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SS = = RGU) Ty AIT STS , EM GALLEN MMe ESSERE uh ie ry iy eS = jy yy hed, OO MEE, MAE EAA < ig f SLA SL J WM EE LLL Na Ch VIN, MELBLEEEASEELEELE bbs Hi Ue CORNELL UNIVERSITY THE Hlower Beterinary Library FOUNDED BY ROSWELL P. FLOWER for the use of the N. Y. STATE VETERINARY COLLEGE 1897 Cornell University Library QP 31.S65 1890 The in of Will 3 1924 0 iii Date Due oot te Fett Library Bureau Cat. No. 1137 Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://archive.org/details/cu31924001042112 THs PES WOEOGY OF THE DOMESTIC ANIMAL A TExt-Book FOR VETERINARY AND MeEpicaL STUDENTS AND PRACTITIONERS. BY ROBERT MEADE SMITH, A.M., M.D., PROFESSOR OF COMPARATIVE PHYSIOLOGY IN THE UNIVERSITY OF PENNSYLVANIA; FELLOW OF THE COLLEGE OF PHYSICIANS AND ACADEMY OF THE NATURAL SCIENCES, PHILADELPHIA; OF THE AMERICAN PHYSIOLOGICAL SOCIETY; OF THE AMERICAN SOCIETY UF NATURALISTS; ASSOCIE ETRANGER DE La SOCIETE FRANGAISE D’HYGIENE, ETC. WITH OVER 400 ILLUSTRATIONS. PHILADELPHIA AND LONDON : F. A. DAVIS, PUBLISHER. 1890. No. 162 7h Entered according to Act of Congress, in the year 1889, by F. A. DAVIS, In the Office of the Librarian of Congress, at Washington, D. C., U.S. A. All rights reserved. Philadelphia: - The Medical Bulletin Printing House, 1231 Filbert Street. TO MY FRIEND AND TEACHER, CARL LUDWIG, IN HUMBLE RECOGNITION OF THE MANY FAVORS CONFERRED ON THE AUTHOR. PREFACE. In lecturing in the Veterinary Department of the Univer- sity of Pennsylvania the author has found it a serious disad- vantage that the students are compelled to rely solely on the notes that they may be able to take during the lectures. | While French students have access to the encyclopedic work of Colin, and those familiar with the German language to the admirable works of Schmidt-Milheim, Bruckmiiller, Munk, Ellenberger, Gurlt, Thanhoffer, Miller, and others, English- speaking students have absolutely no work to which they ean turn to obtain any application of the laws of physiology to the functions of the domestic animals. Commenced originally as outline notes for the author’s own use in lecturing, this work has been published at the request of his students, in the hope that it may supply them with an exponent of the laws of modern physiology applied, as far as possible, to the functions of the domestic animals, and that a recognition of its shortcomings may stimulate inves- tigation of this much-neglected branch of physiology. It is surprising, in view of the ceaseless activity of physiological students throughout all the world, that more attention has not been devoted to the application of improved methods of research to the study of the functions of animals so important in the domestic economy. Unfortunately, investigators in this domain may almost be counted on the fingers, and the field which is yet untouched is almost unbounded. The author, therefore, has been compelled to assume that in many cases the laws of the physiology of man, which, to be sure, have been deduced from experiments (v) vi PREFACE. on animals, are applicable to the vital processes of the domestic animals. Modern physiology rests on the application through experimental research of the laws of physics and chemistry. The fundamental principles of these sciences in their relation to biology have been, therefore, discussed somewhat at length. Experience has taught that a comprehension of the laws of life in the higher mammals is best attained after a familiarization with the vital operation of lower forms. The first part of this book, therefore, deals with the general laws of life, while in the second part these principles are applied to the study of the vital operations in the domestic animals, the study of each function being introduced by a sketch of the mode of development of the mechanism by which that function, in passing from lower to higher forms, is accom- plished. As far as possible the author has acknowledged in the text his indebtedness to various authorities for the matter or manner of his subject, though references to publications, as tending to confuse the student, have been omitted. For illustrations the author is indebted to the liberality of the publisher, Mr. Davis, and to Messrs. Blakiston and H. C. Lea & Co., of Philadelphia; Appleton, Wm. Wood & Co., and Macmillan, of New York; Ferdinand Enke, Stuttgart; Engelmann and F. C. W. Vogel, Leipsic; Paul Parey, Berlin; W. Braumiiller, Vienna; Carl Winter, Heidelberg; Hachette & Cie, Bailliére & Fils, Asselin & Cie, Paris; Simpkin, Marshall & Co., London; Moritz Perles, Vienna, and Hirschwald, Berlin. ROBERT MEADE SMITH. PHILADELPHIA: 332 SOUTH TWENTY-FIRST STREET, January 8, 1889, TABLE OF. CONTENTS. ‘ INTRODUCTION, . . A i PART I. GENERAL PHYSIOLOGY. Tur Puysrotocy or Anima CELLS. SECTION I. Tur STRUCTURE OF ORGANIZED BODIEs. I. THe GENERAL PROPERTIES OF aa a . . . II. THe OriGin or CELLS, . . ‘ III. Tue Mopirication 1n THe Form or ‘Dates, er ‘ ‘ IV. Tue DEVELOPMENT oF TIssUES AND ORGANS, . . SECTION II. CELLULAR PHYSICS. I. Tue Puysican PROCESSES In CELLS, 1. Cohesion, 38; 2. Adhesion, 40; 3. Capillarity, 40; 4. settler: 43 ; 5. Imbibition, 44; 6. Filtration, 48; 7. Diffusion of Liquids, 49; 8. Osmosis, 51; 9. Diffusion of Gases, 56 ; 10. Absorption of Gases, 58. II. Tue PHYSICAL PROPERTIES OF THE TISSUES, 1. Cohesion, 62 ; 2. Elasticity, 65; 3. Optical Cine 68; 4. Electrical Phenomena, 70. III. Mecuanican Movenmnrs IN CELLS, . 1. Motion Produced by Imbibition in Cells, 70 ; 2. Pipa ates. ments, 72; (1) Movements in Protoplasmic Contents of Cells, 73; (2) Ciliary Movement, 77; (8) Movement in Specialized Contractile Tissues, 81. GENERAL ConDITIONs GovERNING ProtopiasMic MovEMENT, . 1. Temperature, 82; 2. Degree of Imbibition, 82; 3. The Supply of Oxygen, 83; 4. Various Chemical and Physical Agents, 84. (vii) PAGE 37 61 70 82 vi PREFACE. on animals, are applicable to the vital processes of the domestic animals. Modern physiology rests on the application through experimental research of the laws of physics and chemistry. The fundamental principles of these sciences in their relation to biology have heen, therefore, discussed somewhat at length. Experience has taught that a comprehension of the laws of life in the higher mammals is best attained after a familiarization with the vital operation of lower forms. The first part of this book, therefore, deals with the general laws of life, while in the second part these principles are applied to the study of the vital operations in the domestic animals, the study of each function being introduced by a sketch of the mode of development of the mechanism by which that function, in passing from lower to higher forms, is accom- plished. As far as possible the author has acknowledged in the text his indebtedness to various authorities for the matter or manner of his subject, though references to publications, as tending to confuse the student, have been omitted. For illustrations the author is indebted to the liberality of the publisher, Mr. Davis, and to Messrs. Blakiston and H.C. Lea & Co., of Philadelphia; Appleton, Wm. Wood & Co., and Maemillan, of New York; Ferdinand Enke, Stuttgart; Engelmann and F. C. W. Vogel, Leipsic; Paul Parey, Berlin; W. Braumiiller, Vienna; Carl Winter, Heidelberg; Hachette & Cie, Bailliére & Fils, Asselin & Cie, Paris; Simpkin, Marshall & Co., London; Moritz Perles, Vienna, and Hirschwald, Berlin. ROBERT MEADE SMITH. PHILADELPHIA: 332 SouTH TWENTY-FIRST STREET, January 8, 1889, TABLE OF. CONTENTS. ; PAGE ' INTRODUCTION, . @ . : z . es . . . 1 PART I, GENERAL PHYSIOLOGY. Tur PuHystoLoay or ANIMAL CELLS. SECTION I. THE STRUCTURE OF ORGANIZED BopDieEs. I. Tue GENERAL PROPERTIES OF sais 3 ‘ ; ‘ » “12 II. Tue Oriein or Cetts, . eg ‘ ‘ . 14 JII. Tue MopIFrIcATION IN THE Penn OF Cas. is ‘ oe Fay 826 IV. Tue DEVELOPMENT OF TISSUES AND ORGANS, . . : . i SECTION II. CELLULAR PHysics. I. Tue Puysican Processus In CELLS, 3 37 1. Cohesion, 88; 2. Adhesion, 40; 3. Capillarity, 40; 4. deibben, 43 ; 5. Imbibition, 44; 6. Filtration, 48; 7. Diffusion of Liquids, 49 ; 8. Osmosis, 51; 9. Diffusion of Gases, 56; 10. Absorption of Gaises, 58. II. Tue PRysicaL PROPERTIES OF THE TISSUES, . : 61 1, Cohesion, 62 ; 2. Elasticity, 65; 3. Optical Sinaia 68; 4 Electrical Phenomena, 70. III. Mrecuanican AoyvuuENTS IN CELLS, . : ; . 10 1. Motion Produced by Imbibition in Cells, 70 ; 2. oe Move. ments, 72; (1) Movements in Protoplasmic Contents of Cells, 73; (2) Ciliary Movement, 77; (3) Movement in Specialized Contractile Tissues, 81. GENERAL ConDITIONS GovERNING ProtopLasMic MovEMENT, . . 82 1. Temperature, 82; 2. Degree of Imbibition, 82; 3. The Supply of Oxygen, 83; 4. Various Chemical and Physical Agents, 84. (vii) vill TABLE OF CONTENTS. SECTION III. CELLULAR CHEMISTRY. I. THE CHEMICAL CONSTITUENTS OF ORGANIZED BODIES, i A. Nirrocenous OrGcanitc CELL-CoNSTITUENTS—PROTEIDS AND THEIR DERIVATIVES, ; : : ; . : Class I. Albumens, 92; (1) Serum-Albumen, 92; (2) ie Ateineet 93; (3) Vegetable Albumens, 93. Class II. Globulins, 96; (1) Vitellin, 97; (2) Myosin, 97; (3) Para- globulin, 97; (4) Fibrinogen, 97; (5) Globulin or Crystallin, 97. Class III. Fibrins, 98. Class IV. Derived Albuminates, 98; (1) Acid Albumen, 98; (2) Alkali Albumen, 101. Class V. Coagulated Proteids, 102. Class VI. Amyloid Substance or Lardacein, 102. Class VII. Peptones, 103. ALBUMINOIDS, 3 ; ‘ : 1. Mucin, 104; 2. Gaia Muntueaes 105 ; a Collagen, 106; (b) Gelatin, 106; (¢) Chondrogen, 107; (d) Chondrin, 107; 3. Elastin, 108; 4. Keratin, 109. . DECOMPOSITION OF ALBUMINOUS BoptrEs, FERMENTS, B. Non- NiROGENGUE Graunic ne Con semmene I. CARBOHYDRATES, . (a) Starches, 112; (1) eee 118; _ aia 115 ; (as Dextrin, 116 ; (4) Glycogen, 116; (5) Inulin, 116. (b) Glucoses, 117; (1) Grape-Sugar, 117; (2) Lievulose, 118; (3) Inosite, 118. (c) Saccharoses, 119; (1) Cane-Sugar, 119; (2) Maltose, 120; (3) Lac- tose, 120; (4) Arabin, 120. II. Hyprocargpons or Farts, C. InorGantc CELL-CONSTITUENTS, : 1. Water, 124; 2. Sodium Chloride, 128; 3. Potassium Chloride, 129 ; 4. Sodio. and Potassium Carbonates, 129; 5. Calcium Carbonate, 130; 6. Magnesium Carbonate, 130; 7. Alkaline Phosphates, 130; 8. Calcium Phosphate, 1383; 9. Magnesium Phosphate, 134; 10. Sodium and Potassium Sulphates, 185; 11. Hydrochloric Acid, 135. II. Tue CuemicaL Processes In CELLS, 1. The Vegetable Cell, 187; 2. The Animal Cell, 142; 3. meen tions, 145; 4. The Consumption and Development of Force in ) Cells, 147. PAGE 85 88 104 109 110 112 112 136 TABLE OF CONTENTS. PART II. SPECIAL PHYSIOLOGY. BOOK FIRST. Tue Nutritive FunNcrTions. SECTION I. Foops. I. VEGETABLE Foops, . ‘ 3 F 5 1. The Cereals, 163 ; 2. The ete ee Pena a 173; 3. Bulbs and Roots, 174; 4. Grasses, 1%. II. Anta Foops, : 2 - . - é F Fi 1. Milk, 188; 2. Meat, 188. III. Inorganic Foops, . ‘ 5 . é * $ A 1. Water, 191; 2. Nutritive ane, 192. IV. THe Dier or ANIMALS, . ‘i , . is , F 3 SECTION II. DIGESTION. I. GENERAL CHARACTERISTICS OF THE DIGESTIVE APPARATUS, . II. PreHeNsion or Foon, : 1. Prehension of Solids, 226; 2. Prehension of Liquids, 236. III. Masrication, 1. Movements of the Jaws, ot ; 2. Aplin of the Teeth. in Mastiva. tion, 245 ; 3. Determination of Age by the Teeth, 255; 4. Action of Tongue, Lips, and Cheeks, 264. IV. Digestion IN THE Mout, The Salivary Secretion, 268 ; 1. The Parotid Secretion, 274; 2. The Submaxillary Secretion, 279; 3. The Sublingual Secretion, 283 ; 4. General Characters of the Salivary Secretion, 284; 5. The Quantity of Saliva, 286; 6. The Physiological Réle of the Saliva, 287; 7. The Mechanism of Salivary Secretion, 298. V. DEGLuTITION, . . s , ‘ . « c 7 VI. Rumination, . : : : “i m RR ‘ . VII. VomiriIngc, .« 5 © © +6 8 2 © «© PAGE 161 188 191 193 226 268 307 316 331 xX: TABLE OF CONTENTS. VIII. Gastric DicEstion, . : . . ‘ : . 1. Chemistry of the Gastric Juice, 342; (a) Pepsin, 346; (6) Milk- Curdling Ferment, 347; (c) The Acid of Gastric Juice, 349; 2. The Action of Gastric Juice on the Food, 351 ; 8. The Secretion of Gastric Juice, 356; 4. Gastric Digestion in Carnivora, 360; 5. Gastric Digestion in Omnivora, 363 ; 6. Gastric Digestion in Soli- pedes, 368; 7. Gastric Digestion in Ruminants, 874; 8. Gastric Digestion in Birds, 379. , IX. Digestion in THE SMALL INTESTINE, . é : I, Bile, 382; 1. The Chemical Characteristics of the Bile, 383; (a) Mucin, 384; (>) The Bile Acids, 884; (¢) The Coloring Matters of the Bile, 387; (d) Cholesterin, 389; (e) The Inorganic Constitu-— ents of the Bile, 390; 2. The Secretion of the Bile, 391; 3. The Physiological Action of the Bile, 393. , II. The Pancreatic Secretion, 396; 1. The Chemical Composition of the Pancreatic Juice, 402; The Pancreatic Ferments, 404; 2. The Action of the Pancreatic Juice on Food-Stuffs, 405; (a) Action on Carbohydrates, 406 ; (0) Action on Fats, 406; (¢) Action on Proteids, 408 ; 3. The Secretion of Pancreatic Juice, 412. III. The Intestinal Juice, 416. IV. Fermentative Processes in the Small Intestine, 418. VY. Intestinal Digestion in Different Animals, 419. X. Dicestion in THE Larce INTESTINE, 1. The Functions of the Cecum, 423; 2. The Functions of the Colon, 429. XI. Tue Comparative Dicestisiiity or Dirrerent Foop-Srurrs, XII. Tue Composirion or Fxces, . . . XIII. Toe Movements of tHE INTESTINES, . . . XIV. Derzacation, . - ‘ ‘ : . . . - SECTION III. ABSORPTION, . : : : ‘ ma” A . ; : ‘ 1. Venous Absorption, 453 ; 2. Absorption by the Lymphatics, 456. SECTION IV. Tue CHyLE, . . . ‘ oe bs : . . . . SECTION V. Tun Lympa, . 7 : . . . 7 . , ‘ PAGE 837 382 453 459 463 TABLE OF CONTENTS. SECTION VI. Tre Boop, . . r . ‘ . 7 1. The Red Blood-Corpuscles, 471; 2. The White Blood-Corpuscles, 479 ; 3. Blood-Plasma and Blood Coagulation, 483 ; 4. The Blood- Serum, 489. SECTION VII. THE CIRCULATION OF THE BLoop, . x ‘ 5 ; ‘ 1. General View of the Organs of Gaadiaies 491; 2. The Action of the Heart, 499; 3. The Hydraulic Principles of the Circula- tion, 516; 4. The Circulation in the Arteries, 523; Blood Pres- sure, 525; Velocity of the Blood, 530; The Pulse, 533; 5. The Circulation in the Capillaries, 536; 6. The Circulation in the Veins, 539; 7 The Influence of the Nervous System on the Heart, 540; The Inhibitory Nerves of the Heart, 549; The Ac- celerator Nerves of the Heart, 551;-8. The Influence of the Nervous System on the Arteries, 552. SECTION VIII. RESPIRATION, . : : ‘ : ‘ 1. General View of the Organs of avin 562; 2. The Mechani- cal Processes of Respiration, 574 ; 3. The Rhythm of Respiration, 579; 4. The Chemical Phenomena of Respiration, 587; 5. The Nervous Mechanism of Respiration, 598; 6. The Influence of Respiration on the Circulation, 605. SECTION IX. THE MAMMARY SECRETION, : = 3 1. The Physical and Chemical Properties of Milk, 610; 2. Casein and. Milk Coagulation, 614; 3. Milk-Sugar, 616; 4. Fat and Cream, 617; 5. The Inorganic Constituents of Milk, 619; 6. Variations in the Quantity and Composition of Milk, 619; 7. The Secretion of Milk, 624; 8. Milk Analysis and Inspection, 681. SECTION X. Tae RENAL SECRETION, . - s 3 , 1. The Physical and Chemical ree ee of Urine, 685; 2.. The Mechanism of Renal Secretion, 640; 3. The Merhaaisn of Mic- turition, 648. - SECTION XI. THE CuraNnEous FUuNcTIONS, . Z me is 5 1. The Swank Secretion, 652; 2. The Sebaceous Secretion of the Skin, 655 ; 8. Cutaneous Absorption, 656; 4. Cutaneous Respiration, 656; 5. The Lachrymal Secretion, 658. - 491 561 609 635 651 xil TABLE OF CONTENTS. SECTION XII. NUTRITION, . ‘ . ‘ M 5 , , - ‘ I. Tye FATE OF THE eae Foop-ConsTITUENTS, j ‘ II. Tue Fare or toe Farry Foop-ConstituEnts, 5 E a III. Tux Fare or tue CARBOHYDRATE Foop-CoNnsTiTUENTS, IV. Tue Sraristics or NurRirion, ‘ ‘ 1. Tissue Changes in Starvation, 674; 2. The Nutritive Processes in Feeding, 680; (a) Feeding with Ga 680; (0) Feeding with Fat, 682; (c) Feeding with Carbohydrates, 683. V. Taz Foop Requrrep By THE HeErprvoRA UNDER DIFFERENT ConDITIONS, : . - VI. Huncer anp THIrst, : : . : ee . : SECTION XIII. ANIMAL HEatT,. . j 5 : : . F . 7 : BOOK SECOND. Tue ANIMAL FUNCTIONS. SECTION I. Tur PuystioLoGy oF MovEMENT, . : i : ‘ 7 1. The Contractile Tissues, 701 ; (a) Chemical Composition of Muscle, 704; (b) Muscular Irritability, 709; (¢) The Phenomena of Mus- cular Contraction, 710 ; (d) The Electrical Phenomena in Muscle, 721; 2. The Applications of Muscular Contractility, 722; 8. Ani- mal Locomotion, 731; 4. The Gaits of the Horse, 739; (a) The Walk, 744; (6) The Amble, 746; (c) The Trot, 748; (d) The Gallop, 749 ; 5. Other Movements in the Horse, 750; (a) Rearing, 750; (b) Kicking, 753; (c) Lying Down and Rising Up, 754; (d) Walking Backward, 754; (e) Swimming, 755 ; 6. Special Mus- cular Mechanisms—The Voice, 757. SECTION ITI. Tue Puystotocy or THE NERvous SYsTEM, . I. Tue CuemicaL AND PuysicAL CHARACTERISTICS OF NERVOUS TISSUES, . ‘ : 7 F F II. Nervous Iprirrasiniry, . . II. Tue ExecrricaL PHENOMENA IN NERVEs, IV. GeneraL PuystoLocy or THE NERVE-CENTRES, 1. Reflex Action, 782; 2. Automatism, 784; 8. Inhibition, 785 ; 4. Augmentation, 785 ; 5. Co-ordination, 785. PAGE 659 660 664 666 672 684 692 693 701 765 TT4 776 179 781 TABLE OF CONTENTS. xiii V. Tue Functions or THE SPINAL CorD, . . é : ‘ “186 (a) The Spinal Cord as a Collection of Nerve-Centres, 789; (b) The Spinal Cord as an Organ of Conduction, 795. VI. Tue Functions or THE BRAIN, . 803 1. The Medulla Oblongata, 810; 2. The eae of the Fibres of the Medulla Oblongata, 818 ; 8. The Pons Varolii, 821; 4. The Cere- bral Peduncles, 821; 5. The Corpora Guadrieeming, 822; 6. The Functions of the Basal Ganglia, 822; 7. The Functions of the Cerebral Lobes, 823 ; 8. The Functions of the Cerebellum, 825. VII. Tue Craniau NERVES, . 3 ‘ F 3 i . . 832 VIII. Tue Sympatuetic Nervous System, . : ‘ ; . 835 IX. GENERAL AND.SPECIAL SENSIBILITY, . : : : . 837 A. THE SENSE oF SMELL, ‘ : 3 : : 2 ; . 841 B. Tue SENSE oF SIGHT, . . 846 1. The Dioptric Mechanisms of the os 85; 2. “Visual Bs aaitibaks 864. C. Tue SEnsE or HEARING, . i : ‘ ‘i ‘ F . 875 D. Tue SENsE or TASTE,. ‘ ‘ 4 F - : ‘ . 893 EK. Tue Sense or Toucu,. é ‘ ‘ eo : ‘i - 897 PART III. Tue REPRODUCTIVE FUNCTIONS, - . . : F 7 . 901 SECTION I. Tur REPRODUCTIVE PROCESSES, : ‘ F . : 903 1. The Reproductive Tissues of the Female, 908 ; 2. The Hepiaiue: tive Tissues of the Male, 913. INTRODUCTION. PuysroLocy treats of the functions or actions of living beings. When these actions or functions occur ina disturbed or irregular manner, they constitute disease, or abnormal life, and become the subject of abnormal physiology or pathology. Normal physiology is the basis of pathology, and a knowledge of the one must precede the intelligent study of the other: just as an acquaintance with the functions of the com- ponent parts of a machine must precede the recognition of disordered movement and the provision of means of repair. Since the functions of the animal body are resident in the various tissues and organs of the body, an acquaintance with the forms and structure of those organs and tissues must precede the study of their functions. The study of anatomy and histology, or microscopic anat- omy, must therefore precede the study of physiology. GENERAL PuysioLocy treats of the functions of organized beings in an abstract anner,—that which regards the general laws of life, whether seen in the animal or vegetable world. Although for the purposes of practical life physiology is divided into several provinces, yet the knowl- edge of general physiology is essential even to special students, since the relation between the different forms of life is very close. VEGETABLE PuysioLocy is concerned solely with the consideration of the vital actions or functions of plants. CompaRaTIVE PuysioLoay treats of the functions of animals below man, with a consideration of the means by which different functions are accomplished by different animal forms. Spectral Puysrotocy is confined to the consideration of the vital phenomena of a single species, single genus, or it may deal with the consideration of a special function. In this book special physiology will refer mainly to the study of the vital phenomena of the domestic animals. ‘ Human Puysionocy treats exclusively of the vital phenomena of man. But, while this branch of physiology is of greater importance to the physician than the other divisions, in consequence of its relations to human pathology and therapeutics, it should not be made the exclu- sive subject of study; for the physiology of man cannot be properly understood without a previous acquaintance with the vital phenomena of 1 (1) 2 INTRODUCTION. the lower animals and plants. For the veterinary physician the study of life in the domestic animals must be of the greatest importance. Every living body is organized,—that is, composed of instruments or organs each one of which is destined to fulfill some special office in the organism called its function, the sum of which functions constitute the life of the individual. Other bodies met with in nature, and not so constituted, are called unorganized, or inorganic, e.g., the mineral. DISTINCTIONS BETWEEN ORGANIZED AND UNORGANIZED Bopies.—Organ- ized and unorganized bodies have few or no correlative points, but stand opposed to each other in almost every characteristic trait. Unorganized matter is only subject to the forces whose generality of action constitutes physical and chemical laws. Organized matter is also controlled to a certain extent by the same laws, and, although there are a great many actions manifested by living bodies which are not readily explicable by the ordinary physical laws, and for which the term “ vital phenomena” is conveniently employed, it does not by any means follow that we have here to deal with any entirely distinct series of laws. The attempt to reduce the so-called vital phenomena to physical and chemical laws has already succeeded in demonstrating the dependence, on physical and chemical principles, of many. functions previously regarded as purely vital in nature, and the hope may be reasonably held for con- tinued progress in this direction. The sciences of physics and chemistry are therefore the foundation-stones of modern physiology. Nevertheless, organized and unorganized matter differ to such an extent that their consideration forms entirely distinct branches of study. The forms, the forces, and the laws of unorganized matter are the sub- jects embraced by physics and chemistry. The forms and forces of living organized matter are the objects of physiological science, or biology. Organic bodies differ from inorganic— 1. In their Origin.—The former spring from a parent, or from previously-existing living matter, either by splitting, budding, seeds, or eggs. The latter have no such origin, but may arise from the combina- tion, under the influence of chemical affinity, of the elements which com- pose them. Spontaneous generation, though claimed by some, has not been satisfactorily established. 2. In their Form.—Organized bodies are usually determinate in their form, rounded in their outline, and, in their simplest expression, either spherical or spheroidal in shape. Unorganized bodies, on the other hand, are irregular in their outline (amorphous), or, if determinate in form, are bounded by plane surfaces and straight lines. 3. Duration of Existence —Organized bodies have a definite time to live, pass through distinct stages of development and growth, and ulti- INTRODUCTION. 3 mately die. But the inorganic body may continue to exist until some disrupting force separates the inorganic elements of which it is com- posed, and enables them to form new combinations; but so long as uninfluenced by such an agency it may remain unchanged for an indefi- nite period. 4, Size.—Organized bodies have a definite limit to which they may attain, varying, however, among individuals of the same species. And. when they exceed the average size of the species it is not by the iucreased size of the individual, but by the continued production of new individuals or a repletion of parts already existing. The unorganized body, on the other hand, is as indeterminate in size as in duration, con- tinuing to grow so long as fresh particles are brought together. 5. Chemical Constitution.—Of the sixty-five simple elements found in nature but about twenty enter into the composition of organized bodies, and of these but four are to be regarded as essential, viz., C.O.H.N., of which at least two are found in every organic compound. The remain- ing elements are called incidental. Unorganized bodies may be simple in their composition, or binary, ternary, quaternary, or higher; but binary is the most usual combination. The molecular constitution of the organic body is also different from the inorganic in being much more complex, both in the number of elements which it contains and the number of atoms, or combining equivalents of those atoms, which exist in a combining equivalent of the compound. Thus, albumen, which forms an important constituent of nearly all organized bodies, may be represented as CoHso2NesOrSs (Schiitzenberger), while ammonium carbonate, an inorganic compound containing the same elements, with the exception of sulphur, may be written as follows: (NH,);CO;+ H,0. From the large number of elements which enter into the composition of organie bodies, and the large number of atoms constituting an organic molecule, arises the great tendency to decomposition by which they are characterized; for, “the greater the number of atoms of an element which enters into the formation of a molecule of a compound, the less is the stability of that compound.” Inorganie compounds are therefore stable; organic bodies, unstable. It was formerly supposed that organic compounds could only be formed under the influence of vitality, and that they could be decom- posed by the chemist, but not recomposed. But this has been shown to be an error, some of the organic acids, alcohols, organic coloring matters, and some of the secondary organic components, such as uric acid and urea, having been synthetically prepared by the chemist. It is thought, therefore, not to be impossible that some of the higher organic com- pounds, such as albumen, may ultimately be also made in the same 4 INTRODUCTION. manner, though thus far all attempts in this direction have been unavail- ing. All those compounds which have as yet been made by synthesis are allied to those which result from a long-continued series of chemical changes in the organism, produced by the action of oxygen upon prod- ucts of disintegration. 6. In their Mode of Growth.—Organized bodies grow by dasiwnilee tion,—the internal deposit of materials by which the unlike become the like. Unorganized bodies grow, or increase in size, by external deposit or accretion. The organized body is dying from the moment of its birth, and requires new materials to repair those losses and for the increase in size. The unorganized body, as the crystal or the stalactite, continues to increase in size so long as fresh particles are deposited upon it. Every part of an inorganic body is therefore alike and independent of the rest, and exhibits the same properties as the whole. The organized body, on the contrary, is made up of a number of dissimilar parts, each of which is more or less dependent upon the others, and each of which requires different materials for its growth and reparation. In the unor- ganized body a small portion serves to determine by analysis the consti- tution of the whole; in other words, it is homogeneous. In the organ- ized body each part is more or less dependent on the remainder, and differs from it in chemical composition; in other words, it is hetero- geneous. Organic compounds, moreover, from the large quantity of. fluid they contain, are usually soft and ductile, while the inorganic body is hard, rigid, and inflexible, and when once the affinities of its chemical elements are satisfied it remains an inert mass. Within the organized living body all is change. Death and repair are ever taking place. From the commencement of its existence its growth, its progress toward maturity, its decline, decay, and death are all made up of an incessant series of changes. It is the constant round of these actions which con- stitutes life; their study is the subject of physiology. It is thus seen that organized are distinguished from unorganized bodies by three cardinal characteristics: 1. The law of nutrition, the most fundamental of all vital laws; since in virtue of it the: organism continues to exist as an active being, and increases from infancy to maturity. 2. The law of development, or differentiation, which causes the organism to pass through the definite cycles of change constituting what we call ages, and leading inevitably to the final changes which we call death. 3. The law of reproduction, another aspect of the first law, in virtue of which the organism gives origin to similar organisms from one generation to another. In no example of inorganic matter can any of these characteristics be found. When inorganic bodies are said to grow, their growth is a process of mere aggregation, one part adhering to another similar part. INTRODUCTION. 5 ‘The growth arises from no internal necessity, as in organic bodies. The bulk is not increased by a process of assimilation which converts the unlike into the like. Minerals do not feed; they cohere. Nor have they any power of development. They pass through no definite cycles of change; they have no stages of growth, no ages, no power of repro- duction. The constant round of actions, therefore, in the organized structure called life,.in them is wanting. They occupy space, but have neither birth nor death. DISTINCTION BETWEEN PLANTS AND ANIMALS.—Organized bodies are divided into two classes,—animals and vegetables—constituting two sep- arate kingdoms, which, though capable of ready recognition when studied in their higher members, seem almost to overlap in their lowest expres- sion. Hence, while the differences between the higher animals and higher ‘plants are so striking as not to need mention, when we examine the lowest forms of life the greatest difficulty will sometimes be met with in the attempt to decide whether the organism is an animal or a vegetable. For when the protozoa, or lowest animals, are compared with the protophyta, .or lowest plants, all the differences which are so striking between the -higher animals and: plants are completely wanting; yet the protozoa are as truly animal as are the vertebrata, and the protophyta just as surely plants. Consequently the definition of an animal or a plant, to be of any scientific value, must include the lowest as well as the highest forms. We found, in our comparison of organic and inorganic matter, that differences in form could be clearly made out. The external charac- -teristics of plants and animals are, however, inadequate to distinguish them. Many animal forms, such as the hydrozoa, are essentially plant- like in their external form, growing from fixed points and even repro- ducing themselves by ‘“ budding,”—a process almost universally holding in the vegetable kingdom. So also the well-known coral polyps and the sponge closely resemble plants in external configuration, and, though undoubtedly animals, were long placed by naturalists in the vegetable kingdom. Then, on the other hand, many plants, examined in respect to their external form alone, would often be confounded with animals, Thus, the germs of many alge, the ciliated zoospores, are scarcely to be dis- tinguished from infusorial animalcules. It was at one time thought that the power of motion was a proof of animality; but many of the lowest plants, such as volvox and the diatoms, possess the power of motion, of changing their location, the instruments being the same as in many animals, viz., cilia. Nor is the power of moving in response to an irritant peculiar to animal life: witness the Mimosa pudica, the sensitive plant, which closes its leaflets 6 INTRODUCTION. on irritation ; the Dionea muscipula, the Venus’ Fly-Trap, the extremities of whose leaves have the power of closing on insects or other bodies brought into contact with them. Plants are also possessed of internal motion: witness the circulation of the sap and the circulatory motions in the interior of many vegetable cells. They also turn spontaneously to the light and extend their rootlets to the most nutritive soil. Again, all animals are not possessed of the power of motion. Sponges, coral polyps, hydroid zoophytes, sea-mats, etc., are* entirely destitute of locomotive power, and spend their entire existence rooted fast to some immovable object. Hence, the possession of motor power is not characteristic of animal life, and its absence does not prove the organism to be a vegetable. : Chemical analysis helps us but little more in the attempt to dis- tinguish animals from vegetables. Carbon and nitrogen compounds form a large proportion of the constituents of each, and a large number of complex combinations found in animal tissues are represented by entirely similar compounds in vegetable matter. There is therefore no one chemi- cal compound whose presence is characteristic of animality or vegetable nature; for “ cellulose,” the substance out of which wood-fibre and the walls of plant-cells are formed, has been ascertained’ to form the greater part of the external coverings of certain molluscous animals (ascidians). So also chlorophyll, the green coloring matter of plants, is the cause of the green color of many infusorial animalctles and of Hydra viridis, while starch has been found in the ventricles of the brain of animals, and is represented by glycogen, a body closely analogous to starch and manufactured by the animal economy. Such examples, therefore, show that chemical examination can give us no definite aid in separating plants and animals. The microscope is also powerless to give us an infallible rule which will enable us to distinguish animal from vegetable tissue. In other words, plants and animals are built up on the same general plan; their intimate structure closely coincides. Both originate in cells, consisting, in their typical form, of a cell-wall, cell-contents, or protoplasm,—nucleus and nucleolus,—and in both the parent cell undergoes subdivision and results in the birth, growth, and development of myriads of other cells, constituting the tissue of the plant or animal, and differing no more from each other than almost any mature animal or vegetable cell does from the germ from which it originated. Nor is the possession of a digestive cavity, mouth, or alimentary tube characteristic of animals; for there are vegetables which possess a stomach, as the Nepenthes, or Pitcher-Plant, which has a cavity cor- responding to a stomach, in which digestive fluids are poured out, and in which digestion and absorption take place. On the other hand, many INTRODUCTION. 7 animals among the protozoa, such as the amceba, have no stomach, the general surface serving not only for the purpose of digestion, but also for absorption, an extemporaneous stomach being formed by wrapping a part of the external general body surface around the substance to be digested. So also in the tape-worms and other parasitic forms of animal life, there is an entire absence of any special aperture for the entrance of nutritive matter, such organisms living by the simple imbibition of nutritive matter in solution. When, however, we examine into the nature and mode of assimila- tion of food, the nutritive processes occurring in the interior of the organism, and the results of the conversion and assimilation of food, then only have we any reliable scientific data for distinguishing animals from plants. In the first place, the food of animals differs from that of plants in its nature. Animals require organic food; plants live on inor- ganic or mineral matter. The nutritive processes in the two kingdoms are also diametrically opposed: the plant absorbs water, ammonia, carbon dioxide and certain salts, and out of these manufactures the albuminoids, carbohydrates and hydrocarbons found in vegetable tissue. The animal feeds on these complex vegetable compounds,—and this holds whether the animal be herbivorous or carnivorous,—and returns to the soil and atmosphere the inorganic matter from which they were manu- factured by the plant; and in the same form, 7.e., carbon dioxide, water, ammonia, and certain salts. The plant therefore converts simple inor- ganic compounds into complex organic compounds, while the animal reduces complex organic matter to its simple inorganic constituents. A further point of distinction between animals and vegetables, and one closely connected with the nutritive processes, is their behavior to the atmosphere. The animal requires for the processes of reduction already mentioned as constituting its mode of nutrition a constant supply of oxygen, which is withdrawn from the atmosphere and returned to it in the form of CO,, representing one of the end products of oxidation of the carbon of its tissues and food. Plants, on the other hand, absorb CO,, and under the influence of sunlight, by the action of their chloro- phyll, break up this CO,, fix the carbon in their tissues, and set free oxygen into the air. The plant thus absorbs what the animal excretes, and the animal absorbs what the plant excretes. We thus see that animals and plants offer striking points of contrast as to the character of their food and the nature of their nutritive processes, and, although there are several apparent exceptions to the general outline here given, their consideration may be deferred to the chapters on the Chemical Processes in Cells. We have found now that all objects in nature must be either organic 8 INTRODUCTION. or inorganic, and we have considered the means by which these bodies may be separated: we, therefore, here leave the inorganic world [ne domain of physics, chemistry, mineralogy, etc.), to confine our studies to the animal kingdom. But here, from the fact that there was great difficulty in separating the lower forms of animal from vegetable life, it must be recognized that animals and plants possess many vital functions in common; and as the simplest expression of these functions must be in the simplest organisms, the study of those functions may best commence in the simple, uncellular organisms, whether animal or vegetable. General physiology will thus deal with the Animal Cell: its form, origin, ‘modifications, constitution, and the various chemical and physical proc- esses concerned in its nutrition, growth, development and reproduction. It will, then, be shown that the higher animals are mere associations of such simple organisms, in which the modification in the characters of the various constituent cells leads to a division of labor. In other words, development of tissues leads to a specialization of function, and Special Physiology will deal with the study of the development of func- tion, especially as seen in our domestic animals. The functions of animals are divided into the Vegetative Functions, the Animal Functions,—or the functions of relation —and the Reproductive Functions. The Vegetative Functions include everything which relates to the nutrition of the animal in its widest sense. As the blood in higher animals is the organ of nutrition, under this head are included (lst) the additions to the blood,—therefore, the description and modes of prehension of Food; Digestion, or the preparation of food for absorption; and Absorption, or the means by which nutritive and other matters enter the blood. The Blood will, then, be considered as a tissue of nutrition or as a carrier to and from the various organs of the body by means of its Circulation. Asa boundary between the additions and (2d) the losses to the blood Respiration will demand attention, while under the latter head come the functions of Secretion and Excretion. The means by which the identity of the individual is preserved concludes the subject of Nutrition and deals with the nutritive value of different foods and their combinations, the adaptment of foods to the different demands on the animal economy, and the subject of Animal Heat. The Animal Fune- tions, or those by which the body is brought into relation with the - external world by means of sensation, power of movement, consciousness, and volition, include the study of the Muscular and Nervous Systems, _ while finally the Reproductive Functions lead to the preservation of the species, and include the subjects of Generation and Development, or Embryology. PART I. GENERAL PHYSIOLOGY. THE PHYSIOLOGY OF ANIMAL CELLS. (9) SECTION I. THE STRUCTURE OF ORGANIZED BODIES. CHEMICAL ANALYSIS has shown that all organized bodies are capable of resolution into simple chemical elements which in themselves do not differ from the elements out of which all matter is composed: in other words, that the simple elements of which organized bodies are built up are universally distributed throughout nature, and that no one element is peculiar to organized matter. The characteristic of organized bodies is, therefore, not to be found in any peculiarity of the matter of which they are composed, but in the manner in which the atoms composing that matter are grouped. In an inorganic body we are accustomed to attribute its chemical properties to the nature, number, and mode of association of its constituent elements, while its physical properties are attributable to the mode of arrangement of its molecules. Analysis of organized bodies shows that in them we have certain elements constantly present in certain definite proportions: it is there- fore warrautable to assume that the chemical properties of organized bodies are, as in the case of inorganic matter, due to the number, nature, and mode of association of their elements. Further, we find in all organized living bodies a certain identity of physical properties: it is therefore warrantable to assume that the physical processes seen in organized bodies are dependent on the mode of arrangement of their constituent molecules. The elements constantly associated in living matter are carbon, nitrogen, oxygen, hydrogen, and sulphur, forming a complex combination, to which the term protoplasm has been applied. ’ This matter, protoplasm, whether found in the tissues of the highest animals or plants, or in the lowest unicellular members of either kingdom, has always the same composition and is always possessed of nearly the same attributes; with the restriction that we have already referred to as to the difference in functions possessed by animals and plants,—differences which will probably in the future be cleared up, and found not to be in contradiction to the statement that protoplasm is the universal basis of organization. All organized bodies are built up of associations of masses of proto- plasm, which from their appearance are termed cells, or, from the func- tions which they fulfill, elementary organisms: and as the physical properties of inorganic matter are dependent on the arrangement of. (11) 12 PHYSIOLOGY OF THE DOMESTIC ANIMALS. their molecules, so the physiological peculiarities of organized bodies are dependent on their cellular structure. Physiology is therefore the study of the properties of cells. Cells possess the properties of Nutrition, Reproduction, Growth, Develop- ment, and in many cases their contents are capable of Motion and mani- festing Irritability. I, THE GENERAL PROPERTIES OF CELLS. Microscopic examination teaches that every living object, from man down to the smallest animalcule invisible to the naked eye,—from the largest tree down to the most microscopic plant,—is built up on the same general plan. In each the same element of organization is found, and every living form is built up of associations of these microscopic units, each of which, even in the most complex forms of life, may be regarded as separate individual organisms.* For even in complex organisms cells to a certain extent carry on a separate and independent existence. We see separate cells originate separately, grow, repro- duce themselves, become diseased and die without the entire organism as a whole taking any part in these different stages of existence of its component parts. The individual life of each separate cell is recognized in the different activities of different cells: the activity of the Fie. L—TYPIcAL ANIMAL organism is the result of the sum of these CELL. RIPE OVUM OF Cat. (Klein) - separate existences. eee TOTee In their typical form both animal and vegetable cells consist of closed vesicles, with homogeneous or striated walls, a viscid albuminous contents, termed protoplasm, containing an aggregation of granules called a nucleus, within which again is a still denser formation called a nucleolus. The cell-contents is frequently vacuolated, 7.e., contains minute cavities filled | with a clear fluid. The contents of the cells, which we shall find to be functionally the most important, is called protoplasm. It is a transparent mass in which numerous granules are suspended, and which possesses in all young cells the property of contractility. It is often seen to be reticulated. In older cells the quantity of fluid diminishes and the cells become firmer and drier, while vacuoles often form and contain fluid. This change in the physical properties of cells is often associated with a visible change in their chemical nature,—thus, with a deposit of coloring matter, starch * Such units of organization are termed cells, from the resemblance which micro- scopic sections of young tissues, whether plant or animal, bear to a honey-comb. THE GENERAL PROPERTIES OF CELLS. 13 granules, fat globules, or granular matter. All substances which coagu- late proteids have the same effect on protoplasm. The vital properties of protoplasm will be studied later. A membrane is usually present in all mature cells, though always absent in embryonic forms. It may therefore be assumed that the mem- brane results from a condensation of the outer layers of the cell-contents. The membrane is apparently homogeneous, .or may be porous. The nucleus, the size of which is generally in proportion to that of the cell, and which is usually oval or spherical, is never absent in early forms of active cells, though it may disappear when the cell reaches maturity. In its mature stage it is generally reticulated,—that is, com- posed of an investing cuticle within which the contents are arranged in the form of a fibrillar net-work. The presence of a nucleus, which is often difficult of recognition on account of its minute size, may be demonstrated through the action of certain reagents, especially dilute acids and staining fluids. Dilute acids render the protoplasm of cells transparent without affecting the nucleus, which consequently becomes more prominent; while staining fluids, such as carmine, hematoxylin, and the anilin dyes, color the nucleus deeper in tint than the cell-contents. The nucleus appears to be especially important in the reproductive func- tions of cells, since when cells multiply by division the division always commences in the nucleus. The nucleolus is simply a closer aggregation of the granules which constitute the nucleus, and is very frequently absent. Both cell-wall and nucleus may be absent from the lowest elementary organisms. As our conception of the structure of the higher animals and. plants is an association of elementary organisms invariably taking origin from asingle cell, our definition of such a simple organism or cell must be modified so as to apply to the description of the simplest conceivable organism capable of carrying on an independent existence. And as we have seen that of the constituents of a typical cell but one, the cell-con- tents, or protoplasm, is essential; and as we know that there are organisms capable of carrying on an independent existence in whom neither cell-wall, nucleus, or nucleolus is to be detected, a cell may be defined as a more or less homogeneous mass of organized material,— protoplasm,—possessing development, growth, reproduction, nutrition, and automatism. : The best known of such undifferentiated forms of cell life is the ameba,—one of the simplest examples of an animal organism. In its lowest form the ameeba (Protameba primitiva, Haeckel) con- sists of a mass of jelly-like, structureless, albuminoid substance (proto- plasm), which, so far as its chemical composition and general attributes 14 PHYSIOLOGY OF THE DOMESTIC ANIMALS. are concerned, cannot be distinguished from the contents of all active forms of cells (Fig. 2). The ameba is capable of spontaneous motion, both as regards change of. external form and of progressing from place to place. Motions may also be evoked by various stimuli ; hence, free protcplasm, in common with muscular fibre and ciliated organisms, is contractile. The peculiarity of protoplasmic motion, as seen in the ameeba, is that motion does not occur around a fixed point, but rather is a flowing motion, such as might occur in the particles of a fluid. Thus, in an ameeba the changes in form and location are effected through the thrust- ing out of lobe-like prolongations of the periphery (pseudopodia), and their subsequent withdrawal or the flowing into these extensions of the remainder of the body. Occasionally one or more of these pseudopodia become gradually more and more constricted, until, finally, a portion becomes entirely separated from the original mass, increases in size, and itself possesses all the proper- ties of the parent stock; hence, protoplasm is reproductive, and possesses the power of growth. Moreover, the move- ments of an amaba are not Fig, 2.—A Non-NUCLEATED C&eLL, THR PRor- necessarily the consequences AMCBA PRIMITIVA, AFTER HAECKEL. (Wundt.) of external stimuli, but may A mae be: ReorgimAlibes liened, , protoplasm is also aufomatic. If watched for some time, an ameeba will often be seen to take into its interior, by flowing around them, small vegetable organisms, of which portions are dissolved and converted into the substance of its body, while the undigested remainder is extruded ; therefore, protoplasm, even in the absence of all digestive organs, possesses the power of nutrition. The ameeba requires for its existence an atmosphere of oxygen, which is absorbed, and which it again partly exhales as carbon dioxide. Protoplasm is therefore respiratory. II. ORIGIN OF CELLS. We have seen that in the ameba a simple mass of undifferentiated protoplasm possesses the powers of reproduction, contractility, respira- tion, irritability, nutrition, and automatism. Every form of life com- mences its existence in the form of just such a simple mass of proto- plasm. Starting with the ovum, and ending with the nucleated elements found in the organs and tissues of the embryo and adult, there is one ORIGIN OF CELLS. a 15 uninterrupted series of generations of cells, each cell becoming so modi- fied as to specialize certain functions which are together possessed by all forms of undifferentiated protoplasm. Thus, in the higher forms certain cells will be found to have become so modified as to have the function of reproduction especially developed; they will therefore constitute the reproductive tissues. In other cells the nutritive functions will become most prominent; they will therefore form part of the tissues whose function is to preserve the nutritive balance of the organism. Specializa- tion of function is therefore the explanation of the development. of tissues; the result is a physiological division of labor. We will have to return to this subject again. The germ of every animal and vegetable organism is a cell which owes its existence to some similar, previously-existing cell. Neglecting the origin and development of cells in the vegetable kingdom, every cell which forms part of the organs or tissues of all forms of animal life originated in and developed from a germ-cell or ovum. The ovum of man and other mammals is a minute mass of protoplasm, corresponding in its general appearance with the description of a typical cell. The protoplasm, or cell-contents, is surrounded by a delicate, striated membrane, the Zona radiata, or vitelline membrane. Within the cell-contents, in addition to numerous minute particles,—the so-called yelk-globules—is a collection of denser particles of protoplasm, Frye, 3—Typrcan ANIMAL —the nucleus, or germinal vesicle, and within — GBLT jflhh OVO oF that, again, one or more still more solid masses, 4+ Zona pelludau; B., germinal —the nucleoli, or germinal spots. The cell-contents is identical in nature and properties with the sub- stance of the ameeba, and before and immediately after fertilization may even be the seat of spontaneous movements of contraction and expan- sion. When mature, its diameter in the domestic animals and man varies from the 5}, to the y$q of an inch (0.18-0.2 mm.). Fertilization leads to a cleavage of the protoplasm into two parts, the nucleus being first divided, so that two new elements originate from the ovum, each consisting of protoplasm and each containing a nucleus. Each of the two new cells thus formed again subdivide into four, these into eight, and so on through many generations, until a large number of new cells, the so-called “ mulberry mass,” results from the subdivision of the original parent cell. According to Schleiden and Schwann, the founders of the cell doc- trine, organic forms of life may originate in one of two ways,—either by the aggregation of granules in a previously-existing homogeneous fluid . 16 PHYSIOLOGY OF THE DOMESTIC ANIMALS. (the blastema), forming the so-called “ free cell-formation,” or by the subdivision of a previously-existing cell,—the “ endogenous cell-forma- tion.” According to the first of these views, which may be compared to the. formation of crystals in a saline solution, granules first develop in a fluid ° which contains all the chemical constituents of the organism, forming the nucleolus of the future cell. Around this other granules are gradually deposited until the nucleus is formed, and the cell-contents and membrane gradually consolidate around this. The first objection to this theory, which, it is seen, implies spon- taneous generation, lies in the fact that no one Fic. 4.-BLoop-Corrusctes as ever been able to demonstrate such a cell- Bee ENT Soerwe formation or to discover the so-called cyto- Bue CHAE BY FIs- blasts. It was then shown that all the cells of the embryo originate in the segmentation spheres of the ovum, and the falsity of this doctrine of free cell- formation is further proved from analogy by the manner in which the connective-tissue cells take part in the development of pathological new formations. There is now no more firmly-established dictum in physi- ology than the statement that every cell originates from a previously- existing cell. (Omnis cellula e cellula.) The other view, which was also to a certain extent advocated by Schwann, as to the origin of cells by sub- division of a parent cell, is exemplified in the mode of reproduction of many of the lower forms of life. Cells may reproduce themselves by simple division of the parent cell or by endogenous division. Cell reproduction always starts in the nucleus. In simple division the nucleus first becomes marked with a furrow, which grad- ‘ ually deepens until the nucleus is divided Fic. 5.—GEMMATION. ABuD- .. : pING GERM-CELL or Gor- into two. The protoplasm of the cells is DIUS, AFTER MEISSNER. a y 4 (Wundt.) then modified in the same way, until two new cells are formed by the division of the parent cell. This process may be followed in the reproduction of the nucleated red blood-corpuscles of the embryo of the chick and even in mammals (Fig. 4). A modification of this form of cell reproduction is sometimes described as “ budding.” This process also starts with the nucleus. A number of nuclei are first formed by the subdivision of the nucleus; these gradually separate; the protoplasm ORIGIN OF CELLS. 17 collects around them so as to form projections from the periphery of the cell, which become more and more constricted until they finally separate (Fig. 5). During division the nuclear membrane disappears, and the nucleus usually divides before the cell-protoplasm, but not directly, by simple cleavage, as was formerly supposed, but indirectly, by karyo- kinesis (from movement of nuclear fibrils). This is an exceedingly com- plicated process. Its different stages may be divided about as follows :— 1. The nuclear fibrils become very distinct, while the nuclear mem- brane disappears and the fibrils of the nuclear net-work become twisted and bent into a more or less dense convolution, while the entire nucleus enlarges. 2. The fibrils unravel into loops arranged around the centre as a wreath or rosette. 3. The peripheral points of the loops become broken and a star- shaped figure of single loops is obtained. This is termed the aster, or star. 4, The loops separate into two groups or new centres. This is the diaster, or double star. 5. The two groups of threads become farther apart, as if attracted by opposite poles, but still remain connected by fine pole-threads, which represent the interstitial nuclear substance. In this stage the figure resembles a spindle. 6. The connection between the two sets of threads is broken. 7. The threads of each set become convoluted. 8. A membrane forms for each set, and thus new daughter nuclei result. (See Fig. 6.) The cell-protoplasm may commence to divide at any stage between the one when the threads aggregate around the two centres and the one when two distinct nuclei are present; or the division of the nucleus may be followed by division of the cell, so giving a cell with two nuclei. It is not proved that this is the universal mode of divisions of nuclei, though it has been observed in all kinds of cells in the embryo, and to a limited degree in theadult. On the contrary,it is probable that amoeboid cells divide by the direct method and that other nuclei may also undergo direct division, or Remak’s division, by simple cleavage, though all the cases in which constriction of nuclei is observed need not be cases of commencing division, as the change in shape may be due to pressure of cell-protoplasm, or to nuclear contractions. (Klein). The second form of cell-formation is termed by Kolliker “ endoge- nous cell-formation,” and consists in the formation of cells within the membrane of the parent cell, which ultimately bursts and discharges its progeny of young cells. The division of the mammalian ovum, the growth of cartilage, and many pathological cell-formations are types of 2 18 PHYSIOLOGY OF THE DOMESTIC ANIMALS. this mode of cell reproduction. The latter example furnishes many instances in which a number of cells with entirely different attributes from the parent cell develop in the interior of a cell, such as the develop- FIG. 6.—KARYOKINESIS. (KTein.) A, ordinary nucleus of a columnar epithelial cell; B,C, the same nucleus in the stage of convolution : D, the wreath, or rosette form; E, the aster, or single star; F, a nuclear spindle frum the Descemet’s endothelium of the frog’s cornea; G, H, I, the diaster: K, two daughter nuclei. ment of pus-corpuscles in the interior of different tissue-cells in inflam- mation (Fig. 7). The best object for the study of cell reproduction by division, and Fie. 7.—THe ForRMAtTION OF Pus-Cor- PUSCLES IN THE INTERIOR OF EPITHE- LIAL CELLS, SHOWING ENDOGENOUS CELL-FORMATION, (fanke.) A, single cylindrical cell from the human bile-duct; B, a similar cell containing two, C containing four, and D numerous pus-cells; E, isolated pus-corpuscles; F, a ciliated epithelial cell from the human respiratory tract, containing a single pus-corpuscle: and G, a pave- ment epithelial cell from the urinary bladder of man, containing numerous pus-corpuscles. the one of most interest for us, is found in the fertilized ovum of mammals, As the ovum approaches maturity, even before impregnation takes place, the germinal vesicle becomes obscure and more and more irregular in out- line, its membrane and reticulum disappear, and the germinal spot is broken up. What remains of the germinal vesicle becomes converted into a striated, spindle-shaped body, which moves to the surface of the ovum, to there undergo division into two parts. One part becomes ex- truded from the ovum to form what is known to embryologists as the polar cell, and is soon followed by a second similar cell, while the portion of the spindle remaining within the ovum forms a new nucleus, the female pronucleus, from which, in conjunction with the male elements, the future embryo is developed. ORIGIN OF CELLS. 19 In the unimpregnated ovule spontaneous contractions are generally seen in the protoplasmic cell-contents. When the egg becomes fertilized these contractions become so modified as to cause the germinal vesicle (or the body resulting from the union of the male and female pronuclei), and then the cell-contents to split into two parts contained within the cell-membrane, which takes no part in this division. These segmentation spheres, as already mentioned, continue to subdivide until an immense number of minute, nucleated, membraneless cells are contained within the vitelline membrane (forming the so-called mulberry mass). From these elements, which become progressively smaller as cleavage goes on, all the tissues of the embryo are formed. At first they all possess mobility (ameboid movements), showing their analogy to the simple ameeba, but at birth this property is only retained by certain cells, Like ameebee, they also grow in size and divide into new individuals. At first all the cells resulting from the segmentation of the ovum are exactly alike: they then undergo certain modifications in arrange- fl in ai Nt aa Dap FIG. $.—OVA OF THE DOG FROM THE FALLOPIAN TUBE, SURROUNDED BY THE ZONA PELLUCIDA, IN WHICH ARE FOUND NUMEROUS SPERMATOZOA, AFTER BiscHorr, (Ranke.) 1, ovum with two segmentation spheres, the Zona pellucida being surrounded by the Membrana gran- ulosa; 2, ovum with four segmentation spheres; 3, ovum with eight segmentation spheres; 4, ovum with innumerable segmentation spheres, forming the mulberry mass. ment and form, different in different classes of animals, from which the different tissues of the embryo are developed. The ova of animals are divided into two classes,—those in which the entire yelk is concerned in the production of the embryo, and those in which a part only serves for this purpose,—while the remainder of the cell- contents is drawn upon for the nutritive needs of the embryo. The first of these which undergoes total segmentation is termed a holoblastic egg; the second undergoes only partial segmentation, and is termed a mero- blastic egg. The ovum of mammals serves for a type of the former class; the ovum of birds is typical of the second class. As already mentioned, the mammalian ovum represents a typical cell; the ovum of the bird differs in many points. Beneath the yelk-membrane is a layer of minute flattened cells, which gradually disappear during the maturing of the egg; while the yelk consists of two parts, one serving for the development of the embryo, the other for its nutrition. The part from 20 PHYSIOLOGY OF THE DOMESTIC ANIMALS. which the embryo is formed is a small, white disk lying directly beneath the vitelline membrane and termed the (read, the blastoderm or cicatricula. In the hen’s egg this disk is about four millimeters in diameter, and is always found in the upper surface of the yelk. If a hen’s egg is hard- ened by boiling, and then cut in two by a vertical section so as to bisect the yelk, the latter will be found not to be perfectly homogeneous, The yelk is clothed externally by a thin layer of different material, which at the edge of the blastoderm passes beneath it and becomes thicker so as to form a bed on which the blastoderm rests, to become connected by a narrow neck with a mass of similar matter occupying the centre of the N.P. CHL. VT. Xs Fic. 9.—DIAGRAMMATIC SECTION OF AN UNINCUBATED FOWL'S EGG, AFTER ALLEN THOMPSON. (Foster and Balfour.) BL, blastoderm; WY, white yelk—this consists of a central, flask-shaped mass and a number of layers arranged concentrically around this; YY, yellow yelk; WT, vitelline membrane; X, layer of more fluid albumen immediately surrounding the yelk; W, albumen, consisting of alternate denser and more fluid layers; CHL, chalaze; ACH, air-chamber at the broad end of the egg—this chamber is merely a space left between the two layers of the shell-membrane ; ISM, internal layer of shell-membrane ; SM, external layer of shell-membrane; S, shell; NP, nucleus of Pander. yelk, which nearly always remains partially fluid in the hard-boiled egg. Within the yelk again are several concentric layers of this white yelk, separated from each other by layers of yellow yelk. The yellow yelk is composed of comparatively large, unnucleated cells filled with highly refractive granules, and containing vitellin, lecithin, and various fatty bodies. The cells which form the white yelk are much smaller, are nucleated, and often a large cell will be seen to contain numerous similar but smaller cells. When the egg is laid by the hen it has already undergone changes which result from fertilization. We will first describe the characters of ORIGIN OF CELLS. 21 the blastoderm when the egg is first laid, and then the changes which have preceded it. The blastoderm of an unincubated fertilized egg may be recognized by the naked eye, when viewed from above, to consist of two parts: an opaque, white circumference, the area opaca, and a central transparent portion, the area pellucida. In the unfertilized egg these divisions are not marked. They are due simply to the way the blastoderm, which is itself entirely transparent, rests on the white yelk. The opaque, circular ring is where the blastoderm is directly in contact with the white yelk, while the central clear portion is due to the fact that the blastoderm is separated from the yelk by a layer of liquid. The white spot often seen in the centre of the blastoderm is the central column of white yelk shining through the transparent membrane (Nucleus of Pander). When the blastoderm is hardened and cut into vertical sections, it is found to be composed of two layers of cells: the upper, small, nucle- ated, cylindrical cells adhering closely together in a single layer and Fig. 10.—SECTION OF AN UNINCUBATED BLASTODERM OF CHICK. (A lein.) A, cells forming the ectoderm ; B, cells forming the endoderm; C, large, formative cells; F, segmen- tation cavity. resting on the white yelk; the lower,an irregular net-work of larger cells which are not nucleated, apparently, but which contain numerous highly refractive granules. These are probably identical with the white-yelk spheres already referred to, and are spoken of as formative cells. The processes which in the hen’s body result in the formation of such an egg are about as follow: In the capsule of the ovary the yelk alone constitutes the egg. It then, just before bursting its capsule, consists of a minute, yellowish, ellipsoidal, cellular body, with a delicate membrane, the vitelline mem- brane, immediately below which in a granular cell-contents, the yelk, lies a lenticular mass of protoplasm, the germinal disk; within this again is a nucleus, the germinal vesicle, containing a nucleolus, or germinal spot. When the ovum becomes mature the ovarian capsule bursts, and the ovum (representing the yelk of the egg as laid) escapes into the oviduct, undergoes impregnation by the spermatozoa found in the upper portion of the oviduct, and has deposited around it the accessory 22 PHYSIOLOGY OF THE DOMESTIC ANIMALS. portions of the egg through secretions from the walls of the oviduct. Thus, the layer of albumen surrounding the yelk is first deposited in the passage of the ovum through the second, tubular portion of the oviduct, the chalaze (see Fig. 9), or twisted, denser portions of Ute albumen, being due to the rotatory motion of the egg against the spiral ridges of the oviduct. The shell-membrane is formed by the organiza- tion of the most external layers of albumen, and the shell is formed in the third portion of the oviduct, or the uterus. The walls of BBS portion of the tube secrete a viscid fluid which surrounds the egg, and in which inorganic particles are deposited. The egg remains in the uterus for from twelve to eighteen hours, and is then expelled through the cloaca, narrow end downward, by its muscular contractions. Fie. U—SURFACK VIEW OF THE EARLY STAGES OF SEGMENTATION IN A Fow.'s EGG, AFTER Coste. (Foster and Balfour.) Lrepresents the earliest stage. ‘Che first furrow, B, has begun to make its appearance in the centre of the germinal disk, whose periphery is marked hy the line A. In 2 the first furrow is completed across the disk, and a second similar furrow at nearly right angles to the first has appeared. The disk thus becomes divided somewhat irregularly into quadrants by four (half) furrows. In a later sta) e, 3, the meridian furrows, B, have increased in number, from four, as in B, to nine, and cross-furrows have also made their appearance. The disk is thus cut up into small central, C, and larger, D, peripheral segments. Several new cross-furrows are seen just beginning, as ex. gr., close to the end of the line of reference, D. About the time the shell is being formed, provided impregnation has taken place, changes occur in the blastoderm, which, though analo- gous to the process of segmentation already mentioned as taking place in the mammalian ovum, yet differs from it. The germinal vesicle first disappears, and a furrow is then seen to run across the germinal disk, dividing it into two halves. This furrow is then met by a second run- ning at right angles to the first; this is then crossed by another, and division of the segments proceeds rapidly by furrows running in all directions until the germinal mass is cut up into an immense number of minute masses of protoplasm, smaller toward the centre than at the periphery of the disk. ‘ The furrows thus formed are not merely superficial, but extend through the entire thickness of the germinal disk: hence the germinal disk is cut up into minute masses of protoplasm. In other words, a ORIGIN OF CELLS. 23 large number of cells has resulted from the segmentation of the parent cell. These cells arrange themselves into an upper layer, with their long Fig. 12.—SuRFACE VIEW OF THE GERMINAL DISK OF A HEN’S EGG DURING THE LATER STAGES OF SEGMENTATION. (Foster and Balfour.) At C, in the centre of the disk, the segmentation masses are very smal] and numerous; at B, nearer the edge, they are larger and fewer: while those at the extreme margin, A, are largest and fewest of all. It will be noticed that the radiating furrows marking off the segments, A, do not reach tu the extreme margin, E, of the disk. 7 The drawing is complete in one quadrant only. It will, of course, be understood that the whole circle should be filled up in a precisely similar manner. axes vertical, their nuclei become distinct, while the lower cells remain large and granular and irregularly placed, forming in this way the unin- cubated blastoderm already described. (See Fig. 10.) A BB Cc OROLOosNO, SEXS SPORE SEIS LESI0 06 Wane o wees 90309 SOW BSS 0 ie Ww Fig. 13.—SECTION OF THE GERMINAL DISK OF A FowL's EGG DURING THE LATER STAGES OF SEGMENTATION. (Foster and Balfour.) This section, which represents rather more than half the breadth of the blastoderm (the middle line being shown at C), shows that the upper and central parts of the disk segment faster than those below and toward the periphery. At the periphery the segments are still very large. One of the larger segments is shown at A. In the majority of segments a nucleus can be seen; and it seems probable that x nucleus is present in them all. Most of the segments are filled with highly refracting spherules, but these are more numerous in some cells (especially the larger cells near the yelk) than in others. In the central part of the blastoderm the upper cells have commenced to form a distinct layer. No segmentation-cavity is present. A, large peripheral cell; B, larger cells of the lower parts of the blastoderm; C, middle line of blasto- derm ; E, edge of the blastoderm adjoining the white yelk; W, white yelk. As a result of incubation a third layer of cells makes its appearance between the two layers of the blastoderm just described, forming an upper, a middle, and a lower layer, or the epiblast, the mesoblast, and the 24 PHYSIOLOGY OF THE DOMESTIC ANIMALS. hypoblast (Fig. 14). From these three layers of cells the embryo is developed. Leaving at this point the changes which occur in the egg of the bird, we have now to follow the analogous changes in the mammalian ovum. We have already seen that in the mammalian ovum one of the first evidences of impregnation is the division of the protoplasm of the at progressively into smaller and smaller segmentation spheres, until the cell-membrane becomes filled with an immense number of minute masses of protoplasm. The general character of this process in its earlier stages is probably identical in all the mammatia. The ovum of the rabbit has been most studied, and the sketch here given is based mainly on Balfour’s summary of the early stages of development in the rabbit’s ovum. The ovum first divides into two nearly equal spheres, of which one Fia. 14.—SECTION OF A BLASTODERM OF CHICK, AT RIGHT ANGLES TO THE Lone AXIS OF THE EMBRYO, AFTER EIGHT Hours’ INCUBATION, ABOUT MIDWAY BETWEEN FRONT AND HIND ENbs. (foster and Balfour.) A, epiblast; B, mesoblast; C, hypoblast; PR, primitive groove; F, fold in the blastoderm produced accidentally ; MC. mesoblast-cell,— the line pwints to one of the peripheral mesoblast-cells lying between epiblast and hypoblast; BD, formative cells. The section shows: (1) the thickening of the mesoblast under the primitive groove, PR, even when it is hardly present at the sides of the groove; (2) the hypoblast, C, early formed asa single layer of spindle- shaped cells; (3) the so-called segmentation cavity, in which coagulated albumen is present. On the floor of this are the large formative cells, BD. is slightly larger and more transparent than the other. The larger sphere and its products will be spoken of as the epiblastic spheres; the smaller one and its products as the hypoblastic spheres. Both these original spheres soon divide into two, and each of these into two more, thus making eight. At first these spheres are spherical, and arranged in two layers formed of four epiblastic and four hypoblastic spheres. Soon, however, one of the hypoblastic spheres passes into the centre, and the whole ovum becomes spherical again. In the next stage each of the four epiblastic spheres divides into two, followed by the division of the hypoblastic spheres into two. The ovum is then made up of sixteen different spheres, nearly of the same size. Of the eight hypoblastic spheres four soon pass to the centre and are surrounded by the eight epiblastic spheres, arranged in the form of a cup. Division of both sets of spheres now continues, the epiblastic layer con- ORIGIN OF CELLS. 25 tinuing to surround the central hypoblastic spheres, both sets continuing to subdivide, until finally the ovum consists of an almost solid mass of hy poblastic spheres surrounded by a layer of epiblastic cells. When the process of segmentation is complete the epiblastic cells are clear and have an irregularly cubical form, while the hypoblastiec cells are polygonal and granular and somewhat larger than the epi- blastic cells. The blastodermic vesicle next forms. This results from the forma- tion of a narrow cavity between the epiblast and hypoblast, which increases in size until it entirely separates these two layers, except at the point where the blastoderm was last in forming (the blastopore). As the cavity increases in size the ovum also enlarges, so that soon it exists in the form of a large vesicle, formed of a thin wall of a single layer of Fig. 15.—OPTICAL SECTIONS OF A RABBIT’S OvUM AT TWO STAGES CLOSELY FOLLOWING UPON THE SEGMENTATION, AFTER E, VAN BENEDEN. (Balfour.) EP, epiblast; HY, primary hypoblast; BP, Van Beneden's blastopore. ‘The shading of the epiblast and hypoblast is diagrammatic. ™ cells,—the epiblastic cells,—with a large cavity, the hypoblastic cells forming a small, ventricular mass attached to the inner side of the epi- blastic cells (Fig. 16). The ovum of the rabbit has now increased in size from 0.09 mm., its size at the close of segmentation, to about 0.28 mm. It is inclosed by the vitelline membrane and a mucous layer " deposited by the walls of the Fallopian tube. As the vesicle continues to enlarge, the hypoblastic cells spread out beneath the epiblast, though remaining thicker in the centre than at the edges, where the cells still possess the power of ameboid movement. The central, thicker portion, which is the commencement of the embryonic area, forms an opaque, circular spot on the blastoderm. The primitive hypoblast now becomes divided into two layers, the lower continuous with the peripheral hypoblast and formed of flattened cells, while the upper is formed of small, rounded elements,—the meso- 26 PHYSIOLOGY OF THE DOMESTIC ANIMALS. blast. The superficial epiblast, again, is formed of flattened cells, which soon become columnar and appear to unite with the rounded elements below, except at the lower part of the embryonic area. Here the blasto- Fic. 16.—RABBIT’S OVUM BETWEEN SEVENTY TO NINETY HOURS AFTER IMPREGNATION, AFTER E, VAN BENEDEN. (Balfour.) BY, cavity of blastodermic vesicle (yelk-sac); EP, epiblast; HY, hypoblast; ZP, mucous envelope (Zona pellucida). derm, as in the chick, is constituted by three layers,—the epiblast, the . mesoblast, and the hypoblast. LITTOVS) SIO OSES S@Oe Cres 5 HY. Fig. 17.—SECTION THROUGH THE OVAL BLASTODERM OF A RABBIT IN THE s SEVENTH DAY, THROUGH THE FRONT PART OF THE PRIMITIVE STREAK. (Balfour.) EP, epiblast; M, mesoblast; HY, hypoblast; PR, primitive streak. The subsequent changes in the development of the blastoderm form the subject of Embryology, and for their consideration the reader is referred to text-books on anatomy. Ill. THE MODIFICATION IN THE FORM OF CELLS. We have seen that originally all the cells formed by cleavage in the egg are absolutely alike. Like the original egg, they are typical cells, consisting of a cell-membrane inclosing finely granular protoplasm, in which a nucleus and nucleolus may be recognized. They only differ from MODIFICATION IN THE FORM OF CELLS. 27 the original cell in size and in as yet unmarked individual char- acteristics which in the speciali- zation of function of the organ- ism will cause them finally, for the most part, to lose all mor- phological resemblance to the parent cell. These differences in cells produced in the development of the organism are very numer- ous. First, as regards their size, we find cells varying from the red blood-cell 3255 to the large ganglion-cell, si, of an inch (Figs. 18 and 19). In nearly all instances where a collection of cells develop into an organ or tissue the original spherical form is lost, often merely from mutual pressure and from alteration in the cell-con- tents, by which the most varied forms are produced. Thus, instead of the spherical form, cells may take on an oval, elon- gated shape (Fig. 20), or may be cylindrical (Fig. 21), or again from mutual pressure may form -regular hexagons. Others may have long, thread-like attach- ments developed, as in the sperm- cells (Fig. 22), or even a number of such prolongations, which as long as the cell is alive continue in active movement (ciliated cells). (See Fig. 21.) Often the nucleus deviates from its spherical form, and may become oval or irregular in out- line, or, as in certain cells of the marrow of bone and in Fig. 18.—RED AND WHITE BLOOD-CORPUSCLES, ENLARGED SIx HUNDRED DIAMETERS. (Ellenber ger.) A, surface view of red corpuscles; B, profile view; C, rou- leaux of red corpuscles ; D, central depression in red corpuscles ; E, cremated red corpuscles; F, small, and G, large white cor- puscles. Fic. 19.— AN ISOLATED GANGLION-CELL OF THE ANTERIOR HORN OF THE HUMAN SPINAL CORD, AFTER GERLACH. (Klein.) A, axis-cylinder; B, pigment. The branched processes of the ganglion-cell break up into the fine nerve net-work shown in the upper part of the figure. PHYSIOLOGY OF THE DOMESTIC ANIMALS. aa a =e 3 Frc. 20.-NoN-STRIATED MUSCULAR FIBRES, ISOLATED. (Klein.) The cross-markings indicate corrugations of the elastic sheath of the individual fibres. Fic. 21.—VARIOUS KINDS OF EPITHELIAL CELLS. (Klein.) A, columnar cells of intestine; B, polyhedral cells of the conjunctiva: C, ciliated conical cells of the trachea; D, ciliated cell of frog’s mouth; E, inverted conical cell of trachea; F, squamous cell of the cavity of the mouth, seen from its broad surface; G, squamous cell, seen edgeways. Fig, 22.—VARI0US KINDS OF SPERMATOZOA. (K lein.) A, spermatozoon of guinea-pig not yet matured; B, the same seon sideways, the head being flat from side to side; C, a spermatozoon of the horse; D, 2 spermatozoon of the newt. 7 toned MODIFICATION IN THE FORM OF CELLS. 29 striped muscle, may undergo reduplication without division of the cell (Fig. 28). The cell-contents, or protoplasm, particularly as regards its granular constituents, may undergo the greatest variation. Often true crystalline Fig. 23,—BONE-CORPUSCLES, WITH THEIR PROLONGATIONS, AFTER ROLLETT. tint.) formations are included in the cell-contents; or vacuoles may form in which different fluids, sometimes watery, sometimes futty, may collect, to again disappear in later stages of the life of the cell. Fig. 24.—DIAGRAM OF DIFFERENT FORMS OF CARTILAGE. (EHllenberger.) A, hyaline; B, fibro-cartilage; C, elastic cartilage ; D, secondary cartilaginous capsule, containing the primary capsule. : Another modification in the form of cells consists in the alteration of the border layers of protoplasm, so that the cell is surrounded by a more or less chemically or morphologically different area, or intercellular 30 PHYSIOLOGY OF THE DOMESTIC ANIMALS. substance, which may present the greatest variety as to quantity. The cell-membrane and so-called cell-capsule belong to these forms of proto- plasmic modification. In cartilage and loose connective tissue this intercellular substance exists in such amount that the still actively moving protoplasmic cells appear to be forced apart by it. (See Fig. 24.) Since the more active vital movements can only originate in the semi-fluid protoplasm of cells, it is evident that the more or less rigid intercellular substance could only take a slight part in organie processes if there were not some means by which it could be brought into close a ACES z =e P| Cast ae ei Gi, aa Fig. 25.—-NERVE-FIBRES. (Thanhoffer.) 1, a, medullated nerve-fibre; b, non-medullated nerve-fibre from the sympathetic of the ox (after Schultze); 2, non-medullated nerve-fibre from Jacobson's organ in the sheep tater Schultze); 3, nerve- fibres with Ranvier's nodes (R), from the sciatic of the frog 5 4, funnel-shaped arrangement of medulla from sciatic of frog, treated with osmic acid; 5, nerve-fibre from frog, with axis-cylinder (t) and so-called horny mesh-work; 6, diagram of medullated nerve-fibre; n, neurilemma; v, medullary sheath; t, axis- cylinder. association with the active vital processes constantly occurring in the interior of cells. Consequently we find the entire intercellular substance pierced of a mesh-work of fine canals, through which the cells send prolongations of their outer layer, which, after numerous subdivisions, serve to connect neighboring cells. By means of these juice-canals interchange between the contents of the various cells is possible and the intercellular substance receives its necessary supply of nourishment, while the connection of cell with cell is an illustration of the loss of individuality of cell-life. Often we find DEVELOPMENT OF TISSUES AND ORGANS. 31 cells connected by branching prolongations: in other cases the exten- sions of the cells—which, to be sure, have a very different function and structure from those already alluded to, but which, nevertheless, serve as connections between cells—so overbalance the cells in extent and number that the latter often appear only as rounded swellings in the extensions (e.g., in the nerves). (See Figs. 25 and 26.) , Fic. 26.—NERVOUS GANGLIONIC CELL AND BRANCHING FIBRES, AFTER KRAUSE. (Thanhoffer.) st, cell body; m, nucleus; me, nucleolus; pr, protoplasmic prolongations; (/, axis-cylinder fibres ; tn, axis-cylinder prolongations, IV. THE DEVELOPMENT OF TISSUES AND ORGANS. The final result of the metamorphosis of cells is the formation of tissues out of which the various organs of the body are built up. 32 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The development of tissue starts in the earliest stages of develop- ment of the egg. We have seen already that, as a result of fecundation, the egg divides into a number of minute segmentation spheres which at first form a solid, mulberry-like mass, and we have now to consider the changes occurring in the mass of simple, undifferentiated cells which result in the development of the tissues and organs of the completed organism. In their early stages, as in the ameeba, each of these cells possesses the powers of development, reproduction, growth, assimilation, respira- tion, and contractility. As the organism passes to a higher stage we find that many of these cells lose these general properties possessed in their entirety by undifferentiated protoplasm, while certain of them are put aside to carry on specific individual functions, Thus,in the young embryo, as in the ameeba, all the cells possess the power of contractility ; as the organism develops, this property becomes restricted to cells form- ing constituents of certain tissues, the contractile tissues, or the muscular system. The amceba, which we have already seen may be regarded as representing one of the units of which the higher organisms are built up, possesses the power of irritability and automatism. In higher forms this property of undifferentiated protoplasm is restricted to a single tissue, the nervous system. The amceba has no part specialized for the various processes of nutrition; any part of its substance may take in nutritive matter, may digest out the portions capable of supplying its nutritive needs, may remove the undigestible residue: any portion of the amoeba is capable of carrying on the metabolic processes by which the matter absorbed as food is converted into protoplasm like itself, and any portion is capable of absorbing the gases necessary for these com- plex chemical processes and of getting rid of the effete products of its nutritive processes. In the higher organisms certain cells are set aside to form the organs concerned in the prehension of food; others have for their sole function the secretion of solvent juices which will digest out the nutritive matters of the food; others are the carriers of the matters absorbed to remote corners of the organisms; and the sole business of certain other cells is to get rid of the useless matter and the products of the waste of the economy. In the ameba any portion may divide off from the parent stock and so originate a new individual; in the higher animals certain tissues or collections of cells have for their sole office the reproduction of cells which shall constitute the starting point of a new organism. In the ameeba, therefore, specialization of function has not commenced; each minute particle of the protoplasm which constitutes it is capable of carrying on all the vital functions. In the higher organ- isms, however, the elementary organisms of which they are built up are so arranged that there may be a division of labor. These collections of DEVELOPMENT OF TISSUES AND ORGANS. 383 cells, marked by a more or less exclusiveness of function, are termed tissues. It must not be overlooked, however, that, though certain func- ‘tions are accentuated in individual tissues, they all possess remnants of all the functions originally seen in undifferentiated protoplasm. Thus, many besides the muscular tissues possess the power of contractility : it is not the nervous system alone which retains the property of responding to irritants, All the tissues are capable of reproducing them- selves in part, and all possess the power of carrying on their own - nutritive processes if suitable food is supplied to them. We have seen that fecundation of the ovum leads to the develop- ment of an immense number of new cells, and we have referred to the modifications in form to which these segmentative spheres may be subjected. ; Tissues are formed from these segmentative spheres in three different ways (Wundt) :— 1. Through formation of layers of cells. 2. Through union of cells. 3. Through excretions by cells. Often all of these methods are united in the formation of a compound tissue which is functionally active as a unit. Such a tissue is called an organ. The classification of tissues is based on anatomical grounds; of organs, on physiological grounds. 1. To the first group belong the epitheliums. In most of these the only modifications which occur in the form of the cells are due to mutual pressure from close contact. Such cells are therefore polygonal or flattened, or, when growth is most marked in one axis, cylindrical. The epitheliums, in series of layers or in single rows, cover the external surfaces of the body as well as the coatings of the digestive, urinary, genital and respiratory tracts which communicate with it, the ducts of glands, and the closed serous sacs. In the latter locality they are called endothelia, in the former epithelia. The hair and nails are modifications of these tissues formed of small elongated cells grown together into almost homogeneous tissues. The terminal portions of the organs of special sense are also epithelial in nature. Epithelial cells are connected by a thin layer of an albuminous cement substance, which during life is in a semi-fluid condition. The shape of the cell may be columnar or squamous. Spindle-shaped and club-shaped cells, as well as goblet cells, ciliated cells, epidermic cells, and prickle cells, are all modifications of these shapes. Endothelial cells are always of the squamous variety, arranged in single layers of flattened, transparent cells with oval nuclei. When their form approaches the columnar, as occasionally is the case in certain serous membranes, they are then in an active state of division, are called germinating cells, and 3 34 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the small spherical lymphoid cells which result are carried to the circu- lation to become white blood-corpuscles. Glandular tissue is also epithelial in nature. Cells are the essential secreting organs of glands, though numerous other tissues enter into their composition. Such cells are usually rounded or polygonal, and are soft in consistence. Frequently the cells rapidly partially break down and are carried off as constituents of the secretion, as colostrum cells, or mucoid corpuscles (moulting); or the destruction of the cell form may be complete and the constituents of the cell enter the secretion in the form of a solution. Muscular tissue forms the third of the group. In the muscles the muscular cells are always closely associated with connective tissue. Such cells may be of two different kinds, different in structure and in function,—the striped and unstriped cells. Muscle-cells are contractile, like ameeboid cells, but contractility is only possible in one definite direc- tion, that of their long axis; muscles, therefore, become shorter and thicker during contraction. ; 2. To the second group of tissues. formed by union of cells belong two tissues in which, in their development, the cells have become greatly elongated, and after absorption of the cell-wall become converted into fibres or tubes; these are the nerves and capillaries. In the nervous tissues certain cells retain their primitive character, the nerve-cells, and only nerve-fibres properly belong to this group of tissues. Nevertheless the nerve-cells are in continuity with the nerve- fibres. The capillaries in a similar manner originate from the arrangement of nucleated, spindle-shaped cells in rows, which become hollowed out through the formation of vaeuoles. The formative cells manifest a ten- dency to send out sprouts which connect with other forming or mature capillaries by which the net-work of capillaries is formed. Lymphatic capillaries are developed in the same way as the blood-vessels. 3. Tissues formed by excretions from cells, forming the third group, may also be called intercellular tissues. Connective tissue is a type of this class. Connective tissues serve to bind together all the organs of the body ; they exist in various forms, which are to a certain extent ‘mutually convertible; they all yield allied chemical products. Connective tissue originates in spherical cells, with very soft proto- plasmic nucleated contents, which ultimately may forma perfectly homo- geneous, laminated, or fibrous intercellular substance. The cells themselves may exist in various different forms, either as tendon-cells, when they are flattened, oblong masses of protoplasm arranged in rows, with round nuclei lying in bundles of fibrils of white connective tissue; as branched cells, found in the cornea, serous mem- DEVELOPMENT OF TISSUES AND ORGANS. 30 branes, and subcutaneous tissues, which, under certain conditions, pre- serve their power of movement; as pigment-cells, which are brauched cells filled, with the exception of their nucleus, with granules; as fat- cells, in which the protoplasmic cell-contents are replaced by a drop of oil, which forces the flattened nucleus against the cell-membrane; and as migratory cells, which are formed in the spaces of fibrous tissue, and which possess the power of amceboid movement. The form of connective tissue in which least change is produced in development is the so-called mucoid or gelatinous tissue. In some of the invertebrates, as in mollusks, this tissue forms the greater part of the body. It consists of a soft, semi-fluid, intercellular substance, in which numerous granules and broken down membraneless cells are suspended. Many of these cells possess the power of amceboid movement. From this tissue in vertebrates the fibrillar connective tissue is de- veloped by the condensation of this intercellular substance into bundles of fibres, held together by an albuminous cement substance, in which the forms of the cells become much changed, becoming flattened and elongated by mutual pressure until the diameter of the cell is not greater than that of the nucleus. The elastic tissues are formed out of the fibrillar connective tissues, which become so modified chemically as to yield elastin and not gelatin. The fibres of elastic tissue are bright yellow in color, usually anastomose, and are sometimes straight, but more often coiled up in bundles. The different forms of development of connective tissue, especially of the intercellular substance, depend upon its different chemical meta- morphoses. Thus, the gelatinous tissues owe their properties to a semi- fluid albuminous body, the connective tissue proper to gelatin-forming bodies, cartilage or chondrin, and the elastic tissues to elastin, etc. Bone is characterized by the deposit of inorganic compounds in its intercellular substance. This hardened tissue then incloses the partially broken down cells, which form the lacune or bone-corpuscles, in which the thickened membrane and nucleus are often visible, though they dis- appear in old bones and their place is then taken by serous fluids, ete. The bones are also rich in vessels which traverse the Haversian canals. As the deposit of salts occurs partly from these and partly from the external membrane, the bones become laminated in structure, some layers being parallel with the canals, others with the exterior. Cartilage is characterized by a sparse intercellular substance which yields chondrin, and by large cells which are often the seat of endoge- nous multiplication. As in bone, so in cartilage, the intercellular sub- stance becomes arranged in the form of capsules around the cells, and may either remain homogeneous (hyaline) or become fibrillar (fibro- 36 PHYSIOLOGY OF THE DOMESTIC ANIMALS. cartilage or elastic cartilage, in which a dense net-work of elastic fibres oceupies the intercellular matrix). Most cartilages, except on articulating surfaces, are covered by a fibrous membrane, the perichondrium, supplied with blood-vessels, lymphatics, and nerves. Bone is surrounded by a fibrous membrane, the periosteum, with an inner layer of oblong nucleated cells, which, from the fact that the bone is developed from them, are termed osteoblasts. Similar cells are also found in the marrow of bones. The organs of the animal body are always composed of several tissues; they may be of three classes, in each one of which some one tissue is especially prominent in function :— 1. Organs whose chief function depends upon tissues of the first class (cells without intercellular substance). a. Glands, which always inaddition to the epithelium contain nerves and blood-vessels. The epithelium is the essential part of glands, skin, mucous and serous membranes. b. Muscles. In these are found muscle-cells as the functionally prominent tissues, though associated with them are connective tissue, blood-vessels, and nerves. 2. Organs whose chief function is manifested through tissues of the second class. a. Compound vessels, arteries, veins, and lymph-vessels. Although the capillaries are formed by union of cells, in larger trunks this mode of formation only applies to the endothelium, on which the other tissues —elastic tissue, connective tissue, and pale muscular fibres—subsequently develop in layers. b, The organs of the nervous system. Nerve-cells and nerve-fibres, formed by union end to end of cells, here form the essential tissues, though blood-vessels and connective tissue are associated with them. 3. Organs whose function is due to intercellular substance. The bony skeleton is the only representative of this group, and the modification of connective tissue known as bone, or its antecedent cartilage, is the characteristic tissue; as secondary tissues, connective tissue and blood- vessels and nerves, representatives of the second class, are also met with. For the mode of development of the compound organs in the _ embryo the reader must be referred to text-books on anatomy or embryology. SECTION. II; CELLULAR PHYSICS. I, THE PHYSICAL PROCESSES IN CELLS. As the tissues and organs of the animal body originate in cells. we should expect that the functions of the higher organisms, which we know to be identical with those of the most elementary forms of life, would to “a certain extent be accomplished by the same general processes. We have already divided the functions of animal life into the vegetative, or nutritive, functions and the functions of relation, and have called atten- tion to the attempt which has been made to reduce the working of these processes to physical and chemical laws. Although in many points this endeavor fails, the operation of the ordinary physical and chemical laws serves to explain many of the complex phenomena of animal life. This is especially seen in the maintenance of the nutrition of the organism. That cells may retain a nutritive balance it is requisite, in the first place, that they be supplied with a proper pabulum, which must pass from the exterior to the interior of the cells. We have found that the typical cell is surrounded by a homogeneous or striated membrane, which, like all other organic tissues, contains a large amount of water closely associated with the ultimate molecules of which that membrane is made up. Hence, the cell-membrane may be regarded as a porous partition whose pores are filled with water, and which separates the cell-contents from the surrounding media. These media may be either gaseous, as the atmosphere; fluid, like the lymph and blood in higher animal forms, or water in aquatic forms of life; or semi-fluid, like the more or less solid intercellular substance. This passage of nutriment from the exterior to the interior of cells is mainly accomplished by purely physical means, not only in simple unicellular organisms but also in higher forms of life, where digestion, or the preparation of food for absorption, has for its object the reduc- tion of food into such forms that the operation of the physical laws of imbibition, capillarity, filtration, diffusion, and osmosis, aided perhaps by chemical affinity, will be sufficient to enable the nutritive mattérs to pass to the interior of cells. When once in the interior of the cells the raw food-products must be transformed into protoplasm similar to that of which the cell-contents . (37) 38 * PHYSIOLOGY OF THE DOMESTIC ANIMALS. is composed. ‘This is a purely chemical process, is accompanied by the liberation of force, and requires for its performance the free access of oxygen. Gases, also, must therefore pass from the exterior to the interior,—a process which the laws of absorption and diffusion of gases are quite suflicient to explain. Again, the chemical processes concerned in the assimilation of food result in the formation of carbon dioxide, urea, kreatin, and other crystalline bodies which are no longer of use and which must be removed; or the cell activity may take on the form of a secretion,—that is, the cell-protoplasm may, from the matter sup- plied to it, manufacture certain substances which in the higher organisms have to be used elsewhere. In either case the products of the proto- plasmic operations must be removed. Here, also, physical laws are all. sufficient. Gases are removed under the laws of gaseous diffusion and absorption. All erystallized products are eliminated by equally simple means. The absorption of fluid by the cell-contents through imbi- bition leads to increase of volume, and hence to increased pressure on the cell-membrane. Filtration thus comes into operation. Or, if the pres- sures within and without the cell are equal, interchange of matters in solution may take place through diffusion and osmosis. All these proc- esses may occur equally well in membraneless cells; for, in all cases, to permit interchange the dividing membrane must be capable of absorbing the fluids or solutions with which it is in contact. The conditions, then, are analogous to those of a body containing fluid by imbibition in con- tact with another fluid. We have now to consider some of the physical processes concerned in these operations. The chemical processes will subsequently receive attention. ; The explanation of the physical processes in cells is to be found in the molecular forces which fluid molecules exert on each other and on solids with which they may be in contact. 1. Coueston is the force which binds together adjacent molecules of the same nature; for example, two molecules of water or two molecules of iron. This attractive force is strongly exerted in solids, less so in liquid, and is absent in gases. It is measured by the force which is required to tear a body asunder. The closer the molecules of a body are together, the greater their cohesive force. Cohesion varies inversely with the square of the distance which separates the molecules; anything, therefore, which drives the molecules apart will tend to weaken their cohesive force. When bodies are heated the expansion which they undergo is due to the Separation of their mole- cules. Hence, when solids are heated their molecules are further and further separated until finally their cohesive force is balanced by the repulsive force, and the bodies pass from a solid to a liquid state. This PHYSICAL PROCESSES IN CELLS. 39 occurs in all cases, provided the heat to which they are subjected does not cause them to undergo chemical change. If a body which has been fused by heat has its temperature still further raised its molecules become so much further separated that the force of cohesion is not suflicient to keep them in contact, and the body then becomes vaporized. In liquids the force of cohesion is not great; hence their molecules are readily displaced and a mass of liquid assumes the shape of the vessel which contains it; in other words, the force of gravity overcomes the force of cohesion. Cohesive force is, nevertheless, present in liquids, and may be demonstrated by the difficulty with which a plate of glass placed horizontally in contact with the surface of water is removed vertically upward, This difficulty is due to the fact that the adhesion of the glass to the water being greater than the cohesion of the water, the molecules of water must be violently separated to permit of the removal of the glass. The spheroidal form assumed by small masses of liquid, as in a drop of dew, a globule of mercury, is due to the working of the force of cohe- sion of the molecules of the liquid. Ina small drop of mercury placed on a surface for which it has no adbesion, as wood or glass, the sum of the mutual attractions of all its molecules being greater than the force of eravity acting on them, the globule assumes the spherical form. If, however, the drop of mercury is large, then the force of gravity increas- ing with the mass of the body becomes greater than its cohesion and the drop becomes flattened. The molecules of all liquids attracting each other, it is evident that the molecules in the free surface of a liquid will be attracted by and will attract those below them, but will exert or will be subjected to no exter- nal attraction. At the surface of liquids, therefore, there is always an inward attraction, which is called surface tension. Of course, in these considerations external accidental pressures and attractions to which the liquid inay be subjected are neglected. The surface tension of liquids is well illustrated by blowing a soap- bubble on the end of a glass tube; as long as the other end of the tube remains closed the elastic tension of the air in the bubble balances the sur- {ace tension of the soap-film, but when the end of the glass tube is opened the tension of the film leads to the contraction and final disappearance of the bubble. So also insects can move on the surface of water without sinking, for the water, not being able to wet their feet, forms a depression, and the elastic reaction of the surface supports them. The case is simi- lar when a sewing-needle is floated on water; as the needle is coated with athin film of oil the water does not adhere to it, the surface becomes depressed, and its increased tension serves to support the weight. Wash- ing the needle first in alcohol, ether, or potash causes it at once to sink. 40 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The importance of these facts will be seen in the explanation of capillary phenomena. 9. ApuHEsION is the molecular attraction exerted between the surfaces of bodies in contact; it may be manifested between solids (as between two freshly-cut surfaces of a leaden bullet, or two pieces of plate-glass),. between solids and liquids (as when a drop remains clinging to a glass rod which has been dipped in water), and between solids and gases (as shown by the bubbles of air which adhere to a glass or metal plate when immersed in water). The adhesion of liquids to solids, which alone of the above will receive attention at present, is greater than the cohesion of liquids, as already mentioned. Thus, when a drop of water is placed on a glass surface it does not assume the spheroidal form, but becomes flattened out, showing that the adhesion of the water to the glass is greater than the cohesion of the water. If, however, the glass plate be greasy, then the drop of water will exert no adhesion to the glass and will remain spheroidal. This adhesion of liquids to solids is not universal, but LAU HAC t Fra. 27, Fre. 28. Fie. 29. Fa. 30. CAPILLARY PHENOMENA. (Ganot.) depends on the nature of both the solid and the liquid. Certain liquids are capable of adhering to, or wetting, certain solids and not others ; and a solid to which one liquid will adhere will be inert, or even repulsive to another. These facts also are of importance in the explanation of capillarity. : 3. CapILLaRity.— When a solid body is placed in contact with a liquid the phenomena (attraction or repulsion) which result are termed capillury phenomena from the fact that they are best seen when capillary tubes (capilius, a hair) are immersed in liquids. As already stated, water is capable of adhering to glass. When a glass rod is dipped into water, the water is raised up against the sides of the rod to form a concave surface above the level of the water, as if no longer subject to the laws of gravity (Fig. 27). If, on the other hand, a glass rod be dipped into mercury, which does not adhere to it, the mercury is depressed around the rod, forming a convex surface ‘below the level of the surrounding fluid (Fig. 28). If glass tubes with narrow bore are immersed in water and mercury, in the former PHYSICAL PROCESSES IN CELLS. 41 the water will rise within the tube considerably above the level of the water outside, and the surface of the water in the tube will be concave (concave meniscus); while the mercury will be depressed in the glass tube below the level of the mercury on the outside and the surface of the mercury within the tube will be convex (conver meniscus) (Figs..29 and 30). If any-two bodies, such as two glass plates, are immersed sufficiently near to-each other in a liquid, the liquid will rise or be depressed between them, according as the liquid has or has not any adhesion to the plates (Fig. 31), the degree of elevation or depression being one-half what it would be if a tube of glass whose diameter equals the distance between the two plates were immersed in the same liquids. If a drop of water be placed in a conical glass tube of small angle and horizontal axis, each end of the drop will have a concave meniscus and it will move from the large to the small end of the tube: if the liquid be mercury, each end will have a convex meniscus and it will move in the reverse direction (Figs. 32 and 33). In the explanation of capillary phenomena two causes deserve attention: first, the cause of. the curvature of the surface, and, second, the cause of the ascent or depression of the liquid within the tube. Fi@. 31. Fig. 32. Fie. 33, The form of the surface of a liquid in contact with a solid depends on the relation between the attraction exerted by the solid on the liquid and the mutual attractions of the molecules of the liquid. Any molecule of a liquid in which-a solid is immersed is acted on by three forces: Ist, gravity ; 2d, the attractive force of the solid for the liquid molecule; and 3d, the cohesive attractions of the other molecules of the fluid. According to the relative intensities of these forces their resultant may occupy one of three positions :— First.—If the attraction of the solid balances the cohesive attrac- tion of the fluid, the resultant of these two forces will coincide with the - force of gravity and the surface of the fluid will be horizontal; for to be in equilibrium the surface of a liquid must be at right angles to the direction of the resultant of all the forces acting on that liquid (Fig. 34). Second.—If the attractive force of the solid for the fluid increases, or if the cohesive force of the liquid diminishes, the resultant will. fall outside of the line of’ gravity or between the line of attraction of the 42 PHYSIOLOGY OF THE DOMESTIC ANIMALS. solid and the line of gravity, and the surface of the liquid being at right: angles to that resultant will be concave (Fig. 35). Third.—If the attraction of the solid for the liquid decreases, or the cohesive attraction of the liquid increases, the resultant will fall to. the other side of the line of gravity, or between the line of cohesive force of the liquid and the line of gravity, and the surface of the liquid, being perpendicular to that resultant, will be convex (Fig. 36). Fria, 34. Fia. 35. , FiG. 36. DIAGRAMS ILLUSTRATING CAUSE OF CURVATURE OF LiquID SURFACES IN CONTACT WITH SOLIDS. (Ganot.) The molecule m is acted on by gravity, in the vertical line m P: is attracted by the plate x. in the line nm, and by the liquid F, in the line w F.” The direction of the resultant m R will depend upon the relative intensities of these forces. If n mand m F balance, the resultant is vertical, m R (Fig. 34), and the surtace is horizontal, If nm increases, or m F decreases, the resultant R is within the angle 7 m P, and the surface is concave (Fig. 35). If m F increases, or x m decreases. the resultant R is within the angle Pm F, and the surface is convex, for the surface of a liquid is always perpendicular to the resultant of forces acting on its molecules (Fig. 36). The ascent or descent of liquid within a capillary tube is dependent on the manner in which the curvature of the surface modifies the prin- ciples of hydrostatic equilibrium. . When a tube of large calibre is immersed in a vessel containing liquid the conditions of equilibrium are the same as in two communicating vessels containing the same fluid. Equilibrium is only possible when the surface of the liquid in both vessels is on the same horizontal plane. For, take any molecule in the plane MN (Fig. 37). It will be subjected to a downward pres- sure equal to the weight of a column of the same fluid, the height of which is equal m to the distance of that molecule from the surface of the fluid within the tube. It will also be subjected to an upward pres- a GENO ey repre OUNOPIMRE which is equal to the weight of a LIQUID PRESSURES. column of liquid whose height is equal to the distance of that plane from the surface of the liquid without the tube. These weights are, however, equal. Therefore every molecule in the plane MN will be subjected to equal and contrary pressures, and will consequently be in equilibrium. , Suppose, however, the tube have a diameter less than one millimeter. The concave surfaces produced by the adhesion of the fluid to the aA | Hl te PHYSICAL PROCESSES IN CELLS. 43 walls of the tube will then intersect, and the surface of the fluid within the tube will be a concave meniscus. In other words, every portion of the surface of the liquid within the tube will be under the attractive influ- ence of the walls of the tube. A certain portion of the fluid within the tube will so be held up by adhesion to the tube, and will hence exert no downward pressure. As a consequence the downward pressure within the tube will be less than the upward pressure of a column of fluid of the same height without the tube. Any molecule on any plane below the surface of the fluid in the tube would so be subjected to two unequal pressures, a greater upward pressure and a lesser downward pressure; the column of liquid will therefore rise within the tube until these two pressures are equal. When, however, the force of cohesion of the liquid is greater than that of adhesion to the walls of the tube, as already explained, the sur- face becomes convex and the surface tension is increased. Since the molecular forces are greater than gravity, the downward pressure in the tube is greater than the upward pressure to which any plane is subjected by the weight of the liquid outside of the tube. The fluid then is de- pressed in the tube until these two pressures are equal. Capillarity partly explains the ascent of the sap in trees, the ascent of oil in a lamp-wick, to a certain extent the movement of the blood and lymph in the capillaries, but more especially the entrance of fluid into porous bodies,—a fact of the greatest importance as underlying the expla- nation of imbibition, filtration, and osmosis. 4, Sotution.—That a stihetance may enter the interior of cells must, as a rule, be in a state of solution; though we shall find, when we study the process of absorption, that there are several exceptions to this statement. The process of solution of solids in fluids is of very general occur- rence in cell life. Almost all food-stuffs are solid, and to be of nutritive value must first be reduced to the form of a solution; even the con- sumption of organic matter in the vital processes of a cell results in the formation of a watery solution, as in the formation of urine, sweat, and the various secretions. When a solid dissolves in a liquid, the cohesion of the molecules of the solid is broken by their adhesion for the molecules of the liquid. When, therefore, the attraction of the liquid for the solid is greater than the cohesion of the solid, the latter is said to be soluble and its molecules separate. The limit of solubility is reached when the attrac- tions of adhesion and cohesion are balanced. Anything that reduces the cohesion of a solid favors its solution ; thus, heat accelerates solution by separating solid molecules through the expansion which it produces, and, by increasing the distance between 44 PHYSIOLOGY OF THE DOMESTIC ANIMALS, the molecules, thereby weakens their cohesive force. Pulverizing, by mechanically separating the molecules to a certain extent, also assists solution. Heat is always essential to the conversion of a solid into a solution. Ordinarily the heat is abstracted from the surrounding media, and is rendered latent in the solution, thus explaining the mode of action of freezing mixtures. The amount of heat so rendered latent in forming a solution is nearly always equivalent to the amount required to melt the body. In certain cases, however, instead of the temperature being lowered in the process of solution, it actually rises, as when caustic potash is dis- solved in water. This depends upon the fact that two contrary proc- esses are going on at the same time; the solution, which tends always to produce a reduction of temperature, and the chemical union of the potash with the water, which, like many other chemical processes, tends to cause an increase of temperature. Consequently, as one or the other of these processes predominates the temperature will fall or rise; or, if the two balance, will remain unchanged. Solubility varies greatly in different bodies and in different liquids. Some solids are soluble only in hot media, and are deposited on cool- ing; others only in cold liquids, and are thrown out of solution when the temperature of the liquid is raised. As a rule, bodies dissolve in liquids which have similar properties; thus crystalline bodies are soluble in water, fats in oil, metals in mercury, and resins in alcohol. “When two or more salts are dissolved in water without chemical action on each other, three conditions result: Ist. The quantity of each salt held in solution is less than when it alone is present, though the combined quantity is greater than when only one salt is used. 2d. The quantity of each is as great as when one only is used; then the total quantity dissolved is the sum of that taken up in each single solution. 3d. The quantity dissolved is greater than when one alone is used, the addition of the second salt in this case increasing the solubility of the first, and often the first increasing also the solubility of the second” (Draper). When the cohesion of the solid and its adhesion for the liquid mole- cules balance, the solution is then said to be saturated. In the case of certain fluids, like alcohol and water, there is no limit to solubility ; their molecules will freely mingle with each other, and the resulting liquid is said to be a mixture, or an emulsion. On the other hand, two liquids may offer an example of true solution, one being only capable of passing to a certain degree between the molecules of the other, as in the case of volatile oils and water, where the limit of solubility is readily reached. 5. Inpipition.—Eyery porous solid may be considered as formed of PHYSICAL PROCESSES IN CELLS. 45 a collection of capillary tubes. When such a solid (e.9., 2 piece of chalk) is immersed in a fluid which is capable of wetting it, the fluid will enter into the pores of the solid through capillarity, and will remain even after the body is removed from the fluid. The solid is then said to have absorbed fluid by imbibition. Organie bodies also are capable of absorb- ing fluid by imbibition, but the process is somewhat different from that of the inorganic porous body. Every organic body, no matter what its consistency, contains always a large amount of water in its composition, to which fluid, as we shall find later, many of the physical properties of the tissues are due. When inorganic bodies contain fluid, that fluid is held in one of two ways,— either chemically united with the body, as in hydrates, or as water of crystallization ; or mechanically in the pores of the solid. Organic bodies occupy a mean between these two. The water in their composition is not in a form of chemical combination, nor is it held mechanically in pores, as in the porous inorganie body, though the conditions are some- what similar to the latter case. That there is a difference, however, is proved by the different effects of the abstraction of water from organic and porous inorganic bodies. The physical characters of, porous, inor- ganic solids, such as baked clay, are not seriously altered by the removal of water contained in their pores. The abstraction of water from semi- solid organic bodies, on the other hand, entirely changes their physical and physiological properties. A piece of connective tissue in its fresh condition is soft, white and glistening, flexible, extensible and elastic. When the water which it contains is removed by drying, it shrivels up, becomes rigid, yellowish in color, brittle, and loses weight. If it be then immersed in water its previous characters will be restored. This differ- ence in the manner in which the water entering into the composition of organic and inorganic bodies is held is explained by the assumption that in the porous inorganic body the water occupies comparatively large spaces between particles of solid, while in the organie body the water surrounds the ultimate molecules of the body. Organic tissues may therefore be defined as bodies whose intermolecular spaces are filled with fluid. As the fluids are held in a different manner in inorganic and organic bodies, it is natural to find that the way in which the fluid is absorbed differs in the two cases. When a dry, porous, inorganic body, such as a piece of chalk, is thrown into water, the water enters the pores of the chalk by capillarity and displaces the air which was contained in its pores. It increases in weight by the addition of the weight of the absorbed water, but does not increase in volume. When a dry organic body, such as a piece of gelatin, is thrown into water no air is displaced, and yet many times 46 ’ PHYSIOLOGY OF THE DOMESTIC ANIMALS. its own volume of water may be absorbed. ‘The gelatin must therefore increase in volume. The fluid in organic imbibition passes into the inter- molecular spaces and separates the molecules. That an organic body may imbibe fluid it is consequently necessary that its molecules be frecly movable. The power of imbibition possessed by the organic tissues is espe- cially due to their albuminoid constituents. Protoplasm is, therefore, above all capable of imbibition, and the rapid formation or disappear- ance of vacuoles in protoplasmic cells may be due to rapid changes in imbibition. Every organic substance has a limit beyond which imbibition is impossible. This limit is lower when the water contains solids in solu- tion, provided the solids are not chemically acted on by the tissues, from the fact that imbibed water is held with greater tenacity by the tissues than are the substances held in solution in the water. Thus, when a tissue saturated with a salt solution is subjected to pressure, the solution first pressed out is more concentrated than that which is forced out when the pressure is subsequently increased ; and in general the fluids lose in concentration in imbibition. Organic tissues therefore absorb water with greater readiness than saline solutions. The importance of this fact will be seen in the explanation of osmosis. The extent of imbibition depends, therefore, on tiie membrane and the nature of the fluid with which it is in contact. Thus it has been found by Liebig that one hundred parts of ox-bladder absorb, of— Water, ‘ - % . 268 volumes. Salt solution ak 204 sp. gr. 9 : . s . 188 es Alcohol (84 per cent. oh é 7 “ . . 38 eS Marrow oil, ‘ ¢ : : : . se Membrane, therefore, has less affinity for a salt solution than for water. This may also be shown by soaking a bladder in water, wiping it dry, and then sprinkling it with common salt. The salt comes in contact with some of the water in the bladder, dissolves, and forms a salt solution. But as the membrane can contain less salt solution than water, some of the solution is expelled and the bladder shrivels up. So also a moistened bladder thrown into aleohol shrivels up, because the alcohol mixes with the water in the bladder; and as the bladder, as shown above, can only absorb one-seventh as much alcohol as water, the solution is driven out. This is the explanation of the use of alcohol and various saline solutions for hardening tissues for making microscopic sections. In the nutrition of animal cells the process of imbibition is an important factor. Every substance which is soluble in water is capable of being appropriated by the protoplasm and may, through imbibition, PHYSICAL PROCESSES IN CELLS. 47 obtain access to the interior of cells, to there undergo the transformations which the needs of the economy necessitate. In cells which possess a closed membrane, capillarity may also be concerned; for there is reason to suppose that the striated appearance which is seen on examining most cell-membranes with a high power under the microscope is in reality due to the presence of minute apertures, or canaliculi. Fluid will therefore enter the pores in the membranes of cells, and so obtain access to the protoplasmic cell-contents. The passage of fluids, however, through the cell-membrane is not necessarily dependent on capillarity. For the cell-membrane, like other organic tissues, is capable of absorbing water by imbibition in the same way in which water is absorbed by gelatin, ze, by entering into its intermolecular spaces. The state of affairs is thus similar to the conditions described in the experiment with the bladder and salt. We have an organic tissue soaked with a fluid in contact with a substance (protoplasm) having an affinity for that fiuid greater than the affinity of the membrane for the fluid; the fluid, therefore, leaves the cell-membrane to enter the protoplasm by organic imbibition. The affinity of protoplasm for water is never satisfied during life: or, in other words, the maximum amount of water capable of being absorbed by cell-contents is never reached. Cells will, therefore, always absorb fluid when brought into contact with it, and by so doing will tend to increase in volume. As, however, the extensibility of cell- membranes is in most cases very limited, the increase in volume of the eell-contents will tend to cause filtration of the fluid contained in the meshes of the protoplasm back through the cell-membrane to the exterior. These facts which we have learned in reference to the imbibition of fluids by organic tissues give but an imperfect idea of the processes of imbibition which take place in living cells. Many fluids which are absorbed by dead tissues are perfectly indifferent to living cells, and there can be no doubt but that imbibition in living tissues is largely governed by the nature of the chemical affinities caused by the chemical processes continually taking place in the interior of active cells. Thus, living tissues (muscles) are incapable of absorbing dilute solutions of sodium salts; the same tissues when dead will absorb it in large amounts. Potassium salts, on the other hand, are rapidly absorbed by the same ’ tissue and almost instantly cause its death, though even in this case the power of imbibition for the potassium salt is greatly increased after death. Again, we shall find that the prolonged activity of many tis- sues, especially the muscles, is manifested in the production of an acid reaction in the cell-contents; under such circumstances, sodium solutions, which are indifferent to these tissues at rest, will now be absorbed by them. 48 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The following figures represent the behavior of the muscular tissue to solutions of different salts (Ranke) :-— Maximum IMBIBITION. 1 PER CENT. NaCl. 1 PER CENT, K CL Living, resting muscle, y ED Positive, but not capable of estimation, as the muscle instantly died. 2 Living, tetanized muscle, . 13 Positive: not to be estimated, ‘ for the same reason as above. Dead muscle, ; ; . 89 186 per cent. Perfectly analogous observations have also been made in the case of the nervous tissues. It would, therefore, appear that living tissues only absorb by imbibition when their vital forces are diminished in energy. In the organism the cells are continually bathed in a fluid which contains the matters necessary for the nutrition of the cells. If the cells have been at rest their nutritive equilibrium has not been disturbed and imbibition does not take place. If, however, they are exhausted by previous activity, imbibition is then inaugurated, nutritive substances enter, the results of cell activity are extruded (acids, etc.), nutritive equilibrium is restored, and imbibition not only ceases, but from the increased volume of the cell-contents pressure is produced on the cell-membrane and the excess of fluid is forced through again to the exterior by filtration. Consequently cells which are most weakened by prolonged activity are the cells which carry on, as a direct result of the chemical affinities. created by that activity, the most active imbibition. By these peculi- arities in the conditions which govern imbibition in living cells is to be explained the peculiar distribution of the inorganic salts in the animal body,—sodium in the fluids, potassium in the solid organs of the body. For, as we know, sodium solutions are indifferent fluids and are not absorbed by the tissues unless they have undergone some depression in energy, while potassium salts in solution are rapidly absorbed and lead to the death, the drowning out of protoplasm. 6. Fitrration ork Transupation is the passage of fluid throngh a membrane dependent upon inequality of hydrostatic pressures ; but that a fluid should so pass it is essential that the membrane be gupatle of absorbing the fluid by imbibition. The greater the affinity of the fluid for the Hembrene (see Imbibition) the more rapidly will the fluid under a moderate pressure pass through the membrane: thus water, or even a saline solution, will filter more rapidly than oil. Filtration will oceur more rapidly through a thin than a thick membrane. The rapidity of filtration is, further, in direct proportion to the pres- sure which the fluid exerts on the membrane, and increases with increas- PHYSICAL PROCESSES IN CELLS. 49 ing temperature. Solutions of different salts pass almost unaltered through membranes, though the filtrate, from the fact that the membrane keeps back some of the water of solution, may be more concentrated. The reverse is true in the filtration of colloids (bodies like glue); there the filtrate contains a smaller percentage of the colloid than the original fluid,—from the fact that the membrane allows more water to pass than gum, albumen, ete. , This explains the fact that colloid bodies, perhaps on account of the great size of their molecules, are with great difficulty removed from the pores of animal and vegetable tissues, especially since it has been. found that if the fluid which contains colloids in solution also contains cerystalloids, less colloid will filter through than if the crystalloids had been absent, and the filtrate is richer in crystalloids than the fluid in the: filter. Crystalloids, therefore, hinder the filtration of colloids; and as- protoplasm is always associated with certain saline bodies, the latter prevent the loss of the albuminoids of the cell-contents. Many of the phenomena of filtration may be explained under the working of the laws of capillarity, especially when the filter is an inorganic, porous solid. When, however, it is an organic membrane, as of course is always the case in the animal or vegetable cell, there the laws of imbi- bition are of prime importance. Cell life furnishes many examples of the process of filtration. When the cell-contents increase in bulk through imbibition the pressure on the interior of the cell-membrane is greater than on the exterior; substances in solution within the cell may then pass through the cell-membrane. The formation of the saline constituents of the various secretions is: probably accomplished in this way. When the flow of blood is obstructed in a vein the pressure back of the obstruction becomes greatly increased, and the water and saline constituents of the blood pass through the walls of the vessel. In this way oedema and dropsies are produced. In the liver, so long as the pressure in the bile-ducts is low, the bile filters from the liver-cells into the bile-ducts. But if the flow of bile is interfered with so as to make only a slight resistance in the bile-ducts, the bile then filters into the hepatic parenchyma, from there into the lymphatics, by which it is carried throughout the body, and jaundice is produced. When the renal secretion comes under consideration it will be found that the process of filtration there fills a very important réle. When fluids pass from the interior to the exterior of cells, or the reverse, they usually come into contact with other fluids. Under certain circumstances these fluids will mix; under others mixing will not occur. Those conditions now demand consideration. 7. Dirruston or Liquips.—The molecules of liquids, as has been already seen, are held together by a force of attraction, or cohesion; the 4 50 PHYSIOLOGY OF THE DOMESTIC ANIMALS. molecules of liquids are also capable of exerting an attractive force on solids, or adhesion. In addition to these two modes of manifestation of molecular force, molecules of liquids are capable of attracting mole- cules of other liquids. If in two different liquids brought into contact the cohesive force between the molecules of each liquid is greater than the attractive force between the molecules of the different liquids, the liquids remain separate and apart, and are said not to be miscible. Water and oil furnish examples of such liquids. If, however, the attraction between the molecules of the different liquids is greater than the cohesive force of either, then the liquids will mix, even against gravity, until the mixture becomes uniform. Such a process of mixing is called diffusion of liquids. It follows, therefore, that whenever two chemically indifferent fluids are brought into contact with one another they mix, even without any disturbing cause, until a perfectly uniform mixture results. Diffusion may he illustrated by filling a small bottle with some saline solution and then placing it in a large jar, which is then carefully filled with distilled water, so poured in as to cover the mouth of the small jar which contains the saline solution, at the same time avoiding any mixing of the fluids by movement. If asmall portion of the water in the large jar is then drawn off carefully from time to time with a pipette, it will be found that the water will contain a gradually increasing quantity of the salt, until finally the jar will be filled with a perfectly uniform saline solution. From such experiments it has been found that the rapidity of dif- fusion increases with the extent of surfaces in contact, with the tempera- ture, and with the difference in concentration of the two fluids; it is, therefore, more rapid at the beginning of the experiment, when the outer jar contains distilled water, than later, when it contains a saline solution. The rapidity of diffusion also varies with the chemical nature of the solutions ; thus, potassium salts diffuse much more readily than sodium salts,—a point which we shall later see is of great importance. Acids dif- fuse very rapidly; alkaline salts and sugar slower, and colloids, perhaps from the fact that they cannot form true solutions, scarcely at all, though colloids in solutions with crystalloids do not interfere with the diffusion of the latter; while, when two salts undergo diffusion together, the least diffusible salt diffuses more rapidly than it would alone. In the different animal tissues, in addition to the intermolecular spaces filled with fluid, we have also larger spaces, or sensible pores, which contain fluids, and which form a system of more or less fine canals traversing the different parts of the body (lymph-spaces, lymph- and blood-capillaries). Therefore every internal part of the animal body is continually bathed in liquid into which fluids leaving the cells are PHYSICAL PROCESSES IN CELLS. bil capable of diffusion. In most cases, however, these fluids are in con- stant motion, and the purely physical phenomena of diffusion are of little importance, particularly when the extreme slowness of ordinary diffusion is remembered. As the composition of the fluids of the body is continually changing, diffusion, greatly aided by the motion of the fluids, will, nevertheless, serve to maintain a certain degree of constancy of composition. It has been already shown that when watery solutions are found on different sides of a membranous partition, as in the case of the cell-con- tents of two neighboring cells whose contents are more or less fluid, the membrane does not serve to keep the fluids apart. For, the membrane: being capable of absorbing liquids by imbibition, the liquids fill the intermolecular spaces of the membrane, and so come in contact with each other; the phenomena of diffusion then commence, though the process is very greatly modified by the behavior of the intervening membrane. As already mentioned, diffusion, with the exception of the part it plays in distributing fluids uniformly through the interior of cells, fills quite a secondary role in the physical processes of the animal economy. Dif fusion as modified by the passage of liquids through an animal membrane occupies a much higher position in point of importance. 8. Osmosis. When two liquids capable of mixing are separated by a membrane which possesses the power of imbibing these liquids, a gradual union of the two liquids takes place through the membrane. This interchange, which is called osmosis, continues until the two liquids are equally mixed; consequently, the final result is the same as if no membrane separated the two liquids, though the process is essentially different; for the diffusion currents must be modified by the molecular forces which the molecules of the membrane exert on the liquids in con- tact with them. If two liquids are poured into the arms of a U-tube (Fig. 38) so that they are in con- tact at A they will mix, but the level will remain the same in both tubes, z.e., equal portions of each liquid pass into one another in equal time; if, on the other hand, a mem- Fie, 38. brane is placed at A the liquids will mix, but the column of liquid will rise in one tube above the original level and sink to a corresponding amount in the other. From which it follows that in the mixing of liquids through a membrane the interchange is unequal, ¢.e., more of one liquid passes than of the other. The current through the membrane is a double one. Thus, if a saturated salt solu. tion is placed in one arm of the tube and an equal quantity of distilled 52 PHYSIOLOGY OF THE DOMESTIC ANIMALS. water be placed in the other, the salt solution will soon be found to have increased in volume and the water to have decreased. If the character of the two liquids is then examined it will be found that the distilled water is no longer pure, but that it contains salt; while the saline solu- tion will be no longer saturated, but of much less density. Salt has therefore passed through to the water and water passed through to the salt solution. There has been, however, as is evident, a difference in the rapidity with which the two substances have traversed the mem- brane. That this process is not at all analogous to filtration—in fact is directly opposed to it—is seen in the continued ascent of the column of liquid in one arm of the tube, showing that the water passes to the salt solution even against a continually increasing hydrostatic pressure. The tendency is therefore for filtration currents to form in the opposite direction to the osmotic current. If one liquid is water and the other salt solution, the amount of water passing to the salt solution for each equivalent of salt passing to the water is called the osmotic equivalent of the salt. The osmotic equivalent is dependent upon the chemical nature of the body and the concentration of its solution. Thus, for sodium chloride it is 4.3, meaning that for every gramme of salt which passes through the membrane 4.3 grm. of water will pass in the opposite direction to the salt. For sodium sulphate it is 11.6; potassium sulphate, 12 ; magnesium sulphate, 11.7 ; aleobol, 4.2; sugar, 7.1. In general the osmotic equivalent increases with the temperature, and varies very greatly with the concentration of the solutions. The rapidity with which different bodies diffuse through a porous membrane is independent of their osmotic equivalent, but is directly dependent upon their chemical nature and solubility, increasing with solubility ; and bodies nearly related as to their chemical composition are also nearly related as to rapidity of diffusion. The rapidity also increases with increasing difference of concentration between the two liquids and with increase of temperature. When two solutions of the same substance but of different denies are allowed to diffuse. into one another, the denser decreases in density and the lighter increases, and the same alterations of volume occur as would be the case were one of the liquids pure water. The osmotic equivalent is in both cases the same, but in the former case the rapidity of osmosis is much less. If two solutions of substances of different chemical composition are allowed to diffuse, the rapidity will increase with increase in the chemical affinity between the two substances. All colloids pass with difficulty through organic membranes, but as they have a strong affinity for water they draw it with vigor throush organic membranes; hence, their osmotic equivalent is very high, though PHYSICAL PROCESSES IN CELLS. 53 the current of water to the colloid is very slow, possibly because the large molecules of the colloids readily stop the pores of the membrane. Albumen in solution passes more readily through a membrane to mix with salt solution than with water. A very concentrated solution of salt, however, prevents osmosis of albumen by simply removing the water from the albuminous solution. When a solution of a diffusible substance, together with a solution of a colloid, is placed on one side of a membrane and pure water on the other, at first none of the colloid passes through the membrane, but simply water to the colloid and the ditfusible substance to the water; hence, albumen may be freed of its salts by diffusion (dialysis), or, if a mixed solution of sugar and gum is subjected to dialysis, only the sugar . passes through the membrane. An exception to this is seen when albumen and salts dialyze with water. First the salts pass, then the albumen passes into the salt solution. Just as we found there were two kinds of imbibition,—the capillary and molecular,—so are there two kinds of osmosis, which differ somewhat according as the partition between the two fluids is a porous, inorganic solid, or an organic tissue capable of absorbing liquid by imbibition. In the case of a porous, inorganic partition the phenomena of osmosis are entirely governed by capillarity and the laws of diffusion of liquids. Certain liquids have a greater tendency to enter capillary tubes than others. When, therefore, two miscible liquids are separated by a porous solid, which may be regarded as a collection of capillary tubes, the liquid which has the greater affinity for the walls of the tube will enter toa greater extent than the other, and will meet the other fluid advancing in the opposite direction, but with less force on account of its lesser affinity. The two liquids thus coming into contact with each other will diffuse into each other, and the pores will be occupied with a mixture of two liquids, for one of which the walls of the tube will have a greater aflinity than “for the other. Then, although diffusion will take place from this mixture into the liquid of greater affinity, the latter continually forcing out some of the mixture, the liquid of lesser affinity will continually increase in ‘volume. In the case of organic membranes, the power possessed by the mem- brane of imbibing different liquids enables osmosis to take place, while the direction of the current is governed by the affinity of the liquids for the membrane. Whichever liquid has the greater affinity for the mem- brane will pass in greatest amount. Here, for the sake of simplifying the matter, we may assume that the liquid which has entered the inter- molecular spaces of the membrane is, to a certain extent, governed by the same conditions which apply to the entrance of liquids into capil- lary tubes. i) | rice PHYSIOLOGY OF THE DOMESTIC ANIMALS. When an organic tissue has absorbed liquid by imbibition, its inter- molecular spaces being filled with that liquid, the liquid, which becomes superficial on the far side of the membrane, is in direct continuity with the body of the liquid having the greater affinity for the membrane, and in direct contact with the liquid of lesser attinity. Diffusion phenomena therefore commence. When a membrane has a tendency to imbibe water, it will absorb more water than salt solution, if placed between water and a salt solu- tion, and will increase in volume. In every pore or intermolecular space of the membrane, therefore, the layer of liquid in contact with the sides of the pores, or with the solid molecules, will contain less salt than water. From the affinity which the two liquids exert on one another this condition will not remain constant, and the rapidity with which the inter- change takes place will depend upon the aflinity of the two liquids for one another; but the interchange will not occur in the same manner as if no membrane were present, 7.e., equal quantities of salt solution and water will not substitute one an- other. Such an interchange will only occur in the centre of the pore, while on the wall of the pores only water will pass; consequently the salt solution will increase in volume Fia. 39.—DIAGRAM ILLUSTRATING OSMOSIS. This figure represents a diagrammatic section of a Spondingly, while the rapidity of single, capillary pore in an organic membrane separating peru : salt solution and water. From the greater affinity of the motion alone the walls will be less 1 $ 5 and the water will diminish corre- Se Ee ete imtccamecr Ulan ae the centre ofthe poxesmon EOD TNE BEVEL G econn Ol ine AlnENeHOM or Whe walls for the water. Therefore, the greater the concentration of the salt solution the higher will be the osmotic equivalent, since the difference of affinity of the membrane for the water as compared with the salt solution will be the more marked. This, however, only applies to salts whose solutions are also imbibed by the membrane; where this is not the case increased concentration produces a decrease in the osmotic equivalent, for in the latter ease there will be more tendency for the membrane to hold the layer of water in contact with the walls of its pores. Different membranes will consequently modify the osmotic exchange of liquids taking place through them. PHYSICAL PROCESSES IN CELLS. 5D Thus, dry membrane will show a higher osmotic equivalent than fresh membranes or dried membranes moistened, from the fact that the membrane retains more water by imbibition, while the passage of the salt is facilitated. If an animal membrane separates water and alcohol, the water will pass in much greater amount, for membrane absorbs water much more readily than alcohol or a mixture of water and alcohol. Aubber or collodium membranes, on the other hand, allow aleohol to pass with greatest readiness, as such membranes absorb aleohol more readily than water. The general phenomena of osmosis may be well illus- trated by the egg-osmometer (Fig. 40). This is prepared by picking off a little of the shell from one end of an egg, taking care to leave the shell-membrane intact, while a glass tube is cemented around a small hole pierced through both shell and shell-membrane at the opposite end. The end at which the shell has been removed and the membrane left undisturbed is then immersed in distilled water. After a time it will be found that water has passed from the out- side to the interior of the egg, as shown by the increased volume, the white of the ege being forced up into the tube cemented on the open end of the egg. At the same time the addition of nitrate of silver to the water in which the egg was immersed will show, by the white precipitate formed, that the chlorides have passed from the inside to the outside of the egg. No trace of albumen, however, is to be seen in the distilled water. The salts of the egg, or its erystalloids, have thus passed by osmosis through the egg-membrane, water has also passed, while the egg-albu- men, a colloid, has been retained. These facts, already alluded to, that crystalloids in solu- tion will pass through an animal membrane, while colloids will not, has been made use of in a process which is fre- quently employed by the chemist to separate bodies of these two classes. Thus, albumen, or any other colloid, may be entirely freed from crystalloids, such as salt or sugar, by placing it on one side of a membrane with a large quantity of distilled water, which is frequently renewed, on the other, Fig. 40.—EGG PRE- The salts pass through the membrane to the water, their SGAREDC RY SARE TaD place being taken by water, while the albumen, with the ILLUSTRATE — OS- exception of becoming more diluted, remains unchanged. inh ACTION. This process is termed dialysis. Osmotic phenomena, consequently, may be referred to the following causes (Wundt) :— 1. The aflinity which the two liquids exert on one another. 2. The relative aflinity which the membrane exerts on the two liquids. 3. On the narrowness of the pores through which the liquids diffuse. 4. On the overcoming of the adhesion of the liquids to the walls of the pores through increase of temperature. The importance of this process in the action of the animal organism is very evident. Nearly all animal tissues are, during their entire life, in 56 PHYSIOLOGY OF THE DOMESTIC ANIMALS. a state of tension from imbibition (swollen) ; therefore, all tissues permit the entrance of watery and saline solutions, and prevent entrance of liquids not miscible with water. The absorption of most of the dissolved food-stuffs, and the removal of deleterious matters, etc., by the glands from the blood rest on osmotic processes. The results as to the different osmotic equivalent of different substances; the behavior of different membranes to diffusion; the different capability of animal matter for imbibing different solutions, all point to the way in which the glands remove different substances from the blood where no other explanation can be found but a membrane and cells capable of absorbing certain’ solutions. The presence of certain salts in the contents of certain cells is without doubt instrumental in shaping the capability of those cells for absorbing definite solutions. 9. Dirrusion or Gases.—In the living organism, in the cell, the vital activities are only carried on when there is an unbroken supply of oxygen conveyed to the cells either in the form of a free gas or in hemoglobin. And, on the other hand, the organism cannot exist unless there is some provision made for the removal of CO,, continually formed in physiological oxidation, and which itself is a deadly poison to cell activity. These two gases are, therefore, the most important which have to be considered. In pulmonated, air-breathing animals there is also a continual exhala- tion of watery vapor; there is also a continual circulation of N in the lungs of animals, as N forms four-fifths of the atmosphere. Gaseous interchange in the organism rests mainly on the laws of diffusion and absorption of gases, though these laws are subject to some slight modification as contrasted with their application to inorganic matter. By gaseous. diffusion is meant the mutual mixing of two or more free gases; and, as in liquid diffusion, it results in a uniform mixture. Gases which pass into a vacuum fill it completely and uniformly; this is also the case when the space into which a gas streams is already occn- pied by a gas which is chemically indifferent to the first; a space filled with an indifferent gas behaves to another gas precisely like a vacuum. If two flasks, each provided with a stop-cock, are connected, one vertically above the other, and the upper one filled with hydrogen, the lightest of gases, and the lower one with carbon dioxide, a heavy gas, if the stop-cocks are now opened, in a short time it will be found that half of the hydrogen, in spite of its lighter specific gravity, has descended into the lower flask, while half of the carbon dioxide has ascended against gravity into the upper flask, so that each flask will contain a uniform mixture of the two gases (Fig. 41). Each gas has diffused into the other as into a vacuum, and what holds for the diffusion of two PHYSICAL PROCESSES IN CELLS. Or gases applies also to the diffusion of several gases; so that the general rule may be formulated: If a number of gases exerting no chemical influence on each other are allowed to enter a space, each gas will diffuse itself uniformly through that space. If the amount of gas in any given space is small or large, or, in other words, no matter what the gaseous pressure may be, another gas will enter that space precisely as if it were a vacuum. : The importance of these laws in explaining the mechanism of gaseous interchange in respiration is very evident. The atmosphere is composed of a mechanical mixture of about ¢ nitrogen and } oxygen, In the process of inspiration a variable amount of this gaseous mixture is drawn into the lungs. It then meets with a gaseous mixture which contains less oxygen than the atmosphere (for a certain amount of the oxygen taken in in previous inspirations has been removed by the blood), and which contains a considerable volume of carbon dioxide removed from the blood. Phenomena of diffusion, therefore, at once commence between the air already in the lungs and that which has entered in inspiration. The air in the lungs becomes gradually poorer in oxygen and richer in carbon dioxide, as the air-cells are approached. Difvusion tends to equal- ize this difference; the oxygen of the inspired air diffuses into the deeper portions of the lungs, the carbon dioxide diffuses from the deeper to the upper portion, the process being a constant one; for the difference in the relative volumes of the two gases in the upper air-passages is maintained by repeated expirations, by which CO, is removed, and inspirations, by which more oxygen is brought into the lungs. The CO, formed in respiration by animal organisms, and thus removed from them in respiration, distributes itself uniformly through the atmosphere, so that there is everywhere a uniform percentage, unless there is a local temporary increase; but then this soon becomes equalized by diffusion, permanent increase being prevented by the absorption processes in the vegetable kingdom. The tension of O in the atmosphere is far greater than that of CO,, as the O is present in far larger proportion, and conversely. Diffusion leads finally to the theoretical result, that all gases in any given space, as in the atmosphere, exist under the same pressure; when, therefore, there is anywhere a temporary increase in the tension of a gas, diffusion commences and tends to continue until there is a uniform distribution and mixing of the different gases. 58 PHYSIOLOGY OF THE DOMESTIC ANIMALS. If two different gases are separated by a porous partition, the gases will mix through that partition. The phenomena under such cireum- stances are similar to what has been described in the case of liquids under osmosis; that is, that different gases pass with different degrees of rapidity through the partition, so that the volume of gas increases on one side of the partition and decreases on the other. If an unglazed, porous, earthenware cup (such as is used ina Grove battery) is closed with a cork through which passes a long, vertical, glass tube, whose end dips into a vessel below containing water, and the cup is covered with a bell-jar containing hydrogen or illuminating gas, the hydrogen will pass through the walls of the cup to the inside faster than the air from the inside can diffuse out. The volume of gas in the interior increasing, bubbles of air will escape through the water from the end of the tube. If now the bell-jar be removed the hydrogen will i diffuse out from the cup faster than the air can enter, the volume of gas within the cup will decrease and the water will rise, from atmospheric pressure, F within the tube. If oxygen be used within the cup instead of atmospheric air, it will be found that the hydrogen will diffuse four times as fast as the oxygen. The density of hydrogen is 1.; that of oxygen 16.; therefore, the law has been made that the rapidity with which different gases under similar conditions (equal pressures) diffuse through thin, porous par- titions into a vacuum or into other gases is in inverse proportion to the square root of the density of the gases (Graham’s law). These general facts may be illustrated by another Praha very simple experiment. If an unglazed earthenware cup be closed by a cork in whieh a water-manometer is inserted and then placed in a larger glass vessel containing vapor of ether, the air from the inside of the cup will diffuse out faster than the five-times-heavier vapor of ether will diffuse in, and the water in the cpen arm of the manometer will sink (Fig. 42). There is, however, here a marked difference from osmosis, for in the diffusion of gases through inorganic partitions or dry organic membranes the nature of the partition is without influence on the rapidity of diffusion. The rapidity of diffusion depends only on the specific gravity of the gas. 10. ABsorPTION OF GASES.—Hxactly as gases diffuse into spaces already occupied by other gases, so also will they diffuse into the inter- molecular spaces of liquids, without any chemical attraction between the gas and the fluid being essential. If a glass tube, closed at one end, is filled with dry, ammoniacal gas, its open end immersed in mercury, and ' PHYSICAL PROCESSES IN. CELLS. ; 59 then a small quantity of water introduced into the tube, the water will almost instantly absorb the gas, which will entirely disappear, and the mercury will rise in the tube, and, with the water, entirely fill it. Just as without so also within liquids, gases exert no pressure on each other; so that a number of gases may diffuse at the same time into any given liquid. We meet, in this solution of gases in liquids, with laws analogous to those which govern the solution of solids in liquids. Every liquid absorbs at any given temperature a fixed quantity of any given gas, just as a certain quantity of liquid will only dissolve a given quantity of asalt. The volumes which a given liquid at a fixed temperature will absorb of different gases are very different, the most readily-liquefied gases being most readily absorbed. The volume of any gas that may be absorbed by a liquid varies greatly with the temperature. As the ‘temperature increases capability of absorption decreases, until at 100° C. water absorbs no gas at all. The exact opposite holds in the case of sohitions, The co-efficient of absorption is the volume of gas which a liquid in free communication with a gas can absorb. It varies with every liquid, every gas, and every temperature. According to Bunsen, a unit of volume of water absorbs— Gas. Temperature. Volume. oo, . r ° 1.7967 Oy yoo]! 9046 N ; 0° . i , , 0.020384 209, , é 3 ‘ 0.01401 0 ; go ‘i ‘ : F 0.04114 20° : ‘i . 0.02838 H oo... ; : ‘ 0.0163 With every increase of pressure the liquid will absorb uniformly- increased amounts of gas. Gases absorbed by liquids do not lose their power of diffusion. Hence, if we bring a liquid which contains a gas under a definite tension, e.g., H,O with CO,, in communication with a space containing another gas, H, the CO, diffuses out of the H,O into the space containing the H. CO, will continue to leave the water until it exists in equal pressure without and within the liquid; so, also, H will diffuse into the water until it has a uniform tension without and within the liquid. An absorbed gas is therefore given up when the tension of the gas is less in the space in communication with the liquid than the tension of the gas in the liquid. When two or more gases are mixed together their absorption by a liquid is proportional to the relative volumes of the gases present in the mix- ture, or to the different gaseous tensions. - In the cell in the animal organism this gaseous interchange occurs 60 PHYSIOLOGY OF THE DOMESTIC ANIMALS. through the cell-wall or the walls of capillaries, ete. These organic tissues, which we have seen to be always filled with liquid, offer very little resistance to the passage of a gas. he animal fluids communicate through these delicate moist tissues almost directly with the gases of the atmosphere. Gases formed by cells, or gases which pass from the exterior to the interior of cells, or even the passage of gases through the membranes of the lungs or gills of animals, are not governed by the law of the dif fusion of gases given above, but their transfer through an animal mem- brane is governed by the co-eflicient of absorption of that tissue for the different gases. This may be illustrated by a very simple experiment devised by Draper, who does not appear, however, to have appreciated its application to gaseous interchange in the animal body. The law of the diffusion of gases through porous partitions is that the rapidity of the diffusion is inversely as the square root of the density of the gas. If the finger be dipped in soap-water and then rapidly passed over the mouth of an empty bottle so as to leave a horizontal film, and the bottle then placed under a bell-jar filled with carbon dioxide, the film soon swells up into an almost hemispherical dome. Or, if the bottle be filled with carbon dioxide, and then exposed to the atmosphere after its mouth has been covered with a soap-film as before, the film is promptly depressed into a deep concavity and bursts. Now, if the film is regarded as a porous partition, the air, being of many times less density than the CO,, should diffuse much more rapidly, according to Graham's law. The reverse, however, is the case. Water, however, of which the film consists, has a much higher co-eflicient of absorption for CO, than it has for oxygen ‘or nitrogen. The CO, is therefore absorbed more rapidly by the film than the gases of the atmosphere, and from its solution in the film dif: fuses rapidly into the atmosphere. The state of affairs is similar in the case of gaseous interchange in animal cells. The membranes of cell are not porous partitions, but are tissues whose molecular interspaces are filled with liquids. That a gas may pass through such a membrane it is necessary, therefore, that the gas be first absorbed by the liquid in the cell-membrane. The readily-absorbed yases, such as CO, will thus diffuse through cell-membranes more rapidly than those with a lower co-eflicient of absorption, such as N, H, or O, the rapidity of absorption being further governed, not only by the co-efficient of absorption, but by the gaseous tension and the temperature. After having passed through the cell-membrane gases will, of course, diffuse into the liquid or gaseous media surrounding those cells, according to the tension of those gases already present. In the case of terrestrial animals this medium is the atmosphere, which is composed of 21-volume per cent. of O and 79 per cent. of N, PHYSICAL PROPERTIES OF TISSUES. 61 with traces of CO, If we imagine in the first place that the tissues are at first free from gas, according to the co-eflicients of absorption and pressure, they will absorb definite volumes of these gases. If we assume that the co-efficient of absorption of the animal liquids for these gases is the same as water, as is actually nearly the case, the co-efficient of absorption for O will be nearly double that of N, and the volumes absorbed will be as 34.91 to 65.09. This is actually the case in large bodies of water, as lakes, etc. Under the conditions we have imagined, of course, only a trace of CO, would be absorbed. We know, however, that CO, is a constant result of cell life; therefore the tension of CO, in animal fluids is far in excess of that in the atmosphere; consequently, instead of an absorp- tion of CO, by the tissues from the air, we will have an exhalation taking place. Similar conditions apply in the case of watery vapor. Hence, the gaseous interchanges between the organism and the atmosphere under the laws of absorption and diffusion are as follow :— Absorption of O and N. Exhalation of CO, and H,O vapor. In animals, however, by far the greater part of O and CO, are carried in chemical combination with hemoglobin, and not in mere solu- tion in the fluids of the body. These conditions, as well as the mechanism of gaseous interchange in the lungs and tissues, will be considered in greater detail under the subject of Respiration. At present enough has been said to show that the laws of diffusion and. absorption are the fundamental principles which underlie these processes. II. THE PHYSICAL PROPERTIES OF TISSUES. We have found that the different animal tissues furnish illustrations of both the solid and liquid forms of matter, varying from a perfect fluid to a solid of almost mineral consistence, and that midway between these extremes what may be termed the semi-fluid tissues are of the greatest importance in the physical and chemical operations of the organism. We know, further, from analysis of the organic tissues, that, no matter what their consistence, they all contain a large proportion of water in their composition; it is to the amount and the manner in which this water is held by the tissues that nearly all the physical properties of the tissues, particularly of the semi-solid tissues, are due. We have already seen that in inorganic bodies, though they may be rich in water, the water is either chemically united to that body, or is held mechanically in capillary pores; while in organic matter the water occupies the intermolecular spaces. The tissues, therefore, resemble solutions in this respect ; thus, in a salt solution the water occupies the 62 PHYSIOLOGY OF THE DOMESTIC ANIMALS. intermolecular spaces of the salt. In solutions, however, the solids are. bound to the water; in tissues, the reverse. Since all fresh, organic tissues contain water, their specific gravity must be comparatively low; drying, by driving off the water, while decreasing their weight by the amount of water displaced, will increase their specific gravity, though even then, like all organic bodies, they will be specifically lighter than most minerals. The specific gravity of dif- ferent tissues will also vary according to the nature of their special con- stituents; thus, adipose tissue will represent one extreme, bones and teeth the other, and tissues which are rich in fat, like the nervous tissues, will be of less specific gravity than those which contain inorganic matters. As the specific gravity of the tissues depends upon their constitu- ents, it wili vary according to the relative proportions of those con- stituents at different ages, in different individuals, and in different nutritive states. No fixed figures can, therefore, be given to represent the specific gravity of the different tissues, but, though not constant, the following represents the average specific gravity of the most important tissues of the human body :— Bones, 1.656 Elastic tissue and tendons, 3 ; : « La Muscles, . ; “ ‘ r ¢ é : 2 - LOB Arteries, . b F 3 : ; ‘ : . 1.096 Veins, 1.05 Nerves, 1.046 1. ConEston.—It follows from what has been said as to the freedom cf molecular movement in most organic tissues, as shown in their capa- bility of imbibition, that their cohesion must be less than that of most inorganic solids. It is highest in the bones, lowest in glands and brain, though it is comparatively high in nerves. Cohesion is there due to the fibrous envelope (neurilemma) and not to the nerve-fibre; and as these sheaths relatively increase as the nerve-trunks subdivide, the cohesion of the fine nervous twigs of the skin is relatively higher than that of the nerve-trunks. The greater the amount of water contained in a tissue the less its cohesion, for the wider apart will be the molecules, and the molecular attraction decreases as the square of the distance which separates them. Consequently desiccation increases cohesion. The order of cohesiveness is inversely as the quantity of water; thus, the following list is arranged with tissues of greatest cohesion and feast water first, and as Ptee increases cohesion decreases :— 1. Bones. 4. Muscles. 7. Intestines, 2. Tendons. 5. Veins. 8. Glands. 3. Nerves. 6. Arteries. 9. Brain. PHYSICAL PROPERTIES OF TISSUES. 63 In youth the tissues have less cohesion than in adult life, from the greater preponderance in the former period of water; while the cohesion again declines in old age, especially in bone and muscle, even though the proportion of water present also diminishes, from. changes in the quantity of inorganic elements. The cohesion of any tissue is not uniform in all directions, but, as is well known, certain tissues may be ruptured in one direction more readily than in another; thus, a costal cartilage is more readily broken transversely than longitudinally. This is even more marked in fibrous. tissues, such as a tendon, where it is much easier to separate the longi- tudinal fibres than it is to rupture them by traction. This may be explained by the fact that the cohesion of any tissue is the resultant of the forces which holds the ultimate molecule of the tissues together, as in a single fibre of connective tissue, and of the adhesive force, which through the mediation, ordinarily of cement substance, holds several collections of similar molecules together. The forces which may act on a tissue to destroy its cohesion may operate in four different ways: by traction, by pressure, by flexion, and by torsion. . All the different tissues behave differently to each of these modes of action. The resistance to traction is measured by the force required to tear. apart the molecules of any tissue; hence, the force required to produce tearing in any tissie must increase with the cross-section of the tissue subjected to strain, and when the cohesion of two different tissues is compared in this respect the comparison must always be reduced to a unit of cross-section. Thus, in the following table the numbers represent the breaking weight in kilogrammes for every square millimeter of surface (Wertheim ):— Bones, . , ee ‘ ‘ ‘ F : . 776 Tendons, . * : F : zi , ; F . 6.94 Muscles, . : : < i : ‘ 3 : . 0.054 Nerves, . i ‘ ‘ : ‘ ‘ 7 ‘ ; 0.98 Arteries, . A z ‘ : F : ; * . 0.16 Veins, : . : i 5 ‘ 5 7 : . 012 This resistance to traction is of great importance in the mechanics of thé organism. The cohesion of the bones, tendons, ligaments, and muscles permits of the accomplishment of mechanical work, while the resistance to distension of the different membranes of the body, such as the aponeuroses, fibrous membranes, etc., is of great value in numerous physiological operations. The resistance to pressure is especially seen in the bony skeleton, articular cartilage, and intervertebral disks. In the pones this is especially very marked. Thus, it has been found that from 1110 to 2300 kilo were required to crush a cube of bone from the compact substance of the 64 PHYSIOLOGY OF THE DOMESTIC ANIMALS. ° bones of the extremity 5 millimeters thick, while only 100 kilo were required to crush a cube of the same size from the spongy substance. The cohesion of the compact substance measured in this way decreases to about the same degree when either the organic matter or the lime salts are removed; it also decreases greatly when the water is removed, showing a deviation from the general statement above made. This resist- ance to pressure plays an important rdle in the support of the body in standing, walking, and jumping, and in the protection from injury of such important organs as the brain, spinal cord, lungs, and heart. The resistance to pressure in the osseous system decreases with age. Thus, Fick has found that a prism of bone 1 square millimeter in size from a man 80 years of age was crushed by a weight of 15.03 kilo, while a similar piece from a man aged 74 years would not sustain a weight of’ 4.33 kilo. The bones of different animals also show great differences in their resistance to pressure. The resistance to flexion and torsion possessed by the different tissues of the body also comes into play in certain physiological operations. Thus, in inspiration the ribs and costal cartilages undergo a slight amount of twisting and bending through the action of the inspiratory muscles, and regain their position during expiration. So, when a weight is lifted and held horizontal by the hand the resistance to flexion pre- vents bending of the bones of the arm. The cohesion of the tissues is always greatest in the direction in which the forces which act on those tissues is usually exerted. Thus, when tissues are ordinarily subjected to the force of traction, their co- hesive force is most developed in a longitudinal direction, and such tis- sues, like tendons and ligaments, are fibrous in structure. When the pressure or force to which tissues may normally be subjected does not lie in any one but in many different directions, as in the resistance which serous membranes and aponeuroses offer to distension, such mem- branes are also fibrous in structure; but the fibres, instead of being parallel to each other as in tendons, in which traction is the only force to which they are subjected, are interiacing and cross each other in every direction. Finally, when pressure is the force which must be resisted, we find the tissues taking the form in which such resistanée: may be best offered; the compact bony tissues are therefore arranged in arches, as in the head of the femur, or in the form of hollow tubes, as in the shafts of the long bones,—two forms which, with the greatest economy of material, offer the greatest resistance to pressure. In the case of the femur its upper end is not only subjected to pressure from. the weight of the body, but also. to flexion; for the head of the femur is not in a line with the long axis of the bone, but lies to one side and is connected with the shaft of the bone by an oblique neck. The PHYSICAL PROPERTIES OF TISSUES. 65 arrangement of the compact substance of the lone is especially fitted to overcome these direct or indirect pressures (Fig. 43). 2. Enasriciry.—The elasticity of the tissues varies in the same way as their cohesion. The moist tissues have, as a rule, a very slight elas- ticity ; that is, they offer slight resistance to external forces which tend to change their form, and in most of the tissues which are rich in water, as the brain and glands, the elasticity is incomplete ; that is, the original form is not regained after the distorting force ceases to act. On the other hand, in the elastic tissues and muscles the force must be excessive to produce permanent distortion. The cohesion of a body is its resistance to tearing forces; elasticity is developed as resistance to alteration in form, and refers to the property by which the original form is regained. The elasticity of a body is therefore great when a great force is required to produce change in form, and vice versd; while the completeness of the elasticity is expressed by the perfection with which the original form is regained after the distorting force ceases to act. Thus, the elas- ticity of lead is great but incom- plete; of rubber, is small but perfect. Elasticity cannot be measured by stretching force alone, but com- pressing, twisting, and bending Oorce Ss s¢ e consi red. forces must als ® | c oaST lered Fic. 48.—DIAGRAM OF THE STRUCTURE The resistance to each of these ah re THE HUMAN FEMUR. ard, forces is the same. The less exten- The fibres, A, by their rigidity, and the fibres, B, by ; : és their tenacity, tend to the support of the weight, as sible a body is, the less compressible illustrated in the bracket, while the latter fibres inter- lace with the arciform fibres, F. is it also, and the more rapidly it vibrates when bent from its position of equilibrium. Organic tissues which are poor in water, as wood and bone, and which possess high elasticity, behave to stretching weights like inorganic bodies,.7.e., the increase in length is proportionate to the weight. In the soft tissues, of less but more complete elasticity, the increase in length produced by heavy weights is proportionately less than that due to smaller weights. The cause of this lies in the greater extensibility of such tissues, through which they are more stretched by small weights than is possible in rigid bodies, because in the latter a much smaller ex- tension would exceed the limit of cohesion; though the use of weights of very great difference shows that the extensibility of rigid bodies is probably also governed by the same laws. 5 66 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The laws for elastic changes in form of all bodies, including the soft organic tissues, is expressed in the diagram given below (Fig. 44). The spaces on the line A B represent the extending weights. The spaces on the line B C represent the increase in length. Thus, if the’ extension of any given tissue by any given weight equal the ordinate, AD, the increase in extending weight by regularly increasing amounts will not produce a proportional increase in length. Each increase will be less than that produced by the previous lesser extending weight, and the line which connects the limits of extension will be a curve which gradually tends to form a horizontal line,—in other words, a hyperbola. In a corresponding figure, representing the extension of an inorganic body, the line D C, instead of being a curve, would be a straight line, and the spaces on the line BC from B to C would be equal, showing that the extension increases regularly with uniform increase in extending weight, A g with the exception above alluded to, when very ereat difference in ex- tending weights is made use of. This difference between organic and in- organic bodies is, without doubt, attributable to the greater extensibility of the former. f The organic tissues have still another char- acteristic which distin- guishes them from the inorganic bodies, viz., when a tissue has been extended by a weight, if the weight is allowed to remain the extension gradually increases, and may not be complete for days or months; this is called elastic after-working. It is present in all elastic bodies, though in rigid bodies it is much less marked, and its limit is sooner reached. The weight which will stretch a prism one square millimeter in area and one meter long one meter, provided the limit of cohesion is not thereby passed, is called the co-efficient of elasticity. The following figures, according to. Wundt, give the co-eflicients of elasticity of some of the more important organic tissues :— Fic. 44. Bones, . ' ‘ 3 4 és ‘ . ‘ 2264, Tendons, - og ; é : . . 1.6698 Nerves, oc 6 jk & 4 8 & (4 9 2Al00% Muscles, . F ‘ i i : : F ‘ . 0.2784 Arteries, ‘ F F ‘ ¥ r ' x . 0.0726 The smallness of these co-eflicients is recognized when it is remembered that for cast-steel it is 19881. PHYSICAL PROPERTIES OF TISSUES. 67 Elasticity is a property of the tissues cf the animal body which is of great importance in many physiological operations. It is a force which acts either against constant forces, such as gravity, or temporary forces, such as muscular action. Thus, the intervertebral disks, through their elasticity, serve to deaden the shock given to the spinal column in jumping; the elastic ligaments of the spinal column serve to preserve it in its normal position without there being a constant strain on the muscles, and in animals in whom the backbone is horizontal it serves to counteract the weight of the abdominal viscera, In the herbivorous animals the yellow elastic tissue of the ligamentum nuchw serves to assist the muscles in supporting the head. In expiration the elasticity of the costal cartilages and ribs, together with that of the lungs,—forces which have to he overcome in inspiration, —tend to restore the thorax to its natural form, and thus drive the air out of the lungs. The elastic tissue of the arteries tends to aid the intermittent pro- pelling force of the heart in producing a constant forward motion of the llood. When the heart contracts it drives a definite quantity of blood into the arterial system, already filled with blood, and thus still further distends the arteries. During the pauses between the contractions of the yentricles the elastic tissue recoils, from the removal of the distending force, on the contents of the blood-vessels, and, backward motion being prevented by the closure of the semi-lunar valves, drives the current of blood forward in the vessels. This point will again be alluded to in more detail under the subject of the Circulation. In addition to these properties most of the tissues of the animal body are also flexible and extensible, the degree varying greatly accord- ing to the structure of the parts. Flexibility and extensibility must not be confounded. Flexibility means capability of being bent or twisted ; extensibility means capability of being increased in length. Thus, the tendons are flexible, but not extensible; were they capable of being in- creased in length it would be at the expense of the force developed by muscles. Tendons are, however, very flexible; they adjust themselves to the position the part may occupy, so that sometimes they transinit muscular force at right angles to the line in which the muscle acts. Liga- ments, again, are flexible, and also somewhat more extensible than tendons. In joints they permit of the free play of one bony surface on the other, and yet by their inextensibility serve to keep the articular surfaces in apposition. In dislocations the articular ligaments are rent, and the bony articular surfaces are no longer in contact: in sprains the limit of elas- ticity of the ligaments has been passed; that is, they have been stretched beyond the point at which their elasticity enables them to regain their original form, and partial ruptures take place. 68 PHYSIOLOGY OF THE DOMESTIC ANIMALS. All the connective tissues are originally flexible and extensible ; these properties become greatly modified in the subsequent development of the tissues of this group. Thus, in cartilage and bone, extensibility has very largely disappeared, especially in the latter, but they are of high elasticity. In dense fibrous tissue, such as aponeuroses, flexibility re- mains, but extensibility has become greatly reduced ; hence the intense - pain produced in inflammation below such tissues; for being inextensible swelling is restrained, and the pressure produced by the products of in- flammation on the nerve-endings is greatly increased. 3. OpricaL CHARACTERISTICS OF TISsvEs (Wundt).—(a) Refraction.— All organic tissues possess a higher refractive index than water. By this is meant that when a ray of light passes obliquely out of one medium into another of different density, it is bent out of its path in a straight line at the surface of separation of the two media, the ratio between the angle of incidence and the angle of refraction being the index of refrac- tion. Though comparative measurements of the different tissues have not been made, we can recognize the ditterence by the sharpness of outline in microscopic examination. Thus, cell-wall, nucleus, and nucleolus are recognized by their difference in refractive powers. When two tissues have the same refractive power they cannot be distinguished by the eye, and if no refractive power is possessed they are homogeneous. Fat, elastic tissue, and horn have the highest refractive power. Watery solutions, as in the vacuoles of plant-cells and in secretions, have least refractive power. Albuminous matters, gelatin-giving intercellular substance, and mucin have about the same refractive index. (b) Power of Absorbing Colors.—In very thin sections most vegetable and animal tissues appear colorless. In thick sections, when examined - by transmitted light, the different colors are absorbed in different degrees. Vegetable tissues absorb the most refractive rays; therefore, in sections of increasing thickness they appear at first yellow and then red. The same rule applies to animal tissues, even when freed from blood, e.g., epithelium and cartilage. Many tissues owe their color to deposits in them of special coloring matters. When this is intense many rays of light are entirely extinguished, and in the spectra of such bodies portions of the spectrum are either entirely absent or dark absorption-bands appear in different parts of the spectrum. The points of occurrence of these absorption-bands are definite and characteristic for each different substance. The spectra of certain bodies of physiological importance, such as the blood, biliary coloring matters, etc., will be referred to under their appropriate headings in the sections on Special Physiology. (c) Double Refraction.—A large number of bodies of crystalline structure haye the property of splitting a single incident ray of light pass- PHYSICAL PROPERTIES OF TISSUES. 69 ing through them into two rays; hence, when an object is seen through such a crystal it appears double, the bifurcation of the ray of light being spoken of as double refraction. Many of the animal tissues are doubly refractive, though this prop- erty is weaker in fresh tissue than after drying. Double refraction is only faintly developed in connective tissue, especially in its youngest stages. Elastic tissue is more highly doubly refractive, as are also car- tilage, bone, nerves, muscles, nails, and hair. Double refraction permits the recognition of the molecular structure of organized tissues. A body whose molecules in all directions are arranged in the same manner produces only single refraction ; one whose molecules are arranged in different directions in different proportions produces double refraction, 7.e., splits the ray of light into two rays, which are polarized perpendicularly to one another, and whose vibrations are therefore in two planes perpendicular to one another. Simple glass is a single refractive medium, but if compressed or stretched in one direction it becomes doubly refractive. The double refractive body can either, as in the last example, refract the ray more or less in one direction than in the direction perpendicular to it, or the light can be transmitted in three perpendicular directions with different velocities. In the inor- ganic world crystals furnish examples of all three cases, Crystals of the regular system (tesseral) are isotropic (singly refractive). In tetragonal and hexagonal forms, which possess an unequal axis and two or three perpendicular equal axes, the refraction is either greater (positive) or less (negative) in the direction of the unequal axis, and such bodies are said to have a single optic axis. Other crystalline forms have three axes, characterized by the transmission of light with different velocities. They have two optic axes not coinciding with the axes of crystallization. In organized bodies all of the above cases are also met with. Most mature tissues are doubly refractive. The optic characteristics are not, however, changed by pressure or stretching. We must conclude from this that the doubly-refractive tissue-mole- cule is suspended in a singly-refractive medium, and that this molecule is unaffected in pressure or stretching just as it remains unaffected in imbibition. Organic tissues are therefore analogous to crystals in their molecular arrangement; and this view is strengthened by the fact that many organic substances which are apparently anything but crystalline in their structure, such as albumen, gluten, and chondrin, possess the power of rotating the plane of polarized light. The most important examples of double refractive power are seen in the muscles and nerves. These will be considered under their special headings. 70 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 4, EvecrricaL Puenomens.—Electrical phenomena may oceur in animal and vegetable tissues under various conditions. Frictional electricity occurs when dry epidermal tissues (hair, outer epidermis) and other bodies of rough surface are rubbed together, as on the skin and clothing. It has no physiological significance. Currents produced by chemical differences in tissues may be seen in plants when a point of the exposed interior is connected with a point of the external surface, the internal section being negative to the exterior. Such currents probably only exist when contact by conductors is made between these two surfaces. In certain animal and vegetable tissues there appear to be elementary parts, which are actively efficient in developing an electrical current. Among such phenomena belong the electrical phenomena observed in certain plants, as the Dionea muscipula; in certain animals, as the torpedo and electric eel, and in the currents developed in muscles and nerves of all animals. The latter will receive consideration under the subjects of Nerve and Muscle. III. MECHANICAL MOVEMENTS IN CELLS. It has been seen that the processes by which cells absorb and give up liquids and gases are reducible to purely physical laws. We have further alluded to the fact that the characteristics of the nutritive proc- esses in animal as distinguished from vegetable cells is the reduction of complex organic compounds in the former to simple, inorganic substances ; while in the vegetable cell, simple, inorganic, elementary compounds are built up into complex organic matter. In vegetable cells force is, there- fore, rendered latent; in animal cells force is liberated. In the animal cell this liberation of energy may take on the form of animal movements from the contractility of protoplasm ; or it may result in the development of heat or of electricity. The consideration of the processes which lead to this liberation of energy will be deferred until after the chemical constituents of cells have been discussed, while heat- formation and the development of electricity will be studied under their appropriate headings in Special Physiology. The movements seen in animal and vegetable organisms may be the result of external causes, such as friction, heat, or chemical action, or they may be apparently spontaneous. Two classes of movement may be distinguished :— 1. Those which are produced by varying tension in the cell-mem- brane, from varying degrees of imbibition of the ccll-contents. é 2. Those which are peculiarly protoplasmic in nature. 1. Morton Propucep By Imprpiron In CELLs—The first of these is especially illustrated by many of the forms of motion which occur in the MECHANICAL MOVEMENTS IN CELLS. 71 vegetable kingdom, such as the turning of leaves toward or away from the light, the regular motion of certain algze, such as diatoms, desmidia, oscillatoria, as well as the irritative motions of certain plants, such as the sensitive plant (Mimosa pudica), or the Venus’ Fly-Trap (Dionea mis- cipula); all of these motions depend upon a change in the physical state of imbibition of certain cells. In the Mimosa pudica, the plant in which motion is most marked, and apparently most closely analogous to that - occurring in the animal kingdom, motion of three different parts may be recognized. While at rest during the day-time the leaf-stems of the sensitive plant form an acute angle with the main stem, the secondary leaf-stems diverge, and the leaves are opened out so that they form a plane surface. When evening comes the leaf-stem sinks downward, the leaves approach each other, as when the fingers of the open hand are adducted to the middle finger, and the leaflets themselves close up so that the sur- faces which during the day-time are the uppermost now come in contact with each other. If the entire plant is shaken the same changes occur as have been just described to take place during the night; or if the under part of any one of the leaf-stems is gently touched, the closing motion is localized in that part of the plant. If, however, the upper portion of the leaf is touched, no change is produced in the position of the leaves or of the stem. The under part of the leaf-stem is seen to be cylindrical in shape, and this represents the sensitive portion of the plant. Briicke, to whom we are indebted for the explanation of the mechanism of this movement, has found that this cylindrical structure which underlies the leaf-stem is composed of a bundle of vessels running through the centre, and between it and the outer green bark there is a layer of very succulent cells, which on the upper and non-sensitive side of the stem are comparatively thick walled, while on the under side the cells are provided with very delicate membranes. If a portion is cut out of this cylindrical stem, the ends immediately become retracted so that each extremity takes on a funnel-like form. If such a cylindrical piece is then divided in the direction of its long axis, each part becomes bent in the form of a bow, so that the externai epidermal side is longer than that bounded by the vascular bundle. This change in tension of the cells is due to a change in distribution of the cell-juice. When the membrane of the under portion of the leaf-stem is touched the cell-juice flows from the lower to the upper cells and into the intercellular spaces ; the tension of the upper cells therefore becomes increased, while that of the lower cells becomes reduced. The stem, therefore, sinks and the leaves close. Movement occurring in the mimosa as a consequence of mechanical irritation, therefore, depends upon differences in degree of 72 PHYSIOLOGY OF THE DOMESTIC ANIMALS. turgescence of certain cells, and has nothing in common with animal motion. : The Dionea muscipula, or Venus’ Fly-Trap, furnishes another illus- tration of movement of parts occurring in the vegetable kingdom. The form of the bilobed leaf, which is the movable part of this plant, is shown in Fig. 45. The two lobes stand at rather less than a right angle to each other, and on each of the inner surfaces are three minute filaments projecting inward. The margins of the leaf are prolonged — into spikes, into each of which a bundle of spiral vessels enters. When any one of these filaments is touched, even by so slight a pressure as would be produced by contact with a hair, the leaves instantly come into apposition, and the spikes interlock like the teeth of a rat-trap. The upper surface of the leaf is covered with minute glands, which furnish a secretion having the power of digesting organic substances. When insects come in contact with these filaments, the leaves close so as to imprison them, and the insects are digested by the acid secretion stimulated by their contact, and absorbed. In this plant the chief seat of the movement is in the thick mass of cells which overlies the central bundles of vessels in f the mid-rib. When any one Fig. 45.—VENUS' FLY-TRAP (Dionea muscipula). Of these filaments on the in- oo. oa INTPS EXPANDED tornal surface of the leaves is touched the impulse travels in all directions through the cellular tissue, independently of the course of the vessels, to the cells at the mid-rib. Fluid thus flowing from the upper cells to the lower, the lower cells greatly increase in tension, while the upper ones become relaxed and the leaves come into apposition. Opening of the leaves is accomplished by a reverse process. In this plant there is therefore to be seen not only a mechanical irritation, which produces mechanical motion by purely mechanical means, but also a chemical irritation through contact of various substances with the leaf, which results in the production of a digestive secretion. 2. ProropLasmic MovEMENTS.—Protoplasmic movements, which may be seen in both the animal and vegetable kingdoms, may be of various kinds. We may meet with movements of free protoplasm, or of proto- plasm while contained within cell-walls. The peculiarity of protoplasmic motion lies in the fact that the particles of the contractile mass do not move around any fixed point, MECHANICAL MOVEMENTS IN CELLS. 73 but that all the particles, as in a liquid, are capable of mutual rearrange- ment of position. Further, the stimulus to motion is not invariably applied from without, but may be self-originating in the interior of the mass. Protoplasm is thus contractile, irritable, and automatic. Protoplasm, wherever found, is a transparent, colorless, apparently homogeneous mass, refracting light somewhat more strongly than water, but less than oil. Where protoplasm may be separated into layers, as in the ectosare and endosare of some of the lower animalcules, protoplasm may be doubly refractive, and when the direction of motion of the protoplasm is constant the optic axis coincides with the line of motion. Protoplasm, as previously indicated, possesses considerable power of imbibition, moderate cohesion, and great extensibility, the degree of each of these physical attributes varying in different forms of protoplasm, and at different times and under different conditions for the same protoplasm. Protoplasm also usually contains a variable number of granules of foreign matter, which are passive in the motions of protoplasm, but which themselves may manifest oscillatory movement (Brownian motion). The reaction of protoplasm is usually faintly alkaline or neutral. Protoplasm may produce movement by means of prolongations of cells, or by the contraction of organized-matter resulting from the metamorphosis of cell-contents. We have therefore to consider— First.—Protoplasmic and cellular motion, whether limited by a cell- membrane, or occurring in free protoplasm. Second.—Motion of the protoplasmic prolongations of cells, as seen in ciliary movement; and Third.—The contraction of substances resulting from the metamor- phosis of cell-contents, as seen in muscular tissue. 1. Movements in Protoplasmic Contents of Cells.—In addition to the Brownian movement, or oscillatory movement of granules which is seen whenever minute particles, whether organic or inorganic, are sus- pended in a fluid, and which are simply due to varying currents produced by differences of temperature, the motion in the protoplasmic contents of cells may be either circulatory (cyclosis) or may result in changes of form. Circulatory movements are seen in numerous vegetable cells, . particularly when the protoplasmic contents have decreased somewhat in amount so as not to fill the entire interior of the cell; the protoplasm is then heaped up against the walls of the cells, and sends prolongations across the interior. These cell-contents may then manifest movements, either of changes of form or of circulation of starch granules, etc., which are imbedded in the protoplasm. If a cell of the Tradescantia virginica is examined under the micro- scope, the protoplasmic cell-contents will be found to be arranged in the 74. PHYSIOLOGY OF THE DOMESTIC ANIMALS. form of an irregular net-work, as represented in Fig. 46. These proto- plasmic threads are the seat of changes, both of form and position. The single filaments may become thicker or thinner, or a new filament may - spring out from and enter and unite with adjoining filaments, or may undergo division into several others, the process being analogous to that already described as characterizing the ama@ba. In addition to this motion in the cell-contents, rotatory movements may also be seen to take place in the protoplasm which is in contact with the walls of the cell, rotation occurring in a constant direction and with almost uniform rapidity around the cell-nucleus, the imbedded chlorophyll and starch- granules rotating in a mass without any decisive change in their relative positions. Such rotatory move- ments are seen in the leaf-cells of the Vallisneria, and various other plants. Similar motions are also seen in the paramcecium and other infusoria. In young animal cells the same character of movement is often present; often when a membrane is absent or is very flexible the pro- toplasmic movements cause a change in the entire shape of the cell, and the motion so produced cannot be distinguished from those of free protoplasm. Occasionally protoplasm _ be- Fig. 46.—TRADESCANTIA CELLS, after Comes free by escaping from the KUNE. . ior A represents the fresh cell suspended in water; B the interior of cells, such as the so-called same cell after moderate, local electrical stimulation. ] +a ] Thi The irritated region extends from a to b, the protoplasm plasmoids of myxomy cetes, mn W hich * being collected into clumps, at cand d, 1 ; : ie (analog, Or eane Gas areenlboribe not only an infernal granular move- ment but also a change of external shape may be made out. Similar phenomena are also seen in those organisms which consist of masses of free protoplasm, such as the monera, rhizopods, polyps, and infusoria. Such protoplasm possesses in an eminent degree the property of contractility,—a term originally applied to striped and unstriped muscles. The changes in form of masses of free protoplasm is identical in nature with that observed in muscular contraction. SEE tegen MECHANICAL MOVEMENTS IN CELLS. , 75 The contractility of protoplasm may be manifested by either partial or total contractions, the latter tending to cause the protoplasm to assume a spherical shape. Partial contractions are much more common, and consist in contractions along certain circumferences of the mass of protoplasm, and thus lead to the production of irregularity in outline. Movements so produced are described as amceboid movements from the fact that they are best seen in the amoeba. Ameeboid movements have already been described, and are exempli- fied in many of the cells of which the bodies of the higher animals are made up. Thus, the colorless blood-corpuscles, lymph-cells, and corneal corpuscles possess throughout their entire life the power of changing | their form in a manner ‘entirely similar to that possessed by the amceba (Fig. 47). Fig. 47.—AMC@BOID MOVEMENT IN A COLORLESS BLOOD-CORPUSCLE OF THE Frog. (£ngelmann.) The temperature was gradually raised from a tom, and then gradually reduced. The most striking illustration of this form of protoplasmic move- ment, seen in adult animals, is exemplified in the motions of pigment- cells in the skin of the chameleon. As is well known, the chameleon is capable of changing the hue of its skin, and this is simply due to the varying degrees of contraction of the pigment-cells, which are situated below the epidermis. When these cells send out branching prolonga- tions to the exterior, the skin surface of the chameleon, from the larger amount of pigment exposed, will take on a dark hue. In the different stages of contraction of these pigment-cells the tint of the skin will vary according as the pigment-cells are seen through a thicker or thinner layer of yellowish or almost colorless epidermal cells. 76 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The two extremes of position of these pigment-cells are represented Ps Se ate VO PA in Figs. 48 and 49. Fi. 48. Fig. 49. PIGMENT LAYER OF THE SKIN OF THE (CHAMELEON IN DIFFERENT DEGREES OF CONTRACTION. (Briicke.) The frog also, as is well known, is another illustration of a change of tint produced by precisely similar processes. From the fact that the movements of these pigment- cells appear to be under the control of the nervous system, they offer an illustration of a transition stage between the independent, automatic move- ment of free protoplasm, as in the body of the ameeba, and the specialization of the fune- tion of movement in the nerv- ous ganglia, nerves, and muscle- cells of higher animals. In certain of the low forms of life protoplasmic motion may take on the form of minute contractile threads thrown out from the body of various rhiz- opods and monera, which dif- ers from the amcboid move- ments just described. In this case long and thin protoplasmic threads in great number extend in every direction from the central mass ; these threads, on whose surfaces fine granules are often seen in active Fia. 50, MECHANICAL MOVEMENTS IN CELLS. 77 motion, are not themselves, usually, the seat of any active change in form, although they slowly and gradually become longer or shorter, or perhaps even divided. They are also capable of being entirely withdrawn into the contractile body-mass. Such a form of motion, or rather the forms resulting from such motion, are represented in Fig. 50. 2. Ciliary Movement.—By ciliary movement is meant the pendulum- like motion possessed by protoplasmic prolongations of fine hair-like threads of numerous animal and vegetable cells. In many of the infusoria the entire external body surface, or a certain limited portion of it, is supplied with minute hair-like appendages, which, by their oscillation, serve as organs of propulsion. In vegetable spores cilia are distributed in a similar manner, and likewise serve as propulsive organs. Fig. 51.—CILIATED EPITHELIAL CELLS FROM THE NASAL Mucous MEm- BRANE OF THE Cow, MAGNIFIED 500 DIAMETERS. (C. F. Miiller.) In the animal kingdom ciliary movement is seen under numerous forms on ciliated epithelial cells lining the nasal passages, antrum, tear- duct and sacs, pharynx and Eustachian tube, middle ear, trachea, bronchi, uterus and Fallopian tube, vas defferens, epididymus, central canal of the spinal cord and brain-ventricles, while cilia also serve as the organ of movement in spermatozoa. The form of the cilium is, as a rule, that of a narrow, hair-like thread. In all of the ciliated epithelial cells of the higher animals, as well as in most spermatozoa, and in many of the lower animals and plants, the length of such cilia may vary from 0.05 mm. to 0.005 mm. (Fig. 51). They are structureless in appearance and colorless, and possess a considerable amount of flexibility and elasticity. Under the influence of various agents they may either swell up by imbibition or 78 ’ PHYSIOLOGY OF THE DOMESTIC ANIMALS. shrivel when desiccated, and their appearances then undergo the same changes as will be described under the alterations of protoplasm. The solutions which coagulate albuminoid bodies also coagulate the ciliate prolongations of cells. Caustic alkalies and most of the concentrated acids dissolve them. In fact, cilia behave to all reagents in a very similar manner to protoplasm. All cilia are invariably connected with a protoplasmic base, and are never on firm membranes. Therefore, when cilia are found in the higher animals on epithelial membranes the free surface of the cell possesses no membrane, but the protoplasmic cell- contents, ina manner similar to that which is found in the epithelial cells of the villi of the small intestine, is.somewhat condensed, apparently non-contractile, homogeneous, or striated, and not capable of imbibition. Such a surface might therefore be described as a protoplasmic cuticle. Cilia pass through this condensed layer of protoplasm to be directly in contact with the protoplasmic contents of the cell below. On each cell of a ciliated epithelial membrane, from ten to twenty such cilia will be distributed over the external surface. In lower forms of animals, as in the spermatozoa of all vertebrates, ciliated cells may possess but a single cilium, as seen in many of the unicellular alge and flagellata. Ciliated epithelial cells are always cylindrical in shape and are nucleated. When a portion of ciliated membrane such as that obtained from the mouth or nasal pharynx of the frog, or from the nasal chamber of almost any animal, is placed under the microscope, the thread-like prolongations of these cells will be found to be in constant motion, by which the cells of one locality make a rapid bending motion in one direction, and then more slowly bend themselves back to their original position. The amplitude of these oscillations varies greatly with the character of the cell and certain external conditions, but on all ecylin- drical epithelial cells taken from the same locality is about equal, and, although the bending may be as much as 90°, it usually varies from about 20° to 50°. The rapidity of oscillation of each cilium may be about six or eight in the second, although under certain circumstances it may be considerably higher, since it is influenced by a. number of external conditions, such as temperature, amount of water contained by imbibition, ete. ‘ : The mechanical force exerted by this pendulum-like motion of the cilia is very considerable. In cells which, like the spermatozoa, are supplied with a single cilium (Fig. 52), the screw-like motion of this appendage is suflicient to produce rapid motion of the entire organism. In the case of ciliary membranes, the vibration, having a greater intensity in one direction than in another, is sufficient to produce forward motion of light bodies brought in contact with them. Thus, if the mucous mem- brane is dissected from the pharynx of the frog and fastened by pins on MECHANICAL MOVEMENTS IN CELLS. 79 a board, any light bodies placed in contact with the ciliated surface of the membrane will be moved comparatively rapidly forward in the direction of oscillation of the cilia; or if the body of the frog is bisected, and a glass tube passed in the mouth and out the cesophagus, which is cut off at the point where it enters the stomach, the motion of the ciliated epithelium lining the pharynx and @sophagus will be sufticient to cause Frq. 52.—SPERMATOZOA OF DIFFERENT ANIMALS. (Thanhoffer.) P, b, a, spermatozoa of Paludina yivipara; Hn, of Helix nemoralis; B, of Blaps mortisaga; Bi, of bull; V, of mole; K, of dog; D, of bat; Em, of man; E, of mouse; C, of canary-bird; L, of horse; Pa, b, of rat, with spermatoblasts; J, of sheep; Be, of frog; R, of Raja batis; Pa, a, spermatoblasts. the body of the frog to advance at a comparatively rapid rate,—as much possibly as one millimeter in the second, or even more. It has been estimated that, in oblique or vertical upward movements, each square centimeter of ciliated membrane can perform in one hour 6.8 gramme millimeters of work, or the cells can lift their own weight more than four meters high (Bowditch). This motion of bodies placed in contact with 80 _ PHYSIOLOGY OF THE DOMESTIC ANIMALS. ciliated surfaces is evidently dependent upon the fact that the intensity of motion is greater in one direction than in the other; otherwise, of course, the effect would be negative. Since ciliated epithelium, as has been already shown, lines most of the tubular structures of the animal body, the effect of the vibratory motion of the cilia will be to propel onward fluids and light particles in contact with the surfaces of the membrane. Thus, the cilia of the Fallopian tube, by their vibrations, serve greatly to assist the onward passage of the ovum through the oviduct. Ciliary motion persists only as long as the cilia are in contact with the protoplasmic contents of cells, although Brucke has found that it is not necessary that the entire cell be in contact with the cilia; for if the free surface of a ciliated membrane is carefully shaved with a sharp knife and the portions cut off examined under a microscope, it will be found that many of the ciliated cells have been divided, and yet, provided a certain portion of the cell-contents is still in contact with the cilia, the latter will still manifest their normal movements. Ciliary movement may persist after the death of the individual where that ciliary motion is not concerned in producing movement of the entire organism; thus, in the ciliated infusoria anything which destroys the life of the animal- cules will arrest ciliary movement; but, in the higher animals, in the cold-blooded groups, motion of ciliated epithelium may persist for days after the death of the animal; while, even in the warm-blooded animals, a number of hours after the death of the organism, the cilia will still be in vibration. This indicates that, in the first place, ciliary movement is not under the control of the nervous system; and, secondly, that it is independent of the state of the entire organism,—at any rate, in the higher forms of life-—since it may persist long after the irritability of ' nerves and muscles has disappeared. Temperature produces the same effects, nearly, on ciliary movement as it exerts on other protoplasmic movements; thus above 45° C: ciliated motion ceases, while at 0° C. it also is arrested, to, however, return again when the temperature is raised. Increase of temperature between these two limits produces increase in the rapidity of oscillation of cilia, while decrease of the temperature produces retardation. : : Every alteration in degree of watery imbibition of epithelial cells exerts an influence on the ciliary movement; especially on the degree of frequency and amplitude of vibration. Increasing the amount of water in the epithelial cells above the normal amount may, at first, increase the vigor of oscillation, but when a certain maximum is passed motion is gradually arrested, as in heat-tetanus ; the cilia coming to rest while bent forward, both cells and cilia being swollen and more transparent, and the nucleus appearing as a distended, watery vesicle. When such a con- MECHANICAL MOVEMENTS IN CELLS. 81 dition is reached the normal condition of the cells may be again restored through the use of desiccating agents, such as salts, which have an affinity for water, provided the watery distension has not lasted too long, nor has passed a certain degree. Abstraction of water again, on the other hand, reduces the rapidity, amplitude, and mechanical force of movement, while the cells and cilia become shriveled and motion is arrested. Like all other evidences of protoplasmic activity, a certain supply of oxygen is necessary for the maintenance of ciliary motion, and here again the same conditions may be determined as will be described under the conditions necessary for protoplasmic movement. So also various chemical influences, alkalies, acids, anesthetics, and poisons produce disturbances of motion dependent upon their influence on the protoplasmic contents of the cells. The influences of electricity on ciliary movement have not been, as yet, very clearly made out, although they also appear to be in accord with the results obtained from the action of electricity on protoplasm. These facts serve to show that ciliary movement is a form of pro- toplasmic movement; for, not only is such motion dependent on the con- nection of the cilia with the cell-contents, but all cilia on a single cell vibrate synchronously, and their motion is dependent upon the condition of the protoplasmic contents of the cells. Anything which interferes with the manifestations of force in protoplasm will interfere with ciliary motion. Ciliary motion, nevertheless, differs from other forms of protoplasmic movement in that it occurs in definite directions, and, with the exception of the spermatozoa and other ciliated organisms, on fixed surfaces. Cilia are contractile but not automatic or irritable, while the con- tents of ciliated cells have apparently lost their power of independent contractility. Cilia may, therefore, be regarded as the organs of move- ment of certain cells. They, consequently, represent a certain stage of specialization of function. 8. Movement in Specialized Contractile Tissue——In the contraction of muscular tissue, specialization of function has advanced a step farther. Free protoplasm originates its own stimulus to contraction, is therefore automatic, and is itself contractile. In ciliated cells the contractile impulse originates in the protoplasmic contents of the cells, which, how- ever, have lost their power of contractility, and transfers the stimulus to contractile organs, the cilia, which are not themselves automatic. In muscular tissue movement depends upon three histologically different tissues: the nervous ganglion, which is automatic and originates the contractile impulse; the nerves, which conduct this impulse to the muscles, which, like cilia, are contractile but not automatic. The phenomena of muscular contraction will be considered under Special Physiology. 82 PHYSIOLOGY OF THE DOMESTIC ANIMALS. GENERAL CONDITIONS GOVERNING PROTOPLASMIC MOVEMENT. The motions of protoplasm are governed hy a large number of con- ditions which are similar for protoplasm, whether of animal or vegetable origin. This fact therefore points to the identity of protoplasm of ani- mal and vegetable forms of life. 1. Temperature.—For every variety of protoplasm there is an upper and lower temperature beyond which spontaneous motion ceases, The minimum temperature at which motion is possible is usually 0° C.; the maximum is 40° C. Between these limits the rapidity of motion usually increases with the increase of temperature, and the temperature at which the motions are most active usually lies several degrees below the maximum temperature, at which point heat-tetanus, or heat-rigor,— in other words, universal contraction of protoplasm ,—occurs, resulting in the assumption of spherical forms analogous to the condition pro- duced by prolonged mechanical, chemical, or electrical irritation. If the temperature is then reduced, the protoplasm may regain its power of spontaneous contractility. At the maximum temperature no optical changes occur in the protoplasm, but if the temperature is raised above this point the protoplasm becomes shriveled and opaque from the coagu- lation of the albuminoids of protoplasm. Vacuoles often form, and the power of contractility is permanently lost. As the temperature is reduced toward the minimum the movements become slower, and con- tractility is finally extinguished. No optical changes are, however, so produced, and an increase of temperature will now renew the power of contractility. Contractility is therefore destroyed by an excess of heat,— is suspended by a low temperature. The changes in shape, asa consequence of change in temperature, are represented in Fig. 58. From a toc the temperature was 12° C. The protoplasm—the white blood-corpuscles of the frog—during that time changed its form but little. The preparation was then placed on the warm stage of the microscope and heated to 50° ©. Almost imme- diately the movements became more active, passing through the forms as shown from d tol. At m commencing and at n complete heat-rigor is shown, while at 0 and p are shown the commencing movements restored by subsequent cooling. 2. The Degree of Imbibition—The amount of water held in com- position by the protoplasm is also of influence on the capability for spontaneous motion. For every form of protoplasm there is a maximum and minimum quantity of water of imbibition beyond which movement ceases. Contraction is impossible when, as a rule, less than 60 per cent. or more than 90 per cent. of water is held by protoplasm. Within these limits the rapidity of contraction increases with the amount CONDITIONS GOVERNING PROTOPLASMIC MOVEMENT. 83 of water, and consequently with the increase of volume and decrease in the index of refraction of the-protoplasm. As the maximum amount of water becomes approached the spherical form is assumed ; so that, there- fore, distilled water, as pointed out in the section on imbibition, kills protoplasm, possibly by the extraction of the salts which are necessary for the life of protoplasm. Thus, salt-water fish are killed by placing in fresh water; the fresh water is then found to increase in its inorganic constituents, which thus evidently must be extracted from the tissues of the animals with which it is in contact. So also desiccation produces shriveling of the protoplasm and an entire disappearance of all power of movement, although in the lower forms of life vitality is not destroyed, FIG. 53.—AM@BOID MOVEMENT IN A COLORLESS BLOOD-CORPUSCLE OF THE Froe. (E£ngelmann.) The temperature was gradually raised from a tom, and then gradually reduced. but becomes latent; and when the proper percentage of moisture is again supplied the protoplasm will regain its power of contracting. This is seen in the infusoria and various low forms of animal and vegetable life, which may be preserved indefinitely when desiccated, and may be restored to active life by placing them in a condition to absorb moisture. 3. The Supply of Oxygen.—Protoplasmic movements require the constant supply of oxygen, although they may continue to live in a medium of much lower oxygen-tension than is seen in the atmosphere. Higher tensions of oxygen than are found in the atmosphere will reduce the motions of protoplasm, which are, however, again renewed when the 84 PHYSIOLOGY OF THE DOMESTIC ANIMALS. pressure of oxygen is diminished. All protoplasmic motion is rapidly arrested in a vacuum. 4. Various Chemical and Physical Agents——V arious chemical agents are capable of modifying the contractility of protoplasm. Thus, a slight excess of acid or of alkali will arrest protoplasmic movement; hence, protoplasmic motions in the cells of various vegetable organisms, such as cara, will be arrested, after two or three minutes, in a one-tenth of one per cent. soda solution. Dilute acids cause coagulation of protoplasm, and will perhaps explain the poisonous action of carbon dioxide and the necessity of its removal from cells as rapidly as formed. Various poisons, such as ether and chloroform, interfere with the activity of protoplasm of all forms, and the similarity of action serves to still further demon- strate the identity of protoplasm. Thus, the alkaloid veratrine produces effects on all forms of protoplasm similar to those so well marked in muscular tissue. Protoplasm, also, like muscular and other irritable tissue, responds to various forms of artificial stimuli, though the degree of susceptibility to such stimuli may vary in different forms of protoplasm. Electrical currents, when powerful, are capable of killing protoplasm, causing it to assume a spherical shape, and to become opaque, shriveled, and granular. Feeble currents slow the spontaneous motions of protoplasm, while strong currents arrest them. Where the contractile tissue jis inclosed in tubular sheaths and the assumption of the spherical form so rendered impossible, as in muscular tissue, an attempt is made to approach the form as nearly as possible. Such protoplasmic cylinders when stimulated become shorter and thicker. Sudden changes of temperature are also capable of producing either increase or decrease in the contractility of protoplasm, the change being more marked the more rapidly the variation in temperature occurs. Absence of light also serves finally to arrest protoplasmic motion, while its presence will lead to increased vigor of contraction, as lrendy referred to in the changes in the contractile pigmented cells of the skin of the chameleon and frog. SECTION III. — CELLULAR CHEMISTRY. I. CHEMICAL CONSTITUENTS OF CELLS. In the consideration of the structure of organized bodies we found that, no matter how complicated their form, all organized matter was capable of being resolved into a unit of organization, which we termed, with Briicke, an elementary organism or cell. Cells, therefore, are the simplest schematic form to which all the various forms of organized bodies are capable of being reduced. Chemi- cal investigation of organized bodies further shows that they are equally simple as regards their elementary composition. Of the sixty-five chemi- cal elements only seven enter with any degree of constancy into the forma- tion of organic compounds; these are oxygen, nitrogen, hydrogen, carbon, sulphur, phosphorus, and iron. By far the greatest number of all organic compounds are composed only of the three elements, carbon, hydrogen, and oxygen, varying in the different relative proportions of each. In one group, represented by the organic acids (succinic acid, C,H,O,), even if we assume that all the hydrogen present is associated with oxygen in the proportion to form water, there always remains a considerable excess of oxygen unaccounted for. In the second group, represented by the carbo-hydrates (glycogen, C,H,0,), we have twice as much hydrogen as oxygen, or, in other words, the oxygen and hydrogen exist only in the proportion to form water. In the third group, composed of these ele- ments, carbon, hydrogen, and oxygen, and represented by the fatty acids (oleic acid, C,gH,,0.), if we suppose that all the oxygen is united with the hydrogen in the proportion to form water, we have still a consider- able excess of hydrogen unaccounted for. Such bodies are, therefore, termed hydro-carbons. In another group of organic compounds, and one of the most im- portant of the constituents of cells, we find nitrogen associated with carbon, hydrogen, and oxygen. Such a group we would therefore term the nitrogenous, in contradistinction to the non-nitrogenous. To this group belong the highly complex organic products (complex as regards their molecular arrangement), which contain sulphur and occa- sionally phosphorus, and still more rarely iron, and which are represented by the albuminous bodies; the nitrogenous organic acids and bases, the (85) 86 PHYSIOLOGY OF THE DOMESTIC ANIMALS. organic alkaloids and indifferent crystalline bodies, some of which contain sulphur, are other members of this group. As yet only three substances of organic origin are known to contain phosphorus; these are lecithin (found in the blood, bile, and serous fluids), glycerin-phosphoric acid (derived from the former, and found in the same localities), and nuclein (found in pus-corpuscles, yelk of egz,and semen). In the living organism these organic compounds are in a state of solution in a relatively large amount of water, and either associated or chemically united with a small percentage of inorganic matter, which modifies, in all probability, the nature of the former, and is itself not without valué in the vital processes. All organic compounds are readily decomposable, either through the action of various chemical reagents, elevation of temperature, or through the processes of fermentation and putrefaction. As the result of all these changes in organic matters simpler compounds are produced. The more complex the molecule of organic matter, the more readily is it subjected to decomposition. The character of these changes, as well as the nature of some of the substances which result from change of various kinds in organic matter, will be subsequently discussed. Of the inorganic constituents of cells by far the most abundant is water, which forms the great bulk of organic bodies. Many vegetable matters may contain as much as 90 per cent. of water, while the animal tissues may contain 75 per cent. or more, though the percentage is by no means constant, and may vary in single tissues according to different physiological or pathological conditions, The inorganic constituents of cells are taken up by the cells already preformed, and, as a rule, again leave the cells in the form in which they entered it. The most prominent exception to this rule is found in the case of carbon dioxide and sul- phuric acid; the former originating in the oxidation of the hydrogen contained in the water of organic constituents, and the latter coming from the oxidation of the sulphur contained in albuminoids. The inor- ganic constituents of animal and vegetable cells in no way differ from similar bodies found in inorganic matter. When found as constituents ‘of cells they have invariably been derived from the atmosphere or the earth, have been absorbed, often without undergoing any change, by: vegetable cells, and have passed from the latter into the interior of animal tissues. Inorganic matter is found in all animal fluids and _ tissues, uthough with great variation as to amount. Certain inorganic constitu- ents—such, for example, as water and sodium chloride—are found invariably in all animal tissues and fluids, while other of the inorganic cell-constituents are limited to the cells of certain special tissues. The inorganic constituents of cells may exist either in the form of gases, salts, free acids, or in certain forms of combination whose exact arrangement has not yet been made out. CHEMICAL CONSTITUENTS OF CELLS. - 87 In addition to the elements which have been already mentioned as forming part of the organic constituents of cells, and which, of course, may exist in other forms, we find also, when organic matter is subjected to combustion, chlorine, fluorine, silicon, potassium, sodium, calcium, magnesium, manganese, iron, nd occasionally copper and lead, in the ash. Of the other elements of organic bodies in incineration the carbon is converted into carbon-dioxide, part of which remains in the form of carbonates in the ash, part of the hydrogen uniting with oxygen to form water. Another portion unites with nitrogen to form ammonia, while the phosphorus and sulphur remain as oxygen compounds, sulphuric and phosphoric acids, united with different bases also in the ash. Of the various chemical compounds which are found in the interior of cells, and which have entered it, either from accidental contact or as foods, or as resulting from the chemical processes in cells, we may make three different groups :— 1. Those which, already formed, exist in inanimate nature, are absorbed, and again leave cells without undergoing any change while forming constituents of organized bodies. Such substances are repre- sented by the inorganic constituents of animal cells. 2. This group comprises those which are already formed exterior to the cells, and which, in the process of assimilation by the cells, undergo a change simply in their mode of molecular arrangement, without under- going any profound chemical metamorphosis. Such constituents are seldom, if ever, removed from the cells in the form in which they entered it, and are, in the chemical process occurring in the interior of the cells, ' always reduced to simpler forms. The organic constituents of cells form this group. They may be either nitrogenous or non-nitrogenous in composition. 3. We meet also with a class of compounds which are themselves developed in the vital processes in cells, as the result of the metamorphosis of either the organic constituents of cells or of the food-products which have been assimilated by the cells. Such bodies may be removed from cells either as complex, organic, excretory products (as types of which urea and kreatin may be mentioned), or they themselves may undergo more profound decomposition before being removed from the interior of the cells. The examination of protoplasm, wherever found in the animal or vegetable kingdom, will show that it contains examples of each of these three classes of compounds. The chemical constituents of organic bodies may, then, be divided into two different groups,—the organic and the inorganic. The organic may again be subdivided into the nitrogenous and the non-nitrogenous. Proteids, with their derivatives, represent the nitrogenous group; the hydro-earbons and carbo-hydrates, with their derivatives, the non- 88 PHYSIOLOGY OF THE DOMESTIC ANIMALS. nitrogenous group. Water and various salts belong to the second, or inorganic group. These will be taken up in turn :— CONSTITUENTS OF CELLS. I. Organic. Il. Inora@anic. Water and Salts. A. Mitrogenous. B. Non-nitrogenous. Proteids and their Derivatives. 1. Carbo-hydrates. 2. Hydro-carbons. Starches and Sugars and Fats and Oils. their Derivatives. A. NITROGENOUS ORGANIC CELL-CONSTITUENTS—PROTEIDS AND THEIR DERIVATIVES. General Characteristics of Proteids—Proteid, or albuminous bodies, is the name given to a number of neutral, nitrogenous products of complex nature widely distributed throughout the animal and vege- table kingdoms, and agreeing more or less in chemical composition and properties with the white of an ege. They are found dissolved in the fluid media of the animal body, as constituents of the digestive juices, and in different degrees of solidity in the various tissues. They are never, during health, eliminated from the body in excretions. They are present during all periods of life. The higher plane of organization of man and the higher animals depends mainly upon the abundance and variety of the albuminous constituents of their tissues; for, while in plants the cell-walls are largely composed of non-nitrogenous matter, such as cellulose, in animals analogous parts are formed of various complex albuminoids. Proteids are organic, colloidal bodies, composed of carbon, hydrogen, oxygen, nitrogen, sulphur, and occasionally phosphorus. * They are absolutely essential to life, whether animal or vegetable, but are exclu- sively of vegetable origin; that is, although they may be assimilated and modified ly the vital processes occurring in animal cells, they must first have been preformed by the chemical processes occurring in ° _ vegetable cells. When found as constituents of the tissues of car- nivorous animals they have been derived directly, with but slight modification, from the herbivora which have served for their food, while the herbivorous animals find them invariably ready formed in the tissues of vegetables which serve as their food, and which require but slight. modification to be converted into the constituents of the NITROGENOUS ORGANIC CELL-CONSTITUENTS. 89 animal tissues. Animals, therefore, do not have the power of manu- facturing albuminoids, although they may transform albuminous bodies of one kind into those of another. Thus, casein may be transformed into the albuminous constituents of muscle-tissue; it may be combined with other substances so as to form, for example, the hemoglobin of the blood-corpuscles, or may become so modified as to form what are termed the derived albuminoids of the different tissues. After serving the purposes of the organism such bodies are excreted, not as proteids, but as products resulting from their retrograde meta- morphosis. All albuminous bodies are so intimately associated with inorganic matter that their isolation in a pure state is a matter of the greatest difficulty, or, it may be, impossibility ; consequently the inciner- ation of albuminous bodies—a process which is accompanied with the development of an odor like burning horn—always leaves anash composed of potassium and magnesium phosphates and small quantities of carbo- nates. If sulphur is regarded as a constant and normal component of proteids and not as an occasional accidental addition, they all possess a very high molecular weight. In all forms of proteids the percentage of chemical elements entering into their composition is only subject to slight variation in the different classes. Thus, according to Hoppe-Seyler, C. may vary from 52.7 to 54.5 per cent.; H., 6.9 to 7.3 per cent.; N., 15.4 to 16.5 per cent.; O., 20.9 to 23.5 per cent.; S., 0.8 to 2.0 per cent. Physical Properties—When dry, albuminous bodies form perfectly amorphous, yellowish, brittle masses without odor or taste, and closely resembling gums in appearance, and, like gums, hygroscopic to a high: degree: they rotate the plane of polarized light to the left,and in watery solutions, which are nearly always opalescent, are not, as a rule, capable of osmosis,—a fact, which seems to show, as Briicke has pointed out, that their condition in the form of fluid is more one of particulate suspension than of true solution. When shaken with fluid oils, the latter are mechanically separated into minute particles, each of which is sur- rounded by a layer of the albuminous solution (emulsion). Some are soluble.in water, others not; nearly all are insoluble in alcohol and ether; most are soluble in strong alkalies and acids, but in the process of solution undergo chemical change. Most of the albuminous bodies may exist in two modifications, either in a soluble or in an insoluble form. They exist usually in the soluble form in animal and vegetable cells, but become insoluble by the action of heat and various chemical reagents. When watery solutions of albuminous bodies are evaporated in a vacuum, or at 40° to 50° C., a yellowish, brittle, soluble residue is left; in other words, albumen may be recovered unaltered in general prop- erties in the dry form from: solutions when suhjected to evaporation by 90 PHYSIOLOGY OF THE DOMESTIC ANIMALS. gentle heat. When heated much above this point albuminous bodies. then pass into the insoluble form (coagulated proteids). Chemical Properties.—Proteids are precipitated out of their solu- tions by the following reagents: the stronger mineral acids, acetic acid and potassium ferro-cyanide; acetic acid and sodium sulphate, lead acetate, mercuric chloride, tannic acid, powdered potassium carbonate added in bulk to saturation, aleohol, ether, and several other substances. Iodine stains most proteids yellow,—a point which may aid in their recognition under the microscope. , : Their presence in solution may be recognized by the following processes :— First, by coagulation. When solutions of albuminoids are gently heated, provided the amount of albumen contained is at all appreciable, a firm coagulum results when the solution has been warmed up to 60° or 70° C. The temperature at which coagulation occurs will vary in different forms of albuminous bodies, and according to the reaction and chemical characteristics of the solvent. If a small amount of a dilute acid is added to 2 solution of an albuminous body coagulation will be found_to occur at a lower temperature than if the ‘solution be neutral; while, on the other hand, the presence of a small amount of alkali will prevent coagulation occurring until the temperature has been raised above the point at which it occurs when the solution is neutral. If a large amount of alkali be present coagulation by heat will be rendered impossible. Neutral salts in small amount in albuminous solution will ‘also lower the temperature of coagulation, whether the solution be faintly acid, faintly alkaline, or neutral. The coagulation of albuminous bodies by heat is only possible when they are in solution, and therefore seems to show that the change from the soluble to the insoluble form produced by heat is not so much dependent upon the heat as upon the heat combined with moisture; for if the atbumen be separated from solution by evaporation below the point of coagulation, the dried albumen so obtained will still possess the power of solubility in water: and yet, if placed in a perfectly dry tube the temperature of the albumen may be raised far above the point of coagulation without any change occurring in the albumen, 7.e., without its losing its power of subsequent solubility in water, and of being coagulated when that solution is raised to the coagulating point. Second: If a solution which is supposed to contain albumen is acidulated with acetic acid, a few drops of potassium ferrocyanide then added, and the fluid boiled, albuminous bodies will be precipitated. Third: If the fluid is acidulated with acetic acid and a small quantity of a strong solution of sodium sulphate then added, and the fluid then boiled, a firm, white coagulum will result. NITROGENOUS ORGANIC CELL-CONSTITUENTS. 91 The first and third of these tests may be used for separating albu- minous bodies from other substances in solution,—a process which is often necessary in the examination of organic fluids. So also if the fluid is acidulated with acetic acid, and then added to a large bulk of strong alcohol, albuminous bodies may*thus be coagulated, and their separation from other ingredients of the solution rendered possible. A precipitate produced by boiling alone is not a sufficient proof of the presence of albumen, since certain substances, such as calcium phosphate in human urine and calcium carbonate in the urine of her- bivora, will be thrown down by boiling. If the precipitate is permanent on the addition of nitric acid after boiling, albumen is present, since the salts above mentioned will be redissolved by the acid. Alkali may also hinder the coagulation of albumen by heat, and an acid reaction is there- fore essential for the employment of this test. Occasionally albumen is present in solution in amount too small to be detected by any of the preceding tests. The detection of traces of albumen is then rendered possible by various color reactions. The Biuret Reaction.—_When a small amount of caustic potash solution is added to a dilute solution of cupric sulphate a precipitate of cupric hydrate will be thrown down. If an excess of potash is now added, the precipitate will be redissolved and the fluid take on a light- blue color. If, however, albuminous bodies be present in solution, and this procedure be carried out, on solution of the precipitate of cupric hydrate the fluid will take on a violet color instead of a blue. This test may be used to detect the presence of albuminous bodies in extremely small amount in solution. It may be'‘also used for the recognition of the albuminous nature of solids. If a solid body which is supposed to contain albuminous bodies be touched first with a drop of cupric sul- phate solution, then with a drop of potash solution, and then washed with water, the spot so treated will be found to have a violet color. This test is also used for the recognition of peptone. A solution of peptone so treated will become red instead of violet. Xantho-proteic Reaction.—When albuminous bodies in solution are boiled with nitric acid, the solution and coagulum, if one be present, take on a yellow color. If the solution be then allowed to cool and strong ammonia added, the upper layers of the solution, or the coagu- lum, if any be present, will become orange colored. Millon’s Reaction.—If a little Millon’s reagent* be added to a solu- tion which contains albumen, if the albumen be present in considerable * Millon’s reagent is prepared by dissolving mercury in its own weight of matte acid by the aid of gentle heat. The solution is then poured into a glass vessel, and twice its volume of water added; a crystalline precipitate will separate in a few hours, and the yellowish supernatant fluid, which may be readily decanted off, is Millon’s reagent. o2 PHYSIOLOGY OF THE DOMESTIC ANIMALS. quantity, a dense, white precipitate will be formed, and when subjected to heat the precipitate will become condensed into the form of a firm coagulum, and will turn red. If but a trace of albumen is present the fluid will simply take on a pinkish color. Schultze’s Test.—When albuminoids in solution are treated with a cane-sugar solution in small quantities and concentrated sulphuric acid then added a beautiful red color is formed. Adamkiewicz’s Test.—If a solution of an albuminous body is strongly acidulated with acetic acid and sodium chloride added in bulk, and then strong sulphuric acid, the fluid will gradually assume « violet-blue color, slightly phosphorescent, and gradually turning dark purple. Frthde’s Vest-—When a mixture of sulpho-molybdie acid is added to a solution of albuminous bodies a dark-blue color is produced. Of the above tests the xantho-proteic and Millon’s reaction may be used for the microscopical detection of the albuminoids. Albuminous bodies may be divided into the following classes :— J. AtBumens.—Albumens are bodies which are soluble in water, and when in solution are coagulated by heat (about 70° C.). They are not precipitated from their solutions by dilute acids, carbonates of the alka- ‘ lies, sodium chloride, or platino-hydroeyanic acid. When dried at about. 40° C., or if evaporated at a lower temperature in a vacuum, they leave a yellowish, friable, inodorous, gummy mass, which. is still soluble in water, and whose solutions possess all the properties of the original solution. Albumens are precipitated from their solution by alcohol, if alkaline salts are present. . Albumens may exist in three different forms, —serum-albumen, egg-albumen, and vegetable albumen. 1. Serum-dAlbumen.—Serum-albumen is found in blood, serum, lymph, serous transudations, and animal secretions. Serum-albumen may be obtained from blood-serum, or any serous transuda- tion, by adding dilute acetic acid, drop by drop, until a flocculent precipitate forms. This precipitate is then filtered off, and the filtrate, after neutralization with a little sodium carbonate, is evaporated in a shallow dish to a small volume, not allowing the temperature to rise above 40° C._ The salts may then be removed by dialysis, changing the water frequently outside of the dialyzer, and again evapo- rating at 40° C. to dryness. So obtained, serum-albumen always contains a slight percentage of salts, but is soluble in water, forming a clear solution, which is somewhat tenacious when concentrated. In the dry condition it is a yellowish, brittle, transparent body capable of being redissolved in water, and its solutions are then coagu- lable by heat. Its solutions are opalescent, and possess a specific levo- rotation for yellow light of —56°. It is precipitated out of its solutions by alcohol, the precipitate being partially redissolved when the alcohol is immediately poured off, but is not coagulated by ether. Most of the NITROGENOUS ORGANIC CELL-CONSTITUENTS. 93 salts of the heavy metals precipitate serum-albumen, as do the mineral acids in large quantities, especially nitric acid. Its point of firm coagu- lation is from 72° to 73° C., although turbidity sets in at about 60° C. The presence of acetic or phosphoric acids, sodium chloride, or other neutral salts, lowers the coagulation-point of serum-albumen, while the presence of sodium carbonate necessitates a higher temperature. It is precipitated by the strong mineral acids from its solution in dilute acids, and the precipitate is readily soluble in concentrated acids; ege-albumen is not. 2. Lgg-Albumen.—In many points egg-albumen, which is contained in the meshes of the fibrous net-work of birds’ eggs, closely resembles serum-albumen. The points of contrast are that its specific rotation is only —35.5°, and when agitated with ether it is gradually precipitated. When injected into a vein or the connective tissue, or when introduced in large quantities into the stomach or rectum of an animal, egg-albumen is found unaltered in the urine, while the injection of serum-albumen produces no such albuminuria. A solution of comparatively-pure egg-albumen may be obtained for testin g by breaking the whites of several hens’ eggs into a beaker, cutting up the mem- branes with scissors so as to free the albumen from their meshes, stirring well with an equal volume of water, and filtering through muslin. The salts may then be removed by dialysis. Dry egg-albumen may be obtained by evaporating the above solution to dryness at 40° C. So prepared, its physical properties agree closely with those of serum-albumen. Its solutions have several properties which enable it to be distinguished from serum-albumen. Hydrochloric acid in small amount produces no precipitate; in larger amount it causes a firm coagulum, which is only with difficulty soluble in excess of acid and in water and neutral salt solutions. 8. Vegetable Albumens.—Albuminous bodies are found dissolved in plant-juices and in the form of a solid in various seeds, and form the most important albuminoids for the nutrition of the herbivorous domestic animals. Their general properties agree with those of egg- and serum- albumen, though they present certain variations among themselves in composition and chemical properties. Thus, the coagulable substancés which may be extracted from peas and horse-beans dissolve readily in lime-water and acetic acid, while the other vegetable albumens do not. The vegetable albumens are, as a rule, poorer in carbon but richer in nitrogen than albumen of animal origin,—a fact possibly accounting for their lesser nutritive value and readiness of assimilation. They usually have phosphorus associated with them. Vegetable albumen is soluble in cold water, and its solutions are coagulable by heat; with dilute acids and alkalies it is converted into an albuminate. In the seeds of certain 94 PHYSIOLOGY OF THE DOMESTIC ANIMALS. - plants there is contained a variety of albumen which, when extracted with warm salt solution and then allowed to cool, forms octahedral crystals. , Various forms of vegetable albuminous bodies have been described :— Vegetable Caseins.—The seeds of the leguminous plants and oleagi- nous grains differ from the cereals, properly so called, in that they do not contain gluten, soluble in alcohol, but, in addition to the albuminoids coagulable by heat, various other albuminous bodies which are insoluble in pure water but soluble in alkaline solutions, from which they may be precipitated by acetic acid, the precipitate being soluble in excess, According to Dumas and Cavours, this substance may even be coagulated by rennet, and is therefore closely analogous to the casein of milk, to be subsequently considered. Three different forms of vegetable casein-like bodies have been described, Legumin, which forms the greater part of the proteid constituents of the leguminous plants; almonds and the lupins contain a substance analogous to vegetable casein to which the name of amandin, or conglutin, has been given; while the part of gluten which is insoluble in alcohol is of similar nature, and has been termed gluten-casein. Legumin.—The watery extract of the seeds of the leguminous plants often has an acid reaction, without doubt due to the presence of phos- phorie acid, which appears to be a necessary component of vegetable casein. Legumin may be obtained by the agitation of powdered legu- — minous seeds with seven or eight times their weight of a one-tenth of one per cent. solution of potassium hydrate. After about six hours the fluid is decanted and allowed to stand from twelve to twenty-four hours at a low temperature, and the residue which then forms is again washed with water. The washings are then collected and precipitated with dilute acetic acid, and the precipitate, washed again with dilute alcohol, is finally precipitated by concentrated alcohol and ether. Freshly-precipitated Jegumin is only very slightly soluble in cold water. Legumin may, however, be extracted from the powdered seeds of the leguminous plants by cold water, its solubility in water being then due to the phosphoric acid of the seeds. It is readily soluble in alkaline solutions, from which it is precipitated by acids and solutions of metallic salts. It is soluble in dilute hydrochloric and acetic acids. When boiled with water it becomes coagulated and insoluble in alkaline solutions and in acids. By prolonged ebullition with sulphuric acid it undergoes decomposition, with the formation of leucin and tyrosin and small quan- tities of aspartic acid. Legumin is also present in oats. Amandin, or conglutin, is contained in sweet and bitter almonds, and is separated from them in the same manner as legumin. It is dis- tinguished from legumin by a greater solubility in dilute acids, though NITROGENOUS ORGANIC CELL-CONSTITUENTS. 95 its general properties coincide with those of legumin. It is distinguished from it, however, by being more soluble than legumin in dilute acids. A substance analogous to vitellin has also been found in the seeds of various plants. It is also termed crystallized vegetable casein. Gluten, or vegetable fibrin, exists in a large number of grains, par- ticularly those of the cereals, and plays an important part in the nutritive value of vegetable foods. It also exists in the growing parts of plants, and in various vegetable juices. It is a compound albuminous body, which differs from all others in that it is soluble in water and in alcohol when traces of free acid or alkali are present. It is only partly and imperfectly soluble in pure water, It may be readily obtained by washing flour under a stream of water, by which the starch is removed, and the gluten then remains in.the form of an elastic, grayish mass. Gluten is only partly soluble in alcohol. According to Ritthausen, gluten contains at least four albuminous substances in addition to vegetable albumen, which has been already described; a body insoluble in alcohol, which is gluten-casein,,or the vegetable fibrin: of Liebig, and three nitrogenous substances soluble in alcohol, to which the name of gluten.fibrin, gliadin, and mucedin have been given. 1. Gluten-Casein.—To prepare this body, fresh gluten is washed first with alcohol, and the insoluble residue is then agitated with two-tenths of one per cent. potash solution, which dissolves out the gluten and leaves an insoluble residue of starch and fatty matters. From the fluid gluten- casein is precipitated in flocculi by the addition of acetic acid sufficient to give a faint acid reaction. It is then washed with water and alcohol, and after desiccation the gluten-casein so prepared is insoluble in hot and cold water. Boiling water, however, causes it to undergo some modification, which renders it insoluble in alkalies and acids. In the fresh state it is soluble in acetic acid, and in alcohol acidulated with acetic acid. All weak. alkaline solutions dissolve fresh gluten-casein, and cause it when dry to first swell up and then dissolve, It is precipi- tated out of these solutions by acids and the mineral salts, forming combinations with the latter. Its properties are very similar to those of legumin and conglutin. It contains more sulphur and less nitrogen than legumin. 2. Gluten-Fibrin.—This body is obtained by distilling the sleohatie solution of gluten until the fluid does not contain more than 40 per cent. of alcohol; a mucilaginous mass rich in gluten-fibrin is then deposited, and may be purified by washing with absolute alcohol and precipitating with ether. It then forms a coherent, tenacious mass, insoluble in water. Its separation from the gliadin and mucedin of gluten depends upon the fact that all are soluble in dilute alcohol, and that gluten-fibrin is almost insoluble in water and very weak alcohol. As the alcohol is distilled off 96 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the gluten-fibrin separates. It dissolves in warm, dilute alcohol, and forms a brownish-yellow solution. When such solutions cool, ‘aid as they undergo evaporation, a white or grayish pellicle forms on the artes: which disappears on agitation. It is more soluble in absolute alcohol than either gliadin or mucedin. Gluten-fibrin is readily dissolved in dilute acid and alkaline solutions, and is precipitated from these solutions by neutralization, or by the addition of metallic salts. 3. Gliadin, or Vegetable Gelatin This body is one of the principles of gluten which is soluble in dilute alcohol. It is obtained by agitating gluten with strong alcohol, which removes gluten-fibrin, dissolving the residue in 1 per cent. potash solution, and, after having precipitated the solution with acetic acid, by extracting the precipitate with alcohol of 75 per cent. at a temperature of 38°C. By this means only gliadin is dissolved, while the mucedin remains. Vegetable gelatin then separates, as the fluid cools, in the form of a gelatinous mass. It may be purified by dissolving in acetic acid and neutralizing the clear solution with potash; the precipitate is then again washed with alcohol and ether. In the fresh state vegetable gelatin has the consistence of a thick mucilage. Absolute alcohol causes it to contract to a hard and yellowish-white mass. Cold water causes it to again swell up and dissolves part of it, and the solution may be precipitated by tannic acid. Submitted to long boiling with water, gliadin becomes insoluble and undergoes partial decomposition. Dilute alcohol dissolves it more readily than pure water. It is insoluble in absolute alcohol. It is very soluble in acids and dilute alkalies, and while in solution in alkalies may be precipitated by the metallic salts, but its solution in acetic acid is not precipitated by mercuric chloride. It contains a considerable percentage of sulphur. 4. Mucedin.—This substance has been but little studied, and is only to be distinguished from vegetable gelatin by its greater solubility in water. Its method of isolation has been already indicated in the pre- ceding paragraphs. These substances approach one another very closely in chemical composition, and it would appear from the processes employed in their isolation that it is by no means certain that they have been obtained pure. On the other hand, their analogy to corresponding bodies of animal origin is not sufficiently striking to justify an munlegous: nomen- clature. For the preceding account of their properties we are indebted mainly to Wirtz (Chimie Biologique). II. Grosuttins.—Globulins are bodies which are insoluble in water but soluble in dilute solutions of sodium chloride. They are coagulable by heat when in solution, and, while soluble in dilute acids and alkalies, are in the process of solution chongedl into derived albumens. They are NITROGENOUS ORGANIC CELL-CONSTITUENTS. 97 precipitated by alcohol and by carbonie acid, and by the addition of a large quantity of water to their solutions; sodium chloride added in bulk to their solutions, as a rule, precipitates them. Five ditferent kinds of globulins have been recognized. 1. Vitellin.—Vitellin is found in the yelk of eggs and in the crys- talline lens. It may be prepared by shaking the yelks of eggs with separate portions of ether until all the yellow color is removed, dissolv- ing the residue in dilute sodium chloride solution, filtering and precipi- tating the filtrate with excess of water. So obtained, it always contains lecithin. It is not precipitated by the addition of sodium chloride in substance to its solutions. It is soluble in dilute acids, and is readily converted into syntonin, and by neutralization and re-solution with alkalies into alkali albuminate. Its point of coagulation ranges from 70° to 80° C. It is also coagulable by alcohol. 2. Myosin.—Myosin is formed in the rigor mortis of muscles, and probably also in the gradual death of all forms of protoplasm. It is precipitated from its solutions in dilute sodium chloride by the addition of common salt in excess. It is also precipitated from its solutions by excessive dilution with water. Its general properties will be more closely considered under the chemistry of muscles. 3. Paraglobulin.—This substance will be described under the con- sideration of the coagulation of the blood. Hammarsten states that a very much larger quantity of this body is found in the blood of domestic animals than has been heretofore supposed. According to him, more than half of all the albuminoids in the blood consists of paraglobulin. 4, Fibrinogen.—This is also a globulin found in the blood, and its consideration will likewise, for the present, be deferred. 5. Globulin, or Crystallin, is contained in the crystalline lens, and it resembles vitellin in that it is not precipitated from its solutions by saturation with sodium chloride, but it is readily precipitated by alcohol. Representatives of the group of globulins are also found in the vege- table kingdom. According to Dr. Sidney Martin, vegetable globulins may be divided into two classes, namely, vegetable myosins and vege- table paraglobulins. The myosins, obtained from the flour of wheat, rye, and barley, have similar properties; they are all readily soluble in 10 to 15 per cent. sodium chloride solution, and are precipitable from this solution by saturation with sodium chloride or magnesium sulphate. They are soluble in 10 per cent. magnesium sulphate solution, and are coagulated in this solution at a temperature of 55° to 60°. If the salt is dialyzed away from the saline solution of myosins, the latter is precipi- tated; but the precipitate is no longer a globulin, since it is insoluble in saline solutions. It is soluble in dilute acids and alkalies (0.2 per cent.) ; it is precipitable from these solutions by neutralization, the precipitate v 98 PHYSIOLOGY OF THE DOMESTIC ANIMALS. being soluble in excess of alkali or acid; that is, the myosin has been converted into a proteid having the properties of an albuminate. If the saline solution of myosin be placed in an incubator at a temperature of 85° to 40°, in twelve to eighteen hours a fine flocculent precipitate falls, while the globulin disappears from the solution; this takes place more rapidly if the saline solution is diluted. The precipitate exhibits the same properties as the precipitate of the globulin by dialysis; that is, at a temperature of 35° to 40° the globulin is transformed into an albu- minate. The ready transformation of the soluble globulin of wheaten flour into an insoluble albuminate is one of the phenomena which take place during the formation of gluten. The second class of vegetable globulins, the paraglobulins, is in dis- tinct contrast with that of the myosins. Two proteids of this class have been found, one in papaw-juice, the other in the seeds of Abrus precatorius (jequirity). Both these globulins exhibit the following properties: they are soluble in saline solutions, and are precipitated by saturation with sodium chloride and magnesium sulphate. Ina 10 per cent. solution of magnesium sulphate, they coagulate between 70° and 75°C. When precipitated from their saline solutions by dialysis, they are still soluble in solutions of sodium chloride and magnesium sulphate of 10 to 15 per cent., not being transformed into albuminates. Nor are they precipitated by long exposure (over three days) to a temperature of 35° to 40°. III. Fisrins.—Fibrins are solid albuminous bodies insoluble in water and sodium chloride, and which swell up to a stiff jelly in dilute acids. When so treated fibrin is coagulable by heat. The fibrin of the blood is produced in the process of coagulation of the blood ; its prop- erties will be studied with the subject of blood coagulation. IV. Derived ALBUMINATES.—Derived albuminates are bodies which are insoluble in water or sodium chloride solutions, but are readily soluble in dilute acids or alkalies. Their solutions are not changed by heat. When neutralized they are precipitated from their solutions, the pre- cipitate being soluble in excess. Derived albuminates may exist in two different forms,—acid albumens and alkali albumens. 1. Acid Albumen.—When a native albumen in solution is subjected to the action of a dilute acid, such as hydrochloric acid, at a tolerably warm temperature its solutions readily lose their power of coagulating when boiled. If, however, the acid is exactly neutralized by the addition of any alkali the albumen is at once precipitated, and the precipitate is again redissolved by an excess of alkali. The native albumen is thus converted into a form of albuminous body which has become insoluble in water and uncoagulable by heat. ‘When acid albumen is precipitated out of its solution by the NITROGENOUS ORGANIC CELL-CONSTITUENTS, 99 addition of an alkali and then subjected to heat, the acid albumen so suspended in water becomes coagulated, and is then indistinguishable from any other coagulated proteid. After precipitation by neutrali- zation, if the precipitate be then dissolved in lime-water, its solution in lime-water will be coagulable on boiling. Acid albumen is precipitated out of its solution by the neutral salts, such as sodium chloride, and by gallic acid and metallic salts. The conversion of albumen into acid albumen from the action of a dilute-acid is a gradual process. If a solution of egg-albumen be acidu- lated with dilute hydrochloric acid, and subjected to a temperature of about 40° C., it will be found, if tested from time to time, that a coagulum still occurs on boiling. The amount of proteid so coagulated by heat will steadily decrease, and the amount of precipitate obtained by neutral- ization will increase correspondingly. After only ten or fifteen minutes it . will be found that if the solution of acid albumen is exactly neutralized all the albumen will have been converted into acid albumen, and if the precipitate is then filtered off and the filtrate tested with the various proteid tests it will be found that all the proteid has apparently disap- peared; or, in other words, has been converted into acid albumen. A certain degree of temperature is necessary for this conversion. If a mixture of albumen solution and dilute acid be surrounded by ice, the process of conversion into acid albumen will be extremely slow. If warmed up to about 40° C., or, in fact, any distance below the tempera- ture of coagulation of the albumen, the process of conversion will be very much more rapid. If finely-chopped muscle is washed in water so as to remove all the soluble albuminous bodies and blood, and the remainder be covered with a large quantity of dilute hydrochloric acid (0.2 per cent.), and kept for about twenty-four hours at a temperature of 40° C., it will be found that the greater part of the muscle will be dissolved ; if the supernatant fluid be filtered off and neutralized, an abundant precipitate of acid albumen will be ‘thrown down in flocculi, which will gradually settle. The acid albumen in this case is derived from the myosin of the muscle, and indicates that the globulins as well as the albumens are capable of heing converted into derived acid albumen. Acid albumen so obtained from muscle is frequently spoken of as syntonin, but is apparently identical in its general behavior under the different tests to the acid albumen derived from either egg- or serum-albumen. So also in the preliminary . stages of gastric digestion of proteids a product is first formed which appears to be identical in character with acid albumen, or syntonin, and. is termed parapeptone. It also is precipitated from its solutions by neutralization, and is apparently formed solely through the action of the acid of the gastric juice on proteids. 100 PHYSIOLOGY OF THE DOMESTIC ANIMALS, Any of the coagulated proteids may be converted into acid albumen through solution in the mineral acids. If a solution of albumen is gently heated to boiling with dilute hydrochloric acid, no coagulum will be formed, from the fact that in the gradual elevation of temperature the albumen in solution has had time to be converted quickly into acid albumen through the action of the acid. If, now, a small quantity of a concentrated mineral acid, especially hydrochloric, be added, an abundant precipitate will form, and this precipitate is soluble in an excess of mineral acid, especially if subjected to heat. It is thus shown that acid albumen is soluble in concentrated mineral acids. It is insoluble in them when they are moderately concentrated, and it is soluble again when they are very dilute. Egg-albumen, in certain respects, differs from serum-albumen in its behavior to dilute acids. If dry serum-albumen is dissolved in a concentrated mineral acid, it is readily converted in its process of solution into acid albumen. If this solution of serum-albumen in concentrated acid is then diluted with twice its volume of water, acid albumen will be precipitated, and if the precipitate is filtered off it may readily be dissolved in water, from the fact that it still holds clinging to it enough acid to make a dilute acid solution. Therefore, it is not a solution of acid albumen in water, but in dilute acid. Egg-albumen is less soluble in concentrated nitric acid or hydrochloric acid, and when precipitated from such a solution it is less readily dissolved in water. Fibrin also is soluble in concentrated mineral acids, and is rapidly converted into syntonin; therefore, it may be said that all proteids are capable of being converted into moxiuadt albumens. Syntonin, dissolved in dilute hydrochloric acid, rotates the plane of yellow light —72° to the left, and this degree of rotation is independent of the concentration of the solution, but may be increased to —84.8° if the solution is heated. Syntonin contains sulphur, as may be readily shown by dissolving some syntonin in liquor potass, and adding a solution of lead acetate and boiling; the fluid will then become brown from -the formation of lead sulphide. When precipitated from its solutions by neutralization acid albumen forms a white, gelatinous substance insoluble in water and sodium chloride solutions, but soluble in lime-water (in which solution, as already stated, it undergoes partial coagulation when boiled), and in dilute acids and alkaline solutions. If, to the solution in lime-water, after having undergone partial coagulation through boiling, magnesium sulphate be added,a still further precipitation will be caused. Cold solutions of acid albumen are not precipitated by magnesium sul- phate, even if the acid albumen be dissolved in an alkaline solution. If, however, the solution of acid albumen and alkali be warmed, it is then precipitated by the addition of magnesium sulphate or calcium chloride, NITROGENOUS ORGANIC CELL-CONSTITUENTS. 101 indicating that, in all probability, the boiling has served to convert tlie acid albumen into an alkali albumen. Acid albumen shows all the reactions of proteids already described. It may be separated from liquids in which it is dissolved by boiling with hydrated oxide of lead. 2. Alkali Albumen.—If any native albumen in solution is subjected to the action of a dilute alkali, such as sodium or potassium hydrate, it will’ undergo changes somewhat similar to those produced by the action of an acid. Alkali albumens, or alkali albuminates, may, therefore, be described as albuminous bodies which are insoluble in water or sodium chloride, but readily soluble in dilute acids or alkalies. Their solutions are not changed by heat. When neutralized they are precipitated from their solutions, the precipitate being soluble in excess of acid, unless alkaline phosphates are present; an excess of acid:is then required to produce precipitation. In this conversion heat facilitates the process, and, as in the case of formation of acid albumen, the conversion is a gradual one. When alkali albumen is precipitated from its solution in alkalies by neutralization with an acid, if an excess of acid be added it is again rapidly dissolved, through its conversion into acid albumen or syntonin. ‘This conversion of alkali albumen into acid albumen is more readily accomplished when the alkali albumen has been freshly precipi- tated. If some time has been allowed to elapse after the precipitation by neutralization, it will still be converted into syntonin by the action of an acid, but not so readily as when freshly precipitated, unless sub- jected to heat (about 60° C.). If alkaline phosphates are present in the solution the alkali albumen is not precipitated on neutralization, but enough acid must be added to convert the basic phosphate into acid phosphate, and, when this is accomplished, the slightest addition of an acid, even of CO,, will then be sufticient to precipitate alkali albumen. Alkali albuminate may exist either in the form of solution or asa solid. If undiluted white of egg is stirred up with a concentrated solu- tion of caustic potash, or with undissolved caustic potassium hydrate, it will gradually be converted into a stiff jelly. If this jelly is washed with water so as to remove the excess of alkali, it may be dissolved in warm water, and will then behave like alkali albumen obtained by the action of alkalies on albuminous solutions. If, before solution in water, the solid alkali albuminate has been washed until most of the alkali has been removed, passing a stream of carbon dioxide through the solution will be sufficient to cause precipitation. If some pieces of solid alkali albuminate are placed in an acid just strong enough to show an acid reaction after the introduction of the albuminate, the latter will become milky-white, shrivel up, and form an elastic mass, the so-called pseudo-fibrin, which will swell up in dilute 102 ‘PHYSIOLOGY OF THE DOMESTIC ANIMALS. (0.1 per cent.) acids without dissolving, but which is soluble in the caustic alkalies, and may be precipitated by neutralization. Alkali albumen, like other albuminous bodies, is also precipitated from its solutions by metallic salts. With alcohol no precipitate is yielded, and alkali albumen is said to contain no sulphur, the sulphur of the albumen from which it is made being removed by the alkali in the process of conversion. It therefore differs from acid albumen and from casein, which contains sulphur. Alkali albumen or albuminate is present in all young cells, in blood- corpuscles and blood-serum, in muscle, pancreas, nerves, crystalline lens, and cornea. It would seem that alkali albuminate may exist in various forms, judging by the difference in effect produced on polarized light by alkali albumen produced from different sources. Thus, alkali albumen produced from serum-albumen has a leevo-rotatory power of —86° ; from egg-albumen, of —47°, and if prepared from coagulated egg-albumen it may be as high as —58.8°. Casein is a form of alkali albuminate which is present in milk. It yields potassium sulphide when left to stand with liquor potasse, and still more quickly when heated with it. It may be prepared from milk by shaking the milk with caustic potash and ether, removing the ether and precipitating the albuminate with acetic acid, and washing the coagulum with water, alcohol, and ether. The other properties of casein will be further studied under the subject of Milk. Alkali albumen, therefore, differs from acid albumens in its not being precipitated on neutralization if alkaline phosphates be present; by its being precipitated by magnesium sulphate in substance in cold solution, but in not being coagulated when boiled in lime-water; and it contains no sulphur. VY. CoaGuLATED Proterps.—It has already been seen that the action of heat on solutions of egg- and serum-albumen, globulins, or on fibrin when suspended in water, or dissolved in saline solutions, serves to coagulate them and to convert them into an insoluble form. Absolute alcohol produces a similar effect on the same bodies; coagulated proteids are insoluble in water, dilute acids and alkalies and neutral saline solu- tions, and, although they are soluble in the strong mineral acids, their solubility is dependent upon the fact that through the action of the acid they are converted into derived albumens. They are readily converted into peptones through the action of the different digestive juices (gastric and pancreatic juices). When freshly formed they are white, flocculent, or cheesy masses which, under the microscope, are entirely amorphous; they hold water and salt solutions with great tenacity. Their chemical characteristics have been very little studied. VI. Amytoip Supsrances on LARDAcEIN.—This is a substance which NITROGENOUS ORGANIC CELL-CONSTITUENTS. 103 appears to be a derivative of fibrin, and is found as a deposit in numerous of the organs of the body, such as the spleen, liver, ete. It is insoluble in water, alcohol, ether, dilute acids, and alkaline carbonates, and is not dissolved by the digestive juices. When acted on by concentrated hy dro- chloric acid it passes into solution and is converted into syntonin, which may be precipitated by dilution with water. With sulphuric acid it dis- solves when boiled, forming:a violet solution, and with strong sulphuric acid it is converted into leucin and tyrosin. In its composition it appears identical with other proteids. It behaves differently, however, to certain of the proteid tests, and must, therefore, be regarded as a modified proteid. Thus, with iodine, instead of the yellow color produced with other proteids, a reddish-brown color is formed. With iodine and chloride of zine or sulphuric acid a violet-bluish color is produced, thus resembling cellulose in its reaction, to which similarity it owes its name of amyloid, though it must be remembered that this is the only point of similarity between amyloid substances and the starchy bodies; for it contains nitrogen, which is absent from all starches, and it cannot be converted into sugar. Aniline violet on amyloid substance causes a reddish-violet color, and is a test which may be readily used for detecting the presence of amyloid degeneration in various animal organs. Amyloid substance yields the Millon’s and xantho-proteic reactions. VII. PrEprones.—A peptone is a modified form of proteid which occurs when any of the albuminous bodies, with the exception of lardacein, are subjected*to the action of gastric or pancreatic juices, prolonged boiling at high temperature under great pressure, or by the action of heat and dilute acids at moderate temperature. Their general charac- teristics will be referred to under the subject of Digestion. In addition to the above classes of albuminous bodies, albumen has been said to exist under two other forms, that of meta-albumen and para- albumen, although as yet very little is known about their characteristics, or in fact whether they are not simply ordinary albuminous bodies modified by the accidental addition of some other substance. Thus, meta-albumen might possibly be regarded as a mixture of albumen and mucin, since it is precipitated by alcohol without undergoing coagulation ; it is not coagu- lated by boiling, although its solutions become cloudy when heated, and it is not precipitated by acetic or hydrochloric acids, or acetic acid and, potassium ferrocyanide. It is, however, precipitated by mercuric chloride and gallic acid. It has been found in ovarian cysts, and in the fluid of ascites. When precipitated by alcohol the precipitate is again soluble in water. Para-albumen has also been found in the fluid of ovarian cysts, where its presence was supposed to be characteristic, but has also been found elsewhere. It is precipitated by alcohol, and when so precipitated 104 PHYSIOLOGY OF THE DOMESTIC ANIMALS. ~ may redissolve again in water. It is not completely coagulated by boil- ing. It is rendered turbid by acetic acid, the cloudiness being removed by an excess of acid or sodium chloride. It is precipitated by nitric acid, potassium ferrocyanide and acetic acid, mercuric chloride, and ace- tate of lead. ALBUMINOIDS. | In the development of the different tissues of the animal body the native albumens already described, which exist in the ovum and embryonic cells, assume a modified form, the condition under which such a modified albumen is present varying considerably in dif- ferent tissues; as already pointed out, the difference in the different tissues, especially in the different members of the connective-tissue group, is dependent upon the modification which the albuminous con- stituents of those cells have undergone. Such bodies have a chemical composition very closely allied to that of native albumens. They are complex, nitrogenous compounds, but they present certain proper- ties in contrast with the true albuminous bodies. As they appear to result from the transformation of those bodies in the animal economy, not as arule being found in the vegetable kingdom, they may be spoken of as the albuminoids of special tissues. In the connective-tissue group are included a number of different tissues, such as white connective tissue, elastic tissue, tendon, bone, cartilage, and dentine, which at first sight appear to have few if any points in common. Yet all these tissues fulfill the same subservient function of connection and support, all originate from the same layer of the blastoderm, and in different periods of life are often changed from one form into the other. The cells of all these tissues are capable of developing a more or less homogeneous intercellular substance, whose chemical composition differs in the different members of this group. When any of the various forms of connective tissue proper are macerated for some days in lime-water or baryta-water, the various elements fall asunder from solution of the connecting cement, which may be precipitated from its solution by dilute acids. This body is mucin, Ifthe ground substance of the different connective tissues after the removal of mucin is boiled in water, they nearly all yield substances somewhat similar to glue; hence they are called collagenous bodies. We will take these up in turn. 1, Mucin.—Mucin, or the cement substance, is found in all mucous secretions as a result of special cell action, and in the tissue of mollusks; and is the substance to which their tenacious character is due. It is found in embryonic connective tissue, and serves to bind together the fibres of tendons, and of connective tissue and epidermis, and is found NITROGENOUS ORGANIC CELL-CONSTITUENTS. 105 in synovial secretions. Mucin may be prepared from the salivary glands by making a watery extract, filtering and precipitating mucin by acetic acid; the precipitate may then be washed with water, with alcohol, and with ether to remove fat. Mucin may also be obtained from tendons by washing well, cutting up into small pieces, extracting them with water to remove soluble albuminous bodies and salts, and then allowing them to stand for several days in lime- or baryta-water. After filtration, acetic acid will precipitate the mucin, which at first is granular, but afterward _ floceulent in appearance, and which may be washed with dilute alcohol or dilute acetic acid. It also may be prepared from ox-gall by precipi- tating with its own volume of alcohol to remove the coloring matter and proteids, dissolving the precipitate in lime-water, after washing with fresh alcohol, and precipitating the mucin from its solution in lime- water by acetic acid. When freshly precipitated, mucin is a glutinous body which may be suspended but not dissolved in water. Mucin is soluble in concen- trated but not in dilute mineral acids. It is also soluble in liquor potasse and lime-water, and the solution is viscid and nearly neutral, When in solution it is not coagulated by boiling, but is precipitated in an insoluble form by acetic acid. Its solutions are precipitated by mineral acids, the precipitate being soluble in a slight excess of acid. It is not precipitated by metallic salts, with the exception of acetate of lead. When boiled for twenty or thirty minutes with dilute sul- phuric acid it acquires the power of reducing the ordinary sugar tests, It again loses this power on prolonged boiling. A body similar to acid albumen is formed at the same time. No precipitate is produced with solutions of mucin by acetic acid and potassium ferrocyanide unless other albuminoids are also present. It gives no precipitate with mercuric chloride, and does not give the biuret reaction for albu- minous bodies; with Millon’s reagent it gives a red color. It therefore possesses several properties which are divergent from those of or- dinary albuminous bodies, and is evidently a proteid body modified through the differentiation of the protoplasm of the cells of the con- nective-tissue group. Mucin appears to be digested by pancreatic but not by gastric juice. Mucin is not soluble in water or alcohol, but swells up very much in the former, particularly in the presence of certain salts. When the mixture is filtered part of the mucin often passes through, and causes a turbid precipitate. The mixture in water possesses no viscidity; it, however, becomes clearer and more tenacious if sodium chloride is added. 2. Collagenous Albuminoids.—Collagenous albuminoids, of which gelatin is the type, are albuminous bodies found in connective tissue, cartilage, and bone, They contain a little less carbon and more nitrogen 106 PHYSIOLOGY OF THE DOMESTIC ANIMALS. than the true albuminous bodies. They are termed gelatinous because gelatin, which is formed by the action of boiling water on these tissues, is the most important representative of the group. It contains— a. Collagen. b. Gelatin. ce. Chondrogen. d. Chondrin. a. Collagen, or gelatinous substance, forms the organic basis of bones and teeth, and of the fibrous parts of tendons, ligaments, and fascia. It derives its name from the fact that by prolonged boiling it is converted into gelatin or glue (KoAAa). Collagen is prepared from bones by soaking in repeated changes of dilute hydrochloric acid; or from tendons by removing mucin by means of lime- or baryta-water, then by repeated washing with water, and finally with very dilute acetic acid. When fresh it is soft, but it shrinks and becomes hard when dry, or when alcohol is added. Collagen is insoluble in cold water; it swells up on dilute acids, and becomes transparent; through the prolonged action of dilute acids collagen dissolves, the solution containing gelatin and acid albumen, the latter, perhaps, being produced by the action of the acid on the residual matter of the connective-tissue cells. It dissolves in liquor potasse, and in boiling dilute acids or in boiling water it dissolves and is rapidly converted into gelatin. b. Gelatin.—Gelatin is prepared, as already indicated, by boiling collagen, or any of the connective-tissue group, in water, and when the solution cools it forms a jelly the’ consistence of which depends upon the percentage of gelatin present. Gelatin, prepared as indicated above, is a product of the trans- formation of connective tissue by the prolonged action of boiling water. It is favored by high temperature (120° C.), as in Papin’s Digester, and the presence of a minute quantity of acid. When dry it forms a yellowish or, if pure, a transparent, tasteless solid, closely resembling a gum in its general appearance and characteristics. It is insoluble in cold water, but when immersed in cold water is able to absorb by imbibition forty times its own weight. It then will forma stiff, tenacious, jelly-like mass. If dry gelatin is boiled in water, it is readily dissolved, and when the solution in water cools the gelatin sets into a stiff jelly if more than 1 per cent. of gelatin is present, the consistence of the jelly depending upon the quantity of gelatin dissolved. When boiled for a long time in water, or if boiled with an acid or alkali, this property of gelatinizing is lost and two peptone-like bodies result. Gelatin is insoluble in alcohol, ether, and chloroform. It is soluble in warm glycerin, such solutions having the power of gelatinizing when cooled. NITROGENOUS ORGANIC CELL-CONSTITUENTS. 107 In solution gelatin rotates the plane of polarized light to the left (—130° at 25° C.). In watery solutions gelatin is precipitated by tannic acid, alcohol, and mercuric chloride; but not by acetic acid, which serves to distinguish it from chondrin; nor by potassium ferrocyanide and acetic acid, which separates it from other proteids; nor acetate of lead, which precipitates chondrin. When boiled with cupric sulphate and potassium hydrate, the blue solution becomes red without depositing oxide of * copper. Gelatin readily undergoes putrefaction, and among the products leucin, ammonia, and some of the fatty acids are found. ce. Chondrogen.—Chondrogen is found in the intercellular substance of hyaline cartilage, and in the cartilage of bone before ossification. It derives its name from the fact that when boiled with water it forms chondrin,—a point which serves to distinguish it from fibro-cartilage, which, when treated in the same way with boiling water, forms gelatin, and not chondrin. Chondrogen is insoluble in cold water, but if dried before- hand, when immersed in cold water will swell up slightly. It swells very slightly in acetic acid, and may be dissolved by the concentrated mineral acids and caustic alkalies. When subjected to prolonged boiling with water it dissolves and forms an opaline solution, which forms a jelly when cooled. d. Chondrin.—As just stated, chondrin is the result of prolonged boiling of chondrogen in water. When solutions of chondrin in water cool they form a stiff jelly, which is insoluble in cold water, but soluble in alkalies and ammonia. When solutions of chondrin are evaporated, a hard, translucent, yellowish, gummy mass results, which is insoluble in alcohol and ether, swells slightly in cold and dissolves tolerably readily in hot water and solutions of the alkalies. Prolonged boiling of watery solutions of chondrin destroys its power of gelatinizing, though the other properties of chondrin are not thereby altered. It is precipi- tated from its solutions by alcohol. It differs from. gelatin in that it is precipitated by the mineral acids even when they are dilute; an excess of the reagent dissolves the precipitate. It is also precipitated by solutions of sulphurous acid. It is precipitated by acetic acid, the precipitate not. being soluble in excess unless some alkaline salt be present. It is precipitated in abundant flocculi by solutions of alum, which readily dissolve in an excess, and the fluid becomes clear and transparent. It is precipitated with acetate and subacetate of lead, nitrate of silver, and cupric sulphate. ‘Tannic acid and chlorine water precipitate it, as in the case of gelatin. It rotates the plane of polarized light to the left. Chondrin also is readily decomposable, and when subjected to prolonged heat with concentrated hydrochloric acid is decomposed, with the formation of nitrogenous compounds which ae the power of reducing the cupro-potassium test; a body resembling acid 108 PHYSIOLOGY OF THE DOMESTIC ANIMALS. albumen is formed at the same time. The same changes follow prolonged boiling with dilute sulphuric acid. There are some grounds for supposing that chondrin is not an individual albuminoid, but that it is rather a mixture of gelatin, mucin, and salts, since its general characteristics are similar to what might be possessed by a combination of these bodies, All the connective tissues, therefore, possess a body which may be transformed into gelatin by boiling, and a cement substance, mucin. _The following statements represent in a few words the distinctive characteristics of mucin, chondrin, gelatin, and albumen :— Mucin.—Precipitated by acetic acid, the precipitate is not dissolved by sodium sulphate. Chondrin.—Precipitated by acetic acid. the precipitate is dissolved by sodium sulphate. Precipitated by lead acetate, alum, silver nitrate, and copper sulphate. Gelatin.—Not precipitated by acetic acid, nor by acetic acid and potassium ferrocyanide, nor by lead acetate. Albumen.—Dissolved by acetic acid, the solution is precipitated by potassium ferrocyanide, or by the addition of alkaline salts and heat. Gelatin and chondrin are mostly to be recognized by their hot solutions forming a jelly when cooled. This, as already mentioned, is not invariably the case, as the property is lost by prolonged boiling, or by boiling with acids. ; Closely allied to these collagenous albuminoid constituents of the connective tissues we meet with two other albuminoids which have many points in common with the above, with the exception that they do not form jellies when their solutions cool. These two bodies are Elastin, obtained from elastic tissue, and Keratin, a nitrogenous body of epithelial origin. : 3. Llastin.—Elastin is the albuminoid principle contained in yellow elastic tissue. When yellow elastic connective tissue is boiled with water, after mucin has been removed, collagen is dissolved. The residue which remains is mainly composed of elastin. Elastin may be prepared by macerating the ligamentum nuche of the ox with ether, and then hot alcohol, to remove the fats; boiling water, to remove collagen and convert it into gelatin, and 10 per cent. caustic soda, and then acetic acid, allowing the boiling in water to continue for at least thirty-six hours, and in the acetic acid for at least six hours. After being subjected to the soda, the remaining tissue is again boiled with dilute acetic acid, well washed with water, and afterward the acid neutralized. After washing with hot water a brittle, yellowish mass is obtained, which recovers its elasticity and fibrous appearance if soaked in dilute acetic acid. Elastin is insoluble in cold or boiling water, and offers remarkable resistance to chemical agents, unless boiled for a very long time. It is NITROGENOUS ORGANIC CELL-CONSTITUENTS. 109 insoluble in alcohol, ether, ammonia, or acetic acid, but it dissolves in caustic potash. Its solutions, however, do not gelatinize. When once dissolved in caustic potash the alkali may be neutralized without throw- ing the elastin out of solution. Tannic acid is the only acid which will precipitate it. Elastin gives the xantho-proteic and Millon’s reactions, and its place among the albuminoids, therefore, seems warranted. When boiled for a long time with sulphuric acid it undergoes decomposition, with the formation of leucin and tyrosin. Elastin contains no sulphur. 4, Keratin.—The epithelial tissues of the animal body—nails, bone, epidermis, and epithelium, as well as horns and feathers—are mainly composed of a substance closely allied to albumen, as it gives leucin and tyrosin on decomposition, to which the name of keratin has been given. Keratin contains sulphur in loose combination, and is in some re- spects closely related to elastin. Keratin is insoluble in alcohol and ether, swells up in boiling water, and is soluble in the caustic alkalies. It is not liable to decomposition. When one of the epithelial structures, such as horn, is subjected to the action successively of boiling water and alcohol, ether, and dilute acids, this substance, keratin, remains behind. But when so obtained it has by no means a constant composition, and it is probable, therefore, that keratin is rather a mixture of several nitrogenous bodies than a single albuminoid. _ Decomposition of the Albuminous Bodies.—As already mentioned, albuminous bodies are the most unstable of all organic compounds, and we have the strongest reason for believing that, even while in the interior of animal and vegetable organisms, the albuminous constituents of proto- plasm are continually the seat of various forms of decomposition which result in the production of simpler organic and inorganic forms. As we. know but very little as to the molecular constitution of the proteid bodies, nothing positive can be said as to the complex chemical processes which result in the production of simpler organic forms. The subject has been a favorite field of research for organic chemists, but as yet scarcely anything tangible has resulted from their labors. An immense amount of valuable information has been attained, but the applicability of the facts so reached to physiological processes is not as yet clearly assured. The chief end products of the decomposition of proteids in the animal cell, which is essentially one of oxidation, are water, carbon dioxide, and urea. What the nature of the substances are which are in- termediary between these end products and albuminoids we do not clearly know, except that certain ones, such as leucin, tyrosin, certain of the carbo-hydrates, such as glycogen and fats, are of constant occurrence and of great importance. The subject of the decomposition of albumen under various chemical and physical agents is an extremely interesting one, but it falls more within the province of works on organic chemistry. 110 PHYSIOLOGY OF THE DOMESTIC ANIMALS. In our study of the processes of metabolism of the animal body, in which we will attempt to trace the course of the food-stuffs after their entrance into the body and in their elimination as various effete products, this subject must necessarily be touched upon; the consideration of the part of this subject which is at all capable of practicable application will be deferred until then. It may only be mentioned here that the simpler an organism the simpler must be the chemical changes in its constituents. Thus, we find that in the elementary vegetable organisms their entire structure is made up of protoplasm, which is practically almost solely albuminoid ; we have then appearing chlorophyll, cellulose, starch, and in still higher forms the various sugar groups, vegetable acids, alkalies, etc. In the animal body a similar state of affairs holds. We may say that the body of an ameeba is composed of simple albuminous matter. In the development of organs we haye a development of supposed chemical derivatives of protoplasm, and the higher the state of development of the organism the more com- plex will be the changes which have resulted from the original proto- plasm. As we have already mentioned, these cell-constituents are organic, nitrogenous and non-nitrogenous, and inorganic bodies. All of the sub- stances which we have heretofore considered are examples of derivatives or modifications of protoplasm, and as protoplasm is essentially albumi- nous they are, therefore, the examples of a modification of albumen. In the waste of albuminous tissues we have an immense number of inter- mediary bodies, partly belonging to the various aromatic series, between albuminous bodies and the simpler end products, water, carbon dioxide, and urea. These bodies result from a progressive series of oxidations, and will receive consideration under the subject of Nutrition. FERMENTS. Various animal and vegetable cells will often be found to contain a class of bodies which are closely allied in composition to albuminous substances, since they contain carbon, nitrogen, hydrogen, oxygen, and sulphur. From the fact that they are able, under certain conditions, to produce reduction in the complexity of organic compounds with the action of water without acting through the development of chemical affinities, and without themselves undergoing change, such bodies are termed soluble ferments, and are derived directly from modifications of the protoplasm of the living organisms in which they originate. Al- though they are apparently allied to albuminoids in their chemical con- stitution, yet when purified they fail to give the proteid reactions; and although we may be pretty sure that such bodies are derived from the physiological splitting up of proteids, we have no exact knowledge as to their structure. When obtained dry by various processes, which NITROGENOUS ORGANIC CELL-CONSTITUENTS. 111 will be considered under the study of the individual ferments in the section on Digestion, they are amorphous, colorless powders, which are highly soluble in water, resemble gums somewhat in appearance, and are precipitated from their solutions by alcohol, corrosive sublimate, and lead acetate. One of their remarkable points of contrast to albuminous bodies is that, when precipitated from solution in water or glycerin by absolute alcohol, if the precipitates are filtered off and dried, they are again perfectly soluble in water, and are still capable of exerting all their actions ; hence, their precipitation is more of a mechanical nature than chemical. Further, when the precipitates formed by the above reagents are decomposed by sulphuretted hydrogen a watery extract of the pre- cipitate will still preserve the original properties of the ferment; in other words, the soluble matter is restored to the water unchanged, and still preserves its specific properties. he ferments are with difficulty freed from albuminoids, and it is in all probability the albuminoid which is chemically precipitated from their solutions by the above reagents, and which in this precipitation carries with it mechanically the ferment. Consequently, this property of the ferment of being precipitated by the above reagents is dependent upon the albuminous bodies which are nearly always associated with it. We shall, further, find that this prop- erty of being carried down by precipitates from solutions is the basis of nearly all the methods which have been employed for the isolation of the different digestive ferments. Ferments obtained from the animal and vegetable kingdom may have the most varied functions. We have but little information concerning the soluble ferments from a chemical point of view. We do not even know whether they all have the same chemical compo- sition, and differ only in some unknown manner in their specific activity. ‘They only are active at a temperature below 60° C., and when in the presence of water; at the temperature of boiling water they are perma- nently destroyed; at lower temperatures their activity is suspended. They do not themselves appear to be influenced in the phenomena of fer- mentation which they inaugurate; ferments are also inactive in the pres- ence of various chemical agents, such as alcohol, the stronger mineral acids, and all the large group of substances which are known as antisep- tics. Ferments may be of two kinds; either organized ferments, such as the yeast-plant, malt, vibrios, bacteria, etc.,—substances which are themselves elementary, cellular organisms,—or the so-called unformed ferments, or enzymes, substances which invariably originate in the interior of animal and vegetable protoplasm, and are soluble and not organized. This latter group comprises all the ferments with which we are par- ticularly interested. Their specific action is in many cases closely analo- gous to that of the formed ferments. There are, however, several points 112 PHYSIOLOGY OF THE DOMESTIC ANIMALS. © of contrast between them. Organized ferments are destroyed by com- pressed oxygen; soluble ferments are not. Solutions of borax prevent the action of the unformed ferments, but aré without influence on the formed ferments. The organized ferments during their action reproduce themselves; the soluble ferments do not act. All the soluble ferments have a high percentage of ash, sometimes as much as 8 per cent. Under the action of ferments, fermentable bodies yield substances whose nature is dependent on that of the ferment. So that any individual ferment- able substance under the influence of different ferments will split up into different substances. The following are the important ferments found in animal organ- isms: ptyalin, found in the saliva and converting starch into sugar; pepsin, found in the gastric juice and in the presence of a dilute acid converting albuminous bodies into peptones ; the milk-curdling ferment, or rennet, found in the gastric juice and coagulating milk in neutral or acid media; the amylolytic ferment of pancreatic juice, converting starch into sugar ; the proteolytic ferment of pancreatic juice, converting proteids into peptones in an alkaline medium; the fat-ferment of pancreatic juice, splitting up neutral, fatty bodies into fatty acids; the milk-curdling fer- ment, also said to exist in pancreatic juice; the inversive ferment, found in intestinal juice and converting cane-sugar into inverted sugar; and the liver-ferment, converting glycogen into sugar. The general subject of the nature of the changes produced by these substances will be con- sidered in the next section; the mode of action of the digestive ferments will be considered under the subject of Digestion. B. NON-NITROGENOUS ORGANIC CELL-CONSTITUENTS. J. Canrso-nypRates. — The carbo-hydrate tissue-constituents are composed of carbon, hydrogen, and oxygen, the latter two in the propor- tion to form water. Although occasionally present as constituents of animal eclls, they are almost exclusively produced by the vegetable king- dom, and present many interesting examples of isomerism. They may be divided into the three following groups:— (a) SrarcuEs (C,H,,0,). (b) Grave-Sucar Group (C,H,,0,). (c) CAnE-Sucar Group (C,,H,0,). The members of the first group may, through the action of dilute acids or the diastatic ferments, be transformed in great part into the second group. The latter undergoes alcoholic fermentation when in contact with malt. (a) Tne Amytosrs, on Starch Group n(C,H,O;).—This group includes starch, dextrin, glycogen, cellulose, granulose, and inulin. NON-NITROGENOUS ORGANIC CELL-CONSTITUENTS. 113 1. Starch, or amylum (n(CgHi.0,) or CrglTg¢0,5), is almost univers- ally distributed throughout the vegetable kingdom, and is the first evi- dence of the decomposition of CO, of the atmosphere by vegetable cells (6 CO,+5 H,O=C,H,,0,+12 0). It is particularly abundant in the cereals, in seeds of the leguminous plants, and in the potato, and in cer- tain roots, tubers; soft stems, and seeds. It forms rounded masses which lie in the plasma of the plant-cells, becoming converted, in the process of germination in seeds and bulbs, into soluble dextrin and sugar. Under Fig. 54. -STARCH-GRANULES, AFTER LOEBISCH. A, pea-starch; B, rice-starch ; C. oat-starch ; D, wheat-starch: E, bean-starch; F, millet-starch; G, corn-starch ; H, rye- starch; I, lentil-starch; K, potato-starch; L, buckwheat-starch; M, barley-starch. microscopic examination starch appears as rounded, glistening granules composed of a series of concentric rings. These granules vary in appear- ance and size according to their source. In size they may vary from 0.004 mm. in diameter, as when found in beet-seeds, to 0.16 mm., as in potato-starch (Fig. 54). In the following table (after Karmarsch) the diameter of the starch- granules from different sources is given. Microscopie examination of 8 114 PHYSIOLOGY OF THE DOMESTIC ANIMALS. different “ meals,” by the shape and size of the granules, will thus near of the recognition of adulteration with inferior meals :— Mm. Starch-granules from Potatoes Cu erage), ... +0.140 (0.10-0.185). Arrowroot, ‘ F . 0.140 ae «Sago, a ‘ » 0.07 se ts Beans, oi ‘ . 0.063 vi «Peas, a . . 0.050 ae « Wheat, ss : . 0,050 a «Rye, ae s . 0.086 ue «Oats, " : . 0.031 ve « Corn, st ‘ . 0.02-0.03 as «Tapioca, . . 0.028 se «Rice, bi ‘i . 0.022 ai «Barley, ee ‘ . 0.025 ss «Buckwheat, ‘ . 0.009 The striated appearance is due to the fact that starch is composed of two substances,—cellulose and granulose, arranged in concentric layers, the cellulose always being external. Granulose stains blue with iodine,—not by the formation of a chemical compound, but by the deposit of the iodine around the starch-molecules,—and cellulose stains a faint yellow. These two substances may be separated hy digesting, at 60° C., one part of starch in forty parts of saturated salt solution containing 1 per cent. of free hydrochloric acid. The granulose then passes into solution, while the cellulose remains. Examined in this way, potato- starch has been found to contain 5.7 per cent. cellulose, wheat-starch ‘2.3 per cent., and arrowroot 3.10 per cent. Under the action of dias- tatic ferments granulose is converted into sugar, while cellulose remains unaltered, . The latent period is indicated by the fact that one pulsation occurred after the stimulation entered the nerve. It is further evident that the inhi- bition persisted some time after the stimulation ceased. In addition to the intrinsic nervous system of the heart, the pulsa- tions of this organ are also governed by impulses coming from the central nervous system. These are of two different kinds,—inhibitory and accelerating. The Inhibitory Nerves of the Heart.—It was discovered in 1848 that stimulation of the pneumogastric nerve or of its divided periph- eral extremity had the effect, in the dog, of retarding the pulsations of the heart, and, when the stimulation was sufticiently strong, of entirely uresting the heart in diastole. This effect is not produced immedi- ately on the application of the electric current to the nerve, but is pre- ceded by a latent period amounting to about one-tenth of a second; so also, the effect lasts a certain time after the shutting off of the current, if the application has not been too prolonged (Fig. 231). On the other 550 PHYSIOLOGY OF THE DOMESTIC ANIMALS. hand, if the current is very strong, the heart may be completely arrested and yet start again during the passage of the current. With weak cur- rents no actual arrest of the heart takes place, but the pauses between the beats are prolonged during the earlier part of the application of the current, and the pulse is thus rendered slow. If the pneumogastric be stimulated in a dog during a blood-pressure experiment some such curve as represented in the diagram will be produced (Fig. 232). The blood pressure is seen to undergo a rapid fall shortly after the application of the current, from the fact that on the cessation of the pulsation of the heart the arteries, through their contractility, empty themselves into the venous system. As the heart again commences to pulsate it throws its contents into the arterial system, which has been already largely depleted of blood, and, as a consequence, the walls of the arteries are rapidly stretched, and we have a correspondingly rapid a Fig, 232.—MANOMETER TRACING FROM THE CAROTID OF A RABBIT ON STIM- ULATION OF THE PNEUMOGASTRIC NERVE. (foster.) The current entered the nerve at @ and was shut off at b. increase in pressure, and therefore a rapid rise in the mercury in the manometer. When the heart is only slowed by stimulation of the pneumogastric, and not completely arrested, the mercury in the manom- eter undergoes extensive oscillations, partly due to inertia, which exaggerates these movements, and partly due to the same cause already mentioned. In other words, between the pulsations of the heart, which succeed each other slowly, the arterial system has time to partially empty itself into the veins. Inhibition of the heart may not only be produced by direct stimu- lation of the pneumogastric, but also may be produced reflexly. If one pneumogastric nerve be divided, and the central end, in connection with the brain, be stimulated with the induction current, the heart will be arrested or slowed as before. If the abdomen of a frog be opened, and the intestine struck sharply, as with the handle of a scalpel, the heart CIRCULATION OF THE BLOOD. 551 will be likewise arrested in diastole. If the mesenteric nerve be stimu- lated by an induction current the heart will also be brought to a sudden standstill. If both pneumogastric nerves be divided, the anterior roots of both spinal accessory nerves be torn out, or the medulla oblongata destroyed, the preceding experiments will all fail. This indicates that in the first case the impulse was conducted through the central stump of the divided pneumogastric to the brain, and there, from a collection of nerve-cells in the medulla oblongata, which is termed the cardio-inhibi- tory centre, is transmitted through the spinal accessory nerve to the pneumogastric plexus, and through the undivided vagus to the heart. If the spinal accessory nerve be pulled out by the roots, the cardio- inhibitory fibres of the pneumogastric undergo degeneration, and four or five days after the operation stimulation of the vagus fails to slow the heart. In the other instance, where irritation of the intestinal surface or mesenteric nerves produces inhibition, the impulse is conducted through the mesenteric and sympathetic chain to the spinal cord, from there to the cardio-inhibitory centre, and from there to the heart. It is probable that the syncope occasionally produced by severe pain, emotions, or sometimes from drinking ice-water when overheated is produced in the same manner, the heart being arrested or slowed through reflex inhibition. It is thus observed that the pneumogastric nerve possesses a function directly opposed to that of most other nerves. When a motor nerve is stimulated it produces contraction of the muscles to which it is dis- tributed. Stimulation of the pneumogastric, on the other hand, produces relaxation of the heart-muscle. The manner by which this effect is produced is in all probability through the inhibition of the motor ganglia of the heart. The cardio-inhibitory centre in the medulla is in constant action, through reflex stimuli conducted to it through the abdominal and cervical sympathetic, and might be compared to the action of a brake on a moving machine. When both pneumogastric nerves are divided, the heart in the dog, and to a less extent in the rabbit, beats very much faster, so that this inhibitory centre is constantly restraining the action of the motor ganglia. The cardio-inhibitory centre may be directly stimulated by sudden anemia of the medulla, as by sudden ligation of both carotids; by sudden venous hyperemia, as by ligation of all the veins of the neck; or by increased venosity of the blood, as by dyspnoea or causing an animal to inhale CO, It may also be reflexly stimulated, as already indicated. The Accelerator Nerves of the Heart.—The action of the heart may not only be retarded or arrested through the stimulation of the pheumogastric, but in the mammal, even after division of both pneumo- 552 PHYSIOLOGY OF THE DOMESTIC ANIMALS. gastrics, it may be accelerated by stimulation of the cervical sympathetic, stimulation of the cervical spinal cord, or in a more marked degree by stimulation of the communicating filaments between the spinal cord and the inferior cervical and the first dorsal ganglia of the sympathetic. These latter fibres are described as the accelerator nerves of the heart, and when stimulated produce an increase in the rate of the heart’s pulse, but with a decreased force, the loss in power being, however, compensated by the increase in rapidity. As a consequence, after stimulation of these nerves the blood pressure remains unchanged, The course of these nerves is different in the rabbit and the dog. The diagrams (Figs. 233 and 234) indicate their most usual course. These accelerator fibres originate from centres in the medulla oblongata and spinal cord, though their exact location has not been determined. It is hy means of stimulation of these fibres, therefore, that stimulation of either the cervical spinal cord or cervical sympa- thetic produces inerease in the rate of the heart’s pulsation. When the cervical spinal cord is stimulated a great increase in blood pressure follows from stimulation of vaso-motor nerves, but that the increased rate of the heart’s contractions is not due to the high blood pressure slone is proved by the oceur- rence of acceleration of the pulse when the ial bats = baa oR ae cervical cord is stimulated, even after section CouRsH or THE Carprac of the splanchnic nerves, when increased blood ACCELERATOR FIBRKS., (Landois.) pressure is prevented. These nerves are not Pp, >; MO, dulla obl ta; = toe . V, inhibitory centre for heart; A-aceely iN Constant activity; in other words, they do erator centre; VAG, vagus; SL, supe- ° . rior, IL inferior laryngeal nerves; SC, not antagonize the pneumogastrics, and when superior cardiac fibres ; H, heart; £, cere- ache a . bral impulse; S, cervical sympathetic; Ciyided the heart does not beat slower. & ca PA bid l< E < = VE = VE Fig, 24.—G1L.L oF THE PERCH. (Jeffrey Bell.) A, branchial artery; B, branchial arch (seen in cross-section) ; C, branches of the branchial vein, V; D, branches of the branchial artery. In the saurians, the thorax in the chelonia, the thoracic walls are rigid and immovable; in the ophidians, the ribs are very numerous and movable, the sternum being absent. A dia- phragm is met with only in the higher sau- rians. In reptiles inspiration is not accom- plished by inhalation, but by deglutition, air being drawn into the pharynx by depression of the hyoid apparatus, and the nares then being closed, the air is forced into the trachea. Expiration is accomplished mainly by the elasticity of the lungs, aided by the abdom- inal muscles, and in saurians and ophidians by the intercostal muscles and the elasticity of the chest-walls. In snakes, as a rule, there is a single, long, cylindrical lung, while the left lung is rudimentary. In birds, though the diaphragm is still absent or rudimentary, the respiratory appa- ratus is more complicated than any yet considered, so that the energy of the respira- tory process is much increased, and yet the general plan of the apparatus is much more closely allied to that of reptiles than of mammals. For each lung may be considered to be sub- divided into lobules, each of which resembles the rudimentary lung of RESPIRATION. 569 the frog, flattened and fixed to the back of the thorax. In addition to the elementary lungs numerous large air-sacs, distributed in various parts of the body, as the abdomen, the muscular interspaces, interior of the bones, ete., are found communicating with the lungs. And as the lining membrane of the bones, as well as of all these cavities, is extremely vascular, it also, in these localities, serves to assist in the aera- tion of the blood by exposure to the air. In fact, if the wind-pipe be tied and an opening be made in the wing-bone, respiration may still go on. This large increase of respiratory surface serves as well as store-room for atmosphere and is well adapted to the purposes of flight, during which the respiratory movements are less free. The lungs and the accessory apparatus of birds is filled with air by the process of suction through the trachea, in consequence of the permanent distended condition of the whole cavity of the trunk from the nature of its bony encasement. Such is the natural condition of this bony frame-work that when no pressure is made upon it it is completely distended ; as a consequence, the lung- tissue permanently attached to the ribs possesses such a degree of elas- ticity as to enable it to spontaneously dilate. Hence, the disposition of the air to fill the distended cavities until, by the action of the external muscles upon the bony frame-work,a portion of the air is expelled and its place again immediately taken by a fresh supply of air on relaxation of these muscles. Inspiration, therefore, in birds, in opposition to what we shall find to be the case in mammals, is passive, while expiration is active and is accomplished by drawing the sternum toward the backbone by muscular contraction, thus compressing the lung and expelling the air. The organs of respiration in man and mammals generally consist of, first, the bony frame-work of the chest; second, the diaphragm and other muscles ; and, third, the trachea, bronchial tubes, and air-vessels. In mammals alone is there a perfect thorax, 7.e., a closed cavity for the heart and lungs, with movable walls and a muscular partition, the diaphragm, separating the thoracic from the abdominal cavity. The trachea is a cylindrical tube consisting of a varying number of cartilaginous rings, imperfect posteriorly in man and most animals. These posterior imperfect spaces are occupied by the muscles which control the calibre of the tube. The use of these cartilaginous rings is to keep the tube patulous, so as to permit the entrance and free egress ‘of air, subserving the same function as the spiral fibres in the interior of the air-vessels of the plant and insect already described. Immediately within the cartilaginous rings, which are bound together by fibrous tissue, is found a fibrous connecting membrane; within that is a mucous membrane continuous with that of the mouth and the pharynx, supplied with cylindrical, ciliated, epithelial cells, the cilia of which vibrate toward the pharynx and serve the purpose of facilitating the discharge of the 570 " PHYSIOLOGY OF THE DOMESTIC ANIMALS. secretions or of any foreign substance which may lodge upon it. When the trachea reaches the second or third dorsal vertebra it bifurcates into two principal bronchi, passing one to each lung, and subsequently these again divide and subdivide in various directions until they have attained the size of the most minute bronchial tubes. The larynx, which is placed at the laryngeal extremity of the trachea, may be considered as corresponding to the base of a tree, the trachea to its trunk, and the bronchi to its different branches; while the ultimate bronchi terminating in the air-vesicles of the lung may be regarded as representing the leaves of the tree. The bronchi have the same anatomical constituents as the trachea, and are composed of carti- laginous rings, musculo-fibrous membrane, and a lining mucous membrane (Fig. 245), The cartilaginous rings are also imperfect, but the imperfect spaces are irregularly dis- tributed, sometimes in front and sometimes at the side. The object of the rings is, of course, the same as those of the trachea. The tubes are thus mere gaseous conduits kept patulous by their cartilaginous constit- uents. In the bronchi a fibrous basement membrane is found, as well as unstriped muscular fibres, and in the bronchi the muscular fibres do not merely connect the ends of the rings, but completely encircle the tubes in the form of annular fibres. These muscular fibres are unstriped and involun- Pre SOOO eE Cone oe tary, and therefore possess the same char- EBX. Welney Bell) acteristics as the unstriped muscular fibre A, eparterial, B, hyparterial ventral (V), and, D, hyparterial dorsal bronchi; found elsewhere, and serve to regulate the PA, pulmonary artery; PV, pulmonary ae calibre of the tubes. The lining mucous membrane of the bronchi is also a ciliated membrane and extends down to the commencement of the finest bronchi. In the mucous membrane are found tubular glands forming a mucous secretion. In the minute bronchi the cartilaginous rings disappear and the bronchioles are then constituted of a layer of circular muscular fibres with an inner epithelial membrane, the cartilaginous rings disappearing when the bronchi have been reduced to about one-thirtieth to one-fiftieth of an inch in diameter. The bronchi ultimately terminate in a dilated portion, termed lobules or it- fundibula, which consist simply of 2 homogeneous membrane abundantly . supplied with blood-vessels. This dilatation is formed by the same material as constitutes the fibrous wall of the tube thrown up into folds, between which ramify the blood-vessels. The contained blood is, there RESPIRATION. 571 fore, exposed on both sides to the atmosphere. As the capillary net- work is spread over several cells, aeration of the blood is thus thoroughly secured, and in this locality the venous blood is converted into arterial. The calibre of these capillaries is extremely simall, being only in diameter equal to the thickness of a red blood-corpuscle. It has been estimated, nevertheless, that the pulmonary capillaries in man are capable of containing about two liters of blood, and it has been further calculated that this amount is renewed ten thousand times in twenty-four hours. And, even making allowances for error in these calculations, it is evident how large is the surface for the interchange of gases between the air and blood. The diameter of the air-vesicles is from one two-hundredth to one- seventicth of an inch. Their number is almost infinite. It has been calculated that about the termination of each bronchus in a mammal are collected seventeen thousand seven hundred and ninety air-cells, and their total number has been computed to be at least six hundred millions, It has been further calculated by Lieberkiihn that the whole extent of respiratory surface of both lungs in man is fourteen thousand square feet, or two hundred square meters, and this surface is attained through the reduplications of the membrane, so occupying the least possible bulk. The air-vesicles gradually increase in number from infancy to adult life, when they remain stationary for a time, after which they decline, so that there is less respiratory surface in infancy and old age than in adult life. The walls of the air-vesicles are highly elastic, from the presence of elastic fibres, which form a close net-work with very fine meshes. Through the presence of this elastic tissue the air-vesicles, therefore, tend contin- ually to contract,—a: phenomenon which, as will be later demonstrated, is of the greatest importance for the process of expiration. All the different parts of the lungs are held together by delicate elastic tissue, and outside of this by a serous membrane, termed the pleura, which covers the external surface of the lungs and is reflected on to the internal surface of the thorax. The pleural membrane thus forms a shut sac, and the lung lies on the outside of it. The thorax is composed of a closed cavity in the form of a truncated cone, of which the sides, back, and a portion of the interior surfaces are formed by the ribs and costal cartilages with their intervening muscles. Its base is oblong, more or less flattened laterally in quad- rupeds and antero-posteriorly in man. The ribs are always more or less curved, with their concavity directed internally. In general, the first rib is the shortest, is less curved, and less inclined to the vertebral column. As arule, it may be stated that in animals in whom the thorax is short the ribs are more curved than in those where the thorax is longer. 572 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The backbone forms a part of the posterior boundary of the chest, the sternum the anterior boundary. Below, the thorax is shut off from the abdominal cavity in mammals by the diaphragm ; above, it is closed by the muscles of the neck. ‘The lungs are suspended in a semi-distended state in the cavity of the thorax, and with the heart and great blood- vessels completely fill it. Since the thorax forms an air-tight cavity there is through the elasticity of the lungs a constant tendency to the production of a vacuum between the pleural surfaces. This tendency to contraction, due to the elastic fibres of the lungs, is of great importance in assisting respiration. If an opening be made into the pleural cavity the atmosphere at once enters,and the lungs then through their elasticity collapse. Atmospheric pressure being the same within and without the lungs, the resistance of the walls of the thorax is the only factor which prevents the collapse of the thorax from the elasticity of the lungs. This tendency to retraction of the thoracic walls is readily seen in the intercostal spaces, particularly if the outer muscular layers be removed. Distinct depressions may then be recognized between each rib, and indicate the negative pressure produced upon the walls of the thorax by the constant tendency to contraction of the lungs. This negative pressure is likewise exerted on the upper and lower extremities of the thorax. There is, therefore, a constant depression of the soft tissues of the neck toward the thoracic cavity, until the increased tension so produced results in equilibrium. So, also, there is a constant tendency to the ascent of the diaphragm in the thoracie cavity by the same means. In the passive state of the thorax there is, therefore, a constant equilibrium produced, which results from the balance between this negative pressure exerted by the lungs and the resistance of the walls of the thorax. The walls of the thorax, in so far as they are constituted by the ribs and diaphragm, are not, however, rigid, but are capable of undergoing change in position. The ribs are acted on by various muscles whose contraction results in an increase in the lateral and antero-posterior diameters of the thorax. The diaphragm is also capable of changing its position, but when it contracts tends to depart from its concave, dome-like position, and become more horizontal. The contraction of the diaphragm, therefore, . serves to increase the vertical diameter of the thorax, As the thorax is increased in its dimensions the lungs are compelled to follow its movements, from the fact that otherwise there would be a production of a vacuum in the pleural cavity. As, however, the lungs likewise become increased in volume, the air in them becomes rarefied, . and since the air within the lungs is in direct communication with the atmosphere the air streams in from without to the interior of the lungs, RESPIRATION. 573 until equilibrium is produced (Fig. 246). On the other hand, if the forces which produce enlargement of the thorax cease to act, the elasticity of the lungs, together with that of the cartilages of the ribs, is now sufficient to produce # return of the thorax to its original volume. The lungs, therefore, now decrease in volume, and as a consequence the air within them tends to become compressed, and, as a result, a portion of the air is expelled through the air-passages to the external atmosphere. The expansion of the thorax constitutes inspiration; the contraction of the thorax constitutes expiration. As the tension of air in the lungs becomes decreased through inspiration, fresh air enters the lungs which is less charged with the carbon dioxide than that previously present in the lungs, while it is also Fig. 246.—DIAGRAMMATIC REPRESENTATION OF TITE RELATIONS BETWEEN THE LUNGS AND THE THORACIC CAVITY, AFTER FUNKE. (Beaurtis.) The bell-jar, 1, represents the thorax; the rubber membrane, 4, the diaphragm ; the membrane, 6, the soft parts of an intercostal space; 2, the trachea, terminating in two rubber bulbs representing the lungs; 3, a manometer for measuring the pressure within the bell-jar. In the figure to the left the atmospheric pressure within the bell-jar is the same as on the outside, and the mercury in the manometer stands at the same level in both arms. If the rubber membrane, 4, is drawn downward hy the button, 5, the cavity of the bell-jar is increased and the atmospheric pressure diminished, as shown by the manometer and the depressed space, 6. The negative pressure thus produced leads to the entrance of air through the tube, 2, into the rubber bulbs, which consequently expand, The action of the diaphragm in producing inspiration is precisely similar. richer in oxygen. By diffusion, from the inequality of these gaseous tensions, we have oxygen brought to the lowermost strata of air in the lungs and carbon dioxide diffusing from them, and when the air again leaves the lungs in expiration it has been the means of introducing oxygen into the lungs and removing carbon dioxide from them. The amount of air which ordinarily enters the lungs in inspiration and is dispelled in expiration is spoken of as the tidal volume. By forcible muscular contractions the capacity of the thorax may be both increased and decreased beyond the dimensions present in gentle respi- ration. The amount of air so drawn in by a forced inspiration is spoken of as complemental air; that expelled from the lungs in violent expiration is spoken of as supplemental air; while, even after forced expiration, a 574 PHYSIOLOGY OF THE DOMESTIC ANIMALS. considerable amount of air remains in the lungs, and this quantity is spoken of as the residual volume. 2. THE MecuanicaL Processes or REsprration.— The Mechanism of Inspiration.—Kvery increase in the diameters of the thorax produces, as a consequence, for the reasons already referred to, an expansion of the lungs; hence, air enters the lungs from the difference in atmospheric pressures. Such a movement is termed an inspiration. It is clear that in the production of inspiration the natural elasticity of the lungs and the thoracic walls must be overcome. Inspiration is, therefore, an active movement and requires the exertion of muscular force. The diameters of the thorax may be increased either through the elevation of the ribs or through the descent of the diaphragm. It is through the latter that in quiet respiration inspiration is produced. The diaphragm may, there- fore, be regarded as the principal muscle of inspiration. In its condition of relax- ation the muscular fibres of the diaphragm together form a curved surface whose con- cavity extends far up into the thorax. When the muscular fibres of the diaphragm shorten they tend to form a straight line between their origins and insertions, and, therefore, the diaphragm in its condition of extreme contraction tends to form an almost plane surface across the lower Fig, Mi -DIAGRAMMATIC REPRE portion of the thorax. The origins and SENTATION OF THE ACTION OF THE Diapunaam. (Béclard.) insertions of the muscular fibres of the If A represent a plane extending in expi- Bike pain sete dupiege: inigarewion 1@PHagm may be regarded as compare the plane A will move toa, whilethediaphragm tively fixed. The central tendon is, moreover, but slightly movable, since it is firmly connected with the organs occupying the mediastinum above, and below is more or less supported by the liver and stomach. It is, there fore, evident that the diaphragm in inspiration cannot become completely flattened, since its curvature corresponds with that of the curvature of the abdominal organs. When the diaphragm, then, contracts, the curve is slightly flattened out, and this muscle may, therefore, be regarded as acting as a curved piston which descends in the cavity of the thorax, and so increases its long diameter; at the moment in which the diaphragm contracts, the ribs in which it is inserted anteriorly are actively elevated. Thus, while the diaphragm in descending tends to lengthen the vertical diameter of the chest, the elevation of the inferior ribs would appear to diminish this diameter. The ascent of the lower ribs is, nevertheless, much less extensive than the descent of the diaphragm. It is further to be noticed that every RESPIRATION. 575 ascent of the ribs produces an increase in the antero-posterior diameter of the thorax; or, in other words, increases the distance between the sternum and vertebral column. Therefore, this ascent of the ribs, so far from diminishing the inspiratory effect of the diaphragm, tends even to increase it. This may be rendered clear by the diagram (Fig. 247), At the same time the diaphragm contracts the abdominal organs are pressed downward, and so cause a projection of the abdominal walls. In forced inspiration the power exerted on the ribs through the dia- phragm is greater than that which tends to elevate the lower ribs. This is especially the case when there is any obstruction to the entrance of air into the lungs. In such cases there is a distinct constriction of the thorax at the points of insertion of the fibres of the diaphragm. This reduction in the circumference of the chest at these points is, however, of but slight importance, since the increase of the thoracic cavity by the greater descent of the diaphragm more than compensates for the decrease in its circumference. It is probable that in all circumstances this de- pression of the lower ribs would be more marked in strong contraction of the diaphragm were it not for the fact that the descent of the ab- dominal organs produces an increased tension in the abdominal walls, and, therefore, offers a certain resistance to the production of this constriction. Colin has estimated that in the horse the diaphragm in inspiration descends from ten to twelve centimeters in the abdominal cavity, thus, to this extent, increasing the long diameter of the thorax, while the transverse diameter at the same time increases from three to four centi- meters. The movements of the ribs in producing inspiration are much more complicated. Each rib articulates by two facets with a costal cavity formed by the junction of the ribs and two contiguous dorsal vertebra. The only movement possible in the ribs, therefore, must occur around a line which passes between these two points of articulation ; or, in other words, nearly coincides with the axis of the neck of the rib. If the ribs , were straight they would be only able to turn around on their own axes ; since, however, the ribs are all curved in different degrees, the turning of the rib around the axis of its neck causes every point of the rib to describe an are of a circle (Fig. 248). Further, the point of articulation of each rib with the vertebral column is on a higher plane than its articulation with the sternum and costal cartilages, the degree of inclination being greatest in the first rib, least in the second, and then gradually increasing until the last rib forms almost the same angle as the first. From this arrangement it is evident that every elevation of the ribs will increase the distance between the sternum and the vertebral column, while the rotation of the ribs will 576 PHYSIOLOGY OF THE DOMESTIC ANIMALS. increase the lateral diameters of the thorax; for, since the ribs form arches, each increasing in its radius from above downward, it is evident that when the lower rib is so elevated as to occupy the position pre- viously held by an upper rib the lateral diameter of the thorax at that point will be greater than before. Still further, the articulations of the ribs with the sternum are more or less fixed, and the resistance, therefore, which these articulations offer to the movement of the ribs m Mm H n WN yf G Fra, 248.—THE ACTION OF THE RIBS:OF MAN IN INSPIRATION. (Béclard.) The shaded parts represent the positions of the ribs in repose. The line A B represents a horizontal plane passing through the sternal extremity of the seventh rib; the line C D represents a horizontal plane touching the superior extremity of the sternum ; the line H G indicates the linear direction of the sternum. When the ribs are elevated, as indicated by the dotted lines, the line A B becomes the plane a 4, the line C D the line cd, and the line 1I G becomes the line / g, the projection of the sternum being the more marked inferiorly. The distance which separates the line M N from the line m x measures the increase in the antero-posterior diameter of the thorax. 4 will in the elevation of the ribs tend to open out the angles between the ribs and their cartilages. By the elevation, consequently, of the ribs, the diameters of the thorax are increased both laterally and in an antero-posterior direction. Hence, everything that tends to elevate the ribs will produce an inspira tory movement; everything which depresses the ribs will produce an expiration. All muscles, therefore, which in any way may produce elevations of the ribs are inspiratory muscles, RESPIRATION. 577 \ The most important muscles of inspiration, which act by elevating the ribs, are the levatores costarum. These are small muscles which rise from the upper sides of the cervical and dorsal vertebre, and are inserted in the posterior surfaces of the ribs. Although these are small muscles, they are inserted near to the axis of rotation of the ribs, and, consequently, but a slight degree of contraction, the lever being so long, will produce considerable elevation of the anterior extremity of the ribs. At the anterior extremity of the upper two ribs are inserted the scalene muscles, which rise from the cervical vertebra, and which in their con- I 0 k f Fig, 49.-SCHEME OF ACTION OF THE INTERCOSTAL MUSCLES. (Landois.) I. When the rods a and 8, which represent the ribs, are raised the intercostal space must be widened (ef>cd). On the opposite side, when the rods are raised, the line g h is shortened (ik< qh, the diree- tion of the external intercostals); 2 m is lengthened (1 m ‘i , . O16 Ash, z ‘i j ‘ i ‘ x . O87 “ 1. Tue PuystcaL AND CHEMIcAL Properties or MILK.—Milk is an opaque fluid, with a sweetish taste and an opalescent bluish tint, in thin layers, and a characteristic odor due to the volatile substances derived from the secretions of the cutaneous glands. Milk is not a homogeneous fluid, but is aty emulsion, which consists of the so-called milk-globules suspended in milk-plasma, the latter con sisting of a solution of albumen, sugar, and salts, Examined under the microscope the milk-globules appear.as highly refractive drops of oil floating in the clear fluid (Figs. 258 and 259). The size of these globules varies from 0.01 to 0.03 millimeter. In colostrum the corpuscles are much larger than in milk, and are capable of ameeboid movements. The milk-corpuscles consist almost ' MAMMARY SECRETION. "| 611 entirely of fat, and are composed of combinations of glycerin with oleic, palmitic, and stearic acids. They are surrounded by a thin layer of casein, not in the form of a solid deposition, but the casein probably exists in a condition of high imbibition rather than in a state of solidity or of true solution. ‘The layer of casein cannot be regarded as consti- tuting a membrane, although it, to a certain -extent, fulfills the same function. If acetic acid is added to a preparation of milk, under the microscope it will be seen that the caseous envelope is dissolved and the oil-globules run together and form irregular masses of oil. When cows’ milk is shaken up with caustic potash and then agitated with ether the oil passes into solution in the ether. The previous subjection to the action of caustic potash is, however, essential, since ether will not dissolve the oil from cows’ milk unless the casein envelopes be previously dissolved by acetic acid or potash. ' ' Fic. 258.—MIcroscopic APPEARANCE OF MILK AND COLOSTRUM. (Landois.) The upper half of the figure represents milk; the lower half colostrum. If milk be allowed to stand for some time the oil-globules, which in freshly secreted milk are uniformly distributed through the milk, now rise to the surface and form a layer largely Se ae of fat, or the so-called cream, The reaction of freshly secreted milk is alee in the herbivora and in the human female, while that of the carnivora is acid. The milk of herbivora frequently will exhibit both an alkaline and an acid reaction, due to the presence of an acid sodium phosphate (H,NAPO,) and of an alkaline disodic phosphate as: Such a reaction is spoken of as amphioter. When milk is allowed to stand, the alkaline reaction, when present, gives place to an acid reaction, which is due to the fermentation of the milk-sugar and its conversion into lactic acid. When the cream is 612 PHYSIOLOGY OF THE DOMESTIC ANIMALS. removed from milk the skimmed milk is less opaque and white, while the edges in contact with the vessel have a distinct bluish tint. : The specific gravity of milk varies from 1018 to 1040. Cows’ milk, when pure, may vary between sp. gr. 1028 and 1034, usually increasing from the first to the eighth month of lactation from 1031 to 1039, In composition milk consists of solids partly dissolved and partly suspended in a fluid plasma, the amount varying from 12 to 13 per cent. Of these solids, 3 to 6 per cent. is represented by the fats, 9.25 per cent, by the other solids. In composition, milk is composed of 85 to 90 per cent. water, casein, albumen, fat, milk-sugar, lecithin, and salts, with carbon dioxide, Fia. 239.—MICROSCOPIC APPEARANCES OF MILK, I; CREAM, II; BuTreER, III; Couos- TRUM OF MARE, IV; AND CoLosTRUM OF Cow, Vv. Thanhoffer.) oxygen and nitrogen gases, urea, and various accidental constituents, such as lactic acid after milk fermentation, hematin, bile coloring- matters,and mucin. It often serves to eliminate various substances such as drugs, among which may be mentioned potassium iodide, iodine, salts of various metals, the oil of garlic, and various other bodies. When filtered through animal membrane or porous-clay filters, the milk-plasma is obtained as a clear, slightly opalescent fluid, which contains casein, serum-albumen, peptone, milk-sugar, salts—in fact, all the constituents of milk, with the exception of the oil-globules and a considerable portion of the casein, the amount of the latter which is kept back being greatly increased when a fresh animal membrane is used as a filter. , é 4 dq a MAMMARY SECRETION. 613 The following tables represent various analyses of this secretion in different animals :— I, ComposiTion OF THE MILK oF DIFFERENT ANIMALS. (AFTER GoRUP- BesaNnEZ, LIEBERMANN, GAUTIER, ETC.) , Woman, CONSTITUENTS. Ass. Cow. Goat. | Sheep. | Mare. Colos- trum. Water, .. . ee 86.27 | 88.91 | 87.77 | 84.08 | 90.70 | 86.56 {86.76 /83.30 | 82.84 Solid: x o0 ogc 13.72 {11.09 | 12.23 | 15.92 | 19.30 | 13.44 }13.24 |16.69 | 17.16 Casein, : 3.50 | 2.92 ne . | 295 | 392 234] 3.23] 170/§ 528 | 737 i 5.73 | 1.64 Butter, . . . .| 5.37 | 2.67 | 3.68 | 5.78 | 1.55 4.03 | 4.48 6.05 6.87 Milk-sugar, . .| 5.13 | 4.36 | 5.55 | 6.51 | 5.80 4.60 | 3.91 3.96 i 8.65 Inorganic salts, | 0.22 | 0.14] 0.23 | 0.35 | 0.50 0.73 | 0.62 | 0.68 ah II. In 100 Parts. Cow. Goat. Sheep. Ass Mare. Sow. | Woman. Water, 85.7 86.4 84.0 91.0 82.8 82.4 88.8 mal : 14.3 13.6 16.0 9.0 17,2 17.6 11.2 asein, 48 353 Abueoks al a ; 53 20 | 16] 61 | 35 al 4.3 4.4 5.4 13 6.9 6.4 3.5 ugar, . 4.0 4.0 41 4.0 4.0 Salts, 06 | 0.7 O78 Buk |, Bef ; 11 | o2 Asses’ milk is nearest in composition to women’s milk; cows’ milk has one-half more fat and almost one-half more albuminoids. Ill. Tue Asu or Mix in 100 Parts. Cows’ MILE. Women’s MILK. (Wildenstein. ) 5 (Weber.) (Haidlen.) Sodium. 2. 2... DL, 4.21 6.38 8.27 Potassium,. . . . . 1 1. 31.59 24.71 15.42 Chlorin, . 2... Wl, 19.06 14.39 16.96 Calcium, fa Be PRS OBS eS fs OF 18.78 17.31 Magnesium, . . . 2... 0.87 1.90 56.52 Phosphoric acid,. . | 1 1. 19.00 29.13 Sulphuric acid, . 2 1) 2.64 1.15 ae Ferrie oxide,» 1 1 1] ] ) 0.10 0.33 0.62 BUN dena aie be trace 0.09 as 614 PHYSIOLOGY OF THE DOMESTIC ANIMALS. IV. THe Revative VALue or Dirrerent Kinps oF Miu. - Waters || itn |) eee. SPN eo Mares’ milk,. . . 2... 91.15 1.03 1.27 6.12 Asses’ 4 & & LA 89.01 3.57 1.85 5.57 Women’s milk, Hee oe? Sad ate 87.24 2.88 3.68 5.78 Goats’ AES 50 oe che Re ap, Sot 86.85 3.79 4.34 3.78 Cows’ BO chests. Googie» de ess 84.28 4.35 6.47 4.34 Sheep's “ ...... 83.30 5.73 6.05 3.96 V. Sonrps 1n a Pint oF MILE. Nitrogenous constituents, : 2 : 3 . 23.9 grammes. Fatty” : : . F - 22.7 Saccharine ‘ 4 F : . 380.3 ne Salts, F ; a A . P . . 40 He 2. Casein AND MiLK CoacuLation.—Casein is a proteid body of an acid reaction which is scarcely soluble in water but soluble in dilute acids and alkalies. In milk its solution is rendered possible by its combina- tion with soluble alkali albuminates and through the presence of calcium phosphate. In amount it varies from 3 to 5 per cent., the relative pro- portions of casein and albumen being from 1.87 per cent. to 4.68 per cent. of the former and from 0.60 per cent. to 1.77 per cent. of the latter. Casein, although closely similar in composition to alkali albumen, is not identical with it, but is probably to be regarded as a combination of alkali albuminate and nuclein. Casein may be obtained from milk by dilution with four times its volume of water, the addition of dilute acetic acid (0.1 per cent.) until a precipitate begins to appear, then passing a current of carbonic acid gas, alvening end washing the precipitate with water, alcohol, and ether. Casein may also be obtained from milk by the addition of magnesium sulphate to saturation. When freed by ether from fats after its preparation by the latter process and dissolved in water, casein is a snow-white powder and in solution rotates yellow light eighty degrees to the left; in dilute alkaline solution, seventy-six degrees to the left; in strong alkaline solution, ninety-one degrees to the left; and in dilute hydrochloric acid, eighty- seven degrees to the left. It leaves no ash on incineration. When milk is boiled the serum-albumen of milk becomes coagulated, while the skim formed is due to the deposition of a thin pellicle of casein due to evaporation, and which is renewed as fast as it is removed. The coagulation of milk depends upon the precipitation of casein. Everything, therefore, which causes casein to become insoluble causes coagulation of milk. Such agents are acids, rennet, tannin, alcohol, and mineral salts. MAMMARY SECRETION. 615 Milk is coagulated by all acids. Several, especially acetic acid in excess, again dissolve the precipitate of casein. Casein is precipitated by acids only when a certain degree of acidity is reached, since alkaline phosphates must be first neutralized; if the alkaline phosphates are removed, even carbon. dioxide is then capable of precipitating casein. The spontaneous coagulation of milk is produced by the development of lactic acid, which is formed from milk-sugar in the milk by the action of bacteria introduced from without or by the action of the lactic acid ferment which appears to be present in milk. In this process the neutral alkaline phosphate is converted into acid phosphate. The casein is sepa- rated from its combination with calcium phosphate and is precipitated, the sugar being decomposed into lactic acid and carbon dioxide. When milk coagulates spontaneously, or, in other words, curdles, it separates into a tough, jelly-like substance or curd, which consists of the insoluble casein and fat, floating in an opalescent acid fluid, or whey. The whey contains the greater part of the salts of the milk, the lactic acid, the undecomposed milk-sugar, and certain amounts of fat and the albumi- noids. That the spontaneous curdling of milk is due to the action of the ferment contained itself in milk (which decomposes the milk-sugar into lactic acid) is proved by the fact that boiling greatly retards the spon- taneous coagulation, evidently through the destruction of this ferment: This lactic acid ferment may be precipitated from milk by the addition of an excess of alcohol. If the ferment is then dissolved in water and added to solutions of milk-sugar it will produce rapid fermentation. The action of the milk-curdling ferment, as pointed out in the chapters on Digestion, is very different. Here, the casein is rendered insoluble by the action of the rennet ferment, even in alkaline fluids and without at all calling in the aid of lactic acid. The salts in milk, especially the calcic phosphate, are essential to the action of milk-curdling ferment; for, when milk is subjected to dialysis, rennet is then rendered incapable of producing coagulation. Spontaneous coagulation of milk may be prevented by the addition of sodie carbonate, boracic or salicylic acids. So, also, the addition of one drop of the ethereal oil of mustard to twenty cubic centimeters of milk will likewise preserve its fluid condition. Colostrum, sows’ milk, and the milk of carnivora coagulate when heated. Boiled milk coagulates spontaneously only with difliculty, and is also more difficult to coagulate with rennet, but when acidulated the casein coagulates even more readily than in fresh milk. A high temperature facilitates both-forms of coagulation. Milk Which has become acid, but which is still fluid, will coagulate when heated. In addition to casein, milk contains other albuminoids, one of which 616 PHYSIOLOGY OF THE DOMESTIC ANIMALS. in all of its characteristics closely resembles serum-albumen. It is present in about 0.5 per cent., though in colostrum it is in much larger percentage. It is there present in about 15 per cent., but: rapidly de. creases for about four weeks, when it reaches its RE eerelaes of 0.5 per cent. When the plasma of milk is slightly acidulated and boiled it coagu- lates between 70° and 80° C. Peptone is also present in small amounts as a transudation from the blood. 3. Mirx-Sucar.—Milk-sugar is an animal carbohydrate found ie in milk; its average percentage is 4.5 per cent., varying from 3 to 7 per cent. or all the constituents of the milk the uillesagan is least influ- enced by external conditions. It is found dissolved in milk-serum and in whey, whether after the spontaneous coagulation of the milk (acid whey) or after the action of rennet (sweet whey). It may be obtained by coag- ulating milk and evaporating the whey until crystals form. It occurs with one molecule of water in rhombic prisms soluble in from five to six parts of cold water and in three parts of boiling water. It is, therefore, very insoluble in comparison with the other forms of sugar. It is only slightly soluble in alcohol and water, and is not readily crystallizable. Its formula may be placed at C,H,,0, Heated up to 100° C. it loses some of its water, and may thus be represented by the formula CyH2On- The specific rotation of milk-sugar containing -water of crystalliza- tion is + 52.53° at 20° C.; anhydrous milk-sugar = + 81.3°. When warmed with alkalies it becomes brown, like dextrose (Moore’s test), and likewise reduces Fehling’s solution. The milk-sugar of the human female, the cow, and the goat agree in their chemical characteristics, their form of oe ease and their action on polarized light. . The spontaneous coagulation of milk is due. to the feemation of lactic acid from milk-sugar, one molecule of milk-sugar forming four molecules of lactic acid. The formula may be represented as follows :— C,3H22031 + H,0 =4(C,H,O3). When lactic acid forms, it unites with the alkaline phosphates to form lactates of the alkalies and acid salts, and coagulation only occurs when all the alkaline phosphates have been converted into acid salts. A slight further development of lactic acid is then sufficient to cause coag- ulation. If two glasses, one containing milk and the other a pure solution of milk-sugar, are subjected to the same conditions, after a few-days the former will contain so much lactic acid that the milk will be coagulated, while not the slightest trace of acidity will be found in the milk-suga’ MAMMARY SECRETION. 617 solution. This proves that the milk contains a ferment which is capable of splitting up milk-sugar into lactic acid. Such a ferment is widely distributed in the animal body. It may be often extracted from the gastric mucous membrane, und is entirely distinct from pepsin or the milk-curdling ferment, since it preserves its action even after the other ferments are destroyed by dilute caustic soda. The ferment may be obtained from milk after dialysis by precipitation with alcohol, and, after drying, dissolving the precipitate in water. Such a precipitate will coagulate milk and will cause the development of lactic acid in solu- | tions of milk-sugar. This ferment has a neutral reaction and is soluble in glycerin. It is destroyed by boiling, and appears to regain its activity when treated with oxygen. This would indicate that it isa ferment generator and not a true ferment, and explains why boiled milk may be kept longer than unboiled ; while the fact that even boiled milk will ultimately coag- ulate is to be attributed to the subsequent development of the ferment through the action of the air. Increase of temperature increases the activity of the ferment. Milk- sugar is not directly fermentable; that is, it cannot be directly converted into aleohol, though by the action of dilute sulphuric or hydrochloric acids it may be partly transformed into a fermentable lactic acid. This process is concerned in the manufacture of koumiss from mares’ milk, which contains a large amount of sugar. A similar fermented liquid may be obtained from cows’ milk through the action of the yeast-plant. 4, Far and Cream.—Fat is present in milk in the form of minute globules, the average percentage being 3 to 34 per cent.,-although it may vary from 24 to 54 per cent. The following fatty acids have been found in milk: Butyric, caproic, caprylic, caprinic, myristic, palmitic, stearic, and oleic. The percentages of palmitic, oleic,and stearic acids vary. So the melting point of butter also varies,as does, also, its specific gravity. Normally, the melting point varies from 32° to 37.5° ©. ' Cows’ butter contains about 68 per cent. palmitin, 30 per cent. olein, and 2 per cent. other fats, the solid fats apparently being more abundant in winter than in summer. The butter may be separated from milk by mechanical agitation (churning), the enveloping layers of casein being thus ruptured. It was formerly supposed that the fatty globule of milk had a solid envelope, because the fat does not pass into solution in ether unless caustic potash had been previously added. At most, however, we may assume that the fat is surrounded by an envelope of fluid casein, rendered more consistent here than elsewhere by the mo- lecular attraction exerted by the fat-globules. Casein is not present in the milk in the form of a true solution, but rather in a high degree of 618 PHYSIOLOGY OF THE DOMESTIC ANIMALS. imbibition; so the effect of caustic potash is to enable the casein to pass into solution, and so render the oil accessible to ether. The absence of any solid envelope of the oil-globule is proved by the absence of any such formation after mechanically breaking up the oil-globules, while the proof of the fact of non-solution of casein in the milk is found in the fact that when milk is filtered through porous earthenware scarcely any casein passes through, while the other albuminoids which are really in solution do so pass. Casein, therefore, in milk acts like the gum around the oil-globules in an artificial mucilage emulsion. , On account of the lighter specific gravity, when milk stands the oil- globules rise to the top and, accompanied by varying amounts of the other constituents of the milk, constitute the cream; the largest rise first, while the smaller ones remain suspended in the body of the milk, The ascent of the cream is the more rapid the smaller the distance the fat-globules have to traverse. Hence, cream is formed more rapidly in broad, shallow vessels than in tall, narrow ones. Unless the temperature of the milk is constant, currents are set up in the milk from the differ- ences of temperature, and the formation of cream is delayed until the entire volume of milk and the external medium are of the same tempera- ture. Hence, shallow metal pans, by leading toa rapid equalization of temperatures, are usually employed for the separation of the cream. As the milk has a greater volume when warm than when cold, the cream will contain less serum when the molecules of the fluid are further separated from each other. So cream formed from warm milk has a higher per- centage of fat in a small volume than cream formed from cold milk, and the higher the temperature at which the formation of cream takes place the smaller the amount of fat left in the skimmed milk. If the cream has been removed from milk by means of the centri- fugal machine the separation is much more complete (often only 0.1 per cent. of fat remaining in the milk), while the milk remains sweet instead of becoming sour, as ordinarily occurs in the usual method of separating the cream. Skimmed milk so obtained is, therefore, a more valuable food, since it still contains all the sugar and is less apt to pro- duce disturbances of digestion. The addition of a small amount of water facilitates, the addition of salt interferes with, the separation of the cream. The following table represents the composition of cream :— Water, . : ‘ 2 ; . F . : . 61.67 Fat, , 3 ‘ & A F 7 . . . 33.48 Casein, . : ‘ é : , é . ‘ . 2.62 Sugar, . ri . . ‘ : : : 3 . 156 Salts, ‘i : . : 3 - A : F . 0.72 By the process of churning, which is only effective after the milk has become slightly acid, only about two thirds of the fat are removed; MAMMARY SECRETION. 619 the other third remains in suspension in the buttermilk. Churning is best accomplished at about 14° C., with thirty to forty strokes of the churn per minute. The average composition of buttermilk may be placed as follows: Fat, 0.50 to 0.75 per cent. ; casein, 3.60 per cent. ; albumen, 3.7 per cent. ; sugar, 0.52 per cent.; ash, 0.52 per cent. ; water, 91.7 per cent. The amount of cream which may be obtained from milk varies very considerably in different animals and under different conditions, and will be subsequently referred to. Usually about 80 per cent. of the entire amount of fat contained in the milk passes into the cream, and if the average percentage of fat in milk be placed at 3.5 per cent., the fat in cream would amount to 2.7 per cent. When butter becomes rancid the volatile fatty acids are set free and acrolein and formic acid are formed from the glycerin. - Skimmed milk has a higher specific gravity than unskimmed milk, from the fact that the lighter constituents, that is, the oils, have been largely removed. The specific gravity of skimmed milk may rise to 1037, or even higher. Its composition may be placed as follows :— Water, . , ‘ ‘ : i : ‘ ‘ . 89.65 Fat, : . r 3 ‘ 5 ‘ ‘ : . 0.79 Casein, . F ‘ : : ‘ , - ' . 8.01 Sugar, . ‘i ‘ a é . . : : . 5.72 Salts, : F Z ‘ : ‘ a : - . 0.83 5. Tue InorGanic Constituents oF Mitx.—In addition to the albu- minoids, fats, and carbohydrates contained in milk, the mineral constitu- ents necessary for the support of the animal body are also present, their average amount being about as follows :— Phosphoric acid, . | . . ‘ . ‘i . . 28.31 Chlorine, ‘ eon ‘ F 3 ‘ P . 16.84 Calcium oxide, : : : A ¥ F ‘ . 27.00 Potassium, . F 2 ‘: ‘ ‘ ‘ F . 17.384 Sodium, . .. és - F F i , : . 10.00 Magnesium, . ej . é ‘ 5 ‘: . 4.07 Ferric oxide, . i : , 3 . : ‘ . 0.62 Oxygen, nitrogen, and carbon dioxide are also present; and since these gases may be entirely removed by pumping, they are, therefore, in a condition of solution in the milk. . Nitrogen is present in 0.7 volumes per cent.; oxygen, 0.1 per cent. ; carbon dioxide, 7.7 per cent. 6. VARIATIONS IN THE QUANTITY AND Composition or Minxk.—'The variations which occur in the quantity and composition of milk are largely dependent on the quantity and composition of the food; in- suffictent food leads to a reduction in both the absolute quantity and solid constituents of the milk. In addition to these conditions, to be 620 PHYSIOLOGY OF THE DOMESTIC ANIMALS. studied in detail directly, the amount and character of the milk depends largely upon the period of pregnancy and suckling, as there is a close sympathy between the secretion of the mammary glands and the genital organs. The period of activity of the mammary gland is inaugurated shortly before the first birth, and shortly thereafter yields the largest amount of secretion, which in the best Dutch cattle may be as large as 30-35 liters each day. This maximum persists for several weeks, and then commences gradually to decline, there being a continual and gradual relative increase in the albuminoids and a decrease in the fats and sugar, and at the end of the tenth month only one-quarter or one-sixth as much milk is secreted as at first. During the first ten months of lactation in the best cows more than 6000 liters may be secreted ; fairly good cows will form 3000 liters, and poor cows not more than 1000 liters of milk in the same time Quite frequently good cows will yield as much milk, nearly, after ten months as in the first week after birth. Colostrum is far richer in solids than the later secretions of milk. Solids, Water. . Immediately after calving, . ; : . 88.4 61.6 1st day after calving, “ 3 3 F . 801° 69.9 2d“ . 6 n'a ‘ » 23.1 76.9 Bd ss : : ‘ : . 15.8 84.7 4th.“ sf : : . - . 149 85.1 Sth“ “ ‘ é ‘ ; . . 13.7 86.3 6th as . : : ‘ . 12.9 87.1 W4th « « se . ; : < . 12.6 87.4 28th “« « a . : : . . 12.4 87.6 The solids contain the following constituents :— Fat. Sugar. Albuminoids. Immediately after calving, 8.4 0.0 15.5 1st day after calving, . 5.9 0.2 13.7 Qa tee s 6.2 0.9 10.9 Bd ie 4.0 2.5 8.6 4th “ « a 4.5 3.6 5.1 Sth “ « ee 3.7 3.9 3.4 6th “ « a 3.0 4.3 2.0 4th “ « ae 2.5 4.3 1.6 28th “« « ns 2.6 4.4 0.7 Colostrum contains 3.3 per cent. salts, and it therefore follows that the percentage of casein must be 11.2 per cent. The quantity of milk depends upon the breed of cow. Some races are good milkers, while others are better as meat producers and beasts of burden. Nevertheless, the quantity of milk is directly proportionate to the degree of development of the mammary gland. Even in two cows of the same breed, and on precisely the same food, the amount of milk secretion will depend upon the degree of development of the glandular tissue. MAMMARY SECRETION. . 621 The following table gives the average milk given by different breeds of Irish and English cattle (Schmidt-Mtilheim):— English Cattle. Breed. of uration | ‘Total Milk. 1. Shorthorns (Wiltshire), . r . 270 days. 2160 quarts. 2. ee a ‘ i . 240 2520 3. i F : . BR 3060 4. Cross-bred (Cheshire), . ‘ . 240 “ 2880 <« 5. Yorkshire, . 270 « 3465 6. Half-bred and Shorthorns (Cheshire), 240 “ 2640 « 7. North-bred and South Devon, Jer- seys and Shorthorns (Devon), . 820 38840“ 8. Yorkshire (Hunts), . . 240 1440 « 9. Half-bred Yorkshire (Hunts), : . 180 « 2520 10. Hereford, . . - 240 . 1920 « 11. Yorkshire (Surrey), . . .. 870 BRD 12. Shorthorns (Yorkshire), . : - 285 * 2142 Average, . : ‘i : : ; 250 “ 2652“ Trish Cattle. Breed. oe ee. Total Nite, 1. Cross-bred, Durham, and Ayrshire (Kerry), . 5 . : . 285 days. 1995 quarts. 2. Cross-bred, Irish, and Shorthorns (Limerick), 7 » 270 ** 24380 = 3. Half-bred, Shorthorns (Cork), . : - 270 ** 2700 «* 4. Cross-bred (Cork), . : . 270 “« 2970 <« Average, . ‘ é : a . 274 = « 2524 As the milk-glands in the cow weigh only about five kilos, with 24 per cent., or 1.2 kilos, solids, it is evident that each gland produces two and ahalf times its own weight in solids. Goats give one-half to one liter of milk daily. Women produce one to one and one-third liters of milk daily. The milk of different breeds of cattle varies not only in quantity, but also in quality. Asa rule, the milk of the Dutch cattle contains the largest percentage of fat and albumen; then come the Swiss and Tyro- lean cows and Normandy cows with greatest percentage of solids. The composition of milk also varies according to the stage of lacta- tion, casein and fat increasing in women up to the second month, while sugar decreases even in the first month. In five to seven months fat decreases. Casein decreases after the ninth to tenth month. Salts increase in first five months and then decrease. In goats casein first sinks, then remains constant, and then increases. Fat gradually decreases. “So, in dogs, albuminous diet increases the fat in milk. This influ- ence is less marked in cows. Fat in food appears to decrease the fat in 622 PHYSIOLOGY OF THE DOMESTIC ANIMALS. milk if there is an insufficient amount of albumen given at the same time. a Carbohydrates in food of carnivora appear to be without influence on amount of milk-sugar. Also,in herbivora, milk-sugar depends for its origin principally on the albumen of the food. The mode of living is of the greatest influence on the milk secretion, When a large quantity of milk is desired, the animals must remain per- fectly at rest, as every excitement or movement, even of the animals’ body muscles, decreases the milk secretion. When the animals are per- fectly motionless the greater part of the blood-stream passes through the glands, and vice versé. Soa much smaller quantity of milk is pro- duced by grazing than by stall-fed animals, and it has been found that even leading cows out to drink decreases the amount of milk. The feeding has also a certain influence on the composition. of the milk; to produce a large quantity of good milk, the animal, naturally, must receive enough food to maintain a good condition. If a poor food is given the milk will not be very seriously influenced, nor will a rich food increase the quantity of milk to any great extent. The milk secre- tion is far more closely dependent on the breed of cattle than on the feeding ; a certain maximum which is peculiar to each individual cannot by any artificial means be increased. Water, of all foods, seems to have the greatest influence on the composition of milk. When large quantities of water have been drunk, the milk contains a higher percentage of water. The amount of albuminoid constituents of the food exerts great influence on both the composition and quantity of the milk. An increase in the pro- teids in the food increases the total quantity and solids of the milk, the fats being relatively more increased than the albuminoids. As an illustration of these facts, Weiske has found that a goat which ona diet of one thousand five hundred grammes potatoes and three hundred and seventy-five grammes chopped straw secreted seven hundred and thirty-nine grammes milk, secreted one thousand and fifty-four grammes milk when two hundred and fifty grammes of meat residue was added to the ration, the fat in the milk increasing from 2.71 per cent. to 3.14 per cent. In carnivora, also, a rich proteid diet leads to the production of a copious secretion, which may be almost completely arrested by confinement to a carbohydrate diet. In the human female, a rich albuminous diet leads not only to an increase in the amount of milk, but also of its solid constituents, as is seen in the following table :-— ; . Sugar and Water. Solids. Fats. Casein. pyttactives. . On scanty diet, . : . 914.0 86.0 8.0 85.5 39.5 One week later, after abun- dant meat diet, . . 880.6 119.4 84.0 87.5 45.4 MAMMARY SECRETION. , 623 In herbivora, carnivora, and omnivora, therefore, the same general rule holds, that an increase in the albuminous constituents of the food increases both the total amount of milk and its percentage in fats. In cows, however, it is to be noted that the relative percentages of casein and fat are not dependent so much on the amount of albumen of the food as on the breed and individual characteristics. The influence of the fatty constituents of the food on the composition of the milk is less marked. It will be shown, under the subject of Nutrition, that the addition of fat to the food serves to reduce the waste of tissue-albumen, and therefore permits the deposition of nitrogenous tissue-constituents. To this extent, by yielding a greater supply of albuminous bodies to the glandular, epithelium, a fatty diet may help the milk secretion, but not, as will be shown directly, by an immediate transfer of the fat of the food to the milk. In fact, the addition of fat to the food even seems to reduce the amount of butter in the milk if the amounts of albuminoids in the food are not amply sufficient for the nutritive needs of the economy. When, however, the albuminoids and other constituents of the food are ample for preserving nutritive equilibrium, the further addition of fat will increase the percentage of butter in the milk. The milk secreted at different hours of the day shows certain con- stant, though small, variations in composition. Morning milk has the largest percentage of water; midday milk the smallest. In 100 Parts. Morning. Noon. Evening. Water, F ‘ é . ‘ 88.46 88.16 88.30 Solids, ; 2 i ; 11.54 11.84 11.70 Butter, . 5 Z 3 ‘ 2.69 2.94 2.82 Milk-sugar, ‘ ‘ . ; 4.87 4.90 4.87 Casein, é . ‘ . 3.15 3.27 3.21 Salts, 2 ‘| . : F 0.828 0.725 0.802 So, also, the first- and last-drawn portions of milk have different com- positions. The last portions have more solids, and especially more fat, than the earlier portions. A difference of four hours in time of milking makes this most apparent. It has been attempted to attribute this differ- ence to the rising of the cream in the udder of the cow, just as occurs in milk standing in a vessel outside the body. The same differences may, however, be made out in human milk, where this mechanical explanation can have but little force. It must not be forgotten that in milking not only ready-formed milk is withdrawn, but during the act new milk is secreted, and it is quite warrantable to suppose the cell processes which result in the production of the solids of the milk are less active in the pauses than during the act of milking or suckling, when the process is stimulated from the irritation of the nipples. y 624 PHYSIOLOGY OF THE DOMESTIC’ ANIMALS. QUANTITATIVE COMPOSITION OF MILK. x 2 ; 3 a 3 d g/42/8i4| 2 | ge) g gi i In 1000 Parts, a 3 S o I g ae a Z £ FI : 3 2 3 Es Ca EI a @ «| 3 ra a > a A a |e] 4 A a a Water, . . . . | 851.98 | 817.40 | 849.90 | 853.15 | 871.80 | 837.48 | 803.20 | 845.62 | 839.72 | 857.70 | 841.80 Solids, . . . . | 148.02 | 182.60 | 150.10 | 146.85 | 128.20 | 162.52 | 196.80 | 154.38 | 160.28 | 142.30 | 158.20 Casein, . . . | 22.56) 41.98 | 87.64] 22.63 | 42.18 | 46.50] 45,62) 32.46 | 34.87) 31.50) 28.52 Albumen, . ./| 3.08] 7.60} 8.00} 882] 5.15] 7.24] 7.90] 1114] °7.382/ 9.10] 10.20 Butter, . . . | 70.88) 79.60| 51.40) 62.80] 32.40) 57.04] 98.80] 64.10 | 68.46 | 62.20] 63.40 Sugar, . . .| 45.90] 48.42] 46.26) 46.20] 42.12) 45.54] 37.26] 39.70} 43.50] 32.92] 49.68 Salts,. . . . 5.60| 5.00} 6.80) 640] 6.00] 620] 7.22) 6.82] 6.14] 678] 6.40 7. Tue Secretion or Mitx.—The mammary glands belong to the type of compound acinous glands, and are constructed on a similar plan to the salivary glands. The alveoli are lateral expansions at the termi- nations of the excretory ducts and are formed of a closed membrane covered, as is also the case with the ducts, with a single layer of cells, whose appearances vary according to the stage of activity of the glands. The secretory cells are composed of polyhedral cellular structures containing a round nucleus and usually a varying number of oily globules. During the stage of greatest activity the secretory cells increase in size, the nucleus often is apparently reduplicated, and the number of oil-globules greatly increased. In active secretion, during .which the oil-globules and cell-contents appear to be extruded, the remaining cells are much smaller and only contain a single nucleus. The excretory ducts, which are short, are likewise supplied with flat epithelial cells and terminate in a canal which in each part of the gland becomes enlarged, especially at the base of the nipple, where it becomes dilated to form the so-called milk-cistern, which is connected at the exterior by several canals which open at the end of the nipple (Fig. 260). This cistern is lined with a mucous membrane composed of cylindrical epi- thelial cells (Fig. 261). In the canals and in the nipple the epithelial coat becomes converted into pavement epithelium. The excretory canals are abundantly supplied with unstriped muscular fibres, which at the opening into the nipple become developed into strong circular layers. It is evident from the composition of milk that its most important constituents must result from a special cell activity, since neither casein nor milk-sugar are found in the blood, and, although fat is a constant constituent of the blood, the amount in comparison with that found in the milk is almost infinitesimal. It follows, therefore, that: the milk, like the other secretions, cannot be regarded as a transudation, but is a result of the protoplasmic activity of the epithelial cells of the mammary glands. But, further, good cows may yield as much as twenty-five kilos of milk daily, containing as much as 2.5 kilos of albuminoids, fats, and sugar. MAMMARY SECRETION, 625 The weight of the milk-gland is not more than 4.8 kilos, with 24.2 per cent. solids, including al! the glandular tissue (vessels, capsule, connective tissue, etc.), or 1.16 kilos solids. Consequently, the gland must renew itself 2.09 times daily to furnish this amount of organic matter if derived Fig. 260.-SECTION OF THE UDDER AND NIPPLE OF THE Cow. ( Thanhoffer.) MILAM) ele rede Gane Peete Te ae ney ee ei solely from the secreting cells. This would, however, require an incred- ibly rapid cell growth, and we are compelled to assume that although the growth and disappearance of the secreting cells is of the greatest im- portance in furnishing the organic constituents of the milk, these sub- stances are not derived solely from the breaking down of the cells, but 40 626 PHYSIOLOGY OF THE DOMESTIC ANIMALS. that in their functional activity they, to a certain extent, simply modify certain substances already existing in the blood and lymph. As regards the production of the fat of milk, oil-globules may be seen to collect in the epithelial cells and escape into the excretory ducts, either by a breaking up of the epithelial cells or by a process of contrac. tion similar to that observed in the ameba in the process of ejecting the residue from digestion. The origin of the fat is, without doubt, in a process of fatty degeneration of the protoplasmic cell-contents, for the cw, OR CW OR HI Fig, 261.—DIAGRAM OF THE FORMATION OF THE NIPPLE, AFTER KLAATSH, (Elienber ger.) I, cat; TI, mare; III, woman; IV, eow. DR, milk-cistern; CW, cutaneous surface. amount of fat contained in milk, so far from being increased, is actually diminished by an increase of fat in the food; while, further, the fats in milk do not necessarily coincide in nature with the fats of the food. On the other hand, an increase in proteid diet increases the amount of fat in the milk. In microscopic examination of the epithelial cells of the mammary glands, oil-globules may be actually seen to increase in size and number until often the protoplasmic contents become almost entirely MAMMARY SECRETION. 627 replaced by oil-globules, which entirely agree in their characteristics with the oil-globules found in milk. So, also, in feeding animals on highly albuminous diet they may even be seen to increase in weight, while at the same time more fat is removed in the milk than could be taken in the food, while the increase in weight indicates that the origin of fat is not from the adipose tissue of the body. On the other hand, it is impossible that in the herbivora the fat of the milk should be derived from the break- ing up of albuminoids in the gland, for the total amount of albuminoids breaking up in the body is insufficient to furnish the fat removed in the mammary secretion. Part must, therefore, be derived from the blood. As regards the casein, this substance is, without doubt, developed at the expense of the albuminous cell-contents, since it is absent from the blood, the alkali albuminate being directly derived from the breaking down of the protoplasm, while the nuclein, which is to be regarded as a constant component part of the casein, is, without doubt, derived from the nucleus which disappears in the process of secretion. This con- version of the albuminous contents into casein is still further evidenced by the fact that the proportion of casein in the milk depends upon the degree of perfection of cell activity. Thus, in the earlier stages of lactation, in the formation of colostrum, the amount of albuminoid matter contained in the milk is greatly in excess of the amount contained in milk after lactation has become thoroughly established, while coinci-, dently with the decrease in albumen there is a proportionate increase in the percentage of casein. A ferment has even been extracted from the mammary gland which possesses the power of converting albumen into casein. The origin of milk-sugar is less clearly established, although it also seems, without doubt, to originate in changes occurring in the proto- plasmic contents of the epithelial cells of the mammary gland. For the amount of sugar in the milk is entirely independent of the amount of carbohydrate constituents of the food, and remains unchanged even when animals are fed on a purely meat diet. It would, therefore, appear that the milk-sugar, casein, and fats are all formed by the direct activity of the epithelial cells as a result of the decomposition of their proto- plasmic contents or their action on the food-constituents in the blood. The other constituents of the milk, the water and salts, evidently result from a direct process of transudation from the blood, with the exception that, without doubt, a certain percentage of the potassium salts and phosphates, like the specific milk-constituents, originate in the metamorphosis of the protoplasm of the secretory cells. The process of secretion of milk may, therefore, be regarded as a process of molting of the epithelial cells, which undergo decomposition and discharge the resulting products into the excretory ducts. 628 PHYSIOLOGY OF THE DOMESTIC ANIMALS. According to the results of Heidenhain, the histological appearance of the cells of the mammary glands differs according as they are examined at the commencement or termination of secretion or while the secretion is at its height. In the first stage of secretion the cells are flattened and lie against the walls of the alveoli, of which they may be regarded as forming a protoplasmic boundary. Their nuclei are at this period spindle-formed, lying close to the contours of the cells, scarcely detectable on examina- (Heidenhain.) a, b, section through the centre of two alveoli of the mammary gland of the dog, the epithelial cells seen in profile; c, surface view of the epithelial cells. tion in transverse section. Seen from above, however, the epithelial cells are found to be polygonal, and each containing a round nucleus. In the terminal period of secretion the cells may be found to have greatly increased in size, possess one to three nuclei, and contain in the portions directed toward the alveoli large numbers of fat-globules. Often the cells may be seen to undergo subdivision, a part falling free into the alveolus (Figs. 262, 263, and 264). Between these two extreme periods . ; Fi@. 264.—MAMMARY GLAND OF Fia. 268.—MAMMARY GLAND OF THE DoG IN SECOND THE Do@ IN MIDDLE STAGE _ STAGE OF SECRETION. (Heidenhain.) OF SECRETION, (Heidenhain.) yarious intermediary stages may be recognized. From these histological changes Heidenhain concludes that in the formation of colostrum the epithelial cells are not dissolved, and that, therefore, the colostrum corpuscles are not fatty, degenerated epithelial cells, but that only the free end of the epithelial cells with their contained oil-globules is liber- ated; that the broken-down protoplasm becomes dissolved in the milk, and the fat-globules are thus set free. MAMMARY SECRETION. 629 As regards the influence on the mammary secretion of the nervous system, while certain data have been clearly established (thus, the influence of the emotions on the mammary secretion is well known), the process is by no means so thoroughly understood as is the case as regards the salivary secretion. It is well known that the maintenance of the milk secretion is closely dependent upon periodic emptying, whether by suckling or milking, of the milk-gland, and the question arises, What connection is there between this emptying of the gland and the act of secretion? Does the reduced internal pressure which follows emptying the gland start the secretion anew, or does the act of suckling or milking stimulate the secretion reflexly? It is clear that when the milk-ducts and cistern are filled with fluid the activity of secretion must be reduced, and when the gland is emptied by milking it again fills itself, at first rapidly, and then more and more slowly ; but that this augmented secretion is not due solely to decreased internal pressure is evident from the following facts: The cavities of the milk-gland of the cow are capable of containing about three thousand cubic centimeters of fluid,—a quantity very much less than may be withdrawn from the milk-gland in a single milking, so that evidently during milking renewed secretion is excited even before the gland is emptied, and, as is well known, frequent milking increases the total milk secreted. It would, therefore, appear that this renewed secretion is produced reflexly from stimulation of the nipple in a manner to be described directly. The first stimulus to the activity of the mammary glands is found usually coincident with the birth of young, although the gland even for several days before birth is the seat of a more or less active secretion. In this way the connection between the generative organs and the mammary glands is clearly indicated. The influence of the nervous system on the secretion of milk has been especially studied by Rohrig. The mammary gland is innervated in quadrupeds (in addition to the ileo-inguinal nerve distributed.to the skin) by the external spermatic nerve. This nerve originates from the lumbar portion of the spinal cord and passes out between the greater and lesser psoas muscles, dividing in the pelvis into three branches, of which one is distributed to the abdominal muscles, while the other two leave the abdominal cavity through the femoral ring accompanying the crural artery, and then, following the course of the external pudic artery, are distributed to the mammary gland. These nerves may be spoken of as the middle and inferior branches of the external spermatic nerve. The middle branch divides at the base of the gland into three twigs: first, a small filament which follows the course of the pudic artery and is lost in its walls; 630 PHYSIOLOGY OF THE DOMESTIC ANIMALS. second, a much larger branch, termed the papillary branch, which is distributed to the nipple; third, one, or occasionally two, glandular branches, which are supplied to the walls of the milk-ducts and the cistern. According to Rohrig, section of the papillary branch produces no change in the milk secretion, but simply causes relaxation of the nipple. Irritation of the peripheral end of this nerve causes erection of the nipple without change of glandular secretion, while irritation of the cen- tral end of this nerve produces considerable increase in the secretion. Section of the glandular branch, on the other hand, produces slow- ing of the amount of secretion by causing relaxation of the walls of the duct, while stimulation of this nerve may increase twenty-fold the secre- tion of milk by causing contraction of the milk-ducts and consequent discharge of their contents. Section of the inferior branch produces great increase in the amount of milk secreted, while the stimulation of the peripheral end of this nerve produces arrest of secretion. The explanation of these two classes of phenomena are understood through a study of the character of this nerve. The median branch is a compound nerve composed of both sensory and motor fibres, the latter being especially found in the papillary branch distributed to the nipple, while the glandular branch is almost solely motor. When the papillary branch is stimulated it produces, by a reflex action, the contraction of the muscular fibres of the exeretory ducts, and so causes discharge of their contents, while it also, in all probability, acts through the inferior branch, and by it also increases the amount of milk formed in a manner to be referred to directly. When the glandular branch is stimulated the muscular fibres of the ducts contract, and, although no more milk may be actually formed, there is, nevertheless, an increase in the amount poured out through the contraction of the walls of the milk-ducts. On the other hand, the inferior branch is a vaso-motor nerve. When its peripheral termination is stimulated, the milk secretion is arrested through the constriction of the blood-vessels supplied to this gland. On the other hand, when it is divided, the blood-vessels become greatly relaxed, more piesa passes through the organ, and its sey is largely increased. Whether any of these processes are associated with the action of true secretory nerves is not known, but from analogy, from what we have seen in the case of the salivary gland, it may be assumed that such is the: case. The explanation of the connection long known between the mechan- ical irritation of the nipple, as in suckling and milking, and the increased MAMMARY SECRETION. 631 secretion of the gland is thus evidently to be found in reflex action, the afferent impulses passing through the sensory nerves of the nipple, the secretory impulses passing through the inferior branch and the glandular branch of this nerve. It is thus seen that, as far as we know, the mammary secretion is dependent upon the amount of blood passing through the glands. Changes in the general blood pressure, by modifying the blood supply of the mammary gland, also influence the amount of milk secreted. Thus, various substances which act as stimuli to the vaso-motor centre, and so produce increase of blood pressure, produce likewise an increase in the amount of milk secreted. Strychnine in small amount, digitalis, caffeine, and pilocarpine are all galactagogues and probably act in this way, while through reduction of blood pressure, as by means of chloral, the milk secretion may be considerably reduced. 8. Miix INSPECTION AND ANALYSIS.—Good cows’ milk is white, with a faint . yellowish tint, and only bluish when diluted. Ifa drop of good milk is placed on the thumb-nail it retains its shape instead of spreading out, as occurs when diluted or unhealthy. Milk is most apt to be adulterated with water, which within cer- tain limits may be detected by determination of the specific gravity. Unskimmed milk possesses a higher specific gravity than that of the skimmed milk from the effect of the removal of the fats, so that a milk from which all the cream has been removed might, if dependence be placed upon the specific gravity alone, be con- sidered as a better specimen than the pure milk. The average specific gravity of normal cows’ milk may be placed at about 1030 at 60° F.; if diluted with half its volume of water the specific gravity will fall to about 1014 or 1016. As a conse- quence, by the determination of specific gravity a general idea may be obtained as tohow much water has been added to diluted milk. The following table may serve to assist in this determination :— With With Skimmed Milk. Unskimmed Milk. A specific gravity of et to 1033 or 1033 to 1029 indicates a pure milk. 3 to 1029 or 1029 to 1026 ‘© milk with 10 per cent, water. fi te 1029 to 1026 or 1026 to 1023. * see ee a ou se 1026 to 1023 or 1023 to 1020 ** ee | Me nt ee 1023 to 1020 or 1020 to 1017. ** stk QE “ The instrument by which the specific gravity of milk is determined is usually termed the lactometer, and simply consists of a hydrometer with a scale running from 1000, which is the specific gravity of distilled water and is marked zero on the scale, to 1034, marked 120, which is the specific gravity of a rich sample of milk. In using the lactometer special attention must be paid to the physical characteristics of the milk, since a little attention would readily detect skimmed milk from unskimmed, although their specific gravity might be the same. In milk rich in cream where the specific gravity might be abnormally low, its physical appearance and the fact that it clings to the instrument would enable it to be recognized, while watered orskimmed milk is bluish and does not cling to the lactometer ; so, if a sample of milk should read above 110 on the lactometer without manifestly being full-bodied, it would be only fair to presume that a portion of the cream had been removed. Milk diluted with spring-water may be recognized by the detection of nitrates in the milk. Sulphuric acid is added to . the milk, the precipitate filtered off, the filtrate distilled, and nitric acid looked for in the distillate. This may be readily accomplished by converting, through milk- sugar, the nitric into nitrous acid. A few drops of pure H,SO,, potassium iodide solution, and boiled starch solution are then added to the distillate; if nitrous acid 1s present iodine is liberated from the potassium iodide solution and the starch is colored blue. 632 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The cream may be roughly determined in milk by placing it in a tall cylindrical glass, graduated into one hundred parts The milk should be allowed to stand in this creamometer for twenty-four hours and the volume of cream separated on the surface may then be determined, one gramme of cream equaling about 0.2 grammes of fat. Good cows’ milk should separate from ten to fifteen volumes of cream. This method is, however, not thorouhgly reliable, since different speci- mens of milk will throw up their cream with different degrees of readiness. The second method, and a much more reliable one, of determining the amount of fat or cream present is by means of the lactoscope. This instrument consists of a little cup with two of its sides formed of two parallel plates of glass, distant from each other halfa centimeter. For applying this test, in addition to such a glass, a jar graduated to one hundred cubic centimeters and a pipette of three cubic centimeters are needed. Three cubic centimeters of milk are taken and shaken up well with one hundred cubic centimeters water, and the mixture then placed in the glass cup with the parallel sides and a lighted stearin candle placed one meter from it in a dark room. Tt at the first experiment the contour of the flame can be seen, the milk is poured back into the large measure and a further measured quantity of undiluted milk added until the contour of the candle-flame is entirely obscured. The percentage of fat is then determined by the following formula: If 2 equal the percentage of fat and 7 the number of cubic centimeters of milk required, then a equals Be + 0.28. Thus, if three cubic centimeters of milk were required to Be 0.23, or z=1.96, the per cent. of fat in the milk. Six cubic centimeters of pure cows’ milk with one hun- dred cubic centimeters water should form a mixture which will obscure the candle- flame; if more milk is required, then the milk has been diluted. Thus, twelve cubic centimeters indicate 50 per cent. water, and eight cubic centimeters about 30 per cent. water. The following table gives the percentages of fat in the milk when the candle-flame is obscured by different amounts of milk in Vogel’s galacto- scope :— obscure the light, the formula would read: = w eubic centimeters of milk indicate . : . ‘ “ “ on -96 per cent. of fat. “ ‘ + “ “ vs SOSHSONSNSOUNSHSbSH 7 PSGGHISSEBLSSHAKSES n i id BRIS COM MMM AM NIH b go ‘ " ROPOPODON po by gogo co eh — mo oo = & Another ready method of estimating the fat in milk is by means of Marchand’s lactobutyrometer. As improved by Caldwell and Parr (Amer. Chem. Journ., Nov. 1885), this method is performed as follows :— The instrument employed consists of a thick glass tube, open at each end, with a stem six cubic centimeters in diameter and twenty-three centimeters long, . graduated in 3; cubic centimeter, and a bulb about eight centimeters in length, _ and of such a capacity that in passing from the lowest graduation on the stem * to the inner end of the stopper in the lower mouth one passes from five to thirty- three cubic centimeters. Then the ether-fat solution will always come within the . range of the graduation on the stem. Closing the lower mouth with a good cork, ten cubic centimeters of the well-mixed sample of milk are delivered into the well-dried tube from a pipette, then eight cubic centimeters of ether (Squibb’s stronger) and two cubic centimeters of 80 per cent. alcohol. Close the smaller mouth of the tube with a cork and mix the liquids by thorough shaking (not violently nor prolonged). Both corks should be held in place by the fingers during this operation, and the upper one should be once or twice carefully MAMMARY SECRETION. 633 ‘removed to relieve the pressure within, otherwise it is apt to be forced out, with consequent loss of material. Lay the tube on its side for a few minutes and then shake it again ; add one cubic centimeter of ordinary ammonia diluted with about its volume of water, and mix as before by shaking ; then add ten cubic centimeters of 80 per cent. alcohol and mix again thoroughly by moderate shaking, holding the tube from time to time in an inverted position. Now, put the tube in water kept at 409 to 45° until the ether-fat solution sepa- rates ; this separation may be hastened by transferring the tube to cold water after it has stood in the warm water for a few minutes, and then returning it to the warm water. Finally, transfer the tube to water at 20°C., and as the level of the liquid falls in the stem by contraction of the main body of it in the bulb, gently tap the side of the tube below the ether-fat solution to dislodge any flakes of solid matter that may adhere to the side. The readings are to be taken from the lowest part of the surface meniscus to the line of separation between the ether- fat solution and the liquid below it. The following table gives the percentages of fat corresponding to each tenth of a cubic centimeter of ether-fat solution down to one cubic centimeter, and for each twentieth of a cubic centimeter thereafter :— Reading. Per Cent. of Fat. Reading. Per Cent. of Fat. 0 ey Say see te! or a 1B8. «4 «4 « » BB Og Re me ee ee 4.0.0. 2. 6 1. 8.68 50. . oe . » 147 14.5. ° . . . . 3,75 6.0. i « La 15.0 Sa oe on 9 SE 7.0. ‘ » 195 15.5 a « 400 8.0. : . 219 16.0 - 418 9.0. " . 2.43 16.5 . 4.26 10.0. . . 2.67 17.0 . . 4.39 10.5. . . 279 17.5 » 4,52 11.0. 3 . 2.91 18.0 - 4.65 11.5, - 3.03 18.5 . 478 12.0. E 3.15 WO. . . . 5.01 125 » 327 cs - 5.14 13.0 . 3.39 20.0 » « « 5.27 This method has been applied with fairly satisfactory results to the milk of a herd of cows receiving bran and cotton-seed meal in their rations, the objection to the unreliability of this method under these circumstances being overcome by ‘the use of the ammonia. Various other forms of lactoscope are used, depending on the property that the opacity of milk varies with and is proportional to the amounts of fats present. Skimmed milk contains smaller fat-globules than intact milk, and this causes a greater cloudiness in proportion to the amount of fat pres- ent than the large ones, and, hence, the application of this test to skimmed milk would give a higher percentage of fat than is actually present. For the quantitative estimation of the different milk-constituents the following methods, taken from Charles’s ‘Physiological and Pathological Chemistry,” are the simplest and require the least apparatus :— 1. The Solids.—(j.) To ten grammes dry sand or powdered gypsum add five cubic centimeters milk, then dry the mixture for a long time at 100° until the weight is constant. The increase in weight is equal to the solids in five cubic centimeters milk. Suppose this to be =05 gramme, then one hundred cubic centimeters milk contain ten grammes, or 10 per cent. solids (Baumhauer). Instead of five cubic centimeters, ten grammes of milk and twenty grammes of dry sea-sand may be weighed in a tared capsule of about fifty cubic centimeters, and evaporated at 100° until the weight is constant. When quite cold, the cap- sule, with its contents, is weighed in a desiccator over sulphuric acid. (ij.) Place a little milk in a platinum capsule, and, having weighed it, add a few drops of alcohol or acetic acid ; evaporate over a water-bath, dividing the coagulum against the sides of the dish, and dry it at 100° to 110° until the weight 18 constant. It is generally completed in six hours (Gerber). Cover carefully before weighing, as the residue is very hygroscopic. zs The total solids should not, as a rule, be much Jess than 11.5 per cent.; cows’ ata for example, varies between 10.5 and 15 per cent.; less than this indicates ilution. : 2. The Butter.—(j.) Shake the milk well, and to twenty cubic centimeters of it add twenty cubic centimeters of a 10 per cent. caustic potash solution and then some ether (sixty to one hundred cubic centimeters), and agitate vigorously 634 PHYSIOLOGY OF THE DOMESTIC ANIMALS. for some time ; on standing, the ethereal solution of the liberated fat rises to the surface and is to be carefully decanted into a weighed porcelain dish. Some more ether is to be added to the alkaline milk, and after vigorous agitation it also is to be transferred, as before, to the capsule. The same process may be repeated several times if necessary. The ethereal extract is now evaporated over a water- bath, and after having been dried in an air-bath at 110° the weight of the residue is to be ascertained ; this multiplied by 5 gives the percentage. With cows’ milk it varies between 2 and 5 per cent., but the normal minimum for fats is about 2.75 (Cameron). 3. The Casein and Albumen.—(j.) (a) Dilute twenty cubic centimeters milk with four hundred cubic centimeters water, and treat the mixture with very dilute acetic acid, added drop by drop, until a flocculent precipitate begins to appear. Now pass a current of carbonic acid gas through the fluid for fifteen to thirty minutes and lay aside for one or two days. Collect the precipitated casein ona weighed filter, wash it with spirit, and then with ether until a drop of the wash- ings leaves no fatty stain on paper; dry at 100° and weigh. Subtract the weight of the filter, and the difference multiplied by 5 gives the percentage of casein. In human milk, precipitate the casein by saturating with magnesic sulphate. (b) The filtrate from the casein precipitate is to be concentrated to a small bulk over a water-bath and an acetic acid tannin solution added so long as any precipitate occurs ; after the precipitate has settled, collect it on a weighed filter, where it is to be washed with dilute spirit until the filtrate gives no blue coloration with ferric chloride (indicating absence of tannin) ; dry now at 100° and weigh. The weight multiplied by 5 gives the percentage of albumen. In cows’ milk the casein varies between 3.3 and 6 per cent., and the other albumens from 0.3 to 0.4 per cent. In diseased milk the casein may be as low as 0.2 per cent., and the other albumens as high as 10 per cent. (ij.) (a) Ten cubic centimeters milk are diluted with one hundred cubic cen- timeters distilled water and well mixed; a copper solution, made by dissolving sixty-three and five-tenths grammes of cupric sulphate in one liter of water, is then added slowly with stirring until the coagulum begins to settle quickly. The whole mixture, together with half the cupric sulphate solution already employed, is then added to some potash solution (fifty grammes of potash to the liter), and after a short interval the clear fluid is filtered off through a filter dried at 110° C.; the precipitate is washed until the washings amount to two hundred and fifty cubic centimeters, and the sugar is to be estimated in this subsequently. (6) The coagulum on the filter is next treated with absolute alcohol, slowly dried, and extracted with ether; the ethereal and alcoholic extracts are then to be distilled, and the fatty residue dried and weighed. The coagulum, after having _been dried at 125°, is weighed, then ignited, the ash deducted, and the difference taken as pure albuminoid (Ritthausen). 4. The Sugar.—(j) Take twenty-five grammes of milk, acidify with hydro- -chioric acid, boil, and filter, washing the coagulum with water; to convert the milk-sugar into glucose, boil the filtrate and washings for an hour or so in a flask, to the mouth of which a long tube has been attached. When the liquid cools, make its volume up to two hundred cubic centimeters and determine the sugar by Fehling’s method, measuring twenty cubic centimeters Fehling’s solution into a flask, diluting with eighty cubic centimeters water, and to the boiling mixture add the diluted filtrate from « Mohr’s burette until the copper is entirely reduced. (ij.) This sugar determination may be readily effected by the polariscope. Measure forty cubic centimeters milk into a flask of one hundred cubic centimeters capacity, add some carbonate of sodium if the milk is not alkaline, and then twenty cubic centimeters moderately concentrated solution of neutral acetate of lead, and shake well; having next fitted the neck of the flask to a long glass tube or to the condenser of a Liebig’s still, boil it over a small flame ; then filter, and test the filtrate with the polariscope. With a one-decimeter tube the percentage of sugar is obtained by multiplying the rotation by 1.44. *For other ready methods of milk analysis and for the detection of foreign substances with which milk may be adulterated the reader is referred to the following articles :—C. Storch, Oesterreicher Vierteljahresschrift fiir Wissen ; Veterindrkunde, 1884, Hefte IT., s. 195; Arch. Sf. Thierheilkunde, 1885, Hefte 5 u. 6, 8. 49; F.G. Short, Amer, Chemical Journ., April, 1887, p. 1005 Morse & Pigott, Zb., April. 1887, p. 108; F. A, Woll, Z0., February, 1887, p. 60; Morse and Burton, Ib., June, 1887, p. 222; £0., July, 1888, p. 322. “ SECTION X. THE RENAL SECRETION. Tue blood not only bears to the different tissues the substances required for their nutrition, but also removes from the tissues the different waste products which result from their various metabolic processes. In the lungs, part of these oxidation products, especially of the carbon compounds, are removed, while the results of nitrogenous waste largely pass through the lungs to be carried through the aorta from the left ventricle to the kidneys, whose function is to remove these nitrogenous excrementitious substances, together with the carbon com- pounds which have passed the lungs, with various salts and water. The product of this functional activity of the kidneys is the urine, which is a pure excretion, since all its constituents are waste products which must be removed from the organism. 1, THe PuystcaAL AND CHEMICAL PROPERTIES OF Unine.—Urine is in general a thin, yellowish colored, transparent fluid (the depth of color depending on the concentration) of a salty taste and peculiar aromatic odor, due to the presence of various volatile acids. Its reaction may be faintly acid, neutral, or alkaline: it rotates the plane of polarized light to the left. The reaction in the carnivora and in fasting or suckling herbivora is acid; in the herbivora and omnivora, when on vegetable diet, it is alkaline. The explanation of the production of an acid renal secretion from the alkaline blood is to be attributed to a specific property of the renal epithelium similar to that possessed by the gastric mucous membrane. The more alkaline the blood, the less acid the urine; hence the great alkalinity of the blood of herbivora causes the urine to have an alkaline reaction. For although sulphuric acid is formed from the decomposition of vegetable just as it is from animal albumen, vegetable foods contain large amounts of organic salts which break up into alkaline carbonates, and so neutralize the sulphuric acid. These salts are absent from the food of carnivora, hence the acids are less perfectly neutralized. It is, therefore, the form of diet which, by modifying the alkalinity of the blood, determines the reaction of the urine. The specific gravity of urine varies between 1005 and 1050. When exposed to the air, the urea undergoes decomposition and is transformed into ammonium carbonate; a part of the ammonia tlien combines with magnesium phosphate, and ammonium-magnesium plos- (635) 636 PHYSIOLOGY OF THE DOMESTIC ANIMALS. phates, together with calcium phosphate, are deposited as a crystalline precipitate. This process is known as ammoniacal fermentation, and is due to the action of ferments derived from the atmosphere. In some animals the urine always deposits mucus derived from the membranes over which it passes. Its quantity is subject to great variations. The most important constituents of the urine are water, salts, gases, and certain specific constituents. Among the salts, potassium com- pounds are more abundant than sodium. Lime and magnesium are in varying amounts. Of the acids H;SO, and P,O,; are most abundant, CO, in combination is found in the urine of the herbivora. When NaCl forms part of the diet, this salt is also a large constituent of urine. The following are the specific constituents of urine :— 1. The decomposition products of the albuminoids, as urea, uric acid, hippuric acid, kreatin and kreatinin, and the combinations of -H,SO, with indol and phenol. 2. Coloring matters, of which urobilin is the best known, 3. Aromatic bodies which give the urine its peculiar odor. The gases CO,, N, and O are found free in the urine. As regards quantitative composition there is great inconstancy. Horse. Ox. Sheep. Hog. Water, . A : , . 90. 91. 89. 98. Organic matter, . % » 5.5 5. 8. 0.5 Inorganic matter, . : » 45 4, 3. 1.5 COMPOSITION OF THE URINE (BOUSSINGAULT). Horse (1). Cow (2). Pig (3). Urea, ‘ . . . 381.0 18.5 4.9 Potass. hippurate, 4.7 16.5 0.0 Alkaline lactates, 20.1 17.2 a Potass. bicarb., 15.5 16.1 10.7 Mag. carb., 4.2 4.7 0.9 Calcium carb., 10.8 0.6 traces Potass. sulph., 1.2 3.6 2.0 Sodium chloride, 07 1.5 1.3 Silica, * 1.0 traces 0.1 Phosphates, 0.0 0.0 1.0 Water and undetermined sub- stances, . é ; F . 910.0 921.3 * 979.1 * 1000.0 1000.0 1000.0 (1) Diet of oats and clover-grass. (2) Diet of hay and potatoes. (3) Diet of cooked potatoes. The water, K, Na, Ca, and Mg compounds are derived directly ' from the blood, and in greater part directly from the food and drink, and in fasting animals from waste of tissues. H,SO, originates in oxidation of the sulphur compounds in food; the phosphates from the oxidation ‘of albuminoids of food and tissues; carbonates, partly directly from RENAL SECRETION. 637 food and drink, partly from modifications of the vegetable acid com- pounds in vegetable foods. The urea and uric acid are the nitrogenous end products of the decomposition of the albuminoids of food and of the tissues. Kreatin and kreatinin are closely dependent on the animal matter taken as food, since, even in muscle, kreatin is formed as a modification of its own albuminoid constituents. Hippuric acid is a combination of glycochol with benzoic acid, and originates, to a great extent, in the constituents of vegetable foods, the cuticular substance of which develops the benzoic acid. ' Phenol is derived from the decomposition of albuminoids in the intestine, and in the excretory ducts of the kidney unites with H,SQ,. Indican originates in indol. Many other substances are accidentally present in urine, such as aromatic constituents of food, alkaloids, metals, bile coloring-matter, ete. The quantity of the urine is dependent on the amount of water taken in food and drink, on the diminution of excretion of water by other organs, especially the skin, on the amount of excretory products, especially urea, and on the amount of substances taken in food, e.g., salts, which must be excreted. It is to be noted that all the water taken as food is not excreted through the kidneys, but that part is removed by the lungs, skin, and intestinal canal, The proportion of water removed through these different organs varies in different species :— In the Urine. Through the Lungs. In herbivora, 20 per cent. of water is removed; 80 per cent. In omnivora, 60 ee ss 40 « In carnivora, 85 ae “ ag 15. Various conditions may, however, modify these proportions. In fasting and suckling animals of both the herbivora and carnivora the urine has the same characters, since in them thie tissues alone are undergoing waste. There is the greatest difference between the urine of carnivora and herbivora. In carnivora the urine is smaller in amount, is acid, clear, and richer in solids, especially urea, uric acid, and kreatin; sodium salts, sulphates, and phospliates are in excess, and the urine has a higher specific gravity. Phenol and sulphuric acid ont are present in small amount and hippuric acid absent when on a purely flesh diet. In herbivora it is larger in amount, is turbid, contains few solids, hippuric acid replaces uric acid, and the reaction is alkaline; urea is present only in small amount. Potassium salts are in excess unless sodium chloride is given with the food. Lime and magnesium, united with CO,, are in abundance, phosphates often absent, sulphates abundant. 638 PHYSIOLOGY OF THE DOMESTIC ANIMALS, That this difference is dependent only on differences in diet is proved by the fact that during fasting the urine of the herbivora agrees in all its characteristics with the urine of the carnivora. Under such circum. stances the herbivora are not consuming vegetable matters, but living at the expense of their own tissues, are then practically carnivorous, and their urine becomes acid, clear, and rich in urea and phosphatic salts. The Urine of the Horse is cloudy and has an alkaline reaction. Its specific gravity varies from 1016 to 1060, 1050 being about the average, It contains a large percentage of mucin, and is therefore viscid and may be drawn into threads. It becomes brown on exposure to the air, deposits CaCO,, and a pellicle forms on it, showing iridescent colors. The characteristics of normal horses’ urine depend largely on the mode of feeding. When fed exclusively on hay and straw the urine is always alkaline, while when oats constitute the principal food it is secreted in small quantity, is turbid, and of acid reaction, and more viscid than alkaline. The influence of the diet on the amount of solids in the urine is shown in the following table :— SOLIDS IN URINE, DaILy RATION, WATER. URINE. In 100 C. C, Total. Hay. Oats. Rial Kilos, Kilos. Grammes. Grammes, 8 kilos. 2 kilos fs 2d 22.31 5.04 The 566.6 he Di HE 1 kilo. 26.33 4.72 11.2 529.4 6 « 4 “ Bon ss 0 21.86 4.99 10.3 511.8 4 « 4 « 2 kilos. 27.55 4.66 102 477.0 4 « GS Oy ew 23.73 4.53 10.4 460.7 fe 6 2.6 ** 24.60 6.03 5.7 346.1 A high percentage of calcium salts is characteristic of horses’ urine. Of the amount contained in the food, from one-third to one-half passes into the urine, while in the ruminant, especially in the sheep, not more than 5 per cent. passes. In the case of potassium the conditions are just reversed. In the sheep 95 per cent. of the potassium in the food passes into the urine, while in the horse at most 66 per cent. appears. The following table gives the percentage of inorganic constituents in one hundred parts of the ash of horses’ urine :— Potassium, . > 4 . i ‘ . 386.85 per cent. Sodium, . ‘ - ; . i ; a SH Oe Calcium, . : ‘. a : a i . 21.92 “ Magnesium, . : 7 3 ‘ : . 441 °° Phosphoric acid, . ‘i . fog Gl ep aig, VEE Sulphuric acid, si A 3 ‘ . « 16 ** Chlorine, F ‘ ‘ : ‘ 5 . 15.36 Silicic acid, . é 3 * 5 ‘ . 0382 RENAL SECRETION. 639 Horses’ urine contains urea and hippuric acid in inverse proportions. When one increases the other decreases, the amount of the latter depend- ing on the amount of green forage or hay or straw, the former on the amount of oats, grains, roots, ete. The percentage of urea in ordinary feeding varies from 2.5 to 4.0 per cent. Very large amounts of aromatic sulphur compounds are present, especially of phenol and indican. The former, with hippuric acid, causes the peculiar odor; the latter, the colors seen in the film which forms when exposed to the atmosphere. Brenzcatechin is also present and is the cause of the brown color which forms on standing. CaCO, is the principal salt, and is rapidly deposited as a sediment. Sulphur compounds are found in varying amounts. Phosphates, except in abundant feeding with grains, are only present in traces. The amount of urine is only about five to six liters daily, evacuated in three to four portions, since a large amount of water is lost through the skin in perspiration. The Urine of the Ox.—The amount of urine depends not only upon the amount of water taken, but especially on the amount of nitrogenous food. Thus, when the diet has been poor in nitrogen, the amount of urine passed daily will vary from 9.7 to 12.6 kilos, and when a richer nitrogenous diet is given the amount will be increased to from 16.3 to 16.8 kilos. This is, without doubt, partly to be attributed to the larger amount of water required in a rich, nitrogenous diet. The evacuation of the urine occurs from eight to ten times daily, averaging about one kilo each time. The character of the food exerts the greatest influence on the reaction of the urine. Fodder rich in alkaline carbonates or com- pounds of the organic vegetable acids occasions an alkaline reaction of the urine. The amount of carbonates in the solids of the urine is directly in proportion to its alkalinity. Carbon dioxide is especially abundant when fed on beets, clover, hay, or bean-straw, when it may amount to 10 or 12 per cent. When fed with oat-straw or barley-straw, the carbon dioxide sinks to from 8 to 6 per cent. Exclusive feeding with wheat-straw is said to cause an acid reaction of the urine on account of the poverty of carbonates and vegetable acids. The total amount of solids in the urine averages about 6.8 per cent., composed of— CG... we 27.8 to 53.1 per cent. H,. - : 3 : 3 F . 85to 69 * N,. : . . . : : . 89to38.6 O,. : 7 : 7 ‘i P . 15.6 to 50.2 aU The quantity and quality of the organic matter in the urine varies greatly according to the food, varying between 4.2 to 11.3 per cent., and is especially dependent upon the digestible, nitrogenous food-stuffs. The non-nitrogenous food-stuffs are without influence on the organic urine 640 PHYSIOLOGY OF THE DOMESTIC ANIMALS. constituents. Uric and hippuric acids are the representatives of the nitrogenous organic constituents. Uric acid and hippuric acid are found in proportions which are governed by the character of the diet in the same way as in the case of the horse. The mineral constituents are like- wise dependent on the food, potassium and lime combinations being especially abundant. The urine of the ox is clear, yellowish, or greenish, and possesses a peculiar, musky odor. Its specific gravity varies from 1020 to 1030, depending on the amount of water in the food. It is always poorer in solids than the urine of the horse. It also contains less sulphuric acid. compounds, especially of the aromatic group, than horses’ urine. The phosphates are entirely absent, or present only in traces, The Urine of the Sheep and Goat is similar to that of the ox, but shows great variation in the salts derived from the food. Its specific gravity varies from 1006 to 1015; the amount from five hundred to eight hundred and fifty cubic centimeters daily. Urea and hippuric acid are present in the proportion of about two to three, the hippuric, contrary to what is the case in the horse, being more abundant when on a diet of young hay rich in proteids. The Urine of the Pig is clear, yellowish, with a faint alkaline reac- tion; specific gravity, 1010 to 1015. It-contains urea, but rarely uric or hippuric acids. The salts depend on the character of food. In general, the urine resembles that of carnivora. The Urine of the Dog is deep yellow in color, acid reaction ; specific gravity, 1050 when fed on meat. It is rich in urea, but contains but little uric acid. Kreatin and indican are present, but no phenol. Mg salts are in larger amount than Ca salts, while the chlorides are scanty ; sulphates and phosphates abundant. It readily undergoes ammoniacal fermenta- tions (from urea) and deposits phosphates. Its composition and character likewise vary greatly with the nature of the food.* 2. Tue MecuantsM or RenaL SEcretion.—The substances which exist in the urine in a state of solution also exist in the blood, and the process of secretion of the urine is, therefore, largely a process of mere infiltration. Nevertheless, certain constituents of the urine are evidently manufactured in the kidney, since their presence has not yet been detected in the blood. Renal secretion is thus possessed of two factors,—a physical process of filtration and a process of true secretion dependent upon the activity of the renal epithelium. The mechanism of the renal secretion is, to a certain extent, capable of explanation by the study of the structure of the kidney. The kidney is composed of a series of fine tubules, which, starting from the hilum * For further details as to the composition of the urine of the domestic animals under different forms of diet the reader is referred to the ‘‘ Encyclopedie der Gesammten Thier- heilkunde,’’ Bd. iv, p. 202. RENAL SECRETION. ; 641 in the medullary portion of the kidney, form, by frequent subdivisions, | a series of straight, branching canals, the so-called urinary tubules. After frequent subdivision each branch terminates in a looped tubule, which, after undergoing various convolutions in the cortical portion of the kidney, terminates in a bladder-like expansion. In each of these expansions enters a small branch of the renal artery, the vas afferens, which undergoes division into a bunch of capillaries which is so placed as to be surrounded by a double layer of the bladder-like expansion of on) .. 0 es i ans BErQa ds ey) b \ ‘e ON \ th: Fig, 265,.-NAKED-EYE APPEARANCES OF THE KIDNEY OF MAN, AFTER Tyson AND HENLE. (Landois.) Fe eee een at tabuies 10 vountary ett a iteal sues 5, artery ; *, transversely coursing medullary rays; A, branch of renal artery; C, renal calyx; U, ureter. the tubules, The relation between this bunch of vessels and the expan- sion of the tubules is similar to what would be expected if a tip of the finger of a glove was inverted from the outside. The collection of capil- laries is, therefore, in contact with the external layer of the tubule, and is surrounded by a space which is in direct communication with the in- terior of these tubes. After having undergone subdivision into eapilla- ries in this expansion of the tubules, the efferent vessel, which collects 41 642 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the blood which has passed through this series of capillaries, again un- dergoes subdivision into a second net-work of capillaries distributed around the urinary tubules. In the glomerulus is represented the filtra- tion apparatus, in which, through the influence of blood pressure, the substances held in solution in the blood-serum may be removed from the blood and forced into the interior of the commencement of the urinary tubules. The conditions are, therefore, evidently different here, where transudations directly enter into the excretory ducts, from what holds in the case of other glands, where the transudations simply pass into lymph and require some other force for their, transference to the secretion. Cortex. ‘\ Boundary or marginal zone. RS Papillary zone. Fic. 266.—LONGITUDINAL SECTION OF A MALPIGHIAN PYRAMID. (Landois.) PF, pyramids of Ferrein; RA, branch of renal artery; RV, lumen of a renal vein receiving an inter- lobular vein; WR, vasa recta; PA, apex of a renal papilla; b embrace the bases of the renal lobules. That this separation of the constituents of the blood through the glom- eruli of the kidney is actually dependent upon the blood pressure is shown by the fact that if the blood pressure be reduced below fifty milli- meters of mercury secretion ceases, while if it be increased the secretion ’ js correspondingly augmented. The contrast between this fact and the secretion of saliva is, therefore, very striking. If, however, pressure is increased by venous obstruction, then, in- stead of an increased secretion, the reverse takes place. That this does not contradict the filtration hypothesis is explainable by the fact that ob struction of the veins increases the pressure in the capillaries, and these ' RENAL SECRETION. 643 so expand in the unyielding capsule of the kidney that the urinary tubules are completely compressed, and filtration is, of course, at once arrested. Various conditions may modify the blood pressure in the kidneys. Thus, for example, the local blood pressure may be increased by general Sub-capsular layer without Malpi- ghian corpuscles. 12. First part of col- lecting tube. 1L. Distal convoluted tubule. A. CoRTEX. 10. Irregular tubule. 3. Proximal — convo- luted tubule. 4, Spiral tube. 9. Wavy part of as- cending limb. 13. Straight part of 2. Constriction or collecting tube. neck. 9. Wavy part of as- 4. Spiral tubule. cending Jimb of 1. Malpighian — tuft Henle's loop. surrounded by Inner stratum of cor- Bowman's capsule. tex without Mal- pighian corpuscles 8 F 8 8. Spiral part of as- cending limb of Henle’s loop. 14 3 B B. BounpDAry ZONE. 5, Descending limb 8 7 of Henle’s loop tube. 7 and 8. Ascending 7 limb of Henle’s loop tube, | ee i, 6 \6) §. Henle’s loop. 45 pf .C C. PAaptLuaRyY ZONE. Fig, 267.—~DIAGRAM OF THE CoURSE OF TWO URINIFEROUS TUBULES, AFTER KLEIN AND NOBLE-SMITH. (Landois,) increase of blood pressure or by a relaxation of the renal artery, accom- panied by the constriction of other vascular areas, which, while dimin- ishing the pressure in the renal artery itself, increases the pressure in its Capillaries. Of course, pressure may be reduced in the kidney by the reverse causes, 644 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The principal constituent of the urine which is removed by a process of filtration is, of course, water. Therefore, in the quantity of urine, S — Sap POG SC LI es See: weeee a rsh Pray va < 24%, r ‘ % . 21 “e 14th “« “ ts ‘ . , ‘ . . 19 ee From this table it is seen that the loss is far greater on the first day of starvation than on any other, and that after the first day the loss gradually becomes less and less marked. It has also been found that age is of marked influence on the degree of loss of body weight in starvation. The younger the animal, the greater the loss. It is also noticed that birds can stand a greater relative loss of body weight from starvation before death occurs than mammals and other warm-blooded animals ; in the latter death only occurs when 40 per cent. of the body weight has been lost. It has been found that if water is freely given, a horse may stand a complete fast for from eight to fifteen days without any serious conse- quences. If this time is, however, passed, even feeding will then be unable to prevent death. Herbivora stand starvation worse than carnivora, even although they lose only one-half as much tissue-albumen ; it is stated that death from starvation in the horse does not occur until the twentieth to the thirtieth day, while a dog may live from forty to sixty days without food before death takes place. If the body of an animal dead of starvation is examined there will be found the greatest difference in the loss which the different tissues have undergone. Adipose tissue suffers most, muscles and viscera less, and nervous system least of all, and this latter fact is worthy of especial notice, since fat forms a large constituent of the nervous system. The body is greatly emaciated; all subcutaneous and perivisceral fat has disappeared; the muscles and other organs are atrophied ; and with the exception of the alimentary canal, in which fluid is generally found, all the tissues are markedly dry and free from water. In the stomach the fluid has an acid reaction; in the intestine there is a slimy fluid matter Which is evidently decomposed bile. 676 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Since fat and muscle have disappeared in largest amount, it is evi- dent the starving animal feeds on its own flesh, and, under such cireum- stances, the urine of the herbivora and carnivora are identical. Of the different organs the percentage of loss of original weight is as follows :— Bones 3 . 13.4 percent. or 5.4 per cent. of total loss. Muscles, . . 805 “ “© 42.2 es Liver, . 3 , Beene « 48 6 a Kidneys, . . 2.9 £0265 OFF « Spleen, . 66.7 « « 0.6 e 4 Pancreas, . 3 DEO. ts «0.1 ee a Testicle, 40.0 « 0.1 es as Lungs, uy (ey « 0.3 ‘ af Heart, 2.6 ‘ « 0.02 « ag Intestine, 18.0 <“ HOO: EE a Brain and Cord, . Bie fe Ord: st ne Skin, , 20.6 <* fe B BE et ee Fat, . 97.0 <“ a Blood, 27.0 “« aaees ue Other organs, 36.8 «50 ff ry Since in fasting all the nitrogen leaves the body in the form of urea, the amount of urea in the urine gives a means of measuring the waste. of the albuminoid constituents of the body. Even up to the time of death the body continues to eliminate urea without, of course, any new albuminoid matter entering the economy, thus showing that there is a cradual and constant waste of proteids in the body. The amount of urea eliminated progressively decreases, as, of course, there is no repair of the stock of proteids from which it is drawn. Thus, a dog, which during feeding eliminates daily 63.96 grammes of urea, during the first day of starvation removes only 14.91 grammes, and there is then a gradual diminution in the amount up to the time of death. Thus, on the fifty-ninth day of starvation the dog alluded to above only eliminated 3.50 grammes of urea. Of course, the richer the tissues are in proteids, the greater will be the difference between the amount of urea eliminated in the first and sub- sequent days of starvation. If before the commencement of the starva- tion experiment the animal has been on a spare diet, less urea will be eliminated in the first days of fasting, and then the decrease in amount will be more gradual than if it had been well fed. The destruction of albumen in starvation is, however, by no means parallel to the amount of proteids in the entire body ; or, in other words, an animal which on the first day of starvation destroys five times as much albumen as on the tenth does not have on the first day five times as much proteid in the body as on the tenth. Voit has found that the excretion of urea on the first day after full feeding is so much greater than under other circumstances that he con- cluded that the amount of proteids in the body is of less importance” i STATISTICS OF NUTRITION, 677 than the amount of albumen in the preceding diet in determining the degree of allhumen destruction in the first days of starvation, and that the albumen destruction from starvation is dependent upon two causes :— 1. A very variable one, which only acts in the first days and which is dependent on the preceding diet and the general condition of the body. 2. A constant cause, which alone remains in force after the cessa- tion of action of the first. The following table shows how the amount of urea excreted increases with the amount of nitrogenous matter in the preceding meals :— Food given Before Urea in Last Day Urea in First Day Starvation. of Feeding. ot Fasting. 2500 grammes meat, a : F , 180.8 60.1 2000 He : : = r 142.9 33.6 1500 “8 ne z ‘ - : 110.8 29.7 800 «s “and 200 grammes fat, 51.8 19.8 Decreasing amount of meat on last day 176 grammes, ; 2 26.2 16.9 Abundance of fat after starvation, x 16.1 15.4 Voit concludes that animals possess, first, a considerable available “store” of albumen, which is capable of being increased by a previous meal rich in albuminoids and which is again rapidly removed in any drain on the economy; and, second, a much larger amount of proteid matter, which represents all the proteids of the animal body and which he terms “tissue-albumen.” Of this latter but a small portion comes under the conditions of decomposition. The rapid fall in elimi- nation of urea in starvation depends upon the using up of the “stored ” albumen; when, however, this is all consumed, then the tissue-albumen in its turn undergoes destruction. Of course, the stored-up albumen is also located in the various tissues. Herbivora contain in their tissues a lesser amount of this stored- up or reserve albumen than do the carnivora; even the tissue-albumen is present in relatively smaller amount. Thus, it has been found that a full-grown ox during starvation will only use up 1.27 kilos of proteids, while, measured by the albuminoid waste in carnivora, at least double the amount of nitrogenous excretion products might be expected. In addition to the influence of these amounts of albumen on the proteid waste of fasting animals, the amount of fat in the animal body is also of moment; the greater the amount of fat, the less the nitrogenous waste, and this holds whether the fat is already stored up in the economy or is given to thin animals in the food. Voit, by giving one thousand five hundred grammes of meat daily to a dog, brought it to a nutritive condition in which the excretion of 678 PHYSIOLOGY OF THE DOMESTIC ANIMALS. urea remained constant. He was then allowed to fast for ten days and the urea estimated (A). He was then fed with the same food, and then for ten days received nothing but one hundred grammes of fat (B). The following results were obtained :— Urea in Urea in Gramines. Grainines, Last day of feeding, . : i ‘ j . 110.8 111.8 1st day of fasting, . . ; ; ; » 26.5 27.2 2d i mF . i ‘ A ‘ . 18.6 16.3 3d oe we “ . ¥ é é . 15.7 14.1 4th ee a ‘ . é F . . 149 12.9 5th a 7 - P ‘ ‘ ‘ . 14.8 12.4 6th a F é ‘< ¢ r . 12.8 10.8 7th ia ae F : i . 12.9 10.5 8th ig : ‘ . ‘ 5 . Al 10.7 9th ne a . ji ‘ ‘ i «ALD 10.2 Through the administration of the fat 14.1 grammes of albumen escaped destruction, or, as Voit expresses it, was “ saved.” Water also exerts a considerable influence on the destructive processes in starvation, a large consumption of water always increasing the excretion of urea. This evidently points to an increased decom- position of proteids, and not a mere increase in the amount of urea washed out, since it has been proved that when water is withheld there is no accumulation of urea in the economy. On the other hand, the most violent muscular movements during starvation produce but little appreciable increase in the amount of urea eliminated, thus showing that the combustion of albuminoids is not the source of muscular force. In earlier times, with the exception of the lime salts in the bones, the inorganic substances found in the animal body were regarded as secondary in importance and, in fact, almost as accidental constituents. Liebig and his scholars first recognized the importance of these bodies; especially Na, Cl, Ca, K, Mg, Fe, and P,O, are absolutely essential for the health of the animal body. If these bodies are removed from the food, or even reduced in amount, the animals rapidly perish, even though supplied with an abundance of organic food. This disturbance of nutrition is not, as was first supposed, because the removal of salts interferes with the activity of the digestive secre- tions, since digestion and absorption, even under such circumstances, is perfectly carried out, but because salts are removed constantly from the body, and if they are not supplied in food the animal rapidly perishes, as these salts are essential to the various functions of the economy. Forster fed a dog with food which was as much as possible freed from salts; as proteids, he used the residue from the manufacture of beef extracts, butter freed from salts, potato-starch washed with HCl, and distilled water. STATISTICS OF NUTRITION. 679 A dog weighing thirty-two kilos, which experience showed could be kept in constant weight by receiving six hundred to seven hundred grammes meat and one hundred and fifty grammes fat, was allowed to eat as much as he would take of the above foods, and yet he rapidly commenced to fail, and in fourteen days was unable to stand from his great weakness. After three weeks disturbance of digestion appeared— indigestion, diarrhoea, and finally vomiting. The comparison of the inorganic income and outgo showed that, as regards phosphoric acid, 21.9 grammes were taken in while 51.7 grammes were excreted; consequently, the dog had lost 29.8 grammes of phos- phoric acid, or ten times the amount which is normally contained in the blood; 7.24 grammes of NaCl were lost. These results show that the body cannot be sustained by organic substances alone, but must also receive a certain amount of inorganic salts. If the amount of salts in the food sinks below a certain figure or is entirely suspended, salts are excreted by the economy, and the body passes into such a state of malnutrition that death speedily results. As regards the amount of inorganic salts required by different animals in order to preserve perfect nutrition, it appears that the amount of NaCl in meat, which amounts to 0.11 per cent., is sufficient for the needs of the carnivorous animal. As a consequence, these ani- mals prefer unsalted to artificially salted foods. It is quite different with the herbivora, for, although these animals, asa rule, receive proportionately quite as much salt in their food as the carnivora, they will, nevertheless, always greedily devour salt. As regards the relative proportion of these salts required by different animals, it appears that all animals require relatively similar propor- tions of chlorine and sodium, but that herbivora take in their daily food at least double as much potassium as carnivora. Thus: One. kilogramme eat, fed with mice, takes daily 0.1434 gramme K, 0.0743 Na, 0.0652 Cl. One kilo ox, fed solely with clover- hay, 0.8575 gramme K, 0.0266 Na, 0.0433 Cl; when fed with beet-roots and oat-straw, 0.2923 gramme K, 0.0674 Na, and 0.0603 Cl. The following table gives the amounts of K, Na, and Cl in various foods :— K. Na. CL. Oat-straw, . : : 5 . 10.40 1.36 2.97 Clover, 7 , 3 ‘ . 21.96 1.39 2.66 Sweet grasses, . é ‘ . 20.80 2.57 8.67 Prairie-grass, . : 3 . 15.28 2.65 4.35 Acid grasses, . : é . 20.60 5.74 4.52 Vetches, 2 . . . 83.98 6.77 3.65 Beet (roots), . ; ; . 84.79 10.24 5.40 Beet (tops), . . . . 46.68 30.80 22.56 Carrot (roots), . . ; . 19.65 12.32 2.90 Sugar-beet (tops), . é . 50.07 25.76 20.16 680 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Bunge has stated that it is this large amount of K in the food of the herbivora that causes them to require so much NaCl. For when potassium salts, the electronegative constituent of which is other than chlorine, such as carbonate, phosphate, or sulphate of potassium, come into watery solution with NaCl at the body temperature they are partly decomposed, both salts give up their acids, and, in addition to potassium chloride, the carbonate, phosphate, and sulphate of sodium result through double decomposition. If these K salts enter the alimentary canal they are rapidly absorbed and meet with NaCl in the blood. As the above interchange then takes place, the blood in attempting to preserve its normal composition allows the new substances rapidly to diffuse away through the kidneys. Consequently, through the taking in of potassium sulphate, carbonate, or phosphate, the blood loses both Na and Cl, and this loss must be replaced by the ingestion of extra amounts of NaCl. Consequently, herbivora, whose diet is rich in K salts, require more NaCl than the carnivora. It is thus seen that the character and extent of the tissue changes in starvation will be largely governed by the previous nutritive condition of the animal. The following table, after Lawes & Gilbert, shows the percentage of albumen, fat, salts, and water in the tissue of animals in ditferent conditions :— In 100 Parts. THE SOLIDS ConTAIN. Solids. Water. |, “ergante Fat. Albumen. 1. Fattened oxen, . : 51.4 48.6 41 31.9 15.0 2. Half-fattened oxen, . 43.9 56.1 5.1 20.7 18.0 3. Fattened sheep, . 53.8 46.2 2.9 37.9 13.1 4. Thin sheep, 4 ‘ 39.0 . 61.0 3.4 19.9 15.9 5. Fattened hogs, . .[ 57.1 42.9 17 44.0 11.9 6. Thinhogs,. .. 41.8 58.2 28 24.6 14.1 2. Tur Nurritive Processes In FEEDING.—(a) Feeding with Meat.— When animals are fed exclusively with fats or carbohydrates there is but little difference in the metamorphosis of proteids other than is seen in stat- vation. So, also, exercise, water, and various other conditions are of little influence. When, however, proteids are given with the food there is an immediate increase in the amount of urea eliminated, for the albumen of the food after being absorbed almost at once undergoes decomposition. Bischoff and Voit found that a fasting dog which eliminated daily twelve grammes of urea, when fed with twenty-five hundred grammes of meat eliminated one hundred and eighty-four grammes of urea daily; the destruction of albumen, therefore, increased more than fifteen fold. It would at first appear that if the same amount of albumen is STATISTICS OF NUTRITION. . 681 given to an animal as is lost during starvation, the destruction of the proteids of the tissues would cease. But since the administration of albumen increases the tissue waste this is not the case, and at least two and a half times as much albumen must be given as the body loses in starvation in order to preserve the balance. If enough of albumen is given to an animal to prevent its drawing on the albuminoids of its tis- sues, then the amount of nitrogen eliminated will just equal the amount contained in the food, and a nitrogenous balance is thus preserved. If, now, to such an animal a larger amount of meat is given, the eliminated nitrogen does not at first increase, and a certain amount of the nitrogen remains in the body to increase the albuminoids of the tissues. Soon, however, the nitrogen eliminated increases until finally a nitrogenous balance is again regained. Every increase in the albumen of the food has the same result—first, an increase in the store of pro- teids of the body, and then an increase of urea, until the nitrogen of the latter equals the nitrogen of the food. A maximum is soon, however, reached in which the limit of albumen which can be digested and ab- sorbed is attained. A similar state of affairs holds in animals in a condition of nitro- genous balance when the albumen of the food is diminished. At first there is no decrease in the amount of urea eliminated, so the albuminoids of the tissues must have been drawn upon to make up the excess of nitrogen in the urine over that of the food. Then in a few days the elimination of nitrogen becomes reduced, until again a nitrogenous bal- ance is regained. Every further decrease in the ration of albumen has the same effect—first, decrease of the store of tissue-albumen, and then nitrogenous balance. The minimum limit is then reached. When too small an amount of albumen is given in food to balance the tissue waste inanition then commences. These facts show that the requisite amount of albumen in the food to prevent excess of tissue waste is dependent on the store of albumen in the body, and that the better the body is nourished hy previous feed- ing the more food must be given to preserve a nutritive balance. Con- sequently, well-nourished animals require more food, badly-nourished animals less food, to preserve an equilibrium. The amount of albumen in the food has, also, an influence on the body fat. If a small amount of albumen undergoes destruction, fat must be given up by the body in order to supply the amount of carbon necessary to form CO,. If the body is rich in fat, and in consequence of abundant albuminous food a large amount of albumen undergoes de- struction, the fat decreases; but if only a little fat is stored up and still a large amount of albumen is given in food, and there is, consequently, a large destruction of albumen, all the nitrogen is eliminated in the urine, 682 PHYSIOLOGY OF THE DOMESTIC ANIMALS. while a part of the carbon remains behind to be stored up as fat. Con- sequently, the body may be kept stationary as regards its store of albumen and fat through the administration of meat alone, but then a large quantity is required. An increase in tissue-fat and albumen may also, to a slight degree, tuke place from the administration of albumen alone, but only in illy-nourished individuals. If peptone is given as food it is entirely destroyed, and the destruc- tion of the tissue-albumen is completely prevented; but there is no increase in the body albumen, thus showing that peptone is earlier destroyed than albumen and ean only partially replace the albumen of the food. If gelatin and gelatinous tissue (bones, tendons, etc.) are given exclusively the destruction of albumen does not cease, thus showing that gelatin cannot replace albumen. But if gelatin and albumen are given together the destruction of albumen is greatly reduced. (b) Feeding with Fat.—The influence of fat on the destruction of albumen is seen in the fact that in fasting animals the destruction of albumen is less in fat than in thin animals; this action is also seen in the administration of proteid foods alone, where the destruction of albumen is less in fat than in thin animals. Indeed, we have seen that in an abundant albuminous diet, whereby the excretion of urea is increased, in fut animals there may even be an increase in the body fat. If fat is given alone as food to a carnivorous animal the destruction of albumen is reduced but not prevented ; when large amounts of fat are given the fat of the body may even increase and yet the animals pass into a state of starvation, for the tissue-albumen is gradually being reduced. If enough albumen is given to cause a nitrogenous balance and then fat is added to the food, the nitrogenous elimination is reduced and all the carbon of the fat does not appear in the CO,; carbon is, therefore, kept back in the body and stored up in the form of fat, while a certain amount of nitrogen also being retained indicates an increase of the body albumen. So, the addition of fat to the food leads to both an increase of tissne-fat and albumen, though this only occurs when a large amount of fat is added to a moderately small amount of albumen. If the amount of albumen is increased the elimination of urea also increases, and, as a consequence of the great destruction of albumen, a certain amount of the fat is spared and is stored up in the body. But if the amount of albumen is reduced more fat is used, up,and fat may even be taken away from the body. The amount of fat in the body in feeding with albumen and fat is also of influence on the metabolism of the body; a body poor in fat, which needs and destroys more albumen, more readily stores up fat; STATISTICS OF NUTRITION. 683 while a body rich in fat, since it needs and destroys less albumen, must draw on its store of fat. Young animals, since they are thin, therefore need more albumen and fat than older ones, while young animals, to fatten, require more food than older ones. It is also easier to fatten thin animals than to make tolerably fat animals still fatter. (c) Feeding with Carbohydrates.—The action of the carbohydrates in nutrition is especially seen in the herbivora, which are incapable of being supported with albumen alone or with albumen and fat. Experi- ment has shown that in so far as they are digestible all carbohydrates have the same influence on the metabolism of the body. This applies to starch, cane-, grape-,and milk-sugar, dextrin, and,to a certain extent, to cellulose. It is generally assumed that all the carbohydrates which enter the animal body unite with the oxygen obtained in inspiration to form CO, and H,0, so that an increase in carbohydrate diet means an increase in the CO, of the expired air. This is not, however, universally true, since under many circumstances the carbohydrates may be retained in the body as fat; on the other hand, it cannot be positively stated whether the carbohydrates which are converted into sugar in digestion are directly oxidized as sugar, or are all first converted into glycogen. Feeding dogs exclusively with carbohydrates has proven that the destruction of tissue-albumen and fat is under such circumstances less than when the animal is deprived of all food, but that the destruction of albumen is constant, and that such animals finally perish from inanition. If albumen is given together with the carbohydrates in increasing quantities, the excretion of nitrogen increases correspond- ingly, but ina much less degree than when albumen alone or albumen and fat constitute the diet ; therefore the carbohydrates in food serve to spare the tissue change in proteids to a greater extent even than fat. Hence, to keep the body in a state of nutritive balance a moderately small amount of albumen is required with a large amount of carbo- hydrates, and, as a consequence, the herbivora are kept in good nutrition with the small amount of albumen found in their food. If the smallest amount of albumen is given with the corresponding amount of carbo- hydrates under which the body weight may be maintained without losing albumen or fat, and then the albumen of the food is increased, the elimination of nitrogen is -also increased, but to a less degree than if albumen was given alone; there is, therefore, now an increase in the albumen and fat of the body. If, now, the amount of carbohydrates is increased without diminishing the quantity of albumen in the food, fat then accumulates in the body; and if the albumen is also increased both albumen and fat accumulate. It is not yet quite clear whether this fat is formed from the carbon 684 PHYSIOLOGY OF TIIE DOMESTIC ANIMALS. of the albumen, as is generally acknowledged to be the case in the car- nivora, or whether fat may not also be formed from the carbohydrates directly. It thus seems clear that the addition of carbohydrates to the diet spares the waste of tissue-albumen and body fat, and the attempt has been made to determine the amount of carbohydrates which in their nutritive value are equivalent to a given amount of fat. This has been fixed by Voit at the ratio of one hundred and seventy-five to one hun- dred ; in other words, one hundred and seventy-five grammes of starch are equivalent to one hundred grammes of fat. Vv. THE FOOD REQUIRED BY THE HERBIVORA UNDER DIFFERENT CONDITIONS. The nutritive processes in the herbivora differ in many respects from those of the carnivora, In the first place, less albumen is destroyed during fasting by the herbivora than is the case in the carnivora. Thus, while in the example given above a dog weighing thirty-five kilos de- stroys daily one hundred and sixty-eight grammes of albumen, an ox weighing five hundred and twenty-two kilos only destroys twelve hundred and seventy grammes. So, also, the herbivora on feeding with carho- hydrates and fat show much less tissue waste than the carnivora, In other respects, with allowances for the different digestive peculiarities of carnivora and herbivora, the nutritive process may be said to be similar. It has been already stated that foods must not only contain repre- sentatives of the proteid, carbohydrate, and fat groups, with salts and water, but the different constituents must be present in definite propor- tions, which may, however, vary according to the demands on the animal. The proportion of albuminous to non-nitrogenous matter in food, 7.e., the proportion of albumen to starch and fat, is spoken of as the nutritive proportion. The average nutritive proportion is attained when the food contains one part proteid to from five to eight parts of non-nitrogenous matter, it being remembered that one hundred parts fat may be replaced _by one hundred and seventy-five parts carbohydrates; 1: 2-4 is spoken of as a narrower nutritive proportion, and 1:8-12 as a wider nutritive proportion. The natural food of the domesticated herbivora has a nutritive pro- portion of 1:4-1:7; thus, ordinary hay has a proportion of 1:5-1:7, and, although it may be regarded as the normal food of ruminants, is not suitable when there is a demand for rapid fat, milk, or work production. In grass the proportion is only 1:4-6, and on such foods cattle produce the most milk; young cattle thrive on it and rapidly put on flesh. Clover has a proportion of 1:5-6, but on account of its large percentage of cellulose is not completely digested, so it is usually combined with some more concentrated food. Before blossoming clover has a proportion of FOOD REQUIRED BY THE HERBIVORA. 685 1:4, or even 1:3, and its use then entails a waste of valuable proteids unless combined with chopped straw so as to bring the proportion down to 1:5. In the cereals the proportion on an average is 1:5-T, being broader in barley and corn than in oats, rye, and wheat; in the hulled fruits, malt, brewers’ grains, and distillery residues the proportion is 1:3, and in rape-seed cake 1:1-2. These latter fodders are, therefore, only applicable under special conditions. After this recapitulation we may consider the principles of feeding somewhat more in detail. Animals which have no work to do besides growing and keeping up their nutrition are nourished perfectly well by grazing if the grass is abundant and of proper composition ; this is the case for sheep, two- to three-year-old horses, and young cattle. If these animals are stall- fed, instead of being put to grass, on account of the perfect quiet and even temperature, the nutritive demands are reduced; so now feeding with hay or straw with some nitrogenous food suffices. A similar state of affairs holds in animals which are stall-fed without being worked, such as oxen in winter months, and the amount of food may here, also, be con- siderably reduced. The data showing the amount of food required are about as follows :— For unworked animals, for every one hundred kilos body weight, 2.5 kilos of solids in the grasses (green fodder) is sufficient; therefore, for the herbivora, for every one hundred kilos body weight, ten kilos of grass, containing 2.5 kilos of solids, and of this 1.3 kilos of digestible matters, is sufficient. In this amount 0.25 kilo is represented by albu- men, non-nitrogenous extractive one kilo, and fat 0.05 kilo; so the ratio of the amount of food to the amount of digestible matter is 1: 4.2. Thus, a horse weighing five hundred kilos may preserve a nutritive equilibrium on a daily ration of seven hundred grammes albumen, two hundred and ten grammes fat, three thousand seven hundred and fifty grammes starch and cellulose, and about twenty kilos of water; the ratio of nitrogenous to non-nitrogenous food being thus 1:5.5. Starch and fat may replace each other, seventeen parts of starch being equivalent to ten parts of fat. In the horse, the carbohydrates are more important heat-producing foods than is the case in man. Wolff has found that of the heat produced, 76 per cent. is due to carbohydrates, 13.5 per cent. to proteids, and 10.1 per cent. to fats. In a general way it may be said that for each kilo of body weight the herbivora requires daily one hundred and fifty grammes albumen, fifty grammes fat, and seven hundred and fifty grammes carbohydrates. Smaller animals require proportionately larger amounts, since the de- structive processes are more active in them. In fattening animals the carbohydrates must be increased; in milking animals the albuminous food-constituents. 686 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Experiment has proved that cattle preserve a nutritive equilibrium when they receive a daily ration calculated for ten hundred kilos of body weight, as follows :— 19.5 kilos clover-hay. Sar ne ‘* 13.0 kilos oat-straw, and 0.6 kilos rape-seed cake. 2.6 ce “ “cc 14,2 “cc “ce st “ce 0.5 “ce “ec ““ 3.2 ee “ec “ce 13.3 a3 barley ce “ce 0.6 (x3 “ce “e 25.6 ‘ fodder-beets, 12.6 “* oat ae ee AO «6 as In the above feeding the animals digested and absorbed for ten hun- dred kilos body weight on an average 0.57 kilo albumen and 7.4 kilos non- nitrogenous matter; hence, the nutritive proportion was 1:13. The above fodder contains on an average 0.05 kilo phosphoric acid, 0.1 kilo lime, and 0.2 kilo alkalies; in addition, for ten hundred kilos body weight, fifty-five kilos water were given. For pregnant animals which are not worked, as brood mares, pas- ture is suflicient; or if stall-fed, hay and straw, the latter with some nitrogenous food, will answer if the total composition is made to cor- respond with that of grass. If the grass and hay are not of the proper composition some accessory food must be added. Especial reference must be paid to the amount of albumen and salts in the food, such as lime and phosphates, as of special importance for the development of the osseous system of the young. In such cases some albuminous food rich in salts is necessary, such as grains. Male breeding animals which do not work must have their food so adjusted that they do not put on fat; not that the amount of organic matter may be reduced, but the food must be concentrated, have a small percentage of indigestible matter, and little water and much albumen. Es- pecially in the coupling season must the food be rich in albumen to make up for the losses through copulation. Fat stallions and bulls are not fruitful. Animals for labor require more than pasture; they require a large amount of albumen, for by it the muscles are enabled to appropriate a larger amount of oxygen; so,also, fat and carbohydrates must be increased, since they give to the muscles the substance which is consumed in muscular activity. Ifthe work is constant the carbon of muscles must always be in excess. Voluminous and watery food must be avoided. The former distends the alimentary canal, and so interferes with respiration, and the latter leads to an accumulation of water in the tissues, and reduces the tension and elasticity of the muscles. So the food must be concentrated, as oats and barley, which are especially valuable on account of-their fat. Cattle on moderate work require per thousand kilos body weight, from 0.7 kilo to 1.6 kilos albumen, non-nitrogenous matters from 8.4 to 12 kilos; the nutritive proportion should thus be 1: 7.5. FOOD REQUIRED BY THE HERBIVORA. 687 This proportion may be reached in the administration of suitable amounts of hay with some concentrated food, or clover-hay with chopped straw. When severe work is required it is advisable to increase the quantity of fat given (as by adding some oil-cake), the nutritive propor- tion being brought to 1:6. Working oxen can stand a larger amount of raw food (hay, etc.) than horses. If rapid work is required of horses, a rich albuminous food such as oats must be given; if prolonged work is demanded, one richer in fat, as corn, is better. If animals are fed for food purposes an increase in the solids and digestible matter of the food is requisite; so the appetite must be stimulated, and yet overloading of the alimentary canal avoided. It is, therefore, advisable gradually to increase the amount of the usual food, to stimulate the secretion by small quantities of salt, if possible, to aid digestion by a previous preparation of the food, such as by giving ground meal, and so to choose the foods that the waste of the organism will be at a minimum. At the commencement of such fattening, the organism must be made rich with albumen: so thin animals must receive a large amount of digestible food, with an extra proportion of fat and carbohydrates, since we have found that under such circumstances there will be least waste of albuminoids. This is accomplished by feeding for about two weeks with 2.5 kilos albumen and 12.5 kilos non-nitrogenous matters per thousand kilos body weight, thus giving a nutritive proportion of 1:5. Then the non-nitrogenous matters must be increased to from 12.5 to 16.25 kilos per thousand kilos body weight, so making the proportion 1:6.5. When the economy becomes rich in albumen and then commences to put on fat, the albumen of the food may be increased to 3.0 kilos, making a proportion of 1:5.5; when it becomes very fat, the solids, especially the indigestible solids, must be reduced, and some oil-cake added to the food. In fattening oxen the water given should be in the proportion of 4-5:1 of the solids given, in sheep 2-3:1. In fattening sheep it has been proved that highly albuminous foods are especially valuable. Ground beans may be used for this purpose (0.5 kilo daily) combined with hay. In fattening sheep the preparatory treatment necessary with cattle may be usually dispensed with, and the diet more rapidly changed from one poor in nitrogenous matters (1:5.5) to one rich in proteids (1:4.5). The diet for sheep must not be too rich in water, so beets are not as valuable as with cattle; the best results are obtained from feeding with good hay and a corresponding amount of crushed beans or cereals. Sheep fatten more rapidly after shearing than before, for then the appetite is better and the thirst less. Young animals which are designed for food purposes will slowly take 688 PHYSIOLOGY OF THE DOMESTIC ANIMALS. on flesh in a good pasture; if an accumulation of fat is desired, additional carbohydrates and fatty food must be given. As a rule, the hog is more readily fattened than the sheep, and the latter than the ox. Race is also of influence. Thin, full-grown hogs at the commencement of fattening require large amounts of food, forty kilos of solids per thousand kilos body weight. Good results are obtained by feeding with crushed barley, corn, or peas, the latter especially, if mixed with steamed potatoes. The use of buttermilk or sour milk enables the amount of food to be reduced and still give satisfactory results. For milk animals the conditions of food have been already consid- ered, and a good pasture is all that is required. When stall-fed, nutritive change is reduced; when food corre- sponding to pasture is given the quantity of milk and butter is increased. In wool-producing animals a larger percentage of proteids is required in the food than in cattle, goats requiring less than sheep. Experiment has proven that sheep (ninety-six kilos in weight) on feeding with hay for one thousand kilos body weight require daily twenty-six kilos, and of this digest 1.32 kilos albumen and 10.53 kilos non-nitrogenous matters (with 0.322 kilo fat). On such feeding the weight increased somewhat, 0.181 kilo albumen and 0.299 fat (reckoned for one thousand kilos body weight) being deposited. The nutritive proportion, therefore, for sheep should be 1:9.3. It has further been determined by Wendee and Hohen- heim that slight loss of weight, within limits, does not interfere with wool production, especially if the food be rich in proteids. By chopping food mastication is, to a certain extent, facilitated, but it cannot be regarded as a substitute for mastication, since the mixing with saliva can only be perfectly performed when the food is thoroughly masticated. The principal object in chopping food is to enable it to be mixed with other materials so as to increase its tastefulness and digesti- bility, or to assist in the administration of other substances. Chopping should never be carried so far as to permit of the food being swallowed without undergoing a certain amount of mastication. The cereals are especially suited for administration under the forms of meals and may be readily mixed with other foods. The readily digestible grains, of course, do not need to be ground, but in the form of meal they may be mixed with less digestible, bulky substances, such as chopped straw. Thorough mastication of the latter is so attained and the grain gives taste to the mixture, without which, probably, the food would be rejected. To horses and sheep all grains the hulls of which are not too hard and thick may be given uncrushed by mixing with chopped straw and the like as long as their organs of mastication are in good condition. Barley is best given to sheep when roughly ground, while the seeds of the legu- minous plants and corn may likewise be ground for sheep and horses. FOOD REQUIRED BY THE HERBIVORA. 689 Grinding of oats is only necessary for old horses or those in which the teeth are changing. Oxen and hogs, as a rule, digest the ground cereals better than the whole grains. According to Lehmann, of the entire grains in a fourteen-months-old ox 48.2 barley and 19.6 per cent. oats remained undigested. In a five-months-old ox 33.0 barley and 6.5 per cent. oats remained undigested. Even after mixing with chopped straw a large part of the entire grains escape digestion and pass through the faces almost entirely unchanged, and still possess the power of germination. Of one hundred kilogrammes of the unground grains fed to hogs Lehmann found in the feces 50.6 kilos of oats, 49.8 kilos of rye, 54.8 kilos of barley, and 4.8 kilos of peas. The experiment, therefore, points in the most emphatic manner to the administration to the ox and hog of all the cereal grains mealed and mixed with other foods. About the only exception to this statement is found in the case of oats. The chopping of dry fodder enables it to be mixed readily with large amounts of more tasty sub- stances. So, also, the young, tender, highly albuminous green foods may be chopped and mixed with less nutritious substances, such as straw. The transition of dry to green feeding and the reverse is facilitated by the mixture of the green fodder with dry, chopped straw. Horses should always receive good hay unchopped, but the straws of the cereals should always be given in a chopped state, since horses will only take the hard straw in small amounts. Chopped food for horses should not be shorter than from one and one-third to two centimeters in length of each piece, since smaller pieces readily lead to obstructive colic, especially if given with meal in a moist condition. For the ox, straw may be chopped into pieces two and one-half to three centimeters long, and mixed well with corn-meal or chopped beets or potatoes in order to make it more tasty. The duration of the interval between different times of feeding of the domestic animals is a matter of considerable importance. Too fre- quent feeding should be avoided on account of the shortening of the necessary pauses between the digestive processes. ‘The ruminants, espe- cially, should not receive more than at most three meals in the day, so as to allow time for rumination. Horses likewise should receive three meals and hogs from three to four meals a day. On the other hand, the inter- vals between feeding should not be too long, on account of the great increase of hunger so produced leading to faulty mastication and imper- fect insalivation of the food. This state of affairs may produce much more serious disturbance in the non-ruminants than in the ruminants. In young cattle from four to six meals may be given a day on account of the relatively smaller size of their stomachs, since three meals scarcely furnish enough to sustain them. So, also, when the fodder is especially fluid the meals may succeed each other every two or three hours, for in 44 690 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Norma Amounts oF Foop ror CaTTLe, Horses, SHEEP, AND SwINr. For every kilogramme of body weight the following amounts of digestible food-stuffs must be contained in the daily ration:— Nrrro-||N aN d GENO Souips. Mews ||. Exrra o7- Far. 2 | 3 ; TERS. IvE MAT- 3 3 TERS. & a tox | 2 CLASS OF ANIMAL. a|4 ald Fi d ral: AS m 513 Bis a [os a | 3 es | = ee al elelell e/a) al e)8lele | é BSL S HESS S/S SUE 2/8 ie 1B sa ele ialeialflalalalea;/a)/ald | 4 Kilogrammes 1. Young Cattle. 2-3 months old, 75 kg. weight, . 21.0 26.0 23.5'|3.0/5.0}4.0!| 9.5/12.5)11.0)/1.5 |2.5 |2.0 |}17.0 |1:4.0 3-6 months ‘old, 150 kg. weight, . 23.5)27.0/25.0.|3.0/3.5]3.0;| 9.5)12.0]11.0)'0.75]1.25}1.0 |/15.0 |1:4.2 6-12 months old, 250 kg. weight, 25.0/30.0/26.0;|2.0/3.0/2.5,) 9.5/12.0/11.0,0.4 |0.8 |0.6 |/14.1 |1:5.0 12-18 a old, 350 | kg. we 25.0/30.0/26.0)|1.8]/2.5}2.0), 9.5]11.0/10.5, 0.3 |0.5 [0.4 ||12.9 |1:5.7 ee old, 425 | kg. weight, . . 25.0 30.0) 26.0)|1.4/1.8}1.5)| 9.0/10.5} 9.5)0.2 |0.4 10.3 |/11.3 |1:6.8 2. Oxen. Atrest, . . . . . |/15.0,20.0)18.0),0.6/0 9/0.7 . 5.5] 7.0) 6 5, 0.1 10.2 |0.15\| 7.35)1:1.0 Working,. . . . . |/24. 0/28. 0|26.0)\1.4/1.8]1.6]; 8.0)10.0} 9.0 10.2 \0.4 0.3 |{10.9 /1:6.0 Severe working, . . |/24.0 32.0 28.0)|2.0)2.8/2.4 10.0 12.0]11.0]|0.4 10.6 0.5 |]13.9 11:51 8. Fattening Cattle. | Ist period, . . . . ||27.030.0:28.5)'2.3)3.0 2.5] 11.0/12.5)12.0/10.5 (0.7 |0.6 /15.1 {1:54 Dai ieee HB Bae 26.0 29.0127. 2,8/3.5|3.0] 11.0)12.0/11.5]/0.6 |1.0 |0.7 115.2 [L4.5 Bd * . . . ,, | 25.0)28.0:26.5 ie 3.3/2.7] 11.0]12.0}11.5}10.5 |0.8 |0.6 114.8 |1:4.8 4. Milk Cows. 21.0 32.0 26.0,2.2/2.8.2.5) 9.5/12.0110.0/10.3506 [0.4 |/12.9 |L-44 5. Horses. : Working,. . . . . |[21.0 27.0 24.0'1.6/2.0/1.8}| 8.0/10.0} 9.0/|0.5 |0.8 |0.6 |/11.4 {1:58 Heavy work, . . . |/23.0 30.0 26.5||2.5/3.0/2.8)| 9.0)12.0/10.5)10.6 |1.0 [0.8 |[14.1 1:4.5 6. Young Sheep. 5-6 months old, 28 kg. weight, . 28.0 32.0 30.0)|2.5}3.5]3.2|| 9.5/11.5]10.5}/0.7 1.0 0.8 |14.5 }1:4.0 6-8 months old, 33-34 kg. weight, . 26.0]28.0 27.0]}2.5/2.8]2.7|| 8.5/10.5] 9.5110.5 |0.8 0.6 ||12.8 |1:4.0 8-11 months old, 37— , 38 kg. weight, . 23.5]26.0)25.0112.0)2.5]2.1|| 7.5) 9.5) 8.5)/0.4 |0.8 0.5 [111 [147 11-15 Beane old, 41 kg. weight, . 23.5125.0/24.5'11.5|2.0|1.7]| 6.5! 8.5! 7.5|/0.3 |0.5 |0.4 |] 9.6 |1:5.0 15-30 months old, 49- || - 43 kg. weight, . . |/21.5 25.0,23.5 1.2/1.6/1.4]] 6.5] 8.5] 7.5//0.25]0.4 |0.3 |} 9.2 {1:60 FOOD REQUIRED BY THE HERBIVORA. 691 NormaL AMOUNTS OF Foop For CaTTLE, Horses, SHEEP, AND SWINE. ( Continued.) Nuit ro-|| Non-NITRO- 3 SoLips. Mae EXTRACT. FAT. 3 3 TERS, IVE MAT- bat % TERS. 3 3 = : : : : as | & CLass OF ANIMAL. : j E d d|¢ g| S 2 3 3 Si. ae ele lalalalzigialeialaie | 3 2/8 & & Ba 3 2/2 (2 2/2/22 (2/2 2/2/24 | 2 Kilogrammes. 7. Wool Sheep. | Coarse-wooled sheep, . |/19.0 24.0/22.0]/1.0,1.5/1.2)) 6.5) 8.5) 7.5)/0.1 [0.3 0.2 || 8.9 |1:6.7 Fine-wooled sheep, . ||21.5,27.0/24.5 a 1.5]| 7.5} 9.0} 8.5}/0.2 |0.4 |0.3 |/10.3 |1:6.2 8. Rams. . ||23.5 27.0/25.0} 2.0 2.5:2.2)) 9.0)12.0/10.5)}0.4 |0.6 0.5 |}13.2 |1:5.3 9, Fattening Sheep. Ist period, . . . ~ |/27.032.029.0/ 2.5 3.5 3.0/11.013.012.0/0.4 0.6 (0.5 115.5 1:45 2d“ yw... |/25.0/30.0/27.0):3.0,.4.0 3.5/)11.0,12.0,11.0)]0.5 |0.7 |0.6 |/15.1 41:3.5 Non-Nitro- genous Ex- : tractive 10. Young Pigs. Matters and 2-3 months old, 25 kg. — weight,. . . . . |/50.0/58.0|54.0||7.0 ae 26.6)31.0 28.5 3-5 months old, 33-50 kg. weight, . . . eles 44.0] 5.0/7.0 6.0)|22.0)26.0)24.0 5-6 months old, 62-63 ae ween gon ee 41.0]/4.0)5.0/4.5)/ 20.0/24.0)22.0 months old, 85 kg. ‘ weight,, . . .. eae 35.0||3.0}4.0/3.5)/18.0 20.0)19.0 -12 months old, 125 kg. weight, . . . //24.0,30.0/27.0)/2.5}3.5/3.0 15.0 18.0/16.5 11. Fattening Pigs. Ist period, . . . . //45.0 48.0146.0)/4.516.0/5.0 )24.5)26.5/26.0)).. . |... |... 81.0 1:5,2 dd. 6. . |[87.0/45.0/40.0/'3.5)4.5]4.5,/21.0/24.5123.0), ..)...).. .|[27.0 [1:58 3d ©... . . |]26.033.0.30.0 2513.5 3.0 |17.0|19.0/18.0 ]...]... |... |/21.0 |1:6.0 12. Breeding Pigs. (Sows and Boars),. . 126.0 32.0 32.0 1.5 2.0/1.8 )1.25)15.0/14.0)...|... |... [15.8 [1:78 cs aa | a | this condition the stomach rapidly empties itself and the feeling of hunger again appears. So, also, when feeding with dry fodder is com- menced it is better at the beginning to give at least four different meals, So as to avoid overdistention andfilling of the stomach with this more bulky food. At the end of fattening the meals may be increased in number and reduced in amount, digestion of small amounts of readily digestible foods being now more readily accomplished. 692 PHYSIOLOGY OF THE DOMESTIC ANIMALS. VI. HUNGER AND THIRST. The sensations which lead to the prehension of solid and liquid foods are known as hunger and thirst. It was previously supposed that hunger was a local sensation which was produced by the absence of food in the stomach. Evidently this is a mistaken idea, else would the rumi- nants never experience this sensation, for in them the stomach is never free from food, even when death occurs from starvation. The appear- ance of hunger coincides with absorption of the matters digested at the previous meal. Although the sensation is apparently referred to the abdomen, it cannot be regarded as a localized sensation, but rather as a peculiar moditeation of the general system similar to that produced in dyspneea; nor, indeed, is the stomach even the starting point of hunger, for the pneumogastrics, the sensory nerves of this organ, may be divided, and if the animals be deprived of food the clearest evidences of hunger are, nevertheless, capable of detection. In spite of this fact, the sensation of hunger is, nevertheless, to a certain extent dependent upon the con- dition of the stomach, as is indicated by the temporary relief of hunger which follows introduction into. the stomach of matter which is not in the slightest, respect nutritious. So, again, even when the stomach is filled with food, if through any disease digestion or absorption or the passage of food into the small intestine are interfered with the hunger may, nevertheless, be intensely felt; and, again, even after a hearty meal digestion may be complete, and the stomach empty for some time before the sensation of hunger appears. In the case of thirst the state of affairs is somewhat similar, except that there the sensation is more distinctly localized in the fauces and may be relieved by the application of moisture to that part. When an animal is deprived of liquid, the blood, from the continued formation of secretions and excretions, rapidly loses its normal percentage of water. The sensation of thirst is evidently due to the irritation of the sensory nerves of the mucous membrane of the pharynx produced by: the drying of the mucous membrane, and while it may be relieved, as already mentioned, by moistening this part, the arrest of thirst is only temporary. But, on the other hand, the thirst may be permanently relieved by the injection of water into the veins and even by enemata of water, and while thirst, therefore, has a local expression, like hunger, it represents the needs of the economy for water; thirst may thus be abolished, even although no water enter the mouth. Every cause, therefore, which diminishes the proportion of fluid in the blood, whether intense heat or exercise which favor cutaneous and pulmonary evaporation, dropsies, abundant hemorrhages, or diabetes, all lead to thirst; so, also, Bale occasion thirst by withdrawing rater from the blood. SECTION XIII. ANIMAL HEat. Ir has been seen that the income of the animal body is represented by complex combinations of carbon, hydrogen, nitrogen, and oxygen, and the introduction of free oxygen in respiration; the outgo of the body, on the other hand, is represented by similar combinations of the same elements in the form of carbon dioxide, water, and urea. The conclusion is thus evident that the absorbed oxygen has within the body undergone combination with carbon and hydrogen with the production of carbon dioxide and water, and that the substances intro- duced as food have all in different degrees united with oxygen. In other words, the nutritive processes in the animal body are represented by a series of oxidations by which the organic food-produets are restored to the inorganic form. Oxidation of any kind will invariably be accom- panied by a production of heat, and we thus see that one of the principal sources of the heat of the animal body is to be looked for in such pro- cesses of oxidation. It is a well-established fact that the combustion of any body, whether rapidly or slowly produced, is accompanied by the evolution of a fixed quantity of heat, provided the energy be not other- wise employed. . Thus, the complete combustion of one gramme of sugar invariably corresponds to the development of four heat-units.* If this combustion takes place in the animal body, it is evident that the same amount of heat must be developed, no matter what may be the character of the substances developed between the starting point and the final termination of the process of oxidation. In the animal body, however, such processes of combustion are rarely as complete as would occur in the incineration of food-stuffs outside of the body. Thus, for example, in albumen the process of oxidation results in the formation of urea, which itself is capable of still further oxidation. Nevertheless, it may be stated with a tolerable degree of accuracy how much-heat is set free in such processes of oxidation of the food-stuffs in the animal body. Knowing the amount of heat developed in the oxidation of one gramme of albumen and the amount developed in the oxidation of a proportionate quantity of urea, deducting the latter from the former will evidently represent the & * By this term, heat-unit, is meant that amount of heat which is required to raise one llogramme of water from 0° C. to 1° C, ; (693) 694 PHYSIOLOGY OF THE DOMESTIC ANIMALS degree of oxidation occurring in the animal body. This factor has been estimated as corresponding to five heat-units. With these data the amount of heat developed in twenty-four hours may be readily calculated. Thus, taking the example given by Fick, the income of the body was represented in round numbers by one hundred and twenty grammes of fat, two hundred and sixty-three grammes of carbohydrates, and one hundred and seventeen grammes of albumen, with the excretion of thirty-nine grammes of urea. The combustion of one gramme of fat is represented by the development of nine and six-tenths heat-units, and, as already seen, one gramme of carbohydrates by four heat-units, and one gramme of albumen by five heat-units. The total amount of heat, there- fore, developed is represented by 120 XK 9.6 4+ 263 X 4 +117 X 5, or, in round numbers, two thousand eight hundred heat-units. The confirma- tion of these figures and their influence in maintaining the heat of the animal body is determined by calorimetric experiments. To accomplish such an experiment, first, the tissue change in twenty-four hours must be calculated; second, the amount of heat liberated by the body in that time; third, the average temperature of the animal body at the com- mencement and end of the experiment; and, fourth, the average heat capacity of the body. As a rule, the difference between the body tem- perature at the commencement and end of such experiments is so slight as not to deserve attention, and the amount of heat set free in twenty- four hours may be regarded as indicating the amount of heat developed in the body. Such experiments do not, however, serve with absolute accuracy to confirm the theoretical figures deduced from the co-efficient of heat production represented above as belonging to the different food-stuffs. In nearly all cases there is an apparent loss of heat over what should be expected from these data. It is to be recollected, in the explanation of this discrepancy, that the energy set free in such oxidations may take on the form either of heat or of mechanical work. In the animal body all these sources of loss of energy occur. All forms of muscular move- ment are accompanied by liberation of energy, and a continual loss of heat is taking place through radiation from the surface of the body, by conduction, by the evaporation from the skin and mucous surfaces, and by the warming of the ingesta. The amount of heat dissipated by the animal body ina condition of health is in close dependence upon the amount produced, upon the difference in teiperature between the animal body and the surrounding medium, and especially upon the relationship between the external surface of the body and the body weight. Thus, small animals for each kilogramme of the body weight set free more heat than large animals. It has been estimated that for each kilogramme of body weight the horse in each hour sets free two and one-tenth heat- ANIMAL HEAT. 695 units; sheep, two and six-tenths heat-units; the dog, four heat-units ; and the sparrow, thirty-two heat-units. The cause of this difference may be found in the fact that the smaller a sphere.the greater is its superficial area in comparison to its cubic contents. The same rule applies, also; to the irregular form of the animal body, in which the smaller it is in pro- portion to the weight of the animal the greater will be its superficial area. It is, however, from the external surfaces that the greatest amount of body heat is dissipated, and it is, therefore, seen why small animals lose proportionately more heat than larger animals. Two different conditions are noted in reference to the heat which is retained in the animal body, and which, therefore, causes the body tem- perature. In the cold-blooded animal the temperature of the body is not constant, but varies with that of the surrounding medium, rarely being more than a few tenths of a degree above it. In the warm-blooded animals, as in mammals and birds, on the other hand, the body tempera- ture is, as a rule, higher than that of the surrounding medium, and is independent of variations in the latter. The cause of this difference of body heat lies in the difference in energy of the tissue changes. In the cold-blooded animals the development of heat is so slight that this amount of heat is at once given up to the cold atmosphere. If the ex- ternal temperature be increased, this dissipation of heat is accordingly diminished, and as a consequence part of the heat produced is retained in the body and increases its temperature. On the other hand, if the external temperature falls, the amount of heat dissipated is increased and the body temperature falls. In animals with a constant body tem- perature the amount of heat, on account of the greater energy of tissue change, is so much greater that but a part alone is given up to the sur- rounding medium. From the fact that the source of temperature is found in the chemical changes o¢curring in the tissues, it is evident that the development of heat will be greater in tissues in which such processes are active than where they are sluggish. The temperature of the animal body will, therefore, vary in different localities ; it will be greater in secreting glands and contracting muscles; it will be less where loss of heat is favored, and, as a consequence, the exterior surfaces of the body will possess a lower temperature than the inner cavities. In the lungs the blood gives up so much heat to the air that the temperature of the blood in the left side of the heart is cooler than that of the right, in spite of the development of heat which accompanies the oxidation of hemoglobin. With this exception the arterial blood, as , ‘being less exposed to loss of heat, may,as a rule, be stated to be warmer than venous blood. The temperature of an organ will, therefore, depend upon the amount of blood circulating through it. Under certain circumstances the venous 696 PHYSIOLOGY OF THE DOMESTIC ANIMALS. blood may increase in temperature over that of the arterial blood ; such a state of affairs is seen in the blood coming from the contracting muscles or from a secreting gland. The blood by its continuous circulation through the body tends to equalize the body temperature, giving up heat to tissues which are cooler than itself and withdrawing heat from those which are warmer. The mean between the highest and lowest temperature of the animal body is spoken of as the body temperature, and is generally represented by the temperature taken in the mouth or in the rectum. The following figures represent the mean average temperatures of the different domestic animals :— Horse, . : ‘ 7 . % . 87.59 to 38° C, Ox br og : ‘ Z ; : > . 88° to 38.59 C. Dog, . _ F * . A F . 88.59 C, Sheep, . , $ y . . . 3899 to 40°C. Chicken, ; a - < i . 420C, Hog, . : ‘ ‘ 3 : 3 . 89° to 400 C. Ass, ‘ , : F ‘ ‘ ‘ . 89.59 to 88° C. Rabbit, . : é F z : : . 89° to 89.59 C. Mouse, . ‘ F 5 ‘ 5 F » 411°C. Cat, 5 ‘ ‘ ‘ é P 5 . 388.59 to 39° C, Goose, . . is ‘ : ‘ , » 415°C, Pigeon, . . P . . é . 420C, While these figures represent the average body temperature, varia- tions within narrow limits may often be observed even in perfectly healthy individuals. A variation of one degree or more indicates some failure in the organism or some departure from the natural process of metabolism. It is, therefore, evident that the mechanisms which regulate the balance between the production and loss of heat must be extremely sensitive. Such a regulating mechanism will prevent an increase of the body temperature either by diminishing the production or increasing dissipation of heat, or, in the other case, by increasing the production and diminishing the loss. Heat, as already indicated, is lost to the body by conduction to the ingesta and egesta, to the expired air, and by conduction and radiation from the skin and through the evaporation of fluid from the surface of the body. The relative amounts of heat lost by these. different channels have been calculated by Helmholtz as follows: through the expired air, 5.2 per cent.; through the water of respiration, 14:7 per cent.; through . the skin, 77.5 per cent. The chief means, therefore, of heat dissipation are through the lungs and skin. The more rapid the respiration the greater will be the loss of heat, and in animals which do not perspire the lungs will represent the main source of heat dissipation, In other animals the skin is, no doubt, the great regulator of the body temper- ture. The more blood passes through the cutaneous vessels, the greater will be the loss of heat through radiation, the greater will be the cuta- ANIMAL HEAT. 697 neous secretion, and, as a consequence, the greater will be the loss of heat through evaporation. Everything, therefore, which dilates the cutaneous blood-vessels will increase the heat dissipation. The working of the mechanism of heat regulation through increasing heat dissipation is well seen in the case of exercise. Every muscular contraction, as already pointed out, leads to an increase of heat production, and, as a consequence, the blood coming from a contracting muscle may be several degrees warmer than the arterial blood supplied to it. Nevertheless, the body temperature, even in severe exercise, is but little elevated above the - average, for the increased exercise leads to an increased demand of oxygen in the inspired air, and, as a consequence, respiration is increased and the amount of heat eliminated through the expired air thereby aug- mented. The action of the heart is likewise accelerated, the circulation through the skin is augmented, perspiration is increased, and a greater amount of heat is given up from the skin by radiation and by the evapo- ration of the perspiration. By this means enough heat is lost to the animal body to balance the increased production. Increase of external temperature likewise prevents an increase in the body temperature by increasing the circulation through the skin and the cutaneous perspiration, and so also increases the loss of heat. On the other hand, if the external temperature is reduced the cutaneous vessels contract, the evaporation of perspiration is prevented, and again a balance is struck between the production and the heat dissipation. The influence of the nervous system on the temperature of the animal body is both directly and indirectly exerted. It has been men- tioned in a previous section that division of the cervical sympathetic nerve is followed not only by contraction of the pupil, but also by an increased temperature of the corresponding side of the head and neck. If this experiment be performed upon a rabbit the increase of tempera- ture is so great as to be readily perceptible to the touch; and if the ears of the rabbit be examined in transmitted light the blood-vessels of the auricle on the side of section of the sympathetic will be found to be greatly dilated. Section of the sympathetic, therefore, by paralysis of the vaso-motor nerves, has occasioned dilatation of the blood-vessels, and the consequent increased vascularity facilitates radiation of heat and so causes a perceptible increase in the temperature of the part. But the increased radiation of heat is also attended with increased heat produc- tion; for the hyperemia produced by vaso-motor paralysis is accom- panied by increased nutritive activity, and heat production is thereby - augmented. Thus, it has been shown by Bidder that excision of a part of the cervical sympathetic in the rabbit is followed within two weeks by a marked increase in the size of the ear on the side of operation; and excision of the celiac plexus has been said to produce intense hyperemia 698 PHYSIOLOGY OF THE DOMESTIC ANIMALS. of the stomach. Numerous instances of pathological increase of nutri- tive activity from increased blood supply and consequent increased tem- perature will doubtless suggest themselves, In addition to this indirect influence of the nervous system through the vaso-motor nerves on calorification, the central nervous system is stated to both directly and reflexly govern the development of heat, though much of the evidence brought forward as to a special nervous mechanism for regulating animal heat is imperfect. Experiments have ‘chiefly been directed toward locating special heat-centres in various parts of the brain. Ott claims that there are four localities in the brain irritation of which increases bodily temperature by from 2.2° to 3.3° (C. These heat-centres are said to be located as follows: 1. In front of and beneath the corpus striatum. 2. The median portion of the corpora striata. 38. Between the corpus striatum and the optic thalamus. 4. The anterior inner end of the optic thalamus. , and is shown in the un- broken line; the latent period, therefore, is indicated by the distance from « to +. The time taken up in the passage of the nerve impulse in the length of nerve between 1 and 2 is indicated by the distance be- tween b and D/, and may be measured by the tuning-fork curve below. The distance between these curves is exaggerated for the sake of simplicity, no value being given for the rate of vibration of the tuning-fork. mum contraction is reached relaxation commences, following the same general course as in shortening, relaxing first slowly then more rapidly, and then more slowly again, the general duration of the active relaxation being somewhat longer than that of contraction. Such are the general characteristics of the curve of a single muscular contraction produced by a single stimulus. If a single stimulus be allowed to follow the first it will be followed, UALS IER ran renee ean Sn a Fig. 280.—TRACING OF A DOUBLE MUSCLE CURVE. (foster.) (To be read from left to right.) While the muscle was engaged in the first contraction (whose complete course, had nothing intervened, is indicated by the lower line in the muscle-curve) a second induction shock was thrown in at such a time that the second contraction began just as the first was beginning to decline. The second curve is seen to start from the first, as does the first from the base line. like the first, by a single muscular contraction. If the interval between the second and first muscular contraction be gradually reduced, a point will ultimately be reached in which the second stimulus enters the nerve before the contraction produced by the first has passed off. The result will be that the muscle will undergo a second shortening, and such a PHYSIOLOGY OF MOVEMENT. 715 curve will be produced as is represented by Fig. 279. The two con- tractions are thus added together and the total shortening may be nearly double that produced by a single contraction (Fig. 280). If a third stimulus is then allowed to pass into the nerve before the second contraction has passed off, a third contraction will be added to the second, and so on in the case of the fourth, fifth, or more. It will be, however, noticed that while the second contraction may be nearly or quite as extensive as the first, the third and fourth progressively decrease in extent, until finally simply a broken line without any extensive increase in contraction will indicate the entrance of the separate stimuli, the stimuli merely serving to keep up the contraction already produced. When the stimulation ceases the muscle then rapidly passes into a condition of rest, relaxation occurring very rapidly. weereweewwe PUUWUW UNCC PETUU TUTOR RUE UWELE PD ENUNTaNwEY @ ru FL ru mr 3 Fa FG. 281.—MUsSCLE THROWN INTO'TETANUS WHEN THE PRIMARY CURRENT OF AN INDUCTION MACHINE IS REPEATEDLY BROKEN AT INTERVALS OF SIXx- TEEN IN A SECOND. (Foster.) (To be read from left to right.) The upper line is that described by the muscle. The lower marks time, the intervals between the ele- vation indicating seconds. The intermediate line shows when the shocks were sent in, each mark corre- sponding to a shock. The lever, which describes a straight line before the shocks are allowed to fall into the nerve, rises almost vertically (the recording surface moving slowly) as soon as the first shock enters the nerve ata. Having risen to a certain height it begins to fall again, but in its fall is raised once more by the second shock, and that to a greater height than before. The third and succeeding shocks have similar effects, the muscle continuing to become shorter, though the shortening at each shock is less. After a while the increase in the total shortening of the muscle, though the individual contractions are still visible, almost ceases. At } the shocks cease to be sent into the muscle, the contractions almost immediately disap- pear, and the lever forthwith commences to descend. The muscle being only slightly loaded, the relaxa- tion is very slow. When the separate stimuli do not follow each other more rapidly than sixteen in a second, the contraction produced by one stimulus has had time to undergo partial relaxation before the following stimulus enters; as a consequence, the point of the lever traces a broken line on the traveling surface (Fig. 281). If, however, the stimuli follow each other more rapidly than this, an apparently constant shortening is produced, in which no variation what- ever in length can be made out. The gradual production of this state of affairs indicates that this apparently constant and uniform contraction is, nevertheless, made up of a large number of individual contractions -added to each other. Such a condition is spoken of as tetanus, and the 716 PHYSIOLOGY OF THE DOMESTIC ANIMALS. curve produced in such a tetanic muscular contraction is represented in Fig. 282. Tetanie contraction requires for its production at least a greater number than sixteen stimuli per second. It may thus be most readily produced by the employment of a rapidly interrupted induction current, Tetanus may, however, also be produced by mechanical stimulation, provided the impulses succeed each other with sufficient rapidity. In the case of chemical stimulation tetanus is the ordinary expression of mus- cular contraction. It is thus evident that the tetanic contraction is composed of a series of vibrations of the muscular fibre, and, as would be expected from this statement, is accompanied by the production of a musical note, the pitch of the note depending upon the number of vibrations of the muscular fibre. Wherever the muscle is artificially thrown into tetanus, as by the action of an interrupted induced current, the number of vibrations, of course, corresponds to the number of contractions, these depending e é a Fig. 282.—TETANUS PRODUCED WITH THE ORDINARY MAGNETIC INTERRUPTER oe AN INDUCTION MACHINE, THE RECORDING SURFACE MOVING SLOWLY, ( Foster.) (To be read from left to right.) maximum of coutraction: Thuis coutinued itll ab cr when the aucsent is atay ol and sainaation commences. * upon the number of interruptions of the current, and, as a consequence, the number of vibrations of the muscle and the corresponding note pro- duced have a pitch which corresponds in vibration to these data. When the ear is placed over a muscle which is thrown into contrac: tion by means of the will a musical tone is likewise appreciated. This serves to indicate that even in a single sharp contraction of a muscle through the action of the will, that apparent single contraction is made up of a number of contractions, and every single muscular movement of the animal body is, therefore, of the nature of a tetanus. The musical note heard indicates that the rate of vibration is 19.5 per second. We may now study the changes which occur in contracting muscle in somewhat more detail. The most obvious is, of course, the change of form. Such a change of form is represented by a decrease in the long axis of a muscle, the shortening, perhaps amounting to three-fifths, of the oD length of the muscle, with a corresponding increase in the cross diameter. PHYSIOLOGY OF MOVEMENT. 717 There is no actual change in bulk in muscular contraction, the increase in thickening being almost precisely proportionate to the decrease in length. “NOILOVHINOD UVTINOSAW JO TAVM AHL 20 XLIDOTIA THL ONIMASVATY WOT SALVUVAITIy—‘Ese ‘ONT (-Aawmyg) .. This fact may be demonstrated by connecting the sciatic nerve of a frog’s leg _ with the poles of an induction machine and then placing the leg in a bottle filled with dilute saline solution, in the stopper of which is inserted a capillary tube. Care should be taken that no air-bubbles are present in the bottle, that the bottle is filled, and that the fluid ascends up a certain distance in the capillary tube. If the leg is then thrown into contraction by passing a current through the wires, 718 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the level of the fluid in the capillary tube will remain almost constant, thus indi- cating an absence of change in the bulk of muscle, for a decrease would, of course, be indicated by a fall of fluid, and increase of bulk would raise the fluid in the capillary tube. By extremely accurate measurements a slight actual decrease in volume may be made out. Thus, Valentine has determined that a muscle witha volume of two thousand seven hundred and six cubic centimeters in contraction in tetanus is reduced to two thousand seven hundred and four cubic centimeters, while its specific gravity increases from 1061 to 1062. When a muscle is thrown into contraction, it does not occur sim- ultaneously in all the muscle-fibres. If a muscle-fibre be placed under a microscope and then thrown into contraction a wave of undulation may be seen to be rapidly propagated from one end of the fibre to the other. This wave is especially sensible if the muscular fibre is fixed at each extremity. If a long muscle, such as the sartorius of the frog, have its motor nerve-filaments paralyzed by curare, and the muscle then thrown into contraction by stimulating one extremity with an induction current, the wave of contraction travels so slowly as almost to be capable of being seen by the eye. If such a muscle be supported Fria. 284.—CURVE ILLUSTRATING THE PROPAGATION OF THE WAVE OF MUSCULAR CONTRACTION. (Marey.) The lower of the two straight lines represents the point of the Jever resting on the muscle nearest the point of stimulation. If the time between the moment of commencing contraction at this spot and that of commencing contraction at the spot on which the second lever rests be measured by counting the vibra- tions of the tuning-fork, the rate of progression of the contraction may be determined. horizontally and two light levers be placed at a distance from each other bearing on the muscle and writing over each other on a recording sur- face (Fig. 283), if the muscle be then thrown into contraction by direct stimulation the levers will not be elevated simultaneously, but a curve similar to that represented in Fig. 284 will be produced. By measur- ing the distance between the commencement of these two contractions and knowing the rate of movement of the recording surface, the rate of progression of the wave may be calculated. If, instead of stimulating the muscle, the nerve (in such an experiment) be stimulated, if no curare have been given both levers will be simultaneously elevated. According to Bernstein, the rate of progression in the muscles of. cold-blooded animals of the wave of contraction is about two to three meters per second. Its rate of progression is much more rapid in the case of warm-blooded animals, PHYSIOLOGY OF MOVEMENT. 719 The irritability of muscle is subject to great variation, and a single irritant is, under different circumstances, capable of producing different results. In an excised muscle the irritability rapidly disappears, although it persists much longer in the muscles of cold-blooded animals than in warm-blooded. In the latter case the irritability of warm-blooded muscles may be somewhat prolonged if the animal be artificially cooled before death. Temperature is of great influence on the irritability of muscle, both an increase or decrease above the normal temperature of the muscle being followed by a decrease in irritability. Again, through repeated contrac- tion the muscle loses its power of being thrown into contraction; it is then said to be in a con- dition of fatigue, due either to the insufficient supply of nutritive substances or to the accumu- lation of the products of decomposition, which, as has been experimentally demonstrated, pro- duce a hurtful action upon the muscle-fibres. In all probability both of these factors are concerned in fatigue. When a contracting muscle is examined under the microscope marked changes in structure may be made out. If a living mus- cular fibre of an insect, for example, which is especially fitted for such study, be examined under the microscope while contracting, a wave of contraction, as already mentioned, may be seen traveling along the surface of the fibre, while at the same time the transverse striations Fre, 285.—MuscuLar Finre approach each other. In the contracted portion fo ee ae each disk has become shorter and broader, while ae — : The muscle is that of Telephorus the band which in a relaxed muscle is light, melanurus treated with osmic neid. : Vhe fibre at ¢ is at rest. at @ the con- in a contracted muscle becomes dark, and the traction begins, at b it has reached its maximum. The right-hand side of band which ina relaxed muscle was dark in the 2, 223,88 iu, caine Hore ae contracted muscle becomes light (Fig. 285). In the process of contraction chemical changes occur; these have been already to a certain extent indicated. The muscle in which reaction was alkaline, in contraction becomes acid through the development of sarcolactic acid, which may even be excreted by the kidneys. During its contraction the muscle absorbs more oxygen from the blood than during its stage of rest, and, as a consequence, venous blood from a resting muscle contains 8.5 per cent., that from a contracting muscle 12.8 per cent. less oxygen than the arterial blood; while the venous blood from a resting muscle contains, as an average, 6.7 per cent., that from a 720 PHYSIOLOGY OF THE DOMESTIC ANIMALS. contracting muscle 10.8 per cent. more carbon dioxide than arterial blood. The amount of oxygen consumed, as may be noticed from these figures, bears no relationship to the amount of carbon dioxide liberated ; whence it follows, as already stated, that the formation of carbon dioxide in a contracting muscle is not a simple process of oxidation, but rather the splitting up of some complex compound. During contraction the glycogen of the muscles becomes reduced, while, on the other hand, there is an increase in the amount of kreatin obtainable from the contracted over that found in the resting muscle. The question, What is the source of the carbon dioxide and lactic acid developed by a contracting muscle? may, perhaps, be answered by the statement that they are derived neither from the albuminous nor fatty constituents of the muscle, but from the carbohydrates, especially from the glycogen, which may even entirely disappear during the stage of contraction of a muscle, even although the amount of nitrogenous decom- position products in the muscle is not increased and the amount of fat not diminished. From the greater demand of oxygen by a contracting muscle we find, as a consequence, a greater increase in the supply of the arterial blood furnished to a muscle in contraction. When a muscle contracts, its arterioles dilate, more blood passes through the muscle, and, as a consequence, the removal of the increased carbon dioxide formed is facilitated. It would appear from this that the source of muscular force is found, not, as was formerly supposed, in the breaking up of albuminoids, but in the chemical changes occurring in muscle which are evidenced by the breaking up of the carbohydrates. This statement may appear contradictory to common experience, which teaches that animals fed with albuminoids do more work than those fed on a diet less rich in albuminoids. Our studies on nutrition have, however, indicated that a large supply of albuminous matter renders possible the use of the larger amount of carbohydrates. This will, perhaps, explain the fact that well-nourished herbivora are able to develop more force than the apparently much more powerful carnivora, and that the activity of muscle does not increase the breaking up of albuminates but increases the elimination of carbon dioxide. The few examples in which muscular work is accompanied by an increased excretion of urea, such, for example, as may be occasionally seen in the horse, are only to be accounted for by the insufficiency of the quantity of carbohydrates administered in the food, this insufficiency necessi- tating a destruction of the proteids for the development of force. As might be supposed from the above, every muscular contraction is accompanied by an elevation of temperature. Such a heat production may be determined experimentally by a thermometer, and, in a general way, it may be stated that within certain limits the greater the work PHYSIOLOGY OF MOVEMENT. : 721 demanded of a muscle, in other words, the greater the resistance to be overcome, the greater will be the amount of heat production; and, asa consequence, in a contracting muscle, not only is energy liberated but heat is developed, which is capable of being converted into actual energy. The heat development of a contracting muscle is not only dependent upon the amount of work done, bet also on the tension of the muscle, and the heat production reaches its maximum when the tension exerted on the muscle is so great that it is not able to contract. Since a muscle in contracting is capable of lifting a weight, it is, therefore, likewise capable of accomplishing work. The amount of work will depend upon the size of the weight, upon the distance to which the weight is lifted, and upon the time during which this lifting con- tinues. It was found that the degree of contraction was proportionate to the degree of stimulation. Therefore, the maximum amount of work capable of being produced by a muscle is accomplished when the maximum weight is lifted. The amount of work which a muscle may perform is, therefore, equal to the product of the weight lifted and the height to which it is lifted: thus, if a muscle contracts where no load is present, it accomplishes no work; or, if it be loaded beyond the point at which the load may be lifted, again no work is accomplished. If the weight be gradually increased, even although it may be lifted, the height to which that lift is accomplished becomes reduced, and, as a consequence, the work diminishes. . The amount of work which a muscle may accomplish is greater in proportion to the transverse section of the muscle, for the longer the muscle the greater is the shortening, and, accordingly, the higher the lift. In muscles within the animal body the amount of shortening which they may attain is never capable of reaching the maximum obtained in a similar excised muscle. The force with which a muscle contracts is greater at the commencement of contraction, and, when a muscle begins to contract, it can, therefore, lift the largest load. If a muscle loaded with a weight be stimulated with a rapidly interrupted induction current, after the muscle has once contracted no further lift is produced and no external work is evident; but if the muscle sustain a weight at the height to which it raised it, the amount of work, in this case the amount of energy developed by the prolonged contrac- tion of the muscle, is converted into heat. When a musele is stimulated with a feeble induced current and the current then gradually increased in strength, it will be found that the height to which the load may be lifted increases with the strength of the stimulus. (d) The Electrical Phenomena in Muscle.—If the gastrocnemius muscle of the frog be excised and its tendinous insertions cut off, and two 46 722, PHYSIOLOGY OF THE DOMESTIC ANIMALS. points of this surface, or the longitudinal surface of the muscle and the transverse section, be connected by non-polarizable electrodes with a sen- sitive galvanometer, at the moment of making the contact a deflection of the galvanometer needle will take place, indicating the presence of a _ galvanic current. The strongest effect is produced when one point of the transverse section and one point of the longitudinal surface are con- nected with a galvanometer; even single fibres, nevertheless, if’ brought into connection with a galvanometer also develop galvanic currents. The direction of the current is from the longitudinal section through the con- ducting wires to the transverse section; within the muscle itself the current passes from the transverse to the longitudinal section. The nearer the one electrode is to the equator and the other to the centre of the transverse section the stronger will be the current, while the current becomes more feeble when one electrode is approached to the outer sur- face and the other to the edge of the transverse section. The existence of a muscle current may further be proved by an experiment which is termed the rheoscopic frog. If the gastrocnemius muscle of a frog be prepared with a long piece of sciatic nerve still in connection with it, and the end ofthe nerve be placed over another excised, fresh gastrocnemius muscle, so as to be in contact with its trans- verse and longitudinal surfaces, contraction of the muscle connected with the nerve occurs at the moment of contact. A single contraction is, however, only produced, but if the nerve be removed from the muscle a second contraction occurs; thus pointing out that the current circulating ‘through the muscle is a constant current and may serve to stimulate other muscles or nerves at the moment of breaking and making the contact. Tf a muscle be prepared as before, connected with a galvanometer, and be ‘found to yield a strong galvanic current, if the muscle be then thrown into tetanus by electrical stimulation of the muscle itself, or of its motor nerve, the needle of the galvanometer will be found ‘to swing back to zero, indicating the disappearance of the muscle current; such a state of affairs is spoken of as the negative variation of the muscle current. 2. Tue APPLICATIONS OF MuscuLAR ConTRACTILITY.—The contractility of muscles serves especially to produce changes in form of the animal body by which single members are thrown out of their condition of ‘equilibrium and changes of location in the animal parts thus produced; or in the case of the unstriped muscles to diminish the capacity of the various cavities of the animal body. Hence, muscles may be classified into two different groups: those without a definite origin and insertion, and those in which definite origin and insertion are present. To the first group belong the hollow muscles surrounding the urinary bladder, gall- bladder, uterus, heart, intestinal canal, blood-vessels, ureters, etc. In such instances the muscular fibres are unstriped and involuntary and are PHYSIOLOGY OF MOVEMENT. 723 arranged in several layers, an oblique, circular, and longitudinal layer being in nearly all cases distinguishable; all these sets of fibres acting simultaneously, the result is to diminish the capacity of the cavity which they inclose. They thus aid in various motions of animal life, such as the propulsion of the blood from the heart and in assisting its onward passage through the arteries, the evacuation of the bladder and rectum, | the emptying of the pregnant uterus, and various other operations which, have been already alluded to. In addition to this group of muscles, the sphincters likewise have no definite origin or insertion, but are found at the various openings of the body, whether the anus, urethra, or mouth, and several other localities. The muscular fibres of the sphincters are circular, and by their contraction serve to close the orifices of these several openings. Of the muscles with definite origin and insertion, either the origin is fixed or both origin and insertion may be movable. In many cases be- longing to the former of these groups the origin is only fixed during muscular action ; thus, in the case of the palato-pharyngeal muscles their characteristic action is only rendered possible by the fixation of their origin through the contraction of the levator palati muscle. Again, both origin and insertion may be movable, the part moved being usually under the control of the will. Thus, in the case of the sterno-mastoid muscle, through its contraction the head may be depressed or the chest elevated. Movement of the animal parts or of the entire animal body is ren- dered possible through the manner in which the skeletal muscles are inserted in the long bones by which lever motion is possible, the bones being regarded as levers, the joint as the fulerum, the insertion of the muscle the point of application of the power, and the centre of gravity of the bone with the resistances overcome by its motion as the load. Thus, muscles arising in one bone and inserted in another will, in their contraction, either move both bones toward each other, or, if one be fixed, will approach the movable to the fixed bone. From the definition of the power-arm of a lever, it is evident that in general the direction of muscles relative to the levers on which they act is very disadvantageous, since their course is almost always more or less parallel to the bony levers. This parallelism is diminished by the swelling of the articular extremi- ties and by the development of more or less marked eminences, such as the olecranon or the trocanters, or by the presence of sesamoid bones. In movements of flexion, however, this parallelism becomes diminished according to the degree of flexion, so that, therefore, at the termination of the act of flexion the muscles are more favorably situated for the de- velopment of power. Certain muscles, however, such as the muscles of mastication, the flexors of the head, the psoas muscles, and the abductors 724 PHYSIOLOGY OF THE DOMESTIC ANIMALS. and adductors of the arm have their insertion almost perpendicular to. the bones on which they act. Although all three classes of levers are met with, in general the lever of the first class comes into play in movements of extension, and that of the third class in movements of flexion. A lever may be @efined as an inflexible bar capable of being freely moved about a fixed point or line, which is called the fulerum. In the first class of lever the fulcrum lies between the weight and the power, and may be illustrated by a common crowbar or a pair of scissors. In levers of the second class the weight lies between the fulcrum and the power, and may be illustrated by the wheelbarrow or nut- cracker. In the third class of lever the power falls between the fulcrum and the weight, and may be illustrated by a pair of fire-tongs or sheep-shears (Fig. 286.) : @ F 0) Ww /\ P F CJ & (2) A WwW P id 8 F Fie. 2 (3) ‘1G. 287.—~DIAGRAMS SHOW- Ww PA ING THE MODE oF Ac- TION OF THE THREE Fra. 286.—THREE CLASSES OF LEVERS. (Landois.) Me ae or LEVERS, W, weight; F, fulcrum; P, power; 1,in levers of first class the fulcrum Dows eae Tas: is between the power and the weight; 2, in levers of second class the weight 3 ; falls between the power, and fulcrum; 3, in levers of third class the power is TRATED BY THE ACTION applied between the fulcrum and weight. The index shows the direction in OF THE ELBOW-JOINT. which the power acts. ( Yeo.) In considering the development of power by the.use of levers, the relation- ship between the power- and the weight-arm has to be considered. The power- Fig. 288.—PARTIAL CONTRACTION OF BicEPSs, (Perrier.) atm of the lever may be defined as the perpendicular distance from the line in which the power acts to the fulcrum; the weight-arm, the perpendicular distance PHYSIOLOGY OF MOVEMENT, 725 from the line in which the weight acts to the fulerum. The Jaw of the lever may be expressed as follows: A power will support a weight as many times as great as itself as the power-arm is times longer than the weight-arm. Thus, for ex- ample, in a lever of the first class, if we suppose that the power-arm be ten times as long as the weight-arm, a weight of one pound at the extremity of the power-arm will support a weight ‘of ten pounds at the extremity of the weight-arm. It must be recollected, however, in the case of the lever, as in every other machine, what is gained in Fic. 290.—Motion oF HEAD AS ILLUSTRA- TING ACTION OF LEVER OF FIRST CLASs. (Béelard.) a, fulerum of the lever,cb; ab is the weight-arm, for the head tends to fall forward by its own weight acting in the line, r. This is prevented by the contraction of the Fig. 289,—ComMPpLerE CONTRACTION OF muscles of the back of the neck acting on the power-arm, c a, Biceps. (Perrier.) in the line, P. power is lost in velocity, and vice versd. Thus, in the case of the third class of lever, power is exchanged for velocity. This may be well represented in the movement of flexion of the human forearm (Figs. 288 and 289). The fulcrum is there found in the elbow-joint, the power is the insertion of the biceps muscles in the bone of the forearm in front of the joint, the weight is carried by the hand. In this arrange- ment it is evident that slight motion at the insertion of the biceps will be greatly multiplied in the case of the hand. Thus, say that the distance from the elbow-joint to the tip of the hand is eighteen inches, the dis- tance from the elbow-joint to the point of insertion of the biceps one inch, motion of one inch at the inser- tion of the biceps will produce motion at the hand of an arc of a circle whose cord is eighteen inches. The forearm is, therefore, in this action an example of the third class of lever. Fic. 291.—MoTIon ILLUSTRATING ACTION oF In general, in the animal body, LEVERS or THE Tuirp CLass. (Béclurd.) ihe point of spplieation of the POWer ag.ln tar ssicee nerere gemma of euge developed by muscular contraction weight (of the body) acts in the line, 0}. acis thus the power lies near the fulerum: hence the ®%™2? the weight-arm. conditions favor the production of velocity of movement at the expense of power, for the power-arm is always shorter than the weight-arm. .The conditions are, however, reversed in the case of the extensor muscles of the limbs when in contact with the ground. Here the joint nearest to which the muscle is inserted is the point of application of the weight, and the fulcrum is the CoLer, & 726 PHYSIOLOGY OF THE DOMESTIC ANIMALS. joint above, far from the insertion of the muscle. Hence, the power-arm is greatly increased. Thus, in the horse, while the foot is on the ground in the con- traction of the extensors the point of application of the weight is in the hock- joint, the point of application of the power in the caleaneum, where the extensors are inserted, and the pastern-joint the fulcrum ; hence the power-arm is long, and, although motion is slow, it is accompanied by a corresponding increase in power. If, however, the hind foot is not on the ground, but is extended as in kicking, then the fulcrum is in the hock-joint, and the power-arm is now short and power is exchanged for velocity. The first class of levers may be represented in such movements as in nodding the head, where the fulcrum is the articular surface of the atlas, the weight being found in the back of the head when the throat muscles contract, in the front of the head when the posterior neck muscles contract (Fig. 290). Movement due to the action of levers of the second class is seen when the body is raised up on tiptoe by the muscles of the calf (Fig. 291). All three orders of levers may come into play in the action of the human elbow-joint. Thus, the first class is illustrated when the forearm is extended on the arm through the contraction of the triceps muscles; in this instance, the hand is the weight, the elbow-joint the fulcrum, and the insertion of the triceps in the olecranon the power (see upper diagram Fig. 287). If the hand rest on the table and the body be raised on it, then the hand is the fulcrum, the triceps is the power, and the humerus, at its articulation in the elbow-joint, the weight, thus illustrating the action of a lever of the second class (see middle diagram 287). The third order, as already mentioned, comes into play when the forearm is flexed on the arm. In the horse the extensors of the forearm (4 D, B D, and C D, Fig. 292) act as levers of the first class, the power-arm being the distance between the summit of the olecranon and the centre of the humero- radial articulation, which forms the fulcrum, while the weight-arm is represented by the Iength of the radius. In man the triceps brachialis (B, Fig. 293), which is the analogue of the olecranon muscles of quad- rupeds, acts also as a lever of the first class, the power-arm, however, being much shorter in man. In the posterior extremity of the horse (Fig. 294), the gluteus medius, the fascia lata, the triceps cruralis, the bifemero-calcaneus, the vastus externus, ete., are also examples of the first class of levers. In the case of the gluteus medius (A B, Fig. 294) the power-arm is the distance from the trochanter to the centre of the acetabular articulation, which is the fulerum, while the weight-arm is the length of the femur. For the gastrocnemius the power-arm is the distance from the summit of the caleaneum to the centre of the hock- joint, which is the fulcrum, while the weight-arm is the length of the metatarsus. The first class of levers is thus mainly represented by the extensors. ; Levers of the third class are mainly represented by the flexors. In the anterior extremity of the horse (Fig. 295) the infraspinatus, the biceps flexor, the metacarpal flexor, and the flexor pedis are all examples of muscles whose action operates through levers of the third class, in each instance the power acting between the fulerum and the weight. In operations of levers of the third class power is exchanged for velocity of motion, from the fact that the power-arm is always shorter than the PHYSIOLOGY OF MOVEMENT. 727 weight-arm. In the posterior extremity of the horse (Fig. 296) the superficial gluteus muscle and the ischio-tibial muscles are levers of the ae third class. Levers of the second class are more rarely met with. In the horse Fic, 292.—ANTERIOR Ex- TREMITY OF THE HORSE IN EXTENSION. (Colin.) AD, BD, and CD, lines of action of the triceps extensor brachii, scapulo- ulnaris, and aconeus muscles. E F, flexor brachii. G H, line of action of flexor pedis muscles. Fic. 293.—SUPERIOR Ex- TREMITY OF MAN. (Colin.) A ¢, line of action of the biceps flexor. B, triceps extensor. Fic. 294—PosTERIOR Ex- TREMITY OF THE HORSE IN EXTENSION. (Colin.) AB, line of action of gluteus medius. CD, line of action of triceps extensor. E F,line of action of gas- trocnemius. G H, line of action of metatarsal flexor. the gastrocnemius acts through a lever of the second class when the foot is in contact with the ground. Then the fulerum is at the point of con- tact of the foot with the ground, the power-arm is the distance from the caleaneum to the ground, the weight-arm the distance from the 728 PHYSIOLOGY OF THE DOMESTIC ANIMALS. ‘astragalo-tibial articulation to the ground, and the resistance is the weight ‘of the body. This mode of action of the gastrocnemius is more evident in man (Fig. 297) when the weight of the body is raised on the toes ‘through the action of this muscle. In the anterior extremity of quad- rupeds the extensors of the forearm (A D, B D,and C D, Fig. 292) also act through levers of the second class when the foot is on the ground, Fig, 295.—THE ANTERIOR EXTREMITY Fig. 296.—POSTERIOR EXTREMITY OF OF THE HORSE IN FLEXION. (Colin.) THE HORSEIN FLEXION. (Colin) A B, line of action of infraspinatus. CD, line A B, line of. action of ‘superficial gluteus of action of biceps flexor.’ E F, line of action of muscle. € D, line of action of ischio-tibial metacarpal flexor. G H, line of action of flexor muscles. ‘EZ F, line of action of metatarsal ” pedis. flexor. GH, lines of action of flexors of foot. -their action serving then to flex the humero-radial articulation, instead of extending it, as occurs when they act with the foot in the air. The movements of the different parts of the animal body depend “upon the union of the different parts of the skeleton with each other and ‘the mode of insertion of the muscles. The movable parts of the skeleton -are designated as joints, the relative positions of the bones forming 2 PHYSIOLOGY OF MOVEMENT. 729 ‘joint being determined by muscular action; for when by the action of muscular force the positions of the bones are changed, the original position is not regained in the cessation of that force. The form of the joint, in which two bones are united end to end, is subject to considerable variation, depending on ‘and governing the direction in which the move- ment may take place. The articular extremities ‘of the bone are covered with articular cartilage, surrounded by closed serous sacs containing a serous fluid, the synovia, which tends to diminish friction between the movable parts. Since the space between articular surfaces con- tains only the synovial fluid, it may be regarded ‘as a vacuum, and atmospheric pressure is itself sufficient to keep the articular surfaces in con- tact, even sustaining the entire weight of the limbs and thus sparing muscular action. The movement between the joint ends is not only governed by the character of the joint, which we will find may be resolved into several differ- ent types, but is further restricted by the cap sular ligament which holds the joints in appo- sition and by the tendinous bands which surround them, in all cases only those move- ments being possible in which the articular surfaces remain in contact. The articulations are divided into three classes: the immovable articulations, or the ‘synarthroses; the mixed, or amphiarthroses ; and the movable, or diarthroses. To the first class belong the sutures and ‘other articulations where the surfaces of the ‘bones are in almost direct contact, not sepa- rated by a synovial cavity, and immovably ‘connected with each other. In the second class the osseous surfaces are connected together by disks of fibro-cartilage, as between the bodies of the vertebre, or the articulating surfaces are covered with fibro-cartilage, partly lined by (a : 2 Fig. 297.-INFERIOR EXTREM- ITY OF MAN, (Colin.) AB C, line of action of biceps flexor. (D, lever of third class.) £, gastroc- nemius. synovial membrane, and bound together by external ligaments, as in the sacro-iliac and pubic symphyses. The third class includes the greatest number of joints in the animal © body, and as mobility is their distinguishing characteristic they are the 730 PHYSIOLOGY OF THE DOMESTIC ANIMALS. only ones with which we are concerned. Four different varieties of thig form of joint have been described, according to the kind of motion permitted in each. a. The Rotatory Joint,or Diarthrosis Rotatoria.—In this class of joint the movement is limited to rotation, the joint being formed by a pivot-like process turning within a ring or the ring on the pivot, the ring being formed partly of bone and partly of ligament. The articulation of the atlas and the occiput is an example of such a joint. In the elbow- joint a similar rotatory articulation is met with, where in the radio-ulnar articulation the ring is formed by the lesser sigmoid cavity and the orbicular ligament while the head of the radius rotates within the ring. Only in animals in whom pronation and supination of the hand are possible does this movement occur; it is, therefore, absent in the horse and ox. In general, it may be said that in animals provided with the clavicle this motion of supination and pronation is usually present. b. The Ball and Socket Joint, or the Enarthrosis.—In this joint motion in all directions is possible, and it is formed by the reception of the globular head of along bone, into a deep, cup-like cavity, hence called ball and socket, the parts being kept in apposition by a capsular ligament and accessory ligamentous, bands. The hip- and shoulder- joints are examples of this class. c. The Hinged or Ginglymous Joint.—In this form motion is only possible in one plane and only in two directions, forward and backward, the articular surfaces being moulded to each other in such a way thata solid cylinder moves within a greater or lesser segment of a hollow cylinder. The joint between the ulna and the humerus is a most perfect example of a ginglymous joint, while the joints between the phalanges and between the inferior and superior maxillary bones of the carnivora are other examples. The pastern-joint of the horse is a modified form of this joint and is often spoken of as a screw-joint. d. The Gliding Joints, or the Arthrodia.—In this class motion of a gliding character takes place. Such joints are formed by the approxima- tion of plane surfaces, or one slightly concave, the other slightly convex, movement between them being limited by the ligaments or the osseous processes surrounding the articulation. Such articulations are seen between the vertebra, metatarsal and tarsal bones, and others. The forces which move the joints are found in the contraction of striped muscular fibres. The extent of contraction for which the muscle is capable depends upon its length, and therefore we speak of long and short muscles. A muscle whose function it is to bring its points of origin and insertion nearer to each other must necessarily be a long muscle, while the muscles whose contraction only leads to slight change of place are usually short muscles. It will always be found that the PHYSIOLOGY OF MOVEMENT. veal length of the muscle-fibre corresponds to the degree of movement which the muscle has to produce. It does not necessarily follow that a muscle whose points of origin and insertion are widely separated.should be a long muscle, since the interval between these two points may be largely taken up by tendons. consists in the movement of the centre of gravity of the body. By the term “the centre of gravity” is understood the point about which all the matter composing the body may be balanced. The attraction of gravity tends to draw every particle of matter downward in a vertical line. The factors of this force may be, therefore, regarded as the sum of an almost infinite number of parallel forces, each of which is acting upon one of the molecules of which that body is composed. Just as the resultant of the force exerted by two horses harnessed to a swingle-tree is equal to the sum of the forces exerted by the horses but applied at a single point at or near the centre of the swingle-tree, so, also, the sum of the forces of gravity may be regarded as acting upon a single point which is near the centre of gravity of that body. In other words, the weight of the body may be considered as concentrated at the centre of gravity. When the centre of gravity is supported the whole body will be in a state of equilibrium; or when the line of direction of the force of gravity, which is thus a vertical line passing through the centre of gravity, falls within the base of the body, or base on which the body stands, it is then said to be stable. . In all regular bodies the centre of gravity will coincide with the central point, while in irregular bodies it will be nearest to that part in which the greatest weight is concentrated. As the centre of gravity of the animal body is within the body it can be directly supported. The stability of the body will be greater the broader the base and the nearer the centre of gravity to the support. The animal body when standing is, however, only at best in a state of unstable equilibrium ; for when slightly displaced from its position of equilibrium, it tends to fall still farther from that position, owing to the fact that the disturbance has lowered the centre of gravity, and equilibrium is not restored until it reaches its lowest possible point. An animal in a recumbent position is in a state of neutral equilibrium ; when its position is changed it tends neither to return to its former position nor to fall farther from it. Stable equi- librium is when a body is so supported that when slightly displaced from its position of equilibrium it tends to return to that position. Such a condition can only occur when displacement raises the centre of gravity. The pendulum is an example of stable equilibrium. Standing is thus a condition of unstable equilibrium in which the centre of gravity is supported from the fact that the line of direction 732 PHYSIOLOGY OF THE DOMESTIC ANIMALS. falls within the base of the figure. The mechanism of standing differs in bipeds and quadrupeds. In man the centre.of gravity lies within the pelvis, about one and a half millimeters in front of the promontory of the sacrum. In the erect attitude of man the feet are directed outward (forming an angle of about fifty degrees), so increasing the base of support, the heels touching, the knees extended, the thighs rotated externally, and the pelvis and trunk bent slightly backward, the arms hanging at the side. In the act of standing, the body not being rigid, balancing must be aided by the assistance of the contraction of various muscles. Ina certain number of joints the action of ligaments in the erect position assists the maintenance of the upright posture; thus, in the attitude already described, where the knees are extended to the utmost, the trunk thrown back, and the head balanced, the anterior hip-ligaments are rendered tense, and the knee- and hip-joint remained fixed without any effort upon the part of the joint-muscles. In the position known as “ standing at ease” the weight of the body rests mainly on one leg, the other forming simply a support to assist the muscles around the support- ing ankle. In this position the joints are not kept locked by the tension of the ligaments, for the pelvis is now somewhat oblique, so as to bring it direetly over the head of the femur. Varying tension in the muscles serves to preserve the balance and prevent fatigue. In the erect posture the ankle supports the weight of the body; the line of gravity falling slightly in front of the axis of rotation of the ankle-joint, the tendency is thus for the body to fall forward at the ankles; this is, however, checked by the calf-muscles, which keep the parts nearly in position of exact equilibrium. In the erect position, the anklejoint being neither flexed nor extended to the utmost forward or backward, motion must be prevented by muscular contraction. Lateral motion at the anklejoint is prevented by the malleoli. When the knee-joint is completely ex- tended no muscular action is required to prevent it from bending, be- cause the line of gravity then passes in front of the axis of rotation and the weight of the body tends to bend the knee backward. Although the ligaments which exert their contraction behind the axis of rotation tend to render this impossible, ordinarily the position is maintained by mus- cular action so exerted that the line of gravity passes slightly behind the axis of the knee, the tendency thus produced of the knee to bend — being checked by the extensor muscles of the thigh. In the hip-joint the line of gravity falls behind the line uniting the joint. When the person is erect, the tendency thus produced of the body to fall backward is prevented by the ileo-femoral ligament. If, however, the knee is not extended to the full extent the line of gravity passes a little behind the axis of rotation of that joint, and the pelvis PHYSIOLOGY OF MOVEMENT. : 733 being slightly flexed on the femora, the axis of the joint lies a little behind the line of gravity, and the inclination thus produced to fall forward is prevented by the glutei muscles, which are likewise concerned in regaining the erect posture after bending the trunk forward. The motions between the pelvis and vertebre are practically so slight as to be disregarded, and the vertebral column, with the exception of the motions existing between the head and the upper ecrvical vertebra, may be re- garded as a rigid column. Between the occiput and atlas lateral and rotatory motions are possible to a considerable extent, so that balancing the head is rendered possible only by co-ordinated muscular contractions, since no ligaments are present which can fix the occipito-atlantoid artic- ulation. ; Sitting is that position of equilibrium where the body is supported ‘on the tubera ischii. The line of gravity may pass either in front of the tubera ischii, in which the body must be supported by some fixed object, or the line of gravity may fall behind the tubera in the backward pos- ture, in which case falling backward may be prevented by leaning upon a support or by the counter-weight of the extended legs. In sitting erect the line of gravity falls between the tubera themselves, and but: slight muscular action, such as is required in the balancing of the head, is sufficient to maintain equilibrium. In quadrupeds the four limbs act like four columns, as in a chair or table, in supporting the centre of gravity of the body, so that the base of support is a parallelogram whose corners are represented by the point of contact of the feet with the ground, and which is about four times as long as it is broad. In consequence of the greater base of support, equi- librium is more readily preserved in quadrupeds than in bipeds. The centre of gravity in the large quadrupeds, such as the horse, ox, etc., liés at the intersection of a line passing vertically behind the xyphoid carti- lage and one passing horizontally through the end of the second third of the sterno-vertebral diameter. In the small quadrupeds, such as the dog, the centre of gravity is located somewhat more anteriorly. From the fact that the centre of gravity lies below the vertebra in quadrupeds, in the erect position the tendency of the weight at the centre of gravity is to curve the vertebral column inward. This is prevented by both mus- cular action and ligamentous support. The fore extremities and scapula are only attached to the trunk through muscular and ligamentous con- nections which are continually on a stretch and so serve to render the shoulder-blade immovable, while by means of the greater serrati muscles the trunk is supported as in a sling, so that it cannot be pushed forward against the shoulder-blade. In the posterior extremities the relationships differ in that the single bones are not, as in the fore extremities, verti- cally over each other. Here, also, the erect position is maintained through 734 PHYSIOLOGY OF THE DOMESTIC ANIMALS. muscular action. When the body is uniformly supported on all four extremities, in the fore limbs the line of direction passes from the shoulder through the centre of the elbow-joint in the axis of the forearm, through the centre of the knee-joint in the axis of the ulna, through the centre of the pastern-joint perpendicular to the ground behind the ball of the foot. Three principal angles are thus formed whose degree depends partly on the angle between the scapula and vertebre and partly on the relative lengths of the different bones. In the case of the anterior extremity the line of direction of the lower bones is almost vertical, but in the case of the upper bones becomes considerably inclined; thus, the scapulo-humeral angle tends constantly to become smaller and smaller on account of the depression of the superior extremity of the scapula and by the projection anteriorly of the scapulo-humeral articulation. This depression and projection are hindered by the action of numerous muscles. The most important muscle concerned in the fixation of the upper extremity is the serratus magnus, which, arising in numerous fan-shaped bundles from the five posterior cervical vertebrae and the first eight ribs, converges to be inserted in the ventral surface of the scapula. This muscle, with its fellow, serves as a muscular sling in which the body is supported between the fore limbs, the axis of motion of the shoulder-blade pass- ing through its insertion in the scapula. The superior extremity of the scapula is sustained by the rhomboid muscles, which draw it upward, as well as by the trapezius, which tend to elevate and advance this bone, so opposing the depression of the scapula through the weight of the trunk. These muscles thus give fixity to the _ scapula. Further, the anterior projection of the scapulo-lumeral angle is prevented by the greater and lesser pectoral muscles, which by their contraction tend to retract this angle. The obliquity of the humerus tends to become exaggerated during standing as well as at each act of striking the foot upon the ground. The pectoralis major and the infra- spinalis muscles, as well as the coraco-radii, tend to prevent this, the latter muscle being especially efficacious, acting not only as a muscle, but a band of unyielding tendinous material running through it enables it to act as a ligament preventing exaggerated flexion of the humerus on the shoulder. That the coraco radii should fulfill this function it is neces- sary that its insertion in the inferior extremity should be fixed. This fixity is accomplished by the five olecranon muscles. At the elbowjoint the lower end of the humerus is fixed by the strong lateral ligaments; reduction of the elbow angle being prevented by the fixation of the olecranon through the contraction of the extensors of the forearm, and anterior deviation by the tendinous expansion of the long flexor of the forearm, its tension increasing with the weight on the shoulder. PHYSIOLOGY OF MOVEMENT. 735 Below the humerus the bones lie, with the exception of the phalanges, in an almost vertical line, flexion being prevented by the five extensors of the forearm. The metacarpus continues the vertical column of which the forearm forms the superior segment, its flexion being prevented by Fig, 208.-ANTERIOR EXTREMITY OF THE Fic. 209.—PoSTERIOR EXTREMITY OF THE Horse in EXTENSION, (Colin.) HORSE IN EXTENSION. (Colin.) AD, BD, and CD, lines of action of the tricepsextens - AB, line of action of gluteus medius. ( D, line of sor brachii, scapulo-ulnaris, and aconeus muscles. EF, action of triceps extensor. E F, line of action of gas- Hlexor brachii. @ H, line of action of flexor pedis mus- trocnemius, GH, line of action of metatarsal flexor. eles, the extensor inserted in its carpal extremity, and which receives in about the middle of its fleshy belly an aponeurotic cord fixed superiorly to the external tuberosity of the humerus. In the phalangeal region the direc- tion of the bony support now becomes oblique, and, while its obliquity 736 PHYSIOLOGY OF THE DOMESTIC ANIMALS. constantly tends to become exaggerated by the weight which the upper extremity supports, it never passes certain limits on account of the pres- ence of the spiral ligament of the pastern-joint. Without this ligamentous support muscular action would be insufficient to prevent extreme flexion, but by means of the ligament, which in the horse and ruminant is composed of powerful non-elastic tendinous fibres, represented in the carnivora by muscular fibre, the support of the body is rendered possible without fatigue. In the case of the posterior limbs great deviation from the vertical is met with, and that their obliquity should be restrained within certain limits considerable muscular effort is required and the mechanical dispo- sitions of the power is more complex (Fig. 298) than in the case of the thoracic members. In the hind leg four angles are met with, viz.: in the hip-joint, the kneejoint, the hock-joint, and the pastern-joint, the degree of these angles being governed by the angle which the axis of the femur makes with the vertebrae and the position in which the hind foot is placed. In the resting position of the hind extremity the line of direc- tion of the body weight passes from the centre of the hip-joint vertically downward to the centre of the hock-joint, and then, deviating about 10° from the direction of the metatarsus, passes behind the pasternjoint to the ground. The pelvis is very oblique relatively to the trunk in the horse, ox, and most ruminants and carnivora. The femur is obliquely connected with the pelvis, downward motion of the pelvis and backward motion of the femur from the body weight being prevented by the abdominal recti muscles, whose tendons, being inserted in the pelvis, by their tension tend to draw the hip-joint anteriorly. The gluteal muscles, arising from the ilium and passing over the hip-joint to the femur, act in the same direction, not only preventing forcing backward of the hip- joint, but in its contraction pressing the hip-joint forward. The leg is, like the femur, flexed, its obliquity being limited by the tension of the tendons of the extensor muscles, which pass over the anterior surface of the knee-joint, by the ligaments of the kneejoint, and by the tibio-tarsal muscle, which in the solipedes throughout its entire length consists of a strong aponeurotic band, thus being analogous in its action to the coraco- radial muscle of the anterior extremity. The flexion of the metatarsus on the leg is limited especially by the gastrocnemius muscles and by the superficial flexor of the phalanges, which in the suspensory ligament becomes reduced to a cylindrical cord and flattened out at its passage over the summit of the caleaneum. The inclination of the phalanges on the metatarsus is prevented by a ligamentous suspensory apparatus similar to that of the anterior extremity. | From the above it is seen that the extremities in standing dinnet the body only by muscular effort, principally that of the extensors: PHYSIOLOGY OF MOVEMENT. 737 Although the flexors participate in many joints, as an example of which it is only necessary to mention the coraco-radial, which, as already stated, offers resistance to the flexion of the arm on the forearm, this action is only rendered possible when the radius is fixed by the olecranon muscles, The support of the head in standing in the case of quadrupeds is accom- plished mainly by the ligamentum nucex, which, originating in the spinous processes of the dorsal vertebrae, terminates in the occipital protuber- ance, being connected at the same time with all the cervical vertehrie. While standing quietly the weight of the horse is supported by both of the fore legs and only one hind leg, the other hind leg being flexed and only the tip of the toe touching the ground. By this means the muscles of the posterior extremity which are concerned in the act of standing are enabled to rest, the weight being borne alternately at varying inter- vals by the opposite hind legs. From the fact that the centre of gravity in quadrupeds lies nearer to the anterior than the posterior extremities, the fore limbs sustain the greater part of the weight of the body. In riding two-thirds of the weight of the rider are borne by the anterior extremities and one-third by the posterior. In every form of animal locomotion the position of the centre of gravity of the body in space is changed, inertia tending to continue the motion inaugurated by the muscular contraction until friction, resistance of the atmosphere, or opposed muscular action arrests it.. In man, movements of locomotion are much simpler than in quad- rupeds, and will, therefore, be first analyzed. The movements in man consist in walking, running, and jumping. In the act of walking in man, by the alternate action of each leg the centre of gravity is advanced so that at each step there is a moment in which the body rests vertically on the foot of one leg (say the right), while the other (the left) is inclined obliquely behind with the heel raised and the toe resting on the ground. Then the latter, slightly flexed to avoid touching the ground, is swung forward like a pendulum, and the toe of the moving leg (the left) then brought to the ground. On this point, as a fulerum, the body is moved forward by a propulsive act of the supporting leg (the right), the centre of gravity becoming thus advanced until it lies vertically over the leg (the left) which has last touched the ground. The body then rests vertically on the left foot, the right now being directed obliquely back- ward. The propulsive movement of the active leg, the one concerned in pushing the body off the ground, gives sufficient impetus to the centre of gravity to carry it by inertia beyond the vertical line on the passive or supporting leg,so that this movement from inertia assists in swinging forward the active leg until it advances a step beyond the passive sup- porting leg (Fig. 299). Hence, after the act of walking is once started, inertia is largely instrumental is maintaining the motion, and but slight 47 738 PHYSIOLOGY OF THE DOMESTIC ANIMALS. muscular exertion is required in walking on level ground. In ascending an incline, however, the active limb has at each step to elevate the weight of the body by extending the knee- and anklejoint by the thigh-exten- sors and calf-muscles, therefore greatly increasing the muscular power required. During walking the trunk leans toward the active leg, owing to the contraction of the glutei muscles and the tensor fascia lata, and is inclined slightly forward to overcome the resistance of the air. The more anteriorly the trunk is advanced the more the centre of gravity of the body tends to lie in the line of the active leg, and, consequently, the stronger is the forward propulsion of the body. Hence, in rapid walk- ing the body is more bent forward than in slow walking. During the advancing of the passive leg the trunk rotates on the head of the active femur and is compensated by the arm of the side of the oscillating leg Fig. 300.—THE DIFFERENT POSITIONS OF THE LEGS OF MAN IN WALKING, AFTER WEBER. A, the propelling leg; B, the ‘ pendulum”’ leg. swinging in the opposite direction, while that on the other side swings in the same direction as the oscillating leg. . Running is distinguished from walking by the fact that at a certain moment the body is raised in the air, neither leg touching the ground. In walking, on the other hand, both feet rest on the ground for the greater part of the step. In running the active leg, as it is forcibly ex- tended from a flexed position, gives the body the necessary impetus, the active leg leaving the ground before the swinging foot has reached the ground. There is thus an interval during which both feet are off the ground, and as each foot comes to the ground it executes a new swing without waiting for the pendulous swing which occurs in walking. In jumping the propulsion of the body takes place from both feet PHYSIOLOGY OF MOVEMENT. 739 simultaneously. A running jump may be made higher or broader than a standing jump from the additional impetus acquired through inertia. 4. THE GaiTs OF THE Horse.—Although the acts of locomotion in quadrupeds are much more complicated than in man, they may be all reduced to variations of three main types—the walk, the trot, and the gallop.* Since in quadrupeds the centre of gravity lies in front of the centre of the trunk, it can only be advanced by power acting from the hind extremities, the fore legs being concerned simply in supporting the trunk. In the horse the posterior extremities are especially fitted for this act by the angular character of their joints, so that in the action of the extensor muscles the hind legs become considerably longer, and the foot remain- ing in contact with the ground, through the contraction of the extensors the result must be to advance the upper extremity of the leg forward ; and the greater the angles of the posterior extremity, the farther the trunk will be advanced in the straightening of the hind leg. The extremity, which in the commencement of the extension of the hind lee was behind, will now be advanced so as to support the trunk, exactly as has been found to be the case with the swinging leg of the walking man, which, immediately after the impulse of the active lee, swings for- ward, and then on its part assumes the réle of the propulsive leg, while the previously active leg now becomes passive. The force of the shock communicated to the trunk by the hind legs will be somewhat diminished by the oblique insertions of the extremities and by the angles between the single bones of the hind leg, while in the fore extremities the shock of the foot striking the ground will be diminished by the soft parts, muscles and fascia, which connect the shoulder-blade to the trunk. Before taking up the consideration of the different gaits of the horse the characters and mode of production of the different movements in the individual limbs first deserve attention, taking up, first, the move- ments of the fore leg and then of the hind leg :— The animal being supposed to be in the erect position, before move- ment of the fore leg takes place the body weight is first shifted, through the contraction of the pectoral muscles, aided by the latissimus dorsi, to the opposite extremity. The shoulder being elevated by the rhomboid -and trapezius muscles, flexion commences with the contraction of the levator humeri, approximating the humerus to the scapula and diminisb- ing the shoulder angle. The principal reduction in the length of the *In the account of the different movements in the gaits of the horse the author has mainly followed the analysis published by Briichmiiller, ‘‘ Lehrbuch der Physiologie,”’ Oes- derretcher Vierteljahresschrift fiir Veterindrkunde, liii, 1880, pp. 97-120, based on instan- taneous photography. Acknowledgment is also due to Colin, ‘‘ Traité de Physiologie Comparée ;” Munk, ‘“‘Physiologie des Menschen und der Sdugethiere ;’’ Boehm, Archiv Sir Wissenschaftliche und Praktische Thierheilkunde, Bd. xiii and xiv; and Schmidt- Milheim, « Physiologie der Haussdugethiere.”’ 740 PHYSIOLOGY OF THE DOMESTIC ANIMALS. axis of the fore leg occurs through the flexion of the knee-joint, which is elevated and advanced by the action of the coraco-radial and humero- radial muscles ; then by the action of the flexors of the carpus and digit the fetlock and pastern-joints are flexed. Fig. 301.—PoSTERIOR EXTREMITY OF THE HORSE IN EXTENSION. (Colin). AB, line of action of gluteus medius. (' JD, line of action of triceps extensor. EF F, line of action of gas- trocnemius. GH, line of action of metatarsal flexor. Fic. 302.—ANTERIOR EXTREMITY OF THE HoRSE IN EXTENSION. (Colin). AD, BD, and CD, lines of action of the triceps exten- sor brachii, scapulo-ulnaris, and aconeus muscles, EF, flexor brachii. G H, line of action of flexor pedis mus- cles. Extension of the fore leg is the reverse of the preceding motions and serves to open out the angles reduced in flexion and so increase the length of the axis of the limb. Extension is still further the reverse of flexion in that the motion commences in the pastern-joint, instead of in PHYSIOLOGY OF MOVEMENT. 741 the shoulder, through the action of the extensor pedis, which, with the metacarpal extensors, converts the angle of the pastern-joints into a straight line, the axis of the phalanges forming an angle anteriorly with the axis of the metacarpus. Simultaneously with this movement the knee becomes extended, the axis of the metacarpus forming a straight line with that of the radius, this movement also being accom- plished by the contraction of the metacarpal extensors. Finally, the fore- um returns to its extended position in a line with the upper arm, partly through the action of the ligaments of the elbow-joint and partly from the contraction of the five olecranon muscles. During this forward motion of the foot in extension the humerus leaves its position of flexion, and the foot striking the ground, the fore limb again becomes vertical, and by the action of the pectoral latissimus dorsi muscles the body weight is again transferred to it. The lever motion of the muscles producing . these movements is seen in Figs. 301 and 302. Instead, however, of the simple motions of flexion and extension above described, which occur when one forefoot is simply raised from the ground and again returned to the same spot, the flexed forearm and carpus may be carried beyond the vertical line through the extension of the humerus by the contraction of the various extensors, aided by the abductors of the humerus, while at the same time the posterior angle of the scapula is drawn backward and downward by the contraction of the rhomboid and trapezius muscles. At first, in the forward motion of the lower end of the humerus flexion is increased, but the farther it advances forward and the more the scapula rotates backward the more the shoulder angle becomes opened, and, under the action of the adductors of the humerus, dire¢ted outward and upward, so that the extensors of the lower joints "are put on the stretch and their contraction converts the flexion of the limb into extension, the fore leg thus describing a pendulum-like motion, and in its extended position is directed forward and downward and strikes the ground in front of its previous position (Fig. 303). Then, from the impulse communicated to the trunk from the hind legs, the weight of the body is gradually transferred to the fore leg, which, the foot remaining on the ground, gradually becomes more and more vertical from the forward motion on it of the trunk (Fig. 304). As, however, the inertia of the moving body carries the shoulder beyond the vertical, the axis of the fore limb is then directed downward and backward, the assumption of this position being aided by the forward rotation of the scapula, while the extensors of the forearm (the foot being fixed on the ground) not only sustain the elbow- and shoulder- joints, but, by their contractions, give an additional forward impetus to the body. The extreme extended position of the limb puts the flexors of the lower joints on the stretch and so leads to their contraction, and 742 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the limb, passing now into flexion, again describes its forward pendulum motion, the point of support of the scapula being the centre of rotation, while the hoof describes an are of a circle. On the other hand, while Fria. 308.—OscILLATION OF THE FLEXED FORE LEG. (Colin.) The hoof describes an arc of a circle, ( BA, the cord, C A, being a measure of the extent of oscillation. the foot is on the ground the shoulder describes the arc of a circle and the centre of rotation is in the foot. The combination of these two movements in both fore legs is seen in Fig. 305. Fig. 304.—OSCILLATION OF THE EXTENDED FORE LEG. (Colin.) The foot being on the ground at D, the shoulder describes an arc of a circle, 4 BC. In the case of the hind leg flexion likewise results in a shortening of the axis of the leg and the reduction of the angles between the dif- ferent bones. The weight being thrown on the opposite extremity by PHYSIOLOGY OF MOVEMENT. 743 the contraction of the adductors, the femur is approached to the ilium by the contraction of the rectus and lumbar and iliac psoas muscles, the knee being elevated anteriorly by the ischio-tibial muscle and the hock- joint flexed by the contraction of the metatarsal flexor, whose tendinous portion, when the stiflejoint is flexed, becomes tensed and mechanically repeats the action on the joint below, the digital region being flexed on the metatarsus. As a consequence of these flexions, produced almost simultaneously, the axis of the limb becomes shorter, is raised from the ground, and advanced in a more or less oblique line. That the foot may again be placed on the ground the above muscles must relax and their antagonists contract. First the femur is extended on the pelvis by the action of the gluteus maximus, whose principal trochanteric branch acts as a lever of the first class. The leg is then extended on the thigh by antec ee, a ee Cie ae > | Ae 0 ily \ : i Fic. 305.—OSCILLATION OF THE ANTERIOR EXTREMITIES, (Colin.) The Beare shows that while one fore leg is describing the pendulum motion the other is acting as a support, while the right fore foot describes the are, y h, the left shoulder describes the are, a/ hf cf, from the impulse given to the centre of gravity of the body through the extension of the hind legs. Then the right shoulder describes the arc, @/ ef f!. "The six positions of the Jeft leg in one complete step are shown at abcdey, the centre of gravity having been advanced from m ton. ‘the rotuleus muscles, the metatarsus in its turn regaining its position on extension through the contraction of the gastrocnemius, the digital region being extended by the phalangeal extensors. The lever action of the muscles which produce these motions is seen in Figs. 249 and 251. In movements of progression each hind limb alternately serves to give an impetus to the body by passing into a condition of extreme ex- tension, the foot being on the ground, and then, passing into a condition of flexion, describes a pendulum motion through the air until the foot again strikes the ground in front of the position which it left. © The pen- dulum motion commences with flexion of the hipjoint and forward motion of the lower end of the femur followed by flexion of the other joints. The greater the advance of the knee the greater the tension of the ex- tensors, until the limb becomes extended and its increased length brings 744 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the foot to the ground, the axis of the lim) being now directed obliquely downward and forward. The body weight is then shifted to this limb through the action of the adductors, the limb again passing into a more or less marked position of flexion. The croup muscles then contracting, the pelvis is advanced, assisted by the extensors of the femur, which find i fixed point in the knee, while at the same time the gastrocnemius muscle, contracting, opens the angle of the hock-joint and elevates the pelvis from the inerease in the length of the axis of the limb. Through these motions the line of the hind leg gradually becomes vertical, passes the perpendicular, and is then directed downward and backward from the advance communicated to the body (Fig. 306). When the highest FIG. 306.—OSCILLATION OF THE EXTENDED HIND LEG, (Colin.) The foot being on the ground at D, the hip-joint describes an arc of a circle, A B C, the lines A D, B D, and C D representing the changing axis of the hind leg. degree of extension is reached the weight is shifted to the opposite limb, and after complete flexion the pendulum motion is repeated. In these motions the hind leg does not move in the plane of the line of direction; in rapid movement the knee and tip of the foot are some- what everted through the action of the iliacus muscle until the foot strikes the ground. In slow motions, on the other hand, especially when bearing heavy weights, the knee is directed inward from the action of the adductors and tension of the femoral fascia, while the hock is everted, thus turning the toe toward the median line. (a) The Walk.—In walking the body is supported by two legs while the other two are describing the pendulum motion, the support being alternately on diagonal feet and then on the two feet of the same side ; PHYSIOLOGY OF MOVEMENT, 745 but as the impulse of the supporting feet is not simultaneously pro- duced, four strokes of the hoof are heard with each step, but at unequal intervals; for when the support comes from the two feet on the same side the preservation of equilibrium compels a more rapid shifting of the body weight to the opposite side than when the diagonal limbs are in action. If we commence the consideration of the act of walking in quadru- peds at the moment in which the one hind leg after completing its pen- dulum motion comes again to the ground, then it occupies a position in which the axis of the limb is directed from behind forward and from above downward. The centre of gravity in consequence of the propul- sive movement advances, the leg and trunk describe an arc of a circle around the foot as a centre, so that the axis of the leg gradually becomes vertical and then advances, and the axis now tends to become Agni! Fic, 307.—THE WALK. (Colin.) directed from before backward and from above downward. At this moment active contraction of the extensor muscles’ occurs and the leg which was the supporting member now becomes an active propulsive member. It leaves the ground, becomes flexed, and swings forward, the femoral articulation now being the centre of movement and the foot describing an are of a circle until it becomes advanced in front of its point of support. It then strikes the ground and the movements are repeated (Fig. 307). At the moment ‘when the hind leg is thus swinging forward the fore leg of the opposite side is likewise advanced, the movement commencing as soon as the propulsive hind leg is ina vertical line. Through the forward movement of the trunk the line of 746 PHYSIOLOGY OF THE DOMESTIC ANIMALS. direction of the fore extremity becomes changed, so that instead of being’ vertical it is directed from above downward and from before backward. The foot must, therefore, be raised from the ground and advanced in the direction in which the trunk is moving, and, striking the ground, again becomes vertical at the moment when the pendulous hind leg strikes the ground. At the moment, then, when the fore leg becomes vertical, the propulsive movement in the opposite hind leg occurs. Then the motion commences in the opposite hind leg and fore leg, the alternation of the limbs being perfectly regular. Thus, suppose the right hind foot to be the propulsive foot, the left fore foot is extended on the ground, the left hind leg is swinging forward, and the right fore foot is just leaving the ground, the body thus being supported on a diagonal pair of feet. Then the right hind foot leaves the ground, the left fore foot is on the ground, the limb having passed the vertical line, the left hind leg is giving the impulse to the body, while the right fore foot is swinging forward. The body is then supported on unilateral feet, the support being of shorter duration than in the first case. Hence, in walking, there is always at any one time an anterior and a posterior limb in the air and an anterior and posterior limb acting as a support, the limbs being raised and replaced in such an order that of the two limbs in the air one is always in advance the half of its course over the other, while of the supporting limbs in one the line of the support is vertical when the other first reaches the ground. i In quadrupeds the length of the step is measured by the distance between the track formed by each separate foot, so that it is, therefore, twice as extensive as in man. When the hind feet reach the foot-prints of the fore feet it is twice as long as the base of support, 7.e., the dis- tance between the pairs of feet at rest. As the motion in walking in quadrupeds is produced by the action of the diagonal extremities, the centre of gravity is first moved to one side and then returned to the centre and then cast to the opposite side. The duration of the step is dependent upon the duration of the swinging of the leg. The higher an animal raises its leg, the shorter is the pendulum and the more rapidly it swings. The rapidity of motion in the walk in the horse varies from one to two meters in the second. In drawing heavy weights or in a very slow walk the relative movement of the feet is somewhat different from that detailed above. Then the elevation of each foot is delayed until the sup- porting feet are firmly on the ground; the body is then always supported on three limbs, by which equilibrium is better preserved. The same sequence of movement is, however, preserved. (b) The Amble.—The amble is a modification of the walk, and is seen in the dromedary, giraffe, and occasionally in ruminants, and more PHYSIOLOGY OF MOVEMENT. 747 seldom still in the horse. It is characterized by the fact that the eleva- tion of the second leg on the same side occurs sooner than in the walk. The.walk merges into the amble when, the body being supported by the two legs on the same side, the two opposite legs are elevated simul- taneously instead of separately, as in the walk (Fig. 308). In the walk the fore leg is always one-half the extent of its move- ment behind the hind leg on the same side, while in the amble both legs on one side move together, so that, therefore, there is a regular change between the feet on each side of the body. Consequently, in the amble the centre of gravity is first shifted to the one side and then to the other, the length of the step in the amble and walk being the same. But from the fact that the supporting limbs are on the same side of the body, to preserve equilibrium the movements must be more rapidly performed ‘i Hi vit ot lM Fic. 308.—THE AMBLE, (Colin.) than in the walk. The gait is, therefore, a faster one, the greater rapidity of the pace being accomplished by the reduction of the time, which cor- responds to the half of the duration of the movement of one leg, since on each side one-fourth of the time is saved. The rate of movement in pacing may approach that of the trot, the velocity often rising to three meters per second. Since the two unilateral propulsive and the two swinging feet always move together, and are always at one time in the same phase of motion, the swinging feet strike the ground together, so that after one pace but two strokes of the feet have been heard. In the rack, which is simply a modification of pacing, the uni- lateral feet act together, but the hind leg in propulsion is somewhat later than the fore foot of the same side in leaving the ground. Four Strokes of the feet are heard in this gait, two rapidly following sounds when the feet of one side strike the ground, separated by a longer interval 748 PHYSIOLOGY OF THE DOMESTIC ANIMALS. from the two rapid sounds when the feet of the opposite side strike the ground. It has been seen that in the movement of locomotion in man there are two periods of time in which both feet are on the ground and only one interval in which only one foot is in contact with the earth. In running, on the other hand, there is a moment in which one of the legs is raised up while the other is still performing the pendulum motion, and, consequently, both legs are at one time in the air, This interval is, how- ever, much shorter than that in which both feet are on the ground. (c) The Trot.—The form of locomotion seen in the horse and more seldoin in the ox and other quadrupeds which corresponds to the act of running in man is termed the trot, in which the fore leg completes its movement with the diagonal hind leg; so that in the trot the diagonal feet and hind limbs at the same moment leave the ground and at the same Saal Fia. 309.—THE Trot. (Colin.) moment again reach it. Therefore, in the trot two strokes of the feet on the ground are heard at each step. In the fast trot an interval occurs between this double stroke of the feet against the ground in which the body is moving through the air with all four feet raised from the ground. This interval is variable, usually being about half the time that the feet are in contact with the ground. In the trot the impulse is communicated to the pelvis from each hind leg alternately, so tending to strain the articulation between the sacrum and vertebra. This is, however, reduced to 2 minimum by the contrac- tion of the ilio-spinalis of the opposite side. In a very fast trot the second pair of feet leave the ground as soon as the first pair have reached the vertical position. Each step in the trot is twice as long as the step in the walk, in rapid trotting the hind feet PHYSIOLOGY OF MOVEMENT. 749 striking the ground considerably in front of the track of the fore feet and the velocity of motion rising to from eight to twelve meters per second. The walk turns into the trot when, the body being supported on two diagonal feet, the opposite hind foot rapidly leaves the ground and swings forward so that it strikes the ground simultaneously with the diagonal fore foot, or by one hind foot, as soon as it strikes the ground, rapidly passing into extension simultaneously with the diagonal fore foot. : (d) The Gallop—The more the long axis of the body coincides with the axis of the propelling hind legs, the greater is the propulsive power of the legs. The angle between the hind legs and the body may be increased by elevation by means of the fore legs, and in the act of galloping the fore legs are raised up, while the main propulsive power comes from the hind legs, so that the gallop is aseries of jumps. Accord- ing to the rapidity of the gallop or run of quadrupeds, four strokes of the feet on the ground are heard in a slow gait or canter, three in the ordinary run, and two in running at full speed. Ordinarily, the legs of the two sides of the body do not act simultaneously, and, according as the right or the left hind leg is extended farthest behind, one speaks of aright- ora left-handed gallop. Thus, in the right-handed run, the lett hind leg, stretched far under the body, first in its extension gives the impulse to the body, the right hind leg at this moment swinging forward to add the impulse of its extension a moment later, while both fore feet are off the ground, swinging forward, the left being the farthest advanced in commencing extension, while the right fore leg is still flexed. Then, while the left hind leg is still on the ground, though extended far behind the body, the right hind leg strikes the ground and adds its impulse in extension, while the extended left fore foot approaches the ground and the swinging right fore foot passes into extension. Then the left fore foot, reaching the ground, acts as a support on which the weight of the body is sustained, both hind legs being extended behind the body, the left being farthest extended, while the extended right fore foot is just about to touch the ground. Finally, the right fore leg reaches the ground and receives the weight of the body, while flexion commences in the left fore leg, both hind legs being now flexed under the body, the left hind foot being somewhat the farthest advanced. - At this moment the left fore foot is raised and the right fore leg, which alone sustains the weight of the body, leaves the ground after having passed the vertical, the body being then entirely free from all support, the fore legs flexed, and the hind legs drawn under the body, the left first reaching the ground. Thus, there is a moment in which, alternately, each limb alone sus- tains the weight of the body, and a moment in which both hind legs are 750 PHYSIOLOGY OF THE DOMESTIC ANIMALS. propelling the body, and one in which both fore legs are supporting it. In the analysis of the movements of the limbs in the run the greatest confusion has existed as to the functions of the fore limbs; this has now, thanks to instantaneous photography, been cleared up. In the first place, it is seen that at one time the body is entirely clear from the ground, and that the weight of the body is not received on one or both of the fore legs, but on one hind leg, advanced under the body so that the foot is nearly under the centre of gravity. In the second place, the fore legs do not serve merely as “‘ props or stilts ” for the support of the body in motion, but are themselves also propelling organs. At first sight this might seem impossible, for the insertion of the fore limbs, acting on the body at rest, and being inserted in front of the centre of gravity, could not advance, but only elevate it, as in rearing. In the running animal, however, the propulsion from the hind legs advances the centre of gravity, but at the same time tends to lower it, and if the fore feet were immovable, the animal would tend to fall forward on its head. This is prevented by the shifting of the fore feet, while at the same time a distinct upward impulse is communicated to the centre of gravity. This may be seen in Mr. Muybridge’s photographs, where there is a distinct elevation of the body at each time the fore legs leave the ground. The centre of gravity of the body is thus acted on by two forces, one from the hind legs tending to advance and lower it, the other from the fore legs tending to elevate it; the resultant of these two forces will evidently be a diagonal between the two; and the upward lift from the fore feet will more than compensate the downward tendency, and the body will be lifted and advanced. In this gait but two strokes of the feet are heard, the first pro- duced by the contact of the left hind leg, lengthened by the fall of the right hind foot, the second by the contact of the left fore foot with the ground, lengthened by the fall of the right fore foot. The interval between the first and second sounds is very short, that between the second and first, while the hind legs are swinging through the air, some- what longer. The length of the strides in the full run may amount to six or seven meters, and a velocity of nearly fifteen meters per second be attained. In a slower run or gallop three strokes of the feet are heard, the body, as in the trot, being supported on the diagonal limbs. The differ- ence of this gait from the trot consists in the fact that in the latter the support on the diagonal limbs is equally prolonged, while in the gallop the support on one pair is longer than on the other. A conception of this gait is obtained if it is imagined that one pair of feet are acting as in the trot, the other as in the movement of jumping. 1. In this gait, when right-handed, the left hind leg is extended on PHYSIOLOGY OF MOVEMENT. 751 the ground and gives the forward impetus to the body; the right hind leg and left fore leg are swinging forward, while the flexed right fore leg is being advanced. 2. The right hind foot and left fore foot then strike the ground and receive the weight of the body; the left hind leg is extended behind the body and about to leave the ground, while the fully extended right fore leg is advanced. 38. Then the right fore leg reaches the ground and sustains the weight of the body until the limb is vertical ; the left hind leg leaves the ground, and the flexed right hind leg and left fore leg are swinging forward. Finally, the right fore foot leaves the ground, the leg being strongly flexed, and the body moves through the air from the impetus from the left, aided by the right, hind leg. The three strokes of the hoof correspond to the three actions described above as 1,2,and 8. The pause between the first and second sounds is short, that between the second and third still shorter, while between the third and first, and while the body is moving through the air, the pause is considerably longer. In this gait, as in the run and long jump, and occasionally in the high jump, the weight of the body when it first reaches the ground is not received on the fore legs, but through rapid flexion the hind legs first touch the ground. . In the canter the action of all the limbs is much slower, the verte- bral column being more raised, the gait, therefore, more resembling the high than the long jump. The fall of the diagonal feet is separated by a short interval; so in the canter four strokes of the hoofs are heard. The plates following page 921, through the kind permission of Pro- vost Pepper, of the University of Pennsylvania, and Mr. Muybridge, are reproduced from the elaborate series of instantaneous photographs made by Mr. Muybridge in the University of Pennsylvania. 5, OTHER MovEMENTS IN THE Horse.—(a) Rearing.—In the act of rear- ing the fore part of the body becomes raised up on the hind extremities, so that the vertebral column leaves the horizontal direction and becomes nearly vertical. The first stage of rearing consists in the fixation of the hind legs, the elevation of the neck and head, and the contraction of the back and lumbar muscles, by which the vertebral column becomes rigid ; then the elevation of the fore legs commences with a slight bowing of the extremities and subsequent powerful extension, by which the feet are raised up from the ground and become flexed. Then there is a powerful contraction of the back muscles (the ilio-spinal, the gluteal muscles, and the ischio-tibial muscles), the anterior extremity of the vertebral column is somewhat raised up, its elevation being assisted by the drawing down of the pelvis by means of the lumbar muscles, so that the weight of the body is now borne by the flexed hind legs (Fig. 310). The vertebral column ordinarily does not quite reach the vertical line, but yet the line of 752, PHYSIOLOGY OF THE DOMESTIC ANIMALS. direction of the centre of gravity may fall behind the hind legs, and then the animal falls over backward. In rearing, the fore legs and hind legs are parallel to each other and always somewhat diagonal; likewise, both fore legs are not elevated simultaneously, but one somewhat precedes the Fig. 310.—REARTING. (Colin.) AB, line of action of ilio-spinal muscles; F G, gluteus maximus; D ©, ischio-tibial muscles; DE, pyramidal prolongation of the vastus. other. The return to the normal condition is accomplished by the drop- ping of the head and neck, the return of the fore legs from their flexed - to the extended condition, so that gravitation alone is sufficient to cause PHYSIOLOGY OF MOVEMENT. 753 the body to return to its natural position supported on all four of its extremities. (b) Kicking.—By this term is understood the elevation and violent ex. tension of the hind legs, with raising of the posterior part of the vertebral (Colin.) VeVERAMORCKEN <7. CD, ischio-tibial muscles; A A D, ilio-spinal muscles; F G, gluteal muscles. Fia. 311.—K1IcKING. column. The first stage of this act consists in the extension of the neck and the dropping of the head toward the ground between the firmly ex- tended fore legs, while the hind legs are flexed by the powerful contrac- tion of the back muscles, which find a fixed point of support in the last 48 754 PHYSIOLOGY OF THE DOMESTIC ANIMALS. cervical vertebra. The pelvis and posterior part of the vertebral column is raised, this elevation being assisted by and coinciding with the sudden extension of the hind legs, the feet leaving the ground and being ex- tended by the muscles of the upper joint of the leg, the lower joints likewise being subsequently extended. Here, also, both fore feet are not parallel on the ground, but one is somewhat advanced in front of the other. The hind foot on the diagonal side is somewhat sooner raised, and, therefore, further extended than the other (Fig. 311). In this act the centre of gravity never nearly approaches the line of direction of the fore legs, so that this position can be maintained but for an instant, the trunk sinking again by its own weight, and is supported by the hind legs, which are now flexed and drawn under the body. (c) Lying Down and Rising Up.—The first stage of lying down in the horse consists in the backward motion of the fore feet and the for- ward motion of the hind feet, thus greatly reducing the base of support. A sudden flexion of the fore legs then occurs, so that the animal falls on its knees; then the hind legs become flexed, so that the posterior surface of the tibiz touches the ground. The act of lying down, therefore, in the horse is practically falling down. While lying one side of the body completely touches the ground, the limbs being extended from the body either in slight flexion or in complete extension. In rising up the extended extremities are drawn to the body, and by the unilateral action of the trunk muscles the body is brought in such a position that the chest and abdomen are in contact with the ground, the fore feet are then extended on the ground, and a fixed point for the back muscles thus being acquired, the contraction of these muscles draws the pelvis forward, so that the hind legs are now enabled to bring the feet against the ground, and by sudden extension-of all the legs the body is raised up. (ad) Walking Backward.—In walking backward in the horse the head and neck are elevated, the spinal column, through the contraction of its muscles, rendered rigid, and the fore legs in a somewhat flexed condition are directed from above backward and downward, and then, in contact with the ground, gradually extended, being assisted by the contraction of the pectoralis major and latissimus dorsi, serve to push the body back- ward from the flexed hind legs. The backward movement occurs by the alternate movement of the diagonal feet; thus, it may commence with the fixation and extension of the right fore foot, then the left hind foot, then the left fore foot, and then the right hind foot. The foot which is raised up is, however, again placed on the ground and commences to act as a supporting member before the foot which is next elevated has left the ground. Consequently, support continues on three feet at one time, and the period of support lasts much longer than that of forward move- ment. Walking backward in quadrupeds is, therefore, an extremely slow PHYSIOLOGY OF MOVEMENT. 755 gait. In this act the centre of gravity is not moved directly forward but oscillates from side to side. (e) Swimming.—In swimming the trunk is almost entirely immersed in the water, the neck extended, and the head held high. The horse swims readily, since its lungs contain a large amount of air, and the rapid movement of the limbs gives to the body an impulse in a horizontal direction, the weight of the body being largely overcome by the buoy- ancy of the water. The movement of the feet consists in rapid pen- dulum-like motions from before backward, and the forward motion of the body results from the resistance which the water offers to the back- ward movement of the feet. The swimming motions in the horse occur regularly in the same direction on each side of the body. ’ The power developed by any mechanical contrivance is estimated by the weight multiplied by the height to which it may be raised in one second ; this is described as a kilogram meter. Animals, therefore, may _ be regarded as machines, since they possess the power of raising a weight to a certain height. Likewise, the motion of a weight on a level surface is to be regarded as a production of work, and whose movement equals the sum of all the resistances which have to be overcome by the animal and the velocity produced. The power of a horse is placed, as an average, at sixty kilogram meters, an ox at sixty kilogram meters, and an ass at thirty-six kilogram meters. The average velocity communicated to the weight in work continued for several hours each day has been placed in the horse at 1.25 meters, the ox 0.8 meter, and the ass 0.8; consequently the unit of power in the horse has been placed at seventy-five kilogram meters, in the ox forty-seven, and ass twenty-nine: so that, therefore, one horse-power would mean a power which would be able to raise seventy- five kilograms one meter high in one second. In referring these figures to the body of animals, it has been calculated that the development of power in animals in one hour, reckoned for each kilogram of body weight, is— 7 In the horse, . F ‘ : . 940 kilogram meters. « «© mule, A ; ‘ F . 800 ae ee oe ORE ASS, : : d : 7 fae ss i fe EE COR, 3g % : ‘ : . 620 ne ne «man, . : y : j . 560 ‘e we In the application of animal power in hauling, or in employing the horse as a draught animal, resistance has to be overcome, since the centre of gravity must be advanced by the power exerted by the hind extremi- ties (Fig. 312). In general, the hauling power of an animal, as in all motors, is governed by the mass moved, therefore through the weight of the animal and through the velocity communicated. The power thus acts in two relationships, through the overcoming of the resistance of the. 756 PHYSIOLOGY OF THE DOMESTIC ANIMALS. weight and the transference of the velocity of the animal to the moving mass. All the arrangements of the hind extremities are especially favor- able for the production of power; thus, reduction of the anterior pelvic angle, accompanied by powerful development of the hips and lumbar muscles. In animals, therefore, with short bones, slight angularity, and short muscles the conditions are most favorable for drawing heavy weights, while animals with long bones, long muscles, and highly angular joints are especially adapted for speed. The position of the centre of gravity in the animal body is especially of influence in the developing power. Since the body weight is the moving force its Fie, 312.—HAULING FROM A COLLAR. (Colin.) The line, A B, indicates the direction of the Feeulfene. of the propelling forces through the lines, A D an . action will be the more developed the farther forward the centre of gravity, since in this way the power-arm of the lever will be increased. Consequently, draught animals sink the head and neck. The power developed by horses has been estimated by raising a certain weight to a certain height by a rope passing over a pulley. Experiments so made have shown that 2 moderately strong horse may raise a weight of ninety-five kilos in one second to 0.8 meter high, from whence horse- power of seventy-six kilogram meters has been deduced. In the same way the power of an ox has been found to be forty-seven and an ass twenty-nine kilogram meters. In drawing a weight, the full power of an PHYSIOLOGY OF MOVEMENT. 757 animal is never employed, but there is always a certain amount of loss from friction and other causes. As most of the contrivances which are employed to enable horses to draw weight consist of attachments which applies the weight to the horse’s shoulders, the weight falls in front of the centre of gravity of the body, and the animal may thus be regarded as pushing the weight ; and as the mass moved is the animal’s body plus the applied weight, the greater the latter the more the centre of gravity of the common mass will be advanced. Hence, in drawing heavy weights the fore limbs will be behind the common centre of gravity, and they, also, in their extension will aid in propelling the body. 6. SpecraL MuscuLarR MEcHANIsMSs.— The Voice.—By the term voice is meant the sound produced in man and the higher animals through the vibration of the column of air forced by the contraction of the thorax between the vibrating vocal cords of the larynx. Speech, of which man Fig, 313—THe HUMAN LARYNX, AS SEEN FIG. 314.—POSITION OF THE HUMAN VOCAL WITH THE LARYNGOSCOPE. (Landois.) atti ON UTTERING A HIGH NOTE. 4, tongue: E., epiglottis: V., valleculla; #., glottis; (Landots.) Bise'vool cords: 'P, position of pharyng; Ss caruags af Ssntorini; W., cartilage of Wrisberg; S. p., sinus alone is capable, consists in certain modifications of the vocal sounds by the parts situated above the larynx; that is, the pharynx, mouth, soft palate, nasal fosse, tongue, teeth, and lips. Speech may, therefore, be described as articulate voice. Voice is produced by the imparting of the vibrations of the vocal cords to the column of air within the respiratory organs. The means by which this is accomplished is entirely analogous to that by which sound is produced in reed instruments. The vocal cords consist of free rims of highly elastic membrane whose tension may be varied by muscular action and whose edges may be approximated or separated (Figs. 313 and 314). When the edges of the vocal cords are in close contact, through a strong muscular expiratory motion the air below the vocal cords becomes greatly condensed and finally its tension is sufficient to overcome the resistance of the closed vocal cords; when the vocal cords are thus 758 PHYSIOLOGY OF THE DOMESTIC ANIMALS. separated air passes between them, and, consequently, rarefaction of the air below takes place, while the cords being elastic, their tension serves to again readily overcome the propulsion of the air from the contraction of the thorax. As a consequence, the edges of the vocal cords are set into rapid vibration and these vibrations are communicated to the column of air both below and above the vocal cords, and as a result a sound which is due to these vibrations is produced ; the vibrations of condensa- tion and rarefaction of the air are the principal causes of the tone, while the cavities above the vocal cords fulfill the part of resonators. Sounds produced in this way, like other musical sounds, may vary in regard to their pitch, intensity, and quality. The pitch of the sound will depend upon the length of the vocal cords, the shorter the vocal cords, the more rapid are the vibrations and the higher the pitch of the note produced. The pitch of the note is further dependent upon the degree of tension of the vocal membrane. As in the case of musical instruments of a similar nature, stringed instruments, or reed instru- ments, the pitch of the note is proportionate to the square root of the tension. In man and other mammals in whom vocal cords are present, the pitch of the note may, therefore, be modified by varying degrees of tension of the vocal cords through the action of different muscles. The intensity of the sound depends primarily upon the strength of the blast of air, so that, therefore, the more vigorous the expiration, the greater will be the amplitude of the vibration of the vocal cords and the greater will be the intensity of the sound, while the action of the dif ferent resonators of the vocal organs, through the sympathetic vibrations induced in their cavities by the vibration of the column of air set into motion by the swaying vocal cords, is added to the fundamental tone that is produced and its intensity is modified. The timbre, or quality of the vocal sounds, as in other musical in- struments, depends upon the over-tones or harmonics which accompany the fundamental note. Changes in the shape of the different resonating cavities of the vocal organs will, by modifying the prominence of dif- ferent over-tones, account for the difference in the voice of different animals. The mode of production and the character of the voice differ very greatly in different members of the animal kingdom. Voice may be pro- duced in all vertebrates possessed of lungs and larynges, while in fishes, where the respiration is branchial and not pulmonary, the production of voice is impossible. In invertebrates the sounds produced in such great variety are in no respect analogous to the voice, since they are produced by entirely different mechanisms. Thus, insects produce sounds (which are especially distinguished for their acuteness) either by the rapid movement of their wings, as in flies and bees, or by rubbing their legs PHYSIOLOGY OF MOVEMENT. 759 on their wing-cases, or their wing-cases on each other or on the thorax orabdomen. In humming insects sound may be produced by forcing the expired air from their stigmata, which are provided with muscular rods and which are thus thrown into vibration, so that in this group of insects, represented by the humming-bees and many dioptera, the closest analogy exists between the production of sound and the production of voice in the vertebrates. a MTG Fig. 315.—INFERIOR LARYNX OF THE TURKEY. (('rtitzner.) A, during voice production: B, in free respiration. (In A! and BI the anterior wall is removed.) _m, st, tr., sterno-tracheal muscles in contracted condition in A and Al; Tr., trachea; v. Tr. R., united tracheal rings, forming the tympanum with its antero-posterior bridge, S. ; B. Sp., bronchi; m.t.e., external tympanic membrane; m. ¢.i., internal tympanic membrane stretched out flat in B and Bl,inA and A! forming sharp folds in the lumen of the bronchi; L. ibr., interbronchial ligament; 6., band run- ning to the dorsal wall of the trachea. Animals below insects, as radiates and mollusks, are all entirely incapable of sound. Among reptiles, certain of them, such as frogs, lizards, and other batrachians, possess true vocal organs. Among am- phibians the frog has a larynx provided with muscles, which produces a sound of varying pitch, dependent upon the strength of the muscular contraction and the force of the expiratory blast. The range of such vibrations is, however, extremely limited. In the Rana esculenta there is on each side of the angle of the mouth a membranous bag which may 760 PHYSIOLOGY OF THE DOMESTIC ANIMALS. be inflated with air, and whose walls, being thin and membranous, are thrown into vibration, and, together with the column of air contained in the oral chamber, aid in producing the characteristic resonance of the croaking of the frog (Fig. 315). In birds the vocal organs are double, a larynx situated at the upper termination of the trachea anda syrinx at its bifurcation constituting a true vocal organ. Two folds of mucous membrane, or three in the case of song-birds, project into each bronchus, and are so acted on by muscles as to vary their tension and adapt them to the production of voice. The superior larynx acts only as an accessory in the production of sound. The number and complexity of the muscular fibres acting on these membranes varies in proportion to the range of voice. In the gallinacea simply a trace of muscular fibre can be recognized; but one pair of muscles is found in the eagle, three pairs in the paroquet, while five pairs are found in song-birds. These muscles have a common origin in the trachea, and their other extremities are inserted into the first ring of the bronchus. In addition to these intrinsic muscles there are others concerned in varying the length of the trachea, so as to alter the length of the vocal tube and, therefore, the pitch of the note produced. The superior organ, or the larynx, is entirely negative in the production of sound, and the performance of tracheotomy below the larynx produces but slight modification in the character of the sound produced. In mammals, as is well known, the greatest variation exists in the character of the sounds produced. The organs for the production of sound are here the larynx and the upper resonating chambers, varying in shape and general character among each other, although in all built on the same general plan as in man. The variations in the voice are dependent upon modifications in the larynx, in the depth of the nasal chambers, the shape of the pharynx, of the various sinuses, and the formation of the mouth and of the laryngeal ventricles. Sound is, how- ever, primarily due in all cases to the vibrations transmitted to the column of air by the swaying to and fro of the vocal cords. The superior or false vocal cords of man are absent in many species of mammals. The glottis of the horse is distinguished by the formation of a semi-lunar fold of mucous membrane below the epiglottis, which serves to form 4 funnel-shaped cavity. The laryngeal ventricles are also well developed. The voice in the horse is produced by a succession of interrupted expira- tory movements, the tension of the vocal cords gradually diminishing during each complete expiration, so that, therefore, the first sounds produced have a higher pitch than the last; the superior ventricles are wanting (Fig. 316). The larynx of the ass differs but slightly from that of the horse. Here, also, there are two vocal cords, the ventricles are well developed, PHYSIOLOGY OF MOVEMENT. 761 but the opening to them is narrow. The voice of the ass is characterized by the fact that it commences in an inspiratory movement in the produc- tion of a sound of high-pitch and it terminates in expiration in the production of a deeper sound. The larynx of ruminants offers considerable differences to that of solipedes. The glottis is short, and the vocal cords can scarcely be dis- tinguished from. the lining membrane of the larynx, and there are no ventricles. The voice in ruminants is, therefore, more imperfect than in the horse, and consists of a sound of low pitch capable of but little variation (Fig. 317). In the hog below the epi- glottis is found a large, mem- branous sack, which fulfills the purpose of a resonator, greatly Fic, 814—LARYNX OF THE HORSE FROM ABOVE AND BEHIND, (Miiller.) a al, thyroid cartilage; b b, arytenoid car- Fie, 317.—LARYNX ae HyYoID BONE OF Ox. tilages; ccf, arytenoid muscles; d d!, aryepiglottic aller.) folds; e, epiglottis, 11!, posterior crico-arytenoid 1, 2, 3, arms of the hyoid bone; 4, thyroid cartilage; 5, body muscles; 2 2!, oblique arytenoid muscles; 33/, of the hyoid bone; 5! and 5//, fork of the hyoid bone; 6, arytenoid anny Ovi a eens, Gena ane a eae ne ere strengthening the intensity of the voice and giving to it its peculiar character. In the hog the inferior vocal cords are inserted into the tracheal border of the thyroid cartilage and the arytenoid cartilages are fused together, the vocal cords are rudimentary, the ventricles are deep and communicate with the interior of the larynx only by a narrow slit. Two characters of sound may be produced by the hog, the one of low pitch, a grunt, which is the habitual sound, while another of very high pitch is only produced when the animal is maltreated or excited. In the dog the vocal cords are well developed, while the false vocal 762 PHYSIOLOGY OF THE DOMESTIC ANIMALS. cords are scarcely perceptible; the ventricles are ample, but their openings are very narrow. The voice in dogs is capable of greater scope than in other of the domestic animals, with the exception, perhaps, of the cat, which is characterized by an almost equal development of the upper and lower vocal cords. The mechanism of the production of the voice, therefore, depends upon the expulsion of a blast of air between two free membranous rims, which are thus thrown into vibration and whose tension and position are capable of modification. The change in the position and tension of the vocal cords is accomplished through the action of the laryngeal muscles. The laryngeal muscles fulfill a double function. In respiration, as has been already mentioned, the glottis is widened during inspiration and the vocal cords tend to approach each other during expiration. In the production of voice the vocal cords are almost always in close contact. The glottis may be dilated by the action of the crico-arytenoid muscles. When they contract the arytenoid cartilages are drawn back- ward, downward, and toward the middle line, so that, therefore, the vocal processes in which the vocal cords are inserted must be ‘separated. A large triangular space is thus formed between the vocal cords as in inspiration. The glottis is constricted by the contraction of the transverse arytenoid muscles, which extend from both outer surfaces of the arytenoid cartilages along their entire length. When these muscles, together with the oblique arytenoid, contract, the arytenoid cartilages are approximated and the glottis closed. During the production of voice the vocal processes of the arytenoid cartilages must be closely approximated, and to accomplish this it is necessary that they be rotated inward and downward. This result is brought about through the contraction of the thyro-arytenoid muscles, which are imbedded in the substance of the vocal cords, and when they contract they so rotate the arytenoid cartilages that the vocal processes turn inward. The glottis is, therefore, narrowed to a mere slit in the anterior part, while a triangular space through which respiration takes place remains open posteriorly. The vocal cords vary in tension according to the degree of con- traction of the crico-thyroid muscles, which pull the thyroid cartilage downward and forward. At the same time the crico-arytenoid muscles act upon the arytenoid cartilages, drawing them slightly backward and maintaining them in that position. In the production of voice, not only must the vocal cords be thrown into tension in the manner above described, but the triangular space of the respiratory part of the glottis between the arytenoid cartilages must likewise be closed. This is accomplished by the contraction of the PHYSIOLOGY OF MOVEMENT. 763 transverse and oblique arytenoid muscles, added to the contraction of the internal thyro-arytenoids. At the same time a concave margin is produced in the vocal cords through the action of the crico-thyroid and the posterior crico-arytenoids (Figs. 318, 319, and 320). if tof oe eeeaneernee: Fic. 318.—ACTION OF THE MUSCLES OF a FI4. 319.—S HORIZONTAL SECTION OF The dotted lines indicate the new positions as- IG. 319.—SCHEMATIC HORIZONTAT sumed by the thyroid cartilage in the action of the THE LARYNX. (Landois.) crico-thyroid muscles. I, position of the horizontally divided arytenoid cartilages 1, cricoid cartilage; 2, arytenoid cartilage; 3, during respiration; from their anterior processes run the con- thyroid cartilage ; 4, true vocal cord; 5, new position verging vocal cords. The arrows show the line of action of the of the thyroid cartilage; 6, new position of the vocal _ posterior crico-arytenoid muscles, resulting in the assumption of cords, the positions indicated by the dotted lines, II, II. Fic. 320.—ScHEME OF THE CLOSURE OF THE GLOTTIS BY THE THYRO- ARYTENOID MUSCLES. (Landois.) q, qT, Position of the ae ptenioid cartilages during quiet respiration ; the arrows indicate the direction t , the positi of of the arytenoid cartilages after the muscles contract. The thyro-arytenoid muscle is the one which principally causes variations in the tension of the vocal cords and, consequently, variations in the pitch of the sounds. When the muscles acting on the vocal cords relax the vocal cords themselves likewise relax from the reduction of the extending force, and 764 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the elasticity of the displaced thyroid and arytenoid cartilages comes into play and causes them to assume their original position. The thyro- arytenoid and the lateral crico-arytenoids may likewise serve to produce relaxation of the vocal cords. To recapitulate: the tension of the vocal cords is principally due to the crico-thyroid and the posterior crico-arytenoids ; the narrowing of the respiratory part of the glottis is accomplished by the transverse and oblique arytenoids ; and the narrowing of the vocal glottis is accom- plished by the contraction of the thyro-arytenoid and the lateral crico- arytenoids, the former muscle likewise increasing the tension of the vocal cords. : With the exception of the crico-thyroid all the intrinsic muscles of the larynx are supplied by the inferior laryngeal nerve. The superior laryngeal nerve supplies the crico-thyroid, and is at the same time the sensory nerve of the mucous membrane of the larynx. For the mechanism of articulated speech the reader is referred to text-books on human physiology. SECTION II... THE PHYSIOLOGY OF THE NERVOUS SYSTEM. Tue different functions of the animal body have been found to require for their fulfillment divers structures different in location and in mode of action. In any one of the single functions of the animal body, such, for example, as the contraction of a muscle, a number of processes are concerned; thus, the inauguration of the muscular contraction requires the conduction to a muscle of a stimulus. The muscle in con- tracting uses up a large supply of oxygen and liberates more carbon dioxide and other retrograde products. Increased muscular contraction, therefore, necessitates a supply to the muscle of a larger amount of arterial blood and the removal from the body through the lungs and kid- neys of the products of the waste of muscular tissue. Muscular activity, therefore, implies accelerated circulation, accelerated respiration, and increased excretion. A similar complexity may be traced in all the other different functions of the animal body. Each modification or even mani- festation of function implies a reflection upon the activity of other asso- ciated processes. This co-ordination of operations, which may be widely different in character and yet closely interdependent, is accomplished by means of the nervous system. The primary object of the nervous system is, therefore, to link together different and widely distant organs, and thus act as the regulator of the actions of the animal body. In animals where specialization of function has not yet appeared no such communication between different parts of the body is required, and, as a Consequence, in such no nervous system is present. As we found that the organs of circulation were largely dependent for their degree of | development on the complexity of. the alimentary apparatus, so it may be found that in a general way the nervous system is developed in pro- portion to the muscular system. This indicates one of the main func- tions possessed by the nervous apparatus for controlling and modifying movement. This is, however, but one side of the importance of the nervous system. In the nervous system is developed in the highest degree the fune- tion of automatism. By this term is meant the power possessed by the lowest forms of protoplasm of receiving impulses from without and modi- fying them into efferent impulses, which may take on the form of motion as their most usual manifestation. - It is thus seen that automatism (765) 766 PHYSIOLOGY OF THE DOMESTIC ANIMALS. implies at least four different operations—the conduction of afferent impulses, the reception and conversion of these afferent into efferent impulses, and the liberation again and conduction of efferent impulses. In the scheme of specialization of function it would only be expected that for the division of labor we should also find that these operations become separated and located in different structures. We find, therefore, the nervous system, in accordance with this purpose, divided into organs of conduction and organs of receiving and liberating nervous impulses. The organs for transmitting nerve impulses constitute the nerves. The organs for modifying and liberating nerve impulses are found in the ganglia or nerve-cells of the nervous system. The scheme of the nervous system, therefore, implies the presence on the periphery of a receptive organ for receiving external impressions. Such an organ is represented by the terminal filaments of the sensory nerves, or, rather, the nerves of general or special sense. It implies a means of communication between this external receptive organ and the nervous ganglia at a distance, the latter possessing the power of receiv- ing the impressions transmitted from the exterior through the afferent sensory nerves. Such a receptive ganglion is again in connection with a cell or collection of cells in which the automatic powers are especially developed, and which, therefore, modify the impressions coming from without and convert them into efferent impressions. The latter are con- ducted from the centre through the efferent or motor nerves to various peripheral organs, whether to the terminal plates in the muscular tissue or to glands, blood-vessels, or the other structures of the animal body. Like all other organic systems, the nervous system becomes more complicated and diversified, reaching a higher stage of perfection in pass- ing from the lowest forms of animal life, in which it first appears, to the higher examples of the animal series. In the protozoa, the lowest subdivision of the animal kingdom, a nervous system in the sense in which we have described it, as constituted of nerve-cells and nerve-fibres, is entirely absent. The undifferentiated protoplasm fulfills all the purposes of the nervous system as demanded by the needs of such an organization. In the animals belonging to the group of infusoria, where we find the first appearance of the development of organs as seen in the contractile cilia as organs of locomotion, the nervous system has not appeared, the movement of such organs being dependent simply upon the automatic properties of the undifferentiated protoplasm; and we find as an illus: tration of this that even in animals higher in the scale, where ciliated organs are commonly found, that such are independent of the nervous system. In the star-fish is found the first clear evidence of nerve fibres and PHYSIOLOGY OF THE NERVOUS SYSTEM. 767 cells connected together to receive and convey impression (Fig. 321), It consists of a ring around the mouth composed of five ganglia of equal size with radiating nerves. From this circle delicate fibres may be traced into the different rays. In lower zodphytes all traces of the nervous system is wanting, and in them the functions of nutrition are accom- plished through the operations of undifferentiated protoplasm. In the mollusks the nervous system has reached a somewhat higher form of development, and two or more ganglia are found located around the gullet and communicating by nerve-fibres with other ganglia in dif. ferent regions of the body, sending off nerves to the different organs. Usually in the mollusks there is a cir- cular ganglion located in the cephalic side of the animal and two abdominal ganglia placed below the cesophagus Fia. 322—NERVOUS SYSTEM OF A GaAS- TEROPOD MOLLUSK. (Perrier.) e ¢, cerebroid ganglia; p, pedal ganglia; 0, otocysts; Fig, 321—NERvous SYSTEM OF THE STAR- v, vl, vl, ganglia of second cesophageal collar; ‘ten. FISH. (Carus.) tacles; y, eyes; x, excrement. and united to the cephalic ganglion and the esophageal ring (Fig. 322). These ganglia are frequently connected with others whose locations will vary in different species. In the articulata, represented by the insects, annelida, and crusta- ceans, the nervous system has become symmetrical (Fig. 323). The ganglia which compose the nervous system may be arranged In pairs on each side of the median line of the body, each pair corre- sponding to a segment of the body, extending throughout its entire length and united to each other so as to form a longitudinal chain of ganglia, which are connected further by transverse commissures. Sometimes the ganglia consist of a single median row. Usually one of the ganglia is more voluminous than the others, and being, as a rule, located in the anterior extremity of the animal, might be compared to 768 PHYSIOLOGY OF THE DOMESTIC ANIMALS. the brain of vertebrates. Such a comparison is warranted by the fact that when nerves of special sense are present they invariably originate from this collection of nerve-cells. Where a distinct cephalie gan- glion is present it is situated above the cesophagus, while all the other portions of the ganglionic chain lie on the ventral side of the body, the commencement of the chain being connected with the cephalic ganglion Fic. 323.-NERVOUS SYSTEM OF AN ARTICULATE. (Perrier.) by a collection of circular fibres around the gullet and spoken of as the . esophageal collar. The number of ganglia in the articulata is very variable; there may be twelve or fifteen pairs or but three. The larger the number of ganglia, the greater their tendency to fusion along the middle line. In all invertebrates the nervous system is composed of such a series of separate and distinct ganglia. PHYSIOLOGY OF THE NERVOUS SYSTEM. , 769 In vertebrates the nervous system has ‘reached 2 much higher stage of development, and here is placed above the digestive canal, in contra- distinction to the position which it occupies when present in the inverte- brates, and is usually inclosed within a bony or cartilaginous cavity ; it is divided into a cephalic portion, confined within the cranium, connected toa long trunk of nerve-cells inclosed within the vertebral canal, con- stituting the spinal cord (Fig. 324). From this central nervous system, FIG. 325.—BRAIN OF PERCH, AFTER CUVIER. (Rynier Jones.) A, cerebellum; B, cerebrum; C, olfactory ganglion; i, olfactory nerves; D, optic ganglion; G, supplementary lobe; H, transverse fibres in the walls of the cerebral ventricle; N, commissure of the optic nerves; P, Q, R, 8, T, U, the third, fourth, fifth, sixth, seventh, and eighth pair of cerebral nerves. FIG. 326.—BRAIN OF FROG SEEN FROM ABOVE. (Niihn.) Fic, 824.—BRAIN AND F F fo 1 L. OLF, olfactory lobes; L.H, hemispherical lobe (fore-brain); VIII, lobe re Corp oF MAN. of the third ventricle; L.O, optic lobes (mid-brain); CBLL, cerebellum (hind- ( ‘arpenter. ) brain); OBL, medulla oblongata; RH, rhomboidal sinus. both from the brain and spinal cord, originate series of fibres which fulfill the functions of conduction of both motor and sensory impulses and which extend to all parts of the body. In connection with this sys- tem, which is spoken of as the cerebro-spinal system, there is usually found 4 more or less independent series of ganglia, which constitutes the sympathetic system. While such a cerebro-spinal system characterizes all vertebrates, it is 49 770 PHYSIOLOGY OF THE DOMESTIC ANIMALS. capable of great variations in development in different members of this group. In fishes and reptiles the brain is less developed than in higher members, no convolutions are found on its surface, and, while the cere. bral hemispheres are not highly marked, the optic. and olfactory lobules are usually comparatively voluminous, while the cerebellum of reptiles and fishes is reduced to a single lobe (Figs. 325 and 326). In birds the hemispheres or cerebral lobes are still, as in the mam- mals, the most voluminous portions of the brain, but here, also, no con- volutions are found and they are not closely united to each other, since the corpus callosum, as well as the pons varolii, is absent (Fig. 327). In birds the analogue of the tubercula quadrigemina, which are four in number in the maminals, are here reduced to two, and, therefore, receive the name of the tubercula bigemina or optic lobes, and are visible at each side of the brain when looked at from above. Fig. 327.—BRAIN OF BIRD (Falco buteo). (Nithn.) I, view of upper surtace. II, view of lower surface: chr, cerebrum; gy, corpora quadrigemina, or bigemina; cbl/, cerebellum; o//, medulla oblongata; 4, hypophysis; opt, optic nerve. In birds the cerebellum is likewise reduced to a single median lobe, and is entirely uncovered by the cerebrum, and being single it possesses no lateral hemispheres; the pons varolii, or the transverse fibres which serve as a commissure for the cerebellar hemispheres, as in mammals, is likewise absent. The characteristics of the mammalian brain will be subsequently alluded to. The nervous system is composed of central masses which are in constant communication with different parts of the body by means of peripheral prolongations which act as organs of conduction. The nervous system exists, therefore, under two forms—the central, composed largely of the so-called nervous ganglia, or nerve-cells, and the organs of conduction, or nerve-fibres. As already indicated, the peripheral termi- nations of the nerves are likewise in connection with corpuscular bodies, PHYSIOLOGY OF THE NERVOUS SYSTEM. 771 which vary in accordance with the character of the nerves with which they are in communication. The nerves or nerve-fibres are simply ANN i FIG, 828,—BRAIN AND NERVOUS SYSTEM OF DIFFERENT ANIMALS, NATURAL SIzE. (Thanhoffer.) 1, brain of ape; 2, domestic cat; 3, squirrel: 4, water-rat; 5, mole; 6, fox; 7, quail; 8, nervous sys- tem of horned beetle; 9, perch; /g, suprapharyngeal ganglion: /d, abdominal ganglion ; vd, end ganglion; b, esophagus; e, nervous cord connecting the pharyngeal ganglion: Crb, cerebrum ; ebl, cerebellum ; mobl, medulla oblongata; olf, olfactory tract: /o, optic lobes; Ch, hemispherical lobes; I-IX (in Fig. 9), : cerebral nerves; vd, vagus ganglion; br. branchial nerves; 10, nervous system of the snail; /g, supra- pharyngeal ganglion; ag, infrapharyngeal ganglion. 772 PHYSIOLOGY OF THE DOMESTIC ANIMALS. organs of conduction, and the nerve-cells, in which each nerve at each end terminates, are for receiving and liberating impulses. Nerves may be of two kinds: afferent or centripetal nerves, which are concerned in the carrying of impulses from the exterior to the cen- tral organs; such nerves are frequently spoken of as sensory nerves: and efferent or centrifugal, which carry impulses from the central portions of the nervous system to the exterior; such nerves are motor nerves. These two distinctions between nerves are not based on any differ- ence in anatomical structure, but are simply functional differences, since it has been found by experiment that nerves may carry impulses in either direction, and by dividing « motor and sensory nerve and con- necting the divided extremities of the one with the other the sensory nerve, after union has taken place, may now carry motor impulses and the motor sensory impulses. The essential part of the nerve-trunk is the so-called axis cylinder, which is composed of a thin filament of undifferentiated protoplasm in no way different, as far as may be determined, from that found in other examples of free protoplasm. This protoplasmic centre, which is com- posed of a number of fine fibrils and constitutes the axis cylinder, is always covered by a thin, transparent membrane, which is termed the primitive sheath. In many instances this is the only covering to the ultimate fibrils of the nerve, such nerves being called non-nedullated nerve-fibres; in others, which are called medullated nerves, within this primitive sheath, and surrounding directly the fibrils of the axis cylin- der, is found a thick layer of double refractive substance, which is termed the medullary sheath or white substance of Schwann (Fig. 329). Each nerye-trunk consists of bundles of nerve-fibres held together by fibrous connective tissue called the epineurium, in which are the blood-vessels with which the nerve-trunk is supplied, lymphatics, and numerous fatty cells. The neurilemma closely resembles sarcolemma in its character; when subjected to long boiling both yield gelatin. Ganglionic cells or nerve-corpuscles vary greatly in size. They may be spherical, ovoid, pyramidal, or of other shapes, and send off usually numerous branched processes, which serve to characterize the cells as multipolar nerve-cells. No cell-membrane is to be detected, but the gan- glia are of soft consistence, containing numerous granules and pigment matter. The nucleus is ordinarily well developed and is disproportionately large to the size of the cell. Two nucleoli are nearly always present. One of the processes of the ganglion is always unbranched and forms the . axis cylinder of the nerve originating or terminating in such a nerve-cell. A nerve, therefore, may be regarded simply as a process of the nerve-' PHYSIOLOGY OF THE NERVOUS SYSTEM. TI3 cell, the white substance of Schwann being added after the separation of the nerve-filament from the ganglion. FIG. 329.—THE STRUCTURE OF NERVOUS TISSUE. (Landois.) 1, primitive fibrilla; 2, axis cylinder; 3, Remak’s fibres: 4, medullated varicose fibre: 5, 6, medul- lated fibre, with Schwann’s sheath; C, neurilemma; /, ¢, Ranvier's nodes; b, white substance of Schwann; d, cells of the endoneurium; «, axis cylinder; x, myelin drops; 7, transverse section of nerve- fibre; 8, nerve-fibre acted on with silver nitrate; I, multipolar nerve-cell from spinal cord; =, axial oylinder process: y, protoplasmic processes—to the right of it a bipolar cell; II, peripheral ganglionic cell, with a connective-tissue capsule; III, ganglionic cell, with, o, a spiral, and, 7, straight process ; m, sheath. The branched processes of nerve-cells are not, as a rule, concerned in the formation of other nerve-trunks except in the bipolar or multi- polar cells, but are concerned in bringing in communication other T74 PHYSIOLOGY OF THE DOMESTIC ANIMALS. adjacent cells, so that impulses may be conducted from one to the other. In the peripheral ganglia connective-tissue corpuscles surround the nerve-cells. I. CHEMICAL AND PHYSICAL CHARACTERISTICS OF NERVOUS TISSUES. The composition of nervous tissue varies according as the examina. tion is made of the white matter of the cerebrum or of the spinal cord, or of the gray matter. The following table represents their average composition :— CHEMICAL COMPOSITION OF NERVOUS TISSUE. Gray Matter. White Matter. Water, “ ‘ 4 . : . 81.6 68.4 Solids, 2 ‘ 3 . ‘ . 18.4 31.6 Proteids, . . : ; ; 3 . 55.4 24.7 Lecithin, . 3 F : F : . 17.2 9.9 Cholesterin and fats, . ‘ ‘ . 18.7 52.1 Cerebrin, . : : 5 ; 0.5 9.5 Substances insoluble in ether, 6.7 ooo Salts, - ‘ ‘ ‘ 1.5 0.5 When brain-matter is incinerated the greater part of the phosphorus of the lecithin becomes phosphoric acid, and the ash, hence, has an acid reaction. The following is the composition of the ash of one hundred grammes brain after removing lecithin :— pee : : ‘ F . f ‘ F ». . 0.411 1, : . ‘ 5 ‘i Fi F ‘ a . 2.524 K,HPO, © » . . 2. 2 { ff o'266 Ca,P,0,, ‘ 2 ‘ ‘ , R ‘i : . 0.013 MgHPO, . . . . 2 2. 4 2 2 0.084 Na,HPO;, < « » =» ww w Js ¢ 4 (ge NaeOe ic f fet HA ik: “ph ca . vec dee Excess CO,, . : : ‘i ‘ , r fi . 0.082 FeP,0,, : . i : is 4 j ‘ . 0.010 6.290 The reaction of the gray matter during life is said to be acid from the presence in the ganglionic masses of lactic acid. The reaction of the white matter is neutral or alkaline. From the above table it is seen that more than half the solids in the gray matter and about one-fourth the solids in the white matter of the nerve-centres consist of proteids, and yet our knowledge of these bodies is very imperfect. The proteids consist of albumen, which is found in the axis cylinder and in nerve-cells; it is soluble in water and coagulates at 75° C.; a globulin-like substance, which may be extracted by means of a 10 per cent. solution of common salt, and which is precipitated by dilution with water and by saturation with salt; and alkali albuminate, which remains CHARACTERISTICS OF NERVOUS TISSUES. 775 in solution when a 10 per cent. salt solution of brain is boiled; it may be precipitated after filtering by the addition of acetic acid. Nuclein, also, is found, especially in the gray matter; while in the sheath of nerve-fibres after the removal of the fatty matters by boiling alcohol and ether a nitrogenous body is found which is termed neuro- keratin, and which in its composition appears closely related to keratin and is especially characterized by the sulphur (2.93 per cent.) which it contains. Neurokeratin is not affected in gastric or pancreatic digestion ; it swells in causti¢ potash and strong sulphuric acid, but only dissolves in these liquids when boiled. Gelatin is likewise found in nerves, but is evidently derived simply from the connective tissue of their sheaths. Fats are present in large amounts, especially in the white matter and in the white substance of Schwann, which appears to be almost solely of a fatty nature. The specific constituents of the brain and nerves are of a highly complex character and may be divided into two groups—those which contain phosphorus in combination and those which are free from phos- phorus. As an example of the first of these, protagon may be mentioned, which, discovered by Liebreich, has been regarded by many chemists, not asa distinct body, but as a mixture of lecithin, a phosphorized fat, with cerebrin, a nitrogenous, non-phosphorized body. Experiments by Gamgee have, however, apparently proven that protagon is a definite chemical body, soluble in cold alcohol with difficulty, readily soluble in warm alcohol and ether. To this substance Gamgee attributes the em- pirical formula CyHaNsPO,. It forms a clear solution with glacial acetic acid. Cerebrin is an example of the special brain-constituents which are free from phosphorus; it appears, however, that cerebrin, as described by Miiller, is not a distinct body, but a mixture of cerebrin, homocere- brin, and encephalin. The entire subject of the organic constituents of the nervous system needs to be re-examined, since on any matter where such diametrically opposite opinions are held the error on both sides must be considerable. Like the muscular tissue, nervous substance when passive has a neutral or even faintly alkaline reaction; after prolonged stimulation cr functional activity, produced in any way, the reaction becomes acid. After death the reaction likewise becomes acid and the nerves become more solid, thus resembling the similar changes which occur in muscle, and, although not thoroughly investigated, in all probability are due to a similar process. Nerve-fibres are free from elasticity, and if divided do not retract ; 776 PHYSIOLOGY OF THE DOMESTIC ANIMALS. their cohesion, due to their connective-tissue constituents, is consider- able. It has been found that a weight of one hundred and ten to one hundred and twenty pounds was required to rupture the sciatic nerve of aman at the popliteal space. The nerves lengthen very considerably before breaking; they, therefore, are extensible. II. NERVOUS IRRITABILITY. As in the case of muscle, nerves are capable of having their func- tional activity called into play by various stimuli; they are, therefore, said, like muscles, to possess the power of irritability. Stimuli which call nervous activity into existence, like muscular stimuli, may be either mechanical, thermal, chemical, electrical, or physi- ological, by which is meant the normal stimuli which excite the nervous system in living bodies. In the case of the nervous system the influence of various stimuli may be made evident, either by allowing them to act upon motor nerves, when the contraction of the muscles evoked will indicate the stimulation of the nerve; or, in the case of sensory nerves, by the pain produced on their application. A mechanical irritant produces stimulation of the nerves by pro- ducing change in the molecular arrangement of the nerve-particles. If the mechanical stimulus, which may be of the nature of a blow, pressure, pinching, and stretching, be sufficiently severe the nerve may then become completely and permanently destroyed, and then lose its power at that point of conducting impressions. A single mechanical stimulation of a motor nerve will produce a single contraction of a muscle. If the stimuli be repeated rapidly at short intervals the contractions may, as in the case of electrical stimulation, be blended together, and when the stimuli succeed each other more frequently than sixteen in the second a prolonged tetanic contraction is produced. The action of variations in temperature on nerve-trunks is somewhat similar to that exerted on muscles. If the nerve of a frog be heated to 45° C. its excitability is first increased and then diminished, and the higher the temperature the greater the excitability and the shorter its duration. If the temperature be raised above 60° the medullary substance becomes disorganized and the nerve loses its excitability. Sudden application of cold or heat acts asa stimulus, and may cause musculur contraction. Increase of tempera- ture above 45° produces tetanus with rapid exhaustion of the nerve. Anything which will rapidly change the chemical composition of a nerve-trunk may act as a nerve stimulus, and, although such stimuli may at first increase a nerve’s excitability, they rapidly diminish its irrita- bility and often result in complete nervous paralysis. NERVOUS IRRITABILITY. T7177 Rapid desiccation of nerves by abstracting the water comes under the head of a chemical stimulus. Sugar, urea, glycerin, and many metallic salts likewise act as stimuli and often produce paralysis. Nerves may likewise be thrown into activity by the application of the electrical current, whether on employing the constant or induced current. When a constant current is allowed to enter a nerve a single contraction is produced at the moment of application of the current, and no other apparent eilect is evident until the current is broken. The breaking of the current again causes a contraction to occur. So, also, in sudden increase or decrease in the strength of a constant current passing through a nerve the same effect will be produced as on making or breaking the current. When a constant current which is too feeble to produce a contraction is allowed to pass into a nerve, and the strength of a current then gradually increased, the degree at which the contraction is produced is spoken of as the minimal stimulus. As the current increases in strength the degree of contractions produced, at first rapidly and then more slowly, increases until a maximum is reached; such a stimulus is spoken of as the maximal stimulus. Asa rule, the effect produced by making the current is more powerful than when the current is broken. Nerves are more sensitive to electrical stimuli than muscles, and a current which, applied directly to a muscle, may be too feeble to produce contraction may throw the muscle into contraction when allowed to pass through its motor nerve. When a strong current is allowed to pass through a motor nerve for some time and the circuit then suddenly broken, instead of a single contraction the muscle will be thrown into tetanus; such a condition is especially produced when the positive pole, or anode, is nearest to the muscle, while, when the negative pole, or cathode, is nearest to the muscle, tetanus occasionally follows the making of the current. This effect is to be explained by the production of a condition which is known as electrotonus, which will be alluded to directly. When a stimulus is applied to any part of a motor nerve a condition of increased excitation is produced and the impulse travels along the nerve, the direction of the motion depending upon the character of the terminal organs with which the nerve is in communica- tion. When, therefore, a motor nerve is stimulated the impulse travels to the periphery ; when the nerve terminates on a cutaneous surface it travels toward the centre, although it must be understood that nerves may conduct impulses in either direction and even carry impulses simultaneously in different directions without interfering with each other. The rate of conduction of nerve impulses is about twenty-seven 778 PHYSIOLOGY OF THE DOMESTIC ANIMALS. and a quarter meters, or ninety feet, per second, in both motor and sensory nerves, and is influenced by various conditions. Reduced temperature or a great increase in temperature reduces the velocity of nerve impulse. Anelectrotonus decreases the velocity of conduction, while kathelectrotonus increases it. The conduction of nerve impulse is destroyed by all conditions which injure the nerve, as by section, ligature, compression, or the use of chemical agents which destroy its excitability at any part of its course, hy the removal of blood, or by the action of certain poisons, as curare, which destroys the conductivity of the terminal motor-nerve filaments. : ‘ When a nerve is subjected to continued stimulation the irritability of the nerve rapidly diminishes ; such a nerve is said to be exhausted or to be in a condition of fatigue. A nerve in which exhaustion has occurred may again regain its activity, provided the stimulation has not been too excessive or too greatly prolonged. In cold-blooded animals stimulation may be much more severe and protracted without producing exhaustion than in warm-blooded animals, and, while nerves are more slowly affected than muscles, the recovery of the former is more slowly accomplished than in the latter. When a nerve-fibre is separated by section from the central nervous system the condition of the nerve will vary according as to the function of the nerve. Provided a nerve be in connection with the nerve-centres which govern its nutritive processes, it may be divided at any part of its course and degeneration of the nerve will only occur in those parts which have been separated from the nutritive centre. Thus, for example, if a motor nerve be divided the peripheral extremity of the nerve will become disorganized, while the part still in connection with the spinal cord will remain intact. If a purely sensory nerve be divided it would at first appear that the same condition prevailed; and if, again, a mixed nerve be divided the peripheral part of thé nerve, including all its branches, will degenerate, while the central parts will remain intact. The centres governing the nutrition of motor and sensory nerves are not, however, as might appear from the above statements, the same. If the anterior root of a spinal nerve be divided before it joins the posterior root the motor fibres in the spinal nerve formed by the union of this anterior and posterior root will degenerate, while the portion remaining in connection with the cord will remain intact. If the pos- terior root be divided between the spinal cord and its ganglion the part of the nerve lying between the point of division and the spinal cord will degenerate, while the peripheral portions of the part between the point of section and the posterior ganglion will remain intact. This indicates ELECTRICAL PHENOMENA IN NERVES. 779 that the nutrition of motor nerves is controlled by the ganglia in the spinal cord, while the ganglion on the posterior root controls the nutri- tion of the sensory fibres. Such ganglia controlling nutrition are spoken of as trophic centres, and nerves, therefore, which are separated from their trophic centres undergo permanent degeneration. The nature of the influence exerted by trophic centres is, however, entirely unknown (Fig. 330). Ifa nerve be divided and the divided ends again brought into con- tact by means of sutures, regeneration takes place, and after a varying time the nerve is again capable of conducting impulses. B c D < Fig. 330.—DIAGRAM OF THE ROOTS OF A SPINAL NERVE SHOWING THE EFFECTS OF SECTION. (Landois.) The black parts represent the degenerated parts. A, section of the nerve-trunk beyond the ganglion ; B, of the anterior root, and C, of the posterior root; D, excision of the ganglion; a, anterior, », posterior roots; g, ganglion. Ill. THE ELECTRICAL PHENOMENA IN NERVES. As in muscles, evidence of the presence of a constant electrical current may be found in nerves. If a section of a nerve be removed from the body and placed upon non-polarizable electrodes in connection with a sensitive galvanometer, a strong electrical current may be observed when the transverse section of the nerve is placed in contact with one of the electrodes and the surface in connection with the other. The current will then pass from the longitudinal section to the transverse section; or, in other words, the natural surface will be positive and the artificial surface negative. The nearer one electrode is to the equator, and the other to the centre of the transverse section, the stronger will be the current produced, and when two points on the surface at equal distance from the equator are connected with the galvanometer no current is obtained. The electro-motor force of the strongest nerve- current has been placed at 0.02 of the Daniells’ element. Like muscle, again, the natural current of nerve undergoes 4 negative variation when the nerve is artificially stimulated. Ifa section of nerve be so connected with a galvanometer as to develop a strong current, and it then be stimulated either by the application of electricity or a chemical or mechanical stimulus, the nerve-current will be found to 780 PHYSIOLOGY OF THE DOMESTIC ANIMALS. disappear. This negative variation travels toward both ends of the nerve, and, like the production of the negative variation of muscle- current, is due to the rapid succession of interruptions of the origin of the current. The statement as regards the negative variation of the nerve- current when the nerve is stimulated by an electrical current requires some modification. The statement holds when the induced current, either in single or rapid shocks, is employed. If the constant current be applied to a nerve which is in connection with the galvanometer the effect on the nerve-current will depend upon the direction of the stimu- lating current. If the constant current be passed through a nerve outside of the part in connection with the electrodes of the galvanometer, so that its current coincides in direction with that of the nerve-current (descending current), the deflection of the galvanometer needle will be increased instead of decreased ; such a state of affairs is spoken of as the positive phase of electrotonus, and is directly proportional in its intensity to the length of nerve, the strength of the galvanic current, and the nearness of application of the stimulus to the section of the nerve in connection with the galvanometer. If, now, the direction of the constant current be reversed, so as to cause the constant current to pass in the opposite direction to the nerve-current, the latter will be diminished; such a condition is spoken of as the negative phase of electrotonus. By the production of electrotonus by means of such a constant polarizing current the excitability of the nerve is greatly modified, not only in the part through which the current is passing, but throughout the entire extent of the nerve. It has been found that at the positive pole the excitability is diminished; this condition is spoken of as anelectro- tonus; at the negative pole the excitability is increased and forms the region of kathelectrotonus, the variation in irritability being most marked in the neighborhood of the poles and decreasing in proportion to the distance from the poles. Between the poles of the polarizing current a point exists where the region of over-stimulation and under-stimulation meet, and where, con- sequently, the excitability of the nerve is unchanged; such a point is spoken of as the neutral point, and with a weak current lies nearer the anode and with a strong current nearer the kathode. The production of this condition serves to explain the character of con- tractions produced on making and breaking a constant current in a motor nerve. When a constant current is allowed to pass through a motor nerve, or, in other words, when a current is closed, the point of greatest stimulation is located at the negative pole and spreads from this point throughout the remainder of the nerve. As a consequence, when the GENERAL PHYSIOLOGY OF NERVE-CENTRES. 781 current is closed the stimulation occurs only at the negative pole at the moment when electrotonus takes place. On the other hand, with the breaking shock, or when the current is opened, the point of greatest stimulation is at the anode and coincides with the disappearance of the electrotonus. ; The contraction which is produced on opening and closing a constant current varies not only with the direction but with the strength of the current. Very feeble currents produce a contraction only on the closing of the current, both with an ascending and descending current, from the fact that the occurrence of kathelectrotonus produces a greater effect on the irritability of the nerve than the disappearance of anelectrotonus. When the current is increased in strength contractions are produced both on opening and on closing the current with either an ascending or descending current. If, again, the current is greatly increased, contrac- tion is only produced on closing the descending current and on opening an ascending current. This is to be explained by the fact that with very strong currents the entire intra-polar portion of the electrotonic nerve is incapable of conducting an impulse, and, as a consequence, ascending currents can cause only an opening contraction. These results may be expressed in the following table, in which R= rest, C —contraction :— Ascending. Descending. On On On On Closing. Opening. Closing. Opening. Weak, r : . ee, R Cc R Medium, . . : « € C C C Strong, : : ‘ . Rk Cc Cc R IV. GENERAL PHYSIOLOGY OF THE NERVE-CENTRES. The nervous system, as already indicated, consists of a combination of ganglion cells united together by nerve-fibres. The second element of the nervous tissue, or nerve-cell, is a mass of protoplasm supplied with a nucleus and nucleolus, from which originate at least two proto- plasmic strands or nerve-fibres, which serve to bind the different elements of the nervous system together. Unfortunately, it is not possible to ob- tain as decisive results by experimentation as to the functions of the nerve-centres as may be determined as regards the nerve-fibres. The properties of the central organs of the nervous system can, therefore, be only indirectly determined. The nerve-centres, by which is meant simply a collection of nervous ganglia, may be divided into two general classes ; one group is located on the surface of the body, and it is adapted to the reception of stimuli originating in various external influences brought to bear on the body surface; the other group of nerve-centres is located in the central nervous system, so-called, —in other words, the spinal cord and brain, or the cerebro-spinal axis. In addition 782 PHYSIOLOGY OF THE DOMESTIC ANIMALS. to these two groups various so-called sporadic ganglia are also to be found in different parts of the body, whose functions, while in the main of the same character as all nerve-cells wherever found, differ according to the functions of the organs with which they are in connection ; they will subsequently receive attention. The external ganglia, or the so-called nerve-corpuscles, vary in char- acter according to the nature of the stimulus which it is their function to receive. They may be distributed over the skin surface and are fitted for recognition of tactile and thermic changes, or they may be specialized for receiving special sensations ; in such cases they constitute the organs of special sense. In addition to these terminals of nerves, which, it will be recog- nized, are simply in connection with afferent nerves, another set of nerve- corpuscles is in connection with the peripheral terminations of the motor nerves and act as organs of distribution for motor impulses. In this group fall the nerve-plates on the voluntary muscles and the ganglionic cells in the walls of the intestinal tube. The central nervous ganglia, located in the cerebro-spinal axis, pos- sess the power of developing, first, reflex action; second, automatism ; third, inhibition; fourth, augmentation ; fifth, co-ordination. These will be alluded to in detatl, Nervous centres are capable of receiving impulses cer to them through afferent nerves, multiplying them, and reflecting the impulses so changed through an efferent nerve. A reflex action, therefore, requires for its expression an afferent nerve, starting from some receptive sur- face,some stimulus applied to that receptive surface, a nervous centre, and an efferent nerve. 1. Reritex Action.—Reflex actions may occur in a number of dif- ferent ways. The impulse reaching the centre through a sensory nerve may _ be reflected through a motor nerve and produce muscular contraction. Such muscular movements, occurring reflexly as the result of stimuli, are entirely involuntary and independent of the will. Such reflex actions are almost innumerable and form an important part of the organic acts of a living animal. As examples may be mentioned the involuntary weep- ing which almost instantly follows the applications of a stimulus to the conjunctiva, the movements of the limbs which occur on tickling the soles of the feet during sleep, movements of vomiting which occur when the soft palate or pharynx are mechanically irritated, coughing following irritation of the laryngeal or tracheal mucous membrane, and a large number of other movements (Fig. 331). The spinal cord offers the best example of the production of reflex motor actions, and, in fact, reflex action may be said to be the main function of the spinal cord and its ganglionic cells may be regarded as GENERAL PHYSIOLOGY OF NERVE-CENTRES. 783 collections of reflex centres. The special characters of reflex action as produced by the conduction of a stimulus through the spinal cord will subsequently receive attention more in detail. At present a general outline of the production of such reflex action is all that is needed. If in an animal the cerebrum be removed by section from the spinal cord,—and such an experiment may be best performed on a cold- blooded animal,—stimuli applied to varying parts of the body surface will result in the production of muscular movement. If in a frog the cerebrum be removed by a section forming a tangent to the anterior part of the tympanic membrane, the frog will apparently be in a normal condition, as far as its posture is concerned. If after the shock of the operation has passed away the toe of such a frog be pinched, the animal will jump; or, in other words, conduction of the sensory impulse to the spinal cord is reflected in the complicated co-ordinated movement of jumping. It is evident, therefore, that the sensory impulse is not simply reflected from the nerve-cell, but that, reaching the nerve-cell, it may there be converted into afferent impulses which may be of the most complex character. Coughing and sneezing, also, are illustra- tions of this statement, where the slightest mechanical irritation of various parts of the respiratory mucous membrane may produce complex muscular movements which are out of all proportion in their complexity and vigor to the afferent impulses which inaugu- er Leber yitiag es ar ae rate them. While this is, however, to a §,skin; M, muscle; N, nerve-cell, with P af, afferent, and ef, efferent, fibres. certain degree true, within limits the nature of the efferent impulse is dependent upon the nature of the afferent impulse. If after removing the cerebrum from a frog the flank of the animal be gently stroked, muscular movement will occur simply as feeble twitching of the muscles at the point of stimulation. If the stimulus be increased in intensity the neighboring muscles are also implicated, and a still further increase in severity in irritation may lead to the implication of nearly all the muscles of the body. A connection may also be recognized between the locality of stimu- lation and the nature of the resulting movement; thus, stimulation of the larynx will invariably cause coughing ; of the mucous membrane of the nostril, sneezing ; of the mucous membrane of the eye, weeping and lachrymation, or, to go back to the lower animals, reflex action following from a stimulus applied to the skin of the brainless frog will be so adapted as to remove the irritating body. Thus, if a scrap of paper moistened with acid be placed on the right flank of such a frog, the 784 _ PHYSIOLOGY OF THE DOMESTIC ANIMALS. right foot will be gradually drawn up and swept over the point of stimulation to remove the stimulus. The apparently purposeful char- acter of such an action is still more strongly manifested if in such an experiment the right foot be firmly held; after a few ineffectual con- tractions of the muscles of the right leg the left leg will then be drawn up to remove the offending body. In all cases, therefore, except in those of the very simplest character, the resulting motion produced reflectively from a stimulus is out of all proportion in complexity to the nature of the stimulation. This complexity is much more marked when the stimulus is applied to the terminal corpuscles of sensory nerves, as in the case above alluded to. If the stimulation be applied to a sensory nerve-trunk the character of the resultant reflex action is, as a rule, of simpler character; or, at least, is to a certain extent free from the apparent purposeful character noticed above. Thus, for example, if an induced current be applied to the central end of a divided sciatic nerve general convulsive movements are produced, but no apparently co-ordinate attempt to remove the stimulus can be detected, even with the employment of the weakest cur- rent. It, therefore, is evident that the character of the reflex action depends upon the nature of the locality of application and intensity of the afferent impulses. 2. AuToMaTISM.—By automatism is meant the power possessed by nerve-centres of apparently originating nervous impulses. It is, how- ever, difficult to draw a line between so-called automatic action and: reflex action. Thus, the act of respiration, which is a favorable example of the so-called automatic action, is in all probability due to, or, at any rate, largely governed by, the character of the impulses brought to that centre through the various afferent nerves. So, again, the regulation of the calibre of the blood-vessels, which is controlled by the automatic power of the vaso-motor centre, is again largely modified by the nature of the afferent impulses brought to it. The clearest example of pure automatic action is to be found in the pulsations of the excised heart. As was seen in the chapter on circula- tion, the heart might be removed from a cold-blooded animal and yet preserve for many hours its power of rhythmical contraction, and it was demonstrated that such automatic action was the result of the function of the nervous ganglia found in the heart. So, also, the movements of the alimentary canal were described as of an automatic character, for although their character is influenced by the contents of the intestinal tube, just as the movements of the heart might be influenced by various afferent impulses, the movements of the intestine may occur in an empty condition of the bowel or they may be absent when the canal is filled. In the spinal cord, therefore, centres GENERAL PHYSIOLOGY OF NERVE-CENTRES. 785 are found which are capable of regularly and rhythmically governing complex movements, and, to that extent, it is automatic: the brain, however, as the seat of mental activity, perception, volition, thought, and memory, is the highest expression of the automatic functions of nervous centres. The automatic functions of the cerebrum will sub- sequently receive consideration in detail. 3. Inmipition.—In a number of examples which were given as illustrations of reflex action, as is well known, the will by its exertion may prevent the appearance of the ordinary reflex result of the stimulus. Thus, for example, touching the eyeball tends to result in the pro- duction of winking; touching the throat, movements of vomiting and coughing ; tickling the soles of the feet, contractions of the muscles of the legs. All of these, as is well known, may be controlled by a volun- tary impulse. os ” One of the clearest illustrations of such inhibition of reflex action and of its development by education is seen in the mechanism of def- cation. In the lower animals defecation is a purely reflex action and, as was described, rcsults from the contact of the fecal mass with the mucous membrane of the rectum. In infants, likewise, the same state of affairs occurs. By education the will-power is capable of inhibiting the operations which result in defecation, or, in other words, checking the action of the nerve-cells which control the co-ordinated movements in this process. A number of other illustrations might be given, of which, perhaps, the clearest instance is seen in the action of the heart. If the pneumogastric nerve be stimulated in an animal in whom the heart is beating in a normal manner with an interrupted current, the heart is almost immediately slowed and may even be brought to a stand- still; such a result is explained by the statement that the pneumogas- trie contains cardio-inhibitory fibres whose stimulation arrests the automatic action of the motor ganglia of the heart. 4, AUGMENTATION.—In contradistinction to inhibition an afferent impulse may inerease action of nerve-centres. Thus, for example, the vaso-motor centre located in the floor of the fourth ventricle controls the calibre of the blood-vessels and keeps their walls in a state of con- traction. The action of the vaso-motor centre may, however, be aug- mented through various afferent impulses, the most striking of which is seen in the great increase of blood pressure which follows stimulation of sensory nerves in curarized animals. 5. Co-orpinaTion.—By this term is meant the power possessed by the cells of the central nervous system of combining complex muscular movements ordinarily of a reflex nature. Thus, for example, the act of deglutition necessitates co-ordinate action of a large number of different 50 786 PHYSIOLOGY OF THE DOMESTIC ANIMALS. groups of muscles, which must in their contraction follow each other ina certain definite sequence; so, also, the act of coughing requires the associa- tion of a number of different muscular movements. Numerous other illus- trations might be given of the combination of complex movements which are governed by so-termed co-ordinating centres; that is, a collection of ganglia located, usually, in the spinal cord or medulla oblongata which govern certain specific movements. Vv. THE FUNCTIONS OF THE SPINAL CORD. The spinal cord is contained within the vertebral canal and is com- posed of white matter externally and gray matter internally, inclosed in membranous sheaths of which the pia mater is adherent to the white AR : ; AR PR’ i Lo Pp P LS P Fia. 882.-TRANSVERSE SECTION OF THE SPINAL Corp. (Landois.) In the centre is the butterfly-form of the gray matter surrounded by white matter. p, posterior, and a, anterior horns of the gray matter; PR posterior roots, AR anterior roots of a spinal nerve; AA the white anterior, L L the lateral, P P the posterior columns. matter; externally is found the dura mater, which lines the vertebral canal and forms a protective coat for the cord, while between the two is found the arachnoid membrane. a. The white matter of the spinal cord is composed of nerve-fibres arranged longitudinally and divided into the so-called anterior, lateral, and posterior columns by the passage of tle roots of the spinal nerves. The anterior fissure is a depression which separates the two anterior columns of the cord, which are bounded, therefore, on one side by the fissure and on the other by the points of origin of the anterior spinal nerve-roots. The anterior fissure does not extend down to the gray matter, which composes the centre-of the cord, but is separated from it by the white commissure. FUNCTIONS OF THE SPINAL CORD. 787 Between the origins of the anterior and posterior nerve-roots are found the lateral columns, while the posterior columns are found between the origin of the posterior nerve-roots and the posterior fissure, which is deeper than the anterior, extending completely down to the gray matter, and filled up by an inner layer of pia mater (Fig. 332). In certain regions of the cord each posterior column may be subdi- vided into an inner part lying next the fissure, the postero-median, or column of Goll, and a larger part next the posterior nerve-roots, the postero-external or column of Burdach. Fic. 333.—TRANSVERSE SECTION OF THE SPINAL CORD IN THE CERVICAL REGION, AFTER BEVAN LEWIS. ( Yeo.) A, anterior gray column; a, anterior white column; J, lateral white column; ac, anterior commis- sure; @r, anterior roots; «/, anterior median fissure; i, intermedio-lateral gray column; ve, vesicular column of Clarke; P, posterior gray column; p, posterior white column; pm, posterior median column; pe, posterior commissure ; cc, central canal; pr, posterior roots; p/, posterior median fissure; ae and ai, external and internal anterior vesicular columns; sy, substantia gelatinosa. The white matter of the spinal cord is composed of medullated fibres, in which the sheath of Schwann is absent, arranged for the most part longitudinally. The nerve-fibres of the nerve-roots have an oblique course, passing from the gray matter through the columns to form spinal nerves; transverse fibres, also, are found, which unite the different col- umns of the spinal cord and connect the gray matter with the columns of the cord. The gray matter is composed of collections of nerve-cells arranged in the form of two crescents, the convex surfaces of which are united by the gray commissure. In the centre of the gray commissure runs the 788 PHYSIOLOGY OF THE DOMESTIC ANIMALS. central canal, which passes from the floor of the fourth ventricle downward and is lined by a layer of cylindrical epithelial cells. The cells of the gray matter of the spinal cord differ greatly in size, those in the anterior horn being much the largest. The gray matter is, also, like the white matter, arranged in columns, although the distinc- tion between these columns may be less readily demonstrated. Thus, the anterior and posterior horns form the anterior and posterior gray columns, while between the two lies the lateral column. The distribution of white and gray matter varies in shape in differ- ent portions of the spinal cord. In the cervical region the lateral white columns are large, the anterior horn of the gray matter is wide and j ! a FiG. 334.—TRANSVERSE SECTION OF THE SPINAL CoRD IN THE LUMBAR EGION, AFTER BEVAN LEWIS. (Yco.) (For references see description under Fig. 333.) large, while the posterior horn is narrow and the transverse diameter of the cord is the longest (Figs. 833, 334 and 335). In the dorsal region both cornua are narrow and of nearly equal breadth, while the cord is smaller and cylindrical. In the lumbar region the gray matter is largest in amount, while the lateral columns are small and the central canal is nearly in the middle of the cord. As a rule, the anterior horn of gray matter is shorter and broader, and does not extend so near to the surface of the cord as does the pos- terior horn, which is more pointed, longer, and narrower, and usually extends nearer to the surface. FUNCTIONS OF THE SPINAL CORD. 789 The spinal cord is not only the path of conduction of nerve impres- sions from the periphery of the brain and the reverse, but is also the seat of a large number of nervous centres which are capable of acting as reflex centres, or even of originating impulses. The functions of the spinal cord are, therefore, to be con- sidered— first, as a collection of nerve-centres, and, second, asa conductor of afferent and efferent impulses. (a) The Spinal Cord asa Collection of Nerve-Centres.— It has been already stated that reflex action requires for its performance afferent and effer- ent nerve-fibres and a nerve- centre, and the spinal cord has pr FF been mentioned as the main ar / ‘seat of the centres of reflex care action Fig. 385.-TRANSVERSE SECTION OF THE SPINAL CORD IN THE DORSAL REGIUN, AFTER BEVAN LEWIS. ( Yeo.) (For references see description under Fig. 333.) When the spinal cord is divided in an animal, the ap- plication of a stimulus to its skin produces muscular movements of | the most diverse kinds, depending, as already indicated, upon the nature, intensity, and the locality of the stimulus. The histology of the spinal cord indicates that, from the direct communication of the posterior roots (which have been found to be paths of con- duction of sensation) through the gray commissure with the anterior roots (which have been found to be the paths of motor impulses), afferent impulses py¢, 336,SecTION OF A SPINAL SEGMENT, k ] VG NILATERAL AND CROSSED reach the spinal cord through a i anes the sensory nerves and are 4 anterior, and P, podteelor eapfasas; M, musele ; S, skin; G, directly conducted to nerve- centres, which again are in communication with motor nerves. It is, therefore, evident that afferent impulses are brought directly to nerve- cells, which again communicate the modified nerve impulse to motor nerves (Fig. 336). In the spinal cord such centres of reflex action may be 790 PHYSIOLOGY OF THE DOMESTIC ANIMALS. readily proved by the entire failure to evoke reflex movements after destruction of the cord. Thus, while reflex movements are produced with the greatest readiness in frogs in whom the cerebrum has been removed, if the spinal cord be then disorganized by passing an instrument down the vertebral canal all reflex movements are then impossible, even although the nerves possess their power of conductivity and the muscles their power of contraction. To appreciate the functions of the spinal cord as a collection of centres for producing reflex action we have only to recall the statements made on the nervous system as met with in the lowest articulata, in which we have a collection of nervous matter, ganglionic in its nature and comparable to the medulla spinalis of vertebrates, with afferent fibres running to and efferent fibres running from these ganglia. Such a type of nervous system is seen in the star-fish. If an irritation be ap- plied to an extremity of the limb of a star-fish a sentient impression is conducted along the sensory nerve to the ganglionic centres, and a motor impulse goes out along the motor nerve and contraction of the muscles supplying the body results. So, if a decapitated centipede be placed upon the ground it begins:to make forward locomotive efforts as soon as the impression is made upon the sentient extremities of the nerves dis- tributed to its feet; this impression is conveyed to the spinal ganglia, and motor impulses are sent out along each one of the legs and loco- motion results. If it comes in contact with an obstacle, however, as high as itself it will mount over it, but if higher it will butt against it its decapitated extremity until all nervous force is exhausted, when it becomes quiet. Still more striking phenomena are present when, after decapitation, the remainder of the body be cut in two; if then the halves of the body be placed upon the ground locomotive efforts will continue in each, but they will not be harmonious. All these movements depend upon physical excitation, and in some instances they require to be excited by the elements in which the animal naturally moves. Thus, if we take a decapitated water-beetle and place it upon the floor no motion results, but place it in water and it begins to move with vigor. The above are examples of reflex action, and result from excitation of sentient surfaces and the conduction of that irritation to a nervous ganglion, and the reflection of that stimulation through a motor nerve. It has been mentioned that the impulses reaching the cord through a single sensory nerve may spread to the adjacent receptive ganglia, and so lead to the transmission of motor impulses through a number of different motor nerves. Ordinarily the degree of reflex action is in proportion to the stimulus. Under certain conditions the irritability of the spinal cord may be so modified that a gentle stimulus may produce excessive stimulation of FUNCTIONS OF THE SPINAL CORD. 791 the motor ganglia of the cord, and so produce violent convulsive move- ments; or the receptivity of the cord may be obtunded through disease or through the action of various poisons, and the most violent stimulus now fail to evoke any reflex action. As an example of the first condition strychnine furnishes a most striking illustration. If a frog be poisoned with strychnine and the cerebrum removed, a degree of stimulation which otherwise would produce but a feeble or perhaps even no reflex action now produces tetanic contractions. Such a result indicates that in the spinal cord every sensible fibre is in direct communication through the gray substance with every motor fibre. In the frog at breeding seasons the spinal cord is in a physiological state of overexcitation; the frog is found at this time clinging obstinately ‘to pieces of bark or stone; just as it does to the body of the female in the act of copulation. Such a condition may be produced by gentle stimulations of the skin of the sternum and of the thumb of the frog, in which an increase of sensibility exists. Here the result is to be attributed not only to the increased receptivity of the spinal cord, but also to the increased sensitiveness of the receptive surfaces. In the normal condition of animals, whether mammals or cold- blooded animals, in whom the brain has been separated from the spinal cord, reflex action only takes place through the application of irritants of a certain intensity and a certain duration. Single electric shocks as a rule produce no result, but if repeated sufficiently often produce a reflex action; such single impulses are con- ducted to the spinal cord and there become added to each other by what is known as a process of summation until a maximum result is attained. If, then, the number of stimulations per second be increased or the de- gree of stimulation be made more severe no further increase in the reflex action is possible. : Pfliger has formulated the following laws of reflex action :— 1. The reflex movement occurs on the same side on which the sen- sory nerve is stimulated, while only those muscles contract whose nerves arise from the same segment of the spinal cord. 2. If the reflex occur on the other side only the corresponding . Muscles contract. 3. If the contractions be unequal upon two sides, then the most vigorous contractions always occur on the side which is stimulated. 4, If the reflex excitement extend to the other motor nerves, those nerves are also affected which lie in the direction of the medulla oblon- gata. 5. All the muscles of the body may be thrown into contraction. (Landois.) In the human body are found mechanisms which may inhibit or 792 PHYSIOLOGY OF THE DOMESTIC ANIMALS. control reflex action, before mentioned, as produced after a mechanical irritation of the conjunctiva. Tickling of the feet leads to an inclination to movement; this also is a reflex action, and, as is well known, such a movement may, by an exertion of the will, be suppressed, such a sup- pression being an inhibition of reflex action. This voluntary control of reflex action may be educated to a certain extent, but only within certain limits. If the stimulus be severe and frequently repeated reflex action occurs in spite of the effort of the will to prevent it. On the other hand, numerous reflex actions are entirely beyond the control of the will; thus the contraction of the iris and parturition are reflex actions over which the will has no control. It may be demonstrated by experiment that a spinal nervous mech- anism exists for the purpose of keeping reflex action in control. If the cerebrum be removed from a frog on a line with the anterior edges of the tympanic membrane reflex action may be readily produced. The best method of studying the influence of different agents on the production of reflex action is that of Tiirck, of Vienna. The frog, from which the cerebrum has been removed, should be suspended vertically by the nose, and if after the shock of the operation has passed away the tip of one toe be dipped in a solution of sulphuric acid it will be rapidly withdrawn ; the duration of immersion before the foot is withdrawn may be taken as indicating the degree of reflex activity of the spinal cord. After each immersion the foot should be dipped into distilled water, so as to wash off the excess of acid and pre- _ vent constant corrosion of the skin. If the time be determined which elapses before the foot is withdrawn from the acid in the frog from whom the cerebrum has been removed, and the cerebro-spinal axis be then again divided on a line tangent to the posterior borders of the tympanic membranes and the toe be again immersed in acid, it will now be found that the foot is withdrawn after a much shorter interval than in the previous experiment. This result would indicate that in some portion of the cerebro-spinal axis between the lines of the two incisions is located a. mechanism which has for its function the controlling of reflex action. If in another frog the cerebrum be removed and the time of immer- sion in the acid determined before reflex action takes place, and now one of the optic lobes be exposed and irritated, as by placing a crystal of com- mon salt in contact with it, it will be found that the frog will retain its foot in the acid for a much longer time than before, or may even entirely fail to remove it. That this result is due to the stimulation of the inhibitory apparatus and not to a paralysis of reflex mechanism is proved by the fact that if the spinal cord be now divided below the medulla oblongata the foot will be as promptly withdrawn, or even more FUNCTIONS OF THE SPINAL CORD. 793 rapidly, from the acid than before; such a mechanism is spoken of as Setschenow’s inhibitory centre. Reflex action may, likewise, be inhibited by stimulation of sensory nerves. As an example of this may be mentioned the familiar experi- ence of our ability to arrest a sneeze by compressing the skin of the nose over the exit of the nasal nerve. Reflex action does not take place when strong electrical irritation is applied to the trunk of a sensory nerve, but tetanus results; while, on the other hand, a much weaker stimulation of the skin, either chemical or mechanical, will readily produce reflex movement. This would, perhaps, indicate that, together with the sensitive fibres, inhibitory nerves pass in the trunks of the nerve to the spinal cord. The reflex functions of the spinal cord may be looked upon as one of the preservative influences of the animal body, guarding all the inlets and outlets of the economy. Through it the movements of respiration are permitted to occur during the hours of sleep and waking. Let this reflex action be lost in the medulla, and respiration ceases, the contents of the rectum are involuntarily evacuated, the useful operation of wink- ing, by which the conjunctiva is kept moist and the eye is protected, is lost, and the acts of coughing and sneezing, so important for removing foreign substances, would be alike impossible. The movements of the intestinal canal, although not entirely de- pendent upon reflex action, are in a certain degree due to it. Many of the phenomena which we consider as voluntary may be classed among those which are reflex in their nature, as when, in walking, we may unconsciously pass around an obstacle in our path, or unconsciously perform many acts which are apparently purely voluntary in nature. As already mentioned, reflex actions are not solely motor in nature, but may result in the production of changes in secretion, in the distribu- tion of blood to a part, or in changes in nutrition. Illustrations of excito-secretory phenomena are very numerous. If we touch the tongue with irritating or sapid substances the secre- tion of saliva begins to flow through the instrumentality of the lingual nerve; the impression is conveyed to the medulla oblongata, whence an efferent impulse is emitted through the chorda tympani, as a result of which the blood-vessels supplying the submaxillary gland are dilated and an increased flow of saliva is produced. It has also been found that if we stimulate the oral cavity the gastric secretion is poured out in large quantities, indicating the action of condiments and spices in conditions of feeble digestion. The reflex vaso-motor results are clearly evident as examples of reflex action. If a sensory nerve is stimulated the tonic action of the vaso-motor centre is increased, and the blood-vessels of the body are 794 PHYSIOLOGY OF THE DOMESTIC ANIMALS. contracted through the reflection of that impulse from the spinal cord through the efferent vaso-motor nerves to the muscles composing the walls of the arterioles. In vaso-motor reflex action phenomena of inhibi- tion are likewise capable of demonstration. Thus, the vaso-motor centre in the body, which is a purely reflex centre, may be inhibited by stimuli passing through certain nerves. If the so-called depressor nerve be stimulated the vaso-motor centre in the medulla is inhibited and dilata- tion of the blood-vessels ensues, as is evidenced by the great fall of blood pressure. So, also, certain nerves when stimulated lead to a dilatation of the blood-vessels by inhibition, in all probability, of the ganglia con- tained within their walls. Such a reflex inhibition of vaso-motor action is seen in the case of the chorda tympani, already referred to, in the reflex stimulation of the nervi errigentes, and a number of other instances. As an example of changes in nutrition due to reflex action, illustra- tions are not as readily found; what is spoken of as sympathy is. an example, however, of changes in nutrition of reflex nature. Surgeons are well aware that when disease of an inflammatory character exists in one eye it is not unusual to find the eye of the other side becoming affected in a similar manner, purely in a reflex manner; as a proof of this may be mentioned that extirpation of the diseased eye is almost invariably followed by a cure of the disease in the remaining one. So, also, section of the supraorbital branch of the fifth pair of nerves leads to disturbances in the cornea which are of a nutritive character and which are probably due to some disturbances of the reflex control of nutrition. It has been already mentioned that in the spinal cord are located a number of collections of cells which have for their function the control of certain complicated co-ordinate movements; such centres exert their action in a reflex manner by the modification which they produce on the afferent impulses brought to them. These centres retain their activity even after the spinal cord has been removed from the medulla by section, but all are to a certain extent controlled by the action of higher reflex centres found in the medulla oblongata and cerebrum. The following represents the most important of these collections of nerve-centres :— First, vaso-motor centres which control the calibre of the blood- _ vessels are found in the floor of the fourth ventricle of the medulla oblongata and distributed throughout the entire spinal axis, as is evidenced by the fact that the dilatation of the blood-vessels which follows division of the spinal cord below the medulla is only transitory, the blood-vessels regaining their normal tone as the shock of the opera- tion passes off. If, however, the spinal cord be entirely destroyed, the blood-vessels become then permanently paralyzed. It is probable that in the cerebro-spinal axis are likewise. found FUNCTIONS OF THE SPINAL CORD. 795 yaso-dilator centres. It thus appears that the calibre of the blood- vessels in the body is regulated by a sollenhion of centres located in the central nervous system. Second, the cilio-spinal centre; this collection of nerve-cells is located in the lower cervical portion of the cord; its functions will be again alluded to. he other centres, as of defecation, micturition, etc., have been already mentioned. (b) The Spinal Cord as an Organ of Conduction.—It has been seen in the consideration of reflex action that modes of communication exist between the different nerve-cells in the spinal cord. It is also evident that in the spinal cord must exist paths of conduction of sensory im- pulses reaching the cord through the posterior roots of the spinal nerves to the brain, and of the conduction of motor impulses from the brain through the anterior spinal roots to the muscles. For when the spinal cord is divided, or when it is altered by disease or injury, the parts which receive their nerves from the portion of the spinal cord situated below that part are paralyzed, both as regards sensation and motion. Impressions made upon these parts are no longer appreciated and voluntary movements can no longer occur in them, even although reflex action may still be present. When the spinal cord is divided above the points of origin of the nerves coming to the muscles of respi- ration, respiration is interfered with; thus, if the spinal cord is divided between the last cervical and the first dorsal vertebre, all the respiratory muscles, with the exception of the diaphragm, are paralyzed. If the spinal cord is divided above the origin of the phrenic nerve, then the diaphragm is likewise paralyzed and death occurs from asphyxia. From these facts it is evident that the spinal cord is the means of communica- tion between the exterior and the brain, and we have now to consider the paths which different impulses follow i in passing from the centre to the periphery and the reverse. In the first place, it would be scarcely conceivable that the irritation from any localized portion of the skin surface could communicate a definite localized sensation to the brain if the afferent impulse was compelled to travel through the Jabyrinthine communications of the gray cells of the spinal cord. Nor, again, could we suppose that a single muscle could be thrown into contraction by the will by passing through the same complicated net-work of cells and fibres. It would be much more natural to look for the paths of communication between the voluntary muscles and the brain on the one side and the sensory end organs and the brain on the other in the white columns of the cord. It does not follow from this fact that the spinal cord may be regarded as a bundle of white fibres connecting the periphery with the brain. Were this the case we should expect that the spinal cord would increase in 796 PHYSIOLOGY OF THE DOMESTIC ANIMALS. size in proportion to the number of nerves entering into it; and that, therefore, the spinal cord should be largest in the cervical portion and gradually taper down to a point in the lumbar region, as if each spinal nerve were a direct loss to the fibres of the spinal cord. Such is not, however, the fact. Sections of the spinal cord taken at different parts of its length indicate that the gray matter of the cord increases with the amount of nerve-fibre passing into each part of the cord, and that, therefore, the largest amounts of gray matter are found in the lumbar and cervical regions at the points of origin of the nerves for the lower and upper extremities; while, if the proportionate area of the lateral columns is com- pared, it will be found that there is a steady increase in the sectional area of this portion of the cord from the lumbar to the cervical region. This fact would indicate that the latter regions are the main paths of con- duction between the brain and the periphery. The proportion between Cervical Fic. 337.—DIAGRAM OF THE ABSOLUTE AND RELATIVE EXTENT OF THE GRAY MATTER AND. OF THE WHITE COLUMNS, IN SUCCESSIVE SEC- TIONAL AREAS, AS WELL AS THE SECTIONAL AREAS OF THE NERVE- Roots. (Landois.) WN R, nerve-roots; A C, LC, PC, anterior, lateral, and posterior columns; Gr, gray matter. different parts of the spinal cord in the different regions and the different areas of the spinal nerves are indicated in the diagram (Fig. 337). In addition to the anatomical division, already alluded to, into anterior, lateral, and posterior columns, the white fibres of the spinal cord have been divided into several secondary columns, according to their functions. In addition to the experimental method, to be alluded to directly, this grouping of the longitudinal fibres of the spinal cord into different systems has been reached through facts acquired through the study of the degeneration of certain parts after specific injury and through the developmental history of the cord in the embryo. Thus, injury of certain parts of the brain is followed by a secondary descending degeneration of certain nerve-fibres (Tiirck) ; section of the cord causes ascending degeneration of certain fibres (Schieferdecker) ; and Flechsig showed that the fibres of the brain and cord in the embryo became FUNCTIONS OF THE SPINAL CORD. 797 covered with myelin at different periods of development, those receiving their myelin last which had the longest course. On the data obtained by this method Flechsig mapped out the following system (Landois) :— 1, In the anterior column lie the (a) uncrossed, or direct pyramidal tract (a in Fig. 338), and, external to it, (0) the anterior ground-bundle, or anterior radicular zone. 2. In the posterior column he distinguishes (¢) Goll’s column, or the postero-median column, and (d) Burdach’s funiculus cuneatus, the pos- terior radicular zone, or the postero-external column, 3. In the lateral columns are (e) the anterior and (/)) the /ateral mized paths, (g) the lateral or crossed pyramidal tract, and (h) the direct cerebellar tract. The rela- tions of these fibres in the cervical region are Shown in Fig. 339. Fig. 338.—ScHEME OF THE CONDUCTING FIG. 339.-SECTION OF THE CERVICAL POR- PATHS IN THE SPINAL AT THE THIRD TION OF THE SPINAL CORD, SHOWING DorsAL NERVE, AFTER FLECHSIG. BY DIFFERENCES OF SHADING THE (Landois.) WuHitE TRACTS SUPPOSED TO BE The black part is the gray matter. v, anterior, hz, FUNCTIONALLY Distinct. (¥eo.) posterior roots; a, direct, and g, crossed pyramidal tracts; A, anterior, P, posterior median fissures; dp, direct , anterior column ground-bundle; c, Goll's column; d, pyramidal, cp, crossed pyramidal tracts; de, direct cere- Posterocexternal column; e¢ and /, mixed lateral paths; pellar, pm, posterior median column (Goll); «2, anterior, , direct cerebellar tracts. ps, posterior root-zones. Of these columns, as we shall find directly, the pyramidal tracts may be traced to the anterior pyramids of the medulla oblongata, where each lateral pyramidal tract crosses to the opposite side, through the pons to the middle third of the crusta, thence to the internal capsule, where they diverge like the rays of a fan through the white matter of the cerebrum to the central convolutions. The direct cerebellar fibres may be traced to the cerebellum, reaching it through the restiform body from Clarke’s column of gray cells, thus directly connecting part of the fibres of the posterior roots with the cerebellum. 798 PHYSIOLOGY OF THE DOMESTIC ANIMALS.. The other systeins of fibres terminate in the medulla oblongata, the column of Goll serving to connect part of the fibres of the posterior roots with the gray nuclei of the funiculi graciles of the medulla oblongata; and the column of Burdach the posterior roots through the restiform body with the vermiform process of the cerebellum, while the anterior and lateral mixed columns communicate with the /vrmatio reticularis of the medulla oblongata, Of these columns the pyramidal tract, the cerebellar tract, and the column of Goll are the only ones which steadily increase in size as the medulla oblongata is approached. Fig, 340.—CoURSE OF THE FIBRES IN THE SPINAL CORD, AFTER F, FLESCH. (Thanhoffer.) Ms, anterior horn; Js, posterior horn; mq, anterior root; mg, 1, 2, 3, fibrous bundles of the anterior root; Ag, posterior root; hy, 1, 2, fibrous bundles of the posterior root; mip, direct pyramidal tract; olp, erossed pyramidal tract; oak, lateral ground-bundle; eaop, direct cerebellar tract; mah, anterior ground- bundle; he, central canal; Co, intermedio-lateral column of Clarke; G, funiculus gracilis of Goll; B, funiculus cuneatus of Burdach; .c, oblique bundles of fibres. Tf we trace by means of the microscope the origins and terminations of the spinal nerves it will be found that the posterior roots of the spinal nerves pass through the white substance of the cord to reach the posterior gray column, in which they break up into fine twigs, uniting with the ganglia of the cord, although their mode of connection with the cells is not capable of ready detection. Having entered the cord, the fibres of the posterior nerve-roots are seen to divide into three different bundles. ; The fibres of the anterior roots may likewise be divided into three FUNCTIONS OF THE SPINAL CORD. 799 different bundles: 1. The median bundle, represented by the black line in the figure (Fig. 340), partly enters into direct union with the cells of the anterior horn, while part passes through the gray matter to enter the anterior commissure and pass to the opposite side of the cord, to termi- nate, in part, in the cells of the anterior horn on this side and partly to pass directly into the anterior white columns. 2. The central bundle of motor fibres passes in part through the anterior horn without forming any connection with its cells, to be lost in the posterior horn, where, in all probability, through union with ganglionic cells it is in communica- tion with the fibres of the posterior roots; the other part of this bundle directly unites with the cells of the anterior horn. 3. The lateral bundle is likewise partly in direct communica- tion with the gray matter of the anterior horn and partly runs up in the lateral columns of the cord (Fig. 341). Further examinations of sections of the cord (right half of above figure) show that the direct and crossed pyramidal tracts of opposite sides of the cord are in com- munication by means of fibres passing through the gray sub- stance into the anterior com- missure, and that the direct Fig. 341.—DIAGRAM ILLUSTRATING THE PATHS cerebellar ¢@ i= PROBABLY TAKEN BY THE FIBRES OF THE as column common NERVE-Roortrs ON, ENTERING THE SPINAL cates with Clarke’s gray col- CoRD, AFTER SCHAFER. (J'ro.) @ ms, anteri dian fi ;p.m./, posterior median fissure ; umn and the latter with the ec couteal canons SR, substantia gelatinosn of Rolando; @ a, fu- niculi of anterior root of a nerve; p, funiculus of posterior root of a column of Goll on the same _ nerve. By following the fibres 1, 2, 3, etc., their course through the i gray matter of the spinal cord may be traced. side of the cord. Some of the fibres of the posterior roots pass upward in the posterior column. They thus form longitudinal commissures between the different ganglia and make up the greater part of the posterior columns. These commissural fibres are evidently concerned in upward conduction of sen- sations, for when the cord is divided they undergo ascending degeneration. The lateral fibres from the posterior root ascend obliquely and divide in the posterior horn, with whose cells they, in all probability, communi- cate, though part of these fibres may be traced as far as the anterior horns. The inner bundle has been traced to the posterior commissure ; its further course or termination is unknown. 800 PHYSIOLOGY OF THE DOMESTIC ANIMALS. It is thus seen that the white fibres of the spinal cord are not in direct communication with the nerve-roots, but only connect different segments of the spinal cord. In each segment of the spinal cord are to be found nerve-centres for the afferent and efferent nerves of definite regions of the body, and commissural fibres connecting that segment with other segments of the cord and with the brain (Fig. 342). Leaving these anatomical considerations of the moment, we have now to examine the data as to the paths of conduction of motor and: sensory impulses through the spinal cord attained through experiments performed upon the spinal cord. The method of such experiments con- sists in attempting to make isolated sections of different parts of the cord and determine the interference of function which results from such mutilations. The difficulty of such experiments is twofold: In the first or on "Semi eetty, Fic, 312.—DIAGRAM ILLUSTRATING THE VARIOUS CHANNELS THROUGH wuich A Moron CELL OF THE CORD MAY BE CALLED INTO ACTION. (Ranney.) A.H, anterior horn; C.P.C, crossed pyramidal column; P, posterior horn; B, column of Burdach; G, column of Goll; 1, fibre for painful sensations ; 2, fibre for tactile sensations; 3, motor cell; 4, motor fibres; 5, fibre from opposite cerebral hemisphere going to cell, 3; 6, ganglion on posterior nerve-root; 7, fibre from cerebral hemisphere of same side going to motor cell, 3. place, it is diflicult to separate the temporary result, due to the shock of the operation, and the permanent results; and, in the case of sensation in the lower animals, to distinguish between reflex action and purely volun- tary movements. In the second place, it is almost impossible to make a section of any isolated portion of the spinal cord without more or less damaging the adjacent portions. Thus, for example, it is almost impos- sible to cut transversely the posterior white columns of the cord without at the same time more or less injuring the gray matter. This difficulty applies to isolated sections attempted on all parts of the spinal cord. Nevertheless, a number of valuable results have been obtained by this method. In the first place, it has been found that section of the cord causes immediate loss of both sensation and motion in all parts supplied by FUNCTIONS OF THE SPINAL CORD. 801 nerves which arise behind the point of injury, with temporary vaso-motor paralysis. ‘The remote effects are secondary descending degencration in the crossed and direct pyramidal tracts and ascending degeneration in the postero-internal columns. If the section is made on one lateral half of the spinal cord (hemisection) paralysis of voluntary movement and yaso-motor paralysis occur on the side of the operation in the parts below, with loss of sensation on the side opposite to the injury and increased sensitiveness on the side of operation, with the exception of alimited area of anesthesia in the part supplied by the sensory nerves destroyed in the operation. There is also the usual ascending and descending degeneration, the former also appearing in the column of Goll on the opposite side. Tf a longitudinal section is made through the posterior fissure of the cord in the median line, little if any loss of motion results (some fibres of the pyramidal tract cross in the anterior commissure), but a consider- able reduction of sensibility. If the posterior white columns are di- - vided there is considerable loss of the tactile, temperature, and muscle senses, although the sensation of pain may still be felt; no loss of motion results. If the antero-lateral columns of white fibres be divided there is a loss of voluntary motion in a corresponding part of the same side of the body. Such a loss of motion, provided the gray matter be not inter- fered with, is temporary, and indicates that the gray matter may take on the function of conduction, ordinarily carried on by the white columns, past the seat of injury. The respiratory and vaso-motor fibres also pass through the antero- lateral white columns. If the gray matter and the posterior white columns be divided sensory or tactile impulses no longer reach the brain, showing that sensory impulses travel in these parts. These facts would indicate that sensory impulses entering the posterior roots of the spinal nerves pass for a certain distance in the posterior columns and then cross over to the gray matter of the opposite side to ascend to the cerebrum in the lateral column in front of the pyramidal tract, while some may pass into the posterior column and others ascend in the gray matter; the fibres concerned in the conduc- tion of “ muscular sense ” apparently do not decussate until the medulla is reached: or they may pass to the cerebellum by the direct cerebellar tract and posterior columns to the restiform body and thence to the cerebellum. On the other hand, voluntary motor impulses after having crossed in the pons varolii and medulla oblongata descend in the antero-lateral columns of white fibres (crossed pyramidal tracts) to leave the cord through the.anterior roots of the spinal nerves, after forming communi- cation with the motor cells of the anterior cornua. The direct pyramidal 51 £02 PHYSIOLOGY OF THE DOMESTIC ANIMALS. oe Y e o 00 00HH 00000009 Cs ~ > e©oo 00000 FIG, 343,—DIAGRAM OF A SPINAL SEGMENT AS A SPINAL CENTRE AND CON- DUCTING MEDIUM, AFTER BRAMWELL. (Landois.) B, right, Bl, left cerebral hemispheres; M O, medulla oblongata; 1, motor tract from right hemi- sphere, largely decussating at M O, and passing down the lateral column of the cord on the opposite side to the muscles M and M1; 2, motor tract from left hemisphere; S, S), sensitive areas on the left side of the body ; 3, 31, the main sensory tract from the left side of the body: it decussates shortly after enter- ing the cord: S2. S23, sensitive areas, and 41, 4, tracts from the right side of the body. The arrows indicate the direction of the impulses. FUNCTIONS OF THE BRAIN. 803 tract descending in the anterior column may either supply the muscles which always act together on both sides of the body; or, according to other observers, they cross in the anterior commissure to join the lateral pyramidal tract (Fig. 343). The paths of conduction of motion and sensation will again receive attention when the upward connections of the different columns of the cord have been traced. : VI. THE FUNCTIONS OF THE BRAIN. In its earliest stage of development the brain simply consists of the dilated extremity of the medullary tube formed by the turning in of the medullary folds of the ectoderm. Almost immediately after the closure of the medullary canal its anterior termination is seen to become differ- entiated into three bilateral symmetrical vesicular dilatations, which are the starting points of the fore-, mid-, and hind- brain. From the fore-brain the cerebral lobes Fic. 345.—DIAGRAM OF A_ VERTICAL LONGITUDINAL SECTION OF A DEVELOPING BRAIN OF A VERTEBRATE ANIMAL, SHOWING THE RELATIONS OF THE THREE CEREBRAL VESICLES TO THE DIFFERENT PARTS OF THE ADULT BRAIN, AFTER HUXLEY. ( Yeo.) a a Olf, olfactory lobes; F.3f, the foramen of Monro; C.S, corpus striatum; Th, cn a optic alanine Pn, pineal glands; b, mid-brain; Cb, cerebellum; Jf.0, medulla Fic. 844.—DIAGRAM OF THE CEREBRAL VES- ICLES OF THE BRAIN OF A CHICK AT THE . oblongata; mp, cerebral hemispheres; TAE, thalamencephalon; Py, pituitary DIAT. ( Yeo.) body; €.Q, corpora quadrigemina; (.C, cruracerebri; P.V, pons varolii; I-XT, 1, 2, 3, cerebral vesicles; 0, regions from which spring the cranial nerves; 1, olfactory ventricle; 2, lateral ven- “ optic vesicles. tricle; 3, third ventricle; 4, fourth ventricle. develop as two hemispherical vesicles (prosencephalon), which, in the brain of the highest mammals, so increase in size upward and backward as to cover more or less completely the remainder of the primary cere- bral vesicle, the mid-, and hind- brain, so that the mid-brain, composed of the optic thalamus, corpora quadrigemina, and corpora striata (mesencephalon), lies beneath the hemispheres. From the hind-brain originate the cerebellum, pons varolii, and the medulla oblongata (myelencephalon). At first all these parts consist of thin-walled vesicles communicating with each other and with the interior of the central canal-of the spinal cord (Figs. 344, 345 and 346). In higher stages of development the walls of these cerebral vesicles become not only thicker and their cavities smaller and smaller, but 804 PHYSIOLOGY OF THE DOMESTIC ANIMALS. elevations (gyri) and depressions (sulci), convolutions and fissures, form so as to give to the brain its characteristic appearance, the degree of external com- plexity differing in different ‘classes of animals. In fact, the strongest point in favor of the high importance of the cerebrum, and especially its connection with the mental functions, is seen in the progressive complexity of its surface in passing from the lower to the higher animals. In fishes, amphibia, and reptiles the cerebral cortex is smooth, and but a faint trace of the formation of fissures is to be seen in birds. In the lowest mammals also the hemispheres are smooth, as in the marsupials, the lowest rodents, if not also in the lowest so-called quadrumana, as in the lemurs. But, ascending to the higher orders of mammals, the hemispheres be- Fia. 346.—DIAGRAM OF A Hor- IZONTAL SECTION OF A VERTEBRATE BRAIN, AFTER HUXLEY. (Yeo.) Olf, Olfactory lobes ; Z.t, lamina termi- nalis; C.S, corpus striatum; 7A, optic thal- amus; Pn, pineal gland; Mh, mid-brain; Cb, cerebellum; M.O, medulla oblongata ; 1, olfactory ventricle; 2, lateral ventricle; 3, third ventricle; 4, fourth ventricle; + itar e tertio ad quartum ventriculum; FM, come more and more sulcated * on the surface, until’ the ridges or convolutions become more and more numerous and complex as we reach the highest mammals or the highest genera in the several orders. The cerebral convolutions may be foramen of Monro; H, optic nerves. said to be characteristic of the brains of mammals, and may be considered, firstly, in regard to their general plan, and, secondly, their relative complexity within that plan. The highest degree of complexity of the cerebral convolutions is seen in the brain of man, of which the most important are represented in the following diagrams (Figs. 347, 348, 849). Each cerebral hemisphere is subdivided on its external surface into five lobes—the frontal, parietal, occipital, temporo-sphenoidal, and island of Reil. ets : In the (1) frontal lobe are found three convolutions—the superior, central, and inferior frontal convolutions. Behind these comes the ascending frontal, sepa- rated from them by the precentral fissure and bounded posteriorly by the fissure of Rolando, which forms the anterior boundary of (2) the parietal lobe, the latter being limited below by the fissure of Sylvius and behind by the parieto-occipital fissure. In this lobe are found the ascending parietal convolutions immediately behind the fissure of Rolando, supramarginal convolution arching around the posterior extremity of the fissure of Sylvius, and the angular gyrus arching around the end of the first temporo-sphenoidal fissure. (8) The temporo-sphenoidal lobe, bounded in front by the fissure of Sylvius, contains three horizontal convolutions, superior, middle, and inferior temporo- sphenoidal convolutions, the first two being separated by the parallel sulcus. (4) The ocetpital lobe is separated from the parietal lobe by the parieto- occipital fissure, and likewise contains three convolutions on its outer surface,—the superior, middle, and inferior occipital convolutions. FUNCTIONS OF THE BRAIN. : 805. (5) The central lobe, or island of Reil, consists of five or six short, stra'ght convolutions (gyri operti) radiating out and back from the anterior perforated spot, and can only be seen when the margins of the fissure of Sylvius are separated. On the inner surface of each hemisphere is the gyrus fornicatus, or convo- lution of the corpus callosum, which terminates posteriorly in the gyrus uncinatus or gyrus hippocampi, Above is the marginal convolution, which is simply the inner surface of the frontal and parietal convolutions, while the inner surface of the ascending parietal convolution is termed the quadrate lobe, or precuneus. The parieto-occipital fissure terminates in the calcarine fissure and, running back- ward in the occipital lobe, incloses the wedge-shaped lobule,—the cuneus. The importance of an acquaintance with the principal cerebral convolutions as here sketched will be seen when the functions of the cerebral cortex are considered. Fig. 347.-LEFT SIDE OF THE HUMAN BRAIN (DIAGRAMMATIC). (Landois.) F frontal, P parietal, O occipital, T temporo-sphenoidal lobes; S fissure of Sylvius; S! horizon- tal, S! ascending ramus of S; ¢, sulcus centralis, or fissure of Rolando; A ascending frontal and B ascending parietal convolutions; Fy superior, Fo middle, and Fg inferior frontal convolutions; #1 superior and /2 inferior frontal fissures; /3, sulcus fracentralis: P, superior parietal lobule; Pe, inferior parietal lobule, consisting of Pe, supramarginal gyrus, and Po!, angular gyrus; ip, sulcus inter- parietalis ; cm, termination of calloso-marginal fissure; Oy first, Og second, O3 third occipital convolu- tions; po, parieto-occipital fissure; 0, transverse occipital fissure; 0g, inferior longitudinal occipital fissure; Ty first, Tz second, Ts third henoidal convolutions; f first, tg second temporo- sphenoidal fissures, P Pp In most ruminants the convolutions are arranged in the form of parallel folds, extending from the front to the back of each hemisphere, but are much more complicated than in the carnivora, where the surface of the hemispheres is divided into four pairs of antero-posterior convo- lutions, distributed around the upper end of the Sylvian fissure and passing from the frontal to the parieto-temporal lobe (Fig. 350). 806 PHYSIOLOGY OF THE DOMESTIC ANIMALS. In the ruminants traces of the fissure of Rolando may be detected, but in none of the ruminants, rodents, marsupials, or even carnivora, with the exception of the seal, is there to be found a backward prolonga- tion of the lateral ventricle foraiee a posterior cornu. In the quadrumana the plan of the arrangement of the cerebral con- volutions to a certain extent resembles that seen in the cerebrum of man. The characteristics of this organization are found—first, in the existence of the occipital lobe, with the prolongation into it of the lateral ventricle; second, the fissures occupy the position of the fissures of the human brain, of which the most important are the fissure of Rolando, dividing the frontal from the parietal lobe, the parieto-occipital fissure Fia. 348.—MEDIAN ASPECT OF THE RIGHT HEMISPHERE. (Landois.) CC, corpus callosum divided longitudinally; Gf, gyrus fornicatus; H, gyrus hippocampi; h, sulcus hippocampi; U, uncinate gyrus; cm, calloso-marginal fissure; F,, first frontal convolution; ¢, terminal portion of fissure of Rolando; A, ascending frontal convolution ; B, ascending parietal convolution and paracentral lobule; Pi’, preecuneus, or quadrate lobule; Oz, cuneus; Po, parieto-occipital fissure; 0, trans- verse eae fissure; oc, calearine fissure; oc!, superior, oc!!, inferior ramus of the same; D, gyrus gyrus occipito-temporalis lateralis (obulus fusiformis) ; Ts, gyrus ovcipito-temporalis medialis Mlbse ‘lingualis). distinguishing the occipital from the parietal lobe; and, third, the fissure of the hippocampi, formed by the folding inward of the cerebral substance along the posterior cornua. In the higher monkeys numerous other fissures complicate the cerebral surfaces and toa certain extent corre- spond with the arrangement of the convolutions in the human brain. In all these may be recognized certain primary frontal, parietal, occipital, and temporal convyolutions, which have a general longitudinal direction. As arule, the cerebral hemispheres are more convoluted in the. larger species of any group of mammals than in the smaller species of the same group. For example, in the pachydermata the highest degree of complexity of the convolutions is found in the elephant. ek FUNCTIONS OF THE BRAIN. 807 The basal ganglia likewise depend for their degree of development upon the position of the animal in the zovlogical series. Thus, the corpora quadrigemina are, as their name implies, divided into four emi- nenees in all mammals, the anterior pair being larger in herbivora and the posterior in carnivora, In birds, reptiles, and fishes they consist only of a single pair of ganglionic masses, and are termed the corpora bigemina, or optic lobes. Fig. 349.—OrniTaL SURFACE OF THE Lert FrontAL LOBE AND THE IsLAND OF REIL, THE TIP OF THE TEMPORO - SPHENOIDAL Lope REMOVED TO SHOW THE LarrEer, (Landois.) aaah sonvelution of the margin of the longitu- issure; O, i = tory lobe removals 7h Oia ee pes FIG. 350.—BRAIN OF Pos, icra aac JI", convolutions of the orbital surface; 1, 1, 1,1, : (Cotin.) under surface of the infero-frontal convolution Ae 1, 2, 3, 4, the four primary convolutions; a, centre for superior under surface of the ascending frontal, and, 5, of cervical muscles; b, for adductors and extensors of anterior ex- the ascending parietal ions; lobe, or island,» eens nee tremity: c, for flexors and rotators of anterior extremity; d motor centre for posterior extremity ; /, centre for facial muscles. So, also, the corpora striata in all vertebrates are covered by the cere- bral hemispheres, but in descending the animal series the reduction in the size of the cerebral lobes gives a relatively greater importance to the corpora striata. The size of the optic and olfactory lobes varies in dif- ferent, groups of animals, being largest in those in which the special Selises associated with these parts of the brain are most highly developed. \ 808 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Further, in descending the vertebrate series, the lateral ventricles become smaller in extent and of simpler form, the posterior cornua being absent in all animals below the quadrumana, with the exception of the seal. The gray matter of the hemispheres likewise diminishes, until in fishes the gray cortex is so thin as to be almost indistinguish- able to the naked eye. The corpus callosum has its highest develop- ment in man, and in the lower mammals becomes both shorter from before backward and thinner, and gradually becomes inclined upward and backward. In the marsupials it is rudimentary, and in no vertebrate lower than mammals is there any trace of the corpus callosum, it being represented in birds, reptiles, amphibia, and fishes merely by transverse commissural fibres crossing at the base of the cerebrum. As the hemi- spheres become reduced in importance there is a corresponding simplifi- cation in the medulla-oblongata and a diminution of the cerebellum and pons, the pons being absent in reptiles, amphibia, and fishes. No olivary bodies or corpora dentata are to be distinguished in animals lower than mammals, the anterior and posterior prominences and restiform bodies often constituting the entire mass of the medulla oblongata. The fourth ventricle, on the other hand, is more clearly marked in the lower animals and is more directly continuous with the central canal and spinal cord. Like the cerebrum, the cerebellum likewise diminishes in passing from the highest to the lowest vertebrates. In birds the bulk of the cerebellum is composed of the vermiform process, while in reptiles, amphibia, and fishes this median portion is alone present. Like the cerebrum, the cerebellum, also, becomes progressively simplified, the lamin or convolutions diminish until they are comparatively few in the bird, while they are absent in reptiles, amphibia, and fishes, in which the surface is quite smooth. In the frog the cerebellum forms a simple, smooth band, and in the lowest fishes is so reduced in size as to no longer cover the medulla oblongata. In many carnivora and ruminants the cerebellum, instead of being composed of broad, smooth, lateral hemispheres joined by the vermiform processes, is very uneven on its surface, and apparently consists of a _ cluster of a number of lobules. The internal structure of the cerebellum likewise becomes simplified and the internal lamine of gray matter disappear. In general, it would ' appear that the more complex the character of the movements of which the animal is capable the higher will be the plane of development of the cerebellum. Only in the large cetaceans and pachyderms is the brain absolutely FUNCTIONS OF THE BRAIN. 809 heavier than in man; thus, in the whale its weight is about five pounds, while in the elephant it varies from eight to ten pounds. Compared with the weight of the body, the brain diminishes in weight in the following order :— In mammals, 1 to 186; in birds, 1 to 212; in reptiles, 1 to 1321; and in fishes, 1 to 5668. In mammals the relative proportion of the brain to the body is smaller in the larger species. Thus, in the ox it is as 1 to 860; the elephant, 1 to 500; the horse, 1 to 400; sheep, 1 to 350; dog, 1 to 305; the cat, 1 to 156; the rabbit, 1 to 140; the rat, 1 to 76; field-mouse, 1 to 31; man, 1 to 36. It is thus seen that in few animals is the brain heavier compared to the body than it is in man, though in a few singing- birds it may amount to as much as 1 to 12. It must not be forgotten that the estimates of the weight of the brain include the sensory and motor ganglia at the base of the cerebrum, the optic thalami, the corpora striati, and the cerebellum, and in the lower mammals these portions of the brain constitute by far the greater part ; hence the size of the cerebral lobes as an index of the power of intelligence is not disturbed by these figures. To recapitulate, the: principal difference noticed in the brain in passing from the highest to the lowest vertebrata is not only in its relative decrease in size but also in its gradual simplification in form and structure, more especially in the cerebral hemispheres and cerebellum. These organs, indeed, gradually become smaller in proportion to the sensory and motor ganglia at the base of the cerebrum; or, in other words, the ganglia exhibit a greater proportionate size as compared with the cerebral hemispheres and cerebellum. In the highest mammals the cerebral hemispheres completely cover the olfactory lobes in front and the corpora quadrigemina behind, and in man even overlap the cerebellum; but in the carnivora, ruminants, and lower mammals the cerebral hemispheres no longer overlap, but even fail to cover any part of the cerebellum, while in the ruminants the anterior part of the hemispheres is so diminished as to permit the projection of the olfactory lobes beyond them. In rodents the cerebral lobes have become still more retracted and now a portion of the corpora quadrigemina becomes visible. In birds, while the olfactory lobes are covered, the optic lobes are exposed, and in reptiles, amphibia, and fishes the cerebral hemispheres become so much further reduced in size as to merely cover the corpora striata with a thin layer of cerebral substance. In the lowest vertebrata the parts of the encephalon thus appear to be arranged in a double symmetrical row, one behind the other. The most* anterior in this row are the ganglionic masses which form the 810 PHYSIOLOGY OF THE DOMESTIC ANIMALS. olfactory lobes; behind them come the cerebral lobes covering the corpora striata, and the third and usually the largest mass, correspond- ing to the optic thalami and corpora quadrigemina; behind them is seen the cerebellum as a small central mass, while the medulla oblongata is the connecting link between the spinal cord below and the basal ganglia of the brain above. These different parts of the brain will be taken up in turn, commencing with the medulla oblongata as the cranial prolongation of the spinal cord. 1. Meputta OsLonaata.—The medulla oblongata, like the spinal cord, is composed of two symmetrical halves, each capable of separation FIG. 351.—SECTION OF THE DECUSSATION OF THE PYRAMIDS. (Landois.) f.la., anterior median fissure, displaced laterally by the fibres decussating at d; V, anterior column; C.a., anterior cornu, with its nerve-cells, a, 6; cc, central canal; S, lateral column; /.r., formatio retic- uluris; ce, neck, and, g, head of the posterior cornu; 7.p.C.J., posterior root of the first cervical nerve: n.c., first indication of the nucleus of the funiculus cuneatus; n.g., nucleus (clava) of the funiculus gra- cilis; 171, funiculus gracilis; H2, funiculus cuneatus; s./.p., posterior median fissure; .c, groups of gangli- onic cells in the base of the posterior cornu. by the naked eye into three different: divisions, the anterior pyramids, the olivary and restiform bodies, and the posterior pyramid, or funiculus gracilis. The lower end of the medulla oblongata, at the point of exit of the roots of the first cervical nerves, is characterized by a deviation of the lateral columns (crossed pyramidal tract) of the cord, which, up to this point running parallel with the axis of the cord, here turn in through the gray substance of the anterior horn and cross to the oppo- site side of the cord in the anterior white commissure to join the direct pyramidal tract. The lateral columns of the cord consequently form a decussation at the bottom of the anterior longitudinal fissure in the FUNCTIONS OF THE BRAIN. 811 medulla, this point of crossing being termed the decussation of the pyramids (Fig. 351). The anterior pyramids are thus made up of the crossed pyramidal tract from the lateral column of the opposite side of the cord, and the direct pyramidal tract from the anterior column of the same side of the cord. Of the pyramidal fibres some pass through the pons directly to the cerebral cortex in a manner to be described directly, some pass to the cerebellum, and some join fibres coming from the olivary body to form the olivary fasciculus. The remainder of the anterior column, the antero-external fibres, lie under the anterior pyramids and form part of the formatio reticularis. In the neighborhood of the first cervical nerve and the point of origin of the first root of the hypoglossal nerve, laterally from the anterior pyramids, lie the remainder of the lateral columns of the cord which have not undergone decussation, the direct cerebellar tract passing backward to rejoin the restiform body and go to the cerebellum; the remaining fibres, passing underneath the olivary bodies and appearing in the floor of the medulla, form the fasciculus teres and pass to the cerebrum. Farther outward from the anterior pyramids are found the gray masses of the olivary bodies, the pyramidal nucleus, and the accessory olivary nucleus, through which passes toward the middle line and backward the remainder of the anterior column. The gray substance of the olivary bodies on section possesses the form of a horseshoe, whose arch is thrown up into numerous folds and whose opening is directed toward the centre of the medulla. It contains numerous small, yellow, pigmented multi- polar ganglion cells, and embraces like a capsule a tract of medullated nerve-fibres which enter through the hylus of the olivary bodies and spread out over the entire inner surface of the gray substance. In all probability some of these fibres terminate in the ganglion cells of the olivary body. The remainder pass through the gray substance of the olivary body and partly unite with the fibrous columns of the restiform bodies and partly surround the exterior surface of the olivary bodies. The gray substance of the pyramidal nucleus and the accessory olivary nucleus resembles in all respects that of the olivary bodies. The former lies in the hylus of the olivary bodies toward the posterior central line of the pyramidal and olivary columns; the latter, in the form of a thin, concave plate of gray matter, lies between the olivary hylus and the corpora restiformes, which, by a collection of gray matter (Clarke’s column), form an unbroken continuation of the posterior columns of the cord to the cerebellum. The restiform bodies form the posterior division of the medulla 812 PHYSIOLOGY OF THE DOMESTIC ANIMALS. oblongata and appear to the naked eye as the immediate continuation of the posterior white columns (postero-external fibres) of the spinal cord. At the level of the foramen magnum they divide and expose the interior gray substance of the spinal cord, which, previously covered by the pos- terior columns, here becomes exposed on the posterior surface. The gray matter at this point also becomes flattened out through the opening of the central canal of the spinal cord, its borders being flattened out laterally. The posterior pyramids form the upward continuation of the postero- median fibres of the posterior columns of the cord. While the gray substance of the spinal cord forms a compact mass - traversed only by the narrow central canal and is everywhere surrounded by a sheath of white substance, in the medulla it becomes exposed and forms a flattened layer, and is divided into two symmetrical halves lying on each side of the median line and bounded only by a slight rim, the last trace of the central spinal canal. This exposed surface of gray matter in the medulla oblongata has the form of an elongated rhomb, whose longest diagonal coincides with the median line, and it forms the floor of the fourth ventricle, communicating above with the aqueduct of Sylvius and below with the central canal of the spinal cord, the lower pointed end of this surface bearing the name of the calamus scriptorius. The gray substance of the floor of the fourth ventricle is entirely similar to that of the spinal cord; it contains a large mass of multipolar gan- glion cells, of which a few form distinct roots and appear to be in direct communication with the cranial motor nerves. The ganglionic origin of the sensory cranial nerves is less distinctly made out. It is, however, clear that all the cranial nerves, from the oculo-motor to the hypoglossal, originate in the medulla oblongata and its annexes. Only the optic and olfactory nerves originate within the cerebrum. The gray matter of the floor of the fourth ventricle forms a direct continuation of the gray matter of the spinal cord, and is to this extent analogous to the anterior columns, the pyramids, and cerebellar fibres, which pass without interruption from the spinal cord into the medulla oblongata. The anterior divisions of the lateral columns of the spinal cord likewise pass without interruption into the medulla oblongata and force themselves between the olivary body and restiform body, without, how- ever, passing farther toward the median line (Fig. 352). From the raphé originate numerous nervous fibres, or so-called internal transverse fibres, which cross the longitudinal fibres of the medulla at a right angle and split up into a large number of smaller bundles, the net-work so formed being described as the reticular forma- tion of the medulla oblongata. This net-work incloses in its spaces numerous multipolar ganglion cells, in which terminate, in all probability, FUNCTIONS OF THE BRAIN. 813 certain of the fibres of the lateral columns of the cord, and so enable the medulla, by bringing it into communication with impressions coming from below, to act as a reflex centre. The transverse fibres of the medulla are to be regarded as commissural fibres connecting the two halves of the medulla, especially the olivary bodies. Closely allied to the anterior surface of the olivary columns are to be found the gray nuclei, or the column of Goll (Keilstring), from which originate the arciform fibres, or the external transverse fibres which surround the entire external surface of the medulla to unite with the ‘internal transverse fibres, from there to pass into the restiform bodies, and from there to the cerebellum. The internal interweaving of the centrifugal and centripetal fibres, the presence of numerous ganglionic cells, and, to a certain extent, the evident union of different classes of nerve-elements, the sym- metrical connection by transverse fibres of both halves of the medulla, all speak in the clearest way as to the high physiological importance of this portion of the central nervous system, both as the seat of reflex centres, as the. origin of numerous cranial nerves, and as the paths of communication from the spinal cord to the brain. As is evident from the anatom- ical description of the medulla, in many respects it forms the most important part of the central ner- vous system. It forms the ganglionic termination of a large number of fibres; most of the cranial nerves find in it their origin, and in it the fla. FIG. 352.—SECTION OF THE MEDULLA OB- LONGATA AT THE SO-CALLED UPPER DECUSSATION OF THE PYRAMIDS. (Landois.) J.la., anterior, s./.p., posterior median __ fissures; n.XI, nucleus of the accessorius vagus; n../J, nucleus of the hypoglossal; d.a., the so-called superior or anterior decussation of the pyramids; py, anterior pyramid; n.ar., nucleus arciformis; ol, median parolivary body ; o, beginning of the nucleus of the olivary body; 7.1, nuclens of the Jateral coluinn; F.r., formutio reticularis ; g, substantia gelatinosa, with (a.V.) the ascending root of the trigeminus; 7.¢., nucleus of the funiculus euneatus ; ne, external nucleus of the funiculus cuneatus; 7.9., nucleus of the funiculus gracilis (or clava); #1, funiculus gracilis; #72, funiculus cuneatus; c.c., central canal; fa, Ja, fa,? external arciform fibres. most diverse systems of the animal body are brought into nervous connection. For the ascending motor and sensory nerves of the spinal cord it forms not only the means of conduction, but is the seat of important centres of co-ordination. These paths, and the most important centres, are represented in diagrammatic form.in Figs, 353 and 354, It has been seen that when the spinal cord is divided below the level of the medulla oblongata in the frog it remains perfectly motionless and 814 PHYSIOLOGY OF THE DOMESTIC ANIMALS. in an apparent condition of almost total paralysis, yet after the shock of the operation has passed off a number of highly complex reflex motions +" may be evoked. If, however, the section of the cord be made at the anterior border of the medulla the position of the frog after the shock of the operation has passed off is more nearly normal, and allusion has been . RQ My Fig. 354.—TRANSPARENT LATERAL VIEW OF THE MEDULLA, SHOWING THE RELATIVE POSITIONS OF THE MOST IMPORTANT NuCLEI; RIGHT HALF oF THE MEDULLA, SEEN FROM THE SURFACE OF SECTION; THE PARTS THAT LIE CLOSER TO THIS SURFACE ARE DEEPER SHADED, AFTER ERB. (Ranney.) Py, pyramidal tract; Py. Kr, decussation of pyramids; F1G. 353.—DIAGRAM OF THE CHIEF TRACTS IN THE MEDULLA, AFTER ERB. (Ranney) The formatio reticularis is represented by shading, Ol., olivary body; V anterior, S lateral, and H pos- terior spinal funiculi; @, pyramido-anterior tract; d, pyramido-lateral tract; Py., pyramidal tract; b, re- mainder of anterior column; ¢, remainder of the lateral column; e, é, cerebello-lateral tract; /, funiculus gra- cilis, and, /?, nucleus of the same; gy, funiculus cunea- tus, and, g!, nucleus of the same; P.c.i., internal fasciculus of the pedune. cerebelli; P.c.e., external fasciculus of the same; urs tract from corp. quadr. to format. retic.; Cq.0., the same to the olivary body; Thal. tract from the thalamus opticus. O, olivary body; 0.s, superior olivary body; V, motor, V!, middle sensory, V/!, inferior sensory nucleus of trigeminus ; VJ, nucleus of abducens; G.,/, genu facialis; VII, nucleus facialis; VIII, posterior median acoustic nucleus; LY, glosso-pharyngeal nucleus Y, nucleus of vagus; VJ, accessorius nucleus; YIJ, hypoglossal nu- cleus; Az, nucleus of the funiculus gracilis; RV, tri- geminus roots; those of the RMS, abducens, and RVIL, facialis. made to the fact that in the mid-brain is seated a centre which inhibits reflex action. When the cerebral lobes only have been removed in the frog, volition is apparently the only function of the animal which is wanting, and in the absence of stimuli of all characters the animal remains absolutely inert. If such a frog is thrown into water it swims; by stimulating its FUNCTIONS OF THE BRAIN. 815 body it may be made to leap; when placed on its back it regains its normal attitude. When placed on an inclined plane it crawls up until it gains a new position, and if such an experiment be made hy placing a frog on a small piece of board, by gradually inclining the board more and more the frog may be made to climb up the board, pass over to the other side, and the piece of wood may be turned over a number of times, the frog always moving with it as long as its equilibrium is dis- turbed. Such a frog will likewise be apparently sensible to light, and if made to jump will avoid objects casting a strong shadow. Such move- ments as above deseribed are evidently carried out by co-ordinating mechanisms and governed by definite afferent impulses (Figs. 355 and 356). It is evident, from the existence of these motions in the frog deprived of its cerebral hemispheres, that the mechanism governing them must lie in parts of the central nervous system below the line of section. No such operations can be effected in » frog in which the medulla has been removed. It follows, therefore, that in the medulla, or perhaps in the corpora quadrigemina and optic lobes, are found the co-ordinating centres of the most complex muscular movement. FIG, 355.—FRoGg WITHOUT ITS CEREBRUM Fig. 356.—FrRoG Wirnour irs CEREBRUM AVOIDING AN OBJECT PLACED IN MovInu ON AN INCLINED BOARD, ITs PaTH. (Landois.) AFTER GOLTZ, (Landois.) In the mammal or bird a similar state of affairs is present, although, as might be expected, complicated to a vreater degree by the more severe shock of the operation. Ina bird or a mammal in which the medulla remains after removal of the cerebral lobes the attitude may become perfectly normal. If placed on its side it will regain its feet. If a bird be thrown into the air it will fly for a considerable distance, perhaps avoiding obstacles, but its movements more resemble those of a stupid, sleepy animal than one in full possession of its faculties. A mammal. also, so operated on can stand, run, and leap, and if placed on its back ean regain its normal position, but if left alone it remains absolutely motionless. If food is placed in the mouth of the animal in whom ablation of the cerebrum has been successfully performed the animal will eat, and the complicated motions of mastication and deglutition will be accomplished with perfect regularity. 816 PHYSIOLOGY OF THE DOMESTIC ANIMALS. In the case of mammals it ought, perhaps with more correctness, to be stated that these highly co-ordinate movements owe their perform- ance to parts above the medulla, since the removal of the optic thalami, crura cerebri, corpora quadrigemina, cerebrum, and pons varolii is usually followed by various forced movements, or the animal lies partly on its side, and, although various complex movements may be produced, they are much more limited than when the higher parts of the brain are left intact. The medulla oblongata is the seat of a large number of centres governing complex co-ordinate movements, of which the following are the most important :— (a) The Respiratory Centre.—This is located in the medulla behind the point of origin of the pneumogastric nerves on both sides of the apex of the calamus scriptorius, between the nuclei of the vagus and spinal accessory nerves. This centre is symmetrically situated, and may be separated by a longitudinal incision without interfering with the respiratory movements. Conditions governing the actions of this centre have been already viven under the subject of respiration. (b) The Cardio-Inhibitory Centre.—As has been previously stated, when the pneumogastric nerve is stimulated it may slow or arrest the heart in diastole, according to the devree of stimulation. The inhibitory fibres of the pneumogastric reach the latter nerve through the spinal accessory and have their origin in the medulla oblongata. The conditions for its action have been likewise given. (c) Lhe Vaxso-Motor Centre—The collection of nerve-cells which govern the vaso-motor nerves, and through them the calibre of the blood- vessels, is located in the floor of the medulla oblongata, extending from the upper part of the floor to within four or five millimeters of the col- umns of the cerebellum. This centre is also a double one, situated sym- metrically on each half of the medulla and each part corresponding to the upward continuation of the lateral columns of the spinal cord. Stimula- tion of this centre causes contraction of all the arteries with a consequent increase in the blood pressure; paralysis causes relaxation and dilatation of the blood-vessels and fall of blood pressure. Its action has also been described. (d) Centre for Closure of the Eyelids.—The centre for the closure of the eyelids lies close to the calamus scriptorius. The afferent impulses reach it through the sensory branches of the fifth cranial nerve from stimuli applied to the cornea, conjunctiva, and skin in the neighborhood of the eye; reaching the centre of impulse, are transferred to the special nerve, through which the afferent impulses reach the orbicularis palpe- brarum. (e) Centre for Sneezing.—The loeation of this centre has not been FUNCTrIONS OF THE BRAIN. 817 accurately determined. Stimuli pass through the internal nasal branches of the trigeminus or olfactory nerves and efferent fibres are found in the nerves coming to the muscles of expiration. (f) Lhe Centre for Coughing.—This centre is placed a little above the respiratory centre. The afferent fibres pass to the centre through branches of the pneumogastric, the efferent in the nerves of expiration “and in those that supply the muscles that close the glottis. (g) Centre for the Movements of Suckling and Mastication.—This centre also has escaped close localization. Afferent paths reach the medulla through the trigeminal and glosso-pharyngeal nerves. The efferent fibres in the case of suction reach the lips through the facial, the tongue through the hypoglossal, and the muscles which depress and elevate the lower jaw through the inferior maxillary division of the fifth nerves. ‘The same nerves are concerned in the movements of mastication, with the exception that when the food passes within the dental arch the hypoglossal is concerned in the movements of the tongue, and the facial with the buccinator. (h) The Centre for the Secretion of Saliva.—This centre lies in the floor of the fourth ventricle. When the medulla is stimulated, if the chorda tympani and glosso-pharyngeal nerves are intact, a profuse secre- tion of saliva is the result, indicating the efferent course of this impulse. Afferent impulses reach the centre through the nerves of taste. (i) The Centre for Deglutition.—This, likewise, is located in the floor of the fourth ventricle. The afferent paths reach the centre through the second and third branches of the fifth pair, the glosso-pharyngeal and the pneumogastric. The efferent channels are found in the motor branches of the pharyngeal plexus. (k) The Centre for the Dilatation of the Pupil._—This centre, like- wise, lies in the medulla oblongata, the efferent fibres passing partly through the trigeminal nerve and partly in the lateral columns of the spinal cord, as far down as the cilio-spinal region, and from there passing out by the lowest two cervical and the two upper dorsal nerves into the cervical sympathetic. The centre is normally excited in a reflex manner by diminishing the amount of light entering the eye. Its action, together with that of the centre for contracting the pupil, will be referred to subsequently. (1) The centre for vomiting is likewise found in the medulla. Its functions have been already described. ) : (m) The medulla oblongata, as discovered by Bernard, exerts a certain influence on the glycogenic function of the liver. When, as already described, a puncture is made in the floor of the fourth ventr icle in the neighborhood of the origin of the pneumogastric uerve temporary glycosuria appears within an hour or an hour and a half after the 52 818 PHYSIOLOGY OF THE DOMESTIC ANIMALS. operation. The method by which this influence on the liberation of sugar by the liver is accomplished has been described under the heading of Glycogenesis. 2. Tue Course of THE FrBres oF THE MEDULLA OBLONGATA.—We have now to attempt to trace the paths of communication of the different divisions of the medulla oblongata with the cerebrum, pons varolii, cor- pora quadrigemina, and, still more important than all, the formation of the hemispheres of the cerebrum and their means of communication by the cerebral peduncles with the mid-brain and its ganglia and with the cerebellum. In tracing up the fibres from the medulla, those most readily followed are the continuations of the restiform bodies, which may be readily detected to pass directly into the cerebellum. Their termination after reaching the cerebellum is only partially cleared up, and before attempt- ing its explanation we must first consider the mode of construction of the cerebellum itself. The cerebellum consists, in the domestic animals and man, of two flattened hemispheres connected across the middle line by the middle lobe or vermiform appendix, which is the fundamental portion of the organ. The white substance of the cerebellum exceeds to a considerable degree the gray matter. The latter is deposited over the entire surface of the two hemispheres of the cerebellum, forming the gray cortex of the cerebellum ; within the inner white medullary substance of the hemisphere is a collection of gray matter known as the dentate or ciliary body, which in its general appearance somewhat resembles that of the olivary bodies found in the medulla oblongata, and which here, also, has the shape of a horseshoe, thrown up into numerous folds, and near which are also found associate nuclei. Although it is clearly established that the main function of the gray matter is to bring the nerve-fibres and nerve- cells into connection with each other, still, as yet, no direct termination of nerve-tubes in the ganglion cells of the cerebellum has been detected. Of course, this does not imply that the terminations of the gray cells in the cortex of the cerebellum with nerve-cylinders may not be readily determined. All attempts, however, to follow up these nerve-fibres has as yet resulted in almost total failure. If, however, we follow the resti- form bodies (which form the inferior peduncles of the cerebellum) it may be seen that « certain amount of their fibres decussates and then enters into the dentate body, forming the so-called intra-ciliary fibres, while another passes externally and forms the extra-ciliary column. In addition to its communication with the medulla, the cerebellum is likewise in communication with the corpora quadrigemina and the pons varolii. The fibres passing from the cerebellum to the corpora quadri- gemina and crura cerebri (superior cerebellar peduncles) originate not FUNCTIONS OF THE BRAIN. 819 only from the extra-ciliary fibres around the corpora dentata, decussating in the pons, but also from the associate nuclei, while the fibres from the extra-ciliary columns alone have been traced into connection with the pons. It, therefore, is evident that the cerebellum is to he regarded as a complicated collection of gray ganglionic masses in unbroken connec- tion with the medulla oblongata and pons on the one side and with the cerebrum on the other. The pons varolii is formed by a collection of the continuations of the reticular formation of the medulla, the pyramids and anterior columns of the medulla, together with the fibres, coming directly by the middle peduncle from the cerebellum. Above the pons the two collections of fibres known as the cerebral peduncles (crura cerebri) approach each other, the point at which the union is accomplished above the medulla being the locality in which the upper end of the fourth ventricle terminates in the aqueduct of Sylvius. In the interior of each cerebral peduncle is found a mass of gray matter, the substantia niger, which separates the fibres of each crus into two layers, the upper layer forming the so-called teymentum cruris and the lower the basis cruris. The upper division of the tegmentum contains also a gray nucleus (nucleus tegmentis). Although these two divisions of the crura are in close anatomical connection, it has been determined with a considerable degree of posi- tiveness that the pyramidal fibres are in direct communication through the basis of the cerebral peduncles with the central convolutions of the cerebral hemisphere on the same side, although whether a direct commu- nication, as in the case of the cerebellum, of these fibres with the gangli- onic cells in the upper surface of the hemispheres exists or not has not yet been determined. Nevertheless, it appears that they form no direct communication with the other gray masses of the hemispheres, the lenticular nucleus, optic thalamus or striated body. And _ since they undergo degeneration only after injury of the central convolutions, it is probable that they are in direct communication with the cortex of the brain. Flechsig claims to have followed them in an unbroken course from the pyramidal columns through the white mass between the lenticular nucleus and optic thalamus, the so-called internal capsule, direct to the gray cortex of the cerebral convolutions. The course of these fibres, together with the other important cerebro-spinal tracts are shown in Fig. 357. The cerebrum is divided by a longitudinal fissure into two hemi- Spheres in man, mammals, and birds, and its external surface is divided by a number of lesser fissures into lobes and convolutions. The cere- brum contains the ganglia of the brain, the optic thalamus or corpus 820 PHYSIOLOGY OF THE DOMESTIC ANIMALS. GE cerebel lar Cory Spinal Cord Fig. 357.—A DIAGRAM DESIGNED TO ILLUSTRATE THE COURSE OF CERTAIN NERVE-TRACTS WITHIN THE CEREBRUM, CrRUS, PONS, MEDULLA, AND SPINAL Cord. Mopiriep From FLECHSIG. (leanney.) 5 V., lenticular nuclens ; rmatio reticularis; C.D., corpus dentatum ; nucleus; (.Q., corpora quadrigemi vround the fissure of Rolando; ec. e from the motor centres of the Tie ray substance (13 and 14); and the lenticular nucleus with the and 7 to the cerebellum; 5, fib colors the tracts with which they “direct cerebellar tract’ of the er of the pons; T.N., trian- ; m,m,m, motor 4 pyramidal tract,’ of the anterior horns of the cortex, the caudate nucleus, and then prolonged as 6 and 10 show by their gray matter of the pons 2 of the superior cerebellar peduncle ; 6, e associated, as well as their origin and termination; Land 17, the inal cord (whose probable termination is not correctly shown in the 3 it probably ends in the vermiform process); 12, the lemniscus or ‘fillet’ tract, cornecting the ivary body with the optic thalamus and the corpora quadrigemina; 13, the cells of the cord connected with the direct pyramidal tract ; VA, the cells of the cord connected with the erossed pyramidal tract ; 1, fibres of the column of Burdach, terminating superiorly in the triangular nucleus: 16, fibres of the column of Goll, terminating superiorly in the elavate mucleus ; 19, fibres of the cord which termina ate in the so-called * reticular formation" directly ; 1S, tibres of the ret. form. going to the cerebellum. FUNCTIONS OF THE BRAIN. 891 striati, the caudate and lenticular nuclei, and the corpora quadrigemina, being connected with the medulla by means of the cerebral peduncles, above which are situated the corpora quadrigemina. In the domestic animals the anterior pair of the corpora quadri- gemina are composed of gray matter, while the posterior are white, in direct opposition to what is the case in man. In herbivora and in the hog the anterior pair are the larger, while in carnivora they are of equal ; size, or the posterior may be somewhat more developed. Between the corpora quadrigemina and the optic thalamus lies the third ventricle, while under the corpora quadrigemina is situated the aqueduct of Sylvius, connecting the third and fourth ventricle. We have now to attempt an explanation of the functions of these different parts of the brain. 3. THe Pons VaAroi.—We have seen that the pons, the superior continuation of the spinal cord, is composed of two sets of fibres. The one, the transverse fibres, constituting the median cerebellar peduncles, serves to connect the two lateral hemispheres of the cerebellum and exists only in animals in which the cerebellum consists of two lobes. The other part of the pons is composed of a mass of gray substance in continuity with that of the medulla and traversed in an antero-posterior direction by the fibres of the medulla, passing up to form the cerebral peduncles. As in the study of other portions of the nervous system, we attempt here to determine the functions of the different parts of the brain by the method of excitation and excision. When the pons is stimulated, either mechanically or by an electric current, pain and muscular spasms are produced, evidently by the mere implication of adjacent motor and sensory paths. Where section of the pons is performed there may be sensazy, motor, or vaso-motor paralysis, together with forced movements when the middle cerebellar peduncles — are involved. Thus, if there be an injury to the lower half of one side of the pons there will be both sensory and motor paralysis of the face on the same side and more or less general paralysis of the opposite side of the body; if the injury be to the upper half of the pons the facial paralysis will be on the same side as the paralysis of the body. The pons, like the spinal cord and medulla, also acts as a reflex centre; although this fact is not capable of direct demonstration, its truth is rendered probable by the higher degree of muscular co-ordination preserved by an animal in which the pons has been retained over animals in whom the section has been earried through the brain below this point. 4. Tue CrrEBraL Prpuncies.—The. cerebral peduncles form the upward prolongation of the pons, and are constituted by those portions of the spinal cord which, after having traversed the pons and medulla, pass upward through the optic thalamus and corpora striata to enter the 822 PHYSIOLOGY OF THE DOMESTIC ANIMALS. cerebral hemispheres. When one of the cerebral peduncles is completely divided it produces paralysis of voluntary movement on the opposite side of the body, with a diminution of the sensibility and vaso-motor paralysis. Section of the basis of both cerebral peduncles totally abolishes all voluntary movements, although reflexes apparently of cerebral origin still persist. g Section of the tegmentum, on the other hand, on both sides entails: the loss of these cerebral reflexes, but allows voluntary motion to remain.’ Injury to one cerebral peduncle causes pain and convulsions on the’ opposite side of the body, while the blood-vessels contract. As the irritative effects pass off these symptoms give place to paralysis. 5. Tue Corpora QuADRIGEMINA.—Destruction of the corpora quad- rigemina on one side causes blindness, which may be either on the side of the injury or on the opposite side, according to the location of the mutilation. Total destruction causes absolute blindness in both eyes, with the absence of the reflex contraction of the pupil when exposed to the light. In addition to blindness, disturbance of equilibrium and inco-ordination of movement result. When stimulated the pupils have been noticed to dilate either on the same side or the opposite side of the body ; this result is probably produced by conduction of the stimulus to the origin of the sympathetic nerve, for after section of the sympathetic dilatation of the pupil no longer takes place. Stimulation of the right anterior tubercle causes the eyes to deviate to the left, while if a vertical incision is made, so as to separate the right and left corpora quadri- gemina, stimulation of one side only causes this movement to take place on one side. The most striking result of injuries to the corpora quadrigemina are the so-called forced movements, evidently due to peculiar unilateral disturbances of equilibrium causing variations from the symmetrical movements of the two sides of the body. These movements may be of various kinds. In the so-called circus movement, instead of moving in: a straight line, the animal runs around in a circle; rolling movement,’ where the animal rolls on its long axis, and the index movement, when the anterior part of the body is moved around the posterior part, which remains at rest. These different forms of movement frequently pass into’ -each other, and they may be produced by injury either of the corpus striatum, optic thalamus, cerebral peduncle, pons, middle cerebellar peduncle, and certain parts of the medulla. 6. Tue Funcrions or THe Basan Ganatra.—(a) The Corpus Striatum.—We have seen that the corpus striatum consists of two parts, the intra-ventricular portion projecting into the lateral ventricle to form’ * the caudate nucleus, and the external portions the lenticular nucleus. t FUNCTIONS OF THE BRAIN. 823 el Lying between these are found the fibres of the anterior division of the internal capsule, which seem to have no connection with these ganglia, Electrical stimulation of these ganglia causes general muscular con- traction on the opposite side of the body. Lesions of either of these ganglia, provided the internal capsule be not injured, do not appear to cause any permanent symptoms, but destruction of the internal capsule causes paralysis of motion or sensibility or both on the opposite side of the body. External to the lenticular nucleus is the external capsule, whose function is unknown, as is also the case as regards the claustrum, which is located externally to the external capsule. (b) The Optic Thalamus.—Scareely anything definite is known as to the functions of this organ, since we have been compelled to abandon the theory supported by Carpenter as to its purely sensory nature. Injury to the thalamus of one side sometimes produces partial paralysis on the opposite side of the body, and, again, sometimes after such an injury hemianesthesia of the opposite side of the body, with or without disturbance of motion, has been observed. Frequently the thalamus may be irritated without producing any evidence of sensation or motion. Since the posterior portion is connected with the origin of the optic nerve it is in all probability concerned in the sense of vision. Together with the corpus striatum, the optic thalamus is perhaps mainly concerned in co-ordinate and complex muscular movements, since the cerebrum may be removed and motion still be normal, provided these basal ganglia are left intact; when, however, they are disturbed normal progression and co-ordinated movements are then rendered impossible. The principal difliculty in determining facts in regard to the func- tions of this part of the brain is that they do not admit of experimental investigation without the most extensive injury to the other parts of the brain. 7. Tue FuNcTIONS OF THE CEREBRAL Loges.—In man and the higher mammals the cerebral lobes represent the greatest part of the brain-sub- stance, and usually will constitute twelve-thirteenths of the entire weight of the brain. The cerebral hemispheres are composed of an internal white substance, representing the continuations of the fibres coming from below which terminate in an external layer of gray matter. The external matter, the cerebral cortex, is folded into convolutions sepa- rated from each other by fissures, some of which being so marked as to permit of the division of the ecrebrum into adjacent lobes. From the cells of the cortex, in all probability, proceed all the motor fibres which are concerned in the production of voluntary movement, and to them come all the fibres from the organs of special and general sense which enable the brain to appreciate external impressions. Some of the fibres 824 | PHYSIOLOGY OF THE DOMESTIC ANIMALS. terminating in the cortex traverse the basal ganglia; others, constituting the so-called pyramidal tracts, proceed from the motor regions of the cerebrum and pass through the white matter and converge in the internal capsule, and from there enter the crura cerebri, thence to the pons, and thence to the opposite side of the medulla oblongata. The white matter of the cerebral lobes may, therefore, be considered merely as the continuation of the paths of conduction of the cord and medulla which terminate in the cells of the gray matter of the convolutions. The consideration of the cerebral lobes resolves itself, therefore, into the study of the functions of the gray matter of the cortex. While the cerebrum has been from time immemorial looked upon as the seat of the will and intelligence, and, in fact, of all the psychical functions, it is only since 1870 that attempts to localize the different functions of the cortex have been attended by any measurable success. In the lower animals, when the cerebral hemispheres are removed slice by slice, the animals simply become more and more dull and stupid, until finally they lose all intelligence. When in pigeons both cerebral hemispheres are removed the animals apparently appreciate no pain during the operation, nor are any movements produced by operations on the cerebral substance. After extirpation of the cerebral lobes they pass into a semi-comatose or stupid condition, and, if not disturbed, remain absolutely motionless, apparently experiencing no sensation of hunger, and will die of starvation in the midst of food without making any effort to feed. If mechanically disturbed, provided the basal ganglia are intact, they are capable of moving in a perfectly normal manner, will, to a certain extent, avoid obstacles, the pupils of their eyes react to light, and they are capable of reacting to violent sudden noises. If food is placed in their mouths they are capable of swallowing it, and, in fact, they preserve the power of completing numerous co-ordinated movements which depend upon reflex stimuli, indicating that the mechanisms concerned in the maintenance of equilibrium are located in the mid-brain, probably in the corpora quadrigemina. If a single cerebral lobe is removed in the lower animals no effect other than the apparent dulling of intelligence is evident. In the higher animals after such a mutilation there is evident a certain dulling of sensibility and difficulty in movement on the opposite side of the body, which, however, finally in the majority of cases gradually disappear. It ‘is concluded from these experiments that the cortex is the chief if not the exclusive seat of intelligence. From the experiments of Fritsch and Hitzig in 1870 dates a new era in our knowledge of the functions of the cerebral cortex. © They found that stimulation by means of electricity of certain circumscribed regions on the surface of the cerebral convolutions was followed by ’ FUNCTIONS OF THE BRAIN. 825 co-ordinated movements in distinct groups of muscles of the opposite side of the body. They indicated certain areas of the cerebral cortex as the actual centres for the production of various movements, and their experiments have been confirmed and extended by a large number of subsequent observers. These points are termed the motor centres of the cortex, and have been located in the dog, the monkey, the cat, sheep, and the rabbit, but are absent in lower animals, such as the frog and fish. They are all found in the anterior part of the parietal lobe, the most important being shown in Fig. 358. When any centre which has been determined to govern any special group of muscles is destroyed or removed the corresponding part of the body is not permanently para- lyzed in the dog, but movements which are produced in that part of the body become irregular and variable, and after a time the disturbance of movement may almost completely disappear. In the monkey and man, on the other hand, destructive lesions of definite motor areas of the cortex cause permanent paralysis, this difference being, perhaps, explainable as due to the higher importance of the cortex in higher species, where it assumes more and more the functions subserved by the basal ganglia in lower animals. A similar series of experiments has led to the localization in the ’ cortex of certain parts which are in close relationship with the organs of sense, for we know that sensory impulses from the opposite side of the body pass upward through the posterior third of the posterior limb of the internal capsule to pass, in all probability, to the cortex of the occipital and temporo-sphenoidal lobes. Excision of these localities leads to disturbances in the appreciation of sensations coming through the sensory organs. Thus, for example, in the dog a locality has been found in the posterior cerebral lobe (outer convex part of the occipital lobe) the destruction of which produces blindness in the opposite eye; or, if both corresponding parts are removed, total blindness results. After extirpation of this part the channels which connect it with the optic nerves undergo degeneration. Centres for hearing and for smelling have also been located. The centre for hearing in the dog lies in the second primary convolution, while in man and the monkey it has been located in the first temporo-sphenoidal convolution. Such disturbances produced by removal of parts of the cortex are, like the motor disturbances, not permanent, but gradually disappear, and dogs rendered deaf or blind by excision of these parts of the cortex again learn to see and to hear,—a fact which is explained by the substitution of function in some corresponding part of the brain-cortex. 8. THE Functions oF THE CEREBELLUM.—Experiments as to the function of the cerebellum have led to the conclusion that it is the great organ for the co-ordination of muscular movements,—a fact which would 826 PHYSIOLOGY OF THE DOMESTIC ANIMALS. alone be rendered probable when it is recognized that the cerebellum is in direct connection not only with all the columns of the spinal cord, Fic. 358.—UPPER SURFACE VIEW OF THE CEREBRUM OF VARIOUS ANIMALS. Landois.) I, cerebrum of the dog; 1, 11, 111, Iv, the four primary convolutions; s, suleus cruciatus; F, Sylvian fossa; 0, olfactory lobe; 1, motor area for the muscles of the neck; 2, extensors and abductors of the fore limb; 3, flexors nd rotators of the fore limb; 4, the muscles of the hind limb; 5, the facial muscles; 6, lateral switching motion of the tail; 7, retraction and abduction of the fore limb; 8, elevation of the shoulder and extension of the fore limb, as in walking; 9, 9, orbicularis palpebrarum. II, aa, retraction and elevation of the angle of the mouth; b, opening of the mouth and movements of the oral centre; cr, platysma; «7, opening of the eye; p, optic nerve; I, ¢, thermic centre. III, cerebrum of rabbit, from above; IV, cerebrum of the pigeon, from above; V, cerebrum of the frog, from above; VI, cerebrum of the carp, from above. In all these o is the olfactory lobe; 1, cerebrum; 2, optic lobe; 3, cerebellum; 4, medulla oblongata. especially with the posterior columns, whose division has been found to lead to inco-ordination, but with the basal ganglia of the cerebrum, which ‘we have found to be especially concerned in this function. It is FUNCTIONS OF THE BRAIN. 827 supposed that the direct cerebellar paths of the cord conduct sensory impressions to the cerebellum, and thus indicate the posture of the trunk and the position of the limbs, while the motor impulses passing’ through the cord may be influenced by fibres passing from the cerebellum through the restiform body to the lateral columns. Injuries of the cerebellum produce no disturbance of the psychical function, nor do they give rise to pain. When, however, the cerebellum is gradually removed, a8 in a pigeon, at first symptoms of weakness and slight disturbance of movement are evident; as more and more of the cerebellum is removed great excitement appears, and the animal now makes violent irregular movements, which, while not similar to conyul- sions, are yet free from all apparent purpose; while co-ordinated movements are impossible vision and hearing, nevertheless, remain intact. Again, section of the middle cerebellar peduncle on one side almost always gives rise to forced movements, the animal revolving rapidly on its own longitudinal axis, and this disturbance is accompanied by nystagmus, or oscillation of the eyeballs. Injury or removal of the lateral lobe produces the same forced movement as section of the middle peduncle. In. mammals the dangers are so great in operations on the cerebellum that but few successes are on record. In operations of extirpation performed on mammals which have proved successful, at first the symptoms are those of irritation of the divided peduncles, and consist in clonic contractions of the muscles of the fore limb, neck, and back, while no sensory disturbances are perceptible. When recovery from the operation is complete the symptoms dependent upon the loss of the cerebellum then appear and consist mainly in disturbances of equilibrium, and, while many muscular groups apparently maintain their muscular tone intact, the power of associating various groups of muscles to produce complex actions is lost. When the injury to or extirpation of the cerebellum has been but superficial the disturbances of co-ordination soon pass off, while if the injury affects the lowest third of the cerebellum the effects are permanent. We may now return to the subject of the conduction of motor and sensory impulses through the central nervous system, summarizing the statements which have been made during the consideration of the func- tions of the spinal cord, medulla oblongata, and brain (Fig. 359). Sensory impulses originating in stimulation of the peripheral termi- nations of afferent or sensory nerves pass into the cord through the posterior roots of the spinal nerves, and the impulse passes either to the cerebrum or cerebellum or both. After entering the cord the fibres of the posterior roots diverge and carry the afferent impulses in different 828 PHYSIOLOGY OF THE DOMESTIC ANIMALS. directions: part of the fibres communicate with the direct cerebellar tract and others with the posterior columns, thus furnishing through the restiform body a direct path to the cerebellum. Other fibres of these roots cross the middle line of the cord a little above where they I h.W. Fig. 359.—-ScHEME OF THE BRAIN. (Landois.) quadrigemina; P, pedunculus cere tegmentum, and p, erv striatum; 2 2, of tho lenticular nue f the optic thalamus; 4 4, of the corpora quadrigemina direct fibres to the cortex cerebri (Fle «); 66, fibres from the corpora quadrigemina to the tegmen m, further course of these fibre: se of these section of the spinal cord; v.W, anterior, and h.W, posterior roots; a a, as commissural fibres; IT, transverse section through the posterior pair of t m of fibr oviation 3 drigemina and orpora q triatum; N 1, nucleus lenticularis; T 0, optic thalamus; V, corpora 1, corona radiata of the corpus rom the corpus striatum and lenticular nucleus to the crusta SS, course of the sensory fibres; R, transverse pedunculi cerebri of man; p, crusta of the peduncle; s, substantia niger; v, corpora quadrigemina with a section of the aqueduct; III, the same of the dog; IV, of anape; V, of the guinea-pig. enter, and some pass up in the lateral column in front of the pyramidal tract, others into the posterior column, and still others ascend in the gray matter on the opposite side of the cord. In the medulla the FUNCTIONS OF THE BRAIN. 829 sensory impulses travel through the reticular formation, through the posterior half of the pons, and enter the teementum of the crura cerebri, pass under the corpora quadrigemina to enter tle posterior third of the posterior limb of the internal capsule, and thence radiate to the cortex of the occipital and temporo-sphenoidal lobe. The path of the sensory fibres, therefore, in some part of its course undergoes decussation, either in the cord, the med ulla, or the pons, so that the cortex of each cerebral hemisphere receives sensory impulses which originate in impressions made on the opposite side of the body : hence, a destructive lesion of the cerebral cortex, internal capsule (posterior third), or of one-half of the cord causes anesthesia of the opposite side of the body. The major part of the crossing, however, occurs in the posterior commissure of the cord. Voluntary motor impulses originate in the cells of the cortex in the motor areas of the cerebrum, pass through the radiating fibres of the white matter of the cerebral hemispheres, to converge into the internal capsule, which is a collection of white nerve-fibres lying between the caudate nucleus and optic thalamus internally and the lenticular nucleus externally. They then enter the basis of the crura cerebri, occupying its middle third, the fibres for the face being next the middle line and those for the leg most external, the fibres for the arm lying between the two; they then pass to the pons, the facial fibres here undergoing decussation (becoming con- nected with the nuclei of the facial and hypoglossal nerves), the others continuing on the same side to the anterior pyramids of the medulla oblongata, where the major part crosses to the opposite side of the cord, where they descend in the lateral column (the crossed pyramidal tract) ; while the uncrossed fibres descend in the anterior columns of the same side, ultimately, in all probability, crossing through the white commissure. All the fibres of both pyramidal tracts terminate at different levels in the multipolar cells of the anterior cornua of the gray matter of the cord, and from each of these cells originates a single unbranched process which, joining with similar fibres, passes out of the cord in'the anterior roots of the spinal nerves. The course of these motor and sensory fibres is like- wise shown in Figs. 360 and 361. The cerebellum receives through its inferior peduncle the afferent fibres derived from the lateral (direct cere- bellar tract) and posterior columns of the cord, as well as from the gray matter. The muscular sense is supposed to be conducted hy means of Clarke’s column, together with the direct cerebellar columns, while tactile sensations pass through Burdach’s column. While, therefore, the sensa- tions of pain are conducted directly to the cerebrum, tactile and muscular sensations first reach the cerebellum and may from thence be conducted to the cerebrum through the superior peduncle of the cerebellum, passing into the posterior part of the corpora quadrigemina and then, perhaps, forming connection with the caudate nucleus. 830 PHYSIOLOGY OF THE DOMESTIC ANIMALS. am Mi f Drigy o wnysiis Fic. 360. Fics. 360 anp 3861..—DiAGRAMS OF THE CoURSE OF THE NERVE-FIRRES IN THE SURSTANCE OF THE BRAIN AND SPINAL CoRD, AFTER AEBY, (22cned.) I, view of a transverse section; II, profile view; TIT, the nuclei of the medulla (partly after Erb). The crosses of color correspomding to the lines upon which they are placed designate the point of section of each tract as it passes through diferent levels (the ers and pons). Ci, dterna! capsule, with radiating fibres (in yellow), pyrunidal dibres (red), aud fibres going to the pons (in purple); PC, the erura cerebra, with the midul fibres and the fibres going to the ganglia of the pons anteriorly, and posteriorly the aubstantin niger, the fillet tract (in dotted lines), the fibres of the superior peduncle of the cerebellum (in blue): Pe, the pedinetes of the cerebellum, showing the fibres going to the cerelirum, the pons, and the FUNCTIONS OF THE BRAIN. 831 argh MLM ago TTEN = NVA on aN ut een yal A gyn WW WEE SW : Fic. 361. medulla: P, pons varoli, with its ganglia on either side (in purple). In III. the nvelei of the cranial hone are numbered to correspond with the nerves. Red is used for the motor nuclei, and blue for on Mh ee The tracts in the cord are designated by the area similarly colored in the cross-section NORE Donec eneath. ef, column of Tiirck; ¢, erossed pyramidal column; a, anterior horn; af, anterior Higher e@: e, direct cerebellar column; b, posterior horn; bf, column of Burdach; d, column of Goll. fibres one are seen b/!, the inferior peduncle of the cerebellum; d/, the fillet or Jemniseus tract: f, the evehen pr ecting the ganglia of the pons with the cerebrum and cerehellum i DIT, the fibres of the superior optic thal pe uncle; h, the cando-lenticnlar and thalamo-cortical fibres; i, the commissural fibres: Th, Tit “mus: ne, nucleus caudatus; nl, nucleus lenticularis; ge. central convolutions. his diagram the course of b/! seems to be in error in not undergoing a decussation. 832 PHYSIOLOGY OF THE DOMESTIC ANIMALS. VII. THE CRANIAL NERVES. The cranial nerves, twelve in number on each side, arise from differ. ent parts of the brain and pass through foramina in the base of the skull, their number being given to them from the order in which they pass out from the base of the brain; other names are, also, given them from the parts to which they are distributed or from their functions. The cranial nerves are either pure sensory nerves, pure motor nerves, or mixed nerves. The pure sensory nerves are the olfactory (1), optic (2), and acoustic (8); the pure motor nerves are the oculo-motor (3), the pathetic (4), and the abducens (6); the trifacial (5), or trigeminus, is a mixed nerve, arising from a distinct motor and a distinct sensory root comparable to the spinal nerves. JRegarding the functions of the other cranial nerves as determined by the functions of their roots, the pneu- mogastric and glosso-pharyngeal are sensory nerves and the facial, spinal-accessory, and hypoglossal nerves are motor. The trunks of these last five nerves, however, contain both atferent and efferent fibres, the pheumogastric receiving efferent fibres from the spinal-accessory and the glosso-pharyngeal from the facial and motor branch of the trigeminus; while the facial receives afferent fibres from the trigeminus, pneumogas- tric, and elosso-pharyngeal, and the hypoglossal sensory fibres from the trigeminus, vagus, and three upper cervical nerves. : The functions of these nerves, although already considered under different subjects, will be here recapitulated. 1. THe OLractrory Nerve. (See Sense of Smell.) 2. Tue Opric Nerve. (See Sense of Vision.) 3. Tue Ocuno-Mororn Nerve.— This nerve arises from the oculo- motor nucleus under the aqueduct of Sylvius, the fibres of origin being traced into the corpora quadrigemina and through the cerebral peduncle into the lenticular nucleus. It contains three sets of fibres which are distributed (1) to all the muscles of eyeball, with the exception of the superior oblique and external rectus muscles and the levator palpebre muscles, (2) to the circular muscles of the pupil, and (3) to the ciliary muscle. Hence, it is the path for voluntary motor impulses to all the muscles of the eyeball, with the exception of the muscles above mentioned, it is the efferent nerve for the reflex contraction of the pupil from the action of light on the retina, and it contains the voluntary motor fibres to the muscle of accommodation (ciliary muscle). 4. Toe Parnuerico Nerve (7rochlearis).—The fibres of the fourth cranial nerve may be traced back from their apparent origin on the outer side of the crus cerebri in front of the pons varolii, beneath the corpora quadrigemina, to the valve of Vieussens (behind the fourth ventricle), on the upper surface of which it is connected by commissural fibres with its CRANIAL NERVES. 833 fellow from the opposite side. The gray nucleus from which it arises is the posterior part of the oculo-motor nucleus in the floor of the aqueduct of Sylvius; it also is connected with a gray nucleus in the part of the floor of the fourth ventricle near to the origin of the fifth nerve. It is a purely motor nerve and is distributed to the superior oblique muscle of the eyeball. 5. Tus Triractan Nerve ( Trigeminus).— This is a mixed nerve, arising, like the spinal nerves, from a motor and sensory root, the latter being supplied with a ganglion (ganglion of Gasser). The anterior, smaller, motor root arises in the motor trigeminal nucleus in the floor of the fourth ventricle, which is connected with the cortical motor centre on the opposite side of the cerebrum; there is also a descending motor root from the corpora quadrigemina. The larger posterior sensory root is connected with the sensory trigeminal nucleus at the level of the pons with the gray matter of the posterior horns of the spinal cord as far as the cervical vertebra, constituting the ascending root, and with the cere- bellum through the crura cerebelli. This extensive origin of the sensory fibres explains the great number of reflex relations of this nerve. After passing through the cranium the trifacial nerve divides into three divisions—the ophthalmic, superior maxillary, and inferior maxillary branches. The ophthalmic division, which receives fibres from the sympathetic nerve, supplies sensory branches to the conjunctiva, lachrymal gland, upper eyelid, brow, and root of nose, trophic fibres to the eyeball, and vaso-motor fibres to the dura mater and lachrymal gland. It is also the afferent nerve for the reflex stimulation of the lachrymal secretion. . The superior maxillary division supplies sensory nerves to the dura mater, to the angle of the eve, skin of temple and cheek, to the teeth in the upper jaw, gums, periosteum, the lower eyelid, bridge and sides of the nose and upper lip as far as the angle of the mouth, nasal chambers, hard and soft palate. By receiving motor fibres from the facial (super- ficial petrosal branch to Meckel’s ganglion) it gives motor nerves to the soft palate and uvula, and, receiving vaso-motor fibres from the cervical plexus, it is the vaso-motor nerve for this entire region. The inferior maxillary division contains all the motor fibres of the fifth nerve and supplies motor nerves to the muscles of mastication, the tensor palati, and tensor tympani muscles. It also contains sensory fibres which are distributed to the mucous membrane of the cheek, lower lip, teeth, external auditory canal, and tip of tongue, the lingual branch being, farther, the special nerve of taste. This division also contains trophic and vaso-motor fibres. 6. Tue Aspucens Nerve.—The sixth cranial nerve arises from the emenentia teres in the fourth ventricle in front of and partly from the 53 834 PHYSIOLOGY OF THE DOMESTIC ANIMALS. nucleus of the facial nerve, its nucleus being connected with the nucleus of the third nerve on the opposite side. It is the motor nerve of the external rectus muscle of the eye. In co-ordinate movements of the eyes its action is involuntary. It receives fibres from the sympathetic nerve in the neck. 7, Tae Factat Nerve.—The facial nerve consists solely of efferent fibres, and arises by two roots from the floor of the fourth ventricle, of which the smaller, through the nerve of Wrisberg, forms a connection with the auditory nerve. The origin of the facial, the facial nucleus, lies behind the origin of the sixth nerve and is connected with the cerebrum of the opposite side. The facial nerve is the motor nerve of the muscles of the face, and hence is called the nerve of expression. It also supplies motor branches to the stylo-hyoid, posterior belly of the digastric, buecinator, stapedius, muscles of the external ear, platysma, and levator palati. It is the secretory nerve of the parotid, and through the chorda tympani of the submaxillary gland. It also contains vaso- motor fibres for the tongue and side of the face and vaso-dilator fibres for the submaxillary gland. Through its anastomoses with the trigeminus and vagus it perhaps contains afferent fibres. 8. Tue Aupitory Nerve.—(See Sense of Hearing.) 9. THE GLosso-PHARYNGEAL NERVE.—This nerve arises from the glosso-pharyngeal nucleus deep in the medulla oblongata near the olivary body, and is connected with the nucleus of the vagus. An ascending root from the spinal cord unites with it and serves for the production of spinal reflexes. It is supplied to the palatine and pharyngeal muscles, but its motor function to these muscles is not absolutely established; possibly its motor fibres are derived from the facial. It is the nerve of taste for the back of the tongue and pharynx, as well as being the nerve of general sensation for these parts, the Eustachian tube and tympanum. 10. Tue PneumocaAstric Nervr.—The vagus nerve has a common nucleus with the ninth and eleventh nerves in the ala cinerea in the lower half of the calamus scriptorius. It contains both afferent and efferent fibres, the latter, probably, being derived from the spinal-acces- sory. The efferent fibres are distributed to the muscles of the pharyns, larynx, trachea, bronchi, cesophagus, stomach, and intestines. It is also the inhibitory nerve of the heart, and contains vaso-motor fibres for the lungs and trophic fibres for the lungs and heart. It is the sensory nerve for the external ear, pharynx, cesophagus, stomach, and respiratory passages. It contains afferent fibres, which may augment or inhibit (laryngeal nerve) the respiratory centre, augment the cardio-inhibitory centre, inhibit the medullary vaso-motor centre (depressor nerve) ; through it afferent impressions may pass which produce the salivary or inhibit the pancreatic secretions. SYMPATHETIC NERVOUS SYSTEM. 835 11. Tue Spinat-Accessory NeErve.—This nerve arises by two separate roots, one from the accessory nucleus of the medulla, which is connected with the nucleus of the vagus, the other between the anterior and posterior roots of the spinal nerves, as far down as the fifth cervical nerve, its fibres in the cord having been traced to a nucleus on the outer side of the anterior cornua. The anterior branch passes entirely into the vagus and gives to it most of its motor fibres and all the cardio- inhibitory fibres. The spinal-accessory is the motor nerve to the sterno- mastoid and trapezius muscles; it receives sensory branches from the cervical nerves. 12. THe HyrogitossaL Nerve.—The hypoglossal nerve arises from two large-celled nuclei in the calamus scriptorius and one adjoining small-celled nucleus, being connected both with the olivary body and the brain. It is the motor nerve for the muscles of the tongue and most of the hyoid muscles. It receives afferent fibres from the fifth and tenth nerves and vaso-motor fibres from the sympathetic. VIII. THE SYMPATHETIC NERVOUS SYSTEM. The great sympathetic nerve, constituted by a ganglionic chain, composed of a series of ganglia connected by nerve-fibres, is located on each side of the vertebral column. Three different forms of structure may be recognized in this portion of the nervous system—the ganglia, the peripheral branches, and the connecting filaments. The two chains situated on each side of the median line are connected by transverse fibres, giving off numerous branches, which anastomose among themselves and form plexuses (Fig. 362). The sympathetic nerve may be divided into three divisions. In the cephalic portion are found the ophthalmic, the spheno-palatine, the otic, the submaxillary, and the sublingual, with the three cervical ganglia. In the thorax and abdomen are found the other two divisions, which like- wise consist of a number of ganglia united together by anastomosing filaments. The ganglia consist of gray substance united with nerve-tubules. The fibres are non-medullated and connect the ganglia. Each spinal nerve forms connections with adjacent sympathetic ganglia hy means of the rami communicantes, which are formed by nerve-fibres coming from both the anterior and the posterior roots of the spinal nerves. In addi- tion to the non-medullated fibres entering into the constitution of the great sympathetic nerve are also fine nerve-tubules, which in their structure are analogous to those of the cerebro-spinal axis. Such filaments are much less abundant than the gray or non-medullated fibres of Remak. The functions of the sympathetic nervous system have already been 836 PHYSIOLOGY OF THE DOMESTIC ANIMALS. given somewhat in detail in previous sections. The most important function which it fulfills in the animal economy is in the regulation of the calibre of the blood-vessels. This has already been described under the subject of the Circulation. The sympathetic likewise possesses a number of independent functions either in the way of inhibiting or stimulating various processes which ordinarily are controlled by the cerebro-spinal nerves. As examples of such action may be men- tioned the automatic ganglia of the heart, the mesenteric plexuses of the intestine, and the sympathetic plexuses of the uterus, Fallopian tubes, and ureters. Of course, here, also, the share of the sym- pathetic in regulating the calibre of the blood-vessels occupies an important position. The sympathetic nerve, also, in addi- tion to such functions in which this nerve may be regarded as. an efferent nerve, carrying impulses from the central ner- vous system, likewise acts as an afferent nerve; as, for instance, in the conduction of sensory impressions from the abdominal viscera through the splanchnic nerves. It has further been claimed that the various ganglia of the sympathetic may themselves act as reflex centres, but no clear demonstration of this statement has ever been reached. Its strongest advo- cate was Claude Bernard, and he pointed to the submaxillary ganglion as an illus- tration of such an independent action on the part of the sympathetic ganglia. We have already discussed the grounds for doubting the correctness of this Fiq@. 362.—SYMPATHETIC NERVE OF statement. THE HorRSE. (Flesch.) a, main trunk: 6, rami communicantes: c, Probably the main function of the g7ay commissural fibres; ¢, roots of the splanch- “s A nie nerve; SpJ, splanchnic nerve. ganglia of the sympathetic nervous system is to modify impulses coming from the central nervous GENERAL AND SPECIAL SENSIBILITY. 837 . ‘system, through the cerebro-spinal nerves, so as to inhibit or modify the function of certain organs. As an illustration of this may be men- tioned the action of the sympathetic upon the pupil. According to Budge, the fibres which are concerned in producing dilatation of the pupil arise from the spinal cord and run from the upper two dorsal and the lowest two cervical nerves into the cervical sympathetic, which conveys them to the head. The influence of the sympathetic in governing the movements of the iris will be given more in detail in the consideration of the eye. ~ Among other branches arising from the cervical part of the sym- pathetic are found motor branches going partly to the external rectus muscle of the eye, vaso-motor branches to the ear, the side of the face, the conjunctiva, the iris, the choroid, and to the vessels of this portion of the alimentary and respiratory tract. Secretory and vaso-motor fibres are distributed to the salivary glands and to the sweat-glands of the integument; while, according to certain authorities, the lachrymal glands receive sympathetic secretory fibres from this portion of the sympathetic. Of the thoracic and abdominal sections of the sympathetic the car- diac plexus, which receives accelerator fibres for the heart, occupies the most important position. The influence of the cceliac plexus of the sympathetic on the heart has already been given. Of the abdominal sympathetic, the cceliac and mesenteric plexuses and the splanchnic nerves are the most important. They also have been already described. It is thus seen that the fibres of the sympathetic nervous system act as conductors of both afferent and efferent impressions. Impressions traveling from the periphery to the centre through the sympathetic nerve do not produce an impression upon the sensorium. In other words, the brain is not capable of taking cognizance of afferent im- pulses traveling through the sympathetic. Nor, on the other hand, can voluntary motor impulses pass through this nerve. IX. GENERAL AND SPECIAL SENSIBILITY. Sensation, or general sensibility, is that function of the brain by which it perceives or becomes conscious of impressions which are made upon the surface of the body or upon the nerves running from the periphery to the nerve-centres. By perception is meant that faculty by which sensations are referred to certain external causes. It is important to understand that all sensations take place, not at the point of contact of the irritant with the periphery, but in the brain itself, and we have evidence of this in the fact that if the brain be in a state of torpor no sensation occurs. Again, if a ligature be passed around an afferent nerve at some point between its origin on the periphery and its termination in the nerve-centre no sensation occurs, no matter how severe be the 838 PHYSIOLOGY OF THE DOMESTIC ANIMALS. stimulation of its peripheral ends; or, if the nerve-trunk be divided, the most powerful irritants may be applied to the peripheral area in which that nerve is distributed without calling forth sensation. When an impression is made upon a sentient surface, that impres- sion so changes the molecular equilibrium in the terminal filaments as to give rise to afferent impressions, which travel along the nerve-trunk to reach the centres of the brain, and it is the final change which occurs within the nerve-cells which is to be spoken of as sensation, and it is only this latter change of which the brain is cognizant. Two kinds of sensibility may be recognized—general and special sensibility. Nerves of general and of special sense are concerned in the perception of these two kinds of sensation. By the term special sensi- bility is understood that sensation which arises from an impression of a peculiar kind and special character, which is capable of atfecting only one kind of nerve; or, rather, which, when applied to one kind of nerve, will invariably produce a sensation peculiar to that nerve. Thus, for example, a stimulus applied to the terminal filaments of the nerve of hearing will invariably be recognized as an auditory sensation ; so a stim- ulus of the optic nerve, whether mechanical, electrical, or chemical, will be recognized as a visual sensation. By general sensibility is meant the appreciation of sensations arising from impressions of a general character applied to the general tegumen- tary surface of the body. Under this head are to be included the tactile sense, the sense of heat and cold, and the muscular sense. The special sensations are the sensations of smell, taste, sight, and audition. Certain conditions are necessary to sensibility. First, there must be a certain degree of vascularity. Unless the part be well supplied with blood it cannot be endowed with either general or special sensibility. An illustration of this may be seen on tying any large artery ; the part to which it is supplied becomes almost instantly numb; the blood is cut off, the vascularity diminishes, and the irritability of the receptive filaments of the nerve becomes depressed. So, also, cold, as is well known, reduces sensibility by diminishing the blood-supply of the part. Secondly, mere vascularity is not, however, sufficient; there must, likewise, be continuity with the nerve-trunk. Unless the afferent fibres be in such continuity with the centre no sensibility, either general or special, may take place. While, finally, the centre itself must be in a state of integrity to recognize or convert into perceptions the impressions brought to it through afferent nerves. When impressions have been frequently repeated upon nerves of general or special sensibility the sensations to which they ordinarily ad- minister become blunted. An illustration of this may readily be drawn from the nerves of special sense. Sights or sounds constantly present GENERAL AND SPECIAL SENSIBILITY. 839 to the eye or ear after a while fail to impress them. So, also, odors may cease to be recognized. This point, however, must not be misunderstood. If continued attention be directed to sensations, instead of being blunted they are exalted. Of this we have numerous examples in the capability of the senses to attain a high degree of acuteness of perception from education. When an impression has been made upon a nerve of special sensi- bility, or even upon one of general sensibility, that impression always remains a certain length of time after the irritating cause has been removed; thus, when an ignited stick is rapidly moved before the eye the impression made upon the retina i each successive position of the burning point remains sufficiently long to appear continuous with that made in the next situation, and thus the appearance of a line of light is obtained. So in the case of the ear; it is well recognized that musical tones are produced by a regular succession of vibrations. When these vibrations succeed each other more frequently than sixteen times in a second they give rise to a continuous tone. When they occur less frequently than sixteen times in a second there is produced a succession of impressions,each one terminating before the other begins. No nerve of special sense can take upon itself the function of any other; thus the auditory nerve is incapable of transmitting visual impressions, nor can the olfactory nerve serve for audition. In the case of the nerves of general sensibility, the incapability of interchange of function cannot be so positively denied, since we know that a motor nerve may so unite with a sensory nerve as to conduct afferent impressions; or in the case of the sense of taste, which is one of the lowest of the special senses, we shall find that there other than the special nerves of taste may, perhaps, serve for conducting gustatory impressions. While the nerves of special sense are especially adapted for receiving certain impressions, they may yet be thrown into a condition of irritability by various stimuli, but each of these stimuli will produce the impression characteristic of the nerve over which it passes. Sensations have been divided into two classes, external and internal, or objective and subjective. External impressions are those which arise from impressions made upon the external surface of the body. By internal impressions are meant those which arise from impressions made upon the internal recesses of the body. All sensations, however, originate and depend upon changes taking place in the gray matter of the brain itself, and, as a consequence, there is no sensation (which in general terms is produced by an impression made upon the peripheral termi- nation of the nerve) which may not to a certain degree be produced by an impression made upon the nerve in its course or at the point in the sensorium where the nerve terminates. To this latter 840 PHYSIOLOGY OF THE DOMESTIC ANIMALS. class of sensations the term subjective is given in contra-distinction to objective sensations, which result from impressions made upon the termination of the nerve. It is a curious fact with regard to internal or subjective sensations that those which arise from impressions made upon a nerve in its course are always referred to the peripheral termination of the nerve on the surface of the body. ‘Thus, if the ulnar nerve is compressed at the elbow-joint the impression is not felt at the point of stimulation, but at the extremity of the fingers. The most common cause of subjective sensations is to be found in changes of the blood-supply of the part; thus, for example, when congestion takes place about the termination of the optic nerve there are flashes of light about the eye; if about the auditory nerve, ringing sounds in the ear. By the term sensory organs is meant those parts of the body by which, through the nerves of sense, the brain becomes cognizant of its surroundings. : By means of the special senses the preservation of both the indi- vidual and of the species is rendered possible. By means of the special senses animals are rendered capable of seeking and recognizing their food and are enabled to avoid danger, and, in a way to be indicated directly, are led to the accomplishment of the act of reproduction. The more restricted the peripheral portion of any nerve of special sense the more delicate is the structure of that terminal organ. In the case of the sensations of taste and of smell the nerves distribute them- selves over a moist mucous membrane which has other functions to fulfill in addition to acting as the peripheral terminations of nerves of special sense. On the other hand, in the case of the nerves of sight and hearing, the terminations are found in structures whose sole function is found in ministering to these special sensations, and in them we find the highest degree of complexity of the end apparatuses. It is, of course, not possible to decide whether or not in the case of the lower animals impressions made upon the nerves of sense affect the brain in the same manner as in man, since in these animals the expression of sensations is greatly restricted: but from the great similarity of struc- ture of the organs of sense in man and in the higher mammals it may be concluded that impressions are appreciated by these animals in the same manner asin man. As a general rule it may be stated that the senses of the domestic animals are quite as highly developed as in man, and in certain instances greatly exceed in acuteness the corresponding sense in man. Usually, in any special class of animals we find one of the special senses developed out of proportion to the others. Domesti- cation has the usual result of reducing the acuteness of the special senses, since the principal cause for their exercise in the protection of the animal is no longer present. SENSE OF SMELL. 841 A. THE SENSE OF SMELL. By the sense of smell animals are to a certain extent facilitated in their search for food, in the avoidance of danger, and in seeking the opposite sex. By the sense of smell is meant the sensation that is created when certain substances in a gaseous form are inhaled by the nostrils. It will be shown that the sense of smell is only excited under certain definite condi- tions and only when the odorous body comes directly in contact with the organs of sense. Here, as in the case of taste, the sensation is locally excited, probably through some chemical influence, and the result is an entirely specific sensation. It is, therefore, unwarrantable to include the sense of smell among the other senses, since it is quite as different from the sense of touch or of taste as from sight or hearing. The action of the organ of smell is, therefore, due to a special nerve, the olfactory nerve, the first cranial pair, which differs from the others in origin, position, extension, and mode of distribution. Under the name of olfactory nerves are usually described the masses of gray matter which arise from the anterior portion of the frontal lobe, and in many animals exist in such bulk as to project beyond the frontal lobes. From the structure of these masses, as well as from comparative anatomy and from their developmental history, it is evident that these parts are not-to be regarded as identical with the peripheral branches of other nerves of sense, or the cranial nerves, but are to be regarded as distinct parts of the brain. In many animals the olfactory lobes are hollow, their ventricles communicating with the other ventricles of the brain. As olfactory nerves only are to be described the fibres which originate from these olfactory bulbs and pass through the cribriform plate of the ethmoid bone to be distributed to the olfactory portion of the nasal cavities. Fibres from the olfactory lobes have been traced in three bundles backward into the cerebral hemispheres, and the centre for smell in the ° cortex of the brain has been located in the tip of the uncinate gyrus on the inner surface of the cerebral hemisphere. Of these three roots, the inner one is small, the middle one is large and curves inward to the anterior commissure around the head of the caudate nucleus and decussates through the anterior commissure to the extremity of the Opposite temporo-sphenoidal lobe. The outer root passes transversely into the pyriform lobe and ends in the anterior extremity of the optic’ thalamus. Microscopic examination of the olfactory fibres, by which are meant the fibres passing through the cribriform plate, shows that they are thin, transparent, fibres, included in a nucleated connective-tissue sheath. 842 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Examination of the structure of the membrane lining the nasal cavities shows marked points of distinction between the region to which the olfactory fibres have been traced and other portions of the nasal cham- bers. The area of distribution of the olfactory nerve is termed the regto olfactoria, and in the main embraces the upper part of the septum and the upper part of the middle turbinated bone. The remainder of the nasal cavity is called the regio respiratoria. The olfactory region has a thicker mucous membrane than the respiratory part. It is covered by a single layer of cylindrical epithelial cells, which contain yellow pigment in sufliciently large quantity to serve even by the naked eye to distinguish this part of the nose from the respiratory passages. The latter division of the nasal cavity is covered by ciliated epithelium and contains tubular glands and serous, acinous glands. In the olfactory region are found between the ordinary cylindrical epithelium cells peculiar FiG. 364.--DIAGRAM ILLUSTRATING THE MODE OF CONNECTION OF THE OL- Fia@. 363.—DIAGRAM OF THE STRUCTURE FACTORY AND CYLINDRICAL CELLS OF THE OLFACTORY REGION, AFTER WITH THE TERMINAL NET-WORK OF EXNER. (Briicke.) THE OLFACTORY NERVE. (Briicke.) C C, the terminal net-work of the olfactory nerve in BB, cylindrical epithelial cells; A, olfactory cell; which both the so-called olfactory cells (A) and cylin- D, protoplasmic mesh-work in which the olfactory nerve drical cells are imbedded. terminates. ‘ spindle-shaped cells with a large nucleus, containing nucleoli, and sending up between the cylindrical cells a narrow projection which in various animals terminates in delicate projecting filaments. These peculiar olfactory cells are said to form a direct communication with the fibres of the olfactory nerve. It is probable, according to Exner, that these cells do not directly unite with the olfactory fibres, but through the mediation of a net-work of protoplasmic prolongations of these cells lying below their bases. Examination has further shown that not only these long so-called SENSE OF SMELL. 843 olfactory cells form communication with this net-work, but, also, processes may be traced into it from the so-called cylindrical cells, and, this being the fact, it would seem unwarrantable now to draw a sharp distinction between the functions of these two classes of cells (Figs. 363 and 364), In the herbivora the convolutions of the inferior turbinated plate are, as a rule, simpler than in the carnivora, but yet more complex than in man. In the ruminants and solipedes the inferior turbinated bone divides into two plates which are rolled around each other in opposite directions. In most of the carnivora it is also similarly convoluted, but the divisions are much more frequent and the spaces between the different leaves narrow. In the case of the inferior turbinated bone the higher degree of complication does not point, as in the case of the superior turbinated bones, to a higher degree of development of the sense of smell, but in animals where this condition is present it is to be regarded as a means of mechanical protection against the entrance of foreign bodies into the nose. The different cavities in connection with the nasal chambers, such as the frontal, sphenoidal, and maxillary sinuses, have no connection with the sense of smell, but are to be regarded simply as extensions of the respiratory parts of the nasal chambers; for their mucous membrane is identical with that lining this portion of the nose and contains no terminal filaments of the olfactory nerve. This also applies to the case of the etlimoidal cells; all these cavities, therefore, are simply concerned in warming the inspired air. Jacobson’s organ, on the other hand, is to be regarded as an acces- sory organ of olfaction. It is present in all mammals, and consists of two narrow tubes protected by cartilage and placed in the lower and anterior part of the nasal septum. Each tube is closed behind, but an- teriorly opens into the nasal chamber by a furrow, the naso-palatine canal. The wall next the middle line is connected with the olfactory epithelium, which is in direct communication with the terminal filaments of the olfactory nerve. The outer wall is covered with columnar, ciliated epithelium. The nose in mammals is generally but slightly detached from the bones of the face. In solipedes and ruminants the nares, which are pos- sessed of a considerable degree of mobility, project but slightly, while in various members of the hog tribe the nose is prolonged anteriorly, forming the snout or muzzle. In the elephant and in the tapir this pro- longation acquires its maximum development. In the cetaceans and other aquatic mammals in which the olfactory nerve is absent, as in the dolphin, or where it is only faintly developed, the nasal chambers lose all significance as organs of olfaction and simply fulfill a respiratory function. 844 PHYSIOLOGY. OF THE DOMESTIC ANIMALS. In birds the sense of olfaction is less strongly developed than in ~ mammals, its place probably being taken by the higher degree of devel- opment of the sense of sight. Asa consequence their nasal chambers are simple; at the most three turbinated plates (anterior, middle, and posterior) are present, and these are simple in form. The olfactory nerve is distributed alone to the posterior turbinated bone. The external nares show great variations in shape, while the posterior nares commu- nicate by a small, slit-like opening with the aural cavity. The olfactory lobes are most highly developed in birds of prey and in palmipedes who feed on living fish. In amphibia the nasal chambers are even less complicated than is the case in birds. The turbinated plates are rudimentary and usually reduced to one in number. In reptiles generally the nasal chambers are limited in extent and are formed of two canals opening externally, and internally communicating with the mouth by two canals passing through the palatine arch. In the fish the olfactory apparatus is not so arranged as to be trav- ersed hy a current of air. In them the olfactory organ consists of two small cavities terminating in a cud-de-sac and opening externally by two nostrils. The bottom of these sacs is generally thrown up into folds, arranged as radii from a central point to which fibres coming from the olfactory lobe have been traced. Water carrying odors to this olfac- tory membrane can affect it but slightly, unless we can conclude that their method of olfaction differs entirely from what holds in air-breathing animals; for we find that if in the latter the nasal chambers be filled with liquid all impression on the sense of smell is impossible. In the invertebrates no organ of smell can be recognized in the ar- ticulates or in the mollusks. It is, nevertheless, certain that in some of the invertebrates, and particularly in insects, the sense of smell is highly developed. It has been supposed that here the antenne or tentacula are the seat of the sense of smell. For any substance to be odorous it must possess two properties. In the first place, it must be volatile—that is, be capable of passing into the atmosphere; and, in the second place, it must to a certain extent be soluble in water, that it may pass by imbibition into the fluid which invariably moistens the olfactory membrane. Odorous substances in- haled with the air are brought into contact with the olfactory mucous membrane and act on the terminal cells of the olfactory nerve and not directly upon the nerve-fibres; for we may conclude that just as neither the optic nerve-fibres are affected by waves of light, nor the auditory nerve-fibres by waves of sound, the fibres of the olfactory nerve are equally insensitive to odors. Smell consists, therefore, in the production of some change, probably of a chemical nature, in the terminal apparatus a “SENSE OF SMELL. 845 in the mucous membrane of the olfactory portion of the nose. Changes there excited are conducted through the nerve-filaments to the brain, and only then become recognized as the sensation of smell. It would appear that the sensation of smell is only developed on the first contact of the odorous particles with the olfactory nerve, and, as a consequence, in order to obtain an exact perception of delicate odors a number of rapid inspirations are taken, the mouth being kept closed. In this way the air is rarified in the nasal chambers and odorous parti- cles stream over the olfactory region. Consequently, if we hold our breath the sensation of smell ceases, even if we are in an atmosphere impregnated with odorous substances. It is further stated that odorous substances taken into the mouth and then expired through the posterior nares produce no sensation of smell, possibly from the fact that in this direction of the atmospheric current the particles are not brought into contact with the olfactory region; while, when bodies are inhaled with the air through the nostrils, the current of entering air is broken up by striking against the inferior turbinated bone, and part of the current passes directly through the respiratory passages and part upward through the olfactory region. The reason why odorous liquids placed in the nostrils are incapable of affecting the sense of smell is perhaps to be explained by the action of the fluid upon the olfactory cells, which perhaps possess a high degree of imbibition and are paralyzed when brought in contact with large quantities of fluid. Even water alone, as we know, will temporarily arrest the sense of smell, and if the nostrils be filled with water some time will elapse after the removal of the liquid before the sense of smell is regained. The amount of substance which may be recognized by the sense of smell is extremely small. Valentin has calculated that g55,5b0,000 Of grain of musk may be recognized by the sense of smell. Even this is, perhaps, an inside estimate, for a grain of musk will for years give its characteristic odor to the atmosphere of a room, and the most deli- cate balance will at the end of this time fail to recognize any reduction in weight, and yet we are compelled to suppose that the odor has been given to the atmosphere through the volatilizing of the particles of the musk, As regards the sense of smell, all attempts to classify the impres- sions which may be made upon it entirely fail. The only distinction which can be made is into what are termed pleasant and disagreeable odors, and yet, of course, these are simply relative terms. We may say that a substance has the odor of turpentine or of roses, but this, of course, gives us no means of classifying the causes of the sensations produced. 846 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The intensity of the sense of smell depends, first, upon the size of the olfactory surface, since we find that in animals in which the sense of smell is most acute the turbinated bones of the olfactory region are most complicated ; secondly, on the concentration of the odorous sub- stance in the air; and, thirdly, on the frequency with which the columns of air containing the odorous particles are conducted to the olfactory organs; hence snifling tends to increase the intensity of odors. The development of the sense of smell is always more highly marked in animals than in man and plays an important part in their organization. Game-dogs, as is well known, will recognize the odor from game-birds at several hundred yards, but even this falls below the acuteness of smell possessed by various animals which are able to scent the presence of man at a distance of a mile or more. B. THE SENSE OF SIGHT. Vision is the perception of the sensation causea by the impression of aray of light upon the retina, and in all animals depends upon the special sensitiveness of the optic nerve-filaments to the vibration of luminous rays. Animals may, nevertheless, be sensible of light without special organs of vision, and may even be capable of giving evidence of the impression of such light; thus, the hydra, although it has no distinct organs of vision, will move around from side to side of the vessel in which it is placed until it has reached that on which the sun is shining and will turn itself toward the seat of light. In its simplest form the visual apparatus is represented by a col- lection of pigment-cells in the outer coverings of the body which are in connection with the ter- mination of afferent nerves. The Ne ee ate (Gey Ue ef pignient absorbs the rye of light, The ocels are (aptitu on the one side (Adand displaced on the and in that function some process, probably of a chemical nature, is excited and the sensitive nerves are stimulated. In the medusa, as the jelly-fish, and at the ends of the rays of the star-fish and other echinoderms similar collections of pigment are found, but as the lens is wanting no distinct image can be formed, and, consequently, in such cases the distinction between light and darkness is all that is possible. In some of the cephalopod mollusks two simple eyes, consisting of a globular lens with transparent media analogous to the SENSE OF SIGHT. 847 cornea of higher animals, are found at the tips of the tentacula. Evi- dences of a choroid and of a nervous net-work representing the retina are also found. Such organs are termed ocelli. It is, therefore, seen that two classes of visual apparatus may be recognized, the simple and the compound; the former consisting simply of a mass of pigment in connection with the nerve-fibres, and the latter of a cornea and of other accessory organs. In many insects and in some crustaceans both species of eyes are found. The simple eyes may be three or more in number and are most usually placed on the summit of the head. In the articulates, such as insects and crustaceans, are found eyes of a special type of construction—what may be termed composite eyes—consisting of a collection of a considerable number of diverging radiating tubes or cones, terminating on the surface in the shape of polygonal opacities and inclosing in their interior a fluid analogous to the vitreous body, while their deep extremity is continuous with the nerve-filament and their Fic. 366.—-SECTION OF THE EYE oF THE COCKCHAFER (Melolontha vulgaris), (Carpenter) A. A, facets of the cornea;’B, transparent pyramids surrounded with pigment; ¢, fibres of the optie nerve; D, trunk of the opticnerve. The same description applies to B, which is a portion of the eye more highly magnified. interior is lined with pigment. Each one of these two eyes, which are frequently but a few millimeters in diameter, often incloses from ten to twenty thousand of these little tubes; while the inclosed membrane, which is analogous to the choroid, is impregnated with pigment over the greater part of its extent, except at the centre, where a transparent opening is present through which the light passes (Fig. 305). These eyes are capable of forming distinct images, but each of the diverging cones, disposed like the rays of a segment of a sphere (Fig. 366), is only capable of transmitting the ray of light which coincides with its long axis; all the other rays, striking more or less obliquely on the internal walls lined with pigment, are absorbed; as a consequence, in such an eye the image is formed by the co-ordination of the rays coming from corresponding isolated points of the object. While, nevertheless, objects may be clearly appreciated by such an eye, a large quantity of light 848 PHYSIOLOGY OF THE DOMESTIC ANIMALS. must be lost by absorption by the pigment, and, as a consequence, the clearness of the image must be sacrificed. The field of vision in such an eye will, of course, depend upon the segment of the sphere represented by the termination of the- cones, since, although the eye is convex, no movement in an orbit is possible. So, again, accommodation is not required in such an eye, since all the rays of light appreciated by each cone must be coincident with the axis of each cone. Therefore, such a compound eye may be regarded simply as a combination of an immense number of ocelli compressed together and taking an angular form, in insects six-sided and in cfustaceans four-sided. The color of the pigment in such eyes varies, being white, yellow, red, green, purple, Fic. 367.—DIAGRAM OF A NO Ty SECTION THROUGH THE HUMAN tYE, €0.) 1, cornea; 2, sclerotic; 3, choroid; 4, ciliary processes; 5, suspensory ligament of lens; 6, so-called posterior chamber between the iris and the lens: 7, iris; 8, optic nerve; 8/, entrance of central artery of retina; 8/!, central depression of retina, or yellow spot; 9, anterior limit of retina; 10, hyaline mem- brane; 11, aqueous chamber; 12, crystalline lens; 13, vitreous humor; 14, circular venous sinus which lies around the cornea; a a, antero-posterior, and b b, transverse axes of bulb. or black. Each cornea, or the termination of each ocellus or tube, is convex on one side and convex or flat on the other, so that, to a certain extent, it takes the part of a lens. Among the invertebrates the eyes of the cuttle-fish are the largest and most perfect, resembling the eyes of higher animals in possessing a crystalline lens and a chamber behind filled with vitreous humor. In the vertebrates the eye is formed by a folding in of the external integument to form a lens and an outgrowth from the optic vesicles of the brain to form a sentient surface, The eyeball in vertebrates consists of an external white, spherical case, or sclerotic coat, which serves to SENSE OF SIGHT. 849 protect the eye from external injury, and, although not transparent, is to a certain extent translucent. Anteriorly it passes into the cornea, which, though equally thick, is absolutely transparent. The latter membrane rises in thickness in front of the eye like a watch-glass. In other words, the radius of curvature of the cornea is that of a smaller circle than that of the body of the eye. The shape of the eye is preserved by two fluids, the aqueous humor filling the cavity behind the cornea, and the denser, jelly-like vitreous humor occupying the larger posterior cavity (Fig. 367). Between these two chambers is a diaphragm the size of whose aper- ture is capable of being modified—the iris. Behind the irjs lies the crys- talline lens and between the vitreous humor and the sclerotic is found the choroid membrane, covered with dark pigment-cells, which are arranged like a mosaic on its inner surface. Between the choroid and the vitreous humor is found the retina, which is the transparent expan- sion, in a number of layers, of the terminal filaments of the optic nerve. The most sensitive part of its surface is that which lies in contact with the black pigment. Externally, in most vertebrates, the eves are protected by eyelids, which are, however, absent in fishes; in them, the eyes being continually bathed in fluid, the lachrymal apparatus is like- wise absent. Their eyes are, as a rule, but slightly mobile, the crystal- line lens is spherical, the cornea almost flat, and the iris but slightly contractile. In most fishes the eyes are placed so far back that the fields of vision are distinct. In reptiles three eyelids are often found, although in some, asin the serpents, they are entirely wanting. In the latter case, as in fishes, the ocular globe is then covered only by the transparent conjunctiva. In many reptiles there is often a rudiment of the lachrymal apparatus. The crystalline lens varies greatly in form. In birds the sense of sight is especially developed. Those which are in the custom of flying at great heights in the atmosphere appear to be able to distinguish with the greatest exactness small bodies on the sur- face of. the earth. In birds, at the centre of the ocular globe and pos- terior to the crystalline lens, is found a peculiar projection of the choroid, impregnated with the choroid pigment and covered by an exten- sion of the retina, which is termed the pectin. It is not known in what way this structure serves to assist vision. Perhaps it contains muscular fibres which act upon the crystalline lens and aid in accommodation. In mammals the ocular apparatus takes about the same form as is seen in the human species, there scarcely being any difference except in the relative volume of the eyeball and the pupillary opening, and in the fact that sometimes the shape of the eyeball is elongated rather than spherical. Animals which pass the greater part of their time under ground are remarkable for the smallness of their eyeballs. In others 54 850 PHYSIOLOGY OF THE DOMESTIC ANIMALS. which are aquatic, such as the cetaceans, the crystalline lens is almost as spherical as in the fish, and in them, also, the difference in the refrangi- bility of the different media of the eye is much less than in animals living in the air. In many mammals, at the base of the eye is found a collection of brilliant pigment-cells, which reflect the rays of light falling upon the retina and so give to these eyes when seen in semi-darkness a peculiar, luminous appearance. This fapetum is yellow in the ox, reddish yellow in the cat, and blue in the horse. In mammals the eyes are placed in orbits whose direction is more or less inclined toward the sides. Only in man, apes, and nocturnal birds of prey are the orbits so arranged that vision may be directed forward simultaneously on the two sides. The lachrymal apparatus of mammals is composed of a single or double lachrymal gland placed at the external angle of the orbit. Car- nivora, rodents, pachyderms, and some ruminants have in addition in the internal angle of the orbital cay- ity the so-called gland of Harder, FIG, 368.—FoRMATION OF AN IMAGE BY REFLECTION. (Ganotl.) The rays from the object A Bare reflected by the mirror N M so as to make their angle of reflection equal to their angle of incidence; if a perpendicular, A D. is Fic. 369.—DIAGRAM ILLUSTRATING RE- let fall from the point, A, and one, B C, from the ‘ - point, B, and the reflected rays prolonged until they FRACTION OF LIGHT. (Ganot.) meet these perpendiculars, the image is apparently The incident ray, S O, on striking the surface, nm, formed behind the mirror at a distance equal to the is bent in the direction O H. S A O being the angle of actual distance of the object in front of the mirror. incidence, H O B the angle of refraction. which furnishes a thick, whitish secretion, which often accumulates at the corresponding angle of the eyelids. Rudiments of this gland are also found in solipedes. The tears are collected by the lachrymal points, which conduct them through the lachrymal duct and nasal canal to the nasal cavities. In certain rodents, the hares in particular, the lachrymal canals are replaced by fissures which establish communication between the conjunctival surface and the nasal fosse. In the study of the appreciation of the impression of a ray of light upon the retina and the formation of an image a comprehension of the laws of light is essential. The eye is furnished with certain mechanisms by which an image is formed somewhat in the same manner as ina camera obscura. Such mechanisms are what are termed the dioptric mechanisms of the eye. Rays of light striking. the retina give rise to SENSE OF SIGHT. 851 sensations, and we shall, therefore, have then to consider the mode of production of the visual sensations. 1. The Dioptric Mechanisms of the Eye——When rays of light proceed from a luminous body they always pass in straight lines, form- ing in their divergence a cone, the apex of which is the luminous body and the base such a plane as may intercept them. So long as the medium is of uniform density rays pass in straight lines, and if they come in contact with an opaque, polished surface they will be reflected, and the angle of reflection is equal to the angle of incidence and lies in the same plane (Fig. 368). Ifthe rays fall perpendicularly to this opaque surface they will be reflected in the same straight line in which they impinged. If the rays fall upon a translucent surface as they emerge from the opposite side they will be found to be bent from their original course F1G. 370.—DIAGRAM ILLUSTRATING REFRACTION. (Landois.) If S, D represent a ray of light passing through water, when it emerges at D into the atmosphere it will be bent away from the perpendicular G D and lie in the direction S$ D. through the medium, and though they pass out of the medium in a line parallel with that in which they entered, yet they are not coincident with it so long as the medium is bounded by. parallel surfaces (Fig. 369). If these rays pass from a rarer to a denser medium they are bent toward the perpendicular at the point of incidence. If they pass from a denser to a rarer medium they are refracted from the perpendicular (Fig. 370). Thus, when an oblique luminous ray passes through a piece of plate- glass its course from the atmosphere is froma rarer to a denser medium, hence it is, in the glass, bent toward the perpendicular; but in passing out it passes from a denser to a rarer medium, hence it is refracted from the perpendicular, and as the two surfaces are parallel the amount of refraction toward the perpendicular is equal to the amount of refrac- tion from the perpendicular; therefore the course of the emergent ray is parallel to the course of the entering ray, although not coincident with it. 852 PHYSIOLOGY OF THE DOMESTIC ANIMALS. By the term “refractive index” is meant the number which shows how many times the sine of the angle of incidence (ab, in Fig. 370, regarding S D as the incident ray) is greater than the sine of the angle of refraction (c d), it being always assumed that in comparing the refractive indices of two media the incident ray passes from air into the medium. On passing from air into water the ray is so refracted that the sine of the angle of incidence is to the sine of the angle of refraction as 4:3; with glass, the proportion is 3:2. Fia, 371.—DIAGRAM ILLUSTRATING THE COMPOSITION OF A CONVEX LENS OF A NUMBER OF PLANE SURFACES. (Ganot.) An illustration, first suggested by Professor Henry Morton, of Hoboken, serves greatly to simplify the conception of refraction. Tt has been stated that in passing from a rarer toa denser medium the luminous ray is bent toward the . perpendicular. Ifa line of men, as of soldiers, be marching obliquely toward the edge of a plowed field, the men first reaching the uneven ground will experience difficulty in walking over the rough surface and their end of the line will move more slowly than the end still remaining on the level ground, and, as a conse- quence, the entire direction of the line of men will be changed. On the other FIG. 372.—DIAGRAM SHOWING REFRACTION BY A DOUBLE CONVEX LENS. (Ganot.) The incident ray, I. B, is refracted at the points of incidence. B, and emergence, D, toward the axis, MN A, which it cuts at F. hand, as they reach the opposite side of the plowed surface the end of the line which first entered will be the first to emerge, and, as a consequence, progress now being easier, that end of the linc will travel faster than the end still remain- ing on the plowed ground, and, therefore, the line of men will now be bent from the perpendicular; and as the entire line emerges the line of progress will be parallel with the original line, but will not be coincident with it. SENSE OF SIGHT. 853 Refraction takes place not only through media with plane surfaces, but likewise through media bounded by curved surfaces, for the circum- ference of a circle may be supposed to be made up of a number of infinitely small, straight lines: this is indicated in the case of a lens in Fig. 371. Rays of light passing through a double convex lens in passing in are bent toward the perpendicular (Fig. 372). Now, if the rays thus acted upon be followed they will be found to meet at a point on the opposite side of the lens, called the focus, at which light and heat rays will converge. Rays of light striking the centre of curvature of both surfaces of the lens will pass through unchanged. Such a line is called the chief axis, and the centre of this line is the optical centre of the lens. Rays passing through the optical centre are termed principal or chief rays. Rays parallel with the principal axis of the lens are refracted so that they are collected on the opposite side of the lens at a point called the principal focus; the distance of this point from the central point of the lens is called the focal distance. On the other hand, it is evident that rays diverging from a luminous point at the principal focus will be so refracted FIG. 373.—DIAGRAM ILLUSTRATING ACTION OF A DOUBLE CONVEX LENS OF HIGH CURVATURE ON DIVERGENT RAYS. (Ganol.) The divergent rays from the luminous point, L, are brought to a focus at 7 behind F, the principal focus at which parallel rays, 5 B, converge. as to be parallel when they pass from the lens. Again, rays of light in the principal axis and from a point beyond the principal focus will converge to a point on the opposite side of the lens (Fig. 378). Four cases are possible: First, when the distance of the light from the lens is equal to the focal distance the focus will lie at the same distance on the opposite side of the lens, z.e., twice the focal distance ; second, if the luminous body approach to the lens, or, what is the same thing, to the focus, then the focal point is moved farther away; third, if the light is still farther from the lens than twice the focal distance, then the focal point comes correspondingly nearer to the lens; fourth, if the rays proceed from a point on the chief axis within the focal distance they will diverge on the opposite side of the lens and not again come toa focus; while, on the other hand, converging rays passing through a convex lens will have their focal distances at a nearer point than that at which ~ parallel rays are collected. These facts are illustrated. in the following diagrams (Fig. 374). 854 PHYSIOLOGY OF THE DOMESTIC ANIMALS. in ordinary lenses the amount of refraction at the centre and at the circumference is not equal. Rays passing through the optical centre, as already stated, pass directly without refraction, while those which pass near the centre are less refracted than those which pass near the circum- I I d Fic. 374.—AcTION OF A CONVEX LENS ON LIGHT. (Landois.) I. m™m, chief axis; O, optical centre; rays (7 ) passing through this centre are principal rays, and are not refracted. II. Parallel rays are collected at a focus, /, /'O being the focal distance. III. Rays diverging from a point, b, on the chief axis, within the focal distance, pass out of the other side of the lens less divergent, but do not come toa focus. IV. Rays from a source of light, /, beyond the principal foons, /, again converge on the opposite side of the lens. V. Formation of an inverted image by a convex lens. ference ; consequently, the amount of refraction incyeases as the circum- ference of the lens is approached. This is known as spherical aberration. Ifa screen be placed in the focus of the rays passing near the centre of A B Cc D E F Fia. 375.—DIFFERENT KINDS OF LENSES, (Ganot.) A, double convex ; B, plano-convex ; C, converging concavo-convex ; D, double concave; E, plano-concave ; F, diverging concavo-convex ; C and F are also called menisous lenses. the lens the resulting image will be bright in its central portion, and will have surrounding it a halo which becomes fainter and fainter as we pass from the centre to the circumference (Fig 376). Spherical aberration may be corrected in two ways: by increasing SENSE OF SIGHT. 855 the density of the lens at its central part, in order that it may act more strongly on rays of light, by which the refracting power is increased at that point; this is accomplished in the crystalline lens of the eye in this manner since it is less dense at the circumference than in the centre: or, spherical aberration may be diminished by placing a diaphragm between the object of which the image is to be formed and the lens, so as to cut off those rays which pass through the circumference and allow the image to be formed only by the central rays. This method, also, is adopted in the construction of the eye, where the movable diaphragm is represented by the iris. Again, another point is to be mentioned: white light, as is well known, is composed of seven colors, which vary in their different degrees of refrangibility—violet, indigo, blue, green, yellow, orange, andred. If a beam of white light is passed through a triangular prism of glass it is FIG. 876.—DIAGRAM ILLUSTRATING SPHERICAL ABERRATION. (Ganot.) The rays passing through the edges of the lens have a shorter focal distance than those passing nearer to the centre. decomposed into its constituent rays, the violet rays being refracted most strongly and the red the least (Fig. 377). A white point ona black ground does not form a simple image on the retina, but many colored points appear after each other. If the eye is accommodated so as to focus to a sharp image the violet rays are refracted most strongly ; the other colors will form concentric diffusion circles, being most marked in the case of the red rays. In the centre of all the colors a white point is produced by their mixture, while around it are placed colored circles. Such an action, of course, produces dimness of the object, and is known as chromatic aberration. This, too, may be corrected in two ways: either by making use of the diaphragm and cutting off the rays passing through the circumfer- ence of the lens; or in optical instruments by the use of two kinds of glass, one of which has a different dispersing power from the other, but 856 PHYSIOLOGY OF THE DOMESTIC ANIMALS. equal refracting power. Of the one a double convex lens is made, of the other a double concave, and the two combined. They must be of dif- ferent dispersive power, or the degree of concavity which would correct the chromatic aberration would also destroy the converging power of the convex lens. In crown glass and flint glass we have such media. The flint glass has greater dispersive power, hence the degree of concavity necessary to correct the chromatic aberration will be attained before the degree of concavity will be reached which would destroy the converging power of the convex lens of crown glass. In the different refractive media of the eye such combinations are to a certain extent represented, and serve, together with the action of the pupil in shutting off the circumferential rays, to correct chromatic aberration. The eye as an optical instrument is analogous to the camera obscura, and forms, in a manner to be described directly, an inverted image in Fia. 377.—DIAGRAM ILLUSTRATING THE DECOMPOSITION, IN PASSING THROUGH Sous WHITE LIGHT INTO THE SEVEN COLORS OF THE SPECTRUM, éclard. r, red; 0, orange; j, yellow; v, green; b, blue; i, indigo; vi, violet. reduced size of objects hefore it. Instead of a single lens, as in the camera, the eye is composed of a number of different refractive media placed behind each other—the cornea, the aqueous humor, and the lens. The field of projection, or the point on which the image is focused, is the retina, and from changes which have recently been discovered to take place in the retina in which the visual purple becomes bleached the analogy to the process of photography is very striking. As is well known, by means of a convex lens an image of any object may be formed upon a screen; thus, if a convex lens be held before a window, and a piece of paper placed behind it as a screen, at a certain SENSE OF SIGHT. 857 distance behind the lens, a reversed image of the window will be formed upon it. The manner in which this image is formed may be represented in the following diagrams (Figs. 378 and 379). In these figures it is seen that rays from any point of the object, which may be regarded as diverging rays, are brought toa point behind the lens. Ifthe figures should be completed, and lines drawn from each indi- vidual point of the objects in the manner represented in the illustrations, it must be evident in tracing each of these lines that a small inverted image - Fra. 378.—DIAGRAM ILLUSTRATING THE FORMATION, BY A DOUBLE CONVEX LENS, OF A SMALLER INVERTED IMAGE. (Ganot.) must be formed behind the lens. If a screen be placed at this point, which corresponds to the focal length of the lens, it is evident that the image will be distinctly defined. On the other hand, if the screen be either approached or removed farther from the lens an indistinct image _will be formed. If the object be farther removed from the lens the image will decrease in size, and to have a distinct image the screen must be approached to the lens; and, conversely, if the object be approached Fia. 879.—DIAGRAM ILLUSTRATING THE FORMATION OF AN IMAGE BY A DOUBLE CONVEX LENS. to the lens the image will be increased in size, and to have sharp definition the screen must be moved farther from the lens. A similar process occurs within the eye, although the refraction of rays of light is much more complicated than in the simple convex lens, for in the eye the ray of light passes through several media and is refracted by each. Nevertheless, in the eye, a small inverted image is formed on the retina, as may be readily determined by removing the eye from a recently killed animal, and if the sclerotic be removed from the 858 PHYSIOLOGY OF THE DOMESTIC ANIMALS. posterior portion of the eyeball the image of external objects in a strong light may be seen upon the retina inverted and reduced in size (Figs. 380 and 381). The principal surfaces by which rays of light passing through the eye are refracted are the cornea and the anterior and posterior surfaces of the lens. Since rays of light passing from the atmosphere to the cornea pass froma rarer to a denser medium, the rays of light will be bent toward the perpendicular. The degree of refraction at this point will be more marked than in passing from the cornea to the aqueous humor, both of which possess the same refractive power. On the other hand, the refraction will be still greater in the lens, so that the rays will be still more strongly deflected inward. It has been seen that rays of light passing through the central point of the optical centre of a convex lens do not undergo refraction, and in a double convex lens of equal curvature the optical centre will coincide with the Fic. 880.—FORMATION OF AN IMAGE IN THE EYE. (Landois.) By following the rays from the objeby A Hye TA Re Bee tod they pare brought to a focus on the retina, geometrical centre. In such a compound, system of refracting media as in the eye the optical centre is less readily determined. It has been determined that in the eye the optical centre lies, not exactly in the centre of the crystalline lens, but between that point and the posterior surface of the lens; consequently, the rays passing through this point will practically undergo no refraction. It has been stated that a screen may be so arranged in relation to a convex lens that a distinct image of the object will fall upon it. This relation is attained when the screen is in the exact focus of the lens. If approached to the lens or removed a greater distance from it the image becomes indistinct. So, also, simi- lar blurring or indistinctness is produced when the distance between the object and the lens is altered. In looking at a distant object the rays of light may be regarded as parallel, and, as is well known, are focused with the greatest readiness upon the retina. The difference between the action of the eye in SENSE OF SIGHT. 859 forming an image and that of a simple lens is evident in the fact that with the normal eye an object may be seen with equal distinctness whether at a great distance or closely approached to the eye. This indicates that there must be some mechanism in the eye by which the focal length of the refracting media can be altered. If the finger be held a short distance before the eye, the other being closed, it may be distinguished with the greatest distinctness. If the finger remain in the same position, and the eye now be fixed on some more distant object, the finger is seen indistinctly, so that at will we may focus our eyes on either the near or the far object and either may be distinctly seen: yet when the eye is arranged for near objects far objects are seen indistinctly, and the reverse. Such an adjustment of the refracting powers of the eye is termed accommodation. It was for a time thought that the accommodation of the eye was accomplished by approaching or withdrawing the receiving surface, the retina, to or from the lens. It Fi. 381—DIAGRAM ILLUSTRATING THE FORMATION OF AN IMAGE ON THE RETINA. ( Yeo.) The rays from the point, a, passing through the cornea, lens, ete., are collected in the retina at. Those from a! meet at L/, and thus the lower point becomes the upper. has, however, been shown that this is not the case, and that accommo- dation is accomplished by changes in the curvature of the crystalline lens. Referring again to our illustration of an object, a convex lens, and a sereen, as has been stated, if we determine the focal length of the lens or the point at which a distinct image will be formed upon the screen and then approach the object to the lens, the screen not being removed from its position, the image will be indistinct. If, now, we remove the object, the screen remaining unmoved, and substitute for the lens originally used one of a greater degree of curvature, the degree of refraction will evidently be greater and the focal length shorter, so that the rays from the object in the near position, being more diverging, may be brought to 2 focus at a point corresponding to that of the less diverging rays from the farther-removed object. So, again, if the point of distinct image be determined and the object farther removed, the screen would then have to be approached to the lens in order to obtain a distinct image. In this 860 PHYSIOLOGY OF THE DOMESTIC ANIMALS. case, also, a distinct image might be formed by substituting a lens of a less degree of curvature. In the eye accommodation is accomplished by muscular action through which the shape of the lens is changed. When the eye after viewing an object at a distance is adjusted to form a sharp image of a nearer object the crystalline lens becomes thicker through an increase of the curvature of its anterior surface. This change may be represented in the following diagram, after Helmholtz (Fig. 382). The left portion of the figure represents the eye adjusted for distant objects, while the right half is accommodated for near objects. It is here seen that the anterior surface is increased in convexity, moving nearer the cornea, and has carried the iris with it. It is well known that the refraction of light rays caused by a convex lens increases with its increase of curvature, and that the focal length of one lens will be longer than Fria. 382.—SCHEME OF ACCOMMODATION FOR NEAR AND DISTANT OBJECTS, AFTER HELMHOLTZ. (Landois.) The right side of the figure represents the condition of the lens during accommodation for a near object, and the left side when the eye is at rest. The letters indicate the same parts on both sides; those on the right side are marked with a stroke. 4, left, B, right half of lens; C, cornea: S, sclerotic; C.S., canal of Schlemm; 1.A., anterior chamber: J, iris; P, margin of the pupil; V, anterior surface, H, posterior surface of the lens; R, margin of the lens; F, margin of the ciliary processes; a b, space be- tween the two former; the line ZX indicates the thickness of the lens during accommodation for a near object; Z ¥, the thickness of the lens when the eye is passive. that of one of greater curvature—in other words, the latter will produce a greater convergence of the light-rays. A similar state of affairs holds in the adjustment of the lens in the eye. When the object of our vision is closely approached to the eye the lens is more convex than when the distance is greater, and its refract- ing power is, therefore, increased and the formation of an image on the retina rendered possible. Of course, with every variation in distance there must be a corresponding variation in the degree of curvature of the lens. The mechanism by which the change in the curvature of the lens is accomplished is the ciliary muscle. The capsule of the lens is attached at its edge to the zone of Zinn, which radiates outward and keeps the lens ina state of constant tension. At the point where the fibres of this SENSE OF SIGHT. 861 ligament are attached to the outer membrane are also attached the fibres of the ciliary muscle. When the eye is in a condition of rest, and, therefore, adjusted for distant objects, the ciliary muscle is relaxed and the zone of Zinn, by means of its elastic tension, pulls on the edges of the lens-capsule, thereby extending the lens in a radial direction toward its edge, diminishing its thickness and flattening its curvature. When we want to focus for near objects the zone is drawn forward and inward _by the contraction of the ciliary muscle. Its tension, therefore, decreases, and the lens, by means of its elasticity, bulges forward from the release of the tension of the capsule of the lens and so increases in thickness, and its anterior surface becomes more curved. It is, therefore, evident ~ why a strain on the eyes is experienced when looking at near objects, since in a condition of rest of the eye the muscle is relaxed and the eye is adjusted for parallel rays or for viewing distant objects; but when near objects are closely examined a prolonged muscular effort is required, and this, like all other muscular exertions, results in fatigue. Fic. 3883.—Myoric EyE. (Landois.) In the normal eye the far point of vision may be placed at an infinite distance, for in the normal eye the degree of refraction of the dioptric media is such that parallel rays of light are brought to a focus on the retina. In myopia, or near-sightedness, parallel rays are not focused on the retina in a condition of rest of the ciliary muscle, but cross within the vitreous humor, and after crossing form a diffused image on the retina. The focal point in the myopic eye for parallel rays falls in front of the retina (Fig. 383). The eyeball is, therefore, too long as compared with the focal length of the refracting media. The near point, on the other hand, or the nearest point at which objects may be distinctly seen, lies abnormally near, and the range of accommodation is diminished. On the other hand, it is conceivable that the refracting media of the eye may be such that, without accommodation, parallel rays of light, instead of being focused on the retina, as in the emmetropic or normal eye, or in front of the retina, as in the myopic eye, will come to a focus behind the retina (Fig. 384). Such a defect is spoken of as hypermetropia, and is due to the fact that the degree of refraction of the media of the 862 PHYSIOLOGY OF THE DOMESTIC ANIMALS. eye is not sufficiently great to bring parallel rays of light to a focus on the retina. When such an eye is at rest only convergent rays are capable of forming a distinct image on the retina, so that, therefore, distinct images can only be formed by rendering all the rays of light which enter the eye convergent; and, therefore, such an individual will not be able to see distinctly without a convex lens in front of the eye. In such an eye the far point is negative, while the near point is abnormally distant and the range of accommodation great. In the bypermetropic eye, consequently, the distance between the retina and the lens is abnormally short. When the eye is accommodated for near objects the pupil contracts ; when in accommodation for distant objects it dilates. So, also, sehen the eye is exposed to a bright light the pupil becomes reduced in size, while, on the other hand, it dilates when the light becomes reduced in intensity. Changes in the pupil are accomplished by the action of the muscular fibres of the iris, which by their relaxation and contraction increase or diminish the size of the pupil. The iris, therefore, fulfills the function of a diaphragm and serves to cut off the circum- ferential rays of light, which otherwise would lead to the production of spherical aberra- tion. So, also, as it contracts FiG. 384-HYPERMETROPIC EYE. (Landois.) in a bright light, it serves to regulate the amount of rays of light entering the eye, while, further, it to a certain extent supports the action of the ciliary muscle, as is seen in the changes which occur in the size of the pupil during accommodation. The iris is supplied with two sets of muscular fibres, the circular or sphincter fibres, which are supplied by the oculo-motor nerve, and the radiating fibres, or the dilator of the pupil, supplied chiefly by the cervical sympathetic and the trigeminus. When the oculo-motor nerve is divided the pupil dilates, owing to the contraction of the dilator fibres, which still preserve their integrity. On the other hand, when the sympathetic is divided in the neck the pupil contracts through the antagonistic action of the sphincter fibres. The contractility of the circular fibres is, nevertheless, the stronger, for if both nerves be stimulated together contraction of the pupil will take place. The radial muscular fibres are especially developed in birds, while they have been Cait to be absent, in many other animals. Changes in the size of the pupil fall under the head of reflex actions, SENSE OF SIGHT. 863 since they cannot be produced through the exercise of the will. When aray of light falls upon the retina it leads to contraction of the pupil, in which the optic nerve is the afferent nerve, the oculo-motor nerve the efferent nerve, while the centre lies in some place in the brain below the corpora quadrigemina. This is proven by the fact that when the optic nerve is divided intense light no longer produces contraction of the pupil, while, also, the division of the third pair renders the pupil insensitive to light, and stimulation of the peripheral portion of the oculo-motor leads to contraction of the pupil. So, also, stimulation of the floor of the aqueduct of Sylvius will, likewise, if the oculo-motor nerve be intact, lead to contraction of the pupil. In contradistinction to what will be found in many instances, two symmetrically disposed centres are not to be found in the brain for gov- erning the movements of the pupil, since in normal conditions a stimulus applied to one optic nerve will lead to contraction of both pupils, while, also, stimulation of the centre will react on both eyes. In addition to the oculo-motor nerve, the iris receives nerve-fibres from the short ciliary nerves coming from the ophthalmic ganglion, which is connected by its root with the third nerve, the cervical sympa- thetic nerve, and the nasal branch of the ophthalmic division of the fifth nerve, It has been mentioned that section of the cervical sympathetic causes contraction of the pupil,and stimulation of the cervical sympa- thetic dilatation of the pupil. It is evident that these effects on the pupil are directly opposite to those seen in the blood-vessels on stimu- lation of the sympathetic nerve. The centre for the dilatation of the pupil likewise lies in the front part of the floor of the aqueduct of Sylvius, while a second or inferior centre, the so-called cilio-spinal centre, lies in the lower cervical portion of the cord and extends downward to the first or third dorsal vertebra. This centre may be reflexly stimulated by irritation of various sensory nerves, when, of course, dilatation of the pupil will take place. It is likewise stimulated by the blood in dyspneea, and also a single centre governs the movements of both pupils, for if one retina be shaded both pupils will dilate. The cilio-spinal centre is in connection with the upper centre for the dilator of the pupil through fibres passing through the lateral columns of the cord, and it, together with the inferior centre, reacts to the same stimuli. When the sympathetic nerve is divided in the neck the pupil con- tracts. This contraction is accompanied by a great increase in the vascu- larity of the iris from the consequent paralysis of the walls of its blood-vessels. This at one time was supposed to be sufficient to explain the production of contraction of the pupil after section of the sym- pathetic. Various other conditions which lead to an increased blood 864 PHYSIOLOGY OF THE DOMESTIC ANIMALS. supply of the iris will influence the size of the pupil. Thus, in forced expiration, by which the returri of the blood from the head is retarded, the pupil is contracted. So, also, when the intra-ocular pressure is dimin- ished, as by puncture of the anterior chamber, there is less resistance to the flow of blood to the blood-vessels of the iris and the pupil is imme- diately contracted. On the other hand, strong muscular exertion, which leads to the blood flowing freely into the contracting muscles, will produce dilatation of the pupil. The size of the pupil may be modified by various drugs. Substances which dilate the pupil are called mydriatics ; those which lead to its con- traction, myotics. Of the former may be mentioned atropine, hom- atropine, duboisine, daturine, and hyoscyamine. They act chiefly by paralysis of the oculo-motor nerve, while also acting slightly upon the dilator fibres, for after complete paralysis of the oculo- motor nerve the moderate dila- tation thereby produced may be intensified by the administration of atropine. Atropine appears to act mainly by a local mechanism, since it produces dilatation of the pupil even after destruction of the ophthalmic ganglion and division of all the nerves of the eye except the optic, and even, according to some authorities, Fig: 1 PGR ill. produce dilatation. of the cat ey ie Sate itnerte rime | Duel: meu eneleed eye ee oe Myotics, of which physostig- mine or eserine is the best known, may produce contraction of the pupil either by stimulation of the oculo-motor nerve or paralysis of the sympathetic. 2. Visual Sensations.—Our considerations of the action of the organ of vision have thus far dealt simply with physical processes. The rays of light entering the eye have been traced backward through the trans- parent media of the eye until they resulted in the formation of an image. When the rays reach the retina, sensory impulses are excited and are carried through the optic nerve to the sensorium, where they give rise to a sensation. The nature of the changes that take place within the retina does not SENSE OF SIGHT. 865 admit of as close analysis as the physical action of the different refract- ing media of the eye. It is known that it is only the layer of rods and cones of the retina that is concerned in the formation of the image, since rays of light pass through the anterior layers of the retina without giv- ing rise to any sensations. The retina is a highly complicated nervous apparatus, which may, by the use of the microscope, be divided into eight and probably ten distinct layers. The innermost layer—z.e., the layer in contact with the vitreous humor—consists of nerve- fibres in which the optic nerve terminates, radiating from the entrance of the optic Fig. 387.—LAYERS OF THE RETINA. (Landois.) Pi, hexagonal pigment cells; Sf, rods and cones; Ee, external limiting membrane; iiuK, external nuclear Fig. 886.—VERTICAL SECTION oF HUMAN RETINA. (Landois.) layer; iugr, external granular layer; inK, internal @, rods and cones; 5, external, Jj, internal limiting nuclear; ingr, internal granular; Ggl, ganglionic Membranes; c, external, and /, internal nuclear layers: nerve-cells; O, fibres of optic nerve; £7, internal limiting €, external, and g, internal granular layers; &, blood- membrane; Rk, fibres of Muller; A, nuclei; Sg, spaces vessel and nerve-cells ; 2, nerve-fibres. for the nervous elements. nerve (Fig. 385). At this point, therefore, the retina will consist only of nerve-tubules. At one spot in the centre of the retina no nerve- fibres are to be distinguished, and on account of its color this point is termed the macula lutea, or yellow spot, and is the point of most acute vision, q The layers of the retina have been described as follows: First, and 3S 866 PHYSIOLOGY OF THE DOMESTIC ANIMALS. most internally, exists a fine limiting membrane; second, externally, a layer of nerve-fibres ; third, a layer of nerve-cells analogous to the gan- glionic cells of the brain; fourth, a granular layer consisting of an indis- tinct mass of fine gray granules ; fifth, the inner granular layer, composed of little round granules; sixth, the intermediate granular layer, in which the granular mass is intermingled with small fibres; seventh, the outer granular layer, analogous to the inner granular layer; ‘eighth, a second -delicate membranous structure; and ninth, the layer of rods and cones (Figs. 386 and 387). It is this most external layer of the retina which is concerned in the reception of the rays of light and the formation of the image. It con- sists of small, transparent rods packed closely together at right angles to the surface of the retina, while at different intervals between them is seen 2 small rod expanded at the end so as to form a conical shape. These cones are especially abundant in the yellow spot, where there is a slight depression in the retina and where no rods are present. 'T'o reach the layer of rods and cones, the rays of light must evidently pass through all the superimposed lay ers, and are finally stopped at the choroid, which, with its pigment layer, thay be regarded as forming a backer ound for the retina. That the nerve-fibies themselves are insensitive to light may be readily determined by proving that the point of entrance of the optic nerve is entirely insensitive to light. If one eye is closed and the other fixed ona black spot on a white sheet of paper and some other small body be gradually moved laterally toward the outside of the field of vision, at a certain distance the moving body will entirely disappear from sight, while, if the motion be continued, it will again come into the field of vision; or if we place two wafers upon a board at a distance of four or five inches apart and stand at about five times this distance, and closing the right eye, with the left look at the right-hand wafer, the left- hand wafer will disappear., The explanation of this is that when so placed the rays of light from the left-hand wafer will be received directly on the optic nerve, and so indicates that the optic fibres themselves are insen- sible to light, and that it is only through the retinal expansion of these fibres that sensations of vision are possible. On the other hand, the macula lutea is the locality of most distinct vision. When we fixedly regard a point with the eye, then the rays of light from that point pass through the middle of the pupil and’ the centre of the lens and fall almost on the centre of the retina, directly on the yellow spot. The for- mation of the macula lutea indicates the reason of its ‘especial sensitive- ness to light, while at the same time pointing out the:constituents of the retina which are concerned in the formation of the image. It has been mentioned that the optic fibres surround the yellow spot. without passing we ‘SENSE OF SIGHT. 867 over it. This would appear to indicate such an adjustment of the con- stituents of the retina as toavoid the slightest interference with rays striking on this point, since we have seen that the optic nerve-fibres are not sensitive. Again, in the yellow spot the cones of the retina are closely packed together, and in addition numerous ganglionic cells are found, while the other layers of the retina are fainter than elsewhere. The yellow color is due to the deposit of numerous yellow pigment cells. If it be admitted in the first place that the optic nerve-fibres are not sensitive to light, and in the second place that the layer of rods and cones represents the sentient surface for light-waves, a connection must evidently exist between the receiving surface and the nerve-fibres to admit of the impression becoming a sensation and being perceived by the brain. Microscopical examination will succeed in tracing a connec- tion by means of fine filaments penetrating all the layers of the retina and connecting the nerve-fibres with the ganglionic cells, the granular layers, and finally with the rods and cones. It is through this path that the irritation caused by the rays of light and received in the meshes of the rods and cones passes to the optic nerve-fibres, and thence to the brain, there creating the sensation of light. Like other nerves of special sense, the fibres of the optic nerve, though insensitive to light, respond to other irritants, and then the brain perceives the sensation peculiar to that special nerve and recognizes that an irritant has acted upon the nerve of vision, and a flash of light is the result. Thus, in cases of section of the optic nerve a flash of light is experienced, and then total darkness follows; so, also, if the optic nerve be stimulated by electricity a sensation of light is the result. All the nerves of special sense to this extent agree in their nature, and the optic nerve no more conveys sound-waves to the brain than does the auditory nerve waves of light; but both nerves at their terminations are supplied with special forms of apparatus, the so-called special sense organs, which only admit of being excited by appropriate stimuli; thus the terminal fibres of the optic nerve are especially adapted for receiving impressions of waves of light, the auditory nerve waves of sound, the difference lying in the different impressions made upon’ different special centres in the brain. As to the mode in which rays of light call into action the specific functions of the layer of rods and cones, but little is definitely known. Recent investigations appear to point to a chemical decomposition being concerned in this process. It is well-known that rays of light produce decomposition in many substances, which are then spoken of as sensitive to light. That a ray of light shall produce such decomposition, it must beabsorbed, We therefore, perhaps, see the explanation of the invariable 868 PHYSIOLOGY OF THE DOMESTIC ANIMALS. existence of pigment cells in the organ of vision. It has been mentioned that the first indication of organs of vision is represented by an accumu- lation of pigment cells, and we never find the presence of an eye which is totally free from such pigment matters. A fact which at first seemed to show exactly how this process was ‘accomplished was the discovery in the retina of the purplish-red pigment, the so-called visual purple, or rhodopsin, which is so extremely sensitive to light that by proper means external objects may actually be photo- graphed in it on the retina. This substance may be extracted from the retina by means of a 2.5 per cent. solution of the bile acids, especially if the eyes have been kept for some time in a 10 per cent. solution of com- mon salt. Kiihne stated that by illuminating the retina actual pictures could be produced on the retina, and that they gradually disappeared. The analogy between this fact and the action on the sensitive plate in the photographic apparatus is very striking, and the further behavior of the purple pigment of the retina would perhaps show that it is concerned in the appreciation of light. Thus, if a rabbit is kept in the dark for some time and then killed, and its retina examined by a monochromatic light, it will be found to be of a brilliant purple-red color with the single exception of the macula lutea; on the other hand, exposure to light will result in quickly bleaching it, but it will, however, have its color restored if the eye be again placed in darkness. Unfortunately, we are as yet entirely unwarranted in forming any such conclusion or affirming any such close connection between this peculiar substance and the sensation of vision by the fact that the pigment is confined to the outer segments of the rods and is absent in the cones, which we have found to be the most sensitive layer; and is, in fact, absent in the macula lutea, which we have found to be the most sensitive point of the retina. Finally, it is absent in pigeons, hens, and bats, although the retina of the latter only consists of cones, while it is found in both nocturnal and diurnal animals. Finally, it is entirely wanting in animals which undoubtedly see very distinctly, and may be entirely removed from the eyes of certain animals, as the monkey, by prolonged exposure to strong light, when the retina will become completely bleached, but will still apparently be perfectly sensitive to light. We cannot, there- fore, at present explain visual sensations as due to chemical changes occurring in this pigment. The discovery of the retinal pigment is, nevertheless, to be regarded as an advance in the elucidation of this sub- ject, for it is almost impossible to conceive that it is not in some way concerned in vision. It has been stated that the two pupils act simultaneously, and as we know the function of the pupil is concerned in regulating the entrance of rays of light to the eye and that vision takes place simul- SENSE OF SIGHT. 869 taneously with the two eyes, the question arises, Why is it that with two retin, each capable of receiving a distinct image, the image so formed by the use of the two eyes is not double? The explanation of this lies not so much in the anatomical distribution of the tunics of the eye as in the fact that when rays of light proceed from a luminous body and fall upon the retin they fall upon parts that are aecustomed to act together. Every point of the image on one retina falls upon a coincident point upon the other. These points are accustomed to act together and we see a single image. The eyes, indeed, receive a double impression, and this may be illustrated by placing two small bodies, as the fingers, at different distances from the eyes. Directing the eyes to the nearer, the more remote will appear double, or, if the eye be directed to the more remote, the nearer will appear double. This is due to the fact that the images of the object upon which the eye is not especially directed do not fall upon coincident parts of the retina. The same thing may be accomplished by throwing the two parts of the retina out of coincidence with each other, when, almost instantaneously, double vision will occur. If, while looking at a single object, we press to one side the globe of one eye, we bring two parts of the retina to act together which did not ordinarily thus coincide. and double vision ensues. Any other cause, such as various poisons, disease, or fatigue, which will disturb the co-ordination of the eyes or such an adjustment of the posi- tion of the eyes that rays of light do not fall upon corresponding or coincident parts, will result in double vision. Again, it has been stated that the image formed upon the retina is an inverted one, and yet it isa matter of common experience that every body is seen in the field of vision as upright. This second mental rever- sion of the image is the result of experience acquired in the exercise of the sense of sight. It is not to be understood that the brain takes cog- nizance of the picture upon the retina and that vision is an actual trans- mission of this image to the sensorium. The mind does not look upon the picture so formed, but vision is a mental act excited by an impres- sion upon the optic nerve whose neurility is excited. There need be no more correspondence between the change in the brain and the image in the eyes than between the signs of the telegraph operator and the words of the written message. It must be remembered that vision consists in the change developed in the central organ as a consequence of changes in the optie nerve. Even supposing that the image on the retina is inverted, what difference does it make? Everything is inverted and the relative position of things is unchanged. All objects hold the same rela- tion to each other whether the image be inverted or erect; hence the mind is not conscious of any inversion. Although each retina receives an image from the object the pictures 870 PHYSIOLOGY OF THE DOMESTIC ANIMALS. are not precisely the same. If we hold up any object and look at it first with the right eye, having the left eye closed, and then with the left eye, having the right eye closed, it will be readily seen that the picture is not precisely the same. With the right eye we sce the right side of the object, and with the left eye the left side. When these two pictures come to be fused in the brain there results an image which differs from either of the other two and which is projected into space, giving the idea of one solid body (Fig. 388). It is upon this principle that the stereoscope is constructed. The stereoscopic picture is composed of two images, one representing the object as seen by the right eye, and another representing the object as seen by the left. When these two pictures are fused the resulting picture is formed, which is a compound of the two, and this fusion of the two images gives the idea of solidity of the object. When the eye has looked at an ob- ject for a long time, especially if that ) object be luminous, the retina becomes g fatigued and no longer capable of re- ceiving impressions from it. If the object be small only a small portion of the retina will be impressed. If we turn away from the object and fix the eye upon a white wall we see a dark spot upon the wall corresponding in size with the object upon which we have been looking. Suppose that we ar fix the eye upon a bright red wafer Fra. 388.—DIAGRAM ILLUSTRATING Br- strongly illuminated, and look at it NOCULAR VISION. (Béclard.) ; The lines from the object indicate that the rays steadily with our eyes, the Trays pro- from the back of the book tall on coincident points of the retina, while each eye, further, has a special fed ceeding from that wafer and falling upon one point of the retina will fatigue that point so that it will not be capable of receiving rays from less luminous objects, and when we turn our eye to the wall we see a spot on the wall like the wafer in size but of a different color, made up of all the colors of the spectrum except red. This combination constitutes what are termed accidental or complementary colors. Again, if we look at a white object for a long time and then look at the wall we see there an object of the size of the original one of a black color. The point of the retina upon which the image fell has become so fatigued that it cannot receive an impression from the fainter rays reflected from the wall, while all the other parts of the retina are impressed by these rays. We, there- SENSE OF SIGHT.' 871 fore, see the wall with a dark spot upon it. These accidental colors are produced by fatigue of the retina, and consist of all the other colors of, the spectrum except that of the luminous object at which we have been looking. The primary colors, so-called, are red, yellow, and blue. The intermediate points of the spectrum are made up by combinations of these; thus, violet is a mixture of red and blue, green of yellow and blue, and orange of red and yellow. Blue is thus the complement of orange and yellow of violet. Fig. 389.—DIAGRAM ILLUSTRATING IRRADIATION. (Stirling.) Tf this diagram is held some distance from the eyes, especially if not exactly focused, the white dot will appear larger than the black, though both are exactly of the same size. When rays of light from a strongly luminous body fall upon the retina they are not confined exactly to the precise points upon which they impinge, but extend themselves to a greater or less degree around them. Thus, if we make a circular white spot upon a black ground, and a black spot of corresponding dimensions upon a white ground, the former will appear considerably larger than the latter, apparently, be- ‘cause the excitation of the retina by the luminous impression tends to spread itself over the adjacent unexcited space (Figs. 389, 390, and 391). The same phenomena are seen when the experiment is performed with Fic. 390.—DIAGRAM ILLUSTRATING IRRA- Fig. 391.—DIAGRAM ILLUSTRATING IRRA- DIATION. (Stirling.) DIATION. ee Laas ; The two white squares appear the larger, and the; The white strip, which is of equal widtl rough- appear to run into ‘each ot! ae and to be joined bya out, appears wider below, between the black squares, white strip. than above. different colored bodies. If the impressing body, though small in size, illuminate the retina strongly, it may irradiate its impression upon the ° surrounding part of the retina and make itself appear larger. In our perceptions of the nature of external objects we find that the sense of vision, like the other sensations, is not infallible, but that 872 PHYSIOLOGY OF THE DOMESTIC ANIMALS. various errors in judgment of visual sensations frequently occur. Some of these admit of explanation, others do not. The most striking example of such an error in perception, and one which is the most readily explained, is as follows :— If a series of parallel vertical black lines, two millimeters in diameter, are drawn on white paper, with equal white areas between them, and then intently regarded in a good light, in a short time the lines will assume the shape seen in Fig. 392 at A. They appear of this. shape because of Fig. 392.—DIAGRAM ILLUSTRATING BERG- i MANN’S EXPERIMENT. (Stirling.) FIG. 393.—ZOLLNER’S LINES. (Stirling.) the manner in which the images of the lines fall on the cones in the yellow spot, as shown in B. If a series of oblique lines are drawn perfectly parallel to each other, and then they are crossed in different directions by a number of short parallel oblique lines, although the long oblique lines are perfectly parallel, the short oblique lines cause them to appear to slope inward or outward, according to the direction of the oblique lines (Fig. 393). In the figure 8 and the capital letter S the upper half to most per- sons appears of about the same size as the lower half. If, however, the page on which they occur be inverted it will be seen that the lower part SSSSSSS58 88888888 Fia. 394. DIAGRAM ILLUSTRATING AN IMPERFECTION OF VISUAL JUDGMENT. (Stirling.) is considerably the larger (Fig. 394); or if the centre of Fig. 395 be fixed at about three or four centimeters from the eye, by indirect vision the broad black and white peripheral areas will appear as small and the ‘lines bounding them as straight as the smaller central areas. If a disk similar to that seen in Fig. 396 is rotated the disk appears to be covered with circles, which, arising in the centre, gradually become _ larger and disappear at the periphery. If, after looking at such a revolv- ing disk for some moments, it be attempted to read a printed page, or to look at a person’s face, the letters appear to move toward the centre, while the person’s face appears to become smaller and recede. If the disk be rotated in the opposite direction the opposite results are obtained. SENSE OF SIGHT. 873 * Movements of the Eye.—The position of the eyeball in the orbit Fic. 895.—DIAGRAM ILLUSTRATING IMPERFECT PERCEPTION OF SIZE. (Stirling ) corresponds to a ball-and-socket joint, and each eyeball is capable of moving around an immovable centre of rotation, which has been found to be Fig. 396.—DIAGRAM ILLUSTRATING RADIAL MOVEMENT. (Stirling.) ' placed a short distance behind the centre of the eye. The movements of the eye are accomplished by six muscles—four straight and two oblique. 874 PHYSIOLOGY. OF THE DOMESTIC ANIMALS. The recti, or straight muscles, all take origin about the optic foramen and radiate outward, being inserted in the globe of the eye on either side, above and below, constituting thus the external and internal straight muscles and the superior and inferior straight muscles. Of the oblique muscles, the superior alone arises from the optic foramen and runs forward over the superior and inner part of the orbit through a pulley in the depression just within the inner extremity of the superior orbital margin, then outward and backward beneath the superior straight muscle, ya peu Fic. 397.—SCHEME OF THE ACTION OF na eee Pee (Landois.) and is inserted in the eyeball midway between the latter and the external straight muscle, the cornea, and the optic nerve. The inferior oblique muscle arises from the anterior portion of the edge of the orbit, and runs by its tendon to be inserted beneath that of the external rectus muscle. The function of the superior oblique muscle is to roll the eye downward and inward, that of the inferior oblique muscle upward and inward, although this may be accomplished by the different recti muscles acting simultaneously. The above diagram indicates the action of the ocular muscles (Fig. 397). F SENSE OF HEARING. 875 ‘The oculo-motor nerve supplies all of the muscles of the eye with the exception of the external rectus and the superior oblique. The ex- ternal rectus muscle is supplied by the abducens, or sixth pair, while the superior oblique is supplied by the patheticus or fourth pair. C. THE SENSE OF HEARING. The sense of hearing or audition may be defined as that sense by which the mind takes cognizance of the undulations of the elastic medium which give rise to the sensation of sound. The mind recog- nizes not the body producing the sound, but the impression made by its vibrations upon the sensorium. Sound, then, does not take place in the ear, but in the brain. When we speak of a resounding string or a sonorous bell we make a mistake; the string and the bell simply vibrate. These vibrations give rise to undulations in the elastic ether, which undulations are transmitted in various directions, and finally through the auditory passages impress the auditory nerve and give rise to sound. The physiological aspects of the question are here alone regarded. Regarding sound as the recognition of the impressions made by vibrating sonorous bodies on the auditory nerve, if every one were deaf there would, of course, be no sound; but, on the other hand, we say that no sound may be produced in a vacuum, although we eo _ that sonorous vibrations still take place; hence we are also permitted in a physical sense to give the above explanation of the word sound. The simplest form of the organ of hearing is a sac filled with fluid, in which the ends of the auditory nerve terminate. In all groups of animals the essential part of the organ of hearing consists in a certain special form of termination of the nerve, which is alone capable of receiving auditory impressions and of transmitting them to the central ganglia of the brain. The more highly complicated forms of auditory apparatus simply depend upon modifications which assist in the trans- mission of sound to this part: In all the invertebrates the organ of hearing is restricted to such a simple sacular form, in some instances containing otoliths, or small, hard granules, and the vibrations of the sonorous body are communicated to the nerve of hearing spread over this sac. In such animals it is prob- able that while a nerve of hearing is present only simple sounds and noises can be recognized, while no difference in pitch or intensity can be distinguished. Such a simple form of apparatus, consisting simply of liquid contained in a sac, is found in mollusks. In crustaceans there is a rudimentary organ of hearing present, placed on each side of the base of the anterior antenne. It likewise consists simply of a membranous sac filled with fluid, and on, which ramify the fibres of the nerve of hearing. , 876 PHYSIOLOGY OF THE DOMESTIC ANIMALS. Many insects are apparently free from any evidences of anything resembling an organ of hearing, yet it is clear that these animals are sensible of external sounds. It is possible that in these animals, as in certain radiates and many mollusks, the vibrations of sound are not appreciated as sound, but, perhaps, as some modification of the sense of touch. In fishes there is no external ear, no tympanic cavity, and no cochlea. The ear is reduced to the membranous part of the vestibule and the semicircular canals, the latter varying from two to three in number, while the vestibule and semicircular canals represent a closed cavity, since there is neither oval nor round window, no tympanic cavity, nor auditory ossicles. Sometimes, as in cartilaginous fishes, the membranous internal ear is lodged in the cartilaginous substance of the bones of the head, while in osseous fishes it is sometimes in part within the bones of the cranium, and part free in the cephalic cavity, resting against the brain. The internal ear is in all cases supplied with terminal fibres of the auditory nerve, and is filled with a liquid in which are found various calcareous concretions of greater or less volume. In reptiles there is no external ear, neither a pinna nor an external auditory canal, the tympanic membrane being flush with the head and lying directly below the skin, although in some instances a drum mem- brane is absent. When present, as is the case in the majority of instances, it communicates generally by a large opening—the Eustachian tube— with the pharynx. The auditory ossicles are usually reduced to two in number. When the tympanic membrane is absent, the ossicles, attached at one side to the oval window, are fastened on the other directly against the external integument. In lizards, crocodiles, and serpents the internal ear is composed of the vestibule, semicircular canals, and cochlea. In them, consequently, the internal ear communicates with the cavity of the tympanum by the oval window and by the round window. The cochlea in them is not con- voluted, but almost straight. In the batrachians no cochlea is present, and, as a consequence, no round window, the internal ear being reduced to the vestibule and the semicircular Gariile: the only communication with the tympanum being by the oval window. In birds the apparatus of hearing is almost as complete as in mam- mals, with the single exception of the external auditory pinna, which is absent. The external auditory canal is formed by a bony canal travers: ing the temporal bone, and the tympanic cavity, separated from this canal by the tympanic membrane, is well developed. It communicates with bony cavities in the interior of almost all the cranial bones, and by the intermediation of the Eustachian tube with the pharynx. The SENSE OF HEARING. 877 internal ear is formed of the vestibule, semicircular canals, and cochlea; the latter, being but little developed, is not convoluted in a spiral form, but, resembling that of lizards and serpents, consists of an almost straight osseous tube canal terminating in a cul-de-sac. In mammals the ear, for the convenience of study, may be divided into three parts—the external, the middle, and the internal ear. Of these three the internal ear is the essential, and the others are simply for the purpose of receiving or modifying impressions from the sounding body. In the external ear we include the auricle, or pinna, and the external auditory meatus, bounded internally by the membrane of the tympanum ; in the middle ear, the tympanum, or drum of the ear, with its contained ossicles; and in the internal ear, that portion situated in the petrous por- tion of the temporal bone, consisting of the semicircular canals, the vestibule, and the cochlea (Fig. 398). Fic. 398.—ScHEME OF THE ORGAN OF HEARING, (Landois.) AG, external auditory meatus; T, tympanic membrane; K, malleus with its head (h), short process (Kf), and handle (m); a, incus with its short process (x) and long process: the latter is united to the stapes (s) by means of the Sylvian ossicle (z); middle ear; 0, fenestra ovalis; r, fenestra rotunda ; xy beginning of the lamina spiralis of the cochlea; pt, its scala tympani; vt, its scala vestibull; V, vestibule; §, saccule; U, utricle; H, semicircular canals; TE, Eustachian tube. ‘The long arrow indicates the line of traction of the tensor tympani; the short, curved one, that of the stapedius. In different groups of mammals a marked ditference is found in the form and size of the auricle, or pinna. This, in the majority of cases, is a trumpet-shaped dilatation of the external auditory canal formed for the purpose of receiving the undulations communicated to the atmosphere, collecting them, and transmitting them inward to the middle ear. This portion of the external auditory canal owes its shape to the cartilages present in it, which in some instances, as in the horse, the ass, the goat, and the rabbit, are erect and straight; while in other cases the cartilages are more delicate and soft, folding on themselves so that the auricles lie 878 PHYSIOLOGY OF THE DOMESTIC ANIMALS. in contact with the side of the head, although they may by the influence of various muscles be drawn into a more or less erect position. Such is the case in the elephant and in the dog. In most mammals the auricle Z BYY xh BY it FINNS it LIZ BS LL PE agit a" ascetes ane eeenneae SEELEY SSH SSIS SOR eS SS Frc. 399.—DIAGRAM OF THE EXTERNAL SURFACE OF THE LEFT TYMPANIC MEMBRANE, (Hensen.) a, head of the malleus; 5, incus; e, joint between malleus and incus; between ¢ and @ is the flaccid portion of the membrane; @x, axis of rotation of ossicles. The deeply shaded central portion is called the “umbo.” is much more mobile than in man, and may be directed toward the source of sound by the contraction of voluntary muscles and thus be enabled to accomplish more successfully its functions. Fic. 400.—-TyMPANIC MEMBRANE AND AUDITORY OSSICLES SEEN FROM THE TYMPANIC CAVITY. (Landois.) M, manubrium, or handle of the malleus; T, insertion of the tensor tympani; h head, 1 F long proc- ess, of the malleus; a, incus with the short (K) and the long (1) processes; S, plate of the stapes; Ax, Ax is the common axis of rotation of the auditory ossicles; S, the pinion-wheel arrangement between the Yoalleus and incus. The external auditory meatus is a canal, partly cartilaginous and partly bony, which varies in length according to the species. Thus, while it is five or six centimeters long in ruminants, it is very short in SENSE OF HEARING. 879 carnivora. It is bounded internally by the tympanic membrane and its function is to conduct to the middle ear the undulations collected by the auricle. In the external auditory canal are found the ééviminous glands secreting the wax, which is principally intended for lubricating purposes, and thus facilitates the transmission of sound, while, also, by its extremely bitter taste it perhaps prevents the entrance of insects. The tympanic membrane forms the boundary between the external auditory canal and the middle ear. This membrane consists of three distinct layers, the outer, the external integument, the middle or fibrous layer, and the inner or mucous layer, continuous with mucous membrane lining the middle ear. ‘This membrane is an elastic, almost unyielding, Frq. 401.—Lert TyMPANUM AND AUDITORY OssICLES. (Landots.) A.G., external meatus; M, membrana tympani, which is attached to the handle of the malleus, n, and near it the short process, p; h, head of the malleus; a, incus; K, its short process, with its ligament; 1, long process; 8, Sylvian ossicle; S, stapes; A x, A x, the axis of rotation of the ossicles, shown in per- spective; t, line of traction of the tensor tympani. The other arrows show the movements of the ossicles when the tensor contracts. membrane, elliptical in form, and is placed obliquely in the floor of the external meatus at an angle of about 40°, being directed from above downward and inward. This oblique position enables a larger surface to be presented to the undulations conducted from the external auditory canal than if it were placed vertically. This membrane is not entirely flat, but at its centre is drawn slightly inward where the handle of the malleus is attached to it, while the short process of the malleus causes aslight bulging of the membrane near its upper margin (Figs. 399 and 400). The middle ear, or the drum of the ear or the tympanum, is bounded by the tympanic membrane on the exterior, and on the interior by the 880 PHYSIOLOGY OF THE DOMESTIC ANIMALS. labyrinth. It connects interiorly with the fauces by the Eustachian tube, and posteriorly with the mastoid cells of the mastoid portion of the tem- poral bone. In some animals these mastoid cells are greatly developed and so form an important augmentation of the tympanic cavity, while the Eustachian tube, which is short and straight in the case of most rumi- nants, is very much dilated in the horse where it forms what may be termed guttural pouches (Fig. 401). 1. eh IL. Te: Fie. 402.—I. Tok MECHANICS OF THE AUDITORY OSSICLES, AFTER HELM- HOLTZ. II. SECTION OF THE MIDDLE EAR, AFTER HENSEN. (Munk.) I. a, malleus; hk, incus; am, long process of incus; s, stapes; the arrows show the direction of mo- tion. II. G, external auditory canal; 2f.t., membrana tympani; C, tympanum; H, malleus; L.S., superior ligamant; S, stapes. Stretching across the middle ear from one side to the other is the chain of bones, each named from its resemblance to some instrument; thus, the malleus, so-called from its resemblance to a hammer, is attached to the membranum of the tympanum by its handle (Fig. 402). The second bone, from its resemblance to an anvil, is called the incus, and is attached on the one side to the malleus and on the other to the stapes or stirrup-bone, which is connected by its base to the membrane Frq@.403.—ExTeRNALAppEARANcE Of the fenestra ovalis, which opens into NESTRA eo es the internal ear. All these ossicles are sine nPRet | neigotal and emeteriorsent’ movable on each other, but they have no iia mccain case lateral connection with any structure. Sometimes at the end of the incus is found a separate bone known as the os orbiculare. In the inner boundary of the middle ear is placed, in addition to the oval window, a second, also communicating with the vestibule, and called the fenestra rotunda, or round window. The internal ear, or labyrinth, is composed of bone, and consists of SENSE OF HEARING. 881 the vestibule, and, communicating with this, three semicircular canals and the cochlea (Figs. 403 and 404). Lining the internal ear and forming a complete cast of the vestibule and semicircular canals is the so-called membranous labyrinth, while between the walls of the membranous > bd a ? Fie. 404.—SCHEME OF THE AUDITORY APPARATUS. (Beaunis.) A, external ear; B, middle ear; C, internal ear; 1, auricle: 2, external auditory canal: 3, tympanic eavity; 4, tympanic membrane; 5, Eustachian tube; 6, mastoid cells; 7, malleus; 8, incus; 9, stapes; 10, round window; 11, oval window; 12, vestibule; 13, cochlea; 14, scala tympani; 15, scala vestibuli; 16, semicircular canal. labyrinth and the semicircular canals and vestibule is a fluid called the perilymph, which is also contained in the cochlea. Within the mem- branous labyrinth is a similar fluid termed the endolymph. In the interior of the membranous labyrinth are often found little particles consisting almost entirely of carbonate of lime, called otoliths, or ear-stones (Fig. 405). A Sometimes these are attached to the walls dy aa. of the membranous labyrinth, and some- d a * times they are found lying loosely and are intended to increase the intensity of the sounds. Fic. 405.—A, OTOLITHS FROM THE The cochlea consists of a spiral SO eee a canal making two and one-half revo- oe ag ele lutions about a central axis. It is divided hy a spiral lamina, partly membranous and partly bony, into two divisions known as scale, of which one is above the other. The superior at its inferior extremity terminates in the vestibule and is known as the 56 882 PHYSIOLOGY OF THE DOMESTIC ANIMALS. scala vestibuli, while the other, or inferior, terminates in the round window and is called the scala tympani. On these lamine spirales are distributed portions of the auditory nerve, which takes origin from the floor of the fourth ventricle and runs into the petrous portion of the temporal bone through the meatus auditorius internus and divides into two divisions, one going to the cochlea and the other to the vestibule near to the end of the semicircular canals. It loses itself upon the walls of the vestibule and the walls of the ampulle, or membranous dilatations at the commencement of the three semicircular canals (Fig. 406). The cochlear nerve is distributed to the scale of the cochlea, where its terminal fibres form connection with Corti’s organ, which is placed “Org. Corti 2 mb. basilaris Lam. spir. oss. Fia. 406.—SCHEME OF THE LABYRINTH AND TERMINATION OF THE AUDITORY NERVE. (Landois.) I. Transverse section of a turn of the cochlea. II. A, ampulla of a semicircular canal: a p, auditory cells, p, provided with a fine hair; T, otoliths. III. Scheme of the human labyrinth. IV. Scheme of a bird's labyrinth. V. Scheme of a fish's labyrinth, in the ductus cochlearis, a small, triangular chamber, cut off from the scala vestibuli by the membrane of Reissner (Fig. 407). Corti’s organ is placed on the membranous portion of the lamina spiralis, and consists of an apparatus composed of the so-called Corti’s arches, each of which consists of two Corti’s rods. Every two rods unite to form an arch, so that there are always two or three inner rods and two outer rods. Toward the apex of the cochlea the rods become longer and the span of the arches increases. The terminal organs of the cochlear nerve are the cylindrical hair-cells described by Corti, of which there are two rows, the row of inner cells resting on a layer of small, granular cells, and the outer cells distributed in three or four rows resting on a basement membrane. Between the outer cells there are Yue SENSE OF HEARING. 883 other cellular structures to be noticed, which are, perhaps, to be regarded as special cells (Fig. 408). Waves of sound falling upon the auditory nerve produce no sound, but only when the terminal organs are stimulated. The Function of Hearing.—To be enabled to understand the use of the different portiors of this complicated organ it will be necessary to refer to some of the more important laws governing the propagation of sound. Sound, as before stated, is the result of the vibrations of elastic bodies, which result in the production of alternate condensation and rarefaction of the surrounding medium. As a consequence, sound-waves Fic. 407.—SCHEME OF THE DucTUS CoCHLEARIS AND THE ORGAN OF CorTI. / (Landois.) N, cochlear nerve; K inner and P outer hair-cells; n, nerve-fibrils terminating in P: a, a, supporting cells; d, cells in the suleus spiralis: z, inner rod of Corti; Mb. Corti, membrane of Corti, or the mem- brana tectoria; 0, the membrana reticularis; H, G, cells filling up the space near the outer wall. are produced, in which the particles vibrate longitudinally, or in the direction of the propagation of the sound, forming so-called waves of condensation and rarefaction, occurring in concentric circles around the sounding body. Like rays of light, sound-waves may be reflected when they impinge upon an opaque solid, and the same rules as to the angle of incidence and reflection prevails. It is this throwing back of sound from a resisting medium that constitutes the echo. When transmitted through the atmosphere these waves of sound » are collected by the auricle, and from the auricle they are transmitted through the external auditory meatus to the membrana tympani,-which is thus thrown into vibration. Thus; they are communicated to the 884 PHYSIOLOGY OF THE DOMESTIC ANIMALS. chain of bones and reach the membrane of the fenestra ovalis. From that point they are communicated to the perilymph, thence to the membranous labyrinth, thence to the endolymph, and finally to the otoliths, which serve to increase the vibratory impression upon the nerve of hearing. This transmission of sound from the exterior and its recognition in the centre plainly involves important considerations with regard to the propagation of sounds. ' Sounds are transmitted in three ways: first, by reciprocation; second, by sympathetic vibration; and, third, by conduction. As regards vibra- tions by reciprocation, if two strings of equal tension, length, and Sc.tym Seer ee Fig. 408.—I. SecTION THROUGH THE UNCOILED CocnLEA. II. SECTION THROUGH THE TERMINAL NERVE-APPARATUS OF THE COCHLEA, AFTER HEUSEN. (JMunk.) I. F.r., Fenestra rotunda; H, the helicotrema; Sf., the stapes. II. 2, Huschke's process; D/, basilar membrane; ¢, Corti's arch; g, supporting cells; h, cylindrical cells; 7, Deiter's hair-cells; c, membrana tectoria; n, nerve-fibres; n/, non-medullated nerve-fibres. density be stretched side by side each one is capable of producing the same musical tone when thrown into vibration. Now, when one of these strings is thrown into vibration the other will fall into vibration by reciprocation, although it be not itself touched. The same thing will occur when the same musical note is sounded on another instrument, as the tuning-fork, if in sufficient proximity. If one of the strings be stretched tighter than the other a higher musical note will be produced. If this string be thrown into vibration near one of lower note the latter will be divided into equal divisions, which are likewise thrown into vibra- tions of reciprocation, and increased sound will result. If, however, SENSE OF HEARING. 885 a string of less tension be thrown into vibration near one of higher tension there will be no response, for no membrane or string can recip- rocate a note lower than its own fundamental note. By the term funda- mental note we mean the lowest note which any string or membrane can produce. If a higher note be sounded alongside of a string of low tension the latter, as before stated, will divide itself, and the divisions will be separated by points of rest, called nodal points, while the intermediate parts of the string in vibration are termed loops. These remarks are true not only of strings, but also of membranes. If some sand be sprinkled on a membrane stretched across a drum-head, so as to be capable of a musical tone, and then another note of precisely the same pitch be struck near it, the sand will begin to dance on the sur- face of the drum-head, thrown into vibrations of reciprocation, and will accumulate on the lines of rest—the nodal lines; but if we sound near it a note higher than that of the membrane stretched across the drum, then the membrane, instead of vibrating across its whole surface, will divide itself, and the sand will collect in dark lines on the nodal points as before. If we sound near the membrane a note lower than its fundamental note, it will not respond. A column of air may be thrown into vibrations of reciprocation by sounding a note in proximity to it. Sounds are also propagated by resonance. If an instrument capable of producing a musical note while vibrating be placed in contact with a medium whose molecules are capable of being thrown into vibration, the ‘second substance will vibrate and increase the intensity of the original sound, even if the medium with which we place the sounding instrument in contact is not itself capable of producing musical tones. Thus, when we strike a tuning-fork under ordinary circumstances in the air the sound is but faintly heard, while if we place the fork in contact with a piece of wood, the sound is greatly increased in intensity. The woody fibres are thrown into vibrations which reciprocate the original sound. Sound is also propagated by conduction, and this occurs when any sonorous body during its vibrations is brought in contact with any medium capable of being thrown into vibration. A familiar example of this is found in the fact that while the tuning-fork held in the air is but indistinctly heard, if placed in contact with the bones of the head it is heard distinctly. In this case the sound is conducted from the tuning- fork to the nerve of hearing through the bones of the head. All media do not conduct sounds with the same degree of rapidity. Solids conduct better than fluids, fluids better than gases, while in a vacuum no sound whatever can be conducted. That a sound may be appreciated, it is evident that it must be con- ducted to the terminal filaments of the auditory nerve in the labyrinth, 886 PHYSIOLOGY OF THE DOMESTIC ANIMALS. and the first process, therefore, to be considered in the study of the function of hearing is the means by which sound-waves reach the laby- rinth, and then the way in which they excite the nerve of hearing. It has been seen that every sonorous body is in a state of vibration and that it transmits these vibrations to the surrounding atmosphere, resulting in waves of condensation and rarefaction traveling in radii from the locality in which the sonorous body is located. It has been further stated that sound-waves may be conducted through any elastic medium, but in the appreciation of sound by the ear evidently the greatest importance is to be placed on the conduction of sound- waves through the air, since the conduction of sounds through solids can but infrequently be of any importance. It has been stated that sound-waves can be conducted through the bones of the head, and although this must be exceptional in the case of man, yet in fishes, where no external ear, auditory canal, or ear-bones are present, it-plays an important part. So, in this case, the sound-waves of the water are directly transferred to the labyrinth. We have now to trace the path of the sound-waves from the sonorous body, through the external ear and auditory canal, through the tympa- num to their termination in the labyrinth, with the operation of the different apparatuses by which this transfer is facilitated. The external ear evidently fulfills the part of an ear-trumpet, and the great improvement in hearing produced by artificial addition to the auricle serves to emphasize this point. The external ear is evidently of a certain amount of assistance in recognizing the direction of sound, but, as is well known, we are liable in this respect to make errors of judgment. The origin of sound-waves is determined simply by the fact that the sound is heard most distinctly when the auditory canal is in the line of propagation of the sound-waves, and, therefore, in order to determine the direction of a sound we turn the head from one side to the other until the sound appears to be the loudest. In the lower animals this is,to a certain extent, facilitated by the exceptional degree of mobility possessed by the auricle, where we must assume that the recognition of the direction of a sound is a matter of greater importance and accom- plished with a greater degree of facility and perhaps exactness. Having reached the auricle, sound-waves enter through the external auditory canal and strike against the tympanic membrane. It has been stated that if a tightly stretched membrane be set into vibration it will produce a sound, the lowest note being termed the fundamental tone; and, further, that if a sound which corresponds with the fundamental tone of such a membrane be sounded in its proximity the membrane will be set in vibration by sympathy. It is evident, if such a fact were ap- plicable to the tympanic membrane, the greatest confusion would result SENSE OF HEARING. 887 in the perception of sounds. Sounds which coincide with the funda- mental tone of the tympanic membrane would so predominate as to drown or confuse all other sounds. The tympanic membrane, however, is free from this disadvantage, while it possesses in the highest degree the power of being set in motion by an immense range of vibrations. Thus, sounds may be recognized that are dependent upon thirty-two vibrations a second up to such an extremely high pitch as sounds with thirty-eight thousand vibrations a second will produce. This property of the tympanic membrane by which it appreciates such a wide range of sounds, while being free from any fundamental tone itself, is due to two factors—in the first place, the funnel-shaped form of the membrane, and, in the second place, its being damped by the chain of ear-ossicles. If a sheet of india-rubber be stretched over a wide tube and be pressed by a rod in the centre perpendicularly inward it will form a funnel-shaped surface curved from within outward. It is evident that in such a mem- brane the tension will vary at different parts, increasing toward the cen- tre. Such a membrane, like the tympanic membrane, will have no funda- mental tone, since its tension is not equal, while the tympanic membrane will also have in principle the same form, since it radiates from the cen- tre, within outward, in a convex form. The tympanic membrane, there- fore, is not very extensible, but its tension is just sufficient to draw it slightly inward from the centre without it being able to produce any audible fundamental tone. -On the other hand, great resistance is offered to the vibrations of the tympanic membrane by its union with the auditory ossicles, which not only deprive the membrane of every trace of a fundamental tone, so that it can accommodate itself equally well to vibrations of every degree of rapidity, but by loading the membrane entirely prevent the occurrence of after-vibrations; so that, therefore, in this respect the ear-bones act like the dampers of the pianoforte, which fall upon the wire after every note has been struck. Another point is worthy of attention in this connection. Since the tympanic membrane possesses the shape of a funnel, the point of greatest vibration must be situated somewhere between the apex and the edge, but the force of all vibrations passes from the sides toward the centre and at this point vibrations of the greatest intensity are produced. Moreover, the tension of the tympanic membrane may be altered by muscular action in away to be directly described. The tympanic membrane is in direct contact with the chain of ear-bones, and this serves to transfer the vibra- tions of the tympanic membrane to the perilymph of the labyrinth, and, likewise, by their points of attachment to different muscles, serve to vary the tension of the membrana tympani and at the same time the pressure on the lymph of the labyrinth. 888 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The ear-ossicles form a jointed chain of bones connecting the mem- brane with the oval window. As is well known, solids are capable of conducting sound-waves by being thrown into molecular vibration, and the rapidity of such conduction is greater on account of the greater elasticity and density than in the atmosphere. From the very fact of the greater rapidity of the conduction through solids the wave length will be longer, but the conduction of sound through the ear-ossicles is entirely distinct from such molecular vibrations. In the transmission of sound-waves from the tympanic membrane to the labyrinth the chain of bones vibrates as a whole. ‘The average wave length of medium tones in the ear varies from one-half to one meter, while in solid bodies it is still greater. The ear-bones are by no means immovably fixed. From their small mass they are extremely light, so that an impulse acting on one end will set the whole chain of bones in motion. Consequently, when waves of sound strike against the tympanic membrane the vibra- tions are transmitted directly to the ear-bones, and they vibrate in a transverse direction and carry the vibrations to the oval window by vibrating in mass and not through molecular vibration. The mode of movement of the ear-ossicles has been a subject of considerable study. As is known, the handle of the malleus is attached to the tympanic membrane through its entire length, while its head pro- jects above the edge of the membrane into the tympanic cavity. Besides this, the malleus is fixed by ligaments in such a way that motion is only possible in a to-and-fro vibration around the so-called axis of rotation, which lies ina plane almost parallel to the tympanic membrane and passes through the neck of the malleus. When the handle of the malleus is drawn inward its head will, of course, move in the opposite direction, and as the handle of the hammer is set in vibration the anvil will also be set in motion through its articulation with the head of the hammer. The incus is only loosely connected by a ligament passing through its short process to the posterior wall of the tympanic cavity in front of the open- ings of the mastoid cells, while its mode of articulation with the malleus has been compared by Helmholtz to the action of cog-wheels; so that when the handle of the malleus moves inward to the tympanic cavity the incus and its long process, which is parallel with the handle of the malleus, also passes inward, from the fact that the head of the malleus pulls the articulating surface of the incus outward. Therefore, the handle of the ‘ malleus and the long process of the incus vibrate in the same direction. As the long process of the incus moves inward it gives an impression to the stirrup-bone, with which it articulates almost at right angles. If, however, as by a great condensation of air in the tympanum, the tym- panic membrane is moved outward it, of course, draws the handle of the malleus with it, and, as a consequence, the hammer-head is forced inward, SENSE OF HEARING. - 889 and the tendency would be to drag the stapes from the oval window. This is, however, prevented by the loose articulation of the malleus and incus, which separate to a certain extent and thus prevent dragging on the stapes (Fig. 409). Hence, the system of ear-ossicles forms an angular lever, which moves around a common axis in a plane vertical to the plane of the membrana tympani, one arm of the lever on which the power of the vibrations act being the hammer-handle, the other, the hammer-head with Fig. 409.—MoVEMENTS OF THE MALLEUS AND INcUS. (Beaunis.) M, malleus; E, incus; A, short process of the incus; R, long process of the incus; P, handle of the malleus; A B, axis of movement of the ossicles. the handle, serving to set the entire fluid of the labyrinth into vibration. The vibrations of the ear-ossicles are, therefore, transverse, although not analogous to the transverse vibrations occurring in a stretched cord, since the ear-ossicles do not vibrate on account of their elasticity, but resemble a system of movable levers. As the long process of the incus is only one-third the length of the handle of the malleus, of course the excursions of the former, and with it the stapes, will be less than that of the tip of the malleus, while, on the other hand, the force of the vibration in the former will be increased; so that the stapes is forced inward by 890 PHYSIOLOGY OF THE DOMESTIC ANIMALS. a more powerful but less extensive vibration. So much for the mode of conduction of sound through the ossicles. By contraction of ‘the muscular fibres in connection with the ear- ossicles the position and tension of the tympanic membrane, as well as the pressure on the lymph of the labyrinth, may be altered. ‘I'wo muscles are found in connection with the ear-ossicles, the tensor tympani and the stapedius muscle. The tensor tympani lies in the osseous groove above the Eustachian tube, and has its tendon inserted into the malleus immediately above the axis. When this muscle contracts the handle of the malleus is pulled inward and the tympanic membrane tightened. As a consequence, the stapes is likewise pressed inward. On the other hand, when this muscle relaxes the elasticity of the axial ligament and of the tympanic membrane itself causes the membrane to again assume its condition of equilibrium. By the increased tension of the tympanic membrane a greater resistance is offered to the sympathetic vibrations when the sound-waves are very intensé, since it has been found that stretched membranes are less susceptible to sympathetic vibrations than are relaxed membranes; and increase of the tension of the tympanic membrane by contraction of this muscle, therefore, serves to protect the auditory apparatus by preventing intense vibrations reaching the nerve terminations. ; The stapedius muscle arises within the pyramidal eminence, and is inserted into the head of the stapes. When it contracts it draws upon the head of the stapes and causes the bone to assume an oblique position, the posterior end of the plate being pressed deeply inward into the fenestra ovalis, while the anterior edge of the plate is displaced outward. The stapes is thus firmly fixed and the annular ligament surrounding the fenestra ovalis becomes more tense. The function of this muscle is likewise directed to preventing the communication of too intense an impulse from the incus to the stapes. The stapedius muscle is supplied by the facial nerve and the tensor tympani by a branch of the trigeminus which passes from the otic ganglion. The chain of bones lies within the tympanic cavity, and it is evident that the vibration of the tympanic membrane will greatly vary -according as the air in the tympanic cavity is in a greater or less degree of condensation. If this space were entirely shut off from the atmos- phere the air in it would evidently soon be absorbed, or, at any rate, undergo change in its composition, and probably be replaced by fluid secretions, since we know that the middle ear is lined by a secreting mucous membrane. By means of the Eustachian tube the ventilation of the middle ear is rendered possible. Through it secretions are con- ducted ont, and by it the equilibrium of pressure between the air in the tympanum and the atmosphere is rendered possible. As soon as the SENSE OF HEARING. 891 pressure of the atmosphere is greater than that within the tympanum the membrane of the tympanum would be pressed inward. On the other hand, if the pressure within the tympanum be greater than thut of the atmosphere the membrane would be pressed outward, and in both cases the movements of the tympanic membrane would be restricted and sound to such an extent interfered with. The equilibrium is maintained through the opening of the Eustachian tube in the act of swallowing,— an act which is performed not only during eating, but also at frequent intervals to carry away the secreted saliva. At other times the Eusta- chian tube is closed, and by this means the conduction of sound-waves downward into the pharynx or the conduction upward of sound-waves. from the voice is rendered impossible. The sound-waves are thus conducted from the tympanic membrane to the chain of ossicles, and thence by the vibration of the stapes to the oval window. The membrane of the fenestra ovalis is, as a consequence, set into transverse vibration, and these vibrations are directly communi- cated to the fluid of the labyrinth. The lymph, like other fluids, is incom- pressible, and if, therefore, the membrane of the oval window be pressed inward there must be a corresponding exit at some other point of the apparatus. ‘This counter-opening is found in the round window, and as soon, therefore, as the stapes vibrates inward the membrane of the circu- lar window vibrates outward, and the pressure upon the fluid of the labyrinth is thus relieved while being set into vibrations corresponding with those of the stapes. . From the oval window the wave travels into the vestibule and from there into the cochlea, and we must assume that it there throws the membranous apparatus with its organ of Corti into vibration. The ves- tibule is, however, divided by the two membranous sacs which it contains into two portions, each containing fluid, the one in connection with the oval window and the other with the round window; so that, therefore, we cannot imagine that the fluid in the vestibule is directly driven by the vibrations of the stirrup-bone to the round window, for the scala vestibuli of the cochlea, which is in connection with the oval window, is shut off from the scala tympani by the membrane, and any wave, there- fore, started by the vibrations of the stapes will pass rapidly up the scala vestibuli, while it will also transfer its vibrations to the membran- ous partition and thus throw the fluid of the scala tympani likewise into vibration. In the cochlea the vibrations of the perilymph throw into vibration the fibres of the basilar membrane and the organ of Corti, consisting of the rods and the inner and outer hair-cells, which may be regarded as a series of stretched strings, a portion of which may be thrown into sym- pathetic vibration independently of the whole. 892 PHYSIOLOGY OF THE DOMESTIC ANIMALS. . The vibrations communicated to these structures in some way give rise to nervous impulses passing into the terminal filaments of the auditory nerve. As to the way in which this is accomplished but little is known. The temptation is strong to find the receiving apparatus in the organ of Corti, which is composed of a long series of rods varying regularly in length and in the span of their arches. The analogy between these structures and, for example, the strings of the piano is very striking. As is well known, a musical tone sounded in front of an open piano will set into vibration the corresponding string of this instrument. The temptation is almost irresistible to suppose that a similar mechanism is concerned in the perception of different sounds. If we could imagine that certain definite parts of the organ of Corti were thrown into vibration only by appropri- ate sounds the complex process of the perception of different musical intervals would be greatly simplified, but the more the subject is examined into the greater are the difficulties surrounding such an explanation. In the first place, the terminal filaments of the auditory nerve have been traced to the inner and outer hair cells, and it must, therefore, be in this locality and not in the rods of Corti that the sensory impulses commence, In the second place, the rods of Corti are entirely absent in birds, who, without doubt, are capable of appreciating musical sounds; while, avain, the variation in length of the rods of Corti would be insufficient to explain the great scope which the ear possesses in the recognition of the pitch of sounds. On the other hand, the basilar membrane is tense in a radial direction and loose longitudinally, and, therefore, as Helmholtz has suggested, may be compared to a series of strings of varying tension and length. : If this basilar membrane be looked upon as the receptive organ we must then assume that each vibration travels up the scala tympani, throws into sympathetic vibration a small part of the basilar membrane, which transfers the vibration to the sensory structures above it. In support of this view it may be mentioned that the radial dimen- sions of the basilar membrane offer a wider field of difference than we find in the length of Corti’s rods. The whole subject is, however, in the highest degree obscure, and all that we can say is that the organ of Corti, composed of the basilar membrane, the rods, and hair-cells, is in some way concerned in the reception of sound-waves; the manner is, however, entirely unknown. After all, it must not be forgotten that the perception of sound takes place not in the ear but in the brain, and that sound-waves, received in whatever way by the terminal filaments of the SENSE OF TASTE. 893 auditory nerve, must be conducted to the brain to be recognized as sounds, and that the analysis of sounds take place not in the ear, although, perhaps, we may have there a special organ set aside for the observation of certain sounds, but in the brain. D. THE SENSE OF TASTE. The sense of taste is generally described as the faculty by which the flavors of different sapid substances is distinguished. It will be shown directly that the sense of taste is much more limited than this, as many substances which are said to be appreciated through the sense of taste are only effective through exciting the sense of smell. The sense of taste even in this restricted sense is more highly developed in man than in other animals, for it is not the sense of taste but the sense of smell which guides animals in their choice of food, for that choice precedes the prehension of food. Even in man and the higher mammals there is a considerable difference of opinion as to what regions of the mouth are endowed with the sense of taste, and this difficulty of location becomes even more marked as we descend the animal series. In animals where a tongue is present it is probable that that organ partakes, with the upper part of the digestive tract, in the property of presiding over the sensation of taste, but in many animals the tongue is absent or is so horny as to pre- clude this possibility. In invertebrates, where no analogue of a tongue exists, if the sense of taste is present, as it would seem without doubt to be, as in insects, its seat must be in the parts about the mouth, such as the proboscis, suckers, etc. In fishes the tongue is rudimentary and in many it is covered with horny scales or even rudimentary teeth, and if the sense of taste is present in this group of animals it is either confined to the upper part of the digestive passages or perhaps to the olfactory cavities. In reptiles a thick, fleshy tongue is often present, but it is more fre- quently slender, sometimes bifid and protractile, and is to be regarded, as already indicated, as an organ for the prehension of food. In birds the sense of taste must be very obtuse, since they swallow their food without comminution, and the tongue is usually hard or semi- cartilaginous, especially at the point. This particularly obtains in her- bivorous birds, while in birds of prey, where the tongue is fleshy, it may perhaps be supposed that the sense of taste is present. In mammals the sense of taste may, to a certain extent, be definitely localized in the tongue, and special sense organs have been detected which apparently preside over this function. The so-called taste bulbs are found on the lateral surface of the circumvallate papilla and upon the external side of the depression which surrounds the central eminence 894. PHYSIOLOGY OF THE DOMESTIC ANIMALS. (Fig. 410). They are also found toa less extent on the fungiform papille, “the papilla of the soft palate and uvula, and even on the posterior surface of the epiglottis and on the inner side of the arytenoid cartilages, and on the vocal cords. These latter localities would seem to throw doubt upon the connection between these structures and their connection with the sense of taste, but the fact that after section of the glosso-pharyngeal nerve these taste bulbs degenerate, and that direct communication can be traced between this nerve and these cells, would, seem to place their position as the terminal organs of the special nerve of taste beyond doubt. These taste bulbs are barrel-shaped and consist of series of nucleated external, almost cylindrical protecting cells, arranged so as to leave an opening,—the so-called gustatory pore. Lying in the axis of such a structure are found from one to ten gustatory cells, some provided with Fra. 410.—STRUCTURE OF THE GUSTATORY ORGANS. (Landois.) I, Transverse section of a circumvallate papilla: W, the papilla; v, v, the wall in section; R, R, the eircular slit of fossa; K, K, the taste bulbs in position; N, N, the nerves. II. Isolated taste bulbs: D. supporting or rotective cells; K, under end; &, free end, open, with the projecting apices of the taste ls. ILI. Isolated protective cell, d, with a taste cell, e. delicate processes at their free extremities, while their lower, fixed ends become continuous with the non-medullated terminations of the nerve of taste (Figs. 411, 412, and 413). The bots of mets in its general characteristics resembles rat of man, and similar papille are found on it. In the different domestic animals, especially in the herbivora, the sense of taste must differ from that in the carnivora, although we have every day evidences of its exist- ence, and we know that in the herbivora likewise decided preference for different substances are manifest, which evidently must be dependent upon differing degrees of excitation of the sense of taste, although the expla- nation of that fact is yet entirely beyond us. Thus, as to why a horse should prefer oats to hay, or the latter to straw, must evidently be ex- plained by some difference in impression of the gulbstusigas on the nerve of taste and not a mere matter of instinct, SENSE OF TASTE. 895 Only four different varieties of taste can be distinguished. Sub- stances may be either bitter, sweet, acid, or saline. Substances to which we attribute the property of flavor owe that characteristic more to their implication of the sense of smell than of taste. Thus, we speak of tasting wines, onions, asafcetida, and so on, while, as is well known, their flavor is due to the excitement of the sense of smell, and not to a specific stimulation of the nerve of taste; this may be readily proven by the disappearance of their characteristic flavors when smell, by closure of the nostrils or by catarrh, is rendered impossible. That substances may be tasted it is necessary, in the first place, u A AN SS Gi 4 SS SS5 SSE SS ss Tne SSS 7 TT ————-— ENS 8 un Fia. 411.—-STRUCTURE OF THE GUSTATORY ORGANS. (Munk.) A, perpendicular section through the taste organs of a rabbit's tongue; g, taste furrows. 3B, isolated protective (a) and (5 c) taste cells. that they should be dissolved in the fluids of the mouth, while the intensity of the sensation will depend upon the size of the surface acted upon and upon the concentration of the solution. It has been found that the following series of substances cease to be distinguished in the order here stated, as they are gradually diluted: syrup, sugar, common salt, aloes, quinine, and sulphuric acid. Thus, quinine may be diluted twenty times more than salt and still be distinguished. The time elapsing between the contact of the substance with the tongue and its appreciation by the taste also varies with different substances. Saline substances are tasted most rapidly. perhaps, from their more rapid diffusion. 896 PHYSIOLOGY OF THE DOMESTIC ANIMALS. The galvanic current is likewise capable of producing the sensation of taste, which varies according to the direction of the current. Thus, a bitter metallic taste is developed when the anode, and an acid taste when the cathode, is placed on the tongue. In this instance it is doubtful whether the sensation of taste is due to a direct stimulation of the taste bulbs or to electrolytic changes occurring through the action of the galvanic current. All the localities in which the taste bulbs have been detected are probably possessed of the sense of taste, although certain regions, as the entrance to the larynx and the hard palate, do not admit of experi- mental demonstration as regards this point. Without doubt the root of the tongue and its tip and margins are gustatory, while it is probable that the under surface of the tongue possesses no power of taste. The nerves which preside over the sense of taste are certain fibres of the lingual and the glosso-pharyngeal. After the lingual nerve is divided the sense of taste disappears from the tip of the tongue. When the glosso-pharyngeal is divided the sense of taste is lost in the posterior Fig. 412.—TASTE FURROW IN MAYER’S FIG. 413.—SECTION OF MAYER’S ORGAN IN THE ORGAN IN THE Hoa. (Csokor.) HORSE. (Csokor.) part of the dorsum of the tongue. Contrary to our experience with the other nerves of special sense, stimulation of the trunks of these nerves does not give rise to the sense of taste, probably owing to the fact that both of these nerves are mixed nerves, and contain other afferent fibres as well as those of the sense of taste. Certain substances seem to possess the power of antagonizing the impressions which others ordinarily make on the terminal filaments of the nerves of taste; thus the taste of bitter and sour substances may to a certain extent be corrected by the admixture of sugar, even without any chemical change occurring in the mixture. Such a result is only to be explained as some kind of interference of the sensations; on the other hand, substances having a sweet taste do not possess the power of modi- fying saline tastes. Any explanation as to why certain substances possess one peculiar taste and others another is in our present state of knowledge impossible, with the single exception of the characteristic taste of acids and alkalies, where we find the characteristic taste associated with certain definite chemical characteristics. , SENSE OF TOUCH. 897 The acuteness of the sense of taste admits of education, but is by no means as delicate as the sense of smell; thus, a solution of one part of sulphuric acid to one thousand of water gives its characteristic taste when only one drop, which may be said to contain about g55 part of a gramme, is placed upon the tongue. E. THE SENSE OF TOUCH. When any portion of the external integument is brought in contact with a foreign body we appreciate what is termed the sensation of touch, aud we are, therefore, warranted in regarding the skin as a sensory organ, inclosing our entire body and adapted to render every part of the body sensible to external impressions. These may be of the most manifold kind, and excite peculiar sensations dependent upon the nature of the contact. To a limited extent this power of tactile sensibility possessed by the integument belongs likewise to the internal mucous surfaces of the body, but only for a short distance from their respective orifices. Tactile sensations, as we shall find directly, vary among themselves, and give us means of determining the physical characters of the body producing the contact and the locality at which the contact takes place. When such a tactile sensation is increased in intensity it may be converted into a painful sensation. If, for example, as in the illustra- tion given by Weber, the edge of a knife is placed on the skin we feel the edge by means of the sense of touch, a sensation is perceived which is referred to the object which has caused it. If, however, the skin is cut by the knife pain is felt, a feeling which is no longer referred to the cutting knife, but which we feel within ourselves, and which indicates to us the fact of a change of condition in our own body. By the sensation of pain we are neither able to recognize the object which causes it nor its nature. Thus, if a body is placed within the mouth we are able to recognize its general characters and to a certain extent its shape, whether it be solid or liquid, hot or cold; but if the body be swallowed tactile sensation disappears as soon as the body reaches the esophagus, and then, if any sensation be excited, it can only be a painful sensation. The sensation caused by a.too hot liquid cannot be distinguished from a corroding acid liquid, or from the passage of an irregular hard body through the cesophagus. The sense of touch is the simplest and is the only universal sense, and exists in all members of the animal kingdom. In the articulata, whether covered by horny (insects) or by calcareous (crustaceans) cover- ings, the sensation of touch is possessed by all parts of the body in common, while it is especially developed in the antenne which project from the sides of the head. in mollusks and zodphytes sensibility is much more obtuse, but is 57 - 898 PHYSIOLOGY OF THE DOMESTIC ANIMALS. likewise distributed over the entire surface of the body, and here, also, is perhaps more highly developed in the tentacles or pseudopods which are so often found. In fishes projecting organs at the side of the buccal opening receive terminations of afferent nerves, and these, together with the fins, may be regarded as especially developed tactile organs, although bere, also, the entire body surface possesses general sensibility. In reptiles no special tactile organ is present, unless the tongue, in certain instances, may fulfill this function. In birds the tactile sensibility of the skin must be to a certain ex- tent interfered with by the thick coating of feathers and the sensibility of the feet by the dense scales which usually cover these parts. In birds in general it is the beak which possesses tactile sensibility in the highest degree. In mammals the greatest variation exists in the specialization of certain parts of the body for the appreciation of tactile sensations. In monkeys, although four hands may be said to be present, they are not to be regarded as sensitive organs as are the hands of man; since, in the first place, their fingers do not possess the power of separate movement and their thumb is much shorter and incapable of being brought into apposition with the fingers; while the palm of the hand, which frequently serves as a means of progression, is covered with calloused epithelium. In certain monkeys with prehensile tails this organ is doubtless possessed of tactile power in the highest degree. In solipedes, ruminants, and carnivora, in whom the extremities of the limbs terminate in a single or double hoof, in claws, or calloused skin, in these localities the sense of touch must be very imperfect. But these parts of the animal body must be capable, nevertheless, of giving distinct notions as regards resistance, solidity, and consistence, since these horny parts rest on a highly developed papillary layer of the derm. In solipedes and ruminants, especially in the former, the lips possess a considerable degree of mobility, and are, as has been shown, the princi- pal organs of prehension and are highly endowed with tactile sensibility. In carnivora the termination of the soft parts about the anterior nares is extremely sensitive and is employed by them as a tactile organ, while it is only a step farther to the hog or the elephant, where the prolongation of this part of the body acquires extreme perfection as an organ of tactile sensibility. In certain animals the long hairs growing from the upper lip, as in the cat and the rat and the seal, are to be regarded as tactile organs, since they conduct tactile impressions to the sensory nerves. Probably, also, the spines of the porcupine fulfill the same function. Like the more specific sensations, the sensations of touch require for SENSE OF TOUCH. 899 ° their production terminal organs which are found in the epidermis of the skin and surrounding the underlying nerve structures. The manner in which the terminal filaments of the sensory nerves are distributed to the skin varies. Five general different modes of distribution have been recognized. The touch corpuscles of Wagner and Meissner lie in the papilla of the true skin and are most numerous in the palm of the hand and the sole of the foot, and especially on the fingers and toes. They are oval or elliptical bodies covered by layers of connective tissue arranged transversely and containing within a granular mass with longitudinally striped nuclei. Each of these corpuscles is surrounded in a special manner by a medullated nerve-fibre which loses its myelin and divides into a number of fibrils within the corpuscle. Pacini’s corpuscles are oval bodies likewise found in the subcu- taneous tissue of the skin of the fingers and toes and of various other localities. They consist of numerous layers of nucleated connective tissue separated from each other by fluid and lying one within the other, like the coats of an onion. Into the axis of each passes a medullated nerve-fibre whose sheath of Schwann becomes united with the capsule. In the interior or central core of the corpuscle each nerve-fibril terminates in a small, hair-shaped enlargement. -Crouse’s corpuscles are elongated or rounded bodies found in the deeper layers of the conjunctiva, the floor of the mouth, and various other mucous surfaces. The sheath of Henle communicates with the nucleated capsule, while the non-medullated fibre is continued into the internal core. Merckel’s tactile corpuscles occur in the beak and tongue of the duck and goose, in the tactile hairs or feelers, and also in the epidermis ‘of man and other mammals. They are composed of a capsule containing two or three or more granular nucleated cells piled one on another in a vertical row. Each corpuscle receives at one side a medullated nerve-fibre which terminates either in the cells themselves or in the transparent protoplasmic substance between the cells. In addition to these special terminal organs of the afferent nerves in many localities their axis cylinder splits up into fibrils to form a nervous net-work which is to be regarded as an organ of sensation. Nerve-trunks are supposed to contain fibres which are especially concerned in conducting painful impressions and tactile impressions, Sensations of temperature fall under the second head. As already indicated, the first of these modes of sensation may be converted into the second. Thus, when a body is brought in contact with the skin we may form a conception of the weight of the body—that is, the amount of pressure 900 PHYSIOLOGY OF THE DOMESTIC ANIMALS. which it exerts upon the skin—and to a certain extent its temperature. If the degree of pressure be greatly increased, the sensation of pressure gives place to one of pain, and so, also, for extremely hot or extremely cold bodies. On the other hand, impressions which are not localized on the terminal organs, as, for example, the passage of the electric current through the skin, are not capable of being regarded as tactile sensations. In other words, we are unable to distinguish one such mode of stimula- tion, except within narrow limits, from another. Thus, for example, the sensation of mechanically pricking the skin is. probably identical with that produced by the passage of the current. Again, the contact of a fluid with the skin will cause a tactile sensation, since it is in contact with the nerve terminations, and if that fluid be an soid and pass below the terminal organs and implicate the nerve-fibres a sensation of pain will be caused ; so that stimulus which when applied only to the nerve terminations may cause a tactile impression, when applied to the nerve-trunk results in a painful sensation. The intensity of the sensation produced by pressure depends almost as much upon the rapidity of the application of the pressure as upon the degree of the pressure. If the increase be gradual, more pressure may be applied with scarcely a perceptible sensation ; while, on the other hand, the rapid application of a less pressure may cause a much more intense sensation. All parts of the skin are not equally susceptible to pressure for the simple reason that all parts are not equally supplied with tactile corpuscles. Jn man the most sensitive localities are on the palmar surface of the fingers, on the forehead, and on the flexor surfaces of the limbs as contrasted with the extensor surfaces. If two points of the skin are subjected to pressure the sensation becomes fused when the two points are sufficiently close. When an im- pression is made upon any part of the body, not only the character but the locality are appreciated. This power, however, of localizing pressure sensations varies in different localities. The following table from Weber gives the minimum distances at which simultaneous stimulation of two points may be recognized as two distinct sensations :— Tip of tongue, . 3 Fi ae | led, millimeter. Palm of last phalanx of finger, 2 é - ae Palm of second phalanx of finger, . » AA ee Tip of nose, . i : ‘i ; ‘ » 66 a White part of lips, ‘ . » 8&8 fe Back of second phalanx of finger, » 1d ad Skin over malar bone, . ‘ . - 15.4 ss Back of hand, , : ‘ ‘ « 298 a Forearm, . F ‘i ‘ ‘5 . . 89.6 es Sternum, % ‘ P : ‘ 3 . 44, se Back, . : : : P . ; . 66. BOOK il. THE REPRODUCTIVE FUNCTIONS. (901) SECTION I, THE REPRODUCTIVE PROCESSES. Aut of the functions of the animal body economy which haveas yet been considered have dealt solely with the preservation of the individual. Through the exercise of the reproductive function is accomplished the preservation of the species. The duration of the life of any single animal is a limited one, and if, therefore, each species did not possess the power of reproducing itself in a new and similar individual the species would eventually die out. The mechanism by which reproduction is accomplished greatly differs in different groups of the animal kingdom. In all vertebrates it is accomplished by the union of two individuals of opposite sexes, male and female. In a large number of the invertebrate animals the two sexes, or at least the two sexual organs, are found united in the same individual, and the different acts of generation are thus accomplished in the body of the same animal; while the mode of reproduction offers a strong analogy to that of the vegetables, which, likewise, contain within the same floral envelope the organs of the two sexes. In other animals still. more imperfect a mode of generation may be observed which is analogous to that of cryptogamous plants. Here no organs of generation can be detected, and reproduction is accomplished by sep- aration of parts of the parent body which possess the power of development and growth. Sometimes the germ detaches itself from the individual in the form of a vesicle, which passes through all the phases of development. Such a mode of reproduction is spoken of as generation by spores. At other times a bud may be noticed to form from within or without the animal, which, after having acquired a more or less complete development, separates itself from the parent, and after the separation continues to grow and develop into a new animal. Such a mode of reproduction is spoken of as gemmiparous generation. Finally, the new organism may develop from the parent organism by a simple process of detachment of a part of the parent, after the separa- tion the detached portion forming a new animal, while the parent replaces the part which was lost. Such a mode of reproduction is spoken of as generation by fission. In all animals provided with organs of generation, whether borne by different individuals or united in the same individual, generation is (903) 904 PHYSIOLOGY OF THE DOMESTIC ANIMALS. invariably accomplished by the formation of an egg by the female and of a fecundating liquid by the male, which, coming in contact with the ege developed by the female organism, gives to the latter its power of independent growth and development. Sometimes the fluid formed by the male comes in contact with the egg of the female after it has passed from the body of the female,‘as is the case in fishcs, while at other times the male fecundates the egg before its exit and while it is still within the body of the female, where it undergoes a certain part of its developmental changes, as in the bird. Finally, the egg fecundated by the male may be retained within the cavity of the female until it has undergone the first phases of its development. : Although numerous differences may be met with in dierent mem- bers of the animal kingdom, these fundamental facts are always observed : on the one side the production of an egg, and on the other the production of a fecundating fluid. :” In all the vertebrates, whether mammals, birds, reptiles, or fishes, generation is accomplished by the union of the two sexes, the sexual organs being found in different individuals. In mammals the process of fecundation takes place within the interior of the sexual organs of the female, and copulation is, therefore, essential. In most reptiles a similar: process takes place, although in some fecundation is external; that is to say, the male extrudes the seminal fluid upon the eggs as they leave the body of the female. This latter process is also that which holds in fishes. In the fishes the eggs, covered, as in the case of the batrachians, with a soft membrane, are usually deposited along the banks or at the bottoms of rivers or ponds, while the male deposits at variable intervals the fecundating liquid. As a consequence of the exposure to so many different causes of destruction a large number of eggs escape fecundation, but the immense number de- posited by the fishes serves, however, to prevent the ultimate extinction of the species. As many as a million eggs have been said to be extruded at one time from the body of the female of various fishes. The ovaries of the female fish are two voluminous glands, which almost fill the abdominal cavity of the fish at the time of spawning. In most of the bony fishes the oviducts are continuous with the ovaries and form the extrusoty canal. In many of the cartilaginous fishes the abdominal extremity of the duct is free, as is the case in mammals, reptiles, and birds. The oviducts open into the cloaca. The testicles form in the male two voluminous glands, opening by means of the spermatic canals either into the cloaca, or by a special opening in the neighborhood of the anus. Jn certain of the cartilaginous fishes fecundation occurs within the body of the female, and there is, ‘therefore, true copulation analogous to that in birds. In these fishes the REPRODUCTIVE FUNCTIONS. 905 eggs are covered by a horny envelope. In others the fecundated eggs remain in the interior of the oviducts and there develop, and the animal bears its young. In reptiles, as in birds, the product of generation comes from the female organs in the state of an egg, while in most cases fecundation precedes, as in the birds, the escape of the egg, and the egg at the time of its exit is contained within a solid envelope, although, as a rule, less resistant than that surrounding the egg of the bird. Various batrachians extrude their eggs before fecundation and the male fecundates them while clinging to the body of the female at the moment of their exit. In cases where copulation takes place the exit of the eggs occurs at a considerable interval after their detachment from the ovary, and the egg retained in the oviduct develops and is not expelled until just at the point at which the young is able to carry on a separate existence; while in some instances, as in some serpents, incubation is terminated and the eggs are ruptured within the body of the female, and the living young are expelled from the body of the mother. Reptiles, as arule, do not incubate their eggs themselves after extrusion, but they de- posit them in the sand or in the water, as in the case of the amphibious reptiles, where the external heat is sufficient to accomplish their incubation. Females of the class of reptiles have two ovaries and two oviducts, which open separately into the cloaca, the oviducts, as in birds and mammals, not being continuous with the ovary, but being free in the abdsminal cavity, and possessing trumpet-shaped extremities analogous to the fimbriated extremities of the Fallopian tubes in mammals. The male organs of generation differ in different species. In the batrachians there are no organs of copulation. The spermatic canals open into the cloaca, and fecundation occurs, as in the birds, by the application of the ani, when fecundation precedes the expulsion of the eggs. In other groups of reptiles a penis is present, into which the spermatic canals open. Of all the reptiles batrachians are the most productive. Turtles extrude four to five eggs, serpents ten to twenty, and frogs many hun- dreds. After escaping from the egg batrachians are not, as a rule, fully developed, but during the first two weeks undergo a true metamorphosis, first existing in the form of tadpoles, deprived of limbs, but having a tail and breathing by branchia situated at the side of the neck. Grad- ually limbs develop and the tail as weil as the giils disappear, and the animal then breathes by lungs. In birds the product of generation leaves the sexual organs of the female while still within the egg, and such animals are, therefore, termed oviparous, although it must not be forgotten that man and other animals 906 PHYSIOLOGY OF THE DOMESTIC ANIMALS. are also in the strict sense of the word oviparous animals, only in them the egg does not leave the body of the female until completely developed. In mammals the fecundated egg passes through the Fallopian tube and becomes arrested in the uterus and is there fixed, and there under- goes what may be termed an internal incubation, while at the same time vascular connections between the egg and the body of the mother are established. In birds, likewise, the fecundated egg passes through the oviduct and there becomes coated with an albuminous layer, around which is finally deposited a layer of calcareous matter which hardens before the egg is extruded. It, therefore, contains within itself the materials necessary for the development of the embryo, and is, as a con- sequence, more voluminous than that of the mammal. The eggs of birds are finally developed by external incubation. Birds, like reptiles, are, as a rule, possessed of no external male organs of copulation. The testicles are placed near the kidneys, and the spermatic canals open at the inferior extremity of the digestive tract at the cloaca, and it is by the application of the anus of the male to the cloaca of the female that fecundation is accomplished. In certain birds, as the ostrich, duck, and goose, a rudimentary penis is, nevertheless, present. The fundamental part of the egg, or the yelk, is formed in the ovary of the female. When the yelk has attained its full development the ovarian capsule breaks and the yelk, inclosed by the vitelline membrane, passes into the oviduct. There it meets with the seminal fluid and becomes enveloped by a layer of albuminous matter, while the yelk undergoes a rotatory movement and the chalaze, or albuminous ligaments, found in the white of the egg are formed. About six hours after the exit from the ovary, and when the egg has reached the lower third of the oviduct, the albuminous layer, or the white of the egg, becomes enveloped by a membrane, at first transparent, and which finally doubles itself into two folds. The fold adhering to the albumen remains in the state of a mem- brane, while calcareous matters are deposited in the more external membrane so as to form the egg-shell. The formation of the shell is much slower than that of the albumen, and it is only after about twenty- four hours that the complete egg is expelled from the inferior part of the oviduct into the cloaca and thence to the exterior, the small point of the egg being first extruded. If examined while still within the oviduct, or immediately after its extrusion, it may be readily determined that characteristic changes have occurred within the germinal vesicle, and these progress until the embryo is completely developed, its life being sustained during the period of incubation by the albuminous matters stored up in the egg, while respi- ration takes place through the pores of the shell membrane. In the case REPRODUCTIVE FUNCTIONS. 907 of birds, in contradistinction to what holds in mammals, segmentation is partial, while the remainder of the yelk contained within the umbilical vesicle, and consequently communicating with the intestine of the bird, serves for its nutrition; as a consequence the umbilical vesicle persists during the entire period of incubation and even up to the time when the bird issues from the shell. The heat necessary for the development of the embryo within the egg is, as a rule, supplied by the body of the mother, but, as is well known, eggs may be artificially incubated, it only being necessary to place them at a constant temperature of from 35° to 40° C., turning them each day. In mammals the female nourishes its young for a variable period after birth through the secretion formed by the mammary glands. In mammals the different acts of generation closely correspond with similar processes in man, the principal differences lying in the number of the young, the duration of gestation, the frequency of the acts of reproduction, and certain anatomical peculiarities relative to the mode of adherence of the foetus or foetuses to the uterine cavity. Among mammals some bear but one young at atime. These are the cow, mare, ass, stag, elephant, and monkey ; the bear, the roebuck, the castor, the marmot, and the guinea-pig three to four; the lion, the tiger, and the leopard four to five; the dog, the fox, the wolf, and the cat five to six ; the rabbit and the water-rat six to eight; the pig and the rat as many as fifteen. The duration of gestation is three weeks in the guinea-pig, four weeks in the rabbit and hare, five weeks in the rat and marmot, six weeks in the ferret, eight weeks in the cat, nine weeks in the dog and fox, ten weeks in the sloth, fourteen weeks in the lion, seventeen weeks in the castor and sow, twenty-one weeks in the sheep, twenty-two weeks in the goat, twenty-four weeks in the roebuck, thirty weeks in the bear, thirty- six weeks in the stag, forty-one weeks in the cow, forty-three weeks in the mare, the ass, and the zebra, forty-five weeks in the camel, and one hundred weeks in the elephant. The number of young borne by mammals is capable of being modi- fied under different conditions. Animals which in a state of nature copulate but once in a year, when reduced to a state of domestication . enter anew into heat and may copulate a short time after the previous birth; this is, without doubt, due to the more abundant nourishment sup- plied to such animals in a state of domestication. The mare may pass into heat ten or twelve days after the birth, the cow after twenty days. The number of young borne by mammals is principally subordinate to the duration of gestation. Small mammals, which carry their young but a short time, as a rule bear more frequently than those in which 908 PHYSIOLOGY OF THE DOMESTIC ANIMALS. gestation is of longer duration. Thus, the water-rat or guinea-pig may bear five or six times a year. In most mammals the uterus is not constituted by a single cavity, as in the human female, but is prolonged more or less on each side, con- stituting what are termed the horns of the uterus. Sometimes, as in car- nivora, the division of the uterus is prolonged up to the vaginal orifice of the uterus. This division of the uterus into two horns, or two pouches, more or less distinct, does not occasion any difference in the mode of connection of the eggs with the uterine mucous membrane. In the carnivora and in rodents the mucous membrane, as in the human species, adheres to the body of the organ and separation is extremely difficult. In solipedes and the pachyderms the uterine mucous membrane is but slightly adherent to the subjacent tissue and may even be thrown into folds. In horned ruminants, as the cow, the mode of union of the egg with the uterine mucous membrane presents a remarkable peculiarity. The foetal placenta occurs in isolated cotyledons, the cotyledons being formed, as in the human species, of vascular loops implanted in the mucous membrane of the uterus, being designated under the name of the uterine cotyledons. These uterine cotyledons exist in the female even before pregnancy and persist after the separation of the foetus and its multiple placenta. When the young of a mammal is born the membranes of the egg and the umbilical cord frequently rupture spontaneously. In other cases the female breaks the membranes and the cord with her teeth. Most car- nivorous animals devour the after-birth. In the horned ruminants the adhesion of the cotyledons of the feetal placenta with the uterine coty- ledons is so close that frequently several days elapse after the birth of the foetus before the placenta becomes detached. In such animals the expulsion of the placenta cannot be facilitated by drawing on the umbili- cal cord without great risk of hemorrhage from rupture of the uterine vessels. When the animal is multiparous the membranes and placenta of each are expelled with the young to which they belong. In certain species of © mammals the young are but slightly developed and are incapable of making use of their limbs. Many such animals, as the marsupials, remain permanently attached to the breasts of the mother while carried in pouches formed by a fold of the integument of the abdomen. 1. Tue Repropucrive Tissues or THE FEMALE.—4 | 4 = ° = oat 160 hoo . t eos 180] 997 i bec 5 140) 08 n30| 97 ‘LUNHD "WONND BALOHEVG ‘SH . h20| 56 = = ° a ° hOO, 46 : A =e CoS tJ ° § 1 Lor Cet == oe ° o a i bed PREY = e— ens a ° N ° a bef COPYRIGHTED, 1888, BY F. A. DAVIS. 50 Charts, in Tablet Form. | Size, Sx12 inches. Price, in the United States and Canada, Post-paid, 50 Cents, Net; Great Britain, 2s. 6d.; France, 8 fr. 60. The above diagram is a little more than one-fifth (x-5) the actual size of the chart and shows the method of plotting, the upper curve being the Temperature, the middle the Pulse, and the lower the Respiration, By this method a full record of each can easily be kept with but one color ink. It is so arranged that all practitioners will find it an invaluable aid in the treatment of their patients. On the back of each chart will be found ample space conveniently arranged for recording ‘Clinical History and Symptoms’’ and ‘‘ Treatment.’ es By its use the physician will secure such a complete record of his cases as will enable him to review them at any time. ‘Thus he will always have at hand a source of individual improvement and benefit in the practice of his profession, the value of which can hardly be overestimated. : 4 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) - BOO Wee ee ON e Physician Himse AND THINGS THAT CONCERN HIS REPUTATION AND SUCCESS. D. W. CATHELL, MLD., a BALTIMORE, MD. Being the MINTH EDITION (Enlarged and Thoroughly Revised) of the “PHYSICIAN HIMSELF, AND WHAT HE SHOULD ADD TO HIS SCIENTIFIC ACQUIREMENTS IN ORDER TO SECURE SUCCESS.” In One Handsome Octavo Volume of 298 Pages, Bound in Extra Cloth. Priee, Post-paid, in United States and Canada, $2.00, Net; Great Britain, 8s. 6d.; France, 12 fr. 40. This remarkable book has passed through eight (8) editions in less ‘than five years, has met with the unanimous and hearty approval of the Profession, and is practically indispensable to every young graduate who aims at success in his chosen profession. It has just undergone a thorough revision by the author, who has added much new matter cover- ing many points and elucidating many excellent ideas not included in former editions. This unique book, the only complete one of the kind % ever written, will prove of inestimable pleasure and value to the practi- |. tioner of. many years’ standing, as well as to the young physician who . needs just such a work to point the way to success. , We give below a few of the many unsolicited letters received by the author, and extracts from reviews in the Medical Journals of the - former editions: “ “<* The Physician Himself’ is an opportune and . ‘The Physician Himself’ is useful alike to the most useful book, which cannot fail to exert a good tyro and the sage—the neophyte and the veteran. It influence on the wzora/e and the business success of is a headlight in the splendor of whose beams a the Medical profession.”— From Prof. Roberts | multitude of our profession shall find their way to Bartholow, Philadelphia, Pa. success.” —Frone Prof, ¥. M. Bodine, Dean Uni- “TI have read ‘The Physician Himself’ with versity of Louisville. . pleasure—delight. It is brimful of medical and “Tt is replete with good sense and sound phi- social philosophy; every doctor in the Jand can | Josophy. No man can read it without realizing that Study it with pleasure and profit. [wish I could | jts author is a Christian, a gentleman, and a shrewd “have read such a work thirty years ago.”"—Fromm observer.” ——From Prof. Edward Warren (Sa), Ba Prof. Fokn S. Lynch, Baltimore, Md. Chevalier of the Legion of Honor, etc., Paris, ‘««The Physician Himself’ interested me so France. . much that I actually read it through at one sitting. “JT have read ‘The Physician Himself,’ care- It is brimful of the very best advice possible for |- fully. I find it an admirable work, and shall advise :,medical men. I, for one, shall try to profit by it.”— | our Janitor to keep a stock on hand in the book de- « From Prof. William Goodell, Philadelphia, partment of Bellevue.”—F rom Prof. William T. te ‘I would be glad if, in the true interest of the Lusk, New York, ** profession in ‘Old England,’ some able practitioner “Tt must impress all its readers- with the belief Ay Fore would prepare a work for us on the same line as that it was written by an able and honest member of -4The Physician Himself.’"—From Dr. Fukes de | V2 profession and for the good of the profession.”’— Styrap, Shrewsbury, England, a From Prof. WH. Byford, Chicage, IL «Lia st favorably impressed with the Rontroigey f wisdom and force of ‘the Bolnts ade in ¢ The Phy- “Tt is saiees with good commen Senses ang i sician Himself,’ and believe the work in the hands | replete with xa lent lacus i sugges Hon ok -of a young graduate will greatly enhance his chances | the eulcene® ee eee —From The Britt ‘for professional success.”"—From Prof. D. Haye. Medical Fourna » London. ; Agnew, Philadelphia, Pa. ; “We rrongly advise every actual ae an ease , i i i ‘production of an ing practitioner of medicine or surgery to have dicot aid aga tee Pak of Drage eateer. 1 | ‘The Physician corey and the more it influences admire its pure tone and feel the value of its practi- | his future conduct the better he will be.”"—From ‘eal points. How I wish I could have read sucha | Zhe Canada Medical. and Surgical ¥ournal, “sguide at the outset of my career!”—From Prof. Montreal. * Sames Nevins Hyde, Chicago, Ill. «We would advise every docior ie well wotgh eu i reat deal of good sense, well | the advise given in this book, and govern his con- ee cbs sore Prof, Oliver Wendell Holmes, duct accordingly.” —/rom The Virginia Medical Harvard University. Monthy. an CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 5 AN IMPORTANT PUBLICATION OF GREAT VALUE TO THE MEDICAL AND LEGAL. PROFESSIONS. t SPINAL CONCUSSION: - Surgically ‘Considered as a Cause of Spinal Injury, and Neurologi- ’ cally Restricted to a Certain Symptom Group, for which is Suggested the Designation _ BRICHSEN’S DISEASE, AS ONE FORM OF THE TRAUMATIC NEUROSES. BY S. V. CLEVENGER, M.D., CONSULTING PHYSICIAN REESE AND ALEXIAN HOSPITALS; LATE PATHOLOGIST COUNTY INSANE ASYLUM, CHICAGO; MEMBER OF NUMEROUS AMERICAN SCIENTIFIC AND MEDICAL SOCIETIES; COLLABORATOR AMERICAN NATURALIST, ALIENIST AND NEUROLOGIST, JOURNAL OF NEUROLOGY AND PSYCHIATRY, JOURNAL OF NERVOUS AND MENTAL DISEASES; AUTHOR OF “‘COM- PARATIVE PHYSIOLOGY AND PSYCHOLOGY,” ‘ARTISTIC ANATOMY,” ETC. For more than twenty years this subject has occasioned hitter con- ‘tention in law courts; between physicians as well as attorneys, and in that time no work has appeared that reviewed the entire field judicially until Dr. Clevenger’s book was. written. It is the outcome of five years’ special study and experience in legal circles, clinics, hospital and private practice, in addition to twenty years’ labor as a scientific student, writer, and teacher. The literature of Spinal Concussion has been increasing of late years to an tmwieldy shape for the general student, and Dr. Clevenger has in this work arranged and reviewed all that has been done by observers since the days of Erichsen and those who preceded him. The different and sometimes antagonistic views of many authors are fully given from the writings of Erichsen, Page, Oppenheim, Erb, Westphal, Abercrombie, Sir Astley Cooper, Boyer, Charcot, Leyden, Rigler, Spitzka, Putnam, Knapp, Dana, and many other European and American students of the subject. The small, but important, work of Oppenheim, of the Berlin University, is fully translated, and constitutes a chapter of Dr. Cleven- ger’s book, and reference is made wherever discussions occurred in American medico-legal societies. me re There are abundant illustrations, particularly for Electro-diagnosis, and to enable a clear comprehension of the anatomical and pathological relations. Ss The Chapters are: I. Historical Introduction; IJ. Erichsen on Spinal Concussion ; III. Page on Injuries of the Spine and Spinal Cord; IV. Recent Discussions of Spinal Concussion; V. Oppenheim on Trau- matic Neuroses; VI. Illustrative Cases from Original and all other Sources; VII. Traumatic Insanity; VIII. The Spinal Column; IX. Symptoms; X. Diagnosis; XI. Pathology; XII. Treatment ;* XIII. Medico-legal Considerations. : nae Other special features consist in a description of modern methods, of diagnosis by Electricity, a discussion of the controversy concerning hysteria, and the author’s original pathological view that the lesion is one involving the spinal sympathetic nervous system. In this latter respect entirely new ground is taken, and the diversity of opinion con-— cerning the functional and organic nature of the disease is afforded a’ basis for reconciliation. ; Fivery Physician and Lawyer should own this work, In one handsome Royal Octavo Volume of nearly 400 pages, with Thirty Wood-Engravings. Net price, in United States and Canada, $2.50, post-paid ; in Great Britain, Ils. 3d.; in France, 15 fr. 6 CF. A. DAVIS, Medical Publisher, Philadelphia, Pa.. U.S.A.) Me , ‘Surgeon to the Municipal Hospital, Paris, and of the Council of State; Member of the Imperial Society JUST READY—A NEW AND IMPORTANT WORK. MEDIAL PNEUMATOLOGY * AEROTHERAPY: OF THE GASES IN MEDICAL AND SURGICAL PRACTICE, WITH ESPECIAL REFERENCE TO THE VALUE AND AVAILABILITY OF OXYGEN, NITROGEN, HYDROGEN, AND NITROGEN MONOXIDE. By d. N. DEMARQUAY, of Surgery; Correspondent of‘the Academies of Belgium, Turin, Munich, etc. ; Offi s of the Legion of Honor; Chevalier of the Orders of Teabella-the- scat Catholic and of the Conception, of Portugal, etc. . TRANSLATED, WITH NOTES, ADDITIONS, AND OMISSIONS, By SAMUEL 8. WALLIAN, A.M., M.D., } 7 Member of the American Medical Association ; Ex-President of the Medical Association of Northern N. : York; Member of the New York County Medical Society, etc. _ Oe ie In one Handsome Octavo Volume of 316 Pages, Printed on Fine Paper, in the Best Style of the Printer’s Art, and Illustrated with 21 Wood-Cuts. United States. Canada (duty paid). | Great Britain. France. NET PRICE, CLOTH, Post-paid, $2.00 F $2.20 8s. 6d. 12 fr. 40 “ ¥%-RUSSIA, « 3.00 3.30 13s. 18 fr. 60 i For some years past there has been a growing demand for something more satisfac- tory and more practical in the way of literature on the subject of what has, by common 4 consent, come to be termed “ Oxygen Therapeutics.” On all sides professional men of. ~ standing and ability are farming their attention to the use of the gaseous elements about 1 us as remedies in disease, as well as sustainers in health., In prosecuting their inquiries, ‘the first hindrance has been the want of any reliable, or in any degree satisfactory, literature on the subject. Purged of the much quackery heretofore associated with it, Aerotherapy is now ‘recognized as a legitimate hey eae of medical practice. Although little noise is made about it, thé\use of Oxygen Gas as a remedy has increased in this country within a few years to such an extent that in New York City alone the consumption for medical pur- . poses now amounts’to more than 300,000 gallons per annum. This work, translated in the main from the French of. Professor Demarquay, contains also a very full account of recent English, German, and American experiences, prepared by Dr. Samuel 8. Wallian, of New York, Whose experience in this field antedates that of any other American writer on the subject. : Plain Talks on Avoided Subjects. —BY— % HENRY N. GUERNSEY, M.D., -Formerly Professor of Materia Medica and Institutes in the Hahnemann Medical College of Philadelphia; , Author of Guernsey’s ‘‘ Obstetrics,’’ including the Disorders Peculiar to Women and : Young Children ; Lectures on Materia Medica, etc. IN ONE NEAT 16mo VOLUME. BOUND IN EXTRA CLOTH. Price, Post-paid, in. United States and Canada, $1.00; Great Britain, 4s. 6d.; France, 6 fr. 20. This is a little volume designed to convey information upon one of the most important subjects con- “nected with our physical and spiritual well-being, and is adapted to both sexes and all ages and conditions of society ; in fact, so broad is its scope that no human being can well afford to be without it, and so ¢éom- prehensive in its teachings that, no matter how well informed one may be, something can yet be learned from this, and yet it is so plain that any one who can read at all can fully understand its meaning. : The Author, Dr. H. N. Guernsey, has had an unusually long and extensive practice, and his teachings in this volume are the results of his observation and actual experience with all conditions of human life. His work is warmly indorsed by many leading men in all branches of professional life, as well as by many whose business connections have caused them to be close observers. * The following Table of Contents shows the scope of the book :— F CONTENTS. Cuaprrer 1.—Inrropuctory. IJ.—Tue Inrant. III.—CuitpHoop. IV.—Apo.ss- CENCE oF THE Marz. V.—ADOLESCENCE OF THE Femate. VI.—MarriaGe: THE Husspanp. VII.— ‘Tre Wirz. VIII].—Hussanp AND Wirz. 1X.—To tHe UnFrortrunats. X.—ORIGIN oF THE SEX. CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 7 \ ———=NEW EDITION Lessons in Gynecology. By WILLIAM GOODELL, A.M., M.D., Ete., Prorgssor or CLinicaL GYNECOLOGY IN THE UNIVERSITY OF PENNSYLVANIA. With 112 THustrations. Third Edition, Thoroughly Revised and Greatly Enlarged. ONE VOLUME, LARGE OCTAVO, 578 PAGES. f This exceedingly valuable work, from one of the most eminent specialists and teachers in gynecology in the United States, is now offered to the profession in a much more complete condition than either of the previous editions. It embraces all the more important diseases and the principal operations in the field of gynecology, and brings to bear upon them all the extensive practical experience and wide reading of the author. It is an indispensable guide to every practitioner who has to do with the diseases peculiar to . women, NATURAL POSITION OF THE WOMB WHEN THE BLADDER IS FULL. : AFTER BRIESKY. 2 4 These lessons are’ so well known that it is en- tirely unnecessary to do more than to call attention to the fact of the appearance of the third ‘edition. It is too good a book to have been allowed to remain » out of print, and it has unquestionably been missed. The author has revised the work with special care, adding to each lesson such fresh matter as the prog-* ress in the art rendered necessary, and he has en- larged it by the insertion of six new lessons. This edition will, without question, be as eagerly sought for as were its predecessors.—American Yournal of Obstetrics. The former editions of this treatise were well received by the profession, and there is no doubt that the new matter added to the present issue makes it more useful than its predecessors.—NVew York Medical Record. ; His literary style is peculiarly charming. There is a directness and simplicity about it which is easier to admire thanto copy. His chain of plain words _. and almost blunt expressions, his familiar compari- - son and homely illustrations, make his writings, like .- his lectures, unusually entertaining. The substance of his teachings we regard as equally excellent.— Phila, Medical and Surgical Reporter, Extended mention of the contents of the. book is unnecessary; suffice it to say that évery important disease found in the female sex is taken up and dis- cussed in a common-sense kind of away. We wish every physician in America could read and carry “ out the suggestions of the chapter on ‘the sexual re- lations as causes of uterine disorders—conjugal » onanism and kindred sins.’’. The department treat- ing of nervous counterfeits of uterine. diseases is- ~, a most valuable one. — Kansas City Medical Index. ; Price, in United States and Canada, Cloth, $5.00; Full Sheep, $6.00. Discount, 20 per cent., making it, net, Cloth, $4.00; Sheep, $4.80. Postage, 27 Cents extra. Great Britain, Cloth, 18s.; Sheep, £1.2s., post-paid, net. France, 30 fr. 80. 7 8 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) , - AMERICAN RESORTS, | WITH NOTES UPON THEIR CLIMATE. By BUSHMROD WW. JAMES, &.M., M.D., , Member of the Aj Associ: i for the Ad t of Soi the American Public Health. Association, the Pennsylvania Historical Society, the Franklin Institute, and the Academy of Natural Sciences, Philadelphia; ‘the Society of Alaskan Natural History and Ethnology, Sitka, Alaska, etc, é WITH A TRANSLATION FROM THE GERMAN, By Mr. S. KAUFFMANN, “@f those chapters of ‘‘ Die Klimate der Erde’ written by Dr. A. Woeikof, of St. Petersburg, Russia, that e ’ relate to North and South America and the islands and oceans contiguous thereto. In One Octavo Volume. Handsomely Bound in Cloth. Nearly 300 Pages. Price, Post-paid, in U. 8. and Canada, $2.00, net. Great Britain, 8s. 6d. France, 12 fr. 40. e ——— This is a unique and valuable work, and useful to physicians in all parts of the country. It is just such ca volume as the Medical Profession have stood in need of for many years. Wé mention a few of the merits it possesses: First. List of all the Health Resorts of the country, arranged according to their climate. Second, Contains just the information needed by tourists, invalids, and those who visit summer or winter resorts. each one should select for health. are practical in reference to localities. Taken altogether, this is by far the most complete ex- _ position of the subject of resorts that has yet been put forth, and it is one that every physician must needs possess intelligent information upon. We predict a large demand ‘for this useful and attractive book.-Bufialo Med. and Surg. Jour. ‘The special chapter on the therapeutics of climate . . is ent for its precauti suggestions in the selec- tion of climates and local conditions, with reference to known pathological indicati and titutional predis- positions.—The Sanitarian. It is arranged in such a manner that it will be of great -service to medical men whose duty it often becomes to rec- ommend a health resort.—N. W. Med. Jour. - A well-arranged map of the United States serves as the frontispiece of the book; and an almost perfect index is appended, while between the two is an amount of informa- _ tion as to places for the health-seeker that cannot be gotten -elsewhere. travelers and to the dootor.— Virginia Med. Monthly. = This is » work that has long been needed, as there is searcely a physician who has not had occasion to look up the authorities on climate, elevation, dryness, humidity, -ete ,etc., of the various health resorts, and has had great -difficulty in finding reliable information. It certainly Third, ‘The latest and best large railroad map for reference. ‘We most cordially recommend the book to. fourth, It indicates the climate Fifth, The author has traveled extensively, and most of his suggestions ought, as it deserves, to receive a hearty welcome from the ascion._-Medical A The book before us is a very comprehensive volume, giving all y inf ti ing climate, tem- perature, humidity, sunshine, and indeed everything neces- sary to be stated for the benefit of the physician or invalid ears ing a health resort in the United States.—Southern ANIC. This work is extremely valuable, owing to the liberal and accurate manner in which it gives information regard- ing the various resorts on the A.nerican continent, without being prejudiced in the least in favor of any particular one, but giving allin a fair manner. . . . All physicians need just such a work, for the doctor is always asked to give information on the subject to his patients. Therefore, it should fipd a place in every physician's library.—The Med. Brief. : The author of this admirable work has long made a study of American climate, from the stand-point of a phy- sician, with a view to ascertaining the most suitable locali- ties for the residence of invalids, believing proper climate to be an almost indispensable factor in the treatment, pre- vention, and cure of many forms of disease. . . . The book evidences careful research and furnishes much useful information not to be found elsewhere.— Pacific Med. Jour. JUST PUBLISHED RECORD-BOOK OF MEDICAL EXAMINATIONS For Life Insurance. Designed by TOE M. EEATING, M.D. - In examining for Life Insurance, questions are easily overlooked and the answers to ‘them omitted; and, as these questions are indispensable, they must be answered before the ease can be acted upon, and the examiner is often put to much inconvenience to obtain this information. . The need has long been felt among examiners for a reference-book in which could be noted the principal points: of an examination, and thereby obviate the necessity of a second visit to the applicant when further information is required. After a careful study of all the forms of examination blanks now used by Insurance Companies, Dr. J. M. Keating has compiled such a record-book which we are sure will fill ‘this long-felt want. ~This record-book is small, neat, and complete, and embraces all the principal points that are required by the different companies. It is made in two sizes, viz.: No. 1, cover- ‘ing one hundred (100) examinations, and No. 2, covering two hundred (200) examina- -tions. The size of the book is 7x 3% inches, and can be conveniently carried in the 7 ‘pocket. NET PRICES, No. 1, For 100 Examinations, in Cloth, No. 2, For 200 Examinations, in Full Leather, with Side Flap, (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S A.) POST-PAID. U.S, and Canada. Great Britain, France. - $8 .50 2s. 6d. 3 fr. 60 - 1.00 4s. 6d. 6 fr. 20 8 | == a = 7 Heart and Circulatio IN INFANCY AND ADOLESCENCE. With an Appendix entitled “Clinical Studies ou th Pulse in Childhood.’ : . —BY— JOHN M. KEATING,.M.D., : Obstetrician to the Philadelphia Hospital, and Lecturer on Diseases of Women and Children; Surgeon to the Maternity Hospital; Physician to St. Joseph’s Hospital; Fellow of the College of Physicians of Philadelphia, etc., —AND— WILLIAM A. EDWARDS, M.D., Instructor in Clinical Medicine and Physician to the Medical Dispensary in the University of Pennsylvania Physician to St. Joseph’s Hospital ; Fellow of the College of Physicians; formerly me Assistant Pathologist to the Philadelphia Hospital, etc. ° : ILLUSTRATED BY PHOTOGRAPHS AND WOOD-ENGRAVINGS. About 225 Pages. 8vo. Bound in Cloth. Price, post-paid, in U. 8. and Canada, $1.50, net; Great Britain, 6s. Gd.; France, 9 fr. 35. There are many excellent text-books on children’s diseases, but they have failed to givea satisfactory cccount of the diseases of the heart ; and, indeed, as far as known, this work of Keating and Edwards’ now presented to the profession is the only systematic attempt that has been made to collect in book form the ‘ abundant material which is scattered throughout medical literature in the form of journal articles, clinical lectures, theses, and reports of societies. _ The authors have endeavored, in their difficult task, to collect these valuable materials and place them within easy reach of those who are interested in this important subject. ‘That they have succeeded will, we believe, be conceded by all who obtain and make use of their very valuable contribution to this hitherto neglected field of medical literature. - ‘ . An appendix, entitled “Clinical Studies on the Pulse in Childhood,” follows the index in the book, and ° will, we are sure, be found of much real value to every practitioner of medicine. The work is made available for ready reference by a well-arranged index. Weappend the table of contents showing the scope of the “book :— : con TtTENTSs— CHAPTER I.—The Methods of Study—Instruments— Foetal Circulation—Congenital Diseases of the Heart—Malformations—Cyanosis. Cuaprer If.—Acute and Chronic Endocarditis— Ulcerative endocarditis. Cu apter 11].—Acute and Chronic Pericarditis. Cuarter 1V.—The treatment of Endo- and Peri- carditis—Paracentesis Pericardii—Hydropericar- dium—Hzmopericardium—Pneumopericardium. Cuapter V.—Myocarditis—Tumors, New Growths, and Parasites : Cuarter Vl.—Valvular Disease: Mitral, Aortic, Pulmonary, and Tricuspid. CuarterR VII.—General Diagnosis, Prognosis, and. Treatment of Valvular Disease. Cuapter VIII,—Endocarditis—Atheroma— Aneu- rism, : Cuarter IX.—Cardiac Neuroses—Angina Pectoris. —Exophthalmic Goitre. ‘ Cuapter X.—Diseases of the Blood: Plethora, Anzmia, Chlorosis, Pernicious Anamia, 1.eu- kzemia--Hodgkin’s Disease—H zmophilia, Throm- bosis, and Embolism. INDEX. : APPEND1X.—Cuinicat Stupres ON THE PULSE in CHILDHOOD. Drs. Keating and Edwards have produced 2 work that will give material aid to every doctor in his practice among children. ‘The style of the book is graphic and pleasing, the diagnostic points are explicit and exact, and the thera- peutical resources include the novelties of medicine as well as the old and tried agents.—Pittshurgh Med. Review. : A very attractive and valuable work has beon given to the medical profession by Drs. Keating and Edwards, iw their treatise on the diseases of the heart and circulation in infancy nnd adolescence, and they deserve the greatest eredit for the admirable manner in which they have col- lected. reviewed, and mado use of the immense amount of material on this important subject.— Archives of Pediatrics. The plan of the work is the correct oné, viz., the sup- plementing of the observations of the hetter class of prac- titioners by the experience of those who have given the subject systematic attention.—Medical Age. It is not a mere compilation, but a systematic treatise, and bears evidence of considerable labor and observation on tho part of the authors. Two fine photographs of. dissec- .. tions exhibit mitral stenosis and mitral regurgitation; there are also a number of: wood-cuts.—Cleveland Medical Gazelte. Sy 7 e E As the works upon diseases of children give little or no attention to diseases of the heart, this work of Drs. Keat- | ing and Edwards will supply a want. We think that there will be no physician, who takes an interest in the affections of young folks, who will not wish to consult it. |. —Cincinnati Med. News. The work takes up, in an,able and seientific manner, diseases of the heart in children. This is « part of the | field of medical science which has not been cultivated to - the extent that the importance of the subject deserves.— Canada Lancet. : : 190 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) PERPETUAL CLINICAL INDEX — MATERIA MEDICA, CHEMISTRY, AND PHARMACY CHARTS. | By A. H. KELLER, Ph.G., M.D. . Consisting of (1) the «Perpetual Clinical Index,’”’ an oblong volume, 9x6 inches, neatly bound in extra Cloth; (2) a Chart of «Materia Medica,’’? 32x44 inches, mounted on muslin, with rollers; (3) a Chart of « Chemistry and Phar- macy,’’? 32x44 inches, mounted on muslin, with rollers. United States. Canada (duty paid). © Great Britain. Franca. Net Price for the Complete Work, $5.00 $5.60 Ells, 30 fr. 30 Read the Following Description and Explanation of the Work: In presenting the objects and advantages of these Charts and « Perpetual Clinical Index” it becomes necessary to state that the Author’s many years’ experience as a physician and Pharmacist enables him to produce, in terse language, a volume of facts that must be of inestimable value to the busy physician and . pharmacist, or to any student of either profession. He has endeavored to describe all that have borne inves- tigation up to date, : : _ The system will prove to be of Brent value in this, that so little labor will be required to add new investigation as fast as may be gathered from new books, journals, etc. The classification is alphabetical and numerical in arrangement, and serves so to unite the various essentials of Botany, Chemistry, and _Materia Medica, that the very thought of the one will readily associate the principal properties and uses, as well as its origin. The «MATERIA MEDICA’ CHART, in the first place, aids at a glance: 1st, Botanical or _U.S. P. Name; 2d, The Common Name;' 3d, Natural Order ; 4th, Where Indigenous; sth, Principal Con- Stituent; 6th, Part Used—herbs, leaves, flowers, roots, barks, etc.; 7th, Medicinal Properties—mainly con- ‘sidered; 8th, The Dose—medium and large. : On this Chart there are 475 first names; Section A. is numbered from 1 to 59, each section commencing with the capital letter, and having its own numbers on both left-hand and right-hand columns, to prevent ' mistakes in lining out, all in quite large type. In the cehtre of the Chart, occupying about 6 inches in width, is a term index of common names. In the second column of Chart, like this: ° ACONITE LEAVES,’ . a 7 . . z, 4A. : Then by reference to 4 A in first column, you there find the Botanical or U.S. P, Name, On this Chart is | also found a brief definition of the terms used, under the heading ‘“ Medicinal Properties.” The « CHEMISTRY’? CHART takes in regular order the U. S. Pharmacopceia Chemicals, with the addition of. many new ones, and following the name, the Chemical Formula, the Molecular Weight, and next the Origin. This is a brief but accurate description of the essential points in the manufacture: The Dose, medium and large; next, Specific Gravity; then, whether Salt or Alkaloid; next, Solubilities, by abbreviation, in Water, Alcohol, and Glycerine, and blank columns for solubilities, as desired. Alkaloids and Concentrations are tabulated with reference numbers for the Perpetual Clinical Index, giving Medicinal Properties, Minute Dose and Large Dose. For example, ALKALOIDS AND CONCENTRATIONS: 1 s A, i MepicinaL PRopertigs. Minute Dose. Larce Doss. (a) Aconitine. Narcotic and Apyretic. 1-500 gr. 1-16 gr. ss Following this, Preparations of the Pharmacopeeia, each tabulated. For example: TINCTURAL. Tinctura, » Druve. AmMounNT. ALCOHOL. Doss. * Aconiti. ipectawe Reid, 60+ P. 5% 02, to 24 gr. 100 ee to 3 drops. * 60 Fineness of Powder as per U. S. P. + P. Macerate 24 hours. Percolate, adding Menstruum to complete (1) pint tincture. They are all thus abbreviated, with a ready reference head-note. - ~Next, Thermometers, Metric Table of Weights, Helps to the Study of Chemistry, Examples in Work- ing Atomic Molecular Formule. Next, Explanation of Terms Used in Columns of Solubilities, List of ost Importaut Elements Now in Use, and Definitions or Terms Frequently Used in Chemistry and Pharmacy. i The ip PERPETUAL CLINICAL INDEX ”’ is a book 6 by g inches, and one-half inch thick. It contains 135 pages, divided as follows (opposite pages blank) : Se: ; The Index to Chemistry Chart occupies two pages; Explanations, Abbreviations, etc., forty pages, with diseases, and with an average of ten references to each disease, leaving room for about forty more remedies for each disease. The numbers refer to the remedies used in the diseases by the most celebrated physicians and surgeons, and’ the abbreviations to the manner in which they are used. Eight pages, numbered and bracketed, for other diseases not enumerated. The Materia Medica, Explanations, Abbreviations, and Remedies suggested for, occupy twenty-six pages. For Abbreviated Prescriptions, seventeen blank pages. ‘Then the Tadese to Alkaloids and Concentrations, These, already enumerated, with their reference, number six blank tabulated pages, for noting any new Alkaloids and Concentrations. Then the Chemistry Index, giving the same number as-on Chart, with Name, Doses, Specific Gravity, Salt or Alkaloid in the same line, as for example: ‘Name. Dosgs. SpeciFic GRAVITY. SaLT oR ALKALOID. Memoranpa. This Memoranda place is for Physicians’ or Pharmacists’ reference notes; and with the addition of several tabulated blank pages, in which to add any new chemical, with doses, etc. The remaining sixteen pages for Materia Medica Index, leaving blanks following each other for new names and reference numbers. To show the ready and permanent use of the ‘Perpetual Clinical Index’’ of the «Chemistry and « Bharmacy’’ Charts or Index in the book, suppose the Physician reads in a book or journal that Caffeine Citras is useful in the disease Chorea, and he wishes to keep a permanent record of that, he refers to the (Chart, and if it does not already, appear there, it can be placed opposite and numbered, and thereafter used for reference. But we find its permanent number is No. 99, So he will write down in the line left blank for future use in his book, in line already used, running parallel with other reference numbers in Chorea, the ‘No. 99, and immediately under he can use the abbreviation in the manner in which it is given. Though years may have passed, he can in a moment, by referring there, see that No. go is good for Chorea. If fail- ing to remember what No. gg is, he glances at the Chart or Index. He sees that No. gg is Caffeine Citras, and he there learns its origin and dose and solubility, and in a moment an intelligent prescription can be “gonstructed. 4 AVIS. Medical Publisher, Philadelphia, Pa., U.S.A.) u New Edition of an Important and Timely Work Just Published. Electricity in the J)iseases of Women, With Special Reference to the Application of Strong Currents. . By G. BETTON: MASSEY, M.D., ‘ Physician to the Gynecological Department of Howard Hospital; Late Electro-Therapeutist to the Phila- delphia Orthopzedic Hospital and Infirmary for Nervous Diseases ; Member of the American Neurological Ass’n, of the Philadelphia Neurological Society, of the Franklin Institute, etc. . 1 Second Eidition. mewvised and Emlargea. WITH NEW AND ORIGINAL WOOD-ENGRAVINGS. HANDSOMELY BOUND IN CLOTH. OVER 200 PAGES. 12mo. Price, in United States and Canada, $1.50, net, post-paid. In Great Britain, 6s. 6d. In France, 9 fr. 35. This work is presented to the profession as the most complete treatise yet issued om the electrical treatment of diseases of women, and is destined to fill the increasing demand for clear and practical instruction in the handling and use of strong currents after the recent methods first advocated by Apostoli. The whole subject is treated from the present — stand-point of electric science with new and original illustrations, the thorough studies of the author and his wide clinical experience rendering him an authority upon electricity itself and its therapeutic applications. The author has enhanced the practical value of the work by including the exact details of treatment and results in a number of cases taken from his private and hospital practice. Fic, 18,—BaLit ELecTRODE FOR ADMINISTERING FRANKLINIC SPARKS. CONTE Ts ” Cuaprter I, Introductory; II, Apparatus required in gynecological applications of the galvanic current ; III, Experiments illustrating the physical qualities of galvanic currents; IV, Action of concentrated gal- vanic currents on organized tissues ; V, Intra-uterine galvano-chemical cauterization; VI, Operative details ef pelvic electro-puncture; VII, The faradic current in gynecology ; VIII, The franklinic current in gyne- cology ; IX, Non-caustic vaginal, urethral, and rectal applications ; X, General percutaneous applicationsin ~° the treatment of nervous women ; XI, The electrical. treatment of fibroid tumors of the-uterus ; XII, The electrical treatment of uterine hemorrhage; XIII, The electrical treatment of subinvolution; XIV, The’ electrical treatment of chronic endometritis and chronic metritis; XV, The electrical treatment of chronic diseases of the uterus and appendages; XVI, Electrical treatment of pelvic pain; XVII, The electrical treatment of uterine displacements ; XVIII, The electrical treatment of extra-uterine ‘pregnancy; XIX, , The electrical treatment of certain miscellaneous conditions ; XX, The contra-indications and limitations te { the use of strong currents. An Appendix and a Copéous Index, including the definitions of terms used in the work, concludes ; the book. The author gives us what hé has seen, and of which he is assured by scientific study is correct. . . . . e are certain that this little work will prove helpful to all physicians who desire to use electricity in the ma t ef the diseases of women.— The American Lancet. To say that the author is rather conservative in, his ideas of the curative powers of electricity is only another sidered, and by means of good wood-cuts the beginner has before his eye the exact method of work required.—The Hedical Register. ‘ = : “The author of this little volume of 210 pages ought to have added to its title, “and a most happy dissertation upon the methods of using this medicinal agent,” for in Be first 100 pages he has contrived to desoribe the techné 0 way of saying that he understands his subject ghly. The mild enthusiasm of our author is unassailable, because it is founded on science and reared with experience.— The Hedical Analeche, The work is well written, exceedingly practical, and can be trusted. We d it to the pro! "—Mary- land Medical Journal. The book is one which should be possessed by every physician who treats diseases of women by electricity.— The Brooklyn Medical Journal. The departments of electro-physics, pathology, and lectro-therapeuties are th ghly and admirably con- 2 CF. A. DAVIS, Medical Publisher, Philadelphia. Pa. U,S-Mocde in as clear and happ author has ever succeeded in doing, and for this part of the’. book alone it is almost priceless to the beginner in the treatment with this agent. . . . . The little book is' worthy the perusal of overy one at all interested in the subject of electricity in medicine.— The Omaha Clinic. , The treatment of fibroid tumor of the uterus will, Pp ‘ps, the | ssion more generally than any other question. This subject has been accorded ample space. ‘The method of treatment in many cases has beam recited in detail, the results im every instance reported ke-, ing beneficial, and in many curative.—Pacyic Med. Jeur. & manner as ne _ IMELARs’ PRACTICAL SURGERY. By J. EWING MEARS, M.D., Leeturer on Practical Surgery and Demonstrator of Surgery in Jefferson Medical College; Professor of Anatomy and Clinical Surgery in the Pennsylvania College of Dental Surgery, etc. With 490 Illustrations. Second edition, revised and enlarged. 794 pp. 42mo, ‘ PRICE, IN UNITED STATES AND CANADA : CLOTH, $3.00. DISCOUNT, 20 PER CENT., MAKING IT, NET, $2.40 ; POSTAGE, 20 CENTS EXTRA. GREAT BRITAIN, 13s. FRANCE, 18 fr. 75. Mears’ Pracrican Surgery includes chapters on Surgical Dress- Yags, Bandaging, Fractures, Dislocations, Ligature of Arteries , Amputa- tions, Hecisions of Bones and Joints. This work gives a complete account of. the methods of antiseptic surgery. The dif-- ferent agents used in antiseptic dressing, their methods of preparation, and. their application in the treatment of wounds are fully described. With this work as a guide it is possible for every surgeon to practice antiseptic surgery. The great advances made in the science and art of surgery are largely due to the introduction of anti- septic methods of wound treatment, and ‘t is incumbent upon every progressive sur- geon to employ them. An examination of this work will co show that it is thoroughly systematic in its plan, so that it is not only useful to the practitioner, who may be - ealled upon to-perform operations, but of great value to the student in his work in the surgical room, where he is required to apply bandages _and fracture dressings, and to perform operations upon the cadaver. The experience of the author, derived from many years’ service as a teacher (private and public) and practitioner, has enabled him to present the topics discussed in such a manner as to fully meet the needs of both prac- _titioners and students. tioner who follows it intelligently cannot easily go astray.— Fournal American Medical Asso'n. We cannot speak too highly of the volume under review.—Canada Med. and Surg. Four. The space devoted to fractures and dislocations taken as a guide in the matters of which it treats, | | —by far the most difficult and xesponsible part of Tt would be hard to point out all the excellences of this bodk. Wecan heartily recommend it to students and to practitioners of surgery.—American Your- nal of the Medical Sciences. We do not know of any other work which‘would be of greater value to the student in connection with his lectures in this department.—Buffalo Medical and Surgical Fournad. The work is excellent. The student or practi- surgery—is ample, and we notice many new illustra~ tions explanatory of the text.—North Carolina Medical Fournal. It is one of the most valuable of the works of its It is full of common sense, and may be safely | i ‘| kind.—New Orleans Med. and Surg. Four. (F. A, DAVIS, Medical ical Publisher, Philac Philadelphia, Pa., U.S.A.) 13 AN ENTIRELY NEW PHYSICIAN'S VISITING LIST: (Te MEDICAL BULLETIN Visitinc [ost PHYSICIAN’S (ALL RECORD. ARRANGED UPON AN ORIGINAL AND CONVENIENT MONTHLY AND WEEKLY PLAN FOR THE DAILY RECORDING OF PROFESSIONAL VISITS. Frequent Rewriting of Names Unnecessary. Tuis Visrtina List is arranged upon a plan best adapted to the most convenient use of all physicians, and embraces a new feature in recording daily visits not found in any other list, consisting of STUB OR HALF LEAVES IN THE FORM OF INSERTS, a glance at which will suffice to show that as the first week’s record of visits is completed the next week’s record may be made by simply turning over the stub-leaf, without the necessity of re- writing the patients’ names. This is done until the month is completed, and the physician has kept his record just as complete in every detail of - VISIT, CHARGE, CREDIT, etc., as he could have done had he used any of the old-style visiting lists,and has also saveD himself three-fourths of the time and labor formerly required in transferring names EVERY week. There are no intricate rulings; everything is easily and quickly under- stood; not the least amount of time can be lost in comprehending the plan, for it is acquired at a glance. é The Three Different Styles Made. The No. 1 Style of this List provides ample space for the DAILY record of seventy (70) different names each month for an entire year - (two full pages, thirty-five [35] names to a page, being allowed to each month), so that its size is sufficient for an ordinary practice; but for. puysicians who prefer a List that will accommodate a larger practice we have made a No. 2 Style, which provides ample space for the daily: record of ONE HUNDRED AND FIVE DIFFERENT NAMES (105) each month for an entire year (three full pages being allowed to each month), and for physicians who may prefer a Pocket Record Book of less thickness than either of these styles we have made a No. 3 Style, in which “ The Blanks for the Recording of Visits In” have been made into removable sections. These sections are very thin, and are made up so as to answer ~ in full the demand of the largest practice, each section providing ample space for the DAILY RECORD OF TWO HUNDRED AND TEN (210) DIFFERENT NAMES for one month; or one hundred and five (105) different names daily each month for two months ; or seventy (70) different names daily each month for three months; or thirty-five (35) different names daily each month for six months. ‘ Four sets of these sections go with each copy of No. 3 Style. Special Features Not Found in Any Other List. In this No. 3 Sryze the PRINTED MATTER, and such matter as the BLANK FORMS FOR ADDRESSES OF PATIENTS, Obstetric Record, Vaccination Record, Cash Account, Births and Deaths Records, etc., are fastened . permanently i in the back of the book, thus reducing its thickness. The addition of one of these removable ‘sections does not increase the size quite an eighth of an inch. This brings the book into such a small com- pass that no one can object to it on account of its thickness, as its bulk 14 iS VERPetr- Hess thai tit Of any visiting list ever published. Ever physician will at once understand that as soon as a section is full it mad <. be taken out, filed away, _ venience or trouble. and another inserted without ‘the least incon- . Abis.. Visiting , List contains a Calendar for the last six months or last year, all of this, and next year; Table of Signs to be used © in Keeping Accounts; Dr. Ely’s Obstetrical Table; Table of Cal- culating the Number of Doses in a given R, ete., ete.; for converting Apothecaries’ Weights and Measures into Grammes; Metrical Avoirdu- pois and Apothecaries’ Weights ; Number of Drops in a Fluidrachm ; Graduated Doses for Children; Graduated Table for Administering Laudanum ; Periods of Eruption of the Teeth; The Average Frequenc of the Pulse at Different Ages in Health; Formula and Doses of ype: dermic Medication; Use of the Hypodermic Syringe; Formule and Doses of Medicine for Inhalation; Formule for Suppositories for the Rectum; The Use of the Thermometer in Disease; Poisons and their Antidotes; Treatment of Asphyxia; Anti-Emetic Remedies; Nasal Douches ; Eye-Washes. Most Convenient Time- and Labor- Saving List Issued. It is evident to every one that this is, beyond question, the best and -mmost convenient time- and labor- saving Physicians’ Record Book ever published. Physicians of many years’ standing and with large practices pronounce this the Best List they have ever seen. It is handsomely bound in fine, strong leather, with flap, including a pocket for loose - memoranda, etc., and is furnished with a Dixon lead-pencil of excellent quality and finish. It is compact and convenient for carrying in the pocket. Size, 4 x 6% inches. + IN THREE STYLES—NET PRICES, POST-PAID. U.S.and Canada. Great Britain. France. | Vir. 75 ' No. Regular Size, for 70 patients daily each month for one year, $1.25 5s. 3. No, 2. Large Size, for 105 patients daily each month for one year, 1.50 .- 68.6. \9fr.35 No. 3. “In which “The Blanks for Recording Visits in’’ are in re- - + 1.795 Ws. 3. 12 fr. 20 ' movable sections, as described above, : . EXTRACTS FROM REVIEWS. «* While each page records only a week’s visits, ryet by an ingenious device of half leaves the names of.the patients require to be written but once a month, and a glance at an opening of the book shows the entire visits paid to any individual in a month. . It will be found a great convenience.”’— , Boston Medical and Surgical Fournal. «Everything about it is easily and quickly. " understood.”’—Canadian Praciitioner. “Of the many visiting lists before the profes- sion, each has some special feature to recommend it, This list is very ingeniously arranged, as by a Series of narrow leaves following a wider one, the name of the patient is written but once during the ‘month, while the account can run for thirty-one . days, space being arranged for a weekly debit and credit summary and for special memoranda. ‘The usual, pages for cash account, obstetrical record, addresses, etc., are included. A large amount of miscellaneous information is presented dn a condensed form.’”? — Occidental Medical Times. ; “Jt is a monthly instead of a weekly record, thus obviating the transferring of names oftener than once a month, There isa Dr. and Cr, column following each week’s record, enabling the doctor to carry a patient’s account for an indefinite time, ‘or until he is discharged, with little trouble.” — dndiana Medical Fournal. «* Accounts can begin and end at any date. Each name can be entered for each day of every month on the same line. To accomplish this, four leaves, little more than one-third as wide as the usual leaf of the book, follow each page. Oppo- site is a full page for the recording of special memoranda, The usual accompaniments of this class of books are made out with care and fitness.’” —The American Lancet. «This is a novel list, and an unusually con- venient one.” — Fournal of the Amer. Med. Assoc. «¢This new candidate for the favor of physi- cians possesses some unique and useful points. The necessity of rewriting names every week is obviated by a simple contrivance in the make-up of its pages, thus saving much valuable time, besides reducing the bulk of the book,” —Bugalo Medical and Surgical ¥ournal. «This list is an entirely new departure, and on a plan that renders posting rapid and easy. It is just what we have often wished for, and really fills a long-felt want.”—7he Medical Watf. «It certainly contains the largest amount of practical knowledge for the medical practitioner in the smallest possible volume, besides enabling the poorest accountant to keep a correct record, and render a correct bill at a moment’s noticc.””— Medical Chips. é —_-- (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 1b HAND-BOOK OF ECLAMPSIA; Notes and Cases of Puerperal Convulsions. BY a J. H. Stusss, M.D., R. B. Ewina, M.D., S. STEBBINS, M.D. E. MICHENER, M.D., 'B. THOMPSON, M.D., Price, in United States and Canada, Bound in Cloth, 16mo, Net, 75 Cents; in Great. Britain, 3 Shillings; in France, 4 fr. 20. In our medical colleges the teachers of Obstetrics @we/? upon the use of blood-letting (phlebotomy) in cases of puerperal convulsions, and to this method Dr. Michener and his fellows give their unqualified support—not to take a prescribed number of ounces, but to béeed for effect, and from a large orifice. This- is plainly and admifably set forth in his book. To bleed requires a cutting instrument,—not necessarily a. Jancet,—for Dr. M. states how in one case a pocket-knife was used and the desired effect produced. < Let the young physician gather courage from this little book, and let the’ more experienced give testi- mony to confirm its teaching. : aaa We have always thought that this treattnent was “lost art'’ of blood-letting, and we must commend the. ~ PP! , and practiced by F x and to such as doubt the efficacy of blood-letting we would commend this little volume.—Southern Clinic, he authors are seriously striving to restore the hysicians generally ; . modesty of their endeavor.—North Carolina Med. Jour. The cases were ably analyzed, and this plea for vene-- section ‘should receive*the most attentive consideration from obstetricians.—Medical and Surgical Reporter. TUST READY. A MANUAL OF INSTRUCTION ~ FOR GIVING Wedish Movement # Massage Treatment. BY PROF. HARTVIG NISSEN, Director of the Swedish Health Institute, Washington, D.C. ; Late Instructor in Physical Culture and Gymnastics at the Johns Hopkins University, Baltimore, Md. ; Author of “ Health by Exercise without Apparatus,’”’ ‘ ILLUSTRATED WITH 29 ORIGINAL WOOD-ENGRAVINGS. In One 12mo Volume of 128 Pages. Neatly Bound in Cloth. Price, post-paid, in United States and Canada, Net, $1.00; in Great Britain, 4s. 3d.; in France, 6 fr. 20. This is the only publication in the English language treating this very important: subject in a practical manner. Full instructions axe given regarding the mode of applying — ; . ~ ‘The Swedish Movement and Massage Treatment in various diseases and conditions of the human system with the greatest degree of effectiveness. Professor Nissen is the best authority in the United States upon this prac- tical phase of this subject, and his book is indispensable to every physician who wishes te- ” know how to use these valuable handmaids of medicine. This manual is valuable to the practitioner, as it contains a terse description of a subject but too little under- stood in this country, . 2... The book is got up very ‘oreditably.— WV. V. Med. Jow'. _ The present volume is a modest account of the appli- eqtion of the Swedish Movement and Massage Treatment, in which the technique of the various procedures are clearly stuted as well-as illustrated in a very excellent manner, —North American Practitioner, This little manual seems to be written by an expert, and to those who desire to know the details connected with the Swedish Movement atid Massage we commend 'the- book.— Practice. This attractive little book presents the subject in a very practical shape, and makes it possible for every. physician te- understand at least how it is applied, if it does not give him. dexterity in the art of its annlication. He can certainty’ acquire dexterity by following the directions so plainly vised in this book.—Chicago Med. Times. a It is so practical and clear in its demonstrations that: peruse this one.—Medical Brief. 16 CF. A. DAVIS, Medical Publisher, Philadelphia. Pa...U.S.A.) if you wish a work of this nature you cannot do better than: Ni JUST READY—THE LATEST AND BEST PHYSICIAN’S ACCOUNT- BOOK EVER PUBLISHED. —====THE PHYSICIAN'S === Account-Book: ALL-KEQUISITE TIMEz ann LABOR2 SAVING BEING A LEDGER AND ACCOUNT-BOOK FOR PHYSICIANS’ USE, MEETING ALL THE REQUIREMENTS OF THE LAW AND COURTS. DESIGNED BY WIbLIAM A. SHIBERT, DL.D., Of Easton, Pa. presse no class of people lose more money through carelessly kept accounts and overlooked or neglected bills than physicians. Often detained at the bedside of the sick until late at night, or deprived of _ even a modicum of rest, it is with great difficulty that he spares the ‘ time or puts himself in condition to give the same care to his own financial interests that a merchant, a lawyer, or even a farmer devotes. It is then plainly apparent that a system of bookkeeping and accounts that, without sacrificing accuracy, but, on the other hand, ensuring it, at the same time relieves the keeping of a physician’s book. of half their eomplexity and two-thirds the labor, is a convenience which will be eagerly welcomed by thousands of overworked physicians. Such a sys- tem has at last been devised, ahd we take pleasure in offering it to the profession in the form of THE Puysician’s ALL-Requisire TIME- AND, Lazor- Savina Account-Boox. ; There is no exaggeration in stating that this Account-Book and Ledger reduces the labor of keeping your accounts more than one-half,. and at the same time secures the greatest degree of accuracy. We may mention a few of the superior advantages of Tur Puysictan’s ALL- Requisite TimE- AND Lazsor- Savina Account-Book, as follow:— First—Will meet all the requirements of the law and courts. Second—Self-explanatory ; no cipher code. Third—Its completeness without sacrificing anything. Fourth—No posting ; one entry or Fifth—Universal; can be commenced at any time of year, and can be continued in- definitely until every account is filled. Sixth—Absolutely no waste of hae ; _ Seventh—One person must needs be sick every day of the year to fill his account, or might be ten years about it and re- quire no more than the space for one account in this ledger. of Eighth—Double the number and many times * more than the number of accounts in any similar book; the 300-page book ‘contains space for 900 accounts, and the: 600-page book contains space for 1800 accounts. linth—There are no smaller spaces. Tenth—Compact without ke eae com- pleteness; every account complete on same page—a decided advantage and recommendation. Eleventh—Uniform size of leaves. Twelfth—The statement of the most com- plicated account is at once before you at any time of month or year—in other words, the account itself as it stands is its simplest statement. Thirteenth—No transferring of accounts, balances, etc. To all physicians desiring a quick, accurate, and comprehensive _ method of keeping their accounts, we can safely say that no book as ‘suitable as this one has ever been devised. NET PRICES, SHIPPING EXPENSES PREPAID. No.1. 300 Pages, for 900 Accounts per Year, Canada. Great 7 ‘ ae Shes oud d in % Russia, Raised InU.S. (duty paid). © Britain. France. Back-Bands, Cloth Sides, . $5.00 $5.50 £0.18s. 30 fr. 36 No. 2. 600 Pages, for 1800 Accounts per Year, Size 10x12, Bound in % Russia, Raised m . 8.00 8.80 1.13s. 49 fr. 40 “ Back-Bands, Cloth Sides, o CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 17 PHYSICIANS INTERPRETER | IN FOUR LANGUAGES. (ENGLISH, FRENCH, GERMAN, AND ITALIAN. ) Specially Arranged for Diagnosis by M. von V. The object of this little work is to meet a need often keenly felt by the busy physician, namely, the need of some quick and reliable method of communicating intelligibly with patients of those nationalities and languages unfamiliar to the practitioner. The plan of the book is a sys- tematic arrangement of questiofis upon the various branches of Practical Medicine, and each question is so worded that the only answer required of the patient is merely Yes or No. and a complete Index renders them always available for quick reference. ‘ The questions are all numbered, The book is written by one who is well versed in English, French, Ger- man, and Italian, being an excellent teacher in all those languages, and who has also had considerable hospital experience. ie Bound in Full Russia Leather, for Carrying in the Pocket. (Size, 5x23 Inches.) 206 Pages. Price, post-paid, in United States and Canada, $1.00, net; Great Britain, 4s. 6d.; France, 6 fr. 20. To convey some idea of the scope of the questions contained in the - Physicians’ Interpreter, we append the Index :— General health Special diet... . Age of patient... Necessity of patients undergoing an opera- HON. conicse ee aes nels fora aieadecsitin ng heiaee seas 63- 70 wisciee .- 71-77 Days of the week. . seis wea 78— 84 Patient’s history: hereditary affections in his family; his occupation; diseases from his childhood up,........... ee ceeeeteee 85-136 Months of the year........... ovte ses Seasons of the year..............66, Symptoms of typhoid fever., .. Symptoms of Bright’s disease... ween o E5Q—168 Symptoms of lung diseases... .169-194 and 311-312 WMI Oa). deae dace ais vin taerictartartea kia eseeeeTQ5-208 PRR OK ES: clans Po sseuswdanan sameness oie 201=232 Paralysis and rheumatism..... » «236-260 Stomach complaints and chills.............. 261-269 The work is well done, and calculated to be of great service to those who wish to acquire familiarity with the h used in questioning More than this, we believe it would be a great help in acquiring a vocabulary to be used in reading medical books, and that it would fur- nish an excellent basis for beginning a study of any one of the languages which it inclydes.—Medical and Surgical Reporter. Many other books of the same sort, with more ex- tensive vocabularies, have been published, but, from their size, and from their being usually devoted to equivalents in English and one other language only, they have not had the advantage which is pre-eminent in this—convenience. It is handsomely printed, and bound in flexible red leather in the form of adiary. It would scarcely make itself felt in one’s hip-pooket, and would insure its bearer againstany ordinary conversational difficulty in dealing with foreign-. speaking people, who ‘are constantly coming into our city hospitals.— New York: Medical Journal. ‘ In our larger cities, and in the whole Northwest. the physician is constantly meeting with immigrant patients, to whom it is difficult for him to make himself understood, or to know what they say in return. This difficulty will NOS. Falls and fainting spells...............2.0-- 271-2977 How patient’s illness began, and when pa- tient was first taken sick........ Soe Names for various parts of the body....... "283-299 The liver.....ctcceeeseseceeeeeues aan ake The memory,........ Bites, stings, pricks. . Eruptions : Previous treatment, . . Symptomsof lead-poisoning................ 320-324 Hemorrhages,...5 4. J..50806% cea ea WARES 325-328 7 Burns and sprains 339-331 The throat The ears. PGR GO nda econes General directions concerning medicines, ~ baths, bandaging, gargling, painting swelling, etc..... 02... aetanstea ee wee 6 63409373 NUMDbeIS isc sa eae ee acess se sa bie cared pages 202-204 | be greatly obviated by use of this little work.— The Phy-, sician and Surgeon. ; The phrases are well selected, and one might practice’ long without requiring more of these languages than this .. little book furnishes.—Phila, Medical Times. . How oftcn the physician is called to attend those with whom the English language is unfamiliar, and many phy- sicians are thus deprived of the means, save through an interpreter, of arriving at a correct knowledge on which to base a diagnosis. An interpreter is not always at hand, but with this pocket interpreter in your hand you are able to ask all the questions necessary, and receive the answer in such manner that you will be able to fully comprehend. —The Medicul Brief. This little volume is one of the most ingenious. aids to the physician which we have seen. We heartily com- mend the book to any one who, being without a knowled of the foreign languages, is obliged to treat those who do not know our own language.—St. Louis Courier of Hedi- cine. It will rapidly supersede, for the practical use of the doctor who cannot take the time to learn another language, all other suggestive works.—Chicago Medical Times. pena AE ARIE AS ‘ 18 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) An Important Aid to Students in the Study of Anatomy. _ THREE CHARTS OF The Nervo-Vascular System. Se eee vara ARRANGED BY W. HENRY PRICE, A.M., M.D., AND S. POTTS EAGLETON. ENDORSED BY LEADING ANATOMISTS. PRICE, IN THE UNITED STATES AND CANADA, 50 CENTS, NET, COMPLETE ; GREAT BRITAIN, 2s. 6d. FRANCE, 3 fr. 60. “NHE NERVO-VASCULAR SYSTEM OF CHARTS” far Excels Every é 3 Other System in their Completeness, Compactness, and Accuracy. - e Part I. The Nerves.—Gives in a clear form not only the Cranial and Spinal Nerves, showing the formation of the different Plexuses and their branches, but also the complete distribution of the SYMPATHETIC Nerves, thereby making it the most complete and — concise chart of thé Nervous System yet, published. ' ae: Part Il. The Arteries.—Gives a unique grouping of the Arterial System, showing the divisions and subdivisions of all the vessels, beginning from the heart and tracing their continuous distribution to the periphery, and showing at a glance the terminal branches of each artery. Part III. The Veins.—Shows how the blood from the periphery of the body is gradually collected by the larger veins, and these coalescing forming. still larger vessels, until they finally trace ‘themselves into the Right Auricle of the heart. * , It is therefore readily seen that ‘The Nervo-Vascular System of Charts” offers the following superior advantages :— 1. It is the ‘only arrangement which combines the Three Systems, and yet each is perfect and distinct in itself. , . 2. It is the only instance of the Cranial, Spinal, and Sympathetie - Nervous Systems being represented on one chart. 3. From its neat size and clear type, and being printed only upon one side, it may be tacked up in any convenient place, and is always : ready for freshening up the memory and reviewing for examination. _ 4. The nominal price for which these charts are sold places them within the reach of all. : ; : a x veins of the human body, giving names, origins, distribu- For the student of anatomy there can possibly be no , tions, and functions, very convenient as memorizers and more concise wiy of acquiring a knowledge of the nerves, veins, and arteries of the human-system. It presents at a glance their trunks and branches in the great divisions of the body. It will save a world of tedious Foading, and will impress itself on the mind as no ordinary vade mecum, even, could. Its price is nominal and its ‘OF THE DoMESTIC ANIMALS. | STUDENTS AND PRACTITIONERS. —BY—— ROBERT MEADE SMITH, A.M., M.D., Professor of Comparative Physiology in University of Pennsylvania; Fellow of the College of Physicians and Academy of the Natural Sciences, Philadelphia ; of the American Physiological Society ; of the American Society of Naturalists; Associé Etranger - de la Société Frangaise D’ Hygiene, etc, « if , Fic, 117.—PARoTID AND SUBMAXILLARY FisTuL2 IN THE HorsE, AFTER COLIN. (Thanhoffer and Tormay.) K, K/, rubber bulbs for collecting saliva ;'cs, cannula in the parotid duct. In One Handsome Royal Octavo Volume of over 950 Pages, Pro- fusely Tllustrated with, more than 400 Fine Wood- Engravings and many Colored Plates. ° United States. Canada (duty paid). Great Britain. | France. NETS PRICES, CLOTH,. .. .. $5.00 . $5.50 £71. 30 fr. 30. i SHEEP,., ... 6.00 6.60 7.6. 36 fr. 28. TH new and important work, the most thoroughly complete in the English language |.’ on this subject, has just been issued. In it the physiology of the domestic animals. . is treated in a most comprehensive manner, especial prominence being given to the sub- >. ject of foods and fodders, and the character of the diet for the herbivora under different. — conditions, with a full consideration of their digestive peculiarities. Without being over-°. |: burdened with details, it forms a complete text-hook of physiology, adapted to the use of ~ students and practitioners of both veterinary and human medicine. This work has already , been adopted as the Teat-Book on Physiology in the Veterinary Colleges of the United . .. States, Great Britain, and Canada. ‘ meee oy CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) ABSTRACTS FROM NREVIEWS22OMITH’S PHYSIOLOGY. Ss es _, The work throughout is well balanced. : ‘Broad, though not encyclopedic, concise " without sacrificing clearness, it combines the essentials of a successful text-book. It * 18 eminently modern, and, although first in the field, is of such grade of excellence that successors must reach a high standard be- fore they become competitors—Annals of Surgery. - - Dr. Smith has conferred a great benefit upon the veterinary profession by his con- ' tribution to their use of a work of immense value, and has provided the American vet- erinary student with the only means b which he can become properly familiar wit! the physiology of our domestic animals. Veterinary practitioners and graduates will read it with pleasure. Veterinary students will readily acquire needed knowledge from its pages, and veterinary schools which would be well equipped for the work they aim to at capnot ignore it as their text-book in physiology — American Vetert- nary Renew. : Dr. Smith’s presentment of his subject _ is as brief as the status of the science per- mits, and to this much-desired conciseness he has added an equally welcome clearness of statement. The illustrations in the work are exceedingly good, and must-prove a valuable aid to the full understanding of the text—Journal of Comparative Medicine and Surgery. We have examined the work in a great many particulars, and find the views so correct, where we have had the means of comparison of statements with those of some recognized authority, that we will be com- pelled hereafter to look to this work as the text-book on physiology of animals. The book will prove of incalculable benefit to eterinarians wherever they may be found; and to the country physician, who is often ‘called upon to attend to sick animals as - well as human beings, we would say, lose no time in getting this work and-let him familiarize himself with the facts it con- tains.— Virginia Medical Monthly. Altogether, Professor Smith’s “ Physi- ology of the Domestic Animals” is a ha production, and will be hailed with delight in both the human medical and veterinary medical worlds. It should. find its place besides in all agricultural libraries.—Pauu Paquin, M.D., V.S., in the Weekly Metical Review. P It may be said that it. supplies to th veterinary student the place in physiology that Chauveau’s incomparable work—“ The ’ Comparative Anatomy of the Domesticated Animals”—occupies in anatomy. Higher praise than this it is not possible to bestow. And since it is true that the same laws of physiology which are applicable to the vital process ofthe domestic animals are also ap- plicable to man, a perusal of this carefully written book will repay the medical student or practitioner.— Canadian Practitioner. The work before us fills the hiatus of which complaint has so often been made, and gives in the compass of less than a thousand pages a very full and. complete account of the functions of the body in both carnivora and herbivora. The author has judiciously made the nutritive functions the strong point of the work, and has devoted special attention to the subject of foods and igestion. In looking through the other sections of the work, it appears to us that a just proportion of space is assigned to each, in view of their relative importance to the practitioner. Thus, while the subject of re- production is dismissed in a few pages, a chapter of considerable length is devoted | to locomotion, and especially to the gaits of the horse —London Te : This is almost the only work of the kind in the English language, and it se fully covers every detail of general and special physiology that there is no room for any rival. he excellence of typographical work, and the wealth, beauty, and clear- ness of the illustrations, correspond with the thoroughness and clearness of the treatise — Albany Medical Annals. It is not often that the medical profes- | sion has the opportunity of reading a new book upon a new subject, and doubtless English-speaking physicians will feel grate- ful to Professor Smith for his admirable and pioneer work in a branch of medical science upon which a great amount of ignor- ance prevails. The last portion of the work is devoted to the reproductive functions, and contains much valuable in- formation upon a portion of animal physi- ology concerning which many are ignorant. The book is a valuable one in every way, and will be consulted largely by veterinary and medical students and practitioners.— Buffalo Medical and Surgical Journal. The appearance of this work is mosb op- portune. It will be much appreciated, as tending to secure the thorough comprehen- sion of function in the domesticated ani- mals, and, in consequence, their general well-being—a matter of world-wide aa tance. ith a thorough sense of gratifica- tion we have perused its pages: throughout we find clear expression, clear reasoning, and that patient accumulation of facts so valuable in a text-book for students — British Medical Journal. For notice this time, I take up the vol- ume on the “Physiology of the Domestic Animals,” by Dr. R. Meade Smith, a volume of 938 pages, closely printed, and dealing with its subject in a manner oatnarae ex- haustive to insure its ae as a text-book for fifteen years at t % very least. Its learning is only equaled by its industry, and its industry by the consistency and skill with which its varied parts are brought together into harmonious, lucid, and in- tellectual unity—Dr. Bensamin . Warp Ricnarpson, in the London Asclepiad. — ~ nas CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U. S.A. ») 35 international Pocket Medical Formulary, ARRANGED THERAPEUTICALLY. = : By @. SUMNER WITHERSTINE, M.S., M.D., Associate Editor of the “Annual of the Universal Medical Sciences ;’’ Visiting Physician of the Home for the Aged, Germantown, Philadelphia ; Late House-Surgeon Charity Hospital, New York. More than 1800 Formule from Several Hundred Well-Known Authorities. ‘With an Appenp1x containing a Posological Table, the newer remedies included ; Important Incompati- bles ; Tables on Dentition and the Pulse ; Table of Drops in a Fluidrachm and Doses of Laudanum graduated for age; Formule and Doses of Hypodermic Medication, including the newer remedies; Uses of the Hypo- dermic Syringe; Formula and Doses for Inhalations, Nasal Douches, Gargles, and Eye-washes ; Formula for Suppositories; Use of the Thermometer in Disease; Poisons, Antidotes, and Treatment; Directions for Post-Mortem and Medico-Legal Examinations; Treatment of Asphyxia, Sun-stroke, etc.; Anti-emetic Remedies and Disinfectants; Obstetrical Table; Directions for Ligation of Arteries ; Urinary Analysis; Table of Eruptive Fevers : Motor Points for Electrical Treatment, etc., etc. 1 This work, thé best and most complete of its kind, contains about 275 printed pages, besides extra blank leaves. Elegantly printed, with red lines, edges, and borders; with illustrations. Bound in leather, with side flap. It contains more than 1800 Formule, exclusive of the large amount of other very valuable matter. Price, Post-paid, in the United States and Canada, $2.00, net;: ; Great Britain, 8s. 6d.; France, 12 fr. 40. WHY EVERY MEDICAL MAN SHOULD POSSESS A COPY OF TEN REASONS THE INTERNATIONAL POCKET MEDICAL FORMULARY. 1. Because it is a handy book of reference, replete with the choicest formula (over 1800 in number) of more than six hundred of the most prominent classical writers and modern practitioners. 2. Because the remedies given are not only those whose efficiency has stood the test of time, but aiso the newest and latest discoveries in pharmacy and medical science, as prescribed and used by the best- known American and foreign modern authorities. 3. Because it contains the latest, largest (66 formulz) and most complete collection of hypodermic formula (including the latest new remedies) ever published, with doses and directions for their use in over fifty different diseases and diseased conditions. |“ 4. Because its appendix is brimful of information, invaluable in office work, emergency cases, and the daily routine of practice. 3 5. Because it is a reliable friend to consult when, in a perplexing or obstinate case, the usual line of treat- ment is of no avail. (A hint or a help from the best authorities, as to choice of remedies, correct dosage, and the eligible, elegant, and most palatable mode of exhibition of the same.) 6. Because it is compact, elegantly printed and bound, well illustrated, and of convenient size and shape for the pocket. : ee] Because the alphabetical arrangement of the diseases and a thumb-letter index render reference rapid and easy. ' ig % favorite formulz. Because, as a student, he needs it for study, collateral reading, and for recording the favorite prescriptions of his professors, in lecture and clinic; as a recent graduate, he needs it as a reference hand-book for daily use in prescribing (gargles, nasal douches, inhalations, eye-washes, suppositories, incompatibies, poisons, etc.) ; as an old practitioner, he needs it to refresh his memory on old remedies and combi- nations, and for information concerning newer remedies and more modern approved plans of treatment. te 10. Because no live, progressive medica] man can afford to be without it. ‘ It is sometimes important that such prescriptions as As long as “combinations are sought'such a book Bécause blank leaves, judiciously distributed throughout the book, afford a place to record and index : have been well established in their usefulness be preserved for reference, and this little volume serves such a purpose better than any other we have seen.—Colwmbus Medical Journal. Without doubt this book is the best one of its class that we have ever seen. . . . . The printing. binding. and general appearance of the volume are beyond praise.— University Medical Magazine. It may be possible to get move crystallized knowledge in an equally small space, but it does not seem probable.— ' Medical Classics. A very handy and valuable book of formule for the physician's pocket.—St. Louis Medical and Surg. Journal. This little pocket-book contains an immense number of prescriptions taken from high authorities in this and other countries.— Northwestern Lancet. This one is the most complete as well as the most conveniently arranged of any that have come under our attention. "The diseases are enumerated in alphabetical order, and for each the latest and most approved remedies from the ablest authorities are prescribed. The book is in- dexed entirely through after the order of the first pages of a ledger, the index letter being printed on morocco leather and thereby made very durable.—Pacijic Medical Journal. : It is a book desirable for the old practitioner and for his younger brothers as well.—St. Joseph Medical Herald. will be of value, especially to those who cannot spare the time required to learn enough of incompatibilities before commencing practice to avoid writing incompatible and dangerous prescriptions. The constant use of such a book by such. prescribers would save the pharmacist much anxiety.— The Druggists’ Circular. In judicious tion, in rat Tature. in arrangement, and in style it leaves nothing to be desired. The editor and the publisher are to be congratulated onthe « production of the very best book of its elass.— Pittsburgh Medical Review. One must see it to realize how much information can be got into a work of so little bulk.—Crneede Medical Record, . To the young physician just starting out in practice this little book with prove an acceptable companion.— Omaha Clinic, The want of to-day is crystallized knowledge. “I'his - neat little volume contains in it the most accessible form. Tt is bound in morocéo in pocket form, with alphabetical divisions of diseases, so that it is possible to turn instantly to the remedy, whatever may be the disorder or wherever the patient may be situated. . ... . To the physician ~ it is invaluable, and others should not he without it. We - heartily commend the work to our readers.— Minnesota Medica! Journal. %6 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) “ _tant subject. The section on the teeth. has also been tration better than most medical subjects, and, as ». the‘accuracy of this little book is beyond question, facts, and the book will be found very convenient | Pittsburgh Medical Review. ‘and Surgical Anatomy. _been taken as the standard. JUST ISSUED. PHYSICIANS’ AND STUDENTS’ READY-REFERENCE SERIES. Se ynopsis of Human Anatomy: Being a Complete Compend of Anatomy, including the Anatomy of the Viscera, and Numerous Tables. BY JAMES K. YOUNG, M.D., Instructor in Orthopedic Surgery and Assistant Demonstrator of Surgery, University of Pennsylvania; Attending Orthopedic Surgeon, Out-Patient epartment, University Hospital, etc. ILLUSTRATED WITH 76 WOOD-ENGRAVINGS. 390 PAGES. : 12mo. HANDSOMELY BOUND IN DARK-BLUE CLOTH. Price, Post-paid, in the United States and Canada, $1.40, net; : Great Britain, Gs. 6d.; France, 9 fr. 25. c While the author has prepared this work especially for students, sufficient de- scriptive matter has been added to render it extremely valuable to the busy practitioner, particularly the sections on the Viscera, Special Senses, : The work includes a complete account of Osteology, Articulations and Ligaments, Muscles, Fascias, Vascular and Nervous Systems, Alimentary, Vocal, and Respiratory and Genito-Urinary Apparatuses, the Organs of Special Sense, and Surgical Anatomy. ‘In addition to a most carefully and accurately prepared text, wherever possible, the value of the work has been enhanced by tables to facilitate and minimize, the labor of students in acquiring a thorough knowledge of this impor- especially prepared to meet the requirements’ of students of Dentistry. ; In its preparation, Gray’s' Anatomy [last edition], edited by Keen, being the anatomical work most used, has 1 ; Anatomy is a theme that allows such concen- | Excellent tables have been arranged, which tersely and clearly present important’ anatomical its value is‘assured. As a companion to the dis- for ready reference.—Columbus Medical Yournad. “secting-table, and a convenient reference for the The book is much more satisfactory than the practitioner, it has a definite field of usefulness.— ‘*remembrances’’ in vogue, and yet is not too cum- bersome to be carried around and read at odd This is a very carefully prepared compend of || moments—a property which the student will readily anatomy, and will be useful’ to students for college appreciate —Weekly Medical Review. or hospital examination. There are some excellent If a synopsis of human anatomy may serve a tables in the work, particularly the one showing the purpose, and we believe it does, it is very important origin, course, distribution, and functions of the that the synopsis should be a good one. — In this cranial nerves.—Medical Record. respect the above work may be recommended asa Dr. Young has compiled a very useful book. || reliable guide. Dr, Young has shown excellent Weare not inclined to approve of compends as a || judgment in his selection of illustrations, in the general rule, but it certainly serves a good purpose numerous tables, and in the classification of the - to have the subject of anatomy presented in a com- various subjects. — Therapeutic Gazette. pact, reliable way, and in a book easily carried to Every unnecessary word has been excluded. out the dissecting-room. This the author has done. of regard to the very limited time at the medical The book is well printed, and the illustrations well student’s disposal. It is also good as a reference “selected. 1f a student can indulge in more than one || book, as it presents the facts about which he wishes © work 6n anatomy,—for, of course, he must havea |} to refresh his memory in the _ briefest manner. general treatise on the subject,—he can hardly do consistent with clearness.— New Vork Medical better than to purchase this compend _ It will save Journal the larger work, and can always be with him during {t is certainly concise and accurate, and should the hours of dissection.—Buffalo Medical and || bein the hands of every student and practitioner.— Surgical Fournal. | The Medical Brief. (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 27 -Universa edical IM a A N N is oo Oe Sciences. A YEARLY REPORT OF THE PROGRESS OF THE. GENERAL SANITARY SCIENCES THROUGHOUT THE WORLD. Edited by CHARLES E. SAJOUS, M.D., LECTURER ON LARYNGOLOGY AND RHINOLOGY IN JEFFERSON MEDICAL COLLEGE, PHILADELPHIA, ETC., AND ‘SEVENTY ASSOCIATE EDITORS, Assisted by over TWO HUNDRED Corresponding Editors and Collaborators. In Five Royal Octavo Volumes of about 500 pages each, bound in Cloth and Half- Russia, Magnificently Illustrated with Chromo-Lithographs, Engravings, ‘ Maps, Charts, and Diagrams. === BEING INTENDED =—— Ist. To assist the busy of all the branches of his p 3 ‘0: ractitioner in his effo fession. rts to keep abreast of the rapid strides 2d. To avoid for him the loss of time involved in searching for that which is new in the profuse and constantly increasing medical literature of our day. $d. To enable him to obtain the greatest ossible benefit of the limited time he is able to devote to reading, by furnishing him with new matter onLy. 4th. To keep him informed of the work done by aux nations, including many other- wise seldom if ever heard from. é 5th. To furnish him with a review of all the new matter contained in the periodicals to which he cannot (through their immense number) subscribe. 6th, To cull for the specialist all that is of a progressive nature in the general and special publications of all nations, and obtain for him special reports from countries in which such publications do not exist, and Lastly, to enable any physician to possess, at a moderate cost, a complete CONTEMPORARY HISTORY OF UNIVERSAL MEDICINE, edited by many of America’s ablest teachers, and superior in every detail, of reat works as ‘“ Pepper binding, etc., etc., a befitting continuation of such rint, paper, A System of Medicine,” ‘“Ashhurst’s International Encyclopedia of Surgery,” ‘ Buck’s Reference Hand-Book of the Medical Sciences,” etc., etc. - ‘ - BDITORIAL STAFF of the ANNUAL of the UNIVERSAL MEDICAL SCIBNCES. ISSUE OF 1888. —Chief Editor, DR. CHARLES E. SAJOUS, Philadelphia. —_ ASSOCIATE STARE. Volume I.—Obstetrics, Gynecology, Pediatrics, Anatomy, Physiology, Pathelogy, Prof. Wm. L. Richardson, Boston. Prof. Theophilus Parvin, Philada. Prof. Louis Starr, bitey cee Prof. J. Lewis Smith, New York Prof. Paul F. Mundé and Dr. E. \ Grandin, New York City. City. . Histology, and Embryology. elphia. Prof. H. Newell Martin and Dr. W. H. Howell, Baltimore. Dr. Chas. S. Minot, Boston. Dr. E. O. Shakespeare, Philadelphia. Dr. W, X. Sudduth, Philadelphia. > Volume II.— Diseases of the Respiratory, Circulatory, Digestive, and Nervous. Systems; Prof. A. L. Loomis, New York City. Prof. Jas. T. Whittaker, Cincinnati. Prof. W. H. Thomson, New York City. Prof. W. W. Johnston, Washington. Prof Jos. Leidy, Philadelphia. Fevers, Exanthemata, etc., ete. Prof. E. C. Seguin, New York City. - Prof. E. C. Spitzka, New York City. Prof.Chas.K. Mills and Dr. J. H.Lloyd, Philadelphia, Prof. Francis Delafield, N. Y. City. Prof. Jas. Tyson, Philadelphia. Prof. N. S. Davis, Chicago. Prof. John Guitéras, Charleston, S. C, Dr. Jas. C. Wilson, Philadelphia. Volume TI.— General Surgery, Venereal Diseases, Ancesthetics, Surgical Dressings, Prof. D. Hayes Agnew, Philadelphia. Prof. Hunter McGuire, Richmond. Prof. Lewis A. Stimson, New York. Prof. P. §. Conner, Cincinnati. Prof. J. Ewing Mears, Philadel phi. Prof. E. L. Keyes, New York City. Volume IV.— Ophthalmol Prof. William Thomson, Philadelphia. Prof. J. Solis Cohen, Philadelphia. Prof. D. Bryson Delavan, New York. Prof. A. Van Harlingen, Philadelphia. 28 Hygiene, Disposal of the Dietetics, etc., etc. Prof, F. R. Sturgis, New York City. Prof. N. Senn, Milwaukee. Prof. J. E. Garretson, Philadelphia. Prof. Christopher Johnston, Baltimore. Dr. Chas: B. Kelsey, New York City. ogy, Otology, Laryngology, ead, et Prof. C. N. Peirce, Philadelphia. Prof. John B. Hamilton, Washington. Prof. H. M. Lyman, Chicago. Prof, 8. H. Guilford, Philadelphia. | Prof. T. G. Morton and Dr. Wm. Hunt, Philadelphia. : Dr. Morris Longstreth, Philadelphia. Dr. Chas. Wirgman, Philadelphia. Dr. C. C. Davidson, Philadetptiia....: Rhinology, Dermatology, Dentistry, c., ete. Dr. Chas. S. Turnbull, Philadelphia. Dr, Edw. C. Kirk, Philadelphia. Dr. John G. Lee, Philadelphia. Dr. Chas. E. Sajous, Philadelphia. \ Last of Collaborators to Dental Department. Prof, James Truman, Philadelphia. Prof. E. H. Angi i i i 5 i " . E. H. Angle, Minneapolis, Minn. Dr. J. D. Patterson, Kansas @it: , Me. Prof. J. A. Marshall, Chicago, Ill. Prof. J. E. Cravens, Indianapolis, Ind. | Dr. J. B. Hodgkin, ‘Washington. pe: A, Chicago, Ill. Prof. R. Stubblefield, Nashville, Tenn. | Dr. RB. RB. Andrews, Cambridge, Mags. ane G. V. Black, Chicago, Ill. : Prof. W. C. Barrett, Buffalo, N. Y. Dr. Albion M. Dudley, Salem, Mass. Pre - C. H. Stowell, Ann Arbor, Mich. | Prof. A. H. Thompson, ‘Topeka, Kan. Dr. Geo. 8S. Allen, New York City. 3 f. L. C. Ingersoll, Keokuk, Iowa. Dr. James W. White, Philadelphia. Dr. G. S. Dean, San Francisco, Cal. poe F.J.S. orgas, Baltimore, Md. | Dr. L. Ashley Fau ht, Philadelphia. Dr. M. H. Fletcher, Cinci: i, Ohio. Bee H. A. Smith, Cincinnati, Ohio. | Dr. Robert 8. I: , Philadelphia. Dr. A. Morsman, Omaha, Neb. rof. C. P. Pengra, Boston, Mass. Dr. W. Storer How, Philadelphia. Dr. G. W. Melotte, Ithaca, N. Y. ‘Volume V.—General and Experimental Therapeutics, Medical Chemistry, Medical . Jurisprudence, Demography, Climatology, etc., ete. Prof. William Pepper, Philadelphia. Prof. George H. Rohé, Baltimore. Dr. W. P. Manton, Detroit i Brof. F. W. Draper, Boston: Dr. Albert L. Gihon, v. 8.N. Dr. Hobart A. Hare, Philadelptin. J. Ww, , Philadelphia. rR. J. ison, Philadelphia. . C. 8. Wi i i i Prof A. Lc Ranaan Nee City. unglison, tp ia. Dr. C. 8. Witherstine, Philadelphia, TES SUBSCRIPTION PRIcE (Including the “SATELLITE” for one year). United States. Canada (duty paid). Great Britain. France. Cloth, 5 Vols., Royal Octavo, - - 15.00 $16.50 £3.65. 93 fr. 95 Half-Rusaia, 5 Vols., Royal Octavo, - 20.00 22.00 4.68. 124 fr. 35 EXTRACTS FROM REVIEWS. .. We venture to say that-all who saw the ANNUAL as it appeared in 1888 were on the lookout for its reappearance this (1889) year; but there are many whose knowledge of this magnificent undertaking will date with this present issue, and to those a mere examina-. tion of the work will suffice to show that it fills a legitimate place in the evolution of knowledge, for it does what no single individual is capable of doing. ; These volumes make readily available to the busy practitioner the best fruits of medical progress for the year, selected by able editors from the current literature of the ° world; such a work cannot be overlooked by anyone who would keep abreast of the times. With so much that is worthy of notice incorporated in one work, and each depart- - ment written up with a minuteness and thoroughness appreciated particularly by the specialist, it would avail nothing to cite particular instances of progress. Let it be suffi- cient to say, however, that while formerly there was a possible excuse for not having the latest information on matters pertaining to the medical sciences, there can no longer be such an excuse while the ANNUAL is published—Journal of the American ie Association. ‘We have before us the second issue of this ANNUAL, and it is not speaking tuo edical -- strongly when we say that the series of five volumes of which it consists forms a most ; Amportant and valuable addition to medical literature. Great discretion and Poowiedye of the subjects treated of are required at the hands of those who have taken charge of the various sections, and the manner in which the gentlemen who were chosen to fill the important posts of sub-editors have acquitted ~ themselves fully justifies the choice made. We know of no branch of the profession to which this AnnvAL could fail to be useful. Dr. Sajous deserves the thanks of the whole, profession for his successful attempt to facilitate the advance of medical literature and practice —London Lancet. : This very valuable yearly report of the progress of medicine and its collateral . sciences throughout the world is a work of very great magnitude and high importance. It is edited by Dr. C. E. Sajous, assisted, it is stated, b seventy associate editors, whose names are given, making up a learned and most weighty list. Their joint labors have combined to produce a series of volumes in which the current progress throughout the world, in respect to all the branches of medical science, is very adequately represented. The general arrangements of the book are ingenious and ae having regard to thoroughness and to facility of bibliographical reference.—British Medical Journal. . ANNUAL, [890. The editor and publishers of the ANNUAL OF THE UNIVERSAL Meprcat Sciences take this opportunity to thank its numerous friends and patrons for the liberal support accorded it in the past, and to announce its publication, as usual, in 1890. Recording, as it does, the progress of the world in medicine and surgery, its motto continues to be, as in the past, “ Improvement,”.and its friends may rest assured that _ no effort wilk be spared, not only to maintain, but to surpass, the high standard of excellence already attained. ; The Subscription Price will be the same as last year’s issue and the issue of 1888. (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 29 —~— ISSUE OF 1889—==— The Annual of the Universal Medical Sciences. In Five Royal Octavo Volumes of over 500 pages each, bound in Cloth aud ‘ Half-Russia, Magnificently Dlustrated with Chromo-Lithographs, ‘ Engravings, Maps, Charts, and Diagrams. THE SUBSCRIPTION PRICE C including the “Satellite” for one year). - 3 United States. Canada (duty paid). Great Brituin. France. Cloth, 5 Vols, Royal Octavo, - - $15.00 $16.50 | £3.68, 93 fr. 95 Half-Russia, 5 Vols., Royal Octavo, - 20.00 22.00 4,65, 124 fr. 35 This work is bound in above styles only, and sold by subscription. PUBLISHED IN CONNECTION WITH THE ANNUAL AND FOR SUBSCRIBERS ONLY. THE SATELLITE —OF THE— ANNUAL OF THE UNIVERSAL MEDICAL SCIENCES. _ A’ Monthly Review of the most important articles upon the practical branches of medicine appearing in the medical press at large, edited by the Chief Editor of the ANNUAL and an able staff. Editorial Staff of the Annual of the Universal Medical Sciences, issue of 1889. Chief Editor, Dr. CHAS. EH. SAJOUS, Philadelphia. ASSOCIATH STAFF. Volume I.—Diseases of the Lungs, Diseases of the Heart, Diseases of the Gastro- Hepatic System, Diseases of the Intestines, Intestinal Entozoa, Diseases of the Kidneys and Bladder, Fevers, Fevers in Children, Diphtheria, Rheu- matism and Gout, Diabetes, Volume Index. ; : Prof, Jas. T. Whittaker, Cincinnati. ' Dr, Jas. C. Wilson, Philadelphia. Prof, A. L. Loomis, New York City. | Prof. Louis Starr, Philadelphia. Prof. E. T Bruen, Philadelphia.” | Prof. J. Lewis Smith, New York. - Prof. W. W. Johnston, Washington. : Prof. N. S. Davis, Chicago. Dr. L. Emmett Holt, New York. | Prof. Jas. Tyson, Philadelphia. Prof. Jos. Leidy, Philadelphia. a4 ; ; Volume II.—Diseases of the Brain and Cord, Peripheral Nervous System, Mental ‘Diseases, Inebriety, Diseases of the Uterus, Diseases of the Ovaries, Diseases of the External Genitals in Women, Diseases of Pregnancy, Obstetrics, Dis- eases of the Newborn, Dietetics of Infancy, Growth, Volume Index. Prof. E. C. Seguin, New York City. Prof W. H. Parish, Philadelphia. Prof. Henry Hun, Albany. Prof. Theophilus Parvin, Philadelphia. Dr. E. N. Brush, Philadelphia. * Prof. Wm. L. Richardson, Boston. Dr. W. R. Birdsall, New York, Dr. A. F. Currier, New York. Prof. Paul F. Mundé, New York City. Prof, Louis Starr, Philadelphia. 2 Prof. Wm. Goodell, Philadelphia. Dr. Chas. S. Minot, Boston. : < Dr. W. C. Goodell, Philadelphia. Volume III.—Surgery of Brain, Surgery of Abdomen, Genito-Urinary Surgery, Dis- eases of Rectum and Anus, Amputation and Resection and Plastic. Surgery, Surgical Diseases of Circulation, Fracture and Dislocation, Military Surgery, ~ Tumors, Orthopedic Surgery, Oral Surgery, Surgical Tuberculosis, ete., Sur- gical Diseases, Results of Railway Injuries, Anesthetics, Surgical Dressings, Volume Index. : fey Prof, N. Senn, Milwaukee. Petey 4 Prof, D. Hayes Agnew, Philadelphia, Prof. E. L. Keyes, New York City. Prof. J. Ewing Mears, Philadelphia. Dr. Chas. B. Kelsey, New York City. Prof. P.S, Conner, Cincinnati. Dr. gabe H. Packard, Philadelphia. Prof. Lewis A. Stimson, New York City. Dr. J. M. Barton, Philadelphia. Volume IV.—Skin Diseases, Ophthalmology, Otology, Rhinology, Diseases of Pharynx, i etc., Intubation, Diseases of Larynx and Cisophagus, Diseases of Thyroid Dr. Morris Longstreth, Philadelphia. Dr. Thos. G, Morton, Philadelphia. Prof. J. E. Garretson, Philadelphia. Prof, J. W. White, Philadelphia. Prof. C. Johnston, Baltimore. eo Prof. E. C. Seguin, New York City. i.” Gland, Legal Medicine, Examination for Insurance, Diseases of the Blood, Urinalysis, Volume Index. Prof. A. Van Harlingen, Philadelphia. Dr. Chas. A. Oliver and Dr. Geo. M. Gould, Philadelphia, Dr. Charles S. Turnbull, Philadelphia. Prof, J. Solis Cohen, Philadelphia. Prof. John Guitéras, Charleston, S. C. Dr. Chas. E. Sajous, Philadelphia. Prof. D. Bryson Delavan, New York: Prof. R. Fletcher Ingals, Chicago. Prof. F. W. Draper, Boston. ° . Prof. Jas. Tyson, Philadelphia. 7 Volume V.—General Therapeutics, Experimental Therapeutics, Poisons, Electric Therapeutics, Climatology, Dermography, Technology, Bacteriology, Embry- : ology, Physiology, Anatomy, General Index. Dr. J. P. Crozer Griffith, Philadelphia. Dr. Hobart A. Hare, Philadelphia. Prof Geo. H. Rohé, Baltimore. Prof. John B.,Hamilton, Washington. Dr. Harold C. Ernst, Boston, Prof, H. Newell Martin, Baltimore. Dr. R. J. Dunglison, Philadelphia. 30 (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) ; a Dr, C. Sumner Witherstiney Philadelphia, Prof. J. W, Holland, Philadelphia. H Prof. A L. Ranney, New York. Dr. Albert H. Gihon, U.S. N. Dr. W. P. Manton, Detroit, Dr, W. X. Sudduth, Philadelphia. , Prof, Wm, T. Forbes, Philadelphia. — THE LATEST BOOK OF REFERENCE ON NERVOUS DISEASES. Lectures on Nervous Diseases, FROM THE STAND-POINT OF CEREBRAL AND SPINAL LOCALIZATION, AND THE LATER METHODS EMPLOYED IN THE DIAGNOSIS AND : TREATMENT OF THESE AFFECTIONS. By AMBROSE L. RANNEY, A.M., M.D., Pr>/cssor of the Anatomy and Physiology of the Nervous System in the New York Post-Graduate Medical School and Hospital ; Professor of Nervous and Mental Diseases in the Medical Department of the University of Vermont, etc. ; Author of ‘The Applied Anatomy of the Nervous System,’ * Practical Medical Anatomy,”’ etc., etc: . PROFUSELY ILIUvVsSstTRATED With Original Diagrams and Sketches in Color by the Author, carefully selected Wood- Engravings, and Reproduced Photographs of Typical Cases. ONE HANDSOME ROYAL OCTAVO VOLUME OF 780 PAGES. “United States. Canada (duty paid). Great Britain. France, CLOTH, - - - $5.50 $6.05 £1.35. 34 fr. 70 SHEEP, - - - 6.50 7.15 1.68, . 40 fr. 45 HALE-RUSSIA, - - 7.00 4.70 1.98. 43 fr. 30 ‘SOLD ONLY BY SUBSCRIPTION. It is now generally conceded that the nervous system controls all of the physical functions to a greater or less extent, and also ‘that-most of the symptoms encountered at the bedside can be explained and interpreted from the stand-point of nervous poyeleey The unprecedented sale of this work during the short period which has elapsed since its publication has already compelled the publishers to print a second edition, wiich is already nearly exhausted. : ¥ We are glad to note that Dr. Ranney has pub- || appeared in medical literature, is presented in com: lished in cs0k form his admirable lectures on nervous || pact form, and thus made easily accessible. In our diseases. His book contains over seven hundred opinion, Dr. Ranney’s book ought to meet with a large pages, and is profusely illustrated with origi- |} cordial reception at the hands of the medical pro- nal diagrams and sketches in colors, and with many || fession, for, even though the author's views may be carefully selected wood-cuts and reproduced photo- || sometimes open. to question, it cannot be disputed graphs of typical cases. A large amount of valua- || that his work bears evidence of scientific method and ble information, not a littleof which has but recently || honest opinion.—American Fournal of Insanity. LECTURE ON THE Diseases of the Nose and Throat. DELIVERED AT THE JEFFERSON MEDICAL COLLEGE, PHILADELPHIA, By CHARLES E. SAdOUS, M.D., Lecturer on Rhinology and Laryngology in Jefferson Medical College; Vice-President of the A _Laryngol A Association; Officer of the Academy of France and of Public Instruction of Venezuela; Corresponding Member of the Royal Society of Belgium, of the Medical Society of Warsaw (Poland), and of the Society of Hygiane of France; Member of the American Philosophical Society, etc., ete. ILLUSTRATED WITH 100 CHROMO-LITHOGRAPHS, FROM OIL PAINTINGS BY THE AUTHOR, AND 93 ENGRAVINGS ON WOOD. ONE HANDSOME ROYAL OCTAVO VOLUME. SOLD ONLY BY SUBSCRIPTION. ? United States. Canada (duty paid), Great Britain. France. Cloth, Royal Octavo, - - - $4.00 $4.40 £0.18s. 24 fr. 60 Half-Russia, Royal Octavo, - 5.00 5.50 1. Is. 30 fr. 30 1B" Since the publisher brought this valuable work before the profession, it has become: Ist, the text-book of a large number of colleges; 2d, the reference-book of the U. 8. Army, Navy, and the Marine Service; and, $d, an umportant and valued addition to the libraries of over 7000 physicians. ° . This book has not only the inherent merit of presenting a clear eaposé of the subject, but it is written with a view to enable the general practitioner to treat his cases himself. To facilitate diagnosis, colored plates are introduced, showing the pepearaee of the differ- ent parts in the diseased state as they appear in nature by artificial light. No error can thus be made, as each affection of the nose and ‘throat has its representative in the 100 chromo-lithographs presented. In the matter of treatment, the indications are so complete that even he slightest procedures, folding of cotton for the forceps, the use of the probe, ‘ete., are clearly explained. : It is intended to furnish the general practitioner || they would appear to him were they seen in the not only with 2 guide for the treatment of diseases of || living subject. Asa guide to the treatment of the the nose and throat, but also to place before hima '|. nose and throat, we can cordially recommend uP representation of the normal and diseased parts as || work.—Boston Medical aud Surgical Fournal. (CF. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) 31 THE MEDICAL BULLETIN MONTHLY—ONE DOLLAR A YEAR. Bright, Original, and Readable. AMES by the best PRAcTICAL writers procurable. 2 VERY article ag BRIEF as is consist- ent with the’ preservation of its selentific value. ‘Tees eree me NOTES by the leaders of the ‘medical profession PHROUGH- OUT THE WORLD. HESE, and many other UNIQUE FEATURES, help to keep THE MepIcAL BULLETIN in its present position as The LEADING LOW PRICE MEDICAL MONTHLY of the WORLD. SUBSCRIBE Now ! TERMS, $1.00 A YEAR IN ADVANCE In United States, Canada, and Mexico. FOREIGN SUBSCRIPTION TERMS, POSTAGE PAID: England, 5 Shillings. Australia, 5 Shillings. France, 6 Francs. Japan, 1 Yen. Germany, 5 Marks. Holland, 3 Florins. F. A. DAVIS, PUBLISHER, PHILADELPHIA, PA., U.S.A. BRANCH OFFICES: 45 East 12th St., New York City, U.S.A. 24 Lakeside Building, 220 8. Clark St., Cor. Adams, Chicago, Tl., U.S.A. 1 Kimball House, Atlanta, Ga., U.S.A. 427 Sutter St., San Francisco, Cal., U.S.A. 139-143 Oxford St,, London, W., England. FOREIGN AGENCIES: PARIS—Le Soudier. VIENNA—Josef Safar, VIII Schlosselgasse, 24. TOKIO, JAPAN-—Z. P. Marnya & Co. === IN PRESS. SECOND EDITION.—— Ointments and Oleates in Diseases of the Skin. —BY— JOHN V. SHOEMAKER, -A.M., M.D., Professor of Materia Medica, Pharmacology, Therapeutics, and Clinical Medicine, and Clinical Professor of Diseases of the Skin in the Medico-Chirurgical College of Philadelphia, eto. 16mo. NEATLY BOUND IN CLOTH. PRICE,IN UNITED STATES AND CANADA, NET, $1.00, POST-PAID ; GREAT BRITAIN, 4s. 3d.; FRANCE, 6 fr. 20. The accompanying Table of Contents will give a general idea of the work: CONTENTS. ATL.—PrHysioLoGicaL ACTION OF THE OLEATES. Part J.—History anp Origin. Part Il.—Process oF MANUFACTURE. Part Part IV.—THerapgutic EFFEect oF THE OLEATES. Parr V.—Orntments: Local Medication of Skin Diseases.—Antiquity of Ointments.—Different Indi- cations for Ointments, Powders, Lotions, etc.—Information about Ointments: Scanty, Scattered, and Insufficient, Fats and Oils: Animal and Vegetable.—Their Chemical Composition.—Comparative Permeability of Oils into Skin; of Animal, of. Vegetable. Incorporation of Medicinal ‘Substances into Fats: (1) Mode of Preparation, (2) Vegetable Powders and Extracts, (3) Alkaloids, (4) Mineral Sub- stances, (5) Petroleum Fats; Chemical Composition; Uses and Disadvantages.—List of Officinal Qint- ments.—Indications.—Substances often Prescribed Extemporaneously in Ointment Form.—Indications. A FULL INDEX RENDERS THE BOOK CONVENIENT FOR QUICK REFERENCE. CRITICISMS OF The profession in both countries is deeply in- debted to Dr. Shoemaker for his excellent work in this department of medicine.—William Whitla, M.D. (Q.U.L). It is the most complete exposition of their action which has yet appeared. They are very valuable accessions to the materia medica, and should be familiar to every practitioner.— Medical and Sur- gical Reporter. 82 FIRST EDITION. To those of our readers who wish to learn the therapeutic effects of a class of preparations which are destined to grow in favor as their merits be- come more generally known, we commend this book. — Fournal of Cutaneous and Venereal Diseases. 7 No. physician’ pretending to treat skin diseases should be without a copy of this very instructive little book.—Canada Medical Record. (F. A. DAVIS, Medical Publisher, Philadelphia, Pa., U.S.A.) Tessa — Sous = SSS a Reece = — LSS