes its globular form. When the 
 egg is somewhat flattened under the microscope in this way, by 
 pressure of the glass slip, the apparent thickness of the vitelline 
 membrane is increased, and it then appears (Fig. 176) as a rather 
 wide, colorless, and pellucid border or zone, surrounding the granu- 
 lar and opaque vitellus. Owing to this appearance, it has some- 
 times received the name of the " zona pellucida." The name of 
 
 HnHAS OrcB, masrnifled 85 
 diameters, a. ViteLllnenieinbraDe. 
 &. Vitellns. c. Germinative vesicle. 
 d. Germinatlve spot. ^ 
 
KGO AND FEMALE OEGAN3 OF GKNE.BATIOK. 545 
 
 vitelline membrane, however, is the one more generally adopted, 
 and is also the more appropriate of the two. 
 
 The vitellus (6) is a globular, semi-solid mass, contained within 
 the vitelline membrane. It consists of a colorless albuminoid sub- 
 stance, with an abundance of minute molecules and oleaginous 
 granules scattered through it. These minute oleaginous masses 
 give to the vitellus a partially opaque and granular aspect under 
 the microscope. Imbedded in the vitellus, usually near its surface 
 and almost immediately beneath the vitelline membrane, there is a 
 clear, colorless, transparent vesicle (c) of a rounded form, known 
 as the germinative vesicle. In the egg of the human subject and of 
 the quadrupeds, this vesicle measures gj^ to 5^^ of an inch in 
 diameter. It presents upon its surface a 
 dark spot, like a nucleus {d), which is known ^^^' ^ ' ^* 
 
 by the name of the germinative spfit. The 
 germinative vesicle, with its nupleus-like 
 spot, is often partially concealed by the 
 granules of the, vitellus by which it is sur- 
 rounded, but it may always be discovered 
 by carfeful examination. 
 
 If the egg be ruptured by excessive pres- humah otuh, mptnred by 
 sure under the microscope, the vitellus is ?"»"'••«; '"owiDg the vueimn 
 
 , ' partially expelled, the germina- 
 
 seen to have a gelatinous consistency. It twe Tesicie at a, and the «mooth 
 is gradually expelled from the vitelline ™' "' "" '"""""' """"'• 
 cavity, but still retains the granules and oil 
 
 globules entangled in its substaifoe. (Fig. 177.) The edges of the 
 fractured vitelline membrane, under these circumstances, present a 
 smooth and nearly straight outline, without any appearance of 
 laceration or of a fibrous Structure. The membrane is, to all ap- 
 pearance, perfectly homogeneous. 
 
 The most essential constituent of the*gg is the vitellus. It is 
 from the vitellus that the body of the embryo will afterward be 
 formed, and the organs of the new individual developed. The 
 vitelline membrane is merely a protective inclosufe, intended to 
 secure the vitellus from injury, and enable it to retain its figure 
 during the early periods of development. 
 
 The egg, as above described, consists therefore of a simple 
 vitellus of minute size, and a vitelline membrane inclosing it. It 
 is such an egg which is found in the human subject, the quadru- 
 peds, most aquatic reptiles, very many fish, and some invertebrate 
 animals. In nearly all thf se species, in fact, where the fecundated 
 35 • 
 
54r6 EGG ANU FEMALE ORGANS OF GENEBATION. 
 
 eggs are deposited and hatched in the water, as well as those in 
 which they are retained in the body of the female until the develop- 
 ment of the young is completed, such an egg as above described is 
 sufficient for the formation of the embryo ; since during its develop- 
 raenj it can absorb freely, either from the water in which it floats, 
 or from the mucous membrane of the female generative organs, the 
 requisite supply of nutritious fluids. But in birds and in the 
 terrestrial reptiles, such as lizards, tortoises, &c, where the eggs 
 are expelled from the body of the female at an early period, and 
 incubated on land, there is no external source of nutrition, to pro- 
 vide for the support of the young animal during its development. 
 In these instances accordingly the vitellus, or "yolk," as it is called, 
 is of very large size ; and the bulk of the egg is still further in- 
 creased by the addition, within the female generative passages, of 
 layers of albumen and various external fibrous and calcareous 
 envelopes. The essential constituents of the egg, however, still 
 remain the same in character, and the process of embryonic deve- 
 lopment follows the same general laws as in other cases. 
 
 The eggs are produced in the interior of certain organs, situated 
 in the abdominal cavity, called the ovaries. These organs consist 
 of a number of globular sacs, or follicles, known as the " Graafian 
 follicles," each one of which contains a single egg. The follicles 
 are connected with each other by a quantity of vascular areolar 
 tissue, which binds them together into a well-defined and consistent 
 mass, covered upon its exterior by a layer of peritoneum. The 
 egg has sometimes been spoken of as a " product," or even as a 
 " secretion" of the ovary. Nothing can be more inappropriate, 
 however, than to compare thg egg with asecretion, or to regard the 
 ovary as in any respect resembling a glandular organ. The egg is 
 simply an organized bo^, growing in the oVary like a tooth in its 
 follicle, and forming a constituent part of the body of the female. 
 It is destined to be finally separated from its attachments and 
 thrown off; but until that time, it is, properly spe8,king, a part of 
 the ovarian texture, and is nourished like any other portion of the 
 female organism. 
 
 The ovaries, accordingly, since they are directly concerned in 
 the production of the eggs, are to be regarded as the essential 
 parts of the female generative apparatus. Beside them, however, 
 there are usually present certain other organs, which play a secon- 
 dary or accessory part in the process of generation. The most 
 important of these accessory organs are»two symmetrical tubes, or 
 
EGG AND FEMALE ORGANS OF GBNEKATION. 547 
 
 Fig. 178. 
 
 oviducts, which are destined to receive the eggs at their internal 
 extremity and convey them to the external generative orifice. The 
 mucous membrane lining the oviducts is also intended to supply 
 certain secretions during the passage of the egg, which are requi- 
 site either to complete its structure, or to provide for the nutrition 
 of the embryo. 
 
 In the frog, for example, the oviduct corftmences at the upper 
 part of the abdomen, by a rather wide orifice, which communicates 
 directly with the peritoneal cavity. It 
 soon after contracts to a narrow tube, 
 and pursues a zigzag course down the 
 side of the abdomen (Fig. 178), folded 
 upon itself in convolutions, like the 
 small intestine, until it opens, near its 
 fellow of the opposite side, into the 
 " cloaca," or lower part of the intestinal 
 canal. The oviducts present the same 
 general characters with those described 
 above, in nearly all species of reptiles 
 and birds ; though there are some modi- 
 fications, in particular instances, which 
 do not require any special notice. 
 
 The ovaries, as well as the eggs which 
 they contain, undergo at particular sea- 
 sons a periodical development or increase 
 in growth™ If we examine the female 
 frog in the latter part of summer or the 
 fall, we shall find the ovaries presAting 
 the appearance of small clusters of minute and nearly colorless 
 eggs, the smaller of which are perfectly (transparent and not over 
 i\js of an inch in diameter. But in the early spring, when the 
 season of reproduction approaches, the ovaries will be found in-, 
 creased to four or five times thei~r former size, and forming large 
 lobulated masses, crowded with dark-colored opaque eggs, measur- 
 ing jij of an inch in diameter. At the approach of the generative 
 season, in all the lower animals, a certain number of the eggs, which 
 were previously in an imperfect and inactive condition, begin to 
 increase in size and become somewhat altered in structure. The 
 vitellus more especially, which was before colorless and transparent, 
 becomes granular in texture as well as increased in volume ; and 
 assumes at the same time, in many species of animals, a black, 
 
 Ffmale Gekebatitr Or- 
 GAKB OP Froq. — a. n. Ovaries. 
 &, b. Oviducts, c, c. Their internal 
 orifices, d. Cloaca, showing exter- 
 naL orifices of oviducta. 
 
548 EOG AND 7EMAL£ OBGAN3 OF OENEBATION. 
 
 brown, yellow, or orange color. In the human subject, however, 
 the change consists only in an increase of size and granulatioH, 
 without any remarkable alteration of color. 
 
 The eggs, as they ripen in this way, becoming enlarged and 
 changed in texture, gradually distend the Graafian follicles and 
 project from the surface of the ovary. At last, when fully ripe, 
 they are discharged fly a rupture of the walls of the follicles, and, 
 passing into the oviducts, are conveyed by them to the external 
 generative orifice, and there expelled. In this way, as successive 
 seasons come round, successive crops of eggs enlarge, ripen, leave 
 the ovaries, and are discharged. Those which are to be expelted 
 at the next generative epoch may always be recognized by their 
 greater degree of development ; . and in this way, in many animals, 
 the eggs of no less than three diiferent crops may be recongized in 
 the ovary at once, viz;, 1st, those which are perfectly mature and 
 ready to be discharged ; 2d, those which are to ripen in the follow- 
 ing season ; and 3d, those which are as yet altogether inafctive and 
 undeveloped. In most fish and reptiles, as well as in birds, this 
 regular process of maturation and discharge of eggs takes place 
 but once a year. In different species of quadrupeds it may take 
 place annually, semi-annually, bi-monthly,, or even monthly; hut 
 in every instance it recurs at regular intervals, and exhibits accord- 
 ingly, in a marked degree, the periodic character which we have 
 seen to belong to riiost of the other vital phenomena. 
 
 Action of the Oviducts and Fernale Generative Passages.-^It frogs 
 and lizards, the ripening and discharge of the eggs take place, as 
 ^bove mentioned in the early spring. At the time of leaving the 
 
 ""■ary, the eggs consist simply of the 
 
 '^" dark-colored and granular vitellus, 
 
 ^ps^l^l^ inclosed in the vitelline membrane. 
 
 ^^P«^ They are then received by the inner 
 
 • ••• y®^F^ extremity of the oviducts, and carried 
 
 ® 'imm^'lM downward by the peristaltic move- 
 
 -(, ment of these canals, aided by the 
 
 mattre froqb' Eaaa.— /I. While more powcrful Contraction of the 
 
 t« tt ;:;::. *• ''" "^""^ abdominal muscles. During the pas- 
 
 sage of the eggs, moreover, the mucous 
 membrane of the oviduct secretes a colorless, viscid, albuminoid 
 substance, which is deposited in successive layers round each egg, 
 forming a thick and tenacious coating or finvelope. (Fig. 179,) 
 When the eggs are finally discharged, this albuminoid matter 
 
EGG AND FEMALE OBGANS OF GENERATION. 549 
 
 absorbs the water in wliicli the spawn is deposited, and swells np 
 into a transparent gelatinous mass, in which the eggs are separately 
 imbedded. This substance supplies, by its subsequent liquefaction 
 and absorption, a certain amount of nutritious material, during the 
 develdpment and early growth of the embryo. • 
 
 In the terrestrial reptiles and in birds, the oviducts perform a 
 still more important secretory function, la the common fowl, the 
 ovary consists, as in the frog, of a large number of follicles, loosely 
 connected by areolariissue, in which the eggs can be seen in different 
 stages of development. (Fig. 180, a.) As the egg which is approach- 
 ing maturity enlarges, it distends the cavity of its follicle, and pro- 
 jects farther from the general surface of the ovary ; so that it hangs 
 at last into the peritoneal cavity, retained only by the attenuated 
 wall of the follicle, and a slender pedicle through which run the 
 bloodvessels by which its circulation is supplied. A rupture of the 
 follicle then occur^, at its most prominent part, and the egg is dis- 
 charged from the lacerated opening. 
 
 At the time of its leaving the ovary, the egg of the fowl consists 
 of a large, globular, orange-colored vitellus, or " yolk," inclosed in 
 a thin and transparent vitelline membrane. Immediately under- 
 neath the vitelline membrane, at one point upon the surface of the 
 vitellus, is a round white spot, consisting of ^ layer of minute 
 granules, termed the " cicatricula." It is in the central part of the 
 cicatricula that the germinative vesicle is fount} imbedded, at an 
 early stage of the development of the egg. At the time of its 
 discharge from the ovary, the germinative vesicle has usually dis- 
 appeared ; but the cicatricula is still a very striking and important 
 part of the vitellus, as it is from this spot that the body of the chick 
 begins afterward to be developed. 
 
 At the same time that the egg protrudes from the surface of the 
 ovary, it projects into the inner orifice of the oviduct; so that, when 
 discharged from its follicle, it is immediately embraced by the upper 
 or fringed extremity of this tube, and commences its passage down- 
 ward. In the fowl, the muscular coat of the oviduct is highly deve- 
 loped, and its peristaltic contractions gently urge the egg from above 
 downward, precisely as the oesophagus or the intestines transport 
 the food in a similar direction. While passing through the first 
 two or three inches of the oviduct (c, d), where the mucous mem- 
 brane is smooth and transparent, the yolk merely absorbs a certain 
 quantity of fluid, so as to become more flexible and yielding in con- 
 sistency. It then passes into a second division of the generative 
 
550 EGG AND FEMALE OB6AN3 OF GENERATION. 
 
 canal, in which the mucous membrane is thick and glandular in 
 texture, and is also thrown into numerous longitudinal folds, which 
 project into the cavity of the oviduct. This portion of the oviduct 
 {d, e), extends over about nine inches of its entire length. In its 
 upper part, the mucous membrane secretes a viscid material, by 
 which the yolk is encased, and which soon consolidates into a gela- 
 tinous, membranous deposit ; thus forming a second homogeneous 
 layer, outside the vitelline membrane. 
 
 Now the peristaltic movements of this part of the oviduct are 
 such as to give a rotary, as well as a progressive motion to the 
 egg ; and the two extremities of the membranous layer described 
 above become, accordingly, twisted in opposite directions into two 
 fine cords, which run backward and forward from the opposite poles 
 of the egg. These cords are termed the '^chalazse," and the mem- 
 brane with which they are connected, the " chalaziferous membrane." 
 
 Throughout the remainder of the second division of the oviduct, 
 the mucous membrane exudes an abundant, gelatinous, albuminoid 
 substance, which is deposited in successive layers round the yolk, 
 inclosing at the same time the chalaziferous membrane and the 
 chalazse. This substance, which forms the so-called albumen, or 
 " white of egg," is semi-solid in consistency, nearly transparent, and 
 of a faint amber color. It is deposited in greater abundance in front 
 of the advancing egg than behind it, and forms accordingly a 
 pointed or conical projection in front, while behind, its outline is 
 rounded oil, parallel with the spherical surface of the yolk. In this 
 way, the egg acquires, when covered with its albumen, an ovoid 
 form, of which One end is round, the other pointed ; the pointed 
 extremity being always directed downward, as the egg descends 
 along the oviduct. 
 
 In the third division of the oviduct (J), which is about three and 
 a half inches in length, the mucous membrane is arranged in longi- 
 tudinal folds, which are narrower and more closely packed than in 
 the preceding portion. The material secreted in this part, and de- 
 posited upon the egg, condenses into a firm fibrous covering, com- 
 posed of three different layers which closely embrace the surface 
 of the albuminous mass, forming a tough, flexible, semi-opaque 
 envelope for the whole. These layers are known as the external, 
 middle, and internal fibrous membranes of the egg. 
 
 Finally the egg passes into the fourth division of the oviduct {g), 
 which is wider than the rest of the canal, but only a little over two 
 inches in length. Here the mucous membrane, which is arranged 
 
EGG AND FEMALE ORGANS OP GENERATION. 
 
 551 
 
 Fig. 180. 
 
 in abundant, projecting, leaf-like villosities> exudes a fluid very rich 
 in calcareous salts. The most external of the three membranes 
 just described is permeated by this fluid, and very soon the calcare- 
 ous matter begins to crystallize in 
 the interstices of its fibres. This 
 deposit of calcareous matter goes 
 on, growing constantly thicker and 
 more condensed, until the entire 
 external membrane is converted into 
 a white, opaque, brittle, calcareous 
 shell, which incloses the remaining 
 portions and protects them from ex- 
 ternal injury. The egg is then driven 
 outward by the contraction of the 
 muscular coat through a narrow por- 
 tion of the oviduct (A), and, gradually 
 dilating the passages by its conical 
 extremity^ is finally discharged from 
 the external orifice. 
 
 The egg of the fowl, after it has 
 been discharged from the body, con- 
 sists, accordingly, of various parts; 
 some of which, as the yolk and the 
 vitelline membrane, entered into its 
 original formation, while the remain^ 
 der have been deposited round it dur- 
 ing its passage through the oviduct. 
 On examining such an egg (Fig. 181), 
 we find externally the calcareous 
 shell (A), while immediately beneath 
 it are situated the middle and internal 
 fibrous shell-membranes (e,/). 
 
 Soon after the expulsion of the egg 
 there is a partial evaporation of its 
 watery ingredients, which are replaced 
 by air penetrating through the pores 
 
 Femalk Oexeratite Oroahs of Fowl..— n. Ovarf. b. GmaSan follicle, from vBich th* 
 egg has jnst been discharged, c. Volk, entering upper extremity ol ovidaci. d, e. Second diVUiou 
 of OTiduct, in which ohalazlfsroas membraa.i, chalazia, and albumen are formed. /. Third p.trtion. 
 In which the flbroas shell membranes are produced, ff. Fourth portion laid open, showing egg 
 completely formed, with calcareous shell, h. Narrow canal throui^b. which the egg is discharged. 
 
55.2 EGG AND FKMALK ORGANS OF GENEBATION. 
 
 « 
 
 Hi the shell at its rounded extremity. The air thus introduced' 
 accumulates between the middle and internal fibrous membranes 
 at this spat, separating them from each other, and forming a cavity 
 or air-chamber (g), which is always found between the. two fibrous 
 metabranes at the rounded end of the egg. Next we come to the 
 albumen or " white" of the egg (d) ; next to the chalaziferous mem- 
 brane and chalazae (c) ; and finally to the vitelline membrane (J) 
 
 Fig. 181. 
 
 Diairram of Fowl's Egg. -^ffl. Tolk. &. Titelline membrane, c. Chalaziferoas membrane, d. 
 Albumea. d, /. Middle and internal shell membranes, g. Air-chamber. A. Calcareous sbelL 
 
 inclosing the yolk (a). After the expulsion of the egg, the external 
 layers of the albumen liquefy; and the vitellus, being specifically 
 lighter than the albumen, owing to the large proportion of oleagin- 
 ous matter which it contains, rises toward the surface of the egg, 
 with the cicatricula uppermost. This part, therefore, presents 
 itself almost immediately on breaking open the egg upon its lateral 
 surface, and is placed in the most favorable position for the action 
 of warmth and atmospheric air in the development of the chick. 
 
 The vitellus, therefore, is still the essential and constituent portion 
 of the egg ; while all the other parts consist either of nutritious mate- 
 rial, like the albumen, provided for the support of the embryo, or 
 of protective envelopes, like the shell and the fibrous membranes. 
 
 In the quadrupeds, another and still more important modification 
 of the oviducts takes place. In these animals, the egg, which is 
 originally very minute in size, is destined to be retained within the 
 generative passages of the female during the development of the 
 embryo. "While the upper part of the'bviduct, therefore, is quite 
 narrow, and intended merely to transmit the egg from the ovary, 
 
EGG AND FEMALE ORGANS OF GENERATION. 553 
 
 and to supply it with a little albuminous secretion, its lower por- 
 tions are very much increased in size, and are lined, moreover, with 
 a mucous membrane, so constructed as to provide for the protection 
 and nourishment of the embryo, during the entire period of gesta- 
 tion. The upper and narrower portions of the oviduct are known 
 as the "Fallopian tubes" (Fig. 182); while the lower and more 
 
 Fig. 182. 
 
 Uterus and Ovaries op the Sow.— «,(?. OTarieK, &,&. Fallopian tubes. .ff,c. Horns uf 
 nieiuH. d. Body of uterus, c. Vagina. 
 
 highly developed portions constitute the uterus. These lower por- 
 tions unite with eaclu'Other upon the median line near their infe- 
 rior termination, so as to form a central organ, termed the " body" 
 of the uterus ; while the remaining ununited parts are known as 
 its " cornua" or " horns." 
 
 In the human subject, the female generative apparatus presents 
 the following peculiarities. The ovaries consist of Graafian follicles, 
 which are imbedded in a somewhat dense areolar tissue, supplied 
 with an abundance of bloodvessels. The entire mass is covered 
 with a thick, opaque, yellowish' white layer of fibrous tissue called 
 the " albugineous tunic." Over the whole is a layer of peritoneum, 
 which is reflected upon the vessels which supply the ovarj', and is 
 continuous with the broad ligaments of the uterus. 
 
 The oviducts commence by a wide expansion, provided with 
 fringed edges, called the " fimbriated extremity of the Fallopian 
 tube." The Fallopian tubes themselves are very narrow and con- 
 voluted, and terminate on each side in the upper part of the body 
 of the uterus. In the human subject, the body of the uterus is so 
 much developed at the expense of the cornua, that the latter hardly 
 appear to have an existence ; and in fact no trace of them is visible 
 externally. But on opening the body of the uterus its cavity, is 
 
554 
 
 EGG AND FEMALE OBGANS OF 6ENEBATION. 
 
 seen to be nearly triangular in shape, its two superior angles run- 
 ning out on each side to join the lower extremities of the Fallopian 
 tubes. This portion evidently consists of the comua, which have 
 been consolidated with the body of the uterus, and enveloped in 
 its thickened layer, of muscular fibres. 
 
 Fig. 183. 
 
 Grneratite OunAKB OF HiTMAM Fehale. — a^ a. Ovaries. &, b. Fallbpiaa tabes. 
 c. Body of uterus, d. Cervix, e. Vagiua. 
 
 The cavity of the body of the uterus terminates below by a con- 
 stricted portion termed the os internum, by which it is separated 
 from the cavity of the cervix. These two cavities are not only 
 different from each other in shape, but differ also in the structure 
 of their mucous membrane and the functions which it is destined 
 to perform. 
 
 The mucous membrane of the body of the uterus in its usual 
 condition is smooth and rosy in color, and closely adherent to the 
 subjacent muscular tissue. It consists of minute tubular follicles 
 somawhat similar to those of the gastric mucous membrane, ranged 
 side by side, and opening by distinct orifices upon its free surface. 
 The secretion of these follicles is destined for the nutrition of the 
 embryo during the earlier periods of its formation. 
 
 The internal surface of the neck of the uterus, on the other hand, 
 is raised in prominent ridges which are arranged usually in two 
 lateral sets, diverging from a central longitudina;! ridge ; presenting 
 the appearance known as the " arbor vitas uterina." The follicles 
 of this part of the uterine mucous membrane are different in struc- 
 ture from those of the foregoing. They are of a globular- or sac- 
 
EGG AND FEMALE ORGANS OF GENERATION. 555 
 
 like form, and secrete a very firm, adhesive, transparent mucus, 
 which is destined to block up the cavity of the cervix during ges- 
 tation, and guard against the accidental displacement of the egg. 
 Some of these follicles are frequently distended with their secretion, 
 and project, as small, hard, rounded eminences, from the surface 
 of the mucous membrane. In this condition they are sometimes 
 designated by the name of " ovula Nabothi," owing to their having 
 been formerly mistaken for eggs, or ovules. 
 
 The cavity of the cervix uteri is terminated below by a second 
 constriction, the "os externum." Below this comes the vagina, 
 which constitutes the last division of the female generative pas- 
 
 The accessory female organs of generation consist therefore of 
 ducts or tubes, by means of which the egg is conveyed from within 
 outward. These ducts vary in the degree and complication of 
 their development, according to the importance of the task assigned 
 to them. In the lower orders, they serve merely to convey the egg 
 rapidly to the exterior, and to supply it more or less abundantly 
 with an albuminous secretion. In the higher classes and in the 
 human subject, they are adapted to the more important function of 
 retaining the egg during the period of gestation, and of providing 
 during the same time for the nourishment of the young embryo. 
 
556 MALE ORGANS OF GENEBATION. 
 
 CHAPTER IV. 
 
 ON THE SPERMATIC FLUID, AND THE MALE 
 ORGANS OF GENERATION. 
 
 The mature egg is not by itself capable of being developed into 
 the 'embryo. If simply discharged from the ovary and carried 
 through the oviducts toward the exterior, it soon dies and is de- 
 composed, like any other portion of the body separated from its 
 natural connections. It is only when fecundated by the spermatic 
 fluid of the male, that it is stimulated to continued development, 
 and becomes capable of a more complete organization. 
 
 The product of the male generative organs consists of a colorless, 
 somewhat viscid, and albuminous fluid, containing an innumerable 
 quantity of minute filamentous bodies, termed spermatozoa. The 
 name spermatozoa has been given to these bodies, on account of 
 their exhibiting under the microscope a very active and continu- 
 ous movemetit, bearing some resemblance to that of certain animal- 
 cules. 
 
 The spermatozoa of the human subject (Fig. 184, a) are about 
 gjj of an inch in length, according to the 'measurements of Kol 
 liker. Their anterior extremity presents a somewhat flattened, 
 triangular-shaped enlargement, termed the " head." The head con 
 stitutes about one-tenth part the entire length of the spermatO' 
 zoon. The remaining portion is a very slender filamentous prO' 
 longation, termed the "tail," which tapers gradually backward, 
 becoming so exceedingly delicate towards its extremity, that it is 
 difficult to be seen except when in motion.- There is no further 
 organization or internal structure to be detected in any part of the 
 spermatozoon ; and the whole appears to consist, so far as can be 
 seen by the microscope, of a completely homogeneous, tolerably 
 firm, albuminoid substance. The terms head and tail, therefore, 
 as justly remarked by Bergmann and Leuckart,' are not used, 
 when describing the different parts of the spermatozoon, in the 
 same sense as that in which they would be applied to the corre- 
 
 ' Vergleichende Physiologie. Stuttgart, 1852. 
 
MALE ORGANS OP GENERATION. 
 
 557 
 
 sponding parts of. an animal, but simply for tte sake of conveni- 
 ence ; just as one might speak of the head of ap arrow, or the tail 
 of a comet. 
 
 In the lower animals, the spermatozoa have usually the same 
 general form as in the human subject ; that is, they are slender 
 filamentous bodies, with the anterior extremity more or less en- 
 larged. In the rabbit they have a head which is roundish and 
 flattened in shape, somewhat resembling thei globules of the blood. 
 In the rat (Fig. 184, b) they are much larger than in man, measur- 
 ing nearly xiu of an inch in length. The head is conical in shape, 
 
 Fig. 184. 
 
 Spkbmatozo*.— a. Human, ft. Of Rat. c. Of Menobranclins. MagniJed 4S0 times. 
 
 about one-twentieth the whole length of the filamgnt, and often 
 slightly curved at its anterior extremity. In the frog and in rep- 
 tiles generally, the spermatozoa are longer than in quadrupeds. 
 In the Menobranchus, or great American water-lizard, they are of 
 very unusual size (Fig. 184, c), measuring not less than ,'j of an 
 inch in length, abo»t one-third of which is occupied by the head, 
 or enlarged portion of the filament. 
 
 The most remarkably peculiarity of the spermatozoa is their 
 
558 MALE ORGANS OP GENERATION. 
 
 very singular and active movement, to whicli we have already 
 alluded. If a drop of fresli seminal fluid be placed under the 
 microscope, the numberless minute filaments with which it is 
 crowded are seen to be in a state of incessant and agitated motion. 
 This movement of the spermatozoa, in many species of animals, 
 strongly resembles that of the tadpole ; particularly when, as in the 
 human subject, the rabbit, &o.^ the spermatozoa consist of a short 
 and well defined head, followed by a long and slender tail. Here 
 the tail-like filament keeps up a constant lateral or vibratory move- 
 ment, by which the spermatozoon is driven from place to place in 
 the spermatic fluid, just as the fish or the tadpole is propelled 
 through the water. In other instances, as for example in the water- 
 lizard, and in some parasitic animals, the spermatozoa have a con- 
 tinuous writhing or spiral-like movement, which presents a very 
 peculiar and elegant appearance when lairge numbers of them are 
 viewed together. 
 
 It is the existence of this movement which first suggested the 
 name of spermatozoa to designate the animated filaments of the 
 spermatic, fluid; and which has led some writers to attribute to 
 them an independent animal nature. This is, however, a very 
 erroneous mode of regarding them ; since they cannot properly be 
 considered as animals, notwithstanding the active character of their 
 movement, and the striking resemblance which it sometimes pre- 
 sents to a voluntary- act. The spermatozoa are organic forms, 
 which are .produced in the testicles, and constitute a part of their 
 tissue ; just as the eggs, which are produced in the ovaries, natu- 
 rally form a, part of the texture of these organs. Like the egg, 
 also, the spermatozoon iaidestined to be discharged from the organ 
 where it grew, and to retain, for a certain length of time afterward, 
 its .vital properties. One of the most peculiar of these properties 
 is its power of keeping in constant motion ; which does not, how- 
 ever, mark it as a distinct animal, but only distinguishes it as a 
 peculiar structure belonging to the parent organism. The motion 
 of a spermatozoon is precisely analogous to that of a ciliated epi- 
 thelium cell. The movement of the latter will continue for some 
 hours after it has been separated from its mucous membrane, pro- 
 vided its texture be not injured, nor the process of decomposition 
 allowed to commence. In the same manner, the movement of the 
 spermatozoa is a characteristic property belonging to them, arhich 
 continues for a certain time, even after they have been separated 
 from the rest of the body. 
 
MALE OKGANS OF GENEBATIOK. 559 
 
 In order to preserve tbeir vitality, the spermatozoa must be 
 tept at the ordinary temperature of the body, and preserved 
 from the contact of the air or other unnatural fluids. In this way, 
 they may be kept without difficulty many hours for purposes of 
 examination. But if the fluid in which they are kept be allowed 
 to dry, or if it be diluted by the addition of water, in'the case of 
 birds and quadrupeds, or if it be subjeofied to extremes of heat or 
 cold, the motion ceases, and the spermatozoa themselves soon begin 
 to disintegrate. 
 
 The spermatozoa are produced in certain glandular-looking 
 organs, the testicles, which are characteristic of the male, as the qva- 
 ries are characteristic of the female. In man and all the higher 
 animals, the testicles are solid, ovoid-shaped bodies, composed 
 principally of numerous long, narrow, and convoluted tubes, the 
 " seminiferous tubes," somewhat similar in their general anatomical 
 characters to the tubuli uriniferi of the kidneys. These tubes lie 
 for the most part closely in contact with each other, so that nothing 
 intervenes between them except capillary bloodvessels and a little 
 areolar tissue. They commence, by blind, rounded extremities, near 
 the external surface of the testicle, and pursue an intricately con- 
 voluted course toward its central and posterior part. They are not 
 strongly adherent to each other, but may be readily unravelled by 
 manipulation, and separated from each other. 
 
 The formation of the spermatozoa, as it takes place in the 
 substance of the testicle, has been fully investigated by Kolliker. 
 According to his observations, as tha age of puberty approaches, 
 beside the ordinary pavement epithelium lining the seminiferous 
 tubes, other cells or vesicles of larger size make their appearance 
 in these tubes, each containing from one to fifteen or twenty nuclei, 
 with nucleoli. It is in the interior of these vesicles that the sper- 
 matozoa are formed ; their number corresponding usually with that 
 of the nuclei just mentioned. They are at first developed in bundles 
 of ten to- twenty, held together by the thin membranous substance 
 which surrounds them, but are afterward set free ^ the liquefac- 
 tion of the vesicle, and then fill nearly the entire cavity of the 
 seminiferous ducts, mingled only with a very minute quantity of 
 transparent fluid. 
 
 In the seminiferous tubes themselves, the spermatozoa are al- 
 ways inclosed in the interior of their parent vesicles ; they are libe- 
 rated, and mingled promiscuously together, only after entering the 
 rete testis and the head of the epididymis. 
 
MALE OBGANS OF GENERATION. 
 
 Beside the testicles, which are, as above stated, the. primary and 
 essential parts of the male generative apparatus, there are certain 
 secondary or accessory organs, by means of which the spermatic 
 fluid is conveyed to the exterior, and mingled with various secre- 
 tions which assist in the accomplishment of its functions. 
 
 As the gperm leaves the testicle, it consists, as above mentioned, 
 almost entirely of the spermatozoa, crowded together in an opaque, 
 white, semi-fluid mass, which fills up the vasa efierentia, and com- 
 pletely distends their cavities. It then enters the single duct 
 which forms the body and lower extremity of the epididymis, 
 following the long and tortuous course of this tube, until it 
 reaches the vas deferens; through which it is still conveyed 
 onward to the point where this canal opens into the urethra. 
 Throughout this course, it is mingled with a glairy, mucus-like 
 fluid, secreted by the walls of the epididymis and vas deferens, in 
 which the spermatozoa are enveloped. The mixture is then depo- 
 sited in the vesiculae seminales, where it accumulates, as fresh quan- 
 tities are produced in the testicle and conveyed downward by the 
 spermatic duct. It is probable that a second secretion is supplied 
 also by the inj;ernal surface of the vesiculse seminales, and that the 
 sperm, while retained in their cavities, is not only stored up for 
 subsequent use, but is at the same time modified in its properties 
 by the admixture of another fluid. 
 
 At the time when the evacuation of the sperm takes place, it is 
 driven out from the seminal vesicles by the muscular contraction 
 of the surrounding parts, apd meets in the urethra with the secre- 
 tions of the prostate gland, the glands of Cowper, and the mucous 
 follicles opening into the urethral passage. All these organs are at 
 that time excited to an unusual activity of secretion, and pour out 
 their different fluids in great abundance. 
 
 The sperm, therefore, as it is discharged from the urethra, is an 
 exceedingly mixed fluid, consisting of the spermatozoa derived 
 from the testicles, together with the secretions of the epididymis 
 and vas deferejis,_the prostate, Cowper's glands, and the mucous fol- 
 licles of the urethra. Of all these ingredients, it is the spermatozoa 
 which constitute the essential part of the seminal fluid. They are 
 the true fecundating element of the sperm, while all the others are 
 secondary in importance, and perform only accessory functions. 
 
 Spallanzani found that if frog's semen be passed through- a suc- 
 cession of filters) so as to separate the spermatozoa from the liquid 
 portions, the filtered fluid is destitute of any fecundating properties; 
 
MALM ORGANS OF GENBKATION. 561 
 
 ■vrhile tte spermatozoa remaining entangled in the filter, if mixed • 
 with a sufficient quantity of fluid of the requisite density for dilu- 
 tion, may still be successfully used for the impregnation of eggs. 
 It is well known, also, that animals or men from whom both,testi- 
 cles have been removed, are incapable of impregnating the female 
 or her eggs ; while a removal or imperfection of any of the other 
 generative organs does not necessarily prevent the accomplishment 
 of the function. 
 
 In most of the lower orders of animals there is a periodical 
 development of the testicles in the male, corresponding in time with 
 that of the ovaries in the female. As the ovaries enlarge and the 
 eggs ripen in the one sex, so in the other the testicles increase in 
 size, as the season of reproduction approaches, and become turgid 
 with spermatozoa. The accessory organs of generation, at the 
 same time, share the unusual activity of the testicles, and Ijecome 
 increased in vascularity and ready to perform their part in the 
 reproductive function. 
 
 In the fish, for example, where the testicles occupy the same 
 position in the abdomen as the ovaries in the opposite sex, these 
 bodies enlarge, become distended with their contdhts, and project 
 into the peritoneal cavity. Each of the two sexes is then at the 
 same time under the influence of a corresponding excitement. The 
 unusual development of the generative organs reacts upon the entire 
 system, and produces a state of peculiar activity and excitability, 
 known as the condition of " erethism." The female, distended with 
 eggs, feels the' impulse which leads to their expulsion; while the 
 male, bearing the weight of the enlarged testicles and the accumu- 
 lation of newly-developed spermatozoa, is impelled by a similar 
 sensation to the discharge of the spermatic fluid. The two sexes, 
 accordingly, are led by instinct at this season to frequent the same 
 situations. The female deposits her 'eggs in some spot favorable 
 to the protection and development of the young ; after which the 
 male, apparently attracted and stimulated by the sight of the new- 
 laid eggs, discharges the spermatic fluid upon them, and their 
 impregnation is accomplished. 
 
 In such instances as the above, where the male and female gene- 
 rative products are discharged separately by the two sexes, the 
 subsequent contact of the eggs with the spermatic fluid would seem 
 to be altogether dependent on the occurrence of fortuitous circum- 
 stances, and their impregnation, therefore, often liable to fail. In 
 point of fact, however, the simultaneous functional excitement of 
 36 
 
562 MALE ORGANS OF GENKBATION. 
 
 • the two sexes and the operation of corresponding instincts, leading 
 them to ascend the same rivers and to frequent the same spots, 
 provide with sufficient certainty for the impregnation of the eggs. 
 In these animals, also, the number of eggs produced by the female 
 is very large, the ovaries being often so distended as to fill nearly 
 the whole of the abdominal cavity ; so that, although many of the 
 eggs may be accidentally lost, a sufficient number will still be im- 
 pregnated and developed, to provide for the continuation of*the 
 species. , 
 
 In other instances, an actual contact takes place between the 
 sexes at the time of reproduction. In the frog, for example, the 
 male fastens himself upon the back of the female by the anterior 
 extremities, which seem to retain their hold by a kind of spasmodic 
 contraction. This continues for one or two days, during which 
 time t]je mature eggs, which have been discharged from the ovary, 
 are passing downward through the oviducts. At last they are ex- 
 pelled from the anus, while at the same time the seminal fluid of 
 the male is discharged upon them, and impregnation takes place. 
 
 In the higher classes of animals, however, and in man, where the 
 egg is to be retained in the body of the female parent during its 
 development, the spermatic fluid is introduced into the female 
 generative passages by sexual congress, and meets the egg at or 
 soon after its discharge from the ovary. The same correspondence, 
 however, between the periods of sexual excitement in the male and 
 female, is visible in many of these animals, as well as in fish and 
 reptiles. This is the case in most species which produce young but 
 once a year, and at a fixed period, as the deer and the wild hog. In 
 other species, on the contrary, such as the dog, as well as the rabbit, 
 the guinea pig, &c., where several broods of young are produced 
 during the year, or where, as in the human subject, the generative 
 epochs of the female recur at' short intervals, so that the particular 
 period of impregnation is comparatively indefinite, the generative 
 apparatus of the male is almost constantly in a state of full deve- 
 lopment; and is excited to action at particular periods, apparently 
 by some influence derived from the condition of the female. 
 
 In the quadrupeds, accordingly, and in the human species, the 
 contact of the sperm with the egg and the fecundation of .the latter 
 take place in the generative passages of the female ; either in the 
 uterus, the Fallopian tubes, or even upon the surface of the ovary ; 
 in each of which situations the spermatozoa have been found, after 
 the accomplishment of sexual intercourse. 
 
PEBIODICAL OVULATION. 563 
 
 CHAPTER V. 
 
 ON PERIODICAL OVULATION, AND THE FUNCTION 
 OF MBNSTBUATIO 
 
 I. PERIODICAL OVULATION. 
 
 We Lave already spoken in general terms of the periodical ripen- 
 ing of the eggs and their discharge from the generative organs of 
 the female. This function is known by the name of " ovulation," 
 and may be considered as the primary and most important act in 
 the process of reproduction. "We shall, therefore, enter more fully 
 into the consideration of certain particulars in regard to it, by 
 which its nature and conditions may be more clearly understood. 
 
 1st. Sggs exist originally in the ovaries, of all animals, as part of 
 their natural structure. In describing the ovaries of fish and reptiles 
 we have said that they consist of nothing more than Graafian vesi- 
 cles, each vesicle containing an egg, and united with the others by 
 loose areolar tissue and a peritoneal investment. In the higher 
 animals and in the human subject, the essential constitution of the 
 ovary is the same ; only its fibrous tissue is more abundant, so that 
 the texture of the entire organ is more dense, and its figure more 
 compact. In all classes, however, without exception, the interior 
 of each Graafian vesicle is occupied by an egg ; and it is from this 
 egg that the young offspring is afterward produced. 
 
 The process of reproduction was formerly regarded as essentially 
 different in the.oviparous and the viviparous animals. In the ovipa- 
 rous classes, such as most fish, and all reptiles and birds, the young 
 animal was well known to be formed from an egg produced by the 
 female ; while in the viviparous animals, or those which bring 
 forth their young alive, such as the quadrupeds and the human 
 species, the embryo was supposed tQ originate in the body of the 
 female, by some altogether peculiar and mysterious process, in 
 consequence of sexual intercourse. As soon, however, as the 
 microscope began to be used in the examination of the tissues, 
 
564 OVULATION AND FUNCTION OF MENSTRUATION. 
 
 the ovaries of quadrupeds were also found to contain eggs. These 
 eggs had previously escaped observation on account of their simple 
 structure and minute size; but they were nevertheless found to 
 possess all the most essential characters belonging to the larger 
 eggs of the oviparous animals. 
 
 The true difference in the process of reproduction, between the 
 two classes, is therefore merely an apparent, not a fundamental one. 
 In fish, reptiles, and birds, the egg is discharged by the female 
 before or immediately after impregnation, and the embryo is subse- 
 quently developed and hatched externally. In the quadrupeds and 
 the human species, on the other hand, the egg is retained within 
 the body of the female until the embryo is developed ; when the 
 membranes are ruptured and the young expelled at the same time. 
 In all classes, however, viviparous as well as OAdparous, the young 
 is produced equally from an egg ; and in all classes the egg, some- 
 times larger and sometimes smaller, but always consisting essentially 
 of a vitellus and a vitelline membrane, is contained originally in 
 the interior of an ovarian follicle. 
 
 The egg is accordingly, as we have already intimated, an integral 
 part of the ovarian tissue. It may be found there long before the 
 generative function is established, and during the earliest periods 
 of life. It may be found without difficulty in the newly bom 
 female infant, and may even be detected in the foetus before birth. 
 Its growth and nutrition, also, are provided for in the same man- 
 ner with that of other portions of the bodily structure. 
 
 2d. These eggs hecome more fully developed at a certain age, when, 
 the generative function is about to be established. During the early 
 periods of life, the ovaries and their contents, like many other 
 organs; are imperfectly developed. They exist, but they are as 
 yet inactive, and incapable of performing any function. In the 
 young chick, for example, the ovary is of small size ; and the eggs, 
 instead of presenting the voluminous, yellow, opaque vitellus which 
 they afterward exhibit, are minute, transparent, and colorless. In 
 the young quadrupeds, and in the human female during infancy 
 and childhood, the ovaries are equally inactive. They are small, 
 friable, and of a nearly homogeneous appearance to the naked eye; 
 presenting none of the enlarged follicles, filled with transparent 
 fluid, which are afterward so ^;eadily distinguished. At this time, 
 accordingly, the female is incapable of bearing young, because the 
 ovaries are inactive, and the eggs which they contain immature. 
 
 At a ^certain period, however, which varies in the' time of its 
 
PERIODICAL OVULATION. 565 
 
 occurrence for different species of animals, the sexual apparatus 
 begins to enter upon a state of activity. The ovaries increase in 
 size, and their circulation becomes more active. The eggs, also, 
 instead of remaining quiescent, take on a rapid growth, and the 
 structure of the vitellus is completed by the abundant deposit of 
 oleaginous granules in its interior. Arrived at this state, the eggs 
 are ready for impregnation, and the female becomes capable' of 
 bearing young. She is then said to have arrived at the state of 
 "puberty," or that condition in which the generative organs are 
 fully developed. This condition is accompanied by a visible 
 alteration in the system at large, which indicates the complete 
 development of the entire organism. In many birds, for example, 
 the plumage assumes at this period more varied and brilliant 
 colors; and in the common fowl the comb, or "crest," enlarges 
 and becomes red and vascular. In the American deer (Cervus 
 virginianus), the coat, which during the first year is mottled with 
 white, becomes in the second year of a uniform tawny or reddish 
 tinge. In nearly all species, the limbs become more compact and 
 the body more rounded ; and the whole external appearance is so 
 altered, as to indicate that the animal has arrived at the period of 
 puberty, and is capable of reproduction. 
 
 3d. Successive crops of eggs, in the adult female, ripen and are 
 discharged independently of sexual intercourse. It was formerly sup- 
 posed, as we have mentioned above, that in the viviparous animals 
 the germ was formed in the body of the female only as a conse- 
 quence of sexual intercourse. Even after the important fa-ct 
 became known that eggs exist originally in the ovaries of these 
 animals, and are only fecundated by the influence of the sperm- 
 atic fluid, the opinion still prevailed that the occurrence of sexual 
 intercourse was the cause of their being discharged from the ovary, 
 and that the rupture of a Graafian vesicle in this organ was a 
 certain indication that coitus had taken place. 
 
 This opinion, however, was altogether unfounded. We already 
 know that in fish and reptiles the mature eggs not only leave the 
 ovary, but are actually discharged from the body of the female 
 while still unimpregnated, and only subsequently come in contact 
 with the spermatic fluid. In fowls, also, it is a matter of common 
 observation that the hen will continue to lay fully-formed eggs, if 
 well supplied with nourishment, without the presence of the cock ; 
 only these eggs, being unimpregnated, are incapable of producing 
 
566 OVULATION AND FUNCTION OF MENSTKUATION. 
 
 chicks. In oviparous animals, therefore, the discharge of the egg, 
 as well as its forniation, is independent of sexual intercourse. 
 
 Continued observation shows this to be the case, also, in the 
 viviparous quadrupeds. The researches of Bisohoff, Pouchet, and 
 Coste have demonstated that in the sheep, the pig, the bitch, the 
 rabbit, &c., if the female be carefully kept, from the male until after 
 the period of puberty is established, and then killed, examination 
 of the ovaries will show that Grraafian vesicles have matured, rup- 
 tured, and discharged their eggs, in the same manner as though 
 sexual intercourse had taken place. Sometimes the vesicles are 
 found distended and prominent upon the surface of the ovary; 
 sometimes recently ruptured and collapsed ; and sometimes in vari- 
 ous stages of cicatrization and atrophy. Bischoff,' in several in- 
 stances of this kind, actually found the unimpregnated eggs in the 
 oviduct, on their way to the cavity of the uterus. In those animals 
 in which the ripening of the eggs takes plape at short intervals, as, 
 for example, the sheep, the pig, and the cow, it is very rare to exa- ' 
 mine the ovaries in any instance where traces of a more or less 
 recent rupture of the Graafian follicles are not distinctly visible. 
 ' One of the most important facts, derived from the examination 
 of such cases as the above, is that the ovarian eggs become deve- 
 loped and are discharged in successive crops, which follow each 
 other regularly at periodical intervals. If we examine the ovary ' 
 of the fowl, for example (Fig. 180), we see at a glance how the eggs 
 grow and ripen, one after the other, like fruit upon a vine. In this 
 instance, the process of evolution is very rapid ; and it is easy to 
 distinguish, at the same tihie, eggs which are almost microscopic in 
 size, colorless, and transparent; those which are larger, firtner, ' 
 somewhat opaline, and yellowish in hue ; and finally those which . 
 are fully developed, opaque, of a deep orange color, and just ready 
 to leave the ovary. 
 
 It will be observed that in this instance the difference between 
 the undeveloped and the mature eggs consists principally in the 
 size of the vitellus, which is furthermore, for reasons previously 
 given (Chap. III.), very much larger than in the quadrupeds. It 
 is also seen that it is the increased size of the vitellus alone, by 
 which the ovarian follicle is distended, and ruptured, and the egg 
 finally discharged. 
 
 ' Memoire sut la cTiute pgriodiqne de I'oeuf, &o., Annales des Sciences Natnrelles, 
 Aoiit— Septembre, 1844. 
 
PERIODICAL OVULATION. 567 
 
 In the human species and the quadrupeds, on the other hand, 
 the microscopic egg never becomes "large enough to distend the 
 follicle by its own size. The rupture of the follicle and the libeua- 
 tion of the egg are accordingly provided for, in these instances, by 
 a totally different mechanism. 
 
 In the earlier periods of life, in man and the higher animals, the 
 egg is contained in a Grraafian follicle which closely embraces its 
 exterior, and is consequently hardly larger than .the egg itself. As 
 puberty approaches, those follicles which are situated near the free 
 surface of the ovary become enlarged by the accumulation of a 
 colorless serous fluid in their cavity. "We then find that the ovary, 
 when cut open, shows a considerable number of globular, transpa- 
 rent vesicles, readily perceptible by the eye, the smaller of which 
 are deep seated, but which increase in size as they approach the 
 free surface of the organ. TheSe vesicles are the Graafian follicles, 
 which, in consequence of the advancing maturity of the eggs con- 
 tained in them, gradually enlarge as the period of generation ap- 
 proaches. 
 
 The Graafian follicle at this time consists of a closed globular 
 sac or vesicle, the external wall of which, though quite translucent, 
 has a fibrous texture under the microscope and is well supplied 
 with bloodvessels. This fibrous and vascular wall is distinguished 
 by the name of the " membrane of the vesicle." It is not very 
 firm in texture, and if roughly handled is easily ruptured. 
 
 The membrane of the vesicle is lined throughout by a thin layer 
 of minute granular cells, which form for it a kind of epithelium, 
 similar to the epithelium of the pleura, pericardium, and. other 
 serous membranes. This layer is termed the membrana granulosa. 
 It adheres but slightly to the membrane of the vesicle, and may 
 easily be detached by careless manipulation before the vesicle is 
 opened, being then mingled, in the form of light flakes and shreds, 
 with the serous fluid contained in the vesicle. « 
 
 At the most superficial part of the Graafian follicle, or that 
 which is nearest the surface of the ovary, the membrana granulosa 
 is thicker than elsewhere. Its cells are here accumulated, in a 
 kind of mound or "heap," which has received the name of the 
 cumulus proligerus. It is sometimes. called the discus proligerus, 
 because the thickened mass, when viewed from above, has a some- 
 what circular or disk-like form. In the centre of this thickened 
 portion of the membrana granulosa the egg is imbedded. It is 
 
568 OVULATION AND FUNCTION OF MENSTRUATION, 
 
 accordingly always situated at the most superficial portion of the 
 follicle, and advances in this way toward the surface of the ovary. 
 • As the period approaches at which the egg is destined to be dis- 
 charged, the Graafian follicle becomes more vascular, and enlarges 
 by an increased exudation of serum into its cavity. It then begins 
 
 Fig. 185. 
 
 Graaftan Follicle, near the period of rupture —a. Membraneof the vesicle. 6. MembraD* 
 graaulosa. c. Cavity of foLlicle. d. Egg. e. Peritoneum. /. Tunica albugLuca. g, g. TisEue uf 
 the ovary. 
 
 to project from the surface of the ovary, still covered by the albu- 
 gineous tunic and the peritoneum. (Fig. 185.) The constant accu- 
 mulation of fluid, however, in the follicle, exerts such a steady and 
 increasing pressure from within outward, that the albugineous tunic 
 and the peritoneum successively yield before it ; until the Graafian 
 follicle protrudes from the ovary as a tense, rounded, translucent 
 
 vesicle, in which the sense pf 
 ^^' ■'^^" fluctuation can be readily per- 
 
 ceived on applying the fingers 
 to its surface. Finally, the pro- 
 cess of effusion and distension 
 still. going on, the wall of the 
 vesicle yields at its most promi- 
 nent portion, the contained fluid 
 is driven out with a gush, by the 
 reaction and elasticity of the 
 neighboring ovarian tissues, car- 
 rying with, it the egg, still en- 
 tangled in the cells of the pro- 
 ligerous disk. 
 
 The rupture of the Graafian 
 vesicle is accompanied, in some instances, by an abundant hemor^ 
 
 OvAET wtTH Graafian Follicle 
 RnpTHRED: atrt, egg just discharged with a 
 portion of raembi'aua granulosa. 
 
PERIODICAL OVULATION. 569 
 
 rhage, which takes place from the internal surface of the congested 
 follicle, and by which its cavity is filled with blood. This occurs 
 in the human subject and in the pig, and to a certain extent, also, in 
 other of the lower animals. Sometimes, as .in the cow, where no 
 hemorrhage takes place, the Graafian vesicle when ruptured 
 simply collapses ; after which a slight exudation, more or less tinged 
 with blood, is poured out during the course of a few hours. 
 
 Notwithstanding, however, these slight variations, the expulsion 
 of the egg takes place, in the higher animals, always in the manner 
 above described, viz., by the accumulation of serous fluid in the 
 cavity of the Graafian follicle, by which its walls are gradually dis- 
 tended and finally ruptured. 
 
 This process takes place in one or more Graafian follicles at a 
 time, according to the number of young which the animal produces 
 at a birth. In the bitch and the sow, where each litter consists of 
 from six to twenty yoiing ones, a similar number of eggs ripen and 
 are discharged at each period. In the mare, in the cow, and in the 
 human female, where tbere is usually but one foetus at a birth, the 
 eggs are matured singly, and the Graafian vesicles ruptured, one 
 after another, at successive periods of ovulation. 
 
 4:th. The ripening and discharge of the egg are accompanied by a 
 peculiar condition of the entire .system, known as the " rutting" condi- 
 tion, or " oestruation." The peculiar congestion and functional 
 activity of the ovaries at each period of ovulation, act by sympathy 
 upon the other generative organs and produce in them a greater or 
 less degree of excitement, according to the particular species of ani- 
 mal. Almost always there is a certain amount of congestion of the 
 entire generative apparatus; Fallopian tubes, uterus, vagina, and 
 external organs. The secretions of the vagina and neighborilig 
 parts are more particularly. affected, being usually increased in quan- 
 tity and at the same time altered in quality. In the bitch, the 
 vaginal mucous membrane becomes red and tumefied, and pours 
 out an abundant secretion which is often more or less tinged with 
 blood. The secretions acquire also at this time a peculiar odor, 
 which appears to attract the male, and to excite in him the sexual 
 impulse. An unusual tumefaction and redness of the vagina and 
 vulva are also very perceptible in the rabbit ; and in some species 
 bf apes it has been observed that these periods are accompanied 
 not only by a bloody discharge from the vulva, but also by an en- 
 gorgement and infiltration of the neighboring parts, extending even 
 
570 OVULATION AND FUNCTION OP MENSTRUATION. 
 
 to the skin of the buttocks, the thighs, and the under part of the 
 tail.i 
 
 The system ai> large is also visibly affected by the process going 
 on in the ovary. In the cow, for example, the approach of an 
 oestrual period is marked by an unusual restlessness and agitation, 
 easily recognized by an ordinary observer. The animal partially 
 loses her appetite. She frequently stops browsing, looks about un- 
 easily, perhaps rung from one side of the field to the other, and then 
 recommences feeding, to be disturbed again in a similar manner 
 after a short interval. Her motions are rapid and nervous, and her 
 hide often rough and disordered ; and the whole aspect of the ani- 
 mal indicates the presence of some unusual excitement. After this 
 condition is fully established, the vaginal secretions show. them- 
 selves in unusual abundance, and so continue for one or two days ; 
 after which the symptoms, both local and general,, subside sponta- 
 neously, and the animal returns to her usual condition. 
 
 It is a remarkable fact, in this connection, that the female of 
 these animals will allow the approaches of the male only during and 
 immediately after the oestrual period ; that is, just when the egg is 
 recently discharged, and ready for impregnation. At other times, 
 when sexual intercourse would be necessarily fruitless, the instinct 
 of the animal leads her to avoid it ; and the concourse of the sexes 
 is accordingly made to correspond in time with the maturity of the 
 egg and its aptitude for fecundation. 
 
 II. MENSTEUATION. 
 
 In the human female, the return of the period of ovulation, is 
 marked by a peculiar group of phenomena which are known as 
 menstruation, and which are of sufficient importance to be described 
 by themselves. 
 
 During infancy and childhood the sexual system, as we have 
 mentioned above, is inactive. No discharge of eggs takes place 
 from the ovaries, and no external phenomena show themselves, 
 connected with the reproductive function. 
 
 At the age of fourteen or fifteen years, however, a change begins 
 to manifest itself. The limbs become rounder, the breasts increase 
 in size, and the entire aspect undergoes a peculiar alteration, which 
 indicates the approaching condition of .maturity. At the same 
 time a discharge of blood takes place from the generative passages, 
 
 ' Poaohet, Theorie positive de I'ovulation, &c. Paris, 1847, p. 230. 
 
MENSTBUATION. 571 
 
 accompanied by some disturbance of the general system, and tbe 
 female is then known to have arrived at the period of puberty. 
 
 Afterwarfi, the bloody discharge just spoken of returns at regular 
 intervals of four weeks ; and, on account of this recurrence corres- 
 ponding with the passage of successive lunar months, its phenomena 
 are 'designated by the name of the "menses" or the "menstrual 
 periods." The menses return with regularity, from the time of 
 their first appearance, until the age of about forty-five years. 
 During this period, the female is capable of bearing children, and 
 sexual intercourse is liable to be followed by pregnancy. After 
 the forty-fifth year, the periods first become irregular, and then 
 cease altogether ; and their final disappearance is an indication that 
 the woman is no longer fertile, and that pregnancy cannot again 
 take place. 
 
 Even during the period above referred to, from the age of fifteen 
 to forty-five, the regularity and completeness of the menstrual 
 periods indicate to a great extent the aptitude of individual females 
 for impregnation. It is well known that all those causes of ill 
 health which derange menstruation are apt at the same time to 
 interfere with pregnancy ; so that women whose menses are habi- 
 tually regular and natural are much more likely to become preg- 
 nant, after sexual intercourse, than those in whom the periods are 
 absent or irregular. 
 
 If pregnancy happen to take place, however, at any time during 
 the child-bearing period, the menses are suspended during the con- 
 tinuance of gestation, and usually remain absent, after delivery, as 
 long as the woman continues to nurse her child. They then re- 
 commence, and subsequently continue to appear as before. 
 
 The menstrual discharge consists of an abundant secretion of 
 mucus mingled with blood. "When the expected period is about 
 to come on, the female is affected -with a certain degree of discomfort 
 and lassitude, a sense of -weight in the pelvis, and more or less dis- 
 inclination to society. These symptoms are in some instances 
 .''lightly pronounced, in others more troublesome. An unusual 
 discharge of vaginal mucus then begins to take place, which soon 
 becomes yellowish or rusty brown in color, from the admixture of 
 a certain proportion of blood ; and by the second or third day the 
 discharge has the appearance of nearly pure blood. The unpleasant 
 sensations which were at first manifest then usually subside ; and 
 the discharge, after continuing for a certain period, begins to grow 
 more scanty. Its color changes from a pure red to a brownish or 
 
572 OVULATION ASD FUNCTION OF MENSTRUATION. 
 
 rusty tinge, until it finally disappears altogether, and the female 
 returns to her ordinary condition. 
 
 The menstrual epochs of the human female correspqud with the 
 periods of cestruation in the lower animals. Their general resem- 
 blance to these periods is too evident to require demonstration. 
 Like them, they are absent in the immature female; and begm 
 to take place only at the period of puberty, when the aptitude for 
 impregnation commences. Like them, they recur during the child- 
 bearing period at regular intervals; and are liable to the same 
 interruption by pregnancy and lactation. Finally, their disappear- 
 ance corresponds with the cessation of fertility. 
 
 The periods of cestruation, furthermore, in many of the lower 
 animals, are accompanied, as we have already seen, with an unusual 
 discharge from the generative passages; and this discharge- is fre- 
 quently more or less tinged with bloOd. In the human female the 
 bloody discharge is more abundant than in other instances, but it 
 is evidently a phenomenon difiering only in degree from that which 
 shows itself in many species of animals. , 
 
 The most complete evidence, hovjever, that the period of: men- 
 struation is in reality that of ovulation, is derived from the results 
 of direct observation. A sufficient number of instances have now 
 been observed to show that at the menstrual epoch a Graafian 
 vesicle becomes enlarged, ruptures, and discharges its egg. Cruik- 
 shank' noticed such a case so long ago as 1797. Negrier' relates 
 two instances, communicated to him by Dr. Ollivier d' Angers, in 
 which, after sudden death during menstruation, a bloody and rup- 
 tured Graafian vesicle was found in the ovary. Bischoff^ speaks of 
 four similar cases in his own observation, in three of which the 
 vesicle was just ruptured, and in the fourth distended, prominent, 
 and ready to burst. Goste* has met with several of the same kind; 
 Dr. Michel' found a vesicle ruptured and filled with blood in a 
 woman who was executed fpr murder while the menses were pre- 
 sent. We have also" met with the same appearances in a case of 
 death from acute disease, on the second day of menstruation. 
 
 ' London Philosophical Transactions, 1797, p. 135. 
 2 Reoherohes sur les Ovaires, Paris, 1840, p. 78. 
 ^ Aunales des Sciences Naturelles, August, 1844. 
 
 * Histoire da Developpement des Corps Organises, Paris, 1847, vol. i. p. 221. 
 
 * Am. Journ. Med. Sci., July, 1848. 
 
 " Corpus Luteum of Menstruation and Pregnancy, in Transactions of American 
 Medical Association, Philadelphia, 1851. 
 
MENSTKUATION. 573 
 
 The process of ovulation, accordingly, in the human female, 
 accompanies and forms a part of that of menstruation. As the 
 menstrual period comes on, a congestion takes place in nearly the 
 ■whole of the generatiye apparatus ; in the Fallopian tubes and the 
 uterus, as well as in the ovaries and their contents. One of the 
 Graafian follicles is more especially the seat of an unusual vascular 
 excitement. It becomes distended by the fluid which accumulates 
 in its cavity, projects from the surface of the ovary, and is finally 
 ruptured in the same manner as we have already described this 
 process taking place in the lower animals. 
 
 It is not quite certain at what particular period of the menstrual 
 flow the rupture of the vesicle and discharge of the egg take place. 
 It is the opinion of Bischoff, Pouchet, and Eaciborski, that the 
 regular time for this rupture and discharge is not at the commence- 
 ment, but towards the termination of the period. Coste' has ascer- 
 tained, from his observations, that the vesicle ruptures sometimes 
 in the early part of the menstrual epoch, and sometimes later. So 
 far as we can learn, therefore, the precise period of the discharge 
 of the egg is not invariable. Like the menses themselves, it may 
 apparently take place a little earlier, or a little later, according to 
 various accidental circumstances; but it always occurs at some 
 time in connection with the menstrual flow, and constitutes the 
 most essential and important part of the catamenial process. 
 
 The egg, when discharged from the ovary, enters the fimbriated 
 extremity of the Fallopian tube, and commences its passage toward 
 the uterus. The mechanism by which it finds its way into and 
 through the Fallopian tube is different, in the quadrupeds and the 
 human species, and in birds and reptiles. In the latter, the bulk 
 of the egg or mass of eggs discharged is so great as to fill entirely 
 the wide extremity of the oviduct, "and they are afterward c6nveyed 
 downward by the peristaltic action of the muscular coat of this 
 canal.. In the higher classes, on the contrary, the egg is micto- 
 scopio in size, and would be liable to be lost, were there not some 
 further provision for its safety. The wide extremity of the Fallo- 
 pian tube, accordingly, which is here directed toward the ovary, is 
 lined with ciliated epithelium; and the movement of the cilia, 
 which is directed from the ovary toward the uterus, produces a 
 kind of converging stream, or vortex, by which the egg is neces- 
 sarily drawn toward the narrow portion of the tube, and subse-, 
 qUently conducted to the cavity of the uterus. 
 
 ' Log oit. 
 
574 OVULATION AND FUNCTION OF MENSTEOATION. 
 
 Accidental causes, however, someijiimes disturb this regular course 
 or passage of the egg. The egg may be arrested, for example, 
 at the surface of the ovary, and so fail to enter the tube at aU. 
 If fecundated in this situation, it will then give rise to " ovarian 
 pregnancy ." It may escape from the fimbriated extremity into the 
 peritoneal cavity, and form attachments to some one of the neigh- 
 boring organs, causing "abdominal pregnancy;" or finally, it may 
 stop at any part of the Fallopian tube, and so give origin to "tubal 
 pregnancy." 
 
 The egg, immediately upon its discharge from the ovary, is ready 
 for impregnation. If sexual intercourse happen to take, place about 
 that time, the egg and the spermatic fluid meet in some part of the 
 female generative passages, and fecundation is accomplished. It 
 appears from various observations of Bischoff, Coste, and others, 
 that this contact may take place between the egg and the sperm, 
 either in the uterus or any part of the Fallopian tubes, or even 
 upon the surface of the ovary. If, on the other hand, coitus do not 
 take place, the egg passes down to the uterus unimpregnated, loses 
 its vitality after a short time, and is finally carried away with the ' 
 uterine secretions. 
 
 It is easily understood, therefore, why sexual intercourse should 
 be more liable to be followed by pregnancy when it occurs about 
 the menstrual epoch than at other times. This fact, which was long 
 since established as a matter of observation by practical obstetri- 
 cians, depends simply upon the coii\cidence in time between men- 
 struation and the discharge of the egg. Before its discharge, the 
 egg is immature, and unprepared for impregnation ; and after the 
 menstrual period has passed, it gradually loses its freshness, and 
 vitality. The exact length of time, however, preceding and follow- 
 ing the 'menses, during which impregnation is still possible, has not 
 been ascertained. The spermatic fluid, on the one hand, retains its 
 vitality for an unknown period after coition, and the egg for an 
 unknown period after . its discharge. Both these occurrences may, 
 therefore, either precede or follow each other within certain limits, 
 and impregnation be still possible ; but the precise extent of these 
 limits is still uncertain, and is probably, more or less variable in 
 different individuals. 
 
 The above facts indicate-also the true explanation of certain 
 
 , exceptional oases, which have sometimes been observed, in which 
 
 fertility exists without menstruation. Various authors (Churchill, 
 
 Eeid, Velpeau, &c.) have related instances of fruitful women in whom 
 
MENSTRUATION. 575 
 
 the menses were very scanty and irregular, or even entirely absent. 
 The menstrual flow is, in fact, only the external sign and accompa- 
 niment of a more important process taking place within. It is 
 habitually scanty in some individuals, and abundant in others. 
 Such variations depend upon the condition of vascular activity of 
 the system at large, or of the uterine organs in particular ; and 
 though the bloody discharge is usually an index of the general 
 aptitude of these organs for successful impregnation, it is not an 
 absolute or necessary requisite. Provided a mature egg be dis- 
 charged from the ovary at the appointed period, menstruation pro- 
 perly speaking exists, and pregnancy is possible. 
 
 The blood which escapes during the menstrual flow is supplied 
 by the uterine mucous membrane. If the cavity of the uterus be 
 examined after death during menstruation, its internal -surface is 
 seen to be smeared with a thickish bloody fluid, which maj be 
 traced through the uterine cervix and into the vagina. The Fallo- 
 pian tubes themselves are sometimes found excessively congested, 
 and filled with a similar bloody discharge. The menstrual blood 
 has also been seen to exude from the uterine orifice in cases of pro- 
 cidentia uteri, as well as in the natural condition by examination 
 with the vaginal speculum. It is discharged by a kind of capillary 
 hemorrhage, similar to that which takes place from the lungs in 
 cases of haemoptysis, only less sudden and violent. The blood does 
 not form any visible coagulum, owing to its being gradually exuded 
 from many minute points, and mingled with a large quantity of 
 mucus. When poured out, however, more rapidly or in larger 
 quantity than usual; as in cases of menorrhagia, the menstrual blood 
 coagulates in the same manner as if derived from any other source. 
 The hemorrhage which supplies it comes from the whole extent of 
 the mucous membrane of the body of the uterus, and is, at the same 
 time, the consequence and the natural termination of the periodical 
 congestion of the parts. 
 
576 MEXSTRUATIOIf AST) PBEGNANCT. 
 
 CHAPTEE VI. 
 
 ON THE CORPUS LUTEUM OF MENSTBUATION 
 AND PREGNANCY. 
 
 After the rupture of the Graafian follicle at the menstrual 
 period, a bloody cavity is left in the ovary, which is subsequently 
 oblijierated by a kind of granulating process, somewhat similar in 
 character to the healing of an abscess. For the Graafian follicle 
 is intended simply for the formation and growth of^ the egg. 
 Aft^r the egg therefore has arrived at maturity and has been dis- 
 charged, the Graafian follicle has no longer any function to per- 
 form. It then only remains for it to pass through a process of 
 obliteration and atrophy, as an organ which has become useless 
 and obsolete. While undergoing this process, the Graafian follicle 
 is at one time converted into a peculiar, solid, globular body, which 
 is called the corpus luteum ; a name given to it on account of the 
 yellow color which it acquires at a certain period of its formation. , 
 
 We shall proceed to describe the corpus luteum in the human 
 species; first, as it follows the ordinary course of .development 
 after menstruation; and secondly, as it is modified in its growth 
 and appearance during the existence of pregnancy. 
 
 I. CORPUS LUTEUM OF MENSTRUATION. 
 
 We have already described, in the preceding chapter, the man- 
 ner in which a Graafian follicle, at each menstrual epoch, swells, 
 protrudes front the surface of the ovary, and at last ruptures apd 
 discharges its egg. At the moment of rupture, or immediately 
 after it, an abundant hemorrhage takes place in the human sub- 
 ject from the vessels of the follicle, by which its cavity is filled 
 with blood. This blood coagulates soon after its exudation, as 
 it would do if extra vasated in any other part of the body, and 
 the coagulum is retained in the interior of the Graafian follicle. 
 
COKPUS LUTEUM OF MENSTRUATION. 57? 
 
 The opening by which the egg makes its escape is usually not an 
 extensive laceration, but a minute rounded perforation, often not 
 more than half a line in diameter. A small probe, introduced 
 through this opening, passes directly into the 
 cavity of the follicle. If the Graafian follicle Fig- 187. 
 
 be opened at this time by a longitudinal inci- 
 sion (Fig. 187), it will be seen to form a globu- 
 lar cavity, one-half to three-quarters of an 
 inch in diameter, containing a soft, recent, 
 dark-colored coagulum. This coagulum has 
 no organic connection with the walls of the 
 follicle, but lies loose in its cavity and may be 
 easily turned out with the handle of a knife. 
 There is sometimes a slight mechanical adhe- 
 sion of the clot to the edges of the lacerated \ " 
 opening, just as the coagulum in a recently 2i:,;'lZ,Tlll" 
 ligatured artery is entangled by the divided menstroation, and aued 
 edges of the internal and middle coats ^ but rhot^"i°^Jit°3'rc: 
 there is no continuity of substance between "on.— «. Tissue of the 
 
 . 111 1 1 i>i ovary. ■&. Kembrane of the 
 
 them, and the clot may be everywhere readily veaicie. o-. pomt of rupture, 
 separated by careful manipulation. The mem- 
 brane of the vesicle presents at this time a smooth, transparent, and 
 vascular internal surface, without any alteration of color, consistency, 
 or texture. 
 
 An important change, however, soon begins to take place, both 
 in the central coagulum and in the membrane of the vesicle. 
 
 The clot, which is at firsl; large, soft, and gelatinous, like any 
 other mass of coagulated blood, begins to contract ; and the serum 
 separates from the coagulum proper. The serum, as fast as it 
 separates from the coagulum, is absorbed by the neighboring parts ; 
 and the clot, accordingly, grows every day smaller and denser than 
 before. At the same time the coloring matter of the blood under- 
 goes the changes which usually take place- in it after extravasation, 
 and is psCrtially reabsorbed together with the serum. This second 
 change is somewhat less rapid than the former, but still a diminu- 
 tion of color is very perceptible in the clot, at the expiration of 
 two weeks. 
 
 The membrane of the vesicle during this time is beginning to 
 undergo a process of hypertrophy or development, by which.it 
 be'comes thickened and convoluted, and tends partially to fill up 
 37 
 
678 
 
 MENSTRUATION AND PKITGNANCy. 
 
 Fig. 188. 
 
 the cavity of the follicle. This hypertrophy and convolution of 
 the membrane just named commences and proceeds most rapidly 
 at the deeper part of the follicle, directly opposite the situation of 
 the superficial rupture. From this point the membrane gradually 
 becomes thinner and less convoluted as it approaches the surface 
 of the ovary and the edges of the ruptured orifice. 
 
 At the end of three weeks, this hypertrophy of the membrane of 
 the vesicle has reached its maximum. The ruptured Graafian fol- 
 licle has now become so completely solidified by the new growth 
 above described, and by the condensation of its clot, that it receives 
 .the name of the corpus luteum. It forms a perceptible prominence 
 on the surface of the ovary, and may be felt between the fingers 
 as a well-defined rounded tumor, which is nearly always somewhat 
 flattened from side to side. It measures about three-quarters of an 
 
 inch in length and half an inch in 
 depth. On its surface may be seen a 
 minute cicatrix of the peritoneum, 
 occupying the spot of the original 
 rupture. 
 
 On cutting it open at this time (Fig. 
 188), the corpus luteum is seen to con- 
 sist, as above described, of a central 
 coagulum and a convoluted wall. 
 The coagulum is semi-transparent, of 
 a gray or light greenish color, more 
 or less mottled with red. The con- 
 otaky cut open, «ho,viuif corpus volutcd Wall is about oue-cighth of 
 luteum divided i^ngiindinaiiy ; tiiree an iuch thick at its dccpest Dart, and 
 
 veeka after menstrnatioa. From a girl .,„. n-i 
 
 aead of haemoptysis. 01 an mdetinite yellowish or rosy 
 
 hue, not very different in tinge from 
 'the rest of the ovarian tissue. The convoluted wall aiid the con- 
 'tained clot lie simply in contact with each other, as at firsty without 
 any intervening membrane or other organic connection; and they 
 may still be readily separated from each other by the hamdle of a 
 Knife or the flattened end of a probe. The corpus luteum at this 
 time may also be stripped out, or enucleated entire, from the ovarian 
 tissue, just as might have been done with the Graafian follicle pre- 
 viously to its rupture. When enucleated in this way, the corpus 
 luteum presents itself under the form of a solid globular or flat- 
 tened tumor; with convolutions upon it somewhat similar in ap- 
 pearance to those of the brain, and covered with the remains of 
 
COBPUS LUTEUM OF MENSTRUATION. 
 
 579 
 
 Otart, sbowlDg corpas 
 luteum four weekH after men- 
 straation ; from a woman de&d 
 of apoplexy. 
 
 ( 
 
 the areolar tissue, by whichit was previously connected with the 
 substance of the ovary. 
 
 After the third week from the close of menstruation, the corpus 
 luteum passes into a retrogr'ade condition. It diminishes.percep- 
 tibly in size, and the central coagulum con- 
 tinues to be absorbed and loses still farther 
 its coloring matter. The whole body under- 
 goes a process of partial atrophy; and at 
 the end of the fourth week it is not more 
 than three-eighths of an inch in its longest 
 diameter. (Fig. 189.) The external cicatrix 
 may still usually be seen, as well as. the 
 point where the central coagulum comes 
 in contact with the peritoneuni. There is 
 still no organic connection between the 
 central coagulum and the convoluted wall ; 
 biit the partial condensation of the clot and. 
 the continued folding of the wall prevent the 
 separation of the two being so easily accom- 
 plished as before, though it may still be 
 effected by careful management. The entire corpus luteum may 
 also still be extracted from its bed in the ovarian tissue. 
 
 The color of the convoluted wall, during th# early part of this 
 retrograde stage, instead of fading, like that of the fibrinous coagu- 
 lum, becomes more strongly marked. From having a dull yellowish 
 or rosy hue, as at first, it gradually as- 
 sumes a brighter and more decided yellow. 
 This change of color in the convoluted 
 wall is produced in consequence a^ a 
 kind of fatty degeneration which takes 
 place in its texture ; a large quantity of oil- 
 globules being deposited in it at this time, 
 as may be readily recognized under the 
 microscope. At the end of the fourth 
 week, this alteration in hue is complete ; 
 and the outer wall of the. corpus luteum 
 is then of a clear chrome-yellow color, by „„.., .v„„,„„ , 
 
 •' ' M/ OvABT, sDowiav corpus 111- 
 
 which it is readily distinguished from alk tenm, Binn weeks atjer meiBlma. 
 
 the neighboring tissues. 
 
 After this period, the process of atrophy 
 and degeneration goes on rapidly. The clot becomes constantly 
 
 Fig. 190. 
 
 tinn ; frnm a girl dead of tuber- 
 cular ineniugitia. 
 
580 MENSTEQATION AND PREGNANCY. 
 
 more dense and shrivelled, and is soon converted into a minute, 
 titellate, white, or reddish-white cicatrix. The yellow wall becomes 
 softer and more friable, as is the case with all tissues undergoing 
 fatty degeneration, and shows less distinctly the marking of its 
 convolutions. At the same time its surfaces become confounded 
 with the central coagulum on the one hand, and with the neigh- 
 boring tissues on the other, so that it is no longer possible to separate 
 thetn fairly from each other. At ther end of eight or nine weeks 
 (Fig. 190) the whole body is reduced to the condition of an insignifi- 
 cant; yellowish, cicatrix-like spot, measuring less than a quarter of 
 an inch in its longest diameter, in which the original texture of the 
 corpus luteum can be recognized only by the peculiar folding and 
 coloring of its constituent parts. Subsequently its atrophy goes on 
 in a less active manner, and a period of seven or eight months some- 
 times elapses before its final and complete disappearance. 
 
 The corpus luteum, accordingly, is a formation which results 
 .from the filling up and obliteration of a ruptured Graafian follicle. 
 Under ordinary .conditions, a corpus luteum is produced at every 
 menstrual period ; and notwithstanding the rapidity with which it 
 retrogrades and becomes atrophied, a new one is always formed 
 before its predecessor has completely disappeared. 
 
 When, therefore, we examine the ovaries of a healthy female, in 
 whom the menses have recurred with regularity for some time 
 previous to death, several corpora lutea will be met with, in different 
 stages of formation and atrophy. Thus we have found, under such 
 circumstances, four, five, six, and even eight corpora lutea in the 
 ovaries at the same time, perfectly distinguishable by their texture, 
 but very small, and most of them evidently in a state of advanced 
 retrogression. They finally ^sappear altogether, and the number 
 of those present in the ovary, therefore, no longer corresponds with 
 that of the Graafian follicles which have been ruptured. 
 
 II. CORPUS LUTEUM OF PEEGNANCY. 
 
 Since the process above described takes place at every menstrual 
 period, it is independent of impregnation and even of sexual inter- 
 course. The mere presence of a corpus luteum, therefore, is no 
 indication that pregnancy has existed, but only that a Graafian 
 follicle has been ruptured and its contents discharged. We find, 
 nevertheless, .that when pregnancy takes place, the appearance of 
 the corpus luteum becomes so much altered as to be readily dis- 
 
CORPUS LUTEUM OP PREGNANCY. 581 
 
 tinguished from that which simply follows the ordinary menstrual 
 process. It is proper, therefore, to speak of two kinds of corpora 
 lutea ; one belonging to menstruation, the other to pregnancy. 
 
 The difference between these two kinds of corpora lutea is not 
 an essential or fundamental difference ; since they both originate in 
 ,the same way, and are composed of the same structures. It is, 
 properly speaking, only a difference in the degree and rapidity of 
 their development. For while the corpus luteum of menstruation 
 passes rapidly through its different stages, and is very soon reduced 
 to a condition of- atrophy, that of pregnancy continues its develop- 
 ment for a long time, attains a larger size and firmer organization, 
 and disappears finally only at a much later period. 
 
 This variation in the development and history of the corpus 
 luteum depends upon the unusually active condition of the pregnant 
 uterus. This organ exerts a powerful sympathetic action, during 
 pregnancy, upon many other parts of the system. The stomach 
 becomes irritable, the appetite is capricious, and even the mental 
 faculties and the moral disposition are frequently more or less 
 affected. The ovaries, however, feel the disturbing influence of 
 gestation more certainly and decidedly than the other organs, since 
 they are more closely connected with the uterus in the ordinary 
 performance of their function. The moment that pregnancy takes 
 place, the process of menstruation is arrested. " No more eggs come 
 to maturity, and no more Graafian follicles are ruptured, during the 
 whole period of gestation. It is not at all singular, therefore, that 
 the growth of the corpus luteum should also be modified, by an 
 influence which affects so profoundly the system at large, as well 
 as the ovaries in particular. 
 
 During the first three weeks of its formation, the growth of the 
 corpus luteum is the same in the impregnated as in the unimpreg- 
 nated condition. After that time, however, a difference becomes 
 manifest. Instead of commencing a retrograde course during the 
 fourth week, the corpus luteum of pregnancy continues its deve- 
 lopment. The external wall grows thicker, and its convolutions 
 more abundant. Its color alters in the same way as previously 
 described, and becomes a bright yellow by the deposit of fatty 
 matter in microscopic globules and granules. 
 
 By the end of the second month, the whole corpus luteum has 
 increased in size to such an extent as to measure seven-eighths of 
 an inch in length by half an inch in depth. (Fig. 191.) The central 
 coagulum has by this time become almost entirely decolorized, so as 
 
582 
 
 MENSTRUATION AND PREGNANCY, 
 
 Corpus Lptbum of pregnancy, at end of pecond 
 month ; from a woman dead from induced abortion. 
 
 to present the appearance of a purely fibrinous deposit. .Sometimes 
 we find that a part of the serum, during its separation from the clot, 
 has accumulated in the centre of the mass, as in Fig. 191, forming a 
 
 little cavity containing" a few 
 Fig- 191- drops of clear fluid and in- 
 
 closed by ar whitish, fibrinous 
 layer, the remains of the solid 
 portion of the clot. It is 
 this fibrinous layer which has 
 sometimes been mistaken for 
 a distinct organized mem- 
 brane, lining the internal sur- 
 face of the convoluted wall, 
 and which has thus led to 
 the belief that the yellow 
 matter of the corpus luteum is normally deposited outside the mem- 
 brane of the Graafian follicle. Such, however, is not its real struc- 
 ture. The convoluted wall of the corpus luteum is the mem])rane 
 of the follicle itself, partially altered by hypertrophy, as may be 
 readily seen by examination in the earlier stages of its growth ; and 
 
 the fibrinous layer, situated 
 internally, is the original 
 bloody coagulum, decolorized 
 and condensed by continued 
 absorption. The existence of 
 a central cavity containing 
 serous fluid, is merely. an oc- 
 casional, not a constant pheno- 
 menon. More frequently, the 
 fibrinous clot is solid through- 
 out, the serum being gradually 
 absorbed, as it separates spon- 
 taneously from the coagulum. 
 During the third and fourth 
 months, the enlargement of the corpus luteum continues ; so that at 
 the end of that time it may measure seven-eighths of an inch in 
 length by three-quarters of an inch in depth. (Fig. 192.) The con- 
 voluted wall is still thicker and more highly developed than before, 
 having a thickness, at its deepest part, of three-sixteenths of an inch. 
 Its color, however, has already begun to fade, and is now of a dull 
 yellow, instead of the bright, clear tinge which it previously ex- 
 
 Fig. 192. 
 
 Corpus Lutbcm of pfegnaiicy, at end of fourth 
 month ; from a woman dead hf polBou. 
 
CORPUS LUTEUM OF PBEGNANCY. 
 
 583 
 
 Fig. 193. 
 
 Hbited. The central coagulum, perfectly colorless and fibrinous 
 in appearance, is often so much flattened by the lateral compres- 
 sion of its mass, that it has hardly a line in thickness. The other 
 relations of the different parts of the corpus luteum remain the 
 same. 
 
 The corpus luteum has now attained its maximum of develop- 
 ment, and remains without any very perceptible alteration during 
 the fifth and sixth months. It then begins to retrograde, diminish- 
 ing constantly in size during the seventh and eighth months. Its 
 external wall fades still more perceptibly in color, becoming of a 
 faint yellowish white, not unlike that which it presented at the end 
 of the third week. Its texture is thick, soft, and elastic, and it is 
 still strongly convoluted. An abundance of fine red vessels can be 
 seen penetrating from the exterior into the 
 interstices of its convolutions. The central 
 coagulum is reduced, by this time to the 
 condition of a whitish, radiated cicatrix. 
 
 The atrophy of the organ continues dur- 
 ing the ninth month. At the termination of 
 pregnancy, it is redticed to the size of half 
 an inch in length and three-eighths of an 
 inch in depth. (Fig. 193.) It is then of a 
 faint indefinite hue, but little contrasted 
 with the remaining tissues of the ovary. 
 The central cicatrix has become very small, 
 and appears only as a thin whitish lamina, 
 with radiating processes which run in be- 
 tween the interstices of the convolutions. 
 The whole mass, however, is still quite firm 
 and resisting to the touch, and is readily 
 distinguishable, both from its size and tex 
 
 ture, as a prominent feature in the ovarian tissue, and a reliable 
 indication of pregnancy. The convoluted structure of its external 
 wall is very perceptible, and the point of rupture, with its external 
 peritoneal cicatrix, distinctly visible. 
 
 After delivery, the corpus luteum retrogrades rapidly. At the 
 end of eight or nine weeks, it has become so much altered that its 
 color is no longer distinguishable, and only faint traces of its con- 
 voluted structure are to be discovered by close examination. These 
 traces may remain, however, for a long time afterward, more or less 
 
 GoRPUB Luteum of preg- 
 nancy, at term ; from a woman 
 dead in delivery from rupture 
 of the uterus. 
 
584: MENSTRUATION AND PREGNANCY. 
 
 concealed in tlie ovarian tissue. We have distinguished them so 
 late as nine and a half months after delivery. They finally disap- 
 pear entirely, together with the external cicatrix which previously 
 marked their situation. 
 
 During the existence of gestation, the process of menstruation 
 being suspended, no new follicles are ruptured, and no new corpora 
 lutea are produced ; and as the old ones, formed before the period of 
 conception, gradually fade and disappear, the corpus luteum which 
 marks the occurrence of pregnancy after a short time exists alone 
 in the ovary, and is not accompanied by any others of older date. 
 In twin pregnancies, we of course find two corpora lutea in the 
 ovaries ; but these are precisely similar to each other, and, being 
 evidently of the same date, will not give rise to any confusion. 
 Where there is but a single foetus in the uterus, and the ovaries 
 contain two corpora lutea of similar appearance, one of them 
 belongs to an embryo which has been blighted by some accident 
 in the early part of pregnancy. The remains of the blighted em- 
 bryo may often be discovered, in such cases, in some part of the 
 Fallopian tubes, where it has , been arrested in its descent toward 
 the uterus. 
 
 After the process of lactation comes to an end, the ovaries again 
 resume their ordinary function. The Graafian follicles mature and 
 rupture in succession, as before, and new corpora lutea follow each 
 other in alternate development and disappearance. 
 
 We find, then, that the corpus luteum of menstruation differs from 
 that of pregnancy, in the extent of its development and the dura- 
 tion of its existence. While the forrtier passes through all the im- 
 portant phases of its growth and decline in the period of two 
 nionths, the latter lasts from nine to ten months, and presents, 
 during a great portion of the time, a larger size and a more solid 
 organization. It will be observed that, even with the corpus 
 luteum of pregnancy, the bright yellow color, which is so import- 
 ant a characteristic, is only temporary in its duration ; not making 
 its appearance till about the end of the fourth week, and again 
 disappearing after the sixth, month. 
 
 The following table contains, in a brief form, the characters of 
 the corpus luteum, as belonging to the two different conditions of 
 menstruation and pregnancy, corresponding with different periods 
 of its development. 
 
COEPUS LUTEUM OF rREGNANOY. 
 
 585 
 
 At the end of 
 three weeks 
 One month 
 
 Two months 
 
 Six months 
 
 Nine months 
 
 CoRins LnTECM of Menstedatiox. Coefus Luteum of Peerxascy. 
 
 Three-qnarters of an inch in diameter ; central clot reddish ; con- 
 voluted wall pale. 
 Smaller ; convoluted wall bright ' Larger ; convoluted wall bright 
 
 yellow ; clot still reddish. 
 
 yv 
 
 How ; clot still reddish. 
 
 Reduced to the condition of an "Seven-eighths of an inch in dia- 
 
 insignificant oicatilz. 
 
 Absent. 
 
 Absent. 
 
 meter ; convoluted wall bright 
 yellow ; clot perfectly decolor- 
 ized. 
 
 Still as large as at end of second 
 month ; clot fibrinous ; convo- 
 luted wall paler. 
 
 One-half an inch in diameter; 
 central clot converted into a 
 radiating cicatrix ; the external 
 wall tolerably thick and con vo 
 luted, but without any bright 
 yellow color. 
 
586 DEVELOPMENT OF THE IMPREGNATED EGG. 
 
 CHAPTEE VII. 
 
 ON THE DEVELOPMENT OF THE IMPREGNATED 
 EGG— SEGMENTATION OP. THE VITELLUS— BLAS- 
 TODERMIC MEMBRANE— FORMATION OF ORGANS 
 IN THE FROG., 
 
 We have seen, in the foregoing chapters, how the egg, produced 
 in the ovarian folliclei, becomes gradually developed and ripened, 
 until it is ready' to be discharged. The egg, accordingly, passes 
 through several successive stages of formation, even while still con- 
 tained within the ovary ; and its vitellus becomes gradually com- 
 pleted> by the formation of albuminous material and the deposit of 
 molecular granulations. The last change which the egg undergoes, 
 in this situation, and that which marks its complete maturity, is the 
 disappearance of the germinative vesicle. This vesicle, which is, in 
 general, a prominent feature of the ovarian egg, disappears but a 
 short time previous to its discharge, or even. just at the period of 
 its leaving the Graafian follicle. 
 
 The egg, therefore, consisting simply of the mature vitellus and 
 the vitelline membrane, comes in contact, after leaving the ovary, 
 and while passing through the Fallopian tube, with the spermatic 
 fluid, and is thereby fecundated. By the influence of fecundation, 
 a new stimulus is imparted to its growth ; and while the vitality 
 of the unimpregnated germ, arrived at this point, would have 
 reached its termination, the fecundated egg, on the. contrary, 
 starts upon a new and more extensive course of development, by 
 which it is finally converted into the body of the young animal. 
 
 The egg, in the first place, as it passes down the Fallopian tube, 
 becomes covered with an albuminous secretion. In the birds, as we 
 have seen, this secretion is very abundant, and is deposited in suc- 
 cessive layers around the vitellus. In the reptiles, it is also poured 
 out in considerable quantity, and serves for the nourishment of the 
 egg during its early growth. In quadrupeds, the albuminous matter 
 is supplied in the same way, though in smaller quantity, by the 
 
SEGMEKTATIOX OF THE VlTEl.LUS. 
 
 587' 
 
 Fig. 194. 
 
 mucous membrane of the Fallopian tubes, and envelopes the egg 
 in a layer of nutritious material. 
 
 A very remarkable change now takes place in the impregnated egg, 
 which is known as the spontaneous division, or segmentation, of the 
 vitellus. A furrow first shows itself, 
 running round the globular mass of the 
 vitellus in a vertical direction, which 
 gradually deepens until it has divided 
 the vitellus into two separate halves or 
 hemispheres. (Fig. 194, a.) Almost at 
 the same time another furrow, run- 
 ning at right angles with the first, 
 penetrates also the substance of the 
 vitellus and cuts it in a transverse 
 direction. The vitellus is thus divided 
 into four equal portions (Fig. 194, h), 
 the edges and aingles of which are 
 rounded off, and which are still con- 
 tained in the cavity of the vitelline 
 membrane. The spaces between 
 them and the internal surface of the 
 vitelline membrane are occupied by 
 a transparent fluid. 
 
 The process thus commenced goes 
 on by a successive formation of fur- 
 rows and sections, in various direc- 
 tions. The four vitelline segments 
 already produced are thus subdivided 
 into sixteen, the sixteen into sixty- 
 four, and so on ; until the whole vi- 
 tellus is converted into a mulberry- 
 shaped mass, composed of minute, 
 nearly spherical bodies, which are 
 called the "vitelline spheres." (Fig. 
 194, c.) These vitelline spheres have 
 a somewhat firmer consistency than 
 
 the original substance of the vitellus ; SEQMB.vTATioir of the vitblujb. 
 and this consistency appears to in- 
 crease, as they successively multiply in numbers and diminish in 
 size. At last they have become so abundant as to be closely 
 crowded together, compressed into polygonal forms, and flattened 
 
588 DEVELOPMEXT OF THE IMPKEGNATED EGG. 
 
 against the internal surface of the vitelline membrane. (Fig 194, d.) 
 They have by this time been converted into true animal cells ; and 
 these cells, adhering to each other by their adjacent edges, form a 
 continuous organized membrane, which is termed the Blastodermic 
 membrane. 
 
 During the formation of this membrane, moreover, the egg, while 
 passing through the Fallopian tubes into the uterus, has increased 
 in size. The albuminous matter with which it was enveloped has 
 liquefied ; and, being absorbed by endosmosis through the vitelline 
 membrane, has furnished the materials for the more solid and ex- 
 tensive growth of the newly-formed structures. It may also be 
 seen that a large quantity of this fluid has accumulated in the 
 central cavity of the egg,' inclosed accordingly by the blastodermic 
 membrane, with the original vitelline membrane still forming an 
 external envelope round the whole. 
 
 The next change which takes place consists in the division or 
 splitting of the blastodermic membrane into two layers, which are 
 known as the external and internal layers of the blastodermic membrane. 
 They are both still composed exclusively of cells ; but those of the 
 external layer are usually smaller and more compact, while those 
 of the internal kre rather larger arid looser in texture; The egg 
 then presents the appearance of a globular sac, the walls of which 
 consist of three concentric layers, lying in contact with and inclos- 
 ing each other, viz., 1st, the structureless vitelline membrane on the 
 outside ; 2d, the external layer of the blastodermic membrane, com- 
 posed of cells ; and 3d, the internal layer Of the blastodermic mem- 
 brane, also composed of cells. The cavity of the egg is occupied 
 by a transparent fluid, as above mentioned. 
 
 This entire process of the segmentation of the vitellus and the 
 formation of the blastodermic membrane is one of the most re- 
 markable and important of all the changes which tjike place during 
 the development of the egg. It is by this process that the simple 
 globular mass of the vitellus, composed of an albuminous matter 
 and oily granules, is converted into an organized structure. For 
 the blastodermic membrane, though consisting only of cells nearly 
 uniform in size and shape, is nevertheless a truly organized mem- 
 brane, made up of fully formed anatomical elements. It is, more- 
 over, the first sign of distinct organization which makes its appear- 
 ance in the egg ; and as soon as it is completed, the body of the 
 new foetus is formed. The blastoderpiic membrane is, in fact, the 
 body of the foetus. It is at this time, it is true, exceedingly simple 
 
BLASTODEKMIC MEMBRANE. 589 
 
 in texture ; but we shall see hereafter that all the future organs! 
 of the body, however varied and complicated in structure, arise out 
 of it, by modification and development of its different parts. 
 
 The segmentation of the vitellus, moreover, and the formation 
 of the blastodermic membrane, take place in essentially the same 
 manner in all classes of animals. It is always in this way that 
 'the egg commences its development, whether it be destined to 
 form a;fterward a fish or a reptile, a bird, a quadruped, or a man. 
 The peculiarities belonging to difierent species show themselves 
 afterward, by variations in the manner and extent of the develop- 
 ment of different parts. In the higher animals and in the human 
 subject the development of the egg becomes an exceedingly com- 
 plicated process, owing to the formation of various accessory 
 organs, which are made requisite by the peculiar conditions under 
 which the development of the embryo takes place. It is, in fact, 
 impossible to describe or understand properly the complex embry- 
 ology of the quadrupeds, and more particularly that of the human 
 subject, without first tracing the development of those species in 
 which the process is more simple. We shall commence our descrip- 
 tion, therefore, with the development of the egg of the frog, which 
 is for many reasons particularly appropriate for- our purpose. 
 
 The egg of the frog; when discharged from the body of the female 
 and fecundated by the spermatic fluid of the male, is deposited in 
 the water, enveloped in a soft elastic cushion of albuminous sub- 
 stance. It is therefore in a situation where it is freely exposed to 
 the light, the air, and the moderate warmth of the sun's rays, and 
 where it can absorb directly an abundance of moisture and appro- 
 priate nutritious material. We find accordingly that under these 
 circumstances the development of the egg is distinguished by a 
 character of great simplicity; since the wfiote of the vitellus is 
 diivctly converted into the body of the embryo. There are no acces- 
 sory organs required, and consequently no complication of the 
 formative process. 
 
 The two layers of the blastodermic membrane, above described, 
 
 represent together the commencement of all the organs of the foetus. 
 
 They are intended, however, for the production of two different 
 
 systems ; and the entire process of their development may be ex- 
 
 /pressed as follows : I7ie external layer of the blastodermic membrane 
 
 ( produces the spinal column and all the organs of animal life; while the 
 
 } internal layer produces the intestinal canal, and all the organs of vege- 
 
 \ tative life. . 
 
590 DEVELOPMENT OP THE IMPREGNATED EGG. 
 
 The first sign of advancing organization in the external layer of 
 the blastodermic membrane shows itself in a thickening and con- 
 densation of its structure. This thickened portion has the form of an 
 elongated oval-shaped spot, termed the " embryonic spot" (Fig. 195), 
 
 the wide edges of which are somewhat 
 Fig. 195. more opaque than the rest of the blasto- 
 
 dermic niembrahe. Inclosed within» 
 these opaque edges is a narrower color- 
 less and transparent space, the ''area 
 pellucida," and in its centre is a delicate 
 line, or furrow, running longitudinally 
 from front to rear, which is called the 
 "primitive trace." 
 
 ■ On each side of the primitive trace, 
 IMPREGNATED E«a. ,,uh Com- 1° t^^ atca pellucida, the substance of 
 mencement of formation of embryo:, the blastodermic membrane piscs UD in 
 
 showing embryonic Rpot, area pella- ., . n , i 
 
 oi<ia,aadpri.nuiveinice. such & manner as to form two n6arly 
 
 parallel vertical plates or ridges, which 
 approach each other over the dorsal aspect of the foetus and are 
 therefore called the "dorsal plates." They at last meet on the 
 median line, so as to inclose the furrow above described and con- 
 vert it into a canal. This afterward becomes the spinal canal, and 
 in its cavity is formed the spinal cord, by a deposit of nervous . 
 matter upon its internal surface. • At the anterior extremity of this 
 canal, its cavity is large and rounded, to aocohimodate the brain 
 and medulla oblongata ; at its posterior extremity it is narrow and 
 pointed, and contains the extremity of the spinal cord. 
 
 In a transverse section of the egg at this stage (Fig. 196), the 
 dorsal plates may be seen approaching each other above, on each 
 side of the primitive furrow or "trace." At a more advanced 
 period (Fig. 197) they may be seen fairly united with each other, 
 so as to inclose the cavity of the spinal canal. At the same time, 
 the edges of the thickened portion of the blastodermic membrane 
 grow outward and downward, so as to spread out more and more 
 over the lateral portions of the vitelline mass. These are called 
 the " abdominal plates ;" and as they increase in extent they tend 
 to unite with each other below and inclose the abdominal cavify, 
 just as the dorsal plates unite above, and inclose the -spinal canal. 
 At last the abdominal plates actually do unite with each other on 
 the median line (at i, Fig. 197), embracing of course the whole 
 internal layer of the blastodermic membrane (a), which incloses in 
 
FORMATION OP ORGANS. 
 
 591 
 
 its turn the remains of the original vitellus and the albuminous 
 fluid which has accumulated in its cavity. 
 
 Fig. 198. 
 
 Fig. 197. 
 
 Transverse section of Eaa in an earl^ 
 stage of derelopmeot.— 1. External lajrer 
 of blastodermic membrane. 2, 2. Dornal 
 plates. 3. Internal layer of bla-stodermic 
 membrane. 
 
 Impkuohatbt) Eoo, at a soinevbat 
 more advanced period. — 1. Umbilicus, or 
 point of union between abdominal plates. 
 2, 2. Dorsal plates united vritb eacb otber 
 on the median line and inclosing tbe spinal 
 canal. 3, 3. Abdominal plates. 4. Sec- 
 tion of spinal column, witb lamina) and 
 ribs. a. Internal layer of blastodermic 
 membrane. 
 
 During this time, there is formed, in the thickness of the external 
 blastoderanio layer, immediately beneath the spinal canal, a longitu- 
 dinal cartilaginous cord, called the " chorda dorsalis." Around the 
 chorda dorsalis are afterwai-d developed the bodies of the vertebras 
 (Fig. 197, 4), forming the chain of the vertebral column ; and the 
 oblique processes of the vertebrae run upward from this point into 
 tbe dorsal plates ; while the transverse processes, and ribs, run out- 
 ward and downward in the abdominal plates, to encircle more or 
 less completely the corresponding portion of the body. 
 
 If we now examine'the egg in longitudinal section, while this 
 J)rocess is going on, the thickened portion of the external blasto- 
 dermic layer may be seen in profile, as at i, I"ig. 198. The anterior 
 portion (2), which will form the head, is thicker than the posterior 
 (3), which will form the tail of the young animal. As the whole 
 mass grows rapidly, both in the anterior and the posterior direc- 
 tion, the head becomes very thick and voluminous, while the tail also 
 begins to project backward, and the whole egg assumes a distinctly 
 elongated form. (Fig. 199.) The abdominal plates at ihe same time 
 
592 
 
 DEVELOPMENT OF THE IMPREGNATED EGG. 
 
 meet upon its under surface, and the point at which they finally 
 unite forms the abdominal cicatrix or umbilicics. The internal blas- 
 todermic layer is seen, of course, in the longitudinal section of the 
 
 Fig. 198. 
 
 Diagram of Frog's Ego, in an early 
 Btage of development ; longitudinal sec- 
 tion.— 1. Thickened portion of external 
 blastodermic layer, forming body of fcetiis. 
 2. Anterior extremity offffitns. 3. Poste- 
 rior extremity. 4. Internal layer of blas- 
 todermic membrane. 5. Cavity of Titellus. 
 
 Fig. 199. 
 
 EoG OF Fboo, in process of develop- 
 ment. 
 
 egg, as well as in the transverse, embraced by the abdominal plates, 
 and inclosing, as before, the remains of the vitellus. 
 
 As the developinent of the above parts goes on (Fig. 200), the 
 head becomes sill larger, and soon shows traces of the formation 
 
 EoG OF F BOG, farther advanced. 
 
 of organs of special sense. The tail also increases in size, and pro- 
 jects farther from the posterior extremity* of the embryo. The 
 spinal cord runs in a longitudinal direction from front to rear, and 
 its anterior extremity enlarges, so as to form the brain and medulla 
 oblongata. ■ In the mean time, the internal blastodermic lay&r,.which 
 is subsequently to be converted into the intestinal canal, has been 
 shut in by the abdominal walls, and still forms a perfectly, closed 
 sac, of a slightly elongated figure, without either inlet or outlet. 
 Afterward, the mouth is formed by a process of atrophy and perfo- 
 ration, which takes place through both external and internal. layers, 
 
FORMATION OF OKGANS. 593 
 
 at the anterior extremity, while a similar perforatibn, at the poste- 
 rior extremity, results in the formation of the anus. 
 
 All these "parts, however, are as yet imperfect ; and, being merely 
 in the" course of formation, are incapable of performing any active 
 function. 
 
 By a Continuation of the same process, the different portions of 
 the external blastodermic layer are further developed, so as to re- 
 sult in the complete formation of the various parts of the skeleton, 
 the integument, the organs of special sense, and the voluntary 
 nerves and muscles. The tail at the same time acquires sufficient 
 size and strength to be capable of acting as an organ of locomo- 
 tion. (Kg. 201.) The intestinal canal, which has been formed from 
 
 Fig. 201. , 
 
 Tadpole fully-developed. 
 
 the internal blastodermic layer, is at first a short, wide, an^i nearly 
 straight tube, running directly from the mouth to the anus. It 
 soon, however, begins to grow faster than the abdominal cavity 
 which incloses it, becoming longer and narrower, and is at the 
 same time thrown into numerous convolutions. It thus presents 
 a larger internal surface for the performance of the digestive 
 process. 
 
 Arrived at this period, the young tadpole ruptures the vitelline 
 membrane, by which he has heretofore been inclosed, and leaves the 
 cavity of.the egg. He at first fastens himself upon the remains*bf 
 the albuminous matter deposited round the egg, and feeds upon itfor 
 a short period. He soon, however, acquires sufficient strength and 
 activity to swim about freely in search of other food, propelling 
 himself by means of his large, membranous, and muscular tail. 
 The alimentary canal increases very rapidly in length and becomes 
 spirally coiled up in the abdominal cavity, so as to attain a length 
 from seven to eight times greater than that of the entire body. 
 
 After a time, a change takes place in. the external form of the 
 young animal. The posterior extremities or limbs begin to show 
 38 
 
59rt DEVELOPMKST OJ^ THB IMPBEGNATED EGG. 
 
 themselves, by "budding or sprouting from the sides of the body, 
 just at the base of the tail. (Fig. 202.) The anterior extremities also 
 grow at this time, but are at first, concealed underneath the integu- 
 ment. They afterward, however, become liberated, and show them- 
 selves externally. At first both the fore and hind legs are very 
 small, imperfect in structure, and altogether useless for purposes of 
 locomotion. They soon, however, increase in size and strength; 
 and while they keep pace with the' increasing development; of the 
 ■whole body, the tail on the contrary ceases to grow, and becomes 
 shrivelled and atrophied. The limbs, in fact, are destined .finally 
 to replace the tail as organs of locomotion; and a time at last 
 arrives (Fig. 203) when -the tail has altogether disappeared, while 
 
 Fig. 202. Fig.- 203. 
 
 TiDFOi.E, with limbs he^innin^ to be formed. PcrfictFKOo. 
 
 the legs have become fully developed, muscular^ and powerful. 
 Then the animal, which was before confined to an aquatic mode 
 of life, becomes capable of living also upon land, and a trans- 
 formation is thus efi:ected from the tadpole into the perfect frog. 
 
 During the same time, other changes of an equally important 
 character have taken place in the internal organs. The tadpole at 
 first breathes by gills; but these organs subsequently become 
 atrophied and disappear, being finally replaced by well developed 
 lungs. The structure of the mouth, also, of the integument, and 
 of the circulatory system, is altered to correspond with the varying 
 conditions and wants of the growing animal ; and all these changes 
 taking place in part successively and in part simultaneously, 
 bring the animal at last to a state of complete formation. 
 
FOKMATION OF ORGANS IN THE FROG. 595 
 
 The process of development may then be briefly recapitulated as 
 follows : — 
 
 1. The blastodermic membrane, produced by the segmentation 
 of the vitellus, consists of two cellular layers, viz., an external and 
 an internal blastodermic layer. 
 
 2. The external layer of the blastodermic membrane incloses by 
 its dor*l plates the cerebro-spinal canal, and by its abdominal 
 plates the abdominal or visceral cavity. 
 
 3. The internal layer of the blastodermic membrane forms the 
 intestinal canal, which becomes lengthened and convoluted, and 
 communicates with the ejfterior by a mouth and anus of secondary 
 formation. 
 
 4 Finally the cerebro-spinal axis and its nerves, the skeleton 
 the organs of special sense, the integument, and the muscles, are 
 developed from the external blastodermic layer ; while the anterior 
 and posterior extremities are formed from the same layer by a pro- 
 cess of sprouting, or continuous growth. 
 
THE UMBILICAL VESICLE. 
 
 CHAPTER VIII. 
 
 THE UMBILICAL TESICLE. 
 
 Fig. 204. 
 
 In the frog, as we have* seen, the abdominal plates, closing 
 together in front and underneath the body of the, animal, shut in 
 directly the whole of the vitellus,, and join each other upon the 
 median line, at the umbilicus. The whole remains of the vitellus 
 are then inclosed in the abdomen of the animal, and in the intestinal 
 sac formed by the internal blastodermic layer. 
 
 In many instances, however, as, for example, in several kinds of 
 fish, and in all the birds and quadrupeds, the abdominal plates do 
 * not immediately embrace the whole of 
 
 the vitelline mass, but tend to close 
 together about its middle; so that, the 
 vitellus is constricted, in this way, and 
 divided into two portions: one internal, 
 and one external. (Fig. 204.) • As the 
 process of development proceeds, the body 
 of the foetus increases in size, out of pro- 
 portion to the vitelline sac, and the con- 
 striction just mentioned becomes at the 
 same time more strongly marked ; so that 
 the separation between the internal and external portions of the 
 vitelline sac is nearly complete. (Fig. 205.) The internal layer of 
 the blastodermic membrane is by the same means divided- into 
 two portions, one of which fornis the intestinal canal, while the 
 other, remaining outside, forms, a sac-like appendage to the abdo- 
 men, which is known by the name of the vmhilical vesicle. 
 
 The umbilical vesicle is accordingly lined by a portion of the 
 internal blastodermic layer, continuous with the mucous membrane 
 of the intestinal canal ; while it is covered on the outside by a por- 
 tion of the external blastodermic layer, continuous with the integu- 
 ment of the abdomen. 
 
 Eggof Fish, showing forma- 
 tion of umbilical vesicle. 
 
THE UMBILICAL VESICLE. 697 
 
 After the young animal leaves the egg, the umbilical vesicle 
 in some species becomes withered and atrophied by the absorption 
 of its contents; while in others, the abdominal walls gradually 
 
 Fig. 205. 
 
 YouDg Fish with umbilical vesicle. 
 
 extend over it, and crowd it back into the abdomen ; the nutritious 
 matter which it contained passing from the cavity of the vesicle 
 into that of the intestine by the narrow passage or canal which 
 remains open between them. 
 
 In the human subject, however, as well as in the quadrupeds, the 
 umbilical vesicle becomes more completely separated from the abdo- 
 men than in the cases just mentioned. There is at first a wide com- 
 munication between the cavity of the umbilical vesicle and that of 
 the intestine ; and this communication, as in other instances, becomes 
 gradually narrowed by the increasing constriction of the abdominal 
 walls. Here, however, the constriction proceeds so far that the 
 opposite surfaces of the canal come in contact with each other, and 
 adhere ; so that the narrow passage previously 
 existing, between the cavity of the intestine 
 and that of the umbilical vesicle, is obliterated, 
 and the vesicle is .then connected with the 
 abdomen only by an impervious cord. This 
 cord afterward elongates, and becomes con- 
 verted into a slender, thread-like pedicle (Fig. 
 206), passing out from the abdomen of the 
 foetus, and connected by its farther extremity 
 with the umbilical vesicle, which is filled with 
 a transparent, colorless fluid. The umbilical ^^^.^HiZllT^ioZb^ 
 vesicle is very distinctly visible in the human fifth week, 
 foetus so late as the end of the third month. 
 After that period it diminishes in size, and is gradually lost in the 
 advancing development of the neighboring parts. 
 
 In the formation of the umbilical vesicle, we have the first varia- 
 
598 THE UMBILICAL VESICLE. 
 
 tion from the simple plan of development described in the preceding 
 chapter. Here, the whole of the vitellus is not directly converted 
 into the body of the embryo; but while a part of it is taken, as 
 usual, into the abdominal cavity, and used immediately for the 
 purposes of nutrition, a part is leil outside the abdomen, in the 
 umbilical vesicle, a kind of secondary organ or appendage of the 
 foetus. The contents of the umbilical vesicle, however, are after- 
 ward absorbed, and so appropriated, finally, to the nourishment of 
 the newly-formed tissues. 
 
AMNION AND ALLANTOIS. 599 
 
 CHAPTER IX. 
 
 AMNION AND ALL ANTOIS.— DEVELOPMENT OP 
 THE CHICK. 
 
 We shall now pr«ceed to the description of two other accessory 
 organs, which are formed, during the development of the fecundated 
 egg, in all the higher classes of animals. These are the amnion and 
 the allantois; two organs which are always found in company with 
 each other, since the object of the first is to provide for the forma- 
 tion of the second. The amnion is formed from the external layer 
 of the blastodermic membrane, the allantois from the internal layer. 
 
 In the frog and in fish, as we have seen, the egg is abundantly 
 supplied with moisture, air, and nourishment, by the water with 
 which it is surrounded. It can absorb directly all the gaseous and 
 liquid substances, which it requires for the purposes of nutrition 
 and growth. The absorption of oxygen, the exhalation of carbonic 
 acid, and the imbibition of albuminous and other liquids, can all 
 take place without difiiculty through the simple membranes of the 
 egg; particularly as the time required for the formation of the 
 embryo is very short, and as a great part of the process of develop- 
 ment remains to be accomplished after the young animal leaves 
 the egg. 
 
 But in birds and quadrupeds, the time required for the develop- 
 ment of the foetus is longer. The young animal also acquires a 
 much more perfect organization during the time that it remains 
 inclosed within the egg ; and {he processes of absorption and exha- 
 lation necessary for its growth, being increased in activity to a 
 corresponding degree, require a special organ for their accomplish- 
 ment. This special organ, destined to bring the blood of the foetus 
 into relation with the atmosphere and external sources of nutrition, 
 is the allantois. 
 
 In the frog and the fish, the internal blastodermic layer, forming 
 the intestinal mucous membrane, is inclosed everywhere, as above 
 described, by the external layer, forming the integument; and 
 
600 AMNION AND ALLANTOIS. 
 
 consequently it can nowhere come in contact ■with the investing 
 membrane of the egg. But in the higher animals, the internal 
 blastodermic layer, which is the seat of the greatest vascularity, 
 and which is destined to produce the allantois, is made to come in 
 contact with the external membrane of the egg for purposes of 
 exhalation and absorption ; and this can only be acconfplished by 
 opening a passage for it through the external germinative layer. 
 This is done in the following manner, by *the formation, of the 
 amnion. 
 
 Soon after the body of the foetus has begun to be formed by the 
 thickening of the external , layer of the blastodermic membrane, 
 a double fold of this external lay^r rises upi on all sides about 
 the edges of the newly -formed embryo ; so that the body of the 
 foetus appears as if sunk in a kind of depression, and surrounded 
 with a membranous ridge or embankment, as in 
 Fig. 207. Fig. 207. The embryo (c) is here seen in profile, 
 
 with the double membranous folds, above, men- 
 tioned, rising up just in advance of the head, 
 and behind the posterior extremity. It must be 
 understood, of course, thafi the same thing takes 
 place on the two sides of the foetus, by the forma- 
 Diagram of fkcuh- tiou of lateral folds simultaneously with the 
 ZIZI'^'.^I appearance of those in front and behind. As it 
 a, viteiius.' 6. External jg theso folds which are destined to form, the 
 
 layer" cff blastodermic • j1 hi j_i h • j.' /* u » 
 
 membrane, o. Body of amniou, they are called the "amniotic folds." 
 embryo, d, d. Amniotic TJie amuiotic folds continue to grow, and ex- 
 b'rane. tend themselves, forward, backward, and laterally, 
 
 until they approach each other at a point over 
 the back of the foetus (Fig. 208), which is termed, the " amniotic 
 umbilicus." Their opposite edges afterward actually come in con- 
 tact with each other at this point, and adhere together, so as to 
 shut in a space or cavity (Fig. 208, 6) between their inner surface 
 and the body of the foetus. This spate, which is filled with a clear 
 fluid, is called the amniotic cavity. At the same time, the intestinal 
 canal has begun to be formed, and the umbilical vesicle has been 
 partially separated from it, by the constriction of the abdominal 
 walls on the under surface of the body. 
 
 There now appears a prolongation or diverticulum (Fig. 208, c) 
 growing out from the posterior portion of the intestinal canal, and 
 following the course of the amniotic fold which has precede^ it; 
 occupying, as it gradually enlarges and protrudes, the space left 
 
AMNION AND ALLANTOIS. 
 
 601 
 
 Froitndated Ego, 
 ^rther advanced. — a. 
 Umbilical - vesicle. &. 
 Amniotic cavity, n, Al- 
 lantois. 
 
 Fig. 209. 
 
 vacant by the rising up of the amnibtio fold. This diverticulum 
 is the commencement of the allantois. It is an elongated mem- 
 branous sac, continuous with the posterior portion of the intestine, 
 and containing bloodvessels derived from those 
 o,f the intestinal circulation. The cavity of the 
 allantois is also continuous with the cavity of 
 the intestine. 
 
 After the amniotic folds have approached and 
 touched each other, as already described, over 
 the back of the foetui, at the amniotic umbilicus, 
 the adjacent surfaces, thus brought in contact, 
 fuse together, so that the cavities of the two 
 folds, coming respectively from front and rear, 
 are separated only by a single membranous par- 
 tition (Fig. 209, c) running from the inner to the 
 outer lamina of the amniotic folds. This parti- 
 tion itself soon after atrophies and disappears ; and the inner and 
 outer laminae become consequently separated from each other. The 
 inner laniina (Fig. 209, o) which remains con- 
 tinuous with the integument of the fcetu«) in- 
 closing the body of the embryo in a distinct 
 cavity, is called the amnion (Fig. 210, b), and 
 its cavity is known as the amniotic cavity. 
 The outer lamina of the amniotic fold, on the 
 other hand (Fig. 209, b), recedes farther and 
 farther from the inner, until it comes in con- 
 tact with the original vitelline membrane, still 
 covering the exterior of the egg ; and by con- 
 tinued growth and expansion it at last fuses 
 with the vitelline membrane and unites with 
 its substance, so that the two membranes form 
 but one. This membrane, formed by the fusion 
 and consolidation of two others, constitutes then 
 the external investing membrane of the egg. 
 
 The allantois, during all this time, j|||^ncreas- 
 ing in size and vascularity. Following the course of the amniotic 
 folds as before, it insinuates itself between them, and of course soon 
 comes in contact with the external investing membrane just de- 
 scribed. It then begins to expand laterally in every direction, 
 enveloping more and more the body of the foetus, and bringing its 
 vessels into contact with the external membrane of the egg. 
 
 Fecundated Ego, 
 with allantois nearly com- 
 plete. — a. Inner lamina of 
 amniotic fold. b. Outer la^- 
 inina of ditto, c. Point 
 where the amniotic folds 
 comO in contact. Thealliin- 
 toiB is seeu penetrating be- 
 tween the inner and outfr 
 laminae of the amniotic 
 folds. 
 
602 AMNION AND ALLANTOIS. 
 
 By a continuation of the" above process, the allantois at last 
 grows to such an extent as to envelope completely the body of the 
 embryo, together with the amnion ; its two 
 Fig. 210. extremities coming in contact with each 
 
 other and fusing together over the back qf 
 the foetus, just as the- amniotic folds had 
 previously done. (Fig. 210.) It lines, there- 
 fore, the whole internal surface of the in- 
 vesting membrane with a flattened, vascu- 
 lar sac, the vessels of which come from the 
 interior of the body of the foetus, and which 
 FEonxDl^^EGo, with still communicates with the cavity of the 
 
 allantois fully formed. -a. Um- intOStiual Caual. 
 
 bllical vesicle. 6. Amnion, v. ._.. , . , - , ^ . , . * 
 
 Allantois. It IS cvidcnt, irom the above description, 
 
 that there is a close connection between the 
 formation of the amnion and that of the allantois. For it is only 
 in this manner that the allantois, which is an extension of the in- 
 ternal layer of the blastodermic membrane, can come to be situated 
 outside the foetus and the amnion, and be brought into relation 
 with external surrounding, media. The two laminas of the amni- 
 otic folds, in fact, by separiating from each other as above described, 
 open a passage for the allantois, and allow it to come in contact 
 with the external membrane of the egg. 
 
 In order to explain more fully the physiological action of the 
 allantois, we shall now proceed to describe the process of develop- 
 ment, as it takes place in the egg of the fowl. 
 
 In order that the embryo may be properljj developed in any 
 case, it is essential that it be freely supplied with air, warmth, 
 moisture, and nourishment. The egg of the fowl contains already, 
 when discharged from the generative passages, a suf&cient quantity 
 of moisture and albuminous material. The necessary warmth is 
 supplied by the body of the parent during incubation ; while the 
 atmospheric gases can pass and repass through the porous egg- 
 shell, and by endosmosis through the fibrous membranes which 
 line its cavity. * fp 
 
 When the egg is first laid, the vitellus, or yolk, is enveloped in 
 a thick layer of semi-solid albumen. On the commencement of 
 incubation, a liquefaction takes place in the albumen immediately 
 above that part of the vitellus which is occupied by the cicatri- 
 cula ; so that the vitellus rises or floats upward toward the surface, 
 by virtue of its specific gravity, and the cicatricula comes to be 
 
DEVELOPMENT OF THE CHICK. 603 
 
 \ 
 
 placed almost immediately underneath the lining membrane of the 
 egg-shell. As the cicatricula is the spot from which the process of 
 embryonic development commences, the body of the young foetus 
 is by this arrangement placed in the most favorable position for 
 the reception of warmth apd other necessary external influences 
 through the egg-shell. The liquefied albumen is also absorbed by 
 the vitelline membrane, and the vitellus thus becomes larger, softer, 
 and more diffluent than before the, commencement of incubation. 
 
 As soon as the circulatory apparatus of the embryo has been 
 fairly formed, two minute arteries are seen to run out from its 
 lateral edges and spread into the neighboring parts of the blasto- 
 dermic membrane, breaking up into inosculating branches, and 
 covering the adjacent portions of the vitellus with a plexus of 
 capillary bloodvessels. The space occupied in the blastodermic 
 membrane, on the surface of the vitellus, by these vessels, is called 
 the arm vasculosa. (Fig. 211.) It is of a nearly circular shape, 
 
 Fig. 211, 
 
 * 
 
 Eoa OF Fowl during early periods of incabatlon j showing the hody of the embryo, and the 
 area vasculosa partially covering the surface of the vitellus. 
 
 and is limited, on its outer edge, by a terminal vein or sinus, called 
 the " sinus terminalis." The blood is returned to the body of the 
 foetus by two veins which p^etrate beneath its edges, one near the 
 head and one near the tail. 
 
 The area vaftculosa tends to increase in extent, as the develop- 
 ment of the foetus proceeds and its circulation becomes more active. 
 It soon covers the upper half, or hemisphere, of the vitellus, and 
 the terminal sinus then runs like an equator round the middle of 
 the vitelline sphere. As the growth of the vascular plexus con- 
 
604 AMNION AND ALLANTOIS. 
 
 tinues, it passes this point, and embraces more and more of the in- 
 ferior, as well as of the superior hemisphere, the vessels converging 
 toward its under surface, until at last nearly the whole of the 
 vitellus is covered with a network of inosculating capillaries. 
 
 The function of the vessels of the area vasculosa is to absorh 
 nourishment from the cavity of the vitelline sac. As the albumen 
 liquefies during the process of incubation, it passes by endosmosis, 
 more and more abundantly, int,o the vitelline cavity; the whole 
 vitellus growing constantly larger and more fluid in consistency. 
 The blood of the foetus, then circulating in the vessels of the area 
 vasculosa, absorbs freely the oleagino-albuminous matters of the 
 vitellus, and, carrying them back to the foetus by the returning 
 veins, supplies the newly-formed tissues and organs with abun- 
 dance of appropriate nourishment. 
 
 During this period the amnion and the allantois have been also 
 in process of formation. At first the body of the foetus lies upon 
 its abdomen, as in, the cases previously described ; but, as it increases 
 in size, it alters its position so as to lie more upon its side. The 
 allantois then, emerging from the posterior portion of the abdominal 
 cavity, turns directly upward over the body of the foetu?, and comes 
 immediately in contact with the shell membrane. (Fig. 212.) It 
 
 ' Fig. 212. 
 
 Eaa OP Fowl at amore advanced period of develo^ent. The body of the f(ctas is enveloped 
 by the amnion, and has the umbilical vesicle hanging from its under surface; while the vascular 
 allantois is been turning upwai-d and spreading out over the internal surface of the shell-membraae. 
 
 then spreads out rapidly, extending toward the extremities and 
 down the sides of the egg, enveloping more and more completely 
 
DEVELOPMENT OF THE CHICK. 605 
 
 the foetus and the vitelline sac, and taking the place of the albumen 
 which has been liquefied and absorbed. 
 
 It will also be seen, by reference to the figure, that the umbilicai 
 vesicle is at the same time formed by the separation of part of the 
 vitellus from the abdomen of the chick ; and the vessels of the area 
 vasculosa, which were at first distributed over the vitellus, now 
 ramify, of course, upon the surface of the umbilical vesicle. 
 
 At last the allantois, by its continued growth, 'envelopes nearly 
 the whole of the remaining contents of the egg ; so that toward the 
 later periods of incubation, at whatever point we break open the 
 egg, we find the internal surface of the shell-membrane lined with 
 a vascular membranous expansion, supplied by arteries which 
 emerge from the abdomen of the foetus. 
 
 It is easy to see, accordingly, with what readiness the absorption 
 and exhalation of gases may take place by means of the allantois. 
 The air penetrates from the exterior through the minute pores of 
 the 'calcareous shell, and then acts upon the blood in the vessels of 
 the allantois very much in the same manner that the air in the minute 
 bronchial tubes and air- vesicles of the lungs acts upon the blood in 
 the pulmonary capillaries. Examination of the egg, furthermore, 
 at various periods of incubation, shows that changes take place in 
 it which are entirely analogous to those of respiration. 
 
 The egg, in the first place, during its development, loses water by 
 exhalation. > This exhalation is not a simple effect of evaporation, 
 but is the result of the nutritive changes going on in the interior 
 of the egg ; since it does not take place, except in a comparatively 
 slight degree, in unimpregnated eggs, or in those which are not 
 incubated, though they may be freely exposed to the air. The 
 exhalation of fluid is also essential to the processes of development, 
 for it has often been found, in hatching eggs by artificial warmth, 
 that if the air of the chamber in which they are inclosed become 
 unduly charged with moisture, so as to retard or jJrevent further 
 exhalation, the eggs readily become spoiled, and the development 
 of the embryo is arrested. The loss of weight during natural incu- 
 bation, principally due to the exhalation of water, has been found 
 by Baudrimont and St. Ange' to be over 15 per cent, of the entire 
 weight of the egg. • ^ 
 
 Secondly, the egg Absorbs oxygen and exhales carbonic acid. 
 The two observers mentioned above, ascertained that during eigh- 
 
 ' Du Dgvelopperaent du Foetus. .Paris, 1850, p. 143. 
 
606 AMMONAND ALLANTOIS. 
 
 teen days' incubation, the egg absorbs nearly 2 per cent, of its 
 weight of oxygen, while the quantity of carbonic acid exhaled from 
 the sixteenth to the nineteenth day of incubation amounts to no less 
 than 3 grains in the twenty-four hours.' It is curious to observe, 
 also, that in the egg during incubation, as well as in the adult 
 animal, more oxygen is absorbed than is returned by exhalation 
 under the form of carbonic acid. 
 
 It is evident, therefore, that a true respiration takes place, by 
 means of the allantois, through the jnembranes of the shell. 
 
 The allantois, however, is not simply an organ of respiration ; it 
 takes part also in the absorption of nutritious matter. As the pro- 
 cess of development advances, the skeleton of the young chick, at 
 first entirely cartilaginous, begins to ossify. The calcareous mat- 
 ter, necessary for this ossification, is, in all probability, derived from 
 the shell. The shell is certainly lighter and more fragile toward 
 the end of incubation than at first ; and, at the same time, the cal- 
 careous ingredients of the bones increase in quantity. The lime- 
 salts, requisite for the process of ossification, are apparently ab- 
 sorbed from the shell by the vessels of the allantois, and by' them 
 transferred to the skeleton of the growing chick ; so that, in the 
 same proportion that the former becomes weaker, the latter grows 
 stronger. This diminution in density of the shell is connected not 
 only with the development of the skeleton, but also with the final 
 escape of the chick from the egg. This deliverance is accomplished 
 mostly by the movements of the chick itself, which become, at a 
 certain period, sufficiently vigorous to br.eak out an opening in the 
 attenuated and weakened egg-shell. The first fracture is generally 
 accomplished by a stroke from the end of the bill ; and it is pre- 
 cisely at this point that the solidification of the skeleton is most 
 advanced. The egg-shell itself, therefore, which at first only serves 
 for the protection of the imperfectly-formed embryo, afterward 
 furnishes the Materials which are used to accomplish its own demo- 
 lition, and at the same time to eflect the escape of the fully deve- 
 loped foetus. 
 
 Toward the latter periods of incubation, the allantois becomes 
 more and more adherent to the internal surface of the shell-mem- 
 brane. At last, when the chick, arrived at the full period of de- 
 velopment, escapes from its confinement, the allantoic vessels are 
 torn off at the umbilicus ; and the allantois itself, cast off as a use- 
 
 t 
 
 » Pp. cjt., pp. 138 and 149. 
 
DKVELOPMENT OF THE CHICK, 607 
 
 less and effete organ, is left behind in the cavity of the abandoned 
 egg-shell. The allantois is, therefore, strictly speaking, a foetal 
 organ. Developed as an accessory structure from a portion of the 
 intestinal canal, it is exceedingly active and important during the 
 middle and latter periods of incubation ; but vsrhen the chick is 
 completely formed, and has become capable of carrying on an in- 
 dependent fexistence, both the amnion and the allantois are detached 
 and thrown off as obsolete structures, their place being afterward 
 supplied by other organs belonging to the adult condition. 
 
608 DEVELOPMENT OF THE EGG IN HUMAN SPECIES. 
 
 CHAPTEE X. 
 
 DEVELOPMENT OP THE EGG IN THE HUMAN 
 SPECIES.— POBMATION. OP THE CHORION. 
 
 We have already described, in a preceding chapter, the manner 
 in Tvhich the outer lamina of the amniotic fold becomes adherent 
 to the adjacent surface of the vitelline membrane, so as to form 
 with it but a single layer ; and in which these two membranes, thus 
 fused and united with each other, form at that time the single ex- 
 ternal investing membrane of the egg. The allantois, in its turn, 
 afterward comes in contact with the investing membrane, and lies 
 immediately beneath it, as a double vascular membranous sac. In 
 the egg of the human subject the development of the membranes, 
 though carried on essentially upon the same plan with that which 
 we have already described, undergoes, in addition, some further 
 modifications, which we shall now proceed to explain. 
 The first of these peculiarities is that the allantois, after spread- 
 ing out upon the inner siurface of 
 ^^" the external investing membrane, 
 
 adheres to, and fuses with it, just 
 as the outer lamina of the amni- 
 otic fold has previously fused 
 with the vitelline membrane. At 
 the same time, the two layers be- 
 longing to the allantois itself also 
 come in contact and fuse toge- 
 ther ; so that the cavity of the 
 allantois is obliterated, and instead 
 of forming a membranous sac con- 
 taining fluid, this organ is convert- 
 eS into a simple vascuh^r memhra'ne. 
 (Fig. 213.) This membrane, 
 moreover, being, after a time, thoroughly fused and united with the 
 two Tyhich have preceded it, takes the place which was previously 
 
 Hdman Ovitm, about the end of the first 
 month ; showing formation of chorion. — 1. 
 Umbilical vesicle, 2, Amnion, 3, Chorion, 
 
FORMATION OF THB CHOKION. 609 
 
 occupied by them. It is then termed the chorion, and thus becomes 
 the sole external investing membrane of the egg. 
 
 We find, therefore, that the chorion, that is, the external coat or 
 investment of the egg, is formed successively by three distinct 
 membranes, as follows: first, the Original vitelline niembrane; 
 secondly, the outer lamina of the amniotic fold ; and, thirdly, the 
 allantois; the last predominating over the two formet by the rapidity 
 of its growth, and absorbing them into its substance, so that they 
 become finally completely incorporated with its texture. 
 
 It is easy to see, also, how, in consequence of the above process, 
 the body of the foetus, in the human egg, becomes inclosed in two 
 distinct membranes, viz., the amnion, which is internal and conti- 
 nuous with the foetal integument, and the chorion, which is external 
 and supplied with vessels from the cavity of the abdomen. THe 
 umbilical vesicle is, of course, situated between the two ; and the 
 rest of the space between the chorion and the amnion is occupied 
 by a semi-fluid gelatinous material, somewhat similar in appearance 
 to that of the vitreous body of the eye. 
 
 The obliteration of the cavity of the allantois takes place very 
 early in the human subject, and, in fact, keeps pace almost entirely 
 with the progress of its growth ;* so that this organ never presents, , 
 in the human egg, the appearance of a hollow sac, filled with 
 fluid, but rather that of a flattened vascular membrane, enveloping 
 the body of the foetus, and forming the external membrane of the 
 egg. Notwithstanding this difference, however, the chorion of the 
 human subject, jn respect to its mode of formation, is the same 
 thing with the allantois of the lower animals ; its chief peculiarity 
 consisting in the fact that its opposite surfaces are adherent to each 
 other, instead of remaining separate and ' inclosing a cavity filled 
 with fluid. 
 
 The next peculiarity of the human chorion is, that it becomes 
 shaggy. Even while the egg is still very small, and has but recently 
 found its way into the uterine cavity, its exterior is already seen 
 to* be covered with little transparent prominences, like so many 
 villi (Fig. 213), which increase the extent of its surface, and assist 
 in the absorption of fluids from without. The villi are at this time 
 quite simple in form, and altogether homogeneous in structure. 
 
 As the egg increases in size, the villi rapidly elongate, and be- 
 come divided and ramified by the repeate* budding and sprouting 
 of lateral ofishoots from every part. After this process of growth 
 39 
 
610 DEVELOPMENT OF THE EGG IN HUMAN SPECIES. 
 
 Fig. 214. 
 
 has gone on for some time, the external surface of the chorion pre- 
 sents a uniformly velvety or shaggy appearance, owing to its heing 
 covered everywhere with these tufted and compound villosities. 
 
 The villosities themselves, when examined by the microscope; 
 have an exceedingly well-marked' and characteristic appearance. 
 (Fig. 214.) They originate from the surface of the chorion by a 
 
 somewhat narrow stem, and divide 
 into a multitude of secondary and 
 tertiary branches, of varjdng size 
 and figure; some of them slender 
 and filamentous, others club-shaped, 
 many of them irfegularly swollen at 
 various points. All of them termi- 
 nate by rounded extremities, giving 
 to the whole tuft' a certain resem- 
 blance to some varieties of sea-weed. 
 The larger trunks and branches of 
 the villosity are seen to contain nu- 
 merous minute nuclei, imbedded in 
 a nearly homogeneous, or finely gra- 
 nular substratum. The smaller ones 
 appear, under a low magnifying 
 power, simply granular in texture. 
 
 These villi are altogether peculiar 
 in appearance, and quite unlike any 
 other structure which may be met with in the body. Whenever we 
 find, in the uterus, any portion of a inembrane having, villosities 
 like these, we may be sure that pregnancy has existed ; for such 
 villosities can only belong to the chorion, and the chorion itself is 
 a part of the foetus. It is developed, as we have seen, as an out- 
 growth from the intestinal canal, and can only exist, accordingly, 
 as a portion of the fecundated egg. The presence of portions of a 
 shaggy chorion is therefore as satisfactory proof of the existence 
 of pregnancy, as if he had found the body of the foetus itself. * 
 
 While the villosities which we have just described are in pro- 
 cess of formation, the allantois itself has completed its growth, and 
 has become converted into a permanent chorion. The bloodvessels 
 coming from the allantoic arteries accordingly ramify over the 
 chorion, and supply it with a tolerably abundant vascular network. 
 The growth of the foetus, moreover, at this time, has reached such 
 a state of activity, that it requires to be supplied with nourishment 
 
 Compound villosity of Human Cho- 
 BIOK, ramified extremity. From a three 
 mouths' foetas. Magnified SO diameters. 
 
FOBMATION OF THE CHORION, 
 
 611 
 
 Fig. 215. 
 
 by vascular absorption, instead of the slow process of imbibition, 
 whicb has heretofore taken place through the comparatively incom- 
 plete and structureless villi of the cho- 
 rion. The capillary vessels, accordingly, 
 with which the chorion is supplied, begin 
 to penetrate into the substance of its vil- 
 losities. They enter the base or stem of 
 each villosity, and, following every divi- 
 sion of its compound ramifications, finally 
 reach its rounded extremities. Here they 
 turn upon themselves in loops (Fig. 215), 
 like the vessels in the papillae of the skin, 
 and retrace their course, to unite finally 
 with the venous trunks of the chorion. 
 The vUli of the chorion are, therefore. 
 
 Extremity 
 
 VILLOSITY nr 
 
 very analogous in structure t8 those of chokion, more lighiy magni- 
 
 .■,*,,' -Ill' n 1 fled; showiug the arrangement of 
 
 the intestine ; and their power of absorp- bioodyes-eis m its interior. 
 tion, as in other similar instances, corre- 
 sponds with the abundance of their ramifications, and the extent 
 of their vascularity. 
 
 It must be remembered, also, that these vessels all come from the 
 abdomen of the foetus; and that whatever substances are taken up 
 by them are transported directly to the interior of the embryo, and 
 used for the nourishment of its tissues. The chorion, therefore, as 
 soon as its villi and bloodv'essels are completely developed, becomes 
 an exceedingly active organ in the. nutrition of the foetus; and con- 
 stitutes, in fact, the only means by which new material can be in- 
 troduced from without. 
 
 The existence of this general vascularity of the chorion affords 
 also, as Coste was the first to point out, a striking indication that 
 this membrane is in reality identical with the allantois of the 
 lower animals. If the reader will turn" back to the illustrations of 
 the formation of the amnion and allantois (Chap. IX.), he will see 
 that the first chorion or investing membrane is formed exclusively 
 by the vitelline membrane, which is •never vascular and cannot be- 
 come so by itself, since it has no direct connection with the foetus. 
 The second chorion is formed by the union of the vitelline mem- 
 brane with the outer lamina of the amniotic fold. Both lamina? 
 of the amniotic fold are at first vascular, since they are portions of 
 the external blastodermic layer, and derive their vessels from the 
 integument of the foetus. But after the outer lamina has become 
 
612 DEVELOPMENT OF THE EGG IN HnjIAN SPECIES. 
 
 completely separated from the inner, by the disappearance of the 
 partition which for a. time connected the two with each other (Fig. 
 209, c), this source of vascular supply is cut off; and the second 
 chorion cannot, therefore, remain vascular after that period. But 
 the third or permanent chorion, that is, the allantois, derives its ves- 
 sels directly from those of the foetus, and retains its connection with 
 them during the whole period of gestation. A chorion, therefore, 
 which is universally and permanently vascular, can be no other 
 than the allantois, converted into an external investing membrane 
 of the egg. 
 
 Thirdly, the chorion, which is at one time, as we have seen, every- 
 where villous and shaggy, becomes afterward partially bald. This 
 change begins to take place about the end of the second month. 
 It commences at a point opposite the situation of the foetus and the 
 insertion of the foetal vessels. Th^ villosities of this region cease 
 growing; and as the entire egg continues to enlarge, the villosities 
 at the point indicated fail to keep pace with its growth, and with 
 the progressive expansion of the chorion." They accordingly he- 
 come at this part thinner and more scattered, leaving the surface 
 of the chorion comparatively smooth and bald. This baldness in- 
 creases in extent and becomes more and more complete, spreading 
 
 and advancing over the adja- 
 ^'8" ^^^' cent portions of the chorion, 
 
 until at least two-thirds of its 
 surface have become nearly 
 or quite destitute of villosities. 
 At the opposite point of the 
 surface of the egg, however, 
 that portion, namely, which 
 corresponds with the insertion 
 of the foetal vessels, the villosi- 
 ties, instead of becoming atro- 
 phied, continue to grow; and 
 this portion of the chorion be- 
 comes even more shaggy and 
 thickly set than before. The 
 consequence ip that the chorion afterward presents a very different 
 appearance at different portions of its surface. (Fig. 216.) The 
 greater part of it is smooth-; but a certain portion, constituting 
 about one-third of the whole, is covered with a soft and spongy 
 mass of long, thickly-set, compound villosities. It is'this thickened 
 
 HrMAH Ovum lit end of third month 
 placental portion of the chorion fully formed. 
 
 showing 
 
.FOBMATION OF THE CHORION. 613 
 
 and staggy portion, whicli is afterward concerned in the formation 
 of the placenta ; while the remaining smooth portion continues to 
 be known under the name of the chorion. The placental portion 
 of the chorion becomes distinctly limited and separated from the 
 remainder by about the end of the third month. 
 
 The vascularity of the chorion keeps pace, in its different parts 
 respectively, with the atrophy and development of its villosities. 
 As the villosities shrivel and disappear over a part of its extent, 
 the looped capillary vessels, which they at first contained, disappear 
 also ; so that the smooth portion of the chorion shows afterward 
 only a few straggling vessels running over its surface, and does not 
 contain any abundant capillary plexus. In the thickened portion, 
 on the other hand, the vessels lengthen and ramify to ^n extent 
 corresponding with that of the villosities in which they are situated'. 
 The allantoic arteries, coming from the abdomen of the foetus, enter 
 the villi, and penetrate through their whole extent ; forming, at the 
 placental portion of the chorion, a mass of tufted and ramified vas- 
 cular loops, while over the rest o'f the membrane they are merely 
 distributed as a few single and scatteted vessels. 
 
 The chorion, accordingly, is the external investing membrane of 
 the egg, produced by the consolidation and transformation of the 
 allantois. The placenta, furthermore, so far as it has now been 
 described, is evidently' a part of the chorion ; that part, namely 
 which is thickened, shaggy, and vascular, while the remainder is 
 comparatively thin, smooth, and membranous. 
 
614 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE. 
 
 CHAPTER XI. 
 
 DEVELOPMENT OF UTEEINB MUCOUS MEMBRANE- 
 FORMATION OF THE DECIDUA. 
 
 In fish, reptiles, and birds, the egg is either provided with a sup- 
 ply of nutritious material contained within its membranes, or it is 
 so placed, after its discharge from the body of the parent, that it 
 can absorb these materials from without. Thus, in the egg of the 
 bird, the young embryo is supported upon the albuminous matter 
 deposited around the vitellus ; while in the frog and fish, moisture, 
 oxygen, saline substances, &c., are freely imbibed from the water 
 in which the egg is placed. 
 
 But in the quadrupeds, as well as in the human species, the egg 
 is of minute size, and the quantity of nutritious matter which it 
 contains is sufl&cient to last only for a very short time. Moreover, 
 the development of the foetus takes place altogether within the body 
 of the female, and no supply, therefore, can be obtained directly 
 from the external media. In these instances, accordingly, the mu- 
 cous membrane of the uterus, which is found to be unusually 
 developed and increased in functional activity during the period of 
 gestation, becomes a source of nutrition for the fecundated egg. 
 The uterine mucous membrane, thus developed and hypertrophjed, 
 is known by the name of the Decidua. 
 
 It has received this name because, as we shall hereafter see, it 
 becomes exfoliated and thrown off, at the same time that the egg 
 itself is finally discharged. 
 
 The mucous membrane of the body of the uterus, in the unimpreg- 
 nated condition, is quite thin and delicate, and presents a smooth 
 and slightly vascular internal surface. There is, moreover, no layer ^ 
 of submucous cellular tissue between it and the muscular substance 
 of the uterus; so that the mucous membrane cannot h'tere,'^as in 
 most other organs, be easily dissected up and separated from the 
 subjacent parts. The structure of the mucous membrane itself, 
 however, is sufficiently welt marked and readily distinguishable 
 
FOKMATIOX OP THK DECIDUA. 
 
 615 
 
 Fig. 217. 
 
 iiii 
 
 Uterine Muoors Mehbeane, ag 
 >ieen in vertical Kection, — a. Free surface. 
 b. Attached tmrftux. 
 
 from that of other parts. It consists, throughout, of minute 
 tubular follicles, ranged side by si3e, and running perpendicularly 
 to the free surface of the mucous membrane. (Fig. 217.) Near 
 this free surface, they are nearly 
 straight; but toward the deeper sur- 
 face of the mucous membrane, where 
 they terminate in blind extremities, 
 they become more or less wavy or 
 spiral in their course. The tubules 
 are about yjj of an inch in diameter, 
 tad are lined throughout with co- 
 lumnar epithelium. (Fig. 218.) They 
 occupy the entire thickness of the ute- 
 rine mucous membrane, their closed 
 extremities resting upon the subjacent 
 
 muscular tissue, while their mouths open into the cavity of the ute- 
 rus. A few fine bloodvessels penetrate the mucous membrane from 
 below, and, running upward, 
 between the tubules, encircle '^' 
 
 their superficial extremities 
 with a capillary network. 
 There is no areolar tissue in 
 the uterine mucous mem- 
 brane, but only a small quan- 
 tity of spindle-shaped fibro- 
 plastic fibres, scattered be- 
 tween the tubules. 
 
 As the fecundated egg is 
 about to descend into the 
 cavity of the uterus, the mu- 
 cous membrane, above de- 
 scribed, takes on an increas- 
 ed activity of growth and 
 an unusual development. It 
 becomes tumefied and vascular ; and, as it increases in thickness, it 
 projects, in rounded eminences or convolutions, into the uterine 
 cavity. (Fig. 219.) In this process, the tubules of the uterus in- 
 crease in length, and also become wider ; so that their open mouths 
 may be readily seen by the naked eye upon the uterine surface, as 
 numerous minute perforations. The bloodvessels of the mucous 
 membrane also enlarge and multiply, and inosculate freely with 
 
 Utkrtne Tdbut.rs, from mucous membrane of 
 nuimpre^nated hnmau uterus. 
 
616 DEVKLOPJIENT OF UTKBINE MUCOUS MEMBBANB, 
 
 eact other ; so that the vascular network encircliug the tubules be- 
 comes more extensive and abundant. 
 
 The internal surface of the uterus, accordingly, after this process 
 has been for some time going on, presents a thick, rich, soft, vas- 
 cular, and velvety lining, quite different from that which is to be 
 found in the unimpregnated condition. In consequence of this 
 difference, the lining membrane of the uterus, in the impregnated 
 condition, was formerly supposed to be an entirely new product, 
 thrown out by fexudation from the uterine. surface, and analogous, 
 in this' respect, to the inflammatory exudations of croup and pleu- 
 risy. It is now known, however, to be no other than the mucousf 
 membrane of. the uterus itself, thickened and hypertrophied to an 
 extraordinary degree, but still retaining all its natural connections 
 and its original anatomical structure. 
 
 The hypertrophied mucous membrane, above described, consti- 
 tutes the Decidva vera. Its formation is confined altogether to the 
 body of the uterus, the mucous membrane of the cervix taking no 
 part in the process, but retaining its .original appearance. The 
 decidua vera, therefore, commences .above, at the orifices of the 
 Fallopian tubes, and ceases below, at the situation of the os inter- 
 num. The cavity, of the cervix, meanwhile, begins to be filled 
 with an abundant secretion of its peculiarly visqid mucus, which 
 blocks Tip, more or less completely, its passage, and protects the 
 internal cavity. But there is no membranous partition at this time 
 covering the os internum, and the mucous membranes of the cervix 
 and of the body of the uterus, though very different in appearance, 
 are still perfectly continuous with each other. When we cut open 
 the cavity of the uterus, therefore, in this condition, we find its 
 internal surface lined with the decidua vera, with the opening of 
 the OS internum below and the orifices of the Fallopian tubes above, 
 perfectly distinct, and in their natural positions. (Fig. 219.) 
 
 As the fecundated egg, in its journey from above downward, 
 passes the lower orifice of the Fallopian tube, it insinuates itself 
 between the opposite surfaces of the uterine mucous membrane, 
 and becomes soon afterward lodged in one of the furrows or de- 
 pressions between the projecting convolutions of the decidua. 
 (Fig. 219.) It is at this situation that an adhesion subsequently 
 takes place between the external membranes of the egg, on the 
 one hand, and the uterine decidua on the other. Now, at the point 
 where the egg becomes fixed and entangled, as above stated, a still 
 more rapid development than before takes place in the uterine 
 
FOBMATION 0¥ THE DECIDUA. 
 
 617 
 
 mucous membrane. Its projecting folds begin to grow up around 
 the egg in such a manner as to partially inclose if in a kind of 
 circumvallation of the decidua, and to shut it off, more or less com- 
 
 Fig. 219. 
 
 Fig. 220. 
 
 Ikprbgnated Uterus; nhowingr 
 formation of decidua, Tlie decidua Is 
 represented in black ; and the egg is 
 seen, at tlie fundus of the uterus, eu- 
 gAged between two of its projecting 
 convolutions. 
 
 IsipaKaNATKD Utkbur, with pro- 
 Jpctiug folds of decidua growing up 
 around the egg. The narrow opening 
 where the edges of the folds approach 
 each otherf^ls seen over the must pi^omi- 
 neut portion of the egig. 
 
 Fig. 221. 
 
 pletely, from the general cavity of the uterus. (Fig. 220.) The egg 
 is thus soon contained in a special cavity of its own, which still 
 ■ communicates for a time with the general cavity of the uterus by 
 a small opening, situated over its most 
 prominent portion, which is known as the 
 " decidual umbilicus." As the above pro- 
 cess of growth goes on, this opening be- 
 comes narrower and narrower, w.hile the 
 projecting folds of decidua approach each 
 other over the surface of the egg. At 
 last these folds actually touch each other 
 and unite, forming a kind of cicatrix 
 which remains for a certain time, to mark 
 the situation of the original opening. 
 
 When the development of the uterus and 
 its contents has reached this point (Eig. 
 221), it will be seen that the egg is com- 
 pletely inclosed in a distinct cavity of its 
 
 own ; being everywhere covered with a decidual layer of new for- 
 mation, which has thus gradually enveloped it, and by which it is 
 concealed from view when the uterine cavity is laid open. This 
 
 iMPRIiUMATKiJ UtKRI.'s; — 
 
 showing egg completely inclosed 
 hj decidua reflexa. 
 
618 DEVELOPMENT OF UTEBIKE MUCOUS MEMBKANE, 
 
 newly-formed layer of decidua, enveloping, as above described, the 
 projecting portion of the egg, is called the Decidua reflexn; because 
 it is reflected over the egg, by a continuous growth from the general 
 surface of the uteri ne mucous membrane. The orifices of the uterine 
 tubules, accordingly, in consequence of the manner ia which the 
 decidua reflexa is formed,- will be seen not only on its external sur- 
 face, or that which looks toward the cavity of the uterus, but also on 
 its internal surface, or that which looks toward the egg. 
 
 The decidua vera, therefore, is the origihal mucous membrane 
 lining the surface of the uterus ; while the decidua reflexa is a new- 
 formation, which has grown up round the egg and inclosed it in a 
 distinct cavity. 
 
 If abortion occur at this time, the mucous membrane of the 
 uterus, that is, the decidua vera, is thrown off, and of course brings 
 away with it the egg and decidua reflexa. On examining the mass 
 discharged in such an abortion, the egg will accordingly be found 
 imbedded in the substance of the decidual membrane. One side 
 of this membrane, where it has been torn away from its attachment 
 to the uterine walls, is ragged and shaggy ; the other side, corres- 
 ponding to the cavity of the uterus, is smooth or gently convoluted, 
 and presents very distinctly the orifices of the uterine tubules; 
 while the egg itself can only be extracted by cutting through the 
 decidual membrane, either from one side or the other, and opening . 
 in this way the special cavity in which it has been inclosed^ 
 
 During the formation of the decidua reflexa, the entire egg, as 
 well as the body of the uterus which contains it, has considerably 
 enlarged. That portion of the uterine mucous membrane situated 
 immediately underneath the egg, and to which the egg first became 
 attached, has also eontinued to increase in thickness and vascularity. 
 The remainder of the decidua vera, however, ceases to grow as 
 rapidly as before, and no longer keeps pace with the increasing 
 size of the egg and of the uterus. It is still very thick and vascu- 
 lar at the end of the third month ; but after that period it becomes 
 comparatively thinner and less glandular in appearance, while the 
 unusual activity of growth and development is concentrated in the 
 egg, and in that portion of the uterine mucous membrane which is 
 in immediate contact with it.. 
 
 Let us now see in what manner the egg becomes attached to the 
 decidual membrane, so as to derive from it the requisite supply of 
 nutritious material. It must be recollected that, while the above 
 changes have beien taking, place in the walls of the uterus, the 
 
FORMATION OP THB DECIBUA. 619 
 
 formation of the embryo in the egg, and the development of the 
 amnion and chorion have been going on simultaneously. Soon 
 after the entrance of the egg into the uterine cavity, its external 
 investing membrane becomes coviered with projecting filaments, or 
 villosities, as previously described. (Ghap. X.) These villosities, 
 which are at first, as we have seen, solid and non- vascular, insinuate 
 themselves, as they grow, into the uterine tubules, or between the 
 folds of the decidual surface with which the egg is in contact, pene- 
 trating in this way into little cavities or foUiclea of the uterine 
 mucous membrane, formed either from the cavities of the tubules 
 themselves, or by the adjacent surfaces of minute projecting folds. 
 When the formation of the decidua reflexa is accomplished, the 
 chorion has already become uniformlv 
 shaggy ; and its villosities, spreading in all ^' 
 
 directions from its external surface, pene- 
 trate everywhere into the follicles above de- 
 scribed, both of the decidua vera underneath 
 it and the contiguous surfece of the decidua 
 reflexa with which it is covered. (Fig. 222.) 
 In this way the egg becomes entangled 
 with the decidua, apd cannot then be read- 
 ily separated from it, without rupturing • 
 some of the filaments which have grown 
 from its surface, and have been, received 
 into the cavity of -the follicles. The nu- ..J^r/clVer. Jrervn! 
 tritious fluids, exuded from the soft and '"*'"«' "' "'""-ion ana decidna'. 
 glandular textures of the decidua, are now 
 
 readily imbibed by the villosities of the chorion ; and a more rapid 
 supply of nourishment is thus provided, corresponding in abun- 
 dance with the increased and" increasing size ,of the egg. 
 
 Very soon, however, a still greater activity of absorption be- 
 comes necessairy ; and, as we have seen in a preceding chapter, the 
 external membrane of the egg becomes vascular by the formation 
 of the allantoic bloodvessels, which emerge from the body of the 
 foetus, to ramify in the chorion, and penetrate everywhere into the 
 villosities with which it is covered. Bach villosity, then, as it lies 
 imbedded in its uterine follicle, contains a vascular loop through 
 wtich the foetal blood circulates, increasing the rapidity .with which 
 absorption and exhalation take place. 
 
 Subsequently, furthermore, these vascular tufts, which are at first 
 uniformly abundant throughout the whole extent of the chorion, 
 
620 DEVELOPMENT OF UTEBIKB MUCOUS MEMBRANE. 
 
 Fig. 223. 
 
 disappear over a portion of its surface, while they at the same time 
 become concentrated and still further developed at a particular 
 spot, the situation of the future placenta. (Pig. 223.) This is the 
 
 spot at which the egg is in contact with 
 the decidua vera. Here, therefore, both 
 the decidual membrane and the tufts 
 of the chorion continue to increase in 
 thickness and vascjularity ; while else- 
 where, over the prominent portion of 
 the dgg, the chorion not only becomes 
 bare of villosities, and comparatively 
 destitute of vessels, but the decidua re- 
 flexa, which is in contact with it, also 
 loses its activity of growth, and be- 
 comes expanded into a thin layer, nearly 
 destitute of vessels, and without any 
 remaining trace of tubules or follicles. 
 The uterine mucous membrane is 
 therefore developed, during the process 
 of gestation, in such a way as to provide 
 for the nourishment of the foetus in the different stages of its growth. 
 At first, the whole of it is uniformly increased in thickness (decidua. 
 vera). Next, a portion of it grows upward around the egg, and 
 covers its projecting surface (decidua reflexa). Afterward, both the 
 decidua reflexa and the greater part of the decidua vera diminish 
 in the activity of their growth, and lose their importance as a means 
 of nourishment for the egg ; while that part which is in contact with 
 the vascular tufts of the chorion continues to grow, becoming ex- 
 ceedingly developed, and takipg an active part in the formation of 
 the placenta. 
 
 In the following chapter, we shall examine more particularly the 
 structure and development of the placenta itself, and of those parts 
 which are immediately connected with it. 
 
 PBEavANT Utbrus; showing 
 formation of placenta, hj ttie united 
 deveiopment of a portion of the de- 
 cidua and the villosities of' the cho- 
 
THE PLACENTA. 621 
 
 CHAPTER XII. 
 
 THE PLACENTA. 
 
 Wk have shown in the preceding chapters that the foetus, during 
 its development, depends for its supply of nutriment upon the lining 
 membrane of the maternal uterus ; and that the nutriment, so sup- 
 plied, is absorbed by the bloodvessels of the chorion, and transported 
 in this w:ay into the circulation of the foetus. In all instances, ac- 
 cordingly, in which the development of the foetus takes place within 
 the body of the parent, it is provided for by the relation thus esta- 
 blished between two sets of membranes; namely, the maternal 
 membranes which supply nourishment, and the foetal membranes 
 which absorb it. 
 
 In some species of animals, the connection between the maternal 
 arid foetal membranes is exceedingly simple. In the pig, for ex- 
 ample, the uterine mucous membrane is everywhere uniformly 
 vascular ; its only peculiarity consisting in the presence of nume- 
 rous transverse folds, which project from its surface, analogous to 
 the valvular conniventes of the small intestine. The external in- 
 vesting membrane of the egg, which is the allantois, is also smooth 
 and uniformly vascular like the other. No special development of 
 tissue or of vessels occurs at any part of these membranes, and 
 no direct adhesion takes place between them; but the vascular 
 allantois or chorion of the foetus is everywhere closely applied to 
 the vascular mucous membrane of the maternal uterus, each of the 
 two contiguous surfaces following the undulations presented by the 
 other. (Fig. 224.) By this arrangement, transudation and absorp- 
 tion take place from the bloodvessels of the mother to those of the 
 foetus, in sufficient quantity to provide for the nutrition of the latter. 
 When parturition takes place, accordingly, in these animals, a very- 
 moderate contraction of the uterus is sufficient to expel its contents. 
 The egg, displaced from its original position, slides easily forward 
 over the surface of the uterine mucous membrane, and is at last 
 discharged without any hemorrhage or laceration of connecting 
 parts. In other instances, however, the development of the foetus 
 requires a more elaborate arrangement of the vascular membranes. 
 
622 
 
 THE PfiACENTA. 
 
 In the cow, for example, the external membrane of the egg, beside 
 being everywhere supplied with branching vessels, presents upon 
 
 Fig. 224. 
 
 F(ETAL Fig, with \ta membraaes, contained in cavi^t/ of atera8.-*a, a, h^ b. Walls of oterns. 
 c, c. Cavity of uterus, d. Amnion, e, e. AUantoia. 
 
 various points of its surface' no less than from seventy to eighty oval 
 spots, at each of which the vessels of the chorion are developed into 
 abundant tufted prominences, hanging from its exterior in thick. 
 Velvety, vascular masses. At each point of the uterine mucous mem- 
 brane, corresponding with one of these tufted masses, the maternal 
 bloodvessels are developed in a similar manner, projecting into the 
 uterine cavity as a flattened rounded mass or cake; which, with that 
 part of the foetal chorion which is adhierent to it, is known by the 
 
 Fig. 225. 
 
 CoTTLRDON OF C w' 8 Ut E B I' 9. — a, a. Surface of fcetal cliorion. ft, &. Blood venaela of foetal 
 chorion, d^ d. Bloodvessels of uterine macons membraae. c, c. Surface of aterine macoas mem- 
 braae. 
 
 name of the Cotyledon, Each cotyledon forms/ therefore, a little 
 placenta. (Fig. 225.) In its substance tbe tufted vascular loops 
 coming from the uterine mucous membrane {d, d) are entangled 
 
TUB PLACENTA. 623 
 
 with those coming from the membranes of the foetus (6, b). There 
 is no absolute adhesion between the two sets of vessels, but only 
 an interlacement pf their ramified extremities; and, with a little 
 care in manipulation,. the fcetal portion of the cotyledon may be 
 extricated from the maternal portion, without lacerating either. In 
 consequence, however, of this intricate interlacement of the vessels, 
 transudation of fluids will evidently take place with great readiness, 
 from one system to the other.: 
 
 The form of placenta, therefore, met with in these animals, is one 
 in which the bloodvessels of the fcetal chorion are simply entangled 
 with those of the uterine mucous membrane. In the human sub- 
 ject, the structure of the placenta is a little more complicated, 
 though the main principles of its formation are the same as in the 
 above instances. 
 
 From what has been said , in the foregoing chapters, it appears 
 that in the human subject, as well as in the lower, animals, the 
 placenta is formed partly by the vascular tufts of the chorion, 
 . and partly by tl* thickened mucous membrane of the uterus in 
 which they are entangled. During the third month, those portions 
 of the chorion and decidua which are destined to undergo this 
 transformation become more or less distinctly limited in their form 
 and dimensions; and a thickened vascular mass, partly maternal 
 and partly fcetal in its origin, shows itself at the spot where the 
 placenta is afterward to be developed. This mass is constituted in 
 the following manner. 
 
 It will be recollected that the villi of the chorion, when first 
 formed, penetrate into follicles situated in the substance of the 
 uterine mucous membrane ; and that after they have become vas- 
 cular, they rapidly' elongate and are developed into tufted ramifi- 
 cations of bloodvessels, each one of which turns upon itself in a 
 loop at the end of the villus. At the same time the uterine follicle, 
 into which the villus has penetrated, enlarges to a similar extent ; 
 sending out branching diverticula, corresponding with the multi- 
 plied ramifications of the villus. In fact, the growth of the follicle 
 and that of the villus go on simultaneously, and keep pace with 
 each other ; the latter constantly advancing as the cavity of the 
 former enlarges. 
 
 But it is not only the uterine follicles which increase in size and 
 in complication of structure at this period. The capillary blood- 
 vessels, which lie between them and ramify over their exterior, 
 also become unusually developed. They enlarge and inosculate 
 freely with each other; so that every uterine follicle is soon covered 
 
624 
 
 THE PLACENTA. 
 
 with an abundant network of dilated capillaries, derived from the 
 bloodvessels of the original decidua. At this time, therefore, each 
 vascular loop of the foetal chorion is covered, first, with a layer 
 forming the wall of the villus. This is in contact with the lining 
 membrane of a uterine follicle, and outside of this again are the 
 capillary vessels of the uterine mucous membrane; so that two 
 distinct membranes intervene between the walls of the foetal capil- 
 laries on the one hand and those of, the maternal capillaries on the 
 other, and &l\ transudation must take place through the substance 
 of these two membranes. 
 
 As the formation of the placenta goes on, the anatomical arrange- 
 ment of the fcetal vessel remains the same. They continue to 
 form vascular loops, penetrating deeply into the decidual mem- 
 brane; only they become constantly more elongated, and their 
 ramifications more abundant and tortuous. The maternal capilla- 
 ries, however, situated on the outside of the uterine follicles, become 
 considerably altered in their anatomical relations. They enlarge 
 excessively; and, by encroaching constantly up^ the little islets 
 or spaces between them, fuse successively with' each other; and, 
 losing gradually in this way the characters of a capillary network, 
 
 become dilated into wide 
 ^'g- 226. sinuses, which communicate 
 
 freely with the enlarged vessels 
 in the muscular walls of the 
 uterus. As the original capil- 
 lary plexus occupied the entire 
 thickness of the hypertrophied 
 decidua, the vascular sinuses, 
 into which it is thus converted, 
 are equally extensive. They 
 commence at the inferior sur- 
 face of the placenta, where it is 
 in contact with the muscular 
 walls of the uterus, and extend 
 through its whole thickness, 
 quite up to the surface of the 
 fcetal chorion. 
 As the maternal sinuses grow upward, the vascular- tufts of the 
 chorion grow downward, and extend also through the entire thick- 
 ness of the placenta. At this period, the development of the blood- 
 vessels, both in the foetal and maternal portions of the placenta, is 
 so excessive that all the other tissues, which originally co-existed 
 
 Extremity of F<etal Tdpt, from haman pla- 
 centa at term, ia its receutconditiou. a,n. Capil- 
 lary bloodvessela. Magnified 13j diameters. 
 
THE PLACENTA. 
 
 625 
 
 Fig. 227. 
 
 ■Hrith them, become retrograde and disappear almost altogether. If 
 a villus from the foetal portion of the placenta be examined at this 
 time by transparency, in the fresh condition (Fig. 226) it will be 
 seen that its bloodvessels are covered only with a layer of homo- 
 geneous, or finely granular material, ^jVts of an inch in thickness, 
 in which are imbedded small oval-shaped nuclei,, similar to those 
 seen at an earlier period in the villosities of the chorion. The vil- 
 losities of the chorion are now, therefore, hardly anything more 
 than ramified and tortuous vascular loops ; 
 the remaining substance of the villi hav- 
 ing been atrophied a,nd absorbed in the 
 excessive growth of the bloodvessels, the 
 abundance and develcipmdht of which 
 can be readily "shown by injection from 
 the' umbilical arteries. (Fig. 227.) The 
 uterine follicles have at the same time 
 lost all trace of their original structure, 
 and have become mere vascular sinuses, 
 into which the tufted foetal bloodvessels 
 are received, as the villosities of the cho- 
 rion were at first received into the uterine 
 follicles. 
 
 Finally, the walls of the foetal blood- 
 vessels having come into close contact with the walls of the maternal 
 sinuses, the two become adherent and fuse together ; so that a time 
 at last arrives, when. we can no longer separate the foetal vessels, in 
 the substance of the placenta, from the maternal sinuses^ without 
 lacerating either the one or the other, owing to the secondary 
 adhesion which has taken place between them. 
 
 The placenta, therefore, when perfectly formed, has the structure 
 which is shown in the accompanying diagram (Fig. 228), repre- 
 senting a vertical section of the organ through its entire thickness. 
 At a, a, is seen the chorion, receiving the umbilical vessels from the 
 body of the foetus through the umbilical cord, and sending out its 
 compound and ramified vascular tufts into the substance of the 
 placenta. At b, b, is the attached surface of the decidua, or uterine 
 mucous membrane ; and at c, c, c, c, are the orifices of uterine ves- 
 sels which penetrate it from below. These vessels enter the placenta 
 in an extremely oblique direction, though they are represented in 
 the diagram, for the sake of distinctness, as nearly perpendicular. 
 When they have once penetrated, however, the lower portion of * 
 40 
 
 Extremity of Fcetal Tuft of 
 bumau placenta; from an iojectPd 
 ftpeo'.men. Maguifled 40 diameters. 
 
626 
 
 THE PLACENTA. 
 
 the decidua, they immediately dilate into the placental sinuses 
 (represented, in the diagram, in black), which extend through the 
 
 Fig. 228. 
 
 Vertical section oi Flacrkta, FchowinsrarranfTemeiit of maternal and Toetat Tessels. a, a. Chiy 
 rion. bj b, Decidua. c, c, c^ c. Orifices of uterine sinuiios. 
 
 whole thickness of the organ, closely embracing all the ramifica- 
 tions of the foetal tufts. It will be seen, therefore, that the placenta, 
 arrived at this stage of completion, is composed essentially of no- 
 thing but bloodvessels. No other tissues enter into its structure; 
 for all those which it originally contained have disappeared, except- 
 ing the bloodvessels of the foetus, entangled with and adherent to 
 the bloodvessels of the mother. 
 
 There is, however, no direct communication between the foetal 
 and maternal vessels. The blood of the foetus is always separated 
 from the blood of the mother by a membrane which has resulted 
 from the successive union and fusion of four different membranes, 
 viz., first, the membrane of the foetal villus ; secondly, that of the 
 uterine follicle ; thirdly, the wall of the foetal bloodvessel ; and, 
 fourthly, the wall of the uterine sinus. The single membrane, how- 
 ever, into which these four finally coalesce, is extremely thin, as 
 we have seen, and of enormous extent, owing to the extremely 
 abundant branching and subdivision of the foetal tufts. These tufts, 
 accordingly, in which the blood of the foetus circulates, are bathed 
 everywhere, in the placental sinuses, with the blood of the mother; 
 and the processes of endosmosis and exosmosis, of exhalation and 
 ♦ absorption, go on between the two with the greatest possible 
 activity. 
 
THE PLACENTA. 627 
 
 It is very easy to demonstrate the arrangement of the foetal 
 tufts in the human placenta. They can be readily seen hj the 
 naked eye, and may be easily traced from their attachment at the 
 under surface of the chorion to their termination near the uterine 
 surface of the placenta. The anatomical disposition of the pla- 
 cental sinuses, however, is much more difficult of examination. 
 During life, and while the placenta is still attached to the uterus, 
 they are filled, of course, with the blood of the mother, and occupy 
 fully one-half the entire mass of, the plaTcenta. But when the pla- 
 centa is detached, 'the maternal vessels belonging to it are torn off 
 at their necks (Fig. 228, c, c, c, c), and the sinuses, being then 
 emptied of blood by the compression to which the placenta is sub- 
 jected, are apparently obliterated ; and the foetal tufts, falling to- 
 gether and lying in contact with each other, appear to constitute 
 the whole of the placental mass. The existence of the placental 
 sinuses, however, and their true extent, may be satisfactorily de- 
 monstrated in the following manner. 
 
 If we take the uteilis of a woman who has died undelivered at 
 the, full term or thereabout, and open it in such a way as to avoid 
 wounding the placenta, this organ will be seen remaining attached 
 to the uterine surface, with all its vascular connections complete. 
 Let' the foetus now be removed hj dividing the umbilical cord, and 
 the uterus, with the placenta attached, placed under water, with its 
 internal surface uppermost. If the end of a blowpipe be now 
 introduced into one of the divided vessels of the uterine walls, and 
 air forced in by gentle insufflation, we can dasily inflate, first, the 
 venous sinuses of the uterus itself, and next, the deeper portions 
 of the placenta ; and lastly, the bubbles of air insinuate themselves 
 everywhere between the foetal tufts, and appear in the most supers 
 ficial portions of the placenta, immediately underneath the transr 
 parent chorion (a, a, Fig. 228) ; thus showing that the placental 
 sinuses, which freely communicate with the uterine vessels, really 
 occupy the entire thickness of the placenta, and are equally exten- 
 sive with the tufts of the chorion. We have verified this fact in 
 the above manner, on four different occasions, and in the presence 
 of Prof. 0. E. G^man, Prof. Geo. T. Elliot, Dr. Henry B. Sands, 
 Prof. T. G. Thomas, Dr. T. 0. Finnell, and various other medical 
 gentlemen of New York. ^ 
 
 If the placenta be now detached and examined separately, it will 
 be found to present upon its uterine surface a number of openings 
 which are extremely oblique in their position, and which are 
 
628 THE PLACENTA. 
 
 accordingly bounded on one side by a very- thin, projecting, cres- 
 centi^dge. These are the orifices of the uterine vessels, passing 
 into the placenta and torn off at their neeks, as above described ; 
 and by carefully following them with the probe and scissors, they 
 are found to lead at once into extensive empty cavities (the pla- 
 cental sinuses), situated between the foetal tufts. We have already 
 shown that these cavities are filled during life with the maternal 
 blood ; and there is every reason to believe that before delivery, 
 and while the circulation is going on, the placenta is at least twice 
 as large as after it has been detached and expelled from the uterus. 
 
 The placenta, accordingly, is a double organ, formed partly by 
 the choriofl and partly by the decidua ; and consisting of maternal 
 and foetal bloodvessels, inextricably entangled and united with each 
 other. 
 
 The part which this organ takes in the development of the foetus 
 is an exceedingly important one. From the date of its formation, 
 at about the beginning of the fourth month, it constitutes the only 
 channel through which nourishment is conveyed from the mother 
 to the foetus. The nutritious materials, which circulate in abun- 
 dance in the blood of the maternal sinuses, pass through the inter- 
 vening membrane by endosmosis, and enter the blood df the foetus. 
 The healthy or injurious regimen, .to which the mother is subjected, 
 will accordingly exert an almost immediate influence upon the 
 child. Even medicinal substances, taken by the mother and ab- 
 sorbed into her circulation, may readily transude through the pla- 
 cental vessels ; and they have been known in this way to exert a 
 specific effect upon the foetal organization. 
 
 The placenta is, furthermore, an organ of exhalation as well as 
 of absorption. The excrementitious substances, produced in the 
 circulation of the foetus, are undoubtedly in great measure disposed 
 of by transudation through the walls of the placental vessels, to be 
 afterward discharged by the excretory organs of ^e mother. The 
 system of the mother may therefore be affected in this manner, by 
 influences derived from the foetus. It has been remarked more 
 than once, in the lower animals, that when the female has two sue 
 cessive litters of young by different males, the young of the second 
 litter will sometimes bear marks rdsembling those of the first male. 
 In these instances, the peculiar influence which produces the ex 
 ternal mark must have been transmitted by the first male directly 
 t.o the foetus, from the foetus to the mother, and from the mother to 
 the foetus of the second litter. 
 
THK PLACKNTA. • 629 
 
 It is also througli the placental circulation that those disturbing 
 effects are produced upon the nutrition of the foetus, which result 
 from sudden shocks or injuries inflicted upon the mother. There is 
 now little room for doubt that various deformities and deficiencies of 
 the foetus, conformably to the popular belief, do really originate, in 
 certain cases, from nervous impressions, such as disgust, fear or anger, 
 experienced by the mother. The mode in which these effects may 
 be produced is readily understood from what has been said above 
 of the anatomy and functions of the placenta. We know very well 
 how easily nervous impressions will disturb the circulation in the 
 brain, the face, the lungs, &c. ; and the uterine circulation is quite 
 as readily influenced b* similar causers physicians see every day 
 in cases of amenorrhoea, menorrhagia, &c. If a nervous shock may 
 excite premature contraction in the muscular fibres of the pregnant 
 uterus and produce abortion, as not unfrequently happens, it is cer- 
 tainly capable of disturbing the course of the circulation through 
 the same organ. But the foetal circulation is dependent, to a great 
 extent, on the. maternal. Since the two sets of vessels are so closely 
 entwined in the placenta, and since the foetal blood has here much 
 the same relation, to the maternal, that the blood in the pulmonary 
 capillaries has to the air in the air- vesicles, it will be liable to de- 
 rangement from similar causes. If the circulation of air through 
 the pulmonary tubes be suspended, that of the blood through 
 the general, capillaries is disturbed also. In the same way, what- 
 ever arrests oir disturbs the circulation through the vessels of the 
 maternal uterus must necessarily be liable to interfere with that 
 in the foetal capillaries forming part of the placenta. And lastfy, 
 as the nutrition of the foetus is provided for wholly by the placenta, 
 it will of course suffer immediately from any such disturbance of 
 the placental circulation. These effects may be manifested either 
 in the general atrophy and death of the foetus; or, if the disturbing 
 cause be slight,, in the atrophy or imperfect development of par- 
 ticular parts ; just as, in the adult,-a morbid cause operating through 
 •the entire system, may be first or even exclusively manifested in 
 some particular organ, which is more sensitive to its inrfuence than 
 other parts. . . ;; 
 
 The placenta must accordingly be regarded as an organ whicli 
 performs, during intra-uterine life, of&ces similar to those of the 
 lungs and the intestine after birth. It absorbs nourishment, reno- 
 vates the blood, and discharges by exhalation various excrementi 
 tious matters, which originate in the processes of foetal nutrition. 
 
630 
 
 DISCHARGE OP THE OVUM. 
 
 CHAPTEE XIII. 
 
 DISCHARGE OF THE OTUM, AND BETEOGRADE 
 DEYELOPMENT (INVOLUTION) OF THE UTERUS. 
 
 DuEiNG the growth of tlft ovum and th*formation of the pla- 
 cental structures, the muscular substance of this uterus also increases 
 in thickness, while the whole organ enlarges, in order to accommo- 
 date the growing foetus and its appendages. The relative positioiTs 
 of the amnion and chorion, furthermore, undergo a change during 
 the latter periods of gestation, and the umbilical cord becomes 
 developed, at the same time, in the following manner. 
 
 In the earlier periods of foetal life, the umbilical cord consists 
 simply of that portion of the allantois lying next the abdomen. It 
 is then very short, and contains the umbilical vessds running in a 
 nearly straight course, and parallel with each other, from the abdo- 
 men of the foetus to the external portions of the chorion. At this 
 time the amnion closely invests the body of the foetus, so that the 
 
 size of its cavity is but little larger 
 ^'8- ^^^- than that of the foetus. (Fig. 229.) 
 
 The space between the amnion 
 and the chorion is then occupied 
 by an amorphous gelatinous ma- 
 terial, in which lies imbedded the 
 umbilical vesicle. 
 
 Afterward, however, the am- 
 nion enlai^ges faster than the cho- 
 rion, and 'encroaches upon the* 
 layer of gelatinous matter situated 
 between the two (Fig. 230), at 
 the same time that an albuminous 
 fluid, the " amniotic fluid," is ex- 
 uded into its cavity, in constantly 
 increasing quantity. Subsequently, the gelatinous layer, above de- 
 scribed, altogether disappears, and the amnion, at about the begin- 
 
 HuMAN Ovum atioiit the end of tne first 
 montli.— 1. Umbilical vesicle. 2. Amnion. 3. 
 Chorion. 
 
ENLARGEMENT OF THE AMNION'. 631 
 
 ning of the fiftli month, comes in contact with the internal surfaqe 
 
 of the chorion. Finally, toward the end of gestation, the contact 
 
 becomes so close between these 
 
 two membranes that they, are Fig- 230. 
 
 partially adherent to each 
 
 other, and it requires a little 
 
 care to separate them without 
 
 laceration. 
 
 The quantity of the amniotic 
 fluid continues to increase dur- 
 ing the latter period of gesta- 
 tion in order to accommodate 
 the movements of the foetus. 
 These movements begin to be 
 perceptible about the fifth 
 
 .I . i-1 ,' 1 HuHAXOruHat end of third moath i bhowing 
 
 month, at which time the enlargement of amaiou. 
 
 muscular system has already 
 
 attained a considerable degree of development, but become after- 
 ward more frequent and more strongly pronounced. The space 
 and freedom requisite for these movements are provided for by the 
 fluid accumulated in the cavity of the amnion. 
 
 The umbilical cord elongates, at the same time, in proportion to 
 the increasing size of the amniotic cavity. During its growth, it 
 becomes spirally twisted from right to left, the two umbilical arte 
 ries winding round the vein in the sam% direction. The gelatinous 
 matter, as already described as existing between the amnion and 
 chorion, while it disappears elsewhere, accumulates in the cord in 
 considerable quantity, covering the vessels with a thick, elastic en- 
 velope, which protects them from injury and prevents their being 
 accidentally compressed or obliterated. The whole is covered by a 
 portion of the amnion,, which is connected at one extremity with the 
 integument*of the abdomen, and invests the whole of the cord with 
 a continuous sheath, like the finger of a glove. (Fig. 231.) 
 
 The cord also contains, for a certain period, the pedicle or stem 
 of *the umbilical vesicle. The situation of this vesicle, it will be 
 recollected, is always between the chorion and the amnion. Its 
 pedicle gradually elongates with the growth of the umbilical cord ; 
 and the vesicle ftself, which generally disappears soon after the 
 third month, sometimes remains as late as the fifth, sixth, or seventli. 
 According to Prof.. Mayer, of Bonn, it may even be found, by care- 
 ful search, at the termination of pregnancy. When discovered in 
 
632 
 
 DISCHARGE OF THE OVCM. 
 
 t^e middle and latter periods of gestation, it presents itself as a 
 small, flattened, and shrivelled v^esicle, situated underneath the 
 amnion, at a variable distance from the insertion of the umbilical 
 cord. A minute bloodvessel is often seen running to it from the 
 cord, an,d ramifying upon its surface. 
 
 Fig. 231. 
 
 {iKATiD Human Uterus and Coktentb, showing the relations of the cord, placenta, mem. 
 hranes, &c , about the end of the seventh month, — 1. Becidua vera. 2..Decidua reflexa. 3. Ghoriou, 
 4. Amnion. 
 
 The decidua reflexa, during the latter months of pregnancy, is 
 constantly distended and pushed back by the increasing size of the 
 egg ; so that it is finally pressed closely against the opposite surfexje 
 of the decidua vera, which still lines the greater part of the uterine 
 cavity. By the end of the seventh month, the opposite surfaces 
 of the decidua vera and reflexa are in complete contact with eaxjh 
 other, though still distinct and capable of being separdffced without 
 difiSculty. After that time, they fuse together and become con- 
 founded with each other ; the two at last forming only a single, 
 thin, friable, semi-opaque layer; in which no trace- bi their origSial 
 glandular structure can be discovered. 
 
 This is the condition of thingS: at the termination of pregnancy. 
 Then, the time Ij^ving arrived for parturition to. take place, the 
 hypertrophied muscular walls of the uterus contract forcibly upon 
 its contents, and the egg is discharged, together with the whole of 
 the decidual uterine mucous membraile. 
 
BEPAHATIOX OP THE PLACENTA. 633 
 
 . In the human subject, as well as in most quadrupeds, the mem- 
 branes of the egg are usually ruptured during the process of par- 
 turition ; and the foetus escapes first, the placenta and the rest of 
 the appendages following a few moments afterward. Occasionally, 
 however, even in the human subject, the egg is discharged entire, 
 and the fcetus liberated afterward by the laceration of the mem- 
 branes. In each case, however, the mode of separation and expul- 
 sion is in all particulars the same. 
 
 The process of parturition, therefore, consists essentially in a 
 
 ^ separation of the decidual membrane, which, on being discharged, 
 brings away the ovum with it. The greater part of the; decidua 
 vera, having fallen into a state of atrophy during the latter months 
 of pregnancy, is by this time nearly destitute of vessels, and sepa- 
 rates, accordingly, without any perceptible hemorrhage; That por- 
 tion, however, which enters into the formation of the placenta, is, 
 on the contrary, excessively vascular ; and when the placenta is 
 separated, and its maternal vessels torn off at their necks, as before 
 mentioned, a gush of blood takes place, which accompanies or 
 immediately follows, the birth of the fcetus. This hemorrhage, 
 which occurs as a natural phenomenon at the time of pSrturition, 
 does not come from the uterine vessels proper. It consists of the 
 blood which was contained in the placental sinuses, and which is 
 expelled from them owing to the compression of the placenta by 
 the walls of the uterus. Since the whole amount of blood thus 
 lost was previously employed in the placental circulation, and since 
 the placenta itself is thrown off at the SBime time, no unpleasant 
 effect is produced upon the mother by such a hemorrhage, because 
 the natural proportion of blood in the rest of the maternal system 
 remains the same. Uterine hemorrhage at the time of parturition, 
 therefore, becomes injurious only when it continues after complete 
 separation of the placenta ; in which case it is supplied by the 
 mouths of the uterine vessels themselves, left open by failure of the 
 
 ■ uterine, contractions. These vessels are usually, instantly closed, 
 after separation of the placenta, by the contraction of the muscular 
 fibres of the uterus. They pass, as we have already mentioned, in 
 an exceedingly oblique direction, from the uterine surface to the 
 placenta ; and the muscular fibres, which cross them transversely 
 above and below, necessarily constrict them, and effectually close 
 their orifices, immediately on being thrown into a state of contraction. 
 Another ver^ remarkable phenomenon, connected with preg- 
 nancy and parturition is the appearance in the uterus of a new 
 
634 DISCHARGE OP THE OVUM. 
 
 mucous membrane, growing underneath the old, and ready to 
 take the place of the latter after its discharge. 
 
 If the internal surface of the body of the uterus be examined 
 immediately after parturition, it will be seen that at the spot, where 
 the placenta was attached, every trace of mucous membrane has 
 disappeared. The muscular fibres of the uterus are here perfectly 
 exposed and bare ; while the mouths of the ruptured uterine sinuses 
 are also visible, with their thin, ragged edges hanging into the 
 cavity of the uterus, and their orifices plugged with more or less 
 abundant bloody coagula. 
 
 Over the rest of the uterine surface, the decidua ve^ a has also 
 disappeared. Here, however, notwithstanding the loss of the ori- 
 ginal mucous membrane, the muscular fibres are not perfectly bare, 
 but are covered with a thin, semi-transparent film, of a whitish color 
 and soft consistency. This film is an imperfect mucous membrane 
 of new formation, which begins to be produced, underneath the 
 old decidua vera, as early as the beginning of the eighth month. 
 We have seen this new mucous mendbrane very distinctly in the 
 uterus of a woman who died undeliv»red at the above period. 
 The old mucous membrane, or decidua vera, is at this time some- 
 what opaque, and of a slightly yellowish color, owing to a partial 
 fatty degeneration which it undergoes in the latter months of preg- 
 nancy. It is easily raised and separated from the subjacent parts, 
 owing to the atrophy of its vascular connectipns; and the new 
 mucous membrane, situated beneath it, is readily distinguished by 
 its fresh color, and healt|||fr, transparent aspect. 
 
 The mucous membrane of the cervix ut^i, which takes no part 
 in the formation of the decidua, is not thrown off in parturition, 
 but remains in its natural position ; and after delivery it may be 
 seen to terminate at the os internum by an uneven, lacerated edge, 
 where it was formerly continuous with the decidua vera. 
 
 Subsequently, a regeneration of the mucous membrane takes place 
 over the whole extent of the body of the uterus. The mucous 
 membrane of new formation, which is already in existence at the 
 time of delivery, becomes thickened and vascular ; and glandular 
 tubules are gradually developed in its substance. At the end of 
 two months after delivery, according to Heschl' and Longet,' it has 
 entirely regained the natural structure of the uterine mucous mem- 
 
 ' Zeitschrift der K. K. Gesellschaft der Aerzte, in Wren, 1852. 
 ' Traits da Physiologie. De Ja Oengration, p. 173. 
 
KETKOGRADE DEVELOPMENT OF THE UTERUS. 635 
 
 brane. It unites at the os interum, by a linear cicatrix, with the 
 mucous membrane of the cervix, and the traces of its laceration at 
 this spot afterward cease to be visible. At the point, however, 
 where the placenta was at- ' 
 
 Fig. 232. 
 
 MUBCULAR FiBRBS OP U NIHPREOir ATBD 
 
 TTTERtTB; from a womaa aged 4Q, dead of pbthisU 
 palmonalis. 
 
 Fig. 233. 
 
 tached, the regeneration of 
 the mucous membrane is 
 less rapid; and a cicatrix- 
 like spot is often visible at 
 this situation for several 
 months after delivery. 
 
 The only further change, 
 which remains to be de- 
 scribed in this connection, 
 is the fatty degeneration 
 and reconstruction of the* 
 muscular substance of the. 
 uterus. This process, which 
 is sometimes known as the 
 "involution" of the uterus, 
 takes place in the following 
 manner. The muscular 
 fibres of the unimpregnated 
 uterus are pale, flattened, 
 spindle-shaped bodies (Fig. 
 232) nearly homogeneous 
 in structure or very faintly 
 granular, and measuring 
 from 3J5 to j^, of an inch 
 in length, by t^ Jg^ to b^'j, 
 of an inch in width. During 
 gestation these fibres in- 
 crease very considerably in 
 size. Their texture becomes 
 much more distinctly granu- 
 lar, and their outlines more 
 strongly marked. An oval 
 nucleus also shows itself in • 
 
 the central part of each fibre. The entire walls of t\^e uterus, at 
 the time of delivery, are composed of such muscular fibres as 
 these, arranged in circular, oblique, and longitudinal bundles. 
 
 About the end of the first week^^fter delivery, these fibres begin 
 
 Muscular Fibrbs op Human tlTERua, ten 
 days arter parturJtloQ ; from a woman dead of puer- 
 peral fever. 
 
636 
 
 DISCHAEGE OP TUK OVUM. 
 
 to undergo a fatty degeaeration. (Fig. 233.) Their granules be- 
 come larger and more prominent, and very soon assume the 
 appearance of molecules of fat, deposited in the substance of the 
 fibrl. The fatty deposit, thuscommenced> inereases in abundanceji 
 and the molecules continue to enlarge until they become converted 
 into fully formed oil-globules, which fill the interior of the fibre 
 
 or less completely. 
 
 Fig. 234. 
 
 more 
 
 and njask, to a certain ex- 
 tent, its anatomical cha- 
 racters. (Fig. 234.) The 
 universal fatty degenera- 
 tion, thus induced, .gives to •• 
 Jihe uterus a softer consist- 
 ency, and a pale yellpwish 
 color which is characteristic 
 .of it at this period. The 
 muscular fibres which have 
 become altered by the fatty 
 deposit are afterward gra- 
 dually absorbed and disap- 
 pear;, their place being 
 subsequently taken by 
 other fibres of new forma- 
 tion, which already begin 
 to make their, appearance before the old- ones have been completely 
 destroyed. As this process goes on, it results finally in a complete 
 renovation of the muscular substance of the uterus. The organ 
 becomes again reduced in size, compact in tissue, and of a pale 
 ruddy hue, as in the ordinary unimpregnated condition. This entire 
 renewal or reconstruction of the uterus is completed,' according to 
 Heschl," about the end of the second month after delivery. 
 
 MUBCDLXB riBBES OF HuMAH Utebdb, three 
 weeks after parti^ltion ; from a woman dead of peri- 
 tonitis. 
 
 Op. cit. 
 
DEVELOPMENT OS THE EUBSYO. 
 
 637 
 
 CHAPTER XIV;. 
 
 DEVELOPMENT OP THE BMBBYO— NEEV OUS SYSTEM. 
 ORGANS OF SENSE, SKELETON, AND LIMBS. 
 
 Fig.' 235. 
 
 The first trace of a spinal cord in the embryo consists of the 
 double longitudinal fold or ridge of the blastodermic membrane, 
 which shows itself at an early period, as aboye described, on each 
 side the median furrow. The two laminae of which this is com- 
 posed, on the right and left sides (Fig. 235, 3,i>), unite with each 
 other in front, forming a rounded dilatation (c), 
 the cephalic extremity, and behind at rf, forming 
 a pointed or caudal extremity. Near the pos- 
 terior extremity, there is a smaller dilatation, 
 which marks the future situation of the lumbar 
 enlargement of the spinal cord. 
 
 .A.S the laminse above described grow upward 
 and backward, they unite with each other upon 
 the median line, so that the whole is converted 
 into a hollow cylindrical cwm, terminating ante- 
 riorly -by a bulbous enlargement, and posteriorly 
 by a pointed enlargement; the central cavity 
 which it contains running continuously through 
 it, from front to rear. 
 
 The next change which shows itself is a divi- 
 sion of the anteripr bulbous enlargement into 
 three secondary compartments or vesicles (Fig. 
 236), which are partially separated from each other by transverse 
 constrictions. These vesicles are known as the three cerebral vesi- 
 cles, from which all the d liferent parts of the encephalon are after 
 ward to be developed. The first, or most anterior cerebral vesicle 
 is destined to form the hemispheres; the second, or middle, the 
 tuberoula quadrigemina ; and the third, or posterior, the medulla 
 •oblongata. All three vesicles are at this time hollow, and their 
 
 Formajtion of Crbe- 
 bho-Spisal Axis.— 
 n, b. Spinal cord. e. Ce- 
 phalic extremity. d. 
 Caudal extremity. 
 
638 
 
 DEVELOPMENT OP THE EMBBTO. 
 
 cavities communicate freely witli eacli other, through the interven- 
 ing constrictions. 
 
 Very soon the anterior and the posterior cerebral vesicles suflfer 
 a further division; the middle one remain- 
 ing undivided. The anterior vesicle thus 
 separates into two portions, of which- the 
 first, or larger, constitutes the hemispheres, 
 while, the second, or smaller, becomes the 
 optic thalami. The third vesicle also sepa- 
 rates intottwo portions, of which the ante- 
 rior becomes the cerebellum, and the pos- 
 terior the mediiia oblongata. 
 
 There are, therefore, at this time five 
 cerebral vesicles, all of whose cavities com- 
 municate with each other and with the 
 central cavity of the spinal cord. The 
 entire cerebro-spinal axis, at the same time, 
 becomes very strongly curved in an ante- 
 rior direction, corresponding with the ante- 
 rior curvature of the body of the embryo 
 (Fig. 237); so that the middle vesicle, or 
 that of the tubercula quadrigemina, occu- 
 ♦ pies a prominent angle at the upper part of 
 
 the encephalon; while the hemispheres and the medulla oblongata 
 are situated below it, anteriorly and posteriorly. 
 
 At first, it will be observed, the relative size of the various parts 
 of the encephalon is ipry different from that which 
 they afterward attain in the adult condition. The 
 hemispheres, for example, are hardly larger than 
 the tubercula quadrigemina ; and the cerebellum 
 is very much inferior in size to the medulla oblon- 
 gata. Soon afterward, the relative position and size 
 of the parts begin to alter. Tiie hemispheres and 
 tubercula quadrigemina grow faster than the poste- 
 rior portions of the encephalon ; and the cerebellum 
 becomes doubled backward over the n^dulla oblon- 
 gata. (Fig. 238.) Subsequently, the hemispheres 
 rapidly enlarge^ growing upward and backward, 
 so as to cover in and conceal both the optic tha- 
 lami and the tubercula quadrigemina ^Fig. 289); the cerebellum 
 tending in the same way to grow backward, and projecting farther 
 
 Formation of the Gsbebbo- 
 SpiwAL Axi^. — 1. Vesicle of 
 tiie liemi-pherpR. 2. Vesicle of 
 tlie tubercula quadrii^emiDa. 3. 
 Vesicle oflhe medulla oblonjfata. 
 
 Fig. 237. 
 
 ^ -^ 4 
 
 FfflTAL Pia, five- 
 eighths of an inch 
 long, showing brain 
 and spioal cord. — 1. 
 Hemiapheres. 2. Tu- 
 bercala quadrigemi- 
 na. 3. CerebeUnm. 
 4. Medulla oblongata. 
 
NEKVOUS SYSTEM. 
 
 639 
 
 and farther over the medulla oblongata. The subsequent higtory 
 of the development of the encephalon is little more than a con- 
 
 Fig. 239. 
 
 F(ETAi. Pig, one and a. quarter inch 
 long. — 1. Heniisiilieres. 2. Tubercula 
 quadrigemina. 3. Cerebellum. 4. Me- 
 dulla oblongata. 
 
 Head of F(etal Fig, three and a 
 half Inches long. — x. Hemlsptieres. 8. 
 Cerebellam. 4. Medulla oblongaia. 
 
 tinuation of the same process ; the relative dimensions of the parts 
 constantly changing, so that the hemispheres become, in the adult 
 condition (Fig. 240), the largest of all the divisions of the ence- 
 
 Fig. 2i0. 
 
 Brain op Adult Fro. — 1. HemisphereE. 3. Cerebellam. 4. Medu'ua oblongata, 
 
 phalon, while the cerebellum is next in size, and covers entirely 
 the upper portion of the medulla oblongata. The surfaces, also, of 
 the hemispheres and cerebellum, which were at first smooth, become 
 afterward convoluted; increasing, in this way, still farther the 
 extent of theii* nervous matter. In the human foetus, these con- 
 volutions begin to appear about the beginning of the fifth month 
 (Longet), and grow constantly deeper and more abundant during 
 the remainder of foetal life. 
 
 The lateral portions of the brain growing at the same time more 
 rapidly than that which is. situated on the median line, they soon 
 project on each side outward and upward r and. by folding over 
 
6i0 DEVKLOPMENT OF THE EMBBYO. 
 
 agaipst eacli other in the median line, form the right and left hemi- 
 spheres, separated from each other by the longitudinal fissure. 
 A similar process of growth taking place in the spinal cord results 
 in the formation of the two lateral columns and the anterior and pos- 
 terior median fissures of the cord. Elsewhere the median fissure is 
 less complete, as, for example, between the two lateral halves of the 
 cerebellum, the two optic thalami and corpora striata, and the two 
 tubercula quadrigemina ; but it exists everywhere, and marks more 
 or less distinctly the division between the two sides of the nervous 
 centres, produced by the excessive growth of their lateral portions. 
 In this way t^e-whole cerebro-spinal axis is converted into a double 
 organ, equally developed upon the right and left sides, and partially 
 divided by a longitudinal median fissure. 
 
 Organs of Special Sense. — The eyes are formed by a diverticulum 
 which grows out on each side from the first cerebral vesicle. This 
 diverticulum is at first hollow, its cavity communicating with that 
 of the hemisphere. Afterward, the passage between the two is filled 
 up with a deposit of nervous matter, and becomes the optic nerve. 
 The globular portion of the diverticulum, which is converted into 
 the globe of the eye, has a very thin layer of nervous matter depo- 
 sited upon its internal surface, which becomes the retina ; the rest 
 of its cavity being occupied by a gelatinous semi-fluid substance, 
 the vitreovs body. The crystalline lens is formed in a distinct fol- 
 licle, which is an offshoot of the integument, and becomes partially 
 imbedded in the anterior" portion of the globe of the eye. The 
 cornea also is originally a part of the integument, and remains 
 partially opaque until avery late period of development. Its tissue 
 clears up, however, and becomes perfectly transparent, shortly be- 
 fore birth. 
 
 The iris is a muscular septum which is formed in front of the 
 crystalline lens, separating tne anterior and posterior chambers of 
 the aqueous humor. Its central opening, which afterward becomes 
 the pupil, is at first closed by a vascular membrane, the pupillary 
 membrane, passing directly across the axis of the eye. The vessels 
 of this membrane, which are derived from those of the iris, subset 
 quently become atrophied. They disappear first from its centre, 
 and afterward recede gradually toward its circumference ; returning 
 always upon themselves in loops, the convexities of which are directed 
 toward the centre of the membrane. The pupillary membrane itself 
 finally becomes atrophied and destroyed, following in this retro- 
 grade process tlje direction of its receding bloodvessels, viz., from 
 
SKELETON AND LIMBS, 641 
 
 tlie centre toward the circumference. It ias completely disappeared 
 by the end of the seventh month. (Cruveilhier.) 
 
 The eyelids are formed by folds of the integument, which 
 gradually project from above and below the situation of the eye- 
 ball. They grow so rapidly during the second and third months 
 that their free margins come in contac^and adhere together, so that 
 they cannot be separated at that time without some degree of vio- 
 lence. They remain adherent from this period until the seventh 
 month (Guy), when their margins separate and they become per- 
 fectly free and movable. In the carnivorous animals, however 
 (dogs and cats), the eyelids do not separate from each other until 
 eight or ten days after birth. 
 
 The internal ear is formed in a somewhat similar manner with 
 the eyeball, by an offshoot. from the third cerebral vesicle; the 
 passage 'between them filling up by a deposit of white substance, 
 which becomes the auditory nerve. The tympanum and auditory 
 meatus are both offshoots from the external integument. 
 
 Skeleton. — At a very early. period of development there appears, 
 as we have already described (Chap. VII.), immediately beneath the 
 cerebro-spinal axis, a cylindrical cord, of a soft, cartilaginous con- 
 sistency, termed the chorda dorsalis. It consists of a fibrous sheath 
 containing a mass of simple cells, closely packed together and 
 united by adhesive material. This cord is not intended to be a 
 permanent part of the skeleton, but is merely a temporary organ 
 destined to disappear as development proceeds. 
 
 Immediately around the chorda dorsalis there are deposited soon 
 afterward a number of cartilaginous plates, which encircle it in a 
 series of rings, corresponding in number with the bodies of the future 
 vertebrae. These rings increase in thickness from without inward, 
 encroaching upon the substance of the chorda dorsalis, and finally 
 taking its place altogether. The thickened rings, which have been 
 filled up in this way and solidified by cartilaginous deposit, become 
 the bodies of the vertebrae ; while their transverse and articulating 
 processes, with the laminae and spinous processes, are formed by 
 subsequent outgrowths from the bodies in various directions. 
 
 When the union of the dorsal plates upon the median line fails 
 to take place, the spinal canal remains open at that situation, and 
 presents the malformation known as spina bifida. This malforma- 
 tion may consist simply in a fissure of the spinal canal, more or less 
 extensive, in which case it may often be cured, or may even close 
 spontaneously ; or it may be complicated with an imperfect deve- 
 41 
 
642 DEVELOPMKNT OF THE EMBRYO. 
 
 lopment or complete absence of the spinal cord at the same spot, 
 when it is accompanied of course by paralysis of the lower ex- 
 tremities, and almost necessarily results in early death. 
 
 The entire skeleton is at first cartilaginous. The first points of 
 ossification show themselves about the beginning of the second 
 month, almost simultaneously in the clavicle and the upper and 
 lower jaw. Then come in the following order, the long bones of 
 the extremities, the bodies and processes of the vertebrae, the bones 
 of the head, the ribs, pelvis, scapula, metacarpus and metatarsus, 
 and the phalanges of the fingers and toes. The bones of the carpus, 
 however, are all cartilaginous at birth, and do not begin to ossify 
 until a year afterward. The calcaneum and astragalus begin to 
 ossify, according to Cruveilhier, during the latter periods of foetal 
 life, but the remainder of the tarsus is .cartilaginous at birth. The 
 lower extremity of the femur begins to ossify, according to the 
 same author, during the latter half of the ninth month. The pisiform 
 bone of the carpus is said to commence its ossification later than 
 any other bone in the skeleton, viz., at from twelve to fifteen years 
 after birth. Nearly all the bones ossify from several distinct points ; 
 the ossification spreading as the cartilage itself increases in, size, 
 and the various bony pieces, thus produced, uniting with each other 
 at a later period, usually some time after birth. 
 
 The limbs appear by a kind of budding process, as offshoots of 
 the external layer of the blastodermic membrane. They are at 
 first mere rounded elevations, without any separation between the 
 fingers and toes, or any distinction between the different articular 
 tions. Subsequently the free extremity of each limb becomes di- 
 vided into the phalanges of the fingers or toes ; and afterward the 
 articulations of the wrist and ankle, knee and elbow, shoulder and 
 hip, appear successively from below upward. 
 
 The posterior extremities, in the human subject, are less rapid in 
 their development than the anterior. Throughout the term of 
 fcetal life, indeed, the anterior parts of the body are generally more 
 voluminous than the posterior. The younger the embryo, the larger 
 are the head and upper extremities in proportion to the rest of the 
 body. The lower limbs and the pelvis, more particularly, are very 
 slightly developed in the early periods of growth, as compared with 
 the spinal column, to which they are attached. The inferior ex- 
 tremity of the spinal column, formed by the sacrum and coccyx, 
 projects at this time considerably beyond the pelvis, forming a tail, 
 like that of the lower animals^ which is curled forward toward the 
 
SKELETON AND LIMBS. 643 
 
 abdomen, and terminates in a pointed extremity. Subsequently the 
 pelvis and the muscular parts seated upon it grow so much faster 
 than the sacrum and coccyx, that the latter become concealed 
 under the adjoining soft parts, and the rudimentary tail accord- 
 ingly disappears. 
 
 The integument of the embryo is. at first thin, vascular, and ex- 
 ceedingly transparent, It afterward becomes thicker, more opaque, 
 and whitish in color ; though even at birth it is more vascular than 
 in the adult condition, and the ruddy color of its abundant capil- 
 lary vessels is then very strongly marked. The hairs begin to 
 appear about the middle of intra-uterine life ; showing themselves 
 first upon the eyebrows, and afterward Upon the scalp, trunk and 
 extremities. The nails are in process of formation from the third 
 to the fifth month ; and, according to Kolliker, are still covered 
 with a -layer of epidermis until after the latter period. The seba< 
 ceous matter of the cutaneous glandules accumulates upon the skin 
 after the sixth month, and forms a whitish, semisolid, oleaginous« 
 layer, termed the vernix caseosa, which is most abundant in the^ 
 flexures of the joints, between the folds of the integument, behind 
 the ears and upon the scalp. 
 
 The cells of the epidermis are repeatedly exfoliated after the first 
 five months of foetal life (Kolliker), and replaced by others of new 
 formation and of larger size. These exfoliated epidermic cells are 
 found mingled with the sebaceous matter of the vernix caseosa in, 
 great abundance. This semi-oleaginous layer, with which the in- 
 tegument is covered, becomes exceedingly useful in the process of 
 parturition, by lubricating the surface of the body, and allowing ii 
 to pass easily through the generative passages. 
 
6J:J: DEVE1.0PMENT OF THE ALIMENTABY CANAL 
 
 CHAPTER XV. 
 
 DETBLOPMBNT OP THE ALIMENTARY CANAL 
 AND ITS APPENDAGES. 
 
 We have already seen, in a preceding chapter, that the intestinal 
 canal is formed by the internal layer of the blastodermic membrane, 
 which curves forward on each side, and is thus converted into a 
 nearly straight cylindrical tube, terminating at each extremity in 
 a rounded cul-de-sac, and* inclosed by the external layer of the 
 blastodermic membrane. The abdominal walls, however, do not 
 unite with each other upon the median line until long after the 
 formation of the intestinal canal ; so that, during' a certain period, 
 the abdomen of the embryo is widely open in front, presenting a 
 long oval excayj^tiOn, in which the nearly straight, intestinal tube 
 is' to be seen, Tunpjng from its anterior to its posterior extremity. 
 
 The formaticjn ofthe stomach takes place in the following man- 
 ner: The alimentary canal, originally straight, soon presents two 
 lateral curvatures at the upper part of the abdomen ; the first to 
 the left, the second to the right. The first of these curvatures 
 becomes expanded into a wide sac, projecting laterally from the 
 median line into the left hypochondrium, forming the great pouch 
 of .the stomach. The second curvature, directed to the right, marks 
 the boundary between the stomach and the duodenum ; and the 
 tube at that point becoming constricted and furnished with a circular 
 layer of muscular fibres, is converted into the pylorus. Immedi- 
 ately below the pylorus, the duodenum again turns to the left ; and 
 these curvatures, increasing in number and complexity, form the 
 convolutions of the small intestine. The large intestine forms a 
 spiral curvature ; ascending on the right side, then crossing over 
 to the left as the transverse colon, and again descending oil the left 
 side, to terminate by the sigmoid flexure in the rectum. 
 
 The curvatures of the intestinal canal take place, however, in an 
 antero-posterior, as well as in a lateral direction, and may be best 
 studied in a profile view, as in Fig. 241. The abdominal walls are 
 
AND ITS APPENDAGES. 645 
 
 here still imperfectly closed, leaving a wide opening at a, h, where 
 the integument of the foetus becomes continuous with the com- 
 mencement of the amniotic membrane, Tb^ intestine makes at 
 
 Fig. 241. 
 
 FormatioQ of Alihrn T AR Y Canal. — a, b. Commencemeiit of amnion, c. e. Intestine, d. 
 Pharynx, e. Urinary bladder. / Allantois, g. Umbilical vesicle, m. Dotted line, showing the 
 place of formation of the (esophagus. 
 
 first a single angular turn forward, and opposite the most promi- 
 nent portion of this angle is to be seen the obliterated duct, which 
 forms the stem of the umbilical vesicle, (g.) A short distance below 
 this point the intestine subsequently enlarges in its calibre, and the 
 situation of this enlargement marks the commencement of the 
 colon. The two portions of the intestine, after this period, become 
 widely different from each other. The upper portion, which is the 
 small intestine, grows mostly in the direction of its length, and 
 becomes a very long, narrow, and convoluted tube : while the lower 
 portion, which is the large intestine, increases rapidly in diameter, 
 but elongates less than the former. 
 
 At the point of junction of the small and large intestines, a late- 
 ral bulging or diverticulum of the latter shows itself, and increases 
 in extent, until the ileum seems at last to be inserted olsliquely into 
 the side of the colon. This diverticulum of the colon is at first 
 uniformly tapering or conical in shape ; but afterward that portion 
 which forms its free extremity, becomes narrow and elongated, and 
 is slightly twisted upon itself in a spiral direction, forming the 
 appendix vermiformis ; while the remaining portion, which is con- 
 tinuous with the intestine, becomes exceedingly enlarged, and' forms 
 the caput cqli. 
 
 The caput coli and the appendix are at first situated near the 
 
646 
 
 DEVELOPMENT OP THE ALIMENTARY CANAL 
 
 Fig. 242. 
 
 umbilicus ; but between the fourth and fifth .moilths (Cruveilhier) 
 their position is altered, and they then become fixed in the right 
 iliac re^on. During the first six months, the internal surface of 
 the small intestine is smooth. At the seventh month, according to 
 Cruveilhier, the valvulse conniventes begin to appear, after which 
 they increase in size till birth. The division of the colon into 
 sacculi by longitudinal and transverse bands, is also an appearance 
 which presents itself only during the last half of foetal life. Pre- 
 vious to that time, the colon is smooth and cylindrical in figure, 
 like the small intestine. 
 
 After the small intestine is once formed, it increases very rapidly 
 in length. It grows, indeed, at this time, faster than the walls of 
 
 the abdomen; so that it can no longer 
 be contained in the abdominal cavity, 
 but protrudes, under the form of an in- 
 testinal loop, or hernia, from the umbili- 
 cal opening. (Fig. 242.) In the human 
 embryo, this protrusion of the intestine 
 can be readily seen during the latter part 
 of the second month. At a subsequent 
 period, however, the walls of the abdo- 
 men grow more rapidly than the intes- 
 tine. They accordingly gradually' en- 
 velop the hernial protrusion, and at last 
 inclose it again in the cavity of the ab- 
 domen. 
 
 Owing to an imperfect development 
 of the abdominal walls, and an imperfect 
 closure of the umbilicus, this intestinal 
 protrusion, which is normal during the early stages of foetal life, 
 sometimes remains at birth, and we then have a congenital umbilical 
 hernia. As the parts at that time, however, have a natural tendency 
 to cicatrize and unite with each other, simple -pressure is generally 
 effectual, in sucli cases, in retaining the hernia within the abdomen, 
 and in producing at last a complete cure. 
 
 Urinary Bladder, Urethra, &c. — It will be recollected that very 
 soon after the formation of the intestine, a vascular outgrowth takes 
 place from its posterior portion, which gradually protrudes from the 
 open walls of the abdomen in front, until it comes in contact with 
 the external investing membrane of the egg; and forms, by its con- 
 tinued growth and expansion, the allaniois. (Fig. 241, /.) It is at 
 
 FtETAL Fro, showing lobp 
 of intestine, forming umbilical 
 hernia ; from n specimen in the 
 anthor'a, possession. From the 
 coDTexity of the loop athinfilament 
 is seen passing to the umbilical 
 vesicle, which is here flattened into 
 a leaf-like form. 
 
AND ITS APPENDAGES. 6i7 
 
 first, as we have shown above, a hollow sac ; but, as it spreads out 
 over the surface of the investing membrane of the egg, its two 
 opposite walls adhere to each other, so that its cavity is obliterated 
 at this situation, and it is thus converted into a single vascular 
 membrane, the cAoriow. This obliteration of the cavity of the 
 allantois commences at its external portion; and gradually extends 
 inward toward the point of its emergence from the abdomen. The 
 hollow tube, or duct, which connects the cavity of the allantois with 
 the posterior part, of the intestine, is accordingly converted, as the 
 process of obliteration proceeds, into a solid, rounded cord. This 
 cord is termed the urachus. 
 
 After the walls of the abdomen have come in contact, and united 
 with each other at the umbilicus, that portion of the above duct 
 which is left outside the abdominal cavity, forms a part of the um- 
 bilical cord, and. remains connected with the umbilical arteries and 
 vein. That portion, on the contrary, which is included in the ab- 
 domen, does not close completely, but remains as a pointed fusiform- 
 sac, terminating near the umbilicus in the solid cord of the urachus, 
 and still communicating at its base with the lower extremity of the 
 intestinal canal. This fusiform sac (Fig. 241, e), becomes the wn- 
 nary hladder ; and in the foetus at term, the bladder is still conical 
 in form, its pointed extremity being attached, by means of the ura- 
 chus, to the internal surface of the abdominal walls at the situation 
 of the, umbilicus. Afterward, the bladder loses this conical form, 
 and its fundus in the adult becomes rounded and bulging. 
 
 The urinary bladder, as it appears from the above description, at 
 first communicates freely with the intestinal cavity. The intestine, 
 in fact, terminates, at this time, in a wide passage, or cloaca, at its 
 lower extremity, which serves as a common outlet for the urinary 
 and intestinal passages. Subsequently, however, a horizontal par- 
 tition makes its appearance just above the point of junction between 
 the bladder and rectum, and grows downward and forward in such 
 a manner as to divide the above-mentioned cloaca into two parallel 
 and unequal passages. The anterior or smaller of these passages 
 becomes the urethra, the posterior or larger becomes the rectum ; 
 and the lower edge of the septum between them becomes finally 
 united with the skin, forming, at its most superficial part, a tole 
 rably wide band of integument, the perineum, which intervenes 
 between the anus and the external portion of the urethra. 
 
 The contents of the intestine, which accumulate during foetal life, 
 vary in different parts of the alimentary canal. In the small intes- 
 
6J:8 DEVELOPMENT OF TUK ALIMENTAET CAITAL 
 
 tine they are semifluid or gelatinous in consistency, of a light 
 yellowish or grayish-white color in the duodenum, becoming yellow, 
 reddish-brown and greenish-brown below. In the large intestine 
 they are of a dark greenish hue, and pasty in consistency ; and the 
 contents of this portion of the alimentary canal have received the 
 name of meconium, from their resemblance to inspissated poppy- 
 juice. The meconium contains a large quantity of fat, as well as 
 various insoluble substances, probably the residue of epithelial and 
 mucous accumulations. It does not contain, however, any trace of 
 the biliary substances (tauro-cholates and glyko-cholates) when care- 
 fully examined by Pettenkofer's test ; and cannot therefore properly 
 be regarded, as is sometimes incorrectly asserted, as resulting from 
 the accumulation of bile. In the contents of the small intestine, on 
 the contrary, traces of bile may be found, according to Lehmann,' 
 so early as between the fifth and sixth months. We have also 
 found distinct traces of bile in the small intestine at birth, but it is 
 even then in extremely small quantity, and is sometimes altogether 
 absent. 
 
 The meconium, therefore, and the intestinal contents generally, 
 are not composed principally, or even to any appreciable extent, of 
 the secretions of the liver. They appear rather to be produced by 
 the mucous membrane of the intestine itself. Even their yellowish 
 and greenish color does not depend on the presence of bile, since 
 the yellow color first shows itself, in very young foetuses, about 
 •the middle of the small intestine, and not at its upper extremity. 
 The material which accumulates afterward appears to extend from 
 this point upward and downward, gradually filling the intestine, 
 and becoming, in the ileum and large intestine, darker and more 
 pasty as gestation advances. 
 
 It is a singular fact, perhaps of some importance in this connec- 
 tion, that the amniotic fluid, during the latter half of foetal life, 
 finds its way, in greater or less abundance, into the stomach, and 
 through that into the intestinal canal. Small cheesy -looking masses 
 may sometimes be found at birth in the fluid contained in the 
 stomach, which are seen on microscopic examination to be no other 
 than portions of the vernix caseosa exfoliated from the skin into 
 the amniotic cavity, and afterward swallowed. According to Kdl- 
 liker,^ the soft downy hairs of the foetus, exfoliated from the skin, 
 
 ' Physiological Chemistry, Philadelphia edition, vol. i. p. 532. 
 = Gewebelehre. Leipzig, 1°52, p. 139. 
 
AND ITS APPENDAGES. 64:9 
 
 are often swallowed in the same way, and may be found in the 
 meconium. 
 
 The gastric juice is not secreted before birth ; the contents of the 
 stomach being generally in small quantity, clear, nearly colorless, 
 and neutral or alkaline in reaction. 
 
 The liver is developed at a very early period. Its size in pro- 
 portion to that of the entire body is, in fact, very much greater in 
 the early months than at birth or in the adult condition. In the 
 foetal pig we have found the relative size of the liver greatest 
 within the first month, when it amounts to very nearly 12 per cent, 
 of the entire weight of the body. Afterward, as it grows less rapidly 
 than other parts, its relative weight diminishes successively to 10 
 per cent, and 6 per cent. ; and is reduced before birth to 3 or 4 per 
 cent. In the human subject, also, the weight of the liver at birth 
 is between 3 and 4 per cent, of that of the entire body. 
 
 The secretion of hile takes place, as we have intimated above, 
 during foetal life, in a very scanty manner. We have found it, in 
 minute quantity, in the gall-bladder, as well as in the small intes- 
 tine at birth ; but it does not probably take any active part in the 
 nutritive or other functions of the foetus before that period. 
 
 The glycogenic function of the liver commences during foetal life, 
 and at birth the tissue of the organ is abundantly saccharine. It is 
 ' remarkable, however, that in the early periods of gestation sugar is 
 produced in the foetus from other sources than the liver. In very 
 young foetuses of the pig, for example, both the allantoic and 
 amniotic fluids are saccharine, a considerable time before any sugar 
 makes its appearance in the tissue of the liver. Even the urine, in 
 half-grown foetal pigs, contains an appreciable quantity of sugar, 
 and the young animal is therefore, at this period, in a diabetic con- 
 dition. This sugar, however, disappears from the urine before birth, 
 and also from the amniotic fluid, as has been ascertained by M. Ber- 
 nard ;' while the liver begins to produce a saccharine substance, and 
 to exercise the glycogenic function, which it continues after birth. 
 
 Development of the Pharynx, (Esophagus, &c. — We have already 
 seen that the intestinal canal consists at first of a cylindrical tube 
 terminated at each extremity of the abdominal cavity by a rounded 
 cul-de-sac (Fig. 241, c, c) ; and that the openings of the mouth and 
 anus are subsequently formed by perforations which take place 
 through the integument and the intervening tissues, and so estab- 
 
 ' Lemons de Physiologie Expgrimentale, Paris, 185.5, p. 398. 
 
650 DEVELOPMENT OP THE ALIMBNTAEY CANAL 
 
 lish a communication with the intestinal tube. The formation of 
 the anterior perforation, and its appendages, takes place in the fol- 
 lowing mianner : — 
 
 After the early development of the intestinal tube in the mode 
 above described, the head increases in size out of all proportion to 
 the remainder of the foetus, projecting as a large rounded mass from 
 the anterior extremity of the body, and containing the brain and the 
 organs of special sense. This portion soon bends over toward the 
 abdomen, in consequence of the increasing curvature of the whole 
 body which takes place at this time. In the interior of this 
 cephalic mass there is now formed a large cavity (Fig. 241, dj, by 
 the melting down and liquefaction of a portion of its substance. 
 This cavity is the pharynx. It corresponds by its anterior extre- 
 mity to the future situatipn of, the mouth; and by its posterior 
 portion to the upper end of the intestinal canal, the future situation 
 of the stomach. It is still, however, closed on all sides, and does 
 not as yet communicate either with the exterior or with the cavity 
 of the stomach.. There is, accordingly, at .this time, no thorax 
 whatever ; but the stomach lies at the upper extremityof the abdo- 
 men, immediately beneath the lower extremity of the pharynx, from 
 which it is separated by a wall of intervening tissue. 
 
 Subsequently, a perforation takes place between the adjacent 
 extremities of the pharynx and stomach, by a short narrow tube, 
 the situation of which is marked by the dotted lines x, in Fig. 241. 
 This tube afterward lengthens by the rapid growth of that portion 
 of the body in which it is contained, and becomes the oesophagus. 
 Neither the pharynx nor oesophagus, therefore, are, properly speak- 
 ing, parts of the intestinal canal,- formed from the internal layer of 
 the blastodermic membrane ; but are, on the contrary, formations 
 of the external layer, from which the entire cephalic mass is pro- 
 duced. The lining membrane of the pharynx and oesophagus is to 
 be regarded, also, for the same reason, as rather a continuation of 
 the integument than of the intestinal mucous membrane ; and even 
 in the adult, the thick, whitish, and opaque pavement epithelium 
 of the oesophagus may be seen to terminate abruptly, by a well- 
 defined line of demarkation, at the cardiac orifice of the stomach ; 
 beyond which, throughout the remainder of the alimentary canal, 
 the epithelium is of the columnar variety, and easily distinguish- 
 able by its soft, ruddy, and transparent appearance. 
 
 As the oesophagus lengthens, the lungs are developed on each 
 side of it by a protrusion from the pharynx which extends and 
 
AND ITS APPENDAGES. 651 
 
 becomes repeatedly subdivided, forming the bronchial tubes and 
 their ramifications. At first, the lungs project into the upper 
 part of the abdominal cavity ; for there is still no distinction be- 
 tween the chest and abdomen. Afterward, a horizontal partition 
 begins to form on each side, at the level of the base of the lungs, 
 which gradually closes together at a central point, so as to form 
 the diaphragm, and finally shuts off altogether the cavity of 
 the chest from that of the abdomen. Before the closure of the 
 ■ diaphragm, thus formed, is complete, a circular opening exists on 
 each side the median line, by which the peritoneal and pleural 
 cavities communicate with each other. In some instances the de- 
 velopment of the diaphragm is arrested at this point, either on one 
 side or the other, and the opening accordingly remains permanent. 
 The abdoniinal organs then partially protrude into the cavity of 
 the chest on that side, forming congenital diaphragmatic hernia. 
 The lung on the afiected side also usually remains in a state of 
 imperfect development. Diaphragmatic hernia of this character is 
 more frequently found upon the left side than upon the right. It 
 may sometimes continue until adult life without causing any seri- 
 ous inconvenience. 
 
 The heart is formed, at a very early period, directly in front of 
 the situation of the oesophagus. Its size soon becomes very large 
 in proportion to the rest of the body ; so that it protrudes beyond 
 the level of the thoracic parietes, covered only by the pericardium. 
 Subsequently, the walls of the thorax, becoming more rapidly 
 developed, grow over it and inclose it. In certain instances, how- 
 ever, they fail to do so, and the heart then remains partially or 
 completely uncovered, in front of the chest, presenting the condition 
 known as ectopia cordis. This malformation is necessarily latal. 
 
 Development of the Face. — While the lower extremity of the 
 pharynx communicates with the cavity of the stomach, as above 
 described, its upper extremity also becomes perforated in a similar 
 manner, and establishes a communication with the exterior. This 
 perforation is at first wide and gaping. It afterward becomes 
 divided into the mouth and nasal passages ; and the different parts 
 of the face are formed round it in the following manner: — 
 
 From the sides of the cephalic mass five buds or processes shoot 
 out, and grow toward each other, so as to approach the centre of 
 the oral orifice above mentioned. (Fig. 243.) One of them grows 
 directly downward from the frontal region (i), and is called the 
 frontal or intermaxillary process, because it afterward contains in 
 
652 
 
 DEVELOPMENT OP THE ALIMENTARY CANAL 
 
 Pig. 243. 
 
 Ukad of Hitman Embrto, 
 at about the twentieth day. After 
 Longet ; from' a specimen in the 
 collection of M. Coste. — 1. Frontal 
 or intermaxillary process. 2. Pro- 
 cetis of superior maxilla. 3. Pro- 
 cess of inferior maxilla. 
 
 its lower extremity the intermaxillary bones, iri which the incisor 
 teeth of the upper jaw are inserted. The next process (2) ori^n- 
 ates from the side of the opening, and, advancing toward the median 
 line, forms, with its fellow of the opposite 
 side, the superior maxilla. The processes 
 of the remaining pair (3) also grow from 
 the side, and form, by their subsequent 
 union upon the median line, the inferior 
 maxilla. The inferior maxillary bone is 
 finally consolidated, in man, into a single 
 piece, but remains permanently divided, 
 in the lower animals, by a suture upon the 
 median line. 
 
 As the frontal process grows from above 
 downward, it becomes double at its lower 
 extremity, and at the same time two oif- 
 shoots show themselves upon its sides, 
 which curl round and inclose two circular 
 orifices, the opening of the anterior nares ; the ofishoots themselves 
 becoming the aire nasi. (Fig. 244.) The mouth at this period is 
 very widely open, owing to the imperfect development of the upper 
 
 and lower jaw, and the incomplete 
 formation of the lips and cheeks. 
 
 The processes of the superior max- 
 illa continue their growth, but less 
 rapidly than those of the inferior ; so 
 that the two sides of the lower jaw 
 are already consolidated with each 
 other, while those of the upper jaw 
 are still separate. 
 
 As the processes of the superior 
 maxilla continue to enlarge, they also 
 tend to unite with each other on the 
 median line, but are prevented from 
 doing' so by the intermaxillary pro- 
 cesses which grow down between them. They then unite with the 
 intermaxillary processes, which have at the same time united with 
 each other, and the upper jaw and lip are thus completed. (Fig. 
 245.) The external edge of the ala nasi also adheres to the superior 
 maxillary process and unites with it, leaving only a curved crease 
 
 Fin. 244. 
 
 H IS A D F H [J M A N £ M B K V o at about 
 
 the sixth week. From a specimen iu the 
 author's possession. 
 
AND ITS APPENDAGES. 653 
 
 or farrow, as a sort of cicatrix, to mark the line, of union between 
 them. 
 
 Sometimes the superior maxillary and the intermaxillary pro- 
 cesses fail to unite with each other ; and we then have the mal- 
 formation known, as hare-lip. The 
 fissure of hare-lip, consequently, as a *''S- 245. 
 
 general rule, is not situated exactly in 
 the median line, but a little to one side 
 of it, on the external edge of the inter- 
 maxillary process. Occasionally, the 
 same deficiency exists on both sides, 
 producing "double hare-lip ;" in which 
 case, if the fissures extend through 
 the bony structures, the central piece 
 of the superior maxilla, which is de- 
 tached from the remainder, contains head or hdmam embrto, abc.nt 
 
 ,1 n • • J. ii 1 the end of the aecotid month. — From a 
 
 the four upper mClSOr teeth, and cor- specimen m the a.thor-, poa.e.»loa. 
 
 responds with the intermaxillary bone 
 
 of the lower animals. In some rare instances the fissure of hare- 
 lip is situated in the median line, the two intermaxillary bones 
 never having united with each other. A case of this kind has 
 been observed by Prof. Jeffries Wyman.' 
 
 The eyes at an early period are situated upon the sides of the 
 head, so that they cannot be seen in an anterior view. (Fig. 243.) 
 As development proceeds, they come t9 be situated farther forward 
 (Fig. 244), their axes being divergent and directed obliquely for- 
 ward and outward. At a later period still they are placed on the 
 anterior plane of the face (Fig. 245), and have their axes nearly 
 parallel and looking directly forward. This change in the situa- 
 tion of the eyes is effected by the more rapid growth of the pos- 
 terior and lateral parts of the head, which enlarge in such a manner 
 as to alter the relative position of the parts seated in front of them. 
 
 The palate is formed by a septum between the mouth and nares, 
 which arises Ml each side as a horizontal plate or offshoot from the 
 superior maxilla. These two plates afterward unite with each 
 other upon the median line, forming a complete partition between 
 the oral and nasal cavities. The right and left nasal passages are 
 also separated from each other by a vertical plate (vomer), which 
 grows from above downward and fuses with the palatal plates be- 
 
 ' Transactions Boston Society for Medical Improvement, March 9th, 1863. 
 
654 DEVELOPMENT OP THE ALIMENTARY CANAL, ETC. 
 
 low. Fissure of tlie palate is caused by a deficiency, more or less 
 complete, of one of the horizontal maxillary plates. It is accord- 
 ingly situated a little on one side of the median line, and is fre- 
 quently associated with, hare-lip and fissure of the upper jaw. The 
 fissures of the palate and of the lip are very often continuous with 
 each other. 
 
 The anterior and posterior pillars of the fauces are incomplete 
 vertical partitions, which grow from the sides of the oral cavity, 
 and tend to separate, by a slight constriction, the cavity of the 
 mouth from that of the pharynx. 
 
 When all the above changes are accomplished, the pharynx, 
 oesophagus, mouth, nares, and fauces, with their various' projections 
 and division^, have been successively formed ; and the development 
 of the upper part of the alimentary canal is then complete, 
 
DEVJfiLOPMENT OF THE KIDNEYS. 
 
 655 
 
 CHAPTER XVI. 
 
 DETELOPMBNT OP THE KIDNEYS, WOLFFIAN 
 BODIES, AND INTEENAL ORGANS OF GENE- 
 RATION. 
 
 Fig. 246. 
 
 The first trace of a urinary apparatus in the embryo, consists of 
 two long, fusiform bodies, which make their appearance in the ab- 
 domen at a very early period, situated on each side the spinal 
 column. These are known by the name of the Wolffian bodies. 
 They are fully formed in the human subject, toward the end of the 
 first month (Coste), at which time they are the largest organs in the 
 cavity of the abdomen, extending from just below the. heart, nearly 
 to the posterior extremity of the body. In the foetal pig, when a 
 little over half an inch in length (Fig. 246), the "Wolffian bodies are 
 rounded and kidney-shaped, and occupy a 
 very large part , of the . abdominal cavity. 
 Their importance may be estimated from the 
 fact that their weight at this time is equal to 
 a little over -j'j of that of the entire body — a 
 proportion which is seven or eight times as 
 large as that of the kidneys in the adult 
 condition. There are, indeed, at this period 
 only three organs perceptible in the abdo- 
 men, viz., the liver, which has begun to be 
 formed at the upper part of the abdominal 
 cavity ; the intestine, which is already some- 
 what convoluted, and occupies its central 
 portion ; and the "Wolffian bodies, which pro- 
 ject on each side the spinal column. 
 
 The "Wolffian bodies, in their intimate 
 structure, closely resemble the adult kidney. They consist of 
 secreting tubules, lined with epithelium, which run from the outer 
 toward the inner edge of the organ, terminating at their free ex- 
 
 F<ET AL Pio, 5^ of an inch 
 long ; from a specimen in the 
 author's possession. 1. Heart. 
 2. Anterior extremity. 3. Pos- 
 terior extremity. 4. Wolffian 
 body. The abdominal walls 
 have been cat away, in order 
 to show the position of the 
 Wolffian bodies. 
 
656 DEVELOPMENT OP THE KIDNEYS. 
 
 tremities in small rounded dilatations. Into each of these dilated 
 extremities is received a globular coil of capillary bloodvessels, or 
 glomerulus, similar to that of the adult kidney. The tubules of the 
 Wolffian body all empty into a common excretory duct, which leaves 
 the organ at its lower extremity, and communicates afterward with 
 the lower part of the intestinal canal, just at the point where the 
 diverticulum of the allantois is given off, and where the urinary 
 bladder is afterward to be situated. The principal, if not the 
 only distinction, between the minute structure of the WolfSan 
 bodies and that of the true kidneys, consists in the size of the 
 tubules and of their ^^lomeruli, these elements being considerably 
 larger in the Wolffian body than in the kidney. In the foetal 
 pig, for example," when about an inch and a half in length, the 
 diameter of the tubules of the Wolffian body is 3 -J 5 of an inch, 
 while in the kidney of the same foetus, the diameter of the tubules 
 is only 7^3 of an inch. The glomeruli in the Wolffian bodies 
 measure ^'5 of an inch in diameter, while those of the kidney mea- 
 sure only T^xi °f ^^ inch. The Wolffian bodies are therefore urinary 
 organs, so far as regards their anatomical structure, and are some- 
 times known, accordingly, by the name of the "false kidneys." 
 There is little doubt that they perform, at this early period, a func- 
 tion analogous to that of the kidneys, and separate from the blood 
 of the embryo an excrementitious fluid which is discharged by the 
 ducts of the organ into the cavity of the allantois. 
 
 Subsequently, the Wolffian bodies increase for a time in size, 
 though not so rapidly as the rest of the body ; and consequently 
 their relative magnitude diminishes. Still later, they begin to 
 suffer an absolute diminution or atrophy, and become gradually 
 less a,nd less perceptible. In the human subject, they are hardly 
 to be detected after the end of the second month (Longet), and in 
 the quadrupeds also they completely disappear long before birth. 
 They are consequently foetal organs, destined to play an important 
 part during a certain stage of development, but to become after- 
 ward atrophied and absorbed, as the physiological condition of the 
 foetus alters. During the period, however, of their retrogression 
 and atrophy, other organs appear in their neighborhood, which 
 become afterward permanently developed. These are, first, the 
 kidneys, and secondly, the internal organs of generation. 
 
 The kidneys are formed just behind the Wolffian bodies, and are 
 at first entirely concealed by them in a front view, the kidneys 
 being at this time not more than a fourth or a fifth part the size of 
 
WOLPFIAN BODIES. 
 
 657 
 
 Fig. 2.7. 
 
 F(ETAL Fi», oue and a baif 
 inches long. From a specimen in 
 tlie author's possessioa. — 1. Wolffl.ia 
 body. 2. Kidney. 
 
 the "Wolffian bodies. (Fig. 247.) As the kidneys, however, subse- 
 quently enlarge, while the "Wolffian bodies diminish, the propor- 
 tions existing between the two organs are 
 reversed ; and the "Wolffian bodies at last 
 come to be mere small rounded or ovoid 
 masses, situated on the anterior surface 
 of the kidneys. (Figs. 248 and 249.) The 
 kidneys, during this period, grow more 
 rapidly in an upward than in a downward 
 direction, so that the "Wolffian bodies 
 come to be situated near their inferior 
 extremity, and seem to have performed 
 a sliding movement from above down- 
 ward, ojrer their anterior surface. This 
 apparent sliding movement, or descent 
 of the "Wolffian bodies, is owing entirely 
 to the rapid growth of the kidneys in an 
 upward direction, as we have already explained. 
 
 The kidneys, during the succeeding periods of foetal life, become 
 in their turn very largely developed in proportion to the rest of the 
 organs; attaining a size, in the foetal pig, equal to -^-i^^ weight) 
 of the entire body. This proportion, however, diminishes again 
 very considerably before birth, owing 
 to the increased development of other 
 parts. In the human foetus at birth, 
 the weight of the two kidneys taken 
 together is yjg that of the entire 
 body. 
 
 Internal Organs of Generation. >— 
 About the same time that the kidneys 
 are formed behind the Wolffian bodies, 
 two oval-shaped organs make their 
 appearance in front, on the inner side of 
 
 the "WnlflWi bodies and between them inches long. From a specimen in 
 , - ." , . rni T T anther's possession, — 1,1. Kidni 
 
 and the spinal column. These bodies are 
 the internal organs of generation ; viz., 
 the testicles in the male, and the ovaries 
 in the female. At first they occupy 
 
 precisely the same situation and present precisely the same appear 
 ance, whether the foetus is afterward to belong to the male or the 
 female sex. (Fig. 248.) 
 42 
 
 Fig. 248. 
 
 Internal Organs of Genr- 
 ATION, &c. ; in a fcetal pig three 
 the 
 neys, 
 
 2, 2. Wolffian bodies. 3, 3. Internal 
 organs of generation ; testicles or 
 oraries. 4. Urinary bladder turned 
 over In front. 6. Intestine. 
 
658 DEVELOPMENT OP THE KIDNEYS. 
 
 . A short distance above the internal organs of generation there 
 commences, on each side, a narrow tube or duct, which runs from 
 above downward along the anterior border of the Wolffian body, 
 immediately in front of and parallel with the excretory duct of this 
 (i^rgan. The two tubes, right and left, then approach each other 
 below ; and, joining upon the median line, empty, together with 
 the ducts of the Wolffian bodies, into the base of the allantois, or 
 what will afterward be the base of the urinary bladder. These tubes 
 serve as the excretory ducts of the internal organs of generation ; 
 and will afterward become the vasa deferenUa in the male, and the 
 Fallopian tubes in the female. According to Coste, the vasa defe- 
 rentia at an early period are disconnected with the testicles ; and 
 originate, like the Fallopian tubes, by free extremities, presenting 
 each an open orifice. It is only afterward, according to tjie same 
 author, that the vasa deferentia become adherent to the testicles, and 
 a communication is established between them and the tubuli semi- 
 niferi. In the female, the Fallopian tubes remain permanently 
 disconnected with the ovaries, except by the edge of the fimbriated 
 extremity ; which in many of the lower- animals becomes closely 
 adherent to the ovary, and envelopes it more or less completely. 
 
 Male O^ans of Gfeneration ; Descent of the Testicles. — In the male 
 foetus there now commences a movement of translation, or change 
 of place, in the internal organs of generation, which is known as 
 the " descent of the testicles." In consequence of this movement, 
 the above organs, which are. at first placed near the middle of the 
 abdomen,, and directly in front of the kidneys, come at last to be 
 situated in t]ie scrotum, altogether outside and below the abdominal 
 cavity. They also become inclosed in a distinct serous sac of their 
 own, the tunica vaginalis testis. This apparent movement of the 
 testicles is accomplished in the same manner as that of the Wolf- 
 fian bodies, above mentioned, viz., by a disproportionate growth of 
 the middle and upper portions of the abdomen and of the organs 
 situated above the testicles, so that the relative position of these 
 organs becomes altered. The descent of the testicles is accompanied 
 by certain other alterations in the organs themselves and their | 
 appendages, which take place in the following manner: 
 
 By the upward enlargement of the kidneys, both the Wolffian 
 bodies and the testicles are soon found to be situated near the 
 lower extremity of the^e organs; (Fig. 249.) At the same time, a 
 slender rounded cord (not represented in the figure) passes from 
 the lower extremity of each testicle in an outward and downward 
 
MALE ORGANS OF GENERATION'. 
 
 659 
 
 Ijitersai. Oboaks or Gekekatiox, 
 &c., in a foetal pig Dearly four inches long^ 
 Prom a specimen in the author's possessioD. — 
 1, 1. Kidneys. 2, 2. Wolffian bodies. 3, 3. 
 Testicles. ' 4. Urinary bladder. &. Intestine. 
 
 direction, crossing the corresponding vas deferens a short distance 
 above its union with its fellow of the opposite side. Below this 
 point, the cord spoken of continues to run obliquely outward and 
 downward; and, passing through 
 the abdominal walls at the situa- ^'8' ^^• 
 
 tion of the inguinal canal, is in- 
 serted into the subcutaneous tis- 
 sues near the symphysis pubis. 
 The lower part of this cord be- 
 comes the gubernaculum testis ; and 
 muscular fibres are soon-developed 
 in its substance which may be 
 easily detected, even in the human 
 foetus, during the latter half of 
 gestation. At the period of birth, 
 however, or soon afterward, these 
 muscular fibres disappear and can 
 no longer be recognized. 
 
 All that portion of the excre- 
 tory tube of the testicle which is situated outside the crossing of the 
 gubernaculum, is destined to become afterward convoluted, and 
 converted into the epididymis. That portion which is situated in- 
 side the same point remains comparatively straight, but becomes 
 considerably elongated, and is finally known as the vas deferens. 
 
 As the testicles descend still farther in the abdomen, they con- 
 tinue to grow, while the Wolffian bodies, on the contrary, diminish 
 rapidly in size, until the latter become much smaller than the tes- 
 ticles ; and at lastj when the testicles have arrived at the internal 
 inguinal ring, the AVolffian bodies have altogether disappeared, or 
 at least- have become so much altered that their characters are no 
 longer recognizable. In the human foetus,- the testicles arriveat 
 the internal inguinal ring, about the termination of the sixth month 
 ("Wilson). 
 
 During the succeeding month, a protrusion of the peritoneum 
 takes place through the inguinal canal, in advance of the testicle ; 
 while the last named organ still continues its descent. As it then 
 passes downward into the scrotum, certain muscular fibres are given 
 off from the lower border of the internal oblique muscle of the 
 abdomen, growing downward with, the testicle, in such a manner as 
 to form a series of loops upon it, and upon the elongating spermatic 
 cord. These loops constitute afterward the cremaster m.uscle. 
 
DEVELOPMENT OF THE KIDNEYS. 
 
 At last, the testicles descend fairly to the bottom of the scrotum 
 the gubemaculum constantly shortening, ' and the vas deferens 
 elongating as it proceeds. The convoluted portion of the efferent 
 duct, viz., the epididymis, then remains closely attached to the body 
 of the testicle ; while the vas deferens passes upward, in a reverse 
 direction, enters the abdomen through the* inguinal canal, again 
 bends downwardi, and joins its fellow of the opposite side ; after 
 which they both open into the prostatic portion of the urethra by 
 distinct orifices, situated on each side the median .line. At the 
 satae time, two diverticula arise from the median portion of the 
 vasa deferentia, and, elongating^in a backward direction, underneath 
 the base of the bladder, become developed into two compound 
 sacculated reservoirs — the vesiculse seminales. 
 
 The left testicle; is a little later in its descent than the right, but 
 it afterward passes farther into the scrotum, and, in the adult condi- 
 tion, usually hangs a little lower than its fellow of the opposite side. 
 After the testicle has fairly passed into the scrotum, the serous 
 pouch, which preceded its descent, remains for a time in communis 
 cation with the peritoneal cavity. In niany of the lower animals, 
 as, for example, the rabbit, this condition is permanent ; and the 
 testicle, even in the adult animal, may be alternately drawn down- 
 ward into the scrotum, or retracted into 
 Fig. 250. the abdomen, by the action of the guber- 
 
 naculum and the cremaster muscle. But 
 in the human foetus, the two opposite 
 surfaces of the peritoneal pouch, covering 
 the testicle, approach each other at the 
 inguinal canal, forming at that point a 
 constriction or neck, which partly shuts 
 off the testicle from the cavity of the 
 abdomen. By a continuation of this pro- 
 cess, the serous surfaces come actually 
 Formation of Tunica 'va- in coutact with cach Other, and, adhering 
 
 GinAi,i6 Testis. — 1. Testicle ^ ,, . ,i ■ ., .. ,,-,. nir, \ 
 
 ■ neaily at the bottom of the scro- togethci at thlS SltUatlOU (Fig. 250, 4), 
 
 turn. 2 Cavity of tunica Ta,;in» lis. form a kind of cicatrix, or umbilicus, by 
 
 3. Cavity of peritoneum. 4. Obliter- ' , t ■ o 
 
 ated neck of peritoneal sac. the Complete closurc and consolidatiou: of 
 
 which the cavity of the tunica vaginalis 
 (2) is finally shut off altogether from the general • cavity of the 
 peritoneum (3). The tunica vaginalis testis is, therefore, originally 
 a part of the peritoneum, from which it is subsequently separated 
 by the process just described. 
 
FEMALE OBGANS OP GENERATION. 661 
 
 The separation of the tunica vaginalis from the peritoneum is 
 usually completed in the human subject before birth. But some- 
 times it fails to take place at the proper time, and the intestine is 
 then apt to protrude into the scrotum, in front of the spermaitic 
 cord, giving rise, in this way, to a congenital. inguinal hernia. (Fig. 
 251.) The parts implicated, however, in this malformation, have 
 still, as in the case of congenital umbili- 
 cal hernia, a tendency to unite with each Fig. 251. 
 other and obliterate the unnatural open- 
 ing; and if the intestine be retained by 
 pressure in the cavity of the abdomen, 
 cicatrization usually takes place at the 
 inguinal canal, and a cure is effected. 
 
 The descent of the testicle, above de- 
 scribed, is not accomplished by the forci- 
 ble traction of the muscular fibres of the 
 gubernaculum, as has been described, by 
 certain writers, but by a simple process cosQEiriTAii»aDi»AiHivR- 
 
 „ .1 . T . 1 . T,v. KIA. — 1. Testicle. 2,2,2. Inteo- 
 
 01 growth takmg place in difierent parts, tine, 
 in different directions, at successive 
 
 periods of foetal life. The gubernaculum, accordingly, has no 
 proper function as a muscular organ, in the human subject, but is 
 merely the anatomical vestige, or analogue, of a corresponding 
 muscle in certain of the lower animals, where it has really an 
 important function to perform. For in them, as we have already 
 mentioned, both the gubernaculum and the cremaster remain fully 
 developed in the adult condition, and are then employed to elevate 
 ■ and depress the testicle, by the alternate contraction of their mus- 
 cular fibres. 
 
 Female Organs of Generation. — At an early period, as we have 
 mentioned above, the ovaries have the same external appearance, 
 ani occupy the same position in the abdomen, as the testicles in the 
 opposite sex. The descent of the ovaries also takes place, to a great 
 extent, in the same manner with the descent of the testicles. When, 
 in the early part of this descent, they have reached the level of the 
 lower edge of the kidneys, a cord, analogous to the gubernaculum, 
 may be seen proceeding from their lower extremity, crossing the 
 efferent duct on each side, and passing downward, to be attached 
 to the subcutaneous tissues at the situation of the inguinal ring. 
 That part of the duct situated outside the crossing of this cord, 
 becomes afterward convoluted, and is converted into the Fallopian 
 
662 DEVELOPMENT OP THE KIDNEYS, ETC. 
 
 tube ; while that point which is inside the same point, becomes con- 
 verted into the uterus. The upper portion of the cord itself becomes 
 the ligament of the ovary ; its lower portion, the round UgaTuent of 
 the uterus. 
 
 As the ovaries continue their descent, they pass below and be- 
 hind the Fallopian tubes, which necessarily perfdrm at the same 
 time a movement of rotation, from before backward and from 
 above downward: j the whole, together with the ligaments of the 
 ovaries and the round ligaments, being enveloped in double folds 
 of peritoneum, which enlarge with the growth of the parts them- 
 selves, and constitute finally the broad ligaments of the uterus. 
 
 It will be seen from what has been said above, that the situation 
 occupied by the "Wolffian bodies in the female is always the space 
 between the ovaries and the Fallopian tubes; for the Wolffian 
 bodies accompany the ovaries in their descent, just as, in the male, 
 they accompany the testicles. As these bodies now become grad- 
 ually atrophied,' their glandular structure disappears altogether; 
 but their bloodvessels, in many instances, remain -as a convoluted 
 vascular plexus, occupying the situation above mentioned. The 
 Wolffian bodies may therefore be said, in these instances, to un- 
 dergo a kind of vascular degeneration. This peculiar degeneration 
 is quite evident in the Wolffian bodies of the foetal pig, some time 
 before the organs have entirely lost their original form. In the 
 cow, a collection of convoluted bloodvessels may be seen, even in 
 the adult condition, near the edge of the ovary, and between the 
 two folds of peritoneum forming the broad ligament. These are 
 undoubtedly vestiges of the Wolffian bodies, which have undergone 
 the vascular degeneration above described. 
 
 While the above changes are taking place in the adjacent organs, 
 the two lateral halves of the uterus fuse with each other more and 
 more upon the median line, and become covered with an exces- 
 sively developed layer of muscular fibres. In the lower animfils, 
 the uterus remains divided at its upper portion, running out into 
 two long conical tubes or cornua (Fig. 182), presenting the form 
 known as the uterus bicornis. In the human subject, however, the 
 fusion of the two lateral halves of the organ is nearly complete; 
 so that the uterus presents externally a rounded, but somewhat 
 flattened and triangular figure (Fig. 183), with the ligaments of the 
 ovary and the round ligaments passing off from its superior angles. 
 But, internally, the cavity of the organ still presents a strongly ' 
 marked triangular form, the vestige of its original division. 
 
FEMALE OEGANS OF GENEKATION. 663 
 
 Occasionally the human uterus, even in the adult condition, re- 
 mains divided into two lateral portions by a vertical septum, which 
 runs from the middle of its fundus downward toward the os in- 
 ternum. This septum may even be accompanied by a partial 
 external division of the organ, corresponding with it iu direction 
 and producing the malformation known as "uterus bicornis." or 
 " double uterus." 
 
 The OS internum and os externum are produced by partial con- 
 strictions of the original generative passage ; and the anatomical 
 distinctions between the body of the uterus, the cervix and the 
 vagina, are produced by the different development of the mucous 
 membrane and muscular tunic in its corresponding portions. 
 During foetal life, however, Be neck of the uterus grows much 
 faster than its body; so that, at the period of birth, the entire 
 organ is very far from presenting the form which it exhibits in the 
 adult condition. In the human fcetus at term, the cervix uteri 
 constitutes nearly two-thirds of the entire length of the organ; 
 while the body forms but little over one-third. The cervix, at 
 this time, is also much larger in diameter than the body ; so that 
 the whole organ presents a tapering form from below upward. 
 The arbor vitse uterina of the cervix is at birth very fully de- 
 veloped, and the mucous membrane of the body is also thrown 
 into three or four folds which radiate upward from the os intetnum. 
 The cavity of the cervix is filled with a transparent semi-solid 
 mucus. 
 
 The position of the uterus at birth is also different from that 
 which it assumes in adult life ; nearly the entire length of the organ 
 being above the level of the symphysis pubis, and its inferior 
 extremity passing below that point only by about a quarter of an 
 inch. It is also slightly anteflexed at the junction of the body and 
 cervix. After birth, the uterus, together with its appendages, con- 
 tinues to descend ; until, at the period of puberty, its fundus is 
 situated just below the level of the symphysis pubis. 
 
 The ovaries at birth are narrow and elongated in form. They 
 contain at this time an abundance of eggs; each inclosed in a 
 Graafian follicle, and averaging gj^ of an inch in diameter. The 
 vitellus, however, is imperfectly formed in most of them, and in 
 some is hardly to be distinguished. The Graafian follicle at this 
 period envelopes each egg closely, there being nothing between its 
 internal surface anJ the exterior of the egg, excepting the thin 
 layer of cells forming the "membrana granulosa." Inside this 
 
664 DEVELOPMENT OF THE KIDNEYS, ^TC. 
 
 layer is to be seen tlie germinative vesicle, with the germinative 
 spot, surrounded by a faintly granular vitellus, more or less 
 abundant in different parts. Some of the Graafian follicles con- 
 taining eggs are asiarge as ^^^ of an inch; others as small as Ttjss. 
 In the very smallest; the cells of the membrana granulosa appear 
 to fill entirely the cavity of the follicle, and no vitellus or germina-, 
 tive vesiqle is to be seen. 
 
DEVELOPMENT OF THB CIBO0LATORY APPARATUS. 665 
 
 CHAPTER XVII. 
 
 DEVELOPMENT OP THE CIRCULATORY 
 . APPARATUS. 
 
 Theee are three distinct forms or phases of development assumed 
 by the circulatory system duftng different periods of life. These 
 different forms of the circulation are intimately connected with the 
 manner iawMch nutrition and respiration, or the renovation of the 
 blood, are accomplished at different epochs ; and they follow each 
 other in the progress of development, as different organs are em- 
 ployed in turn to accomplish the above functions. The first form 
 is that of the vitelline circulation, which exists at a period when the 
 vitellus, or the umbilical vesicle, is the sole source of nutrition for 
 the foetus. The second is the placental circulation, which lasts 
 through the greater part of foetal life, and is characterized by the 
 existence of the placenta ; and the third is the complete or adult 
 circulation, in which the renovation and nutrition of the blood are 
 provided for by the lungs and the intestinal canal. 
 
 First, or Vitelline Circulation. — It has already been shown, in a 
 previous chapter, that when the body of the embryo has begun to 
 be formed in the centre of the blastodermic membrane, a number 
 of bloodvessels shoot out from its sides, and ramify ov«r the 
 remainder of the vitelline sac, forming, by their inosculation, an 
 abundant vascular plexus. The area occupied by this plexus in the 
 blastodermic membrane around the foetus is, as we have seen, the 
 " area vasculosa." In the egg of the fowl (Fig. 252), the plexus is 
 limited, on its external border, by a terminal vein or "sinus — the 
 "sinus terminalis ;" and the blood of the embryo, after circulating 
 through the capillaries of the plexus, returns by several venous 
 branches, the two largest of which enter the body near its anterior 
 and posterior extremities. The area vasculosa is, accordingly, a 
 vascular appendage to the circulatory apparatus of the embryo, 
 spread out over the surface of the vitellus for the purpose of absorb- 
 ing from it the nutritious material requisite for the gtowth of the 
 
666 DEVELOPMENT OF THE CIBCULATORT APPARATUS. 
 
 newly-formed tissues. In the egg of the fish (Fig. 253), the princi- 
 pal'vein is seen passing up in front underneath the head ; while the 
 arteries emerge all along the lateral edges of the body. The entire 
 
 Fig. 252, 
 
 Eoo OF PowL ia process of development, shOTring area vaticulosa, with vitelline circalation, 
 terminal sinna, &c. 
 
 Fig. 253. 
 
 vitellus, in this way, becomes covered with an abundant vascular 
 network, connected with the internal circulation of the fcetus by 
 arteries and veius, 
 
 Very soon, as the embryo and the entire egg increase in size, 
 there are two arteries and two veins which become 
 larger than the others, and which subsequently 
 do the whole work of conveying the blood of 
 the fcetus to and from the area vasculosa. These 
 t\^o arteries emerge from the lateral edges of 
 the foetus, on the right and left sides ; while the 
 two veins re-enter at about the same point, and 
 nearly parallel with them. These four vessels are 
 then termed the omphalo-mesentenc arteries and 
 veins. 
 
 The arrangement of the circulatory apparatus 
 in the interior of the body of the foetus, at this time, is as follows : 
 The heart is situated at the median line, just beneath the head and 
 in front of the oesophagus. It receives at _its lower extremity the 
 trunks of the two omphalo-mesenteric veins, and at its upper 
 extremity divides into two vessels, which, arching over backward, 
 attain the anterior surface of the vertebral column, and then run 
 from above downward along the spine, quite to the posterior 
 
 Egg of Pish (Jar- 
 rabacca), showing vitel- 
 line circulation. 
 
PLACENTAL CIRCULATION. 
 
 667 
 
 extremity of the foetus. These arteries are called the vertebral 
 arteries, on account of their course and situation, running parallel 
 with the vertebral column. They give ofi^ throughout their course, 
 many small lateral branches, -which supply the body of the foetus, 
 and also two larger branches-^the omphalo-mesenterio arteries — 
 which pass out, as above described, into the area vasculosa. The 
 two vertebral arteries remain separate in the upper ^art of the body, 
 but sOon fuse with each other a little below the level of the heart ; 
 so that, below this point, there remains afterward but one large 
 artery, the abdominal aprta, running from above downward along 
 the median line, giving off the omphalo-mesenteric arteries to the 
 area vasculosa, and supplying smaller branches to the body, the 
 walls of the intestine, and the other organs of the foetus. 
 
 The above description shows the origin and formation of the first 
 or vitelline circulation. A dbange, however, now begins to take 
 place, by which the vitellus is superceded, as an organ of nutrition, 
 by the placenta, which takes its place ; and the second or placeMal 
 circulation becomes established in the following manner : — 
 
 Second Circulation. — After the umbilical'vesicle has been formed 
 by the process already described, a part of the vitellus remains in- 
 cluded in it, while the rest is retained in the abdomen and inclosed 
 in the intestinal canal. As these 
 two organs (umbilical vesicle and ^'8- 2.')4. 
 
 intestine) are originally parts of 
 the same vitelline sac, they remain 
 supplied by the same vascular 
 system, viz : the omphalo-mesen- 
 teric vessels. Those which remain 
 within the abdomen of the foetus 
 supply the mesentery and intes- 
 tine ; but the larger trunks pass 
 outward, and ramify upon the 
 walls of the umbilical vesicle. 
 (Fig. 254.) At first, there are, 
 as we have mentioned above, 
 two omphalo-mesenteric arteries 
 emerging from the body, and two 
 omphalo-mesenteric veins return- 
 ing to it ; but soon afterward, the two arteries are replaced by a 
 common trunk, while a similar change takes place in the two veins. 
 Subsequently, therefore, there remains but a single artery and a 
 
 Diagram of YoCKa Embbto akb its 
 VrbbeIiS, Bbowing cfrcnlatioa of umbilical 
 YOBicle. and also that of allantoiB, beginning to 
 be formed. 
 
66^ DEYKLOPMENT OF THE CIBCULATOET APPARATUS. 
 
 single vein, connecting the internal and external portions of the 
 vitelline circulation. 
 
 The vessels belonging to this system are therefore called the 
 omphalo-mesenteric vessels, because a part of them (omphalic ves- 
 sels) pass outward, by the umbilicus, or " omphalos," to the umbili- 
 cal vesicle, while the remainder (mesenteric vessels) ramify upon 
 the mesentery and the intestine. 
 
 At first, the circulation of the umbilical vesicle is more import- 
 ant than that of the intestine ; and the omphalic artery and vein 
 appear accordingly as large trunks, of which the mesenteric ves- 
 sels are simply small branches. (Fig. 254.) Afterward, however, 
 the intestine rapidly enlarges, while the umbilical vesicle dimi- 
 nishes, and the proportions existing between the two sets of vessels 
 
 are therefore reversed. (Fig. 255.) The mesenteric vessels then 
 
 • 
 Fig. 255. 
 
 Diaitrain of Embeto and its Vessels; showing the second clrealation. The pharynx, 
 ffidopbagus, and intesUual caaal, have become farther deyeloiled, and the mesenteric arteries have 
 enlarged, while the umbilical voBicle apd its yascnlar branches are very much reduced in size. The 
 large umbilical arteries are seen passing out to the placenta. 
 
 come to be the principal trunks, while the omphalic vessels are 
 simply minute branches, running out along the slender cord of the 
 umbilical vesicle, and ramifying in a few scanty twigs upon its 
 surface. 
 
DEVBLOPMKNT OF THE ARTERIAL SYSTEM. .669 
 
 In the injean time, the allantois is formed by a protrusion from 
 the lower extremity of the intestine, which, carrying with it two 
 arteries and two veins, passes out by the anterior opening of the 
 body, .and comes in contact with the external membrane of the 
 egg. The arteries of the allantois, which are termed the' umbilical 
 arteries, are supplied by branches of the abdominal aorta ; the um- 
 bilical veins, on the other hand, join the mesenteric veins, and 
 empty with t'hem into the venous extremity of the heart. As the 
 umbilical vesicle diminishes, the allantois enlarges ; and the latter 
 soon becomes converted, in the human subject, into a vascular 
 chorion, a part of which is devoted to the formation of the placenta. 
 (Fig. 255.) As the placenta soon becomes the only source of nutri- 
 tion for the foetus, its vessels are at the same time very much 
 increased in size, and preponderate over all the other parts of the 
 circulatory system. ' During the early periods of the formation of 
 the placenta, there are, as we have stated above, two umbilical 
 arteries and two umbilical veins. But subsequently one of the 
 veins disappears, and the whole of the blood is returned to the body 
 of the foetus by the other, which becomes enlarged in proportion. 
 For a long time previous to birth, therefore, there are in the umbili- 
 cal cord two umbilical arteries, and but a single umbilical vein. 
 
 Such is the second, or placental circulation. It is exchanged, at 
 the period of birth, for the third or adult circulation, in which the 
 blood which had previously circulated through the placenta, is 
 diverted to the lungs and the intestine. These are the organs 
 upon which the whole system afterward depends for the nourish- 
 ment and renovation of the blood. 
 
 During the occurrence of the above changes, certain. other altera- 
 tions take place in the arterial and venous systems, which will now 
 require to be described by themselves. 
 
 Development of the Arterial System.— At an early period of deve- 
 lopment, as we have shown above, the principal arteries pass off 
 from the anterior extremity of the heart in two arches, which curve 
 backward on each side, from the front of the body toward the 
 vertebral column, after which they again become longitudinal in 
 direction, and receive the name of "vertel»ral arteries." Very soon 
 these arches divide successively into two, three, four, and five 
 secondary arches, placed one above the other, along the sides of 
 the neck. (Fig. 256.) These are termed the cervical arches. In the 
 fish, these cervical arches remain permanent, and give off from their 
 convex borders the branchial arteries, in the form of vascular tufts, 
 
670 DEVELOPMENT OF THE CIKO-ULATORT APPARATUS. 
 
 to the gills on each side of the neck ; but in the humaa subject and 
 the quadrupeds, the branchial tufts are never developed, and the 
 cervical arches, as well as the trunks with which they are con- 
 nected, become modified by the progress of development in the 
 following manner : — 
 
 Fig. 256. 
 
 2 
 
 Early coodition of Arterial Ststeh: 
 showing the heart (1), with its two ascend- 
 ing arterial trunks, giving off on each side 
 five cervical arches, which terminate in the 
 vertebral arteries (2, 2). The vertebral arte- 
 ries unite below the heart to form the 
 aorta (3). 
 
 Adult condition of Arterial Sts- 
 T EM. —1,1. Carotids. 2, 2. Vertebrals. 
 3, 3. Kight and left subclavians. 4, 4. 
 Bight and left superior intercostals. 5. 
 Left aortic arch, which remains perma- 
 nent. 6. Bight aortic arch, which die- 
 appears. 
 
 The two ascending arterial trunks on the anterior part of the 
 neck, from which the cervical arches are given off, become con- 
 verted into the carotids. (Fig. 257, 1,1.) The fifth, or uppermost 
 cervical arch, remains at the base of the brain as the inosculation, 
 through the circle of Willis, between the internal carotids and the 
 basilar artery, which is produced by the union of the two verte- 
 brals. The next, or fourjh cervical arch, may be recognized in an 
 inosculation which is' said to be very constant between the superior 
 thyroid arteries, branches of the carotids, and the inferior thyroids, 
 which come from the subclavians at nearly the same point from 
 which the vertebrals are given off. The next, or third cervical arch, 
 remains on each side, as the subclavian artery (3, s). This vessel, 
 
DEVELOPMENT OF THE ARTERIAL SYSTEM. 671 
 
 though at first a mere branch of communicatioa between the caro- 
 tid and the vertebral, has now increased in size to such an extent 
 that it has become the principal trunk, from which the vertebral 
 itself is given off as a small branch. Immediatelj below this point 
 of intersection, also, the vertebral artery diminishes very much in 
 relative size, loses its connection with the abdominal aorta, and 
 supplies only the first two intercostal spaces, under the name of the 
 superior intercostal artery (4, 4). The second cervical arch becomes 
 altered in a very different manner on the two opposite sides. On 
 the left side, it becomes enormously enlarged, so as to give off, as 
 • secondary branches, all the- other arterial trunks which have been 
 described, and is converted in this manner into the arch of the 
 aorta (a). On the right side, however, the coft-esppnding arch (e) 
 becomes smaller and smaller, and at last altogether disappears ; so 
 that, finally, we have only a single aortic arch, projecting to the 
 left of the median line, and continuous with the thoracic and abdo- 
 minal aorta. 
 
 The first cervical arch remains during foetal life upon the left . 
 side, as the " ductus arteriosus," presently to be described. In the 
 adult condition, however, it has disappeared equally upon the right 
 and left sides.- In this way the permanent condition of the arterial 
 circulation is gradually established in the upper part of the body. 
 
 Corresponding changes take place, however, during the same 
 time, in the lower part of the body. Here the abdominal aorta 
 runs undivided, upon the median line, quite to the end of the 
 spinal column; giving off" on each side successive lateral branches, 
 which supply the intestine and the parietes of the body. "When 
 the allantois begins to be developed, two of these lateral ^branches 
 accompany it, and become, consequently, the umbilical arteries. 
 These two vessels increase so rapidly in size, that they soon appear 
 as divisions of the aortic trunk ; while the original continuation of 
 this trunk, running to the end of the spinal column, appears only 
 as a small branch given off at the point of bifurcation. When the 
 lower limbs begin to be developed, they are supplied by two small 
 branches, given off from the umbilical arteries near their origin. 
 
 Up to this time the pelvis and posterior extremities are but 
 slightly developed. Subsequently, however, they grow more 
 rapidly, in proportion to the rest of the body, and the arteries 
 which supply them increase in a corresponding manner. That 
 portion of the umbilical arteries, lying between the bifurcation of 
 the aorta and the origin of the branches going to the lower ex- 
 
672 DEVELOPMENT OF THE CIRCULATOBY APPARATUS. 
 
 tremities,. becomes the common iliaiCS, which in their turn afterward 
 divide into the umbilical arteries proper, and the femorals. Sub- 
 sequently, by the continued growth of the pelvis and lower 
 extremities, the relative size of their vessels is still further in- 
 creased ; and at last the arterial system in this part of the body 
 assumes the arrangement which belongs to the latter periods of 
 gestation. The aorta divides, as before, into the two common iliacs. 
 These also divide into the external iliacs, supplying the lower ex- 
 tremities, and the internaL iliacs, supplying the pelvis; and this 
 division is so placed that the umbilical or hypogastric arteries arise 
 from the internal iliacs, of which they now appear to be secondary • 
 branches. 
 
 After the birth 9[ the foetus, and the separation of the placenta, 
 the hypogastric arteries become partially atrophied, and are con- 
 verted, in the adult condition, into solid, rounded cords, running 
 upward toward the umbilicus. Their lower portion, however, 
 remains pervious, and gives off arteries supplying the urinary 
 .bladder. The obliterated hypogastric arteries, therefore, the rem- 
 nants of the original umbilical or allantoic arteries, run upward 
 from the internal iliacs along the sides of the 
 Fig. 258. urinary bladder, which is the remnant of the ori- 
 
 ginal allantois itself. The terminal continuation 
 of the original abdoming,l aorta, is the arteria 
 sacra media, which, in the adult, runs downward 
 on the anterior surface of the sacrum, supplying 
 branches to the rectum and the anterior sacral 
 
 body; 
 
 nerves. 
 
 Development of the Venous System. — ^According 
 to the observations of M. Coste, the venous system 
 at first presents the same simplicity and symmetry 
 with the arterial. The principal veins of the 
 body consist of two long venous trunks, the ver- 
 tebral veins (Fig. 258), which run along the sides 
 of the spinal column, parallel with the vertebral 
 arteries. They receive in succession all the inter- 
 costal veins, and empty into the heart by two 
 lateral trunks of equal size, the canals of Cumer. 
 When the inferior extremities become developed, 
 their two veins, returning from below, join the 
 vertebral veins near the posterior portion of the 
 and, crossing them, afterward unite with each other, thus 
 
 Early condition of Ve- 
 11008 System; show- 
 ing the vertebra;! veins 
 emptying into the heart 
 by two lateral trnnks, 
 the "canals of Cuvier." 
 
DEVKLOPMENT OF THE VENOUS SYSTEM. 
 
 673 
 
 constituting another vein of new formation 
 (Fig. 259, a), which runs upward a little to the 
 right of the median line, and empties by itself 
 into the lower extremity of the heart. The 
 two branches, by means of which the veins of 
 the lower extremities thus unite, become after- 
 ward, by enlargement, the common iliac veins ; 
 while the single trunk (a) resulting from their 
 union becomes the vena cava inferior. Subse- 
 quently, the vena cava inferior becomes very 
 much larger than the vertebral veins ; and its 
 two branches of bifurcation are afterward re- 
 presented by the two iliacs. 
 
 Above the level of the heart, the vertebral 
 &nd intercostal veins retain their relative size 
 until the development of the superior extremi- 
 ties has commenced. Then two of the inter- 
 costal veins increase in diameter (Fig. 259), and 
 become converted into the right and left sub- 
 clavians ; while those portions of the vertebral 
 veins situated above the subclavians become the 
 right and left jugulars. Just below the junction 
 of the jugulars with the subclavians, a small 
 branch of communication now appears between 
 the two vertebrals(Fig. 259, h), passing over from 
 left to right, and emptying into the right verte- 
 bral vein a little above the level of the heart ; so 
 that a part of the blood coming from the left side 
 of the head, and the left upper extremity, still 
 passes down the left vertebral vein to the heart 
 upon its own side, while a part crosses over by 
 the communicating branch (&), and is finally 
 conveyed to the heart by the right descending 
 vertebral. Soon afterward, this branch of com- 
 munication enlarges so rapidly that it prepon- 
 derates altogether over the left superior verte- 
 bral vein, from which it originated (Fig. 260), 
 and, serving then to convey all the blood coming 
 from the left side of the head and left upper 
 extremity over to the right side above the heart, 
 it becomes the left vena innominata. 
 43 
 
 'Fig. 259. 
 
 VsNors System far- 
 ther advanced, sliowing 
 formation of iliac and aub- 
 clarian veins. — a. Vein of 
 new formation, wliicli be- 
 comes the inferior veua 
 cava. 6. Transverse branch 
 of new formation, -which 
 afterward becomes the left 
 vena innominata. 
 
 Fig. 260. 
 
 Fnrthe- development of 
 theVKNpuei System.— 
 The vertebral veins are 
 much diminished in size. 
 and the caniil of Cnvier, im 
 the left side, is gradual y 
 disappearing, c. Trans- 
 verse branch of new forma- 
 tion, which is to become 
 the vena azygos mlu^r 
 
674 DEVELOPMENT OF THE CIRCULATORY APPARATUS. 
 
 Fig. 261. 
 
 On the left side, that portion of the superior vertebral vein, which 
 is below the subclavian, remains as a small branch of the vena in- 
 nominata, receiving the six or seven upper intercostal veins ; while 
 on the right side it becomes excessively enlarged, receiving the 
 blood of both jugulars and both subclavians, and is converted into 
 the vena cava superior. 
 
 The left canal of Cuvier, by which the left vertebral vein at first 
 communicates with the heart, subsequently becomes atrophied and 
 disappears; while on the right side it becomes excessively enlarged, . 
 and forms the lower extremity of the vena cava superior. 
 
 The superior and inferior venae cavae, accordingly; do not cor- 
 respond with each other so far as regards their 
 mode of origin, and are not to be regarded as 
 analogous veins. For the superior vena cava 
 is one of the original vertebral veins; while 
 the inferior vena cavd^is a totally distinct vein, 
 of new formation, resulting frpm the union of 
 the two lateral trunks coming from the infe- 
 rior extremities. 
 
 The remainder of the vertebral veins finally 
 assume the condition shown in Fig. 261, which 
 is the complete or adult form of the venous 
 circulation. At the lower part of the abdomen, 
 the vertebral veins send inward small trans- 
 verse branches, which communfcate with the 
 vena cava inferior, between the points at which 
 they receive the intercostal veins. These 
 branches of communication, by increasing in 
 size, become the lumbar veins (7), which, in the 
 adult condition,' communicate with each other 
 by arched branches, a short distance to the side 
 of the vena cava. Above the level of the 
 lumbar arches, the vertebral veins retain their 
 original direction. That upon the right side 
 still receives all the right intercostal veins, and 
 becomes the vena azygos major (s). It also 
 receives a small branch of communication from 
 its fellow of the left side (Fig. 260,';,c), and this branch soon enlarges 
 to such an extent as to bring over to the veila azygos major all the ■ 
 blood of the five or six lower intercostal veins of the left side, 
 becoming, in this way, the vena azygos minor (9). The six or seven 
 
 Adnlt Ciindition of Ve- 
 nous System. — 1. Right 
 auricle of heart. 2. Vena 
 cava superior! 3, 3. Jugular 
 veins. 4,4. Subclavian veins. 
 5. Vena cava inferior. 6, 6. 
 niacTelns. 7. Lumbarveins. 
 .S. Vena azygos major. 9. 
 Vena azygos minor. 10. Su- 
 perior intercostal vein. 
 
DEVELOPMENT OF THE HEPATIC CIBOULATIOS,. 675 
 
 upper intercostal veins on the left side still empty, as before, into 
 their own vertebral vein (lo), which, joining the left vena innomi,. 
 nata above, is known as the superior intercostal vein. The left canal 
 of Cuvier has by this time entirely disappeared ; so that all the 
 venous blood now enters the heart by the superior or the inferior 
 vena cava. But the original vertebral veins are still continuous 
 throughout, though very much diminished in size at certain points ; 
 since both the greater and lesser azygous veins inosculate below 
 with the superior lumbar veins, and the superior intercostal vein 
 also inosculates below with the lesser azygous, just before it passes 
 over to the right side. 
 
 There ate still two parts of the circulatory apparatus, the deve- 
 lopment of which presents peculiarities sufficiently important to 
 be described separately. These are, first, the liver and the ductus 
 venosus, and secondly, the heart, with the ductus arteriosus. 
 
 Development of the Hepatic Circulation and the Ductus Yenosiis. — 
 The liver appears at a very early period in the upper part of the 
 abdomen, as a mass of glandular and vascular tissue, which is deve- 
 loped around the upper portion of the 
 omphalo-mesenterio« vein, just below its *''S- 262. 
 
 termination in the heart. (Fig. 262.) As 
 soon as the organ has attained a con- 
 siderable size^ the omphalo-mesenteric 
 vein (i) breaks up in its interior into a 
 capillary plexus, the vessels of which 
 unite again into venous trunks, and so 
 convey the blood finally to the heart. •-""-i..-.-. 
 
 The omphalo-mesenteric vein below the Eariy form of hkpatio cir- 
 hver then becomes the jJortaZmw; while ,eric vein. 2. He,.atic vein. 3. 
 above the liver, and between that organ Hoait. The dotted iine shows tiio 
 
 . ^ ^ . . , n Situation of the futare umbilical 
 
 and the heart, it receives the name 01 vein, 
 the hepatic vein (3). The liver, accord- 
 ingly, is at this time supplied with blood entirely by the portal vein, 
 coming from the umbilical vesicle and the intestine ; and all the 
 blood derived from this source must pass through the hepatic cir- 
 culation before reaching the venous extremity of the heart. 
 
 But soon afterward the allantois makes its appearance, and be- 
 comes rapidly developed into the placenta; and the umbilical vein 
 coming from it joins the omphalo-mesenteric vein in the substance 
 of the liver, and takes part in the formation of the hepatic capillary 
 plexus. As the umbilical vesicle, however, becomes atrophied, and 
 
676 DEVELOPMENT OP THE CIBCULATORY APPARATUS. 
 
 Fig. 263. 
 
 Hepatic Circijlation 
 farllieradvanceij.— 1. I'ortal veiu. 
 2. Umbilical vein. 3. Hepatic 
 vein. 
 
 the intestine also remains rnactiye, while the placenta increases in 
 size and in functional importance, a time soon arrives when the 
 liver receives more blood by the umbilical 
 vein thari by the portal vein. (Fig. 263.) 
 The umbilical vein then passes into the 
 liver at the longitudinal fissure, and sup- 
 plies the left lobe entirely with its own 
 branches. To the right it sends off a large 
 branch of communication, which opens in- 
 to the portlal vein, and partially supplies 
 the right lobe with umbilical blood. The 
 liver is thus supplied with blood from two 
 different sources, the most abundant of 
 which is the umbilical vein; and aU the 
 blood entering the liver circulates, as be- 
 fore, through its capillary vessels. 
 
 But we have already seen that the liver is much larger, in pro- 
 portion to the entire body, at an early period of foetal life, than in 
 the later months. In the foetal pig, when very young, it amounta 
 
 to nearly twelve per cent, of the 
 weight of the whole body ; but be- 
 fore birth it diminishes to seven, six, 
 and even three or four per dent. For 
 some time, therefore, previous to 
 birth, there is much more blood re- 
 turned from the placenta than is re- 
 quired for the capillary circulation 
 of the liver. Accordingly, a vascular 
 duct or canal is formed in its interior, 
 by which a portion of the placental 
 blood is carried directly through the 
 organ, and conveyed to the heart 
 without having passed through the 
 hepatic capillaries. This duct is 
 called the Ductus venosus. 
 
 The ductus venosus is formed by a 
 gradual dilatation of one of the he- 
 patic capillaries at (5) (Fig. 264), which>, enlarging excessively, be- 
 comes at last converted into a wide canal, or branch of communi- 
 cation, passing directly from the umbilical vein below to the hepatic 
 vein above. The circulation through the liver, thus established, is 
 
 Fig. 264. 
 
 Hepatic Circflatiok daring lat- 
 ter part of foetal life,— 1. Portal vein. 2, 
 Umbilical vein. 3. Left branch of umbili- 
 cal vein. 4. Right branch of umbilical 
 vein. 5. Ductus venoHus. 6, Hepatic 
 vein. 
 
Fig. 235. 
 
 DEVELOPMENT OF THE HEPATIC CIKGULATION, 677 
 
 as follows : A certain quantity of venous blood still enters through 
 the portal vein (,), and circulates in a part of the capillary system 
 of the right lobe. The umbilical vein (a), bringing a much larger 
 quantity of blood, enters the liver also, a little to the left, and the 
 blood which it contains divides into three principal streams. One 
 of them passes through the left branch (a) into the capillaries of the 
 left lobe ; another turns off through the right branch (4), and, join- 
 ing the blood of the portal vein, circulates through the capillaries 
 of the right lobe; while the third passes directly onward through 
 the venous duct (5), and reaches the hepatic vein without having 
 passed through any part of the capillary plexus. 
 
 This condition of the hepatic circulation continues until births 
 At that time, two important changes take place. First, the pla- 
 cental circulation is altogether cut off; and secondly, a much larger 
 quantity of blood than before begins 
 ■ to circulate through the lungs and 
 the intestine. The superabundance 
 of blood, previously coming from the 
 placenta, is now diverted into the 
 lungs ; while the intestinal canal, en- 
 tering upon the active performance of 
 its functions, becomes the sole source 
 of supply for the hepatic venous 
 blood. The following changes, there- 
 fore, take place at birth in the ves- 
 sels of the liver. (Fig. 265.) First, 
 the umbilical vein shrivels and be- 
 comes converted into a solid rounded 
 cord (a). This cord may be seen, in 
 the adult condition, running from the 
 internal surface of the abdominal 
 walls, at -the umbilicus, to the longi- 
 tudinal fissure of the liver. It is then 
 known under the name of the round 
 
 ligament. Secondly, the ductus venosus also becomes obliterated, 
 and converted into a fibrous cord. Thirdly, the blood entering the 
 liver by the portal vein (1), passes off by its right branch, as before, 
 to the right lobe. But in the branch (■»), the course of the blood is 
 reversed. This was formerly the right branch of the umbilical 
 vein, its blood. passing in a direction from left to right. It now 
 becomes the left branch pf the portal vein ; and its blood passes 
 
 Adult form of Hepatic CiHorLA- 
 Tios.— 1. Portal v6io. 2. Obliterated 
 umbilical vein, forming the round liga- 
 mcDt; the contiuiiatiou of the dotted 
 lines through the liver shows the situa- 
 tion of the obliterated dnctus venosus. 
 3. Hepatic vein. 4. Left brauch of portal 
 vein. 
 
678 DEVELOPMENT OF THE CIBOULATORY APPAKATUS. 
 
 from right to left, to be distributed to tbe capillaries of the left 
 
 lobe. 
 
 Accordinf to Dr. Guy, the umbilical vein is completely closed at 
 the end of the fifth day after birth. 
 
 Bevehpment of the Heart, and the Ductus Arteriosus. — When the 
 embryonic circulation is first established, the heart is a simple tubu- 
 lar sac (Fig. 266), receiving the veins at its lower extremity, arid 
 giving off the arterial trunks at its upper extremity. By the pro- 
 gress of its growth, it soon becomes twisted upon itself; so that the 
 entrance of the veins, and the exit of the arteries, come to be placed 
 more nearly upon the same horizontal level (Fig. 267); but the 
 entrance of the, veins (i) is behind and a little below, while the exit 
 of the arteries (2) is in front and a little above. The heart is, at 
 this time, a simple twisted tube ; and the blood passes through it 
 in a single continuous stream, turning upon itself at the point of 
 curvature, and passing directly out by the arterial orifice. 
 
 Fig. 266. ' Fig. 267. Fig. 268. 
 
 2 
 
 7 
 
 FffiTAL IIji'AKT, divided 
 
 Earliest form of F (ETA L FffiTAL Heart, twisted into rightand left cavities,— 
 
 Heart. — 1. Venous ex- -upon itself. — 1'. Venous ex- 1. Venous extremity. 2. 
 
 tremity. 2. Arterial ex- tremity. 2. Arterial extre- Arterial extremity. 3, 3. 
 
 tremity, tally. Pulmonary branches. 
 
 Soon afterward, this single cardiac tube is divided into two paral- 
 lel tubes, right and left, by a Ipngitudinal partition, which grows 
 from the inner surface of its walls . and follows the twisted course 
 of the organ itself. (Fig. 268.) This partition, which is indicated 
 in the figure by a dotted line, extends a short distance into the 
 commencement of the primitive arterial trunk, dividing it into two 
 lateral halves, one of which is in communication with the right. side 
 of the heart, the other with the left. 
 
 About the same time, the pulmonary branches (3, 3) are given 
 off from each side of the arterial trunk near its origin ; and the 
 longitudinal partition, above spoken of, is so placed that both these 
 branches fall upon one side of it, and are both, consequently, given 
 off from that division of the artery which is connected with the right 
 side of the heart. 
 
DEVJELOPMENT OF THE HEART. 
 
 679 
 
 Fig. 269. 
 
 FffiTAi- Hr ART Still farther 
 developed.— I Aorta. 2. Ph.- 
 moDury artery. 3, 3. Pul- 
 monary brauches 4. Ductus 
 aitei-iosus. 
 
 Very soon a. superficial line of demarcation, or furrow, shows 
 itself upon the external surface of the heart, corresponding in situa- 
 tion with the internal eeptum; while at the root of the arterial 
 trunk this furrow becomes much deeper, and finally the two lateral 
 portions of the vessel are separated from each other altogether, in 
 the immediate neighborhood of the heart, 
 joining again, however, a short distance be- 
 yond the origin of the pulmonary branches. 
 (Fig. 269.) It then becomes evident that 
 the left lateral division of the arterial trunk 
 is the commencement of the aorta (i); while 
 its right lateral division is the trunk of the 
 pulmonary artery (2), giving off the right 
 and left pulmonary branches (3,3), at a short 
 distance from its origin. That portion of 
 the pulmonary trunk (4) which is beyond 
 the origin of the pulmonary branches, and 
 which communicates' freely with the aorta, is the .Ductus arteriosus. 
 
 The ductus arteriosus is at first as large as the pulmonary trunk 
 itself; aqd nearly the whole of the blood, coming from the right 
 ventricle, passes directly onward through the arterial duct, and 
 enters the aorta without going to the lungs. But as the lungs 
 •gradually become developed, they require a larger quantity of 
 blood for their nutrition, and the pulmpnary branches increase in 
 proportion to the pulmpnary trunk and the ductus arteriosus. At 
 the termination of foetal life, in the 
 human subject, the ductus arteriosus 
 is about as large as either one of the 
 pulmonary branches ; and a very con- 
 siderable portion of the blood, there- 
 fore, coming from the right ventricle 
 still passes onward to the aorta with- 
 out being distributed to the lungs. 
 
 But at the period of birth, the lungs 
 enter upon the acJtive performance of 
 the function of respiration, and imme- 
 diately require a much larger supply 
 of blood. The right and left pul- 
 monary branches then enlarge, so as 
 to become the two principal divisions 
 of the pulmonary trunk. (Fig. 270.) The ductus arteriosus at the 
 
 Fig. 270. 
 
 Hbabt of Infant, showing dis- 
 appearance of arterial duct after birtli 
 .— 1. Aorta. 2. Palmonary artery. 3, 
 3. Pulmonary branches. . 4. Ductus 
 arteriosus becoming obliterated. 
 
680 DEVELOPMENT OP THE CIECULATORY APPARATUS. 
 
 same time becomes contracted and shrivelled to such an extent 
 that its cavity is obliterated ; and it is finally converted into an im- 
 pervious, rounded cord, which remains until adult life, running 
 from the point of bifurcation of the pulmonary artery to the under 
 side of the arch of the aorta. The obliteration of the arterial diict 
 id complete, at latest, by the tenth week after birth. (Cruy.) 
 
 The two auricles are separated from the two ventricles by hori- 
 zontal septa which grow from the internal surface of the cardiac 
 walls ; but these septa remaining incomplete, the auriculo-ventricu- 
 lar orifices continue pervious, and allow the free passage of the 
 blood from the auricles to the ventricles. 
 
 The interventricular septum, or that which separates the two 
 ventricles from each other, is completed at a very early date ; but 
 the interauricular septum, or that which is situated between the 
 two auricles, remains incomplete for a long time, being perforated 
 by an oval-shaped opening, the foramen ovale, allowing, at this 
 situation, a free passage from the right to the left side of the heart. 
 The existence of the foramen ovale and of the ductus arteriosus 
 gives rise to a peculiar crossing of the streams of blood in passing 
 thpoTigh the heart, which is characteristic of foetal life, and which 
 may be described as follows : — 
 
 It will be found upon examination that the two vense cavse, 
 superior and inferior, do not open into the auricular sac on the 
 same plane or in the same direction ; for while the superior vena 
 cava is situated anteriorly, and is directed downward and forward) 
 the inferior is situated quite posteriorly, and passes into the auricle 
 in a direction from right to left, and transversely to the axis of 
 the heart. A nearly vertical curtain or valve at the same time 
 hangs downward behind the orifice of the superior vena cava and 
 in front of the orifice of the inferior. This curtain is formed by 
 the lower edge of the septum of the auricles, which, as we have 
 before stated, is incomplete at this age, and which terminates 
 inferiorly and toward the right in a crescentio border, leaving at 
 that part an oval opening, the foramen ovale. The stream of blood, 
 coraing from the superior vena cava, falls accordingly in front of 
 this curtain, and passes directly downward, through the auriculo- 
 ventricular orifice, into the right ventricle. But the inferior vena 
 cava, being situated farther back and directed transversely, opens, 
 properly speaking, not inJ;o the right auricle, but into the left ; for 
 its stream of blood, falling behind the curtain above mentioned, 
 passes across, through the foramen ovale, directly into the cavity of 
 
DEVELOPMENT OF THE HEART. 
 
 681 
 
 Fig. 271. 
 
 the left auricle. This direction of the current of blood, coming 
 from the inferior vena cava, is further secured by a peculiar mem- 
 branous valve, which exists at this period, termed the Eustachian 
 valve. This valve, which is very thin and transparent (Fig. 271, /), 
 is attached to the anterior border of the orifice of the inferior vena 
 cava, and terminates by a crescentic edge, directed towai'd the left; 
 the valve, in this way, standing 
 as an incomplete membranous 
 partition between the cavity of 
 the inferior vena cava and that 
 of the right auricle. A bougie, 
 accordingly, placed in the in- 
 ferior vena cava, as shown in 
 Fig. 271, lies naturally quite 
 behind the Eustachian valve, 
 and passes directly through 
 the foramen ovale, into the left 
 auricle. 
 
 The two streams of blood, 
 therefore, coming from the su- 
 perior and inferior venae cavse, 
 cross each other upon entering 
 the heart. This crossing of the 
 streams does not take place, 
 however, as it is sometimgs 
 described, in the cavity of the 
 right auricle ; but, owing to the 
 peculiar position and direction 
 of the two veins at this period, 
 with regard to the septum of 
 
 the auricles, the stream coming from the superior vena cava enters 
 the right auricle exclusively, while that from the inferior passes 
 almost directly into the left auricle. 
 
 It will also be seen, by examining the positions of the aorta, pul 
 monary artery, and ductus arteriosus, at this time, that the arteria 
 inuominata, together with the left carotid and left subclavian, are 
 given off from the arch of the aorta, before its junction with the 
 ductus arteriosus, and this arrangement causes the blood of the two 
 venae cavse, not only to enter the heart in different directions, but 
 also to be distributed, after leaving the ventricles, to different parts 
 of the body. (Fig. 272.) For the blood of the superior vena cava 
 
 Heart OF Human Fcetub, at the end of the 
 Bixth month ; from a'tipecinietf in the author's pos- 
 sesHiou. — a. Inferior vena cava. h. Superior vena 
 cava. e. Cavity of rl^ht 'anxicle, laid open from 
 tlie front, d. Appendix auricularis. e. Cavity of 
 riifht ventricle, also laid open. /. Eustachian valve. 
 The bougie, which is placed in the inferior vena 
 cava, can be seen passing behind the Eustachian' 
 valve, just below the point indicated by /, then 
 crossing behind the cavity of the right auricle, and 
 passing through the foramen ovale, to the left side 
 of the heart. 
 
682 DEVELOPMEXT OF THE CIRCULATORY APPARATUS, 
 
 Fig 272. 
 
 passes through the right auricle downward into the right ventricle, 
 thence through the pulmonary artery and ductus arteriosus, into 
 the thoracie aorta, while the blood of the inferior vena cava, enter- 
 ino- the left auricle, passes into the left ventricle, thence into the arch 
 of the aorta, and is distributed to the head and upper extremities, 
 before reaching the situation of the arterial duct. The two streams, 
 therefore, in passing through the heart, cross each other both behind 
 and in front. The venous blood, retilrning from the head and 
 
 ripper extremities by the superior 
 vena cava, passes through the abdo- 
 minal aorta and the umbilical arte- 
 ries, to the lower part of the body, 
 and to the placenta ; while that re- 
 turning from the placenta; by the 
 inferior vena cava, is distributed to 
 the head and upper extremities, 
 through the vessels given off from 
 the arch of the aorta. 
 
 This division of the streams of 
 blood, during a certalin period of 
 foet&l life, is so complete that Dr. 
 John Eeid,' on injecting the infe- 
 rior vena cava with red, and the 
 superior with yellow, in a seven 
 months' human foetus, found that 
 the red had passed through the foramen ovale into the left auricle 
 and ventricle and arch of the aorta, and had filled the vessels of 
 the head and upper extremities; while the yellow had passed into 
 the right ventricle, pulmonary artery, ductus arteriosus, and tho- ' 
 racic aorta, with only a slight admixture of red at the posterior 
 part of the right auricle. All the branches of the thoracic and 
 abdominal aorta were filled with yellow, while the whole of the red 
 had passed to the upper part of the body. 
 
 We have repeated the above experiment several times on the 
 foetal pig, when about one-half and three-quarters grown, first taking 
 the precaution to wash out the heart and large vessels with a wa- 
 tery injection, immediately after the removal of the foetus from the 
 body of the parent, and before the blood had been allowed to coagu- 
 late. The injections used were blue for the superior vena cava. 
 
 Diiijfmm of' CittcufiATroN TnRriuoH 
 Tnii F(ETAL Hkart. — «. Superior vena 
 cavii. 6. Inferior veua cava, r, c, c, c. Arch 
 or aorta and its brasicheB. d. Pulmuuury 
 artery. 
 
 Edinburgh Medical and Surgical Journal, vol. zliii. 183%. 
 
DEVBLOPMENT OF THE HEABT. 683 
 
 and yellow for the inferior. The two syringes were managed, at 
 the same time, by the right and left hands: their nozzles being 
 firmly held in place by the fingers of an assistant. -When the 
 points of the syringes were introduced into the veins, at equal dis- 
 tances from the heart, and the two injections made with equal force 
 and rapidity, it was found that the admixture of the colors which 
 took place was so slight, that at least nineteen-twentieths of the 
 yellow injection had passed into the left auricle, and nineteen-twen- 
 tieths of the blue into the right The pulmonary artery and ductus 
 arteriosus contained a similar proportion of blue, and the arch of 
 the aorta of yellow. In the thoracic and abdominal aorta, however, 
 contrary to what was found by Dr. Keid, there was always an ad- 
 mixture of. the two colors, generally in about equal proportions. 
 This discrepancy may be owing to the smaller size of the head and 
 upper extremities, in the pig, as compared with those of the human 
 subject, which would prevent their receiving all the blood coming 
 from the left ventricle ; or to some differences in the manipulation 
 of these experiments, in which it is not always easy to imitate ex- 
 actly the force and rapidity of the different currents of blood in 
 the living foetus. The above results, howeyer, are such as to leave 
 no doubt of the principal fact, viz., that up to an advanced stage of 
 foetal life, by far the greater portion of the blood coming from the 
 inferior vena cava passes through the foramen ovale, into the left, 
 side of the heart ; while by far the greater portion of that coming 
 from the head and upper extremities passes into the right side of 
 the heartj and thence outward by the pulmonary trunk and ductus 
 arteriosus. Toward the latter periods of gestation, this division 
 of the venous currents becomes less complete, owing to the three 
 following causes : — 
 
 First, the lungs increasing in size, the two pulmonary arteries, as 
 well as the pulmonary veins, enlarge in proportion; and a greater 
 quantity of the blood, therefore, coming from the right ventricle, 
 instead of going onward through the ductus arteriosus, passes to 
 the lungs, and returning thence by the pulmonary veins to the left 
 auricle and ventricle, joins the stream passing out by the arch of 
 the aorta. 
 
 Secondly, the Eustachian valve diminishes in size. This valve, 
 which is very large and distinct at the end of the sixth month 
 (Pig. 271), subsequently becomes atrophied to such an extent that, 
 at the end of gestation, it has altogether disappeared, or is at least 
 reduced to the condition of a very narrow, almost imperceptible 
 
684 DEVELOPMENT OF THE CIRCULATORY APPARATUS. 
 
 membranous ridge, ■wbich can exert no influence on the direction 
 of the current of blood passing by it. Thus, the cavity of the infe- 
 rior vena cava, at its upper extremity, ceases to be separated from 
 that of the right auricle ; and a passage of blood from one to the 
 other may, therefore, more readily take place. 
 
 Thirdly, the foramen ovale becomes partially closed by a valve 
 which passes across its orifice from behind forward. This valve, 
 which, begins to be formed at a very early period, is called the 
 valve of the foramen ovate. It consists of a thin, fibrous sheet, which 
 grows from the posterior surface of the auricular cavity, just to the 
 left of the foramen ovale, and projects into the left auricle, its free 
 edge presenting a thin crescentic border, and being, attached, by its 
 two extremities, to the auricular septum upon the left side. This 
 valve does not at first interfere at all with the flow of blood from 
 right to left, since its edge hangs freely and loosely into the cavity 
 of the left auricle. It only opposes, therefore, during the early 
 periods, any accidental regurgitation from left to right. 
 
 But as gestation advances, while the walls of the heart con- 
 tinue to enlarge, and its cavities to expand in every direction, the 
 fibrous bundles, forming the valve, do not elongate in proportion- 
 The valve, accordingly, becomes drawn downward more and more 
 toward the foramen ovale. It thus comes in contact, with the edges 
 of the interauricular septum, and unites with its substance ; the 
 adhesion taking place first at the lower and posterior portion, and 
 proceeding gradually upward and forward, so as to make the pas- 
 sage, from the right 'auricle to the left, more and more oblique in' 
 direction. 
 
 At the same time, an alteration takes place in the position of the 
 inferior vena cava. This vessel, which at first looked transversely 
 toward the foramen ovale, becomes directed more obliquely for- 
 ward ; so that, the Eustachian valve having mostly disappeared, a 
 part of the blood of the inferior vena cava enters the right auricle, 
 while the remainder still passes jihrough the equally oblique open 
 ing of the foramen ovale. 
 
 At the period of birth a change takes place, by which the 
 foramen ovale is completely occluded, and all the blood coming 
 through the inferior vena cava is turned into the right auricle. 
 
 This change depends upon the commencement of respiration. 
 A much larger quantity of blood than before is then sent to the 
 lungs, and of course returns from them to the left auricle. The 
 left auricle, being then completely filled with the pulmonaiy blood, 
 
DEVELOPMENT OF THE HEART. 685 
 
 no, longer admits a free access from tte right auricle through the 
 foramen ovale j and the valve of the foramen, pr|psed backward 
 more closely against the edges of the septum, becomes after a time 
 adherent throughout, and obliterates the opening altogether. The 
 cutting off of the placental circulation diminishes at the same time 
 the quantity of blood arriving at the heart by the inferior vena 
 cava. It is evident, indeed, that the same quantity of blood which 
 previously, returned from the placenta by the inferior cava, on the 
 right side of the auricular septum, now returns from the lungs, by 
 the pulmonary veins upon the left side of the same septum ; and it 
 is owing to all these circumstances combined, that while before birth 
 a portion of the blood alwiays passed from the right auricle to the 
 left through the foramen ovale, no such passage takes place after 
 birth, since the pressure is then equal on both sides of the auricular 
 septum. 
 
 The foetal circulation, represented in Fig. 272, is then replaced 
 by the adult circulation, represented in Fig. 273. 
 
 Fig. 273; 
 
 Diagram of Adhi.t Ci^cclation tbrobohtht! Heart.—",". Snperior and inferior vens 
 CBvaj. S. Eight ventricle. ,,-. Plllmonay artery, dividing into right and left branches, d. Palmo- 
 nary vein. e. Left ventricle. /. A»rta. 
 
 That portion of the septum of the auricles, originally occupied 
 by the foramen ovale, is accordingly constituted, in the adult con 
 dition, by the valve of the foramen ovale, which has become adhe- 
 
686 DEVELOPMENT OF THE CIBCULATOET APPARATUS. 
 
 rent to the edges of the septum. The auricular septum in the adult 
 heart is, therefye, thinner at this spot than elsewhere ; and presents, 
 on the side of the right auricle, an oval depression, termed the fossa 
 ovalis, which indicates the site of the original foramen ovale. The 
 fossa ovalis is surrounded by a slightly raised ring, the annulus 
 ovalis, representing the curvilinear edge of the original auricular 
 septum; 
 
 The foramen ovale is sometimes completely obliterated within a 
 few days after birth. It often, however, remains partially pervioils 
 for several weeks or months. We have a specimen, taken from a 
 child of one year and nine months, in which the opening is still 
 very distinct; and it is not unfrequent to find a small aperture 
 existing even in adult life. In these instances, however, although 
 the adhesion and solidification of the auricular septum may not be 
 complete, yet no disturbance (^ the circulation "results, and no ad- 
 mixture of blood takes place between the right and left sides of the 
 heart ; since the passage through the auricular septum is always 
 very oblique in its direction, and its valvular arrangement prevents 
 any regurgitation from left to right, while the complete filling of 
 the left auricle with pulmonary blood, as above mentioned, equally 
 opposes any passage from right to left. 
 
DEVELOPMENT OP THE BODY AFTEB BIRTH. CS7 
 
 CHAPTER XVIII. 
 
 DEVELOPMENT OP THE BODY APTBE BIETH. 
 
 The newly-born infant is still very far from having arrived at a 
 state of complete development. The changes through which it has 
 passed during intra-nterine life are not more marked than those 
 which are to follow during the periods of infancy, childhood, and 
 adolescence. The anatomy, of the organs, both internal and ex- 
 ternal, their physiological functions, and even the morbid derange- 
 ments to which they are subject, continue to undergo gradual and 
 progressive alterations, throughout the entire course of subsequent 
 life. The history of development extends, properly speaking, from 
 the earliest organization of the embrypnic tissues to the complete 
 formation of the adult body. The period of birth, accordingly, 
 marks only a single epoch in a constant series of changes, some of 
 which have preceded, while many others are to follow. 
 
 The weight of the newly-born infant is a little over six pounds. 
 The middle point of the body is nearly at the umbilicus, the head 
 and upper extremities being still very large, in proportion to the 
 lower extremities and pelvis. The abdomen is larger and the 
 chest smaller, in proportion, than in the adult. The lower extremi- 
 ties are curved inward, as in the foetal condition, so that the soles of 
 the feet look obliquely toward each other, instead of being directed 
 horizontally downward, as at a subsequent period. Both uppei* 
 and lower extremities are habitua,lly curled upward and forward 
 over the chest and abdomen, and all the joints, are constantly in a 
 semi-flexed position. 
 
 The process of respiration is very imperfectly performed for 
 some time after birth. The expansion of the pulmonary vesicles, 
 and the changes in the circulatory apparatus described in the pre- 
 ceding chapter, far from being sudden and- instantaneous, are, 
 always more or less gradual in their character, and require an 
 interval of several days for their completion. Respiration, indeed 
 
688 DEVKLOPMENT OF THE BODY AFTER BIETH. 
 
 seems to be accomplished, daring this period, to a considerable 
 extent through the skin, which is remarkably soft, vascular, and 
 ruddy in color. The animal heat is also less actively generated 
 than in the adult, and requires to be sustained by careful protec- 
 tion, and by contact with the body of the mother. The young 
 infant sleeps during the greater part of the time; and even whea 
 awake there are but few manifestations of intelligence or percep- 
 tion. The special senses of sight and hearing are dull and inex- 
 citable, though their organs are perfectly formed; and even 
 consciousness seems present only to a very limited extent. Volun- 
 tary motion and sensation are nearly absent ; and the almost con- 
 stant irregular movements of the limbs, observable at this time, 
 are evidently of a reflex or automatic character. Nearly all the 
 nervous phenomena, indeed, presented by the newly-born infant, 
 are of a similar nature. The motions of its hands and feet, the act 
 of suckling, and even its cries and the contortions of its face, are 
 reflex in their origin, and do not indicate the existence of any 
 active volition, or any distinct perception of external objects. 
 There is at first but little nervous connection established with the 
 external world, and the system is as yet almost exclusively occu- 
 pied with the functions of nutrition and respiration. 
 
 This preponderance of the simple reflex actions in the nervous 
 system of the infant, is observable even in the diseases to which it 
 is peculiarly subject for some years after birth. It is at this age 
 that convulsions from indigestion are of most frequent occurrence, 
 and even temporary strabismus and paralysis, resulting from the 
 same cause. It is well known to physicians, moreover, that the 
 effect of various drugs upon the infant is very difierent from that 
 which they eiert upon the adult. Opium, for example, is very 
 much more active, in proportion to the dose, in the infant than in 
 the adult. Mercury, on the other hand, produces salivation with 
 greater difficulty in the former than in the latter. Blisters excite 
 more constitutional irritation in the young than in the old subject ; 
 and antimony, when given to children, is proverbially uncertain 
 and dangerous in its operation. 
 
 The difference in the anatomy of the newly -born infant, and that 
 of the adult, may be represented, to a certain extent, by the fol- 
 lowing list, which gives the relative weight of the most important 
 internal organs at the period of birth ^nd that of adult age ; the 
 , weight of the entire body being reckoned, in each case, as 1000. 
 The relative weight of the adult organs has been calculated from 
 
DEVELOPMENT OF THE BODY AFTEE BIRTH. 
 
 689 
 
 the estimates of Cruveilheir, Solly, 'Wilson, &c. ; that of the organs 
 in the foetus at term f][fcm our own. observations. 
 
 Wei 
 
 
 
 PfflTTTS AT TeRU. 
 
 ADULT. 
 
 ight of the entire body 
 
 . 1000.00 
 
 1000.00 
 
 (( u 
 
 enoephalon 
 
 148.00 
 
 23.00 
 
 ti ft 
 
 liver . 
 
 37.00 
 
 29.00 
 
 (( (( 
 
 heart 
 
 7.77* 
 
 4.17 
 
 tt u 
 
 kidneys . 
 
 6.00 
 
 4.00 
 
 U 11 
 
 renal capsules . 
 
 1.63 
 
 0.13 
 
 It tt 
 
 thyroid gland . 
 
 0.60 
 
 0.51 
 
 tt u 
 
 thymus gland . 
 
 3.00 
 
 0.00 
 
 It will be observed that most of the internal organs diminish in 
 relative size after birth, owing principally to the increased develop- 
 ment of the osseous and muscular systems, both of which are in a 
 very imperfect condition throughout intra-uterine life, but which 
 come into activity during childhood and youth. * 
 
 Within the first day after birth the remains of the umbilical 
 cord begin to wither, and. become completely desiccated by about 
 the third day. A superficial ulceration then takes place about the 
 point of its attachment, and it is separated and thrown off within 
 the first week. After the separation of the cord, the umbilicus 
 becomes completely cicatrized by the tenth or twelfth day after 
 birth. (Guy.) 
 
 An exfoliation and renovation of the cuticle also take place 
 over the whole body soon after birth. According to Kolliker, the 
 eyelashes, and probably all the hairs of the body and head are 
 thrown off and replaced by new ones within the first year. 
 
 The teeth in the newly-born infant are but partially developed, 
 and are still inclosed in their follicles, and concealed beneath the 
 gums. They, are twenty in number, viz., two incisors, one canine, 
 and two molars, on each side of each jaw. At birth there is a thin 
 layer of dentine and enamel covering their upper surfaces, but 
 the body of the tooth and its fangs are formed subsequently by 
 progressive elongation and ossification of the tooth-pulp. The 
 fully-formed teeth emerge from the gums in the following order. 
 The central incisfrs in the seventh month after birth; the lateral 
 incisors in the eighth month ; the anterior molars at the end of the 
 first year ; the canines at a year and a half; and the second molars 
 at two years (Kolliker). The eruption of the teeth in the lower 
 jaw generally precedes by a short time that of the corresponding 
 teeth in the upper. 
 
 During the seventh year a change begins to take place by which 
 44 
 
DEVELOPMENT OF THE BODY AFTER BIRTH. 
 
 Ahe first set of teeth are thrown off and replaced by a second or 
 permanent set, differing in number, size, And shape from those 
 which preceded. The anterior permanent molar first shows itself 
 just behind the posterior temporary molar, on each side. This 
 happens at about six and a half years after birth. At the end of, 
 the seventh year the middle incisors are thrown off and replaced 
 by corresponding permanent teeth, of larger size. At the eighth 
 year a similar exchange takes place in the lateral incisors. In the 
 ninth and tenth years, the anterior and second molars are replaced 
 by the anterior and second permanent bicuspids. In the twelfth 
 year, the canine teeth are changed. In the thirteenth year, the 
 second permanent molars show themselves ; and from the seven- 
 teenth to the twenty-first year, the third molars, or " wisdom teeth," 
 emerge from the gums, at the posterior extremities of the dental 
 arch. (Wilson.) The jaw, therefore, in the adult condition, contains 
 three teeth on each side more than in childhood, making in all 
 thirty -two permanent teeth ; viz., on each side, above and below, 
 two incisors, .one canine, two bicuspids, and three permanent 
 molars. 
 
 The entire generative apparatus, which is still altogether inactive 
 at birth, begins to enter upon a condition of functional activity 
 from the fifteenth to the twentieth year. The entire configuration 
 of the body alters in a striking manner at this period, and the dis- 
 tinction between the"* sexes becomes more complete and well 
 marked. The beard is developed in the male ; and ip the female 
 the breasts assume the size and form characteristic of the condition 
 of puberty. The voice, which is shrill and sharp in infancy and 
 childhood, becomes deeper in tone, and the countenance assumes a 
 more sedate and serious expression. After this period, the mus- 
 cular system increases still further in size and strength, and the 
 consolidation of the skeleton also continues ; the bony union of its 
 various parts not being entirely accomplished until the twenty-fifth 
 or thirtieth year. Finally, all the different orgains of the body 
 arrive at the adult condition, and the entire process of development 
 is then complete. • 
 
INDEX. 
 
 Absorbent glands, 168, 317 
 
 vessels, 167, 317 
 Absorption, 162 
 
 by bloodvessels, 165 
 
 by lacteals, 168 
 
 of fat, 171 
 
 of different lii^aids by animal sub- 
 stances, 312 
 
 of oxygen in respira,tion, 243 
 
 by egg during incubation, 606 
 
 of calcareous matter by allantois, 
 606 
 Acid, carbonic, 242, 246 . 
 
 lactic, in gastric juice, 139 
 . in souring milk, 99, 336 
 
 glyko-oholic, 180 
 
 tauro-cholio, 181 
 ■ pnenmic, 247 
 
 uric, 347, 354 
 
 oxalic in urine, 860 
 Acid fermentation of urine, 360 
 Acidity of gastric juice, cause of, 139 
 
 of urine, 353 
 Acini, of liver, 338 
 Adipose vpsicles, 90 
 
 digestion of, 158, 159 
 Adult pirculation, 670 
 
 establishment of, 685 
 Aerial respiration, 233 
 Age, influence of, on «xhalation of car- 
 bonic acid, 250 
 
 on comparative weight of organs, 
 689 
 Air, quantity of, used in respiration, 238 
 
 alterations of, in respiration, 241 
 
 circulation of, in lungs, 239 
 Air-cells of lungs, 235 
 Air-chamber, in fowl's egg, 552 
 Albumen, 100 
 
 of the blood, 224 
 
 in milk, 335 
 
 of the egg, how produced, 550 
 
 its liquefaction and absorption dur- 
 ing development of foetus, 602- 
 604 
 Albuminoid substances, 95 
 
 digestion of, 141 
 Albuminose, 142 
 
 interference with Trommer's test, 
 143 
 
 with action of iodine and starch, 
 144 
 
 Alimentary canal in different animals, 
 116, 119 
 
 development of, 644 
 Alkalies, effect of, on urine, 354 
 Alkaline chlorides, 71-74 
 
 phosphates, 77 
 ■ carbonates, 76, 77 
 Alkaline fermentation of urine, 360 
 AlKalescence of blood, due to carbonates, 
 
 76 
 Allantois, 599 
 
 formation of, 601 
 
 in fowl's egg, 604 
 
 function of, 605 
 
 in foetal pig, 622 
 Alligator, brain of, 382 
 Amnion, 509 
 
 formation of, 600 
 
 enlargement of, during latter part of 
 pregnancy, 630 
 
 contact with chorion, 631 
 Amniotic folds, 600 
 Amniotic fluid, 630 
 
 its use, 631 
 
 contains sugar at a certain period, 
 648 
 'Amniotic umbilicus, 600 
 Analysis, of animal fluids, 64, 65 
 
 of milk, 112, 334 
 
 of wheat flour, 112 
 
 of oatmeal, 112 
 
 of eggs, 113 
 
 of meat, 113 
 
 of saliva, 124, 126 
 
 of gastric juice, 139 
 
 of pancreatic juice, 155 
 
 of bile, 176 
 
 of blood-globules, 218 
 
 of blood-plasma, 223 
 
 of mucus, 328 
 
 of sebaceous matter, 329 
 
 of perspiration, 331 
 
 of butter, 336 
 
 of urine, 352 
 
 of fluid of thoracic duct, 318 
 
 of chyle and lymph, 320 
 Ahdral and Gavabret, production of 
 
 carbonic acid in respiration, 250 
 Animal functions, 59 
 Animal heat, 253-263 
 
 in different species, 255 
 
 mode of generation, 257 
 
 (691) 
 
692 
 
 INDEX. 
 
 Animal heat influeuced by local causes, 
 261 
 
 in different organs, 262 
 
 increase of, after section of sympa- 
 thetic nerve, 521 
 Animal and vegetable parasites, 532 
 Animalcules, infusorial, 529 
 
 mode of production, 530 
 Annulus ovalis, 686 
 Anterior columns of spinal cord, 380 
 
 their excitability, 402 
 Aorta, development of, 670 
 Aplysia, nervous system of, 375 
 Appetite, disturbed by anxiety, &c., 149 
 
 necessary to digestion of food, 149 
 Aquatic respiration, 233 
 Arch of aorta, formation of, 671 
 Arches, cervical, 670 
 
 transformation of, 671 ^ 
 
 Area pelluoida, 590 
 
 vasculosa, 003, 666 
 Arteries^ 281 
 
 motion of blood in, 282 
 
 pulsation of, 283-285 
 
 elasticity of, 281, 286 
 
 rapidity of circulation in, 289 
 
 omphalo-meseuteric, 666 
 
 vertebral, 669 
 
 umbilical, 669 
 Arterial pressure, 287 
 Arterial system, development of, 669-672 
 Articulata, nervous system of, 376 
 
 reflex action in, 377 
 Articulation of tapeworm, 541 
 Arytenoid cartilages, 240 
 
 movements of, 241 
 Assimilation, 324 
 
 destructive, 341 
 Auditory apparatus, 505 
 
 nerves, 447, 507 
 Auricle, single, of fish, 265 
 
 double, of reptites, birds, and mam- 
 malians, 266, 267 
 
 contraction of, 279 
 -Auriculo-veutricular valves, action of, 
 
 269 
 Axis-cylinder, of nervous filaments, 370 
 Aztec children, 426 
 -Azygous veins, formation of, 673 
 
 Bbaumoht, Dr. , experiments on Alexis St. 
 
 Martin, 135-14B 
 Beknakd, on the different kinds of saliva, 
 125 
 on effect' of dividing Steno's duct, 
 
 131 
 on digestion of fat in intestine, 155 
 on formation of liver-sugar, 2O0, 202, 
 
 '203 
 on decomposition of bicarbonates in 
 
 lung, 247 
 on temperature of blood in different 
 organs, 262 
 
 BiDDEE AND ScHMiDT, on daily quantity 
 of bile, 188 
 on effect of excluding bile from in- 
 testine, 195 
 on reabsorption of bile, 196 
 Bile, 17S 
 
 composition of, 176 
 tests for, 184 
 daily quantity of, 188 
 functions of, 193 
 reaction with gastric juice, 193 
 reabsorption, 196 
 mode of secretion, 337 
 Biliary salts, 177 
 
 of human bile, 183 
 Biliverdine, 103, 176 
 tests for, 184 
 
 passage into the urine, 357 
 Blastodermic membrane, 688 
 Blood, 213 
 
 red globules of, 214 
 white globules, 220 
 plasma, 223 
 coagulation o'f, 225 
 buffy coat, 230 
 entire quantity of, 231 
 alterations of, in respiration, 243 
 temperature of, 254 
 
 in different organs, 262 
 circulation of, 264 
 
 through the heart, 270 
 through the arteries, 282 
 through the veins, 290 
 through the capillaries, 296 
 BoDSSiNOAULT, on chloride of sodium in 
 food, 73 
 on internal production of fat, 93 
 Brain, 381, 417 
 
 of alligator, 382 
 
 of rabbit, 383 
 
 human, 386, 417 
 
 remarkable oases of injury to, 419, 
 
 420 
 size of, in different races, 423, 424 
 
 in idiots, 425 
 development of, 638, 639 
 Branchiae, 232 
 
 of meno-branohus, 233 
 Broad ligaments, formation of, 662 
 Bronchi, division of, 234, 235 
 
 ciliary, motion in, 239 
 Brunner's glands, 152 
 Buffy coat of the blood, 230 
 Butter, 335 
 
 composition of, 336 
 condition in milk, 91, 335 
 Butyrine, 336 
 
 Canals of Cuvier, 672 
 Capillaries, 295 
 
 their inosculation, 296 
 
 motion of hlood in, 297 
 Capillary circulation, 296 
 
INDEX. 
 
 693 
 
 Capillary circulatiou, causes of, 298 
 rapidity of, 301, 302 
 peoiiliarities of, in different parts, 
 303 
 Caput coli, formation of, 645 
 Carbonic acid, in the breath,, 242 
 
 proportion of, to oxygen absorbed, 
 
 242, 243 
 in the blood, 243 
 origin of, in lungs, 247 
 in the blood, 348 
 In the tissues, 248 
 mode of production, 248 
 daily quantity of, 250 
 variations of, 250 
 exhaled by skin, 252 
 
 by egg, during incubation, 606 
 absorbed by vegetable^ 260 
 Carbonate of lime, 76 
 .of soda, 76 
 of potassa, 7^ 
 
 of ammonia, in putrefying urine, 
 360 
 Cardiac circulation, in fcetus, 682 
 
 in adult, 685 
 Carnivorous animals, respiration of, 50, 
 243 
 urine of, 346 
 Cartilagine, 102 
 Caseine, 100 
 Cat, secretion of bile in, 188 
 
 closure of eyelids, after division of 
 sympathetic, 522 
 Catalytic action, 98 
 of pepsin, 142 
 Centipede, nervous system of, 376 
 Centre, nervous definition of, 373 
 Cerebrum, 419. See Hemispheres. 
 Cerebral ganglia, 382. See Hemi- 
 spheres. , 
 Cerebellum, 429 
 
 effects of injury to, 431 
 removal of, 431-434 
 function of, 430 
 development of, 638, 639 
 Cerebro-spinal system, 378, 379 
 
 development of, 637 
 Cervix uteri, 554 
 in foetus, 663 
 Cervical arches, 670 
 
 transformation of, 671 
 Changes, in egg, while passing through 
 oviduct, 548, 551 
 in hepatic circulatiou at birth, 677 
 in comparative size of organs, after 
 birth, 689 
 Chevreuil, -experiments on imbibition, 
 
 312 
 Chick, development of, 602-607 
 (Ihildren, Aztec, 426 
 Chloride of sodium, 71 
 
 its proportion in the animal tissues 
 and fluids, 72 
 
 Chloride of sodium, importance of, in the 
 food, 73 
 
 mode of discharge from the body, 74 
 
 partial decomposition of, in the body, 
 74 
 Chloride of potassium, 74 
 Cholesterin, 176 
 Chorda dorsalis, 591 
 Chorda tympani, 488 
 Chordae vooales, movement of, in respi- 
 ration, 240 
 
 action of, in the production of vocal 
 sounds, 464 
 
 obstruction of glottis by, after divi- 
 sion of pneumogastric, 466, 467 
 Chorion, formation of, 608 
 
 villosities of, 610 
 
 source of vascularity of, 611 
 
 union with decidua, 619 * 
 Chyle, 153, 169, 320 
 
 in lacteals, 170 
 
 absorption of, 171 
 
 by intestinal epithelium, 172 
 
 in blood, 173 
 Ciliary motion, in bronchi, 22] 
 
 in Fallopian tubes, 573 
 Ciliary nerves, 5.14 "" 
 
 Circulation, 264 
 
 in the heart, 270 
 
 in the arteries, 282 ' 
 
 in the veins, 290 
 
 in the capillaries, 297 
 
 rapidity of, 302 
 
 peculiarities of, in different parts, 
 304 
 
 in liver, 339 
 
 in placenta, 621-629 
 Circulatory apparatus, development of, 
 
 665-686 
 "Civilization, aptitude for, of different 
 
 races, 424 
 Classification of cranial nerves, 448 
 Clot, formation of, 225 
 
 separation from serum, 226 
 
 buffed and cupped, 230 
 Coagulation, 98 
 
 of fibrin, 223 
 
 of blood, 225 
 
 of white substance of Schwann, in 
 nerve-fibres, 369 
 CoLiH, on unilateral mastication, 127 
 Cold, resistance to, by animals, 253 
 
 effect of, when long continued, 254 
 Colostrum, 333 
 Coloring matters, 103 
 
 of blood, 102, 218 
 
 of the skin, 103 
 
 of bile, 103 
 
 of urine, 103 
 Commissure, of spinal cord, gray, 381 
 
 white, 381 
 
 transverse, of cerebrum, 387 
 
 of cerebellum, 387 * 
 
694 
 
 INDEX. 
 
 Commissures, nervous, 373 
 
 olfactory, 382, 418 
 Congestion, of ear, &o., after division of 
 
 sympathetic, 521 
 Convolvulus, sexual apparatus of, 540 
 Consentaneous action of muscles, 430 
 Contact, of chorion and amnion, 631 
 
 of decidua vera and reflexa, 632 
 Contraction, of stomach during diges- 
 tion, 145 
 
 of spleen, 208 
 
 of hlood-clot, 226 
 
 of diaphragm and intercostal mus- 
 cles, 236 
 
 of posterior crico-arytenoid muscles, 
 241 ' 
 
 of ventricles, 275 
 
 of muscles after death, 389 
 
 of sphincter ani, 414 
 
 of rectum, 414 
 
 of urinary bladder, 415 
 
 of pupil, under influence of light, 
 367, 435, 501 
 after division of sympathetic, 
 522 
 Cooking, effect of, on food, 114 
 Cord, spinal, 379, 398 
 
 umbilical, 631 
 , withering and separation of, 689 
 
 Corpus callosum, 387 
 Corpus luteum, 576 
 
 of menstruation, 576-580 
 
 of pregnancy, 580-585 
 
 three weeks after menstruation, 578 
 
 four weeks after menstruation, 579 
 
 nine weeks after menstruation, 579 
 
 at end of second month of preg- 
 nancy, 582 
 
 at end of fourth month, 582 
 
 at term, 583 
 
 disappearance of, after delivery, 584 
 Corpora Malpighiana, of spleen, 191 
 Corpora striata, 383, 419 
 Corpora olivaria, 384 
 Corpora Wolffiana, 655 
 CosTE, on rupture of Graafian follicle in 
 
 menstruation, 572, 573 
 Cranial nerves, 446 
 
 classification of, 448 
 
 motor, 449 
 
 sensitive, 449, 450 
 Creatine, 346 
 Creatinine, 346 
 Cremaster muscle, formation of, 659 
 
 function of, in lower animals, 660 
 Crystals, of stearine, 87 
 
 and margarine, 88 
 
 of cholesterin, 177 
 
 of glykocholate of soda, l78 
 
 of biliary matters of dog's bile, 182 
 
 of urea, 343 
 » of creatine, 346 
 
 of creatinine, 346 
 
 Crystals, of urate of soda, 347 
 of uric acid, 354 
 of oxalate of lime, 360 
 of triple phosphate, 362 
 Crystallizable snstances of organic ori- 
 gin, 79 
 Crossing of fibres in medulla oblongata, 
 385, 404 
 of sensitive fibres jn spinal cord, 
 
 405 
 of fibres of optic nerves, 436, 437 
 of streams of blood in foetal heart, 
 681, 682 
 Cebikshank, rupture of Graafian follicle 
 
 in menstruation, 572 
 Cumulus proligerus, 567 
 Cutaneous respiration, 252 
 
 perapira1;ion, 330 
 Cuticle, exfoliation of, during fffital life, 
 643 
 after birth, 689 
 Cysticercus, 537 
 
 transformation of into taenia, 538 
 production of, from eggs of taenia, 
 539 
 
 Death, a necessary consequence of life, 
 
 626 
 Decidua, 614 
 ■ vera, 616 
 reflexa, 618 
 
 union with chorion, 619 
 its discharge in cases of abortion, 
 618 
 at the time of delivery, 633 
 Decussation of anterior columns of spinal 
 cord, 385, 404 
 of optic nerves, 436, 437 
 Degeneration, fatty, of muscular fibres 
 
 of uterus, after delivery, 635 
 Deglutition, 133 
 
 retarded by division of Steno's duct, 
 131 
 by division of pnenmogastrie, 
 463 
 Dentition, first, 689 
 
 second, 690 
 Descent of the testicles, 658 
 
 of the ovaries, 661 
 Destructive assimilation, 341 
 Development of the impregnated egg, 586 
 of allantois, 601 
 of chorion, 608 
 
 of villosities of chorion, 610, 611 
 of decidua, 615, 616 
 of placenta, 621-626 
 of nervous system, 637 , 
 of eye, 640 
 of ear, 641 
 
 of skeleton, 641 • 
 
 of limbs, 642 
 of integument, 643 
 of alimentary canal, 464, 646 
 
INDKX. 
 
 695 
 
 Development of urinary passages, 646 
 
 of liver, 649, 675 
 
 of pliarynx and cesophagus, 650 
 
 of face, 651 
 
 of Wolffian bodies, 655 
 
 of kidneys, 656 
 
 of internal generative organs, 657 
 
 of circulatory apparatus, 665 
 
 of arterial system, 669 
 
 of venous system, 672 
 
 of hepatic circulation, 675 
 
 of heart, 678 
 
 of the body after birth) 687 
 Diabetes, 357 
 
 in foetus, 649 
 Diaphragm, action of in breathing, 237 
 
 formation of, 651 
 Diaphragmatic hernia, 651 
 Diet, iniluence of on nutrition, 108 
 
 on products of respiration, 243 
 
 on formation of urea, 345 
 of urate of soda, 348 
 Diffusion of gases in lungs, 239 
 Digestion, 115 
 
 of starch, 150 
 
 of fats, 153 
 
 of sugar, 150 
 
 of organic substances, 141 
 
 time required for, 146 
 Digestive apparatus of fowl, 117 
 
 of ox, 118 
 
 of man, 119 
 Discharge of eggs from ovary, 649 
 
 independent of sexual intercourse, 
 565 
 
 mechanism of, 568 
 
 during menstruation, 572 
 Discus proligerus, 567 
 Distahee and solidity, application of, by 
 
 the eye, 501, 502 
 Distinction between corpora lutea of 
 
 menstruation and pregnancy, 585 
 Diurnal variations, in exhalation of car- 
 bonic acid, 252 
 
 in production of urea, 345 
 
 in density and acidity of urine, 351 
 Division of nerves, 371 
 
 of heart, into right and left cavities, 
 678 
 DoBSON, on variation in size of spleen, 208 
 Draper, John C, on production of urea, 
 
 345 
 Drugs, effect of, on newly born infant, 
 
 688 
 Ductus arteriosus, 679, 682 
 
 closure of, 679, 680 
 
 venosus, 676 
 
 obliteration of, 677 
 Duodenal glands, 152 
 
 fistula, 190 
 DniEooHBT, on temperature of plants, 256 
 
 on endosmosis of water with differ- 
 ent liquids, 309* 
 
 Ear, 505 
 
 muscular apparatus of, 506 
 development of, 641 ' 
 Earthy phosphates, 74, 77 
 in urine, 353 
 
 precipitated by addition of an alkali, 
 354 
 Ectopia cordis, 651 
 Egg, 544 
 
 its contents, 545 
 
 where formed, 546 
 
 of frog, 547, 548 
 
 of fowl, 549 ■ 
 
 changes in, while passing through 
 
 the oviduct, 549-652 
 pre-existence of, in ovary, 563 
 development of, at period of puberty, 
 
 564 
 periodical ripening and discharge, 
 
 565 
 discharge of, from Graafian follicle, 
 
 568 
 impregnation of, how accomplished, 
 
 561 
 development of, after impregnation, 
 
 586 
 of fowl, showing area vasculosa, 603 
 ditto, showing formation of allantois, 
 
 604 
 of fish, showing vitelline circulation, 
 
 666 
 attachment of, to uterine mucous 
 
 membrane, 617 
 discharge of from uterus, at the time 
 
 of delivery, 633 
 condition of in newly bom infant, 663 
 Elasticity, of spleen, 208 
 
 of red globules of blood, 216 
 of lungs, 235, 237 
 of costal cartilages, 237 
 of vocal cords, 241 
 of arteries, 281 
 Electrical current, effect of on muscles. 
 389 
 on nerve, 391 
 different effects of direct and inverse. 
 
 394 • 
 
 Electrical fishes, phenomena of, 396 
 Electricity, no manifestations of in irri- 
 tated nerve, 397 
 Elevation of temperature, after division 
 
 of sympathetic, 261, 521 
 Elongation of heart in pulsation, 275 
 
 anatomical causes of, 276 
 Embryo, formation of, 686 
 Embryonic spot, 590 
 Encephalon, 381, 417 
 
 ganglia of, 386 
 Endosmosis, 307 
 
 of fatty substances, 171 
 in capillary circulation, 314 
 conditions of, 308 
 cause of, 311 
 
INDEX. 
 
 Endosmosis of iodide of potassiiim, 313 
 
 of atropine, 313 
 
 of nux volnioa, 314 
 Endosmometer, 308 
 
 Enlargement of amnion, during preg- 
 nancy, 630, 631 
 Entozoa, encysted, 534 . 
 
 mode of production, 536 
 Epithelium, in saliva, 124 
 
 of gastric follicles, 134 
 » of intestine, during digestion, 172 
 Epidermis, exfoliation of, in foetal life, 643 
 
 after birth, 689 
 Epididymis, 659 
 Exoretine, 160 
 Excretion, 341 
 
 nature of, 342 
 
 importance to life, 342 
 
 products of, 343 
 
 by placenta, 628 
 Bxcrementitious substances, 342 
 
 mode of formation of, 342 
 
 effect of retention of, 342 
 Exfoliation of cuticle, during foeta} life, 
 643 
 
 after birth, 689 
 Exhalation, 307 
 
 of watery vapor, 71 
 
 from the lungs, 242 
 
 from the skin, 330 
 
 from the egg, during incubation, 606 
 
 of carbonic acid, 242 
 
 of nitrogen, 242 
 
 of animal vapor, 242 
 Exhaustion, of muscles, by repeated irri- 
 tation, 390 
 
 of nerves, by ditto, 392 
 Exosmosis, 308 
 Expiration, movements of, 237 
 
 after section of pneumogastric, 469 
 Extractive matters of the blood, 225 
 Eye, protection of, by movements of pu- 
 pil, 367, 435, 501, 518 
 
 by two sets of muscles, 519 
 Eyeball, inflammation of, after division 
 
 of 5th pair, 455 
 Eyilids, formation of, 641 
 
 Face, sensitive nerve of, 451 
 
 motor nerve, 456 
 
 development of, 651 
 Facial nerve, 456 
 
 sensibility of, 459 
 
 influence of, on muscular apparatus 
 of eye, 457 
 
 of nose, 458 
 
 of ear, 459 
 
 paralysis of, 458, 459 
 Fallopian tubes, 553 
 
 formation of, 661 « 
 
 Farinaceous substances, 79 
 
 in food, 80, 106 
 
 digestion of, 150 
 
 Fat, decomposition of, in the blood, 166, 
 
 173 
 fats, 86 
 
 proportion of, in different kinds of 
 
 food, 88 
 condition, in the various tissues and 
 
 fluids, 88 
 internal source of, 93 
 decomposed in the body, 94 
 indispensable as ingredients of the 
 food, 106 
 Patty matters of the blood, 224 
 Fatty degeneration of deoidua, 634 
 
 of muscular fibres of uterus, after 
 delivery, 635 
 Feces, 160 
 
 Female generative organs, 546 
 of frog, 547 
 of fowl, 549 
 of sow, 553 
 of human species, 554 
 development of, 661 
 Fermentation, 99 
 of sugar, 85 
 acid, of urine, 359 
 alkaline, of ditto, 360 
 Fibrin, 100 
 
 of the blood, 223 
 coagulation of, 223 
 varying quantity of, in blood of dif- 
 ferent veins, 224 
 Fifth pair of cranial nerves, 451 
 its distribution, 452 
 division of, paralyzes sensibility of 
 face, 453 
 and of nasal passages, 454 
 produces inflammation of eye- 
 ball, 455 
 lingual branch of, 456 
 small root 6t, 452 
 Fish, circulation of, 247 
 
 formation of umbilical vesicle jn, 
 . 596 
 
 vitelline circulation,in embryo of,667 
 Fish, electrical, phenomena of, 396 
 Fissure, longitudinal, of brain and spinal 
 cord, 379 
 formation of, 640 
 Fissure of palate; 654 
 Fistula, gastric. Dr. Beaumonf s case of, 
 135 
 mode of operating for, 136 
 duodenal, 190 
 Flint, Prof. Austin, Jr., steroorine, in 
 contents of large intestine, 160 
 cholesterin, in blood of jugular vein, 
 177 
 not discharged with the feces, 177 
 effects of biliary fistula, 196 
 Foetal circulation, first form of, 665 
 
 second form of, 667 
 Follicles, of stomach, 134 
 of Lieberkunn, 151 
 
INDEX. 
 
 697 
 
 Follicles, of Brunner's glands, 152 
 
 Gl-aafian, 546, 567 
 
 of uterus, 654, 615 
 Food, 105 
 
 composition of,'ll2 
 
 daily quantity required, 113 
 
 effect of cooking on, 114 
 Foramen ovale,' 680 
 
 valve of, 684 
 
 closure of, 684 
 Force, nervous, nature of, 395 
 Formation of sugar in liver, 200 
 
 in foetus, 64» 
 Fossa ovalis, 686 
 Functions, animal, 59 
 
 vegetative, ^8 
 
 of teeth, 121 
 
 of saliva, 129 
 
 of gastric juice, 141 
 
 of pancreatic juice, 155 
 
 of intestinal juices, 153 
 
 of bile, 193 
 
 of spleen, 210 
 ^ eft' mucus, 328 
 
 of sebaceous matter, 329 
 
 of perspiration, 331 
 
 of the tears, 832 
 
 Galvanism, action of, on muscles, 389 
 
 ou nerves, 391 
 Ganglion, of spinal cord, 380 
 
 of tuber annulare, 438 
 
 of medulla oblongata, 439 
 
 Casserian, 451 
 
 of Andersoh, 460 
 
 pueumogastric, 461 
 
 ophthalmic, ^14 
 
 spheno-palatine, 489, 514 ^ 
 
 submaxillary, 514 
 
 otic, 515 
 
 semilunar, 516 
 
 impar, 516 * 
 Ganglionic system of nerves, 379, 514 
 Ganglia, nervous, 372 
 
 of ladiata, 373 
 
 of moUusca, 375 
 
 of artiQulata, 376 
 
 of posterior roots of spinal nerves, 
 380 
 
 of alligator's brain, 382 
 
 of rabbit's brain, 383 
 
 of medulla oblongata, 384 
 
 of human brain, 386 
 
 of great sympathetic, 514 
 
 olfactory, 382, 418 
 
 optic, 382, 434 
 Gases, diffusion of, in lungs, 239 
 
 absorption and exhalation of, by 
 lungs, 244 
 by the tissues, 248 
 Gastric follicles, 134 
 Gastric juice, mode of obtaining, 137 
 
 composition of, 139 
 
 Gastric juice, action on food, 141 
 
 interference with Trommer's test, 143 
 interference with action of starch 
 
 and iodine, 144 
 daily quantity of, 147 
 solvent action of, on stomach, after 
 death, 149 
 Gelatine, how produced, 64 
 
 effect of feeding animals on, llJ9 
 Generation, 527 
 
 spontaneous, 527 
 of infusoria, 530 
 of parasites, 533 
 of encysted entozoa, 535 
 of taenia, 538 
 sexual, by germs, 540 
 Germ, nature of; 540 
 Germination, heat produced in, 238 
 Germinative vesicle, 545 
 
 disappearance of, in mature egg, 586 
 Germinative spot, 545 
 Gills, offish, 232 
 
 of menobranchus, 233 
 Glands, of Brunner, 162 
 mesenteric, 168 ' 
 vascular, 210 
 Meibomian, 329 
 perspiratory, 330 
 action of, in secretion, 324 
 Glandulse solitarise and agminatae, 162 
 «Globule3, of blood, 213 
 red, 214 
 
 different appearances of, under 
 
 microscope, 214, 215 
 mutual adhesion of, 215 
 color, consistency, and structure 
 
 of, 216 
 action of water on, 217 
 composition of, 218 
 size, &c., in different animals, 
 219 
 white, 220 
 
 action of acetic acid on, 221 
 red and white, movement of, in 
 circulation, 297 
 Globnline, 101, 218 
 Glomeruli, of Wolffian bodies, 656 
 Glosso-pharyngeal nerve, 459 
 
 action of, in swallowing, 460 
 Glottis, movements of, in respiration, 240 
 in formation of voice, 464 
 closure of, after section of pneumo- 
 gastrios, 467 
 Glycine, 181 
 Glyco-cholic acid, 180 
 Glyco-cholate of soda, 180 
 
 its crystallization, 178, 179 
 Glycogenic function of liver, 200 
 
 in fcetus, 649 
 Glycogenic matter, 204 
 
 Its conversion into sugar, 204 
 GossELiN, experiments ou imbibition by 
 cornea, 313 
 
INDEX. 
 
 Graafian follicles, 5^6, 567 
 
 structure of, 567 
 
 rupture of, and discharge of egg, 568 
 
 ruptured during menstruation, 672 
 
 condition of fcEtus at term, 663 
 Gray substance, of nervous system, 372 
 
 of spinal cord, 380 
 
 of brain, 386 
 
 its want of irritability, 417 
 Great sympathetic, 614 
 
 anatomy of, 515 
 
 sensibility and excitability of, 517 
 
 connection of, with special senses, 
 518 
 
 division of, influence on animal heat, 
 521 
 
 on pupil and eyelids, 522 
 
 reflex actions of, 524 
 Gubernaculum testis, 659 
 
 function of, in lower animals, 661 
 Gustatory nerve, 452, 483 
 
 Hammond, Prof. Wm. A., on effects of 
 non -nitrogenous diet, 108 
 
 on production of urea, 344 
 Hsematine, 102, 218 
 Hairs, formation of, in embryo, 643 
 Hare-lip, 653 
 
 Harvey, on motions of heart, 273 
 Hearing, sense of, 505 
 
 apparatus of, 506 
 
 analogy of with touch, 610, 511 
 Heart, 265 
 
 of fish, 265 
 
 of reptiles, 266 
 
 of mammalians, 267 
 
 of man, 268 
 
 circulation of blood through, 270 
 
 sounds of, 270 
 
 movements of, 273 
 
 impulse, 279 
 
 development of, 651, 678 
 Heat, vital, of animals, 263 
 
 of plants, 256 
 
 how produced, 257 
 
 increased by division of sympathetic 
 nerve, 261,621 
 Hemispheres, cerebral, 419 
 
 remarkable cases of injury to, 419, 
 420 
 
 effect of removal, on pigeons, 421 
 
 effect of disease, in man, 422 
 
 xjomparative.size of, in different races, 
 
 • 423 
 
 functions of, 425 
 
 development of, 638 
 Hemorrhage, from placenta, in parturi- 
 tion, 633 
 Hepatic circulation, 339 
 
 development of, 675 
 Herbivorous animals, respiration of, 50, 
 
 243 
 ? - uriue of, 346, 348 
 
 Hernia, congenital, diaphragmatic, 651 
 umbilical, 646 
 inguinal, 661 
 Hippurate of soda, 348 
 Hunger and thirst, continue after divi- 
 sion of pneumogastrio, 473 
 Hydrogen, displacement of gases in blood 
 by, 245 
 exhalation of carbonic acid in an 
 atmosphere of, 249 
 Hygroscopic property ■ of organic sub- 
 stances, 97 
 Hypoglossal nerve, 477 
 
 Imbibition, 307 
 
 of liquids, by different tissues, 312 
 
 by cornea, experiments on, 313 
 Impulse, of heart, 279 
 Infant, newly-born, characteristics of, 687 
 Infiammation of eyeball, after division 
 
 of 5th pair, 465 
 Infusoria, 529 
 
 dififerent kinds of, 530 
 
 conditions of their produotionf 531 
 
 Schultze's experiment on generation 
 of, 532 
 Inguinal hernia, congenital, 661 
 Injection of placental sinuses from ves- 
 sels of uterusj 627 
 Inorganic substances, as proximate prin- 
 ciples, 69 , 
 
 their source and destination, 78 
 Inosculation, of veins, 291 
 
 of capillaries, 296 
 
 of nerves, 372 
 Insalivation, 123 
 
 importance of, 131 
 function of, 132 
 Inspration, how accomplished, 236 
 
 movements of glottis in, 240 
 Instinct, nature of, 444 
 Integument, respiration by, 252 
 
 development of, 643 
 Intellectual powers, 422 
 
 in animals, 444 
 Intestine, of fowl, 117 
 
 of man, 119 
 
 juices of, ,150 
 
 digestion in, 150-159 
 
 epithelium of, 172 
 
 disappearance of bile in, 196 
 
 development of, 693, 644 
 Intestinal digestion, 160 
 Intestinal juices, 151 
 
 action of, on starch, 163 
 Involution of uterus after delivery, 635 
 Iris, movements of, 367, 435, 501, 518 
 
 after division of sympathetic, 522 
 Irritability, of gastric mucous membrane, 
 137 
 
 of the heart, 276 
 ' , of muscles, 389 
 
 of nerves, 391 
 
INDEX. 
 
 699 
 
 Jackson, Prof. Samuel, on digestion of fat 
 
 in intestine, 1S4 
 Jaundice, 185 
 
 yellow color of urine in, 357 
 
 Kidneys, peculiarity of circulation in, 
 305 
 elimination of medicinal substances 
 
 by, 357 
 formation of, 656 
 EncHENMEiSTEB, experiments on produc- 
 tion of taenia from cysticercuS, 
 538 
 of oysticercus from eggs of 
 tsenia, 539 
 
 Lachrymal secretion, 332 
 
 its function, 333 
 Lactation, 333 
 
 varia.tions in composition of milk 
 during, 337 
 Laoteals, 168, 170, 319 
 
 and lymphatics, 167, 172 
 Larynx, action of, in respiration, 222 
 in formation of voice, 464 
 nerves of, 462, 464 
 protective action of, 466 
 movements in respiration, 466 
 Lassaighe, experiments on saliva, 132 
 
 analysis of lymph, 318 
 Layers, external and internal, of blasto- 
 dermic membrane, 688 
 Lead, salts of, action in distinguishing 
 
 the biliary matters, 183 
 Lehuann, on formation of carbonates in 
 blood, 76 
 on total quantity of blood, 231 
 on effects of non-nitrogenous diet, 
 108 
 Lens, crystalline, action of, 495 
 Leuckaet, on production of oysticercus, 
 
 539 
 LiEBia, on absorption of different liquids 
 
 under pressure, 310 
 Ligament of the ovary, formation of, 662 
 Limbs, formation of, in frog, 594 
 in human embryoj 642 
 Liver, vascularity of, 338 
 lobules of, 338, 339 
 secreting cells, 339, 340 
 formation of sugar in, 200 
 congestion of, after feeding, 207 
 development of, 649, 675 
 Liver cells, 92, 340 
 
 their action in secretion, 340 
 Liver-sugar, formation of, 200 
 after death, 203 
 in foetu^, 649 
 Lobules, of lung, 235 
 of liver, 338, 339 
 Local production of carbonic aoid, 248 
 
 of animal heat, 261 
 Local variations of circulation, 305 
 
 LoNGET, on interference of albuminose 
 with Trommer's test, 143 
 on sensibility of glosso-pharyngeal 
 
 nerve, 459 
 on irritability of anterior spinal 
 roots, 401 
 LoHGET AND Mattbpcci, experiment on 
 signs of electricity in an irritated 
 nerve, 397 
 Long and short-sightedness, 496 
 Lungs, structure of, in reptiles, 234 
 in man, 235 
 alteration of, after division of pneu- 
 mogastrics, 469 
 LympTi, 169,318 
 
 quantity of, 320 
 Lymphatic system, 168, 317 
 
 Magnus, on 'proportions of oxygen and 
 
 carbonic acid in blood, 245 
 Male organs of generation, 556 
 
 development of, 658 
 Malpighian bodies of spleen, 209 
 Mammalians, circulation in, 267 
 Mammary gland, structure of, 333 
 
 secretion of, 334 
 Mabcet, on excretiue, 160 
 Mabey, M., experiments on arterial pul- 
 sation, 285 
 Mastication, 121 
 
 unilateral, in ruminating animals, 
 127 
 
 retarded by suppressing saliva, 131 
 Meconium, 648 
 Medulla oblongata, 384, 439 
 
 ganglia of, 385, 386 
 
 reflex action of, 440 
 
 effect of destroying, 442 
 
 development of, 638 
 Meibomian glands, 329 
 Melanine, 103 • • 
 
 Membrane, blastodermic, 688 
 Membrana granulosa, 567 
 Membrana tympani, action of, 508 
 Memory, connection of, with cerebral 
 
 hemispheres, 425 
 Menobranchus, size of blood-globules in, 
 220 
 
 gills of, 233 
 
 spermatozoa of, 557 
 Menstruation, 570 
 
 commencement and duration of, 571 
 
 phenomena of, 571 
 
 rupture of Graafian follicles in, 572 
 
 suspended during pregnancy, 571, 
 581 
 Mesenteric glands, 168, 317 
 Michel, Dr. Myddleton, rupture of Graaf- 
 ian follicle in menstruation, 572 
 MUk, 333 
 
 composition and properties of, 333, 
 334 
 
 microscopic characters, 335 - 
 
700 
 
 INDEX. 
 
 Milk, souring and coagulation of, 336 
 
 variations in, during lactation, 337 
 Milk-sugar, 83 
 
 converted into lactic acid, 336 
 Mollusca, nervous system of, 375 
 Moore and Penjsook, experiments on 
 
 movements of heart, 275 
 Motion, 400 
 
 Motor cranial nerves, 449 ■ 
 Motor nervous fibres, 403 
 Motor oculi communis, 450 
 
 extemus, 451 
 Movements, of stomach, 145 
 
 of intestine, 164 
 
 of heart, 273 
 
 of chest, in respiration, 237 
 
 of glottis, 240 
 
 associated, 408 
 
 of foetus, 631 
 Mucosine, 101 
 Mucous follicles, 327 
 Mucous membrane, of stomach, 133 
 
 of intestine, 151 
 
 of tongue, 483 
 
 of uterus, 554, 615 
 Mucus, 327 
 
 composition and properties of, 328 
 
 of mouth, 125 
 
 of cervix uteri, 554 
 Muscles, irritability of, 388 
 
 directly paralyzed by sulpho-cyanide 
 of potassium, 390 
 
 consentaneous action of, 430 
 
 of respiration, 236 
 Muscular fibres, of spleen, 208, 209 
 
 of heart, spiral and circular, 277 
 Muscular irritability, 388 
 
 duration after death, 388 
 
 exhausted by repeated irritation, 
 390 
 Masculine, 102 
 
 Nails, formation of, in embryo, 643 
 Negeier, on rupture of Graafian follicle, 
 
 in menstruation, 572 
 Nerve-cells, 372 
 Nerves, division of, 372 
 
 inosculation of, 373 
 
 irritability of, 390 
 
 spinal, 39S 
 
 cranial, 446 .,.,.. 
 
 olfactory, 446 ~~" 
 
 optic, 447 
 
 auditory, 447 
 
 ooulo-motorius, 450 ^ 
 
 patheticus, 451 
 
 motor extemus, 451 
 
 masticator, 452 
 
 facial, 456 
 
 hypoglossal, 477 
 
 spinal accessory, 474 
 
 trifacial (5th pair), 451 
 
 glosso-pharyngeal, 459 
 
 Nerves, pneumogastric, 461 
 
 superior and inferior laryngeal, 4G2 
 
 great sympathetic, 514 
 Nervous filaments, 368 
 
 of brain, 309 
 
 of sciatic nerve, 370 
 
 motor and sensitive, 375 
 Nervous force, how excited, 391 
 
 mature of, 395 
 Nervous tissue, two kinds of, 368 
 Nervous irritability, 390 
 
 how shown, 391 
 
 duration of, after death, 391 
 
 exhausted by excitement, 392 
 
 destroyed by wporara, 393 
 
 distinct from muscular, 395 
 
 nature of, 395 
 Nervous system, 365 
 
 general structure and functions of^ 
 365-387 
 
 of radiata, 373 
 
 of mollusca, 375 
 
 of articulata, 376 
 
 of vertebrata, 379 
 
 reflex action of, 374 
 Network, capillary, in Peyer's glands, 
 162 
 
 in web of frog's foot, 296 
 
 in lobule of liver, 339 
 Newly-born infant, weight of, 687 
 
 respiration in, 687. 
 
 nervous phenomena of, 688 
 
 comparative size of organs in, 689 
 Newport, on temperature of insects, 256 
 Nitric acid, action of, on bile-pigment, > 
 184 
 
 precipitation of uric acid by, 354 
 Nitrogen, exhalation of, in respiration, 
 
 242 
 Nutrition,'-61-364 
 
 Obliteration^ of ductus venosus, 677 
 
 of ductus arteriosus, 680 
 Oculo-motorius nerve, 450 
 CEsophagus, paralysis of, after division 
 of pneumogastric, 463 
 
 developBBient of, 645, 650 
 CEstruation, phenomena of, 569 
 Oleaginous substances, 86 
 
 in different kinds of food, 88 
 
 condition of, in the tissues and 
 fluids, 88-93 
 
 partly produced in the body, 93 
 
 decomposed in the body, 94 
 in the blood, 170 
 
 indispensable as ingredients of the 
 food, 107 
 
 insufficient for nutrition, 108 
 Olfactory apparatus, 489 
 
 protected by two sets of muscles, 520 
 
 commissures, 382, 418 
 Olfactory ganglia, 382, 418 
 
 their function, 418 
 
INDEX. 
 
 701 
 
 Olfactory nerves, 489 
 Olivary bodies, 384 
 Omphalo-mesenterio vessels, 668 
 Ophthalmic ganglion, 514 
 Optic ganglia, 382, 434 
 Optic nerves, 447 
 
 decussation of, 436,437 
 Optic thalami, 41 8 
 
 development of, 638 
 Organs of special sense, 483, 489, 493, 
 507 
 
 development of, 640 
 Organic substances, 95 
 
 indefinite chemical composition of, 
 95 
 
 hygroscopic properties, 97 
 
 coagulation of, 98 
 
 catalytic action, 98 
 
 putrefaction, 99 
 
 source and destination, 104 
 
 digestion of, 141 
 Origin, of plants and animals, 527 
 
 of infusoria, 529 
 
 of animal and vegetable parasites, 
 532 
 
 of encysted entozoa, 534 
 Ossification of skeleton, 642 
 Osteine, 102 
 Otic ganglion, 515 
 Ovary, 541 
 
 of taenia, 541 
 
 of frog, 547 
 
 of fowl, 551 
 
 of human female, 553 
 Ovaries, descent of, in foetus, 661 
 
 condition at birth, 663 
 Oviparous and viviparous animals, dis- 
 tinction between, 563 
 Oxalic acid, produced in urine, 360 
 Oxygen, absorbed in respiration, 242 
 
 daily quantity consumed, 242 
 
 state of solution in blood, 245 
 
 dissolved by blood-globules, 245 
 
 absorbed by the tissues, 248 
 
 exhaled by plants, 260 
 
 Palate, formation of, 653 
 Pancreatic juice, 153 
 
 mode of obtaining, 154 
 
 composition of, 165 
 
 action on fat, 155 
 
 daily quantity of, 155 
 Pancreatine, 101 
 
 in pancreatic juice, 155 
 Panizza, experiment on absorption by 
 
 bloodvessels, 165 
 Paralysis, after division of anterior root 
 of spinal nerve, 402 
 
 direct, after lateral injury of spinal 
 cord, 405 
 
 crossed, after lateral injury of brain, 
 405 
 
 facial, 458 
 
 Paralysis of muscles, by snlpho-cyanide 
 of potassium, 390 
 of motor nerves, by woorara, 393, 
 
 413 
 of sensitive nerves, by strychnine, 
 
 413 
 of voluntary motion and sensation, 
 after destroying, tuber annulare, 
 438 
 of pharynx and oesophagus, after 
 
 section of pneumogastrics, 463 
 of larynx, 465, 467 
 of muscular coat of stomach, 473 
 Paraplegia, refiex action of spinal cord 
 
 in 411 
 Parasites, 532 
 
 conditions of development of, 533 
 mode of introduction into body, 534 
 sexless, reproduction of, 535 
 Parotid saliva, 126 
 Parturition, 633 
 
 Par vagum, 461. See Pneumogastric 
 Patheticus nerve, 451 
 Pelouze, jomposition of glycogenic mat- 
 ter, 204 
 Pelvis, development of, 642 
 Pbhmock and . Moore, experiments on 
 
 movements of heart, 275 
 Pepsine, lOJ. 
 
 in gastric juice, 139 
 Perception of sensations, after removal 
 of hemispheres, 422 
 destroyed, after removal of tuber 
 annulare, 438 
 Periodical ovulation, 563 
 Peristaltic motion, of stomach, 145 
 of intestine, 164 
 of oviduct, 54S, 550 
 Pebeins, Maurice, composition of parotid 
 
 saliva, 126 
 Perspiration, 330 
 
 daily quantity of, 331 
 composition and properties of, 331 
 function, in regulating temperature, 
 831 
 Pettenkofer's test for bile, 185 
 Peyer's glands, 162 
 
 Pharynx, action of, in swallowing, 460, 
 461 
 formation of, 650 
 Phosphate of lime, its proportion in the 
 animal tissues and fluids, 74 
 in the urine, 353 
 precipitated by alkalies, 354 
 Phosphate, triple, in putretying urine, 
 
 362 
 Phosphates, alkaline, 77 
 in urine, 353 
 earthy, 74, 77 
 
 in urine, 353 
 of magnesia, soda, and potassa, 77 
 Phosphorus, not a proximate principle, 63 
 Physiology, definition of, 49 
 
702 
 
 IXDKX. 
 
 Phrenology, 427 
 
 objections to, 428 
 
 practical difficulties of, 428, 429 
 Pigeon, after removal of cerebrum, 421 
 
 of cerebellum, 431 
 Placenta, 621 
 
 comparative anatomy of, 622 
 
 formation of, in human species, 623 
 
 foetal tufts of, 625 
 
 maternal sinuses of, 626 
 
 injection of, from uterine vessels, 
 627 
 
 function of, 628 
 
 separation of, in delivery, 633 
 Placental circulation, 624, 628 
 Plants, vital heat of, 256 , 
 
 generative apparatus of, 540 
 Plasma of the blood, 223 
 Pneumic acid, 247 
 Pneumogastrio nerve, 461 
 
 its distribution, 462 
 
 action of, on pharynx and oesopha- 
 gus, 463 
 on larynx, 464 
 in formation of voice, 464 
 in respiration, 466 
 
 effect of its division on respiratory 
 movements, 466, 467 
 
 cause of death after division of, 470 
 
 influence of, on oesophagus and sto- 
 mach, 473 
 Pneumogastrio ganglion, 461 
 PoGGiALB, on glycogenic matter in but- 
 cher's meat, 205 
 Pons Varolii, 387 
 Portal blood, quantity of fibrin in, 224 
 
 temperature of, 262 
 Portal vein, in liver, 338 
 
 development of, 675 
 Posterior columns of spinal cord, 381 
 Primitive trace, 690 
 Production, of sugar in liver, 200 
 
 of carbonic acid, 246 
 
 of animal heat, 253 
 
 of urea in blood, 343 
 
 of infusorial animalcules, 529 
 
 of animal and vegetable parasites, 
 532 
 Proximate principles, 61 
 
 definition of, 63 
 
 mode of extraction, 64 
 
 manner of their association, 65 
 
 varying proportions of, 66 
 
 three distinct classes of, 67 
 Proximate principles of the first class 
 (inorganic), 69 
 
 of the second class (crystallizable 
 substances of organic origin), 79 
 
 of the third class (organic sub- 
 stances), 95 
 Ptyaline, 124 
 Puberty, period of, 565 
 
 signs of, in female, 570 
 
 Pulsation, of heart, 270 
 
 in living animal, 274 
 
 of arteries, 282 
 Pupil, action of, 367, 435 
 
 contraction of, after division of sym, 
 pathetic, 522 
 Pupillary menfbrane, 640 
 Putrefaction, 99 
 
 of the urine, 358 
 Pyramids, anterior, of medulla oblon- 
 gata, 384 
 
 Quantity, daily, of water exhaled, 71 
 
 of food, 113 
 
 of saliva, 128 
 
 of gastric juice, 147 
 
 of pancreatic juice, 155 
 
 of bile, 188 
 
 of air used in respiration, 238 
 
 of oxygen used in respiration, 242 
 
 of carbonic acid exhaled, 250 
 
 of lymph and chyle, 320 
 
 of fluids secreted and reabsorbed, 323 
 
 of material absorbed and discharged, 
 363 
 
 of perspiration, 331 
 
 of urine, 349 
 
 of urea, 344 
 
 of urate of soda, 348 
 Quantity, entire, of blood in body, 231 
 
 Rabbit, brain of, 383 
 
 Races of men, different capacity of, for 
 
 civilization, 424 
 Radiata, nervous system of, 373 
 Rapidity of circulation, 302 
 Reactions, of starch, 82 
 
 of sugar, 84 
 
 of fat, 86 
 
 of saliva, 124, 125 
 
 of gastric juice, 139 
 
 of intestinal juice, 153 
 
 of pancreatic juice, 155 
 
 of bile, 175 
 
 of mucus, 328 
 
 of milk, 334 
 
 of urine, 353 
 Reasoning powers, 425 
 
 in animals, 444 
 Red globules of blood, 213 
 Reflex action, 374 
 
 in centipede, 377 
 
 of spinal cord, 408 
 
 of medulla oblongata, 440 
 
 of tuber annulare, 443 
 
 of brain, 444 
 
 of optic tubercles, 435 
 
 in newly born infant, 688 
 Regeneration, of uterine mucous mem- 
 brane after pregnancy, 633, 634 
 
 of walls of uterus, 635 
 Regnault and Beiset, on absorption of 
 oxygen, 243 
 
INDEX. 
 
 703 
 
 Reid, Dr. John, experiment on crossing 
 
 of streams in foetal heart, 682 
 Reproduction, 525 
 
 nature and object of, 625, 627 
 
 of parasites, 533 
 
 of taenia, 538 
 
 by germs, 540 
 Reptiles, circulation of, 266 
 Respiration, 232 
 
 by gills, 233 
 
 by lungs, 234 
 
 by skin, 252 
 
 changes in air during, 241 
 
 changes in blood, 243 
 
 of newly born infant, 687 
 Respiratory movements of chest, 236 
 
 of glottis, 240 
 
 after section of pneumogastrics, 466 
 
 after injury of spinal cord, 441 
 Restiform bodies, 385 
 Rhythm of heart's movements, 279 
 Rotation of heart during contraction, 278 
 Round ligament of the uterus, formation 
 of, 662 
 
 of liver, 67.7 
 Rumination, movements of, 118, 127 
 Rupture of Graafian follicle, 568 
 
 iu menstruation, 572 
 Rutting condition, in lower animals, 569 
 
 Saccharine substances, 83 
 
 iu stomach and intestine, 150 
 
 in liver, 200 
 
 in blood, 207 
 
 in urine, 357 
 Saliva, 123 
 
 different kinds of, 125 
 
 daily quantity of, 127 
 
 action on boiled starch, 129 
 
 variable, 130 
 
 does not take place in stomach, 130 
 
 physical function of saliva, 131 
 . quantity absorbed by difierent kinds 
 of food, 132 
 Salivary glands, 125 
 Salts, biliary, 177 
 
 of the blood, 225 
 
 of urine, 353 
 Saponification, of fats, 87 
 SuH AELiNG, on diurnal variations in exha- 
 lation of carbonic acid, 252 
 SoBDLTZB, experiment on^ generation of 
 
 infusoria, 531 
 Scolopendra, nervous system of, 376 
 Sebaceous matter, 328 
 
 composition and properties of, 329 
 
 function of, 329 
 
 in foetus, 643 
 Secretion, 324 
 
 varying activity of, 326 
 
 of saliva, 125 
 
 of gastric juice, 137 
 
 of intestinal juice, 152 
 
 Secretion of pancreatic juice, 164 
 
 of bile, 188, 337 
 
 of sugar iu liver, 200 
 
 of mucus, ^27 
 
 of sebaceous matter, 328 
 
 of perspiration, 330 
 
 of the tears, 332 
 
 of bile in foetus, 649 
 Segmentation of the vitellus, 587 
 Seminal fluid, 566 
 
 mixed cnnstitutiou of, 560 
 Sensation, S98 
 
 remains after destruction of hemi- 
 spheres, 422 
 
 lost after removal of tuber annulare, 
 438 
 
 special conveyed by pneumogastrio 
 nerve, 440, 466, 468 
 Sensation and motion, distinct seat of, in 
 nervous system, 400 
 
 in spinal cord, 403 
 Sensibility, of nerves to electric current, 
 391 
 
 and excitabilityj definition, of, 400 
 
 seat of, in spinal cord, 403 
 
 in brain, 417 
 
 of facial nerve, 459 
 
 of hypoglossal nerve, 477 
 
 of spinal accessory, 475 
 
 of great sympathetic, 517 
 Sensibilityj general and special, 478 
 
 special, of olfactory nerves, 446, 489 
 
 of optic nerves, 447 
 
 of auditory nerves, 447 
 
 of lingual branch of 5th pair, 484 
 
 of glosso-pharyngeal, 460 
 
 of pneumogastrio, 468 
 Sensitive nervous filaments, 375 
 Sensitive fibres, crossing of, in spinal cord, 
 405 
 
 of facial nerve, source of, 459 • 
 Sensitive cranial nerves, 449 
 Septa, inter-auricular and inter-ventri- 
 cular, formation of, 678, 680 
 S^QDARD, on crossing of sensitive fibres 
 
 in spinal cord, 405 
 Serum, of the blood, 227 
 Sexes, distinctive characters of, 540 
 Sexless entozoa, 534 
 Sexual generation, 540 
 Shook, effect of, in destroying nervous 
 
 irritability, 393 
 SiEBOLD, on production of tsenia from 
 
 cysticercus, 638 
 Sight, 492 
 
 apparatus of, 493. See Vision. 
 Sinus terminalis, of area vasculosa, 665 
 Sinuses, placental, 624, 626 
 Skeleton, development of, 641 
 Skin, respiration by, 252 
 
 sebaceous glands of, 328 
 
 perspiratory glands of, 330 
 
 development of, 643 
 
704 
 
 INDEX. 
 
 Smell, 488 
 
 ganglia of, 382, 489 
 
 nerves of, 446, 489 
 
 injured by division of 5th pair, 454 
 Smith, Dr. Southwood, on cutaneous and 
 
 pulmonary exhalation, 331 
 Solar plexus of sympathetic nerve, 516 
 Solid bodies, vision of with two eyes, 502 
 Sounds, of heart, 270 
 
 how produced, 271 
 
 vocal, how produced, 464 
 
 destroyed by section of inferior la- 
 ryngeal nerves, 465 
 of spinal accessory, 475 
 Sounds, acute and grave, transmitted by 
 
 membrana tympani, 508 
 Special senses, 478 
 Species, mode of continuation, 527 
 Spermatic fluid, 656 
 
 mixed constitution of, 560 
 Spermatozoa, 556 
 
 movements of, 558 
 
 foi'matlon of, 559 
 Spina bifida, 641 
 Spinal accessory, 474 
 
 sensibility of, 475 
 
 communication of, with pneumogas- 
 trio, 475 
 
 influence of, on larynx, 475 
 Spinal column, formation of, 591, 641 
 Spinal cord, 379, 398 
 
 commissures of, 381 
 
 anterior and posterior columns, 381 
 
 origin of nerves from, 380 
 
 sensibility and excitability of, 403 
 
 crossed action of, 404 
 
 reflex action of, 408 
 
 protective action of, 413, 414 
 
 influence on sphincters, 414 
 
 efi^ect of injury to, 414 
 
 qn respiration, 441 
 
 formation of, in embryo, 591, 645 
 Spinal nerves, origin of, 380 
 Spleen, 208 
 
 Malpighian bodies of, 209 
 
 extirpation of, 211 
 Spontaneous generation, 527 
 Starch, 79 
 
 proportion of, in different kinds of 
 food, 80 
 
 varieties of, 80-82 
 
 reactions of, 82 
 
 action of saliva on, 129 
 
 digestion of, 150 
 Starfish, nervous system of, 373 
 Steroorine, 160 
 Stereoscope, 503 
 
 St. Martin, case of gastric fistula in, 135 
 Strabismus, after division of motor oculi 
 * communis, 451 
 
 of motor externus, 451 
 Striated bodies, 419 
 Sublingual glaud, secretion of, 125 
 
 Submaxillary ganglion, 514 
 gland, secretion of, 125 
 Sudoriparous glands, 330 
 Sugar, 83 
 
 varieties of, 83 
 
 composition of, 84 
 
 tests for, 84 
 
 fermentation of, 85 
 
 proportion in different kinds of food, 
 
 86 
 source and destination, 86 
 produced in liver, 200 
 discharged by urine in disease, 357 
 Sugar in liver, formation of, 200 
 percentage of, 202 
 produced in hepatic tissue, 203 
 from glycogenic matter, 204 
 absorbed by hepatic blood, 206 
 decomposed in circulation, 206 
 Sulphates, alkaline, in urine, 353 
 Sulphur of the bile, 181 
 
 not discharged with the feces, 197 
 Swallowing, 131 
 
 retarded by suppression of saliva, 
 133 
 -^by division of pneumogastric, 463 
 Sympathetic nerve, 514 
 ^ its distribution, 515 
 
 sensibility and excitability erf, 517 
 influence of, on special senses, 518 
 on pupil, 518 
 
 on nutrition of eyeball, 455 
 on nasal passages, 520 
 on ear, 520, 521 
 on temperature of particular 
 parts, 521 
 reflex actions of, 524 
 
 Tadpole, development of, 592 
 
 transformation into frog, 594 
 Tsenia, 536 
 
 produced by metamorphosis of cys- 
 ticercus, 538 
 
 single articulation of, 541 
 Tapeworm, 636 
 
 mode of genlration, 537 
 Taste, 481 
 
 nerves of, 483 
 
 conditions of, 485 
 
 inj ury of, by paralysis of facial nerve, 
 487 
 Taurine, 181 . 
 Tauro-cholate of soda, 181 
 
 microscopic characters of, 179 
 Tauro-cholic acid, 181 
 Tears, 332 
 
 ~ their function, 332 
 Teeth, of serpent, 121 
 
 of polar bear, 122 
 
 of horse, 122 
 
 of man, 123 
 
 first and second sets of, 689 
 Temperature of the blood, 254 
 
INDEX. 
 
 705 
 
 Temperature of different species of ani- 
 mals, 255 
 
 of the blood in different organs, 262 
 
 elevation pf, after section of sympa- 
 thetic nerve, 261, 521 
 Tensor tympani, action of, 506, 508 
 Tests, for starch, 82 
 
 for sugar, 84 
 
 for bile, 184 
 
 Pettenkofer's, 185 
 Testicles, 559 
 
 periodical activity of, in fish, 561 
 
 development of, 658 
 
 descent of, 658, 659 
 Tetanus, pathology of, 410 
 Thalami, optic, in rabbit, 383 
 
 in man, 418 
 
 function of, 419 
 Thoracic duct, 168, 170 
 Thoracic respiration, 441 
 Tongue, motor nerve of, 477 
 
 sensitive, 452, 456, 483 
 Trichina spiralis, 535 
 Tricuspid valve, 268. See Auriculo-ven- 
 
 trioular , 
 
 Triple phosphate, in putrefying urine, 362 
 Trommer's test for sugar, 84 
 
 interfered with by gastric juice, 143 
 Tuber annulare, 386,438 
 
 effect of destroying, 438 
 
 action of, 439 
 Tubercula quadrigemina, 382, 431 
 
 refiex action of, 435 
 
 crossed action of, 436 
 
 development of, 637, 638 
 Tubules of uterine mucous membrane, 
 
 615 
 Tufts, placental, 625 
 
 Tunica vaginalis testis, formation of, 660 
 Tympanum, function of, in hearing, 508 
 
 Umbilical cord, formation of, 631 
 I • withering and separation of, 689 
 
 J Umbilical hernia, 646 
 
 Umbilical vesicle, 596 
 
 in human embryo, 597 
 
 in chick, 604 
 
 disappearance of, 631 
 Umbilical vein, formation of, 669 
 
 obliteration of, 677 
 Umbilicus, abdominal, 592 
 
 amniotic, 600 • 
 
 decidual, 617 
 Unilateral mastication, in ruminating 
 
 animals, 127 
 Urate of soda, 347 
 
 its properties, source, daily qu3.ntity, 
 &c., 348 
 Urates of potassa and ammonia, 348 
 Urachus, 647 
 Urea, 343 
 
 source of, 343 
 
 mode of obtaining, 344 
 
 45 
 
 Urea, conversion into carbonate of am- 
 monia, 344 
 daily quantity of, 344 
 diurnal variations in, 345 
 decomposed in putrefaction of urine, 
 360 
 
 Uric acid, 347, 354 
 
 Urine, 349 
 
 general character g,ud properties of, 
 
 349 
 quantity and specific gravity, 350 
 diurnal variations of, 351 
 composition of, 352 
 reactions, 353 . 
 
 interference with Trommer's test, 355 
 accidental ingredients of, 355 
 acid fermentation of, 359 
 alkaline fermentation of, 360 
 final decomposition of, 363 
 
 Urinary bladder, paralysis and inflam- 
 mation of, after injury to spinal 
 cord, 415 
 formation of, in embryo, 647 • 
 
 Urosacine, 103 
 
 Uterus, of lower animals, 553 
 of human female, 554 
 mucous membrane of, 614 
 changes in, after impregnation, 615 
 involution of, after delivery, 634 
 development of, in foetus, 661 
 position of, at birth, t)63 
 
 Uterine mucous membrane, 614 
 tubules of, 615 
 conversion into decidua, 615 
 exfoliation of, at the time of delivery, 
 
 633 
 its renovation, '634 
 
 Valve, Eustachian, 681 
 
 of foramen ovale, 684 
 Valves, cardiac, action of, 268 
 
 cause of heart's sounds, 271 
 Vasa deferentia, formation of, 658 
 Vapor, watery, exhalation of, 71 
 
 from lungs, 242 
 
 from the skin, 252 
 Variation, in quantity of bile in different 
 animals, 188 
 
 in production of liver-sugar, 202 
 
 in size of spleen, 208 
 
 in rapidity of coagulatioii of blood, 
 227 
 
 in size of glottis in respiration, 240 
 
 in exhalation of carbonic acid, 250 
 
 in temperature of blood in different 
 parts, 262 
 
 in composition of milk during lac- 
 tation, 337 
 
 in quantity of urea, 345 
 
 in density and acidity of urine, 350 
 Varieties of starch, 80 
 
 of sugar, 83 
 
 of fat, 86 
 
706 
 
 INDEX. 
 
 Varieties of biliary salts in different ani- 
 mals, 182 
 Vegetable foed, necessary to man, 106 
 Vegetable parasites, 532 
 Vegetables, production of heat in, 256 
 
 absorption of carbonic acid and ex- 
 halation of oxygen by, 49, 260 
 Vegetative functions, 58 
 Veins, 290 
 
 their resistance to pressure, 290 
 , absorption by, 165 
 
 action of valves in, 293 
 
 motion of blood through, 291 
 
 rapidity of circulation in, 294 
 
 omphalo-mesenteric, 666 
 
 umbilical, 669 
 
 vertebral, 672 
 Vense cavse, formation of, 673 
 
 position of, in foetus, 681 
 Vena azygos, superior and inferior, for- 
 mation of, 673 
 Venous system, development of, 672 
 Ventricles of heart, single in fish and 
 reptiles, 265, 266 
 
 double in birds and mammalians, 
 267 
 
 situation of, 268 
 
 contraction and relaxation of, 269 
 
 elongation during contraction, 275 
 
 muscular fibres of, 277 
 Veruix caseosa, 643 
 Vertebrata, nervous system of, 378 
 Vertebrae, formation of, 691, 641 
 Vesicles, adipose, 90 
 
 pulmonary, 235 
 
 seminal, 560 . 
 Vesiculffl seminales, 560 
 
 formation of, 660 
 Vicarious secretion, non-existence of, 325 
 Vicarious menstruation, nature of, 325 
 Villi, of intestine, 163 
 
 absorption by, 164 
 
 of chorion, 609-611 
 Vision, 492 
 
 ganglia of, 382, 434 
 
 nerves of, 447, 493 
 
 apparatus of, 493 
 
 distinct, at different distances, 496 
 
 circle of, 499 
 
 Vision, of solid bodies with both eyes, 502 
 Vital phenomena, their nature and pecu- 
 liarities, 54 
 Vitellus, 641 
 
 segmentation of, 587 
 
 formation of, in ovary of foetus, 663 
 Vitelline circulation, 665 
 
 membrane, 544 
 
 spheres, 587 
 Vocal sounds, how produced, 464 
 Voice, formation of, in larynx, 464 
 
 lost, after division of spinal acces- 
 sory nerve, 476 
 Volition, seat of, in tuber annulare, 438 
 Vomiting, peculiar, after division of 
 pneumogastrics, 473 
 
 Water, as a proximate principle, 69 
 its proportion in the animal tissues 
 
 and fluids, 70 
 its source, 70 
 
 mode of discharge from the body, 71 
 Weight of organs, in comparative, newly 
 
 born infant and adult, 689 
 White globules cif the blood, 220 
 . action of acetic acid on, 221 
 sluggish movement of, in circula- 
 tion, 297 
 White substance, of nervous system, 368 
 of Schwann, 368 
 of spinal cord, 380 
 of brain, insensible and inexcitable, 
 417 
 Withering and separation of umbilical 
 
 cord, after birth, 689 
 WollEan bodies, 655 
 structure of, 656 
 atrophy and disappearance of, 656, 
 
 657 
 vestiges of, in adult female, 662 
 Wtman, Prof. Jeffries, on cranial nerves 
 of Eana pipiens, 449 
 fissure of hare-lip on median line, ■ 
 637 
 
 Yellow color, of urine in jaundice, 357 
 of corpus luteum, 579 
 
 Zona pellucida, 544 
 
 THE END. 
 
(LATE LEA & BLAIJ-CHAKD'S,) 
 
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 best arguments we can offer of the merits, and of 
 the useleasness of any commendation on our part of 
 a book already so faypra'bly known to our readers. 
 — Boston Utied. and Surg. Journalj Jan 25, 1666. 
 
 ALLEN (J. M.), IVI. D., 
 Professor of Anatomy in the Pennsylvaaia Medical College, loe. 
 
 THE PRACTICAL ANATOMIST; or, The Student's Guide iu the Dissecting- 
 
 ROOM. With 266 illustrations. In one handsome royal 12mo. volume, of over 600 pages, extra 
 cloth. $a 00. ' r B 1 
 
 We believe it to be one of the most useful works 
 upon the subject ever written. It is handsomely 
 Illustrated, well printed, and will be found of con- 
 venient size for use in tne. dissecting-room.— Med. 
 Examiner. < 
 
 However valuable may be the "Dissector's 
 Guides" which wo, of late, have had occasion to 
 
 notice, we feel confident that the work of Dr. Allen 
 IS superiotvto any of them. We believe with the 
 authoi-, that none is so fully illustrated as this, and 
 the arrangement of the work is such as to facilitate 
 the labors of the student. We most cordially re- 
 commend It to their attention. — Western Lanset. 
 
 ANATOMICAL ATLAS. 
 By Professors H. H. Smith and W. E. HoBNEa. of the! University of Pennsyl- 
 vania. 1 vol. 8vo., extra cloth, with nearly 6-50 illuatrauons. ^F" See Smith, p. 26. 
 
 ABEL (F. A.), F. C.S. AND C. L. BLOXAM. 
 HANDBOOK OP CHEMISTRY, TheoretioaV Practical, and Technical ; with a 
 
 Recommendatory Preface by Dr. HomANN. In one (arge octavo volume, extra cloth, of 663 
 pages, with illustrations. $4 30. . 
 
 ASHWELL (SAMUEL), M. D., 
 
 Obftetric Physician and Lecturer to Guy's Hospital, London. 
 
 A PRACTICAL TREATISE ON THE DliSEASES PECULIAR TO WOMEN. 
 
 Illustrated by Cases derived from Hospital and Private Practice. Third American, from the Third 
 and revised London edition. In one octavo volume, extra cloth, oi 328 pages. 93 SO. 
 The most useful practical work on the subject in I The most able, and cisrtainly the most standard 
 the English language. — Soston Med. and Sitrg-. and practical, work on female diseases that we havs 
 JtfttrnOI; \yetaeea.—Medico-CliiruTeiealReviea. 
 
 ARNOTT (NEILL), M. D. 
 
 BLEMiENTS OF PHYSICS; or Natural PhQosophy, General and Medical. 
 
 Written lor universal use, in plain or non-technibal language. A new edition, by Isaac Ha;s 
 
 M. U. Complete in one octavo volume, leather, of 484 pages, with about two hundred illustra' 
 
 tions. 53 25. 
 
 BIRO (GOLOiNG), A. M., M. D., fcc. 
 URINARY DEPOSITS: THEIR DIAGNOSIS, PATHOLOGY, AND 
 
 THERAPEUTICAL INDICATIONS. Edited by Edmdnd Lloyd Biekett, M. D. A new 
 American, from the last and enlargied London edition. WitheightyiUustrationson wood. Inoae 
 handsomeoctavo volume, of about 400 pages, extra cloth. $3;^. 
 
 BARl6w (GEORGE H.), M. D. 
 
 Physician to Guy's Hospital, London, &c. 
 
 A MANUAL OF THE PRACTICE OF MEDICINE. With Additions by D 
 
 F. CoNDiE, M. D., author of" A Practical Treatise on Diseases of Children," &c. In one hand' 
 
 some octavo volume, extra cloth, of over 600 pages. $2 50. 
 
 We recommend Dr. Barlow'sManual in the warm- I found it clear, concise, practical, and sound Sot 
 
 •ftt manner as a most valuable vade-mecum: We I ton Med. and, Surg. Journal. 
 have had frequent occasion to consult it, and have | 
 
 BUCKLER ON THE ETIOLOGY , PATHOLOGY 
 AND TKEATMENT OF FIBRO-BRONCHI 
 TIS AND RHEUMATIC PNEUMONIA. In 
 one 8vo. volume, extra cloth, pp.150. 91 i&. 
 
 BRODIE'S CLINICAL LOCCTUKUS ON SUR 
 GERY. 1 vol. 8vo. cloth. iSOpp. SI is 
 
 BL»OD AND URINE (MANUALS 0\) nv 
 J. W. GRIFFITH, a. O REESE AWn A 
 MARK WIOK. One'yolnme, myal&t extra 
 cloth, with plates, pg. 460. «1 zs. ' """^ 
 
 JEALE ON THE LAWS OP HEALTH IN RP 
 LATION TO MIND AND BODY In ^e^ff 
 royal 12mo., extra cloth, pp.iiw. SOcMto, 
 
HENRY C. LEA'S MEDICAL 
 
 BUDO (GEORGE), M. D., F. R. S., 
 
 Professor of Medicine in King's College^ London. 
 
 ON DISEASES OF THE LIVER. Third American, from the third and 
 
 enlarged London edition. In one very handsome octavo volume, extra cloth, with four beauti- 
 fully colored plates, and numerous wood-cuts. pp. 500. $4 00. 
 
 Has fairly established for itself a place among^ the 
 claBBical medical literature of England. — British 
 wmd Foreign Medico-Chir. Review. , 
 
 Dr. Budd's Treatise on Diseases of the Liver is 
 now a standard work in Medical literature, and dur- 
 ing the intervals which have elapsed between t))e 
 Buccessive editions, the author has incorporated into 
 
 the text the most striking novelties which have cha- 
 racterized the recentprogress of hepatic physiolcsy 
 ind pathology: so thatalthoughthe size of the book 
 is not perceptibly changed, the history of liver dis- 
 eases is ma<ele more complete, and is kept upon a level 
 with the progress of modern science. It is the best 
 work on Diseases of the Liver in any language.— 
 London Med. Times and Gazette. 
 
 BUCKNILL (J. C), M. D., and DANIEL H. TUKE, M. D., 
 
 Medical Superintendent of the Devon Lunatic Asylum, Visiting Medical Officer to the York Retreat, 
 
 A MANUAL OP PSYCHOLOGICAL MEDICINE; containing the History, 
 
 Nosology, Def rription, Statistics, Diagnosis, Pathology, and Treatment of INSANITY. With 
 a Plate. In one handsome octavo volume, of 536 pages, extra cloth. S4 25. 
 The increase ol mental disease in its various forms, and the difficult questions to'vrhich it is 
 constantly giving rise, reader the subject one of daily enhanced interest, requiring on the part of 
 the physician a constantly greater familiarity with this, the most perplexing branch of his profes- 
 sion. Yet until the appearance of the present volume there has been for some years no work ae. 
 cessible in this country, presenting the results of recent investigations in the Diagnosis and Prog- 
 nosis of Insanity, and the greatly iinproved methods of treatment which have done so much in 
 alleviating the condition or restoring tl!e health of the insane. 
 
 BENNETT (HENRY), M. D. 
 A PRACTICAL TREATISE ON INFLAMMATION OF THE UTERUS, 
 
 ITS CERVIX AND APPENDAGES, and on its connection with Uterine Disease. Sixth 
 
 American, from the fourth and revised English edition. In one octavo volume, of about 500 
 
 pages, extra cloth. $3 75. {Just Issued.) 
 
 This standard work, which has done so much to introduce the modern and improved treatment 
 of female diseases, has received a very careful revision at the handd o( the s\uthor In his preface 
 he slates : " During the past iwo years this revi.- ion of former li bors has been my principal occapa- 
 lion, and in its present state the work may be considered to embody the matured experience of the 
 many years I have devoted to the study of uterine disease." 
 
 BRINTON (WILLIAM), M. D .F. R. S., 
 
 Physician to St. Thomas's Hospital. 
 
 LECTURES ON THE DISEASES OP THE STOMACH, with an introdae- 
 
 lion on its Anatomy and Physiology. From the second and enlarged London edition. With 
 ' illustrations on wood. In one large and handsome octavo volume. $3 25. (Just Ready.) 
 
 nccomplished phveician, who, for many years, has , 
 devuted special attention to the symptomatology, 
 pathology, and treatment of gastrld diseases. — 
 Edittburgh Med. Journal. 
 
 Dr. Brinton's position as a lahorer in medical 
 science and a medical author is fully established, 
 and these lectures have only added to a reputation 
 based on many solid grounds. The work is ao im- 
 portant one, and we argue for it a great place in 
 medical liEerature. — London Lancet, Dec. 3, 1864. 
 
 The entire series of lectures embraced in the 
 volume before us are well worthy of a closestudy 
 on the part of every one desirous of acquiring cor- 
 lect views in relation to tiie nature and treatment 
 of the diseases o| the stomach. Nowhere can be 
 found a more full', accurate, plain, and instructive 
 history of these disenscs, or more rational views 
 respecting their pathology and therapeutics. — Ame- 
 rican Journal of the Med. Sciences^ April, 1865. 
 
 This is'no mere cfmpilation, no crude record of 
 cases, but the carefully elaborated production of an 
 
 BOWMAN (JOHN E.), M.D. 
 PRACTICAL HANDBOOK OF MEDICAL CHEMISTRY. Edited by C. 
 
 L. Bloxam. Fourth American, from the fourth and revised English Edition. In one neat volume, 
 royal l2mo., extra cloth with numerous illustrations, pp. 351. $225. 
 
 ject in view Incidly detailed and explained. And 
 this new edition is not merely a re^print of the last. 
 Wiih a laudable desire to keep the book up tu tae 
 scientific m«rk of the present age, every improve- 
 ment in analytical ifiethod has been introduced. In 
 conclusion, we would only say that, lainiliar from 
 long acquaintnnce witn each page of the former 
 issues <tf this little book, we gladly place beside 
 them another presenting so many acceptable im- 
 provements and additious. — Dublin illedzcaj Press. 
 
 Of this well-known handbook we may say that 
 tt retains all its ild simplicity and clearness of ar- 
 rangement and description, whilst ithaa received 
 from the able editor those finishing couches which 
 the progress uf chemi&tr> has lendt red necessary — 
 - London Med. Times and Gazette, Nov. 29, 1663. 
 
 Nor is any thing huiried over, anything shirked ; 
 open the book where; you will,|yuu find the same 
 careful treatment of the subject manifested, ana the 
 beat process for the attaiLment of the particular ob- 
 
 , BY THE SAIUB AUTHOR. 
 
 INTRODUCTION TO PRACTICAL CHEMISTRY,. INCLUDINO ANA- 
 
 LYSIS .Third American, from the third and revised London edition. With numerous illus- 
 trations' In one neal vqI., royal 12ino., e:Ura qloih S-i !i5 
 
 This iavorite little manual has received a very thurungh and careful revision at the hands of a 
 competent editor, and will be found luUy brought up to the present condiiion of chemical science. 
 Many portions have been fewrittcn, the subjects ol the blow-pipe and volumetric analysis have re- 
 ceived special altentiun, and an addilional chapter! has been appended, .Siudenls uf practical cheni- 
 ulry will, therefore find it, a!> here ofore, a most ci^nvenicnt pud condensed test-book and guide in 
 the opeiations of thelaboraiory. ' ' ' I 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 BUMSTEAD (FREEMAN J.) M. D., 
 Lecturer on Venereal DiaeaaeB at the College of Puygicians and Surgeons, New York, 4;o. 
 
 THE PATHOLOGY AND TEEATMENT OP VENEREAL DISEASES, 
 
 including the results of recent investigations upon the subject. Second edition, thoroughly re- 
 viR(:d and much improved. With illustratiuns on wood. In one very handsome octavo volume, 
 of about 700 pages $5 00 {Just Issued.) 
 
 By far the moBt valuable contribution to this par- 
 ticular branch of practice that has seen the light 
 wUbin the last score of years. His clear and accu- 
 rate descriptions of the various forms of venereal 
 disease, and especially the methods of treatment he 
 proposes, are worthy of the highest encomium. In 
 tlieae respects it is better adapted for the assistance 
 
 u- f every-day practitioner than any other with 
 which we are acquainted. In variety of methods 
 proposed, m minuteness of direction, guided by care- 
 (ttl ducriraination bf varying forms and compUca 
 tiona, we w^ite down the book as unsurpassed. It 
 is a work which should be in the possession of every 
 pj-actitioner.- Cfeicag-o Med. Journal. Nov. 1881. 
 
 Tne fencing admirable volume comes to us, em- 
 bracing the^whole subject of syphilology, resolving 
 many a doubt, correcting and confirming many an 
 entertained opinion, and in our estimation the best, 
 eompletest, fullest monograph on this subject in oar 
 language. ■ As far as the.author*s labors themselves 
 are concerned, we feel it u duty to say that he has 
 not only exhausted his subject, but he has presented 
 to us, without the slightest hyperbole, the best di- 
 gested treatise on these diseases in our language 
 He has carried its literature down to the prestnt 
 moment, and has achieved his task in a manner 
 which cannot but redound to his Qz&iit.— British 
 American Journal^ Oct. 1861. 
 
 We believe this treatise will come to be reerarded 
 as high authority in this branch of medicsl practice, 
 and we cordially commend it to the favorable notice 
 of ourbrethren in the profession. For our own part, 
 we candidly confess that we have received aany 
 new ideas fromits perusal, as well as modified many 
 views which we have long, and, as we now thinK 
 erroneously entertained on the subject of syphilis. 
 
 To sum up all in a few words, this book is one which 
 no practising physician or medical student can very 
 well afford to do without. — American Med Times, 
 Npv.a, 1861. 
 
 The whole work presents a complete history of 
 venereal diseases, comprising much interesting and 
 vaBl,uable material that hasbeen spread through intd- 
 ical journals within the last twenty years— the pe- 
 riod of many eyperiments and investigations on the 
 subject— the whole carefully digested b^ t^e aid of 
 the author^s extensive personal experience, and 
 offeied to the profession m an admirable form. Its 
 completent^ss is secured by good plates; which are 
 especially full in the anatomy of the genital organs. 
 W^e have examined it with great satisfaction, and 
 congratulate the medical profession in America on 
 the nationality of a work ihat may fairly be sailed 
 original. — Berkshire Med. Journal^ Dec IbSL. 
 
 One thing, however, we are impelled to say, that 
 we have met with no other book on syphilis, in the 
 English language, which gave so full, clear, and 
 impartial views of the important subjects on wiiiuh 
 it treats. We cannot, however^ refrain from ex- 
 pressing oursatisfaction with the full and persiiicu- 
 ous manner in which the subjecthas been presented, 
 and the careful attention to minuie details, so use^ 
 ful — not to say indispensable — inu practical Lreatise. 
 In conclusion, if we may be pardoned the use of a 
 phrase now become stereotyped, bat which we here 
 employ in all seriousness and sincerity, we do not 
 hesitate to express tite opinion Ihat Dr. BuinsteadU 
 Treatise on Venereal Diseases is a '* work without 
 which no medical library will hereafter be consi- 
 dered complete." — Boston Med. and Surg. Journal 
 Sept. 5, 1861. 
 
 BARCLAY (A. W.), M. D., 
 
 Assistant Physician to St. George's Hospital, &c.; 
 
 A MANUAL OF MEDICAL DIAGNOSIS; being an Analysis of the Signe 
 
 and Symptoms of Disease- Third American from the second and revised London edition. Id 
 
 one neat octavo volume, extra cloth, of 451 pages. S3 50 (Just Issued ") 
 
 The demand for another edition of this work %hows tbat the vacancy which it attempts to sup* 
 
 ply has been recognized by the profession, and that the efforts of the author to meet the want have 
 
 Deen successful. The revision which it has enjoyed will render it better adapted than before to 
 
 afford assistance to the learner intheprosecutionof his studies, and to thupractilioner who requires 
 
 a convenient and accessible manual for speedy reference in the exigencies of his daily duties. For 
 
 this tatter purpose it-t complete and extensive Index renders it ei^pecially valuable, offering facilities 
 
 for immediately turning to any class of symptoms, or any variety of disea!$e. 
 
 We hope the volume will have an extensive c'ii- 
 
 culation, not among students of medicine only, but 
 
 practitioners also. They will never regret a faith - 
 
 ful study of itspages. — Cincinnati Lancet. 
 
 An important acquisition to medical litentur^. 
 
 The task of composing such a wOtk is neither an 
 easy nor a light one; but Dr.Burclay has performed 
 it in a manner which meets our most unqualified 
 approbation. He is no mere theorist; he knows his 
 work thoroughly, and in attempting to perform it, 
 hasnot exceeded his powers. — British Med. Journal. 
 
 We venture to predict that the work will be de- 
 servedly popular, and soon become, like Watson'i^ 
 Practice, an indispensable necessity to the practi- 
 tioner. — N.A.Med Journal. 
 
 , An inestimable work of reference for the young 
 practitioner and student. — Nashville Med. Journal . 
 
 It IS a work of high merits both from the vast im-, 
 por',ance of the sabject upon which it treats, au(l' 
 also from the real ability displayed in ■t'lt elabora- 
 tion. In conclusion, let us bespeak for this volume 
 that attention of every SLudent of our art which it 
 80 richly deserves — that place in every meaical 
 library which it can so well adorn.' Peninsul^f 
 Medical Journal. 
 
 BARTLETT (EUISHA), M. D, 
 
 THE HISTORY, DIAGNOSIS, AND TREATMENT OF THE FEVERS 
 
 OF THE UNITED STATES. A neW and revised edition. By Alonzo Clark , IVf. D.j Prof, 
 of Pathology and Practical Medicine in the N. V. College of Physicians and Surgeons, dec. lit 
 one octavo volume, of six hundred pages, extra cloth. Price $4 25. 
 
 BROWN (ISAAC BAKER), 
 
 Suigeon- Accoucheur to St. Mary's Hospital, &o. 
 
 ON SOME DISEASES OF WOMEN ADMITTING OF SURGICAL TREAT- 
 MENT. With handsome illustrations. One vol. Svo., extra cloth, pp. 276. $160. 
 Mr. Brown lias earned f'lr himBelf a high reputa- 
 tion inthe operative treatment of sundry diseases 
 and injuries to which females are peculiarly- subject. 
 Wc can truly say of his work that lit is an important 
 addition to obstetrical literature. The operative 
 
 suffffestions and contrivances which Mr. Brown de- 
 scribes, exhibit much practical rfgacity and skUl, 
 
 and merit the careful attentioib of every saiKeon. 
 accoucheur. — Association Journal. 
 
 We have no hesitation in recommending this book 
 tn tje careful attention of all surgeoiia who make 
 female coniplaints a part of their study and practice 
 
 —DuUin i^uarteriy Journal. 
 
6 
 
 HENRY C. LEA»S MEDICAL 
 
 BRANDE {WM, T..1 D, C. 
 Of her MaJJBsty's Mint, &c. ■ 
 
 A»D ALFKED S. TAYLOR, M. D., F. R. S. 
 
 ProfesBurof GhemiBtry and Medical Juriaprudencein 
 Guy'aHoBpital. 
 
 CHEMISTRY.. In one handsome 8vo. volume of 696 pages, extra cloth. $4 50. 
 
 *' Having been engaged in teaching Chemistry in this Metropolis, the one for a period of forty, 
 and the other for a period of thirty years, it has appeared to us that, in spite of the number of books 
 already existing, there was room, for an additional volume, which shtuld be especially adapted for. 
 the ute of students. In preparing such a volume for the press, we have endeavored to bear in 
 mind, that the student in ihe present day lias much to learn, and but a short lime at his disposal for 
 the acquisition of this learning."— ^Authors' Preface. 
 
 In reprinting this volume, its passage through the press has been superintended by a competent 
 chemtst, who has sedulou^ly endeavored to secure the accuracy so necesi-ary in a work of this 
 nature. No notes or additions have been introduced, bul the publishers have been favored by tlie 
 authors with some corrections and revisions of the iitsl twenty-one chapters, which have been duly 
 inserted. 
 
 In so progressive a science as Chemistry, the, latest work always has the advantage of presenting 
 the subject as modified by the results of the latest investigations and discoveries. That this advan- 
 tage has been made the most of, and that the work possesses superior attractions arising from its 
 clearness, simplicity of style, afld lucid arrangement, are manifested by the unanimous testimony 
 of the Engtis^h medical press. , 
 
 It needs uo great sagacity t9 foretell that this book 
 will be, literally, the Handbook in Chemistry of the 
 student and practitioner. For clearness of language, 
 accnracy of description, extent of information, and 
 freedom from pedantry and mysticism of modern 
 chemistry, no other text -book comes into< competition 
 with it. The result is a work which for fulness of 
 matter, for lucidity of arrangement, for clearness of 
 Btyle, is as yet without a rival. And long will it be 
 without a rival. For, although with the necessary 
 advance of chemical knowledge addenda will be re- 
 qaired, there will be little to take away. The funda- 
 mental excellences of the book will remain, preserv- 
 ing it for years to come, what it now is, the best guide 
 to the study of Chemistry yet given to the world. — 
 London Lancet, Dec. 20,1862. 
 
 Most assuredly, time has not abated one whit of the 
 fluency, the vigor, and ihe clearness with which they 
 not only have composed the work before ua, but have, 
 80 to say, cleared the ground for it, by hittin^right 
 
 and left at the affectation, mysticism, and obscurity 
 
 which pervade some late chemical treatises. Thus 
 conceived, and worked oat in the moat sturdy, com- 
 mon sense meihodj this boofegives, in the cl'earest and 
 most summary method possible, all the facts and doc- 
 trinesof chemistry, with more especial reference to 
 the wants of the medical student. — London Medical 
 Times mid Gazette, Mov. 29, 1862. 
 
 If we are not very much mistaken, this book will 
 occupy ^a place which none has hitherto held among 
 chemises ; for, by avoiding the errors of previous au- 
 thors, we have a work which, for its size, is certainly 
 the mq^t perfect of any in the English language. 
 There are sevei'al points to be noted in this volume 
 which separate it ■widely from any of ita compeers- 
 its wide application, not to the medical student only, 
 nor to the student in chemistry merely, but to every 
 branch of science, art, or commerce which is in any 
 way connected with the domain of chemistry. — Lon- 
 donMed. Seview, Feb. 1863. 
 
 BARWELL (RICHARD,) F- R. C. S., 
 
 Assistant Surgeon Charing Cross Hospital, &,c. 
 
 A TREATISE ON DISEASES OF THE JOINTS. Illustrated with engrav- 
 ings on wood. In one very handsome octavo Volume, of about 500 pages, extra cloth ; $5 00. 
 
 ing^ and faithful delineations of disease. — London 
 Med; Times and Gazette^ Feb. 9, lti6l. 
 
 At the outset we may state that the work Is 
 worthy of much praise, and bears evidence of much 
 ithoughtful and careful inquiry, and here and there 
 ■of no siight originality. We have already carrud 
 ttiie notice further than we intended to do, but not 
 to the extent the work deserv<:8. We can only add, 
 that the perusal of itl^as afl^rdcd us gi'eat pleasure. 
 The author has evidently worked very hard at his 
 subject, and his investigations into the Physiology 
 and Pathology of Joints have been carried on in a 
 manner which entitles him to be listened to with 
 attention and respect. We must not omit to men- 
 tion the very admirable plates with which th& vo- 
 lume iseoriched. We seldom meet with suchstnk- 
 
 This volume;wilt be welconfedj as the record of 
 much honest research and careful investigation into 
 the nature and treatment of a' most imfjortant class 
 of disorders. We cannot conclude this notice of a 
 valuable and ustful' book without calling attention 
 to the amount o{bon&Jide work it contains. It is no 
 slight matter for a volume to show laborious iuvea- 
 tigation., and at the same time original thought, on 
 the part uf its auDhor, whom v e may congratulate 
 on the successful completion of his arduous task.— 
 London Lancet, March.9, 1861. 
 
 CARPENTER (WILLIAM BJ, M. D., F. R. S., «£C., 
 
 Examiner in Physiology and Comparative Anatomy in the University of London. 
 
 THE MICROSCOPE AND ITS EEVELATIONS. With an Appendix con- 
 taining the Applications of the JVIicroscope to Clinical Medicine, &c. By F. G. Smith, M. D. 
 Illustrated by four hundred and Ihirly-four beautiful engraving* on wood. In one large and very 
 handsome octavo volume, of 724 pages, extra cloth, $5 25. 
 
 The great importance of the niicroscope as a means of diagnosis, and the number oi microsco- 
 pists who are also physicians, have induced the American publishers, with the author's approval, to 
 ■add an Appendix, careluily prepared by Professor Smith, on the applications of Ihe inf-lrument to 
 clinical medicine, together with an account of Auierican Microscopes, the:"/ modifications and 
 accessories. This portion of the work ,ia illustrated with nearly one hundred wood-cuts, and, it is 
 hoped, will adapt the volume more particularly to the use of the American student. 
 Those who are acquainted wiih Dr. Carpenter's 
 revious writings on Animal and Vegetable Physio- 
 ogy, will fully understand how vasla store of know- 
 
 lt„,, . - 
 
 ledge he is able to bring to bear upon su comprehen< 
 dsive a subject as the revelations of the fnicroscoj;>e ; 
 and even those who have nu pievious acquaintance 
 with Che construction or uses of 'tHis instrument, 
 will find abandanceof information conveyed in clear 
 and siinple language. — Med. Ttmes and Gazette. 
 
 The additions by, Prof. Smich g^iye it a positive 
 claim upnn the profession', for which v/e uoubt not 
 he will rebtiive their sincere thanks. Indeed, we 
 know not where the student of medicint will find 
 such a eouiplete and satisfactory collection of micro- 
 BCtipic facis bearing upon physiology and practical 
 medicine us Is contained in Prof. Smith's appendix; 
 and this of itself, it seems to us, is fully worth the 
 cost of; the volume. — Louisville Medicai Heviev, 
 
ANU SCIJSKTIFIC F UJBLIG ATIONS. 
 
 CARPENTER (WILi.lAM B.), M. D., F. R. S., 
 
 Examiner in Phyniology and Comparative Anatomy in the University of London. 
 
 PRINCIPLES OF HUMAN PHYSIOLOGY; with their chief applications to 
 
 Psychologyj PatholMy, Therapeutics, Hygiene, and Forensic Medicine. A new American, from 
 the last and revised London edition. Withnearlythree hundrediUustrations, Edited, witha4di- 
 ''^**°-^' -U ^J^^^^^^ Gurnet Smith, M. D., Professor of the Institutes of Medicine in the Pennsyl- 
 vania Medical College, &c. In one very large and beautiful octavo volume, oi about nine hundred 
 large pages, handsomely printed, extra cloth, $5 50 
 
 For upwards of thirteen years 0r. Carpenter's 
 work has-been considered by the profession gene- 
 ' rally, both m this country and England, as the most 
 valuable compendium on the subject of physiology 
 in our language . This distinction it owes to the high 
 attamments and unwearied industry of its accom- 
 plished author. The present edition (which, like the 
 ^ast American one, was prepared by the author him- 
 selt), IS the result of such extensive revision, that it 
 may almost be considered* a new work. We need 
 hardly say, in concluding thisbrief notice, that while 
 the work is indispensable to every student of medi- 
 cine in this country, it will amply repay the practi- 
 tioner for its perusal by the interest and value of its 
 contents.^£os£on Med. and Surg. Journal, 
 
 Thiais a standard work— the text-book used by all 
 medical students who read the English language. 
 It has passed through several editions in order to 
 keep pace with the rapidly growing science of Phy- 
 siology. Nothing need be said in its praise, for its 
 merits are universally known ; we have nothing to 
 \ say of its defects, for they only appear where the 
 science of which it treats is incomplete. — Western 
 Lancet. 
 
 The most complete exposition of physiology which 
 any language can at present give. — Brit, and For. 
 ilSed.-Ckirurg. Review. 
 
 The greatest, the most reliable, and the best book 
 oa the subject which we know of in the English 
 language. — Stethoscope . 
 
 To eulogize this great work would be superfluous. 
 We should observe, however, that in this edition 
 the author hsis remodelled a large portion of the 
 former, and the editor has added much matter of in- 
 terest, especially In the form of illustrations. We 
 may confidently recommend it as the most complete 
 work on Human Physiology in our language.— 
 Southern Med. and Surg. Journal. 
 
 The most complete work on the science in our 
 language. — A?n. Med. Journal. 
 
 The most complete work now extant in our lan- 
 guage. — N. O. Med. Register. 
 
 The best text-book in the language on this ex 
 tensive subject. — London Med. Ttmes. 
 
 A complete cyclopsedia of this branch of scienott. 
 —N. Y. Med. Times. 
 
 The profession of this country, and perhaps also 
 of Europe, have anxiously and for sometime awaited 
 the announcement of this new edition of Carpenter's 
 Human Physiology, His former editions have for 
 many years been almost the only text-book on Phy- 
 siology in all our medical schools, and its circula- 
 tion amon^ the profession has been unsurpasBed by 
 any work m any department of medical science. 
 
 It is quite unnecessary for us to speak of this 
 work as its merits would justify. The mere an- 
 nouncement of its appearance will afford the highest 
 pleasiure to every student of Physiology, while its 
 perusal will be of infinite service in advancing 
 physiological science. — Ohio Med.andSurg. Journ 
 
 BY THE SAME AUTHOR. 
 
 ELEMENTS (OR MANUAL) OF PHYSIOLOGY, INCLUDING PHYSIO- 
 
 LOGICAL ANATOMY. Second AirieriCati, from a new and revised London edition. With 
 one hundred and ninety illustrations. In one very handsome octavo volume, leather, pp. 566. 
 $4 00. 
 
 In publishing the first edition of this work, its title was altered from that of the London volume, 
 by the substitution of the word " Elements" for that of " Manual," and with the author's sanction 
 toe title of " Elements" is still retained as being more expressive of the scope of the treatise. 
 
 BV THE SAME A.CTHOK. 
 
 PRINCIPLES OF COMPARATIVE PHYSIOLOGY. New Atnerican, from 
 
 the Fourth and Revised London edition. In one large and handsome octavo volume, with over 
 three hundred beautiful illustrations, pp. 752. Extra cloth, $5 00 
 
 This book should not only be read bat thoroughly 
 studied by every member of the profcBBion. None 
 are too wise or old, to be benefited thereby. But 
 egpeoially to the younger class would we cordially 
 commend it as best fitted of any work in the English 
 language to qualify them for the reception and com- 
 prehension of those truths which are daily being de- 
 veloped in physiology. — Medical Counsellor. 
 
 Without pretending to it, it is an encyclopedia of 
 (he subject, accurate and complete in all respects— 
 a truthful reflection of the advanced state at which 
 the science has now arrived. — Dublin Quarterly 
 Journal of Medical Science. 
 
 A truly magnificent work — in itself a perfect phy- 
 siological BivAy.— Ranking' s Abstract'. 
 
 This work stands without its fellow. It is one 
 few men in Europecould have undertaken; it is one 
 
 no man, we believe, could have brought to so sno- 
 cessful an issue as Dr. Carpenter, ft regnired'for 
 its production a physiologist at once deeply read in 
 the labors of others, capable of taking a general 
 critical, and unprejudiced view of those labors, an<j 
 of combining the varied, heterogeneous materials at 
 his disposal, so as to form an harmonious whole. 
 We feel that-this abstractcan give the reader a very 
 imperfect idea of the fulness of this work, and no 
 idea of its unity, of the admirable vaat ner in which 
 material has been brought, from the most various 
 sources, to conduce to its completeness, of the lucid- 
 ity of the reasoning it contains, or of the clearness 
 of language in which the whole is clothed. Not the 
 profession only, but the scientific world at laiae 
 must feel deeply indebted to Dr. Carpenter for this 
 great work. It must, indeed, add largely even to 
 his high reputation— iffsiMcoiKmM. 
 
 BY THE SAME AUTHOR. (Preparing.) 
 
 PRINCIPLES OP GENERAL PHYSIOLOGY, INCLUDING ORGANIC 
 
 CHEMISTKY AND HISTOLOGY. With a General Sketch of the Vegetable and Animal 
 Kingdom. In one large and very handsome octavo volume, with several hundred illustrations. 
 
 BT THE SAMS AirTHOB. 
 
 A PRIZE ESSAY ON THE USE OP ALCOHOLIC LIQUORS IN HEALTH 
 
 ANIJ DISEASE. New edition, with a Preface by D. F. Cohbie, M. D., and eapiunatioDS of 
 scientific words. In one new 12mo. volume, extra cloth, pp. 178. 60 centra. 
 
8 
 
 HENRY C. LEA'S MEDICAL 
 
 CON DIE (D. F.), M. D., ttc, 
 
 A PRACTICA]. TREATISE ON THE DISEASES OP CHILDREN. Fifth 
 
 edition, revised and augmented , In one large volume, 8vo^, extra cloth, of over 750 pages. $4 50. 
 
 In presenting a new and revised edition ol this favorite work, the publishers have only to state 
 that tne author has endeavored to render it in every respect *' a complete aYid faithful exposition of 
 the pathology and therapeutics of the maladies incident to the earlier stages of existence— a full 
 and exact account'of the diseases of infancy and childhood." To accomplish this he has subjected 
 ' the vphole work to a careful and thorough revision, -rewriting a considerable portion, and adding 
 several new chapters. In ihis manner it i& hoped that any deficiencies which may have previously 
 existed have been supplied, that the recent labors of practitioners and observers have been tho- 
 roughly incorporated, and that in every point the work will be found to maintain the high reputation 
 it has enjoyed as a complete and thoroug-hly practical book of relerence in infantile affections. 
 
 A few notices of previous editions are subjoined. 
 
 Dr. Gondie's BcholarBhip, acumen^ industry, and 
 
 practical sense are manifested in this, as in all his 
 numerouB contributions to science. — pr. Holmes^s 
 Report to the Americem Medical Association. 
 
 Taken as a whole, in our judgment. Dr. Gondie's 
 Treatise ia the one from the perusal of which the 
 practitioner in this country will rise with thegreat- 
 est BSitiBfaLCtion.— Western Journal of Medicine and 
 Surgery^ 
 
 One of the best works upon the Diseases of Chil- 
 dren in the English language. — Western Lancet. 
 
 We feel assured from actual experience that n*. 
 'physician's library can be complete without a cop> 
 ofthiswork. — N Y. Journal of Medicine. 
 
 A veritable pebdiatric encyclopsedia, and an hunoi 
 10 American medical literature. — Ohio Medical and 
 Surgical Journal. 
 
 Wefeel persuaded thatthe American medical pro- 
 fession will 80(m regard it not only aa a very good, 
 but as the very best "Practical Treatise im tht 
 Diseases of Ghildren." — American Medical, Journal 
 
 In the department of infantile therapeutics, the 
 work of Dr. Gondie is considered one ot the best 
 which has been published in the English language, 
 ^Tke Stethoscope. 
 
 We pronounced the first edition to be the best 
 work on the diseases of children in the English 
 language, and, nut withstanding all that has been 
 published, we still regard it in that light. — Medical 
 Examiner. 
 
 The value ofworks by native authors on the dii- 
 eases which the physician is called up^n to eombat, 
 will be appreciated by all ; an'i the work of Dr. Con- 
 die has gained for Itself the character of a safe guide 
 tor students, and a useful work for consultation by 
 those engaged in practice,. — N. Y.. Med Times. 
 
 This is the fourth edition of this deservedly popu- 
 lar treatise. During the interval since the last edi- 
 tion, It has been subjected to a thorough revision 
 by the author; and all new observations in the 
 pathology and therapeutics of children hav« been 
 included in the present volume. As we said btfore, 
 we do not know of a better book on diseases of chil- 
 dren, and to a large part of its recommendations we 
 yield an unhesitating concurrence. — Buffalo Med. 
 ToumaJ^ . 
 
 Perhaps the mostfuU and complete work now be- 
 lOre the profession of the United States; indeed, we 
 iuay aay in the English language. It is vastly supe- 
 rior to most of its predecessors. —Tronsylwawa Med, 
 Journal 
 
 CHRISTISON (ROBERT), M. D., V. P. R. S. E., fcc. 
 
 A DISPENSATORY; or, Commentary on the Pharmacopoeias of Great Britain 
 
 and th« United Stales ; comprising the Natural History, Descriptiou, Chemistry, Pharmacy, Ac- 
 tions, Uses, and Doses of the Articles of the Materia Medica. Second editioii, revised and im- 
 proved, with a Supplement containing the most important New Remedies. With uopiank;^ddi- 
 tions, and two hundred and thirteen large wood-engravings. By R- Eslesfeld Geifehth, M. D. 
 In one very large and handsome octavo volume, extra cloth, of over 1000 pages. W CO 
 
 COOPER (BRANSBY B.), F. R. S. 
 LECTURES ON THE PRINCIPLES AND PRACTICE OF SURGERY- 
 
 In one very large octavo volume, extra cloth, of 750 pages. $2 00. 
 
 COOPER ON THE ANATOMY AND DISKASEg 
 OF THE BREAST, with twenty-five Mlscellane- 
 oas and Surgical Papers. One large volume, im- 
 perial 8vo,, extra cloth, with 3S2 figures, on 36 
 plates. S3 00. 
 
 COOPER ON THE STRUCTURE AND DIS- 
 EASES OF THE TESTIS, AND ON THE 
 THYMUS GLAND. One vol. imperial 8vo., ex- 
 tra cloth, with 177 £gures on 29 plates, f 2 50. 
 
 CLYMEB ON FEVERS: THEIR DIAGNOSIS. 
 PATHOLOGY, AND TREATMENT. In OM 
 octavo volume, leather, of 600 pages. SI 73. 
 
 COLOMBAT DE L'ISERE ON THE DISEASES 
 OF FEMALES, and on the special Hygiene of 
 their Sex. Translated, with many Notes and Ad- 
 ditions, by C. D. Meiss, M.D. Second edition, 
 revised and improved. In one large voluhie, oc- 
 tavo; leather, with nnmerous wood-cuts. pp. 720. 
 S3 73. 
 
 CARSON (JOSEPH), M. D., 
 Professor of Materia Medica and Pharmacy in the University of Pennsylvania, 
 
 SYNOPSIS OF THE COURSE OF LECTUREis ON MATERIA MEDICA 
 
 AND PHARMACY, delivered m the .University of Peanisylvania. With three Lectures on 
 the Modus Operandi of Medicines. Third edition, revised. In one handsome octavro volume. 
 »2 50. 
 
 CURLING (T. B.), F. R.S., 
 
 Surgeon to the London Hospital, President of the Hunterian Society, &c. 
 
 A PKACTICAL TREATISE ON DISEASES OF THE TESTIS, SPERMA- 
 TIC CORD, AND SCROTUM. Second American, from the second and enlarged English edi- 
 Moa. In one handsome octavo volume, extra cloth, with nnmerous illustrations, pp. 420. S2 00 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 9 
 
 CHURCHILL (FLEETWOOD), M. D., M. R. I. A. 
 ON THE THEORY AND PRACTICE OF MIDWIFERY. A new American 
 
 from the fourth revised and enlarged London edition. With Notes and Additions, by D. Francis 
 OoNDiE, M. D., author of a "Practical Treatise on the Diseases of Chil4ren," &c With 194 
 illustrations. In one very handsome octavo volume of nearly 700 large pages, extra cloth, $4 00. 
 This virork has been so long an established favorite, both as a text-boob lor the learner and as a 
 reliable aid in consultation tor the practitioner, that in presenting a new edition it is only necessary* 
 to call attention to the very extended improvements which it has received Having had the benefit 
 of iwo revisions by the author since the last American reprint, it has been materially enlarged, and 
 Dr. Churchill's woU-known conscientious mduslry is a guarantee that every portion has been tho- 
 roughly brought up with the latest results of European investigation in all departments of the sci- 
 ence and art of obstetrics. The recent dale of the last Dublin edition has not left much of novelty 
 for the American editor to introduce, but he l?as endeavored to insert whatever has since appeared, 
 together with such matters as his experience has shown him would be desirable fur the American 
 student, including a large number of illustrations Wiih the sanction of the author he has added 
 in the form of an appendix, some chapters from a little "Manual for Midwivei^ and Nurses," re- 
 cently isi^ued by Dr. Churchill, believing- that the details there presented can hardly fail to prove nt 
 advantage to the junior practitioner. The result of ajj these auditions is that the work now con- 
 tains fully one-half more matter than the last American edition, with nearly one-half more illus- 
 trations, so that notwithstanding tlfe use of a smaller type, the volume contains almost two hundred 
 pages more than before. 
 
 No effort has been spared to securS an improvement in the mechanical execution of the work 
 equal to that which the text has received, and the volume is confidently presented as one of the 
 handsomest that has thifs far been laid before the American profession; while the very low price 
 at which it is offered should secure for it a place in every lecture-room and on every office table. 
 
 A better book in which to learn these important 
 points we have not met than Dr. Churchill's. Every 
 pn^e of it is full of ihBtruction ; the opinion of all 
 wntefs of authority is given on questions of difH- 
 cuity, as well as the directions and advice of the 
 learned auttior himself, to w^hich he adds the result 
 of statiBticalintiuiry, putting statistics in tiieir pio 
 per place and giving them their due weight, and no 
 more. We have never read a book more free from 
 profesBional jealousy than Dr. Churchill's. It ap- 
 pears Co be written with the true design of a book on 
 medicine, viz: to give all that is known on the sub- 
 Jeet of which he treats, both theoretically and prac- 
 tically, and to advance such opinions of his own as 
 he J)elieves will benefit medical science, and insure 
 the safety of the patient. We have said enough to 
 convey to the profession that this book of Dr. Chur- 
 chill's is admirably suited for a book. of reference 
 for the practitioner, as well asAtextTbook for the 
 student, and we hope it may be extensively pur- 
 chased amongst our readers. To them we most 
 strongly recommend it. — Dublin Medical Press 
 
 To bestow praise on a book that has received such 
 marked approbation would be superfluous. We need 
 enly say, therefore, that if the first edition was 
 thought worthy of a favorable reception by the 
 medical public, we can confidently affirm that this 
 will be found much more bo. The lecturer, the 
 practitioner, and the student, may all have recourse 
 to its pages, and derive from their perusal much in- 
 terest and instruction in everything relating to theo- 
 retical and practical midwifery.— i)«6K» Quarttrly 
 Journal of Medical Science. 
 
 A work of -very great merit, and such as we can 
 confidently recommend to the study of every obste- 
 tric practitioner -T-I-ottrfonilfedicoZ Gazette. 
 
 Few treatises y^ill be found better adapted as t 
 text-bo&kfor the student, or as a manual for tfai 
 frequent consultation of the young practitioner.- 
 American Medical Journal. 
 
 Were we redaced to the necessity of having bu^ 
 me work on midwifery, and permitted to choosef 
 ve would unhesitatingly take Churchill. — Western 
 Med. and Surg. Journal. 
 
 It is impossible to conceive a more useful and 
 ilegant manual than Dr. Churchill's Practice of 
 Midwifery. — Provincial Medical Journal. 
 
 Certainly, in our opinion, the very best work on 
 ^le subject which exists. — N. Y. Annalist. 
 
 No work holds a higher position, or is more de- 
 serving of being placed in the hands of the tyro, 
 the advanced student, or the practitioner. — Medical 
 Examiner 
 
 Previous editions have been received witli mark- 
 ed favdr, and they deserved it; but this, reprinted 
 from a very late Dublin edition, carefally revised 
 and brought up by the author to the present' timn, 
 does present an anusualLy accurate and able expo- 
 sition of every important particular embraced in 
 the departmentof midwifery. * * The clearnessj 
 directness, and precision of its teachings, together 
 with the great amount of statistical research which 
 its text exhibits, have served to place it already in 
 the foremost rank of works in this department of re- 
 medial science. — Y Meit and Sv.rg Tournal. 
 
 In our opinion, it forms one o( the best if not t e 
 very best text-book and epitome of obstetric scieuco 
 which we at present possess in the English lan- 
 guage.— ilfon(Aiy./o«r»oi of Medical SeteiMd: 
 
 The clearness and precision of style in which it ia 
 written, and the greatamount(ff statistical research 
 which it contains, have served to place it in the first 
 rank oT works in this departmentof medical science. 
 — JV. Y. Journal of Medicine. 
 
 This is certainly the most perfect system extant. 
 It ia the best adapted for the purposes of a text- 
 30ok, and that which he whose necessities confine 
 lim to one book, should select in preference to all 
 others. — Soutkern Medical and Surgical Journal. 
 
 BY THE SAME AUTHOR 
 
 ON THE DISEASES OF INFANTS AND CHILDREN. Second American 
 
 Edition, revised and enlarged by the author. Edited, with Notes, by W. V. Keatins, M. O. In 
 
 one large and handsome voiume, extra cloth, of over 700 pages. $4 50. 
 
 In preparing this work a second time for the American profession, the author has spared no 
 labor in giving it a very thorough revision, introducing several new chapters, and rewriting others, 
 while every portion of the volume has been subjected to a severe scrutiny. The efforts of the 
 American editor hate been directed to supplying such information relaiive to matters peculiar 
 to this country as might have escaped the attention of the author, and the whole may, there- 
 fore be safely pronounced one of the most complete works on the subject accessible to the Ame- 
 rican Profession. By an alteration in the size! of the page, these very extensive additions have 
 been accommodated without unduly increasing' the size of the work. 
 
 BY THE SAMS AUTHOB.. 
 
 ESSAYS ON THE PUERPERAL FEVER, AND OTHER DISEASES PE- 
 
 CIILIAR TO WOiWEN. Selectedfromthe writings of British Authori- previous to the clos*: of 
 tbeSiffhteenth Century. IaoneneBtocUvovo[ame,extracloth,olabout 450 pages. S2 50. 
 
10 HENRY C. LEA'S MEDICAL 
 
 CHURCHILL (FLEETWOOD), M. D., M. R. I. A., &o 
 ON THE DISEASES OF WOMEN; iifcluding those of Pregnancy and Child- 
 
 bed. A new American edition, revised by the Autiior. With Notes and Additions, by D Fram- 
 cis CoNDiE, M. D., author o) " A Practical Treatise on the Uiseases of Children." With nume- 
 rous illustrations. In one large and handsome octavo volume, extra cloth, of 768 pages. $4 00. 
 This edition of Dr. Churchill's very popular treatise may almost be termed a new work, so 
 thoroughly has he revised it in every portion. It will be fouifd greatly enlarged, and completely 
 brought up to the most recent condition of the subjeot, while the very handsome series of illustra- 
 tions introduced, representing such pathologigal conditions as can be accurately portrayed, present 
 a novel feature, and afford valuable assistance to the young practitioner. Such additions as ap- 
 peared desirable for the American student have been made by the editor, Dr. Condie, while a 
 marked improvement in the mechanical execution keeps pace with the advance in all other respects 
 which the volume has undergone, while the price has,been kept at the former very moderate rate. 
 
 it compriBes, unquestionablj^, one of the meet ex- 
 act and comprehensive expositions of the present 
 state of medical knowledge in respect to the diseases 
 
 of women that has yet been published. — Am. Joum, 
 Med. Sciences. 
 
 This work is the most reliable which we possess 
 on this subject; and is deservedly popular with the 
 profession. — Charleston Med. Joumaly July, 1857. 
 
 We know of no author who deserves that appro- 
 bation, on " the diseases of females," to the same 
 
 extent that Dr. Churchill does. His, indeed, is ths 
 only thorough treatise we know of on the subject : 
 and it may be commended to practitioners and stu- 
 dents as a masterpiece in its particular department, 
 — Tkt Western Journal of Medicine and Surgery. 
 
 As a comprehensive manual for students, or i 
 work of referedce for practitioners, it surpasses any 
 other that has ever issued on the same subject from 
 the British press. — Dublin Quart. Journal. 
 
 DICKSON (S. H.), M. D., 
 
 Professor of Practice of Medicine in the Jefferson Medical College, Philadelphia. 
 
 ELEMENTS OF MEDICINE; a Compendious View of Pathology and There- 
 
 peutics, or the History and Treatment of Diseases. Second edition, revised. In one large and 
 
 handsome octavo volume, of 750 pages, extra cloth. $4 00. 
 
 The steady demand which has so soon exhausted the first edition of this work, sufficiently shows 
 that the author was not mistaken in supposing that a volume of this character was needed— -an 
 elementary manual of praclice, which should present the leading principles of medicine with the 
 practical results, in a condensed and perspicuous manner. Disencumbered of unnecessary detail 
 and fruitless speculations, it embodies what is most requisite for the student to learn, anci at the 
 same time what the active practitioner wants When obliged, m the daily calls of his profession, to 
 refresh his memory on special points. The clear and attractive style of the author renders the 
 whole easy of comprehension, while his long experience gives to his teacbiiigs an authority every- 
 where acknowledged. Few physicians, indeed, have had wider opportunities for observation and 
 experience, and few, perhaps, have used them to better purpose. As the result of a long life de- 
 voted to study and practice, the present edition, revised and brought up to the date of publication, 
 will doubtless maintain the reputation already acquired as a condensed and convenient American 
 text-book on the Practice of Medicine. 
 
 DRUITT (ROBERT), M.R.C.S., &c. 
 THE PRINCIPLES AND PRACTICE OF MODERN SURGERY. A new 
 
 and revised American from the eighth enlarged and improved London edition. Illustrated with 
 
 fQur hundred and thirty-two wood-engravings. In one very handsomely printed octavo volume 
 
 of nearly 700 large pages, extra cloth, $4 00. 
 
 A work which like Druitt's Surgery h«s for so many years mamtamed the position of a lead- 
 ing favorite with all classes of the profession, needs no special recommendation to attract attention 
 to a revised edition. It is only necessary to state that the author has spared no pains to keep the 
 work up to its well earned repulalion of presenting in a small and convenient compass the latest 
 condition of every department of surgery, considered both as a science and as an art; and that the 
 services of a competent American editor ^ve been employed to introduce whatever novelties may 
 have escaped the author's attention, or may prove of service to the American practitioner, As 
 several editions have appeared in London since the issue of the last American reprint, the volume 
 has had the benefit of repeated revisions by the author, resulting in a very thorough alteration and 
 improvement. The extent of these additions may be estimated from the fact that it now contains 
 about one-third more matter than the previous American edition, and that notwithstanding the 
 adoption of a smaller type, the pages have been increased by about one hundred, while nearly two 
 hundred and fifty wood-cuts have been added to the former list of illustrations. 
 
 A marked improvement will also be perceived in the mechanical and artistical execution of the 
 work, which, printed in the best style, on new type, and fine pap^r, leaves little to be desired as 
 regards external finish; while at the very low price affixed it will be found one of the cheapest 
 volumes accessible to the profession. 
 
 This popular volume, now a moat comprehenaive 
 work on surgery, has undergone many corrections, 
 improvemeuts, and additions, and the principles and 
 the practice of the art have been brought down to 
 the latestrecordandobservatiou. Of the operations 
 in surgery it is impossible to speak too highly. The 
 descripiions are so clear and concise, and the illus- 
 trations BO accurate and numerous, ttiat the student 
 can have no difficulty, with instritmentinhand, and 
 book by his side, over the dead body, in obtaining 
 a proper knowledge andisufficient tact in this much 
 neglected department of medical education. — British 
 and Foreign Medico-Chirurg , Review^ Jan. 1S60 
 
 In the present edition the author has entirely re- 
 written many of the chapters, and has incorporatsd 
 the various improvements and additions in modern 
 •urgery. On carefully going over it, we find that 
 
 nothing of real practical importance has been omit- 
 ted ; it presents a faithful epitome of everything re- 
 lating t ) surgery up to the present hour. It is de- 
 servedly a popular manual, both with the student 
 and practitioner.— Loff<2on Lancets Nov. 19, 1859. 
 
 In closing this brief notice, we recommend as cor- 
 diallv as ever this most useful and comprehensive 
 hand-bouk. It must prove a vast assistance, not 
 only to the student of surgery, but also to the busy 
 practitioner who may not have the leisure to devote 
 himself to the study of more lengthy volumes.— 
 London Med. Times and Gazettgj Oct. 23, 1859. 
 
 In a word, this eighth edition of Dr. Bruitt'i 
 Manual of Surgery is all that the surgical student 
 or practitioner could desire. — Dublin Quarttrif 
 Journal of Mid. Sciences, Nov. 1859. 
 
AND SCIKNTIFIC PUBLICATIONS. 
 
 11 
 
 DALTON, JR. (J. C), M. D. 
 PrdfesBor of PhyBiology in the College of FhysicianB, New York. 
 
 A TREATISE ON HUMAN PHYSIOLOGY, designed for the use of Students 
 
 and Practitioners of Medicine. Third edition, reviped, with nearly three hundred illustrations 
 on wood. In one very beautiful octavo volume, of 700 pages', exira cloth, S5 ^5, {Just Issued.) 
 The rapid demand for another edition of this work sufficiently shows that the author has suc- 
 ceeded in his eflbrls to produce a text-book of standard and permanent value, embodying within 
 a moderate compass all that is definitely and positively known within the domain of Human 
 Pfaysiology. His higblk-eputation as an original observer and investigator, is a guarantee that in 
 again revising it he has introduced whatever is necessary to render it thoroughly on a level with 
 the advanced science of the day, and this has been accomplished without unduly increasing the 
 size of the volume. 
 
 No exertion has been spared to maintain the high standard of typographical execution which has 
 rendered this work admittedly one of the handsomest volumes as yet produced in this couniry. 
 
 Itwilibeeeen, therefoxe, that Dr.Dalton'e best 
 efforts have been directed towards ptjifecting his 
 work. The.additiong are marked by the same fea- 
 tures which characterize the remainder of the vol- 
 ume, and render it by far the most desirable text- 
 
 K„„l, _l ^:-l ^._ .1 j_ ^L. 1 ... _^.^L- 
 
 book on physiology to place in the hands of the 
 student which, so far as we are aware, exists in 
 the English language, or'perhgps in any other. We 
 therefore have no hesitation in recommending Dr. 
 Dal ton's book for Che claBseB for which it is intend- 
 ed, satisBed as we are ihat it is better adapted to 
 their uec than any other work of the kind to which 
 they have access. — American Journal of the Med, 
 jSlctenc«5, April, 1861. * 
 
 It is, therefore, no disparagement to the many 
 books upon physiology, most excelien'; in theirday, 
 to say that Daiton^s is the only one that gives us the 
 icience as it was known to the best ptiilosophers 
 throughout the world, at the beginning of the cur- 
 rent year. It states in comprehensive but concise 
 diction, the facts established by experiment, or 
 other method of demonstration, and details, in an 
 nnderstandable manner, how it is done, but abstains 
 from thediscussion of unsettled or theoretical points. 
 Herein it ie unique; and these characteristics rrn 
 der it a text-book without a rival, for those who 
 desire to stujdy physiological science as it is known 
 to its most successful. cultivators. And it is physi- 
 ology thus presented that lies at the foundation of 
 correct pathological knowledge; and this in turn is 
 the basis of rational therapeutics; so that pathi>lo- 
 gy, in fact, becomes of prime importance in the 
 proper discharge of our every-day practical^nCies. 
 — Cincinnati LoMcet^ May, 1861. 
 
 Dr. Dalton needs no word of praise from us. He 
 is universally recognizee as among the 'first, if not 
 the very fii st, of American physiologists now living. 
 The first edition of his admirable work appeared but 
 two year^ since, and the advance of science, his 
 
 own original views and experiments, together with 
 a. desire to supply what he considered some deficien- 
 cies in the first edition, have already made the pre- 
 sent one a necessity, and it will no doubt be even 
 mure eagerly souf;bt for than the first. That it is 
 not merely a reprint, will be seen from the author's 
 statement of the following priucipal additions und 
 alterafioDB which he has made.' The present, likfe 
 the first edition, is printed in the highest style of the 
 printer's art, and the illustrations are truly admira- 
 ble tor their clearness in expressing exactly what 
 their author intended. — Boston Medical and Surgi- 
 cal Journal, March 28, 1861. 
 
 It is unnecessary to give a detail of the additions; 
 suffice it to say, that they are numerous and import- 
 ant, and such as will render the work still' more 
 valuable and acceptable to the profess ion, as -a learn- 
 ed and cT^ginal treatiseon this all-important; branch 
 of mcJicine. All that was said in comcncndation 
 of the getting up of the first edition, and the superior 
 style of the illustrations apply with equal force to 
 this. No better work on physiology can be placed 
 in the hand of the student. — St. Louis Medical and 
 Surgical Journal, May,, 1861. 
 
 Theseadditioiis, while testifying to the learning 
 and industry of the author, render the book exceed- 
 ingly useful, as the most complete expose of a sci- 
 ence, of which Dr. Dalton is doubtless the ablest 
 representative on this side of the Atlantic. — New 
 Orleans Med Times, May, 1861. 
 
 A second edition of this deservedly popular work 
 having been called for in the short space of two 
 years, the author has supplied deficiencies, which 
 existed in the former volume, and has thus more 
 completely fulfilled his design of presenting to the 
 profession a reliable and precise text- book, and one 
 which we consider the best outline on the subiect 
 of which it treats, in any laiisuage. — N. Afnerican 
 Medico- Chirurg. Review, May, lb61. 
 
 DUNGLISON, FORBES, TWEEDIE, AND CONOLLY. 
 THE CYCLOP JEDIA OF PRACTICAL MEDICINE: comprising Treatises on 
 
 the Nature and Treatment of Diseases, Materia Medica, and Therapeutics, Diseases of Women 
 
 and Children, Medical Jurisprudence, &c. &:c. In four large super-royal octavo volumes, of 
 
 3254 double-columned pages, strongly and handsomely boiind, with raised bands. ffilS 00. 
 
 K *^(!* This work contains no less than four hundred and eighteen distinct treatises, contributed by 
 
 •ixty^^ighl distinguished physicians, rendering it a complete library of relerence for the country 
 
 practitioner. 
 
 The most complete work on Practical Medicine 
 •xtant; or, at feast, in our language.— Btt^oio 
 Medical and Surgical Journal. 
 
 For reference, it ia above all price to every prac- 
 titioner. — Western Lancet. 
 
 One of the most valuable medical publications of 
 
 the day as a work of reference it is invaluable. — 
 
 Western .Tournal of Medicine and Surgery. 
 
 It has been to ub, both as learner and teacher, a 
 work for ready and frequent reference, one in which 
 modern English medicine is exhibited in the mpst 
 advantageous light. — Medical Examiner. 
 
 The editors are practitioners of established repu- 
 tation, and the list of contributors embraces many 
 of the most eminent professors and teachers of Lon- 
 don, Edinburgh, Dublin, and Glasgow. It is, in- 
 deed, thegreat raerito) this work that the principal 
 articles have been furnished by practitioners who 
 have not only devoted especial attention to the dis- 
 eases about which they have written, hut have 
 also enjoyed opportunitie* for an extensive ptucti- 
 eal acquaintance with them and whose reputation 
 carries the assurance of their competency justly to 
 appreciate the opinions o' others, while it stamps 
 
 their own dotftrineswitl high and just authority 
 
 AfTU rican Medical Journal . 
 
 DEWEES'S COMPREHENSIVE SYSTEM OF 
 MIDWIFERY. Illustrpted' by occasional cases 
 and many engravings Twelfth edition, with the 
 author's last improvements and corrections In 
 oneoctavovolume, extracloth.offtOOpages. S3 50. 
 
 PBWEBS'S TREATISE ON THE PHYSICAL 
 
 AND MEDICAL TRBATWENT OF CHILD 
 REN. The last edition In one volume, octavo 
 extra cloth, 548 pages 363 80 ' 
 
 OEWEES'S TREATISE ON THE DISEASES 
 OF FEMALES Tenth edition In one volume, 
 octavo extra cloth, 532 pages, witli plates «3 00. 
 
12 
 
 HENRy C. LEA'S MEDICAL 
 
 DUNGLISON (ROBLEY), IV). D., 
 
 PTofeBSor of Institutes of Medicine in the Jefferson Medical College, Philadelphin 
 
 ENLARGED AND REVISED EDITION OP 1865— : Just Issued.) 
 
 MEDICAL LEXICON; a Dictionary of Medical Science, containing a concise 
 Explanation of the various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene, 
 Therapeutics. Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence, and Den- 
 tistry. Notices of Climate and of Mineral Waters; Formulse for Officinal, Empirical, and Dietetic 
 Preparations; with ihe Accentuation and Etymology of I he Terms, and the French and other 
 Synonymes; so as to constitule aFrenth as well as Engli^h Medifeafc; Lexicon. Thoroughly 
 revised and very greatly m-^dified and augmented. In one very large and handsome royal 
 octavo volume, of 1048 double-columned pages, in small type . strongly done up in extra clolh, 
 Sb 00; leather, raited bands, $6 75 
 
 Preface to the New Edition 
 ** The author has again been required to subject his Medical Lexicon to a thorough revision. 
 The progress of Medical Science, and the cnnsequeiit introduction of new subjects and terms, 
 demanded this; and he has embraced the occa^on to render more complete the etymology and 
 accentuation ofth* terms. On no previous revision has so much time and labor been expended by 
 him. Some idea may be formed of this, from the fact, that although the page has been augmented 
 in all iis dimensions, not fewer than between sixty and seventy pages have been added. 
 
 "As the author has remarked on former occasions^ it has ever been his ardent wish to make the 
 work a caiislactorvand desirable — if not indispenirable — lexicon, in whinh the inquirer may search, 
 without disappointment, for every term that has been legitimated in the nomenclature of the science; 
 and he confidently presents this edition as having more claims on the attention of the practitioner 
 and student than its predecessors. 
 
 'Once more the auihor gladly seizes the opportunity afforded him to express his gmteful acknow- 
 ledgments for the vast amount of favor which has been extended to the Dictionary." 
 January, 1S65. 
 The object of the author from the outset has not been to make the work a mere lexicon or dic- 
 tionary of terms, but to afford, under each a condensed view of its various medical relations, and 
 thus to render the work an epitome of the existing condition of medical science. Starting with 
 this view, the immense demand whic.i has Existed for the work has enabled him, in repeated re- 
 visions, to augment its completeness and usefulness, until at length it has attained the position of 
 a recognized and standard authority wherever the language is spouen, * This has only been accom- 
 plished by the earnest determination to bring each successive edition thoroughly on a level with 
 the most advanced condition of contemporary medical science, and on no previous occasion has 
 tnis demanded a more patient and laborious effort than in rendering the present edition fully equal 
 to the wanis of the student of the present day, and in no previous editions has the amount of i^ew 
 matter introduced been so large. While, therefore, the reader who merely desire* a voeabuJary 
 explaining the terms in common use can satisfy himself with the smaller works, such as Hoblyn*s, 
 the student and practi'ioner who wish a work to which they can at all times refer with unfailing 
 confidence for all which it is the province of such a book to supply, must still, as heretofore, keep 
 the latest edition of *' Uunglison's DicTioNARy" within reach. 
 
 The mechanical execution of.this edition will be found greatly superior to that of previous im- 
 pressions. By enlarging the size of the volume to a royal octavo, and hy the employment of a small 
 but clear ty^ on extra fine paper, the additions have been incorporated without materially increas- 
 ing the bulk of the volume, and the matter of two or three ordinary octavos has been compressed 
 into the space of one not unhandy for consultation and reference. 
 A few notices' of the previous editions are subjoined. 
 
 mthor, and have furnished ns with a volnme indis- 
 
 This work. cAe appearance of the fifteenth edition 
 of which it buB become uur duty and pleasure to 
 announce, ie perhaps the most stupendous monument 
 of labor and erudition in medical literature. One 
 would hardly suppose after constant use of the pre- 
 ceding editions, where we have never failed to find 
 a sufficiently full explanation of ever} medical term, 
 that in this edition '^'^ about six thousand subjects 
 and terms have been added^'^with a careful revisioi] 
 and correction of the entire work. It is only neces- 
 Bary to announce the advent of this edition to make 
 it occupy the place of the preceding one on the table 
 of every medical man, as it is without doubt the best 
 and most comprehensive work of the kind which has 
 ever appeared. — Buffalo Med. Joum.i Jan. ,1858. 
 
 The wiirk is a muuument of patient research, 
 skilful judgment, and vast physical labor, that will 
 perpetuate the name of the author more effectuaUy 
 than any possible device of stone or metajl. Dr. 
 Donglison deserves the thanks not only of the Ame- 
 rican profession, butbf the whole medical world. — 
 North Am. Medieo-Chir. Review, Jan. 1858. 
 
 A Medical Dictionary better adapted for the wants 
 of the profession than any other with which we are 
 acquainted, and of a character which places it far 
 above comparison, and competition. — Am Joum. 
 Med. SeienceSj Jan. 1BS6. 
 
 We need only say, that the addition of 6,000 new 
 terms, with their accompanying definitions, may be 
 said to constitute a new work, hy itself. We have 
 examined the Dictionary attentively, and are most 
 happy to pronounce it unrivalled of its kind. The 
 erudition displayed, and the extraordinary industry 
 which must have been demanded, in its preparation 
 and perfectjion] redound to the lasting credit of its 
 
 pensable at the present day, to all who would find 
 themselves au niveau with the highest standards of 
 medical information. — Soston Medical cmd Surgical 
 ^(>ttrMa;,Dec.31, 1857. 
 
 Good lexicons and encyclopedic works generally, 
 ire the most labor-eaving contrivances which lite- 
 rary men enjoy ; and the labor which is required to 
 ;>roduce them in the perfect manner of this example 
 9 something appalling to contemplate. The author 
 tells us in his preface that he has added about six 
 thousand terms and subjects to this edition, which) 
 before, was coitsidered universally as the best work 
 of the kind in any language. — Sillima»^s Journal, 
 March, 1858. 
 
 A complete and thorough exponent of medical 
 terminology, without rival or possibility of rivalry. 
 — Nashville Joum. of Med. and Surg., Jan. 18S8. 
 
 It is universally acknowledged, we believe, that 
 this work is incomparably the best and most com- 
 plete Medical Lexicon m the English language, 
 Comment and commendation areunnecessary, as no 
 one at the present da^ thinks of purchasing any other 
 Medical Dietionar} than this.— 5t. Louis Med. and 
 Surg. Journ.j Jan 1858. 
 
 It is the foundation stone of a good medical libra- 
 ry, and should always be included in the first list of 
 books purchased by the medical student.— ^m. Mtd. 
 Monthly, Jan. 1858. 
 
 It is scarcely necessary to remark that any medi- 
 cal library wanting a copy of Dunerlison's Lexicon 
 must be imperfect. — Cin. Laneetj /an. 1858. 
 
 The present edition we may safely say has no equal 
 in ttie world. — Peninsular Med. Jowmal Jan. IbSS. 
 
AND SqiENTlFIC PUBLICATIONS. 
 
 13 
 
 DUNGLISON (ROBLEY), M.D., 
 ProfeBBOT of InatitttteB of Medicine in tlie Jefferson Medical College, Philadelphia. 
 
 HUMAN PHYSIOLOGY. Eighth edition. Thoroughly revised and exten- 
 
 sively modified and enlarged, with five hundred and thirty-two illustrations.- In two large and 
 handsomely printed octavo volumes, extra cloth, of about 1500 pages, f 7 00. 
 
 In revising this work lor its eighth appearance, the author has spared no labor to render it worthy 
 a continuance o£the very great favor which has been extended to it by the profession. The whole 
 contents have been rearranged, and to a great extent remodelled ; the investigations which of late 
 years have been so numerous and so important, have been carefully examined and incorporatedi 
 wid the work in every respect has been brought up to a level with the present state of the subject. 
 
 u "'V®'" "'^ "'^ author has been to render it a concise but compreihensive treatise', containing the 
 whole body of physiological science, to which the student and man of science can at all times refer 
 with the certainty of finding whatever they are in search of, fully presented in all its aspects ; and 
 on no former edition has the author bestowed more labor to secm:e this result. 
 
 We believe that it can truly be said, no more com- 
 plete repertory of faotB upon the subject treated, 
 ean anywhere be found. The author has, moreover, 
 that enviable tact at deBcription and that facility 
 and ease of expreBsion which render hint peculiarly 
 acceptable to the caxial, or the studious reader. 
 This facuUy, so reQuisite in setting forth many 
 graver and less attractive subjects, lends additional 
 
 ehaims to one always fascinating Boston Mei,. 
 
 Mid Surg. Journal. 
 
 The most complete and satisfactory system of 
 Physiology in the English language. — Amer. Med. 
 Journal. 
 
 The best work of the kilid in the English lan- 
 guage. — Silliman^s Journal. 
 
 The present edition the author has made a perfect 
 mirror of the science as it is at the present hour. 
 As a work upon physiology proper, the science of 
 the functions performed by the body , the student will 
 find it all he wishes. — Nashville Journ. of Med. 
 
 That he has succeeded, moat admirably succeeded 
 in his purpose, is apparent from the appearance of 
 an eighth edition. It is now the great encyclopsedia 
 on the subject, and worthy of a place iii every phy- 
 sician's library. — Western Lancet. 
 
 BY THE SAME AUTHOR. 
 
 aENEKAL THEKAPEUTICS AND MATEKIA MEDICA; adapted for a 
 
 Medical Text-book. With Indexes of Remedies and of Diseases and their Remedies. Sixth 
 Edition, revised and improved. -With one hundred and ninety-three illustrations. In two large 
 and handsomely printed ottavo vols., extra cloth, of about 1100 J>ages. $6 50. 
 
 In announcing a new edition of Dr. Dungliaon's 
 general Therapeutics and Materia Medica, weiiave 
 no words of commendation to bestow upon a w^ork 
 whose merits have been heretofore so often and so 
 justly extolled. It must not be supposed, however, 
 that the present is a mere reprint of the previous 
 edition: the character of the author for laborious 
 researciL, judicious analysis, and clearness of ex- 
 pression, is fully sustained by the numerous addi- 
 tions he has made to the work, and the careful re- 
 vision to which he has subjected the whole.— Jf. A. 
 Medieo-Chir. Revievf, Jan. 1858. 
 
 The work will, we have little doubt, be bought 
 and read by the majority of medical studentsj its 
 size, arrangement, and reliability recommend it to 
 all; no one, we venture to predict, will study it 
 without profit, and there are few to whom it, will 
 not be in sume measure useful as a work of refer- 
 ence. The youn^practitioner, more eBpeciall}^, will 
 find the copious indexes appended to this ediiion of 
 great assistance in the selection and preparation of 
 suitable formulae. — Charleston Med. Journ. and Rs' 
 view. Jan. 1858. 
 
 BT THE SAME AUTHOR- 
 
 NEW REMEDIES, WITH FORMULA FOR THEIR PREPARATION AND 
 
 ADMINISTRATION. Seventh edition, with extensive Additions. In one very large octavo 
 volume, extra cloth, of 770 pages. $4 OO. 
 
 One of the most useful of the author's works.— 
 Southern Medical and Surgical Journal. 
 
 This elaborate and useful volume should be 
 found in every medical library, for as a book of re- 
 ference, for physicians, it is unsurpassed by any 
 other work in existence, and the double index for 
 diseases and for remedies, will be found greatly to 
 anhance its value. — New York Med. Gaxetu, 
 
 The great learning of the author, and his remark- 
 able industry in pushing his researches into every 
 suurce whence information is derivable, have enabled 
 him to throw together an extensive mass of facts 
 and /statements, accompanied by full reference to 
 authorities; which last feature renders the work 
 practically valuable to investigators who desire to 
 examine the original papers.— 'iZ'As Afnerican Journal 
 of Pharmacy. 
 
 ELLIS (BENJAMIN), M.D. 
 THE MEDICAL FORMULARY: being a Collection of Prescriptions; derived 
 
 from the writings and practice of many of the most eminent physicians of America and Europe. 
 Together with me usual Dietetic Preparations and Antidotes for Poisons. To which is added 
 an Appendix, on the Endermic use of Medicines, and on the use of Ether and Chloroform. The 
 whole accompanied with a few brief Pharmaceutic and Medical Obseryations. Eleventh edition, 
 carefully revised and much extended by Robert P. Thomas, M. D., Professor of Materia Me- 
 dica in the Philadelphia College of Pharmacy. In one volume, Svo., of about350 pages. $3 00. 
 (Jtist Isstted.) 
 
 On no previous edition of this work has there been so complete and thorough a revision. The 
 extensive changes in the new United States Pharmacopceia have necessitated corresponding alter- 
 ations m the Formulary, to conform to that national standard, while the progress made in the 
 materia medica and the arts of prescribing and dispensing during the last ten years have been care- 
 fully noted and incorporated throughout. It is therefore presented as not only worthy a continuance 
 of the favor so long enjoyed, but as more valuable than ever to the practitioner and pharmaceutist. 
 Those who possess previous editions will find the additional matter of sufficient importance to 
 warrant their adding the present to their libraries. 
 
14 
 
 HENRY C. LEA'S MEDICAL, 
 
 ERICHSEN (JOHN), 
 ProfesBor of Surgery in University College, London, *e. 
 
 THE SCIENCE AND ART OF SURGERY; being a Trbatisb on Surgioah 
 
 Injuries, Diseases, and Operations. New and improved American, from the second enlarged 
 
 and carefully revised London edition. Illustrated with over fojir hundred engravings on wood. 
 
 In one large and handsome octavo volume, of one thousand closely printed pages, extra cloth, 
 
 $6 CO. 
 
 The very distingudshed favor with which this work has been received on both sides of the Atlan- 
 tic has stimulated the author to render, it even more worthy of the position which it has so rapidly 
 attained as a standard authority. Every portion has been carefully revised, numerous additions 
 have been made, and the most watchful care has been exercised to render it a complete exponent 
 of the most advanced condition of surgical science. In this manner the work has been enlarged by 
 about a hundred pages, whilie the series of engravings has been increased by more than a hundred, 
 rendering it one of the most thoroughly illustrated volumes before the profession. The additions of 
 the author having rendered unnecessary most of the notes of the former American editor, but little 
 has been added in this country ; some few notes and occasional illustrations have, however, been 
 introduced to elucidate American modes of practice. 
 
 It is, in our humble jndgment. decidedly the best 
 book of the kind in the English'language. Strange 
 that just such books are notoftener produced by pub- 
 lic teachers of surg:ery in this country and Great 
 Britain, Indeed, it is a matter of great astonishment 
 but no less true than astonishing, that of the many 
 works on surgery republished in this country within 
 the last fifteen or' twenty years as text-books for 
 medical students, thisis the only one that even ap- 
 proximates to ihe fulfilment of the peculiar wants of 
 youngmen just enteringupon the study ofthisbranch 
 of the profession. — WesumJour.ofMtd. and Surgery. 
 
 Its value is greatly enhanced by a very copious 
 well-arranged index. We regard this as one of the 
 most valuable contributions to modern surgery. To 
 one entering his novitiate of practice, we regard it 
 the most serviceable guide which he can consult. He 
 will find a fulness of detailleadinff him throLgh everv 
 step of the operation, and not deserting him until the 
 final issue of the case is decided. — Sedwscope. 
 
 Embracing, as will be perceived, the whole snrgi 
 cal domain, and each division of itself almost com 
 plete and perfect, each chapterfull and explicit, eacl 
 subject faithfully exhibited, we can only express ou 
 estimate of it iJt the aggregate. We consider it ai 
 
 excellent contribution to surgery, as probably the 
 best single volume now extant' on the subject, and 
 with great pleasure we add it to our text-booEs.— 
 if ashmUe Journal of Medicine and Surgery. 
 
 Prof Eriohsen's work, for its size, has not been 
 surpassed; his nine hundred and eight pages, pro- 
 fusely illustrated, are rich in physiological, patholo- 
 gical, and operative suggestions, doctrines, details, 
 and processes ; and will prove a reliable resourcs 
 for information, both to physician and surgeon, in the 
 hour of peril. — N. O. Med. and Surg;. Journal. 
 
 We may say, after a careful perusal of some of 
 the chapters, snd a more hasty examination uf the 
 remainder, that it must raise the character of the 
 author, and reflect gre^t credit upon the college to 
 which he is professor, and we can cordially recom- 
 mend it as a work of reference beta to students 
 and p'acti tinners. — Med. Times and Gazette. 
 
 We do not hesitatS to say that the volume before 
 us gives a veiy (Admirable practical view of the sci- 
 ence and art ot Surgery Of the present day, and we 
 have no doubt that it will be highly valued as a 
 surgical guide as well by the surgeon. as bv the 
 student of surgery. — Edinburgh Med, and Swg. 
 Journal. 
 
 FISKE FUND PRIZE ESSAYS. — THE EF- 
 FECTS OF CLIMATE ON TUBERCULOUS 
 DISEASE. By Edwin Lee, M.R.C.S , London, 
 and THE INFLUENCE OF PREGNANCY ON 
 THE DEVELOPMENT OF TUBERCLES By 
 
 Edwam Wabrbh, M. D., of Edenton,N. C. To- 
 gether in one neat 8vo. volume^ extracloth. SI 00, 
 FRICK ON RENALAFFECTJON?; their Diag- 
 nosis and Pathology. With illustrations. Qua 
 volume, royal 12mo., extra cloth, 75 cents. 
 
 FERGUSSON (WILLIAM), F. R. S., 
 
 Professor of Surgery in King's College, London, &c. ' 
 
 A SYSTEM OF PRACTICAL SURGERY. Fourth American, from the third 
 
 and enlarged London edition. In one large and beautifully printed octavo volume, of about 700 
 pages, with 393 handsome illustrations, leather. $4 CO. 
 
 FOWNES (GEORGE), PH. D., &c. 
 A MANUAL OF ELEMENTARY CHEMISTRY; Theoretical and Practical. 
 
 With one hundred and ninety-seven illustrations. Edited by Robert Bridges, M. D. In one 
 
 large royal ISmo. volume, of 600 pages, extra cloth, $2 00. 
 ' The death of the Aithor having placed the editorial care of this work in the practised hands of 
 Drs. Bence Jones and A. W. Hoffman, everything has been done in its revision which experience 
 could suggfest to keep it on a level with the rapid advance of chemical science. The additions 
 requisite to this purpose have necesi-itated an enlargement of the page, notwithstanding which the 
 work has been increased by about fifty pages. At the same time every care has been used to 
 maintain its distinctive character as a condensed manual for the student, diyested of all unnecessary 
 detail or mere theoretical speculation. The additions have, of course, been mainly jn the depart- 
 ment of Organic Cheniistry, which has made such rapid progress within the last few years, but 
 yet equal attention has been bestowed on the other branct(es of the subject— Chemical Physics and 
 Inorganic Chemistry— to present all investigations and discoveries of importance^ and to keep up 
 the reputation of the volume as a complete manual of the whole science, admirably adapted for the 
 learner. Bytheuse of a small but exceedingly cjear type the matter of a large octavo is coihpreSsed 
 within the convenient and poi^table limits of a moderate sized duodecimo, and' at the very low price 
 affixed, it is offered as one of the cheapest volumes before the profession. 
 
 The work of Dr 
 
 Dr. Fownes' excellent work'has been universally 
 recognized everywhere in Jiis own and this country, 
 as the best elementary treatise on chemistry in the 
 English topgu^, and is yery generally adopted, we 
 believe, as the standard text- book in all i ur colleges, 
 both literary and scientific .^Charleston Meet. Joum. 
 and Review 
 
 Fownes has long been before 
 the public, and its merits have been fully appreci- 
 ated as the ,beat text-bqok on chemistry now ia 
 existence. We do. not, of course, place it in a rank 
 superior to the works of Brande, Graham, Turner, 
 Gregory, or Gmelin, but we say that, as a work 
 for students, it is preferable to any of them.— ioi» 
 don Journal of U:ediei»t, 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 15 
 
 FLINT (AUSTIN), M, D., 
 
 Professor of the Principles and Practice of Medicine in Bellevae Hosp. Med. College, New Yorlt. 
 
 Now Aeady, 1866. 
 
 THE PRINCIPLES AND PRACTICE OP MEDICINE. For the use of 
 
 , Practitioners aad Students. In one large and handsome octavo volqme of over 850 closely 
 
 printed pages, leather, raised bands, $7 ; handsome extra cloih, $6. 
 
 The want has for some time been felt in this country of a volume' Jvhich, Within a moderate 
 coinpas's, should give a clear and connected view of general and special pathology and therapeutics 
 m their most modern aspect. Re Bent researches have modified many opinions which were formerly 
 universally received on important points both of theory and practice, and these changes have per- 
 haps as yet scarcely received the attention due to' them in the works accessible to the,profefsioh. 
 1 he author s reputation as a teacher is a guarantee that the present volumfe will be fully up to the 
 most advanced state of the science of the day, while his long and varied experience as a practi- 
 tioner will insure that m all practical details his work will be a sound and trustworthy guide. 
 
 BY THE SAME AUTHOB. (Preparing.) 
 
 PHYSICAL EXPLORATION AND DIAGNOSIS OP t)ISBASES APPEOT- 
 
 ING THE RESPIRATORY ORGANS. Second edition. In one large and handsome octavo 
 volume, extia cloth. 
 
 BY THE SAME AUTHOE. 
 
 A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND 
 
 TREATMENT Of- DISEASES OF THE HEART. In one neat octavo volume, of about 
 500 pages, extra oloth.. $3 50. 
 
 We do not know that Dr. Flint has written any- 
 thing which is not first rate; but this, his latest con- 
 tribution to medical literature, in our opinion, sur- 
 passes all the others. The work is most comprehen- 
 sive in its scope, and most sound in the views it enun- 
 ciat£B. The descriptions are clear and methodical ; 
 the statements are substantiated by facts, and are 
 
 made with s4ch simplicity and slhoisrity, that with- 
 out them they would 6arry conviction. The styl^ 
 is admirably clear, direct, and free from dryness. 
 With Dr. Wai^he's excellent treatise before us, we 
 have no hesitation in saying that Dr. Flint's book is 
 the best work on the heart in the English language'. 
 — Boston Med. and Surg. Journal. 
 
 GRAHAM (THOMAS), F. R. S. 
 THE ELEMENTS OP INORGANIC CHEMISTRY, including the Applioar 
 
 tions of the Science in the Arts. New and much enlarged edition, by Henry Watts and Robekt 
 Beidses, M. D. Complete in one large and handsome octavo volume, ol over 800 very large 
 pages, with two hundred and thirty-two wood-cuts, extra cloth. $5 50. 
 »*^ Part II., completing the work from p. 431 to end, with Index, Title Matter, &o., may be 
 had separate, cloth backs and paper sides. Price $3 00. 
 
 From Prof. E. N. Horsfordi Harvard College. 
 
 It has, in its earlier and less perfecteditions, been 
 familiar to me, and the excellence of its plan and 
 the clearness and completeness of its discussions, 
 have long been my admiration. 
 
 No reader of English works on this science can 
 
 afford to be without this edition of Prof. Graham's 
 Elements.^ — Silliman's JournaJ, March, 1858. 
 From Prof. Wolcott Gibhs, N. Y. Free Academy 
 The work is an admirable one in all respects, and 
 its republication here cannot fail to exert a positive 
 influence,upon theprogrcss of science in this country. 
 
 GRIFFITH (ROBERT E,), M. D., tc. 
 A UNIViERSAL FORMULARY, containing the methods of Preparing and Ad- 
 
 ministering Officinal and other Medicines. The whole adapted to Physicians and Pharmaceu- 
 tists. Second Edition, thoroughly revised, with numerous additions, by Robert P. Thomas, 
 M. D., Professor of Materia Medioa in the Philadelphia College of Pharmacy. In one large and 
 handsome octavo volume, extra cloth, of 650 pages, double columns. $4 00. 
 It' was a work requiring much perseverance, and 
 
 when published was looked upon as by far the best 
 
 work of its kind that had issued from the Americaii 
 
 press. Prof Thomas has certainly "improved," as 
 
 well as added to this Formulary, and has rendered jj 
 
 additionally deserving of the confidence of pharma- 
 ceutists and physicians. — Jyn. Joumalof Pharmacy . 
 
 We are happy to announce a new and improved 
 edition of this, one of the most valuable and usefal 
 works that have emanated from an American pen. 
 It would do credit to any country, and will be found 
 of daily usefulness to practitioners of medlcme; it is 
 better adapted to their purposes than the dispensato- 
 ries.— So«<t«rn Med, and Surg. Journal. 
 
 Itisoneofthe most useful books a country practi. 
 tioner can possibly have, — Medical Chronicle. 
 
 This is a work of six hundred and fifty- one pages 
 embracing all on the subject of preparing and adihi- 
 uiBterine medicines that can be desired by the physi 
 cian and pharmaceutist.— Western Lancet. 
 
 The amountof useful, every-day matter, for a prac 
 ticing physician, is really immense.— Bmiom Med 
 and Surg. Journal. 
 
 This edition has been greatly improved by the re- 
 
 vision and ample additions of Dr. Thomas, and is 
 now, we believe, one of the most complete works 
 of its kind in any language. The addition^ amount 
 to aboutseventy pages, and no elForl has been spared 
 to include in them all the recent improvements. A 
 work of this kind appears to us indispensable to the 
 physician, and there is none we can more cordially 
 recommend — -iV. Y. Journal of Medicine. 
 
 Pre-eminent among the best and most useful -com- 
 pilations of the present day will bd found the work 
 before us, which can have been produced only at a 
 very great cost of thought and labor. A short de- 
 scription will suffice to show that we do not put too 
 high an estimate on this work We are not cogni- 
 zant of the existence of a parallel work. Its value 
 wjiil be apparent lo our readers from tne sketch of 
 its contents above given. We strongly recommend 
 it to all who are engaged either in practical medi- 
 cine, or more excl asively with its literature.- Lwid. 
 Med. Gazette. 
 
 A very useful work, and a most complete compen- 
 dium on the subject of materia medica. We know 
 of no work in our language, or any other, so com- 
 prehensive in all its details. — London Lancet, 
 
16 
 
 HENRY 0. LEA'S MEDICAL 
 
 GROSS (SAMUEL D.), M. D., 
 
 Professor of Surgery in the Jefferson Medical College of Philadelphia, &c. 
 
 Enlarged Edition. Now Beady. 
 
 A SYSTEM OF SUKGEE.Y : Pathological, Diagnostic, Therapeutio, and Opera- 
 tive. Illustrated by over Thirtebm Hundred Engravings. Third edition, much enlarged and 
 carefully revised. In two large and beautifully printed royal octavo volumes, of 2200 pages; 
 leather. $15 00. (Justlsstied.) 
 
 The exhaustion within five years of two large editions of so elaborate and comprehensive 
 a work as this is the best evidence that the author wap not mistaken in his estimate of the 
 want which existed of a complete Americ^in System of Surgerjr, presenting the science in all its 
 necessary details and in all its branches, Thai he has succeeded in the attempt to supply this want 
 is shown not only by the rapid sale of the work, but also by the very favorable manner in which it 
 has been received by the organs of the profession in this country and in Europe, and by the fact that 
 a translation is now preparing in Holland — a mark of appreciation not often bestowed on any scien- 
 tific work so extended in size. 
 
 The author has not been insensible to the kindness thus bestowed upon his labors, and in revising 
 the work for a third edition he has spared no pains to render it worthy of the favor with which it 
 has been received. Every portion has been subjected to close examination and revision ; any defi- 
 ciencies apparent have been supplied, and the results of recent progress in the science and artol 
 surgery haVe been everywhere introduced ; while the series of illustrations has been still further 
 enlarged, rendering it one of the most thoroughly illustrated works ever laid before the profession. 
 To accommodate tliepe very extensive additions, the form of the work has been altered to a royal 
 octavo, so that notwithstanding the increase in the mattei and value of the book, its size wi 1 be found 
 more convenient than before. Every care has been taken in the printing to render the typographical 
 ' execution unexceptionable, and it is confidently expected to prove a work in every way worthy oi 
 a place in even the most limited library ofXhe practitioner or student. 
 
 Has Dr. Gross satisfactorily fulfilled this object? 
 A careful perusal of his volumes enables us to ^ive 
 an answer in the affirma tive. Not only has he given 
 to the reader an elaborate and well-written account 
 of his onrn vast experience, but he has not failed to 
 embody in his pages the opinions and practice of 
 surgeons in this and other countries of Europe. The 
 result has been a work of such complrteness, that it 
 has no superior in the systematic treatises on sur- 
 gery which have emanated from English or Conti- 
 nental authors. It has been justly objected that 
 these have been far from coinplete in many essential 
 particulars, many of them having^ been deficiencln 
 some of the mosl important points which should 
 characterize such works Some of them have been 
 elaborate — too elnborate— with respect to certain 
 diseases, while they have merely glanced at, or 
 given an unsatisfactory account of. Others equally 
 important to the surgeon. Dr. Grass has avoided 
 this error; and has produced the most complete work 
 that has yet issued from the press on the science and 
 practice of surgery. It la not, strictlyspeaking, a 
 Dictionary of Surgery, but itgives to the reader all 
 the information that he ma^ require for his treatment 
 of surgical diseases. Having said so much, it might 
 appear superfluous to add another word; but it is 
 only due to Dr. Gross to state that he has embraced 
 the opportunity of transferring to his pages a vast 
 number of engravings from English and othet au- 
 thors, illustrative of the pathology and treatment of 
 surgical diseases. To these are added several hun- 
 dred original Wood-cuts. The work altogether com- 
 mends itself to the attention of British surgeons, 
 from whom it cannot fail to meet with extensive 
 patronage. — London Lancetj Sept. 1, I860,. ~ 
 
 Of Dr. Gross's treatise^ on Surgery we can say 
 no more than that it is the most elaborate and com- 
 
 glete work on this branch of the healing art which 
 as ever been published in any country. A sys- 
 tematic work, it admits of no analytical review; 
 but, did our space permit, we should gladly give 
 some extracts from it, 1o enable our readers to judge 
 of the classical style of the-authoT,,and the exhau st- 
 ing way in which each subject is treated. — Dublin 
 Quarterlif Journal of Med. Science. 
 
 The work is so superior tO" its predecessors in 
 matter and extent, as well as in illustrations and 
 style of publication, that we can honestly recom- 
 mend it as the best work of the kind to be taken 
 home by the young practitioner — Atn. Med. Jolim. 
 With pleasure we record the completion of this 
 long-anticips ted work. The reputatlyn which the 
 author has for many years sustained, both as a sur- 
 geon and as:a writer, had prepared us to expect a 
 treatise of great exceUeuceand originality; but we 
 
 confess we were by no means prepared for the work 
 which is before us — the most complete treatise upon 
 surgery ever published, either in this or any ottitr 
 country, and we might, perhaps, safely say, the 
 most original. There is no subject belonging pro- 
 perly to surgery which has aot received from the 
 authoTadueshare of attention. Dr. Grots has sap- 
 plied a want in surgical literature which has long 
 been felt by practitioners; he has furnished us with 
 a complete practical treatise upon surgery in all its 
 departments As Anriericins, we are proud of the 
 achievement J as surgeons, we are most sincerely 
 thankful to him for his extraordinary labors in our 
 behalf. — JV. Y. Review and Buffalo Med. Journal. 
 The great merit of the work may be stated as 
 follows. It presents surgical science as it exists 
 at the latest date, with all its improvements ; and 
 it discusses every topic in dae proportion. No- 
 thing is omitted, nothing is in excess— CAfcogo 
 Med. Examiner^ Mnyy 1860. 
 
 We cannot close this brief notice of Dr. Gross's 
 most valuable and excellent compendium of Sur- 
 gery without again drawing attention to it, as we 
 did in. our notice of his first edition, as an evidence 
 of the pi;ogres3 our American brethren are making 
 towards establishing a literature of their own.— 
 Dublin Quarterly Journal, Feb. 1863. 
 
 It has been characterized by the representative 
 press and by individual surgeons of the highest 
 eminence; both at home and abroad, as '■'■the hest 
 systemitie work on surgery ever published in the 
 English language ;*^ and that the profession at 
 large have given substantial proofs of their agree- 
 ment to ihis verdict, is sufficie,ncly evident from the 
 fact that translations into European languages have 
 been called for, and that ao shortly after its first 
 appearance, and at a time most nnfavorable to 
 literary "enterp^iEe;?' the Philadelphia puolishers 
 have found it pay to isBtie a '< second edition, much 
 enlarged and carefully revised." — American Med. 
 Monthly, May, 1962 
 
 We are niuch gratified to be able to announce a 
 new edition of this Cyclofpsedia of Surgtry. Con- 
 sidering the large size of the work and its expen- 
 siveness, the extremely rapid sale and exhaustion 
 of an entire edition, not only proves the value of 
 the work, and its adaptation to the wants of the 
 profession, but it speaks well for the inieliigence 
 of American surgeons. — American Medical Times, 
 May, 1862. 
 
 A valuable and even necessary, addition to every 
 surgical library. — Chicago Med. Joum., Dec. 1859. 
 A system of surgery which we think unrivalled 
 in our language.— iritis A American Journal. 
 
 BY THE SAME AUTHOR. 
 
 A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PA?- 
 SAGES. Inoneiiaiidsomeoctavo volume, extra clolh, with illustrations, pp. 468. (2 75. 
 
ANU SCIENTIFIC PU BL, (CATIONS, 
 
 17 
 
 GROSS (SAMUEL D.), M. D. 
 ProfcBsor of Surgery in the JefierBon Medical College of Philadelphia, &c. 
 
 ELEMENTS OF PATHOLOGICAL ANATOMY. Third edition, thoroughly 
 
 revised and greatly improved. In 6ne large and very handsome octavo volume, with about three 
 hundred and fifty beautiful illustrations, of whidh a large number are from original drawings, 
 extra cloth. f4 00. 
 
 The very rapid advances in the Science of Pathological Anatomy during the last few years have 
 rendered essential a thorough modification of this work, with a view of making it a correct expo- 
 nent of the present state of the subject. The very careful manner in which this task has been 
 executed, and the amount of alteration which it has undergone, have enabled the author to say that 
 " with the many changes and improvements now introduced, the work may be regarded almost as 
 a new treatise," while the efforts of the author have been seconded as regards the mechanical 
 execution of the volume, rendering it one of the handsomest productions of the American press. 
 
 BY THE SAME AUTHOR. 
 
 A PBACTICAL TREATISE ON THE DISEASES, INJURIES, AND 
 
 MALFORMATIONS OF THE UBINARY BLADDER, THE PROSTATE GLAND, AND 
 THE URETHRA. Second Edition, revised and much enlarged, with one hundred and eighty- 
 four illustrations. In one large and very handsome octavo volume, of over nine hundred pages, 
 extra cloth, $4 00. 
 
 Philosophical in ite design, methodical in its ar- 
 rangement, ample and sound in its practical details, 
 it may in truth be said to leave scarcely anything to 
 
 be desired on so important a subject Boston Med. 
 
 mnd Surg Jourttal. 
 
 Whoever will peruse the vast amount of valuable 
 practical information it contains, will, we think, 
 
 agree with us, that there is no work in the English 
 language which can make any just pretensions to 
 be its equal. — TV. Y. Journal ofM&diaint- 
 
 A volume replete with truths and principles of thtt 
 atmost value in the investigation of these diseases.— 
 American Medical Journal. 
 
 GRAY (HENRY), F. R. S., 
 Lecturer on Anatomy at St. George's Hospital, London, &c. 
 
 ANATOMY, DESCRIPTIVE AND SURGICAL. The Drawings by H.: V. 
 
 ,;,vGarter, M. i3.,late De.monstrator on Anatomy at St. George's Hospital; tfie Dissefltfions jointly 
 oy the Author and Dr. Carter. Second American, from the second revised arid improved 
 London edition. In one magnificent imperial octavo volume, of over 800 pages, with 388 large 
 and elaborate engravings on "wood. Price in extra cloth, $6 00; leather, raised bands, $7 00^ 
 The speedy exhaustion of a large, edition of this work is sufficient evidence that its plan and exe- 
 cution have been found to present superior practical advantages in facilitating the study of Anato- 
 my In, presentmg it to the profession a second time, the author has availed himself of the oppor- 
 tunity to supply any deiieiencies which experience in -its use had shown to exist, and to correct 
 any errors of delail, to which the first ediiion of a scientific work on so extensive and complicated 
 a science is liable. These improvements have resulted in son^e increase in the size of the volunie, 
 while twenty-six new wood-cuts have been added to the beautiful series of illustrations which 
 form so distinctive a feature of the work. The American edition has been passed through the press 
 under the supervision of a competent professional man, who has taken every care to render it in 
 all respects accurate, and it is now presented, without any increase of price, as fitted to maintain 
 and extend the popularity which it has everywhere acquired. 
 
 With'little trouble, the busy practitioner whose 
 knowledge of anatomy may have become obscured by 
 want of practice, may now resuscitate his former 
 anatomical lore, and be ready for any emergency. 
 It is to this class of individuals, and not to the stu- 
 ' dent alone, that this work will ultimately tend to 
 beof mofit incalculable advantage, and we feel sat- 
 isfied that the library of the medical man will soon 
 be considered incomplete in which a copy of this 
 work does not exist.— Madras Quarterly Journal 
 of Med. Science, July, 1861. 
 
 This edition is much improved and enlarged, and 
 contains several new illustrations by Dr. Westrna- 
 cott. The volume is a complete companion to the 
 dissecting-room, and saves the necesBity of the stu 
 dent possessing a variety of" Manuals." — The Lon- 
 don Lancetj Feb. 9, 1861. 
 
 The work before us ib one entitled to the Jiighest 
 praise, and we accordingly Tvelcome it as a valu- 
 able addition to medical literature. Intermediate 
 in fulness of detail betweer the treatises of "Saar- 
 pey and of Wilson, its cha 'Ctcristic merit! lies in 
 tlie number and excellent,^ of the engravings it 
 contains. Most of these are original, of much 
 larger than ordinary size, and admirably executed. 
 The various parts are also lettered after the plan 
 adopted in Holden's Osteology. It would be diffi- 
 cult to over-estimate the advantages offered by this 
 mode of pietnrial illustration. Bones, ligaments, 
 muscles, hloodvessels, and nerves are each in turn 
 figured, and marked with their appropriate names ^ 
 thus enabi ing thestadent to ccmprehend, at a glance, 
 what would otherwise often be ignored, or at any 
 rate, acquired only by prolonged and irksome ap- 
 plication. In conclusion, we heartily commend the 
 
 work of Mr. Gray to the attention of the medical 
 profession, feeling certain tiijat it should be regarded 
 as one of the most valuable contributions ever made 
 to educational literature. — N, Y. Monthly RevUw.. 
 Dec. 1859, 
 
 In this view, we regard the work of Mr. Gray as 
 far better adapted to the wants of the profession, 
 and especially of the student, than any treatise on 
 inatomyyet published in this country. It is destined, 
 we believe, to supersede Ul oth^s, both as a manual 
 of dissections, and a standard of reference to the 
 student of general or relative anatomy. — N. Y, 
 Journal of Medicine^ Nov. 1859. 
 
 In our judgment, the mode of illustration adopted 
 in the present volume cannot but present many ad- 
 vantages to the studentof anatomy. To the zealous 
 disciple of Vesalius, earnestly desirous ofreal Im- 
 provement, the book w^ili certainly be of immense 
 value; but, at th&pame time, we must also confess 
 that tp those simply desiroi^s of "cramming" it 
 will be an undoubted godsend. The peculiar .value 
 of Mt. Gray's mode of illustration is nowhere more 
 markedly evident than in the chapter on osteology, 
 and especially in those portionswhich treat of the 
 bones of the head and of thsir development. The 
 study of these parts is thus made one of comparative 
 eiise, if not of positive pleasure; and those bugbears 
 of the student, the temporal and sphenoid bnhes, are 
 shorn of half their terrors. It is, in our estimation^ 
 an admirableand complete text- book for the student, 
 and a useful ^^ork of reference for the practitioner; 
 its pictorial character forming a novel element, to 
 
 which we have already sufficiently alluded. Am, 
 
 Joum. Med. Sci.j July, 1859. 
 
18 
 
 HENRy C. LEA'S MEDICAL 
 
 GIBSON'S INSTITUTES AND PRACTICE OF 
 SURGERY. Eighth edition, impvoved aild al- 
 tered. With thirty-fourplates. In two hand some 
 octavo volumes, containing about 1,000 pages, 
 leather, raised bandi. $6 50 
 
 GARDNER'S IttEDICAL CHEMISTRY, for the 
 use of Students and the Profession. ■ la one royal 
 lamo. vol., cloth, pp. 396, with wood-cuts. ©1. 
 
 GLUGE'S ATLAS OF PATHOLOGICAL HIS- 
 TOLOGY Translated, with Notes and Addi- 
 tions by Joseph Leidy, M, D, In one volume, 
 very large imperial quarto, extra cloth, with 320 
 C(^pper. plate Hgures, plain and colored, $4 00. 
 
 HUGHES' INTRODUCTION TO THE PRAC- 
 
 TICE OF AUSCULTATION AND OTHER 
 MODES OF PHYSICAL DIAGNOSIS. IN DIS- 
 EASES OF THE LUNGS AND HEART Se- 
 cond edition 1 vol, royal l*2mo., ax. cloth, pp. 
 304. 81 25. 
 
 HOLLAND'S MEDICAL NOTES AND RE- 
 FLECTIONS. From the third London edition. 
 In one handsome octavo volume, extra cloth, 
 83 50. 
 
 aORNER'S SPECIAL ANATOMY AND HIS- 
 TOLOGY. Eighth edition, Extensivily revised 
 a.nd modified. In two large octavo volumes, ex- 
 tra cloth, of more than 1000 pages, with over 300 
 illustrations, $6 00, 
 
 HILLIER (THOMAS), M. D., 
 
 Physician to the Skin Department of University College Hospital j Physician to the Hospital for Sick 
 
 Children, &c, &c, 
 
 HANDBOOK OF SKIN DTSEA.SES, FOR STUDENTS AND PRACTI- 
 
 TIONERS. In one neat royal 12mo, volume, of aSoiit 300 pages, with two plates ; extra cloth, 
 
 price $2 25. ' (Now Keidy ) 
 
 Fhom the Author's Preface, 
 
 " My object has been to fnrnish to students and praetilioners a trustworthy, practical, and com- 
 pendious treatise, which shall comprise the greater part of what has long been known of cutaneous 
 diseases, and of what has been more recently brought to light by English, French, and German 
 dermatologists, as well as to embody the most important results of my own experien ce in reference 
 to these diseases " 
 
 The author's position both as a lecturer, wr'ter, and practitioner in this department of medicine, 
 IS a guarantee of his ability to accomplish his object in presenting a condensed and conveniejit 
 manual, which shall comprise all that the general praclilioner requires for his guidance, 
 
 A text book well adapted to the student, and the information contained in it shows the author to be an 
 niveau with the scientific medicine of the day. — London Lancet^ Feb. 25, 1665. 
 
 HAMILTON (FRANK H.), M. D., 
 
 Professor of Surgery in the Long Island College Hospital, 
 
 A PRACTICAL ^TREATISE ON FRACTURE^ AND DISLOCATIONS. 
 
 Second edition, revised and improved. In one large and handsome octavo voluinej of over 750 
 
 pages, with nearly 300 illustrations, extra cloth, $5 25. 
 
 The early demand for a new edition of this work shows that it has been successful in securing 
 the confidence of the profession as a standard authority for consultation and reference on its import- 
 ant and difficult subject. ' In again passing it ihrougb the press, the author has taken the opportu- 
 nity to revise it carefully, and introduce whatever improvements have been suggested by further 
 experience arid observation An additional chapter on Gun-shot Fractures will te found to adapt 
 it still more fully to the exigencies of the time. 
 
 Among the many good workers at surgery of whoni 
 Amerifia may now boast r ot the leapt is Frank Hast- 
 ings Hamilton; and the volume before us is (we say 
 it with a pang of wounded patriotism) the best and 
 handiest book on the subject in the Ei^glish lan- 
 guage. It is in vain to attempt a review of it; 
 nearly as vain to seek for any sins, either of pom- 
 mission or omission. We have seen no work on 
 practical surgery which we Would sooner recgm- 
 mend to our orother surgeons, especially those of 
 *' the services," cr those whose practice lies in dis- 
 tricts where a man has necessarily to rely on his 
 own unaided resoarces. The practitioner will find 
 in It directions for nearly every possible accident, 
 easily found and compr-ehendecl ; and much pleasant 
 reading for him to muse over in the after coneidera- 
 tion of his cases. — Edinburgh Med. JouTn'^eh. 1^1. 
 
 This is a valuable contribution to the surgery of 
 most important affections, and is the more welcome, 
 inasmuch as at the present time we do not poBse&s 
 a single complete treatise on Fractures and Dislo- 
 cations In the English language. It has remained for 
 our American brother toproduee a complete treatise 
 upon the subject, and bring together in aconvenienti 
 form those alterations and improvements that have 
 been made from time to time in the treatment of these 
 
 a/fections. Qne great and valuable feature in the 
 work before us is the. fact that it comprises all the , 
 improvements introduced into the practice of both 
 English and American surgery, and though far from 
 omitting mention Of our continental neighbors, the 
 author by no means encourages the notion — but too 
 prevalent in some quarters— that nothing is good 
 unless imported from France or Germany. The 
 latter half of the work is devoted to the considera- 
 tion of the various dislocations and their appropri- 
 ate treatment, and its merit is fully equal to that of 
 the preceding portion. — The London Lancet, May 5, 
 1860. 
 
 It is emphatically the book upon the subjects of 
 which it treats, and we cannot doubt that it will 
 continue so to be for an indefinite period of time. 
 When w&aay, howeverj that we believe it will at 
 once take its place as thebest book for consultation 
 by the practitioner; and that it will form the most 
 complete, available, and reliable guide in emergen- 
 cies of every nature connected witn its subjects; and 
 also that the student of surgery may make it his text- 
 book with entire confidence, and with pleasiire also, 
 from its agreeable and easy style— we ' hink ou^ own 
 opinion may be gathered as to its value. i— Bos Wm 
 Medical and Svrgical Journal^ March 1, 1860. 
 
 HODGE (HUGH L.), M. D., 
 
 Professor of Midwifery aiid the Diseases of Women and Children in the University of Pennsylvania, &c, 
 
 ON DISEASES PECULIAR TO WOMEN, including Displacements of the 
 
 Uterus. With original illustrations. In one beautifully printed octavo volume, of nearly 500 
 pages, extra cloth. $3 75. 
 
 recur — these, taken in connection with the entire 
 competency of the author, to render a correct ac- 
 count of their nature, their causes^and th^ir appro- 
 priate management — his ample experience, his ma- 
 tured jiidgment, and his perfect conscientiousness— 
 
 Thiscontribution towards the elucidation of the 
 pathology and treatment of some of i^he diseases 
 peculiar to women, cannot fail to meet with a favor- 
 able reception from the medical profession. The 
 chara.eter of the partifular maladies of, which the 
 work before us treats; their frequency, variety, and 
 obscniity: the amountot malaiseand even of actual 
 suffering by which they are invariably attended; 
 their obstinacy, the difficulty with which they are 
 overcome, and their disposition again and again to 
 
 The illustrations, which are all original, are drawn to a uniform scale of one-half the natural size, 
 
 invest this publication with an interest and value to 
 which few of the medical treatises of a recent date 
 can lay a stronger, if, perchance, an equal claim.— 
 Am. Journ. Med. Sciences. Jan. 1861. 
 
AND SCIENTIFIC PUBLICATIONS. 19 
 
 HODGE (HUGH L.), M. D., 
 Late Professor of Midwifery, Ac, in the University of PennsylTania. 
 
 PRINCIPLES AND PRACTICE OF OBSTETRICS. In one large quarto 
 
 volume of orer 550 pages,with one hundred and fifiy-eight figures on thirty two beaulifuUy exe- 
 cuted liihographio plates, and numerous wood-cuts in the text. $14 00. (Just Issued.) 
 This work, embodying the results of an extensive practice for more than forty years, cannot fail 
 to prove of the utmost value to all who are engaged in this department of medicine. The author's 
 posiiioii as one of the highest authorities on the subject in this country is well known, and the fruit 
 oi his ripe experience and long observation, carefully matured and elaborated, must serve as an 
 "•>[?' "sble text-book for the student and an unfailing counsel for the practitioner in the emergencies 
 ^!U? *° frequently arise in obstetric practice. 
 
 The illustrations form a novel feature in the work. The lithographic plates are all original, 
 and to insure their absolute accuracy they, have all been copied from photographs taken expressly 
 for the purpose. In ordinary obstetrical plates, the positions of the foetus are represented by dia- 
 grams or sections of the patient, which are of course purely imaginary, and their correctness is 
 scarcely more than a matter of chance with the artist. Their beauty as pictures is thereby increased 
 without corresponding utility to the student, as in practice he must for the most part depend for his 
 diagnosis upon the relative positions of the foetal skull and the pelvic bones of the mother. It is, 
 therefore, desirable that the points upon which he is in future to rfely, should form the basis of his 
 instruction, and consequently in the preparation of these illustrations the skeleton has alone been 
 used, and the aid of photography Invoked, by which a series of representations has been secured of 
 Ijie strictest and most rigid accuracy. It is easy to recognize the value thus added to the very full 
 detai s on the. subject of the Mechanism of Labour with which the work abounds 
 
 it may be added that no pains or expense have been spared to render the mechanical execution oi 
 the volume worthy in every respect of the character and valuS of the teachings it contains. 
 
 HABERSHON (S. O.), M. D., 
 
 AesiBtant Physician to and Lecturer on Materia iVIedica and Therapeutics at Guy's Hospital, &c. 
 
 PATHOLOGICAL AND PKACTfCAL OBSERVATIONS ON DISEASES 
 
 OF THE ALIMENTARY CANAL, (ESOPHAGUS, STOMACH, C^CUM, AND INTES- 
 TINES. With illustrations on wood. In one handsoine octa\ro volume of 312 page», extra 
 cloth. $2 50. 
 
 HOBLYN (RICHARD D,), M. D. 
 A DICTIONARY OF THE TERMS USED. IN MEDICINE AND THE 
 
 COL LATERAL SCIENCES. A new American edition. Revised, with numerous Addftions, 
 by Isaac Hays, M. D., editor of the " American Journal of the Medical Sciences." In one large 
 royal l2mo. volume, cloth, of over 500 double columned pages. $1 50. 
 To both practitioner and student, we recommend 
 
 this dictionary as being convenient in size, accurate 
 
 in definition, and sufficiently full and complete for 
 
 ordinary conaultfLtion.— -Charleston Med. Joum, 
 
 We know of no dictionary better arranged and 
 adapted . 1 1 is not encumbered with the obsolete terms 
 of a bygone age, but it contains all that are now in 
 
 use ; embracing every department of medical sciencfl 
 down to the very latest date. — Western Lancet. 
 
 Hoblyn'B Dictionary has long been a favorite with 
 us. It la the best book of dennitions we have^ and 
 ought always to be ^upon the atudentU table.— 
 Southern Med. and Surg. Journal. 
 
 JONES (T. WHARTON), F. R, S., 
 
 Professor of Ophthalmic Medicine and Surgery in University College, London, &,a. 
 
 THE PRINCIPLES AND PRACTICE OP OPHTHALMIC MEDICINE 
 
 AND SURGERY. With one hundred and seventeen illustrations. Third and revised Ameri- 
 can, with additions from the second London edition. In one handsome octavo volume, extra 
 cloth, oi 4S5 pages. $3 '^5. 
 
 Seven years having elapsed since the appearance of the last edition of this standard work, very 
 considerable additions have been found necessary to adapt it thoroughly to the advance of ophthal- 
 mic sclencb The introduction of the ophthalmoscope has resulted in adding greatly to our know- 
 ledge of the pathology of the diseases of the eye, particularly of its more deeply seated tissues, and 
 corresponding improvements in medical treatment and operative procedures nave been introduced. 
 All these malters the editor has endeavoured to add, bearing in mind the character of the volume as a 
 condensed and practical manual. Toaccommodate this unavoidable increase in the size of the work, 
 its form has been changed from a duodecimo to an octavo, and it is presented as worthy a continu- 
 ance of the favour which has been bestowed on former editions. 
 
 A complete, series of " test-types" for examining the accommodating power of the eye, will be 
 found an important and useful addition. 
 
 JONES (C. HANDFIELD), J^. R. S., St EDWARD H. SIEVEKING, M.D., 
 
 Assistant Physicians and Lecturers in St. Mary's Hospital, London. 
 
 A MANUAL OF PATHOLOGICAL ANATOMY. First American Edition, 
 
 Revised. With three hundred and ninety-seven hand.some wood engravings. In one large and 
 beautiful octavo volume of nearly 750 pages, extra cloth. $3 50. 
 
 As a concise text-book, containinp:, in a condensed 
 form, a complete outline of what is known in the 
 domain of Pathological Anatomy, it is perhaps the 
 best work in the English languaia. Itsgreat merit 
 consists in its completeness and orevity^ and in this 
 respect it supplies a great desideratum in our lite- 
 rature. Heretofore the student of pathology was 
 
 obliged to glean from a great naraber of monographs, 
 and the field was so extensive that but few cnltivatea 
 it with any degree of success. As a simple work 
 of reference, therefore, it is of great value to the 
 student of pathological anatomy, and should be m 
 every physician's library .—W«jier«La»ci<. 
 
20 
 
 HENKy C. LEA'S MEDICAT. 
 
 KIRKES (WILLIAM SENHOUSE), M. D,, 
 
 Demonstrator of Morbid Anatomy at St, Bartholomew's Hospital, &.C. 
 
 A MANUAL OF PHYSIOLOGY. A new Amerixjan, from the third and 
 
 improved London edition. With two hundred illustrations. In one large and handsome royal 
 12moj volunrte, extra cloth, pp. 586. $2 25. a. 
 
 This ia a new and very much improved edition of 
 Dr. Klrkea' well-known Handbook of Physiology. 
 It combines conciseness with completeness, and is, 
 therefore, admirably adapted for consultation by thQ 
 busy practitioner. — Dublin Quarterly Journal . 
 
 One of the very best handbooks of Physiology wt 
 possess— presenting just such an outline of the sci- 
 ence as the student requires during his 'attendance. 
 upon a course of lectures, or for reference whilst 
 preparingfoT examination.— ^Im. Mtdical Journal 
 
 ' Its excellence is in its compactness, its clearness, 
 
 and its carefijlly c-itEsd authorities. It ia the most 
 convenient of text-books. These gentlemen, Messrs. 
 Kirkesand Paget, have the gift of telling us what 
 we want to know, without thinking ' it necessary 
 to tell us all they know*. — Boston Med and Surg. 
 Journal . 
 
 For the student beginning this study, and the 
 practitioner who has^ but leisure to refresh his 
 memoryj this book is invaluable, as it contains all 
 that it 'IS important to know. — Charleston iHirJ, 
 Journal 
 
 KN APP'S TECHNOLOGY ; or, Chemistry applied 
 t(i the Arts and to Manufactures. Edited by Dr. 
 Ronalds, Dr. Richardsom, and Prof. W. R. 
 JoHNson. In tw,o handsome 8vo. vols. , extra cloth, 
 with about 500 wood engravings. $6 00. 
 
 LAYCOCK'S LECTURES ON THE PRINCI- 
 PLES AND METHODS OF MEDICAL OB- 
 SERVATION AND RESEARCH. For the Use 
 of Advanced Students and Junior Practitioners. 
 In one royal 12mo. volume, extra cloth. PriceSl. 
 
 LALLEMAND AND WILSON, 
 
 A PKAGTICAL TREATISE ON THE CAUSES, SYMPTOMS, AND 
 
 TREATMENT OF SPERMATORRHCEA. By M. Lallbmand. Translated and edited by 
 
 Hknry J McDouGALL. Third American edition. To which is added ON DISEASES 
 
 OF THE VESICUL^ SEMINALES; and their associated organs. With special refer- 
 ence to the Morbid Secretions of the Prostatic and Urethral Mucous Membrane. By Marris 
 Wilson, M. D. In one neat octavo volume, of about 400 pp., extra cloth. $2 75. 
 
 LA ROCHE (R.), M. D., &c. 
 
 YELLOW FEVEE, considered in its Historical, Pathological, Etiological, and 
 Therapeutical Relations. Including a Sketch of the Disease as it has occurred in Philadelphia 
 from 1699 to 1854, with an examination of the connections between it and the fevers known under 
 the same name in other parts of temperate as well as in tropical regions. In two larg:e and 
 handsome octavo volumes of nearly 1500 pages, extra cloth. $7 00. 
 We have not time at present, engaged as we are, 
 
 by da^y and by night, in the work of combating this 
 
 very disease, now prevailing in oui city, to do more 
 
 than give this cursory notice of what we consider 
 as undoubtedly the most able and erudite medical 
 publication our country has yet produced But in 
 view of the startlinf; fact, that this, the most malig- 
 nant and unmanageable disease of modern timesj 
 has for several year^ been prevailing in our country 
 to a greater extent than ever before; that it<is no 
 
 longer confined to either large or small cltieii, but 
 penetrates country villages^ plantations, and farm- 
 bouses; that it ia treatea with scarcely better suc- 
 cess now than thirty or forty years ago ; that there 
 is vast mischief done by ignorant pretenders to know- 
 ledge in regard to the disease, and in view of the pro- 
 bability that a majority of southern physicians will 
 be called upon to treat the disease, we trust that this 
 able and comprehensive treatise will be very gene- 
 rally read m the Bouth.. -^Memphis Med. Recorder. 
 
 BY THE same author. 
 
 PNEUMONIA ; its Supposed Connection, Pathological and Etiological, with Au- 
 tumnal Fevers, including an Inquiry into the Existence and Morbid Agency of Malaria. In one 
 handsome octavo volume, extra cloth, of 500 pages. $3 00., 
 
 LEHMANN (C. GJ 
 
 PHYSIOLOaiCAL CHEMISTRY. Translated from the second edition by 
 
 George E. Day, M. D., F. R. S., &c., edited by R. E. Rogers, M. D., Professor of Chemistry 
 in the Medical Department of the University of Pennsylvania, with illustrations selected from 
 Funke's Atlas of Physiological Chemistry, and an Appendix of plates. Complete in two large 
 and handsome octavo Volumes, extra cloth, containing 1200 pages, with nearly two hundred illus- 
 trations. $6 00. . . 
 The work of Lehmann stands unrivalled as the 
 
 The most important contribution as yet made to 
 Physiological) ChemiBtry. — Am. Journal M^d. Sci' 
 cnces, Jan. 18S6. 
 
 most comprehenfiivg book of reference and informa- 
 tion extant onevery branch of the subject on which 
 it treats. — Edinburgh J ournal of Medical Science. 
 
 BY THE SAME AUTHOR. 
 
 MANUAL OF CHEMICAL PHYSIOLOGY. Translated from the German, 
 
 with Notes and Additions, by J. Cheston Mqkkis, M. D., with an Introductory Essay on Vital 
 Force, by Professor Samuel Jackson, M. D., of the University of Pennsylvania. With illus- 
 trations on wood. In one very handsome octavo volume, e;Etra cloth, of 336 pages. J2 25. 
 
 LUDLOW (J. L.), M. O. 
 A MANUAL OF EXAMINATIONS upon Anatomy, Physiology, Surgery, 
 
 Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy, and Therapeutics. To 
 which is added a Medical Formulary. Third edition, thoroughly , revised and greatly extended 
 and enlarged. With 370 illustrations. In one handsome royal 12mo. volume, oi 816 large 
 pages, extra cloth, $3 25, 
 We know of no better cumpahion for the student I crammed into hie head by the various professore to 
 
 during the hours spent in the lecture room, or to re- whom he is compelled to listen. — WesUm Lanal, 
 
 fresh, at a^lance, his meitiory of the various topics | May, 18S7. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 21 
 
 LYONS (ROBERT D.), K. C. C, 
 
 Late Pathologist in-chief to theBiitieh Array in the Crimea, tee. 
 
 A TREATISE ON. FEVER; or, selections from a course of Lectures on Fever. 
 Being part of a course of Theory and Practice of Medicine. In one neat octavo volume, of 362 
 pages, extra cloth ; S2 25. (Just Issued.) 
 v^'''''°^''?^.">'''a'>'ework upon the most remark. 
 
 ^„nS "">«', .>niPortanl; class of diseases to which 
 
 May! 1861!" '''"'*— -M^"*- ■^»«™- »/ ^- Carolina 
 
 We have great pleasure in recommending Dr. 
 
 Lyons' work on Fever to the attention of the pro- 
 fession. It is a work which cannot fail to enhance 
 the author's previous well-earned reputation, as a 
 diligent, careful, and accurate observer. — British, 
 Mea. Journal, March 2, 1861. 
 
 MONTGOMERY (W. F.), M. D., M. R. I. A., «tc., 
 
 Professor of Midwifery in the King and Queen's College of Physicians in Ireland, to. 
 
 AN EXPOSITION OF THE SIGNS A.ND SYMPTOMS OF PREGNANCY. 
 
 With some other Papers on Subjects connected with Midwifery. From the second and enlarged 
 English edition. With two exquisite colored plates, ai)d numerous wood-cuts. In one very 
 handsome octavo volume, extra cloth, of nearly 600 pages, f 3 75. 
 
 A book unusually rich in practical SUggestiong.— 
 Am Journal Med. Sciences, Jan. 1857. 
 
 These several subjects so interesting in them- 
 selves, and so important, every one of them, to the 
 most delicate aild precious of social relations, con- 
 trolling often the honor and domestic peace of a 
 family, the legitimacy of offspring, or the life of its 
 parent, are all treated with an elegance of diction, 
 fulness of illustrations, acuteness and justice of rea- 
 soning, unparalleled in obstetrics, and unsurpassed in 
 medicine. The reader's interest can never flag, so 
 
 fresh, and vigorous, and classical is our author's 
 style J and one forgets, in the renewed charm of 
 ■-Very page, that it, and every line, and every word 
 has been weighed and reweighed through years of 
 p'reparation ; that this is uf all others the book of 
 Obstetric Law, on each of its several topics ; on all 
 points connected with pregn;incy, to be everywhere 
 received as a manual of special jurisprudence^ at 
 once announcing fact, affordingiaTgument, establish- 
 ing precedent, and governing alike the juryman, ad- 
 vocate, and judge — N. A. Sied.-Chir. Revieip. 
 
 MEIGSiCHARLES D.), M. D., 
 
 Lately Professor of Obstetrics, &c. in the Jefferson Medical College, Philadelphia. 
 
 OBSTETRICS : THE SCIENCE AND THE ART. Fourth edition, revised 
 
 and improved. With one hundred and twenty-nine illustrations. In one beautifully printed octav* 
 volume, of seven hundred and thirty latge pages, extra cloth, $500. 
 
 Fkom the Author's Peepace. 
 
 " (n this edition I have endeavored to amend the wort by changes in its form ; by careful cor- 
 rections of many expressions, and by a few omissions and some additions as to the text. 
 
 "The Student will find that I have repast the article on Placenta Prsevia, which I was led to do 
 out of my desire to notice certain hew modes of treatment which I regarded as not only ill founded 
 as to the philosophy of our department, but dangerous to ihe people. 
 
 " In changing the form of my work by dividing it into paragraphs or sections, numbered from 1 
 to 959, 1 thought to present to the reader a oommon-plnoe book of the whole volume Such a table 
 of contents ought to pnove both convenient and useful to a Student while attending public lectures." 
 
 A work which hat enjoyed so extensive a reputation and has been received with such general 
 favor, requires only the assurance that the author has labored assiduously to embody in his new 
 edition whatever has been found necessary to render it fully on a level with the moat advanced 
 slate of the subject. Both as a text-book for the student and as a reliable work of reference for 
 the practitioner, it is therefore to be hoped that the volume will be found worthy a continuance 0/ 
 the confidence reposed in previous editions. 
 
 BY THE SAME ATXTHOR. 
 
 WOMAN : HER DISEASES AND THEIR REMEDIES. A Series of Lee 
 
 tares to his Class. Fourth and Improved edition. In one large and beautifully printed octave 
 
 volume, extra cloth, of over 700 pages. 55 00. 
 
 which cannot fail to recommend the volume to the 
 attention of the reader. — Ranking's Abstract. 
 
 In other respects, in our estimation, too much can- 
 not be said in praise of this work. It abounds with 
 beautiful passages, and for conciseness, for origin- 
 ality, and for all that is commendable in a work on 
 the diseases of females, it is not excelled, and pro- 
 bably not equalled in the English language. On the 
 whole, we know of no work on the diseases of wo- 
 men which we can so cordially commend to the 
 student and practitioner as the one before us. — Ohio 
 Med. and Surg. Journal. 
 
 The body of the book is worthy of attentive con- 
 sideration, and is evidently the production of a 
 clever, thoughtful, and sagacious physician. Dr. 
 Meigs's letters on the diseases of the external or- 
 gans, contain many interesting and rare cases, and 
 miiny instructive observations. We take our leave 
 of Dr. Meigs, with a high opinion of his talents and 
 originality. — The British and Foreign Medico-Chi- 
 rurgical Revievj. 
 
 Every chapter is replete with practical instruc- 
 tion, and bears the impress of being the composition 
 of an acute and experienced mind. There is a terse- 
 ness and at the same time an accuracy in his de- 
 ■cription ol symptoms, and in the rules for diagnosis, 
 
 It contains a vast amount of practical knowledge. 
 3y one who has accurately observed and retained 
 the experience of many years. — Dv^Hn Quarterly 
 Journal. ' 
 
 Full of important matter, conveyed in a ready and 
 agreeable manner. — St. Louis Med. and Surg. Jour. 
 
 There is an off-hand fervor, a glow, and a warm- 
 leartednesB infecting the effort of Dr. Meigs, which 
 is entirely captivating, and which absolutely hur- 
 ries the reader through from beginning to end. Be- 
 sides, the book teems with solid instruction, and 
 It shows the very highest evidence of ability, viz., 
 the clearness with which the information is pre- 
 sented. We know of no better test of one's under- 
 standing a subject than the evidence of the power 
 of lucidly explaining it. The most elementary, as 
 well as the obscurest subjects, under the pencil of 
 Prof. Meigs, are isolated and made to stand out is 
 such bold relief, as to produce distinct impressions 
 
 upon the mind and memory of the reader. Tin 
 
 CharltstoH Med. Journal, 
 
22 
 
 HENRY 0. LEA'S MEDICAL 
 
 MEIGS (CHARLES D.) M. D., 
 
 Lately Professor of Obstetrics,. &c., in Jeiferson Medical College, Philadelphia. 
 
 ON THE NATURE, SIGNS, AND TEEATMENT OP CHILDBED 
 
 FEVER. In a Series of Letters addressed to the Students of his Class. In one handsome 
 octavo volume, extra cloth, of 365 pages. %2 Oi>. 
 
 lectable book. '# * # This treatise upoa child- 
 
 The instrVictlve and' interesting author of this 
 work, whose previouslaborshave placed his coun- 
 trymen under deep and abiding oblig-ations, again 
 challenges their admiration in the fresh and vi^or 
 ousj attractive and racy pages before as. It is a de- 
 
 bed fevers will have an extensive sale, being des- 
 tined, as it deserves, to find a place in the library 
 of every practitioner who scorns tolag in the rear.— 
 Nashville Journ(il of Medieint andSurgery. 
 
 MACLISE (JOSEPH), SURGEON. 
 
 SURGrlCAL ' ANATOMY. Forming one volume, very large imperial quarto. 
 With sixty-eight large and splendid Plates, drawn in the best style and beautifully ci)lored. Con- 
 taining one himdred and ninety Figures, many of them the size of life. Together with copious 
 and explanatory letter-press. Strongly and handsomely bound in extra doth, being one of the 
 cheapest and best executed Surgical works as yet issued in this country. $14 00. 
 
 These plates will be found of the highest practical value, either for consulta- 
 tion in enjergencies or to refresh the recollections of the dissecting room. 
 
 *^* The size of this work prevents its transmission through the post-office as a whole, but those 
 who desire to have copies forwarded by mail, can receive them in five parts, done up in stout 
 wrappers. Price $12 00. 
 
 A work which has no parallel in point of accu- 
 racy and^cheapness in the English language.— iV. T. 
 Journal of Medicine. ' * 
 
 We are extremely gratified to annoance to th« 
 profession the completion of this truly magnificent 
 work, which, as a whole, certainly stands unri- 
 valled, both for accur'acy of drawing, beauty of 
 coloring^ and all the requisite explanations of tha 
 subject in hand. — TA« ifcw Orleans Medical and 
 Surgical Journal . 
 
 One of the greatjest artistic triumphs of the age 
 in Surgical Anatcnny. — British American Medical 
 Joumm^ 
 
 No practitioner whose means will admit should 
 fstil t^'puBsess it. — Ranhing^s Abstract, 
 
 Too much cannot be said in its praise; indeed, 
 we have not language to do it justice. — Ohio Medi- 
 tal and Surgical Journal. 
 
 The most accurately engraved and beautifully 
 colored plates we have ever seen iji an American 
 book — ^^one of the best and cheapest surgical works 
 •ver published. — Buffalo Medical Journal. 
 
 It is very rare that so elegantly printed, ao well 
 illustrated, aiid so useful a work, is offered at so 
 moderate a price.— CAaWss ton Medical Journal . 
 
 Its plates can boast a superiority which places 
 them almost beyond the reach of eompetition, — Medi- 
 tal Examiner, 
 
 Country practitioners will find these plates of im- 
 mense value.— if. Y. Medical Gazette. 
 
 This is by far the ablest work on Surgical Ana- 
 tomy that has come under our observation. Wi 
 know of no other work that would justify a stu- 
 dent, in any degree, for neglect of actual disseo-. 
 tion. In those sudflei? emergencies that so often 
 arise, and which require. theinstantaneouscommand 
 of minute anatomical knowledge, a work of this kind 
 keeps the details Of the dissecting-room perpetually 
 fresh in the memory . — The Western Journal of Medi- 
 cine and Surgery. 
 
 MILLER (HENRY), M, D., 
 
 Professor of Obstetrics and Diseases of Women and Children in the University of Loutsville. 
 
 PRINCIPLES AND PEACTICE OF OBSTETRICS, &c. ; including the Treat- 
 
 mentof Chronic Inflammation of the Cervix and Body of the Uterus considered as a frequent 
 cause of Abortion. With about one hundred illustrations on wood. In one very handsome oc- 
 tavo volume, of over 600 pages, extra cloth. $3 75. 
 
 tion to which its merits justly entitle it — The- Cin- 
 cinnati Lancet and Observer. 
 
 ■ A most respectable and valuable addition to our 
 home medical literature, and one reflecting credit 
 alike on the, author and the institution to which he 
 is attached. The student will find in this work a 
 most useful guide to his studies; the country prac- 
 titioner, rusty in his reading, can obtain from itB 
 pages a fair rfesumfe of the moaern literature of the 
 science; and we hope to see this American produc- 
 tion generally consulted by the profession, — V», 
 Med. Journal. 
 
 We congratulate the author that the task is done. 
 We congratulate him that he has given to the medi- 
 cal public a work which will secure for him a high 
 and permanent position among thp standard autlm- 
 rities on the principles and practice of obstetrics. 
 Congratulations are not less due to the medical pro- 
 fession of this country, on the acquisition of a trea- 
 tise embodying the results of the studies, reflections, 
 and experience of Prof. Miller.'— .?w/faZo Medical 
 Journal. 
 
 In fact, thisvolumemjist take its place among the 
 standard systematic treatises on obstetrics ; a posi- 
 
 MACKENZIE (W.), M. D,, 
 
 Surgeon Oculist In Scotland in ordinary to Her Majesty, &c.&c. 
 
 A PRACTICAL TREATISE ON DISEASES AND INJURIES OF THE 
 
 EYE. To which IS prefixed an Ajiatomical Introduction explanatory of a Horizontal Section of 
 the Human EyebaU, by Thomas Wharton Jones, F. R. S. From the Fourth Revised and En- 
 larged London Edition. With Notes and Additions by Addinell Hewson, M. D., Surgeon to 
 Wills Hospital, &c. &c. In one very large and handsome octavo volume, extra cloth, with plates 
 and numerous wood-clits %Q 50. 
 
 The treatise of Dr. ftlackenzle indisputably holds We consider it the duty of every one who has the 
 the firstplace, and forms, in respect of learning^and love of his profession and the welfare of his patient 
 research, an GncyclopEedia unequalled ;in extent by at heart, to make himself familiar with this the most 
 any other work of the kind, either English or foreign, complete work in the English language upon thedii- 
 —Bixon on Diseases of the Ey*. eases of the eye. — Med. Times and Gazette. 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 25 
 
 PARRISH (EDWARD), 
 
 . Professor of Materia Medica in the Pbiladelpliia College of Pliarmacy. 
 
 A TREATISE ON PHAllMACV'. Desigaed as a Text-book for the Student, 
 
 and as a Guide for the Physician and Pharmaceutist. With many Formulae and Prescriptions. 
 
 Third ediiion, greatly improved. In one handsome octavo volume, of 850 pages, with several 
 
 niindred Illustrations, extra cloth. $5 00. {Just Issued.) 
 
 Though for some time out of print, ihe appearance of a new edition of this work has been de- 
 layed for ihe purpose of embodying io it the results of the new U.S. Pharmacopoeia. The pub- 
 lication of this latter has enabled the Eiuthor to complete hisTevision in the most thorough manner, 
 rhose who have been waiting for the work may therefore rely on obtaining a volume compLCtely 
 On a level with the most advanced condition of pharmaceutical science. 
 
 The favor with which the work has thus far been received shows that the author was not mis- 
 taken in his estimate of the waot of a treatise which should serve as a practical text-l/ook for all 
 engaged in preparing and dispensiag medicines. Such a guide was indispensable not only to the 
 educuied pharmaceutist, but also to that large class of practitioners throughout the country who 
 are obliged to comptnmd their own prescriptions, and who during their collegiate course have no 
 opportunity of obtaining a practical familiarity with the necessary processes and manipulatidns. 
 The rapid exhaustion of two large editions is evidence that the author has succeeded in thoroughly 
 carrying out his object. Since the appearance of the last edition, much has been done to perfect 
 the science ; the new Pharmacopoeia has introduced many changes to which the profession must 
 conform ; and the authnr has labored assiduously to embody in his work all that physicians and 
 pharmaceutists can ask for in such a volume. The new matter aldne will thus be found worth 
 more than the very moderate cost of the Work to those who have been using the previous editions. 
 
 All that we can say of it is that to trie practising 
 physician, and especiall) the country physician, 
 who is generally his own apotliecary, there is hard- 
 ly any book that mightnotDettev be dispensed with 
 It is at the same time a dispensatory and a pharma- 
 cy — Louisville Review. 
 
 A careful examination of this wi»rk enables us to 
 speak of it in the highest terms, as being the best 
 treatise on practical pharmacy with which we are 
 acquainted, and an invaluable vxtZe-mecuTn, not only 
 
 to the apothecary and to those practitioners who 
 are accustomed to prepare tl eir own medicines, but 
 to every medical man and medical student. — Boston 
 Med. and Surg. Journal. 
 
 This is altogether one of the most useful hooka 
 we have seen. It is just what we have long felt to 
 be neeijed by apbthe^caries, students, and practition- 
 ers of medicine, most of whom in this country have 
 to put up their own prescriptions. It bears, upon 
 every page, the impress of practical knotvledge, 
 conveyed in a plain common sense manner, and 
 ada^teU to the oomprehension of all who may read 
 it.— Southern Med. and Surg. Journal. 
 
 That Edward Parriah, in writing a book upon 
 practical Pharmacy some few years ago — one emi- 
 nently original and unique — did the medical and 
 pharmaceutical profesaiunB a great and Valuable ser- 
 vice, no one, we think, wao has had access to its 
 pages will deny; doubly welcome, then, is this new 
 
 edition, containing the added results of his recent 
 and rich experience as an observer, teacher, and 
 practical operator in the pharmaceutical laboratory. 
 The excellent plan of the first is more thoroughlyj 
 — Peninsular Med. Journal, Jan. 1860. 
 
 Of course, all a,pothecarieB who have not already 
 a copy of the.^rst edition will procure one of this ; 
 it is, therefore, to physicians residing; in the counti^ 
 and in small towns, who cannot avail themselves of 
 the skill of ah educated pharmaceutist, that we 
 would espfcially commend this work. In it they 
 will find all that' they desire to know, and should 
 know, but very little of which they do really Know 
 in reference to this important collateral branch of 
 their profession; for it is a well established fact, 
 that, m the eaucation of physicians, while the sci- 
 ence of, medicine is generally well taught, very 
 little attention is paid to the art of preparing them 
 for use, and we know hot how this defect can be so 
 well remedied as by procuring and consulting Dr. 
 Parrish'sexcellent work.— Si. Louis Med. Journal. 
 Jan. I860. 
 
 We know of no work on the subject which would 
 be more indispensable to the physician or student 
 desiring information bn' the subject ofwhich it treats. 
 With Griffith's " Medical Formulary" and this, the 
 practising physician would be supplied with nearly 
 or quite all the mostuseful information on the sub- 
 ject. — Charleston Med. Jour. and Revieto, Jan. 1860, 
 
 PEASLEE (E. R.), M. D,, 
 
 Professoi' uf Physiology and General Pathology in the New York lyiedicai CoUjege. 
 
 HUMAN tilCjTULOGY, ia its relations fco Anatomy^ Phygiology, and Pathology; 
 for the use of Medical Students. With four hundred and thirty-four iUustratioii$. In one hand- 
 some octavo volume, extra cloth, of over 600 pages. $3 75. , 
 
 We would recommendit ascontainingasummary 
 of all that 18 known of the importantsubjects which 
 
 It embraces a library upon che copies discussed 
 within itself, and is just what the teacher and learner 
 need. Wp have not only the whole subject of His- 
 tology , interesting in itself,ably and fully discussed, 
 but what 18 ot infinitely greater interest to the stu- 
 dent, because of greater practical value, are its re- 
 lations to Anatomy, Physiology, and Pathology, 
 which are here fully and satisfactorily set forth. — 
 Nashville Journ. of Med. and Surgery. 
 
 it treats ; of all that is In the great worka of Simon 
 and Lehmann, and the organic chemists in general. 
 Master this one volume, and you know all that is 
 known of the great fundamental principles of medi- 
 cine, and Are have no hesitation in saying that it 
 is an honor so th^ American medical prufession.— 
 St, Louis Mid. and Surg. Journal. 
 
 ROKITANSKY 
 
 Curator of the Imperial Pathological Museum, 
 
 A MAJSUAL OM PATHOLOGICAL 
 
 Bound m two, extra cloth, of about 1200 pages. 
 
 KING, G. H. MooBB, and G. E. Day. $7 50. 
 
 The profesaioli is too well acquainted with tne re- 
 oatation of Rokitansky's work to neoa our asBur- 
 aaee that this is one of the mostprofoand, thorough, 
 and valuable books ever issued from the medical 
 nreas It is sutffeiKi-t.'.andhasnostaBdardof oom- 
 Darison. It is only necessary to announce that it is 
 issued in a form as cheap as is compatible with its 
 
 (CARL), M.D., 
 
 and Professor at the University of Vienna, &a 
 
 ANATOMY. Four volumes, octavj, 
 
 Translated by W. E. Swaine, Edwakd Sieve- 
 
 size and ipreservation, and its sale follows as a 
 matter. of course. .Mo library can be called co n 
 ilete without it. — Buffalo Med. Journal 
 
 An attempt to give our readers any adequate idea 
 jf the vast amount of instruction accumulated in 
 
 .nese volumes, would be feeble and hopeless 
 
 Wiite.n Lancet 
 
 BOYLE'S JlATJfiKlA MEDICA AND THERAPEUTICS; including the 
 
 P^eoaratioIl.•^ oi the PharmacoixEias of London^ Edinburgh, Dublin, and of the United States 
 With many n=w ine.diciu^b. Kdited by Joseph Carson, M. D. With ninety-eight illustrationi' 
 In one large octavo voluuic, extra cloth, of about 700 pages. S3 00. 
 
24 
 
 HENRY C. LEA'S MEDICAL 
 
 NEILL (JOHN), M. O., 
 
 Surgeon to thePenuBylvania Hospital, &c,; and 
 
 FRANCIS QURNEY SMITH, M.D., 
 
 Professor of Institutes of Medicine in the Pennsylvania Medical College. 
 
 AN ANALYTICAL COMPENDIUM OF THE VAEIOUS BRANCHES 
 
 ' OF MEDICAL SCIENCE ; for the Use and Examination of Students. A new edition, revised 
 and improved. In one very large and handsomely printed royal 12ino. volume, of about one 
 thousand pages, with 374 wood-cuts, extra cloth, $4 00. Strongly bouiid in leather, with raised 
 bands. $4 75. 
 
 This work is agtiin presented as eminently worthy ot the favor with which it has hitherto 
 been received. As a book for daily reference by the student requiring a guide to his more elaborate 
 text-books, as a manual for preceptors desiring to stimulate their students by frequent and accurate 
 examination, or as a source from which the practitioners of older date may easily and cheaply acquire 
 a knowledge of the changed and improvement in professional science, its reputation is permanently 
 established. 
 
 The beat work of the kind with which we are 
 acquainted.! — Med. Exwminer. > 
 
 Having made free use of this volume in our ex- 
 aminations oXf pupils, we can epeak from experi- 
 ence in recunim ending it as an admirable compend 
 for students, and as especially useful to preceptors 
 who examine their pupils. It will save the teacher 
 much -labor by enabling him readily to recall all of 
 the points upon which his pupils should be ex- 
 amined. A work oO^his sort should be in the hands 
 of every one who takes pupils into his office witlj a 
 view of examining them ; and thisisunquestionably 
 thebestofits class. — TTonsylvania Med. Journal 
 
 In the rapid course of lectures, where work for 
 
 the students is heavy, and review necessary for an 
 examination, a compend is not only valuable, but 
 it is almost a sine qua non. The one before ub. is, 
 in most of the divisions, the. most unexceptionable 
 of all books of the kind that we know of. The 
 newest and soundest doctrines and che^ latest im-, 
 provements and discoveries are 'explicitly, though 
 concisely, laid before the student There is a claai 
 to whom we very sincerely commend this cheap book 
 as worth its weight in silver — that class is the gradu- 
 ates in medicine of more than ten years' standing. 
 who have not studied medicine since. They wul 
 perhaps Knd outfromitthat the science is not exactly 
 now what it was when they left it off,— TA< S(it4«- 
 scopt 
 
 PI RRIE (WILLIAM), F. R. S, E., 
 
 Professor of Surgery Ln the University of Aberdeen. 
 
 THE PRINCIPLES AND PEACTICE OF SURGERY. Edited by John 
 
 Neill, M. D., Professor of Surgery in the Penna. Medical College, Surgeon to the Pennsylvania 
 Hospital, (fee. In one very handsome 8vo. volume, extra cloth, oi 780 pages, with 316 illustrations. 
 $3 75. 
 
 We know of no other surgical work of a reason- 
 able size, wherein there is so much theory and prac- 
 tice, or where subjects are more soundly or clearly 
 taught. — The Stethoscope . 
 
 Prof. Pirrie, in the work before us, has elabo- 
 
 rately discussed the principles of surgery, and a 
 safe' and effectual practice predicated upon them. 
 Perhaps ho work upon this subject heretofore issued 
 is so full upon the science of the art of surgery.— 
 Nashville Journal of Medicine and Surgery . 
 
 PARKER (LANGSTON), 
 
 Surgeon to the Queen's Hospital, Birmingham, 
 
 THE MODEEN TKEATMENT OF SYPHILITIC DISEASES, BOTH PBI- 
 
 MARY AND SEC0NDARY; comprising the Treatment of Constitutional and Confirmed Syphi- 
 lis, by a safe and suocessfui method. With numerous Cases, Formulae, and Clinical Observa- 
 tions. From tiie Third and entirely rewritten London edition. In one neat octavo volume, 
 , extra 6lothj of 316 pages. S2 50. •* 
 
 ■* PEREIBA (JONATHAN), M.D. 
 
 MATERIA MEDICA AND THERAPEUTICS; being an Abridgment of the 
 late Dr. Pereira's Elements of Materia Medica, arranged in conformity with the briii-h Pharma- 
 copoeia; and adapted to the use of Medical Practitioners, Chemi-^ts, and Drug'gis's, Medical and 
 Pharmaceutical Students, &c. By F. J. Farre, M. D., Senior Physician to' St. Bartholottiew's 
 Hospital, and London Editor of the British Pharmacopeeia; assisted by Robert Bentley, 
 M.R C. S.,(^r6fe__ssor of Materia Medica and Botany to the Pharmaceutical Society of Great 
 Britain; and by Robert Warikgtoh, F. R. S., Chemical Operator lo the Society of Apothecaries. 
 With numerous additions -and references to the United Slates Pharmacopoeia, by Horatio C. 
 Wood, M. D., Professor of T3olany in the Univer-sity of Pennsylvania. , In one large and hand- 
 some octavo vdume of about yOO pages, with numerous illustrations, (fr^arin^.)- 
 
 ROBERTS (WILLIAM) M. D., 
 
 Fhysiciaa to the Manchester ^uyal Infirmary, Lecturer'on Medicine in the Manchester School of . 
 
 Medicine, Sec. 
 
 A PRACTICAL TREATISE ON URINARY AND RENAL DISEASES, 
 
 i, including Urinavy Deposits. Illustrated by numerous ca'esand engravings. In one. handsome 
 octavo volume of over 500 pages, extra cloth, (^st Ready.) 
 
AND SCIENTIFIC PUBLICATIONS. 
 
 a7 
 
 STILLE (ALFRED), M.D,, 
 
 niTTTTr* Professor of the Theory and Practice of Medicine in the University of Pennsylvania. 
 
 THERAPEUTlOa AMD MATEKlA MJDDlCAj a Systematie Treatise on the 
 
 Action and Uses of Medicinal Agents, including- their Description and History. Second Edilion, 
 
 revised and enlarged. In twolarg&and handsome octavo volumes, extra cloth., $10 00. uTust 
 
 Issued,.) 
 
 This work is designed especially for the student and practitioner of medicine, and treats the various ' 
 articles of the Materia Medica from the point of view of the bedside, and not of the shop or oi the^ 
 le^iure-room. While thus endeavoring to give all practical information likely to be useful with' 
 respect to theemployment of special remedies in special affections, and the results to be anticipated 
 from their administratibn, a copious Index of Diseases and their Remedies renders the work emi- 
 nently fitted for reference by showing at a glance ihe difTerent means which, have been employed, 
 and enabling the practitioner to extend his resources in difficult cases with all that the experience 
 of the profession has suggested. 
 
 The speedy demand for another edition of this work sjhows thatit haS acceptably filled an acknow- 
 ledged want Noexertion of the author ha^been wanting to render it worthy a continuance of t-he 
 favor with which it has been received, while an alteration in the typographical arrangement has 
 accommodated the additions without increasing unduly the size of the volumes. 
 
 Rarely, indeed, have we had Bubmiited to ub a 
 work on medicine so ponderous in its dimensions 
 as that now before ub, and yet so fascinating in its 
 contencs. It is, therefore, with a peculiar gratifi- 
 cation that we recognize in Dr. Siillfe the poases- 
 Bion of many of those more distinguished qualifica- 
 tions which entitle him to appYohation,'and which 
 justify him in coming before his medical brethren 
 as an instructor. A comprehensive knowledge. 
 
 tested by a sound and penetrating judgment, joined 
 to a love of progresfl— which a uiecriminating spirit 
 of inquiry has tempered bo as to accept nothing new 
 because it Is new, and abandon nuthmg old because 
 it is old, but v^hichestimateB either accurcing Eo its 
 relations to a just logic and experience — manifests 
 icaelf everywhere, and gives to the guidance of the 
 author all 'he assurance of safety which ihe diffi- 
 culties of his subject can allow^. In conciUBion, we 
 earnestly advise our readers to ascertain for them-' 
 selves, t}y a study of Br. Still6*s vulumea, the great 
 value and interest of the stores of knowledge they 
 present. We have pleaenre in referring rather to 
 the ample treasury of undoubted truth8,'the real and 
 assured conquest of medicine, accumulated by Dr. 
 Stille in his pages ; and commend the aum ofhis la- 
 bors to the attention of our readers, as alike honor- 
 able to our science, and creditable to the zeal, the 
 candor, and the judgment of him who has garnered 
 the whole so CAief ally ,->~Edinburgh Med. Journal. 
 The most recent authority is the one last men- 
 
 tioned, Stille. His great work on <* Materia Medi- 
 ca and Therapeutics," published last year, in two 
 octavo volumes, of some sixteen huii;4red pages, 
 whileitembodies the results of the labor of others 
 up to the time of publication, is enriched with a 
 great amount df original observation and research. 
 we would draw attention, by the way, to the very 
 convenient mode in which the Index is arranged in 
 this work. There fs firstan "Index of Remedies;' 
 next an "Index of Diseases aud their Remedies." 
 Such an arrangement of the Indices, in our opinion, 
 g reatly enhances the practicai value of books of this 
 kind. In tedious, obstinate cases of disease, where 
 we have to try one remedy after another until our 
 stock is pretty nearly exhausted, and we are almost 
 driven to our wit^s end, such an index as the second 
 of the two just mentioned, is precisely what we 
 want. — London Med. Timesand GazettBjAprilj 1861. 
 We think this work will do much to obviate the 
 reluctance to a tihuroughiin vestigation o( this branch 
 of scientific study, for in the wide range of medical 
 literature treasured in the Englisa tongue, we shall 
 hardly And a work written in u style more clear and 
 simple, cunveymg. forcibly the facts taught, and yet 
 free from turbidity and redundancy. There is a fas- 
 cination, in Its pages that will insure to it a wide 
 [lopjilarity and attentive perusal-., and a decree of 
 usafulnesg not often attained througn the influence 
 of a single work. 
 
 SIMPSON (J. Y.), M. D., 
 Professor of Midwiiery,&c., in the University of Edinburgh, &c. 
 
 CLINICAL LECTDKES OM THE DISEASES OF WOMEN. With nu- 
 
 meious illustraliona. In one handsome octavo volume, of over 500 pag-es, extra cloth, $4 00. 
 
 The principal topics embraced in the Lectures are Vesico-Vaginal Fistula, Cancerof the Uterus, 
 Treatment of Oarcnoma by Caustics, Dysmenorrhosa, Amenorrhoea, Closures, Gontraoiions, &c., 
 of tne Vagina, Vulvitis, Causes of Death after Surgical Operations, SuBgieal Fever, Phlegmasia 
 Dolens, Coccyodinia, Pelvic Cellulitis, Pelvib Hsemaioma, Spurious Preghancy, Ovarian Dropsy, 
 Ovariotomy, Cranioclasm, Diseases of the Fallopian Tubes, Puerperal Mania, Sub-InvolUtion and 
 Super-involution of the Uterus, &c. &o. 
 
 As a series of monographs on these important topics — many of which receive little attention 
 in the ordinary text-books — elucidated wilh the extensive experience and readiness of resource for 
 which Professor Simpson is so distinguished, there are lijw practilioners who will not find in its 
 pages matter of the utmost importance in the treatment of obscure and difficult cases. 
 
 SALTER (H. H.), M. D. 
 
 ASTHMA; its Pathology, Causes, Consequences, and Treatment. 
 
 8vo., extra cloth (Just Issued.) $2 50. 
 
 ThelBoni'm of Dr. Salter's worn which is devoted 
 to ircSHiient, is ot great practical inieresi und value. 
 It wouTd lie necessary to loilow him step by slep 
 in lilB remarks, nut only ou the medicinal, bat also 
 on the dii tctie and hygienic trealmeut uf ttie disease, 
 in order lo convey a justnotiunoi mt practical value 
 of this part of his work. This o4r spa ce forbnig, ^^ 
 
 SLAOE lO. D.), M. p. 
 
 DIPHTHERIA : its Nature and Treatment, with an account of the History of 
 
 its Prevalence in various countries. Second and revised edition. In one neat royal 12mo. 
 volume, extra cloth. $1 25. (.Just Issued.) 
 
 In one vol. 
 
 and this we shall little rtgret, if, by our silence, 
 wc Bhou Id ind uce our readers to possess Lhemuelvea 
 of the book itself; a bauk which, without uuubt,de-, 
 serves to be r«nked aming the moat valuable of re- 
 cent,c<intributiuns to ttie medical literature of tins 
 country.— KanA:i«g-'j Abstract^Jna.y 1961. 
 
 Tlie iiiiginul essuy of Dr. Slade, to which the 
 Fiske Fund prize lor 166" was awarded, appeared 
 oriffinallv in tins lourntl. lu the edition beliire us 
 the essay has deeu revised with ev.cent rare, waile 
 such iiduiiiouB have b.eu mnde to it as were sug 
 geated by tue aulhur'a subairqueut ciperitace and 
 
 obaervitinn. In ifs present form, the work furnishes 
 to thescudcntund young pruclilioiier a very faithtul 
 und useful exposition of itit pinicipHl facts lliut are 
 now Known in respect to Mie nature of Uiplithena, 
 itscausxs und treatment. — ytm 7ourn Med Scitnces, 
 Jan. Ib65. ' 
 
2e 
 
 HEIilRY C. LEA'S MEDICAL 
 
 RIGBY (EDWARD), M.D., 
 
 Senior FhyBiciKn to the General Lying-in Hospital, &c. 
 
 A SYSTEM OP MIDWIFEKY. With Notes and . Additional lUustrationa. 
 
 Second American Edition. One volume octavo, extra cloth, 422 pages. $2 SO. 
 
 BY THE SAME AUTHOK. 
 
 ON THE CONSTITUTIONAL TREATMENT OF FEMALE DISEASES. 
 
 Id one neat royal 12mo. volume, extra cloth, of about 250 pages. $1 00. 
 
 KAMSBOTHAM (FRANCIS H.), M.D. 
 TEE PRINCIPLES AND PRACTICE OF OBSTETRIC MEDICINE AND 
 
 SURGEEY, in reference to the Process ol Parturition. A new aud enlarged edition, thoroughly 
 revised by the Author. With Additions by W. V. Keating, M. JD., Professor of Obstetrics, &c., in 
 the Jefferson Medical College, Philadelphia. In one large and handsome imperial octavo volume, 
 of 650 pages, strongly bound in leather, with raised bands; with sixty- four beautiful Plates, and 
 numerous Wood-cuts in the texli containing in all nearly 200 large and beautiful figures. ^.7 00. 
 
 From\Prof. HodgSy of the University of Pa. ■ 
 To the American public, it is most valuable, from its intrinsic undoubted excellence^ and as beicg 
 the best authbrized exponent of British ftl4dwifery. Its circulation will, I trust, be extensive throughout 
 OUT country. i 
 
 It is unnecessary to say anythingin regard to the 
 utility of this work. It is already appreciated in our 
 cojintry for the value of the matter, the clearness of 
 its style, and the fulness of its illustrations. To the 
 physician's library it is inilispensable, while to the 
 student as a text-book, from which to extract the 
 material for laying the foundation of an education on 
 obstetrical science, it has no superior. —OAio Med 
 and Surg. Journal . 
 
 The publishers have secured its success by the 
 
 truly elegant style in which they have brought it 
 out, excelling themselves in its production, espe- 
 cialiy in its plates. It is dedicated to Prof. Meigs, 
 and has the emphatic endorsement of Prof. Hodge, 
 as the best expQjnent of British Midwifery, We 
 knew of no text-book which deserves in all respects 
 to be mure highly recommended to students, and we 
 could wish to see it in the hands of every practitioner, 
 for they will find it invaluable for reference.— Jlfid, 
 Gazette. 
 
 RICORD (P.), M. D. 
 LETTERS ON SYPHILIS. Translated by W. P. Lattimorb, M.D. In one 
 
 neat octavo volume, of 270 pages, extra cloth. $2 Off, 
 
 SMITH (HENRY H.), M. D., AND HORNER (WILLIAM E.), M. D. 
 
 AN ANATOMICAL ATLAS, illustrative of the Structure of the Human Body. 
 
 In one volume, large imperial octavo, extra cloth, with about six hundred and fifty beautiiul 
 
 figures. $4 50. 
 
 The plan of this Atlas, which renders itsope- | of thekind that hasyet appeared; and wemustadil. 
 euliarly convenient lot the student, and its superb ] the very beautiful manner in which it is "got up" 
 artistical execution, have been already pointed out. I is so creditable to the country as to be flatterinB 
 We must congratulate the student upon the cumple- I to our nations! pride. — Afnerican Medical Journal, 
 tiou of tnis Atlaa, as it is the most convenient work | 
 
 SMITH (EDWARD), M.D., LL.D., F.R.S. 
 
 Assistant Physician to the Hospital for Consumption and Diseases of the Chest, Brompton, Scf^ 
 
 CONSUMPTION; ITS EAELY AND EEMEDIABLE STAGES 
 
 neat.ootavo volume of 254 pages, extra cloth. $2 25. (Just Issued.) 
 
 One-half of Dr. Smith's work is devoted to the 
 treatment of TuberculOEis. We find in this portion 
 of the work no occasion to join issue wiih the an- 
 thor j but, on the contrary, much which we would 
 cummend to the reader's attention. Dr. Smith at- 
 taches far greater importance to hygienic measures 
 
 In one 
 
 than to drugs in the treatment of the disease. In 
 taking leave of the Work, we would express the 
 hope that the author will furnish occasions for the 
 renewal of our intercourse as a reader, if not asa 
 leviewer.— Xm. Med. Journal, Jan. 18S3. 
 
 SHARPEY (WILLIAM), M. D., JONES QUAIN, M. D., AND 
 
 RICHARD QUAIN, F. R. S., &c. 
 
 HUMAN ANATOMY. Revised, with Notes and Additions, by Joseph Leidy, 
 
 M.. D., Professor of Anatomy in the Uhiversity of Pennsylvania. Complete in two large octavo 
 voiumes,extracloth,ofaboulthirleen hundred pages. With over500 illustrations. $6 00. 
 
 80I.LY ON THE HUMAN BRAIN j its Structure, 
 Physiology, and Diseases. From the Second and 
 much enlarged London edition. In one octave 
 volume, extra cloth, of 500. pages, with 120 ijvood- 
 outs. I»2 80.' ■' ■ ' 
 
 S'CEY'S OFKHATIVE SURGERY. In one very 
 
 handsome octavo volume, extra cloth, of over 690 
 pages, with about one hundred wood-cuts. 83 29. 
 SIMONS GENjsKai. pathology, as conduc- 
 ive to the Establishment of Rational Principles 
 for the prevention aiiu Cure of Disease In one 
 octavo volume, extra cloth, of 212 pages. 81 45. 
 
AND SCIENTIFIC FUJBL,f CAPTIONS 29 
 
 TODD (ROBERT BENTLEY), M. D,, F. R. S., 
 
 ProfesBor of Physiology In King's College, London ; and 
 WILLIAM BOWMAN, F. R. 5., 
 
 Demonstrator of Anatomy in King's College, London. 
 
 THE PHYSIOLOGICAL ANATOMY AND PHYSIOLOGY OF MAN. With 
 
 about three hundred large and beautiful illustrations on wood. Complete in one large octavo 
 
 volume, of 950 pages, extra cloth. Price $4 75. 
 
 Itis more con else than Carpenter's Principles, and 
 more modern than the accessible edition of Mailer's 
 Elementsj its details are brief, but sufficient; its 
 descriptions vivid j its illustrations exact and copi 
 
 Eus: and its language terse and perspicuous: 
 harleston Med. Journal. 
 
 A magnificent contribution to British medicine, 
 and the American physician who shall fail to peruse 
 it, wili have failed to read one of the most instruc- 
 tive books of the nineteenth century. — N. O. Med, 
 md Surg. Journal, 
 
 TODD (R, B.) M, D., F. R. S., &c. 
 CLINICAL LECTUKBS ON CERTAIN DISEASES OF THE URINARY 
 
 ORGANS AND ON DROPSIES. In one octavo volume, 284 pagesj extra cloth, f 2 50 
 
 BY THE SAME AUTHOR. 
 
 CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one neat 
 
 octavo volume, of 320 pages, extra clotn. #2 50. 
 
 TOYNBEE (JOSEPH), F. R. S., 
 Aural Surgeon to, and Lecturer on Surgery at^ St. Mary's Hospital, 
 
 A PRACTICAL TREATISE ON DISEASES OP THE EAR;; their Diag- 
 
 nosis, Pathology, and Treatment. Illustrated with one hundred engravings on wood. In one 
 very handsome octavo volume, extra cloth, $4 0,0. 
 
 The work is a model of its kind, and every page 
 and paragraph oi it arewortby of the most thorough 
 study. GouBidered all in all — ae an original work, 
 well written, phiiosophically elaborated, and huppi- 
 Iv illustrated with cases and drawings— it le by far 
 the ablest monograph that has ever appeared on the 
 anatomy and diseases of the ear, and one of the most 
 valuable contributions totheartand science of sur- 
 gery in the nineteenth century.— iV. Amer. Medico- 
 Chirurg. RevieWj Sept. 1860, 
 
 We arc speaking within the linriits of mcdest ac- 
 knowledgment, and with a sincere and unbiassed 
 Judgment, when we affirm that as a treatise on Aural 
 
 Surgery, it is without a rival in our language or any 
 other. --Charfesion Med Journ anrf jReu,,gSept. I860. 
 The work of Mr. Toynbee is undoubtedly, upon 
 the whole the moat valuable produciionof tne kind 
 in any language. The author has long been known 
 by his numerous monographs upon subjects con- 
 nected with diseases of Lhe ear, and is now regarded 
 as the Highest authority on most points in his de- 
 partment of science. Mr Toynbee's work, as we 
 have alreauy said, is undoubteuly the moat reliable 
 guide for the study of Che diseases of the ear in any 
 lang,ttage, and should be in the library of every phy- 
 sician.— C/ticVgo Med. Journal, July, 1860. 
 
 WILLIAMS (C. J. B.), M. O.; F. A. S., 
 
 Professor of Clinical Medicine in University College, London, to . 
 
 PRINCIPLES OF MEDICINE, , An Elementaiy View of the Causes, Nature, 
 
 Treatment, Diagnosis, and Prqgnosis of Disease; with brief rfemarks on Hygienics, or tlie pre- 
 servation-of health. A new American, from the third and revised London edition. In one octavo 
 volume, extra cloth, of about 500 pages. I$3 50. (Novi Ready.) 
 
 WHAT TO OBSERVE 
 AT THE BEDSIDE AND AFTER DEATH, IN MEDICAL CASES. 
 
 Published under the authority of the London Society for Medical Observauon. A new American, 
 
 from the second and revised Londoi. edition. In one very handsome volume, royal 12mo., extra 
 
 cloth. $1 00. 
 
 To the observer who prefers accuracy to blunders I One of the finest aids to a young practitioner wo 
 andpfecision to carelessness, this little book is in- have ever seen. — Ptninsular Journal of Mtdieint, 
 valxLo,bl(t,—N.E. Journal of Medicint, I 
 
 WALSHE (W. H.), M. D., 
 
 Professor of the Principles and Practice of Medicine in Utiiversity College, London, to. 
 
 A PRACTICAL TREATISE ON DI-iEASES OF THE LUNGS; including 
 
 the Principles of Physical Diagnosis. Third American, from the third revised and much en- 
 larged London edition. In one vol. octavo, of 468 pages extra cloth ^ J3 DO. 
 The present edition has been carefully revised and much enlarged, and may be said in the main 
 to Bm rewritten. , Descriptions of several diseases, previously omitted, are now introduced; an 
 effort has been made to bring tne description of anatomical characters to the level of the wants of 
 the practical physician ; and the diagnosis and prognosis of each complaint are more cp^pletely 
 considered. The seciions on Treatment and the Appendix have, especially, been largely ex- 
 tended.— Author's Preface. 
 
 BT THE SAME AITTHOjl. 
 
 A PRACTICAL TREATISE ON THE DISEASES OP THE HEART AND 
 
 GREAT VESSELS, including the Principles of Physical Diagnosis Third American, from the 
 
 third revised and much enlarged London edition. In one handsome octavo volume of 420 pages, 
 
 extra cloth, %'i "0. 
 
 The present editjon has been carefully revised ; much new matter has been added, and the entire 
 work in a measure remodelled. Numerous facts and discussions, more or less completely novel, 
 will be found in the descriplion of lae principles of physical diagnosis ; but the chief addilions have 
 been made in the practical portions of the book, Several aHeoiions, of which tittle or no account 
 had been given in the previous editions, are now treated of in detail. — Autlior's Preface 
 
28 
 
 HENRY C. LEA'S MEDICAL 
 
 SARGENT (F. W.), M. D. 
 ON BANDAGING AND OTHER OPERATIONS OF MINOR SURGERY. 
 
 New edition, with an additional chapter on Military Surg-ery. One handsome royal 12mo. vol., 
 
 of nearly 400 pages, with 184 wood cuts. Extra doth, $] 75. 
 
 The value of this; worli as a handy and convenient manual for surg-eons engaged in active duly, has 
 induced the publishers to render it more complete for those purposes by the addition of a chapter 
 on gun-shot wounds' and other matters peculiar to military surgery. ' In its present form, there- 
 fore, it will be found a very cheap and convenient vade-mecum for consultation and reierence in 
 the daily exigencies of military as well as civil practice. 
 
 We consider that no better book could be, placed 
 in the hantiB of an hospital dreBser, or theyoung sur- 
 geon, whose eclucatidn in this respect has not been 
 perfected. V)/e most cordially commend this volume 
 asonewhich themedical student should most close- 
 ly study, to perfect himself in these minor surgical 
 operations in which neatriess and dexttrity are so 
 much Tfequired, and on which a great portion of his 
 Ttputation as a future surgeon must evidently rest. 
 And to the surgeon in practice it must prove itself 
 a valuable volume, as instructive' on many points 
 which he may have forgotten.— ^riiisA Americcm 
 Jowrnai, May, 1662. ■ ^ 
 
 The instruction given upon the subject of Ban- 
 dagingj is alone of great value, and while the author 
 modestly proposes to instruct the students of medi- 
 cine, and the yuunger physicians, we will say that 
 experienced physicians will obtain many exceed- 
 iugly valuable suggestions by its perusal. It will 
 bef(nind one of the most satisfactory- manuals for re- 
 ftrenbe in the field, or hospital yet published; thor- 
 oughly adapted to the wants of Military surgeons, 
 and at the same time equally useful for ready and 
 convenient reference by surgeon^f everywhere.— 
 Buffalo Med. and Surg. Journal, June, 1862. 
 
 OF 
 
 SMITH (W, TYLERl), M. D., 
 
 Physician Accoucheur to St. Mary's Hospital, &o. 
 
 ON PARTURITION, AND THE PRINCIPLES AND PRACTICE 
 
 . OBSTETHICS. In one royal 12mo. volume, extra olotli, of 400 pages. 8150. 
 
 BY THE SAME AUTHOK. 
 
 A PRACTICAL TREATISE ON THE PATHOLOGY AND TREATMENT 
 
 OF LEUCOERHCEA. With numerous illustrations. Iii one very handsome octavo volume, 
 extra eloth, of about 250 pages. $2 00 
 
 TANNER (T. H.), M. D., 
 
 Physician to the Hospital'for Women, &c, 
 
 A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAGNOSIS. 
 
 To which is added The Code of Ethics of the American Medical Association. Third 
 American Edition. In one neal volume, small 12mo., extra cloth. . (Preparirg.) 
 
 TAYLOR (ALFRED S.), M, D., F. R. S., 
 
 Lecturer on Medical Jurisprudence and Cheraistryin Guy's Hospital. 
 
 MEDICAL JURISPRUDENCE. , Fifth American, from the seventh improved 
 
 anr enlarged London edition. WithNotes and References to American Decisions, by Hdwarb 
 Hartshokne.M.D. In one large 8vo. volume; extra cloth, of over 700 pages. $4 00. 
 This standard work having had the advantage of two revisions at the hands of the author since 
 the appearance of the last Atnerican edition, will be found thoroughly revised and brought up com- 
 pletely to the pretenl stale tit' the science. As a work of authority, it must therefore maintain its 
 position, both as a text -book for the student, and a compendious treatise to which the practitiouer 
 CBi! at all limes refer in cases of doubt ordifficulty. . ,, 
 
 American and British le^al medicine. It should be 
 
 No work upon the subject can be put into the 
 hands of students either of law or medicine, which 
 will engage them more clpsely or profitably.; and 
 mine could be offered to the busy practitioner of 
 either calling, for the purpose of casual or hasty 
 reference, that would be more likely to afford the aid 
 desired. We thereforereeommend it as the best and 
 safest manual for daily uise. — American Journal oj 
 Medical Sciences . 
 
 Il is not excess of praise to say that the volumi 
 before us is the very best treatise extant on Medical 
 Jurisprudence In saying this, we do not wish t( 
 be understood as detracting from the merits of thf 
 excellent works of. Beck, Ryan, Traill, Guy, ano 
 others; but in interest and value we think it must 
 be conceded that Taylor is superior to anything thai 
 has preceded it.— iV. W. Medical and Surg.Jonrnal 
 
 in the possession of every physician, as the subject 
 is one of great and increasing impor^nce to the 
 public a^ well as to the profession.— /S<. Loms Med. 
 and .Surg. Journal. ' 
 
 This work of Dr. Taylor's is generally acknow- 
 ledged to be one of the ablest extant on the subject 
 of niedical jurisprudence. It is certainly one of the 
 most attractive op'>Ks that we have met with ; sup- 
 plying so Inuch both to interest and instruct, that 
 we do not hesitate to {affirm that after having once 
 commenced its perusal, few coulil be prevailed upon 
 to desist before completing it. In the last London 
 edition, all the newly observed and accurately rc- 
 ctiroed facts have been inserted,' including much 
 that is recent of Chemi^cal, Microscopical, and Pa- 
 thological research, besidts papers on numerous 
 
 subjects never before published Ckarleston Med. 
 
 Journal and Revieiio . 
 
 It is at once comprehensive and eminently prac- 
 tical, and by universal consent ttands attheheadof 
 
 BM THE SAME AUTHOR. 
 
 ON POISONS:, IN RELATION TO MEDICAL JURISPRUDENCE AND 
 
 MEDICINE. Second American, from a secoiid and revised London edition. In one large 
 
 octavo volume, of 765 pages, extra cloth. $5 00. 
 
 Mr. Taylor's position as the leading fnedical jurist of England, has conferred on him extraordi- 
 nary advaiilages in acquiring experience on these subjects, nearly^all cases of moment being 
 referred to him for examination, as an expert whose testimony i^generally accepted as final. 
 The results of his labors, therefore, as gathered together m this volume, carefully weighed and 
 silled, and presented in the clear and intelligtble style for which he is noted, may be received 
 as an acknowledged authority, and as a guide to be followed with implicit confidence. 
 
 BY THE SAME AUTSOB. AMD WM. BRANDK. 
 
 CHEMISTRY. In one volume 8vo. See "Bbande," p. 6. 
 
AND SCIENTIFKmrBTilCATIONS. 
 
 31 
 
 WILSON (ERASMUS), F. R. S. 
 
 ON DISEASES OF THE SKIN. Fifth American, from the Fifth enlarged 
 London edition. In one handsome octavo volume, of nearly 700 large pages, with illustrations 
 on wood, extia cloth $4 50. 
 
 ■ '^'^^Vp^^s.sical work, which for twenty years has occupied the position of the leading authority 
 in the English language on its important subject, has just received a thorough revision at the hands 
 of the author, and is now presented as embodying the results of the latest investigations and expe- 
 rience on all matters connected with diseases of the skin. The increase in the size of the work 
 shows the industry of the author, and his determination that it shall maintain the position which it 
 has acquired as thoroughly on a level with the most advanced condition of medical science. 
 A few notices of the last edition are appended. 
 
 No matter what other treatises may he in thd libra- 
 ry of the medical attendaat, he needs the clear and 
 suggestive counsels of Wilson, who is thoroughly- 
 posted up on all subjects connected with cutaneous 
 pathology. We ^jave, it is very true, other valuable 
 works on the maladies that invade the skin ; but, 
 compared with the volume under consideration, they 
 .are certainly to be regarded as inferior lights in guid- 
 ing the judgment of the medical man. — Boston Med. 
 and Swg. Journal, Oct. 1857. 
 
 The author adopts a simple and entertaining style. 
 He strives to clear away the complications of ,hla 
 subject, and has thus prodWed a book Ulled with a 
 vast amount of information, in a form so agreeable 
 as to make It pleasant i-eading, even to the uninitiated. 
 More especially doe.s it deserve our praise because of 
 its beautiful and complete atlas, which the American 
 publishers have successfully imitated from the origi- 
 nal plates. We pronounce them by ikr the best imi- 
 tations of nature yet published in our country. With 
 the text-book and atlas at hand, the diagnosis is ren- 
 dered easy and accurate, and the practitioner feels 
 himself safe in his treatment. W.e will add that this 
 work, although it must have been very expensive to 
 the pulTlishers, is not high priced. There is no rea- 
 son! then, to prevent every physicianfrom obtaining 
 a work of such importance, and one which will save 
 him both labor and perplexity. — t^a. Med. Journal, 
 
 As a practical gviide to the classification, diagnosis, 
 and treatment of the diseases of the skin, the book is 
 complete. We know not-hing, considered in this as- 
 ''peet, better in our language; it is a safe authority oa 
 all the ordinary matters which, in this range of dis- 
 eases, engage the practitioner's attention, and pos- 
 sesses the high quality — unknown, we believe, to 
 every older manual, of being on a level with science's 
 high-watermark; a sound book of practice. — London 
 Med. Times. 
 
 ThewritingB of Wilson, upondiaeasesof the skin, 
 are by far the most scientific and practical that 
 have ever been presented to the meaical world on 
 this subject. The pirelenteditionisagreat improve- 
 ment on all its predecesBors. To dwell upon all the 
 great merit's and high claims of the work before us, 
 seriatim^ would indeed be. an agreeable service j it 
 would be a mental homage which we could freely 
 offer, but we should thus occupy an undue amount 
 of space in this Journal. We will, however look 
 a± Bome of the more salien.t points with which it 
 abounds, and which make itincompuva oiy superior to 
 all other treatises on the subject of dermatology N o 
 mere speculative views aire allowed a place in, this 
 volume, which , withoutadoubt;Will,foravery long 
 period, be acknowledged as the chief standard work 
 on dermatology. The principles of an enlighiened 
 and rational therapeia are introduced on ^very ap- 
 propriate occasion. — Am. Jour. Med Science. 
 
 When the first edition of this work appeared 
 about fourteen years ago, Mr Erasmus Wilson hau 
 iBilready given some years to the study of piseases 
 of theSkiUj and he then expressed his intention of 
 devoti&g his filcure life to the elucidation of this 
 branch of TVIedical Science In the present edition 
 Mr. Wilson presents us with the results of his ma- 
 tured experirnce, and, we have now before us not 
 merely a reprint of his former publications, but an 
 en,tirely new and rewritten voiume. Thus, the whole 
 history of the diseases affecting the skin, whether 
 they originate in that structure ur are the mere mani- 
 festations of derangement of internal oirgans,' is 
 brought under notice, and the book includes a mass 
 of ^formation which is spread over a great part of 
 the domain of Medical and Surgical Pathology. We 
 can safely recommend it to the profession as the 
 best work on the subject^^now inexistencein the En- 
 glish language. — Lmidon Med. Times and G-azette. 
 
 ALSO, NOW RE4;DY, 
 
 A SEEIES OF PLATES ILLUSTRATINa WILSON ON DISEASES OP 
 
 THE SKIN; consistingof twenty beautifully execuled plates, of which thirteen are exquisitely 
 colored, presenting the Normal Anatomy and Pathology of the Skhi, and' containing accurate re- 
 presentations of about one hundred varieties of disease, most of them the size of nature. Pricb 
 id cloth. $5 50. ' ' ,. ' . 
 
 In beauty of drawing and accuracy and finish of coloring these plates will be found equal to 
 
 Miything o/ the kind as yet issued in this country. The value of the new edition is enhanced by 
 
 an Eidditional colored plate. 
 
 The plates by which this edition is accompanied 
 leave nothing to be desired, 60 far as excellence of 
 delineation and perfect accuracy of illustration are 
 concerned.— Medico-Ctirurgicaf Review. 
 
 Oftheseplatesitisimposaible to sneak loo highly 
 The representations of the various forms of cutane- 
 ous disease are suigularly|)iccurate, and the color- 
 ing exceeds almost anything we have met with.— 
 British and Foreign Medical Review. 
 
 We hsve already expressed oar high appreciation 
 of Mr. Wilson's treatise on Diseases of the iSkin. 
 The plates arfe comprised in a separate volume, 
 .which we counsel all those who possess the text to 
 purchase. It is. a beautiful specimen of cqlor print- 
 ing, and the representations of the various forms of 
 skin disease are as faithful as is possible in plates 
 of the size.— Soston Med. and Surg. JoumaK Anril 
 8, 1858. IP" 
 
 Also, the TEXT and PLATilS done up in one handsome volume, exira cloth, price $9 50. 
 
 BY THE SAME AUTHOR. 
 
 THE DISSECTOR'S MANUAL; or, Practical and Surgical Anatomy. Third 
 
 American, from the last revised, and enlarged English edition. Modided and rearranged, by 
 WlIAIAM Hunt, M. U., Demonstrator of Anatomy in the University vi Pennsylvania. In one 
 large and handsome royal 12mo. volume, extra cloth, of 582 pages, with 154illu8tration8. S2 00. 
 
 BY THE SA^E AUTHOR. 
 
 HEALTHY SKIN; A Popular Treatise on the Skin and Hair, their Preserva- 
 tion and Management. Second American, from the fourth London edition. One neat volume 
 royal 12mo.,e;ctra cloth, ol about 300 pages, with numerous illustrations. $1 00. ' 
 
38 
 
 HE^UY C. LEA'S MEDICAL 
 
 New and mucli enlarged edition. 
 
 WATSON (THOMAS), M. D., tc, 
 
 Late Physician to tlie Middlesex Hospital, &c. 
 
 LECTURES ON THE PRINCIPLES AND PRACTICE QP PHYSIC. 
 
 delivered at King's Colleg-e, London. A new Americanj fromtbe last revised and enlarged 
 
 Eng'li&h edition, with Additions, by D. Francis Condib, M. D., author of " A Practical Treatise 
 
 on the Diseases of Children," &c. With one hundred and eighty.five illustrations on wood. In 
 
 one very large and handsome volume, imperial octavo, of over 3200 closely printed pages in 
 
 small type; extra cloth, $6 50; strongly bound in leather, with raised bands, ^7 ao. 
 
 That the high reputation of this work might be fully maintained, the author has subjected it to a 
 
 thorough revision ; every portion has been examined with the aid pf the most recent researcl]ies 
 
 m pathology, and the results of modern investigations in both theoretical ^and practical subjects 
 
 have been carefully weighed and embodied throughout its pages. The watchful scrutiny of the 
 
 editor has likewise introduced whatever possesses immediate importance to the American physician 
 
 in relation to diseases incident to our cfimate which are little known in England, as well is those 
 
 points in which experience here has led to different modes of practice ; and he has also added largely 
 
 to the series of illustrations, believing that in this manner v&luabteL assistance may be conveyed to 
 
 Ihe student in elucidating the text. The work will, therefore, be found thoroughly on a level with ■ 
 
 the most advanced state of medical science on l;)oth sides of the Atlantic. 
 
 The addition's which the work has received ar^ shown by the fact that notwithstanding an en- 
 largement in the size of the page, more than two hundred additional pages have been necessary 
 to accommodate the two large volumes of the London edition (which sells at ten dollars), within 
 the compass of a single volume, and m its present form it contains the matter of at least three 
 ordinary octavos. Believing it to be a work which should lie on the table of every physician, 'and 
 be in the hands of every student, the publishers have put it at a price within the reach of all, making 
 it one of the cheapest books as yet presented to the American profession, while at the same time 
 the beauty ol its rnechanical execution renders it an exceedingly attractive volume. 
 
 The fourth edition now appears, so carefully re- 
 vised, as to add considerably to the value of a book 
 alteady acknowledged, wherever the ISrigliah lan- 
 guage is readj to be beyond all comparison the beet 
 systematic work on the Principles and Practice of 
 Physic in the whole range of medical literature. 
 Every lecture contains proof of the extreme anxiety 
 of tjie author to keep pace with ihe advancing know- 
 ledge of the day One scarcely knows whether 
 to admire most the pure, simple, forcible English — 
 the Vast amount of useful praetrcal information 
 condensed into the Lectures^— or the manly, kind- 
 hearted,' unassuming character of the lecturer shin- 
 ing through his work.— LoMd. Med. Times. 
 
 Thus these admirable volumes come before the 
 profession in their fourth edition, abounding in those, 
 distinguished attributes of moderation, judgment, 
 erudite cultivation, clearness, and eloQuence, with 
 which they were from the i&tst in^'es'.eil, but yet 
 richer than'before in the results of m(.rft prolonged 
 observatiuD, and in the able appreciation of the 
 latest advances in pathology and medicine by one 
 of the most profound medical thinkers of the day .— 
 London Lancet. 
 
 The lecturer's skill, his wisdom, his learning, are 
 equalled by the ease of his graceful diction; his elo- 
 quence, and the far higher qualities of candor^' of 
 courtesy J of modesty, and of gener6u6 appreciation 
 of merit in others.— iv A. Med -Chir Review. • 
 
 Watson's unrivalled, perhaps unapproachable 
 work on Practice — the copious addiUons made to 
 which (the fourth edition) have given it 4II the no- 
 velty and much of the interest of a new book.— 
 Charleston Med. Journal. 
 
 Lecturers, practitioners, and students. of medicine 
 will equally hail the, reappearance of tUe work of 
 Dr. Watson in theformo^anew — af"ourth— edition. 
 We merely do justice to our own feelings, and, we 
 are sure, of the whole profession, if we thank him 
 for having, in the trouble and turmoil of a large 
 practice, made leisure to supply the hiatus caused 
 by the exhaustion of the third ediliun. For Dr. 
 Watson has not merely caused the lectures to be 
 reprinted, but scattered through the whole work we 
 find additions or alterations which pruve that the 
 author has in every way sought to bring up his teach- 
 ing to the level of !^he most recent acquisitiunsin 
 science.-rfrit, and For. Medico-Chir. Review. 
 
 New and much enlarged edition. 
 WILSON (ERASMUS), F. R.S. 
 A SYSTEM OF HUMAN ANATOMY, General and Special. A new and re- 
 vised American.from tke last and enlarged Englii^h Edition. Edited by 'W.H.Gobiiecht,M.D.,, 
 Professor of Anatomy in the Pennsylvania JVIedical College, fee. Illustrated with three hundred 
 and ninety-seven engravings on wood. In one large and handsome octavo volume, ol over 600 
 large page^; extra cloth, $4 00. 
 
 The publishers trust that the well earned reputation so long enjoyed by this work will be more 
 than maintained by the present edition. Besidefca very thorough revision by the author, it has-been 
 mo:^t careJ'uUy exumined by the editor, and the efibrtss ot both have been direcied to introducing 
 everything which increased experit nee in its U!*e nas suggested as desirables to render it a complete 
 text-book lot jhose [peeking to obtain or to renew an acquaintance with Human Anatomy. The 
 amount of additions which it has.thus received may be estimated from the fact that the present 
 efdiiion contains over one-fourlb more matter than the la^l, rendering a smaller type and an enlarged 
 flage requisite to keep the volume within a convenient size. The editor has exercised the utmost 
 caution to obtain entire accuracy in the text, and, ha? largely increased the number of illustra- 
 tions, of which there are about one hundif'ed and ^fty more in this edition than in the last, thus 
 bringing distinctly before the eye of the student everything of interest orlrapottance. 
 
 It may be recommended to the student as no less 
 distingui^ed by its accuracy and clearnesB of de- 
 scription tlian by its typographical elegance. The 
 wood-cuts are exquisite. — Brit, and For. Medical 
 Review . 
 
 An elegant edition of one' of the most useful and 
 accurate systems uf unatomicini science which has 
 been issued from the press The illuBtrutions are 
 really beautiful. In its style the work is extremely 
 Concise and intelligible. No one can poasibjy take 
 up this Vdlume without being struck with the great 
 
 bMuty of its mechanical execution, and the clear- 
 ness of the{ descriptiims which it contains lb equally 
 evident. Let students, by all mean« exuinuie tae 
 claims of this work on thfcir notice, before cliey pur- 
 chasti a text-bnok of tihe vitally important science 
 which this volume so fully and easily unfolds.— 
 Lancet. 
 
 We regard it as the best system now extant for 
 students. — Westerii Lancet. 
 
 U therefore receives ourhighestcommendation.— 
 Southern Med. and Surg. Journal. 
 
33 
 
 HENRY C. LEA'S MEDICAL P UBLICATIONST 
 
 WINSLOW (FORBES), M. D., O. C. L., &c. 
 ON OBSCURE DISEASES OP THE BRAIN AND DISORDERS OF THE 
 
 MIND; their incipienl SymptomB, Pathology, Diagnosis, Treatment, and Prophylaxis. Second 
 American, from the third and revised English edition. In one handsome octavo volume, of 
 nearly 600 pages, extra cloth. $4 25. {Just Ready.) 
 
 Pathology. It completely exhausts the sukject, in 
 
 We close this brief and necessarily Very imperfect 
 notice of Dr. Winslow's great and classical work, 
 by expressing our conviction that it is long since so 
 important and beautifully written a volume has is- 
 BuedTrom the British medical press. — DvhlinMed. 
 Press, July ?S, 1660. 
 
 We honestly believe this to be the best book of th6 
 season hanlcing^s Aistract, July, 1860. 
 
 The latter portion of Dr. Winslow's work is ex- 
 .clusively devoted to the consideration of Cerebral 
 
 the same manner as'the previous seventeen chapters 
 relating to morbjd psychical phenomena left nothing 
 unnoticed m reference to the mental symptoms pre- 
 monitory of cerebral disease. It is impossible, to 
 overrate the benefits likely to result from a general 
 perusal of Dr. Winslow's valuaole and deeply in- 
 teresting work. — London Lancet, June 23, 1860. 
 
 It contains an immense .mass of information.— 
 Brit, ami For. Med.-Chir. Beviev, Oct. 1860. 
 
 WEST (CHARLES), M. D., 
 
 Accoucheur to and Lecturer on Midwifery at St. Bartholomew's Hospital, Fhysician to the Hospital for 
 \ Sick Children, &c. 
 
 LECTURES ON THE DISEASES OF WOMEN. SecoDd American, from the 
 
 second London edition. In one handsome octavo volume, extra clotli, of about 500 pages ; 
 price $3 25. * ' 
 
 *^* Gentlemen who received the first portion, as issued in the *' Medjcal News and Library," can 
 now c6laiplete their copies by procuring Part II, being page 309 to end, with Index, Title matter, 
 &c., 8vo.; cloth, price $1 25. 
 
 We mustnow conclude this hastily written sketch 
 with the confident assurance to our readers that the 
 work will weli repay perusal. The conscientious, 
 painstaking, practical physician isapparent on every 
 page. — N. Y. Journal of Medicine. 
 
 We know of no treatise of the kind so complete 
 and yet so comp&ct.~r-Chicago Med. Jour. 
 
 A fairer, more honest, mure earnest, and more re- 
 liable investigator of the 0iany diseases of women 
 and children is not to be found in any country.— 
 Southern Med. and Surg. Journal. 
 
 We have to say of it, briefly and decidedly, that 
 it is the best work on„the subject in any language ,' 
 and that it stamps Dr. West as the facile princeps 
 of British obstetric authors. — Edinb. Med. Journ. . 
 
 We gladly recommend his Lectures as in thehigh- 
 est degree instructive to all who are interestea in 
 obstetric practice. — London Lancet. 
 
 IJappy in his simplicity of manner, and moderate 
 in his exjpression of opinion^ the author is a sound 
 reaaoner and a good practitioner, and his book is 
 worthy of the handsome garb in. which it has ap- 
 peared. — "Virginia Med. Journal. 
 
 We must lake leave of Dr. West's very useful 
 work, with «iur commendation of the clearness of 
 ita style, and theincustry and sobriety of judgment 
 of which it gives evidence.— ^Lontion Med Times. 
 
 Sound judgment and good sense pervade every 
 chapter of-the. book. From its perusal we have de- 
 rived unmixed satisfaction. — Dublin Quart. Jown, 
 
 BY THE SAME AUTHOIL. {Just Reodjf.i 
 
 LECTUEES ON THE DISEASES OF . INFANCY AND CHILDHOOD. 
 
 Fourth American, from the fifth enlarged and improved London edition. In one handsome 
 octavo volume, extra clotli, of about six hundred arid fifty pages, f 4 50. 
 The numerous editions through, which this work has passed on both sides of the Atlantic, are 
 the best evidence that it has met a want felt by the profession: Few practitioners, indeed, have 
 had the opportunilieb of obt-ervation and experience enjoyed, ty the author. Jn his Preface he 
 remarks: 'The preserjt edition embodies the results of 1200 recorded cases, and of nearly 400 
 post-mortem examinations,* collected from between 30,000 and 40,000 children, who, during the past 
 twenty -SIX years have come under my care, either in public or in private practice." The universal 
 favor with which the work has been received shows that the author has made good use of these 
 unusual advantages. 
 
 The three former editions of the work now before 
 as have placed the, author, in tue foremost rank of 
 those physicians who have cievoted special attention 
 to the diseases of early life We attempt no. ana- 
 lysis of this edition, but mayrefer the reader to some 
 of the chapiters to which the largest additions have 
 been made — those on Diphtheria, Disorders of the 
 Mind, and Idiocy, for instance — as a prooi that the 
 work is re.ally a new editiuu; not a mere reprint. 
 in its pretent shape it will be lound of the greatest 
 possible service in the every-day practice of nine- 
 tenths of the profession. — Med. Tim,ei and Gazette^ 
 London, Dtc. 10, 1859. ■■ . 
 
 All things considt red this book of Dr. West is 
 by far theoe&t treatise in our language upon such 
 njodificatiuDB of morbid action and dise&se as are 
 wiiintssedwhen w'e have to deal with infancy and 
 Childhood. It is true that it confines itself to such 
 disorders as come within the province of the phy- 
 tictan, and even with respect to these it is unequal 
 as regards minutentss of consideration, and some 
 
 diseases it omits to notice altogether. But those 
 who know anything of the present condition of 
 paediatrics will readily admit that it would be next 
 to impossible to efiect more, or effect it better, than 
 the accoucheur of St. Bartholomew's has done in a 
 smgle volume. The lecture (XVI.) upon Disordtra 
 of the Mind in chile rcn is an admirable specimen of 
 the value oi the later information conveyed in the 
 
 Lectures of Dr. Gharlea West London Limeetf 
 
 Oct. 22, 1859. 
 
 Since the appearance of the first edition, about 
 eleven years, ago,, the experiencjB of the author, has 
 doubled ; so that, whereas the lectures at first were 
 founded on six hundred observations, and one hun- 
 dred and eighty dissections made among nearly four- 
 teen thousand children, they now embody the results 
 of nine hundred observations, and two hundred and 
 eighty-ei^htpost-mortem examinations made among 
 nearly thirty thtmsand children, who, during the 
 past twecty years, have been under his care.— , 
 British Med. Journal^ Oct. 1, 1859. 
 
 BY THE SAME AUTHOR. 
 
 AN ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE OF ULCEB- 
 
 ATIOW Ot THE OS UTERI. In one neat octavo volume* extra cloth. ^1^.