i CORNELL UNIVERSITY THE FOUNDED BY ROSWELL P. FLOWER for the use of the N. Y. State Veterinary College 1897 5541 Cornell University Library QP 34.D15 1871 A treatise on human ph' III siology ... V 3 1924 001 039 100 The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001039100 A TKEATISE ON HUMAN PHYSIOLOGY: DESIGNED FOR THE USB OF STUDENTS AND PRACTITIONERS OF MEDICINE. BY JOHlSr C. DALTON, M.D., PROFESSOR OP PHYSIOLOQY AND HYGIENE IN THE COLLEGE OP PHYSICIANS AND SURGEONS, NEW YORK; MEMBER OP THE NEW YORK: ACADEMY OF MEDICINE; OF THE NEW YORK PATHOLOGICAL SOCIETY; OF THE AMERICAN ACADEMY OF ARTS AND BCIENOES, BOSTON, MASS. ; OF THE BIOLOGICAL DEPARTMENT OF THE ACADEMY OP NATURAL 8CIBNCEB OF PHILADELPHIA; AND OF THE NATIONAL ACADEMY OP SCIENCES OF THE UNITED STATES OF AMERICA. Ififllt ^dttim |[i^»ud attil ^ttlayjjtl WITH TWO HUNDRED AND EIGHTY-FOUR ILLUSTRATIONS. PHILADELPHIA: HENRY 0. LEA. 1871. >U. i3 \50 Dntered, according to Act of Congress, in the year 1871, by HENEY C. LEA, in the Office of the Librarian of Congress at Washington. ALL RIGHTS BESERTED. 187/ Collins, Printer, 705 Jayne St., Philaixei.phia. TO MY FATHER, / JOHN C. DiLTON, M.D., IN HOMAGE OP HIS LONG AND SUCCESSFUL DEVOTION TO THE SCIENCE AND ART OP MEDICINE, AND 1 rr GRATEFUL RECOLLECTION OF HIS PROFESSIONAL PRECEPTS AND EXAMPLE, IS RESPECTFULLY AND AFFECTIONATELY INSCEIBED. ( "i ) Preface to the Fifth Edition. TN preparing the present edition of this work, the general -*- plan and arrangement of the previous editions have been retained, so far as they have been found useful and adapted to the purposes of a text-book for students of medicine. The incessant advance of all the natural and physical sciences, never more active than vt'ithin the last few years, has furnished many valuable aids to the special investigations of the physiologist; and the progress of physiological research, during the same period, has required a careful revision of the entire work, and the modification or re-arrangement of many of its parts. At this day, nothing is regarded as of any value in natural science which is not based upon direct and intelligible observation or experiment; and accordingly the discussion of doubtful or theoretical questions has been avoided, as a general rule, in the present volume, while new facts, from whatever source, if fully established, have been added and incorporated with the results of previous investigation. A number of .new illustrations have been introduced, and a few of the older ones, which seemed to be no longer useful, have been omitted. In all the changes and additions thus made, it has been the aim of the writer to make the book, in its present form, a faithful exponent of the actual condition of physiological science. New Yokk, October, 1871. CONTENTS. INTRODUCTION. PAGE Definition of Physiology — Its mode of study — Nature of Vital Phenomena — Diyisiou of the subject 83-43 SECTION I. NUTEITION. CHAPTER I. PflOXIMATE PRINCIPLES IN GENERAL. Definition of Proximate Principles — Mode of their extraction — Manner in which they are associated witli each other — Natural variation in their relative quantities — Three distinct classes of proximate principles . , . 45-52 CHAPTER II. PROXIMATE PRINCIPLES OP THE FIRST CLASS. Inorganic substances — Water — Chloride of Sodium — Chloride of Potassium — Pliosphate 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 OP THE SECOND CLASS. Stakch — Percentage of starch In different kinds of food — Varieties of this substance — Properties and reactions of starch — Its conversion into sugar SuOAB — Varieties of sugar — Physical and chemical properties — Tests for sugar — Proportion in different kinds of food — Fats — Varieties — Properties and reactions of fat — Its crystallization — Proportion in difierent kinds of food — Its condition in the body — Internal production of fat — Origin and des- tination of proximate principles of this class ..... 63-79 (vii) yill CONTENTS. CHAPTER IV. 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 — ^Urosaoine — Origin and destruction of proximate principles of this class 80-90 CHAPTEIl y. or FOOD. Importance of inorganic substances as ingredients of food — Of saccharine and starchy substances — Of fatty matters — Insufficiency of these substances when used alone — Effects of an exclusive non-nitrogenous diet — Organic substances also insufficient by themselves — Experiments of 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 . 91-101 CHAPTER YI. 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 — Gastkic Juice, and Stomach Digestiok — 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 Digestiok op Spgak and Starch — Follicles of intestine — Properties of intestinal juice — PANCEBATid Jdice, and THE Digestion op PAT — Composition and properties of pancreatic juice — It.s action on oily matters — Successive changes in intestinal digestion — The large intestine and its contents 102-148 CHAPTER VII ABSORPTION. Closed follicles and villi of small intestine — Peristaltic motion — Absorption by bloodvessels and lymphatics — Chyle — Lymph — Absorbent system— Lac teals and lymphatics — Absorption of fat — Its accumulation in the blood during digestion — Its final decomposition and disappearance . . 149-160 CONTENTS. IX CHAPTER VIII. THE BILE. PAOB Physical properties of the bile — Its composition — Biliverdine — Cholesterin — Biliary salts — Their mode of extraction — Crystallization — Glyko-cholate of soda — Tauro-oholate 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 reabsorptiou — Its ultimate decomposition . . 161-185 OHAPTEE, IX. FORMATION OF SUGAK 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 — Doubts as to the existence of liver-sugar during life — Experiments on this point and their result — Increase in quantity of liver-sugar after death — Absorption of liver-sugar by hepatic veins — Its ac- cumulation in the blood during digestion — Its final decomposition and dis- appearance ............ 186-199 CHAPTER X. THE SPLEEN. Capsule of spleen — Variation in size of the organ — Its internal structure — Malpighian bodies of the spleen — Action of spleen on the blood — Effect of its extirpation 200-204 CHAPTER XI. THE BLOOD. Red Globules of the blood — Their microscopic characters — Structure and com- position — Variations in size in different animals — White Globdles of the blood — Independence of the two kinds of blood-globules — Plasma — Its com- position — Fibrin — Albumen — Fatty matters — Saline ingredients — Extractive matters — CoAacLATioN of the Blood — Separation of clot and serum — Influ- ences hastening or retarding coagulation — Determining causes of coagula- tion — Its dependence on the properties of the fibrin — Disappearance and reproduction of the fibrin — Influence of coagulation in the arrest of hemor- rhage — Entire quantity of blood in the body 205-224 CHAPTER XII. RESPIRATION. Respiratory apparatus of aquatic and air-breathing animals — Structure of lungs in human subject — 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. — Discharge of carbonic acid in the urine— Exhalation by the skin 225-246 X CONTENTS. CHAPTER Xni. 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 ..... 247-258 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 — The sphygmograph — Curves of arterial pul- sation — Dicrotic pulse — Arterial pressure — Rapidity of arterial circulation — The veins — Causes of movement of blood in the veins — Rapidity of venous current — Capillary circulation — Phenomena and causes of capillary circula- tion — Rapidity of entire circulation — Local variations in the capillary cir- culation 259-308 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 ........ 309-325 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 326-344 CONTENTS. X± CHAPTER XVII. EXCEETION. PASB Nature of excretion — Exorementitious substances — Effect of their retention — Urea — Its source — Conversion into carbonate of ammonia — Daily quantity of urea — Its increase by muscular exercise — Creatine — Creatinine — Urate of soda — Urates of potassa and ammonia — General characters of the urine — Its composition — Variations — Accidental ingredients of the urine — Acid and alkaline fermentations — Final decomposition of the urine . . . 345-370 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 — Origin and termination of the nervous filaments — Gray substance — Nerve cells — Nervous system of radlata — Of moUusca — Of articulata — Of mammalia and human subject — Structure of encephalon — Connections of its different parts 371-398 CHAPTER II. OP 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 S99-409 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. . . . 410-429 XU CONTENTS. CHAPTER IV. THE BRAIN. PAGB Seat of sensibility and excitability in different parts of the enoephalon — Olfac- tory ganglia — Optic tlialami— Corpora striata — Hemispheres — Remarkable oases of injury of hemispheres — Effect of their removal — Imperfect develop- ment in idiots — Aztec children — Theory of phrenology — Cerebellum — Effect of its injury or removal — Comparative development in different classes — Tubercula quadrigemina — Tuber annulare — Medulla oblongata — Three kinds of reflex action in nervous system ..... 430-458 CHAPTER V. THE CRANIAL NERVES. Olfactory nerves — Optic nerves — Auditory nerves — Classification of cranial 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 — Pneumogastrio — Its distribution — Influence on pharynx and oesophagus— On larynx — On lungs — On stomach and digestion — Spinal accessory nerve — Hypoglossal . . . 459-491 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 . 492-528 CHAPTER VII. SYSTEM OF THE GREAT SYMPATHETIC. Anatomical arrangement of the sympathetic system — Its ganglia — Its nerves — Its physiological properties — Influence on movement and sensibility — Sluggish action of this nerve— Influence on the special senses — Influence on the circulation — On the temperature of the part — On the color of venous blood — Reciprocal action with cerebro-spinal nerves — Influence on reflex actions — Reflex actions taking place through the great sympathetic . 529-541 CONTENTS. XllI SECTION III. REPRODUCTION. CHAPTER I. ON THE NATURE OF REPRODUCTION, AND THE ORIGIN 01" 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 — Experiments on generation of infusoria — Production of animal and vegetable parasites — Encysted entozoa — Trichina spiralis — Taenia — Cysticercus— Production of taenia from cysticereus — Of oysticerous from eggs of taenia — Plants and animals produced by generation from parents 543-567 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 558-561 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 . . 562-573 CHAPTER lY. ON THE SPERMATIC FLUID, AND THE MALE ORGANS OP GENERATION. The spermatozoa— Their varieties in diiferant species — Their movement — For- mation of spermatozoa in the testicles — Accessory male organs of generation — Epididymis — Vas deferens — Vesiculse seminales — Prostate — Cowper's glands — Function of spermatozoa — Necessary conditions of fecundation Periodical development of the spermatic fluid — Various modes of fecunda- tion .... 574-582 XIV CONTENTS. CHAPTER, V. ON PERIODICAL OVULATION, AND THE rUNCTION OP 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 oestruation — 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 583-595 CHAPTER VI. ON THE CORPUS LUTEUM OF MENSTRUATION AND PREGNANCY. Corpus Luteum op Menstruation — Discharge of blood into the ruptured Graafian follicle — Deoolorizatiou 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 . . . 696-605 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 ........ 606-615 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 . . 616-618 CONTENTS. XV CHAPTEK IX. AMNION AND ALLANTOIS — DEVELOPMENT OP 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 ........ 619-C27 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 fostus — Proofs that the chorion is formed from the allantois — Partial disappearance of villosities of chorion, and changes in its external surface ...... 628-633 CHAPTER XI. DEVELOPMENT OF UTERINE MDCOtJS 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 ..... 634-640 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 fcetal 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 ...... 641-649 XVI CONTENTS. CHAPTER XIII DISCHARGE OP THE OVUM, AND INVOLUTION OF THE UTERUS. PAGE Enlargement of amniotic cavity — Contact of amnion and chorion — Amniotic fluid — Movements of fcetus — Union of deeidua vera and refiexa — Expulsion of the ovum and discharge of decidual membrane — Separation of the pla- centa — Formation of new mucous membrane underneath the old deeidua — Fatty degeneration and reconstruction of muscular walls of uterus 650-656 CHAPTER XIY. DEVELOPMENT OF THE EMBRYO — NERVOUS SYSTEM, ORGANS OP SENSE, SKELETON AND LIMBS. Formation of spinal cord and cerebro-spinal axis — Three cerebral vesicles — Hemispheres — Optic thalami — Tuberoula quadrigemina — Cerebellum — Me- dulla oblongata — Eye — Pupillary membrane — Skeleton — Chorda dorsalis — Bodies of the vertebrae — Laminae and ribs — Spina bifida — Anterior and pos- terior extremities — Tail — Integument — Hair — Vernix caseosa — Exfoliation of epidermis ........ 657-663 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 — Uraohus — Vesico- rectal septum — Perineum — Liver — ^Secretion of bile — Gastric juice — Meconium — Glyco- genic function of liver — Diabetes of fcetus — Pharynx and oesophagus — Dia- phragm — Diaphragmatic hernia — Heart and pericardium — Ectopia cordis — Development of the face ...... 664-674 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 .... 675-684 CONTENTS-. XTU CHAPTER XVII. DEVELOPMENT OF THE CIRCULATORY APPARATUS. PAGE First, or vitelline circulation — Area vasculosa — Sinus terminalis — Vitelline circulation of fish — Arrangement of arteries and veins in body of foetus- Second, or placental circulation — Omphalo-mesenterio arteries and vein — 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 68^706 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 — Difierence 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 707-710 LIST OF ILLUSTRATIONS, ALL OF WHICH HAVE BEBK PKEPAKED FKOM OBIGINAL DRAWINGS, WITH THE EXCEPTION OF SEVENTEEN CKEDITED TO THEIK AUTHORITIES. Fia. 1. Fibula tied in a knol, 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. Stearine .... 8. Oleaginous principles of human fat 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 os 18. Human alimentary canal 19. Skull of rattlesnake 20. Skull of polar bear 21. SkuU of the horse 22. Molar tooth of the horse 23. Human teeth — upper jaw 24. Buccal and glandular epithelium deposited from 25. Gastric mucous membrane, viewed from above 26. Gastric mucous membrane, in vertical section 27. Mucous membrane of pig's stomach SSi. Gastric tubules from pig's stomach pyloric portion 29. Gastric tubules from pig's stomach, cardiac porti "50. Gastric tubules from pig's stomach, middle portion 31. Confervoid vegetable, growing in gastric juice 32. Follicles of Lieberkiihn 33. Brunner's duodenal glands 84 Contents of stomach, during digestion of meat 85. From duodenum of dog, during digestion of meat 36. From middle of small intestine From Rymer Jones From Achille saliva Richard (xix) PAQB 69 64 64 65 65 66 72 73 75 75 76 76 77 77 78 104 105 106 106 109 109 109 110 111 120 120 121 121 121 122 128 139 140 146 146 147 XX LIST OF ILLUSTRATIONS. 37. From last quarter of small intestine 38. One of the closed follicles of Peyer's patches 39. Glandulse agminatse .... 40. Extremity of intestinal villus 41. Panizza's experiment on absorption by 'bloodvessels 42. Chyle, from commencement of thoracic duct 43. Intestinal epithelium, in intervals of digestion 44. Intestinal epithelium, during digestion 46. Lacteals, thoracic duct, &c. 46. Lacteals and Lymphatics . 47. Cholesterin .... 48. Ox-bile, crystallized 49. Glyko-oholate of soda from ox-bile 50. Glyko-cholate and tauro-cholate of soda, from ox-bile 51. Df^'s bile, crystallized .... 52. Humaij .bile, showing crystalline and resinous matters 53. Crystalline and resinous biliary substances, from dog's intestine 54. Duodenal fistula 55. Comminuting machine 56. Cylinders of comminuting machine, in profile 57. Human blood-globules 58. The same, seen out of focus 59. The same, seen within the focus 60. The same, adhering together in rows 61. The same, swollen by addition of water . 62. The same, shrivelled by evaporation 63. Blood-globules of frog 64. White globules of the blood 65. Coagulated fibrin .... 66. Coagulated blood .... 67. Coagulated blood, after separation of clot and serum 68. Head and gills of menobranohus . 69. Lung of frog .... 70. Human larynx, trachea, bronchi, and lungs 71. Single lobule of human lung 72. Diagram illustrating the respiratory movements 73. Small bronchial tube 74. Human larynx, with glottis closed 75. The same, with glottis open 76. Human larynx — posterior view . 77. Circulation of fish 78. Circulation of reptiles 79. Circulation of mammalians 80. Human heart, anterior view 81. Human heart, posterior view 82. Right auricle and ventricle, tricuspid valve open, arterial valves closed 83. Right auricle and ventricle, tricuspid valve closed, artcial valves open '<4. Course of blood through the heart 85. Illustrating production of valvular sounds 86. Heart of frog, in relaxation LIST OF ILLUSTEATI0N3. XXI no. 87. 88. 89. 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 pulsation in an elastic tube Trace of the radial pulse, by sphygmograph Variation of the radial pulse Dicrotic pulse of typhoid pneumonia Dicrotic pulse of typhoid fever Volkmann's apparatus .... The same ...... Chauveau's instrument for measuring arterial current Vein, with valves open .... Vein, with valves closed Small artery, with capillary branches Capillary network .... Capillary circulation .... Diagram of the circulation Follicles of a compound mucous glandule Meibomian glands Perspiratory gland 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 sciatic nerve Nervous filaments from brain Division of a nerve Inosculation of nerves Terminal corpuscle of sensitive nerve Tactile corpuscles Termination of nervous filament in muscle Nerve-cells .... Nervous system of starfish Nervous system of aplysia Nervous system of centipede After Marey After Marey After Marey After Marey After Marey From KoUiker From Ludovic From Todd and Bowman From Lehmann (Funke's Atlas) From Lehmann (Funke's Atlas) From Lehmann (Funke's Atlas) After Frey . After Ihlder . After Rouget After Dr. .1. Dean 387 xxu LIST OF ILLUSTRATIONS. 137. Ceretro-spinal system of man 138. Spinal cord 139. Brain of alligator 140. Brain of rabbit . 141. Medulla oblongata of human brain 142. Diagram of human brain 143. Experiment showing irritability of musslea 144. Experiment showing irritability of nerve 145. Action of direct and inverse currents 146. Diagram of spinal cord and nerves 147. Spinal cord in vertical section 148. Experiment, showing effect of poisons upon nerves 149. Pigeon, after removal of the hemispheres 150. Aztec children .... 151. Brain in situ .... 152. Transverse section of brain 153. Pigeon, after removal of the cerebellum 154. Brain of healthy pigeon in profile 155. Brain of operated pigeon in profile 156. Brain of healthy pigeon, posterior view 157. Brain of operated pigeon, posterior view 158. Inferior surface of brain of cod 159. Inferior surface of brain of fowl 160. Course of optic nerves in man 161. Distribution of fifth nerve upon the face 162. Facial nerve .... 163. Pneumogastric nerve 164. Diagram of tongue 165. Distribution of nerves in the nasal passages 166. Vertical section of eyeball 167. Dispersion of rays of light 168. Action of crystalline lens 169. Action of lens, when too convex 170. Action of lens, when too flat 171. Vision for distant objects 172. Vision for near objects 173. Refraction of lateral rays 174. Skull, as seen by left eye 175. Skull, as seen by right eye 176. Human auditory apparatus 177. Great sympathetic 178. Cat, after division of sympathetic in the neck 179. Different kinds of infusoria 180. Trichina spiralis 181. Tsenia 182. Cysticercus, retracted 183. Cysticercus, unfolded 184. Blossom of Convolvulus 185. Single articulation of Taenia crassioollis 186. Human ovum .... LIST OF ILLUSTRATIONS. JXlll no. 187. Human ovum, ruptured by pressure 188. Female generative organs of frog 189. Mature frogs' eggs 190. Female generative organs of fowl 191. Fowl's egg ... 192. Uterus and ovaries of the sow 193. Generative organs of human female 194. Spermatozoa 195. Graafian follicle . 196. Ovary with Graafian follicle ruptured 197. Graafian follicle, ruptured and filled with blood 198. Corpus luteum, three weeks after menstruation 199. Corpus luteum, four weeks after menstruation . 200. Corpus luteum, nine weeks after menstruation 201. Corpus luteum of pregnancy, at end of second month 202. Corpus luteum of pregnancy, at end of fourth month 203. Corpus luteum of pregnancy, at term 204. Segmentation of the vitellus 205. Impregnated egg, showing embryonic spot 206. Impregnated egg, showing two layers of blastodermic membrane 207. Impregnated egg, farther advanced 208. Frog's egg, at an early period 209. Egg of frog, in process of development 210. Egg of frog, farther advanced 211. Tadpole, fully developed ■212. Tadpole, changing into frog 213. Perfect frog 214. Egg of fish 215. Young fish, with umbilical vesicle 216. Human embryo, with umbilical vesicle 217. Fecundated egg, showing formation of amnion . 218. Fecundated egg, showing commencement of allantois 219. Fecundated egg, with allantois nearly complete 220. Fecundated egg, with allantois fully formed 221. Egg of fowl, showing area vasculosa 222. Egg of fowl, showing allantois, amnion, &o. 223. Human ovum, showing formation of chorion 224. Compound villosity of human chorion 226. Extremity of villosity of chorion 226. Human ovum, at end of third month 227. Uterine mucous membrane 228. Uterine tubules. . 229. Impregnated uterus, showing formation of decidua 230. Impregnated uterus, showing formation of decidua reflexa 231. Impregnated uterus, with decidua reflexa complete 282. Impregnated uterus, showing union of chorion and decidua 233. Pregnant uterus, showing formation of placenta 234. Foetal pig, with membranes 235. Cotyledon of cow's uterus 236. Extremity of foetal tuft, human placenta XXIV LIST OF ILLUSTEATIONS. PIG. 237. Foetal tuft of human placenta injected 238. Vertical section of placenta 239. Human ovum, at end of first month 240. Human ovum, at end of third month 241. Grayid human uterois and contents 242. Muscular fibres of unimpregnated uterus 243. Muscular fibres of human uterus, ten days after parturition 244. Muscular fibres of human uterus, three weeks after parturition 245. Formation of cerebro-spinal axis 246. Formation of cerebro-spinal axis 247. Foetal pig, showing brain and spinal cord 248. Foetal pig, showing brain and spinal cord 249. Head of foetal pig 250. Brain of adult pig 251. Human embryo, about one month old 252. Formation of alimentary canal . 253. Foetal pig, showing umbilical hernia 254. Human embryo, about one month old 255. Head of human embryo, at end of sixth week 256. Head of human embryo, at end of second month 257. Foetal pig, showing WolfSan bodies 258. Foetal pig, showing first appearance of kidneys 259. Internal organs of generation . 260. Internal organs of generation 261. Formation of tunica vaginalis testis 262. Congenital inguinal hernia 263. Egg of fowl, showing area vasculosa 264. Egg of fish, showing vitelline circulation 265. Young embryo and its vessels 266. Embryo and its vessels, farther advanced 267. Arterial system, embryonic form 268. Arterial system, adult form 269. Early condition of venous system 270. Venous system, farther advanced 271. Continued development of venous system 272. Adult condition of venous system 273. Early form of hepatic circulation 274. Hepatic circulation farther advanced 275. Hepatic circulation, during latter part of foetal life 276. Adult form of hepatic circulation 277. Foetal heart 278. Foetal heart 279. Foetal heart 280. Foetal heart 281. Heart of infant 282. Heart of human foetus, showing Eustachian valve 283. Circulation through the foetal heart 284. Circulation through the adult heart 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 INTEODUCTION. 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 brougLi 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 ito 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 \hB 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 Tege- 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. Coiisequently, 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 exan^le, when lie 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 neiyer he in the hast degree inf&rredTfrom 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- 40 iNTRODucTiorr. ditions necessary for their accomplishment exist in the body, and do not exist elsewhere. All chemical phenomena are liable to be modified by surrounding conditions. Many reactions, for example, which will take place at a high temperature, will not take place at a low temperature, and vice versd. Some will take place in the light, but not in the dark ; others will take place in the dark, but not in the light. 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, of animals or vegetables, and which cannot be formed elsewhere; such as fibrin, albumen, casein, pneumio acid, the biliary salts, morphine, ka. 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. 4.1 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 4:2 INTEODUCTION. 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 Nutei- TION of the body in its widest sense. It comprises the history of the proximate principles, their source, the manner of their produc- tion, the proportions in which they exist in different kinds of food and drink, the processes of digestion and absorption, and the 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 IKTBODUCTION. 43 sensation, movement, consciousness, and volition. They are more particularly distinguished by the name of the aniTnal functions. Lastly comes the study of the entire process of Kepkoduction. 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. NUTRITION. CHAPTER I. PEOXIMATE 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 organ, again, on microscopic examination, is seen to be made (45 ) 46 PROXIMATE PBINOIPLES IN GENEBAL. 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 dt is this character which constitutes its organization. But beside the abpve 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 peoximate 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- diepts. In the hard substance of bone, for example, there is, first PROXIMATE PRINCIPLES IN GENERAL. i? water, whicli 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 thfe 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 PBINCIPLKS IN GENERAL. tteirs. 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 PKINCIPLES IN GENEKAL. 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 glykocholate 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 farther 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 PBOXIMATE 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 homogeneous in the bones as in the blood. A proximate principle, therefore, never exists a,lone in any part of the body, but is always intimately associated with a number of others, by a kind of homogeneous mixture or solu- tion. Every animal tissue and fluid contains a number of proximate principles which are present, as we have already mentioned, in certain characteristic proportions. Thus, water is present in very large quantity in the perspiration and the saliva, but in very small quantity in the bones and teeth. Chloride of sodium is compara- tively abundant in the 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 all the proximate principles which are purely inorganic in their nature. These principles are derived mostly from the exterior. They are found everywhere, in unorganized as well as in organized bodies ; and they present them- selves under the same forms and with the 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 Eobin and Verdeil,' 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 ' Chimie Anatomique et Physiologique. Paris, 1853. 62 PBOXIMATK 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 PEOXIMITE PEINCIPLES 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 f(d'lowing 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 op Water ih 1,000 parts in Teeth Bones Cartilage . Muscles . Ligaments Brain Blood Synovial fluid 100 Bile . 130 Milk flSO Pancreatic juice 760 Urine 768 Lymph 789 Gastric juice 795 Perspiration 805 Saliva 880 887 900 936 960 975 986 995 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 OHLOKIDE 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, yiz., 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 expejled in this way, about 48 per cent, is discharged with the urine and feces," and about 52 per cent, by the lungs and skin. The researches of Lavoisier and Seguin, Yalentin, 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 versd. The quantity of water exhaled from the lungs varies also with the state of the pulmonary circulation, and with the temperature and dryness of the atmosphere. The water is not discharged at any time in a state of purity, but is mingled in the urine and feces with saline substances which it holds in solution, and in the cutaneous and pulmonary exhalations with animal vapors and odoriferouu 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 ■ Op. cit., vol. ii. pp. 143 aud 145, 56 PROXIMATE PEINCIPLES OP THE FIRST CLASS, animal frame depends upon the relative quantity of all the ingre- dients of the fluids, as well as on the constitution of the solids themselves; and the chloride of sodium, as one ingredient among many, influences these phenomena to a great extent, though it does not regulate them exclusively. It exerts also an important influence on the solution of various other ingredients, with which it is associated. Thus, in the blood it increases the solubility of the albumen, and perhaps also of the earthy phosphates. The blood-globules, again, which become dis- integrated and dissolved in a solution of pure albumen, are main- tained in a state of integrity by the presence of a small quantity of chloride of sodium. It exists in the following proportions in several of the solids and fluids :'— QCANTITT OF CBLOBIDE OP SODIUM IN 1,000 PAHTS IN THE Muscles .... 2.0 Perspiration .... 2.2 Bones .... 2.5 Urine .... 3.0 Cartilage .... 2.8 Bile . . . . 3.5 Milk .... 1.0 Blood .... 4.5 Saliva .... 1.5 Mucua .... 6.0 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 suflicient 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 ' Robin and Verdeil. CHLOEIDE 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 : — * " 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 matket 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. ' Chimie Agrioole, Paris, 1854, p. 271. 58 PROXIMATE PRINGIPLES OF THE FIRST CLASS. It is discharged with the urine, mucus, cutaneous perspiration, &o., 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: — Qdaktitt of Phosphate op Lime iu 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 cartikges 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 Eobin and Verdeil, op. clt., vol. ii. 193. PHOSPHATE OF LIME. 59 but is intimately ninited witli 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 stiflmess 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.) The phosphate of lime in the body, like most of the inorganic FlBUlA TIED 1.1 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 PRIITOIPLES OF THE FIRST CLASS. proximate principles, is derived directly from tlie food ; as it exists, in various proportions, not only in all kinds of animal food, but also in all the cereal grains, the nutritive roots and tuberous plants, and even in nearly all the fruits. After forming, for a time, a part of the tissues and fluids, it is discharged from the body by the urine, the perspiration, mucus, Sec. Much the larger portion is discharged by the urine. A small quantity also occurs in the feces, but this is probably 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, neoessa,ry to life ; for it is found that, iu the living animal, if a mineral acid be gradually injected into the blood, so dilute as not to coagulate the albumen, death takes place before its alkaline reaction has been completely neutralized.' The carbonate of soda of the blood is partly introduced as such with the food ; but the greater part of it is formed within the body by the decomposition of other salts, introduced with certain fruits and vegetables. These fruits and vegetables, such as apples, cher- ries, grapes, potatoes, &c., contain malates, tartrates, and citrates of soda and potassa. Now, it has been often noticed that, after ' Cl. Bernard. Lectures on the Blood ; reported by W. P. Atlee, M. D. Phila- delphia, 1854, p. 31. PHOSPHATES OP MAGNESIA, SODA, AND POTASSA. 61 tbe use of acescent fruits and vegetables containing the above salts, the urine becomes alkaline in reaction from the presence of the alkaline carbonates. Lehmann ' found, by experiments upon his own person, that, within thirteen minutes after taking half an ounce 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 urinq became alkaline at the end of five, or, at the latest, of twelve minutes. The conversion of these salts into carbonates takes place, therefore, not in the intestine but in the blood. The same observer' found that, in many persons living on a mixed diet, the urine became alkaline in two or three hours after swallowing ten grains of acetate of soda. These salts, therefore, on being introduced into the animal body, are decomposed. Their organic acid is destroyed and replaced by carbonic acid ; and they are then discharged under the form of carbonates of soda and potassa. 7. Cabbonate 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 aoda. 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. Eor 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 'Physiological Chemistry. Philadelphia ed., vol. i., p. 97. 'Physiological Chemistry, vol. ii., p. 130. 62 PROXIMATE PRINCIPLES OF THE FIRST CLASS. organic acids, which give rise, as already deseribed, 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, 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 process of nutrition. PBOXIMATE PKINCIPLES OF THE SECOND CLASS. 63 CHAPTEE III. PROXIMATE PRINCIPLES OP THE SECOND CLASS. The proximate principles belonging to the second class are divided into three principal groups, viz : starch, sugar, and oil. They are distinguished, in the first place, by their organic origin. Unlike the principles of the first class, they do not exist in external 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. Stahoh (CijHjjOjo). — 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, &o., 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 : — ' < ' Perelra on Food and Diet, New York, 1843, p. 59. 64 PROXIMATE PRINCIPLES OF THE SECOND CLASS. Quantity op Stabch IN 100 PARTS IN Rice . 85.07 Wheat flour . . 72.00 Maize . . 80.92 Iceland mos3 . 44.60 Barley meal . . 67.18 Kidney bean . . 35.94 Eye meal . 61.07 Peas . 32.45 Oat meal . 69.00 Potato . . 15.70 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 bo 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 tAvs, the largest ^^-g 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 Grains of Potato Stabch. Fig. 3. hilum, 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 HEISTS to 5^^ of an inch in diameter. They are elongated and cylindrical in form, and the concentric markings are less distinct than in the pre- .btabch gbaihs op bbbmuda abeowboot. ceding variety. The hilum STARCH. 65 Starch Grains of Wheat Fxoub 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 TuiiTT to Tse of an inch ^'*" *" in diameter. They are nearly circular in form, with a round or transverse hilum, 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- dient of the animal body. It was first observed by Purkinje, and afterward by Kdlliker,' that certain bodies are to be found in the interior of the brain, about the late- ral ventricles, in the fornix, septum lucidum and other parts, which present a cer- tain resemblance to starch grains, and which have.there- fore been called "corpora amylacea." Subsequently Virchow* corroborated the above observations, and ascertained the corpora amylacea to be Stabch Grains 0? Indiav CoBir. ' Handbnch der Oewebelehre, Leipzig, 1852, p. 311. ' In American Journal Med. Soi., April, 1854, p. 466. 66 PROXIMATE PRINCIPLES OF THE SECOND CLASS. Starch Gra[ns from Walt, of Lateral Ventricles; from a woman aged 35. really substances of a starchy nature ; since ttey exhibit the usual chemical reactions of vegetable starch. The starch granules of the human brain (Fig. 6) are transparent and colorless, like those ff om ^'^- ^- plants. They refract the light strongly, and vary in size from j^Vir to ■r-['^^ of an inch. Their average is yg'^^ 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 hilum, 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. 07 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 tinie 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° ¥., 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 goiH;^ 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. The varieties of sugar most familiar to us are the fol- lowing : — Cano eugar, Grape sugar, Sugar of starch, Milk sugar, Liver sugar. 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 glu- cose, may be produced by boiling starch for a long time with a dilute 68 PROXIMATE PEINCIPLES OF THE SECOND CtASS. aoid, and is also formed, in certain plapts, by the transformation of their starchy ingredients. Liver sugar and sugar of milk are pro- duced in the tissues of the liver and the mammary gland, by a process of secretion. Honey contains a mixture of several varie- ties of sugar, including- cane sugar and glucose, collected from the sweet juices qf flowering plants and mingled with certain animal ingredients. These varieties of sugar differ but little in their. ultimate chem- ical composition. The following formulse have been established for three of them. Cpine sugar = Cj2H,jO|i Milk sugar = C,jHjjO,j Glucose , = Cf2^jjPif 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 Trommer's test. It depends upon the fact that the saccharine substances have the power of reducing the persalts of copper when heated with them in an alkaline solution. The test is applied in the following manner : A very small quantity 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 SUGAR. 69 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 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 suificient 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 suf&cient 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 more delicate form of the copper test for glucose, is that known as Fehling's liquor, which is an alkaline solution of a double tartrate of copper and potash. It is made as follows : — 70 PROXIMATE PBINCIPLES OF THE SECOND CLASS. Pure crystallized Sulphate of Copper, 500 grains. Neutral Tartrate of Potassa, 2000 grains. A solution of Caustic Soda (of the specific gravity 1.12),- 8750 grains. The neutral tartrate of potassa, dissolved in a little water, is first mixed with the solution of caustic soda. Then the sulphate of copper, dissolved in about 4J fluid ounces of water, is gradually added to the alkaline liquor, which assumes a clear deep-blue color. The whole is finally diluted with water to the volume of Slf fluid ounces. The advantage of Fehling's test liquor is that the quan- tity of copper salt contained in a given volume is accurately known, and consequently not only the presence, but also the amount of sugar in any liquid may be determined by the quantity of test -liquid which it decomposes at a boiling temperature. One cubic centimetre (about J of a fluid, drachm) of Fehling's ' liquor is exactly decolorized by .077 of a grain of glucose. The test is also a very delicate one. One drop of Fehling's liquor will detect yj'g^ of a grain of glucose, dissolved in one cubic centimetre of water, if the test be carefully applied. One precaution however must be taken in the use of this test. As Fehling's liquor is apt to become changed after being exposed for some time to the air, so that it will partially precipitate on boiling even without the presence of sugar, it is essential in every case where a suspected liquid is examined for sugar, that a small portion of the test liquid employed should be previously boiled in order to be sure that it will not precipitate spontaneously. A less convenient but still valuable 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. K the gas be found to be carbonic acid, and the remaining fluid contain alcohol, there can be no doubt that sugar was present at the commencement of the operation. The following list shows the percentage of sugar in various articles of food.' " ' Pereira, op. cit., p. 55. PATS. 71 Qua NTITY OP SdOAB in 100 PARTS IS Figs . 62.50 Wheat flour . 5.40 Cherries 18.12 VLye meal 3.28 Peaches 16.48 Inilian 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 almondd 6.00 Ilumau milk 6.50 Barley meal . . 5.21 Beside the sugar, therefore, which is taken into the alimentary caaal 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 = Cs,, H„ 0,. Margarine ......= C-g Il,j 0,, Stearine = C„jH„,0„ 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, 72 PROXIMATE PKINCIPLES OP THE SECOND CLASS. whicli is a neutral fluid substance, and secondly, a fatty acid, viz ; oleic, margaric, or stearic acid, corresponding to the kind of fat whicli has been used in the experiment. The glycerine remains in a free state, while the fatty acid unites with the alkali employed, forming an oleate, margarate, or stearate. This combination is termed a soap, and the process by which it is formed is called saponification. This process, however, is not a simple decomposition of the fatty body, since it can only take place in the presence of water; several equivalents of which unite with the elements of the fatty body, and enter into the composition of the glycerine, &c., so that the 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 '^* ' 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. Stearibb crystallized from Oleine. Warm Solution in FATS. 73 These substances crystallize in very slender needles, which are sometimes straight, but more often somewhat curved or wavy in their outline. (Fig. 7.) They are always deposited in a more or less radiated form ; and have sometimes a very elegant, branched, or arborescent arrange- ment. When in a fluid state, the fatty substances present themselves under the form of drops or globules, which vary 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 Oleaoinops Principles op Human Fat. Stearioe and Margarine crystallized ; Oleine flnid. 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.' Qhaxtity op Fat is 100 parts in 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 Tolk 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 > Fereira, op. cit., p. 81. 74 PROXIMATE PBINCIPLES OF THE SECOND CLASS. 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 theni 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 FATS. 75 HuHAy Adipose Tissue. of health. These vesicles are transparent, and Lave a somewhat angular form, owing to their mutual compression. (Fig. 9.) They vary in diameter, in the hu- man subject, from yim to j^^ of an inch, and are composed of a thin, structureless ani- mal membrane, forming a closed sac, in the interior of which the oily matter is con- tained. There is here, accord- ingly, no union whatever of the oil with the other proxi- mate principles, but only a mechanical inclusion of it in the interior of the vesicles. Sometimes, when emaciation is going on, the oil partially dis9,ppears 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- Fig. 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 y^r Jstf 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 Crtle, from commeDcement of Thoracic- Duct, from the Dog, 76 PEOXIMATE PRINCIPLES OF THE SECOND CLASS. 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- tides, which have a different refractive power from the serous fluid, interfere with its transparency and give it the white color and ^'S' ■^ • 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 ^xjVtr of ^^ 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. Ckllb of Costal Caktilaous, caotaining Oit Globules. Humaa. FATS. 77 Fig. 13. Hepatic Cells. Human, In the glandular oells 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 globules than the preceding. In some cases of disease, it accumulates in excessive quantity, and produces the state known as fiatty degene- ration of the liver. This is consequently only an ex- aggerated condition of that which normally exists in health. In the carnivorous animals oil exists in considerable quantity in the convoluted portion of the uriniferous tubules. (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 ^8' 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 nRi>' iFEROus Tubules of Dog, from Cortical Portion of Kidney. 78 PROXIMATE PRINCIPLES OF THE SECOND CLASS. MngCULAB FiBRKB OF HUMAN UtEEUS, weekB 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- 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," M. Persoz on geese,' and finally by those of M. Boussingault on geese, ducks, and pigs.^ The observers first ascertained the quantity of "fat existing in the whole body at the commencement of the experiment. The animals were then subjected to a definite nutritious regimen, in which the quantity of fatty matter was duly ascertained by analysis. The experiments lasted for a period varying, in difierent 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- ' Annales de Chim. et de Phys., 3d series, vol. xiv. p. 400. ' Ibid., p. 408. ' Chimie Agrioole, Paris, 1854. PATS. 73 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 thesaccharine 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. 80 PROXIMATE PRINCIPLES OF THE THIRD CLASS. CHAPTER IV. PROXIMATE PEINCIPLES OF THE THIED 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 Verdeil, 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- tirnes 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," whjle 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 ORGANIC SUBSTANCES. 81 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 = Cj5,Hjj,N,„0,2Sj Albumen ..... = Cj.jH.BaNjjOegSj Casein = CsssHjjgNjsOgoS, 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 6 82 PROXIMATE PBINCIPLES OF THE THIRD CLASS. 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 chants 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. OEGANIC SUBSTANCES, 83 Another peculiar phenomenoQ 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 beimg 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- 84 PBOXIMATK PRINCIPLES OF THE THIED CLASS. lytic action by wliicli starcli 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 F I B E I N. — C A S E I N. 85 at present most thoroughly acquainted. The first seven are fluid, or nearly so, and either colorless or of a faint yellowish tinge. 1. FiBBiN. — 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. 86 PROXIMATE PKINCIPLES OF THE THIRD CLASS. 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 by the action of heat. It differs from it, however, in the degree of temperature necessary to coagulation. For while a tolerably abundant solution of albumen is solidified at 160° F., a solution of globuline only becomes turbid at 180°, and requires for its complete coagulation a temperature of 200°. 5. PEPSiNE.-7-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 Eobin, Bernard, &c., as only an artificial pro- duct of the alteration of the gastric tissues. There seems no good reason, furthermore, why we should not designate by this name the organic substance which really exists in the gastric juice. It occurs in this fluid in very small quantity, not over fifteen parts per thousand, it is coagulable by heat, and also by contact with alco- hol. But fl the alcoholic coagulum be well washed, it is again soluble in a watery acidulated fluid. 6. Pancreatike. — 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 varies somewhat in its degree of fluidity. 7. MuscosiNE is the organic substance which is found in the difterent varieties of mucus, and which imparts to them their con- sistency and other physical characters. The distinguishing char- acter of mucosine is its viscidity, by which it is at the same time glutinous and lubricating to the touch. It has the power of ab- sorbing water to some extent, and becomes thinner and more fluid in proportion to the quantity of water which unites with it. It does not solidify by heat, but is coagulated by acetic acid and'by the contact of alcohol. OSTEIN E. — H E M A T I N E. 87 Some of the mucous secretions are so mixed with other fluids that their consistency is more or less diminished ; others, which remain pure, like that of the mucous follicles of the cervix uteri, are nearly semi-solid. No doubt there are different varieties of mucosine produced by the mucous membranes of different regions of the body ; but little is known with regard to their specific characters. The next three organic substances are solid or semi-solid in consistency. 8. Osteins 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. Caktilagine. — 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. Oartilagine, 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 88 PROXIMATE PRINCIPLES OF THE THIRD CLASS. 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 haema- tine to seventeen parts of globuline. The following is the formula for its composition which is adopted by Lehmann : — Hematine ^ CjjH^jNjOgPe. When the blood-globules from any cause become disintegrated, the haematine is readily imbibed after death by the walls of the blood- vessels and the neighboring parts, staining them of a deep red color. This coloration has sometimes been mistaken for an evidence of arteritis ; but is really a simple efiect 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. UROSACINE. 89 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. Thudiohum,' 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 readQy adheres to insoluble matters when they are precipitated from the urine, and is consequently found almost always, to a greater or less extent, as an ingredient in urinary calculi formed of the urates 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 oi 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, haematine, 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. > British Medical Journal, Nov. 5th, 1864. 90 PROXIMATE PRINCIPLES OF THE THIRD CLASS. 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. 91 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,' that if the animals > Comptes Rendus, vol, xiii. p. 256. 92 OF POOD. 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. 93 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,^ 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, ' Natural History of Bees, Edinburgh, 1821, p. 330. ' Annates de Cliim. et de PI173., 3d series, vol. xiv. p. 400. , 94 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, sufBicient for the nutrition of the animal body. Magendie found that dogs, fed exclusively on starch or sugar, perished after a short time with symptoms of profound disturbance of the nutritive functions. An exclusive diet of butter or lard had a similar effect. The animal became exceedingly debilitated, though without much emaciation; and after death, all the internal organs and tissues were found infiltrated with oil. Boussingault' performed a similar experiment, with a like result, upon a duck, which was kept upon an exclusive regimen of butter. " The duck received 1350 to 1500 grains of butter every day. At the end of three weeks it died of inanition. The butter oozed from every part of its body. The feathers looked as though they had been steeped in melted butter, and the body exhaled an unwholesome odor like that of butyric acid." Lehmann was also led to the same result by some experiments which he performed upon himself for the purpose of ascertaining the effect produced on the urine by different kinds of food.' This observer confined himself first to a purely animal diet for three weeks, and afterwards to a purely vegetable one for sixteen days, without suffering any marked inconvenience. He then put himself upon a regimen consisting entirely of non-nitrogenous sub- stances, starch, sugar, gum, and oil, but was only able to continue this diet for two, or at most for three days, owing to the marked disturbance of the general health which rapidly supervened. The unpleasant symptoms, however, immediately disappeared on his return to an ordinary mixed diet. The same fact has been esta- blished more recently by Prof. Wm. A. Hammond,^ in a series of experiments which he performed upon himself. He was enabled to live for ten days on a diet composed exclusively of boiled starch and water. After the third day, however, the general health began ' Chimie Agricole, p. 166. ' Journal fur praktische Chemie, vol. xxvii. p. 257. ^ Experimental Researches, &c., being the Prize Essay of the American Medical Assodiation for 1857. OF FOOD. 95 to deteriorate, and became very much disturbed before tbe 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 ' Comptes Eendus, 1841, vol. xiii. p. 2'7. 96 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. 97 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 th^e 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 suf&cient 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 98 OF FOOD. adopted by the universal and instinctive choice of man, the three difierent 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 beloAging to the saccharine group, together with water and saline matters, in the following proportions : — ' Composition op 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 " magnesia ...... Alkaline carbonates Iron, &o 0.60 100.00 The cereal grains contain albuminoid matters, starch, gum, fat, and salts. The mineral ingredients comprise, according to Payen' and others, the phosphates of lime and magnesia, sulphate of po- tassa, traces of the chlorides of sodium and potassium, together with sulphur and silica. In wheat flour, gluten is the albuminoid matter, sugar and starch the non-nitrogenous principles. ■Composition of Wheat Floue. Gluten .... 7.30 Gum .... 3.30 Starch .... 72.00 Water .... 12.00 Sugar .... 5.40 100.00 The other cereal grains mostiy contain oil in addition to the above. ' The accompanying analyses of various kinds of food are taken from Pereira on Food and Diet, New. York, 1843. 2 Precis des substances alimentaires. Paris, 1865, p. 265. OF FOOD. 99 Composition op Dried Oatmeal. Starch 59.00 Bitter matter and sugar 8.25 Gray albuminous matter . . . . , . . .4.30 Fatty oil 2.00 Gum 2.50 Husk, mixture, and loss 23.95 100.00 Eggs contain albumen and salts in the white, with the addition of oily matter in the yolk. Composition op Egos. White of Egg. Tolk 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 butchef.s meat, we have the albuminoid Aiatter of the muscular fibre and the fat of the adipose tissue. Composition op Ordinaky Butchrh's Meat. Water • 63.42 ' Solid matter . . . .22.28 Fat, cellular tissue, &o 14.30 i 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 100 OF FOOD. be altogetlier witliout 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 . . . . Si " " 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. 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 qartilages, 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 OF FOOD. 101 the appetite and stimulates tlie flo'yr 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. 102 DIGESTION. CHAPTER VI. DIGESTION. Digestion is that process by whicli 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 moiith to anus, called the "alimentary canal," in which it comes in contact with certain digestive fluids, which act DIGESTION". 103 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 difierence 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 104 DIGESTION. glandular, and is provided with numerous se- Kg. 16. crating 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 eflectually operate. The mass then passes into the intes- tine (e), where it meets with the intestinal juices, which complete the process of solution ; and jfrom 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 (6), 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 Alimebtabt Cakai. of Fowl. — a. (EMuphagas. 6. Crop. c. Froventriculus, or secreting stomach, d. Gizzard, or triturating stomach, c. In- testine. /. Two long csecal tubes which open into the in- testine a short distance above its termination. DIGESTION. 105 a boney-combed or reticulated appearance, ^e^a^3lq triturated in the Fig. 17. 1 rS .. ^ c^ ''<^i^ 1 % If ..• * '''" J ? iil H r Compound Stomach op Ox. — a. (Esopha- gus, b. Rumen, or first stomach, c. Reticulum, or second, fourth. d. OmasuB, or third, e Abomasus, /. Duodeaum. (From Rymer Jones.) [bod, already m^outh, and mixed witK the saJfva, is further macerated jnwthe fluids swal- lowed by the animal, which al- ways accumulate in considerable quantity in the reticulum. The next cavity is the omasus, or "psalterium" (cf), 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 ahomasiis, 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 106 DIGESTION. commencement (Fig. 18), we find the cavity of the moutli, ■which is guarded at its posterior extremity by the muscular valve of the isthmus of the fauces. p. ^g Through the pharynx and oesophagus (a), it commu- nicates -with the second compartment, or the sto- mach (6), 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 hiliary and pancreatic ducts (/, g). Finally, we have the large intestine {h, i,j, k), separated from the smaller by the ileo-csecal valve, and ter- minating, at its lower 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 Alimentabt Canal. — a. OSsophaguB. i. Stomach, c. Cardiac orifice. . d. Pylorus, e. Small intestine. /. Biliary duct. g. Pancreatic duct. h. As- cending colon, i. Transrerse colon, J, Descending colon, k, Bectum, DIGESTION. 107 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. Ti^e 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. 108 DIGESTION. 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 fluid ; since, by being broken up into minute particles, it offers a larger surface to the contact of the fluid, and is more readily attacked and dissolved by it. In the structure of the teeth, and their physiological action, there are certain marked differences, corresponding with the habits of the animal, and the kind of food upon which it subsists. In fish and serpents, in which the food is swallowed entire, and in which the process of digestion, accordingly, is comparatively slow, the teeth are sipiply 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 skuli or kattieskake. ,. 1 1 ,1.-1 1,1 ••1 (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 MASTICATION. 109 Fig. 20. edges, each presenting several skarp 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 Bear. Anterior Tiew ; showing incisoru and canines. Fig. 21. Seitll of the Hossb. Fig. 22. 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 betweea 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- molak Tooth of yora. (Fig. 23.) The incisors (a), four in number lagnMrbM^' '" ii each jaw, have, as in other instances, a cutting no DIGESTION. Fig. 23. Human Teeth — Upper Jaw. — a. Incisors. . Anterior molars, d. Posterior molars. edge running from side to side. The canines (J), 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 thecarnivora. 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 im- portance, 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 SALIVA. Ill 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- scope (Fig. 24), is seen to Fig. 24. Buccal AND Glandular Epithelium, witli Granular Matter and Oil-globules; deposited as sedi- ment from human saliva. consist of abundant epithe- lium scales from the internal surface of the mouth, de- tached by mechanical irrita- tion, minute, . roundish, gra- nular, nucleated cells, appa- rently epithelium from the mucous follicles, a certain amount of granular matter, and a few oil-globules. The supernatant fluid has a faint bluish tinge, and becomes slightly opalescent by boil- ing, and by the addition of nitric acid. Alcohol in ex- cess causes the precipitation According to Bidder and Schmidt,' of abundant whitish flocculi, the composition of saliva is as follows : — CoMPOSiTioN_op Saliva. Water .' 995.16 Organic matter 1.34 Sulpho-oyaiiide of potassium 0.06 Phosphates of soiia, 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 secretioBS 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 VerdauungssBifte und Stoffwechsel. Leipzig, 185ii. 112 DIGESTION, of chloride of iron, whicli 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 35 to jV of an inch in diameter. The other extremity of the canula projects from the mouth, between the lips, and the saliva is collected as it runs from the open orifice. This method gives results much more valuable than observations made on salivary fistulas and the like, since the secretion is obtained under leriectly healthy conditions, and unmixed with other animal fluids. SALITA. 113 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 diSerent days, comprising in all three hours and nine minutes, we have collected a little over 3000 grains. The parotid saliva obtained in this way has been analyzed by Prof Maurice Perkins, with the following result : — Composition op Human Paeotid Sahva. Water 983.308 Organic matter precipitable by alcohol 7.352 Substance destructible by heat, but not precipitated by alcohol or acids 4.810 Sulpho-oyanide 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 Prof 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 8 114 DIGESTION. 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. CoHn, Professor of Anatomy and Physiology at the Veterinary School of Alfort/ viz., that in the horse and ass, as well as in the cow and other ruminat- ing animals, the parotid glands of the two opposite sides, during mastication, are never in active secretion at the same time ; but that they alternate with each other, one remaining quiescent while the other is active, and vice 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 ihactive. 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,' who collected from two to three ounces in twenty-four hours from an accidental salivary fistula of Steno's ' Traitg de Physiologie ComparSe, Paris, 1854, p. 468. ' Simon's Chemistry of Man. Phila. ed., 1846, p. 295. SALIVA. 115 duct in the Iniman subject ; from whicli 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 prodiieed 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 breads 4572 grains. ' " " ' meat = 3360 " secreted in intervals of meals = 1 2232 " Total quantity in twenty-four hours ^ 20164 grains ; or rather less than 3 pounds avoirdupois. ' Op. cit., p. 14. 116 DIGESTION. The most important question, connected with this subject, relates to the fuTiction of the saliva in the digestive process. A very remark- able property of this fluid is that which was discovered by Leuchs in Germany, viz., that it possesses the power of converting boiled starch into sugar, if mixed with it in equal proportions, and kept for a short time at the temperature of 100° F. This phenomenon is one of catalysis, in which the starch is transformed into sugar by simple contact with the organic substance contained in the saliva. This organic substance, according to the experiments of Mialhe,' may even be precipitated by alcohol, and 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° P., will yield traces of sugar at the end of half a minute. The rapidity however, with which this action is mani- fested, varies very much, as was formerly noticed by Lehmann, at different times ; owing, in all probability, to the varying constitution of the saliva itself. It is often impossible, for example, to find any evidences of sugar, in the mixture of starch and saliva, under five, ten, or 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 ' Chimie appliqueB h, la Physiologie et h la Therapeutique, Paris, 1856, p. 43. SALIVA. 117 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 is easily recognizable by its reaction with iodine for ten, fifteen, and twenty minutes afterward. In forty-five minutes it is diminished in quantity, and in one hour has usually altogether 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 passagtr 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 118 DIGESTION. from entering tlie cavity of the mouth, its loss does not interfere directly with the chemical changes of the food in digestion, but only with its mechanical preparation. This is the result of direct experi- ments performed by various observers. Bidder and Schmidt,' after tying Steno's duct, together with the common duct of the sub- maxillary and sublingual glands on both sides in the dog, found that the immediate effect of such an operation was " a remarkable diminution of the fluids which exude upon the surfaces of the mouth ; so that these surfaces retained their natural moisture only so long as the mouth was closed, and readily became dry on exposure to contact with the air. Accordingly, deglutition became evidently difiicult 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." Bernard' also found that the only marked effect of cutting off the flow of saliva from the mouth was a dif&culty 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- •I ' Op. oit., p. 3. ' Lemons de Physiologie Expgrimentale, Paris, 1856, p. 146. GASTRIC JUICE, AND STOMACH DIGESTION. 119 phagus was opened at tte 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,' performed upon a horse : — Kind op Food employed. Qdantity of Saliva absoebed. 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 pnce 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 13 accomplished. It is triturated and disintegrated by the teeth, and, at the same time, by the movements of the jaws, tongue, and flheeks, 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 ' Comptes Eendas, vol. xxi. p. 362. 120 DIGESTION", 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, Tiewed from above; from Pig's Sto- macb, Cardiac portion. Magnified 70 diameters. Fig. 26. Free surface of Gastric Mucous Mrhbrahe, viewed ia 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- tiivns 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, ^-f ^ 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 forming a little mass or lobule of glandular tubes. At their upper GASTRIC JUICE, AND STOMACH DIGESTION". 121 Fig. 27. extremities, they open on tlie 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- brame, another kind of glan- dular organ, consisting of closed follicles, similar to the solitary glands of the smaU intestine. These fol- licles, which are not very numerous, are seated in the lower part of the mucous membrane, and enveloped by the caecal extremities of the tubules. (Fig. 27, a.) In the cardiac portion of MucoiTB Membrane OF Pig's Stomach, from ^ Pyloric portion ; vertical section ; showing gastric the StOmach the Superficial tubules, and, at a, a closed follicle. Magnified 70 ^^ ^f ^j^^ mUCOUS mcm- diameters. ^ 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 fbom Pig's Stohagk, Py^loric portion, showing their Cscal Extremities. At a, the torn extremity of a tuhule, showing its cavity. Pig. 29. Gastric Tubulbs from Pig's Stomach; Cardiac portion. At a, a large tubule dividing into two small ones. b. Portion of a tubule, been endwise, c. Its central cavity. 122 DIGESTION. Gasteio Idbcles from Fig's Stouach- middla portion. 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- '^' 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 fill their entire cavity and 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 GASTRIC JUICE, AND STOMACH DIGESTION. 123 probably with many impurities, by causing the animals upon whicli they experimented to swallow sponges attached to the ends of cords, by which they were afterward withdrawn, the fluids which they had absorbed being then expressed and examined. The first decisive experiments on this point, however, were those performed by Dr. Beaumont, of the U. S. Army, on the person of Alexis St. Martin, a Canadian boatman, who had a permanent gas- tric fistula, the result of an accidental gunshot wound. The musket, which was loaded with buckshot at the time of the accident, was discharged, at the distance of a few feet from St. Martin's body, in such a manner as to tear away the integument at the lower part of the left chest, open the pleural cavity, and penetrate, through the 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.' 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 solv-ent 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. &o. Since Dr. Beaumont's time it has been ascertained that similar gastric fistulse 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 ' ExperimentB and Observations upon the Gastrio Juice. Boston, 1834. 124 DIGESTION. through the abdominal parietes in the median line, over the great curvature of the stomach. The anterior waU 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 suflicient quantity of gastric juice for examination, by gently irri- tating the mucous membrane with a gum-elastic catheter, or the end of a glass rod, and by collecting the secretion as it ran in drops from the fistula. On, the introduction of food, he found that the mucous membrane became turgid and reddened, a clear acid fluid collected everywhere in drops underneath the layer of mucus lin- ing the walls of the stomach, and was soon poured out abundantly into its cavity. "We have found, however . that the rule laid down GASTRIC JUICE, AND STOMACH DIGESTIOIT. 125 by Dr. Beaumont ia 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 foodi 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 sufiScient to moisten the gastric mucous membrane, and give it an acid reaction. The gastric juice, which is obtained by irritating the stomach with a metallic catheter, is clear, perfectly colorless, and acid in reaction. A suf&cient quantity of it cannot be obtained by this method for any extended experiments ; and for that purpose, the animal should be fed, after a fast of twenty-four hours, with fresh lean meat, a little hardened by short boiling, in order to coagulate the fluids of the muscular tissue, and prevent their mixing with the gastric secretion. No effect is usually apparent within the first five minutes after the introduction of the food. At the end of that time the gastric juice begins to flow ; at first slowly, and in drops. It is then perfectly colorless, but very soon acquires a slight amber tinge. It then begins to flow more freely, usually in drops, but often running for a few seconds in a continuous stream. In this way from |ij to Siiss may be collected in the course of fifteen 126 DIGJISTION. minutes. Afterward it becomes somewhat turbid witb 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 foUoTsdng 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 op Gastric Juice. Water 975.00 Organic matter 15.00 Lactic acid 4.78 Chloride of sodium 1.70 " " potassium 1.08 " " calcium 0.20 " " ammonium 0.65 Phosphate of lime 1.48 " " magnesia . . . 0.06 « " iron 0.05 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. Eobin and Ver- deil also regard the acid reaction of the gastric juice as due to lac- tic acid; and, finally, Bernard has shown,' 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, which enter into the composition of the fresh juice. I Lefons de Fhysiologie Exp^rimentale, Paris, 1856, p. 396. GASTEIO JUICK, AND STOMACH DIGESTION. 127 Prof. G. Schmidt,' 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 insufScient grounds, as a product of the alteration of the mucus of the stomach. But whatever be its source, since it is ' Annalen der Chemip and Pharmacie, 1854, p. 42. 128 DIGESTION. 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. Pe,psine 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. Fig- 31. 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 j nice is also affected in a remarkable manner by being mingled with hile. We have found that four to six drops of dog's bile precipitate completely with 3j of gastric juice from cospERToiD veoetabi.e, growing in the Gas- the samo animal; so that the trie Juice of the Dog. Tiie fibres have an average . . „ . i 'i- i • diameter of 1-7000 of an inch. whole ot the bihary colormg 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 coq- 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 accompapied 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 GASTRIC JUICE, AND, STOMACH DIGESTION. 129 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 ojly 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. 9 130 DIGESTION. 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° ¥., 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 GASTRIC JUICE, AND STOMACH DIGESTION. 131 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 Hehdomadaire for February 9th, 1355.' 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 maqprated 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 ^fter 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 tbe 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- ' American Journ. Med. Soi., Oct. 1854, p. 319. 2 Nouvelles recherches relatives i. Taction du sue gaatrique sur les substances albuminoides. — Gaz. Held. 9 F^vrier, 1855, p. 103. 132 DIGESTION. ture of honey and gastric juice in equal volumes, no reduction of copper tates 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 js 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 tincttire 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 aiid 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- GASTRIC JUICE, AND STOMACH DIGESTION. 133 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 sufiScient 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 all- 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- 134 DIGESTION. 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 difierent 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. -By 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. Hooks. Minittes. Pig's- feet 1 oa Tripe 1 00 Trout (broiled) 1 30 Yenison steak 1 35 Milk (boiled) 2 00 Eoasted turkey 2 30 « beef 3 00 mutton 3 15 Veal (broiled) 4 00 Salt beef (boiled) 4 15 Koasted 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 24 hours, in the same ani- mal, would be 3 J pounds ; and, by applying the same calculation to GASTEIC JUICE, AND STOMACH DIGESTION. 135 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,' 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 iiss of gastric juice at 100° F. ; the mixture being thoroughly agitated as often as every hour, in order to insure the digestion of as large a quantity of meat as possible. The meat remaining undissolved was then collected on a previously weighed filter, and evaporated to dryness. The dry residue weighed 55 grains. This represented, allowing for the loss by evaporation, 250 grains of the meat, in its natural moist condition ; 50 grains of meat were then dissolved by 3iss of gastric juice, or 33J grains per ounce. From these data we nan 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, ' Annalen der Chemie und Pharmacie, 1854, p. 42. 136 DIGESTION. 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 Eeaumur and Spallanzani, that digestion was a process of chemical solution performed by a digestive fluid. It was said to be impossible that a fluid capable of dissolving animal matters should be secreted by the walls of the stomach without attacking them also, and thus destroying the organ by which it was itself produced. Since that time, various complicated hypotheses have been framed, in order to reconcile these apparently contradictory facts. The true explanation, however, as we believe, lies in this — that the process of digestion is not a simple solution, but a catalytic transformation of the alimentary substances, produced by contact with the pepsine of the gastric juice. We know that all the or- ganic substances in the living tissues are constantly undergoing, in GASTRIC JUICE, AND STOMACH DIGESTION. 137 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 gaslirio 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 slibject 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, 138 DIGESTION. or vexation, ■will take away the appetite and interfere with diges- tion. Any nervous impression of this kind, occurring at the com- mencement of digestion, seems moreover to produce some change which has a lasting effect upon the process ; for it is very often noticed that when any annoyance, hurry, or anxiety occurs soon after the food has been taken, though it may last only for a few moments, the digestive process is not only liable to be suspended for the time, but to b^ 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 Staech. — 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 intestiae. 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 Sss 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 cane sugar be given to a dog with a gastric fistula, while digestion of meat is going on, it disappears in from two to three hours, without any glucose being detected in the fluids withdrawn from the stomach. It is, therefore, either directly absorbed under the form of cane sugar, or passes, little by little, into the duodenum, where the intestinal fluids at once convert it into glucose. It is equally certain that starchy matters are not digested, in the stomach, but pass unchanged into the small intestine. Here they meet with the mixed intestinal fluids, which act at once upon the starch, and convert it rapidly into sugar. The intestinal fluids, taken from the duodenum of a recently killed dog, exert this transforming action upon starch with the greatest promptitude, if mixed with it in a test-tube, and kept at the temperature of 100° F. Starch is converted into sugar by this means much more rapidly and certainly than by the saliva ; and experiment shows that the INTESTINAL JUICES, DIGESTION OF SUGAR, ETC. 139 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, ^'S* ^^■ 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 very complete with regard to the exact nature of the fluids by which this digestion of the starch is accomplished. The juices taken from the duodenum are generally a mixture of three different secretions, viz., the bile, the pancreatic fluid, and the intestinal juice proper. Of these, the bile may be left out of the question ; since it does not, when in a pure state, Follicles of Likbebkithh, fiom Small In- testine of dog. liO DIGESTION. exert any digestive action on starch. The pancreatic juice, on the other hand, has the property of converting starch into sugar ; but it is not known whether this fluid be always present in the duode- num. The true intestinal juice is the product of two sets of glan- dular organs, seated in the substance of or beneath the mucous membrane, viz., the follicles of Lieberkiihn and the glands of Brun- ner. The first of these, or Lieberkiihn's follicles (Fig. 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 glandules, as they are sometimes called, are confined to the upper part of the duo- denum, where they exist as a '^^S- 33. 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. Bach 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 diificulty 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 Buunner's G^LANDS, from Human lutestino. SCODBHAIi PAJSrCBEATIO JUICE, AND THE DIGESTIOH" OF PAT. 141 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 tha,t 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 Lieberkuhn, 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. Panceeatio Juice, and the Digestion op Fat. — The only re- maining ingredients of the food that require digestion are the oily matters. These are not afifected, as we have already stated, by con- tact with the gastric juicp ; 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 valvulse 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 142 DIGESTION. these ducts almost invariably open into the intestine at or near the same point, it was for a long time difficult to decide by which of the two secretions the digestion of the oil was accomplished. M. Bernard, however, first threw some light on this question by ex- perimenting on some of the lower animals, in which the two ducts open separately. In the rabbit, for example, the biliary duct opens as usual just below the pylorus, while the pancreatic duct com- municates with the intestine some eight or ten inches lower down. Bernard fed these animals with substances containing oil, or in- jected melted butter into the stomach ; and, on killing them after- ward, found that there was no chyle in the intestine between the opening of the biliary and pancreatic ducts, but that it was abun- dant immediately below the orifice of the latter. Above this point, also, he found the lacteals empty or transparent, while below it they were full of white and opaque chyle. The result of these ex- periments, which have since been confirmed by Prof. Samuel Jack- son, of Philadelphia,' led to the 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 the whole course of the experiment. Its flow, however, is at all times scanty, compared with that of the gastric juice ; and we have ' American Journ. Med. Sci., Oct. 1854. PANCREATIC JUICK, AND THE DIGES'TION OF FAT. 143 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 specific gravity of 1008 or 1010, and a distinctly alkaline reaction. Its composition, according to the analysis of Bidder and Schmidt, is as follows : — Composition op Pancbeatic Jdice. Water 900.76 Organic matter (pancreatine) 90.38 Cliloride of sodium 7.36 Free soda 0.32 Phosphate of soda 0.45 Sulphate of soda 0.10 Sulpliate of potassa 0.02 , I Lime 54 Combinations of J Magnesia 0.05 I Oxide of iron 0.02 IUOO.IjO 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. After being precipitated by alcohol, the coagulated mat- ter may be re-dissolved in water and thus regain all the original properties of pancreatine. By the last two characters, accordingly, it may be distinguished from albumen, which is not affected by sulphate of magnesia, and which is not soluble in water after being once precipitatfed by alcohol. 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 marked effect. It disintegrates them, and reduces 144 DIGESTION. them to a state of complete emulsion, so that the mixture is at once converted into a white, opaque, creamy-looking fluid. This effect is instantaneous and permanent, and only requires that the two substances be well mixed by gentle agitation. It is singular that some of the German observers should deny that the pancreatic juice possesses the property of emulsioning fat, to a greater extent than the bile and some other digestive fluids ; and should state that although, when shaken up with oil, outside the body, it reduces the oily particles to a state of extreme minuteness, the emulsion is not permanent, and the oily particles "soon separate again on the surface."' We have frequently repeated this experiment with diflerent 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. Eeduced to a soft pulp and mixed abundantly with the saliva, it passes, secondly, into the stomach. Here it excites the secretion of the gastric juice, ' LeJimann's Physiological Chemistry. Philada. ed., vol. i. p. 607. PHENOMEITA OP INTESTINAL DIGESTION. 145 by the influence of whidi 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 10 146 DIGESTION. Fig. 34. "Contents of Stomach bokiko, Dioestiob OF Meat, from llie Dog.— n. Fat Vesicle, filled with opaque, solid, granalar fat. &, b. Bits of partially diniategrated muscular fibre, c. Oil globules. Fig. 35. fibres, fat vesicles, and oil drops; substances whick are easily recognizable under the inicroscop,e, and •wMcb produce a grayish turbidity, in the fluid drawn from the fistula. This turbid admixture grows constantly thicker from the second to the tenth or twelfth hour; after which the intestinal fluids become less abundant, and finally disappear , almost entirely, as the, process of di- gestion comes to an end. The passage of disintegrated muscular tissue into the intes- tine may also be shown, as already mentioned, by killing the animal and, examining the contents of the alimentary canal. During the digestion of muscular flesh and adipose tissue, the stomach contains masses of , softened meat, smeared over with gastric juice, and also a moderate quantity of grayish, grumous fluid, with an acid reaction. This fluid , contains muscular fibres, isolated from each other, and more or less dis- integrated, by the action of the gastric juice. (Fig. 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- Trom Duodekitm of Doo, during Diges- tion OF Meat. — a. Fat Vesicle, with its contents diminishing. The vesicle is beginning to shrivel and the fat breaking up. &, b. Disintegrated muscular fibre, tif c. Oil Olobules. PHENOMENA OF INTESTINAL DIGESTION. 147 Fig. 36. From Middle of Small Intbstive.- Fat vesicles, nettrl7 emptied of their cODtents. Fig. 37. cles also begin to tecome altered in the duodentim. 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 tke 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. Fboh last quabter op Shall Ihtkhtinij. — a, a. Fat vesicles, quite eqipt^r and shrivelled. 148 DIGESTION. 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 ifltestine by excretion. These substances have not all been fully investigated ; for although they are undoubtedly of great importance in regard to the preser- vation of health, yet the peculiar manner in which they are dis- charged by the mucous membrane and united with each other in the feces has interfered, to a great extent, with a thorough investi- gation of their physiological characters. Those which have been most fully examined are the following : — Excretine. — This. was discovered and described by Dr. W. Mar- cet,' as 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, hj'dro- gen, oxygen, and sulphur, in the following proportions: — It is thought to be present mostly in a free state, but partly in union with certain organic acids, as a saline compound. Stercorine. — This substance was found to be an ingredient of the human feces by Prof. A. Flint, Jr." It 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. ' Philoa. Trans., Lend., 1857, p. 410. ' Am. Journ. Med. Sci., Oct., 186a. ABSOBPTION. 149 CHAPTER VII. Kg. 38. ABSORPTION. Beside the glands of Brunner and the follicles of Lieberk'tihn, already described, there are, in the inner part of the walls of the intestine, certain glandular- looking bodies which are termed " glandulse solitarise," and " glandulae agminatse." The glandulsB solitarise are globular or ovoid bodies, about one-thirtieth of an inch in diiameter, situated partly in and partly beneath the in- testinal mucous membrane. Each glaiidule (Fig. 38) is formed of an investing cap- sule, closed on all sides, and containing in its interior a „ . soft pulpy mass, which con- OWE OP THB CLOSED FOLLICLES OP PeTER'S . . Patches, from Small Intestine of Fig. Magnified sistS ofmiuUtC Cellular bodicS, CO diameters. Fig. 39. Olahdul^e AaxiRAT.B, from Small Intestine of Pig. Magnified 20 diameters. imbedded in a homogeneous substance. The inclosed mass is penetrated by capillary bloodvessels, which pass in through the investing cap- sule, inosculate freely with each other, and return upon themselves in loops near the centre of the glandular body. There is no external opening or duct; in fact, the contents of the 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- 150 ABSORPTION. Fig. 40. tissue. The glandulsa 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 EXTKEUITY 07 IHTESTINAI. Villus, from the Dog.— a. Layer of epithelium, b. BloodvesBel. c. Lacteal Teiisel. ABSORPTION. 151 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, vrith 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, tbgether with the refuse of the intestinal secretions. Tliese 152 ABSORPTION. 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 mainly by the bloodvessels. It was formerly supposed that the lacteala ■were the only agents in this process ; but it has now been long known that this opinion was erroneous, and that the blood- vessels 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,' 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 byPanizza,^ 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), which Fig. 41. Pahizza's Experiment. — aa. Intestine, h. Point of ligature of mesenteric vein, v. Opening in intestioe for introduction of poison, d. Opening in mesenteric vein beliind the ligature. > .Journal de Physiologie, vol. i. p. 18. » In Matteuoci's Lectures on the Physical Phenomena of Living Beings, Pereira'" edition, p. 83. ■ABSOBPTION. 153 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 take them up even more rapidly and abundantly than the lacteals. Accordingly the products of digestion, on being taken up by the villi, are absorbed by the capillary bloodvessels and pass into the current of the abdominal venous circulation. After the digestion of food containing a mixture of albuminous and starchy ingredi- ents, both albuminose and sugar are to be found in the blood of the portal vein. These substances, however, do not mingle at once with the general mass of the circulation, but, owing to the ana- tomical distribution of the portal vein, pass first through the capil- lary circulation of the liver. Soon after being introduced into the blood and coming in contact with its organic ingredients, they become altered and converted, by catalytic transformation, into other substances. The albuminose passes, in all probability, into the condition of ordinary albumen, while the sugar rapidly be- comes decomposed, or transformed, and loses its characteristic properties ; so that, on arriving at the entrance of the general cir- culation, both these newly absorbed ingredients have become al- ready assimilated to those which previously existed in the blood. 154 ABSOEPTION. The fatty matters of the digested food are also taken up by the bloodvessels and pass in this way into the circulation. We have already shown that these fatty ingredients, by the action of the pan- creatic juice, are reduced to the condition of an emulsion, forming in the intestine a white milky fluid termed the "chyle." In chyle drawn from the lacteals or the thoracic duct, the fatty mat- ter 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. The oleaginous materials, thus prepared, are absorbed by the bloodvessels of the intestine. The blood of the portal vein during digestion, in the carnivorous animals, contains a considerable amount of fatty matter in a state of minute subdivi- sion, often communicating a turbid or milky appearance to the serum after coagulation ; other observers (Bernard,' Lehmann, Schultz, Simon) have noticed the same fact, and have found the blood of the portal vein to be considerably richer in fat, than that of other veins, particularly whije intestinal digestion is going on wi th acti vity. A difficulty has been experienced in accounting for the absorp- tion 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, ■ Lemons de Fhysiologie Exp^rimentale. Paris, 1856, p. 325. Chtle from comuencemfnt op Thobacio BncT, from the Bog. — The molecules vary in gizo from l-10,OOOth of aa inch downward. ABSOBPTION, 155 like the serum of the blood and the lymph. This has beea de- monstrated by the experiments of Matteucci, in which he made an emulsion with an alkaline fluid containing 43 parts per thou- sand of caustic potassa. Such a solutibn 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 ^^" 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 Bog, while Fig. 44. Intestinal Epitheliuu; 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. 43) these cells are but slightly granular and nearly trans- parent in appearance. But if examined during the diges- tion and absorption of fat (Fig. 44), their substance is seen to be crowded with oily particles, which they have taken up from the intestinal cavity by absorption. The 156 ABSORPTION. 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 in its interior. The fatty substances thus taken up by the portal vein, do not at once enter the general circulation", but pass first through the capil- lary 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. While passing through the pulmonary circulation, 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 emulsion, and are no longer to be recog- nized by the usual tests for ole- aginous substances. The absorption of fatty mat- ters is also accomplished by an- other set of capillary vessels of the intestine, namely, the " lac- teals." Thelacteals, however, are not a special system of vessels by themselves, but are simply a part of the great system of " ab- sorbent" or "lymphatic" ves- sels, which are to be found everywhere in the integuments of the head, the parietes of the trunk, the upper and lower ex- tremities, and in the muscular tissues and mucous membranes throughout the body. The walls of these vessels are thin- ner and more transparent than those of the arteries and veins, !,,„„,„, thobaoic duot, 4o.-.. i-te,- and they are consequently less *^°®- ^- ^«°* ^a™ inferior, c, c Right and left ■ 1 T..11 T T subclavian veins, d. Point of opening of thoracic easily detected by ordinary dis- duct into left subclavian. section. They originate in the tissues of the above-mentioned parts by an irregular plexus. They pass from the extremities toward the trunk, converging and ABSOEPTION". 157 uniting with each other like the veins, their principal branches taking usually the same direction with the nerves and bloodvessels, and passing, at various points in their course, through certain glandular bodies, the "lymphatic or "absorbent" glands. The lymphatic glands, among which are included the mesenteric glands, consist of an external layer of fibrous tissue and a contained pulp or parenchyma. . The investing layer of fibrous tissue sends oft' thin septa or laminae from its internal surface, which penetrate tbe 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 numer- ous 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 Kblliker, like the solitary and agminated glands of the intestine, by a fine network of capillary bloodvessels. The solitary and agminated glands of the intestine are, therefore, closely analogous in their structure to those of the lymphatic system. 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- 158 ABSOBPTION. 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. But while intestinal absorption is going on, after a meal contaia- Fig. 46. LAOIEILS and LTUPnATICS. ing fatty ingredients, the lacteals may be seen as white, opaque vessels, distended with milky chyle, passing through the mesentery, ABSOBPTION'. 159 and converging, from its intestinal border 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. 46.) It is then mingled with the returning current of venous blood, and passes into the right cavities of the heart. The presence of chyle in the lacteals is, therefore, not a constant, but only a periodical phenomenon. 'The fatty substances consti- tuting the chyle begin to be absorbed during the process of diges- tion, 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 system and the thoracic duct. As ,they are discharged into the subclavian vein, and mingled with the blood, they can still be dis- tinguished in the circulating fluid, as a mixture of oily molecules, between the orifice of the thoracic duct and the right side of the heart; while passing through the lungs, however, 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. The fatty substances thus introduced by the bloodvessels and the lacteals are in this way rapidly transformed and assimilated to the ordinary ingredi- ents of the blood. ; 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, not only of the portal vein, but also 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, 160 ABSOKPTION. 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 phe- nomenon. It is, however, a perfectly natural one, and depends simply on the rapid absorption, at certain periods of digestion, of oleaginous substances from the intestine. It can be produced at will, at any time, in the dog, by feeding him with fat meat, and drawing blood, seven or eight hours afterward, from the carotid artery or the jugular vein. This state of things continues for a varying length of time, ac- cording to the amount of oleaginous matters contained in the food. When digestion is terminated, and the fat ceases to be introduced in unusual quantity into the circulation, its transformation and decomposition continuing to take place in l/he 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 BIL5. 161 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 efiect 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 : — 11 162 THE BILE. CoMPOsiTiox OP Ox Bile. Water 880.00 Glyko-cholate of soda \ on nn Tauro-cholate " " ) Biliverdine 1 Fats I J3.42 Oleates, margarates, and stearates of soda and potassa . f Cholesterin J Chloride of sodium Phosphate of soda " « lime " " magnesia Carbonates of soda ami potassa Mucus of the gall-bladder .1.34 15.24 1000.00 BiLiVEKDiNE. — 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 jaiindice. Cholesterin (C^'K^O). — 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 deppsits. 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 THE BILE. 163 Fig. 47.. the subjacent crystals show very distinctly through the substance of those -which are placed above. Cholesterin is not formed in the liver, but originates in the substance of the brain and nervous tissue, from which it may be extracted in large quantity by the action of alcohol. It has also been found, by Dr. W. Marcet,* to exist, in considerable abund- ance, in the tissue of the spleen. From all these tis- sues it is absorbed by the blood, then conveyed to the liver, and discharged with the bile. G'HOLESTEKIK, from an Encysted Tumor- This fact has been fully confirmed by the researches of Prof. A. Flint, Jr.,' who has found that there is nearly one-quarter part more cholesterin in the blood of the jugular vein, returning from the brain, 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. Since cholesterin in a free state is insoluble in the animal fluids, it is probable that it exists in the blood and the bile, as well as in the nervous tissues from which it is derived, under some form of combination, as a lactate, oleate, or 'margarate ; and that it is depos- ited in a crystalline form only after ;being liberated from this com- bination by the action of other substances. The cholesterin, after being poured into the intestine with the bile, is decomposed or transformed into some other substance, since it is not discharged with the feces.' -Its decomposition is probably effected by the contact of the intpstinal fluids. BiLiABT Salts.— By far the inost important and characteristic ingredients of this secretion are the two saline substances mentioned 1 Philosophical Transactions, London, 1857, p. 413. ' Amerioan Journ. Med. Sci., October, 1862. » Prof. A. Flint, Jr., in Am. Journ. Med. Sci., Oct. 1862. 164 THE BILE. above as the glyho-cholate and tauro-cholate of soda. These sub- stances were first discovered by Strecker, in 1848, in the bile of the ox. They are both freely soluble in -water and in alcohol, but in- soluble in ether. One of them, the tauro-cholate, has the property, when itself in solution in water, of dissolving a certain quantity of fat ; and it is probably owing to this circumstance that some free fat is present in the bile. The two biliary substances are obtained from ox bile in the following manner : — The bile is first evaporated to dryness by the water-bath. The 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 beep 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. Ox-bile, extracted with absolute alcohol and precipitated with ether. Gltko-cholate of Soda from Ox-bilX, after two days' crystallization. At the lower part of the flgare the crystals are melting into drops, from the evaporatioii of the ether and absorption of moisture. THE BILE. 165 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- 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 cpnsistency,. and sticky, like Canada -balsam or half- melted resin ; and it is on this account that the ingredients compos- ing it have been called the " resinous matters" of the bile. They have, however, no real chemical relation with true resinous bodies, since they both contain nitrogen, and differ from resins also in other important particulars. At the end of twelve to twenty-four hours, the glyko-cholate of soda begins to crystallize. The crystals radiate from various points in the resinous deposit, and shoot upward into the supernatant fluid, in white, silky bundles. (Fig. 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 dif&cult to keep them under the microscope long enough for a correct drawing and measurement. ^'8- ^*^' The crystallization in the test-tube goes on after the first day, and the crystals in- crease in quantity for three or four, or eten 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 examined by the microscope, it is seen that the crystals of glyko-cholate of soda have increased considerably in thickness (Fig. 50), so that their trans- Gltko-cholatb and Tavro-cholatb op Soda, from Ox-bilb, after xlx days* crystalliza- tion. The glyko-cholate is crystallized ; the tauro- cholate Is ia fluid drops. 166 THE BILE. verse diameter may be readily estimated. The uncrystallizable tauro-cholate appears under the form of circular drops, varying considerably in size, clear, transparent, strongly refractive, and bounded by a dark, well-defined outline. These drops are not to he 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 substaiices present in the watery solution may be 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 ere precipitable by the subacetate; but the glyko-cholate of soda is preeipitable 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 : — fflyko-cholate of soda (NaO,OjjH^jNO,,) 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., glyho-cholic THE BILE. 167 acid (CjjH^jNOipHO). 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-cholio acid is decomposed with the production of two new substances; the first a non-nitrogenous acid body, cholic add (O^jHsjOgjHO) ; the second a nitrogenous neutral body, glycine (C4HJNOJ. 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. Tawro-cholate of soda (^z,0,Qg^^^'&f)^^ is also a very abundant ingredient of the bile. It is said by Eobin and Verdeil' that it is not crystallizable, owing probably to its not having been separated as yet in a perfectly pure condition. Lehmann states, on the con- trary, that it may crystallize,^ when kept for a long time in contact with ether. "We have not been able to obtain this substance, how- ever, in a crystalline form. Its acid constituent, tawo-cholic acid, is a nitrogenous body, like glyko-cholic acid, but differs from the latter by containing in addition two equivalents of su]|»hur. By long boiling in a dilute solution of potassa, it is decomposed with the production of two other substances ; the first of them the same acid body mentioned above as derived from the glyko-cholic, viz., cholic add; and the second a new nitrogenous neutral body, viz., taurine (C^HjNSjOj). The same remark holds good with regard 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-oholates and tauro-cholates are formed, so far as we know, exclusively in the liver ; since they have not been found in the blood, nor in any other part of the body, in healthy animals ; nor even, in the experiments of Kunde, Moleschott, and Lehmann on frogs,' after the entire extirpation of the liver, and consequent ' Chimie Anatomique et Fhysiologiqne, vol. ii. p. 473. ' Physiological Chemistry, Phil, ed., vol. i. p. 209. ' Lehmann's Physiological Chemistry, Phil, ed., v.ol. i. p. 4J6. 168 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 dif[:erent 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, ^.t 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 preoipitation 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- Doa's Bile, extract- ed with absolute alcohol aacL precipitated with ether. THE BILE. 169 Fig. 52 listed. But it is more particularly in tbeir 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 chelate of soda, we shall speak of them simply as the " crys- talline" and " resinous" biliary substances. In cat's bile, the biliary substances act very much as in dog's bile. The ether precipitate of the 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 variousforms and almo'st microscopic in size. (Fig. crtsiaihsb and b* 52). Some of them are feathery in appearance, TER7fr„m°Hum»n Biie.t^ consisting of two or three diverging needles, *™^*^ "ith absolute aico- «,f J 11 1 1 1 . bol and precipitated by With secondary needle-shaped crystals growmg ether. Magnifled 25 di»m^ from their lateral edges. Others, which are'™- larger and more abundant, are octohedral or diamond-shaped, sometimes with irregular sides and truncated angles. Others still 170 THE BILE. assume the form of rosettes, more or less perfect, consisting of shoit, fine, irregular, radiating fibres. These crystals are mingled with an abundant deposit of resinous drops, similar to those of the tauro- chelate 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 thfe 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 human 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 aontain, &c. &c. We have already mentioned the variations in color and specific gravity. The alco- holic solution of dried oxibile, 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 foe Bile. — la investig9.ting 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. 171 elapses, and the quantity of bile existing in tlie 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. Pettenliofer'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 litlle 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 172 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 FOB BILE. 173 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. Eobin and Verdeil' say that its reactions " do not belong exclusively to the bile, and may therefore give rise to mistakes." Some fatty sub- stances and volatile oils (oleine, oleic acid, oil of turpentine, oil of caraway) Ijavebeen 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. ' Op. cit., vol. ii. p. 468. 174 THE BILE. 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.^ 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 biliarjrduct 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 Fbesh Bile. Dky Eesidce. In the cat 102 grains. 5.712 grains. •'dog 140 " 6.916 " " sheep . . . . . . 178 « 9.408 " " rabbit 9.58 « 17.290 « ' Verdaungssaefte und Stoffweohsel. Leipzig, 1852. VARIATIONS AND FUNCTIONS OF BILE. 175 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 140 pounds, the daily quantity of the bile will be certainly not less than 16,940 grains, or very nearly 2| pountjs 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 Isub- 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. 63. Cbtstallihe axd Eesinous Biliaet Spd- s T A K c E B ; from SmaU Intestine of Dog, afiei' two days fasting. 176 THE BILE. color witli 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. Duodenal Fibtula. — a. Stom&cb. 6. Duo- denum, c, c, c. Paucreas ; its two ducts are seen opeDing into the duodenum, one near the orifice of the biliary duct, d, the other a short distance iower down. e. Silver tube passing through the abdominal walls and opening into the duodenum. 1 In Am. Jouru. Med. Soi., April, 1856. 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 difi^rent results. Arnold,' for example, found the quantity to be largest soon after meals, decreasing again after the fourth hour. KoUiker and Miiller,' 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- 2 Ibid., April, 1857. VARIATIONS AND FUNCTIONS OP BILE. 177 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 difScult 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. 12 178 THE BILE. Time after feeding. Quantity of fluid in 15 minutes. Dry residue of same. Quantity of biliary matters. Proportion of biliary matters to dry residue. Immediately 1 hour 640 grains 1,990 " 33 grains 105 " 10 grains , 4 u .30 .03 3 hours 780 " 60 " 4 « .07 6 " 750 " 73 " 3k " .05 9 " 860 " 78 " 4i « .06 12 " 325 " 23 " 3| » .16 15 " 347 " 18 " 4 « .22 18 " — — 21 " 384 " 11 « 1 " .09 24 " 163 " n •• 3i » .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 bik in its passage through the intestine f 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- caecal 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 VABIATIONS AND FUNCTIONS OF BILE. 179 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 vnth the gastric juice. If four drops of dog's bile be added to 3j of gastric juicd 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 180 THE BILE. by alcohol and precipitated by etber, as above described, their watery solution will precipitate with gastric juice, in the same manner as fresh bile would do. Although the biliary matters, however, precipitate by contact with fresh gastric juice, they do not do so with gastric juice which holds alhuminose in solution. We have invariably found that if the gas- tric juice be digested for several hours at the temperature of 100° F., with boiled white of egg, the filtered fluid, which contains an abundance of albuminose, will no longer give the slightest precipi- tate on the addition of bile, or of a watery solution of the biliary substances, even in very large amount. The gastric juice and the bile, therefore, are not finally antagonistic to each other in the digestive process, though at first they produce a precipitate on being mingled together. It appears, however, from the experiments detailed above, that the secretion of the bile and its discharge into the intestine are not confined to the periods of digestion, but take place constantly, and continue even after the animal has been kept for many days with- out food. These facts would lead ns to regard the bile as simply an eoccrementitious 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. 181 and discharged, but furthermore that it be discharged into the intestine, and pass through the tract of the alimentary canal. The most satisfactory experiments of this kind are those of Bidder and Schmidt,' in which they tied the common biliary duct in dogs, and then established a permanent fistula in the fundus of the gall-bladder, through which the bile was allowed to flow by a free external orifice. In this manner the bile was effectually excluded from the intestine, but at the same time was freely and wholly discharged from the body, by the artificial fistula. If the bile therefore were simply an excrementitious fluid, its deleterious ingredients being all eliminated as usual, the animals would not suffer any serious injury from this operation. If, on the contrary, they were found to suffer or die in consequence of it, it would show that the bile has really some important 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 ■ Op. cit., p. 103. 182 THE BILE. essentially interfered with, and none of the food was discharged •with the feces ; but there was much rumbling and gurgling in the iiitestines, and abundant discharge of flatus, more strongly marked in one instance than in the other. There was no pain ; and death took place, at last, without any violent symptoms, but by a simple and gradual failure of the vital powers. A similar experiment has been successfully performed by Prof. A. Flint, Jr.* In this instance the animal lived for thirty-eight days after the operation, and died finally of inanition ; the symp- toms agreeing in every important particular, with those reported by Bidder and Schmidt. How is it, then, that although the bile be not an active agent in digestion, its presence in the alimentary canal is still essential to life ? What of&ce does it perform there, arid how is it finally dis- posed of? We have already shown that the bile disappears in its passage through the intestine. This disappearance may be explained in two different ways. First, the biliary matters may be actually re- absorbed from the intestine, and taken up by the bloodvessels ; or secondly, they may be so altered and decomposed by the intestinal fluids as to lose the power of giving Pettenkofer's reaction with sugar and sulphuric acid, and so pass off with the feces in an insoluble form. Bidder and Schmidt^ have finally determined this point in a satisfactory manner; and have demonstrated that the biliary substances are actually reabsorbed, by showing that the quantity of sulphur present in the feces is far inferior to that contained in the biliary ingredients as they are discharged into the intestine. These observers collected and analyzed all the feces passed, dur- ing five days, by a healthy dog, weighing 17.7 pounds. The entire fecal mass during this period weighed 1508.15 grains. Containing .' '«'''''^'- •••••• 874.20 grains. I Solid residue 633.95 " 1608.15 ' American Journ. Med. Sci., October, 1862. " Op. cit., p. 217. VARIATIONS AND FUNCTIONS OF BILE. 188 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. of sulphur. Substances not of a, biliary nature extracted by muriatic acid and hot alcohol .... 148.800 containing 1.302 grs. of sulphur. 2.387 Fatty acids with oxide of iron . 98.425 Residue consisting of hair, sand,&c., 207.080 633.950 Now, as it Las 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- 184 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 difScult, 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 VABIATIONS AND FUNCTIONS OF BILE. 185 are ; but they are e\ddently 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. 186 FOBMATION OF SUGAB IN THE LIVER. CHAPTER IX. FORMATION OF SUGAE IN THE LIVER. 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- nard' in 1848, and described by him under the name of the glyco.- genic function of the liver. It has long been known that sugar may be 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 ' Nouvelle Fonction du Foie. Paris, 1853. FORMATION OF SUGAR IN THE LIVER. 187 urine has often appeared to be altogether 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, &o., treated in the same way, give no indication of sugar, and do not reduce the salts of copper. Every other organ in the body may be entirely destitute of sugar, but the liver always contains it in considerable quantity, provided the animal be healthy. Even the blood of the portal vein, examined by a similar process, contains no saccharine element, and yet the tissue of the organ supplied by it shows an abundance of saccharine ingredients. It is remarkable for how long a time the liver will continue to exhibit the presence of sugar, after all external supplies of this substance have been cut off. Bernard kept two dogs under his own observation, one for a period of three, the other of eight months,' during which period they were confined strictly to a diet of animal food (boiled calves' heads and tripe), and then killed. Upon exa- mination, the liver was found, in each instance, to contain a propor- tion of sugar fully equal to that present in the organ under ordinary circumstances. The sugar, therefore, which is found in the liver after death, is a normal ingnedient of the hepatic tissue. It is not formed in other parts of the body, nor absorbed from the intestinal canal, but takes ' KouTella Fonotion du Foie, p. 50. 188 FORMATION OF SUGAR Ilf 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 (Mursena anguilla and Raia 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 Pekcentage of Sdgak in the Liveb. . 1.68 In ox . . . . 2.30 . 2.15 " horse . . . 4.08 , 1.69 " goat .... 3.89 .1.94 " birds . . . 1.49 . 1.94 " reptiles . . . 1.04 . 2.00 " fish . . . . 1.45 With regard to the nature and 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,' by the readiness with which it becomes decomposed in the blood — since cane sugar and beet root sugar, if injected into the circulation of a living animal, pass through the system without sensible decom- position, and are discharged unchanged with the urine ; sugar of milk and glucose, if injected in moderate quantity, are decomposed in the blood, but if introduced in greater abundance make their appearance also in the urine; while a solution of liver sugar, though injected in much larger quantity than either of the others, may dis- ■ Lemons de Fhjsiologie Experimentale. Paris, 1855, p. 213. POBMATIOlf OF S0GAR IS THE LIVBB. 189 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 hematic 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 found' 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 ■ Gazette Hebdomadaire, Fans, Oct. 5, 1855. 190 FORMATION OF SUGAR IKT 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,' is as follows : — 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 ' Journal de Physiologie, Paris, 1858, p. 552. FORMATION OF SUGAR IN THE LIVER. 191 blood. If a solution of glycogenic matter be mixed with fresb human saliva, and kept for a few minutes at the temperature of 100° P., 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 transforme(f under similar conditions. The glycogenic matter which is thus destined to be converted into sugar, is formed in the liver by the processes of nutrition. It may be extracted, as we have seen above, from the hepatic tissue of carnivorous animals, and is equally present when they have been exclusively confined for many days to a meat diet. It is not in- troduced with the food ; for the fleshy meat of the herbivora does not contain it in appreciable quantity, though these animals so constantly take starchy substances with their food. In them, the starchy matters are transformed into sugar by digestion, and the sugar so produced is rapidly destroyed after entering the circula- tion ; so that usually neither saccharine nor starchy substances are to be discovered in the muscular tissue. M. Poggiale' found that in very many experiments, performed by a commission of the French Academy for the purpose of examining this subject, glycogenic matter was detected in ordinary butcher's meat only once. "We have also found it to be absent from the fresh meat of the bullock's heart, when examined in the manner described above. Neverthe- less, in dogs fed exclusively upon this food for eight days, glycogenic matter may be found in abundance in the liver, whUe 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- ' Jonmal de Physiologie, Paria, 1858, p. 558. 192 FORMATION OF SUGAB 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. It has been doubted by some observers whether the sugar found in the liver after death really exists in the organ during life. This doubt, which was first raised by Pavy^ in 1858, is based upon the fact that if the liver tissue, after death, be instantly subjected to the action of boiling -yater or strong alcohol, so as to arrest any further catalytic transformation of the glycogenic matter, the watery extract, when examined by the ordinary methods, has been found to yield no indication of sugar, or only slight traces of that substance. It was accordingly believed that the liver during life might contain only the glycogenic matter, but no sugar ; and that the sugar, found a short time after death, was really produced by post-mortem fermentation during the interval which had elapsed. The appearance of sugar under these circumstances must be ad- mitted, at all events, to be exceedingly rapid. In a series, of ex- periments performed in 1869, we have found that if a portion of the liver be excised from the abdomen of the living dog, and immediately cut into thin pieces and immersed in boiling water, when the preliminary operations are completed in so short a time as seventeen seconds or twenty -two seconds, the watery extract of the coagulated tissue, examined in the ordinary way by Trom- mer's test, gives no reduction of the copper oxide ; but at the end of fifty seconds, a distinct though not abundant sugar reaction is manifest. This reaction is decided at the end of one minute, and becomes more and more marked at the end of two, three, four, five and seven minutes successively. It is only within fifty seconds, therefore, according to our own observations, that sugar fails to appear in the liver extract examined in the usual manner. Har- ley^ has even found it, under these circumstances, within an inter- val of less than twenty seconds. But even within this short period the failure to detect sugar in the liver extract, thus examined, de- pends, as we believe, solely upon two causes : first, the small quan- tity of liver tissue employed ; and secondly, the imperfect applica- tion of the copper test. In the first place, when a portion of liver, iProoeedings of the Royal Society of London, vol. ix. p. 300. »Ibid., vol. X. p. 289. FORMATION OF SUGAR IN THE LIVER. 193 removed from the body of the living or recently killed animal, is cut up by scissors into boiling water, only a small amount of the tissue can be treated in this way within a sufficiently short time. In the second place, the watery extract of the liver, as usually made, is more or less turbid and colored by various animal matters extracted at the same time; and the existence of these animal matters, when the sugar itself is present only in small amount, interferes in great measure with the reaction of the copper test. They must therefore be thoroughly removed by the free use of animal charcoal, and the watery extract of the liver tissue must be left absolutely clear and colorless, before we can apply the cop- per test with safety, to determine the presence or absence of sugar. In order to avoid these two causes of error, we have adopted the following method of operating and of preparing the liver ex- tract.' The animal is gently but firmly held upon a table by three assistants, the abdomen widely opened by a single stroke of a very sharp knife, the liver seized and drawn downward, and a portion instantly cut off and passed between the rollers of a com- minuting machine into a vessel filled with strong alcohol or boil- ing water. The comminuting machine consists of two fluted brass cylinders placed horizontally side by side, and made to revolve rapidly toward each other by means of a crank -handle. The nearly Fig. 55. CoMmsmraaiiAOHraBlosedfor grinding the liver snbBtiince. parallel projections and depressions of the cylinders lock into each other, like the teeth of two cog-wheels; and their contiguous sur- ' All the details of this method are given in the New York Medical Journal for July, 18T1. 13 194 FORMATION OP SUGAR IN THE LIVER. faces, at the point of greatest proximity, are separated by a dis- tance of not more than one sixteenth of an inch. Fig. &Q. When a portion of liver substance is passed between the rollers of this machine, it is disintegrated and commi- nuted in the most effectual manner ; and no post-mortem fermentation can take place in any part of it, after it is once ""T"'hfmSfne'Yn;'r:«.r' '=^"'""' In contactwith thc dcohol, cr boiling water. A large quantity of the liver tissue can, by this means, be used in a short time ; from 1000 to 2000 grains being easily comminuted and immersed in the above mentioned liquids, within the space of ten seconds or even less. Meanwhile, a fourth assistant marks the time consumed in the operation by means of a. stop-watch, the second-hand of which is liberated at the instant the portion of liver is cut off, and again stopped when it is comminuted and immersed in alcohol or boiling water. An extract is then made by slowly percolating the alcoholic liquor through the disintegrated liver tissue in a displacement apparatus, evaporating it to dryness over the water bath, and finally making a watery extract, in small volume, of the dry residue ; the liquids being thoroughly clarified and decolorized, at two stages of the operation, by the free use of animal charcoal, carried to such an extent as completely to remove from the final watery solution every trace of turbidity and color. The watery solution, thus prepared, is then examined for sugar, by placing one cubic centimetre of the liquid in a narrow test tube against a black ground, adding one drop of Fehling's copper solution, and raising the mixture to the boiling-point. We have experimented, in the manner above described, upon twenty dogs. In four of the cases, the method employed was that by boiling water ; in the remaining sixteen cases, that by alcohol. The animals were examined four, eight, twelve, and twenty-four hours after feeding; the food consisting always of the fresh or cooked meat of the bullock's heart. The longest time which elapsed from the separation of the liver to its immersion in the alcohol or boiling water was thirteen seconds; the shortest time was three seconds. The average time was six and a quarter POKMATION OP SUGAR IN THE LIVBB. 195 seconds. In every instance the final watery solution gave a dis- tinct and perfectly unmistakable sugar reaction by the copper test. In one half the cases, the presence of sugar alone was determined by this method ; in the remainder, its proportion to one thousand parts of the liver tissue was also ascertained. The following is a list of these experiments, with their results. Experi- Time after Time consumed in Process of Proportion of Glucose in ment. Feeding. taking out Liver. Treatment. lOOOparta of Liver. No. 1 4 hours 13 seconds Alcohol Glucose. No. 2 4 hours 7 seconds (( tt No. 3 4 hours 10 seconds « tt No. i 4 hours 4 seconds tt tt No. 5 8 hours 7 seconds It tt No. 6 8 hours 6 seconds 11 tt No. 7 4 hours 6 seconds Boiling Water tt No. 8 12 hours 6 seconds it it tt No. 9 12 hours 8 seconds tt (( tt No. 10 12 hours 5 seconds « tt it No. 11 4 hours 9 seconds Alcohol 2.093 No. 12 4 hours 5 seconds (( 0.804 No. 13 8 hours 7 seconds tt 1.750 No. 14 8 hours 3 seconds tt 1.510 No. 15 1 2 hours 5 seconds it 1.810 No. 16. 12 hours 6 seconds tt 4.175 No. 17 12 hours 7 seconds " 1.830 No. 18 12 hours 3 seconds " 4.375 No. 19 24 hours 6 seconds " 3.850 No. 20 24 hours 4 seconds tt 2.675 It appears from these results, that, when the requisite precau- tions are adopted, sugar is found in the liver at the earliest period at which it is possible to examine the organ after its separation from the body of the living animal ; the average quantity of sugar existing in the liver tissue, at this time, being at least two and a half parts per thousand. The exact proportion of sugar thus pres- ent in the liver at the instant of death, or within a few seconds afterward, varies from 0.804 to 4.375 parts per thousand. These variations, so far as our observation extends, appear to depend upon individual differences in the animals employed for experi- ment; in the same manner as other ingredients of the tissues and fluids are found to vary, within physiological limits, in different individuals. There is no doubt that the quantity of glucose in the liver in- creases immediately after death. This fact has been observed by all the recent experimenters upon the subject ; and it was even shown by Bernard, as already mentioned, by experiments which 196 FORMATION OF SUGAB IN THE LIVES. we have frequently verified, that sugar ■will be again produced in the liver, separated from the body, after it has once been entirely washed out by a continued watery injection of the hepatic blood- vessels. This is due to the fact that the sugar is produced by a transformation of the glycogenic matter ; and this transformation will go on after death for a certain period, so long as the glyco- genic matter remains unexhausted and the requisite temperature is kept up. Thus the sugar, no longer carried away by the current of the circulation, accumulates in the liver tissue at the expense of the glycogenic matter from which it is formed. This accumu- lation is at first very rapid, but subsequently diminishes in activ- ity with the gradual deterioration of the liver substance. In the following cases, the proportion of glucose per thousand parts was determined at various periods after death. Pbopobtion op GLrcosE in the Lives. at the end of per thottsand part). 5 seconds 1.810 Exp. No. 15. -I 15 minutes 6.792 10.260 f 5 seci 4 15 mil [ Ihou ^^v.^0.19. {^— /« ::::::: S Exp. No. 20. 4 seconds 2.675 1 hour 11.888 4 hours 13.361 12 hours 15.351 As sugar is found, under some circumstances, in minute quantity in the blood of the general circulation, there might perhaps be room for doubt whether the glucose, present in the liver at the moment of death, may not be due to the arterial blood with which the organ is supplied, rather than an ingredient of the hepatic tissue. This, however, is not the case. The question may be set- tled by examining, at the same time with the liver or immediately afterward, some other abdominal organ equally well supplied with arterial blood. In the series of' experiments above described, the spleen was selected for this purpose, and in three cases was taken out within ten minutes after the excision of the liver, treated in precisely the same manner by the alcohol process, and examined for sugar, with the following result. FORMATIOSr OF SUGAR IN THE LIVER. 197 Propobtion of Glucose pbb. Thousand Pabts. Exp. No. 14. Exp. No. 19. Exp. No. 20. At the end of {3 seconds . 10 minutes , f 5 seconds . \ 10 minutes . {4 seconds . 10 minutes . In the Liver . Spleen . Liver , Spleen . Liver . Spleen . 1.510 0. 3.850 0. 2.675 0. It is evident, accordingly, that the liver sugar does not belong to the arterial blood with which the organ is supplied, but is a normal ingredient of the hepatic tissue. There is reason to believe that the sugar, produced in the sub- stance of the liver, is absorbed from it by the circulating blood and carried away by the hepatic veins. A preponderance of sugar in the blood of the hepatic veins over that in other parts of the cir- culation was often recognized by Bernard and other observers, before it was considered as essential to make the examination with- in the first few seconds after death. , Since that time the results of experimenters on this point have been conflicting, some observers, however, still finding a decided preponderance of sugar in the hepatic blood, within a very short period after death, or even during the life of the animal. Prof. A. Flint, Jr ,^ found sugar in the he- patic blood of the dog, obtained within a minute after death by ligature of the vena cava inferior ; and Prof. Lusk " found that in five dogs, the blood of the right side of the heart, removed during life by catheterization through the jugular vein, contained a quan- tity of sugar from two to four times greater than that existing, in the same animals, in the blood of the jugular vein. 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 • New York Medical Journal, January, 1869. ' Ibid., July, 1870. 198 FORMATION OF SUGAR IN THE LIVER. 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 ia the intestine, so the sugar is decomposed in the blood. "We are not yet acquainted, however, with the precise nature of the changes which it undergoes after entering the vascular system. It is very probable, according to the views of Lehmann and Eobin, that it is at first converted into lactic acid (C5H5O5), which decomposes in turn the alkaline carbonates, setting free carbonic acid, and forming 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 jn the blood, as we have already shown to be the FORMATION OP SUGAR IN THE LIVER. 199 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. 200 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 coeliac 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 Dobson* found that the size of the organ increased, from the third hour after feeding up to the fifth ; when it arrived at its maximum, gradually decreasing after that period. When these periodical congestions take place, ' In Gray, on the Structure and Uses of the Spleen. London, 1854, p. 40. THB SPLEEN. 201 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 traheeulse, as they are called, by their frequent branching and mutual interlacement, form a kind of skeleton or framework by which the soft splenic pulp is embraced, and the shape and integrity of the organ maintained. They are composed of similar elements to those of the investing capsule, viz., elastic tissue and involuntary muscular fibres, united with each other by a varying quantity of the fibres of areolar tissue. The interstices between the trabeculae of the spleen are occupied by the splenic pulp; a soft, reddish substance, which contains, beside a few nerves and lymphatics, capillary bloodvessels in great profusion, and certain whitish globular bodies, which may be re- garded as the distinguishing anatomical elements of the organ, and which are termed the Malpighian hodies 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- 202 THE SPLEEN, aided eye, thoiigli they always exist in the spleen in a healthy condition. Their average diameter, according to Kolliker, is ^.^ 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. 203 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-splenio omentum, and then dividing the vessels between the ligatures and the spleen. The wound usually heals without diflculty ; and if the animal be killed some weeks afterward, the only remaining trace of the operation is an adhesion of the omentum to the inner surface of the abdomi- nal parietes, at the situation of the original wound. The most constant and permanent effect of a removal of the spleen is an unusual increase of the appetite. This symptom we have observed in some instances to be excessively developed ; so that the animal would at all times throw himself, with an unnatural avidity, upon any kind of food offered him. We have seen a dog, subjected to this operation, afterward feed without hesitation upon the flesh of other dogs ; and even devour greedily the entrails, taken warm from the abdomen of the recently kiUed 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 204 THE SPLEEN. animal whioli lias 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 iu 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. 205 CHAPTER XL THE BLOOD. The blood, as it exists ia its natural condition, while circulating in tlie vessels, is a thick opaque fluid, varying in different parts of the body from a brilliant scarlet to a dark purple or nearly black color. 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 color- less, transparent, alkaline fluid, termed the plasma, containing water, fibrin, albumen, salts, &o., in a state of mutual solution ; and, sec- ondly, of a large number of distinct cells, or corpuscles, the blood- globules, swimming freely in the liquid plasma. The blood, taken as a whole, consists of blood-globules and plasma, in about equal proportions ; that is, nearly one-half globules and one-half plasma. The specific gravity of these two ingredients is slightly different. That of the plasma is about 1030 ; that of the blood-globules, 1088. Nevertheless, the natural movement of the blood in the vessels keeps them thoroughly mingled together ; and even when the blood is allowed to remain at rest in a glass jar, the globules subside only very slowly and imperfectly. Thus the globules, mingled abun- dantly and uniformly with the fluid plasma, give to the entire mass of the blood an opaque aspect and a deep 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. 57.) Their size varies somewhat, in human blood, even in the same specimen. The greater number of them have a transverse diameter of ^^^g of an inch ; but there are many smaller ones to be seen, which are not more than ^j'^^ or even -^^^-^ of an inch in diameter. Their form is that of a spheroid, very much flattened on its opposite sur- faces, 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- 206 THE BLOOD. wise during its rotation and assume the flattened form indicated at b. The thickness of the globule, seen in this position, is about 75^1^?^ 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 HUMAK Bi,00D-QL0BFi,ES.-a. Bed globnles, tllick odgCS of the globules Bed globules, seen edgewise, c. act aS doublc COnvex lenSCS, 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- 58. 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. seen flatwise. White globule, Bed Globules of the Blood, seen a little beyond the focus of the microscope. BLOOD-GLOBULES. 207 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. 58.) When within it they will appear with a dark rim and a bright ^. .. ° Fig. 59. centre. (Fig. 59.) 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 ^'S- 60. 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 Elood-olobules adhering together, like rolls of coin. 208 THE BLOOD. compressing the globules, forces tliem 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 hav§ been sometimes inadvertently described ; but on the contrary have a consistency which is very nearly fluid. Thev are in consequence exceedingly flexible, and easily elongated, bent, or otherwise distorted by accidental pressure, or in passing through the narrow currents of fluid which often establish them- selves accidentally in a drop of blood under microscopic examina- tion. This distortion, however, is only temporary, and the globules regain their original shape, as soon as the accidental pressure is taken off. The peculiar flexibility and elasticity thus noticed are characteristic of the red globules of the blood, and may always serve to distinguish them from any other free cells which may be found in the animal tissues or fluids. In structure the blood-globules are homogeneous. They have been sometimes erroneously described as consisting of a closed vesicle or cell- wall, containing in its cavity some fluid or semi-fluid substance of a different character from that composing the wall of the vesicle itself. No such structure, however, is really to be seen in them. Each blood-globule consists of a mass of organized ani- mal substance, perfectly or nearly homogeneous in appearance, and of the same color, consistency and composition throughout In some of the lower animals (birds, reptiles, fish) it contains also a granular nucleus, imbedded in the substance of the globule ; but in no instance is there any distinction to be made out between an external cell-wall and an internal cavity. The appearance of the blood-globules is altered by the addition of various foreign substances. If water be added, so as to dilute the plasma, the globules absorb it by imbibition, swell, lose their double central concavity and become paler. If a larger quantity of water be added, they finally dissolve and disappear altogether. When a moderate quantity of water is mixed with the blood, the BLOOD-GLOBULES. 209 Blood-globules water. Birollea by the imbibition of edges of tlie globules, being thicker tban tbe central portions, and absorbing water more abundantly, become turgid, and encroach gradually upon the central part. (Fig. 61.) It is very *''8- ^^■ common to see the central depression under these cir- cumstances, disappear on one side before it is lost on the other, so that the globule, as it swells up, curls over to- wards one side, and assumes a peculiar cup-shaped form (a). This form may often be seen in blood-globules that have been soaking for some time in the urine, or in any other animal fluid of a less density than the plasma of the blood. Dilute acetic acid dissolves the blood-globules more promptly than water, and solu- tions of the caustic alkalies more promptly still. If a drop of blood be allowed partially to evaporate while under the microscope, the globules near the edges of the prepa- ^^^' ^^' ration often diminish in size, and at the same time present a shrunken and crenated ap- pearance, as if minute gran- ules were projecting from their surfaces (Fig. 62); an effect apparently produced by the evaporation of part of their watery ingredients. For some unexplained rea- son, however, a similar dis- tortion is often produced in some of the globules by the addition of certain other ani- mal fluids, as for example the saliva; and a few can even be seen in this condition after the addition of pure water. 14 Blood-olobiti,es, slirgnkeu, with their margioi crenated. 210 THE BLOOD. When separated from tlie other ingredients of the blood and examined by themselves, the globules are found, according to Lel^ mann, to present the following composition : — Composition of the Blood-Globules in 1000 Fakts. 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 " " Phosphate of lime " " magnesia 8.12 1000.00 The most important of these ingredients is the ghbuUne. 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 Eobin 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, 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. BLOOD-GLOBTTLES. 211 The blood-globules of all the -warm-brooded quadrupeds, with the exception of the family of the camelidae, 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 ^y^Tj of an inch, and the two-toed sloth {Bradypits didactylus), in which they are jgVtj of an inch in diameter. In the musk deer of Java they are smaller than in any other known species, measuring rather less than t^^^jjj 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. G-uUiver.* DiAMETEB OF Red Giobdles m the Ape Horse . Ox Sheep . Ooat . Dog . j^jof an inch. Cat . Fox . Wolf . Elephant Red deer Mnsk deer j^jOf an inch. tb'sit In all these instances the form and general appearance of the globules are the same. The only exception to this rule among the mammalians is in the family of the camelidae (camel, drom- ^'8- 63- edary, llama), in which the globules present an oval out line instead of a circular one. In other respects they resem- ble the foregoing. In the three remaining classes of vertebrate animals, viz., birds, reptiles, and fish, the blood-globules differ so much from the above that they can be readily distinguish- ed by microscopic examina- tion. They are oval in form, and contain a colorless gran- ular nucleus imbedded in their Bloos-olobulxs op Fbog. — a. Blood-globule Been edgewise, i. WMte globule. ' In Works of William Hewson, Sydenham edition, London, 184fi, p. 327. 212 THE BLOOD. substance. They are also considerably larger tban tbe blood- globules of the mammalians, particularly in the class of reptiles. In the frog (Fig. 63) they measure ^j^j of an inch in their long diameter ; and in Menohranchus, the great water-lizard of the north- ern lakes, 3^5 of an inch. In Proteus anguinus they attain the size, according to Dr. Carpenter,' of ^^^ of an inch. Beside the corpuscles described above, there are globules of an- other kind to be found in the blood, viz., the white globules. These globules are -much less numerous than the red; the proportion between the two, in human blood, being one white to about three hundred red globules. In reptiles, the relative quantity of the white globules is greater, but they are always considerably less abundant than the red. They differ also from the latter in shape, size, color, and consistency. They are globular in form, white or colorless, and instead of being homogeneous like the others, their substance is filled everywhere with minute dark molecules, which give them a finely granular appearance. (Fig. 57, c.) In size they are considerably larger than the red globules, being about j^Vtt of an inch in diameter. They are also more consistent than the others, and do not so easily glide along in the minute currents of a drop of blood under examination, but adhere readily to the surfaces of the glass. If treated with dilute acetic acid, they swell up and become smooth and circular in outline ; and at the same time a sepa- ration or partial coagulation seems to take place in the sub- stance of which they are com- posed, so that an irregular col- lection of granular matter shows itself in their interior, becoming more divided and broken up as the action of the acetic acid upon the globule is longer continued. (Fig. 64.) This collection of granular matter often assumes a curved or crescentic form, as at a, and Whitb flLOBUiEa of the Bloob; altered by . . , _:_„»„ dimte aoetio acid. somctimes various other irreg- ular shapes. It does not in- ' The Microscope and its Revelations, Philadelphia edition, p. 600. BLOOD- GLOBULES. 213 dicate the existence of a nucleus in the white globule, but it is merely an appearance produced by the coagulating and disintegrat- ing action of acetic acid upon the substance of which it is composed. The chemical constitution of the white globules, as distinguished from the red, has never been determined ; owing to the small quan- tity in which they occur, and the difficulty of separating them from the others for purposes of analysis. The two kinds of blood-globules, white and red, are to be regarded as distinct and independent anatomical forms. It has been sometimes supposed that the white globules were converted, by a gradual transformation, into the red. There is, however, no direct evidence of this ; as the transformation has never been seen to take place, either in the human subject or in the mammalia, nor even its intermediate stages satisfactorily ob- served. When, therefore, in default of any such direct evidence, we are reduced to the surmise which has been adopted by some authors, viz., that the change " takes place too rapidly to be de- tected by our means of observation,'" it must be acknowledged that the above opinion has no solid foundation. It has been stated by some authors (KoUiker, Gerlach) that in the blood of the batraohian reptiles there are to be seen certain bodies intermediate in appearance between the white and the red globules, and which represent dififererit stages of transition from one form to the other ; but this is not a fact which is generally acknowledged. We have repeatedly examined, with reference to this point, the fresh blood of the frog, as well as that of the menobranchus, in which the large size of the globules would give every opportunity for detecting any such changes, did they really exist ; and it is our unavoidable con- clusion from these observations, that there is no good evidence, even in the blood of reptiles, of any such transformation taking place. There is simply, as in human blood, a certain variation in size and opacity among the red globules ; but no such connection with, or resemblance to, the white globules as to indicate a passage from one form to the other. The red and white globules are therefore to be regarded as distinct and independent anatomical elements. They are mingled together in the blood, just as capillary bloodvessels and nerves are mingled in areolar tissue ; but there is no other connection between them, so far as their formation is concerned, than that of juxtapositidn. ' Kolliker, Handbuch der Gewebelehre, Leipzig, 1852, p. 582. 214 THE BLOOD. Neither is it at all probable tbat the red globules are produced or destroyed in any particular part of the body. One ground for the beUef that these bodies were produced by a metamorphosis of the ■white globules was a supposition that they iwere continually and rapidly destroyed somewhere in the circulation ; and as this loss must be as rapidly counterbalanced by the formation of new glo- bules, and as no other probable source of their reproduction ap- peared, they were supposed to be produced by transformation of the white globules. But there is no reason for believing that the red globules of the blood are any less permanent, as anatomical forms, than the muscular fibres or the nervous filaments. They undergo, it is true, like all the constituent parts of the body, a constant interstitial metamorphosis. They absorb incessantly nu- tritious materials from the blood, and give up to the circulating fluid, at the same time, other substances which result from their internal waste and disintegration. But they do not, so far as we know, perish bodily in any part of the circulation. It is not the anatomical forms, anywhere, which undergo destruction and reno- vation in the nutritive process ; but only the proximate principles of which they are composed. The effect of this interstitial nutrition, therefore, in the blood-globules as in the various solid tissues, is merely to maintain them in a natural and healthy condition of integrity. Their ingredients are incessantly altered, by transforma- tion and decomposition, as they pass through various p^rts of the vascular system; but the globules themselves retain their form and texture, and still remain as constituent parts of the circulating fluid. Plasma. — The plasma of the blood, according to Lehmann, has tl»e following constitution : — Composition of the Plasma in 1,000 parts. Water 902.90 Fibrin 4.06 Albumen 78.84 Fatty matters 1.72 Undetermined (extractive) matters 3.94 Qiloride of sodium . > " potassium Phosphates of soda and potassa ...... Sulphates « « *■ ^.55 Phosphate of lime " magnesia 1000.00 PLASMA. 215 The above ingredients are all intimately mingled in the blood- plasma, in a fluid form, by mutual solution; but they may be sepa- rated from each other for examination by appropriate means. The two ingredients belonging to the class of organic substances are the fibrin and the albumen. The fibrin, though present in small quantity, is evidently an im- portant element in the constitution of the blood. It may be ob- tained ia a tolerably pure form by gently stirring freshly drawn blood with a glass rod or a bundle of twigs ; upon which the fibrin coagulates, and adheres to the twigs in the form of slender threads and flakes. The fibrin, thus coagulated, is at first colored red by the hsematine of the blood-globules entangled in it ; but it may be washed colorless by a few hours' soaking in running water. The fibrin then presents itself under the form of nearly ^'8- ^• white threads and flakes, having a semi-solid consist- ency, and a considerable de- gree of elasticity. The coagulation of fibrin takes place in a peculiar manner. It does not solidify in a perfectly homogeneous mass ; but if examined by th( microscope in thin layers it is seen to have a fibroid or filamentous texture. In this condition it is said to be "fibrillated." (Fig. 65.) The filaments of which it is composed are colorless and elastic, and when isolated are seen to be exceedingly minute, being not more than 4TJ5T5 or even ssh^Ts of an inch in diameter. They are in part arranged so as to lie parallel with each other ; but are more gene- rally interlaced in a kind of irregular network, crossing each other in every direction. On the addition of dilute acetic acid, they swell up and fuse together into a homogeneous mass, but do not dissolve. They are often interspersed everywhere with minute granular mole- cules, which render their outlines more or less obscure. Once coagulated, fibrin is insoluble in water and can only be again liquefied by the action of an alkaline or strongly saline solu- tion, or by prolonged boiling at a very high temperature. These CoAauLATED Fibrin, showing its fibrillated oon< dition. 216 THE BLOOD. agents, however, produce a complete alteration in the properties of the fibrin, and after being subjected to them it is no longer the same substance as before. The quantity of fibrin in the blood varies in different parts of the body. According to the observations of various writers, there is for the most part less fibrin in venous than in arterial blood. It is also more deficient in the blood of the large veins near the heart than of those at a distance. It disappears especially during the circulation through the liver and the kidneys ; and, as a general rule, there is no fibrin in the blood of the hepatic or the renal veins. The alhumen 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. A certain quantity of alhuminose is also to be found in the blood, probably derived from the products of digestion. Its average quantity, according to Eobin," is from 2 to 3 parts per thousand. As it is absorbed in considerable quantities from the intestine during digestion, and neither accumulates in the blood nor appears in any of the excretions, it must be transformed into some other substance nearly as fast as it is taken into the blood. The fatty 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 way into the blood, and circulates for a time unchanged. After- wards 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- •Leyons sur lea Humeurs, page 108. COAGULATIOIT OF THE BLOOD, 217 slum, and the phosphates of soda and potassa are the most abundant in both, while the sulphates are present only in minute quantity. The proportions in which the various salts are present are very dif- ferent, according to Lehmann,^ in the blood-globules and in the plasma. Chloride of potassium is most abundant in the globules, while in the plasma chloride of sodium is the most abundant, form- ing rather more than one-half of all the saline ingredients taken together. The phosphates of. soda and potassa are more abundant in the globules than in the plasma. On the other hand, the phos- phates of lime and magnesia are more abundant in the plasma than in the globules. The alkalescence of the plasma is due to the presence of the car- bonate and basic phosphate of soda. It has already been men- tioned, that, while the alkaline phosphates are most abundant in the blood of the carnivora, the carbonates are most abundant in that of the herbivora. Thus Lehmann ' found carbonate of soda in th'e blood of the ox in proportion of 1.628 per thousand parts. The substances known under the name of extractive matters consist of a mixture of different ingredients, of organic origin, 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. There are also to be found, in solution in the blood, wea, urate of soda, creatine, creatinine, sugar, &c. ; all of them crystallizable substances derived from the transformation of other ingredients of the blood, or of the tissues through which it circulates. The relative quan- tity, 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, 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 iQp. cit., vol. i. p. 546. 'Op. cit., vol. i. p. 393, 218 THE BLOOD. 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 suificient to entangle by its solidification all the fluid and semi-flaid ingredients which were mingled with it, and convert ^S- 66. ^T^Q ^ff}xole into a voluminous, trembling, jelly-like mass of coagulated or " clotted " blood, (Fig. 66.) As soon as the clot has fairly formed, it begins to contract and diminish in size. Ex- L V^I^^^^^F' / actly how this contraction of the clot is pro- t \^^^^ ^ duced, we are unable to say; but it is proba- I i "^ ^ bly a continuation of the same process by Bowl of recently Co Aou- which its solidificatiou is at first accomplished, LATED Blood showing the ^j. ^^ ^^^^ ^^g ^ gimilar to it. As the whole mass nmformly solidi- -^ fled. contraction proceeds, the albuminous fluids begin to be pressed out from the meshes in which they were entangled. A few isolated drops first appear on the surface of the clot. These drops soon increase in size and be- 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 COAGULATION OF THE BLOOD. 219 Fig. 67. \\ f 1^ ^ ^ ^K ,^ — ^. on, its edges are separated, and the fluid continues to exude between it and the sides of the vessel. This exudation continues for ten or twelve hours ; the clot growing constantly smaller and firmer, and the expressed fluid more and 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 cht -g^^^ „, coaodiated which is a red, opaque, dense and resisting b^ood, after twswe hours; .. i?ij5i_' J allowing the clot contracted Semi-SOlld mass, COnSlStmg or 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. 67.) The change of the blood in coagulation may therefore be ex- pressed as follows : — Before coagulation the blood consists of Fibrin, lat. GiiOBULEa ; and 2d. Plasma — containing J ii™en, I Water, . Salts. After coagulation it is separated into ■ J f Albumen, 1st. Clot, containing I ^'j^^°*° and 2d. Seeum, containing ] Water, ' i 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 Eobin 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 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 220 THE BLOOD. 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 coaguliim, 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 once coagulated liquefies again at the commence- ment of putrefaction. The blood coagulates also in the interior of the vessels afte.r death, and the stoppage of the circulation. Under thesei circumstances co- agulation takes place less rapidly than if the blood were wholly withdrawn from the body, owing probably to its remaining in con- tact with the smooth internal surfaces of the bloodvessels, and to the more gradual loss of its natural temperature. In man, as a general rule, the blood is found coagulated in the cavities of the heart and large vessels in from twelve to twenty -four hours after death. In the lower animals, coagulation occurs earlier than this, namely, from four to ten hours after death. The blood coagulates in the cavities COAGULATION OF THE BLOOD. 221 of tbe heart sooner than elsewhere, and the clot in the ventricles is often found to be so entangled with the valves and chordae ten- dinese as to be extricated from them with difficulty. Coagulation of the blood takes place also in the interior of the body even during life, whenever, from any cause, there is a local arrest or irwpediment of the circulation. Thus, if blood be ac- cidentally extravasated into the meshes of the areolar tissue, the substance of the brain or spinal cord, or into a serous cavity, it coagulates in these situations, after a short time, and forms a clot which takes the shape of the cavity occupied by it. Even in the vessels themselves, if the blood be arrested or imprisoned in any particular locality by pressure or ligatures, the same result follows. If a ligature be placed upon an artery in the living subject, the blood which stagnates above the ligatured spot coagulates as it would do if entirely removed from the circulation. The clot, under these circumstances, extends from the ligature backward to the situation of the next collateral arterial branch, that is, to the point at which the movement of the circulation still continues. In all cases, during life as after death, the stoppage or retardation of the circulatory movement induces, after a longer or shorter interval, the coagulation of the fibrin of the blood. The coagulation of the fibrin is not a commencement of organization; it is merely its passage from the normal fluid condition to an un- natural state of solidity, as in the coagulation of the other organic substances. The filaments already described, which show them- selves in the clot (Fig. 65), are not, properly speaking, organized fibres, and are entirely different in their chairacter from the fibres of areolar tissue, or any other normal anatomical elements. They are simply the ultimate form which fibrin assumes in coagulating, just as albumen takes the form of granules under the same circum- stances. The clot, therefore, when once formed, even in the inte- rior of the system, as in cases of ligature, apoplexy or extravasa- tion, becomes a foreign body, and is slowly reabsorbed by the neighboring' parts during convalescence. This reabsorption of the clot is progressive, and is accompanied by various changes in its appearance and consistency. At first it is' comparatively volumi- nous, soft, and of a deep red color. Its more fluid parts, or the serum, are then reabsorbed and the clot becomes smaller and denser. The red coloring matter then gradually diminishes, the whole mass becoming constantly more and more decolorized and reduced in size as absorption goes on, until it loses entirely its original ap- 222 THE BLOOD. pearance, and finally altogether disappears. The time required for complete reabsorption varies from a few days to several months, according to the size of the clot and the situation in which extra- vasation has taken place. Fibrin, therefore, is distinguished from the other organic ingre- dients of the blood by its spontaneous coagulation. Its consti- tution is such, that, without the addition of heat or any chemical agent, it necessarily solidifies after a longer or shorter time, pro- vided only that the movement of the blood in the circulation be arrested or seriously impeded. Why then does it not coagulate in the vessels during life, and while the circulation is actually going on ? The answer to this question is as follows : — The fibrin remains fluid during the natural state of the circulation, because, like the other ingredients of the blood, it is constantly undergoing changes which prevent its arriving at the state necessary for coagulation. We can easily understand how this should be the case when we remember, in the first place, the extreme rapidity with which" the blood moves in the vessels of the living body. We shall see here- after 'that from twenty-five seconds to half a minute is sufficient for the blood to accomplish the entire round of the circulation, so that during this time it visits the remotest organs and tissues and returns again to the right side of the heart. Secondly, the fibrin of the blood disappears while passing through the liver and the kidneys. This fact is fully established by the ob- servations of Simon,^ Lehmann," Bernard, and Brown-Sequard.' While there is an abundance of fibrin in both arterial and portal blood, none, or only feeble traces of it, can be found in that of the he- patic or the renal veins. It is, therefore, decomposed or transformed into some other substance while passing through these organs ; and, its quantity in the blood remaining unimpaired, a fresh supply must be as constantly formed elsewhere. By calculating approxima- tively the quantity of blood contained in the whole body, and that passing daily through the liver and kidneys, it is easy to estimate that a quantity of fibrin equal to that in the entire blood is destroyed and reproduced several times over in the course of a single day. Thus the fibrin existing in the blood at any one time is that which has been recently formed ; and before the time arrives at which 1 Chemistry of Man. Day's Translation. Ptiiladelphia, 1846, p. 178. 'Journal fUr praktische Chemie, 1851, p. 205. 8 Journal de la Physiologie. Paris, April, 1858, p. 298. COAGULATION OF THE BLOOD. 223 it -would naturally coagulate while still in the vessels, it has al- ready been decomposed by its usual metamorphosis in the circu- lation, and has been replaced by a new supply of still more recent formation. But if any portion of the blood be shut off from the circulation, by ligature or otherwise, its fibrin remains unaltered, and in due time necessarily coagulates. It is evident, therefore, that the spontaneous coagulation of the fibrin, though a property by which we recognize it when with- drawn from the vessels, is really an abnormal phenomenon, and never takes place in the natural state of the circulation. Nevertheless, the coagulability of the blood is a very character- istic property, and becomes an exceedingly important one under many accidental circumstances. It is, in fact, the natural means by which hemorrhage is arrested, after a wound of any vas- cular tissue. If such a wound be compressed for a short time, a thin layer of blood coagulates between its edges, and the adherent clot thus formed acts as a temporary plug until the parts have per- manently re-united by the slower growth of new tissue. A torn or contused wound bleeds less freely than an incised one, because the blood coagulates more rapidly upon the ragged edges of the lacerated tissues and thus blocks up the opening. When an artery of considerable size is wounded, and the surgeon places a ligature upon its divided extremity, the clot formed behind the ligature acts as a. still more permanent plug and prevents hemorrhage even after the ligature has been thrown off by ulceration. The entire quantity of blood existing in the body is difficult to ascertain with absolute precision. 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 capillaries of the head and abdominal organs. The other methods which have been practised or proposed from time to time are, for the most part, liable to some practical objection. There is no doubt also that the quantity of blood varies within physi- ological limits according to the condition of fasting or digestion ; since it will necessarily be more abundant after the digestion and absorption of a full meal, than in a state of prolonged abstinence. Bernard' has found, furthermore, that if a poisonous substance be injected in definite quantity into the veins of a living animal, it requires a considerably larger quantity to produce death if the animal be in digestion than if he be fasting, since the proportion > Liquides de TOrganisme, Paris, 1859. Tome i., p. 419. 224: THE BLOOD. of the poison to the whole mass of the blood differs in the two cases. The most satisfactory method for ascertaining approxima- tively the entire quantity of blood in the human subject is that adopted by Weber and Lehmann.^ These observers operated upon two criminals who suffered death by decapitation ; in each of which instances both the methods and results were essentially similar. In one of them the quantities obtained were as follows : — 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 in- jected the arteries of the head and trunk with water until it re- turned from the vessels of a pale red or yellow color, collected the fluid thus returned, 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 bddy, 16.65 The weight of the blood, then, in proportion to the entire weight of the body, w^s as 1 : 8 ; and the body of a healthy man, weighing 145 pounds, will therefore contain on the average about 18 pounds of blood. 'Physiological Chemistry, vol. i. p. 638. BESPIBATION. 225 CHAPTEK XII. BESPIBATION. 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 lost its value as a circulating fluid. 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 15 226 EESPIBATION. integument or mucous membranes, whicli 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 „ „ „ \jijja.^ ou^i^, uj^v^ix „^^^.^ .,^^ Head and Gills of Mesobbaschdb. 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 anima,ls, 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 BKSPIBATION. 227 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 pulmonairy 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 ltno rTpRoo, subdivided, and the surface of the respiratory .blowing its interaai 8ur- jnembraue 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 j'j 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 j\ of an inch in diameter, which is termed a " pulmonary lobule." Each pulmonary lobule resembles in its structure the entire frog's lung in miniature. It consists of a 228 EESPIBATION. Fig. 70. Fig. 71. HiTKAs Labthx, Tbachba, Bbokchi, asd Lcnqs; showing the ramification of tba bronchi, and the divisiou of the lungs into lobules. vascular membrane inclosing a cavity; wliicli cavity is divided into a large number of secondary compartments by thin septa or partitions, wliicli project from its internal surface. (Fig. 71.) These secondary cavities are the "pulmonary cells," or " vesicles." Each vesicle is about ^'5 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 J^l^^^'^ ^^^ a mLZ ^on- lined everywhere with a layer of pavement •='•'»' '«*>«• *■ cavity of loboie. .,■,■,. .. .., .1 , . .1 e, e, 0. FulmonaiT cells, or vesi- epitnelium, continuous with that in the cies. EESPIEATOBY MOVEMENTS OP THE CHEST. 229 ultimate broncTiial tubes. The whole extent of respiratory sur- face in both lungs has been calculated by Lieberkiihn^ 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. Eespieatoky 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 vertebras, 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 ' In Simon's Chemistry of Man, Pliilada ed., 184G, p. 109. 230 EESPIBATION. Fig. 72. scaleni muscles, and tbe intercostal muscles tlien contracting simu';. 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 DiAflRAM ILLnSTRATIHO THE " KeSPIRATORT MOVE- MENTS. — a. Cavity of tbe chest. b. Diaphragm. The dark out- lines show the figure of the chest when collapsed ; the dotted lines^ show the same when expauded. BESFIEATOKY MOVEMENTS OF THE CHEST. 231 recurrence of tbese 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, taken as the mean between the sleeping and waking hours, 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,* 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 suflScient to change the air at all in the pulmonary lobules and vesicles. The air which is drawn in with each inspiration penetrates only into the trachea and bronchial tubes, until, it occupies the place of that which was driven out by the last expiration. By the ordinary respiratory movements, therefore, only that small portion of the ' Human Physiology, Pliilada. ed., 1855, p. 300. 232 EESPIBATION. 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 IoTduIgs 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, ■*■*-' , Shall BronchialTdbe, ehowlDg outward along the central part of its ana inwai-a 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. Eespibatoby 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 ba EESPIBATOET MOVEMENTS OP THE GLOTTIS. 233 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 dianieter. 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. Human Laktnx, viewed fVom above in its ordinary post-mortem cooditioa. — a. Vocal cliords. b. Tliyroid cartilage, cc. Ary- tenoid cartilages, o. OpeaiDg of theglottis. 1 The ►ame, with the glottis opened by separation of the vocal chords. — a. Vocal chords. &. Thyroid cartilage, ca. Aryte- noid cartilages, u. Opening of the glottis. which the size of the glottis is alternately enlarged and diminished. At every inspiration, the glottis opens and allows the air to pass freely into the trachea ; at every expiration it collapses, and the air is driven out through it from below. These movements are called the " respiratory movements of the glottis." They correspond in every respect with those of the chest, and are excited or retarded by similar causes. Whenever the general movements of respiration are hurried and labored, those of the glottis become accelerated and increased in intensity at the same time ; 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. 234 EESFIRATIOK. Fig. 76. HrilAN LAKYNX, FOSTERIOa TIEW. — a. Thyroid cartilage. 6. Epi- glottis, cc. Arytenoid cartilage!), li. Cricoid cartilage, ee. Posterior crico- arytenoid muscles. /. Trachea. In the respiratory motions of the glottis, as in those of the chest, the movement of inspiration is an active one, and that of expira- tion passive. In inspiration, the glottis is opened by contraction of the posterior crico-arytenoid muscles. (Fig. 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 way, the size of the glottis may be in- creased from 0.15 to 0.27 square inch. In expiration, the posterior crico- arytenoid muscles are relaxed, and the elasticity of the vocal chorda 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, the CHANGES IN THE AIE DUEING RESPIBATIOK. 235 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 IJ 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, Eegnault 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, 10,339 grains, or rather less than one pound and a half, avoirdupois. The oxygen which thus disappears from the inspired air is not entirely replaced in the carbonic acid exhaled ; that is, there is less oxygen in the carbonic acid which is returned to the air by expira- tion than has been lost during inspiration. There is even more oxygen absorbed than is given off again in both the carbonic acid and aqueous vapor together, which are exhaled from the lungs.* There is, then, a constant disappearance of oxygen from the air used in respiration^ and a constant accumu- lation of carbonic acid. ' Lehmann's Physiological Chemistry, Fhilada. ed., vol. ii. p. 432. 236 RESPIRATION. 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 Eegnault and Eeiset, 26 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.,' its composition remaining otherwise unchanged; and on the other hand it can no longer sustain life when it contains 20 per cent, ot 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 Eespiration. — If we pass froni the consideration of the changes produced in the air by respiration to those which take place in the blood during the same process, we find, as might have been expected, that the latter correspond inversely with the former. The blood, in passing through the lungs, suffers the following alterations : — 1st. Its color is changed from venous to arterial. 1 Longet, Traits de Phyeiologie, Paris, 1859, vol. i. p. 600. CHANGES IN THE BLOOD DURING EESPIEATION. 237 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- lowingj viz : that carbonic acid exists ready formed in the veiious Mood he/ore 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 osygen by the blood ; and if this supply be cut ofij 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 furtherniore that the interchange of gases in the lunga is not complete but partial in its extent. It results from the experiments of Magendie, Magnus, Bernard, and 238 RESPIRATION. Others, that both oxygen and carbonic acid are contained in both venous and arterial blood. Their proportions, however, are dif- ferent, since there is more oxygen in arterial than in venous blood, and more carbonic acid in venous blood than in arterial. Bernard found in a healthy dog ' rather more than 18 per cent, by volume of oxygen in arterial, and only a little more than 8 per cent, in venous blood. He also found, in various analyses,* from 7 to 10 per cent, of carbonic acid in venous bjood, while in arterial blood this gas was reduced to 3 per cent, or even a still smaller propor- tion. The venous blood, then, as it arrives at the lungs, still re- tains a remnant of the oxygen which it had previously absorbed ; and in passing through the pulmonary capillaries 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 sulficient physical displacing power. Magnus found' that freshly drawn arterial blood yielded by simple agitation with carbonic acid more than 10 per cent, of its volume of oxygen. The carbonic acid may also be expelled from venous blood by a current of pure oxygen, or of hydrogen, or, in great measure, by simple agitation with atmospheric air. There is some difiiculty in determining, however, whether the carbonic acid of the blood be altogether in a free state, or whether it be partly in a state of loose chemical combination with a base, under the form of an alkaline bicarbonate. A solution of bicarbonate of soda itself will lose a portion of its carbonic acid, and become reduced to the condition of a carbonate by simple exhaustion under the air-pump, or by agitation with pure hydrogen at the temperature of the body. Lehmann has found' that after the expulsion of all the carbonic acid removable by the air-pump and a current of hydrogen, there still remains, 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. ' Liquides de I'organisme, vol. i. p. 367 et eeq. 'In Robin, Leifons Bur les Humours, p. 57. ' In RoWn and Verdeil, op. cit., vol. ii. p. 84. * Op. cit., vol. i. p. 393. CHANGES IN THE BLOOD DURING RESPIRATION. 239 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 osygen of the blood is in solution principally in the blood- ghhuks, and not in the plasma. The researches of Magnus have shown' that the blood holds in solution 2 J times as much oxygen as pure water could dissolve at the same temperature ; and that while the serum of the blood, separated from the globules, exerts no more solvent power on oxygen than pure w^ater, defibrinated blood, that is, the serum and globules mixed, dissolves quite as much oxygen as the fresh blood itself. The carbonic acid, on the other hand, is held in solution, not only in the blood-globules, but also by the plasma ; for, the plasma, according to Eobin,^ owing to the presence of its alkaline phosphates and carbonates, has the power of dissolving no less than 48 per cent, of its volume of car- bonic acid, a quantity much greater than is ever actually found in the blood. , Both the oxygen and carbonic acid, therefore, are present in solution in the blood-globules; and since the- color of the blood depends entirely upon that of the globules, it is easy to understand why this color should be altered 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 read- ily 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 at- mosphere, become rapidly reddened, 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 > In Robin and Verdeil, op. cit., vol. ii. p. 28. ' Xie90D8 sur les Humeurs, p. 67. 240 RESPIRATION. 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 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 VerdeiP 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, 1 Ilobin and Verdeil, op. cit., vol. ii. p. 460. CHANGES IN THE BLOOD DURING EESPIEATION. 241 the internal surface of the skin, &c. &c. When the blood, there- fore, comes in contact with the pulmonary tissue, which is permeated everywhere by pneumic acid in a soluble form, its alkaline carbonates and bicarbonates, if any be present, are decom- posed with the production on the one. hand of the pneumates of soda and potassa, and on the other of free carbonic acid, which is exhaled. M. Bernard has found^ that if a solution of bicarbonate of soda be rapidly injected into the jugular vein of a rabbit, it becomes decomposed in the lungs with so rapid a development of carbonic acid, that the gas accumulates in the pulmonary tissue, and even in the pulmonary vessels and the cavities of the heart, to such an extent as to cause immediate death by stoppage of the circulation. In the normal condition, however, the carbonates and bicarbonates of the blood arrive so slowly at the lungs that as fast as they are decomposed there, the carbonic acid is readily exhaled by expiration, and produces no deleterious effect on the circulation. Secondly, in the blood. There is little doubt, although the fact has not been directly proved, that some of the oxygen definitely dis- appear^, 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 re-cent condition, has the power of absorbing oxygen and of exhaling carbonic add. G. Liebig, for example,' found that frog's muscles, recently, prepared and com- pletely freed from blood, continued to absorb oxygen and discharge ' Archives G^n^rales de SKcIecine, xvi. 222. ]g 'la Lelimuuu, op. cit., vol, ii. p. 474. 242 EESPIEATION-. 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 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 haa ' In Lehmann, op. cit., vol. ii. p. 442. CHAKGES IN THE BLOOD DURING EESPIEATION. 243 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 solutioa 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. Rather less than one cubic inch is accordingly given off with each ordinary expiration ; and as we have already found that no less than 350 cubic feet of air are in- haled and discharged during twenty-four, hours, this would give fourteen cubic feet of carbonic acid expired per day. This quan- tity is, by weight, 11,433 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. These variations have been very fully investigated by Andral and Gavar- ret,' who found that the principal conditions modifying the amount of this gas produced were age, sex, constitution and development. The variations were very marked in different individuals, notwith- standing that the experiments were made at the same period of th^ 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 op Carbonic Acid per hour. In subject No. I 1207 cubic inches. "2 970 " " "3 1250 « « "4 1250 " « "5 1591 " « 'Annales de Chimie et de Physique, 1843, 3d series, vol. yiii. p. 129. 244 EESPIRATION. With regard to the difference produced by age, it was found that I'rom 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 Gavarret 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 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 CHANGES IN THE BLOOD DURING EESPIRATION. 245 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, contrary to what happens in the male, ceases to increase ; and it afterward remains stationary so long as the menstrual periods recur with regularity. At the cessation of the menses, the quantity of carbonic acid exhaled increases in a notable manner ; then it de- creases again, as in the male, as the woman advances toward old age. 6. During the whole period of pregnancy, the exhalation of car- bonic acid rises, for the time, to the same standard as in women whose menses have ceased. 7. In both sexes, and at all ages, the quantity of carbonic acid is greater as the constitution is stronger, and the muscular system more fully developed. Prof. Scharling, in a similar series of investigations,* found that the quantity of carbonic acid exhaled was greater during the diges- tion of food than in the fasting condition. It is greater, also, in the waking state than during sleep ; and in a state of activity than in one of quietude. It is diminished, also, by fatigue, and by most conditions which interfere with perfect health. •Annales de Chimie et de Physique, vol. viii. p. 490. 246 RESPIRATION. The process of respiration is not altogether confined to the lungs, but the discharge of carbonic acid takes place also, to a slight ex- tent, both by the urine and the perspiration. M. Morin^ has found that the urine always contains gases in solution, of which carbonic acid is considerably the most abundant. The mean result of fif- teen observations showed that urine excreted during the night con- tains about 1.96 per cent, of its volume of carbonic acid. During the day the quantity of this gas contained in the urine varied con- siderably, according to the condition of muscular repose or activ- ity ; since after remaining quiet for an hour or two, it was only 1.19 per cent, of the volume of the urine, while after continued exertion for the same space of time, not only was the urine augmented in quantity, but the proportion of carbonic acid contained in it was nearly doubled, amounting to 2.29 per cent, of its volume. An equal oreven greater activity of gaseous exhalation takesplace by 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, 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 Beclierches snv les gaz litres de I'urine. Journal de Pharmacie et de Chimie, Paris, 1864, vol. xlv. p. 396. A.NIMAL HEAT. 247 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, suf&cient 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 248 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, if the bulb of a delicate thermometer be held for some minutes between the folds of skin in the palm of the hand, it will stand at 97.5° : in the axilla, at 98° ; under the tongue, and protected from contact with the breath, it will reach 99° ; and in the deeper parts of the internal organs, the temperature is no doubt 100°. When the temperature of the air is below this, the external parts of the body, being most exposed to the cooling influences of radiation and conduction, fall a little below the standard, and may indicate 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 Angers, may be 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, however, be so intense and long continued as to affect the general temperature of the blood, it becomes fatal. Every warm-blooded animal has the power of resisting the depressing influence of external cold, both by the internal heat which is con- stantly generated, and by its external covering of fur or feathers, by which this heat is prevented from being too rapidly lost. But when the exposure is so great that the loss of heat is more rapid than its production, the internal temperature begins to fall, and the animal becomes gradually torpid and insensible in proportion as the warmth of the body is exhausted. As a general rule, death results, in the warm-blooded animals, if the temperature of the blood be reduced to about 80°. These animals, accordingly, have a natural internal temperature, at which the blood must be maintained in order to sustain life ; and even the different species 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. ANIMAL HEAT. 249 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- 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,' have found the temperature of Proteus anguinus to be 63.5°, when that of the air was 55.4° ; that of a frog 48", in water at 44.4°' ; that of a serpent 88.46°, in air at 81.5° ; that of a tortoise 84°, in air at 79.5° ; and that of fish to be from 1.7° to 2.5° above that of the surrounding water. The following list" shows the mean temperature belonging to animals of different classes and species, according to the results obtained by various observers. BiBOS. Mammalia. Reptilb. Fish. Animal. ■ Swallow Heron Raven Pigeon Fowl • Oull Squirrel Goat Cat Hare Dog Ox Horao Ape Toad Carp Tench { Mean Tempekatuke. 111.25° 111.2° 108.5°' 107.6° 106.7° 100.0° 105° 102.5° 101.3° 100.4° 100.3° 99.5° 98.2° 95.9° 51.6° 51.25° 52.10° In the invertebrate animals, as a general rule, the internal heat is produced in too small quantity to be readily estimated. In some ' Simon's Chemistry of Man, Philadelphia edition, p. 124. ' Ibid., pp. 123—126. 250 ' a'nimal hkat. of the more active kinds, however, suoli 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 than the exterior. According to the experiments of Mr. Newport,' the interior of a hive of bees may have a temperature of 48°.5. when the external atmosphere is at 34° .5, even while the insects are quiet ; but if they be excited, by tapping on the outside of the hive, it may rise to 102°. In all cases, while the insect is at rest, the temperature is very moderate ; but if kept in rapid motion in a confined space, it may generate heat enough to afiect 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°.' Dutrochet has moreover found, by a series of very ingenious and delicate experiments,^ 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- ' Carpenter's General and Comparative Physiology, Philadelphia, 1851, p. 852. ' Carpenter's Gen. and Comp. Physiology, p. 846. ' Annales des Sciences Natnrelles, 2d series, xii. p. 277. ANIMAL HKAT. 251 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 dif&culty, the proper temperature of the plant. A certain amount of heat was constantly generated, during 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 differen-t 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 252 ANIMAL HEAT. consumed. On the other hand, if it be shut up in a close 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 aa 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 was sup- posed to combine immediately with the carbon of the pulmonary tissues and fluids, producing carbonic acid, and to be at once re- turned under that form to the atmosphere ; the same quantity of heat resulting from the above process as would have been produced by the oxidation of a similar quantity of carbon in wood or coal. Accordingly, he regarded the lungs as a sort of stove or furnace, by which the rest of the body was warmed, through the medium of the circulating blood. It was soon found, however, that this view was altogether erro- neous ; for the slightest examination shows that the lungs are not perceptibly warmer than the rest of the body ; and that the heat- producing power, whatever it may be, does not reside exclusively in the pulmonary tissue. Furthermore, subsequent investigations showed the following very important facts, which we have already mentioned, viz., that the carbonic acid is not formed in the lungs, but exists in the blood before its arrival in the pulmonary capilla- ries ; and that the oxygen of the inspired air, so far from combining with carbon in the lungs, is taken up in solution by the blood- globules, and carried away by the current of the general circulation. It is evident, therefore, that this oxidation or combustion of the blood must take place, if at all, not in the lungS, but in the capil- laries of the various organs and tissues of the body. ANIMAL HEAT. 253 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 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 Eobin and Verdeil in France ; and since that time it has begun to lose ground and give place to a different mode of explanation, more in accordance with the present state of physiological science. We believe it, in fact, to be altogether erroneous; and incapable of explaining, in a satisfactory 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, "^ow we know that 254 ANIMAL HEAT. in the interior of the body many different actions of this nature are constantly going on ; solutions, combinations and decompositions in endless variety, all of which, taken together, are no doubt suffi- cient to account for the production of animal heat, provided the theory of combustion be found insuficient or improbable. 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 evolution 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, jtbst 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 ANIMAL HEAT. 255 quality of the food. Eegnault and Eeiset ' found, that in dogs fed on meat, the oxygen which reappeared under the form of carbonic acid was only 75 per cent, of the whole quantity absorbed ; while in dogs fed on vegetable substances it amounted to over 90 per cent. In some instances,' where the animals (rabbits and fowls) were fed on bread and grain exclusively, the proportion of expired oxygen amounted to 10 i 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 temperature, 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 tha general mass of the blood is not altered. Finally it has been demon ' Annates de Chimie et de Physique, 3d series, xzvi. p. 428. »Ibid. pp. 409-451. 256 ANIMAL HEAT. strated by Bernard that ia the natural state of the system there is a marked difference in the temperature of the different organs and of the blood returning from them.' The method adopted by this experi- 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 vein or vena cava. As the result of many observations,'' Bernard found that in the dog the temperature of the blood in the abdominal aorta varied from 99.5° to 105.5° F. ; in the portal vein, from 100° to 106° ; and in the hepatic vein, from 101° to 106.8°. The warmest blood in the body, accordingly, is that of the hepatic vein, which has already passed through two successive capillary circulations since leaving the arterial system. The greatest increase in temperature, however, according to the above observations, takes place in the liver itself; for, while the average increase between the blood of the aorta and that of the portal vein was rather less than a quarter of a degree, that between the portal vein and the hepatic vein was over half a degree. Furthermore, it is Bernard's conclusion that animal heat ia pro- duced in the substance of the tissues, since these are often warmer than the venous blood coming from them. Thus the stomach and duodenum were found to have a temperature of from half a degree to one degree higher than that of the blood in the portal vein in their vicinity. The blood accordingly receives its heat in great measure from tissue of the organs through which it circulates ; and as the chemical processes of nutrition are necessarily different 'Gazette Hebdomndaire, Avig. 29 and Sept. 26, 1856. 'Le9onB sur les Liquides de 1 org^iuisme, Paris, 1859, vol. i. p. 84. ANIMAL HEAT. 257 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 Dutroohet, in regard to the different parts of the vegetable organism. 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, 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 changes, 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 luugs. 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, 17 258 ANIMAL HEAT. ia their subsequent disintegration, give rise to several excretorv 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. THE CIBCCIiATIOX, 259 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, algas, 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. 260 THE CIRCULATION. 3d. The capillaries; a network of minute inosculating tubuks 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 cue 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. Eor the respiratory apparatus being one of the most important in the body, and the one most closely connected by anatomical relations with Fig- 77. 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 (o) 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 CiRCDLATioic OP FisH. — n. Aorlcle. t. Ventricle, cc. Gills, d. Aorta, ee. Vena cava. THE HEART. 261 Fig. 78. these animals the respiratory process is not a very active one ; but the gills, which are of small sizfe, 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 cavse discharge their blood into the right auricle (a), whence it passes 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 ptlmonary artery. The arterialized blood, returning from the lungs by the pulmonary vein, is discharged into the left auricle (6), and thence into the ventricle (c), where it mingles with the venous blood which has just arrived by the vena9 cavse. In the reptile, therefore, the ' ventricle is a common organ of pro- pulsion, both for the lungs and for the general circulation. In these' animals the aeration of the blood in - the lungs is only partial; a certain portion of the blood 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 acconaplished. Here, accordingly, we find the {wo circulations, general and pulmonary, distinct from each other. (Fig. 79.) All GiBOtTLATIOH OF RePTII.KS.— «. Bight auricle, b. Left auricle, c. Veotricle. d. LiiDgB. e. Aorta. /. Vena cava. 262 THE CIRCULATION. 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 Kg. 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 (t), 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 cov- 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. CiBCUi.ATIOK lie Mahhamans.— a. Rigbt auricle, b^ Right ventricle, v. Pulmonary artery. d. Lungs, e. Pulmonary vein. /. Left auricle, p Left ventricle, h. Aorta. *i. Vena cava. THE HEAKT. 263 Fig. 80. Fig. 81. HuHAH Heart, anterior view. — a. Right ventricle, b. Left ventricle, c. Biglit auricle, d. Left aaricle. e. Pulmonary artery. /. Aorta. HuuAN Hrakt, posterior view. — It, Right ventricle, b. Left ventricle. c. Eight auricle, d. Left auricle. The different cavities of the heart and of the adjacent bloodvessela 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. Bight Adbicls ahdVehtbiole; Anricalo-veDtricnlar Valves open, Arterial Valves closed. auricular, auriculo-ventricular, and aortic and pulmonary orifices ; the auricular orifices being the passages from the venas 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. 264 THE CIRCULATION. 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. KianT AnaiCLB asd VKiYTKicle; Aurictilo-Tentrliiulai Valves 'cloaed, Arterial Valves opea lungs. Eeturning from the lungs, it enters the left auricle, thpnce 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, however, through the. cardiac cavities, is not a continuous and steady flow, but is 9.cconrplislied by alternate contractions and relaxations of the muscular parjetes 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 thepe successive ^ction^ i" called a beat, or pulsation of the heart. Each pulsation of the hesirt is accompanied by certain important phenomena, which require to be studied in detail. These are tho sounds, the movements, and the impulse. THE HEAKT. 265 GonBBE OF Blood through the Heart. — a^n. Vena cava, superior and inferior. b. Eight ventricle, o. Pulmonary artery, d. Fnlmonary vein. e. Left rentricle. /. Aorta. The sounds of the heart are two in number. They can readily be heard by applying the ear over the cardiac region, when they are found to be quite different from each other in position, in tone, and in duration. They are distinguished as the first and second sounds of the heart. The first sound is heard with the greatest intensity over the anterior surface of the heart, and more particularly over the fifth rib and the fifth intercostal space. It is long, dull, and smothered in tone, and occupies one-half the entire duration of a single beat. It corresponds in time with the impulse of the heart in the precordial region, and the stroke of the large arteries in the immediate vicinity of the chest. The second sound follows imme- diately upon the first. It is heard most distinctly at the situation of the aortic and pulmonary valves, viz., over the sternum at the level of tbe third costal cartilage. It is short, sharp, and distinct 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 tjy the first sound, the third by the second sound, and the fourth by an interval of silence, as follows : — 266 THE CIRCULATION. Titne of pulsation. !'1/*'1""'"1 First sound. I 2d " ) 3d . " Second sound. 4th " Interval of silence. The cause of tlie second sound is nniversally 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 tlie 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 ths 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. ■ Dieeiises of the Heart, Eneeland's Translation, Boston. 1846. THE HEAET. 267 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 long 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 rela"tion 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 valv6s. 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 chordas 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- 268 THE CIECULATIOIT. gled with the valvular sound which occurs at the same tims. 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,* 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 Bhod, 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 efiect 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- ■ Heart-Sounds in Health and Disease. Prize Essay of the American Mc-dica^ AsBOOiation. Transactions of 1 858, p. 825. THE HEART. 269 ments of the heart may be made to continue, in favorable cases, for more than an hour ; and its actions may be studied by direct obser- vation, lilre 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 difierent muscular layers of the ventricular walls, crossing each other obliquely, close the opening, so that there is little or no subsequent hemorrhage. When the successive actions of contraction and relaxation have by this means been fairly recognized and distinguished from each other, the cardiac pulsations are seen to be. characterized by the following phenomena. The changes in form and position of the entire heart are mainly dependent on those of the ventricles, 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 2T0 THE OIRCULATIOir. 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 pf opot: 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.' " 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 an elongation of the ventri- cle, by which its point ia 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 mod-em 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 with 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- > Works of William Hiirrey, M.D Sydenham ed., London, 1847, p. 21. ' Philadelphia Medical Examiner, No. 44. THE HKAKT. 271 lion 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 Fboo in A state of relaxa- tion. Heart of Feoo in cont'-action. "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 272 THE CIRCULATION. Fig. 88. Diagram of Sihple LoorsD FiBREB, 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 efiect of di- minishing the size of the heart in every 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, noneof the 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 ^iral direction, from above downward, and from right to left. (Fig. 89.) They converge toward the point of the heart, curi- a's- 69. jjig round the centre of its apex, and then, changing their direction, be- come deep-seated, run upward along Fig. 90. BuLL0CK*8 Hkart. anterior view, showing the Bupei flcial muscular fibres. Left Ventricle op SCLLOCK'S Heart, show- ing the deep fibres. the septum and internal surface of the ventricles, and terminate in the columnse cameae, 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. THE HEABT. 273 90); their points of origin and attachment being still the aui-iculo- 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 t^ds 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 eifect 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 figure necessarily produced by their contraction. This phenomenon, therefore, of the protrusion of the apex Fi(?, 91. 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 Diagram of ciEour-ARFiBBEs diagrams. We shall see that, provided the OP THB Heart, aod their con- - , ^ traction. iibres wcrc arranged m 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 18 274 THE CIRCULATION. Fig. 92 CONTERQINO FiBKBH AT THE Apex of the Uea&t, viewed externally, it will be seen that the superficial fibres coa verge toward its central point in curved lines, as in Fig. 92. It is well known that 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 oi the heart, therefore, its apex rotates on its own axis in the direction 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, midvfay 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 THE HEART. 275 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,' "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. 276 THK CIRCULATION. 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 chesty 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 AKD 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 difierenoe be- THE ABTEBIES AND THE AKTEEIAL CIRCULATION. 277 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 greatfer 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 hhod 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 conteote, 278 THK CIKCULATION. 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 observeid 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 pf the neck, we can distinguish little or no difference in time between the two impulses. The disten- Elongation and curva- sion of the carotid seems to take place at the p°Jib1*"ok'"^""' " ' 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 THE ABTEBIES AND THE ARTERIAL CIRCULATION 279 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,' 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 brisk, 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- > Journal de la Physiologie. Paris, April,. 1869. 280 THE CIBCULATION. 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. M. 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. Bach lever carried upon its extremity a small pen- cil, which marked upon a strip of paper, moving 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 Phlsatioit in an Elastic Tubs, &s iUnatratod by H. filarey's experiment. — 1. Near the distending force. 2. At a distance from it. 3. Still farther remored. It will be seen that the whole time of pulsation is everywhere of equ£|,l 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 THE ARTERIES AND THE ARTERIAL CIRCULATION. 281 remote points, however, the period of expansion beconaes 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 wouijded 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 woujd 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! 282 THE CIRCULATION. 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 arteries or those of medium size. M. Marey has still further developed his contrivance of a move- able lever, registering its own oscillations, in such a manner that it may be adapted to any of the superficial arteries in the living body. The instrument thus perfected is the sphygmograph. It consists of a small ivory plate which presses gentjy upon the artery by means of a fine spring, and which thus rises and falls with each alternate expansion and collapse of the arterial tube. The motion of the ivory plate is, in its turn, communicated to a vertical metal- lic rod, which touches the under surface of the horizontal regis- tering lever near its attached extremity. The oscillating extremity of the lever, when the instrument is in operation, thus follows the movements of the ivory plate, and registers faithfully , upon the strip of paper, the frequency and form of the arterial pulsations. The advantage of this instrument is, that, in the first place, the length of the lever magnifies to the eye the extent of the artesrial oscillations, and thus enables us to perceive movements too delicate to be distinguished by the touch alone ; and, secondly, that, each part of the pulsations being permanently registered upon paper, the most rapid and evanescent changes in the forni of the artery may be afterward studied at leisure, and compared with each other. By the use of the sphygmograph it is shpwn, that, while there is a general resemblance in the form of pulsation of different arte- ries, nearly every vessel to which the instrument can be applied presents certain peculiarities dependent on its size, position, and distance from the heart. ' In the radial artery at the wrist, each pulsation consists of a sudden expansion of the vessel, indicated by a rapid upward movement of the lever, making, in the trace, a, straight, nearly vertical line. This is followed by a gradual descent of the lever, accompanying the systole of the artery, until it reaches, the lowest point of the trace, when the movement of ascension again takes place, and so on alternately. The line of descent, however, is not straight, like that of ascension, but is almost always marked by one, and sometimes two or even three slight undulations, giving it a wavy character, and indicating a THE ARTERIES AND THE ARTERIAL CIRCULATION, 283 corresponding variation in the tension of the artery during the period of its systole. (Fig. 95.) Fig. 95. Tbaoi ot TBI Radial Pulse, taken by the Ephygmograph. There can he no doubt that the undulations in the line of descent are due to an oscillation in the mass of the blood, subsequent to its impulse by the heart, and during the reaction of the arterial system. Marey has shown, by a series of -well-conducted experi- ments,' thiit similar.oscillations are produced when any incompres- sible liquid is driven by a sudden impulse into an elastic tube ; and that these oscillations are indicated by a similar movement of the index of the sphygmograph applied to its surface. When the heart's impulse is moderate, and the tension of the arterial system fully developed, the undulations in the descending line of the pulse are only slightly perceptible ; but when the heart's impulse is more rapid, and the arterial tension diminished, the undulations become more marked. Marey found that he could procure upon his own person traces of different form, in this respect, by simply increasing the temperature of the body by the addition of warmer clothing. 96, 97, 98), are three traces of the radial The following (Figs, Fig. 96. Fig. 97 Fig. 98. Vabiatioitb or tbi Badial Pulsi, under the inflnence of increaaedtemperatnre; after Marey. I Marey. Pliysiologie mjdicale de la circulation du eang. Paris, 1868, p. 266. 284 THE CIBCULATION. pulse obtained in this way, by increasing the quantity of clothinig at intervals of twenty minutes. In certain diseased conditions, accpmpanied by rapid pulsation of the heart with greatly, diminished arterial tension, the rebound or oscillation of the artery becomes so marked, in proportion to the original impulse, that it is easily perceived by the finger, and thus the pulse is apparently reduplicated ; that is, there are two pulsa- tions of the artery for each contraction of the heart, viz. : one due to the original impulse, and another due to the oscillation of the blood in the feebly distended artery. This is the dicrotic pulse which is often present in disisases of a typhoid character. Fig. 99. DicsoTic PCLBZ OF Typbois Pne V HOD I A ; after Marejr. Fig. 100. Dicrotic Pulsi or Ttphoid Fevrr; after Marey. It is evident that the dicrotic character of the pulse is not, in reality, peculiar to diseased conditions, since the sphygmograph shows that it exists more or less perfectly in a state of health; only it is usually too slight in degree to be appreciated by the finger. KoschlakofF' has also succeeded in verifying the results obtained from the sphygmograph, and in demonstrating the mechanism of the dicrotic pulse. He shows that if a liquid be driven by a rapid impulse through an elastic tube, which is connected with two pres- sure gauges, one near the point of entrance of the liquid, the other near its point of exit, the liquid will rise in the first gauge before the increased pressure reaches the second; that it then falls, while the second is rising, and again rises while the second falls ; show- ing an alternate increase and diminution of pressure in the two extremities of the elastic tube. This alternation continues until the pressure is equalized throughout, or until the tube is again distended by a new impulse. The primary cause, therefore, of the motion of the blood in the 1 In Lorain, Etaaes ie Mfedecine cliniqUe. Paris, 1870, page 7S, THE ABTEHIES AND THE ABTEBIAL CIRCULATION. 285 arteries is the contraction of the heart, which, by driving out the blood in interrupted impulses, distends at every stroke the whole arterial system. But the arterial pulse is not exactly synGhronous 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 en- tirely simple phenomenon ; but is made up of the combined effects of two different physical forces. It is due, in the first place, to the intermittent action of the heart, by which the blood is driven in successive impulses from within outward ; and, secondly, to the elasticity of the entire arterial system, by which it is subjected to an unceasing- pressure, during the relaxation as well as during the contraction of the heart. The passage of the blood through the arterial system takes place, accordingly, everywhere under a certain degree of pressure. For these vessels being everywhere elastic, a,nd, filled, witfe. 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 in- serted, 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 or about that level ; thus indicating the pressure to which it was sub- jected in the interior of the vessels. The 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 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 thc; 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. 286 THE CIRCULATION. 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 mercnry 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 th« 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- 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 efi'ects of friction are reduced to a minimum, and the blood in flowing through the vessels meets with the least possible resistance. THE ABTKBIE3 AND THE AK-TEBIAL CIBCUL ATION. 287 Fig. 101. Pig. 102. Volkhanv'b Apparatits 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 some of the large sized arteries in dogs, horses, and calves. The instrument which he employed (Fig. 101) 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 (i) 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 288 THE CIBCULATIOIT. 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. 102), 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. The most exact experiments on the velocity and movement of the blood in the larger arteries and their branches, are those of Chauveau.' He experimented by introducing into the carotid ar- tery of the horse a brass tube with thin walls, about two inches long and a little over ooe-third of an inch in diameter. The tube was in- troduced through a longi- tudinal incision in the walls of the exposed vessel, and secured in position by a ligature near each extremity , so that the arterial current would then pass, without •J e Graduated scale, for measuriDg the extent of the oacU- lations of the needle. ., ^ , , Chauteau's Iksibdhiict, for measuring the any perceptible obstruction, rapidity of the arterial cumnt a. Brass tube, Ictroduced thrOUffh the tube forming ™*** *^® calibre of the artery. — 6. Index-needle passiug ^ , ^' through the elastic membrane in the side of the brana for the time, a part of the tube, and moving by the impulse of the blood-current.— arterial walls. In the of the tube was a small opening, one eighth of an inch long by one sixteenth of an inch wide, which W'as closed by a thin membrane properly secured so as to prevent the escape of the blood. Through the centre of the elastic membrane there was passed a very light metallic needle, the inner extremity of which, somewhat flattened in shape, projected into the interior of the vessel, and received the impulse of the ar- 1 Journal de la Fbysiologie, Paris, October 1860, p. 695. THE AETKBIE3 AND THE ARTERIAL CIRCULATION. 289 terial blood; while the outer portion, prolonged into a slender index, marked upon a semicircular graduated scale the oscillations of the movable inner extremity, and consequently the varying rapidity of the arterial current. The actual velocity, indicated by any given oscillation of the needle, was ascertained beforehand by attaching the apparatus to an elastic tube and passing through it a stream of warm water of known rapidity. The deviation of the needle under these circum- stances being noted, it becomes afterward an exact register for the velocity of the blood in the arterial circulation. Chauveau found, as the result of these experiments, that the details of the circulatory movement differ somewhat in the larger arteries near the heart, and in the smaller branches farther removed. a. In the carotid artery, at the instant of the systole of the heart, the blood is suddenly put in motion with a comparatively high degree of rapidity, amounting on the average to 20 inches per second. At the termination of the heart's systole, and immediately before the closure of the aortic valves, the movement of the blood decreases very considerably, and may even, for the time, be com- pletely arrested. At the instant of closure of the aortic valves, the circulation receives a new impulse, and the blood again moves forward with a velocity, on the ayeragtJ, of 8J inches per second. Subsequently the rapidity of the current diminishes gradually during the period of the heart's inaction, until, at the end of this period and just before a new systole, it is reduced, on the average, to a little less than 6 inches per second. b. In the smaller arterial branches, such as the facial, the move- ment of the arterial current is more uniform than the above. It is considerably less rapid at the moment of the heart's systole ; and on the other hand, it is always comparatively more active during the period of ventricular repose. The secondary impulse, following the closure of the aortic valves, is much less perceptible than in the larger arteries, and may even be altogether absent. 19 290 THE CIBCULATIOlir. 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 and contractile. They are furthermore distin- guished, throughout the limbs, neck, and external portions of the head and trunk, by being provided with valves, consisting of fibrous sheets arranged in the form of festoons, and so placed in the cavity of the vein as to allow the blood to 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 that the veins will sometimes resist a pressure which is sufi&cient to rupture the walls of the arteries.' In one instance the jugular vein supported, without breaking, a pressure equal to a column of water 148 feet in height ; and in another, the iliac vein of a sheep resisted a pressure of more than four atmospheres. The portal vein was found capable of resisting a pressure of six atmospheres ; and in one case, in which the aorta of a sheep was ruptured by a pressure of 158 pounds, the vena cava of the same animal supported a pres- sure equal to 176 pounds. 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 fascia, 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 ' Le(;oDS sur la Physiologie, &o., vol. ir. p. 301. VKNOUS CIRCULATION. 291 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 tbeir 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 ahwndance 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 j ugular, and the brachial veins. The external and internal j ugulars communicate witb 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- 292 THE CIRCULATION tended, Avithout 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 w|lls of the veins, which are thin and flaccid, cannot retain their position, but collapse under the external pressure too rapidly to allow the blood to flow in from behind. In this case, therefore, the vein is simply emptied in the immediate neighborhood of the chest, but the entire venous circulation is not assisted by the movement. The same difference in the effect of an easy and a violent suction movement, may be readily shown by attaching to the nozzle of an air-tight syringe a flexible elastic tube with thin walls, and placing the other extremity of the tube under water. If the piston of the syringe be now withdrawn with a gentle and gradual motion, the water will be readily drawn up into the tube, while the tube itself suffers no visible change ; but if the suction movement be made rapid and violent, the tube will collapse instantly under the pres- sure of the air, and will fail to draw the water into its cavity. A similar effect shows itself in the living body. If the jugular or subclavian vein be exposed in a dog or cat, it will be seen that while the movements of respiration are natural and easy no fluc- tuation in the vein can be perceived. But as soon as the respira- tion becomes disturbed and laborious, then at each inspiration the vein is collapsed and emptied ; while during expiration, the chest being strongly compressed and the inward flow of the blood arrested, the vein becomes turgid with blood which accumulates in it from behind. In young children, also, the spasmodic movements of res- piration in crying produce a similar turgescenoe 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 mziscfes.-^-The veins which convey the blood through the limbs, and the parietes of the head and trunk, lie among volulitary 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 s^re situated between them. The VENOUS CIECULATION. Fig. 104. Fig. 105. 293 Vbin with valveti open. Veiit with valres closed; stream of blood passing otthj 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 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 otheirs, which communicate by cross branches with the first. (Figs. 104 and 105.) 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 294 THE CIRCULATIOX. 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 Id J 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 iergo, 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 nianner as it has been determined for the arteries. The only calculation which has been made in this respect is based upon a comparison of the total capacity of the arterial and venous systems. As the same blood which passes out- ward through the arteries, passes inward again through the veins, the rapidity of its flow in each must be in inverse proportion to the capacity of the two sets of vessels. That is to say, a quantity of blood which would pass in a given time, with a velocity of x, through an opening equal to one square inch, would pass during the same time through an opening equal to two square inches, with a velocity of | ; and would require, on the other hand, a velocity of 2 X, to pass in the same 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 approxirhalive, 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 sufi- THE CAPILLARY CIRCULATION'. 295 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 j^'ug 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. 106, a.) The middle coat then diminishes in thickness, until it is reduced to a single layer of circular, fusiform, unstriped, musS cuhir 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- ^'8' 106. Q^g^ 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. Smail Aktkrt, with its muscular tunie (n), breaking up Into capillaries. From tbe]> Phosphate and \ of soda 1.2 Sulphate ' Phosphate of lime 0.5 1000.0 ' Colin, Physiologie comparge des Animaux domestiquea, vol. ii. p. 111. THE LYMPHATIC SYSTEM. 321 It tlius appears that both the fibrin and the albumen 6f the blood actually transude to a certain extent from the blood'^'essels, 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 21 b22 IMBIBITION AND EXHALATION. the chyle is also riclier 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 TnonsAND Parts. 3^ hours after feeding 2.45 7 " " " 2.20 13 " " " 0.99 18 " " " 1.15 18J " " " 1.99 It would thus appear that the hourly quantity of lymph, after diminishing during the latter stages of digestion, increases again somewhat, about the eighteenth hour, though it is still considera- bly less abundant than while digestion was in active progress. The lymph obtained from the thoracic duct at all periods coagu- lates soon after its withdrawal, owing to the fibrin which it contains ' In Colin, op. cit., vol. ii. p. 18. THE LYMPHATIC SYSTEM. 323 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. Colin' measured the chyle discharged from the thoracic duct of an ox during twenty-four hours, and found it to exceed eighty pounds. In other experiments of the same kind, he obtained still larger quantities.' From two experiments on the horse, extending over a period of twelve hours each, he calculates the quantity of chyle and lymph in this animal as from twelve to fifteen thousand grains per hour, or between forty and fifty pounds per day. But in the ruminating animals, according to his observa- tions, the quantity is considerably greater. In an ordinary-sized cow, the smallest quantity obtained in an experiment extending ovei ' Gazette Hebdomadaire, April 24, 1857, p. 285. ' Colin, op. cit., vol. ii. p. 100. S24 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 640 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. 325 the alimentary canal and adjacent glands, becoming somewbat 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 vesselsy 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 body. In the following table, the quantities are all calculated for a man weighing 140 pounds. Secreted akd Reabsorbed duriko 24 hours. Saliva 20,164 grains, or 2.880 pounds. Gastric juice 98,000 " " 14.000 Bile 16.940 " " 2.420 " Pancreatic juice 13,104 " " 1.872 " Lymph 27,048 " " 3.864 ' 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. 326 SECBKTION. 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 diS'erent 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- SECKETION. 327 fiiits 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 ofi&ce of another. Those instances which have been from time to time reported of such an unnatural action are not, properly speaking, instances of "vicarious secretion;" but only cases in which certain substances, already existing in the blood, have made their appearance in secretions to which they do not naturally belong. Thus cholesterine, which is produced in the brain and is taken up from it by the blood, usually passes out with the bile ; but it may also appear in the fluid of hydrocele, or in inflammatory exuda- tions. The sugar, again, which is produced in the liver and taken up by the blood, when it accumulates in large quantity in the cir- culating fluid, may pass out with the urine. The coloring matter of the bile, in cases of biliary obstruction, may be reabsorbed, and so make its appearance in the serous fluids, or even in the perspira- tion. In these instances, however, the unnatural ingredient is not actually produced by the kidneys, or the perspiratory glands, but is merely supplied to them, already formed, by the blood. Cases of "vicarious menstruation" are simply capillary hemorrhages which take place from various mucous membranes, owing to the general disturbance of the circulation in amenorrhcea. A true secretion, however, is always confined to the gland in which it naturally originates. The force by which the different secreted fluids are prepared in the glandular organs, and discharged into their ducts, is a peculiar one, and resident only in the glands themselves. It is not simply a process of filtration, in which the ingredients of the secretion exude from the bloodvessels by exosmosis under the influence of pressure ; since the most characteristic of these ingredients, as we have already mentioned, do not pre-exist in the blood, but are formed in the substance of the gland itself Substances, even, which already exist in the blood in a soluble form, may not have the power of passing out through the glandular tissue. Bernard 828 SKCRETION. has found' that ferrocyanide of potassium, when injected into the jugular vein, though it appears with great facility in the urine, does not pass out with the saliva; and even that a solution of the same salt, injected into the duct of the parotid gland, is ab- sorbed, taken up by the blood, and discharged with the urine ; but does not appear in the saliva, even of the gland into which it has been injected. The force with which the secreted fluids accumulate in the salivary ducts has also been shown by Ludwig's experi- ments' to be sometimes greater than the pressure in the bloodves- sels. This author found, by applying mercurial gauges at the same time to the duct of 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. > Leqoiis de Fbjsiologie EzpSrimentale. Paris, 1856, tome ii. p. 96 et seq. « Ibid., p. lOe. MUCDS. 329 The principal secretions met with in the animal body are as follows : — 1. Mucus. 6, Saliva. 2. Sebaceons matter. 7. Gastric juice. 3. Perapiration. 8. Pancreatic jujce. 4. The tears. 9. Intestinal juice. 5. Tliemilk. 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 glandule, 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. 110), and surround- ed on its external surface by a network of capillary bloodvessels. These vessels, penetrating deeply into the 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. %, J Follicles of a Coh- The mucus, produced in the manner i-ookd muoodb glakdulk. above described, is a clear, colorless fluid, '^:^.^:"'^:1Z.'^'IZ which is poured out in larger or smaller foii'cie. », 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 330 SECRETION. tougb 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 pulmonary mucus, that is, the fluid secreted by the follicles of the trachea and bronchial tubes, is as follows : — ^ Composition of Polmonart Mucus. Water 955.52 Animal matter 33.57 Fat 2.89 Chloride of sodium 5.83 Phosphates of soda and potassa 1.05 Sulphates " " 0.65 Carbonates " " 0.49 1000,00 The following is the composition of the mucus of the gall-blad- der : — " Mucus OF THE GaLL-BLADDEK. Water 985.00 Mueosine 6.25 Extractive matters 5.41 Chloride of sodium -j Chloride of potassium y 3.06 Carbonate of soda / Phosphates of lime and magnesia 0.25 1000.00 The animal matter of mucus is insoluble in water, though it absorbs this fluid to some extent, becoming slowly more fluid in consistency. Consequently, a concentrated and viscid 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. Mucus 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 char- ' Simon's Chemistry of Man, Philadelphia, 1846, p. 352. ' Bobin, Le9one sur les Humeurs. Paris, 1867, p. 475. SEBACEOUS MATTEB. 331 acter of theiB principal organic ingredient, as well as in the pro- portion of their saline constituents. Its function is for the most part a physical one, viz., to lubricate the mucous surfaces, to defend them from injury, and to facilitate the passage of foreign substances through their cavities. 2. Sebaceous Matter. — The sebaceous matter is distinguished by containing a very large proportion of fatty or oily ingredients.- There are three varieties of this secretion met with in the body, viz., one produced by the sebaceous glands of the skin, another by the ceruminous glands of the external auditory meatus, and a third by the Meibomian glands of the eyelid. The sebaceous 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. Ill), 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.' Fig. 111. ^MR I B O M I A N Ladovic. Glavtdb, artet Simoa^s Chemistry of Man, p. 379. 332 SECRETION. COHFOSITION OF SeBACEOCS MaTTEB. Animal substances 358 Fatty matters 368 Phosphate of lime 200 Carbonate of lime 21 Carbonate of magnesia 16 Chloride of sodium 1 ^ gn Acetate of soda, &c. ' 1000 Owing to the large proportion of steariae 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 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. Pebspiration. — ^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 5J5 of an inch in di- ameter, 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. 112,) A network of capillary vessels envelops the tubular coil and sup- 4^^ plies the gland with the materials JY^ necessary to its secretion, ^f0^ These glands are very abundant in some parts. On the posterior A PIBSPIIIATOET GlAHD, with ItS veB- „„_.•„ ^f il,- 4._„t,T, fl,-, f.}ippV« Bel8; magnified 36 timeB. (After Todd and Bow- pOrtlOU Ot the trUUk, thC CHeCKS, man.)— a. Glandular coil. h. Plexus of vessels. Fig. 112. PEBSPIBATION. 333 and the skin oi the thigh aud leg, there are, according to Krause/ about 500 to the square inch ; on the anterior part of the trunk, the forehead, the neck, the forearm, and the 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 75 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. The fluid derived from this extensive glandular apparatus is the perspiration. It is a clear, colorless, watery liquid, with a dis- tinctly acid reaction, and a specific gravity of 1003 or 1004. Its constitution, according to the average of estimates given by various authors, is as follows : — Composition or the Piespibatios. Water 995.50 Chloride of sodium 2.23 Chloride of potasaium 0.21 Sulphates of soda and potassa 0.01 Salts of organic acids with soda and potassa .... 2.02 1000.00 In addition to the above ingredients, there are present in the perspiration traces of an organic substance similar to albumen, and also a free acid of a volatile nature, which gives to the fluid its acid reaction and odor, but whose specific characters have not been more fully determined. It is known to be volatile since the perspiration, when subjected to evaporation by heat, soon loses its acid reaction and becomes neutral or alkaline. The perspiration is a constant secretion. In a condition of re- pose or of moderate bodily activity, it is exuded upon the surface of the skin in so continuous and gradual a manner that it is at once carried off by evaporation. Consequently, it does not appear in the liquid form, and has, therefore, received the name, under these circumstances, of the insensible transpiration. The entire quantity of fluid discharged from the skin in this way during twenty-four hours, according to the observations of Lavoisier and Seguin,' amounts to 13,500 grains, or nearly two pounds avoirdu- pois. It appears that the exhalation of watery vapor from the lungs, during the same space of time, amounts to over 8000 grains; 1 KoUiker, Handbuch der Gewebelehre, Leipzig, 1852, p. 147. ' Milne Edwards, Lefons sur la Ffajsiologie, &c., vol. ii. p 623. 334 SECBET.ION. SO that from the lupgs and skin combined, the ■watery exhalatioii amounts, on the average, to rather more than three pounds per day. But the cutaneous secretion may be greatly increased by tem- porary causes. An elevated temperature or unusual muscular exertion, or, still more, a combination of the two, will increase the circulation through the skin and largely augment the amount of fluid discharged. It then exudes more rapidly than it can be car- ried off by evaporation, and collects upon the skin as a visible moisture, whence it is known as the sensible perspiration. The amount of perspiration discharged during violent exercise has been known to rise as high as 5000 or 6000 grains per hour ; and Dr. Southwood Smith ' found that the laborers employed in heated gas- works sometimes lost, by both cutaneous and pulmonary exhalation, as much as 3 J pounds' weight in less than an hour. 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 tem- perature of the body is regulated also in the opposite direction, and is prevented from rising above the natural standard as well as fall- ing below it. The temperature of the skin is never so high as that of the internal organs, being slightly cooled by contact with the external atmosphere, so that it rarely, if ever, in the normal state, rises above 97° or 98°. This moderate temperature is un- doubtedly essential to the healthy action of the skin itself, and even the partial cooling of the blood in the cutaneous capillaries is im- portant in regulating the temperature of the whole mass of the circulating fluid. But when, in consequence of unusual muscular exertion, the circulation is quickened, animal heat is more rapidly generated in the internal organs and a larger volume of warm blood is brought to the cutaneous capillaries, the simple contact with the atmosphere is no longer sufficient to keep down its tem- perature to the usual standard. Then the perspiration is exuded in increased abundance, and its evaporation provides for the requi- site cooling of the skin and of the blood circulating in its vessels. Even if exposed to the influence of an atmosphere warmer than 100° F., the body does not become heated up to the temperature ' PhiloBophy of Health, London, 1838, chap. xiii. T E A H S. 335 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 evaporates, and in assum- ing the gaseous form appropriates so much heat that the cutaneous surfaces are reduced 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 instanceshave been known in which a temperature of 400° to 600° has been borne for a time without much inconvenience. But if the air be saturated with moisture, and evaporation from the skin in this way retarded, the body soon becomes unnaturally warm ; and if the exposure be long continued, death is the result. It is easily seen that horses, when fast driven, suffer much more from a warm and moist atmosphere than from a warm and dry one. The experiments of Magendie and others have shown ' that quadrupeds confined in a dry atmosphere suffer at first but little inconvenience, even when the temperature is much above that of their own bodies ; but as soon as the atmo- sphere is loaded with moisture, or the supply of perspiration is ex- hausted, the blood becomes heated, and the animal dies. Death follows in these cases as soon as the blood has become heated up to 10° or 13° F., above its natural standard. The temperature of 113°, which is but little above the natural temperature of birds, is fatal to quadrupeds ; 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 Teaks. — The tears are produced by the lachrymal glands, which are lobulated glandular organs, 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 conjunctiva, in the fold be- tween the eyeball and the outer portion of the upper lid. The secretion is a clear, alkaline, watery fluid, containing an organic I Bernard, Lectures on the Blood. Atlee's translation, Fhila., 1854, p. 25. 336 SEOKETIOK. substance similar to albumen, and saline matters consisting, for the most part, of chloride of sodium. Its composition is as follows : — ' Composition of the Xeass. Water ... 982.C Albuminous matter ......*.. 6.0 Chloride of sodium 13.0 Other mineral salts 0.2 1000.2 The office of the lachrymal secretion is simply to keep the surfaces of the cornea and conjunctiva moist and polished, and to preserve in this way the transparency of the parts. For the evaporation taking place from the exposed surface of the conjunctiva tends to dry the membrane, and would thus destroy its transparency, were not the loss of fluid constantly replaced by the watery film sup- plied from the lachrymal glands. After death, the eyeball at once loses its brilliancy, and its surface becomes dull and tarnished from the stoppage of the lachrymal secretion. During life, as the tears are secreted, they 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. Fig- 113- 5. The Milk.— The mam- mary glands are lobulated organs, resembling closely in their structure the pancreas, the salivary, and the lachrymal glands. They consist of nu- merous secreting sacs or folli- cles, grouped together in lob- ules; each lobule being sup- plied with a common excretory duct, which joins those coming from a.dj acent parts of the gland. (Fig. 113.) In this way, by QiAHBOLAB STRncTURK OF mabma. thcii successivc uniou, they > Robin, Lejons sur Ics Humeurs, Paris, 1867, p. 492. THE MILK. 337 form larger branches and trunks, until they are reduced in num- ber to some 15 or 20 cylindrical ducts, the lactiferous ducts, which open finally, by as many minute orifices, upon the extremity of the nipple. The secretion of the milk becomes fairly established at the end of two or three days after delivery, though the breasts often 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 shown' that it really con- tains a larger aniount 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- bular or oval bodies, from ttVs *<^ botf of an inch in diameter, which are termed the " colostrum corpuscles." (Fig. 114.) These bodies are more yellow and fig- 11*- 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 j^'^^ to tsVt of 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 CoLOBTRiTM CoRPrsciBs, With milk-globnleB ; from a woman, oae day after delivery. 22 ' LehmanD, op. cit., vol. ii. p. 63. 338 SECRETION. about 1030. Its proximate chemical constitution, according to Pereira and Lehmann, is as follows : — Composition of Cow's Milk. Water 870.2 Casein 44.8 Butter 31.3 Sugar 47.7 Soda Chlorides of sodium and potassium ..... Phosphates of soda and potassa Phosphate of lime f 6.0 " " magnesia " iron Alkaline carbonates . Iron, &c. ........ ■ • 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 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 THE MILK. 339 Fig. 115. Milk-Globuleb; from same woman as above, foar days after delivery. Secretion fully established. alterations wliicli 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. 115.) 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 smaller in size than in the colostrum; as the largest of them are not over j^Vo of ^^ i^ich in diameter, and the greater number about xB^TTTj of ail inch. The following is the composition of the butter of cow's milk, according to Eobin and Verdeil : — Margarine ^ . 68 Oleine 30 Batyrine ..... ^ .... 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 340 SECRETION. 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 {G^fi^O^ 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 (C^HjOg). 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 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 hable 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, diaiThoea, and convulsions in the infant. Simon found^ that the constitution of the milk varies from day to day, owing to temporary causes ; and that it undergoes also more permanent modifications, corresponding with the age of the infant. He analyzed the milk of a nursing woman during a period of nearly six months, commencing with the second day after delivery, and repeating his examinations at intervals of eight or ten days. It appears, from these observations, that the casein is at first in small quantity ; but that it increases during the first two months, ai\d ' Op. oit., p. 337. SECEETION OP THE BILE. 341 tiien 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 op 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 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. Imme- ^ig- ^16. diately upon its entrance, the portal vein divides into two branches, right and left, which supply the corresponding por- tions of the liver ; and these branches successively subdi- vide into smaller twigs and ramifications, until they are reduced to the size, according to Kblliker, of j^^-g of an inch in diameter. These veins, with their terminal branches, are arranged in such a man- ner as to include between them Ramification of Portal Vein in Liter. — a. Twig of portel vein. &, i. Interlobular vein. c. Acini. peutagOUal Or hcXagOUal spaces, or portions of the he- patic substance, ^'j to 75 of an inch in diameter in the human sub- ject, which can readily be distinguished by the naked eye, both on 342 SECRETION. 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. 116) are termed the "acini" or "lobules "of the liver; andthe terminal venousbranches, occupying the spaces between the adjacent lobules, are the "interlobular" veins. In the spaces between the lobuleg we also find the minute branches of the hepatic artery, and the com- mencing rootlets of the hepatic ducts. As the portal vein, the hepatic artery, and the hepatic duct enter the liver at the transverse fissure, they, are closely invested by a fibrous sheath, termed Glisson's capsule, which accompanies them in their divisions and ramifications. In some of the lower animals, as in the pig, this sheath extends even to the interlobular spaces, inclosing each lobule in a thin fibrous 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 epaces ; so that here the lobules are nearly in contact with each 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 Fig. 117. Lobule op Liveb, showing distribntioQ of bloodvessels ; miignifled 22 diameters —a. In- terlobular veins, b. Intralobular vein, c, c, 0. Lobular capillary plexus, d, d. Twigs of incer- lobular vein passing to adjacent lobules. SECEETION OF THE BILE. 343 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. 117.) At the centre of each lobule, the 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 TsVtr of an inch in diameter, the "hepatic cells." (Fig. 118.) -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 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. Fig. 118. Hepatic Cklls. From the human subject. It has now been ascertained, however, by the researches of Dr. Leidy, of Philadelphia,' and Dr. Beale, of London,' that they are really contained in the interior of secreting tubules, which pass off from the smaller hepatic ducts, and penetrate everywhere the substance of the lobules. The cells fill nearly or com- pletely the whole cavity of the tubules, and the tubules, themselves lie in close proxi- mity with each other, so as ' American Journal Med. Soi., January, 1848. 2 On Some Points in the Minute Analomy of tlie Liver. London, 1856. 344 SECRETION. 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. SS.CBETIOK. 845 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 846 EXCRETION, under whicli 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. Thev 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 UKEA. 347 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 : — 1. Carbonic acid COj 2. Urea . 3. Creatine . 4. Creatinine 5. Urate of soda 6. Urate of potassa 7. Urate of ammonia CANA NaO.CjHNjOj+HO NH^O,2C5HNi;Oj+HO The physiological relations of carbonic acid have already been studied, at sufi&cient length, in the preceding chapters. The remaining excrementitious substances may be examined together with the more propriety, since they are all ingredients of a single excretory fluid, viz., the urine. Ueea. — This is a neutral, orystallizable, nitrogenous substance, very readily soluble in water, and easily decomposed by various external influences. It occurs in the urine in the proportion *''S- 1^^' of 30 parts per thousand; in the blood, in the normal condi- tion, according to Picard,' in the proportion of 1.6 per ten 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, so that the excretion of urine is suspended, the urea then accumu- U R E A, prepared from urine, and crystallized by Blow evaporation. (After Lehmana.) ' In Milne Edwards, Lejons buv la Phyaiologle, &o., toI. i. p. 297. 348 EXCRETION. lates in the blood,' and presents itself there in considerable quan- tity. It has also been found in the blood, in the human subject, in cases of disease of the kidney, in unnatural proportions, amount. i.ng, in some instances, to 1.5 parts per thousand.' It is not yet known from what source the urea is originally derived ; whether it is 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 been found, however, by Zalesky,' in the muscles of the healthy dog, in the exceedingly minute proportion of from one to two parts per hundred thousand. 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 : — 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- > Prevost and Dumas. Annales de Chimie et de Physique, 1823, tpme xxiii. p. 90. — S£galaB. Journal de Pliysiologie, tome ii. p. 354. — Mitscherlich, Tiedemann, and Gmelin. Poggendorf s Annalen, tome sxzi. p. 303. — CI. Bernard. Liquides d« Torganisme. Paris, 1859, tome ii., Deuxi^me Lejon. » In Milne Edwards, op. oit., vol. i. p. 298. s ITutersacbungen iiber den Uramiselieu Process. Tiibingen, 1865, Table iii. U B E A. 349 duced, it is necessary tbat 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 and others, 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 501 grains. Bischoff, who was a man above ' the average size and weight, by similar experiments ^ found it to be 540 grains. Prof. William A. Hammond,^ whose weight was 205 pounds, found it to be 670 grains. Prof. John C. Draper,' whose weight was 145 pounds, found it 408 grains. It has been shown by Prof. John C. Draper* that there is also a diurnal variation in the normal quantity of urea. A smaller quan- tity 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 treat- ment 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 discharged during the four hours from 6J to 10^ P. M. The quantity of urea varies also with the nature of the food. Lehmann, by experiments on his own person, found that the quan- tity was larger while living exclusively on animal food than with a mixed or vegetable diet; and that its quantity was smallest when confined to a diet of purely non-nitrogenous substances, as starch, sugar, and oil. The following table' gives the result of these ex- periments. Kind or Food. Daily Quantitt or Ubka. Animal • . . 821 grains. Mixed 501 " Vegetable 347 " Non-nitrogenous 237 '< These experiments have since been abundantly confirmed ; so much so as to induce the belief, with some writers, that the varia- tions in the daily quantity of urea are principally, if not altogether, connected with the amount of nitrogenous food consumed. ' Bernard. Le9on3 de Phyaiologie. Paris, 1859, vol. ii. p. 31. 'American Journal Med. Sci., .Tan., 1855, aid April, 1850. " New York Journal of Medicine, March, 1856, *Loc. cit. 'Lehnjann, op. cit., vol. ii. p. 163. 350 EXCRKTION. Finally, the daily quantity of urea varies with the degree of bodily activity. Both Lehmann and Hammond found it very sen- sibly increased by muscular exertion and diminished by repose. The most recent and conclusive investigations on this subject are those of Prof. A. Flint, Jr.,' on the excretions of the pedestrian E. P. Weston, ■while walking an average distance of nearly 64 miles per day for five consecutive days. These experiments have the advantage, in the first place, of being carried out in an instance where an unusual amount of muscular work was performed, while the food taken did not differ essentially from that of an ordinary diet ; and secondly, of being continued for a sufficiently long time, before, during, and after the exertion, to secure results more reli- able than those previously obtained. The pedestrian was under observation for fifteen days ; namely, five days previous to the walk, five days during its continuance, and five days immediately afterward. For the period preceding the walk, the average exercise was about eight miles per day ; for that subsequent to the walk, it was a little over two miles per day. The results obtained during the three periods showed, accordingly, the normal amount of urea excreted by the pedestrian under ordi- nary conditions, the amount discharged during an unusual and nearly continuous muscular exertion, and the subsequent effects of the exertion on the general condition of the system. The nitrogenous ingredients of the food, during all three periods, were also accurately recorded, so that the influence of the food it- self on the amount of urea may be estimated at the same time with that of the muscular exertion. The following table gives- the main results of these experiments, so far as they are connected with our present subject. Daily Quantity of First Period. Pive days before the wallc. Second Period. Five days during the walk. Third Period. Five days after the walli. Urea 628.24 grains. 339.46 " 293.18 " 315.09 " 95.53 722 16 grains. 234.76 " 337.01 " 361.52 " 174.81 726.79 grains. 440.93 " 339.17 " 373.15 " 91.93 Nitrogen in urea Total nitrogen in urea and feces.. Nitrogen in urea and feces per 100 parts of nitrogen in food. It is evident, therefore, that during the time of unusual muscu- lar exertion the daily quantity of urea was increased by nearly fifteen per cent, over that of the previous ordinary condition, the ■ New York Medical Journal, June, 1871. UEEA, 351 nitrogenous elements of the food being at the same time consider- ably diminished ; and that, during the period of exertion, the total quantity of nitrogen discharged by the urea and feces combined was nearly seventy-five per cent, greater than that introduced with the food, while in both the previous and subsequent periods it was from about four and a half to eight per cent. less. During the period of exertion there was a loss of nearly three and a half pounds of bodily weight, and an increase of a similar amount during the subsequent period of rest. The author fairly explains the above loss of weight by the disintegration of muscular tissue, and the subsequent increase by a retention of nitrogenous constituents in the body, to repair the waste thus produced. "During the five days of the walk,' Mr. Weston consumed in all 1,173.80 grains of nitrogen in his food. During the same period he eliminated 1,807.60 grains of nitrogen, in the urine and feces. This leaves 638.80 grains of nitrogen, over and above the nitrogen of the food, which must be attributed to the waste of his tissues, and probably almost exclusively to the waste of his muscular tissue. According to the best authorities, lean meat uncooked, or muscular tissue, contains 3 per cent, of nitrogen. The loss of 633.80 grains of nitrogen would then represent a loss of 21,127.00 grains, or 3.018 lbs. of muscular tissue. The actual loss of weight was 3.450 lbs. This allows about 0.43 lb. of loss unaccounted for, which might be fat or water." Urea exists in the urine of Fig. 120. both the carnivorous and her- bivorous quadrupeds ; but, as a general rule, there is little or none to be found in that of birds, reptiles, or fish. 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 not at all so in ether. By boiling with an alkali, it is either converted into carbonic acid and ammonia, or is decomposed with the production of urea and ' Op. cit., p. 669. Ckeatine, crystallized from hot water. Lehmann.) (After 352 EXCEETION. Fig. 121. an artificial nitrogenous crystallizable substance, termed sarcosine. By being heated with strong acids, it loses two equivalents 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 muscular 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 originates in the muscular tis- sue, is absorbed thence by the blood, and is finally discharged with the urine. Ceeatixine. — 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 It occurs, like creatine, in the muscles, the blood, Creatinine, (After Lehmaua.) crystallized from hot water. alkaline reaction, 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 {G^KSfi^Wy). Uric acid is sometimes CREATININE. — UBATE OF SODA. 353 spoken of as tkough it were itself a proximate principle, and a constituent of the urine; but it cannot properly be regarded aa 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 urates. 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- ^8- ^22. lar masses, with projecting, curved, conical, wart-like excrescences. (Fig. 122.) 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 is a constant ingredient of human urine, in which it is next in im- portance to the urea ; being present in the proportion of rather more than one part per thousand. It has not yet been detected in normal human blood, but has often been found both in the blood and exudations in cases of gouty and rheumatic disease. It is therefore undoubtedly either produced originally in the blood, or else formed in some of the solid tissues, and absorbed from them by the circulating fluid. It is constantly eliminated by the kidneys, in company with the other ingredients of the urine. The average daily quantity of urate of 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 h^fbivora. In the lat- ter, it is replaced by another substance, differing somewhat froin 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 herbivorous, the urate of soda disappears, and is replaced by the hippurate. 23 Uratb of Soda; from a ariaary deposit. 354 EXCRETIOlf. The urates of potassa and ammonia resemble the preceding salt very closely in their physiological relations. They are formed in much smaller quantity than the urate of soda, and appear like it as ingredients of the urine. Formation and General Characters op 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, miisculine, 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 carbon are daily expelled from the body, is one of these substances ; the others are urea, creatine, creatinine, and the urates. We see, then, in what way the organic matters, in ceasing to form a part of the living body, lose their characteristic properties, and are converted into crystallizable substances, of definite chemical composition. It is a kind of retrograde metamorphosis, by which they return more or less to the condition of ordinary inorganic GENERAL CHAEACTERS OF THE UEIKE. 355 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. For, in the first place, the lungs are adapted, by their anatomical structure, to the absorption and exhalation of gases; while the matters discharged by the kidneys are in a liquid' form, the solid substances being dissolved in the water of the urine. Furthermore, the lungs perform a double function, absorbing oxygen at the same time that they exhale carbonic acid ; while the kidneys are exclu- sively occupied in the discharge of the urine, absorbing nothing in return. The kidneys alone, therefore, of all the organs in the body, 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 distinctly 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 35 fluid ounces, and its mean specific 356 EXCKETION. gravity, 1024. Botli its total quantity, however, and its mean specific gravity are liable to vary somewliat from day to day, owing to the different proportions of water and solid ingredients entering into its constitution. Ordinarily the water of the urine is more than sufiicient 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 abov,e 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 DIOENAL VARIATIONS OP THE URINE. 357 quantity of water is often so mucli 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 Fiest. Marcli 20th. Urine of 1st discharge, acid, sp. gr. 1025. " 2d " alkaline, " 1015. " 3d " neaitral, " 1018. " 4th « acid, " 1018. " 6th " acid, «• 1027. OBSEEVATieir Second. March Zlst. Urine of 1st discharge, acid, sp. gr. 1029. " 2d " neutral, " 1022. " 3d " neutral, " 1026. " 4th " aoid, " 1027. " 6th " 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 358 EXCRETION. gravity and acidity of the urine in cases of disease, it mil not be sufficient to examine any single specimen taken at random ; but all the different portions discharged during the day should be collected and examined together. Otherwise,, we should incur the risk of regarding as a permanently morbid symptom what might be nothing more than a purely accidental and temporary variation. Thexhemical 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 Ueihb. Water 938.00 Urea 30.00 Creatine 1.25 Creatinine l.SO Urate of soda -i " potassa [• 1.80 " ammonia ) Coloring matter and \ „„ Mucus i Biphosphate of soda > Phosphate of soda " potassa " magnesia " lime I Chlorides of sodium and potassium 7,80 ' Sulphates of soda and potassa 6.90 12.45 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 mucm of the urine comes from the lining membrane of the REACTIONS OP THE URINE. 359 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 insohible, or very nearly so, in pure wat^r, they are held in solu- tion in the urine by the acid phosphate of soda, above described. They are derived from the blood, in which they exist in considera- ble quantity. When the urine is alkaline, these phosphates are deposited as a light-colored precipitate, and thus communicate a turbid appearance to the fluid. When the urine is neutral, they may still be held in solution, to some extent, by the chloride of sodium, which has the property of dissolving a small quantity of phosphate of lime. The remaining ingredients, phosphates .of soda and potassa, sul- phates and chlorides, are all derived from the blood, and are held directly in solution by the water of the urine. The urine, constituted by the above ingredients, forms, as we have already described, a clear amber-colorad fluid, with a reaction for the most part distinctly acid, sometimes neutral, and occasion- ally slightly alkaline. In its healthy condition it is affected by chemical and physical reagents in the following manner. Boiling the urine does not produce any visible change, provided its reaction be acid. If it be neutral or alkaline, and if, at the same time, it contain a larger quantity than usual of the earthy phos- phates, it will become turbid on boiling ; since these salts are less soluble at a high than at a low temperature. • The addition of nitric or other mineral acid produces at first only 360 EXCBETION, Fig. 123. a sliglit 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 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. It must be remembered that uric acid does not normally exist in the urine under its own form, but in combination with the alkalies, as the urate of soda, potassa, &c. It is only when this combination is destroyed by the addition of a free acid, that the uric acid is liberated, and, owing to its insolubility, appears as a crystalline deposit. Its crystals have most frequently the form of transparent rhomboidal plates, or oval laminae with pointed extremities. They are usually tinged of a yellowish hue by the coloring matter of the urine which is united with them at the time of their deposit. They are frequently arranged in radiated clusters, or small spheroidal masses, so as to present the appearance of minute calcu- lous concretions. (Fig. 123.) 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. 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 anv abnormal condition of the excretion. Ubic Acid; deposited from nriiie. REACTIONS OF THE UEINE. 361 Beside the properties mentioned above, the urine has several others whieh 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 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 hat; 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, grajdsh-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. ' American Jonmal Med. Sci., April, 1856, 362 EXCRETION. 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 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, mahtes, &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 alkahne 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. 11.) of the experiments of Lehmann, in which he found the urine exhi- biting an alkaline reaction, a very few minutes after the administra' tion of lactates and acetates. In one instance, by experimenting upon a person with congenital extroversion of the bladder, in whom the orifices of the ureters were exposed," he found that the urine became alkaline in the course of seven minutes after the ingestion of half an ounce of acetate of potassa. The pure alkalies and their carbonates, according to the same ob- server, produce a similar effect. Bicarbonate of potassa, for example, administered in doses of two or three drachms, causes the urine to become neutral in from thirty to forty-five minutes, and alkaline in the course of an hour. It is in this way that certain " anti-cal- culous" or " anti-lithic" nostrums operate, when given with a view of dissolving concretions in the bladder. These remedies, which are usually strongly alkahne, 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 ' Physiological Chemisty, vol. ii. p. 133. ACCIDKNTAL INGREDIENTS OF THE URINE. 363 successful disintegration and discharge of the calculus, can only tend to increase its size by additional deposit. Ferrocyanide of potassivm, when introduced into the circulation, appears readily in the urine. Bernard* observed that a solution of this salt, after being injected into the duct of the submaxillary gland, could be detected in the urine at the end of twenty niinutes. 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. Mher 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 bik-pigment passes into the urine in great abundance in some cases of jaundice, so that the urine may have a deep yellow or yellowish brown tinge, and may even stain linen clothes, with which it comes in contact, of a similar color. The saline biliary substances, viz., glyko-cholate and tauro-cholate of soda, have occa- sionally, according to Lehmann, been also found in the urine. In these instances the biliary matters are reabsorbed from the hepatic ducts, and afterward conveyed by the blood to the kidneys. Sugar. — When sugar exists in unnatural quantity in the blood * it passes out with the urine. We have repeatedly found that if sugar be artificially introduced into the circulation in rabbits, or injected into the subcutaneous areolar tissue so as to be absorbed by the blood, it is soon discharged by the kidneys. It has been shown by Bernard" that the rapidity with which this substance appears in the urine under these circumstances varies with the quantity in- jected and the kind of sugar used for the experiment. If a solution of 15 grains of glucose be injected into the areolar tissue of a rabbit 1 Lemons de Pbysiologie Exp£rimentale, 1866, p. 111. > Ibid., 1855, p. 214 et leq. 364 EXCRETION. 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 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 suf&cient to produce passive congestion of the kidneys. "When the renal con- gestion is spontaneous in its origin, and goes on to produce actual degeneration of the tissue of the kidneys, as in Bright'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 Ubine duhing 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 : — ACID FEEMENTATION OP THE UEINE. S65 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, 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 366 EXCEETION. 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 dif&cult to understand, therefore, when oxalate of lime is found as a deposit in the urine, how it can previously have been 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, ^ig- 124. and have the form of regular octohedra, or double quad- rangular pyramids, united base to base. (Fig. 124.) 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. The precise source from which the oxalic acid, under these circumstances, is derived has not been fully determined. The most probable explanation is that it is produced from a metamor- phosis of a small portion of the uric acid of the urine. It is known that if uric acid be boiled in twenty parts of water with peroxide of lead, it is decomposed and oxidized with the production, among other substances, of urea and oxalic acid ; and it is supposed that some similar change may take place in the urine, causing the ap- pearance of a minute quantity of oxalic acid, which at once decern'- poses a portion of the lime-salts, and thus appears as a crystalline deposit of oxalate of lime. At the end of some days the changes above described Oxalate of L i m b ; deposited from liealtliy urine, during tlie acid fermentation. ALKALINE FERMENTATION OF THE UEINE. 367 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. Consequer^tly if the urine, when first discharged, be passed through a succession of close filters, so as to separate its mucus, it may be afterward kept, for an indefinite time, without alteration. But under ordina,ry 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 868 BXCBETION. 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 efiect of the alkaline condition of the urine, thus pro- duoed, 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 soda and magnesia. One of these is the "triple phosphate," phos- phate of magnesia and ammonia (2MgO,NH^O,POj+2HO). The other is the phosphate of soda and ammonia (NaO,NHjO,HO,PO,+ 8H0). The phosphate of magnesia and ammonia is formed from the phosphate of magnesia in the urine (3MgO,POj4-7HO) by the replacement of one equivalent of magnesia by one of am- monia. The crystals of this salt are very elegant and charac- teristic. They show themselves throughout all parts of the mix- ture ; growing gradually in the mucus at the bottom, adhering to the sides of the glass, and scattered abundantly over the film which collects upon the surface. By their refract- ive power, they give to this film a peculiar glistening and iridescent appearance, which is nearly always visi- ble at the end of six or seven days. The crystals are per- fectly colorless and transpa- rent, and have the form of triangular prisms, generally with bevelled extremities. Phosphate of Maobesia and Ammohia; (Fig. 125.) Frequently, alsO^ deposited from healthy urine, during alkaliuefermea- ^j^^j^ g^j ^^^ jgg ^^g tatioa. ° ° Fig. 125. RENOVATIOK OF NUTRITIVE PROCESS. 369 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 bpcorae 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 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. Renovatiok 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, in an approximative man- ner, the quantity of these different ingredients of the ingesta and egesta, as compiled from the results of experiment already given in the foregoing pages. 24 370 ) EXCRETION. Absorbed dijiuno 24 hotjbs. Discharged durinq 24 HOURS. Oxygen . . . 1.470 lbs. Carbonic acid . . 1.630 lbs Water . . . 4.535 " Aqueous vapor . 1.155 " Albuminous matter . .305 " Perspiration . 1.930 " Starch . . . .660 « Water of the urine . 2.020 " Fat 220 " Urea and salts . . .137 " Salts . . . .040 " Feces . .3.58 " 7.230 7.230 Eather more than seven pounds, therefore, are absorbed and dis- charged daily by the healthy adult human subject ; and, for a msD 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 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. NERYOUS SYSTEM. CHAPTER I. GENERAL STRUCTURE AND FUNCTIONS OP 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 ( 371 ) 372 GEJUEBAL 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 ifitegument 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 NEKVOUS SYSTEM. 373 contact witli 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 riglit 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. 374 GENEBAL STBUOTUEE AND FUNCTIONS The nervous system consists bf two kinds of nervous tissue, dif- fering from each other in appearances, structure, and physiological endowments. One of these is the white substance, composed of nervous filaments; the other is the gray substance, which contains granular matter and ganglionic cells. The white substance is found in all the trunks and branches of the nerves, on the exterior of the spinal cord and in the internal parts of the brain. The gray substance, on the other hand, forms the external layer or convolu- tions of the brain, as well as various deposits about its base and central parts, the interior of the spinal cord, and a large number of small detached masses, called the sympathetic ganglia, in dif- ferent parts of the body. The filaments and cells constituting these two kinds of nervous tissue are so different in their prop- erties and function as to require for each a separate description. Nervous filaments of the white substance. — The white substance of the nervous system, when examined by the microscope, is seen to be composed everywhere of minute fibres or filaments, the " ul- timate nervous filaments," running in a direction very nearly par- allel 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 ttsbtst! o^ ^"^ inch. In the trunks and branches of the nerves they average ^^^-^ of an inch. The structure of the ultimate nervous filament is as follows : The exterior of each filament con- sists 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. It may, how- ever, be distinguished where the outlines of the nervous filament are strongly curved or indented, as at c in Fig. 126. N ERTOUS Filaments from sciatic nerve. — Ata, , '. /. i • ' -i i the torn extremity of a nervous flliiment with the axis lu the interior of thlS tubular cylinder(i)) protruding from it. At c,the medullary laj-er ™pTnVi-rflnp tlnprp 1(0 " medullary layer," It is this medullary layer which causes the opaque white color of the nervous tissue. Owing to its highly re- fractive power, it appears, in a microscopic view, as a strongly marked double outline on each border of the nervous filament. Finally, there is, inclosed in the medullary, layer, and forming the central part of the filament, a delicate cylindrical or flattened cord, of a finely granulated appearance, known as the " axis cylinder." When white nervous tissue, from the brain or spinal cord, is prepared for the microscope and examined by transmitted light, two remarkable appearances are observed in its filaments, pro- duced by the contact of foreign substances. In the nrst place the unequal pressure, to which the filaments are accidentally subjected in the process of dissection and preparation, produces an irregu- larly bulging or varicose ap- ^ ^. °, , . ^ Fig. 127. pearance in them at various points, owing to the readiness with which the fluid substance in their interior is displaced in different directions. (Fig. 127.) Sometimes spots may be seen here and there, where the nervous matter has been entirely pressed apart in the centre of a filament, so that there appears to be an entire break in its continuity, while the external layers may be still seen, passing across from one portion to the other. When a nervous filament is torn across under the microscope and subjected to pressure, a cer- tain quantity of the fluid substance is pressed. out from its torn ex- tremity, and may be entirely separated from it, so as to present it- self under the form of irregularly rounded drops of various sizes (a, a, a), scattered over the field of the microscope. The vari- cose appearance above alluded to is more frequently seen in the smaller nervous filaments from the brain and spinal cord, owing to their soft consistency and the readiness with which they yield to pressure. The second efiect produced by the artificial preparation of the nervous matter is an alteration or partial coagulation of the fluid Nervous Filausnts from white Bubstnnce of brain. — a, a, a. Soft substance of the filaments pressed out, and floating in irregularly rounded drops. 376 GENERAL STEUCT-UEE AND FUNCTIONS substance of the medullarj layer. In its natural condition this substance has the same consistency throughout, and appears per- fectly transparent and homogeneous by transmitted light. As soon, however, as the nervous filament is removed from its natural sit- uation, and brought in contact with air, water, or other unnatural fluids, the soft substance immediately under the investing mem- brane 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 At first, this change takes place only in the outer portions of the medullary, layer. The coagulating process, however, subsequently goes on, and gradu* ally advances from the edges of the filament toward its centre, until its entire thickness after a time presents the same appear- ance. The eflfect of this process can also be seen in those portions of the white substance which have been pressed out from the in- terior of the filaments, and which float about in the form of drops. These drops are always covered with a layer of coagulated material which is thicker and more opaque in proportion to the length of time^which has elapsed since the commencement of the alteration. 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 sit- uation. In the nervous trunks and branches, however, outside the cranial and spinal cavitie^ 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 matter of the nerves and that of the brain and spinal cord is owing, there- fore, exclusively to the presence of ordinary fibrous tissue in the nerves, while it is wanting in the brain and spinal cord. The con- sistency of the nervous filaments themselves is the same in each situation. A Nerve, accordingly, consists of a bundle or collection of ulti- mate nervous filaments, associated with each other in larger or smaller packets, and bound together by the investing layers of fibrous tissue which form its sheath, or "neurilemma." The neurilemma sends prolongations of fibrous tissue into the interior of the nerve, dividing its filaments into secondary and tertiary OF THE NEBVOUS SYSTEM. 377 bundles, and containing the small bloodvessels destined for the nutrition of the nerve. When a nerve, therefore, divides during its course into several-branches, this does not imply that the fila- ments themselves become branched or divided at this point, but only that some of them leave the bundles with which they were previ- ously associated, and pursue a different direction. (Fig. 128.) A Fig. 128. Fig. 129. InOBCUlatiOD of N £ E T B 8. BiTfslon of a Nkbti, showing portion of nervous tmnk (a), and the Bepnratlon of Its liliinient« (p, e, d, «). nerve which originates, for example, from the spinal cord in the region of the neck, and runs down the upper extremity, dividing and subdividing, to be finally distributed to the integument and muscles 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 filaments 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 transit of the nerve, between its origin and its termination, they remain distinct and anatomically independent of 878 GENERAL STRUCTUBE AND FUNCTIONS eacli other, each filament by itself remaining continuous through- out. When a nerve, furthermore, is said to "inosculate " with another nerve, as when the infra-orbital inosculates with the facial, or the cervical nerves inosculate with each other, this means simply that some of the filaments composing the first nervous bundle separate from it, and cross over to form a part of the second^ while some of those belonging to the second cross over and join the first (Fig. 129) ; but the individual filaments in each instance remain contin- uous and preserve their identity throughout. Accordingly the nervous .fijaments in different nerves, or in the adjacent parts of inosculating nerves, still remain separate and distinct from each dther; and, however they may be associated in the nervous trunks and branches, they may still act independently and preserve their specific characters and functions in every part of their course. Origin and termination of the nervous filaments. — The nervous filaments originate in the gray substance of the nervous centres and terminate in the muscular tissues and sensitive membranes of the periphery. Both at their origin and termination, they present certain modifications in their appearance and structure which de- serve a special notice. The most important of these modifications are a diminution in size and a disappearance of their external parts. Thus in the gray matter of the brain and spinal cord, many of them are very much smaller than elsewhere, and are also des- titute both of the external tubular " envelope and of the medul- lary layer; being, reduced simply to the central cord or axis cylinder. The naked axis cylinder, to which the nerve filament is thus reduced, becomes continuous in many instances, as we shall hereafter see, with the ganglionic cells of the gray matter, the sub- stance of which resembles its own in appearance and consistency. This fact has led manv anatomists to regard the axis cylinder as the most essential constituent part of the nervous filament, since it continues throughout its entire length ; while the medullary layer and the tubular envelope, though superadded during the greater part of its extent, nevertheless cease to exist at a short distance both from its origin and its termination. It is now fully established that the nervous filaments terminate at the periphery by free extremities. Just previous to the final distribution of the nerves, both in the skin and in the muscles, two peculiarities are to be seen in their anatomical arrangement. First, the small nervous branches divide and subdivide with unusual OF THE NEEVOtrS SYSTEM. 379 rapiditj ; and their subdivisions, uniting with each other by inos- culation, form abundant and closely set plexuses, while from these plexuses the nervous jQlaments are given off which immediately, or soon after, terminate in the substance of the tissues. Secondly, both in these plexuseaand in the ramifications given off from them, the nervous filaments themselves undergo division ; so that a single nervous filament, in this 'situation, may give rise to a numl^er of different branches, each branch retaining all the anatomical char- acters of the original filament. A nervous filament may therefore run undivided throughout the long distance from the brain or spinal cord until its arrival at the skin or the muscles, and then, immediately before its final distribution, break up into a number of separate but closely adjacent branches. The ultimate termination of the nervous filaments in the skin has been most distinctly seen, in the so-called " Pacinian bodies " and the "tactile corpuscles." The Pacinian bodies are minute ovoid-shaped masses found in the subcutaneous cellular tissue of the hands and feet, and various other parts of the body, consisting of a series of concentric laminas of "fibrous tissue, with a central cavity, enclosing a transparent, colorless, fluid or semifluid material. A single ultimate nervous filament penetrates the Pacinian body at one extremity and passes into its central cavity. At the point of entrance the external tubular envelope leaves the nervous filament and becomes continuous with the fibrous laminae of the Pacinian body. The medullary layer also disappears, and the nervous fila- ment, thus reduced to its axis cylinder, runs longitudilially through the greater part of the central cavity and terminates, toward its farther end, in either one or several slightly rounded extremities. The " tactile corpuscles " are much smaller than the Pacinian bodies, but are of similar form. They are situated in the substance of the sensitive papillae of the skin and elsewhere. They consist each of an ovoid mass, marked externally with transverse elongated nuclei and striations. Each corpuscle has attached to its surface sometimes two, but frequently only a single nervous filament, which loses its external envelopes, as in the Pacinian body, and termi- nates in some way, not yet fully determined, in the substance of the corpuscle. The simplest form of tactile corpuscle is supposed to be that known under the name of the "terminal corpuscles of the sensitive nerves," found in the conjunctiva, the lips, the tongue, and the soft palate. They are round or elongated' ovoid bodies, consisting of 380 GENERAL STRUCTUEE AND FUNCTIONS a closed sac of connective tissue, sometimes marked with abundant transverse nuclei, and containing a homogeneous or finely gran- ular substance. Into this body is received the ultimate branch of Fig. 131. Fig, 130. Terminal GORPUSCLEof Gensitive nerre ; from the cuu* junctivaof tbecalf. (After Frey.) i 2 3 Taotiie CoRPnsOLES, from the (edge of thej tongue of the eparrow. 1,2,3. Medullated aerve filameDts Hiipplying four tactile corpiiBcles, One filament divides into two branches ; and one of them is traced to near the extremity of the cor- responding corpuscle, where it ends in a cell-like expansion. (After Ihlder.) a nervous filament, which is reduced to its axis-cylinder, and in many cases may be seen to terminate in the interior by a single free extremity. In the muscles, as a rule, each muscular fibTe has, connected with it, at least one nervous filament, and sometimes more than one. The ultimate filament, produced by the branching and subdivision of the original filament, approaches the muscular fibre, usually at right angles, and penetrates its exterior, — the tubular membrane of the filament becoming continuous with the sarcolemma. At the same time its medullary layer ceases abruptly, and the axis- cylinder spreads out into a thin oval expansion of granular matter, interspersed with nuclei, called the " terminal plate," and lying in immediate contact with the contractile substance of the muscular fibre. Some variations have been described in the form and dis- position of the axis-cylinder in the terminal plate, in some of the inferior classes ; but the above represents the essential characters Tebminaiionof Nbbtous OP THE NERVOUS SYSTEM. 381 of the nervous termination in the muscles of man and most of the vertebrate animals. Phyaiohgical properties of the nervous fila- p. jgg merits. — The nervous filaments are organs of communication. They serve as connecting fibres between the nervous centres on the one hand, and the sensitive and muscular tissues on the other. In order to accomplish this, they are endowed with a peculiar power of irritability, by which, when called into action at either extremity, they become excited throughout their entire length, and produce a ni a mkht in muscular fibre corresponding effect at their opposite termi- '""""'"'• (a""-- "^"B^t.) nation. Thus, those which are distributed to the skin, when ex- cited at their peripheral extremities, produce at their point of origin in the brain a sensation corresponding to the external im- pression. On the other hand, those which are distributed to the muscles, when excited at their origin by the impulse of the will, produce immediately a contraction in the muscular fibres at the periphery. This state of physiological action produces no visible change in the nervous filament itself. Its effects are manifest only at the extremities of the nerve, in the organs in which it has its termination. Nevertheless, it is evident that the nervous filament serves to communicate in some- way an action from one of its extrem- ities to the other ; since, if it be divided in any part of its course, the communication at once ceases, and sensations can no longer be perceived in the skin, nor any voluntary contraction excited in the muscles. The nervous filaments however, like the elements of other tissues, have the power of reuniting after they have been divided by section, and may recover in this way the functions which had been tempo- rarily lost. "When a nerve which is distributed both to the skin and muscles is divided in the middle of its course, the reunion of its filaments is indicated, after a time, by the reappearance of sen- sation and voluntary motion in the parts below. Even when a portion of the nerve-trunk has been cut out, the lost fibres may be regenerated and the functions of the nerve restored. In dogs, cats, and rats, according to the observations of Vulpian and others, — especially when the experiment is performed upon young animals, — the nerve may be regenerated and its function restored when even a little more than two inches of its length have been removed. 382 GENERAL STEUCTUEE AND FUNCTIONS Vulpian ' found the sciatic nerve regenerated, in very young rats after the excision of two inches and one-third, in seventeen days • and in young cats, after excision of one inch of the lingual nerve, sensibility has been found to reappear In the tongue in the course of fourteen days. In man and in adult animals a longer time is required for the union or regeneration of a divided nerve, and the restoration of its functions is sometimes completed only after the lapse of several weeks or even months. Gray substance of the nervous tissue. — The second variety of nervous tissue is known as the " gray substance." As its name indicates, it is of a grayish or ashen hue, by which it is readily dis- tinguished from its contrast with the dead white color of the fibrous matter. It consists of a granular intercellular material with nuclei and pigment grains, and containing, imbedded in its substance, beside an abundance of slender nervous filaments numerous ganglionic cells, of great variety in form and size, termed the "nerve cells." As these cells are the most characteristic elements recognizable by the microscope in the gray nervous tissue, its peculiar properties are regarded as principally dependent upon them. Their average size varies in different parts from 3-oVtj to -ris of ^^ iiich in diameter. They usually have a very distinct oval nucleus and a nucleolus, while the substance of the cell is composed of a finely granular material, of soft consistency. They are sometimes of an ovoid or generally rounded form, as in the ganglia of the sympathetic nerve, with a long process or ex- tension of the substance of the cell frequently running out in the form of a filament, resembling the axis-cylinder of a nerve-fibre. In the ganglia of the posterior roots of the spinal nerves they are usually also rounded or oval in form ; often with two similar pro- cesses, extending from the cell in two opposite directions. The above two varieties have received the names respectively of "uni- polar " and " bi-polar " cells. In the gray matter at the base of the brain, and in the interior of the spinal cord, are to be found the most remarkable of the nerve cells, both for form and size. (Fig. 133.) The largest of them measure, according to Kolliker, ^^^ of an inch in diameter. They present frequently three or four, and even five or six, processes or prolongations running in various directions, and are, therefore called "multi-polar" cells. Most of these fibre-like prolongations, as they recede from the border of the cell, become branched and subdivided, and are thus finally reduced • Lejons sur la physiologie du systime nerveux Paris, 1866, p. 256. OF THE NEHVOUS SYSTEM. 383 to filaments of such minute size tliat they can no longer be fol- lowed by the microscope. Fig. 133. One of the prolongations, however, instead of break- ing up into branches, pur- sues an undivided course, and becomes continuous with the axis-cylinder of a nervous filament. In this way the nervous fila- ments may be said, in many instances at least, to have their origin and ter- mination in the ganglionic cells of the gray sub- stance. Physiological properties of the gray substance. — Every collection of gray nervous substance, what- ever may be its form or size, is called a "nervous centre," or a " ganglion." Its function is to receive impressions conveyed to it by the nervous filaments, and to send out by them impulses, which are to be transmitted to distant organs. The ner- vous centres, accordingly, originate nervous power, so to speak, Avhile the filaments and nerves only transmit it. The mode in which this function of the nervous centres is performed is still more unknown to us than that of the filaments and the nerves. The action which takes place in them,during the period of their excitement, is not accompanied by any visible changes, and can only be explained as the operation of a peculiar power de- pendent on their physiological constitution. It is evident that they are essential to the general action of the nervous system, for neither sensation nor movement is ever excited, in the natural con- dition, by aid of the nervous filaments, unless these are in commu- nication with the gray matter of the nervous centres. We have already seen that the function of the nervous system, as a whole, is to associate the different parts of the body in such a manner that a stimulus applied to one organ may excite the activity of another. Now this communication between the two Nerve GuLLSof the gray aubatance ; from the medulia oblongata. (After Dr. J. Dean.) S84r GENERAL STRUCTUBE AND FUNCTIONS organs is not direct, but circuitous. It passes, in all cases, through an intermediate nervous centre, which receives the impression conveyed to it by the nervous filaments from one organ, and imme- diately reacts by sending out a stimulus which calls into activity the other. This is called the " reflex action " of the nervous system, — because the stimulus is first sent inward to the nervous centre and then returned or reflected in the opposite direction. In this process, the intermediate act between the inward and outward passage of the nervous stimulus is always accomplished in the gray substance of the nervous centres. Oeneral arrangement and mode of operation of the nervous system. — The general arrangement of the nervous system is such that in all cases the various nervous centres, or ganglia, are connected, first, with the different organs by the bundles of filaments called nerves ; and secondly, with each other by oth&r bundles which are termed commissures. Thus the entire system is made up of ganglia, nerves, and commissures. One of the simplest forms of animal life in which a nervous system is to be found is probably the five-rayed starfish. This animal be- longs to the type known as radiata; that is, animals whose organs radiate from a central point, so as to form a circular series of similar parts, each organ being repeated at different ^^ points of the circumference. The k ^RtfS^^ starfish (Fig. 134) consists of a central ^^^^'^"^ mass, with five arms or limbs radi- ating from it. In the centre is the mouth, and immediately beneath it the stomach or digestive cavity, DiAOBiiM OF Niiuvons ST3TEM o» wHch sBuds prolongations into every si'A>"''SH- one of the projecting limbs. There is also contained in each limb a portion of the glandular and mus- cular systems, and the whole is covered by a sensitive integument. The nervous system consists of five similar ganglia, situated in the central portion, at the base of the arms. These ganglia are con- nected with each other by commissures, so as to form a nervous collar or chain, surrounding the orifice of the digestive cavity. Each ganglion also sends off nerves, the filaments of which are distributed to the organs contained in the corresponding limb. OF THE NERVOUS SYSTEM. 385 When any stimulus or irritation is applied to the integument of one of the arms, it is transmitted by the nerves of the integument to the ganglion situated near the mouth. Arrived here, it is received by the gray matter of the ganglion, ajid immediately con- verted into an impulse which is sent out by other filaments to the muscles of the corresponding limb; and a muscular contraction and movement consequently take place. The muscles therefore contract in conseq-uence of an irritation which has been applied to the skin. It must be recollected that this action does not necessarily indicate any sensation or volition, nor even any consciousness on the part of the animal. The function of the gray matter is simply to receive the impulse conveyed to it, and to reflect or send back another ; and this may ^ejaocomplished altogether involuntarily, and without the existence or any conscious perception. It is the simplest form of reflex action. Where. the irritation applied to the integument is of an ordinary, character and not very intense, it is simply reflected, as above described, from the corresponding; ganglion back to the same limb. B lit if it be of a peculiar character, or of greater intensity than usual, it may be also transmitted by the commissures to, the. neighboring ganglia ; and so two, three, four, or even all five of the limbs may be set in motion by a stimulus applied to the integument of one of them. Now, as all the limbs of the animal have the, same structure and contain the same organs, their action will also be the same; and the effects of this communication of the stimulus from one to the other by means of commissures will be a repetition, or rather a simultaneous production, of similar movements in, different parts of the body. According to the character, and intensity, therefore, of the original stimulus, it will be followed by a response from one, several, or all of the different parts of the animal frame. It will be seen also that there are, two sets of nervous filaments, differing essentially in their functions. . One set of these fibres run from the sensitive surfaces to the ganglion, and convey the nervous impression inward. These are called sensitive fibres. The other set run from the ganglion to. the, muscles, and carry the nervous impression outward. These are called motor fibres. In the starfish, where the body is composed of a repetition of simi- lar parts arranged round a common centre, and where all the limbs are precisely alike in structure, the several ganglia composing the nervous system are also similar to each other, and act in the same 26 886 GENERAL STBUCTUBE AND FUNCTIONS Fig. 135. "way. But in animals which are constructed upon a different plan, and whose bodies are composed of distinct organs, situated in dif- ferent regions, we find that the nervous ganglia, presiding over the function of these organs, present a corresponding degree of dissimilarity. In Aplysia, for example, which belongs to the type of "mollusca," or soft-bodied animals, the digestive apparatus consists of a mouth, an oesophagus, a triple stomach, and a some- what convoluted intestine. The liver is large, and placed on one side of the body, while the gills, in the form of vascular laminae, occupy the opposite side. There are both testicles and ovaries in the same animal, the male and female functions co- existing, as in many other invertebrate species. All the organs, furthermore, are here arranged without reference to a reg- ular or symmetrical plan. The body is covered with a muscular mantle, which ex- pands at the ventral surface into a tolerably well-developed " foot," or organ of locomo- tion, by which the animal is enabled to change its position and move from one locality to another. The nervous system of this animal is con- structed upon a plan corresponding with that of the entire body. (Fig. 135.) There is a small ganglion (i) situated anteriorly, which sends nerves to the commencement of the digestive apparatus, and is regarded as the oesophageal or digestive ganglion. Immediately behind it is a larger one (2) called the cephalic or cerebral ganglion, which sends nerves to the organs of special sense, and which is regarded as the seat of volition and general sensation for the entire body. Following this is a pair of ganglia (3, 3), the pedal or locoraotory ganglia, which supply the muscular mantle and its foot-like expansion, and which regulate the movement of these organs. Finally, another ganglion (4), situ- ated at the posterior part of the body, sends nerves to the branchiae or gills, and is termed the branchial or respiratory ganglion. All these nervous centres are connected by commissures with the central or cerebral ganglion, and may therefore act either independently or in association with each other, by means of these connecting fibres. NebtouS Ststeh of Api.TalA. — 1. Digeslive or cesopliageal ganglion. 2. Cere- bral ganglion. 3, 3, Fedal or locomotory ganglia. 4. Kespi- T&toty ganglion. OF THE NEBVOUS SYSTEM. 387 In the third type of animals, again, viz., the articuhta, the gene- ral plan of structure of the body is different from Fig. 186. the foregoing, and the nervous system is accord- ingly modified to correspond with it. In these animals, the body is composed of a number of rings or sections, which are articulated with each other in linear series. A very good example of this type may be found in the common 'centipede, or scohpendra. Here the body is composed of twenty -two successive and nearly similar articu- lations, each of which has a pair of legs attached, and contains a portion of the glandular, respira- tory, digestive and reproductive apparatuses. The animal, therefore, consists of a repetition of similar compound parts, arranged in a longitudi- nal chain or series. The only exceptions to this similarity are in the first and last articulations. The first is large, and contains the mouth ; the last is small, and Contains the anus. The first articulation, which is called the " head," is also furnished with eyes, with antennae, and with a pair of jaws, or mandibles. or cektipede. The uervous system of the centipede (Fig. 13 6), corresponding in structure with the above plan, consists of a linear series of nearly equal and similar ganglia arranged in pairs, situated upon the median line, along the ventral surface of the alimentary canal. Each pair of ganglia is connected with the integument and muscles of its own articulation by sensitive and motor filaments ; and with those which precede and follow by a double cord of longitudinal commissural fibres. In the first articu- lation, moreover, or the head, the ganglia are larger than elsewhere, and send nerves to the antennae and to the organs of special sense. This pair is termed the cerebral ganglion, or the "brain." A reflex action may take place, in these animals, through either one or all of the ganglia composing the nervous chain. An im- pression received by the integument of any part of the body may be transmitted inward to its own ganglion and thence reflected immediately outward, so as to produce a movement of the limbs belonging to that articulation alone; or it may be propagated, through the longitudinal commissures, forward or backward, and produce simultaneous movements in several neighboring articula- 888 GKXEBAL STRUCTURE AND FUKCTIONS tions ; or, finally, it may be propagated quite up to tbe anterior pair of ganglia or " brain," where its reception will be accompanied with consciousness, and a voluntary movement reflected back upon any or all of the limbs at once. The organs of special sense, also, com- municate directly with the cerebral ganglia ; and impressions con- veyed through them may accordingly give rise to movements in any distant part of the body. In these animals the ventral ganglia, or those which simply stand as a medium of communication be- tween the integument and the muscles, are nearly similar through- out ; while the first pair, or those which receive the nerves of special sense, and which exercise a general controlling power over the rest of the nervous system, are distinguished from the remainder by a well-marked preponderance in size. In the centipede it will be noticed that nearly' all the organs and functions are distributed in an equal degree throughout the whole length of the body. The organs of special sense alone, with those of mastication- and the functions of perception and volition, are confined to the head. The ganglia occupying this part are there- fore the only ones which are distinguished by any external pecu- liarities; the remainder being. nearly uniform bom in size and activity. In some kinds of articulated animals, however, particular functions are concentrated, to a greater or less extent, in particular parts of the body ; and the nervous ganglia which preside over them are modified in a corresponding manner. In the insects, for example, the body is divided into three distinct sections, viz : the head, containing the organs of prehension, mastication, tact and special sense ; the chest, upon which are concentrated the^ or- gans of locomotion, the legs and wings ; and the abdomen, contain- ing the greater part of the alimentary canal, together with the glandular and generative organs. As the insects have a greater amount of intelligence and activity than the centipedes and other worm-like articulata, and as the organs of special sense are more perfect in them, the cerebral ganglia are also unusually developed* and are evidently composed of several pairs, connected by commis- sures so as to form a compound mass. As the organs of locomo- tion, furthermore, instead of being distributed, as in the centipede, throughout the entire length of the animal, are concentrated upon the chest, the locomotory ganglia also preponderate in size in this region of the body ; while the ganglia which preside over the secre- tory and generative functions are situated together, in the cavity of the abdomen. OF THK NERVOUS SYSTEM. 389 All the above parts, however, are connected, in the same manner as previously described, with the anterior or cerebral pair of gan- glia. In all articulate animals, moreover, the general arrangement of the body is symmetrical. The right side is, for the most part, precisely like the left, as well in the internal organs as in the ex- ternal covering and the lo6omotory appendages. The only marked variation between different parts of the body is in an antero-pos- terior direction ; owing to different organs being concentrated, in some cases, in the head, chest, and abdomen. Finally, in the vertebrate type of animals, comprising man, the quadrupeds, birds, reptiles, and fish, the external parts of the body, together with the locomotory apparatus and the organs of special sense, are symmetrical, as in the articulata ; but the internal organs, especially those concerned in the digestive and secretory functions-, are unsymmetrical and irregular, as in the molluscs. The organs of respiration, however, are nearly symmetrical in the vertebrata, for the reason that the respiratory movements, upon which the function of these organs is immediately dependent, are performed by muscles belonging to the general locomotory apparatus. The nervous system of the vertebrata partakes, accordingly, of the struc- tural arrangement of the organs under its control. That portion which presides over the locomotory, respiratory, sensitive, and in- tellectual functions forms a system by itself, called the cerebrospinal system. This system is arranged in a manner very similar to that of the articulata. It is composed of two equal and symmetrical halves, running along the median line of the body, the different parts of which are connected by transverse and' longitudinal com- missures. Its ganglia occupy the cavities of the cranium and the spinal canal, and send out their nerves through openings in the bony walls of these cavities. The other portion of the nervous system of vertebrata is that which presides over the functions of vegetative life. It is called the ganglionic or great sympathetic system. Its ganglia are situated anteriorly to the spinal column, in the visceral cavities of the body, and are connected, like the others, by transverse and longitudinal commissures. This part of the nervous system is symmetrical in the neck and thorax, but is unsymmetrical in the abdomen, where it attains its largest size and its most complete development. The vertebrate animals, as a general rule, are very much superior to the other classes, in intelligence and activity, as well as in the variety and complicated character of their motions; while their 390 GENERAL STBUCTUBE AND FUNCTIONS Fig. 187. nutritive or vegetative functions, on the other hand, are not particu- larly well developed. Accordingly we find that in these animals the cerebro-spinal system of nerves preponderates very much, in im- portance and extent, over that .of the great sympathetic. The quan- tity of nervous matter contained in the brain and spinal cord is, even in the lowest vertebrate ani- mal, very much greater than that contained in the system of the great sympathetic; and this preponder- ance increases, in the higher classes, just in proportion to their supe- riority in intelligence, sensation, power of motion, and other func- tions of a purely animal character. The spinal cord is very nearly alike in the different classes of ver- tebrate animals. It is a nearly cylindrical cord, running from one end of the spinal canal to the other, and connected at its anterior ex- tremity with the ganglia of the brain. (Pig. 137.) It is divided, by an anterior and 'posterior median fissure, into two lateral halves, which still remain connected with each other by a central mass or commissure. Its inner portions are occupied by gray matter, which forms a continuous ganglionic chain, running from one ex- tremity of the cord to the other. Its outer portions are composed of white substance, the filaments of which run for the most part in a longitudinal direction, connecting the different parts of the cord with each other, and the cord itself with the ganglia of the brain. The spinal nerves are given off from the spinal cord at regular intervals, and in symmetrical pairs ; one pair to each successive portion of the body. Their filaments are distributed to the integu- ment and muscles of the corresponding regions. In serpents, where locomotion is performed by simple, alternate, lateral movements of the spinal column, the spinal cord and its nerves are of the same size throughout. But in the other vertebrate classes, where Cerebro-spinal Ststeh of Man, — 1. Cerebram. 2. Cerebellum. 3,3,3. Spinal cord and nerves. 4, 4. Brachial nerves. 5, 5. Sacral nerves. OP THE NERVOUS SYSTEM. 391 tliere exist special organs of locomotion, sucli as fore and hind legs, wings, and the like, the spinal cord is increased in size at the points where the nerves of these organs are given off; and the nerves themselves, which supply the limbs, are larger than those originating from other parts of the spinal cord. Thus, in the hu- man subject (Fig. 137), the cervical nerves, which go to the arms, and the sacral nerves, which are distributed to the legs, are larger than the dorsal and lumbar nerves. They form, also, by frequent inosculation, two remarkable plexuses, before entering their corre- sponding limbs, viz., the bra- _f '8' ^^^- chial plexus above, and the sacral plexus below. The cord itself, moreover, pre- sents two enlargements at. the point of origin of these nerves, viz., the cervical en- largement from which the brachial nerves (4, 4) are given off, and the lumbar TZZlTSTof spikal coed.-«,6. spio»i enlargement from which the nerves of right and left Bides, showing their two roots. gacral nerVCS (s, s) Originate. d. Origin of anterior root. «. Origin of posterior root. Ti? i • i j -u c. Ganglion of posterior root. It the spiual cord be exa- mined in transverse section (Fig. 138), it will be seen that the gray matter in its central portion forms a double crescentic-shaped mass, with the concavity of the crescents turned outward. These crescentic masses of gray matter, occupying the two lateral halves of the cord, are united with, each other by a transverse band of the same substance, which is called the gray commissure of the cord. Their anterior and posterior por- tions, in front and behind the gray commissure, are called, respec- tively, the anterior and posterior horns of gray matter. Directly in front of the gray commissure is a transverse band of white sub- stance, connecting in a similar manner the white portions of the two lateral halves. It is called the white commissure of the cord. The spinal nerves originate from the cord on each side by two distinct roots ; one anterior, and one posterior. The anterior root (Fig. 138, d) arises from the surface of the cord near the extremity of the anterior horn of gray matter. The posterior root (e) origi- nates at the point corresponding with the posterior horn of gray matter. Both roots are composed of a considerable number of ultimate nervous filaments, united with each other in parallel 392 GKNEBAL STBUCTUBE AND FUNCTIONS bundles. The posterior root is distinguished by the presence of a small ganglion (c), which appears to be incorporated with it, and through which its fibres pass. There is no such ganglion on the anterior root. The two roots unite with each other shortly after leaving the cavity of the spinal canal, and mingle their filaments in a single trunk. It will be seen, on referring to the diagram (Fig. 138), that each lateral half of the spinal cord is divided into two portions, an anterior and a posterior portion. The posterior horn of gray mat- ter comes quite up to the surface of the cord, and it is just at this point (e) that the posterior roots of the nerves have their origin. The whole of the white substance included between this point aSid the posterior median fissure is called the posterior colurf^.^ihe cord. That which is included between the origins of the posterior and those of the anterior roots is called the lateral column; wipe that which is included between the anteriot roots and the anteriSr median fissure is the anterior column. The white "substance of tte cord may then be regarded as consisting for the most part of six longitudinal bundles of nervous filaments, viz., the right and left anterior, the right and left posterior, and right and left lateral columns. The posterior median fissure penetrates deeply into the substance of the cord, quite down to the gray matter, so that the posterior columns appear entirely separated from each other in a transverse section ; while the anterior median fissure is more shal- low and stops short of the gray matter, so that the anterior columns are connected with each other by the white commissure above men- tioned. By the encephalon we mean the whole of. that portion of the cerebro-spinal system which is contained in the cranial cavity. It is divided into three principal parts, viz.y the cerebrum, cerebellum, and medulla oblongata. The anatomy of these parts, though some- what complicated, can be readily understood if it be recollected that they are simply a double series of nervous ganglia, connected with each other and with the spinal cord by transverse and longitudinal commissures. The number and relative size of these ganglia, in different kinds of animals, depend upon the perfection of the bodily organization in general, and more especially on that of the intelli- gence and the special senses. They are most readily described by commencing with the simpler forms and terminating with the more complex. The brain of the Alligator (Fig. 139) consists of five pair of ganglia, ranged one behind the other in the interior of the cranium. OF THE NERVOUS SYSTEM. 393 Fig. 139. Braix uf Alligator factory ganglia. 2. Heniiftpheres, Optic tubercles. 4. Cerebellam. Medulla oblongata. The first of these are two rounded masses (i), lying just above and behind the nasal cavities, which distri- bute their nerves upon the Schneiderian mucous membrane. These are the olfac- tory ganglia. They are connected with the rest of the brain by two long and slender commissures, the " olfactory com- missures." The next pair (a) are some- what larger and of a triangular shape, when viewed from above downward. They are termed the " cerebral ganglia," or the hemispheres. Immediately follow- ing them are two quadrangular masses (s) which give origin to the optic nerves, and are therefore called the optic ganglia. They are termed also the " optic tuber- cles ;" and in some of the higher animals, where they present an imperfect division into four nearly equal parts, they are known as the " tubercula quadrigemina." Behind them, we have a single triangular collection of nervous matter (4), which is called the cerebellum. Finally, the upper por- tion of the cord, just behind and beneath the cerebellum, is seen to be enlarged and spread out laterally, so as to form a broad oblong inass (s), the medulla oblongata. It is from this latter portion of the brain that the pneumogastric or respiratory nerves originate, and its ganglia are therefore sometimes termed the " pneumogastric" or "respiratory" ganglia. It will be seen that the posterior columns of the cord, as they diverge laterally in order to form the medulla oblongata, leave be- tween them an open space, which is continuous with the posterior median fissure of the cord. This space is known as the '• fourth ventricle." It is partially covered in by the backward projection of the cerebellum, but in the alligator is still somewhat open pos- teriorly, presenting a kind of chasm or gap between the two lateral halves of the medulla oblongata. The successive ganglia which compose the brain, being arranged in pairs as above described, are separated from each other on the two sides by a longitudinal median fissure, which is continuous with the posterior median fissure of the cord. In the brain of the alligator this fissure appears to be interrupted at the cerebellum ; 894 GENERAL STBUCTUBE AND FUNCTIONS Fig. 140. tut in the higber classes, where the lateral portions of the cerebel- lum are more highly developed, as in the human subject (Fig. 137). they are also separated from each other posteriorly on the median line, and the longitudinal median fissure is complete throughout. In birds, the hemispheres are of much larger size than in rep- tiles, and partially conceal the optic ganglia. The cerebellum, also, is very well developed in this class, and presents on its sur- face a number of transverse foldings or convolutions by which the quantity of gray matter which it .contains is considerably in- creased. The cerebellum here extends so far backward as almost completely to conceal the medulla oblongata and the fourth ven- tricle. In the quadrupeds, the hemis- pheres and cerebellum attain a still greater size in proportion to the remaining parts of the brain. There are also two other pairs of ganglia, situated beneath the he- mispheres, and between them and the tubercula quadrigemina. These are the corpora striata in front and the optic thalami behind. In Fig. 140 is shown the brain of the rabbit, with the hemispheres laid open and turned aside, so as to show the internal parts in their natural situation. The olfactory ganglia are seen in front (i) con- nected with the remaining parts by the olfactory commissures. The separation of the hemispheres (s, a) shows the corpora, striata (s) and the optic thalami (4). Then come the tubercula quadrigemina (5), which are here composed, as above mentioned, of four rounded masses nearly equal in size. The cerebellum (s) is considerably en- larged by the development of its lateral portions, and shows an abundance of. transverse convolutions. It conceajs from view the fourth ventricle and most of the medulla oblongata. In other species of quadrupeds the hemispheres, increase in size so as to project entirely over the olfactory ganglia in front, and to cover in the tubercula quadrigemina and the cerebellum behind. The surface of the hemispheres also becomes covered with nume- Brain opRabbit, viewed from above.r- 1. Olfactory ganglia. 2 Hemtsplieres, turoed aside. 3. Corpora cttriata. 4. Optic thalami. 5. Tubercula quadrigemina 6. Cerebellunv OF THB NERVOUS SYSTEM. 895 Fig. 141. Tons convolutions, which are curvilinear and somewhat irregular in form and direction, instead of being transverse, like those of the cerebellum. In man, the development of the hemispheres reaches its highest point ; so that they preponderate altogether in size over the rest of the ganglia constituting the brain. In the human brain, accordingly, when viewed from above downward, there is nothing to be seen but the convex surfaces of the hemispheres ; and even in a posterior view, as seen in Fig. 137, they conceal everything but a portion of the cerebellum. All the remaining parts, how- ever, exist even here, and have the same connections and relative situation as in other instances. They may best be studied in the following order. As the spinal cord, in the human subject, passes upward into the cranial cavity, it en- larges into the medulla oblongata as already described. The medulla oblongata presents on each side three projections, two anterior and one posterior. The middle projections on its anterior surface (Fig. 141, i, i), which are called the anterior pyramids, are the con- tinuation of the anterior columns of the cord. They pass onward, underneath the transverse fibres of the pons Varolii, run upward to the corpora striata, pass through these bodies, and radiate upward and outward from their external surface, to terminate in the gray matter of the hemispheres. The projections immediately on the outside of the anterior pyramids, in the medulla oblongata, are the olivary bodies (» j). Each contains in its interior a thin layer of gray matter folded upon itself, forming a convoluted ganglion, which is connected, by longitudinal, radiating and trans- . verse fibres, with other parts of the medulla above and below, and with the corresponding ganglion of the opposite side. The anterior columns of the cord present, at the lower part of the medulla oblongata, a remarkable interchange or crossing of their fibres (4), known as the decussation of the anterior pyramids. Tnis decussation, as shown by Mr. J. L. Clarke,' consists of fibres derived from the lateral columns of the cord, which cross obliquely at the median line, and pass over to be incorporated with the sub ■ Retearcheg ou the Intimate Structure of the Brain, &c. London, Phil. Trans., 1858. Medulla Oblonaata OK HPUAN Bbaih, ante- rior Tlew — 1,1. Anterior py- ramidfl. 2, 2. OHvary bodies. 3, 3. KestUorm bodies. 4. De- cuBsation of the anterior co- luraiiB. The medulla oblong- ata is seen terminated above by the tranaveree fibres of the pons Varolii. 396 GENERAL STRUCTURE AND FUNCTIONS Stance of the opposite anterior columns, tlms increasing their mass at this point, and forming the rounded prominences known as the anterior pyramids. Thus the right side of the brain is connected with the left side of the spinal cord, and the right side of the spinal cord with the left side of the brain. The posterior columns of the cord, as they diverge on each side of the fourth ventricle, form the posterior and lateral projections of the medulla oblongata (a, 3). They are sometimes called the " res- tiform bodies," and are extremely important parts of the brain. They consist in great measure of the longitudinal filaments of the posterior columns, which pass upward and outward, and are distributed partly to the gray matter of the cerebellum. The remainder then pass forward, underneath the tubercula quadri- gemina, into and through the optic thalami ; and radiating thence upward and outward, are distributed, like the continuation of the anterior columns, to the gray matter of the cerebrum. The resti- form bodies, however, in passing upward to the cerebellum, are supplied with some fibres from the anterior columns of the cord, which, leaving the lower portion of the anterior pyramids, join the restiform bodies, and are distributed with them to the cerebellum. From this description it will be seen that both the cerebrum and the cerebellum are supplied with filaments from both the anterior and posterior columns of the cord. In the substance of each restiform body, moreover, there is im- bedded a ganglion which gives origin to the pneumogastric nerve, and presides over the functions of respiration. This ganglion is gurrounded and covered by the longitudinal fibres passing upward from the cord to the cerebellum, but may be discovered by cutting into the substance of the restiform body, in which it is buried. It is the first important ganglion met with, in dissecting the brain from below upward. While the anterior columns are passing beneath the pons Varolii, they form, together with the continuation of the posterior columns and the transverse fibres of the pons itself, a rounded prominence or tuberosity, which is known by the name of the tuber unnulare. In the deeper portions of this protuberance there is situated, among the longitudinal fibres, another collection of gray matter, which though not of large size, has very important functions and connec- tions. This is known as the ganglion of the tuber annulare. Situated almost immediately above these parts we have the cor- pora striata in front, and the optic thalami behind, nearly equal in OF THE NEBVOUS SYSTEM. 3.97 size, and giving passage, as above described, to the fibres of the anterior and posterior columns. Behind them still, and on a little lower level, are the tubercula quadrigemina, giving origin to the optic nerves. The olfactory ganglia rest upon the cribriform plate of the ethmoid bone, and send the olfactory filaments through the perforations in this plate, to be distributed upon the mucous mem- brane of the upper and middle turbinated bones. The cerebellum covers in the fourth ventricle Fig. 142. and the posterior surface of the medulla oblongata ; and finally the cerebrum, which has at- tained the size of the largest ganglion in the cranial cavity, extends so far in all directions, forward, backward, and later- ally, as to form a convoluted arch or vault, completely cover- ing all the remaining parts of the encephalon. The entire brain may there- fore be regarded ag a connected series of ganglia, the arrange- ment of which is shown in the accompanying diagram. (Fig. 142.) These ganglia occur in the following order, counting from before backward: 1st. The olfactory ganglia. 2d. The cere- Orum or hemispheres. 3d. The corpora striata. 4th. The optio thalami. 5th. The tubercula quadrigemina. 6th. The cerebellum. 7th. The ganglion of the tuber annulare. And 8th. The ganglion of the medulla oblongata. Of these ganglia, only the hemispheres and cerebellum are convoluted, while the remainder are smooth and rounded or somewhat irregular in shape. The course of the fibres coming from the anterior and posterior columns of the cord is also to be seen in the accompanying figure. A portion of the anterior fibres, we have already observed, pass upward and backward, with the restiform bodies, to the cerebellum ; while the remainder run forward through the tuber annulare and the corpus striatum, and then radiate to the gray matter of the cerebrum. The posterior fibres, constituting the restitbrm body, are distributed partly to the cerebellum, and then pass forward, as previously described, under- Diagram ofHcujLN Brat K, in vertical Bec- tion; shoffiag tlie situation of tlie different gan- glia, and ttie courtte of tlie fibres. 1. Olfactory ganglion. 2 Hemisphere. 3. Corpus striatum. 4. Optic thalamus. 5. Tubercula quadrigemina. 6. Cerebellum. 7. Ganglion of tuber annulare. 8. Gangliou of medulla oblongata. 398 GENERAL STBUCT0BE AND FUNCTIONS neatli the tubercula quadrigemina to the optic thalmi, whence they are also finally distributed to the gray matter of the cerebrum. The cerebrum and cerebellum, each of which is divided into two lateral halves or "lobes," by the'great longitudinal fissure, are both provided with transverse commissures, by which a connection is established between their right and left sides. The great trans- verse commissure of the cerebrum is that layer of white substance which is situated at the bottom of the longitudinal fissure, and which is generally known by the name of the " corpus callosum." It consists of nervous filamentsy which originate from the gray matter of one hemisphere, converge to the centre, where they be- come parallel, cross the median line, and are finally distributed to the corresponding parts of the hemisphere upon the opposite side. The transverse commissure of the cerebellum is the pons Varolii. Its fibres converge from the gray matter of the cerebellum on one side, and pass across to the opposite ; encircling the tuber annulare with a band of parallel curved fibres, to which the name of " pons Varolii" has been given from their resemblance to an arched bridge. The cerebro-spinal system, therefore, consists of a series of gan- glia situated in the cranio-spinal cavities, connected with each other by transverse and longitudinal commissures, and sending out nerves to the corresponding parts of the body. The spinal cord supplies the integument and muscles of the neck, trunk, and extremities; while the ganglia of the brain, besides supplying the corresponding parts of the head, preside also over the organs of special sense, and perform various other functions of a purely nervous character. OF NEBVOCS IRRITABILITY. 399 CHAPTER II. OF NERVOUS IRRITABILITY AND ITS MODE OP ACTION. We have already mentioned, in a previous chapter, that every organ in the body is endowed with the property of irritability; that is, the property of reacting in some peculiar manner when subjected to the action of a direct stimulus. Thus the irritability of a gland shows itself by increased secretion, that of the capillary vessels by congestion, that of the muscles by contraction. Now the irritability of the muscles, indicated as above by their contraction, is extremely serviceable as a means of studying and exhibiting nervous pheno- mena. We shall therefore commence this chapter by a study of some of the more important facts relating to muscular irritability. The irritability of the muscles is a property inherent in the muscular fibre itself. The existence of muscular irritability cannot be ex- plained by any known physical or chemical laws, so far as they relate to inorganic substances. It must be regarded simply as a peculiar property, directly dependent on the structure and consti- tution of the muscular fibre ; just as the property of emitting light belongs to phosphorus, or that of combining with metals to oxygen. This property may be called into action by various kinds of stimu- lus ; as by pinching the muscular fibre, or pricking it with the point of a needle, the application of an acid or alkaline solution, or the discharge of a galvanic battery. All these irritating applications are immediately followed by contraction of the muscular fibre. This contraiction will even take place under the microscope, whea the fibre is entirely isolated, and removed from contact with any other tissue ; showing that the properties of contraction and irrita- bility reside in the fibre itself, and are not communicated to it by other parts. Muscular irritability continues for a certain time after death. The stoppage of respiration and circulation does not at once destroy the vital properties of the tissues, but nearly all of them retain 400 OF NERVOUS lEBITABILlTT these properties to a certain extent for some time afterward. It is only when the constitution of the tissues has become altered bj being deprived of blood, and by the consequent derangement of the nutritive process, that their characteristic properties are finally lost. Thus, in the muscles, irritability and contractility may be easily shown to exist for a short time after death by applying to the exposed muscular fibre the same kind of stimulus that we have already found to affect it during life. It is easy to see, in the muscles of the ox, after the animal has been killed, flayed, and eviscerated, different bundles of muscular fibres contracting irregu- larly for a long time, where they are exposed to the contact of the air. Even in the human subject the same phenomenon may be seen in cases of amputation ; the exposed muscles of the amputated limb frequently twitching and quivering for many minutes after their separation from the body. The duration of muscular irritability, after death, varies consider- ably in different classes of animals. It disappears most rapidly in those whose circulation and respiration are naturally the most active ; while it continues for a longer time in those whose circula- tion and respiration are sluggish. Thus in birds the muscular irritability continues only a few minutes after the death of the animal. In quadrupeds it lasts somewhat longer ; while in reptiles it remains, under favorable cir- cumstances, for many hours. The cause of this difference is probably that, in birds and quadrupeds, the tissues being very vascular, and the molecular changes of nutrition going on with rapidity, the constitution of the muscular fibre becomes so rapidly altered after the circulation has ceased, that its irritability soon disappears. In reptiles,, on the other hand, the tissues are less vascular than in birds and quadrupeds, and all the nutritive changes go on more slowly. Eespiration and cir- culation can therefore be dispensed with for a longer period, before the constitution of the tissues be- comes so much altered as to destroy altogether their vital properties. Owing to this peculiarity of the cold-blooded maecies at o, ». animals, their tissues may be used with great ad- vantage for purposes of experiment. If a frog's leg, for example, be separated from the body of the animal (Fig. 143), the skin Fig. MS. Faoo's Lrg, vith poles of galvanic l)a^ ter7 applied to tlie AITD ITS MODE OF ACTION. 401 removed, and the poles of a galvanic apparatus applied to the sur- face of the muscle (a, h), a contraction takes place every time the circuit is completed and a discharge passed through the tissues of the limb. The leg of the frog, prepared in this ■way, may be em- ployed for a long time for the purpose of exhibiting the effect of various kinds of stimulus upon the muscles. All the mechanical and chemical irritants which we have mentioned, pricking, pinching, cauterization, galvanism, &c., act with more or less energy and promptitude, though the most eflScient of all is the electric discharge. Continued irritation exhausts the irritability of the muscles. It is found that the irritability of the muscles wears out after death more rapidly if they be artificially excited, than if they be allowed to remain at rest. During life, the only habitual excitant of mus- cular contraction is the peculiar stimulus conveyed by the nerves. After death this stimulus may be replaced or imitated, to a certain extent, by other irritants ; but their application gradually exhausts the contractility of the muscle and hastens its final disappearance. Under ordinary circumstances, the post-mortem irritability of the muscle remains until the commencement of cadaveric rigidity. When this has become fairly established, the muscles will no longer contract under the application of an artificial stimulus. Certain poisonous substances have the power of destroying the irritability of the muscles by a direct action upon their tissue. Sulphocyanide of potassium, for example, introduced into the cir- culation in sufiicient quantity to cause death, destroys entirely the muscular irritability, so that no contraction can afterward be pro- duced by the application of an external stimulant. Nervous Irritability. — The irritability of the nerves is the pro- perty by which they may be excited by an external stimulus, so as to be called into activity and excite in their turn other organs to which their filaments are distributed. When a nerve is irritated, therefore, its power of reaction, or its irritability, can only be esti- mated by the degree of excitement produced in the organ to which the nerve is distributed. A nerve running from the integument to the brain produces, when irritated, a painful sensation ; one dis- tributed to a glandular organ produces increased secretion; one dis- tributed to a muscle produces contraction. Of all these effects-, muscular contraction is found to be the best test and measure of nervous irritability, for purposes of experiment. Sensation cannot of course be relied on for this purpose, since both consciousness and volition are abolished at the time of death. The activity of the 402 OF NKEYOUS IRRITABILITY Fig. 144. glandular organs, owing to the stoppage of the circulation, disappears also very rapidly, or at least cannot readily be demonstrated. The contractility of the muscles, however, lasts, as we have seen, for a considerahle time after death, and may accordingly be employed with great readiness as a test of nervous irritability. The manner of its employment is as follows : — The leg of a frog is separated from the body and stripped of its integument; the sciatic nerve having been previously dissected out and cut off at its point of emergence from the spinal canal, so that a considerable portion of it remains in connection with the separated limb. (Fig. 144.) If the two poles of a galvanic appa- ratus be now placed in contact with different points (a b) of the exposed nerve, and a discharge allowed to pass between them, at the moment of discharge a sudden contraction takes place in the muscles below. It will be seen that this ex- periment . is altogether different from the one re- presented in Kg. 143. In that experiment the galvanic .discharge passes through the muscles themselves, and acts upon them by direct stim- ulus. Here, however, the discharge passes only from a to 6 through the tissues of the nerve, and acts directly upon the nerve alone ; while the nerve, acting upon the muscles by its own pecu- liar agency, causes in this way a muscular eon- traction. It is evident that in order to produce this effect, two conditions are equally essential : 1st. The irritability of the muscles ; and 2d. The irri- tability of the nerve. So long, therefore, as the muscles are in a healthy condition, their contraction, under the influence of a stimulus applied to the nerve, demonstrates the irri- tability of the latter, and may be used as a convenient measure of its intensity. Tlie irritability of the nerve continues after death. The knowledge of this fact follows from what has just been said with regard to ex- perimenting upon, the frog's leg, prepared as above. The irrita- bility of the nerve, like that of the muscle, depends directly upon its anatomical structure and constitution ; and so long as these re- main unimpaired, the nerve will retain its vital properties, though respiration and circulation may have ceased. For the same reason, FBoa*« Leo, vitli sciatic nei-ve (N) at- tached. — ab. Polen of galvanic batterf, ap- plied to nerve. AND ITS MODE OF ACTION. 403 also, as that given above with regard to the muscles, nervous irri- tability lasts much longer after death in the cold-blooded than in the warm-blooded animals. Various artificial irritants may be em- ployed to call it into activity. Pinching or pricking the exposed nerve with steel instruments, the application of caustic liquids, and the passage of galvanic discharges, all have this effect. The electric current, however, is much the best means to employ for this pur- pose, since it is more delicate in its operation than the others, and will continue to succeed for a longer time. The nerve is, indeed, so exceedingly sensitive to the electric cur- rent, that it will respond to it when insensible to all other kinds of stimulus. A frog's leg freshly prepared with the nerve attached, as in Fig. 144, will react so readily whenever a discharge is passed through the nerve, that it forms an extremely delicate instrument for detecting the presence of electric currents of low intensity, and has even been used for this purpose by Matteucci, under the name of the " galvanoscopic frog." It is only necessary to introduce the nerve as part of the electric circuit ; and if even a very feeble cur- rent be present, it is at once betrayed by a muscular contraction. The superiority of electricity over other means of exciting nerv- ous action, such as mechanical violence or chemical agents, pro- bably depends upon the fact that the latter necessa,rily alter and disintegrate more or less the substance of the nerve, so that its irri- tability soon disappears. The electric current, on the other hand, excites the nervous irritability without any marked injury to the substance of the nervous fibre. Its action may, therefore, be con- tinued for a longer period. Nervous irritability, like that of the muscles, is exhausted by repealed excitement. If a frog's leg be prepared as above, with the sciatic nerve attached, and allowed to remain at rest in a damp and cool place, where its tissue will not become altered by desiccation, the nerve will remain irritable for many hours ; but if it be excited, soon after its separation from the body, by repeated galvanic shocks, it soon begins to react with diminished energy, and becomes gra- dually less and less irritable, until it at last ceases to exhibit any further excitability. If it be now allowed to remain for a time at rest, its irritability will be partially restored ; and muscular contrac- tion will again ensue on the application of a stimulus to the nerve. Exhausted a second time, and a second time allowed to repose, it will again recover itself; and this may even be repeated several times in succession. At each repetition, however, the recovery of 401 OF NERVOUS IKKITABILITT nervous irritability is less complete, until it finally disappears alto- gether, and can no longer be recalled. Various accidental circumstances tend to diminish or destroy nervous irritability. The action of the woorara poison, for examnle, destroys at once the irritability of the nerves ; so that in animals killed by this substance, no muscular contraction takes place on irritating the nervous trunk. Severe and sudden mechanical inju- ries often have the same effect ; as where death is produced by violent and extensive crushing or laceration of the body or limbs. Such an injury produces a general disturbance, or shock as it is called, which affects the entire nervous system, and destroys oi suspends its irritability. The effects of such a nervous shock maj frequently be seen in the human subject after railroad accidents, where the patient, though very extensively injured, may remain for some hours without feeling the pain of his wounds. It is only after reaction has taken place, and the activity of the nerves has been restored, that the patient begins to be sensible of pain. It will often be found, on preparing the frog's leg for experiment as above, that immediately after the limb has been separated from the body and the integument removed, the nerve is destitute of irritability. Its vitality has been suspended by the violence in- flicted in the preparatory operation. In a few moments, however, if kept under favorable conditions, it recovers from the shock, and regains its natural irritability. The action of the galvanic current upon the nerves, as first shown by the experiments of Matteucci, is in many respects peculiar. If the current be made to traverse the nerve in the natural direction of its fibres, viz., from its origin towards its distribution, as from a to b in Fig. 144, it is called the direct current. If it be made to pass in the contrary direction, as from b to a, it is called the inverse current. When the nerve is fresh and exceedingly irritable, a muscular contraction takes place at both the commencement and termination of the current, whether it be direct or inverse. But very soon afterward, when the activity of the nerve has become somewhat diminished, it will be found that contraction takes place only at the commencement of the direct and at the termination of the inverse current. This may readily be shown by preparing the two legs of the same frog in such a manner that they remain connected with each other by the sciatic nerves and that portion of the spinal column from which these nerves take their origin. The two legs, so prepared, should be placed each in a vessel of water, with the AND ITS MODE OF ACTION. 405 nervous connectioa hanging between. (Fig. 145.) K the positive pole, a. of the battery be now placed in the vessel which holds leg No. 1, and the negative pole, b, in that containing leg No. 2, it will be seen that the galvanic current will traverse the two legs in op- posite directions. In No; 1, it will pass in a direction contrary to the course of its nervous fibres, that is, it will be for this leg an Fig. 145. inverse current ■, while in No. 2 it will pass in the same direction with that of the nervous fibres, that is, it will be for this leg a direct current. It will now be found that at the moment when the cir- cuit is completed, a contraction takes place in No. 2 by the direct current, while No. 1 remains at rest ; but at the time the circuit is broken, a contraction is produced in No. 1 by the inverse current, but no movement takes place in No. 2. A succession of alternate contractions may thus be produced in the two legs by repeatedly closing and opening the circuit. If the position of the poles, a, h, be reversed, the effects of the current will be changed in a corre- sponding manner. After a nerve has become exhausted by the direct current, it is still sensitive to the inverse ; and after exhaustion by the inverse, it is still sensitive to the direct. It has even been found by Mat- teuoci that after a nerve has been exhausted for the time by the direct current, the return of its irritability is hastened by the subsequent passage of the inverse current ; so that it will become again sensi- tive to the direct current sooner than if allowed to remain at rest. Nothing, accordingly, is so exciting to a nerve as the passage of direct and inverse currents, alternating with each other in rapid succession. Such a mode of applying the electric stimulus is that 406 OF NERVOUS IRE.ITABILITT usually adopted in the galvanic machines used in medical practice, for the treatment of certain paralytic afiectiona. In these machines, the electric circuit is alternately formed and broken with great rapidity,.,thus producing the greatest effect upon the nerves with the smallest expenditure of electricity. Such alternating currents, however, if very powerful, exhaust the nervous irritability more rapidly and completely than any other kind of irritation ; and in an animal killed by the action o^a battery used in this manner, the nerves may be found to be entirely destitute of irritability from the moment of death. The irritability of the nerves is distinct from that of the muscles; and the two may be destroyed or suspended independently of each other. When the frog's leg has been prepared and separated from the body, with the sciatic nerve attached, the muscles contract, as we have seen, whenever the nerve is irritated. The irritability of the nerve, therefore, is manifested in this instance only through that of the muscle, and that of the muscle is called into action only through that of the nerve. The two properties may be separated from each other, however, by the action of woorara, which has the power, as first pointed out by Bernard,' of destroying the irritability of the nerve without affecting that of the muscles. If a frog be poisoned by this substance, and the leg prepared as above, the poles of a galvanic battery applied to the nerve will produce noefl'ect; show- ing that the nervQus irritability h3,s ceased to exist. But if the galvanic discharge, be passed directly through the muscles, contrac- tion at, qnce takes place. The muscular irritability has survived that of the nerves, and must therefore be regarded as essentially distinct from it. It is found, moreover, that the action of woorara, in these cases, is especially exerted, not upon the entire length of the motor fila- ments, but upon their peripheral extremities> at the point where -they join the muscular fibres. If the, trunk of the sciatic nerve, for example, be exposed to the influence of the poison, while its terminal ramifications are protected from it by a ligature of the bloodvessels," galvanization of the nerve above the ligature will still produce contraction in the muscles below. Bernard' has shown this peculiarity in the action of woorara on the motor nerves by a still more striking experiment. He prepared two gastrocneraii ' Le9ons sur la physiologie. du systfeme nerveux. Paris, 1858, vol. i. p. 199. 2 Vulpian, Sysl&me nerveux. Paris, 1866, p. 208. * Substances toxiquea et m^dicamenteases. Paris, 1857, p. 829. XND ITS MODE OF ACTION. 407 iuuscles of the frog, each one having about an inch of its nervous trunk attached. In one, the exposed portion of the nerve is im- niersed for some time in a watch-glass containing an aqueous solu- tion of woorara; and notwithstanding the direct contact of the poison with the nervous trunk,: galvanization of the nerve at this point still causes a muscular contraction in the gastrocnemius. In the other, the muscle. itself is immersed in the solution of woorara, and the nerve is then found to have lost all signs- of irritability. As we know that the muscles then^gelves are not ajQfeoted by woo' rara, it is evident that the influence of the poison is exerted upon the terminal portion of the nervous filaments. It will be recollected, on the other hand, that in cases of -death from the action of sulphocyanide of potassium, the muscular irri- tability is itself destroyed ; so that no contractions occur, even when the galvanic discharge is made to traverse fhe muscular tissue. There are, therefore, two kinds of paralysis : first, a muscular paralysis, in which the muscular fibres themselves are directly affected ; and second, a nervous paralysis, in which the affection is confined to the nervous filaments, the muscles retaining their natural properties, and being still capable of contracting under the influence of a direct stimulus. Bapidity of the Nervous Force. — Some very ingenious experi- ments have been performed by Helmholtz,' in order to determine the rapidity with which a stimulus is transmitted through the nervous fibre. These experiments not only show that a certain interval of time is required for this transmission, but indicate also in an approximate manner the measurement of its rapidity for dif- ferent distances. Helmholtz exposed the muscle of a recently killed animal with the nerve attached. He first passed an electric discharge through the muscle itself, and found that only yj^ of a second intervened between the electric discharge and the muscular contraction. He then, applied the electric stimulus to the nerve in the immediate neighborhood of the muscle, and found that the previous interval was not perceptibly increased. But if; the poles of the battery were applied to the nerve at various distances from the muscle, the interval between the electric discharge and the muscular contraction became longer, as the length of the nervous branch transmitting the impulse was increased, Helmholtz ascer- tained in this way that the rapidity of transmission of the motor impulse in the nerves of the frog was a little over eighty-five feet * Comptes Bendus de 1' Academic des Sciences, Vol. ssjiiii. p. 262. 408 OF NERVOCS IRRITABILITY per second. Similar investigations were subsequently carried out by Baxt, in the laboratory of Helmholtz, in order to determine the rate of transmission of the motor nervous influence in man.' This was done by passing a galvanic discharge between two elec- trodes placed directly above the nerve at varying distances from the muscles to which its filaments were distributed. Thus the galvanic stimulus was applied to the median nerve at the wrist, at the elbow, and at the upper arm near the lower extremities of the coraco-brachialis and deltoid muscles ; and the effect of the stim- ulation was marked by the contraction of the muscles of the ball of the thumb. By accurate measurement it was found that the interval of time between the galvanic discharge and the muscular contraction was greater when the stimulus was applied to the nerve at the upper arm, than when applied at the wrist ; this increased interval being evidently the time required for the propagation of the nervous impulse from one point to the other. The rapidity of transmission, as ascertained by these experiments, was found to vary considerably according to the varying conditions of cold and warmth ; the lowest rate of transmission in the median nerve, from the middle of the upper arm to the wrist, being a little over one hundred feet per second, the highest two hundred and ninety-three feet. The average rate, as deduced from the entire series, cannot be estimated at less than two hundred feet per second. If we regard this as representing the usual rate of transmission in the human motor nerves, and if we estimate the distance from the origin of the motor filaments in the brain to their termination in the muscles of the foot as five feet, the time required to trans- mit the nervous impulse from the brain to these muscles would be one-fortieth of a second. Nature of the Nervous Force. — The special endowment by which a nerve acts and manifests its vitality is a peculiar one, inherent in the anatomical structure and constitution of the nervous tissue. It is manifested, in the foregoing experiments, by its effect upon the con- tractile muscles. But we shall hereafter see that this is, in reality, only one of its results, and that it shows itself, during life, by a variety of other influences. Thus it produces, in one case, sensa- tion; in another, muscular contraction; in another, increased or modified glandular activity ; in another, alterations in the pheno- mena of the circulation. The force, however, which is exerted by ' Mon«tjSlrericlil,d.er Eoniglichen Preussiscfaen Academie. April, 1867, and March, 1870. AND ITS MODE OF ACTIOST. 409 a nerve in a state of activity, and which brings about these changes, is not directly appreciable in any way by the senses, and can be judged of only by its secondary eflFects. We understand enough of its mode of operation, to know that it is not identical with the forces of chemical affinity, of mechanical action, or of electricity. And yet, by acting upon the organs to which the nerves are distributed, it will finally produce phenomena of all these diflferent kinds. By the intervention of the muscles, it results in mechanical action ; and by its influence upon the glands and bloodvessels, it causes chemical alterations in the animal fluids of the most import- ant character. It will even produce well-marked electrical phenomena, which in some cases are so decided, as to have long attracted the attention of physiologists. It has been fully demonstrated that certain fish (gymnotus and torpedo) have the power of generating electricity, and of producing electric discharges, which are often sufficiently powerful to kill small animals that may come within their reach. That the force generated by these animals is in reality electricity, is beyond a doubt. It is conducted by the same bodies which serve as con- ductors for electricity, and is stopped by those which are non-con- ductors of the same. All the ordinary phenomena produced bj the electric current, viz : the heating and melting of a fine con- ducting wire, the induction of secondary currents and of magnetism, the decomposition of saline solutions, and even the electric spark, have all been produced by the force generated by these animals. There is, accordingly, no room for doubt as to its nature. The electrical phenomena, in these cases, are produced by certain organs which are called into activity by the nervous influence. The electrical organs of the gymnotus and torpedo occupy a con- siderable portion of the body, and are largely supplied with nerves which regulate their function. If these nerves be divided, tied, or injured in any way, the electrical organ is weakened or paralyzed, just as the muscles would suffer if the nerves distributed to them were subjected to a similar violence. The electricity produced by these animals, accordingly, is not supplied by the nerves, but by a special generating organ, the action of which is regulated by nerv- ous influence. |41P THE SPINAIi COBD. CHAP.TEE. III. THE SPINAL COED. Wk have alrefadj seen that the spinal cord is a long ganglion, covered with longitudinal bundles of nervous filaments, and occu- pying the cavity of the spinal canal. It sends out nerves which 'supply the mUscles and integument of at least nine-tenths of the whole body, viz.,. those of the neck, trunk, and extremities. All these parts of the body are endowed with two very remarkable properties, the exercise of which depends, directly or indirectly, upon the integrity and activity of the spinal cord, viz., the power of sensation and the power of motion. Both these properties are said to reside in the nervous system, because they are so readily influenced by its condition, and are so closely connected with its physiological action. We shall therefore commence the study of the spinal cord with an examination of these two functions, and of the situation which they occupy in the nervous system. Sensation. — The power of sensation, or sensibility, is the power by which we are enabled to receive impressions from external obje.ets. These impressions are usually of such a nature that we can derive from them some information in regard to the qualities of external objects and the effect which they may produce upon our own systems. Thus, by bringing a foreign body into contact with the skin, we feel that it is hard or soft, rough or smooth, cold or warm. "We can distinguish the separate impressions produced by several bodies of a similar character, and we can perceive whe- ther •either one of them, while in contact with the skin,, be at rest or in motion. This power, which is generally distributed over the external integument, is dependent on the nervous filaments rami- fying in its tissue. For if the nerves distributed to any part of the body be divided, the power of sensation in the corresponding region is immediately lost. SENSATION, '411 The sensibility, thus distributed over the integument, varies in its.acuteness in different parts of the body. Thus, the extremities of the fingers are more sensitive to external impressions than the general surface of the limbs and trunk. The surfaces of the. fingers which lie in contact with each other are more sensitive than their dorsal or palmar suriaces.,. The point of the tongue, the lips, and the orifices of most of the mucous passages are endowed with a sensibility whiohds more acute thanthat of the general- integument. If the impression to which these parts are subjected be. harsh or violent in its character, or. of such a nature as to injure the texture of the integument or its nerves, it then produces a. sensation o? pain. ■It is essential .to notice, however, that the sensation of pain is not a. mere exaggeration of ordinary sensitive impressions, but is one of quite a dififerent character, which is superadded to the others, or takes their place altogether. , Just in proportion as the contact of a foreign body becomes painful, our ordinary perceptions of its phy- sical properties are blunted, and the sense of suffering predominates over ordinary sensibility. Thus if the integument be gently touched with the blade of a knife we easily feel that it is hard, cold, and smooth;: but if anjncision be made with it in the skin, we lose all distinct perception of these qualities, and feel only the suffering produced by the incision. We perceive, also, the difference in temperature between cold and warm substances brought in contact with the skin, so long as this difference is moderate in degree ; but if a foreign body be excessively cold or excessively hot, we can no longer appreciate its temperature by the touch, but only its injurious and destructive effect. Thus the sensation caused by touching frozen carbonic acid is the same with, that produced by a red-hot metal. Both substances blister the surface, but their actual temperatures cannot be distinguished. It is, therefore, a very important fact in this connection, that ihe sensibility to pain is distinct from the power of ordinary sensation. This distinction was first fully established by M. Beau, of Paris, who has shown conclusively that the sensibility to pain may. be diminished or suspended, while ordinary sensation remains. This is often seen in patients who are partially under the influence of ether or chlo- roform. The etherization may be carried to such an extent that the patient may be quite insensible to the pain of a surgical opera- tion, and yet remain perfectly conscious, and even capable of feeling the incisions, ligatures, &c., though he does not suffer from them. It not unfrequently happens, also, when opium has been adminis- 412 THE SPINAL COBD. tered for the relief of neuralgia, that the pain is completely abolished by the influence of the drug, while the patient retains completely his consciousness and his ordinary sensibility. In all cases, however, if the influence of the narcotic be pushed to its extreme, both kinds of sensibility are suspended together, and the patient becomes entirely unconscious of external impressions. Motion. — "Wherever muscular tissue exists, in any part of the body, we find the power of motion, owing to the contractility of the muscular fibres. But this power of motion, as we have already seen, is dependent on the nervous system. The excitement which causes the contraction of the muscles is transmitted to them by the nervous filaments ; and if the nerve supplying a muscle or a limb be divided or seriously injured, these parts are at once paralyzed and become incapable of voluntary movement. A nerve which, when irritated, acts directly upon a muscle, producing contraction, is said to be excitable ; and its excitability, acting through the mus- cle, produces motion in the part to which it is distributed. The excitability of various nerves, however, often acts during life upon other organs, beside the muscles ; and the ultimate effect varies, of course, with the properties of the organ which is acted upon. Thus, the nervous excitement transmitted to a muscle pro- duces contraction, while that transmitted to a gland produces an increased secretion, and that conveyed to a vascular surface causes congestion. In all such instances, the effect is produced by an influence transmitted by the nerve directly to the organ which is called into activity. But in all the external parts of the body muscular contraction is the most marked and palpable effect produced by the direct iiitluence of nervous excitement. "We find, therefore, that so far as we have yet examined it, the nervous action shows itself princi- pally in two distinct and definite forms; first, as sensibility, or the power of sensation, and second, as excitability or the power of pro- ducing motion. Distinct Seat op Sensation and Motion in the Neevous System. — Sensation and motion are usually the first functions which suffer by any injury inflicted on the nervous system. As a general rule, they are both suspended or impaired at the same time, and in a nearly equal degree. In a fainting fit, an attack of apo- plexy, concussion or compression of the brain or spinal cord, or a DISTINCT SEAT OF SENSATION AND MOTION, 413 ■wound of any kind involving the nerves or nervous centres, insen- sibility and loss of motion usually appear simultaneously. It is difficult, therefore, under ordinary conditions, to trace out the separate action of these two functions, or to ascertain the precise situation occupied by each. This difficulty, however, may be removed by examining sepa- rately difi'erent parts of the nervous system. In the instances mentioned above, the injury which is inflicted is comparatively an extensive one, and involves at the same time many adjacent parts. But instances sometimes occur in which the two functions, sensa- tion and motion, are affected independently of each other, owing to the peculiar character and situation of the injury inflicted. Sensa- tion may be impaired without loss of motion, and loss of motion may occur without injury to sensation. In tic douloureux, for example, we have an 'exceedingly painful affection of the sensitive parts of the face, -without any impairment of its power of motion •, and in facial paralysis we often see a complete loss of motion affect- ing one side of the face, while the sensibility of the part remains altogether unimpaired. The above facts first gave rise to the belief that sensation and motion might occupy distinct parts of the nervous system ; since it would otherwise be difficult to understand how the two could be affected independently of each other by anatomical lesions. It has accordingly been fully established by the labors of Sir Charles Bel], Magendie, Miiller, Panizza, and Longet, that the two functions do in reality occupy distinct parts of the nervous system. If any one of the spinal nerves, in the living animal, after being exposed at any part of itscourse outside the spinal canal, be divided, ligatured, bruised, or otherwise seriously injured, paralysis of motion and loss of sensation are immediately produced in that part of the body to which the nerve is distributed. If, on the other hand, the same nerve be pricked, galvanized, or otherwise gently irritated, a painful sensation and convulsive movements are produced in the same parts. The nerve is therefore said to be both sensitive and excitabk ; sensitive, because irritation of its fibres produces a pain- ful sensation, and excitable, because the same irritation causes mus- cular contraction in the parts below. The result of the experiment, however, will be different if it be tried upon the parts situated inside the spinal canal, and particularly upon the anterior and posterior roots of the spinal nerves. If an irritation be applied, for example, to the anterior root of a spiual 414 THE SPINAL CORD. nerve in the living animal, convulsive movements are produced in the parts below, but there is no painful sensation. The anterior root accordingly is said to be excitable, but not sensitive. If the posterior root, on the other hand, be irritated, acute pain is pro- duced, but no convulsive movements. The posterior root is there- fore sensitive, but not excitable. The above facts show the different properties manifested by the two roots of a spinal nerve, when subjected to artificial irrita- tion. Still more important results, as showing what are actually the natural functions of the parts, are derived from the experiment of dividiug separately each of the two roots and observing the effect upon the parts below. These experiments, first performed by Magendie ' in 1822, have been frequently repeated since, and their results fully confirmed. If the posterior root of a spinal nerve, in the living animal, be divided by a transverse section, (as in Fig. 146, a, b,) without injuring the anterior root, it is found that the sensibility of the integument, in the corresponding part of the body, has disappeared, while the power of voluntary motion re- mains unimpaired in the muscles of the same region. On the other, hand, if the anterior root be alone divided (Fig. 146, e, d), leaving the posterior untouched, the power of voluntary motion is abolished in the corresponding muscles, but at the same time the skin retains its sensibility. Thus it is evident that the impressions of sensibility pass to the nervous centres exclusively by the posterior roots, while the stim- ulus which excites the muscles to contraction is conveyed only by the anterior roots. We have therefore a separate localization of sensa- tion and motion in this part of the nervous system ; and it is easy accordingly to understand how one may be impaired without in- jury to the other, or how both may be simultaneously affected, according to the situation and extent of the anatomical lesion. In the two roots of a spinal nerve, furthermore, the nervous action is manifested in two opposite directions. If the posterior root be divided (Fig. 146) at a, b, and an irritation applied to the separated extremity (a), no effect will be produced, because the nerve at this point is cut off from its communication with the nervous centres ; but if the irritation be applied to the attached extremity (6), a painful sensation is immediately the result. The nervous action, therefore, in the posterior root, is manifested in a direction from without inward. If the anterior root, on the other hand, be ^Journal de Pbysiologie Ezp^rimeUtale, Tol< ii. p. 276. SENSIBILITT AND EXCITABILITY IN SPINAL COED. 415 divided at c, d, and its attached extremity {d) be irritated, no effect follows, because the nervous filaments here are no longer in com- munication with the muscles ; but if the separated extremity (c) Diagram ot BriHAL Cokd aks Nkeves. The posterior root ii seen divided at a, b, the anterior at c, d. be irritated, convulsive movements instantly take place. The nervous action, consequently, passes, in the anterior root, in a direc- tion from within outward. The same thing is true with regard to the transmission of sensa- tion and motion in the spinal nerves outside the spinal canal. If one of these nerves be divided in the living animal, and its attached extremity irritated, pain is produced, but no convulsive motion ; if the irritation be applied to its separated extremity, muscular contractions follow, but no painful sensation. There are therefore in the spinal nerves, as elsewhere, two sets of nervous filaments adapted to the performance of two different functions ; viz., the " sensitive " filaments, or those which convey sensation, and the " motor " filaments, or those which excite move- ment. In the roots of the spinal nerves these two sets of fibres are separated from each other, the anterior root being exclusively motor, and the posterior exclusively sensitive. At the point of junction, however, of the two roots, the spinal nerve, as it emerges from the spinal canal, contains both motor and sensitive fibres in- timately mingled in a common trunk. It is therefore called a mixed nerve, serving at the same time, by the two sets of fibres which it contains, for the conveyance of both sensibility and motive power. At the periphery the two sets of filaments again separate, 416 THE SPINAL COBD. the sensitive fibres passing to the integument, and the motor fibres 10 the muscles. Distinct Seat of Sensibility and Excitability in the Spinal Coed. — Various experimenters have demonstrated the fact that different parts of the spinal cord, like the two roots of the spinal nerves, are separately endowed with sensibility and excita- bility. The anterior columns of the cord, like the anterior roots of the spinal nerves, are excitable but not sensitive ; the posterior columns, like the posterior roots of the spinal nerves, are sensitive but not excitable. Accordingly, when the spinal canal is opened in the living animal, an irritation applied to the anterior columns of the cord produces immediately convulsions in the limbs below; but there is no indication of pain. On the other hand, signs of acute pain become manifest whenever the irritation is applied to the posterior columns ; but no muscular contractions follow, other than those of a voluntary or reflex character, Longet has found ' that if the spinal cord be exposed in the lumbar region and com- pletely divided at that part by transverse section, the application of any irritant to the anterior surface of the separated portion pro- duces convulsipns below ; while if applied to the posterior columns behind the point of division, it has no sensible effect whatever. The anterior and posterior columns of the cord are accordingly, so far, analogous in their properties to the anterior and posterior roots of the spinal nerves. The route through which motor and sensitive impulses are transmitted, in the spinal cord, has also been ascertained with tolerable success, by the researches of Magendie, Longet, Brown- Sequard, and Yulpian." The impulse which gives rise to vol- untary motion is transmitted by the white substance of the anterior and lateral columns ; for if these antero-lateral columns be divided in the living animal by a transverse section, all power of voluntary motion is abolished in the parts below. The stim- ulus to sensation, on the other hand, seems to traverse the deeper portions of the cord by filaments which pass through the gray substance. For, according to the experiments of Brown-Sequard, confirmed by Vulpian and Philippeaux,' sensibility is destroyed by division of the gray substance and the anterior portions of the cord, even though the posterior columns be left untouched. The ' Traitg de Physiologie, yol. ii. part 2, p. 8. ' Vulpian. Physiologie du Systfeme nerveuz. Paris, 1866, p. 369. » Ibid. p. 378. CROSSED ACTION OF THE SPINAL C O B D. 417 posterior columns, accordingly, though sensitive to artificial irrita- tion, are not the portions through which sensitive impressions are directly conveyed from the posterior roots of the nerves. It is possible that they' may serve, according to the opinion enter- tained by Vulpian, as longitudinal commissures, connecting with each other different portions of the length of the spinal cord. An irritation accordingly, applied to any part of the integument, is conveyed, along the sensitive filaments of the nerve and its posterior root, to the spinal cord ; then upward, along the commu- nicating fibres of the cord, to the brain, where it produces a sensa- tion corresponding in character with the original irritation. A motor impulse, on the 6ther hand, originating in the brain, is transmitted downward, along the longitudinal fibres of the antero- lateral columns, passes outward by the anterior root of the spinal nerve, and, following the motor filaments of the nerve through its trunk and branches, produces at last a muscular contraction at the point of its 'final distribution. Crossed Action of the Spinal Cord. — As the anterior col- umns of the cord pass upward to join the medulla oblongata, a decussation takes place between the two sides, as we have already mentioned, at the level of the anterior pyramids. The fibres of the right lateral column pass over to the left side of the medulla oblongata, and so upward to the left side of the brain ; while the fibres of the left lateral cplumn pass over to the right side of the medulla oblongata, and so upward to the right side of the brain. This decussation may be readily shown (as in Fig. 141) by gently separating the anterior pyramids from each other, at the lower ex- tremity of the medulla oblongata, where the decussating bundles may be seen crossing obliquely from side to side, at the bottom of *,he anterior median fissure. Below this point, the anterior col- umns remain distinct from each other so far as regaras any exter- nal decussation; but there is still reason for believing that their fibres continue to cross from side to side, in the anterior commis- sure, throughout the cervical portion of the spinal cord. The final result of this interchange is a complete decussation of the motor fibres, and a crossed action of the spinal cord, as a medium of communication for motor impulses. Apoplexy, soft- ening, or mechanical injury, on the right side of the brain, will pro- 27 418 THK SPINAL COED. duce paralysis of the left side of the body; and injury of the left side of the brain will be followed by paralysis of the right side of the body. If the seat of the injury, on the other hand, be lower down, at the level of the medulla oblongata, or at any point where the crossing of the fibres is taking place, it will cause a partial paralysis, on both the same and opposite sides of the body; while if it be seated in one lateral half of the cord, below the level of complete decussation, the paralysis which results will be manifested only on the corresponding side of the body. If the anterior columns of the spinal cord, therefore, be wounded at any point in the dorsal or lumbar region, a paralysis of voluntary motion is produced in the limbs below, on the same side with the injury. But if a similar lesion occur in the brain, the paralysis which results is on the opposite side of the body. Thus it has long been known that an abscess or an apoplectic hemorrhage on the right side of the brain will produce paralysis of the left side of the body; and injury of the left side of the brain will be fol- lowed by paralysis of the right side of the body. The spinal cord has also a crossed action in transmitting, sensi- tive as well as motor impulses. It has been demonstrated by Dr. Brown-Sequard,^ that the crossing of the sensitive fibres in the spinal cord does not take place, like that of the motor fibres, at its upper portion only, but throughout its entire length ; so that the sensitive fibres of the right spinal nerves, very soon after their entrance into the cord, pass over to the left side, and those of the left spinal nerves pass over to the right side. For if one lateral half of the spinal cord of a dog be divided in the dorsal region, the power of sensation remains upon the corresponding side of the body, but is lost upon the opposite side. It has been shown, furthermore, by the same observer,'' that the sensitive fibres of the spinal nerves, when they first enter the cord, join the posterior columns, which are everywhere extremely sensitive ; but that they very soon leave the posterior columns, and, passing through the central parts of the gray matter, reach the opposite side of the spinal cord. If the pos- terior columns, accordingly, be alone divided at any part of the cord, sensibility is not destroyed in all the nerves behind the seat of injury, but only in those which enter the cord at the point of • Experimental Kesearchea applied to Physiology aad Pathology. New York, 1853. ' Memoirs sur la Fhysiologie de la Moelle 4pinifere ; Gazette M^dicale de Paris, 1855. INDEPKNDKNCE OF ITEEV0U3 FILAMENTS. 419 section ; since the posterior columns consist of dififerent nervous filaments, joining them constantly on one side from below, and leaving them on the other to pass upward toward the brain. There are certain important facts which still remain to be noticed regarding the mode of action of the spinal cord and its nerves. They are as follows : — 1. An irritation applied to a spinal nerve at the middle of its course produces the same effect as if it traversed its entire length. Thus, if the sciatic or median nerve be irritated at any part of its coarse, con- traction is produced in the muscles to which these nerves are dis- tributed, just as if the impulse had originated as usual from the brain. This fact depends upon the character of the nervous fila- ments, as simple conductors. Wherever the impulse may originate, the final effect is manifested only at the termination of the nerve. As the impulse in the motor nerves travels always in an outward direction, the effect is always produced at the muscular termination of the filaments, no matter Jiow small or how large a portion of their length may have been engaged in transmitting the stimulus. If the irritation, again, be applied to a sensitive nerve in the middle of its course, the painful sensation is felt, not at the point of the nerve directly irritated, but in that portion of the integument to which its filaments are distributed. Thus, if the ulnar nerve be accidentally struck at the point where it lies behind the inner con- dyle of the humerus, a sensation of tingling and numbness is pro- duced in the last two fingers of the corresponding hand. It is common to hear patients who have suffered amputation complain of painful sensations in the amputated limb for weeks or months, and sometimes even for years after the operation. They assert that they can feel the separated parts as distinctly as if they were still attached to the body. This sensation, which is a real one and not fictitious, is owing to some irritation operating upon the divided extremities of the nerves in the cicatrized wound. Such an irrita- tion, conveyed to the brain by the sensitive fibres, will produce precisely the same sensation aS if the amputated parts were still present, and the irritation actually applied to them. It is on this account also that division of the trifacial nerve is not always effectual for the cure of tic douloureux. If the cause of the difficulty be seated upon the trunk of the nerve, between its point of emergence from the bones and its origin in the brain, it is evident that division of the nerve upon the face will be of no avail ; since the cause of irritation will still exist behind the point 420 THK SPINAL COBD. of section, and the same painful sensations will still be produced in the brain. 2. The irritability of the motor filmnents disappears from within out- ward, that of the sensitive filaments from without inward. According to the researches of Longet/ the irritability of the motor fibres, in an animal recently killed, ceases to manifest itself first in the cen- tral and afterward in the peripheral portions ; disappearing suc- cessively in the anterior columns of the spinal cord, the anterior roots of the nerves, the nervous trunks, and lastly. their branches and ramifications. Thus immediately after the separation of the frog's leg from the body, irritation of the nerve at any point pro- duces muscular contraction in the limb below. As time elapses, however, and the irritability of the nerve diniinishes, the galvanic current, in order to produce contraction, must be applied at a point nearer its termination. Subsequently, the irritability of the nerve is entirely lost in its upper portions, but is retained in the parts situated lower down, from which also, in turn, it afterward disap- pears ; receding in this manner farther and farther toward the ter- minal distribution of the nerve, where it finally disappears alto- gether. On the other hand the signs of irritability in the sensitive nerves disappear first at their extremities. This fact, established by both Longet and Bernard,' and confirmed by most other observers, shpws that sensibility at the time of death recedes from the circumference toward the centre. The skin may have already become insensible while the trunk of the nerve still retains its sensibility ; and sen- sibility continues to be manifested in the spinal cord after it has already disappeared from the nerve itself. 3. Each nervous filament acts independently of the rest ihroughoutits entire length, and does not communicate its irritation to those which are in proximity with it. It is evident that this is true with regard to the nerves of sensation, from the fact that if the integument be touched with the point of a needle, the sensation is referred to that spot alone. Since the nervous filaments coming from it and the adjacent parts are all bound together in parallel bundles, to form the trunk of the nerve, if any irritation were communicated from one sensitive filament to another, the sensation produced would be indefinite and difi'used., whereas it is really confined to the spot irri- • Physiologie, vol. ii. part 2, p. 52. ' Substances Toxiques et M^dicamenteuses, p. 330. INDEPENUENCK OF KEBVOUS FILAMElirTS, 421 tated. If a frog's leg, furthermore, be prepared, with the sciatic nerve attached, a few of the fibres separated laterally from the nervous trunk for a portion of its length, and the poles of a galvanic? battery applied to the separated portion, the contractions which follow in the leg will not be general, but will be confined to those muscles in which the galvanized nervous fibres especially have their distribution. There are also various instances, in the body, of antagonistic muscles, which must act independently of each other, but which are supplied with nerves from a common trunk. The superior and inferior straight muscles of the eyeball, for example, are both supplied by the motor oculi communis nerve. Extensor and flexor muscles, as, for example, those of the fingers, are often supplied by the same nerve, and yet act alternately with- out mutual interference. It is easy to see that if this were not the case, confusion would constantly arise, both in the perception of sensations, and in the execution of movements. 4. There are certain sensations which are excited simultaneously by the same causes, and which are termed associated sensations ; and there are also certain movements which take place simultaneously, and are called associated movements. In the former instance, one of the associated sensations is called up immediately upon the percep- tion of the other, without requiring any direct impulse of its own. Thus, tickling the soles of the feet produces a peculiar sensation at the epigastrium. Nausea is occasioned by certain disagreeable odors, or by rapid rotation of the body, so that the landscape seems to turn round. A striking example of associated movements, on the other hand, may be found in the action of the muscles of the eyeball. The eyeballs always accompany each other in their lateral motions, turning to the right or the left side simultaneously. It is evident, however, that in producing this correspondence of motion, the left internal rectus muscle must contract and relax together with the right external ; while a similar harmony of action must exist between the right internal and the left external. The explana- tion of such singular correspondences cannot be found in the anato- mical arrangement of the muscles themselves, nor in that of the nervous filaments by which they are directly supplied, but must be looked for in some special endowment of the nervous centres from which they originate. 422 THE SPINAL COED. Reflex Action of the Spinal Cokd. — The spinal cord, aa we have thus far examined it, may be regarded simply as a great nerve ■ that is, as a bundle of motor and sensitive filaments, connecting the muscles and integument below with the brain above, and assisting, in this capacity, in the production of conscious sensation and voluntary motion. Beside its nervous filaments, however, it contains also a large quantity of gray matter, and is, therefore, itself a ganglionic centre, and capable of independent action as such. We shall now proceed to study it in its second capacity, aa a distinct nervous centre. K a frog be decapitated, and the body allowed to remain at rest for a few moments, so as to recover from the depressing effects of shock upon the nervous system, it will be found that, although sen- sation and consciousness are destroyed, the power of motion still remains. If the skin of one of the feet be irritated by pinching it with a pair of forceps, the leg is immediately drawn up toward the body, as if to escape the cause of irritation. If the irritation applied to the foot be of slight intensity, the corresponding leg only will move ; but if it be more severe in character, motions will often be produced in the posterior extremity of the opposite side, and even in the two fore legs, at the same time. These motions, it is import- ant to observe, are never spontaneous. The decapitated frog remains perfectly quiescent if left to himself. It is only when some cause of irritation is applied externally, that movements occur as above described. It will be seen that the character of these phenomena indicates the active operation of some part of the nervous system, and par- ticularly of some ganglionic centre. The irritation is applied to the skin of the foot, and the muscles of the leg contract in conse- quence ; showing evidently the intermediate action of a nervOus connection between the two. The effect in question is due to the activity of the spinal cord, operating as a nervous centre. In order that the movements may take place as above, it is essential that both the integument and the muscles should be in communication with the spinal cord by nerv- ous filaments, and that the cord itself be in a state of integrity. If the sciatic nerve be divided in the upper part of the thigh, irritation of the skin below is no longer followed by any muscular contrac- tion. If either the anterior or posterior roots of the nerve be divided, the same want of action results ; and finally, if, the nerve and its roots remaining entire, the spinal cord itself be broken up REFLEX ACTION OF THE SPINAL COBD. 423 Fig. 147. Diagram of Sr IK AL Coed ik Vkk- TICAI. Sbctioit, Bhowlng reflex action, —a. FoBterior root of ipinal nerre. b. Anterior root of spinal nerve. by a needle introdiiced into the spinal canal, the integument may then be irritated or mutilated to any extent, without exciting the least muscular contraction. It is evident, therefore, that the spinal cord acts, in this case, as a nervous centre, through which the irritation applied to the skin is communicated to the muscles. The irritation first passes upward, as shown in the accompanying diagram (Fig. 147), along the sensitive fibres of the posterior root (a) to the gray matter of the cord, and is then reflected back, along the motor fibres of the anterior root (6), until it finally reaches the muscles, and produces a contrac- tion. This action is known, accordingly, as the reflex action of the Spinal cord. It will be remembered that this reflex action of the cord is not accompanied by volition, nor even by any conscious sensation. The function of the spinal cord as a nervous centre is simply to convert an impression, received from the skin, into a motor impulse which is sent out again to the muscles. There is absolutely no farther action than this ; no exercise of will, consciousness, or judg- ment. This action will therefore take place perfectly well after the brain has .been removed, and after the entire sympathetic sys- tem has also been taken away, provided only that the spinal cord and its nerves remain in a •state of integrity. The existence of this reflex action after death is accordingly an evidence of the continued activity of the spinal cord, just as con- tractility is an evidence of the activity of the muscles, and irrita- bility of that of the nerves. Like the two last-mentioned properties, also, it continues for a longer time after death in cold-blooded than in warm-blooded animals. It is for this reason that frogs and other reptiles are the most useful subjects for the study of these pheno- mena, as for that of most others belonging to the nervous system. The irritability of the spinal cord, as manifested by its reflex action, may be very much exaggerated by certain diseases, and by the operation of poisonous substances. Tetanus and poisoning by strychnine both act in this way, by heightening the irritability of the spinal cord, and causing it to produce convulsive movements 424 THK SPINAL CORD. on the application of external stimulua. It has been observed that the convulsions in tetanus are rarely, if ever, spontaneous, but that they always require to be excited by some external cause, such as the accidental movement of the bedclothes, the shutting of a door, or the sudden passage of a current of air. Such slight causes of irritation, which would be entirely inadequate to excite involuntary movements in the healthy condition, act upon the spinal cord, when its irritability is heightened by disease, in such a manner as to pro- duce violent convulsions. Similar appearances are to be seen in animals poisoned by strych- nine. This substance acts upon the spinal cord and increases its irritability, without materially affecting the functions of the brain. Its effects will show themselves, consequently, without essential modification, after the head has been removed. If a decapitated frog be poisoned with a moderate dose of strychnine, the body and limbs will remain quiescent so long as there is no external source of excitement ; but the limbs are at once thrown into convulsions by the slightest irritation applied to the skin, as, for example, the contact of a hair or a feather, or even the jarring of the table on which the animal is placed. That the convulsions in cases of poisoning by strychnine are always of a reflex character, and never spontaneous, is shown by the following fact first noticed by Ber- nard,' viz., that if a frog be poisoned after division of the posterior roots of all the spinal nerves, while the anterior roots are left un- touched, death takes place as usual, but is not preceded by any con- vulsions. In this instance the convulsions are absent simply because, owing to the division of the posterior roots, external irri- tations cannot be communicated to the cord. The reflex action, above described, may be seen very distinctly in the human subject, in certain cases of disease of the spinal cord. If the upper portion of the cord be disintegrated by inflammatory softening, so that its middle and lower portions lose their natural connection with the brain,' paralysis of voluntary motion and loss of sensation ensue in all parts of the body below the seat of the ana- tomical lesion. Under these conditions, the patient is incapable of making any muscular exertion in the paralyzed parts, and is uncon- scious of any injury done to the integument in the same region. Notwithstanding this, if the soles of the feet be gently irritated with a feather, or with the point of a needle, a convulsive twitch- ■ Lemons snrles effets des Substances toxiques et medicamenteuaes, Paris, 1897, p. 357. BEFLEX ACTION OF THE SPINAL CORD. 425 Fig. U8. ing of the toes will often take place, and even retractile movements of the leg and thigh, altogether without the patient's knowledge. Such movements may frequently be excited by simply allowing the cool air to come suddenly in contact with the lower extremities. We have repeatedly witnessed these phenomena, in ja, case of dis- ease of the spinal cord, where the paralysis and insensibility of the lower extremities were complete. Many other similar instances are reported by various authdrs. The existence of this reflex action of the cord has enabled the physiologist to ascertain several other important facts concerning the mode of operation of the nervous system. M. Bernard has demonstrated,' by a series of extremely ingenious experi- ments on the action of poison- ous substances: 1st, that the irritability of the muscles may be destroyed, while that of the nerves remains unaltered ; and 2d, that the motor and sensi- tive nervous filaments may be paralyzed independently of each other. The above facts are shown by the three folloW' ing experiments : — 1. In a living frog (Fig. 148), the sciatic nerve (iV) is exposed in the back part of the thigh, after which a ligature is passed underneath it and drawn tight around the bone and the re- maining soft parts. In this way the circulation is entirely cut off from the limb (d), which remains in connection with thf trunk only by means of the sciatic nerve. A solution of sulphocyanide of potassium is then introduced beneath the skin of the back, at /, in suf- > Le9ons Bur les effets dea substances toxiques et m^dicamenteuses, Paris, 1857, chaps. 23 and 24. 426 THE SPINAL COBD. ficient quantity to produce its specific effect. The poison ig then absorbed, and is carried by the circulation throughout the trunk and the three extremities a, h, c; while it is pre- vented from entering the limb d, by the ligature which has been placed about the thigh. Sulphocyanide of potassium produces paralysis, as we have previously mentioned, by act- ing directly upon the muscular tissue. Accordingly, a gal- vanic discharge passed through the limbs a, b, and c, produces no contraction in them, while the same stimulus, applied to d, is fol- lowed by a strong and healthy reaction. But at the moment when the irritation is applied to the poisoned limbs a, b, and c, though no visible effect is produced in them, an active movement takes place in. the healthy limb, d. This can only be owing to a reflex action of the spinal cord, originating in the integument of a, b, and c, and transmitted, by sensitive and motor filaments, through the cord to d. While the muscles of the poisoned lirribs, there/ore, have been directly paralyzed, the nerves of the same parts have retained their irritability. 2. If a frog be poisoned with woorara by simply placing the poison under the skin, no reflex action of the spinal cord can be de- monstrated after death. We have already shown, from experiments detailed in chapter II., that this substance paralyzes the peripheral extremities of the motor nerves, without affecting the contractility of the muscles. In the above instance, therefore, where the reflex action is abolished, its loss may be owing to a paralysis of both motor and sensitive filaments, or to that of the motor filaments alone. The following experiment, however, shows that the motor filaments are the only ones affected. If a frog be prepared as in Fig. 148, and poisoned by the introduction of woorara at /, when the limb d is irritated, its own muscles react, while no movement takes place in a, b, or c ; but if the irritation be applied to a, b, or c, reflex movements are immediately produced in d. In the poisoned limbs, -therefore, while the mator nerves have been paralyzed, the sensitive filaments have retained their irritability. 8. If a frog be poisoned with strychnine, introduced underneath the skin in sufficient quantity, death takes place after general con- vulsions, which are due, as we have seen above, to an unnatural excitability of the reflex action. This is followed, howevei*, by a paralysis of sensibility, so that after death no reflex movements can be produced by. irritating the skin or even the posterior roots of the spinal nerves. But if the anterior roots, or the motor nerves REFLEX ACTION OP THE SPINAL CORD, 427 themselves be galvanized, contractions immediately take place in the corresponding muscles. In this case, therefore, the sensitive fila- ments have heen paralyzed, while the motor filaments and the muscles have retained their irritability. "We now come to investigate the reflex action of the spinal cord, as it takes place in a healthy condition during life. This action readily escapes notice, unless our attention be particularly directed to it, because the sensations which we are constantly receiving, and the many voluntary movements which are continually executed, serve naturally to mask those nervous phenomena which take place without our immediate knowledge, and over which we exert no voluntary control. Such phenomena, however, do constantly take place, and are of extreme physiological importance. If the surface of the skin, for example, be at any time unexpectedly brought in contact with a heated body, the injured part is often withdrawn by a rapid and convulsive movement, long before we feel the pain, or even fairly understand the cause of the involuntary act. If the body by any accident suddenly and unexpectedly loses its balance, the limbs are thrown into a position calculated to protect the ex- posed parts, and to break the fall, by a similar involuntary and in- stantaneous movement. The brain does not act in these cases, for there is no intentional character in the movement, nor even any complete consciousness of its object. Everything indicates that it is the immediate result of a simple reflex action of the spinal cord. The cord exerts also an important and constant influence upon the sphincter muscles. The sphincter ani is habitually in a state of contraction, so that the contents of the intestine are not allowed to escape. When any external irritation is applied to the anus, or whenever the feces present themselves internally, the sphincter contracts involuntarily, and the discharge of the feces is prevented. This habitual closure of the sphincter depends on the reflex action of the spinal cord. It is entirely an involuntary act, and will con- tinue, ^in the healthy condition, during profound sleep, as complete and efficient as in the waking state. When the rectum, however, has become filled by the accumula- tion of feces from above, the nervous action changes. Then the impression produced on the mucous membrane of the distended rectum, conveyed to the spinal cord, causes at the same time re- laxation of the sphincter and contraction of the rectum itself; so that a discharge of the feces consequently takes place. Now all these actions are to some extent under the control of 428 THE SPINAL COBD. sensation and volition. The distended state of the rectum is usually accompanied, by a distinct sensation, and the resistance of the sphincter may be voluntarily prolonged for a certain period, just as the respiratory movements, which are usually involuntary, may be intentionally hastened or retarded, or even temporarily suspended. But this voluntary power over the sphincter and the rectum is limited. After a time the involuntary impulse, growing more urgent with the increased distension of the rectum, becomes irre- sistible ; and the discharge finally takes place by the simple reflex action of the spinal cord. If the spinal cord be injured in its middle or upper portions, the sensibility and voluntary action of the sphincter are lost, because its connection with the brain has been destroyed.- The evacuation then takes place at once, by the ordinary mechanism, as soon as the rectum is filled, but without any knowledge on the part of the patient. The discharges are then said to be " involuntary and un- conscious." If the irritability of the cord, on the other hand, be exaggerated by disease, while its connection with the brain remains entire, the distension of the rectum is announced by the usual sensation, but the reflex impulse to evacuation is so urgent that it cannot be controlled by the will, and the patient is compelled to allow it to take place at once. The discharges are then said to be simply " involuntary." Finally, if the substance of the spinal cord be extensively de- stroyed by accident or disease, the sphincter is permanently relaxed. The feces are then evacuated almost continuously, without any knowledge or control on the part of the patient, as fast as they descend into the rectum from the upper portions of the intestine. Injury of the spinal cord produces a somewhat different effect on the urinary bladder. Its muscular fibres are. directly paralyzed ; and the organ, being partially protected by elastic fibres, both at its own orifice and along the urethra, becomes gradually distended by urine from the kidneys. The urine then overcomes the elas- ticity of the protecting fibres, by simple force of accumulation, and afterward dribbles away as fast as it is excreted by the kidneys. Paralysis of the bladder, therefore, first causes a permanent disten- sion of the organ, which is afterward followed by a continuous, passive, and incomplete discharge of its contents. Injury of the spinal cord produces also an important, though probably an indirect effect on nutrition, secretion, animal heat, &c.. KEFLEX ACTIOJT OF THE SPINAL CORD. 429 in the paralyzed parts. Diseases of the cord which result in its softening or disintegration, are notoriously accompanied by consti- pation, often of an extremely obstinate character. In complete paraplegia, also, the lower extremities become emaciated. The texture and consistency of the muscles are altered, and the animal temperature is considerably reduced. All such disturbances of nutrition, however, which almost invariably follow upon local para- lysis, are no doubt immediately owing to the inactive condition of the muscles; a condition which naturally induces debility of the circulation, and consequently of all those functions which are de- pendent upon it. It is less easy to explain the connection between injury of the spinal cord and inflammation of the urinary passages. It is, how- ever, a matter of common observation among pathologists, that injury or disease of the cord, particularly in the dorsal and upper lumbar regions, is soon followed by catarrhal inflammation of the urinary passages. This gives rise to an abundant production of altered mucus, which in its turn, by causing an alkaline fermenta- tion of the urine contained in the bladder, converts it into an irri- tating and ammoniacal liquid, which reacts upon the mucous mem- brane and aggravates the previous inflammation. We find, therefore, that the spinal cord, in its character of a nervous centre, exerts a general protective action over the whole body, it presides over the involuntary movements of the limbs and trunk ; it regulates the action of the sphincters, the rectum, and the bladder ; while at the same time it exerts an indirect influ- ence on the nutritive changes in those parts which it supplies with nerves. 430 THE BRAIN. CHAPTER IV. THE BRAIN. By the brain, or encephalon, as it is sometimes called, we mean all that portion of the nervous system which is situated within the cavity of the cranium. It consists, as we have already shown, of a series of different ganglia, connected with each other by transverse and longitudinal commissures. Since we have found the functions of sen.sation and motion, or sensibility and excitability, so distinctly separated in the spinal cord, we should expect to find the same distinction in the interior of the brain. These two properties have indeed been found to be distinct from each other, so far as they exist at all, in the encephalic mass ; but most observers are agreed that they are both confined to very small portions of the brain, in comparison with its entire bulk. According to the investigations of Longet, neither the olfactory ganglia, the corpora striata, the optic thalami, the tuber- cula quadrigemina, nor the white or gray substance of the cerebrum or the cerebellum, are in the least degree excitable. Mechanical irritation of these parts does not produce the slightest convulsive movement in the muscles below. The application of caustic liquids and the passage of galvanic currents are equally without effect. The only portions of the brain in which irritation is followed by convulsive movements are the anterior surface of the medulla ob- longata, the tuber annulare, and the lower part of the crura cerebri ; that, is, the lower and central parts of the brain, containing continu- ations of the anterior columns of the cord. On the other hand, neither the olfactory ganglia, the corpora striata, the tubercula quadrigemina, nor the white or gray substance of the cerebrum or cerebellum, give rise, on being irritated, to any painful sensation. The only sensitive parts are the posterior surface of the medulla oblongata, the restiform bodies, the processus e cerebello ad testes, and the upper part of the crura cerebri ; that is, those portions of the base of the brain which contain prolongations of the posterior columns of the cord. OLFACTORY GANGLIA. — OPTIC THALAMI. 431 The most central portions of the nervous system, therefore, and particularly the gray matter, are usually regarded as destitute of both excitability and sensibility. It is only those portions which serve to condtict sensations and nervous impulses that can be ex- cited by mechanical irritation; not the ganglionic centres them- selves, which receive and originate the nervous impressions. "We shall now study in succession the different ganglia of which the brain is composed. Olfactory Ganglia.— These ganglia, which in some of the lower animals are very large, corresponding in size with the ex- tent of the olfactory membrane and the acuteness of the sense of smell, are very small in the human subject. They are situated on the cribriform plate of the ethmoid bone, on each side of the crista galli, just beneath the anterior lobes of the cerebrum. They send their nerves through the numerous perforations which exist in the ethmoid bone at this part, and are connected with the base of the brain by two longitudinal commissures. The olfactory ganglia with their commissures are sometimes spoken of as the " olfactory nerves." They are not nerves, however, but ganglia, since they are mostly composed of gray matter ; and the term " olfactory nerves" can be properly applied only to the filaments which originate from them, and which are afterward spread out in the substance of the olfactory membrane. It has been found difficult to determine the function of these ganglia by direct experiment on the lower animals. They may be destroyed by means of a strong needle introduced through the bones of the cranium ; but the signs of the presence or absence of the sense of smell, after such an operation, are too indefinite to allow us to draw from them a decided conclusion. The anatomical distribu- tion of their nerves, however, and the evident correspondence which exists,' in different species of animals, between their degree of de- velopment and that of the external olfactory organs, leaves no doubt as to their true function. They are the ganglia of the special sense of smell, and are not connected, in any appreciable degree, with ordinary sensibility, nor with the production of voluntary move- ments. Optic Thalami. — These bodies are not, as their name would imply, the ganglia of vision. Longet has found that the power of sight and the sensibility of the pupil both remain, in birds, after 432 THE BRAIN. the optic thalami have been thoroughly disorganized ; and that arti- ficial irritation of the same ganglia has no effect in producing either contraction or dilatation of the pupil. The optic thalami, however, according to the same observer, have a peculiar crossed action upon the voluntary movements. If both hemispheres and both optic thalami be removed in the rabbit, the animal is still capable of standing and of using his limbs in progression. But if the right optic thalamus alone be removed, the animal falls at once upon his left side ; and if the left thalamus be destroyed, a similar debility is manifest on the right side of the body. In these in- stances there is no absolute paralysis of the side upon which the animal falls, but rather a simple want of balance between the two opposite sides. The exact mechanism of this peculiar functional disturbance is not well understood ; and but little light has yet been thrown, either by direct experiment or by the facts of compa- rative anatomy, on the real function of the optip thalami. CoBPOBA Striata. — The function of these ganglia is equally uncertain with that of the preceding. They are traversed, as we have already seen, by fibres coming from the anterior columns of the cord; and they are connected, by the continuation of these fibres, with the gray substance of the hemispheres. They have therefore, in all probability, like the optic thalami, some connection with sensation and volition ; but the precise nature of this connec- tion is at present altogether unknown. Hemispheres. — The hemispheres, or the cerebral ganglia, con- stitute in the human subject about nine-tenths of the whole mass of the brain. Throughout their whole extent they are entirely destitute, as we have already mentioned, of both sensibility and ex- citability. Both the white and gray substance may be wounded, burned, lacerated, crushed, or galvanized in the living animal, with- out exciting any convulsive movement or any apparent sensation. In the human subject a similar insensibility has been observed when the substance of the hemispheres has been exposed by acci- dental violence, or in the operation of trephining. Very severe mechanical injuries may also be inflicted upon the hemispheres, even in the human subject, without producing any directly fatal result. One of the most remarkable instances of this fact is a case reported by Prof. "William Detmold, of New York,' in > Am. Journ. of Med. Sci., January, 1850. HEMISPHBEES. 433 which an abscess in the anterior lobe of the brain was opened by au incision passing through the cerebral substance, not only without any immediate bad effect, but with great temporary relief to the patient. • This was the case of a laborer who was struck on the left side of the forehead by a piece of falling timber, which produced a compound fracture of the skull at this part. One or two pieces of bone afterward became separated and were removed, and the wound subsequently healed. Nine weeks after the accident, however, headache and drowsiness came on ; and the latter symptom, becom- ing rapidly aggravated, soon terminated in complete stupor. At this time, the existence of an abscess being suspected, the cicatrix, together with the adherent portion of the dura mater, was dissected away, several pieces of fractured bone removed, and the surface of the brain exposed. A knife was then passed into the cerebral sub- stance, making a wound one inch in length and half an inch in depth, when the abscess was reached and over two ounces of pus discharged. The patient immediately aroused from his comatose condition, so that he was able to speak ; and in a few days reco- vered, to a very considerable extent, his cheerfulness, intelligence, and appetite. Subsequently, however, the collection of pus re- turned, accompanied by a renewal of the previous symptoms ; and the patient finally died at the end of seven weeks from the time of opening the abscess. Another and still more striking instance of recovery from severe injury of the brain is reported by Prof H. J. Bigelow in the American Journal of Medical Sciences for July, 1850. In this case, a pointed iron bar, three feet and a half in length, and one inch and a quarter in diameter, was driven through the patient's head by the premature blasting of a rock. The bar entered the left side of the face, just in front of the angle of the jaw, and passed obliquely upward, inside the zygomatic arch and through the anterior part of the cranial cavity, emerging from the top of the frontal bone on the median line, just in front of the point of union of the coronal and sagittal sutures. The patient was at first stunned, but soon recovered himself so far as to be able to converse intelligently, rode home in a common cart, and with a little assistance walked up stairs to his room. He became delirious within two days after the acci- dent, and subsequently remained partly delirious and partly coma- tose for about three weeks. He then began to improve, and at the end of rather more than two months from the date of the injury, was able to walk about. At the end of sixteen months he was in perfect health, with the wounds healed, and with the mental and 28 434 THE BRAIN. bodily functions entirely unimpaired, except that sight was perma- nently lost in the eye of the injured side. This patient survived the injury for a little over twelve years, being able for a great part of the time to do the ordinary work of an ostler, coachman, and farm-laborer, in all of which occupations he was employed at various intervals. He finally died in 1861, after a short illness accompanied by convulsions. The skull, which was subsequently obtained and deposited in the "Warren Anatom- ical Museum,' shows the openings corresponding with the points of entrance and exit of the iron bar. The hemispheres, furthermore, may not only be seriously injured without destroying life, but in many of the lower animals they may be entirely removed without abolishing the powers of sensation and volition. In quadrupeds, the complete removal of the hemispheres is attended with so much hemorrhage that the operation is generally fatal from this cause within a few minutes. In birds, however, it may be performed without any immediate danger to life. Longet has removed the hemispheres in pigeons and fowls, and has kept these animals afterward for several days, with most of the organic functions unimpaired. We have frequently performed the same experiment upon pigeons, with a similar favorable result. The effect of this mutilation is simply to plunge the animal into a state of profound stupor, in which he is almost entirely inatten- tive to surrounding objects. The bird remains sitting motionless upon his perch, or standing upon the ground, with the eyes closed, and the head sunk between the shoulders. (Fig. 149.) The plu- Fig. 149. PlSBON, AFTER SeMOYAI, OP THE HeHISPBESES. 1 J. B. S. Jackson, DescriptiTe Catalogue of the Warren Anatomical Museum, Boston, 1870, p. 145. HEMISPHERES. 435 mage is smooth and glossy, but is uniformly expanded, by a kind of erection of the feathers, so that the body appears somewhat puffed out, and larger than natural. Occasionally the bird opens his eyes with a vacant stare, stretches his neck, perhaps' shakes his bill once or twice, or smooths down the feathers upon his shoulders, and then relapses into his former apathetic condition. This state of immobility, however, is not accompanied by the loss of sight, of hearing, or of ordinary sensibility. All these functions remain, as well as that of voluntary motion. If a pistol be discharged behind the back of the animal, he at once opens his eyes, moves his head half round, and gives evident signs of having heard the report; but he immediately becomes quiet again, and pays no farther attention to it. Sight is also retained, since the bird will sometimes -fix its eye on. a particular object, and watch it for several seconds together. Longet has even found that by moving a lighted candle before the animal's eyes in a dark place, the head of the bird will often follow the movements of the candle from side to side or in a circle, showing that the impression of light is actually perceived by the sensorium. Ordinary sensation also remains, after removal of the hemispheres, together with voluntary motion. If the foot be pinched with a pair of forceps, the bird becomes partially aroused, moves uneasily once or twice from side to side, and is evidently annoyed at the irritation. The animal is still capable, therefore, after removal of the hemi- spheres, of receiving sensations from external objects. But these sensations appear to make upon him no lasting impression. He is incapable of connecting with his perceptions any distinct succession of ideas. He hears, for example, the report of a pistol, but he is not alarmed by it ; for the sound, though distinctly enough perceived, does not suggest any idea of danger or injury. There is accord- ingly no power of forming mental associations, nor of perceiving the relation between external objects. The memory, more particu- larly, is altogether destroyed, and the recollection of sensation is not retained from one moment to another. The limbs and muscles are still under the control of the will ; but the will itself is inactive, because apparently it lacks its usual mental stimulus and direction. The powers which have been lost, therefore, by destruction of the cerebral hemispheres, are altogether of a mental or intellectual character ; that is, the power of comparing with each other different ideas, and of perceiving the proper relation between them. . The same result is well known to follow, in the human subject, 436 THE BKAIN. from injury or disease of these parts. A disturbance of the mental powers has long been recognized as the ordinary consequence of lesions of the brain. In cases of impending apoplexy, for example, or of softening of the cerebral substance, among the earliest and most constant phenomena is a loss or impairment of the memory. The patient forgets the names of particular objects or of particular persons ; or he is unable to calculate numbers with his usual facility. His mental derangement is often shown in the undue estimate which he forms of passing events. He is no longer able to appreciate the true relation between different objects and different phenomena. Thus, he will show an exaggerated degree of solicitude about a trivial occurrence, and will pay no attention to other matters of real importance. As the difficulty increases, he becomes careless of the directions and advice of his attendants, and must be watched and managed like a child or an imbecile. After a certain period, he no longer appreciates the lapse of time> and even loses the dis- tinction between day and night. Finally, when the injury to the hemispheres is complete, the senses may still remain active and impressible, while the patient is completely deprived of intelligence, memory, and judgment. If we examine the comparative development of the hemispheres in different species of animals, and in different races of men, we shall find that the size of these ganglia corresponds very closely with the degree of intelligence possessed by the individual. We have already traced, in a preceding chapter, the gradual increase in size of the hemispheres in fish, reptiles, birds, and quadrupeds : four classes of animals which may be arranged, with regard to the amount of intelligence possessed by each, in precisely the same order of succession. Among quadrupeds, the elephant has much the largest and most perfectly formed cerebrum, in proportion to the size of the entire body ; and of all quadrupeds he is proverbially the most intelligent and the most teachable. It is important to observe in this connection, that the kind of intelligence which characterizes the elephant and some other of the lower animals, and which most nearly resembles that of man, is a teachable intelh- gence ; a very different thing from the intelligence which depends upon instinct, such as that of insects, for example, or birds of pas- sage. Instinct is unvarying, and always does the same thing in the same manner, with endless repetition ; but intelligence is a power which adapts itself to new circumstances, and enables its possessor, by comprehending and retaining new ideas, to profit by experience. HEMISPHERES. 437 It is this quality which distinguishes the higher classes of animals from the lower ; and which, in a very much greater degree, con- stitutes the intellectual superiority of man himself. The size of the cerebrum in man is accordingly very much greater, in propor- tion to that of the entire body, than in any of the lower animals ; while other parts of the brain, on the contrary, such as the olfactory ganglia or the optic tubercles, are frequently smaller in him than in them. For while man is superior in general intelligence to all the lower animals, he is inferior to many of them in the acuteness of the special senses. As a general rule, also, the size of the cerebrum in different races and in different individuals corresponds with the grade of their intelligence. The size of the cranium, as compared with that of the face, is smallest in the savage negro and Indian tribes ', larger in the civilized or semi-civilized Chinese, Malay, Arab, and Japan- ese ; while it is largest of all in the enlightened European races. This difference in the development of the brain is not probably an effect of long-continued civilization or otherwise ; but it is, on the contrary, the superiority in cerebral development which makes some races readily susceptible of civilization, while others are either altogether incapable of it, or can only advance in it to a certain limit. Although all races therefore may, perhaps, be said to start from the same level of absolute ignorance, yet after the lapse of a certain time one race will have advanced farther in civilization than another, owing to a superior capacity for improve- ment, dependent on original organization. The same thing is true with regard to different individuals. At birth, all men are equally ignorant ; and yet at the end of a certain period one will have acquired a very much greater intellectual power than another, even under similar conditions of training, education, &c. He has been able to accumulate more information from the same sources, and to use the same experience to better advantage than his associates ; and the result of this is a certain intellectual superiority, which becomes still greater by its own exercise. This superiority, it will be observed, lies not so much ia the power of perceiving external objects aud events, ^jud of re- cognizing the connection between them, as in that of drawing con- clusions from one fact to another, and of adapting to new combina- tions the knowledge which has already been acquired. It is this particular kind of intellectual difference, existing in a marked degree, between animals, races, and individuals, which cor- 438 THE BRAIN. responds with the difference in development of the cerebral hemi- spheres. We have, therefore, evidence from three different sources that the cerebral hemispheres are the seat of the reasoning powers, or of the intellectual faculties proper. First, when these ganglia are removed in the lower animals, the intellectual faculties are the only ones which are lost. Secondly, injury to these ganglia, in the human subject, is followed by a corresponding impairment of the same faculties. Thirdly, in different species of animals, as well as in different races of men and in different individuals, the develop- ment of these faculties is in proportion to that of the cerebral hemispheres. When we say, however, that the hemispheres are the seat of the intellectual faculties, of memory, reason, judgment, and the like, we do not mean that these faculties are, strictly speaking, located in the substance of the hemispheres, or that they belong directly to the matter of which the hemispheres are composed. The hemi- spherical ganglia are simply the instruments through which the intellectual powers manifest themselves, and which are accordingly necessary to their operation. If these instruments be imperfect in structure, or be damaged in any manner by violence or disease, the manifestations of intelligence are affected in a corresponding degree. So far, therefore, as the mental faculties are the subject of physio- logical research and experiment, they are necessarily connected with the hemispherical ganglia ; and the result of investigation shows this connection to be extremely intimate and important in its character. There are, however, various circumstances which modify, in particular cases, the general rule given above, viz., that the larger the cerebrum the greater the intellectual superiority. The func- tional activity of the brain is modified, no doubt, by its texture as well as by its size ; and an increased excitability may compensate, partially or wholly, for a deficiency in bulk. This fact is some- times illustrated in the -case of idiots. There are instances where idiotic children with small brains are less imbecile and helpless than others with a larger development, owing to a certain vivacity and impressibility of organization which take the place, to a certain extent, of the purely intellectual faculties. This was the case, in a marked degree, with a pair of dwarfed and idiotic Central American children, who were exhibited some years ago in various parts of the United States, under the name of the " Aztec children." They were a boy and a girl, aged respectively HEMISPHERES. 439 about seven and five years. The boy was 2 feet 9| inches high,, and weighed a little over 20 pounds. The girl was 2 feet 5J inches high, and weighed 17 pounds. Their bodies were tolerably well proportioned, but the cranial cavities, as shown by the accompany- ing portraits, were extremely small. The antero-posterior diameter of the boy's head was only 4| inches, the transverse diameter less than 4 inches. The antero- posterior diameter of the girl's head was 4^ inches, the transverse diameter only 3f inches. The habits of these children, so far as regards feeding and taking care of themselves, were those of chil- Fig. 150. Aztec Childkeh. — Taken from Ufe, at five and sevea years of age. dren two or three years of age. They were incapable of learning to talk, and could only repeat a few isolated words. Notwithstand- ing, however, the extremely limited range of their intellectual powers, these children were remarkably vivacious and excitable. While awake they were in almost constant motion, and any new object or toy presented to them immediately attracted their atten- tion, and evidently awakened a lively curiosity. They were ac- cordingly easily influenced by proper management, and understood readily the meaning of those who addressed them, so far as this meaning could be conveyed by gesticulation and the tones of the voice. Their expression and general appearance, though decidedly idiotic, were not at all disagreeable or repulsive; and they were much less troublesome to the persons who had them in charge than is often the case. with idiots possessing a larger cerebral development. It may also be observed that the purely intellectual or reasoning powers are not the only element in the mental superiority of certain races or of particular individuals over their associates. There is 440 THE BBAIN. also a certain rapidity of perception and strength of will which may sometimes overbalance greater intellectual acquirements and more cultivated reasoning powers. These, however, are different facul- ties from the latter ; and occupy, as we shall hereafter see, different parts of the encephalon. A very remarkable physiological doctrine, dependent partly on the foregoing facts, was brought forward some years ago by Gall and Spurzheim, under the name of Phrenology. These observers recognized the fact that the intellectual powers are undoubtedly seated in the brain, and that the development of the brain is, as a general rule, in correspondence with the activity of these powers. They noticed also that in other parts of the nervous system, different functions occupy different situations ; and regarding the mind aa made up of many distinct mental faculties, they conceived the idea that these different faculties might be seated in different parts of the cerebral mass. If so, each separate portion of the brain would undoubtedly be more or less developed in proportion to the activity of the mental trait or faculty residing in it. The shape of the head would then vary in different individuals, in accordance with their mental peculiarities ; and the character and endowments of the in- dividual might therefore be estimated from an examination of the elevations and depressions on the surface of the cranium. Accordingly, the authors of this doctrine endeavored, by examin- ing the heads of various individuals whose character was already known, to ascertain the location of the different mental faculties. In this manner they finally succeeded, as they supposed, in accom- plishing their object ; after which they prepared a chart, in which the surface of the cranium was mapped out into some thirty or forty different regions, corresponding with as many different mental traits or faculties. With the assistance of this chart it was thought that phrenology might be practised as an art ; and that, by one skilled in its application, the character of a stranger might be discovered by simply examining the external conformation of his head. We shall not expend much time in discussing the claims of phre- nology to rank as a science or an art, since we believe that it has of late years been almost wholly discarded by scientific men, owing to the very evident deficiencies of the basis upon which it was founded. Passing over, therefore, many minor details, we will merely point out, as matters of physiological interest, the principal defects which must always prevent the establishment of phrenology as a science, and its application as an art. HEMISPHERES. 441 First, though we have no reason for denying that different parts of the brain may be occupied by different intellectual faculties, there is no direct evidence which would show this to be the case. Phrenologists include, in those parts of the brain which they em- ploy for examination, both the cerebrum and cerebellum • and they justly regard the external parts of these iDodies, viz., the layer of gray matter which occupies their surface, as the ganglionic portion in which must reside more especially the nervous functions which they possess. But this layer of gray matter, in each principal por- tion of the brain, is continuous throughout. There is no anatomical division or limit between its different parts, like those between the different ganglia in other portions of the nervous system ; and consequently such divisions of the cerebrum and cerebellum must be altogether arbitrary in character, and not dependent on any anatomical basis. Secondly, the only means of ascertaining the location of the different mental traits, supposing them to occupy different parts of the brain, would be that adopted by Gall and Spurzheim, viz., to make an accurate comparison, in a sufficient number of cases, of the form of the head in individuals of known character. But the prac- tical difficulty of accomplishing this is very great. It requires a long acquaintance and close observation to learn accurately the character of a single person ; and it is in this kind of observation, more than in any other, that we are proverbially liable to mistakes. It is extremely improbable, therefore, that either Gall or Spurzheim could, in a single lifetime, have accomplished this comparison in so many instances as to furnish a reliable basis for the construc- tion of a phrenological chart. A still more serious practical difficulty, however, is the following. The different intellectual faculties being supposed to reside in the layer of gray substance con- stituting the surfaces of the cerebrum and cerebellum, they must of course be distributed throughout this layer, where- ever it exists. Gall and Spurzheim located all the mental faculties in those parts of the brain which are accessible to external exploration Fig. 151. Diagram of the Brain ih situ, showing those portione which are ex- posed to examination. 442 THE BEAIN. Fig. 152. An examination of different sections of the brain will show, how- ever, that the greater portion of the gray substance is so placed, that its quantity cannot be estimated by an external examination through the skull. The only portions which are exposed to such an examination are the upper and lateral portions of the convex- ities of the hemispheres; together with the posterior edge and part of the under surface of the cerebellum. (Fig. 151.) A very extensive portion of the cerebral surface, however, remains concealed in such a manner that it cannot possibly be subjected to examination, viz., the entire base of the brain, with the under surface of the ante- rior and middle lobes (i, 2); the upper surface of the cerebellum (3) and the inferior surface of the posterior lobe of the cerebrum which covers it (4) ; that portion of the cerebellum situated above tbe medulla oblongata (5) ; and the two opposite convoluted surfaces in the iissure of Sylvius (e, 7), where the anterior and middle lobes of the cerebrum lie in contact with each other. The whole extent, also, of the cerebral surfaces which are opposed to each other in the great longitudinal fissure (Fig. 152), throughout its entire length, are equally protected by their position, and concealed from external examination. The whole of the convoluted surface of the brain must, however, be regarded as of equal im- portance in the distribution of the mental qualities ; and yet it is evident that not more than one-third or one-quarter of this surface is so placed that it can be examined by external manipulation. It must further- more be recollected that the gray matter of the cerebrum and cerebellum is everywhere convoluted, and that the convolutions pene- trate to various depths in the substance of the brain. Even if we were able to feel, therefore, the external surface of the brain itself, it would not be the entire convolutions, but only their superficial edges, that we should really be able to examine. And yet the amount of gray matter contained in a given space depends quite as much upon the depth to which the convolu- tions penetrate, as upon the prominence of their edges. "While phrenology, therefore, is partially founded upon acknow- ledged physiological facts, there are yet essential deficiencies in its scientific basis, as well as insurmountable difi&culties in the way of its practical application. Transverse aectioD of B R A I v, showing depth of great loDgi- tudinal fisanre, at a. CEREBELLUM. 443 Cerebellum. — The cerebellum is the second ganglion of the enoephalon, in respect to size. If it be examined, moreover, in regard to the form and disposition of its convolutions, it will be seen that these are much more complicated and more numerous than in the cerebrum, and penetrate much deeper into its substance. Though the cerebellum therefore is smaller, as a whole, than the cerebrum, it contains, in proportion to its size, a much larger quan- tity of gray matter. In examining the comparative development of the brain, also, in different classes and species of animals,^ we find that the cerebellum nearly always keeps pace, in this respect, with the cerebrum. These facts would lead us to regard it as a ganglion hardly secondary in importance to the cerebrum itself. Physiologists, however, have thus far failed to demonstrate the nature of its function with the same degree of precision as that of many other parts of the brain. The opinion of Gall, which located in the cerebellum the sexual impulse and instincts, is at the present day generally abandoned; for the reason that it has not been found to be sufficiently supported by anatomical and experimental facts, many of which are indeed directly opposed to it. The opinion which has of late years been received with the most favor is that first advocated by Flourens, which attributes to the cerebellum the power of associating or "co-ordinating" the different voluntary movements. It is evident, indeed, that such a power does actually reside in some part of the nervous system. No movements are effected by the independent contraction of single muscles ; but always by several muscles acti% in harmony with each other. The number and complication of these associated movements vary in different classes of animals. In fish, for example, progression is accom- plished in the simplest possible manner, viz., by the lateral flexion and extension of the vertebral column. In serpents it is much the same. In frogs, lizards, and turtles, on the other hand, the four jointed extremities come into play, and the movements are some- what complicated. They are still more so in birds and quadrupeds; and finally, in the human subject they become both varied and complicated in the highest degree. Even in maintaining the ordi- nary postures of standing and sitting, there are many different mus- cles acting together, in each of which the degree of contraction, in order to preserve the balance of the body, must be accurately pro- portioned to that of the others. In the motions of walking and 444 THE BEAIN. running, or in the still more delicate movements of the hands and fingers, this harmony of muscular action becomes still more evident, and is seen also to be absolutely indispensable to the efficiency of the muscular apparatus. The opinion which locates the above harmonizing or associating power in the cerebellum was first suggested by the efiects observed after experimentally injuring or destroying this part of the brain. If the cerebellum be exposed in a living pigeon, and a portion of its substance removed, the animal exhibits at once a peculiar un- certainty in his gait, and in the movement of his wings. If the injury be more extensive, he loses altogether the power of flight, and can walk, or even stand, only with great difficulty. This is not owing to any actual paralysis, for the movements of the limbs are exceedingly rapid and energetic ; but is due to a peculiar want of control over the muscular contractions, precisely similar to that which is seen in a man in a state of intoxication. The movements of the legs and wings, though forcible and rapid, are confused and blundering ; so that the animal cannot direct his steps to any par- ticular spot, nor support himself in the air by flight. He reels and tumbles, but can neither walk nor fly. Fig. 158. PlOBOIf, APTBE EEMOVAI OF THE CBRBBELLDH. The senses and intelligeiice at the same time are unimpaired. It is extremely curious, as first remarked by Longet, to compare the , CEREBELLUM. 445 different phenomena produced by removal of the cerebrum and that of the cerebellum. If we do these operations upon two dif- ferent pigeons, and place the animals side by side, it will be seen that the first pigeon, from whom the cerebrum only has been re- moved, remains standing firmly upon his feet, in a condition of complete repose ; and that when aroused and compelled to stir, he moves sluggishly and unwillingly, but otherwise acts in a perfectly natural manner. The second pigeon, on the other hand, from whom the cerebellum only has been taken away, is in a constant state of agitation. He is easily terrified, and endeavors, frequently with violent struggles, to escape the notice of those who are watching him; but his movements are sprawling and unnatural, and are evidently no longer under the effectual control of the will. (Fig. 153.) If the entire cerebellum be destroyed, the animal is no longer capable of assuming or retaining any natural posture. His legs and wings are almost constantly agitated with ineffectual struggles, which are evidently voluntary in character, but are at the same time altogether irregular and confused. Death generally takes place after this operation within twenty-four hours. We have often performed the above operation, and always with the same effect. Indeed there are few experiments that have been tried upon the nervous system, which give results so uniform and so constant aa this. Taken by themselves, these results would invariably sustain the theory of Mourens, which, indeed, is founded entirely upon them. But we have met with another very important fact, in this respect, which for a long time escaped notice. That is, that birds, which have lost their power of muscular co-ordination from injury of the cerebellum, may recover this power in process of time, notwithstanding thatalargeportionofthe cerebellum hasbeen permanently removed. Usually such an operation upon the cerebellum, as we have men- tioned above, is fatal within twenty -four hours, probably on account of the close proximity of the medulla oblongata. But in some instances, the pigeons upon which we have operated have survived, and in these cases the co-ordinating power became re-established. In the first of these instances, about two-thirds of the cerebellum was taken away, by an opening in the posterior part of the cranium. Immediately after the operation, the animal showed all the usual effects of the operation, being incapable of flying, walking, or even standing still, but reeled and sprawled about in a perfectly helpless manner. In the course of five or six days, however, he had regained 446 THE BEAIIT. a very considerable control over the voluntary movements, and at the end of sixteen days his power of muscular co-ordination was so nearly perfect, that its deficiency, if any existed, was impercep- tible.. He was then killed ; and on examination, it was found that his cerebellum remained in nearly the same condition as immediately after the operation ; about two-thirds of its substance being deficient, and no attempt having been made at regeneration of the lost parts. The accompanying figures, 154 to 157, show the appearances, in this case, as compared with the brain of a healthy pigeon. "We have also met with three other cases, similar to the above, in which about one-half of the cerebellum was removed by operation. The loss of co-ordinating power, immediately after the operation, though less complete than in the instance above mentioned, was perfectly well marked in character ; and in little more than a fort- Fig. 154. Fig. 155. Bbaik of Healthy Pioeoh— Profile Braih of Opeeated Pioeox— Tiew.— 1. Hemisphere. 2. Optic tubercle. 3. Profile view— Bhowing the matilatiou Cerebellum, i. Optic nerve. 6. Medulla ob- of cerebellum, iougata. Fig. 156. Fig. 157. Bkain op Heaxtht Piqeoh— Poste- Brain op Operated Pigeou— rior view. Posterior view— showing the mutilar tion of cerebellum. night the animals had nearly or quite recovered the natural control of their motions. It is evident that in these cases, if the theory of Flourens be cor- rect, two different effects are produced simultaneously by the oper- ation, which ought to be carefully distinguished from each other. The first of these effects is the shock due to the sudden injury of the cerebellum as a whole. This effect is temporary, and may be re- CEEEBELLUM. 447 cotered from in time, provided the animal be sufficiently strong to survive the immediate results of the operation. The remaining effect is that due simply to the loss of the nervous substance; and this second effect must of course be permanent, unless the nervous mat- ter be regenerated. In the cases detailed above, the greatest amount of disturbance seems to have depended upon the sudden injury to the nervous centre as a whole ; and as the immediate effect of this injury passed off, the animals recovered, to a very great extent, their power of muscular co-ordination, notwithstanding that from one-half to two-thirds of the substance of the cerebellum had been permanently lost. It must be remembered, however, that birds, when confined to the limited space of a laboratory, have no oppor- tunity of exercising the more complicated and active movements which are natural to them in a condition of freedom ; and accord- ingly, they might not show any great deficiency of muscular co- ordination while in a state of confinement, and might still be quite incapable of executing the rapid and various movements of natural flight. In birds, therefore, the simpler motions may continue to be per- formed with only a part of the cerebellum remaining ; but we are not sure that, even in these cases, a portion of the co-ordinating power, corresponding with the destruction of nervous substance, has not been permanently lost. ^ Furthermore, there are many facts derived from comparative anat- omy which seem to favor the opinion of Flourens. If we compare different classes of animals with each other, as fish with reptiles, or birds with quadrupeds, in which the development and activity of the entire nervous system vary extremely, the results of the comparison will be often contradictory. But if the comparison be made be- tween different species in which the general structure and plan of organization are similar, we often find the development of the cere- bellum to correspond very closely with the perfection and variety of the voluntary movements. The frog, for example, is an aquatic reptile, provided with anterior and posterior extremities ; but its movements, though rapid and vigorous, are exceedingly simple in character, consisting of little else than flexion and extension of the posterior limbs. The cerebellum in this animal is exceedingly small, as compared with the rest of the brain ; being nothing more than a thin, narrow ribbon of nervous matter, stretched across the upper part of the fourth ventricle. In the common turtle we have another aquatic reptile, where the movements of swimming, diving. 448 THE BEAIN. 1 progression, &o., are accomplished by the consentaneous action of anterior and posterior extremities, and where the motions of the head and neck are also much more varied than in the frog. In this instance the cerebellum is very much more highly developed than in the former. In the alligator, again, a reptile whose motions, both of the head, limbs, and tail, approach very closely to those of the quadrupeds, the cerebellum is still larger in proportion to the remaining ganglia of the encephalon. On the other hand, morbid alterations of the cerebellum, par- ticularly of a chronic nature, such as slow inflammations, abscesses, tumors, &c., have often been observed in the human subject, with- out giving rise to any marked disturbance of the voluntary move- ments. The complete function of the cerebellum, accordingly, as a ner- vous centre, cannot be regarded as positively ascertained ; but so far as we may rely on the results of direct experiment, this orgaa has evidently such an intimate and peculiar connection with the voluntary movements, that a sudden injury inflicted upon its sub- stance is always followed by an immediate and strongly marked disturbance of the co-ordinating power, TuBERCTTLA QuADRiGEMiNA. — These bodies, notwithstanding theirp small size, are- very important in regard to their function. They give origin to the optic nerves, and preside, as ganglia, over the sense of sight ; on which account they are also known by the name of the " optic ganglia." Their development corresponds very closely with that of the external organs of vision. Thus, they are large in fish, reptiles, and birds, in which the eyeball is for the most part very large in proportion to the entire head; and are small in quadrupeds and in man, where the eyeball is, comparatively speaking, of insignificant size. Direct experiment also shows the close connection between the tubercula quadrigemina and the sense of sight. Section of the optic nerve at any point between the retina and the tubercles, produces complete blindness; and destruc- tion of the tubercles themselves has the same effect. But if the division be made between the tubercles and the cerebrum, or if the cerebrum itself be taken away while the tubercles are left un- touched, vision, as we have already seen, still remains. It is the tubercles, therefore, in which the impression of light is perceived. So long as these ganglia are uninjured and retain their connection with the eye, vision remains. As soon as this connection is cut TUBERCULA QUADEIGEMINA. 449 off) or the ganglia themselves are injured, the power of vision is destroyed. The tubercula quadrigemina not only serve as nervous centrea for the perception of light, but a reflex action also takes place through them, by which the quantity of light admitted to the eye is regulated to suit the sensibility of the pupil. In darkness and in twilight, or wherever the light is feeble, the pupil is enlaTged'. by relaxation of its circular fibres, so as to admit as large a quan- tity of light as possible. On first coming into a dark room, ac- cordingly, everything is nearly invisible; but gradually, as the pupil dilates and as more light is admitted, objects begin to show themselves with greater distinctness, and at last we can see toler- ably well in a place where we were at first unable to perceive a single object. On the other hand, when the eye is exposed to an unusually brilliant light, the pupil contracts and shuts out so inuoh of it as would be injurious to the retina. The above is a reflex action, in which the impression received by the retina is transmitted along the optic nerve to the tubercula quadrigemina. From the tubercles, a motor impulse is then sent out through the motor nerves of the eye and the filaments dis- tributed to the iris, and a contraction of the pupil takes place in consequence. The optic nerves act here as sensitive fibres, which convey the impression from the retina to the ganglion ; and if they be irritated in any part of their course with the point of a needle, the result is a contraction of the pupil. This influence is not communicated directly from the nerve to the iris, but is first sent inward to the tubercles, to be afterward reflected outward by the motor nerves. So long as the eyeball remains in connection with the brain, mechanical irritation of the optic nerve, as we have shown above, causes contraction of the pupil ; but if the nerve be divided, and the extremity which remains in connection with the eyeball be subjected to irritation, no effect upon the pupil is pro- duced. The anatomical arrangement of the optic nerves, and the connec- tions of the optic tubercles, are modified in a remarkable degree in different animals, to correspond with the position of the two eyes. In fish, for example, the eyes are so placed, on opposite sides of the head, that their axes cannot be brought into parallelism with each other, and the two eyes can never be directed together at the same object. In these animals, the optic nerves cross each other at the base of the brain without any intermixture of their fibres ; that 29 450 THE BEAIN. from the right optic tubercle passing to the left eye, and that from the left optic tubercle passing to the right eye. (Fig. 158.) The two Fig. 158. Fig. 169. IsrEBioB Surface of Braih OF CoD.—l. Right optic nerre. 2. Left optic nerve. S. Right optic tubercle. 4. Left optic tubercle. 6^ 6, Hemispheres. 7. Uedalla oblongata. Ihfebiob Sitbface of Bkaiit of Fowl. — 1. Right optic nenre. 2. Left optic nerve. 3. Right optic tubercle. 4. Left optic tubercle. 5, 9. Hemispheres. 7. Me- dulla oblongata. nervous cords are here totally distinct from each other throughout their entire length ; and are only connected, at the point of cross- ing, by intervening areolar tissue. Impressions made on the right eye must therefore be perceived on the left side of the brain; while those which enter the left eye are conveyed to the right side of the brain. In birds, also, the axes of the two eyes are so widely divergent that near objects cannot probably be in exact focus for both of them at the same time. The optic nerves are here united, and apparently soldered together, at their point of crossing; but the decussation of their fibres is nevertheless complete. (Fig. 159.) The nervous fila- ments coming from the left side pass altogether over to the right; and those coming from the right side pass over to the left. The result of direct experiment on the crossed action of the tubercles in these animals corresponds with the anatomical arrangement of the nervous fibres. If one of the optic tubercles be destroyed in the pigeon, complete blindness is at once produced in the eye of the opposite side ; but vision remains unimpaired in the eye of the side on which the injury was inflicted. TUBERCULA QUADKIGEMHrA. 451 Rg. 160. CoDRiE OF OpTie Nerves IK Mas.— 1, 2; Bight and left e^eballB. 3. Secaseation or optio nenres. 4, 4. Tabercula quadrigemina. In the human subject, on the other hand, where the visual axes are parallel, and where both eyes are simultaneously directed toward the same object, the optic nerves decussate with each other in such a manner as to form a connection between the two opposite sides, as well as between each tubercle and retina of the same side. (Fig. 160.) This decussation, which is somewhat complicated, takes place in the following manner. From each optic tubercle three different bundles or " tracts" of nervous fibres are given off. One set passes across transversely at the point of decussation, and, turning back- ward, terminates in the tubercle of the opposite side ; another, cross- ing diagonally, continues onward to the opposite eyeball ; while a third passes directly forward to the eyeball of the same side. A fourth set of fibres, still, passes across in front of the decussation, from the retina of one eye to that of the opposite side. We have, therefore, by this arrangement, the two retinae, as well as the two optic tubercles, connected with each other by commissural fibres ; while each tubercle is, at the same time, connected both with its own retina, and with that of the opposite side. It is undoubtedly owing to these connections that when, in the human subject, the eyes are directed in their proper axes, the two retinae, as well as the two optic 1;ubercles, act as a single organ. Vision is single. 452 THE BRAIN. therefore, though there are two images upon the retinae. Douhle vision occurs only when the eyeballs are turned out of their proper direction, soithat the parallelism of their axes is lost, and the image no longer falls upon corresponding parts of the two retinae. Tuber Annulare. — The collection of gray matter imbedded in the deeper portions of the tuber annulare occupies a situation near the central part of the brain, and lies directly in the course of the ascending fibres of the anterior and posterior columns of the cord. This ganglion is immediately connected with the functions of sensa- tion and voluntary motion. We have already seen that these func- tions are not destroyed by taking away the cerebrum, and that they also remain after removal of the cerebellum. According to the ex- periments of Longet, even after complete removal of the olfactory ganglia, the cerebrum, cerebellum) optic tubercles, corpora striata and optic thalami, and when nothing remains in the cavity of the cranium but the tuber annulare and the medulla oblongata, the animal is still sensitive to external impressions, and will still en- deavor by voluntary movements to escape from a painful irritation. The same observer has found, however, that as soon as the ganglion of the tuber annulare is broken up, all manifestations of sensation and volition cease, and even consciousness no longer appears to exist. The only movements which then follow external irritation are the occasional convulsive motions which are due to reflex action of the spinal cord, and which may be readily distinguished from those of a voluntary character. The animal, under these circum- stances, is to all appearance reduced to the condition of a dead body, except for the movements of respiration and circulation, which still go on for a certain time. The tuber annulare must therefore be regarded as the ganglion by which impressions, con- veyed inward through the nerves, are first converted into conscious sensations; and in which the voluntary impulses originate, which stimulate the muscles to contraction. "We must carefully distinguish, however, in this respect, a simple sensation from the ideas to which it gives origin in the mind, and the mere act of volition from the train of thought which leads to it. Both these purely mental operations take place, as we have seen, in the cerebrum; for mere sensation and volition may exist independently of any intellectual action, as they may exist after the cerebrum has been destroyed. A sensation may be felt, for example, without our having the power of thoroughly appreciating MEDULLA OBLONGATA. 453 it, or of referring it to its proper source. This condition is often experienced in a state of deep sleep, when, the body being exposed to cold, or accidentally placed in a constrained position, we feel a sense of suffering without being able to understand its cause. We may even, under such circumstances, execute voluntary movements to escape the cause of annoyance ; but these movements, not being directed by any active intelligence, fail of accomplishing their ob- ject. We therefore remain in a state of discomfort until, on awak- ening, the activity of the reason and judgment is restored, when the offending cause is at once removed. We distinguish, then, between the simple power of sensation, and the power of fully appreciating a sensitive impression and of drawing a conclusion from it. We distinguish also between the intellectual process which leads us to decide upon a voluntary movement, and the act of volition itself. The forijier must precede, the latter must follow. The former takes place, so far as experi- ment can show, in the cerebral hemispheres;, the latter, in the gan- glion of the tuber annulare. Medulla Oblongata. — The last remaining division of the en- cephalon is the medulla oblongata. The most important ganglion contained in this part is the " pneumogastric ganglion," or "nu- cleus," imbedded in the substance of the restiform body, and occu pying the middle and posterior portions of the medulla, where the fibres of the pneumogastric nerve take their origin. This portion of the brain has long been known to be particularly essential to the preservation of life ; so that it has received the name of the "vital point," or the " vital knot." All the other parts of the brain may be injured or removed, as we have already seen, without the imme- diate and necessary destruction of life ; but so soon as the medulla oblongata is broken up, and its ganglion destroyed, respiration ceases instantaneously, and the circulation also soon comes to an end. Eemoval of the medulla oblongata produces, therefore, as its immediate and direct result, a stoppage of respiration ; and death takes place principally as a consequence of this fact. Flourens and Longet have determined, with considerable accu- racy, the precise limits of this vital spot in the medulla oblonga,ta. Flourens ascertained that in rabbits it extended from just above the origin of the pneumogastric nerve, to a level situated three lines and a half below this origin. In larger animals, its extent is pro- portionally increased. Longet ascertained, furthermore, that the properties of the medulla were not the same throughout its entire 454 THE BKAIN. thickness ; but that its posterior and anterior parts might be de- stroyed with comparative impunity, the peculiarly vital spot being confined to the intermediate portions. This vital point accordingly is situated in the layer of gray matter, imbedded in the thickness of the restiform bodies, which has been previously: spoken of as giving origin to the pneumogastric nerves. The precise nature of the connection between this ganglion and the function of respiration may be described as follows. The movements of respiration, which follow each other with incessant regularity through the whole period of life, are not voluntary movements. We may to a certain extent, hasten or retard them at will, but our power over them, even in this respect, is extremely limited ; and in point of fact they are performed, during the greater part of the time, in a perfectly quiet and regular manner, without our volition and even without our consciousness. They continue uninterruptedly through the deepest slumber, and even in a con- dition of insensibility from accident or disease. These movements are the result of a reflex action taking place through the medulla oblongata. The impression which gives rise to them originates principally in the lungs, from the accumulation of carbonic acid in the pulmonary vessels and air-cells, is trans- mitted by the pneumogastric nerves to the medulla, and is thence l-eflected along the motor nerves to the respiratory muscles. These muscles are then called into action, producing an expansion of the chest. The impression so conveyed to the medulla is usually unperceived by the consciousness. It is generally converted directly into a motor impulse, without attracting our attention or giving rise to any conscious sensation. Respiration, accordingly, goes oa perfectly well without our interference and without our knowledge. The nervous impression, however, conveyed to, the medulla, though usually imperceptible, may be made evident at any time by volun- tarily suspending the respiration. As the carbonic acid begins to accumulate in the blood and in the lungs, a peculiar sensation makes itself felt, which grows stronger and stronger with every moment, and impels us to recommence the movements of inspiration. This peculiar sensation, entirely different in character from any other, is designated by the French under the name of " besoin de respir^." It becomes more urgent and distressing, the longer, respiration is suspended, until finally the impulse to expand the chest can no longer be resisted by any effort of the will. During ordinary respiratipn, therefore, each inspiratory move- MEDULLA" OBLONGATA. 455 ment is excited by the partial vitiation of the air contained in the lungs. As soon as a new supply has been inhaled, the impulse to respire is satisfied, the muscles relax, and the chest collapses. In a few seconds the previous condition recurs and the same move- ments are repeated, producing in this way a regular alternation of inspirations and expirations. Since the movements of respiration are performed partly by the diaphragm and partly by the intercostal muscles, they will be differently modified by injuries of the nervous system, according to the spot at which the injury is inflicted. If the spinal cord, for example, be divided or compressed in the lower part of the neck, all the intercostal muscles will be necessarily paralyzed, and respi- ration will then be performed entirely -by the diaphragm. The chest in these cases remaining motionless, and the abdomen alone rising and falling with the movements of the diaphragm, such respiration is called " abdominal" or " diaphragmatic" respiration. It is a common symptom of fracture of the spine in the lower cervical region. If the phrenic nerve, on the other hand, be divided, the diaphragm will be paralyzed, and respiration will then be performed altogether by the rising and falling of the ribs. It is then called "thoracic" or "costal" respiration. If the injury inflicted upon the spinal cord be above the origin of the second and third cervical nerves, both the phrenic and intercostal nerves are at once paralyzed, and death necessarily takes place from suf- focation. The attempt at respiration, however, still continues in these cases, showing itself by ineffectual inspiratory movements of the mouth and nostrils. Finally, if the medulla itself be broken up by a steel instrument introduced through the foramen magnum, so as to destroy the nervous centre in which the above reflex action takes place, both the power and the desire to breathe are at once taken away. No attempt is made at inspiration, there is no strug- gle, and no appearance of sufiering. The animal dies simply by a want of aeration of the blood, which leads in a few moments to an arrest of the circulation. It is owing to the above action of the medulla oblongata that in- juries of this part are so promptly and constantly fatal. When the " neck is broken," as in hanging or by sudden falls upon the head, a rupture takes place of the transverse ligament of the atlas ; the head, together with the first cervical vertebra, is allowed to slid§ forward, and the medulla is compressed between the odontoid pro- cess of the axis in front and the posterior part of the arch of the 456 THE BBAIN. atlas behind. In cases of apoplexy, where any part of the hemi- spheres, corpora striata, or optic thalami, is the seat of the hemor- rhage, the patient generally lives at least twelve hours ; but if the hemorrhage takes place in the medulla itself, or at the base of the brain in its immediate neighborhood, so as to compress its sub- stance, death follows instantaneously, and by the same mechanism as where the medulla is intentionally destroyed. An irregularity or want of correspondence in the movements of respiration is accordingly found to be one of the most threatening of all symptoms in affections of the brain. A disturbance or sus- pension of the intellectual powers does not indicate necessarily any immediate danger to life. Even sensation and volition may be im- paired without serious and direct injury to the organic functions. These symptoms only indicate the threatening progress of the dis- ease, and show that it is gradually approaching the vital centre. It is common to see, however, as the medulla itself begins to be impli- cated, a paralysis first showing itself in the respiratory movements of the nostrils and lips, while those of the chest and abdomen still go on as usual. The cheeks are then drawn in with every inspira- tion and puffed out sluggishly with every expiration, the nostrils themselves sometimes participating in these unnatural movements. A still more threatening symptom, and one which frequently pre- cedes death, is an irregular, hesitating respiration; which sometimes attracts the attention of the physician, even before the remaining cerebral functions are seriously impaired. These phenomena de- pend on the connection between the respiratory movements and the reflex action of the medulla oblongata. We have now, in studying the functions of various parts of the cerebro-spinal system, become familiar with three different kinds of reflex action. The first is that of the spinal cord. Here, there is no proper sensation and no direct consciousness of the act which is performed. It is simply a nervous impression, coming from the integument, and transformed by the gray matter of the spinal cord into a motor impulse destined for the muscles. This action will take place after the removal of the hemispheres and the abolition of consciousness) as well as in the ordinary condition. The respiratory action of the medulla oblongata is of the same general character ; that is, it is not necessarily connected with either volition or consciousness. The only peculiarity in, this instance is that the original nervous impression is of a special , character, and its influence is finally MEDULLA OBLONGATA. 457 exerted upon a special muscular apparatus. Actions of this nature are termed, par excellence, reflex actions. The second kind of reflex action takes place in the tuber annu- lare. Here the nervous impression, which is conveyed inward from the integument, instead of stopping at the spinal cord, passes onward to the tuber annulare, where it first gives rise to a con- scious sensation ; and this sensation is immediately followed by a voluntary act. Thus, if a crumb of bread fall into the larynx, the sensation produced by it excites the movement of coughing. The sensations of hunger and thirst excite a desire for food and drink. The sexual impulse acts in precisely the same manner ; the percep- tion of particular objects giving rise immediately to special desires of a sexual character. It will be observed, in these instances, that in the first place, the nervous sensation must be actually perceived, in order to pro- duce its effect ; and in the second place that the action which follows is wholly voluntary in character. But the most important peculiarity, in this respect, is that the voluntary impulse follows directly upon the receipt of the sensation. There is no intermediate reasoning or intellectual process. We do not cough because we know that this is the most effectual way to clear the larynx ; but simply because we are impelled to do so by the sensation which is felt at the time. We do not take food or drink because we know that they are necessary to support life, much less because we under stand the mode in which they accomplish this object ; but merely because we desire them whenever we feel the sensation of hungei and thirst. All actions of this nature are termed instinctive. They are volun. tary in character, but are performed blindly ; that is, without any idea of the ultimate object to be accomplished by them, and simply in consequence of the receipt "of a particular sensation. Accord, ingly experience, judgment, and adaptation have nothing to do with these actions. Thus the bee builds his cell ean, p 49. FIFTH PAIR. 465 lifter emerging from the outer and tinder surface of the pons Varolii, passes forward over the inner extremity of the petrous portion of the temporal bone. It there expands into a crescentic- shaped swelling, containing a quantity of gray matter with which its fibres are intermingled, and which is known as the Gasserian ganglion. The fibres of the smaller root, passing forward in com- pany with the others, do not take any part in the formation of this ganglion, but may be seen passing beneath it as a distinct bundle, and continuing their course forward to the foramen ovale, through which they emerge from the skull. In front of the anterior and external border of the Gasserian ganglion, the fifth nerve separates into three principal divisions, viz., the ophthalmic, the superior maxillary, and the inferior maxillary. The first of these divisions, viz., the ophthalmic, is so called because it passes through the orbit of the eye. It enters the sphenoidal fissure, and runs along the upper portion of the orbit, sending branches to the ophthalmic gan- glion of the sympathetic, to the lachrymal gland, the conjunctiva, and the mucous membrane of the lachrymal sac. It also sends off a small branch (nasal branch) which penetrates into the nasal pas- sages and supplies the Schneiderian mucous membrane. It then emerges upon the face by the supra-orbital foramen, and is distri- buted to the integument of the forehead and side of the head as far back as the vertex. The second division of this Pig_ igi_ nerve, or the superior maxillary, r^^^^^^^ passes out by the foramen rotun- ^^^^^^^^^k dum, and runs along the longitu- — KIH^^^^^^^^ dinal canal in the floor of the or- bit, giving off branches during its passage to the teeth of the upper jaw and to the mucous membrane of the antrum maxillare. It final- ly emerges upon the middle of the face by the infra-orbital foramen, and is distributed to the integu- ment of the lower eyelid, nose, cheek, and upper lip. The third, or inferior maxillary division of the fifth pair, which is Bi9T»iBUTio» or Fifth nebti the largest of the three, Icavcs the UPOK THE Face.— o. Gasserian ganglion. -^ p ii • i i ,. 1. Ophthalmic division. 2. Superior maxii- cavity ot the crauium by the fora larjr division. 3. Inferiorniaxillarjr division. mCU OValc. It COmprisCS a COn- 80 ^ 466 THE CRANIAL NERVES. siderable portion of the large root of the nerve, and all the fibres of the small root. This division is therefore a mixed nerve, contaimng both motor and sensitive fibres, while the two former are exclusively sensitive. It is distributed, accordingly, both to muscles and to the sensitive surfaces. Soon after emerging from the foramen ovale it sends branches to the temporal muscle, to the masseter, the bucci nator, and to the internal and external pterygoids ; that is, to the muscles which are particularly concerned in the movements of the lower jaw. It also sends sensitive filaments to the integument of the temple, to that of a portion of the external ear and external audi- tory meatus. The third division of the fifth pair, then passing downward and forward, gives ofif a branch of considerable size, the lingual branch, which is distributed to the mucous membrane of the anterior two-thirds of the tongue, and which also sends filaments to the arches of the palate and to the mucous membrane of the cheek. The remaining portion of the third division, after giving a few branches to the mylo-hyoid muscle and to the anterior belly of the digastric, then enters the inferior dental canal, sends filaments to the teeth of the lower jaw, emerges at the mental foramen, and is finally distributed to the integument of the chin, lower lip, and inferior part of the face. This nerve is accordingly distributed to the sensitive surfaces, that is, the integument and mucous membranes about the face,, and to the muscles of mastication. A few of its fibres are sent also to the superficial muscles of the face, such as the buccinator and the orbicularis oris ; but these fibres are sensitive in their character, and serve merely to impart to the muscles a certain degree of sensibility. It has been ascertained by Longet that if the various branches of this nerve be irritated by a galvanic current, no con- vulsive movements whatever are produced in those superficial muscles of the face, which it supplies with filaments; but if its smaller or non-ganglionic root be irritated in the same way, con- tractions instantly follow in the muscles of mastication. The fifth pair is the most acutely sensitive nerve in the whole body. Its irritation by mechanical means always causes intense pain, and even though the animal be nearly unconscious from the influence of ether, any severe injury to its large., root is almost invariably followed by cries which indicate the extreme sensibility of its fibres. If this nerve be completely divided, in the living animal, within the cranium, at the situation of the Gasserian ganglion, the operation FIFTH PAIR. 467 is followed by total loss of sensibility in the skin of the face and in the adjacent mucous membranes. The conjunctiva, upon the affected side, is then completely insensible, and may be touched with the point of a needle or the blade of a knife, without exciting any un- easiness, and even without the consciousness of the animal. Probes and needles may be passed into the nostril, and the lips or the cheek may be pinched, pierced or cut, without exciting the least sign of sensibility. The animal is entirely indifferent to all me- chanical injuries upon the affected side, though upon the opposite side the parts retain their natural sensibility. Owing to the paralysis of the Ungual nerve, also, after this ope- ration, the tongue, in its anterior two-thirds, becomes insensible to ordinary irritations, and loses, beside, the power of taste. Another peculiar effect of the division of the fifth pair depends upon the paralysis of its motor fibres, which are distributed, as we have seen, to the muscles of mastication. In many of the lower animals, consequently, the movements of mastication become ex- ceedingly enfeebled upon the affected side. In the cat, for example, an animal in which mastication is usually very thoroughly per- formed, this process becomes excessively laborious, so that the animal after this operation cannot masticate solid meat, but requires to be fed with that which has already been cut in pieces. The fifth pair, beside supplying the sensibility of the integument of the face, has a peculiar and important influence on the organs of special sense. This influence appears to consist in some connection between the action of the fifth pair and the processes of nutrition ; so that .when the former is injured, the latter very soon become deranged. For the perfect action of any one of the organs of special sense, two conditions are necessary : first, the sensibility of the special nerve belonging to it, and secondly, the integrity of the component parts of the organ itself. Now as the nutrition of the organ is, to a certain extent, under the control of the fifth pair, any serious injury to this nerve produces a derangement in the tissues of the organ, and consequently interferes with the due performance of its function. The mucous membrane of the nasal passages, for example, is supplied by two different nerves; first, the olfactory, distributed throughout its upper portion, by which it is endowed with the special sense of smell ; and, secondly, the nasal branch of the fifth pair, distributed throughout its middle and lower portions, by which it is supplied with ordinary sensibility. 468 THE CRANIAL NERVES. Since the fifth pair, accordingly, supplies general sensibility to the nasal passages, this property ■will remain after the special sense of smell has been destroyed. If, however, the fifth pair itself be divided, not only is general sensibility destroyed in the Schneiderian mucous membrane, but a disturbance begins to take place in the nutrition of its tissue, by -which it is gradually rendered unfit for the performance of its special function, and the power of smell is finally lost. The mucous membrane, under these circumstances, becomes injected and swollen, and the nasal passage is obstructed by an accumulation of puriform mucus. According to Longet, the mucous membrane also assumes a fungous consistency, and is liable to bleed at the slightest touch. The effect of this alteration is to blunt or altogether destroy the sense of smell. It is owing to a similar unnatural condition of the mucous membrane that the power of smell is always more or less impaired in cases of coryza and influenza. The olfactory nerves become inactive in consequence of the morbid alteration in their mucous 'membrane, and in the secretions which cover it. The influence of this nerve over the organ of visionis still more remarkable. It has been known for many years that division of the fifth pair within the cranium, or of its ophthalmic branch, is fol- lowed by an inflammation of the corresponding eye, which usually goes on to complete and permanent destruction of the organ, Immediately after the operation, the pupil becomes contracted and the conjunctiva loses its sensibility. At the end of twenty-four hours, the cornea begins to become opaline, and by the second day the conjunctiva' is already inflamed and begins to discharge a purulent secretion. The inflammation, after commencing in the conjunctiva, increases in intensity and soon spreads to the iris, which becomes covered with a layer of inflammatory exudation. The cornea grows constautly more opaque, until it is at last altogether impermeable to light, and vision is consequently sus- pended. Blindness, therefore, does not result in these instances from any direct affection of the optic nerve or of the retina, but is owing simply to opacity of the cornea. Sometimes the diseased action goes on until it results in ulceration of the cornea and dis- charge of the humors of the eye; sometimes, after the lapse of several days, the inflammatory appearances subside, and the eye is finally restored to its natural condition. It has been observed, however, that although the above conse- quences always follow division of the fifth pair, when performed at FACIAL NEBVE. 469 tlie level of tte GasseriaD ganglion, or between it and tbe eyetall, they are either much diminished in intensity or altogether wanting when the division is made at a point posterior to the ganglion. This circumstance has led to the belief that the influence of the fifth pair on the nutrition of the eyeball does not reside in its own proper fibres, but in some filaments of the sympathetic nerve which join the fifth pair at the level of the Gasserian ganglion. If the section accordingly be made at this point, or in front of it, the fibres of the sympathetic will be divided with the others, and inflammation, of the eye will result ; but if the section be made behind the ganglion, the fibres of tbe sympathetic will escape division, and the injurious effects upon the eye will be absent. It is certain that inflammation of the eye sometimes follows division of the fifth nerve, and some- times is wanting ; but the precise reason of this variation is not fully understood. Division of the fifth pair destroys also the general sensibility of the external auditory meatus, the lining membrane of which is supplied by its filaments. Inflammation of this membrane and its consequent alterations, it is well known, interfere seriously with the sense of hearing. It is no uncommon occurrence for an accu- mulation of cerumen to take place after inflammation of this part, so as to block up the auditory canal and produce partial or com- plete deafness. It has not been ascertained, however, whether division of the fifth pair is usually followed by similar changes in this part. The lingual branch of the fifth pair supplies the anterior ex- tremity and middle portion of the tongue both with general sensi- bility and with the power of taste. The sensibility of the tongue is accordingly provided for by two different nerves ; in its anterior two-thirds, by the lingual branch of the fifth pair ; in its posterior third, by the fibres of the glosso-pharyngeal. The facial branches of the fifth pair are the ordinary seat of tic douloureux. • This affection is not unfrequently confined to either the supra-orbital, the infra-orbital, or the mental branch ; and the pain may be accurately traced in the direction of their diverging fibres. It has already been mentioned that the painful sensations sometimes also follow the course of the facial, owing to some sensi- tive filaments which that nerve receives from the fifth pair. Facial. — This nerve, the " seventh pair," according to the mod- ern enumeration of the cranial nerves, leaves the side of the me- 470 THE CRANIAL NEBVES. Fig. 162. dulla oblongata, just behind the pons Varolii. Its fibres are traced to a oollection of gray matter in' the upper part of the medulla continuous with that from which the roots of the sixth pair origi- nate. The facial nerve, after leaving the side of the medulla, passes onward through the petrous portion of the temporal bone, emerges at the stylo-mastoid foramen, bends round beneath the external ear, and passes forward through the substance of the parotid gland, forming a plexus called the " pes anserinus," by the abundant inosculation of its different branches. It then sends its filaments forward in a diverging course, and is finally distributed to the mus,cles of the external ear, to the frontalis. and superciliaris muscles, to the orbicularis oculi, the compressors and dilators of the nares, the orbicularis oris, and to the elevators and depressors of the lips ; that is, to the superficial muscles of the face, which are concerned in the production of expression. (Fig. 162.) The facial, consequently, is the motor nerve of the face. It has nothing to do with transmitting sensitive impressions, since it has been frequently shown that after section of the fifth pair, the facial remaining entire, the sensibility of the face is completely lost ; so that the integument may be cut, pricked, S!5^^SB^^9R^^^V^ pierced, or lacerated, without any sign of pain being exhibited by the animal. The facial, therefore, does not transmit sen.sation from these parts ; and its division, which was formerly resorted to in cases of tic douloureux, is accordingly alto- gether incapable of relieving neuralgic pains. This nerve, however, is directly connected with muscular action, since mechanical or galvanic irritation of its fibres produces con- vulsive twitching in the ears, nostrils, lips, and cheeks. If the facial nerve be divided in one of the lower animals, as, for example, in the cat, immediately after its emergence from the stylo-mastoid foramen, it will be found that complete muscular paralysis has occurred in all those parts to which the nerve is dis- tributed, while the power of sensation remains unimpaired. The animal is incapable of moving the ear, which remains constantly in Facial Hesvs. FACIAL NEEVE. 471 the same position. There is also incapacity of closing the eyelids, owing to paralysis of the orbicularis oculi, and the eye accordingly remains constantly open, even when the opposite eye is closed ; as during sleep, or in the act of winking. If the conjunctiva be touched, the animal feels the irritation, and endeavors to escape from it ; but the eyeball is only drawn partially backward into the socket by the action of the recti muscles, and the third eyelid pushed partly across the cornea. The complete closure of the eye is impossible. It will be observed, accordingly, that precisely oppo- site effects are ^produced upon the eyelids by paralysis of the oculo- motorius nerve, and by that of the facial. In the former instance, owing to the paralysis of the levator palpebrse superioris, the eye is always partially closed ; in the latter, owing to paralysis of the orbicularis, it is always partially open. The movements of the nares are also suspended on the side of the injury, and if the angle of the mouth be examined on that side, it will be found to hang down lower than on the opposite side, and to be constantly partly open, owing to the paralysis of the orbicularis oris and the eleva- tors of the angle of the mouth. These are the only inconveniences which follow the division of the facial nerve in the cat, but in some other of the lower animals, where various muscular organs in this region are particularly de- veloped, the consequences are more troublesome. Thus, in the rabbit, the ear, upon the affected side, falls down, and cannot be raised or pointed in different directions ; and as the movements of the ear are important in these animals, as aids to the hearing, the per- fection of this sense must be considerably impaired by paralysis of the facial nerve. In the horse, it has been noticed by Bernard,' that division of the facial on both sides is fatal by suffocation. For this animal breathes exclusively through the nostrils, which open widely at the time of inspiration, to allow the admission of air. If these movements be suspended, by paralysis of the facial nerve, the nostrils immediately collapse, and the animal dies by suffocation. In the human subject, the facial nerve is occasionally paralyzed upon one side, sometimes from sympathetic irritation, sometimes from organic disease in the petrous portion of the temporal bone, or within the cranial cavity near the origin of the nerve. In either case, an extremely well-marked affection is the result, known as ' Lemons 8ur la Physiologie et la Fathologie du SyatSme Nerveux, Paris, 1858, Tol. ii. p. 38. 472 THK CEANIAL NEKVES. •' facial paralysis." This condition is cbiefly characterized by an entire absence of expression on the affected side of the face. The lower eyelid sinks downward, from paralysis of the orbicularis muscle, and cannot be closed. The corner of the mouth also falls downward, and the whole lower part of the face is drawn over to the opposite side, by the force of the antagonistic muscles. The lips are unable to retain the fluids of the mouth; and the saliva dribbles away from between them, giving to that side of the face a remarkably vacant and helpless appearance. The principal inconvenience, however, suffered by the human subject in facial paralysis, depends upon the want of action of the muscles about the lips and cheek. In drinking, the fluids escape by the corner of the mouth, and in mastication the food has partly a tendency to escape by the same opening, and partly accumulates, on the affected side, between the gums and the cheek, owing to the paralysis of the buccinator muscle, which receives its niotor fila- ments from the facial nerve. Thus, the action of all the superficial facial muscles is suspended, the expression of the face is destroyed, and the movements of the lips and the prehension of the food seriously interfered with. Though the facial, however, be essentially a motor nerve, yet its principal branches distributed to the face have a certain degree of sensibility ; that is, when these branches are irritated in the middle of their course, the animal immediately gives evidence of a painful sensation. Longet has shown, by an extremely ingenious mode of experiment,' that this sensibility of the branches of the facial does not depend on any sensitive fibres of their own, but upon those which they derive from inosculation with the fifth pair. He exposes, for example, the facial nerve in the dog, and, irritating its principal branches one after the other, at each application of the irritant there are evident signs of pain. He then divides the facial nerve at its point of exit from the stylo-mastoid foramen, and finds that, after this operation, the sensibility of its branches still remains. The fibres, accordingly, upon which this sensibility depends, do not pass out with the trunk of the nerve, but are derived from some other source. The experimenter, then, upon another animal, divides the fifth pair within the skull, leaving the facial untouched; and afterward, on irritating as before the ex- ' Traits de Physiologie, vol. ii. pp. 354-367. GLOSSO-PHAETNGEAL. 473 posed branches of the latter nerve, he finds that its sensibility has entirely disappeared. It is by filaments, accordingly, derived from the fifth pair, that a certain degree of sensibility is communicated, to the branches of the facial. These facts account for the peculiar circumstance that, in cases of tic douloureux, the spasmodic pain sometimes follows exactly the course of the facial nerve, viz : from behind the ear forward upon the side of the face ; and yet the section of this nerve does not put an end to the neuralgia, but only causes paralysis of the facial muscles. Glosso-Phakyngeal. — This nerve originates from the gray matter of the upper and posterior portion of the medulla ob- longata, emerges from the side of the medulla, and enters the posterior foramen lacerum in company with the pneumogastric and spinal accessory. While in the jugular fossa it presents a gangliform enlargement, called the ganglion of Andersch, below the level of which it receives branches of communication from the facial and the. spinal accessory. It then runs downward and forward, and is distributed to the mucous membrane of the base of the tongue, pillars of the fauces, soft palate, middle ear, and upper part of the pharynx. It also sends some branches to the constrictors of the pharynx and the neighboring muscles. Longet has found this nerve at its origin to be exclusively sensitive ; but below the level of its ganglion it has been found by him, as well as by various other observers, to be both sensitive and motor, owing to the fibres of communication received from the motor nerves mentioned above. Its final distribution is, however, as we have seen, principally to sensitive surfaces. The principal ofiice of this nerve is to impart the sense of taste to the posterior third of the tongue, to which it is distributed. It also presides over the general sensibility of this part of the tongue, as well as that of the fauces and pharynx. Dr. John Eeid,' who has performed a great variety of experiments upon this nerve, comes to the following conclusions in regard to it. First, that it is essentially a sensitive nerve, since there are unequi- vocal signs of pain when it is pricked, pinched, or cut. Second, that irritation of this nerve produces convulsive movements of the throat and lower part of the face ; but that these movements are, in great measure, not direct, but reflex in their character, since they ' In Todd'3 Cyclopae.li.a of Anatomy and Physiology, article Glosso-pharyngeal Nerva^ 471 THE CRANIAL NEEVES. ■will take place equally well after the glosso-pharyngeal has been divided, if the irriiation be applied to its cranial extremity. Third, that this nerve supplies the special sensibility of taste to a portion of the tongue ; but that it is not the exclusive nerve of this sense, since the power of taste remains, after it has been divided on both sides. There are certain reflex actions, furthermore, which take place through the medium of the glosso-pharyngeal nerve. After the food has been thoroughly masticated, it is carried, by the move- ments of the tongue and sides of the mouth, through the fauces, and brought in contact with the mucous membrane of the pharynx. This produces an impression which, conveyed to the medulla oblongata by the filaments of the glosso-pharyngeal, excites the muscles of the fauces and pharynx by reflex action. The food is consequently grasped by these muscles, without the concurrence of the will, and the process of deglutition is commenced. This action is not only involuntary, but it will frequently take place even in opposition to the will. The food, once past the isthmus of the fauces, is beyond the control of volition, and cannot be returned except by convulsive action, equally involuntary in its character. Natural stimulants, therefore, applied to the mucous membrane of the pharynx, excite deglutition ; unnatural stimulants, applied to the same part, excite vomiting. If the finger be introduced into the fauces and pharynx, or if the mucous membrane of these parts be irritated by prolonged tickling with the end of a feather, the sensation of nausea, conveyed through the glosso-pharyngeal nerve, is sometimes so great as to produce immediate and copious vomit- ing. This method may often be successfully employed in cases of poisoning, when it is desirable to excite vomiting rapidly, and when emetic medicines are not at hand. Pneumogasteic. — Owing to the numerous connections of the pneumogastric with other nerves, its varied and extensive distribu- tion, and the important character of its functions, this is properly regarded as one of the most remarkable nerves in the whole body. Owing to the wandering course of its fibres, which are distributed to no less than four difierent vital organs, viz., the heart, lungs, stofnach and liver, as well as to several other parts of secondary importance, it has been often known by the name of the par vagum. The pneumogastric arises from a collection of gray matter in the posterior and middle portions of the medulla oblongata, alreadj PNEUMOGASTRIC NERVE. 475 spoken of as the "nucleus" of tlie pneumogastrio nerve. It emerges, by a number of separate filaments, from the lateral por- tion of the medulla, in the groove between the olivary and resti- form bodies. These filaments unite into a single trunk, which passes out of the cranium through the jugular canal, where it is provided with a ganglionic swelling, the "jugul&,r ganglion of the pneumogastrio nerve." Immediately below the level of this gan- glion the nerve receives an important Jf^^^ branch of communication from the spinal F ^MK^^^^Ik. accessory, and afterward from the fa- ^^^^i^'VIjI^ cial, the hypoglossal, and the anterior branches of the first and second cervi- cals. According to the results obtained by Longet, whose experiments appear to be »BH|B^^^ the most conclusive on this point, the jnA^^^^ pneumogastrio is, at its origin, exclu- sively a sensitive nerve. Galvanic irri- tation applied to the roots of the nerve, when carefully separated from the me- dulla and from all adjacent filaments, is not found to produce any muscular con- tractions ; but if the stimulus be applied to the trunk of the nerve, below the level of the jugular ganglion, muscular con- tractions are excited, owing to the mo- tor filaments which have already joined it from the above-mentioned sources. The pneumogastric therefore becomes, after emerging from the cranial cavity, a mixed nerve ; and has accordingly, in nearly all its branches, a double distri- bution, viz., to the mucous membranes and the muscular coat of the organs to ■which it belongs. The ordinary sensibility of the pneu- mogastric nerve, however, as all experi- menters have observed, is exceedingly dull, in comparison with that of the other sensitive cranial nerves. We have often divided this nerve in the middle of the neck, without any distinct manifestation of pain being Biagram of Pnbituooabtbxo N BBVE, with itspriiicipal branches. — L. Pharyngeal branch. 2. Supe- rior laryngeal. 3. Inferior laryn- geal. 4. Pnlmonary branches. 5. Stomach. 6. Liver. 476 THE CRANIAL NEEVES. given by the animal ; and though Bernard has found that at some times its sensibility is well marked, while at others it is very in- distinct, he is not able to say upon what special physiological con- ditions this difference depends. While the pneumogastrio, how- ever, is decidedly deficient, as a general rule, in ordinary sensibility, it possesses, as we shall see hereafter, a sensibility of a peculiar kind, which is exceedingly important for the maintenance of the vital functions. In passing down the neck, this nerve sends branches to the mu- cous membrane and muscular coat of the pharynx, oesophagus, and respiratory passages. Among the niost important of these braijchea are the two laryngeal nerves, viz., the superior and inferior. The superior laryngeal nerve, which is given off frOm the trunk of the pneumogastrio just after it has emerged from the cavity of the skull, passes downward and forward, penetrates the larynx by an opening in the side of the thyro-hyoid membrane, and is distributed to the mu- cous membrane of the larynx and glottis, and also to a single laryn- geal muscle, viz., the crico-thyroid. This branch is therefore partly muscular, but mostly sensitive in its distribution. The inferior la- ryngeal branch is given off just after the pneumogastrio has entered the cavity of the chest. It curves round the subclavian artery on the right side and the arch of the aorta on the left, and ascends in the groove between the trachea and oesophagus, to the larynx. It then enters the larynx between the cricoid cartilage and the pos- terior edge of the thyroid, and is distributed to all the muscles of the larynx, with the exception of the crico-thyroid. This branch is, therefore, exclusively muscular in its distribution. The trunk of the pneumogastrio, after supplying the above branches, as well as sending numerous filanaents to the trachea and oesophagus in the neck, gives off in the chest its pulmonary branches, which follow the bronchial tubes in the lungs to their minutest ramifications. It then passes into the abdomen and gup- plies the muscular and mucous layers of the stomach, ramifying over both the anterior and posterior surfaces of the organ ; after which its fibres spread out and are distributed to the liver, spleen, pancreas, and gall-bladder. The functions of the pneumogastrio will now be successively studied in the various organs to which it is distributed. Pharynx and (Esophagus. — The reflex act of deglutition, which has already been described as commencing in the upper part of the pharynx, by means of the glosso-pharyngeal, is continued in the PNEUMOGASTBIC NERVE. 477 lower portion of the pharynx and throughout the oesophagus by the aid of the pneumogastric. As the food is compressed by the superior constrictor muscle of the pharynx and forced downward, it excites the mucous membrane with which it is brought in contact and gives rise to another contraction of the middle constrictor. The lower constrictor is then brought into action in its turn in a similar manner ; and a wave-like or peristaltic contraction is thence pro- pagated throughout the entire length of the oesophagus, by which the food is carried rapidly from above downward, and conducted at last to the stomach. Each successive portion of the mucous mem- brane, in this instance, receives in turn the stimulus of the food, and excites instantly its own muscles to contraction ; so that the food passes rapidly from one end of the oesophagus to the other, by an action which is wholly reflex in character and entirely withdrawn from the control of the will. Section of the pneumogastric, or of its pharyngeal and oesophageal branches, destroys therefore at the same time the sensibility and the motive power of these parts. The food is no longer conveyed readily to the stomach, but accumulates in the paralyzed oesophagus, into which it is forced by the voluntary movements of the mouth and fauces, and by the continued action of the upper part of the pharynx. It must be remembered that the general sensibility of the oeso- phagus is very slight, as compared with that of the integumdnt, or even of the mucous membranes near the exterior. It is a general rule, in fact, that the sensibility of the mucous membranes is most acute at the external orifices of their canals ; as, for example, at the lips, anterior nares, anus, orifice of the urethra, &c. It diminishes constantly from without inward, and disappears altogether at a certain distance from the surface. The sensibility of the pharynx is less acute than that of the mouth, but is still sufficient to enable us to perceive the contact of ordinary substances; while in the oesophagus we are not usually sensible of the impression of the food as it passes from above downward. The reflex action takes place here without any assistance from the consciousness ; and it ia only when substances of an unusually pungent or irritating nature are mingled with the food, that its passage through the oesophagus pro- duces a distinct sensation. Larynx. — We have already described the course and distribution of the two laryngeal branches of the pneumogastric. The superior laryngeal nerve is principally the sensitive nerve of the larynx. Its division destroys sensibility in the mucous membrane of this 478 THE CRANIAL NERVES. organ, but paralyzes only one of its muscles, viz : the crico-thyroid. Galvanization of this nerve has also been found to induce con- tractions in the crico-thyroid, but in none of the other muscles belonging to the larynx. The inferior laryngeal, on the other hand, is a motor nerve. Its division paralyzes all the muscles of the larynx except the crico-thyroid ; and irritation of its divided extremity produces contraction in the same muscles. The muscles and mucous membrane of the larynx are therefore supplied by two different branches of the same trunk, viz., the superior laryngeal nerve for the mucous membrane, and the inferior laryngeal nerve for the muscles. The larynx, in man and in all the higher animals, performs a double function ; one part of which is connected with the voice, the other with respiration. The formation of the voice in the larynx takes place as follows. If the glottis be exposed in the living animal, by opening the pharynx and oesophagus on one side, and turning the larynx for- ward, it will be seen that so long as the vocal chords preserve their usual relaxed condition during expiration, no sound is heard, except the ordinary faint whisper of the air passing gently through the cavity of the larynx. When a vocal sound, however, is to be produced, the chords are suddenly made tense and applied closely to each other, so as to diminish very considerably the size of the orifice; and the air, driven by an unusually forcible expiration through the narrow opening of the glottis, in passing between the vibrating vocal chords, is itself thrown into vibrations which pro- duce the sound required. The tone, pitch, and intensity of this sound, vary with the conformation of the larynx, the degree of ten- sion and approximation of the vocal chords, and the force of the expiratory effort. The narrower the opening of the glottis, and the greater the tension of the chords, under ordinary circumstances, the more acute the sound ; while a wider opening and a less degree of tension produce a graver note. The quality of the sound is also modified by the length of the column of air included between the glottis and the mouth, the tense or relaxed condition of the walls of the pharynx and fauces, and the state of dryness or moisture of the mucous membrane lining the aerial passages. Articulation, on the other hand, or the division of the vocal sound into vowels and consonants, is accomplished entirely by the lips. tongue, teeth, and fauces. These organs, however, are under the PNEUMOGASTRIC NERVE. 479 control of other nerves, and the mechanism of their action need not occupy us here. Since the production of a vocal sound, therefore, depends upon the tension and position of the vocal chords, as determined by the action of the laryngeal muscles, it is not surprising that division of the inferior laryngeal nerves, by paralyzing these muscles, should produce a loss of voice. It has been sometimes found that in very young animals the crico-thyroid muscles, which are the only ones not affected by division of the inferior laryngeal nerves, are still sufficient to give some degree of tension to the vocal chords, and to produce in this way an imperfect sound ; but usually the voice is entirely lost after such an operation. It is a very remarkable fact, however, in this connection, that all the motor filaments of the pneumogastric, which are concerned in the formation of the voice, are derived from a single source. It will be remembered that the pneumogastric, itself originally a sensitive nerve, receives motor filaments, on leaving the cranial cavity, from no less than five different nerves. Of these filaments, however, those coming from the spinal accessory are the only ones necessary to the production of vocal sounds. For it has been found by Bischoff and by Bernard' that if all the roots of the spinal acces- sory be divided at their origin, or if the nerve itself be torn away at its exit from the skull, all the other cranial nerves remaining untouched, the voice is lost as completely as if the inferior laryn- geal itself had been destroyed. All the motor fibres of the pneu- mogastric, therefore, which act in the formation of the voice are derived, by inosculation, from the spinal accessory nerve. In respiration, again, the larynx performs another and still more important function. In the first place, it stands as a sort of guard, or sentinel, at the entrance of the respiratory passages, to prevent the intrusion of foreign substances. If a crumb of bread accidentally fall within the aryteno-epiglottidean folds, or upon the edges of the vocal chords, or upon the posterior surface of the epiglottis, the sensibility of these parts immediately excites a violent expulsive cough, by which the foreign body is dislodged. The impression received and conveyed inward by the sensitive fibres of the superior laryngeal nerve, is reflected back upon the expiratory muscles of the chest and abdomen, by which the instinctive movements of coughing are accomplished. Touching the above parts with the point of a needle, or pinching them with the blades of a forceps, ' Reoberches Expfirimentalea snr les fonctions du nerf spinal. Paris, 1851. 480 THE CBAjNIAL NERVES. will produce the same effect. This reaction is essentially dependent on the sensibility of the laryngeal onucous membrane ; and it can no longer be produced after section of the pneumogastric nerve, or of its superior laryngeal branch. In the second place, the respiratory movements of the glottis, already described in a previous chapter, are of the greatest, importance to the preservation of life. We have seen that at the moment of inspiration the vocal chords are separated from each other, and the glottis opened, by the action of the posterior crico-arytenoid muscles • and that in expiration the muscles and the vocal chords are both relaxed, and the air allowed to pass out readily through the glottis. The opening of the glottis in inspiration, therefore, is an active movement, while its partial closure or collapse in expiration is a passive one. Furthermore, the opening of the glottis in inspiration is necessary in order to afford a sufficiently wide passage for the air, in its way to the trachea, bronchi, and pulmonary vesicles. Now we have found, as Budge and Longet had previously no- ticed, that if the inferior laryngeal nerve on the right side he divided while the glottis is exposed as above, the respiratory move- ments of the right vocal chord instantly cease, owing to the para- lysis of the posterior crico-arytenoid muscle on that side. If the inferior laryngeal nerve on the left side be also divided, the para- lysis of the glottis is then complete, and its respiratory movements cease altogether. A serious difficulty in respiration is the imme- diate consequence of this operation. For the vocal chords, being no longer stretched and separated from each other at the moment of inspiration, but remaining lax and flexible, act as a double valve, and are pressed inward by the column of inspired air ; thus par- tially blocking up the passage and impeding the access of air to the lungs. If the pneumogastrics be divided in the middle of the neck, the larynx is of course paralyzed precisely as after section of the inferior laryngeal nerves, since these nerves are given oft' only after the main trunks have entered the cavity of the chest. The immediate effect of either of these operations is to produce a difficulty of inspiration, accompanied by a peculiar wheesiing or sucking noise, evidently produced in the larynx and dependent on the falling together of the vocal chords. In very young animals, as, for example, in pups a few days old, in whom the glottis is smaller and the larynx less rigid than in adult dogs, this difficulty is much more strongly marked. Legallois' has even seen a pup ' In Longet'a Traitfi de Phyaiologie, vol. ii. p. 324. PNEUMOGASTKIO NERVE. 481 two days old almost instantly suffocated after section of the two inferior laryngeal nerves. We have found that, in pups two weeks old, division of the inferior laryngeals is followed by death at the end of from thirty to forty hours, evidently from impeded respiration. / The importance, therefore, of these movements of the glottis in respiration becomes very evident. They are, in fact, part and parcel of the general respiratory movements, and are necessary to a due performance of the function. It has been found, moreover, that the. motor filaments concerned in this action are not derived, like those of the voice, from a single source. While the vocal movements of the larynx are arrested, as mentioned above, by division of the spinal accessory alone, those of respiration still go on; and in order to put a stop to the latter, either the pneumo- gastrios themselves must be divided, or all five of the motor nerves from which their accessory filaments are derived. This fact has been noticed by Longet as showing that nature multiplies the safe- guards of a function in proportion to its importance ; for while the spinal accessory, or any other one of the above-mentioned nerves, might be affected by local accident or disease, it would be very improbable that any single injury should paralyze simultaneously the spinal accessory, the facial, the hypoglossal, and the first and second cervicals. The respiratory movements of the larynx are consequently much more thoroughly protected than those which are merely concerned in the formation of the voice. . Lungs. — The influence of the pneumogastric upon the function of the lungs is exceedingly important. The nerve acts here, as in most other organs to which it is distributed, in a double or mixed capacity ; but it is principally as the sensitive nerve of the lungs that it has thus far received attention. It is this nerve which conveys from the lungs to the medulla oblongata that peculiar impression known as the demand for breath, which excites by reflex action the diaphragm and intercostal muscles, and keeps up the play of the respiratory movements. As we have already shown, this action is an involuntary one, and will even take place when consciousness is entirely suspended. It may indeed be arrested for a time by an effort of the will ; but the impression conveyed to the medulla soon becomes so strong, and the stimulus to inspiration so urgent, that they can no longer be resisted, and the muscles contract in spite of our attempts to restrain them. A very remarkable effect is accordingly produced on respiration 31 482 THE CBANIAL NERVES. by simultaneous division of both pneumogastric nerves. This experiment is best performed on adult dogs, which may be ether- ized, and the nerves exposed while the animal is in a condition of insensibility, avoiding, in this way, the disturbance of respiration, which would follow if the dissection were performed while the ani- mal was conscious and sensible to pain. After the effects of the etherization have entirely passed off, and respiration and circulation have both returned to a quiescent condition, the two nerves, which have been previously exposed and secured by a loose ligature, may be instantaneously divided, and the effects of the operation readily appreciated. Immediately after the division of the nerves, when performed in the above manner, the respiration is hurried and difficult, owing to the sudden paralysis of the larynx and partial closure of the glottis by the vocal chords, as already described. This condition, how- ever, is of short continuance. In a few moments, the difficulty of breathing and the general agitation subside, the animal becomes perfectly quiet, and the only remaining visible effect of the opera- tion is a diminished freqitency in the movements of respiration. This diminution is frequently strongly marked from the first, the number of respirations falling at once to ten or fifteen per minute, and be- coming, in an hour or two, still farther reduced. The respirations are performed easily and quietly ; and the animal, if left undisturbed, remains usually crouched in a comer, without giving any special signs of discomfort. If he be aroused and compelled to move about, the frequency of the respiration is temporarily augmented ; but as soon as he is again quiet, it returns to its former standard. By the second or third day, the number of respirations is often reduced to five, four, or even three per minute ; when this is the case, the animal usually appears very sluggish, and is roused with difficulty from his inactive condition. At this time the respiration is not only diminished in frequency, but is also performed in a peculiar manner. The movement of inspiration is slow, easy, and silent, occupying several seconds in its accomplishment ; expiration, on the contrary, is sudden and audible, and is accompanied by a well marked expulsive effort, which has the appearance of being, to a certain extent, voluntary in character. The intercostal spaces also sink inward during the lifting of the ribs ; and the whole movement of respiration has an appearance of insufficiency, as if the lungs were not thoroughly filled with air. This insufficiency of respira- PNEUMOGASTBIO NERVE. 483 tion is undoubtedly owing to a peculiar alteration in the pulmonary- texture, which has by this' time already commenced. Death takes place at a period varying from one to six days after the operation, according to the age and strength of the animal. The only symptoms accompanying it are a steady failure of the respiration, with increased sluggishness and indisposition to be aroused. There are no convulsions, nor any evidences of pain. After death the lungs are found in a peculiar state of solidification, which is almost exclusively a consequence of this operation, and which is entirely different from ordinary inflammatory hepatization. They are not swollen, but rather smaller than natural. They are of a dark purple color, leathery and resisting to the feel, destitute of crepitation, and infiltrated with blood. Pieces of the lung cut out sink in water. The pleural surfaces, at the same time, are bright and polished, and their cavity contains no effusion or exudation. The lungs, in a word, are simply engorged with blood and empty of air ; their tissue having undergone no other alteration. These changes are not generally uniform over both lungs. The organs are usually mottled on their exterior ; the variations in color corresponding with the different degrees of alteration exhibited by different parts. The explanation usually adopted of the above consequences fol- lowing division of the pneumogastrics is as follows : The nerves being divided, the impression which originates in the lungs from the accumulation of carbonic acid, and which is destined to excite the respiratory movements by reflex action, can no longer be trans- mitted to the medulla oblongata. The natural stimulus to respira- tion being wanting, it is, accordingly, less perfectly performed. The respiratory movements diminish in frequency, and, growing con- tinually slower and slower, finally cease altogether, and death is the result. The above explanation, however, is not altogether sufficient. It accounts very well for the diminished frequency of respiration, but not for its partial continuance. For if the pneumogastric nerves be really the channel through which the stimulus to respiration is conveyed to the medulla, the difficulty is not to understand why respiration should be retarded after division of these nerves, but why it should continue at all. In point of fact, the respiratory movements, though diminished in frequency, continue often for some days after this operation. This cannot be owing to force of habit, or to any remains of nervous influence, as has been some- 484 THK CEANIAL NERVES. times suggested, since, when the medulla itself is destroyed, respira- tion, as we know, stops instantaneously, and no attempt at move- ment is made after the action of the nervous centre is suspendedi It is evident, therefore, that the pneumogastric nerve, though the chief agent by which the respiratory stimulus is conveyed to the medulla, is not the only one. The lungs are undoubtedly the organs which are most sensitive to an accumulatipn of carbonic acid, and an imperfect arterialization of the blood ; and the sensa- tion which results from such an accumulation is accordingly first felt in them. There is reason to believe, however, that all the vas- cular organs are more or less capable of originating this impression, and that all the sensitive nerves are capable, to some extent, of trans- mitting it. Although the first disagreeable sensation, on holding the breath, makes itself felt in the lungs, yet, if we persist in sus- pending the respiration, we soon become conscious that the feeling of discomfort spreads to other parts ; and at last, when the accu- mulation of carbonic acid and the impurity of the blood have become excessive, all parts of the body suffer alike, and are per- vaded by a general feeling of derangement and distress. It is easy, therefore, to understand why respiration should be retarded,, after section of the pneumogastrics, since the chief source of the stimulus to respiration is cut ofi'; but the movements still go on, though more slowly than before, because the other sensitive nerves, which con- tinue to act, are also capable, in an imperfect manner, of conveying the same impression. The immediate cause of death, after this operation, is no doubt the altered condition of the lungs. These organs are evidently very imperfectly filled with air, for some time previous to death; and their condition, as shown in post-mortem examination, is evi- dently incompatible with, a due performance of ; the respiratory function. It is not at all certain, however, that these alterations in the pulmonary tissue are directly dependent on division of the pneumogastric nerves. It must be recollected that when the sec- tion of the pneumogastrics is performed in the middle pf the neck, the filaments of the inferior laryngeal nerves are also divided, and the narrowing of the glottis,, produced by their paralysis,^ must necessarily interfere with the free admission of air into the chest. This difficulty, either alone or combined with the diminished fre- quency of respiration, must have a very considerable effect in im- peding the pulmonary circulation, and bringing the lungs into snob a condition as unfits them for maintaining life. PNEUMOGASTEIC NERVE. 485 In order to ascertain the comparative influence upon tte lungs of division of the inferior laryngeals and that of the other filaments of the pneumogastrics, we have resorted to the following experi- ment. Two pups were taken, belonging to the same litter and of the same size and vigor, about two weeks old. In one of them (No. 1) the pneumogastrics were divided in the middle of the neck ; and in the other (No. 2) a section was made at the same time of the inferior laryngeals, the trunk of the pneumogastrics being left un- touched. For the first few seconds after the operation, there was but little difference in the condition of the two animals. There was the same obstruction of the breath (owing to closure of the glottis), the same gasping and sucking inspiration, and the same frothing at the mouth. Very soon, however, in pup No. 1, the respiratory movements became quiescent, and at the same time much reduced in frequency, falling to ten, eight, and five respirations per minute, as usual after section of the pneumogastrics ; while in No. 2 the respiration continued frequent as well as laborious, and the general signs of agitation and discomfort were kept up for one or two hours. The animal, however, after that time became exhausted, cool, and partially insensible, like the other. They both died, between thirty and forty hours after the operation. On post-mortem inspection it was found that the peculiar congestion and solidification of the lungs, considered as characteristic of division of the pneumogastrics, existed to a similar extent in each instance ; and the only appre- ciable difference between the two bodies was that in No. 1 the blood was coagulated, and the abdominal organs natural, while in No. 2 the blood was fluid and the abdominal organs congested. We are led, accordingly, to the following conclusions with regard to the effect produced by division of this nerve. 1. After section of the pneumogastrics, death takes place by a pecu- liar congestion of the lungs. 2. This congestion is not directly produced by division of the nerves, but is caused by the imperfect admission of air into the chest. In adult dogs, the closure of the glottis from paralysis of the laryngeal muscles is less complete than in pups; but it is still sufficient to exert a very decided influence on respiration, and to take an active part in the production of the subsequent morbid phenomena. We therefore regard the death which takes place after division 486 THE CRANIAL NERVES. of both pneumogastrio nerves, as produced in the following man- ner: — The glottis is first narrowed by paralysis of the laryngeal mus- cles, and an imperfect supply of air is consequently admitted, by each inspiration, into the trachea. Next, the stimulus to respiration being very much diminished, the respiratory movements take place less frequently than usual. From these two causes combined, the ' blood is imperfectly arterialized. But the usual consequence of such a condition, viz., an increased rapidity of the respiratory movements, does not follow. The imperfect arterialization of the blood does not excite the respiratory muscles to increased activity as it would do in health, owing to the division of the pneu- mogastrics. At the same time, the accumulation of carbonic acid in the blood and in the tissues begins to exert a narcotic effect, diminishing the sensibility of the nervous centres, and tending to retard still more the movements of respiration. Thus all these causes react upon and aggravate each other ; because the connec- tion, naturally existing between imperfectly arterialized blood and the stimulus to respiration, is now destroyed. The narcotism and pulmonary engorgement, therefore, continue to increase, until the lungs are so seriously altered and engorged that they are no longer capable of transmitting the blood, and circulation and respiration come to an end at the same time. ■ It must be remembered, also, that the pneumogastrio nerve has other important distributions, beside those to the larynx and the lungs; and the effect produced by its division upon these other organs has no doubt a certain share in producing the results which follow. Bearing in mind the very extensive distribution of the pneumogastrio nerve and the complicated character of its func- tions, we may conclude that after section of this nerve death takes place from a combination of various causes; the most active of which is a peculiar engorgement of the lungs and imperfect per- formance of the respiratory function. Stomach, and Digestive Function. — After division of the pneumo- gastrio nerves, the sensations of hunger and thirst remain, and the secretion of gastric juice continues. Nevertheless the digestive function is disturbed in various ways, though not altogether abo- lished. The appetite is more or less diminished, as it would be after any serious operation, but it remains sufficiently active to show that its existence is not directly dependent on the integrity of the pneumogastrio nerve. Digestion, however, very seldom takes PNEUMOGASTBIC NERVE. 487 place, to any considerable extent, owing to the following circum- stances : The animal is frequently seen to take food and drink with considerable avidity ; but in a few moments afterward the food and drink are suddenly rejected by a peculiar kind of regurgitation. This regurgitation does not resemble the act of vomiting, but the substances .swallowed are again discharged so easily and instan- taneously as to lead to the belief that they had never passed into the stomach. Such, indeed, is actually the case, as any one may convince himself by watching the process, which is often repeated by the animal at short intervals. The food and drink, taken volun- tarily, pass down into the oesophagus, but owing to the paralysis of the muscular fibres of this canal, are not conveyed into the stomach They accumulate consequently in the lower and middle part of the oesophagus ; and in a few moments are rejected by a sudden anti- staltic action of the parts, excited, apparently, through the influence of the great sympathetic. The muscular coat of the stomach is also paralyzed to a con- siderable extent by section of this nerve. Longet has shown, by introducing food artificially into the stomach, that gastric juice may be secreted and the food be actually digested and disappear, when introduced in small quantity. But when introduced in large quantity, it remains undigested, and is found after death, with the exterior of the mass softened and permeated by gastric juice, while the central portions are unaltered, and do not even seem to have come in contact with the digestive fluid. This is undoubtedly owing both to the diminished sensibility of the mucous membrane of the stomach, and to the paralysis of its muscular fibres. The peristaltic action of the organ is very important in digestioh, in order to bring successive portions of the food in contact with its mucous membrane, and to carry away such as are already softened or as are not capable of being digested in the stomach. This constant movement and agitation of the food is probably also one great stimulus to the continued secretion of the gastric juice. The digestive fluid will therefore be deficient in quantity after division of the pneumogastrio nerve, at the same time that the peristaltic movements of the stomach are suspended. Under these circum- stances, the secretion of gastric juice may be sufficient to permeate and digest small quantities of food, while a larger mass may resist its action, and remain undigested. The effect produced by division of these nerves on the digestive, as on the respiratory organs, is therefore of a complicated character, and results from the combined 488 THE CRANIAL NERVES. action of several different causes, wMch influence and modify each other. The effect produced upon the liver by section of the pneunjo- gastrics, as well as the influence usually exerted by these nerves upon the hepatic functions, has been so little studied that nothing definite has been ascertained in regard to it. We shall therefore pass over this portion of the subject in silence. Spinal Accessory. — This nerve originates, by many filaments, from the side of the medulla oblongata, immediately below the level of the pneumogastric, and also from the lateral column of the spinal cord, between the anterior and posterior roots of the upper five or six cervical nerves. The nerve has, accordingly, two sets of root-fibres, viz., the spinal roots, or those originating from the lateral portion of the spinal cord ; and the medullary roots, or those originating from the medulla oblongata. The fibres of spinal ori- gin pass upward, uniting into a slender rounded filament, which enters the cavity of the cranium by the foramen magnum, and is then joined by the fibres which originate from the medulla oblon- gata. The spinal accessory nerve, thus constituted, passes out from the cavity of the skull by the posterior foramen lacerum, in company with the glosso-pharyngeal and pneumogastric nerves. Immediately afterward it divides into two principal branches: First, the internal or anastomotic branch, which joins the pneumo- gastric nerve, and becomes mingled with its fibres ; and, secondly, the external or muscular branch, which passes downward and out- ward, and is distributed to the sterno-mastoid and trapezius mus- cles. The internal or anastomotic branch, as has been well shown by Bernard,' is composed exclusively of the medullary roots of the nerve, while the external or muscular branch consists altogether of the fibres originating from the spinal cord. The spinal accessory is essentially a motor nerve. It has been found, both by Bernard and Longet, to be insensible at its origin, like the anterior roots of the spinal nerves; but if irritated after its exit from the skull, it gives signs of sensibility. This sensibility it acquires from the filaments of inosculation which it receives from the anterior branches of the first, second, and third cervical nerves. Though its external branch, accordingly, is exclusively distributed to muscles, as we have already seen, this branch contains some sensi- tive fibres, which have the same destination. The reason for this ' Recherches Experiment ales sur les Fonctions du Nerf Spinal. Paris, 185T SPINAL ACCESSOR Y. 489 anatomical fact, viz., that motor nerves are supplied during their course with sensitive fibres, becomes evident when we reflect that the muscles themselves possess a certain degree of sensibility, though less acute than that which belongs to the skin. The sensibility of the muscles is undoubtedly essential to the perfect performance of their function ; and as the motor nerves are incapable, by them- selves, of transmitting sensitive impressions, they are joined, soon after their origin, by other filaments which communicate to them this necessary power. The most important result which has been obtained by experi- ment upon the spinal accessory nerve, is that its internal or anasto- motic branch is directly connected with the vocal movements of the glottis. It has been found by Bischoff, by Longet, and by Bernard, that if the spinal accessory nerves on both sides, or their branches of inosculation with the pneumogastrio, be divided or lacerated, the pneumogastrio nerves themselves being left entire, the voice is instantly lost, and the animal becomes incapable of making a vocal sound. We have also found this result to follow, in the cat, after the spinal accessory nerves have been torn out by their roots, through the jugular foramen. The animal, after this operation, can no longer make an audible sound. At the same time the respira- tory movements of the glottis go on undisturbed, and most of the other animal functions remain unaffected. The fibres of communication, therefore, derived from the spinal accessory, pass to the pneumogastrio nerve and become entangled with its other filaments, so that they can no longer be traced by anatomical dissection. They pass downward, however, and become a part of the motor fibres of the inferior laryngeal or recurrent ibranches of the pneumogastrio; being finally distributed to the ■muscles of the larynx, which they supply with those nervous influ- ences which are required for the formation of the voice. The special function of the external or muscular branch of the spinal accessory is not so fully understood. This branch, as we have seen, is distributed to the sterno-mastoid and trapezius mus- cles. But these muscles also receive filaments from the cervical spinal nerves ; and, accordingly, they still retain the power of mo- tion, to a certain degree, after the external branches of the spinal accessory have been divided on both sides. The spinal accessory is, accordingly, a nerve of very peculiar distribution. For it partly supplies motor fibres to the pneumo- gastrio nerve, and is partly distributed to two muscles, both of •490 THE CRANIAL NEKVE3. which also receive motor nerves froni another source. Sir Charles Bell,- noticing the close connection between this nerve and the pneumogastric, regarded the two as associated also in their func- tion, as nerves of respiration. He considered, therefore, the exter- nal branch of the spinal accessory as destined to assist in the movements of respiration, when these movements become unusu- ally laborious, by bringing into play the stemo-mastoid and trape zius muscles, in aid of the action of the intercostals. He therefore called this nerve the " superior respiratory nerve." But the most satisfactory explanation of this peculiarity is that proposed by M. Bernard. According to this explanation, whenever a muscle, or set of muscles, derive their nervous influence from two different sources, this is not for the purpose of assisting them in the 'performance of the same function, but of enabling them to perform two different functions. We have seen this already exemplified in the muscles of the larynx. For these muscles perform certain movements of respiration for which they receive indirectly filaments from the facial, hypoglossal, and cervical nerves. But they also perform the movements necessary to the formation of the voice, the nervous stimulus for which is derived altogether from the spinal accessory. The internal branch of the spinal accessory, accordingly, excites, in the parts to which it is distributed a function which is incompa- tible with respiration. For the movements of respiration cannot go on while the voice is sounded; and a necessary preliminary to the production of a vocal sound, is the temporary stoppage of respiration. The movements of respiration, therefore, and the movements of the voice alternate with each other, but are never simultaneous ; so that the internal branch of the spinal accessory is antagonistic to the motor fibres of the larynx derived from other nerves. It is thought by M. Bernard, that the fibres of the external branch of the spinal accessory have also a function which is anta- gonistic to respiration. For respiration is naturally suspended in all steady and prolonged muscular efforts. In these efforts, such as those of straining, lifting, and the like, the movements of respira- tion cease, the spinal column is made rigid by the contraction of its muscles, and the head and neck are placed in a fixed position, principally by the contraction of the stemo-mastoid and trapezius muscles. The function of the spinal accessory, in both its branches, is therefore regarded as destined to excite movements which are HYPO-GLOSSAL. 491 incompatible with those of respiration ; and which accordingly come into play only when the ordinary movements of respiration have been temporarily suspended. Hypoglossal. — The hypoglossal nerve originates from a collec- tion of gray matter, in the medulla oblongata, which is termed the ' hypoglossal nucleus," ' and which is a continuation of the ante- rior horn of gray matter of the spinal cord. Its fibres emerge from the lower portion of the medulla, just outside the anterior pyramids, and passing through the anterior condyloid foramen, are finally distributed to the muscles of the tongue. Irritation of the nerve in any part of its course produces convulsive twitching in this organ. Its section paralyzes completely the movements of the tongue without afiecting directly the sensibility of its mucous membrane. This nerve, accordingly, is the motor nerve of the tongue. If irritated at its origin, the hypoglossal nerve, according to the experiments of Longet, is entirely insensible ; but if the irri tation be applied in the middle of its course, signs of pain are immediately manifested. Its sensibility, like that of the facial, is consequently derived from its inosculation with other sensitive nerves, after its emergence from the skull. 1 Dr. John Dean. Gray Sabstance of the Medulla, &c., p. 18. 492 THE SPECIAL SENSES. CHAPTEK VI. THE SPECIAL SENSES. Geneeal and Special Sensibility. — We have already seen that there exists, in the general integument, a power of sensation, by which we are made acquainted with surrounding objects and some of their most important physical qualities. By this power we feel the sensations of heat and cold, and are enabled to distinguish between hard and soft substances, rough bodies and smooth, solids and liquids. This kind of power is termed General Sensibility, because it resides in the general integument, and because by its aid we obtain information with regard to the simplest and most material properties of external objects. The general sensibility, thus existing in the integument, is an endowment of the sensitive nerves derived from the cerebro-spinal system. These nerves ramify in the substance of the skin, and by subsequent inosculation form a minute plexus in the superficial portions of the tissue of the cbrium. From this plexus, the ulti- mate filaments, reduced to an exceedingly minute size, pass up- ward into the conical papillae with which the free slirface of the corium is covered. In the papillae the nervous filaments terminate, sometimes by loops returning upon themselves, and sometimes ap- parently by free extremities. The papilla are also supplied with looped capillary bloodvessels, and are capable of receiving an abundant vascular injection. These papillae appear to be the most essential organs of general sensation, since the sensibility of the skin is most acute where they are most abundant and most highly developed, as, for example, on the palm of the hand and the tips of the fingers. The best method of measuring accurately the sensibility of dif- ferent regions is that adopted by Professors Weber and Valentin. They applied the rounded points of a pair of compasses to the integument of different parts, and found that if they were held very near together they could no longer be distinguished as sepa- GENERAL AND SPECIAL SENSIBILITY. 493 rate points, but the two sensations were confounded into one. The distance, however, at which the two points failed to be distinguished from each other, was much shorter for some parts of the body than for others. Prof. Valentin's measurements,* which are the most varied and complete, give the following as the limits of dis- tinct perception in various parts :— Paris Line. At the tip of tongue .483 " palmar surface of tips of fingers .... .723 " " " of second phalanges . . . 1.558 " " " of first phalanges .... 1.660 " dorsum of tongue 2 500 " dorsal surface of fingers 3.900 " cheek 4.541 " back of hand 6.966 " skin of throat 8.292 " dorsum of foot 12.525 " skin over sternum 15.875 " middle of back 24.208 This method cannot, of course, give the absolute measure of the acuteness of sensibility in the different regions, since the two points might be less easily distinguished from each other in any one re- gion, and yet the absolute amount of sensation produced might be as great as in the surrounding parts ; still it is undoubtedly a very accurate measure of the delicacy of tactile sensation, by which we are enabled to distinguish slight inequalities in the surface of solid bodies. We find, furthermore, that certain parts of the body are particularly well adapted to exercise the function of general sen- sation, not only on account of the acute sensibility of their integu- ment, but also owing to their peculiar formation. Thus, in man, the hands are especially well formed in this respect, owing to the articulation and mobility of the fingers, by which they may be adapted to the surface of solid bodies, and brought successively in contact with all their irregularities and depressions. The hands are therefore more especially used as organs of touch, and we are thus enabled to obtain by their aid the most delicate and precise information as to the texture, consistency, and configuration, of foreign bodies. But the hands are not the exclusive organs of touch, even in the human subject, and in some of the lower animals, the same func- ' In Todd's Cyclopaedia of Anatomy and Physiology, vol. ir., article on Touch, by Dr. Carpentp- 494 THE SPECIAL SENSES. tion is fully performed by various other parts of the body. Thus in the cat and in the seal, the long bristles seated upon the lips are used for this purpose, each bristle being connected at its base with a highly developed nervous papilla : in some of the monkeys the extremity of the prehensile tail, and in the elephant the end of the nose, which is developed into a flexible and sensitive proboscis, is employed as an organ of touch. This function, therefore, may he performed by either one part of the body or another, provided the accessory organs be developed in a favorable manner. About the head and face, the sensibility of the skin is dependent mainly upon branches of the fifth pair. In the neck, trunk, and extremities it is due to the sensitive fibres of the cervical, dorsal, and lumbar spinal nerves. It exists also, to a considerable extent, in the mucous membranes of the mouth and nose, and of the pas- sages leading from them to the interior of the body. In these situations, it depends upon the sensitive filaments of certain of the cranial nerves, viz., the fifth pair, the glosso-pharyngeal, and the pneumogastric. The sensibility of the mucous membranes is most acute in those parts supplied by branches of the fifth pair, viz., the conjunctiva, anterior part of the nares, inside of the lips and cheeks, and the anterior two-thirds of the tongue. At the base of the tongue and in the fauces, where the mucous membrane is suppHed by filaments of the glosso-pharyngeal nerve, the general sensibility is less perfect; and finally it diminishes rapidly from the upper part of the oesophagus and the glottis toward the stomach and the lungs. Thus, we can appreciate the temperature and consistency of a foreign substance very readily in the mouth and fauces, but these qualities are less distinctly perceived in the oesophagus, and not at all in the stomach, unless the foreign body happen to be excessively hot or cold, or unusually hard and angular in shape. The general sensibility, which is resident in the skin and in a certain portion of the mucous membranes, diminishes in degree from with- out inward, and disappears altogether in those organs which are not supplied with nerves from the cerebro-spinal system. It is particularly to be observed, however, that while the general sensibility of the skin, and of the mucous membranes above men- tioned, varies in acuteness in different parts of the body, it is every- where the same in kind. The tactile sensations, produced by the co'ntact of a foreign body, are of precisely the same nature whether they be felt by the tips of the fingers, the dorsal or palmar surfaces of the hands, the lips, cheeks, or any other part of the integument. TASTE. 495 The only difference in tlie sensibility of these parts lies in the de- gree of its development. But there are certain other sensations which are different in kind from; those perceived by the general integument, and which, owing to their peculiar and special character, are termed special sensations. Such are, for example, the sensation of light, the sensation of sound, the sensation of savor, and the sensation of odors. The special sensibility which enables us to feel the impressions derived from these sources is not distributed over the body, like ordinary sensi- bility, but is localized in distinct organs, each of which is so con- stituted as to receive the special sensation peculiar to it, and no other. Thus we have, beside the general sensibility of the skin and mucous membranes, certain peculiar faculties or special senses, as they are called, which enable us to derive information from ex- ternal objects, which we could not possibly obtain by any other means. Thus light, however intense, produces no perceptible sen- sation when allowed to fall upon the skin, but only when admitted to the eye. The sensation of sound is perceptible only by the ear, and that of odors only by the olfactory membrane. These different sensations, therefore, are not merely exaggerations of ordinary sensibility, but are each distinct and peculiar in their nature, and are in relation with distinct properties of external objects. In examining the organs of special sense, we shall find that they each consist — First, of a nerve, endowed Avith the special sensibility required for the exercise of its peculiar function ; and. Secondly, of certain accessory parts, forming an apparatus more or less compli- cated, which is intended to assist in its performance and render it more delicate and complete. We shall take up the consideration of the special senses in the following order. First, the sense of Taste ; second, that of Smell ; third, that of Sight ; and fourth, that of Hearing. Taste. — We. begin the study of the special senses with that of Taste, because this sense is less peculiar than any of the others, and differs less, both in its nature and its conditions, from the ordinary sensibility of the skin. In the first place, the organ of taste is no other than a portion of the mucous membrane, beset with vascular and nervous papillae, similar to those of the general integument. 496 THE SPECIALSENSE8. Secondly, it gives us impressions of suet substances only aa are actually in contact with sensitive surfaces, and can establish no communication with objects at a distance. Thirdly, the surfaces which exercise the sense of taste are also endowed with general sen- sibility ; and Fourthly, there is no one special and distinct nerve of taste, but this property resides in portions of two different nerves, viz., the fifth pair and the glosso-pharyngeal ; nerves which also supply general sensibility to the mouth and surrounding parts. The sense of taste is localized in the mucous membrane of the tongue, the soft palate, and the fauces. The tongue, which is more particularly the seat of this sense, is a flattened, leaf-like, muscular organ, attached to the inner surface of the symphysis of the lower jaw in front, and to the os hyoides behind. It has a vertical sheet or lamina of fibrous tissue in the median line, which serves as a framework, and is provided with an abundance of longitudinal transverse and radiating muscular fibres, by which it can be elon- gated, retracted, and moved about in every direction. The mucous membrane of the fauces and posterior third of the tongue, like that lining the cavity of the mouth, is covered with minute vascular papillae, similar to those of the skin, which are, however, imbedded and concealed in the smooth layer of epithe- lium forming the surface of the organ. But about the junction of its posterior and middle thirds, there is, upon the dorsum of the tongue, a double row of rounded eminences, arranged in a V-shaped figure, running forward and outward, on each side, from the situa- tion of the foramen caecum ; and, from this point forward, the upper surface of the organ is everywhere covered with an abundance of thickly-set, highly developed papillae, projecting from its surface, and readily visible to the naked eye. These lingual papillae are naturally divided into three different sets or kinds. First, the filiform papillae, which are the most nume- rous, and which cover most uniformly the upper surface of the organ. They are long and slender, and are covered with a some- what horny epithelium, usually prolonged at their free extremity into a filamentous tuft. At the edges of the tongue these papilla are often united into parallel ranges or ridges of the raucous mem- brane. Secondly, the fungiform papillse. These are thicker and larger than the others, of a rounded club-shaped figure, and covered with soft, permeable epithelium. They are most abundant at the tip of the tongue, but may be seen elsewhere on the surface of the organ, scattered among the filiform papillae. Thirdly, the circum- TASTE. 497 vallate papillse. These are tte rounded eminences whicli form the V-shaped figure near the situation of the foramen caecum. They are eight or ten in number. Each one of them is Surrounded by a circular wall, or circumvallation, of mucous membrane, which gives to them their distinguishing appellation. The circumvalla- tion, as well as the central eminence, has a structure similar to that of the fungiform papillae. The sensitive nerves of the tongue, as we have already seen, are two in number, viz., the lingual branch of the fifth pair, and the lingual portion of the glosso-pharyngeal. The lingual branch of the fifth pair enters the tongue at the anterior border of the hyo- glossua muscle, and its fibres then run through the muscular tissue of the organ, from below upward and from behind forward, with- out any ultimate distribution, until they reach the mucous mem- brane. The nervous filaments then penetrate into the lingual papillae, where they finally terminate. The exact mode of their termination is not positively known. According to Kolliker, they sometimes seem to end in loops, and sometimes by free extremities. The lingual portion of the glosso-pharyngeal nerve passes into the tongue below the posterior border of the hyo-glossus muscle. It then divides into various branches, which pass through the mus- cular tissue, and are finally distributed to the mucous membrane of the base and sides of the organ. Fig. 164. BiAGBAU or Tosanii, With lUeeiuUire Dervesand papilla.— 1. LisKual branch of flftb pai^ 2. GiosBo-pharyngeal nerve. The mucous membrane of the base of the tongue, of its edges, and its under surlace near the tip, as well as the mucous membrane of the mouth and fauces generally, is also supplied with mucous follicles, which furnish a viscid secretion by which the free surface of the parts is lubricated, 32 498 THE SPECIAL SENSES. Finally, the muscles of the tongue, it will be rememhered, are animated exclusively by the filaments of the hypoglossal nerve. The exact seat of the sense of taste has been determined by placing in contact with different parts of the mucous membrane a small sponge, moistened with a solution of some sweet or bitter substance. The experiments of Vernifere, Longet and others have shown that the sense of taste resides in the whole superior surface, the point and edges of the tongue, the soft palate, fauces, and part of the pharynx. The base, tip, and edges of the tongue seem to possess the most acute sensibility to savors, the middle portion of its dorsum less of this sensibility, and its inferior surfaces little or none. Now as the whole anterior part of the organ is supplied by the lingual branch of the fifth pair alone, and the whole of its posterior portion by the glosso-pharyngeal, it follows that the sense of taste, in these different parts, is derived from these two different nerves. Furthermore, the tongue is supplied, at the same time and ly the same nerves, with general sensibility and with the special sensibility of taste. The general sensibility of the anterior portion of the tongue, and that of the branch of the fifth pair with which it is supplied, are sufiiciently well known. Section of the flfbh pair destroys the sensibility of this part of the tongue as well as that of the rest of the face. Longet has found that after the lingual branch of this nerve has been divided, the mucous membrane of the anterior two- thirds of the tongue may be cauterized with a hot iron or with caustic potassa, in the living animal, without producing any sign of pain. Dr. John Reid, on the pther hand, together with other experi- menters, has determined that ordinary sensibility exists in a marked degree in the glosso-pharyngeal, and is supplied by it to the parts to which this nerve is distributed. Accordingly we must distinguish, in the impressions produced by foreign substances taken into the mouth, between the special impressions derived from their sapid qualities, and the general sema- tions produced by their ordinary physical properties. As the tongue is exceedingly sensitive to ordinary impressions, and as the same body is often capable of exciting both the tactile and gustatory functions, these two properties are sometimes liable to be confounded with each other by careless observation. The truly sapid qualities, however, the only ones, properly speaking, which we perceive by the sense of taste, are such savors as we designate by the term sweet, bitter, salt, sour, alkaline, and the like. But there are many TASTE. 499 Other properties, belonging to various articles of food, which belong really to the class of ordinary physical qualities and are appre- ciated by the ordinary sensibility of the tongue, though we usually speak of them as being perceived by the taste. Thus a starchy, viscid, watery, or oleaginous taste is merely a certain variety of con- sistency in the substance tasted, which may exist either alone or in connection with real savors, but which is exclusively perceived by means of the general sensibility. So also with a pungent or burning taste, such as that of red pepper or any other irritating powder. The quality oi piquancy in the preparation of artificial kinds of food is always communicated to them by the addition of some such irritating substance. The styptic taste seems to be a combination of an ordinary irritant or astringent effect with a peculiar taste, which we always associate with the former quality in astringent sub- stances. There is also sometimes a liability to confound the real taste of certain substances with their odorous properties, or flavors. Thus in most aromatic articles of food, such as tea and coffee, and in various kinds of wine, a great part of what we call the taste is in reality due to the aroma, or smell which reaches the nares during the act of swallowing. Even in many solid kinds of food, such as freshly cooked meats, the odor produces a very important partf of their effect on the senses. We can easily convince ourselves of this by holding the nose while swallowing such substances, or by recol- lecting how much a common catarrh interferes with our perception of their taste. The most important conditions of the sense of taste are the fol- lowing : — In the first place, the sapid substance, in order that its taste may be perceived, must be brought in contact with the mucous mem- brane of the mouth in a state of solution. So long as it remains solid, however marked a savor it may possess, it gives no other impression than that of any foreign body in contact with the sensi- tive surfaces. But if it be applied in a liquid form, it is then spread over the surface of the mucous membrane, and its taste is imme- diately perceived. Thus it is only the liquid and soluble portions of our food which are tasted, such as the animal and vegetable juices and the soluble salts. Saline substances which are insoluble, such as calomel or carbonate of lead, when applied to the tongue, produce no gustatory sensation whatever. The mechanism of the sense of taste is, therefore, in all proba- 500 THE SPECIAL SENSES. bility, a direct and simple one. The sapid substances in solution penetrate the lingual papilla by endosmosis, and, coming in actual contact with the terminal nervous filaments, excite their sensibility by uniting with their substance. We have already seen that the rapidity with which endosmosis will take place under certain con- ditions is sufficiently great to account for the almost instantaneous perception of the taste of sapid substances when introduced into the mouth. It is on this account that a free secretion of the salivary fluids is so essential to the full performance of the gustatory function. If the mouth be dry and parched, our food seems to have lost its taste; but when the saliva is freely secreted, it is readily mixed with the food in mastication, and assists in the solution of its sapid ingredi- ents ; and the fluids of the mouth, thus impregnated with the savory substances, are absorbed by the mucous membrane, and excite the gustatory nerves. An important part, also, is taken in this process by the movements of the tongue ; for by these movements the food is carried from one part of the mouth to another, pressed against the hard palate, the gums, and the cheeks, its solution assisted, and the penetration of the fluids into the substance of the papillae more rapidly accomplished. If a little powdered sugar, or some vege- table extract be simply placed upon the dorsum of the tongue, but little effect is produced ; but as soon as it is pressed by the tongue against the roof of the mouth, as naturally happens in eating or drinking, its taste is immediately perceived. This efiect is easily explained ; since we know how readily movement over a free sur- face, combined with slight friction, will facilitate the imbibition of liquid substances. The nervous papillae of the tongue may there- fore be regarded as the essential organs of the sense of taste, and the lingual muscles as its accessory organs. The full effect of sapid svhstances is not obtained until they are actu- ally swallowed. During the preliminary process of mastication a sufficient degree of impression is produced to enable us to perceive the presence of any disagreeable or injurious ingredient in the food, and to get rid of it, if we desire. But it is only when the food is carried backward into the fauces and pharynx, and is compressed by the constrictor muscles of these parts, that we obtain a complete perception of its sapid qualities. For at that time the food is spread out by the compression of the muscles, and brought at once in contact with the entire extent of the mucous membrane possessing gustative sensibility. Then, it is no longer under the control of the TASTE. 501 ■will, and is carried by the reflex actions of the pharynx and oeso- phagus downward to the stomach. The impressions of taste made upon the tongue remain for a cer- tain time afterward. When a very sweet or very bitter substance is taken into the mouth, Ave retain the taste of its sapid qualities for several seconds after it has been ejected or swallowed. Conse- quently, if several different savors be presented to the tongue in rapid succession, we soon become unable to distinguish them, and they produce only a confused impression, made up of the union of various different sensations ; for the taste of the first, remaining in the mouth, is mingled with that of the second, the taste of these two with that of the third, and so on, until so many savors become confounded together that we are no longer able to recognize either of them. Thus it is notoriously impossible to recognize two or three different kinds of wine with the eyes closed, if they be repeat- edly tasted in quick succession. If the substance first tasted have a particularly marked savor, its taste will preponderate over that of the others, and perhaps pre- vent our recognizing them at all. This effect is still more readily produced by substances which excite the general sensibility of the tongue, such as acrid or stimulating powders. In the same manner as a painful sensation, excited in the skin, prevents the nerves, for the time, from perceiving delicate tactile impressions, so any pungent or irritating substance, which excites unduly the general sensibility of the tongue, blunts for a time its special sensibility of taste. This effect is produced, however, in the greatest degree, by substances which are at the same time sapid, pungent and aromatic, like sweet- meats flavored with peppermint. Advantage is sometimes taken of this in the administration of disagreeable medicines. By first taking into the mouth some highly flavored and pungent substance, nauseous drugs may be swallowed immediately afterward with but little perception of their disagreeable qualities, A very singular fact, in connection with the sense of taste, is that it is sometimes affected in a marked degree by paralysis of the facial nerve. No less than six cases of this kind, occurring in the human subject, have been collected by M. Bernard, and we have also met with a similar instance in which the peculiar phenomena were well marked. M. Bernard has furthermore seen a similar effect upon the taste produced in animals by division of the facial nerve within the cranium. The result of these experiments and observations is as follows : "When the facial nerve is divided or seriously injured 502 THE SPECIAL SENSES. Tjy organic disease, before its emergence from the stylo-mastoid foramen, not only is there a paralysis of the superficial muscles of the face, but the sense of taste is diminished on the corresponding side of the tongue. If the tongue be protruded, and salt, citric acid or sulphate of quinine be placed upon its surface on the two sides of the median line, the taste of these substances is perceived on the affected side more slowly and obscurely than on the other. It is not, therefore, a destruction, but only a diminution of the sense of taste, which follows paralysis of the facial in these instances. At the same time the general tactile sensibility of the tongue is unal- tered, retaining its natural acuteness on both sides of the tongue. The exact mechanism of this peculiar influence of the facial nerve upon the sense of taste is not perfectly understood. It may he considered as certain, however, that it is derived through the medium of that branch of the facial nerve known as the chorda tympani. This filament leaves the facial at the intumescentia gangliformis, in the interior of the aqueduct of Fallopius, enters the cavity of the tympanum, passes across the membrane of the tym- panum, and then, emerging from the cranium, runs downward and forward and joins the lingual branch of the fifth pair. It then ac- companies this nerve as far as the posterior extremity of the sub- maxillary gland. Here it divides into two portions ; one of which passes to the submaxillary ganglion, and, through it, to the sub- stance of the submaxillary gland, while the other continues onward, still in connection with the lingual branch of the fifth pair, and, in company with the filaments of this nerve, is distributed to the tongue. The chorda tympani thus forms the only anatomical connection between the facial nerve and the anterior part of the tongue. When the fecial, accordingly, is divided or injured after its emergence from the stylo-mastoid foramen, no effect is produced upon the sense of taste; but when it is injured during its course through the aqueduct of Fallopius, and befc3re it has given off the chorda tym- pani, this nerve suffers at the same time, and the sense of taste is diminished in activity, as above described. It is probable that this effect is produced in an indirect way, by a diminution in the activity of secretion in the lingual follicles, or by some alteration in the vascularity of the parts. Smell. — The main peculiarity of the sense of smell consists in the fact that it gives us intelligence of the physical character of bodies in ^ gaseous or vaporous condition. Thus we are enabled to SMELL. 503 perceive the existence of an odorous substance at a distance, and when it is altogether concealed from sight. The minute quantity of volatile material emanating from it, and thus pervading the atmosphere, comes in contact with the mucous membrane of the nose, and produces a peculiar and special sensation. The apparatus of this sense consists, first, of the olfactory mem- brane, supplied by the filaments of the olfactory nerve, as its special organ ; and secondly, of the nasal passages, with the tur- binated bones and the muscles of the anterior and posterior nares, as its accessory organs. At the upper part of the nasal fossae, the mucous membrane is very thick, soft, spongy and vascular, and is supplied with mucous follicles which exude a secretion, by which its surface is protected and kept in a moist and sensitive condition. It is only this portion of the mucous membrane of the nares which is supplied by filaments of the olfactory nerve, and which is capable of receiving the impressions of smell ; it is therefore called the Olfactory membrane. Elsewhere, the nasal passages are lined with a mucous membrane which is less vascular and spongy in structure, and which is called the Schneiderian membrane. The filaments derived from the olfactory ganglia, and which penetrate through the cribri- form F^^165. plate of the ethmoid ^ bone, are distributed to the mucous membrane of the su- perior and middle turbinated bones, and to that of the upper part ofthe septum nasi. The exact mode in which these filaments terminate in the ol- factory membrane has not been definitely ascertained. They are of a soft consistency and gray color, and, after di- viding and ramifying freely in the membrane, appear to become lost in its substance. It is these nerves which exer- cise the special function of smell. They are, to all appearance, incapable of receiving ordinary impressions, and must be regarded as entirely peculiar in their Distribution op Nerves in thr Nasal Passages. — 1. Olfactory gauglioa, with its nerveit 2. Nahal branch of fifth pair. 3. Spheuo-palatioe ganglion. 504 THE SPECIAL SENSES. nature and endowments. The nasal passages, however, are supplied with other nerves beside the olfactory. The nasal branch of the ophthalmic division of the fifth pair, after entering the anterior part of the cavity of the nares, just in advance of the cribriform plate of the ethmoid bone, is distributed to the mucous membrane of the in- ferior turbinated bone and the inferior meatus. Thus the organ of smell is provided with sensitive nerves from two different sources, viz., at its upper part, with the olfactory nerves proper, derived from the olfactory ganglion (Fig. 165, i), which are nerves of special sensation ; and secondly, at its lower part, with the nasal branch of the fifth pair (2), a nerve of general sensation. Beside which, the spheno-palatine ganglion of the great sympathetic (s) sends fila- ments to the mucous membrane of the whole posterior part of the nasal passages, and to the levator palati and azygos uvulae muscles. Finally, the muscles of the anterior nares are supplied by filaments of the facial nerve. The conditions of the sense of smell are much more special in their nature than those of taste. For, in the first place, this sense is excited, not by actual contact with the foreign body, but only with its vaporous emanations ; and the quantity of these emanations, sufficient to excite the smell, is often so minute as to be altogether inappreciable by other means. We cannot measure the, loss of weight in an odorous body, though it may affect the atmosphere of an entire house, and the senses of, all its inhabitants, for days and weeks together. Secondly, in the olfactory organ, the special sensibility of smell and the general sensibility of the mucous mem- brane are separated from each other and provided for by different nerves, not mingled together and exercised by the same nerves, as is the case in the tongue. In order to produce an olfactory impression, the emanations of the odorous body must be drawn freely through the nasal passages. As the sense of smell, also, is situated only in the upper part of these passages, whenever an unusually faint or delicate odor is to be per- ceived, the air is forcibly directed upward, toward the superior turbinated bones, by a peculiar inspiratory movement of the nos- trils. This movement is very marked in many of the lower animals. As the odoriferous vapors arrive in the upper part of the nasal passages, they are undoubtedly dissolved in the secretions of the olfactory membrane, and thus brought into relation with its nerves. Inflammatory disorders, therefore, interfere with the sense of smell, both by checking or altering the secretions of the part, and by SMELL. 505 producing an unnatural tumefaction of the mucous membrane, which prerents the free passage of the air through the nasal fossae. As in the case of the tongue, also, we must distinguish here between the perception of true odors, and the excitement of the general sensibility of the Schneiderian mucous membrane by irri- tating substances. Some of the true odors are similar in their nature to impressions perceived by the sense of taste. Thus we have sweet and sour smells, though none corresponding to the alkaline or the bitter tastes. Most of the odors, however, are of a very peculiar nature and are difficult to describe ; but they are always distinct from the simply irritating properties which may belong to vapors as well as to liquids. Thus, pure alcohol has little or no odor, and is only irritating to the mucous membrane ; while the odor of wines, of cologne water, &c., is communicated to them by the presence of other ingredients of a vegetable origin. In the same way, pure acetic acid is simply irritating ; while vinegar has a peculiar odor in addition, derived from its vegetable impurities. Ammonia, also, is an irritating vapor, but contains in itself no odoriferous principle. The sensations of smell, like those of taste, remain for a certain time after they have been produced, and modify in this way other less strongly marked odors which are presented afterward. As a general thing, the longer we are exposed to a particular odor, the longer its effect upon our senses continues ; and in some cases it may be perceived many hours after the odoriferous substance has been removed. Odors, however, are particularly apt to remain after the removal or destruction of the source from which they were derived, owing to their vaporous character, and the facility with which they are entangled and retained by porous substancea such as plastered walls, woollen carpets, and hangings, and woollen clothes. It is supposed to be in this way that the odor of a post- mortem examination will sometimes remain so as to be perceptible for several hours or even an entire day afterward. But this alone does not fully explain the fact. For if it depended simply on the retention of the odor by porous substances, it would afterward be perceived constantly, until it gradually and continuously wore off; while in point of fact, the physician who has made an autopsy of this kind does not afterward perceive its odor constantly, but only occasionally, and by sudden and temporary fits. The explanation is probably this. As the odor remains con- stantly by us, we soon become insensible to its presence, as in the 606 THE SPECIAL SENSES. case of all otter continuous and unvarying impressions. Our at- tention is only called to it when we meet suddenly with another and familiar odor. This second odor, we find, does not produce its usual impression, because it is mingled with and modified by the other, which is more persistent and powerful. Thus we are again made aware of the former one, to which we had become insensible by reason of its constant presence. The sense of smell is comparatively feeble in the human species, but is excessively acute in some of the lower animals. Thus, the dog will not only distinguish different kinds of game in the forest by this sense, and follow them by their tracks^ but will readily dis- tinguish particular individuals by their odor, and will recognize articles of dress belonging to them by the minute quantity of odor- iferous vapors adhering to their substance. Sight. — The sight undoubtedly occupies the first rank in tie list of special nervous endowments. It is the most peculiar in its operation, and the most immaterial in its nature, of all the senses, and it is through it that we receive the most varied and valuable impressions. The physical agent, also, to which the organ of sight is adapted, and by which its sensibility is excited, is more subtle and peculiar than any of those which act upon our other senses. For the senses of touch, taste, and smell require, for their exercise, the actual contact of a foreign body, either in a solid, liquid, or aeriform condition; and even the hearing depends upon the me- chanical vibrations of the atmosphere, or some other sonorous medium. But the eye does not need to be in contact with the luminous body. It will receive the impressions of light with per- fect distinctness, even when they are transmitted from an immea- surable distance, as in the case of the fixed stars ; and the light itself is not only immaterial in its nature, so far as we can ascertain, but is also capable of being transmitted through space without the intervention of any material conducting medium, yet discoverable. Finally, the apparatus of vision is more complicated in its struc- ture than that of any other of the special senses. This apparatus consists, first, of the retina, as a special sensitive nervous membrane ; and secondly, of the vitreous body, crystalline lens, choroid, scle- rotic, iris and cornea, together with the muscles moving the eye- ball and eyelids, lachrymal gland, &c., as accessory organs. The arrangement of the parts, constituting the globe of the eye, is shown in the following figure. (Fig. 166;) SIGHT, S07 The filaments of the optic nerve, after running forward and pene- trating the posterior part of the eyeball, spread out into the sub- stance of the retina (3), thus forming a delicate and vascular nerv- Fig. 166. Vertical Section of the Etcball. — I. Sclerotic. 2. Choroid. 3. Betini. 4 Lena. S. Hyulo.il oiembraue. 6. Curoea. 7. Iris. 8. Vitreous body. ous expansion, in the form of a spheroidal bag or sac, with a wide opening in front, where the retina terminates at the posterior mar- gin of the ciliary body. This expansion of the retina is the essen- tial nervous apparatus of the eye. It is endowed with the special sensibility which renders it capable of receiving luminous impres- sions; and, so far as we have been able to ascertain, it is incapable of perceiving any other. On the outside, the retina is covered by the choroid coat (a), a vascular membrane, which is rendered opaque by the presence of an abundant layer of blackish-brown pigment-cells, and which thus absorbs the light which has once passed through the retina, and prevents its being reflected in such a way as to confuse and dazzle the sight. Inside the retina is the vitreous body, a transparent spheroidal mass of a gelatinous consistency, which is surrounded and retained in position by a thin, structureless mem- brane, called the hyaloid membrance (s), lying immediately in contact with the internal surface of the retina. The le7is (4) is placed in front of the vitreous body, in the central axis of the eye- ball, enveloped in its capsule, which is continuous with the hyaloid membrane. Just at the edge of the lens, the hyaloid membrane divides into two laminae, which separate from each other, leaving between them a triangular canal, tlie canal of Petit, which can be seen in the above figure. In front of the lens is the iris (•»), a nearly 508 THE SPECIAL SENSES. vertical muscular curtain, formed of radiating and concentric fibres, pierced at its centre with a circular opening, the pupil, through which the light is admitted, and covered on its posterior surface with a continuation of the choroidal pigment, which excludes the passage of any other rays than those which pass through the pupil. At the same time, the whole globe is inclosed and protected by a thick, fibrous, laminated tunic, which in its posterior and middle portions is opaque, forming the sclerotic (i), and in its anterior por- tion is transparent, forming the cornea (e). The muscles of the eye- ball are attached to the external surface of the sclerotic in such a way that the cornea may be readily turned in various directions ; while the eyelids, which may be opened and closed at will, protect the eye from injury, and, with the aid of the lachrymal secretion, keep its anterior surfaces moist, and preserve the transparency of the cornea. The organ of vision is supplied with nerves of ordinary sensi- bility by the ophthalmic branch of the fifth pair. The filaments of this nerve which terminate about the eye are distributed mostly to the conjunctiva, lachrymal gland, and skin of the eyelids; while a very few of them run forward in company with the ciliary nerves proper, and are distributed to the ciliary circle and iris. All these parts, therefore, but more particularly the conjunctiva and skin of the eyelids, possess ordinary sensibility, which appears to be totally wanting in the deeper parts of the eye. The ophthalmic ganglion gives off the ciliary nerves, which are distributed to the iris and ciliary muscle. Finally, the muscles moving the eyeball and eye- lids are supplied with motor nerves from the third, fourth, sixth and seventh pairs. Of all the properties and functions belonging to the different structures of the eyeball, the most peculiar and characteristic is the special sensibility of the retina. This sensibility is such that the retina appreciates both the intensity and the quality of the light- that is to say, its color and the different shades which this color may present. On account of the form, also, in which the retina is constructed, viz., that of a spheroidal membranous bag, with an opening in front, it becomes capable of appreciating the direction from which the rays of light have come, and, of course, the situation of the luminous body and of its different parts. For the rays which enter through the pupil from below can reach the retina only at its upper part, while those which come in from above, can reach it only at its lower part ; so that in both instances the rays strike the SIGHT. 509 sensitive surface perpendicularly, and thus convey the impression of their direction from above or below. But beside the sensibility of the retina, the perfection and value of the sense of sight depend very much on the arrangement of the accessory organs, the most important of which is the crystalline lens. The function of the crystalline lens is to produce distinct perception of form and outline. For if the eye consisted merely of a sensitive retina, covered with transparent integument, though the impressions of light would be received by such a retina they could not give any idea of the form of particular objects, but could only produce the sensation of a confused luminosity. This condition is illus- trated in Fig. 167, where the arrow, o, h, represents the luminous object, and the vertical dotted line, at the right of the diagram, represents the retina. Eays, of course, will diverge from every point of the object in every direction, and will thus reach every part of the retina. The different parts of the retina, consequently, 1, 2, 3, 4, will each receive rays coming both from the point of the arrow, a, and from its butt, h. There will therefore be no distinc- tion, upon the iretina, between the different parts of the object, and no Fig. 167. Kg. 168. definite perception of i^s outline. But if, between the object and the retina, there be inserted a double convex refracting lens, with the proper curvatures and density, as in Fig. 168, the effect will be dif- ferent. For then all the rays emanating from a will be concentrated at X, and all those emanating from h will be concentrated at y. Thus the retina will receive the impression of the point of the arrow separate from that of the butt ; and all parts of the object, in like manner, will be distinctly and accurately perceived. This convergence of the rays of light is accomplished to a certain extent by the other transparent and refracting parts of the eyeball ; but the lens is the most important of all in this respect, owing to its superior density and the double convexity of its figure. The distinctness of vision, therefore, depends upon the action of the 510 THE SPECIAL SENSES. lens in converging all the rays of light, emanating from a given point, to an accurate focus, at the surface of the retina. To accom- plish this, the density of the lens, the curvature of its surfaces, and its distance from the retina, must all be accurately adapted to each other. For if the lens were too convex, and its refractive power excessive, or its distance from the retina too great, the rays would converge to a focus too soon, and would not reach the retina until after they had crossed each other and become partially dispersed, as in Fig. 169, The visual impression, therefore, coming from any particular point in the object, would not be concentrated and dis- tinct, but diflfused and dim, from being dispersed more or less over the retina, and interfering with the impressions coming from other parts. On the other hand, if the lens were either too flat, or placed Fig. 169, Fig. 170. too near the retina, as in Fig. 170, the rays would fail to come together at all, and would strike the retina separately, producing a confused image, as before. In both these cases, the immediate cause of the confusion of sight is the same, viz., that the rays coming from the same point of the object strike the retina at different points:; but in the first instance, this is because the rays have actually con- verged, and then crossed ; in the second, it is because they have only approached each other, but have never converged to a focus. Another important particular in regard to the action of the lens is the accommodation of the eye to distinct vision at different distances. It is evident that the same arrangement of refractive parts, in the eye, will not produce distinct vision when the distance of the ob- ject from the eye is changed. If this arrangement be such that the object is seen distinctly at a certain distance, and the object be then removed to a remoter point, the image will become confused; for the rays will then converge to a focus at a point in front of the retina ; since, being less divergent when they strike the lens, the sanie amount of refraction will bring them together sooner than before. On the other hand, if the object be moved to a point nearer SIGHT. 511 the eye, the rays, becoming more divergent as they strike the lens, will converge less rapidly to a focus, and vision will again become indistinct. This may easily be seen by the aid of a very simple experiment. If two needles be placed upright, at different distances from the eye, one for example at eight and the other at eighteen inches, but nearly in the same linear range, and if then, closing one eye, we look at them alternately with the other, we shall find that we can- not see both distinctly at the same time. For when we look at the one nearer the eye, so as to perceive its form distinctly, the image of the more remote one becomes confused ; and when we see the more remote object in perfection, that which is nearer loses its sharpness of outline. This shows, in the first place, that the same condition of the eye will not allow us to see two objects at different distances with distinctness at the same time ; and secondly that, on looking from one object to the other, there is a change of some kind in the focus of the eye, by which it is adapted to different distances. Indeed we are conscious of a certain effort at the time when the point of vision is transferred from one object to the other, by which the eye is adapted to the new distance ; and this alteration is not quite instantaneous, but requires a certain interval of time for its completion. The precise manner in which this accommodation is effected has given rise to much discussion. It evidently might be accomplished, either, 1st, by a change in the curvature of the cornea, or 2d, by a change in the curvature of the lens, or 3d. by an . antero-posterior movement of the lens, by which its distance from the retina might be increased or diminished, or 4th, by a change in the figure of the entire eyeball, by which its longitudinal axis might be elongated or shortened. All these causes have in turn been supposed to be active in producing the requisite effect. The facts now known in regard to the matter are as follows: — I. In the first place it is certain that accommodation of the eye for distant objects is a passive condition, — that for near objects an active one. When we look at distant images, the eye is compara- tively at rest. It is when we fix the sight upon near objects that we are conscious of an active change in the eye, which requires a certain exertion on our part ; and this exertion is the more marked, asi the objects which we examine are more closely situated. Con- tinued application of the eye to near objects may even produce a perceptible fatigue, which gives place to a sense of repose on again 512 THE SPECIAL SENSES. directing our siglit to the distance. Our sensations, also, in vision of near objects, give the impression that this active accommodation of the eye is accomplished, in some way, by muscular eflFort. II. In the second place, it is now rendered sufficiently certain from the investigations of Bonders ' and others, that the active ac- commodation of the eye, for vision of near objects, is accomplished by an increased convexity of the crystalline lens. If the eye be ac- commodated for vision of a distant object, and a candle be then held near the front of the eye, and a little on one side, an observer will see three reflected images of its flame in the eyeball, viz., one reflection from the anterior surface of the cornea, one from the ante- rior surface of the lens, and one from the posterior surface of the lens. Now, if the patient change his sight from the distant to- a near object, accurate measurements will show that the reflection on the cornea remains unaltered, but that the reflected image on the anterior surface of the lens diminishes in size and approximates to that on the cornea. Both these changes indicate that, in accommo- dation for near objects, the anterior surface of the lens becomes more convex and approaches the cornea. The image on the posterior sur- face of the lens at the same time diminishes slightly in size, but does not alter its position, showing that this surface of the lens, also, becomes a little more convex, but does not move either forward or Fig. 171. VimOK f OB DiSTAHT OlIJICIS. backward. The unaltered appearance of the reflection on the cor- nea shows that this part of the eye does not change its convexity. We can now see how these alterations produce the required changes in accommodation. When the eye is accommodated for distant vision, the lens assumes the form which is normal to it, when in repose and unaffected by external agencies. Its curva- tures are then such that rays coming from distant points, and hav- ing consequently but a slight divergence, are brought to a focuS behind the lens, exactly at the sensitive surface of the retina. (Fig, 171.) 1 Accommodation and Refraction of the Eye. Sydenham Ed., London, 1864, p. 10. SIGHT, 513 If, with the eye in this condition, the sight be turned toward a near object, its image is imperfectly perceived ; since the lens, which was suflBciently convex for distant objects, is still too flat for the widely divergent rays of near objects, and the image upon the retina IS accordingly diffused and indistinct, as in Fig. 170. But by the change of form above described, * ' the lens, in accommodating the eye to near vision, becomes more convex, especially on its ante- rior surface ; and, its refractive power being thus increased, it becomes capable of bringing the •divergent rays to a focus at the Vision »0B Nun objiois. retina, and theobject is distinctly perceived, as in Fig. 172. It will also be seen that if, with the eye thus accommodated, the eight be directed again to remote objects, they in their turn will appear indistinct ; since the strongly convex lens is too highly re- fractive for rays coming from a distance, and the image will be dif- fused, as in Fig. 169. . To produce distinct vision at a distance, the lens must return to its original form, as in Fig. 171. It is supposed that the alteration of the form of the lens, in these changes, is due to a circular compression of its edges, by some or all of the fibres of the ciliary muscle. It is this active compression which increases its convexity in vision of near objects. "When this pressure ceases, the lens resumes its former shape, by the pas- sive elasticity of its tissue, and becomes again adapted for distant vision. A little examination shows, also, that the amount of accommoda- tion, necessary to distinct vision, varies very much for different distances. A much greater accommodating power is required for near distances than for remote ; since the di|^rence in divergence between rays, entering the pupil from a dist3.nce of one inch and from that of six inches, is much greater than the difference between six inches and a yard, or even distances which are immeasurably remote. Indeed, for fill distances beyond a certain limit, the differ- ence in divergence of the rays is practically imperceptible, and no sensible change in accommodation is required for objects beyond that limit. It is for near distances, then, that we find the necessary changes of accommodation most marked, and these changes become greater and more dif&cult, the nearer to the eye the object is situ- ■ 511 THE SPECIAL SENSES. ated, until at last a limit is reached beyond which they become im- possible. The eye accordingly cannot be made to see distinctly at very short distances. For all ordinary eyes, accommodation fails and vision becomes imperfect, when the object is placed at a dis- tance of less thaa six inches from the eye. But from that point outward, the healthy eye can adapt itself to any distance at which light is perceptible, even to the immeasurable distances of the fixed stars. ' Circle of Vision. — Since the opening of the pupil will admit rays of light coming from various directions, there is in front of the eye a circle, or space, within which luminous objects are perceived, and beyond which nothing can be seen, becaiifle the rays, coming from ithe side or from behind, cannot enter the .pupil. This space, within which external objects can be perceived, is called the " circle of vision." But, for short distances, there is only a single point, in the centre of the circle of vision, at which objects can be seen distinctly. Thus, if we place ourselves in front of a row of vertical stakes or palisades, we can see those directly in front of the eye with perfect distinctness, but those at a little distance on each side are only per- ceived in a confused and uncertain manner. On looking at the middle of a printed page, in the direct range of vision, we see the distinct outlines of the letters ; while at successive distances from this point, the eye remaining fixed, we can distinguish first only the separate letters with confused outlines, then only the words, and lastly only the lines and spaces. Fig. 178. This is because rays of light coming into the eye very obliquely, in a lateral or vertical direction, are not brought to their proper focus. Thus, in Fig. 173, the rays diverging from the point a, directly in SIGHT. 515 front of the eye, fall upon the lens in such a way that they are all brought together at x, at the surface of the retina ; but those coming from b fall upon the lens so obliquely that, for rays having an equal divergence with those coming from a, there is more difference in their angles of incidence, and of course more difference in the amount of their refraction. They are consequently brought together more rapidly, and on reaching the retina are dispersed ovef the space y, z. The perfection of the eye, as a visual apparatus, is very much increased by the action of the iris. This organ, as we have already mentioned, is a nearly vertical muscular curtain, placed in front of the lens, attached by ifs external margin to the junction of the cornea and sclerotic, and pierced about its centre by the circular opening of the pupil. It Consists, according to most anatomists, of ' two sets of muscular fibres — viz., the circular and the radiating. The circular fibres, which are much the most abundant, are arranged in concentric lines about the inner edge of the iris, near the pupil ; the others are said to radiate in a scattered manner, from; its central parts to its outer margin. The action of these two sets of fibres is to contract and enlarge the orifice of the pupil. The circular fibres, in contracting, draw together the edges of the pupil, and so diminish its opening ; and when these are relaxed, the radiating fibres come into play, and hj drawing apart the edges of the orifice, enlarge the pupillary opening. The action of the circular fibres, at the same time, is much the most marked and important of the two. For when the whole muscular apparatus of the eye is paralyzed by the action of belladonna, or by the division of the third pair of nerves, or in the general relaxation of the muscular system at the moment of death, the pupil is invariably dilated, probably by the passive elasticity of its tissues. During life, however, these different conditions of the pupil cor- respond with the different degrees of light to which the eye is ex- posed. In a strong light, the pupil contracts and shuts out the superfluous rays ; in a feeble light, it dilates, in order to collect into the eye all the light which can " be received from the object. This contractile and expansive movement of the pupil is a reflex action. It is not produced by the direct impression of the light upon the iris itself, but upon the retina; since, if the retina be affected with complete amaurosis, or if the light b6 entirely shut out from it by an opacity of the lens, no such effect is produced, though the iris itself be exposed to the direct glare of day. From the retina the impression is transmitted, through the optic nerve, to tht; 516 THE SPBCIALSBNSES. optic tubercles and the brain, thence reflected outward by the oculo- motocius nerve to the ophthalmic ganglion, and so through the ciliary nerves to the iris. - The pupil is subject, however, to various other nervous influences beside the impressions of light received by the retina. Thus in poisoning by opium, it is contracted ; in coma from compression of the brain, it is dilated ; in natural sleep it is contracted, and the eye- ball rolled upward and inward. In various mental conditions, the pupil is also enlarged or diminished, and thus modifies the expres- sion of the eye ; . and in viewing remote objects, it is generally enlarged, while, in looking at near object^ it is comparatively con- tracted. But still, the, most constant and .'important function be- • longing to the iris is the admission or exclusion of the rays, accord- ing to the intensity of the light. Our impressions of distance and solidity, in viewing external objects, are produced mainly "by the combined action of the two eyes. For, as the eyes are seated a certain distance apart from each other in the head, when they are both directed toward the same object, their axes meet at the point of sight; and form a certain angle with each other ; and this angle varies with the distance of the object. Thus, when the object is within a short distance, the axes of the two eyes will necessarily be very convergent, and the angle which they form with each other a large one; but for remote objects, the visual axes will become more nearly parallel, and their angle con- sequently smaller. It is on this account that we can always dis- tinguish whether any person at a short distance is looking a^w, or at some other object in our direction; since we instinctively appreciate, from the appearance of the eyes, whether their visual axes meet at the level of our own face. In looking at a landscape, accordingly, we do not see the whole of it distinctly at the same moment, but only those parts to which out attention is immediately directed. This is because, in the first place, the focus of distinct vision varies, in each eye, for different distances, as we have seen in a former paragraph; and secondly, because both eyes can only be directed* together, at one time, to objects at a certain distance. Thus, when we see the foreground or the middle ground distinctly, the distance is vague and uncer- tain, and when we direct our eyes more particularly to the horizon, objects in the foreground become indistinct. In this way we ap- preciate the difierenoe in distance between the various portions of the landscape, as a whole. In the case of particular objects, we are SIGHT. 517 assisted also by the alteration in their individual characters ; for distance produces a diminution, both in apparent size and in in- tensity of color. The combined action of the two eyes is also very valuable, for near objects, in giving us an idea of solidity or projection. Eor within a certain distance, the visual axes when directed together Fig. 174. Fig. 175. As BEEK BT THE LeFT EyB. As SEES BY THE BlOBT ETE. at a solid object, are so convergent that the two eyes do not receive the same image. As in Figs. 174 and 175, which represbnt a skull as seen by the two eyes, when placed exactly in front of the ob- server at the distance of eighteen inches or two feet, the right eve will see the object partly on one side, and the left eye partly on the other. And by the union or combination of these two images by the visual organs, the impression of solidity is produced. By the employment of double pictures, so drawn as to represent the appearances presented to the two eyes by the same object, and so arranged that each shall be seen only by the corresponding eye, a deceptive resemblance may be produced to the actual projection of solid objects. This is accomplished ia the contrivance known as the Stereoscope. Thus, if two pictures similar to those in Figs. 174 and 175 be so placed that one shall be seen only with the right eye and the other only with the left, the combination of the two figures will take place as if they came from the real object, and all the natural projections will come out in relief. But this effect is produced only in the case of objects situated within a moderately short distance. For very remote objects, we lose the impression of solidity, since the difference in the images on the two eyes becomes so slight as to be inappreciable, and we see 518 THE SPECIAL SENSES. only a plane expanse of surface, with sharp outlines and various shades of color, but no actual projections or depressions. The sensibility of the retina is such that it cannot distinguish luminous points which are received upon its surface at a very minute distance from each other. In this particular, the sensibility of the retina resembles that of the. skin, since we have already found that the integument cannot distinguish the impressions made by the points of two needles placed a very short distance iapart. The delicacy of this discriminating power, in the retina, is immeasurably superior to that of the skin ; and yet it has its limits, even in the nervous expansion of the eye. For if we look at an object which is excessively minute, or which is so remote that its apparenti size is very much diminished, we lose the power of distinguishing its different partsj and can no longer perceive its real ' outline. -This is a very different condition from that in which the confusion of vision arises from defect of focusing in the eye, as, for example, in long or shoyt-sightedness, or where the object is placed too near the eye or too much on one side. For when the difficulty depends simply on its minute size or its remote- ness, the rays coming from the top of the object and those coming from the bottom, are all brought to their proper focus at distinct points on the retina — only these points are too near each other for the retina to distinguish them apart. Consequently we can no longer appreciate the form of the object. For the same reason, when we mix together minute grains of a different hue, we produce an intermediate color. If yellow and blue be mingled in this way, we no longer perceive the separate blue and yellow grains, but only a uniform tinge of green; and white and black granules, mixed together, produce, at a short dis- tance, the appearance of a continuous shade of gray. Impressions, once produced upon the retina, remain for a short time afterward. Usually these impressions are so evanescent after the removal of their immediate cause, and are so soon followed by others which are more vivid, that we do not notice their existence. They may very readily be demonstrated, howerver, by swinging rapidly in a circle before the eyes, in a dark room, a stick lighted at one end. As soon as the motion has attained a certain degree of velocity, the impression produced on the retina, when the lighted end of the stick arrives at any particular spot, remains until it has completed its revolution and has again reached the same point; so that the effect thus produced upon the eye is that of a continu- HE A EI KG 619 0U3 circle. of light. The same fact has been illustrated bj the optical contrivance, known as the Thaumairope, in which successive pictures of similar figures in different positions, aremade to revolve rapidly before the eye,.and thus to produce the apparent effect of a single figure in rapid motion; — since the eye fails to perceive the intervals between the different pictures. The sense of vision, therefore, through the impressions of light, gives us ideas of form, size, color, position, distance, and movement. But these ideas may; also be excited by impressions derived from an internal source, as well as those produced by rays coming from without. And it is one of the most striking peculiarities of the sense of sight that these ideal or internal impressions which are excited in it by various causes, are much more vivid and powerful than those of any other of the senses. Thus, in a dream, we often see external objects, with all their visible peculiarities, of light, color form, &o., nearly or quite as distinctly as when we are awake ; but the imaginary impressions- of sound, in this condition, are always comparatively faint, and those of taste, smell, and touch, almost entirely imperceptible. Even in a reverie, in the waking condi- tion, when the absorption of the mind in its own thoughts ia com- plete, and we are withdrawn altogether from outward influences, we see objects which have no present existence as if they were actually before us. It is this sense also which becomes most easily and thoroughly excited in certain nervous disorders ; as, for exam- ple, in delirium tremens, where the patient often sees passing before his eyes extensive and magnificent landscapes, crowds of human faces and figures, and series of towns and cities, which seem to be depicted upon the imagination with a force and distinctness, mxich superior to that of other delirious impressions. Since the sense of sight, therefore, depends less directly than the other senses upon •the actual contact of material objects, it is also more easily thrown into activity when withdrawn from their influence. HKAEiNS.-^The sense of hearing depends: upon the vibrations excited in the atmosphere by sonorous bodies, which are themselves first thrown into vibration by various causes, 'and which then com- municate similar undulations to the surrounding air. These sono- rous vibrations are of such a character that they cannot be directly appreciated by ordinary sensibility, but the result of numerous and well-directed physical experiments on this subject leaves no doubt whatever of their existence; and when such vibrations are commu- 520 THE SPECIAL SENSES. nicated to the auditory apparatus, they produce in it the sensation of seund. In the case of the aquatic animals, which pass their entire exist- ence beneath the surface of the water, the water itself, which is capable of vibrating in the same way, communicates the sonorous impressions to the organ of hearing; but^ in terrestrial animalsj and particularly in man, it is the atmosphere which always serves as the medium of transmission. The auditory apparatus, in man and in the quadrupeds, consists, first, of a somewhat expanded, and trumpet-shaped mouth, or ex- ternal ear, destined to receive and collect the sonorous impulses coming from various quarters. This external ear is constructed of a cartilaginous framework, covered with integument, loosely attached to the bones of the head, and more or less movable by means of various- muscles, which by their contraction turn its expanded orifice in different directions. In man, the movements of the external ear are almost always inappreciable, though the mus- cles may be easily demonstrated ; but in many of the lower animals these movements are exceedingly varied and extensive, and play a very important part in the working of the auditory apparatus. At the bottom of the external ear, its orifice is prolonged into a tube or canal, the external auditory meatus, partly cartilaginous and partly bony, which penetrates the lateral part of the temporal bone in a nearly horizontal and transverse direcJtion. In the human subject, this canal is a little over one inch in length, and is lined by a continuation of the external integument. The integument toward its outer portion is beset with small hairs, and provided with ceruminous glands which supply a secretion of a waxy or resinous consistency. By these means the passage is protected from the accidental ingress of various foreign bodies. Secondly, at the bottom of the external meatus the auditory pas- sage is closed by a thin fibrous membrane, stretched across its cavity, called the membrana tympani. Upon this membrane are received the sonorous vibrations which have been collected by the external ear and conducted inward by the external auditory meatus. Behind the membrana tympani is the cavity of the middle ear, or the cavity of the tympanum. This cavity communicates posteriorly with the mastoid cells, and anteriorly with the pharynx, by a narrow passage, lined with ciliated epithelium, and running downward, forward and inward, called the Eustachian tube. A chain of small bones, the malleus, incus, and stapes,^ is stretched across the cavity of the HEARING. 621 tympanum, and forms a communication between the membrana tympani on the outside, and the membrane closing the foramen ovale in the petrous portion of the temporal bone. All the vibra ■ tions, accordingly, which are received by the membrana tympani, are transmitted by the chain of bones to the membrane of the foramen ovale. The tension of the membranes is regulated by three small muscles, the tensor tympani, laxator tympani, and stapedius muscles, which arise from the bony parts in the neighborhood, and are inserted respectively into the neck and long process of the mal- leus and the head of the stapes, and which draw these bones for- ward and backward upon their articulations. Thirdly, behind the membrane of the foramen ovale lies the labyrinth, or internal ear. This consists of a complicated cavity, excavated in the petrous portion of the temporal bone, and com- prising an ovoid central portion, the vestibule, a double spiral canal, the cochlea, and three semicircular canals, all communicating by means of the common vestibule. AH parts of this cavity contain a watery fluid termed the perilytpph. The vestibule and semi- circular canals also contain closed membranous sacs, suspended in the fluid of the perilymph, which reproduce exactly the form of the bony cavities themselves, and communicate with each other in a similar way. These sacs are filled with another watery fluid, the endolymph ; and the terminal filaments of the auditory nerve are distributed upon the membranous sac of the vestibule and upon the ampullae, or membranous dilatations, at the commencement of the three semicircular canals. The remaining portion of the audi- tory nerve is distributed upon the septum between the two spiral canals of the cochlea. Thus, the essential or fundamental portion of the auditory appa- ratus is evidently the internal ear, a cavity, partly membranous and partly bony, in which is distributed a nerve of special sense, the auditory nerve, capable of appreciating sonorous impressions. The accessory parts, on the other hand, are the chain of bones and the membrane of the tympanum, which communicate the sonorous vibrations directly to the internal ear ; and the meatus and extei'nal ear, which collect them from the atmosphere. The reception of sonorous impulses is therefore accomplished in a very indirect way. For the sonorous body first commiinicates its vibrations to the atmosphere. By the atmosphere these vibrations are communicated to the membrana tympani. From the membrana tympani, they are transmitted, through the, chain of bones, to the membrane of the 522 THE SPECIAL SENSES. foramen ovale; thence to the perilymph, or fluid of the lahyrinthio cavity, and from the perilymph to the membranoua parts of the labyrinth and the, nerves which are distributed upon them, The arrangement of the diflerent parts composing the tympanum is of the greatest importance for the perfect enjoyment of the sense ' Fig. 176. Hitman Auditory AppARATrs, showiog external auditory meatas, tympaDam, and laby- rinth. of hearing. For the air on the two sides of the membrane of the tympanum should be in the same condition of elasticity in order to allow of the proper vibration of the membrane ; and this equilibrium would be liable to disturbance if the air within the tympanum were completely confined, while that outside is subjected to variations of barometric pressure. By means of the Eustachian tube, how-, ever, a communication is established between the cavity of the tympanum and the exterior, and the free vibration of the membrane is thus secured. The exact tension of the memhrana tympani itself is also provided for, as we have already observed, by the action of the two muscles inserted into the malleus and the stapes. By the contraction of the internal muscle, of the malleus, or tensor tympani, the membrane of the tympanum is. drawn, in ward and rendered more tense than usual. The action of the stapedius muscle is by some : thought to relax the membrana tympani, by others to assist in. the tension both of this membrane and that of the foramen ovale, to which the stapes is attached. But there is no doubt that both these mus- cles, by their combined or, alternate action,can:regulate.the tension HEARING 523 of the tympanic membrane, to an extraordinary degree of nicety, and thus increase the ease and delicacy with which various sounds are distinguished. For if the membrane be so put upon the stretch that its fundamental note shall be the same with that of the sound which is to be heard, it will vibrate more readily in consonance with the undulations of the atmosphere, and the sound will be more distinctly heard. On the contrary, if the membrane be too highly stretched, very grave sounds may not be heard at all, until its tension is diminished to the requisite degree. Contrary to what is sometimes asserted, the communication of sonorous impulses to the internal ear is accomplished altogether hy means of the tympanum and chain of hones. It has been thought that sounds were transmitted, in many instances, directly to the internal ear by the medium of the cranial bones. This was inferred from such facts as the following. If a tuning-fork, in vibration, be taken between the teeth, its sound will appear very much louder than if it were simply held near the external ear ; and if, while it is so held, one of the ears be closed, the sound will appear very much louder on that side than on the other. The sound will also be heard if the tuning-fork be applied to the upper part of the cranium or the mastoid process, with a similar increase of resonance on closing the ears. Finally our own voices are heard, though the ears be both closed, and the sound is much louder with the ears closed than open. These are the facts which have led to the belief that, in such instances, the sound was communicated directly through the bones of the head, vibrating in consonance with the sounding body. But a little examination will show that such is not the case. When we hold the end of a vibrating tuning-fork between the teeth, we no longer hear the sound at the vibrating extremity of the instru- ment or its neighborhood, but in the mouth and the nasal fossae. It is the vibration of the air in these passages which produces the sound ; and this vibration is communicated to the cavity, of the tympanum, perhaps through the Eustachian tube. The apparent increase of sound, also, on closing the ears, which could not be ex- plained on supposing it to be conducted directly to the internal ear through the bones of the cranium, is due to the same cause. For it can easily be seen, on trying the experiment, either with a tuning-fork held between the teeth, or simply with our own voices, that this apparent itiorease of sound takes place only when the ears are closed by genile pressure. If the pressure be excessive. 524 THE SPECIAL SENSES. SO that the integument is forced inwJird into the meatus and the air in the meatus subjected to undue compression, the sound no longer appears louder in the corresponding ear, and may even be lost altogether. The apparent increase of sound, therefore, in such cases, when the ear is gently closed, is due to the fact that the meatus is thua converted into a reverberatory cavity, by which the vibrations of the tympanum are increased in intensity. But if the air in the meatus be too much compressed by forcible closure, the vibrations of the tympanum are then interfered with and the sound is dimi- nished or destroyed. In all cases, then, it is the sonorous vibrations of the air which produce the sound, and these vibrations are received invariably by the membrane of the tympanum, and thence transmitted to the internal ear by the chain of bones. The cranial bones are incapable of communicating these vibrations to the labyrinth and its contents, except very faintly and imperfectly. For common experience shows that even the loudest and sharpest sounds, coming from without, are almost entirely lost on closing the external ears ; and our own respiratory and cardiac sounds, which are so easily heard as soon as the chest is connected with the ear by a flexible stethoscope, are entirely inaudible to us in the usual condition. The exact function of the different parts of the internal ear is not well understood. It has been thought to be the office of the semicircular canals to determine the direction from which, the sono- rous impulses are propagated. This opinion was based upon the curious fact that these canals, always three in number, are placed in such positions as to correspond with the three different direc- tions of vertical, lateral, and longitudinal extension ; for one of them is nearly vertical and transverse, another vertical and longi- tudinal, and the third horizontal in position. The sonorous im- pulses, therefore, coming in either of these directions, would be received by only one of the semicircular canals (by direct conduc- tion through the bones of the head) perpendicularly to its own plane ; and an intermediate direction, it was thought, might be appreciated by the combined efiect of the impulse upon two adja- cent canals. Enough has already been said, however, in regard to the commu- nication of sound directly through the bones of the head to the in- ternal ear, to show that this cannot be the mode in which the direc- tion of sound is ascertained. Indeed, when we hear any loud and HEARING. 525 ■well-marked sound coming from a particular region, suet as the music of a military band or the whistle of a locomotive, we have only to close the external ears to lose our perception both of the sound and its direction. The direction of sonorous impressions is appre- ciated in a different way. In the first place, we feel that the sound comes from one side or the. other, by its making a more distinct impression on one ear than the opposite; and by inclining the head slightly in various directions, we easily ascertain whether the sound becomes more or less acute, and so judge of its actual source. Many of the lower animals, whose ears are very large and movable, use this method to great extent. A horse, for example, when upon the road, often keeps his ears in constant motion, feeling, as it were, in the distance, for the origin of the various sounds which excite his attention. Beside the above, we are further assisted in our judgment of the direction of sounds by our previous knowledge of the localities, the direction of the wind, and the manner in which the sound is reflected by surrounding objects. When these sources of informa- tion fail us, we are often at a loss. It is notoriously difScult, for example, to judge of the place of the chirping of a cricket in a perfectly closed room, or of the direction of a bell heard on the water in a thick fog. The sense of hearing has a much closer analogy with ordinary sensibility than that of sight. Thus, in the first place, hearing is accomplished by the direct intervention and contact of a materia") body — the atmosphere ; for sonorous impulses cannot bo produced in a vacuum, and we hear no sound from a bell rung under an exhausted receiver. Secondly, the nature of the impressions pro- duced by sound is such that we can often describe them by the same terms which are applied to ordinary sensations. Thus, we speak of sounds as sharp and dull, piercing, smooth, or rough ; and we feel the impulse of a sudden and violent explosive sound, like that of a hhw upon the tympanum. By this sense, therefore, we distinguish the quality, intensity, pitch, duration, and direction of sonorous impulses. The delicacv with which these distinctions are appreciated varies considerablv in different individuals ; and in different kinds of animals there is reason to believe that the diversity is much greater, some of them being almost insensible to sounds which are readily-perceived by others. In man, the number and variety of tones whi^h can usually be discriminated is very great; and this sense, accordingly, in the 526 THE SPECIAL SENSES. complication and finish of its apparatus, and the perfection and deli- cacy of its action, must be regarded as second only to that of vision On the Senses in Geneeal. — There are several facts connected ■with the operation of the senses, both general and special, which are common to all of them, and which still remain to be considered. In the first place, an impression of any kind, made upon a sensi- tive organ, remains for a time after the removal of its exdting cause. We have already noticed this in regard to the senses of taste, smell, and sight, but it is equally true of the hearing and the touch. Thus, if the skin be touched with a piece of ice, the acute sensa- tion remains for a few seconds, whether the ice be removed or not. For the higher order of the special senses, the time during which this secondary impression remains is a shorter one. In the ease of hearing, however, it has been measured with tolerable approach to accuracy ; for it has been found that, if the sonorous undulations follow each other with a greater rapidity than sixteen times per second, they become fused together into a continuous sound, pro- ducing upon the ear the impression of a musical note. The varying pitch of the note depends upon the rapidity with which the vibra- tions succeed each other. When the succession of vibrations is very rapid, a high note is thfe result, and when comparatively slow, a low note is produced ; but when the number of impulses falls below sixteen per second, we then perceive the distinct vibration?, and so lose the impreission of a continuous note. All the senses, in the second place, hecoma accustomed to a con- tinued im^pression, so that they no longer perceive its existence. Thus, if a perfectly uniform pressure be exerted upon any part of the body, the compressing substance after a time fails to excite any sensation in the skin, and We remain unconscious of its existence. In order to attract our notice, it is then necessary to increase or diminish the pressure ; while, so long as this remains uniform, no efiect is perceived. But if, after the skin has thus become accus- tomed to its presence, the foreign body be suddenly removed, our attention is then immediately excited, and we notice the absence of an impression, in the same way as if it were a positive sensation. We all know how rapidly we become habituated to odors, whether agreeable or disagreeable in their nature, in the confined air of a • close apartment ; although, on first entering from without, our attention may have been attracted by them in a very decided manner. A continuous and, uniform sound, also,; like the steady rumbling of carriages, or the monotonous hissing of boiling water, ON. THE SENSES IN GENEBAL. 527 becomes after a time inaudible to us; but as soon as the sound ceases, we notice the alteration, and our attention is at once excitedi The senses, accordingly, receive their stimulus more from the varia- tion and contrast of external impressions, than from these impres' sions themselves. Another important paTticulary in regard to the senses, is their capacity for education^ The proofs of this are too common and too apparent to need more than a simple allusion. The touch may be so trained that the blind may read words and sentences by its aid, in raised letters, where an ordinary observer would hardly detect anything more than a barely distinguishable inequality of surface. The educated eye of the artist, or the naturalist, , will distinguish variations of color, size, and outline, altogether inappreciable to ordinary vision ; and the senses of taste and smell, in those who are in the habit of examining wines and perfumes, acquire a similar superiority of discriminating power. In these instances, however, it is mot probable that the organ of sense itself becomes any more perfect in organization, or more susceptible to sensitive impressions. The increased functional power, developed by cultivation, depends rather upon the greater delicacy of the ^erc«p<«»e and discnm^waiiw^feculties. It is a mental and not a physical superiority which gives the painter or the naturalist a greater power of distinguishing colors and outlines, and which enables the physician to detect nice variations of quality in the sounds of the heart or the respiratory murmur of the lungs. The impressions of external objects, therefore, in order to produce their complete effect, must first be received by a sensitive appa- ratus, which is perfect in organization and functional activity; and, secondly, these impressions must be subjected to the action of an intelligent perception, by which their nature, source and rela- tions are fully appreciated. That part of the nervous system which we have hitherto studied, viz., the cerebro-spinal system, consists of an apparatus of nerves and gfinglia, destined to bring the individual into relation with the external world. ' By means of the special senses, he is made cognizant of sights, sounds, taste, and odors, by which he is attracted or repelled, and which guide him in the pursuit and choice of food. By the general sensations of touch and the volun- tary movements, he is enabled to alter at will his position and location, and to adapt them to the varying conditions under which he may be placed. The great passages of entrance into the body, 528 THK SPECIAL SENSES. and of exit from it, are guarded by the same portion of the nerv- ous system. The introduction of food into the mouth, and its passage -through the oesophagus to the stomach, are regulated by the same nervous apparatus ; and even the passage of air through the larynx, and its penetration into the lungs, are equally under the guidance of sensitive and motor nerves belonging to the cerebro-spinal system. It will be observed that the above functions relate altogether either to external phenomena or to the simple introduction into the body of food and air, which are destined to undergo nutritive changes in the interior of the frame. If we examine, however, the deeper regions of the body, we find located in them a series of internal phenomena, relating only to the substances and materials which have already penetrated into the frame, and which form or are forming a part of its structure. These are the purely vegetative functions, as they are called ; or those of growth, nutrition, secretion, excretion, and reproduction. These functions, and the organs to which they belong, are not under the direct influence of the cerebro-spinal nerves, but pre regulated by another portion of the nervous system, viz., the " ganglionic system ;" or, as it is more commonly called, the " sys- tem of the great sympathetic." SYSTEM OF THE GREAT SYMPATHETIC. 529 CHAPTER VII. SYSTEM OP THE GREAT SYMPATHETIC. The sympathetic system consists of a double chain of nervous ganglia, running from the anterior to the posterior extremity of the body, along the front and sides of the spinal column, and connected with each other by slender longitudinal filaments. Each ganglion is reinforced by motor and sensitive filaments derived from the cerebro- spinal system, and thus the organs under its influence are brought indirectly into communication with external objects and phenomena. The nerves of the great sympathetic are distributed to organs over which the consciousness and the will have no imme- diate control, as the intestine, kidneys, heart, liver, &c. Anatomical arrangement of the sympathetic system. — The first sympathetic ganglion in the head is the ophthalmic ganglion. It is situated within the orbit of the eye, on the outer aspect of the optic nerve. It communicates by slender filaments with the carotid plexus, which forms the continuation of the sym- pathetic system from below; and receives a motor root from the oculo-motorius nerve, and a sensitive root from the ophthalmic branch of the fifth pair. Its filaments of distribution, known as the " ciliary nerves," pass forward upon the eyeball, pierce the sclerotic, and finally terminate in the iris. The next division of the great sympathetic in the head is the spheno-palatine ganglion, situated in the spheno-maxillary fossa. It communicates, like the preceding, with the carotid plexus, and receives a motor root from, the facial nerve, and a sensitive root from the superior maxillary branch of the fifth pair. Its filaments are distributed to the levator palati and azygos uvula3 muscles, and to the mucous membrane about the posterior nares. The third sympathetic ganglion in the head is the submaxillary, situated upon the submaxillary gland. It communicates with the superior cervical ganglion of the sympathetic by filaments which accompany the facial and external carotid arteries. It derives its sensitive filaments from the lingual branch of the fifth pair, and its 84 530 SYSTEM OF THE GBEAT SYMPATHETIC. motor filaments from the facial nerve, by means of the chorda tympani. Its branches of distribution pass to the sides of the tongue and to the submaxillary and sublingual glands. The last sympathetic ganglion in the head is the otic ganglion. It is situated just beneath the base of the skull, on the inner Fig- 177. side of the third division of the fifth pair. It sends fila- ments of communication to the carotid plexus; and re- ceives a motor root from the facial nerve, and a sensitive root from the inferior maxil- lary division of the fifth pair. Its branches are sent to the internal muscle of the mal- leus in the middle ear (tensor tympani), to the circumflexus palati, and to the mucous membrane of the tympanum and Eustachian tube. The continuation of the sympathetic nerve in the neck consists of two and some- times three ganglia, the su- perior, middle, and inferior. These ganglia communicate with each other, and also with the anterior branches of the cervical spinal nerves. Their filaments follow the course of the parotid artery and its branches, covering them with a network of inter- lacing fibres, and are finally distributed to the substance of the thyroid gland, and to the walls of the larynx, trachea, pharynx, and oesophagus. By the superior, middle, and inferior cardiac nerves, they also supply sympathetic fibres to the cardiac plexuses and to the substance of the heart. Course and distribution of tbe Great THETIC. SYSTEM OF THE GREAT SYMPATHETIO. 531 In the chest, the ganglia of the sympathetic nerve are situated on each side the spinal column, just over the heads of the ribs, with which they accordingly correspond in number. Their communi- cations with the intercostal nerves are double ; each sympathetic ganglion receiving two filaments from the intercostal nerve next above it. The filaments originating from the thoracic ganglia are distributed upon the thoracic aorta, and to the lungs and oesophagus. In the abdomen, the continuation of the sympathetic system con- sists principally of the aggregation of ganglionic enlargements situated upon the oceliac artery, known as the semilunar or coeliac ganglion. From this ganglion a multitude of radiating and inoscu- lating branches are sent out, which, from their diverging course and their common origin from a central mass, are termed the "solar plexus." From this, other diverging plexuses originate, which accompany the abdominal aorta and its branches, and are distrib- uted to the stomach, small and large intestine, spleen, pancreas, liver, kidneys, supra-renal capsules, and internal organs of generation. Beside the above ganglia there are in the abdomen four other pairs, situated in front of the lumbar vertebrae, and having similar connections with those occupying the cavity of the chest. Their filaments join the plexuses radiating from the semilunar ganglion. In the pelvis, the sympathetic system is continued by four or five pairs of ganglia, situated on the anterior aspect of the sacrum, and terminating, at the lower extremity of the spinal column, in a single ganglion, the " ganglion impar," which is probably to be regarded as a fusion of two separate ganglia. The entire sympathetic series is in this way composed of nume- rous small ganglia which are connected throughout, first, with each other ; secondly, with the cerebro-spinal system ; and thirdly, with the internal viscera of the body. Physiological properties of the sympathetie nerve. — The prop- erties and functions of the great sympathetic have been less successfully studied than those of the cerebro-spinal system, owing to the anatomical difficulties in the way of reaching and operating upon this nerve for purposes of experiment. The cerebro- spinal axis and its nerves are easily exposed and subjected to exami- nation. It is also easy to isolate particular portions of this system, and to appreciate the disturbances of sensation and motion conse- quent upon local lesions or irritations. The phenomena, further- more, which result from experiments upon this part of the nervous apparatus, are promptly produced, are well-marked in character, 532 SYSTEM OF THE GREAT SYMPATHETIC. and are, &3 a general rule, readily understood by the experimenter. On the' other hand, the principal part of the sympathetic system is situated in the interior of the chest and abdomen ; and the mere operation of opening these cavities, so as to reach the ganglionic centres, causes such a disturbance in the functions of vital organs, and such a shock to the system at large, that the results of these experiments have been always more or less confused and unsatis- factory. Furthermore, the connections of the sympathetic gangUa with each other and with the cerebro-spinal axis are so numerous and so scattered, that these ganglia cannot be completely isolated without resorting to an operation still more mutilating and injuri- ous in its character. And finally, the sensible phenomena which are' obtained by experimenting on the great sympathetic are, in many caseS) slow in making their appearance, and not particularly striking or characteristic in their nature. Notwithstanding these- difficulties, however, some facts have been ascertained with regard to this part of the nervous system, which give us a certain degree of insight into its character and functions. Influence on movement and sensibility. — The great sympa- thetic is endowed both with sensibility and the power of ex- citing motion ; but these properties are less active here than in the cerebro-spinal system, and are exercised in a differ- ent manner. If we irritate, for example, a sensitive nerve in one of the extremities, or apply the galvanic current to the poste- rior root of a spinal nerve, the evidences of pain or of refles action are acute and instantaneous. There is no appreciable inter- val between the application of the stimulus and the sensations which result from it. On the other hand, experimenters who have operated upon the sympathetic ganglia and nerves of the chest and abdomen find that evidences of sensibility are distinctly manifested here also, but much less acutely, and only after somewhat prolonged application of the irritating cause. These results correspond very closely with what we know of the vital properties of the organs which are supplied either principally or exclusively by the sym- pathetic; as the liver, intestine, kidneys, &c. These organs are insensible, or nearly so, to ordinary impressions. We are not con- scious of the changes and operations going on in them, so long as these changes and operations retain their normal character. But they are still capable of perceiving unusual or excessive irritations, and may even become exceedingly painful when in a state of m- flammation. There is the same peculiar character in the action of the motor SYSTEM OF THE GEEAT SYMPATHETIC. 533 nerves belonging to the sympathetic system. If the facial or hypo- glossal, or the anterior root of a spinal nerve be irritated, the con- vulsive movement which follows is instantaneous, violent, and only momentary in its duration. But if the semilunar ganglion or its nerves be subjected to a similar experiment, no immediate effect is produced. It is only after a few seconds that a slow, vermicular, progressive contraction takes place in the corresponding part of the intestine, which continues for some time after the exciting cause has been removed. Morbid changes taking place in organs supplied by the sympa- thetic present a similar peculiarity in the mode of their produc- tion. If the body be exposed to cold and dampness, for example, congestion of the kidneys shows itself perhaps on the following day. Inflammation of any of the internal organs is very rarely established within twelve or twenty-four hours after the application of the exciting cause. The internal processes of nutrition, together with their derangements, which are regarded as especially under the control of the great sympathetic, always require a longer time to be influenced by incidental causes, than those which are regulated by the nerves and ganglia of the cerebro-spiual system. Influence on the special senses. — In the head, the sympa- thetic has a close and important connection with the exercise of the special senses. This is illustrated more particularly in the case of the eye, by its influence over the alternate expan- sion and contraction of the pupil. The ophthalmic ganglion sends off a number of ciliary nerves, which are distributed to the iris. It is connected, as we have seen, with the remaining sympathetic ganglia in the head, and receives, beside, a sensitive root from the ophthalmic branch of the fifth pair, and a motor root from the oculo-motorius. The reflex action by which the pupil contracts under a strong light falling upon the retina, and expands under a diminution of light, takes place, accordingly, through this ganglion. The impression conveyed by the optic nerve to the tubercula quadrigemina, and reflected outward by the fibres of the oculo-motorius, is not transmitted directly by the last named nerve to the iris ; but passes first to the ophthalmic ganglion, and is thence conveyed to its destination by the ciliary nerves. The reflex movements of the iris exhibit consequently a some- what sluggish character, which indicates the intervention of a part of the sympathetic system. The changes in the size of the pupil do not take place instantaneously, with the variation in the amount of light, but always require an appreciable interval of time. If 534 SYSTEM OF THE GEEAT SYMPATHETIC. ■we pass suddenly from, a brilliantly lighted apartment into a dark room, we are unable to distinguish surrounding objects until a certain time has elapsed, and the expansion of the pupil has taken place ; and vision even continues to grow more and more distinct for a considerable period afterward, as the expansion of the pupil becomes more complete. Again, if we cover the eyes of another person with the hand or a folded cloth, and then suddenly expose them to the light, we shall find that the pupil, which is at first dilated, contracts somewhat rapidly to a certain extent, and after- ward continues to diminish in size during several seconds, until the proper equilibrium is fairly established. Furthermore, if we pasa suddenly from a dark room into the bright sunshine, we are imme- diately conscious of a painful sensation in the eye, which lasts for a considerable time ; and which results from the inability of the pupil to contract with suf&cient rapidity to shut out the excessive amount of light. All such exposures should be made gradually, so that the movements of the iris may keep pace with the varying quantity of stimulus, and so protect the eye from injurious impres- sions. The reflex movements of the iris, however, though accomplished through the medium of the ophthalmic ganglion, derive their original stimulus, through the motor root of this ganglion, from the oculo-motorius nerve. For it has been found that if the oculo- motorius nerve be divided between the brain and the eyeball, the pupil becomes immediately dilated, and will no longer contract under the influence of light. The motive power originally derived from the brain is, therefore, in the case of the iris, modified by passing through one of the sympathetic ganglia before it reaches its final destination. An extremely interesting fact in this connection is the following. Of the three organs of special sense in the head, viz., the eye, the nose, and the ear, each one is provided with two sets of muscles, superficial and deep, which together regulate the quantity of stimu- lus admitted to the organ, and the mode in which it is received. The superficial set of these muscles is animated by branches of the facial nerve ; the deep-seated or internal set, by filaments from a sympathetic ganglion. Thus, the front of the eyeball is protected by the orbicularis and levator palpebrse superioris muscles, which open or close the eye- lids at will, and allow a larger or smaller quantity of light to reach the cornea. These muscles are supplied by the oculo-motorius and SYSTEM OP THE GREAT SYMPATHETIC. 535 Fig. 178. facial nerves, and are for the most part voluntary in their action. The iris, on the other hand, is a more deeply seated muscular curtain, which regulates the quantity of light admitted through the pupil. Its muscular fibres are supplied, as we have seen, by fila- ments from the ophthalmic ganglion, and their movements are involuntary in character. Division of the sympathetic nerve in the middle of the neck has accordingly a very singular and instantaneous effect on the muscular apparatus of the eye. Within a very few seconds after the above operation has been performed upon the cat, the pupil of the corresponding eye becomes strongly contracted, and remains in that condition. At the same time the third eyelid, or " nictitating membrane," with which these ani- mals are provided, is drawn par- tially over the cornea, and the upper and lower eyelids also approxi- mate very considerably to each other; so that all the apertures guarding the eyeball are very perceptibly narrowed, and the ex- pression of the face on that side is m ^ / 'TWSSKBF \ \ altered in a corresponding degree. ■/^ ^ [\ ."TTylVX This effect upon the pupil has ■ V ^/ ^ > been explained by supposing the Cat, after section of the right sympathetic. circular fibres of the iris, Or the constrictors of the pupil, to be animated exclusively by nervous filaments derived from the oculo- motorius; and the. radiating fibres, pr the dilators, to be supplied by the sympathetic. Accordingly^.while division of the oculo- motorius would produce dilatation of the pupil, by paralysis of the circular fibres only, division of the sympathetic would be followed by exclusive paralysis of the dilators, and a permanent contraction of the pupil would consequently take place. The above explanation, however, is not entirely satisfactory ; since, in the first place, division of the oculo-motorius, as the experiments of Bernard have shown,^ does not by itself produce complete dilata- tion of the pupil ; and, secondly, after division of the sympathetic nerve in the cat, as we have already shown, not only is the pupil ' Lemons sur la Physiologie ct la Pathologie du Syst&me Nerveux, Paris, 1858, vol. ii. p. 203. 536 SYSTEM OF THE GREAT SYMPATHETIC. contracted, but both the upper and lower eyelids and the nictitating membrane are also drawn partially over the cornea, and assist in excluding the light. The last-named effect cannot be owing to any direct paralysis, from division of the fibres of the sympathetic. It is more probable that the section of this nerve operates simply by exaggerating for a time the sensibility of the retina, owing to the vascular congestion of the parts; and that the partial closure of the eyelids and pupil is a secondary consequence of that condition. In the olfactory, apparatus, the anterior or superficial set of muscles are the compressors and elevators of the alse nasi, which are animated by filaments of the facial nerve. By their action, odoriferous vapors, when faint and delicate in their character, are snuffed up and directed into the upper part of the nasal passages, where they come in contact with the most sensitive portions of the olfactory membrane ; or, if too pungent or disagreeable in flavor, are excluded from entrance. These muscles are not very im- portant or active in the human subject ; but in many of the lower animals with a more active and powerful sense of smell, as, for example, the carnivora, they may be seen to play a very important part in the mechanism of olfaction. Furthermore, the levators and depressors of the velum palati, which are more deeply situated, serve to open or close the orifice of the posterior nares, and accom- plish a similar ofBce with the muscles already named in front. The levator palati and azygos uvulse muscles, which, by their action, tend to close the posterior nares, are supplied by filaments from the spheno-palatine ganglion, and are involuntary in their character. The ear has two similar sets of muscles, similarly supplied. The first, or superficial set, are those moving the external ear, viz., the anterior, superior, and posterior auriculares. Like the muscles of the anterior nares, they are comparatively inactive in man, but in many of the lower animals are well developed and important. In the horse, the deer, the sheep, &c., they turn the ear in various directions so as to catch more distinctly faint and distant sounds, or to exclude those which are harsh and disagreeable. These muscles are supplied by filaments of the facial nerve, and are voluntary in their action. The deep-seated set are the muscles of the middle ear. In order to understand their action, we must recollect that sounds are trans- mitted from the external to the middle ear through the membrane of the tympanum, which vibrates, like the head of a drum, on receiving sonorous impulses from without. SYSTEM OP THE GREAT SYMPATHETIC. 537 The membrane of the tympanum, accordingly, which is an elastic sheet, stretched across the passage to the internal ear, may be made more or less sensitive to sonorous impressions by varying its con- dition of tension or relaxation. This condition is regulated, as we have already seen, by the combined action of the two muscles of the middle ear, viz., the tensor tympani and the stapedius. The first named muscle, the action of which is perfectly well understood, is supplied with nervous filaments from the otic ganglion of the sympathetic. By its contraction, the handle of the malleus is drawn inward, bringing the membrana tympani with it, and putting this membrane upon the stretch. On the relaxation of the muscle, the chain of bones returns to its ordinary position, by the elasticity of the neighboring parts, and the previous condition of the tympanic membrane is restored. This action, so far as we can judge, is purely involuntary. But the stapedius muscle is separately supplied by a minute branch of the facial nerve. It is probable that this arrange- ment enables us to make also a certain degree of voluntary exer- tion, in listening intently for faint or distant sounds. In all these instances, the reflex action taking place in the deeper seated muscles, originates from a sensation which is con- veyed inward to the cerebro-spinal centres, and is then transmitted outward to its final destination through the medium of one of the sympathetic ganglia. Influence on the circulation. — Perhaps the most important fact concerning the sympathetic is that of its influence over the vascularity and nutrition of the parts supplied by it. In the first place, the division of the sympathetic produces immediately a vascular congestion in the corresponding parts. If the sympathetic be divided, in the rabbit, in the middle of the neck, a vascular congestion of all parts of the head, on the corre- sponding side, immediately follows. This congestion is most dis- tinctly evident in the thin and transparent ears ; and within a few minutes after the operation, the difference in their appearance on the two sides is strongly pronounced. All the vessels of the ear on the affected side become turgid with blood ; and many whic> were before imperceptible, become distinctly visible. This effect of the division of the sympathetic, which was first pointed out by Bernard, we have often verified. It lasts for a considerable time and we have even seen it very distinct at the end of three weeks. It remains for a longer time when a portion of the nerve has been cut out, or the cervical ganglion extirpated, than when its filaments 638 SYSTEM OP THE GREAT SYMPATHETIC. have been simply divided by a transverse section. It finally dis- appears when the separated filaments have been re-united and their functional activity restored. The vascular. congestion thus produced by division of the sym- pathetic nerve is- accompanied by three important phenomena, all intimately connected with each other. First, the quantity of blood circulating in the part is increased, and the rapidity of its movement accelerated. The bloodvessels are not in a state- of passive congestion, due to an obstruction to the return of the venous blood. On the contrary, all the vessels of the part are simultaneously dilated, a larger quantity of blood passes through the capillaries in a given time, and returns by the veins in greater abundance than before. Secondly, there is a remarkable elevation of temperature in the affected part. This elevation of temperature is very perceptible to the touch in the ear of the rabbit and even in the integument of the corresponding side of the head. Measured by the thermometer, it has been found by Bernard to reach, in some cases, 8° or 9° F. It is evidently due to the increased quantity of blood circulating in the vessels of the part ; since the blood coming from the iate- rior and warmer parts of the body supplies the ear with more heat in proportion to the greater abundance and rapidity with which it traverses the vascular tissues. Thirdly, the color of the venous blood in the affected part becomes brighter and more ruddy. This effect is also due to the increased rapidity of the circulation. As the arterial blood is deprived of its oxygen and darkened in color by the changes of nutrition which usually take place in the tissues, if the rapidity of the cir- culation be suddenly increased, a certain proportion of the blood escapes deoxidation, and its change in color, from arterial to venous, is incomplete^ The blood accordingly, under these circumstances, returns by the veins of the affected part in greater abundance, of a higher temperature, and of a more ruddy color, than on the un- injured side of the body. Now it is found that, when a vascular congestion of the part has been thus produced by division of the sympathetic, if that portion of the divided nerve which remains in connection with the tissues be irritated by electricity, all the above effects rapidly disappear ; the bloodvessels of the ear and corresponding side of the head contract to their previous diameter, the quantity of blood circulating through the tissues is diminished, the temperature of the parts is reduced SYSTEM OF THE GREAT SYMPATHETIC. 539 in a corresponding degree, and the blood in the veins returns to its ordinary dark color. The variations in the rapidity of the cir- culation dependent on the condition of the sympathetic nerve are shown by Bernard ' in the following experiment. In a living rab- bit the upper part of one ear is cut off with a pair of very sharp scissors, so that the blood may escape in jets from the divided ends of the small arteries. The force and height of the arterial jets having been observed, the sympathetic nerve is then divided in the middle of the neck on the corresponding side. Immediately the blood escapes from the wounded ear in greater abundance, and the arterial jets rise to double or even triple their former height. The galvanic current is then applied to the divided extremity of the sympathetic, above the point of section, when the streams of blood escaping from the wound gradually diminish and disappear ; but recommence and again increase in intensity so soon as the galvanization of the nerve is suspended. The same author has shown that a similar influence is exerted by the sympathetic nerve upon the circulation in the limbs.^ If the lumbar nerves of one side be divided, in the dog, within the cavity of the spinal canal, a paralysis of motion and sensibility is produced in the corresponding limb, but there is no change in its vascularity or temperature; while if the lumbar portion of the sympathetic be divided or excised, without disturbing the spinal nerves, all the signs of increased temperature and activity of the circulation are at once manifested in the limb below, without any loss of motion or sensibility. Exsection of the first thoracic gan- glion of the sympathetic produces similar effects in the anterior extremity ; and these effects are diminished or suspended by elec- trical irritation applied to the upper end of the divided nerve. Division of the sympathetic nerve, accordingly, produces a dila- tation of the vessels and consequent increased rapidity of the circu- lation, and causes the blood to retain its red color even in the veins- while galvanization of the same nerve produces contraction of the vessels, diminishes the quantity of the circulating fluid, and causes the change in color of the blood, from arterial to venous. , The same thing takes place in the glandular organs. If the sub- maxillary or parotid gland be exposed in the living animal,' so > Journal de la Physiologle. July, 1862, p. 397. " Journal de la Physiologle, loo. cit. ■• Bernard. Lejons sur les Liquides de I'Organiame. Paris, 1859, vol. i. p. 230, et seq. 540 SYSTEM OF THE GKEAT SYMPATHETIC. long as the gland is in its ordinary condition it will be seen that the blood passing through it is converted from arterial to venous, and returns dark colored by the veins. But if the filament of the sym- pathetic nerve which accompanies the external carotid artery be divided, the quantity of blood flowing through the gland is at once increased, and at the same time appears of a red color in the veins. The same changes occur when the'gland is excited to secretion by stimulating the organs of taste. An antagonism appears to exist, in the regulation of the circula- tion in the vascular organs, between the sympathetic nerve and the motor filaments derived from the cerebro-spinal system. For if the branch of the chorda tympani which penetrates the submaxillary gland be galvanized, it produces an excitement of the glandular secretion," increased activity of the circulation, and a. red color of the blood in the veins. The division of this nerve is followed by a contrary result. The effects produced, therefore, by galvanization of the chorda tympani are those produced by division of the sym- pathetic ; and the effects produced by galvanizing the sympathetic are those which follow division of the chorda tympani. The vascularity of the parts, accordinigly, as well as the functional activity of the vascular organs, are under the control of the nervous system. The filaments of the sympathetic nerve, as we have seen, accompany everywhere the bloodvessels, enveloping the arterial branches with an abundant plexus, and following them to their minutest ramifications. These sympathetic fibres appear to act by causing a contraction in the organic muscular fibres of the small arteries, and thus to regulate the resistance of these vessels, and the passage of the blood through them. "When the sympathetic nerve is excited, the vessels are contracted, the blood passes through them but slowly, and is fully converted, during its passage, into venous blood. When the influence of this nerve is diminished or sus- pended, the vessels are dilated, the circulation is increased, and the blood, passing through the vessels with greater rapidity, does not suffer the nutritive changes which result in the alteration of its color from arterial to venous. Influence on reflex actions. — The influence of the sympathetic nerve and the consequences of its division upon the thoracic and abdominal viscera have been only very imperfectly in- vestigated by experimental methods. It undoubtedly serves as a medium of reflex action between the sensitive and motor 1 Bernard. Op. cit., toI. i. p. 312. SYSTEM OF THE GREAT SYMPATHETIC. 541 portions of the digestive, excretory, and generative apparatuses ; and it is certain that it also takes part in reflex actions in which the cerebro-spinal system is at the same time interested. There are accordingly three different kinds of reflex action, taking place wholly or partially through the sympathetic system, which may be observed to occur in the living body. 1st. Reflex actions taking place from the internal organs, through the sympathetic and cerebro-spinal systems, to the voluntary muscles and sensitive surfaces. — The convulsions of young children are often owing to the irritation of undigested food in the intestinal canal. Attacks of indigestion are also known to produce temporary amau-^ rosis, double vision, strabismus, and even hemiplegia. Nausea, and a diminished or capricious appetite, are often prominent symptoms of early pregnancy, induced by the peculiar condition of the uterine mucous membrane. 2d. Reflex actions taking place from the sensitive surfaces, through the cerebro-spinal and sympathetic systems, to the involuntary muscles and secreting organs. — Imprudent exposure of the integument to cold and wet, will often bring on a diarrhoea. Mental and moral impressions, conveyed through the special senses, will affect the motions of the heart, and disturb the processes of digestion and secretion. Terror, or an absorbing interest of any kind, will pro- duce a dilatation of the pupil, and communicate in this way a pecu- liarly wild and unusual expression to the eye. Disagreeable sights or odors, or even unpleasant occurrences, are capable of hastening or arresting the menstrual discharge, or of inducing premature delivery. 3d. Reflex actions taking place, through the sympathetic system, from one part of the internal organs to another. — The contact of food with the mucous membrane of the small intestine excites a peristaltic movement in the muscular coat. The mutual action of the diges- tive, urinary and internal generative organs upon each other takes place through the medium of the sympathetic ganglia and their nerves. The variations of the capillary circulation in different abdominal viscera, corresponding with the state of activity or re- pose of their associated organs, are to be referred to a similar nerv- ous influence. These phenomena are not accompanied by any consciousness on the part of the individual, nor by any apparent intervention of the cerebro-spinal system. SECTION III. REPRODUCTION. CHAPTER I. ON THE NATURE OP REPRODUCTION, AND THE ORIGIN OP PLANTS AND ANIMALS. The process of reproduction is the most characteristic, and in many respects the most interesting, of all the phenomena presented by organized bodies. It includes the whole history of the changes taking place in the organs and functions of the individual at suc- cessive periods of life, as well as the production, growth, and de- velopment of the new germs which make their appearance by generation. For all organized bodies pass through certain well-defined epochs or phases of development, by which their structure and functions undergo successive alterations. We have already seen that the living animal or plant is distinguished from inanimate substances by the incessant changes of nutrition and growth which take place in its tissues. The muscles and the mucous membranes, the osse- ous and cartilaginous tissues, the secreting and .circulatory organs, all incessantly absorb oxygen and nutritious material from with- out, and assimilate their molecules ; while new substances, produced by a retrogressive alteration and decomposition, are at the same time excreted and discharged. These nutritive changes correspond in rapidity with the activity of the other vital phenomena ; since the production of these phenomena, and the very existence of the vital functions, depend upon the regular and normal continuance of the nutritive process. Thus the organs and tissues, which are always the seat of this double change of renovation and decav, ( 543 ) 544 NATURE OF EEPEODUCTION. retain nevertheless their original constitution, and continue to be capable of exhibiting the vital phenomena. The above changes, however, are not in reality the only ones which take place. For although the structure of the body and the composition of its constituent parts appear to be maintained in an unaltered condition, by the nutritive process, from One moment to another, or from day to day, yet a comparative examination of them at greater intervals of time will show that this is not pre- cisely the case ; but that the changes of nutrition are, in point of fact, progressive as well as momentary. The composition and pro- perties of the skeleton, for example, are not the same at the age of twenty-five that they were at fifteen. At the later period it con- tains more calcareous and less organic matter than before ; and its solidity is accordingly increased, while its elasticity is diminished. Even the anatomy of the bones alters in an equally gradual manner ; the medullary cavities enlarging with the progress of growth, and the cancellated tissue becoming more open and spongy in texture. We have already noticed the difference in the quantity of oxygen and carbonic acid inspired and exhaled at different ages. The muscles, also, if examined after the lapse of some years, are found' to be less irritable than formerly, owing to a slow but steady and permanent deviation in their intimate constitution. The vital properties of the organs, therefore, change with their varying structure ; and a time comes at last when they are per- ceptibly less capable of performing their original functions than before. This alteration, being dependent on the varying activity of the nutritive process, continues necessarily to increase. The very exercise of the vital powers is inseparably connected with the sub- sequent alteration of the organs employed in them ; and the func- tions of life, therefore, instead of remaining indefinitely the same, pass through a series of successive changes, which finally terminate in their complete cessation. The history of a living animalor plant is, therefore, a history of successive epochs or phases of existence, in each of which the struc- ture and functions of the body differ more or less from those in every other. Every living being has a definite term of life, through which it passes by the operation of an invariable law, and which, at some regularly appointed time, comes to an end. The plant germinates, grows, blossoms, bears fruit, withers, and decays. The animal is born, nourished, and brought to maturity, after which he retrogrades and dies. The very commencement of existence, by NATURE OF EEPEODUCTION. 545 leading through its successive intermediate stages, conducts at last necessarily to its own termination. But -while individual organisms are thus constantly perishing and disappearing from the stage, the particular kind, or species, remains in existence, apparently without any important change in the cha- racter or appearance of the organized forms belonging to it. The horse and the ox, the oak and the pine, the different kinds of wild and domesticated animals, even the different races of man himself, have remained without any essential alteration ever since the earliest historical epochs. Yet during this period innumerable individuals, belonging to each species or race, must have lived through their natural term and successively passed out of existence. A species may therefore be regarded as a type or class of organized beings, in which the particular forms or structures composing it die off con- stantly and disappear, but which nevertheless repeats itself from year to year, and maintains its ranks constantly full by the regular accession of new individuals. This process, by which new organ- isms make their appearance, to take the place of those which are destroyed, is known as the process of reproduction or generation. Let us now see in what manner it is accomplished. It has always been known that, as a general rule in the process of generation, the young animals or plants are produced directly from the bodies of the elder. The relation between the two is that of parents and progeny ; and the new organisms, thus generated, become in turn the parents of others which succeed them. For thia reason, wherever such plants or animals exist, they indicate the previous existence of others belonging to the same species ; and if by any accident the whole species should be destroyed in any par- ticular locality, no new individuals could be produced there, unless by the previous importation of others of the same kind. The commonest observation shows this to be true in regard to those animals and plants with whose history we are most familiarly acquainted. An opinion, however, has sometimes been maintained that there are exceptions to this rule ; and that living beings may, under certain circumstances, be produced from inanimate substances, without any similar plants or animals having preceded them; presenting, accordingly, the singular phenomenon of a progeny without parents. Such a production of organized bodies is known by the name of spontaneotis generation. It is believed by the majority of physiologists at the present day that no such spontaneous gen- eration ever takes place ; but that plants and animals are always 35 546 NATURE OF REPRODUCTION. derived, by direct reproduction, from previously existing parents of the same species. As this, however, is a question of some im- portance, and one which has been frequently discussed in works on physiology, we shall proceed to pass in review the facts which have been adduced in favor of the occurrence of spontaneous generation, as well as those which would lead to its disproval and rejection. It is evident, in the first place, that many apparent instances of spontaneous generation are found to be of a very different character as soon as they are subjected to a critical examination. Thus grass- hoppers and beetles, earthworms and crayfish, the swarms of minute insects that fill the air over the surface of stagnant popls, and even frogs, moles, and lizards, have been supposed in former times to be generated directly from the earth or the atmosphere ; and it was only by investigating carefully the natural history of these animals that they were ascertained to be produced in the ordinary manner ■ by generation from parents, and were found to continue the repro- duction of their species in the same way. A still more striking instance is furnished by the production of maggots in putrefying meat, vegetables, flour paste, fermenting dung, &c. If a piece of meat be exposed, for example, and allowed to undergo the process of putrefaction, at the end of a few days it will be found to contain a multitude of living maggots which feed upon the decomposing flesh. Now these maggots are always produced under the same conditions of warmth, moisture and exposure, and at the same stage of the putrefactive process. They are never to be found in fresh meat, nor, in fact, in any other situation than the one just mentioned. They appear, consequently, without any similar individuals having existed in the same locality ; and considering the regularity of their appearance under the given conditions, and their absence elsewhere, it has been believed that they were spontaneously generated, under the influence of warmth, moisture, and the atmosphere, from the decaying organic substances. A little examination, however, discovers a very simple solution of the foregoing difficulty. On watching the exposed animal or vegetable substances during the earlier periods of their decompo- sition, it is found that certain species of flies, attracted by the odor of the decaying material, hover round it and deposit their eggs upon its surface or in its interior. These eggs, hatched by the warmth to which they are exposed, produce the maggots ; which are simply the young of the winged insects, and which after a time become transformed, by the natural progress of development, into INFUSORIAL ANIMALCULES. 547 perfect insects simiLar to their parents. The difficulty of account- ing for the presence of the maggots by generation, therefore, de- pended simply on the difference in appearance between them and their parents. This difference, ho-wever, is merely a temporary one, corresponding with the difference in age, and disappears when the development of the animal is complete; just as the young chicken, when recently hatched, has a different form and plumage from those which it presents in the adult condition. Nearly all the causes of error, in fact, which have suggested at various times the doctrine of spontaneous generation, have been derived from these two sources. First, the ready transportation of eggs or germs, and their rapid hatching under favorable cir- cumstances ; and secondly, the different appearances presented by the same animal at different ages, in consequence of which the youthful animal may be mistaken, by an ignorant observer, for a different species. These sources of error are, however, so readily detected, as a general rule, by scientific investigation, that it is hardly necessary to point out the particular instances in which they exist. In fact, whenever a rare or comparatively unknown animal or plant has been at any time supposed to be produced by sponta- neous generation, it has only been necessary, for the most part, to investigate thoroughly its habits and functions, to discover its secret methods of propagation, and to show that they correspond, in all essential particulars, with the ordinary laws of reproduction. The limits, therefore, within which the doctrine of spontaneous genera- tion can be applied, have been narrowed in precisely the same degree that the study of natural history and comparative physiology has advanced. At present, indeed, there remain but two classes of phenomena which are ever supposed to lend any support to the above doctrine ; viz., the existence and production, 1st, of infuso- rial animalcules, and 2d, of animal and vegetable parasites. "Wo shall now proceed to examine these two parts of the subject in succession. Infusorial Animalcules. — If water, holding in solution or- ganic substances, be exposed to the contact of the atmosphere at ordinary temperatures, it is found after a short time to be filled with swarms of minute living organisms, which are visible only by the microscope. The forms of these microscopic animalcules are exceedingly varied ; owing either to the great number of species m existence, or to their rapid alteration during the successive pe- 548 NATURE OF REPRODUCTION', Fig. 179. Different kinds of Infdsobi nods of their growth. Ehrenberg has described more than 300 different varieties of them. They are generally provided with cilia attached to the exterior of their bodies, and are, for the most part, in constant and rapid motion in the iluid which they inhabit. Owing to their presence ia animal and vegetable watery infusions, they have received the name of "infusoria," or " infusorial animalcules." Now these infusoria are always produced under the conditions which we have de- scribed above. The animal or vegetable substance used for the infusion may be pre- viously baked or boiled, so as to destroy all living germs which it niight accidentally contain; the water in which it is infused may be carefully distilled, and thus freed from all similar contamination ; and yet the infusorial animalcules will make their appearance at the usual time and in the usual abundance. It is only requisite that the infusion be exposed to a moderately elevated temperature, and to the access of atmospheric air; conditions which are equally necessary foi maintaining the life of all animal and vegetable organisms, what- ever be the source from which they are derived. Under the above circumstances, therefore, either the animalcules must have been produced by spontaneous generation in the watery infusion, or their germs must have been introduced into it through the medium of the atmosphere. No such introduction has ever been directly de- monstrated, nor have even any eggs or germs belonging to the infusoria ever been detected. Nevertheless, there is every probability that the infusoria are produced from germs, and not by spontaneous generation. Since the infusoria themselves are microscopic in size, it is not surprisihg that their eggs, which must be smaller still, should have escaped observation. We know, too, that in many instances the minute germs of animals or plants may be wafted about in a dry state by the atmosphere, until, by accidentally coming in contact with warmtk and moisture, they become developed and bring forth living organ- INFUSORIAL ANIMALCULES. 549 isms. The eggs of the infusoria, accordingly, may be easily raised and held suspended in the atmosphere, under the form of minute dust-like particles, ready to germinate and become developed when- ever they are caught by the surface of a stagnant pool, or of any artificially prepared infusion. In point of fact, the atmosphere does really contain an abundance of such dust-like particles, even ■when it appears to be most transparent and free from impurities. This may be readily demonstrated by admitting a single beam of sunshine into a darkened apartment, when the shining particles sus- pended in the atmosphere become immediately visible in the track of the sunbeam. Again, if a perfectly clean and polished mirror be placed with its face upward in a securely closed room, and left undisturbed for several days, its surface at the end of that time will be found to be dimmed by the settling upon it of minute dust, deposited from the atmosphere. There is no reason, therefore, for disbelieving that the air may always contain a sufficient number of organic germs for the production of infusorial animalcules. A certain degree of doubt, however, still remains respecting the origin of some kinds of infusoria, owing to the fact that they will make their appearance, under some circumstances, in organic infu sions which have been subjected to a boiling temperature and after- ward kept in hermetically closed vessels. The most recent and perhaps the most satisfactory experiments of this kind are those of Prof. Jeffries Wyman,' who operated with infusions of both animal and vegetable substances. He boiled these infusions undei the ordinary pressure of the atmosphere, that is, at a temperature of 212° F., for periods varying from fifteen minutes to two hours, in glass vessels so arranged that the atmospheric air could only gain access to their interior through tubes filled with red-hot iron wire. Any germs passing into the solution with the atmosphere would undoubtedly, therefore, be destroyed by contact with the heated iron. Nevertheless, he found, after some days, that living infusoria had made their appearance in the solutions. In other instances he placed the fresh solutions in hermetically sealed glass vessels, which were then smbmerged, for from five to fifteen minutes, in boiling water under a pressure of two to five atmospheres, that is, at a tem- perature of 250° to 307° F. In none of these experiments did the infusoria appear as soon aw ' American Journal of Science and Arts. Second Scries, vol. 84, p. 79. 550 NATURE OF EEPRODUOTION. in similar infuaions exposed to the air ; and althougL simple bell ing for a short time does not prevent the subsequent appearance of living organisms, yet a prolonged boiling at the ordinary tempera- ture, or a short. boiling at unusually high temperatures, does so pre- vent it. According to Prof. "Wyman, the appearance of infuaorial life is. absolutely prevented by exposure of the organic solution to ordinary boiling for five hours, or to boiling for fifteen minutes under a pressure of five atmospheres. The only difficulty, therefore, in supposing the infusoria which appear in these cases to be produced from previously existing germs, is that we must attribute to these germs the power of with- standing, for a certain time, a temperature at and above that of boiling water. This is not an impossible supposition, for two rea- sons. First, because this power is limited, as we have seen, even for these infusoria ; which do not appear in a solution which has once been boiled for a long time, or at a very high temperature, even though it be kept afterward at the ordinary temperature of the air. Secondly, because we know already that certain species of plants and animals will easily withstand an elevated temperature which is fatal to others. The amphibious reptiles, for example, are easily killed by being confined in water at 100° E., which is the natural temperature of the warm-blooded animals. Because the temperature of boiling water, therefore^ is fatal to the germs of many kinds of animals, we cannot be sure that it is necessarily fatal to those of all. Dr. S. Weir Mitchell ' has even found that vibriones, the infusoria which most frequently appear in boiled organic solu- tions, will also grow and thrive in the venom of the rattlesnake; when beginning to putrefy, and when it is still a deadly poison to all the higher animals. . It is therefore probable that the infusoria of organic solutions are produced from germs which have the power of withstanding, to a certain degree, the action of a high temperature. Animal and Vegetable Parasites. — This very remarkable group of organized bodies is distinguished by the fact that they live either upon the surface or in the interior of other animal or vegetable organisms. Thus, the mistletoe fixes itself on the branch^ ' Researches on the Yenom of the Rattlesnake Smithsonian Contributions to Knowledge. Washington, 1861, pp. 32, 53. ANIMAL AND VEGETABLE PARASITES. 551 of aged trees ; the Oidium albicans vegetates upon the mucous sur- faces of the mouth and pharynx ; the Botrytis Bassiana attacks the body of the silkworm, and plants itself in its tissues ; while many species of trematoid worms live attached to the gills of fish and of water-lissards. These parasites are usually nourished by the fluids of the animal whose body they inhabit. Bach particular species of parasite is found to inhabit the body of a particular species of animal, and is not found elsewhere. They are met with, moreover, as a general rule, only in particular organs, or even in particular parts of a single organ. Thus the Tricocephalus dispar is found only in the cfficum ; the Strongylus gigas in the kidney ; the Distoma hepati- cum in the biliary passages. The Distoma variegatum is found only in the lungs of the green frog, the Distoma cylindraceum in those of the brown. The Taenia solium is found in the intestine of the human subject in certain parts of Europe, while the Bothrio- cephalus latus occurs exclusively in others. It appears, therefore, as if some local combination of conditions were necessary to the production of these parasites ; and they have been supposed, accord- ingly, to originate by spontaneous generation in the localities where they are exclusively known to exist. A little consideration will show, however, that the above condi- tions are not, properly speaking, necessary or sufficient for the production, but only for the development of these parasites. All the parasites mentioned above reproduce their species by generation. They have male and female organs, and produce fertile eggs, often in great abundance. The eggs contained in a single female Ascaris are to be counted by thousands ; and in a tapeworm, it is said, even by millions. Now these eggs, in order that they may be hatched and produce new individuals, require certain special conditions which are favorable for their development; in the same manner as the seeds of plants require, for their germination and growth, a certain kind of soil and a certain supply of warmth and moisture. It is accordingly no more surprising that the Oxyuris vermicularis should inhabit the rectum, and the Ascaris lumbricoides the ileum, than that the Lobelia inflata should grow only in dry pastures, and r^e Lobelia cardinalis by the side of running brooks. The lichens flourish on the exposed surfaces of rocks and stone walls ; while the fungi vegetate in darkness and moisture, on the decaying trunks of dead trees. Yet no one imagines these vegetables to be spon- taneously generated from the soil which they inhabit. The truth 552 NATURE OF REPEODUCTION. is simply this, that if the animal or vegetable germ be deposited in a locality which affords the requisite conditions for its development it becomes developed; otherwise not. Each female Ascaris pro- duces, as we have said, many thousands of ova. Now, though the chances are very great against any particular one of these ova being accidentally transported into the intestinal canal of another individual, it is easy to see that there are many causes in opera- tion by which some of them might be so transported. By far the greater number undoubtedly perish, from- not meeting with the conditions necessary for their development. One in a thousand, or perhaps one in a million, is accidentally introduced into the body of another individual, and consequently becomes developed there into a perfect Ascaris. The circumstance, therefore, that particular parasites are confined to particular localities, presents no greater difliculty as to their mode of reproduction, than the same fact regarding other animal and vegetable organisms, Neither is there any difficulty in accounting for the introduction of parasitic germs into the interior of the body. The air and the food offer a ready means of entrance into the respiratory and digestive passages ; and, a parasite once introduced into the intes- tine, there is no difficulty in accounting for its presence in any of the ducts leading from or opening into the alimentary canal. Some parasites are known to insinuate themselves directly underneath the surface of the skin ; as the Pulex penetrans or " chiggo" of South America, and the Ixodes Americanus or "tick." Others, like the CEstrus bovis, penetrate the integument for the purpose of depositing their eggs in the subcutaneous areolar tissue. Some may even gain an entrance into the bloodvessels, and circulate in this way all over the body. Thus the Filaria rubella is found alive in the bloodvessels of the frog, the Distoma haematobium in those of the human subject, and a species of Spiroptera in those of the dog. It is easy to see, therefore, how, by such means, parasitic germs may be conveyed to any part of the body ; and may even be deposited, by accidental arrest of the circulation, in the substance of the solid organs. The most serious difficulty, however, in the way of accounting for the production of parasitic organisms, was that presented by the existence of a class known as the encysted or sexless entozoa. These parasites for the most part occupy the interior of the solid organs and tissues, into which they could not have gained access by the ANIMAL AND VEGETABLE PAKASITES. 553 mucous canals. Thus the Ccenurus cerebralis is found imbedded in the substance of the brain, the Trichina spiralis in the voluntary muscles, and the Cysticercus cellulosse in the areolar tissue of va- rious parts of the body. They are also distinguished from all other parasites by two peculiar characters. First, they are enclosed in a distinct cyst, with which they have no organic connection and from which they may be read- ily separated ; and secondly, ^'g- J 80. their generative organs are either imperfectly developed or. altogether wanting. The Trichina spiralis, for example, . (Fig. 180,) is enclosed in an ovoid cyst, composed of an organic material deposited in ° , 111 Triohiha Spiralis; fi:om muflcles of thigh of concentric layers; the whole human »ubject. Magnified M dlametew. enveloped in a membranous or tubular prolongation tapering from the two extremities. The worm lies loose in the central cavity of the cyst, coiled up in a spiral form. Now we have seen that it is easy to account for the conveyance of these or any other parasites into the interior of vascular organs and tissues ; the eggs from which they are produced being trans- ported by the bloodvessels to any part of the body, and there re- tained by a local arrest of the cipillary circulation. In the case of the encysted entozoa, however, we have a much greater difficulty ; since many of these parasites are entirely without sexual organs or generative apparatus of any sort, nor have they ever been dis- covered in the act of producing eggs, or of developing in any manner a progeny similar to themselves. It appears, accordingly, difficult to understand how animals, which are without a sexual apparatus, shbuld have been produced by sexual generation. As it is certain that they can have no progeny, it would seem equally evident that they must have been produced without a parentage. This difficulty, however, serious as it at first appears, is susceptible of a very simple explanation. The case is in many respects analogous to that of the maggots, hatched from the eggs of flies in putrefying meat. These maggots are also without sexual organs; for they are still imperfectly developed, and in a kind of embryonic condi- tion. It is only after their metamorphosis into perfect insects, that generative organs are developed and a distinction between the 554 NATURE OF REPRODUCTION, Pig. 181. sexes manifests itself. This is, indeed, more or less the case with all animals and with all vegetables. The blossom, which is the sexual apparatus of the plant, does not appear, as a general rule, until the growth of the vegetable has continued for a certain time,' and it has acquired a certain age and strength. Even in the human subject the sexual organs, though present at birth, are still very imperfectly developed as to size, and altogether inactive in func- tion. It is only later that these organs acquire their full growth, and the sexual characters become complete. In very many of the lower animals the sexual organs are entirely absent at birth, and appear only at a later period of development. Now the encysted or sexless entozoa are simply the undeveloped young of other para- sites which propagate by sexual generation.; the membrane in which they are inclosed being either an embryonic envelope, or else an adventitious cyst formed round the para- sitic embryo. These embryos have come, in the natural course of their migrations, into a situation which is not suitable for their com- plete development. Their development is accordingly arrested at that point; and the parasite never reaches the adult condition, until removed from the situation in which it has been placed, and transported to another locality. The above explanation has been demon- strated to be the true one, more particularly with regard to the Taenia, or tapeworm, and several varieties of Cysticercus. The Tsenia' (Mg. l81) is a parasite of which different species are found in the intestine of the human subject, the dog, cat, fox, and other of the lower animals. Its upper extremity, termed the " head," con- sists of a nearly globular mass, presenting upon its lateral surfaces a set of four muscular disks, or "suckers," and terminating anteriorly in a conical projection which is provided with a crown of curved processes or hooks, by which the parasite attaches itself to the intestinal mucous membrane. To this " head" succeeds a slender ribbon-shaped neck, which is at first smooth, but T.SSIA. ANIMAL AND VEGETABLE PARASITES. 555 which soon becomes transversely -wrinkled, and afterward divided into distinct rectangular pieces or " articulations." These articula- tions multiply by a process of successive growth or budding, from the wrinkled portion of the neck ; and are constantly removed farther and farther from their point of origin by new ones formed behind them. As they gradually descend, by the process of growth, farther down the body of the tapeworm, they become larger and begin to exhibit a sexual apparatus, developed in their interior., In each fully formed articulation there are contained both male and female organs of generation ; and the mature eggs, which are produced in great numbers, are thrown off together with the articu- lation itself from the lower extremity of the tapeworm. Since the articulations are successively produced, as we have mentioned above, by budding from the neck and the back part of the head, the para- site cannot be effectually dislodged by taking away any portion of the body, however large ; since it is subsequently reproduced from the head, and continues its growth as before. But if the head itself be removed from the intestine, no further reproduction of the articu- lations can take place. The Oysticercus is an encysted parasite, different varieties of which are found in the liver, the peritoneum, and the meshes of the areolar tissue in various parts of the body. It consists (Fig. 182) first, of a globular sac, or cyst (a), which is not adherent to the tissues of the organ in which the parasite is found, but may be easily sepa- Fig. 182. Fig. 183. Ctsticebcus. — a. External cjst. b In- teroal sac, coQtalniag fluid, o. I^arrow canal, formed by inrolntloR 'of walls of sac, at the bottom of which is the head of the tienia. Ctsticercub, unfolded. rated from them. In its interior is found another sac (h), lying loose in the cavity of the former, and filled with a serous iluid. This second sac presents, at one point upon its surface, a puckered depression, leading into a long, narrow canal (c). This canal, which is formed by an involution of the walls of the second sac, presents 556 NATURE OF BEPRODUCTIOU. at its bottom a small globular mass, like the head of the Taenia, provided with suckers and hooks, aud supported upon a short slender neck. If the outer investing sac be removed, the narrow canal just described may be everted by careful manipulation, and the parasite will then appear as in Fig. 183, with the head and neck resembling those of a Taenia, but terminating behind in a dropsical sac-like swelling, instead of the chain of articulations which are characteristic of the fully formed tapeworm. Now it has been shown, by the experiments of Kiichenmeister, Siebold, and others, that the Cysticercus is only the imperfectly developed embryo; or young, of the Taenia. "When the mature articulation of the tapeworm is thrown off, as already mentioned, from its posterior extremity, the eggs which it incloses have already passed through a certain period of devielopment, so that each one contains an imperfectly formed embryo. The articulation, contain- ■ ing the eggs and embryos, is then taken, with the food, into the stomach of another animal ; the substance of the articulation, to- gether with the external covering of the eggs, is destroyed by di- gestion, and the embryos are thus set free. They then penetrate through the walls of the stomach, into the neighboring organs or the areolar tissue, and becoming encysted in these situations, are there developed into cysticerci, as represented in Fig. 182. After- ward, the tissues in which they are contained being devoured by a third animal, the cysticercus passes into the intestine, fixes itself to the mucous membrane, and, by a process of budding, produces the long tape-like series of articulations, by which it is finally con- verted into the full-grown Taenia. Prof. Siebold found the head of the Cysticercus fasciolaris, met with in the liver of rats and mice, presenting so close a resem- blance to the Taenia crassicollis, inhabiting the intestine of the cat, that he was led to believe the two parasites to be identical. This identity was, in fact, proved by the experiments of Kiichenmeister ; and Siebold afterward demonstrated' the same relation to exist between the Cysticercus pisiformis, found in the peritoneum of rab- bits, and the T^nia serrata, from the intestine of the dog. This experimenter succeeded in administering to dogs a quantity of the cysticerci, fresh from the body of the rabbit, mixed with milk ; and on killing the dogs, at various periods after the meal, from three hours to eight weeks, he found the cysticerci in various stages of ' In Buffalo Medical Journal, Feb. 1853 ; also in Siebold on Tape and Cystio W^orms, Sydenham translation : London, 1857, p. 59. ANIMAL AND VEGETABLE PARASITES. 557 development in the intestine, and finally converted into the full grown Taenia, with complete articulations and mature eggs. Dr. Kiichenmeister' has also performed the same experiment, with success, on the human subject. A number of cysticerci were ad- ministered to a criminal, at different periods before his execution, varying from 12 to 72" hours ; and upon post-mortem examination of the body, no less than ten young taeniae were found in the intestine, four of which could be distinctly recognized as specimens of Taenia solium. On the other hand, both Leuckart and Kiichenmeister' have shown that the eggs of Taenia solium, introduced into the body of the pig, will give rise to the development of Cysticercus cellulosae ; thus demonstrating that the two kinds of parasites are identical in their nature, and differ only in the manner and degree of their development. Finally, it is now known, principally from the investigations of Leuckart,' that Trichina spiralis is reproduced, in a similar manner, by the process of generation. This parasite is found, as above de- scribed, in an encysted and sexless condition, in the muscular tissue of the human subject, and also in that of the pig. AVhen the flesh of the pig, infested with such parasites, is taken, either raw or im- perfectly cooked, into the stomach, the cysts are digested, and the worm, set free from its confinement, rapidly increases in size in the intestine, and acquires fully developed sexual organs ; — so that the females, after the first week, produce an abundance of living young. These imperfect or embryonic worms penetrate the mucous mem- brane of the intestine, in great numbers, and find their way into the muscular tissue, where they become encysted; and there remain without further development, until again transferred into the stom- mach of a living animal. There remains, accordingly, no good reason for believing that even the encysted parasites are produced by spontaneous genera- tion. Whatever obscurity may hang round the origin or repro- duction of this class of animals, the direct investigations of the physiologist always tend to show that they do not, in reality, form any exception to the general law in this respect ; and the most probable opinion, from the facts at present within our knowledge, is that organized beings, animal and vegetable, wherever they may be found, are always the progeny of previously existing parents. 1 On Animal and Vegetable Parasites, Sydenham translation: London. 1857, p 115. s Op. cit., p. 120. ' Untersuchungen iiber Trichina spiralis. Leipzig, 1860. 558 PEXUAL GENERATIOJSr. CHAPTEE II. ON SEXUAL GENERATION, AND THE MODE OP ITS ACCOMPLISHMENT. Fig. 184. The function of generation is performed bj means of two sets of organs, each of which gives origin to a peculiar product, capable of uniting with the other so as to produce a new individual. These two sets of organs, belonging to the two different sexes, are called the male and female organs of generation. The female organs produce a globular body called the germ, or egg, which is capable of being developed into the body of the young animal or plant ; the male organs produce a substance which is necessary to fecundate the germ, and enable it to go through with its natural growth and development. Such are the only essential and uni- versal characters of the organs of gene- ration. These organs, however, exhibit various additions and modifications in different classes of organized beings, while they show throughout the same fundamental and essential characters. In the flowering plants, for example, the blossom, which is the generative apparatus (Fig. 184), consists first of a female organ containing the germ (a), situated usually upon the highest part of the leaf-bearing stalk. This is surmounted by a nearly straight column, termed the pistil (&), dilated at its summit into a globular expansion, and occupying the centre of the flower. Around it are arranged several slender filaments, or stamens, bear- ing upon their extremities the male organs, or anthers (c, c). The BlOSEOH of CoSTOLTULns PURPUBEUB. (Morula^ glory.) — a. Germ. h. Pistil, c. c. Stamens^ with anthers, d. Corolla, c. Calyx. SEXUAL GKNEBATION. 659 Fig. 185. "whole is surrounded by a circle or crown of delicate and brilliantly colored leaves, termed the corolla {d), which is frequently provided with a smaller sheath of green leaves outside, called the calyx (e). The anthers, when arrived at maturity, discharge a fine organic dust, called the pollen, the granules of which are caught upon the extremity of the pistil, and then' penetrate downward through its tissues, until they reach its lower extremity and come in contact with the germ. The germ thus fecundated, the process of genera- tion is accomplished. The pistil, anthers, and corolla wither and fall off, while the germ increases rapidly in size, and changes in form and texture, until it ripens into the mature fruit or seed. It is then ready to be separated from the parent stem ; and, if placed in the proper soil, will germinate and at last produce a new plant similar to the old. In the above instance, the male and female organs are both situated upon the same flower; as in the lily, the violet, the con- volvulus, &o. In other cases, there are separate male and female flowers upon the same plant, of which the male flowers produce only the pollen, the female, the germ and fruit. In others still, the male and female flowers are situated upon different plants, which otherwise resemble each other, as in the willow, poplar, and hemp. In animals, the female organs of generation are called ovaries, since it is in them that the egg, or "ovum," is produced. The male organs are the testicles, which give origin to the fecun- dating product, or "seminal fluid," by which the egg is fer- tilized. "We hJive already men- tioned above that in the articula- tions of the tapeworm the ovaries and testicles are developed to- gether. (Fig. 185.) The ovary (a, a, a) is a series of branching follicles terminating in rounded extremities, and communicating with each other by a central canal. The testicle (6) is a narrow, convoluted tube, very much folded SlNOLB ARTlCL'LATIOir OP T^NI, Cbabsicollis, from small intestiue of cat- a, a, a. Ovary ailed with eggs. b. Testicle, c Geaital orifice. 560 SEXUAL GENEBATION. upon itself, whicli opens by an external orifice (c) upon the lateral border of the articulation, about midway between its two ex- tremities. The spermatic fluid prpduced in the testicle is intro- duced into the female generative passage, which opens at the same spot, and, penetrating deeply into the interior, comes in contact with the eggs, which are thereby fecundated and rendered fertile. The fertile eggs are afterward set free by the rupture or decay of the articulation, and a vast number of young are produced by their development. In snails, also, and in some other of the lower animals, the ovaries and testicles are both present in the same individual ; so that these animals are sometimes said to be " hermaphrodite," or of double sex. In reality, however, it appears that the male and female organs do not come to maturity at the same time ; but the ovaries are first developed and perform their function, after which the tes- ticles come into activity in their turn. The same individual, there- fore, is not both male and female at any one time; but is first female and afterward male, exercising the two generative functions at different ages. In all the higher animals, however, the two sets of generative organs are located in separate individuals; and the species is consequently divided into two sexes, male and female. All that is absolutely requisite to constitute the two sexes is the existence of testicles in the one, and of ovaries in the other. Beside these, however, there are, in most instances, certain secondary or acces- sory organs of generation, which assist more or less in the accom- plishment of the process, and which occasion a greater diflerence in the anatomy of the two sexes. Such are the uterus and mammary glands of the female, the vesicul» seminales and prostate gland of the male. The female naturally having the immediate care of the young after birth, and the male being occupied in providing food and protection for both, there are also corresponding differ- ences in the general structure of the body, which affect the whole external appearance of the two sexes, and which even show them- selves in their mental and moral, as well as in their physical characteristics. In some cases this difference is so excessive that the male and female would never be recognized as belonging to the same species, unless they were seen in company with each other. Not to mention some extreme instances of this among insects and other invertebrate animals, it will be sufiicient to refer to the well- Irnown examples of the cock and the hen, the lion and lioness, the SEXUAL GEUEBATION. 561 buck and the doe. In the human species, also, the distinction between the sexes shows itself in the mental constitution, the dis- position, habits, and pursuits, as well as in the general conforma- tion of the body, and the peculiarities of external appearance. We shall now study more fully the character of the male and female organs of generation, together with their products, and the manner in which these are discharged from the body, and brought into relation with each other. 86 662 KGG AND FBUALE OBOAKS OF GENEBATION. CHAPTEE III. ON THE EGG, AND THE FEMALE ORGANS OP GENERATION. Fig. 186. The egg is a globular body which varies considerably in size in different classes of animals, according to the peculiar conditions under which its development is to take place. In the frog it mea- sures ^j of an inch in diameter, in the lamprey ^^, in quadrupeds and in the human species tsu- It consists, first, of a membranous external sac or envelope, the vitelline membrane; and secondly, of a spherical mass inclosed in its interior, called the vitellus. The vitelline niemhrane in birds and reptiles is very thin, measur- ing often not more than y^i^^ of an inch in thickness, and is at the same time of a somewhat fibrous texture. In man and the higher animals, on the contrary, it is perfectly smooth, structure- less and transparent, and is about j^Vir of an inch in thickness. Notwithstanding its delicate and transparent appearance, it has a considerable degree of resistance and elasticity. The egg of the human subject, for example, may be perceptibly flattened out under the microscope by pressing with the point of a needle upon the slip of glass which covers it ; but it still remains unbroken, and when the pressure is removed, readily resumes its globular form. When the egg is somewhat flattened under the microscope in this way, by pressure of the glass slip, the apparent thickness of the vitelline membrane is increased, and it then appears (Fig, 186) as a rather wide, colorless, and pellucid border or zone, surrounding the granu- lar and opaque vitellus. Owing to this appearance, it has some- times received the name of the " zona pelluoida." The name of ErHAir OrrM, roagnifled 8S diameters, u. VUelliuemembrane. b. Vitellus, c. GermioatlTeTesicle. d. Germinatire spot. SGG AND FEMALE OB6AXS OP GENEBATION. 563 vitelline membrane, however, is the one more generally adopted, and is also the more appropriate of the two. The vitellus (6) is a globular, semi-solid mass, contained within the vitelline membrane. It consists of a colorless albuminoid sub- stance, with an abundance of minute molecules and oleaginous granules scattered through it. These minute oleaginous masses give to the vitellus a partially opaque and granular aspect under the microscope. Imbedded in the vitellus, usually near its surface and almost immediately beneath the vitelline membrane, there is a clear, colorless, transparent vesicle (c) of a rounded form, known as the germinative vesicle. In the egg of the human subject and of the quadrupeds, this vesicle measures gjg to 5^^ of an inch in diameter. It presents upon its surface a dark spot, like a nucleus {d), which is known ^'8' ^^'^■ by the name of the germinative spot. The germinative vesicle, with its nucleus-like spot, is often partially concealed by the granules of the vitellus by which it is sur- rounded, but it may always be discovered by careful examination. If the egg be ruptured by excessive pres- humah otuk, ruptured by sure under the microscope, the vitellus is ?"»"■": "'■■"'ing the viteiius ^ ^ partiallx expelled, the germiDa- seen to have a gelatinous consistency. It tire veBicie at a, and the smootii is gradually expelled from the vitelline ^;^'^" "' *"' '"""''"' "'™- cavity, but still retains the granules and oil globules entangled in its substance. (Fig. 187.) The edges of the fractured vitelline membrane, under these circumstances, present a smooth and nearly straight outline, without any appearance of laceration or of a fibrous structure. The membrane is, to all ap- pearance, perfectly homogeneous. The most essential constituent of the egg is the vitellus. It is from the vitellus that the body of the embryo will afterward be formed, and the organs of the new individual developed. The vitelline membrane is merely a protective inclosure, intended to secure the vitellus from injury, and enable it to retain its figure during the early periods of development. The egg, as above described, consists therefore of a simple vitellus of minute size, and a vitelline membrane inclosing it. It is such an egg which is found in the human subject, the quadru- peds, most aquatic reptiles, very many fish, and some invertebrate animals. In nearly all those species, in fact, where the fecundated 564 EGG AND FEMALE ORGANS OF GENERATION. eggs are deposited and hatched in the water, as -well as those in which they are retained in the body of the female until the develop- ment of the young is completed, such an egg as above described is sufficient for the formation of the embryo ; since during its develop, ment it can absorb freely, either from the water in which it floats, or from the mucous membrane of the female generative organs, the requisite supply of nutritious fluids. But in birds and in the terrestrial reptiles, such as lizards, tortoises, &o., where the eggs are expelled from the body of the female at an early period, and incubated on land, there is no external source of nutrition, to pro- vide for the support of the young animal during its development. In these instances accordingly the vitellus, or " yolk," as it is called, is of very large size ; and the bulk of the egg is still further in- creased by the addition, within the female generative passages, of layers of albumen and various external fibrous and calcareous envelopes. The essential constituents of the egg, however, still remain the same in character, and the process of embryonic deve- lopment follows the same general laws as in other cases. The eggs are produced in the interior of certain organs, situated in the abdominal cavity, called the ovaries. These organs consist of a number of globular sacs, or follicles, known as the "Graafian follicles," each one of which contains a single egg. The follicles are connected with each other by a quantity of vascular areolar tissue, which binds them together into a well-defined and consistent mass, covered upon its exterior by a layer of peritoneum. The egg has sometimes been spoken of as a " product," or even as a "secretion" of the ovary. Nothing can be more inappropriate, however, than to compare the egg with a secretion, or to regard the ovary as in any respect resembling a glandular organ. The egg is simply an organized body, growing in the ovary like a tooth in its follicle, and forming a constituent part of the body of the female. It is destined to be finally separated from its attachments and thrown off; but until that time, it is, properly speaking, a part of the ovarian texture, and is nourished like any other portion of the female organism. The ovaries, accordingly, since they are directly concerned in the production of the eggs, are to be regarded as the essential parts of the female generative apparatus. Beside them, however, there are usually present certain other organs, which play a secon- dary or accessory part in the process of generation. The most important of these accessory organs are two symmetrical tubes, or EGG AND FEMALE OBGANS OF GENERATION. 565 Fig. 188. o.viducts, which are destined to Tieceive the eggs at their internal extremity and convey them to the external generative orifice. The mucous membrane lining the oviducts is also intended to supply certain secretions during the passage of the egg, which are requi- site either to complete its, structure, or to provide for the nutrition of the embryo. In the frog, for example, the oviduct commences at the upper part of the abdomen, by a rather wide orifice, which communicates directly with the peritoneal cavity. It soon after contracts to a narrow tube, and pursues a zigzag course down the side of the abdomen (Fig. 188), folded upou itself in convolutions, like the small intestine, until it opens, near its fellow of the opposite side, into the " cloaca" or lower part of the intestinal canal. The oviducts present the same general characters with those described above, in nearly all species of reptiles and birds ; though there are some modi- fications, in particular instances, which do not require any special notice. The ovaries, as well as the eggs which they contain, undergo at particular sea- sons a periodical development or increase in growth. If we examine the female frog in the latter part of summer or the fall, we shall find the ovaries presenting the appearance of small clusters of minute and nearly colorless eggs, the smaller of which are perfectly transparent and not over t\^ of an inch in diameter. But in the early spring, when the season of reproduction approaches, the ovaries will be found in- creased to four or five times their former size, and forming large lobulated masses, crowded with dark-colored opaque eggs, measur- ing y'j of an inch in diameter. At the approach of the generative season, in all the lower animals, a certain number of the eggs, which were previously in an imperfect and inactive condition, begin to increase in size and become somewhat altered in structure. The vitellus more especially, which was before colorless and transparent, becomes granular in texture as well as increased in volume ; and assumes at the same time, in many species of animals, a black, Female Gesebative Or- gans OP Froo. — a, a. Ovaries. 6, b. Oviducts, c, c. Thoii- internal orifices. (2. Cloaca, Bhowing exter- nal orifices of oviducts. EGG AND FEMALE OBGANS OF GENERATION. brown, yellow, or orange color. In the human subject, however the change consists only in an increase of size and granulation, without any remarkable alteration of color. The eggs, as they ripen in this way, becoming. enlarged and changed in texture, gradually distend the Graafian follicles and project from the surface of the ovary. At last, when fully ripe, they are discharged by a rupture of the walls of the follicles, and, passing into the oviducts, are conveyed by them to the external generative orifice, and there expelled. In this way, as successive seasons come round, successive crops of eggs enlarge, ripen, leave the ovaries, and are discharged. Those which are to be expelled at the next generative epoch may always be recognized by their greater degree of development; and in this way, in many animals, the eggs of no less than three different crops may be recongized in the ovary at once, viz., 1st, those which are perfectly mature and ready to be discharged ; 2d, those which are to ripen in the follow- ing season ; and 3d, those which are as yet altogether inactive and undeveloped. In most fish and reptiles, as well as in birds, this regular process of maturation and discharge of eggs takes place but once a year. In different species of quadrupeds it may take place annually, semi-annually, bi-monthly, or even monthly; but in every instance it recurs at regular intervals, and exhibits accord- ingly, in a marked degree, the periodic character which we have seen to belong to most of the other vital phenomena. Action of the Ovidttcts and Female Generative Passages. — In frogs and lizards, the ripening and discharge of the eggs take place, as above mentioned in the early spring. At the time of leaving the ovary, the eggs consist simply of the ^'B" ^^^' dark-colored and granular vitellus, inclosed in the vitelline membrane. They are then received by the inner ^*** V^M^'^^ extremity of the oviducts,- and carried • ^t^%^ downward by the peristaltic move- ^ ment of these canals, aided by the matuee Progs' EaoB.—n. While more powcrful Contraction of the Btiii ia the ovavy b. After passing abdominal musclcs. During the pas- tlirough the oviduct. '-' sage of the eggs, moreover, the mucous membrane of the oviduct secretes a colorless, viscid, albuminoid substance, which is deposited in successive layers round each egg, forming a thick and tenacious coating or envelope. (Fig. 189.) When the eggs are finally discharged, this albuminoid matter EGG AND FEMALE ORGANS OF GENERATION, 567 absorbs the water in which the spawn is deposited, and swells np into a transparent gelatinous mass, in which the eggs are separately imbedded. This substance supplies, by its subsequent liquefaction and absorption, a certain amount of nutritious material, during the development and early growth of the embryo. In the terrestrial reptiles and in birds, the oviducts perform a still more important secretory function. In the common fowl, the ovary consists^ as in the frog, of a large iiumber of follicles, loosely Connected by areolar tissue, in which the eggs can be seen in different stages of development. (Fig. 190, a.) As the egg which is approach- ing maturity enlarges, it distends the cavity of its follicle, and pro- jects farther from the general surface of the ovary ; so that it hangs at last into the peritoneal cavity, retained only by the attenuated wall of the follicle, and a slender pedicle through which run the bloodvessels by which its circulation is supplied. A rupture of the follicle then occurs, at its most prominent part, and the egg is dis- charged from the lacerated, opening. At the time of its leaving the ovary, the egg of the fowl consists of a large, globular, orange-colored vitellus, or " yolk," inclosed in a thin and transparent vitelline membrane. Immediately under- neath the vitelline membrane, at one point upon the surface of the vitellus, is a round white spot, consisting of a layer of minute granules, termed the " picatricula." It is in the central part of the cicatricula that the germinative vesicle is found imbedded, at an early stage of the development of the egg. At the time of its discharge from the ovary, the germinative vesicle has usually dis- appeared ; but the cicatricula is still a very striking and important part of the vitellus, as it is from this spot that the body of the chick begins afterward to be developed. At the same time that the egg protrudes from the surface of the ovary, it projects into the inner orifice of the oviduct; so that, when discharged from its follicle, it is immediately embraced by the upper or fringed extremity of this tube, and commences its passage down- ward; In the fowl, the musfcular coat of the oviduct is highly deve- loped, and its peristaltic contractions gently urge the egg from above downward, precisely as the oesophagus or the intestines transport the food in a similar direction. While passing through the first two or three inches of the oviduct (c, d), where the mucous mem brane is smooth and transparent, the yolk merely absorbs a certain quantity of fluid, so as to become more flexible and yielding in con- sistency. It then passes into a second division of the generativa EGG AND FEMALE OBGANS OP GENEBATION. canal, in which, the mucous membrane is thick and glandular in texture, and is also thrown into numerous longitudinal folds, which project into the cavity of the oviduct. This portion of the oviduct {d, e), extends over about nine inches of its entire length. In its upper part, the mucous membrane secretes a viscid material, by which the yolk is encased, and which soon consolidates into a gela- tinous, membranous deposit ; thus forming a second homogeneous layer, outside the vitelline membrane. Now the peristaltic movements of this part of the oviduct are such as to give a rotary, as well as a progressive motion to the egg ; and the two extremities of the membranous layer described above become, accordingly, twisted, in opposite directions into two fine cords, which run backward and forward from the opposite poles of the egg. These cords are termed the " chalazse," and the mem- brane with which they are connected, the " chalaziferous membrane." Throughout the remainder of the second division of the oviduct, the mucous membrane exudes an abundant, gelatinous, albuminoid substance, which is deposited in successive laye;rs round the yolk,, inclosing at the same time the chalaziferous membrane and the chalazse. This substance, which forms the so-called albumen, or " white of egg," is semi-solid in consistency, nearly transparent, and of a faint amber color. It is deposited in greater abundance in front of the advancing egg than behind it, and forms accordingly a pointed or conical projection in front, while behind, its outline is rounded oif, parallel with the spherical surface of the yolk. In this way, the egg acquires, when covered with its albumen, an ovoid form, of , which one end is round, the other pointed; the pointed extremity being always directed downward, as the egg descends along the oviduct. In the third division of the oviduct (/), which is about three and a half inches in length, the mucous membrane is arranged in longi- tudinal folds, which are narrower and more closely packed than in the preceding portion. The material secreted in this part, and de- posited upon the egg, condenses into a firm fibrous covering, com- posed of three different layers which closely embrace the surface of the albuminous mass, forming a tough, flexible, semi-opaque envelope for the whole. These layers are known as the external, middle, and internal fibrous membranes of the egg. Finally the egg passes into the fourth division of the oviduct (j-), which is wider than the rest of the canal, but only a little over two inches in length. Here the mucous membrans, which is arranged EGO AND FEMALE ORGANS OP GENERATION. 569 Fig. 190. in abundant, projecting, leaf-like villosities, exudes a fluid very rich in calcareous salts. The most external of the three membranea just described is permeated by this fluid, and very soon the calcare- ous matter begins to .crystallize in the interstices of its fibres. This deposit of calcareous matter goes on, growing constantly thicker and more condensed, until the entire external membrane is converted into a white, opaque, brittle, calcareous shell, whiA incloses the remaining portions and protects them from ex- ternal injury. The egg is then driven outward by the contraction of the muscular coat through a narrow por- tion of the oviduct (A), and, gradually dilating the passages by its conical extremity, is finally discharged from the external orifice. The egg of the fowl, after it has been discharged from the body, con- sists, accordingly, of various parts ; some of which, as the yolk and the vitelline membrane, entered into its original formation, while the remain- der have been deposited round it dur- ing its passage through the oviduct. On examining such an egg (Fig. 191), we find externally the calcareous shell (h), while immediately beneath it are situated the middle and internal fibrous shell-membranes (e, /). Soon after the expulsion of the egg there is a partial evaporation of its watery ingredients, which are replaced by air penetrating through the pores Pemalb Gbhbratite Okoans of Fowl.— «. Ovary, b. Graafian follicle, from which the eg? has jnat been discharged. <;. Yolk, entering npper extremity of ovidacfc. d,e. Second divislou of oviduct, in which chalaziferous membrane, chalazs, aod albumen are formed. /. Third portion, 1q which the fibrous shell membranes are produced, g. Fourth portion laid open, showing egg completely formed, with calcareous shell. A. Narrow canal through which the egg is discharged. 570 ESQ AND FEMALE OEGANS OP GENERATION. of the shell at its -rounded extremity. The air thus introduced accumulates between the middle and internal fibrous membranes at this spot, separating them from each other, and forming a cavity or air-chamber (gr), which is always found between the two fibrous membranes at the rounded end of the egg. Next we come to the albumen or " white" of the egg {d); next to the chalaziferous mem- brane and chalazae (c) ; and finally to the vitelline membrane (i) Fig. 191. Diagram of Fowl's Eao. — ra. Yolk. &. Vitelline membrane, c. Chalaziferons membrane, d. Albumen, e, /. Middle and internal shell membranes, g. Air-chamber, h. Calcareous shell. inclosing the yolk (a). After the expulsion of the egg, the external layers of the albumen liquefy ; and the vitellus, being specifically lighter than the albumen, owing to the large proportion of oleagin- ous matter which it contains, rises toward the surface of the egg, with the cicatricula uppermost. This part, therefore, presents itself almost immediately on breaking open the egg upon its lateral surface, and is placed in the most favorable position for, the action of warmth and atmospheric air in the development of the chick. The vitellus, therefore, is still the essential and constituent portion of the egg ; while all the other parts consist either of nutritious mate- rial, likei the albumen, provided for the support of the embryo, or of protective envelopes, like the shell and the fibrous membranes. In the quadrupeds, another and still more important modification of the oviducts takes place. In these animals, the egg, which is originally very minute in size, is destined to be retained within the generative passages of the female during the development of the embryo. While the upper part of the oviduct, therefore, is quite narrow, .and intended merely to transmit the egg from the ovary. EGG AND FEMALK ORGANS OP GENERATION. 571 and to supply it with a little albuminous secretion, its lower por- tions are very much increased in size, and are lined, moreover, with a mucous membrane, so constructed as to provide for the protection and nourishment of the embryo, during the entire period of gesta- tion. The upper and narrower portions of the oviduct are known as the "Fallopian tubes" (Fig. 192); while the lower and more Fig. 192. Utebdb akd Otabies op the Sow.— o, a. Ovaries. R, 6. Fallopian talies. c,c. Hams of atoruB. d. Body of uterus, e Vagina. highly developed portions constitute the uterus. These lower por- tions unite with each other upon the median line near their infe- rior termination, so as to form a central organ, termed the " body" of the uterus ; while the remaining ununited parts are known as its '• cornua" or ." horns." In the human subject, the female generative apparatus presents the following peculiarities. The ovaries consist of Graafian follicles, which are imbedded in a somewhat dense areolar tissue, supplied with an abundance of bloodvessels. The entire mass is covered with a thick, opaque, yellowish white layer of fibrous tissue called the " albugineous tunic." Over the whole is a layer of peritoneum, which is reflected upon the vessels which supply the ovary, and is continuous with the broad ligaments of the uterus. The oviducts commence by a wide expansion, provided with fringed edges, called the " fimbriated extremity of the Fallopian tube." The Fallopian tubes themselves are very narrow and con- voluted, and terminate on each side in the upper part of the body of the utefus. In the human subject, the body of the uterus is so much developed at the expense of the cornua, that the latter hardly appear to have an existence ; and in fact no trace of them is visible externally. But on opening the body of the uterus its cavity is 572 EGG AND FEMALE ORGANS OP GENERATION, seen to be nearly triangular in shape, its two superior angles run- ning out on each side to join the lower extremities of the Fallopian tubes. This portion evidently consists of the cornua, which have been consolidated with the body of the uterus, and enveloped in its thickened layer of muscular fibres. Fig. 193. Gesebatite OEa^NS OF HvMAs Fehale. — a, a. Oraries. i,t. Fallopian tubes. t. Body of uterus, d. Cervix, n. Vagina. The cavity of the body of the uterus terminates below by a con- stricted portion termed the os internum, by which it is separated from the cavity of the cervix. These two cavities are not only different from each other in shape, but differ also in the structure of their mucous membrane and the functions which it is destined to perform. The mucous membrane of the body of the uterus in its usual condition is smooth and rosy in color, and closely adherent to the subjacent muscular tissue. It consists of minute tubular follicles somewhat similar to those of the gastric mucous membrane, ranged side by side, and opening by distinct orifices upon its free surface. The secretion of these follicles is destined for the nutrition of the embryo during the earlier periods of its formation. The internal surface of the neck of the uterus, on the other hand, is raised in prominent ridges which are arranged usually in two lateral sets, diverging from a central longitudinal ridge ; presenting the appearance known as the " arbor vitse uterina." The follicles of this part of the uterine mucous membrane are different in struc- ture from those of the foregoing. They are of a globular or sac- EGG AND FEMALE ORGANS OP GENERATION. 673 like form, and secrete a very firm, adhesive, transparent mucus, which is destined to block up the cavity of the cervix during ges- tation, and guard against the accidental displacement of the egg. Some of these follicles are frequently distended with their secretion, and project, as small, hard, rounded eminences, from the surface of the mucous membrd,ne. In this condition they are sometimes designated by the name of " ovula Nabothi," owing to their having been formerly mistaken for eggs, or ovules. The cavity of the cervix uteri is terminated below by a second constriction, the "os externum." Below this comes the vagina, which constitutes the last division of the female generative pas- The accessory female organs of generation consist therefore of ducts or tubes, by means of which the egg is conveyed from within outward. These ducts vary in the degree and complication of their development, according to the importance of the task assigned to them. In the lower orders, they serve merely to convey the egg rapidly to the exterior, and to supply it more or less abundantly with an albuminous secretion. In the higher classes and in the human subject, they are adapted to the more important function of retaining the egg during the period of gestation, and of providing during the same time for the nourishment of the young embryo. 574 KALE OBGANS OF GENEBATION. CHAPTEE IV. ON THE SPERMATIC FLUID, AND THE MALE ORGANS OF GENERATION, The mature egg is not "by itself capable of being developed into the embryo. If simply discharged from the orary and carried through the oviducts toward the exterior, it soon dies and is de- composed, like any other portion of the body separated from its natural connections. It is only when fecundated by the spermatic fluid of the male, that it is stimulated to continued development, and becomes capable of a more complete organization. The product of the male generative organs consists of a colorless, somewhat viscid, and albuminous fluid, containing an innumerable quantity of minute filamentous bodies, termed spermatozoa. The name spermatozoa has been given to these bodies, on account of their exhibiting under the microscope a very active and continu- ous movement, bearing some resemblance to that of certain animal- cules. Anatomical characters of the spermatozoa. — The spermatozoa of the human subject (Fig, 194, a) are about g^^ of an inch in length, according to the measurements of Kolliker, Their anterior extremity presents a somewhat flattened, triangular- shaped enlargement, termed the "head," The head constitutes about one - tenth part the entire length of the spermatozoon. The remaining portion is a very slender filamentous prolon- gation, termed the " tail," which tapers gradually backward, becoming so exceedingly delicate towards its extremity, that it is diflficult to be seen except when in motion. There is no further organization or internal structure to be detected in any part of the spermatozoon; and the whole appears to consist, so far as can be seen by the microscope, of a completely homogeneous, tolerably firm, albuminoid substance. The terms head and tail, therefore, as justly remarked by Bergmann and Leuckart,' are not used, when describing the different parts of the spermatozoon, in the same sense as that in which they would be applied to the corre- ' Verglelchende Fhysiologie. Stuttgart, 1852, MALE OBGAXS OF GENEBATIOK. 575 sponding parts of an animal, but simply for the sake of conveni- ence ; just as one might speak of the head of an arrow, or the tail of a comet. In the lower animals, the spermatozoa have usually the same general form as in the human subject; that is, they are slender filamentous bodies, with the anterior extremity more or less en- larged. In the rabbit they have a head which is roundish and flattened in shape, somewhat resembling the globules of the blood. In the rat (Fig. 194, b) they are much larger than in man, measur- ing nearly y^^ of an inch in length. The head is conical in shape, Fig. 194. Spkkhatozoa. — a. HnmaD. ft. Of Bat. >.-. Of Mesobnachus. HagaiSed 4S0 times. about one-twentieth the whole length of the filament, and often slightly curved at its anterior extremity. In the frog and in rep- tiles generally, the spermatozoa are longer than in quadrupeds. In the Menobranchus, or great American water-lizard, they are of very unusual size (Fig. 194, c), measuring not less than ^j of an inch in length, about one-third of which is occupied by the head, or enlarged portion of the filament. The most remarkable peculiarity of the spermatozoa is their 576 MALE OEQANS OF GKNEEATIOIT. very singular and active movement, to which we have already alluded. If a .drop of fresh seminal fluid be placed under the microscope, the numberless minute filaments with which it is crowded are seen to be in a state of incessant and agitated motion. This movement of the spermatozoa, in many species of animals, strongly resembles that of the tadpole ; particularly when, as in the human subject, the rabbit, &c., the spermatozoa consist of a short and well defined head, followed by a long and slender tail. Here the tail-like filament keeps up a constant lateral or vibratory move- ment, by which the spermatozoon is driven from, place to place in the spermatic fluid, just as the fish or the tadpole is propelled through the water._^ In other instances, as fof example in the water- lizard, and in some parasitic animals, the spermatozoa have a con- tinuous writhing or spiral-like movement, which presents a very peculiar and eldgant appearance when large numbers of them are viewed together. It is the existence of this movement which first suggested the name, of spermatozoa to designate the animated filaments of the spermatic fluid ; and which has led some writers to attribute to them an independent animal nature. This is, however, a very erroneous mode; of regarding them ; since they cannot properly he considered as animals, notwithstanding the active character of their movement, and the striking resemblance which it sometimes pre- sents to a voluntary act. The spermatozoa are organic forms, which are prod|iced in the testicles, and constitute a part of their tissue; just as the eggs, which are produced in the ovaries, natu- rally form a pajrt of the texture of these organs. Like the egg, also, the spermatozoon is destined to be discharged from the organ where it grew, and to retain, for a certain length of time afterward, its vital properties. One of the most peculiar of these properties is its power of keeping in constant motion ; which does not, how- ever, mark it as a distinct animal, but only distinguishes it as a peculiar structure belonging to the parent organism. The motion of a spermatozoon is precisely analogous to that of a ciliated epi- thelium cell. The movement of the latter will continue for some hours after it has been separated from its mucous membrane, pro- vided its texture be not injured, nor the process of decomposition allowed to commence. In the same manner, the movement of the spermatozoa is a characteristic property belonging to them, which continues for a certain time, even after they have been separated from the rest of the body. MALE ORGANS OF GENERATION. 577 In order to preserve their vitality, the spermatozoa must be kept at the ordinary temperature of the body, and preserved from the contact of the air or other unnatural fluids. In this way, they may be kept without difficulty many hours for purposes of examination. But if the fluid in which they are kept be allowed to dry, or if it be diluted by the addition of water, in the case of birds and quadrupeds, or if it be subjected to extremes of heat or cold, the motion ceases, and the spermatozoa themselves soon begin to disintegrate. The spermatozoa are produced in certain glandular-looking organs, the testicles, which are characteristic of the male, as the ova- ries are characteristic of the female. In man and all the higher animals, the testicles are solid, ovoid-shaped bodies, composed principally of numerous long, narrow, and convoluted tubes, the '' seminiferous tubes," somewhat similar in their general anatomical characters to the tubuli uriniferi of the kidneys. These tubes lie for the most part closely in contact with each other, so that nothing intervenes between them except capillary bloodvessels and a little areola,r tissue. They commence, by blind, rounded extremities, near the external surface of the testicle, and pursue an intricately con- voluted course toward its central and posterior part. They are not strongly adherent to each other, but may be readily unravelled by manipulation, and separated from each other. The formation of the spermatozoa, as it takes place in the substance of the testicle, has been fully investigated by Kolliker. According to his observations, as the age of puberty approaches, beside the ordinary pavement epithelium lining the seminiferous tubes, other cells or vesicles of larger size make their appearance in these tubes, each containing from one to fifteen or twenty nuclei, with nucleoli. It is in the interior of these vesicles that the sper- matozoa are formed ; their number corresponding usually with that of the nuclei just mentioned. They are at first developed in bundles of ten to twenty, held together by the thin membranous substance which surrounds them, but are afterward set free by the liquefac- tion of the vesicle, and then fill nearly the entire cavity of the- seminiferous ducts, mingled only with a very minute quantity ot transparent fluid. In the seminiferous tubes themselves, the spermatozoa are al- ways inclosed in the interior of their parent vesicles; they are libe- rated, and mingled promiscuously together, only after enteriag the- reto testis and the head of the epididymis. 37 578 MALE ORGANS OF GENERATIOX. Beside the testicles, whicb are, as above stated, the primary and essential parts of the male generative apparatus, there are certain secondary or accessory organs, by means of which the spermatic fluid is conveyed to the exterior, and mingled with various secre- tions which assist in the accomplishment of its functions. As the sperm leaves the testicle, it consists, as above mentioned, almost entirely of the spermatozoa, crowded together in an opaque, white, semi-fluid mass, which fills up the vasa efierentia, and com- pletely distends their cavities. It then enters the single duct which forms the body and lower extremity of the epididymis, following the long and. tortuous course of this tube, until it' reaches the vas deferens; through which it is still conveyed onward to the point where this canal opens into the urethra. Throughout this course, it is mingled with a glairy, mucus-like fluid, secreted by the walls of the epididymis and vas deferens, in which the spermatozoa are enveloped. The mixture is then depo- sited in the vesiculas seminales, where it accumulates, as fresh quan- tities are produced in the testicle and conveyed downward by the spermatic duct. It is probable that a second secretion is supplied also by the internal surface of the vesiculse seminales, and that the sperm, while retained in their cavities, is not only stored up for subsequent use, but is at the same time modified in its properties by the admixture of another fluid. At the time when the evacuation of the sperm takes place, it is driven out from the seminal vesicles by the muscular contraction of the surrounding parts, and meets in the urethra with the secre- tions of the prostate gland, the glands of Cowper, and the mucous follicles opening into the urethral passage. All these organs are at that time, excited to an unusual activity of secretion, and pour out their diflerent fluids in great abundance. Necessary conditions of fecundation hy tlie spermatic fluid. — There are several conditions which are essential to the successful accom- plishment of the act of fecundation. First, the spermatozoa must be present and in a state of active vitality. We have shown already that the sperm, at the moment of its discharge from the urethra, is an exceedingly mixed fluid, consisting of the spermatozoa derived from the testicles, to- gether with the secretions of the epididymis and vas deferens, the prostate, Cowper's glands, and the mucous follicles of the urethra. Of all these ingredients, it is the spermatozoa MALK ORGANS OF GENERATIOK. 579 whicli constitute the essential part of the seminal fluid. They are the true fecundating element of the sperm, while all the others are secondary in importance, and perform only accessory functions. Spallanzani found that if frog's semen be passed through a suc- cession of filters, so as to separate the spermatozoa from the liquid portions, the filtered fluid is destitute of any fecundating properties ; while the spermatozoa remaining entangled in the filter, if mixed with a sufficient quantity of fluid of the requisite density for dilu- tion, may still be successfully used for the impregnation of eggs. It is well known, also, that animals or men from whom both testi- cles have been removed, are incapable of impregnating the female or her eggs, notwithstanding that all the other generative organs may remain uninjured. The spermatic fluid, furthermore, must be in a fresh condition, so that the spermatozoa themselves retain their anatomical characters and their active movement. The ex- periments of Spallanzani,' on artificial impregnation in the cold- blooded animals, have shown that, if the above conditions be pre- served, the spermatic fluid, removed from the seminal ducts of the male, is capable of successfully fecundating the eggs of the female. But if it be allowed to remain too long exposed to the atmosphere, or to an unnatural temperature, it loses its impregnating power and becomes inert. So long as the spermatozoa continue in active motion, they are usually found to retain their physiological prop- erties; the cessation of this movement, on the other hand, being a sign that their vitality is exhausted, and that they are no longer capable of impregnating the egg. Secondly, both eggs and spermatozoa must have arrived at a certain degree of development before fecundation can take place. Previous to this time the immature eggs are incapable of impreg- nation, and the imperfectly developed spermatozoa have not yet acquired their fecundating power. This necessary process of growth takes place within the generative organs ; and when it is complete, both the spermatozoa of the male and the eggs of the female are ready to be discharged, and are in a condition to exert upon each other the necessary mutual influence. The fecundating power, however, of the spermatozoa, when fully developed, is exceedingly active. Spallanzani found that three grains of the spermatic fluid of the frog, diffused in water, was sufficient for the impregnation of several thousands of eggs. The process also seems to be accomplished almost instantaneously, since the ' Experiences pour servir & I'histoire de la generation. Geneva, 1786. 580 MALE ORGAN'S OP GENERATION. eggs which had been allowed to remain in the fecundating mix- tare for only a single second were successfully impregnated and became afterward hatched at the end of the usual period. Thirdly, in order to accomplish fecundation, the spermatozoa must come into actual contact with the egg or its immediate en- velopes. Spallanzani first demonstrated this fact by attaching some mature eggs to the concave surface of a watch-glass, which he then placed, in an inverted position, over a second watch-glasg containing fresh spermatic fluid. The eggs, which were allowed to remain in this way for several hours exposed to the vapor of the spermatic fluid, but without touching its surface, were after- ward found to have failed of impregnation ; while others, which were actually moistened with a portion of the same sperm, became developed into living tadpoles. There is even reason to believe that the spermatozoa, at the time of impregnation, actually penetrate into the interior of the egg, and thus come into contact with t.he substance of the vitellus. Spermatozoa have been seen in the interior of the egg, by Martin Barry, Newport, and Bischofif, in the frog and the rabbit, and by other observers in various invertebrate animals. The sub- stance of the spermatozoon, thus introduced into the egg, undoubt- edly becomes liquefied and united with the substance of the vitel- lus ; so that the fecundated egg is a combination of materials de- rived from both the male and female organisms. Periodical development of the spermatic fluid. — In most of the lower orders of animals there is a periodical development of the testicles in the male, corresponding in time with that of the ovaries in the female. As the ovaries enlarge and the eggs ripen in the one sex, so in the other the testicles increase in size, as the season of reproduction approaches, and become turgid with spermatozoa. The accessory organs of generation, at the same time, share the unusual activity of the testicles, and become increased in vascularity and ready to perform their part in the reproductive function. In the fish, for example, where the testicles occupy the same position in the abdomen as the ovaries in the opposite sex, these bodies enlarge, become distended with their contents, and project into the peritoneal cavity. Each of the two sexes is then at the same time under the influence of a corresponding excitement. The unusilal development of the generative organs reacts upon the entire system, and produces a state of peculiar activity and excitability. MALE OBGANS OF GENERATION. 581 known as the condition of " erethism." The female, distended with eggs, feels the impulse which leads to their expulsion ; while the male, bearing the weight of the enlarged testicles and the accumu- lation of newly-developed spermatozoa, is impelled by a similar sensation to the discharge of the spermatic fluid. The two sexes, accordingly, are led by instinct at this season to frequent the same situations. The female deposits her eggs in some spot favorable to the protection and development of the young ; after which the male, apparently attracted and stimulated by the sight of the new- laid eggs, discharges the spermatic fluid upon them, and their impregnation is accomplished. In such instances as the above, where the male and female gene- rative products are discharged separately by the two sexes, the subsequent contact of the eggs with the spermatic fluid would seem to be altogether dependent on the occurrence of fortuitous circum- stances, and their impregnation, therefore, often liable to fail. In point of fact, however, the simultaneous functional excitement of the two sexes and the operation of corresponding instincts, leading them to ascend the same rivers and to frequent the same spots, provide with sufficient certainty for the impregnation of the eggs. In these animals, also, the number of eggs produced by the female is very large, the ovaries being often so distended as to fill nearly the whole of the abdominal cavity ; so that, although many of the eggs may be accidentally lost, a sufficient number will still be im- pregnated and developed, to provide for the continuation of the species. In other instances, an actual contact takes place between the sexes at the time of reproduction. In the frog, for example, the male fastens himself upon the back of the female by the anterior extremities, which seem to retain their hold by a kind of spasmodic contraction. This continues for one or two days, during which time the mature eggs, which have been discharged from the ovary, are passing downward through the oviducts. At last they are ex- pelled from the anus, while at the same time the seminal fluid of the male is discharged upon them, and impregnation takes place. In the higher classes of animals, however, and in man, where the egg is to be retained in the body of the female parent during its development, the spermatic fluid is introduced into the female generative passages by sexual congress, and meets the egg at or soon after its discharge from the ovary. The same correspondence, however, between the periods of sexual excitement in the male and 582 MALE ORGANS OF GENEEATION. female, is visible in many of these animals, as well as in fish and reptiles. This is the case in most species which produce young but once a year, and at a fixed period, as the deer and the wild hog. In other species, on the contrary, such as the dog, as well as the rabbit, the guinea pig, &c., where several broods of young are produced during the year, or where, as in the human subject, the generative epochs of the female recur at short intervals, so that the particular period of impregnation is comparatively indefinite, the generative apparatus of the male is almost constantly in a state of full deve- lopment ; and is excited to action at particular periods, apparently by some influence derived from the condition of the female. In the quadrupeds, accordingly, and in the human species, the contact of the sperm with the egg and the fecundation of the latter take place in the generative passages of the female ; either in the uterus, the Fallopian tubes, or even upon the surface of the ovary ; in each of which situations the spermatozoa have been found, aiter the accomplishment of sexual intercourse. PBKIODICAL OVULATION. 583 CHAPTER V. ON PERIODICAL OVULATION", AND THE FUNCTION OP MENSTRUATIO I. PERIODICAL OVULATION. We have already spoken in general terms of the periodical ripen- ing of the eggs and their discharge from the generative organs of the female. This function is known by the name of " ovulation," and may be considered as the primary and most important act in the process of reproduction. We shall, therefore, enter more fully into the consideration of certain particulars in regard to it, by which its nature and conditions may be more clearly understood. 1st. Eggs exist orighially in the ovaries of all animah, as part of their natural structure. In describing the ovaries of fish and reptiles we have said that they consist of nothing more than Graafian vesi- cles, each vesicle containing an egg, and united with the others by loose areolar tissue and a peritoneal investment. In the higher animals and in the human subject, the essential constitution of the ovary is the same ; only its fibrous tissue is more abundant, so that the texture of the entire organ is more dense, and its figure more compact. In all classes, however, without exception, the interior of each Graafian vesicle is occupied by an egg ; and it is from this egg that the young offspring is afterward produced. The process of reproduction was formerly regarded as essentially different in the oviparous and the viviparous animals. In the ovipa- rous classes, such as most fish, and all reptiles and birds, the young animal was well known to be formed from an egg produced by the female ; while in the viviparous animals, or those which bring forth their young alive, such as the quadrupeds and the human species, the embryo was supposed to originate in the body of the female, by some altogether peculiar and mysterious process, in consequence of sexual intercourse. As soon, however, as the microscope began to be used in the examination of the tissues, 584 OVULATION AND FUNCTION OF MENSTRUATION. the ovaries of quadrupeds were also found to contain eggs. These eggs had previously escaped observation on account of their simple .structure and minute size; but they were nevertheless found to possess all the most essential characters belonging to the larger eggs of the oviparous animals. The true difference in the process of reproduction, between the two classes, is therefore merely an apparent, not a fundamental one. lu fish, reptiles, and birds, the egg is discharged by the female before or immediately after impregnation, and the embryo is subse- quently developed and hatched externally. In the quadrupeds and the human species, on the other hand, the egg is retained within the body of the female until the embryo is. developed; when the membranes are ruptured and the young expelled at the same time. In all classes, however, viviparous as well as oviparous, the young id produced equally from an egg ; and in all classes the egg, some- times larger and sometimes smaller, but always consisting essentially of a vitellus and a vitelline membrane, is contained originally in the interior of an ovarian follicle. The egg is accordingly, as we have already intimated, an integral part of the ovarian tissue. It may be found there long before the generative function is established, and during the earliest periods of life. It may be found without difBoulty in the newly born female infant, and may even be detected in the foetus before birth. Its growth and nutrition, also, are provided for in the same man- ner with that of other portions of the bodily structure. 2d. These eggs become more fully developed at a certain age, when tli£ generative function is about to be established. During the early periods of life, the ovaries and their contents, like many other organs, are imperfectly developed. They exist, but they are as yet inactive, and incapable of performing any function. In the young chick, for example, the ovary is of small size ; and the eggs, instead of presenting the voluminous, yellow, opaque vitellus which they afterward exhibit, are minute, transparent, and colorless. In the young quadrupeds, and in the human female during infancy and childhood, the ovaries are equally inactive. They are small, friable, and of a nearly homogeneous appearance to the naked eye ; presenting none of tbe enlarged follicles, filled with transparent fluid, which are afterward so readily distinguished. At this time, accordingly, the female is incapable of bearing young, because the ovaries are inactive, and the eggs which they contain immature. At a certain period, however, which varies in the time of its PERIODICAL OVULATION. 685 occurrence for different species of animals, the sexual apparatus begins to enter upon a state of activity. The ovaries increase in size, and their circulation becomes more active. The eggs, also, instead of remaining quiescent, take on a rapid growth, and the structure of the vitellus is completed by the abundant deposit of oleaginous granules in its interior. Arrived at this state, the eggs are ready for impregnation, and the female becomes capable of bearing young. She is then said to have arrived at the state of " puberty," or that condition in which the generative organs are fully developed. This condition is accompanied by a visible alteration in the system at large, which indicates the complete development of the entire organism. In many birds, for example, the plumage assumes at this period more varied and brilliant colors; and in the common fowl the comb, or "crest," enlarges and becomes red and vascular. In the American deer (Cervus virginianus), the coat, which during the first year is mottled with white, becomes in the second year of a uniform tawny or reddish tinge. In nearly all species, the limbs become more compact and the body more rounded ; and the whole external appearance is so altered, as to indicate that the animal has arrived at the period of puberty, and is capable of reproduction. 3d. Successive crops of eggs, in the adult female, ripen and are discharged independently of sexual intercourse. It was formerly sup- posed, as we have mentioned above, that in the viviparous animals the germ was formed in the body of the female only as a conse- quence of sexual intercourse. Even after the important fact became known that eggs exist originally in the ovaries of these animals, and are only fecundated by the influence of the sperm- atic fluid, the opinion still prevailed that the occurrence of sexual intercourse was the cause of their being discharged from the ovary, and that the rupture of a Graafian vesicle in this organ was a certain indication that coitus had taken place. This opinioQ, however, was altogether unfounded. "We already know that in fish and reptiles the mature eggs not only leave the ovary, but are actually discharged from the body of the female while still unimpregnated, and only subsequently come in contact with the spermatic fluid. In fowls, also, it is a matter of common observation that the hen will continue to lay fully-formed eggs, if well supplied with nourishment, without the presence of the cock ; only these eggs, being unimpregnated, are incapable of producing 686 OVULATION AND FUNCTION OF MENSTRUATION. chicks. lu oviparous animals, therefore, the discharge of the e^g, as well as its formation, is independent of sexual intercourse. Continued observation shows this to be the case, also, in the viviparous quadrupeds. The researches of Bischoflf, Pouchet, and Coste have demonstated that in the sheep, the pig, the bitch, the rabbit, &c., if the female be carefully kept from the male until after the period of puberty is established, and then killed, examination of the ovaries will show that Graafian vesicles have matured, rup- tured, and discharged their eggs, in the same manner as though sexual intercourse had taken place. Sometimes the vesicles are found distended and prominent upon the surface of the ovary; sometimes recently ruptured and collapsed ; and sometimes in vari- ous stages of cicatrization and atrophy. Bischoff,' in several in- stances of this kind, actually found the unimpregnated eggs in the oviduct, on their way to the cavity of the uterus. In those animals in which the ripening of the eggs takes place at short intervals, as, for example, the sheep, the pig, and the cow, it is very rare to exa- mine the ovaries in any instance where traces of a more or less recent rupture of the Graafian follicles are not distinctly visible. One of the most important facts, derived from the examination of such oases as the above, is that the ovarian eggs become deve- loped and are discharged in successive crops, which follow each other regularly at periodical intervals. If we examine the ovary of the fowl, for example (Fig. 190), we see at a glance how the eggs grow and ripen, one after the other, like fruit upon a vine. In this instance, the process of evolution is very rapid ; and it is easy to distinguish, at the same time, eggs which are almost microscopic in size, colorless, and transparent; those which are larger, firmer, somewhat opaline, and yellowish in hue ; and finally those which are fully developed, opaque, of a deep orange color, and just ready to leave the ovary. It will be observed that in this instance the difference between the undeveloped and the mature eggs consists principally in the size of the vitellus, which is furthermore, for reasons previously given (Chap. III.), very much larger than in the quadrupeds. It is also seen that it is the increased size of the vitellus alone, by which the ovarian follicle is distended and ruptured, and the egg finally discharged. ' MSmoire sur la chute pfiriodique de I'ceuf, &o., Annales des Sciences Naturelles, Aodt— Septembre, 1844. PKKIODICAL OVULATION. 587 In the human species and the quadrupeds, on the other hand, the microscopic egg never becomes large enough to distend the follicle by its own size. The rupture of the follicle and the libera- tion of the egg are accordingly provided for, in these instances, by a totally different mechanism. In the earlier periods of life, in man and the higher animals, the egg is contained in a Graafian follicle which closely embraces its exterior, and is consequently hardly larger than the egg itself. As puberty approaches, those follicles which are situated near the free surface of the ovary become enlarged by the accumulation of a colorless serous fluid in their cavity. We then find that the ovary, when cut open, shows a considerable number of globular, transpa- rent vesicles, readily perceptible by the eye, the smaller of which are deep seated, but which increase in size as they approach the free surface of the organ. These vesicles are the Graafian follicles, which, in consequence of the advancing maturity of the eggs con- tained in them, gradually enlarge as the period of generation ap- proaches. The Graafian follicle at this time consists of a closed globular sac or vesicle, the external wall of which, though quite translucent has a fibrous texture under the microscope and is well supplied with bloodvessels. This fibrous and vascular wall is distinguished by the name of the "membrane of the vesicle." It is not very firm in texture, and if roughly handled is easily ruptured. The membrane of the vesicle is lined throughout by a thin layer of minute granular cells, which form for it a kind of epithelium, similar to the epithelium of the pleura, pericardium, and other serous membranes. This layer is termed the membrana granulosa. It adheres but slightly to the membrane of the vesicle, and may easily be detached by careless manipulation before the vesicle is opened, being then mingled, in the form of light flakes and shreds, with the serous fluid contained in the vesicle. At the most superficial part of the Graafian follicle, or that which is nearest the surface of the ovary, the membrana granulosa is thicker than elsewhere. Its cells are here accumulated, in a kind of mound or " heap," which has received the name of the cumulus proUgerus. It is sometimes called the discus proligerus, because the thickened mass, when viewed from above, has a some- what circular or disk-like form. In the centre of this thickened portion of the membrana granulosa the egg is imbedded. It is 588 OVULATION AND FUNCTION OP MENSTRUATION. accordingly always situated at the most superficial portion of the follicle, and advances in this way toward the surface of the ovary. As the period approaches at wMch the egg is destined to be dis- charged, the Graafian follicle becomes more vascular, and enlarges by an increased exudation of serum into its cavity. It then begins Fig. 195. Graafiav Follicle, near the period of rupture —a. Membrane of the vesicle. 6. MembraD& grannlosa. o. Cavity of follicle, d. Egg. e. Peritoneum. /. Tunica albuginea. g, g. Tissue of the ovary, to project from the surface of the ovary, still covered by the albu- gineous tunic and the peritoneum. (Fig. 195.) The constant accu- mulation of fluid, however, in the follicle, exerts such a steady and increasing pressure from within outward, that the albugineous tunic and the peritoneum successively yield before it ; until the Graafian follicle protrudes from the ovary as a tense, rounded, translucent vesicle, in which the sense of ''''s- 196. fluctuation can be readily per- ceived on applying the fingers to its surface. Finally, the pro- cess of effusion and distension still going on, the wall of the vesicle yields at its most promi- nent portion, the contained fluid is driven out with a gush, by the reaction and elasticity of the neighboring ovarian tissues, car- rying with it the egg, still en- tangled in the cells of the pro- ligerous disk. The rupture of the Graafian vesicle is accompanied, in some instances, by an abundant hemor- OVARV WITH GkAAPIAN FOLLICLE roptured: at ra, egg just diKcbarged with a portion of membraoa granulosa. PERIODICAL OVULATION". 589 phage, which takes place from the internal surface of the congested follicle, and by which its cavity is filled with blood. This occurs in the human subject and in the pig, and to a certain extent, also, in other of the lower animals. Sometimes, as in the cow, where no hemorrhage takes place, the Graafian vesicle when ruptured simply collapses ; after which a slight exudation, more or less tinged with blood, is poured out during the course of a few hours. Notwithstanding, however, these slight variations, the expulsion of the egg takes place, in the higher animals, always in the manner above described, viz., by the accumulation of serous fluid in the cavity of the Graafian follicle, by which its walls are gradually dis- tended and finally ruptured. This process takes place in one or more Graafian follicles at a time, according to the number of young which the animal produces at a birth. In the bitch and the sow, where each litter consists of irom six to twenty young ones, a similar number of eggs ripen and are discharged at each period. In the mare, in the cow, and in the human female, where there is usually but one foetus at a birth, the eggs are matured singly, and the Graafian vesicles ruptured, one after another, at successive periods of ovulation. 4th. Tlie npening and discharge of the egg are accompanied by a peculiar condition of the entire system, known as the " rutting" condi- tion, or " oestruation." The peculiar congestion and functional activity of the ovaries at each period of ovulation, act by sympathy upon the other generative organs and produce in them a greater or less degree of excitement, according to the particular species of ani- mal. Almost always there is a certain amount of congestion of the entire generative apparatus; Fallopian tubes, uterus, vagina, and external organs. The secretions of the vagina and neighboring parts are more particularly affected, being usually increased in quan- tity and at the same time altered in quality. In the bitch, the vaginal mucous membrane becomes red and tumefied, and pours out an abundant secretion which is often more or less tinged with blood. The secretions acquire also at this time a peculiar odor, which appears to attract the male, and to excite in him the sexual impulse. An unusual tumefaction and redness of the vagina- and vulva are also very perceptible in the rabbit ; and in some species of apes it has been observed that these periods are accompanied not only by a bloody discharge from the vulva, but also by an en- gorgement and infiltration of the neighboring parts, extending even 590 OVULATION AND FUNCTION OF MENSTRUATION. to the skin of the buttocks, the thighs, and the under part of the tail.i The system at large is also visibly affected by the process going on in the ovary. In the cow, for example, the approach of an cestrual period is marked by an unusual restlessness and agitation, easily recognized by an ordinary observer. The animal partially loses her appetite. She frequently stops browsing, looks about un- easily, perhaps runs from one side of the field to the other, and then recommences feeding, to be disturbed again in a similar manner after a short interval. Her motions are rapid and nervous, and her hide often rough and disordered ; and the whole aspect of the ani- mal indicates the presence of some unusual excitement. After this condition is fully established, the vaginal secretions show them- selves in unusual abundance, and so continue for one or two days; after which the symptoms, botb local and general, subside sponta- neously, and the animal returns to -her usual condition. It is a remarkable fact, in this connection, that the female of these animals will allow the approaches of the male only during and immediately after the cestrual period ; that is, just when the egg is recently discharged, and ready for impregnation. At other times, when sexual intercourse would be necessarily fruitless, the instinct of the animal leads her to avoid it ; and the concourse of the sexes is accordingly made to correspond in time with the maturity of the egg and its aptitude for fecundation. II. MENSTEUATION. In the human female, the return of the period of ovulation is marked by a peculiar group of phenomena which are known as menstruation, and which are of sufficient importance to be described by themselves. During infancy and childhood the sexual system, as we have mentioned above, is inactive. No discharge of eggs takes place froni the ovaries, and no external phenomena show themselves, connected with the reproductive function. At the age of fourteen or fifteen years, however, a change begins to manifest itself. The limbs become rounder, the breasts increase in size, and the entire aspect undergoes a peculiar alteration, which indicates the approaching condition of maturity. At the same time a discharge of blood takes place from the generative passages, ' Ponohet, Thgorie positive de rovulation, &c. Paris, 1847, p. 230. MENSTRUATION, 691 accompanied by some disturbance of the general system, and the female is then known to have arrived at the period of puberty. Afterward, the bloody discharge just spoken of returns at regular intervals of four weeks; and, on account of this recurrence corres- ponding with the passage of successive lunar months, its phenomena are designated by the name of the "menses" or the "menstrual periods." The menses return with regularity, from the time of their first appearance, until the age of about forty-five years. During this period, the female is capable of bearing children, and sexual intercourse is liable to be followed by pregnancy. After the forty-fifth year, the periods first become irregular, and then cease altogether ; and their final disappearance is an indication that the woman is no longer fertile, and that pregnancy cannot again take place. Even during the period above referred to, from the age of fifteen to forty-five, the regularity and completeness of the menstrual periods indicate to a great extent the aptitude of individual females for impregnation. It is well known that all those causes of ill health which derange menstruation are apt at the same time to interfere with pregnancy ; so that women whose menses are habi- tually regular and natural are much more likely to become preg- nant, after sexual intercourse, than those in whom the periods are absent or irregular. If pregnancy happen to take place, however, at any time during the child-bearing period, the menses are suspended during the con- tinuance of gestation, and usually remain absent, after delivery, as long as the woman continues to nurse her child. They then re- commence, and subsequently continue to appear as before. The menstrual discharge consists of an abundant secretion of mucus mingled with blood. When the expected period is about to come on, the female is affected with a certain degree of discomfort and lassitude, a sense of weight in the pelvis, and more or less dis- inclination to society. These symptoms are in some instances slightly pronounced, in others more troublesome. An unusual discharge of vaginal mucus then begins to take place, which soon becomes yellowish or rusty brown in color, from the admixture of a certain proportion of blood ; and by the second or third day the discharge has the appearance of nearly pure blood. The unpleasant sensations which were at first manifest then usually subside ; and the discharge, after continuing for a certain period, begins to grow more scanty. Its color changes from a pure red to a brownish or 592 OVULATION AND FCNCTION OF MENSTRUATION. rusty tinge, until it finally disappears altogether, and the female returns to her ordinary condition. The menstrual epochs of the human female correspond with the periods of cestruation in the lower animals. Their general resem- blance to these periods is too evident to require demonstration. Like them, they are absent in the immature female ; and begin to take place only at the period of puberty, when the aptitude for impregnation commences. Like them, they recur during the child- bearing period at regular intervals; and are liable to the same interruption by pregnancy and lactation. Finally, their disappear- ance corresponds with the cessation of fertility. The periods of cestruation, furthermore, in many of the lower animals, are accompanied, as we have already seen, with an unusual discharge from the generative passages ; and this discharge is fre- quently more or less tinged with blood. In the human female the bloody discharge is more abundant than in other instances, but it is evidently a phenomenon differing only in degree from that which shows itself in many species of animals. The most complete evidence, however, that the period of men- struation is in reality that of ovulation, is derived from the results of direct observation. A sufiBcient number of instances have now been observed to show that at the menstrual epoch a Graafian vesicle becomes enlarged, ruptures, and discharges its egg. Oruik- shauk' noticed such a case so long ago as 1797. Negrier' relates two instances, commimicated to him by Dr. OUivier d' Angers, in which, after sudden death during menstruation, a bloody and rup- tured Graafian vesicle was found in the ovary. Bischoff' speaks of four similar cases in his own observation, in three of which the vesicle was just ruptured, and in the fourth distended, prominent, and ready to burst. Coste* has met with several of the same kind. Dr. MicheP found a vesicle ruptured and filled with blood in a woman who was executed for murder while the menses were pre- sent. We have also" met with the same appearances in a case of death from acute disease, on the second day of menstruation. > Loodon Philosophical Tiansaotions, 1797, p. 135. 2 Reoherohes sur les Ovaires, Paris, 1840, p. 78. ^ Aunales des Sciences Natnrelles, August, 1844. * Histoire dn Developpement des Corps Organises, Paris, 1847, vol. i. p. 221. ' Am. Jonm. Med. Sci., July, 1848. " Corpus Luteum of Menstruation and Pregnancy, in Transactions of American Medical Association, Philadelphia, 1851. MENSTK17ATI0N. 593 The process of ovulation, accordingly, in the human female, accompanies and forms a part of that of menstruation. As the menstrual period comes on, a congestion takes place in nearly the whole of the generative apparatus ; in the Fallopian tubes and the uterus, as ■well as in the ovaries and their contents. One of the Graafian follicles is more especially the seat of an unusual -vascular excitement. It becomes distended by the fluid which accumulates in its cavity, projects from the surface of the ovary, and is finally ruptured in the same manner as we have already described this process taking place in the lower animals. It is not quite certain at what particular period of the menstrual flow the rupture of the vesicle and discharge of the egg take place. It is the opinion of Bischofif, Pouchet, and Eaciborski, that the regular time for this rupture and discharge is not at the commence- ment, but towards the termination of the period. Coste' has ascer- tained, from his observations, that the vesicle ruptures sometimes in the early part of the menstrual epoch, and sometimes later. So far as we can learn, therefore, the precise period of the discharge of the egg is not invariable. Like the menses themselves, it may apparently take place a little earlier, or a little later, according to various accidental circumstances ; but. it always occurs at some time in connection with the menstrual flow, and constitutes the most essential and important part of the catamenial process. The egg, when discharged from the ovary, enters the fimbriated extremity of the Fallopian tube, and commences its passage toward the uterus. The mechanism by which it finds its way into and through the Fallopian tube is diflerent, in the quadrupeds and the human species, and in birds and reptiles. In the latter, the bulk of the egg or mass of eggs discharged is so great as to fill entirely the wide extremity of the oviduct, and they are afterward conveyed downward by the peristaltic action of the muscular coat of this canal. In the higher classes, on the contrary, the egg is micro- scopic in size, and would be liable to be lost, were there not some further provision for its safety. The wide extremity of the Fallo- pian tube, accordingly, which is here directed toward the ovary, is lined with ciliated epithelium; and the movement of the cilia, which is directed from the ovary toward the uterus, produces a kind of converging stream, or vortex, by which the egg is neces- sarily drawn toward the narrow portion of the tube, and subse- quently conducted to the cavity of the uterus. ' Iioc cit. 38 594 OVULATION AND FUNCTION OF MENSTRUATION. Accidental causes, however, sometimes disturb this regular course or passage of the egg. The egg may be arrested, for example, at the surface of the ovary, and so fail to enter the tube at all. If fecundated in this situation, it will then give rise to " ovarian pregnancy." It may escape from the fimbriated extremity into the peritoneal cavity, and form attachments to some one of the neigh- boring organs, causing "abdominal pregnancy;" or finally, it may stop at any part of the Fallopian tube, and so give origin to "tubal pregnancy." The egg, immediately upon its discharge from the ovary, is ready for impregnation. If sexual intercourse happen to take place about that time, the egg and the spermatic fluid meet in some part of the female generative passages, and fecundation is accomplished. It appears from various observations' of Bischoff, Coste, and others, that this contact may take place between the egg and the sperm, either in the uterus or any part of the Fallopian tubes, or even upon the surface of the ovary. If, on the other hand, coitus do not take place, the egg passes down to the uterus unimpreguated, loses its vitality after a short time, and is finally carried away with the uterine secretions. It is easily understood, therefore, why sexual intercourse should be more liable to be followed by pregnancy when it occurs about the menstrual ppoch than at other times. This fact, which was long since established as a matter of observation by practical obstetri- cians, depends simply upon the coincidence in time between men- struation and the discharge of the egg. Before its discharge, the egg is immature, and unprepared for impregnation ; and after the menstrual period has passed, it gradually loses its freshness and vitality. The exact length of time, however, preceding and follow- ing the menses, during which impregnation is still possible, has not been ascertained. The spermatic fluid, on the one hand, retains its vitality for an unknown period after coition, and the egg for an unknown period after its discharge. Both these occurrences may, therefore, either precede or follow each other within certain limits, and impregnation be still possible ; but the precise extent of these limits is still uncertain, and is probably more or less variable in different individuals. The above facts indicate also the true explanation of certain exceptional cases, which have sometimes been observed, in which fertility exists without menstruation. Various authors (Churchill, Reid, Velpeau, &c.) have related instances of fruitful women in whom MENSTRUATION', 695 the menses were very scanty and irregular, or even entirely absent. The menstrual flow is, in fact, only the external sign and accompa- niment of a more important process taking place within. It is. habitually scanty in some individuals, and abundant in others. Such variations depend upon the condition of vascular activity of the system at large, or of the uterine organs in particular; and though the bloody discharge is usually an index of the general aptitude of these organs for successful impregnation, it is not an absolute or necessary requisite. Provided a mature egg be dis: charged from the ovary at the appointed period, menstruation pro- 'perly speaking exists, and pregnancy is possible. , The blood which escapes during the menstrual flow is supplied by the uterine mucous membrane. If the cavity of the uterus be examined after death during menstruation, its internal surface is seen to be smeared with a thickish bloody fluid, which may be traced through the uterine cervix and into the vagina. The Fallo- pian tubes themselves are sometimes found excessively congested, and filled with a similar bloody discharge. The menstrual blood has also been seen to exude from the uterine orifice in cases of pro- cidentia uteri, as well as in the natural condition by examination with the vaginal speculum. It is discharged by a kind of capillary hemorrhage, similar to that which takes place from the lungs in cases of haemoptysis, only less sudden and violent. The blood does not form any visible coagulum, owing to its being gradually exuded from many minute points, and mingled with a large quantity of mucus. When poured out, however, more rapidly or in larger quantity than usual, as in cases of menorrhagia, the menstrual blood coagulates in the same manner as if derived from any other source. The hemorrhage which supplies it comes from the whole extent of the mucous membrane of the body of the uterus, and is, at the same time, the consequence and the natural termination of the periodical congestion of the parts. 596 MENSTRUATION AND PREGNANCY. CHAPTER VI. ON THE CORPUS LUTBXJM OF MENSTRUATION AND PREGNANCY. After the rupture of tte Graafian follicle at the menstrual period, a bloody cavity is left in the ovary, which is subsequently obliterated by a kind of granulating process, somewhat similar in character to the healing of an abscess. For the Graafian follicle is intended simply for the formation and growth of the egg. After the egg therefore has arrived at maturity and has been dis- charged, the Graafian follicle has no longer any function to per- fornv. It then only remains for it to pass through a process of obliteration and atrophy, as an organ which has become useless and obscjlete. While undergoing this process, the Graafian follicle is at one time converted into a peculiar, solid, globular body, which is called the corpus luteum ; a name given to it on account of the yellow color which it acquires at a certain period of its formation. We shall proceed to describe the corpus luteum in the human species ; first, as it follows the ordinary course of development after menstruation ; and secondly, as it is modified in its growth and appearance during the existence of pregnancy. I. CORPUS LUTEUM OF MENSTRUATION. We have already described, in the preceding chapter, the man- ner in which a Graafian follicle, at each menstrual epoch, swells, protrudes from the surface of the ovary, and at last ruptures knd discharges its egg. At the moment of rupture, or immediately after it, an abundant hemorrhage takes place in the human sub- ject from the vessels of the follicle, by which its cavity is filled with blood. This blood coagulates soon after its exudation, as it would do if extravasated in any other part of the body, and the coagulum is retained in the interior of the Graafian follicle. CORPUS LUTEUM OP MENSTRUATION. 597 Fig. 197. The opening by whicli the egg makes its escape is usually not an extensive laceration, but a minute rounded perforation, often not more than half a line in diameter. A small probe, introduced through this opening, passes directly into the cavity of the follicle. If the Graafian follicle be opened at this time by a longitudinal inci- sion (Fig. 197), it will be seen to form a globu- lar cavity, one-half to three-quarters of an inch in diameter, containing a soft, recent, dark-colored coagulum. This coagulum has no organic connection with the walls of the follicle, but lies loose in its cavity and may be easily turned o,ut with the handle of a knife. There is sometimes a slight mechanical adhe- sion of the clot to the edges of the lacerated opening, just as the coagulum in a recently ligatured artery is entangled by the divided edges of the internal and middle coats; but there is no continuity of substance between them, and the clot may be everywhere readily separated by careful manipulation. The mem- brane of the vesicle presents at this time a smooth, transparent, and vascular internal surface, without any alteration of color, consistency, or texture. An important change, however, soon begins to take place, both in the central coagulum and in the membrane of the vesicle. The clot, which is at first large, soft, and gelatinous, like any other mass of coagulated blood, begins to contract ; and the serum separates from the coagulum proper. The serum, as fast as it separates from the coagulum, is absorbed by the neighboring parts ; and the clot, accordingly, grows every day smaller and denser than before. At the same time the coloring matter of the blood under- goes the changes which usually take place in it after extravasation, and is partially reabsorbed together with the serum. This second change is somewhat less rapid than the former, but still a diminu- tion of color is very perceptible in the clot, at the expiration of two weeks. The membrane of the vesicle during this time is beginning to undergo a process of hypertrophy or development, by which it becomes thickened and convoluted, and tends partially to fill up Graafian Foxliclii recently I'uptared daring menstruation, and filled with a. bloody coagulum ; shown in longitudinal sec- tion. — a. Tissue of the ovary. 6. Membrane of the vesicle, c. Point of rupture. MENSTRUATION AND PEEGNANCY. the cayitj of the follicle. This hypertrophy and convolution of the membrane just named commences and proceeds most rapidly at the deeper part of the follicle, directly opposite the situation of the superficial rupture. From this point the membrane gradually becomes thinner and less convoluted as it approaches the surface of the ovary and the edges of the ruptured orifice. At the end of three weeks, this hypertrophy of the membrane of the vesicle has reached its maximum. The ruptured Graafian fol- licle has now become so completely solidified by the new growth above described, and by the condensation of its clot, that it receives the name of the corpus luteum. It forms a perceptible prominence on the surface of the ovary, and may be felt between the fingers as a well-defined rounded tumor, which is nearly always somewhat flattened from side to side. It measures about three-quarters of an inch in length and half an inch in depth. On its surface may be seen a minute cicatrix of the peritoneum, occupying the spot of the original rupture. On cutting it open at this time (Fig. 198), the corpus luteum is seen to con- sist, as above described, of a central coagulum and a convoluted wall. The coagulum is semi-transparent, of a gray or light greenish color, more or less mottled with red. The con- voluted wall is about one-eighth of an inch thick at its deepest part, and of an indefinite yellowish or rosy hue, not very different in tinge from the rest of the ovarian tissue. The convoluted wall and the con- tained clot lie simply in contact with each other, as at first, without any intervening membrane or other organic connection ; and they may still be readily separated from each other by the handle of a knife or the flattened end of a probe. The corpus luteum at this time may also be stripped out, or enucleated entire, from the ovarian tissue, just as might have been done with the Graafian follicle pre- viously to its rupture. "When enucleated in this way, the corpus luteum presents itself under the form of a solid globular or flat- tened tumor, with convolutions upon it somewhat similar in ap- pearance to those of the brain, and covered with the remains of V A B. Y cut open, showiug corpus luteum divided longitudinally; three 'weeks after menBtruatioa. From a girl dead of hemoptysis. COKPUS LUTEUM OF MENSTRUATION. 599 the areolar tissue, by which it was previously connected with the substance of the ovary. , After the third week from the close of menstruation, the corpu« iuteum passes into a retrograde condition. It diminishes perciep- tibly in size, and the central coagulum con- tinues to be absorbed and loses still farther its coloring matter. The whole body under- goes a process of partial atrophy; and at the end of the fourth week it is not more than three-eighths of an inch in its longest diameter. (Fig. 199.) The external cicatrix may still usually be seen, as well as the point where the central ooagulum comes in contact with the peritoneum. There is still no organic connection between the central coagulum and the convoluted wall ; but the partial condensation of the clot and the continued folding of the wall prevent the separation of the two being so easily accom- plished as before, though it may still be effected by careful management. The entire corpus Iuteum also still be extracted from its bed in the ovarian tissue. The color of the convoluted wall, during the early part of this retrograde stage, instead of fading, like that of the fibrinous coagu- lum, becomes more strongly marked. From having a dull yellowish or rosy hue, as at first, it gradually as- sumes a brighter and more decided yellow. This change of color in the convoluted wall is produced in consequence of a kind of fatty degeneration which takes place in its texture ; a large quantity of oil- globules being deposited in it at this time, as may be readily recognized under the microscope. At the end of the fourth week, this alteration in hue is complete ; and the outer wall of the corpus Iuteum isthenof a clear chrome-yellow color, by which it is readily distinguished from all the neighboring tissues. After this period, the process of atrophy and degeneration goes on rapidly. The clot becomes constantly OvAEY, showing corpcji Iuteum Tour weekn after mea- Btraation , from a woman deud of apoplexy. mav Fig. 200. Otart, showing corpus lii team, nine weeks after menstrua tion; from, a girl dead of tuber- cular meningitis. 600 MENSTRUATION AND PEEGNANCT. more dense and shrivelled, and is soon converted into a minute, stellate, white, or reddish-white cicatrix. The yellow wall becomes softer and more friable, as is the case with all tissues undergoing fatty degeneration, and shows less distinctly the marking of its convolutions. At the same time its surfaces become confounded with the central coagulum on the one hand, and with the neigh- boring tissues on the other, so that it is no longer possible to separate them fairly from each other. At the end of eight or nine weeks (Fig. 200) the whole body is reduced to the condition of an insignifi- cant, yellowish, cicatrix-like spot, measuring less than a quarter of an inch in its longest diameter, in which the original texture of the corpus luteum can be recognized only by the peculiar folding and coloring of its constituent parts. Subsequently its atrophy goes on in a less active manner, and a period of seven or eight months some- times elapses before its filnal and complete disappearance. The corpus luteum, accordingly, is a formation which results from the filling up and obliteration of a ruptured Graafian follicle. Under ordinary conditions, a corpus luteum is produced at every menstrual period ; and notwithstanding the rapidity with which it retrogrades and becomes atrophied, a new one is always formed before its predecessor has completely disappeared. "When, therefore, we examine the ovaries of a healthy female, in whom the menses have recurred with regularity for some time previous to death, several corpora lutea will be met with, in different stages of formation and atrophy. Thus we have found, under such circumstances, four, five, six, and even eight corpora lutea in the ovaries at the same time, perfectly distinguishable by their texture, but very small, and most of them evidently in a state of advanced retrogression. They finally disappear altogether, and the number of those present in the ovary, therefore, no longer corresponds with that of the Graafian follicles which have been ruptured. II. CORPUS LUTEUM OP PREGNANCr. Since the process above described takes place at every menstrual period, it is independent of impregnation and even of sexual inter- •course. The mere presence of a corpus luteum, therefore, is no indication that pregnancy has existed, but only that a Graafian follicle has been ruptured and its contents discharged. We find, nevertheless, that when pregnancy takes place, the appearance of the corpus luteum becomes so much altered as to be readily dis- CORPUS LUTEUM OF PREGNANCY. 601 tinguished from that which simply follows the ordinary menstrual process. It is proper, therefore, to speak of two kinds of corpora . lutea ; one belonging to menstruation, the other to pregnancy. The difference between these two kinds of corpora lutea is not an essential or fundamental difference ; since they both originate in the same way, and are composed of the same structures. It is, properly speaking, only a difference in the degree and rapidity of their development. For while the corpus luteum of menstruation passes rapidly through its different stages, and is very soon reduced to a condition of atrophy, that of pregnancy continues its develop- ment for a long time, attains a larger size and firmer organization, and disappears finally only at a much later period. This variation in the development and history of the corpus luteum depends upon the unusually active condition of the pregnant uterus. This organ exerts a powerful sympathetic action, during pregnancy, upon many other parts of the system. The stomach becomes irritable, the appetite is capricious, and even the mental faculties and the moral disposition are frequently more or less affected. The ovaries, however, feel the disturbing influence of gestation more certainly and decidedly than the other organs, since they are more closely connected with the uterus in the ordinary performance of their function. The moment that pregnancy takes place, the process of menstruation is arrested. No more eggs come to maturity, and no more Graafian follicles are ruptured, during the whole period of gestation. It is not at all singular, therefore, that the growth of the corpus luteum should also be modified, by an influence which affects so profoundly the system at large, as well as the ovaries in particular. During the first three weeks of its formation, the growth of the corpus luteum is the same in the impregnated as in the unimpreg- nated condition. After that time, however, a difference becomes manifest. Instead of commencing a retrograde course during the fourth week, the corpus luteum of pregnancy continues its deve- lopment. The external wall grows thicker, and its convolutions more abundant. Its color alters in the same way as previously described, and becomes a bright yellow by the deposit of fatty matter in microscopic globules and granules. By the end of the second month, the whole corpus luteum has increased in size to such an extent as to measure seven-eighths of an inch in length by half an inch in depth. (Fig. 201.) The central coagulum has by this time become almost entirely decolorized, so as 602 MENSTEUATION ANfi PEEGNANCY. to present the appearance of a purely fibrinous deposit. Sometimes we find that a part of the serum, during its separation from the clot has accumulated in the centre of the mass, as in Fig. 201, forming a little cavity containing a few ^'S- 201. drops of clear fluid and in- closed by a whitish, fibrinous layer, the remains of the solid portion of the clot. It is this fibrinous layer which has sometimes been mistaken for a distinct organizetJ mem- brane, lining the internal sur- — - face of tbe convoluted wall, CoRPiJa LoTEDM of pregnancy, at end of second - l,' l, T, i month ; from a, woman dead from induced abortion. ^'Hd WhlCh has thUS led tO the belief that the yellow matter of the corpus luteum is normally deposited outside the mem- brane of the Graafian follicle. Such, however, is not its real struc- ture. The convoluted wall of the corpus luteum is the membrane of the follicle itself, partially altered by hypertrophy, as may be readily seen by examination in the earlier stages of its growth ; and the fibrinous layer, situated Fig. 202. • X 11 ■ i-i • • , internally, is the original bloody coagulum, decolorized and condensed by coDtinued absorption. The existence of a central cavity containing serous fluid, is merely an oc- casional, not a constant pheno- menon. More frequently, the fibrinous clot is solid through- out, the serum being gradually absorbed, as it separates spon- taneously from the coagulum. During the third and fourth months, the enlargement of the corpus luteum continues ; so that at tbe end of that time it may measure seven-eighths of an inch in length by three-quarters of an inch in depth. (Fig. 202.) The con- voluted wall is still thicker and more highly developed than before, having a thickness, at its deepest part, of three-sixteenths of an inch. Its color, however, has already begun to fade, and is now of a dull 7ellow, instead of the bright, clear tinge which it previously ex Corpus Luteom of pregnancy, at end of fourth month ; from a woman dead by poison. COEPUS LUTKUM OF PREGNANCY. 603 Fig. 203. Mbited. The central coagulum, perfectly colorless and fibrinoua in appearance, is often so much flattened by the lateral compres- sion of its mafes, that it has hardly a line in thickness. The other relations of the different parts of the corpus luteum remain the same. The corpus luteum has now attained its maximum of develop- ment, and remains without any very perceptible alteration during the fifth and sixth months. It then begins to retrograde, diminish- ing constantly in size during the seventh and eighth months. Its external wall fades still more perceptibly in color, becoming of a faint yellowish white, not unlike that which it presented at the end of the third week. Its texture is thick, soft, and elastic, and it is still strongly convoluted. An abundance of fine red vessels can be seen penetrating from the exterior into the interstices of its convolutions. The central coagulum is reduced by this time to the condition of a whitish, radiated cicatrix. The atrophy of the organ continues dur- ing the ninth month. At the termination of pregnancy, it is reduced to the size of half an inch in length and three-eighths of an inch in depth. (Fig. 203.) It is then of a faint indefinite hue, but little contrasted with the remaining tissues of the ovary. The central cicatrix has become very small, and appears only as a thin whitish lamina, with radiating processes which run in be- tween the interstices of the convolutions. The whole mass, however, is still quite firm and resisting to the touch, and is readily distinguishable, both from its size and tex ture, as a prominent feature in the ovarian tissue, and a reliable indication of pregnancy. The convoluted structure of its external wall is very perceptible, and the point of rupture, with its externa; peritoneal cicatrix, distinctly visible. After delivery, the corpus luteum retrogrades rapidly. At the end of eight or nine weeks, it has become so much altered that its color is no longer distinguishable, and only faint traces of its con voluted structure are to be discovered by close examination. These traces may remain, however, for a long time afterward, more or less Corpus Luteum of preg- nancy, at term ; from a woman dead in deliverT* from ruptnre of the uterus. 604 MENSTRUATION AND PREGNANCY. concealed ia the ovarian tissue. We have distinguished them so late as nine and a half months after delivery. They finally disap- pear entirely, together with the external cicatrix which previously marked their situation. During the existence of gestation, the process of menstruation being suspended, no new follicles are ruptured, and no new corpora lutea are produced ; and as the old ones, formed before the period of conception, gradually fade and disappear, the corpus luteum which marks the occurrence of pregnancy after a short time exists alone in the ovary, and is not accompanied by any others of older date. In twin pregnancies, we of course find two corpora lutea in the ovaries ; but these are precisely similar to each other, and, being evidently of the same date, will not give rise to any confusion. Where there is but a single foetus in the uterus, and the ovaries contain two corpora lutea of similar appearance, one of them belongs to an embryo which has been blighted by some accident in the early part of pregnancy. The remains of the blighted emr bryo may often be discovered, in such cases, in some part of the Fallopian tubes, where it has been arrested in its descent toward the uterus. After the process of lactation comes to an end, the ovaries again resume their ordinary function. The Graafian follicles mature and rupture in succession, as before, and new corpora lutea follow each other in alternate development and disappearance. We find, then, that the corpus luteum of menstruation differs from that of pregnancy in the extent of its development and the dura- tion of its existence. While the former passes through all the im- portant phases of its growth and decline in the period of two months, the latter lasts from nine to ten months, and presents, during a great portion of the time, a larger size and a more solid organization. It will be observed that, even with the corpus luteum of pregnancy, the bright yellow color, which is so import- ant a characteristic, is only temporary in its duration ; not making its appearance till about the end of the fourth week, and again disappearing after the sixth month. The following table contains, in a brief form, the characters of the corpus luteum, as belonging to the two different conditions of menstruation and pregnancy, corresponding with different periods of its development. CORPUS LUTEUM OF PREGNANCY. 605 CoBFUa LUTEDM OF MeKSTBDATIOK. CORPrS LuTEUM OP Pkegsakct. At the end of Three weeks One month Two months Six months Nxne months Three-quarters of an inch in diameter ; central clot reddish ; con volnted wall pale. Smaller ; convoluted wall bright yellow ; clot still reddish. Reduced to the condition of an insignificant cicatrix. Absent. Absent. Larger ; convoluted wall bright yellow ; clot still reddish. Seven-eighths of an inch in dia- meter ; convoluted wall bright yellow ; clot perfectly decolor- ized. Still as large as at end of second month ; clot fibrinous ; convo- luted wall paler. One-half an inch in diameter ; central clot converted into a radiating cicatrix ; the external wall tolerably thick and con vo • luted, but without any bright yellow color. DEVELOPMENT OF THE IMPBEGNATEC EGG. CHAPTEE VII. ON THE DEVELOPMENT OP THE IMPREGNATED EGG— SEGMENTATION OP THE VITELLUS— BLAS- TODERMIC MEMBRANE— PORMATION OP ORGANS IN THE FROG. We have seen, in the foregoing chapters, how the egg, produced in the ovarian follicle, becomes gradually developed and ripened, until it is ready to be discharged. The egg, accordingly, passes through several successive stages of formation, even while still con- tained within the ovary ; and its vitellus becomes gradually com- pleted, by the formation of albuminous material and the deposit of molecular granulations. The last change which the egg undergoes, in this situation, and that which marks its complete maturity, is the disappearance of the germinative vesicle. This vesicle, which is, in general, a prominent feature of the ovarian egg, disappears but a short time previous to its discharge, or even just at the period of its leaving the Graafian follicle. The egg, therefore, consisting simply of the mature vitellus and the vitelline membrane, comes in contact, after leaving the ovary, and while passing through the Fallopian tube, with the spermatio fluid, and is thereby fecundated. By the influence of fecundation, a new stimulus is imparted to its growth ; and while the vitality of the unimpregnated germ, arrived at this point, would have reached its termination, the fecundated egg, on the contrary, starts upon a new and inore extensive course of development, by which it is finally converted into the body of the young animal. The egg, in the first place, as it passes down the Fallopian tube, becomes covered with an albuminous secretion. In the birds, as we have seen, this secretion is very abundant, and is deposited in suc- cessive layers around the vitellus. In the reptiles, it is also poured out in considerable quantity, and serves for the nourishment of the egg during its early growth. In quadrupeds, the albuminous matter is supplied in the same way, though in smaller quantity, by the SEGMENTATION OF THE VITELLUS. 607 Fig. 204. mucous membrane of the Fallopian tubes, and envelopes the egg in a layer of nutritious material. A very remarkable change no w takes place in the impregnated egg, which is known as the spontaneous division, or segmentation, of the vitellus. A furrow first shows itself, running round the glob alar mass of the vitellus in a vertical direction, which gradually deepens until it has divided the vitellus into two separate halves or hemispheres. (Fig. 204, a.) Almost at the same time another furrow, run- ning at right angles with the first, penetrates also the substance of the vitellus and cuts it in a transverse direction. The vitellus is thus divided into four equal portions (Fig. 204, b), the edges and angles of which are rounded off, and which are still con- tained in the cavity of the vitelline membrane. The spaces between them and the internal surface of the vitelline membrane are occupied by a transparent fluid. The process thus commenced goes on by a successive formation of fur- rows and sections, in various direc- tions. The four vitelline segments already produced are thus subdivided into sixteen, the sixteen into sixty- four, and so on ; until the whole vi- tellus is converted into a mulberry- shaped mass, composed of minute, nearly spherical bodies, which are called the "vitelline spheres." (Fig. 204, c.) These vitelline spheres have a somewhat firmer consistency than the original substance of the vitellus ; and this consistency appears to in- crease, as they successively multiply in numbers and diminish in size. At last they have become so abundant as to be closely crowded together, compressed into polygonal forms, and flattened SeOHEVTATION of the VlTElLUS 608 DEVKLOPMENT OF THE IMPREGNATED EGG. against the internal surface of the vitelline membrane. (Fig 204, d.) They have by this time been converted into true animal cells ; and these cells, adhering to each other by their adjacent edges, form a continuous organized membrane, which is termed the Blastodermic membrane. During the formation of this membrane, moreover, the egg, -vrbile passing through the Fallopian tubes into the uterus, has increased in size. The albuminous matter with which it was enveloped has liquefied ; and, being absorbed by endosmosis through the viteUine membrane, has furnished the materials for the more solid and ex- tensive growth of the newly-formed structures. It may also be seen that a large quantity of this fluid has accumulated- in the central cavity of the egg, inclosed accordingly by the blastodermic membrane, with the original vitelline membrane still forming an external envelope round the whole. The next change which takes place consists in the division or splitting of the blastodermic membrane into two layers, which are known as the external and internal layers of the blastodermic membrane. They are both still composed exclusively of cells ; but those of the external layer are usually smaller and more compact, while those of the internal are rather larger and looser in texture. The egg then presents the appearance of a globular sac, the walls of which consist of three concentric layers, lying in contact with and inclos- ing each other, viz., 1st, the structureless vitelline membrane on the outside ; 2d, the externiil layer of the blastodermic membrane, com- posed of cells ; and 3d, the internal layer of the blastodermic mem- brane, also composed of cells. The cavity of the egg is occupied by a transparent fluid, as above mentioned. This entire process of the segmentation of the vitellus and the formation of the blastodermic membrane is one of the most re- markable and important of all the changes which take place during the development of the egg. It is by this process that the simple globular mass of the vitellus, composed of an albuminous matter and oily granules, is converted into an organized structure. For the blastodermic membrane, though consisting only of cells nearly uniform in size and shape, is nevertheless a truly organized mem- brane, made up of fully formed anatomical elements. It is, more- over, the first sign of distinct organization which makes its appear- ance in the egg ; and as soon as it is completed, the body of the new foetus is formed. The blastodermic membrane is, in fact, the body of the foetus. It is at this time, it is true, exceedingly simple BLASTODERMIC MBMBBANE, 609 in texture ; but we shall see hereafter that all the future organs of the body, however varied and complicated in structure, arise out of it, by modification and development of its different parts. The segmentation of the vitellus, moreover, and the formation of the blastodermic membrane, take place in essentially the same manner in all classes of animals. It is always in this way that the egg commences its development, whether it be destined to form afterward a fish or a reptile, a bird, a quadruped, or a man. The peculiarities belonging to different species show themselves afterward, by variations in the manner and extent of the develop- ment of different parts. In the higher animals and in the human subject the development of the egg becomes an exceedingly com- plicated process, owing to the formation of various accessory organs, which are made requisite by the peculiar conditions under which the development of the embryo takes place. It is, in fact, impossible to describe or understand properly the complex embry- ology of the quadrupeds, and more particularly that of the human subject, without first tracing the development of those species in which the process is more simple. "We shall commence our descrip- tion, therefore, with the development of the egg of the frog, which is for many reasons particularly appropriate for our purpose. The egg of the frog, when discharged from the body of the female and fecundated by the spermatic fluid of the male, is deposited in the water, enveloped in a soft elastic cushion of albuminous sub- stance. It is therefore in a situation where it is freely exposed to the light, the air, and the moderate warmth of the sun's rays, and where it can absorb directly an abundance of moisture and appro- priate nutritious material. We find accordingly that under these circumstances the development of the egg is distinguished by a character of great simplicity; since the whole of the vitellus is directly converted into the body of the embryo. There are no acces- sory organs required, and consequently no complications of the formative process. The two layers of the blastodermic membrane, above described, represent together the commencement of all the organs of the foetus. They are intended, however, for the production of two different systems ; and the entire process of their development may be ex- pressed as follows : Tlie external layer of the blastodermic membrane produces the spinal column and all the organs of animal life; while the internal layer produces the intestinal canal, and all the organs of vege- tative life, 89 610 DEVELOPMENT OF THE IMPREGNATED EGG. The first sign of advancing organization in the external layer of the blastodermic membrane shows itself in a thickening and con- densation of its structure. This thickened portion has the form of an elongated oval-shaped spot, termed the " embryonic spot" (Fig. 205), *». the wide edges of which are somewhat ^'g ' 205. more opaque than the rest of the blasto- dermic membrane. Inclosed within these opa(|Ue edges is a narrower cplor- less and transparent space, the "area pellucida," and in its centre is a delicate line, or furrow, running longitudinally from front to rear, which is called the "primitive trace.'' On each side of the primitive trace, iMPBEaNATBD Ego, ■«->th con,. 11 the area pellucida, the substance of mencement of formation of embiy..: the blastodermic membrane rises up in showing embryonic spot, area peUu- ., . n cida, and primitiTo trace. such a manner as to lorm two nearly parallel vertical plates or ridges, which approach each other over the dorsal aspect of the foetus and are therefore called the "dorsal plates." They at last meet on the median line, so as to inclose the furrow above described and con- vert it into a canal. This afterward becomes the spinal canal, and in its cavity is formed the spinal cord, by a deposit of nervous matter upon its internal surface. At the anterior extremity of this canal, its cavity is large and rounded, to accommodate the brain and medulla oblongata ; at its posterior extremity it is narrow and pointed, and contains the extremity of the spinal cord. In a transverse section of the egg at this stage (Fig. 206), the dorsal plates may be seen approaching each other abovCj on each side of the primitive furrow or "trace."' At a more advanced period (Fig. 207) they may be seen fairly united with each other, so as to inclose the cavity of the spinal canal. At the same time, the edges of the thickened portion of the blastodermic membrane grow outward and downward, so as to spread out more and more over the lateral portions of the vitelline mass. These are called the " abdominal plates ;" and as they increase in extent they tend to unite with each other below and inclose the abdominal cavity, just as the dorsal plates unite above, and inclose the spinal canal At last the abdominal plates actually do uiiite with each other on ihe median line (at i. Fig. 207), embracing of course the whole internal layer of the blastodermic membrane (s), which incloses in FORMATION OF ORGANS. 611 its turn the remains of the original vitellus and the albuminous fluid which has accumulated in its cavity. Fig. 206. Fig. 207. Transverse section of Eoa In an earlf stage of development. — 1. External layer of blastodermic membrane. 2, 2. Dorsal plates. 3. Internal layer of blastodermic membrane. Ihpeeqnated Eoo, at a soraewbat more advanced period. — 1. Vmbilicns, or point of union between abdominal plates. 2, 2. Dorsal plates naited with each other on the median line and inclosing the spinal canal. 3, 3. Abdominal plates. 4. Sec- tion of spinal column, with lamlnie »nd ribs. a. Internal layer of blastodermio membrane. During this time, there is formed, in the thickness of the external blastodermic layer, immediately beneath the spinal canal, a longitu dinal cartilaginous cord, called the " chorda dorsalis." Around the chorda dorsalis are afterwa,rd developed the bodies of the vertebrae (Fig. 207, 4), forming the chain of the vertebral column; and the oblique processes of the vertebrse run upward from this point into the dorsal plates ; while the transverse processes, and ribs, run out- ward and downward in the abdominal plates, to encircle more or less completely the corresponding portion of the body. If we now examine the egg in longitudinal section, while this process is going on, the thickened portion of the external blasto- dermic layer may be seen in profile, as at i, Fig. 208. The anterior portion (a), which will form the head, is thicker than the posterior (s), which will form the tail of the young animal. As the whole mass grows rapidly, both in the anterior and the posterior direc- tion, the head becomes very thick and voluminous, while the tail also begins to project backward, and the whole egg assumes a distinctly elongated form. (Fig. 209.) The abdominal plates at the same time 612 DEVELOPMENT OF THE IMPREGNATED EGG. meet upon its under, surface, and the point at which they finally unite forms the abdominal cicatrix or umbilicus. The internal blas- todermic layer is seen, of course, in the longitudinal section of the Fig. 208., Fig. 209. Siagiamof Fsoq'b Ess, in anearljr Btag^e of development ; longitudinal sec- tion. — 1. Thickened portion of external blaetodermic layer, forming body of fcetua. 2. Anterior extremity of foetns. . 3. Poste- rior extremity. 4. Internal layer of blas- todermic membrane. 5. Cavity of Titellu's. Boa or Fboo, in process of develop- ment. egg, as well as in the transverse, embraced by the abdominal plates, and inclosing, as before, the remains of the vitellug. „ ,;> As the development of the above parts goes on (Fig, 210), the head becomes still larger, and soon shows traces of the formation Eoo OF Fboq, farther advanced. of organs of special sense. The tail also increases in size, and pro- jects farther from the posterior extremity of the embryo. The spinal cord runs iu a longitudinal direction from front to rear, and its anterior extremity enlarges, so as to form the braim and medulla oblongata. In the mean time, the internal blastodermic -layer, which is subsequently to be converted into the intestinal canal, has been shut in by the abdominal walls, and still forms a perfectly closed sac, of a slightly elongated figure> without either inlet or outlet. Afterward, the mouth is formed by a process of atrophy and perfo- ration, which takes place through both external and internal layers, FOKMATIOU OF OEOAN3. 613 at the anterior extremity, while a similar perforation, at the poste- rior extremity, results in the formation of the anus. All these parts, however, are as yet imperfect ; and, being merely in the course of formation, are incapable of performing any active function. By a continuation of the same process, the different portions of the external blastodermic layer are further developed, so as to re- sult in the complete formation of the various parts of the skeleton, the integument, the organs of special sense, and the voluntary muscles and nerves. The tail at the same time acquires sufficient size and strength to be capable of acting as an organ of locomo- tion. (Fig. 211.) The intestinal canal, which has been formed from Fig. 211. Tadpole (ally developed. the internal blastodermic layer, is at first a short, wide, and nearly straight tube, running directly from the mouth to the anus. It soon, however, begins to grow faster than the abdominal cavity which incloses it, becoming longer and narrower, and is at the same time thrown into numerous convolutipns. It thus presents a larger internal surface for the performance of the digestive process. Arrived at this period, the young tadpole ruptures the vitelline membrane, by which he has heretofore been inclosed, amd leaves the cavity of the egg. He at first festens himself upon the remains of the albuminous matter deposited round the egg, and feeds upon it for a short period. He soon, however, acquires sufficient strength and activity to swim about freely in search of other food, propelling himself by means of his large, membranous, and fnusciilar tail. The alimentary canal increases very rapidly in length and, becomes spirally coiled up in the abdominal cavity, so as to attain a length from seven to eight times greater than that of the entire body. After a time, a change takes place in the external form of the young animal. The posterior extremities or limbs begin to show 614 DEVELOPMENT OF THE IMPEEGNATBD EGG. themselves, by budding or sprouting from the sides of the body just at the base of the tail, (Fig. 212.) The anterior extremities also grow at this time, but are at first concealed underneath the integu ment. They afterward, however, become liberated, and show them- selves externally. At first both the fore and hind legs, are very small, imperfect in structure, and altogether useless for purposes of locomotion. They soon, however, increase in size and strength; and while they keep pace with the increasing development of the whole body, the tail on the contrary ceases to grow, and becomes shrivelled and atrophied. The limbs^ in fact, are destined finally to replace the tail as organs of locomotion; and a time at last arrives (Fig. 213) when the tail has altogether disappeared, while Fig. 212. Fig. 213. Tadpole, with limbs beginniog to be formed. Perfect Fkoo. the legs have become fully developed, muscular and powerful. Then the animal, which was before confined to an aquatic mode of life, becomes capable of living also upon land, and a trans- formation is thus effected from the tadpole into the perfect frog. During the same time, other changes of an equally important character have taken place in the internal organs. The tadpole at first breathes by gills; but these organs subsequently become atrophied and disappear, being finally replaced by well developed lungs. The structure of the mouth, also, of the integument, and of the circulatory system, is altered to correspond with the varying conditions and wants of the growing animal ; and all these changes taking place, in part successively and in part simultaneously, bring the animal at last to a state of complete formation. FORMATIOX OF ORGANS IN THE FBOG. 615 The process of development may then be briefly recapitulated as follows : — 1. The blastodermic membrane, produced by the segmentation of the vitellus, consists of two cellular layers, viz, an external and an internal blastodermic layer, 2. The external layer of the blastodermic membrane incloses by its dorsal plates the cerebro-spinal canal, and by its abdominal plates the abdominal or visceral cavity, 8. The internal layer of the blastodermic membrane forms the intestinal canal, which becomes lengthened and convoluted, and communicates with the exterior by a mouth and anus of secondary formation. 4. Finally the cerebro-spinal axis and its nerves, the skeleton the organs of special sense, the integument, and the muscles, are developed from the external blastodermic layer ; while the antenor and posterior extremities are formed from the same layer by a pro- cess of sprouting, or continuous growth. 616 THE UMBILICAL YESIGLK. CHAPTER VIII. THE UMBILICAL VESICLE. Pig. 214. In the frog, as we have seen, the ahdominal plates, closing together in, front and underneath the body of the animal, shut in directly the whole of the vitellus, and join each other upon the median line, at the umbilicus. The whole remains of the vitellus are then inclosed in the abdomen of the animal, and in the intestinal sac formed by the internal blastodermic layer. In many instances, however, as, for example, in several kinds of fish, and in all the birds and quadrupeds, the abdominal plates do not immediately embrace the whole of the vitelline mass, but tend to close together about its middle; so that the vitellus is constricted, in this way, and divided into two portions: one internal, and one external. (Fig. 214.) As the process of development proceeds, the body of the foetus increases in size, out of pro- portion to the vitelline sac, and the con- striction just mentioned becomes at the same time more strongly marked ; so that the separation between the internal and external portions of the vitelline sac is nearly complete. (Fig. 215.) The internal layer of the blastodermic membrane is by the same means divided into two portions, one of which forms the intestinal canal, while the other, remaining outside, forms a sac-like appendage to the abdo- men, which is known by the name of the umhilical vesicle. The umbilical vesicle is accordingly lined by a portion of the internal blastodermic layer, continuous with the mucous membrane of the intestinal canal ; while it is covered on the outside by a por- tion of the external blastodermic layer, continuous with the integu- ment of the abdomen. Gas OF Fish, showing forma- tion of nmbilical vesicle. THE UMBILICAL TKSICLE. 617 After the young animal leaves the egg, the umbilical vesicle in some species becomes withered and atrophied by the absorption of its contents; while in others, the abdominal walls gradually TouDg Fish with ttmbilical vesicle. extend over it, and crowd it back into the abdomen ; the nutritious matter which it contained passing from the cavity of the vesicle into that of the intestine by the narrow passage or canal which remains open between them. In the human subject, however, as well as in the quadrupeds, the umbilical vesicle becomes mor,e completely separated from the abdo- men than in the cases just mentioned. There is at first a wide com- munication between the cavity of the umbilical vesicle and that of the intestine; and this communication, as in other instances, becomes gradually narrowed by the increasing constriction of the abdominal walls. Here, however, the constriction proceeds so far that the opposite surfaces of the canal come in contact with- each other, and adhere ; so that the narrow passage previously existing, between the cavity of the intestine Fig. 216. and that of the umbilical vesicle, is obliterated, and the vesicle is then connected with the abdomen only by an impervious cord. This cord afterward elongates, and becomes con- verted into a slender, thread-like pedicle (Fig. 216), passing out from the abdomen of the foetus, and connected by its farther extremity with the umbilical vesicle, which is filled with a transparent, colorless fluid. The umbilical J:,Z^.f:j:."LTZ vesicle is very distinctly visible in the human flfth weeit. foetus so late as the end of the third month. After that period it diminishes in size, and is gradually lost in the advancing development of the neighboring parts. In the formation of the umbilical vesicle, we have the first variar 618 THE UMBILICAL VBSIGLB. tion from the sirrvple plan of development described in the preceding chapter. Here, the whole of the vitellus is not directly converted into the body of the embryo ; but while a part of it is taken, as usual, into the abdominal cavity, and used immediately for the purposes of nutrition, a part is left outside the abdomen, in the umbilical vesicle, a kind of secondary organ or appendage of the foetus. The contents of the umbilical vesicle, however, are after- ward absorbed, and so appropriated, finally, to the nourishment of the newly-forme^ tissues. AMNION AND ALLANTOIS. 619 CHAPTER IX. AMNION AND ALL ANTOIS.— DEVELOPMENT* OP THE CHICK. • We shall now proceed to the description of two other accessory organs, which are formed, during the development of the fecundated egg, in all the higher class^ of animals. These are the amnion and the allantois ; two organs which are always found in company with 6ach other, since the object of the first is to provide for the forma- tion of the second. The amnion is formed from the external layer of the blastodermic membrane, the allantois from the internal layer. In the frog and in fish, as we have seen, the egg is abundantly supplied with moisture, air, and nourishment, by the water with which it is surrounded. It can absorb directly all the gaseous and liquid substances, which it requires for the purposes of nutrition and growth. The absorption of oxygen, the exhalation of carbonic acid, and the imbibition of albuminous and other liquids, can all take place without difiiculty through the simple membranes of the egg; particularly as the time required for the formation of the embryo is very short, and as a great part of the process of develop- ment remains to be accomplished after the young animal leaves the egg. But in birds and quadrupeds, the time required for the develop- ment of the foetus is longer. The young animal also acquires a much more perfect organization during the time that it remains inclosed within the egg ; and the processes of absorption and exha- lation necessary for its growth, being increased in activity to a corresponding degree, require a special organ for their accomplish- ment. This special organ, destined to bring the blood of the foetus into relation with the atmosphere and external sources of nutrition, is the allantois. In the frog and the fish, the internal blastodermic layer, forming the intestinal mucous membrane, is inclosed everywhere, as above described, by the external layer, forming the integument; and 620 AMNION AND ALLANTOIS. consequently it can nowhere come in contact with the investing membrane of the egg. But in the higher animals, the internal blastodermic layer, which is the seat of the greatest vascularity, and which is destined to produce the allantois, is made to come in contact with the external membrane of the egg for purposes of exhalation and absorption ; and this can only be accomplished by opening a passage for it through the external germinative layer. This is done in the following manner, by the formation of the amnion. Soon, after the body of the foetus has begun to be formed by the thickening of the external layer of the blastodermic membrane, a double fold of this external layer rises up on all sides about the edges of the newly-formed embryo ; so that the body of the foetus appears as if sunk in a kind of depression, and surrounded with a membranous ridge or embankment, as in Fig. 217. The embryo (c) is here seen in profile, with the double, membranous folds, above men- tioned, rising up just in advance of the head, and behind the posterior extremity. It must be understood, of course, that the, same thing takes place on the two sides of the foetus, by the formar 'Diagram of fecon- tiou of lateral folds simultaneously with the VZlLnlt'^mZ^l appearance pf those in front and behind., As it a. viteiius. ». External jg thcse folds which are dcstincd to form the layer of 'blastodermic . .i n i j_i // • j.- ^ i t n membrane, c. Body of ■ amuion, they are called the "amniotic folds." embryo. d,a. Amniotic The amuiotio folds coutinuc to grow, and ex- fjlds. «. Vitelline mem- .,., , „ j-li jjii.ii brane. tsud themselvcs, forward, backward, and Jaterally, until they approach each other at a poii)t over the back of the foetus (Fig. 218), which is termed the "amniotic umbilicus." Their opposite edges afterward actually come in con- tact with each other at this point, and adhere together, so as to ' shut in a space or cavity (Fig. 218, 6) between their inner surface and the body of the foetus. This space, which, is filled with a clear fluid, is called the amniotic cavity. At the same time, the intestinal canal has begun to be formed, and the umbilical vesicle hsis been partially separated from it, by the constriction of the abdoi|iin4 walls on the under surface of the body. There now appears a prolongation or diverticulum (Fig. 218, c) growing out from the posterior portion of the intestinal canal, and following the course of the amniotic fold which has preceded it; occupying, as it gradually enlarges and proti-udes, the space left AMNION AND ALLANTOIS. 621 Fig. 218. Fecdkdatt.s Egq, farther advaaced. — a. Umbilical vesicle, d. Amniotic cavity, c. Ai- laatois. Fig. 219. vaijdut bj? the rising up of the amniotic fold. This diverticulum is the commencement of the allantois. It is an elongated mem- branous sac, continuous with the posterior portion of the intestine, and containing bloodvessels derived from those of the intestinal circulation. The cavity of the allantois is also continuous with the cavity of the intestine. After the amniotic folds have approached and touched each other, as ' already described, over the back of the foetus, at the amniotic umbilicus, the adjacent surfaces, thus brought in contact, fuse together, so that the cavities of the two folds, coming respectively from front and rear, are separated only by a single membranous par- tition (Fig. 219, c) running from the inner to the outer lamina of the amniotic folds. This parti- tion itself soon after atrophies and disappears ; and the inner and outer laminae become consequently sepai-ated from each other. Tho inner lamina (Fig. 219, a) which remains con- tinuous with the integunient of the foetus, in- closing the body of the embryo in a distinct cavity, is called the amnion (Fig. 220, b), and its cavity is known as the amniotic cavity. The outer lamina of the amniotic fold, on the other hand (Fig. 219, b), recedes farther and farther from the inner, yntil it comes in con- tact with the original vitelline membrane, still covering the exterior of the egg ; and by con- tinued growth and expansion it at last fuses with the vitelline membrane and unites with its substance, so that the two membranes form but one. This membrane, formed by the fusion and consolidation of two others, constitutes then the external investing membrane of the egg. The allantois, during all this time, is increas- ing in size and vascularity. Following the course of the amniotic folds as before, it insinuates itself between them, and of course soon comes in contact with the external investing membrane just de- scribed. It then begins to expand laterally in every direction, enveloping more and more the body of the foetus, and bringing its vessels into contact with the external membrane of the egg. Fecundated Ego, with allantois nearly com- plete. — a. Inner lamina of amniotic fold. b. Onter la- mina of ditto, c. Point where the amniotic folds come in contact. The allan- tois is seen penetrating be- tween the inner and outer lamina of the amniotic folds. 622 AMNION AND ALLANT0I3. By a continuation of the above process, tlie ailantois at last grows to such an extent as to envelope completely the body of the embryo, together with the amnion; its two Fig. 220. extremities coming in contact with each other and fusing together over the back of the foetus, just as the amniotic folds had previously done. (Fig. 220.) It lines, there- fore, the whole internal surface of the in- vesting membrane with a flattened, vascu- lar sac, the vessels of which come from the interior of the body of the foetus, and which FEonNDATKT'Eoa, with Still communicatcs with the cavity of the ailantois fully formed. -o. Urn- intestinal Caual. bllical vesicle, b. Amuion. c. . . , . , , , . Ailantois. it IS evident, irom the above description, that there is a close connection between the formation of the amnion and that of the ailantois. For it is only in this manner that the ailantois, which is an extension of the in- ternal layer of the blastodermic membrane, can come to be situated outside the foetus and the amnion, and be brought into relation with external surrounding media. The two lamince of the amni- otic folds, in fact, by separating from each other as above described, open a passage for the ailantois, and allow it to come in contact with the external membrane of the egg. In order to explain more fully the physiological action of the ailantois, we shall now proceed to describe the process of develop- ment, as it takes place in the egg of the fowl. In order that the embryo may be properly developed in any case, it is essential that it be freely supplied with air, warmth, moisture, and nourishment. The egg of the fowl contains already, when discharged from the generative passages, a sufficient quantity of moisture and albuminous material. The necessary warmth is supplied by the body of the parent during incubation ; while the atmospheric ga^es can pass and repass through the porous egg- shell, and by endosmosis through the fibrous membranes which line its cavity. "When the egg is first kid, the vitellus, or yolk, is enveloped in a thick layer of semi-solid albumen. On the commencement of incubation, a liquefaction takes place in the albumen immediately above that part of the vitellus which, is occupied by the cicatri- cula; so that the vitellus rises or floats upward toward the surface, by virtue of its spoifio gravity, and the cicatricula comes to be DEVELOPMENT OF THE CKIOK. 623 placed almost immediately tmderneath the lining membrane of tlie egg-shell. As the cicatricula is the spot from which the process of embryonic development commences, the body of the young foetua is by this arrangement placed in the most favorable position for the reception of warmth and other necessary external influences through the egg-shell. The liquefied albumen is also absorbed by the vitelline membrane, and the vitellus thus becomes larger, softer, and more diffluent than before the commencement of incubation. As soon as the circulatory apparatus of the embryo has been fairly formed, two minute arteries are seen to run out from its lateral edges and spread into the neighboring parts of the blasto- dermic membrane, breaking up into inosculating branches, and covering the adjacent portions of the vitellus with a plexus of capillary bloodvessels. The space occupied in the blastodermic membrane, on the surface of the vitellus, by these vessels, is called the arm vasculosa. (Fig. 221.) It is of a nearly circular shape, Fig. 221. Ea<} OF Fowl dnring early periods of incabatlon ; aliowiQg the body of the embryo, and the area vasculoaa partially covering the surface of the vltellas. and is limited, on its outer edge, by a terminal vein or sinus, called the " sinus terminalis." The blood is returned to the body of the foetus by two veins which penetrate beneath its edges, one near the head and one near the tail. The area vasculosa tends to increase in extent, as the develop- ment of the foetus proceeds and its circulation becomes more active. It soon covers the upper half, or hemisphere, of the vitellus, and the terminal sinus then runs like an equator round the middle of the vitelline sphere. As the growth of the vascular plexua con- 624 AMNION AND ALLANTOIS. tinues, it passes this point, and embraces more and more of the in- ferior, as well as of the superior hemisphere, the vessels converging toward its under surface, until at last nearly the whole of the vitellus is covered with a network of inosculating capillaries. The function of the vessels of the area vasculosa is to absorb nourishment from the cavity of the vitelline sac. As the albuinen liquefies during the process of incubation, it passes by endosmosis, more and more abundantly, into the vitelline cavity; the whole vitellus growing constantly larger and more fluid in consisteney. The blood of the- foetus, then circulating in the vessels of the area vasculosa, absorbs freely the oleagino-albUminous matters of the vitellus, and, carrying them back to the foetus by the returning veins, supplies the newly-formed tissues and organs with abun- dance of appropriate nourishment. During this period the amnion and the allantois have been also in process of formation. At first the body of the foetus lies upon its abdomen, as in the cases previously described ; but, as it increases in size, it alters its position so as to lie more upon its side. The allantois the4 emerging from the posterior portion of the abdominal cavity, turns directly upward over the body of the foetus, and comes immediately in contact with the shell membrane. (Fig. 222.) It Fig. 222. Eaa OF Fowl at a more advanced period of development. The body of the foctas is enveloped by the amnion, and hae the umbilical vesicle hanging from its under surface; while the vascular allantois is seen taming upward and spreading ont over the internal surface of the shell-mem braoe, then spreads out rapidly, extending toward the extremities and down the sides of the egg, enveloping more and more completely DEVELOPMENT OP THE CHICK. 625 the foetus and the vitelline sae, and taking the place of the albumen which has been liquefied and absorbed. It will also be seen, by reference to the figure, that the umbilical vesicle is at the same time formed by the separation of part of the viteilus from the abdomen of the chick ; and the vessels of the area vasculosa, which were at first distributed over the viteilus, now ramify, of course, upon the surface of the umbilical vesicle. At last the allantois, by its continued growth, envelopes nearly the whole of the remaining contents of the egg ; so that toward the later periods of incubation, at Whatever point we break open the egg, we find the internal surface of the shell-membrane lined with a vascular membranous expansion, supplied by arteries which emerge from the abdomen of the foetus. It is easy to see, accordingly, with what readiness the absorption and exhalation of gases may take place by means of the allantois. The air penetrates from the exterior through the minute pores of the calcareous shell, and then acts upon the blood in the vessels of the allantois very much in the same manner that the air in the minute bronchial tubes and air- vesicles of the lungs acts upon the blood in the pulmonary capillaries. Examination of the egg, furthermore, at vaj-ious periods of incubation, shows that changes take place in it which are entirely analogous to those of respiration. The egg, in the first place, during its development, loses water by exhalation. This exhalation is not a simple effect of evaporation, but is the result of the nutritive changes going on in the interior of the egg ; since it does not take place, except in a comparatively slight degree, in unimpregnated eggs, or in those which are not incubated, though they may be freely exposed to the air. The exhalation of fluid is also essential to the processes of development, for it has often been found, in hatching eggs by artificial warmth, that if the air of the chamber in which they are inclosed become unduly charged with moisture, so as to retard or prevent further exhalation, the eggs readily become spoiled^ and the development of the embryo is arrested. The loss of weight during natural incu- bation, principally due to the exhalation of water, has been found by Baudrimont and St. Ange' to be over 15 per cent, of the entire weight of the egg. Secondly, the egg absorbs oxygen and exhales carbonic acid. The two observers mentioned above, ascertained that during eigh- ' Dn DfiTeloppetnent du Foetus. Paris, 1850, p. 143. 626 AMNION AND ALLANTOIS. teen days' incubation, the egg absorbs nearly 2 per cent, of its weight of oxygen, while the quantity of carbonic acid exhaled from the sixteenth to the nineteenth day of incubation amounts to no less than 3 grains in the twenty-four hours.' It is curious to observe, also, that in the egg during incubation, as well as in the adult animal, more oxygen is absorbed than is returned by exhalation under the form of carbonic acid. It is evident, therefore, that a true respiration takes place, by means of the allantois, through the membranes of the shell. The allantois, however, is not simply an organ of respiration ; it takes part also in the absorption of nutritious matter. As the pro- cess of development advances, the skeleton of the young chick, at first entirely cartilaginous, begins to ossify. The calcareous mat- ter, necessary for this ossification, is, in all probability, derived from the shell. The shell is certainly lighter and more fragile toward the end of incubation than at first ; and, at the same time, the cal- careous ingredients of the bones' increase in quantity. The lime- salts, requisite for the process of ossification, are apparently ah- sorbed from the shell by the vessels of the allantois, and by them transferred to the skeleton of the growing chick ; so that, in the same proportion that the former becomes weaker, the latter grows stronger. This diminution in density of the shell is connected not only with the development of the skeleton, but also with the final escape of the chick from the egg. This deliverance is accomplished mostly by the movements of the chick itself, which become, at » certain period, sufficiently vigorous to break out an opening in the attenuated and weakened egg-shell. The first fracture is generally accomplished by a stroke from the end of the bill ; and it is pre- cisely at this point that the solidification of. the skeleton is most advanced. The egg-shell itself, therefore, which at first only serves for the protection of the imperfectly-formed embryo, afterward furnishes the materials which are used to accomplish its own demo- lition, and at the same time to efieot the escape of the fully deve- loped foetus. Toward the latter periods of incubation, the allantois becomes more and more adherent to the internal surface of the shell-mem- brane. At last, when the chick, arrived at the full period of de- velopment, escapes from its confinement, the allantoic vessels are torn off at the umbilicus ; and the allantois itself, cast off as a use- ' Op. cit., pp. 138 and 149. DEVELOPMENT OP THE CHICK. 627 less and effete organ, is left behind in the cavity of the abandoned egg-shell. The allantois is, therefore, strictly speaking, a foetal organ. Developed as an accessory structure from a portion of the intestinal canal, it is exceedingly active and important during the middle and latter periods of incubation; but when the chick is completely formed, and has become capable of carrying on an in- dependent existence, both the amnion and the allantois are detached and thrown off as obsolete structures, their place being afterward supplied by other organs belonging to the adult condition. 628 DEVELOPMENT OP THE EGG IN HCilAN SPECIES. CHAPTER X. DEVELOPMENT OF THE EGG IN THE HUMAN SPECIES— FORMATION OP THE CHORION. We have already described, in a preceding chapter, the manner in which the outer lamina of the amniotic fold becomes adherent to the adjacent surface of the vitelline membrane, so as to form with it but a single layer ; and in which these two membranes, thus fused and united with each other, form at that time the single ex- ternal investing membrane of the egg. The allantois, in its turn, afterward comes in contact with the investing membrane, and lies immediately beneath it, as a double vascular membranous sac. In the egg of the human subject the development of the membranes, though carried on essentially upon the same plan with that which we have already described, undergoes, in addition, some further modifications, which we shall now proceed to explain. The first of these peculiarities is that the allantois, after spread- ing out upon the inner surface of Fig. 223. jjjg external investing membrane,- adheres to, and fuses with it, just as the outer lamina of the amni- otic fold has previously fused with the vitelline membrane. At the same time, the two layers he- longing to the allantois itself also come in contact and fuse toge- ther ; so that the cavity of the allantois is obliterated, and instead of forming a membranous sac con- taining fluid, this organ is convert- ed into a simple vascular membrane. (Fig. 223.) This membrane, moreover, being, after a time, thoroughly fused and united with the two which have preceded it, takes the place which was previously HiTUAN 07I7H, about the end of the first month ; showing formation of chorion. — 1. Uinhilical vesicle. 2. Amnion, 3, Chorion. FORMATION OV THK CHORION, 629 occupied by them. It is then termed the chorion, and thus becomes the sole external investing membrane of the egg. We find, therefore, that the chorion, that is, the external coat or investment of the egg, is formed successively by three distinct membranes, as follows: first, the original vitelline membrane; secondly, the outer lamina of the amniotic fold ; and, thirdly, the allantois ; the last predominating over the two former by the rapidity of its growth, and absorbing them into its substance, so that they become finally completely incorporated with its texture. It is easy to see, also, how, in consequence of the above process, the body of the foetus, in the human egg, becomes inclosed in two distinct membranes, viz,, the amnion, which is internal and conti- nuous with the foetal integument, and the chorion, which is external and supplied with vessels from the cavity of the abdomen. The umbilical vesicle is, of course, situated between the two ; and the rest of the space between the chorion and the amnion is occupied . by a semi-fluid gelatinous material, somewhat similar in appearance to that of the vitreous body of the eye. The obliteration of the cavity of the allantois takes place very early in the human subject, and, in fact, keeps pace almost entirely with the progress of its growth ; so that this organ never presents, in the human egg, the appearance of a hollow sac, filled with fluid, but rather that of a flattened vascular membrane, enveloping the body of the foetus, and forming the external membrane of the egg, Notwithstanding this difference, however, the chorion of the human subject, in respect to its mode of formation, is the same thing with the allantois of the lower animals ; its chief peculiarity consisting in the fact that its opposite surfaces are adherent to each other, instead of remaining separate and inclosing a cavity filled with fluid. The next peculiarity of the human chorion is, that it hecomes shaggy. Even while the egg is still very small, and has but recently found its way into the uterine cavity, its exterior is already seen to be covered with little transparent prominences, like so many villi (Fig, 223), which increase the extent of its surface, and assist in the absorption of fluids from without. The villi are at this time quite simple in form, and altogether homogeneous in structure, As the egg increases in size, the villi rapidly elongate, and be- come divided and ramified by the repeated budding and sprouting of lateral offshoots from every part. After this process of growth 630 DEVELOPMENT OF THE EGG IN HUMAN SPECIES. Fig. 224. has gone on for some time, the external surface of the chorion pre- sents a uniformly velvety or shaggy appearance, owing to its being covered everywhere with these tufted and compound villosities. The villosities themselves, when examined by the microscope, have an exceedingly well-marked and characteristic appearance. (Fig. 224.) They originate from the surface of the chorion by a somewhat narrow stem, and divide into a multitude of secondary and tertiary branches, of varying size and jBgure ; some of them slender and filamentous, others club-shaped, many of them irregularly swollen at various points. All of them termi- nate by rounded extremities, giving to the whole tuft a certain resem- blance to some varieties of sea-weed. The larger trunks and branches of the villosity are seen to contain nu- merous minute nuclei, imbedded in a nearly homogeneous, or finely gra- nular substratum. The smaller ones appear, under a low magnifying power, simply granular in texture. These villi are altogether peculiar in appearance, and quite unlike any other structure which may be met with in the body. Whenever wo find, in the uterus, any portion of a membrane having villosities like these, we may be sure that pregnancy has existed ; for such villosities can only belong to the chorion, and the chorion itself is a part of the foetus. It is developed, as we have seen, as an out- growth from the intestinal canal, and can only existj accordingly, as a portion of the fecundated egg. The presence of portions of a shaggy chorion is therefore as satisfactory proof of the existence of pregnancy, as if he had found the body of the foetus itself. While the villosities which we have just described are in pro- cess of formation, the allantois itself has completed its growth, and has become converted into a permanent chorion. The bloodvessels coming from the allantoic arteries accordingly ramify over the chorion, and supply it with a tolerably abundant vascular network. The growth of the foetus, moreover, at this time, has reached such a state of activity, that it requires to be supplied with nourishment Componiid villosity of Hcmah Cho- BION, Tamifled extremity. From a three months' foetus. Magnified 30 diameters. FORMATION OF THE CHOKION. 681 by vasculur absorption, instead of the slow process of imbibition, which has heretofore taken place through the comparatively incom- plete and structureless villi of the cho- rion. The capillary vessels, accordingly, Fig- 225. ■with which the chorion is supplied, begin to penetrate into the substance of its vil- losities. They enter the base or stem of each villosity, and, following every divi- sion of its compound ramifications, finally reach its rounded extremities. Here they turn upon themselves in loops (Fig. 225), like the vessels in the papillje of the skin, and retrace their course, to unite finally with the venous trunks of the chorion. The villi of the chorion are, therefore, - . .. , j.iiv »*■'**. vj. v^\j v/uvx&wu c*i\y, v^\ji.\ji\jA\jj Extremity of tillositt of very analogous in structure to those of choeion, more iiighiy Eagai- .^ ' , ,' 1,1* n 1 ^^^ > Bhowiug the arrangement of the intestme; and their power of absorp- woodvesseie in its interior, tion, as in other similar instances, corre- sponds with the abundance of their ramifications, and the extent of their vascularity. It must be remembered, also, that these vessels all come from the abdomen of the foetus ; and that whatever substances are taken up by them are transported directly to the interior of the embryo, and used for the nourishment of its tissues. The chorion, therefore, as soon as its villi and bloodvessels are completely developed, becomes an exceedingly active organ in the nutrition of the foetus ; and con- stitutes, in fact, the only means by which new material can be in- troduced from without. The existence of this general vascularity of the chorion affords also, as Coste was the first to point out, a' striking indication that this membrane is in reality identical with the allantois of the lower animals. If the reader will turn back to the illustrations of the formation of the amnion and allantois (Chap. IX.), he will see that the first chorion or investing membrane is formed exclusively by the vitelline membrane, which is never vascular and cannot be- come so by itself, since it has no direct connection with the foetus. The second chorion is formed by the union of the vitelline mem- brane with the outer lamina of the amniotic fold. Both laminae of the amniotic fold are at first vascular, since they are portions of the external blastodermic layer, and derive their vessels from the integument of the foetus. But after the outer lamina has become 632 DEVELOPMENT OF THE EGG IN HUMAN SPECIES. completely separated from the inner, by the disappearance of the partition -which for a time connected the two with each other (Fig. 219, c), this source of vascular supply is out off; and the second chorion cannot, therefore) remain vascular after that period. But the third or permanent chorion, that is, the allantois, derives its ves- sels directly from those of the foetus, and retains its connection with them during the whole period of gestation. A chorion, therefore, which is universally and permanently vascular, can be no other than the allantois, converted into an external investing membrane of the egg. Thirdly, the chorion, which is at one time, as we have seen, every- where villous and shaggy, becomes afterward partially bald. This change begins to take place about the end of the second month. It commences at a point opposite the situation of the foetus and the insertion of the foetal vessels. The villosities of this region cease growing ; and as the entire egg continues to enlarge, the villosities at the point indicated fail to keep pace with its growth; and with the progressive expansion of the chorion. They accordingly be- come at this part thinner and more scattered, leaving the surface of the chorion comparatively smooth and bald. This baldness in- creases in extent and becomes more and more complete, spreading and advancing over the adja- Fig. 226. ggjj^ portions of the chorion, until at least two-thirds of its surface have become nearly or quite destitute of villosities. At the opposite point of the surface of the egg, however, that portion, namely^ which corresponds with the insertion of the foetal vessels, the villosi- ties, instead of becoming atro- phied, continue to grow; and this portion of the chorion be- comes even more shaggy and thickly set than before. The consequence is that the chorion afterward presents a very different appearance at different portions of its surface. (Fig. 226.) The greater part of it is smooth ; but a certain portion, constituting about one-third of the whole, is covered with a soft and spongy mass of long, thickly-set, compound villosities. It is this thickened HuHAH OvuHst end of third montb ; sboiring placental portion of the chorion fnlly formed. FORMATION OF THE CHORION. 633 and sliaggy portion, wbicli is afterward concerned in the formation of the placenta ; while the remaining smooth portion continues to be known under the name of the chorion. The placental portion of the chorion becomes distinctly limited and separated from the remainder by about the end of the third month. The vascularity of the chorion keeps pace, in its different parts respectively, with the atrophy and development of its villosities. As the villosities shrivel and disappear over a part of its extent, the looped capillary Vessels, which they at first contained, disappear also ; so that the smooth portion of the chorion shows afterward only a few straggling vessels running over its surface, and does not contain any abundant capillary plexus. In the thickened portion, on the other hand, the vessels lengthen and ramify to an extent corresponding with that of the villosities in which they are situated. The allantoic arteries, coming from the abdomen of the foetus, enter the villi, and penetrate through their whole extent ; forming,- at the placental portion of the chorion, a mass of tufted and ramified vas- cular loops, while over the rest of the membrane they are merely distributed as a few single and scattered vessels. The chorion, accordingly, is the exteinal investing membrane of the egg, produced by the consolidation and transformation of the allantois. The placenta, furthermore, so far as it has now been described, is evidently a part of the chorion ; that part, namely which is thickened, shaggy, and vascular, while the remainder is comparatively thin, smooth, and membranous. / 634 DEVELOPMENT OF UTERINE MUCOUS MEMBRANE. CHAPTER XI. DEVELOPMENT OF UTERINE MUCOUS MEMBRANE- FORMATION OF THE DEOIDUA. In fish, reptiles, and birds, the egg is either provided with a sup- ply of nutritious material contained within its membranes, or it is so placed, after its discharge from the body of the parent, that it can absorb these materials from without. Thus, in the egg of the bird, the young embryo is supported upon the albuminous matter deposited around the vitellus ; while in the frog and fish, moisture, oxygen, saline substances, &c., are freely imbibed from the water in which the egg is placed. But in the quadrupeds, as well as in the human species, the egg is of minute size, and the quantity of nutritious matter which it contains is sufficient to last only for a very short time. Moreover, the development of the foetus takes place altogether within the body of the female, and no supply, therefore, can be obtained directly from the external media. In these instances, accordingly, the mu- cous membrane of the uterus, which is found to be unusually developed and increased in functional activity during the period of gestation, becomes a source of nutrition for the fecundated egg. The uterine mucous membrane, thus developed and hypertrophied, is known by the name of the Decidua. It has received this name because, as we shall hereafter see, it becomes exfoliated and thrown offj at the same time that the egg itself is finally discharged. The mucous membrane of the body of the uterus, in the unimpreg- nated condition, is quite thin and delicate, and presents a smooth and slightly vascular internal surface. There is, moreover, no layer of submucous cellular tissue between it and the muscular substance of the uterus; so that the mucous membrane cannot here, as in most other organs, be easily dissected up and separated from the subjacent parts. The structure of the mucous membrane itself, however, is sufficiently well marked and readily distinguishable FORMATION OF THE DKCIDUA. 635 Fig. 227. Utbrihe Mvcors ME»BBAiiE,as EeeD in vertical section. — a. Free surface, b. Attached surface. from that of other parts. It consists, throughout, of minute tubular follicles, ranged side by side, and running perpendicularly to the free surface of the mucous membrane. (Fig. 227.) Near this free surface, they are nearly straight; but toward the deeper sur- face of the mucous membrane, where they terminate in blind extremities, they become more or less wavy or spiral in their course. The tubules are about j^^ of an inch in diameter, and are lined throughout with co- lumnar epithelium. (Fig. 228.) They occupy the entire thickness of the ute- rine mucous membrane, their closed extremities resting upon the subjacent muscular tissue, while their mouths open into the cavity of the ute- rus. A few fine bloodvessels penetrate the mucous membrane from below, and, running upward between the tubules, encircle their superficial extremities with a capillary network. There is no areolar tissue in the uterine mucous mem- brane, but only a small quan- tity of spindle-shaped fibro- plastic fibres, scattered be- tween the tubules. As the fecundated egg is ftbout to descend into the cavity of the uterus, the mu- cous membrane, above de- scribed, takes on an increas- ed activity of growth and an unusual development. It becomes tumefied and vascular ; and, as it increases in thickness, it projects, in rounded eminences or convolutions, into the uterine cavity. (Fig. 229.) In this process, the tubules of the uterus in- crease in length, and also become wider ; so that their open mouths may be readily seen by the naked eye upon the uterine surface, as numerous minute perforations. The bloodvessels of the mucous membrane also enlarge and multiply, and inosculate freely with Utbrine TuBai.R?, from mucous membrane or uuimpregnated human uterus. 636 DEVELOPMENT OF UTEBIITE MUCOUS MEMBEANE, each other ; so that the vascular network encircling the tubules be- comes more extensive and abundant. The internal surface of the uterus, accordingly, after this process has been for some time going on, presents a thick, rich, soft, vas- cular, and velvety lining, quite different from that which is to be found in the unimpregnated condition. In consequence of this difference, the lining membrane of the uterus, in the impregnated condition, was formerly supposed to be an entirely new product, thrown out by exudation from the uterine surface, and analogous, in this respect, to the inflammatory exudations of croup and pleu- risy. It is now known, however, to be no other than the mucous membrane of the uterus itself, thickened and hypertrophied to an extraordinary degree, but still retaining all its natural connections and its original anatomical structure. The hypertrophied mucous membrane, above described, consti- tutes the Decidua vera. Its formation is confined altogether to the body of the uterus, the mucous membrane of the cervix taking no part in the process, but retaining its original appearance. The decidua vera, therefore, commences above, at the orifices of the Fallopian tubes, and ceases below, at the situation of the os inter- num. The cavity of the cervix, meanwhile, begins to be filled with an abundant secretion of its peculiarly viscid mucus, which blocks up, more or less completely, its passage, and protects t}ie internal cavity. But there is no membranous partition at this time covering the os internum, and the mucous membranes of the cervix and of the body of the uterus, though very different in appearance, are still perfectly continuous with each other. When we cut open the cavity of the uterus, therefore, in this condition, we find its internal surface lined with the decidua vera, with the opening of the OS internum below and the orificeaof the Fallopian tubes above, perfectly distinct, and in their natural positions. (Fig. 229.) As the fecundated egg, in its journey from above downward, passes the lower orifice of the Fallopian tube, it insinuates itself between the opposite surfaces of the uterine mucous membrane, and becomes soon afterward lodged in one of the furrows or de- pressions between the projecting convolutions of the decidua. (Fig. 229.) It is at this situation that an adhesion subsequently takes place between the external membranes of the egg, on the one hand, and the uterine decidua on the other. Now, at the point where the egg becomes fixed and entangled, as above stated, a still more rapid development than before takes place in the uterine FORMATION OF THE DBOIDUA. 637 mucous membrane. Its projecting folds begin to grow up around the egg in such a manner as to partially inclose it in a kind of circumvallation of the decidua, and to shut it off, more or less corn- Fig. 229. Fig. 230. iHFEEa^iLTEO Uteehb; nhoving .formatioa of decidua. The decidua is represented in black ; and the egg is fieen, at the fundus of the aterus, en- gaged between two of its 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. Fiif. 281. pletely, from the general cavity of the uterus. (Fig. 230.) The egg is thus soon contained in a special cavity of its own, which stiil 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 othelr 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. 231), it will be seen that the egg is coni- 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 Impregnated UTERns;— showing egg completely inclo.-ed by decidua reflexa. 638 DEVKLOPMENT OF UTERINE MUCOUS MEMBKANE. newly -formed layer of decidua, enveloping, as above described, the projecting portion of tbe egg, is called tbe Decidua reflexa; because it is reflected over the egg, by a continuous growth from the general surface of the uteri ne mucous membrane. The orifices of tbe .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 smootb 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 yera, 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 tbe 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 B-OKMATION OP THE DECIDUA. 639 Fig. 232. formation of the embryo in the egg, and the development of the amnion and chorion have been going on simultaneously. Soon after the entrance of the egg into the uterine cavity, its external investing membrane becomes covered with projecting filaments, or viliosities, 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 decidua ,reflexa with which it is covered. (Fig. 232.) 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. "Very 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. Bach villosity, then, as it lies imbedded in its uterine follicle, contains a vascular loop through which the foetal blood circulates, increasing the rapidity with which absorption and exhalation take place. Subsequently, furthermore, these vascular tufts, which are at first uniformly abundant throughout the whole extent of the chorion. Impregnated UTZRas; BhowlDg Goimectioii betweeQ vil- losities of chorion and decidual membrauea. 640 DEVELOPMKNT OP UTBBINE MUCOUS MEMBBANE. Fig. 233. 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. 233.) This is the spot at which the egg is in contact with the decidua vera. Here, therefore, both ^m^a&i:^^^,.^^,^.,-^^.,^,,^ • ■> the decidual membrane and the tufts P -jtigWHl'L- of t^s 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 t\ '^k ~ ^^ / destitute of vessels, but the decidua re- 1 ^\^^N-,;7^^^-^ flexa, which is in contact with it, also lb I §^ I loses its activity of growth, and be- K i ^^ / comes expanded into a thin layer, nearly ^ \Mxy 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 formatioa of placenta, by the united development of a portion of the de- cidua and the Tillosltiea of the cho- rion. THE PLACENTA. 641 CHAPTER XII. THE PLACENTA. We have shown in the, preceding chapters. that the foetus, during its development, depends for its supply of nutriment upon the lining membrane of the maternal uterus ; and that the nutriment, so sup- plied, is absorbed by the bloodvessels of the chorion, and transported in this way into the circulation of the foetus. In all instances, ac- cordingly, in which the development of the foetus takes place within the body of the parent, it is provided for by the relation thus esta- blished between two sets of membranes; namely; the maternal membranes which supply nourishment, and the foetal membranes which absorb it. In some species of animals, the connection between the maternal 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 valvulse 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. 234.) 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. 41 642 THE PLACENTA. In the cow, for example, the external membrane of the egg, beside being everywhere supplied with branching vessels, presents upon Fig. 234. FffiTAL Fig, wifcli Its membranes, contained in cavity of ntenis.- c, c. Cavity or uterus, d. Amnion, e, e. Allantois. a, u,b, b. Walla of nleru. various points of its surface no less than from seYenty to eighty oval spots, at each of which the vessels of the chorion are developed into abundant tufted prominences, hanging from its exterior in thick, velvety, vascular masses. At each point of the uterine mucous mem- brane, corresponding with one of these tufted masses, the maternal bloodvessels are developed in a similar manner, projecting into the uterine cavity as a flattened rounded mass or cake; which, with that part of the foetal chorion which is adherent to it, is known by the Fig. 235. Cotyledon of Cow'aUiEKra. — a, u. Surface of foetal chorion. b,b. BloodvesBels of fatal chorion, d, d. Bloodvessels of uterine mucous membrane, c, c. Surface of uterine mucous mem- brane. name of the Gotyledon. Each cotyledon forms, therefore, a little placenta, (Fig. 235.) In its substance the tufted vasoular loops coming from the uterine mucous membrane {d, d) are entangled THE PLACBNTA. 643 with those coining from the membranes of the foetus {b, I). There is no absolute adhesion between the two sets of vessels, but only an interlacement of their ramified extremities; and, with a little care in manipulation, the foetal portion of the cotyledon may be extricated from the maternal portion, without lacerating either. In consequence, however, of this intricate interlacement of the vessels, transudation of fluids will evidently take place with great readiness, from one system to the other. The form of placenta, therefore, met with in these animals, is one in which the bloodvessels of the foetal chorion are simply entangled with those of the uterine mucous membrane. In the human sub- ject, the structure of the placenta is a little more complicated, though the main principles of its formation are the same as in the above instances. From what has been said in the foregoing chapters, it appears that in the human subject, as well as in the lower animals, the placenta is formed partly by the vascular tufts of the chorioh, and partly by the thickened mucous membrane of the uterus in which they are entangled. During the third month, those portions of the chorion and decidua which are destined to undergo this transformation become more or less distinctly limited in their form and dimensions; and a thickened vascular mass, partly maternal and partly foetal in its origin, shows itself at the spot where the placenta is afterward to be developed. This mass is constituted in the following manner. It will be recollected that the villi of the chorion, when first formed, penetrate into follicles situated in the substance of the uterine mucous membrane ; and that after they have become vas- cular, they rapidly elongate and are developed into tufted ramifi- cations of bloodvessels, each one of which turns upon itself in a loop at the end of the villus. At the same time the uterine follicle, into which the villus has penetrated, enlarges to a similar extent ; sending out branching diverticula, corresponding with the multi- plied ramifications of the villus. In fact, the growth of the follicle and that of the villus go on simultaneously, and keep pace with each other ; the latter constantly advancing as the cavity of the former enlarges. But it is not only the uterine follicles which increase in size and in complication of structure at this period. The capillary blood- vessels, v^hjch lie between them and ramify over their exterior, also become unusually developed. They enlarge and inosculate freely with each other; so that every uterine follicle is soon covered 614 THE PLACENTA. with an abundant network of dilated capillaries, derived from the bloodvessels of the original decidua. At this time, therefore, each vascular loop of the foetal chorion is covered, first, with a layer forming the wall of the villus. This is in contact with the lining membrane of a uterine follicle, and outside of this again are the capillary vessels of the uterine mucous membrane; so that two , distinct membranes intervene between the walls of the foetal capil- laries on the one hand and those of the maternal capillaries on the other, and all transudation must take place through the substance of these two membranes. As the formation of the placenta goes on, the anatomical arrange- ment of the foetal vessel remains the same. They continue to form vascular loops, penetrating deeply into the decidual mem- brane; only they become constantly more elongated, and their ramifications more abundant and tortuous. The maternal capilla- ries, however, situated on the outside of the uterine follicles, become considerably altered in their anatomical relations. They enlarge excessively; and, by encroaching constantly upon the little islets or spaces between them, fuse successively with each other; and, losing gradually in this way the characters of a capillary network, become dilated into wide Fig- 236. sinuses, which communicate freely with the enlarged vessels in the muscular walls of the uterus. As the original capil- lary plexus occupied the entire thickness of the hypertrophied decidua, the vascular sinuses, into which it is thus converted, are equally extensive. They commence at the inferior sur- face of the placenta, where it is in contact with the muscular walls of the uterus, and extend through its whole thickness, quite up to the surface of the foetal chorion. As the maternal sinuses grow upward, the vascular tufts of the chorion grow downward, and extend also through the entire thick- ness of the placenta. At this period, the development of the blood- vessels, both in the foetal and maternal portions of the placenta, is so excessive that all the other tissues, which originally co-existed Extremity of Fietal Toy t, from human pla- centa at term, ia itB recoQt condition, a, a. Capil- lary bloodvesseU. Maguiiied 133 diameierB. THE PLAOEITTA. 64r5 with them, become retrograde and disappear almost altogether. If a villus from the fcetal portion of the placenta be examined at this time by transparency, in the fresh condition (Fig. 236) it will be seen that its bloodvessels are covered only with a layer of homo- geneous, or finely granular material, -j^V^ of an inch in thickness, in which are imbedded small oval-shaped nuclei, similar to those seen at an earlier period in the villosities of the chorion. The vil- losities of the chorion are now, therefore, hardly anything more than ramified and tortuous vascular loops ; the remaining substance of the villi hav- ^ig- 237. ing been atrophied and absorbed in the excessive growth of the bloodvessels, the abundance and development of which can be readily shown by injection from the umbilical arteries. (Fig. 237.) The uterine follicles have at the same time lost all trace of their original structure, and have become mere vascular sinuses, into which the tufted foetal bloodvessels are received, as the villosities of the cho- rion were at first received into the uterine Extremity of fietai. topt of rt ■... ^ hnmau placenta; from an injected lOillCleS. specimen. Maguified 40 diameters. Finally, the walls of the foetal blood- vessels having come into close contact with the walls of the maternal sinuses, the two become adherent and fuse together ; so that a time at last arrives, when we can no longer separate the fcetal vessels, in the substance of the placenta, from the maternal sinuses, without lacerating either the one or the other, owing to the secondary adhesion which has taken place between them. The placenta, therefore, when perfectly formed, has the structure which is shown in the accompanying diagram (Fig. 238), repre- senting a vertical section of the organ through its entire thickness. At a, a, is seen the chorion, receiving the umbilical vessels from the body of the foetus through the umbilical cord, and sending out its compound and ramified vascular tufts into the substance of the placenta. At b, I, is the attached surface of the decidua, or uterine mucous membrane ; and at c, c, c, c, are the orifices of uterine ves- sels which penetrate it from below. These vessels enter the placenta in an extremely oblique direction, though they are represented in the diagram, for the sake of distinctness, as nearly perpendicular. When they have once penetrated, however, the lower portion of 646 THE PLACENTA. the decidua, they immediately dilate into the placental sinuses (represented, in the diagrarxi, in black), which extend through the Fig. 238. Vertical tecUon of Placest A, Bhowlng arntngenient of maternal and foital vessels. a,a. Chiv rion. bf b. Decidaa. &', c, c, e. Orifices of nterine sinuses. whole thickness of the organ, closely embracing all the ramifica- tions of the foetal tufts. It will be seen, therefore, that the placenta, arrived at this stage of completion, is composed essentially of no- thing but bloodvessels. No other tissues enter into its structure ; for all those which it originally contained have disappeared, except- ing the bloodvessels of the foetus, entangled with and adherent to the bloodvessels of the mother. There is, however, no direct communication between the foetal and maternal vessels. The blood of the foetus is always separated from the blood of the mother by a membrane which has resulted from the successive union and fusion of four different membranes, viz., first,, the menibrane of the foetal villus; secondly, that of the uterine follicle; thirdly, the wall of the foetal bloodvessel; and, fourthly, the wall of the uterine sinus. The single membrane, how- ever, into which these four finally coalesce, is extremely tbin, as we have seen, and of enormous extent, owing to the extremely abundant branching and subdivision of the foetal tufts. These tufts, accordingly, in which the blood of the foetus circulates, are bathed everywhere, in the placental sinuses, with the blood of the mother ; and the processes of endosmosis and exosmosis, of exhalation and absorption, go on between the two with the greatest possible activity. THE PLACENTA. 6i7 It is very easy to demonstrate the arrangement of the foetal tufts in the human placenta. They can be readily seen by the naked eye, and may be easily traced from their attachment at the Tinder surface of the chorion to their termination near the uterine surface of the placenta. The anatomical disposition of the pla- cental sinuses, however, is much more difficult of examination. During life, and while the placenta is still attached to the uterus, they are filled, of course, with the blood of the mother, and occupy fully one-half the entire mass of the placenta. But when the pla-, centa is detached, the maternal vessels belonging to it are torn off" at their necks (Fig. 288, c, c, c, c), and the sinuses, being then emptied of blood by the compression to which the placenta is sub- jected, are apparently obliterated ; and the foetal tafts, falling.to- gether and lying in contact with each other, appear to constitute the whole of the placental mass. The existence of the placental sinuses, however, and their true extent, may be satisfactorily de- monstrated in the following manner. If we take the uterus of a woman who has died undelivered at the full term or thereabout, and open it in such a way as to avoid wounding the placenta, this organ will be seen remaining attached to the uterine surface, with all its vascular connections complete. Let the foetus be now removed by dividing the umbilical cord, and the uterus, with the placenta attached, placed under water, with its internal surface uppermost. If the end of a blowpipe be now introduced into one of the divided vessels of the uterine walls, and air forced in by gentle insufflation, we can easily inflate, first, the venous sinuses of the uterus itself, and next, the deeper portions of the placenta ; and lastly, the bubbles of air insinuate themselves .everywhere between the foetal tufts, and appear in the most super- ficial portions of the placenta, immediately underneath the trans- parent chorion (a, a, Fig. 238) ; thus showing that the placental sinuses, which freely communicate with the uterine vessels, really occupy the entire thickness of the placenta, and are equally exten- sive with the tufts of the chorion. We have verified this fact in the above manner, on six different occasions, and in the presence of Prof. C. E. Gilman, Prof. Geo. T. Elliot, Prof. Henry B. Sands, Prof. T. G-. Thomas, Dr. T. 0. Finnell, and various other medical gentlemen of New York. If the placenta be now detached and examined separately, it will be found to present upon its uterine surface a number of openings which are extremely oblique in their position, and which are 648 THE PLACENTA. accordingly bounded on one side by a very thin, projecting, crea- centic edge. These are the orifices of the uterine vessels, passing into the placenta and torn off at their necks, as above 4escribed ; and by carefully following thein with the probe and scissors, they are found to lead at once into extensive .empty cavities (the pla- cental sinuses), situated between the foetal tufts. We have already shown that these cavities are filled during life with the maternal blood ; and there is every reason to believe that before delivery, and while the circulation is going on, the placenta is at least twice as large as after it has been detached and expelled from the uterus. The placenta, accordingly, is a double organ, formed partly by the chorion and partly by the decidua ; and consisting of maternal and fcetal bloodvessels, inextricably entangled and united with each other. The part which this organ takes in the development of the foetus is an exceedingly important one. From the date of its formation, at about the beginning of the fourth month, it constitutes the onlj channel through which nourishment is conveyed from the mother to the foetus. The nutritious materials, which circulate in abun- dance in the blood of the maternal sinuses, pass through the inter- vening membrane by endosmosis, and enter the blood of the foetus. The healthy or injurious regimen, to which the mother is subjected, will accordingly exert an almost immediate influence upon the child. Even medicinal substances, taken by the mother and ab- sorbed into her circulation, may readily transude through the pla- cental vessels ; and they have been known in this way to exert a specific effect upon the foetal organization. The placenta is, furthermore, an organ of exhalation as well as of absorption. The excrementitious substances, produced in the circulation of the foetus, are undoubtedly in great measure disposed of by transudation through the walls of the placental vessels, to be afterward discharged by the excretory organs of the mother. The system of the mother may therefore be affected in this manner by influences derived from the foetus. It has been remarked more than once, in the lower animals, that when the female has two suc- cessive litters of young by different males, the young of the second litter will sometimes bear marks resembling those of the first male. Tn these instances, the peculiar influence which produces the ex ternal mark must have been transmitted by the first male directly to the foetus, from the foetus to the mother, and from the mother to the foetus of the second litter. THE PLACENTA, 64:9 It is also through the placental circulation that those disturbing effects are produced upon the nutrition of ,the foetus, which result from sudden shocks or injuries inflicted upon the mother. There is now little room for doubt that various defor,mities and deficiencies of the foetus, conformably to the popular belief, do really originate, in certain cases, from nervous impressions, such as disgust, fear or anger, experienced by the mother. The mode in which iheae effects may be produced is readily understood from what has been said above of the anatomy aud functions of the placenta. We know very well how easily nervous impressions will disturb the circulation in the brain, the face, the lungs, &c. ; and the uterine circulation is quite as readily influenced by similar causes, as physicians see every day in cases of amenorrhoea, menorrhagia, &o. If a nervous shock may excite premature contraction in the muscular fibres of the pregnant uterus and produce abortion, as not unfrequently happens, it is cer- tainly capable of disturbing the course of the circulation through the same organ. But the foetal circulation is dependent, to a great extent, on the maternal. Since the two sets of vessels are so closely entwined in the placenta, and since the foetal blood has here much the same relation to the maternal, that the blood in the pulmonary capillaries has to the air in the air-vesicles, it will be liable to de- rangement from similar causes. If the circulation of air through the pulmonary tubes be suspended, that of the blood through the general capillaries is disturbed also. In the same way, what- ever arrests or disturbs the circulation through the vessels of the maternal uterus must necessarily be lis^ble to interfere, with tha.t in the foetal capillaries forming part, of the placenta. And lastly, as the nutrition of the foetus is provided for wholly by the placenta, It will of course suffer immediately from any such disturbance of the placental circulation. These effects may be manifested either m the general atrophy and death of the foetus ; or, if the disturbing cause be slight, in the atrophy or imperfect development of par- ticular parts ; just as, in the adult, a morbid cause operating through the entire system, may be first or even exclusively manifested in some particular organ, which is more sensitive to its influence than other parts. The placenta must accordingly be regarded as an organ which performs, during intra-uterine life, offices similar to those of the lungs and the intestine after birth. It absorbs nourishment, reno- vates the blood, and discharges by exhalation various excrementi- tious matters, which originate in the processes of foetal nutrition. 660 DISCHARGE OF THE OVUM. CHAPTEE XIII. DISCHARGE OF THE OTUM, AND EETROGBADB DEVELOPMENT (INVOLUTION) OF THE UTERUS. DUEING the growth of the ovum and the formation of the pla- cental structures, the muscular substance of the uterus also increases in thickness, while the whole organ enlarges, in order to accommo- date the growing foetus and its appendages. The relative positions of the amnion and chorion, furthermore, undergo a change during the latter periods of gestation, and the umbilical cord becomes developed, at the same time, in the following manner. In the earlier periods of foetal life, the umbilical cord consists simply of that portion of the allantois lying next the abdomen. It is then very short, and contains the umbilical vessels running in a nearly straight course, and parallel with each other, from the abdo- men of the foetus to the external portions of the chorion. At this time the amnion closely invests the body of the foetus, so that the size of its cavity is but little larger ^'8- ^^^- than that of the foetus. (Fig. 239.) The space between the amnion and the chorion is then occupied by an amorphous gelatinous ma- terial, in which lies imbedded the umbilical vesicle. Afterward, however, the am- nion enlarges faster than the cho- rion, and encroaches upon the layer of gelatinous matter situated between the two (Fig. 240), at the same time that an albuminous fluid, the "amniotic fluid," is ex- uded into its cavity, in constantly increasing quantity. Subsequently, the gelatinous layer, above de- scribed, altogether disappears, and the amnion, at about the begin- HrHAN Ovvu about the end of the first month.— 1. Umbilical vesicle. 2. Amnion. 3. Chorion. ENLARGEMENT OF THE AMNION. 651 HuHAN OruH alend ofthirdmoath; showing enlargement of amnion. ning of the fifth month, comes in contact with the internal surface ot the chorion. Finally, toward the end of gestation, the contact becomes so close between these two membranes that they are Fig- 2*0. partially adherent to each other, and it requires a little care to separate them without laceration. The quantity of the amniotic fluid continues to increase dur- ing the latter period of gesta- tion in order to accommodate the movements of the foetus. These movements begin to be perceptible about the fifth month, at which time the muscular system has already attained a considerable degree of development, but become after- ward more frequent and more strongly pronounced. The space and freedom requisite for these movements are provided for by the fluid accumulated in the cavity of the amnion. The umbilical cord elongates, at the same time, in proportion to the increasing size of the amniotic cavity. During its growth, it becomes spirally twisted from right to left, the two umbilical arte- ries windmg round the vein in the same direction. The gelatinous matter, as already described as existing between the amnion and chorion, while it disappears elsewhere, accumulates in the cord in considerable quantity, covering the vessels with a thick, elastic en- velope, which protects them from injury and prevents their being accidentally compressed or obliterated. The whole is covered by a portion of the amnion, which is connected at one extremity with the integument of the abdomen, and invests the whole of the cord with a continuous sheath, like the finger of a glove. (Fig. 241.) The cord also contains, for a certain period, the pedicle or stem of the umbilical vesicle. The situation of this vesicle, it will be recollected, is always between the chorion and the amnion. Its pedicle gradually elongates with the growth of the umbilical cord : and the vesicle itself, which generally disappears soon after the third month, sometimes remains as late as the fifth, sixth, or seventh. According to Prof. Mayer, of Bonn, it may even be found, by care- ful search, at the termination of, pregnancy. When discovered iv 652 DISCHARGE OF THE OTCM, the middle and latter periods of gestation, it presents itself as s small, flattened, and shrivelled vesicle, situated underneath the amnion, at a variable distance from the insertion of the umbilical cord. A minute bloodvessel is often seen running to it from the cord, and ramifying upon its surface. Fig. 241. uratidHithan Uterus andCoxtektb, ehowing the relations of the cord, placenta, mem, braues, &c., about the end of the seventh month. — 1. Becidua vera. 2..]>ecidua reflexa. S. Chorioiv. 4. Amnion. The decidua reflexa, during the latter months of pregnancy, is constantly distended and pushed back by the increasing size of the egg ; so that it is finally pressed closely against the opposite surface of the decidua vera, which still lines the greater part of the uterine cavity. By the end of the seventh month, the opposite surfaces of the decidua vera and reflexa are in complete contact with each other, though still distinct and capable of being separated without difficulty. After that time, they fuse together and become con- founded with each other ; the two at last forming only a single, thin, friable, semi-opaque layer, in which no trace of their original glandular structure can be discovered. This is the condition of things at the termination of pregnancy. Then, the time having arrived for parturition to take place, the hypertrophied muscular walls of the uterus contract forcibly upon its contents, and the egg is discharged, together with the whole of the decidual uterine mucous membrane. SEPARATION OF THE PLACENTA. 653 In the human subject, as well as in most quadrupeds, the mem- branes of the egg are usually ruptured during the process of par- turition ; and the foetus escapes first, the placenta and the rest of the appendages following a few moments afterward. Occasionally, however, even in the human subject, the egg is discharged entire, and the foetus liberated afterward by the laceration of the mem- branes. In each case, however, the mode of separation and expul- sion is in all particulars the same. The process of parturition, therefore, consists essentially in a separation of the decidual membrane, which, on being discharged, brings away the ovum with it. The greater part of the decidua vera, having fallen into a state of atrophy during the latter months of pregnancy, is by this time nearly destitute of vessels, and sepa- rates, accordingly, without any perceptible hemorrhage. That por- tion, however, which enters into the formation of the placenta, is, on the contrary, excessively vascular ; and when the placenta is separated, and its maternal vessels torn off at their necks, as before mentioned, a gush of blood takes place, which accompanies or immediately follows the birth of the foetus. This hemorrhage, which occurs as a natural phenomenon at the time of parturition, does not come from the uterine vessels proper. It consists of the blood which was contained in the placental sinuses, and which is expelled from them owing to the compression of the placenta by the walls of the uterus. Since the whole amount of blood thug lost was previously employed in the placental circulation, and since the placenta itself is thrown off at the same time, no unpleasant effect is produced upon the mother by such a hemorrhage, because the natural proportion of blood in the rest of the maternal system remains the same. Uterine hemorrhage at the'time of parturition, therefore, becomes injurious only when it continues after complete separation of the placenta; in which case it is supplied by the mouths of the uterine vessels themselves, left open by failure of the uterine contractions. These vessels are usually instantly closed, after separation of the placenta, by the contraction of the muscular fibres of the uterus. They pass, as we have already mentioned, in an exceedingly oblique direction, from the uterine surface to the placenta ; and the muscular fibres, which cross them transversely above and below, necessarily constrict them, and effectually close their orifices, immediately on being thrown into a state of contraction Another very remarkable phenomenon, connected "With preg- nancy and parturition is the appearance in the uterus of a new 654 DISCHARGE OF THE OVUM. mucous membrane, growing underneath the old, and ready lo take the place of the latter after its discharge. If the internal surface of the body of the uterus be examined immediately after parturition, it will be seen that at the spot where the placenta was attached, every trace of mucous membrane has disappeared. The muscular fibres of the uterus are here perfectly exposed and bare ; while the mouths of the ruptured uterine sinuses are also visible, with their thin, ragged edges hanging into the cavity of the uterus, and their orifices plugged with more or less abundant bloody coagula. Over the rest of the uterine surface, the decidua vera has also disappeared. Here, however, notwithstanding the loss of the ori- ginal mucous membrane, the muscular fibres are not perfectly bare, but are covered with a thin, semi-transparent film, of a whitish color and soft consis|;ency. This film is an imperfect mucous membrane of new formation, which begins to be produced, underneath the old decidua vera, as early as the beginning of the eighth month. We have seen this new mucous membrane very distinctly in the uterus of a woman who died undelivered at the above period. The old mucous membrane, or decidua vera, is at this time some- what opaque, and of a slightly yellowish color, owing to a partial fatty degeneration which it undergoes in the latter months of preg- nancy. It is easily raised and separated from the subjacent parts, owing to the atrophy of its vascular connections; and the new mucous membrane, situated beneath it, is readily distinguished by its fresh color, and healthy, transparent aspect. The mucous membrane of the cervix uteri, which takes no part in the formation of the decidua, is not thrown off in parturition, but remains in its "natural position; and after delivery it may be seen to terminate at the os internum by an uneven, lacerated edge, where it was formerly continuous with the decidua vera. Subsequently, a regeneration of the mucous membrane takes place over the whole extent of the body of the uterus. The mucous membrane of new formation, which is already in existence at the time of delivery, becomes thickened and vascular ; and glandular tubules are gradually developed in its substance. At the end of two months after delivery, according to HeschP and Longet,' it has entirely regained the natural structure of the uterine mucous mem- ' Zeitsehrift der K. K. Gesellschaft der Aerzte, in Wien, 1852. • Traits de Physiologie. De la OSnfiration, p. 173. EKTBOGRADK DEVELOPMENT OF THE UTEBCS. 655 Mirsctn.AK Fibbes of Uvihpbbqnatbd Utebfb; from a woman aged 40, dead of phcbiais pulmonalis. brane. It unites at the os interum, by a linear cicatrix, vritli the mucous membrane of the cervix, and the traces of its laceration at this spot afterward cease to be visible. At the point, however, where the placenta was at- tached, the regeneration of ^'S- 242. the mucous membrane is less rapid; and a cicatrix- like spot is often visible at this situation for several months afl«r delivery. The only further change, which remains to be de- scribed in this connection, is the fatty degeneration and reconstruction of the muscular substance of the uterus. This process, which is sometimes known as the "involution" of the uterus, takes place in the following manner. The muscular fibres of the unimpregnated uterus are pale, flattened, spindle-shaped bodies (Fig. 242) nearly homogeneous in structure or very faintly granular, and measuring from ^^5 to j^5 of an inch in length, by tuhbt! ^ sAn of an inch in width. During gestation these fibres in- crease very considerably in size. Their texture becomes much more distinctly granu- lar, and their outlines more strongly marked. An oval nucleus also shows itself in the central part of each fibre. The entire walls of the uterus, at the time of delivery, are composed of such muscular fibres, arranged in circular, oblique, and longitudinal bundles. About the end of the first week after delivery, these' fibres begin Fig. 243. HiractrLAR Fibres of Human Utebus, tea days after partaritioa; from a womaa dead of puer* peral fever. 656 DISCHAKGE OF THE OVUM. to undergo a fatty degeneration, (Fig. 243.) Their grantdes be- come larger and more prominent, and very soon assume the appearance of molecules of fat, deposited in the substance of the fibre. The fatty deposit, thus commenced, increases in abundance and the molecules continue to enlarge until they become converted into fully formed oil-globules, which fill the interior of the fibre more or less completely, ^'8- 244. and niask, to a certain ex- tent, its anatomical cha- racters. (Fig. 244,) The universal fatty degenera- . tion, thus induced, gives to the uterus a softer consist- ency, and a pale yellowish color which is characteristic of it at this period. The muscular fibres which have become altered by the fatty deposit are afterward gra- dually absorbed and disap- pear; their place being subsequently taken by other fibres of new forma- tion, which already begin to make their appearance before the old ones have been completely destroyed. As this process. goes on, it results finally in a complete renovation of the muscular substance of the uterus. The organ becomes again reduced in size, compact in tissue, and of a pale ruddy hue, as in the ordinary unimpregnated condition. This entire renewal or reconstruction of the uterus is completed, according to Heschl,' about the end of the second month after delivery. iTTScnxAK Fibres of Huuan Uterus, three weeks after partarltlon ; from a woman dead of peri- tonitis. Op. cit. BEVELOFMENT OF TH£ SUBBYO. 657 CHAPTER XIV. DEVELOPMENT OP THE EMBRYO— NERVOUS SYSTEM, ORGANS OF SENSE, SKELETON, AND LIMBS. Fig. 215. The first trace of a spinal cord in the embryo consists of the double longitudinal fold or ridge of tbe blastodermic membrane, which shows itself at an early period, as above described, on each side the median furrow. The two laminae of which this is com- posed, on the right and left sides (Fig. 245, a, b), unite with each other in front, forming a rounded dilatation (c), the cephalic extremity, and behind at d, forming a pointed or caudal extremity. Near the pos- terior extremity, there is a smaller dilatation, which marks the future situation of the lumbar enlargement of the spinal cord. ^.s the laminse above described grow upward and backward, they unite with each other upon the median line, so that the whole is converted into a hollow cylindrical cord, terminating ante- riorly by a bulbous enlargement, and posteriorly by a pointed enlargement; the central cavity which it contains running continuously through it, from front to rear. The next change which shows itself is a divi- sion of the anterior bulbous enlargement into three secondary compartments or vesicles (Fig. 246), which are partially separated from each other by transverse constrictions. These vesicles are known as the three cerebral vesi- cles, from which all the different parts of the encephalon are after ward to be developed. The first, or most anterior cerebral vesicle is destined to form the hemispheres; the second, or middle, the tuberoula quadrigemina ; and the third, or posterior, the medulla oblongata. All three vesicles are at this time hollow, and their 42 Formation of C r r £ ■ bro-Spihati Axis.— a, b. Spinal cord. e. Ce- phalic extremity. d. Caudal extremity 658 DEVELOPMENT OF THE EMBBTO. Fig. 246. cavities communicate freely with eacli other, through the interven- ing constrictions. Very soon the anterior and the posterior cerebral vesicles suffer a further division ; the middle one remain- ing undivided. The anterior vesicle thus separates into two portions, of which the first, or larger, constitutes the hemispheres, while the second, or smaller, becomes the optic thalami. The third vesicle also sepa- rates into two portions, of which the ante- rior becomes the cerebellum, and the pos- terior the medulla oblongata. 'There are, therefore, at this time five cerebral vesicles, all of whose, cavities com- municate with each other and with the central cavity of the spinal cord. The entire cerebro-spinal axis, at the same time, becomes very strongly curved in an ante- rior direction, corresponding with the ante- rior curvature of the body of the embryo (Fig. 247); so that the middle vesicle, or that of the tubercula quadrigemina, occu- pies a prominent angle at the upper part of the encephalon, while the hemispheres and the medulla oblongata are situated below it, anteriorly and posteriorly. At first, it will be observed, the relative size of the various parts of the encephalon is very different from that which they afterward attain in the adult condition. The hemispheres, for example, are hardly larger than the tubercula quadrigemina ; and the cerebellum is very much inferior in size to the medulla oblon- gata. Soon afterward, the relative position and size of the parts begin to alter. The hemispheres and tubercula quadrigemina grow faster than the poste- rior portions of the encephalon ; and the cerebellum becomes doubled backward over the medulla oblon- gata. (Fig. 248.) Subsequently, the hemispheres rapidly enlarge, growing upward and backward, so as to cover in and conceal both the optic tha- lami and the tubercula quadrigemina (Fig. 249); the cerebellum tending in the same way to grow backward, and projecting farther Formation of the Cerebro- spinal Axis. — 1. Vesicle of the hemispheres. 2. Vesicle of the tubercula quadrigemina. 3. Vesicle of the medulla oblongata. Fig. 247. FffiTAii Pra, flve- eigbtfas of au inch long, showing brain and Bpinal cord.— 1. Hemispheres. 2. Tu- bercula quadrigemi- na. 3. Cerebellum. 4. Medulla oblongata. NERVOUS SYSTEM. 659 and fartter over the medulla oblongata. The subsequent history of the development of the enoephalon is little more than a con- Fig. 248. Fig 249. FtETAL FiQ, one and a qnarter Inch lon^. — 1. Hemispheres. 2. Tubercula quadrigemina. 3. Cerebellum. 4. Me- dulla oblongata. Head of F(£tal Fia, tbreeanda half incues long. — 1. Hemispnerea, 3. CereDellum. 4. Uedulla oblongata. tinuation of the same process ; the relative dimensions of the part* constantly changing, so that the hemispheres become, in the adulr condition (Fig. 250), the largest of all the divisions of the ence- Fig. 250. Brain of Adult Ptg. — 1. Hemispheres. 3. Cerebellum. 4. Medulla oblongata. phalon, while the cerebellum is next in size, and covers entirely the upper portion of the medulla oblongata. The surfaces, also, of the hemispheres and cerebellum, which were at first smooth, become afterward convoluted; increasing, in this way, still farther the extent of their nervous matter. In the human foetus, these con- volutions begin to appear about the beginaing of the fifth month (Longet), and grow constantly deeper and more abundant during the remainder of foetal life. The lateral portions of the brain growing at the same time more rapidly than that which is situated on the median line, they soon project on each side outward and upward ; and, by folding over 660 DBVELOPMENT OF THE EMBRYO. against each other in the median line, form the right and left hemi- spheres, separated from each other by the longitudinal fissure. A similar process of growth taking place in the spinal cord results in the formation of the two lateral columns and the anterior and pos- terior median fissures of the cord. Elsewhere the median fissure is less complete,, as, for example, between the two lateral halves of the cerebellum, the two optic thalami and corpora striata, and the two tubercula quadrigemina ; but it exists everywhere, and marts more or less distinctly the division between the two sides of the nervous centres, produced by the excessive growth of their lateral portions. In this way the whole cerebro-spinal axis is converted into a double organ, equally developed upon the right and left sides, and partially divided by a longitudinal median fissure. Organs of Special Sense. — The eyes are formed by a diverticulum which grows out on each side from the first cerebral vesicle. This diverticulum is at first hollow, its cavity communicating with that of the hemisphere. Afterward, the passage between the two is filled up with a deposit of nervous matter, and becomes the optic nerve. The globular portion of the diverticulum, which is converted into the globe of the eye, has a very thin laye^ of nervous matter depo- sited upon its internal surface, which becomes the retina ; the rest of its cavity being occupied by a gelatinous semi-fluid substance, the vitreous body. The crystalline lens is formed in a distinct fol- licle, which is an offshoot of the integument, and becomes partially imbedded in the anterior portion of the globe of the eye. The cornea also is originally a part of the integument, and remains partially opaque until a very late period of development. Its tissue clears up, however, and becomes perfectly transparent, shortly be- fore birth. The iris is a muscular septum which is formed in front of the crystalline lens, separating the anterior and . posterior chambers of the aqueous humor. Its central opening, which afterward becomes the pupil, is at first closed by a vascular membrane, the pupillary membrane, passing directly across the axis of the eye. The vessels of this membrane, which are derived from those of the iris, subse- quently become atroplijed. They disappear first from its centre, and afterward recede gradually toward its circumference ; returning always upon themselves in loops, the convexities of which are directed toward the centre of the membrane. The pupillary membrane itself finally becomes atrophied and destroyed, following in this retro- grade process the direction of its receding bloodvessels, viz., from SKELETOX AND LIMBS. 661 the centre toward the circumference. It has completely disappeared by the end of the seventh month. (Oruveilhier.) The eyelids are formed by folds of the integument, which gradually project from above and below the situation of the eye- ball. They grow so rapidly during the second and third months that their free margins come in contact and adhere together, so that they cannot be separated at that time without some degree of vio- lence. They remain adherent from this period until the seventh month (Guy), when their margins separate and they become per- fectly free and movable. In the carnivorous animals, however (dogs and cats), the eyelids do not separate from each other until eight or ten days after birth. The internal ear is formed in a somewhat similar manner with the eyeball, by an offshoot from the third cerebral vesicle; the passage between them filling up by a deposit of white substance, which becomes the auditory nerve. The tympanum and auditory meatus are both offshoots from the external integument. Skeleton. — At a very early period of development there appears, as we have already described (Chap; VII.), immediately beneath the cerebro-spinal axis, a cylindrical cord, of a soft, cartilaginous con- sistency, termed the eliorda dorsalis. ' It consists of a fibrous sheatb containing a mass of simple cells, closely packed together and united by adhesive material. This cord is not intended to be a permanent part of the skeleton, but is merely a temporary organ destined to disappear as development proceeds. Immediately around the chorda dorsalis there are deposited soon afterward a number of cartilaginous plates, which encircle it in a series of rings, corresponding in number with the bodies of the future vertebrae. These rings increase in thickness from without inward, encroaching upon the substance of the chorda dorsalis, and finally taking its place altogether. The thickened rings, which have been filled up in this way and solidified by cartilaginous deposit, become the bodies of the vea-tebrse ; while their transverse and articulating processes, with the laminse and spinous processes, are formed by subsequent outgrowths from the bodies in various directions. When the union of the dorsal plates updn the median line fails to take place, the spinal canal remains open at that situation, and presents the malformation known as spina bifida. This malforma- tion may consist simply in a fissure of the spinal canal, more or less extensive, in which case it may often be cured, or may even close spontaneously ; or it may be complicated with an imperfect deve- 662 DEVELOPMENT OF THE EMBBTO. lopment or complete absence of the spinal cord at the same spot, when it is accompanied of course by paralysis of the lower ex- tremities, and almost necessarily results in early death. The entire skeleton is at first cartilaginous. The first points of ossification show themselves about the beginning of the second month, almost simultaneously in the clavicle and the upper and lower jaw. Then come in the following order, the long bones of the extremities, the bodies and processes of the vertebrae, the bones of the head, the ribs, pelvis, scapula, metacarpus and metatarsus, and the phalanges of the fingers and toes. The bones of the carpus, however, are all cartilaginous at birth, and do not begin to ossify until a year afterward. The calcaneum and astragalus begin to ossify, according to Cruveilhier, during the latter periods of foetal life, but the remainder of the tarsus is cartilaginous at birth. The lower extremity of the femur begins to ossify, according to the same author, during the latter half of the ninth month. The pisiform bone of the carpus is said to commence its ossification later than any other bone in the skeleton, viz., at from twelve to fifteen years after birth. Nearly all the bones ossify from several distinct points ; the ossification spreading as the cartilage itself increases in size, and the various bony pieces, thus produced, uniting with each other at a later period, usually some time after birth. The limbs appear by a kind of budding process, as offshoots of the external layer of the blastodermic membrane. They are at first mere rounded elevations, without any separation between the fingers and toes, or aiiy distinction between the different articula- tions. Subsequently the free extremity of each limb becomes di- vided into the phalanges of the fingers or toes ; and afterward the articulations of the wrist and ankle, knee and elbow, shoulder and hip, appear successively from below upward. The posterior extremities, in the human subject, are less rapid in their development than the anterior. Throughout the term of foetal life, indeed, the anterior parts of the body are generally more voluminous than the posterior. The younger the embryo, the larger are the head and upper parts in proportion to the rest of the body. The lower limbs and the pelvis, more particularly, are very slightly developed in the early periods of growth, as compared with .the spinal column, to which they are attached. The inferior ex- tremity of the spinal column, formed by the sacrum and coccyx, projects at this time considerably beyond the pelvis, forming a tail, like that of the lower animals, which is curled forward toward the SKELETON- AND LIMBS. 663 Fig. 251. aLdomen, and terminates in a pointed extremity. The entire lower half of the body, with the spinal column and appendages, is also strongly twisted, from left to right ; so that the pelvis is not only curled forward, but also faces at right angles to the direction of the head and upper part of the body. Subsequently the spinal column becomes straighter and loses its twisted form. At the same time the pelvis and the muscular parts seated upon it grow so much faster than the sacrum and coccyx, that the latter become concealed under the adjoining soft j)arts, and the rudimentary tail accordingly disappears. The integument of the embryo is at first jm thin, vascular, and exceedingly transpar-"^^ ent. It afterward becomes thicker, more opaque, and whitish in color; even at birth, however, it is considerably more vascular than in the adult condition, and the ruddy color of its abundant capillary vessels very strongly marked. The hairs begin to appear about the middle of intra-uterine life; showing themselves fi.rst upon the eyebrows, and afterward upon the scalp, trunk and extremities. The nails are in process of formation from the third to the fifth month ; and, according to KoUiker, are still covered with a layer of epidermis until after the latter period. The sebaceous matter of the cutaneous glandules accumulates upon the skin after the sixth month, and forms a whitish, semi- solid, oleaginous layer, termed the vernix caseosa, which is most abundant in the flexures of the joints, between the folds of tha integument, behind the ears and upon the scalp. HuHAN EHBaTO, about one month old. Showing the large nize of the head and upper parts of the body; — the twisted form of tlie spinal column ; — the rudimentary condition of the upper and lower extremities; — and the rudiment- ary tail at the end of the spinal column. 664 DEVELOPMENT OF THE ALIMENTABT CANAL CHAPTER XV. DEVELOPMENT OP THE ALIMENTARY CANAL AND ITS APPENDAGES. We have alre&,dy seen, in a preceding chapter, that the intestinal canal is formed by the internal layer of the blastodermic membrane; which curves forward on each side, and is thus converted into a nearly straight cylindrical tube, terminating at each extremity in a rounded cul-de-sac, and inclosed by the external layer of the blastodermic membrane. The abdominal walls, however, do not unite with each other upon the median line until long after the formation of the intestinal canal ; so that, during a certain period, the abdomen of the embryo, is widely open in front, presenting a long oval excavation, in which the nearly straight, intestinal tube is to be seen, running from its anterior to its posterior extremity. The formation of the stomach takes place in the following man- ner : The alimentary canal, originally straight, soon presents two lateral curvatures at the upper part of the aibdomen ; the first to the left, the second to the right. The first of these curvatures becomes expanded into a wide sac, projecting laterally from the median line into the left hypochondrium, forming the great pouch of the stomach. The second curvature, directed to the right, marks the boundary between the stomach and the duodenum ; and the tube at that point becoming constricted and furnished with a circular layer of muscular fibres, is converted into the pylorus. Immedi- ately below the pylorus, the duodenum again turns to the left ; and these curvatures, increasing in number and complexity, form the convolutions of the small intestine. The large intestine forms a spiral curvature ; ascending on the right side, then crossing over to the left as the transverse colon, and again descending on the left side, to terminate by the sigmoid flexure in the rectum. The curvatures of the intestinal canal take place, however, in an antero-posterior, as well as in a lateral direction, and may be best studied in a profile view, as in Fig. 252. The abdominal walls are AND ITS APPENDAGES. 665 here still imperfectly closed, leaving a wide opening at a, I, where the integument of the foetus becomes continuous with the com- mencement of the amniotic membrane. The intestine makes at Fig. 252. Formation of A ti z H E N T A R T Canal. — ra, 6. Commencement of amnion, c, c. Intestine, d. Pharynx, e. Urinary bladder. / Allantoie. g. Umbilical vesicle. ». Dotted line, showing ILe place of formation of the oeBophagus. first a single angular turn forward, and opposite the most promi- nent portion of this angle is to be seen the obliterated duct, which forms the stem of the umbilical vesicle, {g^ A short distance below this point the intestine subsequently enlarges in its calibre, and the situation of this enlargement marks the commencement of the colon. The two portions of the intestine, after this period, become widely different from each other. The upper portion, which is the small intestine, grows mostly in the direction of its length, and becomes a very long, narrow, and convoluted tube ; while the lower portion, which is the large intestine, increases rapidly in diameter, but elongates less than the former. At the point of junction of the small and large intestines, a late- ral bulging or diverticulum of the latter shows itself, and increases in extent, until the ileum seems at last to be inserted obliquely into the side of the colon. This diverticulum of the colon is at first uniformly tapering or conical in shape ; but afterward that portion which forms its free extremity, becomes narrow and elongated, and is slightly twisted upon itself in a spiral direction, forming the appendix vermiformis ; while the remaining portion, which is con- tinuous with the intestine, becomes exceedingly enlarged, and forms the caput coli. The caput coli and the appendix are at first situated near the 666 DEVELOPMENT OF THE ALIMENTARY CANAL Fig. 253. umbilicus ; but between the fourth and fifth months (Cruveilhier) their position is altered, and they then become fixed in the right iliac region. During the first six months, the internal surface of the small intestine is smooth. At the seventh month, according to Cruveilhier, the valvulae conniventes begin to appear, after which they increase in "size till birth. The division of the colon into sacculi by longitudinal and transverse bands, is also an appearance which presents itself only during the last half of foetal life. Pre- vious to that time, the colon is smooth and cylindrical in figure, like the small intestine. After the small intestine is once formed, it increases very rapidly in length. It grows, indeed, at this time, faster than the walls of the abdomen; so that it can no longer be contained in the abdominal cavity, but protrudes, under the form of an in- testinal loop, or hernia, from the umbili- cal opening. (Fig. 253.) In the human embryo, this protrusion of the intestine can be readily seen during the latter part of the second month. At a subsequent period, however, the walls of the abdo- men grow more rapidly than the intes- tine. They accordingly gradually en- velop the hernial protrusion, and at last inclose it again in the cavity of the ab- domen. Owing to an imperfect development of the abdominal walls, and an imperfect closure of the umbilicus, this intestinal protrusion, which is normal during the early stages of fcetal life, sometimes remains at birth, and we then have a congenital umbilical hernia. As the parts at that time, however, have a natural tendency to cicatrize and unite with each other, simple pressure is generally effectual, in such cases, in retaining the hernia within the abdomen, and in producing at last a complete cure. Urinary Bladder, Urethra, &c. — It will be recollected that very soon after the formation of the intestine, a vascular outgrowth takes place from its posterior portion, which gradually protrudes from the open walls of the abdomen in front, until it comes in contact with the external investing membrane of the egg, and forms, by its con- tinued growth and expansion, the allantois. (Fig. 252, /.) It is at FiETAL Pro, showing loop of inteBtine, forming nmbilical bernia ; from a specimen in tlie author's possession. From the convexity of the loop a thinfiament is seen passing to the umbilical vesicle, which is here flattened into a leaf-like form. AND ITS APPENDAGES. 667 first, as we have shown above, a hollow sac , but, as it spreads out over the surface of the investing membrane of the egg, its two opposite walls adhere to each other, so that its cavity is obliterated at this situation, and it is thus converted into a single vascular membrane, the chorion. This obliteration of the cavity of the allantois commences at its external portion, and gradually extends inward toward the point of its emergence from the abdomen. The hollow tube, or duct, which connects the cavity of the allantois with the posterior part of the intestine, is accordingly converted, as the process of obliteration proceeds, into a solid, rounded cord. This cord is termed the urachus. After the walls of the abdomen have come in contact, and united with each other at the umbilicus, that portion of the above duct which is left outside the abdominal cavity, forms a part of the um- bilical cord, and remains connected with the umbilical arteries and vein. That portion, on the contrary, which is included in the ab- domen, does not close completely, but remains as a pointed fusiform sac, terminating near the umbilicus in the solid cord of the urachus, and still communicating at its base with the lower extremity of the intestinal canal. This fusiform sac (Fig. 252, e), becomes the uri- nary bladder ; and in the foetus at term, the bladder is still conical in form, its pointed extremity being attached, by means of the ura- chus, to the internal surface of the abdominal walls at the situation of the umbilicus. Afterward, the bladder loses this conical form, and its fundus in the adult becomes rounded and bulging. The urinary bladder, as it appears from the above description, at first communicates freely with the intestinal cavity. The intestine, in fact, terminates, at this time, in a wide passage, or chaca, at its lower extremity, which serves as a common outlet for the urinary and intestinal passages. Subsequently, however, a horizontal par- tition makes its appearance just above the point of junction between the bladder and rectum, and grows downward and forward in such a manner as to divide the above-mentioned cloaca into two parallel and unequal passages. The anterior or smaller of these passages becomes the urethra, the posterior or larger becomes the rectum ; and the lower edge of the septum between them becomes finally united with the skin, forming, at its most superficial part, a tole rably wide band of integument, the perineum, which intervener between the anus and the external portion of the urethra. The contents of the intestine, which accumulate during foetal life, vary in different parts of the alimentary canal. In the small intes- DEVELOPMENT OF THE ALIMENTABT CANAI, tine they are semifluid or gelatinous in consistency, of a light yellowish or grayish- white color in the duodenum, becommg yellow reddish-brown and greenish-brown below. In the large intestine they are of a dark greenish hue, and pasty in consistency ; and the contents of this portion of the alimentary canal have received the name of meconium, from their resemblance to inspissated poppy- juice. The meconium contains a large quantity of fat, as well as various insoluble substances, probably the residue of epithelial and mucous accumulations. It does not contain, however, any trace of the biliary substances (tauro-cholates and glyko-cholates) when care- fully examined by Pettenkofer's test ; and cannot therefore properly be regarded, as is sometimes incorrectly asserted, as resulting from the accumulation of bile. In the contents of the small intestine, on the contrary, traces of bUe may be found, according to Lehmann,' so early as between the fifth and sixth months. We have also found distinct traces of bile in the small intestine at birth, but it is even then in extremely small quantity, and is sometimes altogether absent. The meconium, therefore, and the intestinal contents generally, are not composed principally, or even to any applreciable extent, of the secretions of the liver. They appear rather to be produced by the mucous membrane of the intestine itself. Even their yellowish and greenish color does not depend on the presence of bile, since the yellow color first shows itself, in very young foetuses, about the middle of the small intestine, and not at its upper extremity. The material which accumulates afterward appears to extend from this point upward and downward, gradually filling the intestine, and becoming, in the ileum and large intestine, darker and more pasty as gestation advances. It is a singular fact, perhaps of some importance in this connec- tion, that the amniotic fluid, during the latter half of foetal life, finds its way, in greater or less abundance, into the stomach, and through that into the intestinal canal. Small cheesy-looking masses may sometimes be found at birth in the fluid contained in the stomach, which are seen on microscopic examination to be no other than portions of the vernix caseosa exfoliated from the skin into the amniotic cavity, and afterward swallowed. According to Kdl- liker,^ the soft downy hairs of the foetus, exfoliated from the skin, ' Physiological Chemistry, Philadelphia edition, vol. i. p. 632. 2 Gewebelehre. Leipzig, 1P52, p. 139. AND ITS APPENDAGES. 6(59 are often swallowed in the same way, and may be found in the meconium. , The gastric j'uiee is not secreted before birth ; the contents of the stomach being generally in small quantity, clear, nearly colorless, and neutral or alkaline in reaction. < The liver is developed at a very early period. Its size in pro- portion to that of the entire body is, in fact, very much greater in the early months than at birth or in the adult condition. In the foetal pig we have found the relative size of the liver greatest within the first month, when it amounts to very nearly 12 per cent, of the entire weight of the body. Afterward, as it grows less rapidly than other parts, its relative weight diminishes successively to 10 per cent, and 6 per cent. ; and is reduced before birth to 3 or 4 per cent. In the human subject, also, the weight of the liver at birth is between 3 and 4 per cent, of that of the entire body. The secretion of bile takes place, as we have intimated above, during foetal life, in a very scanty manner. We have found it, in minute quantity, in the gall-bladder, as well as in the small intes- tine at birth ; but it does not probably take any active part in the nutritive or other functions of the foetus before that period. The glycogenic function of the liver commences during foetal life, and at birth the tissue of the organ is abundantly saccharine. It is remarkable, however, that in the early periods of gestation sugar is' produced in the foetus from other sources than the liver. In very young foetuses of the pig, for example, both the allantoic and amniotic fluids are saccharine, a considerable time before any sugar makes its appearance in the tissue of the liver. Even the urine, in half-grown foetal pigs, contains an appreciable quantity of sugar, and the young animal is therefore, at this period, in a diabetic con- dition. This sugar, however, disappears from the urine before birth, and also from the amniotic fluid, as has been ascertained by M. Ber- nard ;' while the liver begins to produce a saccharine substance, and to exercise the glycogenic function, which it continues after birth. Development of the Pharynx, (Esophagus, &c. — We have already seen that the intestinal canal consists at first of a cylindrical tube terminated at each extremity of the abdominal cavity by a rounded cul-de-sac (Fig. 252, c, c) ; and that the openings of the mouth and anus are subsequently formed by perforations which take place through the integument and the intervening tissues, and so estab- ■ Le,ons de Pliysiologie Exp^rimentale, Paris, 1855, p. 398. 670 DEVELOPMENT OF THE ALIMENTARY CANAL lish a communication with the intestinal tube. The formation of the anterior perforation, and its appendages, takes place in the fol- lowing manner : — After the early development of the intestinal tube in the mode above described, the head increases in size out of all proportion to the remainder of the foetus, projecting as a large rounded mass from the anterior extremity of the body, and containing the brain and the organs of special sense. This portion soon bends over toward the abdomen, in consequence of the increasing curvature of the whole body which takes place at this time. In the interior of this cephalic mass there is now formed a large cavity (Fig. 252, d), by the melting down and liquefaction of a portion of its substance. This cavity is the pharynx. It corresponds by its anterior extre- mity to the future situation of the mouth ; and by. its posterior portion to the upper end of the intestinal canal, the future situation of the stomach. It is still, however, closed on all sides, and does not as yet communicate either with the exterior or with the cavity of the stomach. There is, accordingly, at this time, no thorax whatever ; but the stomach lies at the upper extremity of the abdo- men, immediately beneath the lower extremity of the pharynx, from which it is separated by a wall of intervening tissue. Subsequently, a perforation takes place between the adjacent extremities of the pharynx and stomach, by a short narrow tube, the situation of which is marked by the dotted lines x, in Fig. 241. This tube afterward lengthens by the rapid growth of that portion of the body in which it is contained, and becomes the oesophagus. Neither the pharynx nor oesophagus, therefore, are, properly speak- ing, parts of the intestinal canal, formed from the internal layer of the blastodermic membrane ; but are, on the contrary, formations of the external layer, from which the entire cephalic mass- is pro- duced. The lining membrane of the pharynx and oesophagus is tc be regarded, also, for the same reason, as rather a continuation of the integument than of the intestinal mucous membrane ; and even in the adult, the thick, whitish, and opaque pavement epithelium of the oesophagus may be seen to terminate abruptly, by a well- defined line of demarkation, at the cardiac orifice of the stomach : beyond which, throughout the remainder of the alimentary canal, the epithelium is of the columnar variety, and easily distinguish- able by its soft, ruddy, and transparent appearance. As the oesophagus lengthens, the lungs are developed on each side of it by a protrusion from the pharynx which extends and AND ITS APPENDAGES. 671 becomes repeatedly subdivided, forming the bronchial tubes and their ramifications. At first, the lungs project into the upper part of the abdominal cavity ; for there is still no distinction be- tween the chest and abdomen. Afterward, a horizontal partition begins to form on each side, at the level of the base of the lungs, which gradually closes together at a central point, so as to form the diaphragm, and finally shuts off altogether the cavity of the chest from that of the- abdomen. Before the closure of the diaphragm, thus formed, is complete, a circular opening exists on each side the median line, by which the peritoneal and pleural cavities communicate with each other. In some instances the de- velopment of the diaphragm is arrested at this point, either on one side or the other, and the opening accordingly remains permanent. The abdominal organs then partially protrude into the cavity of the chest on that side, forming congenital diaphragmatic hernia. The lung on the affected side also usually remains in a state of imperfect development. Diaphragmatic hernia of this character is more frequently found upon the left side than upon the right. It may sometimes continue until adult life without causing any seri- ous inconvenience. The hw,rt is formed, at a very early period, directly in front of the situation of the oesophagus. Its size soon becomes very large in proportion to the rest of the body ; so that it protrudes beyond the level of the thoracic parietes, covered only by the pericardium. Subsequently, the walls of the thorax, becoming more rapidly developed, grow over it and inclose it. In certain instances, how- ever, they fail to do so, and the heart then remains partially or completely uncovered, in front of the chest, presenting the condition ^known as ectopia cordis. This malformation is necessarily iatal. Development of the Face. — While the lower extremity of the pharynx communicates with the cavity of the stomach, as above described, its upper extremity also becomes perforated in a similar manner, and establishes a communication with the exterior. This perforation is at first wide and gaping. It afterward becomes' divided into the mouth and nasal passages ; and the different parts of the face are formed round it in the following manner : — From the sides of the cephalic mass five buds or processes shoot out, and grow toward each other, so as to approach the centre of the oral orifice above mentioned. (Fig. 254.) One of them grows directly downward from the frontal region and is called the frontal or intermaxillary process because it afterward contains in 672 DEVELOPMENT OF THE ALIMENTARY CANAL Fig. 254. Human Embrto, about one month old: showing the growth of the frontal process downward, and that of the superior and inferior maxillary processes from the side; also the lateral situation of the eye. From a specimen in the author's possession. its lower extremity the intermaxillary bones, in which the incisor teeth of the upper jaw are inserted. The next process originates from the side of the opening, and, advancing toward the median line, forms, with its fellow of the opposite side, the superior maxilla. The processes of the remaining pair also grow from the side, and form, by their subsequent union upon the median line, the inferior max- illa. The inferior maxillary bone is finally consolidated, in man, into a single piece, but remains permanently divided, in the lower animals, by a suture upon the me- dian line. '. As the frontal process grows from above downward, it becomes double at its lower extremity, and at the same time two off- shoots show themselves upon its sides which curl round and enclose two circular orifices, the opening of the anterior nares ; the offshoots themselves becoming the alse nasi. (Fig. 255.) The mouth at this period is very widely open, owing to the imperfect development of the upper and lower jaw, and the incomplete for- mation of the lips and cheeks. Fig. 255, The processes of the superior max- illa continue their growth, but less rapidly than those of the inferior ; so that the two sides of the lower jaw are already consolidated with each other, while those of the uppef jaw are still separate. s, As the processes of the superior maxilla continue to enlarge, they also tend to unite with each other on the median line, but are prevented from doing so by the intermaxillary pro- cesses which grow down between them. They then unite with the intermaxillary processes, which have at the same time united with each other, and the upper jaw and lip are thus completed. (Fig. 256 .) The external edge of the ala nasi also adheres to the superior maxillary process and unites with it, leaving only a curved crease , Head OF HITHA.V Embryo at about the sixth week. From a specimen iu the author's possession. AND ITS XTTKSDXGSS. 673 or furrow, as a sort of cicatrix, to mark the line of union between them. Sometimes the superior maxillary and the intermaxillary pro- cesses fail to unite with each other; and we then -have the mal- formation known as hare-lip. The fissure of hare-lip, consequently, as a ^^S- 256. general rule, is not situated exactly in the median line, but a little to one side of it, on the external edge of the inter- maxillary process. Occasionally, the same deficiency exists on both sides, producing "double hare-lip ;" in which case, if the fissures extend through the bony structures, the central piece of the superior maxilla, which is de- tached from the remainder, contains hbad of hdman embkto, atont .1 n ■ ■ ^ ..1 1 the end of the Hecond month. — From a the four upper mcisor teeth, and cor- .p„.mea m the author-. po..e.«on. responds with the intermaxillary bone of the lower animals. In some rare instances the fissure of hare- lip is situated in the median line, the two intermaxillary bones never having united with each other. A case of this kind has been observed by Prof. Jeffries Wyman.' The eyes at an early period are situated laterally, each on one side of the head. (Fig. 254.) As development proceeds, they come to be situated farther forward (Fig. 255), their axes being divergent and directed obliquely forward and outward. At a later period still they are placed on the anterior plane of the face ^Fig. 266), and have their axes nearly parallel and looking directly (forward. This change in the situation of the eyes is effected by the more rapid growth of the posterior and lateral parts of the head, which, enlarge in such a manner as to alter the relative position of the parts seated in front of them. The palate is formed by a septum between the mouth and nares, which arises on each side as a horizontal plate or offshoot from the superior maxilla. These two plates afterward unite with each other upon the median line, forming a complete partition between the oral and nasal cavities. The right and left nasal passages are also separated from each other by a vertical plate (vomer), which grows from above downward and fuses with the palatal plates be- ■ Transactions Boston Society for Medical ImproTement, March 9tb, 1863. 48 674 DEVELOPMENT OF THE ALIMENTABT CASTAL, ETC. low. Fissure of the palate is caused by a deficiency, more or less complete, of one of the horizontal maxillary plates. It is accord- ingly situated a little on one side of the median line, and is fre- quently associated with hare-lip and fissure of the upper jaw. The fissures of the palate and of the lip are very often continuous with each other. The anterior and posterior pillars of the fauces are incomplete vertical partitions, which igrow from the sides of the oral cavity, and tend to separate, by a slight constriction, the cavity of the mouth from that of the pharynx. When all the above changes are accomplished, the pharynx, oesophagus, mouth, nares, and fauces, with their various projections and divisions, have been successively formed ; and the development of the upper part of the alimentary canal is then complete. ,,, DKVJfiLOPMENT OF THE KIDNEYS. 675 CHAPTER XVI. DEVELOPMENT OP THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL ORGANS OF GENE- RATION. Fig. 257. The first trace of a urinary apparatus in tlie embryo, consists of two long, fusiform bodies, which make their appearance in the ab- domen at a very early period, situated on each side the spinal column. These are known by the name of the Wolffian bodies. They are fully formed in the human subject, toward the end of the first month (Coste), at which time they are the largest organs in the cavity of the abdomen, extending from just below the heart, nearly to the posterior extremity of the body. Jn the foetal pig, when a little over half an inch in length (Fig. 257), the Wolffian bodies are rounded and kidney-shaped, and occupy a very large part of the abdominal cavity. Their importance may be estimated from the fact that their weight at this time is equal to a little over -j'j of that of the entire body — a proportion which is seven or eight times as large as that of the kidneys in the adult condition. There are, indeed, at this period only three organs perceptible in the abdo- men, viz., the liver, which has begun to be formed at the upper part of the abdominal cavity ; the intestine, which is already some- what convoluted, and occupies its central portion ; and the Wolffian bodies, which pro- ject on each side the spinal column. The Wolffian bodies, in their intimate structure, closely resemble the adult kidney. They consist of secreting tubules, lined with epithelium, which run from the outer toward the inner edge of the organ,, terminating at their free ex- FoTAT. Pis, % of an inch long; from a specimen in the author*8 possession. 1. Hrart. 2. Anterior extremity. 3. Pos- terior extremity. 4. Wolffian body. The abdominal vails have been cat away, in order to show the position of the Wolffian bodies. 676 DEVELOPMENT OF THE KIDNEYS. tremities in small rounded dilatations. Into each of these dilated extremities is received a globular coil of capillary bloodvessels, or glomerulus, similar to that of the adult kidney. The tubules of the WolfiSan body all empty into a common excretory duct, which leaves the organ at its lower extremity, and communicates afterward with the lower part of the intestinal canal, just at the point where the diverticulum of the allantois is given off, and where the urinary bladder is afterward to be situated. • The principal, if not the only distinction in minute structure, between the WolfiSan bodies and the true kidneys, consists in the size of the tubules and of their glomeruli; these elements being considerably larger in the Wolffian body than in the kidney. In the foetal pig, for example, when about an inch and a half in length, the diam- eter of the tubules of the Wolffian, body is 3^5 of an inch, while in the kidney of the same foetus, the diameter of the tubules is onlyryJs of an inch. The glomeruli in the Wolffian bodies measure -^ of an inch in diameter, while those of the kidney mea- sure only y ^5 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 .^^Iso they completely disappear long before birth. They are consequently foetal organs, destined to play an important part during a certain stage of development, but to become after- ward atrophied and absorbed, as the physiological condition of the foetus alters. During the period, however, of their retrogression and atrophy, other organs appear in their neighborhood, which become afterward permanently developed. These are, first, the kidneys, and secondly, the internal organs of generation. The kidneys are formed just behind the Wolffian bodies, and are at first entirely concealed by them in a front view, the kidneys being at this time not more than a fourth or a fifth part the size of WOLFFIAN BODIES. 677 Fig. 258. F(ETAL Fio, one and a half Inches long. I'rom » apecimen In the author's poBsessiou.—li Woiffiao hodjr. 2. Kidney. the Wolffian bodies. (Fig. 258.) As the kidneys, however, subse. quently enlarge, while the Wolffian bodies diminish, the proper 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. 259 and 260.) 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 foetal life, become in their turn very largely developed in proportion to the rest of the organs ; attaining a size, in the foetal pig, equal to ^'^ (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 kidneys taken together is yjg that of the entire body. Internal Organs of Generatio.n. — 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 foetus is afterward to belong to the male or the female sex. (Fig. 269.) Fig. 259. IXTEKKAL ObOAHS 07 GeHE- BATloir, &c. ; in a foetal 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 ox ovaries. 4. I^rinary bladder turned over in front, fi. Intestine. 678 DEVELOPMENT OP THE KIDNEYS. A short distance above the internal organs of generation there commences, on each side, a narrow tube or duct, which runs from above downward along the anterior border of the Wolfl^n 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 ;bodie3, 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 I]allopian 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 tJie Testicles.- — In the male foetus there now commences a movement of translation, or change of place, in the internal organs of generation, which is known as the " descent of the testicles." In consequence of this movement, the above organs, which are at first placed near the middle of the abdomen, and directly in front of the kidneys, come at last to be situated in 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 t^ike place in the following manner. By the upward enlargement of the kidneys, both the WolflSan bodies and the testicles are soon found to be situated near the lower extremity of these organs. (Fig. 260.) 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. 679 IVTBRITAL OrQANB OF Oe1«EBATION, &c.f in a foetal pig Dearly fonr Inches long. F:'om a specimen in the author's possession. — 1, 1. Kidneys. 2, 2. Wolffian bodies. 3, S. Testicles. 4. Urinary bladder. S. lutestioe. 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 gubemaculum 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 gubemaculum, 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 Wolflian 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. 680 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 body 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 j 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 vaisa deferentia, and, elongating in a backward direction, underneath the base of the bladder, become developed into two compound sacculated reservoirs — the vesiculse seminales. The left testicle is a little later in its descent than the right, but it afterward passes farther into the scrotum, and, in the adult condi- tion, usually hangs a little lower than its fellow of the opposite side. After the testicle has fairly passed into the scrotum, the serous pouch, which preceded its descent, remains for a time in 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 the abdomen, by the action of the guber- naculum and the cremaster milsele. 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 in contact with each other, and, adhering together at this situation (Fig. 261, t), form a kind of cicatrix, or umbilicus, by the complete closure and consolidation ot which the cavity of the tunica vaginalis (a) is finally shut off altogether from the general cavity of the peritoneum (a). The tunica vaginalis testis is, therefore, originally a part of the peritoneum, from which it is subsequently separated by the process just described. Fig. 261. Formation of TuvicA Va- oiNALis Tbbih. — 1. Testicle nearly at the bottom of the scro' torn. 2 Cavity of tanica vaginiillB. 3. Cavity of periton^nm. 4. Obliter' ated neck of peritoneal sac. FEMALE ORGANS OP QEK-fiBATION. 681 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 ingumal hernia. (Fig. 262.) 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. 2fi2. other and obliterate the unnatural open- ing ; and if the intestine be retained by pressure in the cavity of the abdomen, cicatrization usually takes place at the inguinal canal, and a cure is effected. The descent of the testicle, above de- scribed, is not accomplished by the 'forci- ble traction of the muscular fibres of the gubernaculum, as has been described by certain writers, but. by a simple process coHOBuiTALinaiiiKALHER- „ ., , . 1 • T«. »IA.— 1. Testicle. 2,2,2. lutea. ot growth taking place in diflerent parts, tine, in different directions) at successive periods of fcetal 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 Orgam 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 682 DEVELOPMENT OF THE KIDNEYS, ETC. tube; while that point which is inside the same pointy becomes con- verted into the uterus. The upper portion of the cord itself becomes the Uffament 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 Wolfl&an bodies in the female is always the space between the ovaries and the Fallopian tubes; for the Wolffian bodies accompany the ovaries in their descent, just as, in the male, they accompany the testicles. As these bodies now become grad- ually atrophied, their glandular structure disappears altogether; but their bloodvessels, in many instances, remain as a convoluted vascular plexus, occupying the situation above mentioned. The Wolffian bodies may therefore be said, in these instances, to un- dergo a kind of vascular degeneration. This peculiar degeneration is quite evident in the Wolffian bodies of the foetal pig, some time before the organs have entirely lost their original form. In the cow, a collection of convoluted bloodvessels may be seen, even in the adult condition, near the edge of the ovary, and between the two folds of peritoneum forming the broad ligament. These are undoubtedly vestiges of the Wolffian bodies, which have undergone the vascular degeneration above described. While the above changes are taking place in the adjacent organs, the two lateral halves of the uterus fuse with each other more and more upon the median line, and become covered with an exces- sively developed layer of muscular fibres. In the lower animals, the uterus remains divided at its upper portion, running out into two long conical tubes or cornua (Fig. 192), presenting the form known as the vierus 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. 193), with the ligaments of the ovary and the round ligaments passing off from its superior angle?. But, internally, the cavity of the organ still presents a strongly marked triangular form, the vestige of its original division. FSMALE ORGANS OF GENERATION. 683 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 foetal 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 vitae 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 jj^ 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 DEVELOPMENT OF THE KIDNEYS, ETC, layer is to be seen tTie germinative vesicle, with the germinativo 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 tts'sj. In the very smallest, the cells of the membrana granulosa appear to fill entirely the cavity cf the follicle, and no vitellus or germina tive vesicle ip to be seen. DEVKLOPMENT OF THE OIRCULATOET APPARATUS. 685 CHAPTER XVII. DEVELOPMENT OP THE CIRCULATORY APPARATUS. Theee 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 fcetus. 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. 263), 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 npar 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 686 DEVELOPMENT OF THE ClRCULATOBT APPARATUS. newly-formed tissues. In the egg of the fish (Fig. 264), 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. 263. Enn op Fowl In prncesa of derolopment, showing area vasculoaa, with Titelline clrcuiatlon, terminal einua, &c. Fig. 264. 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 foetug/onthe 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 omphah-mesenteric arteries and SooF Fish (Jar- rabacca), Bhowing Titel- line circulation. veins. The arrangement of the circiilatoi'y 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 PLACENTAL CIBOULATIOK. 687 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 vasoulosa. The two vertebral arteries remain separate in the upperpart 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 foetus. 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 ^S- 265. 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. 265.) 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 Yodhq Ehbbto ak» iia Vrsselb, showing circalatioa of nmblUoAl vesicle, and also that of allantois, beginning to be formed. DEVELOPMENT OF THE CIKCULATOBY APPAKATUS. single vein, connecting the internal and external portions , of tlio 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. (Eig. 265.) 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.? (^ig- 266.) . The mesenteric vessels then Fig. 266. Diagram of Embrto and itr Vrsbrls: nhowing the second circulation. Tlie pharynx, (esophagas, and intestiual canal, have become further developed, and the moRenteric arterie^'haVf enlarged, while the umbilical veeicle and its vascnlar branches are rerf much reduced in size. The large nmbilical arteries are seen passing ont 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 A.BTEEIAL SYSTEM. 689 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. 266.) As the placenta soon becomes the only source of nutri- tion for the foetus, its vessels are at the same time very much increased in size, and preponderate over all the other parts of the circulatory system. During the early periods of the formation of the placenta, there are, as we have stated above, two umbilical arteries and two umbilical veins. But subsequently one of the veins disappears, and the whole of the blood is returned to the body of the foetus by the other, which becomes enlarged in proportion. For a long time previous to birth, therefore, there are in the umbili- cal cord two umbilical arteries, and but a single umbilical vein. Such is the second, or placental circulation. It is exchanged, at the period of birth, for the third or aduU circulation, in which the blood which had previously circulated through the placenta, ia 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, certam other altera- tions take place in the arterial and venous systems, which will now require to be described by themselves. Devehpment of the Arterial System.-r^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. 267.) These are termed the cervical arches. In the fish, these cervical arches remain permanent, and give off from their convex borders the branchial arteries, in the form of vascular tufts, 44 690 DEVELOPMENT OF THE CIBflULATORY 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. 267. Fig. 268. Early cboditiOD of ^RTBRiATi Ststeh; showiug the heart (IJ, with its two ascend- lag arterial trunlcs, ^iyinjf off on each side five cervical arcliea, which terminate in the vertehral arteries (2, 2). The vertebral a< te- riea unite below the heart to form the aorta (3). Adult condition of Artertai. Sys- tem .-^1, 1. (larotida. 2, 2. Vertehrala. 3, 3. Right and left subclavian^. 4, 4. Itight'and left superior imercostala. 5. Left aorticarch, which remains perma* noiit. 6. RKght aortic arch, whichdia- appeara. The two ascending arterial trunks on the anterior part of the neck, from which the cervical arches are given off, become con- verted info the carotids. (Fig. 268, i, i.) 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 (a, 3). This vessel, DEVELOPMENT OF THE ARTERIAL STSTEM. 691 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 (s). On the right side, however, the corresponding arch (e) becomes smaller and smaller, and at last altogether disappears ; so that, finally, we have only a single aortic arch, projecting to the left of the median line, and continuous with the thoracic and abdo- minal aorta. The first cervical arch remains during foetal life upon the left side, as the " ductus arteriosus," presently to be described. In the adult condition, however, it has disappeared equally upon the right and left sides. In this way the permanent condition of the arterial circulation is gradually established in the upper part of the body. Corresponding changes take place, however, during the same time, in the lower part of the body. Here the abdominal aorta runs undivided, upon the median line, quite to the end of the spinal column ; giving off on each side successive lateral branches, which supply the intestine and the parietes of the body. When the allantois begins to be developed, two of these lateral branches accompany it, and become, consequently, the umbilical arteries. These two vessels increase so rapidly in size, that they soon appear as divisions of the aortic trunk ; while the original continuation of this trunk, running to the end of the spinal column, appears only as a small branch given off' at the point of bifurcation. When the lower limbs begin to be developed, they are supplied by two small branches, given off from the umbilical arteries near their origin. Up to this time the pelvis and posterior extremities are but slightly developed. Subsequently, however, they grow more rapidly, in proportion to the rest of the body, and the arteries which supply them increase in a corresponding manner. That portion of the umbilical arteries, lying between the bifurcation of tiae aorta and the origin of the branches going to the lower ex- 692 DEVELOPMENT OF THE CIKCOLATOEY APPAEATU8. 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 foetus, and the separation of the placenta, the hypogastric arteries become partially atrophied, and are con- verted, in the adult condition, into solid, rounded cords, running upward toward the umbilicus. Their lower portion, however, remains pervious, and gives off arteries supplying the urinary bladder. The obliterated hypogastric arteries, therefore, the rem- nants of the original umbilical or allantoic arteries, run upward from the internal iliacs along the sides of the Fig. 269. 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. 269), which run along the sides of the spinal column, parallel with the vertebral arteries. They receive jn succession all the inter- costal veins, and empty into the heart by two lateral trunks of equal size, the canals of Owmer, 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 BarlyconditioQofVE- jrous Ststeh; show- ing the vertebral veins emptying into the heart by iwo lateral trunlcs, the "canals of Cnvier." DEVELOPMENT OF THE VENOUS SYSTEM. 693 constituting another vein of new formation (Fig. 270, 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- waird, by enlargement, the common iliac veins ; while the single trunk (a) resulting from theii: 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. 270), 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. 270, J), 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 (J), 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. 271), 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. VasoiTB System far- ther advanced, Sbowing formation of iliac and sub- clavian veins. — a. Vein of new formation, wliich be- comes the inferior vena cava. b. Transverse branch of new formation, which afterward becomes the left vena innominata. Fig. 271. Furthei- development of theVBMOca System.— The veitebral veins are much diminished in size, and the canal of Cavier, on the left side, is gradually disappearing, c. Trans- verse branch of new forma- tion, which is to becoma the vena azygos minor. 694 DEVELOPMENT OF THE CIRCULATOBT APPARATUS. Fig. 272. On the left side, that portion of the Superior vertebral vein, whicli 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. 272, 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 ^r ^^^ 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. 271,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 Vf,- Houa Stbtem. — 1. Right auricle of heart. 2, Vena cava superior. 3, 3. Jugular vetua. 4,4. Subclaviaa veina. A. Vena cava inferior. 6, 6. Uiacveina. 7. Lum'bar veins. 8. Veca azygos major. 9. Vena azygos minor. 10. Su- perior intercostal vein. DEVELOPMENT OF THE HEPATIC CIBCULATIOX. 695 upper intercostal veins on the left side still empty, as before, into their own vertebral vein (lo), which, joining the left vena innomi- nata above, is known as the superior intercostal vein. The left canal of Cuvier has by this time entirely disappeared'; so that all the venous blood now enters the heart by the superior or the inferior vena cava. But the original vertebral veins are still continuous throughout, though very much diminished in size at certain points ; since both the greater and lesser azygous veins inosculate below with the superior lumbar veins, and the .superior intercostal vein also inosculates below with the lesser azygous, just before it passes over to the fight 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 tne 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 ^'S- ^^^- termination in the heart. (Fig, 273.) As ■' soon as the organ has attained a con- f-\\r~\ I siderable size, the omphalo-mesenteric ^^-L3 J vein (i) breaks up in its inteiior into a ^L^^^B^ ^ . capillary plexus, the vessels of which hHHWBb^^ f ■ unite again into venous trunks, and so ^^gj^^ ^P convey the blood finally to the heart. ■"--■;-:-.-: The omphalo-mesenteric veib below the Eariy form of hepatic cir,- T J.1 1 ii J 7 • 1-1 CDLATioN., 1. Orophalo-mesen- hver then becomes the portal vein ; while ,„;„ ^.i„ j H,pJi„ ^^i„ 3 above the liver, and between that organ »«»•'• Tbo dotted itne shows tiia t . . • .1 p situatioa of the future umbilical and the heart, it receives the name or yein. 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 DEVELOPMENT OP THE CIKCULATOBY APPARATUS. Fig. 274. Hepatic Circuljition farther advanced. ~1. Portal Tein. 2. Umbilical veiD. 3. Hepatic Tein. 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. 274.) 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 fcetal pig, when very young, it amounts to nearly twelve per cent, of the weight of the whole body ; but he- 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, avascular duct or canal is formed in its interior, by which a portion of the placental km 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 (s) (Fig. 275), 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. 275. Hepatic CiscnLATioN during lat- ter part of foetal life. — 1. Portal veia. 2, Umbilical vein. 3. Left branch of nmbili- cal vein, 4. Bight branch of umbilical vein. 6. Ductus Tenouna. 6, Hepatic vein. DEVELOPMENT OF THE HEPATIC CIRCULATION. 697 Fig. 276. as follows : A certain quantity of venous blood still enters through the portal vein (i), 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 (s), 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. 276.) First, the umbilical vein shrivels and be- comes converted into a solid rounded cord (3). 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 CiRcnLA- Trow. — 1. Portal vein, 2. Obliterated umbilical vein, forming tbe round liga- ment; the continuation of the dotted lines through the liver t^ows the eitna- tiou of the obliterated ductns veoosns. 3. Hepatic vein. 4. Left branch of portal vein. 698 Ca\rELOPMENT OP THE CIBCULATOBT APPARATUS. from right to left, to be distributed to the capillaries of the left lobe. According to Dr. Guy, the umbilical veiu is completely closed at the end of the fifth day after birth. Developmeni of the Start, and the Ductus Arteriosus. — When the embryonic circulation is first established, the heart is a simple tubu- lar sac (Fig. 277), 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. 278); 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 streamj turning upon itself at the point of curvature, and passing directly out by the arterial orifice. Fig. 277. Earliefit form of'F(ET al Hgakt. — 1, Venous ex- tremity. 2. Arterial ex- tremity. Fig. 278. Fig. 279. FcETAii Hkart, twisted upon itself. — 1. Veuous ex- tremity. 2l Arterial extre- mity. F<£TAL Heart, divided into riglit aud 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. 279.) 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 beart, 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 HEAKT. 690 Fig. 280. TaiTAL Heart still farther developed.— I Aorta. 2. Puj- moDary artery. 3, S. Pal- monary brauchea 4, Ductild arteriosus. Tery soon a superficial line of demarcation, or furrow, shows itself upon the external surface of the heart, corresponding in situa- tion With the internal septum; while at ihe 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. 280.) 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 (a), 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 festal 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. 281.) The ductus arteriosus at the Fig. 281. Hbart of Ikfaht, showing die. appearance of arterial duct after birtd. — 1. Aorta. 2 Pulmonary artery. 3, S. Pulmonary branches. 4. DuctUf arteriosus becoming obliterated ^ 700 DEVELOPMENT OF THE CIECULATOBY APPARATUS. / same time becomes contracted and shrivelled to such an extent that its cavity is obliterated ; and it is finally converted into an ini- 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 cavse, superior and inferior, do not open into the auricular sac on the same plane or in the same direction ; for while the superior vena cava is situated anteriorly, and is directed downward and forward, the inferior is situated quite posteriorly, and passes into the auricle in a direction from right to left, and transversely to the axis of the heart. A nearly vertical curtain or valve at the same time hangs downward behind the orifice of the superior vena cava and in front of the orifice of the inferior. This curtain is formed by the lower edge of the septum of the auricles, which, as we have before stated, is incomplete at this age, and which terminates inferiorly and toward the right in a 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 HEABT. 701 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. 282./), 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 Fig. 282. 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. 282, lies naturally quite behind the Eustachian valve, and passes directly through the foramen ovale, into the left auricle. The two streams of blood, therefore, coming from the su- perior and inferior venae cavse, cross each other upon entering the heart. This crossing of the streams does not take place, however, as it is 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 entera the right auricle exclusively, while that from the inferior passes almost directly into the left auricle. It will also be seen, by examining the positions of the aorta, pul- monary artery, and ductus arteriosus, at this time, that the arteria inuominata, together with the left carotid and left subclavian, are given off from the arch of the aorta, before its junction with the ductus arteriosus, and this arrangement causes the blood of the two venae cavae, not only to enter the heart in different directions, but also to be distributed, after leaving the ventricles, to different parts of the body. (Fig. 283.) For the blood of the superior vena cava Heast OF HtTHAN T (STUB, at the end of the sixth month ; from a (specimen in the author's pos- Besitioa. — a. Inferior vena cava. h. Superior vena cava. e. Cavity of right auricle, laid open from the front, d. Appendix anricularlB. e, Cavit" ot right ventricle, also laid open. /. Bustachian valve. The bougie, which is placed in the inferior vena cava, can be seen paBBiog behind the EuEtacbian valve, juBt below the point indicated by /, then eroBslng behind the cavity of the right auricle, and passing through the foramen ovale, to the left Bide of the heart. 702 DEVELOPMENT OF THE CIBCULATOBT APPARATUS. 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 'H'-i: i"" ■ ■ ' "■. " Upper extremities by the superior Fig' 283. 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 Eeid,' on injecting the infe- rior vena cava with red, and the superior with yellow, in a seven months' human foetus, found that the red 'had passed through the foramen ovale into the- left auricle and ventricle and arch of the aorta, and had filled the vessels of the head and upper extremities ; while the yellow had passed into the right ventricle, pulmonary artery, ductus arteriosus, and tho- racic aorta, with only a slight admixture of red at the posterior part of the right auricle. All the branches of the thoracic and abdominal aorta were filled with yellow, while the whole of the red had passed to the upper part of the body. We have repeated the above experiment several times on the foetal pig, when about one-half and three-quarters grown, first taking the precaution to wash out the heart and large vessels with a wa- tery injection, immediately after the removal of the foetus from the body of the parent, and before the blood had been allowed to coagu- late. The injections used were blue for the superior vena cava, Diagram or Circulation throuor THE F(ETAL Heart^— a^ Biiperior Yena cava. 6. Inferior veaa cava. e,c,c,o. Arch of aorta and its braoches. d. Pulmonary artery. EdinbuTgh Medical and Surgical Journal, vol. zliii. 1835. DKVELOPMENT OP THE HEAET. 703 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 nimeteen-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. Eeid, 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 aotly the force and rapidity of the different currents of blood m 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: — rirst; 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. 282), 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 70J: DEVELOPMENT OF THE CIRCULATOBT 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 interau'rioular 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. 705 no longer admits a free access from tbe 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 th6 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. 283, is then replaced by the adult circulation, represented in Fig. 284. Fig. 284. «J Diagram of Adult Cibculation through th" Heart. — n, n. Superior and inferior vense caTHj. A. Right ventricle, c. Palmonaiy artery, dividing into right and left branches, d Pulmu- nary rein, 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- 45 706 DEVELOPMENT OF THE CIECULATORy 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 /os«a 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 he 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. BEVELOPMENT OF THE BOUY AFTER BIETH. 707 CHAPTEE XVIII. DEVELOPMENT OF THE BOBY APTEE BIETH. The newly-born infant is still very far from having arrived at a state of complete development. The changes through which it has passed during intra-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, hoth 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 between six and seven 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 extrelni- 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. Eespiration, indeed 708 DEVELOPMKNT OF THE BODY AFTEK BIETF. seems to be accomplislied, 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 dif&culty 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 reprtsented, 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 BTtTB AT Term. Adult. 1000.00 1000.00 148.00 23.00 37.00 29.00 7.77 4.17 6.00 4.00 1.63 0.13 0.60 0.51 3.00 0.00 DEVELOPMENT OP THE BODY APTEE BIBTH. 709 the estimates of Oruveilheir, Solly, Wilson, &c. ; that of the oi-gans in the foetus at term from our own observations. Weight of the entire body " encephalqn liver .... "■ heart " kidneys " renal capsules . " thyroid gland . " thymus gland . 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, tha 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 J^eth 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 (Kblliker). 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 710 DEVELOPMENT OF THE BODY AFTEB BIRTH. the first set of teeth are thro-wn 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, 15G, 819 vessels, 156, 319 Absorption, 149 by bloodvessels, 152 by lacteals, 156 of fat, 154 of different liquids by animal sub- stances, 814 of oxygen in respiration, 235 by egg during incubation, 625 of calcareous matter by allantois, 626 Acid, carbonic, 235, 240, 'Zil lactic, in gastric juice, 126 in souring milk, 84, 340 glyko-cholic, 166, 167 tauro-cholic, 167 pneumic, 240 uric, 352, 360 oxalic in urine, 866 Acid fermentation of urine, 365 Acidity of gastric juice, cause of, 126 of urine, 359 Acini, of liver, 341 Adipose vesicles, 75 digestion of, 146, 147 Adult circulation, 705 establishment of, 706 Aerial respiration, 226 ' Age, influence of, on exhalation of car- bonic acid, 244 on comparative weight of organs, 709 Air, quantity of, used in respiration, 231 alterations of, in respiration, 234 circulation of, in luugs, 232 Air-cells of lungs, 228 Air-chamber, in fowl's egg, 670 Albumen, 85 of the blood, 216 in milk, 338 of the egg, how produced, 568 Us liquefaction and absorption dur- ing development of foetus, 622, 623 Albuminoid substances, 80 digestion of, 129 Albuminose, ISO interference with Trommer's test, 181 with action of iodine and starch, 132 in the blood-plasma, 216 Alimentary canal in different animals, 102 in human subject, 106 development of, 664 Alkalies, effect of, on urine, 360 Alkaline chlorides, 55-58 phosphates, 61 carbonates, 60, 61 Alkaline fermentation of urine, 367 Alkalescence of blood, due to carbonates, 60 and basic phosphates, 217 Allantois, 619 formation of, 621 in fowl's egg, 624 function of, 625 in foetal pig, 641 Alligator, brain of, 393 Amnion, 619 formation of, 620' enlargement of, during latter part of pregnancy, 650, 651 contact with chorion, 652 Amniotic folds, 620 Amniotic fluid, 650 its use, 651 contains sugar at a certain period, 669 Amniotic umbilicus, 620 Analysis, of animal fluids, 48, 49 of milk, 98, 338 of wheat flour, 98 of oatmeal, 99 of eggs, 99 of meat, 99 of saliva, 111, 113 of gastric juice, 126 of pancreatic juice, 143 of bile, 162 of blood-globules, 210 of blood-plasma, 214 of mucus, 330 of sebaceous matter, 332 of perspiration, 333 of butter, 889 of urine, 358 of fluid of thoracic duct, 320 of chyle and lymph, 322 Andeal and Gavabret, production of carbonic acid in respiration, 243 Animal functions, 43 Animal heat, 247 in different species, 249 mode of generation, 251 influenced by local causes, 255 in different organs, 256 (711) 712 INDEX. Animal heat, increase of, after section of sympathetic nerve, 538 Aninial and vegetable parasites, 550 Animalcules, infusorial, 547 mode of production, 548 Annulus ovalis, 706 Anterior columns of spinal cord, 392 their excitability, 416 Aorta, development of, 690 Aplysia, nervous system of, 386 Appetite, disturbed by anxiety, &c., 138 necessary to digestion of food, 138 Aquatic respiration, 226 Arch of aorta, formation of, 690 Arches, cervical, 689 transformation of, 690 Area pellucida, 610 vasculosa, 623, 685 Arteries, 276 motion of blood in, 277 pulsation of, 278 elasticity of, 277, 281 rapidity of circulation in, 286 omphalo-mesenterie, 686 vertebral, 687 umbilical, 689 Arterial pressure, 285 Arterial system, development of, 689 Articulata, nervous system of, 887 reflex action in, 388 Articulation of tapeworm, 559 Arytenoid cartilages, 234 movements of, 234 Assimilation, 826 destructive, 845 Auditory apparatus, 522 nerves, 460, 521 Auricle, single, of fish, 260 double, of reptiles, birds, and mam- malians, 261, 262 contraction of, 275 Auriculo-ventricular valves, action of, 204 Axis-cylinder, of nervous filaments, 375, 378 Aztec children, 439 Azygous veins, formation of, 694 Baxt, on the rapidity of the nervous force, 408 Beaumont, Dr., experiments on Alexis St. Martin, 123, 132, 134 Eernabd, on the different kinds of saliva, 112 on effect of dividing Steno's duct, 118 on digestion of fat in intestine, 142 on formation of liver-sugar, 186, 188, 189 on variable action of poisons, 223 on decomposition of bicarbonates in lung, 241 on temperature of blood in difForent organs, 256 Bernard, on the influence of the nerves on local circulation, 538, 539, 540 on the origin of the spinal accessorjj nerve, 488 Bidder and Schmidt, on daily quantitv of bile, 174 on effect of excluding bile from in- testine, 181 on reabsorption of bile, 182 Bile, 161 composition of, 162 tests for, 170 daily quantity of, 174 quantity discharged after eating, 178 functions of, 179 reaction with gastric juice, 179 reabsorption, 182 mode of secretion, 841 in the foetus, 669 Biliary salts, 163 of human bile, 169 Biliverdine, 88, 162 tests for, 170 passage into the urine, 363 BisCHOFP, on daily quantity of urea, 849 on entrance of spermatozoa into the interior of the egg, 580 on rupture of Graafian follicle in menstruation, 592 Blastodermic membrane, 608 Blood, 205 red globules of, 205 white globules, 212 plasma, 214 coagulation of, 217 entire quantity of, 223 alterations of, in respiration, 236 temperature of, 248 in diff'erent organs, 256 circulation of, 259 through the heart, 265 through the arteries, 276 through the veins, 290 through the capillaries, 295 BoDSSiNGAiiLT, on chloride of sodium in food, 57 on internal production of fat, 78 Brain, 892, 430 of alligator, 392 of rabbit, 394 human, 397, 430 remarkable cases of injury to, 432, 433 size of, in different races, 487 in idiots, 488 development of, 658, 659 Branchiae, 225 of meno-branchus, 226 Broad ligaments, formation of, 682 Bronchi, division of, 227, 228 ciliary motion in, 232 INDEX. •713 Brown-Sequard, on crossing of sensitive . fibres in spinal cord, 418 on disappearance of fibrin in liver and kidneys, 222 on transmission of sensibility tlirough spinal cord, 416 Brunner's glands, 140 Butter, 76, 98, 338 composition of, 339 condition in milk, 76, 338 Butyrine, 339 Canals of Cuvier, 692 Capillaries, 295 their inosculation, 295 motion of blood in, 296 Capillary circulation, 295 causes of, 298 rapidity of, 300 local variations in, 303, 538 peculiarities of, in different parts, 307 Caput ooli, formation of, 665 Carbonic acid,, in tlio breath, 235 proportion of, to oxygen absorbed, 235, 236 in the blood, 237 origin of,' in lungs, 240 in the blood, 241 in the tissues, 241 mode of production, 242 daily quantity of, 243 variations of; 244 in the urine, 246 exhaled by skin, 246 by egg, during incubation, 625 absorbed by vegetables, 25 • Carbonate of lime, 60 of soda, 60 of potassa, 61 of ammonia, in putrefying urine, 367 Cardiac circulation, in foetus, 702 in adult, 264, 705 Carnivorous aninials, respiration of, 34, 286 urine of, 351 Cartilagine, 87 Caseine, 85 Cat, secretion of bile in, 174 closure of eyelids, after division of sympathetic, 535 Catalytic action, 83 of pepsin, 130 Centipede, nervous system of, 387 Centre, nervous, definition of, 383 Cerebrum, 432. See Hemispheres. Cerebral ganglia, 386, 432. See Hemi- . spheres. Cerebellum, 443 effects of injury to, 444 removal of, 444, 448 Cerebellum, function of, 443 development of, 658, 659 Cerebro-spinal system, 389, 390 development of, 657 Cervix uteri, 572 in foetus, 683 Cervical arches, 689 transformation of, 690 Changes, in egg while passing through oviduct, 567, 669 in hepatic circulation at birth, 697 in comparative size of organs after birth, 709 Chauveatt, experiments on rapidity of the arterial current, 288 ; Chevreuil, experiments on imbibition, 314 Chick, development of, 622 Children, Aztec,, 439 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, 162 Chorda dorsalis, 611, Chorda tympani, influence of, on circu- lation in submaxillary gland, 54U on the sense of taste, 602 Chordae vocales, movement of, in respi- ration, 234 action of, in the production of vocal sounds, 478 obstruction of glottis by, after divi- sion of pneumogastric, 480 Chorion, formation of, 628 villosities of, 630 source of vascularity of, 631 union wi(h decidua, 639 Chyle, 75, 141, 164, 322 in lacteals, 158 absorption of, 154 by intestinal epithelium, 155 in blood, 159 Ciliary motion, in bronchi, 232 in Fallopian tubes, 693 Ciliary nerves, 533 Circulation, 259 in the lieart, 265 in the arteries, 276 in the veins, 290 in the capillaries, 295 local variations of, 303 modified by nervous influence, 538 rapidity of, 300 peculiarities of, in different parts, 307 in liver, 342 in placenta, 641, 646 714 INDEX. Circulatory apparatus, development of, 685 Civilization, aptitude for, of different races, 436 Clarke, J. L. Esq., on decussation of anterior pyramids, 395 Classification of cranial nerves, 461 Clot, formation of, 217 separation from serum, 218, 219 composition of, 219 Coagulation, 83 of fibrin, 215 of blood, 217 of medullary layer, in nerve-fibres, 375, 376 Colin, on unilateral mastication, 114 on the daily quantity of chyle, in the ox, 328 Cold, resistance to, by animals, 247 effect of, when long continued, 243 Colostrum, 837 Coloring matters, 87 of blood, 87, 210 of the skin, 88 of bile, 88, 162 of urine, 89, 336 Commissure, of spinal cord, gray, 391 white, 391 transverse, of cerebrum, 398 of cerebellum, 398 Commissures, nervous, 384 olfactory, 893, 431 Congestion, of ear, &c., after division of sympathetic, 538 Consentaneous action of muscles, 443 Contact, of chorion and amnion, 651 of decidua vera and reflexa, 052 Contraction of stomach during digestion, 132 of spleen, 201 of blood-clot, 218 of diaphragm and intercostal mus- cles, 229 of posterior crico-arytenoid muscles, 234 of ventricles, 270 of muscles after death, 399, 400 of sphincter ani, 427 of rectum, 427 of urinary bladder, 428 of pupil, under influence of light, 373, 449, 515 after division of sympathetic, 535 Convolvulus, sexual apparatus of, 558 Cooking, effect of, on food, 100 Cord, spinal, 390, 410 umbilical, 651 withering and separation of, 709 Corpus, callosum, 398 Corpus luteum, 596 of menstruation, 596 of pregnancy, 600 Corpus luteum, three weeks after men- struation, 598. four weeks after menstruation, 599 nine weeks after menstruation, 599 at end of second month of preg- nancy, 602 at end of foiirth month, 602 at term, 603 disappearance of, after delivery, 604 Corpora Malpighiana, of spleen, 201 Corpora striata, 432 Corpora olivaria, 395 Corpora Wolffiana, 675 CosTB, on rupture of Graafian follicle in menstruation, 592, 593 Cranial nerves, 459 classification of, 461 motor, 462 sensitive, 462, 463 Creatine, 351 Creatinine, 352 Cremaster muscle, formation of, 679 function of, in lower animals, 680 Crystals, of stearine, 72 and margarine, 73 of cholesterin, 163 of glyko-cholate of soda, 164, 165 of biliary matters of dog's bile, 108 of biliary matters of human bile, 169 of urea, 347 of creatine, 351 of creatinine, 352 of urate of soda, 858 of uric acid, 360 of oxalate of lime, 366 of triple phosphate, 308 Crystallizable substances of organic ori- gin, 63 Crossing of fibres in medulla oblongata, 395, 417 of sensitive fibres in spinal cord, 418 of fibres of optic nerves, 450, 451 of streams of blood in foetal heart, 701, 702 Ckuikshank, rupture of Graafian follicle in menstruation, 592 Cumulus proligerus, 587 Cutaneous respiration, 246 perspiration, 332 Cuticle, exfoliation of, after birth, 709 Cysticercus, 555 transformation of, into taenia, 556 production of, from eggs of taenia, 557 Dean, John, M. D., on the origin of the fifth and sixth pairs of cranial nerves, 464 on the origin of the hypoglossal nerve, 491 Death, a nece?sary consequence of life, 644 INDEX. 715 Decidua, 634 vera, 686 reflexa, 038 union with chorion, 639 its discbarge in cases of abortion, 638 at the time of delivery, 653 Decussation, of anterior columns of spi- nal cord, 395, 417 of sensitive fibres, in the spinal cord, 418 of optio nerves, 450, 451 Degeneration, fatty, of muscular fibres of uterus, after delivery, 655 Deglutition, 119 retarded by division of Steno's duct, 118 by division of pneumogastric, 477 Dentition, first, 709 second, 710 Descent, of the testicles, 678 of the ovaries, 681 Destructive assimilation, 345 Development, of impregnated egg, 606 of allantois, 621 of chorion, 628 of villosities of chorion, 629, 630 of decidua, 634 of placenta, 641 of nervous system, 657 of eye, 660 of ear, 661 of skeleton, 661 of limbs, 662 of integument, 663 of alimentary canal, 613, 664 of urinary passages, 666 of liver, 669, 695 of pharynx and oesophagus, 670 of face, 671 of Wolffian bodies, 675 of kidneys, 676 of internal generative organs, 677 of circulatory apparatus, 685 of arterial system, 689 of venous system, 692 of hepatic circulation, 695 of heart, 698 of the body after birth, 707 Diabetes, 363 in foetus, 669 Diaphragm, action of, in breathing, 229 formation of, 671 Diaphragmatic hernia, 671 Dicrotic pulse, 284 Diet, influence of, on nutrition, 94 on products of respiration, 236 on formation of urea, 349 of urate of soda, 853 Diffusion of gases in lungs, 232 Digestion, 102 ' Digestion, of starch, 138 of fats, 141 of sugar, 138 of organic substances, 129 time required for, 184 Digestive apparatus, of fowl, 104 of ox, 105 of man, 106 Discharge of eggs from ovary, 566, 567 independent of sexual intercourse, 585 mechanism of, 588 during menstruation, 592 Discus proligerus, 587 Distance and solidity, appreciation of, by the eye, 516, 517 Distinction between corpora lutea of menstruation and pregnancy, 605 Diurnal variations, in exhalation of car- bonic acid, 245 in production of urea, 349 in density and acidity of urine, 337 Division, of nerves, 377 of heart, into right and left cavities, 698 DoBSON, on variation in size of spleen, 200 DoNDEBS, on accommodation and refrac- tion of the eye, 512 Dkapek, John C, on production of urea, 849 Drugs, effect of, on newly born infant, 708 Ductus arteriosus, 699, 702 closure of, 699, 700 veYiosus, 696 obliteration of, 697 Duodenal glands, 140 fistula, 176 Ddtbochet, on temperature of plants, 250 on endosmosis of water with difi'er- ent liquids, 312 Ear, 520 muscular apparatus of, 521 development of, 661 Earthy phosphates, 58, 61 in urine, 859 precipitated by addition of an alkali, 360 Ectopia cordis, 671 Egg, 562 its contents, 563 where formed, 564 of frog, 565, 566 of fowl, 567 changes in, while passing through the oviduct, 568 pre-existence of, in ovary, 588 development of, at period of puberty, 584 periodical ripening and discharge, 585 716 INDEX. Egg, dJRcharge of, from Graafian follicle, 088 impregnation of, how accomplished, 578 development of, after impregnation, of fowl, showing area Tasculosa, 623, 686 ditto, showing formation of allantois, 624 of fish, showing vitelline circulation, 686 attachment of, to uterine mucous membrane, 637 discharge of, from uterus, at the time of delivery, 683 condition of, in newly born infant, 683 Elasticity, of spleen, 201 of red globules of blood, 208 of lungs, 228, 230 of costal cartilages, 230 of vocal cords, 234 of arteries, 277 Electrical current, effect of, on muscles, 400 on nerve, 402 different effects of direct and inverse, 405 Electrical fishes, phenomena of, 409 Elevation of temperature, after division of sympathetic, 538 Elongation of heart in pulsation, 270 anatomical causes of, 271 Embryo, formation of, 606, 609 Embryonic spot, 610 Encephalon, 392, 430 - ganglia of, 393 Endosmosis,- 309 of fatty substances, 154 in capillary circulation, 816 conditions of, 810 cause of, 313 of iodide of potassium, 315 of atropine, 315 of nux vomica, 316 Endosmometer, 310 Enlargement of amnion, during preg- nancy, 650 Entozoa, encysted, 552 mode of production, 554 Epithelium, in saliva. Ill of gastric follicles, 121 of intestine, during digestion, 155 Epidermis, exfoliation of, after birth, 709 Epididymis, 679 Excretine, 148 Excretion, 345 nature of, 345 importance to life, 346 products of, 347 by placenta, 648 Excrementitious substances, 346, 347 mode of formation of, 346 effect of retention of, 346 Exfoliation of cuticle, after birth, 709 Exhalation, 309 of watery vapor, 55 from the lungs, 235 from the skin, 246, 333 from the egg, during incubdtion, 625 of carbonic acid, 235, 237, 246 of nitrogen, 235 of animal vapor, 236 Exhaustion, of muscles, by repeated irritation, 401 of nerves, by ditto, 403 Exosmosis, 309 Expiration, movements of, 230 after section of pneumogastric, 482 Extractive matters of the blood, 217 Eye, protection of, by movements of pu- pil, 373, 449, 515 by two sets of muscles, 534 ,, Eyeball, inflammation of, after division of fifth pair, 468 development of, 660 Eyelids, formation of, 661 Face, sensitive nerve of, 464 motor nerve of, 469 development of, .671 Facial nerve, 469 sensibility of, 472 influence of, on muscular apparatus of eye, 471 of nose, 471 of ear, 471 paralysis of, 471 Fallopian tubes, 571 formation of, 681, 682 Farinaceous substances, 63 in food, 64, 92, 98 digestion of, 138 Fat, absorption of, 154 decomposition of, in the blood, 156, 159 Fats, 71 , ^ proportion of, in different kinds of food, 73 condition of, in the various tissues and fluids, 74 internal vsource of, 78 decomposed in the body, 79 indispensable as ingredients of the food, 93 Fatty matters of the blood, 216 Fatty degeneration, of decidua, 654 of muscular fibres of uterus, after delivery, 655 Feces, 148 ■Fecundation, necessary conditions of, 5/8 FEHtiMo's test for sugar, 69 INDEX. 717 Female generative organs, 064 of frog, 565 of fowl, 569 of sow, 571 of human species, 572 development of, 681 Fermentation, 84 of sugar, 70 acid, of urine, 365 alkaline, of ditto, 867 Fibrin, 85 of the blood, 215 coagulation of, 215 varying quantity of, in blood of dif- ferent veins, 216 disappearance of, in liver and kid- neys, 216, 222 Fifth pair of cranial nerves, 464 its distribution, 465 division of, paralyzes sensibility of face, 467 and of nasal passages, 468 produces inflammation of eyeball, 468 lingual branch of, 469 large root of, 464 small root of, 466 Fish, circulation of, 260 formation of umbilical vesicle in, 616 vitelline circulation, in embryo of, 686 electrical phenomena of, 409 Fissure, longitudinal, of brain and spinal cord, 390 formation of, 660 Fissure of palate, 674 Fistula, gastric. Dr. Beaumont's case of, 123 Prof. Schmidt's case, 127 mode of operating for, 123 duodenal, 176 Flint, Prof. Austin, on first sound of heart, 268 Flint, Prof. Austin, Jr., stercorine, in contents of large intestine, 148 cholesterin, in blood of jugular vein, 163 not discharged with the feces, 163 effects of biliary fistula, 182 sugar in blood of hepatic vein, 197 experiments on increase of urea by exercise, 350 Foetal circulation, first form of, 685 second form of, 687 Follicles, of stomach, 120 of Lieberkiihn, 189 of Brunner's glands, 140 Graafian, 564 of uterus, 635 Food, 91 composition of, 98, 99 daily quantity required, 99 effect of cooking on, 100 Foramen ovale, 700 valve of, 704 closure of, 704, 705 Force, nervous rapidity of, 407 nature of, 408 Formation of sugar in liver, 186 in foetus, 669 Fossa ovalis,706 Functions, animal, 43 vegetative, 42 of teeth, 108 of saliva, 116 of gastric juice, 128, &c. of pancreatic juice, 144 of intestinal juices, 138 of bile, 179 of spleen, 202 of mucus, 331 of sebaceous matter, 882 of perspiration, 334 of the tears, 336 Galvanism, action of, on muscles, 400 on nerves, 402 Ganglion, of spinal cord, 391, 422 of tuber annulare, 896, 452 of medulla oblongata, 893, 396, 453 Gasserian, 465 of Andersch, 473 pneumogastric, 475 ophthalmic, 529 spheno-palatine, 503, 529 submaxillary, 529 otic, 530 semilunar, 581 impar, 531 Ganglionic system of nerves, 389, 529 Ganglia, nervous, 383 of radiata, 384 of moUusca, 386 of articulata, 387 of posterior roots of spinal nerves, 392 of alligator's brain, 393 of rabbit's brain, 394 of medulla oblongata, 395 of human brain, 397 of great sympathetic, 529 olfactory, 393, 481 optic, 393, 448 Gases, diffusion of, in lungs, 232 absorption and exhalation of, by lungs, 235 by the tissues, 241 Gastric follicles, 121 Gastric juice, mode of obtaining, 124, 125 composition of, 126 its action on food, 129 interference with Trommer's test, 131 interference with action of starch and iodine, 132 daily quantity of, 134 718 INDEX. Gastric juice, solvent action of, on stom- ach, after death, 137 Gelatine, how produced, 48 effect of feeding animals on, 95 Generation, 544 spontaneous, 545 of infusoria, 547 of parasites, 560 of encysted entozoa, 552 of taenia, 554 sexual, by germs, 558 Germ, nature of, 558 Germination, heat produced in, 250 Germinative vesicle, 563 disappearance of, in mature egg, 606 Germinative spot, 563 Gills, of fish, 225 of menobranchus, 226 Glands, of Brunner, 140 mesenteric, 157 vascular, 202 Meibomian, 331 perspiratory, 332 action of, in secretion, 327 Glandulse solitarise and agminatse, 140 Globules, of blood, 205 red, 205 different appearances of, under microscope, 206, 207 mutual adhesion of, 207 color, consistency, and structure of, 208 action of water on, 209 composition of, 210 size, &c.,indifferentanimals,211 white, 212 action of acetic acid on, 212 red and white, movement of, in circulation, 297 Globuline, 86, 210 Glomeruli, of Wolffian bodies, C76 Glosso-pharyngeal nerve, 473 action of, in swallowing, 474 Glottis, movements of, in respiration, 233 in formation of voice, 478 closure of, after section of pneumo- gastrics, 480 Gluten, in wheat flour, 98 Glycine, 167 Glyco-cholio acid, 166 Glyco-cholate of soda, 166 its crystallization, 164, 165 Glycogenic function of liver, 186 in fcetus, 669 Glycogenic matter, 190 its conversion into sugar, 191 GossELiH, experiments on imbibition by cornea, 315 Graafian follicles, 564, 587 structure of, 587 rupture of, and discharge of egg, 588 ruptured during menstruation, 592 Graafian follicles, condition of, in foetus at term, 683 Gray substance, of nervous system, 382 of spinal cord, 390 of brain, 397 its want of irritability, 430 Great sympathetic, 529 anatomy of, 630 sensibility and excitability of, 532 connection of, with special senses, 533 division of, influence on animal heat, 638 on the circulation. 537 on pupil and eyelids, 635 reflex actions of, 540 Gubernaculum testis, 679 function of, in lower animals, 680 Gustatory nerves, 467, 469, 473 Hammond, Prof. Wm. A., on effects of non-nitrogenous diet, 94 on production of urea, 349 Hairs, formation of, in embryo, 663 Hare-lip, 673 Hakley, on the appearance of sugar in the liver, 192 Haevet, on motions of heart, 270, 275 Hearing, sense of, 519 apparatus of, 522 analogy of, with touch, 525 Heart, 260 of fish, 260 of reptiles, 261 of mammalians, 262 of man, 263 circulation of blood through, 265 sounds of, 265 movements of, 268 impulse, 270, 274 development of, 671, 698 Heat, vital, of animals, 247 of plants, 250 how produced, 261 increased by division of sympathetic nerve, 538 Hblmholtz, on rapidity of nervous force, 407 Hematine, 87, 210 Hemispheres, cerebral, 432 remarliable cases of injury to, 432, 433 effect of removal, on pigeons, 434 effect of disease, in man, 436 comparative size of, in different races, 437 functions of, 438 development of, 658 Hemorrhage, from placenta, in parturi- tion, 653 Hepatic circulation, 341 development of, 695 INDEX. 719 Herbivorous animals, respiration of, 84, 236 urine of, 351, 353 Hernia, congenital, diaphragmatic, 671 umbilical, 666 inguinal, 681 Hippurate of soda, 353 Honey, composition of, 68 Hunger and thirst, continue after divi- sion of pneumogastric, 486 Hydrogen, displacement of gases in blood by, 238 exhalation of carbonic acid in an atmosphere of, 243 Hygroscopic property of organic sub- stances, 82 Hypoglossal nerve, 491 Imbibition, 309 of liquids, by different tissues, 314 by cornea, experiments on, 315 Impulse, of heart, 270, 274 Infant, newly born, characteristics of, 707 Inflammation of eyeball, after division of fifth pair, 468 Infusoria, 547 different kinds of, 548 conditions of their production, 649 Wyman's experiments on, 549 Inguinal hernia, congenital, 681 Injection of placental sinuses from ves- sels of uterus, 647 Inorganic substances, as proximate prin- ciples, 53 their source and destination, 62 Inosculation, of veins, 291, 293 of capillaries, 296 of nerves, 377 Insalivation, 110, 117 importance of, 118 function of, 119 Inspiration, how accomplished, 229 movements of glottis in, 238 Instinct, nature of, 457 Integument, respiration by, 246 development of, 663 Intellectual powers, 486, &c. in animals, 458 Intestine, of fowl, 104 of man, 106 juices of, 138 digestion in, 138-147 epithelium of, 155 disappearance of bile in, 178, 182 development of, 613, 664 Intestinal digestion, 138 Intestinal juices, 138, 141 action of, on starch, 138 Involution of uterus after delivery, 655 Iris, movements of, 373, 449, 515, 533 after division of sympathetic, 535 Irritability, of gastric mucous membrane, 124 of the heart, 271 of muscles, 400 of nerves, 402 Jackson, Prof. Samuel, on digestion of fat in intestine, 142 Jaundice, 162 yellow color of urine in, 363 Kidneys, peculiarity of circulation in, 305, 306 elimination of medicinal substances by, 363 formation of, 675 KoscHLAKOFF, Verification of the sphyg- mograph, 284 KucHENMEisTEB, experiments on produc- tion of taenia from cysticercus, 556, 557 of cysticercus from eggs of taenia, 657 Lachrymal secretion, 835 its function, 886 Lactation, 836 variations in composition of milk during, 337 Lacteals, 156, 158, 321 and lymphatics, 158 Larynx, action of, in respiration, 233 in formation of voice, 478 nerves of, 476, 477 protective action of, 479 Lassaigne, experiments on saliva, 119 analysis of lymph, 320 Layers, external and internal, of blasto- dermic membrane, 608 Lead, salts of, action in distinguisbing the biliary matters, 169 Lehmann, on formation of carbonates in blood, 60 on total quantity of blood, 224 on effects of non-nitrogenous diet, 94 on disappearance of fibrin in liver and kidneys, 222 Lens, crystalline, action of, 509 Leuceart, on production of cysticercus, 557 of Trichina spiralis, 657 LiEBiQ, on absorption of difi'erent liquids under pressure, 312 Ligament, of the ovary, formation of, 682 round, of the uterus, 682 broad, of the uterus, 682 Limbs, formation of, in frog, 614 in human embryo, 662 Lime, phosphate of, 58 in the tissues and fluids, 68, 59 in .the food, 60 720 INDEX. Lime, carbonate of, 60 oxalate of, in urine, 3G6 Liver, vascularity of, 341 lobules of, 341, 342 secreting cells, 348 formation of sugar in, 1 86 congestion of, after feeding, 198 development of, 669, 695 Liver-cells, 348 their action in secretion, 344 Liver-sugar, formation of, 186 its accumulation after death, 189, 196 its proportion during life, 195 nature and properties of, 188 its source, 187,189, 197 mode of production, from glycoge- nic matter, 190, 191 decomposed in the circulation, 198 its production in foetal life, 669 Lobules, of lung, 228 of liver, 341, 342 Local production of carbonic acid, 241 of animal heat, 255 L6cal variations of circulation, 303, 307 LoNGXT, on interference of albuminose with Trommer's test, 181 on sensibility of glosso-pharyngeal nerve, 473 of pneumogastric nerve, 475 on irritability of anterior columns of spinal cord, 416 on disappearance of irritability in motor and sensitive nerves, 420 Lungs, structure of, in reptiles, 227 in man, 228 alteration of, after division of pneu- mogastrics, 483 LusK, Prof., proportion of sugar in car- diac and jugular blood, 197 Lymph, 157, 321, 322 quantity of, 328, 325 Lymphatic system, 156, 158, 8X9 Magendie, on absorption by blood-ves- sels, 1.52 on distinct seat of sensation and motion, 414 Magnus, oxygen in the blood, 238, 239 Male organs of generation, 574, 577 development of, 678 Malpighian bodies of spleen, 201 Mammalians, circulation in, 262 Mammary gland, structure of, 336 secretion of, 337 Mabcet, on excretine, 148 Maebt, M., experiments on arterial pul- sation, 280, 282 Mastication, 108 unilateral, in ruminating animals, 114 retarded by suppressing saliva, 118 Meconium, 668 Medulla oblongata, 895, 453 ganglia of, 396, 397 reflex action of, 454 effect of destroying, 455 development of, 658 Medullary layer, of nervous filaments, 375 . Meibomian glands, 331 Melanine, 88 Membrane, blastodermic, 608 Membrana granulosa, 587 Membrana tympani, action of, 520 Memory, connection of, with cerebral hemispheres, 485, 436, 438 Menobranchus, size of blood-globules in, 212 gills of, 226 spermatozoa, 575 Menstruation, 590 commencement and duration of, 591 phenomena of, 591 rupture of Graafian follicles in, 592 suspended during pregnancy, 691, 601 Mesenteric glands, 157, 819 Michel, Dr. Myddleton, rupture of Graafian follicle in menstruation, 592 Milk, 336 composition and properties of, 98, 338 microscopic characters of, 839 souring and coagulation of, 340 variations in, during lactation, 340 Milk-sugar, 68 converted into lactic acid, 84, 340 Mitchell, S. Weir, M. D., on production of vibriones in the venom of the rattlesnake, 650 MoUusca, nervous system of, 386 Mooue and Pennock, experiments on movements of heart, 270 MoBiN, carbonic acid in the urine, 246 Motion, 412 Motor cranial nerves, 461, 462 Motor nervous fibres, 385 Motor oculi communis, 463 externus, 464 Movements, of stomach, 182 of intestine, 151 of heart, 268 of chest, in respiration, 229 of glottis, 233 associated, 421 of foetus, 651 Mucosine, 86 Mucous follicles, 329 Mucous membrane, of stomach, 120 of intestine, 139, 149, 150 of tongue, 497 of uterus, 572, 634 INDEX. 721 Mucus, 329 compositioa and properties of, 330 of mouth, 112 of cervix uteri, 573 Muscles, irritability of, 399 directly paralyzed by sulpho-cyanide of potassium, 401 consentaneous action of, 443 of respiration, 229 Muscular fibres, of spleen, 200 of heart, spiral and circular, 272 Muscular irritability, 399 duration after death, 400 exhausted by repeated irritation, 401 Musouline, 87 Nails, formation of, in embryo, 663 Negeibr, on rupture of Graafian follicle in menstruation, 592 Nerve-cells, 382, 383 Nerves, division of, 377 inosculation of, 378 irritability of, 401, 402 regeneration of, after division, 382 spinal, 390, 413 cranial, 459 olfactory, 469 optic, 460 auditory, 460 ooulo-motorius, 463 patheticus, 464 motor exteruus, 464 masticator, 466, 467 facial, 469 hypoglossal, 491 spinal accessory, 488 trifacial (fifth pair), 464 glosso-pharyngeal, 473 pneumogastrio, 474 superior and inferior laryngeal, 476 great sympathetic, 629 Nervous filaments, 374 of brain, 375 of sciatic nerve, 374 division of, 379 origin and termination of, 378 motor and sensitive, 385 Nervous force, how excited, 402 rapidity of, 407 nature of, 408 Nervous tissue, two kinds of, 374 Nervous irritability, 381, 401 how shown, 402 duration of, after death, 402 exhausted by excitement, 403 destroyed by woorara, 406 distinct from muscular, 406 nature of, 408 Nervous system, 371 general structure and functions of, 371-398 46 Nervous system, of radiata, 384 of moUusca, 386 of articulata, 387 of vertebrata, 389 reflex action of, 384 Network, capillary, in Peyer's glands, 149 in intestinal villus, 150 in web of frog's foot, 296 in lobule of liver, 342 Neurilemma, 376 Newly-born infant, weight of, 707 respiration in, 707 nervous phenomena of, 708 comparative size of organs in, 709 Newport, ou temperature of insects, 250 Nitric acid, action of, on bile-pigment, 171 precipitation of uric acid by, 360 Nitrogen, exhalation of, in respiration, 235 Nucleus, of medulla oblongata, 453 Nutrition, 45 Obliteration, of ductjus venosus, 697 of ductus arteriosus, 699, 700 Oculo-motorius nerve, 463 (Esophagus, paralysis of, after division of pneumogastric, 477 development of, 669 CEatruation, phenomena of, 589 Oleaginous substances, 71 in different kinds of food, 73 condition of, in the tissues and fluids, 74, 79 partly produced in the body, 78, 79 decomposed in the body, 79 in the blood, 216 indispensable as ingredients of the food, 93 insufficient for nutrition, 94 Olfactory apparatus, 503 protected by two sets of muscles, 636 commissures, 393, 459 Olfactory ganglia, 393, 459 their function, 459 Olfactory nerves, 503 Olivary bodies, 395 Omphalo-mesenteric vessels, 686 Ophthalmic ganglion, 529 Optic ganglia, 393, 448 Optic nerves, 460 decussation of, 449, 450, 451 Optic thalami, 431 development of, 658 Organs of special sense, 497, 503, 507, 522 development of, 660 Organic substances, 80 indefinite chemical composition of, 80, 81 hygroscopic properties of, 82 722 INDEX. Organic substances, coagulation of, 83 catalytic action, 83 putrefaction, 84 source and destination, 89, 90 digestion of, 129 exhaled "by the breath, 236 Origin, of plants and animals, 545 of infusoria, 548 of animal and vegetable parasites, 551 ~ of encysted entozoa, 554 Ossification of skeleton, 662 Ostein e, 87 Otic ganglion, 530 Ovary, 559, 504 of taenia, 559 of frog, 565 of fowl, 567 of human female, 571, 572 Ovaries, descent of, in foetus, 681 condition at birth, 683 Oviparous and viviparous animals, dis- tinction between, 583 Oxalate of lime, in urine, 366 Oxalic acid, produced in urine, 365 Oxygen, absorbed in respiration, 235, 237 daily quantity consumed, 235 state of solution in blood, 238 dissolved by blood-globules, 239 absorbed by the tissues, 241 exhaled by plants, 264 Pacinian bodies of the skin, 379 Palate, formation of, 673 Pancreatic juice, 141 mode of obtaining, 142 composition of, 143 action on fat, 143, 144 daily quantity of, 143 Pancreatine, 86 in pancreatic juice, 143 Panizza, experiment on absorption by bloodvessels, 152 Paralysis, after division of anterior root of spinal nerve, 414 direct, after lateral injury of spinal cord, 418 crossed, after lateral injury of brain, 417, 418 facial, 472 of muscles, by sulpho-cyanide of potassium, 401 < of motor nerves, by woorara, 406 of sensitive nerves, by strychnine, 426 of voluntary motion and sensation, after destroying tuber annulare, 452 of pharynx and oesophagus, after section of pneumogastrics, 476, 477 of larynx, 479, 480, 485 of muscular coat of stomach, 487 Paraplegia, reflex action of spinal cord in, 424 Parasites, 550 conditions of development of, 551 mode of introduction into body, 552 sexless, reproduction of, 554 Parotid saliva, 112, 113 Parturition, 653 Par vagum, 474. See Pneumogastric. Pathetious nerve, 464 Pavt, on the post-mortem formation of liver-sugar, 192 Payen, mineral ingredients of cereal grains, 98 Pelocze, composition of glycogenic mat- ter, 190 Pelvis, development of, 662 Pennook and Moore, experiments on movements of heart, 270 Pepsiue, 86 in gastric juice, 127 Perception of sensations, after removal of hemispheres, 435 destroyed after removal of tuber annulare, 452 Periodical ovulation, 583 Peristaltic motion, of stomach, 132 of intestine, 151 of oviduct, 566, 568 PnEKiNS, Prof. Maurice, composition of parotid saliva, 113 Perspiration, 332 daily quantity of, 333 composition and properties of, 333 function, in regulating temperature, 334 Pettenkofer's test for bile, 171 Peyer's glands, 149 Pharynx, action of, in swallowing, 474 formation of, 670 Philippeaux, transmission of sensitive impressions in spinal cord, 41B Phosphate of lime, its proportion in the animal tissues and fluids, 58 in the food, 60 in the urine, 359 precipitated by alkalies, 360 Phosphate, triple, in putrefying urine, 368 Phosphates, alkaline, 61 in urine, 359 earthy, 58, 61 in urine, 359 of magnesia, soda, and potassa, 61 Phosphorus, not a proximate principle, 47 Physiology, definition of, 33 Phrenology, 440 objections to, 441 practical difficulties of, 441, 442 Pigeon, after removal of cerebrum, 434 of cerebellum, 444 INDEX. 723 Placenta, 641 coraparative anatomy of, 642 formation of, in human species, 643 foetal tufts of, 645 maternal sinuses of, 646 injection of, from uterine vessels, 647 function of, 648 separation of, in delivery, 653 Placental circulation, 644, 646 Plants, vital heat of, 250 generative apparatus of, 558 Plasma of the blood, 214 Pneumio acid, 240 Pneumogastric nerve, 474 its distribution, 475 action of, on pharynx and oesopha- gus, 476 on larynx, 477 in formation of voice, 478 in respiration, 479 effect of its division on respiratory movements, 480, 482 cause of death after division of, 484 influence of, on oesophagus ajjd stomach, 487 Pneumogastric ganglion, 475 PoGQiALB, on glycogenic matter in butch- er's meat, lul Pons Varolii, 395 Porta;l blood, temperature of, 256 Portal vein, in liver, 341 development of, 695 Posterior columns of spinal cord, 302 Primitive trace, 610 Production, of sugar in liver, 186 of carbonic acid, 240 of animal heat, 251 of urea in blood, 347 of infusorial animalcules, 548 of animal and vegetable parasites, 551 Proximate principles, 45 definition of, 47 mode of extraction, 48 manner of their association, 49 varying proportions of, 51) 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), 80 Pty aline. 111 Puberty, period of, 585 signs of, in female, 590 Pulsation, of heart, 261 in living animnl, 269 of arteries, 278 Pulse, arterial, 278 radial, 282 Pulse, dicrotic, 284 Pupil, action of, 373, 449, 515, 533 contraction of, after division of sym- pathetic, 535 Pupillary membrane, 660 Putrefaction, 84 of the urine, 364 Pyramids, anterior, of medulla oblon- gata, 395 decussation of, 395 Quantity, daily, of water exhaled, 55 of food, 100 of saliva, 114 of gastric juice, 134 of pancreatic juice, 143 of bile, 174 of air used in respiration, 231 of oxygen used in respiration, 235 of carbonic acid exhaled, 243. of lymph and chyle, 323 of fluids secreted and reabsorbed, 325 of material absorbed and discharged, 370 of perspiration, 333 of urine, 355, 356 of urea, 349 of urate of soda, 353 Quantity, entire, of blood in body, 2:i3 Rabbit, brain of, 394 Races of men, different capacity of, fop civilization, 437 Radiata, nervous system of, 384 Rapidity, of the arterial current. 286, 288 of the venous circulation, 294 of the capillary circulation, 3C0 general, of the circulation, 301 of the nervous force, 407, 408 Reactions, of starch, 66 of sugar, 68 of fat, 71 of saliva. 111, 112 of gastric juice, 127 of intestinal juice, 141 of pancreatic juice, 143 of bile, 161 of mucus, 329 of milk, 338 of urine, 355 Reasoning powers, 438 in animals, 458 Red globules of blood, 205 Reflex action, 384. 407 in star-fish, 385 in centipede, 387 of spinal cord, 422 of tubercula quadrigemina, 449 of medulla oblongatn, 451 of tuber annulare, 457 of brain, 458 724 INDEX. Eeflex action, in newly bom infant, 708 Regeneration, of divided nerves, 382 of uterine mucous membrane after pregnancy, 654 of walls of uterus, 656 Regnacli and Reiset, on absorption of oxygen, 236 Reid, Dr. John, experiment on crossing of streams in foetal heart, 702 on glosso-pharyngeal nerve, 473 Reproduction, 543 nature and object of, 545 of infusoria, 548 of parasites, 551 of taenia, 554 by germs, 558 Reptiles, circulation of, 261 Respiration, 225 by gills, 225, 226 by lungs, 227 by skin, 246 changes in air during, 235 changes in blood, 236 thoracic, 455 abdominal, 455 of newly 'born infant, 707 Respiratory movements of chest, 229 of glottis, 232 after section of pneumogastrics, 480, 482 after injury of spinal cord, 455 Restiform bodies, 396 Rhythm of heart's movements, 274 Robin, on albuminose in the blood, 216 on carbonic acid in the blood, 239 Rotation of heart during contraction, 278 Round ligament of the uterus, formation of, 682 of liver, 697 Rumination, movements of, 105, 114 Rupture of Graafian follicle, 588 in menstruation, 592, 597 Rutting condition, in lower animals, 589 Saccharine substances, 67 in stomach and intestine, 138, 139 in liver, 186 ' in blood, 217 in urine, 363 Saliva, 110 different kinds of, 112 daily quantity of, 114, 115 action on boiled starch, 116 variable, 116 does not take place in stomach, 117 physical function of saliva, 117 quantity absorbed by different kinds of food, 119 Salivary glands, 112 Salts, biliary, 163 of the blood, 216 of urine, 359 Saponification, of fats, 72 ScHAKLiNG, on diurnal variations in ex- halation of carbonic acid, 245 on exhalation of carbonic acid through the skin, 246 Schmidt, Prof. C, on human gastric fis- tula, 127 on quantity of gastric juice, 135 Scolopendra, nervous system of, 387 Sebaceous matter, 331 composition and properties of, 332 function of, 332 in foetus, 663 Secretion, 326 varying activity of, 328 of saliva, 112 of gastric juice, 119 of intestinal juice, 139 of pancreatic juice, 141 of bile, 161-341 of sugar in liver, 186 of mucus, 329 of sebaceous matter, 331 of perspiration, 382 of the tears, 335 of bile in foetus, 669 Segmentation of the vitellus, 607 Seminal fluid, 574 mixed constitution of, 578 Sensation, 410 remains after destruction of hemi- spheres, 434 lost after removal of tuber annulare, 452 special, conveyed by pneumogastric nerve, 481 Sensation and motion, distinct seat of, in nervous system, 412 in spinal cord, 415 Sensibility, of nerves to electric current, 402 definition of, 410 seat of, in spinal cord, 415 in brain, 430 of facial nerve, 472 of hypoglossal nerve, 491 of spinal accessory, 488 of great sympathetic, 532 Sensibility, general and special, 492 special, of olfactory nerves, 459 of optic nerves, 460 of auditory nerves, 460 of lingual branch of fifth pair, 469 of glosso-pharyngeal, 473 of pneumogastric, 481 Sensitive nervous filaments, 385 Sensitive fibres, crossing of, in spinal cord, 418 of facial nerve, source of, 472 Sensitive cranial nerves, 461, 462 Septa, inter-auricular and inter-ventri- cular, formation of, 698 INDEX. 725 Serum, of the blood, 219 Sexes, distinctive characters of, 560 Sexless, entozoa, 652 Sexual generation, 558 Shook, effect of, in destroying nervous irritability, 404 SiEBOLD, on production of tsenia from cvsticerous, 556 Sight, 506 apparatus of, 507. See Vision. Simon, disappearance of fibrin in liver and kidneys, 222 Sinus terminalis, of area vasculosa, 685 Sinuses, placental, 644 Skeleton, development of, 661 Skin, respiration by, 246 sebaceous glands of, 331 perspiratory glands of, 332 development of, 663 Smell, 502 ganglia of, 393, 431 nerves of, 503 injured by division of fifth pair, 468 Smith, Dr. Southwood, on cutaneous and pulmonary exhalation, 334 Solar plexus of sympathetic nerve, 531 Solid bodies, vision of, with tvpo eyes, 517 Sounds, of heart, 265 how produced, 266 vocal, how produced, 478 destroyed by section of inferior la- ryngeal nerves, 479 of spinal accessory, 489 , Sounds, acute and grave, transmitted by membrana tympani, 521 Spallamzani, experiments on digestion, 122 on artificial impregnation of eggs, 579 Special senses, 492 Species, mode of continuation, 545 Specific gravity, of the saliva, 111 of gastric juice, 126 of pancreatic juice, 143 of the bile, 161 of the blood, 205 of the lymph, 320 of the urine, 356 Spermatic fluid, 574 mixed constitution of, 578 Spermatozoa, 574 anatomical character of, 574 movements of, 576 formation of, 677 entrance of, into the egg, 680 Sphygmograph, 282 Spina bifida, 661 Spinal accessory, 488 sensibility of, 488 communication of, with pneumogas- trie, 488, 489 influence of, on larynx, 489 Spinal column, formation of, 611, 661 Spinal cord, 390, 410 commissures of, 391 anterior, lateral, and posterior col- umns, 392 origin of nerves from, 390 sensibility and excitability of, 41 6 crossed action of, 417 reflex action of, 422 protective action of, 427 influence on sphincters, 427 effect of injury to, 428 on respiration, 465 formation of, in embryo, 611, 661 Spinal nerves, origin of, 390 Spleen, 200 Malpighian bodies of, 201 extirpation of, 203 Spontaneous generation, 545 Starch, 63 proportion of, in different kinds of food, 64 varieties of, 64-66 reactions of, 66 action of saliva on, 116 digestion of, 138 Starflsh, nervous system of, 384 Stercorine, 148 Stereoscope, 617 St. Martin, case of gastric fistula in, 123 Strabismus, after division of motor ocuU communis, 464 of motor externus, 464 Striated bodies, 432 Sublingual gland, secretion of, 112 Submaxillary ganglion, 529 gland, secretion of, 112 circulation in, influenced by nerves, 539, 540 Sudoriparous glands, 332 Sugar, 67 varieties of, 67 composition of, 68 tests for, 68 fermentation of, 70 proportion in different kinds of food, 71 source and destination of, 71 produced in liver, 186 discharged by urine in disease, 363 Sugar in liver, formation of, 186 accumulation after death, 189, 196 proportion during life, 195 nature and properties of, 188 source of, 187, 189, 197 produced from glycogenic matter, 190, 191 decomposed in circulation, 198 Sulphates, alkaline, in urine, 369 Sulphur of the bile, 167 not discharged with the feces, 183 Swallowing, 119 726 INDEX. Swallowing, retarded by suppression of saliva, 118 by division of pneumogastrio, 476, 477 Sympatlietic nerve, 529 physiological properties of, 531 influence of, on movement and sensi- bility, 532 on the special senses, 533 on the circulation, 537 on animal heat, 538 on the color of venous blood, 538, 540 on reflex actions, 540. Tactile corpuscles, of the skin, 379, 380 Tadpole, development of, 609 transformation into frog, 614 Taenia, 554 produced by metamorphosis of oys- ticercus, 556 single articulation of, 559, Tapeworm, 554 mode of generation, 556 Taste, 495 nerves of, 497 conditions of, 599 injury of, by paralysis of facial nei-ve, 501 Taurine, 167 Tauro-oholate of soda, 167 microscopic characters of, 165 Tauro-oholjc acid, 167 Tears, 335 their function, 336 Teeth, of serpent, 108 of polar bear, 109 of horse, 109 of man, 110 first and second sets of, 709 Temperature, of the blood, 248 of different species of animals, 249 of the blood in different organs, 256 elevation of, after section of sym- pathetic nerve, 538 Tensor tympani, action of, 522 . Terminal corpuscles, of the sensitive nerves, 379, 380 Termination of nervous filaments, in the skin, 379 in the muscles, 380 Tests, for starch, 66 for sugar, 68 for bile, 170 Pettenkofer's, 171 Testicles, 577 periodical activity of, in fish, 580 development of, 678 descent of, 679 Tetanus, pathology of, 423 Thalami, optic, in rabbit, 394 in man, 397, 431 Thalami, optic, function of, 432 Thoracic duct, 156, 158 Thoracic respiration, 455 Thpdichtjm, Dr., on urosacine, 89 Tongue, motor nerve of, 491 sensitive nerve of, 466, 473, 497 Trichina spiralis, 553 Tricuspid valve, 264. See Auriculo ven- tricular. Triple phosphate, in putrefying urine, 368 Trommer's test for sugar, 68 interfered with by albuminose, 131 Tuber annulare, 396, 452 effect of destroying, 452 action of, 453, 457 Tuberoula quadrigemina, 393, 394, 397, 448 reflex action of, 449 crossed action of, 450 development of, 658 Tubules, gastric, 121 of uterine mucous membrane, 635 Tufts, placental, 645 Tunica vaginalis testis, formation of, 680 Tympanum, function of, in hearing, 521, 522, 528 Umbilical cord, formation of, 651 withering and separation of, 709 Umbilical hernia, 666 Umbilical vesicle, 616 in human embryo, 617 in chick, 624 disappearance of, 651 Umbilical vein, formation of, 689 obliteration of, 697 Umbilicus, abdominal, 612 amniotic, 620 decidual, 637 Unilateral mastication, in ruminating animals, 114 Urate of soda, 352 its properties, source, daily quan- tity, &c., 353 Urates of potassa and ammonia, 354 Urachus, 667 Urea, 347 source of, 347 mode of obtaining, 348 conversion into carbonate of am- monia, 348 daily quantity of, 349 diurnal variations in, 349 increased by muscular exertion, 350 decomposed in putrefaction of urine, 367 Uric acid, 352, 360 Urine, 354 general character and properties of, 354 quantity and specific gravity, 355 INDEX. 727' Urine, diurnal variationa of, 356 composition of, 358 reactions, 359, 360 interference with Trommer's test, 361 accidental ingredients of, 862 carbonic acid in, 246 acid fermentation of, 365 alkaline fermentation of, 367 final decomposition of, 369 Urinary bladder, paralysis and inflam- mation of, after injury to spinal cord, 429 formation of, in embryo, 667 Urosacine, 89 Uterus, of lower animals, 571 of human female, 572 mucous membrane of, 634 changes in, after impregnation, 035, 636 involution of, after delivery, 655 development of, in foetus, 682 position of, at birth, 683 Uterine mucous membrane, 634 tubules of, 635 conversion info decidua, 636 exfoliation of, at the time of deliv- ery, 653 renovation of, 654 Valve, Eustachian, 701 of foramen ovale, 704 Valves, cardiac, action of, 264 cause of heart's sounds, 266 Vasa deferentia, formation of, 678 Vapor, watery, exhalation of, 55 from lungs, 235 from the skin, 333 Variation, in quantity of bile in different animals, 174 in size of spleen, 200 in rapidity of coagulation of blood, 219 in size of glottis in respiration, 233 in exhalation of carbonic acid, 243 in temperature of blood in different parts, 256 in composition of milk, during lac- tation, 340 in quantity of urea, 349 in density and acidity of urine, 356, 357 Varieties, of starch, 64 of sugar, 67 of fat, 71 of biliary salts in different animals, 168 Vegetable food, necessary to man, 92 Vegetable parasites, 550, 551 Vegetables, production of heat in, 250 absorption of carbonic acid and ex- halation of oxygen by, 254 Vegetative functions, 42 Veins, 290 their resistance to pressure, 290 absorption by, 152 action of valves in, 293 motion of blood through, 291 rapidity of circulation in, 294 omphalo-mesenteric, 686 umbilical, 689 vertebral, 692 Vense cavae, formation of, 693 position of, in foetus, 700 Vena azygos, major and minor, forma- tion of, 694 Venous system, development of, 692 Ventricles of heart, single in fish and reptiles, 260, 261 double in birds and mammalians, 262 situation of, 262 contraction and relaxation of, 269 elongation of, 270 muscular fibres of, 272 Vernix caseosa, 663 Vertebrata, nervous system of, 389 Vertebrae, formation of, 611, 661 Vesicles, adipose, 75 pulmonary, 228 seminal, 578 Vesiculse seminales, 578 formation of, 680 Vibriones, in putrefying rattlesnake venom, 550 Vicarious secretion, non-existence of, 327 Vicarious menstruation, nature of, 327 Villi, of intestine, 150 absorption by, 151 of chorion, 630, 632 Vision, 606 ganglia of, 393, 394, 397, 448 nerves of, 460 apparatus of, 507 distinct, at different distances, 510 circle of, 614 of solid bodies with both eyes, 517 Vital phenomena, their nature and pecu- liarities, 38 VitelluB, 563 segmentation of, 607 formation of, in ovary of foetus, 684 Vitelline circulation, 685 membrane, 562 spheres, 607 Vocal sounds, how produced, 478 Voice, formation of, in larynx, 478 lost, after division of spinal acces- sory nerve, 489 Volition, seat of, in tuber annulare, 452 Vomiting, peculiar, after division of pneumogastrics, 487 VcLPiAN, on regeneration of divided nerves, 382 728 INDEX. VuLPiAN, on transmission of nervous im- pulses in the spinal cord, 416 Water, as a proximate principle, 53 • its proportion in the animal tissues ' and iluids, 54 its source, 54 mode of discharge from the body, ' 55 Weight of organs, comparative,- in newly born infant and adult, 709 Wheat flour, composition of, .98 White globules, of the blood, 212 action of acetic acid on, 212 sluggish movement of, in circula- tion, 297 White substance, of nervous system, 374 of spinal cord, 390 of brain, insensible and inexcitable, 430 Withering and separation of umbilical cord, after birth, 709 Wolffian bodies, 675 structure of, 676. atrophy and disappearance of, 676 vestiges of, in adult female, 682 Woorara, paralyzing action of, on motor nerves, 406 Wyman, Prof. Jeffries, on cranial nerves of Rana pipiens, 462 fissure of hare lip on' median line, 673 on production of infusoria in organic solutions, 549 Yellow color, of urine in jaundice, 863 of corpus luteum, 599 Zaieskt, urea in healthy muscles, 348 Zona pellucida, 562 THE END. 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This is followed by the " Quabteely Summary of Improvements ans Disooverieb IN THE Medical Sciences'," classified and arranged under different heads, presenting a very complete digest of all tha^t is new and interesting to the physician, abroad as well as at home. Thus, during the year 1872, the "Journal" furnished to its subscribers Eighty-four Original Communications, One Hundred and Twenty-nine Reviews and Bibliograph- ical Notices, and Three Hundred and seven articles in the Quai:terly Summaries, mak- ing a total of about Five Hundred articles emanating from the best professional minds in America and Europe. That the efibrts thus made to maintain the high reputation of the " Journal" are successful, is shown by the position accorded to it in both America and Europe as a national exponent of medical progress :— Dr. Haya keeps his great American Quarterly, in matter it contains, and lias established for itself a wiiich lie is now assisted by Dr. Minis Hays, at the' reputation in every country where medicine is cul- head of his country's medical periodicals. — Dublin Medical Frees aiS, Circular, March 8, 1871. Of English periodicals the Lancet, and of American the Am. Journal of the^ Medical -Scieneesi are to be regarded as necessities to the reading practitioner.— N Y. Medical Gazette, Jan. 7, IS71. The American Journal of the Medical Sciences yields to none in the amount of original and borrowed The subscription price of the "American Journal of the Medical Scif,ncbs" has aever been raised, during its Ibtig career. It is still Five Dollars per annum ; and when paid for in ad vance, the subscriber receives in addition the " Medical News and Library," making in all about 1500 large octavo pages per annum, free of postage. 11. THE MEDICAL NEWS AND LIBRARY is a monthly periodical of Thirty-two large octavo pages, making 384 pages psr annum. Its "News Department" presents the current information of the day, with Clinical Lectures and Hospital Gleanings; while the " Library Department" is de- voted to publishing standard works on the various branches of medical science, paged separately, so that they can be removed and bound on completion; In this manner suDscribers have received, without expense, such works as " Watson's Practice," •' ToDD AND Bowman's Physiology," "West on Children," "Maloaignb's Subgeey," i&c. &c. . And with January 1873 will be commenced the publication of Dr. McCall l^iyated as a science. — Brit, and Ibr. Med.-Ghirurg. Jieoiew, April, 1871. ' One of the best of its kind. — London LatKet, Aug. 20, 1870. Almost the only one that circulates everywhere, all over the Union and in Europe. — Londeifia 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. Dnnglison's work as most thorough, spieutiflc, 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 JBngUsh Dic- tionary is to every one who would keep up his knowl- edge 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. — Aim,. Jour. Med. Sciences, April, 18H5. The value of the present edition has been greatl; 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 8v/rg. Journal, April, 1865. It has the rare merit that it certainly has no rival in the English language for accuracy and extent of references. — London Jlfedieal Gazette, E 'OBLTN [RICHARD D.), M.D. A DICTIONARY OF THE TERMS USED IN MEDICINE aJ^D THE COLLATERAL SCIENCES. Revised, with numerous additions, by Isaac Hats, M.D., Editor of the "American Journal of the Medical Sciences." In one large royal 12mo. Tolume of over 600 double-columned pages; extra cloth, Jl 50 ; leather, $2 00. It is the best book of definitionB we have, and ought always to be apon tbe ttudent'B table.— Sout/wrn Bed. and Surg. Journal Henry C. Lea's Publtcations — (Manuals), 'nJEILL {JOHN), M.D., and CfMITH (FRANCIS Q,), M.D., ^ ' '^ Prof, of the InstUtUes of Medicine in the Univ. of Penna. AN ANALYTICAL COMPENDIUM OP THE VARIOUS BKANCHES OF MEDICAL SCIENCE j for the Use and Examination of Students. A new edition, revised and improved. In one very large apd handsomely printed royal 12mo. volume, of about one thousand pages, with 374 wood outs, extra cloth, $4; strongly bound in leather, with raised bandfc, $4 75. The Gompend of Drs. Neill and Smith is incompara- bly the most valuable work of its class ever published fa this coantry. Attempts bave been made in various quarters to squeeze Anatomy, Physiology, Sui^ery, the Practice of Medicine, Obstetrics, Materia Medica, and Chemistry into a single manual; but the opera- tioQ has signally failed in the hands of all up to the advent of " Neill and Smith's" volume, which is quite a miracle of success. The ontlines of the whole are admirably drawn and illustrated, and the authors are eminently entitled to the gi'atefnl consideration of the student of every class.— JV. 0. Med. and Surg. , Journal, There are but few students or practitiouere of me- dicine unacquainted with the former editions of this unassuming thongh 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 factstreaeuredup In this little volume. A com- plete portable library so condensed that the student may make it his constant pocket companion.— TTe^t- em 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 most of the divisions, the most unexceptionable of all books of the kind tha^we know of. Of course It is useless for UB to recommend it to all last coarBe students, but there is a class to whom we very sincerely commend this cheap 'book as worth its weight la silver — th»t class is the graduates in medicine of more than tea years' standing, who have not studied mr^dicine since. They will perhaps find out from it that the science is not exactly now what it was when they left it oS.—The Stethoscope. TTARTSHORNE [HENRY), M. />., Professor of Hygiene in the University of Pennsylvania. A CONSPECTUS OF THE MEDICAL SCIENCES; containing Handbooks on Anatomy, Physiology, Chemistry, Materia Medica, Practical Medioinn, 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. {Lately Published.) 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 desirous of obtaining within a moderate compass, a view of the existing condition of the various departments of science connected with medicine. This work is a remarkably complete one in its way, and comes nearer to our idea of what a Couspectas 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 beeo seen before in the various works upon gen- eral and special subjects, yet they will be none the less valuable to the beginner. Every medical student who desires a reliable refresher to his memory when the pressure of lecturer 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 from 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 Ifi, 1869. TTJDLO 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 roysl 12mo. 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. /TANNER [THOMAS HA WKES), M. D., Sfc. A MANUAL OF CLINICAL MEDICINE AND PHYSICAL DIAG- NOSIS. Third American from the Second London Edition. Revised and Enlarged hy Tilbury Fox, ^. D», Physician to the Skin Department in UniversiCy College Hospital, Ac. In oneneatvolumesraall l2mo.,ofabout375 pages, extra cloth. $150. {Just Issued.) *#* By reference to the ** Prospectus of Journal" on page 3, it will be seen that this work is offered as a premium for procuring new subscribers to the "American Journal op the Medicax. Sciences." Taken as a whole, it is the most compact vade me- cum for the use of the advanced student and junior practitioner with which we are acquainted.— Boston Med. and Surg. Journal, Sept. 22, 1870. It eontains so much that is valuable, presented in 80 attractive a form, that it can hardly be spared even in the presence of more fall and complete works. The additions made to the volume by Mr. Fox very materially enhance its value, and almost make it a new work. Its convenient size makes it a valuable companion to the country practitioner, and if con- stantly carried by him, would often render him good service, and relieve many a doubt and perplexity. — Leavenworth Med. Herald^ 3v\y, 1870. The objections commonly, and justly, urged againut the general run of "compeuds," "conspectuses/' and other aids to indolence, are not applicable to this little volume, which contains in concise phrase just thone practical details that are of most use in daily diag- nosis, but which the young practitioner finds it difll- cult to carry always in his memory without some quickly accessible means of reference. Altogether, the book is one which we can heartily commend to those who bave uot opportunity for extensive read- ing, or who, having read much, still wish an ooca- sional practical reminder. — N. T. Med. Qazette, Nov, 10, 1870. 6 Henry C. Lea's Publications — {Anatomy). ■QUAY (HENRY), F.R.S., Lecturer on Anatomy at St, George's Hospital, London. ANATOMY, DESCRIPTIVE AND SURGICAL. The Drawings by H. v. Carter, M. D., late Demonstrator on Anatomy at St. George's Hospital; the Disaeo- tions jointly by the Author and Dr. Carter. A new American, from the fifth enlarged and improved London edition. In one magnificent imperial octavo volnme, of nearly 900 pages, with 465 large and elaborate engravings on ^od. Price in extra cloth, $6 OOi; leather, raised bands, $7 00. { J us^ 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 knedicine and surgery, thus rendering it both a guide for the learner, and an admirable work of reference for the active practitioiaer. The en- gravings form a speciaJ feature in the ■wor'k, 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; wjiile combining, as it does, a complete Atlas of Anatomy, with a thorough treatise on sy8tejna,tie, descriptive, and applied Anatomy, the work will he found of essential use to all physicians who receive students in their ofi&ces, relieving both preceptor and pupil of much labor in laying the groundwork of a thorough medical education. Notwithstanding the enlargement of this edition, it has been kept at its former very moderate price, rendering it one of the cheapest works now before the profession. The illustrations are beautifully executed, and ren- der this work an indispensable adjunct to the library of the surgeon. This remark applies with great force to those surgeons practising at a distance from our large cities, as the opportunity of refreshing their memory by actual dissection is not always attain- able.— Canada Med. Journal, Aug. 1870. The work is too .well known and appreciated by the profession to need any comment. ' No medical man can afford to be without it, if its only jperit were to serve as a reminder of that which so soon becomes forgotten, when not called into frequent use, viz., the relations and names of the complex organism of the human body. The present edition is much improved. ^California Med. Gfazette, July, 1870. Gray's Anatomy has been so long the standard of Pjsrfeqtion with every student of anatomy, that we need do ho more than call attention to the improve- ment in the present edition. — I>etroit Beview of Med. and Pharm-t Aug. 1870. From time to time, as successive editions have ap- peared, we have "bad much pleasure in expressing the general judgment of the wonderful excellence of Gray's Anatomy. — Gincinnati Lancet, July, 1870. Altogether, ii is unquestionably the most complete and serviceable text-book in elnatomy that has ever been presented to the student, and forms a Htriking contrast to the dry and perplexiug volumes on the same subject through which their predeceiiKors strug- gled in days gone by. — N. T. Med. Reaord, Jane 16, 1870. To commend Gray's Anatomy to the medical pro- fession is almost as much a work of supererogation as it would be to give a favorable notice of the Bible in the religious press. To say that it is the most complete and conveniently arranged text book of its kind, is to repeat what each generation of stadenta has learned as a tradition of thp elders, and verifled by personal experience. — If. T. Med. Gazette, Deo. 17, 1870." OMITH (HENRY H.), M.I?., and TJORNER ( WILLIAM E.), M.D., Prof, of Surgery in the Univ. of Penna., Ac. Late Prof, of Anatomy in tJie Univ. of Penna., Ac. AN ANATOMICAL ATLAS, illustrative of the Structure of the Human Body. In one volume, large imperial octavo, extra cloth, with ^bout six hundred and fifty beautiful figures. $4 50. The plan of this Atlas, which renders it so pecn- the kind that has yet appeared; and we mnstadd, liarly convenient for the student, and its superb ar- the very beautiful manner in which it is "got np," tisticai execution, have beenalreadypointed out. We is so creditable to the country as to ))6 flatteringto must congratulate the student upon the completion our national pride. — American MedicalJoitrnal. of this i-tlas, as it is the most convenient work of OHARPEY ( WILLIAM), M.D., and Q VAIN {JONES §• RICHARD). ■ HUMAN ANATOMY. Revised, with Notes and Additions, by Joskph LEisr, M.D., Professor of Anatomy in the University of FennsjLvania. Complete in two large octavo volumes, of about 1300 pages, with 511 illustrations; extra oloth, $6 00. The very low price of this standard work, and its completeness in all-depjtrtments of the sabjeot, should command for it a place in the library of all anatomical students. JTODGES, (RICHARD M.), M.D., -*-i Late Demonstrator of Ariatomy in the Medical Departrmnt of Harvard Uni/versity. PRACTICAL DISSECTIONS. Second Edition, thoroughly revised. In one neat royal 12mo. volnme, half-bound, $2 00. The object qf this ^ork is to present to the anatomical ({tudent a clear and concise description of that which he is expected to observe in an ordinary couise of dissections. The author has endeavored to omit unnecessary details, and to present the subje Jt in the form which many years' experience has shown him to be the most convenient and intelligible to the student. In the revision of thp present edition, he has sedulously labored to render the volume more worthy of the favor with which it has heretofore been receivj^A- Hbnrt C. Lea's Publications — (Anatomy). ^/ILSOJSr (ERASMUS), F.R.S. A SYSi'EM or HUMAN ANATOMY, General and Special. Edited by W.H. OoBBECHT, M.D., Professor of deaeral and Surgical Anatomy in the Medical Col- lege of Ohio. Illustrated with three hundred and ninety-seven engravings on wood. In one large and handsome octavo volume, of over 600 large pages; extra cloth, $4 00 j lea- ther, $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 dii'ected 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 thu present edition contains over one-fourth more aiatter 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 editoi 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 oi importance. JJEATH {CHRISTOPHER), F. R. C. S., ^~*^ 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. Keen, M.D., Lecturer on Pathologioai Anatomy in the Jefferson Medical College, Philadelphia. Ill one handsome royal 12mo. volume of 578 pages, with 24.1 iilustrationa. Extra cloth, $3 50 i leather, $4 00. {Lately Publisked.) Dr. Eeeu, the American editor of this work, in his preface, Bays : "In presenting this American edition of * Heath's Practical Anatomy,* I feel that I have been intttrumeutal in sapplying a want long felt for a real dissector's manual," and this assertion of its editor we deem is fully justified, after an examina- trion of its contents, for it is really an excellent work, I ndeed, we do not hesitate to say, the best of its class with which we are acquainted ; resembling Wilson In terse and clear description, excelling most of the su-called {Practical anatomical dissectors in the scope of the subject and practical selected matter. . . . In reading this work, one is fuicibly impressed with the great pains the author takes to impress the sub- \Sfii upon the mind of the student. Heis lull of rare and pleasing little devices to aid memory in main- taining its hold upon the slippery slopes of anatomy. —(Si. Louia Med. and Surg. Journal, Mar. 10, 1871. It appears to us certain that, as a guide in dissec- tion, and as a work containing facts ol anatomy in brief ancP easily understood form, this manual is complete. This work contains, also, very perfect illustrations of parts which can thus be mure easily Such manuals of anatomy are always favorite works with medical students. We would earnestly recom- mend this one to their attention; it has excellences which make it valuable as a guide iu dissecting, as well as in studying anatomy.— Su/a to Medical and S^gical Journal, Jan. 1871. The hrst English edition was issued about six years ago, and was favorably received not only on account of the great reputation of its author, but also from its great value and excellence as a guide-book to the practical anatomist. The American edition has un- dergune some alterations and additions which will no doubt _enhaace its value materially. The conve- nience of (he student has been carefully consulted in the arrangement of the text, and the directions giren for the prosecution of certain dissections will be duly appreciated. — Canada Lanc^, Feb. 1871. This is an excellent Dissector's Manual ; one which is not merely a descriptive manual of anatomy, but a guide to the student at the dissecting table, enabling him, though a beginner, to prosecute his work intel- ligently, and without assistance. The American edi- tor has made many valuable alterations and addi- understood and studied ; iu this respect it compares tions to the original work. — Am. Journ, of Obstetrics, favorably with works of much greater pretension. | Feb. 1871. JUAGLISE (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 oi life; together with copious explanatory letter-press. Strongly and handsomely bound in extra cloth Price $U 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, t6 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 lai'ge 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 refreshed by those clear and distinct dissecliona can compete with it. — Lancet. _. - -. j The work of Maclise on surgical anatomy is of the highest valiie. * In some respects it is the best pabli- catioa of its kind we have seen, and is worthy of a place in the library of any medical man, while the student could scarcely make a better investment than this, — The Western Joumalo/ Mediaineomd Surgery. Ko such lithographic illustrations of surgical re- gions have hitherto, we think, been given. While the operator is shown every vessel and nerve where uu operation is contemplated, the exact anatomist is which every one must appreciate who iias a particle of enthusiasm. The £nglish medical press has quite exhausted the words ol praise, in recummendiug this admirable treatise. Those who have any cnrioeiiy 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 survey of the artistical skiil exhibited in these fac-similes wf nature. — Boston Med. and Surg. Jowrnal. HOKNER'S SPECIAL ANATOMY AND HISTOLOQT. I Eighth edition, extensively revised and modified. I In 2 vols. Svo., of over 1000 pages, with more than iJOO wood-cuts j extra cluch, $t> 00. . 8 Henby C. Lea's Publications — (Physiology). ItfARSHALL iJOHN), F. B. S., Jxt. Professor of Surgery in ITnivereitj/ College, London^ Ac. OrTLINES OF PHYSIOLOGY, HUMAN AND COMPARATIVE. With Additions by Francis Gurnby Smith, M. D., Professor of the Institutes of Medir cine in the University of Pennsylvania, &q. With numerous illustrations. In one large and handsome octavo volume, of 1026 pages, extra cloth, $6 50 ; leather, raised bands. $7 50. 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 &%t- 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 ^he important disco- veries of modern science in the various cognate de- partments of investigaUou. This is especially visible In the variety of interesting information derived from the departraepts of chemisti^y 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 Bngllsh language any compend of physiology more useful to the student than this work. — 8t. Louis Med. and Surg. Journal, Jan. 1869. It quite fulfils, in our opinion, the author's design of making it truly educationalitk its character — which Le, perhaps, the highest commendation that can be asked. — Am. Journ. Med. Seienaes, 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 human and compara- tive, with which we are acquainted. To speak of this work in the terms ordinarily used on such occa- sions would not be agreeable to ourselves, and would fail to do j ustice to its author. To write such a book requires a varied and wide range of knowledge, con- siderable power of analysis, correct judgment, skill 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 deaewe.— 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. Marshairs treatise might be reviewed favorably without even opening the covers. There are few, if any, more accomplished anatomists and pfaysiologiijts than the distingnished professor 6f 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 30 unreservedly as this. — British Med. Journal, Jan. 25, 1868. rfARPENTER [WILLIAM 5.), 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 FbanCis Gurnet Smith, 'M. D., Professor of the Institutes eiroi( Xev. of Med. and Pharm,, Feh. 1S72. The best work of the kind In the English language. — N. T. Psychological Journal, Jan. 1872. The work is constructed with direct reference to the wants of medical and pharmaceutical students; and, although an English work, the points of differ- ence between the British and United States Pharma- copoeias are indicated, making it as useful here as in England. Altogether, the hook is one we can heart- ily recommend to practitioners as well as students. —N. T. Med. Journal, Dec. 1871. It differs from other text-hooks in the following particulars : first, in the exclusion of matter relating to compounds which, at present, are only of interest to the scientific chemist; secondly, in confaininji the chemistry of every suhstance recognized' tifflcially or In general, as a remedial agent. It will he found a most valuable hook for pupils, assistants, and others engaged in medicine and pharmacy, and we heartily commend it to our readers. — Canada Lancet, Oct. 1871. When the original English edition of this work was published, we had occasion to express our high ap- preciation of its worth, and also to review, in con- siderable detail, the main features of the book. As the arrangement of subjects, and the main part of the text of the present edition are similar to the for- mer publication, it will be needless for us to go over the ground a second time ; we may, however, call at- tention to a marked advantage possessed by the Ame- {Nearly Ready.) rican work— we allude to the introduction of the chemistry of the preparations of the United States Pharmacopoeia as well as that relating to the British authority. — Canadian PJiarmaceutical Journal Nov. 1871. ' Chemistry has borne thenarae of beingahard snh- jeot to master by the student of medicine, and chie^fly because so much of it consists of compounds only of interest to the scientific chemist; in this work such portions are modified or altogether left out, and in the arrangement of the subject matterof the work, practical utility is sousrht after, and we think fully attained. We commend it for its clearness and order to both teacher and pupil. — Oregon Med. and Sura Reporter, Oct. 1871. 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 consitutes for him a sound and useful text-book on the subject We commend it to the notie^ pf svery medical, ae 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 hook a high compliment. — The Lancet. Br. Attfield's book is written in a clear and able manner; it in & •work, sui generis Q,nd without a rival ; it will he welcomed, we think, byevery reader of the 'Pharmacopffiia,' and is quite as well suited for the medical student as for the pharmacist.— TAe Ohemi- cal News. 'WOHLEB AND FITTIG. ^^ OUTLINES OP ORGANIC CHEMISTRY. Translated with Ad- ditiona from the Eighth German Edition. By, Ira Remsen, M.D., Ph.D., Professor of Chemistry and Physiqs in Williapis College, Mass. In one handsome volume, royal 12mo. of 650 pp. extra cloth, $3. {Just Ready.) As the numerous editions of the original attest, this work is the leading text-hook and ?tnndnrd authority throughout Germany on its important and intricate subject — a position won for it by the clearness and conciseness which are its distinguishing characteristics. The translation has been executed with the approbation of Profs. Wohler and Fittig, and numerous additions and alterations have been introduced, so as to render it in every respect on u level with the most advanced condition of the science. r\DLINO ( WILLIA M), ^--' Lecture" on Chemistry at St. Bartholomew'' 8 Hospital, Ac. 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.) As a work for the practitioner it cannot be excelled. It is written plainly and concisely, and gives in 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 valnahle 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.— Bichmiond and Louisville Med. Journal, Dec. 1869. rtALLOWAY {ROBERT), F.C.S., ^-^ Prof, of Applied Oliemistry in the Royal College of Science for Ireland, &c. A MANUAL OF QUALITATIVE ANALYSIS. From the Fifth Lon- don Edition. In one neat royal 12mo. volume, with illustrations ; extra cloth, $2 5^. (J«J* Issued.) The success which has carried this work through repeated editions in England, and its adoption as a text-book in several of the leading institutions in this country, show. that the authqr has suc- ceeded in the endeavor to produce a sound practical manual and book of reference for the che- mical student. Prof. Galloway's books are deservedly in high esteem, and this American reprint of the fifth edition (1869) of his Manual of Qualitative Analysis, will be acceptable to many American students to whom the English edition is not accessible. — Am. Jour, of Sci- ence and Arts, Sept. 1872. We regard this volume as a valuable addition to the chemical text-books, and as particularly calcu- lated to instruct the student in analytical researches of the inorganic compounds, the important vegetable acids, and of compounds and various secretions and excretions of animal origin.— ilm. Journ. of Pharm.t Sept. 1872. Henry 0. Lea's Publications — (Ghemistry, Pharmacy, die). 11 pHANDLER (CHARLES F.]. and fIRANDLER (WILLIAM H.), L/ Prnf. of Ohemiatryin the N. Y. Coll. of ^ Prof, of GkimUetry in the Lehigh Phfirmacy. UniwrHty. THE AMERICAN CHEMIST: A Monthly Journal of Theoretical, Analytical, and Technical Chemistry. Each number averaging forty large double col- umned pages of reading matter. Price $5 per annum in advance. Single numbers, 50 cts. (X^ Specimen numbers to parties proposing to subscribe will be sent to any address on receipt of 25 cents. *#* Subscriptions can begin with any number. The rapid growth of the Science of Chemistry and its infinite applications to other sciences and arts render a journal specially devoted to the subject a necessity to those whose pursuits require familiarity with the details of the science. It has been the aim of the conductors of "Thb American Cbemist" to supply this want in its broadest sense, and the reputation which the periodical has already attained is a sufficient evidence of the zeal and ability with which they have discharged their task. Assisted by an able body of collaborators, their aim is to present, within a moderate compass, an abstract of the progress of the science in all its departments, scientific and technical. Import- ant original communications and selected papers are given in full, and the standing of the " Chem- ist" is such as to secure the contributions of leading men in all portions of the country. !^esides this, over one hundred journals and transactions of learned societies in America, Great Britain, France, Belgium, Italy, Russia, and Germany are carefully scrutinized, and whatever they offer of interest is condensed and presented to the reader. In this work, which forms a special feature of the '* Chemist," Jrhe editors have the assistance of M. Alsberg, Ph.D., Prof. Gr. F. Barker, T. M. Blossom, E.M., H. G. Bolton, Ph.D., Prof. T. Egleston, E.M , H. Endemann, Ph.D., Prof. C. A. Goessmann, Ph.D., S. A. Goldschmidt, A.M., E.M., E. J. Hallock, Prof. C. A. Joy, Ph.D., J. P. Kimball, Ph.D., 0. G. Mason, H. Newton, E.M., Prof. Frederick Prime, Jr., Prof. Paul Schweitzer, Ph.D., Waldron Shapleigh, Romyn Hitchcock, and Elwyn Waller, E.M. From the thoroughness and completeness with which this department is conducted, it is believed that no periodical in either hemisphere more faithfully reflects the progress of the science, or presents a larger or more carefully garnered store of information to its readers. 'OWNES (GEORGE), PkTd. 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 Bridg^es, M. D. In one large royal 12mo. volume, of about 850 pp., extra cloth, $2 75 ; leather, $3 25. (Lately lasited.) This work is bo well known that it seems almost BuperflaoQs for us to apeak about U. 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 frec[ueutl7 occurred, what treatise on chemistry they should procure, we have always re- commended Fowues*, 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 perspicDOus diction, contains all the most receat discoveries, and is of moderate price. — Gindnnati Med. Repertory, Aug. 1869. Large additions have been made, especially la the department of organic chemistry, and we know of no other work that has greater claims on the pbyHician, pharmaceutist, or student, than this. We cheerfully recommend it as the best text-book on elementary chemistry, and bespeak for it thr careful attention of students of pharmacy.— OAi'ca^o 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.— .Boaiow Med. and Surg. Journal, Aug. 12, 1869. Here is a new edition which has been long watched- for by eager teachers of chemistry. In its new garb, r 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. ^ It will continue, as heretofore, to hold the first rank IS a text-book for students of medicine. — Chicago Med. Examiner^ Aug. 1869. This work, longthe recognized Manual of Chemistry, appears as a tenth edition, under the able editorship '>f Bence Jones and Henry Watts. The chapter on the General Principles of Chemical Philosophy, and the greater part of the organic chemistry, have been lewritten, and the whole work revised in accordance with the recent advances in chemical knowledge. It remains the standard text-book of chemistry.— i)u6- Un 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-hooks in our language. This success has arisen from the fact1;hat 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 re-iuisite for a student's hand-book has been attained. — The Ohemieal NewSj Feb. 1869. 'DOWMAN (JOHN E.),M. D. PRACTICAL HANDBOOK OF MEDICAL CHEMISTRY. Edited by 0. L. Bloxait, Professor of Praotieal Chemistry in King's College, London. Fifth American, from the fonrth and revised English Edition. In one neat volume, royal 12ma. , pp. 351, with numerous illaetrations, extra cloth. $2 25. ^T THE SAME AUTHOR. INTRODUCTION TO PRACTICAL CHEMISTRY, INCLUDING ANALYSIS. Fifth American, from the fifth and revised London edition. With numer- ous illustrations. In one.neat vol., royal 12mo., extra cloth. $2 25. KNAPP'S TECHNOLOGY ; or Chemistry Applied to I very handsome octavo volumes, with 600 wood the Arts, and to Manufaotnres. With American engraTings, extra cloth, $6 00. additions, by Prof. Waltbb B. Johxsos. In two I 12 Henry C. Lea's Publications — (Mat. Med. and Therapeutics). pARRlSH [ED WARD), Professor of Materia Medica in the Philadelphia OoUege 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 Formulae and Prescriptions. Third Edition, greatly improved. In one handsome octavo volume, of 850 pages, with' several hundred illustrations, extra cloth. $5 00; leather, $6 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 refer- ences; under Emplastrum, 36 ; Extracts, 159; Lozenges, 25; Mixtures, 55; Pills, 66; Syrups, 131 ; Tinctures, 138j Unguentum', 57, &o. We have examined this large volume with a good deal of care, and find that the author has completely exhausted the subject upon which he treats ; a more complete work, we think, it would be imposBibie to find. To the student of pharmacy the work is indis- pensable ; indeed, so far as we knpw, it is the only one of its kind in existence, and even to the physician or medical stndent 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. Jov/rnal, Kov. 1864. The medical student and the practising physician win find the volume of inestimable worth for study and reference. — San Francisco Med. Press, July, 1864. When we say that this book Is in some respects the best which has been published od 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 oifXj book. — The London Ghemieal 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 iti merits. — BvMin Quarterly Joitr. of Medical Scimctt August, 1864. S 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 Fourth edition, revised and enlarged. In two large and handsome octavo volumes. {Pre- parin-g. ) abroad its reputation as a standard treatise on Materia Dr. Still^'s splendid work on therapeutics and ma- teria medica. — London Med, Times^ April 8, 1865. JOr. Stills stands to-day one of the best and most honored 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 hi% fame even bad he done nothing more. — The Western Journal of Medicine, Dec, 1868. We regard this work as the best one on Materia filedica in the English language, and as such it de- serves the favor it has received. — Am. Joum. Medi' cat Sciences, July 1868. We need not dwell ou the merits of the third edition of this magnificently conceived work. It is the work on 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 woi'th 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. I'or purposes of practice, Still6's book is almogt 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 ts well accLuainted with this work. At home and Medica is securely established. It is second to no work on the subject in the English tongue, and, in- deed, is decidedly superior, in some respects, to any other. — Paei^e Med. and Surg Journal, July, 1868. Stmt's Therapeutics is incomparably the best work on the subjept.— i\^. ¥. Med. Gazette, Sept. 26, 1868. Dr. Still^'a 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. T. Med. Journal, Oct. 1868. The rapid exhaustion of two editions of Prof. Stilld'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 upun the subject in the English language. The present edition is fully up to the most recent advance in the science and art of therapeutics. — Lea^ewieorth Medi- cal Herald, Aug. 1868. The work of Prof. StlU^ has rapidly taken a high place in professional esteem, and to say that a third edition is demanded and now appears before ns, sufil- 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. — CHneinnati Lancet, Aug. 1863. QRIFFITH {ROBERT E.), M.D. A UNIVERSAL FORMULARY, Containing the Methods of Pre- paring and Administering Officinal and other Medicines. The \rhole adapted to Physioiani and Fhanaaceutists. Second edition, thoronghly revised, with numerous additions, b; BoBEBT P. Thomas, M.D., Professor of Materia Medica in the Philadelphia College of Pharmacy. 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 Rbstedies, presents under the head of each disease the remedial agents which have been usefully exhibited in it, with reference to the formulae containing them — ^while another of Phabmaceutioal and Botanical Nabies, and a very thorough Gsnkbai Index afford the means of obtaining at once any information desired. The Formicary itself ifl arranged alphabetically, under the heads of the leading constituents of the prescriptions. We know of nooe in our language, or any other, bo comprehensive in its details. — London Lanoet, One of the most complete works of the kind in any langnage. — Edinburgh Med. J&wmal. We are not cognizant of tiie existence of a parallel work. — London Mid, QoKtti. H'ENEY C. Lea's Publications — {Mat. Med. and Therapeutics). 13 JDEREIRA [JONATHAN), M.D., F.R.S. and L.S. MATERIA MEDIC A 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, ka. By F. J. Farre, M.D., Senior Physician to St. Bartholomew's Hospilial} and London Editor of the British Pharmacopoeia ; assisted by Robert Bentley, M.R.C.S., Professor of Materia Medica and Botany to tbe Pharmaceutical Society of Great Britain; and by Robert Warington, F.R.S. , Chemical Operator to the Society of Apothecaries. With numerous additions and references to the United States Pharmacopoeia, by Horatio C. Wood, M.D., Professor of Botany in the University of Pennsylvania. In one large and handsome octavo volume of 1040 closely printed pages, with 236 illustrations, extra cloth, $7 00; 'leather, raised bands, $8 00 The task of the American editor has evidently been ao sinecure, for not only has he given to us all that U contained in the abridgment usefal for oar pur- poBBS, but by a careful and judicious embodiment of over a hundred ne'w remedies has increased the size of the former work fully one-third, besides adding many new illastrations, some of which are original. We unhesitatingly say that by ao doing he has pro- portionately Increased the value, not only of the con- densed edition, but has extended the applicability of the great original, and has placed his medical coun- trymen uuder lasting obligations to him. The Ame- rican physician now han all that is needed in the shape of a complete treatise on materia medica, and*^ the medical student has a text-book which, for prac- tical utility and intrinsic worth, stands unparalleled. Although of considerable size, it is none too large for the purposes for which it has been intended, and every medical man should, in justice to himself, spare a place for It upon his book-shelf, resting assured that the more he consults it the better he will be satisfied of its excelleaee.— ^. Y. Hed. Record, Nov. 15, 1866. It win fill a place which no other work caujoccupy lu the library of the physician, btudeut, and apothe- e&ry. —Boston Med. and Swrg. Journal, Nov. 8, 1866. Of the many works on Materia Medica which have appeared since the issuing of the British Pharmaco- poaia, none will be more acceptable to the student and practitioner than the present. Pereira's Materia Medica had long ago asserted for itself the position of being the most complete work on the subject in the English language. But its very completeaess stood in the way of its success. Except in the way of refer- ence, or to tho^e who ma4e a special study of Materia Medica, Dr. Pereira's work was too full, and its pe- rusal required an amoant of time which few had at their disposal. Dr. Farre has veryjudiciously availed himself of the opportunity of the publicatiou of the new Pharmacopoaia, bybrin^ngoutan abridged edi- tion of the great work. This edition of Pereira is by no means a mere abridged re-issue, but contains many improvements, both in th6 descriptive and thera- peutical departments. We can recon^mend it as a very excellent and reliable text-book. — Edinburgh Med. Jovnmal, February, 1866. The reader cannot fail to be impressed, at a glance, with the exceeding value of this work as a compend of nearly all useful knowledge on the materia medica. We are greatly indebted to Professor Wood for his adaptation of it to our meridian. Without his emen- dations and additions it would lose much of its value to the American student. With them it is an Ameri- can \iook..^ Pacific Medical and Swrgical Journal, December, 1866/ fJLLIS (BENJAMIN), M,D, THE MEDICAL FORMULARY: being a Collection of Prescriptions derived from the writings and practice of many of the most eminent physicians of America , and Europe. • Together with the usual Dietetic Preparations and Antidotes for Poisons. The whole accompanied with a few brief Pharmaceutic and Medical Observations. Twelfth edi- tion, carefully revised and much improved by Albert H. Smith, M. D. In one volume 8vu. of 376 pages, extra cloth, $3 00. {Lately Published.) This work has remained for some time out of print, owing to the anxious care with which the Editor has sought to render the present edition worthy a continuance of the very remarkable favor which has carried the volume to the unusual honor of a Twelfth Edition. He has sedu- lously endeavored to introduce in it all new preparations and combinations deserving of confidence, besides adding two new classes, Antemetics and Disinfectants, with brief references to the inhalation of atomized fluids, the nasal douche of Thudichum, suggestions upon the method of hypodermic injection, the administration of anaesthetics, &o. &o. To accommodate these numerous additions, he has omitted much which the advance of science has rendered obsolete or of minor importance, notwithstanding which the volume has been increased by more than thirty pages. A new feature will be found in &, copious Index of Diseases and their remedies, which cannot but increase the value of the work as a suggestive book of reference for the working practition er. Every preca ution has been taken to secure the typographical accuracy so necessary in a work of this nature, and it Is hoped that the new edition will fully maintain the position which f Ellis' Formulary" has long occupied. flARSON [JOSEPH), M.D,, V Profeasor of Materia Medica and Pha^rmaoy in the University of PennsyHania, r Professor of Stirgery in the Jefferson Medical Oollege of Philadelphia. ELEMENTS OP PATHOLOGICAL ANATOMY. Third edition, thoroUglily revised and greatly improved. In one large and very handsome octavo volume of nearly 800 pages, with about three hundred' and fifty beautiful illustrations, of which a large number are from original drawings ; extra cloth. $4 00. TONES [G. HANDFIELD), F.R.S., and SIEVEKINO {ED. K), M.D., ^ Assistant Physicians and Lecturers in St. Mary's Hospital. A MANUAL OF PATHOLOGICAL ANATOMY. First American edition, revised. With three hundred and ninety-seven handsome wood engravings. • In one large and beautifully printed octavo'volume of neaily 750 pages, extra cloth, $3 60. ARCLAY (A. W.), M. D. A MANUAL OF MEDICAL DIAGNOSIS; being an Analysis of the Signs and Symptoms of Disease. Third American from the second and revised London edition. In one neat octavo volume of 451 pages, extra cloth. $3 50. B TYILLIAMS [CHARLES J. B.), M.D., ' ' Professor of CliniQaL Medicine in Unvoersity GoUege, London. PRIlSrCIPLES OF MEDICUSTE. An Elementary Yiew ot the Causes, Nature, Treatment, Diagnosis, and Prognosis of Disease j with brief remarks on HygienicB, or the preservation of health. A new American, from the third and revised London edition. In one octavo volume of about 500 pages, extra cloth,. $3 50. fiUNGLISON, FORBES, TWEEDIE, AND CONOLLY. THE CYCLOPAEDIA OF PRACTICAL MEDICINE: comprising Treatises on the Nature and Treatment of Diseases, Materia Medioa and Therapeutics, Diseases of Women and Children, Medical Jurisprudence, Ac. &o. In four large super-royal octavo volumes, of 3254 double-columned pages, strongly and handsomely hound in leather, $15 ; extra cloth. $11. *i)f * This work contains no less than four hundred and eighteen distinct treatises, contributed bv sixty-eight distinguished physicians. JPOX [ WILSON), M.D., -I- Holme Prof, of Olmical Med., Un-ivereity Coll., London. THE DISEASES OF'THE STOMACH: Being the Third Edition of the "Diagnosis and Trentment of the Varieties of Dyspepsin, " Revised and Enlarged. With illustrations. In one handsome octavo volume. {In Press.) The pvesent edition of Dr. Wilson Fox's very ad mi- I Dr. Fox has put forth a volnmo of uncommon ex- TaWe work differs from Ihe preceding in that it deals cellence, wjiich we feel very sure will lak« a high with other maladies than dyspepsia only.— London rank among works that treat of the 8tomaoh.-.im. Med. Times, Feb. 8, 1873. I PractiMmer, March, 1873. Henry G. Lea's Publications — {^Practice of Medicine). 15 WLINT {AUSTIN), M.D., ■*- Professor of the Prtactples and Practice of Medicine in Bellevue Med. College, 2f. T. * A* TREATISE OJST THE PRINCIPLES AND PRACTICE OF MEDICINE ; designed for tlie use of Students and Practitioners of Medicine. Fourth edition, revised and enlarged. In one large and closely printed octavo volume of about 1 100 pa^es J handsome extra oloth, $6 00 ; or strongly bound in leather, with raised bands, $7 00. {Nearly Ready.) By common consent of the English and American medical press, this work has been assigned to the highest position as a complete and compendious text-book on the most advanced condition of medical science. At the very moderate price at which it is offered it will be found one of the cheapest volumes now before the profession. Admirable and unequalled. — Western Journal of Medicine, Nov. 1869. Dr. Flint's work, thongh claiming no higher title than that of a text-book, is really more. He is a man of large clinical experience, and his hook is fall of such masterly descriptions of disease as can only be drawn by a man intimately acquainted with their various forms. It is not so long since we had the pleasure of reviewing his first eaition, and we recog- nize a great improvement, especially in the general part of the work. It is a work which we can cordially recommend to our readers as fully abreast of the Bci- encQ of the day. — Edinburgh Med. Jovrnal, Oct. '69. One of the best works of the kind for the practi- tioner, and the most convenient of all for the student. — ^m. Joum. Med. Sciences^ Jan. 1869. This work, which stands pre-eminently as the ad- vance standard of medical science up to the present time in the practice of medicine, has for its author one who is well and widely known as one of the leading practitioners of this continent. In fact, it is seldom that any work is ever issued from the press more deserving of universal recommendation. — Do- minion Med. Journal^ May, 1869. The third edition of this most excellent book scarce- ly needs any commendation from us. 'The volume, as ft stands now, is really a marvel : first of all, it is flxcellently printed and bound — and we encounter th,at luxury of America, the ready-cut pages, which fcheTapkees are 'cute enough to insist upon — nor are these by any means trifles ; but the contents of the book are astonishing. Not only is U wonderful that any one man can have grasped in his mind the whole icope of medicine .with that vigor which Dr. Flint shows, but the condensiad yet clear way in which this is done ia a perfect literary triumph. Dr. Flint is pre-eminently one of the strong men, whose right to do this kind of thing is well admitted ; and we say no more thau the truth when we affirm that he ia 7ery nearly the only living man that could do it with mch results as the volume before ua. — The London Practitioner, March, 1869. This is in some respects the best text-hook of medl- eiue in our language, and it is highly appreciated on the other side of the Atlantic, inasmuch as the first edition was exhausted in a few months. The second edition was little more than a reprint, but the present has, as the author says, been thoroughly revised. Much valuable matter has been added, and by mak- ing the type smaller, the bulk of the volume is not much increased. The weak point in many American wurks is pathology, but Dr. Flint has taken peculiar pains on this point, greatly to the value of the book. —London Me^. Times and Gazette, Feb. 6, 1869. BARLOW'S MANUAL OF THE PRACTICE OF 1 TODD'S CLINICAL LECTURES ON CERTAIN ACUTE MEDICINE. With Additions by D. F. Cokdie, Diseases. In one neat octavo volume, of 320 pages, M. D. 1 vol. 8vo., pp. 600, cloth. $2 50. I extra cloth. $2 50. p A VY {F. W.), M. D., F. R. .ST., Senior Asst. Physician to and Lecturer on Physiology, at Guy's Hospital, Stc, A TREATISE ON THE FUNCTION OF DIGESTION ; its Disor- ders and their Treatment. .From the second London edition. In one handsome volume, small octavo, extra oloth, $2 00. {Lately Published.) The work before us is one which deserves a wide circulation. We know of no better guide to the etudy of digestion and its disorders, — Bt. Louitt Med. atCd Burg. Journal, July 10, 1869. A thoroughly good book, being a careful systematic treatise, and safficieutly exhaustive for all practical pui-poses.— iea-uercworfft Med. Serald, July, 1869. A yefy valuable work ou the subject of which It treats. Small, yet it is fall of valuable iaformation. — Cincinnati Med. Repertory, June, 1869. nRINTON (WILLIAM), M.D., F.R.S. •'^LECTURES ON THE DISEASES OF THE STOMACH; with an Introduction on its Anatomy and Physiologj. From the second and enlarged London edi- tion. With illustrations on wood. In one handsome octavo volume of about 300 pages, extra oloth. $3 25. , flHAMBERS (T. K.), M. D., v-/ Consulting PhyHdan to St. Mary^a Hospital^ London, &c. THE INDIGESTIONS; or, Diseases of the Digestive Organs Functionally Treated. Third and revised Edition. In one handsome ootavo voliime of 3S3 pages, extra oloth. $3 00. {Lately Fublished.) So very large a proportion of the patients applying to every general practitioner suffer from' some form of iudigeRtion, that whatever aids him in their man- agement directly "puts money in his purse," and in- directly does mure than anything else to advance his reputation with the public. From this purely mate- rial point of view, settiujf aside its higher claims to merit, we know of no more desirable acquisition to a physician's library than the book before us. He who should commit its contents to his memory would Hnd itf: price an investment of capital that retnroed him a most usurious rate of interest. — N. Y. Medical Gazette, Jan. 28, 1871. JOT THE SAME AUTHOR. {Lately Published) RESTORATIVE MEDICINE. An Harveian Annual Oration, deliv- ered at the Royal College of Physicians, London, on June 24, 1871. With Two Sequels. In one very handsome volume, small 12mo., extra oloth, $1 00. 16 Henry C. Lea's Publications — {Practice of Medicine). fTARTSHORNE {HENRY), M.D., J. J. Profesnor of Hygiene in the Univerffity of Pennsylvania. ESSENTIALS OF THE PRINCIPLES AND PRACTICE OF j\JeM- CINE. A handy-book for Students and Practitioners. Third edition, revised and im- proved. In one handsome royal 12mo, volume of 487 pages, clearly printed on small type, oloth, $2 38; half bound; $2 63. (Now Rmdy.) The very remg^kable favor which has been bestowed upon this work, as manifested in the ex- haustion of two large editions within four years, shows that it has successfully supplied a want felt by both student and practitioner of a volume which at a moderate price and in a convenient size should afford a clear and compact view of the most modern teachings in medical practice. In preparing the work for a third edition, the author has sought to maintain its character by very numerous additions, bringing it fully up to the science of the day, but so concisely framed that the size of the volume is increased only by thirty or forty pages. The extent of the new informa- tion thus introduced may be estimated by the fact that there have been two hundred and sixty separate additions made to the text, containing references to one hundred and eighty new authors. This little epitome of medical knowledge has al- ready been noticed by us. It is a vade mecum of value, including in a short space most of what is es- sential in the science and practice of medicine. The third edition is well up to the present day in the modern methods of treatment, and i o the use of newly discovered drugs.— Soaiow Med. and Surg. Journal, Oct. 19, 1871. Certainly very few volumes contain so much pre- cise information within so small a compass.— i^T, Y. MpJi. Journal, "So-v. 1871. The diseases are conveniently classified; symptoms, canaation, diagnosis, prognosis, and treatment are carefully considered, the whole being marked by briefness, but clearness of expression. Over 250 for- mulas are appended, intended as examples merely, not as guides for unthinking practitioners. A com- plete index facilitates the use of this little volume, in which all important remedies lately introduced, such as chloral hydrate and carbolic acid, have received their full ahareof attention. — Am. Journ, of Pfitxrm.,- Nov. 1871. It is an epitome of the whole science and practice of medicine, and will be found most valuable to the practitioner for easy reference, and especially to the student in attendance upon lectures, whose time is too much occupied with many studies, to consalt the larger works. Such a work must always be in great demand. — Cincinnati Med. Repertory, Nov. 1871. IT^ATSON (THOMAS), M. D., SfC. LECTURES ON THE PRINCIPLES AND PRACTICE OP PHYSIC. Delivered at King's College, London. A new American, from the Fifth re- vised and enlarged English edition. Bdited, with additions, and several hundred illus- trations, by Henry Hartshorne, M.D., Professor of Hygiene in the University of Penn- sylvania. In two large and handsome 8vo. vols. Cloth, $9 00; leather, $11 00. (Justready.) with the assistance of Professor George Johnson, his successor in the chair of Practice of Medi- cine in King's- College, the author has thoroughly revised this work, and has sought to bring it on a level with the most advanced condition of the subject. As he himself remarks: "Consider- ing the rapid advance of medical science during the last fourteen years, the present edition would be worthless, if it did not differ much from the last" — but in the extensive alterations and addi- tions that have been introduced, the effort of the author has been to retain the lucid and coHo- quiaj style of the lecture-room, which has made the work so deservedly popular with all classes of the profession. Notwithstanding these changes, there are some subjects on which the American reader might reasonably expect more detailed information ,than has been thought requisite in England, and these deficiencies the editor has endeavored to supply. The large size to which the work has grown seems to render it necessary to print it in two vol- umes, in place of one, as in the last American edition. It is therefore presented in that shape, handsomely printed, at a very reasonable price, and it is hoped that it will fully maintain the position everywhere hitherto accorded to it, of the standard and classical representative of Eng- lish practical medicine. At length, after many months of expectation, we have the satisfaction of finding ourselves this week in possession of a revised and enlarged edition of Sir Thomas Watson's celebrated Lectures. It is a sub- ject for congratulation and for thankfulness that Sir Thomas Watson, during a period of comparative lei- sure, after a long, laborious, and most honorable pro- fessional career, while retaining full possession of his bigh mental faculties, should bave employed the op- portunity to submit his Lectures to a more thorough revision than was possible during the earlier and busier period of his life. Carefully passing in review some of the most intricate and important pathological and practical questions, the results of his clear insigbt and hisealmjudgmentare now recorded for the bene- fit ofmankind, inlanguage which, for precision, vigor, and classical elegance, has rarely been equalled, and never surpassed The revision has evidently been most carefully done, and the results appear in almost every page. — £rit. Med. Journ., Oct. 14, 1871. No word-s can convey the pleasurable satisfaction that we feel in looking over the revised edition of the admirable lectures of this distinguished author. The earnestness which marked his whole profes- sional career leads him, in a characteristic manner, to devote his last leisure hours to the correction of his gi-eat classic work. The lectures are so well known and so justly appreciated, that it is scarcely neces- sary to do more than call attention to the special advantages of the last over, prev^ious editions. In the revision, the author has displayed all the charms and Hd vantages of great culture and a ripe experi- ence combined with the soundest judgment and sin- cerity of purpose. The author's rare combination of great scientific attainments combined with won- derful forensic eloquence has exerted extraordinary, influence over the last two generations of physicians. His clinical descriptions of most diseases have never been equalled ; and on this score at least his work will live long in the future. The work will be sought by all who appreciate a great 'boo^.—Amer. . Journal of Syphilography, July, 1872.. We are exceedingly gratified at the reception of this new edition of Watson, pre-eminently the prince of English authors, on "Practice." We, who read the first editioD as it came to us tardily and in frag- ments through the "Medical Kews and Library," shall never forget the great pleasure and profit we derived from its graphic delineations of disease, its vigorous style and splendid English. Maturity of years, extensive observaiion, profound research, and yet continuous enthusiasm, have combined to give us in this latest edition a model of professional excellence in teaching with rare beauty in the mode of communication. But this, classic needs no eulo- giura of ours. The selection of Prof. Hartshorne as the American editor, is to us peculiarly gratifying, and must insure even larger popularity and more general sale to American readers. Every guarantee is thus afforded that in every part the book will be found up to the times. Will it do to repeat the re- mark we have seen somewhere: " No library can be considered complete without it?" Although the phrase may not savor of originality, it is, heverthe- less, most emphatically true. — Chicago Med. Journ.f July, 1872. Henet O. Lea's Publications— (Diseases of Lungs and Heart). 17 WLINT [AUSTIN), M.D„ ■*- Professor of the Principles and Practice of Medicine in Bellevue Hospital Med. College, If. Y. A PRACTICAL TREATISE ON THE DIAGNOSIS, PATHOLOGY, AND TREATMENT OF DISEASES OF THE HEART. Second revised and enlarged edition. In one ootaro volume of 550 pages, with a plate, extra cloth, $4. {Just Issued.) The author has sedulously improved the opportunity afforded him of revising this work. Portions of it have been rewritten, and the whole brought up to alevel'withthe most advanced condition of science. It must therefore continue to maintain its pbsition as the standard treatise on the subject. Dr. Flint chose a difficult subject for his reaearohes, and has' Bhown remarkable powers of observation and reflection, as well as great industry, in his treat- ment of it. His book mast be considered the fnllest and clearest practical .treatise on those subjects, and ebonld be in the hands of all practitioners and stu- dents. It is a credit to American medical literature. ~Amer. Journ. of the Med. Sciences, July, 1S60. We question the fact of any recent American author In our profession being more extensively known, or more deservedly esteemed in this country than Br. Flint. We willingly acknowledge his success, more particularly in the volume on diseases of the heart, in making an extended personal clinical study avail- able for purposes of illustration. In connection.with cases which have boen reported by other trustworthy observers. — Brit, and Por. Med.-Ohirwrg. Review. In regard to the merits of the work, we have no heflitationin pronouncioig it full, accurate, and judi- cious. Considering the present state of science, saoh a work was much needed. It should be in~the hands of every practitioner. — Chicago Med. Journ. With more than pleasure dO we hail the,advant Of this' work, for it fills a wide gap on the list of text- books for our schools, and is, for the practitioner, the most valuable practical work of its kind. — N. 0. Med. News. B T THE SAME AUTHOR. ' -^ PRACTICAL TREATISE ON THE PHYSJCAL EXPLORA-" TION OF THE CHEST AND THE DIAaNOSIS OP DISEASES* AFFEOTINa THE BESPIHATORY ORGtANS. Second and revised edition. In one handsome octavo volume of 595 pages, extra cloth, $4 50. which pervades his whole work lend an additional force to its thoroughly practical character, which cannot fail to obtain for it a place as a standard'work on diseases of the respiratory system. — London Lancet. Jan. 19, 1867. Dr. Flint's treatise is one of the most trustworthy guides which he can consult. The, style la clear and distinct, and is also concise, being free from that tend- ency to over-refinement and unnecessary minuteness which characterizes many works on the same B,v\y- ]%ct.—D-ublin Medical Press, Feb. 6, 1867. The chapter on Phthisis is replete with interest ; and his remarks on the diagnoses, especially in the early stages^'are remarkable for their acumen and gfreat practical value. Dr. Flint's style is clear and elegant, and the tone of freshness and originality This is an admirable book. Excellent in detail and execution, nothing better could be desired by the practitioner. Dr. Flint enriches his subject with much solid and not a little original observation.— Ranking^s Abstract, Jan. 1867. pOLLER (HENRY WILLIAM), M. D., -*• Physician to St. George's Hospital, London. ON DISEASES OP THE LUNGS AND AIR-PASSAGES. Their Pathology, Physical Diagnosis, Symptoms, and Treatment. From the second and revised English edition. In one handsome octavo volume of about 500 pages, extra cloth, $3 50. Dr. Fuller's work on diseases of the chest was so accordingly we have what might be with perfect jus- favorably received, that to many who di^d not know tice styled an entirely new work from his pen, the the extent of his engagements, it was a matter of won- portion of the Work treating of the heart and great der that it should be allowed to remain three years vessels being excluded. Nevertheless, this volume is out of print. Determined, however, to improve it, of almost equal size with the first.— Irfwidon Medical Dr. Fuller would not consent to a mere reprint, and Times and Gazette, July 20, 1867. y^ILLIAUS {C. J. B.), M.D., Senior Consulting Phyaioian to the Eospttalfor Oomvmption, Brampton, and ymLLIAMS (CHARLES T.), jH.D., Physician to the Hospital for Consumption. PULMONARY CONSUMPTION; Its Nature, Varieties, and Treat- ment. With an Analysis of One Thousand cases to eJcempli^ its duration. In one neat octavo volume of about 350 pages, extra cloth. (Jiist Isst&ed.) $2 50. previous author; but probably there is no malady, the treatment of which has been so much improved within the last twenty years as pulmonary consump- tion. To ourselves, Dr. Williams's chapters on Treat- ment are amoDgst the most valuable and attractive in the book, and would alone render it a standard work of reference. In conclusion, we would record our opinion that Dr. Wiiliams's great reputation is fully maintained by this book. It is undoubtedly one of the most valuable works in (he language upon any special disease.— Xone2. Med. Times and Gaz.. Nov. 4, 1871. He can still speak from a more enormous experi- ence, and a closer study of the morbid processes in- volved in tuberculosis, than most living men. -He owed it to himself, and to the importance of the sub- ject, to embody his views in a separafe work, and we are glad that he has accomplished this duty. After all, the grand teaching which Br Williams has for the profession is to be foiind in his therapeutical chapters, and in the history of individual cases ex- tended, by dint of care, over ten, twenty, thirty, and even forty years. — London Lancet, Oct. 21, 1871. His results are more favorable than those of any LA ROCHE 9N PNEUMONIA. 1 vol. 8vo., extra cloth, of 600 pages. Price $3 00. BUCKLER ON FIBRO-BRONCHITIS AND RHBD- MATIC PNEUMONIA. 1 vol. 8vo. $1 25. FISKE FUND PRIZE ESSAYS ON CONSUMPTION. 1 vol Svo„ extra cloth. $1 00. SMITH ON CONSUMPTION ; ITS EARLY AND RE- MEDIABLE STAGES. 1 vol. 8vo., pp. 254. $2 25. SALTER ON ASTHMA. 1 voL 8vo. $2 50. WALSHE ON THE DISEASES OP THE HEART AND GREAT VESSELS. Third American edition. In 1 vol. Bvo., 420 pp., cloth. $3 00. 18 Henry C. Lea's Publications — (Practice of Medicine). f?OBERTS (WILLIAM), M. D., ■*■*' iecturer ori Medicine in the Manchester School of Medicine, 4c. A PRACTICAL TREATISE ON URINARY AND RENAL DI8- Ej^SES, including Urinary Deposits. Illustrated by numerous eases and engravings. Ser- end American, from the Second Revised ajid Enlarged London Edition. In one large and handsome octavo volume of 616 pages, with a colored plate ; extra clo.th, $4 50. {Just Ready.) The author has subjected this work to a very thorough revision, and has sought to embody in it the results of the latest experience and investigations. Although every effort has been made to keep ifc within the limits of its former size, it has been enlarged by a hundred pages, many new wood-Quts have been introduced, and also a colored plate representing the appearance of the different varieties of urine, while the price has been retained at t"he former very moderate rate. In every respect it is therefore presented as worthy to maintain the position which it has acquired as a leading authority on a large, important, and perplexing class of affections. A few notices of the first edition are appended.' The plan, it will thus be seen, is very complete, aal the manner in which It has been carried cutis iu the biffhest degree satisfactory. The chaTa'cters of the different deposits are very well described, and the microscopic appearances they present are illus- trated by numerous well executed engravings. It only remains to us to strongly recommend to our readers Dr. Roberts's work, as containing an admira- ble risumi of the present state of knowledge of uri- nary diseases, and as a sate and reliable guide to the clinical observer. — Edi%.^ed. Jour. The most complete and practical treatise upon renal diseases we have examined. It is peculiarly .adapted to the wants of the majority of Americali practition- ers from its clearness and simple aniiouncemeht of the facts in relation to diagnosis and treatment of urinary disorders, and contains in co^ndensed form the investi- gations of Bence Jones, Bird, Beale, Hassall, Prout, and a host of other well-known writers upon this sub- ject. The characters of urine, Jphysiological and pa- thological, as indicated to the naked eye as well as by microscopical and chemical investigations, are con- cisely represented both by des^ripnon and by well executed engravings, — Cincinnati Journ. of Med, T>ASHAM ( W. R.), M. D., ■*-' Senior Physician to the Westminster Hospital^ &c. RENAL DISEASES: a Clinical Guide to their Diagnosis and Treatment. With illustrations. In one neat royal 12mo. volume of 304 pages. $2 00. {Jusi Issued.) The chapters on diagnosis and treatment are very good, and the student and young practitioner will find them full of valuable practical hiuts. The third part, on the urine. Is excellent, and we cordially recommend its perusal. The author has arranged his matter in a somewhat novel, aad, we think, use- ful form. Here everything can be easily found, and, what is more important, easily read, for all the dry details of larger books here acquire a new interest from the author's arrangement. This part of the book is full of good work. — Brit, and For. MedicO' OhirurgicaZ Seview, July, 1870. The easy descriptions and compact modes of state- ment render the book pleasing^and convenient.— ^m. Journ. Med'. Sciences, July, 1870. A book that we believe will be found a valuable assistant to the practitioner and guide to the student. — Bdltimdre Med. Journal, July, 1870. -The treatise of Dr. Basham differs from the rest in its special adaptation to clinical study, and its con- densed and almost aphorismal style, which makes it easily read and, easily understood. Beaides, the au^ihor expresses some new views, which are well worthy of consideration. The volume is a valuable addition to this department of kuowledge.-rrPoci^ Med. and Swrg. Journal, July, 1870. MORLAND ON RETENTION IN THE BLOOD OF THE ELEMENTS OF THE URINARY SECRETIOM. 1 vol. 8vo., extra cloth. 75 cents. TONES [C. HANDFIELD), M. D., ^ Physician to Bt. Mary'a Bospital, &c. CLINICAL OBSERVATIONS DISORDERS. Second American Edition. extra cloth, $3 25. Taken as a whole, the work before us furnishes a abort but reliable account of the pathology and treat- ment of a class of very common but certainly highly obscure disorders. The advanced student will ffnd it a rich mine of valuable facts, while the medical prac- titioner will derive from it many a suggestive hint, to aid him in the diagnosis of "nervous cases," and in determining the true indications for their ameliora- tion or cure. — Amer. Journ. Med. Set., Jan. 1867. ON nJNCTIONAL NERVOUS In onfi handsome octavo volume of 348 pages, We must cordially recommend it to the profeesion of this country as supplying, ia a great measure, a deficiency which exists in the medical literature ol the English language.— iV«w York Med. Journ., April, 1867. The volume is a most admirable one— full of hints and practical suggestion's. — Canada Med. Juumal, April, 1867. N DISEASES OF THE SPINAL COLUMN AND OF THE NERVES. By C. B. KADCLiFr, M. D., and others. 1 vol. 8vo., extra cloth, $1 60. OLADE (D. D.), M.D. DIPHTHERIA; its Nature and Treatment, with an account of the His- tory of Its Prevalence in various Countries. Second and revised edition. In one neat royal 12mo. volume, extra oloth. $.1 26. TTUDSON{A.), M:D., M. R. I. A., •*"*• Physician to the Meath Hospital . LECTURES ON THE Cloth, $2 60, STUDY OF FEVER. In one vol. 8vo., extra TYONS (ROBERT D.), K. C. 0. A TREATISE ON FEVER ; or, Selections from a Course of Lectures on Fever. Being part of a Course of Theory and Practice of Medicine. In one neat octave volume, of 362 pages, extra cloth. $2 25. Henry C. Lea's Publications — (Venereal Diseases^ etc.). 19 T>UMSTEAD (FREEMAN J.), M.D.. -*-' Professor of Venereal Diseases at the Col. of Phys. and Surg. , New York, &c. THE PATHOLOGY AND TREATMENT OF YENEEEAL DIS- EASES. Including the results of recent investigations upon the subject. Third edition, rerised and enlarged, with illustrations. In one large and handsome octavo volume of over 700 pages, extra cloth, $5 00 ; leather, $6 00. {Just IssttM.) In preparing this standard work again for the press, the author has subjected it to a very thorough revision. Many portions have been rewritten, and much new matter added, in order to bring it completely on a level with the most advanced condition of syphilograpby, but by careful compression of the text of previous editions, the work has been increased by only sixty-four pages. The labor thus bestowed upon it, it is hoped, will insure for it a contiuuanoe of its position as a complete and trustworthy guide for the practitioner. It is the most complete book with which we are ac- quainted in the language. The latest views of the best authorities are put forward, aad the information is well arranged — a great point for the student, and still more for the practitioner. The Subjects of vis- ceral syphilis, syphilitic affectiouR of the eyes, and the treatment of syphilis by repeated inoculations, are very fully 6X%c\XBBBdi..— London Lancet, Jam. 7, 1871. Dr. Bumstead's work is already so universally known as the best treatise in the English language on venereal diseases, that it may seem almost superfiu- oas to say more of it than that a new edition has been Issued. But the author's indastry has rendered this new edition virtually a new work, and so merits as much special commendation as if its predecessors had not been published. As a thoroughly practical book on a, class of diseases which form a large-^hare of nearly every physician's practice, the volume before us is by far the best of wMch we have knowledge.— N. r. Medical Gazette, Jan. 28, 1871. It is rare in the history of medicine to find any one book which contains all that a practition^ needs to know; while the possessor of "Bumstead on Vene- real" has no occasion to look outside of its covers for anything practical connected with the diagnosis, his- tory, or treatment of these affections. — N. Y. Medical Jomrnal, March, 1871. (lULLERIER [A.), and V Burgeon to the Sdpital du Midi. nUMSTEAD {FREEMAN J.), •*^ Professor of Venereal piseases in the Gollegeof Physicians offid Surgeoris, N. T. 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 $3 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 well 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 PrdctUioThpr, 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 bet'ore 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. CuHerier 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 for its kind is more necessary for them to have. —California Med. Gazette, March, 1869. The most splendidly, illustrated work in the lan- giiage, 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. CuUerier 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. CuUorier's work, with inci- dental remarks by one of the most eminent American syphilographers, Mr. Bumstead. — Brit, and For. Medico-Ghir. Eeview, July, 1869. // ILL (BERKELEY), Surgeon to the Lock Hospital, London. ON SYPHILIS AND LOCAL one handsome octavo volume ; extra cloth Bringing, as it does, the entire literature of the dis- flftse 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 carefnl attention to the manifold aspects and details of its subject, it is wonderfally concise. All these qualities render It an especially valuable book to the beginnet. In CONTAGIOUS DISORDERS. , $3 25. (Lately Published.) to whom we would most earnestly recommend its study ; while it is no less useful to the practitioner. — St. Louis Med. aiid Surg. Journal, May, 1869. The most convenient and ready book of -reference we have met with.— Jr. r. Med. Record, May 1, 1869. Most admirably arranged for both student and prac- titioner, no other work on the subject equalfe it; it Is more simple, more easily studied. — Buffalo Med. arid Surg. Journal, Inarch, 1^69. ^EISSL (H.), M.D. A COMPLETE TREATISE ON VENEREAL DISEASES. Trans- lated from the Second Enlarged Germnn Edition, by Frederic R. Sturgis, M.D. In one octavo volume, with illustrations. (Preparing.) 30 Henry C. Lea's Publications— (Diseases of the Shin). y^ILSON {ERASMUS), F.R.S. ON DISEASES OP 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. A SERIES OF PLATES ILLUSTRATINa "WILSON ON DIS- EASES OF THE SKIN;"oonai8tiEgof 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. Such a work as the one before us is a most capital and acceptable belp. Mr. Wilson bas 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 oi 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 edii- tion published separately, .There are twenty of these platen, nearly all of them colored to nature, and ex- hibiting with great fidelity the various groups of diiieases. — OinoinnaM Lancet. No one treating skin diseases shonid be without a copy of this standard work. — Oanadd Lancet &.agust, 1863. We can safely recommend it to the profession as the best work on the sabject now in existence in the English language.— JMedicaJr^mefl and Gazette. Mr. Wilson's volume is an excellent digest of the actual amonnt of knowledge of cutaneous diseases; it includes almost every fact or opinion of importance connected with the anatomy and pathology of the skin.— JBrififiA and Foreign Medical Review. ^T TBE SAME AUTHOR. THE STUDENT'S BOOK OF CUTANEOUS MEDICINE and Dis- EASES OF THB SKIN. In One very handsome royal 12mo. volume. $3 50. {Lately latued.) fully up to the times, and is thoroughly (stocked with most valuable information. — New York Med. Seeordt Jan. IS, 1867. The most convenient manual of diseases of the skin that can be procured by the student. — Ghicago Ited. Jommal, Dee. 1866. JY'ELIGAN {J. MOORE), M.D., M.R.I. A. A PRACTICAL TREATISE ON DISEASES OF THE SKIN. Fifth American, froni the second and enlarged Dublin' edition by T. W. £elcher, M.B. In one neat royal 12mo. volume of 462 pages, extra cloth. $2 25. Fully equal to all the requirements of students and hheir value justly estimated ; in a word, the work is young practitioners. — Didtlin Med. Press. ' " - ■■ , . .. _ .., 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 can be none which can com- pare with it in practical value. AH the late disco- veries in Dermatology have been duly noticed, and ^Y THE SAME AUTHOR, ATLAS OF CUTANEOUS DISEASES. In one beautiful quarto volume, with exquisitely colored plates, &c., p^;esenting about one hundred varieties of disease. Extra cloth, $5 50, The diagnosis of eruptive disease, however, under all circumstances, is very difficult. Nevertheless, Dr. Neligan has certainly, ''asfaraspossible/'given a faithful and accurate represeutation 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 £o examine also the "Practical Treatise]" and we are inclined to consider it a very superior work, com- bining accurate verbal description with sound views of the pathology and treatment of eruptive* diBeaeea. — Glasgow Med. Jowrnal, 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 m&tk.Suffalo Med. Journal. TJILLIER (THOMaS), M.D., •^■^ Ph/ysician to the Skin Department of University College Hospital, &e. HAND-BOOK OF SKIN DISEASES, for Students and Practitioners, Second American Edition. In one royal 12mo. volume of 358 pp. With IlluBtrationg. Extra cloth, $2 25. We can conscientiously recommend it to the stu- dent; the style is clear and pleasant to read, the matter is good, and the descriptions of disease, with the modes of treatment recommended, are frequently illustrated with well-recorded cases. — LoTidon Med, Times and Gazette, April 1, 1865. It is a concise, plain, practical treatise on the vari- ous diseases of the akin ; just such a work, indeed, as was much needed, both by medical students and practitioners. ~- CMoafro M^ical Examiner, May, 1865'. ANDERSON [McGALL), M.D., -^1 Physician to the Dispensary for Skin Diseases, Glasgow^ &G. ON THE TREATMENT OF DISEASES OP THE SKIN. With an Annlysis of Eleven Thousand Consecutive Cases. In one vol. 8vo. (Publishing in the Medical News and Library for 1873^) The very practical charaoter of this work and the extensive experience of the author, cannot fail to render it acceptable to the subscribers of the "American Journal op the Medioil Sciences." When completed in the "News and LiBRARr," it will be issued separately in a neat octavo volume. Henry C. Lba*s Publications — (Diseases of Children). 21 KIMITH (J. LE WIS), M. J)., *^ Pro/essor of Morbid Anatomy in the Bp.llevue ffospital Med. College, If. Y. A COMPLETE PRACTICAL TREATISE ON THE DISEASES OF CHILDKEN. SecoDd Edition, revised and greatly enlarged. In one handsome octavo volume of 742 pages, extra cloth, $5 ; leather, $6. {Now Ready,) From the Preface to the Second Edition. In presenting to the profession the second edition of his work, the author gratefully acknow- ledges the favorable reception accorded to the first. He has endeavored to merit a continuance of this approbation by rendering the volume much more complete than before. Nearly twenty additional diseases have been treated of, among which may be named Diseases Incidental to Birth, Rachitis, Tuberculosis, Scrofula, Intermittent, Remittent, and Typhoid Fevers, Chorea, and the various forms of Paralysis. Many new formulae, which experience has shown to be useful, have been introduced, portions of the text of a less practical nature have been con- densed, and other portions, especially those relating to pathological histology, have been rewritten to correspond with recent discoveries. Every effort has been made, however, to avoid an undue .enlargement .of the volume, but, notwithstanding this, and an increase in the size of the page, the number of pages has been enlarged by more than one hundred. 227 West 49th Street, New York, April, 1872. The work will be found to contain nearly one-third more matter than the previous Edition, and it is confidently presented as in every respect worthy to be received as the standard American text-book on the subject. Eminently practical as well as Judicious in its teachings. — Gincinnati Lancet and 0&«., July, 1872. A standard work that leaves littfe to be deaired. — Indiana Journal of Medicine, July, 1872. We k^ow of no book ou this subject that we can more cordially recommend to the medical student and thepra.ctitioner.—Gincinnati Clinic, June 29, *72. We regard it as superior to any other single work ou the diseases of infancy and childhood. — Detroit Sev. of Med. and Pharmacy, Aug. 1S72. We confess to increased enthusiasm in recommend- ing this second edition. — St. Louis Med. and Surg. Journal, Aug. 1872. rtONDIE (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 oloeely- • printed pages, extra cloth, $5 25 ,* leather, $6 25. {Lately Issued.) 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 certaiply has no equal. — iVew York Med. Hecord^ March 2, 1868. The present edition, which is the sixth, is fully np to the times in thediscussioaof all those points in the pathology and treatment of infantile diseases which have been brought forward by the German and French m'EST (CHARLES), M.D., ' ' Physician to the Hospital/or Sick Children, Ac. LECTURES ON THE DISEASES OP INFANCY AND CHILD- HOOD. Fourth American from the fifth revised and enlarged English edition. In one large and handsome octavo volume of 656 oloaely-printed pages. Extra cloth, $4 50; leather, $5 50. Of all the English writers on the diseases of chil- dren, there is no one so entirely satisfactory to us as Br. West, For years we have held his opinion as Jndicial, and ha^e regarded him as one of the highest living authorities in the difflcnlt department of medi' cal science in which he is most widely known.— Boston Med, and Surg, Journal, April' 26, 1866. VT THE SAME AUFHOB, (Lately Issued.) ON SOME DISORDERS OF THE NERVOUS SYSTEM IN CHILD- HOOD; being the Lumleian Lectures delivered at the Royal College of Physicians of Lon- don, in March, 1871. In one volume, small 12mo., extra cloth, $1 00. 'MITE [EUSTACE), M. D., Physician to the Northwest London Free Dispensary for Sick Children. A PRACTICAL TREATISE ON THE WASTING DISEASES OF INFANCY AND CHILDHOOD. Second American, from the second revised and enlarged English edition. In one handsome octavo volume, extra cloth, $2 50. {Lately Issued.) S^ This is in every way an admirable book. The modest title which the author has chosen for It scarce- ly conveys an adequate idea of the many subjects upon which it treats. Wasting is so constant an at- tendant upon the maladies of childhood, that a trea- tise upon the wasting diseases of children must neces sarily embrace the consideration of many affections of which it is a symptom ; and this is excellently well done by Dr. Smith. The book might fairly be de- scribed as a practical handbook of the common dis- eases of children, so numerous are the affections con- sidered either collaterally or directly. We are acquainted with no safer guide to the treatment of children's diseases, and few works give the insight into the physiological and other peculiarities of chil- dren that Dr. Smith's book does.— £rit. Med. Journ., April S, 1871. /^ UERSANT (P.), M. D., ^-^ Bonorary Surgeon to the Hospitalfor Sick Children, Paris. SURGICAL DISEASES OF INFANTS AND CHILDREN. Trans- lated by R. J. Dunglison, M. D. In one neat octavo volume, extra cloth, $2 50. {Now Ready) DBWEES ON THE PHYSICAL AMD MEDICAL TEEATMEHT OF OHILDEEN. Eleventh edition. 1 vol 8to. of S48 pages. $2 80. Henry C. Lea's Publications — {Diseases of Women). AVELINO {JAMES H.), and TUILTSHIRE {ALFBED), M.D., -^^ PhysUinn to the Hospital for Women and, <' AssiatantPhyel'^an- Accoucheur to St. Children. Gary's Hospital. THE OBSTETRICAL JOURNAL of Great Britain and Ireland; Including Mid'wifeey, nnd the' Diseases oj? Women and Infants. With an American Supplement, edited by Willtam F. Jbnks, M.D. A monthly of about 80 octavo pages, Tery handsoaely printed. Subscription, Five Dollars per annum. Single Numbers, 60 cents each. Commencing -with'April, 1873, the ObstetHonl Journal will consist of Original Papers by Brit, ish and Foreign Contributors ; Transactions of the Obstetrical Societies in England and abroad ; Reports of Hospital Practice; Reviews and Bibliographiiial Notices ; Articles and Notes, Edito- rial, Historical, Forensic, and Miscellaneous ; Selections from Journals; _Oori:espondence, &c. Collecting together the vast amoiint of material daily accumulating iH this iniportant and ra- pidly improving department of medical science, the value of the information which it will pre- sent to the subscriber maybe estimated from the character of the gentlemen who have already promised their sijpport, including such names as those of Drs. Atthill, RbBERT Barnes, Henry Rennet, Thomas Chambers, Fleetwood Chcrohill, Matthews Duncan, QrAhy Hewitt, Braxton Hicks, Alfred Meadows, W. Leishman, Alex. Simpson Tyler Smith, Bdwakd J. Tilt, Spencer Wells, Ac. &e. ; in short,the representative men of British Obstetrics and Gyaoe- In order to render the Obstetrical Journal fuliy adeqiiate to the wants of the American profession, each number will contain a Supplement devoted to the advances made in Obstetrics and Gynffidology on this side of the Atlantic. This portion of the Journal will be under the editorial charge of Dr. William F. Jenks, to whom editorial oommutucations, exchanges, books for review, Ac, may be addressed, to the care of the publisher. . , , j , *.«* Gentlemen desiring complete sets will do well to forward their orders without delay! rrnOMAS (T.GAILLARD],M.D., ^ ^^^ J- Professor of Obstetrics, &o., in the College of Physicians and Surgeons, If. T., &c. A PRACTICAL TREATISE ON THE DISEASES OP WOMEN. Third edition, enlarged and thoroughly revised. In one large and handsome octavo volume of 784 pages, with 246 illustrations. Cloth, $5 00 ; leather, $6 00. (Just Issued.) The author has taken advantage of the opportunity afforded by the call for another edition of this work to render it worthy a continuance of the very remarka;ble favor with which it has been received. Every portion has been subjected to a conscientious revision, several new chapters have been added, aiid no labor spared to makeit a complete treatise on the most advanced con- dition of its important subject. The present edition therefore contains about one-thifd more matter than the previous one, notwithstanding which the price has been maintained at the former very moderate rate, rendering this one of the cheapest volumes accessible to the profession Aa compared with the first edition, five new cTiap- ters on dysmeuorrhrea, peri-uterine fluid tumors, composite tumors of the ovary, solid' tumors of the ovary, and chlorosis, have been added. Twenty- sevea additional wood-cuts have been introduced, many suljjects have been subdivided, and all have received important interstitial increase. In fact, the book has been praotically rewritten, and greatly in- creased in value. Briefly, we may say that we know of no book which so completely and concisely repre- sents the present state of gynecology ; none so full of well-digested and reliable teaching ; none which bespeaks an author more apt in research and abun- dant in resources. — N: Y. Med. Record, May 1, IS72. "We should not be doing our duty to the profession' did we not tell those who are unacquainted with the book, how much it is valued by gynfflcologists, and how it is in many respects one of the best text-books on the subject we possess in our language. We have _ no hesitation in recommending Dr. Thomas's work as one of the most cotaplete of its kind ever published. It should be in the possession, of every practitioner for reference and for study.— ioradora Lancet, April 27, 1872i. Our author is not one of those whose views * ' never change.'* On the contrary, they have been modified in many particulars to accord with the'progress made in this department of medical science : hence it has the freshness of an entirely new work. No general prac- titioner can afford to be without it. — St. Louis Med. and Surg. Journal, May, 1873. Its able author need not fear comparison between it and any similar work in the English language ; nay more, as a text- book for students and as a guide f ir practitioners, we believe it is unequalled. In the libraries of reading physicians we meet with it oftener than any other treatise on diseases of womep. Weconclnde our brief review by repeating the hearty commendation of this volume gi'-en when we com- menced: if either student or practitioner can get hut one book on diseases of women, that hook should he "Thomas." — ^jner. Jour. Med. Sciences, ti-sril, 1872. We are free to say that we regard Dr. Thomas the beet Americanauthority on diseases of women. Seve- ral others have written,, and written well, but none have so clearly and carefully arranged their text and instruction as Dr. Ihom&s.—OinotnnaitLancaanil Observer, May, 1S72. We deem it scarcely necessery to recommend this work to physicians as it is now wide^ known, and most of them already possess it, or wRl 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. Sazette, June, 1869. If not the best work extant on the subject of which It treats, it is certainly second to none 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 now flrtaly established as tfte American text-book of Gynacology.— JT. T. 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- flrmed the opinion we gave at that time.— Cincinnati Lancet, Aug. 1869. It is 80 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.— .y. T. Med. Journal, April, 1869. Henry C. Lea's Publications — (Diseases of Women). JTODGE (HUGH L.), M.D., ■*-*■ Smerittia Professor of Obstetrics, Ac, in the Vniversfiy of Pennsylvania. ON DISEASES PECULIAH TO WOMEN; including Displacements of the Uterus. With original illustrations. Second edition, revised and enlarged. In one beautifully printed oc,taTO 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 made 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 Prof. "W. H. Btford, of the Sitsh Medical Gollege, Chicago. The book bears tlie impress of a master hand, ai^d must, as its predecessor, prove acceptalile to the pro- fession. Id 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- rase its pages without learning something new. The book, which Is by no means a large one, is divided into two grand sections, eo 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 whiich 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 refprred to by our author. As a coDtrihution to the study of women's diseases, it is of great value, and is abundantly able to stand on Us 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 render it doubly welcome. —Pacific Med. and Surg. Journal, Oct. 1868. "W-EST (CHARLES), M.D. LECTURES ON THE DISEASES OF WOMEN. Third American, from the Third London edition. In one neat octavo volume of about 550 pages, extra 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. 1861. 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 of ten years' patient investiga- tion in one 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 vast amount of Instruction he has afforded ias. ^is valuable treatise needs no eulojgy 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 revise^, and Is well worthy of the fame it ha& already obtained. — D-ub. Med. Quar. Jour. As a writer. Dr. West stands, lu our opinion, se- cond only to Watson, the "Macaulay of Medicine;" 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 road 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. — If. A. Med.-Ohirurg 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. — iV. T.Joumalqf Medicine. We have to say of it, briefiy and decidedly, that it is the best work on the subject in any language, and that it stamps Dr. West as the facile princes 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. T>ARNES (ROBERT), M. D., F.R. G.P., , -*-' Obstetric Physician to St. Thomas* s Hospital, Ac. A CLINICAL EXPOSITION OP THE MEDICAL AND SURGI- C AL DISEASES OF WOMEN. In one handsome octavo volume with illustrations. (Fre- paring,) CHnRCHILL ON THE PUERPEKAL FEVER AND OTHER DISEASES PECULIAR TO WOMEN. 1 vol. 8vo., pp. 4fj0, extra cloth. $2 dO. DEWEES'S TREATISE ON THE DISEASES OF FE- MALES. With Illustrations. Eleventh Edition, with the Author's last improvements and correc- tions. In one octavo volume of 536 pages, witl plates, extra cloth. $3 00. WEST'S ENQUIRY INTO THE PATHOLOGICAL IMPORTANCE OP ULCERATION OP THE OS UTERI. 1 vol. iivo., extra clotb. $1 2j. MEIGS ON WOMAN: HER DISEASES AND THEIK REMEDIES. A Series of Lectures to his Class. Fourth and Improved Edition. 1 vol. 8vo., over 700 pages, extra cloth, $5 00 ; leather, *6 00. MEIGS ON THE NATURE, SIGNS, AND TREAT- MENT OF CHILDBED FEVER. 1 voL 8vo., pd 365, extra cloth. %i 00. ASHWELL'S PRACTICAL TREATISE ON THE DIS- EASES PECULIAR TO WOMEN. Third American, from the Third and revised London edition 1 vol' 8vo., pp. 828, extra cloth. $3 60. 24 Henry C. Lea's Publications — {Midwifery). JJODOE [HOGH L.), M.I)., EmerUws Profeaaor of Midwifery, &e., in ihe tTniverHty of Pennsylvania, ie. THE PRINCIPLES AND PRACTICE OP OBSTETRICS. Illus- 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 almple 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 vblume the whole science and art of Obstetrics. An elaborate text is combined with accnrate and va- ried pictorial illustrations, so that no fact or principle Is left unstated or unexplained. — Am. Med. Times, Sept. 3, lS64:i 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, en receipt of six cents in postage stamps. JIANNER {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 on wood. In one handsoicne octavo volume of about 500 pages, extra cloth, $4 25. We have examined Professor Hodge's work with great-satisfaction; every topic is elaborated most fully. The views of the author are comprehenglve, and conqisely stated. The rules of practice are judi- cious, and will enable the practitioner to meet every emergency of obstetric complication with confidence. — Qhicago 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. — Pacijit 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 certain! y highly instructive, and in the main, we believe, correct. The great attention wjiich the author has devoted to the mechanism of partui'ition, 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. The very thorough revision the work has undergone has added greatly to its practical value, and inci-eased materially its efiiciency as a guide to the student and to the young practitioner. — Am. Journ. Med. Sci., April, 1868. With the immense variety of subjects treated of and 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- mend 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.— iV. T. Med. Record, March 16, 1868. We bave much pleasure in calling the attention of our readers to the volume produced by Dr. Tanner, the second edition of a woi'k that was, in its original state even, acceptable to the profession. We recom- mend obstetrical students, young and old, to have this volume ii) their collections. It contains not only a fair statement of the signs, symptoms, and diseases of pregnancy, but comprises in addition much inter- esting relative matter that is not to be found in any other work that we can name. — Edinburgh Meti. Journal, Jan. 1868. s WAYNE [JOSEPH GRIFFITHS), M.D., Physician- Aeeoucheur to the British General Hospital, &o. OBSTETRIC APHORISMS FOR THE USE OF STUDENTS COM- MENCING MIDWIFERY PRACTICE. Second American, from the Fifth and Revised London Edition, with Additions by E. R. Hutchins, M. D. With Illustrations. In one neat 12mo. volume. Extra cloth, $1 25. {Now Ready.) answers the purpose. It is not only valuable for youifg 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. Jmtrnal, Sept. 10, 1870. A studied perusal of this little book baa 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 refponsibility, and when he ought to send for assistance. — if. Y. Medical Journal, May, 1870. It is really a capital little compendium of the sub- ject, and we recommend youngpractitioners to buy it and carry it with them when called toattend 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 materiaUy added by his notes and the concluding chapters to the com- pleteness and general value of the hoo'k.'^Ghioago Med. Journal, Feb. 1870. The manual before us containsin exceedingly small compass — small enough to carry in the pockei — 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. 'i^bis is a mostadmirable little work, and completely T][riNCKEL [F.], ' ' Prn/essnr and Director of the Gynmcological Clinic in the Unifoersify of Rostock, A COMPLETE TREATISE ON THE PATHOLOGY AND TREAT- MENT OF CHILDBED, for Students and Practitioners. Translated, witli the consent of tlie author, from the Second German Edition, by James Read Chadwick, M D. In one octavo volume. (Preparing ) Henet 0. Lba's Publications — (Midwifery). 25 ILfEIOS (CHABLES D.), M.D., ^^ Lately Professor of Obetetrtcs, &o. , in the Jefferson Medical Oollege, 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 oar author has more par- ticalarly 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.— Canada Medical Journal^ July, 1867. The original edition is already so extensively and Tavorably 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 ralnable acquisition to the practitioner, it is eo con- densed as to constitute a moist eligible and excellent text-book for the student.— iSou^Aern Med. and Surg. Journal^ July, 1867. pAMSBOTEAM {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, &c., in the Jefferson Medical College, Philadelphia. In one large and handsome imperial octavo volume of 650 pages, strongly bound in leather, with raised bands; with sixty-four beautiful plates, and numeroas 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 practitipner will find U, as a book of reference, surpassed by none other. — St^hoscope. The character and merits of Dr. Bamsbotham'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. 5^0 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 ed ucation 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. QHUBGHILL [FLEETWOOD), M.D., M.R.I. A. ON THE THEORY AND, PRACTICE OP MIDWIFERY. Anew 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,'' &o. 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 Midwives 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 almost 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 workp on this branch of medical science are equal to it, certainly none excel it, whether in regard ko theory or practice, and In one respect it is superior to all others, viz., in its Btatistical 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. Journcd. llfONTGOMERY (W. F.), M.D., Professor of Midvnfery in the King^ 8 and Queen* s CoUege of Physicians in Ireland. AN EXPOSITION OE THE SIGNS AND SYMPTOMS OE PREG- NANCY. With some other Papers on Subjects oonueoted with Midwifery. From the second and enlarged English edition. With two exquisite colored plates, and numerous wood-cuts. Id one very handsome octavo volume of nearly 600 pages, extra cloth. $3 75. BIOBT'S STSTBM OF MIDWIFEKT. With Notes And Additional lUnstratiouH. Second American edition. One volume octavo, extra cloth, 122 pag^s. •2 SO. DEWEES'S COMPKEHENSIVE SYSTEM OF MID- WIFEBT. Twelfth edition, with the anthor's last ImproTements and oorrectlons. In one octavo vol- ume, extra cloth, of 800 pages. ^ 60. Henry C. Lea's Publications — (Surgery). Q' IS OSS {SAM DEL D.), M.D., Pro/easor of Surgery in the Jefferson Medical College of PMladelpMa. A SYSTEM OF SURGEEY: Pathological, Diagnostic, Therapeutic, and Operative. Illustrated by upwards of Fourteen Hundred Engravings. Fifth edition carefully revised, and improved. In two large and beautifully printed imperial octavo vol! umes of about 2300 pages, strongly bound in leather, with raised bands, $ 1 5. {Just Ready.) 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. In the present revision no pains have been spared by the author to bring it in every respect fully up to the day. To effect this a large part of the work has been rewritten, and the whole enlarged by nearly one- fourth, notwithstanding which the price has been kept at its former very moderate rate. By the use of a close, though ve;:y 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 bo the domain of surgery is treated in detail, so that the student who possesses this work may be aaid to have in it a surgical library. It must long remain the most comprehensive work oa this important part of medicine.— 5o*to» Medical and Surgical Journal^ March 23, 1865. We have compared it with most of our standard works, such as those of Erichsen,, Miller, -Eergusson, 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' minutPe 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 Ms 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 iis upon the shelves of our library. — Ganada 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 recommenda>tion . of [he work, both as regards matter and style, which we made when noticing its first appearance. — British and Foreign Medico- Chirurgical Re^ieio, Oct. 1865. The most complete work that has yet issued from!' the press on the science and practice of surgery. — Lundon Lancet. This system of surgery is, we predict, destined to take a commanding position in our surgical litera- ture, and be ihe crowning glory of the author's well earned fame. As an authority on general surgical subjects, this worli is long to occupy a pre-emineni place, not only at home, hut abroad. We have no hesitation in pronouncing it without a rival in oqr language, and equal to the best systems of surgery in any language.— iV. Y. Med. Journal. Wot only by far the best textrbook on the subject, as a whole, within the reach of American students, but one wl^ich will be much more tli^n ever likely to be resorted to and regarded as a-high' authority abroad.— .4m. lov/rnal Med. Science, Jan. 1865. The work contains everything, minor and major, operative and diagnostic, ihcluding mensuration and examination, venei'eal diseabos, and uterine manipu- ,lation8 and operations. It is a complete Thesaurus of modern surgery, where the student and practi- tioner snail not seek in vain for what they desire.— San Francisco Med. Pr^a, Jan. 1865. Open it wherb we may, we find sound practical in- formation conVriy6d 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) sCrOhg claim on the gratitude of the f ature of surgical sciencQ.—EdiTUnirgh Med. Jowmal, Jan. 1805. A glance at the w-ork Is sufficient to show chat the author and publisher have spared no labur in making it the most complete '.'System of Surgery" ever pub- liphed in any country.— 5^. Louia Med. and Surg. Journal, April, 1865. A system of surgery which we think unrivalled in our language, and which will indelibly associate hie name with surgical science. And what, in onr opin- ion, enhances the value of the work is that, while the practicing 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 snbiie- quently to follow. — The Brit. Am.Journ., Montrml. DY THE SAME AUTHOR. A PRACTICAL TREATISE ON FOREIGN BODIES IN THE AIR-PASSAGES. In 1 vol. 8vo. cloth, with illustrations, pp. 468. $2 75. SKET'S OPERATIVE SUKGERY. In 1 vol. Svo. cloth, of over 650 pages; with about 100 wood-cats. COOPER'S LECTURES ON THE PRINCIPLES AND Practice op SuaaEKT. In 1 vol. Svo. cloth, 750 p. $2. GIBSON'S INSTITUTES AND PRACTICE OP SUR- QEHY. Eighth edition, improved and altered. With thirty-four plates. In two handsome octavo vel- umei^, abouLlOOO pp., leather, raised bands. $6 50. MILLER {JAMES), J-KM. jjote Professor ofSiergery in the University of Edinburgh, &e. 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. $3 75. DF TMS SAME AUTHOR. THE PRACTICE OF STTRGERT. Fourth American, from the last Edinburgh edition. Sevised b; the American editor. Illustrated by three hundred and gixty-four engravings on wood. In one large octavo volume of nearly 700 pages, extra cloth. $3 75. ^ARGENT {F. W.), M.D. ON BANDAGING AND OTHER OPERATIONS OF MINOR SUR- GERY. N'ew edition, with an additional chapter on Military Surgery. One handsome royal 12mo. volume, of nearly 400 pages, with 184 wood-cuts. Extra cloth, $1 76. Henry C. Lea's Publications — (Surgery). 27 J^SHHURST [JOHN, Jr.), M.D., Surgeon to the EpUcnpal Esopital, FhilacUVphia. THE PRINCIPLES AND PRACTICE OF SURGERY. In one very large and handsome octaTO volume of aboat 1000 pages, with nearly 550 illustrations, extra cloth, $6 50; leather, raised bands, $7 50, {Just Issued.) The object of the author has been to present, within as condensed a compass as possible, a complete treatise on Surgery in all its branches, suitable both as a text-book fpr the student and a work of reference for the practitioner. So much has of late years J}een done for the advance- ment of Surgical Art and Science, that there seemed to be a want of a work which should present the latest aspects of every subject,, ^nji which, by its American character, should render accessible to the profession at large the experience of the practitioners, of both hemispheres. This has been the aim of the author, and it is hoped that the volume will b.e found to fulfil its purpose satisfac- torily. The plan and general outline of the work will be seen by the annexed CONDENSED SUMMARY OF CONTENTS. Chapter I. Inflammation. II. Treatment of Inflammation. III. Operations in general : Anaesthetics. IV. Minor Surgery. V. Amputations. VI. Special Amputations. VII. Effects of Injuries in General : Wounds. VIII. Gunshot Wounds. IX. Injuries of Bloodvessels. X. Injuries of Nerves, Muscles and Tendops, Lymphatics, Bursse, Bones, apji Joints. XI. Fractures. XII. Special Fractures. XIII. DislbcatiOns. XIV. Effects of Heat and Cold. ' XV. Injuries of the Head. XVI. Injuries of the Back. XVII. Injuries of the Fac,e and Neck. XV III. Injuries of the Chest. XIX. Injuries of the Abdomen and Pelvis. XX. Diseases resulting from Inflammation. XXI. Erysipelas. XXII. Pyaemia. XXIII. Diathetic Diseases : Struma (in- cluding Tubercle and Scrofula); Rickets. XXIV. Venereal Diseases ; ^Gonorrhoea and Cbancroid. XXV. Venereal Diseases continued : Syphilis. XXVI. Tumors., XXVII. Surgical Diseases of Skin, Areolar Tissue, Lymphatics, Muscles, Tendons, and Bursee. XXVIII. Surgical Disease of Nervous System {including Tetanus). XXIX. Surgical Diseases of Vascular System {includ- ing Aneurism). XXX. Diseases of Bone. XXXT. Diseases of Joints. XXXII. Excisions. XXXIII. OrthopEBdic Surgery. XXXIV. Diseases of Head and Spine. XXXV. Diseases of the Eye. XXXVI. Diseases of the Bar. XXXVII. Diseases of the Face an ji Nec-k. XXXVIII. Diseases of the Mouth, Jaws, and Throat. XXXIX. Diseases of the Breast. XL. Hernia. XLX. Special Hernise. XLII. Diseases of intestinal Canal. XLIII. Diseases of Abdominal Organs, and various operations on the Abdomen. XLIV. Urinary Calculus. LXV. Diseases of Bladder and Prostate. XLVI. Diseases of Urethra. XLVII. Diseases of Generative Organs. Index. Its author has evidently tested the writings an4 experiences of the pHst and present in the crucible of a careful, analylic. and honorable mind, and faith- fully endeavored to bring his work up to the level of the highest standard of practical surgery He is fraak and definite, and gives ub opinions, and gene- rally sound ones, instead of a mere r'esu-m'e of the opinionB of others He is conservative, but not hide- bound by authority. His style is clear, elegant, and scholarly. The work is an admirable text hook, and a useful book of reference It is a credit to American professional literature, and one of the first ripe fruits of'the soil fertilized by the blood of our late unhappy M7AV.—N. Y. Med. Record, "Feb. 1, 1S72. Indeed, the work as a whole must be regarded as an excellent and doncise exponent of modern sur- gery, and as such it will be found a valuable text- hook for the student, and a useful book of reference for the general practitioner,— if. X. Med. Journal, Feb. 1872. , Itgivps us great pleasure to call the attention of the prqfession to this ejccellent work. Our knowledgeof ttstaientedand accomplished author led us to expect from him a very valuable treatise upon subjects to which he has repeatedly given evidence of having pro- fitably devoted much timeaud labor, and we are in no way dieappointed-— f/i^^. Med. 2^meff,I'eb. 1, 1872. piRRIE ( WILLIAM), F, R. S. E., -*■ Professor of Surgery in the University of Aberdeen. THE PRmOIPLES AND PRACTICE OP SURGERY. Edited by John Neill, M. D., Professor of Surgery in the Pepna. Medioal College, Surgeon to the Pennsjlrania Hospital, ha. In one very handsome octavo volume of 780 pages, with 3](i illustrations, extra cloth. $3 75. TJAMILTON (FRANK K), M.D., Professor of Practures and IHslocations, Ac, in BeUeoue Hosp. Med. OqUege, New York. A PRACTICAL TREATISE ON FRACTURES AND DISLOCA- TIONS. Fourth edition, thoroughly revised. In one large and handsome octavo volume ol nearly 800 pages, with several hundred illustrations. Extra cloth, $5 75; le9.ther, $6 75. {J^(.st Issued. ] It is not, of course, our intention to review, in ex- tenao, Hamilton on "Fractures and Dislocations." Eleven yejirs ago such review might hot'have been out of place ; to-day the work is an authority,. so well, so generally, and so favorably known, that it only remains for the reviewer to say that a new edition is just out, and it is better than either of its predeces- sors. — Cincinnati Clinic, Oct. 14, 1S71. Undoubtedly the best work on Fractures and Die- locations in the English language. — Cincinnati Med. Repertory, Oct. 1871. We have once more before us Dr. Hamilton's admi- rable treatise, which we have always considered the most complete and reliable work on the subject. As a whole, the work is without an equal in thelitera- tnre of the profession. — Boston Med. and Surg 'Jowrn., Oct. 12, 1871. It is unuecessary at this time to commend the book, except to such as are beginoers in the stiidy of this particular branch of surgery. Every practical sur- geon ib this country and abroad knows of it as a most trustworthy guide, and one which they, in common with ns, would unqualifiedly recommend as the high- est authority in any language. — N. Y,-Med. Record Oct IB, 1871. M ORLAND (TT. W.), M.D. DISEASES OF THE URINARY ORGATsTS; a Compendium of their Diagnosis, Pathology, and Treatment. With illustrations In one large and handsome ootavo volume of about 600 pages, extra cloth. $3 60. 28 Hbnrt C. Lea's Pttblioations — (Surgery). PJRIOBSEN (JOHN E.), ■*-• Professor of Surgery in University College, London, etc. THE SCIENCE AND ART OP SURaERY; being a Treatise on Sur- gical Injuries, Biseases, and Operations. Revised by the author from the Sixth and enlarged English Edition. Illustrated by over seven hundred engravings on wood. In two large and beautiful octavo volumes of over 1700 pages, extra cloth, $9 00 ; leather $11 00. {Just Ready.) Author^s "Preface to the New American Edition. ' ' The favorable reception with which the ' Science and Art of Surgery* has been honored by the Surgical Profession in the United States of America has been not only a source of deep gratifica- tion and of just pride to me, but has laid the foundation, of many professional friendships that are amongst the agreeable and valued recollections of my life. "I have endeavored to make the present edition of this work more deserving than its predecessors of the favor that has been accorded to them. In consequence of delays that have unavoidably occurred in the publication of the Sixth British Edition, time has been afforded to me to add to this one several paraigraphs which I trust will be found to increase the practical value of the work.'* London, Oct. 1872. On no former edition of this work has the author bestowed more pains to render it a complete and satisfactory exposition of British Surgery in its modern aspects. Every portion has been sedu- lously revised, and a large number of new illustrations have been introduced. In addition to the material thus added to the English edition, the author has furnished for the American edition such material as has accumulated since the passage of the sheets through the press in London, so that the work as now presented to the American profession, contains his latest views and experience. The increase in the size of the work has seemed to render necessary its division into two vol- umes. Great care has been exercised in its typographical execution, and it is confidently pre- sented as in every respect worthy to maintain the high reputation which has rendered it a stand- ard authority on this department of medical science. These are onl^ a few of tlie points in which the preaeut edition of Mr. Erichsen'E work surpasseH its predecessors. Throughout there is evidence of a laborious care and 'solicitade in seizing the passing knowledge of the day, which reflects the greatest credit on the author, and much enhances the value of his work. We can only admire the industry which has enabled Mr. Ericheen thun to succeed, amid the distractions of active practice, in producing emphatic- ally THE book of reference and study for British prac- titioners of surgery. — London Lancet, Oct. 26, 1872. Considerable changes have been made in this edi- tion, and nearly a hundred new illn'strations have been added. Itls difiicult in a small compass to point out the alterations and additions ; for, as the author states in his preface, theyare not confined to anyone portion, but are distributed generally through the .subjects of which the work treats. Certainly one of the mof^t valuable sections of the hook seems to as to be that which treats of the diseases of the arteries and the operative proceedings which they necessitate. In few text-books is so much carefully arranged in- formation collected. — London Med. Times and Gaz., Oct. 26, 1872. The entire work, complete, as the great English treatise on Surgery of our own time, is, we can assnre our readers, equally well adapted for the most junior student, and, asa book of reference, for the advanced practitioner. — Dublin Quarterly Journal. ■DT THE SAME AUTHOR, {Just Issued.) ON RAILWAY, AND OTHER INJURIES OF THE NERYOUS SYSTEM. In a small octavo volume. Extra cloth, $1 00. D RUITT (ROBERT), M.R.C.S., J-c. 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 f leather, $5 00. perspicuously, as to elucidate every important topic. The fact that twelve edilions have already been called for, in these days of active competition, would of Itself show it to possess marked anperiority. We have examined the book most thoroughly, and can say that this success is well merited. His book, moreover, possesses the inestimable advantages of having the subjects perfectly well arranged and das- ufled, and of being written in a style at once clear md succinct. — Am. Journal of Med. Sciences. All that the surgical student or practitioner could desire. — DtMin Quarterly Journal. It is a most admirable book. We dp not know when we have examined one with more pleasure. — Boston Med, and Surg. Journal. In Mr. Druitt's book, though containing only some seven hundred pages, both the principles and the , practice of surgery are treated, and so clearly and ASnTON{T. J.). ON THE DISEASES, INJURIES, AND MALFORMATIONS OF THE RECTUM AND ANUS ; with remarks on Habitual Qonstipation. 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. niGELO W {HENRY J.), M. D., •^ Professor of Surgery in the Massachusetts Med. College, ON THE MECHANiSM OF DISLOCATION AND FRACTURE OF THE HIP. With the Reduction of the Dislocation by the FJexion Method. With numerous original illustrations. In one very handsome octavo volume. Cloth. $2 50. {Lately/ Issued.) Heney C. Lea's Publications — (Surgery). 'DRYANT (THOMAS), F.B.C.S., -*-' Surgeon to Ouy^s Hospital. THE PRACTICE OF SURGERY. With over Five Hundred En- gravings on Wood. In one large and very handsome octavo volume of nearly 1000 pages, extra cloth, $6 25 ; leather, raised bands, $7 25. {Jtist Ready.) The distinguished reputation of. the author and the extended experience which he has enjoyed as surgeon to one of the largest of the London hospitals, are an earnest of the value of his labors. Though entitled a "Practice of Surgery," it will be seen by the subjoined summary of the contents that it is by no means confined to operative surgery, but that it presents also a view of the prin- ciples which should guide the surgeon in his daily practice. Nearly all of the very full series of, illustrations have been prepared expressly for the work. iNTBODUCTioif. — I. On Eepair and Inflammation, ii. On Traumatic Fever, Septicaemia, and Py- aemia. III. On Trismus and Tetanus, iv. Delirium Tremens, v. Contusions : Wounds of the Scalp, Blood Tumors, Osteitis, vi. Injuries of the Cranium, Tii. Concussion of the Brain. Tin. Injuries of the Brain and its Membranes, complicating Fracture, ix. Compression of the Brain, x. £e- sults of Injuries to the Head, xi^ On Fractures of the Skull, xii. The Operation of Trephining. XIII. Diseases of the Scalp and Cranium, xiv. Spina Bifida. XV. Injuries of the Spine, xvi. lutira-Spinal Inflammation, Spinal Paralysis, Railway Concussion, xvii. Fractures, Dislocations, and Wounds of the Spine, xviii. Curvature of the Spine, xix. Injuries and Diseases of the Nerves. XX. Surgical Affections of the Nose. xxi. Surgical Affections of Larynx and Trachea, xxii. Sur- gery of the Chest, xxiii. Wounds of the Heart, xxiv. Diseases of the Arteries, xxv. Aneurism. XXVI. Ligature of Arteries, xxvii. Injuries and Diseases of the Veins, xx^viii/ Affections of the Lips, etc. XXIX. Diseases of the Jaws, etc. xxx. Affections of the Pharynx, xxxi. Injuries of the Abdomen, xxxir. Hernia, xxxiii. Varieties of Hernise. xxxiv. Trusses, xxxv. Surgery of the Anus, xxxvi. Diseases of the Integuments : Wounds, xxxvii. Poisoned Wounds, xxxviii. Burns, xxxix. Skin Grafting. XL. Boils, etc. XLi. Gangrene, etc. XLii. Ulcers. XLiii. mor- tification. XLiy. Erysipelas, xlt. Diseases of the Lymphatics. XLYI. Diseases Of the Kidney. XLVii. Diseases of the Bladder, xltiii. Diseases of the Prostate, xlix. Urinary Deposits, i.. Stone in the Bladder. Li. Lithotrity. Lii. Lithotomy. Liii. Stone in the Female Bladder. Liv. Stricture of the Urethra, lv. Retention of Urine. Lvr. Afi'ections of the Penis. Lvii. Haeraato- cele, etc. lviii. Diseases of the Testicle. Lix. Sterility. LX. Affections of the Female Geni- tals. LXi. Ovariotomy, lxii. Venereal Disease, lxiii. Syphilis. LXiv. Tumors. Lxv. Anatomy of Tumors, lxvi. Tumors of the Breast, lxvii. Diseases of the Thyroid Gland, lxtiii. Wounds of the Joints. LXix. Dislocations. Lxx. Dislocations of the Upper Extremity. Lxxi. Disloca- tions of tho Lower Extremity, lxxii. Pathology of Joint Diseases. Lxxiii. Diseases of Special Joints. Lxxiv. Treatment of Joint Disease, lxxv. Excision and Amputation in Joint Disease. Lxxvi. Osteo-arthritis. Lxxvii. Diseases of the Bones, lxxviii. Tumors of Bone. Lxxix. Frac- tures. Lxxx. Fractures of the Upper Extremity. Lxxxi. Fractures of the Lower Extremity. Lxxxii. Complicated Fractures, lxxxiii. Gunshot Injuries. Lxxxiv. Feigned and Hysterical Dis- ease. Lxxxv. Affections of the Muscles and Tendons. Lxxxvi. Ganglions. Lxxxvii. Orthopeedic Surgery, lxxxviii. Ansesthetics. Lxxxix. Shock, xo. Amputation, xci. Special Amputations, xcii. Elephantiasis, xciii. Affections of the External Ear. xciv. Parasites. WELZaST (X 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 oloth, $5 00; leather, $6 00, {Lately Issued.) In this respect the work before us is of much more Bervice to the general practitioner than thoee heavy compilations which, in giving every person's views, too often neglect to specify those which are most in accordance with the author's opinions, or in general acceptance. We have no hesitation In recommending this treatise, as, on the whole, of all BngllKh works on the subject, the one best adapted to the wants of the general practitioner.— £d£ndur^A. Med, Journal, March, 1870. A treatise of rare merit. It Is practical, compre- hensive, and yet concise. Upon those subjects usually found difficult to the student, he has dwelt at length aqd entered into full explanation. After a careful perasal of its contents, we can unhesitatingly com- mend it to all who desire to consult a really good work on ophthalmic science. The American edition of Mr. Wells' treatise was superintended in its passage through the press by Dr. I. Minis Hays, who has added some notes of his own where it seemed desira- ble. He has also introduced more than one hundred new additional wood-cuts, and added selections from the test-types of Jaeger and of Snellen. — Leavenworth MecL. Herald, Jan. 1870. Without doubt, one of the best works upon the sub- ject which has ever been published ; it is uompleie on the subj ect of which it treats, and is a necessary work for every physician who attempts to treat diseases of the eye.— -Dominion Med. Journal, Sept. 1869. TA WSON (GEORGE), F. B. C. S., Engl, ■*-• Assistant Surgeon to the Royc^l London Ophthalmic Hospital, Moorjields, Ac. 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 oloth, $3 50. It is an admirable practical book in the highest and best sense of the phrase. — London Medical Times and OoMette, May 18, 1867. 30 Henkt C. Lea's Publications — {Surgery, &c.). TA URENCE {JOHN Z.), F. R. C. S., Editor of the OpMhalmic Bemew, &c. A HANDY-BOOK OF OPHTHALMIC SURGERY, for the use of Practitioaera. Second Edition, revised and enlarged. With numerous illustrations. In one very handsome octavo volume, extra cloth, $3 00. {Lately. Issued.) For those, however, who muBt assume the, care of diseases, and injuries of the e^e, and who are too much pressed for time to study the classic works on thesuhject, or those recently published by Stellwag, Wells, Bader, and others, Mr. Laurence will prove a safe and trastworthy guide. He has-described in this edition those novelties which have secured th.e conlEl- deuce of the profession since the appearance -of his last. To the portion of the book devoted to a de^^crip- tion of the optical defects of the eye, the publisher has given increase,d value by the addition of several pages of SneUeQ*B tebt-types, so generally used to test the acuteness of vision, and w^ich are difflcalt to ob- tain in this country. The volume has been conside- rably enlarged and improved by the revision and ad- ditions of its author, ,e3cprefi8|ly for ^the American edition,. — Am. Journ. Med. Sciences, Jan. lS70. jyjlLES {PHILIP S.), M. D., Surgeon V. S. J^. MECHANICAL THERAPEUTICS: a Practical Treatise on Surgical Apparatus, Appliances, and Elementary Operations : embracing ■ Minor Surgery, Band- aging, Orthopraxy, andthe Treatment of Braotures and Dislocations. With six hundred an'd 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 shonld in our opinion become a standard worls in the hands of evei-y 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. rp HO MP SON {SIR HENR Y) ', ■'- Surgeon and Professor of Clinical Surgery to University College Hospital. LECl^URES ON DISEASES OP THE URINARY ORGANS. With Illustrations on wood. In one neat octavo volame, extra cloth. $2 25. on which Sir Henry Thompson speaks with more au- thority than that in which he has specially gathered his laurels,; in addition to this, the converuational style of instruction, which is retained ia.filiese printed lectures, .gives them an attraciiveness which a sys- tematic treatise can never possess. — LoTUion Medical ^inies and Graeette, April 24, 1869. Thefee lectures stand the severe test. They are iU- structive without being tedious, and simple without being diffuse; and they include many of those prac- tical hints so useful for the student, and even, more valuable to the young practitioner. — Edinburgh Med. •Journal, April, 1869. Very few words of ours are necessary to reconlmend these lectures to the profession. There is ho Subject VT THE SAME AUTHOR, ON THE PATHOLOGY AND TREATMENT OF STRICTURE OF THE URETHUA AND URINARY' FISTUL.^. With plates and wood-outs. From the third and revised English edition. In one very handsome octavo volume, extracloth, %'6 &0. {Lately Ftibiished.) ■ # ' This classical work has so long b^en 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 a)i^l^o£ 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 acc,epted as the authority, upon the I ably known by thepi'ofei^^ion as thip before us, must Hubjects of which it treats, an extended notice would I create a demand for it frum those who would keep be a work of supererogation. The simple announce- 1 themselves well up in this department of surgery.— ment of another edition of a work so well, and favorr | St. Lo,uia Med. A^ehi'oes, Fdb. IS70. rPATLOR {ALFRED S.), M.D., •* ieeiurer on Med. JuHsp. and Chemistry in Chty^s HoepitaU MEDICAL JURISPRUDENCE. Seventh American Edition. Edited by John J. Reese, M.D., Prcf. of Med. Jarisp. in the Univ. of-Penn. in one large octavo volume. {Preparing.) The present edition of this valuable manual is a I partment of medicine for students atad the general great Improvement on those which have preceded it. practitioner in our language. — Boston Med. arid Surg. It makes thus by far the best guide-book in this de- f Journal^ Dec. 27, 1866. ■DY THE SAME AUTHOR. {Nearly Ready.) THE PRINCIPLES AND PRACTICE OP MEDICAL JURISPRU- DBNCB. Second Edition, Revised, with numerous Illustrations. I? two very large octavo volumes. This great work is now recognized in EngFand as the fullest and most anthoritative treatise on every department of its important subject. In laying it, in its improved form; before the Ameri- can profession, the pnblidhec trusts that it will assume the same position in this country. Henry C. Lea's Publications — (Psychological Medicine, dtc). 31 rPDKE {DANIEL HACK), M.D., -^ Joint author of ' * The Manual of PaychologiGal Medicine^ ' ' &c, ILLUSTRATIONS OF THE INFLUENCE OF THE MIND UPON THE BODY IN HEALTH' AND DISEASE. Designed to illustrate the Aotion of the Imagination. In one handsome octavo volume of 416 pages, extra cloth, $3 25. {Now Ready.) The object of the author in this work has been to show not only the effect of the mind in caus- ing and intensifying disease, but also its curative influence, and the use which may be made of the imagination and the emotions as therapeutic agents. Scattered facts bearing upon this sub-^ ject have long been familiar to the profession, but no attempt has hitherto been made to collect and systematize them so as to render them available to the practitioner, by establishing the seve- ral phenomena upon a scientific basis. . In the endeavor thus to convert to the use of legitimate medicine the means which have been employed so successfully in many systems of quackery, the author has produced a work of the highest freshness and interest as well as of permanent value. -DLANDFORD {G. FIELDING), M. D., F. R. C P., -^-' Lecturer on Psychological Medicine at the School of St. Qeorg^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 Kay, M. B. In one very handsome octavo Tolume of 471 pages: extra cloth, $3 25. {Just Issued.) This volume is presented to meet the want,' so frequently expressed, of a comprehensive trea- tise, in moderate compass, on the.pathologyj diagnosis, a,nd treatment of insanity. To render it of more value to the practitioner in this country, Dr. Ray has added an appendix which affords in- formation, not elsewhere to he found in so accessible a form, to physicians who may at any moment be called u^on to take action in relation to patients. It Batisi&es a want which must have heen sorely felt by the busy general practitioners of this country. It takes the form of a manual of clinical deecription of the Tarions forms of insanity, with a descriplion of the mode of examining persons snspec.ted of in- sanity. We call particular attention to this. feature of the book, as 'giving it a unique value to the gene- ral practitioner. If we pass from theoretical conside- rations to descriptions of the varieties of insanity as actually seen in practice and the appropriate treat- ment for them, we And in Dr. Blandford'ts wurk a considerable advance over previous writings on the subject. His pictures of the various forms of mental diijease are so clear and good that no reader can fail to be struck with their superiority to those given in irdia&ry manuals in the English language or (so far as onr owu reading extends) in any other. — London Practitioner, Feb. 1871, W: 'INSLOW (FORBES), M.D., D.G.L., §-c. ■ ON OBSCURE DISEASES OE THE BRAIN AND DISORDERS OP 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. TEA [HENRY C), SUPERSTITION AND FORCE: ESSAYS ON THE WACER 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. {nStely Published.) We know of no single work which cpntains, in so small a compass, so much illustrative of tbestrangest operations of the human mind. Foot-notes give the authority for each statement, showing vast research and wonderful industry. We advise our confr&res to read this book and ponder its teachings. — Chicago Med. Journal, Aug. 1870. As a work of curious inquiry on certain outlying points of obsolete law, "Superstition and Force" is one uf the most remarkable books we have met with. ^London Atfienceum, Nov. 3, 1866. He has thrown a greatdealof light upon what must be regarded as one of the most instructive tia well as interesting phases of human society and progress. . . The fuluess and breadth with which be has cai-ried out bis comparative survey of this repulsive field of history [Torture], are such as to preclude our doing justice to the work within our present limits. But here, &s throughout the volume, there will be found a wealth of illustration and a critical grasp of the philosophical import of facts which will reader Mr. Lett's labors of sterling value to the bistoncal stu- dent.— iOTirfon. Saturday Review, Oct. 8, 1870. As a book ofready reference on the subject, it is of the highest yalue.^- Westminster JReview, Oct. 1867. B J THE SAME AUTHOR. {Late y Published.) 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. The story was never told morejsalmly or with ^ literary phenomenon that the head of oneoftbe first American houses is also the writer of some of its most greater learning or wiser thought. We doubt, indeed. if any other study of this field can be compared with this for clearness, accuracy, and power. ^ — Chicago E.vanuner, Dec. 1870. Mr. Lea'slatestwork, "Studies in Church History," fully sustains the promise of the first. It deals with three' subjects — the Temporal Power, Benefit of Clergy, and flxcommunication, the record of whi<^ hais a peculiar importance for the English utudent, and is a chapter on Ancient Law likely to be regarded as final. We can hardly pass from our mention of such works as tbet-e — with which that on "Sac'erdotAl Celibacy" should be included — without noting the original books. — London AthencBum, Jan. 7, 1871. Mr. Lea lias done great honor to himself and this country by the admirable works he has written on eQclesiological a'ud cognate subj ects. We have already had occasion to commend his "Superstition and Force" and his "History, of Sacerdotal Celibacy." The pret-ent volume is fully as admirable in its me- thod oT dealing with topics and iuHhe thoroughnesh— a quality 80 frequently lacking in American authors— with which they are investigated. — N. Y. Jowmalof Psychol Medicine, July, 1^0. 33 Henry C. Lea's Publications. INDEX TO CATALOpUE. American Joarnal of the Medical Sciences American Chemist (The) .... Abstract, Half-Yearly, of the Sled Sciences Anatomical Atlas, by Smith and Horner Anderson on Diseases of the Skin Ashton on the Rectum and AniiB. Attfield'B Chemistry Asliwell on Diseases of Females Ashliarst'B 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 B.) Practical Chemistry Bowman's (John E.) Medical Chemistry Buckler on Bronchitis Bumstead on Venereal . . . Bumstead and CuUerier'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 Medioa . C hambevs on the Indigestions Chambers's Restorative Medicine 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 . CuUerier'e Atlas of Venereal Diseases Cyclopedia of Practical Medicine . Dalton's Human Physiolft^ . De Jongh on Cod-LiverOiL . De wees' s System of Midwifery Deweea on Diseases of Females . Dewees on Diseases of Children . Druitt's Modern Surgery Dunglison's Medical Dictionary . Dunglison'B Human Physiology . DungUson on New Remedies ELlia's Medical Formulary, by Smith . Brichsen's System of Surgery Ericbsen on Nervous Injuries Flint on 'Respiratory Organs . Flint on the Heart Flint's Practice of Medicine . Pownes's Elementary Chemistry . Fox on Diseases of the Stomach . Fttlleron the Lungs, &c. Green's Pathology and Morbid Anatomy Gibson's Surgery G luge's Pathological Histology, by Leidy Galloway's Qualitative Analysis . Gray's Anatomy Griffith's (R. E.) Universal Formulary Qi'oss ou Foreign Bodies in Air-Passages Gross's Principles and Practice of Surgery Gross's Pathological Anatomy Guersant on Surgical Diseases of Children Bartshorne's Essentials of Medicine . Hartsborne's Conspectus of the Medical Sciences Bamilton on Dislocations and Fractures Heath's Practical Anacomy . Hoblyn'B MedicaLDictionary' Bodge on Women . Hodge's Obstetrics . Hodges' 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. Handfleld) on Nervous Disorders Kirkes^ Physiology \ Knapp's Chemical Technology \Lea'6 Superstition and Force PAGE 1 11 3 Lea's Studies in Church History . 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'B Physiological Chemistry, 2 vols, Lehmann's Chemical Physiology . Ludlow'B Manual of Examinations Lyons on Fever . . Maclise's Surgical Anatomy . . . Marshall's Physiology .... Medical News and Library . Meigs's Obstetrics, the Science and 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 Uisemia . . , Neill and Smith's Compendium of Med. Science Neligan's Atlas of Diseases of the Skin Neligan on Diseases of the Skin . Obstetrical Journal .... Odling's Practical Chemistry Pavy on Digestion .... Prize Essays on Consumption Parrish's Practical Pharmacy Pirrie's System of Surgery . Pereira's Mat. Medica and Therapentica, abridged Quain and Sharpey's Anatomy, by Leidy Ranking's Abstract . ■. Radcllff and others on the Nerves, &c. Roberts on Urinary Diseases . Ramsbotham on Parturition . Rigby's Midwifery,. >■ . . . Rokitansky's Patholqgical Anatomy . Boyle's Materia Medica and Therapeutics Salter on Asthma . ■ . Swayne's Obstetric Aphorisms Sargent'^s Minor Surgery Sharpey and Qaain's Anatomy, by Leidy Simon's General Pathology . . Skey's Operative Surgery . Slade on Diphtheria , . . . j Smith (J. L.) on Children . . . fl 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 Stmt's Therapeutics .... Tanner's Manual of Clinical Medicine . Tanner on Pregnancy' .... Taylor's Medical Jurisprudence . Taylor's Principles and Practice of Med Jurisp. Tuke on the Influence of the Mind Thomas on Diseases of Females . Thompson on Urinary Organs Thompson on Stricture .... Todd on Acute I)iseases . . , . Wales on Surgical Operations Wals he on the Heart Watson's Practice of Physic . Wells on the Eye . . . ' . West on Diseases of Females West on Diseases of Children West on Nervous Disorders of Children West on Ulceration of Oa Uteri . What to Observe in Medical Cases Williams's Principles of Medicine Williams on Consumption . Wilson's Human A;iatomy . Wilson on Diseases of the Skin . Wilson's Plates on Diseases of the Skin Wilson's Handbook o^ Cutaneous Medicine WUson on Spermatorrhosa . Winslow on Brain and Mind Wiihler's Organic Chsmistry Winckel on Childbed Zei«8l on Venereal . - , . PA as 31