A TREATISE ON HUMAN PHYSIOLOGY; DESIGNED FOR THE USE OF STUDENTS AND PRACTITIONERS OF MEDICINE. BY JOHN C. DALTON, M.D., .< •• PROFESSOR "F PHYSIOLOGY AND MICROSCOPIC ANATOMY IN THE COLLEGE OF PHYSICIANS AND SURGEONS, NEW \ORK; MEMBER OF THE NEW YORK ACADEMY OF MEDICINE; OF THE NEW YORK PATHO- LOGICAL SOCIETY; OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES, BOSTON, MASS.; OF THE BIOLOGICAL DEPARTMENT OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA; AND OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. laurtft €Yxthn, gebmfc anfc inkrpfo. WITH TWO HUNDRED AND SEVENTY-FOUR ILLUSTRATIONS. PHILADELPHIA: HENRY C. LEA. 1867. QT Entered according to the Act of Congress, in the year 1864, by BLANCHARD AND LEA, in the Office of the Clerk of the District Court of the United States in and for the Eastern District of the State of Pennsylvania. «*«&..- ' 1891 < r / PHILADELPHIA: COLLINS, PRINTER, 705 JAYXE STREET. TO MY FATHEE, JOHN C. DALTON, M.D., IN HOMAGE OF HIS LONG AND SUCCESSFUL DEVOTION TO THE SCIENCE AND ART OF MEDICINE, AND III GRATEFUL RECOLLECTION OP HIS PROFESSIONAL PRECEPTS AND EXAMPLE, IS RESPECTFULLY AND AFFECTIONATELY INSCRIBED. ( i« ) PREFACE TO THE FOUBTH EDITION. The progress made by Physiology and the kindred Sciences during the last few years has required, for the present edition of this work, a thorough and extensive revision. This progress has not consisted in any very striking single discoveries, nor in a decided revolution in any of the departments of Physiology; but it has been marked by great activity of investigation in a multi- tude of different directions, the combined results of which have not failed to impress a new character on many of the features of physiological knowledge. It is also to be remarked that new acquisitions of real importance, in any one branch of Natural Science, are almost always found to have such a connection, either direct or indirect, with the associate departments, as to occasion in them, at the same time, some modification or enlargement. This is eminently true of the invention and improvement of in- struments or other means of discovery in Natural Science; such improvements being usually found applicable, in some way, to various kinds of investigation. Improvements in the construc- tion of microscopes, in photography, in galvano-electric and thermo-electric apparatus, and in the various contrivances for measuring minute intervals of time and space, have all been ser- viceable in this way. It is by the aid of such improvements that Ilelmholtz succeeded in measuring the rate of transmission of the nervous force, and that many facts have been ascertained in regard to the character of the pulse, of muscular action, and of vi PREFACE. the physical changes in the eye during the act of vision at dif- ferent distances. Investigations of the habits and functions of any of the lower animals seldom fail to exert some influence on our knowledge of the higher, owing either to anatomical resemblances or to a physiological connection between them. Such are the discov- eries made by Virchow, Leuckart, and others, in the structure and history of parasitic animals affecting the domestic quadrupeds and the human subject; and the investigations of Prof. J. Wy- man, on the appearance of vibriones in organic infusions, and the conditions which favor or prevent their reproduction. In the revision and correction of the present edition, the author has endeavored to incorporate all such improvements in physiological knowledge with the mass of the text in such a manner as not essentially to alter the structure and plan of the work, so far as they have been found adapted to the wants and convenience of the reader. Special acknowledgment deserves to be made of the investigations of J. Lockhart Clarke, Esq., on the Gray Substance of the Spinal Cord; and those of Dr. John Dean, on the Medulla Oblongata and Trapezium; which have now placed our knowledge of the structure of the spinal cord and base of the brain in a new position, of the greatest impor- tance to the physiology of these parts. Several new illustrations are introduced, some of them as additions, others as improvements or corrections of the old. Al- though all parts of the book have received more or less complete revision, the greatest number of additions and changes wore required in the Second Section, on the Physiology of the Ner- vous System. New York, 1867. CONTENTS. INTRODUCTION. PAGE Definition of Physiology—Its mode of study—Nature of Vital Phenomena— Division of the subject '.........83-43 SECTION I. NUTRITION. CHAPTER I. PROXIMATE PRINCIPLES IN GENERAL. Definition of Proximate Principles—Mode of their extraction—Manner in which they are associated with each other—Natural variation in their relative quantities—Three distinct classes of proximate principles . . . 45-52 CHAPTER II. PROXIMATE PRINCIPLES OF THE FIRST 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—Their discharge—Nature of their function .... 53-62 CHAPTER III. PROXIMATE PRINCIPLES OF THE SECOND CLASS. Starch—Percentage of starch in different kinds of food—Varieties of this substance—Properties and reactions of starch—Its conversion into sugar— Sugar—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 of this class . .......63--78 (vii) viii CONTENTS. CHAPTER IY. PROXIMATE PRINCIPLES OF THE THIRD CLASS. PAGE General characters of organic substances—Their chemical constitution—Hygro- scopic properties —Coagulation —Catalysis—Fermentation—Putrefaction— Fibrin—Albumen—Casein—Globuline—Pepsine—Pancreatine—Mucosine— Osteine — Cartilagine — Musculine —Hsematine —Melanine— Biliverdine — Urosacine—Origin and destruction of proximate principles of this class 79-88 CHAPTER Y. OF 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 Magendie on exclusive diet of gelatine or fibrin—Food requires to contain all classes of proximate principles—Composition of various kinds of food—Daily quantity of food required by man—Digestibility of food—Effect of cooking . 89-98 CHAPTER VI. DIGESTION. Nature 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—Intestinal Juices, and the Digestion of Sugar and Starch__ Follicles of intestine—Properties of intestinal juice—Pancreatic Juice, and the Digestion of fat—Composition and properties of pancreatic juice__Its action on oily matters—Successive changes in intestinal digestion—The large intestine and its contents ......... 99-145 CHAPTER VIP ABSORPTION. Closed follicles and villi of small intestine—Peristaltic motion__Absorption by bloodvessels and lymphatics—Ch vie—Lymph—Absorbent system— Lac teals and lymphatics—Absorption of fat—Its accumulation in the blood during digestion—Its final decomposition and disappearance . . 146-158 CONTENTS. ix CHAPTER VIII. THE BILE. PAGE Physical properties of the bile—Its composition—Biliverdine—Cholesterin— Biliary salts—Their mode of extraction—Crystallization—Glyko-cholate of soda—Tauro-cholate 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 . . 159-183 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 ........ 184-191 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 . . . . . . 192-196 CHAPTER XI. THE BLOOD. Red Globules of the blood—Their microscopic characters—Structure and com- position—Variations in size in different animals—White Globules 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 serum—Influ- ences hastening or retarding coagulation—Coagulation not a commencement of organization—Formation of buffy coat—Entire quantity of blood in body 197-215 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 . 216-236 X 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 ..... 237--SS47 CHAPTER XIV. THE CIRCULATION. Circulatory 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 ......... 248-290 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 chyle—Their quantity—Liquids secreted and reabsorbed in twenty- four hours •••..... 291-307 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 308-324 CONTENTS. xi CHAPTER XVII. EXCRETION. PAGB Nature of excretion—Excrementitious substances—Effect of their retention— Urea—Its source—Conversion into carbonate of ammonia—Daily 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 ...... 325-348 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 nervous tissue—Fibres of white substance—Their minute structure—Division and inosculation of nerves—Gray substance—Nervous system of radiata—Of mollusca—Of articulata—Of mammalia and human subject—Structure of encephalon—Connections of its different parts . . . 349-371 CHAPTER II. OF NERVOUS IRRITABILITY, AND ITS MODE OF ACTION. Irritability of muscles—How exhibited—Influences which exhaust 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 372-381 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. . . . 382-400 Xll CONTENTS. CHAPTER IV. THE BRAIN. PAG 8 Seat of sensibility and excitability in different parts of the encephalon—Olfac- tory ganglia—Optic thalami—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— Tuberculaquadrigemina—Tuber annulare—Medulla oblongata—Three kinds . 401_4oq of reflex action in nervous system . • • • • *VI *'" CHAPTER V. THE CRANIAL NERVES. Olfactory nerves—Optic nerves—Auditory nerves—Classification of crania's nerves—Motor nerves—Sensitive nerves—Motor oculi 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—Pneuinogastric—Its distribution —Influence on pharynx and oesophagus—On larynx—On lungs—On stomach and digestion—Spinal accessory nerve—Hypoglossal . . . 430-462 CHAPTER VI. THE SPECIAL SENSES. General and special sensibility—Sense of touch in the skin and mucous mem- branes—Nature of the special senses—Taste—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 vapors—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—Hearing—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 . 463-499 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 . 600-5IU CONTENTS. xiij SECTION III. REPRODUCTION. CHAPTER I. ON THE NATURE OF REPRODUCTION, AND THE ORIGIN OF PLANTS AND ANIMALS. PAGB Nature and objects 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 infusoria—Conditions of their development—Schultze's experiment on generation of infusoria—Pro- duction of animal and vegetable parasites—Encysted entozoa—Trichina spiralis—Taenia—Cystieercus—Production of taenia from cysticercus—Of cysticercus from eggs of taenia—Plants and animals always produced by generation from parents ...... 513-527 CHAPTER II. ON SEXUAL GENERATION AND THE MODE OF 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 528-531 CHAPTER III. ON THE EGG, AND THE FEMALE ORGANS OF 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 . . 532-543 CHAPTER IV. ON THE SPERMATIC FLUID, AND THE MALE ORGANS OF GENERATION. The spermatozoa—Their varieties in different species—Their movement—For- mation of spermatozoa in the testicles—Accessory male organs of generation — Epididymis—Vas deferens — Vesiculae seminales — Prostate—Cowper's glands—Function of spermatozoa—Physical conditions of fecundation 644-550 XIV CONTENTS. CHAPTER* V. ON PERIODICAL OVULATION, AND THE FUNCTION OF MENSTRUATION. PAGE Periodical Ovulation—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 cestruation—Menstruation—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 551-563 CHAPTER VI. ON THE CORPUS LUTEUM OF MENSTRUATION AND PREGNANCY. Corpus Luteum of Menstruation—Discharge of blood into the ruptured Graafian follicle—Decolorization of the clot, and hypertrophy of the membrane of the vesicle—Corpus luteum of menstruation, at the end of three weeks—Yellow coloration of convoluted wall—Corpus luteum of menstruation at the end of four weeks—Shrivelling and condensation of its tissues—Its condition at the end of nine weeks—Its final atrophy and disappearance—Corpus Luteum of Pregnancy—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 . . . 564-57 if CHAPTER VII. ON THE DEVELOPMENT OF THE IMPREGNATED EGG. Segmentation of the vitellus—Formation of blastodermic membrane—Two layers of blastodermic membrane—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 . . . . . . . . 574-&8b 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 . . 684-586 CONTENTS. CHAPTER IX. AMNION AND ALLANTOIS—DEVELOPMENT OF THE CHICK. PAGE Necessity for accessory organs in the development of birds and quadrupeds- Formation of amniotic folds—Their union and adhesion—Growth of allantois from lower part of intestine—Its vascularity—Allantois in 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 ••....., 587-595 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 villosities—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 . . . . . . * 596-601 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—Decidua reflexa—Inclosure of egg by decidua reflexa—Union of chorion with decidua—Changes in the relative development of different portions of chorion and decidua ..... 602-608 CHAPTER XII. THE PLACENTA. Nourishment of foetus by maternal and foetal vessels—Arrangement of 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 ...... 609-617 XVI CONTENTS. CHAPTER XIII DISCHARGE OF THE OVUM, AND INVOLUTION OF THE UTERUS. PAGE Enlargement of amniotic cavity—Contact of amnion and chorion—Amniotic fluid—Movements of foetus—Union of decidua 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 decidua— Fatty degeneration and reconstruction of muscular walls of uterus 618-624 CHAPTER XIV. DEVELOPMENT OF THE EMBRYO—NERVOUS SYSTEM, ORGANS OF SENSE, SKELETON AND LIMBS. 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 vertebras—Laminae and ribs—Spina bifida—Anterior and pos- terior extremities—Tail—Integument—Hair —Vernix caseosa—Exfoliation of epidermis ........ 625-631 CHAPTER XV. 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—Urachus—Vesico-rectal septum —Perineum — Liver—Secretion of bile—Gastric juice—Meconium—Glyco- genic function of liver—Diabetes of foetus—Pharynx and oesophagus—Dia- phragm—Diaphragmatic hernia—Heart and pericardium—Ectopia cordis— Development of the face ...... 632-642 CHAPTER XVI. DEVELOPMENT OF THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL ORGANS OF GENERATION. Wolffian 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 «... 643-652 CONTENTS. xvii 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-mesenteric arteries and vein— Circulation 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—Aorta and pulmonary artery—Ductus arteriosus —Foramen ovale and Eustachian valve — Changes in circulation at the period of birth...........653-674 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..........675-678 2 LIST OF ILLUSTRATIONS ALL OP WHICH HAVE BEEN PREPARED PROM ORIGINAL DRAWINGS, WITH THE EXCEPTION OF EIGHT CREDITED TO THEIR AUTHORITIES. tl<3. I. Fibula tied in a knot, after maceration in a dilute acid 2. Grains of potato starch 3. Starch grains of Bermuda arrowroot 4. Starch grains of wheat flour 5. Starch grains of Indian corn 6. Starch grains from wall of lateral ventricle 7. Stea'rine .... 8. Oleaginous principles of human fa 9. Human adipose tissue 10. Chyle 11. Globules 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 . . . From Rymer Jones 18. Human alimentary canal 19. Skull of rattlesnake . . . From Achille- 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. Gastric tubules from pig's stomach, middle portion 31. Confervoid vegetable, growing in gastric juice . 32. Follicles of Lieberkiihn .... 33. Brunner's duodenal glands 34 Contents of stomach, during digestion of meat . 35. From duodenum of dog, during digestion of meat 36. From middle of small intestine (xix) Richard PAGE 59 64 64 65 65 66 71 72 74 74 75 75 76 76 77 101 102 103 105 106 106 106 107 108 117 117 118 118 118 119 125 136 137 143 143 144 XX LIST OF ILLUSTEATIONS. Fia 37 From last quarter of small intestine PAGE 144 38. One of the closed follicles of Peyer's patches 146 39. Glandulse agminatse . . 146 40. Extremity of intestinal villus .... . 147 41. Panizza's experiment on absorption by bloodvessels 149 42. Chyle, from commencement of thoracic duct . 151 43. Lacteals, thoracic duct, &c. . 152 44. Lacteals and lymphatics ..... 154 45. Intestinal epithelium, in intervals of digestion . 156 46. Intestinal epithelium, during digestion . 156 47. Cholesterin ..... . 161 48. Ox-bile, crystallized ..... . 162 49. Glyko-cholate of soda from ox-bile . 162 50. Glyko-cholate and tauro-cholate of soda, from ox-bile . . 163 51. D<^g's bile, crystallized ..... . 166 52. Human bile, showing crystalline and resinous matters. . . 167 53. Crystalline and resinous biliary substances, from dog's intestin* i . 173 54. Duodenal fistula ...... . 174 55. Human blood-globules ..... . 198 56. The same, seen out of focus .... . 198 57. The same, seen within the focus .... . 199 58. The same, adhering together in rows . 199 59. The same, swollen by addition of water . . 201 60. The same, shrivelled by evaporation . 201 61. Blood-globules of frog ...... . 204 62. White globules of the blood . . 205 63. Coagulated fibrin ....... . 207 64. Coagulated blood ....... . 210 65. Coagulated blood, after separation of clot and serum . 211 66. Recent coagulum ....... . 214 67. Coagulated blood, clot buffed and cupped . 214 68. Head and gills of menobranchus . . 217 69. Lung of frog ....... . 218 70. Human larynx, trachea, bronchi, and lungs . 219 71. Single lobule of human lung . . . . . . 219 72. Diagram illustrating the respiratory movements . 221 73. Small bronchial tube ...... . 223 74. Human larynx, with glottis closed . . . . . 224 75. The same, with glottis open . . . . . . 224 76. Human larynx — posterior view . . . . . 225 77. Circulation of fish . ... . 249 78. Circulation of reptiles • . 250 79. Circulation of mammalians . . 251 80, Human heart, anterior view . 252 81. Human heart, posterior view . 252 82. Right auricle and ventricle, tricuspid valve open, arterial valve 3 closed 252 83. Right auricle and ventricle, tricuspid valve closed, arterial valv 2s open 253 84. Course of blood through the heart . 254 85. Illustrating production of valvular sounds . 257 86. Heart of frog, in relaxation ...... . 260 LIST OF ILLUSTRATIONS. xxi no. 87. 90. 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. 135. 136. Heart of frog, in contraction Simple looped fibres .... Bullock's heart, showing superficial muscular fibres Left ventricle of bullock's heart, showing deep fibres Diagram of circular fibres of the heart . Converging fibres of the apex of the heart Artery in pulsation 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 glandul Meibomian glands Perspiratory gland 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 system of 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 brain Experiment showing irritability of muscles Experiment showing irritability of nerve Action of direct and inverse currents Diagram of spinal cord and nerves From Kolliker From Ludovic From Todd and Bowman From Lehmann (Funke's Atlas) From Lehmann (Funke's Atlas) From Lehmann (Funke's Atlas) XXII LIST OF ILLUSTRATIONS. FIG. 137. Spinal cord in vertical section 138. Experiment, showing effect of poisons upon nerves 139. Pigeon, after removal of the hemispheres 140. Aztec children .... 141. Brain in situ .... 142. Transverse section of brain 143. Pigeon, after removal of the cerebellum 144. Brain of healthy pigeon in profile 145 Brain of operated pigeon in profile 146. Brain of healthy pigeon, posterior view 147. Brain of operated pigeon, posterior view 148. Inferior surface of brain of cod 149. Inferior surface of brain of fowl 150. Course of optic nerves in man 151. Distribution of fifth nerve upon the face 152. Facial nerve 153. Pneumogastric nerve 154. Diagram of tongue 155. Distribution of nerves in the nasal passages 156. Vertical section of eyeball 157. Dispersion of rays of light 158. Action of crystalline lens 159. Action of lens, when too convex 160. Action of lens, when too flat 161. Vision for distant objects 162. Vision for near objects 163. Refraction of lateral rays 164. Skull, as seen by left eye 165. Skull, as seen by right eye 166. Human auditory apparatus 167. Great sympathetic 168. Cat, after division of sympathetic in the neck 169. Different kinds of infusoria 170. Trichina spiralis L71. Taenia .... 172. Cysticercus, retracted 173. Cysticercus, 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 . 186. Ovary with Graafian follicle ruptured LIST OF ILLUSTRATIONS. xxiii no. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208, 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. Graafian follicle, ruptured and filled with blood Corpus luteum, three weeks after menstruation Corpus luteum, four weeks after menstruation . Corpus luteum, nine weeks after menstruation Corpus luteum of pregnancy, at end of second month Corpus luteum of pregnancy, at end of fourth month Corpus luteum of pregnancy, at term Segmentation of the vitellus Impregnated egg, showing embryonic spot Impregnated egg, showing two layers of blastodermic membrane Impregnated egg, farther advanced Frog's egg, at an early period . Egg of frog, in process of development Egg of frog, farther advanced . Tadpole, fully developed Tadpole, changing into frog Perfect frog Egg of fish Young fish, with umbilical vesicle Human embryo, with umbilical vesicle Fecundated egg, showing formation of amnion . Fecundated egg, showing commencement of allantois Fecundated egg, with allantois nearly complete Fecundated egg, with allantois fully formed Egg of fowl, showing area vasculosa Egg of fowl, showing allantois, amnion, &o. Human ovum, showing formation of chorion Compound villosity of human chorion Extremity of villosity of chorion Human ovum, at end of third month Uterine mucous membrane Uterine tubules. . Impregnated uterus, showing formation of decidua Impregnated uterus, showing formation of decidua reflexa Impregnated uterus, with decidua reflexa complete Impregnated uterus, showing union of chorion and decidua Pregnant uterus, showing formation of placenta Foetal pig, with membranes Cotyledon of cow's uterus Extremity of foetal tuft, human placenta Foetal tuft of human placenta injected . Vertical section of placenta Human ovum, at end of first month Human ovum, at end of third month Gravid human uterus and contents Muscular fibres of unimpregnated uterus Muscular fibres of human uterus, ten days after parturition Muscular fibres of human uterus, three weeks after parturition Formation of cerebro-spinal axis Formation of cerebro-spinal axis XXIV LIST OF ILLUSTRATIONS. FIG. . ■ "■ '*■ *f> 237. Foetal pig, showing brayi and spinal cord 238. Foetal pig, showing brain and spinal cord 239. Head of foetal pig ' . . V , 240. Brain of adult pig : . 241. Human embryo, about one inonth old 242. Formation of alimentary 'canal'.,.v . ...j,. 243. Foetal pig, showing umbilical hernia. \~_, *■**'. 244. Human embryo, about one month old . 245. Head of human embryo, at end of sixth week . 246. Head of human embryo, at end of second month 247. Fcetal pig, showing Wolffian bodies 248. Foetal pig, showing first appearance of kidneys 249. Internal organs of generation 250. Internal organs of generation 251. Formation of tunica vaginalis testis 252. Congenital inguinal hernia 253. Egg of fowl, showing area vasculosa 254. Egg of fish, showing vitelline circulation 255. Young embryo and its vessels 256. Embryo and its vessels, farther advanced 257. Arterial system, embryonic form 258. Arterial system, adult form 259. Early condition of venous system 260. Venous system, farther advanced 261. Continued development of venous system 262. Adult condition of venous system 263. Early form of hepatic circulation 264. Hepatic circulation farther advanced 265. Hepatic circulation, during latter part of fcetal life 266. Adult form of hepatic circulation 267. Foetal heart 268. Foetal heart 269. Foetal heart 270. Fcetal heart 271. Heart of infant 272. Heart of human foetus, showing Eustachian valve 273. Circulation through the foetal heart 274. Circulation through the adult heart PAGF 626 627 627 627 631 633 634 640 640 641 643 645 645 647 648 649 654 654 655 656 658 658 660 661 661 662 663 664 664 665 666 666 666 667 667 669 670 673 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, 3 ( 33 ) 34 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 placed under the requisite external conditions, present certain active phenomena, which are characteristic of them, and by which they may be recognized. INTRODUCTION. 35 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 to 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, &c, 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, from the 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 36 INTRODUCTION. 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 be 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. 37 As, for example, when 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 is already 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 practical results. For if we were to observe a phenomenon in discordance 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 phe- nomenon, but, on the contrary, depends upon it, and derives its whole authority from it. Such mistakes, however, have been re- peatedly 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, from any original principles, 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; and all our knowledge of the properties of these two bodies is derived from this and similar experiments. 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 38 INTRODUCTION. the latter can never be 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- 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 of 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 INTRODUCTION. 39 phenomena, though 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 immediately 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- ■10 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 versa. Some will take place in the light, but not in the dark; others will take place in the dark, but not in the light. Because a chemical reaction, therefore, takes place under one set of conditions, we cannot be at all sure that it will take place under others, which are different. The chemical conditions of the living 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, this process is prevented, 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 substances which make their appearance in the living body, both of animals and vegetables, and which cannot be formed elsewhere; such as fibrin, albumen, casein, pneumic acid, the biliary salts, morphine, &c. These substances cannot be manu- factured 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 they are different in their conditions and in their results, and are consequently peculiar and characteristic. Another set of vital phenomena are those which are manifested INTRODUCTION. 41 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 which 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 which 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 regarded as not different in any respect from the ordinary chemical changes taking place outside the body. This, however, is not only erroneous in theory, but conduces also to a vicious mode of study. 42 INTRODUCTION. For it draws away our attention from the phenomena themselves and their real characteristics, and leads us to deduce one set of phe- nomena 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 Nutri- 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 con- 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 Nervous System. These phenomena are not exhibited by vegetables, but belong exclusively to animal or- ganizations. They bring the animal body into relation with the external world, and preserve it from external dangers, by means of INTRODUCTION. 43 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 Eeproduction. 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 have 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. NU TUITION. CHAPTER I. PROXIMATE PRINCIPLES IN GENERAL. The study of Nutrition begins naturally with that of the proxi- 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. Each 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, the osseous system; all the arteries, the 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 oro-an n°-ain, on microscopic examination, is seen to be made ( 45) 46 proximate principles in general. up of minute bodies, of definite size and figure, which 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, there 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, systems, 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 which 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 together 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. 47 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. The difference in consistency between the solids and fluids does not, therefore, indicate any radical difference in 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 any 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 solution 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 48 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 elements, oxygen, hydrogen, and carbon, as on the particular forms of com- bination, viz., water and sugar, under which they are present. It 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 of 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 solidifies 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 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 principles in general. 49 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 or 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, &c. &c. When a chemical decomposition is unavoidable, it must be kept in sight and 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 carbonates 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 4 50 proximate principles in general. 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 solid — not crystallized, as in ice, 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 form. 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 Jnneiwnoou^ in the bones as in the blood. A proxira«^5fOmcrple7 A*9^pre, never exists alone in any part of thejIMrv. btrtrw---alwaysp_mtimately associated with a number of otlera, btfij^ £^d^fg jionioieneous mixture or solu- Every animal fl^eCfe and fluid cofi^jos a number of proximate principles which ara^gj^jhl, ^^ have already mentioned, in certain characteristic proportions. Thus, water is present in very large quantity in the perspiration and the saliva, but in yerj small quantity in the bones and teeth. Chloride of sodium is compara- tively abundant in the blood 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 some 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 principles in general. 51 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 anal- ysis of an animal fluid, in which the relative quantity of its different ingredients is expressed in numbers, we must under- stand that such an analysis is always approximative, and not ab- solute. The proximate principles are naturally divided into three differ- ent classes. The first of these classes comprises aLVt/he# proximate principles which are purely inorganic in their nature. VJJhese 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 same properties in the interior of the animal frame as elsewhere, They are crystallizable, and have a definite chemical composition. They comprise such substances as water, chloride of sodium, carbonate and phosphate of lime, &c. The second class of proximate principles is known as crystal- lizable substances of organic origin. This is the name given to them by Kobin and Verdeil,1 whose classification of the proxi- mate principles is the best which has yet been 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 interior of organized bodies, and are not found in external nature as the ingredients of inorganic substances. Such are the different kinds of sugar, starch, and oil. The third class comprises a 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 differ from those of the first by their 1 Chinrie Anatomique et Physiologique. Paris, 1853. 52 proximate principles in general. 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 are 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 phrase- ology. This class includes such substances as albumen, fibrin, casein, &c. proximate principles of the first class. 53 CHAPTER II. PROXIMATE PRINCIPLES OF THE FIRST CLASS. The proximate principles of the first class, or those of an inor- ganic nature, are very numerous. Their most prominent characters 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. Water.—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; water 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 54 proximate principles of 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 Verdeil from various observers, showing the proportion of water per thousand parts, in different solids and fluids:— Quantity of Water in 1,000 parts in Epidermis . 37 Bile .... 880 Teeth . 100 Milk 887 Bones . 130 Pancreatic juice 900 Cartilage . . 550 Urine 936 Muscles . . 750 Lymph 960 Ligaments . 768 Gastric juice 975 Brain . 789 Perspiration . 986 Blood . 795 Saliva 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 quantity 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 over 4 J 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 CHLORIDE OF SODIUM. 55 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,1 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 the 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 versa. 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 fluids 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 1 Op. cit., vol. ii. pp. 143 and 145. 56 PROXIMATE PRINCIPLES OF THE FIRST CLASS. Quantity of Chloride of Sodium in 1,000 parts in the 2 Bile 3.5 2.5 Blood 4.5 1 Mucus 6 1.5 Aqueous humor 11 3 Vitreous humor 14 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:'— Muscles Bones Milk Saliva Urine 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 sufficient 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 Boussingault, in his experiments on the 1 Robin and Verdeil. CHLORIDE OF SODIUM. 57 fattening of animals. These observations were made upon six bullocks, selected, as nearly as possible, of the 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:—l " 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 difficulty; 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. 1 Chimie Agricole, Paris, 1854, p. 271. 58 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:— Quantity of Phosphate of Lime in 1,000 parts in the Enamel of the teeth . . 885 Muscles . . . .2.5 Dentine . . . .643 Blood . . . .0.3 Bones . . . .550 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. 59 but is intimately united with the animal matter of the 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 in 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 continues 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 i» a knot, after ma- ceration in a dilute acid. (From a speci- men in the museum of the Coll. of Physi- cians and Surgeons.) 60 proximate 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 taken in 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.1 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. Lehmann2 found, by experiments upon his own person, that, within thirteen minutes after taking half an ounce 1 CI. Bernard. Lectures on the Blood ; reported by W. F. Atlee, M. D. Phila' delphia, 1854, p. 31. 2 Physiological Chemistry. Philadelphia ed., vol. i. p. 97. phosphates of magnesia, soda, and potassa. 61 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 observer1 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. Carbonate 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 small 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, 1 Physiological Chemistry, vol. ii. p. 130. 62 proximate principles of the first class. and their definite chemical composition, but also 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 the 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 soda 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 other ingredients of the animal frame, which are necessary to the procetes of nutrition. proximate principles of the second class. 63 CHAPTER III. PROXIMATE PRINCIPLES OF 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 nature, but are only found as ingredients of organized bodies. They exist both in animals and in vegetables, though in 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 (C12H,0O]0).—The first of these substances 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 used 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:—l 1 Pereira on Food and Diet, New York, 1843, p. 59. 64 proximate principles of the SECOND class. Rice Maize Barley meal Rye meal Oat meal Quantity of Starch in 100 parts in . 85.07 Wheat flour , . 80.92 Iceland moss . 67.18 Kidney bean . . 61.07 Peas . 59.00 Potato . 72.00 44.60 35.94 32.45 15.70 Fig. 2. When purified from foreign substances, starch is a white, light powder, which gives rise to a peculiar crackling sensation when rubbed between the fingers. When examined by the mi- croscope, it is seen to be composed of solid granules, which, while they have a general resemblance to each other, differ somewhat in va- rious particulars. The starch grains of the potato (Fig. 2) vary considerably in size. The smallest have a diameter of tttW, the largest 7^ of an inch. They are irregu- larly 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 hilus, 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 Grains of Potato Starch. Fig. 3. l 2o0"TT to sis of an inch in Starch Grains op Bermuda Arrowroot. diameter. They are elongated and cylindrical in form, and the concentric markings are less distinct than in the pre- ceding variety. The hilus starch. 65 Starch Grains op Wheat Flour. 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 arrowroot. They vary from Txsisjsjito vise ofan incn Fig' 4' 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- Fis- 5- dient of the animal body. It was first observed by Purkinje, and afterward by Kolliker,1 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 Virchow2 corroborated the above observations, and ascertained the corpora amylacea to be Starch Grains of Indian Corn. 1 Handbuch der Gewebelehre, Leipzig, 1852, p. 311. 2 In American Journal Med. Sci., April, 1854, p. 466. O ()Q PROXIMATE PRINCIPLES OF THE SECOND CLASS. Fie. 6. Starch Grains from Wall op Lateral Ventricles; from a woman aged 3.3. 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 transparent and colorless, like those from plants. They refract the light strongly, and vary in size from 7 ?Vtt to ttVo of an inch. Their average is ygV^j of an inch. They are some- times rounded or oval, and sometimes 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 other, 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. 67 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. Sugar.—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 particulars: 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 substances 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. r Cane sugar, Anim 1 fMHksuSar> Vege a l (jrape SUgar, -J Liver sugar, suSars' (sugar of starch. SUgarS- ( 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 milk are produced in the tissues of the liver and the mammary gland, and the sugar of 63 PROXIMATE PRINCIPLES OF THE SECOND CLASS. honey is prepared in some way by the 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 ....••= C2JH22022 Milk sugar .....•= C24H24021 Glucose ...•••• = C24H2b023 Cane 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 sugar, 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 close 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 Trammer'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 of 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, the 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 SUGAR. 69 of copper, even when present in large quantity. Maple 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 particularly 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 mixed 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.1 1 Pereira, op. cit., p. 55. 70 PROXIMATE PRINCIPLES OF THE SECOND CLASS. Quantity of Sugar ix 100 parts is Figs . 62.50 Wheat flour. 4.20 to 8.48 Cherries 18.12 Rye meal 3.28 Peaches 16.48 Indian meal 1.45 Tamarinds 12.50 Peas 2.00 Pears 11.52 Cow's milk . 4.77 Beets . 9.00 Ass's milk . 6.08 Sweet almonds 6.00 Human milk 6.50 Barley meal . . 5.21 Beside the sugar, therefore, 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 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, disap- pears 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.......= C9I HS7 013 Margarine ......= C-6 Il75 012 Stearine ......= CU2H141017 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 less. The fats are all 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 alkali, they are decomposed, and as the result of the decomposition there are formed two new bodies; first, glycerine, FATS. 71 which is a neutral fluid substance, and secondly, a fatty acid, viz: oleic, margaric, or stearic acid, corresponding to the kind of fat which 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 fatty 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 oleaginous 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 them hold in solution the more solid. Generally speaking, in the s' '' living 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. Stearine crystallized from Oleine. Warm Solution in 72 PROXIMATE PRINCIPLES OF THE SECOND CLASS. Fig. 8. These substances crystallize, in very slender needles, which are sometimes straight, but more often somewhat curved or wavy m 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 indefi- 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 smaller. 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 following list shows the percentage of oily matter present in various kinds of animal and vegetable food.1 Quantity of Fat in 100 parts in Oleaginous Principles of Human Fat. Stearine 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 1 Pereira, op. cit., p. 81. FATS. 73 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 other; 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 serous 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 and 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 74: PROXIMATE PRINCIPLES OF THE SECOND CLASS. of health. These vesicles are transparent, and have a somewhat angular form, owing to their mutual compression. (Fig. 9.) They vary in diameter, in the hu- Fig. 9. man subject, from g^ to .j^ Human Adipose Tissue. 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- Fis-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 T7^^ 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 Chyle, from commencement of Thoracic Duct, from the Dog. FATS. 75 by transmitted light only as minute dark granules. 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 FlS-11- 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, Globules of Cow's Milk. the globules vary somewhat in size, but their average diameter is ^xhttj- 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. Culls of Costal Cartilaues, containing Oil- Globules. Human. 76 PROXIMATE PRINCIPLES OF THE SECOND CLASS. Hepatic Cells. Human. 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. 13), generally in smaller FiS-13- globules than the preceding. In some cases of disease, it accumulates in excessive quantity, and produces the state known as fatty 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. (Fig. 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 the 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 Urinu'euous Tub ui.es of Dog, from Cortical Portion of Kidney. FATS. 77 Muscular Fibres of Hum an Uterus, three weeks after parturition. 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- g* 15' 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 fat 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,1 M. Persoz on geese,2 and finally by those of M. Boussingault on geese, ducks, and pigs.3 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 by the 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. 1 Annales de Chim. et de Phys., 3d series, vol. xiv. p. 400. 3 Clrimie Agricole, Paris, 1854. Ibid. 408. 78 PROXIMATE 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 cane 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 accumulation 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 be transported 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 oily 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 PRINCIPLES OF THE THIRD CLASS. 79 CHAPTER IV. PROXIMATE PRINCIPLES OF 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 organic substances was given to them by Robin and Yerdeil, by whom their distinguishing pro- perties were first accurately described. They have not only an organic 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 term " 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 sometimes 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 known by the name of the " nitrogenous substances," while the sugars, starch, and oils have been called " non-nitrogenous." 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 remainder 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 80 PROXIMATE PRINCIPLES OF THE THIRD 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 equivalents 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 chemical 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:— Fibrin......= C29ell22,N,u092s, Albumen.....=^11,^,0^ Cas«in......= C,8SH228N36o£0s2 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. 81 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 diffused 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. Thus 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. 6 82 PROXIMATE PRINCIPLES 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 an 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- ORGANIC SUBSTANCES. 83 lytic action by which 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 crystallizable 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 which we are 84 PROXIMATE PRINCIPLES 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. Fibrin.—Fibrin is found in the blood; where it exists, in the human subject, 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 carnivora. 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, though it resembles it in some respects; it is properly 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 temperature 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 small quantity of albumen has been sometimes found in the saliva. 3. 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 important as an article of food, being the principal organic ingredient in 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. 85 What is called vegetable casein or " legumine," is different from the 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.—This 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 Robin, 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, ft occurs in this fluid in very small quantity, 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. Pancreatine.—This is the organic substance of the pancreatic juice, 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. 56 PROXIMATE PRINCIPLES OF THE THIRD 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. Cartilagine.—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. Musculine.—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 always 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. Hematine is the coloring matter of the red globules of the blood. It is nearly fluid like the globuline, and is united 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:— Hematine.....= C44H22N306Fe. When the blood-globules from any cause become disintegrated, the hsematine 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.—UROSACINE. 87 of arteritis; but is really a simple effect of post-mortem imbibition, as above stated. 12. Melanine.—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, &c. 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. Biliverdine 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 acid 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 (Robin), 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. Urosacine is the yellow coloring matter of the urine. It con- sists of the same ultimate elements as the other coloring matters, but occurs in the urine in such minute quantity, that the relative pro- portion of its elements has never been determined. According to Dr. Thudichum,1 it is easily soluble in water, less so in ether, and still less in alcohol;—and by some simple change in its compo- sition, probably by oxidation, its yellow color passes into a red. It readily adheres to insoluble matters when they are precipitated from the urine, and is consequently found almost always, to a greater or i British Medical Journal, Nov. 5th, 1864 88 proximate principles of the third class. less extent, as an ingredient in urinary calculi formed of the urates or of uric acid. When the urates are thrown down also in the form of a powder, as a urinary deposit, they are usually colored more or less deeply, owing to the red or yellowish red urosacine which is precipitated 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, hgematine, globuline, and all the other varieties of organic matter that cha- racterize the different tissues. These varieties, therefore, originate as such in the animal economy by the catalytic changes which the ingredients of the blood undergo in nutrition. Only a very small 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- face. 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 destructive assimi- lation, and their elements are finally eliminated and discharged under other forms of combination. OF food. 89 CHAPTER V. OF FOOD. Under the 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 substances," 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 own 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 the supply of solid food only is withdrawn. A man may pass eight or ten hours, for example, without solid 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,1 that if the animals 1 Comptes Rendus, vol. xiii. p. 256. 90 OF 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, &c, 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 oleaginous 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 food; 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 facts, 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 indispensable 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 FOOD. 91 derived, under 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,2 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 some 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 slowly 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 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 oily matters may sometimes be produced in the body from the sugars, 1 Natural History of Bees, Edinburgh, 1821, p. 330. 2 Annales de Chim. et de Phys., 3d series, vol. xiv. p. 400. 92 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. Boussingault1 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.2 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 Dr. Wm. A. Hammond,3 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 1 Chimie Agricole, p. 166. 2 Journal fiir praktische Chemie, vol. xxvii. p. 257. 3 Experimental Researches, &c, being the Prize Essay of the American Medical Association for 1857. OF FOOD. 93 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 not 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 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 1 Comptes Rendus, 1841, vol. xiii. p. 2^7. 94 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 oils, 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 be 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 mention ed, 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 these 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 the OF FOOD. 95 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 properties ; 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 96 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 :—1 Composition of Cow's Milk. Water............87.02 Casein ............ 4.48 Butter............3.13 Sugar of milk .......... 4.77 Soda ..........." Chlorides of potassium and sodium ..... Phosphates of soda and potassa ...... Phosphate of lime ........ }• 0.60 " magnesia ....... Alkaline carbonates ........ Iron, &c........ 100.00 In wheat flour, gluten is the albuminoid matter, sugar and starch the non-nitrogenous principles. Composition of Wheat Flour. Gluten .... 7.30 Gum .... 3.80 Starch .... 72.00 Water .... 12.00 Sugar .... 5.40 ----- 100.00 The other cereal grains mostly contain oil in addition to the above. Composition 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 . . . . . .N .23.95 100.00 Eggs contain albumen and salts in the white, with the addition of oily matter in the yolk. 1 The accompanying analyses of various kinds of food are taken from Pereira on Food and Diet, New York, 1843. OF FOOD. 97 Composition of Eggs. White of Egg. Yolk of Egg. Water .... 80.00......53.78 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 meat, we have the albuminoid matter of the muscular fibre and the fat of the adipose tissue. Composition of Ordinary Butcher's Meat. ., . , .,,,,, QS -rt S Water.....63.42 Meat devoid of fat . . 85. i0 < t Solid matter .... 22.28 Fat, cellular tissue, &c....... . . .14.30 100.00 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 coffee 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 or fat . . . . 3V " " 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. 7 98 OF 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. 99 CHAPTER VI. DIGESTION. Digestion is that process by which 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 ammonia. 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 semi-solid at the time when it is taken, and insoluble 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, in the human species, coagulated and solidified by 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 100 DIGESTION. upon it in 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 grains, and are nearly always entangled among vegetable cells and fibres of an indigestible character. In those instances 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 (b) 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. 101 glandular, and is provided with numerous se- Fig-16. 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 feeding, 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 descends 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, which give it Alimentary Canat, of Fowl. — a. (Esophagus, b. Crop. c. Proventriculus, or secreting stomach, d. Gizzard, or triturating stomach, e. In- testine. /. Two long caecal tubes which open into the in- testine a short distance above its termination. 102 DIGESTION. Compound Stomach of Ox.—a. (Esopha- gus, b. Rumen, or first stomach, c. Reticulum, or second, d. Omasus, or third, e. Abomasus, or fourth. /. Duodenum. (From Rymer Jones.) a honey-combed or reticulated appearance. Here the food, already triturated in the mouth, and 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 abomasus, 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 and 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 digestive apparatus in man resembles almost exactly that of the carnivora. 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, they are so softened by the process of cooking as to become nearly or quite as 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. 108 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. — lg 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 (/, g). Finally, we have the large intestine (h, i,j, Jc), separated from the smaller by the ileo-caecal valve, and ter- minating, at its lower ex- 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 Human Alimentary Canal. — a. (Esophagus. b. Stomach, c. Cardiac orifice, d. Pylorus. «. Small intestine. /. Biliary duct. g. Pancreatic d«ct. h. As- cending colon, i. Transverse colon. J. Descending colon, k. Rectum. 104 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 valvulse 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 stomach; third, with the bile; 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 the various elements of the food are affected in different ways by these different digestive fluids; and as the result of their com- bined action, the ingredients of the alimentary mass are successively reduced to a fluid condition, and are then taken up by the vessels of the intestinal mucous membrane. The action which is exerted 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 instance 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 be examined separately, and their action on the aliment- ary substances in the different regions of the digestive apparatus successively investigated. MASTICATION. 105 Mastication.—In the first division of the alimentary canal, viz., the mouth, the food undergoes simultaneously two different 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 action of a solvent Quid; 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 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 proc«ss 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 skitll of rattlesnake. ,i i i ■ i • i t i -i (After Achille-Richard.) 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 106 DIGESTION. Fig. 20. edges, each presenting several sliarp points, arranged generally in 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 maxilla. (Fig. 21.) They are used merely for cutting off the grass or herbage, on which the animal feeds. The canines are either absent or slightly developed, and the real process of mastication is Skull of Polar Beak. Anterior view; showing incisors and canines. Fig. 21. Skcll of the Horse. performed altogether by the molars. These are large and thick (Fig. 22), and present a broad, flat surface, diversified by variously folded and projecting ridges of enamel, with shal- low grooves between them. By the lateral rub- bing motion of the roughened surfaces against each other, the food is effectually comminuted 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 Molar Toot h of the Horse. Grind- ing surface. SALIVA. 107 Fi*. 23. >J Human Teeth — UpperJa w.—a. Incisors, b. Canines Anterior molars, d. Posterior molars. edge running from side to side. The canines (b), which are situated immediately behind the former, are much less prominent 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 of the carnivora. 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 human 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.—At the same time that the food is masticated, it is mixed in the cavity of the mouth 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 108 DIGESTION. specific gravity of 1005. When first discharged, it is frothy and opaline, 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. scoPe (Fi£- 2^> is seen t0 consist of abundant epithe- lium scales from the internal surface of the mouth, de- ,»/?. \ tached by mechanical irrita- te) *.| J/© J ^ \ tion, minute, roundish, gra- v/j)/ - ' - / /-r53-r>\ \ nular, nucleated cells, appa- V| \ @ ~~^o'f-$~~ l\ ren^y epithelium from the @^r M ''o°'//^jr> \S|^l^|Mf mucous follicles, a certain •*' ' ,v \/x^\_/"~^ / amount of granular matter, .■§)'■.,, \ at° *■ / and a few oil-globules. The Cy \^ "^ ' / supernatant fluid has a faint bluish tinge, and becomes slightly opalescent by boil- bcccal and glandular epithelium, with ™g, and by the addition of Granular Matter and Oil-globules; deposited as sedi- nitric acid. Alcohol in eX- ment from human saliva. . ... cess causes the precipitation of abundant whitish flocculi. According to Bidder and Schmidt,1 the composition of saliva is as follows:— Composition of Saliva.. Water...........995.16 Organic matter ......... 1.34 Sulpho-cyanide 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 is of two kinds. The first, which is known by the name of ptyaline, is derived from the secretions of the submaxillary and sublingual glands. It is this substance which gives the saliva its viscidity. It is coagulable by alcohol, but not by a boiling temperature. The other organic mat- ter present in the saliva, which is derived from the secretion of the parotid gland, is not viscid, but coagulates by heat. The whole saliva therefore becomes slightly turbid on being raised to a boiling temperature. The sulpho-cyanogen may be detected by a solution 1 Verdauungsssefte und Stoffwechsel. Leipzig, 18512. SALIVA. 109 of chloride of iron, which produces the characteristic red color of sul- pho-cyanide 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, which 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 degree of viscidity than that from the submaxillary. The mucous secre- tion of the follicles of the mouth, which 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 when received in a glass vessel, but adheres strongly to the surface of the glass. We have 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 ^ to aV OI> an mcn m 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. 110 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 differs 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 abundance. 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 different clays, 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 College of Physicians and Surgeons, with the following result :— Composition op Human Parotid Saliva. Water........... 983.308 Organic matter precipitable by alcohol ..... 7.352 Substance destructible by heat, but not precipitated by alcohol or acids........... 4.810 Sulpho-cyanide of sodium. . . . . . . . 0.330 Phosphate of lime.........0.240 Chloride of potassium........0.900 Chloride of sodium and carbonate of soda .... 3.060 1000.000 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 boiling temperature, by nitric acid, and 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 masks 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. Ill saliva contains sulpho-cyanogen, which may be detected, as we have already seen, after the organic matters have been precipitated by alcohol. A very curious fact has been observed by M. Colin, Professor of Anatomy and Physiology at the Yeterinary School of Alfort,1 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 versa. In these animals mastication is said to be unilateral, 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 each 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 the 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,2 who collected from two to three ounces in twenty-four hours from an accidental salivary fistula of Steno's 1 Traite de Physiologie Comparee, Paris, 1854, p. 468. * Simon's Chemistry of Man. Phila. ed., 1846, p. 295. 112 DIGESTION. duct in the human subject; from which it was supposed that the total amount secreted by 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 total quantity of saliva, based on the amount secreted in the intervals of mastication, would be a very imperfect one. We may make a tolerably accurate calculation, however, by ascertaining 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 = 12232 " Total quantity in twenty-four hours = 20164 grains ; or rather less than 3 pounds avoirdupois. Op. cit., p. 14. SALIVA. 113 The most important question, connected with 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,1 may even be precipitated by alcohol, and kept 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 boiled 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 temperature of 100° F., 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 fifteen 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. This property of the saliva, however, is rather an incidental than an essential one; and although starchy substances are really con- verted 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 1 Chimie appliquee a la Physiologie et a la Therapeutique, Paris, 1856, p. 43. 8 114 DIGESTION. 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 mastication into the stomach. It might be supposed that the saccharine con- version of starch, after being commenced in the mouth, might continue and be completed in the stomach. We have convinced ourselves, however, by frequent experiments, that this is not the case. If a dog, with a gastric fistula, be fed with a mixture of meat and boiled starch, and portions of the fluid contents of the stomach withdrawn afterward through the fistula, the starch ia 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 disappeared; but no sugar is to be detected at any time. Sometimes the starch dis- appears more rapidly than this; but at no time, according to our ob- servations, is there any indication of the presence of sugar in the gas- tric fluids. It is now generally acknowledged also, by most 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, therefore, of saliva on starch, though a curious and interesting pro- perty, has 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 SALIVA. 115 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,1 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 difficult 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 were constantly ready to drink." Bernard3 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 retarded. The alimentary masses passed down the oesophagus at longer intervals, and their interior was no longer moist and pasty, 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- ' Op. cit., p. 3. 2 Lecons de Physiologie Experimentale, Paris, 1856, p. 146. 116 DIGESTION. 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 difference 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,1 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 much mastication, 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 preliminary preparation is accomplished. 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 stomach. Gastric Juice, and Stomach Digestion.—The mucous mem- brane of the stomach is distinguished by its great vascularity 1 Comptes Rendus, vol. xxi. p. 362. gastric juice, and stomach digestion. 117 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 what 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 encircled by a capillary ' network. In the pyloric portion (Fig. 26), the eminences are more Fig. 25. Fig. 26. Fig. 25. Free surface of Gastric Mucous Membrane, viewed from above; from Pig's Sto- mach, Cardiac portion. Magnified 70 diameters. Fig. 26. Free surface of Gastric Mucous Membrane, viewed in vertical 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- 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 parts of the stomach. In the pyloric portion of the pig's stomach (Fig. 27, next page), they are nearly straight or slightly tortuous tubules, 7Tif of an inch in diameter, lined with small glandular epithelium cells, and ter- minating in blind extremities at the under surface of the mucous membrane. In their lower half they are often branched, two or more lateral diverticula passing off from the principal tubule, and formino- a little mass or lobule of glandular tubes. At their upper 118 DIGESTION. Fig. 27. extremities, they open on the free surface of the mucous mem brane, in the interspaces between the projecting folds or villi, Among these tubular glan- dules there is also found, in the gastric mucous mem- brane, another kind of glan- dular organ, consisting of closed follicles, similar to the solitary glands of the small intestine. These fol- licles, which are not very numerous, are seated in the lower part of the mucous membrane, and enveloped by the csecal extremities of the tubules. (Fig. 27, a.) In the cardiac portion of Mucous Membrane of Pis s Stomach, from x Pyloric portion; vertical section ; showing gastric the Stomach the Superficial diabmeter8aild' *' "' ' Cl°Sed f°mCle' ^"^ ^ Part °f the MUCOUS mem- brane contains very wide circular tubes lined with large distinctly marked cylinder epithe- lium cells. (Fig. 29.) These tubes divide at a certain distance from the surface, and the tubules which result from their division become Fig. 28. Fig. 29. Fig. 28. Gastric Tubules from Pio's Stomach, Pyloric portion, showing their Caecal Extremities. At a, the torn extremity of a tubule, showing its cavity. Fig. 29. Gastric Tubules from Pig's Stomach; Cardiac portion. At a, a large tubule dividiug into two small ones. b. Portion of a tubule, >een endwise, c. Its central cavity. GASTRIC JUICE, AND STOMACH DIGESTION. 119 much reduced in size, and are lined with small rounded cells of glandular epithelium. They finally terminate, like the others, in rounded extremities at the bottom of the mucous mem- Fig- 30- brane. In the middle portion of the stomach the tubules, which are here very long, in comparison both with those near the cardia and those near the pylorus, are also distinguished by being filled, in addition to the ordinary glandular epithe- lium, with very large, rounded, granular nucleated cells, which often seem to -.. . . . . n 6A8IIIIC TUBUIE8 FROM PlG'8 STOMiCH' middle nil their entire cavity and portion. project from their sides, giv- ing them an irregularly tumefied or varicose appearance. These tubules, with large granular cells, are considered, by some authors, as the most important agents in the secretion of the gastric juice. All the gastric tubules, however, in the various parts of the stomach, probably combine to produce the digestive fluid. 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 120 DIGESTION. 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, wag 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 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 diameter, 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 extracted for examination. Dr. Beaumont experimented upon this person at various intervals from the year 1825 to 1832.1 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 effect of various kinds of stimulus on the secretion of the stomach, the rapidity with which the process of digestion takes place, the com- parative digestibility of various kinds of food, &c. &c. 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 1 Experiments and Observations upon the Gastric Juice. Boston, 1834. GASTRIC JUICE, AND STOMACH DIGESTION. 121 through the abdominal parietes in the median line, over the great 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 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- in a- the walls of the stomach, and was soon poured out abundantly into its cavity. We have found, however. that the rule laid down 122 DIGESTION. 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 fistulas 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 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 abundant 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 sufficient 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 sufficient 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 3iiss may be collected in the course of fifteen GASTRIC JUICE, AND STOMACH DIGESTION. 123 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 to 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 filtration from accidental impurities. Obtained in this way, the gastric juice is a clear, watery fluid, without any appreciable vis- cidity, very distinctly acid to test paper, of a faint amber 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, Bidder and Schmidt, and other observers: — Composition of Gastric Juice. Water...........975.00 Organic matter......... 15.00 Lactic acid..........4.78 Chloride of sodium........ l-^0 potassium 1. " " calcium........ 0.20 " " ammonium ......•• 0-65 Phosphate of lime.........I-48 magnesia 0.06 « " iron.........°-05 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 present, but regards lactic acid as the most abundant and important ingredient of the two. Bobin and Ver- deil also regard the acid reaction of the gastric juice as due to lac- tic acid; and, finally, Bernard has shown,1 by a series of well con- trived 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 chlorides, svhich enter into the composition of the fresh juice. 1 Lecons de Physiologic Exp6rimentale, Paris, 1856, p. 396. 124 DIGESTION. Prof. C. Schmidt,1 in Germany, has also had an opportunity oJ examining the human gastric juice in a case of gastric fistula, simi lar to that of Alexis St. Martin. This was the case of a healthy woman, 35 years of age, who, in consequence of a local inflamma- tion, became affected with a gastric fistula situated below the left breast, in the ninth intercostal space. Prof. Schmidt found the gastric juice obtained from this fistula similar to that of the dog, except that it contained a smaller proportion of organic matter, of free acid, and of solid ingredients generally; — the whole secretion being, at the same time, more abundant in quantity. From our own observations, already alluded to, we have no doubt that both the quantity and density of the gastric juice vary, within certain limits, in different individuals of the same species;— the proportion of solid ingredients being less when the secretion is more abundant, and greater when the secretion is in small quantity. 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 alka- line carbonate. The most important ingredient of the gastric juice, beside the free acid, is its organic matter or "ferment," which is known under the name of pepsine. This name, "pepsine," was origi- nally 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 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 of the stomach. But whatever be its source, since it is 1 Annalen der Chemie und Pharmacie, 1854, p. 42. GASTRIC JUICE, AND STOMACH DIGESTION. 125 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. It is precipitated also, and coagulated, by a boiling tem- perature; and the gastric juice, accordingly, after being boiled, becomes turbid, and loses altogether its power of dissolving alimentary sub- stances. Gastric juice is also affected in a remarkable manner by being mingled with bile. We have found that four to six drops of dog's bile precipitate completely with 3j of gastric juice from conpervoid vboetabi.ii, growing in the Gas- the same animal; so that the trie Juice of the Dog. The fibres have an average diameter of 1-7000 of an inch. 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 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. 31); 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 its 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, &c, it is found, as Dr. Beaumont formerly observed, to exert a solvent action 126 DIGESTION. on these substances 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, affects 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, opaque 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 dissolved, so that the muscular bundles become more distinct, and separate from each other. 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. GASTRIC JUICE, AND STOMACH DIGESTION. 127 The time required for the complete liquefaction of 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, and 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 cheese is entirely converted into albuminose, and dissolved under that form. A very considerable portion of raw white of egg, how- ever, dissolves in the gastric juice directly as albumen, and 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 time if it be separated and filtered, the filtered fluid has a distinct, brownish 128 DIGESTION. 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 68). 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 Hebdomadaire for February 9th, 1855.2 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 of food, already contains some albuminose in solution, 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 well marked deposit. This interference will take place when sugar is present in very large proportion. We have found that in a mix- 1 American Journ. Med. Sci., Oct. 1854, p. 319. 2 Nouvelles recherches relatives a Paction du sue gastrique sur les substances albuminoides.— Gaz. Hebd. 9 Ftvrier, 1855, p. 103. GASTRIC JUICE, AND STOMACH DIGESTION. 129 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 5j 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 be 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 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 peristaltic 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- 9 130 DIGESTION. 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 along 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 curvature 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, in opening the abdomen, any such energetic or extensive contrac. tions of the stomach, even when full of food, as may be easily excited in the 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 that the 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- GASTRIC JUICE, AND STOMACH DIGESTION. 131 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 requires 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 examining 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:— Kind op Food. Hours. Mixutes. 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 00 Salt beef (boiled).......4 15 Roasted pork........5 15 The comparative digestibility of different substances varies more or less in 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-quarters of gastric juice. The total quantity, therefore, for 21 hours, in the same ani- mal, would be 3J pounds; and, by applying the same calculation to 132 DIGESTION. 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. Schmidt,1 in his experiments on the gastric fistula of the human subject already alluded to, found the secretion of gastric juice even more abundant than the above; since, in a woman weighing only 117 pounds, he obtained, as the mean result of several observations, over one pound of gastric juice from the fistula in the course of an hour. Owing, however, to the great variation in the secretion of the gastric juice at different times, according to the activity of diges- tion, we have endeavored to determine the question of its total daily quantity in a different manner, by experimenting as follows 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 ,liss 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 siss 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 the same amount, beside other articles of food, is often taken by the human subject in the course of a day; — and yet, to dissolve this quantity, no less than thirteen pints of gastric juice will be necessary. This quantity, or any approximation 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 im- mediately 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 incessantly restored to it by the other. A very large quantity, 1 Annalen der Cliemie und Pharmacie, 1854, p. 42. GASTRIC JUICE, AND STOMACH DIGESTION. 133 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- lowing 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 sufficient to smear over and penetrate the half digested pieces of meat; and, secondly, in the living animal, gastric 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 Reaumur 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 131 DIGESTION. the process of nutrition, 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 putrefactive 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 difficulty. 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, INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 135 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 chance 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 of 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 small 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 3ss 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 136 digestion. 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 starchy 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 rapidity with which this passage of the starch into the duodenum takes place varies, to some extent, in different animals, Fls- 32, according to the general ac- tivity of the digestive appa- ratus ; but it is always a comparatively rapid process, when the 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- complished by the action of the intestinal juices. Our knowledge is not verv Foi,uclE8 0F lieberkuhn, from smaii in- ° J testine of dog. 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, PANCREATIC JUICE, AND THE DIGESTION OF FAT. 137 Fie. 33. 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 Lieberkuhn and the glands of Brun- ner. The first of these, or Lieberkiihn's follicles (Fig. 32), 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. 33), or the duodenal glandulse, 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 difficulty 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 Portion of one of Bkunner's Glands, from Human Intestine. Duodenal 138 DIGESTION. 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. From 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 valvulaj 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 pancreatic juice, and the digestion of fat. 139 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,1 led to the conclusion 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, an incision made in the upper part of the abdo- men, a little to the right of the median line, and a loop of the duo- denum, together with the lower extremity of the pancreas which lies adjacent to it, drawn out at the external wound. The pancre- atic 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. When the effects of etherization have passed off, the animal may be fed, and soon after the digestive process has commenced, the pan- creatic 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 1 American Journ. Med. Sci., Oct. 1854. 110 digestion. 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 364 grains per hour; but as the pancreatic juice in the dog is secreted with freedom only during digestion, and as this process 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 distinctly alkaline reaction. Its composition, according to the analysis of Bidder and Schmidt, is as follows:— Composition of Pancreatic Juice. Water...........900.76 Organic matter (pancreatine) ....... 90.38 Chloride of sodium ......... 7.36 Free soda...........0.32 Phosphate of soda.........0.45 Sulphate of soda ......... 0.10 Sulphate of potassa ......... 0.02 {Lime ........ 0.54 Magnesia ....... 0.05 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 fluid. It 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 PHENOMENA OF INTESTINAL DIGESTION. 141 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."1 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 suffer 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. Beduced 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, 1 Lehmann's Physiological Chemistry. Philada. ed., vol. i. p. 507. 142 DIGESTION. by the influence of which 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 intervening 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 Trommer'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 PHENOMENA OF INTESTINAL DIGESTION. 143 Contents of Stomach during Digestion of Meat, from the Dog.—a. Fat Vesicle, filled with opaque, solid, granular fat. b, b. Bits of partially disintegrated muscular fibre, c. Oil globules. Fig. 35. fibres, fat vesicles, and oil drops; substances which are easily recognizable under the microscope, and which produce a grayish „. _. turbidity in the fluid drawn tiK. 34. J 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. 34.) The fat vesicles are but little or not at all altered in the stomach, and there are only a few free oil globules to be seen floating in the mixed fluids, contained in the cavity of the organ. In the duodenum the muscular fibres are further disintegrated. (Fig. 35.) 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- From Duodenum of Dog, during Diges- tion of Meat.—a. Fat Vesicle, with its contents diminishing. The vesicle is beginning t» shrivel and the fat breaking up. b, b. Disintegrated muscular fibre, c, c. Oil Globules. 73 144 DIGESTION. From Middle of Small Intestine.—a, a. Fat vesicles, nearly emptied of their contents. Fig. 37. cles also begin to become altered in the duodenum. The solid granular fat of beef, and similar 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. 36 and 37) these changes continue. The mus- cular fibres become constantly more and more disintegrated, and a large quantity of granu- lar debris is produced, which is at last also dissolved. The fat also progressively disappears, and the vesicles maybe 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, one after another, by the vessels of the mucous membrane, and carried away by the current of the circulation. From last quarter of Small Intestine. —a, a. Fat vesicles, quite empty and shrivelled. THE LARGE INTESTINE AND ITS CONTENTS. 145 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 different 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,1 as a characteristic ingredient of the human feces. It is a slightly alkaline, crystallizable substance, insoluble in water, but soluble in ether and hot alcohol. It crystallizes in radiated groups of four- sided prismatic needles. It fuses at 204° F., and burns at a higher temperature. It is non-nitrogenous, and consists of carbon, hydro- gen, oxygen, and sulphur, in the following proportions: — C78 H78 02 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.2 It was found by Prof. Flint both in the human feces and those of the dog; and was obtained by him in proportions varying from .0007 to .003 of the whole mass of the feces. 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 fat, fatty acids, and the remnants of undigested food. Vegetable cells and fibres may be detected, and some debris of the disintegrated muscu- lar fibres may almost always be found after a meal composed of ani- mal and vegetable substances. But little absorption, accordingly, takes place in the large intestine. Its office is mainly confined to the separation and discharge, of certain excrementitious substances. 1 Philos. Trans., Lond., 1857, p. 410. 2 Am. Journ. Med. Sci., Oct., 1862. 10 146 absorption. CHAPTER VII. ABSORPTION. Beside the glands of Brunner and the follicles of Lieberklihn, already described, there are, in the inner part of the walls of the intestine, certain glandular- g' looking bodies which are termed " glandulas solitariae," and " glandulse agminatas." The glanduIsb solitarise 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. 38) is formed of an investing cap- sule, closed on all sides, and containing in its interior a „ „ „ soft pulpy mass, which con- One of the closed Follicles of Peyer's r rJ Patches, from Small Intestine of Pig. Magnified sists of minute Cellular bodies, imbedded in a homogeneous 50 diameters. FiV. 39. Glaicdul;e Aominat.w, from Small Intestine of l'ig. Magnified 20 diameters. 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 vesicle, 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- ABSORPTION. 117 Fig. 40. tissue. The glandulae agminatse (Fig. 39), 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. 40), 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 epithelial 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 hXTREHITIT OF I >' T E 8 T I K A I, Villus, from the Dog.—a. Layer <>! epithelium, b. Bloodvessel, c. Lacteal 118 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-fluid mass contained in the intestinal cavity, as the roots of a tree penetrate the soil; and they imbibe the liquefied portions of the food, with a rapidity 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 may 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 diameter, 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 relaxation, 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 small intestine, there remains only the undigestible portion of the food, together with the refuse of the intestinal secretions. These ABSORPTION. 149 pass through 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. This was first shown by Magendie,1 who found that the absorption of poisonous substances would take place, in the liv- ing animal, both from the cavity of the intestine and from the tis- sues of the lower extremity, notwithstanding that all communica- tion through the lacteals and lymphatics was cut off, and the passage by the bloodvessels alone remained. These results were afterward corroborated by Panizza,2 who succeeded in detecting the substance which had been absorbed in the venous blood returning from the part. This observer opened the abdomen of a horse, and drew out a fold of the small intestine, eight or nine inches in length (Fig. 41, a, a), which Fig. 41. Panizza's Experiment.—ta. Intestine, b. Point of ligature of mesenteric vein. c. Opening in intestine for introduction of poison, d. Opening in mesenteric vein behind the ligature. i Journal de Physiologie, vol. i. p. 18. 2 In Matteucci's Lectures on the Physical Phenomena of Living Beings, Pereira'r edition, p. 83. 150 ABSORPTION. he included between two ligatures. A ligature was then placed (at b) upon the mesenteric vein receiving the blood from this portion of intestine; and, in order that the circulation might not be inter rupted, an opening was made (at d) in the vein behind the ligature, so that the blood brought by the mesenteric artery, after circulating 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 prevented 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 compression was maintained upon the vein. But as soon as the blood was allowed to pass again through the vessels, 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 ABSORPTION. 151 contact with its organic ingredients, they become altered and con- verted, by catalytic transformation, into other substances. The albuminose passes into the condition of ordinary albumen, and probably also partly into that of fibrin; while the sugar rapidly becomes decomposed, and loses its characteristic properties; so 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. 42), it still presents itself in the same condition and retains all the chemical properties of oil. Fig. 42. 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, Chyle from commencement ok Thoracib . . p DrcT, from the Dog.—The molecules vary in size after a meal containing fatty from i-ie,oooth of aa'men 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. 43 ) It is then mingled with the returning current of venous blood, and passes into the right cavities of the heart 162 ABSORPTION. 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 throughout the body. The walls of these vessels are thinner and more transparent than those of the arteries and veins, and 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 laminse 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 Kolliker, like the solitary and agminated glands of the Lacteals, Thoracic Duct, &c.—a. Intes- tine, b. Vena cava inferior. e, e. Right and left subclavian veins, d. Point of opening of thoracic duct into left subclavian. ABSORPTION. 153 intestine, by a fine network of capillary bloodvessels. The solitary and agminated glands of the 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 glands is not precisely understood. Each lymphatic vessel, as it enters the gland, breaks up into 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 which 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. 44.) 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, 154 ABSORPTION. but only after 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 digestion, as soon as they have been disintegrated and emulsioned by the action of the intestinal fluids. As digestion proceeds, they accumulate in larger quantity, and gradually fill the whole lacteal Fig. 44. system and the thoracic duct. As they are discharged into the subclavian vein, and mingled with the blood, they can still be dis- ABSORPTION. 155 tinguished in the circulating fluid, as a mixture of oily 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 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 Bernard1 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 is 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 difficulty 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, for pure water, it is not true for slightly alkaline fluids, like the serum of the blood and the lymph. This has been de- 1 Lecons de Physiologic Experimentale. Paris, 1856, p. 325. 156 ABSORPTION. 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 taste, and its action on reddened litmus paper is about equal to that of the lymph and chyle. If this emulsion were placed in an endosmometer, together with a watery alkaline solution of similar strength, it was found that the oily particles penetrated through the animal membrane without Flg" 45, 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 endosmosis 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. Intestinal Epithelium fasting. from the Dog, while Fig. 46. Intestinal Epithelium the digestion of fat. from the Dog, during The epithelial cells covering the external surface of the villus are the first active agents in this absorption. In the intervals of digestion (Fig. 45) these cells are but slightly granular and nearly trans- parent in appearance. But if examined during the diges- tion and absorption of fat (Fig. 46), their substance is seen to be crowded with oily particles, which they have taken up from the intestinal cavity by absorption. The ABSORPTION. 157 oily matter then passes onward, penetrating deeper and deeper into the substance of the villus, until it is at last received by the capil- lary vessels and lacteals in its centre. 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 158 ABSORPTION. 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 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. THE BILE. 159 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:— 160 THE BILE. Composition of Ox Bile. Water . Glyko-cholate of soda Tauro-cholate " " Biliverdine . Fats . Oleates, margarates, and stearates of soda and potassa Cholesterin ........ Chloride of sodium ....... Phosphate of soda ....... " " lime....... " " magnesia ...... Carbonates of soda and potassa ..... Mucus of the gall-bladder ...... 1000.00 Biliverdine.—Of the above mentioned ingredients, biliverdine is peculiar to the bile, and therefore important, 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. Cholesterin (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 water. 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 ingredient in most biliary calculi; and is found also in different regions 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. 47) 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 | 90.00 13.42 1 I I- 15.24 1.34 THE BILE. 161 the subjacent crystals show very distinctly through the substance Cholesterin is not formed in the Fig. 47. Cholesterin, from an Encysted Tumor. of those which are placed above 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,1 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. This fact has been fully confirmed by the researches of Prof. A. Flint, Jr.,7 who has found that there is nearly one-quarter part more cholesterin in the blood of the jugular vein, returning from the brain, than 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 of the hepatic vein. The cholesterin, however, after being poured into the intestine with the bile, is decomposed or transformed into some other sub- stance, since it is not discharged with the feces.3 Its decomposition is probably effected by the contact of the intestinal fluids. Biliary Salts.—By far the most important and characteristic ingredients of this secretion are the two saline substances mentioned above as the glyko-cholate and tauro-cholale 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 them, the tauro-cholate, has the property, 1 Philosophical Transactions, London, 1857, p. 413. 2 American Jouru. Med. Sci., October, 18G2. 5 Prof. A. Flint, Jr., in Am. Journ. Med. Sci., Oct. 1832. 11 162 THE BILE. when itself in solution in water, of dissolving a certain quantitv 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 dry 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-cholate of soda, the coloring matter and more or less of the fats originally present in the bile. On the addition of a small quantity 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 glyko-cholate and tauro-cholate of soda, thrown down under the form of heavy flakes and granules, part of which subside to Fig. 48. Fig. 49. Glyko-cholate of Soda from Ox-bile, after two days' crystallization. At the lower part of the figure the crystals are melting into drops, from the evaporation of the ether and absorption of moisture, the bottom of the test-tube, while part remain for a time in suspen- sion. Gradually these flakes and granules unite with each other and fuse together into clear, brownish-yellow, oily, or resinous- Ox-bile, extracted with absolute ulcohol and precipitated with ether. THE BILE. 163 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 drops. 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 crj^stals radiate from various points in the resinous deposit, and shoot upward into the supernatant fluid, in white, silky bundles. (Fig. 48.) 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. 49.) 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. Flg" 50* 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-cholate, however, is uncrystallizable, and re- mains in an amorphous con- dition. If a portion of the deposit be now removed and r Glyko-cholate asd Tauro-cholate of examined by the micrOSCOpe, Soda, from Ox-bile, after six days' crystalliza- ... .i . ,i , i n tion. The glvko-cholate is crystallized ; the tauro- lt is seen that the crystals of . , . . .„;., Arnnc •' cholate is in fluid drops. glyko-cholate of soda have increased considerably in thickness (Fig. 50), so that their trans- verse diameter may be readily estimated. The uncrystallizable tauro-cholate appears under the form of circular drops, varying 16i THE BILE. considerably in size, clear, transparent, strongly refractive, and bounded by a dark, well-defined outline. These drops qre not to be distinguished, by any of their optical properties, from oil-globules, as they usually appear under the 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 he separated from each other by the following means. On the addi- tion of 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 filtration, 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 subsequent 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 (NaO,C52H42NOn) crystallizes, when precipi- tated by ether from 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-cholic THE BILE. 165 acid (Ci2H42NOu,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 (C48H3g09,HO); the second a nitrogenous neutral body, glycine (C4I1SN0J. 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 not exist originally 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 glyko-cholic acid. Tauro-cholate of soda (NaO,CJ2H4SNS2014) is also a very abundant ingredient of the bile. It is said by Bobin and Verdeil1 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,2 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-cholic 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 acid; and the second*a new nitrogenous neutral body, viz., taurine (C4H7NS206). The same remark holds good with regard to 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,3 after the entire extirpation of the liver, and consequent 1 Chimie Anatomique et Physiologique, vol. ii. p. 473. 1 Physiological Chemistry, Phil, ed., vol. i. p. 209. 3 Lehmann's Physiological Chemistry, Phil, ed., vol. i. p. 476. 166 THE BILE. Fig. 51. 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-cholate 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 secretions of different species of animals, Strecker found so great a resemblance between them, that he was disposed to regard 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 quantity 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. 51); while in ox-bile it is usually twelve, and often twenty- four or even forty-eight hours before crystallization is fully estab- D o a' s B i l e, extract- ed with absolutealcohol und precipitated with ether. THE BILE. 167 Fig. 52. Ushed. 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 the 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 cholate 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 alcoholic solution contains here also a crys- talline and a resinous substance ; both of which are precipitable from their watery solution by sub- acetate of lead, but neither of them by the acetate. In human bile there is also a crystallizable sub- stance ; but this substance, according to our own observations, is in much smaller quantity than in the foregoing cases. In the alcoholic extract of dried human bile, which has been precipitated by ether, the crystals which show themselves are of various forms and almost microscopic in size. (Fig. crystalline anbb»- 1. sinous Biliary Mat- 52). Some of them are feathery in appearance, TErs from Human BHe, ex- consisting of two or three diverging needles,tracted ;ith absol"te/f o ° ° hoi and precipitated by with secondary needle-shaped crystals growing ether. Magnified 25 diame- from their lateral edges. Others, which are the ter8' most abundant and characteristic, are octohedral or diamond-shaped, sometimes with irregular sides and truncated angles. Others st''1 168 THE BILE. assume the form of rosettes, more or less perfect, consisting of short, line, irregular, radiating fibres. These crystals are mingled with an abundant deposit of resinous drops, similar to those of the tauro- cholate of soda from ox-bile. If the biliary deposit from human bile, thus prepared, be sepa- rated by decantation and dissolved in water, it precipitates from the watery solution by both the acetate and subacetate of lead. This might, perhaps, be attributed to the presence of two different sub- stances, 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 fil- tered, the filtered fluid gives no precipitate afterward by the subace- tate ; and if first precipitated by the subacetate, it gives no precipi- tate after filtration by the acetate. The entire biliary ingredients, therefore, of human bile are precipitated by both or either of the salts, of lead. In pig's bile no crystallizable ingredient has been discovered, but the ether-precipitate is altogether resinous in appearance. Its watery solution, however, is abundantly precipitated, as in humarj bile, by both the acetate and subacetate 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 for 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 TESTS FOR BILE. 169 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 cases of jaundice. But it is very insufficient for anything like accurate investigation, since the 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's 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 the 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 proportion 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 170 THE BILE. 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 or twenty-five minutes. If foreign matters, again, not of a biliary nature, be also present, they 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 in 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 dingy 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 TESTS FOR BILE. 171 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 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. Various objections have been urged against this test. It has been stated to be uncertain and variable in its action. Robin 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 the 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, empyreu- matic odor is developed at the same time; but we do not get the lake 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 presence of any of the above substances. > 1 Op. cit., vol. ii. p. 468. 172 THE BRE. 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. Variations and Functions of Bile.—With 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 1852.1 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. Each observation usually occupied about two hours, during which period the temporary fluctuations occasionally observ- able in the quantity of bile discharged were mutually corrected, so far as the entire result was concerned. The animal was then killed, weighed, and carefully 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 abdominal 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 ingredients 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. Dry Residue. In the cat......102 grains. 5 712 grains. •'dog......140 " 6.016 " " sheep . . . „ 178 " 9.408 " " rabbit......9"i8 " 17.290 " 1 Verdaungssaefte und Stoffwechsel. Leipzig, 1852. VARIATIONS ANV^i ^UNCTIONS OF BILE. 173 Since, in the 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. 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 110 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 juice, and discharged only during the digestive process. In order to determine this point, we have performed the following series of experiments on dogs. The animals 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 always 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 ether preci- pitate of the alcoholic solu- tion; the resinous substance, under the form of rounded, oily-looking drops (Fig. 53), 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 Fig. 53. Ckystallivb and Resinous Biliary Stb stances; from Small Intestine of Dog. after two days fasting. 174 THE BILE. 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, in 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-bladder, 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 different periods, they came to the conclusion that the flow Fig. 54. Duode nal Fistula.— a. Stomach, b. Duo- denum, c, c, c. Pancreas ; its two ducts are seen opening into the duodenum, one near the orifice of the biliary duct, d, the other a short distance lower down. e. Silver tube passing through the nbdorainal walls and opening into the duodenum. of bile 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 fifteen hours. Other observers, how- ever, have obtained different results. Arnold,1 for example, found the quantity to be largest soon after meals, decreasing again after the fourth hour. Kolliker and Miiller,2 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- » In Am. Journ. Med. Sci., April, 1856. * Ibid., April, 1857. VARIATIONS AND FUNCTIONS OF BILE. 175 ing on this point, were performed on dogs, by making a permanent duodenal fistula, on the same plan that gastric fistulas have so often been established for the examination of the gastric juice. (Fig. 54.) An incision was made through the abdominal 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 when 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. 176 THE BILE. Time after Quantity of fluid Dry residue Quantity of Proportion of feeding. in 15 minutes. of same. biliary matters. biliary matters to dry residue. Immediately 640 grains 33 grains 10 grains .30 1 hour 1,990 " •• 105 " 4 '• .03 3 hours 7S0 " 60 " 4 " .07 6 " 750 " 73 " 3} " .05 9 " 860 " 78 " 4.V " .06 12 " 325 « 23 " 3| " .16 15 " 347 " 18 " 4 " .22 18 " _ — — — 21 " 384 " 11 " 1 " .09 24 " 163 •' 9 J " °4 .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? 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 upon the intestine at various 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 a light 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 substances 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. 177 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 like 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 12 178 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 albuminose 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 regard 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 discharged 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 effete 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. 179 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,1 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 function 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 1 Op. cit., p. 103. 180 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.1 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 suo-ar and sulphuric acid, and so pass off with the feces in an insoluble form. Bidder and Schmidt2 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, _ . . . ( Water ...... 874.20 grains. Containing „„„ „ ° i Solid residue.....633.95 " 1508.15 1 American Journ. Med. Sci., October, 1862. 2 Op. cit., p. 217. VARIATIONS AND FUNCTIONS OF BILE. 181 The solid residue was composed as follows:— Neutral fat, soluble in ether . . 43.710 grains. Fat, with traces of biliary matter . 77.035 " Alcohol extract with biliary matter 58.900 containing 1.085 grs Substances not of a biliary nature extracted by muriatic acid and hot alcohol .... 148.800 containing 1.302 grs 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- of sulphur. of sulphur. 182 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, we 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 difficult, 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. 183 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 secretion, 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. 181 FORMATION OF SUGAR IN THE LIVER. CHAPTER IX. FOEMATION OF SUGAK IN THE LITER. Beside the secretion of bile, the 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- nard1 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 abundantly 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 1 Nouvelle Fonction du Foie. Paris, 1853. FORMATION OF SUGAR IN THE LIVER. 185 urine has often appeared to be altogetlier out of proportion to that which 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,1 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 1 Nouvelle Fonction du Foie, p. 50. 186 FORMATION OF SUGAR IN THE LIVER. its origin 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 (Muraena anguilla and Baia 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 in 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 Percentage of Sugar in the Liver. 1.68 In ox 2.15 " horse 1.09 " goat . 1.94 " birds 1.94 " reptiles 2.00 " fish . 2.30 4.08 3.89 1.49 1.04 1.45 With regard to the nature and properties 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,1 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- 1 Lemons de Physiologie Experimentale. Paris, 1855, p. 213. FORMATION OF SUGAR IN THE LIVER. 187 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 tissue, 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, will 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 found1 that if all the sugar contained in 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 1 Gazette Hebdomadaire, Paris, Oct. 5, 1S55. 188 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 washed 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,1 is as follows :— C)2H]2Ol2. 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 Trommer'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 1 Journal de Physiologie, Paris, 1858, p. 552. FORMATION OF SUGAR IN THE LIVER. 189 blood. If a solution of glycogenic matter be mixed with fresh human saliva, and kept for a few minutes at the temperature of 100° F., 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. Poggiale1 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- 1 Journal de Physiologie, Paris, 1858, p. 558. 190 FORMATION OF 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 goes 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 Bobin, that it is at first converted into lactic acid (C6H606), which decomposes in turn the alkaline carbonates, setting free carbonic acid, and forming FORMATION OF SUGAR IN THE LIVER. 191 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. 192 THE SPLEEN. CHAPTER X. THE SPLEEN. 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 cceliac 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 that the spleen is subject to occasional and per- haps regular variations in size, owing to the varying condition of the abdominal circulation. Dr. William Dobson1 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 that period. When these periodical congestions take place, 1 In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40. THE SPLEEN. 193 the organ becoming turgid with blood, the capsule is distended; and limits, by its resisting power, the degree of tumefaction 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, stiff, 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 attached to the internal surface of its investing capsule. These 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 trabeculaa 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 bifurcation 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- 13 194 THE SPLEEN. aided eye, though they always exist in the spleen in a healthy condition. Their average diameter, according to Kolliker, is f2 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 (Kolliker, 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 not 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. 195 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 sj^mptom 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 196 THE SPLEEN. animal which has been subjected to the operation; and life may 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. 197 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 blood-globules, 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. 55.) Their size varies somewhat, in human blood, even in the same specimen. The greater number of them have a transverse diameter of goVo 0I an inch; but there are many smaller ones to be seen, which are not more than 35V0- or even 4^3- of an inch 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 flatwise, 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 198 THE blood. Human Blood-globules.—a. Red globules, seen flatwise, b. Red globules, seen edgewise, c. White globule. T&o-oo" 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 above the level of the fluid. Consequently, if the object-glass be carried upward by the adjusting screw of the microscope, and lifted away from the stage, so that Fig- 56. 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. Red Globules of the Blood, seen a little beyoud tbe focus of the microscope. blood-globules. 199 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. 56.) When within it they will appear with a dark rim and a bright centre. (Fig. 57.) 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 the bodies de- signated by it. This term will, consequently, be employed when- ever we have occasion to speak of the blood-globules 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 Blood-globules adhering together, like rolU of coin. 200 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 or 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. Thev 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. 201 Fig. 59. edges of the globules, being thicker than the central portions, and absorbing water more abundantly, become turgid, and encroach gradually upon the central part. (Fig. 59.) It is very 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 Blood-globui.es, swollen by the imbibition of 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- lg' 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. 60); an effect apparently produced by the evaporation of part Df 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-globui.es, shrunken, with their margins crenated. 202 THE BLOOD. The entire mass of the blood-globules, in proportion to the rest of the circulating fluid, can only be approximately measured by the eye in a microscopic examination. In ordinary 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 more 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 of the Blood-Globules in 1000 Parts. Water............688.00 Globuline...........282.22 Hematine ........... 16.75 Fatty substances .......... 2.31 Undetermined (extractive) matters . . . . . .2.60 Chloride of sodium ........ -> " potassium ........ Phosphates of soda and potassa ...... Sulphate " "......[ 8<12 Phosphate of lime ........ " " magnesia ....... J 1000.00 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 be largely diluted, however, the globuline is dissolved, as already mentioned, and the blood-globules are destroyed. Globuline coagulates by heat; but, according to Robin and Verdeil, only becomes opalescent at 160°, and requires for its complete coagulation a temperature of 200° F. The hematine 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. 203 mechanically deposited in the globuline, but the two substances are intimately mingled throughout the mass of the blood-globule, just as the fibrin and albumen are mingled in the plasma. Hematine 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 directly 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 hematine 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 camelidse, 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 3^0 of an inch, and the two-toed sloth (Bradypus didactylus), in which they are ssVtt 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^^ 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.1 Ape DIAMETE 1 of R OF K an ini ED L h. rLORULES IN THE Cat . • 4 4ffi)0f an inch Horse . *bVo" 11 Fox 4TVff K Ox 4ZW If Wolf . SS7) 0" k Sheep . ss'is 14 Elephant 1 3 7 ,7 1 !( Goat . (Ts'.TiJ u Red deer sVo-o- oi> an lncn iQ 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,1 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 plasma of the blood, therefore, after the removal of the fibrin, be exposed to the temperature of 160° F., it solidifies almost completely ; so that only a few drops of water remain that 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 fatly matters 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. cit., vol. ii. p. 202. COAGULATION OF THE BLOOD. 209 way into the blood, and circulates for a time unchanged. 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,1 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 of extractive matters consist of a mixture of different ingredients, belonging mostly to the class of organic substances, which have not yet been separated in a state of sufficient 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 Lehmann2 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 crystalliza- 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, 1 Op. cit., vol. i. p. 546. 2 Op. cit., vol. i. p. 393. 11 210 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 the 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- nous, trembling, jelly-like mass, which is known by the name of the "crassamentum," or "clot." (Fig. 64.) As soon as the clot has fairly formed, it begins to contract and diminish in size. Ex- actly how this contraction of the clot is pro- duced, we are unable to say; but it is proba- bly a continuation of the same process by which its solidification is at first accomplished, or at least one very similar to it. As the 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- Fig. 64. Bowl of recently Coagu- lated Blood, showing the whole mass uniformly i^lidi- fied COAGULATION OF THE BLOOD. 211 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 Fig. 65. growing constantly smaller and firmer, and the expressed fluid more and more 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 clot Bowl of CoAorLATED which is a red, opaque, dense and resisting blood, after twelve hours; ... . . „ showing the clot contracted semi-solid mass, consisting of the fibrin and and floating in 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. 65.) The change of the blood in coagulation may therefore be ex- pressed as follows:— Before coagulation the blood consists of f Fibrin, 1st. Globules; and 2d. Plasma—containing \ ' | Water, [ Salts. After coagulation it is separated into f Albumen, 1st. Clot, containing { \ "n an and 2d. Serum, containing \ Water, I Globules; » ( 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, in 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 212 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 the 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. 63), 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. 213 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 effect 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 tendineae 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. 211 THE BLOOD. Fig. 66. 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. 66.) 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, he- 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., 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. 67.) Fig. 67. }OWl Of COAOULATKD Blood, showing the clot buffed and cupped. COAGULATION OF THE BLOOD. 215 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 Lehmann1 ascertained as nearly as possible the quantity of blood in two criminals who suffered 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 17| pounds of blood. 1 Physiological Chemistry, vol. i. p. 638. 216 RESPIRATION. CHAPTER XII. RESPIRATION. The blood as it circulates in the arterial system has a bright scarlet 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 membrane, 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 branchise; that is, delicate filamentous prolongations of some part of the RESPIRATION. 217 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. 68), 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 „ _ vi^i* ^ , f Head and Gills op Menobranchus. 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 branchial 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 21S RESPIRATION. 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. 69.) By this arrangement, the extent of surface presented to the air by the pulmonary membrane 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. 70) 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; and 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 T'2 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 Lcno of Frog, showing its internal sur- face. RESPIRATION. Fig. 70. 219 Human Larynx, Traciika, Bronchi, and Lungs; showing the ramification of the bronchi, and the division of the lungs into lobules. vascular membrane inclosing a cavity; which cavity is divided into a large number of secondary compartments by thin septa or partitions, which project from its internal surface. (Fig. 71.) These secondary cavities are the "pulmonary cells," or " vesicles." Each vesicle is about 75 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 Kolliker, are ^i;,^™^ lined everywhere with a layer of pavement chial t,lbe- *• Cavity of lobule. -,! v . -,i ,1 , • ,i c,c,c. Pulmonary cells, or vesi- epitnelium, continuous with that in the ciea. 220 RESPIRATION. ultimate bronchial tubes. The whole extent of respiratory sur- face in both lungs has been calculated by Lieberkiihn1 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 air. 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 effected 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. 72.) 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 the 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 1 In Simon's Chemistry of Man, Philada. ed., 1846, p. 109. RESPIRATORY MOVEMENTS OF THE CHEST. 221 Fig. 72. 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. The 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 Diagram illustrating the Respiratory Move- ments.— a. Cavity of the chest. b. Diaphragm. The dark out- lines show the figure of the chest when collapsed ; the dotted lines show the same when expanded. 222 RESPIRATION. recurrence of these alternating movements of inspiration and expi. ration, fresh portions of air are constantly introduced 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 of air 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 from 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; and it will require several successive respirations before all the air 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,1 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 air in the cavity of the chest. It is evident, however, from the foregoing, that the inspiratory and expiratory movements of the chest cannot be sufficient 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 1 Human Physiology, Philada. ed., 1855, p. 300. RESPIRATORY MOVEMENTS OF THE GLOTTIS. 223 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. 73. 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, ° . Sm all Bronchi al Tube, showing outward along the Central part Of itS and inward current, produced by ciliary motion. cavity. (Fig. 73.) 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. Eespiratory 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 bo 221 RESPIRATION. 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. 74. Fig. 75. Human Larynx, viewed from above The same, with the glottis opened by in its ordinary post-mortern condition.—a. separation of the vocal chords.—a. Vocal Vocal chords, b. Tliyroid cartilage, cc. Ary- chords. 6. Thyroid cartilage, cc. Aryte- tenoid cartilages, o. Opening of theglottis. noid cartilages, o. Openingof 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 ; and 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 AIR DURING RESPIRATION. 225 ^.76. 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. 76.) 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- tilages 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. 75.) In this vtHErwMH TVyroW^rti"^"^!! Way, the Size Of the glottis may be in- glottis, cc. Arytenoid cartilages, d. in r\ ^ i- . /\ c\hr • i Cricoid cartilage, ee. Posterior crico- creased from 0.15 to 0.27 square inch. arytenoid muscle.. /. Trachea. 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 Eespiration.—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, tha 15 226 RESPIRATION. air is found to have become altered in the following essential par- ticulars, viz:— 1st. It has 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 Valentin, the average quantity of water, exhaled daily from the lungs, is 8100 grains, or about 15 pounds avoirdupois. A more important change, however, suffered by the air in respi- ration, consists in its loss of oxygen, and its absorption 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, 7,131 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.1 There is, then, a constant disappearance of oxygen from the air used in respiration, and a constant accumu- lation of carbonic acid. 1 Lehmann's Physiological Chemistry, Philada. ed., vol. ii. p. 432. CHANGES IN THE BLOOD DURING RESPIRATION. 227 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 carnivora, 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 Regnault and Reiset, 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. Owing to the changes detailed above, the air which is used for breathing becomes rapidly deteriorated and unfit to sustain life. For as respiration goes on, the oxygen of the air constantly dimin- ishes and the quantity of carbonic acid increases. It has been found that, as a general rule, the air is entirely unfit for respiration when its proportion of oxygen is reduced from 21 to 10 per cent.,1 its composition remaining otherwise unchanged; and on the other hand it can no longer sustain life when it contains 20 per cent, of carbonic acid. Both these changes therefore combine to vitiate the respired air, unless it be constantly renewed from an external source. Beside the carbonic acid, however, a certain amount of organic matter is also exhaled with the breath. It is this organic matter in a vaporous condition which causes the heavy and oppressive odor in the atmosphere of an ill-ventilated apartment, in which many persons are breathing at the same time. Although produced in comparatively small quantity, it is probably one of the most delete- rious substances exhaled from the lungs in respiration; and, when allowed to accumulate in the atmosphere, gives rise to many of the injurious effects resulting from imperfect ventilation. Changes in the Blood during Bespiration.—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 correspon-5. inversely with the former. The blood, in passing through the lungs, suffers the following alterations:— 1st. Its color is changed from venous to arterial. 1 Longet, Traite" de Physiologie, Paris, 1859, vol. i. p. 600. 228 RESPIRATION. 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 venous 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 follows: The blood comes to the lungs already charged with carbonic acid. In passing 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. Since the blood in the 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 off, 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 becomes fatal by a rapid deterioration of the circulating fluid, and by its poisonous effect on the nervous system. 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, CHANGES IN THE BLOOD DURING RESPIRATION. 229 that both oxygen and carbonic acid are contained in both venous and arterial blood. Magnus1 found that the proportion of oxygen to carbonic acid, by volume, in arterial blood was as 10 to 27 ; 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 combination. 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 sufficient physical displacing power. Magnus found2 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 difficulty 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 found3 that after the expulsion of all the carbonic acid removable by the air-pump and a current of hydrogen, there still remains, in ox's blood, 0.1628 per cent, of carbonate of soda; and he estimates that this quantity is sufficient 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 form 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-globules, and not in the plasma. The researches ' In Lehmann, op. cit., vol. i. p. 570. 2 In Robin and Verdeil, op. cit., vol. ii. p. 34. s Op. cit., vol i. p. 393. 230 RESPIRATION. of Magnus have shown1 that the blood holds in solution 2 J times 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 serai- 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 internal 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 acid 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 ' In Robin and Verdeil, op. cit., vol. ii. p. 28. CHANGES IN THE BLOOD DURING RESPIRATION. 231 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, previously to its entrance into the lungs. It was then imagined that the oxidation of carbon, and the consequent produc- tion of carbonic acid, took 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 Verdeil1 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 ingredients, 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 found2 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. 1 Robin and Verdeil, op. cit., vol. ii. p. 460. 2 Archives Gen de M6d., xvi. 222. 232 RESPIRATION. 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 analogous 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- lanzani, 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 and of exhaling carbonic acid. Gr. Liebig, for example,1 found 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 fresh 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 1 In Lehmann, op. cit., vol. ii. p. 474. 2 Ibid., p. 442. CHANGES IN THE BLOOD DURING RESPIRATION. 233 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 carbonic acid on the one hand, and of various other substances on the other, with which we are not yet fully 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 process. 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,1 which are regarded as the most accurate on this subject, an 1 In Lehmann, op. cit., vol. ii. p. 439. 234 RESPIRATION. 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,1 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 subject 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:— Quantity c-f Carbonic Acid per hocr. In subject No. 1.....1207 cubic inches. 970 1250 1250 1591 With regard to the difference produced by age, it was found that from 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 so 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 1 Annales de Chimie et de Physique, 1843, 3d series, vol. viii. p. 129. CHANGES IN THE BLOOD DURING RESPIRATION. 235 diminishes with the approach of old age, as in men. Pregnancy, occurring at any time in the above period, immediately produces a temporary increase in the quantity of carbonic acid. The strength of the constitution, and more particularly the deve- lopment of the muscular 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 according to the age; and that independently of the weight of the individual subjected to experiment. 3. 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 16 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, 236 RESPIRATION. 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,1 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 the 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 by Prof. Scharling,2 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. A certain amount of odoriferous organic matter is also given off by the skin as well as by the lungs. In the truly amphibious animals, that is, those which breathe by lungs, and can yet remain under water for a long 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 cuticle, 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 comparative inactivity, the exhalation and absorption of gases continue to take place through the skin, and the process of respiration goes on without interruption. 1 Annales de Chimie et de Physique, vol. viii. p. 490. 2 In Carpenter's Human Physiology, Philada. ed., 1855, p. 308. ANIMAL HEAT. 237 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 different. If a thermometer be introduced 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 afterward 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 238 ANIMAL HEAT. heat takes place with 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 ends of the fingers, may become cooled down considerably below the standard temperature, and may even be congealed, if the cold be severe; but the temperature of the internal organs and of the blood still remains the same under all ordinary exposures. If 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 if 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 animals, 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. 239 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, in 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,1 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 list2 shows the mean temperature belonging to animals of different classes and species. Birds. Mammalia. Reptile. Fish. Animal. Swallow Heron Raven j Pigeon | Fowl I Gull Squirrel Goat Cat Hare Ox Dog Man Ape Toad Carp Tench { Mean Temperature. 11 lo. 25 llic.2 108O.5 107°.6 106O.7 100O.0 105O 102O.5 101O.3 100O.4 990.5 990.4 98Q.6 950.9 5 lO. 6 5 lo. 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 1 Simon's Chemistry of Man, Philadelphia edition, p. 124. 2 Ibid., pp. 123—126. 240 ANIMAL HEAT. than the exterior. According to the experiments of Mr. Newport,1 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 66°.J Dutrochet has moreover found, by a series of very ingenious and delicate experiments,3 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 sensible 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° F., 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 1 Carpenter's General and Comparative Physiology, Philadelphia, 1851, p. 852. 2 Carpenter's Gen. and Comp. Physiology, p. 846. 3 Annales des Sciences Naturelles, 2d series, xii. p. 277. ANIMAL HEAT. 241 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 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; and charcoal, which is nearly pure carbon, is frequently employed by itself. These substances, when burned, 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 measured, either by the quantity of carbon consumed, or by that of carbonic acid produced. It may be made to go on, also, either slowly or rapidly, 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 consumed, On the other hand, if it be shut up in a olose stove, to which the air is admitted slowly, it produces only a slight elevation of temperature, and may require a much longer time for its complete disappearance. Nevertheless, for the same quan- tity of carbon consumed, the amount of heat generated, as well as "16 212 ANIMAL HEAT. that of carbonic acid produced, will be equal in 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 are 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, and 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 might be owing to an oxidation or combustion of carbon. Ac- cording to Lavoisier, the oxygen taken into the lungs Avas 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 formecLin 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 HEAT. 243 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 elements, which are introduced in comparatively small 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 elements, 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 Robin 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 manner, 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 physiological 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 constantly see in external nature. The sun's rays, mechanical friction, electric currents, and more particularly a great variety of 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 varietv, all of which, taken together, are amply sufficient to account for the production of animal heat, provided the theory of combustion be found insufficient or improbable. 244 ANIMAL HEAT. II. In vegetables there is an internal production of heat, as well as in animals; a fact which has been fully demonstrated by the experiments of Dutrochet and others, already described. In vege- tables, however, the absorption 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 it 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 the 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 evplution of heat is sus- pended. Dutrochet 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, just 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 a different process. 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 also passes out by the lungs; but this is a pure assumption, resting on no direct evidence, 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. Regnault and Reiset1 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 Chiniie et de Physique, 3d series, xxvi. p. 428. ANIMAL HEAT. 245 in dogs fed on vegetable substances it amounted to over 90 per cent. In some instances,1 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 the 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 it is produced from sugar in the alcoholic fermentation. We understand from this how to ex- plain 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 tempera ture, by modifying the nutritive changes which take place in the tissues. Local inflammations increase very sensibly the temperature of the part in which they are seated, while that of the general mass of the blood is not altered. Finally it has been demon strated 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.2 The method adopted by this experi • 1 Annales de Chimie et de Physique, 3d series, xxvi. pp. J09-451. * Gazette Hebdomadnire, Aug. 29 and Sept. 26, 1856. 246 ANIMAL HEAT. menter was to introduce, in the living animal, the bulb of a fine ther- mometer successively into the bloodvessels entering and those leav- ing 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, in the first 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- ism. 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. But 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 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. 247 Animal heat, then, is a phenomenon which 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 ohanges, in which all the tissues of the body successively or simul- taneously take part. Their relation is precisely that which ex. ists between the food introduced into the stomach, and the urine discharged by the kidneys. The tissues require for their nutri- tion 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 follow 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. 248 THE CIRCULATION. 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 parts 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 is accomplished; 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 the carbonic acid, first produced in the tissues, is finally exhaled from the lungs. In the liver, the kidneys, and the skin, other substances still are produced or eliminated, and these local processes are all necessary to the preservation of the general organization. The circulating fluid is, therefore, in the higher animals, a means of transportation, 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. 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 convey the blood from the heart to the different tissues and organs of the body. THE HEART. 249 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 their component parts; and 4th. The veins; a set of converging vessels, destined to collect the blood from the capillaries, and return it to the heart. In each of these different parts of the circulatory appa- ratus, the movement of the blood is peculiar and dependent on special conditions. It will therefore require to be studied in each one separately. THE HEART. The structure of the heart, and of the adjacent vessels, va- ries in different classes of animals, owing to the different arrangement of the respiratory organs. For the respiratory apparatus being one of the most important in the body, and the one most closely connected by anatomical relations with the organs of circulation, the latter are necessarily modified in structure to correspond with the former. In fish, for exam- ple (Fig. 77), 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 veins unite upon the median line to form the aorta (d) by which the blood is finally distributed throughout the frame. In Circitlation OP FIsn. — n. Auricle, b. Ventricle, cc. Gills, d. Aorta, ee. Vena: cavas. 250 THE CIRCULATION. these animals 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 and one ven- tricle. (Fig. 78.) The venae cavae discharge their blood into the right auricle (a), whence it passes Fig. 78. into the ventricle (c). From the ventricle, a part of it is carried into the aorta and distributed 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 venas cavae. 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 being carried to the lungs by the pulmonary artery, 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, also takes an important share in the aeration of the blood. In quadrupeds and the human species, however, the respiratory process is not only exceedingly active, but the lungs are, at the same time, the only organs in which the aeration of the blood is fully accomplished. Here, accordingly, we find the two circulations, general and pulmonary, distinct from each other. (Fig. 79.) All Circulation of Reptii.es. — a. Right auricle 6. Left auricle, c. Ventricle. d. Lungs, e. Aorta. /. Vena cava. THE HEART. 251 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 therefore a double circulation and a double Fig- 79. heart; the two sides of the organ, though united exter- nally, being separate inter- nally. The mammalian heart consists of a right auricle and ventricle (a, b), receiving the blood from the vena cava (i), and driving it to the lungs; and a left auricle and ventri- cle (/ g) receiving the blood from the lungs and driving it outward through the arterial 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 under- stand before we can properly appreciate its action and movements. The entire organ has a more or less conical form, its base being situ- ated 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, surrounded by the pericardium, but capable of a certain de- gree of lateral and rotatory motion. The auricles, which have a smaller capacity and thinner walls than the ventricles, are situ- ated at the upper and posterior part of the organ (Figs. 80 and 81); 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. 80), and in a posterior view the greater portion of the right ventricle is con cealed by the left (Fig. 81); while in both positions the apex of the heart is constituted altogether by the point of the left ventricle. Circulation in M a mm ali ans. — n. Right auricle, b. Right ventricle, c. Pulmonary artery. d. Lungs, e. Pulmonary vein. /. Left auricle, g Left ventricle, h. Aorta, i. Vena cava. 252 THE CIRCULATION. Fig. 80. Fig. 81. Human Ueart, anterior view.— Human Hhart, posterior view.— n. Right ventricle. 6. Left ventricle. «. Right ventricle. 6. Left ventricle. c. Right auricle, d. Left auricle, e. c. Right auricle, d. Left auricle. Pulmonary artery. /. Aorta. The different cavities of the heart and of the adjacent bloodvessels on each side, though continuous with each other, are partially sepa- rated by certain constrictions. These constricted orifices, by which the different cavities communicate, are known by the names of the Fig. 82. Right Auricle and Ventricle; Auriculo-ventricular Valves open, Arterial Valves closed. auricular, auriculo-ventricular, and aortic and pulmonary orifices; the auricular orifices being the passages from the venae cavae and pulmonary veins into the right and left auricles; the 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 HEART. 253 The auriculo-ventricular, aortic, and pulmonary orifices are fur- nished with valves, which allow the blood to pass readily from the auricles to the ventricles, and from the ventricles to the arte- ries, but shut back in such a manner as to prevent its return in the 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 ven- tricle. (Fig. 82.) On the contraction of the right ventricle, the tri- cuspid valves shut back, preventing its return into the auricle (Fig. 83); and it is thus driven through the pulmonary artery to the Fig. 83. Right Auricle and Ventricle; Auriculo-ventriculai Valves closed, Arterial Valves open. lungs. Beturning 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. 84.) This movement of the blood, hoAvever, 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- charged into the arteries. Each one of these successive actions i<- called a beat, or pulsation of the heart. Each pulsation of the heart i3 accompanied by certain important, phenomena, which require to be studied in detail. These are tbo sounds, the movements, and the impulse. 254 THE CIRCULATION. Fig. 84. Course of Blood through the Hfart—n, a. Vena cava, superior and inferior. 6. Right ventricle, c. Pulmonary artery, d. Pulmonary vein. e. Left ventricle. /. Aorta. The sounds of the heart are two in number. They can readily he 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 sternum at the level of the third costal cartilage. It is short, sharp, and distinet in tone, and occupies only about one-quarter of the whole time of a pulsation. It is followed by an equal interval of silence; after which 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:— THE HEART. 255 M* quarter J p. I 2d " ) Time of pulsatiou. j 3d „ gecond gound L 4th " Interval of silence. 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 different 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 to a variety of 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 par- ticles 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, for the most part, a similar origin with the second; and that it is dependent mainly on the closure of the auriculo-ventricular valves. The reasons for this conclusion are the following: — 1st. The second sound is undoubtedly caused by the closure of the semilunar valves, and in the action of the heart the move- ments of the two sets of valves alternate with each other precisely as do the first and second sounds; and the sudden tension of the valvular fibres is calculated to produce a similar effect in each instance. 1 Diseases of the Heart, Kneeland's Translation, Boston. 1846. 256 TnE CIRCULATION. 2d. The first sound is heard most distinctly over the anterior surface ' of the ventricles, where the tendinous cords supporting the auriculo- ventricular valves are inserted, and where the sound produced by the tension of these valves is most readily conducted 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 lon<> as these orifices, and the cavities to which they lead, have their normal dimensions. An unnatural souffle may indeed originate from this cause when the orifices of the heart are diminished in size, as by calcareous or fibrinous deposits; but in these instances the sound so produced is an abnormal one, and different in charac- ter from the natural first sound of the heart. A souffle may also occur in cases of aneurism; and a similar sound may even be pro- duced 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 con- sequence 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 size of the different orifices is in proportion to the quantity of the circulating fl uid; and there is no more reason for believing that the passage of the blood should give rise to a sound in the cardiac cavities than in the larger arteries or veins. 4th. The difference in character between the two sounds of the heart probably depends, in great measure, on the different arrange- ment of the two sets of valves. The second sound is short, sharp, and distinct, because the semilunar valves are short and narrow, superficial in their situation, and supported by the 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 ten- dineae, 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. 85.) 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 heard a friction sound, or sound of impulsion, produced by the collision of the point of the heart with the parietes of the chest. This sound, which is most distinctly heard in the fifth intercostal space, is min- THE HEART. 257 gled with the valvular sound which occurs at the same time. It is different, however, in character from the latter, and may usually be distinguished from it by careful examination. It has been observed by Prof. Austin Flint,1 that it may be more or less completely elimi- nated, by ausculting the heart at a distance from its apex, so that the first sound may then be heard purely valvular in quality, and entirely similar to the second sound in all its essential character? Fig. 85. 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 the 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 insufflation through the trachea. By keeping up a steady artificial respiration, the move- 1 Heart-Sounds in Health and Disease. Prize Essay of the American Medica; Association. Transactions of 1858, p. 825. 17 258 THE CIRCULATION. ments of the heart may be made to continue, in favorable cases, foi 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 relaxation of the ventricles f 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 different 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, which contract simultaneously with each other, and which constitute 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 HEART. 259 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 point of the heart protrudes, and, coming in contact with the walls of the chest, produces the cardiac impulse. This action was well described by Dr. Harvey.1 " The heart," he says, " is erected, and rises upward to a point, so that at this time it strikes against the chest and the pulse is felt ex- ternally." This phenomenon is due to au elongation of the ventri- cle, by which its point is thrown forward at the same time that its sides are drawn together. The elongation of the heart, however, has often been denied by physiological writers. The only modern observers, so far as we are aware, who have recognized its exist- ence, are Drs. C. W. Pennock and Edward M. Moore, who performed a series of very careful and interesting experiments on the action of the heart, in Philadelphia, in the year 1839.* These experi- menters 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 ven- tricle 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 the statement of these ob- servers by the result of our own experiments on dogs, rabbits and frogs. The appearances presented by the heart, in active motion, are somewhat modified by the direction in which it is examined. If viewed anteriorly, the right ventricle writh the conus arterio- sus, situated over the front of the organ, comes prominently into view; and its fibres, running from above downward and from right to left, tilt the apex of the heart, at the time of contraction, diago- nally forward and to the right side. But if the heart be turned upward, so as to expose the posterior surface of the organ, which is constituted almost altogether by the left ventricle, the elongation of its figure, at the moment of contraction, may be distinctly seen. At this time, the sides of the ventricle approximate each other and its point protrudes; so that the transverse diameter of the heart is diminished, and its longitudinal diameter increased. This does not appear to be due to a recoil of the entire heart, but is a real elonga- 1 Works of William Harvey, M.D. Sydenham ed., London, 1847, p. 21. 2 Philadelphia Medical Examiner, No. 44. 260 THE CIRCULATION. tion of its figure; since it takes place also when the base of the organ is seized with a pair of forceps, at its junction with the large vessels, and held in an immovable position. The above action can also 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 contraction of the heart is an active movement, its relaxation entirely a passive one. The difference between these two conditions of the heart, and the forcible character of its contraction, may be seen in the following manner. If the heart of the frog, or even of 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 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. 86); its base, while in a condition of rest, bulging out laterally, while the apex is compara- tively obtuse. Fig. 86. Fig. 87. Heart of Froo in contraction. When the heart, held in this position, is touched with the point of a needle (Fig. 87), 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. Let us now see in what manner this change in the figure of the ventricles during contraction is produced. If the muscular fibres THE HEART. 261 Fig. 88. Diagram of Simple Looped Fibres, in relaxation and con- traction. 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 effect of di- minishing the size of the heart in everv direction. This effect can be seen in the accompanying hypothetical diagram (Fig. 88), 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 ofthe muscular fibres of the heart run throughout 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 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. 89.) They converge toward the point of the heart, curl- ing round the centre of its apex, and then, changing their direction, be- come deep-seated, run upward along Fig. 90. Bullock's Hkabi, auterior view, showing the superficial muscular fibres. Left Ventricle of Bullock's Heart, show- ing the deep fibres. the septum and internal surface of the ventricles, and terminate in the columnar carneae, and in the inner border of the auriculo ventricular ring. The deeper layers of fibres, on the contrary, are wrapped round the ventricles in a nearly circular direction (Fig. 262 THE CIRCULATION. Fig. 91. 90); 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 that its sides are drawn together. This effect is illustrated in the accompanying diagram (Fig. 91), where the white lines show the figure of the heart during relaxation, with the course of its circular fibres, while the dotted line shows the narrowed and elongated fio-ure necessarily produced by their contraction. This phenomenon, therefore, of the protrusion of the apex 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 elongation 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 diagrams, we shall see that, provided the fibres were arranged in simple longitudi- nal loops (Fig. 88), their contraction would merely have the effect 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. 91), the apex would be simply protruded, also in a direct line, without deviating, or twisting either to the right or to the left. But in point of fact, the superficial fibres, as we have already de- scribed, run spirally, and, curling round the point of the heart, turn inward toward its base; so that if the apex of the organ be Diagram of Circular Fibres of the Heart, aud their con- traction. THE HEART. 263 viewed externally, it will be seen that the superficial fibres con- verge toward its central point in curved lines, as in Fig. 92. It is well known that Fie- 92- every curved muscular fibre, at the time of its shortening, necessarily approximates more or less to a straight line. Its curva- ture 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 contraction of the heart, therefore, its • , • • ,1 j- ,• Converging Fibres at apex rotates on its own axis in the direction THE APEX 0F THE Hbabt< indicated by the arrows in Fig. 92, 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 very perceptible to the 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 is peculiar and somewhat complicated. Each pulsation is made up of a double series of con- tractions and relaxations. The two auricles contract together, and 261 THE CIRCULATION. 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 two pistons) 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 peristaltic motion, except that it is more sudden and vigorous. 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, not from any secondary or hypothetical sources, but from direct and careful study of the phenomena in the living animal. "First of all," he says,1 "the auricle contracts, and in the course of its contraction 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 artery; 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 that 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, ' Op. cit., p. 31. THE ARTERIES' AND THE ARTERIAL CIRCULATION. 265 yet all the wheels seem to 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 accordingly 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 protrudes, strikes against the walls of the chest, and twists from left to right, the auriculo-ventricular valves shut back, the first sound is produced, and the blood 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 series 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 condensed lavers of areolar tissue. The essential anatomical difference be- 266 THE CIRCULATION. 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 less distinctly 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 they originate. 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 blood through the arteries is primarily caused by the contractions of the heart; but it is, at the same time, regulated and modified by the elasticity of the vessels. The mode in which 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 auricle, 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, THE ARTERIES AND THE ARTERIAL CIRCULATION. 267 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 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. 93.) The vessel even rises up partially out of its bed, particularly where 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 arterial 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 little or no difference in time between the two impulses. The disten- Elongation and eva- sion of the carotid seems to take place at the ,u,eofa" ABTER* " * PULSATION. 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 to be 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 268 THE CIRCULATION. 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 shown, particularly by the investi- gations of M. Marey,1 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 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 pulse is produced in the follow- ing way:— The contraction of the left ventricle is a brusque, 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 certain proportion of its force is used in expanding the distensible 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 its 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 powerful 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- 1 Dr. Brown-Sequard's Journal de Physiologie, April, 1859. THE ARTERIES AND THE ARTERIAL CIRCULATION. 269 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. 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 different 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. 94. Curves of the Arterial Pulsation, as illustrated by M. Marey's experiment.—1. Near the distending force. 2. At a distance from it. 3. Still farther removed. 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 270 THE CIRCULATION. remote 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, 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 imperceptible. 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. Whatever 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 impulses into each other, and the water is driven out from the farther extremity in a continuous stream. THE ARTERIES AND THE ARTERIAL CIRCULATION. 271 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 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. It is due, in the first place, to 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; and secondly, to the alternating contraction 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, therefore, under a certain degree of constant pressure. For these ves- sels 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 arterial 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, presses upon the surface of the 272 THE CIRCULATION. mercury 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, but rises and falls with the pulsations of the heart. Thus, at every contraction of the ventricle, the mercury rises for 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 farther and farther from the centre of the circulation. 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 through glass or metallic tubes, has compara- THE ARTERIES AND THE ARTERIAL CIRCULATION. 273 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 the blood in flowing through the vessels meets with the least possible resistance. Fig. 95. Fig. 96. Volkmann 's Apparatus for measuring the rapidity of the arterial circulation. 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 blood-globules can- not be distinguished in it on microscopic examination, but only a 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 18 271 THE CIRCULATION. some of the large sized arteries in dogs, horses, and calves. The instrument which he employed (Fig. 95) 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 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 given signal, the two plugs were suddenly turned in opposite directions, the stream of blood would be turned out of its course (Fig. 96), 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 the blood in a given time could be readily measured upon a scale attached to the side of the glass tube. Volkmann found, as the average 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 consequently more flaccid and compressible than the arteries, and less elastic aud 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 pass 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 VENOUS CIRCULATION. 275 that the veins will sometimes resist a pressure which is sufficient to rupture the walls of the arteries.1 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. 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 channels, 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 with 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 1 Leqons sur la Physiologie, &c, vol. iv. p. 301. 276 THE CIRCULATION. 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. 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. VENOUS CIRCULATION. 277 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- piration in crying 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. The contraction 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 Fig. 97. Fig. 98. Vein with valves open. Vein with valves closed; stream of blood passing off by a lateral channel. 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 27S THE CIRCULATION. toward the heart; and 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 account 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 the pressure of the muscles, may readily find a passage through others, which communicate by cross branches with the first. (Figs. 97 and 98.) 3. 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 respiration 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 flaccidity 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- THE CAPILLARY CIRCULATION. 279 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 time through an opening equal to one- half a square inch. Now the capacity of the entire venous system, 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 course. THE CAPILLARY CIRCULATION. 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 commencing rootlets of the veins on the other. They vary somewhat in size in different organs, and in dif- ferent species of animals; their average diameter in the human subject being a little over 3-$-$-$ of an inch. They are composed of a single, transparent, homogeneous, somewhat elastic, tubular membrane, which is provided at various intervals with flattened, oval nuclei. As the smaller arteries 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 muscular. (Fig. 99, a.) The middle coat then diminishes in thickness, until it is reduced to a single layer of circular, fusiform, unstriped, mub- 280 THE CIRCULATION. Small Artery, with its muscular tunic (a), breaking up into capillaries. From the^ia mater. eukr fibres, which in their turn disappear altogether, as the artery merges at last in the capillaries; leaving only, as we have already mentioned, a simple, homogene- ous, nucleated, tubular mem- brane, which is continuous with the internal arterial tunic. The capillaries are further dis- tinguished from both arteries and veins by their frequent inoscula- tion. The arteries constantly di- vide 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 cir- cumference toward the centre. But the capillaries simply inos- culate with each other in every direction, in such a manner as to form an interlacing network or plexus, the capillary plexus (Fig. 100), which is exceedingly rich and abundant in some organs, less so in others. The spaces in- cluded 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 tis- sue they form long parallelo- fl^KSIB ■BF'CnS H^hW grams; in the areolar tissue, £^■$3 Sllll v'H irregular shapeless figures, corresponding with the di- rection of the fibrous bun- dles of which the tissue is composed. In the mucous membrane of the large intes- tine, the capillaries include hexagonal or nearly circular spaces, enclosing 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. Capillary Network from web of frog's foot. THE CAPILLARY CIRCULATION. 281 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 field by the smaller arteries, shooting through them with great rapidity and in successive impulses, and flowing off 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 » Fig. 101. 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. 101) 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 with 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 difference 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 Capillary Circulation in web of frog's foot. 282 THE CIRCULATION. following each other in single file. The flexibility and semi-fluid consistency of these globules are here very apparent, from the 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 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 affected 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 without 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, &c, are appropriated in special proportions by the different 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, and converted into new materials, characteristic of the different tissues. In this way are produced the musculine of the 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 for 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 THE CAPILLARY CIRCULATION. 283 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 a terminal ramification of still smaller and more numerous vessels, and so lose themselves at last in the capillary network. By this final increase of the vascular surface, the equalization of the heart's action is completed. There is no longer any intermitting or pulsatile character in the force which acts upon the circulating fluid; and the blood, as it is delivered from the arteries, moves through the capillary vessels under a perfectly continuous and uni- form 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,1 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 in 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 in 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 1 Todd and Bowmann, Physiological Anatomy and Physiology of man, vol. ii. p. 350. 284 THE CIRCULATION. 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 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 them- selves are elastic, notwithstanding the delicate texture of their walls; 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 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 will 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. THE CAPILLARY CIRCULATION. 285 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 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. An important class of phenomena connected with this part of the subject consists of the heal variations in the capillary circulation. These variations are often very marked, and show themselves in many different parts of the body. The pallor or suffusion of the face under mental emotion, the congestion of the mucous membranes during the digestive process, and the local and defined redness of the skin produced by any irritating application, are all instances of this sort. These changes are due to the contraction and dilatation of the more minute arterial branches which supply the part with blood, under the influence of nervous action. We have already seen that these smaller arteries are provided with organic muscular fibres; and that in their smallest branches, which immediately com- municate with the capillaries, the middle coat is composed exclu- sively of such muscular fibres. These vessels, therefore, by their state of comparative contraction and dilatation, regulate, to a cer- tain extent, the quantity of blood admitted to a part. When con- tracted they resist more strongly the impulsive force of the arterial current, and the blood enters the capillaries in smaller quantity. When dilated they allow a freer access to the capillaries and admit the blood in greater abundance. These changes in the condition of the smaller arteries, and the consequent variations in the capillary circulation, are caused by dif- ferent nervous influences, some of which are occasional and acci- dental, while others recur with a certain degree of regularity, as in the periodical excitement of the digestive organs. 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.) 286 THE CIRCULATION. 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 wliich 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, to disseminate a com- paratively small quantity of blood over a very large space, so that the chemico-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 slow, yet as the distance to be passed over between the arteries and veins is very small, the blood requires but a short time to tra- verse 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,1 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 corresponding 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 1 Physical Phenomena of Living Beings, Pereira's translation, Philada. ed., 1848, p. 317. LOCAL VARIATIONS. 287 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 Horse,1 the mean duration was 28 seconds. " Dog •' " " » 15 « " Goat " « " « 13 « " Fox " " « « J2A " " Rabbit " " " « 7 « 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 same 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 1 In Milne Edwards, Lecons sur la Physiologie, &c, vol. iv. p. 3f>4. 288 THE CIRCULATION. 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 to the 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 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; while 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 circulation 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 different composition as it returns from different organs. In the brain and spinal cord it gives up those ingredients LOCAL VARIATIONS. 289 Fig. 102. 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 paro- tid 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 ele- ments of the digested food; and in the liver, gives up substances des- tined finally to produce the bile, at the same time that it absorbs sugar, which has been produced in the he- patic tissue. In the lungs, again, it is the elimination of carbonic acid and the absorption of oxygen that constitute its principal changes. It has been already remarked that the temperature of the blood varies in different veins, according to the pe- culiar chemical and nutritive changes going on in the organs from 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 man- ner. In the lungs it changes from blue to red; in the capillaries of the general system, from red to blue. But its tinge also varies very consid- erably in different parts of the gen- eral 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. 19 Diagram of the Circulation.—1. Heart. 2. Lungs. 3. Head and upper extremities. 4. Spleen. 5. Intestine. 6. Kidney. 7. Lower extremities. 8. Liver. 290 THE CIRCULATION. We must regard the circulation of the blood, therefore, not as a simple process, but as made up of many different circulations, going on simultaneously in different organs. This may be represented in diagram, as in Fig. 102, where the variations of the circulation, in different parts of the body, are indicated in such a manner as to show, in some degree, the complicated character of its phenomena. The circulation is modified in these different parts, not only in its mechanism, but also in its rapidity and quantity, and in the nutri- tive 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 apparatus, absorbs the materials requisite for the nourishment of the body; another, in circulating through the lungs, exhales the carbonic acid which it has accumulated elsewhere, and absorbs the oxygen Avhich is to be transported to distant tissues. 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. 291 CHAPTER XV. IMBIBITION AND EX HAL ATI 0 N.—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 a 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 they have become mingled, to a certain extent, with each other. A part of the salt will have passed into the distilled water, giving it a saline taste; and a 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 has 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 292 IMBIBITION AND EXHALATION. the more scanty passage of the salt outward to the water is called exosmosis. The mode usually adopted 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 fluid 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 endosmosis. 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 animal mem- brane. This is an indispensable requisite for the success of the ex- periment. 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. 293 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 dilute. But the force of endos- mosis varies with different liquids, even when they are of the same density. Dutrochet measured the force with which water passes through the mucous membrane of the ox-bladder into different solutions of the same density. He found that the force varies with different substances, as follows:l — Endosmosis of water, with a solution of albumen . . 12 " " " sugar ... 11 " " " gum ... 5 " " " gelatine . . 3 The position of the membrane 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. 1 In Matteucci's Lectures on the Physical Phenomena of Living Beings. Philada., 1848, p. 48. 291 IMBIBITION AND EXHALATION. Generally speaking, endosmosis 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,1 that when the endosmometer was filled with dilute hydrochloric acid and placed in distilled water, at the tem- 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 that 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. Liebig2 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 Inches of Mercury. For alcohol ........ 52 For oil ......... 37 For solution of salt ....... 20 For water.........13 There are some cases in which endosmosis takes place with- out being accompanied by exosmosis. This occurs 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 whole be then placed in a goblet of water, endosmosis will take place very freely from the water 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, 1 In Milne Edwards, Lecons sur la Physiologie, &c, vol. v. p. 164. s In Longet's Traite de Physiologie, vol. i. p. 384. THE LYMPHATIC SYSTEM. 295 however, the accumulation of fluid in the interior becomes so ex. cessive as to burst the shell-membrane, and then the two liquids become mingled with each other. 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. For 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. The 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 is the active agent which determines their passage. The mem- brane 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. 296 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 either 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 removed 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 Parts of Cartilage, Tendon, Elastic ligament, I absorb in Cornea, i 24 hours, Cartilaginous ligament, Dried fibrin, J 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 of them 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 absorption 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 Water. Saline Solution. Oil. ' 231 parts. 125 parts. 178 " 114 " 8.6 parts 148 " 30 " 7.2 " 461 " 370 " 9.1 « 319 " 3.2 « L 301 " 154 " In Longet's Traite de Physiologie, vol. i. p. 383. THE LYMPHATIC SYSTEM. 297 imbibed fluid penetrates the 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,1 that if a watery solution of iodide of potassium be dropped upon the cornea of a living rabbit, 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 of 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 cornea, 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 circulating in 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, 1S55. 298 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 bv a continuous current, those portions of it which have become contaminated are immediately carried away by the stream, and 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 the 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 minutes; 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 endosmosis and exosmosis. We have already seen that the network of capil- lary bloodvessels results from the excessive division and ramifi- cation 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 dissemi- nated in the most intricate manner throughout the substance of the organs and tissues. Thus, the blood is brought into intimate con- tact with the surrounding tissues, over a comparatively large 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. 299 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.1 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 also found the transudation of iodine through the glandular tissue to be exceedingly rapid, by the following experi- ment. The parotid duct is 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 is 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 shows 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 1 Le.ons de Physiologie Expgriraentale, Paris, 1856, p. 107. 300 IMBIBITION AND EXHALATION. body, 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 is shown by experiment, will im- bibe different substances with different degrees of facility. Thus, the blood contains more chloride of sodium than chloride of potas- sium; but the muscles, which it supplies with nourishment, con- tain 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 en- dosmotic power. Furthermore, we have seen that albumen, under ordinary condi- 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 of pressure to which a fluid is subjected has great influence in determining its endosmotic action. A sub- stance which passes but slowly under a low pressure, may pass 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 THE LYMPHATIC SYSTEM. 301 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, more 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 generally 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,1 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. 44): 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 1 Physiologie comparee des Animaux domestiques, Paris, 1856, vol. ii. p. 68. 302 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 by 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,1 of the fluid obtained from the thoracic duct of the cow:— Parts per thousand. Water..........9G4.0 Fibrin .......... 0.9 Albumen •••...... 28.0 Fat ...•......0.4 Chloride of sodium . . . . . . . 5.0 Carbonic •> Phosphate and > of soda ...... 1.2 Sulphate J Phosphate of lime . . . . . . . o.5 1000.0 1 Colin, Physiologie oomparee des-Animaux domestiques, vol. ii. p. 111. THE LYMPHATIC SYSTEM. 303 It thus appears that both the fibrin and the albumen of the blood actually transude to a certain extent from the bloodvessels, 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 discharged by the thoracic duct is the absorption of fatty substances from the intestine during digestion. Whenever fatty substances exist in 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 absorbed by the lymphatics of the mesentery, and transported by them through 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 chyle; 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 during 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 304 IMBIBITION AND EXHALATION. the 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. Rees:'— Water . Albumen Fibrin . Spirit extract Water extract Fat Saline matter Lymph. Chyle. 965.36 902.37 12.00 35.16 1.20 3.70 2.40 3.32 13.19 12.33 traces. 36.01 5 85 7.11 1,000.00 1,000.00 When a canula, accordingly, is introduced into the thoracic duct at various periods after feeding, the fluid which is 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 the introduction of fat food. Soon after feeding, however, as we have already 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 Parts 3^ hours after feeding . 2.45 7 u u . 2.20 13 " U (( . 0.99 18 " it a . 1.15 18} " u u . 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 which it contains 1 In Colin, op. cit., vol. ii. p. 18. THE LYMPHATIC SYSTEM. 305 in small quantity. After coagulation, a separation takes place be- tween the clot and serum, 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 influences the chyle and lymph are incessantly carried from 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. Colin1 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.2 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 Hebdomadaire, April 24, 1857, p. 285. ' Colin, op. cit., vol. ii. p. 100. 20 306 IMBIBITION AND EXHALATION. 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 half. 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 we 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 of 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. 307 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, thus secreted and reabsorbed during twenty-four hours, will enable us to estimate the activity with which endosmosis and exosmosis go on in the living bodv. In the following table, the quantities are all calculated for a man weighing 140 pounds. Secreted and Reabsorbed during 24 hours. Saliva 20,104 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 " " 3.804 " 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. 308 SECRETION. 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 different 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 tears 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 inorganic salts of the blood; and these ingredients, in varying proportions, are common to all, or nearly all, of the secreted fluids. But each secre- tion is also distinguished 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. Thus the gastric juice contains pepsine, which is formed only in the tubules of the gastric mucous membrane; the pancreatic juice contains pancrea- tine, formed only in the pancreas; and the bile contains tauro-cho- late of soda, formed only in the liver. As the blood circulates through the capillaries of the gland, its watery and saline constitu- SECRETION. 309 ents transude in certain quantities, and are discharged into the ex- cretory duct. At the same time, the glandular cells, which have themselves been nourished by the blood, produce a new substance by the catalytic transformation of their organic constituents; and this new substance is discharged also into the excretory duct and completes the constitution 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. 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 amenorrhoea. 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 310 SECRETION. has found1 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'2 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 Steno 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 absorbing 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. 1 Lecons de Physiologie Experi men tale. Paris, 1856, tome ii. p. 96 et seq. 2 Ibid., p. 106. MUCUS. 311 The principal secretions met with in the animal body are as follows:— 1. Mucus. 6. Saliva. 2. Sebaceous matter. 7. Gastric juice. 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 follicles or glandulae, in which the mucus is prepared. These folli- cles are most abundant in the lining membrane of the mouth, nares, pharynx, 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. 103), and surround- ed on its external surface by a network of capillary bloodvessels. These vessels, penetrating deeply into the F. .„„ 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. follicles of a com- The mucus, produced in the manner pound mucous glandule. i , ..,. . ,. n • i From the human subject. (Aftei above described, is a clear, colorless fluid, Koiiiker.)-*. Membrane of the which is poured out in larger or smaller follicle- 6>c- Epithelium of the quantity on the surface of 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 312 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,1 is as follows:— Composition of Pulmonary Mucus. Water...........955.52 Animal matter Fat..... Chloride of sodium . Phosphates of soda and potassa Sulphates " " Carbonates " " 33.57 2.89 5.83 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 Mattee.—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., 1846, p. 352. sebaceous matter. 313 Fig. 104. glands of the 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 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. 104), the follicles are ranged along the sides of an excretory 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 of the integument lining the meatus, in 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.1 Meibomian Ludovic. Glands, aftel Composition of Sebaceous Mattfr. Animal substances ...... Fatty matters ....... Phosphate of lime ...... Carbonate of lime ...... Carbonate of magnesia Chloride of sodium Acetate of soda, &c. I 358 368 200 21 16 37 1000 Owing to the large proportion of stearine in the fatty ingredients of the sebaceous matters, they have a considerable degree of con. sistency. Their office 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. 311 SECRETION. 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 by 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. Perspiration.—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 ^^ of an inch in diameter, 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. 105.) A network of capillary vessels envelops the tubular coil and sup- plies the gland with the materials necessary to its secretion. These 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,1 about 500 to the square inch; on the anterior part of the trunk, the forehead, the neck, the forearm, and the back 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 y1^ 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. Perspiratory G land, with its ves- sels ; magnified 3°> tim^s. (After Todd and Bow- man.)—a. Glaudular coil. 6. Plexus of vessels. 1 Kolliker, Handbuch der Gewebelehre, Leipzig, 1852, p. 147. PERSPIRATION. 315 It is easy to understand, therefore, that a very large quantity of fluid may be supplied from so extensive a glandular apparatus. It results from the researches of Lavoisier and Seguin1 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 Smith2 found that the laborers employed in gas works lost sometimes as much as 3| 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,3 is as follows:— Composition of the Perspiration. Water...........995.00 Animal matters, with lime ........ .10 Sulphates, and substances soluble in water . . . . 1.05 Chlorides of sodium and potassium, and spirit-extract . . 2.40 Acetic acid, acetates, lactates, 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 1 Milne Edwards, Lemons sur la Physiologie, &c, vol. ii. p. 623. 2 Philosophy of Health. London, 1838, chap. xiii. 3 Simon. Op. cit., p. 374. 316 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 shown1 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 portion 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. Atlee's translation, Phila., 1854, p. 25. THE MILK. 317 surfaces of the cornea and conjunctiva moist and polished, and to preserve in this way the transparency of the parts. 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 resembling 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. 106.) In this way, by Fig. 106. 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 glandular structure op mamma. breasts often contain 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 shown1 that it really con- tains a larger amount 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- 1 Lehmann, op. cit., vol. ii. p. 63. 318 SECRETION. Fig. 107. bular or oval bodies, from T1lST} to -glv of an mca in diameter, which are termed the " colostrum corpuscles." (Fig. 107.) These bodies are more yellow and opaque than the true milk- globules, as well as being very much larger. They have a 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 2tJ!5Tj to tsVo- OI> an inch in 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 nipple, 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 Corpuscles, with milk-globules; from a woniau, one day after delivery. Composition of Cow's Milk. Water Casein Butter Sugar Soda Chlorides of sodium and potassium Phosphates of soda and potassa Phosphate of lime " " magnet; " " iron Alkaline carbonates Iron, &c. J 870.2 44.8 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. 319 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. 108.) These globules are nearly fluid at the temperature of the body, and have a perfectly circular out- line. In the perfect milk, they are very much more abundant and Fig. 108. Milk-Globules; from same woman as above, four days after delivery. Secretion fully established. 320 SECRETION. smaller in size than in the colostrum; as the largest of them are not over w'gv 0I an incn in diameter, and the greater number about Tpoo OI> an inch. The following is the composition of the butter of cow's milk, according to Robin and Verdeil:— Margarine..........68 Oleine..........30 Butyrine.......... 2 100 It is the last of these ingredients, the butyrine, 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. No such 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 (C24H24024) may be 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 (C6H6Ofl). 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 free lactic acid then coagulates the casein, and the milk SECRETION OF THE BILE. 321 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 found1 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 first 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 quantity of arterial blood with which it is supplied is extremely small in comparison with that which it receives from 1 Op. cit., p. 337. 21 322 SECRETION. the portal system. The blood which has circulated through the capillaries of the stomach, spleen, pancreas, and intestine is col- lected by 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 an 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, -Js to T'.T 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. 109) Fig-™9» 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 Ramification of Portal Vein iir Liver.—a. Twig of portal vein. b,b. Interlobular veins, c. Acini, 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 investment, 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 interlobular spaces; so that here the lobules are nearly in contact with each SECRETION OF THE BILE. 323 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. 110.) At the centre of each lobule, the Fig. 110. Lobule op Liver, showing distribution of bloodvessels ; magnified 22 diameters —a. a. la- terlobular veins. 6. Intralobular vein, c, c, c. Lobular capillary plexus, d, d. Twigs of inter- lobular vein passing to adjacent lobules. converging capillaries unite into a small vein (b), 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 T5Vo- of an inch in diameter, the "hepatic cells." (Fig. 111.) 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 321 SECRETION. 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,1 and Dr. Beale, of London,3 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, „ f. , .. . themselves lie in close proxi- Hepatic Cells. Prom the human subject. ? 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 glandular cells of the organ, and gives up to them the nutritious materials which are afterward converted into the ingredients of the bile. American Journal Med. Sci., January, 1848. On Some Points in the Minute Anatomy of the Liver. London, 1856. EXCRETION. 325 CHAPTER XVII. EXCRETION. We 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, haematine 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 326 EXCRETION. 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 capable 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 discharged 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 upon 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. 327 four days to produce a fatal result. A fatal result, however, is cer- tain to follow, at 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 exist in the human body are as follows: C02 c,H,N,0, 1. Carbonic acid 2. Urea . 3. Creatine . 4. Creatinine 5. Urate of soda 6. Urate of potassa 7. Urate of ammonia C8H9N304 C8H7N302 Na0,C5HN2024-H0 KO,C5HN202 NH40,2C5HN202-f-H0 The physiological relations of carbonic acid have already been studied, at sufficient 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. Urea.—This is a neutral, crystallizable, nitrogenous substance, very readily soluble in water, and easily decomposed by various external influences. It occurs in the urine in the proportion Fis- 112< of 30 parts per thousand; in the blood, according to Picard,1 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- Psea, prepared from urine, and crystallized by slow evaporation. (After Lehmann.) In Milne Edwards, Lecons sur la Physiologie, &c, vol. i. p. 297. 328 EXCRETION. tion of 1.4 per thousand.1 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:— C2H4N202=Urea. NH3,C02=Carbonate of ammonia. H2 02=Water. 2 C2H6N204 N2H6C204 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. Dr. William A. Hammond,2 whose weight was 205 pounds, by similar experiments found it to be 670 1 Robin and Verdeil, vol. ii. p. 502. 2 American Journal Med. Sci., Jan., 1855, and April, 1856. UREA. 329 grains. Dr. John C. Draper,1 whose weight was 145 pounds, found it 408 grains. No urea is to be detected in the urine of very young children;2 but it soon makes its appearance, 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 no means certain; since in a state of general bodily activity it is not only the urea, but the excretions generally, car- bonic acid, perspiration, &c, which are increased in quantity simul- taneously. Hammond also found, in his own person, that unusual mental application alone, all the other conditions, of diet, exercise, &c, remaining the same, raised the daily quantity of urea from 670 to 748 grains per day. 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 table3 gives the result of these ex- periments. Kind of Food. Daily Quantity op Urea. Animal........798 grains. Mixed........487 " Vegetable........337 " Non-nitrogenous......231 " Finally, it has been shown by Dr. John C. Draper4 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| to 10| P. M. Urea exists in the urine of the carnivorous and many of the 1 New York Journal of Medicine. March, 1853. 2 Robin and Verdeil, vol. ii. p. 500. ' Lehmann, op. cit., vol. ii. p. 163. * Loc. cit. 330 EXCRETION. Creatine, crystallized from hot water. (After Lehmann.) herbivorous quadrupeds ; but there is little or none to be found in that of birds and reptiles. Creatine.—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- H3. 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«114- 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 Creatinine, (After Lelimaun.) crystallized from hot water. CREATININE.— URATE OF SODA. 331 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 more 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 (C^HNjO^HO). 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- n^ lar masses, with projecting, curved, conical, wart-like excrescences. (Fig. 115.) 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 Urate op Soda; from a urinary deposit. 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 332 EXCRETION. soda discharged 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 CHARACTERS OF THE URINE. 333 carbon are daily expelled from the body, is one of these substances; the others ^-re 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 ordinary quantity of urine discharged daily by a healthy adult is about 3xxxv, and its mean specific 334 EXCRETION. gravity, 1024. Both its total quantity, however, and its mean specific gravity are liable to vary somewhat from day to day, owinc 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 the 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. 335 quantity of water is often so much diminished that 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 character? of this variation:— Observation First. March 20th. Urine of 1st discharge, acid, sp. gr. 1025. " 2d " alkaline, " 1015. " 3d " neutral, " 1018. " 4th " acid, " 1018. " 5th " acid, " 1027. Observation Second. March 21sr. Urine of 1st discharge, acid, sp. gr. 1029. " 2d " neutral, " 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 336 EXCRETION. gravity and acidity of the urine in cases of disease, it will not he 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 of the Urine. Water...........938.00 Urea...........30.00 Creatine ........... 1.25 Creatinine..........1.50 Urate of soda -» " potassa J-........1.80 " ammonia J Coloring matter and 1 „» Mucus f Biphosphate of soda Phosphate of soda " potassa \.......12.45 " magnesia " lime Chlorides of sodium and potassium......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 REACTIONS OF THE URINE. 337 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 ai 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, sub 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 onlv 22 338 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 laminse 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- FJg- 116- lous concretions. (Fig. 116.) 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 reaction, it becomes immediately turbid from a deposit of the earthy phos- phates, which are insoluble in alkaline fluids. c a ic a c i d ; deported from urine. 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 of interfering with the mutual reaction of starch and iodine, and even REACTIONS OF THE URINE. 339 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 iodine 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 ha^ 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 color 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 substances 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 Urine.—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 by a kind of filtration, it is not surprising that most medicinal and poisonous substances, introduced into the circulation, should be 1 American Journal Med. Sci., April, 185G. 310 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 kidneys, 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,1 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 dissolving 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. Bernard2 observed that a solution of 1 Physiological Chemisty, vol. ii. p. 133. 2 Leqons de Physiologie Experimentale, 1856, p. 111. ACCIDENTAL INGREDIENTS OF THE URINE. 341 this salt, after being injected into the 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, iodine 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. Ether 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 producing anaes- thesia. The bile-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 Bernard1 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 15 grains of glucose be injected 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 1 Lecons de Phys. Exp., 1855, p. 214 et seq. 312 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 J grains of cane sugar, introduced in the same way, fail to be com- pletely destroyed in the circulation, 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 sufficient 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's 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 time, 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 of 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 URINE. 343 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 frequently 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 oxalic acid is also sometimes produced, in a similar manner with the lactic. It is very certain that the deposit of oxa- late of lime, far from being 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 344 EXCRETION. Fig. 117. 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. 117.) 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 advances, it loses the power of pro- ducing lactic and oxalic acids, and becomes a ferment capable of acting by catalysis 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 of Lime; deposited from healthy urine, daring the acid fermentation. ALKALINE FERMENTATION OF THE URINE. 345 may be afterward kept, for an indefinite time, without 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 thus produced neutralize a corresponding quantity of 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 disap- pears 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 fairly 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 carbonate of ammonia on the phosphates of 346 EXCRETION. soda and magnesia. One of these is the "triple phosphate," phos- phate of magnesia and ammonia (2MgO,NH40,POJ+2HO). The other is the phosphate of soda and ammonia (NaO,NH40,HO,PO,-f 8HO). The phosphate of magnesia and ammonia is formed from the phosphate of magnesia in the urine (3MgO,P05-f 7H0) 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. Phosphate of Magnesia and Ammonia; (Fig. 118.) Frequently, alsO) deposited from healthy nrine, during alkaline fermen- their , d j ^ tation. ° ° 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 a similar 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 RENOVATION BY NUTRITIVE PROCESS. 347 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 freely given off 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. Renovation 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 during 24 hours. Discharged during 24 hours. 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 " .220 " Urea and salts .110 " Salts .040 " Feces .320 " 7.070 7.070 Rather 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 348 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 produced by a direct oxidation of carbon; but originates by a pro- cess of decomposition, throughout the tissues of the body, somewhat 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. SECTION II. NERVOUS SYSTEM. CHAPTER I. GENERAL STRUCTURE AND FUNCTIONS OF THE NERVOUS 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 ( 349 ) 350 GENERAL 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:— Each organ and tissue in the body has certain properties peculiar 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 example, 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. 351 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, by the thoracic and abdominal muscles, 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 organiza- tion is a 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 har- mony 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, where 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. 352 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 fibrous 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 diameter of to^tftt of an inch. In the trunks and branches of the nerves they average j^t 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 longitu- dinally through the central part of each filament, is a narrow ribbon-shaped cord, of rather firm consistency, and of a semi- transparent grayish aspect. This central portion is called the "axis cylinder." It is enveloped everywhere by the semi-fluid white substance, and the whole invested by the external tubular 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. 353 preparation, produces an irregularly bulging or varicose appearance in them at various points, owing to the readiness with which the semi-fluid white substance in their interior is displaced in different directions. (Fig. 119.) 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 Fig. 119. 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 Sl!ims filaments from white substance of - _. . . . . brain.—a, a, a. Soft substance of the filaments pressed form Of irregularly rounded „ut, and floating in irregularly rounded drops. 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 effect 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. 120.) At first, this change takes place only in the outer portions of the white substance of Schwann. The coagulating process, however, subsequently goes on, and 23 354 GENERAL STRUCTURE 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. 119, a.) These FiS- 12°- drops are always covered with a layer of coagulated material which is thicker and more opaque in propor- tion to the length 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. These pri- mary bundles are again united into secondary, the secondary into Nervous Filaments from sciatic'nerve, showing their coagulation. — At a, the torn extremity of a nervous filament with the axis cylinder (b) protruding from it. At c, the white substance of Schwann is nearly separated by accidental 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 NERVOUS SYSTEM. 355 tertiary, &c. 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. 121.) 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 themselves divide, and even form sometimes minute plexuses, when they have finally arrived at their destination and are about to terminate in the sensitive or muscular parts; but during the whole previous tran- „ . . . Division of a Nerve, showing portion of Sit Ot the nerve, between its OH- nervous trunk («), and the separation of its gin and its termination, they re- fllameilt8(6>cented in black ; and the egg is seen, at the fundus of the uterus, en- paged between two of it« projecting convolutions. Impregnated Uterus, with pro- jecting folds of decidua growing up around the egg. The narrow opening where the edges of the folds approach each other, is seen over the most promi- nent portion of the egg. 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, while 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 (Fig. 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 [mpeeii.vai\.ii U t e k u 8; —. showing egg completely inclo.-ed by decidua reflexa. 606 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE. newly-formed layer of decidua, enveloping, as above described, the projecting portion of the egg, is called the Decidua reflexa; because it is reflected over the egg, by a continuous growth from the general surface of the uterine mucous membrane. The orifices of the uterine tubules, accordingly, in consequence of the manner in 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 original 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 continued 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 been taking place in the walls of the uterus, the FORMATION OF THE DECIDUA. 607 Fig. 222. formation of the embryo in the egg, and the development of tho amnion and chorion have been going on simultaneously. Soon after the entrance of the egg into the uterine cavity, its external investing membrane becomes covered with projecting filaments, or villosities, as previously described. (Chap. 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 follicles 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 uniformly 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 surface of the decid ua reflexa with which it is covered. (Fig. 222.) In this way the egg becomes entangled with the decidua, and 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- tritious fluids, exuded from the soft and 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. Yery soon, however, a still greater activity of absorption be- comes necessary; 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. Each villosity, then, as it lies imbedded in its uterine follicle, contains a vascular loop through which the fcetal 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, Impregnated Uterus; showing connection between vil- losities of chorion and decidual membraues. 02482007�925 608 DEVELOPMENT OF UTERINE 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. (Fig. 223.) This is the spot at which the egg is in contact with the deci d ua vera. Here, therefore, both the decidual membrane and the tufts of the chorion continue to increase in thickness and vascularity; while else- where, over the prominent portion of the egg, 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 taking 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. Pregnant Uterus; showing formation of placenta, by the united development of a portion of the de- cidua and the villosities of the cho- THE PLACENTA. 609 CHAPTER XII. THE PLACENTA. We have shown in the preceding chapters that the fcetus, 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 way into the circulation of the fcetus. 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 and 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 valvulae 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. 39 610 THE PLACENTA. In the cow, for example, the external membrane of the egg, beside being everywhere supplied with branching vessels, presents upon Fig. 224. F an incn- The glomeruli in the Wolffian bodies measure JE of an inch in diameter, while those of the kidney mea- sure only y^ of an 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 and 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 fcetus 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 WOLFFIAN BODIES. 645 Fig. 248. Fcetal Pig, one and a half inches long. From a specimen in the author's possession.—1. Wolffian body. 2. Kidney. the Wolffian bodies. (Fig. 248.) As the kidneys, however, subse quently enlarge, while the Wolffian bodies diminish, the propor tion existing between the two organs is 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. 249 and 250.) 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, over their anterior surface. This apparent sliding movement, or descent of the Wolffian bodies, is owing to the rapid growth of the kidneys in an up- ward direction, as we have already explained. The kidneys, during the succeeding periods of fcetal 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 ^ (in 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 Sidneys taken together is T|g 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 Wolffian bodies and between them 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 fcetus is afterward to belong to the male or the female sex. (Fig. 249.) Internal Oroaws of Gene- ration, &c. ; in a fcetal pig three inches long. From a specimen in the author's possession.—1, 1. Kidneys. 2, 2. Wolffian bodies. 3, 3. Internal organs of generation; testicles or ovaries. 4. Urinary bladder turned oyer in front. 5. Intestine. 646 DEVELOPMENT OF 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 organ. 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 deferentia 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 the 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 Organs of Generation; Descent of the Testicles.—In the male fcetus 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 kMneys, come at last to be situated in the 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 these organs. (Fig. 250.) 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. 647 Internal Organs op Generation, &c, in a foetal pig nearly four inches long. From a specimen in the author's possession.— 1, 1. Kidneys. 2, 2. Wolffian bodies. 3, 3. Testicles. 4. Urinary bladder. 5. 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- tion of the inguinal canal, is in- serted into the subcutaneous tis- sue 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 last, when the testicles have arrived at the internal inguinal ring, the Wolffian 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 arrive at 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 muscle. 648 DEVELOPMENT OF THE KIDNEYS. At last, the testicles descend fairly to the bottom of the scrotum the gubernaculum 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 bodv of the testicle; while the vas deferens passes upward, in a reverse direction, enters the abdomen through the inguinal canal, again bends downward, 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 same 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 vesiculee 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 communi- cation with the peritoneal cavity. In many 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« 251- 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 contact with each other, and, adhering ginalis Testis.—1. Testicle , .... ,„. _-_, . nearly at the bottom of the scro- together at this situation (Fig. 251, 4), turn. 2 Cavity of tunica vaginalis. form a ^[n^ Qf cicatrix, Or UmbiHcUS, by 3. Cavity of peritoneum. 4. Obliter- i ated neck of peritoneal sac. the complete closure and consolidation 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 ORGANS OF GENERATION. 649 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 spermatic cord, giving rise, in this way, to a congenital inguinal hernia. (Fig. 252.) 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. 252. 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 bv a simple process congenital inguinalher- „ . . . . . ,.* nia. —1. Testicle. 2,2,2. lutes- ot growth taking place in different 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, and 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 650 DEVELOPMENT OF 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 becomea the ligament of the ovary ; its lower portion, the round ligament of the uterus. As the ovaries continue their descent, they pass below and be- hind the Fallopian tubes, which necessarily perform at the same time a movement of rotation, from before backward and from above downward; 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 t more upon the median line, and become covered with an exces- sively developed layer of muscular fibres. In the lower animals, 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. B£MALE ORGANS OF GENERATION. 651 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 in 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 fcetal life, however, the 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 foetus 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 internum. 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 B£? 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 envelops each egg closely, there being no fluid between its internal surface and the exterior of the egg, but only the thin layer of cells forming the "membrana granulosa." Inside this 652 DEVELOPMENT OF THE KIDNEYS, ETC. layer is to be seen the 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 as large as ^^ of an inch; others as small as Tocs- 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 vesicte i? to be seen. DEVELOPMENT OF THE CIRCULATORY APPARATUS. 653 . CHAPTER XVII. DEVELOPMENT OF THE CIRCULATORY APPARATUS. There are three distinct forms or phases of development assumed by the circulatory system during different periods of life. These different forms of the circulation are intimately connected with the manner in which 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 over 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. 253), 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 growth of the 654 DEVELOPMENT OF THE CIRCULATORY APPARAT US. newly-formed tissues. In the egg of the fish (Fig. 254), 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. 253. Ego of Fowl in process of development, showing area vasculosa, with vitelline circulation, terminal sinus, &c. Fig. 254. vitellus, in this way, becomes covered with an abundant vascular network, connected with the internal circulation of the foetus by arteries and veins. 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 foetus to and from the area vasculosa. These two arteries emerge from the lateral edges of the fcetus, 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-mesenteric 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 Fisn (Jar ra'iacca), showing vitel- line circulation. PLACENTAL CIRCULATION. 655 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 off, throughout their course, many small lateral branches, which supply the body of the foetus, and also two larger branches—the omphalo-mesenteric arteries— which pass out, as above described, into the area vasculosa. The two vertebral arteries remain separate in the upper part 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 aorta, 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 fcetus. The above description shows the origin and formation of the first or vitelline circulation. A change, however, now begins to take place, by which the vitellus is superseded, as an organ of nutrition, by the placenta, which takes its place; and the second or placental 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 FlS- 255- 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. 255.) 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 Young Embryo and its Vessels, showing circulation of umbilical vesicle, and also that of allantois, beginning tj be formed. 656 DEVELOPMENT OF THE CIRCULATORY 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. 255.) 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. 256.) The mesenteric vessels then Fig. 256. Diagram of Embryo and its Vessels; showing the second circulation. The pharynx, oesophagus, and intestinal can;il, have become further developed, and the mesenteric arteries have enlarged, while the umbilical vesicle and its vascular 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. DEVELOPMENT OF THE ARTERIAL SYSTEM. 657 In the mean 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 them 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. 256.) 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 fcetus 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 oigans 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 "vertebral 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. 257.) These are termed the cervical arches. In the fish, these cervical arches remain permanent, and give off from theii convex borders the branchial arteries, in the form of vascular tufts 42 658 DEVELOPMENT OF THE CIRCULATORY APPARATUS. to the gills on each side of the neck; but in the human 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. 257. Fig. 258. Early condition of Arterial System: 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 Sys- tem.—1,1. Carotids. 2, 2. Vertebrals. 3, 3. Right and left subclavians. 4, 4, Right and left superior intercostals. 5. Left aortic arch, which remains perma- nent. 6. Right aortic arch, which dis- 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. 258, 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 fourth 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, 3). This vessel, DEVELOPMENT OF THE ARTERIAL SYSTEM. 659 though at first a mere branch of communication 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. Immediately 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 (5). On the right side, however, the corresponding arch (6) 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 fcetal 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- 660 DEVELOPMENT OF THE CIRCULATORY APPARATUS. tremities, becomes the common iliacs, 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 of the fcetus, and the separation of the placenta, the hypogastric artesries become partially atrophied, and are con- verted, in the adult condition, into solid, rounded cords, running upward toward the umbilicus. Their lower portion, however, vemains 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 urinary bladder, which is the remnant of the ori- ginal allantois itself. The terminal continuation of the original abdominal 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 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. 259), 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 Cuvier, When the inferior extremities become developed, their two veins, returning from below, join the vertebral veins near the posterior portion of the body; and, crossing them, afterward unite with each other, thus Fig. 259. Early condition of V e- sobs System; show- ing the vertebral veins emptying into the heart by iwo lateral trunks, the "canals of Cuvier." DEVELOPMENT OF THE VENOUS SYSTEM. 661 constituting another vein of new formation (Fig. 260, 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 and 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. 260), 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. 260, b), 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 (b), 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. 261), 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. Fig. 260. Venods System far- ther advanced, showing formation of iliac and sub- clavian veins.—a. Vein of new formation, which be- comes the inferior vena cava. b. Transverse branch of new formation, which afterward becomes the left vena innominata. Fig. 261. Further development «f the Venous System.— The vertebral veins are much diminished in size, and the canal of Cuvier, on the left side, is gradually disappearing, c. Trans- verse branch of new forma- tion, which is to become the vena azygos minor. 662 DEVELOPMENT OF THE CIRCULATORY APPARATUS. Fig. 262. 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 cava is a totally distinct vein, of new formation, resulting from 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. 262, 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 communicate 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. 261, c), and this branch soon enlarges to such an extent as to bring over to the vena 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 Adult condition 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. Iliac veins. 7. Lumbar veins. 8. Vena azygos major. 9. Vena azygos minor. 10. Su- perior intercostal vein. DEVELOPMENT OF THE HEPATIC CIRCULATION. 663 upper intercostal veins on the left side still empty, as before, into their own vertebral vein (10), 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 are 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 Venosus.—■ 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-mesenteric vein, just below its FiS* 263- termination in the heart. (Fig. 263.) As soon as the organ has attained a con- siderable size, the omphalo-mesenteric vein (1) 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. The omphalo-mesenteric vein below the Early form of hepatic cik- liver then becomes the portal vein; while ^™- ^^^TI above the liver, and between that organ Heart- The dotted nne shows the -i .1 •, ., . ., „ situation of the future umbilical and the heart, it receives the name of vein. the hepatic vein (2). 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 664 DEVELOPMENT OF THE CIRCULATORY APPARATUS. Fig. 264. Hepatic Circulation farther advanced.—1. Portal vein. 2. Umbilical vein. 3. Hepatic vein. the intestine also remains inactive, while the placenta increases in size and in functional importance, a time soon arrives when the liver receives more blood by the umbilical vein than by the portal vein. (Fig. 264.) 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 portal 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 all 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 amounts 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 cent. 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. 265), 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. 265. Hepatic Circulation during 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 venosus. 6. Hepatic vein. DEVELOPMENT OF THE HEPATIC CIRCULATION. 665 Fig. 266. as follows: A certain quantity of venous blood still enters through the portal vein (1), and circulates in a part of the capillary system of the right lobe. The umbilical vein (2), 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 (3) 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 birth. 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. 266.) First, the umbilical vein shrivels and be- comes converted into a solid rounded cord (2). 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 (4), 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 of the portal vein; and its blood passes Adult form of Hepatic Circula- tion.— 1. Portal vein. 2. Obliterated umbilical vein, forming the round liga- ment; the continuation of the dotted lines through the liver shows the situa- tion of the obliterated ductus venosus. 3. Hepatic vein. 4. Left branch of portal vein. 666 DEVELOPMENT OF THE CIRCULATORY APPARATUS. from right to left, to be distributed to the capillaries of the left lobe. According to Dr. Guy, the umbilical vein is completely closed at the end of the fifth day after birth. Development of the Heart, and the Ductus Arteriosus.—When the embryonic circulation is first established, the heart is a simple tubu- lar sac (Fig. 267), receiving the veins at its lower extremity, and 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. 268); 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. 267. 2 Y// Earliest form of Fcetal Heart. — 1. Venous ex- tremity. 2. Arterial ex- tremity. Fig. 268. Fig. 269. Fcetal Heart, twisted upon itself.—1. Venous ex- tremity. 2. Arterial extre- mity. Fcetal Heart, divided into right and left cavities.— 1. Venous extremity. 2. Arterial extremity. 3, 3, Pulmonary branches. Soon afterward, this single cardiac tube is divided into two paral- lel tubes, right and left, by a longitudinal partition, which grows from the inner surface of its walls and follows the twisted course of the organ itself. (Fig. 269.) 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. DEVELOPMENT OF THE HEART. 667 Fig. 270. Fcetal Heart still farther developed.—1 Aorta. 2. Pul- monary artery. 3. 3. Pul- monary branches 4. Ductus arteriosus. Yery soon a superficial line of demarcation, or furrow, shows itself upon the external surface of tne heart, corresponding in situa- tion with the internal septum; 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. 270.) 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; and 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 pulmonary branches increase in proportion to the pulmonary 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 active 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. 271.) Fig. 271. Heart of Infant, showing dis- appearance of arterial duct after birto —1. Aorta. 2 Pulmonary artery. 3, 3. Pulmonary branches. 4. Ductu; arteriosus becoming obliterated. The ductus arteriosus at the 668 DEVELOPMENT OF THE CIRCULATORY 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 duct is complete, at latest, by the tenth week after birth. (Guy.) 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 through the heart, which is characteristic of foetal life, and which may be described as follows:— It will be found upon examination that the two venae cavae, 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 crescentic border, leaving at that part an oval opening, the foramen ovale. The stream of blood, coming 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 into 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. 669 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. 272. /), is attached to the anterior border of the orifice of the inferior vena cava, and terminates by a crescentic edge, directed toward 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. 272, 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 cavae, cross each other upon entering the heart. This crossing of the streams does not take place, however, as it is sometimes 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 innominata, 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 cavaa, not only to enter the heart in different directions, but also to be distributed, after leaving the ventricles, to different pari3 of the body. (Fig. 273.) For the blood of the superior vena cava Fig. 272. Heart of Human Fcetus, at the end of the sixth month ; from a specimen in the author's pos- session.—a. Inferior vena cava. b. Superior vena cava. c. Cavity of right auricle, laid open from the front, d. Appendix auricularis. e. Cavity o! right 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. 670 DEVELOPMENT OF THE CIRCULATORY APPARATUS. Fig 273. passes through the right auricle downward into the right ventricle, thence through the pulmonary artery and ductus arteriosus, into the thoracic aorta, while the blood of the inferior vena cava, enter- ing 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, returning from the head and upper 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 certain period of foetal life, is so complete that Dr. John Beid,1 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, Diagram of Circulation through the Fcetal Heart.—a. Superior vena cava. 6. Inferior vena cava, c, c, c, c. Arch of aorta and its branches, d. Pulmonary artery. 1 Edinburgh Medical and Surgical Journal, vol. xliii. 1835. DEVELOPMENT OF THE HEART. 671 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, however, 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 heart, 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 (Fig. 272), 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 672 DEVELOPMENT OF THE CIRCULATORY APPARATUS. membranous ridge, which 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 ovale. 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 through 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 pulmonary blood, DEVELOPMENT OF THE HEART. 673 no longer admits a free access from the right auricle through the foramen ovale; and the valve of the foramen, pressed 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 always 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. 273, is then replaced by the adult circulation, represented in Fig. 274. Fig. 274. Diagram of Adult Circulation through the Heart.—a, a. Superior and inferior vena cava. b. Eight ventricle, c. Pulmonary artery, dividing into right and left branches, d. Pulmo- aary vein. e. Left ventricle. /. Aorta. 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- 43 674 DEVELOPMENT OF THE CIRCULATORY APPARATUS. rent to the edges of the septum. The auricular septum in the adult heart is, therefore, 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 pervious 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 of 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 OF THE BODY AFTER BIRTH. 675 CHAPTER XVIII. DEVELOPMENT OP THE BODY AFTER BIRTH. 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-uterine 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 embryonic 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 upper and lower extremities are habitually 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. Bespiration, indeed 676 DEVELOPMENT OF THE BODY AFTER BIRTH. seems to be accomplished, during 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 when 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 different from that which they exert 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 and 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 AFTER BIRTH. 677 the estimates of Cruveilheir, Solly, Wilson, &c.: that of the organs in the foetus at term from our own observations. Fetus at Term. AD0LT. entire body . 1000.00 1000.00 encephalon 148.00 23.00 liver . 37.00 29.00 heart 7.77 4.17 kidneys 6.00 4.00 renal capsules 1.63 0.13 thyroid gland 0.60 0.51 thymus gland 3.00 0.00 It will be observed that most of the internal organs diminish ia 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 incisors 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 678 DEVELOPMENT OF THE BODY AFTER BIRTH. the 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 in 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 organs of the body arrive at the adult condition, and the entire process of development is then complete. INDEX. Absorbent glands, 152, 301 vessels, 152, 301 Absorption, 146 by bloodvessels, 149 by lacteals, 153 of fat, 155 of different liquids by animal sub- stances, 296 of oxygen in respiration, 226 by egg during incubation, 593 of calcareous matter by allantois, 594 Acid, carbonic, 226, 230, 327 lactic, in gastric juice, 123 in souring milk, 83, 320 glyko-cholic, 164 tauro-cholic, 165 pneumic, 231 uric, 331, 338 oxalic in urine, 344 Acid fermentation of urine, 343 Acidity of gastric juice, cause of, 123 of urine, 337 Acini, of liver, 322 Adipose vesicles, 74 digestion of, 143, 144 Adult circulation, 673 establishment of, 674 Aerial respiration, 217 Age, influence of, on exhalation of car- bonic acid, 234 on comparative weight of organs, 677 Air, quantity of, used in respiration, 222 alterations of, in respiration, 235 circulation of, in lungs, 223 Air-cells of lungs, 219 Air-chamber, in fowl's egg, 540 Albumen, 84 of the blood, 208 in milk, 319 of the egg, how produced, 538 its liquefaction and absorption dur- ing development of foetus, 590, 591 Albuminoid substances, 79 digestion of, 126 Albuminose, 127 interference with Trommer's test, 128 with action of iodine and starch, 129 Alimentary canal in different animals, 100 in human subject, 103 development of, 632 Alkalies, effect of, on urine, 338 Alkaline chlorides, 55-58 phosphates, 61 carbonates, 60, 61 Alkaline fermentation of urine, 644 Alkalescence of blood, due to carbonates, 60 Allantois, 588 formation of, 589 in fowl's egg, 592 function of, 593 in foetal pig, 610 Alligator, brain of, 366 Amnion, 587 formation of, 588 enlargement of, during latter part of pregnancy, 618, 619 contact with chorion, 620 Amniotic folds, 588 Amniotic fluid, 618 its use, 619 contains sugar at a certain period, 637 Amniotic umbilicus, 588 Analysis, of animal fluids, 48, 49 of milk, 96, 318 of wheat flour, 96 of oatmeal, 96 of eggs, 97 of meat, 97 of saliva, 108, 110 of- gastric juice, 123 of pancreatic juice, 140 of bile, 160 of blood-globules, 202 of blood-plasma,- 207 of mucus, 312 of sebaceous matter, 813 of perspiration, 315 of butter, 320 of urine, 336 of fluid of thoracic duct, 302 of chyle and lymph, 304 Andral and Gavarret, production of carbonic acid in respiration, 234 Animal functions, 43 Animal heat, 237 in different species, 239 (679) 680 INDEX. Animal heat, mode of generation, 241 influenced by local causes, 245 in different organs, 246 increase of, after section of sympa- thetic nerve, 509 Animal and vegetable parasites, 520 Animalcules, infusorial, 517 mode of production, 518 Annulus ovalis, 674 Anterior columns of spinal cord, 365 their excitability, 887 Aorta, development of, 658 Aplysia. nervous system of, 359 Appetite, disturbed by anxiety, &c, 134 necessary to digestion of food, 135 Aquatic respiration, 217 Arch of aorta, formation of, 658 Arches, cervical, 659 transformation of, 658 Area pellucida, 578 vasculosa, 591, 654 Arteries, 265 motion of blood in, 266 pulsation of, 267 elasticity of, 266, 270 rapidity of circulation in, 272 omphalo-mesenteric, 654 vertebral, 657 umbilical, 659 Arterial pressure, 271 Arterial system, development of, 657 Articulata, nervous system of, 360 reflex action in, 361 Articulation of tapeworm, 529 Arytenoid cartilages, 225 movements of, 225 Assimilation, 308 destructive, 325 Auditory apparatus. 493 nerves, 431, 492 Auricle, single, of fish, 249 double, of reptiles, birds, and mam- malians, 250, 251 contraction of, 264 Auriculo-ventricular valves, action of, 253 Axis-cylinder, of nervous filaments, 352, 354 Aztec children, 410 Azygous veins, formation of, 662 Beaumont, Dr., experiments on Alexis St. Martin, 120, 129, 131 Bernard, on the different kinds of saliva, 109 on effect of dividing Steno's duct, 115 on digestion of fat in intestine, 139 on formation of liver-sugar, 184, 186, 187 on decomposition of bicarbonates in lung, 231 Bernard, on temperature of blood in dif- ferent organs, 246 on the influence of the nerves on local circulations, 508 on the origin of the spinal accessory nerve, 459 Bidder and Schmidt, on daily quantity of bile, 172 on effect of excluding bile from in- testine. 179 on reabsorption of bile, 180 Bile, 159 composition of, 160 tests for, 168 daily quantity of, 172 quantity discharged after eating, 176 functions of, 177 reaction with gastric juice, 177 reabsorption, 180 mode of secretion, 321 Biliary salts, 161 of human bile, 167 Biliverdine, 87, 160 tests for, 168 passage into the urine, 341 Bischoff, on rupture of Graafian follicle in menstruation, 560 Blastodermic membrane, 576 Blood, 197 red globules of, 197 white globules, 204 plasma, 207 coagulation of, 209 buffy coat; 214 entire quantity of, 215 alterations of, in respiration, 227 temperature of, 238 in different organs, 246 circulation of, 248 through the heart, 254 through the arteries, 266 through the veins, 274 through the capillaries, 281 Boussingault, on chloride of sodium in food, 57 on internal production of fat, 77 Brain, 366, 401 of alligator, 366 of rabbit, 367 human, 370, 401 remarkable cases of injury to, 403, 404 size of, in different races, 407, 408 in idiots, 409 development of, 626, 627 Branchiae, 216 of meno-branchus, 217 Broad ligaments, formation of, 653 Bronchi, division of, 218, 219 ciliary, motion in, 223 Brown-Sequard, on crossing of sensitive fibres in soinal cord, 389 INDEX. 681 Brunner's glands, 137 Huffy coat of the blood, 214 Butter 319 composition of, 320 condition in milk, 75, 319 Butyrine, 320 Canals of Cuvier, 660 Capillaries, 279 their inosculation, 280 motion of blood in, 281 Capillary circulation, 281 causes of, 282 rapidity of, 285 local variations of, 285 peculiarities of, in different parts, 288 Caput coli, formation of, 633 Carbonic acid, in the breath, 226 proportion of, to oxygen absorbed, 226, 227 in the blood, 228 origin of, in lungs, 231 in the blood, 232 in the tissues, 232 mode of production, 232 daily quantity of, 234 variations of, 234 exhaled by skin, 236 by egg, during incubation, 593 absorbed by vegetables, 244 Carbonate of lime, 60 of soda, 60 of potassa, 61 of ammonia, in putrefying urine, 344 Cardiac circulation, in foetus, 670 in adult, 254, 673 Carnivorous animals, respiration of, 34, 227 urine of, 329 Cartilagine, 86 Caseine, 84 Cat, secretion of bile in, 172 closure of eyelids, after division of sympathetic, 510 Catalytic action, 82 of pepsin, 127 Centipede, nervous system of, 360 Centre, nervous definition of, 357 Cerebrum, 403. See Hemispheres. Cerebral ganglia, 366, &c. See Hemi- spheres. Cerebellum, 413 effects of injury to, 415 removal of, 415-418 function of, 414 development of, 626, 627 Cerebro-spinal system, 362, 363 development of, 625 Cervix uteri, 542 in foetus, 651 Cervical arches, 657 Cervical arches, transformation of, 658 Changes in egg, while passing through oviduct, 536, 539. in hepatic circulation at birth, 665 in comparative size of organs, after birth, 677 Chevreuil, experiments on imbibition, 296 Chick, development of, 590 Children, Aztec, 410 Chloride of sodium, 55 its proportion in the animal tissues and fluids, 56 importance of, in the food, 56 mode of discharge from the body, 58 partial decomposition of, in the body, 58 Chloride of potassium, 58 Cholesterin, 160 Chorda dorsalis, 579 Chorda tympani, influence of, on circu- lation in submaxillary gland, 508 on the sense of taste, 473 Chordae vocales, movement of, in respi- ration, 224 action of, in the production of vocal sounds, 449 obstruction of glottis by, after divi- sion of pneumogastric, 451 Chorion, formation of, 596 villosities of, 598 source of vascularity of, 599 union with decidua, 607 Chyle, 74, 139, 151, 304 in lacteals, 154 absorption of, 155 by intestinal epithelium, 156 in blood, 157 Ciliary motion, in bronchi, 223 in Fallopian tubes, 561 Ciliary nerves, 500 Circulation, 248 in the heart, 254 in the arteries, 266 in the veins, 274 in the capillaries, 279 local variations of, 285 regulated by nervous influence. 285 rapidity of, 286 peculiarities of, in different parts, 288 in liver, 323 in placenta, 609, 614 Circulatory apparatus, development of, 653 Civilization, aptitude for, of different races, 408 Clarke, J. L. Esq., on decussation of anterior pyramids, 369 Classification of cranial nerves, 432 Clot, formation of, 209 separation from serum, 210, 211 682 INDEX. Clot, composition of, 211 buffed and cupped, 214 Coagulation, 82 of fibrin, 207 of blood, 209 of white substance of Schwann, in nerve-fibres, 353 Colin, on unilateral mastication, 111 Cold, resistance to, by animals, 237 effect of, when long continued, 238 Colostrum, 317 Coloring matters, 86 of blood, 86, 202 of the skin, 87 of bile, 87, 160 of urine, 87, 336 Commissure, of spinal cord, gray, 365 white, 365 transverse, of cerebrum, 371 of cerebellum, 371 Commissures, nervous, 357 olfactory, 366, 402 Congestion, of ear, &c, after division of sympathetic, 507 Consentaneous action of muscles, 414 Contact, of chorion and amnion, 619 of decidua vera and reflexa, 620 Contraction of stomach during diges- tion, 129 of spleen, 192 of blood-clot, 210 of diaphragm and intercostal mus- cles, 220 of posterior crico-arytenoid muscles, 225 of ventricles, 259 of muscles after death, 373 of sphincter ani, 398 of rectum, 398 of urinary bladder, 399 of pupil, under influence of light, 351, 419, 486 after division of sympathetic, 510 Convolvulus, sexual apparatus of, 528 Cooking, effect of, on food, 98 Cord, spinal, 363, 382 umbilical, 618 withering and separation of, 677 Corpus callosum, 371 Corpus luteum, 564 of menstruation, 564 of pregnancy, 568 three weeks after menstruation, 566 four weeks after menstruation, 567 nine weeks after menstruation, 567 at end of second month of preg- nancy, 570 at end of fourth month, 570 at term, 571 disappearance of, after delivery, 572 Corpora Malpighiana, of spleen, 193 Corpora striata, 367, 403 Corpora clivaria, 369 Corpora Wolffiana, 643 Coste, on rupture of Graafian follicle in menstruation, 560, 561 Cranial nerves, 430 classification of, 432 motor, 433 sensitive, 433, 434 Creatine, 330 Creatinine, 330 Cremaster muscle, formation of, 647 function of, in lower animals, 648 Crystals, of stearine, 71 and margarine, 72 of cholesterin, 161 of glyko-cholate of soda, 162, 163 of biliary matters of dog's bile, 166 of biliary matters of human bile, 167 of urea, 327 of creatine, 330 of creatinine, 330 of urate of soda, 331 of uric acid, 338 of oxalate of lime, 344 of triple phosphate, 346 Crystallizable substances of organic ori- gin, 63 Crossing of fibres in medulla oblongata, 369, 388 of sensitive fibres in spinal cord, 389 of fibres of optic nerves, 420, 421 of streams of blood in foetal heart, 669, 670 Cruikshank, rupture of Graafian follicle in menstruation, 560 Cumulus proligerus, 555 Cutaneous respiration, 236 perspiration, 314 Cuticle, exfoliation of, during foetal life, 631 after birth, 677 Cysticercus, 525 transformation of, into taenia, 526 production of, from eggs of taenia, 527 Dean, John, M.D., on the origin of the fifth and sixth pairs of cranial nerves, 435 on the origin of the hypoglossal nerve, 461 Death, a necessary consequence of life, 514 Decidua, 602 vera, 604 reflexa, 606 union with chorion, 607 its discharge in cases of abortion, 606 at the time of delivery, 621 Decussation of anterior columns of spinal cord, 369, 388 of sensitive fibres the spinal cord, 389 INDEX. 683 Decussation of optic nerves, 420, 421 Degeneration, fatty, of muscular fibres of uterus, after delivery, 624 Deglutition, 116 retarded by division of Steno's duct, 115 by division of pneumogastric, 457 Dentition, first, 677 Becond, 678 Descent of the testicles, 646 of the ovaries, 649 Destructive assimilation, 325 Development of the impregnated egg, 574 of allantois, 589 of chorion, 596 of villosities of chorion, 597, 598 of decidua, 602 of placenta, 609 of nervous system, 625 of eye, 628 of ear, 629 of skeleton, 629 of limbs, 630 of integument, 631 of alimentary canal, 581, 632 of urinary passages, 634 of liver, 637, 663 of pharynx and oesophagus, 638 of face, 639 of Wolffian bodies, 643 of kidneys, 644 of internal generative organs, 645 of circulatory apparatus, 653 of arterial system, 657 of venous system, 660 of hepatic circulation, 663 of heart, 666 of the body after birth, 675 Diabetes, 342 in foetus, 637 Diaphragm, action of, in breathing, 220 formation of, 639 Diaphragmatic hernia, 639 Diet, influence of, on nutrition, 92 on products of respiration, 227 on formation of urea, 329 of urate of soda, 332 Diffusion of gases in lungs, 223 Digestion, 99 of starch, 135 of fats, 138 of sugar, 135 of organic substances, 126 time required for, 131 Digestive apparatus of fowl, 101 of ox, 102 of man, 103 Discharge of eggs from ovary, 537 independent of sexual intercourse, 553 mechanism of, 556 during menstruation, 560 Discus proligerus, 555 Distance and solidity, appreciation of, by the eye, 487, 488 Distinction between corpora lutea of menstruation and pregnancy, 573 Diurnal variations, in exhalation of car- bonic acid, 236 in production of urea, 329 in density and acidity of urine, 335 Division of nerves, 355 of heart, into right and left cavities, 666 Dobson, on variation in size of spleen, 192 Donders, on accommodation and re- fraction of the eye, 483 Draper, John C, on production of urea, 329 Drugs, effect of, on newly born infant, ' 676 Ductus arteriosus, 667, 670 closure of, 667, 668 venosus, 664 obliteration of, 665 Duodenal glands, 137 fistula, 174 Dutrochet, on temperature of plants, 240 on endosmosis of water with differ- ent liquids, 292 Ear, 491 muscular apparatus of, 492 development of, 629 Earthy phosphates, 68, 61 in urine, 337 precipitated by addition of an alkali, 338 Ectopia cordis, 639 Egg, 632 its contents, 533 where formed, 534 of frog, 536 of fowl, 537 changes in, while passing through the oviduct, 538 pre-existence of, in ovary, 551 development of, at period of puberty, 552 periodical ripening and discharge, 553 discharge of, from Graafian follicle, 556 impregnation of, how accomplished, 549 development of, after impregnation, 574 of fowl, showing area vasculosa, 591, 654 ditto, showing formation of allantois, 592 of fish, showing vitelline circulation, 654 684 INDEX. Egg, attachment of, to uterine mucous membrane, 605 discharge of, from uterus, at the time of delivery, 621 condition of, in newly born infant, 651 Elasticity of spleen, 192 of red globules of blood, 200 of lungs, 219, 221 of costal cartilages, 221 of vocal cords, 225 of arteries, 266 Electrical current, effect of, on muscles, 373 on nerve, 375 different effects of direct and in- verse, 378 Electrical fishes, phenomena of, 381 Elevation of temperature, after division of sympathetic, 509 Elongation of heart in pulsation, 259 anatomical causes of, 260 Embryo, formation of, 574 Embryonic spot, 578 Encephalon, 366, 401 ganglia of, 370 Endosmosis, 291 of fatty substances, 155 in capillary circulation, 298 conditions of, 292 cause of, 295 of iodide of potassium, 297 of atropine, 297 of nux vomica, 298 Endosmometer, 292 Enlargement of amnion, during preg- nancy, 618 Entozoa, encysted, 522 mode of production, 524 Epithelium, in saliva, 108 of gastric follicles, 118 of intestine, during digestion, 156 Epidermis, exfoliation of, in fcetal life, 631 after birth, 677 Epididymis, 647 Excretine, 145 Excretion, 325 nature of, 325 importance to life, 326 products of, 327 by placenta, 616 Excrementitious substances, 326, 327 mode of formation of, 326 effect of retention of, 326 Exfoliation of cuticle, during fcetal life, 631 after birth, 677 Exhalation, 291 of watery vapor, 55 from the lungs, 226 from the skin, 314 from the egg, during incubation, 593 ! Exhalation of carbonic acid, 226, 226 236 of nitrogen, 226 of animal vapor, 227 Exhaustion, of muscles, by repeated irri- tation, 374 of nerves, by ditto, 376 Exosmosis, 292 Expiration, movements of, 221 after section of pneumogastric, 453 Extractive matters of the blood, 209 Eye, protection of, by movements of pu- pil, 351, 419, 486 by two sets of muscles, 505 Eyeball, inflammation of, after division of 5th pair, 439 Eyelids, formation of, 629 Face, sensitive nerve of, 435 motor nerve, 440 development of, 639 Facial nerve, 440 sensibility of, 443 influence of, on muscular apparatus of eye, 442 of nose, 442 of ear, 441 paralysis of, 442 Fallopian tubes, 641 formation of, 649 Farinaceous substances, 63 in food, 64, 90, 96 digestion of, 135 Fat, absorption of, 155 decomposition of, in the blood, 155, 158 Fats, 70 proportion of, in different kinds of food, 72 condition, in the various tissues and fluids, 72, 73 internal source of, 77 decomposed in the body, 78 indispensable as ingredients of the food, 91 Fatty matters of the blood, 208 Fatty degeneration of decidua, 623 of muscular fibres of uterus, aftei delivery, 624 Feces, 145 Female generative organs, 634 of frog, 535 of fowl, 539 of sow, 541 of human species, 542 development of, 649 Fermentation, 83 of sugar, 69 acid, of urine, 343 alkaline, of ditto, 344 Fibrin, 84 of the blood, 207 coagulation of, 207 INDEX. 685 Fibrin, varying quantity of, in blood of different veins, 208 Fifth pair of cranial nerves, 435 its distribution, 436 division of, paralyzes sensibility of face, 438 and of nasal passages, 439 produces inflammation of eye- ball, 439 lingual branch of, 440 large root of, 435 small root of, 437 Fish, circulation of, 249 formation of umbilical vesicle in, 584 vitelline circulation, in embryo of, 654 Fish, electrical, phenomena of, 381 Fissure, longitudinal, of brain and spinal cord, 363 formation of, 628 Fissure of palate, 642 Fistula, gastric, Dr. Beaumont's case of, 120 Prof. Schmidt's case, 124 mode of operating for, 120, 121 duodenal, 174 Flint, Prof. Austin, on first sound of heart, 257 Flint, Prof. Austin, Jr., stercorine, in contents of large intestine, 145 cholesterin, in blood of jugular vein, 161 not discharged with the feces, 161 effects of biliary fistula, 180 Foetal circulation, first form of, 653 second form of, 655 Follicles of stomach, 117 of Lieberkiihn, 136 Follicles, of Brunner's glands, 137 Graafian, 534 of uterus, 603 Food, 89 composition of, 96, 97 daily quantity required, 97 effect of cooking on, 98 Foramen ovale, 668 valve of, 672 closure of, 672, 673 Force, nervous, rapidity of, 379 nature of, 380 Formatian of sugar in liver, 184 in foetus, 637 Fossa ovalis, 674 Functions, animal, 43 vegetative, 42 of teeth, 105 of saliva, 113 of gastric juice, 125, &c. of pancreatic juice, 140 of intestinal juices, 138 of bile, 177 Functions, of spleen, 194 of mucus, 312 of sebaceous matter, 313 of perspiration, 315 of the tears, 316 Galvanism, action of, on muscles, 37b on nerves, 375 Ganglion, of spinal cord, 364 of tuber annulare, 422 of medulla oblongata, 423 Casserian, 436 of Andersch, 444 pneumogastric, 423 ophthalmic, 500 spheno-palatine, 474, 500 submaxillary, 500 otic, 501 semilunar, 502 impar, 502 Ganglionic system of nerves, 363, 500 Ganglia, nervous, 356 of radiata, 357 of mollusca, 359 of articulata, 360 of posterior roots of spinal nerves, 364 of alligator's brain, 366 of rabbit's brain, 367 of medulla oblongata, 368 of human brain, 370 of great sympathetic, 500 olfactory, 366, 402 optic, 366, 419 Gases, diffusion of, in lungs, 223 absorption and exhalation of, by lungs, 226 by the tissues, 232 Gastric follicles, 117 Gastric juice, mode of obtaining, 120 composition of, 123 Gastric juice, action on food, 126 interference with Trommer's test, 128 interference with action of starch and iodine, 129 daily quantity of, 131 solvent action of, on stomach, after death, 134 Gelatine, how produced, 48 effect of feeding animals on, 93 Generation, 515 spontaneous, 515 of infusoria, 518 of parasites, 521 of encysted entozoa, 523 of taenia, 526 sexual, by germs, 528 Germ, nature of, 528 Germination, heat produced in, 240 Germinative vesicle, 533 disappearance of, in mature egg, 574 Germinative spot, 533 Gills, of fish, 216 of menobranchus, 217 686 INDEX. Glands, of Brunner, 137 mesenteric, 152 vascular, 194 Meibomian, 313 perspiratory, 314 action of, in secretion, 308, 309. Glandulae solitariae and agminatae, 146 Globules, of blood, 197 red, 197 different appearances of, under microscope, 198, 199 mutual adhesion of, 199 color, consistency, and structure of, 200 action of water on, 201 composition of, 202 size,&c, in different animals, 203 white, 204 action of acetic acid on, 205 red and white, movement of, in circulation, 281 Globuline, 85, 202 Glomeruli, of Wolffian bodies, 644 Glosso-pharyngeal nerve, 444 action of, in swallowing, 445 Glottis, movements of, in respiration, 224 in formation of voice, 449 closure of, after section of pneumo- gastrics, 451 Glycine, 165 Glyco-cholic acid, 164 Glyco-cholate of soda, 161, 164 its crystallization, 162, 163 Glycogenic function of liver, 184 in foetus, 637 Glycogenic matter, 188 its conversion into sugar, 188 Gosselin, experiments on imbibition by cornea, 297 Graafian follicles, 534, 555 structure of, 555 rupture of, and discharge of egg, 556 ruptured during menstruation, 560 condition of, in foetus at term, 651 Gray substance, of nervous system, 356 of spinal cord, 364 of brain, 370 its want of irritability, 401 Great sympathetic, 500 anatomy of, 601 sensibility and excitability of, 503 connection of, with special senses, 504 division of, influence on animal heat, 609 on the circulation, 507 on pupil and eyelids, 510 reflex actions of, 511 Gubernaculum testis, 647 function of, in lower animals, 648 Gustatory nerve, 440, 468 Hammond, Wm. A., M. D., on effects of non-nitrogenous diet, 92 Hammond, Wm. A., M. D., on production of urea, 328 Hairs, formation of, in embryo, 631 Hare-lip, 641 Harvey, on motions of heart, 257, 259. 264 Hearing, sense of, 490 apparatus of, 491 analogy of, with touch, 496 Heart, 249 of fish, 249 of reptiles, 250 of mammalians, 251 of man, 252 circulation of blood through, 254 sounds of, 254 movements of, 257 impulse, 259, 263 development of, 639, 666 Heat, vital, of animals, 237 of plants, 240 how produced, 241 increased by division of sympathetic nerve, 509 Helmholtz, on rapidity of nervous force, 379 Hematine, 86, 202 Hemispheres, cerebral, 403 remarkable cases of injury to, 403, 404 effect of removal, on pigeons, 406 effect of disease, in man, 406 comparative size of, in different races, 407 functions of, 409 development of, 626 Hemorrhage, from placenta, in parturi- tion, 621 Hepatic circulation, 323 development of, 663 Herbivorous animals, respiration of, 50, 34, 227 urine of, 330, 332 Hernia, congenital, diaphragmatic, 639 umbilical, 634 inguinal, 649 Hippurate of soda, 332 Hunger and thirst, continue after divi- sion of pneumogastric, 457 Hydrogen, displacement of gases in blood by, 229 exhalation of carbonic acid in an atmosphere of, 233 Hygroscopic property of organic sub- stances, 81 Hypoglossal nerve, 461 Imbibition, 291 of liquids, by different tissues, 296 by cornea, experiments on, 297 Impulse, of heart, 259, 263 Infant, newly-born, characteristics of, 675 Inflammation of eyeball, after division of 5th pair, 439 Infusoria, 517 different kinds of, 518 conditions of their production, 619 Wyman's experiments on, 519 Inguinal hernia, congenital, 649 Injection of placental sinuses from ves- sels of uterus, 615 Inorganic substances, as proximate prin- ciples, 53 their source and destination, 62 Inosculation, of veins, 275, 277 of capillaries, 280 of nerves, 355, 356 Insalivation, 107 importance of, 115 function of, 116 Inspiration, how accomplished, 220 movements of glottis in, 224 Instinct, nature of, 428 Integument, respiration by, 236 development of, 631 Intellectual powers, 406, &c. in animals, 428, 429 Intestine, of fowl, 101 of man, 103 juices of, 135 digestion in, 135-144 epithelium of, 156 disappearance of bile in, 177, 180 development of, 581, 632 Intestinal digestion, 135 Intestinal juices, 135, 137 action of, on starch, 138 Involution of uterus after delivery, 623 Iris, movements of, 351, 419, 486, 504 after division of sympathetic, 510 Irritability, of gastric mucous membrane, 121 of the heart, 260 of muscles, 373 of nerves, 375 Jackson, Prof. Samuel, on digestion of fat in intestine, 139 Jaundice, 169 yellow color of urine in, 341 Kidneys, peculiarity of circulation in, 289 elimination of medicinal substances by, 341 formation of, 644 Kuchenmeister, experiments on produc- tion of taenia from cysticercus, 526 of cysticercus from eggs of taenia, 527 Lachrymal secretion, 316 its function, 317 Lactation, 317 'EX. 687 Lactation, variations in composition of milk during, 321 Lacteals, 152, 154, 303 and lymphatics, 154 Larynx, action of, in respiration, 224 in formation of voice, 449 nerves of, 447, 448 protective action of, 450 movements in respiration, 224 Lassaigne, experiments on saliva, 116 analysis of lymph, 302 Layers, external and internal, of blasto- dermic membrane, 576 Lead, salts of, action in distinguishing the biliary matters, 167 Lehmann, on formation of carbonates in blood, 60 on total quantity of blood, 215 on effects of non-nitrogenous diet, 92 Lens, crystalline, action of, 480 Leuckart, on production of cysticercus, 527 of Trichina spiralis, 527 Liebig, on absorption of different liquids under pressure, 294 Ligament of the ovary, formation of, 650 Limbs, formation of, in frog, 582 in human embryo, 630 Liver, vascularity of, 322 lobules of, 322, 323 secreting cells, 324 formation of sugar in, 184 congestion of, after feeding, 191 development of, 637, 663 Liver-cells, 324 their action in secretion, 324 Liver-sugar, formation of, 184 after death, 187 in fcetus, 637 Lobules, of lung, 219 of liver, 322, 323 Local production of carbonic acid, 232 of animal heat, 245 Local variations of circulation, 285, 289 Longet, on interference of albuminose with Trommer's test, 128 on sensibility of glosso-pharyngeal nerve, 444 on irritability of anterior spinal roots, 386 Lungs, structure of, in reptiles, 218 in man, 219 alteration of, after division of pneu- mogastrics, 452 Lymph, 153, 302, 304 quantity of, 304, 307 Lymphatic system, 152, 154, 301 Magendie, on absorption by blood-ves- sels, 149 on distinct seat of sensation and mo- tion, 385 688 INDEX. Magnus, on proportions of oxygen and carbonic acid in blood, 229 Male organs of generation, 547 development of, 646 Malpighian bodies of spleen, 193 Mammalians, circulation in, 251 Mammary gland, structure of, 317 secretion of, 318 Marcet, on excretine, 145 Marey, M,, experiments on arterial pul- sation, 269 Mastication, 105 unilateral, in ruminating animals, 111 retarded by suppressing saliva, 115 Meconium, 636 Medulla oblongata, 368, 423 ganglia of, 369, 370 reflex action of, 424 effect of destroying, 426 development of, 626 Meibomian glands, 313 Melanine, 87 Membrane, blastodermic, 576 Membrana granulosa, 555 Membrana tympani, action of, 491 Memory, connection of, with cerebral hemispheres, 409 Menobranchus, size of blood-globules in, 204 gills of, 217 spermatozoa of, 545 Menstruation, 558 commencement and duration of, 559 phenomena of, 559 rupture of Graafian follicles in, 560 suspended during pregnancy, 559, 569 Mesenteric glands, 152, 301 Michel, Dr. Myddleton, rupture of Graaf- ian follicle in menstruation, 560 Milk, 317 composition and properties of, 96, 318 microscopic characters, 319 Milk, souring and coagulation of, 320. variations in, during lactation, 321 Milk-sugar, 68 converted into lactic acid, 320 Mitchell, S. Weir, M.D., on production of vibriones in the venom of the rattle- snake, 520 Mollusca, nervous system of, 359 Moore and Pennock, experiments on movements of heart, 259 Motion, 384 Motor cranial nerves, 433 Motor nervous fibres, 387 Motor oculi communis, 434 externus, 435 Movements, of stomach, 129 of intestine, 148 of heart, 257 Movements, of chest, in respiration, 220 of glottis, 224 associated, 392 of foetus, 619 Mucosine, 85 Mucous follicles, 311 Mucous membrane, of stomach, 117 of intestine, 137 of tongue, 467 of uterus, 542, 602 Mucus, 311 composition and properties of, 312 of mouth, 109 of cervix uteri, 543 Muscles, irritability of, 372 directly paralyzed by sulpho-cyanide of potassium, 374 consentaneous action of, 414 of respiration, 220 Muscular fibres, of spleen, 192 of heart, spiral and circular, 261 Muscular irritability, 372 duration after death, 373 exhausted by repeated irritation, 374 Musculine, 86 Nails, formation of, in embryo, 631 Negrier, on rupture of Graafian follicle in menstruation, 560 Nerve-cells, 356 Nerves, division of, 355 inosculation of, 356 irritability of, 374 spinal, 386 cranial, 430 olfactory, 430 optic, 431 auditory, 431 oculo-motorius, 434 patheticus, 435 motor externus, 435 masticator, 437 facial, 440 hypoglossal, 461 spinal accessory, 459 trifacial (5th pair), 435 glosso-pharyngeal, 444 Nerves, pneumogastric, 445 superior and inferior laryngeal, 447 great sympathetic, 500 Nervous filaments, 352 of brain, 353 of sciatic nerve, 354 division of, 355 motor and sensitive, 359 Nervous force, how excited, 375 rapidity of, 379 nature of, 380 Nervous tissue, two kinds of, 352 Nervous irritability, 374 how shown, 375 duration of, after death, 375 INDEX. 689 Nervous irritability, exhausted by excite- ment, 376 destroyed by woorara, 377 distinct from muscular, 379 nature of, 380 Nervous system, 349 general structure and functions of, 349, 371 of radiata, 357 of mollusca, 359 of articulata, 360 of vertebrata, 363 reflex action of, 358 Network, capillary, in Peyer's glands, 146 in intestinal villus, 147 in web of frog's foot, 280, 281 in lobule of liver, 323 Newly-born infant, weight of, 675 respiration in, 675 nervous phenomena of, 676 comparative size of organs in, 677 Newport, on temperature of insects, 240 Nitric acid, action of, on bile-pigment 169 precipitation of uric acid by, 338 Nitrogen, exhalation of, in respiration, 226 Nucleus, of medulla oblongata, 423 Nutrition, 45, 348 Obliteration, of ductus venosus, 665 of ductus arteriosus, 668 Oculo-motorius nerve, 434 Oesophagus, paralysis of, after division of pneumogastric, 448 development of, 637 CEstruation, phenomena of, 557 Oleaginous substances, 70 in different kinds of food, 72 condition of, in the tissues and fluids, 72-77 partly produced in the body, 77 decomposed in the body, 78 in the blood, 155 indispensable as ingredients of the food, 91 insufficient for nutrition, 92 Olfactory apparatus, 474 protected by two sets of muscles, 506 commissures, 366, 402 Olfactory ganglia, 366, 402 their function, 402 Olfactory nerves, 430 Olivary bodies, 369 Omphalo-mesenteric vessels, 654 Ophthalmic ganglion, 500 Optic ganglia, 366, 418 Optic nerves, 431 decussation of, 420, 421 Optic thalami, 402 development of, 626 Organs of special sense, 468, 474, 478, 493 44 Organs, development of, 628 Organic substances, 79 indefinite chemical composition of, 79, 80 hygroscopic properties, 81 coagulation of, 82 catalytic action, 82 putrefaction, 83 source and destination, 88 digestion of, 126 exhaled by the breath, 227 Origin, of plants and animals, 515 of infusoria, 518 of animal and vegetable parasites, 521 of encysted entozoa, 523 Ossification of skeleton, 630 Osteine, 86 Otic ganglion, 501 Ovary, 529, 534 of taenia, 529 of frog, 535 of fowl, 539 of human female, 541 Ovaries, descent of, in foetus, 649 condition at birth, 651 Oviparous and viviparous animals, dis- tinction between, 551 Oxalic acid, produced in urine, 344 Oxygen, absorbed in respiration, 226 daily quantity consumed, 226 state of solution in blood, 229 dissolved by blood-globules, 229 absorbed by the tissues, 232 exhaled by plants, 244 Palate, formation of, 641 Pancreatic juice, 138 mode of obtaining, 139 composition of, 140 action on fat, 140, 141 daily quantity of, 140 Pancreatine, 85 in pancreatic juice, 140 Panizza, experiment on absorption by bloodvessels, 149 Paralysis, after division of anterior root of spinal nerve, 386 direct, after lateral injury of spinal cord, 389 crossed, after lateral injury of brain, 389 facial, 443 of muscles, by sulpho-cyanide of potassium, 374 of motor nerves, by woorara, 377, 397 of sensitive nerves, by strychnine, 397 of voluntary motion and sensation, after destroying tuber annulare, 422 of pharynx and oesophagus, after section of pneumogastrics, 458 690 INDEX. Paralysis of larynx, 449, 451 of muscular coat of stomach, 458 Paraplegia, reflex action of spinal cord in, 395 Parasites, 520 conditions of development of, 521 mode of introduction into body, 522 sexless, reproduction of, 523 Parotid saliva, 110 Parturition, 621 Par vagum, 445. See Pneumogastric. Patheticus nerve, 435 Pelouze, composition of glycogenic mat- ter, 188 Pelvis, development of, 630 Pennock and Moore, experiments on movements of heart, 259 Pepsine, 85 in gastric juice, 124 Perception of sensations, aftei removal of hemispheres, 406 destroyed, after removal of tuber annulare, 422 Periodical ovulation, 551 Peristaltic motion, of stomach, 129 of intestine, 148 of oviduct, 536, 538 Perkins, Maurice, composition of parotid saliva, 110 Perspiration, 314 daily quantity of, 315 composition and properties of, 315 function, in regulating temperature, 315 Pettenkofer's test for bile, 169 Peyer's glands, 146 Pharynx, action of, in swallowing, 445, formation of, 638 Phosphate of lime, its proportion in the animal tissues and fluids, 58 in the urine, 337 precipitated by alkalies, 338 Phosphate, triple, in putrefying urine, 340 Phosphates, alkaline, 61 in urine, 337 earthy, 58, 61 in urine, 337 of magnesia, soda, and potassa, 61 Phosphorus, not a proximate principle, 47 Physiology, definition of, 33 Phrenology, 411 objections to, 412 practical difficulties of, 413 Pigeon, after removal of cerebrum, 405 of cerebellum, 415 Placenta, 609 comparative anatomy of, 610 formation of, in human species, 611 foetal tufts of, 613 maternal sinuses of, 614 injection of, from uterine vessels, 615 Placenta, function of, 616 separation of, in delivery, 621 Placental circulation, 6f2, 614 Plants, vital heat of, 240 generative apparatus of, 628 Plasma of the blood, 207 Pneumic acid, 231 Pneumogastric nerve, 445 its distribution, 446 action of, on pharynx and oesopha- gus, 447 on larynx, 448 in formation of voice, 449 in respiration, 450 effect of its division on respiratory movements, 451 cause of death after division of, 454 influence of, on oesophagus and stomach, 457 Pneumogastric ganglion, 423 Poggiale, on glycogenic matter in but- cher's meat, 189 Pons Varolii, 371 Portal blood, quantity of fibrin in, 208 temperature of, 246 Portal vein, in liver, 322 development of, 663 Posterior columns of spinal cord, 365 Primitive trace, 578 Production, of sugar in liver, 184 of carbonic acid, 230 of animal heat, 237 of urea in blood, 327 of infusorial animalcules, 518 of animal and vegetable parasites, 521 Proximate principles, 45 definition of, 47 mode of extraction, 48 manner of their association, 49 varying proportions of, 50 three distinct classes of, 51 Proximate principles of the first class (inorganic), 53 of the second class (crystallizable substances of organic origin), 63 of the third class (organic sub- stances), 79 Ptyaline, 108 Puberty, period of, 553 signs of, in female, 558 Pulsation, of heart, 253 in living animal, 258 of arteries, 267 Pupil, action of, 351, 419 contraction of, after division of sym- pathetic, 510 Pupillary membrane, 628 Putrefaction, 83 of the urine, 345 Pyramids, anterior, of medulla oblon gata, 368 decussation of, 369 INDEX. 691 Quantity, daily, of water exhaled, 55 of food, 97 of saliva, 111 of gastric juice, 131 of pancreatic juice, 140 of bile, 172 of air used in respiration, 222 of oxygen used in respiration, 226 of carbonic acid exhaled, 234 of lymph and chyle, 304 of fluids secreted and reabsorbed, 307 of material absorbed and discharg- ed, 347 of perspiration, 316 of urine, 333, 334 of urea, 328 of urate of soda, 332 Quantity, entire, of blood in body, 215 Rabbit, brain of, 367 Races of men, different capacity of, for civilization, 408 Radiata, nervous system of, 357 Rapidity of circulation, 286 of the nervous force, 379 Reactions, of starch, 66 of sugar, 68 of fat, 70 of saliva, 108, 109 of gastric juice, 123 of intestinal juice, 138 of pancreatic juice, 140 of bile, 159 of mucus, 312 of milk, 318 of urine, 337 Reasoning powers, 409 in animals, 429 Red globules of blood, 197 Reflex action, 358 in centipede, 361 of spinal cord, 392 of medulla oblongata, 424 of tuber annulare, 427 of brain, 428 of optic tubercles, 419 in newly born infant, 676 Regeneration, of uterine mucous mem- brane after pregnancy, 622 of walls of uterus, 624 Regnault and Reiset, on absorption of oxygen, 227 Reid, Dr. John, experiment on crossing of streams in fcetal heart, 670 on glosso-pharyngeal nerve, 444 Reproduction, 513 nature and object of, 515 of infusoria, 518 of parasites, 521 of taenia, 524 by germs, 528 Reptiles, circulation of, 250 Respiration, 216 by gills, 217 by lungs, 218 by skin, 236 changes in air during, 225 changes in blood, 227 of newly born infant, 675 Respiratory movements of chest, 220 of glottis, 224 after section of pneumogastrics, 452 after injury of spinal cord, 425 Restiform bodies, 369 Rhythm of heart's movements, 263 Rotation of heart during contraction, 262 Round ligament of the uterus, formation of, 650 of liver, 665 Rumination, movements of, 101, 111 Rupture of Graafian follicle, 556 in menstruation, 560, 565 Rutting condition, in lower animals, 557 Saccharine substances, 67 in stomach and intestine, 135 in liver, 184 in blood, 191 in urine, 341 Saliva, 107 different kinds of, 109 daily quantity of, 111 action an boiled starch, 113 variable, 113 does not take place in stomach, 114 physical function of saliva, 115 quantity absorbed by different kinds of food, 116 Salivary glands, 109 Salts, biliary, 161 of the blood, 209 of urine, 337 Saponification, of fats, 71 Scharling, on diurnal variations 'm ex- halation of carbonic acid, 236 Schmidt, Prof. C, on human gastric fis- tula, 124 on quantity of gastric juice, 132 Scolopendra, nervous system of, 360 Sebaceous matter, 312 composition and properties of, 313 function of, 313 in fcetus, 631 Secretion, 308 varying activity of, 310 of saliva, 109 of gastric juice, 121 of intestinal juice, 137 of pancreatic juice, 140 of bile, 172, 321 of sugar in liver, 184 of mucus, 311 of sebaceous matter, 312 of perspiration, 314 of the tears, 316 692 INDEX. Secretion of bile in fcetus, 637 Segmentation of the vitellus, 575 Seminal fluid, 544 mixed constitution of, 548 Sensation, 382 remains after destruction of hemi- spheres, 406 lost after removal of tuber annulare, 422 special conveyed by pneumogastric nerve, 424 Sensation and motion, distinct seat of, in nervous system, 384 in spinal cord, 387 Sensibility of nerves to electric current, 375 and excitability, definition of, 382, 384 seat of, in spinal cord, 387 in brain, 401 of facial nerve, 443 of hypoglossal nerve, 462 of spinal accessory, 459 of great sympathetic, 503 Sensibility, general and special, 463 special, of olfactory nerves, 430 of optic nerves, 431 of auditory nerves, 431 of lingual branch of 5th pair, 469 of glosso-pharyngeal, 444 of pneumogastric, 452 Sensitive nervous filaments, 359 Sensitive fibres,crossing of, in spinal cord, 389 of facial nerve, source of, 443 Sensitive cranial nerves, 435 Septa, inter-auricular and inter-ventri- cular, formation of, 666 Serum, of the blood, 211 Sexes, distinctive characters of, 530 Sexless entozoa, 522 Sexual generation, 528 Shock, effect of, in destroying nervous irritability, 377 Siebold, on production of taenia from cysticercus, 526 Sight, 477 apparatus of, 478. See Vision. Sinus terminalis, of area vasculosa, 653 Sinuses, placental, 612, 614, Skeleton, development of, 629 Skin, respiration by, 236 sebaceous glands of, 313 perspiratory glands of, 314 development of, 631 Smell, 473 ganglia of, 366, 474 nerves of, 430, 474 injured by division of 5th pair, 439 Smith, Dr. Southwood, on cutaneous and pulmonary exhalation, 315 Solar plexus of sympathetic nerve, 502 Solid bodies, vision of, with two eyes, 488 Sounds, of heart, 254 how produced, 255 vocal, how produced, 449 destroyed by section of inferior la- ryngeal nerves, 450 of spinal accessory, 4(50 Sounds, acute and grave, transmitted by membrani tympani, 494 Special senses, 40ti Species, mode of continuation, 515 Spermatic fluid, 544 mixed constitution of, 548 Spermatozoa, 544 movements of, 546 formation of, 547 Spina bifida, 629 Spinal accessory, 459 sensibility of, 459 communication of, with pneumogas- tric, 460 influence of, on larynx, 460 Spinal column, formation of, 579, 621 Spinal cord, 363, 382 commissures of, 365 anterior, lateral, and posterior col- umns, 365 origin of nerves from, 364 sensibility and excitability of, 387 crossed action of, 388 reflex action of, 392 protective action of, 398 influence on sphincters, 398 effect of injury to, 398 on respiration, 425 formation of, in embryo, 579, 629 Spinal nerves, origin of, 364 Spleen, 192 Malpighian bodies of, 193 extirpation of, 195 Spontaneous generation, 515 Starch, 63 proportion of, in different kinds of food, 64 varieties of, 64-66 reactions of, 66 action of saliva on, 113 digestion of, 135 Starfish, nervous system of, 357 Stercorine, 145 Stereoscope, 488 St. Martin, case of gastric fistula in, 120 Strabismus, after division of motor oculi communis, 435 of motor externus, 435 Striated bodies, 403 Sublingual gland, secretion of, 109 Submaxillary ganglion, 500 gland, secretion of, 109 circulation in, influenced by nerves, 508 Sudoriparous glands, 314 Sugar, 67 varieties of, 67 Sugar, composition of, 68 tests for, 68 fermentation of, 69 proportion in different kinds of food, 70 source and destination, 70 produced in liver, 184 discharged by urine in disease, 341 Sugar in liver, formation of, 184 percentage of, 186 produced in hepatic tissue, 187 from glycogenic matter, 188 absorbed by hepatic blood, 190 decomposed in circulation, 190 Sulphates, alkaline, in urine, 337 Sulphur of the bile, 165 not discharged with the feces, 181 Swallowing, 115, 116 retarded by suppression of saliva, 115 by division of pneumogastric, 458 Sympathetic nerve, 500 its distribution, 501 sensibility and excitability of, 503 influence of, on special senses, 504 on pupil, 504 on nutrition of eyeball, 440 on nasal passages, 506 on ear, 506, 507 on local circulations, 507 on temperature of particular parts, 509 reflex actions of, 511 Tadpole, development of, 580 transformation into frog, 582 Taenia, 524 produced by metamorphosis of cys- ticercus, 526 single articulation of, 529 Tapeworm, 524 mode of generation, 526 Taste, 466 nerves of, 468 conditions of, 470 injury of, by paralysis of facial nerve, 472 Taurine, 165 Tauro-cholate of soda, 165 microscopic characters of, 162, 163 Tauro-cholic acid, 165 Tears, 316 their function, 317 Teeth, of serpent, 105 of polar bear, 106 of horse, 106 of man, 107 first and second sets of, 677 Temperature of the blood, 238 of different species of animals, 239 of the blood in different organs, 246 elevation of, after section of sympa- thetic nerve, 509 Tensor tympani, action of, 493 ex. 693 Tests, for starch, 66 for sugar, 68 for bile, 168 Pettenkofer's, 169 Testicles, 547 periodical activity of, in fish, 549 development of, 646 descent of, 647 Tetanus, pathology of, 394 Thalami, optic, in rabbit, 367 in man, 402 function of, 403 Thoracic duct, 152, 154 Thoracic respiration, 425 Thudichum, Dr., on urosacine, 87 Tongue, motor nerve of, 461 sensitive, 437, 440, 468 Trichina spiralis, 523 Tricuspid valve, 252. See Auriculo-ven- tricular. Triple phosphate, in putrefying urine, 346 Trommer's test for sugar, 68 interfered with by gastric juice, 127 Tuber annulare, 370, 422 effect of destroying, 422 action of, 423, 427 Tubercula quadrigemina, 366, 418 reflex action of, 419 crossed action of, 420 development of, 626, 627 Tubules of uterine mucous membrane, 603 Tufts, placental, 613 Tunica vaginalis testis, formation of, 648 Tympanum, function of, in hearing, 492 Umbilical cord, formation of, 619 withering and separation of, 677 Umbilical hernia, 634 Umbilical vesicle, 584 in human embryo, 585 in chick, 592 disappearance of, 619 Umbilical vein, formation of, 657 obliteration of, 665 Umbilicus, abdominal, 580 amniotic, 588 decidual, 605 Unilateral mastication, in ruminating animals, 111 Urate of soda, 331 its properties, source, daily quan- tity, &c, 332 Urates of potassa and ammonia, 332 Urachus, 635 Urea, 327 source of, 327 mode of obtaining, 328 conversion into carbonate of am- monia, 328 daily quantity of, 328 diurnal variations in, 329 694 INDEX Urea, decomposed in putrefact on of urine, 344 Uric acid, 331, 338 Urine, 333 general character and properties of, 333 quantity and specific gravity, 334 diurnal variations of, 335 composition of, 336 reactions, 337 interference with Trommer's test. 339 accidental ingredients of, 339 acid fermentation of, 343 alkaline fermentation of, 344 final decomposition of, 346 Urinary bladder, paralysis and inflam- mation of, after injury to spinal cord, 399 formation of, in embryo, 635 Urosacine, 87 Uterus, of lower animals, 541 of human female, 542 mucous membrane of, 602 changes in, after impregnation, 603, 604 involution of, after delivery, 622 development of, in fcetus, 650 position of, at birth, 651 Uterine mucous membrane, 602 tubules of, 603 conversion into decidua, 604 exfoliation of, at the time of deliv- ery, 621 its renovation, 622 Valve, Eustachian, 669 of foramen ovale, 672 Valves, cardiac, action of, 252 cause of heart's sounds, 255 Vasa deferentia, formation of, 646 Vapor, watery, exhalation of, 55 from lungs, 226 from the skin, 315 Variation, in quantity of bile in different animals, 172 in production of liver-sugar, 186 in size of spleen, 192 in rapidity of coagulation of blood, 211 in size of glottis in respiration, 224 in exhalation of carbonic acid, 234 in temperature of blood in different parts, 246 in composition of milk, during lac- tation, 321 in quantity of urea, 329 in density and acidity of urine, 334, 335 Varieties of starch, 64 of sugar, 67 of fat, 70 of biliary salts in different animals, 166 Vegetable food, necessary to man, 90 Vegetable parasites, 520 Vegetables, production of heat in, 240 absorption of carbonic acid and ex- halation of oxygen by, 244 Vegetative functions, 42 Veins, 274 their resistance to pressure, 274 absorption by, 149 action of valves in, 277 motion of blood through, 275 rapidity of circulation in, 278 omphalo-mesenteric, 654 umbilical, 657 vertebral, 660 Venae cavae, formation of, 661 position of, in foetus, 668 Vena azygos, major and minor, forma- tion of, 662 Venous system, development of, 660 Ventricles of heart, single in fish and reptiles, 249, 250 double in birds and mammalians, 251 situation of, 252 contraction and relaxation of, 258 elongation of, 259 muscular fibres of, 261 Vernix caseosa, 631 Vertebrata, nervous system of, 363, Vertebrae, formation of, 579, 629 Vesicles, adipose, 74 pulmonary, 219 seminal, 548 Vesiculse seminales, 548 formation of, 648 Vibriones, in putrefying rattlesnake venom, 520 Vicarious secretion, non-existence of, 309 Vicarious menstruation, nature of, 309 Villi, of intestine, 147 absorption by, 148 of chorion, 598, 600 Vision, 477 ganglia of, 366, 418 nerves of, 431 apparatus of, 478 distinct, at different distances, 481 circle of, 485 of solid bodies with both eyes, 488 Vital phenomena, their nature and pecu- liarities, 38 Vitellus, 533 segmentation of, 675 formation of, in ovary of fcetus, 652 Vitelline circulation, 653 membrane, 532 spheres, 575 Vocal sounds, how produced, 449 Voice, formation of, in larynx, 449 lost, after division of spinal acces- sory nerve, 460 INDEX. 695 polition, seat of, in tuber annulare, 422 Vomiting, peculiar, after division of pneumogastrics, 457 Water, as a proximate principle, 53 its proportion in the animal tissues and fluids, 54 its source, 54 mode of discharge from the body. 55 Weight of organs, comparative in newly born infant and adult, 677 White globules of the blood, 204 action of acetic acid on, 205 sluggish movement of, in circula- tion, 282 White substance, of nervous system, 352 of Schwann, 352 of spinal cord, 364 Wnite substance, of brain, insensible and inexcitable, 401 Withering and separation of umbilical cord, after birth, 677 Wolffian bodies, 643 structure of, 644 atrophy and disappearance of, 644 vestiges of, in adult female, 650 Wyman, Prof. Jeffries, on cranial nerves of Rana pipiens, 433 fissure of hare-lip on median line, 641 on production of infusoria in organic solutions, 519 Yellow color, of urine in jaundice, 341 of corpus luteum, 567 Zona pellucida, 532 THE END. HENEY C. LEA.'S (LATE LEA & BLANCHARD's) CLASSIFIED O^T^I_.Oa TTIE3 OF MEDICAL AND SUKGICAL PUBLICATIONS, In asking the attention of the profession to the works contained in the following pages, the publisher would state that no pains are spared to secure a continuance of the confidence earned for the publications of the house by their careful selection and accuracy and finish of execution. The printed prices are those at which books can generally be supplied by booksellers throughout the United States, who can readily procure for their customers any works not kept in stock. Where access to bookstores is not convenient, books will be sent by mail post-paid on receipt of the price, but no risks are assumed either on the money or the books, and no publications but my own are supplied. Gentlemen will therefore in most cases find it more convenient to deal with the nearest bookseller. 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Where these are not accessible, remittances for the "Journal" may be made at the risk of the publisher, by forwarding in registered letters. Address, HENRY C. LEA, Nos. 706 and 708 Sansom St.. Philadelphia, Pa. 4 Henry C. Lea's Publications—(Dictionaries). -QUNGLISON (ROBLEY), M.D., "^ Professor of Institutes of Medicine in Jefferson Medical College, Philadelphia. MEDICAL LEXICON; A Dictionary of Medical Science: Con- taining a concise »xplanation of the various Subjects and Terms of Anatomy, Physiology Pathology, Hygiene. Therapeutics, Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence, and Dentistry. Notices of Climate and of Mineral Waters; Formulte for Officinal, Empirical, and Dietetic Preparations; with the Accentuation and Etymology oi the Terms, and the French and other Synonymes; so as to constitute a French as well as English Medical Lexicon. Thoroughly Revised, and very greatly Modified and Augmented. In one very large and handsome royal octavo volume of 1048 double-columned pages, in small type; strongly done up in extra cloth, $6 00 ; leather, raised bands, $6 75. The object of the author from the outset has not been to make the work a mere lexicon or dictionary 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 which has existed for the work has enabled him, in repeated revisions, to augment its completeness and usefulness, until at length it has attained the position of a recognized and standard authority wherever the language is spoken. The mechanical exe- cution of this edition will be found greatly superior to that of previous impressions. By enlarging the size of the volume to a royal octavo, and by the employment of a small but clear type, on extra fine paper, the additions have been incorporated without materially increasing the bulk oi 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. It is undoubtedly the most complete and useful medical dictionary hitherto published in this country. —Chicago Med. Examiner, February, 1S65. What we take to be decidedly the best medical die- It would be a work of supererogation to bestow a word of praise upon this Lexicon. We can only wonder at the labor expended, for whenever we refer to its pages for information we are seldom disap- pointed in finding all we desire, whether it be in ac- centuation, etymology, or definition of terms.—New York Medical Journal, November, 1865. It would be mere waste of words in us to express our admiration of a work which is so universally and deservedly appreciated. The most admirable work of its kind in the English language. As a book of reference it is invaluable to the medical practi- tioner, and in every instance that we have turned over its pages for information we have been charmed by the clearness of language and the accuracy of detail with which each abounds We can most cor- dially and confidently commend it to our readers.— Glasgow Medical Journal, January, 1866. A work to which there is no equal in the English language.—Edinburgh Medical Journal. It is something more than a dictionary, and some- thing less than an encyclopaedia. This edition of the well-known work is a great improvement on its pre- decessors. The book is one of the very few of which it may be said with truth that every medical man should possess it.—London Medical Times, Aug. 26, 1865. Few works of the class exhibit a grander monument of patient research and of scientific lore. The extent of the sale of this lexicon is sufficient to testify to its usefulness, and to the great service conferred by Dr. Robley Dunglison on the profession, and indeed on others, by its issue.—London Lancet, May 13, 1865. The old edition, which is now superseded by the new, has been universally looked upon by the medi- cal profession as a work of immense research and great value. The new has increased usefulness; for medicine, in all its branches, has been making such progress that many new terms and subjects have re- cently been introduced : all of which may be found fully defined in the present edition. We know of no other dictionary in the English language that can bear a comparison with it in point of completeness of Bubjects and accuracy of statement.—N. Y. Drug- gists' Circular, 1865. For many y«ars Dunglison's Dictionary has been the standard book of reference with most practition- ers in this country, and we can certainly commend tionary in the English language. The present edition is brought fully up to the advanced state of science. For many a long year "Dunglison" has been at our elbow, a constant companion and friend, and we greet him in his replenished and improved form with especial satisfaction.—Pacific Med. and Surg. Jour- nal, June 27, 1865. This is, perhaps, the book of all others which the physician or surgeon should have on his shelves. It is more needed at the present day than a few years back.—Canada Med. Journal, July, 1865. It deservedly stands at the head, and cannot be surpassed in excellence.—Buffalo Med. and Surg. Journal, April, 1865. We can sincerely commend Dr Dunglison's work as most thorough, scientific, and accurate. We have tested it by searching its pages for new terms, which have abounded so much of late in medical nomen- clature, and our search has been successful in every instance. We have been particularly struck with the fulness of the synonymy and the accuracy of the de- rivation of words. It is as necessary a work to every enlightened physician as Worcester's English Dic- tionary is to every one who would keep up his know- ledge of the English tongue .to the standard of the present day. It is, to our mind, the most complete work of the kind with which we are acquainted.— Boston Med. and Surg. Journal, June 22, 1865. We are free to confess that we know of no medical dictionary more complete; no one better, if so well adapted for the use of the student; no one that may be consulted with more satisfaction by the medical practitioner.—Am. Jour. Med. Sciences, April, 1865. The value of the present edition has been greatly enhanced by the introduction of new subjects and terms, and a more complete etymology and accentua- tion, which renders the work not only satisfactory and desirable, but indispensable to the physician.— Chicago Med. Journal, April, 1865. No intelligent member of the profession can or will be without it.— St. Louis Med. and Surg. Journal, April, 1865. It has the rare merit that it certainly has no rival this work to the renewed confidence and regard of in the Euglish language for accuracy and extent of our readers.—Cincinnati Lancet, April, 1665. I references.— London Medical Gazette. TTOBLYN (RICHARD D.), M. D, A DICTIONARY OF THE TERMS USED IN MEDICINE AND THE COLLATERAL SCIENCES. A new American edition, revised, with numerous additiens, by Isaac Hays, M.D., Editor of the "American Journal of the Medical Sciences." In one large royal 12mo. volume of over 500 double-columned pages; extra cloth, $1 50 ; leather, $2 00. It is the best book of definitions we have, and ought always to be upon the student's table.— Southern Mtd. und Surg. Journal. Henry C. Lea's Publications—(Manuals). 5 £fEILL {JOHN), M.D., and &MITH (FRANCIS G.), M.D., Prof, of the Institutes of Medicine in the Univ. of Penna. AN ANALYTICAL COMPENDIUM OF THE VARIOUS 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 12mo. volume, of about one thousand pages, with 374 wood cuts, extra cloth, $4; strongly bound in leather, with raised bands, $4 75. The Compeud of Drs. Neill and Smith is incompara- bly the most valuable work of its class ever published In this country. Attempts have been made in various quarters to squeeze Anatomy, Physiology, Surgery, the Practice of Medicine, Obstetrics, Materia Medica, and Chemistry into a single manual; but the opera- tion has signally failed in the hands of all up to the adveut of "Neill and Smith's" volume, which is quite a miracle of success. The outlines of the whole are admirably drawn and illustrated, and the authors are eminently entitled to the grateful consideration of the student of every class.—N. 0. Med. and Surg. Journal. There are but few students or practitioners of me- dicine unacquainted with the former editions of this unassuming though highly instructive work. The whole science of medicine appears to have been sifted, as the gold-bearing sands of El Dorado, and the pre- cious facts treasured up in this little volume. A com- plete portable library so condensed that the student may make it his constant pocket companion.— West- ern Lancet. In the rapid course of lectures, where work for the students is heavy, and review necessary for an exa- mination, a compend is not only valuable, but it is almost a sine qua non. The one before us is, in ni'jt>t of the divisions, the most unexceptionable of all books of the kind that we know of. Of course it is useless for us to recommend it to all last course students, but there is a class to whom we very sincerely commend this cheap book as worth its weight in silver—that class is the graduates in medicine of more than ten years' standing, who have not studied medicine since. They will perhaps find out from it that the science is not exactly now what it was when they left it off.—The Stethoscope. TTARTSHORNE (HENRY), M. D., Professor of Hygiene in the University of Pennsylvania. A CONSPECTUS OF THE MEDICAL SCIENCES; containing Handbooks on Anatomy, Physiology, Chemistry, Materia Medica, Practical Medicine, Surgery, and Obstetrics. In one large royal 12mo. volume of 1000 closely printed pages, with over 300 illustrations on wood, extra cloth, $4 50 ; leather, raised bands, $5 25. (Jvst Issued.) The ability of the author, and his practical skill in condensation, give assurance that this work will prove valuable not only to the student preparing for examination, but also to the prac- titioner desrirous of obtaining within a moderate compass, a view of the existing condition of the various departments of science connected with medicine. less valuable to the beginner. Every medical student who desires a reliable refresher to his memory when the pressure of lectures and other college work crowds to prevent him from having an opportunity to drink deeper in the larger works, will find this one of the greatest utility. It is thoroughly trustworthy fr"rn beginning to end ; and as we have before intimated, a remarkably truthful outline sketch of the present state of medical science. We could hardly expect it should be otherwise, however, under the charge of such a thorough medical scholar as the author has already proved himself to be.—N. York Med. Record, March 15, 1869. This work is a remarkably complete one in its way, and comes nearer to our idea of what a Conspectus should be than any we have yet seen. Prof. Harts- home, with a commendable forethought, intrusted the preparation of many of the chapters on special subjects to experts, reserving only anatomy, physio- logy, and practice of medicine to himself. As a result we have every department worked up to the latest date and in a refreshingly concise and lucid manner. There are an immense amount of illustrations scat- tered throughout the work, and although they have often been seen before in the various works upon gen- eral and special subjects, yet they will be none the J DDLO W (J. L.), M. D. 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 12ino. volume of 816 large pages, extra cloth, $3 25; leather, $3 75. The arrangement of this volume in the form of question and answer renders it especially suit- able for the office examination of students, and for those preparing for graduation. WANNER (THOMAS HA WKES), M. D., ice. A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAG- NOSIS. Third American from the Second London Edition. Revised and Enlarged by Tilbury Fox, M D., Physician to the Skin Department in University College Hospital, &c. In one neat volume small 12mo., of about 375 pages, extra cloth. $150. (Just Issued.) This favorite little work has remained out of print for some years in consequence of the pressing engagements which have prevented the author from giving it the thorough revision which it re- quired. The great advance which has taken place of late in the means and appliances for observation and diagnosis has necessitated a very considerable enlargement of the work, so that it now contains about one-half more matter than the last edition. The Laryngoscope, Ophthalmo- scope, Sphygmograph, and Thermometer have received special attention. The chapter on the diagnostic indications afforded by the Urine has been much enlarged, and a section has been inserted on the administration of Chloroform. Special attention has been given to the medical anatomy of regions and organs, and much has been introduced relative to pericardial, endocardial. abdominal, and cerebro-spinal diseases. On every subject coming within its scope such additions have been made as seemed essential to bring the book on a level with the most advanced condi- tion of medical knowledge ; and it is hoped that it will continue to merit the very great favor with which it has hitherto been received. 6 Henry C. Lea's Publications—{Anatomy). pRA Y (HENR Y), F. R. S., Lecturer on Anatomy at St. George's Hospital, London. ANATOMY, DESCRIPTIVE A^D SURGICAL. The Drawings hy H. V. Carter, M. D., late Demonstrator on Anatomy at St. George's Hospital; the Dissec- tions jointly by the Author and Dr. Carter. A new American, from the fifth enlarged and improved London edition. In one magnificent imperial octavo volume, of nearly 5(>0 pages, with 465 large and elaborate engravings on wood. Price in extra cloth, $6 00; leather, raised bands, $7 00. (Just Issued.) The author has endeavored in this work to cover a more extended range of subjects than is cus- tomary in the ordinary text-books, by giving not only the details necessary for the student, but also the application of those details in the practice of medicine and surgery, thus rendering it both a guide for the learner, and an admirable work of reference for the active practitioner. The en- gravings form a special feature in the work, many of them being the size of nature, nearly all original, and having the names of the various parts printed on the body of the cut, in place of figures of reference, with descriptions at the foot. They thus form a complete and splendid series, which will greatly assist the student in obtaining a clear idea of Anatomy, and will also serve to refresh the memory of those who may find in the exigencies of practice the necessity of recalling the details of the dissecting room; while combining, as it does, a complete Atlas of Anatomy, with a thorough treatise on systematic, descriptive, and applied Anatomy, the work will be found of essential use to all physicians who receive students in their offices, relieving both preceptor and pupil of much labor in laying the groundwork of a thorough medical education. Notwithstanding its exceedingly low price, the work will be found, in every detail of mechanical execution, one of the handsomest that has yet been offered to the American profession; while the careful scrutiny of a competent anatomist has relieved it of whatever typographical errors existed in the English edition. A few notices of previous editions are subjoined. Thus it is that book after book makes the labor of the student easier than before, and since we have seen Blanchard & Lea's new edition of Gray's Ana- tomy, certainly the finest work of the kind now ex- tant, we would fain hope that the bugbear of medical students will lose half its horrors, and this necessary foundationof physiological science will be much fa- cilitated and advanced.—N. 0. Med. News. The various points illustrated are marked directly on the structure; that is, whether it be muscle, pro- cess, artery, nerve, valve, etc. etc.—we say each point is distinctly marked by lettered engravings, so that the student perceives at once each point described as readily as if pointed out on the subject by the de- monstrator. Most of the illustrations are thus ren- dered exceedingly satisfactory, and to the physician they serve to refresh the memory with great readiness and with scarce a reference to the printed text. The surgical application of the various regions is also pre- sented with force and clearness, impressing upon the student at each step of his research all the important relations of the structure demonstrated.—Cincinnati Lancet. This is, we believe, the handsomest book on Aaa- tomy as yet published in our language, and bids fair to become in a short time the standard text-book of our colleges and studies. Students and practitioners will alike appreciate this book. We predict for it a bright career, aud are fully prepared to endorse the statement of the London Lancet, that "We are not acquainted with any work in any language which can take equal rank with the one before us." Paper, printing, binding, all are excellent, and we feel that a grateful profession will not allow the publishers to go unrewarded.—Nashville Med. and Surg. Journal. milTH (HENRYH.), M.D., and JJORNER ( WILLIAM E.), M.D., Prof, of Surgery in the Univ. of Penna., &c. Late Prof, of Anatomy in the Univ. of Penna., See. 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 beautiful figures. $4 50. The plan of this Atlas, which renders it so pecu- I the kind that has yet appeared; and we must add, liarly convenient for the student, and its superb ar- | the very beautiful mauner in which it is "got up " tistical execution, have been already pointed out. We is so creditable to the country as to be flattering to must congratulate the student upon the completion our national pride.—American Medical Journal. of this Atlas, as it is the most convenient work of I TJARTSHORNE (HENRY), M.D., Professor of Hygiene, etc., in the University of Pennsylvania. A HAND-BOOK OF HUMAN ANATOMY AND PHYSIOLOGY, for the use of Students, with 176 illustrations. In one volume, royal 12mo. of 312 pages; extra cloth, $1 75. (Jtist Issued.) QHARPEY (WILLIAM), M.D., and Q UAIN (JONES §• RICHARD). HUMAN ANATOMY. Revised, with Notes and Additions, hy Joseph Leidy, M. D., Professor of Anatomy in the University of Pennsylvania. Complete in two large octavo volumes, of about 1300 pages, with 511 illustrations; extra cloth, $6 00. . The very low price of this standard work, and its completeness in all departments of the subject, should command for it a place in the library of all anatomical students. ALLEN (J. M.), M.D. THE PRACTICAL ANATOMIST; or, The Student's Gtjtde in thu Dissecting Room. With 266 illustrations. In one very handsome royal 12mo. volume, of over 600 pages; extra cloth, $2 00. Oae of the most useful works upon the subject ever written.—Medical Examiner. Henry C. Lea's Publications—(Anatomy). 7 fyiLSON (ERASMUS), F.R.S. A SYSTEM OF HUMAN ANATOMY, General and Special. A new and revised American, from the last and enlarged English edition. Edited by W. H. Go- bkbcht, M. D., Professor of General and Surgical Anatomy in the Medical College of Ohio. Illustrated with three hundred and ninety-seven engravings on wood. In one large and handsome octavo volume, of over 604) large pages; extra cloth, $4 00; leather, $5 00. The publisher trusts that the well-earned reputation of this long-established favorite will be more than maintained by the present edition. Besides a very thorough revision by the author, it has been most carefully examined by the editor, and the efforts of both have been directed to in- troducing everything which increased experience in its use has suggested as desirable to render it a complete text-book for those, seeking to obtain or to renew an acquaintance with Human Ana- tomy. The amount of additions which it has thus received may be estimated from the fact that th« present edition contains over one-fourth more matter than the last, rendering a smaller type and an enlarged page requisite to keep the volume within a convenient size. The author has not only thus added largely to the work, but he has also made alterations throughout, wherever there appeared the opportunity of improving the arrangement or style, so as to present every fact in its most appropriate manner, and to render the whole as clear and intelligible as possible. The editor has exercised the utmost caution to obtain entire accuracy in the text, and has largely increased the number of illustrations, of which there are about one hundred and fifty more in this edition than in the last, thus bringing distinctly before the eye of the student everything of interest or importance. JJEATH (CHRISTOPHER), F. R. C. S., -*-J- Teacher of Operative Surgery in University College, London. PRACTICAL ANATOMY: A Manual of Dissections. From the Second revised and improved London edition. Edited, with additions, by W. W. Keem, M.D., Lecturer on Pathological Anatomy in the Jefferson Medical College, Philadelphia. In one handsome royal 12mo. volume of 578 pages, with 247 illustrations. Extra cloth, $3 50; leather, $4 00. (Just Issued.) Numerous as the published guides for dissectors . dium ; itisfulland yetconcise, while its directions for have been scarcely any seem to fulfil all the require- the use of the kuife are judiciously woven into the meats of the student. Valuable anatomical informa- general mass of anatomical details. The additions tion is often sacrificed to lengthy discussions on nice- made by the American editor bear the evidences of ties of incisions and rules for "delicate processes of mauipulation by an experienced anatomist, who is disintegration of the cadaver : while occasionally the thoroughly alive to the needs of the studeut at thedis "Dissectors," as these works are familiarly called, secting table. They are profuse, practical, aud appro- are swollen into the ponderous dimeusions of system- J priate The volume occupies from five to sixhuudred atic treatises on descriptiveanatomy. The work before pages, and is a beautiful specimen of typographical us seems to have successfully aimed at a happy me- '■ execution.—Am. Joum. of Med. Sci., Oct. l»70. [TODGES, (RICHARD M.), M.D., ■*--*- Late Demonstrator of Anatomy in the Medical Department of Harvard University. PRACTICAL DISSECTIONS. Second Edition, thoroughly revised. In one neat royal l2mo. volume, half-bound, $2 00. The object of this work is to present to the anatomical student a clear and concise description of that which he is expected to observe in an ordinary course of dissections. The author has endeavored to omit unnecessary details, and to present the subject in the form which many years' experience has shown him to be the most convenient and intelligible to the student. In the revision of the present edition, he has sedulously labored to render the volume more worthy of the favor with which it has heretofore been received. MACLISE (JOSEPH). SURGICAL ANATOMY. By Joseph Maclise, Surgeon. In one volume, very large imperial quarto; with 68 large and splendid plates, drawn in the best style and beautifully colored, containing 190 figures, many of them the size of life; together with copious explanatory letter-press. Strongly and handsomely bound in extra cloth. Price $14 00. As no complete work of the kind has heretofore been published in the English language, the present volume will supply a want long felt in this country of an accurate and comprehensive Atlas of Surgical Anatomy, to which the student and practitioner can at all times refer to ascer- tain the exact relative positions of the various portions of the human frame towards each other and to the surface, as well as their abnormal deviations. Notwithstanding the large size, beauty and finish of the very numerous illustrations, it will be observed that the price is so low as to place it within the reach of all members of the profession We know of no work on surgical anatomy which can compete with it.— Lancet. The work of Maclise on surgical anatomy is of the highest value. In some respects it is the best publi- cation of its kind we have seen, and is worthy of a place in the libiary of any medical man, while the student could scarcely make a better investment tha n thi6.—The Western Journal of Medteine and Surgery. No such lithographic illustrations of surgical re- gions have hitherto, we think, been given. While the operator is shown every vessel and uerve where »n operation is contemplated, the exact anatomist is refreshed by those clear and distinct disseclions, which every one must appreciate who has a particle of enthusiasm. The English medical press has quite exhausted the words of praise, in recommending this admirable treatise. Those who have any curiosity to gratify, in reference to the perfectibility of the lithographic art in delineating the complex mechan- ism of the human body, are invited to examine our specimen copy. If anything will induce surgeons and students to patronize a book of such rare value and everyday importance to them, it will be a sui v&y of the artistical skill exhibited in these fac-similes of nature.—Boston Med. and Surg. Journal. HORNER'S SPECIAL ANATOMY AND HISTOLOGY. Eighth edition, extensively revised aud modified. In 2 vols. Svo , of over 1000 pages, with more than 300 wood-cuts ; extra cloth, $6 00. 8 Henry C. Lea's Publications—(Physiology). TifARSHALL (JOHN), F. R. S., JJM. Professor of Surgery in University College, London, &c. OUTLINES OF PHYSIOLOGY, HUMAN AND COMPARATIVE. With Additions by Francis Gurney Smith, M. D., Professor of the Institutes of Medi.' cine in the University of Pennsylvania, &c. With numerous illustrations. In one larse and handsome octavo volume, of 1026 pages, extra cloth, $6 50; leather, raised bands $7 50. (Just Issued.) In fact, in every respect, Mr. Marshall has present- ed us with a most complete, reliable, and scientific work, and we feel that it is worthy our warmest commendation.—St. Louis Med. Reporter, Jan. 1869. This is an elaborate and carefully prepared digest of human and comparative physiology, designed for the use of general readers, but more especially ser- viceable to the student of medicine. Its style is con- cise, clear, and scholarly; its order perspicuous and exact, and its range of topics extended. The author and his American editor have been careful to bring to the illustration of the subject the important disco- veries of modern science in the various cognate de- partments of investigation. This is especially visible in the variety of interesting information derived from the departments of chemistry and physics. The great amount and variety of matter contained in the work is strikingly illustrated by turning over the copious index, covering twenty-four closely printed pages in double columns.—Silliman's Journal, Jan. 1869. We doubt if there is in the English language any compend of physiology more useful to the student than this work.—St. Louis Med. and Surg. Journal, Jan. 1869. It quite fulfils, in our opinion, the author's design of making it truly educational^ its character—which is, perhaps, the highest commendation that can be asked.—Am. Journ. Med. Sciences, Jan. 1869. We may now congratulate him on having com- pleted the latest as well as the best summary of mod- ern physiological science, both hnman and compara- tive, with which we are acquainted; To speak of this work in the terms ordinarily used on snch occa- sions would not be agreeable to ourselves, and would fail to do justice to its author. To write such a book requires a varied and wide range of knowledge, con siderable power of analysis, correct judgment,' «kill in arrangement, and conscientious spirit. It must have entailed great labor, but now that the task has been fulfilled, the book will prove not only invaluable to the student of medicine and surgery, but service- able to all candidates in natural science examinations to teachers in schools, and to the lover of nature gene^ rally. In conclusion, we can only express the con- viction that the merits of the work will command for it that success which the ability and vast labor dis- played in its production so well deserve.—London Lancet, Feb. 22, 1868. If the possession of knowledge, and peculiar apti- tude and skill in expounding it, qualify a man to write an educational work, Mr. Marshall's treatise might be reviewed favorably without even opeuing the covers. There are few, if any, more accomplished anatomists and physiologists than the distinguished professor of surgery at University College; and he has long enjoyed the highest reputation as a teacher of physiology, possessing remarkable powers of clear exposition and graphic illustration. We have rarely the pleasure of being able to recommend a text-book so unreservedly as this.—British Med. Journal, Jan.. 25, 1868. /CARPENTER ( WILLIAM B.), M. D., F. R. S., v Examiner in Physiology and Comparative Anatomy in the University of London. PRINCIPLES OF HUMAN PHYSIOLOGY; with their chief appli- cations to Psychology, Pathology, Therapeutics, Hygiene and Forensic Medicine. A new American from the last and revised London edition. With nearly three hundred illustrations. Edited, with additions, by Francis Gtjrney Smith, M. D., Professor of the Institutes of Medicine in the University of Pennsylvania, &c. In one" very large and beautiful octavo volume, of about 900 large pages, handsomely printed; extra cloth, $5 50; leather, raised bands, $6 50. We doubt not it is destined to retain a strong hold on public favor, and remain the favorite text-book in our colleges.—Virginia Medical Journal. With Br. Smith, we confidently believe "that the present will more than sustain the enviable reputa- tion already attained by former editions, of being one of the fullest and most complete treatises on the subject in the English language." We know of none from the pages of whieh a satisfactory knowledge of the physiology of the human organism can be as well obtained, none better adapted for the use of such as take up the study of physiology in its reference tof the institutes and practice of medicine.—Am. Jour. Med. Sciences. The above is the title of what is emphatically the great work on physiology; and we are conscious that it would be a useless effort to attempt to add any- thing to the reputation of this invaluable work, and can only say to all with whom our opinion has any influence, that it is our authority.—Atlanta Med. Journal. T>Y THE SAME AUTHOR. PRINCIPLES OF COMPARATIVE PHYSIOLOGY. New Ameri- can, 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. As a complete and condensed treatise on its extended and important subject, this work becomes a necessity to students of natural science, while the very low price at which it is offered places it within the reach of all. ITIRKES (WILLIAM SENHOUSE), M.D. A MANUAL OF PHYSIOLOGY. A new American from the third and improved London edition With two hundred illustrations. In one large and hand- some royal 12mo. volume. Pp. 586. Extra cloth, $2 25; leather, $2 75. It is at once convenient in size, comprehensive in design, and concise in statement, and altogether well adapted for the purpose designed.—St. Louis Med. and Surg. Journal. The physiological reader will find it a most excel- lent guide in the study of physiology in its most ad- vanced and perfect form. The author has shown himself capable of giving details sufficiently ample in a condensed and concentrated shape, on a science in which it is necessary at once to be correct and not lengthened— Edinburgh Med. and Surg. Journal. Henry C. Lea's Publications—(Physiology). 9 T)ALTON (J. C), M.D., Professor of Physiology in the College of Physicians and Surgeons, New Yorlt, &c. A TREATISE ON HUMAN PHYSIOLOGY. Designed for the use of Students and Practitioners of Medicine. Fourth edition, revised, with nearly three hun- dred illustrations on wood. In one very beautiful octavo volume, of about 700 pages, extra cloth, $5 25 ; leather, $6 25. From the Preface to the New Edition. '' The progress made by Physiology and the kindred Sciences during the last few years has re- quired, for the present edition of this work, a thorough and extensive revision. This progress has not consisted in any very striking single discoveries, nor in a decided revolution in any of the departments of Physiology ; but it has been marked by great activity of investigation in a multitude of different directions, the combined results of which have not failed to impress a new character on many of the features of physiological knowledge. ... In the revision and correction of the present edition, the author has endeavored to incorporate all such improve- ments in physiological knowledge with the mass of the text in such a manner as not essentially to alter the structure and plan of the work, so far as they have been found adapted to the wants and convenience of the reader. . . . Several new illustrations are introduced, some of them as additions, others as improvements or corrections of the old. Although all parts of the book have received more or less complete revision, the greatest number of additions and changes were required in the Second Section, on the Physiology of the Nervous System." The advent of the first edition of Prof. Dalton's Physiology, about eight years ago, marked a new era In the study of physiology to the American student Under Dalton's skilful management, physiological science threw off the long, loose, ungainly garments of probability and surmise, in whieh it had been ar- rayed by most artists, and came among us smiling and attractive, in the beautifully tinted and closely fitting dress of a demonstrated science. It was a stroke of genius, as well as a result of erudition and talent, that led Prof. Dalton to present to the world a work on physiology at once brief, pointed, and com- prehensive, and which exhibited plainly in letter and drawings the basis upon which the conclusions ar- rived at rested. It is no disparagement of the many excellent works on physiology, published prior to that of Dalton, to say that none of them, either in plan of arrangement or clearness of execution, could be compared with his for the use of students or gene- ral practitioners of medicine. For this purpose his book has no equal in the English language.— Western Journal of Medicine, Nov. 1867. A capital text-book in every way. We are, there- fore, glad to see it in its fourth edition. It has already been examined at full length in these columns, so that we need not now further advert to it beyond remark- ing that both revision and enlargement have been most judicious.—London Med. Times and Gazette, Oct 19, 1867. No better proof of the value of this admirable work could be produced than the fact that it has al- ready reached a fourth edition in the short space of eight years. Possessing in an eminent degree the merits of clearness and condensation, and being fully brought up to the present level of Physiology, it is undoubtedly one of the most reliable text-books upon this science that could be pla<>oT T)r Taylor. In one handsome 8vo. volume of 764 pages, extra cloth, $5 00; leather, $6 00.' From Dr. Taylor's Preface. "The revision of the second edition, in consequence of the death of my lamented collonsrue bns devolved entirely upon myself. Every chapter, and indeed every page, has been revised' and numerous additions made in all parts of the volume. These additions have been restricted chiefly to subjects having some practical interest, and they have been made as concise as possible in order to keep the book within those limits which may retain for it the character of a SiniW'a Mnnual "—London, June 29, 1867. oiuaent s A book that has already so established a reputa- I This second American edition of an excellent tro» Hon. as has Brande and Taylor's Chemistry, can | tise on chemical science is not a mere reDublifstinn hardly need a notice, save to mention the additions ' from the English press, but is a revision ami ,» and improvements of the edition. Doubtless the ; largement of the original, under the supervision of work will long remain a favorite text-book in the ' the surviving author, Dr. Taylor. The favors.} 1» schools, as well as a convenient book of reference for all.— N. Y. Medical Gazette, Oct. 12, 1867 For this reason we hail with delight the republica- tion, in a form which will meet with general approval and command public attention, of this really valua- ble standard work on chemistry—more particularly as it has been adapted with such care to the wants of the general public. The well known scholarship of its authors, and their extensive researches for many years in experimental chemistry, have been long ap- preciated in the scientific world, but in this work they have been careful to give the largest possible amount of information with the most sparing use of technical terms and phraseology, so as to furnish the reader, "whether a student of medicine, or a man of the world, with a plain introduction to the science and practice of chemistry."—Journal of Applied Chem- . Medical Times istry, Oct. 1867. opinion expressed on the publication of the former edition of this work is fully sustained by the present revision, in which Dr. T. has increased the size of the volume, by an addition of sixty -eight pages.—Am Journ. Med. Sciences, Oct. 1867. The Handbook in Chemistrt or the Stp2>b;»t.— For clearness of language, accuracy of description extent of information, and freedom from pedantry and mysticism, no other text-book comes into com- petition with it.—The Lancet. The authors set out with the definite purpose of writing a book which shall be intelligible to any educated man. Thus conceived, and worked ont ia the most sturdy, common-sense method, this book gives in the clearest and most summary method possible all the facts and doctrines of chemistry — 0 DLING (WILLIAM), Lecturer on Chemistry, at St. Bartholomew''s Po.vj,/f il, A-c. A COURSE OF PRACTICAL CHEMISTRY, arranged for the Use of Medical Students. With Illustrations. From the Fourth and Revised London Edition In one neat royal 12mo. volume, extra cloth. $2. (Lately Issued.) Asa work for the practitioner it cannot be excelled. It is written plainly and concisely, and givesin a very small compass the information required by the busy practitioner. It is essentially a work for the physi- cian, and no one who purchases it will ever regret the outlay. In addition to all that is usually given in connection with inorganic chemistry, there are most valuable contributions to toxicology, animal and or- ganic chemistry, etc. The portions devoted to a dis- cussion of these subjects are very excellent. In no work can the physician find more that is valuable and reliable in regard to urine, bile, milk, bone, uri- nary calculi, tissue composition, etc. The work is small, reasonable in price, and well published — Richmond and Louisville Med. Journal, Dec. 1869. ~DOWMAN (JOHN E.),M. D. PRACTICAL HANDBOOK OF MEDICAL CHEMISTRY. Edited by C L. Bloxam, Professor of Practical Chemistry in King's College, London. Fifth American, from the fourth and revised English Edition. In one neat volume, royal 12mo., pp. 351, with numerous illustrations, extra cloth. $2 25. (Now Ready.) The fourth edition of this invaluable text-book of Medical Chemistry was published in England in Octo- ber of the last year. The Editor has brought down the Handbook to that date, introducing, as far as was compatible with the necessary conciseness of such a work, all the valuable discoveries in the science which have come to light since the previous edition was printed. The work is indispensable to every student of medicine or enlightened practitioner. It is printed in clear type, and the illustrations are numerous and intelligible.—Boston Med. and Surg. Journal. JjY THE SAME AUTHOR. ____ INTRODUCTION TO PRACTICAL CHEMISTRY, INCLUDING ANALYSIS. Fifth American, from the fifth and revised London edition. With numer- ustrations. In one neat vol., royal 12mo., extra cloth. $2 25. (Now Ready.) One of the most complete manuals that has for a long time been given to the medical student.— Atrienatum. "We regard it as realizing almost everything to be desired in an introduction to Practical Chemistry. It is by far the best adapted for the Chemical stndeDt of any that has yet fallen in our way.—British and Foreign Medieo-Chirurgical Review. The best introductory work on the subject with which we are acquainted.—Edinburgh Monthly Jour. QRAHAM (TFfoMAS), F.R.S. THE ELEMENTS OF INORGANIC CHEMISTRY, including the Applications of the Science in the Arts. New and much enlarged edition, by Henry Watts and Robert Bridges, M. D. Complete in one large and handsome octavo volume, of over 800 very large pages, with two hundred and thirty-two wood-outs, extra cloth. $5 50. J ' KNAPP'S TECHNOLOGY ; or Chemistry Applied to the Arts, and to Manufactures. With American additions, by Prof. Walter E. Johsson. In two very handsome .octavo volumes, with 000 wood engravings, extra cloth, $6 00. xiiSNitY \j. jjjfiA s rubijiuaxiujns—y\juviiM!>try, Pharmacy,&c). J^OWNES (GEORGE), Ph. D. A MANUAL OF ELEMENTARY CHEMISTRY; Theoretical and Practical. With one hundred and ninety-seven illustrations. A new American, from the tenth and revised London edition. Edited by Robert Bridges, M. D. In one large royal 12mo. volume, of about 850 pp., extra cloth, *2 75 ; leather, $3 25. (Just Issued.) Some years having elapsed since the appearance of the last American edition, and several revisions having been made of the work in England during the interval, it will be found very greatly altered, and enlarged by about two hundred and fifty pages, containing nearly one half more matter than before. The editors, Mr. Watts and Dr. Bence Jones, have labored sedulously to render it worthy in all respects of the very remarkable favor which it has thus far enjoyed, by incorporating in it all the most recent investigations and discoveries, in so far as is compatible with its design as an elementary text-book. While its distinguishing characteristics have been pre- served, various portions have been rewritten, and especial pains have been taken with the department of Organic Chemistry in which late researches have accumulated so many new facts and have enabled the subject to be systematized and rendered intelligible in a manner formerly impossible. As only a few months have elapsed since the work thus passed through the hands of Mr. Watts and Dr. Bence Jones, but little has remained to be done by the American editor. Such additions as seemed advisable have however been made, and especial care has been taken to secure, by the closest scrutiny, the accuracy so essential in a work of this nature. Thus fully brought up to a level with the latest advances of science, and presented at a price within the reach of all, it is hoped that the work will maintain its position as the favorite text- book of the medical student. the General Principles of Chemical Philosophy, and the greater part of the organic chemistry, have been rewritten, and the whole work revised in accordance with the recent advances in chemical knowledge. It remains the standard text-book of chemistry.—Dub- lin Quarterly Journal, Feb. 1869. There is probably not a student of chemistry in this country to whom the admirable manual of the late Professor Fownes is unknown. ' It has achieved a success which we believe is entirely without a paral- lel among scientific text-books in our language. This success has arisen from the fact that there is no En- glish work on chemistry which combines so many excellences. Of convenient size, of attractive form, clear and concise in diction, well illustrated, and of moderate price, it would seem that every requisite for a student's hand-book has been attained. The ninth edition was published under the joint editor- ship of Dr. Bence Jones and Dr. Hofmann; the new one has been superintended through the press by Dr. Bence Jones and Mr. Henry Watts. It is not too much to say that it could not possibly have been in better hands. There is no one in England who can compare with Mr. Watts in experience as a compiler in chemical literature, and we have much pleasure in recording the fact that his reputation is well sus- tained by this, his last undertaking.—The Chemical News, Feb. 1869. Here is a new edition which has been long watched for by eager teachers of chemistry. In its new garb, and under the editorship of Mr. Watts, it has resumed its old place as the most successful of text-books.— Indian Medical Gazette, Jan. 1, 1869. This work is so well known that it seems almost superfluous for us to speak about it. It has been a favorite text-book with medical students for years, and its popularity has in no respect diminished. Whenever we have been consulted by medical stu- dents, as has frequently occurred, what treatise on chemistry they should procure, we have always re- commended Fownes', for we regarded it as the best. There is no work that combines so many excellen- ces. It is of convenient size, not prolix, of plain perspicuous diction, contains all the most recent discoveries, and is of moderate price.—Cincinnati Med. Repertory, Aug. 1869. Large additions have been made, especially in the department of organic chemistry, and we kuow of no other work that has greater claims on the physician, pharmaceutist, or student, than this. We cheerfully recommend it as the best text-book on elementary chemistry, and bespeak for it the careful attention of students of pharmacy.—Chicago Pharmacist, Aug. 1869. The American reprint of the tenth revised and cor- rected English edition is now issued, and represents the present condition of the science. No comments are necessary to insure it a favorable reception at the hands of practitioners and students. — Boston Med. and Surg. Journal, Aug. 12, 1869. It will continue, as heretofore, to hold the first rank as a text-book for students of medicine.—Chicago Med. Examiner, Aug. 1869. This work, long the recognized Manual of Chemistry, appears as a tenth edition, under the able editorship of Bence Jones and Henry Watts. The chapter on A TTFIELD (JOHN), Ph. D., "^ Professor of Practical Chemistry to the Pharmaceutical Society of Great Britain, &c. CHEMISTRY, GENERAL, MEDICAL, AND PHARMACEUTICAL; including the Chemistry of the U. S. Pharmacopoeia. A Manual of the General Principles of the Science, and their Application to Medicine and Pharmacy. In one handsome royal 12mo. volume of about 550 pages. (Nearly Ready.) It contains a most admirable digest of what is spe- cially needed by the medical student in all that re- lates to practical chemistry, and constitutes for him a sound and useful text-book on the subject..... We commend it to the notice of every medical, as well as pharmaceutical, student. We only regret that we had not the book to depend upon in working up the subject of practical and pharmaceutical chemistry for the University of London, for which it seems to us that it is exactly adapted. This is paying the book a high compliment.— The Lancet. Dr. Attfield's book is written in a clear and able manner; it is a work sui generis and without a rival; it will be welcomed, we think, by every reader of the 'Pharmacopoeia,' and is quite as well suited for the medical student as for the pharmacist.—The Chemi- cal News. A valuable guide to practical medical chemistry, and au admirable companion to the "British Phar- macopoeia " It is rare to find so many qualities com- bined and quite curious to note how much valuable Information finds a mutual interdependence.—Medi- cal Times and Gazette. It is almost the only book from which the medical student can work up the pharrnacopojial chemistry required at his examinations.—The Pharmaceutical Journal. At page 350 of the current volume of this journal, we remarked that " there is a sad dearth of [medical] students' text-books in chemistry." Dr. Attfield's volume, just published, is rather a new book than a second edition of his previous work, and more nearly realizes our ideal than any book we have before seen on the subject.—The British Medical Journal. The introduction of new ftiatter has not destroyed the original character of the work, as a treatise on pharmaceutical and medical chemistry, but has sim- ply extended the foundations of these special depart- ments of the science.—The Chemist and Druggist. We believe that this manual has been already adopted as the class-book by many of the professors in the public schools throughout the United Kingdom. ... In pharmaceutical chemistry applied to the phar- macopoeia, we know of no rival. It is, therefore, par- ticularly suited to the medical student.—The Medical Press and Circular. 12 Henry C. Lea's Publications—(Mm. Med. avd Therapeutics). pARRISH (EDWARD), Professor of Materia Medica in the Philadelphia College of Pharmacy A TREATISE ON PHARMACY. Designed as a Text-Book for the Student, and as a Guide for the Physician and Pharmaceutist. With many Formula; and Prescriptions. Third Edition, greatly improved. In one handsome octavo volume of 850 pages, with several hundred illustrations, extra cloth. $5 00. The immense amount of practical information condensed in this volume may be estimated from the fact that the Index contains about 4700 items. Under the head of Acids there are 312 ref ences; under Emplastrum, 36; Extracts, 159; Lozenges, 25; Mixtures, 55; Pills 56- 8™!!' 131; Tinctures, 138; Unguentum, 57, Ac. ' ' °*ruP3' We have examined this large volume with a good deal of care, and fiud that the author has completely exhausted the subject upon which he treats ; a more complete work, we think, it would be impossible to find. To the student of pharmacy the work is indis- pensable ; indeed, so far as we know, it is the only one of its kind in existence, and even to the physician or medical student who can spare five dollars to pur- chase it, we feel sure the practical information he will obtain will more than compensate him for the outlay.—Canada Med. Journal, Nov. 1864. The medical student and the practising physician will find the volume of inestimable worth for study and reference.—San Francisco Med. Press, July, 1S64. When we say that this book is in some respects the best which has been published on the subject in the English language for a great many years, we do not wish it to be understood as very extravagant praise. In truth, it is not so much the best as the only book.— The London Chemical News. An attempt to furnish anything like an analysis of Parrish's very valuable and elaborate Treatise on Practical Pharmacy would require more space than we have at our disposal. This, however, is not so much a matter of regret, inasmuch as it would be difficult to think of any point, however minute and apparently trivial, connected with the manipulation of pharmaceutic substances or appliances which has not been clearly and carefully discussed in this vol- ume. Want of space prevents our enlarging further on this valuable work, and we must conclude by a simple expression of our hearty appreciation of its merits.— Dublin Quarterly Jour, of Medical Science, August, 1864. 8 TILLE (ALFRED), M.D., Professor of Theory and Practice of Medicine in the University of Penna THERAPEUTICS AND MATERIA MEDICA; a Systematic Treatise on the Action and Uses of Medicinal Agents, including their Description and History Ihird edition, revised and enlarged. In two large and handsome octavo volumes of about 1700 pages, extra cloth, $10 ; leather, $12. abroad its reputation as a standard treatise on Materia Medica is securely established It is second to no work on the subject in the English tongue, and, in Dr. Stille's splendid work on therapeutics and ma- teria medica.—London Med. Times, April 8, 1865. Dr. Stille stands to-day one of the best and most houored representatives at home and abroad, of Ame- rican medicine; and these volumes, a library in them- selves, a treasure-house for every studious physician, assure his fame even had he done nothing more.__The Western Journal of Medicine, Dec. 1868. We regard this work as the best one on Materia Medica in the English language, and as such it de- serves the favor it has received.—Am. Journ. Medi- cal Sciences, July 1868. We need not dwell on the merits of the third edition of this magnificently conceived work. It is the work ou Materia Medica, in which Therapeutics are prima- rily considered—the mere natural history of drugs being briefly disposed of. To medical practitioners this is a very valuable conception. It is wonderful how much of the riches of the literature of Materia Medica has been condensed into this book. The refer- ences alone would make it worth possessing. But it is not a mere compilation. The writer exercises a good judgment of his own on the great doctrines and points of Therapeutics For purposes of practice Still6's book is almost unique as a repertory of in- formation, empirical and scientific, on the actions and uses of medicines.—London Lancet, Oct. 31, 1868. Through the former editions, the professional world is well acquainted with this work. At home and deed, is decidedly superior, in some respects, to anv other.— Pacific Med. and Surg Journal, July, 1868'. Stille's Therapeutics is incomparably the best work on the subject.— N. Y. Med. Gazette, Sept. 26,1868. Dr. StillC's work is becoming the best known of any of our treatises on Materia Medica. . . . One of the most valuable works in the language on the subjects of which it treats.— N. Y. Med. Journal, Oct. 186S. The rapid exhaustion of two editions of Prof. Stille's scholarly work, and the consequent necessity for a third edition, is sufficient evidence of the high esti- mate placed upon it by the profession. It is no exag- geration to say that there is no superior work upon the subject in the English language. The present edition is fully up to the most recent advance iu the science and art of therapeutics.—Leavenworth Medi- cal Herald, Aug. 1868. The work of Prof. Stille" has rapidly taken a high place in professional esteem, and to say that a third edition is demanded and now appears before us, suffi- ciently attests the firm position this treatise has made for itself. As a work of great research, and scholar- ship, it is safe to say we have nothing superior. It is exceedingly full, and the busy practitioner will find ample suggestions upon almost every important point of therapeutics.— Cincinnati Lancet, Aug. 1868. QRIFFITH (ROBERT E.), M.D. A UNIVERSAL FORMULARY, Containing the Methods of Pre- paring and Administering Officinal and other Medicines. The whole adapted to Physicians and Pharmaceutists. Second edition, thoroughly revised, with numerous additions, by Robert P. Thomas, M.D., Professor of Materia Medica in the Philadelphia College of Pnarmacy In one large and handsome octavo volume of 650 pages, double-columns. Extra cloth, $4 00; leather, $5 00. Three complete and extended Indexes render the work especially adapted for immediate consul- tation. One of Diseases and theib Remedies, presents under the head of each disease the remedial agents which have been usefully exhibited in it, with reference to the formula containing them—while another of Pharmaceutical and Botanical Names, and a very thorough General Index aflord the means of obtaining at once any information desired. The Formulary itself is arranged alphabetically, under the heads of the leading constituents of the prescriptions. On^oYtVlllfil^Z lan*™«V'»?7 °Jther' S° comPrehensive In its details.-ionrfon Lancet. One of the most complete works of the kind in any language.—iMi»j&ur°* Med Journal We are not cognizant of the existence of a parallel ^.-LondonTmd. Gazette. Hexry C. Lea's Publications—(Mat. Med. and Therapeutics). 13 J>EREIRA (JONATHAN), M.D., F.R.S. and L.S. MATERIA MEDICA AND THERAPEUTICS; being an Abridg- ment of the late Dr. Pereira's Elements of Materia Medica, arranged in conformity with the British Pharmacopoeia, and adapted to the use of Medical Practitioners, Chemists and Druggists, Medical and Pharmaceutical Students, UMSTEAD (FREEMAN J), M.D., •*-* Professor of Venereal Diseases at the Col. of Phys. and Surg., New York, &c. THE PATHOLOGY AND TREATMENT OF VENEREAL DIS- EASES. Including the results of recent investigations upon the subject. Third edition, revised and enlarged, with illustrations. In one large and handsome octavo volume of over 700 pages, extra cloth, $5 00. (Now Ready.) Well known as one of the best authorities of the present day on the subject.—British and For. Med.- Chirurg. Review, April, 1866. A regular store-house of special information.— London Lancet, Feb. 24, 1866. A remarkably clear and full systematic treatise on the whole subject.—Lond. Med. Times and Gazette. The best, completest, fullest monograph on this subject in our language.—British American Journal. Indispensable in a medical library.—Pacific Med. and Surg. Journal. We have no doubt that it will supersede in America pULLERIER (A.), and ^ Surgeon to the Hdpital du Midi. every other treatise on Venereal.—San Francisco Med. Press, Oct. 1864. A perfect compilation of all that is worth knowing on venereal diseases in general. It fills up a gap which has long been felt in English medical literature. —Brit, and Foreign Med.-Chirurg. Review, Jan., '65. We have not met with any which so highly merits our approval and praise as the second edition of Dr. Bumstead'swork.—Glasgow Med. Journal, Oct. 1864. We know of no treatise in any language which is its equal in point of completeness and practical sim- plicity.—Boston Medical and Surgical Journal, Jan. 30, 1S64. T>U3ISTEAD (FREE31 AN J), -*-** Professor of Venereal Diseases in the College of Physicians and Surgeons, N. Y. AN ATLAS OF VENEREAL DISEASES. Translated and Edited by Freeman J. Bumstead. In one large imperial 4to. volume of 328 pages, double-columns, with 26 plates, containing about 150 figures, beautifully colored, many of them the size of life; strongly bound in extra cloth, $17 00 ; also, in five parts, stout wrappers for mailing, at S3 per part. (Lately Published.) Anticipating a very large sale for this work, it is offered at the very low price of Three Dol- lars a Part, thus placing it within the reach of all who are interested in this department of prac- tice. Gentlemen desiring early impressions of the plates would do we1! to order it without delay. A specimen of the plates and text sent free by mail, on receipt of 25 cents. We wish for once that our province was not restrict- ed to methods of treatment, that we might say some- thing of the exquisite colored plates in this volume. —London Practitioner, May, 1869. As a whole, it teaches all that can be taught by means of plates and print.—London Lancet, March 13, 1869. Superior to anything of the kind ever before issued on this continent.—Canada. Med. Journal, March, '69. The practitioner who desires to understand this branch of medicine thoroughly should obtain this, the most complete and best work ever published.— Dominion Med. Journal, May, 1869. This is a work of master hands on both sides. M. Cullerier is scarcely second to, we think we may truly say is a peer of the illustrious and venerable Ricord, while in this country we do not hesitate to say that Dr. Bumstead, as an authority, is without a rival. Assuring our readers that these illustrations tell the ■whole history of venereal disease, from its inception to its end, we do not know a single medical work, which foi- its kind is more necessary for them to have. —California Med. Gazette, March, 1869. The most splendidly illustrated work in the lan- guage, and in our opinion far more useful than the French original.—Am. Journ. Med. Sciences, Jan.'69. The fifth and concluding number of this magnificent work has reached us, and we have no hesitation in saying that its illustrations surpass those of previous numbers.—Boston Med. and Surg. Journal, Jan. 14, 1869. Other writers besides M. Cullerier have given us a good account of the diseases of which he treats, but no one has furnished us with such a complete series of illustrations of the venereal diseases. There is, however, an additional interest and value possessed by the volume before us ; for it is an American reprint and translation of M. Cullerier's work, with inci- dental remarks by one of the most eminent American syphilographers, Mr. Bumstead. The letter-press is chiefly M. Cullerier's, but every here and there a few lines or sentences are introduced by Mr. Bumstead ; and, as M. Cullerier is a unicist, while Mr. Bumstead is a dualist, this method of treating the subject adds very much to its interest. By this means a liveliness is imparted to the volume which many other treatises sorely lack. It is like reading the report of a conver- sation or debate ; for Mr. Bumstead often finds occa- sion to question M.Cullerier's statements or inferences, and this he does in a short and forcible way which helps to keep up the attention, and to make the book a very readable one.—Brit, and For. Medieo-Chir. Review, July, 1869. H' ILL (BERKELEY), Surgeon to the Lock Hospital, London. ON SYPHILIS AND LOCAL CONTAGIOUS DISORDERS one handsome octavo volume ; extra cloth, $3 25. (Lately Published.) Bringing, as it does, the entire literature of the dis- ease down to the present day, and giving with great ability the results of modern research, it is in every respect a most desirable work, and one which should find a place in the library of every surgeon.—Cali- fornia Med. Gazette, June, 1869. Considering the scope of the book and the careful attention to the manifold aspects and details of its subject, it is wonderfully concise. All these qualities render it an especially valuable book to the beginner, to whom we would most earnestly recommend its 6tudy; while it is no less useful to the practitioner.— St. Louis Med. and Surg. Journal, May, 1869. In The author, from a vast amount of material, with all of which he was perfectly familiar, has under- taken to construct a new book, and has really suc- ceeded in producing a capital volume upon this subject.—Nashville Med. and Surg. Journal, May, 1869. The most convenient and ready book of reference we have met with.—N. Y. Med.. Record, May 1, 1869. Most admirably arranged for both student and prac- titioner, no other work on the subject equals it; it is more simple, more easily studied.—Buffalo Med. and Surg. Journal, March, 1869. allemand and wilson. 'a practical treatise on the causes, symptoms, AND TREATMENT OF SPERMATORRHEA. By M. Lallemand. Fifth American edition. To which is added-----ON DISEASES OF THE VESICULiE SEMINALES. By Makris Wilson, M.D. In one neat octavo volume, of about 400 pp., extra cloth, $2 75. 20 Henry C. Lea's Publications—(Diseases of the Skin). WILSON (ERASMUS), F.R.S. ON DISEASES OF THE SKIN. With Illustrations on wood. Sev- enth American, from the sixth and enlarged English edition. In one large octavo volume of over 800 pages, $5. (Lately Published.) A SERIES OF PLATES ILLUSTRATING "WILSON ON DIS- EASES OF THE SKIN;" consisting of twenty beautifully executed plates, of which thir- teen are exquisitely colored, presenting the Normal Anatomy and Pathology of the Skin, and embracing accurate representations of about one hundred varieties of disease, most of them the size of nature. Price, in extra cloth, $5 50. Also, the Text and Plates, bound in one handsome volume. Extra cloth, $10. From the Preface to the Sixth English Edition. The present edition has been carefully revised, in many parts rewritten, and our attention hag been specially directed to the practical application and improvements of treatment. And, in conclusion, we venture to remark that if an acute and friendly critic should discover any differ- ence between our present opinions and those announced in former editions, we have only to ob- serve that science and knowledge are progressive, and that we have done our best to move onwasd with the times. The industry and care with which the author has revised the present edition are shown by the fact that the volume has been enlarged by more than a hundred pages. In its present improved form it will therefore doubtless retain the position which it has acquired as a standard and classical authority, while at the same time it has additional claims on the attention of the profession as the latest and most complete work on the subject in the English language. Such a work as the one before us is a most capital and acceptable help. Mr. Wilson has long been held as high authority in this department of medicine, and his book on diseases of the skin has long been re- garded as one of the best text-books extant on the subject. The present edition is carefully prepared, and brought up in its revision to the present time. In this edition we have also included the beautiful series of plates illustrative of the text, and in the last edi- tion published separately. There are twenty of these plates, nearly all of them colored to nature, and ex- hibiting with great fidelity the various groups of diseases treated of in the body of the work.—Cin- cinnati Lancet, June, 1863. No one treating skin diseases should be without a copy of this standard work.— Canada Lancet. August, 1863. We can safely recommend it to the profession as the best work on the subject now in existence in the English language.—Medical Times and Gazette. Mr. Wilson's volume is an excellent digest of the actual amount of knowledge of cutaneous diseases; it includes almost every fact or opinion of importance connected with the anatomy and pathology of the skin.—British and Foreign Medical Review. These plates are very accurate, and are executed with an elegance and taste which are highly creditable totheartisticskill of the American artist who executed them.—St. Louis Med. Journal. The drawings are very perfect, and the finish and coloring artistic and correct; the volume is an indis- pensable companion to the book it illustrates and completes.—Charleston Medical Journal. ■DY THE SAME AUTHOR. ---- THE STUDENT'S BOOK OF CUTANEOUS MEDICINE and Dis- eases of the skin. In one very handsome royal 12mo. volume. $3 50. (Lately Issued.) ffELIGAN (J. MOORE), M.D.,M.R.I.A. A PRACTICAL TREATISE ON DISEASES OF THE SKIN Fifth American, from the second and enlarged Dublin edition by T. W. Belcher, M.D. In one neat royal 12mo. volume of 462 pages, extra cloth. $2 25. Fully equal to all the requirements of students and young practitioners. It is a work that h,as stood its ground, that was worthy the reputation of the au- thor, and the high position of which has been main- tained by its learned editor.—Dublin Med. Press and Circular, Nov. 17, 1869. Of the remainder of the work we have nothing be- yond unqualified commendation to offer. It is so far the most complete one of its size that has appeared, and for the student there cau be none which can com- pare with it in practical value. All the late disco- veries in Dermatology have been duly noticed, and their value justly estimated; in a word, the work is >F THE SAME AUTHOR. — fully up to the times, and is thoroughly stocked with most valuable information.—New York Med. Record, Jan. 15, 1867. This instructive little volume appears once more- Since the death of its distinguished author, the study of skin diseases has been considerably advanced, and the results of these investigations have been added by the present editor to the original work of Dr. Keli- gan. This, however, has not so far increased its bulk as to destroy its reputation as the most convenient manual of diseases of the skin that can be procured by the student.—Chicago Med. Journal, Dec. 1866. B1 ATLAS OF CUTANEOUS DISEASES. In one beautiful quarto volume, with exquisitely colored plates, Ac, presenting about one hundred varieties of Extra cloth, $5 50. inclined to consider it a very superior work, com disease The diagnosis of eruptive disease, however, under all circumstances, is very difficult. Nevertheless, Dr. Neligan has certainly, "as far as possible," given a faithful and accurate representation of this class of diseases, and there can be no doubt that these plates will be of great use to the student and practitioner in drawing a diagnosis as to the class, order, and species to which the particular case may belong. While looking over the "Atlas" we have been induced to examine also the "Practical Treatise," and we are bining accurate verbal description with sound views of the pathology and treatment of eruptive diseases. —Glasgow Med. Journal. A compend which will very much aid the practi- tioner in this difficult branch of diagnosis Taken with the beautiful plates of the Atlas, which are re- markable for their accuracy and beauty of coloring, it constitutes a very valuable addition to the library of a practical man.—Buffalo Med. Journal. TJILLIER (THOMAS), M.D., -*• Physician to the Skin Department of University College Hospital, &c. HAND-BOOK OF SKIN DISEASES, for Students and Practitioners. Second American Edition. In one royal 12mo. volume of 358 pp. With Illustrations. Extra cloth, $2 25. (Just Issued.) Henry C. Lea's Publications—(Diseases of Children). 21 SMITH (J. LE WIS), M. D., ^-* Professor of Morbid Anatomy in the Bellevue Hospital Med. College, N Y. A COMPLETE PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. In one handsome octavo volume of 620 pages, extra cloth, $4 75 ; leather, $5 75. We have no work upon the Diseases of Infancy and Childhood which can compare with it.—Buffalo Med. and Surg. Journal, March, 1869. The description of the pathology, symptoms, and treatment of the different diseases is excellent.—Am. Med. Journal, April, 1869. So full, satisfactory, and complete is the information to be derived from this work, that at no time have we examined the pages of any book with more pleasure. The diseases incident to childhood are treated with a clearness, precision, and understanding that is not often met with, and which must call forth the ap- proval of all who consult its pages.—Cincinnati Med. Repertory, May, 1S69. The author of this volum is well known as a valued contributor to the literature of his specialty. The faithful manner in which he has worked in the public institutions with which he has been connected, the conscientious regard for truth which has for years characterized all his researches, the great amount of experience which he has been enabled to acquire in j sicians in their investigation of disease in children. the treatment of infantile diseases, and the care which j Boston Med. and Surg. Journal, March 4, 1869. pONDIE (D. FRANCIS), M.D. A PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. Sixth edition, revised and augmented. In one large octavo volume of nearly 800 closely- printed pages, extra cloth, $5 25; leather, $6 25. (Lately Issued.) he has accustomed himself to take in the study of the significant facts relating to the pathological anatomy of the iiseasesof childhood, emiuently fit him for the task which he has taken upou himself The remark- able faculty of bringing out salient points aud stating concisely other less important facts, enables him to crowd within a small compass a vast amount of prac- tical information. The attention given to the treat- ment of the various maladies, as well as the presen ta- tion of all the recently accepted pathological views, make it one of the most valuable treatises, within its present compass, that can be placed in the hands of any seeker after truth.— N. Y. Med. Record, March 16, 1869. We have perused Dr. Smith's book with not a little satisfaction; it is indeed an excellent work; well and correctl y written; thorough ly up to the modern idea s; concise, yet complete in its material. We cannot help welcoming a work which will be worthy of reliance as a text-book for medical students and younger phy- The present edition, which is the sixth, is fully up to the times in the discussion of all those points in the pathology and treatment of infantile diseases which have been brought forward by the Germau and French teachers. As a whole, however, the work is the best American one that we have, and in its special adapta- tion to American practitioners it certainly has no equal. — New York Med. Record, March 2, 1868. No other treatise on this subject is better adapted to the American physician. Dr. Condie has long stood before his countrymen as one peculiarly pre-eminent in this department of medicine His work has been so long a standard for practitioners and medical stu- dents that we do no more now than refer to the fact that it has reached its sixth edition. We are glad once more to refresh the impressions of our earlier days by wandering through its pages, and at the same time to be able to recommend it to the youngest mem- bers of the profession, as well as to those who have the older editions on their shelves.—St. Louis Med. Reporter, Feb. 15. 1868. WEST (CHARLES), M.D., ' ' Physician to the Hospital for Sick Children, &c. LECTURES ON THE DISEASES OF INFANCY AND CHILD- HOOD. Fourth American from the fifth revised and enlarged English edition. In one large and handsome octavo volume of 656 closely-printed pages. Extra cloth, $4 50; leather, $5 50. Dr. West's volume is, in our opinion, incomparably the best authority upon the maladies of children that the practitioner can consult.—Cincinnati Jour. of Medicine, March, 1866. We have long regarded it as the most scientific and practical book on diseases of children which has yet appeared in this country.—Buffalo Medical Journal. Of all the English writers on the diseases of chil- dren, there is no one so entirely satisfactory to us as Dr. West. For years we have held his opinion as judicial, and have regarded him as one of the highest living authorities in the difficult department of medi- cal science in which he is most widely known.— Boston Med. and Surg. Journal, April 26, 1866. SMITH (EUSTACE), M. D., ^ Physician to the Northwest London Free Dispensary for Sick Children. A PRACTICAL TREATISE ON THE WASTING DISEASES OP INFANCY AND CHILDHOOD. Second American, from the second revised and enlarged English edition. In one handsome octavo volume, extra cloth, $2 50. (Now Ready.) In this brief treatise, the author has made one of a purpose of clinical usefulness, he has succeeded in producing a treatise on the causes of chronic wastiug so complete that but little could be added, ami yet >o concise that it would be almost impossible to give a synopsis of his views in fewer words than the book itself contains.—N. Y. Med. Gazette, April 2, 1S70. the most valuable contributions to medical literature that has been given to our profession for many years. To supply the want of information on this subject is the task which Dr Smith has set himself, and admi- rably has he performed it. Keeping steadily in view S1UERSANT (P.), M. D., *^~ Honorary Surgeon to the Hospital for Sick Children, Paris. SURGICAL DISEASES OF INFANTS AND CHILDREN. Trans- lated by R. J. Dunglison, M. D. (To appear in the Medical News and Library for 1871.) As this work embodies the experience of twenty years' service in the great Children's Hospital of Paris it can hardly fail to maintain the reputation of the valuable practical series of volumes which have been laid before the subscribers of the " American Journal of the Medical Sci- ences." For terms, see p. 3. _______________ DEWEES ON' THE PHYSICAL AND MEDICAL TREATMENT OF CHILDREN. Eleventh edition. 1vol. 8vo. of olS pages. $2 80. 22 Henry C. Lea's .Publications—(Diseases of Women). /THOMAS (T. GAILLARD),M.D., J- Professor of Obstetrics, &c. in the College of Physicians and Surgeons, N. Y., &c. A PRACTICAL TREATISE ON THE DISEASES OF WOMEN. Se- cond edition, revised and improved In one large and handsome octavo volume of 650 pages, with 225 illustrations, extra cloth, $5; leather, $6. From the Preface to the Second Edition. In a science so rapidly progressive as that of medicine, the profession has a rigntto expect that when its approbation of a work is manifested by a call for a new edition, the author should re- spond by giving to his book whatever of additional value may be derivable from more extended experience, maturer thought, and the opportunity for correction. Fully sensible of this, the author of the present volume has sought by a careful revision of the whole, and by the addition of a chapter on Chlorosis, to render his work more worthy of the favor with which it has been received.—New York, March, 1869. If the excellence of a work is to be judged by its rapid sale, this one must take precedence of all others upon the same, or kindred subjects, as evidenced in the short time from its first appearance, in which a new edition is called for, resulting, as we are informed, from the exhaustion of the previous large edition. We deem it scarcely necessery to recommend this work to physicians as it is now widely known, and most of them already possess it, or will certainly do so. To students we unhesitatingly recommend it as the best text-book on diseases of females extant.—St. Louis Med,. Reporter, June, 1869. Of all the army of books that have appeared of late years, on the diseases of the uterus and its appendages, we know of none that is so clear, comprehensive, and practical as this of Dr. Thomas', or one that we should more emphatically recommend to the young practi- tioner, as his guide.—California Med. Gazette, June, 1869. If not the best work extant on the subject of which it treats, it is certainly second to noue other. So short a time has elapsed since the medical press teemed with commendatory notices of the first edition, that it would be superfluous to give an extended re- view of what is no w firmly established as the American text-book of Gynaecology.—N. Y. Med. Gazette, July 17, 1869. This is a new and revised edition of a work which we recently noticed at some length, and earnestly commended to the favorable attention of our readers. The fact that, in the short space of one year, this second edition makes its appearance, shows that the general judgment of the profession has largely con- firmed the opinion we gave at that time.—Cincinnati Lancet, Aug. 1869. It is so short a time since we gave a full review of the first edition of this book, that we deem it only necessary now to call attention to the second appear- ance of the work. Its success has been remarkable, and we can only congratulate the author on the brilliant reception his book has received.—N. Y. Med. Journal, April, 1869. We regard this treatise as the one best adapted to serve as a text-book on gynecology.— St. Louis Med. and Surg. Journal, May 10, 1869. The whole work as it now stands is an absolute indispensable to any physician aspiring to treat the diseases of females with success, and according to the most fully accepted views of their aetiology and pa- thology.—Leavenworth Medical Herald, May, 1S69. We have seldom read a medical book in which we found so much to praise, and so little—we can hardly say to object to—to mention with qualified commen- dation. We had proposed a somewhat extended review with copious extracts, but we hardly kuow where we should have space for it. We therefore content ourselves with expressing the belief that every practitioner of medicine would do well to pos- sess himself of the work.—Boston Med. and Surg. Journal, April 29, 1869. The number of works published on diseases of women is large, not a few of which are very valuable. But of those which are the most valuable we do nut regard the work of Dr. Thomas as second to any. Without being prolix,, it treats of the disorders to which it is devoted fully, perspicuously, and satisfac- torily. It will be found a treasury of knowledge to every physician who turns to its pages. We would like to make a number of quotations from the work of a practical bearing, but our space will not permit The work should find a place in the libraries of all physicians.—Cincinnati Med. Repertory, May, 1869. No one will be surprised to learn that the valuable, readable, and thoroughly practical book of Professor Thomas has so soon advanced to a second edition. Although very little time has necessarily been allowed our author for revision and improvement of the work, he has performed it exceedingly well. Aside from the numerous corrections which he has found neces- sary to make, he has added an admirable chapter on chlorosis, which of itself is worth the cost of the volume.—N. Y. Med. Record, May 15,1869. QHURCHILL (FLEETWOOD), M. D., 31. R. I. A. ESSAYS ON THE PUERPERAL FEVER, AND OTHER DIS- EASES PECULIAR TO WOMEN. Selected from the writings of British Authors previ- ous to the close of the Eighteenth Century. In one neat octavo volume of about 450 pages, extra cloth. $2 50. A SHWELL (SAMUEL), 31. D., •*■•*- Late Obstetric Physician and Lecturer at Guy's Hospital. A PRACTICAL TREATISE ON THE DISEASES PECULIAR TO WOMEN. Illustrated by Cases derived from Hospital and Private Practice. Third Ame- rican, from the Third and revised London edition. In one octavo volume, extra cloth, of 528 pages. $3 50. RIG BY ON THE CONSTITUTIONAL TREATMENT MALES. With illustrations. Eleventh Edition, OF FEMALE DISEASES. In one neat royal 12mo with the Author's last improvements and correc volume, extra cloth, of about 250 pages. $1 00. tions. In one octavo volume of 536 pages, with DEWEES'S TREATISE ON THE DISEASES OF FE- plates, extra cloth, $3 00. T>ARNES (ROBERT), M.D., F.R.C.P., ■J-* Obstetric Physician to St. Thomas' Hospital, *c. A PRACTICAL TREATISE ON THE DISEASES OF WOMEN. In one handsome octavo volume with illustrations. (Preparing.) Henry C. Lea's Publications—(Diseases of Women). 23 TJODGE (HUGH L.), M.D., ■*•-*- Emeritus Professor of Obstetrics, &c, in the University of Pennsylvania. ON DISEASES PECULIAR TO WOMEN; including Displacements of the Uterus. With original illustrations. Second edition, revised and enlarged. In one beautifully printed octavo volume of 531 pages, extra cloth. $4 50. (Lately Issued.) In the preparation of this edition the author has spared no pains to improve it with the results of his observation and study during the interval which has elapsed since the first appearance of the work. Considerable additions have thus been mnde to it, which have been partially accom- modated by an enlargement in the size of the page, to avoid increasing unduly the bulk of the volume. From Prop. W. H. Byford. of the Rush Medical College, Chicago. The book bears the impress of a master hand, and must, as its predecessor, prove acceptable to the pro- fession. In diseases of women Dr. Hodge has estab- lished a school of treatment that has become world- wide in fame. Professor Hodge's work is truly an original one from beginning to end, consequently no one can pe- ruse its pages without iearning something new. The book, which is by no means a large one, is divided into two grand sections, so to speak: first, that treating of the nervous sympathies of the uterus, and, secondly, that which speaks of the mechanical treatment of dis- placements of that organ. He is disposed, as a non- believer in the frequency of inflammations of the uterus, to take strong ground against many of the highest authorities in this branch of medicine, and the arguments which he offers in support of his posi- tion are, to say the least, well put. Numerous wood- cuts adorn this portion of the work, and add incalcu- lably to the proper appreciation of the variously shaped instruments referred to by our author. As a contribution to the study of women's diseases, it is of great value, and is abundantly able to stand on its own merits.—N. Y. Medical Record, Sept. 15, 1868. In this point of view, the treatise of Professor Hodge will be indispensable to every student in its department. The large, fair type and general perfec- tion of workmanship will reuder it doubly welcome —Pacific Med. and Surg. Journal, Oct. 1868, Third American, In one neat octavo volume of about 550 pages, extra WEST (CHARLES), 31.D. LECTURES ON THE DISEASES OF WOMEN. from the Third London edition. cloth. $3 75 ; leather, $4 75. The reputation which this volume has acquired as a standard book of reference in its depart- ment, renders it only necessary to say that the present edition has received a careful revision at the hands of the author, resulting in a considerable increase of size. A few notices of previous editions are subjoined. The manner of the author is excellent, his descrip- tions graphic and perspicuous, and his treatment up to the level of the time—clear, precise, definite, and marked by strong common sense. — Chicago Med. Journal, Dec. 1S61. We cannot too highly recommend this, the second edition of Dr. West's excellent lectures on the dis- eases of females. We know of no other book on this subject from which we have derived as much pleasure and instruction. Every page gives evidence of the honest, earnest, and diligent searcher after truth. He Is not the mere compiler of other men's ideas, but his lectures are the result often years' patient investiga- tion in oue of the widest fields for women's diseases— St. Bartholomew's Hospital. As a teacher, Dr. West is simple and earnest in his language, clear and com- prehensive in his perceptions, and logical in his de- ductions.—Cincinnati Lancet, Jan. 1862. We return the author our grateful thanks for the va«t amount of instruction he has afforded us. His valuable treatise needs no eulogy on our part. His graphic diction and truthful pictures of disease all speak for themselves.— Medico-Chirurg. Review. Most justly esteemed a standard work.....It bears evidence of having been carefully revised, and is well worthy of the fame it has already obtained. —Dub. Med. Quar. Jour. As a writer. Dr. West stands, in our opinion, se- cond only to Watson, the "Macaulay of Me'dicine;" he possesses that happy faculty of clothing instruc- tion in easy garments; combining pleasure with profit, he leads his pupils, in spite of the ancient pro- verb, along a royal rdad to learning. His work is one which will not satisfy the extreme on either side, but it is one that will please the great majority who are seeking truth, and one that will convince the student that he has committed himself to a candid, safe, and valuable guide.—N. A. Med.-Chirurg Review. We must now conclude this hastily written sketch with the confident assurance to our readers that the work will well repay perusal. The conscientious, painstaking, practical physician is apparent on every page.—N. Y. Journal of Medicine. 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.—Edinburgh Med. Journal. We gladly recommend his lectures as in the highest degree instructive to all who are interested in ob- stetric practice.—London. Lancet. We know of no treatise of the kind so complete, and yet so compact.—Chicago Med. Journal. Y THE SAME AUTHOR. T> AN ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE OF ULCERATION OF THE OS UTERI. In one neat octavo volume, extra cloth. $1 25. MEIGS (CHARLES />.), M. D., JjJL Late Professor of Obstetrics, &c. in Jefferson Medical College, Philadelphia. WOMAN: HER DISEASES AND THEIR REMEDIES. A Series of Lectures to his Class. Fourth and Improved edition. In one large and beautifully printed octavo volume of over 700 pages, extra oloth, $5 00 ; leather, $6 00. TDY THE SAME AUTHOR. ---- ON THE NATURE, SIGNS, AND TREATMENT OF CHILDBED FEVER. In a Series of Letters addressed to the Students of his Class. In one handsome octavo volume of 365 pages, extra cloth. $2 00. SI3IPSON (SIR JAMES Y.), M.D. CLINICAL LECTURES ON THE DISEASES OF WOMEN. With numerous illustrations. In one octavo volume of over 500 pages. Second edition,preparing. 24 Henry C. Lea's Publications—(Midwifery). TJODGE (HUGH L.), M.D., Emeritus Professor of Midwifery, &c. in the University of Pennsylvania, &c. THE PRINCIPLES AND PRACTICE OF OBSTETRICS. Plus- trated with large lithographic plates containing one hundred and fifty-nine figures from original photographs, and with numerous wood-cuts. In one large and beautifully printed quarto volume of 550 double-columned pages, strongly bound in extra cloth, $14. The work of Dr. Hodge is something more than a simple presentation of his particular views in the de- partment of Obstetrics; it is something more than an ordinary treatise on midwifery; it is, in fact, a cyclo- paedia of midwifery. He has aimed to embody in a single volume the whole science and art of Obstetrics. An elaborate text is combined with accurate and va- ried pictorial illustrations, so that no fact or principle is left unstated or unexplained.—Am. Med. Times, Sept. 3, 1864. We should like to analyze the remainder of this excellent work, but already has this review extended beyond our limited space. We cannot conclude this notice without referring to the excellent finish of the work. In typography it is not to be excelled; the paper is superior to what is usually afforded by our American cousins, quite equal to the best of English books. The engravings and lithographs are most beautifully executed. The work recommends itself for its originality, and is in every way a most valu- able addition to those on the subject of obstetrics.— Canada Med. Journal, Oct. 1864. It is very large, profusely and elegantly illustrated, and is fitted to take its place near the works of great obstetricians. Of the American works on the subject it is decidedly the best.—Edinb. Med. Jour., Dec. '64. #** Specimens of the plates and letter-press will' be forwarded to any address, free by mail, on receipt of six cents in postage stamps. We have examined Professor Hodge's work with great satisfaction; every topic is elaborated most fully. The views of the author are comprehensive and concisely stated. The rules of practice are judi- cious, aud will enable the practitioner to meet every emergency of obstetric complication with confidence. —Chicago Med. Journal, Aug. 1864. More time than we have had at our disposal since we received the great work of Dr. Hodge is necessary to do it justice. It is undoubtedly by far the most original, complete, and carefully composed treatise on the principles and practice of Obstetrics which has ever been issued from the American press.—Pacific Med. and Surg. Journal, July, 1864. We have read Dr. Hodge's book with great plea- sure, and have much satisfaction in expressing our commendation of it as a whole. It is certainly highly instructive, and in the main, we believe, correct. The great attention which the author has devoted to the mechanism of parturition, taken along with the con- clusions at which he has arrived, point, we think, conclusively to the fact that, in Britain at least, the doctrines of Naegele have been too blindly received. —Glasgow Med. Journal, Oct. 1864. T fANNER (THOMAS H.), M.D. ON THE SIGNS AND DISEASES OF PREGNANCY. First American from the Second and Enlarged English Edition. With four colored plates and illustrations In one handsome octavo volume of about 500 pages, extra cloth, $4 25. state even, acceptable to the profession. We recom- mend obstetrical students, young and old, to have this volume in their collections. It contains nut only a fair statement of the signs, symptoms, and diseases of pregnancy, but comprises in addition much inter- on wood. The very thorough revision the work has undergone has added greatly to its practical value, and increased materially its efficiency as a guide to the student and to the young practitioner.—Am. Joxim. Med. Sci., April, 1868. With the immense variety of subjects treated of aud the ground which they are made to cover, the im- possibility of giving an extended review of this truly remarkable work must be apparent. We have not a single fault to find with it, and most heartily com- meud it to the careful study of every physician who would not only always be sure of his diagnosis of pregnancy, but always ready to treat all the nume- rous ailments that are, unfortunately for the civilized women of to-day, so commonly associated with the function.—i\T. F. Med. Record, March 16, 1868. We have much pleasure in calling the attention of our readers to the volume produced by Dr. Tanner, the second edition of a work that was, in its original esting relative matter that is not to be found in any other work that we can name.—Edinburgh Mea. Journal, Jan. 1868. In its treatment of the signs and diseases of preg- nancy it is the most complete book we know of, abounding on every page with matter valuable to the general practitioner.—Cincinnati Med. Repertory, March, 1868. This is a most excellent work, and should be on the table or in the library of every practitioner.—Hum- boldt Med. Archives, Feb. 1868. A valuable compendium, enriched by his own la- bors, of all that is known on the signs and diseases of pregnancy.—St. Louis Med. Reporter, Feb. 15,1868. s WAYNE (JOSEPH GRIFFITHS), M.D., Physician-Accoucheur to the British General Hospital, &c. OBSTETRIC APHORISMS FOR THE USE OF STUDENTS COM- MENCING MIDWIFERY PRACTICE. From the Fourth and Revised London Edition, with Additions by E. R. Hutchins, M. D. With Illustrations. In one neat 12mo. vol- ume. Extra cloth, $1 25. (Just Issued.) aDswers the purpose. It is not only valuable for young beginners, but no one who is not a proficient in the art of obstetrics should be without it, because it condenses all that is necessary to know for ordi- nary midwifery practice. We commend the book most favorably.—St. Louis Med. and Surg. Journal, Sept. 10, 1870. It is really a capital little compendium of the sub- ject, and we recommend young practitioners to buy i t and carry it with them when called to attend cases of labor. They can while away the otherwise tedious hours of waiting, and thoroughly fix in their memo- ries the most important practical suggestions it con- tains. The American editor has materially added by his notes aud the concluding chapters to the com- pleteness and general value of the book.—Chicago Med. Journal, Feb. 1870. The manual before us containsin exceedingly small eoinpass—small enough to carry in the pocket,—about all there is of obstetrics, condensed into a nutshell of Aphorisms. The illustrations are well selected, and serve as excellent reminders of the conduct of labor— regular and difficult —Cincinnati Lancet, April, '70. This is a moi tadiuirable little work, and completely A studied perusal of this little book has satisfied us of its eminently practical value. The object of the work, the author says, in his preface, is to give the student a few brief and practical directions respect- ing the management of ordinary cases of labor ; and also to point out to him in extraordinary cases when and how he may act upon his own responsibility, aud when he ought to send for assistance.—A*. 1'. Medical Journal, May, 1870. Henry C. Lea's Publications—(Midwifery). 25 MEIGS (CHARLES D.), M.D., ^-'-*- Lately Professor of Obstetrics, &c, in the Jefferson Medical College, Philadelphia. OBSTETRICS: THE SCIENCE AND THE ART. Fifth edition, revised. With one hundred and thirty illustrations. In one beautifully printed octavo volume of 760 large pages. Extra cloth, $5 50; leather, $6 50. It is to the student that our author has more par- ticularly addressed himself; but to the practitioner we believe it would be equally serviceable as a book of reference. No work that we have met with so thoroughly details everything that falls to the lot of the accoucheur to perform. Every detail, no matter how minute or how trivial, has found a place.— Cana,da Medical Journal, July, 1867. The original edition is already so extensively and favorably known to the profession that no recom- mendation is necessary; it is sufficient to say, the present edition is very much extended, improved-, and perfected. Whilst the great practical talents and unlimited experience of the author render it a most valuable acquisition to the practitioner, it is so con- densed as to constitute a most eligible and excellent text-book for the student.— Soutliern Med. and Surg. journal, July, 1867. ftAMSBOTHAM (FRANCIS H), M.D. THE PRINCIPLES AND PRACTICE OF OBSTETRIC MEDI- CINE AND SURGERY, in reference to the Process of Parturition. A new and enlarged edition, thoroughly revised by the author. With additions by W. V. Keating, M. D., Professor of Obstetrics, Ac, 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 text, containing in all nearly 200 large and beautiful figures. $7 00. We will only add that the student will learn from It all he need to know, and the practitioner will find it, as a book of reference, surpassed by none other.— Stethoscope. The character and merits of Dr. Ramsbotham's work are so well known and thoroughly established, that comment is unnecessary and praise superfluous. The illustrations, which are numerous and accurate, are executed in the highest style of art. We cannot too highly recommend the work to our readers.—St. Louis Med. and Surg. Journal._________ To the physician's library it is Indispensable, 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.—Ohio Med. and Surg. Journal. When we call to mind the toil we underwent in acquiring a knowledge of this subject, we cannot but envy the student of the present day the aid which this work will afford him.— Am. Jour, of the Med. Sciences. SlHURCHILL (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 Condie, M. D., author of a "Practical Treatise on the Diseases of Chil- dren," Ac. With one hundred and ninety-four illustrations. In one very handsome octavo volume of nearly 700 large pages. Extra cloth, $4 00 ; leather, $5 00. In adapting this standard favorite to the wants of the profession in the United States, the editor has endeavored to insert everything that his experience has shown him would be desirable for the American student, including a large number of illustrations. With the sanction of the author, he has added, in the form of an appendix, some chapters from a little "Manual for Mid wives and Nurses," recently issued by Dr. Churchill, believing that the details there presented can hardly fail to prove of advantage to the junior practitioner. The result of all these additions is that the work now contains fully one-half more matter than the last American edition, with nearly one- half more illustrations; so that, notwithstanding the use of a smaller type, the volume contains ainioet two hundred pages more than before. These additions render the work still more com- plete and acceptable than ever; and with the excel- lent style in which the publishers have presented this edition of Churchill, we can commend it to the profession with great cordiality and pleasure.—Cin- cinnati Lancet. Few works on this branch of medical science are equal to it, certainly none excel it, whether in regard to theory or practice, and in one respect it is superior to all others, viz., in its statistical information, and therefore, on these grounds a most valuable work for the physician, student, or lecturer, all of whom will find in it the information which they are seeking.— Brit. Am. Journal. The present treatise is very much enlarged and amplified beyond the previous editions but nothing has been added which could be well dispensed with. An examination of the table of contents shows how thoroughly the author has gone over the ground, and the care he has taken in the text to present the sub- jects in all their bearings, will render this new edition even more necessary to the obstetric student than were either of the former editions at the date of their appearance. No treatise on obstetrics with which we are acquainted can compare favorably with this, in respect to the amount of material which has been gathered from every source.—Boston Med. and Surg. Journal. There is no better text-book for students, or work of reference and study for the practising physician than this. It should adorn and enrich every medical library.—Chicago Med. Journal. MONTGOMERY (W. F.), M.D., JJ-L pr„fessor of Midwifery in the King's and Queen's College of Physicians in Ireland. AN EXPOSITION OF THE SIGNS AND SYMPTOMS OF PREG- NANCY. With some other Papers on Subjects connected with Midwifery. From the second and enlarged English edition. With two exquisite colored plates, and numerous wood-cuts. In one very handsome octavo volume of nearly 600 pages, extra cloth. $3 75. RIGBY'S SYSTEM OF MIDWIFERY. With Notes and Additional Illustrations. Second American edition. One volume octavo, extra cloth, 422 pages. $2 50. DEWEES'S COMPREHENSIVE SYSTEM OF MID- WIFERY. Twelfth edition, with the author's last improvements and corrections. In one octavo vol- ume, extra cloth, of 600 pages. $3 50. 26 Henry C. Lea's ruBLicATiONS—(Surgery). G 1ROSS (SAMUEL D.), M.D., Professor of Surgery in the Jefferson Medical College of Philadelphia. A SYSTEM OF SURGERY: Pathological, Diagnostic, Therapeutic, and Operative. Illustrated by upwards of Thirteen Hundred Engravings. Fourth edition carefully revised, and improved. In two large and beautifully printed royal octavo volumes of 2200 pages, strongly bound in leather, with raised bands. $15 00. The continued favor, shown by the exhaustion of successive large editions of this great work proves that it has successfully supplied a want felt by American practitioners and students. Though but little over six years have elapsed since its first publication, it has already reached its fourth edition, while the care of the author in its revision and correction has kept it in a constantly im- proved shape. By the use of a close, though very legible type, an unusually large amount of matter is condensed in its pages, the two volumes containing as much as four or five ordinary octavos. This, combined with the most careful mechanical execution, and its very durable binding renders it one of the cheapest works accessible to the profession. Every subject properly belonging to the domain of surgery is treated in detail, so that the student who possesses this work may be said to have in it a surgical library. tioner shall not seek in vain for what they desire.— San Francisco Med. Press, Jan. 1S65. Open it where we mayi we find sound practical in- formation conveyed in plain language. This book is no mere provincial or even national system of sur- gery, but a work which, while very largely indebted to the past, has a strong claim on the gratitude of the future of surgical science.—Edinburgh Med. Journal, Jan. 1865. It must long remain the most comprehensive work on this important part of medicine.—Boston Medical and Surgical Journal, March 23, 1865. We have compared it with most of our standard works, such as those of Erichsen, Miller, Fergusson, Syme, and others, and we must, in justice to our author, award it the pre-eminence. As a work, com- plete in almost every detail, no matter how minute or trifling, and embracing every subject known in the principles and practice of surgery, we believe it stands without a rival. Dr. Gross, in his preface, re- marks "my aim has been to embrace the whole do- main of surgery, and to allot to every subject its legitimate claim to notice;" and, we assure our readers, he has kept his word. It is a work which we can most confidently recommend to our brethren, for its utility is becoming the more evident the longer it is upon the shelves of our library.—Canada Med. Journal, September, 1865. The first two editions of Professor Gross' System of Surgery are so well known to the profession, and so highly prized, that it would be idle for us to speak in praise of this work. — Chicago Medical Journal, September, 1865. We gladly indorse the favorable recommendation of the work, both as regards matter and style, which we made when noticing its first appearance.—British and Foreign Medico-Chirurgical Review, Oct. 1865. The most complete work that has yet issued from the press on the science and practice of surgery.— London Lancet. This system of surgery is, we predict, destined to take a commanding position in our surgical litera- ture, and be the crowning glory of the author's well earned fame. As an authority on general surgical subjects, this work is long to occupy a pre-eminent place, not only at home, but abroad. We have no hesitation in pronouncing it without a rival in our language, and equal to the best systems of surgery in any language.—N. Y. Med. Journal. Not only,by far the best text-book on the subject, as a whole, within the reach of American students, but one which will be much more than ever likely to be resorted to and regarded as a high authority abroad.—Am. Journal Med. Sciences, Jan. 1S65. The work contains everything, minor and major, operative and diagnostic, including mensuration and examination, venereal diseases, and uterine manipu- lations and operations. It is a complete Thesaurus of modern surgery, where the student and practi- A glance at the work is sufficient to show that the author and publisher have spared no labor in making it the most complete "System of Surgery" ever pub- lished in any country.—St. Louis Med. and Surg Journal, April, 1865. The third opportunity is now offered during our editorial life to review, or rather to indorse and re- commend this great American work on Surgery. Upon this last edition a great amount of labor has been expended, though to all others except the author the work was regarded in its previous editions as so full and complete as to be hardly capable of improve- ment. Every chapter has beeu revised; the text aug- mented by nearly two hundred pages, and a con- siderable number of wood-cuts have been introduced. Many portions have been entirely re-written, and the additions made to the text are principally of a praC' tical character. This comprehensive treatise upon surgery has undergone revisions and enlargements, keeping pace with the progress of the art and science of surgery, so that whoever" is in possession of this work may consult its pages upon any topic embraced within the scope of its department, and rest satisfied that its teaching is fully up to the present standard of surgical knowledge. It is also so comprehensive that it may truthfully be said to embrace all that is actually known, that is really of any value in the diagnosis and treatment of surgical diseases and acci- dents. Wherever illustration will add clearness to the subject, or make better or more lasting impression, it is not wanting; in this respect the work is eminently superior.—Buffalo Med. Journal, Dec. 1864. A system of surgery which we think unrivalled in our language, and which will indelibly associate hia name with surgical science. And what, in our opin- ion, enhances the value of the work is that, while the practising surgeon will find all that he requires in it, it is at the same time one of the most valuable trea- tises which can be put into the hands of the student seeking to know the principles and practice of this branch of the profession which he designs subse- quently to follow.—The Brit. Am. Journ., Montreal. DF THE SAME AUTHOR. A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PASSAGES. In one handsome octavo volume, extra cloth, with illustrations. pp. 468. $2 75. SEEY'S OPERATIVE SURGERY. In oae very handsome octavo volume, extra cloth, of over 650 pages; with about 100 wood-cats. $3 25. A SHHURST (JOHN, Jr.), M. D.. -£*- Surgeon to tlie Episcopal Hospital, Philadelphia. THE PRINCIPLES AND PRACTICE OF SURGERY. For the use of Students and Practitioners. In one very handsome octavo volume, with several hundred illustrations. (Preparing.) Henry C. Lea's Publications—(Surgery). 27 fJRICHSEN (JOHN), -*-* Senior Surgeon to University College Hospital. THE SCIENCE AND ART OF SURGERY; being a Treatise on Sur- gical Injuries, Diseases, and Operations. From the Fifth enlarged and carefully revised London Edition. With Additions by John Ashhvrst, Jr., M. D., Surgeon to the Episcopal Hospital, &c. Illustrated by over six hundred Engravings on wood. In one very large and beautifully printed imperial octavo volume, containing over twelve hundred closely printed pages : cloth, $7 50 ; leather, raised bands, $8 50. (Just Issued.) This volume having enjoyed repeated revisions at the hands of the author has been greatly enlarged, and the present edition will thus be found to contain at least one-half more matter than the last American impression. On the latest London edition, just issued, especial care has been bestowed. Besides the most minute attention on the part of the author to bring every portion of it thoroughly on a level with the existing condition of science, he called to his aid gentlemen of distinction in special departments. Thus a chapter on the Surgery of the Eye and its Appendages has been contributed by Mr. Streatfeild ; the section devoted to Syphilis has been rearranged under the supervision of Mr. Berkeley Hill; the subjects of General Surgical Diseases, including Pyaemia, Scrofula, and Tumors, have been revised by Mr. Alexander Bruce ; and other professional men of eminence have assisted in other branches. The work may thus be regarded as embodying a complete and comprehensive view of the most advanced condition of British surgery; while such omissions of practical details in American surgery as were found have been supplied by the editor, Dr. Ashhurst. Thus complete in every respect, thoroughly illustrated, and containing in one beautifully printed volume the matter of two or three ordinary octavos, it is presented at a price which renders it one of the cheapest works now accessible to the profession. A continuance of the very remarkable favor which it has thus far enjoyed is therefore confidently expected. those enlightened surgeons of the present day, who regard an acquaintance with the manual part of sur- gery as only a portion of that knowledge which a The high position which Mr. Erichsen's Scieuce and Art of Surgery has for some time attained, not only in this country, but on the Continent and in America, almost limits the task of the reviewer, on the appear- ance of a new edition, to the mere announcement. Elaborate analysis and criticism would be out of place ; and nothing remains to be done except to state in general terms that the author has bestowed on it that labor which such a work required in order to be made a representative of the existing state of surgical science and practice. Of the merits of the book as a guide to the "Science and Art of Surgery" it is not necessary for us to say much. Mr. Erichsen is one of surgeon should possess.—British Medical Journal, Jan. 2, 1869. Thus the work bears in every feature a stamp of novelty aud freshness which will commend it to those who are making its acquaintance for the first time, whilst those who have found it a safe guide and friend in former years will be able to refer to the new edition for the latest information upon any point of surgical controversy.—London Lancet, Jan. 23,1869. DF THE SAME AUTHOR. (Just Issued.) ON RAILWAY, AND OTHER INJURIES OF THE NERYOUS SYSTEM. In small octavo volume. Extra cloth, $1 00. MILLER (JAMES), IH- Late Professor of Surgery in the University of Edinburgh, &c. PRINCIPLES OF SURGERY. Fourth American, from the third and revised Edinburgh edition. In one large and very beautiful volume of 700 pages, with two hundred and forty illustrations on wood, extra cloth, %'i 75. J>Y THE SAME AUTHOR. ---- THE PRACTICE OF SURGERY. Fourth American, from the last Edinburgh edition. Revised by the American editor. Illustrated by three hundred and sixty-four engravings on wood. In one large octavo volume of nearly 700 pages, extra cloth. $3 75. acquired. The author is an eminently sensible, prac- It is seldom that two volumes have ever made so profcund an impression in so short a time as the "Principles" and the "Practice" of Surgery by Mr. Miller, or so richly merited the reputation they have tical, and well-informed man, who knows exactly what he is talking about and exactly how to talk it.— Kentucky Medical Recorder. TJIRRIE ( WILLIAM), F. R. S. E.. J- Prof essor of Surgery in the University of Aberdeen. THE PRINCIPLES AND PRACTICE OF SURGERY. Edited by John Neill, M. D., Professor of Surgery in the Penna. Medical College, Surgeon to the Pennsylvania Hospital, &c. In one very handsome octavo volume of 780 pages, with 316 illustrations, extra cloth. $3 75. S ARGENT (F. W.), M.D. ON BANDAGING AND OTHER OPERATIONS OF MINOR SUR- GERY. New edition, with an additional chapter on Military Surgery. One handsome royal 12mo. volume, of nearly 400 pages, with 184 wood-cuts. Extra cloth, $1 75. We cordially commend this volume as one which the medical student should most closely study; and to the surgeon in practice it must prove itself instruct- Exceeil'ngly convenient and valuable to all mem- bers of the profession.—Chicago Medical Examine); May, 1862. The very best manual of Minor Surgery we have seen.— Buffalo Medical Journal. ive on many points which he may have forgotten.— Brit. Am. Journal, X»y. 1862. 28 Henry C. Lea's Publications—(Surgery). T\RUITT (ROBERT), M.R.C.S., fyc. THE PRINCIPLES AND PRACTICE OF MODERN SURGERY. A new and revised American, from the eighth enlarged and improved London edition. Illus- trated with four hundred and thirty-two wood-engravings. In one very handsome octavo volume, of nearly 700 large and closely printed pages. Extra cloth, $4 00; leather, $5 00. All that the surgical student or practitioner could ■ theoretical surgical opinions, no work that we are at desire.—Dublin Quarterly Journal. | present acquainted with can at all compare with it. It is a most admirable book. We do not know ! It is a compendium of surgical theory (if we may use when we have examined one with more pleasure.— [ tne word) and practice in itself, and well deserves Boston Med. and Surg. Journal. the estimate placed upon it.— Brit. Am. Journal. In Mr. Druitt's book, though containing only some | Thus enlarged and improved, it will continue to seven hundred pages, both the principles and the \ rank among our best text-books on elementary sur- practice of surgery are treated, and so clearly and i gery.—Columbus Rev. of Med. and Surg. perspicuously, as to elucidate every important topic, j We must close this brief notice of an admirable The fact that twelve editions havealready been called work by recommending it to the earnest attention of for, in these days of active competition, would of ! every medical student.—Charleston Medical Journal itself show it to possess marked superiority. We ; and Review. have examined the book most thoroughly and can A text-Dook which the general voice of the profes- say that this success is wel merited His book I „ion ,n both E land and America ha8 commen*jed a88 moreover, possesses the inestimable advantages of one of the most admirable .g Surgery are too well known to every one to Whether we view Druitt's Surgery as a guide to ; need any further eulogium from us.—Nashville Med. operative procedures, or as representing the latest ' Journal. TJAMILTON (FRANK H), M.D., Professor of Fractures and Dislocations, &c. in Bellevue Hosp. Med. College, New York. A PRACTICAL TREATISE ON FRACTURES AND DISLOCA- TIONS. Third edition, thoroughly revised. In one large and handsome octavo volume of 777 pages, with 294 illustrations, extra cloth, $5 75. In fulness of detail, simplicity of arrangement, and American professor of surgery; and his book adds accuracy of description, this work stands unrivalled, one more to the list of excellent practical works which So far as we know, no other work on the subject in have emanated from his country, notices of which the English language can be compared with it. While have appeared from time to time in our columns du- congratulating our trans-Atlantic brethren on the ring the last few months.—London Lancet, Dec. 15, European reputation which Dr. Hamilton, along with '"' many other American surgeons, has attained, we also may be proud that, in the mother tongue, a classical work has been produced which need not fearcompa- 1866. These additions make the work much more valua- ble, and it must be accepted as the most complete monograph on the subject, certainly in our own, if rison with the standard treatises of any other nation, not even in any other language. — American Journal —Edinburgh Med. Journal, Dec. 1866. Med. Sciences, Jan. 1867 The credit of giving to the profession the only com plete practical treatise on fractures and dislocations in our language during the present century, belongs This is the most complete treatise on the subject in English language.— Ranking's Abstract, Jan. 1867. A mirror of all that is valuable in modern surgery. to the author of the work before us, a distinguished Richmond Med. Journal, Nov. 1866 BRODIE'S CLINICAL LECTURES ON SURGERY. 1 vol. 8vo., 350 pp.; cloth, $1 25. COOPER'S LECTURES ON THE PRINCIPLES AND Practice of Surgery. In one very large octavo volume, extra eloth, of 750 pages. $2 00. GIBSON'S INSTITUTES AND PRACTICE OF SUR- SERT. Eighth edition, improved and altered. With thirty-four plates. In two handsome octavo vol- umes, about 1000 pp., leather, raised bands. $6 50. MACKENZIE ON DISEASES AND INJURIES OP THE EYE. 1 vol. 8vo., 1027 pp., extra cloth. |6. ASHTON (T. J.). ON THE DISEASES, INJURIES, AND MALFORMATIONS OF THE RECTUM AND ANUS; with remarks on Habitual Constipation. Second American, from the fourth and enlarged London edition. With handsome illustrations. In one very beautifully printed octavo volume of about 300 pages. $3 25. We can recommend this volume of Mr Ashton's in the strongest terms, as containing all the latest details of the pathology and treatment of diseases connected with the rectum.—Canada Med. Journ., March, 1866. One of the most valuable special treatises that the physician and surgeon can have in his library.__ Chicago Medical Examiner, Jan. 1866. The short period which has elapsed since the ap- pearance of the former American reprint, and the numerous editions published in England, are the best arguments we can offer of the merits, and of the use- tessness of any commendation on our part of a book already so favorably known to our readers.—Boston Med. and Surg. Journal, Jan. 25, 1866. JJORLAND (W. W.), M.D. DISEASES OF THE URINARY ORGANS; a Compendium of their Diagnosis, Pathology, and Treatment. With illustrations. In one large and handsome octavo volume of about 600 pages, extra cloth. $3 50. J^RYANT (THOMAS), F.R.C.S. THE PRACTICE OF SURGERY. A Manual, with numerous engravings on wood. In one very handsome volume. (Preparing.) Henry C. Lea's Publications—(Surgery). 29 W ELLS (J. SOELBERG), Professor of Ophthalmology in King's College Hospital, &c. A TREATISE ON DISEASES OF THE EYE. First American Edition, with additions; illustrated with 216 engravings on wood, and six colored plates. Together with selections from the Test-types of Jaeger and Snellen. In one large and very handsome octavo volume of about 750 pages: extra cioth, $5 00; leather, $6 00. (Lately Issued.) A work has long been wanting which should represent adequately and completely the present aspect of British Ophthalmology, and this want it has been the aim of Mr. Wells to supply. The favorable reception of his volume by the medical press is a guarantee that he has succeeded in his undertaking, and in reproducing the work in this country every effort has been made to render it in every way suited to the wants of the American practitioner. Such additions as seemed desirable have been introduced by the editor, Dr. I. Minis Hays, and the number of illustrations has been more than doubled. The importance of test-types as an aid to diagnosis is so universally acknowledged at the present day that it seemed essential to the completeness of the work that they should be added, and as the author recommends the use of those both of Jaeger and of Snellen for different purposes, selections have been made from each, so that the practitioner may have at command all the assistance necessary. The work is thus presented as in every way fitted to merit the confidence of the American profession. represented in the preface, in producing " an English treatise on the diseases of the eye, which should embrace the modern doctrines and practice of the His chapters are eminently readable. His style is dear and flowing. He can be short without over-con- densing, and accurate without hair splitting. These merits appear in a remarkable degree when he comes to treat of the more abstruse departments of his sub- ject, and contrast favorably with the labored obscurity which mars the writiugs of some greater authorities in the same line. We congratulate Mr. Wells upon the success with which he has fulfilled his ideal, as British and Foreign Schools of Ophthalmology." The new school of Ophthalmology may also be congratu- lated in having found an exponent who is neither a bigoted partisan of everything new, nor a scoffer at everything old.—Glasgow Med. Journal, May, 1S69. /TOYNBEE (JOSEPH), F.R.S., J- Aural Surgeon to and Lecturer on Surgery THE DISEASES OF THE EAR ment. With one hundred engravings on handsomely printed octavo volume of 440 The appearance of a volume of Mr. Toynbee's, there- fore, in which the subject of aural disease is treated in the most scientific manner, and our knowledge in respect to it placed fully on a par with that which we possess respecting most other organs of the body, is a matter for sincere congratulation. We may rea- sonably hope that henceforth the subject of this trea- tise will cease to be among the opprobria of medical science.—London Medical Review. at St. Mary's Hospital. : their Nature, Diagnosis, and Treat- wood. Second American edition. In one very pages; extra cloth, $4. The work, as was stated at the outset o' our notice, is a model of its kind, and every page and paragraph of it are worthy of the most thorough study. Con- sidered all in all—as an original work, well written, philosophically elaborated, and happily illustrated with cases and drawings—it is by far the ablest mo- nograph that has ever appeared on the anatomy and diseases of the ear, and oue of the most valuable con- tributions to the art and science of surgery in the nineteenth century.—N. Am. Med.-Chirurg. Review. J A URENCE (JOHN Z.), F. R. C. S., "^ Editor of the Ophthalmic Review, &e. A HANDY-BOOK OF OPHTHALMIC SURGERY, for the use of Practitioners. Second Edition, revised and enlarged. With numerous illustrations. In one very handsome octavo volume, extra cloth, $3 00. (Lately Issued.) No book on ophthalmic surgery was more needed. Designed, as it is, for the wants of the busy practi- tioner, it is the ne plus ultra of perfection. It epito- mis-.es all the diseases incidental to the eye in a clear aud masterly manner, not only enabling the practi- tioner readily to diagnose each variety of disease, but affording him the more important assistance of proper treatment. Altogether this is a work which ought certainly to be in the hands of every general practi- tioner.—Dublin Med. Press and Circular, Sept. 12, bb. We cordially recommend this book to the notice of our readers, as containing an excellent outline of modern ophthalmic surgery.— British Med. Journal, October 13, 1866. _________ Not only, as its modest title suggests, a "Handy- Book" of Ophthalmic Surgery, but an excellent and well-digested resumi of all that is of practical value in the specialty.—New York Medical Journal, No- vember, 1S66. This object the authors have accomplished in a highly satisfactory manner, and we know no work we can more highly recommend to the "busy practi- tioner" who wishes to make himself acquainted with the recent improvements in ophthalmic science. Such a work as this was much wanted at this time, and this want Messrs. Laurence and Moon have now well supplied.—Am. Journal Med. Sciences, Jan. 1867. T A WSON (GEORGE), F. R. C. S., Engl., J-J Assistant Surgeon to the Royal London Ophthalmic Hospital, Moorfields, &c. INJURIES OF THE EYE, ORBIT, AND EYELIDS: their Imme- diate and Remote Effects. With about one hundred illustrations. In one very hand- some octavo volume, extra cloth, $3 50 This work will be found eminently fitted for the general practitioner. In cases of functional «r structural diseases of the eve, the physician who has not made ophthalmic surgery a special ■tnriv can in most instances, refer a patient to some competent practitioner. Cases of injury, V^ver suxiervene suddenly and usually require prompt assistance, and a work devoted espe- ?inilv to'them cannot but prove essentially useful to those who may at any moment be called upon tt at such accidents. The present volume, as the work of a gentleman of large experience, may be considered as eminently worthy of confidence for reference in all such emergencies. It is an admirable practical book in the highest and best sense of the phrase.— London Medical Times and Gazette, May IS, 1867. 30 Henry C. Lea's Publications—(Surgery). TX7ALES (PHILIP S.), 31. D., Surgeon U.S.N MECHANICAL THERAPEUTICS: a Practical Treatise on Surgical Apparatus, Appliances, and Elementary Operations: embracing Minor Surgery, Band. aging, Orthopraxy, and the Treatment of Fractures and Dislocations. With six hundred and forty-two illustrations on wood. In one large and handsome octavo volume of about 700 pages : extra cloth, $5 75 ; leather, $6 75. A Naval Medical Board directed to examine and report upon the merits of this volume, officially states that " it should in our opinion become a standard work in the hands of e'very naval sur- geon ;" and its adoption for use in both the Army and Navy of the United States is sufficient guarantee of its adaptation to the needs of every-day practice. The title of this book will give a reasonably good idea of its scope, but its merits can only be appreci- ated by a careful perusal of its text. No one who un- dertakes such a task will have any reason to com- plain that the author has not performed his duty, and has not taken every pains to present every subject in a clear, common-sense, and practical light. It is a unique specimen of literature in its way, in that, treating upon such a variety of subjects, it is as a whole so completely up to the wants of the student and the general practitioner. We have never seen any work of its kind that can compete with it in real utility and extensive adaptability. Dr. Wales per- fectly understands what may naturally be required of him in the premises, and in the work before us has bridged over a very wide gap which has always here- tofore existed between the first rudiments of surgery and practical surgery proper. He has emphatically given us a comprehensive work for the beginner ; and when we say of his labors, that in their particular sphere they leave nothing to be desired, we assert a great deal to recommend the book to the attention of those specially concerned. In conclusion, we would state, at the risk of reiteration, that this is the most comprehensivebookon the subject that we have seen ; is the best that can be placed in the hands of the stu- dent in need of a first book on surgery, and the most useful that can be named for such general practition- ers who, without any special pretensions to surgery, are occasionally liable to treat surgical cases.—N. Y. Med. Record, March 2, 1868. It is certainly the most complete and thorough work of its kind in the English language. Students aud young practitioners of surgery will find it invaluable. It will prove especially useful to inexperienced coun- try practitioners, who are continually required to take charge of surgical cases, under circumstances precluding them from the aid of experienced surgeons. —Pacific Med. and Surg. Journal, Feb. 1868. The title of the above work is sufficiently indica- tive of its contents. We have not seen for a Jong time (in the EQglish language) a treatise equal to this in extent, nor one which is better adapted to the wants of the general student and practitioner. It is not to the surgeon alone that this book belongs; the physician has frequent opportunities to fill an emer- gency by such knowledge as is here given. Every practitioner should make purchase of such a book— it will last him his lifetime.—St. Louis Med. Re- porter, Feb. 186S. T>1GEL0 W (HENRY J.), 31. D., -*-* Professor of Surgery in the Massachusetts Med. College. ON THE MECHANISM OF DISLOCATION AND FRACTURE OP THE HIP. AVith the Reduction of the Dislocation by the Flexion Method. With numerous original illustrations. In one very handsome octavo volume. Cloth. $2 50. (Lately Issued.) graph is largely illustrated with exquisitely executed We cannot too highly praise this book as the work of an accomplished and scientific surgeon. We do not hesitate to say that he has done much to clear up the obscurities connected with the mechanism of dis- location of the hip-joint, and he has laid down most valuable practical rules for the easy and most suc- cessful management of these injuries. The mono- woodcuts, after photographs, which help to elucidate the admirable subject-matter of the text. We cor- dially commend the " Hip," by Dr. Bigelow, to the attention of surgeons.—Dublin Quarterly Journal of Medical Science, Feb. 1870. /TH03IPSON (SIR HENR Y), •*• Surgeon and Professor of Clinical Surgery to University College Hospital. LECTURES ON DISEASES OF THE URINARY ORGANS. With illustrations on wood. In one neat octavo volume, extra cloth. $2 25. These lectures stand the severe test. They are in- structive without being tedious, and simple without being diffuse; aud they include many of those prac tical hints so useful for the student, and even more valuable to the young practitioner.—Edinburgh Med. Joxirnol, April, 1869. Very few words of ours are necessary to recommend these lectures to the profession. There is no subject on which Sir Henry Thompson speaks with more au- thority than that in which he has specially gathered his laurels; ia addition to this, the conversational style of instruction, which is retained in these printed lectures, gives them an attractiveness which a sys- tematic treatise can never possess.—London Medical Times and Gazette, April 21, 1869. B Y THE SAME AUTHOR. ON THE PATHOLOGY AND TREATMENT OF STRICTURE OF THE URETHRA AND URINARY FISTULA. With plates and wood-cuts. From the third and revised English edition. In one very handsome octavo volume, extra cloth, $3 50. (Just Issued.) This classical work has so long been recognized as a standard authority on its perplexing sub- jects that it should be rendered accessible to the American profession. Having enjoyed the advantage of a revision at the hands of the author within a few months, it will be found to present his latest views and to be on a level with the most recent advances of surgical science. With a work accepted as the authority upon the I ably known by the profession as this before us, muet subjects of which it treats, an extended notice would | create a demand for it from those who would keep be a work of supererogation. The simple aunouuee- I themselves well up in this department of surgery.— ment of another edition of a work so well and favor- | St. Louis Med. Archives, Feb. 1870. Henry C. Lea's Publications—(Medical Jurisprudence, dec). 6i /TAYLOR (ALFRED S.), 31.D., ■* Lecturer on Med. Jurisp. and Chemistry in Guy's Hospital. MEDICAL JURISPRUDENCE. Sixth American, from the eighth and revised London edition. With Notes and References to American Decisions, by Cle- ment B. Penrose, of the Philadelphia Bar. In one large octavo volume of 776 pages, extra cloth, $4 50 ; leather, $5 50. know but that his next case may create for him an emergency for its use. To those who are not the for- tunate possessors of a reliable, readable, interesting, and thoroughly practical work upon the subject, we would earnestly recommend this, as forming the best The sixth edition of this popular work comes to us in charge of a new editor, Mr. Penrose, of the Phila- delphia bar, who has done much to render it useful, not only to the medical practitioners of this country, but to those of his own profession Wisely retaining the references of the former American editor, Dr. Hartshorne, he has added many valuable notes of his own. The reputation of Dr. Taylor's work is so well established, that it needs no recommendation. He is now the highest living authority on all matters con- nected with forensic medicine, and every successive edition of his valuable work gives fresh assurance to his many admirers that he will continue to maintain his well-earned position. No one should, in fact, be without a text-book on the subject, as he does not groundwork for all their future studies of the mure elaborate treatises.—New York Medical Record, Feb. 15, 1867. The present edition of this valuable manual is a great improvement on those which have preceded it. It makes thus by far the best guide-book in this de- partment of medicine for students aud the general practitioner in our language.—Boston Med. andSurg. Journal, Dec. 27, 1866. -DLANDFORD (G. FIELDING), M. D., F. R. C P., J-" Lecturer on Psychological Medicine at the School of St. George's Hospital, &c. INSANITY AND ITS TREATMENT: Lectures on the Treatment, Medical and Legal, of Insane Patients. With a Summary of the Laws in force in the United States on the Confinement of the Insane. By Isaac Ray, M. D. In one very handsome octavo volume of 471 pages: extra cloth, $3 25. (Just Ready.) In reprinting this work, an Appendix has been added, prepared by Dr. Isaac Ray, embracing a summary of the laws of the several States with respect to Certificates of Insanity, and the Con- finement of the Insane. ___________________ TXTINSLOW (FORBES), M.D., D.C.L.,frc. ON OBSCURE DISEASES OF THE BRAIN AND DISORDERS OF THE MIND; their incipient Symptoms, Pathology, Diagnosis, Treatment, and Pro- phylaxis. Second American, from the third and revised English edition. In one handsome octavo volume of nearly 600 pages, extra cloth. $4 25. (Lately Issued ' It is an interesting volume that will amply repay for a careful perusal by all intelligent readers.— Chicago Med. Examiner. Feb. 1866. A work which, like the present, will largely aid the practitioner in recognizing and arresting the first insidious advances of cerebral and meutal disease, is one of immense practical value, and demands earnest attention and diligent study on the part of all who have embraced the medical profession, and have thereby undertaken responsibilities in which the welfare and happiness of individuals and families are largely involved. We shall therefore 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 issued from the British medical press.—Dublin Medical Press. It is the most interesting as well as valuable book that we have seen for a long time. It is truly fasci- nating.—Am. Jour. Med. Sciences. Dr. Winslow's work will undoubtedly occupy an unique position in the medico-psychological litera- ture of this country.—London Med. Review. TEA (HENRY C). -^SUPERSTITION AND FORCE: ESSAYS ON THE WAGER OF LAW, THE WAGER OF BATTLE, THE ORDEAL, AND TORTURE. Second Edition, Enlarged. In one handsome volume royal 12mo. of nearly 500 pages; extra cloth, $2 75. irged. (Just Issued.) The copious collection of facts by which Mr. Lea has illustrated his subject shows in the fullest manner the constant conflict and varying success, the advances and defeats, by which the progress of humane legisla- tion has been and is still marked. This work fills up with the fullest exemplification and detail the wise remarks which we have quoted above. As a book of ready reference on the subject it is of the highest value.—Westminster Review, Oct. 1867. When—half in spite of himself, as it appears—he sketches a scene or character in the history of legalized error and cruelty, he betrays so artistic a feeling, and a humor so fine and good, that he makes us regret it was not within his intent, as it was certainly within his power, to render the whole of his thorough work more popular in manner.—Atlantic Monthly, Feb. '67. This is a book of extraordinary research. Mr. Lea has entered into his subject con amore; and a more striking record of the cruel superstitions of our un- happy Middle Ages could uot possibly have been com- piled. . . . As a work of curious inquiry on certain outlying points of obsolete law, "Superstition and Force" is one of the most remarkable books we have met with.—London Athenawm, Ho v. 3, 1866. T)V THE SAME AUTHOR. (Just Issued.) B STUDIES IN CHURCH HISTORY—THE RISE OF THE TEM- PORAL POWER—BENEFIT OF CLERGY—EXCOMMUNICATION. In one large royal 12mo. volume of 516 pp. extra cloth. $2 75. Altogether the book is a useful addition to the po- is showu in weaving in anecdote and picturesque n.,UL literature of a most important aud too little stories, without impairing the now of the relation or known department of medieval history.-London the proper dignity o the coinpositiou.-tfart/ord SaturdayPReview, Feb. 26, 1870. Courant, Jan. 22 1,70. „.„,.,,. Th«v are careful studies by a thorough scholar in We recommend the book as a highly instructive thrinU 1n"re°tlng 0f all historical fields, made discussion ot matters which are always of interest to tne most imom s ;,,A\rP fln,i recorded with hon- scholars, and which are just now clothed with a *pe- ^tV Th^who"*> *!KfTC theTeepe't interest; cial importance.-*. Y. Nation, Feb. 3, 1S70. the style is masculine and animated, and great skill 32 Henry (j. lea's publications. INDEX TO CATALOGUE. Allen's Dissector and Practical Anatomist American Journal of the Medical Sciences Abstract, Half-Yearly, of the Med Sciences Anatomical Atlas, by Smith and Horner Ashton on the Rectum and Anus . Attfield's Chemistry .... Ashwell on Diseases of Females . Ashhurst's Surgery .... Barnes on Diseases of Women Bryant's Practical Surgery . Blandford on Insanity .... Basham on Renal Diseases . Brinton on the Stomach Bigelow on the Hip .... Barclay s Medical Diagnosis . . Barlow's Practice of Medicine Bowman's (John E.) Practical Chemistry Bowman's (John E.) Medical Chemistry Brande & Taylor's Chemistry Brodie's Clinical Lectures on Surgery . Buckler on Bronchitis .... Bucknill and Tuke on Insanity . Bumstead on Venereal .... Bumstead and Cullerier's Atlas of Venereal Carpenter's Human Physiology . Carpenter's Comparative Physiology . Carpenter on the Use and Abuse of Alcohol Carson's Synopsis of Materia Medica . Chambers on the Indigestions Christison and Griffith's Dispensatory Churchill's System of Midwifery . Churchill on Puerperal Fever Condie on Diseases of Children . Cooper's (B. B.) Lectures on Surgery . Cullerier's Atlas of Venereal Diseases Cyclopedia of Practical Medicine . Dalton's Human Physiology . De Jongh on Cod-Liver Oil . Dewees's System of Midwifery Dewees on Diseases of Females . . Dewees on Diseases of Children . . Dickson's Practice of Medicine Druitt's Modern Surgery Dunglison's Medical Dictionary . Dunglison's Human Physiology . Dunglison on New Remedies Ellis's Medical Formulary, by Smith . Erichsen's System of Surgery Erichsen on Nervous Injuries Flint on Respiratory Organs . Flint on the Heart..... Flint's Practice of Medicine . Fownes's Elementary Chemistry . Fuller on the Lungs, &c. Gibson's Surgery..... Gluge's Pathological Histology, by Leidy Graham's Elements of Chemistry . Gray's Anatomy..... Griffith's (R. E.) Universal Formulary Gross on Foreign Bodies in Air-Passages Gross's Principles and Practice of Surgery Gross's Pathological Anatomy Guersant on Surgical Diseases of Children Hartshorne's Essentials of Medicine . Hartshorne's Conspectus of the Medical Sciences Hartshorne's Anatomy and Physiology Hamilton on Dislocations and Fractures Harrison on the Nervous System . Heath's Practical Anatomy . Hoblyn's Medical Dictionary Hodge on Women..... Hodge's Obstetrics..... Hodge's Practical Dissections Holland's Medical Notes and Reflections Horner's Anatomy and Histology Hudson on Fevers, .... Hill on Venereal Diseases Hillier's Handbook of Skin Diseases Jones and Sieveking's Pathological Anatomy Jones (C. Handfield) on Nervous Disorders Kirkes' Physiology..... Knapp's Chemical Technology . Lea's Superstition and Force Lea's Studies iu Church History . Lallemand and Wilson on Spermatorrhoea La Roche on Yellow Fever . La Roche on Pneumonia, &c. Laurence and Moon's Ophthalmic Surgery Lawson on the Eye .... Laycock on Medical Observation . Lehmann's Physiological Chemistry, 2 vols. Lehmann's Chemical Physiology . Ludlow's Manual of Examinations Lyons on Fever..... Maclise's Surgical Anatomy . Marshall's Physiology .... Mackenzie on Diseases of the Eye Medical News and Library . Meigs's Obstetrics, the Science aDd the Art Meigs's Lectures on Diseases of Women Meigs on Puerperal Fever Miller's Practice of Surgery . Miller's Principles of Surgery Montgomery on Pregnancy . Morland on Urinary Organs . Morland on Uraemia Neill and Smith's Compendium of Med. Science Neligan's Atlas of Diseases of the Skin Neligau on Diseases of the Skin Odliug's Practical Chemistry Pavy on Digestion r . Prize Essays on Consumption Parrish's Practical Pharmacy Pirrie's System of Surgery . Pereira's Mat. Medica and Therapeutics, abridged Quain and Sharpey's Anatomy, by Leidy Ranking's Abstract .... Radcliff aad others on the Nerves, &e. Roberts on Urinary Diseases . Ramsbotham on Parturition . Rigby on Female Diseases Rigby's Midwifery..... Rokitansky's Pathological Anatomy . Royle's Materia Medica and Therapeutics Salter on Asthma..... Swayne's Obstetric Aphorisms .. . Sargent's Minor Surgery Sharpey and Quain's Anatomy, by Leidy Simon's General Pathology . Simpson on Females .... Skey's Operative Surgery Slade on Diphtheria .... Smith (J. L.) on Children Smith (H. H.) and Horner's Anatomical Atlas Smith (Edward) on Consumption . Smith on Wasting Diseases of Children Solly on Anatomy and Diseases of the Brain Stille's Therapeutics .... Tanner's Manual of Clinical Medicine . Tanner on Pregnancy..... Taylor's Medical Jurisprudence . Thomas on Diseases of Females . Thompson on Urinary Organs Thompson on Stricture .... Todd and Bowman's Physiological Anatomy Todd on Acute Diseases .... Toynbee on the Ear .... Wales on Surgical Operations Walshe on the Heart .... Watson's Practice of Physic . Wells on the Eye..... West on Diseases of Females . . West on Diseases of Children West on Ulceration of Os Uteri . What to Observe in Medical Cases Williams's Principles of Medicine Wilson's Human Anatomy . Wilson on Diseases of the Skin . Wilson's Plates on Diseases of the Skin Wilson's Handbook of Cutaneous Medicine Wilson on Spermatorrhoea . Winslow on Brain and Mind PAOl 10 \^ / ^ /l \ - -v ^ \/- -0? AUfA \.^ nsn s^ X / J \ 1 4>T X 4 .#* ,# a*>" 1 \S ^v x X-,«cr V '«o06 -f J Jp J?% X / %f *** V\Tf *^\ NLM032060612